WO1981002592A1

WO1981002592A1 - Circular knitting machines

Info

Publication number: WO1981002592A1
Application number: PCT/GB1981/000043
Authority: WO
Inventors: J Klee
Original assignee: Bentley Eng Co Ltd; J Klee
Priority date: 1980-03-12
Filing date: 1981-03-12
Publication date: 1981-09-17
Also published as: GB2083083A; JPS57500294A

Abstract

In a circular knitting machine a racking mechanism has an evenly cut rackwheel (1), cam means for imparting racking motions to pawl carrier (7, 8), a plurality of pawls (3, 4, 5, 6) mounted on each of the carriers (7, 8) for conjoint movement, masking means (12) mounted on the rackwheel (1) to prevent a pawl of said plurality of pawls (3, 4, 5, 6) from engaging a tooth of the rackwheel (1) during a racking motion and a first movable bluffing means (13) to prevent to prevent another of said plurality of pawls (3, 4, 5, 6) from engaging a tooth of the rackwheel (1).

Description

TITLE:

Circular Knitting Machines

DESCRIPTION:

This invention relates to racking mechanisms for circular knitting machines, particularly machines for the manufacture of socks and stockings.

The invention aims to provide a racking mechanism for applying racking strokes selectively to a rackwheel which may be uniformly cut or rackwheel assembly rotatable conjointly with a control or programme drum. A small number of different parts of simple and robust construction may be used and the "reading" of the rack selection by the operator may be facilitated whilst providing safe operation of the mechanism.

The invention provides a circular knitting machine having a needle cylinder, a control drum for controlling the knitting operation performed by the cylinder and a racking mechanism for incrementally advancing the control drum when required, said racking mechanism including a pair of pawls mounted on each of a pair of pawl carriers so as to engage when desired at a particular position on the periphery of a rack wheel, cam means on a shaft rotatable in a predetermined relationship to the needlecylinder rotation to move the carriers so that each pair of pawls performs an early and a late stroke in seriatim fashion during a pre determined extent of revolution of the needle cylinder, cam operated bluffing means for engaging a predetermined one of each pair of pawls to make their early stroke ineffective and selecting means mounted on the periphery of the rackwheel which one of the pawls should be effective in advancing the rackwheel for a subsequent increment.

Using the invention, four pawls can be made to "recognise" a particular tooth of the rackwheel and so move that tooth onward during a predetermined stage of cylinder revolution. Only two cams need to be provided to advance the pawls. An operative can instantly determine at what time the control drum is intended to be moved. A direct selection can be used.

DRAWINGS:

Figure 1 is a perspective view from one side of the rackwheel of a racking mechanism of the invention showing a pair of pawls engaged in a tooth of the rackwheel at the end of a racking stroke and a pair of pawls about to start a racking stroke;

Figure 2 is a perspective view similar to Figure 1 but from the other side of the rackwheel; Figure 3 is a view similar to Figure 1, but showing the nearside pawl bluffed directly by a masking plate secured in a tooth of the rackwheel; and Figure 4 is a view similar to Figure 2, but with the rackwheel teeth broken away to show a bluffing slide located within a central groove formed in the rackwheel.

Specific embodiment

In Figure 1 an evenly cut rackwheel has a central groove 2 cut midway of the width of the rackwheel teeth to a depth just below the roots of the teeth. A pair of pawls 3 and 4 are arranged to cooperate with teeth on one side of the groove 2 and another pair of pawls 5 and 6 are arranged to cooperate with the teeth on the other side of the groove 2. The pairs of pawls are pivotably mounted at 9 on pawl carriers 7 and 8, one_. carrier to each pair of pawls. The pawls are biased towards the rackwheel 1 by resilient springs (not visible). The carriers 7 and 8 have cam follower rollers (not shown) through which they are reciprocated by four lobed cams of the type shown in British Patent 1,094,924 so as to provide a total of eight possible racks, four to each carrier, during every two cylinder revolutions. The pawls can be raised clear of the rackwheel 1 by a common rod 10 which is fixed on a pivotable arm 11 carried suitable on a pivot pin (not shown) secured to the frame of the knitting machine. The rod 10 projects, at one side, over the usual follower for a timing chain (not shown) so that it can be raised and lowered by the passage of chain studs in the usual manner. When the rod 10 is lowered as a chain stud passes under the timing chain follower, the pawls can be lowered towards the rackwheel and, on each foward stroke of the carriers 7 and 8, each pair of pawls will tend to rack the wheel 1 simultaneously unless prevented from doing so by rack selecting means.

