Method and apparatus for stacking sheet materials

Abstract

A sheet stacking and pallet loading system configured to stack sheets of material on a first pallet while holding a second pallet in a staging position above the first pallet. The system can include an elevator for supporting the first pallet in a loading position while the sheets are stacked on the first pallet. After a sufficient quantity of sheets has been stacked thereon, the elevator can lower the first pallet from its loading position. The second pallet can then be lowered from its staging position such that the sheets can be stacked thereon. The system can further include extendable pallet supports which can be extended to support the second pallet while the first pallet is being lowered by the elevator. The pallet loading system can further include a pallet-grasping assembly having, first, a frame movable along a track and, second, one or more end-effectors movable relative to the frame for engaging a pallet.

1 . A pallet loading system, comprising:
 a track defining a path;   a frame movable along the path between a pallet-obtaining position and a pallet-delivering position;   a first pallet-engaging assembly comprising:
 a first actuator movably mounted to said frame; and 
 a first end-effector operably coupled with said first actuator, wherein said first actuator is configured to move said first end-effector into engagement with the pallet in a first direction; 
   a second pallet-engaging assembly comprising:
 a second actuator movably mounted to said frame; and 
 a second end-effector operably coupled with said second actuator, wherein said second actuator is configured to move said second end-effector into engagement with the pallet in a second direction; and 
   a third pallet-engaging assembly comprising:
 a third actuator movably mounted to said frame; and 
 a third end-effector operably coupled with said third actuator, wherein said third actuator is configured to move said third end-effector into engagement with the pallet in a third direction, wherein said first direction, said second direction, and said third direction are different. 
   
   
   
       2 . The pallet loading system of  claim 1 , wherein said frame further comprises a first actuator guide, a second actuator guide, and a third actuator guide, wherein said first actuator is movable relative to said frame along said first actuator guide, wherein said second actuator is movable relative to said frame along said second actuator guide, and wherein said third actuator is movable relative to said frame along said third actuator guide. 
   
   
       3 . The pallet loading system of  claim 2 , wherein said first direction is substantially parallel to said second direction, and wherein said third direction is substantially perpendicular to said first direction and said second direction. 
   
   
       4 . The pallet loading system of  claim 2 , wherein said third direction is transverse to at least one of said first direction and said second direction. 
   
   
       5 . The pallet loading system of  claim 1 , wherein said first actuator is further configured to extend said first end-effector away from said frame in a direction transverse to said first direction, wherein said second actuator is further configured to extend said second end-effector away from said frame in a direction which is transverse to said second direction, and wherein said third actuator is further configured to extend said third end-effector away from said frame in a direction which is transverse to said third direction. 
   
   
       6 . The pallet loading system of  claim 1 , wherein said first actuator is configured to extend and retract said first end-effector in a substantially vertical direction, wherein said second actuator is configured to extend and retract said second end-effector in a substantially vertical direction, and wherein said third actuator is configured to extend and retract said third end-effector in a substantially vertical direction. 
   
   
       7 . The pallet loading system of  claim 1 , wherein said first direction is substantially parallel to said second direction, and wherein said third direction is substantially perpendicular to said first direction and said second direction. 
   
   
       8 . A sheet stacking system, comprising:
 a frame;   an elevator having at least one pallet support surface configured to support a first pallet in an elevated position;   a first sheet support configured to receive and support a first sheet of material, wherein said first sheet support is rotatably mounted relative to said frame, and wherein said first sheet support is rotatable between a sheet-receiving position and a sheet-dropping position;   a second sheet support configured to receive and support the first sheet of material, wherein said second sheet support is rotatably mounted relative to said frame, wherein said second sheet support is rotatable between a sheet-receiving position and a sheet-dropping position, wherein said first and second sheet supports are configured to drop the first sheet of material onto the first pallet when said first and second sheet supports are rotated into their sheet-dropping positions, wherein said first and second sheet supports are configured to receive a second sheet of material when said first and second sheet supports are rotated back into their sheet-receiving positions, and wherein said first and second supports are configured to stack the second sheet of material onto the first sheet of material when said first and second sheet supports are rotated into their sheet-dropping positions once again;   a pallet loading system configured to hold a second pallet above the first pallet, wherein said elevator is configured to move the first pallet between the elevated position and a lower position after a sufficient quantity of sheets of material have been stacked on the first pallet;   at least one first extendable pallet support; and   at least one second extendable pallet support, wherein said first and second extendable pallet supports are configured to support the second pallet after they have been extended.   
   
   
       9 . The sheet stacking system of  claim 8 , wherein said first and second extendable pallet supports are retractable, and wherein said elevator is configured to reposition said at least one pallet support surface beneath the second pallet in order to support the second pallet after said first and second extendable pallet supports have been retracted. 
   
   
       10 . The sheet stacking system of  claim 8 , wherein said first and second extendable pallet supports are slidably mounted relative to said frame. 
   
   
       11 . The sheet stacking system of  claim 8 , wherein said first and second extendable pallet supports are configured to be extended as said elevator is lowered from said elevated position. 
   
   
       12 . The sheet stacking system of  claim 8 , wherein said first and second sheet supports are slidably mounted relative to said frame. 
   
   
       13 . A method of stacking sheets of material, comprising:
 positioning a first pallet on an elevator;   stacking sheets of material on the first pallet;   positioning a second pallet above the first pallet;   lowering the first pallet after a predetermined quantity of sheets have been stacked on the first pallet;   extending pallet supports for supporting the second pallet; and   lowering the second pallet onto the pallet supports.   
   
   
       14 . The method of  claim 13 , further comprising the steps of:
 removing the first pallet from the elevator;   positioning the elevator beneath the second pallet; and   retracting the pallet supports such that the second pallet can be supported by the elevator.   
   
   
       15 . The method of  claim 14 , further comprising the steps of:
 stacking sheets of material on the second pallet;   positioning a third pallet above the second pallet;   lowering the second pallet after a predetermined quantity of sheets have been stacked on the second pallet;   extending the pallet supports for supporting the third pallet; and   lowering the third pallet onto the pallet supports.   
   
   
       16 . The method of  claim 14 , wherein said second pallet is positioned above the first pallet as sheets of material are stacked onto to the first pallet. 
   
   
       17 . The method of  claim 14 , further comprising the steps of:
 positioning the elevator and the first pallet beneath the second pallet; and   retracting the pallet supports such that the second pallet can be supported by at least one of the first pallet and the sheets of material stacked on the first pallet.   
   
   
       18 . A pallet loading system, comprising:
 a track defining a path;   a frame movable along the path between a pallet-obtaining position and a pallet-delivering position;   a first pallet-engaging assembly comprising:
 a first actuator movably mounted to said frame; and 
 a first end-effector operably coupled with said first actuator, wherein said first actuator is configured to move said first end-effector into engagement with the pallet in a first direction; 
   a second pallet-engaging assembly comprising:
 a second actuator movably mounted to said frame; and 
 a second end-effector operably coupled with said second actuator, wherein said second actuator is configured to move said second end-effector into engagement with the pallet in a second direction, and wherein said first direction and said second direction are different; and 
   a stationary third pallet-engaging assembly, wherein said third pallet-engaging assembly comprises a third end-effector which is extendable relative to said frame.