Abstract:
Stators for an electrical actuator of a type which may be used in weaving looms and weaving systems wherein a stack of armature plates having two-spaced sections are wrapped with an electrically conductive wire to create two coils afterwhich the stack is folded to sever severable bridge elements of the stack and to form an armataure to define a tubular housing for a rotor.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional application of Ser. No. 09/218,300, Filed Dec. 22, 1998 now U.S. Pat. No. 6,237,213 in the name of the same inventors. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electrical actuator for forming the shed in a weaving loom, particularly for controlling the harness cords of a weaving system of the Jacquard type or the frames of a dobby, and to a process for manufacturing such an actuator. The invention also relates to a weaving system comprising such an actuator, and to a weaving loom equipped with such a system. 
     2. Brief Description of the Related Art 
     In weaving systems of the Jacquard type, it is known to drive, in phase opposition, two frames each bearing a plurality of griffes or horizontal knives adapted to displace, vertically, hooks connected to the harness cords by a pulley or block mechanism. Mechanical or electro-mechanical devices are provided to immobilize these hooks along their vertical stroke. This known type of device necessitates considerable power for moving the griffe frames, which power is furnished by the drive shaft of the weaving loom, this leading to said loom being overdimensioned. 
     It is also known to use a rotating motor such as a step motor or a servo-motor to control a small cord belonging to a weaving loom, linearly. Taking into account the large number of electric motors used in the weaving system associated with a weaving loom, a number which may attain and even exceed 10,000, these motors must be of minimum space requirement and cost, while having considerable reliability. In particular, winding of the conducting wire must effected rapidly while guaranteeing a sufficient level of quality. In addition, the stator must have dimensions adapted to those of the rotor which, in order to optimize its inertia, must have a diameter which is as small as possible. Finally, the manufacturing tolerances of the metal plates constituting the stacks forming the stators must not hinder manufacture thereof nor reduce their yield. 
     It Is an object of the present invention to propose an electrical rotating actuator adapted to control displacement of one or more harness cords, which is compact and simple to manufacture. 
     SUMMARY OF THE INVENTION 
     To that end, the invention relates to an electrical actuator for forming the shed in a weaving loom, particularly for controlling the harness cords of a weaving system of the Jacquard type or the frames of a dobby, comprising a rotor and at least one stator whose armature is formed by a stack of metal plates, characterized in that the stator is formed by at least two stator elements disposed side by side along the axis of rotation of the rotor, each stator element comprising two zones for reception of a winding of electrically conductive wire, at least certain of the metal plates of each zone disposed opposite one another being mated. 
     Thanks to the invention, it is possible to produce an electrical rotating actuator in which the electromagnetic flux circulating in the stator is optimum whatever the manufacturing tolerances of the plates constituting it and, in particular, whatever the variations in thickness existing in a batch of plates. In effect, the fact that the plates are mated, in the two zones of reception of the conducting wire winding, allows an efficient transfer of the electromagnetic flux from one zone towards the other. 
     According to a first advantageous aspect of the invention, the mated plates in each zone are formed from a single plate extending over the whole length of the armature. Thanks to this aspect of the invention, if one plate is thicker or thinner than its neighbors variation in thickness is found over the whole length of the armature and consequently in the two zones of reception of the electric wire winding. There is therefore no defect in alignment of the plates constituting the armatures, this promoting the electromagnetic flux. 
     According to another advantageous aspect of the invention, the plates comprise, in their central part and before the armature is shaped., a cleavable bridge connecting parts intended to be partially surrounded by said electrically conducting wire winding. Thanks to this aspect of the invention, the actuater is easy to manufacture and therefore of relatively low cost, insofar as the winding of the stator can be made flat, therefore at high speed, before the final geometry of the stator is attained by rupture of the cleavable bridge. 
