Patent Publication Number: US-4544000-A

Title: Synchronized rotating dobby for weaving looms

Description:
The present invention relates to rotating dobbies for controlling the heddle frames mounted on weaving looms. 
     In rotating dobbies, the reciprocating vertical movement of the heddle frames is conventionally achieved by oscillating parts which may be constituted, depending on the case, by rod-lever assemblies or by roller-bearing levers, these oscillating parts being controlled by actuating elements (in the form of eccentrics in the first case, cams in the second) mounted on the main shaft of the mechanism. This shaft performs an intermittent movement of rotation and, every time it stops, i.e. every half-revolution of said shaft, at each of the blades of the dobby (i.e. the actuating unit associated with each heddle frame) and as a function of the design or weave to be obtained on the fabric being woven, the reading device must connect the actuating element either to said shaft in order to control the oscillating part or to a fixed point in order to effect angular immobilization of the latter. 
     Such selective connection is generally obtained with the aid of a mobile coupling mechanism in the form of a key or pawl, subjected to the action of two pivoting levers disposed on either side of the shaft in order to actuate said mobile mechanism in the two positions of stop thereof, each pair of pivoting levers being placed under the dependence of the reading device of the dobby. 
     Applicant&#39;s French Pat. No. 81 20502 of Oct. 29, 1981, and corresponding U.S. Pat. No. 4,444,225 proposes mounting the mobile coupling mechanism, preferably made in the form of a tilting pawl, on a plate laterally fixed to the corresponding actuating element, the pawl in question cooperating, under the effect of appropriate elastic means, with a drive disc fitted on the main shaft in order to allow coupling of this shaft with the actuating element and control of the corresponding heddle frame. Furthermore, elastic return means was provided to associate with each of the pivoting levers intended for actuating the mobile mechanism or pawl, said elastic return means tending to engage the end of these levers in a notch made in the above-mentioned lateral plate, such engagement ensuring angular immobilization of said plate and of the actuating element to which it is fixed, at the same time as the disengagement of the pawl. 
     Tests have shown that such an arrangement gave complete satisfaction in operation. However, as will be demonstrated hereinbelow in greater detail, it allows correct functioning only in one direction of rotation, whereas, for the pick-seeking and unweaving operations, it is necessary to be able to drive the dobby in reverse. 
     It is an object of the present invention to overcome this drawback and to produce a rotating dobby of the &#34;synchronized&#34; type, capable of operating equally well in forward and in reverse motion. 
    
    
     The invention will be more readily understood on reading the following description with reference to the accompanying drawings, in which: 
     FIG. 1 is a schematic transverse section through a dobby according to the invention, this section showing the arrangement for actuating one of the blades of the dobby in question. 
     FIGS. 2, 3 and 4 are diagrams illustrating the displacement of the pivoting actuating levers, in forward motion, in reverse motion and in a synchronized dobby, respectively. 
     FIGS. 5 and 6 show on a larger scale the section of one and the other notch made on the periphery of one of the lateral plates of the dobby according to FIG. 1. 
    
