Abstract:
A dishwasher includes a tub, a spraying device and a washing liquid supply device. The spraying device is disposed in the tub and includes a number of spray nozzles. The spraying device is rotatable about a first axis, the first axis being approximately vertical when the dishwasher is in a working position. The washing liquid supply device supplies the spraying device with washing liquid. The spraying device includes a rotatable spray control device that opens and closes a flow path of washing liquid to the spray nozzles so as to provide pulsed spray jets.

Description:
[0001]     Priority is claimed to German patent applications DE 10 2005 026 558.8, filed Jun. 8, 2005, and DE 10 2006 012 080.9, filed Mar. 14, 2006, the entire subject matters of which are hereby incorporated by reference herein.  
         [0002]     The invention relates to a dishwasher with a tub, in which at least one spraying device fitted with spray nozzles is mounted so as to rotate around an axis that is at least approximately vertical in the position in which the dishwasher is used, said dishwasher having means to supply the spraying device or the spray nozzles with washing liquid.  
       BACKGROUND  
       [0003]     In conventional dishwashers, the spray jets that come out of the spraying nozzles consist of a sequence of drops. When they strike the surface of the dishes to be washed, the individual drops form a liquid surface that can impair the cleaning effect of the subsequent drops. For this reason, it is known from EP 0 659 381 B1 to operate a spraying device intermittently with an alternating sequence of spraying time periods and pauses. This is achieved by switching the circulation pump on and off. Swiss patent CH-PS 384 795 describes a dishwasher in which pulse-modulated liquid jets are used to clean items. The modulation is achieved by a hydraulic ram or else by valves or slides. EP 1 040 786 B1 discloses a dishwasher having a spray arm in which auxiliary nozzles are switched on intermittently in addition to the main nozzles. The auxiliary nozzles are opened and closed by means of a spring mechanism that is actuated through an increase in the circulation pump pressure.  
         [0004]     Moreover, prior-art dishwashers (EP 0 943 282 B1) having several spray arms also make use of so-called alternating or interval washing in which only one of the spray arms is supplied with washing liquid at a time while the feed to the other arms is blocked. Since this reduces the amount of liquid in the liquid lines leading to the spray arms, the possibility exists of operating the circulation pump at a smaller liquid throughput rate, thus saving water.  
         [0005]     Moreover, the prior art also describes spray arms that are configured in such a way that they pay special attention to problem areas in the dishwasher tub. Reference is made here, for instance, to EP 0 974 302 B1, which discloses a cleaning device for a dishwasher whose spray arm has so-called corner spray nozzles. Another solution from the state of the art is known, for example, from German Utility Model 297 18 777. This publication discloses that a main dishwashing arm as well as an auxiliary dishwashing arm, which is rotatably attached to the main dishwashing arm, brushes along the wall of the dishwasher and is guided through the corner areas under the influence of the centrifugal force. These are, for example, solutions from the state of the art that are intended to improve the cleaning results especially in problem areas in the dishwasher tub. These solutions according to the state of the art increase the spatial efficiency of the cleaning but not the efficiency of the individual spray jets that come out of the spray arm and act on the dishes during the cleaning procedure.  
       SUMMARY OF THE INVENTION  
       [0006]     Therefore, it is an object of the present invention to provide a modulation of the spray jets in a simple manner in a dishwasher, thereby attaining a better cleaning effect while concurrently saving water.  
         [0007]     The present invention provides a dishwasher including a tub, a spraying device and a washing liquid supply device. The spraying device is disposed in the tub and includes a plurality of spray nozzles. The spraying device is rotatable about a first axis, the first axis being approximately vertical when the dishwasher is in a working position. The washing liquid supply device is configured to supply the spraying device with washing liquid. The spraying device includes a rotatable spray control device configured to open and close a flow path of washing liquid to the spray nozzles so as to provide pulsed spray jets.  
