Patent Publication Number: US-4322702-A

Title: Electromagnetic relay

Description:
BACKGROUND OF THE INVENTION 
     The invention concerns an electromagnetic relay with a trough-shaped base body or member consisting of insulating material, which serves as a carrier for the functional elements of the relay and which is closeable by means of a flat cover which is supported at least partially on the edge of the base member. 
     A relay of this sort is already known from German Pat. No. 2,332,989, incorporated herein by reference. The advantage of such a construction is that the cover can be punched from a sheet or film in the shape of a flat plate. Therefore, this cover is significantly simpler and cheaper to manufacture than other covers with edges which are shaped on or with holding elements which must be manufactured by means of injection molding or similar methods. For anchoring the cover in the case of the known relay, on the yoke of the magnet a holding element is shaped for example, similar to a dove tail and which is brought into engagement with a perforation in the cover. The stamping of the yoke of the magnet with the holding element shaped on nevertheless brings about a relatively rapid wear of the tool; besides this, it is unfavorable for some applications if the holding element is accessible as a metallic part on the surface of the relay. When voltage-carrying parts are arranged in the vicinity, therefore, an additional insulation must be provided. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to design a relay of the kind described above with a cover in the shape of a flat plate in such manner that no metal parts appear on the surface of the housing for the holding of the cover. According to the invention, this problem is solved in that on the base member, two holding lugs are shaped on which overlap the surface of the cover in directions opposing one another. 
     These holding lugs can be shaped onto the housing during its manufacture in the transfer molding process or a corresponding method. In this manner, the punching of the yoke is simplified and simultaneously the insulation of the relay housing is improved. 
     Under certain circumstances it is advantageous that the cover displays recesses which are displaced with respect to the holding lugs and which correspond to their size. Such recesses can be dispensed with if the holding lugs are provided on the housing edge. In another embodiment, however, the holding lugs are arranged in a practical manner on an intermediate wall approximately in the middle of the housing. In this case, a recess of the cover which narrows in the direction of insertion is advantageous. The cover is thereby placed with the recess over the holding lugs and is fastened by means of a simple sliding on. In a practical further development, besides this it is provided that ribs corresponding to the size of the recesses are provided in the housing, displaced with respect to the lugs. These ribs after sliding on of the cover lie under the recess so that the relay remains protected against dust despite the recess in the cover. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a relay housing with cover in accordance with the invention; 
     FIGS. 2 and 3 show two views of the housing during sliding on of the cover; and 
     FIG. 4 shows a further embodiment of the housing and the cover. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a relay housing 1 in the form of a trough which is open upwardly. This housing 1 is closed by means of a plate-shaped cover 2. The cover is layed on an inner recess 1a in the shape of a step of the housing edge lb so that it is surrounded all the way around by the housing edge; thus its surface terminates with the housing edge. 
     For fastening of the cover, a raised rib 4 with a holding lug 5 on both sides is shaped on a housing intermediate wall 3. Correspondingly, the cover 2 has a recess 6, the wider part 6a of which corresponds to the width of the holding lugs 5 and the narrowed part 6b of which corresponds to the width of the rib 4. So that the cover can be slid on, the parts 6a, or respectively, 6b of the recess 6 in each case are somewhat wider than the lugs 5, or the rib 4, respectively. 
     FIGS. 2 and 3 respectively show the sliding on of the cover from above, in section. The cover 2 is placed with the recess 6a over the holding lugs 5 and is anchored under the holding lugs 5 by means of displacement in direction of the arrow 7. In order to cover the wide opening 6a of the cover which is necessary for the insertion of the cover, a widened rib 8 is provided in the housing. With the cover set on, therefore, the recess 6a is brought to lie over this rib 8, so that the interior of the relay is protected against dust. 
     FIG. 4 shows a further embodiment. The relay housing 11 is in this case provided with two holding lugs 13 which are shaped on edge regions which lie opposite one another. The cover 12 has lateral recesses 16, corresponding in each case to the holding lugs for the insertion. Block out ribs 17 are also provided to cover the recesses 16 when the cover is in position. In an embodiment form which is not further depicted, these recesses 16 could also be left out. In this case, the cover must be pushed through under the holding lugs 13 from the beginning. 
     In the case of the inventive relay, the cover can be cheaply manufactured as a simple punched part. The cover is protected against falling out upward by means of the holding lugs and laterally by means of the housing edge, even in the case of high impact stresses. Otherwise, the cover can also be removed in a simple manner without disruption in the case of reworking of the relay, and can be replaced again. 
     Although various minor modifications may be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon, all such embodiments as reasonably and properly come within the scope of my contribution to the art.