This invention relates to circular knitting machines and concerns particularly a device applicable to machines with relatively small diameter cylinders (generally less than 12.7 cm or 5 inches) and fitted with quality control drums (also known as main control drums). It is common practice with such knitting machines to effect the introduction into and withdrawal of yarns from the knitting needles using "move" studs located at selected intervals of a continuous driven chain. Through levers the "move" studs actuate cams on the quality control drum, and further levers in contact with the cams direct stitch fingers each containing yarn, into or out from the knitting needles.

Furthermore by altering the height and profile of cams, and by means of levers causing movement of the knitting needle butts, the stitch size and hence the length of yarn in each knitted course can be kept constant or varied according to a predetermined plan.

In addition to the yarns which are knitted into fabric other yarns may be inserted into or through knitted loops and such yarns are described as being "laid" into the fabric. One type of yarn commonly "laid" into knitted fabric is termed elastic yarn or elastic thread, consisting usually of one or more continuous filaments of Spandex or of latex rubber being, in order the exercise control over it, covered by wrapping it within one or more layers of a fine staple yarn such as cotton or a fine synthetic filament, yarn, such as continuous filament nylon. Whereas with such yarns that are laid into the fabric it is common practice that the introduction to and withdrawal from knitting are effected by "move" studs on the continuous driven chain as already described, it is usual that the control of the length of yarn laid in each

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knitted course is effected by means of a yarn "furnisher" located and operating quite apart from the quality control drum. These yarn "furnishers" may be for example, the "disc" type for which the length of yarn laid into each knitted course of fabric depends on the radial distance of the yarn track from the centre of the disc.

Such yarn furnishers are adjustable to supply a fixed selected length of yarn for each course of knitted fabric. In order to alter the length of elastic yarn in each course it is customary to stop the knitting operation and make appropriate adjustments to the furnisher before recommencing Che knitting operator.

Should one desire to continuously vary the length of yarn laid into a knitted course of fabric it is usual to employ a variable speed electric motor, in which the motor speed, and therefore the yarn speed and length of yarn per knitted course, are controlled by a cam of selected profil coupled with the main drive of the knitting machine through gear train.

This invention concerns a simpler and less expensive mechanical arrangement that may be used to contro the feeding of "laid in" yarn on conventional knitting machines. There is thus provided by the present invention a knitting machine having a disc or cone type yarn furnishe to regulate the feed of a "laid in" yarn, yarn guide means co-operating with the surface of the yarn furnisher to hold the yarn in feeding relationship therewith, said guide mean being movable relative to said surface to control the position of said guide means on said surface to vary the rate of yarn feed, a cam track on the quali-ty control drum of the knitting machine having a profile determined in accordance with the required yarn feed rates, and means operable by the cam track to control said movement of the yarn guide means.

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Thus the "laid in" yarn feed speed may be changed and therefore the length of yarn laid into each knitted course of fabric may be varied either from one fixed value in one part of the fabric to another value in a succeeding part of the same fabric, or continuously in any part of the fabric.

More specifically there is provided a yarn feed control for a knitting machine comprising a feed member having a surface of revolution and mounted for rotation o the axis of said surface, means to rotate said feed member about said axis at a predetermined speed, yarn guide means arranged to hold the yarn in frictional drive contact with said surface so feed movement is imparted to the yarn by the rotation of the feed member and the rate of feed is proportional to the radius of the location of the contact between the yarn and said surface from the axis of the surface, said guide means being movable relative to the surface of revolution to adjust the location of the contact between the surface and the yarn, and means to control the movement of the guide means in a predetermined extent and sequence during a knitting cycle.

Referring now to the drawing in which the basic componentry is illustrated without reference to the total knitting machine in order to emphasise the elements of the invention and to simplify the drawings by the elimination of the extremely complex structure and mechanism of a knitting machine . However persons familiar with knitting machines can readily understand how the mechanism can be incorporated into known types of knitting machines . A knitting machines suitable for this purpose is that marketed under the name ESTA.

The yarn package 17 supplies the thread 16 to the knitting machine via the guide 18 thread tensioning devices 19, and thread feed control 25. The feed control comprises a disc 22 supported by the spindle 22a for rotation in a horizontal plane relative to the frame of

the machine indicated generally at 26. The shaft 22a is driven from one of the various power sources on the knitting machine so as to rotate at a steady speed in a clockwise direction as viewed in Figure 1 of the drawings. The upper face of the disc 22 is flat and has a surface finish which will establish suitable friction contact with the thread 16 to feed the thread forward without slippage between the thread 16 and the disc 22.

The bracket 14 is pivotally mounted by the pin 15

10 to the machine frame 26 so that the bracket 14 may have a limited oscillating pivotal movement relative to the frame 26 about the pin 15. The axis of the pin 15 is parallel to the axis of the shaft 22a. Carried by the bracket 14 is an arm 23 which projects over the disc 22 and carries

15 adjacent its free end, a wheel 21. The wheel 21 is supported on the arm 23 for rotation about. a horizontal axis located in a plane at right angles to the axis of the ' shaft 22a.

