GB2073788A - Improvements in Fabric Manufacture - Google Patents

Abstract

A heddle element J through which a warp yarn passes is provided with two pairs of latches F. Heddle drive member H, I, reciprocate over the shed stroke and have heddle driving lugs, G, which can engage one or other of the latches F when these are appropriately set. A control member C is moved to set one of each pair of the latches when heddle J is to be moved to manipulate a shed yarn. The control member is actuated by further drive member A reciprocating over a small stroke to cyclically apply a magnetically susceptible part CL of the control member to a respective electromagnetic element, coil D. If coil D is energised part CL is held with control member C in an upper position for a cycle of member A. If coil D is not energised the control member C moves down with member A. <IMAGE>

Description

SPECIFICATION Improvements in Fabric Manufacture This invention relates to fabric manufacture such as patterned weaving and knitting and more particularly to the selection of threads for patterned fabric weaving of tapes, ribbons, webs, belts, elastics, labels and the like.

One loom of known form can weave plain tapes and the like at high speeds, typically 3000 weft yarn cycles (or picks) per minute. However the weft yarn is of one colour only while the warp shed is of fixed layout.

To achieve patterned weaving on a high speed narrow fabric loom several problems must be overcome.

The fabric is typically some 65 mm wide having up to about 400 yarns to the warp. The weft is inserted at about 3000 cycles (picks) per minute. This allows some 20 milliseconds for warp selection and positioning. The required angle of the shed (opening) between the upper and lower warp yarns is typically a minimum of 140; a shed lift of some 50 mm is needed, depending on the relation to the fell position.

It is an object of the invention to provide a control apparatus enabtg the manufacturer of patterned fabrics over a range of speeds including such high speeds using warp yarn selection.

According to the invention there is provided a heddle arrangement for warp yarn selection in the shed of a loom including a heddle element supported for warp positioning movement, means to drive the heddle to each extreme of the warp positioning movement and link means to selectively link or not link a heddle and a heddle drive means to enable the drive means to drive the heddle to a desired warp position in the shed, the link means being selectively operable by a control signal too small to drive the heddle.

The link means may be resilient members on the heddle or the drive means. The link means control signal may be of electrical, mechanical, fluid pressure or other form. The control signal may be appled to the link means by an intermediate such as a mechanical control element or elements.

According to a particular aspect of the invention there is provided in or for a high speed patterned fabric making machine a heddle apparatus for warp yarn control including for each warp yarn a heddle element and for each heddle element two pairs of latches and a control member for the latches, the apparatus also including opposed heddle drive members continuously reciprocal over a required warp yarn shed stroke and having heddle driving lugs to selectively drivingly co-operate with one of the said latches at a time to link the heddle to one of the drive members to move the heddle of the selected latch and means to operate the control member to either operate a latch to co-operate with the drive member lug or not so-operate a latch, the control member operating means including a control element drive member continuously reciprocable over a stroke smaller than the shed stroke and a control element shift means individually operable to shift the element into or out of engagement with its drive means to respective non-operation or operation of the control means, whereby any required one or more of the warp yarns can be moved to form the shed on each weft cycle of the machine.

Preferably the yarns are left in the shed-forming position from pick to pick being only moved when the position of the yarn in the shed is to be changed. This avoids the need to move each yarn at every weft cycle.

The shift means may be an electromagnet energisable to attract a resiliently biassed part of the control element to hold it against its bias out of said engagement.

Typically the control apparatus controls up to 400 warp yarns at up to 3000 weft cycles per minute in a Jacquard loom.

Embodiments of the invention will now be described with reference to the accompanying drawings in which: Figure 1 shows one part of a heddle control arrangement embodying the invention, Figure 2 shows the other part of the heddle control arrangement in Figure 1 and details of electromagnet coils for the arrangement and Figure 3 shows in outline the heddle arrangement applied to a narrow fabric loom in place of the heald frame.

