US3265455A

US3265455A - Knockdown steel shelving and cabinet hardware therefor

Info

Publication number: US3265455A
Application number: US443119A
Authority: US
Inventors: Irwin J Ferdinand; Dale R Lopatka
Original assignee: Hirsh Manufacturing Co SA Co
Current assignee: Hirsh Manufacturing Co SA Co
Priority date: 1965-01-28
Filing date: 1965-01-28
Publication date: 1966-08-09
Anticipated expiration: 1983-08-09
Also published as: GB1131262A; NL6601063A

Description

g- 1966 'l. J. FERDINAND ETAL 3, 5,

KNOCKDOWN STEEL SHELVING AND CABINET HARDWARE THEREFOR Filed Jan. 28. 1965 4 Sheets-Sheet 1 m E m m w EO FL R WE L mm g- 1966 1. J. FERDINAND ETAL 3,265,455

KNOCKDOWN STEEL SHELVING AND CABINET HARDWARE THEREFOR Filed Jam 28, 1965 4 sheets-sheet 2 D m A OMK mm WR mEO .F 5 E M MD ATT'Y g- 9, 1966 1. J. FERDINAND ETAL 3,265,455

KNOCKDOWN STEEL SHELVING AND CABINET HARDWARE THEREFOR Filed Jan. 28. 1965 -4 Sheets-Sheet 3 3K)? 271%, 222 1%: '1. II

58 FIG'B I! h I I ma g 5 I "1 I w l WP O WEI v H I 1' I! f '8 i i I 20 v Q00 LL HI. j IO l0 25s Min HHIHHiii: mum mm... W] -+|7 204* 258 FIG. l4 F 1) I I I9 -I f I f .0 f r] I I I. I8 21+- I j I 258 L258 +|3 2 I INVENTORS IRWIN J. FERDINAND g- 9, 1965 l. J. FERDINAND ETAL 3,265,455

KNOCKDOWN STEEL SHELVING AND CABINET HARDWARE THEREFOR Filed Jan. 28. 1965 4 Sheets-Sheet 4 FIG. 16

ATTORNEY INVENTORS United States Patent 3,265,455 KNGQKDQWN STEEL SHELVING AND CABHNET HARDWARE THEREFGR Irwin .l. Ferdinand, Giencoe, and Dale R. Lopatlra, Glenview, iii, assignors to S. A. Hirsh Mfg. o., Siaoitie,

ill, a carp-oration of iilinois Fitted 28, 1965, Ser. No. 443,119 9 Ciairns. (Cl. 312295) This application is a continuation-in-part of our copending applications, Serial Nos. 184,045, now abandoned, and 362,150, filed April 2, 1962, and April 23, 1964, respectively.

The present invention relates to knockdown steel shelving of the type embodying vertically spaced horizontally disposed rectangular shelves which are releasably secured at their corners to vertical upright supports or corner posts. More specifically, the invention relates to a novel shelving unit wherein both the shelves and the corner posts are of improved design so that, individually, they inherently possess a high degree of weight bearing strength and rigidity and are so interrelated that when the parts are assembled with one another, they provide a novel rugged interfitting relationship of excellent appearance which is of great strength against buckling or side sway. The invention also is concerned with novel corner fastening means whereby the four corner regions of the various shelves are quickly and easily secured to the adjacent corner posts in rigid relationship that results partly from the interrelated design of the shelves and corner posts and partly from the provision of a concealed novel clamping means whereby the interfitting shelves and corner posts are drawn hard against one another. Still further, the invention is concerned with a novel arrangement of cabinet hardware whereby the steel shelving of the present invention may, by the application of such hardware, be expanded to a cabinet design with the normally open four 7 sides thereof, boxed in, so to speak, and with sliding door panels being provided at the front of the shelving.

The shelves which are associated with knockdown shelving of the type under consideration preferably are provided with downturned marginal strengthening flanges of plural thickness or full box design. Heretofore, in connection with such shelving, it has been considered essential in the interests of shelving rigidity to employ small strutlike reaction brackets (commonly referred to as corner clips) which extend at an angle of 45 between adjacent marginal flanges as shown in said application. These reaction brackets underlie the respective corner region of the shelves and have centrally located holes therein which are aligned with cooperating holes in the adjacent corner posts so that fastening bolts which are passed through the holes will serve to draw the posts inwardly of the shelves in a diagonal direction into corner notches which are provided for their reception.

Shelving of this arrangement has many advantages but is possessed of certain limitations, one limitation arising from the fact that the diagonal clamping action offered by the fastening bolts is divided into two vectorial thrusts, the directions involved being at right angles to each other. Furthermore, the thrusts involved are not direct thrusts but rather they are camming thrusts on a 45 bias so that an extra tightening force on the threaded parts of the fastening bolts is required to assure joint rigidity. Additionally, the corner clips involved must be designed to fit the flanges between which they extend and since, in several designs of the shelving the longitudinal flanges of the shelves differ from the transverse flanges, right and left hand types or corner clips must be supplied, and some difliculty is encountered therefrom in erecting the shelving despite painstaking directions which are supplied in the instruction sheets accompanying such shelving.

Patented August 9, 1966 Approximately ninety-eight percent of such shelving is designed for household consumer use and, therefore, ease of assembly is a primary consideration, secondary only to self rigidity and attractiveness when the installation is complete. Shelving designs which leave little to be desired from a functional point of view have been rejected for lack of ease of assembly and disassembly. Consumers upon occasion have been obliged to return to the seller for assistance in erecting the shelving, and sometimes even the seller has been unable to enlighten the consumer with comparatively simple constructions unless previously given instructions by the manufacturer. It follows therefore that the simpler the erection procedure involved in connection with a given design of shelving, the more favourable will be its reception on the competitive market.

The present invention is designed to overcome many of the limitations that are attendant upon the construction and use of present day steel knockdown shelving now on the market designed for household consumer use and, toward this end, the invention contemplates the provision of a novel shelving unit which offers advantages over present day shelving units, both functionally and from the standpoint of appearance and ease of assembly and erection.

