US3762787A

US3762787A - Insulated article storage unit

Info

Publication number: US3762787A
Application number: US00181306A
Authority: US
Inventors: F Grubb
Original assignee: Sperry Rand Corp
Current assignee: Sperry Corp
Priority date: 1971-09-17
Filing date: 1971-09-17
Publication date: 1973-10-02
Anticipated expiration: 1990-10-02
Also published as: JPS4840555A; DE2245453A1; FR2153886A5; IT963199B; DE2245453B2; AU4296072A; CA967217A; AU466716B2; GB1365741A

Abstract

A heat resistant cabinet having one or more compartments for storing articles. Each compartment comprises a rectangular container having a hermetically sealable cover. The containers are each individually supported by a conventional file drawer suspension mechanism for movement into and out of corresponding bays in the cabinet casing. One or more cells are formed in the container walls. A particulate mixture having heat absorbing characteristics is contained in such cells and thus the filled portion of each cell serves as a heat sink under conditions where the unit is exposed to intense external heat. By using filler materials having a high heat of fusion the temperature in the inner container is temporarily stabilized when the melting point of the substance employed is exceeded. At least one conductive plate is mounted within each cell in contact with the filler to aid in the transfer of heat thereto.

Description

D United States Patent 11 1 110 3,762,787

Grubb 1 Oct. 2, 1973 1 INSULATED ARTICLE STORAGE UNIT [75] Inventor: Fred H. Grubb, Marietta, Ohio Pnmary Exammerflpaul G'Hlam AltorneyFrank A. Seemar et a1. [73] Assignee: Sperry Rand Corporation, New

York 57 ABSTRACT [22] Flled' Sept. 197] A heat resistant cabinet having one or more compartl l PP 181,306 ments for storing articles. Each compartment comprises a rectangular container having a hermetically 52 us. c1. 312/214, 109/80 sealab'e Cove The F'* each indlviduif'ly 51 1m. 01 A47b 81/00, F25d 11/00 suppmed by a mnvenmfal drawer suspens'o [58] Field of Search 312/214; 109/76, mechamsm and cmespord' 09/82 83 84 29 80 ing bays in the cabinet casing. One or more cells are i formed in the container walls. A particulate mixture having heat absorbing characteristics is contained in [56] References Cited such cells and thus the filled portion of each cell serves UNITED STATES PATENTS as a heat sink under conditions where the unit is ex- 683,851 10/1901 Cronenberg 252/70 posed to intense external heat; using materials l'850'l66 3/1932 252/70 having a high heat of fusion the temperature in the Z: 2: inner container is temporarily stabilized when the melt- 2:48:689 2/1939 Gibson 'i: 109/82 ing point of the substance employed is ex ceeded. At 1408966 H968 Garmer u l09/80 least one conductlve plate is mounted w1th1n each cell 3 45 21 2 972 Radfordm' H 09 2 in contact with the filler t0 aid in the transfer Of heat 3,066,847 12/1962 Fortune 109/82 x thereto- 3,272,580 9/1966 Dean et al. 312/214 3,559,594 2 1971 Miller 109/84 4 Claims 6 Drawmg Flgures PAIENIEDOBI 2mm 3.762.787 sum 10F 5 gag m/rr/vrae. reza A4 'euea.

PATENTED 21 73 SHEET 2 BF 3 INSULATED ARTICLE STORAGE UNIT BACKGROUND OF THE INVENTION The present invention relates to article storage equipment and more particularly to new and useful improvements in heat resistant filing cabinets.

In the filing cabinet art, it is well known to provide an insulated storage unit having an outer fire'resistant casing surrounding one or more inner layers of heat resistant material such as gypsum, concrete orthe like. These layers provide a heat barrier in the walls of the unit. Generally the relative degree of protection desired determines the thickness, type and amount of material used.

