U.S. patent number RE35,663 [Application Number 07/783,129] was granted by the patent office on 1997-11-18 for method and apparatus for transportation of materials.
This patent grant is currently assigned to Hitachi, Ltd.. Invention is credited to Hirokazu Ihara, Shoji Miyamoto, Kinji Mori, Masayuki Orimo, Yasuo Suzuki.
United States Patent |
RE35,663 |
Mori , et al. |
November 18, 1997 |
Method and apparatus for transportation of materials
Abstract
A plurality of machine tools are disposed along a circulating
conveyor transporting materials to be processed by the machine
tools, and material selector subsystems associated with the
respective machine tools are provided together with a load/unload
command subsystem. The material selector subsystems exchange
information therebetween to track materials loaded on the conveyor
under command of the load/unload command subsystem so as to reserve
materials requested by the individual machine tools. Each of the
reserved materials is unloaded from the conveyor under command of
the load/unload command subsystem as soon as it arrives at the
position of the corresponding machine tool.
Inventors: |
Mori; Kinji (Yokohama,
JP), Suzuki; Yasuo (Ebina, JP), Orimo;
Masayuki (Machida, JP), Miyamoto; Shoji
(Kawasaki, JP), Ihara; Hirokazu (Machida,
JP) |
Assignee: |
Hitachi, Ltd. (Tokyo,
JP)
|
Family
ID: |
16234617 |
Appl.
No.: |
07/783,129 |
Filed: |
March 31, 1992 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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454860 |
Jan 16, 1990 |
Re. 33862 |
Mar 31, 1992 |
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143960 |
Jan 14, 1988 |
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Reissue of: |
547133 |
Oct 31, 1983 |
04564102 |
Jan 14, 1986 |
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Reissue of: |
454860 |
Jan 16, 1990 |
RE033862 |
Mar 31, 1992 |
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Foreign Application Priority Data
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Oct 29, 1982 [JP] |
|
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57-189060 |
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Current U.S.
Class: |
198/341.07;
198/349.7; 29/563; 700/169 |
Current CPC
Class: |
B23Q
41/00 (20130101); G05B 19/4189 (20130101); G06Q
10/08 (20130101); G05B 2219/32082 (20130101); Y10T
29/5124 (20150115); Y10T 29/5196 (20150115); Y02P
90/02 (20151101); Y02P 90/20 (20151101); Y02P
90/28 (20151101) |
Current International
Class: |
B23Q
41/00 (20060101); G05B 19/418 (20060101); B65G
043/00 () |
Field of
Search: |
;198/341,356,358,465.2,340,349.7,349.9,346.1 ;29/563,564,33P
;364/474,478,825.23,900 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2230633 |
|
Jan 1973 |
|
DE |
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2442659 |
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Mar 1976 |
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DE |
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56-152558 |
|
Nov 1981 |
|
JP |
|
2109278 |
|
Jun 1983 |
|
GB |
|
Primary Examiner: Bidwell; James R.
Attorney, Agent or Firm: Antonelli, Terry, Stout &
Kraus
Parent Case Text
.Iadd.This application is a .Iaddend..Badd.reissue of, and a
continuation of, U.S. reissue application Ser. No. 454,860, filed
Jan. 16, 1990, now U.S. Reissue Pat. No. Re. 33,862, issued Mar.
31, 1992, which is .Baddend..Iadd.a continuation of U.S.
application Ser. No. 143,960, filed .Iaddend..Iadd..[..[.Dec. 22,
1989.]..]..Iaddend. .Badd.Jan. 14, 1988, .Baddend..Iadd.now
abandoned, which is a reissue of U.S. application Ser. No. 547,133,
.Iaddend..Badd.filed Oct. 31, 1983, .Baddend..Iadd.now U.S. Pat.
No. 4,564,102. .Iaddend.