Briefly, in carrying out the invention, the shelves are provided with full box-type marginal longitudinal flanges, three of which are rigidified by the provision of coextensive longitudinally extending ribs therealong. The fourth wall of each box flange incorporates a double thickness of sheet metal. Thus, extreme rigidity is offered in the long direction of the shelves. The corners of the shelves are notched or cut-away to expose the end edges of the thus rigidified box flanges and the exposed ends thereof are designed for clamping cooperation with the corner posts. The corner posts themselves are of three-quarter box desi n, i.e., channel shaped with the webs of the channels rigidified by coextensive ribs. The channel webs oppose the ends of the box flanges on the shelves and fastening means are provided for drawing the ribbed webs of the corner posts hard and directly against the open ends of the box flanges. The ribs of the corner posts bear against the edges of the double thickness walls of the box flange and also against the end edges of the ribs 0n the walls which oppose the double thickness walls so that workhardened portions of the shelf flanges and work-hardened portions of the adjacent corner posts cooperate with each other to assimilate the full tightening pressure of the fastening devices and, moreover, when the fastening devices are drawn tight, the metal of the corner posts in the vicinity of the ribs is self seating in the metal of the box flanges so that a direct rigidity is affected between the box flanges and corner posts which hasnot been present heretofore with earlier knockdown shelving employing diagonal corner clips. With such extreme rigidity between the corner posts and the longitudinal box flanges of the shelves, longitudinal rocking of the assembled shelving is eliminated even with high loading limits. Transverse rocking of the shelving is restrained by the inherent rigidity of the shelves along their short transverse dimension.

The invention further contemplates the provision of a novel form of corner fastening means whereby the upright corner posts are securely clamped against the end edges of the box flanges as set forth above. The clamping direction is a right angle one as distinguished from the acute angle one of the diagonal direction of clamping associated with shelving which employs corner bracing clips and it involves the use of a novel T-nut construction which cooperates with a fastening bolt which preferably is in the form of a coarse thread sheet metal screw. The T-nut is in the form of a small spring tempered sheet metal stamping which fits through a pair of aligned slots provided in the side walls of the associated box flange so that the T-nut effectively spans transversely across and through the box flange. The fastening screw associated with the T-nut is passed through one of a series of vertically spaced holes provided in the web portion of the channel-like corner post and it projects longitudinally into the open end of the box-flange and finds threaded engagement with a hole formed in the T-nut. Upon tightening of the fastening screw, the corner post is drawn directly against the open end of the box flange.

The hole in the sheet metal T-nut presents an on-edge helical thread upset in the direction against the load thereon for cooperation with the fastening screw and thus it is essential that the T-nut be inserted through the slots in the box flange so that the proper on-edge relationship will obtain. To prevent improper insertion of the T-nut through the slots, co-operation means on the T-nut and box flange are provided which assures proper T-nut insertion.

Means also are provided for latching the T-nut in position within the slots provided for it in the box flange so that after a preliminary insertion of the T-nut it can be either withdrawn or forced to its full limit within the box flange. When forced to its full limit it will not become dislodged during handling of the associated shelf as when manipulating the shelf into position against the various corner posts preparatory to applying the fastening screws. Thereafter, little occasion will arise requiring removal of the T-nut even if it is desired to change the elevation of a given shelf inasmuch as the T-nut once properly installed cooperates only with the shelf for reaction purposes and does not change its position in the box-flange, although the fastening screw may be moved to different locations along the corner post.

The provision of a shelving unit and corner fastening means of the character briefly outlined above being the principal object of the invention, it is another object to provide a shelving unit wherein all of the elements associated with the fastening means are substantially concealed from view when the erection procedure has been completed. This object is attained by the provision of a reinforced trim flange on each corner post which overlies and conceals the exposed head portions of the various associated T-nuts, and by locating the heads of the fastening screws deep within the channel portions of the corner posts so that they are visible only when seen from an unlikely point of view endwise of the shelving.

Insofar as the ability to convert the shelving unit of the present invention to a cabinet-type structure, no modification whatsoever of the basic shelving components is required and, by the addition to, and installation upon, the basic erected steel shelving, of the cabinet hardware of the present invention, the shelving unit may be expanded into a cabinet structure having side and rear enclosure panels with sliding door panels at the front of the various units Which cooperate to make up the shelving assembly and a double height cabinet can also be accomplished like a book case if desired.

The cabinet hardware of the present invention includes a novel door frame which interlocks with the front edge regions of adjacent superimposed horizontal shelves proper, the frame itself being of the knockdown type and having associated therewith novel corner fastening means whereby the horizontal components thereof may be secured to the vertical components at the corners of the frame. Sliding doors are provided within the door frame and these run in tracks or guideways which are of more or less conventional design. End panels are provided for enclosing the ends of the shelving units and these are receivable without hardware fittings or any modification whatsoever of the basic shelving components. Finally, the cabinet hardware includes retaining rails for a back panel and these retaining rails interlock with the front edge regions of adjacent superimposed horizontal shelves proper in a manner similar to that in which the front door frame interlocks with such shelves. All of the cabinet hardware is capable of assembly, both upon itself and upon the erected basic shelving, utilizing only fastening screws to effect the assembly.

Further objects of the invention contemplate shelving and cabinet conversion units wherein the principal constituent parts thereof are susceptible to conventional rolling processes and require for their completion no machining operations so that the shelving and cabinet hardware as a whole may be manufactured at a low cost; units which are rugged and durable and which will withstand rough usage and heavy loads; a construction which may be assembled and disassembled with the aid of only a single tool, namely a screw driver; one which possesses no sharp edges or corners and which is devoid of abrupt protrusions; one which allows for wide manufacturing tolerances; one which is attractive in its appearance and pleasing in its design; and one which otherwise is well adapted to perform the services required of it. These and further desirable features characterize the structure and production of embodiments of the present invention.

Other objects and advantages of the invention, not at this time enumerated, will readily suggest themselves as the nature of the invention is better understood.

In the accompanying four sheets of drawings forming a part of this specification, two illustrative embodiments of the invention have been shown.

In these drawings:

FIG. 1 is a fragmentary perspective view of a corner region of a shelving unit constructed in accordance with the principles of the present invention;

FIG. 2 is a sectional view taken substantially on the horizontal plane indicated by the line 22 of FIG. 1 and in the direction of thearrows;

FIG. 3 is a fragmentary inside or underneath perspective view of the corner region shown in FIG. 1;

FIG. 4 is a fragmentary exploded perspective view illustrating the manner of installation of certain corner fastening means associated with the shelving unit of the invention;

FIG. 5 is an exploded sectional view taken substantially on the horizontal plane indicated by the line 55 of FIG. 1 in the direction of the arrows and illustrating certain self-seating relationships which exist between the corner posts and shelves of the shelving unit;

FIG. 6 is an assembled sectional view similar to FIG. 5 and taken substantially on the horizontal plane indicated by the line 66 of FIG. 1 in the direction of the arrows;

FIG. 7 is a perspective view of a T-nut employed as an element of the fastening means of the present invention;

FIG. 8 is a plan view of the T-nut of FIG. 7;

FIG. 9 is an end view of the T-nut of FIG. 7;

FIG. 10 is a side view of the T-nut of FIG. 7;

FIG. 11 is a perspective view of a slightly modified form of T-nut capable of being employed in connection with the invention;

FIG. 12 is an enlarged sectional view similar to FIG. 2, showing the modified T-nut of FIG. 12 substituted in the assembly.