         [0008]     The interruption of the spray jets in the manner according to the invention improves the cleaning result in a simple manner in that it reduces the liquid surface formed on the dishes to be cleaned. Such a liquid surface can diminish the cleaning effect of the spray jet. Moreover, with the present invention water is saved without the occurrence of “dead zones” where the dishes are less exposed to the spraying. Since the alternating interruption of the spray jets causes their pressure to be increased, dirt adhering to the dishes is removed more effectively, so that a better cleaning result is achieved despite the fact that water is being saved. Pulsed spray jets act upon the dishes to be cleaned, which leads to a more efficient cleaning operation. Here, the spraying device is supplied by the circulation pump so that, as a result of the changed rotational speed of the circulation pump, the size or the interval of the drops can be quickly changed. Volume flows are created in the spraying device when the circulation pump is operated. These volume flows are employed to bring about functional changes and/or movements in the spraying device. According to the invention, by means of a certain volume flow, a functional element is moved and/or driven from one position into the other. This change in position serves to influence the parameters of the spray jets. Due to the fact that the spray arm is provided with rotating means that cause the spray nozzles to open and close so as to create pulsed spray jets, the jet shape, the jet speed, the jet type, the jet direction, the spray drop interval and the nozzle position are all influenced. In this context, the means are rotated exclusively by the washing liquid that is circulated in the dishwasher tub by the circulation pump.  
         [0009]     In a first advantageous embodiment, the means are arranged in the area of the axis of rotation of the spraying device and they can be rotated in the plane of the spraying device at a rotational speed that differs from that of the spraying device. This allows for a simple construction and the rotating capacity of the spraying device is not impaired.  
         [0010]     In this embodiment, the means comprise at least one cylindrical closing element having passage openings in the outer wall, whereby the cylinder axis coincides with the axis of rotation. Owing to its simple construction, such a closing element can be used in a serially produced spray arm without a need for major structural changes.  
         [0011]     It is advantageous for the openings in the outer wall of the closing element to be positioned in such a way relative to the channels connected to the spray nozzles that only the path of the washing liquid to some of the channels is interrupted during a relative rotation between the closing element and the spraying device. A simultaneous closing of all of the nozzles would cause the entire circulating liquid mass to be decelerated, so that the energy of the moved liquid column and thus its cleaning effect would be reduced. Besides, the slow rotation of the closing element brought about by this deceleration would increase the static friction, thus promoting jamming of the element. In a simple manner, the alternating closing and opening in the case of a spray arm having precisely two spray arm halves is achieved by an odd number of closure surfaces. In this context, it is advantageous for the closing element to have three closure surfaces. As a result, the force brought to bear by the pressure of the washing liquid is more uniformly distributed over the individual closure surfaces, thus avoiding tilting of the closing element and resultant jamming. Moreover, the modulation frequency is raised which, in turn, enhances the cleaning performance.  
         [0012]     According to a second embodiment, the means comprise a cylindrical body whose circumference is provided with cutouts that lie in the area that overlaps with the spray nozzles arranged on the spray arm. Here, the axis of rotation of the body is arranged parallel to the main direction in which the spray arm extends.  
         [0013]     The closing element or the body can be driven by an electric motor, by one or more magnets or else by the rotation of the spraying device by means of a gear that is operatively connected to said spraying device.  
         [0014]     In an advantageous embodiment, the closing element or the body is made to rotate by the liquid flowing to the spray nozzles. Consequently, no additional drives are needed. Here, a turbine can be employed as the drive. Thus, all that needs to be provided on the spray arm is a space to accommodate the closing element or the body; no other structural modifications are necessary in order to realize the drive.  
