Patent Publication Number: US-7213422-B2

Title: Needle selection device for weft knitting machine

Description:
TECHNICAL FIELD 
   The present invention relates to a needle selecting apparatus for a weft knitting machine capable of selecting appropriate knitting needles provided in the weft knitting machine in correspondence with various types of knitting operations. 
   BACKGROUND ART 
   In a conventional weft knitting machine, various modified knitting organizations are produced by combining three basic positions of knitting, tucking and welting (missing) in knitting operations by means of knitting needles. In a structure of a typical weft knitting machine, a carriage reciprocates along a needle bed having a plurality of needle grooves in a longitudinal direction, and each knitting needle performs knitting operation through a cam mechanism included in the carriage. The carriage is accompanied with a yarn supply member for supplying a knitting yarn to the knitting needles which perform knitting operation, and the plural knitting needles sequentially carry out the knitting operation in correspondence with the yarn supply position of the yarn supply member. The cam mechanism is basically formed to correspond to the knitting operation in the knitting position, and a needle selecting apparatus for selecting the knitting needles for the tucking or welting position is provided in each needle groove. 
   The applicant of the invention previously proposed needle selecting apparatus in Japanese Unexamined Patent Publications JP-A 6-200454, JP-A 6-220752, JP-A 9-241952 and other publications.  FIG. 13  schematically shows a structure of a needle selecting mechanism disclosed in JP-A 9-241952, which is partially modified for the sake of descriptive convenience. A weft knitting machine  1  has a carriage  3  which reciprocates along a needle bed  2  extending in a longitudinal direction. Grooves to which needle plates  4  are fitted in predetermined intervals are formed on the needle bed  2  in the longitudinal direction. Needle grooves  5  are provided between the needle plates  4 , and knitting needles  6  are disposed in the needle grooves  5  where the knitting needles  6  can be slidingly displaced. The weft knitting machine  1  includes at least a pair of the front and rear needle beds  2  whose front faces extend in parallel with the longitudinal direction, and the needle beds  2  are opposed to each other with a needle bed gap  7  interposed therebetween. However, only a side cross section of one of the needle beds  2  is shown in this figure and the other is omitted for the sake of descriptive convenience. Also, the sliding displacement direction of the knitting needle  6  is inclined upward toward the needle bed gap  7 , but the inclination of the needle bed  2  is omitted and such a posture that the knitting needle  6  is slidingly displaced in a horizontal direction is shown. The carriage  3  is attached to the front and rear needle beds  2  in such a manner as to cross over the needle bed gap  7 , and is accompanied with a yarn supply member for supplying a knitting yarn along the needle bed gap  7 . 
   The knitting needle  6  has a needle main body  8  as the front haft and a needle jack  9  as the rear half when the needle bed gap  7  is the front and the opposite side is the rear in each needle groove  5  as viewed from the side of the weft knitting machine  1 . A hook and other components for receiving a knitting yarn used for knitting operation are provided at the front end of the needle main body  8 . The needle jack  9  has a driving butt  9   a  for advancing and retracting the knitting needle  6  within the needle groove  5 . The needle jack  9  disposed in the needle groove  5  has a bent shape such that the butt  9   a  can project toward the carriage  3  by elasticity. When the butt  9   a  projects toward the carriage  3 , a knitting cam  10  provided on the carriage  3  acts on the knitting needle  6 , whereby the needle  6  can advance and retract in the needle groove  5  with respect to the needle bed gap  7 . 
   A needle selecting apparatus  11  is provided for each knitting needle  6  for controlling the action of the knitting cam  10  given to the knitting needle  6 . The needle selecting apparatus  11  includes a selecting jack  12  and a selector  13 . The selecting jack  12  is disposed in the rear region of the needle jack  9  near the carriage  3 , and a butt  12   a  projects toward the carriage  3 . The position of the selecting jack  12  is determined by the selector  13  such that the butt  12   a  is positioned in any of B position, H position and A position. The selector  13  has butts  13   a ,  13   b  and  13   c  which project toward the carriage  3 , and is shifted within the needle groove  5  by the action of a selector cam  14  provided on the carriage  3 . When the selector  13  shifts to the front, a tip  13   d  pushes and advances the selecting jack  12 . The advanced position of the selecting jack  12  is determined by action of a needle selection actuator  15  which is disposed near the carriage  3  in such a position that the rear half of the selector  13  is sandwiched between the needle selection actuator  15  and the selector cam  14 . 
   The selector  13  disposed in the needle groove  5  has a bent shape such that an armature  13   e  formed in a position facing the needle selection actuator  15  in the rear half region can be separated from the needle selection actuator  15  by elasticity. When the selector cam  14  pushes the butt  13   c  disposed in the rear region, the armature  13   e  contacts the needle selection actuator  15  and is magnetically attracted thereto. The needle selection actuator  15  has two release positions, for example, where the attraction is released to conduct needle selection by energization for each knitting needle  6 . The selector cam  14  has cam grooves in positions corresponding to the respective release positions so as to advance the selector  13  when the attraction for the armature  13   e  of the selector  13  is released and the butt  13   b  projects toward the carriage  3 . When the attraction for the armature  13   e  is released in the release position disposed ahead of the traveling carriage  3 , the selector  13  advances to a position corresponding to the knitting operation (A position). When the attraction is released in the release position disposed behind the traveling carriage  3 , the selector  13  advances to a position corresponding to the tucking operation (H position). When the attraction is not released in either position, a position corresponding to the welting operation (B position) is maintained. 
   The selecting jack  12  is pushed by the tip  13   d  of the selector  13  and thereby advances within the needle groove  5 . The butt  12   a  of the selecting jack  12  at each position is pressed by a B presser  16  and an H presser  17  provided on the carriage  3 . By pushing down the butt  12   a  and sinking the selecting jack  12  into the needle groove  5 , the needle jack  9  is also pushed down into the needle groove  5  whereby the butt  9   a  is separated from the knitting cam  10 . The B presser  16  is provided to correspond to the welting position (B position) as a non-operative position of the knitting operation, and separate the butt  9   a  from the knitting cam  10  for almost the entire stroke. The H presser  17  is provided to correspond to the tucking position (H position). In this position, the knitting cam  10  acts on the butt  9   a  until the needle main body  8  advances part of the way toward the needle bed gap  7 , and subsequently the H presser  17  pushes down the butt  12   a  to separate the butt  9   a  from the knitting cam  10 . In the knitting position (A position), no presser is provided and the knitting cam  10  acts on the knitting needle  6  for the entire stroke. 
