Control signal transfer device for a position detecting sensor

A control signal transmitting device is used for a control device, such as a position detecting device. The transmitting device includes a position detecting sensor, and a receiving device situated near the position detecting sensor. The position detecting sensor includes a sensing device, a radio wave transmitting device electrically connected to the sensing device, and a device for directing the radio wave in one direction. The radio wave transmitting device emits radio wave in a direction opposite the sensing device upon receiving a signal from the sensing device. The receiving device includes a radio wave receiving device disposed to face the radio wave transmitting device for receiving the radio wave transmitted from the transmitting device, and a shielding device for covering the receiving device to receive the radio wave from one direction.

BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
The present invention relates to a control signal transfer device, which 
transfers electric ON/OFF information transmitted from a position 
detecting sensor to a receiving device through radio wave, to thereby 
control a position of a work or a machine. 
Conventionally, in order to transfer electric ON/OFF information, i.e. 
signal, transmitted from a position detecting sensor to a control or 
receiving device, an electric wire is installed between the position 
detecting sensor and the control device. However, the electric wire may 
possibly be cut. Especially, in case an attaching surface of the position 
detection sensor is irregular or in a turret form, the electric wire may 
be turned or tangled. Thus, a wireless device for transmitting a signal 
has been utilized. 
The first method in the wireless transmitting methods uses dielectric 
coupling. In this method, an induction coil, to which alternate current is 
supplied through the control device, is located adjacent to an induction 
coil provided in a position detecting sensor to form electromotive force. 
Inductance of the induction coil in the position detecting sensor is 
changed due to ON/OFF operation of a switch of the position detecting 
sensor, by which the alternate current is changed. The change of the 
alternate current is detected and amplified to thereby control the control 
device. 
As the second method in the wireless transmitting methods, an infrared 
irradiation device, such as LED, is formed in a main body of a position 
detecting sensor. An ON/OFF signal outputted from the position detecting 
sensor is changed to electric current, which is then supplied to the 
infrared irradiation device to output a light signal. The light signal is 
received by a light receiving device situated away from the position 
detecting sensor, and is changed again to electric signal, which is 
amplified to supply control current to the control device. 
As the third method in the wireless transmitting methods, an ON/OFF signal 
obtained from the position detecting sensor is changed to radio wave by, 
for example, FM modulation, which is outputted from a transmitting antenna 
installed on the position detecting sensor. The radio wave is received by 
a receiving antenna situated away from the position detecting sensor, and 
is detected and amplified to supply control current to the control device. 
One of the wireless device is disclosed in U.S. Pat. No. 4,339,714. 
In the first method, the distance between the induction coil of the 
position detecting sensor and the induction coil formed at the control 
device is very narrow, such as 1 mm. Thus, in case metal powder, such as 
iron powder, is filled or clogged in the gap between the two induction 
coils facing each other, induction rate changes to cause malfunction of 
the control operation. 
In the second method, cutting oil or powder may attach to the irradiation 
device and the light receiving device, or cross a light path. As a result, 
light transferred to the light receiving device is reduced or completely 
shut off, so that control may not be made completely. 
In the third method, there is no possibility of trouble by the cutting oil 
or cutting powder as in the first and second methods, but there is a time 
lag until starting the operation of an oscillation circuit for the radio 
wave and receiving, detecting and amplifying circuits. Thus, the problem 
lies in a time lag or rise time from the output of the ON/OFF signal to 
the operation of the control circuit. 
For example, in case a transmitting speed for a cutting blade, such as bit, 
is 100 mm/min., it is required that the rise time for obtaining an 
accuracy of 1 micrometer is less than 0.6 milli-second. 
Further, it is required to prevent malfunction of the control device in 
case there is a radio wave shielding material in a middle of the 
transmitting antenna and the receiving antenna. For this purpose, the 
output of the radio wave must be increased, and the receiving sensitivity 
must be raised. As a result, in case the same kind of devices are 
installed parallel to each other, the radio waves are interfered or mixed 
to cause error operation. 
Therefore, it is required to solve the problems by, such as changing 
frequencies in each model, to thereby increase cost of the devices. 
Further, in case sensitivity for receiving the radio wave is raised, other 
radio waves may be caught by the receiving antenna, which may cause error 
operation. 
