Abstract:
A motive assembly for moving a plurality of warp yarns ( 32 ) in a loom between upper and lower shed positions, the motive assembly including a plurality of selectively controllable ultrasonic cyclic motors ( 10 ), each of which is drivingly connected to one or a group of said warp yarns ( 32 ) for moving the warp yarn(s) ( 32 ) between upper and lower shed positions.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a motive assembly for selectively controlling shedding of warp threads in a loom. 
     SUMMARY OF THE INVENTION 
     According to a general aspect of the present invention there is provided a motive assembly for moving a plurality of warp yarns in a loom between upper and lower shed positions, the motive assembly including a plurality of selectively controllable ultrasonic cyclic motors, each of which is drivingly connected to one or a group of said warp yarns for moving the warp yarn(s) between upper and lower shed positions. 
     Preferably the ultrasonic cyclic motor is a piezo motor, preferably operating at a frequency of between 20-40 KHz. 
     The motor may be drivingly connected to the warp yarn by a rigid elongate heald rod which is driven by the motor. The motor may directly contact the elongate heald rod in order to displace it longitudinally. Alternatively, the motor may drive the heald rod indirectly via a transmission means such as a drive gear or wheel. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     Various aspects of the present invention are hereinafter described with reference to the accompanying drawings, in which: 
     FIG. 1 is a schematic perspective view of a first embodiment according to the present invention; 
     FIG. 2 is a side view of the first embodiment showing additional detail; 
     FIG. 3 is a side view similar to FIG. 2 showing a modification to the first embodiment. 
     FIG. 4 is an end view of a second embodiment according to the present invention. 
     FIG. 5 is a view of the assembly showing a heald rod connected to a harness; 
     FIG. 6 is a side view of a third embodiment according to the present invention; 
     FIG. 7 is a side view of a fourth embodiment according to the present invention; and 
     FIG. 8 is a schematic diagram illustrating the principle of operation of an ultrasonic motor as used in the present invention; 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring initially to FIG. 8, there is shown an ultrasonic motor  10  including a casing  11  which houses a drive finger  12 . The drive finger  12  is arranged to cyclically move along a cyclic path from a retracted position A (as shown) to an extended position B (shown in broken lines) and then whilst in its extended position, to the position C and then retracted to position D and then whilst in its retracted position, to position A. 
     The finger  12  is driven at high speed through the cycle of positions A,B,C and D, preferably by piezo-electric elements (not shown) housed within the casing  11 . 
     The direction of movement through the cycle may be A to B to C to D or may be reversed, viz A to D to C to B depending upon the applied electrical current. 
     By placing a member  14  to be driven in the path of the finger  12  whilst it moves between positions B to C (or vice versa), it is possible for the finger  12  to drive, in a stepwise manner, the member  14  in the same direction of travel. 
     This type of motor operates at high speeds, typically at cycles of between 20 to 140 KHz. The motor typically has a cross-sectional dimension of about 8 mm×4 mm and a length of about 25 mm. 
     A first embodiment of the invention is illustrated in FIGS. 1 and 2. 
     In this embodiment, a rigid and elongate rigid heald rod  30  is directly connected to a heald eye  31  through which a single warp yarn  32  passes. 
     A drive wheel  40  having a frictional surface for frictionally driving the heald rod  30  is provided for movement of the heald rod  30 . The drive wheel  40  is rotated by a motor  10  driving a shaft  39  upon which wheel  40  is fixedly mounted. A reaction roller  41  is resiliently urged towards wheel  40  to maintain frictional contact between the wheel  40  and heald rod  30 . 
     The roller  41  is resiliently urged by biasing means  44  which may be a spring  45  or other compression material. If desired, the roller  41  may be replaced by a static member, such as a ceramic plate, which makes sliding contact with the heald rod  30 . The heald rods move a plurality of warp yarns in a loom between upper and lower shed positions singly or in groups. 
     Preferably, as shown in FIG. 2, upper and lower guides  50 , 51  are provided for guiding longitudinal movement of the heald rod  30 . The guides  50 ,  51  not only positively define the longitudinal path of movement of the heald rods but also provide support against lateral flexure of the rod. Such support enables relatively thin heald rods  30  to be used. 
     Preferably, sensing means (not shown) are provided for cooperation with the heald rod  30  in order to sense the longitudinal position of the heald rod  30  in order to determine when it has reached its upper and/or lower shed position. 
     Preferably when the heald rod  30  is at its upper or lower shed position, the motor  10  is de-activated with the finger  12  in its extended position. This enables the finger  12  to act as a brake to restrain movement of the heald rod  30 . 
     In FIG. 3 there is provided a modification to the arrangement shown in FIGS. 1 and 2 wherein an additional motor  10 ′ is provided for driving shaft  39 . 
     Preferably, as seen in FIGS. 1 to  3 , the motors  10 , 10 ′ are arranged to extend in the direction of movement of the heald rod  30 . This enables a compact arrangement to be achieved and helps to achieve a high density of warp yarns. 
     A further modification is shown in FIG. 4 wherein more than one motor  10  is arranged along the shaft  39 . This modification applies to the arrangements shown in both FIGS. 1 and 3. 
     In FIG. 5, the heald rod  30  is shown as being connected to a harness  60  of flexible cords  61 . This enables a single heald rod  30  to control movement of a group of warp yarns. 
     A further modification to the arrangements shown in FIGS.  1 , 3  and  4  is illustrated in FIG. 6 wherein biasing means  70 , for example in the form of a spring or an elastic cord, such as Lycra, is provided for applying tensile forces to the heald rod  30 . 
     A further embodiment  200  is illustrated in FIG. 7 wherein motors  10  are arranged to directly drive the heald rod  30  by the fingers  12  actually making contact therewith. 
     Preferably at least a pair of opposed motors  10   a  and  10   b  are provided operating on opposite sides of the heald rod  30 . 
     As illustrated two pairs of motors are provided. However, it will be appreciated that one or more motors  10  may be positioned to one side only of the heald rod  30  and that a reaction member be located on the other side. 
     It will be appreciated that the heald rods and motors  10  may be directly incorporated into a loom or may be incorporated into a separate jacquard machine for being situated or mounted on a loom. 
     It will be noted the shaft  39  and wheel  40  are of different diameter and so the peripheral speed of the wheel is higher than that of the shaft  39 . Typically the ratio is 1:3. 
     However, it will be appreciated that the wheel  40  may have the same or smaller diameter than the shaft  39 .