Commercial lifting device-power unit with safety mechanism

A commercial power unit and safety mechanism for a hydraulic floor jack, comprising:

• a rectangular frame having a forward end, a rearward end, and sides with the rearward end having a tubular control handle extending therefrom with a control knob at the upper end of the handle;
• a pair of longitudinal side flanges extending upward from the frame;
• a pivotal lifting means mounted on the frame including a pair of parallel lift arms having rearward ends interconnected by a lateral push bar and having forward ends rotatable upward for lifting a load;
• a pair of longitudinal U channel tracks facing inward and attached to the inner side flanges within the frame and retaining the ends of the lateral push bar therein;
• a hydraulic cylinder having an extendable ram for pushing the lateral push bar forward along the tracks for raising the forward ends of the lift arms, and a releasable control valve for retracting the ram and the lateral push bar for lowering the forward ends of the lift arms;
• the tubular handle enclosing a control shaft extending from the control knob to the releasable control valve;
• the control knob is rotatable in the clockwise direction to close the release valve and is rotatable in the counter-clock-wise direction to release the control valve;
• the power unit further including a rectangular block bridge for positioning on and across the forward ends of the lift arms, whereby the power unit functions as a hydraulic floor jack;
• the safety mechanism comprising:
• a toothed rack bar secured on the vertical wall of at least one of the U channel tracks and extending from the rearward end to the forward end thereof;
• the lateral push bar having a bore hole in at least one of the ends thereof;
• a generally cylindrical dog slidably supported within each said bore hole of the push bar and having a proximal end thereof, and having a distal end thereof extendable from the end of the push bar for engaging a respective tooth of said rack bar, whereby said dog is for advancing the push bar in the forward direction and securing the push bar from retracting in the rearward direction;
• biasing means urging the distal end of each said dog into the respective tooth of each said rack bar, for mechanically securing the push bar as it is advanced within the tracks, whereby the lift arms are retained in the respective elevated position independent of any release of pressure by the hydraulic cylinder, and
• means for releasing each said dog from said rack bar by rotation of the control knob in the counter-clockwise direction, whereby the safety mechanism is automatically disengaged with the release of the control valve.