Automatic tool changer with electromagnetically readable tool holder having an electromagnetically coupling stopper for numerical control

A tool holder is enclosed in a rack which is moved by a belt for automatic tool exchange. A stopper member provided for the rack is fitted into a positioning groove formed in a flange portion of the tool holder, thereby preventing the rotation of the holder. A magnetic induction coupling apparatus is buried in the bottom of the tool holder positioning groove. A magnetic induction coupling apparatus of a reader/writer disposed at the external position is arranged so as to face the magnetic induction coupling apparatus of the tool holder. Information is written into or read out of a memory module attached in the tool holder by way of the magnetic induction coupling between both of those coupling apparatuses. The stopper member of the rack is arranged between the magnetic induction coupling apparatus of the tool holder and the magnetic induction coupling apparatus of the reader/writer and has a magnetic material to magnetically couple these coupling apparatuses.

BACKGROUND OF THE INVENTION 
The present invention relates to an automatic tool changer for 
automatically exchanging a tool to a machine tool such as a machining 
center or the like by use of a tool holder having therein a memory module 
to store information such as size, use time, and the like of a tool and, 
more particularly, to an automatic tool changer having a magnetic 
induction coupling apparatus for transmitting a signal between a holder 
and a reader/writer by a magnetic induction coupling. 
As a tool holder which is used in an automatic tool changer, in U.S. Pat. 
Application No. 06/924,342, entitled "INFORMATION PROCESSING APATUS OF 
TOOL," and filed Oct. 24, 1986 by the inventor, and now U.S. Pat. No. 
4,809,426 there is disclosed a tool holder in which a memory module is 
provided in the tool holder so that the holder itself has various kinds of 
information necessary for tool change and tool management, such as 
numbers, use times, and the like of the tools attached to the tool holder, 
and a power source is supplied from an external reader/writer to the tool 
holder and at the same time, data is written into or read out of the tool 
holder by a contactless method owing to a magnetic induction coupling. 
FIGS. 1A and 1B show an example of a state in which a magnetic induction 
coupling apparatus for contactless data transmission is attached to a tool 
holder. 
In FIGS. 1A and 1B, reference numeral 10 denotes a tool holder. A flange 
portion 14 is formed subsequent to a tapered shaft portion 12. Positioning 
grooves 14-1 and 14-2 are formed at two positions in the periphery of the 
flange portion 14. A magnetic induction coupling apparatus 16-1 is buried 
into a bottom portion of the positioning groove 14-1. 
As shown in FIG. 2A, the magnetic induction coupling apparatus 16-1 of the 
tool holder 10 has a structure such that two coil grooves 20-1 and 22-1 
are coaxially formed so as to open in the edge surface of a disc-shaped 
magnetic core 18-1 made of ferrite or the like, and induction coils 24-1 
and 26-1 are wound in 15 the coil grooves 20-1 and 22-1, respectively. 
FIG. 2B shows a plan view of the side of a magnetic pole surface of the 
magnetic induction coupling apparatus 16-1 in FIG. 2A. 
A magnetic induction coupling apparatus 16-2 of a reader/writer which is 
disposed in the outside is arranged so as to face the magnetic induction 
coupling apparatus 16-1 through a gap l. The magnetic induction coupling 
apparatus 16-2 of the reader/writer also has a structure such that 
induction coils 24-2 and 26-2 are wound in coil grooves 20-2 and 22-2 
formed in a magnetic core 18-2 in a manner similar to the coupling 
apparatus 16-1. 
However, the tool holder 10 with such a structure that the magnetic 
induction coupling apparatus 16-1 is buried in the bottom portion of the 
positioning groove 14-1 has the following problems. Namely, the magnetic 
core 16-1 and induction coils 24-1 and 26-1 cannot be made relatively 
large because of the dimensional limitation of the positioning groove of 
the tool holder 10, the electromagnetic inductive force attenuates in 
reverse proportion to almost the cube of a contactless transfer distance, 
and the like. From these reasons, the contactless transfer distance when a 
pair of magnetic induction coupling apparatuses 16-1 and 16-2 are disposed 
so as to face as shown in FIG. 2A is set to at most about 4 mm. 
On the other hand, for example, in the case of a BT 50 tool holder based on 
the MAS standard, depths of positioning grooves 14-1 and 14-2 in the tool 
holder 10 are set to 14.6 mm from the outer periphery of the flange 
portion 14. Therefore, even if the magnetic induction coupling apparatus 
16-2 of the reader/writer is disposed so as to face the magnetic induction 
coupling apparatus 16-1 of the holder 10 from the outside of the flange in 
the tool holder 10, data cannot be written into and read out of the memory 
module. 
