Abstract:
A device for hooking a heddle of a weaving loom of the Jacquard type to a harness cord of the loom that includes an endpiece molded on an upper end of the heddle. The endpiece including an aperture for the passage and wedging of the cord and a housing for receiving two strands of the cord. The device also includes a rigid sleeve reciprocally slidably mounted on the endpiece between a first position, in which it allows access to the aperture, and a second position, in which it covers the aperture and exerts a compressive force for constricting the aperture and blocking access to the lower end of the cord. The device may also be used for hooking one or more cords on a string.

Description:
BACKGROUND OF THE INVENTION FIELD OF THE INVENTION 
   The invention relates to a device for hooking a heddle on a harness cord of a weaving loom of the Jacquard type or a harness cord on a string of a Jacquard loom, and to a Jacquard loom equipped with such a device. The invention also relates to a method for the manufacture of such a device and to a method for hooking a heddle on a Jacquard harness cord by means of such a device. 
   BRIEF DESCRIPTION OF THE PRIOR ART 
   A Jacquard mechanism hook is conventionally associated with a string to which one or more cords are connected, the set of cords forming the harness of the Jacquard mechanism. In its lower part, each cord has to be hooked to the upper end of a heddle which comprises an eye for the passage of a warp thread. To carry out this hooking, it is known from EP-A-0 915 195 to injection-mould on the upper end of a heddle an endpiece which forms an orifice for the passage and wedging of the lower part of a cord, a flexible sheath of synthetic material being then slipped around the endpiece in order to assist in immobilizing the lower part of the cord. To exert a significant clamping force, such a sheath must have a relatively large thickness, thus giving rise to friction between the various sheaths mounted on adjacent heddles during the crossing of two heddles driven in opposite movements when the layout density of the heddles is high. These sheaths must also be relatively long in order to exert a sufficient clamping force. In practice, the length of these sheaths is at least greater than their strokes in order to prevent their ends from catching with one another. As a result of this, these sheaths, having considerable length and diameter, form a compact assembly in the upper part of the heddles, this assembly limiting access to the warp threads through the harness during maintenance operations. It also happens that these sheaths yield, thus giving rise to a risk of slipping of the cords in relation to the endpieces. 
   There are, moreover, heat-shrinkable sheaths which are placed onto the upper ends of the heddles after a cord has been knotted. Once heat-shrunk, these sheaths have a highly irregular external shape which is the image for the shape which they surround, this external shape having protuberances causing premature wear during repeated contacts at the crossing between the sheaths mounted on adjacent heddles. 
   It is also known from the FR-A-2 822 479 to use a tubular portion made of plastic or of metal in order to clamp the lower end of a cord in a longitudinal slot formed in an endpiece injection-moulded on the upper end of a heddle. The V-shape of the slot does not allow an efficient clamping of the cord which risks slipping when the loom is in operation, which makes the control of the heddle inaccurate and may cause faults in the shed. Furthermore, the slot, which extends over the entire length of the endpiece, embrittles this endpiece in the region of the injection-moulding zone of the heddle. An additional endpiece has to be mounted in the lower part of the tubular section, thus complicating the mounting operation. Finally, before the wedging of the cord, the tubular section is separated from the endpiece completely, so that it can slide level with the eye and with the bottom of the heddle. 
   The invention is intended more particularly to remedy these disadvantages by providing a novel hooking device, the overall diametral size of which may be greatly reduced, thus allowing a high layout density of the heddles, thereby making efficient hooking possible, and which is easy to mount. 
   SUMMARY OF THE INVENTION 
   The invention relates to a device for hooking a first element, of an assembly for the formation of the shed in a weaving loom of the Jacquard type, on a second element belonging to this assembly, the hooking device comprising an endpiece injection-moulded on the upper end of the first element and comprising two first branches, between which is defined an aperture for the passage of the lower end of the second element, this end comprising two strands which extend upwards from a portion of this second element received in this aperture. This device is characterized in that the endpiece comprises two second branches, between which is defined a housing for receiving the abovementioned strands, and in that it also comprises a metallic sleeve mounted on the endpiece and movable in translational motion on this endpiece between a first position, in which the sleeve allows access to the abovementioned aperture and does not interact with the second branches, and a second position, in which the sleeve exerts on the first branches and on the second branches a centripetal force for constricting the aperture and the housing and for wedging the abovementioned portion of the lower end of the second element and the adjacent strands respectively in the aperture and in the housing which are defined by the endpiece. 
