WO1992014020A1

WO1992014020A1 - Fire-resistant safe

Info

Publication number: WO1992014020A1
Application number: PCT/US1992/000355
Authority: WO
Inventors: Mark E. Preston
Original assignee: John D. Brush & Co., Inc.
Priority date: 1991-01-30
Filing date: 1992-01-14
Publication date: 1992-08-20

Abstract

A fire-resistant safe in the form of a file cabinet has a main body (10) and two drawers (40, 42) received in a front wall (20) of the main body. The main body and drawer heads (50, 52) of both drawers are made with external and internal resin shells (54, 56, 58, 60) filled with insulation material (62, 64). When exposed to fire, a portion of the resin material burns away leaving gaps between the insulation materials of the main body and drawer heads. However, convection air currents that become established in vertical sections of the gaps (74) are controlled by inclining or offsetting portions (84, 90) of the front wall to avoid concentrations of heat that can promote burning through the gaps.

Description

TITLE

FIRE-RESISTANT SAFE

TECHNICAL FIELD

The invention relates to the field of fire protec¬ tion, and in particular, fire-resistant safes for protecting contents from fire.

BACKGROUND

Fire-resistant safes are designed to protect their contents from exposure to high temperatures of fire for predetermined periods of time. The safes are usually con¬ structed with external and internal shells that encapsulate a space filled with insulating material. The external shell forms the outer surface of the safe and cooperates with the internal shell to form a shuttering for molding the insulation material in place within walls of the safe. The insulation material is generally made of a mixture that solidifies in a mold but retains a large amount of water within the solidified mass of the material.

Fire-resistant safes also have openings for receiving contents; and the openings in safe bodies are closed by doors, drawer heads, or other types of closures for protecting the contents of the safes. The closures may also be constructed with external and internal shells filled with the same insulating material. The openings in the safe bodies are surrounded by a frame that joins the external and internal shells of the safe bodies. Similarly, the external and internal shells of the closures are joined by a peripheral region that fits within the frame of the safe bodies to close the openings in the safes.

The external and internal shells of many fire- resistant safes are made of steel to provide additional structural strength and to conduct heat away from hot spots by dissipating the heat over a larger area of the safes. However, intermediate portions of the steel shells, which form the frames in the safe bodies and the peripheral regions of the closures, conduct heat into the interior of the safes. In addition, the steel shells tend to warp when heated and produce, between the safe openings and the closures, passages that admit hot gasses into the safes.

Other fire-resistant safes have external and internal shells made of a molded resin material. Although the resin material is combustible and burns away from the outer surfaces of the insulation material in a fire, the resin material of the frames and the peripheral regions of the closures only partially melts away leaving a seal between the safe openings and closures. The frames of the safe openings and closures are made deep enough in cross section through the safes so that, after the resin material covering the outer surfaces of the insulation material has burned away, a softened or plasticized portion of the resin material remains in the opening to seal the closures to the safe bodies. The resin seal resists heat conduction and the passage of hot gasses into the safes.

However, since the resin material of the shells exhibits low thermal conductivity in relation to steel, the resin shells do not dissipate as much heat away from hot spots. The corners of the safes are especially vulnerable to "burn through" because the corners are exposed to heat on three sides. Accordingly, additional insulating material is used in the corners of the safes to provide more uniform protection against burn through over the exposed areas of the safes.

In addition to the heat concentrations in portions of the safes exposed to fire from more than one direction, other heat concentrations are evident in front walls of the safes at the top corners of the frames joining jamb members that enclose opposite sides of the openings with a framing member that encloses the top of the openings. Under especially severe conditions, the resin material in the top corners of the frames may be entirely burned away exposing a hole through the resin seal between the safe openings and closures.

SUMMARY OF INVENTION

I have discovered a source of the problem of heat concentrations at the top corners of the frames between resin shells of safe openings and closures. This discovery provides a basis for implementing a variety of solutions that would not have been apparent without the discovery.

