Automated warehouse and method for controlling stacker crane in automated warehouse

Support columns are mounted at both front and rear ends of a stacker crane 4 to form a mast having a gate shape. An elevation frame having the size which is twice as large as a front space of a rack is provided at the mast, and a base of a slide fork is moved back and forth in a travel direction relative to the elevation frame. An elevation motor for the elevation frame and front and rear travel motors are provided under the mast.

TECHNICAL FIELD

The present invention relates to an automated warehouse having a stacker crane. In particular, the present invention relates to an automated warehouse which makes it possible to provide racks and stations along the entire length of the travel range of a stacker crane.

BACKGROUND ART

In the stacker crane, drive mechanisms such as a travel motor, an elevation motor, a drum, a control panel are provided in a space extending from a position in front of, or behind a mast of a cart, to the end of the cart. Therefore, the overall length of the stacker crane is significantly larger than the width of an elevation frame, and the travel route distance (the distance between both terminals of the travel rail) is larger than the total length of the racks. Therefore, in some spaces along the travel rail, no rack or station is provided. Under the circumstances, the desired storage efficiency in the automated warehouse cannot be achieved. In this regard, in a related conventional technique, Laid-Open Patent Application No. 6-24511 proposes a technique of providing a plurality of slide forks on an elevation frame of a stacker crane.

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

An object of the present invention is to improve the storage efficiency in an automated warehouse.

Another object of the present invention is to make it possible to transfer an article to the adjacent space (front space) or the like without the travel of a stacker crane.

Still another object of the present invention is to provide specific structure to achieve the foregoing objects.

Means for Solving the Problems

According to the present invention, in an automated warehouse comprising a rack and a stacker crane which travels along the rack, the stacker crane includes a mast, a travel motor and an elevation motor provided in a cart, and an elevation frame having a transfer apparatus elevated and lowered along the mast by the elevation motor.

The mast of the stacker crane includes support columns provided near both front and rear ends of the cart in a travel direction of the stacker crane to form a gate shape, and has a width which is larger than a front space of one rack. The automated warehouse further comprises:

means for moving the transfer apparatus on the elevation frame, in the travel direction of the stacker crane; and

control means for controlling the means for moving, to move the transfer apparatus toward the front side of the stacker crane at the time of transferring an article at a front end in a travel route of the stacker crane, and move the transfer apparatus toward the back side of the stacker crane at the time of transferring an article at a rear end in the travel route of the stacker crane.

According to another aspect of the present invention, in a method of controlling a stacker crane in an automated warehouse, the stacker crane travels along a rack, and includes a mast, a travel motor and an elevation motor provided in a cart, and an elevation frame having a transfer apparatus elevated and lowered along the mast by the elevation motor. The method comprises the steps of:

forming a mast of the stacker crane to have a gate shape by providing support columns of the mast near both front and rear ends of the cart of the stacker crane, the mast having a width larger than a front space of one rack;

moving the transfer apparatus on the elevation frame, in the travel direction of the stacker crane; and

moving the transfer apparatus toward the front side of the stacker crane at the time of transferring an article at a front end in a travel route of the stacker crane, and moving the transfer apparatus toward the back side of the stacker crane at the time of transferring an article at a rear end in the travel route of the stacker crane.

Preferably, the width between the support columns of the mast is an integer multiple of the front space of the rack.

Further, preferably, the support columns of the mast of the stacker crane are provided at both of front and rear ends of the cart, and the elevation motor and the travel motor are provided in the cart at positions between the support columns of the mast.

