Patent Publication Number: US-6664488-B2

Title: Contactor with a front mask

Description:
FIELD OF THE INVENTION 
     The present invention relates to an electromechanical contactor comprising a casing which houses a moving contact holder, the casing having a front portion equipped with connection terminals accessible through a front face, as well as a pushbutton which is connected to the contact holder and which is visible and accessible through the front face. 
     BACKGROUND OF THE INVENTION 
     Contactors of this type are currently used for controlling low voltage electrical loads. The fixing of an electromechanical ancillary block having an auxiliary signalling function or another function which may be used in an automation plan, on the front of the casing of such a contactor, is frequently provided. The ancillary block has auxiliary contacts and a mobile component positioned in such a way that it cooperates with the push-button of the contactor unit in order to control the auxiliary contacts. The ancillary block may be attached to the contactor unit so as to be removable, usually by means of catches provided on the front face of the casing. It turns out that the state of the contactor may be viewed according to whether the push-button is protruding or recessed relatively to the front face; on the other hand the push-button is also used for manually testing the proper operation of the contactor&#39;s mobile contact holder. Now it may be dangerous to carry out this test, which actually switches the load while the contactor is energized. 
     The object of the present invention is to prevent the push-button from being actuated manually, without affecting the possibility of viewing the state of the contactor, by taking advantage of the arrangements made on the front of the contactor&#39;s casing for providing fixation of a front ancillary block or by taking advantage of similar arrangements. 
     According to the invention, the contactor&#39;s casing provides on its front face and near the mobile pushbutton, fitting or snap-on catches, suitable for receiving an ancillary block which may be coupled with the push-button or suitable for mounting in the direction of the casing&#39;s height; a cover is removably assembled on the front portion of the casing so as to hide the push-button, by being mounted on the front portion of the casing by means of assembling shapes cooperating with the catches. In this manner, the mounting of the cover makes use of the existing catches for assembling an ancillary block and/or facilitates straightforward assembly as for an ancillary block. 
     Advantageously, the cover may be a small plate which has a transparent portion located in front of the push-button and a hollowed-out portion edged with guide grooves for fitting and sliding onto the catches, in the direction of the contactor&#39;s height; abutment shoulders provided at the end of the grooves preferably cooperate with abutment portions notably provided on the catches. 
     The cover preferably has a width substantially the same as that of the casing and a height such that the terminals remain accessible when it is assembled with the casing, while it provides on one long side a transverse surface adjacent to the terminals, making wiring easier. 
    
    
     BRIEF DESCRITPION OF THE DRAWINGS 
     A description of a non-limiting embodiment of the invention will be made hereafter with reference to the appended drawings. 
     FIG. 1 shows a contactor in accordance with the invention, without any front cover, in perspective. 
     FIG. 2 is a same view showing the cover assembled with the casing of the contactor. 
     FIG. 3 is a diagrammatic elevational view showing the front portion of the contactor and an ancillary block or the cover not assembled together. 
     FIG. 4 is an exploded top view of the front portion of the contactor and the cover. 
     FIG. 5 shows the front portion of the contactor with the cover in perspective from above. 
     FIG. 6 is a perspective view of the cover. 
    
    
     DESCRITIPION OF THE PREFERRED EMBODIMENTS 
     The contactor as shown comprises a casing  10  with a front portion  10   a  and a rear portion  10   b . The rear portion  10   b  is designed to enable the contactor to be fixed onto a holder, whereas the front portion  10   a  has a front face  11  provided with apertures  12  for access to the terminals  13 . In the present example, the terminals have a monitoring or controlling function, whereas the contactor&#39;s other terminals  14 , i.e. power terminals, are located at the rear of the terminals  13 . It is obvious that any other arrangement of the terminals may be provided, wherein the terminals  13  may in particular, be power terminals. 
     The front face  11  is provided with an opening  15  through which protrudes the free end  16   a  of a mobile push-button  16  either firmly joined or connected to a mobile contact holder, not shown, which is housed in the casing  10  and which is able to move perpendicularly to the front face  11  in response to the pull of an electromagnet. The end  16   a  of the push-button is protruding when the contactor is at rest (state illustrated in FIG. 1) and recessed when the contactor is activated. When an ancillary block  30  of auxiliary contacts is added to the contactor, as described later on with reference to FIG. 3, the push-button has the role of a driving unit for the ancillary block&#39;s own contact holder unit. In addition, the push-button has a testing function, enabling an operator to check, by pressing the push-button, whether the contactor is operating normally. 
     Provision is made for two fixed tenons  17  provided with grooves  18  towards the outside (to the left and to the right in FIG. 1) on the one hand and on the other hand a guide flange  19  next to the fixed tenons and provided with grooves  19   a  towards the outside, both protruding from the front face  11  of the casing  10 . The grooves  18  and  19   a  enable the ancillary block  30  or a cover  20  to slide parallel to the front face  11  of the contactor and the direction of the contactor&#39;s height (direction indicated by the arrow in FIG.  3 ). Sliding the ancillary block or the cover enables them to catch on the fixed tenons  17  and the flange  19 , here by fitting together. Additionally the tenons  17  have an abutment function for the ancillary block or the cover. 
     The cover  20  is a small plate made of opaque insulating plastic material with a generally rectangular contour provided with a transparent central window-like portion  21  located, in the mounted position (FIG.  2 ), in front of the drive end  16   a  of the pushbutton  16 , so that it is possible to see the state of the latter and consequently determine whether the contactor is in the on or off state. It is understood that at the same time the cover prevents the operator from carrying out any test operation. 
     The cover  20  comprises towards the front face  11  of the contactor a rear surface  20   a , which comes into contact with the face  11 , when fitted into place and is kept in close contact with this front face by clearance effects notably from the grooves  23 . The cover  20  provides a hollowed-out portion  22  edged with guide grooves  23  so that it may be slid over the components  17 ,  19 , with abutment shoulders  24  at the end of the grooves which cooperate with the tenons  17 . The grooves  23  have a first portion  23   a  cooperating with grooves  19   a  and a second portion  23   b , narrower than portion  23   a , cooperating with grooves  18  (themselves being less far apart than grooves  19   a ). The cover may thus be engaged and held in place very easily, like a passive ancillary. In addition, a passage  25  for a lead sealing unit  26  which is intended for jamming the push-button, opens into the lower part of the hollowed-out portion  22 . At its upper portion, the cover  20  provides a flat transverse surface  27  which facilitates wiring within the apertures  12  for accessing the terminals  13 . 
     The ancillary block  30  has a rear surface  31  provided with a socket  32  which may move perpendicularly to the front face  11  of the casing  10  and which may be coupled onto the end  16   a  of the pushbutton  16 . The block  30  may be applied onto the front face  11  (see FIG.  3 ). The ancillary block  30  has guide grooves  33  able to cooperate with the grooves  18  of the tenons  17  and with the grooves  19   a  of the flange  19 . Shoulders  34  are provided on the edge of the grooves  33  so that they are applied against the tenons  17  at the end of travel during the fitting, according to the arrow in FIG.  3 . It is obvious that if other means are provided for fitting or snapping the ancillary block onto the contactor&#39;s casing, the cover may be removably fixed to the front portion of the casing  10  by these means.