Abstract:
Electromagnetic switching device including a movable contact-holder fitted with a set of contact bridges bearing movable power contacts that operate in conjunction with fixed contacts, and an electromagnet composed of a coil, a fixed framework and movable framework. The movable contact-holder includes an assembling device including at least one elastic clipping foot for fastening the movable contact-holder of the electromagnet to the movable contact-holder, characterized in that the assembling device is equally suitable for direct and indirect assembly of the movable framework onto the movable contact-holder according to the type of movable framework used in DC or AC electromagnets.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electromagnetic switching device comprising a movable contact-holder fitted with a set of contact bridges that operate in conjunction with fixed contacts, also comprising an electromagnet composed of a coil, a fixed framework and movable framework, the movable framework of the electromagnet being associated with the contact-holder and causing the contact-holder to move in translation in order to open or close the contacts. 
     2. Discussion of the Background 
     French patent FR 2518308 discloses a contactor-type electromagnetic switching device comprising an electromagnet powered by an alternating current. The contact-holder of the contactor has a lower cavity containing the movable framework of the electromagnet, the movable framework being fastened by means of a pin passing through the framework and introduced into the body of the contact-holder on each side of the cavity. The movable framework of the electromagnet is the type of E-shaped magnetic circuit commonly used for electromagnets powered by alternating currents and the way the contact-holders are assembled is consequently appropriate to the invention. However, this mode is difficult to implement for the blade-type movable framework used in electromagnets powered by direct currents, the blade being too thin to allow a fastening pin to pass through it. 
     U.S. Pat. No. 5,281,937 discloses a contactor-type electromagnetic switching device comprising a movable framework of an electromagnet consisting of a plane blade whose shape is suitable for it to be fastened to the mobile contact-holder of the contactor by means of elastic clipping feet provided on the contact-holder. However, this fastening method cannot be adapted directly to a movable framework consisting of an E-shaped magnetic circuit. 
     SUMMARY OF THE INVENTION 
     The invention thus relates to an electromagnetic switching device in which the different types of movable electromagnet frameworks (particularly depending on whether they are AC or DC powered) may be assembled using the same movable contact-holder, this associations being advantageously achieved rapidly, thereby allowing a considerable reduction in the number of different parts required to manufacture an entire range of contactors. 
     According to the invention the switching device comprises a movable contact-holder fitted with a set of contact bridges and includes an electromagnet composed of a coil, a fixed framework and a movable framework. This movable framework is fitted by being clipped onto the movable contact-holder by assembling means suitable for both direct and indirect assembly. Said assembling means comprise at least one elastic clipping foot on the movable contact-holder. For example, assembly is said to be direct when the movable framework of the electromagnet is a magnetic blade comprising direct assembling means composed of two pins on the blade that clip directly into the elastic feet of the movable contact-holder. Assembly is said to be indirect when the movable framework of the electromagnet is, for example, a movable magnetic circuit comprising indirect assembly means composed of an intermediary part constructed as part of said magnetic circuit that can be clipped into the elastic feet of the movable contact-holder. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other characteristics of the present invention will be better understood from the following description which refers to the attached figures where: 
     FIG. 1 is a cross-section of the electromagnetic switching device of the invention; 
     FIG. 2 is a perspective view of the movable contact-holder of the device associated with a first type of moveable electromagnet framework; 
     FIG. 3 is a cross-section of the assembly shown in FIG. 2; 
     FIG. 4 shows the assembly of FIG. 2 fitted with a second type of movable framework; 
     FIG. 5 is a cross-section of the assembly shown in FIG. 4; 
     FIGS. 6 and 7 show how the contact-holder and the movable framework of FIG. 2 are assembled. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The switching device  1  shown in FIG. 1 is an electromagnetic contactor comprising various dual cutoff power poles. 
     Each power pole comprises a bridge of movable contacts  10  fitted with contact studs  11  and  12  that operate in conjunction with fixed contacts  13  and  14 . Each contact bridge  10  is fitted in a central protective housing  21  in the body of a movable contact-holder  2 . The movable contact bridges  10  are displaced by the translation movement of movable contact-holder  2  which is activated by means of an electromagnet  3 . 
     In FIG. 1 electromagnet  3  comprises a coil  31 , a fixed framework  32  and a plunging-type movable framework  30  that is subject to force provided by conical spring  37  that is mounted on the framework, the spring being slack when the said framework is in the rest position. When movable framework  30  is attracted to the fixed framework  32 , it causes movable contact-holder  2  to move in translation and close the contacts. When the movable framework  30  is moved to its rest position by the spring  37  changing from its compressed to its slack position, the contacts are opened. 
     The body  20  of the movable contact-holder is extended towards the electromagnet  3  by two lower sections  22  located on either side of contact-holder  2 . The movable framework  30  of the electromagnet is fastened to the two lower sections  22  of the contact-holder  2  by clip-type assembly means. On contact-holder  2  these assembly means consist of at least one elastic clipping foot  23 . In one preferred embodiment each lower section  22  of the contact-holder  2  has an elastic clipping foot  23  each of which has a fastening notch  24  facing into the body  20  together with, located underneath said fastening notch  24 , an internal oblique lateral bevel  24   a . Each notch  24  also has an upper edge  24   b  turned towards the body  20 . 
