Method and apparatus for immersion-process

In a method and an apparatus for plating a plurality of kinds of works, an unattended route-free vehicle transports the works to a number of processing tanks to immerse the works in the processing tanks. A controller calculates a processing time of the processing tanks and a transporting time needed for the vehicle to transport the works to the processing tanks and renders the vehicle to transport one kind of the works during the immersion-processing of another kind of the works, thereby performing the plating process of a plurality of kinds of works one after another.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an immersion-processing method and apparatus for 
plating or surface-treating metallic products. 
2. Description of the Related Art 
In the conventional production of slide fasteners, various plating, such as 
copper-plating, nickel-plating, zinc-plating or brass-plating, have been 
made on slide fastener parts of zinc alloy to meet various demands. In 
each conventional plating processes, as disclosed in, for example, 
Japanese Patent Laid-Open Publication No. Sho 55-14595, parts (hereinafter 
called the works) to be plated are suspended by hangers movable 
horizontally over and along a succession of fixed processing tanks and are 
immersed in the processing tanks by lowering and raising the hangers. The 
works suspended by the hangers are transported by a dedicated transporting 
unit which moves along a pair of rails fixed to the ceiling, and the 
driving of which is controlled by a computer. Further, data about 
processing conditions, such as a processing time of the works and a 
current value, are read and stored by the computer; based on the data, the 
hangers are moved by the transporting unit over the processing tanks to 
perform the plating of a plurality of works simultaneously. 
Japanese Patent Laid-Open Publication No. Sho 63-30399 discloses a 
transportation system for transporting works to each of successive 
processing tanks. In the transportation system, the works are transported 
by a carriage movable on a pair of rails fixed to the floor so that the 
carriage is movable between two series of processing tanks parallel to the 
rails. A hanger-manipulator arm mounted on the vehicle for suspending the 
works can position hangers over each processing tank series and is 
horizontally turnable and vertically movable to immerse the works in the 
processing tanks. 
This plating line is exemplified by a nickel-plating line, a brass-plating 
line and a zinc-plating line; each kind of works common in plating type 
are plated in an individual shared plating line. In this conventional 
plating line, a multiplicity of processing tanks filled with the same kind 
of plating liquid are arranged in an effort to improve the manufacturing 
efficiency in mass production, and for this purpose, a plurality of 
various pre-processing tanks (electrolytic degreasing tank, weak-acid 
neutralizing tank, etc.) used. 
According to the foregoing prior art, since the processing tanks of each 
step and their associated devices are arranged in the factory as a 
dedicated line, it is useful when manufacturing the same kind of products 
by a large quantity, but when manufacturing various kinds of products by a 
small quantity, many steps and facilities would be wasteful in flexible 
manufacturing, thus lowering the availability. Further, in recent years, 
plating lines are required to perform various plating processes demanded 
by customers quickly, and it is necessary to manufacture many kinds of 
products efficiently without adding any facility and hence increasing the 
cost of production. 
As it depends on the variation of the number of works and the number of 
kinds of the works, availability of each plating line differs from one 
another. As a result, there would be an excess of processing tanks in a 
low-availability plating line, while there would be a shortage of 
processing tanks in a high-availability plating line. Yet if they increase 
the number of hangers or carriages was increased to solve such problem, a 
large scale of addition and reconstruction of facilities would have been 
inevitable and quick measures could not have been taken to cope with the 
added facilities. 
Further, there are some plated works which require to be re-plated with the 
same or different kind of plate and sometimes it is necessary to provide 
another series of processing tanks for the re-plating. On such occasion, 
the works would not be plated in a single substantially continuous series 
of processing steps and they are transported between the first series of 
processing tanks to the second series of processing tanks for the 
re-plating manually. 
