GB672711A - Improvements in or relating to spring assembly - Google Patents

Abstract

672,711. Spring mechanisms. GENERAL BRONZE CORPORATION. June 3, 1949 [June 3, 1948], No. 14944/49. Class 108(iii) [Also in Group X] A spring assembly comprises a pair of spaced bracket members, a rod rotatably mounted in one of the bracket members and having a fin extending h e 1 i - cally around the peripheral face thereof in one direction to a point between the ends of the rod and extendi n g helically around the peripheral face thereof in the other direction from the point towards the other end of the rod, a guide member attached to the other of the brackets and telescopically receiving the rod, the guide member having a guideway complemental to the fin on the rod, and a coiled tension and torsion spring attached to the rod at one of its ends and to the guide at its other end, whereby when the rod and guide are telescopically moved in relation to each other, the tensional and torsional forces of the spring will be varied. In the arrangement shown, as applied to a balancer for a vertically slidable window sash, a spring 10 is secured at its upper end 12 to one end of a rod 14 which is rotatably mounted at that end, in a bracket 18 attached to a window frame. The lower end of the spring is secured to a tubular guide 24 and a bracket 28 which is attached to a window sash. The spring is prestressed both tensionally and torsionally. The other end of the rod 14 is located within the guide 24 by an abutment 14<SP>1</SP>. A guideway 26 at the upper end of the tube 24 co-operates with fins 34 and 36 on the rod 14, which are formed by twisting the rod in opposite directions from an intermediate point 7-7 towards each end. In operation, extension of the assembly from the position shown in Fig. 8, increases the tension on the spring 10 and decreases the torsional effect thereon, due to the rotation of the rod 14 relative to the guide tube 24, until the guideway 26 is coincident with the intermediate section 7-7 of the rod. Further extension of the assembly rotates the rod in the opposite direction and the increased tension of the spring is then substantially counteracted by an increasing torsional effect thereon. In a modification, Figs. 11 and 12 (not shown), the torsional pre-stressing of the spring 10 is adjustable by means of a pin to which the guide tube 24 is secured and which is rotatably mounted in the bracket 28, the pin being held against rotation by the spring, by means of a pawl mounted on the bracket which engages notches on a head on the pin. The spring assembly may be enclosed in a casing 32, which is secured to the bracket 18. The Specification includes formulae for determining the lengths of the fins from each end of the rod to the point 7-7.