GB2173824A - Tufting machines - Google Patents

Abstract

This invention relates essentially to a dent plate assembly for use in a tufted carpet making machine. The assembly comprises a number of flexible dents 3 made preferably from spring steel which are removably secured in a dent plate 1 by a capping strip 5 so that the plate, the capping strip and exposed parts of the dents all present a smooth coplanar fabric contacting surface. Each dent has a forward part in the form of a slender projection, a mid-part tapering towards the forward part and a rear part that fits removably into a slot in the dent plate. <IMAGE>

Description

SPECIFICATION Improvements in or relating to tufting machines This invention relates to an improved dent plate assembly for use in a tufting machine and to an improved dent for use in the same.

One important method of making carpets involves a tufting process in which a carpet backing is passed under tension from a supply roll over a support where the backing is subjected to the action of vertically reciprocating tufting needles threaded with yarn. As the needles move up and down through the carpet backing they co-operate with loopers oscillating backwards and forwards in the machine direction beneath the support causing tufts of yarn to become anchored into the carpet backing thus forming the pile of the carpet. As the pile is formed the resulting carpet leaves the support and is wound up on a take-off roll. The quality and type of carpet which can be made in this way can be varied in a number of different ways. For example by using one form of looper co-operating with a scissor mechanism a so called cut-pile carpet can be made.On the other hand if this cutting operation is omitted and a different form of looper is employed a so-called loop pile carpet will be obtained. The height of the pile can also be varied since this depends upon the degree of proximity of the loopers to the zone in which the tufting operation takes place. The coarseness of the pile will depend upon the gauge of yarn being fed by the needles. Consequently if the count of the yarn to be tufted is required to be altered so as to make a carpet of different specification the needles will have to be changed to a corresponding gauge.

Conventional supports for the carpet backing comprise a rectangular plate positioned at right angles to the direction of movement and in the same plane of the backing. The edge of the plate remote from the supply roll is provided with an array of elements or dents which are arranged side by side in spaced apart relationship and extend beyond the edge of the dent plate. As the needles move downwards they pass first through the carpet backing and then through spaces between the dents after which the needles then engage with the loopers in the manner described. The forms of dents vary to some extent. Thus some dents are bifurcated, consequently each needle then passes between the bifurcations of the corresponding dent.Considerable force is applied by the needles and owing to the presence of slubs in the yarn being tufted or other defects the dents are liable to become distorted or broken in use thus necessitating replacement of the dent plate. Consequently a practice has developed of using dent plate assemblies in which an individual needle can be replaced rather than the whole assembly. In these assemblies the dents are positioned in slots in the dent plate and are held in position by a capping strip.

Existing tufting machines enable carpets to be made having a wide range of qualities, pile heights and pile densities. Nevertheless they have not been found satisfactory for the production of carpets particularly of the loop pile variety having very low pile heights i.e. less than about 4mm. This disadvantage is of considerable importance because there is a substantial demand, especially in the contract carpet trade, for looped pile carpets having pile heights of less than 4mm.

Whilst the scope of this invention is not to be limited by any theory relating to the failure of conventional tufting machines to produce carpets of this kind it appears that differences in level between the capping strips and the dents results in yarn passing through the needles accumulating on the surface of the carpet being formed. Furthermore the effect on the backing of the unlevel support is to cause the backing to vibrate and this reduces the efficiency of the tufting process. In addition existing designs of dents do not permit the loopers to oscillate sufficiently close to the dents for very low pile heights to be achieved. Accordingly this invention provides a new dent plate assembly and a new dent which enables carpets to be made having pile heights of less than 4mm in addition to carpets having conventional pile heights.

Accordingly this invention provides a dent plate assembly comprising a substantially rectangular plate having a recess extending along one edge thereof and a plurality of spaced apart slots formed into the base of the recess and extending to the edge of the plate and a plurality of dents positioned within the slots and presenting a fabric contacting surface the dents being secured removably within the slots by a capping strip the surface of the plate and the exposed surface of the capping strip and the carpet contacting surface of each of the dents all lying in substantially one plane.

A further aspect of this invention comprises a new dent for the manufacture of tufted carpets comprising an elongated element made from strong resilient material having a forward part comprising a smooth, slender projection devoid of sharp edges, a mid part thickened to increase the strength of the dent and a rear part adapted to fit removably into the slot of a dent plate, the forward part and the mid part each presenting a fabric contacting surface which is coplanar with one another.

