Secure Solenoid Driven Deadbolt Lock

In an electronic deadbolt lock having a housing, a reciprocating bolt that extends from and retracts into the housing, a keep solenoid connected to drive the bolt, the keep solenoid having an electromagnetic coil and a plunger for linear reciprocating travel inwardly and outwardly relative to and under the influence of the coil, the keep solenoid being configured to remain retracted without power to the coil when retracted and to remain extended without power to the coil when extended, the improvement comprising:

• a pivoted lever mounted for pivoting about a pivot point on the housing, the lever having a first arm on a first side of the pivot point and a second arm on a second side of the pivot point, the first arm having an end connected to the plunger so as to be swung in either of two opposed rotational directions about the pivot point by inward and outward movement of the plunger,
• the second arm of the lever having an outer end extending to a position near the bolt,
• a pivoted link connecting the bolt with the outer end of the second arm, at pivot connections on the second arm's outer end and on the bolt, and
• the second arm of the lever and the link being configured such that when the bolt is fully extended the link and the second arm are aligned, with said pivot point of the lever and the two pivot connections of the link all in alignment,
• whereby, with the bolt fully extended, inward force exerted on the bolt from outside the housing cannot be effective to retract the bolt because of the alignment of the link and the second arm of the lever.