The rack selecting means, or rack bluffing means, consists of four devices:- a. Direct bluffing devices for masking the teeth of the rackwheel 1 and fixed to the rackwheel. b. Movable bluffing device for acting on the inner pawls 4 and 5 nearest the groove.2, of the two pairs of pawls. c. Movable bluffing device for acting on all four pawls. d. Movable bluffing device for preventing racking by all the pawls until a subsequent timing chain stud is advanced under the chain follower, inspite of the pawls being lowered by a chain stud already under the follower. This bluffing device acts in the same manner as the collapsible nose feeler la described in British Patent 1,094,924

Bluffing Devices a

The direct bluffing devices (see Figure 3) consist simply of suitably shaped blocks or masking pieces 12 which are secured by any appropriate means in a tooth space of the rackwheel 1. The block may be only wide enough to engage (bluff) a single pawl as shown, or it may be wide enough to span both pawls of a pair. Preferably the direct bluffing devices prevent all pawls except one from engaging each tooth to ensure that, each tooth is only engaged by the intended pawl. Many of the Figures do not show the direct bluffing devices for ease of representation.

Bluffing Device b

The movable bluffing device b consists of a slide 13 having an angled nose which rests in the central groove 2 in the rackwheel. The slide is high enough to prevent the two inner pawls 4 and 5 from engaging. the rackwheel 10 by engaging the wider noses of the inner pawls and lifting them to above the rackwheel teeth. The slide 13 is reciprocated forwards and backwards in its groove by cam means (not shown) in similar manner to the feelers, 1,2,3 and 4, shown in Figure 1 of British Patent 1,094,924. The timing of movement of the slide 13 is such that it remains forward (as shown in

Figure 4 where it masks the tooth 15 adjacent the inner pawl 4) for half a revolution of the needle cylinders and then withdraws to expose the tooth 15 for the second half revolution of the needle cylinder. Thus, on every first half revolution of the needle cylinders, the inner pawls 4 and 5 cannot rack the rackwheel. By masking a rackwheel tooth with narrow blocks 12 situated under the outer pawls 3 and 6, no rack will take place during the first half revolution of the needle cylinder when the four pawls are lowered by a chain stud. The outer pawls are bluffed by the masking blocks and the inner pawls are bluffed by the slide 13. However, at the end of the half revolution of the needle cylinder, the slide 13 is withdrawn and the inner pawls, 4 and 5, can engage the unmasked parts of the tooth. Therefore, by appropriately fixing a masking block in the tooth under one of the inner pawls, as well as the outer pawls, either of the two inner pawls can be prevented from engaging the tooth, when the slide 13 is withdrawn.

By using the correct combination of masking blocks it is possible to select one of the four pawls to rack the tooth during any of the four quarter revolutions of the needle cylinder.

If the rod 10 is lowered when the pawls are disposed as shown in Figure 1, then:

To obtain a rack in the first quarter revolution, no blocks 12 are required. Slide 13 is forward, bluffing pawl 4, but pawl 3 can engage the tooth.

To bluff a first quarter revolution, a block 12 is located under pawl 3. Slide 13 is forward. Pawls 3 and 4 cannot engage tooth on the first quarter revolution. To rack in the second quarter revolution, pawls 3 and 4 are bluffed as above. No block is provided under pawl 6. Slide 13 is forward bluffing pawl 5, but pawl 6 can engage the rackwheel tooth.

To bluff in the second quarter revolution, blocks 12 are located under pawls 3 and 6. Slide 13 is forward. Pawls 5 and 6 cannot engage tooth on the second quarter -revolution. To rack in the third quarter revolution, blocks 12 are under pawls 3 and 6. Slide 13 is moved back after half a revolution allowing pawl 4 to engage the tooth.

To bluff in the third quarter revolution, blocks 12 are provided tinder pawls 3 and 6 and the slide 13 in its forward position has bluffed for half a revolution. The slide 13 is retracted but a bJ ock 12 under pawl 4 prevents a rack on the third quarter revolution. To rack in the fourth quarter revolution, blocks 12 are provided under pawls 3, 4 and 6, but slide 13 having moved back after half a revolution, allows pawl 5 to engage the tooth.