   Wires  18  and  19  penetrate the needle groove  5  in the longitudinal direction of the needle bed  2  to restrict the range of sliding displacement of the selecting jack  12  in the needle groove  5 . Concaves  12   b ,  12   c  and  12   d  disposed inside a forked portion into which the rear wire  19  is inserted engage with the wire  19  to maintain the respective positions of the selecting jack  12 . A guide cam which acts on the butt  12   a  is provided on the selector cam  14  so that the selecting jack  12  can retract to an initial position as the welting position after the knitting operation by the knitting cam  10  is completed. 
   JP-A 6-220752 discloses three-position locking type needle selecting apparatus capable of selecting the above-described three positions of A, H and B for needles and locking these positions such that a pushed-down condition of a butt on a selecting jack can be maintained even when the selecting jack is pushed up by a selector to advance to A position and the pressing by a selecting jack presser provided on a carriage is released. JP-A 6-200454 discloses two-position locking type needle selecting apparatus in which B position is shared by the non-operating welting position and the tucking position, and knitting needles are locked in B position in which a needle selection actuator operates at earlier timing. By locking in the welting position, a butt of a needle jack does not engage with a knitting cam while a carriage is traveling. As a result, occurrence of frictional damage and other damage of the butt and the knitting cam is reduced and sliding resistance caused by the shift of the carriage is decreased, thereby reducing the power cost. 
   In the weft knitting machine in which the knitting needles  6  perform knitting operations using the knitting cam  10  of the carriage  3  as illustrated in  FIG. 13 , advantages such as prevention of frictional damages and the like and the power cost reduction are expected to be offered by providing the above-described locking mechanism. Furthermore, in addition to the basic knitting operation, another advantage is expected to be offered in a process where a stitch loop is tightened in cooperation with sinker apparatus prior to knitting a new stitch, as disclosed in International Patent Publication WO01/36730. In this step, a stitch holding hook provided at the tip of the sinker is raised from a stitch pressing position to temporarily release the stitch from the stitch holding hook prior to formation of a new stitch. In this condition, the knitting needle is retracted from a needle bed gap to tighten the stitch by a stitch cam on the preceding side which is provided in a descending position where the knitting needle is retracted from the needle bed gap. Subsequently, the tip of the sinker is again lowered, thereby allowing the stitch to be caught by the stitch holding hook. Through this process prior to the stitch formation, the stitch already formed can be securely pressed by the sinker and the succeeding stitch loop can be successfully formed. 
   In this “preceding retraction” function, the “preceding retraction” is performed by the stitch cam on the preceding side of the knitting system with respect to the traveling carriage  3 . At this stage, the butt  12   a  of the selecting jack  12  for the knitting needle  6  for which the non-operative welting position is selected as to the preceding stitch loop is released from the pressing by the B presser  16 . As a result, the butt  9   a  of the needle jack  9  rises from the needle groove  5  and is then lowered by the action of the stitch cam on the preceding side. It is not preferable, however, that the knitting needle  6  which did not form a stitch is retracted at the time of the “preceding retraction” as described. A knitting yarn is drawn through the knitting needle every time the knitting system of the carriage  3  passes on the knitting needle  6  in B position where no operation is to be performed, which may give undesirable effects in terms of knitting operation such as wearing and cutting of yarn. 
   For solving the problem arising from the “preceding retraction”, locking the condition where the selecting jack is sunk in the welting position is also effective. However, in the locking mechanisms disclosed in JP-A 6-200454 and JP-A 6-220752, the advancing and retracting action of the selector is essential and thus pressers and other components are required for controlling this action. As a result, a large distance between the knitting systems is needed to provide a plurality of knitting systems on the carriage, which makes the carriage large-sized. 
   Alternatively, the unnecessary descending action of the knitting needles can be avoided by extending the width of the B presser which pushes down the butt of the selecting jack in the welting position to the position where the stitch loop is tightened or other actions are performed for the step where the stitch loop is tightened or other actions are performed. However, since the selecting jack is returned to B position as the initial position prior to the stitch loop formation at each knitting system, the butt of the selecting jack corresponding to the knitting needle for which the position selected is changed from B position to H position is also pressed by the B presser until the knitting needle advances to H position at the start of knitting operation by the succeeding knitting system when the carriage has a plurality of the knitting systems. As a result, when the knitting needle being pressed in this manner reaches the stitch cam used for the preceding retraction, the preceding retraction cannot be carried out. Accordingly, the length of the carriage in the traveling direction required by the cam increases and thus a distance between the neighboring knitting systems is enlarged, which makes the carriage large in size. 
   DISCLOSURE OF THE INVENTION 
   It is an object of the invention to provide a needle selecting apparatus which is included in a weft knitting machine and has an improved mechanism for locking needle selection positions so as to lock needle selection positions without advancing and retracting a selector. 
   The invention provides a needle selecting apparatus for a weft knitting machine comprising a needle bed having a plurality of needle grooves in rows; a carriage including a selecting mechanism and a cam mechanism, the carriage traveling along the needle bed; and knitting needles each disposed in the needle groove and each having a butt on which the cammechanism of the carriage acts, the needle selecting apparatus comprising: 
   selectors disposed in each of the needle grooves, for shifting a selecting jack to select any of positions predetermined in correspondence with a plurality of knitting operations including non operation, the selecting jack being capable of being selectively separated from the cam mechanism by pressing the butt from the carriage in cooperation with the selecting mechanism of the carriage with respect to the butt of the knitting needle within each needle groove, the positions being established such that an initial position of the selecting jack corresponds to a non-operative position; 
   a holding member disposed in a predetermined position in a vicinity of each of the selecting jacks located in the initial position at a distance from the selecting jack; and 
   a locking member provided for each of the selecting jacks, wherein when the selecting jack is pressed from the carriage at the initial position, the locking member is fitted in a space between the selecting jack and the holding member formed on the needle groove so as to maintain the pressed condition of the selecting jack by the locking member inserted between the selecting jack and the holding member, and when the selecting jack is shifted to a position other than the non-operative position by the selector, the locking member is separated from the space so as to release the pressed condition of the selecting jack. 
