The prior art contains many teachings pertaining to toggle type closure fasteners. Some examples of prior United States patents of general interest in relation to this invention are the follwing, made of record herein under 37 C.F.R. 1.56:
U.S. Pat. No. 497,445 PA1 U.S. Pat. No. 567,621 PA1 U.S. Pat. No. 783,338 PA1 U.S. Pat. No. 1,339,174 PA1 U.S. Pat. No. 1,863,863 PA1 U.S. Pat. No. 1,899,822 PA1 U.S. Pat. No. 3,109,675 PA1 U.S. Pat. No. 3,145,038 PA1 U.S. Pat. No. 3,162,419 PA1 U.S. Pat. No. 3,174,784 PA1 U.S. Pat. No. 3,534,992 PA1 U.S. Pat. No. 3,706,467 PA1 U.S. Pat. No. 4,049,301
A prime object of the invention is to improve on the known prior art through provision of a closure fastener which is non-handed in comparison to conventional casement and awning type window locks. The mechanism embodied in the invention includes a shallow lock case and filler element which can be flush mounted on one side of a casement window frame and the like so that no parts of the mechanism project into the window sight line when the lock is closed and no parts project into the room to cause interference with window hangings in any position of the mechanism. The entire mechanism is simple, extremely strong and durable and very compact.
Another important object of the invention is to provide an action which is very powerful for drawing a sash or other closure inwardly or forcing it outwardly to release a stuck sash. This action involves an over-dead-center mechanism which inhibits forced entry because of a tendency of the mechanism to tighten the locking action rather than release it in response to opening pressure on the closure or sash.
Another object and feature of the invention is the provision in the fastener or lock of an essentially straight line draw-in motion which is not critical in relation to alignment with the keeper or strike mounted on the sash.
Other objects and advantages of the invention will appear to those skilled in the art during the course of the following detailed description.