Device for actuating heddles of looms with positive control in both directions of a single contact roller

Abstract: Control device for actuating frame heddles with limitation of the axial thickness in looms, comprising a pair of mutually opposed cams having conjugate profiles for the positive control in both directions of the lever systems for connection with the heddles, in which the control of the movement is transmitted to a single contact roller, the surface of which is in positive, direct contact with the surfaces of the opposed cams, at least one of the two actuation shafts of the cams being adjustable in centre-to-centre spacing with respect to the other for the purpose of eliminating the initial play between the components and for subsequent taking-up of predetermined play caused by wear.

Description: The subject of the present invention is a control device having pairs of mutually opposed cams with conjugate profiles for actuating heddles in looms, the device having a minimal axial dimension. In the art of looms which produce the finished cloth by starting from threads constituting the weft and the warp, the need is known for actuating the heddle frames in an alternating, controlled and monitored motion, while maintaining the highest possible speed with minimum dial overall dimension for the purpose of minimizing the depth of the shed and therefore the stroke travelled by the heddle. For this purpose, so-called weave-control machines have been constructed, for actuating the leverage mechanisms controlling the heddle frames, said weave-control machines using positive actuations having conjugate cams connected to the lever mechanisms controlling said heddle frames, as shown for example in FR-A-502375. Such machines, however, have certain important limitations, among which are the low torsional stiffness of the rocker arms and the need to apply a so-called preload force to the coupling between control cam and yielding roller for the purpose of reducing as far as possible the plays between the control cams and the rollers carried by the rocker arms; said preload, however, removes a portion of the load available for actuating the heddle, thus compelling a reduction in the movement speed of the heddle frames. The problem therefore arises of creating a device of the cam type for the positive control in both directions of the actuations of heddles for looms, which shall be of minimal axial dimension so that it may be contained within the maximum space available determined by the pitch of the heddles, shall make possible the use of the whole of the effective load for moving the heddles with a consequent increase in velocity for given conditions, shall assure the maximum accuracy of coupling between rollers and cams for the purpose of reducing the plays between them and shall be provided with the maximum possible stiffness. The device must, furthermore, be easy to fit and to regulate to allow manual intervention at any time to eliminate play that may have arisen due to wear of the components or the replacement of the sets of cams. Said results are achieved by the present invention, which provides a control device for actuating the heddle frames in looms, the device having a minimal axial dimension, comprising a pair of mutually opposed cams having conjugate profiles for the positive control in both directions of the lever systems for connection with the heddles, in which the movement controlled by the cams is transmitted to a single contact roller, the surface of which is in positive, direct contact with the surfaces of the opposed cams, at least one of the two actuation shafts for the cams being adjustable in centre-to-centre spacing relative to the other for the purpose of eliminating initial play between the components and for the subsequent taking-up of predetermined play caused by wear. A preferred form of construction of the control device for actuating the heddle frames in looms according to this invention provides that the centre of rotation of said contact roller shall be disposed on the straight line connecting the centres of rotation of the control cams and that said roller shall be mounted rotatable on a pin carried by one arm of a knee-joint lever rotating about its own axis and the other arm of which is connected to the actuating lever systems for the heddles. In the control device for actuating the heddle frames with limitation of the axial thickness in looms, it is furthermore provided in a variant that the control of the cams shall be applied to a rigid arm of a knee-joint lever, the surfaces of said arm in contact with the cams being shaped according to a curve such that the locus of the centres of curvature of the contact points is preferably composed of a straight line passing through the centres of rotation of said cams; said arm, furthermore, may in an alternative arrangement have a longitudinal aperture symmetrical about the axis of said arm which makes possible, upon coupling with the cams, a compression of the arm adapted for creating an elastic reaction which permits any predetermined play to be taken up. It is provided also that, in the control device according to the present invention, the coupling between cams and roller shall be effected by means of configurations of the cams and of the roller in which: the outer rim both of the cams and of the roller is flat; or the outer rim of the cams is U-shaped to retain and guide the flat rim of the roller; or the outer rim of the roller is U-shaped for retaining and guiding the flat rims of the cams. Further details will be understood from the following description, prepared with reference to the attached drawings, in which there are shown: in Fig. 1: a diagram showing the principles of the control device according to the present invention; in Fig. 2: a partly sectioned view of an example of embodiment of the device of Fig. 1; in Fig. 3: a partial section of the detail of coupling between cams and roller; in Figs. 4a and 4b: examples of a variant of the device according to the present invention; in Figs. 5a, b, c: examples of coupling guidance between cams and roller. As Figure 1 shows, the control device for actuating the heddles 1 of looms is composed essentially of pairs of mutually opposed cams 2 and 3 having a conjugate profile, keyed respectively to a rotatable shaft 2a and 3a, between which is disposed a roller 4, the external surface 4b of which is in contact with the surfaces of the cams 2 and 3. Said roller, actuated by rolling of said cams, is mounted on an arm 5a of a lever 5, of which the other arm 5b is connected in known manner to the lever systems 6 (Fig. 1) for actuating the heddles 1. In the arrangement according to this invention, the centres of rotation of the cams and of the roller lie on a single connecting axis of these centres of rotation. In greater detail (Fig. 2), inside a closed supporting structure 10, the upper cams 2 are keyed on the fixed rotating shaft 2a and are spaced apart by spacer pieces 2b formed on these cams, the cams being held together by fixing tie bars 9; the lower cams 3, in turn, are keyed to a shaft 3a and spaced apart by spacer pieces and held together in the manner described for the cams 2. The lower shaft 3a is mounted in a cradle 11, which can pivot about the pin 12 so that the shaft 3a can be displaced from its working position with the cradle 11 bearing against the pin 5a of the lever 5 to a remote position which allows the cams to be released, for example for the purpose of replacing them after they have deteriorated due to wear. Between the external surfaces of the two cams 2 and 3, the yielding roller 4 is inserted, which is mounted free to rotate about a pin 4a fixed to one arm 5b of the knee-joint lever 5, rotatable about its pivot pin 5a, and the other arm 5b of which is connected in known manner to the lever systems for controlling the stroke of the heddles. The coupling between the cams 2 and 3 and the roller 4 may be effected according to the examples of Fig. 5, in which in a) there is shown a coupling according to the present invention, with a flat contact rim both of the roller and of the cams; in b) a first possible variant with a roller having a U-shaped rim which retains and guides the outer rims of the cams; in c) a second variant, with the outer rim of the roller flat and with the cams having their rims U-shaped to retain and guide the roller. With the axial arrangement of the centres of rotation of the two cams and of the roller it is therefore possible to apply a thrust onto the roller from one cam, which thrust is compensated by the reaction of the other cam, in this manner obtaining an optimum contact of the respective surfaces of rotation without reducing the effective load for raising the heddles, and thereby making possible, for a given set of conditions, an increase in the velocity of movement of these heddles. One of the cams being adjustable in position, it is furthermore possible to eliminate also the plays resulting from any wear, always keeping the optimum contact between the surfaces of the cams and of the roller. In Fig. 4a there is shown a constructional variant of the control device according to the present invention, in which the yielding roller 4 is replaced by a rigid arm 8, the external contact surfaces 8a of which are curved in such a manner that the locus of the points constituting the centre of curvature, instant by instant in contact with the cams, shall also be formed by the line joining the centres of rotation of the cams 2 and 3; with this configuration, the transmission plays are further reduced, one pivot pin being eliminated. In Fig. 4b there is also illustrated an improvement to the rigid arm 8, which here possesses an aperture 8b symmetrical about the longitudinal axis of the arm, which aperture allows the arm to be slightly compressed at the instant of coupling with the cams, thus obtaining an elastic reaction capable of absorbing further play that may exist between the surfaces of contact between cams and arm. Numerous variants may be introduced, without thereby departing from the scope of the present invention in its general characteristics; in particular, it is evident that the centres of rotation of the two cams and of the roller could also not lie on a single straight line connecting together these centres themselves and how it is possible to vary the centre-to-centre spacing between the centres of rotation of the cams by acting on both the rotation shafts, instead of keeping one shaft fixed and acting only on the other.

