Patent Application
20080135123
The invention relates to a cloth take-up or draw-off apparatus for drawing-off a cloth in a weaving machine in accordance with the preamble of claim 1 and to a weaving machine with a cloth draw-off apparatus of this kind.
High demands are nowadays being placed on the quality of cloth. This holds to a particular degree for technical fabrics, such as for example fabrics for airbags in the automotive industry. In fabrics of this kind it is important among other things that the weft density be maintained exactly. In order to achieve the required weft density, a comparatively high fabric tension must be produced. This places stringent requirements on the cloth draw-off apparatus, since, on the one hand, the fabric, which enables a not very good purchase, i.e. is slippery, must not be damaged and, on the other hand, must under no circumstances slip. Under these requirements, conventional cloth draw-off apparatuses reach their limits in that they can not completely prevent the slippage of the fabric. As soon as the fabric slips, the weft density, which is controlled via the fabric draw-off, is no longer precisely correct. In the event of a temporary standstill of the weaving machine a slipping back of the fabric can lead to stop marks or in more severe cases even to damage to the machine.
A further problem arises when, as in the case of airbags, two fabric layers are to be woven one above the other at the same time. If “drawing” takes place at only one of the fabric layers in the cloth draw-off apparatus, displacements between the fabric layers and thus the development of folds can occur. In this case the two fabric layers have different weft densities, which can not be tolerated.
A conventional cloth draw-off apparatus is described in the patent specification CH 619 497. The cloth draw-off apparatus described includes a fabric draw-off roller, which will be termed the draw-in roller in the following ing, about which the fabric is led, and a deflection roller which is pressed against the draw-in roller and which will be termed the pressing roller in the following. Furthermore, the cloth draw-off apparatus which is described in CH 619 497 includes an additional fabric deflection point which is arranged between the breast beam and the draw-in roller and close to the draw-in roller and pressing roller in order to increase the angle of wrap β with respect to the draw-in roller. Through this measure a possible slippage of the fabric on the draw-in roller can be reduced. As explained in the previous section, this measure does not suffice in all cases, however, in order to completely eliminate the slippage of the fabric on the draw-in roller.
The object of the invention is to make available a cloth draw-off apparatus for drawing off a fabric in a weaving machine by means of which a slippage of the fabric in the cloth draw-off apparatus is reduced or avoided. In addition, the cloth draw-off apparatus should also be suitable for drawing off two-layered fabrics. A further object of the invention consists in making available a weaving machine with a cloth draw-off apparatus of this kind.
This object is satisfied in accordance with the invention by the cloth draw-off apparatus which is characterized in claim 1 as well as by the weaving machine which is characterized in claim 10.
The cloth draw-off apparatus for taking up a fabric in a weaving machine includes a first driven draw-in roller around which the fabric is led and in addition a second driven draw-in roller around which the fabric is led. The angle of wrap with respect to the draw-in rollers, i.e. the angle over which the fabric lies in contact on the draw-in rollers in each case, is preferably as large as possible, for example between 100° and 356° and advantageously between 180° and 350°. In a preferred embodiment the cloth draw-off apparatus also includes at least one pressing roller in order to press the fabric against the first or second draw-in roller.
In a further preferred embodiment the first and second draw-in rollers are each connected to a driving means, for example to a drive shaft and/or a gear and/or to a chain sprocket, which are coupled to one another. The coupling can for example take place via respective chain sprockets and a chain. In a first variant the driving means are designed such that the draw-in rollers have the same direction of rotation, and in a second variant such that the draw-in rollers have opposite directions of rotation. At least one of the two draw-in rollers is preferably connected via a slip coupling or a frictional clutch to the respective driving means.
The second draw-in roller is preferably arranged at a distance from the first draw-in roller; and the draw-in rollers are preferably arranged one above the other, with it being possible for one of the two draw-in rollers for example to be installed in the weaving machine in place of a cloth beam.
In a further preferred embodiment the cloth draw-off apparatus additionally includes a deflection roller or a deflection bar which is arranged in front of the first draw-in roller. The deflection roller or deflection bar is preferably designed to have low friction, in that it is for example provided with a low friction coating, e.g. with a hard chromium layer, which can be matted or blasted.
