EP0129812B1

EP0129812B1 - Device guiding and braking the weft yarn at the inlet of the shed in shuttleless looms

Info

Publication number: EP0129812B1
Application number: EP84106919A
Authority: EP
Inventors: Nello Pezzoli
Original assignee: Vamatex SpA
Current assignee: Vamatex SpA
Priority date: 1983-06-24
Filing date: 1984-06-18
Publication date: 1990-07-25
Anticipated expiration: 2004-06-18
Also published as: IT8321779A0; ATE54963T1; DE3482802D1; IT1163596B; EP0129812A2; EP0129812A3

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

This invention concerns a guiding and braking device to improve weft yarn insertion at the inlet of the shed in gripper looms.
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.
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.
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.
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.
There are already known to be in technique - for example from the DE-A-2534494 - auxiliary devices for selvedge forming apparatuses, which comprise an elastic element pressing on the counterblade of the loom cutting devices, in order to guide and clamp the weft yarn between the fabric being formed and the gripper.
Nevertheless such devices are not suited, nor have they ever been used or designed to solve the above problem.
This problem is now solved by the present invention, which concerns a device to improve the insertion of the weft yarn in the carrying gripper of gripper looms equipped with a weft cutting device having a movable blade and a fixed counterblade aligned generally in the weft path direction, said device providing to guide and brake the weft yarn at the inlet of the shed, between the already formed fabric and the carrying gripper, at the moment in which said gripper engages said weft yarn and carries it therewith, characterized in that it comprises an elastic element applied to the weft cutting device of the loom and having a length which presses on a first portion of the counterblade of said cutting device, the weft yarn being pulled between said length of the elastic element and the counterblade by the weft carrying gripper as it enters the shed, and in that the counterblade has a second portion extending beyond the first portion in the direction of insertion of the weft, which second portion is not pressed by the elastic element.
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 device according to the invention; and
Fig. 2 shows, on a reduced scale, a second embodiment of the guiding and braking device according to the invention, applied to a cutting device as that of figure 1.

As shown in figure 1 of the drawing, the weft yarn t just tied to the fabric T being formed on the loom, passes through a known-type cutting device C which has to perform the cutting thereof, before being engaged by the carrying gripper P (drawn in dashed lines in its position preceding insertion in the shed). According to the invention. an elastic element 2 - formed, in this embodiment, as a metal strap - is applied to said cutting device C, of which only the counterblade 1 is shown. said metal strap 2 comprising a first substantially vertical length 3, for connection to the cutting device C and adjustment in respect thereof. and a second V-shaped length 4 following downward the first length 3.
The metal strap 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 metal strap 2.
The apex of the V-shaped length 4 of the metal strap 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 metal strap, which pressure can therefore be adjusted by acting on the screw 6.
As shown in the drawing, the weft yarn t passes through the cutting device C engaging the counterblade 1 externally to the strap 2. It is hence guided and braked by the V-shaped length 4 of said strap 2, which is elastic and resilient.
In the embodiment of figure 2, the elastic element is in the form of a wire 2A and comprises a first length 9, substantially parallel to the counterblade 1, and a second length 10 formed as a hook, an intermediate part 11 of which engages with the counterblade 1, pressing against the working surface thereof.
Said wire 2A is adjustably fixed to the cutting device C by means of a connection plate 12.
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 elastic element (2, 2A), so as to require no kinematic motion and to exclude any tension variations 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 adjustments.
The elastic elements 2 and 2A are preferably in the form of a metal strap and of a wire, as shown in the drawing. It is however understood that they could also be made in other forms. Also the mounting and adjustment of the elastic elements 2 or 2A, in respect of the cutting device C, could differ from those illustrated, which have been given by mere way of example.

Claims

1. Device in a gripper loom to improve the insertion of the weft yarn (t) in the carrying gripper (P) of gripper looms equipped with a weft cutting device having a movable blade and a fixed counterblade aligned generally in the weft path direction, said device providing to guide and brake the weft yarn (t) at the inlet of the shed, between the already formed fabric (T) and the carrying gripper (P), at the moment in which said gripper engages said weft yarn and carries it therewith, characterized in that said device comprises an elastic element (2, 2A) applied to the weft cutting device of the loom and having a portion (4, 11) which presses on a first portion of the counterblade (1) of said cutting device, the weft yarn being pulled between said length (4, 11) of the elastic element (2, 2A) and the counterblade (1) by the weft carrying gripper (P) as it enters the shed, and in that the counterblade (1) has a second portion extending beyond the first portion in the direction of insertion of the weft, which second portion is not pressed by the elastic element (2, 2A).

2. Device as in claim 1), wherein said elastic element (2, 2A) is applied to the cutting device through a pair of pressure screws (5) with horizontal axis and is adjustable in height by means of a screw (6) with vertical axis.

3. Device as in claim 1), wherein said elastic element is formed as a metal strap (2) having a substantially vertical length (3) for connection and adjustment, and an operative V-shaped length (4) pressing with an intermediate portion thereof on the counterblade (1).

4. Device as in claim I), wherein said elastic element is formed as a wire (2A) having a first length (9) substantially parallel to the counterblade (1) and a second length ending into a hook (10), an intermediate portion of said second length pressing on the counterblade (1).