FIG. 13 is a front perspective view of a complete shelving unit showing the cabinet hardware of the present invention operatively installed thereon the original unit thus being expanded into a cabinet-like structure;

FIG. 14 is a front view of the structure shown in FIG. 13;

FIG. 15 is a fragmentary exploded perspective view of the corner region of a door frame employed in connection with the cabinet hardware of the present invention;

FIG. 16 is a fragmentary sectional view taken substantially along the vertical plane indicated by the line 1616 of FIG. 15, but with the parts assembled and with the fastening screw in position;

FIG. 17 is an enlarged fragmentary sectional view taken substantially along the line 1717 of FIG. 14, the view being limited to the door frame structure at the front of the shelving;

FIG. 18 is an enlarged fragmentary sectional view taken substantially along the line 1818 of FIG. 14, the view being limited to the door frame structure at the front of the shelving;

FIG. 19 is an enlar ed fragmentary sectional view taken substantially along the line 1Q19 of FIG. 14;

FIG. 20 is an enlarged fragmentary sectional view taken substantially along the line 202il of FIG. 14, the view being limited to the rear panel support at the rear of the shelving; and

FIG. 21 is an enlarged fragmentary sectional View taken substantially along the line 21-21 of FIG. 14, the view being limited to the rear panel support at the rear of the shelving.

Referring now to the drawings in detail and in particular to FIG. 1 wherein one corner region of a shelving unit constructed according to the present invention has been fragmentarily illustrated, the unit involves in its general or anization a series of four corner posts, only one of which has been illustrated and designated in its entirety at 10, and two or more shelves, one of which has been illustrated and designated in its entirety at 12. The various corner posts and shelves 112 are identical.

The shelves 12 and corner posts 10 are rigidly secured together in their operative assembled relationship by means of counterpart fastening devices each of which includes a T-nut 14 and a fastening bolt 16 in the form of an elongated sheet metal screw. The T-nut 14 constitutes a reaction member for assimilating the thrust of the fastening screw which serves to clamp the corner post It) rigidly to the shelf 12 in a manner that will be made clear presently.

The shelf 12 is generally of rectangular configuration and it includes a horizontal planar supporting or body portion 21 having downturned transversely extending marginal flanges 22 and downwardly and longitudinally extending marginal flanges 24. The transverse flanges 22 are single thickness flanges and are provided with reentrant reverse ends (FIG. 4) 2-6 at their lower edges for reinforcing purposes.

The longitudinal flanges 24 are box flanges and, as best seen in FIG. 4, each flange includes inside and

outside walls

28 and 30 respectively, a bottom wall 32 and a dual thickness top wall 34. The

walls

28 and 30 are reinforced by spaced apart reinforcing ribs 36, while the bottom wall 32 is reinforced by a single central rib 38. This rib 38 constitutes an important feature of the present invention in that it cooperates with a counterpart rib on the corner post 10 in a manner and for a purpose that will be made clear presently. The upper edge region of the box flange 24 projects a slight distance above the horizontal plane of the planar body portion 2t of the shelf 12 by reason of a vertical connecting flange 40 between the body portion and top wall 34, the flange 4t constituting a marginal restraining flange to prevent supported objects from rolling or sliding from the upper surface of the shelf. The four ribs 36 are inwardly rolled ribs while the rib 38 in the bottom wall 32 is an outwardly rolled rib. The four corners of the shelf 12 are notched or cut-away as indicated at 42 (FIG. 4)- for reception of selected regions of the corner posts therein in a manner that also will be described in detail subsequently.

The details of the corner posts 10 are best illustrated in FIGS. 1, 2 and 4. Each post is of rolled sheet metal construction, preferably of heavier gauge metal than that of the shelf 12 and comprises a main body portion of channel-shape cross section including

side walls

50 and 52 and a connecting web 54. The web is provided with a series of vertically spaced holes 56 therethrough for selective reception of the fastening screw 16 to the end that the shelf 12 may be secured to the post 10 at selected elevations therealong. The side wall 50 is provided with a narrow laterally turned trim flange 58. The side wall 52 is provided with a comparatively wide reentrant trim flange 62 which terminates in a lateral bearing flange 64- which is preferably overformed approximately 3.

The vertical corner post 10 is adapted to seat within the corner notch 42 with the web 54 of the channeLshaped body portion opposing and bearing against the adjacent open end or rim of the box flange 24 as best seen in FIGS. 1 and 2. The web 54 is formed with a central coextensive outwardly rolled rib 66 (FIGS. 1 to 6 inclusive) which makes a seat for the web when the post It? is drawn against the box flange 24. As will be described in greater detail presently, the manner in which the rib 66 cooperates with the rib 38 on the bottom wall of the box flange 24 and with the dual thickness top wall 34, constitutes one of the important features of the present invention.

When the corner post 10 is in its operative position within the notch 42 (FIGS. 1 and 2), the trim flange 58 overlies the outside face of the depending flange 22. Similarly, the trim flange 62 overlies the outside wall 31) of the box flange 24 and the bearing flange 64 opposes this Wall in close proximity thereto.

in order to fasten the corner post it} securely to the shelf 12 within the notch 42, the previously mentioned fastening device including the T-nut 14 and fastening screw 16 are provided. The T-nut 14 projects through and is anchored in a pair of transversely registering slots 7% and 72 (FIGS. 4, 6 and 7) formed in the outside and inside

walls

30 and 28 respectively and is designed for threaded engagement with the fastening screw 16 which is passed through one of the holes 56 in the channel web 54 and enters the open rim or end of the box flange 24 endwise as shown in FIG. 2.

The T-nut 14 is of sheet metal construction and, as shownin FIGS. 8 to 11 inclusive, it is in the form of a stamping having a flat generally rectangular body or shank portion 74 provided with marginal side flanges 76 which are split longitudinally as at 78 to form retaining latch fingers St? which extend at a small angle to the planes of the flanges 76. The fiat shank portion 74 is the working portion which engages the edges of the slots "iii and 72 for reaction purposes.

