Closed Cam Track for a Circular Knitting Machine

1. Field of the Invention.

This invention relates to needle actuating camming for knitting machines, and especially to needle actuating camming for high speed circular knitting machines.

2. Description of the Prior Art

It has been the practice to provide separate raise and stitch cams in circular knitting machines for raising and lowering knitting needles and to permit needles to move between the raise and stitch cams without being positively controlled. Large impact forces resulted whenever a needle butt first engaged a raise cam after leaving a stitch cam, or first engaged a stitch cam after leaving a raise cam, and the cam surface as well as the needle butts sustained excessive wear and damage as a consequence. Such impact forces increase with increased speeds and it therefore became necessary to run machines at quite limited speeds in order to prevent frequent shut-downs for repair. Also in the extent to which there was a lack of positive control of needles by a closed cam track closely confining needle butts as they were actuated by raise and stitch cams, needle butts tended to bounce off the surfaces of raise and stitch cams and of guard cams causing excessive vibration, noisy operation of the machine and excessive wear and damage to the engaging parts.

In accordance with the invention a knitting machine is provided with a closed cam track for the butts of knitting needles. The track includes needle raising portions and needle lowering portions as well as bridging portions which provide a smooth transition for needle butts moving between the raising and lower portions of the track and minimizes forces on the needle butts. The bridging portions are each defined by a circular arc on one side of the track and two circular arcs on the opposite side, having the same radius as the circular arc on the said one side.

FIG. 1 is an elevational view showing a cam track according to the invention on adjacent cam section blocks of a circular knitting machine.

FIG. 2 is a perspective view of one of the cam section blocks of FIG. 1.

Referring to the drawings, reference character 10 designates a cam section block of a circular knitting machine. Cam face plates 12 and 14 are each secured to block 10 as by a screw 16 and held against angular movement as by locating pins 18 and 20. Such face plates 12 and 14 on section block 10 and corresponding other face plates on other section blocks such as the face plates 12' and 14' secured to cam section block 10' disposed adjacent to the section block 10 define like portions such as 22 and 22' of a closed cam track 24 for needle butts 25 around the cylinder of a machine.

Each of the like parts such as 22 and 22' of the closed cam track 24 as viewed from left to right in the drawing includes a generally straight ascending portion, an upper curved bridging portion, a straight descending portion, a lower curved bridging portion, and a straight ascending portion. Reference characters 26, 28, 30, 32 and 34 designate the generally ascending portion, the upper bridging portion; the straight descending portion, the lower bridging portion and the straight ascending portion respectively of the cam track 24 as formed by face plates 12 and 14, and reference characters 26', 28', 30', 32' and 34' designate corresponding portions of the cam track formed by face plates 12' and 14'.

Each upper bridging portion of the cam track 24 is defined by an upper circular arc such as arc 36 and arc 36' of bridging portions 28 and 28' respectively, and by the two lower circular arcs such as the arcs 38 and 40 of the bridging portion 28 and the arcs 38' and 40' of the bridging portion 28'. Each lower bridging portion of the camming track 24 is defined by a lower circular arc such as arc 42 of bridging portion 32 and arc 42' of bridging portion 32', and by two upper circular arcs such as arcs 44 and 46 of bridging portion 32 and the arcs 44' and 46' of the bridging portion 32'.

All circular arcs such as 36, 38, 40, 36', 38' and 40' of the upper bridging positions of the closed cam track have the same radius. The top circular arc of each upper bridging portion is tangent on one side to a line defining the upper edge of the adjacent generally straight portion of the cam track, and on the other side is tangent to a line defining the adjacent upper edge of the straight descending portion of the track. One circular arc at the bottom side of each upper bridging portion of the track is tangent to the line defining the lower edge of the adjacent generally ascending portion of the cam track and the other circular arc at the bottom of each upper bridging portion of the track is tangent to a line defining the bottom edge of the adjacent portion of the cam track. Arc 36 for example is tangent to line 48 defining the upper edge of ascending portion 26 of the cam track and to line 50 defining the upper edge of the descending portion 30 of the cam track. Arc 38 is tangent to line 52 defining the lower edge of generally ascending portion 26 and arc 40 is tangent to line 54 defining the lower edge of the straight descending portion 30. Similarly arc 36' is tangent to line 48' defining the upper edge of ascending portion 26' of the cam track and to line 50' defining the upper edge of the descending portion 30' of the cam track, whereas arc 38' is tangent to line 52' defining the lower edge of generally ascending portion 26' and arc 40' is tangent to line 54' defining the lower edge of the straight descending portion 30'.

All circular arcs such as 42, 44, 46, 42', 44' and 46' of the lower bridging portions of the closed cam track have the same radius which is slightly less than the radius of the circular arcs at the upper bridging portions of the closed track. The bottom circular arc of each lower bridging portion is tangent on one side to a line defining the lower edge of the descending portion of the cam track, and on the other side is tangent to a line defining the adjacent lower edge of the straight ascending portion of the track. One circular arc at the top side of each lower bridging portion of the track is tangent to the line defining the upper edge of the adjacent descending straight portion of the track and the other circular arc at the bottom of each lower bridging portion of the track is tangent to a line defining the upper edge of the adjacent ascending portion of the track. Arc 42, for example, is tangent to line 54 defining the lower edge of the descending portion of the track and to a line 56 defining the lower edge of the adjacent ascending portion of the track. Arc 44 is tangent to line 50 defining the upper edge of the descending portion of the track and arc 46 is tangent to a line 58 defining the upper edge of the adjacent ascending portion of the track. Similarly, arc 42' is tangent to line 54' defining the lower edge of the descending portion of the track and to a line 56' defining the lower edge of the adjacent ascending portion of the track. Arc 44' is tangent to line 50' defining the upper edge of the descending portion of the track and arc 46' is tangent to line 58' defining the upper edge of the adjacent ascending portion of the track.

The initial ascending portion of the cam track on each section block is out-of-alignment with the terminal ascending portion of the track in the adjacent cam section block. As shown such initial ascending portions of the cam track are offset as at 60 in the down direction from the terminal ascending portions of the track. The lower edge of each initial ascending portion of the track is therefore lower than the lower edge of the adjacent terminal portion of the track at the point where a needle butt 25 leaves one cam section block and enters the next section block. In addition the upper edge of each initial ascending track portion is flared as at 62 so as to cause it to extend above the upper edge of the adjacent terminal ascending portion of the track in the region where a needle butt leaves one cam section block and enters the next. The downward displacement of the terminal ascending positions of the track with respect initial ascending portions of the track and the flaring of the upper side of the initial ascending portions as described assures freedom of movement of needle butts between cam section blocks despite dimensional variations within prescribed limits in the width of the track or in the section blocks.

Although the invention has been described in its preferred form with a certain degree of particularity, it is to be understood that the present disclosure of the preferred form has been made by way of example only and that numerous changes in the details of construction and the combination of parts may be resorted to without departing from the spirit and scope of the invention.