GB2165996A

GB2165996A - Operating means for electrical equipment within a sealed enclosure

Info

Publication number: GB2165996A
Application number: GB08426849A
Authority: GB
Inventors: Anthony Mckenzie Owler
Original assignee: Expo Safety Systems Ltd
Current assignee: Expo Safety Systems Ltd
Priority date: 1984-10-24
Filing date: 1984-10-24
Publication date: 1986-04-23
Also published as: GB2165996B; GB8426849D0

Abstract

A sealed enclosure (5) containing electrical equipment liable to generate a spark is located in a region containing gases or vapours which may be ignited by the sparks. To enable control or operation of the equipment from outside the enclosure, which may be filled with inert gas and maintained at superambient pressure, an actuator device (1) is provided which has a shaft (4) extending sealingly through an aperture in the enclosure wall (5). Sealing is effected by an O-ring (7) around the shaft (4) and which is compressed by a flange (9, 10) carried by the shaft and acted upon by a spring (11) which serves not only to compress the O-ring but to return the shaft to a predetermined axial position. The end of the shaft within the enclosure controls the equipment directly or acts on a key or switch of the equipment eg. a computer keyboard. <IMAGE>

Description

SPECIFICATION Operating means for electrical equipment within a sealed enclosure The invention relates to the operation of electrical equipment mounted within a sealed enclosure from a location exterior to the enclosure.

Electrical equipment for use in a region containing flammable gases or vapours and capable of producing a spark which could ignite such gases or vapours is confined within an enclosure within which a non-ignitable gas is maintained at a super-ambient pressure, to ensure that the ignitable gas or vapour is excluded. It is in many instances desirable to control or operate electrical equipment, for example, keyboards for the control of computer equipment, in regions in which explosive gases or vapours occur, but confinement of the equipment within a sealed enclosure to prevent the possibility of an explosion from a spark produced within the equipment, prevents access to it.The problem consequently arises of providing an economicai means whereby control and switching operations can be performed within a sealed enclosure by manual manipulation of actuator elements located outside it.

The invention accordingly provides an actuator device for transmission of mechanical movement through a partition separating regions at different pressures, the device comprising an actuator member having a manually engageable end at one side of the partition and guided for axial movement in an aperture through the partition to actuator equipment on the other side thereof, and sealing means compressed by spring means axially locating the actuator member in a predetermined position.

The invention also provides an actuator device for control of electrical equipment within a sealed enclosure, the actuator device comprising an elenongate member extending through an aperture in the enclosure wall and being guided for axial movement, the member being actuatable manually at the end thereof outside the enclosure to effect a control operation on the electrical equipment therewithin, a seal element around the member, and spring means acting to urge the member to a predetermined axial position and to urge the seal element to effect a seal between the member and the enclosure wall.

Conveniently, the seal element is an O-ring around the actuator member and received between a flange or like portion of the member, or a washer positioned thereon, and the inner face of the enclosure wall. The spring means is advantageously a compression spring around the shaft having one end acting on a formation of the shaft or indirectly by way of the washer engaging the O-ring. The other end of such a spring can bear on an abutment spaced from the enclosure wall and within the enclosure, preferably in the form of a plate apertured to guidingly receive the shaft therethrough.

The invention thus provides a simple and economical means of operating, for example, keyboard equipment within a pressurized enclosure from outside the enclosure by operating through the enclosure wall but without substantially jeopardizing the enclosure seal.

The invention will be more fully understood from the following illustrative description and the accompanying drawing, in which: Figure 1 is a sectional side view of one of an array of actuator devices in accordance with the invention; and Figure 2 is a partial perspective view on a smaller scale of the array of actuator devices.

The illustrated actuator array comprises individual actuator devices 1 arranged in rows and columns in positions corresponding to those of the keys of computer keyboard equipment (not shown) which is located within a sealed enclosure, and which is to be operated from outside it by means of the actuator devices. The enclosure is for use in a region containing gases or vapours which might be ignited by sparks occurring within the keyboard or associated electrical equipment and the interior of the enclosure is maintained at a super-ambient pressure to exclude the ignitable gases and vapours.

Each of the actuator devices comprises a push button 2 secured to one end of a shaft 4 extending sealingly through an aperture in the enclosure wall 5. So as to be guided for axial movement, the shaft 4 extends also through an aperture, aligned with the enclosure wall aperture, in a guide plate 5 secured within the enclosure to extend parallel to the enclosure wall at a position suitably spaced from it. The keyboard equipment is fixed in position within the enclosure with each of the shafts 4 extending along the direction in which a respective key of the equipment must be depressed to actuate the key.

