GB2299347A - Cam system for a circular knitting machine - Google Patents

Abstract

A universal cam system for the cylinder or dial of a circular knitting machine provides at a single station the facility for knit/tuck/miss selection and for loop transfer movements in both directions. The plural functions of the cam system are achieved by means of a gate cam (7) for moving needles from the knitting and tucking needle paths into a loop transfer donation needle path (Fig.1B), a selectively engageable raising cam (16) which raises all needles into a loop transfer acceptance path; and a lowering cam (14) associated with the said raising cam, movable to a position in which it lowers all needles from the loop transfer acceptance path (Fig.1C). When the gate cam (7), which is pivotal and associated with a guard cam (12), is inactive knit/tuck/miss patterning takes place. A cam (11) effects latch opening for loop-opening needles (Fig.1B).

Description

TITLE: Cam system for a Circular Knitting Machine DESCRIPTION: Field of the Invention r The invention relates to the field of circular knitting machines, and provides a novel cam system for a cylinder or dial of such a knitting machine. The cam system is referred to in this Specification as a universal cam system because it can direct selected knitting needles of the machine to follow a knit, tuck, miss, loop transfer donation or loop transfer acceptance path of movement.

Background Art In a cylinder and dial knitting machine it is known to provide a number of knitting and loop transfer stations distributed around the periphery of the machine. At the knitting stations, needle selection can cause the needles to follow knit, tuck or non-knit paths, and preferably each needle is individually selectable at each knitting station to follow a selected one of those paths.

Individual needle selection is attainable electromagnetically, for example as taught in GB-A -2133425.

The loop transfer stations may involve the transfer of loops to the dial needles and/or the transfer of loops to the cylinder needles. At each loop transfer station, needle selection at the donating position (cylinder or dial) is on an individual needle selection basis, whereas there is no selection and all needles move equally at the loop acceptance position (dial or cylinder).

For each circular knitting machine the initial cam layout must be chosen with a view to anticipating the more common knit and loop transfer sequences that may be demanded in use. For example, an 18 station knitting machine may be set up with 12 knitting stations and 6 loop transfer stations. If the sequence were symmetrical, with each two consecutive knitting stations being followed by a loop transfer station, then the sequence "knit; loop transfer to cylinder; knit; loop transfer to dial...." could be accommodated only by selecting needles not to knit at one knitting station in each pair of adjacent knitting stations.That is clearly inefficient as compared to utilizing every station, but for such pattern selections the only way to maximize productivity in the knitting process has been to interrupt knitting long enough for complete cam systems to be unbolted from the machine and re-mounted in the desired knit/loop transfer sequence.

The Invention This invention is based on a realization of the productivity benefits of having, in a circular knitting machine, a universal cam system which permits, through needle selection, individual knitting needles to be directed in any of knit, tuck, transfer loop donation, transfer loop receiving and inactive needle movements. If every cam system on a circular knitting machine is such a universal cam system, then any pattern sequence of knit, miss, tuck, loop transfer to cylinder and loop transfer to dial needle movements can be accommodated without being forced to have some of the knitting stations inactive.

The universal cam system of the present invention is in effect a superimposition of knitting and selecting stations to provide, at a single station of a knitting machine, selection between the various knitting movements of the needles- and between loop transfer movements in both directions (cylinder to dial as well as dial to cylinder).

The invention provides a cam system for a circular knitting machine comprising non-knitting, knitting and tucking needle paths for needles passing the cam system, characterized in that a gate cam is movable to a position in which it moves selected needles from the knitting and tucking needle paths into a loop transfer donation needle path; a selectively engageable raising cam is provided for raising all needles into a loop transfer acceptance path; and a lowering cam associated with the said raising cam is movable to a position in which it lowers all needles from the loop transfer acceptance path.

The gate cam is preferably pivotably mounted so that when it is in one rotary position it permits selected needles to follow their knitting or tucking needle paths, but when it is in a second rotary position it blocks the movement of the selected needles into a part of their knitting and tucking paths and directs them instead into a loop donation transfer path. Preferably the gate cam is associated with a blocking cam which blocks the movement of the needles into the loop transfer donation path when the gate cam is in its one rotary position but opens the loop transfer donation path when the gate cam is in its second rotary position. For ease of operation the gate cam and blocking cam are movable only in synchronism from a single control lever.

Preferably the gate cam is associated with a supplementary raising cam for raising the needles again, at the end of the loop transfer process, to nearly clearing height so as to bring the needle latches into engagement with a latch opener. The supplementary raising cam is advantageously movable into such an operating position only when the gate cam is moved to its operative position to effect the loop transfer donation needle movement.

