Abstract:
A dishwasher that includes: a tub configured to accommodate an object; a main arm that is configured to (i) rotate about a first axis inside the tub, (ii) guide first water of the incoming water through a first flow path and second water of the incoming water through a second flow path, and (iii) spray the first water to the object; an auxiliary arm that is configured to (i) rotate about a second axis inside the tub and (ii) spray the second water to the object; and an auxiliary arm connector that couples the main arm to the auxiliary arm and that is rotatable with the auxiliary arm, the auxiliary arm connector including: an auxiliary flow path guide that is configured to (i) guide the second water from the main arm to the auxiliary arm and (ii) control water pressure of the second water is disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to Korean Patent Application No. 10-2016-0072197, filed on Jun. 10, 2016, whose entire disclosure is hereby incorporated by reference. 
       TECHNICAL FILED 
       [0002]    The present application generally relates to a dishwasher. 
       BACKGROUND 
       [0003]    A dishwasher is an apparatus which washes off debris such as food waste remaining on dishes or cookware (hereinafter referred to as “objects to the washed”) using wash water. 
         [0004]    In general, the dishwasher includes a washing tub for providing a washing space, a dish rack provided in the washing tub while accommodating objects to be washed, a spray arm for spraying the wash water, a sump for storing wash water, and a supply flow path for supplying the wash water stored in the sump to the spray arm. 
         [0005]    In general, wash water is sprayed onto the objects by rotation of the spray arm for spraying wash water to perform washing dishes. Recently, a dishwasher additionally includes an auxiliary arm spraying the wash water. 
       SUMMARY 
       [0006]    This specification describes technologies for a dishwasher. 
         [0007]    In general, one innovative aspect of the subject matter described in this specification can be embodied in a dishwasher comprising: a tub configured to accommodate an object; a main arm that is configured to (i) rotate about a first axis inside the tub, (ii) receive incoming water from a water source, (iii) guide first water of the incoming water through a first flow path and second water of the incoming water through a second flow path, and (iv) spray the first water to the object; an auxiliary arm that is coupled to the main arm and that is configured to (i) rotate about a second axis inside the tub and (ii) spray the second water to the object; and an auxiliary arm connector that couples the main arm to the auxiliary arm and that is rotatable with the auxiliary arm, the auxiliary arm connector including: an auxiliary flow path guide that is configured to (i) guide the second water from the main arm to the auxiliary arm and (ii) control water pressure of the second water. 
         [0008]    The foregoing and other embodiments can each optionally include one or more of the following features, alone or in combination. In particular, one embodiment includes all the following features in combination. The auxiliary flow path guide is configured to change a water flow direction of the second water. The auxiliary arm connector includes: a flow path formation rib that is coupled to an inner surface of the auxiliary flow path guide and that is configured to divide the incoming water into the first water and the second water. The flow path formation rib is configured to control the water pressure of the second water based on volume of the second water. The auxiliary arm connector includes: a plurality of reinforcing ribs that are coupled to an outer surface of the auxiliary flow path guide and that are configured to support the auxiliary flow path guide. The auxiliary arm includes: a plurality of nozzles that is configured to spray the second water to the object, and wherein each of the plurality of reinforcing ribs includes: one or more depressed grooves for preventing interference with the nozzles of the auxiliary arm. The auxiliary arm includes: one or more first auxiliary nozzles that are configured to spray a first portion of the water that has passed through the second flow path in a first direction, and one or more second auxiliary nozzles that are configured to spray a second portion of the water that has passed through the second flow path in a second direction. The second direction is opposite to a direction that the auxiliary arm rotates. The plurality of reinforcing ribs include: one or more first reinforcing ribs that are coupled to a first portion of the auxiliary flow path guide, and one or more second reinforcing ribs that are coupled to a second portion of the auxiliary flow path guide. A number of the one or more second reinforcing ribs is more than a number of the one or more first reinforcing ribs. The dishwasher further includes a supporting part that is coupled to the auxiliary arm, the supporting part including a coupling hole. The auxiliary arm connector includes: a shaft that is coupled to the supporting part, the shaft being configured to be inserted into the coupling hole of the supporting part, and an insertion key that is protruded from the shaft and that is configured to couple the shaft to the auxiliary arm. The auxiliary arm is configured to rotate within a first angle, and wherein the shaft is configured to rotate about the second axis. The supporting part further includes: a key groove that is coupled to the coupling hole and that is configured to be inserted into the insertion key, and wherein the key groove is spaced apart from the insertion key. The auxiliary arm further includes: a reflective plate that is configured to block water from the coupling hole or the key groove. The auxiliary arm connector further includes: an extending pipe that couples the main arm to the auxiliary flow path guide and that is configured to guide the second water to the auxiliary flow path guide. The extending pipe further includes: one or more sealing ribs that are protruded from an outer surface of the extending pipe and that are configured to block water leaking between the extending pipe and the auxiliary arm, and a plurality of flow path formation protrusions that are protruded from the outer surface of the extending pipe and that are configured to flow a portion of the second water toward the sealing ribs. The auxiliary arm connector is integrated into the main arm. The dishwasher further includes a first gear that is coupled to the tub and that is configured to rotate with the main arm; a second gear that is coupled to the main arm and that is configured to rotate based on rotation of the main arm; and a linker that is coupled to the main arm and the auxiliary arm and that is configured to rotate the auxiliary arm based on rotation of the second gear. The linker is configured to rotate the auxiliary arm using an elastic force. 
         [0009]    The subject matter described in this specification can be implemented in particular embodiments so as to realize one or more of the following advantages. Comparing to a conventional dishwasher, a dishwasher includes a specific spray arm that increase a sprayed area of water. Thus, the dishwasher can efficiently wash objects in the dishwasher. In particular, the spray arm can rotate using driving force of sprayed water without using a separate driving device. In addition, the spray arm can spray water at various angles using a main arm and an auxiliary arm. 
         [0010]    The details of one or more embodiments of the subject matter of this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a diagram illustrating an example dishwasher. 
           [0012]      FIG. 2  is a diagram illustrating an example sump cover and an example spray arm assembly. 
           [0013]      FIG. 3  is a diagram illustrating an example spray arm assembly. 
           [0014]      FIG. 4  is a diagram illustrating an example sump cover and an example spray arm assembly. 
           [0015]      FIG. 5  is a diagram illustrating an example main arm. 
           [0016]      FIG. 6  is a diagram illustrating an example main arm in  FIG. 5 . 
           [0017]      FIG. 7  is a diagram illustrating an example upper housing of the main arm in  FIGS. 5-6 . 
           [0018]      FIG. 8  is a diagram illustrating an example auxiliary arm connector of the main arm in  FIGS. 5-6 . 
           [0019]      FIG. 9  is a diagram illustrating an example lower housing of the main arm in  FIGS. 5-6 . 
           [0020]      FIG. 10  is a diagram illustrating an example lower housing of the main arm in  FIGS. 5-6 . 
           [0021]      FIGS. 11-14  are diagrams illustrating an example auxiliary arm. 
           [0022]      FIGS. 15-17  are diagrams illustrating an example fixed gear. 
           [0023]      FIGS. 18-21  are diagrams illustrating an example spray arm holder. 
           [0024]      FIGS. 22-23  are diagrams illustrating an example flow path converter. 
           [0025]      FIG. 24  is a diagram illustrating an example fixed gear, an example spray arm holder, and an example flow path converter. 
           [0026]      FIGS. 25 and 26  are diagrams illustrating an example operation of a flow path converter. 
           [0027]      FIGS. 27-30  are diagrams illustrating an example eccentric gear. 
           [0028]      FIG. 31  is a diagram illustrating an example fixed gear and an example eccentric gear. 
           [0029]      FIGS. 32-34  are diagrams illustrating an example linker. 
           [0030]      FIGS. 35-37  are diagrams illustrating an example first elastic butter and an example first auxiliary arm connector. 
           [0031]      FIG. 38  is a diagram illustrating an example linker. 
           [0032]      FIG. 39  is a diagram illustrating an example operation of a linker. 
           [0033]      FIG. 40  is a diagram illustrating an example operation of an auxiliary arm. 
           [0034]      FIGS. 41 and 42  are diagrams illustrating an example operation of a spray arm. 
           [0035]      FIG. 43  is a diagram illustrating an example operation of an auxiliary arm. 
       
    
    
       [0036]    Like reference numbers and designations in the various drawings indicate like elements. 
       DETAILED DESCRIPTION 
       [0037]    Additionally, in describing the components of the present disclosure, there may be terms used like first, second, A, B, (a), and (b). These are solely for the purpose of differentiating one component from the other and not to imply or suggest the substances, order or sequence of the components. In this specification, a component is described as “connected”, “coupled”, or “linked” to another component. In some implementations, it means that one component is directly “connected”, “coupled”, or “linked” to another component. In some other implementations, it means that one component is indirectly “connected”, “coupled”, or “linked” to another component through a third component. 
         [0038]      FIG. 1  illustrates an example dishwasher.  FIG. 2  illustrates an example sump cover and an example spray arm assembly.  FIG. 3  illustrates an example spray arm assembly. 
         [0039]    In  FIGS. 1 and 2 , the dishwasher  1  may include a washing tub  1  forming a washing space tin this example, a door  30  selectively opening/closing the washing space, a dish rack  40 , in which objects to be washed are accommodated, provided in the washing tub  10 , a sump provided in the washing tub  10  while storing wash water, and a spray arm assembly  100  provided in the washing tub  10  while spraying wash water onto the objects to be washed. 
         [0040]    The dish rack  40  may be mounted to be withdrawable to a front of the washing tub  10 . The dish rack  40  may include an upper dish rack or a lower dish rack, which is provided an upper part or a lower part of the washing tub  10 , respectively. The dish rack  40  may be withdrawn from the washing tub  10  to the front of the washing tub  10 , to place or remove the objects. 
         [0041]    The sump may include a sump cover  50 , a filter  40  provided at the sump cover  50  while filtering foreign substances included in the wash water after washing the objects, and a filter cover. The sump may receive the wash water from the outside through a water pipe  80 . The wash water sprayed into the washing tub  10  may be drained through a separate drain. Although not illustrated, a water supply pump for transferring the wash water stored in the sump to the spray arm assembly  100  may be provided in the sump. 
         [0042]    In some implementations, in the sump cover  50 , the foreign substances, such as food waste, included in the wash water sprayed into the washing tub  10  may be filtered by the filter  70  and the filter cover  60 , which are provided at the sump cover  50 . The wash water may be collected in the sump through the filter  70  and the collected wash water may be returned to the spray arm assembly  100  by the water supply pump, which is provided in the sump. For example, the wash water supplied through the water pipe  80  may be recycled multiple times. 
         [0043]    In this example, the filter cover  60  forms a part of the sump cover  50 . The filter cover  60  may be formed at a lower front part of the washing tub  10  (for example, a lower part of the washing tub  10  adjacent to the door  30 ). The filter  40  is provided at a central part of the filter cover  60  to be inserted into the filter cover  60 . Upon detachment of the filter  40 , the filter cover  60  may be provided to be detached from the sump cover  50  according to detachment of the filter  70 . 
         [0044]    In some implementations, the spray arm assembly  100  is rotatably inserted into the central part of the filter cover  60  while a spray arm holder seating part  53  for receiving the wash water is formed. A water hole  59  for supplying the wash water is formed to pass through a central part of the spray arm holder seating part  53 . A pair of coupling bosses  51  for fixing a fixed gear  500  of the spray arm assembly  100 , which will be described, is formed at and protrudes from both sides of the spray arm holder seating part  53 . 
         [0045]    In addition, supporting bosses  55  for supporting a spray arm holder  600 , which is seated in the spray arm holder seating part  53 , are protruded at an upper part of the spray arm holder seating part  53 . Each supporting boss  55  may be extended to have a certain height in order to prevent the wash water or the foreign substances introduced into the sump cover  50  from being introduced into the spray arm holder seating part  53 . 
         [0046]    In some implementations, the water hole  59  for transferring the wash water is formed at the central part of the spray arm holder seating part  53 . Seating ribs  57  are formed at an inner circumferential surface of an end of the water hole  59 . The seating ribs  57  correspond to an end part of the spray arm holder  600  inserted into the spray arm holder seating part  53  and each seating rib is upwardly extended to the spray arm holder  600 . 
         [0047]    In this example, the seating ribs  57  are formed to surround extensions  636  formed at the spray arm holder  600  so as to minimize water leakage between the spray arm holder  600  and the spray arm holder seating part  53 . The spray arm holder seating part  53  will be explained in detail when the spray arm holder  600  is described below. 
         [0048]    As illustrated in  FIG. 3 , the spray arm assembly  100  is mounted at the sump cover  50  such that the wash water stored in the sump is sprayed onto the objects accommodated in the dish rack  40 . In some implementations, an upper spray arm provided between the upper dish rack and the lower dish rack and a top spray arm provided at an upper part of the upper dish rack as well as the spray arm assembly  100  may be further provided in the dishwasher  1 . 
         [0049]    In some implementations, the spray arm assembly  100  may include a spray arm  200  including a main arm  300  for spraying the wash water and auxiliary arms  400   a  and  400   b  rotatably coupled to the main arm  300 , the spray arm holder  600  coupled to a lower part of the spray arm  200  to receive the wash water from the sump cover  50  while rotatably supporting the spray arm  500 , the fixed gear  500  fixed to the sump cover  50  to prevent detachment of the spray arm holder  600 , an eccentric gear  800  rotatably coupled to the spray arm  200  while being geared to the fixed gear  500  to rotate and revolve along an outer circumferential surface of the fixed gear  500  according to rotation of the spray arm  200 , and a linker  900  coupled to the spray arm  200  and reciprocating according to rotation of the eccentric gear  800  to transfer rotational force to the auxiliary arms  400   a  and  400   b.    
         [0050]    In this example, the spray arm assembly  100  may be provided at the upper part of the dish rack  400  as well as the lower part thereof, unlike what is illustrated in  FIG. 2 . Furthermore, a plurality of spray arm assemblies  100  may be provided to spray the wash water toward the upper and lower parts of the dish rack  40 , respectively. 
         [0051]    The spray arm  200  may include the main arm  300  formed by coupling a main arm upper housing  310  and a main arm lower housing  340  and at least one of auxiliary arms  400   a  and  400   b  rotatably coupled to the main arm upper housing  310  of the main arm. 
         [0052]    In some implementations, the main arm  300  may include a first main arm  300   a  and a second main arm  300   b , which are extended in opposite directions with respect to a center of rotation of the spray arm assembly  100 . The auxiliary arms  400   a  and  400   b  may include a first auxiliary arm  400   a  and a second auxiliary arm  400   b , which are provided between the first and the second main arms  300   a  and  300   b  with respect to the center of rotation of the spray arm assembly  100 , respectively, while the first and the second auxiliary arms  400   a  and  400   b  are coupled to be spaced apart from the first and the second main arms  300   a  and  300   b  at a certain angle, respectively. 
         [0053]    In some implementations, a plurality of nozzles  314   a ,  315   a ,  314   b ,  315   b , and  317   b  for spraying the wash water introduced into the main arm  300  may be formed at upper parts of the first and the second main arms  300   a  and  300   b . The wash water introduced into the main arm  300  from the sump may be sprayed through the nozzles  314   a ,  315   a ,  314   b ,  315   b , and  317   b  in an upper direction of the main arm  300  and in an opposite direction to a direction of rotation of the main arm  300 . 
         [0054]    Thus, the main arm  300  may wash the objects accommodated in the dish rack  40  by the wash water sprayed from the nozzles  314   a ,  315   a ,  314   b ,  315   b , and  317   b  while driving force for rotating the main arm  300  may be achieved by the wash water sprayed from the nozzles  314   a ,  315   a ,  314   b ,  315   b , and  317   b.    
         [0055]    The main arm lower housing  340  of the main arm  300  is formed at a lower surface of the main arm  300 . A spray arm holder coupler  356  accommodating at least part of the spray arm holder  600  is protruded at the main arm lower housing  340 . The wash water is supplied to the first and the second main arms  300   a  and  300   b  and the first and the second auxiliary arms  400   a  and  400   b  through the spray arm holder coupler  356 . 
         [0056]    In some implementations, the main arm  300  may include a first extension  300   c  and a second extension  300   d , which are radially extended from the center of the spray arm holder coupler  356 . A first auxiliary arm connector  330   a  and a second auxiliary connector  330   b , at which the auxiliary arms  400   a  and  400   b  are rotatably mounted, may be formed at the first extension  300   c  and the second extension  300   d , respectively. 
         [0057]    In this example, the first and the second main flow paths  301   a  and  301   b  for guiding the wash water introduced through the spray arm holder  600  to the first and the second main arms  300   a  and  300   b  may be formed. The first and the second auxiliary flow paths  301   c  and  301   d  for guiding the wash water to the first and the second extensions  300   c  and  300   d  may be formed. 
         [0058]    When the main arm  300  is rotated by driving force generated by spraying of the wash water sprayed from the first and the second main arms  300   a  and  300   b , the first and the second auxiliary arms  400   a  and  400   b  may reciprocally rotate within a certain angle range due to the linker  900  according to rotation of the main arm  300  working along rotation of the main arm. A plurality of nozzles  414   a ,  415   a ,  414   b ,  415   b ,  422   a  and  422   b  may be formed at the first and the second auxiliary arms  400   a  and  400   b  for spraying the wash water introduced into the main arm  300 . 
         [0059]    In some implementations, the auxiliary arms  400   a  and  400   b  may include the first auxiliary arm  400   a  rotatably connected to the first extension  300   c  and the second auxiliary arm  400   b  rotatably connected to the second extension  300   d . A part of the wash water introduced into the main arm  300  may be transferred to the first and the second auxiliary flow paths  301   c  and  301   d  (see  FIG. 14 ) formed in the first and the second auxiliary arms  400   a  and  400   b . In some implementations, a separate decorative panel  430   a  may be attached to an upper surface of the spray arm  200  to cover the spray arm  200 . 
