GB648990A - Spring construction more especially for balancing sash-windows or the like - Google Patents

Abstract

648,990. Springs. VRIES, A. DE, and VRIES, L. DE. March 5, 1948, No. 6964. [Class 108(iii)] [Also in Group X] A spring construction, more especially for balancing sash windows &c. comprises one or more springs which on being extended or compressed are simultaneously wound up or unwound whereby the reaction force is varied in a desired manner over the compression or extension range. The winding or unwinding may be effected by a twisted . strip or by a screw threaded bar. The arrangement showr in Fig. 1 comprises a pair of telescoping tubes 1, 2 containing two halves 3, 4 of a coil spring which merge at 5 where they are connected to a tube 7 by a pin 6. The tube 7 is slotted at both ends 8 to receive two spiral members 9, the twists of which are reversed at points 10 and which are connected with the spring ends 11. A 25 Kg. window sash is attached to the upper end of tube 2, and the lower end of tube 1 is attached to the frame. The spring halves 3, 4 are biassed to exert an upward force of 15 Kgs. and to exert a torque on the tube 7, i.e. they tend to unwind in a clockwise direction as viewed from above. so that the vertical component of the torque which will resist compression of the balance is 10 Kgs. Thus the effective upward force on the sash is 25 Kgs. As the sash is lowered to the halfway position the compression force of the spring increases to 25 Kgs. and the tube 7 rotates to wind up the spring, but due to the increase in pitch of the spirals 9 the vertical components of the torque decrease and become zero when the slots are at points 10. The resultant upward force is therefore 25 Kgs. When the sash is further lowered the force due to the compression of the spring increases to 35 Kgs., and the vertical component of the torque, because 'of the reversal of direction and decrease in pitch of the spirals, tend to contract the spring balance with a force of 10 Kgs. Thus the effective upward force is again 25 Kgs., the weight of the sash. In the construction shown in Fig. 2 the twisted strip 12 is fastened to the window frame at 13 and 16, and the slotted bushing 14. slidable on the strip, is secured to the spring 15 which is fixed at the upper end to the frame at 16. When the window is moved the projection 17 thereon carries the bushing 14 which is also rotated by the strip. The spring is therefore simultaneously stretched and wound as the window is closed, and compressed or unwound as it is raised. As the spring is tensioned, on closing, it exerts an increasing upward vertical force, but the vertical component of the torque exerted on the spiral decreases at the same rate. because of the increase in the pitch of the spiral. Thus the effective upward force remains constant. Specification 648,989 is referred to.