   The invention is characterized in that the holding member disposed within each needle groove is a penetrating member which penetrates the needle bed in a direction where the needle grooves are provided in rows and contacts the selecting jack on the side facing the carriage to hold the selecting jack within the needle groove, and 
   the locking member is forced by a spring to be fitted in a space between the penetrating member and the selecting jack on a side facing the carriage. 
   The invention is characterized in that the selecting jack has a thin-wall portion which has a small thickness on both sides in a plate thickness direction and is disposed in a vicinity of the penetrating member to face the penetrating member in the initial position, 
   the locking member has a forked engaging portion for receiving the thin-wall portion from both sides in the thickness direction, and a fitting portion allowed to enter into the space between the penetrating member and the selecting jack on the side facing the carriage, and 
   the needle selecting apparatus further comprises a spring provided between the thin-wall portion of the selecting jack and the engaging portion of the locking member, for forcing the locking member so as to cause the fitting portion to enter into the space. 
   The invention is characterized in that the selecting jack has a groove which is substantially U-shaped and has a smaller width at an opening of the groove and is open at a position which is disposed in the vicinity of the penetrating member and faces the penetrating member in the initial position, and 
   the locking member has a forked engaging portion which is inserted into the groove and pressed from both sides of the groove to be forced toward the penetrating member, and a fitting portion allowed to advance into the space between the penetrating member and the selecting jack on the side facing the carriage. 
   The invention is characterized in that the holding member within each needle groove is a concave portion formed on a side of the selecting jack, and 
   the locking member is a plate spring formed on a side surface of the selecting jack and having a tip which is forced so as to project toward the side and is fitted into the concave portion so as to prevent the selecting jack from being displaced toward the carriage. 
   The invention is characterized in that the cam mechanism of the carriage has a function for retracting a knitting needle whose butt is not separated prior to execution of the plural knitting operations. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other and further objects, features, and advantages of the invention will be more explicit from the following detailed description taken with reference to the drawings wherein: 
       FIGS. 1(   a ) and  1 ( b ) are side cross-sectional views showing a needle selecting apparatus  21  included in a weft knitting machine  20  according to a first embodiment of the invention, in a condition where a selecting jack  22  in an initial position as a non-operative welting position is not pressed, and in a locked condition where the selecting jack  22  in the welting position is pressed, respectively; 
       FIG. 2  is a side cross-sectional view illustrating an entire structure of a needle bed  32  including the needle selecting apparatus  21  shown in  FIG. 1 ; 
       FIG. 3  is a plan view illustrating a cam arrangement on a carriage  33  shown in  FIG. 2 ; 
       FIGS. 4(   a ) and  4 ( b ) are side cross-sectional views each illustrating an entire controlled condition of the needle bed  32  corresponding to  FIG. 1 ; 
       FIG. 5  is a side cross-sectional view illustrating a non-pressed condition where a selector  23  and the selecting jack  22  are set in a tucking position by selector cams  24  in the needle selecting apparatus  21  shown in  FIG. 1 ; 
       FIGS. 6(   a ) and  6 ( b ) are front views each explaining how an enlarged distance between knitting systems affects the weft knitting machine  20  through a simplified illustration; 
       FIGS. 7(   a ) and  7 ( b ) are a plan view and a side view, respectively, each illustrating an enlarged shape of a locking member  30  shown in  FIG. 1 ; 
       FIGS. 8(   a ) and  8 ( b ) are a plan view and a side view, respectively, each partially illustrating enlarged structure and shape of a thin-wall portion  22   f  of the selecting jack  22  to which the locking member  30  is attachable; 
       FIGS. 9(   a ) and  9 ( b ) are side cross-sectional views showing a needle selecting apparatus  71  according to a second embodiment of the invention, in a condition where a selecting jack  72  in an initial position as a non-operative welting position is not pressed, and in a locked condition where the selecting jack  72  in the welting position is pressed, respectively; 
       FIGS. 10(   a ) and  10 ( b ) are a side view of a locking member  75  shown in  FIG. 9 , and a partial side view around a groove  72   e  of the selecting jack  72 , respectively; 
       FIGS. 11(   a ) and  11 ( b ) are side cross-sectional views showing a needle selecting apparatus  81  according to a third embodiment of the invention, in a condition where a selecting jack  82  in an initial position as a non-operative welting position is not pressed, and in a locked condition where the selecting jack  82  in the welting position is pressed, respectively; 
       FIGS. 12(   a ) and  12 ( b ) are a plan view and a side view, respectively, illustrating a shape of a plate spring  88  shown in  FIG. 1 ; and 
       FIG. 13  is a side cross-sectional view illustrating a needle selecting apparatus  21  provided on a needle bed of a conventional weft knitting machine. 
   

   BEST MODE FOR CARRYING OUT THE INVENTION 
   Now referring to the drawings, preferred embodiments of the invention are described below. 
   Embodiments of the invention are hereinafter described with reference to  FIGS. 1 through 12 . Mechanisms, components and parts and the like having the same names as those in the part of the invention already described above or in the part corresponding to the related art already described above with reference to  FIG. 13  have basically the same functions and structures even if different reference numerals are given, and repetitive description of those is sometimes omitted. The posture of a needle bed and the front-rear direction based on a needle bed gap are determined in the same manner as in  FIG. 13 . Position A, position H and position B correspond to knitting, tucking and welting (missing) positions, respectively, in each embodiment. 