         [0060]    The spray arm  200  may be rotated by a separate driving device. The spray arm  200  may be rotated by driving force of the wash water sprayed from the nozzles  314   a ,  315   a ,  314   b ,  315   b , and  317   b  formed at the first and the second main arms  300   a  and  300   b  and the nozzles  414   a ,  415   a ,  414   b ,  415   b ,  422   a , and  422   b  formed at the first and the second auxiliary arms  400   a  and  400   b.    
         [0061]    That is, the spray arm  200  may be rotated by driving force generated by spraying the wash water without a separate driving device, such as a motor. 
         [0062]    The spray arm holder  600  may be coupled to the lower part of the spray arm  200  to be fixed to the spray arm  200 . Accordingly, the spray arm holder  600  may be rotated with the spray arm  200  while functioning as a central shaft of rotation of the spray arm  200 . 
         [0063]    The spray arm holder  600  includes a main arm inserter  610  coupled to the spray arm holder coupler  356  formed at the main arm  300  in an inserted manner, a separation preventing part  620  protruding from a lower part of the main arm inserter  610  to prevent the fixed gear  500  from being separated, and a sump inserter  630  rotatably inserted into the spray arm holder seating part  53  of the sump cover  50 . 
         [0064]    In the state where the spray arm holder  600  is coupled to the spray arm  200 , the spray arm holder  600  may be inserted into the spray arm holder seating part  53  of the sump cover  50  to be rotatably supported thereby. Furthermore, the wash water supplied from the sump may be supplied to an inside of the spray arm holder  600  through the water hole  59 . The wash water introduced into the spray arm holder  600  may be supplied to the first and the second flow paths  301   a  and  301   b  or the first and the second auxiliary flow paths  301   c  and  301   d  through the flow path converter  700 . 
         [0065]    The flow path converter  700  may be accommodated in the spray arm holder  600  and may function to convert the flow path of the wash water supplied from the spray arm holder  600  to the spray arm  200  into the first and the second main flow paths  301   a  and  301   b  or the first and the second auxiliary flow paths  301   c  and  301   d.    
         [0066]    In some implementations, the flow path converter  700  may be inserted into the spray holder coupler  356  of the main arm  300  and may convert the flow path of the wash water as the flow path converter  700  moves up and down at the inside of the spray arm holder coupler  356  according to supply and stoppage of the wash water. 
         [0067]    The flow path converter  700  includes a rotary plate  710  in which a plurality of opening holes  722   a ,  722   c  are formed, a plurality of upper inclined protrusions  720   a ,  720   b ,  720   c ,  720   d  for rotating the rotary plate  710  at a certain angle when the flow path converter  700  ascends according to supply of the wash water, and a plurality of lower inclined protrusions  730   a ,  730   b ,  730   c ,  730   d  for rotating the rotary plate  710  at a certain angle when the flow path converter  700  descends according to stoppage of the wash water. 
         [0068]    The fixer gear  500  may be fixed to the sump cover  50  to prevent the spray arm holder  600  coupled to the spray arm  200  from being separated while limiting movement of the spray arm holder  600  such that it is possible to rotate the spray arm  200 . 
         [0069]    A rim  510 , through which the spray arm holder coupler  356  formed at the main arm  300  rotatably passes, while gears are formed at an outer circumferential surface thereof, and fasteners  530  extending from both ends of the rim  510  to be coupled to the coupling bosses  51  of the sump cover  50 . 
         [0070]    In some implementations, in the state where the spray arm holder coupler  356  is inserted into the fixed gear  500 , the spray arm holder  600  is coupled to the spray arm holder coupler  356 . Then, the fixed gear  500  may be fixed to the coupling bosses  51  provided at the sump cover  500  through a separate fastener (e.g. a screw, not shown). 
         [0071]    Accordingly, in the state where the fixed gear  500  is fixed to the sump cover  50 , the fixed gear  500  may prevent the spray arm holder  600  from being separated from the spray arm holder seating part  53  of the sump cover  500 , thereby preventing separation of the spray arm  200 , while the spray arm holder  600  may rotatably support the spray arm  200 . 
         [0072]    In a lower surface of the spray arm  200 , the eccentric gear  800  may be rotatably mounted at the fixed gear  500  in a geared manner. The eccentric gear  800  may revolve along a circumferential surface of the fixed gear  500  fixed to the sump cover  50  according to rotation of the spray arm  200  while the eccentric gear  800  may be rotated by engagement with the fixed gear  500 . 
         [0073]    The eccentric gear  800  includes a rim  810 , in which gears are geared to the fixed gear  500 , provided at a circumferential surface of the thereof; a rotation shaft support protrusion  820  provided at an inside of the rim  810  to be rotatably coupled to a rotation shaft of the main arm  300 , and an eccentric protrusion  830  spaced apart from a rotation center of the rotation shaft support protrusion  820  while converting rotational force into linear reciprocating motion in order to transfer the linear reciprocating motion to the linker  900 . 
         [0074]    The linker  900  may be movably mounted at a lower part of the spray arm  200  to be rotated with rotation of the spray arm  200 . The linker  900  may allow the auxiliary arms  400   a  and  400   b  to reciprocally rotate in a longitudinal direction according to rotation of the eccentric gear  800  by rotation of the spray arm  200 . 
         [0075]    The linker  900  includes a rim-shaped body  910  having an elongated through hole in which the spray arm holder coupler  256  is linearly movable within a certain interval, the first and the second main links  920   a  and  920   b  extending from the rim-shaped body  910  to be coupled to the first and the second main arms  300   a  and  300   b  in a linearly movable manner, and first and the second auxiliary links  950   a  and  950   b  extending from the rim-shaped body  910  while being spaced apart from the first and the second main links  920   a  and  920   b  at an certain angle to be coupled to the first and the second auxiliary arms  400   a  and  400   b  while reciprocally rotate the first and the second auxiliary arms  400   a  and  400   b  according to movement of the rim-shaped body  910 . In this example, an eccentric gear container  940 , into which the eccentric protrusion  830  of the eccentric gear  800  is inserted, while supporting the eccentric gear  800  is formed at the second main link  920   b.    
         [0076]    A coupling process of each configuration constituting the spray arm assembly  100  as described above will be briefly explained with reference to  FIGS. 3 and 4 . 
         [0077]      FIG. 4  illustrates an example sump cover and an example spray arm assembly.  FIG. 4  illustrates a cross-sectional view taken along a line X′-X″ in  FIG. 2 . 
         [0078]    First, the first and the second auxiliary arms  400   a  and  400   b  are rotatably inserted into the first and the second auxiliary arm connectors  330   a  and  330   b  of the main arm  300 . The spray arm holder coupler  356  formed at the lower part of the spray arm  200  is inserted into the rim-shaped body  910  of the linker  900 . 
         [0079]    In this example, the first and the second main links  920   a  and  920   b  of the linker  900  may be coupled to the first and the second main arms  300   a  and  300   b  in a linearly reciprocating manner. The first and the second auxiliary links  950   a  and  950   b  of the linker  900  may be coupled to the first and the second auxiliary arms  400   a  and  400   b  to rotate the first and the second auxiliary arms  400   a  and  400   b  according to reciprocating motion of the linker  900 . The eccentric gear protrusion  830  is inserted into the eccentric gear container  940  formed at the second main link  920   b , such that the eccentric gear  800  may be supported by and be rotatably provided at the lower part of the main arm  300 . 
         [0080]    Then, the fixed gear  500  may be rotatably coupled to the spray arm holder coupler  356  formed at the lower part of the spray arm  200  in an inserted manner. In this example, the eccentric gear  800  supported by the eccentric gear container  940  of the second main link  920   b  may be coupled to the gears formed at the fixed gear  500  in an engagement manner, such that the eccentric gear  800  may rotate and revolve along the outer circumferential surface of the fixed gear  500  according to rotation of the main arm  300 . 
         [0081]    In some implementations, the flow path converter  700  is inserted into the spray arm holder coupler  356 . The flow path converter  700  may be accommodated in the main arm inserter  610  provided at the spray arm holder  600 . 
         [0082]    As the wash water is introduced into the main arm inserter  610 , the flow path converter  700  ascends to the main arm inserter  610  by travel pressure of the wash water. Upon stoppage of the wash water, as internal water pressure of the main arm inserter  610  decreases, the flow path converter  700  descends. 
         [0083]    In addition, the spray arm holder  600  is coupled to the lower part of the spray arm holder coupler  356 . Accordingly, separation of the fixed gear  500  from the spray arm holder coupler  356  due to the spray arm holder  600  may be prevented. 
         [0084]    Sequentially, while being inserted into the sump inserter  630  formed at the lower part of the spray arm  600 , the fasteners  530  of the fixed gear  500  is coupled to the coupling bosses  51  of the sump cover  50  and the fixer gear  500  is fixed to the sump cover  50  by a separate fastener. 
         [0085]    That is, the fixed gear  500  is rotatably coupled to the spray arm holder coupler  356  of the spray arm  200  before the spray arm holder  600  is coupled to and is fixed to the spray arm  200  at the lower part of the fixed gear  500 . Then, the spray arm holder  600  is rotatably seated at the spray arm holder seating part  53  of the sump cover  50  and the fixed gear  500  is fixed to the sump cover  50 . 
         [0086]    Accordingly, the fixed gear  500  of the elements of the spray arm assembly  100  is fixed to the sump cover  50 , alone. The spray arm  200 , the spray arm holder  600 , and the linker  900  of the spray arm assembly  100  are rotatably provided at the sump cover  50 . In this example, upward movement of the spray arm holder  600  may be limited by the fixed gear  500 , thereby being prevented from separating from the spray arm seating part  53 . 
         [0087]    In this example, operation of the spray arm assembly  100  will be briefly explained. 
         [0088]    First, the wash water introduced through the water pipe  80  moves to the sump using the separate water supply pump and is introduced into the spray arm assembly  100  through the water hole  59  formed at the spray arm holder seating part  53  of the sump cover  50 . The wash water introduced into the spray arm assembly  100  may be sprayed onto the objects to be washed through the first and the second main arms  300   a  and  300   b  or the first and the second auxiliary arms  400   a  and  400   b.    
         [0089]    In this example, the spray arm  200  may be rotated in a direction opposite to a spraying direction of the wash water by driving force according to the wash water sprayed by the first and the second main arms  300   a  and  300   b  or the first and the second auxiliary arms  400   a  and  400   b.    
         [0090]    In this example, supply of the wash water to the first and the second main arms  300   a  and  300   b  or the first and the second auxiliary arms  400   a  and  400   b  may be changed by operation of water flow path conversion of the flow path converter  70  according to supply or stoppage of the wash water using the water supply pump. 
         [0091]    In some implementations, as the spray arm  200  rotates, the eccentric gear  800  provided at the lower part of the main arm  300  rotates and revolves along the outer circumferential surface of the fixed gear  500 . That is, in the state where the fixed gear  500  is fixed to the sump cover  50 , the fixed gear  50  maintains the fixed state regardless of rotation of the spray arm  200 . In the state where the eccentric gear  800  is rotatably coupled to the main arm  300 , the eccentric gear  800  is geared to the fixed gear  500  such that the eccentric gear  800  may revolve along the outer circumferential surface of the fixed gear  500  according to rotation of the main arm  300 . 
         [0092]    In some implementations, the eccentric protrusion  830  of the eccentric gear  800  is inserted into the second main link  830   b  of the linker  900 . The eccentric protrusion  830  performs a circular motion with respect to the center of the rotation to have a certain interval according to rotation of the eccentric gear  800 . Thus, the linker  900  into which the eccentric protrusion  830  is inserted linearly reciprocates due to rotation of the eccentric protrusion  830  at the lower part of the main arm  300 . 
         [0093]    In this example, the first and the second auxiliary arms  400   a  and  400   b  are connected to the first and the second auxiliary links  950   a  and  950   b  of the linker  900 . The first and the second auxiliary arms  400   a  and  400   b  connected to first and the second auxiliary links  950   a  and  950   b  reciprocally rotates according to the reciprocating motion of the linker  900  such that a spraying angle of the wash water sprayed from the first and the second auxiliary arms  400   a  and  400   b  may be changed. 
         [0094]    In this example, each configuration of the spray arm assembly  100  will be described in detail, with reference to the accompanying drawing. 
         [0095]    First, the main arm  300 , i.e. a main configuration of the spray arm assembly  100 , will be described in detail, with reference to the accompanying drawing. 
         [0096]      FIG. 5  illustrates an example main arm. 
         [0097]    As illustrated in  FIG. 5 , the main arm  300  may include the first and the second arms  300   a  and  300   b  having an asymmetric structure while extending in opposite directions, respectively, and the first and the second extensions  300   c  and  300   d  between the first and the second arms  300   a  and  300   b  while inclinedly extending at a certain angle with respect to the first and the second main arms  300   a  and  300   b . In this example, the first and the second auxiliary arms connectors  330   a  and  330   b , which are rotatably coupled to the first and the second auxiliary arms  400   a  and  400   b , may be formed at the ends of the first and the second extensions  300   c  and  300   d , respectively. 
         [0098]    In some implementations, the flow path for transferring the wash water in the main arm  300  may be formed by the main arm upper housing  310  for forming the upper part of the main arm  300  and the main arm lower housing  340 . 
         [0099]    In this example, in the main arm upper housing  310 , the first and the second upper main arms  312   a  and  312   b  forming the upper part of the first and the second main arm  300   a  and  300   b  and first and the second upper extensions  322   a  and  322   b  for forming the upper part of the first and the second extensions  300   c  and  300   d  are formed. 
         [0100]    In addition, in the main arm lower housing  340 , the first and the second lower main arms  341   a  and  341   b  forming the lower part of the first and the second main arm  300   a  and  300   b  and first and the second lower extensions  351   a  and  351   b  for forming the lower part of the first and the second extensions  300   c  and  300   d  are formed. In this example, the first and the second auxiliary arm connectors  330   a  and  330   b  and the first and the second upper main arms  312   a  and  312   b  may be formed at the ends of the first and the second main arms  312   a  and  312   b  in an integrated manner. 
         [0101]    In this example, an angle between the first main arm  300   a  (or the second main arm  300   b ) and the first extension  300   c  (or the second extension  300   d ) may be an obtuse angle D 2 . An angle between the first main arm  300   a  (or the second main arm  300   b ) and the second extension  300   d  (or the first extension  300   c ) may be an acute angle D 1 . 
         [0102]    That is, a certain angle between a central line passing through a center of the first and the second arms  300   a  and  300   b  and a central line passing through a center of the first and the second extensions  300   c  and  300   d  may be formed at the center of rotation. 
         [0103]    In this example, since the obtuse angle D 2  between the first and the second main arms  300   a ,  300   b  and the first and the second extensions  300   c  and  300   d  is formed, a detachment space of the filter  70  and the filter cover  60  which are provided at the lower part of the spray arm  200  may be secured. 
         [0104]    However, if the detachment space is secured regardless of the angle between the first and the second main arms  300   a ,  300   b  and the first and the second extensions  300   c  and  300   d , the angle between the first and the second main arms  300   a ,  300   b  and the first and the second extensions  300   c  and  300   d  may be varied. 
         [0105]    In some implementations, the angle between the first and the second main arms  300   a ,  300   b  and the first and the second extensions  300   c  and  300   d  may be a right angle. Various modifications thereof are possible according to design change of the main arm  300 . The angle between the first and the second main arms  300   a ,  300   b  and the first and the second extensions  300   c  and  300   d  is not limited thereto. 
         [0106]    Furthermore, the first and the second main arms  300   a  and  300   b  may be asymmetrically formed with respect to the first and the second extensions  300   c  and  300   d . However, the forming state of the first and the second main arms  300   a  and  300   b  is not limited thereto. The first and the second main arms  300   a  and  300   b  may be symmetrically formed respect to the first and the second extensions  300   c  and  300   d.    
         [0107]    As illustrated, the main arm  300  may form the flow path for transferring the wash water by coupling the main arm upper housing  310  to the main arm lower housing  340 . 
         [0108]      FIG. 6  illustrates an example main arm in  FIG. 5 .  FIG. 6  illustrates a cross-sectional view along a line A′-A″ in  FIG. 5 . 
         [0109]    As illustrated in  FIG. 6 , the main arm  300  may be formed by coupling the main arm upper housing  310  to the main arm lower housing  340 . In this example, the main arm upper housing  310  and the main arm lower housing  340  may be integrated using heat/ultrasonic welding. 
         [0110]    Thus, the first and the second main flow paths  301   a  and  301   b  of the first and the second main arms  300   a  and  300   b  and the first and the second auxiliary flow paths  301   c  and  301   d  of the first and the second extensions  300   c  and  300   d  may be formed at the lower surface of the main arm upper housing  310 . In addition, welding ribs  327  are formed at to the main arm lower housing  340  to be welded. 
         [0111]    In addition, in the upper surface of the main arm lower housing  340 , welding steps  357 , at which the welding ribs  327  is welded, having a shape corresponding to the welding ribs  327  are formed along outer circumferential surfaces of the first and the second main flow paths  301   a  and  301   b  of the first and the second main arms  300   a  and  300   b  and the first and the second auxiliary flow paths  301   c  and  305  of the first and the second extensions  300   c  and  300   d . The welding ribs  327  and the welding steps  357  will be described in detail when the main arm upper housing  310  and the main arm lower housing  340  are described. 
         [0112]    Hereinafter, the main arm upper housing  310  of the main arm  300  will be described in detail, with reference to the accompanying drawing. 
         [0113]    Again, referring to  FIG. 5 , an upper shape of the main arm upper housing  310  will be explained. 
         [0114]    As illustrated in  FIG. 5 , a first inclined surface  313   a  having a downward slope in an opposite direction to a rotation direction of the spray arm  200  may be formed at the upper surface of the first upper main arm  312   a  of the main arm upper housing  310 . A second inclined surface  313   b  having a downward slope in an opposite direction to a rotation direction of the spray arm  200  may be formed at the upper surface of the second upper main arm  312   b.    
         [0115]    In this example, the first and the second inclined surfaces  313   a  and  313   b  may be extended to the first and the second upper extensions  322   a  and  322   b  to have inclinedly curved shapes. The first and the second inclined surfaces  313   a  and  313   b  may be formed in order to widen a range of spraying angles of a plurality of the nozzles  314   a ,  315   a ,  314   b ,  315   b  formed at the first upper main arm  312   a  and the second upper main arm  312   b.    
