SET OF CLIPS FOR INSERTING THE WEFT THREAD INTO SHUTTLE-FREE LOOMING

Description

[0001] The present invention refers generally to a gripper assembly of a weft yarn for the insertion in shuttle-less weaving looms.

[0002] More particularly, the invention relates to a pair of grippers (carrier or bringer gripper and pulling or taker gripper) of the negative exchange type and suitable for the production of woven and warp weaving looms in shuttle-less looms, with innovative elements for holding the yarn between the gripping elements, so as to ensure a reliable grip of the weft, transport to the center of the fabric, switch and release of the yarn exiting the fabric using a wide range of yarns for classic fabrics and technical fabrics The weaving insertion techniques, which characterize the looms without shuttle to produce woven weaves of warp and weft, now widespread, are of the gripper type, projectile, air jet, water jet. The water jet loom is not very versatile and with problems of pollution, the air-jet loom is moderately versatile but with high energy consumption, while the projectile loom is medium-high versatility but with limits for control of the weft yarn tension and mechanically complex. The gripper technology is very widespread due to its high versatility characteristics combined with good productivity levels. The grippers are the devices of the loom dedicated to the operation of inserting the weft through the warp and a gripper loom is generally provided with a pair of grippers, one on each side, respectively of carrier and of traction, which moves with alternate motion and opposed, each from an external position to the fabric to the center of the same where it reverses the motion to return to its starting position external to the fabric.

[0003] Of the pair of grippers, a first gripper, defined as bringer, grabs the head of weft to bring it to the center of the fabric where it switches it with the second gripper, called the taker gripper, which grabs the head and drags it to the external edge of the second half of the fabric.

[0004] The switch of the weft yarn between the bringer gripper and the taker gripper at the center of the fabric can be of the positive or negative type. The positive switch inside the warp step takes place with the intervention at the center of the fabric of special gripper opening hooks, which, projecting between the yarn of the lower part of the warp, actuate the closing or opening of the holding organs of the weft of the grippers for transferring the yarn from one to the other gripper. Such blades or hooks, source of interference with the warp, are incompatible with various types of fabric and generally result in wear and costs for spare parts.

[0005] The negative switch of the yarn between the bringer gripper and the taker gripper is caused by the traction caused by weft-weaving devices, placed at the entrance of the fabric, which act on the yarn while it is inserted between the holding elements; the aforesaid holding elements are arranged to obtain a controlled friction on the yarn and slide it between the gripping elements perpendicularly to the axis of the yarn, without slipping out longitudinally.

[0006] In each weft insertion cycle, the yarn coming from one edge of the fabric is selected by the color selector, inserted into the bringer gripper, sliding between the holding elements, cut and carried to the point of switch with the taker gripper, which, with its own holding elements, it grabs the head and completes the insertion.

[0007] Generally, the grippers have guide profiles which predispose the yarn lying between an abutment and a resilient rocker pin with respect to a horizontal axis and longitudinal holding elements constituted by the part of the pin which, driven by a reaction spring, retains the yarn resting on an element below that can be rigid or elastic.

[0008] The holding points of the taker gripper up to now in use are of the type with surfaces kept close by a spring-operated rocker arm between which the yarn is inserted, or of the fixed wedge type with an angle suitable to allow progressive locking by friction of the yarn pulled towards the vertex; a combination of a fixed wedge and an elastic blade is also used, which remains close to the support and is also closed when the yarn is released at the end of insertion.

[0009] In the phase of the weft switch process, the taker gripper hooks the yarn presented by the bringer gripper, holding it while it is inserted between the holding members until it locks between them without sliding during the dragging path; moreover, when the taker gripper is out of the fabric, it must be able to open instantaneously to release the yarn which must leave the holding points practically in the absence of friction.

[0010] The object of the present invention is to provide a gripper assembly for inserting the weft yarn in shuttle-less weaving looms, which sequentially ensures grip of the weft, transport to the center of the fabric, switch and release of the output yarn with high reliability for a wide range of twisted, parallel, fancy, multi-filament, single-filament yarns, metalized strips or metallic yarns, for each type of fabric.

[0011] For this purpose, according to the present invention, a pair of grippers of the negative switch type is used, with innovative components of the members for gripping and holding the yarn.

[0012] This and other objects are achieved by a gripper assembly for inserting the weft yarn in shuttle-less weaving looms, according to the attached claim 1.

[0013] Further detailed technical features of the gripper assembly according to the invention are reported in the subsequent dependent claims. In the configuration of the bringer gripper of the present invention, a rocker pin, rotating about a preferably vertical axis of the gripper body, is provided, on one side, with a yarn gripping arm which in section has a wedge shape, with angle to the vertical plane equal to that of the part of the profile against which it is pushed backed by a leaf spring which acts on the other side of the rocker pin.