In the conventional automatic tool changer, as shown in FIGS. 3 and 4, tool 
holders 10-1, 10-2, 10-3, . . . are enclosed in racks 36-1, 36-2, 36-3, . 
. . of the automatic tool changer by fitting each rotation preventing 
stopper 34 into each positioning groove 14-2, respectively. Therefore, the 
magnetic induction coupling apparatus 16-2 of a reader/writer 28 is 
attached to the magnetic induction coupling apparatus 16-1 of the tool 
holder 10-2 which has moved to a predetermined writing/reading position in 
a manner such that the coupling apparatus 16-2 can be freely lifted up and 
down by an air cylinder 30 which is controlled by an air valve 32. Given 
to this, the following processes are executed. 
(I) A desired tool holder, e.g., the tool holder 10-2 of FIGS. 3 and 4 is 
moved and stopped just under the air cylinder 30. 
(II) After confirming that the tool holder 10-2 has been stopped, the air 
valve 32 is turned on to lift down the air cylinder 30. 
(III) The magnetic induction coupling apparatus 16-2 is allowed to approach 
the magnetic induction coupling apparatus 16-1 of the tool holder 10-2 b 
the descent of the air cylinder 30. After confirming that both magnetic 
induction coupling apparatuses are located within a predetermined 
distance, data is written or read out. (IV) After completion of the data 
writing or reading operations, the air cylinder 30 is lifted up. After 
confirming the ascent of the air cylinder 30, the movement of the next 
tool holder is started. 
Further, to realize the operations in the above items (I) to (IV), an 
elevating mechanism having the air cylinder 30 and air valve 32 must be 
provided for the automatic tool changer. On the other hand, prior to 
writing or reading data, it is necessary to execute a preparing operation 
to position the magnetic induction coupling apparatuses, so that the 
processing time becomes long. Thus, there are problems such that the 
structure of the mechanism becomes complicated, the cost increases, and 
reliability is lacking as the magnetic induction coupling apparatus is 
frequently lifted up and down. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an automatic tool 
changer in which a magnetic induction coupling apparatus of a 
reader/writer can be disposed so as to face a magnetic induction coupling 
apparatus of a tool holder at an enough distance away from each other. 
Another object of the invention is to provide an automatic tool changer in 
which by merely arranging a magnetic induction coupling apparatus of a 
reader/writer from the outside of the outer periphery of a flange of a 
tool holder so as to face the tool holder, a power source can be supplied 
to a memory module of the tool holder and data can be written into or read 
out of the memory module. 
Still another object of the invention is to provide an automatic tool 
changer in which a magnetic member to transfer an induction field is 
arranged between a magnetic induction coupling apparatus of a tool holder 
and a magnetic induction coupling apparatus of a reader/writer. 
Still another object of the invention is to provide an automatic tool 
changer in which a magnetic member to transfer an induction field is 
arranged between two magnetic induction coupling apparatuses integrally 
with a stopper member of a rack. 
Namely, the invention relates to an automatic tool changer in which a tool 
holder is enclosed in a rack in a state in which a stopper member is 
fitted into a positioning groove formed in a flange portion of the tool 
holder. 
In the tool holder, the magnetic induction coupling apparatus is buried in 
the bottom portion of the positioning groove formed in the flange portion, 
and this tool holder has therein a memory into and from which data is 
written or read out by a contactless method by this magnetic induction 
coupling apparatus with the magnetic induction coupling apparatus of the 
reader/writer. 
The stopper member to stop the rotation of the tool holder enclosed in the 
rack has a multi-layer annular structure which is obtained by coaxially 
arranging a plurality of cylindrical or rod-shaped magnetic materials each 
having a circular, rectangular, or elliptic shape or the like in 
accordance with the core edge shape of the magnetic induction coupling 
apparatus. One end of the stopper member is arranged so as to face the 
magnetic induction coupling apparatus buried in the bottom portion of the 
positioning groove of the tool holder and the other end is arranged so as 
to face the magnetic induction coupling apparatus of an external 
apparatus. 
Therefore, the stopper member for stopping the rotation of the tool holder 
and for positioning this holder is interposed between the magnetic 
induction coupling apparatus of the tool holder and the magnetic induction 
coupling apparatus of the external reader/writer, thereby magnetically 
coupling them. 
