Device for programming rotary dobbies in weaving machines

Abstract: Device for programming rotary dobbies to operate the heald frames in weaving machines, said dobbies being of the type wherein the rods (3) to control the heald frames are operated by connecting rods (2), each mounted onto an eccentric ring (5) rotating in respect of the main dobby shaft (1), the dobby also including a disk (13) caused to rotate by said shaft (1) and a selection lever (7) pivoted on said eccentric ring (5) and apt to engage said disk (13) with a tooth end (11) thereof, under the action of a spring (12). The device comprises a control lever (14) having projecting end profiles (14A, 14B) for controlling said selection lever (7), wherein one of the projecting end profiles is formed with a tooth (14B), pivoted into a slot having two divergent abutting walls (14X, 14Y), and kept in contact with one of said walls (14X) by a spring (14D) so as to be able to oscillate up to contacting the other wall (14Y), in order to shift the positive engagement with said selection lever (7) in the condition of reverse movement of the dobby.

Description: The present invention concerns a device for programming rotary dobbies to operate the heald frames in weaving machines. As known, in a weaving machine or loom, the positioning of the heald frames which determine the weft pattern of the finished fabric, should be programmed according to a preset sequence, apt to establish the position which each frame should take up at each rotation of the main shaft, which issues the controls to the oscillating devices operating such frames, in order to place them in one of the two required - high or low - positions. Since the main dobby shaft is operated according to an intermittent cycle, with a dead center at each half turn (180° rotation), the control device should, in correspondence of each pause of said shaft, be apt to connect, or not connect, the rotation shaft to a cam or similar device operating the linkages moving the frames, and thereby determine, in one case, the change of position of said frames and, in the other case, keep said frames in the previous position. The dobbies operating the heald frames in looms should thus be controlled by means of special devices apt to carry out the programming thereof, such devices allowing to determine, by way of suitable actuators, the change of the respective positions of the control means which, in turn, change the position of the frames. In technique, there are already known for example from EP-116002 devices for programming dobbies which, however, have a number of drawbacks: among them, the need to stop the shaft at each half turn, so as to be able to dispose of the time required to cancel the previous programming and set up a new one for the following half turn. It is evident how programming devices of this type determine an increase in the idle times of the machine, to the detriment of the useful working time. Another drawback of the known-type programming devices - wherein a single control is provided, with pressure times on the control levers synchronized with the center line of the motion diagram, both for the forward movement and for the reverse movement - lies in the high probability of errors in selecting the clockwise or anticlockwise direction, it being moreover indispensable, with such devices, to perform some idle half turns when having to search for the weft and reset the correct reading step. The technical problem having to be faced is to thus realize a device for programming dobbies - particularly rotary dobbies to operate the heald frames in weaving machines - which allows to select the position of the heald frames, without stopping the rotation of the main shaft at each half turn, and which allows an independent selection of the frames for the clockwise rotation and, respectively, the anticlockwise rotation. Such a device is also required to impart a reduced stress on the warp yarns and to reduce stresses and efforts in the dobby members, so as to allow very high working speeds and thereby reach the lowest possible power consumption. Said results are obtained with the present invention, which relates to a device for programming rotary dobbies to operate the heald frames in weaving machines, said dobbies being of the type wherein the rods to control the heald frames are operated by connecting rods, each mounted onto an eccentric ring rotating in respect of the main dobby shaft, the dobby also including a disk caused to rotate by said shaft and a selection lever pivoted on said eccentric ring and apt to engage said disk with a tooth end thereof, under the action of a spring, said device comprising a control lever rotating about a fixed fulcrum under the action of thrust means and in opposition to return spring means, so that projecting end profiles of said control lever may take up a position along or, alternatively, beyond the trajectory of the end of said selection lever opposite to its tooth end, in order to cause or, alternatively, prevent the engagement of said lever with the rotating disk, the rotation of the control lever taking place during the rotation of the main dobby shaft. According to the invention, said device is characterized in that one of the projecting end profiles of said control lever is formed with a tooth, pivoted at the corresponding end of said lever into a slot having two divergent abutting walls, and kept in contact with one of said walls by a spring so as to be able to oscillate up to contacting the other wall, in order to shift the positive engagement with said selection lever in the condition of reverse movement of the dobby. The spring acting on the