In a further preferred embodiment the cloth draw-off apparatus additionally includes a deflection apparatus which is arranged between the first and second draw-in roller in such a manner that oppositely moving fabric sections do not contact one another. In particular when the draw-in rollers are arranged one above the other the probability is high that on its way to the lower draw-in roller the fabric section coming from the upper draw-in roller or the upper pressing roller makes contact with the fabric which is being led about the upper draw-in roller, which can lead to an undesirable frictional stress or, in the case of a two layered fabric, to a mutual displacement of the fabric layers, since the transport directions of the fabric sections at the point of contact are opposite to one another. Through the additional deflection apparatus between the first and the second draw-in rollers a situation can be prevented in which oppositely moving fabric sections make contact with one another.
In a further preferred embodiment at least one of the pressing rollers is arranged substantially vertically above the respective draw-in roller. Thanks to the substantially vertical arrangement the pressing force which is produced by the weight of the respective pressing roller is a maximum. If the draw-in rollers are arranged one above the other and the upper pressing roller is located substantially vertically above the upper draw-in roller, then a further force component, which reinforces the pressing force of the upper pressing roller, arises through the tension which acts on the fabric section between the first and second draw-in rollers.
In addition the invention includes a weaving machine having a cloth draw-off apparatus in accordance with any one of the above described embodiments.
The cloth draw-off apparatus in accordance with the invention has the advantage that it reduces or avoids a slippage of the fabric in the cloth draw-off apparatus. In addition the development of folds in the case of a two layered fabric can be reduced to an acceptable degree, for example in that, as described, the fabric deflection is designed to involve low friction. Furthermore, the fabric can be cut after the draw-off apparatus at any time without the weaving process being disturbed, which is advantageous, above all when no cloth beam and no external draw-off apparatus are provided to help the drawing-off operation. The cloth draw-off apparatus in accordance with the invention can be formed from two individual cloth draw-off apparatuses which are advantageously of the same design. For example two conventional cloth draw-off apparatuses, each with a draw-in roller and a pressing roller. This enables a simple and economical manufacture.
The above description of embodiments serves merely as an example. Further advantageous embodiments result from the subordinate claims and the drawings. Moreover, individual features from the described or illustrated embodiments can also be combined with one another in the context of the present invention in order to form new embodiments.
The invention will be explained in the following in more detail with reference to the exemplary embodiment and with reference to the drawings. Shown are:
In the view shown in
In a further advantageous variant at least one of the pressing rollers is arranged substantially vertically above the respective draw-in roller. In
In the exemplary embodiment the draw-in rollers 3, 5 are each connected to a driving means, for-example to a drive shaft or a gear or to a chain sprocket, which are coupled to one another. The coupling of the driving means and thus of the draw-in rollers can take place either purely mechanically, for example via two chain sprockets which are connected by a chain, or electronically through synchronization. In a first variant the driving means are coupled in such a manner that that the draw-in rollers 3, 5 have the same direction of rotation, and in a second variant in such a manner that that directions of rotation of the draw-in rollers are opposite. In the case of opposite directions of rotation, for example in a two layered fabric, tension can be exerted once on the upper layer and once on the lower layer. In a further advantageous variant the coupling between the driving means is designed so as not to be rigid, for example in that at least one of the two draw-in rollers is connected to the respective driving means via a slip coupling or frictional clutch and/or in that at least one of the driving means is provided with a frictional clutch.
As shown in
The weaving machine with the cloth draw-off apparatus in accordance with the invention is suitable for the manufacture of high quality fabrics, such as e.g. technical fabrics in which the weft density must be maintained exactly. The thus equipped weaving machine is also suitable for the manufacture of two layered fabrics, with the development of folds due to displacements between the fabric layers being low in comparison with conventional weaving machines. Particularly advantageous in addition is the simple installation of the cloth draw-off apparatus in accordance with the invention into a weaving machine if the latter already has a first driven draw-in roller and the otherwise usual cloth beam is replaced by a second draw-in roller, about which the fabric is led. In this case the normally present cloth beam drive can be used as a drive for the second draw-in roller.