Claims
We claim: 1. A method for transportation of materials in a
work-processing system including a plurality of work-processing
means processing materials transported thereto by transporting
means, comprising the steps of loading newly externally supplied
materials on said transporting means detecting material transported
by said transporting means by using a detector means associated
with each of said work-processing means and storing the results of
detection; issuing a material request from any work-processing
means when the work-processing means requires a material which is
not detected by said work-processing means; communicating the
material request from the work-processing means which issued the
material request to other processing means; causing each of said
work-processing means to search a requested material indicated by
the material request; based on the stored results of detection
while keeping coordination with the other work-processing means in
response to receipt of the material request; reserving said
requested material for the work-processing means which issued the
material request when said material is found on said transporting
means as a result of the searching step while maintaining the
material request when the searching step cannot find said requested
material on said transporting means; and unloading said reserved
material from said transporting means upon arrival of said material
at the position of said work-processing means which issued the
material request thereby supplying said material to said
work-processing means. 2. An apparatus for transportation of
materials in a work-processing system including a plurality of
work-processing means processing materials transported thereto by
transporting means, comprising load/unload commanding means for
commanding loading of newly externally supplied materials on said
transporting means and commanding unloading of said materials from
said transporting means; transmission control means provided for
each of said work-processing means for transmitting a material
request issued from work-processing means associated therewith to
other work-processing means and receiving a material request
transmitted from the other work-processing means; and material
selector means provided for each of said work-processing means and
comprising means at each work-processing means for storing the
material request issued from the work processing associated
therewith and the material requests transmitted from the other
work-processing means; means at each work-processing means for
detecting materials on said transporting means and storing the
results of detection, means for searching a requested material
based on the contents of said material request storing means and
said means for storing the results of detection while keeping
coordination among said work-processing means, means for reserving
the requested material when it is found by said searching means
that the requested material on said transporting means and
reporting a reservation of requested material to other
work-processing means, and means for continuously issuing a
material request when said workprocessing means cannot find the
requested material on said transporting means. 3. An apparatus
according to claim 2, wherein each of said work-processing means
comprises a first subsystem for carrying out a work process and a
second subsystem including said material selector means and said
transmission control means, said transmission control means being
connected through a transmission path to the transmission control
means of the other work-processing means. 4. An apparatus according
to claim 3, wherein each of said work-processing means further
comprises means for reporting to the load/unload commanding means
that requested material is not reserved after repeated issuance of
a material request a predetermined number of times, so as to cause
said load/unload commanding means to
supply the requested material. .Iadd.5. A method for processing
materials in a processing system including a plurality of
subsystems which process at least one selected material and operate
independently of each other, a means for relatively moving
materials with respect to said subsystems and a transmission medium
connected with said subsystems for transmitting information
relating to the materials to said subsystem, comprising the
following steps executed by each of said subsystems:
transmitting information relating to the materials moved by said
moving means to said transmission medium;
receiving information relating to the materials moved by said
moving means and transmitted from other subsystem through said
transmission medium;
selecting at least one necessary material from among the materials
moved by said moving means based on the received information
relating to the materials from said transmission medium; and
processing said selected material upon arrival said selected
material..Iaddend..Iadd.6. A method for processing materials
according to claim 5, which further includes a step of reserving
said necessary material when it is selected by said selecting step
so as to process said selected material upon arrival of said
reserved material..Iaddend..Iadd.7. A method for processing
materials according to claim 5, wherein said moving means comprises
a means for transporting said materials, and a means for loading
said materials on said transporting means..Iaddend..Iadd.8. A
method for processing materials according to claim 5, wherein said
information on the materials comprises information showing the
presence of a material which has been moved by said moving
means..Iaddend..Iadd.9. An apparatus for processing material
comprising:
a plurality of first subsystems each of which processes at least
one selected material;
means for relatively moving the materials with respect to said
subsystems;
a plurality of second subsystems associated with said first
subsystems, respectively, and connected to a transmission medium,
each of said second subsystems configured to operate independently
of each other based on information on said transmission medium and
including means for transmitting information relating to the
materials moved by said moving means to said transmission medium;
and
means for selecting at least one necessary material from among the
materials moved by said moving means based on the information
relating to the materials transmitted from other subsystems and
received from said transmission medium, and each of said first