     FIGS. 1(   a ) and  1 ( b ) each schematically illustrate a cross-sectional structure of a needle selecting apparatus according to a first embodiment of the invention. In this embodiment, a selecting jack  22  of a needle selecting apparatus  21  included in a weft knitting machine  20  can be locked so as to maintain a pressed condition in an initial position where knitting operation is not performed.  FIG. 1(   a ) shows a condition where the selecting jack  22  in an initial position as a non-operative welting position is not pressed, while  FIG. 1(   b ) shows a condition where the selecting jack  22  is pressed. The needle selecting apparatus  21  includes a selector  23  for shifting the selecting jack  22 . The selector  23  has a plurality of butts  23   a ,  23   b  and  23   c , and the selector cams  24  act on the butts  23   a ,  23   b  and  23   c  to drive the selector  23 . A tip  23   d  of the selector  23  contacts the selecting jack  22  to advance the selecting jack  22 . An armature  23   e  is formed on a rear end of the selector  23 . The armature  23   e  contacts a needle selection actuator  25  when the selector cam  24  presses the butt  23   c , and is magnetically attracted to the needle selection actuator  25 . 
   A butt  22   a  of the selecting jack  22  which is advanced to a position different from the initial position is returned to B position as the initial position while guided by a guide cam  26 . The initial position of the selecting jack  22  is a welting position, where a missing condition in which a knitting yarn is not knitted is selected. In the initial position, the butt  22   a  is pressed by a B presser  27 . Wires  28  and  29  are provided to control displacement of the selecting jack  22 . The wire  29  is sandwiched by a forked portion in the rear half region of the selecting jack  22 . The wire  29  engages with concave portions  22   b ,  22   c  or  22   d  to select the knitting, tucking or welting position. 
   In this embodiment, a locking member  30  is attached to the selecting jack  22 . When the B presser  27  presses the butt  22   a  of the selecting jack  22  in the welting position as the initial position shown in  FIG. 1(   b ), the locking member  30  enters into a space between the selecting jack  22  and the wire  28 . The locking member  30  is forced by a spring  31 . The selecting jack  22  has a contact portion  22   e  with which the tip  23   d  of the selector  23  can contact in both the conditions where the butt  22   a  is not pressed as shown in  FIG. 1(   a ) and where the butt  22   a  is pressed as shown in  FIG. 1(   b ). The locking member  30  is attached to a thin-wall portion  22   f  extending from the butt  22   a  of the selecting jack  22  to the contact portion  22   e . The structures associated with the locking member  30  and the thin-wall portion  22   f  will be described later with reference to  FIGS. 8 and 9 . 
   When the selecting jack  22  is shifted to the tucking position or the knitting position by the selector  23  which is driven by the selector cams  24 , the locking member  30  is drawn from the space between the wire  28  and the selecting jack  22  whereby the locked condition shown in  FIG. 1(   b ) is released. The selecting jack  22  lifts until a limit is provided by the wire  28  due to resiliency of the needle jack which is in a pressed condition. In the lifting condition, the butt  22   a  can be pressed by a presser in the tucking position and driven by the guide cam  26 . The guide cam  26  retracts the butt  22   a  to return the selecting jack  22  to the initial position. Since the wire  28  contacts the selecting jack  22  to restrict the lifting of the selecting jack  22  when the selecting jack  22  retracts, there is no space between the wire  28  and the selecting jack  22  and thus the locking member  30  cannot enter into the space. As a result, the locking member  30  is pressed toward the front by the wire  28 , whereby the spring  31  is compressed and pressed against the thin-wall  22   f  of the selecting jack  22 . 
   The needle selecting apparatus  21  having the above structure is provided on a needle bed  32  of the weft knitting machine  20 , and is driven and controlled by the selector cams  24  and the needle selection actuator  25  provided on the carriage  33 . The selecting jack  22  and the selector  23  are accommodated within a needle groove  35  formed between needle plates  34  provided in rows on the needle bed  32 , and have fixed external shapes which are cut out from metal plate material. The wires  28  and  29  are penetrating members made of piano wire or other material which penetrate the needle plates  34  in the longitudinal direction of the needle bed  32 . Metal straps may be employed as the penetrating members. When the selecting jack  22  is sunk within the needle groove  35  in the pressed condition or in the locked condition, the tip thereof pushes down the knitting needle  36  into the needle groove  35 , thereby preventing the knitting needle  36  from performing knitting operation. 
     FIG. 2  illustrates an entire structure of the needle bed  32  of the weft knitting machine  20  including the needle selecting apparatus  21  shown in  FIG. 1 . This figure shows only one of the needle beds  32  opposed to each other with the needle bed gap  37  disposed therebetween in the same manner as in FIG.  13 . The knitting needle  36  is a latch needle having a hook and a latch at the front end of a needle main body  38 . The knitting needle  36  carries out knitting operation when a knitting cam  40  provided on the carriage  33  acts on a butt  39   a  of a needle jack  39 . The needle selecting apparatus  21  selectively separates the butt  39   a  from the knitting cam  40  by pressing the butt  22   a  of the selecting jack  22  using the B presser  27  provided on the carriage  33  or other component to push down the selecting jack  22  and thereby sink the needle jack  39  within the needle groove  35 . The knitting needle  36  may be a needle having stitch transferring function or a composite needle. 
   A sinker apparatus  41  for pushing down a knitting yarn after a stitch is knitted is provided on the needle bed  32  in the vicinity of the tip of the needle bed gap  37 . The sinker apparatus  41  has a movable sinker  42  which is forced by a spring to push down a knitting yarn using a knitting yarn holding hook  42   a  disposed at the tip of the movable sinker  42  in an advancing direction toward the needle bed gap  37 . When the movable sinker  42  is driven, a sinker control cam  44  provided on the carriage  33  guides a butt  43   a  of a sinker jack  43 . The applicant of the invention discloses the structure and action of a weft knitting machine which includes a sinker apparatus having a movable sinker of this type in Japanese Examined Patent Publication JP-B2 5-83657 or others. In this embodiment, it is possible to temporarily raise the knitting yarn holding hook  42   a  of the movable sinker  42  from the needle bed gap  37  so as to retract the knitting needle  36  and tighten a stitch prior to knitting the stitch as disclosed in International Patent Publication WO01/36730. 
