Patent Publication Number: US-4484168-A

Title: Electromagnetic relay

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an electromagnetic relay. 
     Published German patent application DE-OS No. 30 08783 discloses a relay in which the coil form together with the U-yoke carrying the foil-spring portion consists of one single molded plastic part. This type of relay has proved well suitable in practice. However, to obtain high accuracies during manufacture of the relay, it is necessary to adhere exactly to the molding conditions of the coilform, especially to the temperature, and the mixing ratios in the case of plastic materials mixed with reinforcing fiber materials. 
     It is the object of the present invention to permit an economical and qualitatively high-grade manufacture of the foil-spring portion while maintaining the same good or even better functioning thereof, in spite of low precision requirements in manufacturing the coilform. 
     SUMMARY OF THE INVENTION 
     According to the principal aspect of the invention, in a relay of the type described above the crosspiece with the foil-spring portion is an inexpensive punched part made of a suitable resilient material, such as spring bronze. By elastically deflecting the legs of the U-yoke of the relay and/or the crosspiece, the crosspiece can easily be engaged into slots formed in the legs. In this way, it is possible to replace the cross-piece with the foil-spring portion by a different one whose spring action acts in a different intensity and/or in a different angle upon the tilting armature of the relay. Thus, the coilform can also be used with differently designed tilting armatures, hence e.g., for different types of relays. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a perspective view of a coilform incorporating the crosspiece of the invention; and 
     FIG. 2 is a longitudinal sectional view of the same coilform wound and provided with a magnet system. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a relay coilform 1 injection-molded from an elastic plastic material. Molded to one flange 2 of the coilform are two legs 4, 5 extending in the direction of the coil axis 3. Each leg 4 and 5 is provided at its end 6 with at least one slot 7. The slots are engaged by flap members 8 formed on the ends of a crosspiece 9 of an elastic resilient material. The engagement is effected by elastically deflecting the legs 4, 5 and/or the crosspiece 9. Both the slots 7 and the flap members 8 are so designed that there is obtained a fixing of the crosspiece 9 without any backlash. In this way, the legs 4, 5 together with the crosspiece 9 form a U-shaped yoke. 
     The crosspiece 9 has an integral foil-spring portion 10 which resiliently presses against the angular edge of an angular tilting armature 12 of the magnetic circuit consisting of the core 13 and the magnetic yoke 14. A magnetic coil 15 is wound around the core of the coilform. The crosspiece 9 with the integral foil-spring portion 10 may be formed of a resilient metal, such as spring bronze, by a stamping operation or the like. 
     For increasing the strength of the coilform 1, especially when subjected to higher temperatures, the plastic material may be reinforced with fiber, such as glass fibers.