Patent GB-661386-A (GB)
Title: Improvements in or relating to movement and vibration dampers
IPC: F16F7/02
Filed: 1948-06-17
Abstract: 661,386. Vibration dampers. POWNALL, G. L. DU T. June 16, 1949 [June 17, 1948], No. 16275/48. Class 108(iii) In a vibration damper of the type comprising friction elements mounted for relative rctation in pressure contact with one another, the friction elements are loaded by electromagnetic means controlled by an automatic device adapted to reduce the electromagnetic loading on relative movement of the elements in one direction and to increase the loading on relative movement of the elements in the reverse direction. In the arrangement shown, a shaft 21 journalled in a back-plate 10 and a cover member 18, carries an annular member 22. which is slidably mounted thereon and which houses an electric winding 24. The latter co-operates with a winding 13 carried bv the back-plate 10. Annular friction elements 26 and 27, carried by the members 22 and 18 respectively and interspaced floating friction elements 28, are loaded by attraction between the cover plate 10 and member 22 upon energization of one or both coils 13 or 24, the current to one or both of which is controlled to vary the degree of resistance offered by the friction elements to relative rotation. In a modification, Fig. 2 (not shown) the friction elements which comprise the outer face of a slidably mounted electromagnet engaging through a floating friction lining, a friction member carried by the shaft, are loaded by repulsion between the electromagnets. In either arrangement. the coils may be connected in series or in parallel. The control device is housed in an annular member 16 and comprises a metal disc 41. Fig. 3, which is freely mounted on and insulated from a spigot of the shaft 21 and on which is freely mounted a rocking lever 43. An insulating pad 47 at one end of the lever is spring- loaded, by a blade spring 45 fixed to a lip 46 on the disc 41, on to a pin 48 carried by an arm 49 which is secured to the spigot adjacent the disc 41. The pin 48 also bears against an insulating pad 50 secured to the disc 41. A contact 51 at the other end of the lever 43 co-operates with a contact 52. insulated from the disc 41. and connected to an arcuate conducting member 56 having a lip 56a forming a continuation of the lip 46. Spring-loaded brushes 58, 59 bearing on the lips 56a and 46 and carried by an annular insulating member 62 mounted in the member 16, are connected through fittings 63 to a terminal 66 and one end of the ceil 13 respectively, and also to opposite ends of a resistance winding housed in a peripheral channel 65 of the member 62. The other end of coil 13 is connected to a terminal 69 and. where the two coils are series connected, the terminal 69 is also connected, through a brush (not shown). to a slip-ring 70, Fig. 1, which is insulated from and fixed to the member 22. One end of the coil 24 is connected to the ring 70 and the other end " earthed" through the member 22. In the application to a vehicle suspension, upward movement of an axle relative to the chassis, effects displacement of disc 41 through the medium of pad 50 to maintain contacts 51. 52 open, the coils 13. 24 being connected in series with the resistance. On downward movement of the axle. the disc 41 is restrained by friction of brushes 58, 59 and the contacts 51. 52 are closed by movement of the arm 49 to short-circuit the resistance through the member 56, spring 45, and disc 41. Where the coils are connected in parallel, the resistance is replaced by the contacts 51. 52 being arranged to disconnect one of the coils 13 or 24. a condenser being connected across the contacts to prevent sparking. Clearance between the electromagnetic cores may be maintained, irrespective of wear of the friction surfaces by the means disclosed in Specification 661.121.