Abstract:
An electronic jacquard including a plurality of elongate heald hooks ( 1   a   , 1   b ) movable longitudinally between upper and lower shed positions and a plurality of electrically operable selection devices ( 50 ) for co-operation with the heald hooks ( 1   a   , 1   b ) for selectively retaining the heald hooks ( 1   a   , 1   b ) at one of said shed positions, each selection device including a latch ( 4   a   , 4   b ) movable between a latched position and a non-latched position, the latch ( 4   a   , 4   b ) when at said latched position being capable of latching engagement with the heald hook ( 1   a   , 1   b ) in order to retain it at said shed position, and an ultrasonic cyclic motor ( 55 ), preferably a piezo-electric motor, drivingly arranged to move the latch ( 4   a   , 4   b ) from its non-latched position to its latched position.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an electronic jacquard, in particular for controlling warp selection in a weaving loom. 
     BACKGROUND OF THE INVENTION 
     In conventional electromagnetic jacquards, see for example EP 0188074, the jacquard selectively controls raising and lowering of warp yams between upper and lower shed positions. 
     In EP 0188074 a pair of hooks are connected via a pulley to one or more harness cords which in turn is (are) connected to healds through which the warp yarns pass. 
     The jacquard is provided with selection devices which selectively operate to capture one or other of a pair of hooks when that hook is at its uppermost position. This action, in co-operation with the pulley, results in the harness cord raising or retaining the heald and warp yarn at the top of the V shaped shed opening on the warp bed on the loom. Not to select/capture the hook results in the heald/warp lowering or remaining at the bottom of the V shaped shed opening. 
     In other types of jacquard, a single hook is connected to the harness cord such that raising/lowering of the single hook directly results in raising/lowering of the heald. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention there is provided an electronic jacquard including a plurality of elongate heald hooks movable longitudinally between upper and lower shed positions and a plurality of electrically operable selection devices for co-operation with the heald hooks for selectively retaining the heald hooks at one of said shed positions, each selection device including a latch movable between a latched position and a non-latched position, the latch when at said latched position being capable of latching engagement with the heald hook in order to retain it at said shed position, and an ultrasonic cyclic motor, preferably a piezo-electric motor, drivingly arranged to move the latch from its non-latched position to its latched position. 
     Preferably the latch is biased to its non-latched position so as to be capable of moving from its latched position to its non-latched position under the influence of said bias. 
     Preferably the latch is mounted on a support arm which is formed of a resilient material, preferably spring steel, the arm being fixedly mounted at one end to a body of the selection device and carrying said latch at its opposite end. 
     Preferably the piezo-electric motor is arranged to move an actuator member which engages the support arm, preferably at a location intermediate the ends of the arm, in order to move the latch to its latched position. 
     Preferably, the hooks are arranged in pairs for raising/lowering a harness pulley, and each selection device preferably includes a pair of latches and a single motor arranged to control movement of both latches to their respective latched positions. 
     Preferably each latch is arranged to be rotated upon retaining engagement with a hook when at its latch position, biasing mans being provided to resist said rotation. 
     According to another aspect of the present invention there is provided an electronic jacquard including a plurality of elongate heald hooks movable longitudinally between upper and lower shed positions and a plurality of electrically operable selection devices for co-operation with the heald hooks for selectively retaining the heald hooks at one of said shed positions, each selection device including a latch movable between a latched position and a non-latched position, the latch when at said latched position being capable of latching engagement with the heald hook in order to retain it at said latch position, the latch when at said latched position being movable between a retention position and a release position, biasing means being provided to resiliently bias the latch to its release position, the hook and latch co-operating such that the hook on engagement with the latch causes the latch to move to its retention position against said resilient bias, and an electrically operable actuator for selectively moving the latch to its latched position. 
     Preferably the actuator is an ultrasonic cyclic motor, preferably a piezoelectric motor. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     Reference is now made to the accompanying drawings, in which: 
     FIG. 1 is a schematic side view of an embodiment according to the present intention illustrated in a first operational position; 
     FIGS. 2 to  7   a/b  are similar views to FIG. 1 showing the embodiment in different operational positions; 
     FIG. 8 is a front view of an upper portion of a heald hook shown in FIG. 1; and 
     FIG. 9 is a schematic diagram illustrating the principle of operation of an ultrasonic motor as used in the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring initially to FIG. 1, there is shown a selection device  50  arranged to control a pair of heald hooks  1   a ,  1   b  which operate to raise and lower a harness pulley (not shown). 
     The selection device  50  includes a body  9  made for example from plastic, having guide channels  3   a ,  3   b  for guiding longitudinal movement of the upper portion of the heald hooks  1   a ,  1   b  respectively. 
     The selection device  50  includes an electrically operable actuator  55  which is arranged to drive an actuator member  5  either to the left or right as required. Preferably the actuator  55  is an ultrasonic cyclic motor, preferably a piezo-electric motor having an elongate casing  11  from one end of which projects a drive output in the form of a drive finger  2 . The actuator member is preferably in the form of a block or rod of a suitable material which is connected at opposite ends to arms  58   a ,  58   b  of a bracket  58 . The arms  58   a ,  58   b  are movable to enable movement of the actuator member  5  to the left or right of casing  111 . In addition the bracket is biased by biasing means preferably in the form of a spring  7 , in order to maintain positive contact between the drive finger  2  and the actuator member  5 . 
     Referring initially to FIG. 9, there is shown an ultrasonic motor  110  including a casing  111  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  111 . 
     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. 
     The selection device  50  also includes a pair of latches  4   a  and  4   b  which are each movable from a non-latched position (as seen in FIG. 1) to a latched position (as seen by reference to the latch co-operating with heald hook  1   a  in FIG.  2 ). 