After the resin material of the external shells burns away, a portion of the resin material is also burned into jamb regions (i.e., in the jamb members of the frame and in the peripheral portions of the closures confronting the jamb members) creating gaps between the insulating material of the safe body and the closure. Although, at least initially, the gaps do not penetrate the resin seal, the gaps burned in the jamb regions provide vertical passageways for movement of air along the jambs. Resin material burning in the jamb regions is believed to induce convection air currents that carry heated air and products of combustion along the jambs producing concentrations of heat at the top corners of the frame.

This phenomena may be referred to as the "chimney effect" because similar to the function of a chimney, the gaps burned in the resin material of the jamb regions are heated by fire and induce vertical drafts of air in the gaps that tend to further promote the fire. However, the vertical air passageways burned in the jamb regions are obstructed at the top of the jambs by the framing member enclosing the top of the opening. Accordingly, the heat and products of combustion carried by the convection air currents rising along the jambs become concentrated at the top corners of the frame and promote burning through the top corners of the frame more rapidly than the remaining portions of the frame. My invention provides a number of solutions to this problem, each treating a different aspect of the chimney effect. For example, one of my solutions provides for inclining an upper portion of the safe including the top corners of the frame away from the vertical path of the convection air currents to prevent the top corners of the frames from obstructing the convection air currents. Although the convection air currents carry heated air through the jamb regions, the heated air is permitted to exhaust from the jamb regions without concentrating significantly more of the heat at the top corners of the frame.

Another solution provides for deflecting convection air currents away from sensitive portions of the safe. A portion of the safe including a section of the jamb regions is inclined toward the vertical path of the convection air currents to move the currents away from other portions of the safe. For example, the convection air currents can be deflected into a plane that is offset from the top corners of the frame so that the vertical paths of the convection air currents are not significantly obstructed by the top corners of the frame.

Yet another solution provides for interrupting convection air currents along the jamb regions so that at least part of their heat energy is dissipated over less sensitive areas of the safe. A portion of the safe including a section of the jamb regions is offset from the vertical path of the convection air currents in either of two directions. For example, a section of the jamb regions may be offset into the front face of the safe leaving a vertical space separating two other sections of the jamb regions. At least part of the heat energy of the convection air currents is dissipated in the space separating the two other sections of the jamb regions. Alternatively, adjacent sections of the jamb regions may be offset within the front face of the safe dividing the jamb regions into sections that are out of alignment with each other. Only part of the heat energy carried by currents in one of the offset sections of the jamb regions is added to the heat energy carried by separate currents in the other of the offset sections of the jamb regions.

All of the just-mentioned solutions provide for controlling paths of convection air currents with respect to different sections of the jamb regions and, thus, treat the source of the problem in the top corners of the frames instead of its effects. The exemplary solutions may be used individually or in combination with each other to provide further protection against burn through in the top corners of the frames.

DRAWINGS

Figure 1 is a front view of my fire-resistant safe arranged as a two-drawer file cabinet.

Figure 2 is a cross-sectional side view of the same file cabinet with one of the two drawers opened to show a portion of a frame for receiving the drawers.

Figure 3 is a front view of the file cabinet similar to Figure 1 but with parts burned away to show gaps in a jamb region along which convection air currents may be established in a fire.

Figure 4 is a cross-sectional side view of the file cabinet similar to Figure 2 showing various relationships between the convection air currents and a front wall of the file cabinet.

Figure 5 is a front view of an alternative two-drawer fire-resistant file cabinet similar to the file cabinet of the preceding figures but including different width drawers. DETAILED DESCRIPΩON

One embodiment of my fire-resistant safe is depicted as a two-drawer file cabinet in Figs. 1 and 2. The file cabinet has a main body 10 supported on a base 12. The main body 10, including the base 12, is formed by an external shell 14 and an internal shell 16 that have a space between them filled with an insulation material 18. The two shells 14 and 16, together with the insulation material 18, also define in the main body 10 a front wall 20, a back wall 22, two side walls 24 and 26, and a top wall 28. The front wall 20 is formed with an opening surrounded by a frame 30 that joins the external shell 14 and internal shell 16. The frame includes two side members or jambs 32 and 34, a top member 36, and a bottom member 38.

