JPH04212229A - Photoelectric switch - Google Patents

Abstract

PURPOSE:To prevent dust from sticking to the front surfaces of projecting and receiving parts of light and reduce a cost of maintenance for cleaning by jetting air from air jetting holes provided near the projecting and receiving parts of light so as to form an air curtain in the front of the projecting and receiving parts of light. CONSTITUTION:Clean compressed air flowing in from an air inflow port 13 flows through an air circulation path 8 to jet from upper and lower air-jetting holes 12 to form an air curtain in front of a projecting glass and to collide with the glass near the center of the front of the glass 11 so as to flow outside. This air curtain flows off outward dust and such floating in the surrounding air so as to prevent them to stick on the glass 11. Accordingly, light from a light-projecting part 3 is projected through the glass 11 and the reflection light becomes incident on the light-receiving part 6 through the glass 11. Thereby, the projecting and receiving surfaces of a photoelectric switch are prevented from adhesion of dust so as to reduce a cost of maintenance for cleaning.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric switch that detects the presence or absence of an object to be detected based on the amount of light projected from a light projecting section or reflected and incident on a light receiving section.

0002

[Prior Art] If dust or opaque liquid adheres to the light-emitting and light-receiving surfaces of a photoelectric switch, the functionality of the photoelectric switch will deteriorate, and in some cases it may become unusable, so it is best not to use it in such environments. It is a principle. However, in recent years there has been no contact,
Due to its characteristics such as high accuracy and fast response, it is increasingly being used in manufacturing and inspection lines even in environments with a lot of dust. In particular, there are cases where the production line itself has no choice but to spray a translucent agent toward the light emitting and light receiving surfaces of the photoelectric switch. Under such adverse environment, conventionally,
The projection and reception surfaces were manually cleaned mechanically at predetermined intervals. Moreover, instead of the method of periodically cleaning, a method has also been adopted in which the amount of light received by the photoelectric switch is constantly monitored and an alarm is issued when the amount of light received drops below a predetermined value. Another method is to blow air from outside to prevent dust from adhering.

0003

SUMMARY OF THE INVENTION As described above, the method of mechanically cleaning the light emitting/receiving surfaces manually at predetermined intervals is troublesome to maintain and increases maintenance costs. Furthermore, even with methods that constantly monitor the amount of light received by a photoelectric switch and issue an alarm when the amount of light received drops below a predetermined value, the reality is that cleaning the projecting and receiving surfaces after an alarm is issued relies on humans. be. Furthermore, the method of blowing air from the outside to prevent the adhesion of dust and the like has the disadvantage that depending on the shape of the photoelectric switch, air vortices can be created and dust can be drawn in.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the conventional device and to provide a photoelectric switch in which dust does not adhere to the light emitting and light receiving surfaces.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a photoelectric switch including a light projecting section and a light receiving section that receives light projected from the light projecting section. The present invention is characterized in that an air ejection hole is provided in the vicinity of the light emitting part and the light receiving part for ejecting air to the front surface of the light projecting part and the light receiving part to form an air curtain.

[0006]

[Operation] Air is ejected from the air outlet provided near the light emitter and light receiver to form an air curtain in front of the light emitter and light receiver. This prevents dust from entering, and prevents dust from adhering to the front of the emitter/receiver section.

[0007]

[Example] Fig. 1 shows an example of a photoelectric switch according to the present invention.
and FIG. 2, FIG. 1 is a schematic configuration diagram of a photoelectric switch,
FIG. 2 is a perspective view thereof. As shown in FIG. 1, the photoelectric switch includes a light projecting section 3 consisting of a light projecting element 1, a light projecting lens 2,
A light receiving section 6 consisting of a light receiving element 4 and a light receiving lens 5 is mounted on a printed circuit board 10 and housed in a case 7. The case 7 is composed of an inner wall 7a and an outer wall 7b, and an air flow passage 8 is formed between the inner wall 7a and the outer wall 7b, and the opening of the case 7 is covered with a cover 9 on the upper surface via a packing (not shown). Further, the inner wall 7a and the outer wall 7b of the case 7 are provided with openings in front of the light projecting section 3 and the light receiving section 6, and the openings are blocked from the inside and outside of the case 7 and the air flow path 8 by a protective glass 11. A large number of air ejection holes 12 are provided horizontally above and below a protective glass 11 provided on an outer wall 7b of the case 7. The air ejection hole 12 is provided so that the opening thereof is inclined so that the air is ejected along the front surface of the protective glass 11 as much as possible. 13 is an air inlet, and 14 is an electrical signal cord connector.

