BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a heald frame, and to a weaving machine equipped with at least one such frame. 
   2. Brief Description of the Related Art 
   It is known to equip a weaving machine with heald frames which are to be driven in a vertically oscillating movement by means of an appropriate device, such as a heald loom or a dobby. 
   Such a heald frame first of all comprises a body which is formed by the reversible assembly of two posts and two cross-members. During operation, the posts are substantially vertical, while the cross-members are substantially horizontal. Each cross-member also supports a catching member, also called a bar, which permits the fixing of a corresponding end of the healds of the weaving machine. 
   The invention relates more particularly to such a heald frame which is provided with damping means interposed between the cross-members and the healds in the region of at least one end thereof. In this manner, during oscillation of the frame, some of the direct contact between the catching member and the healds is suppressed, which reduces the vibrations caused by the healds&#39; rebounding on the bars and, consequently, the overall wear to which those various mechanical elements are subjected, while increasing the service life. 
   Heald frames are known which are provided with damping means against which a first end of the heald comes to bear before the opposite end of the heald comes into contact with the corresponding catching member. 
   This known solution has a disadvantage, however, in that it induces substantial bending of the cross-member supporting the damping means. The cross-member is therefore subjected to considerable vibrations, so that it is weakened. 
   SUMMARY OF THE INVENTION 
   In the light of the above, the invention proposes to remedy that disadvantage of the prior art. 
   To that end, the invention relates to a heald frame for a weaving machine. The frame includes two posts and two cross-members and a damping member, each cross-member being provided with a catching member suitable for receiving a corresponding end of at least one heald of the frame. The damping means which are mounted to at least one corresponding catching member or cross-member and against which at least one end of the heald engages when the frame is in a stationary state and the heald is in a rectilinear configuration, such that when a compression zone of a first end of the at least one heald is engaging the damping member, a traction zone at the other end of the at least one heald substantially engages an adjacent catching member. 
   The invention relates also to a weaving machine equipped with at least one heald frame as defined above. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood, and other advantages will become more clearly apparent, in the light of the description which will be given hereinbelow of a weaving machine and of two heald frames in accordance with the principle of the invention, which are given solely by way of non-limiting examples and with reference to the accompanying drawings, in which: 
       FIG. 1  is a skeleton view, in diagrammatic form, of a weaving machine according to the invention; 
       FIG. 2  is a view in transverse section, according to line II-II in  FIG. 1 , showing part of a heald frame belonging to the weaving machine of  FIG. 1 , in particular with regard to the mutual fixing of a cross-member, a catching member and a heald belonging to the frame; and 
       FIG. 3  is a view in transverse section, analogous to that of  FIG. 2 , showing a variant of the invention. 
   


   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   In  FIG. 1 , a dobby  1  of a type known per se is intended to move a heald frame  2  belonging to a weaving machine M, according to a vertically oscillating movement indicated by the arrows F 1  and F′ 1 . To that end, a driving arm  1   a  of the dobby is coupled to each heald frame  2  by means of rods and oscillating levers. The machine M comprises a plurality of frames, generally from six to twenty-four, only one of which is shown in  FIG. 1  for the sake of clarity. 
   Each frame  2  comprises a body which is formed by the assembly of two posts  4 ,  4 ′ and two cross-members  6 ,  6 ′. The posts  4 ,  4 ′ extend generally in a direction parallel to the direction of vertical oscillation Z-Z′ of the frames, namely vertically during operation. In addition, the cross-members  6 ,  6 ′ extend in a direction Y-Y′ perpendicular to the above-mentioned direction Z-Z′, namely horizontally during operation. 
   Each upper and lower cross-member  6  and  6 ′, respectively, is equipped, in known manner, with a corresponding catching member or bar  8 ,  8 ′. The bars  8  and  8 ′, which will be described in greater detail hereinbelow, permit the fixing of the upper and lower ends, respectively, of various healds  10  belonging to the frame  2  of the weaving machine M. 
     FIG. 2  shows the fixing of the upper end of a heald  10  to the upper cross-member  6  by means of the bar  8 . It is to be noted that the fixing of the lower end of the heald  10  to the cross-member  6 ′ is carried out in an analogous manner by means of the bar  8 ′. With this in mind, the mechanical elements of the lower cross-member  6 ′, of the lower bar  8 ′ and of the lower end of the heald  10 , which are analogous to those of the upper cross-member  6 , the upper bar  8  and the upper end of the heald  10 , respectively, bear the same numerals with the associated reference “prime”. 
   The structure of the upper cross-member  6 , which is conventional, will not be described in greater detail in the following. The bottom face of the cross-member  6 , facing the heald  10 , is prolonged by a rib  6   1  extending over the whole of the major dimension of the cross-member. 