selection lever and the spring acting on the tooth profile of the control lever are suitably dimensioned, so that the action of the first spring may not be overcome by the action of the second spring. The invention will now be described in further detail, with reference to a preferred embodiment thereof, illustrated by way of example on the accompanying drawings, in which: Fig. 1A is a diagrammatic part section view illustrating a rotary dobby, to which the device of the invention is applied in the position of start of a half turn; Fig. 1B is a section view similar to that of fig. 1, illustrating the dobby with the device, during a half turn, with change of position of the frame; Fig. 2A is a part section view illustrating the dobby with the device, during the selection step, at the end of the half turn in the condition of forward movement; Fig. 2B is a section view illustrating the same device, during a half turn, with the frame kept in the same position; Fig. 3A shows a detail of the device illustrated in the previous figures, with the dobby in a condition of forward movement, before the selection lever starts to disengage from the disk; Fig. 3B shows the same arrangement of fig. 3A, but with the selection lever in a fully disengaged position; Fig. 4A shows a detail of the device illustrated in figs. 1A to 2B, in a condition of reverse movement, before the selection lever starts to disengage from the disk; Fig. 4B shows the same arrangement of fig. 4A, during the step in which, according to the invention, the selection lever start to disengage with a delayed shifting movement; Fig. 4C shows the same arrangement of figs. 4A and 4B, but with the selection lever in a fully disengaged position; and Figs. 5A to 5C are diagrams illustrating, respectively, the working steps of the selection lever in the condition of forward movement and of reverse movement of the dobby, and the rotation steps of the dobby shaft. As shown on the drawings, the device of the present invention forms part of a dobby, which comprises a rotation shaft 1, onto which there is keyed a connecting rod 2 comprising a projecting part 2A, pivoted in 3A to the rod 3 controlling the heald frames (not shown), and a substantially circular ring 2B carrying two rollers 2C in opposite positions. A bearing 4 is inserted at the centre of the connecting rod 2, onto the inner race of said bearing there being mounted an eccentric ring 5 apt to rotate in respect of the shaft 1, as will be seen hereinafter. A rocking lever 7, or selection lever, is mounted oscillating on the eccentric ring 5 by means of a pivot 6 or like, said lever 7 having shaped ends 8 and 9 as well as a tooth 11 on its inward side opposite to the end 9. A spring 12, positioned between the eccentric ring 5 and the end 9 of the lever 7, imparts a returning action on said lever 7 and thus tends to cause its rotation so as to draw the tooth 11 close to the rotation axis of the shaft 1. On said shaft 1 there is finally keyed a disk 13, onto the periphery of which there are formed two slots 13A and 13B, positioned diametrically opposite in respect of the rotation centre of said disk 13 set on the axis of the shaft 1. Onto the disk 13 there is keyed the inner race of a bearing, onto the outer race of which there is keyed the eccentric ring 5, so as to thus rotate about the shaft 1. The disk 13 lies on the same plane as the lever 7, so that the tooth 11 of said lever may engage into one of the two slots 13A or 13B of said disk, and disengage therefrom. The dobby is completed by a C-shaped control lever 14, an end of which comprises a projecting profile 14A formed in one piece therewith, while its other end has a movable projecting profile formed with a tooth 14B, oscillating between abutting walls 14X and 14Y and kept in position against the first one of said walls by a spring 14D. The control lever 14 oscillates about a fulcrum 14C between a first position, determined by the drawing action of a spring 15 and by an abutment 16, and a second position, determined by the thrust imparted by a programming actuator 17, the action of which is diagrammatically illustrated by two arrows A and B, for the condition of forward movement and, respectively, of reverse movement. The dobby works as follows: as the shaft 1 starts its half turn (fig. 1A) - and in the case of forward movement and of having set the programming so as to change the position of the frame - the programming actuator 17 imparts no thrust on the control lever 14 which, under the action of the spring 15, oscillates against the abutment 16, thereby leaving the rocking selection lever 7 under the returning action of the spring 12, with its tooth 11 engaged into the slot 13A. In this condition, the eccentric ring 5 is engaged with the disk 13 which, rotating with the shaft 1 during its half turn (fig. 1B), thereby draws into rotation said ring 5 and consequently the connecting rod 2 which, while rotating, draws along the frame control rod 3 causing it to change position. Before the half turn has been completed (fig. 1B), the programming actuator 17 presets the control for the next half turn, in the sense - in the example shown - of keeping the frame in the previous position. Said actuator 17 thus imparts no thrust on the lever 14, and when the tooth 14B contacts (fig. 2A) the rear surface 8A of the end 8 of the lever 7, shaped with a rising front, it causes said lever 7 - while the rotation of the disk 13 continues - to rotate about its pivot 6, thereby causing the tooth 11, at its opposite end, to gradually disengage from the slot 13A of the disk 13. Once the dead center of the half turn has been reached (fig. 2A), the selection