GB853135A - Speed governor for electric motors - Google Patents

Abstract

853,135. Centrifugal switches. LIMIT ENGINEERING GROUP Ltd., and COLLINS, A. L. Oct. 3, 1958 [Feb. 24, 1958; June 11, 1958], Nos. 5859/58 and 18737/58. Class 38 (5). [Also in Groups XXVI and XXXV] A switch for controlling the speed of an electric motor comprises a plastic disc 40 having an upturned edge 41 and a central sleeve 42 which is a tight fit on the commutator 43. Two weights 45 and 46 are arranged to slide radially on ball bearings 51 with metal U-shaped members 47, 48 secured to the disc 40. Springs 58, 59 attached to insulating rods 56, 57 pull the weights 45, 46 inwards and cause silver contacts 54, 55 carried thereon to engage the commutator 43 through cut-away parts of the sleeve 42. Certain connections from armature 70 that would normally go to the commutator segments engaged by contacts 54, 55 are taken instead to stiff wires 63, 64 extending from the weights 45, 46, respectively, via holes 65, 66 in disc 40. The normal motor brushes are shown diagrammatically at 67 (Fig. 2) and engage the commutator in the usual manner. When the motor speed rises above a desired value one of the contacts 54, 55 first breaks engagement with its associated commutator segment and opencircuits at least part of the armature until the speed falls and contact is re-established. In a modification (Figs. 4 and 5, not shown) the rods 56, 57 are conductive and act as bridging members across metal pins half-embedded in semi-circular projections formed integrally with disc 40. The weights do not carry contacts for engagement with the commutator but are connected to respective segments via the wires 63, 64 and the broken armature windings are connected to the bridged metal pins in disc 40. The springs 58, 59 are insulated from the rods 56, 57 by sleeves thereon. Either embodiment may be mounted on the motor shaft at the end remote from the commutator, and for the first arrangement the sleeve 42 then carries a split metal ring to take the place of the commutator segments engaged by contacts 54, 55. For spark suppression the casing 40 may be moulded in a material having a relatively low electrical resistance or may have resistance paths provided therein.