Patent Publication Number: US-6668595-B2

Title: Weft knitting machine with transfer mechanism

Description:
TECHNICAL FIELD 
     The present invention relates to a flat knitting machine with transfer mechanism comprising a transfer jack bed (hereinafter it is referred to as “TR jack bed”) in which a number of transfer jacks (hereinafter they are referred to as “TR jack”) each having a loop retaining portion at a front end thereof are embedded and which is arranged over needle beds, and a transfer cam mechanism for transferring the loop between the TR jacks of the TR jack bed and the knitting needles of the needle beds. 
     BACKGROUND ART 
     A flat knitting machine comprising a pair of front and back needle beds holding knitting needles in such a manner as to be advanced and retracted in needle grooves formed on upper surfaces of the needle beds, at least either of which is racked horizontally with respect to the opposite needle bed, and at least one transfer jack bed located over the at least one needle bed and holding transfer jacks in such a manner as to freely advance and retract in the grooves formed on an upper surface thereof is known from Japanese Patent No. 2794144. In the flat knitting machine disclosed by this publication, the TR jack bed and the needle beds are structured so that they can be racked longitudinally relative to each other to transfer a loop between the knitting needles of the front and back needle beds and between the knitting needle of the needle bed and the TR jack of the TR jack bed. The flat knitting machine thus structured enables a loop retained by the knitting needle of the needle bed to be transferred to an adjacent needle of the same needle bed by transferring the loop retained by the knitting needle of the needle bed to the TR jack of the TR jack bed, first; then racking the TR jack bed; and then transferring the loop retained by the TR jack to the adjacent needle of the needle bed. 
     Japanese Laid-open (Unexamined) Patent Publication No. Hei 11 (1999)-1850 discloses a flat knitting machine with a transfer mechanism which is structured so that when a loop retaining portion of the TR jack is retracted across a loop retained on the TR jack to transfer the loop to a knitting needle, the TR jack can be retracted while keeping its front end in the depressed state. 
     In the flat knitting machine disclosed by the publication of Japanese Patent No. 2794144 cited above, the TR jack is advanced and retracted linearly in the horizontal direction on a level higher than a front end of the needle bed. Due to this, when the loop retained on the TR jack is transferred to the knitting needle, the loop is stretched and elongated to deteriorate the quality of the knitted fabric. 
     To solve this problem involved in the publication of Japanese Patent No. 2794144, the flat knitting machine disclosed in Japanese Laid-open (Unexamined) Patent Publication No. Hei 11 (1999)-1850 is structured so that when the loop retaining portion of the TR jack is retracted across the loop retained on the TR jack to transfer the loop to the knitting needle, the TR jack can be retracted, while keeping its front end in the depressed state, to reduce the load on the loop. 
     However, both of the flat knitting machines disclosed by the publications cited above are structured so that when the TR jack is in its advanced position over the needle bed gap between the needle beds, the TR jack can be positioned on a level higher than the front ends of the needle beds, in order to avoid interference with the knitting needle and the sinker plate on the needle bed when racked. In this structure, the loop retaining portion at the front end of the TR jack cannot be swung vertically in the advanced position of the TR jack. Due to this, a load is put on the loop retained on the loop retaining portion of the TR jack in the advanced position of the TR jack. 
     In the light of the problems mentioned above, the present invention has been made. It is an object of the invention to provide a flat knitting machine with a transfer mechanism wherein when the loop retaining portion of the TR jack is in its advanced position, the loop retaining position of the TR jack can be held in its raised position or released therefrom in a selective manner and also can be lowered an increased distance to further reduce the load on the loop. 
     DISCLOSURE OF THE INVENTION 
     The present invention provides a flat knitting machine with a loop transfer mechanism comprising a pair of front and back needle beds, arranged in a confronting relation and holding knitting needles in such a manner as to freely advance and retract in grooves formed in upper surfaces of the needle beds, at least one of which is racked relative to the opposite needle bed, and at least one transfer jack bed, provided over the at least one needle bed and holding transfer, jacks, each having a loop retaining portion at a front end portion thereof, in such a manner as to freely advance and retract in grooves formed in upper surface of the at least one transfer jack bed, 
     wherein the transfer jack is structured so that when the loop retaining portion is advanced to an advanced position over a needle bed gap between the front and back needle beds, the loop retaining portion can be held in such a manner as to swing between its raised position and its lowered position; 
     wherein there is provided transfer jack holding means for holding the loop retaining portion in its raised position at least as high as a level to avoid interference with knitting members arranged on the needle beds while the needle bed is racked, when the loop retaining portion of the transfer jack retaining a loop thereon is in the advanced position; and 
     wherein there is provided transfer jack controlling means for controlling the transfer jack holding means to selectively hold the loop retaining portion of the transfer jack in its raised position and release it from its held state. 
