GB2210632A - High speed circular warp knitting machine - Google Patents

Abstract

A circular warp knitting machine for knitting stitch chains connected by laid in elastic weft to form a net e.g. for covering food products comprises a weft laying device (50) which rotates relative to the stationary needles (34) and lays the weft (27) around the outside of the needles, the laying device also acting as a deflector to displace the warp threads outwardly as it passes. The warp threads are fed by horizontal guides incorporating latch openers. The elastic thread packages (26, 27) are mounted in a stationary position away from the knitting head to reduce the revolving mass and the space necessary to accommodate the revolving mass. Furthermore, the packages (26, 27) can be paired in 'top and tailed' relationship. A plurality of like knitting heads (22) is mounted in relatively close proximity in a single machine frame and the warp threads (20) are fed from a power driven warp beam (14). <IMAGE>

Description

HIGH SPEED KNITTING MACHINE The present invention relates to a machine for producing tubular fabrics consisting of a number of separate chain stitches connected by a spirally inlaid thread typically, elastic or similar yarn. In particular, the invention relates to a high speed knitting machine for knitting netting for covering food products, and in particular meat.

A high speed knitting machine should satisfy a number of desirable criteria in addition to being reliable, fast and relatively inexpensive. It should permit the fabric to be continuously knitted and should require a minimal amount of space and be relatively lightweight. The supplies of yarn should be readily changed or added to without interrupting the operation of the machine and a counterweight should not be required which results in imbalance at high speed.

Prior art knitting machines are of two general types.

The first type consists of a machine which can make several rolls at a single time using a reciprocal movement. However, this machine is large and the reciprocal movement is very slow, thus limiting the amount of rolls which can be produced in a certain time. The second type of machine uses a circular movement, however, this produces only a single roll at a time and the size of the elastic bobbin limits the amount of continuous netting which can be made without stopping. Also, when the weft package is empty is must be stopped, reset and retensioned before it can then operate. This takes time and the overall speed of the machine is relatively slow.

In addition, because the machine rotates, a counterweight is required for balance, which is heavy, and also requires space within the machine which results in the overall machine taking up a relatively large area.

An object of the present invention is to provide an improved knitting machine which obviates or mitigates the aforesaid disadvantages. This is achieved by providing a knitting machine in which the elastic thread packages are mounted in a stationary position away from the knitting head. This results in reducing the revolving mass and the space necessary to accommodate the revolving mass. Furthermore, the commencement of wind on the package can be left as a tail which is knotted to the free end of a second package thus permitting the machine to run continuously without stopping to change packages.

This arrangement also permits a plurality of like knitting heads to be mounted in relatively close proximity in a single machine frame in such a manner that chain stitches can be fed from a power driven warp beam.

In a preferred arrangement, a plurality of knitting heads are mounted on a knitting head frame fed from a single warp and stationary creels can be mounted at the sides of the frame for supplying respective knitting heads. The knitting head frame can also include a fabric take-off roll for receiving the knitted fabric from each of the knitting heads. In an alternative arrangement the knitting heads may be mounted on a frame fed by a plurality of warps.

Each knitting head consists of a hollow cylinder haying a plurality of grooves called tricks, in the outer wall, in which needles are disposed. A fixed feeder is disposed above the cylinder with arms which are slightly offset from the position of the tricks.

The fixed feeder permits the warp yarn to be fed through onto the needle and into the inside ofthe cylinder.

Disposed between the cylinder and the fixed feeder is a rotating weft feeder and yarn deflector. Rotation of the feeder is synchronised with a cam which raises the needles so that the fixed feeder deflects the warp yarn and lays the elastic weft yarn outside the needle so that as the needle rises and falls the rubber yarn is trapped between the chain stitches in a spiral fashion to provide radial and circumferential elasticity or rigidity in the knitted fabric.

The fixed feeders are mounted radially in the supported feeder head head support tube through which passes a tube mounted in bearings and carrying the feeder and deflector so that these can be rotated by a synchronised drive while feeding the inlay weft thread.

