Patent Abstract:
In order to make a small space requirement, a low energy requirement and therefore an increased weaving frequency possible in a shedding apparatus, a spring drive is proposed which is connected to magnetically acting holding means. The holding means are capable of holding the heddle frame in an upper shed position and in a lower shed position counter to the spring force. Furthermore, the heddle frame is connected to a linear motor. A heddle movement can be initiated by said linear motor. According to the invention, the spring drive is configured as a tension/compression spring which is designed in such a way that, during operation of the heddle frame at the resonant frequency of the spring drive the greater part of the kinetic energy can be obtained from the spring drive.

Full Description:
This application claims priority of PCT application PCT/CH2007/000475 having a priority date of Sep. 28, 2006, the disclosure of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The invention relates to a shedding apparatus for a weaving machine, in particular for a ribbon weaving machine. 
     BACKGROUND OF THE INVENTION 
     Shedding apparatuses for weaving machines which have a heddle apparatus and a heddle frame are known in principle from numerous documents. WO-A-98/24955 discloses a weaving machine in which the dragging element for dragging the warp threads of a weaving machine and comprising for example a heddle frame is clamped between two springs. There, the dragging element oscillates and a holding device is capable of stopping the oscillation for a certain time, and so forming a shed during the weft insertion. The holding device from WO-A-98/24955 is intended to be controllable by means of a control unit. Permanent magnets which can be influenced by electromagnets have already been proposed for this. 
     However, the configuration with the two springs of WO-A-98/24955 takes up a relatively large space, as the drawings there also show. Furthermore, the controlled holding device is complicated, even if it takes the form of permanent magnets, because of the electromagnetic influence on the permanent magnets. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to improve a shedding apparatus for weaving machines which have a heddle apparatus and a heddle frame. 
     The object is achieved by a shedding apparatus. In this case, the measures of the invention firstly result in a very small space requirement. The kinetic energy of the heddle motion can be provided for the most part by a tension/compression spring. The tension/compression spring is in this case set up in such a way that, in an upper position and in a lower position, it respectively provides a great potential energy as a force which moves the heddle in the direction of a middle position. The middle position is preferably characterized in that, in this position, no potential energy is emitted by the spring, but instead the heddle has a maximum speed, and is then moved further into the other position respectively, that is to say the lower position or the upper position, the tension/compression spring then being able to take up the kinetic energy of the heddle in the form of potential energy. In order, however, to make a controlled heddle motion possible, and optional pausing in the upper position or lower position, magnetically acting holding means are respectively provided in the upper position and the lower position, means which stop the heddle motion and hold the heddle in the respective position. In order to make a controlled motion possible, an optionally switchable, electric linear motor is additionally provided. Together with the spring force, it overcomes the holding force of the holding means and can therefore free the heddle from its held position. In principle, the linear motor is therefore intended for releasing the heddle from the holding means and initiating the heddle moving operation. Furthermore, the linear drive means serves the purpose of compensating for energy losses and adapting the heddle apparatus to changing operating conditions. The heddle apparatus is controlled exclusively by the control of the linear motor. 
     It is advantageous if at least 75% of the kinetic energy is taken from the tension/compression spring, and the linear motor provides at most 25% of the kinetic energy. 
     An advantageous refinement of the invention is obtained if the holding means are formed in an uncontrolled manner as permanent magnets which interact with magnetic counter-holders. 
     A form is particularly advantageous, since the entry of the magnetically acting holding elements, which are advantageously formed from iron, into the effective range of the coil magnets avoids direct contact, resulting in particularly low-noise running of the shedding apparatus. 
     Advantageously, no force is exerted on the heddle frame in a third shed position, between the upper shed position and the lower shed position. 
     It is particularly advantageous with respect to the allocation of space and the dynamic properties of the system if the tension/compression spring is formed as a leaf spring, and thereby formed in an ring-like manner. It goes without saying that in this context a ring does not have to be interpreted as a circular formation. Rather, the term “ring-like” is to be understood as meaning closed formations such as round, oval, elliptical or similarly formed springs, which are possibly suitable for accommodating components within them for the purpose of reducing the space requirement. In one particular embodiment, it is provided that the spring force to be applied is divided between two springs, which are arranged at the ends of the heddle apparatus. In order to eliminate the transverse forces, it is advantageous if the heddle apparatus is formed symmetrically with respect to its center axis. 