     wherein the transfer jack holding means includes a transfer jack controlling member which is fitted in a recess formed in the transfer jack bed in a freely advance-and-retract manner; 
     wherein the transfer jack controlling member and the transfer jack are brought into engagement with each other by their relative movement in the advancing-and-retracting direction, whereby the loop retaining portion of the transfer jack is held in its raised position when the loop retaining portion is in its advanced position; and 
     wherein when the loop retaining portion is in the advanced position, the transfer jack controlling member is moved to release the engagement between the transfer jack controlling member and the transfer jack, so as to allow the loop retaining portion of the transfer jack to be lowered. 
     It is preferable that the recess is formed on a top surface of the transfer jack and the transfer jack controlling member is slidably fitted in the recess; wherein the recess has an engaging portion, formed at a bottom of the recess at a rear end portion thereof, to engage with a rear end portion of the transfer jack controlling member; wherein a notch for the rear end portion of the transfer jack controlling member to be inserted into so as to allow the transfer jack to swing is formed in the bottom of the recess at a location forward of the engaging portion; and wherein the transfer jack controlling means puts the transfer jack controlling member in a location at a rear of the recess to bring the transfer jack and the transfer jack controlling member into engagement with each other and puts the transfer jack controlling member in a location at a front of the recess to release the engagement between the transfer jack and the transfer jack controlling member. 
     It is preferable that the transfer jack holding means includes a transfer jack controlling member which is fitted in a recess formed in the transfer jack bed in a freely advance-and-retract manner; wherein the transfer jack controlling member and the transfer jack are brought into engagement with each other by their relative movement in the advancing-and-retracting direction, whereby the loop retaining portion of the transfer jack is held in its raised position when the loop retaining portion is in its advanced position; and wherein when the loop retaining portion is in the advanced position, the transfer jack controlling member is moved to release the engagement between the transfer jack controlling member and the transfer jack, so as to allow the loop retaining portion of the transfer jack to be lowered. 
     It is preferable that the recess is formed on a top surface of the transfer jack and the transfer jack controlling member is slidably fitted in the recess; wherein the recess has an engaging portion, formed at a bottom of the recess at a rear end portion thereof, to engage with a rear end portion of the transfer jack controlling member; wherein a notch for the rear end portion of the transfer jack controlling member to be inserted into so as to allow the transfer jack to swing is formed in the bottom of the recess at a location forward of the engaging portion; and wherein the transfer jack controlling means puts the transfer jack controlling member in a location at a rear of the recess to bring the transfer jack and the transfer jack controlling member into engagement with each other and puts the transfer jack controlling member in a location at a front of the recess to release the engagement between the transfer jack and the transfer jack controlling member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a vertical sectional view of a flat knitting machine with a transfer mechanism according to an embodiment of the present invention. 
     FIG. 2 is a partly enlarged view of FIG.  1 . 
     FIG. 3 is a side elevation view of a TR jack and a TR jack controlling member. 
     FIG. 4 is a perspective view of a TR jack control cam operated when the loop is transferred from a knitting needle to the TR jack. 
     FIG. 5 shows the TR jack, the TR jack controlling member and the knitting needle when the TR jack and the TR jack controlling member are in the positions A-D of FIG.  4 . 
     FIG. 6 is a perspective view of the TR jack control cam operated when the loop is transferred from the TR jack to the knitting needle. 
     FIG. 7 shows the TR jack, the TR jack controlling member and the knitting needle when the TR jack and the TR jack controlling member are in the positions E-H of FIG.  6 . 
     FIG. 8 shows the second embodiment of the invention. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     In the following, certain preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a vertical sectional view of a flat knitting machine and reference numeral  1  denotes the entirety of the flat knitting machine. FIG. 2 is a partly enlarged view of FIG.  1 . FIG. 3 is a side elevation view of a TR jack and a transfer jack controlling member (hereinafter it is referred to as “TR jack” controlling member). FIG. 4 is a perspective view of a group of TR jack control cams. 
