Means for automatically releasing a jack system

In a two-part jack system which includes a jack stand having a load-bearing member supported from vertically telescoping members, one of which has ratchet teeth and another of which carries a spring-loaded pawl for selectively engaging the ratchet teeth, and a power unit having arms for directly supporting the load-bearing member in order to extend or retract said jack stand;

• an automatic release mechanism operable when said power unit is being utilized to retract said jack stand, for disengaging said pawl from said ratchet to thereby permit complete retraction of said jack stand in a single movement, comprising:
• an extension arm on said pawl;
• a pusher member carried on said power unit for selectively engaging said extension arm so as to cause said pawl to disengage from said ratchet teeth;
• spring means urging said pusher member towards said extension arm;
• means coupled to said pusher member for selectively restraining its movement;
• and,
• said restraining means being adapted to be selectively disabled whenever said power unit is utilized for retracting said jack stand.

A system of jacking apparatus comprising:

• a jack stand including a base portion and a telescoping vertical stand, said telescoping stand having a vertically extending series of ratchet teeth carried thereon, a vertically extending ratchet arm pivotally supported at a mid-point along its length from said base portion, a ratchet pawl on the upper end of said ratchet arm, and a ratchet locking spring interposed between said base portion and said ratchet arm and urging said ratchet arm to move pivotally relative to said jack stand base portion in a direction such as to cause said pawl to lockingly engage one of said teeth;
• a power unit adapted to be removably attached to said jack stand in aligned relationship thereto whenever said jack stand is to be extended or retracted, said power unit having lifting means selectively operable during times when said power unit is thus attached for supporting and raising said telescoping stand;
• automatic release means carried by said power unit, and selectively operable whenever said power unit is attached to said jack stand and it is desired to retract said jack stand, for applying a spring force against the lower end of said ratchet arm in a direction such as to unlock said pawl;
• and
• the spring force of said automatic release means being insufficient to overcome said ratchet locking spring when a vertical load carried upon said telescoping frame locks the ratchet pawl to one of the ratchet teeth, but being more than sufficient to do so when there is no vertical load on said telescoping frame;
• whereby when said jack stand is to be retracted, said power unit may first be attached thereto, said power unit lifting means may then be operated for raising said telescoping stand to remove the load forces from the pawl, upon the lifting of the load said automatic release means will then overcome said ratchet locking spring thereby causing said pawl to unlock from said ratchet teeth, and said lifting means may then be operated in reverse so as to retract said jack stand.