DEVICE FOR CONTROLLING THE GRIPPER STRAPS ON LOOMS

Abstract: A device for controlling both negative and positive weft carrying grippers (3) on a continuous weft feed loom, wherein a connecting rod-crank mechanism (10) controls rectilinear translation of a slide (11) along fixed guide means (12), and the slide (11) is fitted with a nut screw (20) engaging a worm (14) which is mounted in idle manner on a fixed support (13) integral with the guide means (12) and is fitted with a pinion (18) controlling the gripper strap (2) the nut screw (20) comprising two half elements (30) having respective worm reading means (21) and movable relatively in relation to each other along the worm axis (A) and in opposite directions by a cam (32); and the half elements (30) of the nut screw (20) being fitted in angularly fixed manner to the slide (11), or to an element mounted in idle manner on the slide (11), about the worm axis (A), and the angular position of which is controlled by cam (32) means as a function of the axial position of the slide (11).

Description: DEVICE FOR CONTROLLING THE GRIPPER STRAPS ON LOOMS TECHNICAL FIELD The present invention relates to a device for controlling the gripper straps on looms, and in particular for controlling, according to a desired law of motion, both a positive and negative weft carrying gripper on a continuous weft feed loom. BACKGROUND ART Known devices for controlling the gripper straps on continuous weft feed looms consist of a connecting rod-crank drive mechanism for translating along a straight guide a slide fitted with means for engaging a variable-pitch worm screw mounted in idle manner parallel to, and on a support integral with, the guide. The screw is thus rotated, according to a predetermined law, by the reciprocating translatory movement of the slide, so as to transmit a reciprocating rotatory movement, having a predetermined law, to a toothed pinion fitted angularly integral with the screw, and which in turn, and in known manner, controls translation of a flexible gripper strap wound partially about the pinion . Known devices of the aforementioned type, though they do provide for varying the law of motion of the gripper strap by means of a relatively straightforward mechanical operation on the device itself, and for gradually taking up any slack between the screw profiles (or threads) and means for reading/engaging the same, are nevertheless mechanically complex, expensive to produce, and unreliable, particularly as regards the reading/engaging means which normally consist of idle rollers with an oblique axis in relation to the screw. DISCLOSURE OF INVENTION It is an object of the present invention to provide a straightforward, reliable, relatively inexpensive device for controlling the gripper straps on continuous weft feed looms, and which provides for taking up any working slack. It is a further object of the present invention that the above device should be easily adaptable for enabling variations in the law of motion of the gripper strap and so converting the negative gripper control device into a positive gripper control device and vice versa, with no need for specialized (only trained) personnel, and in a relatively short space of time (2-3 hours) . According to the present invention, there is provided a device for controlling the gripper straps on continuous weft feed looms, and of the type comprising a connecting rod-crank drive mechanism for controlling translation of a slide along a straight path defined by fixed guide means; a worm screw parallel to said path and mounted in idle manner on a fixed support integral with said guide means, the worm screw being fitted to a pinion controlling the gripper strap; and a nut screw fitted to the slide and having worm screw reading means by which it engages the worm screw for rotating it as a consequence of translation of the slide along said path; characterized by the fact that the nut screw comprises at least two half elements having respective said worm screw reading means and mounted on the slide so as to move relatively in relation to each other along the worm screw axis; and first cam means fitted to the slide, for relatively displacing in opposite directions said half elements of the nut screw, and taking up any slack between respective worm screw threads and said reading means. According to a first embodiment of the present invention, the half elements consist of two half shells formed by longitudinally sectioning the nut screw along a diametrical plane of the worm screw. A first half shell is mounted in axially fixed manner, while the other is mounted in axially movable manner, and presents an opening in which is inserted in axially slack manner a spherical-wedge-shaped cam varying angularly in axial thickness. According to a second embodiment of the present invention, the half elements of the nut screw consist of two rings formed by transversely sectioning the nut screw perpendicular to the worm screw axis, and the two rings are both mounted in axially movable manner, with the spherical-wedge-shaped cam inserted between the adjacent ends of the same and cooperating with both. The spherical-wedge-shaped cam is mounted for rotation, parallel to the worm screw axis, inside a radial seat in which it is lockable angularly via axial pressure means; and the half elements are fitted in angularly fixed