GB2253862A - A thread delivery device for textile machines - Google Patents

Abstract

A thread delivery device for a textile machine such as a loom or warp knitting machine which processes groups of threads (1) e.g. from a warp beam 51 with a regulatable drive (5) has a low-mass thread rocker (3) upstream of the processing station and in addition differences between the delivered and required thread length cause surplus thread to be stored in an intermediate thread store (4). The store (4) has a thread guide element such as a tubular roll (45) rotatable in bearings on the free ends of supporting arms (42) which in turn are mounted on a torsionally rigid tube (41) which is loaded in the pivoting direction e.g. by a spring (441) acting through a loading arm (43). The arm (43) further cooperates with sensors (54) to control the drive of the warp beam (51) in accordance with the position of the guide element (45). Instead of the spring (441) the loading may be applied by a pneumatic, hydraulic or electromagnetic device. <IMAGE>

Description

A THREAD DELIVERY DEVICE FOR PROCESSING GROUPS OF THREADS IN TEXTILE MACHINES This invention relates to a thread delivery device which processes groups of threads in textile machines, particularly warp knitting machines and weaving machines.

A known textile machine for processing groups of threads employs a regulatable drive and a thread delivering device, such as is described in DD 274710. This known device uses a low-mass thread rocker which, during the binding-in cycle, compensates for the differences in thread length with an intermediate thread store which accommodates the differences between the thread length supplied and the thread length processed. Sensors associated with the rocker influence the delivery drive.

For guiding the group of threads a thread guide element is pivotable on a plurality of levers and is rotatable in bearings on the levers about its own axis. The thread guide element is deflected transversely to the group of threads by at least one resilient loading element.

The thread guide element of the intermediate thread store is in the known device constructed as a thin rotating shaft. The thin shaft is mounted lengthwise along the machine axis on the free ends of a plurality of identical levers which are disposed to be freely pivotable about a uniform axis fixed with respect to the frame of the machine. Each of the levers carrying the thread guide element is subjected to a precisely defined uniform force. To ensure a simple simultaneous adjustability of this uniform force, pistons, preferably diaphragm pistons, are provided on the levers and these pistons are acted upon by a uniform pneumatic or hydraulic pressure system. The pressure in this system is adjustable at minimal cost and is evenly distributed over all the levers.In addition to the very accurate adjustment of the loading of the intermediate thread store, by virtue of the small masses which have to be moved and the minimal friction, this known device allows a very sensitive and rapid conversion of the drive for thread delivery through the warp beam which can occur simultaneously over the total working width of the machine. At the same time, the level of the forces acting on the group of threads remains at the level once adjusted, regardless of any sudden occurrence of differences in thread length between the length of thread running off the warp beam and the thread length processed in the same time.

However, the disadvantage of this known device resides in the fact that in addition to the relatively high cost of the loading elements adjustable to a virtually uniform loading level it is necessary to provide an additional energy system for loading the diaphragm pistons. This makes the machine expensive and increases the cost of servicing the machine.

An object of this invention is to overcome these drawbacks. In addition, the invention seeks to retain the advantages of the known device in terms of regular loading of the thread group which can be attained in the event of suddenly occurring differences between delivery and processing and of switching over the drive in a very short time while retaining a constant thread tension and with the minimum possible energy expenditure, rendering thereby a large number of individual mechanical loading elements indispensable for the many levers which carry the thread guide element without installing an additional energy system in the machine.

According to the invention there is provided a thread delivery device for a textile machine processing groups of threads, particularly a warp knitting machine or weaving machine which has a regulatable drive for the groups of warp threads; said device comprising a low mass thread rocker which during the binding-up cycle compensates for the differences in thread length with an intermediate thread store which accommodates the differences between the thread length Supplied and the thread length processed, a thread guide element pivotable on a plurality of levers about a fixed axis, an adjustable resilient loading element for deflecting the thread guide element transversely to the group of threads, the levers carrying the thread guide element being rotationally rigidly mounted on a torsionally rigid tube pivotable about the fixed axis and at least one loading lever for transferring force from the adjustable loading element to the tube.

If the rotating thread guide element is constructed as a low-mass hollow shaft on the periphery of which are disposed bearings, such as ball bearings, mounting the support levers, the masses of inertia and the friction forces are so reduced that even with pulsating differences in thread length, friction conditions which give rise to tension peaks in the thread group are avoided.

The loading element may take the form of one or several springs having a flat characteristic curve. In the case of knitting or weaving machines having a large working width, it is expedient to dispose on the tube carrying the thread guide element at least two loading levers at a relatively considerable distance from each other. The loading elements are then preferably associated with a common adjusting device.

