GB2449911A

GB2449911A - An enclosure

Info

Publication number: GB2449911A
Application number: GB0710987A
Authority: GB
Inventors: John Maynard
Original assignee: Thales Holdings UK PLC
Current assignee: Thales Holdings UK PLC
Priority date: 2007-06-07
Filing date: 2007-06-07
Publication date: 2008-12-10
Also published as: GB0710987D0

Abstract

The enclosure comprising first and second rigid bodies with generally cylindrical, axial end portions 21, 31 which mate telescopically to form a cylindrical hydraulic seal allowing axial relative movement of the rigid bodies, the surfaces of the walls of the end portions 21, 31 being frusto-conical with the same angle to their common axis to facilitate relative axial movement of the rigid bodies during assembly and disassembly of the enclosure without jamming. The enclosure is a radar apparatus mast amplifier equalizer unit body 2 with a cover 3 providing the portions 21, 31. The portion 31 has axially spaced channels 5, 6 with o-rings 51, 61 for the sealing. The cover 3 is held by a series of axial screws 8. The enclosure can be a radome formed of a body telescopically locating over a base with the same sealing structure.

Description

AN ENCLOSURE

The invention relates to an enclosure comprising first and second rigid bodies with generally cylindrical axial end portions which are arranged to mate telescopically to 1_.......1 L.. .1.. .......1..._J *L.. .___1__1.. ...

101111 4 %..yliliUI IL.4I IIyUI4UIIL. 5C41, dJ.IU L11C IIAVCIILIOII is p4.1 1iUU1d11 d1L110U11 1101 exclusively useful in a radome and in hydraulically sealed enclosures for electrical apparatus to be used at sea or in harsh environments.

Hydraulic seals are used in applications with either rotary or reciprocating motion They are intended for use in high pressure dynamic applications involving hydraulic fluids. 0-rings are a versatile and economical form of hydraulic seal. To ensure sufficient compression of an 0-ring seal for successful hydraulic sealing, fine tolerances in the mating surfaces need to be specified. Typically, the maximum exclusion gap needs to conform to British Standard specification BS4518.

0-nng hydraulic seals are typically used at the junction of two cylindrical rigid bodies, with telescopic engagement. It is often required for these bodies to be assembled and disassembled, for example to gain access to the interior of an enclosure which they form when they are engaged. Many attempts have been made to increase the fine tolerances by considering the material and the hardness of the 0-ring seal, but it has not been possible to increase tolerances enough to solve the problem of the inter-engaging rigid bodies becoming jammed, for example in the case of an access cover to a housing.

In the example of an access cover, which may be generally disc-shaped with extenor handles, the main methods used in the past to fit or to remove the access cover have involved positioning tightening screws around the circumference of the cover and sequentially tightening each screw a little at a time. This method ensures that the access cover does not move out of line and that it is assembled over the housing correctly, without jamming against the edge of the housing. This method, although time-consuming, is proven to work on units up to about im in diameter but has not been used on larger units. The method is a long and difficult process.

The purpose of the present invention is to overcome the difficulties of assembling and disassembling one rigid body against another rigid body in a telescopic fashion using a cylindrical hydraulic seal.

ml -._ ___J _1___._il I Lie iiiveiiiioii piuviucs au euieiosuie i.ui11piisii1 iiisi dilU seeoiiu iigiu uuuies wan generally cylindrical, axial end portions which mate telescopically to form a cylindrical hydraulic seal allowing axial relative movement of the rigid bodies, the surfaces of the walls of the end portions being frusto-conical with the same angle to their common axis to facilitate relative axial movement of the ngid bodies dunng assembly and disassembly of the enclosure without j animing.

The frusto-conical shape of the end portions allows considerable tolerance in the angle between the axes of the first and second rigid bodies during assembly and disassembly, without causing jamming, and this can be explained in terms of a camming action between the walls of these end portions. The invention enables this arrangement to be applied to enclosures considerably greater than one metre in diameter, and of very large weight, even of the order of 100kg or more, substantially reducing the risk ofjamming, and improving the ease and speed of assembly and disassembly.

In order that the invention may be better understood, embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which Figure 1 is a side view of a mast amplifier equalizer unit embodying the invention; Figure 2 is an enlarged cross-sectional view of portion A of Figure 1; Figures 3a to 3f show sequential views during removal of the cover of a unit similar to that of Figures 1 and 2; Figure 4 is a side view of radar apparatus embodying the invention; and Figure 5 is an enlarged cross-sectional view of portion B of Figure 4.

A first embodiment of the invention is shown in Figures 1 and 2. A mast amplifier equalizer unit I comprises a ngid, generally cylindrical housing 2 for an amplifier and other electronic equipment. This housing 2 is sealed hydraulically against the exterior by means of a generally disc-shaped cover 3 which has a pair of handles 4 which are diametrically opposed and enable the heavy cover 3 to be lifted. With reference to the common axis 7 of the housing 2 and the cover 3, an axial end portion 21 of the housing mates telescopically over an axial end portion 31 of the cover 3, with end portion 31 fitting inside end portion 21. The end portions 21 and 31 have mutually opposed walls which are frusto-conical, at the same angle to the common axis 7, this angle being typically in the range of 5 to 100 (determined by the radius struck from one end of a chord through the centreline of the taper to ensure the joint will tip apart without contact occurring at the small end of the taper), most preferably (the smallest angle possible to ensure hydraulic forces are virtually identical to a parallel piston seal).