The T-nut is preferably formed from spring steel stock so that the latch fingers 8ft retain their small angle bias but are capable of being deflected inwardly to permit entry of the body portion of the T-nut into and through the slot 70, after which the fingers 80 will again become spread apart to retain the T-nut in position against a dislodgment from the box flange 24. The T-nut 14 is further provided with a T-head 82 which bears against the outside face and the outer wall 70 of the box flange 24 when the T-nut is in its installed position. Preferably the head 82 has spring ends 83 thereon which are inclined out of the general plane of the head Siland deflect slightly when the T-nut is thrust home with force to provide clearance for the latch fingers 80 to attain their latching positions. Additionally, the ends 83 serve to properly center the T-nut in position between the two

walls

28 and 30 so that when the fastening screw 16 is tightened, the adjacent edge of the outside wall will not oppose the nar-' row area of the body portion of the T-nut at the base of the T-head 80, such area being unsupported by the side flanges 76. In other words, the spring ends 83 limit the extent to which the T-nut may be pushed into the slots 70 and 72.

The body of shank portion 74 of the T-nut is formed with an opening 84 therethrough of keyhole design and the marginal region 86 of this opening is progressively outstruok or raised to provide a helical edge 88 (FIGS. 7, 8, 9 and 11) which is offset bodily away from the working face of the body portion 74 to constitute a oneturn tooth designed for threaded cooperation with the threaded fastening screw 16. Since the fastening screw 16 may enter the opening 84 for proper on-edge cooperation with the helical edge 88 by extending axially of the opening in one direction only, a blocking ear or flange 90 (FIG. 4) projects partially across the slot '70 from one side thereof and allows entry of the T-nut 14 in only the proper position of orientation. When the T-nut 14 is operatively installed within the box flange 24, it will assimilate the pulling force of the threaded clamping or fastening screw 16, thus constituting a reaction element for the screw. The reaction force of the T-nut is, in turn, balanced on and assimilated by corresponding side edges of the slots 70 and 72 in the

side walls

30 and 28 respectively.

In assembling the corner post upon the shelf 12, the T-nut 14 will first be operatively installed in the box flange 24. This operation may be effected by aligning the body portion 74 of the T-nut with the registering slots '70 and '72 so that the side flanges 7 6 straddle the blocking flange 91B and thereafter forcing the T-nut endwise through the slot 70 until the T-head engages the outside face of the side wall 313 of the box flange 2 4. The spring ends 83 and latch fingers 8% will yield to allow entry of the T-nut through the slot 711 and, after the fingers have passed through the slot, they will snap into locking position as shown in FIG. 9. Thereafter the T-nut may not be removed from its installed position and the shelf 12 may be handled without danger of the T-nut falling from its installed position preparatory to application of the fastening screw 16.

The proper hole 56 in the corner post 10 is then selected for the desired shelf elevation and the fastening screw 16 is passed endwise through this hole and caused to enter the adjacent open end of the box flange 24 and make threaded engagement with the thread-providing opening 84 of the previously installed T-nut. Tightening of the fastening screw with the aid of a suitable tool such as a screwdriver will bring the rib 66 of the corner post into register and engagement with bot-h the dual thickness top Wall 34 of the box flange 24 and the rib 38 in the bottom wall thereof, while at the same time the

trim flanges

58 and 6 2 (FIG. 2) will assume their overlying relationship with respect to the

flanges

22 and 24 as previously described, the trim flange 6-2 serving to conceal the head 82 of the T-nut 14.

It is to be particularly noted at this point that upon final tightening of the fastening screw 16 the vertically disposed rib 66 (FIGS. 5 and 6) will be drawn hard against the dual thickness top wall 34 of the box flange 24 and will actually crush the metal of the adjacent edges of this dual thickness wall sufficiently to establish a self formed seat such as has been indicated at 92 in FIG. 5. Similarly and as shown in FIG. 6, this rib 66 will be drawn hard against the adjacent edge of the horizontal rib 36 on the bottom wall 32 of the box flange 24 and will establish a self-formed seat 94. The creation of these two spaced apart self-formed

seats

92 and 94 greatly rigidify the corner post and self-assembly against rocking movement of the shelving in a transverse direction so that it is not essential that cross braces or the like be employed in connection with the shelving. Rigidity of the shelving against rocking movement in a longitudinal direction is, of course, inhibited by the extreme rigidity of the box flange 24 when under on-edge compression.

It is also to be noted that the vertical extent of the slots 70 and 72 is substantially equal to the distance between the center lines of the two horizontally extending ribs 36 on the walls and 28 so that the opposite ends of the slots lie directly at the apices of the ribs. Thus, when lateral pulling force is applied to the T-nut by the fastening screw 16, the reaction force offered by a portion of each of four ribs 36 prevents peeling or tearing of the sheet metal of the box flange 24 at the corners of the slots 70 and 72.

Finally, it is to be noted that because the trim flange 62 conceals the head portion 82 of the T-nut 14 and because the head of the fastening screw 16 is disposed deep within the channel portion of the vertical corner post 10, all portions of the composite fastening mean-s are substantially concealed from view. Although the head of the fastening screw 16 may be seen when the shelving is viewed on end through a small limited angu lar range of viewing, such viewing of the shelving is seldom available when the shelving is put to use.

It has been stated previously that the spring fingers 8 3 on the T-head 82 of the T-nut 14 serve to prevent the adjacent edge region of the outside wall 30 of the box flange 24 from registering with or opposing the narrow area near the base of the T-head when the fastening screw 16 is drawn taut. A more positive means for preventing the T-nut from being pushed too far through the slots 71) and 72 is provided in connection with the modified form of T-nut 114 shown in FIGS. 11 and 12. Additionally, means are provided in connection with the T-nut 114 for insuring that the T-nut will be pushed sufficiently far into the registering holes 71? and 72 and remain so positioned that the distal edge of the T-nut remote from the T-hea-d will register with the inside wall 28 so that the latter may assimilate the lateral thrust of the T-nut when the fastening screw 16 is drawn taut.

The T-nut 114 of FIGS. 11 and 12 is similar in many respects to the T-nut 14 and therefore, in order to avoid needless repetition of description, corresponding reference numerals, but of a higher order, have been applied to the various corresponding parts as between the disclosures of FIGS. 2 and 8, and FIGS. 12 and 13, these two pairs of views being similar in their disclosures.