Referring now to the drawings, Figure 1, this shows a heddle J, of 1 mmx2 mm cross-section, and approximately 300 mm long, made from steel in an experimental version, run in guide slots. The upper end of the heddle has an eye for one warp yarn to pass through or other means of controlling the path of one warp yarn. Carbon fibre materials may be suitable instead of steel. Attached to the heddle are link means of two pairs of flag-like spring. steel components, latches F, which, if forced to lie flat against the heddle, lie in the path of special driving lugs G, which are attached, one pair to each, to two driving cross-members H and I, the latches subsequently engaging the driving lugs as the driving crossmember traverses its stroke. The latches may be attached by solder and/or rivets or formed to clip to the heddle.These cross-members H and I, are reciprocating continuously with the desired output stroke Z-Z' (the 50 mm shed lift), their motions being half a cycle out of phase. Consequently whilst member I is rising through distance X-X', the other member H is descending through W-W' and vice-versa. Thus motion in either direction is available depending upon which driving lug G is engaged.

Members H and I are in front of heddle J in Figure 1.

The flag-like latches F are controlled by a control element C which is movable bodily a small distance Y-Y', approximately 2 mm, being the difference between the control element either being in a position so as to act on a latch to force it to lie flat against the control element or being in a position such that there is clearance between the latch and the control element. This much smaller motion Y Y' of the control element C is derived from a third cross-member A moving continuously with a 3 mm stroke denoted by U-U'. The control element has a lower spring steel portion CL bent towards crossmember A. The upper part of element C can be steel, carbon fibre etc., as is the heddle J, the two parts being rigidly joined.Normally the shape of the lower portion CL of the control element C holds it in engagement with the member A, for example in a slot under a presser element B. However, at the top of the stroke, the control element portion CL is pushed out of mesh with the member A by presser B having motion V'-V" to lie flat against a coil block E, position V". Block E is shown in Figure 2. This block contains small electrical coils D which, if energised, create a magnetic field to hold the respective control element C out of engagement with member A for one cycle. The control element lower portion CL is of a magnetically susceptible material and can complete a magnetic circuit including the coil core and the block. The coils D are also shown only in Figure 2.Typically coils of 1100 turns of 40 SWG enamelled copper wire are wound on a 3 mm core to an outer diameter of 7.5 mm and a length of 12 mm. The coils are placed alternately in upper and lower layers with a 4 mm core pitch.

Since the magnetic field does no mechanical work, and the magnetic circuit has no air gaps when the presser pushes the element portion CL against the coil, the coil can be smaller and require far less power than a conventional solenoid performing such a selection duty. Additionally, due to the shape of the faces of block E and cross-member A, once the cross-member has started to descend the control element C cannot re-engage the cross-member until it next reaches the top of its stroke. Thus the proportions of the cycle over which the coil must be supplied with power is small. In practice the coil can be driven directly by a single stage transistor amplifier connected to the TTL (transistor-transistorlogic) output of a microprocessor control. The presser B which operates the control element C is driven in any suitable manner. Clearly other eiectromagnetic arrangements are possible.For example the coils could be vertical with L-shaped cores and a common pole-piece at one end. The arrangement described has operated at 1 500 picks per minute in an experimental form.

The sequence of operation is set out below 1. Cross-member A, rises, U-U'.

2. As cross-member A reaches the top of the stroke, U, the presser B advances, V'-V".

3. Lower end of control element C is pressed against core of coil, D. Then: Either 4a Coil is energised, control element is retained against coil block E.

or 4b Coil, D, is not energised so control element remains biassed against presser, B.

5a If heddle element, J is at lower position, Z', lower latches of each pair, F, and F3, are closed.

5b Cross-member, A, descends, U'- U, taking control element to lower position, Y.

6a Closed latch engages lug, G, of rising crossmember, Horl.

6b If heddle element, J, is at upper position, Z, upper latches of each pair F2 and F4, are closed.

7a Heddle element is driven to upper position, Z.

7b Closed latch engages lug descending crossmember H or I.

NB If heddle element is already in upper position no latches are closed.

8b Heddle element is driven to lower position, Z'.

NB If heddle element is already in lower position no latches are closed.

The heddles are positioned in a matrix of 25 rows of 1 6 selectors for the 65 mm fabric mentioned above. A space 4 mmx 12 mm of almost unlimited depth is thus available to receive each heddle and controls.