With this configuration, clean compressed air that flows in from the air inlet 13 flows through the air flow path 8 and is ejected from the upper and lower air ejection holes 12, forming an air curtain in front of the protective glass 11. It collides near the center of the front surface of the protective glass 11 and flows outward. This air curtain blows away dust particles floating in the surrounding air and prevents them from adhering to the protective glass 11. Therefore, the light from the light projecting section 3 is always projected through the transparent protective glass 11, and the reflected light enters the light receiving section 6 through the transparent protective glass 11 and is received.

FIG. 3 is a perspective view of a photoelectric switch showing another embodiment of the present invention. In this embodiment, the air outlet hole 12
are the protective glass 11 of the emitter 3 and the protective glass 1 of the receiver 6.
A large number of them are arranged in a vertical direction on the outside of 1. In this way, the photoelectric switch can be housed in a case 7 having a bottomed inner wall 7c and an outer wall 7d, and the cover 9 can be provided only on the upper part, which is convenient for manufacturing.

FIGS. 4 and 5 are a front view and a plan view showing still another embodiment of the present invention. Figures 1 and 3
In the embodiment shown in Fig. 4, an air flow passage is provided inside the case housing the photoelectric switch.
As shown in FIG. 1, an air flow passage 8 made of a pipe is installed along the outer wall of a case 7 that houses the same photoelectric switch body as in the embodiments of FIGS. 1 and 3, and the terminal 8a of this air flow passage 8 is closed. A slit-shaped air ejection hole 12 as shown in FIG. 5 is provided in the side wall of the airflow passage 8 corresponding to the protective glass 11 on the front surface of the light projector 3 and the light receiver 6. As shown in FIG.

Clean compressed air flowing in from the air inlet 13 flows through the air flow passage 8 and is ejected from the slit-shaped air ejection hole 12 to the front surface of the protective glass 11 as shown by the arrow P, forming an air curtain. This prevents dust particles floating in the air from entering and adhering to the protective glass 11.

With the air flow passage 8 provided along the outer wall of the case 7 in this way, the air flow passage 8 and the air jet hole 12 can be made detachable, and can be attached to an already completed photoelectric switch at a later date. Is possible.

FIGS. 6 and 7 show yet another embodiment of the invention. In this embodiment, an air flow passage 8 constituted by a pipe is attached to the outer wall of the case 7 with a mounting bracket 15 in the same manner as shown in FIG. A hole 12 is attached to the front surface of the light projecting section 3 and the light receiving section 6 between the protective glasses 11-11. Therefore, the air jet holes 12 are provided on both the light projecting section 3 side and the light receiving section 6 side.

Clean air is blown out from this air blowing hole 12 in the direction of the arrow Q, forming an air curtain.

In the photoelectric switch shown in FIGS. 4 and 6, the air blowout hole 12 is formed in the shape of a slit, but instead of this slit 12, a large number of round holes are lined up like the ones shown in FIGS. 1 and 3. It may be provided.

FIG. 8 is a perspective view showing still another embodiment of the present invention. In this embodiment, an air flow path 8 consisting of a box with an air inlet 13 is attached to the outer wall, in this example, the side wall, of a case 7 that houses the same photoelectric switch body as in the embodiments shown in FIGS. 1 and 3. It is being An air blowing hole 12 is provided in the side wall of the airflow passage 8 to blow clean air in the direction of the arrow R toward the protective glass 11 on the front surface of the light projecting section 3 and the light receiving section 6. FIG. 9 is a perspective view including a partial cross section showing the detailed structure of this air flow passage 8.
A partition plate 16 separates the passage of air from 3 to the air blowout hole 12.
partition to ensure that air is blown out evenly from each part of the air outlet. Alternatively, the air ejection holes are partitioned with a partition plate 17 so that the opening areas are even, so that air is blown out more evenly. These form a more uniform air curtain.

