EP1013807A1

EP1013807A1 - Lever to operate the weft yarn gripping devices in a pair of weft carrying and drawing grippers for looms

Info

Publication number: EP1013807A1
Application number: EP99113423A
Authority: EP
Inventors: Ermanno Franz
Original assignee: SOMET Societa Meccanica Tessile SpA
Current assignee: Promatech SpA
Priority date: 1998-12-23
Filing date: 1999-07-12
Publication date: 2000-06-28
Also published as: CN1107752C; CN1257946A; TW571011B; HK1029381A1; KR20000057084A; IT1304699B1; ITMI982805A1

Abstract

In a lever to operate the weft yarn gripping devices, in a pair of weft carrying and drawing grippers for shuttleless looms, the fulcrum of said lever (1; 10) is fixed to the gripper body by fixing means which are external to the peripheral surface enveloping the lever (1; 10).

Description

The present invention concerns a lever to operate the weft yarn gripping devices in a pair of weft carrying and drawing grippers for shuttleless looms and, in particular, the lever hingeing means.
As known, there is a persistent request on the textile market to constantly improve the weft transport grippers of looms, and the devices mounted thereon, so that such members may be apt to guarantee a perfect working even on the most modern looms in very critical weaving conditions. In fact, for the production of high-quality precious fabrics, the looms are required to provide increasingly higher weaving performances, which particularly involve a high warp yarn tension, the use of very thin or delicate weft yarns or of yarns with other special physical characteristics, and a reduced shed angle; all this, combined with very high loom working speeds.
To obtain the aforementioned high weaving performances, it is thus indispensable for a basic component of the loom, such as the pair of weft carrying/drawing grippers, to undergo constant improvements in order to guarantee the required performances of weft yarn insertion, together with a sufficiently long working life of the grippers. Especially in planning the grippers, there has been a progressive reduction in size of the single components, so as to produce grippers having a reduced mass and smaller dimensions, and thus apt to stand more safely the alternate stresses imparted thereon and to reduce the inertial loads on the loom.
To satisfy these requirements, the Applicant has conceived and set up an improved structure for the pair of weft carrying/drawing grippers, thanks to which it is possible to simultaneously obtain both an increase in the rigidity and wear resistance of the grippers, and a reduction in the mass thereof. Said structure is the object of the copending European Patent Application 99106429.6, the contents of which are incorporated herein by way of reference.
In planning the aforecited pair of grippers, besides their general structural characteristics it has also become considerably important to reduce in size the single devices mounted thereon and, particularly, for what concerns the present invention, the weft yarn gripping devices. Of course, the object of said reduction in size is to allow reducing the overall dimensions of the grippers, with the double advantage of thereby reducing both the mass of the grippers and the shed angle required to allow the grippers to move between the warp yarns.
The inventor of the present invention has thus concentrated his attention on the weft yarn gripping devices, particularly facing the problem to study a more compact structure for the lever operating such devices. As known, in fact, the lever operating the weft yarn gripping devices is normally fixed to the body of the gripper, in correspondence of its hingeing point, by way of coaxial fixing means. The hingeing axis of said lever thus has a fairly wide diametral width - seen that it must house the screw or rivet for its anchorage to the gripper body - whereby, with such an enlarged diametral width, it affects the final dimensions of the lever.
The object of the present invention is to thus supply an improved fixing system for the lever operating the weft yarn gripping devices, in a pair of weft carrying and drawing grippers for looms, said fixing system having a more compact structure, and at the same time a higher mechanical resistance, to allow reducing the dimensions of the gripper body meant to house the device, and simultaneously guarantee an increased resistance of said device to the mechanical stresses imparted thereon.
According to the present invention, said object is reached with a lever to operate the weft yarn gripping devices in a pair of weft carrying and drawing grippers for shuttleless looms, of the type wherein the fulcrum of said lever is fixed to the gripper body through suitable fixing means, characterized in that said fixing means are external to the peripheral surface enveloping the lever.
In a first embodiment of the invention, said fulcrum consists of a cylindrical cavity formed in the gripper body, into which engages, freely rotatable, a cylindrical portion of the lever mating therewith, said cavity being formed between a cylindrical surface integral with the gripper body and an opposed cylindrical surface of a counterthrust block fixed to the gripper body through said fixing means.