The information required to control the coil drives for warp selection by heddle control is conveniently stored in a microprocessor with a semi-conductor memory and associated amplifiers etc. to suit the coil drive. Clearly other storage and drive arrangements can be used e.g. paper tape, as will be readily apparent to those skilled in the electrical control art. While electrical control is convenient clearly other means such as mechanical or fluid pressure could be used.

Although the embodiments described above use latches mounted on the heddle to form the link means to link the heddle selectively with a drive means other link means may be used to embody the invention. The link means may be mounted on the heddle drive and may be of other mechanical form and may be in one piece or assembled from pieces of material of different resilience to more easily provide both good response to the control action and adequate strength to transmit the heddle drive.

The arrangement described produces the required heddle control action, including accelerations of up to 250 g for the moving parts, to meet the cycle time limits and space limits for warp selection.

At the same time to fully exploit the patterning possibilities weft selection is desirable. Reference is therefore directed to the co-pending Application by the same Applicants entitled "Improvements in Manufacture of Fabric" which describes weft selection.

One machine to which the invention may be applied is a narrow fabric loom to which it will give a Jacquard capability with a speed of up to 3000 picks a minute when suitably adjusted. For convenience the description will refer to the Bonas Varitex 2/65 machine which is also referred to in the above application on weft selection.

The arrangement shown in Figure 3 replaces the heald frames and pattern chains and is positioned below the warp plane. This position allows good access to the warp and maintains a low centre of gravity for the machine.

The heddle elements JN are arranged on a staggered matrix of 25 rows of 1 6 elements. Guides K, L, M are provided. This allows a 4 mm pitch along the rows and a 12 mm mean pitch between rows while keeping within the fabric width and space available. This tight packing of the elements is achieved as alternate rows are turned to face the rear of the machine. Thus the driving cross-members IN, HN can be used by the two rows of elements which face them thus reducing the number of crossmembers by half as well as using the space more effectively.

The driving cross-members are attached at their ends to respective arms R and S pivoted at RP, SP below the fell of the fabric. Thus the stroke of each cross member is proportional to the distance of the cross member from the line of the fell. This is to reduce the movement of the heddle elements to the minimum required to produce a specified shed angle x. The front and back reeds are shown at FR and BR. The control cross-members BN are also linked at their ends but the same motion is required for all of these members since the movement required by all the control elements to provide reliable "switching" of the latches is a function of latch shape and is the same irrespective of position.The coil blocks are indicated at EN, and the pressers B and B' and their respective control element portions CL and CL' are paired for one control cross-member AN, as indicated in outline in Figure 2.

The motions for both sets of cross-members may easily be derived from eccentrics or cranks or other drives in well-known manner since the exact form of the motion is generally not critical.

Advantageous features of the arrangements described are as follows.

The warp threads are only moved when necessary, e.g. if it is required that a warp thread be held in the top of the shed for two successive picks then the yarn is raised prior to the first pick, held stationary in the up position until the second pick is inserted and only then moved if the low position is required for the third pick. Many other systems return all the threads to a common position, usually the centre or bottom of the shed, on each cycle, the selection for the next pick then taking place from this position.

The stroke of the driving cross-members can be arranged to be proportional to their distance back from the fell so a common shed angle is formed by all of the warp threads. This can be fixed at the minimum required for weaving and as a result each warp thread is only displaced the absolute minimum necessary. Many other systems lift all of the warp threads the same amount, this stroke being determined by the shed angle subtended by the threads controlled at the furthest distance from the fell: thus any threads controlled nearer to the fell, which would ideally require a smaller stroke to subtend the same angle, are moved a distance greater than the minumum required.

The mechanism requires an input signal which is directly related to the position required of the warp yarn so should a selection error occur it will not affect subsequent selection. Some systems operate in such a way that the signal dictates only a change of position of the yarn; in such systems if an error occurs it is perpetuated in subsequent selections.

The system can be positioned below the weaving area so access to, and visibility of, the heddle area is good from the normal operator position making threading operations easier. This also allows the addition above the weaving area of the multi-yarn feed arrangement that is needed with a weft selection system.

The electrical coils do no mechanical work and operate with a flux circuit composed almost entirely of materials with a high magnetic permeablilty. Thus the coils themselves can be very small and require only a low signal power input. A suitable driving signal can be derived far more easily, and cheaply, from the output of a microprocessor.