     An advantageous shedding apparatus has a number of heddle apparatuses arranged in a group. It is particularly advantageous in this respect if the tension/compression springs are arranged alternating with one another, one or more on top and one or more underneath. 
     In the case of the embodiment with stop magnets and magnetic counter-holders, it is more advantageous if they heddle apparatus has a support frame that is connected to the heddle frame and encloses a fixed block part. In this case, the stop magnets and the magnetic counter-holders are arranged on the upper and lower parts of the support frame or on the upper side and underside of the block part, respectively. If the block part then has a respectively adjustable upper part and lower part, these can be adjusted according to the inclination of the running of the warp threads of the upper shed and the lower shed, respectively. 
     It is advantageous if the linear motor has a flat coil, which is arranged in the plane of the heddle frame. 
     The aforementioned elements to be used according to the invention, as well as those claimed and described in the following exemplary embodiments, are not subject to any particular conditions by way of exclusion in terms of their size, shape, use of material and technical design, with the result that the selection criteria known in the respective field of application can be used unrestrictedly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of a shedding apparatus for weaving machines with a heddle apparatus and a heddle frame are described in more detail below on the basis of the drawings, in which: 
         FIG. 1  shows the weaving region of a weaving machine with a shedding apparatus according to a first embodiment of the present invention, in side view; 
         FIG. 2  shows a single heddle apparatus of the shedding apparatus from  FIG. 1  in a view from the front; 
         FIG. 3  shows a force diagram for the sequences of movements of the heddle motion of the apparatus according to  FIGS. 1 and 2 ; 
         FIG. 4  shows a shedding apparatus with a heddle apparatus according to an alternative embodiment of the present invention in a perspective view; 
         FIG. 5  shows an enlarged representation of a detail from  FIG. 4 ; 
         FIG. 6  shows the weaving region of a weaving machine with a shedding apparatus according to a further embodiment of the present invention, in side view; and 
         FIG. 7  shows a single heddle apparatus of the shedding apparatus from  FIG. 6  in a view from the front. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first exemplary embodiment for carrying out the present invention is represented in  FIGS. 1 and 2 . 
       FIG. 1  shows the diagram of the weaving region of a weaving machine in side view. A shedding apparatus with a number of heddle apparatuses  2  serves the purpose of opening warp threads  50  to form a weaving shed with an upper shed and a lower shed, into which a weft insertion element inserts a weft thread with every change of shed. A weaving reed  42  beats up the inserted weft thread at the edge of the fabric produced. 
     As  FIG. 2  reveals, each heddle apparatus  2  includes a heddle frame  4 , with heddle supports  6 , on which heddles  40  for guiding the warp threads  50  are arranged. In the present example, the heddles  40  are grouped together in four groups for four weaving locations of a ribbon weaving machine. The heddle frame  4  is connected to a linear motor  12  by way of a heddle connector  8 . In  FIG. 1 , the heddle apparatus  2  has at the top and bottom and upper, fixed stop magnet  24  and a lower, fixed stop magnet  26 , which in the state in which they are brought into close proximity, interact with the respective magnetic counter-holders  30  and  32 , which are assigned to the moved heddle frame  4 . 
     In  FIG. 2 , the heddle apparatus  2  is represented from the front. Shown in  FIG. 2  as an addition to the representation in  FIG. 1  is a leaf spring  14 , which is formed in a ring-like manner and assists a heddle motion in the vertical direction. One particular feature of this exemplary embodiment is that here the lower stop magnet  26  is accommodated within the leaf spring  14  and the corresponding lower magnetic counter-holder  32  is mounted on the leaf spring  14 . The stop magnet  24  is mounted on the spring holder  20 , which holds the leaf spring. In this exemplary embodiment, the upper magnetic counter-holder  30  is attached to the heddle frame  4 , while the upper stop magnet  24  is fixedly mounted. 
     The heddle apparatus is formed symmetrically with respect to a center line M, in order to avoid transverse forces. 
