GB2531022A

GB2531022A - A sealed housing for a camera

Info

Publication number: GB2531022A
Application number: GB1417727.3A
Authority: GB
Inventors: Barton Neil
Original assignee: Oxalis Group Ltd
Current assignee: Oxalis Group Ltd
Priority date: 2014-10-07
Filing date: 2014-10-07
Publication date: 2016-04-13
Also published as: GB201417727D0

Abstract

A sealed housing (10) for housing a camera (100) is configured to exclude the atmosphere external to the sealed housing away from the camera. The sealed housing has a viewing portion through which light can pass to reach the camera inside the sealed housing, and the viewing portion comprises a viewing window (50) and a protective window (40). The protective window forms an outside surface of the sealed housing, and the viewing window is spaced apart from the protective window and forms an internal surface of the sealed housing. Preferably the windows are made of germanium.

Description

A SEALED HOUSING FOR A CAMERA

DESCRIPTION

The present invention relates to a sealed housing for a camera.

The use of cameras in some environments can present a risk of explosion, for example if electrical activity within the camera causes ignition of explosive gases within the environment.

Such environmental conditions may for example occur on oil rigs, and cameras may be required to be housed in housings that keep them isolated from the environment, even if struck by a specified impact force. For example, the BS EN 60079 specification relating to explosive atmospheres requires that electrical equipment shall be submitted to the effect of a 1kg test mass falling vertically from a height, and that the test should not produce damage invalidating the type of protection of the electrical equipment. The 1kg test mass has a 25mm diameter hemispheric impact head made of hardened steel.

Protection against this type of impact may be difficult to achieve, particularly if the impact occurs on a part of the housing that is designed to transmit electromagnetic radiation to the camera. A known housing for an infra-red camera uses a Germanium viewing window to enable effective transmission of infra-red light through the housing to the camera. However, Germanium is a delicate material, and so the viewing window is typically covered over by a metal grill to help protect it from impacts. Other types of viewing window materials may also require covering by a grill in order to protect the viewing window from impacts.

One of the problems of covering the protective window with a grill is that the grill may interfere with the electromagnetic radiation received by the camera, and obscure parts of the environment from the camera. This is particularly true for cameras with wide viewing angles, where the pitch of the grill cannot be made large enough for the grill to avoid obscuring at least part of the environment.

The grill may result in reduced image quality from the camera, since parts of the imagery provided by the camera may only show the grill, rather than the environment outside the housing.

It is therefore an object of the invention to improve upon the known art.

According to an embodiment of the invention, there is provided a sealed housing for housing a camera inside the sealed housing. The sealed housing is configured to exclude the atmosphere external to the sealed housing away from the camera. The sealed housing has a viewing portion through which electromagnetic radiation can pass to reach the camera inside the sealed housing, and the viewing portion comprises a viewing window and a protective window. The protective window forms an outside surface of the sealed housing, and the viewing window is spaced apart from the protective window and forms an internal surface of the sealed housing.

Therefore, the viewing window of the sealed housing is protected by a separate protective window, the protective window serving to protect the viewing window from damage from any impacts against the sealed housing. Since the protective window is formed of a material that allows electromagnetic radiation to pass through the protective window towards the camera, the view of the environment seen by the camera will not be obscured by the protective window.

The protective window may act as a sacrificial window, which breaks upon a sufficiently large impact against it, to help absorb the energy of the impact and prevent any damage occurring to the underlying viewing window.

Since the protective window is spaced apart from the viewing window, the shock from the impact is not directly transmitted by the protective window to the viewing window, helping to prevent damage to the viewing window. The viewing window may for example be substantially parallel to the protective window.

Accordingly, the viewing window may remain intact and continue to maintain the seal between the camera and the external environment, so that any explosive gases within the environment do not reach the camera inside of the housing.

The protective window and the viewing window may be in the form of plates which form respective internal and external surfaces of the sealed housing. Then, the light may pass through the material of the plates in order to reach the camera inside of the housing.