Referring now to FIGS. 11 and 12, the T-nut 114 remains substantially the same as the T-nut 14 except for the addition to the T-nut 1 14 of an inclined outwardly extending flange 175 along the edge of the body portion 174 remote from the T-head 182, and also the addition of a transverse rib 177 on the body portion 174 near the base of the T-head 182. When the T-nut 114 is in position within the slots and 72 as shown in FIG. 13, the inclined flange interlocks with one side edge of the slot 72 and prevents axial shifting of the T-nut outwardly of the shelf 12. Similarly, with the T-nut 114 in position, the rib 1'77 interlocks with one side edge of the slot 7t and prevents inward movement of the T-nut 114 at the time of installation to such an extent that the edge of the slot 71? might become misaligned with the main body portion 174 and oppose or register with the narrow area of the body portion 174 near the base of the T-head and which is not reinforced by the side flanges 175. In connection with the T-nut 1 14, the spring fingers 183 do not exert a centering function on the T-nut as a whole. However, their inclination prevents them from protruding unduly from the surface of the outside flange 30 so that they are unlikely to con-. stitute obstructions for interference with adjacent objects such as the clothing of a person in the vicinity of the shelving. Otherwise the T-nut 114 functions in a manner similar to the T-nut 14. The T-nuts 14 and 114 are, obviously, useable interchangeably with the illustrated shelving of the present invention.

FIGS. 13 to 21, inclusive, illustrate the cabinet hardware by means of which the primary shelving just described may be expanded quite easily into a cabinet-type structure by closures for the normally open sides thereof. Particularly referring to FIGS. 13 and 14, closure means are provided whereby a door frame'200 may be applied to the front of any given shelving unit and supported on the upper edge of flange 40 on the lower shelf and the lower or bottom wall or edge 32 of a flange 40 on the upper shelf of a selected pair of vertically spaced shelves 12 respectively. A pair of sliding

door panels

202 and 204 are utilized to form a closure for the normally open front of the shelving. Ordinarily, the door frame 261) will be of such height and the installation thereof made so that the frame bridges the distance between the extreme uppermost shelf and the extreme lowermost shelf in the series of shelves. However, by selection of the proper door frame height, any two shelves 12, including adjacent shelves, if desired, may be thus bridged by the door panels 2&2 and 2tl4. For example, if a given shelving unit contains four superposed shelves 12, and the door frame extends between the uppermost and the lowermost shelves, the completed cabinet will have two enclosed intermediate shelves within the same. The presence or absence of intermediate shelves is a matter of choice and does not affect the nature of the installation.

The cabinet hardware further includes a pair of steel retaining channels or rails 206 and 208 (FIGS. 20 and 21) for a back panel closure 210, and end panel closures 212 for closing the openings at the normally open ends of the shelving the nature and installation of which will be described subsequently. The panels 212 are receivable in the shelving structure without the use of retaining hardware as will also be described presently.

Referring now to FIGS. and 19 inclusive, the front panel closure includes a door frame 200 comprising a horizontally disposed upper and lower compound rolled

steel frame members

214 and 216 and vertically dis posed side [

frame members

218 and 220. The upper and

lower frame members

214 and 216 are identical and there fore a description of one of them will sufiice for the other. However, in the utilization of these two frame members the respective vertical orientations thereof are reversed, the lower member 210 being turned 180 end for end with respect to the upper member 214.

As best seen in FIGS. 15 and 18, the lower horizonta door frame member 216 is generally of S-shaped channel configuration in cross section and it includes a downwardly facing hook portion 222 which hooks over the front upstanding top wall 34 of the raised or upwardly pnojecting portion of the front box flange 24 of the lowermost shelf 12, and an oppositely upwardly facing cradle or channel portion 224 which lies outside the confines of the shelving unit as a whole. The frame member 216 is substantially coextensive with the width or extent of the shelving unit. The hook portion 222 includes an inside leg 226 which lies flush with the flange 40, an outside leg 228 which lies flush against the wall 30 of the box flange 24, and a flat connecting bight portion 230 which rests upon the top wall '34.

The channel portion 224 includes an outside leg 232, an inside leg which is the previously mentioned common leg 228, and a connecting bight portion 234. The tbight portion 234 constitutes the top wall of the downwardly facing hook portion 222, while the bight portion 234 constitutes the bottom wall of the upwardly facing cradle portion or channel 224.

As previously mentioned, the upper horizontal door frame member 214 is identical with the lower door frame member 216 but is inverted so that the hook portion 222 may hook under the bottom wall 32 of the box flange 24 of the uppermost shelf 12 and so that the channel portion 224 establishes a downwardly facing channel which opposes the upwardly facing channel established by the corresponding channel portion of the lower door frame member 216. As will be described in detail presently, the two opposing channels serve to support and confine therebetween the two sliding

door panels

202 and 204, together with certain guide rail and cushioning structure whereby the two door panels are maintained in their respective offset planes of horizontal sliding movement, cradle portion 224 (FIGS. 15 and 18) having a narrow inturned retaining flange 236 for this purpose.

Referring now to FIG. 15, the two vertical

door frame members

218 and 220 are identical so that a description of one of them will suffice for the other. Each side member 218 is generally of Z-shape configuration in transverse cross section and includes a relatively wide outer flange 240, a narrow inner flange 242 and a connecting frame 244 defining a channel similar to channel 224.

id The outer flange 240 is provided with a reversely turned marginal flange 246. The respective inner flanges 242 are received in clamped relationship between the front box flanges 24 of the shelves and the flanges 64 of the front corner posts 10.

Novel corner fastening means are provided at each of the four corners of the door frame 200 each [fastening means constituting a connection 'between one of the horizontal frame members and an adjacent vertical frame member. One of these corner fastening means is shown in detail in FIG. 15. The outside flange 240 of the side frame member 218 and the outside flange 232 of the bottom frame member 216 are each mitered at 45 as indicated at 256) and 252 respectively, and the two

inturned flanges

246 and 236 are likewise mitered as at 254 and 256 respectively so that when the adjacent ends of the two

frame members

218 and 216 are brought together in their proper relationship, the miters mate to provide a flush and hair line joint indicated at 258 as shown in FIGS. 13 and 14.

The joint 258 is reinforced and maintained secure by means of a backing reinforcement in the form of a bracket 266 which is suitably spot welded or otherwise permanently secured to the side frame member 218. The bracket 269 includes a flat rectangular base plate 262 secured to the inside face of the connecting flange 244, a laterally turned side flange 264 secured to the outside leg 232 of the member 218, and a shelf portion 234 of the cradle portion 224 of the frame member 216 by means of a pair of spacer tabs 268. The shelf portion 266 is formed with a threaded hole 270 in the central region thereof, this hole registers vertically with a tapered hole 272 formed in the bight portion 234 of the cradle portion 224 (FIG. 16). A V-head sheet metal screw 274 passes through the two

holes

270 and 272 and draws the two adjacent ends of the

frame members

216 and 218 together.