         [0116]    In some implementations, the first nozzles  314   a  spraying the wash water in a vertical direction of the spray arm  200  and first inclined nozzles  315   a  inclinedly formed in an opposite direction to a rotation direction of the spray arm  200  to generate driving force which allows the spray arm  200  to be capable of rotating may be formed at the first inclined surface  313   a.    
         [0117]    Furthermore, second nozzles  314   b  spraying the wash water in a vertical direction of the spray arm  200  and second inclined nozzles  315   b  inclinedly formed in an opposite direction to a rotation direction of the spray arm  200  to generate driving force which allows the spray arm  200  to be capable of rotating may be formed at the second inclined surface  313   b.    
         [0118]    In this example, the first and the second nozzles  314   a  and  314   b  and the first and the second inclined nozzles  315   a  and  315   b  may be formed to have different radiuses or to have different sprayed areas, with respect to the center of rotation of the main arm upper housing  310 . 
         [0119]    In some implementations, in the case of the first and the second nozzles  314   a  and  314   b  and the first and the second inclined nozzles  315   a  and  315   b , the quantity thereof may be increased or decreased in order to secure the sprayed areas of the wash water and to form of driving force for rotation of the spray arm  200 . Forming positions and spray directions may be varied. 
         [0120]    Furthermore, the first and the second inclined nozzles  315   a  and  315   b  may be formed to have various spray angles in order to secure washing areas. However, the first and the second inclined nozzles  315   a  and  315   b  may be formed to have the total of driving force due to the wash water sprayed from the first and the second inclined nozzles  315   a  and  315   b  may be equal to or greater than minimum driving force for rotation of the spray arm  200 . 
         [0121]    In addition, an upper marker  317   a  having a certain figure or character shape may be formed at a surface of the first upper main arm  312   a  to check a welding direction of the main arm upper housing  310  upon welding of the main upper housing  310  and the main arm lower housing  340 . 
         [0122]    Furthermore, a separate central nozzle  317   b  may be further formed at the center of rotation of the first upper main arm  312   a  or the second upper main arm  312   b  to spray the wash water to the center of rotation of the main arm  300 . In this example, since the nozzles formed at the first and the second upper main arms  312   a  and  312   b  are uniformly distributed, the central nozzle  317   b  may be formed at one side of the first upper main arm  312   a  or the second upper main arm  312   b.    
         [0123]    The first and the second auxiliary arm connectors  330   a  and  330   b  supporting the first and the second auxiliary arm  400   a  and  400   b  are rotatably formed at the first and the second upper extensions  322   a  and  322   b . First and the second ports  324   a  and  324   b  are formed at the ends of the first and the second upper extensions  322   a  and  322   b  to communicate with the first and the second auxiliary arm connectors  330   a  and  330   b.    
         [0124]    In some implementations, separate first and the second central nozzles  326   a  and  326   b  may be further formed at centers of rotation of the first and the second upper extensions  322   a  and  332   b  in order to spray the wash water to the center of rotation of the main arm  300 . In this example, in the case of the first and the second extensions  322   a  and  322   b , since the nozzles  414   a ,  415   a ,  414   b ,  415   b ,  422   a ,  422   b  are formed at the first and the second auxiliary arms  400   a  and  400   b  only (see  FIG. 12 ), a small amount of wash water may be sprayed onto the centers of the first and the second extensions  322   a  and  322   b . Thus, the separate first and the second central nozzles  326   a  and  326   b  may be further formed at the first and the second upper extensions  322   a  and  322   b.    
         [0125]    In addition, the first and the second central nozzles  326   a  and  326   b  may be formed to have different radiuses at the center of rotation of the main arm  300 . The first and the second central nozzles  326   a  and  326   b  may be formed in different shapes in order to have different washing efficiency. For example, the first central nozzle  326   a  may be formed to have a slot shape. The second central nozzle  326   b  may be formed to have a circular shape. 
         [0126]      FIG. 7  illustrates an example upper housing of the main arm in  FIGS. 5-6 . 
         [0127]    In some implementations, as illustrated in  FIG. 7 , the welding ribs  327  for being welding to the main arm lower housing  340  are formed at the lower part of the upper main arm  310 . Herein the welding ribs  327  are formed to extend to define the first and the second main arms  312   a  and  312   b  and the first and the second upper extensions  322   a  and  322   b , thereby forming the first and the second main flow paths  301   a  and  301   b  and the first and the second auxiliary flow paths  301   c  and  301   d.    
         [0128]    In addition, a cross-shaped upper flow path formation rib  328  is formed at the center of rotation of the main arm upper housing  310  to define the flow path, such that wash water may be introduced into the first and the second main flow paths  301   a  and  301   b  and the first and the second auxiliary flow paths  301   c  and  301   d  through the main arm lower housing  340 , which will be described below. 
         [0129]    In some implementations, in the first and the second main flow paths  301   a  and  301   b  and the first and the second auxiliary flow paths  301   c  and  301   d , a plurality of ribs may be formed inside the welding ribs  327  to guide the flow path of wash water moving to the first and the second main flow paths  301   a  and  301   b  and the first and the second auxiliary flow paths  301   c  and  301   d.    
         [0130]    In this example, the first and the second upper ribs  316   a  and  316   b  formed at the first and the second main flow paths  301   a  and  301   b  may be protruded from the upper flow path formation rib  328  to insides of the first and the second main flow paths  301   a  and  301   b . The first and the second upper ribs  316   a  and  316   b  may be provided to be in contact with first and the second lower ribs  324   a  and  342   b  formed at the main arm lower housing  340 , which will be described below, in order to form the flow paths. 
         [0131]    Furthermore, the first and the second extension upper ribs  325   a  and  325   b  formed at the first and the second auxiliary flow paths  301   c  and  301   d  may be protruded from the upper flow path formation rib  328  to insides of the first and the second auxiliary flow paths  301   c  and  301   d . The first and the second extension upper ribs  325   a  and  325   b  may be provided to be in contact with first and the second extension lower ribs  352   a  and  352   b  formed at the main arm lower housing  340 , which will be described below, in order to form the flow paths. 
         [0132]    In some implementations, in the case of the first and the second extension upper ribs  325   a  and  325   b  formed at the first and the second auxiliary flow paths  301   c  and  301   c , the first and the second extension upper ribs  325   a  and  325   b  may be inclined to correspond to the shapes of the first and the second ports  324   a  and  324   b  such that the wash water flowing through the first and the second auxiliary flow paths  301   c  and  301   d  may be smoothly introduced into the first and the second ports  324   a  and  324   b  formed at the first and the second extensions  300   c  and  300   d.    
         [0133]    The first and the second auxiliary arm connectors  330   a  and  330   b  and the first and the second extensions  300   c  and  300   d  are formed at the ends of the first and the second upper extensions  322   a  and  322   b  in an integrated manner. The first and the second auxiliary arm connectors  330   a  and  300   b  are formed in opposite directions to each other while having the same shape. Hereinafter, only the first auxiliary arm connector  330   a  formed at the first upper extension  322   a  will be described below. 
         [0134]      FIG. 8  illustrates an example auxiliary arm connector of the main arm in  FIGS. 5-6 . 
         [0135]    As illustrated in  FIG. 8 , the first auxiliary arm connector  330   a  includes an extending pipe  331  communicating with the first port  324   a  of the first upper extension  322   a , and an auxiliary flow  334  communicating with an end of the extending pipe  331  and converting the flow path of the wash water upwards, and a shaft  338  extending at an end of the auxiliary flow path guide  334  to rotatably supporting the first auxiliary arm  400   a.    
         [0136]    In this example, a plurality of sealing ribs  332   a ,  332   b ,  332   c  are provided between the extending pipe  331  and the first auxiliary arm  400   a  to seal water leaking. For example, the sealing ribs  332   a ,  332   b ,  332   c  can have ring shapes. Flow path forming protrusions  333   a  are provided between the extending pipe  331  and the auxiliary flow path guide  334 . The auxiliary flow path guide  334  introduces a part of the wash water into the extending pipe  331 . In some implementations, the flow path forming protrusions  333   a  can be provided on an outer circumferential surface of the extending pipe  331 . The flow path forming protrusions  333   a  can be symmetrically provided on the surface of the extending pipe  331 . 
         [0137]    In this example, the sealing ribs  332   a ,  332   b ,  332   c  and the flow path forming protrusions  333   a  may be symmetrically formed at an inner circumferential surface of the first auxiliary arm  400   a . That is, when the sealing ribs  332   a ,  332   b ,  332   c  and the flow path forming protrusions  333   a  completely adhere to the first auxiliary arm  400   a , rotation of the first auxiliary arm  400   a  may be restricted by frictional force. Thus, a space between the first auxiliary arm  400   a , and the sealing ribs  332   a ,  332   b ,  332   c  and the flow path forming protrusions  333   a  may be formed such that the first auxiliary arm  400   a  can rotate. 
         [0138]    In some implementations, a space between a pair of sealing ribs of the sealing ribs  332   a ,  332   b , and  332   c  may be equal to or greater than a width of each foreign substance discharge hole  419   a  (see  FIG. 13 ) formed at the first auxiliary arm  400   a , which will be described below. 
         [0139]    In this example, in the case of the foreign substance discharge holes  419   a  of the first auxiliary arm  400   a , when the wash water is introduced into the first auxiliary arm  400   a , the wash water may be partially introduced by pressure of the wash water between the extending pipe  331  and the first auxiliary arm  400   a  through the flow path forming protrusion  333   a , and the introduced wash water may discharge the foreign substances introduced between the extending pipe  331  and the first auxiliary arm  440   a  through the foreign substance discharge hole  419   a.    
         [0140]    In addition, an upper supporting protrusion  333   b  and a lower supporting protrusion  333   c  are protruded at a front upper surface and a rear lower surface of the extending pipe  331 . The upper supporting protrusion  333   b  and the lower supporting protrusion  333   c  prevent the sealing ribs  332   a ,  332   b , and  332   c  and the flow path forming protrusions  333   a  from being damaged by insertion error when the extending pipe  331  is inserted into the first auxiliary arm  440   a , or from being damaged when the spray arm assembly  100  moves in the state where the auxiliary arm  400   a  is coupled to the spray arm assembly  100 . 
         [0141]    The upper supporting protrusion  333   b  and the lower supporting protrusion  333   c  are formed to have the same heights as the sealing ribs  332   a ,  332   b , and  332   c  or the flow path forming protrusions  333   a  or to have comparatively large areas, such that the upper supporting protrusion  333   b  and the lower supporting protrusion  333   c  may be formed to have higher strength than sealing ribs  332   a ,  332   b , and  332   c  or the flow path forming protrusions  333   a.    
         [0142]    The auxiliary flow path guide  334  may extend from the end of the extending pipe  331  and may be formed to have a drum-shaped body with an open upper part and having a certain length. The auxiliary flow path guide  334  is formed to allow a direction of the wash water passing through the extending pipe  331  to be changed upwards, such that the wash water flows to the nozzles  414   a ,  415   a , and  422   a  of the first auxiliary arm  400   a.    
         [0143]    A flow path formation rib  335   a  extending in a longitudinal direction of the auxiliary flow path guide  334  may be further provided in the auxiliary flow path guide  334 . To reinforce the auxiliary flow path guide  334 , the flow path formation rib  335   a  may extend in a vertical direction in the auxiliary flow path guide  334  to maintain a shape of the auxiliary flow path guide  334 . In addition, the flow path formation rib  335   a  may allow inner volume of the auxiliary flow path guide  334  to be decreased such that pressure of the wash water passing through the auxiliary flow path guide  334  may be temporarily increased. 
         [0144]    In some implementations, an inclined part  335   b  may be formed at a front end of the flow path formation rib  335   a  (i.e. the extending pipe  331  side) to prevent the foreign substances from becoming stuck in the flow path formation rib  335   a  when the wash water introduced into the extending pipe  331  with the foreign substances is introduced into the flow path formation rib  335   a.    
         [0145]    Furthermore, a plurality of horizontal reinforcing ribs  337   a  may be formed at both sides of the auxiliary flow path guide  334  to reinforce the auxiliary flow path guide  334  from horizontal impact applied to the auxiliary flow path guide  334 . A plurality of vertical reinforcing ribs  336   a  may be formed at the upper part and the lower part of the auxiliary flow path guide  334  to reinforce the auxiliary flow path guide  334  from vertical impact and load applied to the auxiliary flow path guide  334 . 
         [0146]    In this example, in impact applied to the auxiliary flow path guide  334 , vertical impact and load may be more greatly applied to the auxiliary flow path guide  334  than horizontal impact and load. Thus, there may be more vertical reinforcing ribs  336   a  than horizontal reinforcing ribs  337   a.    
         [0147]    Furthermore, the vertical reinforcing ribs  336   a  and the horizontal reinforcing ribs  337   a  may be formed nearby an inner circumferential surface of the first auxiliary arm  440   a . Thus, the vertical reinforcing ribs  336   a  and the horizontal reinforcing ribs  337   a  allow inner volume of the first auxiliary arm  440   a  to be decreased such that pressure of the wash water supplied to the first auxiliary arm  440   a  is temporarily increased, in the manner of the flow path formation rib  335   a.    
         [0148]    In some implementations, a plurality of depressed grooves  336   b  and  337   b  may be formed at outsides of the vertical reinforcing ribs  336   a  and the horizontal reinforcing ribs  337   a  to prevent interference with the nozzles formed at the first auxiliary arm  400   a.    
         [0149]    For example, since the vertical reinforcing ribs  336   a  and the horizontal reinforcing ribs  337   a  are inserted into the first auxiliary arm  400   a  and are formed adjacent to the inner circumferential surface of the first auxiliary arm  400   a , the nozzles  414   a ,  415   a , and  422   a  formed at the first auxiliary arm  400   a  may be closed by the vertical reinforcing ribs  336   a  and the horizontal reinforcing ribs  337   a  upon rotation of the first auxiliary arm  400   a.    
         [0150]    Thus, a plurality of depressed grooves  336   b  and  337   b  may be further formed at the outsides of the vertical reinforcing ribs  336   a  and the horizontal reinforcing ribs  337   a  such that the wash water may be introduced into the nozzles  414   a ,  415   a , and  422   a  upon rotation of the first auxiliary arm. 
         [0151]    The shaft  338  is protruded from an end of the auxiliary flow path guide  334  to be inserted into an inner end of the first auxiliary arm  400   a  to rotatably support the first auxiliary arm  400   a . The shaft  338  may be formed at a position spaced apart from the extending pipe  331  to disperse load applied to the first auxiliary arm  400   a.    
         [0152]    In some implementations, an insertion key  338   a  is protruded at one side of an end of the shaft  338 . The insertion key  338   a  is inserted into a key groove  417   a  (see  FIG. 14 ) formed at the first auxiliary arm  400   a  to prevent the first auxiliary arm  400   a  from being separated from the shaft  338 . To this end, in the state where the first auxiliary arm  400   a  is normally installed, the insertion key  338   a  and the key groove  417   a  may be provided at opposite directions to each other. 
         [0153]    For example, when the first auxiliary arm  400   a  is coupled to the first auxiliary arm connector  330   a , the first auxiliary arm  400   a  is inserted in reverse such that the insertion key  338   a  of the shaft  338  may be reversely inserted into the key groove  417   a  of the first auxiliary arm  400   a . After being completely inserted into the first auxiliary arm  400   a , the first auxiliary arm  400   a  turns in reverse, again such that the insertion key  338   a  of the shaft  338  cannot be separated from the key groove  417   a.    
         [0154]    Hereinafter, the main arm lower housing  340  of the main arm  300  will be described in detail with reference to the accompanying drawings. 
         [0155]      FIG. 9  is a diagram illustrating an example lower housing of the main arm in  FIGS. 5-6 .  FIG. 10  is a diagram illustrating an example lower housing of the main arm in  FIGS. 5-6 . 
         [0156]    As illustrated in  FIGS. 9 and 10 , the main arm lower housing  340  as described above includes the first and the second lower main arms  341   a  and  341   b  for forming the lower parts of the first and the second main arms  300   a  and  300   b , and the first and the second lower extensions  351   a  and  351   b  for forming the lower parts of the first and the second extensions  300   c  and  300   d . A spray arm holder coupler  356  is protruded at the lower part of the center of rotation of the main arm lower housing  340 . 
         [0157]    In this example, shapes of the first and the second lower main arms  341   a  and  341   b  and the first and the second lower extensions  351   a  and  351   b  are formed to correspond to those of the first and the second upper main arms  312   a  and  312   b  and the first and the second upper extensions  322   a  and  322   b , respectively. The detailed description of formation directions of the first and the second lower main arms  341   a  and  341   b  and the first and the second lower extensions  351   a  and  351   b  is omitted. 
         [0158]    In some implementations, the welding steps  357 , to which the welding ribs  327  of the main arm upper housing  310  is welded, is formed at the upper surface of the main arm lower housing  340 , as illustrated in  FIG. 9 . In this example, the welding steps  357  is extended to define the first and the second lower main arms  341   a  and  341   b  and the first and the second extensions  531   a  and  531   b  in order to form the first and the second main flow paths  301   a  and  301   b  and the first and the second auxiliary flow paths  301   c  and  301   d.    
         [0159]    A cross-shaped lower flow path formation rib  354  is formed at the central part of the spray arm holder coupler  356  to define the flow paths, such that the wash water may be introduced into the first and the second main flow paths  301   a  and  301   b  and the first and the second auxiliary flow paths  301   c  and  301   d.    
         [0160]    In some implementations, in the first and the second main flow paths  301   a  and  301   b  and the first and the second auxiliary flow paths  301   c  and  301   d , a plurality of lower ribs  342   a ,  342   b ,  352   a , and  352   b  may be formed at an inside of the welding steps  357  (i.e. an inside for forming each flow path) to be in contact with the upper ribs  316   a ,  316   b ,  325   a , and  325   b  of the main arm upper housing  310 , respectively in order to guide the flow path of the wash water moving through the first and the second main flow paths  301   a  and  301   b  and the first and the second auxiliary flow paths  301   c  and  301   d.    