In the above-mentioned plating, the plated works would be deteriorated, 
e.g. discolored, when they are left in wet for a long time; in order to 
cope with this problem, a drying step is added. Grease and dust would 
stick to the accumulated works due to the atmosphere in the factory, or a 
natural oxidized film would occur on the metal surface; in order to cope 
with this problem, facilities for performing electrolytic degreasing, 
washing, weak-acidic saturation, etc. are added. Therefore, although these 
added facilities are common facilities among the individual processing 
lines, under the influence of the availability of each processing line 
they belong to, they are not used efficiently. Accordingly, the cost of 
production and the space occupied by the facilities are increased, thus 
lowering the productivity. If the first and the second plating steps can 
be performed continuously, the drying step and the pre-processing step 
would be unnecessary. 
Further, the same problems as those described above also exist in the 
process of surface-treatment, such as alumite-treatment and a 
predetermined process to be performed by immersing the works in some 
liquid. 
SUMMARY OF THE INVENTION 
With the foregoing prior art problems in view, it is an object of this 
invention to provide a method and an apparatus for performing many kinds 
of immersion-processes efficiently with a simple construction. 
According to a first aspect of the invention, there is provided a method 
for immersion-processing a plurality of kinds of works, comprising: 
providing a number of processing tanks 12 in which the works 10 are to be 
immersed for immersion-process, such as plating or surface-treating, and 
means, such as an unattended route-free vehicle 14, for transporting the 
works 10 to the processing tanks 12; calculating a processing time of each 
of the processing tanks 12 and a transporting time needed for the 
transporting means 14 to transport the works 10 to the processing tanks 
12; and transporting one kind of the works 10 to one of the processing 
tanks 12 by the transporting means 14, during the immersion-processing of 
another kind of the works 10, to perform the immersion-process of the 
plurality of kinds of works 10 one after another. The unattended 
route-free vehicle 14 transports another kind of the works 10 to another 
processing tank 12 when one kind of the works 10 is immersed in the 
processing tanks 12 for more than a predetermined time. 
According to a second aspect of the invention, there is provided an 
apparatus for immersion-processing a plurality of kinds of works, 
comprising: a number of processing tanks 12 in which the works 10 are to 
be immersed for immersion-process; means 14, such as an unattended 
route-free vehicle, for transporting the works 10 to the processing tanks 
12; and a controller 20 being of a computer for calculating a processing 
time of the processing tanks 12 and a transporting time needed for the 
transporting means 14 to transport the works 10 to the processing tanks 12 
and for rendering the transporting means to move to an arbitrary one of 
the processing tanks 12. 
According to a third aspect of the invention, there is provided an 
apparatus for immersion-processing a plurality of kinds of works, 
comprising: a plurality of processing tanks 12 in which the plurality of 
kinds of works 10 are to be immersed for immersion-process, the processing 
tanks 12 being composed of a shared pre-processing block 30 in which a 
number of common processing tanks 12 to be commonly used for 
pre-processing the plurality of kinds of works 10 is disposed, a dedicated 
processing block 34 in which a number of dedicated processing tanks 12 
each dedicated to a different immersion-process for each kind of the works 
10 is disposed, and a shared post-processing block 37 in which a number of 
common processing tanks 12 to be commonly used for post-processing of the 
plurality of kinds of works 10 is disposed; means, such as an unattended 
route-free vehicle 14, for transporting the works 10 to each processing 
tank 12; and a controller 20 for calculating a processing time of each 
processing tank 12 and a transporting time needed for the transporting 
means 14 to transport the works 10 to each processing tank 12 and for 
rendering the transporting means 14 to an arbitrary one of the processing 
tanks 12. Each of the blocks includes a buffer tank 40 for which an 
immersing time of the works 10 can be set to an arbitrary value and which 
is disposed at a trailing end of each block. 
The unattended route-free vehicle 14 is wirelessly connected to the 
computer 20, which is in turn connected to a network in the factory. The 
processing tanks 12 are to be commonly used for immersion-processing of 
the plurality of kinds of works 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A typical embodiment of this invention will now be described in detail with 
reference to the accompanying drawings. An immersion-processing apparatus 
of the embodiment is a plating apparatus comprising, as shown in FIG. 1, a 
plurality of processing tanks 12 for plating a plurality of kinds of works 
10, and an unattended route-free vehicle 14 movable along a traveling line 
16. The processing tanks 12 are filled individually with a predetermined 
pre-processing liquid, a plating liquid and washing water. The works 10 to 
be plated are suspended by a predetermined hanger 18 and are immersed in 
the processing tanks 12. 