It will be understood that the corner fastening means disclosed in FIG. 15 and described above is duplicated at each of the three other corners of the door frame 200.

The sliding door arrangement which is associated with the assembled door frame 20%) is best illustrated in FIGS. l7, l8 and 19. As shown in these views, the two sliding doors 2'92 and 294 are held in their proper offset sliding relationship at the top and bottom of the door frame by antifriction guide members 275 which may be formed of a suitable plastic material and each provides a pair of

guide channels

276 and 278 for the two

doors

202 and 204 respectively. The guide channels provide vertical clearance whereby the doors can be inserted in the top channel, raised to clear the bottom channel, pushed in at the bottom channel for slidable support. The base portion 284) of the upper guide member 265 is fixedly secured to the bight portion 234 of its respec tive cradle portion 224 by means of an elongated strip of adhesive tape 282, both sides of which are of an adhesive nature. The base portion of the lower guide member is similarly secured to its respective bight portion 234 by two such strips of tape 284 between which there is sandwiched a spacer strip 286 which is provided for the purpose of maintaining the elevation of the guide member sufliciently high that equal exposure of the two members 275 at the top and bottom of the door frame will occur for appearance purposes.

It will be observed that once the door frame is assembled, with or without the doors in place it can be easily slipped edgewise in a horizontal direction onto the supporting shelves before the last front post is assembled and before the other front post is tightened into position. The hook portions 222 will slide onto the box flanges 24 of the respective shelves and the inner flanges 242 (FIG. 19) will be clamped under the edges of the bearing flanges 64 on the trim flanges 62 of the front posts 10 when they are finally tightened into place.

It has been stated previously that no modification of the basic steel shelving illustrated in FIGS. 1 to 12 inclusive is required for installation of the cabinet hardware described above. However, if desired, the outwardly rolled ribs 38 on the bottom walls 32 of the box flanges 24 of the various shelves 12 may be omitted so that the hook portions 222 will lie flush with the raised

portions

34 and 40 of the box flanges. Ordinarily, Where heavy gauge steel is employed for the shelving, the ribs 38 will be omitted and are not shown in FIGS. 15, 17, 18 and 20. But, where light gauge steel is employed, the ribs 38 will be retained for reinforcing purposes since the shelving, per se, is marketed for use with or without the cabinet hardware of the present invention.

As shown in FIGS. 13 and 19, the end panels 212 may be rabbeted at their vertical side edges as indicated at 291) in FIG. 19 so that these side edges will fit behind the trim flanges 58 associated with the vertical corner posts 1!} in securely clamped relationship, when the screws 16 are tightened, the fastening screws 16 serving to draw these trim flanges against the edges if the panels 212 and in turn, hold the latter against the end edges of the shelves 12. The panels 212 may terminate flush with the upper surface of the uppermost shelf 12 as shown in FIG. 13, or they may be full-height panels which terminate flush with the extreme upper ends of the corner posts If No cabinet hardware is required for holding these end panels 212 in position, the fastening screws 16 being the sole panel-clamping means employed.

Referring now to FIGS. 20 and 21, the back panel 210 (see also FXG. 13) can like the door frame be slipped edgewise into place just before the last rear post 10 is assembled and thereafter the panel is held in position between two generally Z-shaped steel channel strips 301? and 392 of identical configuration but inverted to each other in their respective positions. The lower strip 302 presents an inverted hook portion 304 which hook over the top wall 34 of the rear box flange 24 on the lowermost shelf 12 and an upright cradle channel portion 306 which supports the lower edge of the'back panel 211). Similarly, the upper strip 300 presents an upright hook portion 304 which hooks under the bottom wall 32 of the rear box flange 24 and an inverted cradle channel portion 306 which opposes the cradle portion of the lower strip 302 and confines the upper edge of the back panel 210. The two strips 300 land 3192 constitute the sole vertical supporting means for the back panel while the facing overformed flanges 64 of the rear corner posts 10 wedge and prevent horizontal and rearward displacement at the side edges thereof.

Referring again to FIGS. 1 and 2, it will be observed that the uppermost shelf 12 is installed upon the four corner posts 10 so that it lies an appreciable distance below the horizontal plane of the upper ends of the corner posts. To lend a finished and attractive appearance to the cabinet structure, a table-type top 310 of rectangular design may be positioned on the upper ends of the four corner posts and secured thereto in any suitable manner or, alternatively, allowed to rest thereon by gravity. The uppermost shelf 12 thus constitutes an intermediate storage shelf immediately below the table top 3 10. If desired, the end panels 212 may extend upwardly to the level of the table top 3 10 or they may terminate flush with the uppermost shelf 12 as shown. If the table top 312 is omitted, the uppermost shelf 12 may be disposed substantially in the horizontal plane of the upper ends of the four corner posts with their ends closed and the height of the side panels 212 and the back panel 210, as well as the door frame 200, may be such as to effect complete enclosure of the space within the shelf outlines.

It is to be noted that the herein described cabinet hardware lends itself readily to multiple installation on superposed shelf units. As shown in FIG. 17, the upwardly projecting portion of the box flange 24 is available for reception thereover of the hook portion 222 of a second door frame assembly which may be installed immedi ately above the illustrated door frame assembly without interference by the latter. Similarly to downwardly projecting portion of the box flange 24 as shown in FIG. 18 is available for reception thereunder of the hook portion :222 of a lower door frame assembly, the shelves being spaced to accommodate the double height cabinet.

The invention is not to be limited to the exact arrangement of parts shown in the accompanying drawings or described in this specification as various changes in the details of construction may be resorted to without departing from the spirit of the invention. For example, whereas no cross bracing for the shelving has been illustrated herein and none is considered necessary, such can be used if desired by the customer as where the height of the shelving with one unit on another is deemed to require it. Additionally, while the terms long longitudinal and transverse in the above description refer to the long and short dimensions respectively of the shelf 12, obviously the box flange 24 may extend marginally along the short dimension of the shelf if desired. Therefore, only insofar as the invention has partciularly been pointed out in the accompanying claims is the same to be limited.