     The operating mode of the shedding apparatus is now described below, according to the exemplary embodiment described above. The heddle frames  4  with the heddle supports  6  are raised and lowered for the purpose of shedding. As the driving means for this movement, the spring drive, in the exemplary embodiment the leaf spring  14  arranged on the spring holder  20 , and a linear motor  12  interact. The linear motor  12  comprises a flat coil  34  and an upper coil magnet  36  and a lower coil magnet  38 , which are arranged on the heddle connector  8 . During the lifting or lowering movement, the greatest proportion of energy is applied by the spring drive. However, the movement is initiated by the linear motor  12 , as described below. 
     By means of the upper stop magnet  24  or the lower stop magnet  26  and the respective magnetic counter-holders  30  and  32 , the heddle frame  4  is securely held in the upper end position or the lower end position—which correspond to the upper shed position and the lower shed position of the warp threads of a weaving shed—as long as the linear motor  12  is not in operation. This is achieved by the stop magnets  24  and  26 , which are formed as permanent magnets, having a greater holding force than the restoring force of the leaf spring  14  in the case of the deflection to the end positions. It should be pointed out that the holding force of the permanent magnets  24  and  26  has a short range and is therefore only relevant at all in the vicinity of the magnetic counter-holders  30  and  32 , and consequently only in or in the vicinity of the respective end position. 
     In order then to set the heddle frame  4  in motion, in order therefore to initiate a shedding motion from the upper end position into the lower end position or from the lower end position into the upper end position, the linear motor  12  is put into operation. The sum of the effective forces of the linear motor  12  and the spring force of the leaf spring  14  in the deflected state, that is to say in one of the end positions, is greater than the holding force of the permanent magnets  24  and  26 , respectively. 
     When the holding force of the permanent magnets  24  and  26  is overcome, the motion of the heddle is brought about for the most part by the spring force of the leaf spring  14 , and the linear motor  12  moves along with this motion without significantly contributing to it. When the other end position is reached, that is to say for example when the lower stop magnet  26  enters the effective range of the lower magnetic counter-holder  32 , the renewed end position is reached and the leaf spring  14  remains deflected, since the force of the permanent magnet  26  in this position is greater than the restoring force of the leaf spring  14 , and the linear motor  12  does not assist the latter. 
     The force profile of the motion is shown in the diagram of forces in  FIG. 3 . In the exemplary embodiment mentioned here, the ring-like leaf spring  14  is operated in the linear range, so that the spring force diagram  100  can be represented by a straight line. The spring force is assisted by the warp thread force  106  only insignificantly, so that the warp thread force  106  plays no part here. The stop magnet diagram  102  clearly shows the short range of the magnetic forces, which only act when the stop magnets  24 ,  26  are in the direct vicinity of the magnetic counter-holders  30 ,  32  and an end position has been assumed. The diagram of coil forces  104  of the linear motor  12  has a constant force in the operating mode described here, which may be directed in one direction or the other, depending on polarity. 
     In the exemplary embodiments described here, the linear motor  12  is formed in such a way that, in addition to the upper position and the lower position, a middle position of the heddle can be assumed, and the heddle can be moved from this middle position into the upper position or into the lower position. 
     This operating mode has the purpose that a rest position can be assumed, a position in which the leaf spring  14  does not exert any force on the heddle frame. The heddle apparatus is controlled exclusively by means of the linear motor, which for this purpose is connected to a control unit of a weaving machine in a way that is not represented in any more detail. 
       FIG. 4  and  FIG. 5  show a shedding apparatus according to a second exemplary embodiment, comprising a multiplicity of heddle apparatuses  2   1 - 2   6  with in each case a heddle frame  4  according to a preferred exemplary embodiment. Of the heddle frames  4 , only the heddle supports  6  are represented here. In the embodiment that is shown in  FIGS. 4 and 5 , the heddle frames  4  are connected at the top or bottom by means of a heddle connector  8  to a support frame  10 , which for its part is connected to a linear motor  12  and then further connected to a leaf spring  14  or  16  formed in a ring-like manner. The lower leaf springs  14  are attached to a lower, fixed shedding block  18  with a spring holder  20 , whereas the upper leaf springs  16  are attached to an upper, fixed shedding block  22 , likewise with a spring holder  20 . The leaf springs  14  and  16  act in turn as tension/compression springs and the spring arrangement and adjustment is chosen such that the heddle frames  4  are in the middle shed position in the rest position of the springs  14 ,  16 . 