In a second embodiment of the invention, said fulcrum consists of a pin onto which is pivoted said lever, said pin being housed into a seat provided therefor in the gripper body, an end of said pin being connected to said fixing means.
The invention will now be described in further detail with reference to some preferred embodiments thereof, illustrated by way of example on the accompanying drawings, in which:
Fig. 1 is an axonometric exploded view of a weft carrying gripper incorporating a first embodiment of the lever to operate the weft yarn gripping device, according to the present invention;
Fig. 2 is an axonometric view showing the operating lever - disassembled in the circle II of fig. 1 - in a mounted position;
Fig. 3 is an enlarged scale view - similar to fig. 2 - showing the operating lever with partly sectional and removed portions;
Fig. 4 is an axonometric view showing a detail of fig. 2, which represents - on an enlarged scale and with partly sectional and removed portions - the seat for said operating lever;
Fig. 5 is an axonometric exploded view of a weft drawing gripper incorporating a second embodiment of the lever to operate the weft yarn gripping device, according to the present invention;
Fig. 6 is an axonometric view showing the gripper, illustrated in fig. 5, in a mounted position;
Fig. 7 is an axonometric view showing a detail of fig. 6, which represents - on an enlarged scale and with partly sectional and removed portions - the pivoting bush of the operating lever of fig. 5 or 6; and
Fig. 8 is an axonometric view showing a detail of fig. 6, which represents - on an enlarged scale and with partly sectional and removed portions - the pivoting system of the operating lever of fig. 5 or 6.
The first embodiment of the lever to operate the weft yarn gripping device, according to the present invention, will now be described in detail with reference to figs. 1 to 4, which clearly illustrate the shape of the operating lever 1. The lever 1 comprises - in addition to a front gripping portion 1a and to a rear operating portion 1p, of a type known per se - a central cylindrical portion 1c, radiused in a V-shape to said portions 1a and 1p. Said central cylindrical portion 1c of the lever 1 bears onto a mating cylindrical surface 2 of a support base S of the lever 1, the revolution axis of said cylindrical surface 2 coinciding with the desired rotation axis of the lever 1. Said lever is produced from blanked steel, bent and forged, while the base S is made from thermoplastic material - for example nylon, eventually with the addition of teflon ^® or other lubricating fillers - and fixed to the gripper body by screw means, as described in the aforecited copending European Patent application.
The central portion 1c of the operating lever 1 is secured in position, against the cylindrical surface 2 of the support base S, by a counterthrust block 4 (fig. 3). Also said block is made from thermoplastic material and comprises a cylindrical portion which perfectly mates with the corresponding cylindrical surface of the portion 1c of the lever 1, having the same width of said surface. This structure is completed by two vertical walls 3 of the support base S (fig. 4), projecting sideways from the two external edges of the cylindrical surface 2 and delimiting on both sides the lever 1 to which they are perfectly adjacent. The walls 3 comprise two opposite holes, into one of which is inserted a pin 6 (fig. 2) for fixing the counterthrust block 4. Said pin 6 crosses entirely the block 4, in correspondence of the through hole 4f provided therein, and is fastened - by snapping or screwing - into the opposite hole of the wall 3. Said walls 3 finally comprise lateral nibs 3n at the top, between which is restrained an upper projecting portion of the block 4, thereby preventing any possible rotation of said block about the pin 6.
Thanks to this arrangement the lever 1 has only one degree of freedom, which means - more exactly - that it is merely apt to rotate about the fulcrum formed by the cylindrical bearing surface 2 of the support base S. In fact, the presence of the counterthrust block 4 eliminates any possibility for the lever 1 to move in a vertical direction and in a longitudinal horizontal direction, save for the required backlash, while the walls 3 prevent any movements of the lever 1 in a transversal horizontal direction. By suitably carrying out the injection molding process of the thermoplastic resin portions, using materials with good characteristics of dimensional stability, it is thus possible to obtain the required precision of alignment between the axis about which rotates the lever 1 - namely, as already said, the revolution axis of the cylindrical surface 2 of the support base S - and the weft yarn gripping surface, defined by a lamina 5 fixed to said support base. In this respect, it should in fact be noted that a perfect coplanarity between the gripping portion 1a of the lever 1 and the support base S (or the lamina 5) guarantees the homogeneity of the pressing force during sliding of the weft yarn between the gripping members, thereby preventing pressure peaks which cause a number of defects in the fabric and/or deteriorate the quality of the yarn, for example causing its "defibration".