Thus, by merely fixing the magnetic induction coupling apparatus on the 
reader/writer side to the outside of the outer periphery of the flange of 
the tool holder without elevating this coupling apparatus, the power 
supply and data writing and reading operations can be performed by a 
contactless method with the magnetic induction coupling apparatus of the 
holder positioning groove which is located at a distance. On the other 
hand, as no movable portion exists, the reliability is high and, further, 
data can be written or read out while moving the tool holder. Moreover, as 
it is sufficient that the stopper member is formed in a magnetic transfer 
shape adapted to the magnetic pole surface of the magnetic induction 
coupling apparatus, the cost can be reduced. 
The above and other objects, features, and advantages of the present 
invention will become more apparent from the following detailed 
description in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 5 is an explanatory diagram showing an embodiment of a stopper member 
for a tool holder in an automatic tool changer of the present invention. 
In FIG. 5, when considering the magnetic induction coupling apparatus with 
the structure shown in, e.g., FIG. 2A, a stopper member 38 has a 
multi-layer annular structure in which a pipe 40 made of ferrite having 
the same cross sectional shape as an outer peripheral core, a ferrite pipe 
42 having the same cross sectional shape as a intermediate core, and a 
ferrite cylinder 44 having the same cross sectional shape as the central 
core are respectively coaxially arranged. Nonmagnetic material layers 46 
and 48 each consisting of plastics or the like are filled in the spaces 
between the outer peripheral pipe 40 and the intermediate pipe 42 and 
between the intermediate pipe 42 and the central cylinder 44, 
respectively. Further, an attaching member 50 is integrally attached to 
the outer peripheral pipe 40 in order to fixedly attach the stopper member 
38 to a rack enclosing portion of the automatic tool changer. 
FIG. 6 is an exploded assembly diagram of the stopper member 38 shown in 
FIG. 5. The intermediate ferrite pipe 42 is inserted into the outer 
peripheral pipe 40 made of ferrite through the nonmagnetic material layer 
46 consisting of plastics or the like. The central ferrite cylinder 44 is 
inserted into the intermediate ferrite pipe 42 through the nonmagnetic 
material layer 48 consisting of plastics or the like. 
As shown in the exploded assembly diagram of FIG. 6, the stopper member 
shown in FIG. 5 may have a structure such that the ferrite pipes 40 and 
42, ferrite cylinder 44, and nonmagnetic material layers 46 and 48 
consisting of plastics or the like are individually molded and 
respectively coaxially assembled. Or, it is also possible to constitute in 
a manner such that the ferrite pipes 40 and 42 and cylinder 44 are 
coaxially arranged and thereafter, the nonmagnetic material layers 46 and 
48 are filled by performing the injection molding using plastics. 
FIG. 7 is a explanatory diagram showing an enclosing state of the tool 
holder to a rack of the automatic tool changer having the stopper member 
38 shown in FIGS. 5 and 6. 
In FIG. 7, a plurality of racks 36-1, 36-2, 36-3, . . . are enclosed in the 
tool holders 10-1, 10-2, 10-3, . . . , respectively. When looking at the 
rack 36-1 locating at the writing/reading position, the tool holder 10-2 
is formed with the positioning grooves 14-1 and 14-2 at two positions of 
the flange portion. As shown by a broken line, the magnetic induction 
coupling apparatus 16-1 is buried into the bottom portion of the 
positioning groove 14-1. 
The stopper member 38 shown in FIG. 5 is fixed to the lower portion of, 
e.g., the rack 36-2 by the attaching member 50 as illustrated in FIG. 8. 
The positioning groove 14-1 on the side in which the magnetic induction 
coupling apparatus 16-1 of the tool holder 10-2 is buried is fitted into 
the stopper member 38, thereby preventing the rotation of the tool holder 
10-2 in the state in which the tool holder was enclosed in the rack. 
Further, the magnetic induction coupling apparatus 16-2 of the 
reader/writer 28 is fixed to the position on the outside which faces the 
stopper member 38 fixed to each of the racks 36-1, 36-2, 36-3, . . . which 
are moved by a belt. Therefore, the magnetic induction coupling apparatus 
16-1 of the tool holder 10-2 is arranged so as to face the magnetic 
induction coupling apparatus 16-2 on the side of the reader/writer 28 
through the stopper member 38. The power supply and data writing/reading 
operations are executed to the memory module provided in the tool holder 
10-2 by way of the contactless magnetic induction coupling. 
The operation of the present invention will now be explained. 
