GB648989A - An arrangement for winding up or unwinding spiral springs more especially for balancing sash-windows or the like - Google Patents

Abstract

648,989. Springs. VRIES, A. DE, and VRIES, L. DE. March 5, 1948, No. 6963. [Class 108(iii)] [Also in Group X] In an arrangement for winding up or unwinding spiral springs, more especially, for balancing sash windows &c. a twisted strip having part of its length twisted in one direction and part in the other, or a screw threaded bar with a part of righthand thread and a part of left-hand thread, is used first to twist the spring in one direction and then in the other as the strip or bar is moved relatively to the spring. Fig. 1 shows the invention applied to a window sash 1 slidably mounted in the frame 2. A tension spring 3 between the sash and frame is attached at one end to the sash at 4, and at the other end 5 to a tube 6 which is attached by a fastener 7 to the frame at 8. A torsion spring 9 within the tube 6 is fixed to the tube at its upper end, and at the lower end is fixed to a slotted bushing 10 which is mounted for rotation in tube 6 and at 11 engages the spiral member 12 which is secured to the spring 3 at 13, reverses its direction of twist at 14, and whose pitch decreases from 14 towards each end. The sash weighs 25 Kgs, and when the window is fully opened spring 3 exerts an upward force of 15 Kgs, and spring 9 is biassed so that it tends to unwind in a clockwise direction when viewed from above, and exert a rotational force. The upward vertical component of which is 10 Kgs., so that the resultant upward force is 15 Kgs. As the window is moved to the half-way position, spring 3 is stretched so that the force it exerts increases to 25 Kgs., and spring 9 is still further wound, but due to the increase in the pitch of the spiral it exerts a decreasing upward vertical force which becomes zero at point 14 where the pitch is 90 degrees. At the half-way position, therefore, the resultant upward force is again 25 Kgs., and spring 9 is biassed to its maximum extent. When the sash is further lowered spring 3 is stretched and the upward force it exerts increases to 35 Kgs. at the closed position, and spring 9 is unwound by the action of the spiral, but because the pitch of the spiral decreases spring 9 experts an increasing vertical force, in a downward direction because of the hand of the spiral, which becomes 10 Kgs. in the closed position, so that the resultant is again an upward force of 25 Kgs., the weight of the sash. The tension spring may be replaced by a compression spring in another arrangement.