However, in addition to such physical aspects of the surrounding walls, other factors are frequently involved. For example, if the stored records are in the form of magnetic tape or microfilm, consideration must also be given to design criteria relative to characteristics, such as flammability and resistance to moisture-of such stored articles. Thus, in most insulated storage products the specifications are established in accordance with the type of articles to be accommodated thereby. To this end, Underwriters Laboratories, Inc. has performed conventional tests to establish and define standard criteria based on the environmental limits of specific categories of articles used in everyday business, such as office records, microfilm, magnetic tapes, etc. Fire resistant storage products conforming to .such standards are rated in accordance with the length of the exposure period during which the various categories of articles stored therein would be protected under prescribed intense external heat conditions.

Prior art insulated filing cabinets of the typediscussed above generally include a readily accessible storage compartment. For example, a heat resistant filing cabinet having a plurality of insulated compartments carried individually by a like plurality of file drawer suspension mechanisms and including means to facilitate access to such compartments during ,daily business operations, is shown in U. S. Pat. No. 3,272,580, L. R. Dean, et al., issued Sept. 13, 1966, and assigned to the assignee of the present application. U. S. Pat. No. 2,148,689, G. R. Gibson, et al., issued Feb. 28, 1939, is a further example of prior art insulated storage cabinets.

Accordingly, it is an object of this inventionto provide an improved heat resistant storage unit for maintaining the temperature of its inner compartment at a predetermined level for a required period of time under conditions where the unit is exposed to intense external heat.

A further object is to provide a heat resistant storage unit which includes a storage compartment having a wall with an inner cell at least partly filled with a heat absorbing substance comprising a particulate material having a relatively high heat of fusion, and a heat conductive element in contact with the filler for facilitating the transfer of heat when the unit is exposed to intense heat.

The above and other objects and advantages of the present invention will become more apparent from a consideration of the following detailed description taken together with the accompanying drawings.

BRIEF SUMMARY OF THE INVENTION The present invention contemplates heat resistant storage equipment of the nature mentioned in the above objects, and more particularly an improved insulated storage unit having a conductive plate mounted within the walls of at least one inner cell partly filled with'aheat absorbing substance.

One specific embodiment of the invention comprises a cabinet having an outer heat barrier composed of a layer of suitable insulating material such as concrete, gypsum, Portland cement, or the like. The cabinet includes one or more bays for accommodating a like number of storage containers to which access is readily permitted. Each container is mounted within the cabinet and includes an inner storage compartment. An inner cell, in the form of a cavity within one or more of the container walls, is partly filled with a heat absorbing substance. This filler becomes a heat sink .under conditions where the storage unit is exposed to intense heat. Heat sinks are commonly used to divert ;heat away from those areas or elements on which excessive temperature levels would have a deleterious affect. Grystalline sodium acetate trihydrate (NaC H O 3l-I O) is exemplary of the substance used as the principal ingredient of the heat sink filler for the present invention.

As pointed out, the present invention encompasses the use of a heat absorbing substance alone or in combination with other substances as a heat sink mixture. The sink absorbs heat under conditions where theunit is exposed to excessive external heat. Accordingly, heat 'is accumulated in the walls of the container and thus effectively delays the rise in temperature within the inner storage compartment. It should further be noted that the invention specifically contemplates a heat sink with varying quantities of filler throughout the walls of the container. A conductive plate extends into the filler, regardless of the level thereof, to provide a con venient path for heat transfer through the air space in the cell to the heat sink. The plate also functions as a path-to divert heat from critical areas of the structure .and thereby reduce leakage at such areas into the storage compartment.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a portion of an insulated filing cabinet in which one embodiment of the present invention is incorporated;

FIG. 2 is a partial cross sectional side elevation taken through the top bay of the filing cabinet shown in FIG. 1;

FIG. 3 is a cross sectional side elevation taken through a container having a top in sealed engagement with the upper peripheral edges of the side walls;

FIG. 4 is a sectional view taken along the line 4-4 of FIG. 3;

FIG. 5 is a cross sectional front elevation taken through a container and a portion of the cabinet; and FIG. 6'is a partial enlarged corner portion of the cross sectional view of the container shown in FIG. 5.

'DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings for a more detailed description of the present invention, a filing cabinet having a conventional configuration, generally designated by reference numeral 10 in FIG. 1, illustrates by way of example a heat resistant article storage unit in which the present invention may be embodied. The configuration shown comprises a three drawer filing cabinet having a top wall ll, side walls 12 (only one shown), a rear wall 13 (see FIG. 2), and a bottom wall (not shown in FIG. 1 similar to top wall 11. Three identical drawers 14 are provided, each having a front face in which a centrally located drawer pull 15, is mounted. The drawers are manually movable into and out of unit by means of conventional suspension mechanisms 16 (one of which is shown in FIG. 1). Each drawer includes a container 17 having an inner storage compartment for carrying vital articles, such as microfilm records retained on reels 18, shown in phantom outline.

Filing unit 10 further comprises spaced horizontal partitions 20 (one shown in FIG. 2) which cooperate with adjoining wall members to define individual insulated bays. In FIG. 2, one drawer 14 is illustrated in closed position. Walls ll, 13 and partition 20 (shown in section) comprise a layer of heat resistant material such as gypsum or other material of similar characteristics commonly used as a heat barrier in insulated equipment. Each drawer also includes a face layer 21 of similar heat resistant material for surrounding container 17 by insulated walls when the drawer is closed. The peripheral edge at the cabinet opening for each bay is provided with a continuous groove 22 (FIG. 2) adapted to receive a complementary projection 23 formed on the face of each drawer for interfitting engagement when the drawer is closed.

Now turning to the structure of container 17, a top member 24 (FIGS. 2 and 3) is adapted to hermetically seal the storage compartment when the drawer is in closed position. A gasket 25 (FIG. 3) is affixed to top 24 for this purpose. To gain access to the compartment, top 24 can be either automatically or manually manipulated. An automatic mechanism for this purpose is disclosed in the Dean, et al., patent mentioned above.

The unit thus far described refers to structure found in prior art heat resistant filing cabinets. The present invention, although readily embodied in such structure is not limited thereto. For example, it will become apparent that the present invention could be used in a safe cabinet, which is the equivalent of a one section filing cabinet, or any other type of insulated storage unit.

Insofar as the specific structure of container 17 is concerned, FIGS. 3, 4 and 5 show a front wall 26, a rear wall 27, and opposing

side walls

28, 30, all four of which walls extend from a bottom wall 31 to form an open box configuration. Top 24 is shown in closed position (FIGS. 2, 3 and 5) to complete the storage compartment. It has been mentioned above that top 24 may be handled by a mechanism responsive to the position of the drawer. The top handling mechanism disclosed in the Dean, et al., patent mentioned above retains top 24 in the cabinet (see FIG. 1) during translation of the drawer.

The upstanding walls of container 17 (FIGS. 3, 4 and 5) include an outer casing 32, an inner casing 33, and a layer of heat resistant material comprising urethane foam, a commercially available heat barrier material. More specifically, outer casing 32 consists of four integral sides arranged in the rectangular configuration shown in section in FIG. 4. The inner casing is likewise formed from four integral sides and further includes an integral rectangular bottom sheet 34. An outer bottom sheet 35 (FIG. 3) is secured to the bottom edges of outer casing 32 along upwardly turned flange 36. The

heat resistant .layer consists of

rectangular foam slabs

37, 38, 40, 41 and 42, interfitted to form a rectangular box in the space between inner casing 33 and outer casing 32. A sheet of asbestos 43 disposed along the top surface of slab 42 completes the internal layer structure.

'A cell within the upstanding walls of the container is defined by the inwardly facing surfaces of

slabs

37, 38, 40 and 41, and the outwardly facing surfaces of inner casing 33. A filler material 44 is retained in the cell. The amount of filler used depends on various interrelated characteristics, such as physical dimensions of the container, properties of the filler material, and the type of article being protected. Pertinent characteristics of this nature are discussed in subsequent portions of this description.

