Sinker mechanism for flat knitting machines

Abstract: A sinker mechanism which includes multiple knitting needles (2) placed in parallel above a needle bed (20) with each sinker (21) being mounted so that it can rock up and down so that its tip descends between adjacent knitting needles (2). A yarn-catching hook (26) is provided at one sinker end ; downward pressure is applied by a spring (28) that can be removed from and replaced into the sinker so the yarn-catching hook (26) will drop between adjacent knitting needles (2), and this downward force is adjustable so the yarn-catching hook's position is a function of the tension in the yarn it is holding. The thickness of the upper half of the needle plate (22) is reduced by at least the thickness of the sinker, thereby creating a step, in which a semicircular concavity (32) is created under this cut-out area, and the needle plates (22) and knitting needles (2) are regularly spaced and mounted in parallel on the needle bed (20). This sinker also has a yarn-catching hook that positions the loop so that it has a contact surface (21) near the hook that touches the front cam (4), it has a surface in its middle that rests in the semicircular concavity of the needle plate (22), and it has a contact surface (31) at the other end that touches the rear cam (3). The sinker is located in the cut-out portion of the needle plate (22) with the capability to rock up and down so that its back end can be linked to the end of the needle plate, and that the plate and is configured so that an arm projects to touch the rear cam (3). A spacer is provided whose front end is adjacent to the sinker's middle portion when the sinker is joined to the needle plate, and the spacer's back end is joined to the needle plate beside the sinker at a point higher than the knitting needle.

Description: Background of the Invention The present invention relates to a sinker mechanism for flat knitting machines. The sinker mechanisms for flat knitting machines of the prior art are characterized in that multiple knitting needles are placed in parallel and have the capability of sliding in and out of the needle bed, and that each sinker is fixed to the needle bed, its tip being located between adjacent knitting needles. In the prior art, a previously formed loop is held by the sinker, but if the knitting width must be expanded abruptly-- during fashioning, for example--a takedown device will pull the narrow-width loop with great force, whereas the force applied to press down the first course of loops is insufficient, resulting in uneven loops. To remedy this problem, a so-called "waste course" was used so the knitting could be adjusted gradually to the required width. This "waste course" tended to reduce productivity. German patent application DE 3917934 solved the problem of the "waste course" by making sinkers capable of rocking. In that patent, the sinker is characterized in that it is J-shaped and supported by a mounting pin in the middle with a press-down part at the end near the knitting needle which positions loops, and with a spring support projecting from one part of the sinker. This spring support allows widening without going through a "waste course", but presents the disadvantage of being too high and bulky because its movement is controlled by cams on the carriage and because it has a fixed mounting pin at its middle region. In addition, since its spring support is part of the sinker, it is made of the same material as the sinker, and the spring modulus cannot be adjusted. This is a serious defect in a knitting machine designed to produce varieties of patterns Moreover, since the sinker has a pin in the middle, replacing it is a problem: when the pin is pulled out, the spring support causes the sinker to pop out. Installation of the sinker requires substantial time and effort because of this spring support's tendency to push out the sinker. German patent No.1585281 discloses an arrangement where a sinker spring acts indirectly in a sinker via an intermediate pivotal member provided with teeth which mesh with teeth on a rear portion of the sinker. The sinkers and intermediate pivotal members are mounted respectively on separate common axles. Despite being easier to remove than in the case of DE 3917934 the sinker springs are still difficult to remove and the intermediate pivotal members add extra play to the sinker operation, in the meshing arrangement. Further, the whole arrangement around the tip of the needles is complicated, and requires a wide interval between adjacent needles which necessitates widening of gaps between tip portions of the sinkers and the needles. The object of the present invention is to provide a sinker mechanism for flat knitting machines that obviates these shortcomings; in addition to improving productivity by eliminating the "waste course" step, it also applies the proper tension to the loops regardless of the type of yarn used. SUMMARY OF THE INVENTION To achieve this objective, the invention