The needle selection for needles passing through the knitting and tucking paths may be an electromagnetic selection operating on an individual needle selection basis, and the needle control throughout each needle movement may be by the butts of needles and/or needle jacks engaging with appropriate cam surfaces in the cam system. The needle jacks may be pivotably or rockably mounted relative to their needles, or may be on spring tails of the needles, or may be spring tailed jacks.

Preferably the needle jacks are pivotably mounted on their associated needles. The raising cam may be selectively engaged by raising butts of the needle jacks into engagement with a fixed raising cam, or by moving the cam itself into the path of the jack butts. The raising cam, when it engages the jack butts, simply raises all needles to a loop transfer acceptance level.

The lowering cam should at that stage be moved to its position in which it lowers the needles which have been extended to accept the loop transfer. Preferably the lowering cam is pivotably mounted so that when it is in one rotary position it is out of the needle path and when it is in a second rotary position it effects the appropriate needle lowering. Preferably it acts on the needle butts. If the supplementary raising cam, referred to above, is present in the cam system, then that supplementary raising cam should be in its inoperative position when the lowering cam is used, since both cams preferably act on the needle butts, in substantially the same angular location. For example, it may be decided to mount the supplementary raising cam in a slideway, and to slide it to an inoperative 'parked' position when the cam system is used for anything other than loop donation transfer movement of selected needles. The lowering cam can then occupy the space occupied by the supplementary raising cam when the cam system is used for loop transfer acceptance.

The provision of a universal cam system according to the invention at every successive knitting station around a circular knitting machine enables any desired sequence of knitting and loop transfer operations to be achieved around the machine, with no need to unbolt cam systems and yarn feeding devices or to have inactive knitting stations to accommodate different pattern requirements.

Machine down-time is therefore reduced, and the elimination of inactive knitting stations means that production is always at the maximum potential.

Drawings Figure 1 is a view of the cam layout of a universal three track selection cam system according to the invention for a dial or cylinder of a circular knitting machine. The drawing is in three sections, labelled 1A, 1B and 1C each showing one particular cam selection.

Figure 2 is a view of a cam layout of a universal two track selection cam system according to the invention for a dial or cylinder of a circular knitting machine. Figure 2 is in four sections 2A, 2B, 2C and 2D, each showing one particular cam selection.

Referring first to Figure 1, there is shown in section 1A the knitting and tucking cam selection of a cylinder or dial cam system according to the invention. Two rows of butts are shown, passing through the cam system. The upper row of butts are needle butts, and the lower row of butts are jack butts. The needle jacks may be, for example, pivotting jacks and may be used in association with an electromagnetic selecting mechanism.

The butts are shaded for identification purposes. The needle and jack butts of needles selected to knit vre unshaded; those of needles selected to tuck are shown in solid black; and those of needles that are not selected are shown partially shaded.

The movement of the needles selected to knit is as follows. The jack butts first rise up a lower raising cam 1 to tucking level. They then rise up an upper raising cam 2 and down a lowering cam 3, again to approximately tucking level. The jack butts then pass down a lowering cam 4 to draw a loop. The drawing of the loop is finished by a further lowering cam 5 and guard cam 6 which together act on the needle butts as opposed to the jack butts, so as to provide an accurate control of the drawn loop length. The lowering cams 4 and 5 and the guard cam 6 can be moved to a position about five or more needles to the right as shown in section 1A of Figure 1, to achieve delayed knockover if a tighter fabric is required. The delayed knockover positions of those three cams are shown in phantom line at cams 4', 5' and 6' respectively.Needles selected to tuck pass up the raising cam 1 in the same way, but have their jack butts depressed to an extent such that they pass in front of the upper raising cam 2 and remain at tucking height until they reach the lowering cam 24.

Needles which are not selected to knit have their jack butts depressed to a position fully received between the trick walls, so that they are not engaged by any of the cams and miss the lower raising cam 1. On the other hand the needle butts, which do project from the trick walls, engage the lowering cam 5 as in the above described movement of the knit and tuck selected needles, so that there is one small element of needle movement as the needles pass through the cam track, even for those needles which are not selected to knit. If the cam system is to be used as a lmop tasir bew , then it may be used to control either the donation or the acceptance of needle loops. Loop transfer donation is illustrated in section 1B of Figure 1.Selected needle and jack butts are shown unshaded, and unselected butts are shown solid black. The selected jack butts pass initially up the raising cam 1 as in section 1A of the Figure. At the top of the cam surface 1, however, the upward movement of the jack butts is continued by their engagement with a gate cam 7 which is a rotary cam pivotted about pivot pin 8.