manner inside a nut screw body mounted in axially fixed but angularly idle manner on the slide about the worm screw axis. The angular position of the nut screw body may be fixed by means of a lock member, or controlled as a function of the axial position of the slide by second cam means mounted integral with said fixed support. This therefore provides for an intrinsically straightforward, reliable, inexpensive device, capable, nonetheless, of taking up any working slack between the worm and nut screw. Moreover, the same device may be produced in a simplified "basic" version permitting no adjustment (unless by operating in conventional manner on the linkages) to the law of motion imparted to the gripper strap, by virtue of the nut screw body in which the two (or more) half elements are housed being formed in one piece with (or fitted to) the slide; or in a "perfected" version featuring a worm rotation "correcting" meehanism coaxial with the worm, and which provides for adjusting speed in a truly straightforward, reliable and flexible manner. The latter version, which is destined to operate predominantly with positive gripper controls operating at slower speeds but requiring greater characterization of the law of motion for meeting various weaving requirements, is nevertheless convertible into the "basic" version by simply removing the second cam means and fitting the nut screw body to the slide, thus enabling operation with less characteristic laws of motion but at higher speeds typical, for example, of negative gripper control requirements. BRIEF DESCRIPTION OF DRAWINGS Further objects and advantages will be revealed in the following description of a preferred non-limiting embodiment of the present invention, and with reference to the accompanying drawings, in which: Figure 1 shows a schematic view of the main components of a device in accordance with the present invention; Figures 2 and 3 show respective larger-scale cross sections of different axial portions of the Figure 1 device; Figure 4 shows a larger-scale top plan view of a detail on the Figure 1 device; Figure 5 shows a possible variation of a second detail on the Figure 1 device; Figure 6 shows a schematic view in perspective of a further detail on the device according to the present invention. BEST MODE FOR CARRYING OUT THE INVENTION Number 1 in Figure 1 indicates a device for controlling the control strap 2 of a known positive or negative weft carrying gripper 3 (shown only schematically for the sake of simplicity) on a known continuous weft feed loom (not shown) . Device l comprises a known connecting rod-crank drive mechanism 10 for controlling, according to a predetermined law, translation of a slide 11 along a straight path defined by fixed guide means consisting, in the example shown, of a straight cylindrical bar 12 mounted on a fixed support or frame 13 on which mechanism 10 is also mounted together with a known motor (not shown) . A fixed-pitch worm screw 14 with a number of threads 15 (four in the example shown) is provided parallel to the path of slide 11 and mounted in idle manner on support 13. Worm 14 rotates about its own axis A parallel to bar 12, and is fitted, on end 16 projecting from support 13, with a known pinion 18 controlling gripper strap 2, which, being flexible, winds partially about pinion 18 and meshes with it like a rack by means of holes (not shown) engaged successively by the teeth on pinion 18. Device 1 is functionally completed by a nut screw 20 carried on slide 11 and having means for reading (or engaging) worm 14 and defined, in the example shown, by straightforward helical grooves 21, each engaged by a respective thread 15. By means of grooves 21, nut screw 20 meshes with worm 14 for rotating it as a consequence of translation of slide 11 along bar 12. Consequently, the reciprocating motion produced by mechanism 10 is converted into reciprocating translatory movement of slide 11; which results in reciprocating rotation of worm 14 according to a predetermined law depending on the geometric characteristics of threads 15; which is converted into reciprocating rotation of pinion 18 in the direction of the arrows (Figure 1) , and into reciprocating translation, according to the desired law, of strap 2 meshing with pinion 18, and therefore also of gripper 3. According to the present invention, nut screw 20 comprises two (in the example shown) or more (according to a variation not shown) half elements 30 (Figures 2 and 3) having respective worm reading means 21, and mounted on slide 11 so as to move relatively in relation to each other along axis A of worm 14. Slide 11 also presents cam means 32 for relatively displacing half elements 30 in opposite directions and so taking up any wear-induced or post-assembly slack between threads 15 and grooves 21 of nut screw 20. With special reference to Figures 2, 3 and 4, half elements 30 are fitted in angularly fixed manner inside a substantially- cylindrical nut screw body 35 axially integral with slide 11. Body 35 may be mounted integral in one body with slide 11, e.g. formed in one piece with the same, or, as in the example shown and for the reasons explained later on, be mounted in axially fixed but angularly idle manner on slide 11, about axis A of worm 14. For example, slide 11 presents an eye, or rather slider, 36 engaging bar 12 in sliding manner; and a pair