[0014] The tension of the yarn, given by the braking of the weft external to the fabric, determines by friction a force resulting from the contrast between the two inclined surfaces; this force, transversal to the pin, tends to bring it to a further closure and therefore improves the restraint in running with limited force of the closing spring and, consequently, to facilitate the entry of the yarn into the pin, which is ultimately self-locking.

[0015] Further objects and advantages of the present invention will become clearer from the following description, relating to an exemplary and preferred, but not limiting, embodiment of the gripper assembly for inserting the weft yarn in shuttle-less weaving looms, according to the invention, and from the attached figures, in which: figure 1 shows a side view of a bringer gripper or pliers used according to the present invention; figure 2 shows an enlarged plan view of the bringer gripper of figure 1, according to the present invention; figure 3 shows a cross-sectional view of the bringer gripper of figure 1, according to the present invention; figure 4 shows a plan view of a taker gripper according to the present invention; figure 5 shows an enlarged view of the detail (A) of the taker gripper of figure 4, in a first operating position, according to the present invention; figure 6 shows an enlarged view of the lower side of the detail (A) of figure 5, according to the present invention.

[0016] With reference to the attached figures, the gripper assembly according to the invention substantially comprises a bringer gripper and a taker gripper.

[0017] In particular, the bringer gripper comprises a main body (1) with a shaped end adapted to be fixed to a command element, a weft guide profile (2), a rocker lever (3) hinged on a rotation pin (4) and a reaction spring (6); the gripper element consists of a pin (5) for gripping the rocker lever (3), which is rotating about a preferably vertical axis of the main body (1) of the gripper, while the spring (6) maintains in closure the pin of the lever (3) on one side and pushes it on the other side to an inclined plane which, thanks to the pull of the yarn (7), makes it self-locking.

[0018] In particular, the bringer gripper, advancing towards the selected weft and arranged in a nearly horizontal position, inserts the yarn (7), coming from a bobbin and present by a selector, at the grip points constituted by an abutment (8) and from the intersection between the pin (5) and the abutment surface of the weft guide profile (2).

[0019] The traction force of the yarn and the effect of the frictional force between the yarn (7) and the holding surfaces tend to pull the pin (5) towards the abutment surface of the weft guide profile (2) and, due to the effect of the support angles, to further tighten the grip of the yarn (7) without increasing the spring load (6) with particular benefit for low resistance, fancy plots or for technical fabrics.

[0020] Always according to the invention, the taker gripper, which exchanges the yarn (7) at the center of the fabric with the bringer gripper, comprises a main body (10) having a shaped end to be fixed to the tape or rod which makes the stroke, a central part, which includes a lever (12) for operating the opening or closing of the zone for gripping the yarn (7) and a longitudinally sliding element, consisting of a rod (11) made of flexible material, which has a terminal part or slider (14) that slides in a hook-shaped portion (15), arranged at the opposite end (A) of the main body (10).

[0021] The slider (14) is pushed by a spring (13) towards the projecting profile (17) inside the hook portion (15) and against the surface (16) of the aforesaid portion (15), which forms a determined angle with the slider (14), while an elastic blade (18), integral with the slider (14), is pushed against the surface (16), from which it separates, at the opening of the slider (14), due to the effect of guide profile (17), which causes the blade (18) to move away from the surface (16) because the blade (18) rests with the relative tooth (19) to the slider (14).

[0022] The switch of the weft yarn from the bringer gripper to the taker gripper begins with the insertion of the yarn (7) between the surface (16) of the hook-shaped portion (15) and the profile (20) of the blade (18). Since the blade (18) is flexible, it is distanced from the surface (16) according to the pull and the thickness of the yarn (7) resting on the surface (16) with an adjustable preload acting on the screw (21) that allows to adapt the gripper to the types of weaves in process.

[0023] After this first section, particularly favorable for low resistance plots, the yarn continues towards the vertex of the angle formed by the surface (16) and by the slider (14) up to the point allowed by its thickness, in correspondence with which, it's blocked by of the frictions involved between the yarn (7) and the grip elements of the gripper. The opening for releasing the yarn (7) is obtained by the pressure of an external profile on the lever (12), which by rotating causes the rod (11) to slide to the slider (14), causing it to withdraw from the portion (A) in the shape of a hook (15).

[0024] The rod (11), which is elastically inflected in the main body (10) of the taker gripper, keeps the slider (14) pushed towards the profile (17) of the hook (15) of the gripper and, moving backwards, moves away from the surface (16), creating an opening that leaves the yarn (7) free to abandon the aforementioned taker gripper.

[0025] The removal of the slider (14) from the surface (16) of the hooked shaped portion (15) drags with it the elastic blade (18), which, resting with the tooth (19) to the slider (14), follows the movements. In this way, the taker gripper opens simultaneously both the fixed wedge and the elastic part and the yarn (7) leaves the grip element free from friction.