The cylindrical surface 2 has a minimum angular development dimensioned so as to stand, without getting deformed, the load imparted on the lever by the elastic reaction of the springs M (visible in fig. 1) acting on the portion 1a of the lever 1, when said lever opens through operation of its rear operating portion 1p. The maximum angular development of said surface 2 should instead be dimensioned so as not to interfere with the desired movement of the lever 1. An optimal angular development of the surface 2 is, for example, between 70° and 90°, and preferably about 80°. The cylindrical surface of the counterthrust block 4 has an angular development corresponding to that of the surface 2, or if desired, lower than that, due to the reduced loads which this element has to stand during working of the lever 1.
If the cylindrical surface of the block 4 has an angular development equal to that of the surface 2, the cylindrical portion 1c of the lever 1 should have an angular development wider than that of the surface 2 by an angle at least equal to the maximum rotation angle of the lever 1; only this arrangement allows in fact to guarantee a correct rotation, with no interferences, of the cylindrical portion 1c inside the annular cylindrical cavity formed between the surface 2 of the support base S and the corresponding cylindrical surface of the counterthrust block 4.
As it appears evident from the previous description, the first embodiment of the operating lever fully reaches the object of the present invention. Said lever may in fact be reduced in size at will, exclusively in function of the weft yarn gripping requirements, i.e. quite apart from the problems connected with the insertion into the lever of its fixing means. Said means are in fact fully external to the peripheral surface enveloping the lever and may thus be dimensioned independently from its size. On the other hand, the lever 1 is guided in a very precise and reliable manner, seen that it moves between cylindrical surfaces with a remarkable angular development; this is highly advantageous also for the working life of the lever, since the wear caused by the repeated angular movements of the lever affects a surface which is far wider than that of the conventional pins. Finally, a possible take-up of the backlashes can be obtained by simply replacing the block 4 - without hence involving the lever 1 - eventually increasing its size, so as to take into account any wear which might have affected the surface 2 of the support base S.
Figs. 5 to 8 illustrate a second embodiment of the lever to operate the weft yarn gripping devices, according to the present invention, applied to a weft drawing gripper. Also in this case, the lever 10 is produced from blanked steel, bent and forged, but its central portion 10c develops on a vertical plane, and not on a horizontal plane as in the previous embodiment. The portion 10c is drilled in correspondence of the rotation axis of the lever 10 and subjected to a local surface hardening treatment. A bush 11 of integral hard metal - produced with an underwater cutting technique, with no further grinding - is then inserted into the pivoting seat, thus formed, and fixed into said seat by braze welding.
The lever 10 is then inserted into the gripper body, and precisely between the parallel walls 12 forming its end portion, and is fixed to said walls - freely rotatable - by means of the pin 13. Also said pin 13 is made from integral hard metal and is welded, in correspondence of an end thereof, to the end of a connection plate 14 perpendicular thereto. The other end of said plate 14 is drilled and connected to one of the walls 12 of the gripper body by means of a safety screw 15, parallel to the pin 13; said screw 15 is thus suitably spaced from the pin 13, for example by a distance equal to 8-10 mm.
Also the above arrangement hence allows to reach the object of the present invention, namely to prevent the means fixing the fulcrum of the lever 10 from interfering with the body of said lever and thereby affecting the dimensions thereof. In fact, according to the invention, the fixing element consisting of the screw 15 is offset in respect of the rotation axis of the lever 10, in correspondence of which there is only the pin 13 of hard metal, having a small diameter, for example of 2 mm only. The seat for the bush 11 must hence be sized merely in function of the small dimensions of said pin 13 and can thus be far smaller than the seats for the operating levers adopted up-to-date, which had to house also the fixing screw coaxial to the rotation pin of said lever. This obviously allows to carry out at will a corresponding reduction in size of the operating lever, without thereby interfering with the overall resistance of said lever. Moreover, the reduced dimensions of the hole forming the seat for the bush 11 produce less stresses into the body of the lever 10, thereby lengthening its working life.
The present invention has been described with reference to two particular preferred embodiments thereof, but it is evident that its protection scope is not limited to said embodiments but extends to any possible variants, within reach of a technician skilled in the art, falling within the definitions of the invention given in the following claims.

