TRANSFER SYSTEM FOR LOOMS

Abstract: A transfer system for looms, including at least one weft carrying gripper (14) fitted to a flexible reciprocating strap (12); and guide means (11) for guiding the strap (12) through the shed, parallel to the reed (9); the guide means (11) consisting of a number of C-shaped hooks fitted to the batten (8) of the loom, frontwards of the reed (9), and having the open side facing the reed (9); the strap (12) traveling entirely inside the hooks (11) , and having, on at least part of its length, an appendix (25) extending towards the reed (9) and engaging the open side of the hooks (11); the strap (12) preferably "floating" inside the hooks (11), and being fitted with the gripper (14), projecting frontwards, by means of a rigid rod (30) fitted to the strap (12) so as to cooperate in guidance of the system; and a positive gripper shoulder being fittable to the batten, rearwards of the hooks (11) but frontwards of the reed (9), so as not to interfere with the strap (12).

Description: TRANSFER SYSTEM FOR LOOMS TECHNICAL FIELD The present invention relates to a transfer system for looms, in particular for guiding one or more weft carrying grippers back and forth through the shed on the loom. BACKGROUND ART The transfer systems of continuous weft feed looms substantially consist of a pair of opposite grippers - respectively a carrying and a drawing gripper - fitted integral with the respective opposite ends of flexible straps which are translated back and forth through the shed, in a direction perpendicular to the feed direction of the warp yarns, by the reciprocating rotary movement of respective control pinions. The grippers thus carry the weft yarn through the shed formed by the heddles, so as to form the fabric downstream from the batten and reed, which is then collected on the beam. For supporting the strap through the shed, known transfer systems feature pairs of opposite facing guide elements between which the opposite longitudinal sides of the strap are guided. Known systems of the aforementioned type are invariably unreliable, due to the severe stress produced by periodic inversion of the movement of the grippers, and the high chafing speeds and small size of the guide surfaces, all of which may result in jamming and/or interference between the straps and the warp yarns, thus resulting in frequent breakage of the yarns. DISCLOSURE OF INVENTION It is an object of the present invention to provide a transfer system substantially of the aforementioned type but designed to overcome the aforementioned drawbacks, and which in particular is inexpensive to produce, highly reliable, and provides for a high degree of flexibility of the loom to which it is fitted. According to the present invention, there is provided a transfer system for looms, comprising at least one weft carrying gripper fitted to a flexible reciprocating strap; and guide means for guiding the strap through the shed in a substantially horizontal plane and parallel to the reed; characterized by the fact that: (i) - the guide means consist of a number of C-shaped hooks fitted to the batten on the loom, to the front of, and with the open side facing, the reed; and by the fact that: (ii) - the strap travels entirely inside the hooks, and presents, at least along the portion to be fed through the shed, a cross section smaller than the inside dimension of the hooks perpendicular to the plane of travel, and of the same size as the inside dimension of the hooks parallel to the plane of travel, so that, as it travels back and forth, the strap is guided in contact with, and with substantially no slack between, respective opposite first inner surfaces of the hooks on the open side and on the side opposite the open side of each hook, and never comes into contact with respective second inner surfaces of the hooks on the sides of the hook parallel to the plane of travel. Moreover, on at least part of the portion to be fed through the shed, the strap presents an appendix extending towards the reed and engaging the open side of the hooks during travel of the strap. In this way, the warp yarns run no risk of being "pinched" between the strap and the guide surfaces of the hooks, even in the event of severe dynamic stress of the gripper straps. According to a preferred embodiment of the present invention, the strap is fitted with the weft carrying gripper, projecting frontwards, by means of a rigid, substantially straight rod butt fitted head to head and seamlessly to the strap; and the rod comprises a guide body with a cross section identical to the inside shape and size of the hooks; and means for parting the warp yarns, projecting outwards of the hooks towards the reed to prevent interference between the guide body and the warp yarns, and connected integral with the guide body by means of a rib designed to fit through the open side of each hook in substantially slackfree manner. In this way, over a portion equal to its entire length, the rod is substituted for the flexible strap, and is guided in substantially slackfree manner inside and in contact with all the inner surfaces of the hooks, for preventing the strap from deflecting outside the plane of travel even in the event of severe dynamic stress, as well as for .preventing any interference inside