         [0015]     The turbine blades can be situated on a shaft that extends through the center of the closing element or the body. However, it is advantageous to arrange the turbine blades inside the closing element or the body since then, the space needed to accommodate the element is kept small. Moreover, with this embodiment, the closing element or the body can be mounted, or supported, on one side which, in turn, reduces the complexity of the components. Here, it is advantageous for a stub shaft arranged on the closing element to run through a sliding bearing arranged in the center of the spraying device. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     The drawings show embodiments of the present invention in schematic form that will be described in greater detail below. The following are shown:  
         [0017]      FIG. 1  an exploded view of a spray arm  7  constructed according to the invention;  
         [0018]      FIG. 2 a  simplified schematic depiction of a dishwasher  1  with a tub  2  and spray arms  7 ;  
         [0019]      FIG. 3 a  top view of a sectional diagram of a spray arm  7  constructed according to the invention;  
         [0020]      FIG. 4 . 1  a longitudinal section through a spray arm  7 , with a closing element that is moved magnetically;  
         [0021]      FIG. 4 . 2  a top view of a partial section of the spray arm  7  according to  FIG. 4 . 1 ;  
         [0022]      FIG. 5 . 1  a longitudinal section through a spray arm  7 , with a closing element that is moved by a turbine;  
         [0023]      FIG. 5 . 2  a top view of a partial section of the spray arm  7  according to  FIG. 5 . 1 ;  
         [0024]      FIG. 6 . 1  a longitudinal section through another spray arm  7 , with a closing element that is moved by a turbine;  
         [0025]      FIG. 6 . 2  a top view of a partial section of the spray arm  7  according to  FIG. 6 . 1 ;  
         [0026]      FIG. 7  an overview of closing elements with differently shaped closure surfaces and openings;  
         [0027]      FIG. 8  an advantageous embodiment of a closing element with reference to a three-dimensional model;  
         [0028]      FIG. 9 a  perspective view of another embodiment with a body having a horizontal axis of rotation;  
         [0029]      FIG. 10 a  detailed view of the rotation drive by means of turbine blades;  
         [0030]      FIG. 11  another variant of the rotation drive by means of an angular gear;  
         [0031]      FIG. 12 a  sectional side view through a spray arm with an integrated, cylindrical body; and  
         [0032]      FIGS. 13, 14  other variants of bodies having a horizontal axis of rotation. 
     
    
     DETAILED DESCRIPTION  
       [0033]      FIG. 1  shows a spray arm  7  constructed according to the invention, belonging to a household dishwasher  1  shown in greater detail in  FIG. 2 . The dishwasher  1  has two dish racks  3  and  4  arranged one above the other in a rectangular dishwasher tub  2 , and a cutlery tray  5  is located above the upper rack  3 . Alternatively, the cutlery basket can be integrated into one of the racks  3  and  4  instead of the cutlery tray  5 . Inside the rectangular dishwasher tub  2 , underneath the upper rack  3  and the lower rack  4 , spray arms  7 . 1  and  7 . 2 , respectively, are rotatably mounted on liquid laden spray arm holders  6 . 1  and  6 . 2 , respectively, while a third spray arm  7 . 3  rotates on another spray arm holder  6 . 3  above the cutlery tray  5 .  
         [0034]     The rotatable spray arms  7  are fitted with spray nozzles  8  (see  FIG. 1 ) that are arranged in such a way that the entire load of dishes present in the racks  3 ,  4  and  5  are exposed to the washing liquid coming out of the spray nozzles  8 . Here, the spray arms  7  are supplied with washing liquid by a circulation pump  9  via pipelines  10 . The circulation pump  9  is connected via another pipeline  11  to the lowest point  12  of the cuboidal cleaning chamber  2  and it suctions the liquid that has accumulated there through generally known filters and once again pumps the liquid through the nozzles  8  of the spray arms  7 , whereby a recoil force caused by the discharge of the washing liquid causes the spray arms  7  to rotate, which is indicated in  FIG. 1  by the arrow  13 .  
         [0035]     The liquid is fed to the spray arm  7  shown in a detailed view in  FIG. 1  via a feed line  10  that makes a transition to the spray arm holder designated here with the reference numeral  6 . The spray arm  7  itself is configured as a symmetrical hollow body and is mounted in a familiar manner so as to rotate on the holder  6 . For this purpose, a swivel nut  19 . 1 , in which a sliding bush  19 . 2  is secured, is screwed to the holder  6 ; the end of the sliding bush  19 . 1  that is visible in  FIG. 1  and that protrudes towards the outside has an external thread (not shown here) that is screwed by an internal thread (likewise not shown here) to an accommodation space  14  of the spray arm. Inside the hollow body, channels  15  and  16  lead from the accommodation space  14  into both ends of the spray arm halves  71  and  72 , and spray nozzles  8  are arranged on the top and bottom of the walls of said channels. A cylindrical, here annular, closing element  20  is inserted into the accommodation space  14 . As a result, the cylinder axis of the closing element coincides with the axis of rotation of the spray arm  7 , which is indicated by the broken line  17 . The outer wall of the closing element  20  has openings  21  and, between those, closed areas  22  that function as closure surfaces, so that any relative movement between the spray arm  7  and the closing element causes the individual channels  15  and  16  to be alternatingly opened or closed.  FIG. 3  shows the closing element  20  in a position in which the left-hand spray arm half  72  is opened while the right-hand half  71  is closed. The closure surfaces  22  are indicated here as a black annular section and the openings  21  as a white section. The emerging liquid is indicated by the arrows  18 .  
