GB1497146A - Plunger solenoid - Google Patents

Abstract

1497146 Electromagnets LAKETOWN MFG CORP Inc 1 April 1975 [1 April 1974] 13248/75 Heading H1P A cylindrical pull solenoid 10 (Fig. 3) is secured to a support (not shown) by a threaded shank 22 on endplate 21 with a central cylindrical ferromagnetic sleeve 24 as a leakage flux path the outer end of which is located in a central hole of the endplate, and the inner end is located at the midsection of the solenoid without extending at the midsection of the solenoid without extending over the airgap 37 to shunt the flux. An elongated brass tube 26 within the sleeve supports an elongate slidable cylindrical ferromagnetic plunger 27 therein whose outer end carries a snap ring 28 retaining a concentric biasing coil spring 31. The endplate 19 carries a ferromagnetic polepiece 32 extending inwardly towards plunger 27 with a stepped cylindrical head fitting into cylinder 26; the larger diameter 33 of the polepiece fitting into the solenoid to absorb the useful and lakage fluxes without saturation. Faces 34, 36 of polepiece 32 and plunger 27 are normally spaced by gap 37 and a wound solenoid 38 is located inside shell 16 between end plates 19, 21 with energization leads 17; the crosssection of sleeve 24 providing a magnetic path for leakage flux across the radial gap between the sleeve 24 and shell 16. The cross-sectional area of polepiece 32 at diameter 33 provides a magnetic path for the total radial leakage flux between polepiece 32 and shell 16 plus the active flux across gap 37. The dimensions a, b, c are proportioned to minimize leakage flux and optimize working flux. In a modification (Figs. 5, 6, not shown) the fixed polepiece has a removable head of e.g., ferromagnetic stainless steel threaded thereto, and in a further modification the head has a cone-shaped recess receiving a similarly coneshaped face of the plunger.