provides a sinker mechanism for a flat knitting machine comprising a plurality of needle plates, sinkers and knitting needles mounted in parallel on a needle bed characterised in that an upper portion of each needle plate is reduced in thickness by at least the thickness of a sinker thereby creating a step, the step being provided with a semicircular concavity and the sinker having a complementary convex semicircular surface received for rocking movement in said concavity of the needle plate, means for controlling the rocking movement of the sinker, and a spacer mounted between each needle plate and the sinker of an adjacent needle plate. Preferably the knitting machine is characterised in that said means for controlling the rocking movement of the sinker comprises a contact surface near the yarn catching hook of the sinker said contact surface abutting a front control cam and a rear contact surface which abuts a rear control cam, the spacers each having an arm having a hooked end forming a detent for receiving a pivot allowing limited pivotal movement of the spacers. The sinker desirably comprises a spring, preferably a coiled spring. Desirably, the sinker mechanism is further characterised in that the sinker further comprises a spring, and preferably comprises a sinker plate and a spring removably arranged in the mechanism by a press-down plate received in grooves of the needle plate and of the spacer. By the invention, the knitting width can be expanded instantly, as the knitted fabric held by the sinker is pressed down creating the appropriate tension in the loop at each knitting needle. In addition, when the knitting needle is moved forward by the carriage and the tension in the loop to be knocked over is increased, this tension, transmitted by the yarn-catching hook, will cause the sinker to press up against the wire spring, thereby easing the tension. Thus, no excessive tens ion is applied to the loop to be knocked over, and the yarn is prevented from stretching or breaking. In addition, since the sinker rests in the cut-out portion of the needle plate, the knitting needle is located along the sinker and the needle plate, and since the spacer is joined to the needle plate at a point higher than the sinker, it is easy to replace damaged needles underneath the spacer by raising the spacer up on its pivot. BRIEF DESCRIPTION OF THE DRAWINGS The attached drawings show one embodiment of the present invention. Figure 1 is an exploded view of a portion of the flat knitting machine carriage that controls the knitting needles and sinkers. Figure 2 is a top view of the sinker; Figure 3 is a side view of a sinker in the A-A position of Figure 1; Figure 4 shows the component parts of a sinker; Figure 5 is a side view of a sinker in the B-B position of Figure 1; Figure 6 is a side view of a sinker in the C-C position of Figure 1; Figure 7 is a side view of a sinker in the D-D position of Figure 1; Figure 8 is a side view of a sinker in the E - E position of Figure 1; and Figure 8 is a side view of a sinker in the F-F position of Figure 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Following is a detailed explanation of the present invention, using the above drawings of the embodiment; Figure 1 is a simplified view of the mechanism of the flat knitting machine carriage that controls the knitting needles and sinkers, where (1) is the knitting cam; (3) is a sinker-controlling rear cam located in front of the knitting cam (1) ; and (4) is a sinker-controlling front cam located in front of the rear cam (3). The above sinker-controlling front cam (4) has a cam profile (5) on its lower edge; and the sinker-controlling rear cam (3) consists of a cam profile (6) on its lower edge, and movable cams (8), (9), (10) and (11) that are acted on by coiled springs (7) so as to project below the edge of the plate; sinker-controlling front cam (4) and rear cam (3) are secured respectively by bolts (14) and (13) to a bracket (12) that projects from the main body of the carriage (see Figure 3). Of these above movable cams (8), (9), (10), (11), cams (8) and (10) are for forward motion, and cams (9) and (11) are for reverse motion. Knitting cam (1) consists of a triangle-like needle-raising cam (15), another triangle-like cam (16) directly above needle-raising cam (15), and two triangle-like cams (17) sliding on the lateral faces of (16), and a control groove (19) is formed between needle-raising cam (15) and triangles (16) and (17), through which the butts (18) of needles (2) travel. As shown in Fugure 2, needle plates (22) accompanied with movable sinkers (21) are placed at regular intervals on needle bed (20), knitting needles (2) controlled by knitting cam (1) are placed between needle plates (22), so that hooks (23) at the end of the knitting needles (2) could slidably move forward to and backward from the rim of needle bed (20), and spacers (24) are placed above knitting needles (2). Each movable sinker (21) consists of thin sinker plate (25) between