   The use of a metallic sleeve makes it possible for the latter to remain cylindrical with a predetermined cross section, in practice circular, after it has been placed onto the endpiece equipped with a cord. Thus, the overall diametral size of the hooking device can be effectively controlled, thus limiting the risks of wear due to friction. In view of its rigid nature, the tube can exert a sufficient clamping force, whilst it can be substantially shorter and less thick than a conventional sheath. The result of this is that accessibility to the lower part of the harness and to the upper part of the set of heddles is greatly improved, as is accessibility to the warp threads for manual repairs to the harness. In view of the small length of the sleeve, the device can be light-weight. On account of the reduced diameter of the sleeve, the frictional forces are greatly reduced or even eliminated. Owing to the rigidity of the sleeve, the slip resistance of the cord is stable over time. The fact that the strands adjacent to the portion of the second element which is engaged in the aperture are received in the housing defined between the second branches makes it possible to obtain a blocking force distributed over the length of these strands, this being especially effective. 
   According to advantageous, but not mandatory, aspects of the invention, such a device may incorporate one or more of the following characteristics:
         The second branches are provided with free ends which are distant from one another when the sleeve is in its first position and which together form the upper end of the endpiece when the sleeve is in its second position.   A first end of the sleeve which is located towards the front of the latter when it passes from its first position to its second position is widened forwards. In this case, the second end of the sleeve may be convergent, extending away from its first end.   The sleeve and the endpiece are provided with complementary means which form an abutment stopping the translational movement of the sleeve from its first position towards its second position. By virtue of the stop means, a positioning of the tube is obtained, thus facilitating the mounting operation and the visual check of the good positioning of the heddles in terms of height. The aesthetic appearance of the harness is also improved. There may be provision for the sleeve and the endpiece likewise to be provided with complementary means forming an abutment stopping the translational movement of the sleeve from its second position towards its first position. The means forming an abutment advantageously comprise a relief which is formed on an outer peripheral surface of the endpiece and against which one end of the sleeve comes to bear when the sleeve arrives in one of its positions from the other position. The relief may comprise at least one tooth, against which one end of the sleeve comes to bear when the sleeve arrives in its first position from its second position, this tooth being compatible with a displacement of the sleeve towards its first position from a position opposite the second position.   The sleeve and the endpiece are provided with complementary means for immobilizing the sleeve on the endpiece in the second position by the cooperation of shapes. These immobilization means may likewise consist of abutment means stopping the translational movement of the sleeve from its first position towards its second position. These immobilization means advantageously comprise at least one reentrant relief formed in a running part of the sleeve and at least one complementary relief formed on a part of the endpiece which is elastically deformable when the sleeve passes from its first position to its second position. There may be provision for the complementary relief to be formed on one of the two first branches.   The sleeve is made from stainless steel or from a copper-based alloy, with a wall thickness smaller than 0.6 mm, preferably smaller than 0.3 mm, more preferably of the order of 0.1 mm.   The endpiece possesses, level with or in the vicinity of each of its ends, a substantially conical or frustoconical zone which is convergent, extending away from the opposite end. This makes it possible to limit the risks of catching between adjacent devices mounted on a loom.   The second branches are provided with means for centring one of the strands according to a longitudinal axis of the endpiece. The invention also relates to a weaving loom of the       

   Jacquard type which comprises at least one hooking device, as described above. Such a loom is more economical, and the changes of its harness are easier and quicker than those of the prior art. 
   The invention also relates to a method for the manufacture of a device, as described above, which comprises steps involving:
         a) installing the sleeve on the first element at a distance from its upper end,   b) injection-moulding the endpiece on the first element, and   c) if appropriate, displacing the sleeve towards its-first position on the endpiece.       

   Step c) is optional, in as much as it can be carried out later, particularly when the device is used for hooking a heddle on a harness cord. 
   Finally, the invention relates to a method for hooking a heddle of a weaving loom on a Jacquard harness cord by means of a device, as described above, this method comprising steps involving:
         d) introducing the cord into the aperture of the endpiece,   e) arranging the strands in the housing formed between the second branches, and   f) displacing the sleeve from its first position towards its second position.       

