GB1467857A - Transmission mechanism employing magnetic attraction - Google Patents

Abstract

1467857 Magnetic gearing Z G BLJUMSHTEIN and S V DMITRIEV 16 Nov 1974 49703/74 Heading F2Q In a gear mechanism, Figs. 5, 6, particularly for use in a fluid pressure indicating instrument, a frame comprising plates 1 and spacers 2 rotatably supports a driven toothed wheel 7 and a driving toothed sector 6, on axes such that no mechanical contact between the mutually opposing teeth can occur, and two permanent magnets 9, together with L-shaped magnetic yoke members 12, are fixed to the frame and provide magnetic flux through two flux paths, jointly passing through the air-gap between the teeth of wheel 7 and sector 6, which are each composed of a soft ferromagnetic material, thereby deriving a magnetic pull between the opposing teeth and permitting torque to be transmitted between them. Wheel 7 is mounted on a shaft 8 which may carry an indicating pointer, and sector 6 is adjustably mounted by screws 14 on a drive link 5, pivoted on a shaft 4, and which may be driven by the displacement of an aneroid, membrane or Bourdon tube pressure sensor. Two additional magnets 15 may optionally be fitted as a means of reducing friction at the bearings of shaft 8, by compensating for the radial magnetic force on the teeth. In an alternative embodiment, Figs. 11, 12, a permanent magnet 31 is mounted between two concave driving toothed sector members 29, jointly opposing a broad-faced toothed wheel 7, and providing a single and compact magnetic flux path, through an air-gap which may be adjusted by means of an eccentric screwed bush 32 carrying the sector pivot shaft 4. In further alternative embodiments, a single permanent magnet may be fixedly supported centrally between twin toothed sector members which may have inwardly-facing contrate teeth or bevel teeth, opposed to the end faces of a piniontype toothed driven wheel. A partition of diamagnetic material may be placed in the airgap between the teeth, as a sealing wall around the sensor element forming a protection against explosion. The toothed sector may have progressive variations in the pitches between adjacent teeth along its arc, as a means of providing a non-linear scale law relating output indication to sensor displacement, or alternatively, as a means to linearize the scale law of a sensor whose displacement with pressure is non-linear.