Claims: Control device for actuating the heddles in looms, the device having a minimal axial dimension, comprising a pair of mutually opposed cams having conjugate profiles for the positive control in both directions of the lever systems for connection with the heddles; characterized by the fact that the movement controlled by the cams is transmitted to a single contact roller, the surface of which is in positive, direct contact with the surfaces of the mutually opposed cams, at least one of the two actuating shafts for the cams being adjustable in centre-to-centre distance with respect to the other for the purpose of eliminating the initial play between the components and for the subsequent taking-up of predetermined play caused by wear. Control device for actuating the heddles in looms, the device having a minimal axial dimension, according to Claim 1, characterized by the fact that the centre of rotation of said contact roller is preferably disposed on the straight line connecting together the centres of rotation of the control cams. Control device for actuating the heddles in looms, the device having a minimal axial dimension, according to Claim 1, characterized by the fact that said roller is mounted rotatable about a pin carried by one arm of a knee-joint lever, pivotal about its own axis and the other arm of which is connected to the lever systems for actuating the heddles. Control device for actuating the heddles in looms, the device having a minimal axial dimension, according to Claim 1, characterized by the fact that the control of the cams is applied to a rigid arm of a knee-joint lever, the surfaces of said arm in contact with the cams being shaped according to a curve such that the locus of the centres of curvature of the contact points is preferably formed by a straight line passing through the centres of rotation of the cams. Control device for actuating the heddles in looms, the device having a minimal axial dimension, according to Claim 4, characterized by the fact that said arm possesses a longitudinal aperture symmetrical about the axis of the arm which makes possible, upon coupling with the cams, a compression of the arm adapted for creating an elastic reaction, which allows possible predetermined plays to be taken up. Control device for actuating the heddles in looms, the device having a minimal axial dimension, according to the preceding Claims, characterized by the fact that the outer rim of said cams and of said roller is flat. Control device for actuating the heddles in looms, the device having a minimal axial dimension, according to Claims 1 to 5, characterized by the fact that the outer rim of the cams is U-shaped to retain and guide the flat rim of the roller. Control device for actuating the heddles in looms, the device having a minimal axial dimension, according to Claims 1 to 5, characterized by the fact that the outer rim of the roller is U-shaped to retain and guide the flat rims of the cams.

Inventors: BERETTA GIOVANNI, BERETTA, GIOVANNI
Applicants: BREVTEX SA
Application year: 1990
Main classification: D03C5
IPC codes: F16H25, D03C13, D03C5