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood and other advantages of the latter will become apparent more clearly in the light of the following description of three embodiments of the hooking device and of a Jacquard loom which are in accordance with its principle, this description being given solely by way of example and being made with reference to the accompanying drawings in which: 
       FIG. 1  is a partial diagrammatic illustration of a weaving loom according to the invention; 
       FIG. 2  is a perspective view, on a larger scale, of a device for hooking the upper end of a heddle on the lower end of a cord, the device being in a first configuration; 
       FIG. 3  is a longitudinal section along the line III-III in  FIG. 2 ; 
       FIG. 3A  is a side view, on a larger scale, of the detail  3 A in  FIG. 3 ; 
       FIG. 4  is a view, similar to  FIG. 2 , when the hooking device is in a second configuration; 
       FIG. 5  is a longitudinal section along the line V-V in  FIG. 4 ; 
       FIG. 5A  is a cross section, on a larger scale, along the line A-A in  FIG. 5 ; 
       FIG. 5B  is a cross section, similar to  FIG. 5A , for a hooking device according to a second embodiment of the invention; 
       FIG. 6  is a longitudinal section, on a larger scale, of a sleeve used in the device of  FIGS. 1 to 5 ; 
       FIG. 7  is a section along the line VII-VII in  FIG. 6 ; and 
       FIG. 8  is a view, corresponding to the detail VIII in  FIG. 5 , of a hooking device according to a third embodiment. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The loom M illustrated in  FIG. 1  is equipped with a Jacquard mechanism  2  which controls a plurality of strings  4 , only one of which is illustrated and the lower end of which is associated with a plurality of cords  6 , the assembly of cords forming the harness H of the loom. The lower end  6   a  of each cord  6  is connected to the upper end  8   a  of a heddle  8 , each heddle being provided with an eye  8   b  for the passage of a warp thread  10  and being subjected to the action of a return spring  12  fixed to the frame  14  of the loom by means of a rod  16 . 
   The heddles  8  may also be controlled individually by the mechanism  2 , in which case each cord  6  is displaced individually by means of this mechanism. 
   Within the meaning of the present description, the adjective “upper” relates to a part or an element of a device which is directed upwards in a normal configuration of use of the loom M, that is to say upwards in  FIG. 1 , whilst the adjective “lower” designates a part or an element directed downwards in this configuration. 
   A hooking device  20  is used for connecting the upper end  8   a  of each heddle  8  to the lower end  6   a  of the corresponding cord  6 . This device  20  comprises an endpiece  22  injection-moulded on the end  8   a  in the form of a substantially cylindrical body  221  of circular cross section. Beyond the end  8   a , the body  221  is prolonged by two branches  222  and  223 , between which is defined an aperture  224 , of which the dimensions in the plane of  FIGS. 3 and 5  may vary as a function of a possible mutual approach of the branches  222  and  223  which are elastically deformable. 
   The branches  222  and  223  meet one another in a zone  225  which is opposite the body  221  and from which extend two other branches  226  and  227 , the free ends  226   a  and  227   b  of which extend at a distance from one another when the endpiece  22  is not stressed, as illustrated in  FIGS. 2 and 3 . 
   The end  6   a  of the cord  6  can be engaged in the aperture  224 . The two strands  6   b  and  6   c  formed by the cord  6  on either side of its part  6   d  received in the aperture  224  then extend along the zone  225  and are engaged in a through-gap  228  defined between the branches  226  and  227 . The two strands  6   b  and  6   c  extend upwards from the portion  6   d  of the cord  6  which is received in the aperture  224 . 
   As illustrated by the arrows F 1  and F 2  in  FIG. 2 , the end  6   a  can be engaged in the aperture  224  and then the strands  6   b  and  6   c  can be turned towards the gap  228  which thus forms a housing for receiving these strands. 
   The central longitudinal axis of the endpiece  22  is designated by X 22 , this axis coinciding with the longitudinal axis X 8  of the heddle  8 . 
   Each branch  222  and  223  is provided with a part  222   a ,  223   a  reentrant in the direction of the axis X 22  with respect to the rest of the branches  222 ,  223 . These parts  222   a  and  223   a  thus define two zones  222   b  and  223   b  recessed with respect to the outer surfaces  222   c  and  223   c  of the branches  222  and  223  over most of their length. 
   A metallic sleeve  24  is mounted on the endpiece  22  and is intended for locking the end  6   a  of the cord  6  with respect to this endpiece when the adjustment of the height of the heddle  8  has been carried out by setting the position of this end  6   a  with respect to the endpiece  22 . In a most advantageous way, the sleeve  24  is made from stainless steel or from a copper-based alloy, such as brass, so that it does not risk rusting, even if the loom M is liable to operate in a damp or aggressive environment. The sleeve  24  has a circular cross section over most of its length, and its wall is thin, its thickness being smaller than 0.3 mm, preferably in the neighborhood of 0.1 mm. In practice, the wall thickness of the sleeve  24  may be selected lower than 0.6 mm. 
   The end  241  of the sleeve  24  is widened, that is to say is divergent, extending away from its running part  242 . The opposite end  243  is convergent in the direction of the central axis X 24  of the sleeve  24  and extending away from the part  242 . 
