Patent ID: 8142131

Claim:
A clamping apparatus for lifting a rectangular layer of items on a pallet comprising: a frame; four clamping arms pivotably mounted on the frame for pivoting with respect to the frame with a single degree of freedom and positioned on the frame so as to be able to grasp a rectangular layer of items on a pallet from four sides of the layer, each clamping arm including a contact portion for contacting a side of the layer to be lifted, each clamping arm defining a four-bar linkage which controls an angle of the contact portion with respect to the vertical as the clamping arm pivots with respect to the frame, wherein the four-bar linkage of each clamping arm includes a lever portion which is pivotably connected to the contact portion of the clamping arm and which is pivotably supported by the frame for pivoting with a single degree of freedom about a pivot point which is fixed with respect to the frame and a rigid control rod which extends alongside the lever portion and which has an upper end which is pivotably supported by the frame for pivoting with a single degree of freedom about a pivot point which is fixed with respect to the frame and a lower end pivotable with respect to the contact portion, the contact portion includes an elongated rigid plate-shaped panel having a front upright surface for opposing a side of the layer of items to be lifted and a plurality of mounting lugs secured to a back upright surface of the panel and pivotably connected to a lower end of the lever portion and a lower end of the control rod, the control rod is pivotable about a first axis with respect to the frame and about a second axis with respect to the contact portion, the first and second axes being parallel to each other and spaced from each other in a lengthwise direction of the control rod, and it is possible to draw a line which is parallel to the first and second axes and passes through the control rod and the lever portion of the clamping arm; and a plurality of drive mechanisms connected to the clamping arms to pivot the clamping arms with respect to the frame, each drive mechanism applying a torque to one of the lever portions to pivot the lever portion with respect to the frame.