In addition to the low power of the signals to drive the coils, the operating cycle of the selectors requires the signal only over a small proportion (approx. 20%) of the machine cycle as mentioned above. Thus the total average power requirement is small as is the resistive power loss and consequent heat generation in the coils.

All the electrical and magnetic components are stationary. This helps to provide the reliability required since conductors are not being stressed, manufacture is cheaper since no moving electrical contacts are needed, and the relatively heavy magnetic materials do not require power and strong mechanism to move them.

The total number of moving parts is lower. The cross-members are "shared" by many elements and since they are moving continuously they can be designed to give high reliability and low power consumption. The only individual moving parts for each yarn are the heddle elements and control elements which would be suitable for mass production keeping replacement and maintenance costs low.

As described only friction holds in position the heddle elements which are not to be moved. At the moment of maximum warp tension at beat up, those yarns which are being moved will be close to the middle of the stroke and thus the force due to the tension is taken by let off device on the warp beam. However the tension in those threads held, either at the top or the bottom of the shed, will act so as to bring the elements to the centre. Thus some form of retaining device, acting on the stationary elements between selections, can be added to assist in reliable operation of the system.

If a heddle element is not required for the manufacture of a particular fabric, then it can be made to remain stationary to reduce wear, noise and power consumption. To do this the relevent control element must provide a constant signal due to its position. If this signal to the coil is removed, the control element will stay permenently meshed with the control cross-member and reciprocate continuously. If a signal is applied to the coil for each pick, the control element will be stationary with its lower end held against the coil block and the heddle will be stationary in the upper position.

However the elements could be "parked" with no signal applied by a means of mechanically locking the end of the control element against the coil block thus providing inert heddles for unused ends.

The arrangements and techniques described above permit the manufacture of patterned fabrics at high speed. Although specifically described for a narrow Jacquard weaving machine the invention is equally applicable to other looms, to knitting machines for yarn control and selection and to carpet making processes as well as other textile uses. The term "fabric" throughout this specification refers to any textile use as well as those specifically mentioned.

The control techniques described above in terms of heddles and warp yarn selection may be used for other yarn selection uses for example in a weft selector to use a heddle-like element to move a yarn to a picking position.

Claims (9)

Claims

1. A heddle arrangement for warp yarn selection in the shed of a loom including a heddle element supported for warp positioning movement, means to drive the heddle to each extreme of the warp positioning movement, means to drive the heddle to each extreme of the warp positioning movement and link means to selectively link or not link a heddle and a heddle drive means to enab!e the drive means to drive the heddle to a desired warp position in the shed, the link means being selectively operable by a control signal too small to drive the heddle.

2. An arrangement according to Claim 1 in which the link means includes a resilient member.

3. An arrangement according to Claim 2 in which the link means is mounted on the heddle or the drive means.

4. An arrangement according to any one of Claims 1 to 3 including at least one intermediate mechanical element to apply the control signal to the link means.

5. An arrangement according to any one of Claims 1 to 4 in which the control signal is of electrical, mechanical or fluid pressure form.

6. A heddle arrangement according to any one of Claims 1 to 5 in or for a high speed patterned fabric making machine of a heddle apparatus for warp yarn control including for each warp yarn a heddle element and for each heddle element two pairs of latches and a control member for the latches, the apparatus also including opposed heddle drive members continuously receiprocal over a required warp yarn shed stroke and having heddle driving lugs to selectively drivingly co-operate with one of said latches at a time to link the heddle to the drive member to move heddle of the selected latch anc! means to operate the control member to either operate a latch to co-operate with the drive member lug or not so-operate a latch, the control member operating means including a control element drive member continuously reciprocable over a stroke smaller than the shed stroke and a control element shift means individually operable to shift the element into or out of engagement with its drive means to respective non-operation or operation of the control means, whereby any required one or more of the warp yarns can be moved to form the shed on each weft cycle of the machine.

7. Arrangement according to Claim 6 in which the shift means is an electro-magnet energisable to attract a resiliently biassed part of the control element to hold it against its bias out of said engagement.

8. An arrangement according to any one of Claims 1 to 7 to control warp yarn selection at up to 3000 weft cycles per minute.

9. A heddle arrangement substantially as herein described with reference to the accompanying drawings.