         [0161]    First and the second lower ribs  342   a  and  342   b  may be protruded from the lower flow path formation rib  335   a  to the inside of the first and the second main flow paths  301   a  and  301   b  while being in contact with the first and the second upper ribs  316   a  and  316   b  formed at the main arm upper housing  310  to form the first and the second flow paths  301   a  and  301   b.    
         [0162]    Furthermore, the first and the second extension lower ribs  352   a  and  352   b  may be protruded from the lower flow path formation rib  335   a  to the inside of the first and the second auxiliary flow paths  301   c  and  301   d  while in contact with the first and the second extension upper ribs  325   a  and  325   b  to form the first and the second auxiliary flow paths  301   c  and  301   d.    
         [0163]    In some implementations, in the case of the first and the second extension lower ribs  352   a  and  352   b  formed at the first and the second auxiliary flow paths  301   c  and  301   d , the first and the second extension lower ribs  352   a  and  352   b  formed at the first and the second auxiliary flow paths  301   c  and  301   d  may be inclined to correspond to the shapes of the first and the second ports  324   a  and  324   b  such that the wash water flowing through the first and the second auxiliary flow paths  301   c  and  301   d  may be smoothly introduced into the first and the second ports  324   a  and  324   b  formed at the first and the second extensions  300   c  and  300   d.    
         [0164]    The spray arm holder coupler  356  is formed to have a cylindrical shape. Spray arm holder coupler protrusions  356   a  are protruded at both lower parts of an outer circumferential surface of the spray arm holder coupler  356 . In the spray arm holder coupler  356 , the main arm inserter  610  of the spray arm holder  600  is inserted into the spray arm holder coupler  356 . When the spray arm holder  600  in an inserted state is rotated in one direction, the spray arm holder  600  may be held at the spray arm holder coupler protrusions  356   a  such that the spray arm holder  600  may be fixed. When the spray arm holder  600  in an inserted state is rotated in the other direction, the spray arm holder  600  may be separated from the spray arm holder coupler protrusions  356   a  such that the spray arm holder  600  may be separated. 
         [0165]    In some implementations, the spray arm holder coupler  356  is formed at the main arm lower housing  340 , as illustrated in  FIG. 1 . The lower flow path formation rib  354  is formed at an inside of the spray arm holder coupler  356 . The inside of the spray arm holder coupler  356  is divided by the lower flow path formation rib  354  to define first and the second main flow path inlets  354   a  and  354   b  and first and the second extension flow path inlets  354   c  and  354   d  such that the wash water may be introduced into the first and the second main flow paths  301   a  and  301   b  and the first and the second auxiliary flow paths  301   c  and  301   d.    
         [0166]    In this example, the first and the second main flow path inlets  354   a  and  354   b  and the first and the second extension flow path inlets  354   c  and  354   d  may communicate with the first and the second main flow paths  301   a  and  301   b  and the first and the second auxiliary flow paths  301   c  and  301   d , respectively. The first and the second main flow path inlets  354   a  and  354   b  and the first and the second extension flow path inlets  354   c  and  354   d  may be sequentially opened or closed by the flow path converter  700 , while will be described below. 
         [0167]    In some implementations, a washing nozzle  343   a  for spraying the wash water to the rotation shaft of the spray arm assembly  100  is formed at an end of the first lower main arm  341   a . Upon rotation of the spray arm  200 , the washing nozzle  343   a  sprays the wash water to the rotation shaft, such that residual foreign substances at the lower part of the washing tub  10  and the sump cover  50  may be introduced into the filter cover  60  and the filter  70 . 
         [0168]    Furthermore, a lower marker  344   a  having a certain figure or character shape may be formed at a central part of the first lower main arm  341   a  to check a welding direction of the main arm lower housing  340  upon welding of the main upper housing  310  and the main arm lower housing  340 . 
         [0169]    In some implementations, the first and the second guide protrusions  345   a  and  345   b  are protruded at the first and the second lower main arms  341   a  and  341   b , to which where the first and the second main links  920   a  and  920   b  are coupled to reciprocate. Since the first and the second guide protrusions  345   a  and  345   b  are movably coupled to the first and the second main links  920   a  and  920   b  of the linker  900 , the first and the second extension steps  346   a  and  346   b  are formed at the first and the second guide protrusions  345   a  and  345   b  to prevent the first and the second main links  920   a  and  920   b  from being separated. In addition, a gear rotation shaft  347   b  rotatably coupled to the eccentric gear  800  is protruded at the second lower main arm  341   b.    
         [0170]    In this example, the linker  900  movably coupled to the first and the second guide protrusion  345   a  and  345   b  performs reciprocating motion along the first and the second guide protrusions  345   a  and  345   b  according to rotation of the eccentric gear  800  coupled to the gear rotation shaft  347   b . Furthermore, movement of the linker  900  in the state where the spray arm holder  600  is inserted into the rim-shaped body  910  may be restricted by the spray arm holder  600 . 
         [0171]    Thus, the gear rotation shaft  347   b  coupling the first and the second guide protrusions  345   a  and  345   b  for guiding movement of the linker  900  to the eccentric gear  800 , and the center of the spray arm holder  600  inserted into the linker  900  may be collinear. 
         [0172]    In some implementations, a plurality of drain lines  356   b  extending between the first and the second lower main arms  341   a  and  341   b , and the first and the second lower extensions  351   a  and  351   b  may be formed at an outer circumferential surface of the spray arm holder coupler  356 . The drain lines  356   b  may be formed at the lower surface of the main arm lower housing  340  along the welding steps  357  formed at the upper surface of the main arm lower housing  340 . 
         [0173]    In the drain lines  356   b , upon rotation of the spray arm  200 , the residual foreign substances and the wash water at the lower surface of the main arm lower housing  340  are discharged from the main arm lower housing  340  by centrifugal force due to rotation of the spray arm  200 . 
         [0174]    Hereinafter, the first and the second auxiliary arms  400  and  400   b  which are main components of the spray arm assembly  100  will be explained in detail with reference to accompanying drawings. 
         [0175]      FIGS. 11-14  illustrate an example auxiliary arm.  FIG. 14  illustrates cross-sectional views taken along lines B′-B″ and C′-C″ in  FIG. 13 , respectively. 
         [0176]    In some implementations, the first and the second auxiliary arms  400   a  and  400   b  have almost identical structures. There are differences in formation positions and shapes of a plurality of nozzles  414   a ,  415   a ,  414   b ,  415   b ,  422   a , and  422   b . Accordingly, the first and the second auxiliary arms  400   a  and  400   b  are not separately described. The first auxiliary arm  400   a  will be representatively described below. A different structure of the second auxiliary arm  400   b  from that of the first auxiliary arm  400   a  may be added when describing the first auxiliary arm  400   a.    
         [0177]    As illustrated in  FIGS. 11 and 12 , the first auxiliary arm  400   a  includes an auxiliary arm housing  410   a  rotatably coupled to the first auxiliary arm connector  330   a  while spraying the wash water supplied from the first auxiliary arm connector  330   a  according to operation of the linker  900  (see  FIG. 43 ), and a decorative panel  430   a  coupled to an upper part of the auxiliary arm housing  410   a  to form the upper surface of the auxiliary arms  400   a  and  400   b.    
         [0178]    The auxiliary arm housing  410   a  includes an auxiliary arm flow path part  411   a  having a cylindrical shape while including an auxiliary arm flow path  412   a  into which the first auxiliary arm connector  330   a  is inserted, and extension ribs  423   a  (see  FIG. 36 ) provided at the upper side of the auxiliary arm flow path part  411   a  while extending in a longitudinal direction at both sides of the auxiliary arm flow path part  411   a , corresponding to an appearance of the first extension  300   c , and having symmetric shapes. 
         [0179]    In this example, the extension ribs  423   a  may be symmetric with respect to a longitudinal direction of the upper surface of the auxiliary arm flow path part  411   a  and may be formed to be bent downwards with respect to the auxiliary arm flow path part  411   a  while extending in a longitudinal direction at both sides of the auxiliary arm flow path part  411   a . The decorative panel  430   a  may be fixed and supported at outer sides of the extension ribs  423   a.    
         [0180]    In some implementations, the first auxiliary nozzles  414   a  for spraying the wash water substantially perpendicular to the first auxiliary arm  400   a , and first auxiliary inclined nozzles  415   a  inclinedly formed in a direction opposite to a rotation direction of the first auxiliary arm  400   a  to generate driving force capable of rotating the spray arm  200  when the wash water is sprayed by the first auxiliary arm  400   a  may be formed at the upper side of the auxiliary arm flow path part  411   a.    
         [0181]    The decorative panel  430   a  formed to cover the upper surface of the auxiliary arm housing  410   a  may have a certain thickness and include a polished metallic plate. The decorative panel  430   a  may be press-molded to correspond to the upper surface shape of the auxiliary arm housing  410   a.    
         [0182]    In some implementations, in an inside of the decorative panel  430   a , a plurality of through holes  431   a ,  431   b , and  431   c  are formed at positions corresponding to the first auxiliary nozzles  414   a  and the first auxiliary inclined nozzles  415   a  to expose the first auxiliary nozzles  414   a  and the first auxiliary inclined nozzles  415   a.    
         [0183]    In addition, upon mounting the decorative panel  430   a , a plurality of fixing pins  434   a , which is held at the extension ribs  423  of the auxiliary arm housing  410   a  to be fixed, is formed at an outer circumferential surface of the decorative panel  430   a . The fixing pins  434   a  bend to an inside of the lower side of each extension rib  423  to fix the decorative panel  430   a  to the auxiliary arm housing  410   a . In some implementations, a separate adhesive as well as the fixing pin  434   a  may be used between the decorative panel  430   a  and the auxiliary arm housing  410   a  to fix the decorative panel  430   a  to the auxiliary arm housing  410   a.    
         [0184]    In addition, a pivoting protrusion  425   a  coupled to the first auxiliary link  950   a  of the linker  900  is formed at the lower part of the auxiliary arm flow path part  411   a . A stoppage protrusion  427   a  is formed by bending an end of the pivoting protrusion  425   a  to hold the first auxiliary link  950   a . The stoppage protrusion  427   a  may extend to a center side of the spray arm  200  for coupling of the first auxiliary link  950   a . Furthermore, the stoppage protrusion  427   a  may be formed to be shorter than at least first pivoting elongated holes  971   a  formed at the first auxiliary link  950   a . The stoppage protrusion  427   a  may be formed to be held at the first pivoting elongated hole  971   a  when the linker  900  is mounted. 
         [0185]    In some implementations, each of the first auxiliary nozzles  414   a  and the first auxiliary inclined nozzles  415   a  may be formed to have a circular hole shape or a slot shape in order to enlarge the area where the wash water is sprayed. Furthermore, the sprayed directions of the first auxiliary nozzles  414   a  and the first auxiliary inclined nozzles  415   a  may be formed to generate driving force in which the spray arm  200  is capable of rotating upon rotation of the first auxiliary arm  400   a.    
         [0186]    For example, driving force due to the wash water sprayed from the first auxiliary nozzles  414   a  and the first auxiliary inclined nozzles  415   a  may be increased or decreased by rotation of the first auxiliary arm  400   a . However, the direction of driving force due to the wash water sprayed from the first auxiliary nozzles  414   a  and the first auxiliary inclined nozzles  415   a  may be constantly formed. 
         [0187]    In some implementations, as illustrated in  FIGS. 13 and 14 , a coupling hole  416   a , into which the shaft  338  of the first auxiliary arm connector  330   a  is inserted, is formed at an end of an inside of the auxiliary arm flow path  412   a . In this example, the end of the inside of the auxiliary arm flow path  412   a  is defined as a supporting part  416 . For example, the coupling hole  416   a  may be formed at the supporting part  416 . The shaft  338  may be inserted into the coupling hole  416 . Furthermore, in the supporting part  416 , the key groove  419   a , into which the insertion key  338   a  formed at the shaft  338  is inserted, connected to the coupling hole  416   a  may be further formed. 
         [0188]    In this example, the key groove  417   a  formed at the coupling hole  416   a  may be formed to be opposite to the insertion key  338   a  in the state where the first auxiliary arm is normally mounted. For example, when the first auxiliary arm  400   a  in the reverse state is inserted into the first auxiliary arm connector  330   a  such that the shaft  338  of the first auxiliary arm connector  330   a  is inserted into the coupling hole  416   a  while the insertion key  338  of the shaft  338  is inserted into the key groove  417   a  of the coupling hole  416   a.    
         [0189]    Then, when the first auxiliary arm connector  330   a  is completely inserted into the first auxiliary arm  400   a , the first auxiliary arm  400   a  rotates such that the position of the key groove  417   a  of the coupling hole  416   a  is spaced apart from the position of the insertion key  338  of the shaft  338 , thereby preventing the first auxiliary arm  440   a  from being separated from the first auxiliary arm connector  330   a.    
         [0190]    In some implementations, a reflective plate  418   a  is formed at the outside of the coupling hole  416   a  of the first auxiliary arm  400   a  to prevent the wash water discharged from the coupling hole  416   a  and the key groove  417   a  from being scattered. In the case where the coupling hole  416   a  and the key groove  417   a  of the first auxiliary arm  400   a  is formed at an end of the auxiliary arm flow path  415  where the wash water moves, when the wash water is scattered from the first auxiliary nozzles  414   a  or the first auxiliary inclined nozzles  415   a  of the first auxiliary arm  400   a , the little amount of the wash water may be discharged through the coupling hole  416   a  and the key groove  417   a . The wash water discharged through the coupling hole  416   a  and the key groove  417   a  may be inadvertently scattered to the inner wall of the washing tub  10 . Accordingly, the reflective plate  418   a  may be provided to prevent the wash water discharged through the coupling hole  416   a  and the key groove  417   a  from scattering and may drop to the sump cover  50 . 
         [0191]    In addition, the foreign substance discharge holes  419   a  are formed at the extending pipe  331  of a front end (i.e. a part provided at the extending pipe  331  of the first auxiliary arm connector  330   a ) of the auxiliary arm flow path part  411   a  to discharge the foreign substances introduced into the auxiliary arm flow path  412   a  of the auxiliary arm flow path part  411 . The foreign substance discharge holes  419   a  are formed between a pair of sealing ribs of a plurality of sealing ribs  332   a ,  332   b , and  332   c  formed at the extending pipe  331  of the first auxiliary arm connector  330   a.    
         [0192]    Accordingly, when the wash water is introduced into the auxiliary arm flow path  412   a  of the first auxiliary arm  400   a , a part of the wash water may be introduced into the extending pipe  331  through the flow path forming protrusion  333   a  by pressure of the wash water. The introduced wash water may be discharged with the foreign substances introduced between the extending pipe  331  and the first auxiliary arm  400   a.    
         [0193]    In this example, the first auxiliary arm  400   a  performs reciprocating rotational motion about the first auxiliary arm connector  330   a  according to rotation of the spray arm  200 . As the wash water is sprayed from the first auxiliary nozzles  414   a  and the first auxiliary inclined nozzles  415   b , the driving force generated by the nozzles  414   a  and  415   a  may be increased or decreased. 
         [0194]    In some implementations, a first driving nozzle  422   a  (see  FIG. 12 ) for generating driving force of the first auxiliary arm  400   a  may be further formed at an end of the auxiliary arm flow path part  411   a . The first driving nozzle  422   a  may be inclined in a direction opposite to a rotation direction of the first auxiliary arm  400   a . The first driving nozzle  422   a  may generate greater driving force than driving force generated by the first auxiliary inclined nozzle  415   a . The first driving nozzle  422   a  may allow driving force of the first auxiliary arm  400   a  to be directed upwards. In addition, the first driving nozzle  422   a  may be formed to wash an outer part of the washing tub  10 . 
         [0195]    In some implementations, an auxiliary arm divergent flow path  413   a  (see  FIG. 14( c ) ) having a smaller area than that of the auxiliary arm flow path  412   a  may be further formed at the auxiliary arm flow path  412   a  to supply the wash water to the first driving nozzle  422   a . In the auxiliary arm divergent flow path  413   a , pressure of the wash water sprayed from the first driving nozzle  422   a  may be increased by decrease of a cross-sectional area of the flow path where the wash water flows. 
         [0196]    In some implementations, the first and the second auxiliary arms  400   a  and  400   b  may have physically similar structures. However, positions of the first auxiliary nozzles  414   a  and the first auxiliary inclined nozzles  415   a  are different. For example, the first and the second auxiliary nozzles  414   a  and  414   b  and the first and the second auxiliary inclined nozzles  415   a  and  415   b  which are formed at the first and the second auxiliary arms  400   a  and  400   b , respectively, may be formed to have different sprayed areas upon rotation thereof. Accordingly, if the same first auxiliary arms  400   a  (or the second auxiliary arms  400   b ) are mounted at the first and the second auxiliary arm connectors  330   a  and  330   b , the same sprayed areas may be provided by the first auxiliary arms  400   a  (or the second auxiliary arms  400   b ), thereby decreasing washing efficiency. 
         [0197]    Thus, an auxiliary arm marker may be further formed to distinguish the first and the second auxiliary arms  400   a  and  400   b . In this example, the auxiliary arm marker may be formed at the lower surface of the auxiliary arm housing  410   a  and may be formed to have a certain figure or character shape. 
         [0198]    In some implementations, separate reinforcing ribs  424   a  (see  FIG. 13 ) may be formed to reinforce the extension rib  423  forming the auxiliary arm housing  410   a . Positions of the reinforcing ribs  424   a  formed at the first and the second auxiliary arms  400   a  and  400   b  are different such that the first and the second auxiliary arms  400  and  400   b  may be distinguished from each other. For example, when the position of the reinforcing rib  424   a  formed at the first auxiliary arm  400   a  is L 1 , the position of the reinforcing rib  424   a  formed at the second auxiliary arm  400   b  is L 2  such that the first and the second auxiliary arms  400  and  400   b  may be distinguished. 
