Description

5 The invention is related to a pre unwinding device for use in a weaving loom, more in particular a spooUess weaving loom using a woof injector.

Weaving looms, in particular those from the latter type, are provided with a pre unwinding device that unwinds a 10 woofthread from a supply bobbin to produce a texture, and a winding device in particular a hydraulic or pneumatic injector that is positioned in between the supply bobbin and a device, for the introduction of the woofthread in between the chainthreads. 15 The winding device winds the thread by a relative rotation of the thread with respect to the winding device, in adjacent, wether separated or unseparated, windings. In general the winding device is stationairy and the thread is wound onto it by an rotating arm that is hollow in general. 20 The thread is drawn off from the winding device by the above mentioned device, for instance the injector en transferred in between the chainthreads.

After drawing off the required length of the threa ^' d, which equals approximately the width of the total system of 25 adjacent chainthreads, the drawing of the thread is stopped en the thread is cut.

To cause the stopping of the thread, in order to determine the length of the woofthread, a stopping device is provided in a receiving cilinder which surrounds the winding 30 device, that is positioned and shaped in such a way that as soon as the threaddischarge from the winding device has to stop moving, is activated within the receiving cilinder and the continuation of the transport is impeded.

The stopping device can be a pin for example that is 35 driven electro-magnetically and moves about perpendicular to the axis of the winding device.

In between the winding device and the surrounding

cylinder the thread moves towards the cylinder and from this point towards the device, for instance the injector, to introduce the woofthread in between the chainthreads.

The surrounding cylinder is usually provided with a do eshaped extension including a downstream located central discharge opening for the thread.

By suitably dimensioning of the winding device and the surrounding receiving cylinder and a correct installation of the stopping device, it is possible to achieve only a slight knicking of the discharged thread. This implies a smooth winding of the thread in order to prevent, also for thin and vulnerable threads, needless friction which might result in clewformation , damage to threads and possibly breakage.

Such a correct dimensioning and positioning is almost impossible if the winding device shows a variable adjustable diameter and the receiving cylinder does not show a variable diameter.

Such types of devices are known and e.g. described in EP-A-9 111 274 5.4. At a smaller diameter setting of the winding body and an unchanged diameter of the receiving cylinder the annular clearance in between these parts is increased, and therefore the thread might undergo a larger "knick".

This problem could be solved by decreasing the diameter of the receiving cylinder. This implies practically the usage of different receiving cylinders with different diameters or a receiving cylinder with variable diameter. Both solutions are either to cumbersome and/or to complex and therefore expensive. An object of the invention is to solve these disadvantages and obtain further advantages.

A pre unwinding device according to the invention for use in a spooUess weaving loom, in particular using a woofinjector, comprising a central shaft enclosed by a housing, whereby the thread is taken from a supply coil, and by a relative rotation of the central shaft and a windingbody, is wound on that body in adjacent eventually

separated strands, whereby the winding body shows a adjustable diameter in a plane perpendicular to the central shaft and is situated within a surrounding receiving cylinder for thread leaving the winding body, provided with a stopping device having such a shape and position that at the moment that the threaddischarge from the winding body has to be ended, the stopping device can be activated within the receiving cilinder, is characterized in that the receiving cylinder and the stopping device are oveable in a plane almost perpendicular to the central axis of the winding body. The movement of the recieving cylinder and the stopping device in the apparatus according to the invention is adapted to the change of the diameter of winding body and preferrably in such a way that at all settings of the diameter of the winding body the clearance in between the winding body and the receiving cylinder at the location of the stopping device is equal. Therefore the "knick" of the thread will always be almost the same. Because the stopping device is moved as well, the stopping device can be activated always in a space of the same dimensions.

An effective embodiment of the invention is obtained in when the receiving cylinder and the stopping device are connected together. For all changes in the diameter of the winding body and a related adapted displacement of the receiving cylinder an constant situation on the spot of the stopping device is automatically guaranteed.

The change of the diameter of the winding body and the related motion of the receiving cylinder wil be effected manually in general in a stationairy apparatus. It is possible by means of a suitable construction to couple both changes.

In a preferred embodiment of the device according to the invention a disc- or ringshaped device is located downstream with respect to the winding body within the receiving cylinder, almost perpendicular to the central axis of the winding body, with a diameter smaller than the diameter of the receiving cylinder and at least equalling the largest

adjustable diameter of the winding body.