the shed between the guide body and warp yarns, and so preventing jamming and/or breakage of the yarns. According to a further characteristic of the present invention, the guide body of the rod is fitted removably to the strap for enabling fast, easy changeover of the grippers, in particular when switching from a negative gripper - i.e. with uncontrolled weft grip and changeover - to a positive gripper. In this case, the system comprises an additional flat profiled shoulder element for a positive gripper control rod, which section is fitted removably to the batten, rearwards of the hooks but frontwards of the reed, for enabling a perfected negative gripper machine to be adapted rapidly to operate with a positive gripper with no risk of the gripper control mechanism interfering with the strap, by virtue of the section cooperating solely with the " gripper or with the rod by which the gripper is fitted to the strap. BRIEF DESCRIPTION OF DRAWINGS Further objects and advantages of the present invention will be revealed in the following description of a preferred non-limiting embodiment, and with reference to the accompanying drawings, in which: Figure 1 shows a schematic view of the main components of a loom; Figure 2 shows a three-quarter front view of the system according to the present invention; Figures 3, 4 and 5, show larger-scale views of respective details of the Figure 2 system; Figures 6 and 7 show schematic operating diagrams of the system according to the present invention; Figures 8 and 9 show the negative to positive gripper transformation provided for by the Figure 2 syste . BEST MODE FOR CARRYING OUT THE INVENTION With reference to Figure 1, here and hereinafter, the terms "front" and "rear" are intended with respect to the feed direction of the warp yarns and fabric indicated by arrow A. The machine in Figure 1 comprises a warp beam 1 from which warp yarns 3 are reeled off by a yarn carrier 2; respective heddles 4 for parting yarns 3 and forming the shed through which the weft yarn 5 is inserted; and a known rocking device consisting of a batten 8 and a reed 9, for compacting the inserted weft yarns and forming, downstream from the shed, fabric 6 which is wound in known manner on to a cloth beam 7. Weft yarn 5 is inserted into the shed in known manner by a transfer system 10 (Figures 2, 6 and 7) by which it is withdrawn in known manner (not shown) from a reel to the side of the shed. In the example shown, system 10 comprises a number of guide hooks 11 (Figures 3 and 4) located inside the shed, aligned perpendicular to direction A of yarns 3, and equally spaced (e.g. 20-30 mm apart) ; and at least one flexible strap 12 (Figures 3 and 5) moving back and forth in the direction of arrows B (Figure 2) , and fitted on one end 13 with a weft carrying gripper 14 - in the example shown, a negative gripper - for withdrawing weft yarn 5. Strap 12 is made of known material (e.g. an elastomer reinforced with appropriate fiber and/or metal inserts) and presents a number of holes 15 by which the end (not shown) opposite end 13 engages a known pinion (not shown) by which strap 12 is driven. In the example shown, gripper 14 - which is a negative drawing gripper is guided by strap 12 only about halfway along the shed, into the so-called "changeover" region, wherein weft 5 is carried by a corresponding known carrying gripper (not shown) also forming part of system 10. Said carrying gripper is carried in the same way as gripper 14 by a strap identical to strap 12 and driven symmetrically in the same way but on the opposite side, which is not shown for the sake of simplicity in that, for the purpose-of the present invention, the following description relative to strap 12 and gripper 14 also applies to the other gripper and control strap. On the basis of the above, therefore, in the shed region, strap 12 clearly lies and translates in a substantially horizontal plane "of travel" parallel to direction A; and hooks 11 are fitted integral with batten 8, frontwards (i.e. downstream in relation to direction A) of reed 9 (Figures 6 and 7) so that strap 12 translates parallel to reed 9. According to the present invention, hooks 11 are C-shaped with the open side 16 facing reed 9; and each hook 11 (Figure 4) is defined by a continuous vertical side 17 opposite and facing side 16; and by two respectively top and bottom sides 18. Inwards of each hook 11, the above sides define respective contact and shoulder surfaces: horizontal top and bottom surfaces 19 and 20; and vertical surface 21 facing open side 16. Open side 16 in turn defines two first contact and shoulder surfaces 22 facing and opposite surface 21 and respectively adjacent to surfaces 19 and 20; and, at the opening, two second contact and shoulder surfaces 23 facing each other and parallel to surfaces 19 and 20. Strap 12 (Figure 5) presents a cross section of the same shape as the channel defined by each hook 11 - in the example shown, substantially rectangular - and, for a length covering at least part of the portion of the strap to be fed through the shed, presents a laterally projecting longitudinal appendix or rib 25 extending towards reed 9. According to the present invention (Figure 3) , strap 12 travels entirely and in "floating" manner inside hooks 11. More specifically, at least