FIELD OF THE INVENTION 
     The invention relates to a connecting rod extending between the heddle frame of a weaving machine and the heddle frame actuating lever of a shed-forming machine which controls same, which connecting rod has at least one pivot joint arranged transversely with respect to the longitudinal direction and which consists preferably of two partial bolts which can be moved into one another and which rest on one another, wherein each partial bolt is secured to a plate which can be moved at least partially axially with respect to the pivot joint, and which is designated to be received in an opening of the heddle frame or the heddle frame actuating lever. 
     BACKGROUND OF THE INVENTION 
     In the case of form-lockingly operating weaving machines, the heddle frames are both during lifting and also during lowering operated directly by the shed-forming machine. This requires a rigid connection between the lifting units of the shed-forming machine and the weaving frame. Connecting elements are known, among others from Swiss Pat. No. 538 559, which are inserted into the heddle frame actuating device, in particular between the heddle frame and the free arm of a lever of the heddle frame actuating device. These connecting elements can carry out various functions. They create the hinged connection to the heddle frame and permit a problem-free exchange of the heddle frame during a changing of the fabric article on the weaving machine. They permit furthermore by changing their length, an adjustment of the basic position of the heddle frame. The connecting element achieves a play-free power transmission and if necessary an easy exchange in the case of a defect, while maintaining the power transmission both during the pull or draw cycle and also during the push cycle. 
     Such connecting elements have usually at least one pivot joint which rests between two sheet-metal plates, which bolt is connected to the free arm of a lever or with the heddle frame. Since modern weaving machines operate at high speeds, there exists the demand that these connecting elements are of a very low mass and yet still very strong. The heretofore used weldable material has proven to be of insufficient strength at high operating speeds and stresses. 
     The purpose of the invention is to provide a connecting element of a light, simple, however, strong structure, of a highly solid material, without using welding or soldering points during assembly. The requirement remains that the pivot joints for facilitating a quick exchange of the heddle frame can be installed and removed easily in axial direction out of the opening in the heddle frame or in the lever. Of course, the connecting element must be arranged within the heddle frame division and may not have any parts which project toward adjacent heddle frames. That is, the width of thickness of the heddle frame is to be equal to or less than the heddle frames. 
     SUMMARY OF THE INVENTION 
     The objects and purposes of this invention are met by providing a connecting rod of the above-mentioned type, which is characterized inventively by two clamping rails which are arranged spaced from one another corresponding with the width of the plates, which clamping rails are connected by at least one operable clamping member, wherein each clamping rail has on each side a groove extending along the longitudinal edge, the profile of which corresponds with the edge profile of the plates and the plates are arranged in pairs between the clamping rails. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     Exemplary embodiments of the invention are illustrated in the drawing, in which: 
     FIG. 1 is a perspective view of a connecting rod embodying the invention; 
     FIG. 2 is a side view of said rod in a released condition and engaged with a heddle frame and actuating lever; 
     FIG. 3 is a top view of the same rod; 
     FIG. 4 illustrates in an enlarged scale a cross-sectional view of said rod; and 
     FIG. 5 is a perspective view of a modified embodiment. 
    
    
     DETAILED DESCRIPTION 
     The connecting rod according to FIGS. 1 to 4 consists of four plates 1,2 and 3,4, which cooperate with each other in pairs. One plate 1,3 of each plate pair has on one free end thereof a pivot bolt part which is a hollow bushing structure 10,30; each of the other plates 2,4 of each plate pair has a pivot bolt part which is a pin 20,40 which is received in the opening in the bushing. The plates are engaged on their edges by two elongated profiled rails 5,6 made of a springy material and clamped therebetween. Each profiled rail has an elongated groove 50,60 therein extending along the longitudinal side edges thereof. The cross sectional shape of the grooves corresponds with the shape of the edges of the plates, for example a V-shaped groove form and a V-shaped edge form. The rails 5,6 are clamped with the plates 1 to 4 positioned therebetween by means of several screws 7. 
     To install the connecting rod, for example in an opening in a heddle frame 21 (FIG. 2), at least one screw 7 is loosened. The springy clamping rails 5,6 are lifted or spread apart, as is illustrated in FIG. 2. The plate 4 can, as is illustrated in FIG. 1, be moved laterally in the axial direction of the pin 40 so that the bushing structure 30 can be introduced into a not-illustrated opening in the heddle frame 21. A fastening of the connecting rod to the heddle frame 21 occurs in a reversed sequence. The connecting rod can be connected to an actuating lever 22 by introducing the bushing 10 into an opening 23 in the lever 22 in a similar manner, as also shown in FIG. 2. 
     Two pairs of plates 1,3 or 2,4 are clamped in a single groove 50,60 in the clamping rails 5,6. To adjust the length of the connecting rod, it is sufficient to loosen at least one screw and to move the two plates which are connected together through a pin-bushing connection. With this, the length of the connecting rod and simultaneously the basic position of the heddle frame can be adjusted. 
     If the connecting rod is to be unchangeable in its length, the plates 1,3 or 2,4 can be made in one piece. FIG. 4 does not show the rails 5,6 cross hatched for reasons of clarity in illustration. 
     FIG. 5 illustrates a modified embodiment. Two of the side plates and the two clamping rails are connected to one single tubelike part 8 of rectangular cross section. A slot 90 exists between the clamping parts 9. However, one will recognize from the drawing that the grooves 50,60 and a bushing structure 10 are within the tubelike part 8. Reference numeral 3 identifies one of the two plates to be inserted. The plates 3 are in turn clamped between the grooves 50,60 by a not-illustrated screw received in slot openings 70. The part 8 may have continuous grooves 50,60 extending lengthwise of the connecting rod. The bushing 10 and pin 20 in FIG. 5 are similar to and cooperate in the same manner as the bushings 10 and 30 and pins 20 and 40 described hereinabove with respect to the embodiment of FIG. 1. The plates supporting the bushing 10 and pin 20 in FIG. 5 are flexible, so that the free ends thereof can be pulled away from each other to separate the pin 20 from engagement with the bushing 10. 
     Although particular preferred embodiments of the invention have been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the rearrangement of parts, lie within the scope of the present invention.
A connecting rod having two clamping rails between which are clamped plates extending in a plane perpendicular to the plane of the clamping rails. The clamping is accomplished by screws. The plates have pivot joints which can be moved into one another at their ends. The connecting rod is adjustable in length.