ARRANGEMENT FOR CONTROLLING THE MOVEMENT OF THE WEFT CONVEYING GRIPPERS IN SHUTTLELESS LOOMS

Abstract: In a shuttleless loom, the movement of the weft conveying grippers is controlled by straps (2) moved backwards and forwards by gearwheels (1) mounted at the loom shed ends, the peripheral teeth of said gear­ wheels meshing with longitudinally aligned slots (3) provided at the centre of the straps. The engagement between the straps and the gearwheeis is constant and precise over a wide arc of the wheels, thanks to guides extending over the whole of said arc and acting on the lateral portions of the straps, and it takes place between elongated slots in the straps and correspondingly shaped teeth, with round-edged periphery, of the gearwheels.

Description: "ARRANGETENT FOR CONTROLLING THE MOVEMENT OF THE ITEFT CONVEYING C;nIPpERS IN SIftTTTLElESS LOOWIS" -*-* Tins invention relates to important improvements in the means for controlling the reciprocating movement of the teft conveying grippers in shuttleless looms. As known, one of the most serious problems in shuttleless looms is the control of the reciprocating movement of the weft conveying grippers, and this problem is the more difficult to solve the higher the loom speed. Many solutions have been adopted up to date, but none can be considered satisfactory. In particular, where flexible straps are used for controlling the grippers, the problem of the high temperatures - which the continually repeated slidings between the parts, at very high speed, tend to produce - has not been suitably solved. For this type of arrangement, it appears substantially essential to improve the conditions under which the reciprocating rotary motion is transmitted from the gearwheels to the gripper control straps, kith regard to: - the precision of the engagement between the gearwheel teeth and the strap slots; - the smoothness of the engagenent between said teeth and said slots; - the fle=v-ibility of the straps and the fact that such flexibility should continue throughout the extent of the straps; - the distribution of stresses in the straps; - the unifornity of a precise engagement between the gearwheels and the straps over the-entire length through which this engagement extends. The present invention now provides an arrangement for controlling the movement of the weft conveying grippers in shuttleless looms, which satisfies the lishes of loom constructors and users in terms of the various listed requirements, and constitutes a modern, rational and satisfactory solution to the stated problems, also idien high and very high eating speeds are involved. The arrangement for controlling the movement of the -eft conveying grippers according to the invention, of the type using a pair of gearwheels hitch perform short reciprocating rotations at the loom shed ends, and a pair of gripper advancement straps having longitudinally aligned central slots meshing i-ith the teeth of said gearwheels, is characterised essentially by the fact that it comprises continuous fixed guides extending over a wide arc of the gearwheels along the periphery thereof and at a short distance therefrom, and acting on both lateral portions of the straps in order to keep them in constant and precise engagement wXith said gearwheels along said arc. Advantageously, the slots in said straps are of elongated rectangular shape, and the teeth of said gearwheels are of a corresponding shape, and have a roundedged periphery. The invention is described in detail hereinafter l.ith reference to a preferred embodiment thereof illustrated by '.-ay of example in the accompanying drawings, in hich: Figure 1 is an eternal vie@ of the arrangement according to the invention, in correspondence of one of the geart-heels; Figure 2 is a cross-section on the line II-II of figure 1 showing the engagement @etween the gearwheels and the straps of the arrangement of Figure 1 and the action of the fixed guides associated to said gear.-lleels in ensuring continuity and accuracy of such engagement; ; Figure 3 is a view of one of the gearwheels of the arrangement of Figure l, showing the shape of its teeth; Figure 4. shows a strap of said arrangement cooperating with the gearwheel of Figure 3; and Figure 5 is a cross-section through the strap of Figure 1.. With reference to the drawings, the arrangement according to the invention comprises, on cach side of a loon, a gearwheel 1 controlling a strap 2, to impart cn said strap and on the gripper carried thereby the to-and-fro movements -hich govern the insertion of the -eft yarn into the loom shed. The strap 2 comprises at its centre a row of elongated rectangular slots 3, -:hich are different in shape and dimensions from all the slots provided up to date in the straps used for similar purposes, and which are clearly short in Figures 4 and 5. Through such slots, the strap 2 meshes '-:ith the peripheral teeth 4 - of corresponding or complementary shape (see figure 3) - of the gearwheel 1, over a aside arc of l.rhich it extends, said teeth being also distinguished by their round-edged periphery. The arc of the gearwheel 1, over \11i.ch the strap 2 extends, is defined by guides 5 which partly surround the wheel close thereto. As clearly shown in Figure 2 of the drawings, the guides 5 are U-shaped so as to act at 6 and 7 on the lateral strap portions to the side of the slots 3, and thereby ensure a continuous and reliable engagement into said slots of the base of the teeth 4, which substantially project from the periphery of the gearwheel 1. Important advantages are obtained with the described arrangement for a correct transmission of the reciprocating motion to the @eft conveying grippers in loo.ns. Firstly, the thorough engagement of the gearwheel teeth 4 into the strap slots 3 - made precise by the shape of the teeth and slots, and made continuous and accurate by the presence and configuration of the guides 5 - determines the mutual positioning between the strap and the gearwheels (or overlap) with a precision so far inconceivable, thereby allowing a particularly even distribution of the loads over the teeth and thus less wear, reduced temperatures and less noise. In addition, the elongated rectangular shape of the strap slots 3 substantially reduces the bending stresses in the straps and facilitates their deformation shen meshing z.-ith the gearwheels, with no harmful consequences as far as strength and "ear. In practice, the straps bend 'ith a greater continuity than those of conventional technique (which comprise much smaller and , in particular, less elongated slots). Finally, the round-edged periphery of the gearwheel teeth 4 ensures a smooth engagement, smith no impact or wear, between the gearwheels 1 and the straps 2. It is understood that variants and modifications could be made to the illustrated embodiment of the invention, without thereby departing from the scope of the invention itself.

Claims: CLAIMS 1) An arrangement for controlling the movement of the weft conveying grippers in shuttleless looms, of the type using a pair of gearwheels "hitch perform short reciprocating rotations at the loom shed ends, and a pair of gripper advancement straps having longitudinally aligned central slots meshing with the teeth of said gearwheels, characterised in that it comprises continuous fixed guides extending over a wide arc of the gearwheels along the periphery thereof and at a short distance therefrom, and acting on both lateral portions of the straps to the side of said slots in order to keep the straps in constant and precise engagement with said gearwheels along said arc. 2) An arrangement as in claim 1, wherein the slots in said straps are of substantially elongated rectangular shape, and the teeth of said gearwheels are of corresponding or complementary shape. 3) An arrangement as in claim 2, wherein said teeth substantially project from said gearwheels and have a round-edged periphery.

Inventors: PEZZOLI, NELLO
Applicants: VAMATEX S.P.A.
Application year: 1982
Main classification: D03D47
IPC codes: D03D47