The unattended route-free vehicle 14 is movable to a predetermined position 
along the traveling line 16 as electromagnetically, optically or 
magnetically guided. The movement of the route-free vehicle 14 is 
controlled by a controller 20; as a control signal from the controller 20 
is received by a receiver of the route-free vehicle 14 via a radio unit 
22, the route-free vehicle 14 moves to a predetermined position. The 
unattended route-free vehicle 14 has a non-illustrated arm such as a 
manipulator to hold and move the hanger 18. 
The controller 20 being a computer is connected to an in-company LAN 
network 24 and to a production-management-dedicated computer 26, etc. 
Further, a plurality of sequencers 28 connected respectively to each of 
the processing tanks 12 is connected to the network 24. 
The processing tanks 12, as shown in FIG. 2, includes a degreasing line 30, 
which has a stockyard 11 and is a shared pre-processing step to be 
commonly used for various plating processes, a sub-plating line 32 for 
performing various kinds of sub-plating processes, a number of dedicated 
plating lines 34 for performing various predetermined plating processes 
after the sub-plating processes. In the stockyard 11, a plurality of works 
10 waiting for plating processes are arranged in order. The degreasing 
line 30 and the sub-plating line 32 are commonly used for various plating 
and are disposed as a common pre-processing block. Each of the dedicated 
plating lines 34 are respectively dedicated to a single kind of plating 
and are disposed as a dedicated processing block altogether. Further, a 
common post-processing line 37 for performing finishing processes, such as 
washing and neutralizing, which are common to various plating and a number 
of dryers 39 are disposed as a common post-processing block. Downstream of 
the common post-processing block, another stockyard 13 exists in which the 
plated and finished works 10 are to be arranged in order. Each of the 
lines 30, 32, 34, 37 as defined in blocks are formed of the processing 
tanks 12 in a suitable combination and along the lines of processing tanks 
12, a traveling line 16 of the unattended route-free vehicle 14 extends. 
Before plating, the surface of the work 10 to be plated is polished as a 
pre-process to eliminate any rough surface. Then the plating is started. 
In the pre-process in the pre-processing block, the work 10 is immersed in 
alkaline liquid and washed in water and is then immersed in alkaline 
liquid in which a current flows so that possible grease and dust are 
removed off the work surface. Then the work 10 is washed to clear alkaline 
liquid drops off its surface. In the sub-plating line 32, the alkali 
liquid on the work surface is neutralized, and an oxidized film is removed 
off the work surface by acid-activation process, whereupon the work 10 is 
washed in water. 
Then the work 10 is firstly plated with copper as a sub-plate. This 
sub-plate serves to improve the adhesion of a dedicated nickel plate (or 
zinc plate or brass plate) to the surface of the work 10. The resulting 
work 10 is washed in water to clear the copper-plating liquid drops off 
its surface. 
Subsequently, in the dedicated plating line 34, the work 10 is plated with 
nickel and then washed. After that, the work 10 is treated with the 
post-process and dried to complete a succession of steps of plating 
process. As demand arises, an additional metal plate such as for 
black-nickel, tin-nickel-alloy or gold, may be plated over the resulting 
work 10. In this case, the dedicated plating line 34 dedicated for the 
demanded kind of plating may be additionally provided. 
The operation of the above-mentioned apparatus will now be described. As 
shown in FIG. 1, in the apparatus for plating process of the embodiment, 
the hanger 18 suspending the work 10 is transported to a predetermined 
processing tank 12 by the unattended route-free vehicle 14 under the 
control of the controller 20. 
The processing tanks 12 includes short-time intermediate tanks 36, such as 
acid-activating tanks, from which the works 10 have to be moved to the 
next step after the lapse of a relatively short predetermined period; 
long-time intermediate tanks 38, such as various plating tanks, whose 
processing time is so long that another hanger 18 can be moved during the 
process; and buffer tanks 40, such as washing tanks, from which the 
hangers 18 are not necessarily removed after the lapse of a predetermined 
period. 