This invention is illustrated but not restricted by the following drawings in which: Figure 1 shows a side view of part of a tufting machine incorporating an invention plate assembly.

Figure 2 shows a side view of one of the invention dents shown in Fig. 1.

In Fig. 1 a dent plate (1) has a recess (2) into extending to the edge of the plate. A number of slots arranged in parallel are formed in the base of the recess extending in the machine direction to the edge of the plate.

A dent (3) is removably located in each slot and horizontal movement of the dent within the slot is prevented by a pip (4) extending from the dent into a correspondingly shaped cavity in the inner wall of the recess. The dents are held firmly within the recess by a capping strip (5) which is secured in place by screws (not shown) passing vertically through the capping piece into the base of the plate.

The vertical portion (6) of the dent abuts the forward edge of the capping piece (5), and the unrecessed part of the dent plate, the exposed surface of the capping piece and the upper surface of each of the dents all form a level fabric supporting surface.

The dent shown in the figures consists of an elongated member made from strong resilient material for example a strip of spring steel having a thickness of about 0.025 ins. The forward part (7) is conviently about 0.5 ins in length, is slender and is provided with a rounded end (8) to prevent snagging of yarns particularly those made of man made fibres.

The strength of the dent is augmented by the tapered widening (9) and the length of the taper is preferably about twice that of the forward part, whilst the length of the whole article is about 2 ins. i.e. about four times that of the forward part. In operation, carpet backing (10) from a supply roll (11) is passed over the support surface provided by the dent plate, the capping strip and the upper surfaces of the dents until it passes beneath a row of tufting needles (12) mounted upon a reciprocating needle bar (13). As the needles move downwards they pass between the dents and co-operate with the loopers (14) which oscillate backwards and forwards in the machine direction. During this stage carpet pile is introduced into the backing and the resulting carpet passes from the support and is wound up on the take-off roll (15).

The invention dents and the dent assembly containing them have a number of advantages not posessed by their conventional counterparts. For example by introducing the tapered reinforcement (9) longer and thinner dents can be employed and as a result the loopers can be brought nearer to the tufting needles. This in turn enables carpets of very low pile heights to be made. Furthermore the resilience of the dents enables the same dents to be used for needles of different gauges. If a change of dents becomes necessary because of breakage or other failure the capping strip (5) can be readily removed to permit the replacement. A further advantage lies in the production of patterned carpets using staggered needlebars since the extent to which the dents protrude from their slots in the dent plate can be varied to correspond with the degree of stagger of the needles thus enabling patterns to be formed. Finally the level fabric support surface formed by the dent plate, the capping strip and the upper surfaces of the dents reduces significantly vibration of the backing and the problem of yarn passing through the needles accumulating on the surface of loop pile carpets.

Claims (8)

1. A dent for use in the manufacture of tufted carpets comprising an elongate element made from strong resilient material comprising a forward part in the form of a slender projection devoid of sharp edges, a mid part tapering toward the forward part and a rear part adapted to fit removably into the slot of a dent plate the forward part and the mid part presenting a smooth coplanar fabric contacting surface.

2. A dent according to claim 1 wherein the end of the projection is rounded.

3. A dent accordihg to either of claims 1 or 2 when made from a strip of spring steel.

4. A dent plate assembly comprising a substantially rectangular plate having a recess extending along one edge thereof and a plurality of spaced apart slots formed into the base of the recess and extending to the edge of the plate and a plurality of dents secured removably within the lots by a capping strip, the plate, the capping strip and the dents presenting a smooth coplanar fabric contacting surface.

5. A dent plate assembly according to claim 4 where the dents are any of those claimed in any one of claims 1 to 3.

6. A process of making a carpet with a tufted pile comprising passing continuously a carpet backing over a dent plate assembly as claimed in either of claims 4 or 5 introducing pile materials into the backing by means of a plurality of tufting needles secured to a needle bar situated above the backing and reciprocating in a direction at right angles to the direction of movement of the backing and causing the needles to co-operate with a plurality of loopers situated below the backing and oscillating in the direction of movement of the backing and continuously removing carpet from the dent plate assembly.

7. Dents as hereinbefore described with particular reference to the drawings.

8. Dent plate assemblies as hereinbefore described with particular reference to the drawings.