subsystems including means responsive to selection of at least one
necessary material by the associated second subsystem for
processing said selected material upon arrival
thereof..Iaddend..Iadd.10. An apparatus for processing materials
according to claim 9, further including means for reserving said
necessary material when it is selected by said selecting means so
as to process said selected material upon arrival of said reserved
material. .Iaddend..Iadd.11. An apparatus for processing materials
according to claim 9, wherein said moving means comprises means for
transporting said materials..Iaddend..Iadd.12. An apparatus for
processing materials according to claim 9, wherein said information
on the materials comprises information showing the presence of a
material which has been moved by said moving
means..Iaddend..Iadd.13. A method for transportation of materials
in a processing system including a plurality of processing means
processing materials transported thereto by transporting means,
comprising the steps of: loading materials on said transporting
means; issuing a material request from any processing means when
the processing means requires a material; communicating the
material request from the processing means which issued the
material request to other processing means; detecting materials
transported by said transporting means by using a detector means
associated with at least one of said processing means and storing
the results of detection; causing each of said processing means to
search a requested material indicated by the material request,
based on the stored results of detection; reserving said requested
material for the processing means which issued the material request
when said material is found on said transporting means as a result
of the searching step; and unloading said reserved material from
said transporting means upon arrival of said material at the
position of said processing means which issued the material request
thereby supplying said material to said processing
means..Iaddend..Iadd.14. An apparatus for transportation of
materials in a processing system including a plurality of
processing means processing materials transported thereto by
transporting means, comprising load/unload commanding means for
commanding loading of materials on said transporting means and
commanding unloading of said materials from said transporting
means; transmission control means provided for each of said
work-processing means for transmitting a material request issued
from processing means associated therewith to other processing
means and receiving a material request transmitted from the other
processing means; and material selector means provided for each of
said processing means and comprising means for storing the material
request issued from the processing means associated therewith and
the material requests transmitted from the other processing means;
means for detecting materials on said transporting means and
storing the results of detection; means for searching a requested
material based on the contents of said material request storing
means and said means for storing the results of detection; and
means for reserving the requested material when it is found by said
searching means that the requested material on said transporting
means and reporting a reservation of requested material to other
processing means..Iaddend..Iadd.15. An apparatus according to claim
14, wherein each of said processing means comprises a first
subsystem for carrying out a material process and a second
subsystem including said material selection means and said
transmission control means, said transmission control means being
connected through a transmission path to the transmission control
means of the other processing means..Iaddend..Iadd.16. An apparatus
according to claim 15, wherein each of said processing means
further comprises means for reporting to the load/unload commanding
means that requested material is not reserved after repeated
issuance of a material request a predetermined number of times, so
as to cause said load/unload commanding means to supply the
requested material..Iaddend..Iadd.17. A method for controlling
machine tools in a distributed system having a plurality of
subsystems, each of which has a machine tool and controller for
operating an associated machine tool and a transmission medium
connected with said subsystems for transmitting information to said
subsystems, comprising the following steps executed by each of said
subsystems:
transmitting the information to said transmission medium;
receiving information transmitted from other subsystems through
said transmission medium;
independently determining whether or not the machine tool is
operated based on the received information from said transmission
medium; and
operating said machine tool based on the independently
determined
result..Iaddend..Iadd.18. A method for controlling machine tools in
a distributed system having a plurality of subsystems, each of
which has a machine tool for processing at least one material and a
controller for operating the machine tool, a means for relatively
moving materials with respect to said subsystems and a transmission
medium connected with said subsystems for transmitting information
relating to the materials to said subsystems, comprising the
following steps executed by each of said subsystems:
transmitting information relating to the materials moved by said
moving means to said transmission medium;
receiving information relating to the materials moved by said
moving means and transmitted from other subsystems through said
transmission medium;
independently determining whether or not the machine tool is
operated for processing the material moved by said moving means
based on the received information relating to the materials from
said transmission medium: and
operating the machine tool based on the independently determined
result..Iaddend..Iadd.19. A material selector subsystem,
comprising:
means for detecting a pallet on a conveyor;
a pallet detector for receiving signals from the detecting
means;
a material selector for selectively unloading materials from the
conveyor;
a material selector controller operatively associated with the
material selector, including a processor, an interface operatively
associated with the pallet detector, an interface operatively
associated with the information transmission controller, a material
tracking file operatively associated with the processor, a
requested material data file operatively associated with the
