GB2173517A - An accessory for a domestic knitting machine - Google Patents

Abstract

A yarn brake for a domestic knitting machine consists of a plurality of pairs of discs (22, 24) spaced apart along a straight rigid rod (20) of uniform non-circular section so that yarn to be knitted passes between the discs of a pair. The discs have central holes of the same shape as the rod so that they cannot rotate, but at least one of each pair can slide on the rod. A biassing compression spring is housed in a spacing sleeve freely mounted on the rod between adjacent pairs of discs. One or more pegs on one disc can freely enter a complementary socket on the other disc to act as retainers for the yarn to guard against its displacement from between the discs. The rod is carried in brackets at each end which engage the needle bed or an adjacent fixture. Each disc pair may tension a single yarn as for intarsia work or two yarns which are to be combined. <IMAGE>

Description

SPECIFICATION An accessory for a domestic knitting machine Technical Field This invention relates to domestic knitting machines in which the usual needle bed carries a plurality of conventional latch needles and a carriage slidable lengthwise of the needle bed having on its underside a cam groove for successively engaging the butts of all the operative needles to be used for a given knitting operation and reciprocating them in accordance with the chosen pattern of the fabric to be produced.Such domestic knitting machines can be used in two modes: (1) normal knitting, in which one or more yarns is fed to the carriage from a ball or cone of yarn at the rear of the machine via an overhead spring-loaded tensioning arm resiliently mounted on the top of a mast or pillar carried on the back of the needle bed; (2) "Intarsia" or picture knitting in which a plurality of yarns, generally of equal thickness, and usually of different colours, are drawn from their respective balls or cones at the front of the machine (usually placed on the floor) and laid in the open hooks of the appropriate needles which are then reciprocated by a special "intarsia" carriage. Before each traverse of the carriage adjacent yarns are crossed over, first one way then the other alternatively, in order to avoid gaps or holes in the fabric at the boundaries of different colours.

In both modes, it is desirable to maintain a constant, relatively light, tension in the yarn as it is fed to the needle. In the first or normal mode of knitting, it is sometimes desired to knit a yarn which is a composite of a plurality of separate threads or filaments which differ as to colour or nature e.g. a mixture of natural and artificial threads or filaments-which are coalesced into a single composite yarn as they are fed to the carriage. Prior to their coalescence, however, tensions in the several filaments are random, and differences can result in the "looping" of a slacker filament which in turn can lead to its being missed by a needle.

Background Art Hitherto, when knitting with a composite yarn composed of a plurality of different filaments with the machine set up for operation in mode (1) above, the only way of ensuring equality of length and tension among all the filaments when they reach the needles has been to twist them together first before feeding them as twisted yarn via the overhead spring-loaded tensioning arm at the head of the mast. But the only way of achieving such twisting is by bodily spinning all the supplies of the filaments-whether in the form of balls or cones or other kinds of packages opposed to spinning the filaments after they have been drawn from stationary packages.

When the number and variety of packages is large the mechanical problem of handling the whole assembly to be spun calls for precision engineering to combat problems of unbalanced rotating masses, and hence the cost,size and weight are serious limitations on the viability of the system for domestic knitting machines.

In the absence of such elaborate means for equalising the lengths of and tensions in the component filaments of a composite yarn, the machine operator must constantly finger the separate filaments as they are fed down to the carriage in order to smooth out any individual slackness in the filaments, and the human factor involved can result in its own problems of inequality of tension.

In the case of intarsia knitting, it is common practice for the knitter to gather all the yarns together as they are drawn from their respective cones or balls and to hold them in the fingers of one hand while they are first laid by the other hand on the appropriate needles and crossed over, as is necessary if the integrity of the finished fabric is to be preserved at each boundary between different yarns, and then knitted by the carriage. By this system accurate control of the tension in each yarn is subject to human error, and irregularities are inevitable, even for experienced knitters. Moreover, this manual system of feed of the yarns to the needle does not eliminate the risk of tangling of the yarns, involving frequent stoppages for corrective action.

Disclosure of the Invention The present invention provides a yarn or thread brake to be interposed in the run of a yarn or thread from its ball or cone or other package to the needles, and consisting of a straight substantially rigid rod of uniform noncircular cross-section and a plurality of pairs of mating cheek plates or discs mounted thereon at intervals lengthwise of the rod. Each disc has a central hole of the same shape as the cross-section of the rod, the hole in each disc of each pair being a close enough fit to prevent rotation of the disc relative to the rod while allowing freedom of displacement of at least one disc axially of the rod.A light spring acts centrally on at least the said one disc of a pair to bias it into contact with its fellow, whilst the discs of each pair have mutually freely interengageable guard or retainer formations which bridge the gap between the mating surfaces of the pair at a radial distance from the axis of the rod greater than the periphery of the hole in each disc by an amount sufficient to allow a yarn or filament to pass freely between the guard formation and the rod so as to prevent the yarn from being deflected out of engagement with the discs.