     The flat knitting machine  1  comprises a pair of front and back needle beds  2   a,    2   b  arranged in an inversed V shape with their front ends confronting each other and a TR jack bed  8  placed over the front needle bed  2   a  (hereinafter it is simply referred to as the front bed) and holding TR jacks  6  in TR jack grooves  4  formed in an upper surface of the TR jack bed. The TR jack bed  8  is so structured as to be racked in a longitudinal direction of the needle beds  2   a,    2   b  by drive means, not shown. The needle beds  2   a,    2   b  are provided with needle plates  12  standing in the grooves formed on a needle bed base plate  10 . Needle grooves  14  are formed between the adjacent needle plates  12 ,  12 , and the knitting needles  16   a,    16   a  are held in the needle grooves  14  in such a manner as to be advanced toward a center line W-W of a needle bed gap between the front and back needle beds  2   a,    2   b  and retracted therefrom. The front bed  2   a  and the back needle bed  2   b  (hereinafter it is simply referred to as the back bed) are so structured as to be racked in the longitudinal direction of the needle bed  2   a,    2   b  by means of drive means, not shown. 
     In the illustration, the flat knitting machine uses slide needles. Each slide needle is structured so that a hook  34  of a knitting needle  16  placed in the needle groove  14  is opened and closed by a butt, not shown, of a needle jack  24  having a protrusion  22  to be engaged with a recess  20  formed at the rear end of the needle  16  and a butt  28  of a slider  26  being advanced and retracted via cams  32   a,    32   b  on a pair of front and back carriages  30   a,    30   b  which are moved in reciprocation by driving means, not shown. 
     The slider  26  is formed by two thin plates being combined in an overlapped relation. When the slider  26  is advanced toward the hook  34  of the needle  16 , front end portions of the slider  26  are spread out by the hook  34  of the needle  16  to form a loop transfer space in a loop  36 . The loop  36  is retained on a shoulder portion  38  of the spread-out slider  26  and is raised up to the loop transfer position. The knitting needle  16  is held in the needle groove  14  via a band  40  fitted therein in the longitudinal direction of the needle bed  2 . The needle jack  24  is placed in the needle groove  14 , together with a select jack and a selector, not shown, and is so structured that when pressed by a presser of the carriage  30  in the direction of being sunk into the needle groove  14 , the needle jack  24  causes the butt to move down to a disengaged position from the cam on the carriage  30 . 
     Fixed sinkers  44   a,    44   b  are provided between the adjacent needles  16 ,  16  at the needle bed gap  42  between the front and back needle beds  2   a,    2   b.  The TR jack bed  8  has the supporting portions formed by upwardly extended portions  46  of the needle plates  12  placed at a specified distance in the front bed  2   a.  The TR jack bed  8  holds the TR jacks  6  in the TR jack grooves  4  formed at the same pitch as the pitch of the needle grooves  14  in the needle bed  2   a.  Each of the TR jacks  6  has a loop retaining portion  48  formed at a front end thereof and needle selecting butts  50   a,    50   b  formed at a rear end thereof. The TR jack  6  is pressed against a side wall of the TR jack groove  4  by a bending portion  52 , to prevent the rash action. 
     The TR jack  6  has, on the top surface, an advancing-and-retracting motion controlling butt  54  having front and back surfaces to abut with the cam on the carriage  30   a;  a clearing cam acting portion  56  provided at a front end portion of the TR jack  6 ; and the bending portion  52  arranged therebetween. Also, the TR jack  6  has, on a bottom surface thereof, an inclined surface  58  which becomes gradually higher toward the front end and has a configuration to allow the TR jack  6  to swing around a virtual axis  60 . 
     The TR jack  6  has a recess  62  formed between the advancing-and-retracting motion controlling butt  54  and the clearing cam acting portion  56 . The recess  62  has an engaging surface  68 , formed on a bottom thereof, to engage with a rear end portion  66  of the TR jack controlling member  64  as mentioned later. The recess  62  has a notch  70  formed in the engaging surface  68 . The notch  70  has an inclined surface which becomes gradually higher toward the front end, extending from a location forward of the engaging surface  68  and lower than a plane of the bottom of the recess  62  to a location over the virtual axis  60 , so that when the TR jack  6  swings around the virtual axis  60 , the rear end portion  66  of the TR jack controlling member  64  can be received in the notch  70 . 