processor, a pallet monitoring timer operatively associated with
the processor, a material request monitoring timer operatively
associated with the processor, and an interface for connecting the
subsystem with a materials processor for processing a selected one
of the materials on the conveyor; and
an information transmission controller for exchange of information
with at least one other material selector
subsystem..Iaddend..Iadd.20. The subsystem according to claim 19,
wherein the material selector controller further comprises an
input/output buffer operatively associated with the processor for
storing data of requested material and transferring said data to
the requested material data file..Iaddend..Iadd.21. The subsystem
according to claim 19, wherein the material tracking file stores
data comprising material name data and a status data indicating
whether a material has been reserved for another material selector
subsystem..Iaddend..Iadd.22. The subsystem according to claim 19,
wherein the requested material data file comprises material name
data and a status data to be found in the material tracking file to
broadcast from the material selector controller via an information
transmission log for reserving still unreserved
materials..Iaddend..Iadd.23. A method for manufacturing a product
in a distributed system including a plurality of subsystems for
transmitting information between said subsystems, said method
comprising the following steps executed by each of said
subsystems:
transmitting the information to said transmitting medium;
receiving the information transmitted from other subsystems through
said transmission medium;
independently selecting operation to be performed by its own
subsystem based on the received information from said transmission
medium; and
executing the selected operation based on the result of the
selecting
step..Iaddend..Badd.24. A producing system comprising;
transporting means for transporting materials to be used for
production of an object;
a plurality of subsystems of machine tools each for processing at
least a selected one of the materials transported by said
transporting means;
detecting means provided to each of said subsystems for detecting
the materials transported by said transporting means;
unloading means provided to each of said subsystems for unloading
from said transporting means the materials which the associated
subsystem requires;
a plurality of control means respectively provided to each of said
subsystems for controlling the unloading means of the associated
subsystem; and
transmitting means for transmitting therethrough information among
the plurality of control means which have been provided to each of
said subsystems, respectively,
wherein a control means includes means for instructing the
associated uploading means to unload materials based on a request
for material issued by the associated subsystem, a detection of
materials by the associated detecting means and information
transmitted through said transmitting
means from the other control means..Baddend..Badd.25. The producing
system according to claim 24, wherein the information transmitted
through said transmitting means includes material information
regarding the materials transported by said transporting
means..Baddend..Badd.26. The producing system according to claim
25, wherein said control means includes first holding means for
holding information as to material requested by the associated
subsystem and second holding means for holding information
transmitted through said transmitting means from said other than
control means..Baddend..Badd.27. The producing system according to
claim 26, wherein said control means broadcasts a request for
material issued by the associated subsystem to the control means
provided to the other subsystems with reference to information held
in the first and second holding means..Baddend..Badd.28. The
producing system according to claim 27, wherein said control means
includes means for searching the information held in the second
holding means to discover the identity of material requested by the
request for material broadcasted from any of the other subsystems
and means for reserving the material whose identity is discovered
by the searching..Baddend..Badd.29. A processing system for
processing materials comprising:
plurality of subsystems;
transporting means for transporting the materials to be processed
circulatingly through the subsystems;
a transmission medium connecting the subsystems in a loop for
transmitting information relating to the materials through the
loop,
wherein said subsystems operate independently of each other based
on the information on said transmission medium and each of said
subsystems includes a transmitter of information relating to
materials to the transmission medium, a receiver of information
relating to the materials from the transmission medium and means
for determining whether or not one of the materials is to be
processed based on the received information and processes the one
material according to the determination..Baddend..Badd.30. The
processing system according to claim 29, including an additional
subsystem operatively associated with said transmission medium and
comprising a transmitter of information relating to materials to
the transmission medium, a receiver of information relating to the
materials from the transmission medium, and means for loading newly
supplied materials on said transporting means and means for
unloading already processed materials..Baddend..Badd.31. A method
of processing materials in a processing system including a
plurality of subsystems, and transmission medium connected with the
subsystems for transmitting information relating to the materials
to said subsystems, said subsystems operating independently of each
other based on the information on said transmission medium, said
method comprising the steps of:
circulating the materials through said subsystems by transporting
means;
transmitting, in each of said subsystems, information relating to
the materials from said transmission medium;
receiving, in each of said subsystems, said information relating to
the materials from said transmission medium;
determining, in each of said subsystems, whether or not one of the
materials transported thereto by said transporting means is to be
processed based on the received information; and
processing, in each of said subsystems, the one material responsive
to the determination to process the one material..Baddend..Badd.32.
