JP2017203789A - Explosion-proof type camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve impact resistance of a window part without limiting the window part to a small diameter, and without leading to reduction in image quality, and to improve explosion proofness of an explosion-proof type camera.SOLUTION: An explosion-proof type camera has a camera main body 10 housed in an explosion-proof housing 20 having a shooting window part 22a. An inner flange part 22b is formed that protrudes inward around the window part of the explosion-proof housing, and the window part is covered from an inner side with an elastic sheet 31. A window plate 32 is arranged in an inner side surface of the elastic sheet, and the elastic sheet and window plate have transmissivity of shooting light by the camera main body. The window plate is fixed to the explosion-proof housing in a state where a perimeter edge part of the elastic sheet is tightly held by the inner flange part and the window plate. The window plate is fixed to the explosion-proof housing due to adhesive 33, and the elastic sheet or the adhesive is applied that is low in Young's modulus.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an explosion-proof camera in which a camera body is housed in an explosion-proof housing having a shooting window.

When installing a surveillance camera in a place where explosive gas may exist, it is necessary to obtain an explosion-proof certification for the camera used.
In the explosion-proof certification to obtain the explosion-proof certification, if there is a window part in the equipment, there is a test (impact test) that drops a weight of 1 kg from the height of 40 cm to the window part. There is an example in which measures are taken to prevent damage by making it as thick as several tens of millimeters.
In another example, a metal grid is arranged in front of the window so that the weight does not hit the window plate.
In Patent Document 1, the window size is reduced so that the weight of the impact test does not hit the window plate.

JP 2015-23412 A

In an explosion-proof camera in which the camera body is housed in an explosion-proof housing with a shooting window, if a grating is provided in front of the window, there is a problem that the grating is reflected and the image quality deteriorates, and the image passes through the grating. There is a problem that flying objects collide with the window plate.
In addition, reducing the size of the window part restricts the selection of lenses that can be used. For example, a large-diameter lens cannot be used, and the problem that flying objects collide with the window plate cannot be eliminated.

  The present invention has been made in view of the above-described problems in the prior art, and in an explosion-proof camera in which a camera body is housed in an explosion-proof housing having a shooting window, the window is limited to a small aperture. It is another object of the present invention to improve the impact resistance of the window portion and improve the explosion-proof property without causing deterioration in image quality.

The invention according to claim 1 for solving the above-described problems is an explosion-proof camera in which a camera body is housed in an explosion-proof housing having a window for photographing.
An inner flange portion projecting inward is formed around the window portion of the explosion-proof housing,
The window is covered from the inside by an elastic sheet,
A window plate is disposed on the inner surface of the elastic sheet,
The elastic sheet and the window plate have transparency of photographing light from the camera body,
In the explosion-proof camera, the window plate is fixed to the explosion-proof housing in a state in which a peripheral edge portion of the elastic sheet is sandwiched between the inner flange portion and the window plate.

  The invention according to claim 2 is the explosion-proof according to claim 1, wherein the compressive strain in the thickness direction of the peripheral portion of the elastic sheet is housed in 1/5 to 0 and the window plate is fixed to the explosion-proof housing. Type camera.

  The invention according to claim 3 is the explosion-proof camera according to claim 1 or 2, wherein the elastic sheet has a Young's modulus of 10 [kPa] to 150 [MPa].

  The invention according to claim 4 is the explosion-proof camera according to any one of claims 1 to 3, wherein the window plate is fixed to the explosion-proof housing by an adhesive.

  The invention according to claim 5 is the explosion-proof camera according to claim 4, wherein the Young's modulus of the adhesive after curing is from 10 [MPa] to 500 [MPa].

  A sixth aspect of the present invention is the explosion-proof camera according to any one of the first to fifth aspects, wherein the aperture of the window portion exceeds 25 [mm].

  A seventh aspect of the present invention is the explosion-proof camera according to any one of the first to sixth aspects, wherein the outer surface of the elastic sheet is the outermost surface on the photographing optical path.

According to the present invention, the impact resistance of the window portion is improved by the elastic sheet against an explosion outside and inside the explosion-proof housing, and the explosion-proof property is achieved without restricting the window portion to a small diameter. Can be improved.
Since the elastic sheet and the window plate are transparent to photographing light from the camera body (infrared rays in the case of an infrared camera), the image quality is not deteriorated.

1 is an exploded perspective view of an explosion-proof camera according to an embodiment of the present invention. It is sectional drawing of the imaging | photography optical axis direction of the explosion-proof type camera which concerns on one Embodiment of this invention.

  An embodiment of the present invention will be described below with reference to the drawings. The following is one embodiment of the present invention and does not limit the present invention.