needle plate (22) and spacer (24) above knitting needle (2) and rocks up and down by the action of front cam (4) and rear cam (3). Each sinker plate (25) consists of a yarn-catching hook (26) at the front end, contact surface (27) behind said hook (26) that touches sinker-controlling front cam (4); next to surface (27) is located wire hook (29) which engages one end of depressing wire spring (28) in order to lower and hold yarn-catching hook (26). Behind wire spring hook (29) of sinker plate (25), there is downward-curving semicircle (30) that serves as rotation support, and contact surface (31) that touches rear cam (3). Needle plate (22), on which sinker plate (25) rests, consists of a cut-out portion in its upper-half part at one end whose thickness is reduced by the thickness of sinker plate (25); underneath this cut-out portion, there is a semicircular concavity (32) centered with respect to the cut-out portion, that supports downward-curving half circle (30), and the rest of the sinker can rock up and down in the slit created by the cut-out portion of needle plate (22) and spacer (24). More specifically, needle plate (22) is made of a long thin sheet. The thickness of the upper portion of the front portion of needle plate (22) is reduced by half, leaving cut-out portion (50) at half height. Because of cut-out portion (50), there is a step in the middle of needle plate (22). Underneath cut-out portion (50), there is semicircular concavity (32), and behind cut-out portion (50) there is supporting stud (51) which almost reaches the height of groove (33) and has a transverse hole (52). Thus, when sinker plate (25) is placed between needle plate (22) and spacer (24), and press-down plate (34) is inserted in the grooves (33) of needle plate (22) and spacer (24), spacer (24) is immobilized and, at the same time, free end (28a) of wire spring (28) under press plate (34) is pushed down, thereby pushing yarn-catching hook (26) of sinker plate (25) down and holding it there. The elasticity of this wire spring is preset so that during knockover, for example, when the tension in previously formed loop (35), which is hooked and held by yarn-catching hook (26), exceeds the nominal tension, sinker plate (25) will swivel to raise the yarn-catching hook so the tension in previously formed loop (35) is kept at the nominal level. In addition, the function of spacer (24) is to prevent sinker (21) above needle plate (22) from rattling, and its thickness (width) must therefore be equal to the thickness (width) of the knitting needles. Spacer (24) consists of arm (54) with hook (53) at its end, supported by a pivot of wire (55) (see Figure 3) which passes through hole (53) of stud (51) of needle plate (22). Spacer (24) is above knitting needle (2) which is between the needle plates (22), and hook (53) at the end of arm (54) holds supporting pivot (55) that passes through hole (52) in stud (51) of needle plate (22); the spacer (24) can thus rotate up on supporting pivot (55). Rotating sinker (21) in this manner ensures that it will move smoothly without being subjected to excess force. Following is a description of the sinker mechanism for flat knitting machines: In Figure 1, when the carriage moves from right to left and sinker (21) reaches the A-A position, knitting needle (2), as shown in Figure 3, is retracted from needle bed (20), contact surface (27) of sinker (21) touches sinker-controlling front cam (4), and contact surface (31) is pushed down by movable cam (8) of rear cam (3). Sinker plate (25) then rotates counter-clockwise on support surface (30) which rests in semicircular concavity (32). When sinker (21) moves to the B-B position, butt (18) of knitting needle (2) is slightly raised by needle-raising cam (15), and hook (23) of knitting needle (2), shown in Figure 5, is pushed out slightly beyond the rim of needle bed (20). Meanwhile, contact surface (31) of sinker (21) is detached from movable cam (8), and sinker plate (35) is rotated clockwise by wire spring (28) until contact surface (31) touches cam profile (6) under sinker-controlling rear cam (3), and knitting needle (2) is pushed down by yarn-catching hook (26) at the front end while holding previously formed loop (35). When the carriage moves further left and sinker (21) reaches the C-C position shown in Figure 1, butt (18) of knitting needle (2) is pushed all the way to the top of needle-raising cam (15), as shown in Figure 6, and hook (23) is pushed out noticeably beyond the rim of needle bed (20). Sinker plate (25) is now at the point where tension in previously formed loop (35) held by yarn-catching hook (26) balances the force of wire spring (28), and when it reaches the back end of knitting needle (2), the tension is previously formed loop (35) held by yarn-catching hook (26) increases considerably. The tension is eased when latch (42) of hook (23) is opened and the yarn slips over the latch. The tension is eased further as yarn-catching hook (26) moves upward, thereby maintaining