    
     Referring now to the drawings, in the same manner as in FIG. 1 of the drawings of U.S. Pat. No. 4,444,225 mentioned hereinabove, FIG. 1 shows at 1 the main shaft of the dobby, driven by an intermittent movement of rotation with a stop every 180°. This shaft 1 receives a series of roller bearings, of number equal to that of the heddle frames of the loom, and on each roller bearing is idly mounted an eccentric 2 laterally fixed to a plate element 3. On each eccentric 2 is idly mounted the opening of a connecting rod 4 whose free end is coupled to a pivoting arm 5 which, through a cable 6a, causes vertical displacement of the heddle frame 6 of the blade in question. Between two contiguous eccentrics 2, the shaft 1, provided with teeth, bears a drive disc 7 which is fixed thereto and on whose periphery are cut two diametrically opposite radial drive notches 7a. These notches 7a are adapted to receive, selectively, the terminal finger 8a of a pawl 8 articulated on a pin 9 borne by the lateral plate 3 of the corresponding eccentric 2; a spring 10 tends permanently to return the finger 8a of the pawl 8 in the direction of shaft 1. 
     Control of each pawl 8 is achieved by two pivoting levers 11 pivotally borne by fixed pins 12 oriented parallel to shaft 1. Each lever 11 is in the form of a bracket and is biassed by a spring 13 to abut against a corresponding fixed stop 14. These two stops 14 thus define on each lever 11 an actuating tail 11a, adapted to be controlled by push elements (arrows 15) of the reading device of the dobby. 
     Opposite its tail 11a, each lever 11 presents a nose element 11b, diametrically opposite the similar nose element 11b of the other lever with respect to shaft 1; each nose element 11b is adapted to engage in an immobilizing notch 3a made radially in a projecting ramp or lug 3b of the plate 3. Opposite this notch 3a, the tilting pawl 8 borne by the plate in question comprises a terminal heel 8b adapted to actuate said pawl by contacting the nose element 11b engaged in said notch 3a. 
     The foregoing desription is vertually identical to that given in U.S. Pat. No. 4,444,225 mentioned above, with the result that it does not require detailed explanation as to the normal functioning of the dobby. It will suffice to recall that, in the absence of actuation of the push elements 15 of the reading device, the springs 13 tend, upon each stop of the plate 3 opposite the nose element 11b of one or the other of the two pivoting levers 11, to engage said nose element in the notch 3a, which has the simultaneous effect of angularly immobilize said plate (and with it, the eccentric 2 and the connecting rod 4) and also to cause disengagement of the pawl 8 by withdrawal of its finger 8a from the notch 7a in which it was introduced. On the other hand, when a lever 11 has its actuating tail depressed by a push element 15 against the spring 13 which is associated therewith, the pawl 8, under the action of spring 10, tends to engage its finger 8a in one or the other of the two notches 7 a of the corresponding disc 7, thus ensuring coupling between said disc and the eccentric 2 and consequently effecting actuation of the connecting rod 4 and the heddle frame 6 during each rotation of shaft 1 through 180°. 
     It should be observed here that, for the finger 8a to be engaged in a notch 7a, it is obviously indispensable to have a perfectly precise positioning of parts 7 and 8. Furthermore, it will be noted that, once this engagement is effected, the action of the push element 15 on the lever 11 must be maintained somewhat after the shaft has resumed its movement taking with it the disc 7 and the eccentric 2. In the diagram of FIG. 2, F 1  indicates the direction of rotation of shaft 1, 11 the relative displacement of the lever in question and A the stopping time of the rotation of shaft 1. It can therefore be observed that the nose element 11b of lever 11 remains disengaged from notch 3a for a short lapse of time α after the said shaft has resumed its rotation. 
     If it is now desired that shaft 1 and the whole of the dobby be capable of rotating in opposite direction F 2  (FIG. 3), the lapse of time α for maintaining the control of pawl 8 will be located on the opposite side from that shown in FIG. 2. However if it is intended to produce a synchronized mechanism adapted to operate equally well in both directions F 1  and F 2 , two lapses of time α disposed on either side of the stop time A of shaft 1 must be provided, as illustrated in FIG. 4. 
     Now, if this arrangement were adopted in the case of the rotating dobby according to U.S. Pat. No. 4,444,225, the nose element 11b would be withdrawn from the notch 3a before the drive disc 7 is completely stopped. Under these conditions, the eccentric 2, under the effect of the vibrations inherent in the continuous rotation of parts 1 and 7, would risk off-setting angularly with respect to said parts, in which case one notch 7a would no longer be located in exact register with the finger 8a of the pawl 8. There would then be a defective selection. 
     To overcome this drawback and to allow a satisfactory synchronized rotating dobby to be produced in practice, the present invention consists in providing each of the plates 3 of the dobby with a projecting ramp or lug 3c provided opposite the ramp or lug 3b mentioned above, and in cutting in this second lug 3c a second notch 3d diametrically opposite immobilizing notch 3a. 
     FIGS. 5 and 6 clearly show the profiles of the two notches 3a and 3d of the same plate 3 and it will be observed that the lateral walls of the notch 3a, relatively deep, are oriented parallel to the oblique sides of the nose element 11b to give a perfectly precise angular position to plate 3 and thus to ensure effective hold for as long as contact is maintained. However, the notch 3d is on the other hand cut to a smaller depth and comprises flared lateral walls, oriented parallel to the end bevels of the sides of the nose element 11b. 
     It will be understood that, under these conditions, cooperation of a nose element 11b with notch 3d holds the angular immobilization of the plate 3 during lapses of time α, both in forward motion and in reverse. On the other hand, due to the flared section of notch 3d, the retaining action cannot oppose rotation of the plate, because nose element 11b is automatically ejected when said plate starts a new movement of rotation after stoppage. 
     The engagement of nose element 11b of one or the other of the two levers 11 of each blade in the corresponding notch 3d makes it possible to effect a second positioning of the eccentric 2 by the second lever 11, which positioning remains during lapse of time α and consequently avoids any risk of untimely angular offset. It will further be noted that since the release of pawl 8 occurs before stoppage A of shaft 1, said pawl has the whole period of this stoppage to penetrate its finger 8a into notch 7a so that very high operational speeds may thus be attained without risk of error. 
     It must, moreover, be understood that the foregoing description has been given only by way of example and that it in no way limits the domain of the invention which would not be exceeded by replacing the details of execution described by any other equivalents. In particular, the invention may be applied to dobbies in which the actuating elements are not constituted by eccentrics associated with connecting rods, but by cams sectioned to control roller-bearing levers coupled to the heddle frames 6. In the same way, and although the tilting pawls seem to be the most advantageous embodiment for the mobile coupling mechanism, radially displaced keys may, however, be employed.