As shown in FIGS. 1 and 2, the explosion-proof camera of the present embodiment includes a camera body 10, a camera fixing base 11, an explosion-proof housing rear portion 21, an explosion-proof housing front portion 22, an elastic sheet 31, And a window plate 32.
The elastic sheet 31 and the window plate 32 are transmissive to transmit the photographing light (photosensitive area light) of the camera body 10. In particular, it is preferable to select one having good transparency for the photosensitive region. The camera body 10 is an infrared camera, and therefore, the elastic sheet 31 and the window plate 32 are excellent in transparency that transmits infrared rays.
The explosion-proof housing rear portion 21 and the explosion-proof housing front portion 22 constitute a cylindrical explosion-proof housing 20, which withstands external pressure and exhibits high explosion-proof properties. A shooting window 22 a is provided in the explosion-proof housing front portion 22. The explosion-proof housing front portion 22 is formed with an inner flange portion 22b protruding inward around the window portion 22a.
The explosion-proof housing rear portion 21 and the explosion-proof housing front portion 22 are also cylindrical bodies, and the threaded openings of each other are detachably screwed together to form an integral cylindrical body to form the explosion-proof housing 20.
An explosion-proof camera is configured by housing the camera body 10 in an explosion-proof housing 20 having such a photographing window 22a. The angle of view of the camera body 10 is disposed in the window portion 22a.
As shown in FIG. 2, the window portion 22 a is covered with an elastic sheet 31 from the inside. A window plate 32 is disposed on the inner surface of the elastic sheet 31. In this arrangement, the inner surface of the elastic sheet 31 is aligned with the outer surface of the window plate 32. The window portion 22a is a circular opening. The elastic sheet 31 and the window plate 32 are substantially circular with the same diameter that fits within the inner diameter of the front part 22 of the explosion-proof housing beyond the aperture of the window 22a, and are arranged with the edges thereof substantially coincided with each other. The outer surface of the window plate 32 is covered with an elastic sheet 31 within the aperture 22a. Further, the elastic sheet 31 and the window plate 32 are fixed to the explosion-proof case front portion 22 of the explosion-proof case 20 with the peripheral edge of the elastic sheet 31 sandwiched between the inner flange portion 22 b and the window plate 32. Yes. The window plate 32 is fixed to the explosion-proof housing front portion 22 with an adhesive 33, whereby the elastic sheet 31 is also fixed to the explosion-proof housing front portion 22 while being sandwiched between the inner flange portion 22b and the window plate 32. Has been. There is no problem even if the elastic sheet 31 is directly adhered to the front part 22 of the explosion-proof housing by attaching an adhesive to the peripheral edge of the elastic sheet 31.

The explosion-proof camera according to the present embodiment has a pressure-proof explosion-proof structure in which the camera body 10 is surrounded by an explosion-proof housing 20, and the dangerous gas outside the explosion-proof housing 20 is not ignited even if the camera body 10 generates a spark for some reason. To do.
The window plate 32 is fitted together with the elastic sheet 31 in the front part 22 of the explosion-proof case, and the outer surface side of the elastic sheet 31 is brought into contact with the inner flange part 22b of the front part 22 of the explosion-proof case. 33 is fixed.
The elastic sheet 31 may be fixed to the inner flange portion 22b with an adhesive tape.
When the window plate 32 and the elastic sheet 31 are pushed into the front part 22 of the explosion-proof housing, the elastic sheet 31 is compressed and deformed at the portion in contact with the inner flange part 22b, but the surface is distorted (becomes convex). It is necessary to suppress the deformation of the elastic sheet 31 so as not to affect the optical performance.
For this reason, it is preferable that the compression strain (shrinkage rate in the optical axis direction) of the elastic sheet 31 is reduced to 1/5 to 0 of the original sheet thickness when the window plate 32 and the explosion-proof housing front portion 22 are bonded. This compressive strain can be controlled by adjusting the pressing force for pressing the window plate 32 toward the inner flange portion 22b during bonding.
As another measure or a measure to be implemented together, the aperture of the window portion is a size exceeding 25 mm, more preferably 40 mm or more, the peripheral deformation portion of the elastic sheet 31 and the optical effective range in the center (of the camera body 10). The optical performance degradation due to the deformation of the elastic sheet 31 may be prevented by separating the distance from the (viewing angle arrangement range).

