Storage and Retrieval Crane With Dual Drives

The present invention relates to automated storage and retrieval systems and methods, and more particularly to a crane that is used for storing and retrieving loads on storage racks.

U.S. Pat. No. 3,913,766 discloses a storage and retrieval crane system that includes a tower having a pair of spaced columns and a tower drive for moving the tower horizontally along rails on a floor between storage racks. A carriage is coupled to a carriage drive mounted on the tower for vertical movement between the columns. A shuttle table is carried by a telescoping by-directional assembly on the carriage, and is coupled to a shuttle drive mechanism for moving the shuttle horizontally from the carriage in directions lateral to the direction of movement of the tower along the floor. By control of motion of the tower along the floor, the carriage on the tower and the shuttle on the carriage, parts are selectively stored in and retrieved from storage racks that extend along opposite sides of the tower rails.

A basic problem in storage and retrieval systems and methods of this character lies in potential malfunction or failure of any one of the drive mechanisms, which in turn causes the entire crane to be taken out of service. It is a general object of the present invention to provide a storage and retrieval system and method that will reduce or eliminate down-time associated with drive system failure in the prior art.

A storage and retrieval crane system in accordance with a presently preferred embodiment of the invention comprises a tower having a pair of spaced columns and a tower drive mechanism for moving the tower horizontally along a floor between storage racks. A carriage is coupled to a carriage drive mechanism for vertical movement between the columns, and a shuttle is coupled to a shuttle drive mechanism on the carriage for moving the shuttle horizontally from the carriage in directions lateral to direction of movement of the tower along the floor. At least one of the drive mechanisms, and preferably all of the drive mechanisms, include primary and secondary drive arrangements, and facility for selectively alternately connecting one or the other of the primary and secondary drive arrangements to drive the tower, carriage or shuttle. Thus, in the preferred embodiment of the invention, each of the drive mechanisms is fully redundant, so that machine drive may be switched from primary to secondary mechanisms in the event of failure without significant down-time or loss of production.

The invention, together with additional objects, features and advantages thereof, will be best understood from the following description, the appended claims having accompany drawings in which:

FIG. 1 is an elevational view of a crane in accordance with one presently preferred embodiment of the invention;

FIG. 2 is a perspective view of the drive system for elevating the carriage;

FIG. 3 is an exploded perspective view of the system for driving the crane tower horizontally;

FIG. 4 is an elevational view of the shuttle and shuttle drive mechanism carried on the carriage in FIG. 1; and

FIG. 5 is an elevational view of a crane in accordance with a modified embodiment of the invention.

The disclosure of U.S. Pat. No. 3,913,766 is incorporated herein by reference.

FIG. 1 illustrates a stacker crane 10 having a pair of vertical masts or columns 12, 14. A horizontal drive 16 is carried at the base of crane 10 beneath a maintenance platform 18 for driving crane 10 horizontally along a pair of rails (not shown). The usual shock absorbers 20 cushion the crane when the crane is stopped. A carriage 22 is movably supported between columns 12, 14. A vertical or hoist drive assembly 24 is carried at the lower end of column 14. A first cable 26 extends from a drum 28 (FIGS. 1 and 2) over pulleys or sheaves 30 at the upper end of crane 10, and thence to carriage 22 around a sheave 30a and back to the frame to a tie-off point not shown. Likewise, a second cable 31 (FIG. 2) extends from a drum 35 around pulleys or sheaves 30 and 32 at the upper end of crane 12, and thence to the opposing end of carriage 22 around a sheave 32a and back to the frame to a tie-off point not shown. Thus, rotation of drums 28, 35 winds or unwinds cables 26, 31, and either raises or lowers carriage 22 between columns 12, 14.

As shown in FIG. 2, hoist drive 24 comprises a primary electric hoist motor 34 that is connected through a coupling 36 to a right-angle gear or mitre box 38. A tachometer 40 is mounted on motor 34 for indicating speed of rotation, and a disc brake 42 is mounted on and coupled to motor 34 for preventing rotation of motor 34 when not in use. A secondary electric hoist motor 34a, with associated tachometer 40a and disc brake 42a, is connected by a coupler 36a to a right-angle gear or mitre box 38a. The two gear boxes 38, 38a are connected through respective clutches 44, 44a to a third gear or mitre box 46, which provides an output through a coupler 48 to a drum drive box 50. Cable drums 28, 35 are mounted on opposed sides of box 50. Clutches 44, 44a may comprise conventional chain-type clutches. When the chain is mounted in clutch 44, for example, and disfunction of motor 34, coupling 36 or gear box 38a is detected, the chain may be readily manually removed and placed in clutch 44a, and whereby secondary drive motor 34a becomes fully operational through the associated coupling 36a and gear box 38a. Clutches 44, 44a may also comprise jaw-type mechanical clutches that are so interlocked that only one may be engaged at a time, or may comprise interlocked disc or cone clutches. Alternatively, clutches 44, 44a may comprise any suitable type of electrically operated clutch for fully automated remote control of the hoist drive mechanism.