of supporting tabs 37, each shaped like a main bearing with two half rings secured by studs 38 (or other means) , which extend to include worm 14 and define a fork between which body 35 housing nut screw 20 is mounted in idle manner, the whole coaxial with worm 14. The relative angular position of nut screw body 35 may be fixed, e.g. as determined by the position of a hole 40 (Figures 1 and 2) formed through one of tabs 37 to which body 35 is fitted angularly integral by means of an eye 41 and a screw, pin or other connecting member (not shown) engaging both eye 41 and hole 40; or it may be controlled "dynamically" as a function of the axial position of slide 11 by cam means 45, which may be fitted integral with fixed support 13, parallel to axis A, at worm 14. According to a first embodiment shown in Figures 1, 2, 3 and 4, half elements 30 of the nut screw consist of two half shells 30a and 30b formed by longitudinally sectioning nut screw 20 along a diametrical plane of worm 14. Half shell 30b is mounted in axially fixed manner to nut screw body 35 by means of pins 50 (or other means) , while the other half shell 30a is mounted in axially movable manner in relation to nut screw body 35, and presents, radially outwards, an opening or slot 51 in which is inserted, in axially slack manner, a spherical-wedge-shaped cam 52 varying angularly in thickness measured along axis A. Spherical-wedge-shaped cam 52 (Figure 4) cooperates with one side of opening 51, and is mounted for rotation, parallel to axis A, inside a radial seat 55 formed in an appropriately shaped portion of nut screw body 35. In a second embodiment shown in Figure 5, half elements 30 of the nut screw consist of two rings 30c and 30d formed by transversely sectioning nut screw 20 perpendicular to axis A of worm 14. Both rings are mounted in axially movable manner in relation to nut screw body 35, and between the adjacent ends of the rings is inserted a spherical-wedge-shaped cam 52 identical to the previous one and varying angularly in axial thickness. Spherical-wedge-shaped cam 52 thus cooperates on either side with said adjacent ends of rings 30c and 30d - in the example shown, with respective portions 60 of the rings provided for the purpose - and, as already described, is mounted for rotation, parallel to axis A, inside seat 55 in nut screw body 35. In both the above embodiments, cams 52 are supported on a pin 62 fitted through seat 55 parallel to worm 14, and may be locked angularly as required via axial pressure means. In the example shown, pins 62 are mounted idly through body 35, are threaded at at least one end, and present respective lock nuts (or heads) 63 on the outside of body 35, for locking pins 62 angularly inside seats 55. Cams 52 are fitted in fixed manner to respective pins 62, and present a prismatic control head 65 grippable by means of a tool and projecting from seat 55 outwards of body 35. Half elements 30 of the nut screw are lockable angularly inside body 35 by virtue of being externally prismatic, and being housed inside a mating prismatic cavity 70 formed inside body 35, parallel to the axis of worm 14. As shown in Figure 6, half elements 30 preferably present radial channels 71 for feeding lubricant directly to the worm reading means - in the example shown, defined by straightforward through openings terminating laterally in helical grooves 21 and supplied by gravity, on the outside of half element 30, with oil from a pipe 75. If necessary, channel 71 may be closed on the outside of element 30 and connected directly in fluidtight manner (by means of a union) to pipe 75 for enabling pressurized lubricant supply. In actual use, any slack between worm 14 and reading means 21 on nut screw 20 is easily adjusted according to the present invention by loosening the means locking pin 62, and gripping head 65 for rotating cam- 52 in such a direction as to bring the progressively thicker portions of the cam into contact with nut screw 20. In this way (Figure 4), the axially free half shell 30a is so stressed by cam 52 as to slide axially in the direction of the arrow, parallel to worm 14, and cam 52, aS | it penetrates gradually inside opening 51, acts on the lateral wall of the opening until the required slack is achieved. In the Figure 5 embodiment, on the other hand, operation of cam 52, which is identical to that described above, provides for progressively parting rings 30c and 30d, parallel to axis A, and so adjusting any slack between grooves 21 and threads 15. Both the above systems are of course mechanically equivalent, in that the first (Figure 4) acts on the entire length of nut screw 20 but involves only half of threads 15, while the second (Figure 5) acts on a length equal to half the length of nut screw 20 (rings 30c and 30d are the same length) but involves all of threads 15. For normal use, e.g. with negative grippers and high translation speeds of gripper 3, body 35 is maintained integral with slide 11, and pinion 18 is rotated reciprocatingly according to the required law, as described previously. For applications requiring greater flexibility, e.g. for achieving highly characteristic laws of motion but lower gripper speeds typical of positive grippers, body 35 need simply be released, e.g. by removing the lock member from elements 40 and 41, to enable body 35 to rotate about axis A, and support 13 