     According to another advantageous aspect of the invention, each plate extends, in a direction substantially perpendicular to the cleavable bridge, by a finger, a finger of one plate extending from one side of the bridge that it comprises, while the fingers of the two adjacent plates extend, in the same direction, on the other side of bridges that they comprise,. This construction of the cores or armatures of the stators allows a shaping of the stator, in order to produce the air gap, by wedging the fingers formed in the plates with respect to one another. 
     In that case, the fingers of the plates may be provided to be adapted to imbricate in one another, after rupture of the cleavable bridges. Such imbrication of the fingers of the plates forming the armatures of the stators allows a good electromagnetic contact therebetween and consequently a maximum conduction of the electromagnetic flux in the corresponding air gap. 
     The plates forming the stator elements are advantageously disposed head-to-tail. Thanks to this aspect of the invention, the distribution of the fingers on either side of the cleavable bridges may be obtained with one sole plate geometry, which greatly simplifies manufacture. 
     According to another advantageous aspect of the invention, the actuator comprises a base provided with two housings each adapted to receive a part of a stator, this base being provided with means for connecting each stator with pins for electrical supply of the actuator. This base serves as bearing structure for the actuator according to the invention. 
     The invention also relates to a process for manufacturing an actuator as described hereinbefore and, more specifically, to a process characterized in that it consists in producing each stator element of the actuator by winding flat on an armature and in bending the latter in order to bring the ends closer together, a housing for reception of a rotor being formed by bringing these ends closer. Flat winding of the armatures may be effected at very high speed, possibly on a plurality of armatures disposed in parallel, this enabling the manufacturing costs to be minimized. 
     According to a first advantageous aspect of the process according to the invention, bending of the armature is effected by rupture of cleavable bridges. The presence of the cleavable bridges guarantees a precise positioning of the different parts constituting the armature up to the instant of rupture of these bridges. 
     In that case, it may, in addition, be provided that bending of the armature results in the imbrication of fingers distributed alternately on either side of the cleavable bridges. 
     According to another advantageous aspect of the process according to the invention, it includes a step of overmolding of each stator of the actuator on a base provided with means for electrical supply of the stator or stators. The base defines the relative positioning of the stators before overmoulding thereof, while allowing their electrical supply. This base therefore makes it possible to obtain an overmolded actuator, therefore of low cost in large quantities, while guaranteeing a satisfactory level of reliability. 
     The invention also relates to a weaving system which comprises one or more of the actuators as described hereinabove or manufactured as indicated hereinabove, and to a weaving loom equipped with such a system. This system is easier to employ and maintain than the prior art devices, and allows a yarn-to-yarn control of a Jacquard loom harness. The yield of a weaving loom according to the invention is therefore substantially improved with respect to the known art. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be more readily understood on reading the following description of an electrical rotating actuator according to its principle, with reference to the accompanying drawings, in which: 
     FIG. 1 is a longitudinal section through an actuator according to the invention. 
     FIG. 2 is a transverse section along line II—II of FIG.  1 . 
     FIG. 3 is a view in perspective of two adjacent plates belonging to the armature of a stator element of the actuator of FIGS. 1 to  2 . 
     FIG. 4 is a view in perspective of a stack of plates, of the type shown in FIG. 3, intended to form the armature of a stator element, in a first manufacturing step. 
     FIGS. 5 to  7  are views similar to FIG. 4, illustrating the stator element at three other successive manufacturing steps. 
     FIG. 8 is a view in perspective of the stator element obtained, shown in the course of installation on a receiving base, and 
     FIG. 9 is a partial schematic section of the stator element along line IX—IX of FIG.  8 . 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawings and firstly to FIG. 1, the electrical rotating actuator I is intended to ensure the winding, on a pulley  2 , of a harness cord  3  connected to one or more warp yarns of a weaving system of Jacquard type. The actuator  1  is a two-phase actuator. It comprises a stator formed by two stator elements  4  and  5  overall aligned along an axis XX′ and adapted to cooperate with a rotor  6  formed by a tube  7  centered on an axis XX′. The tube  7  is preferably made of an amagnetic material, such as for example brass. The tube  7  contains two permanent magnets  8  and  9 , disposed opposite the two stator elements  4  and  5 . 