     FIG. 3  shows a cam arrangement on a cam carrying surface of the knitting system disposed on the carriage  33  shown in  FIG. 2  in such a position as to be opposed to the needle bed  32 , placing the needle bed gap  37  side shown in  FIG. 2  in the upper part of the figure. As described above, the carriage  33  includes the knitting cam  40 , the selector cams  24 , the sinker control cam  44 , and the B presser  27 . An H presser  45  is provided in H position corresponding to the position of the butt  22   a  when the selecting jack  22  is in the tucking position. As illustrated in  FIG. 2 , the needle selection actuator  25  is actually disposed not on the cam carrying surface of the carriage  33  but in a position opposed to the cam carrying surface and determined such that the needle selection actuator  25  can attract the armature  23   e  of the selector  23  disposed between the needle selection actuator  25  and the carriage  33 . However, the needle selection actuator  25  is shown in a corresponding position by a virtual line for the sake of descriptive convenience. The carriage  33  according to this embodiment is equipped with a plurality of knitting systems. The figure shows a preceding system  47  and a succeeding system  48  as viewed in the shift direction of the carriage  33  from the left to the right as indicated by an arrow  46 . When a needle having stitch transferring function or a composite needle is employed as the knitting needle  36 , a cam for controlling such function is added. Additionally, as long as the initial position can be locked as the non-operative welting position, the cams and the pressers may be changed to alter the number and the type of knitting operation the knitting needle  36  can select in other positions. 
   The knitting cam  40  includes a needle raising cam  50  for advancing the knitting needle  36  toward the needle bed gap  37 , a bridge cam  51  for regulating the advanced condition of the knitting needle  36 , stitch cams  52  and  53  for retracting the knitting needle  36  and other components. The stitch cams  52  and  53  can be displaced in the sloping direction of the sloped cam surface of the needle raising cam  50  while being opposed to the sloped cam surface, and determine a stitch density according to the displacement amount. More specifically, the stitch density is determined by a sloped cam surface of the stitch cam  53  opposed to the needle raising cam  50  on the succeeding side with respect to the needle raising cam  50 . The actions for retracting the knitting needle  36  and tightening a stitch prior to stitch knitting as described above are performed by the stitch cam  52  on the preceding side, that is, a sloped cam surface of the stitch cam  52  on the preceding side with respect to the sloped cam surface opposed to the needle raising cam  50 . The sloped cam surface of the stitch cam  52  is opposed to an upper half cam surface of the guide cam  26 . 
   The succeeding system  48  is herein described, and similar actions are carried out in the preceding system  47  except for the action in the welting position. The butt  39   a  of the needle jack  39  is guided through a cam groove formed between cam surfaces provided on the stitch cams  52  and  53  and the bridge cam  51  and cam surfaces of the needle raising cam  50  and the guide cam  26  along a route indicated by a broken line in the knitting position where the butt  39   a  projects from the needle groove  35  toward the carriage  33 . In H position where the butt  22   a  of the selecting jack  22  is in the tucking position, the butt  39   a  of the needle jack  39  is separated from the knitting cam  40  while the butt  22   a  is being pressed by the H presser  45 . Thus, the butt  39   a  moves along a route indicated by a dotted line and the needle raising cam  50  acts on the butt  39   a  only halfway. 
   In the welting position where the butt  22   a  of the selecting jack  22  is pressed by the B presser  27 , the butt  39   a  travels along a route indicated by an alternate long and short dash line when the preceding system  47  is locked. When the invention is not applied, the butt  39   a  moves along a route indicated by an alternate long and two short dashes line. On the preceding system  47  side, the butt  39   a  also moves along the route indicated by the alternate ling and short dash line when the preceding knitting operation is in the locked condition. More specifically, in the locked condition, the butt  39   a  of the selecting jack  39  remains sunk within the needle groove  35  and does not engage with the cam groove of the knitting cam  40  as long as the welting position continues to be selected in the next knitting system. Accordingly, in the locked condition, it is possible to prevent the stitch cam  52  on the preceding side from retracting the knitting needle  36  in the welting position until any position other than the welting position is selected. 
   The lower half of the guide cam  26  on the preceding side functions as a cam surface for the butt  22   a  of the selecting jack  22 , and compulsorily guides the butt  22   a  to the initial position when the selecting jack  22  exists in the knitting position or the tucking position other than the welting position as the initial position. The lower end position to which the guide cam  26  guides the butt  22   a  is required to coincide with the position where the B presser  27  presses the butt  22   a . The B presser  27  and the H presser  45  have flat pressing surfaces  27   a  and  45   a , respectively, which project from the cam carrying surface toward the needle bed  32  so as to obtain a sufficient amount for pressing the butt  22   a  to sink the butt  39   a  of the needle jack  39  within the needle groove  35 . Sloping surfaces  27   b ,  27   c ,  45   b , and  45   c  which are crosshatched in the figure are provided on the pressing surfaces  27   a  and  45   a , respectively, on both the preceding and succeeding sides to smoothly guide the top of the butt  22   a  to the pressing surfaces of the B presser  27  and the H presser  45 . 
   Each of the selector cams  24  which act on the butts  23   a ,  23   b  and  23   c  of the selector  23  includes selector guide cams  60  and  61 . The selector cams  24  are each positioned in front of the preceding system  47 , between the preceding system  47  and the succeeding system  48 , and behind the succeeding system  48 . That is, the selector cams  24  are provided between the knitting systems and before and after the knitting systems. The preceding side and the succeeding side of the selector cam  24  provided between the knitting systems are symmetrical. The selector cams  24  disposed before and after the knitting systems act on the butts  23   a ,  23   b  and  23   c  in the inner region where the knitting systems are positioned. 
   A cam groove for A position  62  and a cam groove for H position  63  are formed below the selector guide cam  60 . The selector guide cam  61  guides the butt  23   b  of the selecting jack  23  to return the butt  23   b  to the initial position. The armature  23   e  of the selecting jack  23  is magnetically attracted to the needle selection actuator  25 , whereby the butt  23   c  is separated from the selector guide cam  60 . Coil magnetic poles  25   a  and  25   b  of the needle selection actuator  25  are disposed symmetrical with respect to the center so as to release the magnetic attraction. 