Accordingly, in one aspect of the present invention there is provided a knitting head for use with a knitting macnine, said knitting head comprising: a fixed hollow cylinder having a cylinder wall with a plurality of curcumferentially spaced grooves disposed in said wall, each groove having a needle with a hook at its upper end disposed therein, said hollow cylinder being disposed in a cam box having rotary cam means adapted to be coupled to each needle so that rotation of said rotary cam means causes displacement of each needle along its respective groove, stationary warp yarn delivery means disposed above said hollow cylinder for feeding a warp yarn from a remote location to each respective needle, rotatable weft yarn delivery means disposed between said hollow cylinder and said stationary warpyarn delivery means for delivering a weft yarn from a remote location around the periphery of said hollow cylinder, the speed of rotation of said rotary cam means and said rotatable weft yarn delivery means being synchronised whereby, in use, upon rotation of said rotary cam means and said rotatable weft yarn delivery means displacement of said needles causes chain stitches to be made which are fed inside said cylinder, and said rotatable weft yarn delivery means delivers said weft yarn outside said cylinder so that when said needle is displaced within said groove the tension in said weft yarn pulls it over the top of the needle to be trapped in a subsequent stitch.

Preferably, said needle includes a pivotable latch for preventing said weft yarn from being hooked by said needle on a downward stroke. Conveniently, said grooves are disposed in an outer wall of said hollow cylinder and said needle hooks face outwardly.

Preferably also, the knitting head and needle grooves are generally vertically disposed and the warp yarn is .fed to said knitting head in a generally vertical direction.

Preferably, said stationary warp yarn delivery means comprises a plurality of stationary warp yarn delivery elements, a respective element being associated.

with a respective needle and being vertically disposed above said needle but being slightly offset therefrom to permit said needle to lie vertically above said element to collect a length of thread as it descends.

Conveniently, said element is in the form of a generally horizontal bar having an aperture therein through which said warp yarn is passed. Conveniently also, each element includes a latch stop for restricting the upward pivotable movement of each latch on said needle.

Conveniently, said rotatable weft yarn delivery means comprises a generally planar horizontal weft yarn rotatable feeder and deflector element, said rotatable feeder and deflector element being coupled to a rotatable hollow yarn delivery tube which is adapted to be driven by drive means, said tubular element and said rotating feeder and deflector having passage means through which a weft thread can be fed to be disposed outside the periphery of the hollow cylinder. Conveniently, the deflector includes an outer cam portion for deflecting the warp yarn outside the periphery of the hollow cylinder as said deflector rotates.

Conveniently, the weft yarn may be an elastic thread and said warp yarn is made of a substantially inextensible material or alternatively both yarns may be elastic.

Conveniently also, said tubular yarn delivery tube is rotatable via bearing means in a support tube which is fixed and coupled to said stationary warp delivery means.

Accordingly, in another-aspect of the invention there is provided a knitting machine comprising: warp yarn delivery means for delivering a plurality of warp yarns to at least one knitting head, said knitting head being dipsosed in a knitting head frame and the knitting head receiving a plurality of warp yarns, said knitting head frame having a plurality of weft yarn package holders disposed at a remote position from said knitting head, at least one package holder being adapted to supply at said least one knitting head with weft yarn, and a fabric take-off roll disposed in said knitting head frame for receiving knitted fabric from said knitting machine.

Conveniently, said knitting machine has a plurality of knitting heads and said warp is driven by warp drive rollers and said warp yarn is fed across to said knitting head frame via a warp sheet. Conveniently also, yarn tnesioning devices are provided for controlling the tension of each yarn fed to respective knitting beads.

Alternatively said knitting machine has a single head and said warp yarn is fed to said single head from a creel having a plurality of package holders.

Accordingly, in yet another aspect of the invention there is yet provided a method of knitting a tubular fabric comprising the steps: feeding a plurality of warp yarn threads to a knitting head; feeding at least one weft yarn to said knitting head and disposing said weft intiially around the periphery of said knitting head by a rotary movement, and synchronising the movement of needles within said knitting head to cause the weft yarn disposed around the periphery of said knitting head to be trapped between successive stitches of said warp yarn to create a tubular structure.

Conveniently, said method includes the step of feeding the warp and weft yarns from a remote stationary location. Preferably said warp yarns are fed vertically downwards to vertically disposed knitting heads.

Conveniently also, the rotation of the weft yarn feed delivery means and the rate movement and displacement of the needles in each knitting head is synchronised.

Conveniently also, two package holders are provided for each knitting head and the package holders are adapted to be tied together to provide substantially continuous knitting by each knitting head to produce a continuous tubular fabric.

