Abstract:
The lever ( 11 ) is fitted with two rollers ( 20 A,  20 B) which are supported by a core ( 21 ) provided with a mounting bore ( 21 B) on an articulated shaft, wherein the rollers ( 20 A,  20 B) are both mounted between two webs of a pair of webs which are added to the core ( 21 ). The webs ( 22 A,  23 B) are on the whole planar. A first web ( 22 A) of each pair of webs is partially engaged in a hollow housing ( 21 C) created on the lateral surface ( 21 D) of the core ( 21 ). The second web ( 23 B) of the same pair is maintained at a distance from the first web. The hollow housings ( 21 C) are created on the two opposite lateral surfaces ( 21 D) of the core ( 21 ) of the lever ( 11 ).

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a cam follower lever used in a cam weave mechanism and to a method of manufacturing such a lever. The invention also relates to a cam weave mechanism comprising such a lever and a loom fitted with such a mechanism. 
   2. Brief Description of the Related Art 
   In the field of looms, cam weave mechanisms are known that comprise a series of oscillating levers in numbers equal to those of the heddle frames to be mounted on the looms, each oscillating lever being designed to be coupled to one of the frames and fitted with two rollers which interact with two tracks of a complementary cam rotated by a common shaft. The twin tracks of one and the same cam are offset axially and the rollers supported by the associated lever must have the same axial offset as the tracks of the cam. 
   To do this, it is known practice, for example from EP-A-0 225 266, to mount the rollers of a lever protruding either side of a core. This generates twisting or overhanging moments on the shafts that support the rollers, which induces flexings, mechanism fatigues, even breakages of these elements and a loss of precision during operation. EP-A-0 225 266 also proposes to mount the rollers of a lever in grooves machined in solid cores that are relatively thick. Such a technique is extremely costly, particularly because the core of the lever is relatively voluminous. 
   Furthermore, it is a known practice from FR-A-2 317 395 to produce a lever formed essentially of two flanges provided with steps. It is also known from FR-A-2 259 173 to mount the rollers of a lever in a yoke between two pairs of flanges that are cambered and mounted in opposition. The steps and cambers of the main portions of the flanges of the known levers are supposed to make it possible to compensate for the offset between the rollers and the mid-plane of the lever. In practice, they are subjected to flexing forces that are too high for the metal sheets forming them, which causes them to deform and even break. 
   SUMMARY OF THE INVENTION 
   It is these disadvantages that the invention proposes more particularly to remedy by proposing a new cam follower lever which allows an axial offset of the rollers, in order to allow their alignment with the twin tracks of a complementary cam, and in which it is not necessary to provide steps or cambers likely to deform under load. 
   With this in mind, the invention relates to a lever with cam followers of a cam weave mechanism, this lever being fitted with two rollers supported by a core, while these rollers are each mounted between two flanges of a pair of flanges fitted to this core, characterized in that these flanges are globally flat, in that a first flange of each pair of flanges is partially engaged in a recessed housing made on a lateral face of this core while the second flange of the same pair is held at a distance from the first, and in that the recessed housings provided for the first flanges of the two pairs of flanges are made on the two opposite lateral faces of the core of the lever. 
   Thanks to the invention, the axial offset of the two cam followers of the lever is obtained by an appropriate positioning of the recessed housings made on the core of the lever, while the flanges that are globally flat do not risk deforming at a camber or a step. 
   According to a first embodiment of the invention, a spacer for the spacing of the second flange and of the core may be provided. According to another embodiment, the second flange is provided with a heel for pressing on the core of the lever, this heel making it possible to hold a main portion of the second flange at a distance from a main portion of the first. According to another embodiment, it is the core itself that is provided with at least one heel for pressing on the second flange, this heel also making it possible to hold the main portions of the flanges at a distance. 
   Irrespective of the embodiment considered, the respective mid-planes of the rollers are parallel, situated either side of and substantially at equal distances from the mid-plane of the core of the lever. 
   According to another advantageous aspect of the invention, each roller can be mounted about its respective articulation shaft by means of a roller bearing whose rolling elements are held in position by means of two plates placed either side of this shaft, between this shaft and each of the flanges of one and the same pair, these plates extending radially, from this shaft, at least to the rolling elements of the bearing, a portion of the shaft and the plates forming a stack immobilized between the flanges. 
   The invention also relates to a method of manufacturing a lever with cam followers as previously described and, more specifically, to a method that comprises steps consisting in:
     a) mounting two pairs of two globally flat flanges onto the core of the lever with no bore, partially engaging one flange of each pair in a recessed housing made in a lateral face of this core,   b) immobilizing the flanges on this core, particularly by riveting, then   c) drilling bores for an articulation shaft of a cam follower to pass into each pair of flanges,   d) engaging a roller and, where necessary, a portion of its articulation shaft between the two flanges of each pair, and   e) installing and immobilizing relative to these flanges all or a portion of the shafts for articulating the rollers on the lever.   

