GB2100297A - Yarn gripping and cutting device in circular knitting machine for producing open fabric - Google Patents

Abstract

A yarn gripping and cutting device for a cylinder and dial circular knitting machine for open fabric having a needleless sector for producing comprises a yarn pick-up member (13) associated with each yarn feed (9) and being carried rotatably on a rotary structure overlying the dial (2). The yarn (11) to be cut as it reaches the needleless sector, is engaged in a peripheral notch (15) on the pick-up member (13) and the latter is rotated to bring the yarn (11) under a pressure element (19) and cut it by means of a fixed blade arranged to cooperate with said notch (15). The yarn (11) to be knitted in at the end of the needleless sector is guided by a yarn feeding plate (25) toward the needles, and led into a second notch (16) on the yarn pick-up member (13). The latter is once again rotated to release the yarn (11) from the pressure element (19) as the notch (16) moves past under it. <IMAGE>

Description

SPECIFICATION Yarn gripping and cutting device in a cylinder and dial circular knitting machine for producing open fabric This invention relates to a yarn gripping and cutting device in a cylinder and dial circular knitting machine for producing open fabric.

A machine of this same general type is described in U.S. Patent No. 3,521,466. It includes a cylinder and dial which are each provided with a needle-less area, thereby the knitted fabric, rather than in tubular form, is produced in an open form with two selvedges located respectively on either sides of the needleless area. On this machine, the cylinder and dial are held stationary, and externally of them a structure is arranged to rotate which carries the cams for actuating the cylinder and dial needles as well as the yarn feeding fingers with their respective yarn cones. Each yarn, after undergoing knitting at the needle-carrying area, is cut off at the beginning of the needle-less area, and then reinserted to knit or replaced with another yarn at the end of the needle-less area.

Several devices are known for cutting the yarns on machines of this type, one of which, having a particularly simple construction, is described in U.S. Patent No. 3,640,094 by this same Applicant.

The latter device is arranged on the dial at the beginning of the needle-less area, and comprises a movable blade, arranged to slide in a substantially radial groove on the dial, and a counterblade cooperating with the movable blade and being arranged substantially tangentially to the dial. The device further comprises yarn pick-up elements effective to bring the yarn to the cutting position, such elements being also radially movable on the dial. For actuating these elements and the movable blades, cams are provided which extend in a ring-like configuration on the rotary structure above the dial and engage respective butts formed on the cutting blade and pick-up elements.The cams have a profile such as to produce a retraction movement first of the yarn gripping elements, thus bringing the yarn under a gripping assembly adapted to hold it firmly down for the cutting operation, and then of the movable blade for the cutting operation proper in cooperation with the counterblade. Subsequently thereto, the pick-up elements first, and then also the movable blade, are pushed again outwards in preparation to a fresh cutting operation as the yarn arrives from the next yarn feed.

However, this device is liable to a comparatively fast wear rate; since it is operative for all the yarn feeds. Furthermore, the impiementation of the actuating cams for the pickup elements and movable blade involves considerable material consumption and labor, since the cams must extend along the entire length of a circumference and have as many exactly profiled regions as are the yarn feeds. The blade itself, moreover, is of somewhat critical construction, because it has the same thickness dimension as the needles. The cut off end of the yarn on the feeding finger side is let free and can not always be correctly gripped for reinsertion to knit, especially where lively and elastic yarns are used.In order to adjust the machine to accept different fabric width dimensions, the whole device must be shifted, a rather time-consuming operation because it also implies manipulation of the cylinder and dial needles, which needles must be removed when the fabric width is to be reduced and added when the fabric width is to be increased.

It is a primary object of this invention to overcome such prior limitations and shortcomings of conventional yarn cutting devices, by providing a yarn gripping and cutting device in a machine of the type indicated, which affords a reliable gripping action on the yarn and a reliable release of the yarn at the right position as it is reinserted to knit, even where elastic and lively yarns are used, and which requires no arrangement of circular actuating cams for the effectuation of the yarn gripping and cutting operations.