         [0036]     In order to prevent the two spray arm halves  71  and  72  from always being blocked in the same position, and thus to prevent the creation of “dead zones” that are not reached by the spray jets, the closing element  20  is moved, so that the closure surfaces end up in constantly changing spray arm positions in front of the channels  15  and  16 . A moveable mounting is provided that allows the closing element to rotate at a speed that differs from the rotational speed of the spray arm  7 .  
         [0037]     The subsequent  FIGS. 4 . 1 ,  4 . 2 ,  5 . 1 ,  5 . 2 ,  6 . 1  and  6 . 2  show spray arms  7  in which the closing element  20  in its active position rotates at a speed that differs from the rotational speed of the spray arm  7 . Closing element  20  is rotated via rotation device  30  to  33 . In the embodiment depicted in  FIGS. 4 . 1  and  4 . 2 , the rotation device  30  to  33  is made up of magnets  30  to  33 . The spray arm  72  is coupled to a holder  6  that is fitted with oppositely poled magnets  30  and  31 . An axis  25  connected to the closing element  20  extends into the holder  6  all the way into the area of these magnets  30  and  31 . This end of this axis  25  has magnets  32  and  33  that are arranged crosswise and that are likewise oppositely poled. The closing element  20  itself is rotatably mounted inside the accommodation space  14  by a means that has been described elsewhere. When the spray arm  7  executes a rotational movement, the magnets  30  to  33  cause the closing element  20  to execute a pendulum movement. In this process, openings  21  and closure surfaces  22  are alternatingly moved in front of the channels  15  and  16 , thus opening or closing the nozzles  8  present there.  
         [0038]     In other embodiments the rotation device  30  to  33  is made up of an electric motor that rotates the closing element  20 , or by a gear mechanism that rotates the closing element via the movement of the spray arm.  
         [0039]      FIGS. 5 . 1  and  5 . 2  as well as  6 . 1  and  6 . 2  show spray arm variants in which the closing element  20  is likewise rotatably mounted in the accommodation space, where the element  20  is made to rotate by means of turbine blades  40  or  50 . This has the advantage that a rotational movement is brought about by the flowing liquid  18 , so that no additional, wear-prone drives are necessary. Here, the rotational speed is dependent on the throughput volume as well as on the dimensioning of the turbine blades  40  or  50  and it can be selected in such a manner that it differs from the speed of the spray arm  7 . In the best case, the tilting direction of the turbine blades  40  or  50  is configured in such a way that a direction of rotation opposite to that of the spray arm  7  is established. The blades  40  can be arranged on a shaft  26  that extends through the center of the closing element  20 ; see  FIGS. 5 . 1  and  5 . 2 . With this arrangement, the shaft  26  also has to be bearing-mounted, which calls for additional effort and can give rise to blocking due to a possible tilting movement of the entire arrangement. For this reason, it is advantageous for the turbine blades  50  to be placed inside the closing element  20 , as shown in  FIGS. 6 . 1  and  6 . 2 . They can then be integrally formed onto the closing element  20  which, on the one hand, simplifies the production and, on the other hand, means that only a small space is needed to accommodate the element.  
         [0040]      FIG. 7  shows various closing elements designated with the reference letters a to f, which differ from each other in terms of the number of openings and their shape and size. The element designated with the reference letter a has four openings, and thus also four closure surfaces, with two pairs facing each other. As a result, a simultaneous blockage of all of the spray nozzles is achieved in a spray arm  7  having two halves. The closing element designated with the reference letter b has three openings and closure surfaces. The symmetrical arrangement means that it is always only one half of a spray arm  7  having two halves that is blocked.  
         [0041]     Element c shows a variant having relatively small openings, while closing elements d and e have openings that are the same width as the closure surfaces; f shows an element having very narrow closure surfaces. For the rest, the closing elements c and e, which have round openings or elliptical openings, differ from elements d and f, which have rectangular openings.  