     In the example shown in FIG. 2 movable framework  30  is an E-shaped laminated mobile magnetic circuit comprising a core  35  with a longitudinal axis X, a rectangular cross-section aperture  34  that runs through core  35  transversal to longitudinal axis X and three frameworks  36  perpendicular to the core designed to be attracted by the fixed framework  32  when a current is passed through coil  31 . This type of movable framework is generally used for an AC electromagnet. 
     The means for indirectly assembling movable magnetic circuit  33  to contact-holder  2  consist of an intermediate part such as a metal key  4  that is required because the measurements of movable circuit  33  are not suitable to allow for the elastic feet  33  to separate. Key  4  is more or less rectangular in shape and has two ends  40  running lengthwise. It is fastened to movable circuit  33  by being elastically inserted into aperture  34  in core  35 . Once inserted, key  4  has a longitudinal curve that enables it to stay in position by pressing against the inner surfaces of aperture  34 . Lastly, key  4  is sufficiently long to be clipped between the two elastic feet  23  but with sufficiently small depth and thickness to allow its ends  40  to be housed inside notches  24 . 
     In the example shown in FIG. 4 movable framework  30  is the type of more or less rectangular magnetic blade  38  commonly used for DC electromagnets and has a plane upper surface  38   b  facing contact-holder  2 . The means for directly assembling the movable magnetic blade  38  onto the contact-holder  2  consist of two pins  38   a  located on opposite edges of blade  38 . These edges have a chamfer  38   c  and are designed to be clipped directly into the elastic feet  23  of movable contact-holder  2 . 
     In addition, an insulating flange  27  located under the central housings  21  and above elastic feet  23  separates the power poles from the movable framework to avoid any damage to the electromagnet during arcing when the contacts are opened. 
     The measurements of the lower section  22  of the movable contact-holder relative to the position of elastic feet  23  and insulating flange  27  are calculated so that the movable framework  30  is pressed against an lower surface  27   a  of the said flange to save space inside the device. Positioning means  50  are provided on the said flange to reinforce the abutment of the movable framework and ensure that it is pressed against insulating flange  27 . These means consist of two bosses  51  placed on the lower surface  27   a  of flange  27 . The bosses are advantageously separated by a distance equivalent to the width of the core  35  of E-shaped movable circuit  33  so that they operate in conjunction with the edges of the core so that it is positioned and fits between said two bosses. 
     The thickness of the magnetic blade  38  is calculated so that once it has been assembled with contact-holder  2  it can rest directly on the upper edges  24   b  of the notches  24  and against the lower surface  27   a  of flange  27 . Means  52  to complement means  50  are provided on upper surface  38   b  of blade  38 . Said complementary means  52  may consist of cavities that operate in conjunction with bosses  51  to position and anchor blade  38  against insulating flange  27 . 
     As shown in FIGS. 6 and 7, the movable framework of the electromagnet is clipped onto movable contact-holder  2 . Movable framework  30 , in this case E-shaped movable circuit  33 , is brought near the lower section  22  of the movable contact-holder parallel to the lower surface  27   a  of flange  27 , key  4  being positioned in an axis Y that passes through the two elastic feet  23 . The ends  40  of key  4  are then pressed against the oblique bevels  24   a  of elastic feet  23 , then when they are pushed towards the flange in the direction indicated by arrow F, the elastic feet  23  separate towards the outside of body  20  of the movable contact-holder to enable ends  40  of the key to enter notches  24 . When the ends are inserted, releasing movable circuit  33  causes the elastic feet  23  to return to the rest position, thereby retaining the framework. In order to facilitate fitting, key  4  has two apertures  41  near its ends  40 . A tool designed to exert the movement required to clip the movable circuit in place fits into these two apertures. 
     Aperture  34 , which is rectangular in cross-section, has four internal surfaces of which upper internal surface  34   b  is the nearest to insulating flange  27 . The two ends of aperture  34  form four edges at right angles with core  35  of magnetic circuit  33 , upper edge  34   a  matching the edge formed by upper inner surface  34   b . Once movable framework  33  has been fitted into movable contact-holder  2 , the shape of key  4  has a longitudinal curve which ensures that it is only maintained by three points of contact, i.e. the two ands  40  of key  4  resting on the upper edges  24   b  of fastening notches  24  (see FIGS.  6  and  7 ); in addition, the central section of key  4  rests on the upper internal surface  34   b  of aperture  34 . Thus by bearing on the upper edges  24   b  of notches  24 , they key  4  exerts elastic pressure on the upper inner surface  34   b  of aperture  34 , thereby helping to press movable circuit  33  against the lower surface  27   a  of the flange  27  of contact-holder  2  between the two bosses  51 . In addition, the longitudinal curve of key  4  prevents it coming into contact with upper edges  34   a  of aperture  34 , thereby avoiding premature wear of the key after a certain number of movements by the electromagnet of the electromagnetic contactor. 
     Assembly is identical when the movable framework of the electromagnet is a blade  38 . Once the blade has been brought close to the lower section  22  of the movable contact-holder parallel to lower surface  27   a  of flange  27 , the chamfers  38   c  of the two pins  38   a  press against the oblique bevels  24   a ; then when the blade  38  is pushed in the direction indicated by arrow F, the elastic feet  23  separate towards the outside of body  20  of the movable contact-holder to enable the pins  38   a  of the blade to enter notches  24  in the elastic feet.