In the final analysis, the result is that by the very simplest means, only a drive of relatively low output needs to be associated with the driving of the warp beam or of a thread delivery mechanism disposed downstream of the warp beam.

For practical purposes, the goods produced with a machine with a thread delivery device in accordance with the invention surprisingly exhibit only insignificant tolerances in their weight per unit of surface area. At the transitions between a high thread consumption and a very low thread consumption, even at high machine speeds, no mesh lengths are produced which diverge from the desired value.

The invention will be described in greater detail hereinafter with reference to the accompanying drawing, in which: Figure 1 is a diagrammatic end view of a thread delivery device constructed in accordance with the invention on a warp knitting machine, and Figure 2 is a diagrammatic part-sectional side view of a portion of the intermediate thread store in the embodiment of Figure 1.

A warp knitting machine, for example a crochet machine, has in the region of a mesh forming zone 2 a thread laying bar 21 with thread guides for a group 1 of warp threads. On crochet machines for producing a double-sided knitting pile material, such thread groups can be envisaged for the rear and front pile thread system, the knitting thread system and possibly for the weft thread system.

Upstream on the thread run side of the thread laying bar 21 is a so-called thread rocker 3 which maintains the thread or group of warp threads 1 taut in rhythm with stitch formation. This thread rocker 3 consists of a very low-mass profile element 31 mounted on a plurality of leaf springs 32 distributed lengthwise of the machine and mounted on a rail or shaft 33 which is adjustable in a peripheral direction in relation to the frame. This low-mass construction, even with very high machine frequencies, permits a uniform level of tension in the warp thread group 1 during the stitch forming cycle.

The thread rocker 3 is in turn preceded in the thread run by an intermediate thread store 4 which consists of a rigidly mounted guide roll 40 and a thread guide element 45 which is mounted for oscillation in the frame.

The task of the intermediate thread store 4 is to accommodate or set aside the possibly abruptly occurring differences between the thread length delivered and that which is processed while retaining a constantly low thread tension which is required for stitch forming.

The thread guide element 45 is a hollow shaft 451 guided in bearings, such as ball bearings 421, at the free ends of supporting levers 42. All the supporting levers 42 are mounted on a tube 41 which is mounted to pivot in bearings, such as ball bearings 411, about an axis 412 which is fixed with respect to the frame. The tube 41 is light and torsionally rigid. The fixing of the supporting levers 42 which are preferably made from light metal on the tube 41 is expediently accomplished by a clamping connection. Engaging the tube 41, expediently in another direction from the supporting levers 42 is a loading lever 43. Like the supporting levers 42, the loading lever 43 is relatively long and of low-mass.

Engaging the free end of this loading lever is a spring 441, the other end of which is mounted rigidly to the frame. The spring 441 is relatively long and has a small wire cross-section to provide a very flat characteristic.

It is important that the spring 441 applies virtually constant force for the stitch forming process to the thread guide element 45 over a travel of about 20 to 30 mm. In this area, a spring force of about 5 to 15 p per thread is anticipated.

The initial tension of the spring 441 can be adjusted either at the clamping point which is rigid with the frame or at the point of attack on the loading lever 43.

In the case of machines having a large working width, it is sensible to provide two or more loading levers 43. These would then need to be fixed on the tube 41 in such a way that they are distributed at relatively large intervals over the working width. In such an arrangement, it is important to keep as small as possible the tolerances in the loading of the thread guide element 45 over the width of the machine.

Since, as a rule, the loading of the thread guide element 45 has to be adjusted while the machine is running, it is a good idea for the means of adjusting the loading elements 441 of the individual loading levers 43 to be so coupled with one another that the force of all the loading elements 441 is simultaneously changed by the same amount. If the fixed points are adjusted by springs through levers, then this can be accomplished by a shaft coupling the levers together.

A lever which is rigidly secured to the tube 41 serves as an actuator for a plurality of sensors 54 disposed along the maximum angle of oscillation of the intermediate thread store 4. These sensors 54 are linked to a controller for controlling an electric motor 52, for driving and positioning a warp beam 51 as a function of the position of the intermediate thread store 4 at any given moment. The motor 52 and the warp beam 51 provide a regulatable drive for the group of threads 1.

If these sensors 54 indicate a major reserve in the intermediate thread store 4, then the speed of the motor 52 is reduced. On the other hand, if the sensors 54 indicate a smaller reserve in the intermediate thread store 4, then the rotary speed of the motor 52 which drives the warp beam 51 is increased. This correction of the speed of the motor 52 occurs in addition to the controlled variation in the rotary speed as a function of the length of the thread to be delivered per rack and the variation in the current diameter of windings on the warp beam 51.