Preferably, the adjacent pairs of discs are spaced apart lengthwise of the rod by a rigid sleeve which is freely slidable on the rod and at least one end of which has an enlarged socket to accommodate a helical compression spring and provide an abutment for the spring at the inner end of the socket, the spring being free to bear against the disc adjacent the mouth of the socket so as to urge it into contact with its fellow.

Conveniently, the rod is fixed at each end in a bracket or arm whose other end is engageable with the machine frame or with a support structure for the machine so as to locate the rod in a desired position relative to the needle bed.

In this specification, the term "uniform noncircular cross section" defines cross sectional shapes of constant external dimensions throughout the length of a rod. It includes mainly circular shapes whose regular arcuate circumferences are interrupted by a rib or key; by a groove or keyway; by a flat, or by any other formation which breaks the uniformity of the circular curvature of the circumference.

Whatever the contour of the cross-section of the rod, the hole in each disc is substantially identical to ensure that the disc does not rotate on the rod uner friction from yarn running between opposite faces of each pair of discs.

Brief Description of the Drawings Practical embodiments of the invention will now be described, by way of illustration only thereof, with reference to the accompanying drawings in which: Figure 1 is a perspective view of a typical domestic knitting machine set up for intarsia knitting and fitted with a yarn brake attachment according to the present invention; Figure 2 is an enlarged side view, partly in section, of the attachment shown in Fig. 1; Figure 3 is a plan view of one pair of mating discs as seen when the rod is cut on the medial plane between them and they are swung apart about an axis in that plane; Figure 4 is an underplan view of each disc of the pair seen in the same relationship as in Fig. 3;; Figures 5 and 6 are side elevations of alternative forms of bracket for a yarn brake designed for use in intarsia knitting, and Figure 7 is a view similar to Fig. 1 showing a brake according to the invention positioned for use when a number of separate threads or filaments are to be coalesced into a single yarn at the needles.

Detailed Description of the Drawings Referring first to Fig. 1, a conventional domestic knitting machie 10 is shown producing an intarsia or picture fabric 12 from three different yarns 14a, 14b and 14c. No support structure for the machine 10 is shown. This may be an ordinary table or a specially designed frame. The choice is the user's Each yarn is drawn from a respective cone 14 which is customarily placed on the floor in front of the machine 10.The carriage 16 is reciprocable, in the usual manner, lengthwise of the bed 10 to operate the required number of needles, and specially designed for intarsia knitting in that the cam (not shown) on its underside which engages the butts of all the operative needles is contoured so as first to project the hooks of the needles forward of the sinkers, without projecting the free tips of the open latches clear of the sinkers, so as to receive the several yarns 14a, 14b, 14c... as dictated by the pattern to be knitted; then to retract the needles to draw the hooks behind the sinkers in a stitch-forming action; and finally to project the hooks again between the sinkers to expose the open hooks for receiving the next runs of the several yarns, and so on. The knitted fabric 12 is thus suspended in front of the sinkers in the normal manner.

As hitherto carried out, an intarsia knitting operation requires that the knitter should hold all the yarns 14a, 14b, 14c... in the fingers of one hand while the other is used to traverse the carriage 16 to and fro. This not only results in irregularity of tension in each yarn as well as between yarns during knitting, but also, by grouping the several yarns very close together in the hand, encourages tangling of the yarns both as they leave their respective cones 14 and between the fingers and the needles, especially at cross-over. It is these hazards which the present invention seeks to avoid by providing (see also Figs.

2-6) a yarn brake, generally indicated at 18.

This consists of a rod 20 of non-circular cross-section (in the example illustrated, the rod 20 is of square section) on which are mounted at regular intervals along its length a plurality of pairs of smooth-faced discs 22, 24. Each disc is centrally pierced by a hole 26 (Figs. 3 and 4) of complementary shape to, but slightly larger than, the cross-section of the rod 20 so as to prevent rotation of the disc on the the rod while allowing relative axial displacement. The circumference of each disc is also well rounded to present a smooth, snag-free edge to each run of yarn between them. In Fig. 2, the yarn 14d is shown passing between the left hand pair of discs 22, 24 above the rod 20, and the yarn 14e is shown passing below the rod 20 between the adjacent pair of discs 22, 24. These two different yarn paths between the discs are illustrated to show the possibility of using a single pair of discs 22, 24 to tension and separate two yarns, thus tending to minimise or eliminate tangling even when the runs of two yarns are quite close together, as may be dictated by a particular intarsia pattern.