A further object of the invention is to provide a device as indicated, which can facilitate changing the width of the knitted fabric.

These and other objects, such as will be apparent hereinafter, are achieved by a yarn gripping and cutting device in a cylinder and dial circular knitting machine for producing open fabric, wherein the cylinder and dial both have a needle-fitted area and a needle-less area, and wherein yarn feeds are driven of relative motion with respect to the cylinder and dial and the device operates at the needle-less area, the device being characterized in that it comprises a pick-up member associated with each yarn feed and being carried rotatably on a rotary structure driven of relative motion with respect to the cylinder and dial and cooperating with a respective cutting blade and respective gripping element carried stationary on said rotary structure, as well as control means arranged at a yarn gripping and cutting area and needle-less area for controlled rotation of said pick-up member at the beginning of said needle-less area between a yarn pick-up position and a yarn gripping and cutting position, and at the beginning of the needle-fitted area between said gripping position and a fresh yarn pick-up position with selective release of a yarn intended each time for knitting.

On a machine incorporating such a device, therefore, instead of a single cutting member to cut off the yarns from all the feeds, a plurality of yarn cutting and gripping members are provided, each associated with a respective yarn feed. The control of actuating means, arranged at the gripping and cutting area and needle-less area, no longer extend as cams encompassing the dial.

Consequently, the constructional and economical expenditure connected with the implementation of the circular cams overlying the dial is removed, while the seemingly high expenditure in construction resulting from the provision of plural cutting members is amply offset not only by their reduced wear, and accordingly lower replacement requirements thereof, but also by a more reliable retention of the cut off yarn, even in the case of lively and elastic yarns, thanks to the gripping element associated with the pick-up member, and by a more convenient adaptation of the machine to different fabric widths.In fact, it is no longer necessary to each time shift the whole cutting assembly, and it will be sufficient to just remove or add a small set of needles and re-arrange the control means for the rotating pick-up members, such that the latter are rotated each time at different areas of the dial.

Further features and advantages of the invention will be more apparent from the following description of a preferred embodiment thereof, given herein by way of example only and illustrated in the accompanying drawings, where: Figure 1 is a side elevation view of a device according to this invention, showing the needleless area of a machine of the type indicated; Figure 2 is a plan view of the device and related portion of the machine of Figure 1; Figure 3 is a fragmentary axial section view of the machine shown in the preceding figures, taken at the last needle grooves on the cylinder and dial before the needle-less area; Figure 4 is a very schematical representation in plan view of a portion of a circular knitting machine incorporating a device of this invention, including a plurality of yarn feeds and rotating yarn pick-up members;; Figures 5, 6, 7 and 8 show respectively, in schematic form, the successive steps of yarn gripping and cutting at the end of the latter knitting, the first three figures being top plan views and the last mentioned figure a side view; and Figures 9, 10, 11 and 12 respectively illustrate in schematic form the successive steps of release of a yarn for its insertion to knit, the first and last two mentioned figures being top plan views and the second figure a side view.

With reference to the cited drawing figures, a machine will be described hereinafter which comprises a stationary cylinder and dial, and a rotary structure carrying the yarn feeding fingers, the yarn feed cones, and cams for actuating the needles of both the cylinder and dial. However, it will be appreciated that an inventive device may also be incorporated to machines having cams, cones, and feeding fingers supported in a fixed position and the cylinder and dial arranged to rotate.

The machine comprises a cylinder 1 and dial 2, which are provided with grooves 3, respectively 4, for needles 5, respectively 6, the grooves and needles extending to occupy but a segment of the machine, thereby defining an area 7 without needles on both the cylinder 1 and dial 2.

Arranged to revolve about the cylinder 1 is a structure 8 carrying cams for actuating the needles 5 and a plurality of yarn feeds 9, each with a plurality of yarn feeding fingers 10. The yarn feeding fingers 10 are controlled in a conventional manner and receive each a yarn 11 from cones, not shown, carried on a second rotary structure 12 which overlies the dial 2 and also carries control or actuating cams for the needles 6. The direction of rotation of the two structures 8 and 12 is indicated by the arrows R.