It is therefore an object of the invention to provide a control signal 
transfer device for a position detecting sensor, which can prevent radio 
interference among the same devices as well as other radio waves by using 
very weak radio wave for a short distance as a transmission medium. 
Another object of the invention is to provide a control signal transfer 
device as stated above, wherein rise time of the circuits is shortened by 
simplifying the circuits. 
A further objects of the invention is to provide a control signal transfer 
device as stated above, wherein the device is economical and easy to use, 
and is not affected by cutting oil and cutting powders. 
Further objects and advantages of the invention will be apparent from the 
following description of the invention. 
SUMMARY OF THE INVENTION 
In the present invention, a control signal transfer device for a position 
detecting sensor includes means for emitting radio waves from an end 
portion of a housing, which is formed in the housing of the position 
detecting sensor, and means for receiving the radio waves formed at a 
position opposite the end portion of the housing and at a predetermined 
distance away from the end portion. The electric ON/OFF information signal 
outputted from the position detecting sensor is transferred to a control 
circuit formed outside the housing through radio waves between the 
emitting means and the receiving means. The end portion of the housing is 
protected by a cover made of a material for permitting the radio waves to 
pass therethrough. 
The housing of the position detecting device is installed on an attaching 
surface of a machine, such as cutting machine. When the machine is used 
and moved, a measuring arm of the position detecting sensor touches a work 
or table to change the position of the arm. As a result, a switching 
mechanism operates to output an ON/OFF signal, so that an oscillation 
circuit operates, and radio wave is emitted from a transmitting antenna 
installed in the housing. 
The emitted radio wave is received by a receiving antenna provided at the 
opposite side of the transmitting antenna, and is detected and amplified 
to control a control circuit for the work or table.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
FIGS. 1(a), 1(b), 2(a) and 2(b) show a first embodiment of the invention. 
FIG. 1(a) is a front section view of a position detecting sensor. 
A housing 1 is made of a material, such as metal, for shielding radio wave, 
and a measuring arm 2 having a contact 3 at a front end thereof is formed 
to project from the housing 1. The measuring arm 2 is held by a bearing 
portion 4 formed in the housing 1. 
A switch body 5 is situated in the housing 1, and includes a lid 6 having a 
fixed contact point 7. The center of the lid 6 forms a bearing portion for 
an actuator 9 in a T shape in a cross section. The actuator 9 includes a 
movable contact point 8 facing the fixed contact point 7. 
An operation plate 10 is fixed at a right end of the measuring arm 2 (FIG. 
1(a)), and is urged by a strong spring 11 so that the arm 2 is always 
urged in the left direction. The actuator 9 is also urged by the operation 
plate 10 in the left direction opposite the force of a weak spring 12, so 
that the movable contact point 8 is separated from the fixed contact point 
7. The operation plate 10 is fixed to the housing 1 by a pin 13 to prevent 
rotation thereof. 
A printed board 15 for retaining thereon electric circuits at the side of 
the position detecting sensor, which are shown in FIG. 2(a), is fixed to 
the housing 1 by screws (not shown). Lead wires 14 extending to the 
contact points 7, 8 are fixed to the board 15. The board 15 is provided 
with the electric circuits and a transmitting antenna 16, which is formed 
by winding coils over ferrite in the form of a rod. 
Batteries 17 are disposed in the housing 1, and a cover 18 covers the 
batteries 17. 
The housing 1 includes threads 19 on the right side, so that the housing 1 
is attached to an attaching portion 21 of a machine, such as a cutting 
machine, by means of a nut 20. A cover 22 made of a material for allowing 
radio waves to pass therethrough, such as plastic, is attached to the 
housing 1 to seal the housing. 
FIG. 1(b) shows a section view of the control device including a radio wave 
receiving device. The control device includes a main body 31 formed of a 
material to shield radio waves, such as metal, and a printed board 32 
fixed to the main body 31. The printed board 32 is provided with circuit 
members 33, and a receiving antenna 34 formed by winding coils over 
ferrite in the form of a rod. A cover 35 made of a material for allowing 
radio waves to pass therethrough, such as plastic, is attached to the main 
body 31 to seal the same. 
Further, the main body 31 includes a rear lid 36, and an attaching plate 
37. A lead wire 38 connects the printed board 32 to a control section and 
an electric source. 