The protective window and the viewing window may be formed from the same material as one another. In the case of an infra-red camera, the material may be Germanium, although other types of materials such as, but not limited to, Calcium Fluoride (CaF2), Zinc Sulphide (ZnS), Zinc Selenide (ZnSe), Aluminium (Al) are also contemplated.

The viewing portion may be held by a viewing surround of the sealed housing, and the viewing surround may hold the viewing window and the protective window spaced apart from one another. Advantageously] the viewing surround may comprise an outside mount to which the protective window is mounted, and an inside mount to which the viewing window is mounted. For example, the viewing surround may comprise a hole, and the protective window and the viewing window may each span across the hole to seal the inside of the sealed housing away from the outside environment.

The inside mount may comprise a retaining clip for clipping into the hole and retaining the viewing window between the retaining clip and the inside mounting surface. The outside mount may comprise a shock absorbing material around the hole, the protective window being mounted to the shock absorbing material. Then, the shock absorbing material helps to absorb any impacts against the protective window, reducing the chances of the protective window breaking, and reducing transmission of shock from the protective window to the remainder of the sealed housing. The shock absorbing material may for example be plastically deformable foam.

Embodiments of the invention will now be described by way of non-limiting example only and with reference to the accompanying drawings, in which: Fig. 1 shows a schematic front view of a sealed housing according to an embodiment of the invention; and Fig. 2 shows a cross-sectional diagram of the sealed housing of Fig. 1, and shows an infra-red camera which has been fixed inside of the sealed housing.

The figures are not to scale, and same or similar reference signs denote same or similar figures.

An embodiment of the invention will now be described with reference to Figures 1 and 2. Figure 1 shows a front view of a sealed housing 10, and Figure 2 shows a cross-section of the sealed housing 10 taken along line AA marked on Figure 1. The front of the sealed housing 10 comprises a disk shaped plug 20, and the disk shaped plug 20 is plugged into an end of a cylinder 25 containing an infra-red camera 100 (refer to Figure 2). The disk shaped plug 20 and cylinder 25 are formed of steel in this embodiment, although other types of materials could alternatively be used. The disk shaped plug 20 provides a front wall of the sealed housing 10.

The disk shaped plug 20 has a hole formed through it, generally designated by arrow 21. The hole 21 extends from an outside to an inside 60 of the sealed housing, and is blocked firstly by a protective window 40 towards the outside of the sealed housing, and secondly by a viewing window 50 towards the inside 60 of the sealed housing. The protective window 40 and the viewing window 50 are spaced apart from one another by a distance DS along the length of the hole 21.

The protective window 40 is a circular plate of Germanium that is 5mm thick, and the viewing window 50 is a circular plate of Germanium that is 10mm thick. Although, the thicknesses may vary according to the intended application and the impact force against which the protective window 40 is to protect. Clearly, the thicker the protective window and the viewing window, the lower the light transmission to the camera, but the higher the impact protection.

The hole 21 comprises an outside mounting surface 22, which is defined by a shoulder reducing the width of the hole 21 in a direction from the outside towards the inside of the sealed housing. The outside mounting surface 22 is ring-shaped, and has a ring of plastically deformable foam 45 mounted upon it. The protective window 40 is inserted into the hole 21 until it abuts the plastically deformable foam 45, and then a steel retaining plate 30 is affixed to the front of the disk shaped plug using five bolts 32, to hold the protective window 40 in place within the hole 21.

The retaining plate 30 has a viewing hole 35 that is co-axial with the hole 21, and the viewing hole 35 exposes the protective window 40 to the external environment.

In the event that the protective window 40 becomes broken, it can easily be replaced by undoing the bolts 32 and removing the retaining plate 30.

The hole 21 also comprises an inside mounting surface 23, which is defined by a shoulder reducing the width of the hole 21 in a direction from the inside 60 towards the outside of the sealed housing. The inside mounting surface 23 is ring-shaped, and the viewing window 50 is inserted into the hole 21 until is abuts the inside mounting surface 23. Then, a ring-shaped retaining clip 55 is inserted into the hole to hold the viewing window in place within the hole 21. The ring-shaped retaining clip 55 comprises a rubber C-ring 57 that presses against the viewing window 50 and helps damp down any shock or vibrations that are transmitted to the viewing window 50.