     Each of the latches  4   a  and  4   b  is mounted on one end of a resilient arm  10 , the opposite end of arm  10  being fixedly mounted to the body  9 . Accordingly the resilient arm  10  is arranged to act as biasing means for biasing each of the latches  4   a  and  4   b  to its non-latched position. 
     Preferably each of the latches  4   a  and  4   b  is formed from a moulded plastics material. Preferably each arm  10  is formed from a spring strip material such as spring steel. 
     The actuator member  5  is arranged to engage the arm  10  at a position intermediate the ends of the arm  10  and so enables a suspended latch  4   a  or  4   b  to be pushed through a hole  6  formed in the hook  1  (see FIGS.  1  and  8 ). Thus each selection device  50  when actuated acts to move latches  4   a  and  4   b  into the holes  6  in their respective hooks  1   a  and  1   b  and thus capture the hook when required. The length of the hook  1  above the hole  6  is not important but the hole  6  must align with the latches  4   a  and  4   b  when the hook is raised to its uppermost position. 
     In FIG. 1 the motor  2  has moved the actuator member  5  to a central position where the latches  4   a  and  4   b  are not required to engage with the hole  6  in either hook  1 . Hook  1   a  is shown at its uppermost position and hook  1   b  is at its lowest position. 
     FIG. 2 shows a latch  4   a  at its latched position whereat it has been pushed through the hole  6  of hook  1   a  by actuator member  5  following the operation of motor  2  moving the actuator member  5  to the left. Since both latches  4   a  and  4   b  are biased towards the centre, ie. to their non-latched position, then latch  4   b  has been allowed to move towards the left moving further away from hook  1   b.    
     FIG. 3 illustrates an example of pre-selecting latching of a heald hook. 
     As required by prior art EP 0188074 at some time later in the cycle from the selection point, the hook  1   a  has been captured by latch  4   a  at its uppermost position and hook  1   b  has been raised by its lifting member up from the lowest position of hook travel. Since in this case it is necessary to retain the second hook  1   b  at its upper position, the motor  2  has been actuated to move the actuator member  5  to the right. As illustrated in FIG. 3, this has caused latch  4   b  to engage the upper portion of hook  1   b  and has thus pre-loaded the latch  4   b  ready to engage hole  6  in hook  1   b  when the hook is raised to the uppermost position (this is shown in FIG.  4 ). It is not essential but preferable that this pre-load function is used in high speed jacquards. 
     In accordance with the preferred embodiment of the invention, the latch  4   a  has been mechanically interlocked with hook  1   a  and no longer requires actuator member  5  to hold it at its latch position. 
     For practical reasons there may be a neutral position wherein actuator member  5  is located central to body  9  and at this position neither latch  4   a  nor  4   b  is pushed by member  5 ; ie. both latches are in their non-latched position. However, this neutral condition is not essential. It will be appreciated that the member  5  does not require a neutral position between latches  4   a  and  4   b  for the selection device to operate correctly. For example to avoid retention of hook  1   a , motor  2  is actuated to move member  5  to the right against latch  4   b  whether or not latch  4   b  is engaged in hook  1   b  as the spring component of latch  4   b  takes up the travel of block  5  to the right. 
     FIG. 6 illustrates the mechanical load path. 
     Starting with the downward force on the hook L 1  the load is transferred via the latch L 2 , arm L 3 , latch anchor L 4 , selector body L 5 , L 6  and finally the interface contact between the selector body and the frame L 7 . 
     Apart from friction contact between the spring arm L 3  and the actuator member  5 , the load path misses out the actuator  55  and member  5  thus avoiding any distortion of the actuator material or connecting wires. The actuator life is not effected by the selector loads allowing the selector body to be manufactured in a compact, flexible scale. 
     In FIGS. 7 a ,  7   b  there is illustrated an example of achieving impact reduction. 
     It is normal for jacquard hooks to be captured by stiff latches. This has the effect of suddenly stopping the harness while it is in motion causing an impact on the latch and the harness. 
     Similarly, when the hook is lifted from the latch there is a sudden motion of the harness which results in a steep force change in the selector device and that member of the jacquard used to lift the hook. 
     Both the forces produced when retaining the hook on the latch and the forces produced when the hook is lifted from the latch can be reduced by incorporating a resilient latch design. FIG. 7 a  shows the position of latch  4   a  before the hook  1   a  has moved down onto the latch. This position is referred to as the release position. A short time later the hook  1   a  has moved down and the position of the latch  4   a  is changed to that shown in FIG. 7 b . This position is referred to as the retention position. 
     The hook  1   a  has loaded the latch  4   a  which due to the shape of the recess  11  in the selector body  9  and the resilience of the spring arm  10  has allowed the latch  4   a  to rotate creating a torque reaction which reduces the deceleration of the hook and harness inertia and thus impact. 
     Similarly when the hook is raised from the latch by its lifting member on the jacquard the situation changes from diagram  7   b  to that of  7   a . During this time the hook lifting is assisted by the reaction force from latch  4   a  thus reducing the force on the hook lifting member and reducing the rate of change of force on the latch. 
     By this means the resilient construction of the latch  4   a  and its recess  11  reduce the effects of capturing and releasing the hook  1   a.    
     It will be appreciated that the preferred embodiment of the invention enables operation of two movable latches for capturing either or both co-operating hooks at the top of their stroke utilising a single ultrasonic piezo motor driving an actuator member against the spring arm carrying the latches. 
     The latches have a mechanical means of interlocking with the hook such that once engaged, the actuator member may be removed from the spring arm while the latch is carrying the downward load of the hook.