Textiles: knitting – Independent-needle machines – Circular
Reissue Patent
1997-10-02
2003-07-01
Calvert, John J. (Department: 3741)
Textiles: knitting
Independent-needle machines
Circular
Reissue Patent
active
RE038161
ABSTRACT:
The prevent invention relates to apparatus for producing tubular fabrics consisting of a number of separate chain stitches connected by an inlaid thread typically, elastic or similar yarn. In particular, the invention relates to a high speed yarn knitting apparatus for knitting netting for covering food products, and in particular meat.
High speed yarn knitting apparatus 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 to avoid imbalance at high speed. The high speed knitting apparatus should have yarn positioning apparatus which uses a minimal number of moving parts and wear and tear of knitting elements and yarn should also be minimised. Higher tensions of yarn should be obtainable so that knitting speeds can be increased. The apparatus should also minimise the splitting of yarn and the dropping of stitches.
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 of knitted fabric 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 yarn package limits the amount of continuous netting which can be made without stopping. The yarn package is mounted to rotate with the cambox which means that the speed of rotation and hence knitting is limited. Also, when the weft package is empty the machine 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 package 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.
Existing circular knitting machines which are also designed to make a chain stitch structure use one of two generally accepted methods of supplying yarn to the needles of the knitting head. One method uses rotating or reciprocating guides which wrap the yarn around the needles. The elastic or other weft yarn is fed from the outside and is laid between the needles from the outside. This requires the weft yarn package to rotate with the cam box. In another method, stationary guides are present and rely on being struck by the needles so as to deflect the needles behind the yarn. The yarn is then caught by the open hook of the needle as the needle descends. Again, the weft yarn package revolves with the cam box.
These existing methods have a number of problems. The former method uses reciprocating guides requiring a machine which is relatively complicated and uses a considerable number of moving parts. In the second method, as the needles strike the guides there is considerable wear and tear on both the needles and the guides. This can cause splitting of the yarn and dropping of stitches as well as broken knitting elements.
An object of the present invention is to provide an improved knitting apparatus and yarn tensioning apparatus which obviates or mitigates the aforesaid disadvantages. This is achieved by providing a high speed knitting apparatus in which the elastic thread packages are mounted in a stationary position away from the knitting head and the yarn is fed from the exterior to the inside of each knitting head. Yarn is laid down outside each needle as the needle rises but falls behind the needle as the stitch is made allowing a stationary package. This results in reducing the revolving mass and the space necessary to accommodate the revolving mass. Furthermore, since the weft package is stationary, 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.
A yarn guide is included for each needle of the knitting head so that yarn is moved under tension within the guide by a rotating member with minimal friction to a position where the needle will trap the yarn on its downward stroke.
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 weft yarn to 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 having a plurality of grooves called tricks, in the outer wall, in which needles are disposed. Fixed feeders are disposed above the cylinder to offer the warp yarns to the needle. Disposed between the cylinder and the fixed feeder is a rotating weft feeder and yarn deflector. Rotation of the feeder is synchronized with a cam which raises the needles so that the feeder deflects the warp yarn within the yarn guide and guides 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 and falls behind the needle as a stitch is made, 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 support tube through which passes a tube mounted in bearings and carrying the weft feeder and deflector so that these can be rotated by a synchronised drive while feeding the inlay weft thread. The fixed feeders are wire staples which are shaped so that pre-tensioning of the yarn before it reaches the guide ensures that the yarn lies in front of and to one side of the open hook of the needle, and limits yarn movement when contacted with the placer. The staple has a curved portion for defining the path of the yarn as it is moved. The placer is a planar element which has a curved portion which pushes the yarn along the internal rim of the feeder from a first position to a second position where the yarn is trapped.
Accordingly, in one aspect of the present invention there is provided 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 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 warp yarn delivery means for delivering a weft yarn from a remote location outside the cylinder and from the inside to the outside of said rotatable weft delivery means so that the weft yarn is laid on the outside of each successively rising needle,
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
Alston & Bird LLP
Calvert John J.
Scotnet (1974) Limited
Worrell Jr. Larry D.
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