         [0042]      FIG. 8  shows a closing element  60  whose geometrical relationships have been optimized. It is configured as a one-piece component and is preferably made of plastic. For bearing purposes, a stub shaft  62  is formed onto a disk-shaped bottom part  61  in the axis of rotation, said stub shaft being inserted into a bore in the center of the accommodation space  14  (see  FIG. 1 ). The bore functions as a sliding bearing, as a result of which the static friction between the closing element  60  and the spray arm  7  is reduced, thus allowing the element  60  to rotate in the first place. On the opposite side of the bottom part, the stub shaft  62  continues with a reduced diameter as a removal pin  63 , thus facilitating installation and subsequent removal. Moreover, three symmetrically arranged bodies  64  rise from the edge of the bottom part  61  and these bodies form the closure surfaces  65  as well as the slanted turbine blades  66  needed for driving purposes. Openings  67  having a rectangular cross section have been left free between the closure surfaces, whereby the arc length of the closure surfaces  65  and of the openings  67  is about the same and amounts to approximately 60°.  
         [0043]     The above-mentioned design of the closing element as described above entails the following advantages:  
         [0044]     When used in a symmetrical construction, three closure surfaces  65  ensure the alternating closing of the spray arm halves  71  and  72  (see  FIG. 3 ). An alternating blocking of one spray arm half  71  or  72  at a time means that mainly the liquid in the spray arm  7  is decelerated and then accelerated again. In contrast to this, a simultaneous blocking of both halves  71  and  72  causes the liquid in the entire feed line to be decelerated as well as accelerated. In this case, the spray arm  7  would have to have a very low angular velocity in order to achieve sufficient spray jet heights. This low rotational speed promotes jamming of the closing element  60 . The above-mentioned alternating blocking of one spray arm half  71  or  72  is also achieved with closing elements having any odd number of openings or closure surfaces, but actual practice has shown that three openings  67  are especially conducive to attaining a uniform rotational movement; one single closing element would give rise to strong tilting moments that could also cause jamming. The extension of the closure surfaces  65  over an angle of approximately 60° translates into sufficiently long spraying pauses so as to achieve the above-mentioned improvement of the cleaning effect. If the number of closure surfaces is larger if the closing element is designed as shown in  FIG. 7   f , it would only be possible to attain very short spraying pauses, and moreover there would not be much space available to accommodate the turbine blades  66 . The pitch and the surface area of the turbine blades  66  are dimensioned in such a way that a pulse sequence within the desired frequency range between 2 and 12 Herz can be achieved.  
         [0045]     In the embodiments shown in FIGS.  9  to  14 , instead of the closing element  20  or  60 , cylindrical bodies  105  are employed whose axis of rotation  120  is arranged so as to be horizontal in the main extension direction  121  of the spray arm.  FIG. 9  shows a perspective view of such an embodiment of a spray arm  101  in a dishwasher that is not depicted in greater detail. The spray arm  101  here is mounted so as to rotate around a vertical axis  102  in a dishwasher tub (see  FIG. 11 ). The spray arm  101  is fitted with spray nozzles  103  that are supplied with washing liquid via a circulation pump (likewise not shown here). As can be seen in the perspective depiction of  FIG. 9 , rotating means  104  are provided in the spray arm  101 , said means causing the spray nozzles  103  to open and close so as to create pulsed spray jets. Here, the washing liquid causes the means  104  to rotate. As can be seen in the perspective depiction of  FIG. 9 , but also clearly in  FIG. 12 , the means  104  comprise a cylindrical body  105  whose circumference is provided with cutouts  106  that lie in the area that overlaps with the spray nozzles  103  arranged on the spray arm  101 . Consequently, the rotation of the cylindrical body  105  causes the nozzles  103  to be opened and closed again at certain time intervals. If the cylinder  105  rotates at a constant rotational speed, the nozzles  103  discharge pulsed water jets. These pulsed spray drops then clean the soiled dishes considerably more effectively.  