Two drawers, namely top drawer 40 and bottom drawer 42, are carried between respective pairs of conventional sliding tracks 44 and 46 that are anchored to the side walls 24 and 26 of the main body. The opening in the front wall 20 is sized to receive respective top and bottom drawer heads 50 and 52 attached to ends of the drawers. The drawer heads 50 and 52 are also formed by respective external shells 54 and 56 and internal shells 58 and 60 encapsulating respective spaces filled with insulation materials 62 and 64. The external and internal shells of the respective drawer heads 50 and 52 are joined by peripheral regions 66 and 68 that fit within the frame 30 for closing most of the opening in the front wall 20. However, a bottom peripheral surface 70 of the region 66 fits against a top peripheral surface 72 of the region 68 for closing a remaining part of the opening in the front wall. In closed positions, the drawer heads 50 and 52 complete front wall 20 of the cabinet.

Preferably, the external and internal shells of the main body 10 and each of the drawer heads 50 and 52 are made of a resin material that can be molded to desired shapes in respective blow molding operations. U.S. Patent 4,828,786 of the present assignee discloses details of a blow molding operation appropriate for this purpose. The insulation material is preferably made of a mixture of water, cement, water-retaining fibers, and a foaming agent. Additional details of a suitable mixture are provided in U.S. Patent 4,263,365, also of the present assignee. Both of the just-mentioned patents of the present assignee are hereby incorporated by reference to provide specific details of the blow molding process and of the insulation material.

Figs. 3 and 4 illustrate two views of the same fire-resistant cabinet after the front wall 20 has been exposed to fire. The fire has burned away from the front wall 20 portions of the external resin shell 14 of the main body and the external resin shells 54 and 56 of the two drawer heads. The removal of the external shell portions exposes the insulation material 18 of the main body and the insulation material 62 and 64 of the drawer heads. The view of Fig. 4 shows that outer portions of the resin material of the frame 30 and peripheral regions 66 and 68 have also burned away. The removal of the resin material from portions of the frame 30 and peripheral regions 66 and 68 leaves a gap 74 between the insulation material 18 of the main body and the insulation material 62 and 64 of the drawer heads.

The gap 74 includes respective channels 76 and 78 burned in jamb regions defined by the jamb members 32 and 34 and the confronting portions of the peripheral regions 66 and 68 adjacent to the respective jambs. Although convection air currents 80 and 82 can be established along the respective channels 76 and 78, my fire-resistant cabinet includes a number of features that control the paths of the convection air currents to provide more uniform protection against burn through in the jamb regions. For example, a top portion 84 of the front wall is inclined away from vertical paths of the convection air currents 80 and 82 so that the currents are not substantially obstructed by top member 36 of the frame. This feature avoids concentrations of heat in the top corners of the frame 30 where the two jamb members 32 and 34 meet the top member 36. Other features include offsetting respective center portions 86 and 88 of the two drawer heads with respect to both the top member 36 of the frame and the adjacent peripheral surfaces 70 and 72 of the drawer heads. A bottom portion 90 of the front wall is inclined away from the base 12 to provide a gradual connection between the base and the offset center portion 88 of the bottom drawer head. Also, respective bottom and top portions 92 and 94 of the drawer heads are oppositely inclined to provide a gradual connection between the adjacent peripheral surfaces 70 and 72 and the center portions 86 and 88 of the respective drawer heads.

This arrangement of various inclined and offset portions of the front wall 20 of the cabinet accomplishes several purposes. First, the convection air currents 80 and 82 along the respective jamb regions are initially deflected away from the base into an offset plane defined by the center portions 86 and 88 of the respective drawer heads. Second, the convection air currents are carried at a distance from more sensitive areas of the channels 76 and 78, including an area where the adjacent peripheral surfaces 70 and 72 of the drawer heads meet the channels. Third, the channels carrying the respective convection air currents in the offset plane are interrupted by a space between the center portions 86 and 88 defined by the inclined surfaces 92 and 94 of the drawer heads. The space allows the convection air currents 80 and 82 carried in portions of the channels between the bottom drawer head 52 and the main body 10 to dissipate part of their energy before reentering other portions of the same channels between the top drawer head 50 and the main body 10.

