Conveyors: power-driven – With means to facilitate working – treating – or inspecting... – Means to convey a palleted load back and forth between an...
Reexamination Certificate
2001-02-15
2003-02-18
Bidwell, James R. (Department: 3651)
Conveyors: power-driven
With means to facilitate working, treating, or inspecting...
Means to convey a palleted load back and forth between an...
C198S347100
Reexamination Certificate
active
06520312
ABSTRACT:
FOREIGN PRIORITY
This application claims the right of foreign priority to German Application No. 100 07 024.8 filed on Feb. 16, 2000, and to European Application No. 00 116 129.8 filed on Jul. 31, 2000, and both applications are incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
Interlinked production systems are used in mass production to be able to process workpieces in the most inexpensive and reliable manner in a number of processing stations. Typical applications for interlinked production systems are found in the automobile industry, for example for the highly efficient fabrication of motor and transmission components.
The line production is known as a classical example of an interlinked production system, in which the flow of parts between the individual processing stations is controlled over a belt, which serves as a buffer at the same time. Portals branch off to the side from the belt to the individual processing stations.
The coupling of a plurality of processing stations via portals is known as a further example of an interlinked production system, where belt buffer stores are arranged between the individual or several processing stations for decoupling. Such belt buffer stores are conveyor belts with which individual parts are conveyed or stored. Such buffers normally receive about 10 to 20 parts and can make up for certain fluctuations caused by delays at the associated processing stations.
However, a drawback is that the belt buffer stores are only designed for a small number of parts, so that when larger disruptions occur at one or more processing stations of the processing system, the entire system shuts down in short time. In addition, the handling of individual parts can have negative effects on their quality, because damage may occur. Furthermore, when emptying one of the buffers, one must first wait until all of the parts have been used up. This is a problem when a so-called one-piece-flow operation is important, i.e. when the processing steps are to be controlled so that one part passes through the various processing stations in sequence without being stored intermediately as far as possible. With a one-piece-flow operation, short throughput times are basically achievable, however, the productivity of the production system is reduced because the smallest machine idle time can lead to so-called linkage losses.
A one-piece-flow operation is practically impossible with the above-mentioned conveyor belt, through which the individual processing stations can be connected and coupled to one another through portals.
The use of a belt as conveying means and at the same time the use of buffering between the individual processing stations does allow a certain buffering with differing outputs of the individually coupled stations, however, the entire system cannot be designed for high productivity and short throughput times. The different cycle times of the individual stations necessarily negatively effect the output of the entire system.
Furthermore, the information flow associated with the individual parts is very difficult to control. This is especially a problem when the quality of the individual parts is to be fully documented.
When changing the two mentioned production systems to produce different parts, the entire system must at first be emptied before the fabrication of the other parts can begin. It is also basically known to couple so-called automated cells to one or more processing stations. A number of carriers for stacks of parts are contained in the cells which serve as buffers. With the coupled automated cells, the stations are supplied with fresh parts independent of the processing fluctuations and finished parts are received therein (see for example EP 0 673 711 A1 or EP 0 865 869 A1).
The coupling of all processing stations of the entire production system, for example having 20 or 30 stations, takes place from outerlying intermediate stores which are arranged between automated cells of the associated processing stations. Stacks of workpieces are transported by roller carts or wagons between these intermediate stores and the automated cells.
The higher requirement for storage and parts inventory for the entire system has proven to be a disadvantage. In addition, human intervention is required at the predetermined cycle intervals to promptly transport the stack of part carriers between the intermediate stores and the automated cells. This basic dependency on manual operations is considered to be at least partially disadvantageous in automated production systems.
It is also basically known to automatically couple different processing stations of an interlinked production system and the intermediately arranged buffers through transportation systems without a driver. The high investment and the complicated control and software for the total system has proven to be a disadvantage, where at the same time, an increased danger of accidents can occur. Furthermore, the reliability up until now has largely not been sufficient.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved interlinked production system which allowes a flexible control of the flow of the parts processed therein, even through a large system with several processing stations.
It is a further object of the present invention to provide an improved interlinked production system suitable for a one-piece-flow operation on the one hand and allowing operation using buffers for higher productivity on the other hand.
It is a further object of the present invention to provide an improved interlinked production system being as inexpensive as possible and flexible at the same time.
It is still another object of the present invention to provide an improved interlinked production system having a high reliability.
It is another object of the present invention to provide an improved interlinked production system requiring only a very limited space.
These and other objects of the present invention are achieved with an interlinked production system of the above-mentioned type, where in at least three buffers are provided, the buffers being configured to receive part carriers and having at least two stack positions, a transfer device being provided for transferring part carriers between the stack positions within the buffer. The object of the invention is completely achieved in this manner.
According to the present invention, the transportation of parts through the interlinked production system is ensured with the aid of one or more portals with portal grippers which are drivable thereon. The production system, which has at least three buffers, preferably however a plurality of buffers in communication with a corresponding number of processing stations, is flexibly interlinked through the buffers, which are configured to receive part carriers, whereby the disadvantages of belt stores are avoided. The capacity of the buffers can be adapted to the individual requirements and also to the given condition of the total system by the transfer device for transferring the part carriers between the stack positions within the buffer.
Human intervention is not necessary in the system for transporting the stacks of workpiece carriers. Rather, operating personnel is only necessary for the purposes of control and monitoring and for emergencies.
It is also possible, if desired to introduce additional part carriers into the buffers from the outside or to remove same. In this manner, an extremely flexible operation for the entire production system is made possible.
A one-piece-flow can be achieved in that the buffer capacity is not utilised or is minimised. Minimal throughput times and minimal stores can be achieved.
In another strategy, certain minimum capacities can be set for the buffers to achieve the highest possible productivity. At the same time it is possible to use specially configured buffers at various locations in the total system to account for differing machine cycle times, shorter machine idle times and even to account for changes in the production sys
Bidwell James R.
Felsomat GmbH & Co. KG
Henneman & Saunders
Henneman, Jr. Larry E.
LandOfFree
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