The arm 23 is pivotally connected to the bracket

20 14 y the shaft 27 for movement about an axis parallel to the axis of the wheel 21. The torsional spring 24 is connected between the arm 23 and the adjustment knob 24a mounted on the shaft 27 secured to the bracket 14. The spring 24 urges the ^" wheel 21 towards the disc 22 to hold

25- the yarn 16 in frictional drive contact with the disc 22. The other end of the shaft 27 has a reduced diameter pin portion 28 which is received in the forked arm 12a of the bell crank member 12. The other arm of the bell crank member 12 is connected to the operating rod 11.

-"- The spring 13 is connected between the forked arm 12a of the bell crank and a fixed part of the frame 26 to urge the bracket 14 to pivot in a direction that moves the arm 23 in a direction to bring the wheel 21 towards the centre of the disc 22. The adjustment screw 14a is threadably engaged in the lug 26a attached to the machine frame, and may be set to establish the basic position of the wheel 21

relative to the centre of the disc 22. The screw 14a thus sets the basic minimum feed rate of the yarn.

The rocker arm 10 is journalled through the bearings 6 on the shaft 7 which is fixedly supported by the frame of the knitting machine not shown. One end of the rocker arm is pivotally connected at 11a to the push rod 11, the rocker arm 10 has two portions 8 and 8a carrying respective cam followers 9 and 9a. The cam followers 9 and 9a are threadable engaged in- apertures in the portions 8 and 8a so that they may be adjusted relative to the cams 3 and 3a respectively. The portions 8 and 8a are interconnected by the bar 4 which is also connected to the portion 5 so that they all operate as a integral rigid arm. The cams 3 and 3a are mounted on respective drums

2 and 2a which are arranged co-axial to rotate independently on the shaft 1. It is common practice to provide a plurality of such cam drums on* knitting machines and they are drive.n in an appropriate manner from a motor. in the drawing the drum 2a is provided with a continuous ring of ratchet teeth 2b so that the drum 2a may be ^* driven by a pawl in a step-wise motion. This provides a convenient means of rotating the drum 2a at a substantially reduced speed to that of drum 2. The bracket 10a is attached to a fixed part of the machine frame 26 to act as a guide for the rocker arm 10.

The provision of the two cams 3 and 3a enables the adjustment to the yarn feed rate to be made in accordance with two independent parameters. These adjustments may be made at different points in the knitting cycle and may also be superimposed one on the other. For example, the cam 3a may be used to make a change in the'rate of feed between two portions of the fabric each portion comprising a number of courses. The cam 3 may be used to effect an adjustment in the yarn feed rate between successive courses of the fabric over a large number of courses.

Also as previously referred to, the cam 3a may be used to effect the change in feed rates between two portions of the fabrics, each comprising a number of courses, and in addition the cam 3 may effect a change in the feed rate between each successive course in one of those portions of the fabric.

It will also be appreciated thta in some applications only one cam is required. Also a further cam follower may be provided on portion 5 of the rocker arm 10 to co-operate with a third cam.

The pivotally mounted bracket 14 may be modified for linear sliding movement on the frame 26 to effect the adjustment of the position of contact of the yarn 16 with the disc 22. The sliding movement of the bracket 14 can be effected by the crank member 12 if the crank member is mounted to operate in a plane at right angles to that shown in the drawings,

Example 1

In one part of knitted fabric it is desired to alter by 10 mm the course length of yarn laid by the yarn furnisher into the knitted fabric in one part as compared with another.

At the point of contact of the driven disc and the free running wheel the elastic yarn is extended 657 ₀ . The leverage ratio of the device is 3.94.

The length of extended yarn per course = 16.5 mm. Therefore the difference in radial position of the free running wheel for the feeding of the yarn into the two portions of fabric = 165/2'Tr ^' mm.

The rise to be made by the cam is

165 ⁼ 2Tf x 3 . 94

= 0 . 67 mm

Example 2

Over approximately 60 knitted courses in the leg fabric of a sock it is desired to reduce the length of elastic yarn laid into the fabric by 24 mm per course of knitted fabric.

For knitting machine the following data apply:-

Cam profile changes 0.001 inch in depth (= 0.0254 mm) per single move of the ratchet which is equivalent to two courses of knitted fabric. Leverage ratio of the device is 4.08 to 1. Two rotations of the driven disc equals one knitted course of fabric and the elastic yarn is extended to 607. of its relaxed length at the point of contact with the driven disc. A single ratchet move will cause the point of contact with the driven disc. A single ratchet move will cause a radial change of the yarn track in the driven disc = 0.0254 x 4.08 = 0.1036 mm and a circumferential change In length of yarn track = 0.1036 x 2 = 0.650 mm and in length of yarn laid in one course of knitted fabric = 0.650 x 2 = 1.30 mm (elastic yarn in extended state)

= 1.30 x (elastic yarn in relaxed state)

160

= 0.813 mm number of single moves required - '■— = 29.6 which will

0.813 cover

2 x 29 .6 = approx . 60 courses .

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