   When the coil magnetic pole  25   a  which is on the preceding side when the carriage  33  travels in the direction indicated by the arrow  46  is energized, the butt  23   c  engages with the cam groove for A position  62 . In this condition, the butt  23   c  is guided along the route indicated by the broken line to advance the selector  23  and shift the selecting jack  22  to the knitting position. When the coil magnetic pole  25   a  on the preceding side is not energized but the coil magnetic pole  25   b  on the succeeding side is energized, the butt  23   c  engages with the cam groove for H position  63 . In this condition, the butt  23   c  is guided along the route indicated by the dotted line to advance the selector  23  and shift the selecting jack  22  to the tucking position. When the selecting jack  22  reaches the tucking position, the butt  22   a  is pressed by the H presser  45 . 
   The sinker control cam  44  includes a raising cam  65  for raising the knitting yarn holding hook  42   a  from the needle bed gap  37  at the time of knitting yarn supply and the above-described preceding retraction in knitting operation, a lowering cam  66  for lowering the raised knitting yarn holding hook  42   a  toward the needle bed gap  37 , and a lowering cam  67  for lowering the knitting yarn holding hook  42   a  after knitting operation is finished. The butt  43   a  of the sinker jack  43  is guided to a cam groove formed by the raising cam  65 , the lowering cam  66  and the lowering cam  67 , and is displaced along the route indicated by the alternate long and two short dashes line at the time of traveling in the direction indicated by the arrow  46 . 
     FIGS. 4(   a ) and  4 ( b ) each illustrate the entire needle bed  32 , showing the conditions where the selecting jack  22  of the needle selecting apparatus  21  in the initial position is not pressed and pressed in correspondence with  FIGS. 1(   a ) and  1 ( b ), respectively. In the non-pressed condition shown in  FIG. 4(   a ), the butt  39   a  of the needle jack  39  projects out and the knitting cam  40  acts on the butt  39   a . In the pressed condition shown in  FIG. 4(   b ), the butt  39   a  is sunk within the needle groove  35  whereby the knitting cam  40  does not act on the butt  39   a . Since the locked condition is maintained by means of the locking member  30  according to this embodiment, the condition where the butt  39   a  of the needle jack  39  is sunk within the needle groove  35  continues even after the pressed condition of the butt  22   a  of the selecting jack  22  is released. 
     FIG. 5  illustrates the needle selecting apparatus  21  shown in  FIG. 1 , showing a condition where the selector  23  and the selecting jack  22  are set in the tucking position (H position) by means of the selector cams  24 . The needle selection actuator  25  is selectively driven so that the butt  23   c  of the selector  23  engages with the cam groove for H position  63  of the selector guide cam  60 . Since the locking member  30  is positioned away from the wire  28 , the locking member  30  cannot enter into the space between the wire  28  and the selecting jack  22  even when the butt  22   a  of the selecting jack  22  is pressed from the carriage  33 . Thus, a locked condition is not established. 
     FIGS. 6(   a ) and  6 ( b ) are simplified illustrations each explaining how an enlarged distance between the knitting systems affects the weft knitting machine  20 .  FIG. 6(   a ) shows an example in this embodiment, while  FIG. 6(   b ) shows an example having an enlarged distance between the knitting systems without providing a locking function. A carriage  33 ′ shown in  FIG. 6(   b ) requires a larger distance d′ between the preceding system  47  and the succeeding system  48  than a distance d there between in the carriage  33  shown in  FIG. 6(   a ). Thus, a length L′ of the carriage  33 ′ is larger than a length L of the carriage  33 . When the carriages  33  and  33 ′ knit a knitting area  70  having the same width W, the carriage  33  travels in a range of W+2L in  FIG. 6(   a ) and the carriage  33 ′ travels in a range of W+2L′ in  FIG. 6(   b ). In the carriage  33  according to this embodiment, since the selecting jack  22  is locked in the welting position to sink the butt  39   a  of the knitting needle  36  within the needle groove  35 , the carriage  33  can be made compact and the weight and cost and also the power cost can be decreased. Additionally, since unnecessary actions given to the butt  39   a  such as unnecessary preceding retraction are reduced, undesirable effects on the knitting yarn, the butt  39   a  and others can be decreased. 
     FIGS. 7(   a ) and  7 ( b ) are enlarged views of the locking member  30  shown in  FIG. 1 .  FIG. 7(   a ) is a plan view as viewed from above in  FIG. 1 , while  FIG. 7(   b ) is a side view as viewed from the front in  FIG. 1 . The locking member  30  is a plate component made of an elastic material such as a metal plate having a thickness similar to that of the selecting jack  22 , and has a forked engaging portion  30   a  and a fitting portion  30   b . The fitting portion  30   b  can enter into a space between the wire  28  and the selecting jack  22  on the carriage side there of, which space is produced by pressing the selecting jack  22  in the welting position. A holding member  30   c  is formed in the intermediate position between the engaging portion  30   a  and the fitting portion  30   b.    
     FIGS. 8(   a ) and  8 ( b ) are enlarged views each partially illustrating the shape and the structure of the thin-wall portion  22   f  of the selecting jack  22  to which the locking member  30  is attachable.  FIG. 8(   a ) is a plan view corresponding to  FIG. 7(   a ), while  FIG. 8(   b ) is a side view corresponding to  FIG. 7(   b ) The selecting jack  22  has the thin-wall portion  22   f  which is disposed in the vicinity of the penetrating member such as the wire  28  and faces the penetrating member in the initial position. The thin-wall portion  22   f  has a thickness which decreases on both sides of the selecting jack  22  in the plate thickness direction. The thin-wall portion  22   f  has a notch  22   g  near the wire  28  as to retain the holding member  30   c  shown in  FIG. 7 . The thin-wall portion  22   f  also has a concave portion  22   h  at the center of the thin-wall portion  22   f  so as to accommodate the spring  31 . The thin-wall portion  22   f  and the notch  22   g  are so formed as to switch between the condition where the locking member  30  compresses the spring  31  and is pushed against the front components as shown in  FIG. 1(   a ) and the locked condition where the locking member  30  projects toward the rear region by the spring force of the spring  31  as shown in  FIG. 1(   b ) when the locking member  30  is attached. 