     Also, the TR jack  6  has a protrusion  72  formed at the bottom. When the TR jack  6  is retracted, the protrusion  72  is brought into abutment with the TR jack bed  8  and pushes the loop retaining portion  48  of the TR jack  6  up to its raised position. 
     The TR jack controlling member  64  is slidably fitted in the recess  62  formed between the advancing-and-retracting motion controlling butt  54  and the clearing cam acting portion  56 . The TR jack controlling member  64  has, on the top at a front end portion thereof, an advancing-and-retracting motion controlling butt  74  having front and rear surfaces with which the cam mounted on the carriage  30   a  is abutted. The TR jack controlling member  64  has a bending portion  76  which is formed between the rear end portion  66  and the advancing-and-retracting motion controlling butt  74  to press the TR jack controlling member  64  against the side wall of the TR jack groove  4 , so as to prevent the rash action. 
     The TR jack  6  and the TR jack controlling member  64  are held in the TR jack groove  4  by a band  78  fitted therein in the longitudinal direction of the TR jack bed  8 . When the rear end portion  66  of the TR jack controlling member  64  rides on the engaging surface  68  of the TR jack  6 , the TR jack  6  and the TR jack controlling member  64  are brought into engagement with each other and the TR jack  6  is held down from above by the band  78  through the TR jack controlling member  64 . As a result of this, the swinging motion of the TR jack  6  is suppressed and the TR jack  6  holds the loop retaining portion  48  in its raised position. 
     When the TR jack  6  is in the advanced position where the protrusion  72  of the TR jack  6  is not abutted with the TR jack bed  8 , the TR jack controlling member  64  is moved to release the riding relation or the engagement between the engaging surface  68  of the TR jack  6  and the rear end portion  66  of the TR jack controlling member  64 . Then, the gap by the notch  70  is left between the TR jack  6  and the rear end portion  66  of the TR jack controlling member  64 . The gap thus formed and the inclined surface  58  formed on the bottom of the TR jack  6  enable the TR jack  6  to swing around the virtual axis  60 . 
     Two different groups of TR jacks  6 , on which the needle selection butt  50   a,    50   b  are formed at different positions, respectively, are arranged alternately every one inch on the TR jack bed  8 . The TR jacks  6  selected by needle selection actuator  80   a,    80   b  disposed in different phases of the carriage  30  with respect to the moving direction of the carriage  30  are advanced toward and retracted from the needle bed gap  42 . 
     TR jack control cams  82  mounted on the carriages  30   a  comprise a first cam group  84  and a second cam group  86 . The first cam group  84  acts on the advancing-and-retracting motion controlling butt  54  of the TR jack  6 , and the second cam group  86  acts on the advancing-and-retracting motion controlling butt  74  of the TR jack controlling member  64  and the clearing cam acting portion  56  of the TR jack  6 . 
     The first cam group  84  comprises guide cams  88 ,  90 , and the second cam group  86  comprises guide cams  92 ,  94 ,  96  and a clearing cam  98  to act on the cam operating portion  56 . 
     In the illustrated embodiment, a track for the advancing-and-retracting motion controlling butt  54  of the TR jack  6  selected to be in its advanced position and a track for the advancing-and-retracting motion controlling butt  74  of the TR jack controlling member  64  selected to be in its advanced position are formed to be different from each other. 
     In the illustrated embodiment, movable guide cams, such as retractable guide cams, may be used in place of the fixed guide cams  88 ,  90 ,  92 ,  94 ,  96  mounted on the carriages  30   a.    
     Needle selection actuators  80   a,    80   b  each have an acting surface  100   a,    100   b  which is high at a center portion thereof and low at both ends thereof with respect to the moving direction of the carriage  30   a.  When the TR jacks  6  used for the loop transfer pass through the needle selection actuators  80   a,    80   b,  the needle selection actuators are shifted from the inoperative position to the operative position, so that the needle selection butts  50   a,    50   b  are pushed out forward by the acting surfaces  100   a,    100   b.  When the TR jacks  6  unused for the loop transfer pass through the needle selection actuators, the needle selection actuators  80   a,    80   b  are held in their inoperative positions to prevent those TR jacks  6  from being advanced. 
     In the following, description will be given on operation in the knitting process wherein the loop  36  retained on the knitting needle  16   b  of the back bed  2   b  is transferred to the TR jack  6 , first, and, then, after the back bed  2   b  is racked, the loop as was transferred to the TR jack is transferred to an adjacent knitting needle  16   b  of the back bed  2   b.    