In the example shown in the drawings, the thread supply is achieved by the warp beam 51 which is driven under control. Naturally, it is also possible in a known manner to deliver the thread group 1 by a pair of delivery rollers which are driven under control. In this case, naturally, the signals from the sensors 54 must be fed to the controller of this drive. However, it must be taken into account that such delivery rollers usually work with slip. As a function of the braking force applied at the warp beam 51, the time taken to attain a normal midway position will be greater than when regulating a warp beam drive.This is the case because, by means of the friction drive, the thread group 1 can only be exposed to an approximately equal friction force and in this way minimal variations in rotary speed of the delivery rollers can only have a limited effect on the delivery rate of the group of threads 1. For this reason, preference is given to using the delivery device for machines which have positively driven warp beams. In this situation, the signals provided by the sensors 54 can be used also for controlling both the driving motor 52 for the warp beam 51 and also for a coupling positioned between this motor 52 and the warp beam 51.

For better understanding of the invention, the device will be described again in terms of the way it functions.

The positioning control for the warp beam 51, is having regard to the current warp beam diameter and the thread length to be processed per rack, so adjusted that it moves the warp beam 51 at an average peripheral speed.

If, now, for example by virtue of a change in bending, extremely few threads are processed from one stitch row to another, then the low-mass warp beam 51 is unable synchronously to follow this sudden change. The resultant excess quantity of thread is however temporarily accommodated by the intermediate thread store 4. The intermediate thread store 4 needs to react within approx. 60 ms and the difference in thread length between two rows of stitches must be accommodated while retaining the average thread tension. In the case of a polythread system, this may be as much as 20 mm per row of stitches.

So that thread storage can be achieved without any harmful effects on the thread rocker 3 disposed immediately upstream of the stitch forming points, the spring force 441 which pretensions the immediate thread store 4 must on the one hand be so strong that it is able to displace the thread guide element 45 by this amount in the available 60 ms. On the other hand, the spring force must only be sufficiently strong that the thread can be processed with an average technologically related low thread tension - approx. 3 to 15 p.

Both conditions are met by a device comprising the elements according to the invention. While the low masses of the components of the intermediate store member 4 allow a brief variation in the position of the hollow shaft 451, the low friction mounting of the hollow shaft 451 on the loading lever or levers 43 obviates the creation of voltage pulses due to sudden and briefly occurring friction co-efficients.

As can be appreciated from the drawing, it is important to maintain uniform the friction conditions between the thread guide element 45 and thread over the entire working range, so also securing the conditions of rotation for the hollow shaft 451 which forms the thread guide element 45. This task can be assisted if the hollow shaft 451 is divided in the region of the mounting or bearings of the loading levers 43 or if its crosssection is markedly reduced.

Deflection of the intermediate thread store 4 causes the lever which actuates the sensors 54 to move into the region of one of these sensors 54. These generate signals to the controller 53 which in turn causes the motor 52 to assume a higher or lower rotary speed, By virtue of the relatively maior travel of the intermediate thread store 4, this latter is in a position to accommodate relatively wide differences in the thread length without altering the level of tension in the warp thread group 1. The controlled drive 52, 53 for the warp beam 51 therefore has relatively long time to adapt itself to the new conditions, i.e. to accelerate or decelerate delivery. The power for driving the warp beam 51 can be kept very low and the gear mechanism which is associated with the motor 52 may be of correspondingly simple construction and of minimal dimensions.

Instead of the intermediate thread store 4 being loaded by one or more springs 441, it is naturally also possible to use pneumatic, hydraulic or electromagnetic loading elements if their dimensions correspond to the conditions set out hereinabove.

Claims (5)

1. A thread delivery device for a textile machine processing groups of threads, particularly a warp knitting machine or weaving machine which has a regulatable drive for the groups of threads; said device comprising a low mass thread rocker which during the binding-in cycle compensates for the differences in thread length with an intermediate thread store which accommodates the differences between the thread length supplied and the thread length processed, a thread guide element pivotable on a plurality of levers about a fixed axis, an adjustable resilient loading element for deflecting the thread guide element transversely to the group of threads, the levers carrying the thread guide element being rotationally rigidly mounted on a torsionally rigid tube pivotable about the fixed axis and at least one loading lever for transferring force from the adjustable loading element to the tube.

2. A thread delivery device according to Claim 1 wherein the guide element is a tubular roll or hollow shaft which is mounted in bearings at the free ends of the supporting levers.

3. A thread delivery device according to Claim 1 or 2, wherein the adjustable loading element takes the form of one or a plurality of springs each with flat spring characteristics.

4. A thread delivery device according to any one of Claims 1 to 3, wherein there are two loading levers disposed at a considerable distance from one another.

5. A thread delivery device or textile machine substantially as described with reference to, and as illustrated in, any one or more of the Figures of the accompanying drawings.