One or more processing tanks 12 from the processing tank 12 next to one 
buffer tank 40 to the next buffer tank 40 is treated as a single 
processing block. From the processing tank 12 next to one buffer tank 40 
to one long-time intermediate tank 38, or from one long-time intermediate 
tank 38 to the next long-time intermediate tank 38, or from one long-time 
intermediate tank 38 to one buffer tank 40 is treated as a single moving 
block. Accordingly, a succession of plating process is treated as a group 
of processing blocks. Therefore, after confirming the security of the work 
10 in a single processing block, a control program can transmits the data 
of the process in a single moving block to the unattended route-free 
vehicle 14, thus flexibly coping with any processing step. 
Plating conditions (such as the processing order of the processing tanks 12 
and a processing time of each processing tank 12) of the works 10 are set 
individually for each lot of products by the production management 
computer 26 and are transmitted to the individual controllers 20 to be 
managed there. On receiving a current position of the route-free vehicle 
14 from the vehicle 14, and a processing status of the work 10 and a 
lapsed time of processing of the work 10, which is immersed in the 
individual processing tank 12, from the sequencer 28, the controller 20 
creates a processing route of the next step for the work 10 which is going 
to finish its process in the processing tank 12 it currently being 
immersed as well as a control data for the unattended route-free vehicle 
14 and transmits the data to the vehicle 14. According to the received 
control data, the route-free vehicle 14 moves and transports the hanger 
18. The control program of the controller 20 is programmed so as to 
prevent any crash between the individual works 10 in the processing tanks 
12, to secure the safe transportation of the works, which is being 
processed in the long-time intermediate tank 38, to the next step after 
the lapse of a designated processing period, and to prevents any crash 
between the route-free vehicles 14. 
The controller 20 control the route-free vehicle 14 and the hanger 18 as 
follows. Firstly, as shown in FIG. 3, first the current position of the 
route-free vehicle 14 is confirmed by the radio unit upon termination of 
the transportation of a particular work 10. Then, in regard to the every 
processing tank 12, the controller 20 obtains information whether the work 
10 is immersed in it or not, lot number of the works 10, and a lapsed time 
to process the individual work 10 from the sequencers 28 and calculates a 
remaining time of processing of the individual work 10. 
Then regarding the processing tank 12 in which the hanger 18 exists, the 
controller 20 calculates a remaining time to process the work 10 immersed 
in the processing tank 12, to check whether or not the processing of the 
work 10. 
If the processing of the work 10 is completed, the hanger 18 suspending the 
work 10 is transported to the next step. The hanger 18 is moved to the 
designated processing tank 12 as it is lifted by the non illustrated arm 
of the vehicle 14, and then immersed in the designated processing tank 12 
as it is brought down by the arm. Whereupon, in regard to the processing 
tank 12 in which the work 10 exists, the controller 20 calculates the 
remaining time to process the work 10. 
Assuming that the processing of the work 10 in the long-time intermediate 
tanks 38 has not yet been completed, if the remaining time to process the 
work 10 is less than a predetermined time, e.g. a period for the 
route-free vehicle 14 to transport the work and to return, and if the 
route-free vehicle 14 stays waiting by the processing tank 12, the vehicle 
14 waits there till the next process. Assuming that the route-free vehicle 
is not waiting by the processing tank 12, if the remaining time to process 
the work 10 in the processing tank 12 is less than a predetermined time 
and if the route-free vehicle 14 is not moved toward the position of the 
processing tank 12 yet, the route-free vehicle 14 is moved. 
If the route-free vehicle 14 has already been moved toward the processing 
tank 12, the controller 20 calculates a transporting time needed for the 
route-free vehicle 14 to transport the work 10 from the long-time 
intermediate tank 38 to the next step after the process of the work 10 in 
the long-time intermediate tank 38 is terminated. If the next step is the 
re-plating process in the long-time intermediate tank 38, the controller 
20 calculates a processing time in the long-time intermediate tank 38 and 
a transporting time needed for the route-free vehicle 14 to transport the 
work 10 to the next step after this processing. Then the controller 20 
reserves a time to use the route-free vehicle 14 after termination of the 
current process. 