   The length of the sleeve  24  is designated by L 24 . This length is substantially smaller than that of the flexible sheaths used, for example, with the device known from EP-A-0 915 195. In practice, the length L 24  is between 10 and 40 mm, preferably of the order of 20 mm. 
   The sleeve  24  is provided with three localized dishings  244  uniformly distributed about the axis X 24  and reentrant in the direction of this axis. These three dishings or neckings define the minimized inside diameter of the sleeve  24 , that is to say the nominal outside diameter of a component capable of being received in this sleeve in the region of these dishings. 
   The body  221  is provided with two teeth  221   a , each defined between a surface  221   b  perpendicular to the axis X 22  and a surface  221   c  inclined in the direction of this axis, extending away from the aperture  224 . 
   When the device  20  is to be manufactured, the sleeve  24  is shaped by means of conventional cutting and dishing techniques. It is then slipped onto the end  8   a  of the heddle  8  and displaced at a distance from this end in the direction of the eye  8   b . The endpiece  22  is then injection-moulded on the end  8   a . The sleeve  24  can subsequently be returned towards its first position illustrated in  FIGS. 2 and 3 , this being possible in spite of the presence of the teeth  221   a  because of the inclined nature of the surfaces  221   c  which allow the end  243  to pass over the teeth  221   a . Once this passing has taken place, the tooth  221  forms an abutment with respect to a movement of the sleeve  24  in the direction of the eye  8   b . The configuration of  FIGS. 2 and 3  is thus assumed. 
   Alternatively, the sleeve  24  may be kept at a distance from the endpiece  22  or engaged on this endpiece, but without its end  243  going beyond the teeth  221   a.    
   Once the end  6   a  of the cord  6  is put in place and the adjustment of the height of the heddle has been carried out, the cord is cut to length in order to provide the strand  6   b , whilst the strand  6   c  prolonged upwards in order to form the intermediate part of the cord  6 . The sleeve  24  is then displaced in the direction of the arrows F 3 , that is to say in a reciprocating movement parallel to the axes X 22  and X 24 , which then coincide, and in a direction moving away with respect to the eye  8   b  of the heddle  8 . This makes it possible to reach the second position, illustrated in  FIGS. 4 and 5 , in which the end  241  of the sleeve  24  comes to bear against a shoulder  229  formed in two parts  229   a  and  229   b  on the outer surfaces of the branches  226  and  227 . Thus, the end  241  and the shoulder  229  form an abutment with respect to the displacement of the sleeve  24  from its position of  FIG. 2  to that of  FIG. 4 . On account of this displacement, the branches  222  and  223 , on the one hand, and the branches  226  and  227 , on the other hand, approach one another, at the same time constricting the aperture  224  and the gap  228 . To be precise, the rigid nature of the sleeve  24  allows it to exert on the branches  222 ,  223 ,  226  and  227  a centripetal or compressive force E 1  in the direction of the axes X 22  and X 24 , this force being sufficient to block the strands  6   b  and  6   c  in the gap  228  as a result of the mutual approach of the ends  226   a  and  227   a , and to wedge the part  6   d  of the end  6   a  in the aperture  224 . 
   In this region, an amplification effect is obtained with regard to the clamping force E 1  which is exerted by the sleeve  24  in the region of the parts  222   a  and  223   a  in order to “close” the branches  222  and  223  which tend to pivot about their fastening points on the zone  225 . The end  6   a  of the cord is thus firmly gripped in the then flattened aperture  224 . Where the strands  6   b  and  6   c  are concerned, these are likewise firmly pressed against the zone  225  and gripped between the branches  226  and  227  on account of the force E 1 . 
   As may be gathered more particularly from  FIG. 5A , the mutually confronting surfaces  226   b  and  227   b  of the branches  226  and  227  are concave, with a shape allowing them to center the strand  6   c  on the axis X 22  when the force E 1  causes them to approach one another. In the example illustrated in  FIG. 5A , the surfaces  226   b  and  227   b  each comprise two parallel portions connected by means of an inclined portion. 
   As illustrated in  FIG. 5B  for a variant of the invention, the surfaces  226   b  and  227   b  may be substantially in the form of an open V, thus likewise making it possible to center the strand  6   c  on the axis X 22.    
   The cross sections corresponding to  FIGS. 5A and 6B  are taken in a part of the endpiece  22  where only the strand  6   c  is present, the strand  6   b  being received in the housing  228  over only part of the height of this housing. 
   The displacement of the tube  24  from its first position towards its second position makes it possible to bring one of the dishings  244  level with one of the zones  222   b  and  223   b  of the branches  222  and  223 , thus causing immobilization in the configuration of  FIGS. 4 and 5  by the snapping of the sleeve  24  on the endpiece  22 . The clamping force of the sleeve  24  is thus secure. 
