Cam mechanism for circular knitting machine

A cam mechanism for a circular knitting machine includes stitch cams each of which is provided with main cam wall sections adapted to control the position of each descending needle after its operating butt has come into contact on its upper side with the one of the main cam wall sections. The stitch cam is also formed with auxiliary cam wall sections of substantially the same contours as the main ones for guiding the needle on the underside of either the same or another operating butt to permit smooth movement of the needle while the operating butt is being controlled by the main cam wall sections. The two cam wall sections cooperate to guide the needles without irregular motion of their butts or needle points.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a cam mechanism for a circular knitting machine, 
and more specifically to stitch cams of the mechanism which will stabilize 
the path of the points of knitting needles in the machine. 
2. Description of the Prior Art 
It has been often the case with circular knitting machines in operation 
that the butts of needles on their way from the clearing zones to the 
stitching or needle-lowering zones strike against the cam walls of the 
stitch cams, rebound from the walls, and then strike them again. The 
repetition of striking and rebounding can result in vertical oscillation, 
inclination, and other irregularities in needle motion, and hence 
instability in hook positions and adverse effects on knitting in rows of 
uniform loops. The irregular motion of the knitting needles has been a 
serious problem particularly for plaiting stitch because the yarns to form 
the knit and purl tend to be reversed to give knitted products of inferior 
quality. 
BRIEF SUMMARY OF THE INVENTION 
The present invention contemplates the provision of a cam mechanism for a 
circular knitting machine which will eliminate the foregoing disadvantages 
by means of stitch cams each of which is formed with main cam wall 
sections adapted to control the position of each descending needle after 
its operating butt has come into contact on its upper side with one of the 
main cam wall sections, and also formed with auxiliary cam wall sections 
of substantially the same contours as the main sections which guide the 
needle on the underside of either the said or another operating butt to 
permit smooth movement of the needle while its operating butt is being 
controlled by the main cam wall sections, so that the two cam wall 
sections cooperate to avoid irregular motion of the operating butt or 
butts, or of the point, of each knitting needle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the drawing, specifically to FIGS. 1 and 2 which show a cam 
mechanism embodying the invention, a cylindrical cam holder of a circular 
knitting machine is generally indicated at 1, with a series of raising 
cams 2 connected end to end in a circular arrangement and secured to the 
inner lower part of the cam holder, in such a manner that each raising cam 
2, in the raising zone, can be in sliding contact with the underside of 
the lower operating butt 7b of each knitting needle 7 to be described 
later. Guard cams 3 and guide cams 4, each of which is adapted to contact 
the upper side of the upper operating butt 7a of each needle in the 
clearing zone that follows the raising zone, are alternately connected end 
to end in a circular arrangement and secured to the inner upper part of 
the cam holder 1. To the inner center part of the cam holder are fastened 
stitch cams 5 connected end to end in a circular arrangement so that the 
upper side of the lower operating butt 7b and the under side of the upper 
operating butt 7a of each needle can contact each of the stitch cams 5 in 
the stitch zone after the clearing zone. The stitch cams 5 are slidingly 
shiftable somewhat upward and downward to adjust the stitch dimensions. 
The guard cams 3, guide cams 4, and stitch cams 5 combinedly form an upper 
track 6a in zigzag fashion, while the stitch cam 5 and raising cams 2 
define a lower zigzag track 6b. Into these tracks 6a, 6b are fitted, 
respectively, the upper and lower operating butts 7a, 7b of the knitting 
needles 7 which, in turn, are mounted in a number of vertical grooves cut 
in the knitting cylinder. Each of the raising cams 2 includes a 
needle-raising cam wall section 2a ascending leftwardly as viewed in FIG. 
1 so as to be in sliding contact with the underside of the lower operating 
butt 7b of each needle 7 and to force the needle upward with the 
revolution of the knitting cylinder. On the underside of each stitch cam 5 
facing the lower track 6b is formed a needle-lowering cam wall section 5a 
declining leftwardly as shown to be in sliding contact with the upper side 
of the lower operating butt 7b of each needle thereby to lower the same. 