On a machine of this type, as is known, the yarn knitted by the needles is cut off upon the respective yarn feeding finger reaching the needleless area, while that same yarn, or another yarn of the same feed, is presented to the needles for knitting as the end of the needle-less area is reached. This operation is repeated at each yarn feed.

In accordance with the invention, this yarn gripping and cutting device comprises, for each feed 9, a pick-up member 13 picking up the yarn 1 which member is carried rotatably on the rotary structure 12, e.g. through a bell-crank arm 14 attached to the rotary structure. The pick-up member 13 has a disk-like configuration and is provided with plural peripheral notches 15, 16, the notches 1 5 sloping preferably in a direction opposite to the direction of rotation of the member 13 relatively to the arm 14, as indicated by the arrow S, and the notches 1 6 being of preference cut radially.The notches 15, which function as yarn cutting or severing notches as explained hereinafter, are radially less deep and circumferentially wider than the notches 1 6, which function as yarn release notches as explained hereinafter. The corner edges of the notches 1 6 are at least slightly blunted, whereas at least the bottom corner edge of the notches 1 5, or trailing edge in the direction of rotation S, is a sharp edge.

Fastened to the arm 14 is a cutting blade 17, which extends substantially tangentially below the pick-up member 13 in contact relationship with the bottom face thereof. The width of the blade 1 7 in the radial direction of the pick-up member 1 3 is such as to completely cover the cutting notches 15, but only incompletely cover the release notches 1 6.

To the arm 14 is also attached a support 1 8 which extends substantially radially above the pick-up member 1 3 and carries a gripping element in the form of a pressure element 19, preferably formed from a relatively hard elastic material, which extends downwardly from above along an inclined direction in the direction of rotation S of the pick-up member 1 3 and contacts under pressure at the bottom the top face thereof. The width of the pressure element 1 9 in the radial direction of the pick-up member 1 3 is greater than the radial depth of the notches 1 5 and 1 6.

With the bottom or lower face of the pick-up member 13, there is made rigid a rotation star 20 having as many points as are the pairs of notches 1 5 and 1 6, preferably four points. The star 20 is a part of a drive or control means adapted to produce a controlled rotation of the pick-up member, as explained hereinafter. Such means also comprises an engagement means composed, of a peg 21 attached to the dial 2 at the beginning of the needle-less area 7 and extending upwardly to engage with the rotation star 20.The arrangement is such that as the pick-up member 13 moves past, the peg 21 causes the star 20, and hence the pick-up member 13, to perform a rotation by an angle which corresponds to the distance between two successive homologous notches 15, respectively 16, in the present embodiment a 90 angle, and so that the star 20 stops again in position for a successive identical rotation.

Said engagement means further comprises a second peg 22, also attached to the dial 2 but at the beginning of the needle-fitted area, above the first grooves 4. More specifically, the peg 22 is attached to a small block 23 cantilever supported on a bracket 24, in turn attached to the dial 2; thus, under the block 23, there is room for the movement of the needles 6, and the peg 22 can interfere at the top with the rotation star 20 to rotate the latter through an equal angle to that produced by the peg 21.

Also attached to the dial 2, short of the beginning of the area fitted with needles, is a guiding plate 25 which extends vertically at the very edge of the dial 2 and has a front corner edge 26 sloping downwards in the direction of rotation R of the rotary structures 8 and 12. The height is, of course, selected such as not to hinder the movement of the pick-up member 13.

The operation of the device described hereinabove will be next discussed with particular reference to Figures 5 to 12.

