Patent Application
20070183870
The invention relates to a storage and retrieval system and, in particular, to such a system having at least one mast and a deposit and retrieval system that can be moved vertically along the mast.
Storage and retrieval systems are generally known. They have at least one vertical mast, on which a deposit and removal system can be moved vertically. The mast is supported at its lower end via at least two spaced-apart running wheels, which are mounted such that they can rotate in a base cross arm. The running wheels roll on a base rail, which at the same time is used for guiding the running wheels. One or more running wheels are driven for this purpose by a motor. A further rail is arranged in the region of the upper mast end, which further rail extends parallel to the running rail and is used for guiding the mast end. The guidance takes place by means of guide rollers, which are mounted such that they can rotate at the mast end and roll on both sides on the guide rail.
One disadvantage with the known storage and retrieval system is the fact that, when the storage and retrieval system is moved, oscillations of the upper mast end may occur.
The various embodiments of the present invention provide a storage and retrieval system with which the mast oscillations can be damped.
According to an aspect of the invention, a storage and retrieval system includes at least one friction roller and an eddy current brake driven by the friction roller. The friction roller rolls on and bears against the guide rail and is subjected to a force. The eddy current brake absorbs the oscillation energy, such as by converting the oscillation energy into heat and, therefore, provides effective damping of the mast oscillations. In order to damp the oscillations in particular when moving into an intended position, the eddy current brake can be electrically connected.
In one embodiment, the friction roller is subjected to a force by means of magnetic attraction. The eddy current brake may be operated via a permanent gear with an adjustable gear transmission ratio. The guide roller may take on the function of the friction roller. The eddy current brake may be an electric motor.
In one embodiment of the eddy current brake, the electric motor is a squirrel-cage asynchronous motor having an air gap, the size of this air gap being selected such that a correspondingly large magnetic field is induced. In this embodiment, a gear is expediently used for the purpose of adapting to the rotation speed. Particularly large eddy currents may be achieved if the electric motor is in the form of a squirrel-cage asynchronous motor having a constant air gap.
These and other objects, advantages and features of this invention will become apparent upon review of the following specification in conjunction with the drawings.
Embodiments of the invention will be described in more detail below with reference to a drawing, whose single figure shows a side elevation of an upper most end of a storage and retrieval system according to an aspect of the invention.
Referring now to the drawings and the illustrative embodiments depicted therein, the upper mast end 1 of a storage and retrieval system 20 is shown. Details of the lower mast end of the storage and retrieval system are conventional and will not be described in detail. Suffice it to say, the mast is supported at its lower end on a running rail 8 via running wheels 9, only one of which is shown, which roll on the top of the rail. One of the running wheels is driven by a motor 10, with the result that the storage and retrieval system can be moved along the running rail, which at the same time provides for the guidance of the mast of the storage and retrieval system.
In the region of the upper mast end 1, a guide rail 2 arranged in the top region extends parallel to lower running rail 8. In this case, the upper mast end is connected to the guide rail 2 via freely rotatable guide rollers 11, only one of which is shown. The guide rollers roll on the side faces 3 of the guide rail 2. In the illustrated embodiment, the guide rollers subjected to magnetic attraction, bear on both sides against the guide rail 2, although spring force, or the like, may be used to provide attraction. The desired frictional relationships are achieved by means of the guide rollers being pressed against the guide rail 2.
As shown in the figure, a further roller, which is subjected to a force and is in the form of a friction roller 4, bears against one of the two side faces 3. When storage and retrieval system 20 is moved, friction roller 4 rolls along the guide rail 2 and at the same time bears against the guide rail, such as at a face 3. As will be described in more detail below, the friction roller may be subjected to a force by means of magnetic attraction.
The friction roller 4 is connected to the mast end 1 via a gear assembly 5 having gear wheels 5a, 5b, the gear wheels 5a, 5b being connected to one another via a toothed belt 6. By varying the diameter of one or both wheels 5a, 5b, the gear ratio may be changed to suit the application.
The gear wheel 5b is positioned on the shaft of an eddy current brake 7, which in this case is in the form of a squirrel-cage asynchronous motor 7a and is fixedly connected to the mast end 1. The electric motor has a constant air gap to perform the function of an eddy current brake 7, i.e., the squirrel-cage asynchronous motor 7a is electrically connected in a corresponding manner and therefore converts the mechanical movement energy of the mast tip 1 into heat via eddy currents. The air gap of motor 7a is selected in terms of its size such that in each case a correspondingly large magnetic field is induced. In this case, the gear 5 is used for adapting the rotation speed to the optimum rotation speed of the squirrel-cage asynchronous motor 7a, i.e., the rotation speed at which the asynchronous motor eddy current brake 7 is at its most effective.
A direct current may be applied to the asynchronous motor 7a when the mast is approaching the intended stopping position. In this manner, damping of the mast movement may be limited to positions of the mast when it is moving into the intended stopping position. The eddy current brake 7a can otherwise be selectively connected during the movement or prior to the movement of the mast to the intended stopping position.
The use of the gear 5 makes it possible to position the asynchronous motor 7a at various locations along the mast. It is therefore not necessary for the asynchronous motor 7a to be attached directly in the region of the guide rail 2.
In an alternative embodiment, friction roller 4 may also perform the function of one of the guide rollers 11. In this manner, one roller may both partially guide the mast and at the same time transmit the movement of the mast tip to the squirrel-cage asynchronous motor 7a. In this manner, it is possible to omit the guide rollers 11 which lie on the same side as the friction roller 4, the friction roller 4 also taking on the guiding function on this side.
Alternatively, the electric motor may be in the form of a synchronous motor having a short-circuited winding to provide the desired damping effect.
Changes and modifications in the specifically described embodiments can be carried out without departing from the principles of the invention which is intended to be limited only by the scope of the appended claims, as interpreted according to the principles of patent law including the doctrine of equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2005 039 643.7 | Aug 2005 | DE | national |