   According to an optional feature, provision may be made to interpose a separating spacer between another flange of each pair and the core of the lever. It is also possible to provide that, during step d, the user engages, between the flanges, plates for laterally holding rolling elements forming a bearing between the roller and its articulation shaft. 
   The invention also concerns a cam weave mechanism that comprises at least one lever as described hereinabove or manufactured according to the method described hereinabove. Such a mechanism may operate at a higher speed and be more reliable than those of the prior art because its cam follower levers do not risk deforming, including under load and at high speed. 
   The invention relates finally to a loom fitted with a weave mechanism as mentioned hereinabove, such a loom being easier to use than the known looms. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood and other advantages of the latter will appear more clearly in light of the following description of three embodiments of a roller lever and of a weave mechanism complying with its principle, and a method of manufacturing such a lever, given solely as an example and made with reference to the appended drawings in which: 
       FIG. 1  is a partial schematic representation of the principle of a loom according to the invention; 
       FIG. 2  is a view on a larger scale of detail II in  FIG. 1 ; 
       FIG. 3  is a partial section along the line III-III in  FIG. 2 ; 
       FIG. 4  is a view on a larger scale of detail IV in  FIG. 3 , the cam being omitted; 
       FIG. 5  is a section of the lever along the line V-V in  FIG. 2 ; 
       FIG. 6  is a view similar to detail VI in  FIG. 5 , although on a larger scale, for a lever complying with a second embodiment of the invention and 
       FIG. 7  is a view similar to  FIG. 6  for a lever complying with a third embodiment of the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The loom M shown in  FIG. 1  comprises several heddle frames only one of which is shown in  FIG. 1 . The various frames of the loom M operate in a vertical oscillation movement shown by the double arrow F 1  and imparted by a cam mechanism  10  whose output levers  11  act respectively on connecting rods  12  associated with bent levers  13  connected together and to the frame  1  by connecting rods  14 . 
   The levers  11  are provided in a number equivalent to the number of heddle frames  1  and mounted so as to pivot, as shown by the double arrow F 2 , about a common shaft  15  held by the frame  16  of the mechanism  10  and protected by a cap  17  shown in dot-and-dash lines. 
   The mechanism  10  also comprises several complementary cams only one of which is shown with reference number  18  and which each define two twin tracks  18 A and  18 B on which press respectively two rollers  20 A and  20 B supported by a lever  11 . 
   Each lever  11  comprises a steel core  21  which forms an extension  21 A to which one of the connecting rods  12  is coupled. The core  21  also defines a bore  21 B for mounting onto the shaft  15 . This bore must be defined precisely in order to allow an appropriate positioning of the lever  11  relative to its environment. 
   One denotes P 21  the mid-plane of the core  21  at the extension  21 A and of the bore  21 B. To interact effectively with the tracks  18 A and  18 B of the cam  18 , the rollers  20 A and  20 B must have their respective mid-planes P 20A  and P 20B  placed either side of the plane P 21 . The mid-planes P 20A  and P 20B  are planes perpendicular to the axes of rotation X 20A  and X 20B  of the rollers  20 A and  20 B and situated at equal distances from the sides of these rollers. To support the roller  20 A, the core  21  is fitted with two flanges  22 A and  23 A forming a pair placed either side of the roller  20 A and of the core  21 . 
   To allow the distribution of the mid-planes of the rollers relative to that of the core  21 , the flange  22 A that is globally flat is partially engaged in a depression  21 C made on the lateral face  21 D of the core  21  opposite to that of the side on which lies the mid-plane P 20A  relative to the mid-plane P 21 . The depression  21 C is formed in the thickness of the core  21  and makes it possible to receive a portion of the flange  22 A whose edge  22 A 1  has substantially the same geometry as the edge  21 C 1  of the depression  21 C, which helps the positioning of the flange  22 A when the lever  11  is assembled and confers much rigidity to the assembly. 
   The flange  23 A is placed on the opposite side of the flange  22 A relative to the roller  20 A and is held away from the flange  22 A by a packing piece or spacer  24 A inserted between the flange  23 A and the lateral face  21 F of the core  21  opposite to the face  21 D. 
   Thus, because the flange  22 A is partially engaged in the depression  21 C, the flanges  22 A and  23 A, that are flat, define between them a volume with a thickness E for receiving the roller  20 A offset relative to the mid-plane P 21  of the core  21 . The roller  20 A is slightly thinner than the value of E. 
   In the same manner, the roller  20 B is housed between two flanges  22 B and  23 B of a pair of flanges mounted either side of the core  21 , the flange  22 B being partially engaged in a depression  21 G made in the thickness of the core  21  on the side of the face  21 F. A packing piece-spacer  24 B makes it possible to hold the flange  23 B at a distance from the face  21 D and from the flange  22 B, which makes it possible to define a housing to receive the roller  20 B offset relative to the plane P 21  opposite to the housing for receiving the roller  20 A. 