     FIGS. 9(   a ) and  9 ( b ) are cross sectional views each schematically illustrating a structure of a needle selecting apparatus included in a weft knitting machine according to a second embodiment of the invention. In a needle selecting apparatus  71  according to this embodiment, a selecting jack  72  can be locked to maintain a pressed condition in the initial position where no knitting operation is performed, similarly to the preceding embodiment.  FIG. 9(   a ) shows a condition where the selecting jack  72  in the initial position as the welting position is not pressed, while  FIG. 9(   b ) shows a condition where the selecting jack  72  is pressed. The needle selecting apparatus  71  has a selector  73  for shifting the selecting jack  72 . The selector  73  has a plurality of butts  73   a ,  73   b  and  73   c . The actions of the selector cams  24  given to the butts  73   a ,  73   b  and  73   c  so as to drive the selector are basically the same as those in the needle selecting apparatus  21  in  FIGS. 1(   a ) and  1 ( b ). A tip  73   d  of the selector  73  contacts the butt  72   a  of the selecting jack  72  to advance the selecting jack  72 . An armature  73   e  disposed near the rear end of the selector  73  contacts the needle selection actuator  25  and is magnetically attracted thereto when the selector cams  24  press the butt  73   c . Concave portions  72   b ,  72   c  and  72   d  are also provided such that the selecting jack  72  engages with and positions the wire  29  in the same manner as in the needle selecting apparatus  21  shown in  FIGS. 1(   a ) and  1 ( b ). 
   The selecting jack  72  according to this embodiment has a groove  72   e  which is disposed in the vicinity of the tip of the selecting jack  72  and faces the wire  28  in the initial position. A locking member  75  is inserted in to the groove  72   e  and is movable forward and backward with in the groove  72   e . The locking member  75  is a plate component made of an elastic material such as a metal plate. An engaging portion  75   a  as the front half of the locking member  75  is inserted into the groove  72   e , and a fitting portion  75   b  as the rear half of the locking member  75  projects from an opening of the groove  72   e  toward the wire  28 . 
     FIG. 10(   a ) is a side view illustrating the shape of the locking member  75 , while  FIG. 10(   b ) is a side view partially illustrating the shape of the selecting jack  72  around the groove  72   e . As illustrated in  FIG. 10(   a ), the locking member  75  has the engaging portion  75   a  as the front half and the fitting portion  75   b  as the rear half. The engaging portion  75   a  is forked at the tip, and has a smaller width at the base end in the vertical direction. The fitting portion  75   b  is formed next to the base end of the engaging portion  75   a  having the smaller width. As illustrated in  FIG. 10(   b ), the groove  72   e  of the selecting jack  72  is substantially U-shaped, and has an opening  72   f  which has a smaller width. The groove  72   e  includes the opening  72   f , a parallel portion  72   g  which has a constant and larger width than that of the opening  72   f , and a sloping portion  72   h  which is formed next to the parallel portion  72   g  and has a smaller width. 
   In the locking member  75  according to this embodiment, the forked tip of the engaging portion  75   a  receives resilient force when the locking member  75  curves along the sloping portion  72   h  of the groove  72   e , and is forced toward a direction where the locking member projects from the groove  72   e . More specifically, the shape of the locking member  75  itself allows the fitting portion  75   b  to project out in to the locked condition as shown in  FIG. 10(   b ) in cooperation with the sloping portion  72   h  of the groove  72   e . The selecting jack  72  and the locking member  75  are accommodated within the needle groove  35  formed between the needle plates  34 . Since the selecting jack  72  and the locking member  75  are sandwiched between the needle plates  34  from both sides in the plate thickness direction, the selecting jack  72  and the locking member  75  do not come off in the plate thickness direction as long as the difference between the width and the thickness of the needle groove  35  is not too large. Since the width of the engaging portion  75   a  of the locking member  75  is larger than the width of the opening  72   f  of the groove  72   e  of the selecting jack  72 , the engaging portion  75   a  is regulated to separate from the groove  72   e  toward the opening  72   f.    
     FIGS. 11(   a ) and  11 ( b ) are cross-sectional views each schematically illustrating a structure of a needle selecting apparatus included in a weft knitting machine according to a third embodiment of the invention. In a needle selecting apparatus  81  according to this embodiment, a selecting jack  82  can be locked to maintain a pressed condition in the initial position where no knitting operation is performed, similarly to the preceding embodiments.  FIG. 11(   a ) shows a condition where the selecting jack  82  in the initial position as the welting position is not pressed, while  FIG. 11(   b ) shows a condition where the selecting jack  82  is pressed. The needle selecting apparatus  81  has a selector  83  for shifting the selecting jack  82 . The selector  83  has a plurality of butts  83   a ,  83   b  and  83   c . The actions of the selector cams  24  given to the butts  83   a ,  83   b  and  83   c  so as to drive the selector  83  are basically the same as those in the needle selecting apparatus  21  in  FIG. 1 . A tip  83   d  of the selector  83  contacts the butt  82   a  of the selecting jack  82  to advance the selecting jack  82 , and an armature  83   e  disposed near the rear end of the selector  83  contacts the needle selection actuator  25  and is magnetically attracted there to when the selector cams  24  press the butt  83   c , in the same manner as in the embodiment shown in  FIG. 9 . Concave portions  82   b ,  82   c  and  82   d  are also provided such that the selecting jack  82  engages with and positions the wire  29  in the same manner as in the needle selecting apparatus  21  shown in  FIGS. 1(   a ) and  1 ( b ). 
   A needle plate  84  according to this embodiment has a holding concave portion  86  in a position corresponding to a wall surface of a needle groove  85  between the wire  28  and the butt  82   a  when the selecting jack  82  is in the initial position. An attaching concave portion  82   e  to which a plate spring  88  as a locking member is attached is formed on the selecting jack  82 . 
     FIGS. 12(   a ) and  12 ( b ) each illustrate a shape of the plate spring  88 .  FIG. 12(   a ) is a plan view and  FIG. 12(   b ) is a side view of the plate spring  88 . In the plan view of  FIG. 12(   a ), the selecting jack  82  is also shown by a virtual line. The plate spring  88  has a folded tip  88   a  and a flat base end  88   b . The base end  88   b  is attached to the attaching concave portion  82   e  of the selecting jack  82 . The tip  88   a  projects from the attaching concave portion  82   e  toward the side of the selecting jack  82  when external force is not applied. The tip  88   a  is pressed against the side of the needle plate  84  as a wall surface except for the portion where the holding concave portion  86  is formed within the needle groove  85 , whereby the tip  88   a  is pressed into the attaching concave portion  82   e.    