Advantages of the Invention

In the present invention, the mast has a gate shape, and has a width larger than the front space of one rack. Therefore, the travel motor or the elevation motor can be placed under the elevation frame, without increasing the height of the cart. Therefore, protrusion of the cart from the front side, or the back side can be eliminated, or minimized. Since the transfer means can move on the elevation frame, at the time of transferring the article at the front end of the travel route, it is possible to move the transfer apparatus toward the front side of the stacker crane, and at the time of transferring the article at the rear end of the travel route, it is possible to move the transfer apparatus toward the back side of the stacker crane. In this manner, it is possible to provide racks and stations along substantially the entire distance of the travel route of the stacker crane, and improvement in the storage efficiency in the automated warehouse is achieved. Further, since the width between the support columns of the mast is large, the stacker crane has stable structure, and the stacker crane cannot be vibrated easily. Further, by combining horizontal movement of the transfer apparatus and travel of the stacker crane, it is possible to reduce the time to arrive at the target front space.

In the case where the width between the support columns of the mast is an integral multiple of the front space of the rack, for example, if the width between the support columns of the mast is twice as large as the front space of the rack, it is possible to transfer the article between the adjacent front spaces without travel of the stacker crane, and if the width between the support columns of the mast is three times as large as the front space of the rack, it is possible to transfer the article to the front space which is away by a distance which is twice as large as the front space of the rack.

In the case where the support columns of the mast are provided at both of the front end and the rear end of the cart of the stacker crane, and the elevation motor and the travel motor are provided in the cart under the mast, in the space between the front end and the rear end of the cart, even if there is a dead space because the overall length of the stacker crane is larger than the width of the mast, it is possible to minimize the dead space.

DESCRIPTION OF THE NUMERALS

EMBODIMENTS

FIG. 1 to 6show an embodiment and a modified embodiment. In the drawings, a reference numeral2denotes an automated warehouse, a reference numeral4denotes a stacker crane, a reference numeral6denotes a rack, and a reference numeral8denotes a travel rail. For example, a pair of racks6are provided on the left and right sides of the travel rail8. In the embodiment, only the rack on one side is shown. Part of the front space of the rack6is used as a station for storage and retrieval of articles. For example, the storage and retrieval station is provided by moving the left or right end of the rack6to the central side beyond the left or right end of the travel rail8. As shown in, e.g.,FIG. 1, the left and right ends of the rack6and the left and right ends of the travel rail8are provided at the same positions. In the case where the storage and retrieval station is provided outside the rack6in the travel direction, the end of the area for transferring articles in the storage and retrieval station substantially matches the end of the travel rail8.

Structure of the stacker crane4will be described. A reference numeral10denotes a mast having a gate shape. A pair of support columns11are provided on the front side and on the back side in the travel direction of the stacker crane4. Alternatively, four support columns including two support columns on the front side and two support columns on the back side may be provided, or three support columns including two support columns on one of the front side and the back side, and one support column on the other of the front side and the back side may be provided. The elevation frame12is elevated, and lowered along the mast10. The width of the elevation frame12along the travel direction of the stacker crane4is twice as large as the front space of the rack6. InFIG. 1, the width of the front space is denoted by “W”. The width of the elevation frame12is not limited to the size which is twice as large as the front space of the rack6. Preferably, the width of the elevation frame12is an integer multiple (2or more) of the front space of the rack6. A base14moves forward or backward in the travel direction of the elevation frame12, and transfer means such as a slide fork16, a SCARA arm, or a conveyor is mounted on the base14. A reference numeral18denotes an article on the slide fork16. For example, the article18is a semiconductor cassette, or a cassette for use of reticles for exposure of semiconductors or liquid crystals.

A reference numeral20denotes a cart of the stacker crane4. The width of the cart20, between the front side and the back side in the travel direction is equal to the width of the mast10. The support columns11of the mast10are provided on both front and rear ends of the cart20. A reference numeral22denotes an elevation motor for elevating and lowering the elevation frame. A reference numeral24denotes a travel motor for driving drive wheels26for travel of the stacker crane4. The elevation motor22and the travel motor24are provided in the cart20, and the elevation motor22and the travel motors24do not protrude forward, or protrude backward from the area under the mast10. In the embodiment, the total number of the drive wheels26is two, including one front wheel and one rear wheel, and a pair of the travel motors24are provided on the front side and on the back side. Alternatively, in the case where the total number of the drive wheels is four, including front and rear, and left and right wheels, for example, in total, four travel motors24may be provided on the front and back sides, and on the left and right sides. In the embodiment, one elevation motor22is provided at the center of the cart20. Alternatively, a plurality of the elevation motors22may be provided.