A pair of axially spaced cylindrical channels 5,6 are formed in the end portion 31 of the cover 3, facing the end portion 21, and when assembled these channels contain 0-rings 51, 61 respectively for forming an hydraulic seal. The seal is lubricated with an appropriate grease or other lubricant, not shown. In this embodiment, although it is not always necessary, angularly-disposed circumferential screws, one of which 8 is shown in Figure 2, are provided to secure the cover 3 in its mating hydraulically sealed position as shown. Each screw 8 fits in a bore 32 in the cover 3 and is in threaded engagement in a threaded bore 22 in the housing 2.

A similar enclosure 1' is illustrated in Figures 3a to 3f, this containing a similar cover 3' mating with a housing 2', only a portion of which is illustrated in Figurs 3a to 3f. The process of removal of the cover 3' from the housing 2' is illustrated in sequence from Figure 3a to Figure 3f, and this shows how the frusto-conical surfaces provide for considerable angular tolerance relative to the axis 7 during the process, without causing jamming.

Radar apparatus embodying the invention is illustrated in Figures 4 and 5. The radar apparatus 10 compnses a radome 11 which is typically around 5cm thick, and constitutes a rigid body which mates with an hydraulic seal against a base 12. The axial end portion Ill of the radome 11 mates telescopically with the axial end portion 121 of the base 12, and their engaging outer walls are both frusto-conical with the same angle relative to the axis. This angle is preferably in the range (determined by the radius struck from one end of a chord through the centreline of the taper to ensure the joint will tip apart without contact occurring at the small end of the taper), most preferably (the smallest angle possible to ensure hydraulic forces are virtually identical to a parallel piston seal). As shown in Figure 5, a pair of cylindrical, axially spaced channels 15, 16 accommodate respective 0-rings 151, 161 for hydraulic sealing, and again these are lubncated with an appropriate grease or lubricant.

In order to secure the rigid bodies together, a set of angularly-disposed, circumferential bolts or screws 13 is provided. As shown in Figure 5, each screw 13 extends through a bore 132 in the base 12, a bore 135 in the end portion 111 of the radome 11, and into threaded engagement with a nut 133 held within a channel 134 formed in the end portion Ill adjacent the hydraulic seal.

The radome Ii may be assembled and disassembled in a similar manner to the cover 3' shown in Figures 3a to 3f, without causing jamming.

The screws 13 are tightened sufficiently to ensure that the 0-ring seals are compressed sufficiently to form an adequate hydraulic seal.

As will be appreciated from a consideration of these examples of the application of the invention, the frusto-conical surfaces which in effect constitute tapered edges, allow considerable time and money to be saved by reducing the risk of one of the rigid bodies getting jammed against the other during installation or removal. This particular form of seal eliminates the need for a tightening method such as the sequential tightening of screws, thereby reducing manufacturing and assembly time.

It will be understood that the invention is not limited to the particular embodiments described, and that it could be applied to different forms of enclosure where hydraulic sealing is required between ngid or at least relatively rigid bodies. The rigid bodies could have any shape although it is intended that they have generally cylindrical portions which can mate telescopically together.

Claims

CLAIMS: I. An enclosure comprising first and second rigid bodies with

generally cylindrical, axial end portions which mate telescopically to form a cylindrical hydraulic seal allowing axial relative movement of the rigid bodies, the surfaces of the walls of the end portions being frusto-conical with the same angle to their common axis to facilitate relative axial movement of the rigid bodies during assembly and disassembly of the enclosure without jamming.
2. An enclosure according to Claim 1, in which the wall of at least one said end portion is formed with at least one cylindrical channel to receive an 0-ring hydraulic seal facing the wall of the mating end portion.
3. An enclosure according to Claim 2, comprising two said cylindrical channels which are parallel and axially spaced.
4. An enclosure according to Claim 2 or Claim 3, comprising at least one said 0-ring hydraulic seal fitted in a respective cylindrical channel.
5. An enclosure according to any preceding claim, in which the first rigid body is an access cover with at least one external handle, and the second rigid body is a sealed housing.
6. An enclosure according to Claim 5, in which the axial end portion of the access cover fits inside the end portion of the housing telescopically
7. An enclosure according to any of Claims 1 to 4, in which the first rigid body is a radome and the second rigid body is a base for mounting the radome, the enclosure being configured to house a radar antenna assembly.
8. An enclosure according to Claim 7, in which the axial end portion of the radome fits outside the end portion of the base telescopically.
9. A radar assembly comprising an enclosure according to Claim 7 or Claim 8.
10. An enclosure according to any of Claims 1 to 8, in which the rigid bodies are formed with fittings at their end portions for securing them together at their sealed mating position.
11. An enclosure according to Claim 10, in which the fittings comprise bores for SLLW.
12. An enclosure substantially as described herein with reference to Figures 1 and 2; or Figures 4 and 5; of the accompanying drawings.