FIG. 9 is an explanatory diagram showing enlargedly a state in which the 
magnetic induction coupling apparatuses 16-1 and 16-2 are disposed so as 
to face each other through the stopper member 38 as shown in FIGS. 7 and 
8. The magnetic induction coupling apparatus 16-1 is buried in the bottom 
portion of the positioning groove 14-1 of the tool holder 10. The coupling 
apparatus 16-1 is constituted in a manner such that two coil grooves 20-1 
and 22-1 are formed so as to open in one end of the disc-shaped magnetic 
core 18-1 and the induction coils 24-1 and 26-1 ar wound in the coil 
grooves 20-1 and 22-1. 
The magnetic induction coupling apparatus 16-2 on the reader/writer side is 
disposed in the outside of the outer periphery of the flange in which the 
positioning groove 14-1 is formed. A distance between the coupling 
apparatus 16-2 and the magnetic induction coupling apparatus 16-1 on the 
holder side is set to ten and a few millimeters or more. The stopper 
member 38 having the ferrite multi-layer annular structure shown in FIGS. 
5 and 6 is interposed between those coupling apparatuses 16-1 and 16-2. 
The magnetic induction coupling apparatus 16-2 on the reader/writer side 
has the same structure as that of the magnetic induction coupling 
apparatus 16-1 on the side of the tool holder 10. 
It is now assumed that current is flowed through the induction coils 24-2 
and 26-2 provided for the coupling apparatus 16-2 on the reader/writer 
side. First, as shown by broken lines, almost all of magnetic fluxes are 
generated from the inside induction coil 24-2 excluding partial leakage 
fluxes pass through the central ferrite cylinder 44 and intermediate 
ferrite pipe 42 and then pass through the magnetic core 18-1 of the 
opposite holder side, thereby enabling the induction coil 24-2 on the 
reader/writer side and the induction coil 24-1 on the holder side to be 
strongly magnetically coupled. 
This magnetic coupling is also similarly performed with respect to the 
induction coil 26-2 wound to the outside of the magnetic induction coil 
24-2. Namely, as shown by solid lines, almost all of the magnetic fluxes 
are generated by the induction coil 26-2 excluding partial leakage fluxes 
pass through the intermediate ferrite pipe 42 and outer peripheral ferrite 
pipe 40 and then pass through the magnetic core 18-1 of the magnetic 
induction coupling apparatus 16-1 on the opposite holder side, thereby 
enabling the induction coils 26-2 and 26-1 to be strongly magnetically 
coupled. 
The magnetic fluxes are attenuated only in the portions of a gap l.sub.1 on 
the holder side and a gap l.sub.2 on the reader/writer side. By limiting 
the sum (l.sub.1+l.sub.2) of these gap distances to a value of, e.g., 4 mm 
or less, data can be written or read out by a contactless coupling between 
the magnetic induction coupling apparatuses 16-1 and 16-2 through the 
stopper member 38. 
Further, as will be obvious from FIGS. 7 and 8, the stopper member 38 is 
attached to each of the racks 36-1, 36-2, 36-3, . . . of the automatic 
tool changer. When the automatic tool changer operates, the stopper member 
38 moves together with the tool holder. On the other hand, since the 
magnetic induction coupling apparatus 16-2 on the reader/writer side is 
fixed, when the stopper member 38 on the holder side has moved just over 
the fixed magnetic induction coupling apparatus 16-2 on the reader/writer 
side, it is sufficient to write or read data into or from the memory 
module on the holder side. The data writing/reading operations can be also 
performed after the movement of the tool holder was once stopped or during 
the movement of the tool holder. 
Since the foregoing embodiment has been described with respect to an 
example of the stopper member 38 for the magnetic induction coupling 
apparatuses 16-1 and 16-2 using the disc-shaped magnetic cores 18-1 and 
18-2, this example relates to an example in the case where the circular 
pipes of the shapes according to the magnetic pole surface shapes of the 
cores 18-1 and 18-2 are arranged so as to have a multi-layer annular 
structure. However, since the similar performance can be obtained even 
when the shapes of the magnetic cores 18-1 and 18-2 of the magnetic 
induction coupling apparatus are polygon such as a rectangle, an ellipse, 
or the like, the stopper member can be also formed in a polygonal shape 
such as a rectangle or the like, or an elliptical shape in accordance with 
the shapes of the cores. 
In the foregoing embodiment, ferrite has been used as a cylindrical or rod 
shaped magnetic material which forms the stopper member and plastics have 
been used as a nonmagnetic material to fill the space between the 
cylindrical magnetic materials. However, the invention is not limited to 
these materials. The stopper members can be also formed by use of a proper 
ferromagnetic material and a nonmagnetic material.