Upon completion of a knitting course, the yarn 11 just knitted, which extends from the last needle 5 or 6 to the yarn feeding finger 10, is engaged by the pick-up member 13 in a notch 1 5 thereof owing to the pick-up member 1 3 moving together with the rotary structure 1 2 and feeding finger 10, as shown in Figure 5. Upon the rotation star 20 engaging the first fixed peg 21 , the pick-up member 13 begins to rotate while continuing in its translatory movement, as shown in Figure 6. The yarn 11 is gradually brought to pass under the pressure element 1 9 until the notch 1 5 moves past the pressure element 19, as shown in Figure 7.The rotational movement of the pick-up member 13, however, continues until the fixed blade 1 7 comes into operation, which in cooperation with the lower trailing edge of the notch 1 5 will sever the yarn (Figure 8), the yarn being held by the pressure element 19. It should be further noted that if the feeding finger 10 were raised and the yarn 11 positioned out of the notch 1 5 before the pick-up member 1 3 begins to rotate, it would nevertheless be caught by the notch 1 5 during the rotation of the pick-up member 13, because the yarn 11 would be in all cases stretched against the edge of the pick-up member 13, between the notch 1 5 and pressure element 19, owing to the raising of the feeding finger 10 moving the yarn 11 toward the machine axis.Thus, the yarn 11 is caught unfailingly at the end of its knitting and transported under the pressure element 1 9 to be severed.

Upon reinsertion of the yarn 11 to knit, there first occurs, in a known manner, the lowering of the respective feeding finger 10. That lowering movement will bring the yarn 11 to contact the edge of the pick-up member 13, as shown in Figure 9. In this position, during the translatory movements of the feeding finger 10 and pick-up member 13, the yarn is engaged by the sloping leading edge 26 of the guiding plate 25, as shown in Figure 10, and is gradually lowered into position to be picked up by the needles 5, 6, while being retained by the pressure element 1 9 onto the pickup member 13.At the same time, the yarn 11 will slip along the outer edge of the pick-up member 1 3 until it enters the notch 16, located shortly before the pressure element 1 9. That movement is assisted by the guiding plate 25 and by the fact that the yarn begins to be knitted by the first needles (Figure 11). At this stage, the rotation star 20 engages with the second fixed peg 22, which will produce a rotation of the pick-up member 1 3 in the same direction as before. The yarn 11, being caught in the notch 1 6 and knitted by the needles 5 and 6, is progressively removed from under the pressure element 1 9 as the notch 1 6 moves past under it.It should be noted that the yarn 11 is not pulled out from under the pressure element 1 9, and that it is the rotational movement itself of the pick-up member 13 which, by virtue of the notch 16, gradually forms an empty space under the pressure element 1 9 for the release of the yarn 11. Also to be noted is the fact that said empty space in no way affects the other yarns held down by the pressure element 1 9 against the top surface of the pick-up member 13, since they are not engaged in any notch 1 6 and continue to be retained because, even while the notch 1 6 moves past it, the pressure element 19 always remain in contact with a portion of the surface of the pick-up member 13.

Upon the notch 1 6 moving past and beyond the pressure element 19, the yarn 11 is fully released, as shown in Figure 12. The rotational movement of the pick-up member 13 continues until the star 20 is released by the peg 22, that is until a fresh position is reached by the pick-up member 1 3 which is identical to that shown in Figures 2 and 5, namely ready to again pick up a yarn as the needle-less area 7 is reached. Being provided with four pairs of notches 1 5, 1 6, the pick-up member 1 3 is now in a diametrically opposed position to that occupied at the beginning of the needle-less area.

It will be appreciated how the operational steps just described will occur each time that a feed assembly 9 and related pick-up member 1 3 moves through the needle-less area 7, such steps taking place each time for one yarn, the other yarns of the same feed being left gripped.between the pressure element 19 and pick-up member 13.

The foregoing device not only ensures, therefore, a reliable picking up of the yarn and reliable cutting and gripping thereof, so that the device is also suitable for use with elastic and lively yarns, but also a longer life of the various components involved in cutting and retaining the yarn, since they only work for a single feed.