lever 7 is totally rotated in the outward direction, being engaged onto the roller 2C, while the tooth 11 is fully disengaged from the slot 13A. The eccentric ring 5 thus remains idle in respect of the disk 13, whereby, during the next half turn (fig. 2B), the heald frame controlled by the rod 3 is kept in the previous position. Figs. 3A and 3B show in detail how the lever 14 controls the selection lever 7 during the aforedescribed working steps of the device according to the invention, in the condition of forward movement of the dobby; said steps are illustrated on the diagram of fig. 5A, starting from point 1 - when the lever 7 starts to disengage from the disk 13, due to contact of the tooth 14B with its rear end surface 8A (fig. 3A) - up to point 2 - when the lever 7 is fully released through disengagement of its tooth end 11 from the slot 13A of the disk 13 (fig. 3B). Figs. 4A to 4C show instead, also in detail, how the lever 14 controls the selection lever 7, during the corresponding working steps of the device according to the invention, in the condition of reverse movement of the dobby; said steps are illustrated on the diagram of fig. 5B, starting from point 3 up to point 4. As can be noticed from this diagram - by comparing it with the diagram of fig. 5A, and with the diagram of fig. 5C which illustrates the movement of the dobby shaft 1 - in the condition of reverse movement, the positive contact of the control lever tooth 14B with the selection lever 7 takes place, according to the invention, in a way such as to determine a shifting sf in respect of the condition of forward movement. This is obtained thanks to the particular assembly of the tooth 14B which is apt to oscillate, against the action of the spring 14D, between the abutting wall 14X and the abutting wall 14Y. Since the action of the spring 14D is less strong than the action of the spring 12 which presses the lever 7 against the disk 13 (or, in any case, the action of the first spring never overcomes the action of the second one), when the tooth 14B gets in contact with the end 8A of the lever 7 - in the condition of reverse movement (fig. 4A) - said lever 7 remains motionless, while the tooth 14B oscillates (fig. 4B) up to abutting against the wall 14Y. Only at this stage (point 3 of the diagram of fig. 5B), the tooth 14B causes the selection lever 7 to start its oscillation - with the desired shifting, which prevents any jams on changing of the condition from forward movement to reverse movement - until the tooth 11 of said lever totally disengages from the slot 13A of the disk 13 (fig. 4C, and point 4 of the diagram of fig. 5B). With the aforedescribed and illustrated arrangement - the working of which has just been explained - the present invention allows, as seen, to select the position of the heald frames without requiring to stop the rotation of the dobby shaft 1 at each half turn, and thus preventing any possible jams during that step; furthermore, it allows an independent selection of the frames, both in the condition of forward movement and in the condition of reverse movement, thereby considerably increasing the dobby speed, with obvious advantages for the productivity of the weaving machine to which said dobby is associated. It is understood that - as it will appear evident to an expert of the art - there may be other practical embodiments of the invention, differing from the one described heretofore, but all rightfully falling within the protection scope of the present invention.

Claims: Rotary dobby with device for programming the same, to operate the heald frames in weaving machines - said dobbies being of the type wherein the rods (3) to control the heald frames are operated by connecting rods (2), each mounted onto an eccentric ring (5) rotating in respect of the main dobby shaft (1), the dobby also including a disk (13) caused to rotate by said shaft (1) and a selection lever (7) pivoted on said eccentric ring (5) and apt to engage said disk (13) with a tooth end (11) thereof, under the action of a spring (12) and said device comprising a control lever (14) rotating about a fixed fulcrum (14C) under the action of thrust means (17) and in opposition to return spring means (15), so that projecting end profiles (14A, 14B) of said control lever (14) may take up a position along or, alternatively, beyond the trajectory of the end (8) of said selection lever (7) opposite to its tooth end (11), in order to cause or, alternatively, prevent the engagement of said lever (7) with the rotating disk (13), the rotation of the control lever (14) taking place during the rotation of the main dobby shaft (1) - characterized in that one of the projecting end profiles of said control lever (14) is formed with a tooth (14B), pivoted at the corresponding end of said lever into a slot having two divergent abutting walls (14X, 14Y), and kept in contact with one of said walls (14X) by a spring (14D) so as to be able to oscillate up to contacting the other wall (14Y), in order to shift the positive engagement with said selection lever (7) in the condition of reverse movement of the dobby. Rotary dobby with device for programming the same, to operate the heald frames in weaving machines as in claim 1), wherein the spring (12) acting on the selection lever (7) and the spring (14D) acting on the tooth profile (14B) of the control lever (14) are dimensioned so that the action of the first spring (12) may not be overcome by the action of the second spring (14D).

Inventors: CREMONESI GIAN LUIGI, CREMONESI, GIAN LUIGI
Applicants: FIMTEXTILE SPA, FIMTEXTILE S.P.A.
Application year: 1996
Main classification: D03C1
IPC codes: D03C1