   The rib  6   1  is prolonged by a lug  6   2  which, in transverse section, is substantially lozenge-shaped. 
   The catching bar  8  is formed by a thin metal sheet which has been folded back on itself, the thickness e of which is, for example, around 0.7 mm. It comprises first of all a region  8   1  permitting the fixing of the bar  8  to the cross-member  6  by cooperative shaping thereof. 
   More precisely, the fixing region is formed by two limbs  8   21  and  8   22  which are generally L-shaped and the angles of which are disposed facing one another in such a manner as to cover the above-mentioned lug  6   2 . It is also to be noted that the limbs  8   21 ,  8   22  constitute the free ends of the folded metal sheet forming the catching bar  8 . The existence of the lug  6   2 , associated with the limbs  8   21  and  8   22 , accordingly imparts a removable nature to the fixing of the bar  8  to the cross-member  6 . 
   The two limbs  8   21  and  8   22  come together, facing the cross-member  6 , in an intermediate region  8   3  of reduced transverse cross-section. Finally, the region  8   3  is prolonged by a region  8   4  which is intended to catch the heald  10 , which will be described in greater detail in the following. 
   The heald  10  comprises, in conventional manner, a filiform element  10   1  provided with an eyelet  10   2 , shown in  FIG. 1 , for the passage of a warp thread (not shown). At each end of the heald, the filiform element  10   1  is prolonged by two principal limbs  10   3  which define a receiver  10   4  for receiving the bar  8 . The mouth of the receiver is bordered by two teeth  10   5  of the heald, which teeth extend towards one another to form a neck  10   6  of restricted transverse dimensions. 
   Returning to the catching region  8   4 , that region has an approximately rectangular transverse cross-section, the dimensions of which are slightly greater than those of the intermediate region  8   3 . In its lower portion remote from the cross-member  6 , the catching region  8   4  forms a U-shaped reentrant portion  8   5 , the core  8   51  of which is turned towards the cross-member  6 . 
   The reentrant portion serves to hold a damping element  12  of a type known per se, which is a flexible element made, for example, of a polymeric material, an elastomeric material or the like. Such a damping element, which extends over substantially the whole of the major dimension of the cross-member  6 , is held by clamping and/or adhesive bonding in the U-shaped internal volume of the reentrant portion  8   5 . It will be noted that the damping element  12  is received in the receiver  10   4  for receiving the bar  8 . 
   When the weaving machine M is in its use configuration, the intermediate region  8   3  is received in the neck  10   6 , while the catching region  8   4  is received in the receiver  10   4 . The same is true of the lower end of the cross-member, the various mechanical elements being disposed symmetrically relative to the median horizontal axis of the frame  2 . 
   More precisely, s 1  denotes the surfaces of the upper catching bar  8  which are capable of coming to bear directly on the facing surfaces S 1  of the heald, belonging to the two teeth  10   5 . The direct bearing surfaces s 1  and S 1  form a traction zone of the heald, opposite the compression zone, corresponding to the free surfaces of the damping element  12  and those C 1  facing the heald  10 . 
     FIG. 2  shows the heald in a stationary state in which it is substantially rectilinear. When the upper end of the heald is bearing directly, by way of its surfaces S 1 , against the facing upper surfaces s 1  of the bar  8 , the lower end of the heald bears substantially against the lower damping element  12 ′, in the region of its lower compression surfaces C′ 1 . Of course, in a manner not shown in  FIG. 2 , when the lower end of the heald is bearing directly, by way of its traction surfaces S′ 1 , on the surfaces s′ 1  of the lower bar  8 ′, the upper portion of the heald bears substantially, by way of its upper compression surfaces C 1 , against the upper damping element  12 . 
   It should be noted that this arrangement is aimed at nominal manufacturing dimensions, it being understood that the manufacturing tolerances, in particular those relating to the straightness of the cross-members, enable these nominal dimensions to be achieved only approximately, in practice with greater or lesser deviations associated with these geometrical deviations. However, it is the average, or nominal, values which will obey the principle of the substantially simultaneous double contact, as mentioned above. 
   Such a measure is advantageous. The upper and lower cross-members  6  and  6 ′, respectively, are subjected to vibrations during operation, which imparts a variable nature to their spacing. The healds come into contact with the bar and with the damping element, respectively, sometimes by way of their traction surfaces and sometimes by way of their compression surfaces, the impacts on the compression surfaces contributing to damping the vibrations. 
   The fact that substantially simultaneous bearing is provided on the lower or upper traction surfaces and on the upper or lower compression surfaces allows the cross-members  6  and  6 ′ to be operated in a configuration in which the healds are substantially rectilinear. This is favourable to the transmission of a maximum compression force. One of the two cross-members, which acts as a damper, therefore absorbs a considerable force and allows the bending of the other cross-member to be reduced, then providing a traction force. In other words, the heald control force is transmitted by the two cross-members at the same time, which reduces the bending of the cross-members substantially by half. 