   As illustrated in  FIG. 11(   b ), when the butt  82   a  of the needle jack  82  is pressed from the carriage  33 , the tip  88   a  of the plate spring  88  engages with a step formed by the side of the needle plate  84  and the holding concave portion  86  so as to maintain the locked condition. The holding concave portion  86  has a sufficient space for accommodating the tip  88   a  of the plate spring  88  to which no load is applied. However, in positions other than the locked position, the selecting jack  82  needs to freely move in the needle groove  85  without receiving more than necessary sliding load. When the selector  83  is shifted to the tucking position or the knitting position, the tip  88   a  of the plate spring  88  is separated from the step of the holding concave portion  86  to release the locked condition. When the tip  88   a  is pressed against the side of the needle plate  84  and pushed into the attaching concave portion  82   e  of the selecting jack  82 , the selecting jack  82  can freely move within the needle groove  85 . During unlocked condition, the locked condition is not established only by returning the selecting jack  82  to the welting position as the initial position as shown in  FIG. 12(   a ). 
   The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and the range of equivalency of the claims are therefore intended to be embraced therein. 
   INDUSTRIAL APPLICABILITY 
   According to the invention as described above, when an initial position of a selecting jack which is shifted by a selector within a needle groove is established in a position where no knitting operation is performed and the selecting jack is pressed from a carriage, a locking member is fitted to a space between the selecting jack and a holding member which is formed in a predetermined position in the vicinity of the selecting jack in the initial position with at a distance from the selecting jack so as to maintain the pressed condition of the selecting jack by means of the locking member inserted between the holding member and the selecting jack. Accordingly, the needle selection position can be locked without advancing and retracting the selecting jack. Since a butt of a knitting needle is separated from a cam mechanism of the carriage while the pressed condition of the selecting jack is maintained, knitting operation is not performed. When the selecting jack is shifted to a position other than the non-operative position by a selector, the locking member separates from the space to release the pressed condition of the selecting jack. Thus, the action of the cam mechanism given to the butt of the knitting needle can be controlled by pressing the selecting jack via a presser provided on the carriage in accordance with types of knitting operation. Since the initial position of the selecting jack corresponds to the non-operative position for the knitting needle, the locking member does not require the selector and the selecting jack to be shifted as long as the cam mechanism of the carriage is continuously in the non-operative condition while passing through the knitting needle. As a result, abrasion and damage caused by the shifting and the power cost can be reduced. 
   According to the invention, the holding member is formed by a penetrating member which contacts the selecting jack on the side facing the carriage in each needle groove to retain the selecting jack within the needle groove, and the locking member which is forced by a spring is fitted to a space between the selecting jack and the penetrating member by pressing the selecting jack from the carriage. Accordingly, the pressed condition of the selecting jack from the carriage can be transferred to the pressed condition of the selecting jack from the holding member via the locking member so as to maintain the pressed condition of the selecting jack. When the selecting jack is shifted from the non-operative initial position to other positions corresponding to other types of knitting operation, the locking member separates from the space and the pressed condition is released. Thus, knitting needle can be controlled by selecting the pressed condition of the selecting jack in accordance with the types of knitting operation. 
   According to the invention, the selecting jack has a thin-wall portion which has a smaller thickness on both sides in the plate thickness direction and is disposed in the vicinity of the penetrating member and faces the penetrating member in the initial position. A forked engaging portion of the locking member receives the thin-wall portion from both sides in the thickness direction and a fitting portion of the locking member is allowed to enter into the space between the penetrating member and the selecting jack on the side facing the carriage. Thus, the locking member can be disposed within the small space between the selecting jack and the penetrating member in the needle groove. Since a spring for forcing the locking member so as to cause the fitting portion to enter into the space is provided between the thin-wall portion of the selecting jack and the engaging portion of the locking member, the fitting portion of the locking member can be caused to enter into the space to maintain a pressed condition when the selecting jack in the initial position is pressed from the carriage. 
   According to the invention, the selecting jack has a substantially U-shaped cut portion which is open at a position which is in the vicinity of the penetrating member and faces the penetrating member in the initial position. The cut portion of the selecting jack has a smaller width at the opening. The locking member has a forked engaging portion which is inserted into the cut portion and pressed from both sides of the cut portion to be forced toward the penetrating member, and a fitting portion which is allowed to enter into the space between the penetrating member and the selecting jack on the side facing the carriage. Thus, the fitting portion of the locking member can be caused to enter into the space to maintain the pressed condition when the selecting jack in the initial position is pressed from the carriage. 
   According to the invention, a concave portion as a holding member is formed on the side of the selecting jack within each needle groove. A locking member provided on the side surface of the selecting jack is a plate spring having a tip which projects to the side by force and is fitted to the concave portion so as to prevent the selecting jack from being displaced toward the carriage. Thus, the pressed condition can be maintained. The pressed condition is released when the selecting jack is shifted to a position other than the initial position. Accordingly, the knitting needle can be controlled by selecting the pressed condition of the selecting jack in accordance with the types of knitting operation. 
   According to the invention, the cam mechanism of the carriage has a function for retracting a knitting needle whose butt is not separated from the cam mechanism before the cam mechanism acts on the butt of the knitting needle to selectively perform a plurality of knitting operations. Thus, preceding retraction for tightening a stitch or other actions can be carried out in cooperation with a sinker apparatus. Since the pressed condition of the selecting jack is maintained by means of the locking member for the knitting needle in the non-operative position, the butt of the knitting needle is kept separated from the can mechanism until the pressed condition is released so as to prevent preceding retraction or other actions from being executed. It is also possible to avoid undesirable effects on a knitting yarn during knitting operation such as wearing and cutting of yarn caused by drawing a knitting yarn through the knitting needle every time the cam mechanism of the carriage passes through the knitting needle in the position where no operation is to be performed.