be fitted with cam means 45 defined, in the example shown, lay a curved plate 81 (Figures 2 and 3) having its center of curvature coincident with axis A of the worm, and by an opening 82 of predetermined shape (Figures 1 and 3) formed through and along the generating lines of plate 81. According to the present invention, provision is made on the outside of body 35 for a pawl 80 - either fixed or secured in removable manner (e.g. by screwing it inside a radial hole in body 35) - projecting radially from body 35 and designed to engage cam means 45 (if provided) - in the example shown, to roll inside opening 82. In this way, nut screw 20 is forced to rotate relatively in relation to worm 14 and according to a law depending on the contour of opening 82, which rotation, depending on whether it is in the same or opposite direction to the rotation of worm 14, increases or decreases the angle of rotation of worm 14 so as to increase or decrease acceleration of gripper 3 as required. Theoretically, it may also be possible to invert rotation of pinion 18 prior to inverting translation of slide 11, providing the correction imparted by the shape of opening 82 exceeds the helix angle of worm 14. Clearly, therefore, the device described poses practically no limits to the law of motion of gripper 3; and - a useful feature for achieving a longitudinally compact device - may also be operated as a straightforward overgear by adding rotation of nut screw 20 to that of worm 14.

Claims: CLAIMS 1) A device for controlling the gripper straps on continuous weft feed looms, and of the type comprising a connecting rod-crank drive mechanism for controlling translation of a slide along a straight path defined by fixed guide means; a worm screw parallel to said path and mounted in idle manner on a fixed support integral with said guide means, the worm screw being fitted to a pinion controlling the gripper strap; and a nut screw fitted to the slide and having worm screw reading means by which it engages the worm screw for rotating it as a consequence of translation of the slide along said path; characterized by the fact that the nut screw comprises at least two half elements having respective said worm screw reading means and mounted on the slide so as to move relatively in relation to each other along the worm screw axis; and first cam means fitted to the slide, for relatively displacing in opposite directions said half elements of the nut screw, and taking up any slack between respective worm screw threads and said reading means. 2) A device as claimed in Claim 1, characterized by the fact that said half elements of the nut screw are fitted in angularly fixed manner inside a nut screw body axially integral with the slide. 3) A device as claimed in Claim 2, characterized by the fact that said nut screw body is mounted integral in one body with the slide. 4) A device as claimed in Claim 2, characterized by the fact that the worm screw is a fixed-pitch worm; and said nut screw body is mounted in axially fixed but angularly idle manner on the slide, about the axis of the worm; the angular position of said nut screw body being controlled as a function of the axial position of the slide by second cam means mounted integral with said fixed support. 5) A device as claimed in one of the foregoing Claims from 2 to 4, characterized by the fact that said half elements of the nut screw consist of two half shells formed by longitudinally sectioning the nut screw along a diametrical plane of the worm; a first half shell being mounted in axially locked manner to the nut screw body; and the other half shell being mounted in axially movable manner in relation to the nut screw body, and presenting, radially outwards, an opening in which is inserted, in axially slack manner, a spherical-wedge-shaped cam varying angularly in axial thickness; the spherical-wedge-shaped cam cooperating with one side of the opening, and being mounted for rotation, parallel to the axis of the worm, inside a radial seat in said nut screw body, in which it is lockable angularly via axial pressure means. 6) A device as claimed in one of the foregoing Claims from 2 to 4, characterized by the fact that said half elements of the nut screw consist of two rings formed by transversely sectioning the nut screw perpendicular to the axis of the worm; both said rings being mounted in axially movable manner in relation to the nut screw body; a spherical-wedge-shaped cam varying angularly in axial thickness being inserted between the adjacent ends of said rings; and the spherical-wedge-shaped cam cooperating on either side with said adjacent ends of the rings, and being mounted for rotation, parallel to the axis of the worm, inside a radial seat in said nut screw body, in which it is lockable angularly via axial pressure means. 7) A device as claimed in Claim 5 or 6, characterized by the fact that said half elements of the nut screw are externally prismatic, and are housed inside a mating prismatic cavity formed parallel to the worm axis and inside said nut screw body. 8) A device as claimed in any one of the foregoing Claims, characterized by the fact that said half elements of the nut screw present radial channels for supplying lubricant directly to said worm reading means. 9) A device for controlling the gripper straps on 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