That moves the needle butts upwardly into a loop transfer donation cam track in which they are lifted further by a loop transfer raising cam 9 and then lowered by a loop transfer lowering cam 10. Control then passes back to the jack butts which move down the lowering cam 4; and finally the needle butts engage the lowering cam 5 and guard cam 6 to lower the needles to their fully retracted positions.

Rotation of the cam 7 to its alternative position as shown in section 1B is accompanied by raising of a cam 11 which raises the needles into the path of a latch opening device (referred to herein as a latch opening cam 11).

The latch opening cam 11 is raised from the position shown in Figure 1A to that in Figure 1B, which has the effect of momentarily raising the needles after the loop transfer has been completed, so that the latch opening device can ensure that all latches are in their open position prior to the next knitting station. The latch opening cam 11 occupies the same space as would have been occupied by the lowering cam 5 and guard cam 6 if they had been in their delayed timing positions 5' and 6' respectively of section 1A of Figure 1, so that these two cams must be located in their normal positions prior to use of the cam system as a loop transfer box.

A guard cam 12 is shown in section 1A of Figure 1, lying across the mouth to the gate cam track. That cam acts simply to guard against needles jumping past the knit and tuck cam track into the WaGszc cam track in high speed operation. The guard cam 12 is pivotted around a pivot pin 13, so that when the gate cam 7 is moved to the position shown in section 1B of Figure 1, the guard cam 12 moves automatically and simultaneously to the position which it occupies in section 1B, opening the mouth of the gate cam track.

The universal cam system of Figure 1 can also be used for the acceptance of needle loops at a loop transfer station. In that configuration of the cam system, the gate cam 7, guard cam 12 and latch opening cam 11 are in the positions shown in section 1A of Figure 1, but a rotary cam 14 is lowered to provide a needle lowering timed to occur about three needle positions later than the lowering cam 5.

The needle selection associated with section 1C of Figure 1 is simply a raising of all jack butts, timed to occur when those butts have passed the raising cam 1 and arrive in a cam track 15 for loop transfer acceptance. Those butts then rise up a cam surface 16 to acceptance height and are then depressed so as to miss the lowering cam 4.

The needles remain at acceptance height until the needle butts pass down the lowering cam 14.

Thus the cam system illustrated in Figure 1 performs a three knitting selection (knit, not knit and tuck) and also functions as a loop taes;r system for either donation or acceptance of transferred loops, by suitable manipulation of the gate cam 7 and associated guard cam 12, the latch clearing cam 11 and the lowering cam 14.

Figure 2 illustrates the largely similar but slightly modified cam system for use with two-track selection on the knitting machine. Similar or identical parts in Figure 2 have the same reference numerals as those in Figure 1. As will be appreciated from 5eztoa 2A, the cam system arrangement is the same, the difference being in the needle Fiction. Figure 2 in section 2A shows the needle path or knit selection, and in section 2B shows the needle path or tuck selection.

Claims (8)

CLAIMS:

1. A cam system for a circular knitting machine comprising non-knitting, knitting and tucking needle paths for needles passing the cam system, characterized in that a gate cam is movable to a position in which it moves selected needles from the knitting and tucking needle paths into a loop transfer donation needle path; a selectively engageable raising cam is provided for raising all needles into a loop transfer acceptance path; and a lowering cam associated with the said raising cam is movable to a position in which it lowers all needles from the loop transfer acceptance path.

2. A cam system according to claim 1, wherein the gate cam is pivotably mounted, and is rotatable between a first rotary position in which it permits selected needles to follow their knitting or tucking needle paths, and a second rotary position in which it blocks the movement of the selected needles into a part of their knitting and tucking paths, and directs them instead into a loop donation transfer path.

3. A cam system according to claim 2 wherein the gate cam is associated with a blocking cam which blocks the movement of the needles into the loop donation transfer path when the gate cam is in its first rotary position, but opens the loop transfer donation path when the gate cam is in its second rotary position.

4. A cam system according to claim 3, in which the gate cam and the blocking cam are movable only in synchronism from a single control lever.

5. A cam system according to any preceding claim, wherein the gate cam is associated withsupplementary raising cam for raising the needles again, at the end of the loop transfer process, to nearly clearing height so as to bring the needle latches into engagement with a latch opener.

6. A cam system according to claim 1, wherein the raising cam is a fixed raising cam for engagement with the butts of needle jacks of all needles raised at a loop transfer selection station, for raising all needles to a loop transfer acceptance level.

7. A cam system according to any preceding claim, wherein the lowering cam is pivotably mounted and is rotatable between a first rotary position in which it is out of the needle path and a second rotary position in which it effects the appropriate needle lowering.

8. A universal cam system for providing, at a single station of a knitting machine, selection between the various knitting movements of the needles and between loop transfer movements in both directions, substantially as described herein with reference to the drawings.