Device guiding and braking the weft yarn at the inlet of the shed in shuttleless looms

Abstract

 The object is to guide and brake the weft yarn which - at the moment of its insertion into the carrying gripper of a shuttleless weaving loom - passes through the cutting device to be cut. The said guiding and braking are obtained by means of a resilient elastic lamina 2, which is mounted on the cutting device and which presses onto the counterblade 1 of said device with a length 4 apt to mate with said counterblade 1.

Description

[0001] It is known that in shuttleless looms - of the type wherein the weft is fed through the shed by a pair of grippers, the carrying and the drawing gripper, exchanging said weft at the centre of the shed - the operation involving the gripping of the weft by the carrying gripper at the inlet of the shed, and its simultaneous cutting in respect of the already formed fabric, forms the start of the working cycle and is an essential premise for correctly carrying said cycle.

[0002] The proper issue of this initial operation requires to adopt grippers and cutting devices which are apt to guarantee a perfect working with the different types of weft being inserted into a same fabric or into different types of fabric, and even with yarns having an irregular count.

[0003] Usually, a setting of the cutting times and of the gripper retaining means, which may be acceptable for a certain type of yarn, is not suitable for other types of yarns, while the use of yarns having an irregular count prevents proper working when said irregularity is present in the gripping and cutting phase and area.

[0004] Attempts have been made to make the gripping independent from the cutting times, by inserting in looms clamping pincers. In this case, however, the weft insertion on the gripper gives rise to serious problems: in fact the weft yarn, subjected to stretching, may easily break; this may lead to missing of the weft, or else - if the weft portion which has remained on the carrying gripper is not removed by its clamping means - it may cause a running defect in the subsequent working cycle.

[0005] The present invention proposes to solve the above mentioned problem by other means and in a satisfactory manner for any working condition. The invention in fact provides to apply a resilient elastic lamina to the device designed to cut the weft yarn, said lamina pressing on the counterblade of said cutting device with a portion thereof apt to mate with said counterblade and thereby guiding and braking the weft yarn between the already formed fabric and the gripper.

[0006] The invention will now be described in further detail, with reference to the accompanying drawing, which illustrates two preferred embodiments thereof and in which:

Fig. 1 is a perspective view of part of the loom cutting device, to which is applied a first embodiment of the guiding and braking lamina according to the invention; and .

Fig. 2 shows, on a reduced scale, a second embodiment of the guiding lumina according to the invention, applied to a cutting device as that of figure 1.

[0007] As shown in figure 1 ot the drawing, the weft yarn t just tied to the fabric T being formed on the loom passes through, before being engaged by the carrying gripper P (drawn in dashed lines in its position preceding insertion in the shed), a known type cutting device C, which has to perform the cutting thereof. According to the invention, a resilient elastic lamina 2 is applied to said cutting device C, of which only the counterblade 1 is shown, said lamina 2 comprising a first substantially vertical length 3, for connection to the cutting device C and adjustment in respect thereof, and a second cuspidal length 4 (shaped as widened V) following downward the first length 3.

[0008] The lamina 2 is fixed to the cutting device C by being inserted into an appropriate seat and locked therein by a pair of pressure screws 5 with horizontal axis, after having adjusted its position in height by way of the upper screw 6 with vertical axis which retains, between its head and a nut 7, the upper square bent end 8 of said lamina 2.

[0009] The apex of the cuspidal length 4 of the lamina 2 elastically bears onto the counterblade 1 of the cutting device C with a pressure depending on the position in height of the length 3 of said lamina, which pressure can therefore be adjusted by acting on the screw 6.

[0010] As shown in the drawing, the weft yarn t passes through the cutting device C engaging the counterblade 1 externally to the lamina 2. It is hence guided and braked by the cuspidal portion 4 of said lamina 2, which is elastic and resilient.

[0011] In the embodiment of figure 2, the lamina 2A comprises a first length 9, substantially parallel to the counterblade 1, and a second length 10 in the form of a hook, an intermediate part 11 of which engages with the counterblade 1, mating with the working surface thereof.

[0012] Said lamina 2A is adjustably fixed to the cutting device C by means of a connection plate 12.

[0013] The adopted arrangement causes the weft yarn to remain permanently stretched and to take up the cutting and gripping positions most suited for the operation; it eliminates all motion relative to the cutting device, onto which is fixed the lamina, so as to require no kinematic motion and_' to exclude any tension variation deriving from movements in respect of the cutting member; it lets free the small weft yarn tail attached to the fabric; it is self-cleaning because the weft yarn passage removes all impurity; it introduces no inertias on the yarn (as it has no motion of its own and it operates merely in function of elastic deformations, which vary according to the weft yarn count and adapt themselves thereto); and it allows a very wide range of adjustment.

[0014] The lamina 2 and the lamina 2A are preferably shaped as metal straps, as shown in the drawing. It is however understood that they could also be made in the form of wire, with substantially equal results. Also the mounting and adjustment of the laminae 2 or 2A in respect of the cutting device C could differ from those illustrated, which have been given by mere way of example.

[0015] Any further variants and modifications of the invention, which will appear evident to the skilled in the art, are intended to fall within the scope of the invention itself.

Claims

1) Device to guide and brake the weft yarn at the inlet of the shed in shuttleless weaving looms, characterized in that it comprises a resilient elastic lamina, applied to the weft cutting device and pressing on the counterblade of said device with a portion thereof apt to mate with said counterblade, thereby guiding and braking the weft yarn between the already formed fabric and the gripper at the moment of its insertion in said gripper.

2) A device as in claim 1), wherein said lamina comprises a substantially vertical length for connection and adjustment, and an operative cuspidal length apt to engage with the counterblade.

3) A device as in claim 2), wherein said substantially vertical length of the lamina is fixed to the cutting device by a pair of pressure screws with horizontal axis and is adjustable in height by means of a screw with vertical axis.

4) A device as in claim 1), wherein said lamina comprises a length substantially parallel to the counterblade and a length ending into a hook, an intermediate part of which length engages with the counterblade.

5) A device as in claim 1), wherein said lamina is a metal strap.

6) A device as in claim 1), wherein said lamina is a wire.

Drawing