When the sensor and the control device are installed, the transmitting 
antenna 16 and the receiving antenna 34 are spaced apart from each other 
at several tens millimeters. Since the housing 1 and the main body 31 are 
made of materials for shielding radio waves, such as metal, the radio wave 
emitted from the transmitting antenna 16 does not spread widely and is 
received by the receiving antenna 34. 
FIG. 2(a) shows a circuit for the position detecting sensor. A switch 40 is 
formed of the fixed contact point 7, the movable contact point 8, and the 
actuator 9. The transmitting antenna 16 is an oscillating coil formed by 
winding the coils over the rod shape ferrite. The oscillating coil 
operates as the antenna 16. The circuit includes a trimmer capacitor 41, 
an oscillation transistor 42 and quartz oscillator 43. For example, 40 MHz 
is used as an oscillating cycle. 
FIG. 2(b) shows a circuit diagram for the control device. The circuit 
includes the receiving antenna formed by winding the coils over the rod 
shape ferrite, a capacitor 51 and a trimmer capacitor 52. The circuit 
further includes a super-regeneration detection circuit 53, a 
low-frequency amplifier 54, a rectifier circuit 55, a direct current 
amplifier 56, a switching circuit 57, a control circuit 58, e motor 59 and 
a commercial electric source 60. 
Next, an operation of the present invention is explained. When a work or 
table (not shown) moves and touches the contact 3, the measuring arm 2 and 
the operation plate 10 move from the position as shown in FIG. 1(a) to the 
right direction, so that the actuator 9 is moved in the right direction by 
the spring 12. As a result, the movable contact point 8 contacts the fixed 
contact point 7, whereby the oscillation circuit as shown in FIG. 2(a) 
operates to emit radio wave from the transmitting antenna 16. 
The radio wave transmitted from the antenna 16 is received by the receiving 
antenna 34. As shown in FIG. 2(b), the signal from the antenna 34 is 
detected by the super-regeneration detection circuit 53, and after 
low-frequency of the signal is amplified by the low-frequency amplifier 
54, it is rectified by the rectifier circuit 55. Then, the signal is 
amplified by the direct current amplifier 56, and is outputted to the 
control circuit 58 through the switching circuit 57. In the control 
circuit, electricity for operating the work or table, i.e. motor 59, is 
shut off, and if required, a brake is applied to the motor 59, to thereby 
stop the motor 59. As a result, the position of the work or table can be 
set properly. 
Experiments is made in the condition that 32 MHz of the quartz oscillator 
43 is used, the distance between the transmitting antenna 16 and the 
receiving antenna 34 is between 50 and 100 mm, and the moving speed for 
the work or table is 100 mm/min. As a result, it is possible to stop the 
work or table at the accuracy of 1 micrometer in average. 
In the above embodiment, the measuring arm 2 of the position detecting 
sensor is formed to move in one, i.e. right direction in FIG. 1(a). 
However, it is possible to move the measuring arm 2 by combining two or 
three forces in different directions. 
FIG. 3 shows a second embodiment of the invention. In the first embodiment 
as shown in FIG. 1(a), a sensing section including the components from the 
measuring arm 2 to the lead wires 14, and a transmitting section including 
the components from the printed board 15 to the batteries 17 are all 
retained in the housing 1. In the second embodiment, however, a housing 
for the sensing section and a case for the transmitting section are formed 
separately. 
In particular, the sensing section includes a housing 101, in which a 
measuring arm 102 having a contact 103 is supported by a supporting shaft 
104 penetrating through an inner wall of the housing 101. A first location 
detecting section 105 is formed inside the housing 101, and includes a 
first fixed contact point 106 and a first movable contact point 107, which 
are separated by a spring (not shown) in a normal condition. 
Also, a second location detecting section 108 is formed inside the housing 
101 opposite the first location detecting section 105. The second location 
detecting section 108 includes a second fixed contact point 109 and a 
second movable contact point 110, which are separated by a spring (not 
shown) in a normal condition. 
Center positioning devices 111, 112 are formed in the housing 101 
symmetrically relative to the central plane of the housing 101 for 
returning or positioning the measuring arm 102 in the center position. The 
center positioning devices 111, 112 are formed of pushers 113, 114 and 
springs 115, 116. The central line passing through the first and second 
location detecting sections 105, 108 is parallel to the center line 
passing through the center positioning devices 111, 112, and is arranged 
normal to the supporting shaft 104. 