As shown inFIG. 2, a timing belt28is provided in the elevation frame12, and the timing belt28is driven by a motor30, a decelerator32, and a pulley33to move the base14of the slide fork16between the front support column11and the rear support column11. Means for moving the base14is not limited to the timing belt28, and can be chosen arbitrarily. For example, chains or ball screws may be used. A suspension member such as a timing belt34may be placed in the support column11, and the suspension member is fixed to a protrusion36protruding from the elevation frame12. For example, a plurality of rollers38are provided for guiding the protrusion36along the inner surface of the support column11.

FIG. 3shows positions of the elevation motor22, the travel motors24, or the like in the cart20. For example, the timing belt34is guided into the cart20through a pulley40, and driven by a decelerator42connected to the elevation motor22. Further, the output of the travel motor24is decelerated by a decelerator41, and transmitted to the drive wheels26. The method of decelerating the motors22,24can be chosen arbitrarily. As can be seen fromFIG. 3, the front side and the back side of the cart20are symmetrical with each other. The range where the motors22,24protrude from the cart20in a direction perpendicular to the travel rail3is limited to an area under the elevation frame12in a plan view, A reference numeral50denotes a control unit for controlling the motors22,24, and the motor30, and controlling travel of the stacker crane4, elevation of the elevation frame, and movement of the base14.

FIG. 4shows a position of the timing belt34. The timing belt34is provided to extend around inside the gate shape mast10and the cart20. The timing belt34is guided by the pulleys40,44, or the like, and driven by the decelerator42or the like. Instead of the timing belt34, a wire, a steel belt, or a rope may be used.

Operation of the stacker crane4is shown inFIG. 5. In the case of moving an article to, or from a row6aat an end of the rack6, the base14is moved to a position denoted by “a”. In the case of moving an article to, or from a row6bat the other end of the rack6, the base14is moved to a position of a chain line denoted by “b” inFIG. 5. In any of the positions other than the above, the base14may be moved to the position “a” or the position “b”, as long as the position of the base14is determined to minimize the travel distance. Reference numerals52,53denote stations. In the case of transfer to, or from the station52, the base14is moved to the position “a”, and in the case of transfer to, or from the station53, the base14is moved to the position “b”.

FIG. 6is a view showing a stacker crane according to a modified embodiment. Unless specifically noted, the features of the stacker crane are the same as those shown inFIGS. 1 to 5. The timing belt34is divided into one timing belt34aand the other timing belt34b, and a pair of elevation motors22a,22bare used for driving the timing belt34ausing the elevation motor22a, and driving the timing belt34busing the elevation motor22b.

Advantages of the embodiments will be described below.

(1) Since the cart20does not protrude forward, or backward from the support columns11, it is possible to provide the rack6or the stations52,53over the entire range along the travel route of the stacker crane4. Accordingly, it is possible to increase the storage efficiency per area of providing the rack6or the stations52,53in the automated warehouse. In particular, the advantage is large in a clean room or the like where the cost in terms of floor area is large.
(2) Since the width of the mast10is large, the stacker crane has stable structure. Further, since the travel motors and elevation motors can be provided symmetrically on the front side and the back side, along the travel direction the force applied to the cart is symmetrical on the front side and the back side. In the structure, the stacker crane4is not shaken significantly, and the control can be implemented easily.
(3) The article can be transferred between the adjacent front spaces of the left and right racks5, without travel of the stacker crane4. In the case where the stacker crane4travels, and the base14moves at the same time, the travel distance can be reduced by the distance corresponding to the size of the front space. Thus, it is possible to shorten the cycle time of the stacker crane4.
(4) Since the travel motors and the elevation motors are provided in the cart20having the width which is twice as large as the front space of the rack6, it is not necessary to increase the height of the cart20. Thus, the dead space of the rack in the height direction is minimized.