     With reference to FIGS. 4 and 5, the loop transfer from the knitting needle  16   b  of the back bed  2   b  to the TR jack  6  will be described. 
     FIG. 5 A-D show the relations among the TR jack  6 , the TR jack controlling member  64  and the knitting needle  16   b  when the advancing-and-retracting motion controlling butt  54  of the TR jack  6  and the advancing-and-retracting motion controlling butt  74  of the TR jack controlling member  64  are in the positions A-D in FIG.  4 . The arrow X of FIG. 4 indicates the traveling direction of the carriage  30   a.  The advancing-and-retracting motion controlling butt  54  of the TR jack  6  and the advancing-and-retracting motion controlling butt  74  of the TR jack controlling member  64  are traveled from left to right. 
     In FIG. 4, the advancing-and-retracting motion controlling butt  54  of the TR jack  6  selected to be in the advanced position in order to transfer the loop from the knitting needle  16   b  of the back bed  2   b  to the TR jack is moved along the track “a” and the advancing-and-retracting motion controlling butt  74  of the TR jack controlling member  64  selected is moved along the track “b”. The advancing-and-retracting motion controlling butt  54  of the TR jack  6  unselected to be in the advanced position is moved along the track “c” and the advancing-and-retracting motion controlling butt  74  of the TR jack controlling member  64  unselected is moved along the track “b”. 
     The TR jacks  6  and the TR jack controlling member  64  are moved from left to right in the course where the loop is transferred. When the TR jacks  6  and the TR jack controlling member  64  are moved up to the position A of FIG. 4, the needle selection actuator  80   a  is shifted from the inoperative position to the operative position, in order to advance the TR jack  6  to receive the loop  36 . 
     When the TR jack  6  and the TR jack controlling member  64  are moved up to the position B, the knitting needle  16   b  of the back bed  2   b  from which the loop  36  is transferred is raised up to the loop transfer position, after the loop  36  goes, out of the hook  34  of the knitting needle  16   b  and is retained on the shoulder  38  of the slider  26 . The TR jack  6  to which the loop  36  is transferred starts advancing toward the needle bed gap  42 , after the needle selection butts  50   a  of the selected TR jack  6  are abutted with the acting surfaces  100   a  of the needle selection actuators  80   a.    
     As a result of the TR jack  6  being advanced by the needle selection actuators  80   a,  the rear end portion  66  of the TR jack controlling member  64  rides on the engaging surface  68  in the recess  62  formed in the TR jack  6 , as shown in FIG. 5-B, bringing the TR jack  6  into engagement with the TR jack controlling member  64 . 
     In the position C, the TR jack  6  is further advanced toward the needle bed gap  42  by the guide cam  90 . In parallel with this, the TR jack controlling member  64  located in the recess  62  of the TR jack  6  is also moved toward the needle bed gap by the advance of the TR jack  6 . Also, the slider  26  retaining the loop  36  on its shoulder  38  is further raised to place the loop  36  in position on the center line W-W of the needle bed gap. 
     In the positions A-C, since the protrusion  72  formed at the bottom of the TR jack  6  is in abutment with the TR jack bed  8  and also the rear end portion  66  of the TR jack controlling member  64  rides on the engaging surface  68  of the TR jack  6 , the TR jack  6  holds the loop retaining portion  48  in the raised position, without swinging around the virtual axis  60 . 
     In the position D, the loop retaining potion  48  of the TR jack  6  is advanced to its advanced position and goes into the loop  36  retained on the slider  26 . In the position D, although the TR jack  6  is put in the advanced position where the protrusion  72  of the TR jack  6  is not in abutment with the TR jack bed  8 , since the rear end portion  66  of the TR jack controlling member  64  is in the position to ride on the engaging surface  68  of the TR jack  6  and thereby the TR jack  6  and the TR jack controlling member  64  are in engagement with each other, the TR jack  6  holds the loop retaining portion  48  in the raised position, without swinging. Then, the knitting needle  16   b  is moved downwards, to transfer the loop  36  from the knitting needle  16   b  to the TR jack  6 . Then, the carriages  30   a,    30   b  pass, with the loop retaining portion  48  of the TR jack  6  receiving the loop  36  thereon kept in its raised position. This state is kept unchanged even after the passage of the carriages  30   a,    30   b.  Then, the back bed  2   b  is racked. Since the loop retaining portion  48  of the TR jack  6  is held in its raised position during the racking of the back bed, the loop retaining portion  48  is prevented from being interfered with the knitting members such as the sinker plates  44   a,    44   b  and the knitting needles  16   a,    16   b.    