Container 17 is enclosed by removable top 24 having inner and outer rectangular casing sheets, 45 and 46, respectively. FIG. 5 shows flange portions, 48 and 50, extending downwardly from the side edges of sheet 46 whereby guidance of top 24 into its closed position is facilitated. More specifically, top 24 includes a heat resistant slab 51 comprising a layer of urethane foam along the inner surface of outer casing sheet 46. Four strips of

similar foam material

52, 53, 54 and 55 are disposed in a rectanguiar configuration in the vicinity of the outer edge of top 24, and between the inner surface of layer 51 and the outwardly facing surface of sheet 45. The top wall structure also includes an L-shaped flange 56 (see FIG. 6) spaced from the end of layer 51 and flange 56 by a folded flexible strip 57 (FIG. 6) of insulating material such as asbestos. Flange 56 is spaced from the upstanding walls of container 17 by gasket 25 mounted along the downwardly facing peripheral edge of top 24. Gasket 25 is affixed to the edge of inner casing sheet 45 to hermetically seal the inner storage compartment of the container under closed conditions. An inner cell is provided in top 24 between the inwardly facing surface of layer 51 and the outwardly facing surface of sheet 45. This cell is further defined by the inner edge surfaces of

strips

52, 53, 54 and 55.

Referring again to the upstanding walls of container 17, heat

conductive elements

58, 60, 61 and 62 comprising four similar rectanguiar plates, are spaced substantially equidistantly between the side walls of the cell. These elements which are at the heart of the present invention consist of a plate of aluminum, copper, or any other conductive material, mounted, (as shown in detail at FIG. 6) between a strip of asbestos 63 (extending along a downwardly extending flange portion 64 of outer casing 32) and a sheet of asbestos 65. Downwardly extending integral flange portion 66, of inner casing 33 completes the mounting arrangement for element 60.

In one method of fabricating container 17, the inner and outer casings are first secured together in the course of securing

elements

58, 60, 61 and 62 in place between

asbestos elements

63 and 65.

Urethane slabs

37, 38, 40, and 41 are then inserted from the bottom and placed adjacent the inwardly facing surfaces of the outer walls with the edge along the grooves formed by downwardly extending flange portion 64 (see FIG. 6) of outer casing 32. The layers are affixed to the casing surface by any suitable bonding agent. The cell is thus formed and ready to receive filler material 44. When the appropriate amount of filler has been poured into the cell, asbestos sheet 43 is affixed to the surface of bottom casing sheet 34, thereby enclosing the cell cavity. Finally, slab 42 is placed in position and bottom sheet 35 is fitted thereover and affixed to outer casing 32.

Top 45 is fabricated in a similar manner. Layer 5] is secured to casing sheet 46 followed by placement of flange 56 and strip 57. Foam strips 52, 53, 54, 55 are then affixed to layer 51 by suitable adhesive means to form a centrally located cell in the top. A predetermined amount of filler is poured into the cell and inner casing sheet 45 is secured in palce to enclose the cell. As mentioned above standard means are employed to secure together various casing sheets, flange members, and the like. Lastly, gasket 25 is affixed along the edge of inner casing sheet 45 to complete the top structure.

The present invention is embodied in structure wherein a heat sink is provided in one or more walls of an insulated container, such that a certain amount of heat penetrating an outer barrier layer of heat resistant material is consumed by the tiller substance at a temperature determined by the melting point thereof. This filler, generally designated by reference numeral 44 throughout the drawings, comprises sodium acetate trihydrate in the crystalline form, which is readily available from commercial sources in various bulk grades. For example, the Allied Chemical Corporation distributes this compound in course, medium or line grades. The medium grade which has been found to be suitable consists of a white crystalline compound in particulate form not dissimilar to common table salt or epsom salt. It has a density of 1.45 grams per cc, melts at or about l36.4 F, has a heat of fusion approximately four times as large as an equal volume of water and becomes anhydrous at 248 F. maitained at The heat of fusion of sodium acetate trihydrate permits consumption of heat at about 320 BTUs per pound in a relatively low temperature region, i.e., 136.4 F. Accordingly, the amount of heat energy absorbed by a particular volume of the compound may be calculated and this data, combined with the data for determining the amount of heat transferred to such volume, is adequate for use in the determination with a relatively high degree of accuracy the length of time a heat sink can be maintained at 136.4" F. Stated in a more general way, this compound will consume heat energy transferred to it in an amount determined by its volume, and at a rate proportional to the temperature increment in excess of the melting point.