The method according to claim 31, further comprising the steps
of:
1oading newly externally supplied materials on said transporting
means; and
unloading already processed materials from said transporting
means..Baddend .
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and apparatus for transportation
of material, in which materials to be machined by individual
machine tools are continuously circulated on a conveyor, and a
specific one selected from among them is unloaded from the conveyor
to be supplied to a specific machine tool when the specific
material is requested by the specific machine tool.
2. Description of the Prior Art
Hitherto, materials to be machined by individual machine tools
according to the production schedule have been previously
distributed to corresponding ones of the machine tools, or such
materials have been stored in a warehouse so that a specific one
selected from them can be supplied by a conveyor from the warehouse
to a specific machine tool upon request for machining by the
machine tool. However, the former method is not applicable to a
production system in which the production schedule is frequently
changed resulting in a corresponding change of the machine tools
participating in material processing or the production schedule
cannot be sufficiently laid out in advance. According to the latter
method, on the other hand, pallets on which the materials are
carried, respectively, are marked by a central unit according to
the production schedule with the addresses of specific machine
tools which are scheduled to process the materials and the pallets
are transported by the conveyor. Thus, in the case of the latter
method, the relationship between the machine tools and the
materials to be processed thereby must be preliminarily determined.
Further, an addressing error of the central unit results in
maloperation of the whole system. Further, it has been required for
the central unit to collect and process a vast amount of
information, since the central unit must always exactly grasp the
operating state and occurrence of operational failure, if any, of
the individual machine tools. Furthermore, the latter method, in
which a material is not transported to a machine tool by the
conveyor until the machine tool requests distribution of such a
material, has been defective in that a considerably long period of
time is required until the material is actually supplied to the
machine tool after the request is issued.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a method
and apparatus for transportation of materials, which can easily
deal with a change of the production schedule, operational failure
of a machine tool and maintenance required for the machine tools,
and in which any error of material selection does not result in
mal-operation of the whole system.
The present invention which attains the above object is featured by
the fact that materials required for production are placed on a
circulating conveyor to be continuously circulated past a plurality
of machine tools so that materials requested by the individual
machine tools can be readily selected from among those circulated
to the positions of the machine tools, and material selector
subsystems belonging or connected to the machine tools respectively
exchange information therebetween to track the materials being
circulated so that a requested material can be readily reserved and
then unloaded from the conveyor upon arrival at the position of the
machine tool scheduled for machining it.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing the general structure of a
preferred embodiment of the system according to the present
invention.
FIG. 2 is a diagrammatic elevation view showing the arrangement of
pallets and materials on the conveyor shown in FIG. 1.
FIG. 3 is a block diagram showing the structure of one form of one
of the material selector subsystems shown in FIG. 1.
FIG. 4 is a block diagram showing the structure of one form of the
material selector controller shown in FIG. 3.
FIG. 5 shows data stored in one form of the material tracking file
shown in FIG. 4.
FIG. 6 shows data stored in one form of the requested material data
file shown in FIG. 4.
FIGS. 7 to 12 are flow charts illustrating the operation of the
material selector subsystem shown in FIGS. 3 and 4.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows the general structure of a preferred embodiment of the
system according to the present invention.
Referring to FIG. 1, a material transporting conveyor 2 is
circulated continuously in a direction shown by an arrow past a
plurality of distributed machine tool subsystems 11 to 15 and a
load/unload command subsystem 16. Material selector subsystems 31
to 35 and 36 are connected to the machine tool subsystems 11 to 15
and the load/unload command subsystem 16 respectively so as to load
and unload in a well-known manner selected materials on and from
the conveyor 2. These material selector subsystems 31 to 36 are
interconnected by an information transmission loop 4 for exchange
of information of materials on the conveyor 2 and information of
their positions on the conveyor 2.