The housing 101 also includes a shank 117 having a tapered portion 118, 
which can be fixed to a tapered hole formed in a machine when installed in 
the machine. 
A connecting portion 119 is attached at one end to the housing 101 and at 
the other end to a case 120 of the transmitting section. The case 120 
includes therein circuit boards 121, to which circuit elements 122 and a 
transmitting antenna 123 are fixed, and a battery 124. 
In FIG. 3, lead wires 125, 126 are attached to the housing 101 and the case 
120, respectively, and are connected together by a connector 127. A side 
wall of the case 120 is made of a material for preventing radio wave from 
passing therethrough, and a front end of the case 120 is made of a 
material for allowing radio wave to pass therethrough, such as plastic. 
A control device 128 is the same as in the control device shown in FIG. 
1(b), including a receiving antenna 129. A side wall of the case of the 
control device 128 is made of a material for preventing radio wave from 
passing therethrough, and a front end of the case is made of a material 
for allowing radio wave to pass. 
The circuits of the position detecting sensor and the control device of the 
second embodiment are the same as in the first embodiment. Thus, the 
explanation thereof is omitted. 
In the second embodiment, for example, when the contact 103 touches a work 
or table to move in the downward direction in FIG. 3, the measuring arm 
102 rotates in a counterclockwise direction as the center of the support 
shaft 104, so that the movable contact point 107 contacts the fixed 
contact point 106. Consequently, an ON signal is transmitted to the 
transmitting circuit elements 122, and radio wave is emitted from the 
transmitting antenna 123 through the circuits as explained in FIG. 2(a). 
The emitted radio wave is received by the receiving antenna 129 of the 
control device 128, and is processed as explained in FIG. 2(b) to control 
the work or table. 
In the second embodiment, the control device 128 can be installed freely 
when comparing the first embodiment. Also, in the second embodiment, the 
work or table can be maintained within a specific range because of the two 
switches. 
As explained above, the switches, i.e. fixed contact point 7 and movable 
contact point of FIG. 1 and fixed contact points 106, 109 and movable 
contact points 107, 110 of FIG. 3, are explained as normal-open switches, 
but these switches may be normally closed and output OFF signals. In this 
case, the control device may receive radio wave all the time, and when 
stop of the radio wave is detected, the control mechanism may be operated. 
In order to prevent loss of battery life, as soon as an OFF signal is 
detected, the switching circuit may be operated to emit radio wave. 
Further, in case radio wave is emitted all the time, and the radio wave is 
shut off when receiving an ON or OFF signal, it is possible to shorten 
rise time for the circuits to thereby increase the accuracy. In this case, 
in experiments, the rise time of 5 micro second was obtained. In case a 
transmitting speed of a work or table is 100 mm/min., theoretically, it is 
possible to obtain the accuracy of 0.8 micro meter. In this case, since a 
life of the battery is shortened, a large capacity of a battery may be 
formed in the housing of the sensor as indicated in numeral 130 in FIG. 3. 
In the present invention, the transmitting antenna and the receiving 
antenna are formed closely to face each other, and transmission and 
reception of the radio waves except for the direction of the facing 
antennas are shielded. Thus, even if the same devices are installed close 
to each other, interference or mixing of the radio waves is prevented. It 
is unnecessary to change the models of the devices when installing close 
to each other. Also, the possibility of interference by other radio wave 
is very low, so that the machine can be controlled reliably. 
Also, the oscillation circuit which delays the rise time of the circuit is 
simplified, so that the rise time of the circuit is made quickly. Accuracy 
of 1 micrometer may be controlled. Further, since the oscillation circuit 
which requires electricity is simplified as stated above, battery 
consumption is low. Thus, maintenance of the device is easy. Moreover, 
since the position detecting sensor and the antenna of the receiving 
section are sealed, it is not affected by cutting oil and cutting powder. 
Thus, the invention is especially useful for a control signal transfer 
device for a metal processing machine, such as cutting machine. 
While the invention has been explained with reference to the specific 
embodiments of the invention, the explanation is illustrative, and the 
invention is limited only by the appended claims.