         [0199]    In some implementations, an upward inclination surface  428   a  (see  FIG. 14( a ) ), inclined upwards at a certain angle D 3  in an outer direction, may be formed at the lower surface of the end of the first auxiliary arm  400   a . The upward inclination surface  428   a  may be formed to prevent the washing tub  10  from being in contact with the spray arm  200  upon rotation or stoppage of the spray arm  200 . 
         [0200]    Hereinafter, the fixed gear  500  of the spray arm assembly  100  will be described in detail, with reference to the accompanying drawing. 
         [0201]      FIGS. 15-17  illustrate an example fixed gear.  FIG. 17  illustrates a cross-sectional view taken along a line D′-D″ in  FIG. 16 . 
         [0202]    The fixed gear  500  includes a rim  510 , through which the spray arm holder coupler  356  formed at the main arm lower housing  340  rotatably passes, and at which a plurality of first gear teeth  512  is formed, a fasteners  530  extending from both sides of the rim  510  to be coupled to the coupling bosses  51  of the sump cover  50 , and a shielding rib  520  extending from one side of the rim  510  downwards to shield the inside of the fixed gear  500 . 
         [0203]    In this example, the rim  510  has a ring shape to be greater than the outer circumferential surface of the spray arm holder coupler  356 . A plurality of first gear teeth  512  is formed along an upper outer circumferential surface. At least three space maintaining protrusions  514  is protruded at an inner circumferential surface of the rim  510  to maintain a space between the spray arm holder coupler  356  and the fixed gear  500  and to prevent friction. 
         [0204]    In some implementations, upper surfaces of the first gear teeth  512  and an upper surface of the rim  510 , on which the first gear teeth  512  are formed, may be formed to be inclined downwards at a certain angle D 4  in an outside direction of the rim  510 . For example, when washing using the wash water, the wash water and the foreign substances may be introduced into upper parts of the first gear teeth  512 . For draining and discharge of the wash water and the foreign substances, the upper surfaces of the first gear teeth  512  and the upper surface of the rim  510  may be inclined downward in an outer direction of the rim  510 . 
         [0205]    Furthermore, a support surface  516  being in contact with the separation preventing part  620  of the spray arm holder  600  is formed at the lower surface of the rim  510 . The support surface  516  may be inclined upward to the center of the rim  510 . 
         [0206]    In some implementations, upon rotation of the spray arm  200 , the spray arm holder  600  coupled to the spray arm  200  rotates. In the state where the spray arm holder  600  is inserted into the spray arm holder seating part  53  of the sump cover  50 , the spray arm holder  600  receives pressure of the wash water upwards and thus rotates in a floating manner. In this example, the spray arm holder  600  may float in a horizontal direction by the spray arm holder  600  and the space of the spray arm holder  600 . 
         [0207]    In this example, when the spray arm holder  600  ascends due to pressure of the wash water according to rotation of the spray arm  200 , the support surface  516  of the rim  510  may prevent the separation preventing part  620  of the spray arm holder  600  from floating using the inclination of the support surface  516 . 
         [0208]    In addition, the fasteners  530  extend at both sides of the rim  510  in a lower direction of the rim  510 . The coupling hole  532 , into which the coupling bosses  51  of the sump cover  50  are inserted, is formed. The coupling hoe  532  may be fixed by a separate coupling member (e. g. a screw, not shown). 
         [0209]    In some implementations, the shielding rib  520  is formed at a front side of the rim  510  (i.e. the door  30  side) to shield the spray arm holder  600  provided in the fixed gear  500 . For example, upon detachment of the filter  70  and the filter cover  60  which are provided at the front side of the shielding rib  520 , the shielding rib  520  may prevent the foreign substances from being introduced into the inside of the fixed gear  500  or may prevent a user&#39;s hand from being inserted therein. 
         [0210]    Hereinafter, the spray arm holder  600  of the spray arm assembly  100  will be described in detail, with reference to the accompanying drawing. 
         [0211]      FIGS. 18-21  illustrate an example spray arm holder. 
         [0212]    As illustrated in  FIGS. 18-21 , the spray arm holder  600  includes the main arm inserter  610  inserted into the spray arm holder coupler  356  of the spray arm  200  while forming a space for mounting the flow path converter  700 , the separation preventing part  620  formed at an outer circumferential surface of the main arm inserter  610  to be fixed to the spray arm holder coupler  356  while being held at the support surface  516  of the fixed gear  500 , and the sump inserter  630  protruding from the lower part of the main arm inserter  610  while being rotatably inserted into the spray arm holder seating part  53 . 
         [0213]    In this example, an outer circumferential surface of the main arm inserter  610  is formed to correspond to an inner circumferential surface of the spray arm holder coupler  356 . A valve chamber  612  into which the flow path converter  700  is inserted is formed. A plurality of support protrusions  614  being in contact with lower inclined protrusions  730   a ,  730   b ,  730   c , and  730   d  of the flow path converter  700  are form at the lower surface of the valve chamber  612 . A hollow hole where the wash water is introduced is formed at a central lower part of the valve chamber  612 . 
         [0214]    In this example, the number of the support protrusions  614  may be increased and decreased according to the number of the flow paths formed at the spray arm  200 . Since the first and the second main flow paths  301   a  and  301   b  and the first and the second auxiliary flow paths  301   c  and  301   d  are formed, at least four support protrusions  614  may be provided. 
         [0215]    Furthermore, each support protrusion  614  may be formed in a rotated state at about 30 to 45 degrees with respect to the formation angle of the lower flow path formation rib  354  forming the first and the second main arm inlets  354   a  and  354   b  and the first and the second extension flow path inlets  354   c  and  354   d.    
         [0216]    The separation preventing part  620  is enlarged to be greater than the main arm inserter  610  at the lower part of the main arm inserter  610 . A main arm seating part  622  being in contact with a lower end of the spray arm holder coupler  356  is formed. A gripping part  624  for mounting the spray arm holder  600  to the spray arm holder coupler  356  is formed at the outer circumferential surface of the main arm seating part  622 . 
         [0217]    In this example, a holding protrusion  622   a  is formed at the inner circumferential surface of the main arm seating part  622  to hold the spray arm holder coupler protrusion  356   a  formed at the outer circumferential surface of the spray arm holder coupler  356 . The spray arm holder coupler protrusion  356   a  and the holding protrusion  622   a  are formed to be fixed or released according to rotation of the spray arm holder  600 . 
         [0218]    In addition, when the separation preventing part  620  rotates at the upper surface of the gripping part  624  while being in contact with the support surface  516  of the fixed gear  500 , a plurality of antifriction protrusions  626  may be formed to decrease friction of the support surface  516 . In some implementations, a plurality of engagement grooves  624   a  may be further formed at the outer circumferential surface of the gripping part  624 , thereby easily rotating when the spray arm holder  600  is mounted. 
         [0219]    In some implementations, a plurality of wear prevention ribs  616  are formed at the lower surface of the main arm inserter  610  to minimize contact with the support boss  55  of the spray arm holder seating part  53  when the spray arm holder  600  is inserted into the spray arm holder seating part  53 . 
         [0220]    In some implementations, the sump inserter  630  is formed to communicate with the central part of the main arm inserter  610 . The sump inserter  630  is hollow such that the wash water supplied from the sump may be introduced therein. The extension  636  is formed at the lower end of the sump inserter  630  to be held at the seating ribs  57  formed at the spray arm holder seating part  53  of the sump cover  50 . 
         [0221]    In addition, a plurality of sealing ribs  634  protruding toward the inner circumferential surface of the spray arm holder seating part  53  may be formed at the lower side of the outer circumferential surface of the sump inserter  630 . A plurality of space maintaining protrusions  632  may be formed at the upper side of the outer circumferential surface of the sump inserter  630  to maintain a space between the inner circumferential surface of the spray arm holder seating part  53  and the outer circumferential surface of the sump inserter  630 . 
         [0222]    Hereinafter, the flow path converter  700  of the spray arm assembly  100  will be described in detail, with reference to the accompanying drawing. 
         [0223]      FIGS. 22-23  illustrate an example flow path converter.  FIG. 24  illustrates an example fixed gear, an example spray arm holder, and an example flow path converter.  FIG. 24  illustrates a cross-sectional view taken along a line X′-X″ in  FIG. 2 . 
         [0224]    As illustrated in  FIGS. 22-24 , the flow path converter  700  may include the disk-shaped rotary plate  710  inserted into the valve chamber  612  of the spray arm holder  600 , the first, second, third, and fourth upper inclined protrusions  720   a ,  720   b ,  720   c , and  720   d  formed at the upper rotary plate  710  while being inserted into the lower flow path formation rib  354  of the main arm lower housing  340  to rotate the rotary plate  710 , and first, second, third, and fourth lower inclined protrusions  730   a ,  730   b ,  730   c , and  730   d  formed at the lower part of the rotary plate  710  while being held at the support protrusions  614  formed at the valve chamber  612  of the spray arm holder  600  to rotate the rotary plate  710 . 
         [0225]    The rotary plate  710  is accommodated in the valve chamber  612  of the spray arm holder  600 . The rotary plate  710  may perform reciprocating motion upwards and downward in the valve chamber  612  according to water pressure of the wash water passing through the valve chamber  612 . 
         [0226]    Accordingly, the rotary plate  710  may be formed a disk shape to correspond to a cross-sectional shape of the valve chamber  612 . In this example, a plurality of space maintaining protrusions  712  is formed at the outer circumferential surface of the rotary plate  710  to maintain a space between the inner circumferential surface of the valve chamber  612  and the outer circumferential surface of the rotary plate  710  and to minimize friction. 
         [0227]    In some implementations, the first and the second opening holes  722   a  and  722   c  may be formed at the first and third upper inclined protrusions  720   a  and  720   c  for the wash water to pass through. When the upper inclined protrusions  720   a ,  720   b ,  720   c , and  720   d  are inserted into the lower flow path housing  354  of the main arm lower housing  340 , the first and the second opening holes  722   a  and  722   c  may communicate with the first and the second main arm inlets  354   a ,  354   b  or the first and the second extension inlets  354   c , and  354   d  of the main arm lower housing  340 . 
         [0228]    In this example, the first, second, third, and fourth upper inclined protrusions,  720   a ,  720   b ,  720   c , and  720   d  may be provided at positions corresponding to the first and the second main arm inlets  354   a ,  354   b  and the first and the second extension inlets  354   c , and  354   d  of the main arm lower housing  340 . 
         [0229]    Furthermore, the first, second, third, and fourth upper inclined protrusions,  720   a ,  720   b ,  720   c , and  720   d  may be spaced apart from the center of the rotary plate  710  and the outer circumferential surface of the rotary plate  710  at a certain interval. In this example, the first and the second opening holes  722   a  and  722   c  may be formed at outsides of the first and third upper inclined protrusions  720   a  and  720   c , which face with the first and the second opening holes  722   a  and  722   c , of the first, second, third, and fourth upper inclined protrusions,  720   a ,  720   b ,  720   c , and  720   d.    
         [0230]    In some implementations, the first and the second rotation inclined surfaces  721   a  and  721   c  may be further formed between the first and third upper inclined protrusions  720   a  and  720   c  and the rotary plate  710 . When the flow path converter  700  ascends or descends, the first and the second rotation inclined surfaces  721   a  and  721   c  may form rotation resistance such that the flow path converter  700  may be rotated by the wash water passing through the first and the second opening holes  722   a  and  722   c.    
         [0231]    Thus, upon supply of the wash water, the flow path converter  700  may be rotated by the wash water passing through the first and the second opening holes  722   a  and  722   c  in one direction. Upon stoppage of the supply of the wash water, when the flow path converter  700  descends due to load thereon, the flow path converter  700  may be rotated by the wash water passing through the first and the second opening holes  722   a  and  722   c  in one direction. 
         [0232]    In some implementations, the first and the second anti-inflow protrusions  726   b  and  726   d  spaced apart from the second and fourth upper inclined protrusions  720   b  and  720   d  at a certain distance while closing the first and the second main arm inlets  354   a  and  354   b  (or the first and the second extension inlets  354   c  and  354   d ) may be formed at the insides of the second and fourth upper inclined protrusions  720   b  and  720   d.    
         [0233]    In this example, when the first and the second anti-inflow protrusions  726   b  and  726   d  are opened by the first and the second main arm inlets  354   a  and  354   b  (or the first and the second extension inlets  354   c  and  354   d ), the first and the second anti-inflow protrusions  726   b  and  726   d  may close the inlets inserted into the first and the second main arm inlets  354   a  and  354   b  (or the first and the second main arm inlets  354   a  and  354   b ) such that they are not opened. 
         [0234]    Furthermore, each of the first, second, third, and fourth upper inclined protrusions,  720   a ,  720   b ,  720   c , and  720   d  are formed at the first upper inclined surface  723   a  and the second upper inclined surface  725   a . Each upper corner  727   a  is formed between the first and the second upper inclined surfaces  723   a  and  725   a.    
         [0235]    In this example, the first upper inclined surface  723   a  is formed in a rotation direction of the flow path converter  700  and the second upper inclined surface  275   a  is formed in a rotation direction opposite to the rotation direction. The first and the second upper inclined surfaces  723   a  and  725   a  are formed to have different angles. The first upper inclined surface  723   a  may be formed to have a greater angle of inclination than that of the second upper inclined surface  725   a.    
         [0236]    In some implementations, the first, second, third, and fourth lower inclined protrusions  730   a ,  730   b ,  730   c , and  730   d  are held at the support protrusions  614  provided at the valve chamber  612  to rotate the rotary plate  710 . The first, second, third, and fourth lower inclined protrusions  730   a ,  730   b ,  730   c , and  730   d  may be provided to be spaced apart from one another at 90 degrees, with respect to the center of the rotary plate  710 . 
         [0237]    In this example, in the first, second, third, and fourth lower inclined protrusions  730   a ,  730   b ,  730   c , and  730   d , each lower corner  737   a  is formed between first and the second lower inclined surfaces  733   a  and  735   a.    
         [0238]    In this example, the first lower inclined surface  733   a  is formed in a rotation direction of the flow path converter  700 , and the second lower inclined surface  735   a  is formed in a direction opposite to the rotation direction. The first and the second lower inclined surfaces  733   a  and  735   a  are formed to have different angles. The first lower inclined surface  733   a  may be formed to have a smaller angle of inclination than that of the second lower inclined surface  735   a.    
         [0239]    Hereinafter, a process of opening or closing the first and the second main arm inlets  354   a  and  354   b  or the first and the second extension inlets  354   c  and  354   d  by the flow path converter  700  will be described in detail, with reference to the accompanying drawing. 
         [0240]      FIGS. 25 and 26  illustrate an example operation of a flow path converter. 
         [0241]    As illustrated in  FIGS. 25 and 26 , when the wash water is supplied through the inlet  638  formed at the sump inserter  630  of the spray arm holder  600 , the flow path converter  700  provided at the valve chamber  612  ascends by water pressure of the supplied wash water. 
         [0242]    As the flow path converter  700  ascends, the first, second, third, and fourth upper inclined protrusions,  720   a ,  720   b ,  720   c , and  720   d  are inserted into the first and the second main arm inlets  354   a  and  354   b  and the first and the second extension inlets  354   c  and  354   d  of the lower flow path formation rib  354  formed at the main arm lower housing  340 , respectively. 
         [0243]    In this example, the wash water introduced into the inlets  638  may be introduced into the first main arm inlet  354   a  through the first opening hole  722   a . The wash water passing through the second opening hole  722   c  may be introduced into the second main arm inlet  345   b.    
         [0244]    In some implementations, the first extension inlet  354   c  and the second extension inlet  354   d  are closed by the rotary plate  710 . Accordingly, introduction of the wash water through the first and the second extension inlets  354   c  and  354   d  is blocked. 
         [0245]    In some implementations, when supply of the wash water stops, pressure of the wash water for transferring the flow path converter  700  upwards is removed, such that the flow path converter  700  descends due to weight thereof. In this example, when the wash water passes through the first and the second opening holes  722   a  and  722   c  in the descending flow path converter  700 , the flow path converter  700  is rotated at a certain angle in one direction by the first and the second rotation inclined surfaces  721   a  and  721   c  formed at the first and the second opening holes  722   a  and  722   c.    
         [0246]    Accordingly, the first, second, third, and fourth lower inclined protrusions  730   a ,  730   b ,  730   c , and  730   d  provided at the flow path converter  700  slip on the support protrusions  614  provided at the spray arm holder  600  to be rotated at a certain angle more in one direction, thereby being held at the support protrusions  614 . 
         [0247]    In this example, when the flow path converter  700  descends, the first, second, third, and fourth lower inclined protrusions  730   a ,  730   b ,  730   c , and  730   d  are held at the support protrusion  614  while the flow path converter  700  rotates at a certain angle in one direction. 
         [0248]    In this example, the flow path converter  700  may rotate at about 90 degrees. The reason for this is that, the first and the second lower inclined surfaces  733   a  and  735   a  provided at the first, second, third, and fourth lower inclined protrusions  730   a ,  730   b ,  730   c , and  730   d  occupy an angle of 90 degrees on a circumferential surface of the rotary plate  710 . 
         [0249]    Although not illustrated, after the flow path converter  700  descends, the wash water is introduced through the inlets  638  formed at the sump inserter  630  again such that the flow path converter  700  ascends. As the flow path converter  700  ascends, the first, second, third, and fourth upper inclined protrusions,  720   a ,  720   b ,  720   c , and  720   d  are respectively inserted into the first and the second main arm inlets  354   a  and  354   b  and the first and the second extension inlets  354   c  and  354   d  of the lower flow path formation rib  354  formed at the main arm lower housing  340 . 
         [0250]    In this example, when the wash water is supplied, the flow path converter  700  ascends due to pressure of the wash water and the wash water passes through the first and the second opening holes  722   a  and  722   c  in the ascending flow path converter  700 . In this example, the wash water passing through the first and the second opening holes  722   a  and  722   c  pressurizes the first and the second rotation inclined surfaces  721   a  and  721   c  formed at the first and the second opening holes  722   a  and  722   c . The flow path converter  700  is rotated at a certain angle in one direction by pressure applied to the first and the second rotation inclined surfaces  721   a  and  721   c  by pressure of the wash water. 