These and other aspects of the invention will become apparent from the following description when taken in combination with the accompanying drawings in which: Fig. 1 is a diagrammatic and-perspective vie of a knitting machine consisting of a plurality of knitting heads in accordance with an embodiment of the invention; Fig. 2 is an enlarged said elevation of a knitting head in accordance with an embodiment of the invention; Fig. 3 is a plan view taken on the lines 3 - 3 of Fig. 2 and depicting the shape of the weft yarn feeder and deflector, and Figs. 4a to g depict sequential stages in the knitting of a tubular fabric by the knitting head in accordance with the present invention.

Reference is first made to Fig. 1 of the drawings which depicts a high speed knitting machine generally indicated by reference numeral 10 in which warp yarn 12 is fed from a warp drum 14 driven by warp drive rollers 16 across a generally horizontal warp sheet 20. The warp yarns are downwardly fed from the warp sheet 20 to a plurality of knitting heads 22 disposed at the top of a knitting head frame 24. At the side of the knitting head frame 24 is disposed a plurality of weft yarn package holders 26 and the weft yarn 27 is also fed to respective knitting heads on the frame. The woven tubular fabric is knitted,as will be later described in detail and the tubular fabric is supplied to fabric take-off rolls 28 for storing the knitted tubular fabric.

It will be appreciated that there is a plurality of separate knitting heads disposed in relatively close proximity on a single knitting head frame and the weft yarn package holders 26 are disposed at the side of the frame and one pair of weft package holders can be used to supply a single knitting head. Alternatively, a single creel can be used to supply a single knitting head.

It will be appreciated that the advantage of this arrangement is that the tail of one package can be tied onto the free end of the next creel to provide subs tan- tially continuous knitting of the tubular fabric and also that the knitting heads are limited to a relatively small area minimising the volume and weight requirements.

Reference is now made to Fig. 2 of the drawings which depicts one of the knitting heads 22 as shown in Fig. 1 in greater detail. Each knitting head 22 consists of a vertically disposed hollow cylinder 30 which in turn is mounted in a cam box 32. The cylinder 30 is fixed and on its exterior periphery a plurality of vertical grooves 34 are disposed spaced equidistantly around the circumference of the cylinder 30. As will be later described in detail, the grooves, or "tricks",as they are known in the art and each contain a single needle 36 for performing the knitting operation. Disposed above the cylinder 30 are the warp and weft yarn feeding means. The warp yarn feeding means is provided via a plurality of radially disposed feeding elements 38 of which two are shown in detail.Each warp feeding element consists of a generally horizontal bar having an aperture 39 therein through which the warp yarn passes to be gathered by the needle 36 as will be described. The warp yarn feeding elements 38 are stationary and are secured to the knitting frame.

As best seen in Fig.s. 2 and 3, the weft yarn feeding means consists of two parts. The first part is a generally vertically disposed tube 40 which is mounted on bearings 42 within a tube support 44. The tube 40 is rotatable by a timing pulley 46 coupled to a timing drive belt 4B and coupled to the bottom of the tube 40 is a generally planar weft yarn feeder and warp yarn deflector generally indicated by reference numeral 50.

The deflector has a channel 52 therein which communicates with the interior 41 of the tube 40 through which the weft yarn 27 can be fed to the tail 54 of the feeder and thence to the knitting head. It will be appreciated that the deflector 50 has an arcuate portion 56, parts of which extends beyond the outer radius of the cylinder 30, and this is for deflecting the warp yarn sideways beyond the periphery of the cylinder 30 during the knitting process to lay down the weft yarn 27 in a spiral fashion as will be described. It will be appreciated that the timing belt and timing pulley cause the tubular portion 40 and deflector 52 to rotate simultaneously and this rotation is synchronished with the rotation of rotating means in the cam box which causes the needles to be displaced vertically upwards and downwards within the respective grooves as will be described.

Reference is now made to Figs. 4a through g of the drawings which depicts the operation of a single needle to knit part of a tubular fabric. It will be appreciated that the other needles in the knitting head operate in an indentical manner. Fig. 4a depicts a warp yarn 12 fed through the aperture 39 Of the warp feeder element 38 to the needle 36 and then to the fabric 58 consisting of a chain stitch. In this figure the needle is shown totally within the groove 34. It will be seen that the needle carries a pivotable latch 60 for preventing inadvertent hooking of the elastic weft yarn as will be described.