What is claimed is:

1. In combination, a steel shelving unit including a pair of vertical front corner posts having trim flanges, upper and lower vertically spaced horizontal shelves secured at their front corners to said corner posts, the front edges of said shelves in combination with said trim flanges of the corner posts defining a rectangular front access opening communicating with the interior of the shelving, a rectangular door frame including upper and lower horizontal frame members extending between said corner posts and vertical side frame members extending between the two shelves and having inner flanges alongside said vertical side frame members disposed in supported relation between aid trim flanges and front edges of said shelves, means for securing the upper horizontal frame member to the front edge region of the upper shelf, in mutually supported relationship, means for securing the lower horizontal frame member in supported relation to the front edge region of the lower shelf, said upper frame member presenting a downwardly facing channel portion and said lower frame member presenting an upwardly facing channel portion opposed to said downwardly facing cradle portion, an anti-friction guide strip disposed in each cradle portion and substantially coextensive therewith, each guide strip being formed with a medial flange thereon dividing its respective cradle portion into inner and outer channels, an outer door panel having its upper and lower edges slidable in the outer channels defined by said guide strips, and an inner door panel having its upper and lower edges slidable in the inner channel defined by said guide strips.

2. In a rectangular sheet metal door frame of the character described, upper and lower horizontal frame members and vertical side frame members, the upper frame member defining an elongated narrow horizontal top Wall, the lower frame member defining an elongated narrow horizontal bottom wall, the side frame members each defining a narrow elongated vertical side wall, each vertical side Wall being disposed in edge-to-edge abutting relationship with an adjacent horizontal wall, each of said walls being formed with an inwardly extending front flange with all of said flanges lying in a common vertical plane, the end regions of said flanges being relieved on a 45 bias with the adjacent relieved edges abutting each other in edge-to-edge relationship, and means for rigidly securing each pair of abutting wall edges together in their respective edgeto-edge relationship, said means comprising an attachment bracket including a base plate welded in face to face relationship to the associated vertical wall, a laterally turned vertical flange on said base plate disposed in face-to-face relationship against the adjacent front flange on said associated vertical wall, and a laterally turned horizontal shelf flange spaced from and parallel to the associated horizontal wall, the distal edge of said horizontal shelf flange being provided with a lateral spacer foot engaging said associated horizontal wall, there being vertically aligned holes in said laterally turned horizontal shelf flange and said associated bottom wall, and a fastening screw projecting through the hole in said associated bottom wall and threadedly received in the hole in said laterally turned horizontal shelf flange.

3. In an adjustable knock down sheet metal shelving unit the combination of vertically spaced generally rectangular horizontally disposed shelves each having a flat shelf portion and a vertical flange portion along one edge extending an appreciable distance above and below the shelf portion, elongated upright corner posts secured to the shelves in shelf supporting relationship, each corner post having a trim flange portion overlapping respective end portions of said flange portions of the vertically spaced shelves, a rectangular sheet metal door frame supported by said flange portions including upper and lower horizontal frame members and vertical side frame members, the upper frame member defining an elongated narrow horizontal top wall marginally terminating in a reentrant channel portion encompassing the lower edge of the flange portion of the upper shelf, the lower frame member defining an elongated narrow horizontal bottom wall marginally terminating in a reentrant channel portion received and resting on the upper edge of the flange portion of the lower shelf, the side frame members each defining a narrow elongated vertical side wall having a marginal flange on one side resting against the faces of said depending flange portions and received under and restrained by said trim flange portions of said corner posts, each vertical side wall being disposed in edge-toedge abutting relationship with an adjacent horizontal wall, each of said walls being formed with an inwardly extending front flange with all of said front flanges lying in a common vertical plane, the end regions of said front flanges being relieved on a 45 bias with the adjacent relieved edges abutting each other in edge-to-edge relationship, rigidly securing each pair of abutting wall edges together in their respective edge-to-edge relationship a unitary attachment bracket including a base plate on the associated vertical wall, a laterally turned vertical flange on said base plate disposed in face-to-face relationship against the adjacent front flange on said associated vertical wall, a laterally turned horizontal shelf flange spaced from and parallel tothe associated horizontal wall, the distal edge of said horizontal shelf flange being provided with a lateral spacer foot engaging said associated horizontal wall, there being vertically aligned holes in said laterally turned horizontal shelf flange and said associated bottom wall, and a fastening screw projecting through the hole in said associated bottom wall and threadedly received in the hole in said laterally turned horizontal shelf flange against mislaignment under mutually reinforcing pressures exerted between said channel portion and the marginal flanges by the shelf flanges and post flanges.

4. The combination comprising a knockdown sheet metal shelving unit having vertically spaced horizontally disposed rectangular shelf members supported upon upright corner posts,

each shelf member being provided with a marginal flange which has a depending portion projecting downwardly an appreciable distance below the general plane of the shelf,

said corner posts being of uniform crosssectional contour throughout their lengths and having horizontally extending trim flanges overlapping the ends of said projecting flange portions to define a space between them and an opening between the shelf flanges to the shelf area between said shelves,

a closure for said opening including a closure member disposed in the plane of said trim flanges and having vertical marginal edges received in said spaces and 14 engaged in supported relationship by said trim flanges and shelf flanges against relative movement in any horizontal direction,

and means interengaging said shelf members and the upright corner posts for looseness of one of said shelf members to release said closure member from said supported engagement during assembly and disassembly thereof with respect to the shelving unlt and involving relative movement of one of the shelves with respect to the corner posts.

5. The combination called for in claim 4 in which said shelf and depending flange portion are cut away at each corner region to receive the corner posts and said interengaging means including threaded means 1nterengaging the posts and the flange portion at each end thereof for drawing the posts towards and against the end of the flange portions and telescoping and securing said marginal edges in said space between said trim flanges and the flange portions to rigidify the assembly as a unitary assembly.

6. The combination comprising a knockdown sheet metal shelving unit having vertically spaced horizontally disposed rectangular shelves supported upon upright corner posts, I

each shelf being provided with a longitudinal margmal vertical flange which has portions projecting upwardly and downwardly appreciable distances above and below the general plane of the shelf,

said corner posts having trim flanges overlappmg the ends of said projecting flange portions to define therewith an opening that provides access to the space between said shelves,

a closure assembly for closing said opening including channel members having channel portions disposed in the plane of said trim flange-s and opening towards each other and also hook portions in the plane of the vertical flanges engaging the projecting flange portions which define the top and bottom of said openings,

means interengaging said channel members to hold said hook portions in engagement with said projecting flange portions against relative vertical movement,

said trim flanges engaging said interengaging means for holding same against lateral horizontal movement, and

means releasably interengaging one of the corner posts and said shelves for lateral movement thereof for disengaging and engaging the trim flanges and said interengaging means during assembly and disassembly.