   Since the flanges  22 A,  22 B,  23 A and  23 B are flat, they have no special deformation zone and have sufficient rigidity to effectively hold the rollers  20 A and  20 B after having been riveted to the core  21  by means of rivets  26 . When the flanges are riveted, the spacers  24 A and  24 B are sandwiched between the core  21  and the flanges  23 A and  23 B respectively. 
   Because of the geometry of the flanges and the distribution of the depressions  21 C and  21 G, the mid-planes P 20A  and P 20B  are parallel, situated either side of the plane P 21  and substantially at equal distances from the latter. 
   As can be seen from particularly  FIGS. 3 and 4 , the roller  20 B consists of a ring mounted above a composite fixed shaft  27 B that is formed of an annular piece  27 B 1  and a rivet  27 B 2  to immobilize the piece  27 B 1  relative to the flanges  22 B and  23 B. Between the elements  20 B and  27 B 1 , rolling elements  28 B are placed forming a bearing allowing the roller  20 B to rotate with little friction. 
   To hold the rolling elements  28 B in place relative to the elements  20 B and  27 B 1 , two plates  29 B 1  and  29 B 2  are provided placed either side of the piece  27 B 1  between this piece and the flanges  22 B and  23 B respectively, these plates extending radially at least to the rolling elements  28 B, which provides good stability of the bearing formed by these rolling elements, while the flanges  22 B and  23 B do not overlap the rolling elements in a zone of the roller that is provided to be engaged between certain portions of the cam  18 , as can be seen from  FIG. 3 . 
   Attaching the rivet  27 B 2  thus makes it possible to create, with the elements  22 B,  23 B,  29 B 1 ,  29 B 2  and  27 B 1 , a fixed and robust structure making it possible to support, guide and rotate the rolling elements  28 B and the roller  20 B. 
   In the same manner, the rolling elements  28 A are placed between the rollers  20 A and an annular piece  27 A 1  belonging to its articulation shaft  27 A and immobilized between the flanges  22 A and  23 A by means of a rivet  27 A 2 . Holding plates, of which only one is visible in  FIG. 2  with reference number  29 A 2 , make it possible to hold the rolling elements  28 A in place, including in the portion of the bearing thus formed which protrudes from the volume comprised between the flanges  22 A and  23 A. 
   The lever  11  is manufactured by creating a preform of the core  21  that substantially conforms to the finished piece. The flanges  22 A,  23 A,  22 B and  23 B are then mounted onto the core  21  in the positions indicated hereinabove. It is then possible to drill in the flanges  22 A,  23 A,  22 B and  23 B bores for the rivets  27 A 2  and  27 B 2  to pass through. It may be possible then to finish the previously rough-machined bore  21 A. This is why the relative position of these bores is defined precisely and takes account of any mounting inaccuracies of the flanges on the core  21 . 
   After drilling these bores, it is possible to insert between each pair of flanges a roller  20 A or  20 B previously associated with an annular piece  27 A 1  or  27 B 1  and with the rolling elements forming a bearing  28 A or  28 B, these rolling elements being held in position by the retainer plates  29 A 1 ,  29 B 1  and  29 B 2  placed either side of the annular pieces. The composite structure thus created is moved between the flanges of each pair of flanges to align the central drillhole of the annular piece with the bore made in the flanges, which then makes it possible to install the rivets  27 A 2  and  27 B 2 . 
   This mounting method is particularly simple and rapid and makes it possible to obtain a precise positioning of the roller rotation shafts relative to one another and relative to the core of each lever. 
   In the second embodiment of the invention shown in  FIG. 6 , the elements similar to those of the first embodiment bear identical reference numbers. This embodiment differs from the preceding embodiment in that no spacer is provided but in that each flange  23 A and  23 B is provided with a heel  23 A 1  or  23 B 1  which makes it possible to maintain a sufficient spacing E between the flanges  22 A and  23 A on the one hand, and  22 B and  23 B on the other hand, such that the rollers  20 A and  20 B are offset either side of the mid-plane P 21  of the core  21 . The flanges  23 A and  23 B may be considered globally flat because they are flat on the larger portion of their surface that faces the rollers  20 A and  20 B. 
   In the third embodiment of the invention shown in  FIG. 7 , the elements similar to those of the first embodiment bear identical reference numbers. This embodiment differs from the preceding embodiment in that heels  21 J and  21 K are made on the core  21  and are made in a single piece with the latter, the flat flanges  23 A and  23 B pressing respectively against these heels, while the flanges  22 A and  22 B are partially inserted into depressions  21 C and  21 G made at the same level as the heels and on the faces opposite to the latter. 
   As in the first two embodiments, the depressions  21 C and  21 G are made on two opposite faces  21 D and  21 F of the core  21 , the heels  21 J and  21 K also being made on these two opposite faces. As hereinabove, the heels  21 J and  21 K make it possible to maintain a sufficient spacing E between the flanges  22 A and  23 A on the one hand, and  22 B and  23 B on the other hand. 
   The levers of the second and third embodiments may be assembled according to a method similar to that described in relation to the first embodiment. 
   Irrespective of the embodiment in question, the flanges may have the same thickness or different thicknesses.