     Next, with reference to FIGS. 6 and 7, the loop transfer from the TR jack  6  to the knitting needle  16   b  of the back bed  2   b  will be described. FIG. 6 is a perspective view of the TR jack control cam  82 . FIG.  7 -E-H shows the relations among the TR jack  6 , the TR jack controlling member  64  and the knitting needle  16   b  when the advancing-and-retracting motion controlling butt  54  of the TR jack  6  and the advancing-and-retracting motion controlling butt  74  of the TR jack controlling member  64  are in the positions E-H of FIG.  6 . The arrow Y of FIG. 6 indicates the traveling direction of the carriage  30   a.  The advancing-and-retracting motion controlling butt  54  of the TR jack  6  and the advancing-and-retracting motion controlling butt  74  of the TR jack controlling member  64  are traveled from right to left. In FIG. 6, the advancing-and-retracting motion controlling butt  54  of the TR jack  6  selected to be in the advanced position in order to transfer the loop from the knitting needle  16   b  of the back bed  2   b  to the TR jack is moved along the track “e” and the advancing-and-retracting motion controlling butt  74  of the TR jack controlling member  64  selected is moved along the track “f”. 
     After the completion of the loop transfer from the knitting needle  16   b  of the back bed  2   b  to the TR jack  6  and the racking of the back bed  2   b,  the carriage  30   a  is reversed and starts traveling in the direction indicated by the arrow Y. When the TR jack  6  is moved up to the position E of FIG. 6, the knitting needle  16   b  to receive the loop  36  is advanced, so that the hook  34  of the knitting needle  16   b  is advanced into the loop  36 . At this time, the TR jack  16  and the TR jack controlling member  64  are in engagement with each other, so that the loop retaining portion  48  is held in its raised position. 
     In the position F, the TR jack controlling member  64  is further moved toward the needle bed gap by the guide cam  94 . As a result of this, the rear end portion  66  of the TR jack controlling member  64  is moved away from the engaging surface  68  of the TR jack  6 , so that the engagement between the TR jack  6  and the TR jack controlling member  64  is released. Then, the clearing cam  98  mounted on the second cam group  86  of the TR jack control cam  82  acts on the clearing cam action portion  56  of the TR jack  6  to force the TR jack  6  to swing around the virtual axis  60 , so as to lower down the loop retaining portion  48  to its lowered position. At this swinging motion of the TR jack  6 , the rear end portion  66  of the TR jack controlling member  64  is slotted into the notch  70  formed in the recess  62  of the TR jack  6 . 
     When the engagement between the TR jack  6  and the TR jack controlling member  64  is released, the loop retaining portion  48  of the TR jack  6  is lowered down to some extent by the tensile force of the loop  36  retained on the loop retaining portion  48 . In the illustrated embodiment, the TR jack control cam  82  is provided with a clearing cam  98 , to ensure that the loop retaining portion  48  is lowered down to its lowered position. 
     In the position G, the TR jack  6  is retracted, so that the loop retaining portion  48  which is in the lowered position is pulled out from the loop  36 . At this time, the loop retaining portion  48  of the TR jack  6  is in its lowered position. Accordingly, when the loop  36  goes out of the loop retaining portion  48 , the load put on the loop  36  is reduced and also the loop  36  is reliably retained in the hook  34  of the knitting needle  16   b.    
     In the position H, the TR jack  6  is further retracted and the TR jack controlling member  64  is also retracted. This retracting motion of the TR jack  6  brings the protrusion  72  at the bottom of the TR jack  6  into abutment with the top of the TR jack bed  8 , so that the loop retaining portion  48  of the TR jack  6  is returned to its raised position. This causes the rear end portion  66  of the TR jack controlling member  64  to ride on the engaging surface  68  of the TR jack  6  and brings the TR jack  6  and the TR jack controlling member  64  into engagement with each other. As a result of this, the loop  36  is released from the TR jack  6 , and the loop transfer from the TR jack  6  to the knitting needle  16   b  is completed. 
     While in the illustration, the loop transfer between the TR jack  6  and the knitting needle  16   b  of the back bed  2   b  has been described above, the same operation is yielded for the loop transfer between the TR jack  6  and the knitting needle  16   a  of the front bed  2   a.    