the tension in previously formed loop (35) held by yarn-catching hook (26) at its nominal level. When the carriage moves further left and sinker (21) reaches the D-D position, shown in Figure 1, butt (18) of knitting needle (2) is pushed down by triangle-like cam (16), as shown in Figure 7, while hook (23) of knitting needle (2) holds yarn (41) fed by carrier (40). At this point, rear contact surface (31) of sinker plate (25) is pushed down by movable cam (10) of rear cam (3) and, as a result, sinker (21) is rotated counter-clockwise on downward curving semicircle (30), raising yarn-catching hook (26) of sinker plate (25) almost above knitting needle (2) and preparing for knockover. When sinker (21) moves to the E-E position in Figure 1, butt (18) of knitting needle (2) is pushed all the way down by triangle-like cam (17), retracting hook (23) completely into the needle bed (see Figure 8). Wire spring (28) then forces sinker plate (25) to rotate clockwise until contact surface (31) of the rear cam pushes up movable cam (11) and touches cam profile (6) underneath sinker-controlling rear cam (3), and the tip of sinker (21) is pushed below knitting needle (2) while yarn-catching hook (26) holds previously formed loop (35). At this point, a new loop is created in hook (23) of knitting needle (2) by yarn (41) fed by carrier (40), and the size of the new loop is determined by how far knitting needle (2) moves back in relation to yarn-catching hook (26) of sinker plate (25) holding yarn (41). In the process of moving from the D-D position to the E-E position, old loop (35) located beyond latch (42) of hook (23) closes latch (42) as knitting needle (2) pulls back, and passes over said closed latch (42). Since the knocked-over loop is greatly stretched as hook (23) passes through it, excessive tension may be created in old loop (35) held by yarn-catching hook (26) of sinker plate (25). This increased tension forces sinker place (25) to rotate counter-clockwise on downward curving semicircle (30) against wire spring (28) to ease the tension, thus keeping constant the tension in yarn (35) held by yarn-catching hook (26). This helps prevent breaks when yarn (41) fed by carrier (40) is of less stretchable material, such as cotton. When the carriage moves further left and sinker (21) reaches the F-F position shown in Figure 1, butt (18) of knitting needle (2), is raised slightly from the E-E position, as shown in Figure 9, at the bottom of triangle-like cam (17), and hook (23) of knitting needle (2) is then pushed out slightly beyond the rim of needle bed (20), causing slack in old loop (35) held by hook (23). But wire spring (28) prevents this slackening by pushing and holding down yarn-catching hook (26). Old loop (35) is thus held by hook (23) and prevented from dropping. If knitting needle (2) is damaged and needs to be replaced, it can easily be taken out by pivoting spacer (24) on supporting pivot (55). In the above embodiment, wire spring (28) serves to push and hold down yarn-catching hook (26). A coiled spring may be used instead of wire spring (28), or else the sinker plate may be made of spring steel to achieve the same effect.

Claims: A sinker mechanism for a flat knitting machine comprising a plurality of needle plates (22), sinkers (21) and knitting needles (2) mounted in parallel on a needle bed (20) characterised in that an upper portion (50) of each needle plate (22) is reduced in thickness by at least the thickness of a sinker thereby creating a step, the step being provided with a semicircular concavity (32) and the sinker having a complementary convex semicircular surface (30) received for rocking movement in said concavity (32) of the needle plate (22), means (27,4,31,8) for controlling the rocking movement of the sinker, and a spacer (24) mounted between each needle plate (22) and the sinker of an adjacent needle plate (22). A sinker mechanism for a flat knitting machine as claimed in claim 1 characterised in that said means for controlling the rocking movement of the sinker (21) comprises a contact surface (27) near the yarn catching hook (26) of the sinker (21) said contact surface (27) abutting a front control cam (4) and a rear contact surface (31) which abuts a rear control cam (11), the spacers (24) each having an arm (54) having a hooked end forming a detent (53) for receiving a pivot (55) allowing limited pivotal movement of the spacers (24). A sinker mechanism as claimed in claim 1 or claim 2 characterised in that the sinker further comprises a spring (28). A sinker mechanism as claimed in any of claims 1, 2 or 3 characterised in that a sinker plate (25) and a spring (28) are removably arranged in the mechanism by a press-down plate (34) received in grooves (33) of the needle plate (22) and of the spacer (24).

Inventors: SHIMA MASAHIRO, YABUTA MASAHIRO, SHIMA, MASAHIRO, YABUTA, MASAHIRO
Applicants: SHIMA SEIKI MFG, SHIMA SEIKI MFG., LTD.
Application year: 1990
Main classification: D04B15
IPC codes: D04B15, G03G9