Reference is now made to Fig. 4b which shows the needle 36 rising after the passage of the deflecting element 52 which causes the warp yarn 12 to be deflected outwards away from the needle 36 and simultaneously the weft yarn is laid on the open side or outward side of the needle hook 37. After the passage of the deflecting element 52 the needle 36 rises further leaving the weft yarn 27 on the open latch 60 and permitting the warp yarn 12 to return to its original position.

As the needle continues to rise as best seen in Fig. 4d, the latch 60 slips from beneath the thread 27 and pivots upwardly but is prevented from closing the needle hook 39 by a latch stop 62 disposed on the element 38. In rising the needle hook 39 causes the yarn 12 to have passed inside the hook and a new length of thread is connected from the aperture 39 as the needle 36 descends.

It will also be seen in Fig. 4e that the latch 60 has returned to a downwardly oriented position. The warp thread 27 remains outside the needle 36 and lies under the open latch 60. As the needle descends as shown in Fig. 4f the latch is closed by the old stitch and the weft yarn 27 thus preventing the weft yarn 27 from being snagged in the hook 37.

sçhen the needle has been retracted into the groove 34 the tension in the weft yarn 27 pulls it over the top of the needle 37 so that it is disposed on the cylinder inside the needle and, on the next ascent of the needle for the next stitch, the weft yarn is trapped between successive stitches. When this is repeated for each needle in the knitting head a tubular fabric results which consists of a plurality of vertically disposed chain stitches coupled by a spirally wound weft yarn which is made of an elastic fabric. Depending on the number of cams fitted in the cam box the needle will continue to knit plain chain stitches until the next circuit of the feeder.

As the tubular fabric is knitted it is fed out as aforedescribed to the fabric take-off roll 28.

It will be appreciated that modifications may be made to the embodiment hereinbefore described without departing irom the scope of the invention. For example, it will be appreciated that the number of needles and the type of stitching may be varied as required to knit different tubular fabrics. In addition, it will be appreciated that the weft or warp threads could be doubled to provide a heavier stitch and the rotation rate of the deflector and rotary cam box drive can be varied although it has to be syncronised to permit a satisfactory knitting operation. It will also be appreciated that other means may be used to prevent the hook 37 from snagging on the yarn during the downward stroke although the present arrangement is straightforward and elegant in its simplicity.It will also be appreciated that the warp and weft yarns may be made of elastic or non-elastic materials although the warp yarn is generally non-elastic and the weft yarn is elastic. Also, two or more packages may be used to supply a single knitting head and this number can be varied depending on the speed of knitting and the amount of tubular fabric to be made. It will be appreciated that the knitting heads could be disposed in a non-vertical orientation, for example, horizontally and the warp yarns also fed to the knitting heads horizontally.

It will also be appreciated that a single knitting head could be used which is fed from a creel containing two or more packages instead of a beam or frame.

Advantages of the invention are that high speed knitting of a tubular fabric can be achieved in a simple and efficient manner. The knitting can be made continuous by simply tying the end of one package to the beginning of another package and this avoids the necessity for stopping and reloading the machine every time the package runs empty with the results that retensioning of resetting is also avoided. A plurality of knitting heads can be disposed in a single frame in proximity to each other to minimise the space requirements and to facilitate inspection of the machine and also production of the tubular fabric.

Claims (23)

1. A knitting head for use with a knitting machine, said knitting head comprising: a fixed hollow cylinder having a cylinder wall with a plurality of circumferentially spaced grooves disposed in said wall, each groove having a needle with a hook at its upper end disposed therein, said hollow cylinder being disposed in a cam box having rotary cam means adapted to be coupled to each needle so that rotation of said rotatary cam means causes displacement of each needle along its respective groove, stationary warp yarn delivery means disposed above said hollow cylinder for feeding a warp yarn from a remote location to each respective needle, rotatable weft yarn delivery means disposed between said hollow cylinder and said stationary warp yarn delivery means for delivering a weft yarn from a remote location around the periphery of said hollow cylinder, the speed of rotation of said rotary cam means and said rotatable weft yarn delivery means being synchronised whereby, in use, upon rotation of said rotary cam means and said rotatable weft yarn delivery means displacement of said needles causes chain stitches to be made which are fed inside said cylinder, and said rotatable weft yarn delivery means delivers said weft yarn outside said cylinder so that when said needle is displaced within said groove the tension in said weft yarn pulls it over the top of the needle to be trapped in a subsequent stitch.

