US Patent 8052121 Scissor jack

The invention involves a scissor jack having four arms hingedly arranged to provide two opposite elbows between a base and a load support. A pair of trunnions at the elbows is connected by a threaded shaft. A movable brace is supported between the arms. The brace strengthens and adds support to the jack assembly. In a preferred embodiment, the brace includes a guide assembly which slidably engages the shaft and connectors pivoted between the guide and each of the four arms. The connectors are extensible socket and rod arrangements. Each connector includes a coil spring located over the rod in the socket. The four springs are compressed on extension of the jack to assist in lifting a load.