   Moreover, during oscillation of the frame  2 , the presence of the upper and lower damping elements  12  and  12 ′, respectively, enables the axial oscillation vibrations of the healds and their impacts on the bars to be reduced. This therefore brings about a reduction in the overall wear to which the healds and the bars are subjected and, consequently, an increase in their service life. 
   In  FIG. 2 , the upper and lower bars  8  and  8 ′ are equipped with damping means  12  and  12 ′, respectively. It is possible, however, to provide only one of the bars  8  or  8 ′ with such damping means, while the other bar  8 ′ or  8  is devoid of such means. In that case, when the only damping means  12  or  12 ′, which are integral with the bar  8  or  8 ′, are in contact with the compression surfaces of the facing end of the heald, the other end thereof is advantageously in contact, by way of its traction surfaces S′ 1  or S 1 , with the other facing catching bar  8 ′ or  8 . 
     FIG. 3  shows a first alternative embodiment of the invention. In that Figure, mechanical elements analogous to those of  FIG. 2  have been assigned the same reference numerals, increased by 100. As in the first embodiment, the mechanical elements of the lower cross-member  106 ′, of the bar  108 ′ and of the lower end of the heald  110  are analogous to those of the upper cross-member  106 , the upper bar  108  and the upper end of the heald, respectively. 
   The heald  110  in this embodiment differs from the preceding example in that it is asymmetrical. Each of its ends is generally C-shaped, the filiform element  110   1  being prolonged by a single limb  110   3  from which there extend an intermediate tooth  110   31  and a return portion  110   32 . The tooth and the return portion, which are directed towards one another, define with the limb  110   3  two channels  110   41 ,  110   42 . 
   In contrast to the preceding example, the catching bar  108  is fixed to the cross-member  106  by adhesive-bonding or riveting means (not shown) or alternatively by other equivalent means. The catching bar  108  comprises a catching region  108   4 , the ends of which penetrate into the channels  110   41 ,  110   42 . 
   The cross-member  106  is further provided with a damping element  112  which is fixed, for example, by adhesive bonding. In contrast to the first embodiment, the damping element  112  is situated opposite the free end E of the heald, relative to the filiform body  110   1  thereof. 
   Analogously to the first embodiment,  FIG. 3  shows the heald  110  in the stationary state in which the heald is substantially rectilinear. When the upper end of the heald is bearing directly, by way of its surfaces S 101 , against the facing upper surfaces s 101  of the bar  108 , the lower end of the heald bears substantially against the lower damping element  112 ′, in the region of its lower compression surfaces C′ 101 . Moreover, in a manner not shown in  FIG. 3 , when the lower end of the heald is bearing directly by way of its traction surfaces S′ 101  on the surfaces s′ 101  of the lower bar  108 ′, the upper portion of the heald bears substantially, by way of its upper compression surfaces C 101 , against the upper damping element  112 . 
   The invention is not limited to the examples that have been described and shown. 
   For example, the heald may have a different form from that shown in  FIGS. 2 and 3 . For example, the heald may have a generally J-shaped cross-section, in a manner known per se. In that case, the heald is equipped with a principal limb, while it is provided with only an upper return portion and does not have a lower tooth. The heald may also have an O-shaped cross-section, in a manner known per se, for frames equipped with sliders, likewise of the conventional type. 
   Moreover, the heald may have a generally C-, J- or O-shaped cross-section, while the damping means are received in the internal volume of the C, J or O, in contrast to the embodiment of  FIG. 3  and similarly to the embodiment of  FIG. 2 . Moreover, the heald may be U-shaped, while the damping means are situated opposite the free end of the heald, relative to its filiform element, in contrast to the embodiment of  FIG. 2  and similarly to  FIG. 3 .
The invention concerns a frame comprising two posts ( 4, 4′ ) and two cross-members ( 6, 6′ ), a catching member ( 8, 8′ ) adapted to receive one corresponding end of at least one heald ( 10 ), and damping means ( 12, 12′ ) against which at least one end of the heald is urged to be pressed. At least when the frame is stationary, the heald being substantially rectilinear, when one first end of the or each heald ( 10 ) is pressed, either on a first catching member ( 8 ) at the traction zone (S 1 ) thereof, or on a first damping means ( 12 ) at the compression zone (C 1 ) thereof, the other end of the or each heald ( 10 ) is pressed, either on other damping means ( 12 ′) at the compression zone (C′ 1 ) thereof, or on another catching member ( 8′ ) at the traction zone (S′ 1 ) thereof.