US Patent 9702166 Secure solenoid driven deadbolt lock

An electronic lock driven by a keep solenoid has a non-direct mechanical connection between the solenoid plunger and the slidable deadbolt of the lock. The connection includes a pivoted lever connected to the plunger and a link between the lever and the deadbolt, these components being arranged in such a way that when the deadbolt is fully extended the pivot point of the lever and pivot points on both ends of the link, with the lever and with the deadbolt, are in alignment. The mechanical arrangement prevents retraction of the extended deadbolt by pushing inward on the deadbolt, which is a problem with a deadbolt driven directly by a solenoid plunger.