     Elements  4  and  5  comprise windings  4   a  and  5   a  of electrically conducting wire, such as copper wire, wound around stacks  4   b  and  5   b  of magnetically conducting plates. The shape of the stacks  4   b  and  5   b  is such that they form a circular housing  10  for receiving the tube  7 . The size of the housing  10  defines the air gap of the stator elements  4  and  5  with respect to the rotor  6 . 
     Other forms of rotors, possibly provided with outer magnetized tiles, might also be incorporated in the actuator of the invention. 
     The rotating actuator according to the invention functions efficiently when the two magnets  8  and  9  have differently oriented polarities, the value of the angle of shift being able in principle to be included between 0 and 180°. In practice, it is included between 60 and 120°. However, the value of 90° presents, for a two-phase actuator, the additional advantage that it enables the best electromagnetic yield and an optimized start to be obtained whatever the position of stop of the actuator. 
     The stacks  4   b  and  5   b  which constitute the armatures or cores of the stators  4  and  5  are formed by plates  20  which are visible, in particular, in FIG.  3 . All these plates have the same geometry and comprise two parts  20   a  and  20   b  intended to be partially surrounded by the windings  4   a  and  5   a  and provided, at their ends, with a semi-circular notch  20   c  intended to form the housing  10 . In their central part, the plates  20  comprise a cleavable bridge or tongue  20   d,  , i.e. one which is adapted to be separated from parts  20   a  and  20   b  for example by bending. 
     The part  20   a  of each plate  20  has a finger  20   e  which extends substantially perpendicularly to the bridge  20   d.  The other part  20   b  does not comprise such a finger. The plates  20  are disposed head-to-tail, i.e. side by side, one plate out of two being pivoted through 180° about an axis ZZ′ which is substantially vertical in FIG. 3, with the result that each part  20   a  of the plates located inside the stacks  4   b  and  5   b  adjoins two parts  20   b.  while parts  20   b  respectively adjoin parts  20   a  of the adjacent plates. In this way the fingers  20   e  of the different plates extend on each side of the bridges  20   d,  the fingers of one plate extending on one side of the bridge that it comprises, while the fingers of the two adjacent plates extend, in the same direction, on the other side of the bridges that they comprise. 
     A stack is formed by a variable number of plates, for example included between  12  and  50 , particularly of the order of 32. When a stack  4   b  is formed and as is apparent in FIG. 4, the fingers  20   e  extend, alternately, on either side of the cleavable bridges  20   d,  while the notches  20   c  define two hollow semi-cylinders intended to form the housing  10 . 
     Manufacture of one of the stators used in the actuator of the invention includes a step in which flanges  21  made of insulating material, visible in FIG. 5, are overmoulded around the stack  4   b.  These flanges maintain the different plates  10  of the stack  4   b  in position with respect to one another and define two zones  20   f  and  20   g  for winding of the electrically conducting wire. 
     Certain flanges  21  bear studs  21  a around which the ends or certain intermediate parts of the wire intended to form the winding  4   a  may be wound. The winding  4   a  is wound around the armature  4   b  by rotating the latter about an axis Y-Y′ shown in FIG. 6, with the result that the winding may be produced very rapidly and “flat”, i.e. by rotating the stack or armature  4   b  about a single axis. The wire  22  passes from zone  20   f  to zone  20   g,  being wound, over at least one turn, around the studs  21   a.    
