Abstract:
A proximity detection switch, including a housing with a switching block controlled by a sensor component contained therein and housing connection elements for external connection via a cable, the body and a removable cover each having a flange part for cooperatively forming a flange that defines a sealed aperture for a cable to pass therethrough. The device further includes a detachable cable-entry coupling for sliding engagement with the body along a direction approximately perpendicular to the plane of the bottom wall of the body.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a movement or proximity detection switching device, including a sensitive component to carry out this detection, and a body defining a housing for a switch assembly controlled by the sensitive component and connected to the outside via an electrical connection cable, the housing being closed by a removable cover. 
     Description of Prior Art 
     Limit or safety switches for industrial use are well known (for example XCK-J products, see Telemecanique catalogue “Limit switches”, April 1999). Cabling the contact block of such devices is difficult and the different devices in a range require different casings when it is required to connect to these casings cables of different diameters or to add to these casings cable entries equipped with different threads. 
     The document WO-99/27 551 shows a limit switch wherein the body and the cover each have a threaded half flange to receive a maiden nut of a seal coupling. The effect of tightening the nut is to distort or reposition the cover, which corrupts the seal qualities of the device. 
     SUMMARY OF THE INVENTION 
     The purpose of the invention is to make it easier to assemble and to cable, in the body of such devices, a switching block equipped with connection elements, ensuring the assembly is well sealed, while allowing cables of different diameters or couplings with different characteristics to be used without modifying the body. 
     According to the invention, the detachable cable entry coupling is introduced by means of fitting elements, by a sliding movement along a direction approximately perpendicular to the main wall of the cover, in guiding and holding means provided in the body. It is possible in this way to add to a same device body couplings which are differentiated by their internal diameter or by their thread type. 
     The guiding and holding means of the body are preferably rectilinear and the fitting elements of the coupling form a frame fitted on its sides with insertion means complementing the guiding and holding means, the switching block and the coupling being introduced into the device body in a same direction. The frame is to advantage symmetrical, located at the end of the coupling and housed partly in the housing of the switching block and partly in guiding and holding means provided in the cover. 
     The coupling carries an external seal and the cover is mounted on the body by means of pivoting elements, preferably hooks, provided near one end and has at the other end a screw for fixing to the body, the pivoting elements being offset relative to the plane of the main wall of the cover so as to increase the tightening torque of the seal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The description will be given below of a non-restrictive embodiment of the invention, in relation to the appended drawings. 
     FIG. 1 shows in perspective a limit switch according to the invention. 
     FIG. 2 is a side view on a smaller scale of the switch. 
     FIG. 3 shows in elevation the removable coupling of the switch. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The switching device shown in the figures is a limit switch, which includes a body  10  and, as a component sensitive to the movement of an object, a pivoted lever assembly  11  fixed to the body near a first end  10   a  of the latter. The body is parallelepiped in general shape and defines near this end  10   a  a housing  11   a  to receive a part of the assembly  11 ; the body also defines in its intermediate part  10   c  a housing  12   a  to receive, by insertion along a direction Y, a detachable switching block  12  which is activated by the assembly  11 , the housing  12   a  normally being closed by a cover  20 . The switching block  12  has mechanical or electronic switching elements and it is connected to a component or circuit external to the device by means of connection elements  12   b  to which are connected conductors collected into a cable C (see FIG. 2) which is held by a coupling  30  itself fixed to the body  10  towards a second end lob of the latter. The block  12  has towards the top (FIGS. 1 and 2) a snap-on wafer  12   c,  which conceals the connector area after cabling. The body  10 , the cover  20  and the coupling  30  are made of an insulating or metal material. 
     The body  10  of the device has approximately plane lateral walls  13  and a plane bottom wall  14  of plane P which delimit the housing  12   a . At the end lob, the body  10  has a wall  15  for the cable C to pass through. The wall  15  has a semicircular cut-out which forms a half flange  16  to constitute a channel for the cable C. Towards the inside of the body relative to the flange are provided rectilinear means  17  for guiding and holding the coupling, for example grooves and/or ribs orientated perpendicular to the plane P of the bottom wall  14  (vertical in the figures). 
     A cover  20  is fixed to the body so as to close the aperture through which the switching block  12  is introduced. It includes a main closure wall  21 , which is plane or skew, extending approximately parallel to the plane P of the rear surface  14 , so as to cover the housing  12   a.    
     The cover  20  has transverse walls  22  which become narrower from its foot end  22   b , which is close to lob, towards its head end  22   a , which is close to  10   a . The walls  22  have for example a general trapezoidal or triangular shape and each end in a hook  23  intended to be supported on the body by engaging with a grip  18  provided in a lateral wall  13  of the body at a significant distance from the wall  21 , for example halfway between the walls  21  and  14 . Instead of hooks  23 , snap-on pivots may be provided. The grips  18  are located nearer the wall  15  than the means  17  and below the axis X (FIG.  2 ). In the middle of its head end  22   a , the cover  20  has a hole intended for a screw  24 , this screw engaging with a tapped hole of the body so as to provide the fixing of the cover. 
     The cover  20  has a wall fitted with a semi-circular cut-out which forms a half flange  26  complementing the half flange  60  of the body  10 . Rectilinear means  27  for guiding and holding the coupling  30  (vertical in the figures), for example symmetrical with the means  17  relative to the assembly drawing, are provided inside the cover. Moreover, the cover  20  carries on its periphery a bi-injected seal bead  28  intended to engage with the upper edge of the body which edges the housing  12 . 
     The coupling  30  has a body  31  with a general revolution shape equipped with a partly threaded channel  32  of axis X to receive the cable C and a fitting not shown providing the local seal round the cable. The fitting is put under pressure by a component not shown which is screwed into the threaded part of the channel  32 . 
     The coupling has a cylindrical part adapted to the half flanges  16 ,  26  with an external groove  33  in which is housed a sealing O-ring  34 , which seal engages therefore with the half flanges; in its part intended to be housed inside the body  10 , the coupling  30  has an assembly frame  36  approximately square or rectangular. The flange  36  forms a symmetrical frame provided on its sides with rectilinear insertion means  37  (for example ribs and/or grooves) complementing the means  17  in the body so as to allow a detachable assembly of the coupling. The means  37  engage with the means  17 ,  27  by fitting; the means in question may have a snap-on or hard friction effect added to the fitting effect. 
     The couplings  30  may thus differ in their part holding the cable and/or in their cable gland threading while preserving a part integrated with the body, particularly an assembly flange  36 , which remains unchanged. The symmetrical H-shape of the frame makes it possible to assemble it in the body in two positions offset to 180° and to obtain a similar fitting in the body and in the cover. 
     Cabling the switching block  12  can be comfortably carried out when the block has been introduced along the direction Y perpendicular to the bottom wall  14  inside its housing  12   a  of the body  10 . The coupling  30  of the type suitable for the cable, and engaged on the cable, is then slid into the means  17  along the same direction Y, with contact made between the seal and the half flange  16 . The cover  20  is engaged by its hooks  23  onto the grips  18  and by its means  27  onto the means  37  of the coupling, then is set to pivot around these grips, whereas the O-ring  34  is supported on the half flange  26 . Tightening the single fixing screw  24  allows the seal  34  to be put under pressure, and for this to be done with a force which is increased by offsetting the hooks  18  relative to the plane P of the wall  21  of the cover. 
     The invention, described in relation to a limit or safety switch, also applies to all proximity detectors including terminal blocks or removable switching blocks.