An apparatus for feeding one or more fibre threads

TECHNICAL FIELD

The present invention refers to an apparatus for feeding one or more fibre threads, e.g. of glass, at an adjustable feeding rate, comprising at least two synchronously driven feed rollers forming at least one nip for the fibre thread and consisting of a first motor driven roller and a second co-rotating roller.

BACKGROUND OF THE INVENTION In robot-controlled production, there are usually a high demand for precision in the delivery of raw material. For example, when feeding fibre thread to a robot-controlled fibre feeding apparatus, the feeding rate may be about 10 meters per second, wherein the quality of the product is highly dependent upon an exact control of the feeding. A prerequisite for such an exact control is that the feed rollers are synchronously driven at the right speed, without damages to the thread. Damages may occur if a thread which is composed of a large number of single thin threads is subjected to wear, e.g. because the feeding rollers are not driven synchronously, so that one side of the fibre is either braked or subjected to wear. This can lead to a negative influence upon the strength of the thread, and that a part of the thread is worn away, so that the required amount of material is not supplied to the robot.

The feeding rollers, of which one thus is mechanically operated and the other is only co-rotating, can be driven synchronously in different ways. For example, gearwheels, a chain transmission or a toothed belt can be used for synchronisation of the feeding rollers. However, all these known transmissions exhibit drawbacks in an environment

which is subjected to comparatively large amounts of fine fibre dust from the thread.

Also, it is advantageous if the feeding rollers and their driving means can be housed in a manner which requires little space and reduces the weight, to facilitate mounting upon a robot arm.

It is also important that the driving of the feeding rollers is reliable, with little need for attention and maintenance.

THE TECHNICAL PROBLEM

One object of the present invention is therefore to provide a device for feeding fibre thread, which fulfils the above discussed prerequisites.

THE SOLUTION

For this purpose the invention is characterized in that the motor driven roller and/or the co-rotating roller are/is provided with one or more, each in its respective peripheral slot in the cylindrical mantle surface of the roller housed O-ring of an elastic incompressible material, e.g. rubber, which O-ring bears on the peripheral surface of the adjacent roller to transmit the rotary motion by means of friction.

Preferably, the contact surface of the co-rotating roller toward the O-ring/rings is provided with a friction enhancing knurling.

DESCRIPTION OF THE DRAWINGS

The invention will be described here below with reference to an embodiment shown in the accompanying drawing, in which Fig. 1 shows schematically a feeding apparatus in a side view, and Fig. 2 shows the feeding rollers in view from above. DESCRIPTION OF EMBODIMENTS

The feeding apparatus schematically shown in Fig. 1 is used mounted upon a not shown robot arm, for feeding out fibre thread 10 and binding agent in the form of powder from not shown magazines, for example to moulds for plastic products.

Preferably, the robot arm is freely movable in the room and is governed by a micro processor, which can be programmed.

The fibre thread 10 is drawn from its magazine into the feeding apparatus by means of two feeding rollers 11, 12, which form a nip for the fibre thread and comprise a first motor driven roller 11 and a second co-rotating roller 12.

The roller 12 has a displaceable bearing which is pressed in the direction towards the roller 11 by means of a compression spring 13. The roller 11 is driven in a speed adjustable manner by means of a not shown driving motor.

The rollers 11, 12 feed the fibre thread 10 forward via a compressed air ejector 14 and a tube 15, which is bent to about 90° and emerges into the nip between a knife roller 16 and a support roller 17.

The fibre thread pieces cut by the knife roller 16 are blown out through an ejector pipe 18 which is provided with a connection 19 for compressed air. Also, the ejector pipe 18 is provided with a connection 20 to a conduit for supply of a pulverulent bonding agent.

The motor driven roller 11 is provided with two in a respective slot 21 in the cylindrical mantle surface of the roller housed O-rings 22 of an elastic incompressible material, e.g. rubber. The O-rings bears on the peripheral surface of the adjacent roller 12 and transmit the rotary motion to said roller by means of friction, so that the rotation of both rollers is synchronized.

The surface of the roller 12 is provided with a knurling 23 to enhance friction between the O-rings 22 and the roller 12.

The invention is not limited to the embodiments described here above, but several variants are conceivable within the scope of the following claims. For example, both the rollers 11, 12 may be provided with O-rings, in order to increase the contact surface.