[0026] In practice, the taker gripper includes a first elastic element and a second rigid element, which open simultaneously in phase of releasing the yarn (7), and the elastic rod (11), mounted in an inflected position, sliding longitudinally, causing the area of gripping to open between the slider (14) and the blade (18), while the blade (18) allows a gradual beginning of restraining of the yarn(7) until it stops at the bottom of the fixed angle between the surface (16) and slider (14) and a quick opening for the release.

[0027] From the above description the characteristics of the gripper assembly for inserting the weft yarn in shuttle-less looms, which is the subject of the present invention, are clear, just as the advantages are clear.

Claims

1. A gripper assembly for inserting the weft yarn in shuttle-less looms, comprising a bringer gripper and a taker gripper, said grippers being suitable to produce weft and warp woven fabrics by making a first step of the weft grip, a second step of transport to the center of the fabric, a third step of switching and a fourth step of completing the transport and releasing the yarn in the fabric, wherein said taker gripper, which exchanges the yarn (7) at the center of the fabric between said taker gripper and said bringer gripper and complete the insertion, comprises a main body (10), shaped on one side to be fixed to a tape or rod, a central part with a drive lever (12) for opening or closing a zone of gripping of the yarn (7), a longitudinally sliding rod (11), elastically inflected within the main body (10), and a slider (14), slidable into a hook-shaped portion (15), which retracts away from a surface (16) of said hook-shaped portion (15) and, characterized in that said slider is pushed against a guide profile (17) of the hook-shaped portion (15), and in that said slider drags with it an elastic blade (18), which leans with a tooth (19) against said slider (14) and follows the movements of said slider (14), thus simultaneously opening said slider (14) and said elastic blade (18) in order to release the yarn (7) from said taker gripper.

2. A gripper assembly as claimed in claim 1, characterized in that said bringer gripper comprises a main body (1) with a shaped end apt to be fixed to a tape or rod, a weft guide profile (2), a rocker arm or lever (3) hinged on a rotation pin (4) and a reaction spring (6), said bringer gripper having a gripper pin (5) of said rocker lever (3), which is rotatable about a vertical axis of the main body (1) of said gripper and said reaction spring (6) being able to maintain in closure said gripper pin (5) at one side, and to make said pin (5), at the opposite side, leaning against a sloping plane, so as to have a self-tightening condition.

3. A gripper assembly as claimed in claim 2, characterized in that said pin (5) is pulled towards an abutment surface of said weft guide profile (2), thanks to the pulling force of the yarn (7) and thanks to the friction force between the yarn (7) and the abutment surfaces, so as to tighten said yarn (7) without increasing the load of said reaction spring (6).

4. A gripper assembly as claimed in at least one of the preceding claims, characterized in that said slider (14) is driven by an elastic element (13) towards a guide profile (17) of said hook-shaped portion (15) and against said surface (16) of the hook-shaped portion (15), which forms an angle with said slider (14).

5. A gripper assembly as claimed in at least one of the preceding claims, characterized in that said elastic blade (18) is integral with said slider (14) and is pushed against said surface (16) of the hook-shaped portion (15), said elastic blade (18) moving away from said surface (16) at the opening of said slider (14), due to the effect of said guide profile (17) which causes said elastic blade (18) to stay away from said surface (16), so that said elastic blade (18) rests, with a relative tooth (19), on said slider (14).

6. A gripper assembly as claimed in at least one of the preceding claims, characterized in that said yarn (7) is inserted between said surface (16) of the hook-shaped portion (15) and a profile (20) of said elastic blade (18), said elastic blade (18) being spaced from said surface (16) as a function of the traction and thickness of the yarn (7) and as a function of the preload of said elastic element (13), which is adjustable by means of a screw (21), depending on the types of wefts.

7. A gripper assembly as claimed in at least one of the preceding claims, characterized in that the yarn (7) is released by pressure of an outer profile of said drive lever (12), said outer profile being able to rotate and slide said longitudinal element (11) which is integral with said slider (14), so as to send away said slider (14) from said hook-shaped portion (15).

8. A gripper assembly as claimed in at least one of the preceding claims, characterized in that said sliding rod (11) which is inflected elastically within the main body (10) of the taker gripper pushes said slider (14) against said guide profile (17) of the taker gripper, said slider (14) being able to retract and move away from said surface (16), so as to create an opening which leaves the yarn (7) free to leavesaid taker gripper.

9. A gripper assembly as claimed in claim 8, characterized in that, when said slider (14) is moved away from said surface (16) of the hook-shaped portion (15), said elastic blade (18) is dragged and leans against said slider (14) and follows the movement of said slider (14), so that the yarn (7) is released from said taker gripper without frictions.