Ahead of the needle-lowering cam wall section 5a are formed successively a 
tread cam wall section 5b, a relief cam wall section 5c for roving-back, 
and a needle-pressing cam wall section 5d, in the advancing order as 
shown. These cam wall sections 5a through 5d represent the main cam wall 
sections which regulate the needle positions during stitching. On the 
opposite side of each stitch cam 5 that faces the upper track 6a are 
formed auxiliary cam wall sections 5e of substantially the same contours 
as the main cam wall sections to guide the upper operating butt 7a of each 
needle on its underside so as to permit smooth movement of the needle 
while its lower butt 7b is in sliding contact with any of the main cam 
wall sections. The spacing between the underside of the upper operating 
butt 7a and the auxiliary cam wall sections as determined in the direction 
of vertical movement of each knitting needle 7 is designed to be small 
enough to ensure smooth running of the needle without any inclination or 
irregular motion and corresponding to the knitting speed of the machine. 
The operation of the cam mechanism according to the invention will now be 
described. As the knitting cylinder (not shown) revolves and each of the 
knitting needles 7 moves in the directions of arrows in FIG. 1, the 
underside of the lower operating butt 7b at the starting point of the 
raising zone comes into sliding contact with the needle-raising cam wall 
section 2a so that the needle 7 begins to raise. During its ascent the 
latch of the needle 7 is opened by a loop and the hook is fed with yarn. 
At the end of the ascent the lower operating butt 7b is released from the 
needle-raising cam wall section 2a, and the needle under protection by the 
guard cam 3 moves horizontally through the clearing zone. Further turning 
of the cylinder brings the lower operating butt 7b to the starting point 
of the stitch zone where the upper side of the butt 7b strikes against the 
main cam wall section, i.e., the needle-lowering cam wall section 5a, of 
the stitch cam 5. The reaction tends to force the butt 7b away from the 
main cam wall section, but the underside of the upper operating butt 7a, 
in turn, is kept in sliding contact with the corresponding one of the 
auxiliary cam wall sections 5e, thus preventing the lower operating butt 
7b from being liberated from any part of the main cam wall sections. As 
described, the operating butts of each needle 7 are controlled in motion 
by the main and auxiliary cam wall sections, and move through the tracks 
in sliding contact with the main cam wall sections without the possibility 
of any unintended irregular motion. During the downward movement of the 
lower operating butt 7b along the main cam wall section of the stitch cam 
5, the hook and latch of the needle cooperate to form a loop. As the 
cylinder revolves further, tension imparted to the yarn by the roving-back 
phenomenon pulls the needle 7 upward. Consequently, the lower operating 
butt 7b travels in sliding contact with the main cam wall sections of the 
stitch cam 5, i.e., the tread cam wall section 5b, relief cam wall section 
5c for roving-back, and needle-pressing cam wall section 5d, in the order 
mentioned. Then, the lower operating butt leaves the stitch cam into 
sliding contact with the next raising cam. Throughout this period of 
transfer, the both upper and lower butts of the needle are guided by the 
main and auxiliary cam wall sections as stably as in the descent, and are 
smoothly shifted to the next zone without any irregular motion of the 
needle. 
While the main and auxiliary cam wall sections in the embodiment have been 
described as provided on opposite sides of the stitch cam, they may be 
shifted in relative position as shown in FIG. 3 to obtain equally 
satisfactory results. In a further modification, the main and auxiliary 
cam wall sections may take the form of both sides of a groove as in FIG. 
4, in which case the needle may have only one operating butt instead of 
two as in the preceding embodiments. 
According to the present invention, as described in detail, each stitch cam 
5 is formed with main cam wall sections adapted to control the position of 
each descending needle 7 after its operating butt has come into contact on 
its upper side with one of the main cam wall sections, and is also formed 
with auxiliary cam wall sections of substantially the same contours as the 
main sections for guiding the needle on the underside of either the same 
or another operating butt to permit smooth movement of the needle while 
its operating butt is being controlled by the main cam wall sections, so 
that the two cam wall sections cooperate to avoid irregular motion of the 
operating butt or butts, or of the point, of the knitting needle. In this 
way the yarn is smoothly picked up to form uniform loops, even in plaiting 
stitch. Moreover, the stability of needle motion permits high-speed 
knitting operation to a great advantage. 
It will be obvious to those skilled in the art that the principles of this 
invention are even more advantageously applicable to sinker cams.