Abstract: An extendible multi-frame stand includes at least three frames arranged in a telescoping relationship, having a single coherent alignment and locking mechanism which includes alignment means for preventing relative rotation between the first and second frames, alignment means for preventing relative rotation between the second and third frames, means for locking the second and third frames at the limits of their longitudinal extension positions, and cam-operated releasable locking means for controlling extension and retraction of the second and third frames relative to each other and to the first frame.

Abstract: A two-part jack system includes a mechanical jack stand with a ratchet mechanism and a ratchet release, and a power unit that may be selectively aligned with and attached to the jack stand for raising or lowering it. A unitary control mechanism carried by the power unit selectively locks the power unit in an aligned position relative to the jack stand, and also selectively releases the ratchet release of the jack stand. A locking mechanism is carried in part by the jack stand and in part by the power unit. The unitary control mechanism has three different operating positions. In one operating position the locking mechanism is kept locked while the ratchet release is left in an unreleased state; in a second operating position the locking mechanism is kept locked while the ratchet release is released; and in the third operating position the locking mechanism is held in an unlocked condition while the ratchet release is left in an unreleased state.

Abstract: An extendible jacking apparatus including first, second and third normally vertical frames arranged in telescoping relationship, and containing a locking mechanism for automatically locking the first and second frames together while the third frame is being raised, locking the second and third frames together when the third frame is fully raised, and unlocking the first and second frames to allow extension of the second frame. Conversely, the locking mechanism is automatically reversible as the jack is lowered, unlocking the second and third frames and relocking the first and second frames upon the second frame being fully retracted into the first, allowing the third frame to allow be fully retracted into the first and second frames.

Abstract: A hydraulic power unit for a two-part jack system, having lifting arms which are raised or extended by means of hydraulic power whenever an associated jack stand is to be either raised or extended. The necessary hydraulic pressure is generated manually, by use of a hand pump. The power unit includes a single release valve which operates automatically as an excess-pressure bleed-off valve whenever the hydraulic cylinder pressure exceeds design capacity, and is also adapted to be controlled manually from the handle of the power unit for unloading total hydraulic pressure whenever the lifting arms are to be lowered. The release valve and all of its associated mechanisms are mounted in or on a single metallic block which is very easily manufacturable.

Abstract: A two-part jack system includes a mechanical jack stand with a ratchet mechanism and a ratchet release, and a power unit that may be selectively aligned with and attached to the jack stand for raising or lowering it. A unitary control mechanism carried by the power unit is adapted to selectively lock the power unit in an aligned position relative to the jack stand, and also to selectively release the ratchet release of the jack stand. A locking mechanism is carried in part by the jack stand and in part by the power unit. The unitary control mechanism has three different operating positions. In one operating position the locking mechanism is kept locked while the ratchet release is left in an unreleased state; in a second operating position the locking mechanism is kept locked while the ratchet release is released; and in the third operating position the locking mechanism is held in an unlocked condition while the ratchet release is left in an unreleased state.