FIG. 2 shows, for example, that each of materials A, B, C, and so
on is carried on one of the pallets 61 to 6n which are loaded on
the conveyor 2 and no material is carried on a pallet 62.
The load/unload command subsystem 16 applies a command to the
material selector subsystem 36 for loading newly externally
supplied materials from the warehouse on the conveyor 2 or
unloading materials from the conveyor 2 for storing the materials
to the warehouse.
FIG. 3 shows the internal structure of one form of the material
selector subsystem 31. The subsystems 32 to 35 are arranged in the
same manner as the subsystem 31.
Referring to FIG. 3, the material selector subsystem 31 includes a
pair of material detectors 71 and 72 for detecting a pallet on the
conveyor 2, a pallet detector 73 receiving the output signals from
the detectors 71 and 72, a material selector 74 for selectively
loading or unloading materials to or from the conveyor 2, a
material selector controller 75 for controlling the material
selector 74, and an information transmission controller 76 for
controlling exchange of information between the material selector
subsystem 31 and the other material selector subsystems.
FIG. 4 shows the internal structure of one form of the material
selector controller 75 shown in FIG. 3. Referring to FIG. 4, the
material selector controller 75 includes a processor 80, an
interface 81 connected to the pallet detector 73, an interface 82
connected to the information transmission controller 76, an
input/output buffer 83, a material tracking file 84, a requested
material data file 85, a pallet monitoring timer 86, a material
request monitoring timer 87, and an interface 88 connected to the
machine tool subsystem 11.
FIGS. 5 and 6 show data stored in the material tracking file 84 and
requested material data file 85 respectively, by way of
example.
FIGS. 7 to 12 are flow charts illustrating, by way of example, the
steps of processing by the processor 80 shown in FIG. 4.
The operation of the material selector subsystem 31 shown in FIGS.
3 and 4 will now be described with reference to FIGS. 5 to 12.
The data of a material requested for a workpiece that can be
processed now is broadcast from the machine tool subsystem 11 to
the material selector controller 75 (block 101 in FIG. 7). The
material selector controller 75 stores the data of requested
material once in the input/output buffer 83. If the data in the
buffer 83 is the data of requested material, the data is
transferred into the requested material data file 85 (block 102 in
FIG. 7).
On the other hand, when passage of a pallet is detected by the
material detector 71 (block 109 in FIG. 8), the data of the
material on the detected pallet is transmitted from the information
transmission controller 76 to the downstream material selector
subsystems by way of the information transmission loop 4. In the
material selector controller 75 in each of the downstream material
selector subsystems, the data of the material, transmitted thereto
from the upstream material selector subsystem through the
information transmission loop 4, information transmission
controller 76 and interface 82, is stored once in the input/output
buffer 83 and then stored in the material tracking file 84 (blocks
110 and 111 in FIG. 8). In this manner, data of materials are
transmitted sequentially from the upstream material selector
subsystem to be stored in the material tracking file 84 in each of
the downstream material selector subsystems, and, at the same time,
the data of the materials on the pallets departing toward the
downstream material selector subsystems from the position of the
material detector 72 in each of the material selector subsystems
are erased from the material tracking file 84. Thus, in the
downstream material selector subsystem next adjacent to the
directly upstream material selector subsystem, the data of the
materials on the pallets 61 to 63 are stored in the material
tracking file 84 in a sequential order as shown in FIG. 5. FIG. 5
shows that each pallet data is composed of a material name data and
a status data, and the status data designated by the symbol R.sub.1
indicates that the material B is reserved for the material selector
subsystem 31.
