CH640895A5 - Method and device for inserting weft threads on a loom - Google Patents

Description

The present invention relates to a method and a device for picking up the weft thread at the exit of the crowd from a loom.

In the most common weaving looms, the weft is gripped at its exit from the crowd by a marginal clamp while it is still held by its insertion means. This process takes time because, if it is for example insertion by projectile, it must be stopped and placed in position so that the marginal clamp can take it. All of these maneuvers involve wasted time.

To avoid them, looms were built in which the projectile dropped the wire before it stopped. The wire is then sucked near its release point and then gripped by a marginal forceps. The latter method has the disadvantage of requiring a suction pump which absorbs power. In addition, it is not as reliable as a mechanical means because the forces acting on the wire are then relatively low.

The moment of arrival of the projectile at the exit of the crowd being variable, it was considered to control the marginal clamp by the passage of the projectile. This can be done either directly by mechanical means, or indirectly through an electrical circuit. Mechanical control has the disadvantage of a shock between the control member and the projectile moving at a speed of the order of 20 to 40 m / s, a shock which can produce unacceptable deformations. The electrical control can be carried out for example by means of proximity detectors reacting to the passage of the projectile and triggering the control member using an electromagnet. This process introduces a minimum delay of 4 ms, which represents a difference in frame length of 80 mm when the speed of the projectile varies from 20 to 40 m / s at the exit of the crowd.

In trades without shuttle using, to pass the weft through the crowd, water, air or kinetic energy of the mass of the wire as described in Swiss patent N ° 503134, the wire is free when leaving the crowd and must be taken by some means to avoid a jump and to equalize its tension. Generally, the outgoing wire is sucked into a tube and the length of the wire entering this tube to ensure its retention causes considerable losses. These losses can be reduced by removing part of the retained wire through the crowd, which involves a loss of time.

The present invention aims to overcome these drawbacks.

The method according to the invention makes it possible to retain a weft thread at the exit from the crowd of a weaving loom, the weft being drawn from a reserve situated outside the crowd, and is characterized in that the thread, out of the crowd, comes into contact with a surface which moves in its plane and leads the wire to a second surface substantially parallel to the first which pinches the wire between these two surfaces.

This process is particularly well suited to looms whose wire is pulled through the crowd by a clamp projectile as to looms whose frame is inserted by its own kinetic energy.

The invention also relates to a device for implementing the aforementioned method. This device is characterized in that a first surface located on the path of the wire is arranged at the exit of the crowd so as to be able to move in its own plane and has means for driving the wire in the direction of its movement towards a second surface substantially parallel to the first and rubbing on it with a pressure such that the wire drawn between these two surfaces is held under a determined tension.

Possibly, after having been clamped between the two surfaces, the thread is carried in the zone of marginal pliers which closes in rhythm with the loom on the thread introduced between its two jaws by the movement of the movable surface.

The invention and the advantages which it brings are however better understood thanks to the description which follows and which is illustrated by the appended figures, this description being given as an indication but not limiting.

Fig. 1 shows a side view of a projectile loom on which is mounted a device according to the invention.

Fig. 2 is a plan view of the same trade.

Fig. 3 shows a front view of the same trade.

Fig. 4 shows a plan view of a weft insertion loom by the kinetic energy contained in the mass of the wire, on which is mounted a device according to the invention.

Fig. 5 shows a front view of the same trade.

The weft thread 1 has passed through the crowd formed by the warp threads 2 and the comb 4, drawn by the projectile 3. The comb 4 is integral with the flap 5. The projectile 3, after having slipped on the comb 4, enters the guide 6 which moves with the comb controlled by the leaf 5. Under this guide 6, a fixed part 7 has a groove 8 of rounded shape whose center of curvature coincides with the center of rotation of a brush 9. The position of this brush is defined so that it rubs the side of the projectile 3 along which

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deploys the weft thread 1. To ensure the continuity of the surface against which the brush 9 rubs, the guide 6 also has the same radius of curvature as the brush 9. This rotates in the direction of arrow 10 with the disc 11 on which it is fixed. A clamp 13-16 is housed between the comb 4 and the guide 6; its fixed part has a foot 14 which is fixed to the leaf 5 in the same way as the comb 4 and the guide 6. A recess 15 gives way to the movable part 16 of the clamp. This movable part 16 pivots around an axis 17 fixed in the recess 15. The movable part 16 comprises two branches: one for gripping pick 1 under the effect of a spring (not shown), the other for open the clamp by means of the double lever 18 moved by a control 19 and acting on the lever 16 by means of an adjustment screw 20. This lever 18 rotates around an axis 21 secured to the fixed part 7.

The operation of the device according to the invention is as follows. When the projectile arrives at the level of the brush 9, the weft thread 1, released from the projectile, is driven downwards by said brush 9; it then slides into the cylindrical housing 8 provided in the guide 6 and into the fixed part 7. During this movement, the wire is pulled on the part 13 in the clamp 13-16 which is open. When the leaf begins its stroke, the clamp 13-16 moves away from the screw 20 and closes before the wire is released from the action of the brush.