In the past, the high heat of fusion of sodium acetate has given rise to its use in various commercial mixtures. For example, U.S. Pat. No. l,850,l66 Bell, issued Mar. 22, i932, relates to an improved heat storing mixture for warming devices, consisting of sodium acetate as the heat storing ingredient. in use, devices of this nature reduce the mixture employed, consisting primarily of sodium acetate trihydrate in Bell, to a liquid condition in a sealed compartment whereupon such liquid gives off its stored heat when returning to its crystalline condition. Known applications include food warmers, plates, dishes, coffee pots, foot warmers and the like, in which the receptacle may be warmed by placing it in boiling water until the mixture liquifies.

In the preferred embodiment, pure sodium acetate trihydrate is an exemplary heat absorbing substance used as a filler in amounts determined by a desired period of heat regulation at its melting point. Regulation characteristics are varied when various other substances are introduced into the mixture. Experimentation has been carried out with mixtures including varying amounts of heat resistant materials, such as particulate vermiculite, particulate perlite or fine sawdust. it is also possible to mix different heat absorbing substances with the sodium acetate trihydrate. This directly affects the melting point as well as the heat consuming capacity of the filler mixture. On the other hand, by mixing various insulative materials such as vermiculite with one or more heat absorbing substances, a heat barrier is provided in the same physical location as the heat sink.

It should be pointed out that a filler substance in particulate form is desirable, in that, among other things, it facilitates filling methods and quantitative measuring. A heat sink if formed in the cell at a level in proportion to the maximum consumption of heat energy for various specified standards, as discussed above. Accordingly, the void or space above the filler will vary. Any undesirable consequence of such space has been obviated by the present invention. Furthermore, use of only one or two walls having heat sinks is also expressly contemplated within the scope of the present invention.

Accordingly, an important feature of the present invention resides in the fact that the presence of air space is not critical in that the tiller substance is primarily a heat sink to absorb heat and not intended to function as a heat barrier. in this regard, the physical heat transfer characteristics of the structure may be employed to actually enhance the ability of the heat sink to protect the contents in the storage compartment. Of course, in a device of this type heat penetrating the outer heat barriers will seek the path of least resistance, thus, referring to FIG. 6 of the drawing, if heat penetrates slab 51, it will find its way to filler 44, and thereby be diverted from the inner compartment. This is not true in the vicinity of gasket 25 which presents a vulnerable area for heat leakage into the storage compartment via the upper edge of outer casing 32 to inner casing 33. Due to the general concentration of metalic elements in the area in the vicinity of the gasket, the asbestos buffering becomes less effective at extremely high temperatures. It is not uncommon for insulated storage devices to include problem areas such as this in the vicinity of the enclosure. Depending on the method of access there is always a peripheral edge that must be hermetically sealed to maintain humidity conditions. This edge leakage problem is obviated in the present invention by means of the mentioned heat conductive elements which provide a convenient path to the heat sink from the area of gasket 25. The importance of such elements is even more evident when considering the tendency of crystalline materials to settle during shipment and use. Absent such plates the air space or void so formed could tend to cause an increase in leakage to the compartment at high temperatures.

The Underwriters Laboratories, Inc., having recognized the liklihood of air spaces occuring regardless of filler level, has established an amount by weight that should be used for various labeling standards for fire resistant units using particulate fillers and having specifled container dimensions. Hence, standards are established notwithstanding existence of present or future voids. Of course, for economical reasons it is beneficial to use only that amount of filler necessary to fulfill requisite container protection characteristics. Regardless of container filler requirements, the mentioned conductive plates improve leakage characteristics in most instances and especially under extremely high temperature conditions where the cell is only partly filled.