         [0251]    In this example, the first, second, third, and fourth upper inclined protrusions,  720   a ,  720   b ,  720   c , and  720   d  are inserted into the first and the second main arm inlets  354   a  and  354   b  and the first and the second extension inlets  354   c  and  354   d  of the lower flow path formation rib  354  while the flow path converter  700  is rotated at a certain angle more in one direction. 
         [0252]    In this example, the flow path converter  700  may rotate at about 90 degrees. The reason for this is that, the first and the second upper inclined surfaces  723   a  and  725   a  provided at first, second, third, and fourth upper inclined protrusions,  720   a ,  720   b ,  720   c , and  720   d  occupy an angle of 90 degrees on a circumferential surface of the rotary plate  710 . 
         [0253]    In this example, the first and the second opening holes  722   a  and  722   c  communicate with the first and the second extension inlets  354   c  and  354   d  instead of the first and the second main arm inlets  354   a  and  354   b . Accordingly, the wash water introduced into the inlet  638  may be introduced into the first extension inlet  354   c  through the first opening hole  722   a . The wash water passing through the second opening hole  722   c  may be introduced into the second extension inlet  354   d.    
         [0254]    In some implementations, the first and the second main arm inlets  354   a  and  354   b  are closed by the rotary plate  710 . Accordingly, introduction of the wash water through the first and the second main arm inlets  354   a  and  354   b  is blocked. 
         [0255]    The water supply pump provided at the sump may intermittently supply the wash water. In detail, after the wash water is supplied to the spray arm holder  600  for a certain time, the supply of the wash water may be suspended for a certain time. 
         [0256]    For example, the sump performs the supply and stoppage of the wash water. Thus, as the flow path converter  700  ascends and descends repeatedly to rotate, the first and the second main arm inlets  354   a  and  354   b  and the first and the second extension inlets  354   c  and  354   d  may be alternately opened and closed. 
         [0257]    Hereinafter, the eccentric gear  800  of the spray arm assembly  100  will be described in detail, with reference to the accompanying drawing. 
         [0258]      FIGS. 27-29  illustrate an example eccentric gear. 
         [0259]    As illustrated in  FIGS. 27 to 29 , the eccentric gear  800  may include a rim  810 , at which a plurality of second gear teeth  812  is formed, provided at the outer circumferential surface of the eccentric gear  800 , rotation shaft support protrusions  820  in which a gear rotation shaft  347   b  is accommodated, and an eccentric protrusion  830  inserted into the linker  900  to move the linker  900  with reciprocating motion. 
         [0260]    In this example, the rim  810  is formed to be ring-shaped. A plurality of second gear teeth  812  is formed along the outer circumferential surface. An anti-friction rib  816  is formed to be protruded at the lower surface of the rim  810  to minimize friction between the rim  810  and the eccentric gear container  940  of the linker  900  supporting the eccentric gear  800 . 
         [0261]    In some implementations, inclined surfaces  814  which are inclined downwards at a certain angle D 5  in an outer direction of the rim  810  are formed at upper surfaces of the second gear teeth  812 . For example, when washing using the wash water, the wash water and the foreign substances may be introduced into upper parts of the second gear teeth  812 . For draining and discharge of the wash water and the foreign substances, the upper surfaces of the second gear teeth may be inclined downward at a certain angle D 5  in an outer direction of the rim  810 . 
         [0262]    In addition, the rotation shaft support protrusions  820  are protruded at the inner circumferential surface of the rim  810  forming the eccentric gear  800  in order to support the outer circumferential surface of the gear rotation shaft  347   b  formed at the second lower main arm  341   b  of the main arm lower housing  340 . The rotation shaft support protrusions  820  are in line contact with the gear rotation shaft  347   b  such that friction between the rotation shaft support protrusions  820  and the gear rotation shaft  347   b  may be relatively decreased. 
         [0263]    Furthermore, the rotation shaft support protrusions  820  are protruded at the inner circumferential surface of the rim  810  forming the eccentric gear  800 . For example, a plurality of spaces is formed between the rotation shaft support protrusions  820 . The spaces between the rotation shaft support protrusions  820  are provided as spaces where the rotation shaft support protrusions  820  are capable of being deformed elastically. When external force is applied to the rim  810  of the eccentric gear  800 , the rotation shaft support protrusions  820  are deformed at adjacent spaces to thus secure spaces for deformation of the rim  810 . 
         [0264]    In some implementations, protrusions  822  for securing the supported state of the gear rotation shaft  347   b  are formed at an end of the rotation shaft support protrusions  820 . In the case where the gear rotation shaft  347   b  is supported by the rotation shaft support protrusions  820 , when the eccentric gear  800  is rotated, the eccentric gear  800  is movable due to the spaces between the rotation shaft support protrusions  820 . Thus, in order to secure the supported state of the gear rotation shaft  347   b , each protrusion  822  may be extended to have a certain height. 
         [0265]    In addition, the protrusions  822  functions to secure a mounting position of the eccentric gear  800 . The eccentric gear  800  is mounted at the lower part of the second lower main arm  341   b . Separation of the eccentric gear  800  is prevented by the linker  900 . 
         [0266]    In some implementations, the linker  900  is provided at the lower part of the second lower main arm  341   b . The eccentric gear  800  may be provided downward at a distance corresponding to at least the thickness of the linker  900 , or a thickness of the eccentric gear  800  may be increased. As a result, as each protrusion  822  is formed to have a greater height L 3  than the thickness of the linker  900 , the mounting position of the eccentric gear  800  may be secured without increase of the thickness of the eccentric gear  800 . 
         [0267]    In addition, a rotation shaft ring  824  being in line contact with the gear rotation shaft  347   b  along the circumferential surface thereof may be further formed at the ends of the protrusions  822 . The protrusions  822  are formed at the rotation shaft support protrusions  820  such that the support state of the gear rotation shaft  347   b  may be secured. However, since the protrusions  822  are extended from the rotation shaft support protrusions  820 , the eccentric gear  800  may be movable due to the spaces between the protrusions  822  and rotation shaft support protrusions  820 . Accordingly, the rotation shaft ring  824  may be further formed to secure the support state of the gear rotation shaft  347   b.    
         [0268]    In some implementations, the eccentric protrusion  830  is be protruded from the lower part of the eccentric gear  800  to be spaced apart from the rotation shaft of the eccentric gear  800  by a certain interval L 4 . Furthermore, the eccentric protrusion  830  is inserted into the eccentric gear container  940  of the linker  900 , in which the eccentric gear  800  is accommodated. Thus, the eccentric protrusion  830  may be formed to have a height L 5  equal to or greater than the thickness of the eccentric gear container  940 . 
         [0269]    When the eccentric gear  800  is geared to the fixed gear  500  to rotate and revolve along the outer circumferential surface of the fixed gear  500 , the eccentric protrusion  830  converts rotational force of the eccentric gear  800  into linear reciprocating motion to be transferred to the linker  900 . 
         [0270]    In this example, the space L 4  between the eccentric protrusion  830  and the rotation shaft relates to a reciprocating distance and the rotation angles of the first and the second auxiliary arms  400   a  and  400   b , which rotate according to the reciprocating motion of the linker  900 . For example, as the space between the eccentric protrusion  830  and the rotation shaft is increased, the reciprocating distance of the linker  900  may be increased. As the reciprocating distance of the linker  900  is increased, the rotation angles of the first and the second auxiliary arms  400   a  and  400   b  may be increased. 
         [0271]    In this example, the eccentric protrusion  830  may protrude at the support protrusions  820  of the eccentric gear  800  in an opposite direction to the protrusions  822 . Furthermore, in the case where the eccentric position of the eccentric protrusion  830  overlaps an insertion area of the gear rotation shaft  347   b  supported by the support protrusions  820 , rotation shaft grooves  832  may be further formed in the eccentric protrusion  830  (i.e. the area into which the gear rotation shaft  347   b  is inserted) for insertion of the gear rotation shaft  347 . 
         [0272]    In this example, in the case of the rotation shaft grooves  832 , in order to prevent friction between the outer circumferential surface of the gear rotation shaft  347   b  and the rotation shaft grooves  832  in the manner of the rotation shaft support protrusions  820 , rotation shaft groove support protrusions  834  being in line contact with the outer circumferential surface of the gear rotation shaft  347   b  to support the gear rotation shaft  347   b  may be further formed at the rotation shaft grooves  832 . 
         [0273]    In some implementations, the rim  810  forming the eccentric gear  800 , the rotation shaft support protrusions  820 , and the eccentric protrusion  830  may be formed of synthetic resins using injection molding in an integrated manner. However, at least one of the rims  810  forming the eccentric gear  800 , the rotation shaft support protrusions  820 , and the eccentric protrusion  830  may be separately formed to be assembled to the others, if needed. 
         [0274]    Hereinafter, a coupling state of the fixed gear and the eccentric gear will be described in detail, with reference to the accompanying drawing. 
         [0275]      FIG. 30  illustrates an example eccentric gear.  FIG. 30  illustrates a cross-sectional view taken along a line Y′-Y″ in  FIG. 2 .  FIG. 31  illustrates an example fixed gear and an example eccentric gear. 
         [0276]    As illustrated in  FIGS. 30 and 31 , the eccentric gear  800  is rotatably inserted into the gear rotation shaft  347   b  formed at the second lower main arm  341   b  of the main arm lower housing  340 . The eccentric gear  800  is supported by the eccentric gear container  940  of the linker  900 . The second gear teeth  812  of the eccentric gear  800  are geared to the first gear teeth  512  of the fixed gear  500 . 
         [0277]    In some implementations, as described above, the number of second gear teeth  812  formed at the eccentric gear  800  and first gear teeth  512  formed at the fixed gear  500  may depend on rotation of the spray arm  200  and rotational motion of the first and the second auxiliary arms  400   a  and  400   b.    
         [0278]    In this example, when the number of first gear teeth  512  formed at the fixed gear  500  and the number of second gear teeth  812  formed at the eccentric gear  800  have a certain multiple relationship, rotation and cycles of the spray arm  200  and the patterns of rotational motion of the first and the second auxiliary arms  400   a  and  400   b  may have a certain period according to the multiple relationship between the first and the second gear teeth  512  and  812 . 
         [0279]    For example, when there is particular multiple relationship between the numbers of first and the second gear teeth  512  and  812 , rotational motion of the first and the second auxiliary arms  400   a  and  400   b  may be constantly repeated according to rotational position of the spray arm  200 . Thus, spray pattern of the wash water sprayed from the first and the second auxiliary arms  400   a  and  400   b  may be fixed. 
         [0280]    In this case, since the spray pattern of the wash water sprayed from the spray arm  200 , the spray pattern of the wash water sprayed from the first and the second auxiliary arms  400   a  and  400   b , and the sprayed areas are repeated with a certain cycle, the sprayed positions of wash water sprayed from the first and the second auxiliary arms  400   a  and  400   b  are fixed. 
         [0281]    That is, when the sprayed positions of wash water sprayed from the first and the second auxiliary arms  400   a  and  400   b  are fixed, the sprayed areas of wash water sprayed from the first and the second auxiliary arms  400   a  and  400   b  are limited, thereby decreasing washing capacity due to the first and the second auxiliary arms  400   a  and  400   b . When the sprayed positions of wash water sprayed from the first and the second auxiliary arms  400   a  and  400   b  are fixed, the sprayed range of the wash water is fixed, thereby decreasing washing capacity of the dishwasher  1 . 
         [0282]    Thus, it is necessary to vary the spraying patterns of the wash water sprayed from the first and the second auxiliary arms  400   a  and  400   b . To this end, the number of first gear teeth  512  formed at the fixed gear  500  and the number of second gear teeth  812  formed at the eccentric gear  800  may be formed to have a relative prime relationship therebetween. When the number of first gear teeth  512  formed at the fixed gear  500  and the number of second gear teeth  812  formed at the eccentric gear  800  are formed to have a relative prime relationship therebetween, the rotation pattern cycle of the fixed gear  500  and the eccentric gear is longer than in the case of a multiple relationship between the numbers of first and the second gear teeth  512  and  812 . Thereby, the spray patterns of the wash water sprayed from the first and the second auxiliary arms  400   a  and  400   b  may be varied. 
         [0283]    In some implementations, each of the second gear teeth  812  formed at the eccentric gear  800  has a smaller diameter than that of each of the first gear teeth  512  formed at the fixed gear  500 . Under-cut of the second gear teeth  812  may be generated by the first and the second gear teeth  512  and  812 . Thus, under-cut holes  812   a  may be further formed to prevent abrasion of the second gear teeth  812  due to friction. 
         [0284]    Furthermore, when the fixed gear  500 , at which the first gear teeth  512  are formed and the eccentric gear  800 , at which the second gear teeth  812  are formed, are made of the same material, there is abrasion due to friction therebetween. 
         [0285]    In this case, there is a disadvantage with respect to the maintenance of the fixed gear  500  and the eccentric gear  800 . Accordingly, the fixed gear  500 , at which the first gear teeth  512  are formed and the eccentric gear  800 , at which the second gear teeth  812  are formed, may be formed of different materials. The fixed gear  500  may be formed of a harder material than the eccentric gear  800 . 
         [0286]    In some implementations, upon washing, if the foreign substances become stuck between the first gear teeth  512  of the fixed gear  500  and the second gear teeth  812  of the eccentric gear  800 , it becomes impossible to rotate the eccentric gear  800 . In this case, when the fixed gear  500  and the eccentric gear  800  are engaged, rotation of the spray arm  200  may be limited by the eccentric gear  800 . 
         [0287]    In this example, the eccentric gear  800  is supported by a plurality of rotation shaft support protrusions  820 . The rotation shaft support protrusions  820  may be elastically deformed into the spaces L 5  formed between the rotation shaft support protrusions  820 . Accordingly, when the foreign substances are stuck between the first gear teeth  512  of the fixed gear  500  and the second gear teeth  812  of the eccentric gear  800 , force due to the volume of the foreign substances is applied to the rim  810  of the eccentric gear  800  and the rotation shaft support protrusions  820  in the rim  810  are elastically deformed. Thereby, the eccentric gear  800  may be rotated along the fixed gear  500  regardless of whether the foreign substances are stuck between the first gear teeth  512  and the second gear teeth  812 . 
         [0288]    Hereinafter, the linker  900  of the spray arm assembly  100  will be described in detail, with reference to the accompanying drawing. 
         [0289]      FIGS. 32-34  illustrate an example linker.  FIG. 34  illustrates a cross-sectional view taken along a line E′-E″ in  FIG. 2 . 
         [0290]    As illustrated in  FIGS. 32-34 , the linker  900  includes the rim-shaped body  910  having an elongated hole in which the spray arm holder coupler  356  of the main arm lower housing  340  is movably inserted, the first main link  920  extending from the rim-shaped body  910  to the first main arm  300   a  to be movably coupled thereto, the second main link  920   b  extending from the rim-shaped body  910  to the second main arm  300   b  to be movably coupled thereto while being coupled to the eccentric gear  800 , the first auxiliary link  950   a  extending to the first extension  300   c  to be coupled to the first auxiliary arm  400   a , and the second auxiliary link  950   b  extending to the second extension  300   d  to be coupled to the second auxiliary arm  400   b.    
         [0291]    In this example, the elongated hole  911  into which the spray arm holder coupler  356  is inserted is formed in the rim-shaped body  910 . The elongated hole  911  has a width corresponding to a diameter of the spray arm holder  600  to move the linker  900  with respect to the spray arm holder  600 , and a length corresponding to moving distance of the linker  900 . The elongated hole  911  may be formed as an enlarged hole H 1  having a greater size than that of the spray arm holder coupler  356  and a different hole H 2  having a center which is spaced apart from a center of the hole H 1  at a moving distance, L 6  i.e. the moving distance of the linker  900 . 
         [0292]    In some implementations, in the inner circumferential surface of the elongated hole  911 , the upward reinforcing rib  913  is extended to the upper side of the rim-shaped body  910  to reinforce the rim-shaped body  910 . In the outer circumferential surface of the elongated hole  911 , the downward reinforcing rib  914  is extended to the lower side of the rim-shaped body  910  to reinforce the rim-shaped body  910 . 
         [0293]    In this example, the upward reinforcing rib  913  and the downward reinforcing rib  914  reinforce the rim-shaped body  910  while discharging the wash water and the foreign substances introduced into the upper part of the linker  900 . 
         [0294]    For example, introduction of the wash water and the foreign substances introduced into the upper part of the linker  900  to the spray arm holder coupler  356  is prevented by the upward reinforcing rib  913  formed at the upper side of the rim-shaped body  910  in the rim-shaped body  910  and is guided downward of the linker  900  according to the downward reinforcing rib  914  formed at the lower side of the rim-shaped body  910  at the outside of the rim-shaped body  910 . 
         [0295]    Furthermore, in the case of the downward reinforcing rib  914 , the first and the second links  920   a  and  920   b  and the first and the second auxiliary links  950   a  and  950   b  extend to form the downward reinforcing rib  914 . Accordingly, in order to form the first and the second links  920   a  and  920   b  and the first and the second auxiliary links  950   a  and  950   b , the downward reinforcing rib  914  may be formed to have a greater height than that of each of the first and the second links  920   a  and  920   b  and the first and the second auxiliary links  950   a  and  950   b.    
         [0296]    In some implementations, cutting parts  918  corresponding to the shape of the spray arm  200  are formed in part of the outer circumferential surface of the rim-shaped body  910  to prevent the linker  900  from being exposed to the outside of the spray arm  200 . For example, the cutting parts  918  may be formed between the first main arm  300   a  and the first extension  300   c , and between the second main arm  300   b  and the second extension  300   d.    
         [0297]    That is, there are obtuse angles D 2  (see,  FIG. 5 ) between the first main arm  300   a  and the first extension  300   c , and between the second main arm  300   b  and the second extension  300   d  such that the linker  900  provided below the spray arm  200  may be easily exposed above the spray arm  200 . However, positions of the cutting parts  918  are not limited and the cutting parts  918  may be formed at different positions, if needed. 
         [0298]    The first main link  920   a  may include a first extending plate  921   a  extending to the first main arm  300   a  in the downward reinforcing rib  914  of the rim-shaped body  910 , a first drain hole  927   a  formed in the first extending plate  921   a , and a first moving elongated hole  929   a  formed at an end of the first extending plate  921   a  to be movably coupled to the first guide protrusion  345   a  of the first lower main arm  341   a.    