For transporting the hanger 18 waiting in the buffer tank 40, the 
controller 20 checks whether or not the following transporting conditions 
are satisfied, and if satisfied, moves the hanger 18 to the next 
processing tank: first of all, the destination-side processing tank is 
open; in the processing tanks between the individual buffer tanks, there 
do not exist between the leading processing tank and the buffer tank a 
number of works more than the number of the buffer tanks and preliminary 
buffer tanks; while the work in the buffer tank is transported to the next 
step, the processing time of the work in process in another long-time 
processing tank will not terminate; and if the long-time intermediate tank 
38 exists at the destination side, the transporting time needed for the 
route-free vehicle 14 to transport the work after termination of the 
processing time of the processing tank does not coincide with the 
transportation of the work from another long-time intermediate tank to the 
buffer tank. Further, in transporting the works 10, priorities are 
assigned to the works of the long-time intermediate tank 38; in the 
absence of any processed work 10 in the long-time intermediate tank 38, 
priorities are assigned to the works near the terminal end of the 
processing step. 
According to the plating apparatus of this embodiment, since upon 
completion of process of the work 10, the controller 20 obtain a route 
along which the work 10 is to be transported by the route-free vehicle 14, 
it is possible to decide the order of processing of the works 10 and the 
order of moving of the route-free vehicles 14 and to process many kinds of 
works 10 concurrently so that the order of introduction of the works 10 to 
the processing tank 12 also can be changed freely, thus considerably 
increasing the processing efficiency. 
Further, since the pre-processing tanks 30 and the post-processing tanks 
are shared tanks 37, it is possible to perform various plating processes 
with improved efficiency. And the long-time intermediate tanks 38 for 
performing predetermined plating processes can be arranged in a relatively 
free fashion. It is also possible to reduce the whole size of the 
apparatus to a minimum and to flexibly cope with any change of the plating 
process. Furthermore, it is possible to secure a reliable processing-step 
control free from jamming of works in the processing lines and to prevent 
oxidation of the surfaces of the works and sticking of dust to the plated 
work surfaces. 
Furthermore, as shown in FIG. 3, according to the plating apparatus of this 
embodiment, it is possible to modify the number of the processing tanks 12 
according to the availability of each dedicated plating lines 34 easily. 
When the number of the processing tanks 12 is changed, the setting of the 
controller 20 for the number of the processing tanks 12 in each dedicated 
plating lines 34 is also changed. Whereupon, the traveling line 16 of the 
rout-free vehicle 14 is partly modified. Because of this modification, the 
distance of the traveling line 16 is changed and the controller 20 newly 
calculates the running time of the rout-free vehicle 14. Then, the 
controller 20 transmit the command, which is based on the result of the 
calculation, to the rout-free vehicle 14 to transport the hanger 18 
according to the steps described in the above. 
Although, the buffer tanks 40, from which the hangers 18 are not 
necessarily removed after the lapse of a predetermined period, are 
arranged at the end of the dedicated plating lines 34 in this embodiment, 
they may be arranged in a different line, i.e., the line composed of a 
plurality of the buffer tanks 40. 
The method and apparatus of this invention should by no means be limited to 
the illustrated embodiments and may be applied to other 
immersion-processing, such as processing of metal products (e.g., 
alumite-processing), and surface-treating, coating and dyeing of resin 
products, as well as other surface-treating. 
According to the immersion-processing apparatus and method, since many 
kinds of processing tanks are combined, it is possible to efficiently 
perform various immersion-processes concurrently in parallel, to reduce 
the whole size of the apparatus as compared to the conventional art, in 
which a plurality of processing lines are arranged independently of one 
another, and to flexibly cope with any change of processing steps. 
Further, by using a single processing tank 12 commonly for a plurality of 
kinds of works 10, it is possible to improve the availability of the 
processing tanks 12 and to perform immersion-processing efficiently in a 
reduced area occupied by the apparatus.