         [0046]     In order to generate the rotation, turbine blades  107  are formed in the cylindrical body  105 , here especially on the inlet side, such as depicted in detail in  FIG. 10 . Another variant of the drive for the cylindrical body  105  is shown in  FIG. 11 . Here, in order to generate the rotation, a toothed wheel rim  108  is arranged on the free end on the inlet side of the cylindrical body  105 , said toothed wheel rim  108  being operatively connected to a toothed wheel rim  109  arranged on the fixed axis of rotation ( 102 ) of the feed line. Thus, when the spray arm  101  rotates around the vertical axis, this causes the cylindrical body  105  to turn along with it.  
         [0047]      FIG. 12  once again illustrates how the individual spray nozzles  103  are opened and closed. The water enters the spray arm  101  in the direction indicated by the arrow and, in the manner depicted by the rotation arrow shown here, the individual nozzles  103  open when the individual cutouts  106  pass. This figure also especially shows the mounting of the cylindrical body  105 , whereby here, in order to mount the cylindrical body  105 , the latter acquires a conical shape at its end, with the cone tip  110  forming the bearing contact point in the spray arm  101 . Here, only the tip  110  of the cone should be in direct contact with the stationary area. The front contact surface should be kept small through the configuration of the cone tip  110 . This is achieved by means of the water flow. The water flow presses the rotating system against the cone tip  110  and only achieves radial contact in the rear area.  
         [0048]     Another embodiment of the invention is shown in  FIG. 13 , whereby it is characterized in that the means  104  likewise comprise a cylindrical body  105  whose circumference is provided with outlet nozzles  111  arranged so as to be radially slanted in the cylinder wall, whereby the wing-like spray arm  101  laterally overlaps areas of the body  105 , in other words, the cylindrical body  105  is mounted so as to rotate between the two spray arm legs  112  and  113 . Here, the washing liquid jets coming out of the outlet nozzles  111  arranged at a slant automatically cause the body  105  to rotate, which is indicated in the figure by the arrows drawn with a thick line. In this embodiment, the inner cylinder  105  is configured in such a way that the spray nozzles  111  concurrently serve as driving nozzles. Here, the spray nozzles  111  are set at the greatest slant possible. The water that is now being sprayed through the offset nozzles  111  generates recoil forces that are distributed along the spray arm  101 . These recoil forces cause the body  105  to rotate. Consequently, no additional drive elements are needed to rotate the body  105 . Due to the positioned, rotating spray nozzles  111 , the water jets cover a great deal of the space. Each nozzle  111  can differ in terms of its shape, number and type, for example, it can create a fanning jet, so that the risk of soiling is small since no dirt can collect between the rotating cylinder  105  and the spray arm  101 . The movable openings of the rotating inner cylinder  105  permit the nozzles  111  to be configured in many different ways. For instance, the nozzle shape, nozzle type, number of nozzles and nozzle position on every cylinder cutout can be designed differently. At various points in time, the nozzles  111  of the spray arm  101  free different spray jets in different directions. This ensures that a larger space is covered by the water jets.  
         [0049]     The embodiment shown in  FIG. 14  is characterized in that the means  104  comprise individual rotating bodies  105  arranged along the extension of the spray arm  101 , said bodies being fitted with closure baffles  114  that pass over outlet nozzle openings on the spray arm  101 . For this purpose, the single body  105  has a cruciform shape and the closure baffles  114  are formed onto the legs  116  and  117 . Advantageously, the closing elements  114  here comprise curved surface elements  115  that have been adapted to the shape of the spray arm. In order to keep the individual bodies  105  rotating here, the cruciform legs  116  and  117  are shaped so as to have the form of turbine blades. Several individual spray turbines, as shown in the example of  FIG. 14 , can generate an individual water jet coverage. Here, the closing elements  114  with the appertaining turbine are driven by means of the water flow. The closing elements  114  of the turbine can preferably be made, for example, of rubber. The inner surface of the cylinder is better sealed in this manner. In this case, it is particularly advantageous that the use of rubber material reduces the risk of dirt on the turbine blades. Moreover, due to the individual turbines, the nozzles  103  are individual and independent of each other. Different nozzles  103  can be arranged in each case, and they differ in terms of their shape, number and type. Furthermore, the drop size is dependent on the pressure and therefore can be adjusted individually by changing the rotational speed of the circulation pump.