Claims

Lever to operate the weft yarn gripping devices in a pair of weft carrying and drawing grippers for shuttleless looms, of the type wherein the fulcrum of said lever (1; 10) is fixed to the gripper body by suitable fixing means, characterized in that said fixing means (6; 15) are external to the peripheral surface enveloping the lever (1; 10).
Lever as in claim 1), wherein said fulcrum consists of a cylindrical cavity formed in the gripper body, into which engages, freely rotatable, a cylindrical portion (1c) of the lever (1) mating therewith, said cavity being formed between a cylindrical surface (2) integral with the gripper body and an opposed cylindrical surface of a counterthrust block (4) fixed to the gripper body through said fixing means (6).
Lever as in claim 2), wherein the revolution axis of said cylindrical surface (2) of the gripper body coincides with the rotation axis of the lever (1).
Lever as in claim 3), wherein said axis is horizontal.
Lever as in claim 2), wherein said cylindrical surface (2) is formed into a support base (S) for the gripping members, made from thermoplastic material and fixed to the gripper body by screw means.
Lever as in claim 5), wherein said counterthrust block (4) is made from thermoplastic material and is fixed, by means of a pin (6) which entirely crosses said block (4), into a seat (3, 3n) formed in said support base (S).
Lever as in claim 6), wherein said seat for the counterthrust block (4) is formed in one piece with said support base S and comprises two parallel vertical walls (3), drilled along the axis of said pin (6) and provided with lateral nibs (3n) at the top, apt to laterally restrain an upper projecting portion of said block (4).
Lever as in claim 7), wherein the distance between said walls (3) substantially corresponds to the width of the central cylindrical portion (1c) of the lever (1) and to the width of said counterthrust block (4).
Lever as in any one of the previous claims, wherein the angular development of said cylindrical surface (2), integral with the gripper body, ranges between a minimum such as to allow said surface (2) to stand, without getting deformed, the maximum load imparted on the lever (1), and a maximum such as to prevent said surface (2) from interfering with the rotary movement of said lever (1).
Lever as in claim 9), wherein said angular development is between 70° and 90°, and preferably about 80°.
Lever as in claim 1), wherein said fulcrum consists of a pin (13), onto which is pivoted the lever (10), said pin (13) being housed into a seat provided therefor in the gripper body, an end of said pin (13) being connected to said fixing means (15).
Lever as in claim 11), wherein an end of said pin (13) is fixed to one end of a connection plate (14) perpendicular thereto, the other end of said plate (14) being provided with a hole into which are housed said fixing means consisting of a safety screw (15) parallel to said pin (13) and engaged into the gripper body.
Lever as in claim 12), wherein the distance between said pin (13) and said safety screw (15) is of about 8-10 mm.
Lever as in claim 11) of metallic material, wherein the pivoting seat for said pin (13) is subjected to a surface hardening treatment.
Lever as in claim 14), wherein said pivoting seat houses a bush (11) of integral hard metal, produced with an underwater cutting technique and fixed into said seat by braze welding.