In addition to such plates, asbestos sheet 65 may be utilized adjacent thereto to further enhance the function of the heat sink. This sheet acts as an auxiliary heat barrier and thereby deters radiation of heat inwardly from the plate and accordingly improves distribution of heat absorbed throughout the sink filler, thus further adding to the general protective properties.

Many advantages of the present invention are implicit if not explicit from the above description. One particular advantage is the ability of an insulated unit employing a heat absorbing particulate filler to efficiently stabilize the temperature of storage compartments therein at a relatively low temperature. For example, to obtain a UL label for storage cabinets for the storage of magnetic tapes and discs, microfilm, and the like, one of the several requirements is that a unit must be capable of maintaining the heat in the storage compartment at a maximum temperature of 150 F for a predetermined time period under external temperature conditions of 2,000 F. Thus, by providing a heat sink filler of sodium acetate trihydrate in a known amount for absorbing the heat transferred through insulated walls when subjected to such intense heat, the inner temperature can be stabilized at about 137 F for a predetermined period.

Another advantage is the nonflammable nature of inorganic salts such as sodium acetate trihydrate. Thus, intense heat conditions do not give rise to the danger of combustion or explosion during testing of prototypes or during an actual fire.

Furthermore, the particulate form of the filler material lends itself to convenient manufacturing methods. in this regard, the conductive plate obviates the need for packing under pressure. Any void that occurs from settling or that is specified implicitly from a requirement for filling with a predetermined quantity, is inconsequential. An air space is in fact desirable because when and if a fire does occur the filler material is subject to expansion. Even though in general practice units exposed to fire are replaced, the present invention makes it possible until a replacement is available to continue use without deleterious effects caused by the expansion of filler (in the liquid state) into the storage compartment. The filler is confined to its cell under expansion conditions, and thereby temporary or pennanent future use of the unit involved is possible.

it will be appreciated that many other advantages and features are presented by the above described invention. Furthermore, various changes can be made in the design and arrangement of parts without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.

I claim:

I. An improved heat resistant storage unit comprising A. a rectangular cabinet,

B. a storage container mounted within said cabinet,

said container comprising a removable top, a bottom wall and side walls affixed to said bottom wall and extending therefrom to form a rectangular storage compartment,

C. sealing means disposed in the area of adjacency between the peripheral edge portions of said top and said side walls,

D. said container side walls including at least one layer of insulating material,

E. a cell formed inwardly of said insulating layer in at least one of said side walls,

F. filler mean disposed in said cell, said filler means comprising particulate sodium acetate trihydrate,

G. heat conductive means,

H. means for mounting said heat conductive means in each of said side walls having a cell formed therein, whereby said heat conductive means is at least partly embedded in said particulate sodium acetate trihydrate., and

i. said mounting means adapted to retain said conductive means with one edge thereof terminating adjacent said sealing means to facilitate transfer of heat to said filler means via said conductive means under intense external heat conditions.

2. An improved heat resistant storage unit as set forth in claim 1 wherein said heat conductive means comprise a metal plate, and said mounting means are further adapted to retain said plate in parallel with the faces of the side wall within which it is mounted.

3. An improved heat resistant storage unit as set forth in claim 2 wherein said plate of heat conductive material includes a surface portion having dimensions substantially the same as the rectangular dimensions of said one side wall.

4. An improved heat resistant storage unit as set forth in claim 1 wherein said heat conductive means comprise a rectangular metal plate composed of a thin sheet of aluminum and said aluminum plate is substantially completely embedded in said particulate sodium acetate trihydrate.

* t: i t k

Claims

2. An improved heat resistant storage unit as set forth in claim 1 wherein said heat conductive means comprise a metal plate, and said mounting means are further adapted to retain said plate in parallel with the faces of the side wall within which it is mounted.
3. An improved heat resistant storage unit as set forth in claim 2 wherein said plate of heat conductive material includes a surface portion having dimensions substantially the same as the rectangular dimensions of said one side wall.
4. An improved heat resistant storage unit as set forth in claim 1 wherein said heat conductive means comprise a rectangular metal plate composed of a thin sheet of aluminum and said aluminum plate is substantially completely embedded in said particulate sodium acetate trihydrate.