The camera 100, which does not form part of the sealed housing, is fixed within the sealed housing 10 for receiving infra-red light IR via the protective window 40 and viewing window 50. In this embodiment, the infra-red camera is for taking tomography (temperature) measurements, although other types of camera could alternatively be fixed inside the sealed case.

Further embodiments falling within the scope of the appended claims will also be apparent to the skilled person. For example, the sealed housing may be other shapes, such as rectangular, instead of cylindrical. Furthermore, alternate means may be used to connect the protective window and the viewing window to the disk shaped plug 20. For example, the protective window may be mounted directly on the outside of the disk shaped plug 20 around the hole 21, and the viewing window may be mounted directly on the inside of the disk shaped plug 20 around the hole 21.

Claims

CLAIMS1. A sealed housing for housing a camera inside the sealed housing, the sealed housing configured to exclude the atmosphere external to the sealed housing away from the camera, the sealed housing having a viewing portion through which light can pass to reach the camera inside the sealed housing, and wherein the viewing portion comprises a viewing window and a protective window, wherein the protective window forms an outside surface of the sealed housing, and wherein the viewing window is spaced apart from the protective window and forms an internal surface of the sealed housing.
2. The sealed housing of claim 1, wherein the viewing window and the protective window are in the form of plates which form respective internal and external surfaces of the sealed housing.
3. The sealed housing of claim 1 or 2, wherein the viewing portion is held by a viewing surround of the sealed housing, and wherein the viewing surround holds the viewing window and the protective window spaced apart from one another.
4. The sealed housing of claim 3, wherein the viewing surround comprises an outside mount to which the protective window is mounted, and an inside mount to which the viewing window is mounted.
5. The sealed housing of claim 3 or 4, wherein the viewing surround comprises a hole, and wherein the protective window and the viewing window each span across the hole.
6. The sealed housing of claim 5, wherein the hole has a length extending between the inside and the outside of the sealed housing, and a width that varies along the length of the hole, and wherein the width of the hole is greater at opposing ends of the hole than between where the protective window and the viewing window span across the hole.S
7. The sealed housing of claim 6, wherein a reduction in the width of the hole from the outside of the housing towards the inside of the housing provides an outside mounting surface for the protective window, and wherein a reduction in the width of the hole when moving from the inside of the housing towards the outside of the housing provides an inside mounting surface for the viewing window.
8. The sealed housing of any one of claims 5 to 7 when appended to at least claim 4, wherein the inside mount comprises a retaining clip for clipping into the hole and retaining the viewing window between the retaining clip and the inside mounting surface.
9. The sealed housing of any one of claims 5 to 8 when appended to at least claim 4, wherein the outside mount comprises a shock absorbing material around the hole, the protective window being mounted to the shock absorbing material.
10. The sealed housing of claim S when appended to claim 7, or the sealed housing of claim 9 when appended to claim 7, wherein the shock absorbing material connects the protective window to the outside mounting surface.
11. The sealed housing of claim 9 or 10, wherein the shock absorbing material is plastically deformable foam.
12. The sealed housing of claim 7, or claim 8 when appended to claim 7, 01 claim 9 when appended to claim 7, or claim 10, or claim 11 when appended to claim 10, wherein the viewing window is connected to the inside mounting surface.
13. The sealed housing of any one of claims 3 to 12, wherein the viewing surround is formed in a front wall of the sealed housing, wherein the viewing surround further comprises a retaining plate having a viewing hole, wherein the retaining plate is secured to the front wall of the housing, and wherein the protective window is exposed to the external environment through the viewing hole.
14. The sealed housing of claim 13 when appended to claim 12, wherein the protective window is retained between the retaining plate and the outside mounting surface.
15. The sealed housing of any preceding claim, wherein the protective window and the viewing window are both formed of Germanium.
16. The sealed housing any preceding claim, wherein the viewing portion is transparent to infra-red light.