2. A knitting head as claimed in claim 1 wherein said needle includes a pivotable latch for preventing said weft yarn from being hooked by said needle on a downward stroke.

3. A knitting head as claimed in claim 1 or claim 2 wherein said grooves are disposed in an outer wall of said hollow cylinder and said needle hooks face outwardly.

d, A knitting head as claimed in any one of claims 1 to 3 wherein the knitting head and needle grooves are generally vertically disposed and the warp yarn is fed to said knitting head in a generally vertical direction.

5. A knitting head as claimed in any preceding claim wherein said stationary warp yarn delivery means comprises a plurality of stationary warp yarn delivery elements, a respective element being associated with a respective needle and being vertically disposed above said needle but being slightly offset therefrom to permit said needle to lie vertically above said element to collect a length of thread as it descends.

6. A knitting head as claimed in claim 5 wherein said element is in the form of a generally horizontal bar having an aperture therein through which said warp yarn is passed.

7. A knitting head as claimed in claim 6 or claim 7 wherein each element includes a latch stop for restricting the upward pivotable movement of each latch on said needle.

8. A knitting head as claimed in any preceding claim wherein said rotatable weft yarn delivery means comprises a generally planar horizontal weft yarn rotatable feeder and deflector element, said rotatable feeder and deflector element being coupled to a rotatable hollow yarn delivery tube which is adapted to be driven by drive means, said tubular element and said rotating feeder and deflector having passage means through which a weft thread can be fed to be disposed outside the periphery of the hollow cylinder.

9. A knitting head as claimed in claim 8 wherein the deflector includes an outer cam portion for deflecting the warp yarn outside the periphery of the hollow cylinder as said deflector rotates.

10. A knitting head as claimed in any preceding claim wherein the weft yarn is an elastic thread and said warp yarn is made of a substantially inextensible material or both yarns are elastic.

11. A knitting head as claimed in any one of claims 8 to 10 wherein said tubular yarn delivery tube is rotatable via bearing means in a support tube which is fixed and coupled to said stationary warp delivery means.

12. A knitting machine comprising: warp yarn delivery means for delivering a plurality of warp yarns to at least one knitting head, said knitting head being.disposed in a knitting head frame and the knitting head receiving a plurality of warp yarns, said knitting head frame having a plurality of weft yarn package holders disposed at a remote position from said knitting head, at least one package holder being adapted to. supply at said least one knitting head with weft yarn, and a fabric take-off roll disposed in said knitting head frame for receiving knitted fabric from said knitting machine.

13. A knitting machine as claimed in claim 12 wherein said knitting machine has a plurality of knitting heads and said warp is driven by warp drive rollers and said warp yarn is fed across to said knitting head frame via a warp sheet.

14. A knitting machine as claimed in claim 12 or claim 13 wherein yarn tensioning devices are provided for controlling the tension of each yarn fed to respective knitting heads.

15. A knitting machine as claimed in claim 12 wherein said knitting machine has a single head and said warp yarn is fed to said single head from a creel having a plurality of package holders.

16. A method of knitting a tubular fabric comprising the steps of: feeding a plurality of warp yarn threads to a knitting head, feeding at least one weft yarn to said knitting head and disposing said weft yarn intitially around the periphery of said knitting head by a rotary movement, synchronising the movement of needles within said knitting head to cause the weft yarn disposes around the periphery of said knitting head to be trapped between successive stitches of said warp yarn to create a tubular structure.

17. A method as claimed in claim 16 wherein said method includes the step of feeding the said warp and weft yarns from a remote stationary location.

18. A method as claimed in claim 16 or claim 17 wherein said warp yarns are fed vertically downwards to vertically disposed knitting heads.

19. A method as claimed in anyone of claims 16 to 18 wherein the rotation of the weft yarn feed delivery means and the rate movement and displacement of the needles in each knitting head is synchronised.

20. A method as claimed in anyone of claims 16 to 19 wherein two package holders are provided for each knitting head and the package holders are adapted to be tied together to provide substantially continuous knitting by each knitting head to produce a continuous tubular fabric.

21. A knitting head substantially as hereinbefore described with reference to the accompanying drawings.

22. A knitting machine substantially as hereinbefore described with reference to the accompanying drawings.

23. A method of knitting a tubular fabric substantially as hereinbefore described.