Furthermore, replacement of worn components is facilitated, in particular replacement of the fixed blade 17 and pressure element 1 9. Adaptation of the machine for the production of different width fabrics is also quite easily carried out, it requiring but the pegs 21 and/or 22 to be mounted at a different location and the removal or addition of few needles 5, 6. In particular, to decrease the fabric width, it will be sufficient to remove but few needles 5,6 at the area of operation of the peg 21 or 22, while the other needles 5, 6 located between the removed needles and needle-less area 7 may be left on to perform their usual movements without this affecting the yarn in any way, the yarn being no longer, or not yet, in position to be caught by the needles themselves.

The invention as described is susceptible to many modifications and variations, without departing from the scope of the instant inventive concept. Thus, as an example, a yarn sucking mouth could be provided in the knitting area at the beginning of the segment fitted with needles.

Moreover, the number of notches 15 and 16 and consequently the rotation angle of the pick-up member 13 may be varied to deviate from what has been described and illustrated herein. Of course, it would also be possible to support the pick-up members 13 and yarn feeding fingers 10 through a stationary portion of the machine, and to rotate the pegs 21 and 22 together with the cylinders 1 and dial 2.

Claims (9)

1. A yarn gripping and cutting device for a cylinder and dial circular knitting machine for producing open fabric, wherein the cylinder and dial both have a needle-fitted area and a needleless area, and wherein yarn feeds are driven of relative motion with respect to the cylinder and dial and the device operates at the needle-less area, characterized in that it comprises a yarn pick-up member associated with each yarn feed and being carried rotatably on a rotary structure driven of relative motion with respect to the cylinder and dial and cooperating with a respective cutting blade and respective gripping element carried stationary on said rotary structure, as well as control means arranged at a yarn gripping and cutting area and needle-less area for controlled rotation of said pick-up member at the beginning of said needle-less area between a yarn pick-up position and a yarn gripping and cutting position, and at the beginning of the needle-fitted area between said gripping position and a fresh yarn pick-up position with selective release of a yarn intended each time for knitting.

2. A device according to Claim 1, characterized in that said yarn gripping member comprises a disk having a plurality of peripheral notches for engagement with and transporting yarn to a gripping and cutting position and to a release position.

3. A device according to Claim 2, characterized in that said notches comprise pairs of notches, each notch pair including a yarn cutting notch and a yarn releasing notch, said cutting notches being radially less deep and circumferentially wider than said release notches.

4. A device according to Claim 1, and either Claim 2 or 3, characterized in that said gripping member comprises a pressure element operative to apply a pressure on one face of said disk-like pick-up member, said pressure element having, in a radial direction with respect to said disk-like pick-up member, a larger dimension than the radial depth of said notches.

5. A device according to one or more of the preceding claims, characterized in that said cutting blade extends substantially tangentially to said pick-up member to cooperate with said cutting notches, said blade having, in a radial direction with respect to said disk-like pick-up member, a width adequate to cover said cutting notches completely and said release notches incompletely.

6. A device according to Claims 4 and 5, characterized in that said pressure element and said cutting blade are arranged to contact opposed faces of said disk-like pick-up member.

7. A device according to Claim 1 and one or more of Claims 2 to 5, characterized in that said control means for the controlled rotation of said pick-up member comprises a rotation star made rigid with said disk-like pick-up member and being provided with a point number matching the pair number of said notches, and an engagement means adapted to engage with said rotation star to rotate said star through an angle corresponding to the distance between two successive homologous of said notches, respectively at the beginning of the needle-less area and beginning of the needle-fitted area.

8. A device according to Claim 7, characterized in that said pick-up member is carried on a rotary structure of the machine, and that said engagement means comprises a first peg attached to the dial at the beginning of the needle-less area and a second peg attached to the dial at the first grooves of the needle-fitted area.

9. A device according to one or more of the preceding claims, characterized in that short of the beginning of the needle-fitted area there is arranged a yarn guiding plate, said yarn guiding plate extending vertically and having a sloping front corner edge inclined downwards from above in the direction of movement of said gripping element relatively to said guiding plate, for guiding yarn to a position to be picked up by needles.

1 0. A yarn gripping and cutting device in a cylinder and dial circular knitting machine for producing open fabric, substantially as herein described with reference to the accompanying drawings.