Another way of interrupting convection air currents in respective channels of the jamb regions is illustrated in an alternative embodiment of Fig. 5. The alternative embodiment is also a file cabinet with a main body 100 and two drawer heads 102 and 104 closing an opening in a front wall 106 of the main body. The main body 100 and the two drawer heads 102 and 104 are also formed with external and internal shells of a molded resin material filled with an insulation material. However, in addition to providing a space between offset center portions 108 and 110 of the respective drawer heads, the drawer heads 102 and 104 are made of different widths. Accordingly, channels 112 and 114, where they might be formed in the jamb regions between the top drawer head 102 and the main body 100, are offset with respect to where channels 116 and 118 might be formed in the jamb regions between the bottom drawer head 104 and the main body. Respective convection air currents 124 and 126 in the channels 116 and 118 adjacent to the bottom drawer head are interrupted by the offset between the channels so that most of the energy of the respective air currents 124 and 126 is dissipated over less sensitive areas of the front wall 106, and only a small portion of this energy contributes to respective convection air currents 120 and 122 in the channels 112 and 114 adjacent to the top drawer head.

The two above-described embodiments illustrate a number of ways in which convection air currents established along gaps in the jamb regions between drawer heads and main bodies of fire-resistant files may be controlled to prevent the convection air currents from prematurely burning through more sensitive sections of the jamb regions. All of the depicted ways provide for inclining or offsetting sections of the jamb regions with respect to vertical paths of convection air currents rising along the jamb regions. Of course, a variety of different combinations of inclining or offsetting the sections of the jamb regions may be used to prolong the effectiveness of the resin seal or a seal made from another combustible material in the jamb regions. The same teaching may be applied to protect jamb regions in a variety of other types of fire-resistant enclosures including conventional safes with front opening doors.

Claims

I CLAIM:

1. A fire—resistant safe for protecting contents of the safe from fire comprising: a safe body including a front wall with an opening for receiving the contents; a closure sized to fit within said opening for completing said front wall of the safe; a frame surrounding said opening including jambs enclosing opposite sides of said opening connected by a frame member enclosing a top of said opening; top corners of said frame defined by respective intersections of said jambs with said frame member; and means for controlling paths of convection air currents induced by fire to reduce concentrations of heat in at least one of said top corners of the frame.

2. The safe of claim 1 in which said means for controlling paths of convection air currents includes inclining a portion of said front wall including said top corners of the frame away from a vertical path of convection air currents rising along said jambs to prevent said top corners of the frame from significantly obstructing the convection air currents rising along said jambs.

3. The safe of claim 1 in which said means for controlling paths of convection air currents includes inclining a portion of said front wall toward a vertical path of convection air currents rising along said jambs to deflect the convection air currents away from said top corners of the frame.

4. The safe of claim 1 in which said means for controlling paths of convection air currents includes offsetting a portion of said front wall with respect to a vertical path of convection air currents rising along said jambs for interrupting the path of convection air currents and dissipating at least part of the heat energy carried by the currents over other areas of the safe.

5. The safe of claim 4 in which said portion of the front wall is offset between two other portions of said front wall leaving a space within which part of the heat energy carried by the convection air currents is dissipated.

6. The safe of claim 4 in which said portion of the front wall is offset with respect to an adjacent portion of said front wall leaving between said adjacent portions respective sections of said jambs that are out of alignment with each other so that only part of the heat energy carried by convection air currents in one of said jamb sections is added to the heat energy carried by separate convection air currents in the other of said jamb sections.