Fig. 2 also shows each yarn 14d, 14e bearing against a retainer or guard formation 28 radially outward of the yarn with respect to the rod 20. This guard prevents yarn from being laterallly displaced from between the discs 22, 24 of a pair. The right-hand side of Fig. 2, which is in section through the axis of the rod 20, shows the retainer or guard 28 as a peg on the disc 24 of a pair which freely engages a co-acting socket 30 in the other disc 22 of the pair. As seen in Fig. 3, two pegs 28 are carried by each disc 24, spaced angularly about the axis of the rod 20. The pegs 28 are fixed on the inward or mating face of each disc 24 and the sockets 30 are formed on the mating face of each disc 22.

The angular spacing of the pegs 28 and sockets 30 is shown as less than 1800-i.e. the pegs 28 of each pair are not diametrically opposite each other. This arrangement is advantageous when the yarn brake 18 is mounted close in front of, say, a ribbing attachment (not shown) and facilitates the threading of a yarn between a pair of discs 22, 24 on the side of the rod 20 nearest the attachment by ensuring that the discs are orientated on the rod with one of the pegs 28 located, by virtue of the asymmetry of their mutual angular disposition, further in front of the plane of the attachment than it would with symmetrical disposition of the pegs, at the same time preserving a separation between the yarns.

Each disc 22, 24 is lightly spring-loaded into contact with its fellow in a pair by means of a helical compression spring 32 housed mainly in a socket 34 formed in one end of a tubular spacer 36 which slides freely on the rod 20.

The inner end of the socket 34 provides an abutment for one end of the compression spring 32 the other end of which abuts the adjacent end of a hub or concentric collar 38 on each disc 22 which telescopes into the mouth of the socket 34 and is axially long enough to remain normally within that mouth so as to protect the compression spring 32 from being fouled at any time by yarn or any other external body. The end of each spacer 36 opposite to the socket 34 bears against the disc 24 of an adjacent pair.

The discs 22, 24 are preferably synthetic resin plastic mouldings having smooth, polished mating faces, the guard formations 28, 30 and the hubs 38 being moulded integral with their respective discs. In one working arrangement, the springs 32 are of pre-galvanised steel wire having a diameter of 0.716 mm. wound in 17 coils (active coils-15) each of 18 mm. outside diameter with a free length of 27 mm. The spring rate is 0.03 N/mm (3.06 gm/mm), and the load at 19 mm is 0.24N (25 gm). As described above, both discs 22, 24 of each pair are free to slide on the rod 20, as also are the spacers 36, so that any one pair of discs 22, 24 can be separated far enough to allow yarn to be slipped over a guard peg 28 when it is to be introduced between the mating faces of the discs. In normal operation, all the guard pegs 28 remain in engagement with their complementary sockets 30.

Figs. 5 and 6 show two alternative shapes of bracket or arm for supporting the rod 20 during intarsia knitting. The cranked bracket 40 of Fig. 5 is that shown in the working position in Fig. 1. One extremity is enlarged to form a boss or socket 42 into which one end of the rod 20 can be inserted and lockedeither permanently or, preferably, detachably.

The other arm 44 of the bracket is of a length, and set at an angle, such that it can be either inserted into a socket provided for the purpose on the underside of the needle bed 10 or held by the weight of the machine on the surface of a table on which the machine is placed. The bracket 40 locates the rod 20 and the assembly of discs 22, 24 and spacers 36 at a level below the needles which is convenient for the operator to handle each yarn 14a... for laying in the hooks of the appropriate needles. Sometimes, however, a ribbing attachment is used with the needle bed 10. This is another needle bed which is suspended substantially vertically below the hooks of the needle bed 10. When such a ribber is fitted, the bracket 46 shown in Fig. 6 is used.The lower end of this bracket carries the same socket 42 for holding the rod 20, but its other end is formed as a square hook 48 of a shape and dimension to engage over the bed of the ribber. The rod 20 is then positioned adjacent the bottom edge of the ribber.