     In the support frames  10 , the magnetic counter-holders  30  and  32  are respectively attached from the inside at the top and bottom. The lower shedding block  18  and the upper shedding block  22  respectively have at the upper and lower ends a block part  28 , to which stop magnets  24  and  26  are attached. In the present exemplary embodiment, the stop magnets  24  and  26  are arranged in an inclined plane. In this respect, the inclinations are adjustable according to the desired inclination of the running of the warp thread of the upper shed and the lower shed, respectively. 
     The linear motors  12  have in each case electrical conductors  46 , which are led to a connection plate  48 , by way of which the linear motors  12  can be connected to a control unit. 
     A further exemplary embodiment for carrying out the present invention is represented in  FIGS. 6 and 7 . 
       FIG. 6  shows the diagram of the weaving region of such a weaving machine according to a further exemplary embodiment in side view. The shedding apparatus with the heddle apparatuses  2  corresponds to the first exemplary embodiment and is not described any further here. 
     In  FIG. 6 , the heddle apparatus  2  respectively has above and below the flat coil  34  of the linear motor  12  an upper and lower magnetically acting holding element  130 ,  132 —in the exemplary embodiment made of iron—which alternately enter the magnetic field of the coil magnets  26  and  38  and form with them upper and lower holding means  130 ,  36 ;  132 ,  38 . 
     The heddle apparatus is in turn formed symmetrically with respect to a center line M, in order to avoid transverse forces. 
     By means of the upper holding means  130 ,  36  or the lower holding means  132 ,  38 , the heddle frame  4  is in turn securely held in the upper end position or the lower end position—which correspond to the upper shed position and the lower shed position of the warp threads of a weaving shed—as long as the linear motor  12  is not in operation. This is achieved by the holding means having a greater holding force than the restoring force of the leaf spring  14  in the case of the deflection to the end positions. It should be pointed out that the holding force of the holding means has a short range and is therefore only relevant at all in the state in which it has entered the range of the counter-element, and consequently only in or in the region of the respective end position. 
     In order then to set the heddle frame  4  in motion, in order therefore to initiate a shedding motion from the upper end position into the lower end position or from the lower end position into the upper end position, in this exemplary embodiment too the linear motor  12  is put into operation. The sum of the effective forces of the linear motor  12  and the spring force of the leaf spring  14  in the deflected state, that is to say in one of the end positions, is greater than the holding force of the holding means. 
     When the holding force of the holding means is overcome, the motion of the heddle is brought about for the most part by the spring force of the leaf spring  14 , and the linear motor  12  moves along with this motion without significantly contributing to it. When the other end position is reached, the leaf spring  14  remains deflected, since the holding force of the holding means in this position is greater than the restoring force of the leaf spring  14 , and the linear motor  12  does not assist the latter. 
     LIST OF DESIGNATIONS 
     
         
           2  heddle apparatus 
           2   1 - 2   6  group of heddle apparatuses 
           4  heddle frame 
           6  heddle support 
           8  heddle connector 
           10  support frame 
           12  linear motor 
           14  leaf spring 
           16  leaf spring 
           18  shedding block 
           20  spring holder 
           22  shedding block 
           24  upper stop magnet 
           26  lower stop magnet 
           28  block part 
           30  upper magnetic counter-holder 
           32  lower magnetic counter-holder 
           34  flat coil 
           36  upper coil magnet 
           38  lower coil magnet 
           40  heddles 
           42  weaving reed 
           44  reed support 
           46  electrical conductors 
           48  connection plate 
           50  warp threads 
           100  spring force diagram 
           102  magnetic force diagram 
           104  coil force diagram 
           106  warp thread force diagram 
           130  upper holding element 
           132  lower holding element 
         M center line

Technology Classification (CPC): 3