To minimize or prevent escape of the pressurized non-ignitable gas within the enclosure, a sealing means is provided between the shaft 4 and the wall 5. In the illustrated embodiment, this seal is effected by an O-ring 7 of appropriate resilient material received between the inner surface of the wall and a washer 9 held in place on the shaft 4 by a circlip 10. A helical compression spring 11 is received around the shaft and acts between the circlip 10 and the wall 6, to maintain the O-ring 7 under compression.

The drawing shows the actuator device 1 in its normal position in which the pressure of the spring 11 maintain an effective seal around the aperture in the enclosure wall 5, and retains the shaft in an out-of-use position axially with the button 2 spaced from the wall. In this position, the inner end of the shaft 4, or of an extension rod fitted to it, lightly engages the associated key of the keyboard equipment within the enclosure. To operate this key, the button 2 needs to be depressed only momentarily and for a short distance, so that there ensues only a minimal relaxation of the seal and no substantial escape of the non-ignitable gas from the enclosure occurs. As soon as the pressure of the operators' fingers on the button 2 is removed the spring 11 restores the shaft 4 to its outof-use position, and the seal to full effect.

The guide plate 6 is provided to provide axial guidance for the shafts 4, at a spacing from the enclosure wall 5 appropriate to this function and to the pressure exerted by the springs 11. In an alternative arrangement, the wall 6 is the wall of the enclosure, and the wall 5 is a gland or accessory plate secured to the enclosure wall at an appropriate spacing and forming part of a pressurized subenclosure.

Each button 2 can be moulded in plastics material with an appropriate symbol, that is, a symbol corresponding to that of associated key of the keyboard equipment moulded into its outer face. The buttons 2 are also formed with appropriate recesses to receive the outer end of the shafts 4 to which securement is made in any suitable way. The shafts 4 may be of metal for example brass or steel, but could instead be of plastics material, for example a polycarbonate. The buttons 2 and the shafts 4 can be transparent, so that light can be transmitted through them from bulbs located inside the enclosure.

Although described herein with reference to the actuation of conventional modified keyboard equipment, it will be evident that such equipment can be modified so that the shafts of the actuator devices of the invention are an integral part of the equipment. A single actuator device can be employed where for example only a single switch within the pressurized enclosure has to be actuated. The invention can of course be embodied in a variety of ways other than as specifically described.

Claims

1. An actuator device for use in control of equipment within an enclosure, the device being arranged to extend through an aperture in the enclosure wall in sealed relation thereto with a portion of the device external to the enclosure for selective operation to effect a control function on the equipment therewithin.

2. A device as claimed in claim 1 wherein the device is sealed to the enclosure wall by a resilient member biassed to a sealing condition by a spring acting as a return spring for the device.

3. An actuator device for transmission of a control movement through a wall, the device comprising an elongate member extending through an aperture in the wall, a seal means sealing the member to the wall, guide means guiding the member for axial movement, and spring means biassing the member to a predetermined axial position.

4. A device as claimed in claim 3 wherein the spring means acts on the seal means to ensure or enhance the sealing effect thereof.

5. A device as claimed in claim 3 wherein the seal means comprises an O-ring around the member and received between the wall and a flange on the member.

6. A device as claimed in claim 5 wherein the spring means acts between the flange and the guide means.

7. A device as claimed in claim 3, 4, 5 or 6 wherein the spring means comprises a heli cal compression spring through which the member extends.

8. A device as claimed in any one of claims 3-7 wherein the guide means comprises a guide member having an aperture aligned with the aperture in the enclosure wall and having the member extending therethrough.

9. A device as claimed in claim 8 wherein the guide member comprises a wall arranged to extend parallel to and internally or externally of the enclosure wall.

10. A device as claimed in any preceding claim wherein the device comprises a shaft with a button carried on an end of the shaft externally of the enclosure.

11. A device as claimed in claim 10 wherein the shaft is of transparent or translucent material for light transmission from a light source within the enclosure.

12. An actuator device substantially as herein described with reference to the accompanying drawings.

13. A sealed enclosure having therein equipment liable to generate a spark and at least one device as claimed in any preceding claim extending through an aperture in the enclosure wall for control of the equipment from outside the enclosure.

14. An enclosure as claimed in claim 13 having associated therewith means for producing superambient pressure in the enclosure interior.

15. An enclosure as claimed in claim 13 or 14 containing non-ignitable gas.

16. An enclosure as claimed in claim 13, 14 or 15 wherein the actuator device has a portion within the enclosure located so as to act on a key or switch member of the equipment on operation of the device.

17. An enclosure as claimed in claim 13, 14 or 15 wherein the actuator device is an integral part of the equipment.