The window plate 32 is a window material such as germanium (Ge), silicon (Si), sapphire (Al2O3), calcium fluoride (CaF2), barium fluoride (BaF2), zinc selenide (ZnSe), zinc sulfide (ZnS). ), Chalcogenide glass, quartz (SiO2), magnesium fluoride (MgF2), lithium fluoride (LiF), and the like.
The elastic sheet 31 preferably has a Young's modulus in the range of 10 [kPa] to 150 [MPa] for impact relaxation.
As the elastic sheet 31, for example, there is a highly elastic sheet having translucency such as Dionon THV manufactured by 3M.
Adhesion of the window plate 32 needs to be elastic so as not to peel off when an impact is applied, and it is preferable to use an adhesive 33 having a Young's modulus after curing of 10 [MPa] to 500 [MPa]. . An example is ThreeBond's TB1539.
The camera body 10 is fixed to the camera fixing base 11 with screws, and the camera fixing base 11 is fixed to the explosion-proof housing rear portion 21 with screws 21b. The cable 10a of the camera body 10 is pulled out from the cable hole 21a in the rear part 21 of the explosion-proof housing. The cable 10a incorporates a power source and a signal line for the camera body 10, and extends to a control unit (not shown).

In the explosion-proof test, there is a test (impact test) in which a weight of 1 kg with a hemispherical hardened steel with a diameter of 25 mm is dropped vertically onto a window from a height of 40 cm. In the case of the explosion-proof camera according to the present embodiment, since the impact of the weight is mitigated by the elastic sheet 31, a normal window plate can be used without changing the material and thickness of the window plate 32 and increasing the strength.
Explosion-proof equipment requires that exterior parts must be able to withstand the pressure when an explosion occurs inside, and an explosion test is performed. In contrast, the internal pressure applied to the window plate 32 when an internal explosion occurs is advantageous because the elastic sheet 31 relaxes, and the elastic sheet 31 and the window plate 32 can be prevented from being damaged. At this time, since the elastic sheet 31 is pressed by the inner flange portion 22b, the internal pressure applied to the window plate 32 can be received by the elastic sheet 31, and the window is prevented from being broken due to the elastic sheet 31 and the window plate 32 being detached. it can.
As described above, the impact resistance of the window portion 22a is improved by the elastic sheet 31 against an explosion outside and inside the explosion-proof housing 20, and the window portion 22a is not limited to a small diameter. The explosion-proof property can be improved.
Therefore, it is preferable that the elastic sheet 31 has an outer surface that is the outermost surface on the photographing optical path as shown in FIG. If a component such as a lens is disposed outside the elastic sheet 31, it may be damaged and the explosion-proof property may be reduced. In addition, it is also possible to affix and carry out the protection sheet | seat for the purpose of adhesion prevention of a dirt, damage prevention, etc. on the outer surface of the elastic sheet 31 exposed in the window part 22a. This is to prevent the image quality from being deteriorated due to dirt or scratches.
As described above, an explosion-proof camera can be configured with no significant increase in cost and weight. In particular, explosion-proof devices tend to increase in weight because the thickness of the explosion-proof housing is increased to improve strength, and if the weight at the window portion can be reduced, it works effectively to reduce the total weight.

DESCRIPTION OF SYMBOLS 10 Camera main body 10a Cable 11 Camera fixing stand 20 Explosion-proof housing | casing 21 Explosion-proof housing rear part 21a Cable hole 21b Screw 22 Explosion-proof housing front part 22a Window part 22b Inner flange part 31 Elastic sheet 32 Window board 33 Adhesive

Claims (7)

In an explosion-proof camera that houses the camera body in an explosion-proof enclosure with a window for shooting,
An inner flange portion projecting inward is formed around the window portion of the explosion-proof housing,
The window is covered from the inside by an elastic sheet,
A window plate is disposed on the inner surface of the elastic sheet,
The elastic sheet and the window plate have transparency of photographing light from the camera body,
An explosion-proof camera in which the window plate is fixed to the explosion-proof housing in a state where a peripheral edge portion of the elastic sheet is sandwiched between the inner flange portion and the window plate. 2. The explosion-proof camera according to claim 1, wherein a compressive strain in a thickness direction of a peripheral portion of the elastic sheet is within a range of 1/5 to 0 and the window plate is fixed to the explosion-proof housing. The explosion-proof camera according to claim 1 or 2, wherein the elastic sheet has a Young's modulus of 10 [kPa] to 150 [MPa]. The explosion-proof camera according to any one of claims 1 to 3, wherein the window plate is fixed to the explosion-proof housing with an adhesive. The explosion-proof camera according to claim 4, wherein the Young's modulus of the adhesive after curing is 10 [MPa] to 500 [MPa]. The explosion-proof camera according to any one of claims 1 to 5, wherein a diameter of the window portion exceeds 25 [mm]. The explosion-proof camera according to any one of claims 1 to 6, wherein an outer surface of the elastic sheet is an outermost surface on a photographing optical path.

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