Abstract: A bridge traverses along lift arms of a power unit, having leveling pads with inner rectangular plates and roller bearings; and each lift arms has an inner slide plate. The bridge has the general shape of a rectangular block and has a first longitudinal recess in each side, having a width slightly larger than the width of the slide rail, and a depth equal to the thickness of the slide rail. The bridge has a second longitudinal recess in each side having a width slightly larger than the diameter of the roller bearings and a depth slightly larger than the thickness of the roller bearings. The bridge is biased in the forwardly direction along the slide rails by a rectangular pusher frame. The pusher frame has a pair of side plates, with each outer side having a longitudinal recess therein slightly larger than the width of the slide rail and a depth equal to the thickness of the slide rail.

Abstract: A power unit has a frame with a bottom and a pair of lift arms with a cover plate, and a bridge. A lower latch member has a forward end, a middle portion and a rearward end with the middle portion pivotally connected near the lower inner side of one of the lift arms. The rearward end is angled downward, extending below the lower side of the lift arm. The rearward end is biased downwardly and is engagable with the bottom of the frame. The forward end has an upward finger with a beveled-up nose thereon that is engagable with a downward lateral flange at the forward end of the bridge. The bridge is retained by the forward end of the lower latch member, and whereby when the lift arm is lowered to the lowermost position, the forward end is automatically released. An upper latch member has a forward end, a middle portion and a rearward end, with the middle portion pivotally connected to a pivot arm extending downwardly from the cover plate.