FIG. 3 illustrates horizontal drive 16 as comprising a pair of electric motors 52, 52a, each with associated disc brakes 54, 54a and tachometers 56, 56a. Each motor 52, 52a is connected through an associated clutch 58, 58a to a mitre or gear box 60, 60a. A coupling 62 interconnects gear boxes 60, 60a, and a coupling 64 interconnects gear box 60 with a horizontal drive gear box 66. Gear box 66 is connected to the horizontal drive shaft (not shown) for propelling crane 10 along the floor-mounted tracks. Once again, as discussed in detail above, clutches 58, 58a alternately and selectively connect motors 52, 52a to drive the horizontal drive gear box 66. Clutches 58, 58a may be of any suitable type as discussed above.

FIG. 4 illustrates the shuttle drive mechanism carried by carriage 22. Specifically, three shuttles 70, 72, 74 are illustrated as being interconnected by a shuttle drive shaft 76 and various couplings 78. Each shuttle 70, 72, 74 carries an associated pad or table for supporting the desired workpiece, illustrated in FIGS. 1 and 4 as a pick-up truck body. Shuttles 70, 72, 74 are themselves of conventional bi-directional telescoping design, as disclosed in the above-referenced patent, for example. A pair of shuttle drive mechanisms 80, 82 are respectively disposed on opposed ends of carriage 22, and are coupled to respective opposed ends of shuttle drive shaft 76. Each drive mechanism 80, 82 comprises an electric motor 84, 84a with associated spring-set brake 86, 86a and an output connected to a right-angle gear or mitre box 88, 88a. Boxes 88, 88a are respectively connected to associated clutches 90, 90a, which again are selectively and alternately connected to drive shaft 76. Clutches 90, 90a may be of any suitable type as discussed above. A spring-set brake 92 is directly coupled to drive shaft 76 to prevent drift in the event of power loss.

FIG. 5 illustrates a modified crane system 100, in which reference numerals identical to those employed in connection with FIGS. 1-4 indicate identical parts or elements. Crane system 100 in FIG. 5 differs from crane system 10 in FIGS. 1-4 primarily in two respects. First, the horizontal drive mechanism 102 is divided in the manner of the shuttle drive mechanism illustrated in FIG. 4, so as to provide two completely independent drive mechanisms. That is, referring to FIGS. 3 and 5, the electric motors 52, 52a are disposed on opposite sides of towers 12, 14, and operate through respective independent clutches and gear boxes for driving a main support wheel. Thus, as distinguished from drive arrangement 16 in FIG. 3 in which both motors 52, 52a must operate through common gear boxes 60, 62. The drive motors are independently connected to the crane in FIG. 5. The horizontal drive would not be disabled by failure of the gear box 60, 66 or the coupler 64 in FIG. 3. Likewise, the hoist drive is now divided into separate drive segments 104, 104a respectfully disposed on opposite sides of the crane. This particular arrangement has the advantage that a single cable 106 extends from drum 28 to drum 35, trained around the sheaves or pulleys 30, 32 at the upper end of crane 100, and around corresponding pulleys 30a, 32a on carriage 22. Thus, when operating hoist drive 104, for example, hoist drive 104a is locked by operation of associated disc brake 42a so as to provide an anchor for the cable. The cable is wound onto and unwound from drum 28 by operation of motor 34 for raising or lowering carriage 22.

Thus, in all embodiments of the invention, at least one and preferably all of the tower, carriage and shuttle drive mechanisms comprise primary and secondary drive mechanisms that are at least partially if not completely independent from each other, and with facility for selectively and alternately connecting one or the other of the primary and secondary drive mechanisms to the associated tower, carriage or shuttle. Both the primary and the secondary drive mechanisms comprise an electric motor coupled to an associated gear box, and a clutch for selectively and alternately connecting one or the other of the gear boxes to drive the associated mechanism.