Bluffing Device c

This serves for distinguishing between first and second revolutions of the needle cylinder (see Figure 4). As a timing chain stud lowers the rod 10 and releases the pawls during two revolutions of the needle cylinders, racking if only the above mentioned' devices were used, would occur in the first revolution. If a rack or racks are required in the second revolution but not in the first, the combination of blocks 12 and slide 13 positions will be exactly as set out above for the first revolution, but εn additional bluffing device 16 is used in conjunction with a peg 17 mounted in the side of the rackwheel adjacent a tooth. Holes are positioned adjacent each tooth, space so that for "second revolution"" racking the bluff member 16 can be raised by an appropriately positioned peg during th.e "first revolution" of the needle cylinder. Such raising lifts the rod 10 and bluffs the pawls 3,4, 5 and 6. At the end of the two strokes of each pair of pawls, the bluff member 16 is withdrawn to the lowered position shown in Figure 4 thus allowing the pawls to lower and "read" the combination of masking pieces 12 and slide- 13 positions, during the second revolution of the needle cylinders. The forwards and backwards movement of the member 16 is obtained similarly to that described for slide 13, but at half the frequency. For a "first revolution" racking no peg is required and the member 16 merely reciprocates in the low position where it may be supported by a flange such as 18, (figure 4) formed on the side of the rackwheel 1.

Bluffing Device d

A further bluffing device (Figure 1) consists of a collapsible nose or follower 19 which is pivotably and/or slidably attached by a shoulder screw 20 to a slide 21. The nose 19 is shown in the lowered position having been withdrawn from a peg 22. The nose 19 can only be raised onto a peg by movement of the rackwheel which advances a peg 22a from behind the nose. The slide 21 functions in an analogous way as the feeler bar 1 in British Patent 1.094,924. The slide 21 is advanced by an appropriate cam to the position shown in Figure 1 and remains in the advanced position, during racks 2-8 inclusive, of any 8 rack sequence of a quarter revolution each initiated by a chain stud. The slide 21 withdraws just prior to the first rack of any sequence, and therefore, allows rack 1 to take place. It is advanced immediately after rack 1 to be available for bluffing any remaining racks 2-8 should they not be required until a subsequent chain stud is advanced under the chain follower. The slide 21 repeats its reciprocatory action every two revolutions of the needle cylinder and the nose 19 merely reciprocates in the low position shown in Figure 1 after it has been removed from a peg at the end of a racking sequence. If there is no peg 22a. following immediately behind peg 22 the nose 19 may be allowed to rest on a flange 23 formed on the side of the rackwheel 1.

The bluffing device d functions as follows. Consider that a timing chain stud has caused release of the pawls by lowering the rod 10 and that a racking sequence is in progress. It may be that, having taken one or more racks of the eight racking strokes made available by the chain stud, it is desired to cease racking before the eighth rack has taken place and before the follower has dropped off the chain stud. However, the last rack which was taken (say, for instance rack 5), would bring up a further tooth of the rackwheel which is due to be racked when the next chain stud is advanced under the chain follower. Unless this tooth is temporarily bluffed it will be racked prematurely if it is a higher numbered rack than the last one taken, Therefore, a peg 22 is fixed adjacent the tooth and is advanced under nose 19 on the last rack (rack 5 in this instance) thus raising the nose 19 and rod 10 for the remainder of the sequence (racks 6-8 in this instance).

Modification

Having described the system of racking in principle, it can be seen that a number of variations may be made within the scope of the invention. For instance, the bluffing device 16, shown in Figures 2 and 4 can be made to positively distinguish between first and second cylinder revolutions. The pegs 17 and 17a as shown are situated adjacent tooth spaces, however, if two holes are drilled adjacent to each tooth space, it is possible to place a peg either in a forward position or a rearward position relatively to a single tooth space. If the peg is in the forward position as shown in Figures 2 and 4, the. follower 16 will rest on it during the first revolution of the needle cylinders and withdraw to the low position during the second revolution. By placing the peg in the rearward position (which would be between pegs 17 and 17a) the follower would be held high during the second revolution and lowered during the first revolution. Thus, by placing the peg in the appropriate position, it is possible to ensure that no racking can take place on a "wrong' revolution of the needle cylinder. Such a safeguard is highly desirable when racking occurs to cause the needle cylinder to either go into reciprocation or out of reciprocation, but the expedient may be used at any time to ensure that the possibility of mis- -racking is minimised.