         [0299]    In this example, the first extending plate  921   a  extends to have a smaller width than that of the first main arm  300   a . A first reinforcing rib  923   a  extending to the lower side of the first extending plate  921   a  is formed at the inner circumferential surface of the first extending plate  921   a  (i.e. the outer circumferential surface of the first drain hole  927   a ). A plurality of wear prevention protrusions  925   a  is formed at the upper surface of the first extending plate  921   a  to prevent friction between the first extending plate  921   a  and the first lower main arm  341   a.    
         [0300]    In some implementations, when the wash water and the foreign substances are introduced into the upper part of the extending plate  921   a , the first reinforcing rib  923   a  functions to guide the wash water and the foreign substances to the lower side of the first extending plate  921   a.    
         [0301]    In addition, the first moving elongated hole  929   a  extends parallel to the reciprocating direction of the linker  900 . The first moving elongated hole  929   a  may be formed to have a greater length than a moving distance of reciprocating motion of the linker  900 . 
         [0302]    The second main link  920   b  may include a second extending plate  921   b  extending from the downward reinforcing rib  614  to the second main arm  300   b , the eccentric gear container  940  depressed to the lower side of the center of the second extending plate  921   b  to accommodate the eccentric gear  800 , and a second moving elongated hole  939   b  formed at the end of the second extending plate  921   b  to be movably coupled to the second guide protrusion  345   b  of the second lower main arm  341   b.    
         [0303]    In some implementations, the second extending plate  921   b  extends to have a smaller width than that of the second main arm  300   b . The eccentric gear container is formed in the second extending plate  921   b.    
         [0304]    In this example, the second moving elongated hole  939   b  extends parallel to the reciprocating direction of the linker  900 . The second moving elongated hole  939   b  may be formed to have a greater length than a moving distance of reciprocating motion of the linker  900 . 
         [0305]    In some implementations, a rotation gear insertion slot  917  is formed at the downward reinforcing rib  914  at a position where the second extending plate  921   b  is formed. The rotation gear insertion slot  917  allows the eccentric gear  800  accommodated in the eccentric gear container  940  to be exposed at the fixed gear  500 . The eccentric gear container  940  may extend to the second main arm  300   b  at the lower side of the downward reinforcing rib  914 . 
         [0306]    In addition, in order to accommodate the eccentric gear  800  in the eccentric gear container  940 , the eccentric gear container  940  may be formed to have a depth greater than the height of the eccentric gear  800  except for the height of the eccentric protrusion  830 . 
         [0307]    Furthermore, a recessed part  941  is formed at the upper surface of the eccentric gear container  940  to prevent direct contact between the eccentric gear  800  and the eccentric gear container  940 . At least three wear prevention ribs  943  being in contact with the anti-friction ribs  816  of the eccentric gear  800  may be protruded at the recessed part  941 . 
         [0308]    In addition, an eccentric protrusion insertion slot  945 , into which the eccentric protrusion  830  of the eccentric gear  800  is inserted, and second drain holes  947  for discharging the wash water and the foreign substances introduced into the eccentric gear container  940  are formed at the recessed part  941  of the eccentric gear container  940 . 
         [0309]    In this example, each second drain hole  947  extends in a perpendicular direction to a moving direction of the linker  900 . Accordingly, as the eccentric gear  800  inserted into the gear rotation shaft  347   b  rotates, the eccentric protrusion  830  of the eccentric gear  800  generates external force parallel to the first and the second elongated holes  929   a  and  939   b  such that the linker  900  may perform reciprocating motion. 
         [0310]    In this example, the eccentric protrusion insertion slot  945  is formed to have a size equal to or greater than a radius of rotation of the eccentric protrusion  830 . A direction of the eccentric protrusion insertion slot  945  may be differently set depending on moving distances of the linker  900 . That is, when the direction of the eccentric protrusion insertion slot  945  is formed to be perpendicular to the moving direction of the linker  900 , the greatest reciprocating distance of the linker  900  may be provided. 
         [0311]    In some implementations, the centers of the elongated hole  911  of the rim-shaped body  910 , the first moving elongated hole  929   a  of the first main link  920   a , the second moving elongated hole  939   b  of the second main link  940 , and eccentric protrusion insertion slot  945  of the eccentric gear container  940  may be collinear. The reason for this is that, reciprocating motion of the linker  900  may be effectively performed according to the reciprocating motion of the linker  900  by the eccentric gear  800   
         [0312]    In addition, the first auxiliary link  950   a  extends to the first extension  300   c  and is coupled to the pivoting protrusion  425   a  formed at the first auxiliary arm  400   a  which is rotatably coupled to the first extension  300   c . In this example, the first auxiliary link  950   a  may include the first elastic buffer  960   a  extending from the downward reinforcing rib  914  of the rim-shaped body  910  to the first extension  300   c  and the first auxiliary arm coupler  970   a  formed at the end of the first elastic buffer  960   a  to be coupled so as to the pivoting protrusion  425   a.    
         [0313]    Furthermore, the second auxiliary link  950   b  extends to the second extension  300   d  and is coupled to the pivoting protrusion  425   a  formed at the second auxiliary arm  400   b  which is rotatably coupled to the second extension  300   d . In this example, the second auxiliary link  950   b  may include the second elastic buffer  960   b  extending from the downward reinforcing rib  914  of the rim-shaped body  910  to the second extension  300   d  and the second auxiliary arm coupler  970   b  formed at the end of the second elastic buffer  960   b  to be coupled to the pivoting protrusion  425   a.    
         [0314]    In some implementations, the rim-shaped body  910 , the first and the second main links  920   a  and  920   b , and the first and the second auxiliary links  950   a  and  950   b  may be separately formed and then may be assembled. However, for convenience of manufacturing, the rim-shaped body  910 , the first and the second main links  920   a  and  920   b , and the first and the second auxiliary links  950   a  and  950   b  may be formed by injection molding in an integrated manner. 
         [0315]    In this example, the first and the second elastic buffer  960   a  and  960   b  and the first and the second auxiliary arm couplers  970   a  and  970   b  may be formed to have identical shapes and may be formed to be symmetric with respect to the rim-shaped body  910 . Thus, the first and the second elastic buffer  960   a  and  960   b  and the first and the second auxiliary arm couplers  970   a  and  970   b  are not separately described. The first elastic buffer  960   a  and the first auxiliary arm coupler  940   a  will be representatively described below. 
         [0316]      FIGS. 35-37  illustrate an example first elastic butter and an example first auxiliary arm connector.  FIG. 36  illustrates a cross-sectional view taken along a line F′-F″ in  FIG. 35 .  FIG. 37  illustrates a cross-sectional view taken along a line G′-G″ in  FIG. 35 . 
         [0317]    As illustrated, the first auxiliary arm coupler  970   a  includes the first pivoting elongated hole  971   a , to which the pivoting protrusion  425   a  formed at the lower part of the first auxiliary arm  400  is inserted is formed, formed at the end of the first auxiliary link  950   a  and a first inclined surface  973   a  formed at an adjacent part of the first pivoting elongated hole  971   a  of the lower surface of the first auxiliary arm coupler  970   a  to secure a pivoting space of the pivoting protrusion  425   a  when the first auxiliary arm  400   a  pivots. 
         [0318]    In this example, in the upper surface of the first auxiliary arm, the first elongated hole  971   a  corresponding to the shape of the lower part of the first auxiliary arm  400   a  is recessed, and both side of the first auxiliary arm coupler  970   a  is protruded (see  FIG. 36 ). In some implementations, the wash water and the foreign substances introduced into the upper surface of the first auxiliary arm coupler  970   a  move from both sides of the first auxiliary arm coupler  970   a  due to the shape of the first auxiliary arm coupler  970   a  to the first pivoting elongated hole  971   a , thereby being discharged through the first pivoting elongated hole  971   a.    
         [0319]    In some implementations, the first pivoting elongated hole  971   a  may be formed to have a certain length into which the pivoting protrusion  425   a  formed at the first auxiliary arm  400   a  may be inserted. The length of the first pivoting elongated hole  971   a  may be equal to or greater than that of each stoppage protrusion  427   a  formed at the pivoting protrusion  425   a . Furthermore, the first pivoting elongated hole  971   a  may have a width such that interference between the pivoting protrusion  425   a  and the first pivoting elongated hole  971   a  does not occur when the linker  900  performs reciprocating motion for rotating the first auxiliary arm  400   a.    
         [0320]    Furthermore, when the pivoting protrusion  425   a  of the first auxiliary arm  400   a  is inserted into the first pivoting elongated hole  971   a  formed at the first auxiliary arm coupler  970   a , the position of the first auxiliary arm coupler  970   a  may be a position at which the first pivoting elongated hole  971   a  is not in direct contact with the pivoting protrusion  425   a  or a position forming minimum contact between the first pivoting elongated hole  971   a  and the pivoting protrusion  425   a.    
         [0321]    That is, when the linker  900  performs reciprocating motion for rotating the first auxiliary arm  400   a , the first pivoting elongated hole  971   a  of the first auxiliary arm coupler  970   a  presses the pivoting protrusion  425   a  to rotate the first auxiliary arm  400   a . Thereby, abrasion of the pivoting protrusion  425   a  or the first pivoting elongated hole  971   a  may occur. Thus, contact between the first pivoting elongated hole  971   a  and the pivoting protrusion  425   a  is minimized to prevent abrasion of the first pivoting elongated hole  971   a  and the pivoting protrusion  425   a.    
         [0322]    In some implementations, the first elastic buffer  960   a  may include a pair of first extension links  961   a  extending from the downward reinforcing rib  914  of the rim-shaped body  910  to the center of the first auxiliary arm connector  330   a , a pair of second extension links  965   a  extending to outsides of a pair of first extension links  961   a  to be spaced apart from each other at a certain interval at the outside of the first auxiliary arm connector  330   a , and an elastic link  963   a  at outsides of a pair of first extension links  961   a  and insides of a pair of second extension links  965   a  to connect the end of each of first extension links  961   a  to the end of a corresponding the second extension links  965   a.    
         [0323]    In this example, as a pair of first extension links  961   a  extend from the downward reinforcing rib  914 , each first extension link  961   a  may be formed as a bar having a decreased cross-sectional area. A pair of first extension links  961   a  may be formed to be symmetric with respect to the center between the first extension links  961   a.    
         [0324]    The reason for this is that, as the first extension link  961   a  has elastic force and the rim-shaped body  910  performs reciprocating motion according to rotation of the eccentric gear  800 , kinetic force of the reciprocating motion is transferred to the first auxiliary arm connector  330   a  and strength of the rim-shaped body  910  is maintained. For example, a pair of first extension links  961   a  is formed to be symmetric since the first extension links  961   a  maintain strength along a motion direction according to reciprocating motion of the rim-shaped body  910 . 
         [0325]    In some implementations, a pair of second extension links  965   a  extends from the first auxiliary arm connector  330   a  to the rim-shaped body  910  while being spaced apart from each other at a certain interval at the outsides of a pair of first extension links  961   a . In this example, as the second extension links  965   a  extend from the first auxiliary arm connector  330   a  to the rim-shaped body  910 , each second extension link  965   a  may be formed in the shape of a bar having an increasing cross-sectional area. A pair of second extension links  965   a  may be formed to be symmetric with respect to the center between the second extension links  965   a.    
         [0326]    In some implementations, the elastic link  963   a  connects the end of each first extension link  961   a  to the end of each second extension link  965   a  to provide elastic force parallel to and in a perpendicular to the reciprocating direction of the first auxiliary arm connector  330   a.    
         [0327]    That is, since the first and the second extension links  961   a  and  965   a  extend parallel to each other, when kinetic force is applied to the first and the second extension links  961   a  and  965   a  in a direction perpendicular to the extending direction of the first second extension links  961   a  and  965   a , elastic force may be generated. However, when kinetic force is applied to the first and the second extension links  961   a  and  965   a  in a direction parallel to the extending direction, elastic force may not be generated. 
         [0328]    Accordingly, the elastic link  963   a  may connect the ends of the first and the second extension links  961   a  and  965   a  to each other such that they are inclined at a certain angle, so that elastic force may be generated in other directions, which are not generated in the first and the second extension links  961   a  and  965   a.    
         [0329]    The elastic link  963   a  may include bending parts  964   a  curvedly formed at one side connected to the first extension link  961   a  and at the other side connected to the second extension link  965   a . The bending parts  964   a  may increase directional range in which elastic force is generated at the bending parts  964   a.    
         [0330]    In some implementations, when points of contact between the first extension links  961   a , the second extension links  965   a  and the elastic links  963   a  repeatedly receives elastic force, damage due to stress concentration may occur. Thus, link reinforcing parts  967   a  may be further formed at the points of contact between the first extension links  961   a , the second extension links  965   a  and the elastic links  963   a  to prevent damage due to stress concentration. In this example, each link reinforcing part  967   a  being in contact with the end of each link in a longitudinal direction of the outer circumferential surface of the link may be formed to have a cylindrical shape. 
         [0331]    Furthermore, as illustrated in  FIG. 37 , when the wash water and the foreign substances are introduced into the upper part of the first elastic buffer  960   a , a horizontal width of each of the first extension links  961   a , the second extension links  965   a  and the elastic links  963   a  may be smaller than a vertical width thereof, thereby discharging the wash water and the foreign substances. For example, when the horizontal width of each of first extension links  961   a , the second extension links  965   a  and the elastic links  963   a  is greater than the vertical width thereof; the wash water and the foreign substances remain at the upper part of the first elastic buffer  960   a.    
         [0332]    Furthermore, in the cross-sectional view of each of the first extension links  961   a , the second extension links  965   a  and the elastic links  963   a , when the horizontal width is less than the vertical width, the buffering effect of the first elastic buffer  961   a  may be effective. For example, as illustrated, when the cross-sections of the first extension links  961   a , the second extension links  965   a  and the elastic links  963   a  are formed, the linker  900  may be formed to be perpendicular to a reciprocating direction such that elastic force may be effectively generated in a moving direction of the linker  900 . 
         [0333]    Furthermore, elastic force of the first elastic buffer  960   a  may be varied depending on materials or shapes of the first extension links  961   a , the second extension links  965   a  and the elastic links  963   a . For example, the first extension links  961   a , the second extension links  965   a  and the elastic links  963   a  may be formed of materials having different elasticities, thereby controlling elastic force of the first elastic buffer  960   a . In some implementations, thicknesses, lengths, widths of the first extension links  961   a , the second extension links  965   a  and the elastic links  963   a  may be changed to control elastic force of the first elastic buffer  960   a . Furthermore, formation angles or shapes of the elastic links  963   a  connecting the first extension links  961  to the second extension links  965   a  may be changed to control elastic force of the first elastic buffer  960   a.    
         [0334]    In some implementations, elastic deformation range of the first elastic buffer  960   a  may be obtained by spaces between the first extension links  961   a , the second extension links  965   a  and the elastic links  963   a . For example, when the spaces between first extension links  961   a , the second extension links  965   a  and the elastic links  963   a  are increased, elastic deformation range of the first elastic buffer  960   a  may be increased. When the spaces between first extension links  961   a , the second extension links  965   a  and the elastic links  963   a  are decreased, elastic deformation range of the first elastic buffer  960   a  may be decreased. 
         [0335]    In addition, since the first elastic buffer  960   a  corresponds to the shape of the lower surface of the first extension  300   c  at which the first elastic buffer  960   a  is provided, the first extension links  961   a , the second extension links  965   a  and the elastic links  963   a  may be formed to have different heights and different vertical widths. 
         [0336]    In some implementations, elastic force of the first elastic buffer  960   a  satisfies minimum elastic force, in which the linker  900  performs reciprocating motion according to rotation of the eccentric gear  800  and generated kinetic force of the linker  900  is transferred to the first auxiliary arm  400   a  to rotate the first auxiliary arm  400   a , and elastic force, in which kinetic force of the linker  900  is absorbed not to be transferred to the first auxiliary arm  400   a  when the first auxiliary arm  400   a  is restricted. 
         [0337]    In some implementations, there is a possibility of rotation restraint of the first auxiliary arm  400   a  due to some cause such as deposition of the foreign substances. In this case, the linker  900  transferring power to the first auxiliary arm  400   a , the eccentric gear  800 , the spray arm  200 , and the fixed gear  500  may be sequentially restricted by the rotation restraint of the first auxiliary arm  400   a.    
         [0338]    That is, upon the rotation restraint of the first auxiliary arm  400   a , reciprocating motion of the linker  900  is restricted by the first auxiliary arm  400   a . Rotation of the eccentric gear  800  for performing reciprocating motion of the linker  900  is restricted by restraint of reciprocating motion of the linker  900 . Relative rotation of the eccentric gear  800  and the fixed gear  500  is restricted by restraint of rotation of the eccentric gear  800  to thus restrict rotation of the spray arm  200  coupled to the eccentric gear  800 . 
         [0339]    In this example, upon rotation restraint of the first auxiliary arm  400   a , the first elastic buffer  960   a  of the first auxiliary arm  950   a  absorbs force transferred from the linker  900  as elastic force, thereby performing the reciprocating motion of the linker  900 . Thus, despite of restraint of the first auxiliary arm  400   a , the linker  900  may perform the reciprocating motion for rotating the first auxiliary arm  400   a . Thereby, the linker  900  transferring power to the first auxiliary arm  400   a , the eccentric gear  800 , the spray arm  200 , and the fixed gear  500  may be operated. 
         [0340]    Hereinafter, the mounted state of the linker  900  will be described in detail with reference to the accompanying drawings. 
         [0341]      FIG. 38  illustrates an example linker. 
         [0342]    As illustrated in  FIGS. 38, 2 and 3 , the first extension  300   c  and the second extension  300   d  of the main arm  300  are coupled to the first auxiliary arm  400   a  and the second auxiliary arm  400   b , respectively. The eccentric gear  800  may be inserted into the gear rotation shaft  347   b  formed at the second main arm  300   b  of the spray arm  200 . 
