GB381635A - Improvements relating to dash pots - Google Patents

Abstract

381,635. Dashpots. ELLISON, Ltd., G. and ELLISON, G., Wellhead Lane Works, Perry Bar, Birmingham. July 25, 1931, No. 21336. [Class 108 (iii).] A dashpot which is adapted for controlling the solenoid plunger in an electric circuit-breaker tripping mechanism comprises a cylinder a containing oil or other fluid, the cylinder having a tapered bore at b in which normally rests the outer piston portion f. The piston-rod g carries an inner portion e of the piston, the outer and inner portions of the piston being tapered internally and externally so that there is a normal working clearance between these portions. A spring j extends between the lower piston portion and a sleeve h which is normally held against a shoulder i on the piston-rod, the upper end of the sleeve being a small distance from the transverse portion of the outer piston part f. With moderate pulls on the piston corresponding to moderate overloads the inner piston portion is first moved upward relatively to the outer piston portion until the upper end of the sleeve h engages the transverse part of the outer portion f so that the space between the piston portions, while greatly reduced, is not completely closed and the oil has two parallel paths, one between the periphery of the outer piston portion and the cylinder wall and the other between the two piston portions, the oil in the latter path passing through a hole or holes l in the upper piston portion. If desired the flow through the latter path may be further retarded by a plate m resting on the upper piston portion as shown. With very strong forces applied suddenly to the piston, however, the upward force on the lower piston portion, in addition to the movement between the piston portions already described, produces extra relative motion between the pistonportions due to compression of the spring j, so that the space between these portions is completely closed and the flow of oil entirely restricted to the path between the periphery of the outer piston portion and the wall of the cylinder. After the force acting on the piston rod is removed the piston parts return to their original position, the rate of restoration being rapid owing to the separation of the piston parts due to the spring j and also to relative motion between the upper end of the sleeve h and the transverse part of the outer piston portion f. The disc m rises in the return motion allowing a free flow of oil through the holes l. Specification 218,137, [Class 108 (iii), Springs &c.], is referred to.