In similar manner the bluffing device 13 (Figure 4) could be made to positively distinguish between racking in a first half revolution and a second half revolution. The slide 13 can be provided with suitable bluffing projections for engaging projections on the outer pawls 3 and 6. Thus when the slide is retracted to unmask a tooth under the inner pawls 4 and 5, the retracting movement could cause bluffing projections carried by the slide 13 to mask the parts of the tooth under the outer pawls. Thus, forward movement of the slide would cause bluffing of the inner pawls and unbluffing of the outer pawls and reverse movement of the slide would cause bluffing of the outer pawls and unbluffing of the inner pawls.

A further variation in the arrangement could be to mount the pairs of racking pawls in 'U' shaped channel section rings which completely surround the rackwheel. The rings could be oscillated to and fro on the rackwheel by. linkages coupled to the slides 7 and 8 or coupled to bell-crank levers instead of slides.

Using the finvention, a rackwheel can have teeth which are clearly recognisable to effect any give particular rack of No 1 up to No 8. The selection, being effected partly by masking pieces and partly by bluffing elements, is relatively safe and the timing is likely to be less critical than with prior art arrangements.

A timing chain can be conveniently arranged to cooperate in appropriately timed relationship with the racking mechanism.

In the mechanism of the invention the pawls fulfill two purposes at the some timer firstly the pawls serve to transmit the racking force from the carrier to the rackwheel; and secondly the pawls are made to act as sensing devices to give appropriate racks only. The bluffing device b merely enables certain pawl to participate in sensing and its operation is thus less critical than were the bluff itself is intended to govern selection. The bluffing device b operates thus without interruption but the pawls themselves are instrumental in whether racking occurs in the unbluffed condition. The mechanism can thus be executed in a simple mechanical arrangement.

When one pawl is "chasing" a tooth already moving by the operation of another pawl, the timing of the selection operation is not changed with respect to the angular position of the rackwheel. Ccimoound bluffing motions, which are difficult to control because they arise out of the interaction of a number of elements, each with its own manufacturing tolerance, are reduced.

Claims

CLAIMS:

1. Circular knitting machine having a needle cylinder, a control drum for controlling the knitting_. operation performed by the cylinder needles and a racking mechanism for incrementally advancing the control drum when required, said racking mechanism including a pair of pawls mounted on each of a pair of pawl carriers so as to engage when desired at a particular position on the periphery of a rack wheel, cam means on a shaft rotatable in a predetermined relationship to the needle cylinder rotation to move the carriers so that each pawl of each pair performs an early and a late stroke, the respective pairs acting in seriatim fashion during a predetermined extent of revolution of the needle cylinder, cam operat.ed" bluffing means for engaging a predetermined one of each pair of pawls to make their early stroke ineffective and selecting means mounted on the periphery of the rackwheel for controlling which one of the pawls should be effective in advancing the rackwheel for a subsequent increment.

2. Circular knitting machine according to claim 1 in which the rack wheel is uniformly cut and masking means are mounted in substantially all teeth to indicate which pawl is to be used for racking that tooth.

3. Circular knitting machine according to claim 1 in which the cam operated bluffing means is arranged to slide to and fro in a central groove in the rack wheel to lift side ways projecting parts of the appropriate pawls.

4. Circular knitting machine according to claim 1 in which the cam means provide two racking motions for each of the carriers in the course of a single cylinder revolution period.

5. Circular knitting machine according to claim 4 in which the racking mechanism is activated for the two cylinder revolution period by a timing control means, and a second movable bluffing means is provided responsive to programming means for bluffing all pawls in a first cylinder revolution period.

6. Circular knitting machine according to claim 5 in which the second movable bluffing means, is additionally capable of bluffing all pawls in a first and / or second half of the activation period by appropriate programming means.

7. Circular knitting machine mechanism according to claim 5 or claim 6 in which the second movable bluffing means is cam operable.

8. Circular knitting machine mechanism according to claim 5 in which a third bluffing means is provided for bluffing racking motions up to the end of the activation period but movable to unbluff at the next following activation period.