| 摘要 |
A floor jack includes a frame having a handle with a control knob, and a pair of pivotal lift arms elevated by pushing the rearward ends by a push bar of a hydraulic cylinder. The cylinder has a control valve attached to a control shaft extending from the control knob. A pair of guide rail are attached to the bottom of the frame; and a pair of rack bars are slidably mounted on each guide rail, and has a forward end pivotally attached to the push bar. A pair of dogs are positioned above the rack bar, each having a rearward end pivotally attached to the frame and a forward for engaging a tooth of the rack bar. The forward end of the dogs engage the rack bar as the lift arms are elevated; and in the event of a hydraulic failure, the dogs lock the lift arms in the elevated position. A release includes a cam tube having a V slotted opening in the underside thereof. A swing plate has a cam follower stud slidably engaged within the V slotted opening. The swing plate includes linkage that is actuated by rotation of the control knob. An initial rotation of the control knob automatically rotates the cam tube to release the dogs, and further rotation opens the valve to lower the lift arms. |
| 主权项 |
1. A safety mechanism for a hydraulic floor jack, including a rectangular frame having a forward end, a rearward end, a bottom, sides, and a pair of longitudinal side flanges extending upward from the frame, with the rearward end having a tubular control handle pivotally attached and extending with a rotatable control knob at the upper end of the handle; a pivotal lifting system mounted on the frame including a pair of parallel lift arms having rearward ends interconnected by . a lateral push bar and having forward ends interconnected by a rectangular lifting plate pivotally mounted thereon, and rotatable upward for lifting a load; a pair of longitudinal U channel tracks attached to the inner side flanges within the frame and retaining the ends of the lateral push bar therein; a hydraulic cylinder, actuated by pumping the control handle, 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 for lowering the forward ends of the lift arms; the tubular handle enclosing a control shaft extending from the control knob to the rearward end of the frame and including a U-joint and coupling interconnecting the shaft to the control valve; the control knob is rotatable in the clockwise direction to close the control valve and is rotatable in the counterclockwise direction to open the control valve; the safety mechanism comprising:
at least one guide rail, each fixed to the bottom of the rearward end of the frame and extending longitudinally therefrom; at least one slidable rack bar, each having forward ratcheting teeth and a forward end pivotally linked to the push bar for traversing along said guide rail as the push bar is advanced and retracted; at least one dog, each positioned and extended above said rack bar, each said dog having a rearward end pivotally attached to the frame, and having a forward end with a downward lug for engaging a respective tooth of said rack bar as said rack bar is advanced with the push bar; whereby in the event of any loss of hydraulic pressure, said dog is for retaining said rack bar from rearward movement; thereby safely locking the lift arms in the elevated position; and means for automatically disengaging the forward lugs of said dog from said rack bar with rotation of the control knob. |