     Thus, according to the present invention, when the TR jack  6  is put in its advanced position, the TR jack  6  can selectively hold the loop retaining portion  48  in its raised position and release it from that held state. 
     Next, description on the second embodiment of the present invention will be given with reference to FIG.  8 . 
     In the second embodiment as well, a TR jack  102  is held in a TR jack groove  4 , and the TR jack  102  has on the top an advancing-and-retracting motion controlling butt  104  and a clearing cam acting portion  106  and also has a recess  108  formed therebetween. A TR jack controlling member  110  is slidably fitted in the recess  108 . 
     In the second embodiment, the notch is not formed in the recess  108  of the TR jack  102 , but instead, a circular arc  112  is formed on a bottom of the TR jack  102  and a circular arc  114  is formed on a top of the TR jack controlling member  110  at a rear end thereof, those circular arcs  112 ,  114  being made to have the same curvature, which is different in construction from the previous embodiment. 
     When the TR jack  102  is put in its advanced position, the TR jack controlling member  110  is moved forward of the recess  108  of the TR jack  102  until the center of the circular arc  112  formed on the TR jack  102  and the center of the circular arc  114  formed on the TR jack controlling member  110  come to coincides with each other. The TR jack  102  cannot be swung until the center of the circular arc  112  and the center of the circular arc  114  comes to coincides with each other. Also, when a rear end portion  116  of the TR jack controlling member  110  is located on an engaging surface  120  located rearward of a virtual axis  118  of the TR jack controlling member  110  in the recess  108  of the TR jack  102 , the TR jack  102  is not swung, so that a loop retaining portion  122  of the TR jack  102  is held in its raised position. 
     In the embodiment illustrated above, when the needle bed  2   b  is racked after the completion of the loop transfer from the knitting needle  16   b  to the TR jack  6 , the loop retaining portion  48  of the TR jack  6  which is in its advanced position is held in its raised position. This raised position is intended to mean that the loop retaining portion  48  is raised up to a position at least as high as a level to avoid interference with knitting members arranged on the needle beds  2   a,    3   b.    
     While in the illustrated embodiment, the TR jack  6  is structured to move linearly in the horizontal direction from the retracted position to the advanced position, this structure may be modified such as, for example, by the loop retaining portion of the TR jack being lowered for a while before it reaches the advanced position, first, and, then, the TR jack located in the advanced position being made to selectively hold the loop retaining portion in its raised position and release it from that held state. Alternatively, the TR jack may be moved in the horizontal direction from its lowered position and, when located in its advanced position, may selectively hold the loop retaining portion in its raised position and release it from that held state. 
     Although the flat knitting machine  1  including the slide needles as the knitting needles  16   a,    16   b  and the fixed sinkers  44   a,    44   b  has been illustrated in the embodiments above, the present invention may be practically worked even by using latch needles for the knitting needles and movable sinkers in place of the fixed sinkers. 
     While preferred embodiments of the invention have been illustrated above, it is to be understood that the present invention is not limited thereto but may practically be embodied variously within the sprit and scope of the present invention. 
     Capabilities of Exploitation in Industry 
     As mentioned above, the present invention enables the loop retaining portion of the TR jack to be selectively held in its raised position and released from its held state when the TR jack is in its advanced position. Hence, possible interference of the TR jack with the knitting members can be avoided by holding the loop retaining portion in its raised position when the needle bed is racked. In addition, the load put on the loop can be reduced by lowering down the loop retaining portion to its lowered position when the TR jack is located in its advanced position. 
     Also, when the TR jack is put in the advanced position, the loop retaining portion can be held in its raised position and released from its held state by simply moving the TR jack controlling member. The loop retaining portion can be held in its raised position by bringing the TR jack controlling member into engagement with the TR jack. The loop retaining portion can be lowered down to its lowered position by releasing the engagement between the TR jack controlling member and the TR jack. Consequently no complicated structure is required for holding the loop retaining portion in its raised position and releasing it from its held state. 
     Also, the engaging portion for the TR jack and the rear end portion of the TR jack controlling member to be engaged with each other and the notch for the rear end portion of the TR jack controlling member to be inserted into when the TR jack is swung are formed in the recess formed in the TR jack. With this construction, the feature that the loop retaining portion can selectively be held in its raised position when the TR jack is in the advanced position and the feature that the TR jack can be swung when the loop retaining portion is released from the state of being held in the raised position can both be provided without any complicated structure.