7. In a fire-resistant safe for protecting contents from fire of the type including a safe body and a closure, both constructed with external and internal shells that encapsulate respective spaces filled with insulation material; said external shells form outer surfaces of the safe and said internal shells enclose an interior space for storing the contents of the safe; said external and internal shells of said safe body are joined by an intermediate portion of the shells forming in a front wall of said safe body a frame having top corners adjacent to a pair of jamb members of said frame, and said external and internal shells of said closure are joined by another intermediate portion forming in said closure a peripheral region that fits together with said frame; said jamb members of the frame together with surfaces of said peripheral region adjacent to said jambs define respective jamb regions; and at least one of said intermediate portions is made from a combustible material so that when the safe is exposed to the fire, a portion of said combustible material is burned away leaving respective channels in said jamb regions between said insulation material of the safe body and the closure; the improvement in which: said safe is constructed with means for inhibiting convection air currents carried in said channels of the jamb regions from concentrating heat in said top corners of said frame.

8. The safe of claim 7 in which said combustible material is a thermoplastic resin material that provides for resisting passage of hot gasses of the fire into said interior of the safe.

9. The safe of claim 8 in which said means for inhibiting convection air currents prevents convection air currents from burning a passage into said interior of the safe through said thermoplastic resin in said top corners of the frame significantly in advance of other passages burned through said thermoplastic material elsewhere along said jamb region into said interior of the safe.

10. The safe of claim 9 in which said means for inhibiting convection air currents includes inclining a portion of said front wall including a section of said jamb regions joined with said top corners of the frame away from a vertical path of convection air currents rising in channels of another section of said jamb regions.

11. The safe of claim 9 in which said means for inhibiting the convection air currents includes inclining a portion of said front wall including a section of said jamb regions toward a vertical path of convection air currents rising in channels of said inclined section of said jamb regions to move the convection air currents away from other sections of said jamb regions.

12. The safe of claim 9 in which said means for inhibiting convection air currents includes offsetting a portion of said front wall including a section of said jamb regions with respect to a vertical path of convection air currents rising in channels of another section of said jamb regions.

13. The safe of claim 12 in which said sections of the jamb regions are offset in a direction that projects from said front wall of the safe.

14. The safe of claim 12 in which said sections of the jamb regions are offset in a plane that includes said front wall of the safe.

15. A fire-resistant file cabinet comprising: a main body mounted on a base; a front wall of said main body including an opening that is surrounded by a frame; corner portions of said frame joining two side members of said frame with a top member that encloses a top portion of said opening in the front wall; a first drawer mounted slidably within said main body; a first drawer head attached to said first drawer including a first peripheral region that fits within said frame; a second drawer mounted slidably within said main body; a second drawer head attached to said first drawer including a second peripheral region that fits within said frame; said first and second drawer heads are movable to closed positions that complete said front wall; a first portion of said front wall extends in a substantially vertical plane with respect to said base; a second portion of said front wall is inclined with respect to said vertical plane in a direction toward said main body; and said first and second portions of the front wall cooperate to offset said corner portions of the frame from convection air currents in said vertical plane.

16. The file cabinet of claim 15 in which said first and second peripheral regions include adjacent surfaces that are offset from said vertical plane in a direction toward said main body.

17. The file cabinet of claim 16 in which said first and second drawer heads include surfaces that are inclined away from said main body to deflect convection air currents away from other surfaces of said drawers.

18. The file cabinet of claim 15 in which at least one of said frame and said first and second peripheral regions is made of a combustible material so that when the file is exposed to the fire, a portion of said combustible material is burned away leaving a gap in said front wall between said safe body and said first and second drawer heads.

19. The file cabinet of claim 18 in which said second portion of the front wall is inclined with respect to said vertical plane so that convection air currents rising in said gap are not significantly obstructed by said top corners of the frame.

20. The file cabinet of claim 19 in which said first and second peripheral regions include mating surfaces that are offset from said vertical plane in a direction toward said main body.

21. The file cabinet of claim 18 in which one of said drawer heads is made wider than the other of said drawer heads to interrupt currents rising in said gap.

22. The file cabinet of claim 18 in which said first and second drawer heads include surfaces that are inclined away from said base to deflect convection air currents rising in said gap away from other surfaces of said drawers.