along the portion to be fed through the shed, i.e. the portion presenting appendix 25, strap 12 presents, in cross section, vertical dimensions (i.e. measured perpendicular to the plane of travel) smaller than the inside dimensions of hooks 11, and horizontal dimensions (i.e. measured parallel to the plane of travel) equal to the inside dimensions of hooks 11. As it translates back and forth, strap 12 engages the open side 16 of hooks 11 with appendix 25, so that strap 12 is guided in substantially slackfree manner between and in contact with opposite vertical inner surfaces 21, 22 and surfaces 23 perpendicular to the same, but without ever contacting horizontal inner surfaces 19, 20 parallel to the plane of travel. With reference to Figure 2, strap 12 is fitted with weft carrying gripper 14 by means of a rigid, substantially straight "rod" type element 30 projecting frontwards and butt fitted seamlessly to strap 12. Rod 30 comprises a guide body 31 coaxial with strap 12 and which over its entire length therefore engages hooks 11 in place of strap 12. Unlike strap 12, however, body 31 presents a cross section identical in shape and size to the inside of hooks 11, and is therefore guided in substantially slackfree manner through hooks 11 and in contact with both surfaces 21, 22 and surfaces 19, 20 of each hook 11 (Figure 7) . Rod 30 also comprises a longitudinal rib 33 projecting outwards of hooks 11 towards reed 9 and connected integral with guide body 31 by a rib 34 designed to fit through open side 16 of each hook in substantially slackfree manner and be guided between surfaces 23 in place of appendix 25 of strap 12. In cross section, perpendicular to the plane of travel of strap 12 (Figure 7) , rib 33 is larger than the inside dimensions of hooks 11 and tapers towards reed 9. In actual use, therefore, the transfer system according to the present invention provides for smooth operation with no jamming and no breakage of the yarn. In the more highly stressed region, in fact, flexible strap 12 is replaced through guide hooks 11 by body 31 of rod 30 which, being rigid and guided in slackfree manner, provides for better withstanding the peak loads caused by sharp deceleration of gripper 14 prior to being inverted. Moreover, rib 33 provides for parting the warp yarns 3 (Figure 7) to prevent any possibility of interference between the warp yarns and guide body 31 traveling inside hooks 11; while, in the shed regions occupied by strap 12, any interference with warp yarns 3 is prevented (Figure 6) by the clearance between strap 12 and sides 18. Rod 30 is preferably fitted removably to strap 12 by means of parts of both designed to travel inside hooks 11. More specifically, body 31 is so shaped that a portion of it overlaps the appropriately thinner end portion 13 of strap 12, and both are connected by means of fastening members, e.g. screws 40 (Figure 2) , fitted in recessed manner through both strap 12 and body 31. Weft carrying gripper 14 may also be fitted removably to rod 30 in any known manner (as shown by the dotted line in Figure 2) , or be formed in one piece with it. In the first case, as the member withstanding the sliding stress, and hence subject to wear, is rod 30, the above arrangement provides for eliminating frequent replacement of gripper 14. Also, connecting the grippers to the strap by means of rod 30 provides for reducing offbalance due to the mass of the grippers, and, together with the design of hooks 11, reduces wear by virtue of the size of the guide surfaces. Finally, in both cases, fitting the weft carrying grippers removably to the straps provides for easily converting the same transfer system from a negative gripper to a positive gripper system. With reference to Figures 8 and 9, in fact, system 10 according to the present invention optionally comprises a known flat profiled shoulder element 41 (formed in one piece or in a number of separate elements only provided where controlled opening of the grippers is to take place) for a known rod (not shown) of a positive gripper 42 fitted to the side of and projecting from body 31 of the rod or a similar rod 30, and extending towards reed 9. As shown in Figure 8, profiled element 41 is so formed as to be fittable removably to batten 8, rearwards of hooks 11 but frontwards of reed 9, so as never to interfere with strap 12 despite cooperating in sliding and known manner with gripper 42 and/or the respective rod, as shown in Figure 9. Figure 9 shows a cross section of transfer system 10 at the changeover region, and, in addition to positive carrying gripper 42, also shows a positive drawing gripper 43 also cooperating with profile 41 and fitted in the same way as gripper 42 to a strap 12 opposite and identical to the one shown; and a (known) control lever 44 for opening the grippers. As can be seen, conversion of the machine featuring system 10 is fast and straightforward, and consists simply in changing the grippers (possibly together with respective rod elements 30) , and in assembling/disassembling element 41, which presents an assembly base 46 with recesses 45 for housing hooks 11, and appropriate removable fastening members, such as screws 47. This provides for converting the machine with only a limited amount of downtime, and so achieving a truly flexible system.