     The stator element  4  may then be formed. The ends of the two halves of the rid winding  4   a  at the notches  20   c,  are brought closer by bending the plates  10  substantially perpendicularly to axis Y-Y′, imparting to the plates  20  two forces F 1  and F 2 , shown in FIG.  7 . These forces F 1  and F 2  induce the rupture of the cleavable bridges  20   d  which are evacuated in a direction F 3 , while the fingers  20   e  of the different plates  20  are imbricated in each other so as to constitute a single armature on the electromagnetic plane. In other words, the alternation of the fingers  20   e  disposed on each side of the cleavable bridges  20   b,  makes it possible to obtain, by wedging and cooperation of form, a single armature  4   b  formed by the stack of the plates  20 . When the two halves of the stator  4  are bent down towards each other, they define, as is visible in FIG. 8, the housing  10  for receiving the rotor  6 . This housing defines the air gap of the stators  4  and  5 . 
     The fact that the plates  20  extend over the whole length of the armature  4   b  in the position of FIGS. 4 to  6 , ensures that, even in the event of variation in thickness of the plates  20 , a sufficient space is arranged for receiving a finger  20   e  between the two adjacent fingers. In fact, in the position of FIG. 7, taking into account the manufacturing tolerances, the width of the space defined between two fingers  20   e,  belonging to two plates  20  oriented in the same way, is determined by the width of the intermediate plate located between these two plates. This width may be assumed to be equal to that of the finger that the intermediate plate bears. 
     In this way, the width of the free space for receiving the finger of the intermediate plate is always equal to the width of this finger. 
     In this way, the two opposite plate parts which belong to the two halves of the armature  4   b,  come from the same plate. They are therefore mated and, in particular, present the same thickness. 
     FIG. 8 shows a base  23  for receiving that part of the rotor  4  opposite the part which bears the housing  10 . This base  23  is provided with two housings  24  and  25  for receiving the two elements  4  and  5  forming the stator. The element  4  is positioned, in a direction F 4 , in the base  23  while element  5  (not shown), is positioned in similar manner in the housing  25 . The base  23  comprises an extension  26  adapted to receive four pins  27  for electrical supply of the stator  5 . Means for electrically connecting each stator  4  or  5  with the corresponding pins  27  are constituted by electric cables moulded in the base  23 , by tracks formed on the lower surface of the housings  24  and  25 , or by any other equivalent means. In FIG. 1, the connection of the elements  4  and  5  with the pins  27  is shown schematically by cables  28 . It will be noted that the studs  21  a may serve as connection points between the cables  28  and the wire  22 . 
     When the two elements  4  and  5  are in place in the housings  24  and  25  of the base  23 , they may be overmolded in an electrically insulating material, such as for example an elastomer, in order to constitute a monobloc, shock-resistant assembly. 
     As is more clearly apparent in FIG. 9, when the stator element  4  is formed, the fingers  20   e  of the different plates are disposed alternately on either side of the line of axis XX′ in the plane of FIG.  9 . Taking into account the mode of manufacturing the stator element  4 , each finger  20   e  is opposite a part of plate  20   h  which belongs to the same plate  20  before rupture of the cleavable bridge, with the result that the variations in thicknesses e 1 , e 2 , e 3  and e 4  of the plates  20  do not induce a defect in alignment of the elements  20   e  and  20   h  with respect to one another. Under these conditions, the electromagnetic flux optimally transits between the two zones  20   f  and  20   g  of the armature  4   b.    
     It will be understood that the end plates of the winding zones  20   f  and  20   g  are not necessarily mated as there is no risk of wedging at their level and as the magnetic flux remains optimum in the rest of the stator element. 
     The actuator thus produced is very satisfactory as far as cost price is concerned and functions correctly whatever the manufacturing tolerances of the plates constituting the stator elements. A large number may therefore be mounted on a Jacquard type system for forming the shed on a weaving loom. 
     Although it has been described essentially with reference to an actuator for Jacquard system, the invention is also applicable to textile machines in general and, in particular, to weaving looms equipped with dobby, for controlling the heddle frames, or to hosiery machines for controlling the needles.