         [0343]    In this example, the linker  900  is movably coupled to the spray arm holder coupler  356  of the main arm  300  through the elongated hole of the rim-shaped body  910  of the linker  900 . In addition, the first and the second main links  920   a  and  920   b  of the linker  900  are movably coupled to the first and the second guide protrusions  345   a  and  345   b . The first and the second auxiliary links  950   a  and  950   b  are coupled to the pivoting protrusions of the first and the second auxiliary arms  400   a  and  400   b.    
         [0344]    Firstly, the pivoting protrusion  425   a  of the first auxiliary arm  400   a  is movably inserted into the first pivoting elongated hole  971   a  of the first auxiliary link  950   a . In this example, when the first pivoting elongated hole  971   a  of the first auxiliary link  950   a  is held to the pivoting protrusion  425   a , in order to insert the stoppage protrusions  427   a  formed at the pivoting protrusion  425   a , the first elastic buffer  960   a  formed at the first auxiliary link  950   a  is elongated at a certain distance while bending due to elastic force, such that the stoppage protrusions  427   a  are inserted into the first pivoting elongated hole  971   a . Then, the first elastic buffer  960   a  is restored to be held at the pivoting protrusion  425   a  of the first pivoting elongated hole  971   a  after insertion of the stoppage protrusions  427   a.    
         [0345]    In addition, the pivoting protrusion  425   a  of the second auxiliary arm  400   b  is movably inserted into the second pivoting elongated hole  971   b  of the second auxiliary link  950   b . In this example, when the second pivoting elongated hole  971   b  of the second auxiliary link  950   b  is held to the pivoting protrusion  425   a , in order to insert the stoppage protrusions  427   b  formed at the pivoting protrusion  425   a , the second elastic buffer  960   b  formed at the second auxiliary link  950   b  is elongated at a certain distance while bending due to elastic force, such that the stoppage protrusions  427   b  are inserted into the second pivoting elongated hole  971   b . Then, the second elastic buffer  960   b  is restored to be held at the pivoting protrusion  425   b  of the second pivoting elongated hole  971   b  after insertion of the stoppage protrusions  427   b.    
         [0346]    In some implementations, the first guide protrusion  345   a  of the first main arm  300   a  is movably inserted into the first moving elongated hole  929   a  of the first main links  920   a . The first extension step  346   a  formed at the first guide protrusion  345   a  is inserted into the first moving elongated hole  929   a  in an interference-fit manner, such that the first guide protrusion  345   a  is movably inserted and separation thereof is prevented by the first extension step  346   a.    
         [0347]    Furthermore, the second guide protrusion  345   b  of the second main arm  300   b  is movably inserted into the second moving elongated hole  929   b  of the second main links  920   b . The second extension step  346   a  formed at the second guide protrusion  345   b  is inserted into the second moving elongated hole  929   b  in an interference-fit manner, such that the second guide protrusion  345   b  is movably inserted and separation thereof is prevented by the second extension step  346   b.    
         [0348]    In this example, the eccentric gear  800  movably coupled to the gear rotation shaft  347   b  of the lower part of the second main arm  300   b  is supported by the eccentric gear container  940  of the second main link  920   b . Furthermore, the eccentric protrusion  830  of the eccentric gear  800  is inserted into the eccentric protrusion insertion slot  945  formed at the eccentric gear container  940  of the second main link  920   b.    
         [0349]    Then, the fixed gear  500  is additionally coupled to the spray arm holder coupler  356 . The fixed gear  500  is mounted to surround the circumferential surface of the spray arm holder coupler  356 . For example, the spray arm holder coupler  356  is inserted into the rim  510  of the fixed gear  500 . In this example, the first gear teeth  512  of the fixed gear  500  are geared to the second gear teeth  812  of the eccentric gear  800 . 
         [0350]    Sequentially, the spray arm holder  600  is additionally coupled to the spray arm  200 . First, after the spray arm holder  600  is inserted into the spray arm holder coupler  356 , when the spray arm holder coupler  356  is rotated at a certain angle, the holding protrusion  622   a  of the spray arm holder  600  is held at the spray arm holder coupler protrusions  656   a  of the spray arm holder coupler  356 , such that the spray arm holder  600  is fixed to the spray arm holder coupler  356 . 
         [0351]    Then, the sump inserter  630  of the spray arm holder  600  is inserted into the spray arm holder seating part  53  and the fasteners  530  of the fixed gear  500  is coupled to the coupling bosses  51  of the sump cover  50 , thereby finishing the process mounting the spray arm  200 . 
         [0352]    Hereinafter, the first and the second auxiliary arms  400   a  and  400   b  according to reciprocating motion of the linker  900  will be described, with reference to the accompanying drawing. 
         [0353]      FIG. 39  illustrates an example operation of a linker.  FIG. 40  illustrates an example operation of an auxiliary arm. 
         [0354]    In this example, (a), (b), (c), and (d) of  FIG. 39  are bottom views illustrating the spray arm assembly  100 , in which the eccentric gears  800  are rotated at 0, 90, 180, and 270 degrees, respectively.  FIG. 40( a )  is a cross-sectional view illustrating the first spray arm without rotation and  FIG. 40( b )  is a cross-sectional view illustrating the rotated first spray arm. 
         [0355]    Referring to  FIGS. 39( a ) and 40( a ) , when the eccentric gear  800  is not rotated i.e. is in the initial state, the eccentric protrusion  830  is provided at one side in the eccentric protrusion insertion slot  945 . In this case, the first auxiliary arm  200  is provided parallel to the main arm  300 . In this example, when the wash water is supplied to the spray arm  200 , rotation of the spray arm  200  starts using the wash water sprayed from the first and the second main arms  300  and  300   b  or the first and the second auxiliary arms  400   a  and  400   b.    
         [0356]    As the spray arm  200  rotates, the eccentric gear  800  provided at the spray arm  200  is geared to the fixed gear  500  fixed to the sump cover  50  to rotate and to revolve along the outer circumferential surface of the fixed gear  500 . 
         [0357]    Referring to  FIGS. 39( b ) and 40( b ) , when the eccentric gear  800  rotates at 90 degrees in a counterclockwise direction by rotation of the spray arm  200 , the eccentric protrusion  830  inserted into the eccentric protrusion insertion slot  945  of the linker  900  moves in one direction to transfer the linker  900  in one direction A. 
         [0358]    As the linker  900  moves in one direction A, the first and the second links  920   a  and  920   b  are guided by the first and the second guide protrusions  345   a  and  345   b  formed at the first and the second main arms  300  and  300   b  so as to move. The first auxiliary link  950  rotates the pivoting protrusions  425   a  of the first and the second auxiliary arms  400   a  and  400   b  in one direction. 
         [0359]    Accordingly, the first and the second auxiliary arms  400   a  and  400   b  rotate at a certain angle in a clockwise direction. In this example, the angle to which the first and the second auxiliary arms  400   a  and  400   b  are capable of being rotated may be about 15 to 40 degrees. 
         [0360]    Referring to  FIG. 39( c ) , when the eccentric gear  800  further rotates at 90 degrees in a counterclockwise direction by further rotation of the spray arm  200 , the eccentric protrusion  830  inserted into the eccentric protrusion insertion slot  945  of the linker  900  moves in the other direction to transfer liner  900  in a direction B opposite to a direction A. Accordingly, the linker  900  is returned to its original position as illustrated in  FIGS. 39( a ) and 40( a ) . In addition, the first and the second auxiliary arms  400   a  and  400   b  are rotated by the first and the second extensions  300   c  and  300   d  in a counterclockwise direction to be returned to their original positions. 
         [0361]    Referring to  FIG. 39( d ) , when the eccentric gear  800  further rotates at 90 degrees in a counterclockwise direction by further rotation of the spray arm  200 , the linker  900  is moved by the eccentric protrusion  830  along the direction B. 
         [0362]    In this example, the first auxiliary arm  400   a  rotates to a certain angle in a counterclockwise direction (i.e. a direction opposite to a direction of  FIG. 40( b ) ). In this example, the first and the second auxiliary arms  400   a  and  400   b  may rotate to about 15 to 40 degrees. 
         [0363]    In some implementations, the first and the second auxiliary arms  400   a  and  400   b , and the linker  900  may simultaneously rotate at the same angle. The linker  900  may perform reciprocating motion at a distance between the center of rotation of the eccentric gear  800  by rotation of the eccentric gear  800  and the eccentric protrusion  830 . 
         [0364]    Hereinafter, a principle of rotating the spray arm  200  according to spraying the wash water at the first and the second main arms  300   a  and  300   b  and the first and the second auxiliary arms  400  and  400   b  will be described. 
         [0365]      FIGS. 41 and 42  illustrate an example operation of a spray arm.  FIG. 43  illustrates an example operation of an auxiliary arm. 
         [0366]    As illustrated in  FIG. 41 , the first and the second main arms  300   a  and  300   b  include a plurality of first and the second nozzles  314   a  and  314   b  and a plurality of first and the second inclined nozzles  315   a  and  315   b . In detail, the first main arm  300   a  may include a plurality of first nozzles  314   a  and a plurality of first inclined nozzles  315   a . Furthermore, the second main arm  300   b  may include a plurality of second nozzles  314   b  and a plurality of second inclined nozzles  315   b . When the first and the second main arm inlets  354   a  and  354   b  are opened by the flow path converter  700 , the wash water may be simultaneously sprayed from a plurality of first and the second nozzles  314   a  and  314   b  and a plurality of first and the second inclined nozzles  315   a  and  315   b.    
         [0367]    In this example, the first and the second inclined nozzles  315   a  and  315   b  spray the wash water in a direction opposite to the rotation direction of the first and the second main arms  300   a  and  300   b . The wash water sprayed from the first and the second inclined nozzles  315   a  and  315   b  may be biased to have an acute angle with respect to a rotation plane. 
         [0368]    Accordingly, the main arm  300  may be rotated by driving force generated by the wash water sprayed from the biased first and the second inclined nozzles  315   a  and  315   b . That is, when the wash water is sprayed from the first and the second inclined nozzles  315   a  and  315   b , a certain torque value capable of rotating the spray arm  200  may be generated. 
         [0369]    In some implementations, torque applied to the spray arm  200  by the wash water sprayed from the first inclined nozzles  315   a  of the first main arm  300   a  and torque applied to the spray arm  200  by the wash water sprayed from the second inclined nozzles  315   b  of the second main arm  300   b  are oriented in the same direction with respect to the center of rotation of the spray arm  200 . 
         [0370]    In some implementations, at least one of the first and the second inclined nozzles  315   a  and  315   b  may be biased to spray the wash water at a tangent relative to the rotation trace of the spray arm  200 . In this case, torque may be further increased by spraying the wash water. 
         [0371]    In addition, the first and the second nozzles  314   a  and  314   b  may spray the wash water in a vertical direction or in the same direction as the first and the second inclined nozzles  315   a  and  315   b . The first and the second nozzles  314   a  and  314   b  and the first and the second inclined nozzles  315   a  and  315   b  may be oriented at different angles to spray the wash water at various angles. 
         [0372]    As illustrated in  FIG. 42 , the first and the second auxiliary arms  400   a  and  400   b  include a plurality of first and the second auxiliary nozzles  414   a  and  414   b  and a plurality of first and the second auxiliary inclined nozzles  415   a  and  415   b . In detail, the first auxiliary arm  400   a  may include a plurality of first auxiliary nozzles  414   a  and a plurality of first auxiliary inclined nozzles  415   a . Furthermore, the second auxiliary arm  400   b  may include a plurality of second auxiliary nozzles  414   b  and a plurality of second auxiliary inclined nozzles  415   b . When the first and the second auxiliary arm inlets  354   c  and  354   d  are opened by the flow path converter  700 , the wash water may be simultaneously sprayed from a plurality of first and the second auxiliary nozzles  414   a  and  414   b  and a plurality of first and the second auxiliary inclined nozzles  415   a  and  415   b.    
         [0373]    In this example, the first and the second auxiliary inclined nozzles  415   a  and  415   b  spray the wash water in a direction opposite to the rotation direction of the first and the second auxiliary arms  400   a  and  400   b . The wash water sprayed from the first and the second auxiliary inclined nozzles  415   a  and  415   b  may be oriented so as to form an acute angle with respect to a rotation plane. 
         [0374]    Accordingly, the main arm  400  may be rotated by driving force generated by the wash water sprayed from the biased first and the second auxiliary inclined nozzles  415   a  and  415   b . That is, when the wash water is sprayed from the first and the second auxiliary inclined nozzles  415   a  and  415   b , a certain torque value capable of rotating the spray arm  400  may be generated. 
         [0375]    In some implementations, since the first and the second auxiliary arms  400   a  and  400   b  are rotated in the same direction, the amount of torque and directions of the sprayed wash water may be changed by the wash water sprayed from the first and the second auxiliary nozzles  414   a  and  414   b  and the first and the second auxiliary inclined nozzles  415   a  and  415   b.    
         [0376]    Hereinafter, spraying direction of the wash water in the first and the second auxiliary arms  400   a  and  400   b , the first and the second auxiliary nozzles  414   a  and  414   b , and the first and the second auxiliary inclined nozzles  415   a  and  415   b  will be described. In this example, the first and the second auxiliary arms  400   a  and  400   b  rotate in the same direction and torque is generated in the same direction. Thus, the first auxiliary arm  400   a  will be described by way of example, and a detailed description of the second auxiliary arm  400   b  will be omitted. 
         [0377]    In this example, the change of spraying direction when the first auxiliary arm  400   a  rotates in a reciprocating manner will be described in detail with reference to the accompanying drawing. 
         [0378]      FIG. 43  illustrates an example operation of an auxiliary arm. 
         [0379]    In this example,  FIG. 43( a )  shows that the first auxiliary arm  400   a  does not rotate.  FIG. 43( b )  is a view showing the first auxiliary arm  400   a  maximally rotates in a clockwise direction.  FIG. 43( c )  is a view showing the first auxiliary arm  400   a  maximally rotates in a counterclockwise direction. 
         [0380]    Referring to  FIG. 43( a ) , the wash water is simultaneously sprayed from the first auxiliary nozzle  414   a  and the first auxiliary inclined nozzle  415   a . The spraying direction A 1  of the wash water by the first auxiliary nozzle  414   a  and the spraying direction A 2  of the wash water by the first auxiliary inclined nozzle  415   a  may be oriented towards a left upper side. 
         [0381]    Furthermore, each of the spraying directions A 1  and A 2  of the wash water sprayed from the first auxiliary nozzle  414   a  and the first auxiliary inclined nozzle  415   a  may always form an acute angle with respect to the rotation plane of the spray arm  200 . Accordingly, torque may be applied to the first auxiliary arm  400   a  in a rotation direction of the spray arm  200  by the wash water sprayed from the first auxiliary nozzle  414   a  and the first auxiliary inclined nozzle  415   a    
         [0382]    Referring to  FIG. 43( b ) , in the case where the first auxiliary arm  400   a  maximally rotates in one direction, each of the spraying directions A 1  and A 2  of the wash water sprayed from the first auxiliary nozzle  414   a  and the first auxiliary inclined nozzle  415   a  may be oriented in a direction opposite to the rotation direction of the spray arm  200 . Thus, when the first auxiliary arm  400   a  rotates in a clockwise direction, torque may be applied to the first auxiliary arm  400   a  in a rotation direction of the spray arm  200 . 
         [0383]    Referring to  FIG. 43( c ) , in the case where the first auxiliary arm  400   a  maximally rotates in the other direction, each of the spraying directions A 1  and A 2  of the wash water sprayed from the first auxiliary nozzle  414   a  and the first auxiliary inclined nozzle  415   a  may be oriented in a direction opposite to the rotation direction of the spray arm  200 . Thus, when the first auxiliary arm  400   a  rotates in the other direction, torque may be applied to the first auxiliary arm  400   a  in a rotation direction of the spray arm  200 . 
         [0384]    In the case of the spraying direction A 1  of the wash water sprayed from the first auxiliary nozzle  414   a , when the first auxiliary arm  40  maximally rotates in the other direction, the wash water may be sprayed in a vertical upper direction. This may be a problem since torque direction applied to the spray arm  200  is changed. 
         [0385]    Thus, the rotation angle of the first auxiliary arm  400   a  should be less than the spraying angle of the first auxiliary nozzle  414   a . The term “spraying angle” means an angle formed by the spraying direction A 1  of the wash water of the first auxiliary nozzle  414   a , in the case where the first auxiliary arm  400  does not rotate, and a vertical line passing through the first auxiliary arm  400   a.    
         [0386]    Furthermore, the rotating angle of the first auxiliary arm  400   a  should be less than the spraying angle of the first auxiliary inclined nozzle  415   a . The term “spraying angle” means the angle formed by the spraying direction A 2  of the wash water of the first auxiliary inclined nozzle  415   a , in the case where the first auxiliary arm  400  does not rotate, and a vertical line passing through the first auxiliary arm  400   a.    
         [0387]    Thus, even if the first auxiliary arm  400   a  maximally rotates in both directions, the spraying direction A 1  of the first auxiliary nozzle  414   a  and the spraying direction A 2  of the first auxiliary inclined nozzle  415   a  may be always oriented in a direction opposite to the rotation direction of the spray arm  200  such that torque may be applied to the first auxiliary arm  400   a  in the rotation direction of the spray arm  200 . 
         [0388]    In the dishwasher  1 , the first and the second auxiliary arms  400   a  and  400   b  are rotatably mounted to the main arm  300  such that reciprocating rotation, as well as rotation of the main arm  30 , is performed. Thereby, the spraying angles may be varied. Accordingly, washing efficiency of the dishwasher  1  may be improved. 
         [0389]    Furthermore, the main arm  300  rotates by driving force generated by spraying the wash water while the first and the second spray arms  200  rotate. Thereby, there is no need for any separate driving source. 
         [0390]    In addition, rotational force of the spray arm  200  may be converted into reciprocating rotational force of the first and the second auxiliary arms  400   a  and  400   b  by interaction of the fixed gear  500 , the eccentric gear  800 , and the linker  900 . Accordingly, there is no need for any driving source for rotating the first and the second auxiliary arms  400   a  and  400   b.