JPS5818828A - Photoelectric switch - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photoelectric switch, and particularly to a photoelectric switch having a dustproof function.

Since photoelectric switches use light, there is a problem in that detection performance deteriorates if dust adheres to or accumulates on the lens or protective glass of the detection surface. The smaller the diameter of the light beam, such as a photoelectric switch using an optical fiber, is more susceptible to this performance deterioration.

Conventionally, there has been a method to prevent the adhesion and accumulation of dust by creating a well-known air curtain, but this method increases the size of the entire device.

Maintenance is also difficult. As an alternative method, a detection head may be mounted on an ultrasonic transducer table and vibrated. However, this method cannot be said to be a preferable method because it may cause fatigue of the detection head due to vibration, change in detection characteristics due to vibration of the optical axis, and breakage of wiring, fibers, etc.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned conventional drawbacks and to provide an optical 'lE switch that does not attract or accumulate dust on the detection head or the like.

In order to achieve the above objectives, the photoelectric switch of this invention has a transparent film placed on the front surface of the detection head of the photoelectric switch, a case body and the transparent film form a sealed structure, and a vibrator is provided within this sealed structure. The vibration of the vibrator vibrates the transparent film to sift out dust.

The present invention will be described in detail below with reference to embodiments shown in the drawings.

FIG. 1 is a longitudinal sectional view of a photoelectric switch using an optical fiber, which is a detailed embodiment of the present invention.

The detection head 2 at the tip of the optical fiber 1 is fixed to the case body 6, and a transparent film 5 is attached to the front of the detection head 2.
are arranged. Transparent film 5 and case body 6. The covers 7m and 7b form a sealed structure. The vibrator 5 is fixed to the base 9 with silicone rubber 4, for example. The fixed point is set approximately at the vibration +3 node, and the base body 9 is integrally constructed with the main body case 6. The vibrator 6 is driven by an oscillation circuit on the printed circuit board 8 to vibrate.

As the vibrator 6, for example, a piezoelectric vibrator is used.

As shown in FIG. 3(b), the piezoelectric vibrator is constructed by bonding a piezoelectric ceramic plate 3b onto a metal plate 3a. When a voltage is applied to each lead wire 3c, the piezoelectric ceramic plate 3b Since distortion occurs due to the piezoelectric effect, it vibrates and generates sound waves as shown in FIG. This sound wave reaches its maximum when the signal frequency of the applied oscillation circuit is the resonant frequency of the piezoelectric vibrator. Note that the vibration +3 is provided with a small hole 3d through which the detection head 2 or the detection light beam passes.

In the photoelectric switch shown in Figure 1, when a signal voltage is sent to vibration +3 from the oscillation circuit of the printed circuit board 8, vibration starts and a sound wave is generated, and this sound wave is transmitted to the transparent film 5 and causes it to vibrate, so that it adheres to the transparent film 5. To prevent dust from adhering or accumulating. Note that since the vibration is caused by sound waves in the air, the large mass of the case body 6, base 9, etc. does not vibrate, so the optical fiber and the detection head do not vibrate, so that no optical axis deflection or fatigue of the optical fiber occurs. Furthermore, since the vibrating surface of the vibrator is arranged parallel to the transparent film, sound waves can be transmitted efficiently.

FIG. 3 is a longitudinal sectional view of a photoelectric switch showing another embodiment of the present invention. A vibrator 3 is fixed to the main body case B via silicone rubber 4. This is different from the one shown in FIG. 1 in that the +3 vibration plane is perpendicular to the transparent film 5 and parallel to the optical axis.

Since the vibration surface is perpendicular to the transparent film 5, the transmitted vibration energy is small, but there is an advantage that the case can be made smaller.

In the above embodiment, for convenience of assembly, the case body, the case cover, and the transparent film form a sealed structure, but the case body and the case cover may have an integral case structure.

According to the photoelectric switch of the present invention as described above.

Since the detection head is installed in a sealed structure formed by a case and a transparent film, there is no dust attached to the detection head itself, and the transparent film is vibrated with a vibrator to sift out dust. Because of this, it is possible to use a small amount of power (several tens to
100ruW)? 'It can efficiently prevent dust from adhering to and accumulating on the detection surface.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of a photoelectric switch showing an embodiment of the present invention, Fig. 2 is a diagram showing a specific example of a vibrator used in carrying out the invention, and Fig. The diagram showing the vibration state, FIG. 2 (1)) is a plan view thereof. FIG. 3 is a longitudinal sectional view of a photoelectric switch showing another embodiment of the present invention. 1; Optical fiber; 2; Detection head. 5; Vibrator; 4; Silicone rubber. 5; Transparent film, 6; Main body case. 7a, 7b; cover; 7; printed circuit board. 9; Substrate. Patent applicant Tateishi Electric Co., Ltd. Agent Patent attorney Shigeru Nakamura

Claims (4)

[Claims] (1) A transparent film is placed on the front surface of the photoelectric 71-inch detection head that is installed inside the case, and the case body and the transparent film form a sealed structure.A vibrator is provided within this sealed structure, and the vibration of the vibrator is A photoelectric switch characterized in that the transparent film is vibrated. (2) The Ω photoelectric switch according to claim 1, wherein the vibrator is a piezoelectric vibrator in which a piezoelectric magnetic plate is bonded to a metal plate. (3) The photoelectric switch according to claim 1 or 2', wherein the vibrator is arranged so that its vibrating surface is parallel to the surface of the transparent film plate. (4) The photoelectric switch according to claim 3, wherein the vibrator is provided with a small hole through which the detection head or detection light beam passes.