The version shown in fig. 4 and 5 is suitable for weft insertion by the only kinetic energy contained in the mass of the wire. The wire is launched in the form of a loop which takes place in the crowd by transforming its kinetic energy into a force which moves with the loop and tightens the wire.

The weft 30 is launched into the crowd formed by the warp threads 31 and the comb 32. The comb 32 has a reinforcement 33 located at a certain distance from the last tooth, this to allow passage to pliers 34. A rotary brush 35 slightly touches the outside of the reinforcement 33. A scissor 36 is provided a few millimeters from the fabric at the point of shaping.

When the loop of the wire 30 arrives on the brush 35, its unwinding is interrupted and the unwinding force T is canceled; it follows a jump in the branch 30 'of the wire 30 at a speed which is a function of the voltage drop, the elasticity of the wire and its specific mass.

Ng

V = T- -

* jump where T = tension in grams N = metric number of the wire g = constant of gravitation C = speed of propagation of the disturbance

C = y / mjË

640,895

where m = specific mass of the wire

E = modulus of elasticity of the wire.

Furthermore, the voltage T created by the unwinding of the loop is known:

V2

T = -

Ng from where:

V2

V - -

v jump ç

V being the speed of the loop.

Example: Loop of cotton thread moving at the speed of 30 mis.

The speed of disturbance C for a cotton thread is known to be around 1500 m / s, hence:

^ jump = ®, 6 m / s

It suffices to give the brush 35 a speed VB in the direction of the arrow so that the deposited wire is carried between the brush 35 and the reinforcement 33 before being completely removed by the projection at the speed VR. If the length of the strand 30 "is 1 and the length between the first impact of the loop on the brush and the reinforcement 33 V, the speed of the brush VB should be greater than VR. L / l, in the example given digital, VB> 0.3 m / s.

By this method, a released pick can be retained.

During the first centimeters of movement of the comb towards the fabric 37, the end of the pick will continue to be retained between the brush 35 and the reinforcement 33; during this time, the clamp will close and keep the wire taut to facilitate its cutting by the chisel 36.

By this method, it is possible to retain a pick released at the exit of the crowd without taking time out of the insertion of the wire, that is to say without reduction in production.

The nature of the brush must be chosen according to the wire to be worked. The brush can also be replaced by a homogeneous, smooth or rough, more or less elastic surface. However, it is essential that the coefficient of friction of this surface is large enough.

A particularly advantageous solution consists in using a surface that is electrostatically charged or that uses any other attractive force. The movement of this surface can be either continuous, as in the examples shown, or cyclic, controlled by the trade. Another form of movable surface is advantageously constituted by a wire mesh or a perforated plate closing a suction channel.

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2 sheets of drawings

Claims (10)

640,895 1. Method for retaining a weft thread released at the exit of the crowd from a weaving loom, the weft being drawn from a reserve located outside the crowd, characterized in that the thread, leaving the crowd , comes into contact with a surface which moves in its plane and drives the wire towards a second surface substantially parallel to the first which pinches the wire between these two surfaces and maintains it under a determined tension. 2. Method according to claim 1, in which the wire is drawn into the crowd by an insertion member, the wire deploying on one of the faces of this insertion member, characterized in that the movable surface moves transversely from the movement of the insertion member on the face cooperating with the wire. 2 3. Method according to claim 1, in which the weft thread is inserted into the crowd by its own kinetic energy in the form of a loop, characterized in that the moving surface moves across the path of the weft thread . 4. Device for implementing the method according to claim 1, intended to retain a weft thread released at the exit of the crowd from a weaving loom, characterized in that a first surface located on the path of the thread is arranged at the exit of the crowd so as to be able to move in its own plane and has means for driving the wire in the direction of its movement towards a second surface, substantially parallel to the first and rubbing on it with a determined pressure , the wire drawn between these two surfaces being held under a determined tension. 5. Device according to claim 4, characterized in that the movable surface is a rotating brush. 6. Device according to claim 4, characterized in that the movable surface is an insulating surface carrying an electrostatic charge, the wire being retained on this surface by electrostatic forces. 7. Device according to claim 4, characterized in that the movable surface is constituted by a perforated surface or a wire mesh closing a suction channel, the wire being pressed on this surface by a current of air. 8. Device according to one of claims 4 to 7, characterized in that it comprises a marginal clamp whose closing and opening are controlled by the loom and which is arranged so that the thread driven between the two surfaces is introduced into this clamp. 9. Device according to one of claims 4 to 7, characterized in that it comprises a suction mouth arranged so that the wire driven between the two surfaces is carried before the mouth by the movement of the movable surface. 10. Device according to claim 4, characterized in that it comprises a guide, one face of which is an extension of the face of an insertion member cooperating with the wire and on which the movable surface is intended to move.