Fig. 7 shows a yarn brake 18a according to the invention fixed on the conventional mast 50 at the back of the needle bed 10. Two pairs of discs 22, 24 are mounted on a rod 20 carried in a bracket 52, and each pair is shown as engaging two strands or filaments 14m, 14n or 14r, 14s respectively, separation being achieved as shown in Fig. 2 by means of the guard pegs 28. These filaments may differ in colour, or in texture, or in physical composition, according to the requirements of the fabric to be knitted. For example, three filaments may be different coloured wools and the fourth may be an artificial mono-filament.

Each one is drawn from its respective cone or ball (not shown) which can be placed relatively closer together than usual because the steadying effect of the yarn brake 18a reduces the risk of tangling prior to their passage between the respective pairs of discs 22, 24. Thereafter, the strands or filaments are coalesced in their passage between the conventional adjustable-tension discs 54 (which are now set at zero tension) and through the feed loop or eye 56 of a spring-loaded or resilient feed arm 58 which automatically compensates for the changes in distance between the tension discs 54 and the carriage 16 as the latter is traversed along the needle bed 10.

Generally, the pressure exerted by each pair of discs 22, 24 on a yarn passing between them is only sufficient to keep the yarn straight between the discs and the next point at which it is handled-the needles in Fig. 1 and the adjustable tensioner 54 in Fig. 7-so as to combat any tendency of yarns to tangle on this section of their path. The discs also fulfil the other useful function of allowing the cones balls or reels in which the yarns are packed to be placed at smaller spacings than could be accommodated when they yarns are fed direct to the needles.

Although in the foregoing description both discs 22, 24 of a pair have been described as free to slide on the rod 20, it is to be understood that one disc of a pair may be fixed to provide an abutment for the respective spring 32. The rims of the discs can also be flared to facilitate the introduction of yarn between them. Nor need they be circular; they can be square or any other shape. In a still further modification, more than two discs or plates can be grouped together under the action of one spring; thus, three or more discs can be mounted side by side on the rod 20 to provide brakes for several yarns. In such a multiple disc assembly, an intermediate disc can be regarded as paired with the disc on either side.

It is to be understood in this specification that the terms "cheek plate" and "disc" mean a rigid article whose radial surfaces are flat, as opposed to being spherically or conically dished or convex.

Claims (7)

1. A yarn brake for a domestic knitting machine comprising a straight substantially rigid rod of uniform non-circular cross-section; a plurality of cheek plates or discs spaced in pairs lengthwise of the rod, at least one of each pair being freely slidable on the rod and each disc having a central hole of the same shape as the cross-section of the rod so as to prevent relative rotation of the disc on the rod; and a light spring acting centrally on each disc to bias it into contact with its partner in the same pair, the discs of each pair having mutually interengageable retainer or guard formations which span the gap between them at a radial distance sufficient to allow a yarn filament to pass freely between a formation and the surface of the rod so as to prevent bodily lateral disengagement of the yarn from between the discs.

2. A yarn brake according to claim 1 wherein each pair of discs has two sets of mutually interengageable guard formations located on respective radii so that two yarn filaments can be laid between the discs on opposite sides of the rod.

3. A yarn brake according to claim 1 or 2 wherein a rigid tubular spacer loosely embrac ing the rod determines the interval lengthwise of the rod between adjacent pairs of discs, at least one end of the tubular spacer having an enlarged coaxial socket housing a helical loading spring adapted to bear against the outer surface of one of the discs so as to bias it axially against its partner.

4. A yarn brake according to claim 1, 2 or 3 wherein the rod is carried at each end in a bracket or arm whose other end is engageable with the machine structure or a support therefor so a to locate the rod in a desired position relative to the needle bed.

5. A yarn brake according to claim 4 wherein the brackets or arms are adapted to support the rod in front and below the needle bed at a distance such as to keep to a suitably low maximum the angle through which yarn must deflect on leaving a pair of discs when, for example, an intarsia carriage is in use on the needle bed.

6. A yarn brake according to claim 4 wherein the brackets or arms are adapted to support the rod at a location behind the conventional mast or pillar which carries the usual spring-loaded feed arm for normal single-yarn knitting, the rod lying below the level of the top of the mast to facilitate the feed of a plurality of filaments of, say, different colour or composition, to the feed loop or eye at the free end of the spring-loaded arm so as to maintain a common tension in all the separate filaments prior to their blending into a single yarn.

7. A yarn brake for a domestic knitting machine substantially as hereinbefore described with reference to the accompanying drawings.