Patent GB-792530-A (GB)
Title: Improvements in or relating to electro-magnetic clutches
IPC: F16D27/08
Filed: 1956-07-09
Abstract: 792,530. Friction clutches. SOC. ANON. FRANCAISE DU FERODO. July 9, 1956 [July 7, 1955], No. 21252/56. Class 80 (2). An electromagnetically engaged friction clutch of the type having a driving yoke 10 supporting the solenoid and carrying a plate 13 adapted to engage a driven friction disc 15 while an armature 12 carries a plate 14 adapted to engage the other side of the friction disc, is characterized by yielding means connecting the yoke 10 to the disc 14, and/or the armature 12 to the disc 13, so that chatter in the clutch caused by roughness of the working surfaces, or by changes in expansion of the clutch parts due to increase of temperature under working conditions, is absorbed or reduced. In the form shown in Fig. 1, radially projecting lugs 116 on the plate 13 are each provided with two holes 20 to receive pins 17, 27. The pins 17 are screwed at 18 into the yoke 10, and pass with radial clearance through their holes 20. The pins 27 are screwed into the radially projecting lugs 116 of the plate 13 and have reduced end portions 30 carrying spring washers 32 and hard washers 33. When the solenoid is energized, the armature 12 and plate 14 move leftwards of Fig. 1, to engage the plate 14 with the disc 15 and also move the disc 13 leftwards, thus compressing the spring washers 32 and ensuring a gradual take-up of drive. When the faces 26, 25 of the yoke 10 and plate 13 engage, an air gap is still maintained between the yoke and the armature. The driven disc 15 is provided with friction segments the number of which is determined in relation to the number of radially projecting lugs 116, so that deforma-. tion of the clutch parts as the clutch slips does not cause resonant vibrations within a critical range of vibrations emanating from a prime mover driving the clutch &c. In the modification shown in Figs. 2, 3, the radially projecting lugs 116 are provided with holes 36, 37, the holes 37 being of elliptical cross-section with the major axes of the ellipses lying along the radii of the disc 13. Pins 42 passing through the holes 37 are screwed into the yoke 10 and have diameters equal to the diameters of the minor axes of the ellipses. Pins 38 passing with clearance through the holes 36 are screwed into the yoke 10 and carry springs 39 lying in diametrically enlarged portions of the holes to bias the disc 13 towards the yoke. In the form shown in Figs. 4, 5, the armature 12 and plate 14 are secured together by bolts 44. Tangential strips 43 connect the armature 12 to the yoke 10, while the plate 13 is secured to the yoke by tangential tongues 45. Spring strips 46 bias the disc 13 away from the yoke 10. Pins 48 screwed into the yoke 10 pass with clearance through holes 47 in the radially projecting lugs 116 of the plate 13. The tongues 45 and the play between the pin 48 and its hole 47 allow the disc 13 to expand radially. In the form shown in Fig. 6, pins 55 are screwed into the yoke 10 and pass with clearance through holes 58 in the disc 13. Compression spring 60 surrounds the ends of the pins 55 and bias the disc 13 to the left, while interdigitating axial projections 50, 51 on the yoke and disc connect these two parts for rotary motion. The arrangement is such as to permit radial expansion of the disc 13, while the springs 60 cushion the engagement of the clutch. In another form, Fig. 7 (not shown), a pin screwed into the armature 12 passes with clearance through a hole in the disc 14, and rocking edges on disc 14, adjacent to the pins, engage the armature 12. In a further modification, Fig. 8 (not shown), pins screwed into the yoke 10 pass with clearance through holes in the disc 13, a washer of fibre or other suitable thermally insulating and/or magnetic flexible material surrounding each pin and lying between the yoke and disc.