In this case, these partition plates 16 and 17 may be provided inside the air flow path 8 made up of a box as shown in FIG. If a part of the side wall of the flow path 8 on the case side is opened, and the partition plates 16 and 17 are provided from this opening 19, manufacturing becomes easier. In this case, a packing 18 is provided around the opening 19 to prevent air leakage from the joint when the case 7 is joined to the side wall of the case 7. In addition, 20 in FIG. 8 is a movable shielding cover, which is used to shield the light projected from the light projecting section and stop the operation as a photoelectric switch, if necessary.

In this embodiment, only a reflective photoelectric switch in which a light emitting part and a light receiving part are integrated has been described, but even in a case where the light emitting part and light receiving part are separated, each one is provided with an air outlet hole and the light emitting part and the light receiving part are separated. An air curtain can be formed on the front surface of the light projecting part or the light receiving part, and air blowing holes can be provided all around the light projecting part and the light receiving part.

[0019]

According to the present invention, air is blown out in front of the light emitting part and the light receiving part of the photoelectric switch to form an air curtain, thereby preventing dust from forming in front of the light emitting part and the light receiving part. There is no possibility of dust adhering to the
There is no need to stop the photoelectric switch due to a reduction in the amount of light received, and therefore, there is an effect that the operating rate of the production line, etc. can be improved. Furthermore, the photoelectric switch with high precision and high speed response can be used not only in production lines but also in places where a lot of dust is generated, and the range of application of the photoelectric switch can be significantly expanded.

Further, in the second to seventh aspects of the present invention, in which the air flow passage is attached to the outer wall of the case, the air outlet hole can be attached to an already completed photoelectric switch.

[Brief explanation of the drawing]

FIG. 1 is a plan view with a cover removed showing a schematic configuration of a photoelectric switch showing an embodiment of the photoelectric switch of the present invention.

[Figure 2]
An assembled perspective view of the photoelectric switch of the present invention shown in FIG.

FIG. 3 is an assembled perspective view showing different embodiments of the photoelectric switch of the present invention.

FIG. 4 is a front view showing still another embodiment of the photoelectric switch of the present invention.

FIG. 5 is a plan view of the photoelectric switch of the present invention shown in FIG. 4.

FIG. 6 is a front view showing still another embodiment of the photoelectric switch of the present invention.

FIG. 7 is a plan view of the photoelectric switch of the present invention shown in FIG. 6.

FIG. 8 is an assembled perspective view showing still another embodiment of the photoelectric switch of the present invention.

FIG. 9 is a perspective view including a partial cross section showing an example of the detailed structure of the air flow passage in FIG. 8;

FIG. 10 is a perspective view showing a different example of the detailed structure of the airflow passage in FIG. 8;

[Explanation of symbols]

3. Light projecting section 6 Light receiving part 8 Air flow passage 12 Air blowout hole 16 Partition plate 17 Partition plate 18 Packing

Claims (7)

[Claims] Claims: 1. A photoelectric switch comprising a light projecting section and a light receiving section that receives light projected from the light projecting section, wherein air is blown out in front of the light projecting section and the light receiving section to create an air curtain. A photoelectric switch characterized in that an air ejection hole to be formed is provided adjacent to the light projecting section and the light receiving section. 2. A photoelectric switch comprising a light projecting section and a light receiving section that receives light projected from the light projecting section, wherein air is blown out in front of the light projecting section and the light receiving section to create an air curtain. 1. A photoelectric switch characterized in that an air flow passage having an air ejection hole is provided on an outer wall of a photoelectric switch case. 3. The photoelectric switch according to claim 2, wherein the air flow path is composed of a pipe with a closed end, and an air jet hole is formed in the side wall of the pipe. 4. The photoelectric switch according to claim 2, wherein the air flow path is comprised of a box having an air inlet, and an air outlet hole is formed in the side wall of the box. 5. The photoelectric switch according to claim 4, wherein a partition plate is provided inside the air flow path to equalize the flow of air. 6. The photoelectric switch according to claim 4, wherein the air ejection hole is provided with a partition plate that divides the air ejection hole into equal opening areas. 7. The photoelectric switch according to claim 5, wherein a packing is provided around the opening provided for manufacturing the partition plate.