GB2173838A

GB2173838A - Fire-resistant enclosures

Info

Publication number: GB2173838A
Application number: GB08608410A
Authority: GB
Inventors: Michael Francis Warren Sharp; George William Dyson
Original assignee: Chubb and Sons Lock and Safe Co Ltd
Current assignee: Gunnebo UK Ltd
Priority date: 1985-04-12
Filing date: 1986-04-07
Publication date: 1986-10-22
Also published as: EP0199491A2; EP0199491A3; GB8509382D0; GB8608410D0; GB2173838B

Abstract

The apron sections 12 and 14 in the body and door of a data cabinet are made from steel strips having rows of elongate slots 17 running in the circumferential direction of the closure with the slots in adjacent, rows displaced in pitch, These slots thus lie across the temperature gradient from the external skins 2/8 to the internal skins 1/7 of the body and door so that the heat conduction pathways across the aprons are long and tortuous, thus reducing the rate of heat inleak to the cabinet while retaining sufficient structural rigidity in the closure region. <IMAGE>

Description

1 GB2173838A 1

SPECIFICATION

Fire-resistant enclosures The present invention relates to fire-resistant enclosures for the protection of temperature sensitive articles and is concerned especially with the construction of fire-resistant cabinets or files intended for the storage of electronic data-processing media such as magnetic discs 75 and tapes. Information stored on magnetic media rapidly degrades if the record carrier is heated to a temperature above about 60C (or about WC in the case of so-called diskettes or floppy discs) and fire-resistant equipment for storing these kinds of material (for conve nience termed herein ---datacabinets-) must therefore be capable of maintaining an internal temperature below the appropriate value at which degradation commences, when exposed 85 to fire conditions over a specified period.

The bodies of data cabinets are convention ally constructed with internal and external steel skins which are joined together around the opening for the door (or other closure member, eg drawer). Between these skins are enclosed selected thermally insulative and/or adsorptive materials which serve to restrict the transfer of heat through the walls of the cabinet from the exterior to its interior. In de- 95 signing such cabinets it is also important to minimise the amount of heat which can be conducted directly from the external to the internal skin through the structure which de fines the margins of the door opening. For this reason, it is commonplace to unite the skins through wooden framing members, since wood is a material of substantially lower ther mal conductivity than steel and the wooden frame can thus act as a useful heat-break be- 105 tween the skins. However, to reduce still fur ther the conduction of heat through this region of the cabinet by employing materials of even lower inherent thermal conductivity for this part of the structure conflicts with the need to 110 maintain a structure of sufficient rigidity and load-bearing capacity.

The present invention seeks to provide a solution to this problem and accordingly pro poses to configure at least part of the skin of 115 a data cabinet body in the region of the body which defines an access opening for the en closure in such a way as to define a tortuous path for the conduction of heat through such skin from the exterior to the interior of the enclosure, preferably by providing in that part of the skin a plurality of elongate slots extend ing in the circumferential direction of the open ing (that is to say perpendicular to the tem perature gradient from the exterior to the in- 125 terior). By thus increasing the effective length of the path along which the heat must pass, the effective rate of conduction through the skin to the interior of the cabinet can be reduced, notwithstanding that the material of the 130 skin has a relatively high inherent thermal conductivity. The performance of the cabinet may therefore be improved while still retaining a traditional high-strength materia [-notably steel -as the primary skin material.

A similar technique may be applied to the skin structure of the door, drawer or other closure member for a data cabinet.

The nature of the invention will be more fully understood from the ensuing description of a preferred embodiment thereof, taken in conjunction vkith the accompanying drawings, in which:

Figure 1 is a horizontal section taken through one portion of a data cabinet in accordance with the invention, showing the junction of its door and body and Figure 2 is a side elevation of one form of steel strip for use in constructing an apron portion of the cabinet's door or body.