   The zones  222   b  and  223   b  and the dishings  244  may likewise serve as an abutment with respect to the displacement of the sleeve  24  from its first position towards its second position. In this case, the sleeve is shorter than that illustrated in the figures, in such a way that its front end  241  does not interfere with the shoulder  229 , the stopping of the displacement F 3  of the sleeve from its first position towards its second position being obtained when the dishings  244  engage in the zones  222   b  and  223   b.    
   In any event, the fact that the front end  241  of the sleeve  24  is widened prevents this front end from marking or damaging the plastic forming the endpiece  22  during the displacement of the sleeve from its first position towards its second position. The widened nature of the end  241  is illustrated in the figure as the result of an outward deformation of the end  241 . Alternatively, this widened nature could be obtained by means of an inner chamfer of the end  241 , the outer surface of which would not be deformed. 
   The immobilization obtained in the configuration of  FIGS. 4 and 5  is reversible in that it is possible to displace the sleeve  24  again towards the position of  FIGS. 2 and 3  by expelling the dishings  244  from the zones  222   b  and  223   b  by means of an elastic deformation of the branches  222  and  223  which is of the same type as that which occurs at the termination of the stroke of displacement of the sleeve  24  from its first position towards its second position. 
   The use of the sleeve  24  makes it possible to control and limit the overall diametral size of the device  20 , the maximum outside diameter D 20  of the device  20  then being determined by the thickness of the branches  226  and  227 , without the sleeve  24  increasing this diameter. 
   The heddles can thus be laid out in a high density, whilst the risks of premature wear of the hooking devices are reduced or even eliminated. 
   The body  221  forms, in its part opposite the branches  226  and  227 , a tube of small diameter  221   d  connected to the main part of the body  221  by means of a frustoconical zone  221   e  convergent in the direction of the eye  8   b . In the configuration of  FIGS. 4 and 5 , the outer end surfaces  226   c  and  227   c  of the branches  226  and  227  are rounded and convergent towards the axis X 22 , opposite the zone  225 , with a substantially frustoconical shape. The upper end of the device  20 , this upper end being defined by these surfaces, is thus shaped so as to limit shocks or friction with adjacent devices when this device is displaced upwards with respect to the adjacent devices. The zone  221   e  has the same function when the device  20  is displaced downwards. 
   In view of its small thickness and of its relatively modest length L 24 , the sleeve  24  is lightweight and does not appreciably increase the inertia of the assembly formed by a cord  6  and by a heddle  8 . On account of the very good definition of the location of the tube  24  in the position of  FIGS. 4 and 5  by virtue of the abutment means  229  and  241  and/or  222   b  and  223   b , it is easy to check that it is put in place correctly, especially when numerous heddles are juxtaposed in a predetermined configuration, in as much as the corresponding sleeves then have to be substantially aligned. 
   The mode of displacement of the sleeve  24  from its first position towards its second position and even in the opposite direction makes it possible to consider an automation of the corresponding movement, thus achieving an appreciable timesaving and laborsaving. 
   On account of the reversible nature of the putting in place of the sleeve  24  in the position of  FIGS. 4 and 5 , an adjustment in the length of the cord may be considered, the sleeve  24  being temporarily displaced towards its configuration of  FIGS. 2 and 3  and then being returned to its place in its configuration of  FIGS. 4 and 5 , without any impairment in the clamping force obtained by means of the sleeve  24 . 
     FIG. 8  relates to a second embodiment in which the elements similar to those of the first embodiment bear the same references. The aperture  224  of this embodiment is not surrounded completely by material, the branch  223  being interrupted and forming an aperture  223 o for the lateral introduction of the portion  6   d  of the cord  6  in the aperture  224 . Once the sleeve  24  is in place, this portion  6   d  is gripped in the aperture  224  by the branches  222  and  223 . 
   In the device of the invention, the part of the body  221  which is injection-moulded on the end  8   a  of the heddle is separate from the part which is formed from the elements  222  to  229  and by means of which the end  6   a  of the cord is blocked. Thus, the hooking structure of the cord does not risk weakening the connection between the endpiece  22  and the heddle  8 . 
   The sleeve  24  has been illustrated with a continuous circular cross section. It could be split longitudinally or be formed by the winding of a metal sheet with partial overlap. 
   The device may likewise serve for the connection between one or more harness cords  6  and a string  4 . In this case, the upper end or upper ends of the cord or cords  6  is or are injection-moulded in the body  221  and the lower end of the string  4  is wedged in the aperture  224 .