When the data of the requested material stored in the requested
material data file 85 is also stored in the material tracking file
84 as shown in FIG. 5 (block 103 in FIG. 7) and when arrival of the
pallet carrying the requested material is detected by the material
detector 71 (block 109 in FIG. 8), and, then, when the material
selector controller 75 is informed of the lapse of a predetermined
period of time after detection of the pallet arrival, from the
pallet monitoring timer 86 (block 113 in FIG. 8), the material
selector controller 75 commands the material selector 74 to unload
the specific material from the position of the pallet on the
conveyor 2 (block 115 in FIG. 8). The above-mentioned predetermined
period of time is selected such that the material selector 74 is
ready for unloading the material from the pallet detected by the
material detector 71 when the predetermined period of time has
lapsed after the detection. The material selector 74 supplies the
specific material to the machine tool subsystem 11. At the same
time, the material selector controller 75 erases the data of the
unloaded or removed material from both of the material tracking
file 84 and the requested material data file 85 (block 116 in FIG.
8).
If the data of the material B stored in the requested material data
file 85 is not found in the material tracking file 84, the status
data of the material B in the requested material data file 85 is
set at the "waiting" state W, and a flag indicative of the
"Waiting" state W is then set (block 106 in FIG. 7). At the same
time, a request for the material B is broadcast from the material
selector controller 75 by way of the information transmission loop
4 (block 107 in FIG. 7), and the material request monitoring timer
87 is set (block 108 in FIG. 7).
When each of the other material selector subsystems receives the
request for the material B broadcast from the specific material
selector controller 75 and transmitted by way of the information
transmission loop 4 (block 117 in FIG. 9), it searches whether or
not the specific material B is included in its material tracking
file 85 (block 118 in FIG. 9), and a reservation flag R.sub.1
indicative of reservation of the corresponding pallet 63 is set
when the material B is included in its material tracking file 84
and is not still reserved (blocks 119 and 120 in FIG. 9). Then, the
fact that the requested material B is now reserved is broadcast
from the material selector controller 75 of that subsystem to the
material selector controller 75 having broadcast the request for
the material B (block 121 in FIG. 9). When the requested material B
is found, the material selector controller 75 sets the reservation
flag R.sub.1 indicative of reservation of the requested material B
in the requested material data file 85.
If two or more of the material selector subsystems answer booking
of the reservation of the material B in response to the request for
the material B, (blocks 129 and 130 in FIG. 11), the material
selector controller 75 selects only one of the reserved pallets
from among them and broadcasts cancellation of the reservation to
the other pallets (block 132 in FIG. 11). When the
reservation-cancelled pallet is included in the material tracking
file 84 in each of the material selector controllers 75 receiving
the broadcast informing the cancellation of reservation, the
material selector controller 75 resets the material reservation
flag of the corresponding pallet (blocks 122, 123 and 124 in FIG.
10).
When the material selector controller 75 having broadcast the
request for the material B does not receive the answer informing
reservation of the request material B from any one of the other
subsystems in spite of the fact that the material request
monitoring timer 87 has timed a predetermined period of time, a
request waiting flag W indicative of waiting a request for the
material B is set in the requested material data file 85 (blocks
125, 126, 127 and 128 in FIG. 11). Thereafter, the material
selector controller 75 broadcasts the request for the material of
waiting state at predetermined constant time intervals. When the
booking of reservation of the material B is answered, the request
waiting flag W is reset, and the material reservation flag R, is
set (blocks 129, 130 and 131 in FIG. 11).
When the material B cannot be reserved although the material
request has been broadcast more than a predetermined number of
times (blocks 133 and 134 in FIG. 12), the material selector
controller 75 of the subsystem 31 displays the impossibility of
reservation, and, at the same time, broadcasts it to the other
material selector controllers (block 135 in FIG. 12). Upon
receiving this broadcast informing the impossibility of material
reservation, the material selector subsystem 36 displays it too and
calls for supply of the specific material to the system from the
external source.
It will be understood from the forgoing detailed description of the
present invention that distributed machine tools can select
required materials to meet any machining demand, and the system can
deal with operational failure and recovery of whichever machine
tool at whatever time and can also deal with a system expansion, so
that there is no need for previously arranging the material
distribution schedule. Further, the present invention can save the
useless length of time required hitherto for the transportation of
materials to the machine tools whenever such materials are
requested, and can also save the space required for storage of
materials.
While the present invention has been described with reference to
its application to a system including a plurality of distributed
machine tools by way of example, it is apparent that the present
invention is not in any way limited to application to such a
specific system, and is applicable also to any one of assembling,
working and other processing systems.
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