7. The combination comprising a knockdown sheet metal shelving unit having upper and lower vertically spaced horizontally disposed rectangular shelves supported upon upright corner posts,

the lower shelf being provided with a front marginal upstanding flange portion which projects upwardly an appreciable distance above the general plane of the shelf and the upper shelf being provided with a front marginal downwardly projecting flange portion which projects downwardly an appreciable distance below the general plane of the shelf,

said corner posts and shelf flanges defining a cage-like shelving structure having a normally open front exposing the interior of the structure,

a closure assembly for closing said open front including upper and lower horizontal sheet metal channel members,

the upper channel member having an upwardly facing hook portion along one edge engaging th d wardly projecting flange portion of the upper shelf,

the lower channel member having downwardly facing hook portion along one edge engaging the upwardly projecting flange portion of the lower shelf,

said channel members having channels along their other edges opening toward each other,

and a pair of door panels carried in said channels and independently movable therein between relative positions in one of which they close said opening and in another one of which they close only a portion of said opening.

8. The combination comprising a knockdown sheet metal shelving unit having upper and lower vertically spaced horizontally disposed rectangular shelves supported upon upright corner posts having trim flanges,

each shelf being provided with a depending marginal flange having a portion which projects upwardly a slight distance above the general plane of the shelf,

said corner posts and shelves defining a cage-like shelving structure with openings at the front and back which expose the space between the shelves,

a closure assembly for closing one of said openings of said shelving unit and comprising a rectangular door frame including upper and lower horizontal sheet metal frame members and vertical frame members disposed between said trim flanges,

the upper frame member being provided with a downwardly facing channel portion and a substantially coextensive upwardly facing hook portion encompassing the depending flange of the upper shelf,

the lower frame member being provided with an upwardly facing channel portion opposing said downwardly facing channel portion and a substantially coextensive downwardly facing hook portion encompassing said upwardly projecting flange portion of the lower shelf,

double groove door slide track members facing each other secured in said opposing channel portions, and

a pair of sliding door panels slidably mounted each in a horizontally spaced pair of said grooves and independently movable therein between relative positions wherein they close the normally open side of said shelving unit and expose at least a portion of the interior of the shelving unit in another position,

said vertical frame members engaging said trim flanges and being held thereby against lateral movement induced by the sliding of the doors.

9. The combination comprising a knockdown sheet metal shelving unit having upper and lower vertically spaced horizontally disposed rectangular shelves supported upon upright corner posts having trim flanges,

each shelf being provided with a depending marginal flange having its upper edge portion exposed above the general plane of the shelf,

said corner posts and shelves defining a cage-like shelving structure with openings at the front and back which expose the space between the shelves, a closure assembly for closing one of said openings of said shelving unit comprising a plurality of doors 5 and a rectangular door frame for supporting doors movably therewithin and including upper and lower horizontal sheet metal frame members engaging the vertical faces of said flanges and vertical side frame members disposed between said trim flanges, the upper frame member being provided with a downwardly facing channel portion and a substantially coextensive upwardly facing hook portion encompassing the depending flange of the upper shelf, the lower frame member being provided with an upwardly facing channel portion opposing said downwardly facing channel portion and a downwardly facing portion engaging said upper edge portion of the lower shelf in supported relationship, said vertical frame members having laterally extending flange elements disposed between said trim flanges and said vertical faces of said shelf flanges and being held thereby against lateral and outward movements with respect to the shelves under action of said movement of the doors.

References Cited by the Examiner UNITED STATES PATENTS CLAUDE A. LE ROY, Primary Examiner.

45 FRANK B. SHERRY, CHANCELLOR E. HARRIS,

Examiners.

F. DOMOTOR, Assistant Examiner.

Claims

1. IN COMBINATION, A STEEL SHELVING UNIT INCLUDING A PAIR OF VERTICAL FRONT CORNER POSTS HAVING TRIM FLANGES, UPPER AND LOWER VERTICALLY SPACED HORIZONTAL SHELVES SECURED AT THEIR FRONT CORNERS TO SAID CORNER POSTS, THE FRONT EDGES OF SAID SHELVES IN COMBINATION WITH SAID TRIM FLANGES OF THE CORNER POSTS DEFINING A RECTANGULAR FRONT ACCESS OPENING COMMUNICATING WITH THE INTERIOR OF THE SHELVING, A RECTANGULAR DOOR FRAME INCLUDING UPPER AND LOWER HORIZONTAL FRAME MEMBERS EXTENDING BETWEEN SAID CORNER POSTS AND VERTICAL SIDE FRAME MEMBERS EXTENDING BETWEEN THE TWO SHELVES AND HAVING INNER FLANGES ALONGSIDE SAID VERTICAL SIDE FRAME MEMBERS DISPOSED IN SUPPORTED RELATION BETWEEN SAID TRIM FLANGES AND FRONT EDGES OF SAID SHELVES, MEANS FOR SECURING THE UPPER HORIZONTAL FRAME MEMBER TO THE FRONT EDGE REGION OF THE UPPER SHELF, IN MUTUALLY SUPPORTED RELATIONSHIP, MEANS FOR SECURING THE LOWER HORIZONTAL FRAME MEMBER IN SUPPORTED RELATION TO THE FRONT EDGE REGION OF THE LOWER SHELF, SAID UPPER FRAME MEMBER PRESENTING A DOWNWARDLY FACING CHANNEL PORTION AND SAID LOWER FRAME MEMBER PRESENTING AN UPWARDLY FACING CHANNEL PORTION OPPOSED TO SAID DOWNWARDLY FACING CRADLE PORTION, AN ANTI-FRICTION GUIDE STRIP DISPOSED IN EACH CRADLE PORTION AND SUBSTANTIALLY COEXTENSIVE THEREWITH, EACH GUIDE STRIP BEING FORMED WITH A MEDIAL FLANGE THEREON DIVIDING ITS RESPECTIVE CRADLE PORTION INTO INNER AND OUTER CHANNELS, AN OUTER DOOR PANEL HAVING ITS UPPER AND LOWER EDGES SLIDABLE IN THE OUTER CHANNELS DEFINED BY SAID GUIDE STRIPS, AND AN INNER DOOR PANEL HAVING ITS UPPER AND LOWER EDGES SLIDABLE IN THE INNER CHANNELS DEFINED BY SAID GUIDE STRIPS.