Claims: CLAIMS 1) A transfer system for looms, comprising at least one weft carrying gripper fitted to a flexible reciprocating strap; and guide means for guiding the strap through the shed in a substantially horizontal plane and parallel to the reed; characterized by the fact that: (i) - the guide means consist of a number of C-shaped hooks fitted to the batten on the loom, to the front of, and with the open side facing / the reed; and by the fact that: (ii) - the strap travels entirely inside the hooks, and presents, at least along the portion to be fed through the shed, a cross section smaller than the inside dimension of the hooks perpendicular to the plane of travel, and of the same size as the inside dimension of the hooks parallel to the plane of travel, so that, as it travels back and forth, the strap is guided in contact with, and with substantially no slack between, respective opposite first inner surfaces of the hooks on the open side and on the side opposite the open side of each hook, and never comes into contact with respective second inner surfaces of the hooks on the sides of the hook parallel to the plane of travel. 2) A transfer system as claimed in Claim 1, characterized by the fact that, on at least part of the portion to be fed through the shed, the strap presents an appendix extending towards the reed and engaging the open side of the hooks during travel of the strap. 3) A transfer system as claimed in Claim 2, characterized by the fact that the strap is fitted with the weft carrying gripper, projecting frontwards, by means of a rigid, substantially straight rod butt fitted head to head and seamlessly to the strap; said rod comprising a guide body with a cross section of the same shape and size as the inside of the hooks, and which is guided in substantially slackfree manner, and as a consequence of the movement of the strap, between both the first and second opposite inner surfaces of each hook. 4) A transfer system as claimed in Claim 3, characterized by the fact that said rod also comprises means for parting the warp yarns and projecting outwards of the hooks towards the reed, so as to prevent interference between the guide body and the warp yarns; said means being connected integral with the guide body by means of a rib designed to fit through the open side of each hook in substantially slackfree manner. 5) A transfer system as claimed in Claim 4, characterized by the fact that the guide body of the rod is fitted removably to the strap by means of fastening members fitted in recessed manner through the strap and the body of the rod, inside the parts of the same designed to travel inside the hooks. 6) A transfer system as claimed in any one of the foregoing Claims from 3 to 5, characterized by the fact that the weft carrying gripper is fitted removably to said rod. 7) A transfer system as claimed in one of the foregoing Claims, characterized by the fact that it also comprises a flat profiled shoulder element for a positive gripper rod and fittable removably to the batten, rearwards of the hooks but frontwards of the reed, so as never to interfere with the strap and to cooperate solely with said gripper or said rod. 8) A transfer system for looms, substantially as described and illustrated herein with reference to the accompanying drawings.

Inventors: BONACINA CARLO, BONACINA, CARLO
Applicants: BONACINA CARLO, INTERPATENTS LTD, BONACINA, CARLO, INTERPATENT LIMITED
Application year: 1993
Main classification: D03D47
IPC codes: D03D47