Referring to Fig. 1, the illustrated cabinet is preferably constructed in accordance with the process described in our published United Kingdom patent application No. 2153405 and has a body with inner and outer steel skins 1 and 2 between which are encased successive layers of -phase-change- material 3, polyurethane or other insulative foam 4, and an outer layer of concrete, plaster or the like waterbearing material reinforced by a steel mesh 6. The door of the cabinet likewise comprises inner and outer steel skins 7 and 8 between which are encased successive layers of the same "phase-change," insulative and water100 bearing materials 9/10/11.

In the region of its junction with the door, cabinet body includes a steel apron 12 which is attached to the inner skin 1 through a timber heat-break frame 13. The surface of the door which faces the body apron 12 is likewise formed as a steel apron 14 which is attached to its inner skin 7 through another timber heat-break frame 15. A door seal 16 is also carried in a rebate between the frame 15 and skin 17. In each of the aprons 12 and 14 there are formed rows of elongate slots 17, running in the circumferential direction of the door opening, which together with the respective timber frames 13 and 15 serve to reduce the rate of heat conduction from the respective outer to the respective inner skins of the body and door un der fire conditions.

Fig. 2 illustrates one example of a steel strip which can be used for constructing the aprons 12,14. In this case there are five rows of the slots 17, although it will be appreciated that the number of rows employed in any particular construction is open to considerable variation in accordance with the dimensions of the apron concerned. The slots are provided in a repeating pattern along the length of the strip with the slots in each row displaced from those in the next adjacent rows by one half pitch. There are thus defined between the the skin on the 2 GB2173838A 2 slots a series of -bridges- 18 spaced across the strip in staggered relation sufficient to maintain the structural integrity of the strip for the service it must perform, but so disposed that the heat conduction pathways across the strip (that is to say from the exterior to the interior of the cabinet) are long and tortuous, involving passage in the direction parallel to the slots 17 from one--- bridge-18 to the next.

In the course of constructing the cabinet body and door the respective water-bearing layers 5 and 11 are cast in-situ. The slots 17 in each apron 12,14 are accordingly covered on the inside with adhesive tape 19,20 (Fig. 1) to prevent extrusion of the water-bearing paste through the slots. In the final assembly the slotted aprons 12,14 are conveniently faced with strips of intumescent material 21,22 adapted to swell up and seal the air gap between the door and body under fire conditions.

Although in the embodiment of cabinet illustrated herein the slots 17 are provided only in the---apron-sections 12 and 14 of the door and body it is envisaged that still better performance may be achieved from the cabinet by including similar slots or equivalent relieved portions also in the metal skin sections out- wardly adjacent thereto, such as in the faces designated as 2' and 8' in Fig. 1.

Claims

1. An enclosure for the protection of tem- perature-sensitive articles, the body of which comprises one or more layers of thermal barrier material enclosed by a skin at least in the region of said body which defines an access opening for the enclosure; wherein at least part of said skin in said region is configured in such a way as to define a tortuous path for the conduction of heat through such skin from the exterior to the interior of the cabinet.

2. An enclosure for the protection of tem- perature-sensitive articles, the closure member for an access opening of which comprises one or more layers of thermal barrier material enclosed by a skin at least in the region of said closure member which is juxtaposed to the body of the enclosure around said access opening; wherein at least part of said skin in said region is configured in such a way as to define a tortuous path for the conduction of heat through such skin from the exterior to the interior of the cabinet.

3. An enclosure according to claim 1 or claim 2 wherein there are provided in the aforesaid part of said skin a plurality of elongate slots extending in the circumferential di- rection of the access opening.

4. An enclosure according to claim 3 wherein there are a plurality of parallel rows of said slots with the slots in each row being displaced in pitch from the slots in the next adjacent row(s).

5. An enclosure for the protection of temperature-sensitive articles substantially as hereinbefore described with reference to the accompanying drawings.

Printed in the United Kingdom for Her Majesty's Stationery Office, Dd 8818935, 1986, 4235.

Published at The Patent Office, 25 Southampton Buildings. London, WC2A lAY, from which copies may be obtained.