This disc- or ringshaped body is intended to improve the course of the thread after the drawing off from the winding body. The thread is guided by the edge of the disc. The disc- or ring shaped body can have a fixed position with respect to the winding body, but preferrably it is moved sideways together with the receiving cylinder and the stopping device. In this way the situation at the spot of the stopping device is the same for each alteration of the diameter of the winding body, making one disc or ring sufficient, which would be impossible when the disc has an fixed position with respect to the winding body.

If a disc- or ringshaped body is used, as described above, the stopping device is positioned in such way that it is activated in between the clearance of recieving cylinder and the disc or ring, and closes this space locally. If the stopping device is pinshaped it can be activated in a space in the edge of the disc or ring.

It is remarked that US-P-5 133 388 describes a disc with an upstanding edge guiding the thread that leaves the winding body in a small slit in between the upstanding edge and the interior of the receiving cylinder. The stopping device can be located here.

The invention will be illustrated by means of a schematic drawing. In the drawing figure 1 shows a longitudinal section of the embodiment of a pre unwinding device according to the invention, and figure 2 shows an improved embodiment of the device according to figure l.

In figure 1 [1] is a central axis that is supported in a housing [2] by means of bearing [3]. This axis rotates in the direction of the arrow. Fixed to the housing [2] is a baseplate [4] supporting the stationairy winding body [5]. By a supplying device [6] for the thread that is connected to the axis [1], the thread [7] is wound on the winding body [5]. The fingers [8] and [9] are provided to move the windings in the direction of the axis. These fingers protrude through openings in the winding body [5]. These

fingers are connected to a driver [10] provided with a bearing [11] that is positioned excentrically in a known manner with respect to the central axis of the driving axis thereby forming a small angle. By this way of bearing the fingers [8] and [9] are following an elliptical pattern having a component parallel to the central axis and a component radial to the axis. Such a construction of the driver is described eg in US-P-4 632 154 and Japanese patent 43 377/91. In the latter patent the winding body is constructed from an cylindersurface and its axis coincedances with the driving axis , and is divided in sectorshaped elements. Thes sectorshaped elements are adjustable radially whereby the diameter of the surrounding plane of these elements is increased or decreased. Different constructions for adjustment of the diameter of the winding body are possible.

In figure 1 [15] is a body of revolution with an almost cylindrical part [16] adjacent to the winding body [5] and an adjacent balloonshaped part [17] provided with an discharge device for the thread [18]. [19] is a stopping body that blocks the thread (20) that is being drawn off from the winding body, at the right moment.

It is obvious that at different diameters of the winding body [5], realized eg by the construction of Japanese patent 43 377/91, the clearance in between the body and the part [16] is variable.

At the spot of stopping device [19] this can be seriously disadvangeous because, as is stated above, the thread that is drawn off from the winding body [5] receives a to large "knick" easily, resulting in the above mentioned disadvantages.

This problem is solved according to the invention by moving the receiving cylinder [16] and the stopping body in a direction almost perpendicular to the axis of the winding body [5], like indicated by the arrow [21]. In this way the clearance in between the body [5] and the part [16] at the spot of the stopping device can be kept constant. At the

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other hand the clearance in between the body [5] and the receiving cylinder [16] opposite the stopping body can increase or decrease, but this is no problem because no stopping body is present at that spot. Although is is possible to move stopping body [19] and receiving cylinder [16] independantly it is preferred with respect to the simplicity of the construction and its adjustment, to connect the stopping body [19] and the receiving cylinder [16] with each other. In figure 1 [13] and [14] indicate a positioning device, as described by the Dutch patent application 920 1436 (published 1st March 1994) . This part is not essential for the present invention.

In figure 2 [25] is a discshaped device that is positioned almost perpendicular to the axis of the winding body and is connected heretoo. The stopping body [19] is activated in the space in between the receiving cylinder or the balloonshaped extension [17] and the disc [25]. This results in a more fluent course of the thread [20]. Disc [25] can be connected to winding cylinder [16] and stopping device [19].

Figure 2 indicates the parts in the same manner using the same numbers corresponding to the related parts of ^' figure 1. The stopping body [19] is prefereably pinshaped and formed and positioned in such way that it corresponds to a clearance in the edge of disc [25] in the stopped position.

Disc [25] is preferably moved together with the receiving cylinder [16] and the stopping body [19].CLAIMS

1. A pre unwinding device according to the invention for use in a spooUess weaving loom, in particular using a woofinjector, comprising a central shaft enclosed by a housing, whereby the thread is taken from a supply coil, and by a relative rotation of the central shaft and a windingbody, is wound on that body in adjacent eventually separated strands, whereby the winding body