Sliding door

April 21, 1964

3,129,752

T. C. WHITING

SLIDING DOOR

<img file="US3129752A_D0001.tif" />

ATTORNEYS,

April 21, 1964

T. C. WHITING

SLIDING DOOR

3,129,752

<img file="US3129752A_D0002.tif" />

United States Patent Office

3,129,752

Patented Apr. 21, 1964

3,129,752

SLIDING DOOR

Theo C. Whiting, Akron, N.Y., assignor to T. Whiting Ivlfg. Inc., Akron, N.Y., a corporation of New York

Filed Nov. 25, 1960, Ser. No. 71,828

Ciaims. (Ci. 160—363)

This invention relates to a door and is more particularly illustrated as embodied as a door for closed cargo trucks to close and render weather-tight the doorway through which the cargo is taken into and removed from the truck. However the invention can be embodied in closures for stationary structures, such as garages, business places and homes, or closures for other mobile structures.

One of the principal objects of the invention is to provide a closure which can be manually moved to its open and closed positions and which is very low in cost while at the same time being of rugged construction and standing up under conditions of severe and constant use without getting out of order or requiring repairs.

Another object is to provide such a door which is smooth and uniform in action through the full range of opening and closing the same and which is self-centering and occupies a minimum of cargo space.

Another object of the invention is to provide such a door which is free from rattles or other noises and which reliably seals the doorway against the weather.

Another object of the invention is to provide such a doorway which can be made of a wide range of materials in the form of laterally manually flexible sheets which are rigid in the direction of their broad surfaces so· as to be capable of being pushed or drawn around or along curved tracks. Suitable materials, in addition to sheet metal are opaque or translucent plastics.

Another object of the invention is to provide such a door which can be made to have adequate rigidity and strength to resist heavy impacts, such being obtained either by the application of slats of wood or the like to the laterally flexible sheets or by making these laterally flexible sheets of corrugated form so as to be rigid against transverse bending in one direction while at the same time being free to follow curved tracks in the other direction.

Another object is to provide such a door which is free from service difficulties and in which, in particular, the lubricant in the tracks providing the sliding surfaces can be impregnated in liners for the rails so as not to require replacement.

Another object is to provide such a door which can be readily counterbalanced, especially when slats are provided, and in which the counterbalancing mechanism is substantially wholly contained within the rails along which the door moves so as to be out of sight and out of danger of being injured or accidentally injuring anyone.

Other objects and advantages of the invention will be apparent from the following description and drawings in which:

FIG. 1 is a vertical longitudinal section through the rear end of a truck body having a rear door made in accordance with a simplified form of the present invention in which the door is not counterbalanced.

FIG. 2 is an enlarged fragmentary horizontal section through one of the rear corners of the body across the doorway and the door therein, this section being taken generally on line 2—2, FIG. 1.

FIG. 3 is a fragmentary enlarged view similar to FIG. 1 and showing in greater detail a vertical transverse cross section through the upper end of the door when closed.

FIG. 4 is a fragmentary enlarged view similar to FIG. 1 and showing in greater detail a vertical section through the sill of the doorway and through the bottom part of the door, this section being identified by line 4—4, FIG. 2.

FIG. 5 is a fragmentary vertical longitudinal section taken generally on line 5—5, FIG. 2 with the door removed and this section also being taken through the curved portion of the rail which joins its vertical part alongside the doorway to its generally horizontal part extending under the roof.

FIG. 6 is a view similar to FIG. 2 and illustrating a modified form of the invention.

FIG. 7 is a fragmentary section taken generally on line 7—7, FIG. 6.

FIG. 8 is a fragmentary horizontal section taken generally on line 8—8, FIG. 6.

FIG. 9 is a fragmentary vertical section taken generally on line 9—9, FIG. 7.

FIG. 10 is a view similar to FIG. 4 of a further modified form of the invention.

FIG. 11 is a view similar to FIGS. 2 and 6 of the form of the invention illustrated in FIG. 10.

FIG. 12 is a view similar to FIGS. 2, 6 and 11 of a still further modified form of the invention.

FIG. 13 is a view similar to FIGS. 5 &gt;and 7 of the modified form of the invention illustrated in FIG. 12.

FIG. 14 is a view similar to FIGS. 2, 6, 11 and 12 of a further modified form of the invention.

Referring more particularly to the form of the invention shown in FIGS. 1-5, the numeral 1® represents the body of truck, this body having the usual floor or platform 11, side walls 12 and roof 13, the rear end of which roof is shown as extended downwardly, as indicated at 14, to provide the upper limit of the doorway 16 at the rear of the truck body and which doorway extends from the floor to the bottom of the downward extension 14 and from one side wall 12 to the other. The bottom of this doorway is formed by a sill 18 which also forms the rear cross bar of the platform 11 and the upper part of this doorway is formed by a horizontal transverse angle iron 19 which also forms one of the structural members of the body. The cargo is loaded into the truck body and removed therefrom through this doorway.

In transit the doorway 16 is closed by a vertically movable door which is made of one or more sheets 2®, 21 of laterally manually flexible sheet material which is rigid in the direction of its broad surfaces so as to be capable of being pushed or drawn along the straight and curved portions of side tracks or rails indicated generally at 22. Each rail is suitably mounted at the sides 12 of the truck body to have a vertical straight portion 23 along each side of the doorway 16, a curved portion 24 continuing from the upper end of this straight portion 23 and curving upwardly and horizontally toward the front of the truck body, and an upper straight portion 25 forming a continuation of each curved portion 24 and arranged in closely spaced relation to the roof 13 so as to provide maximum cargo space within the body when the door is open.

Each of these tracks is preferably made of metal in the form of a tube of C-shaped form in cross section to provide a longitudinal slot 26 extending from one end of the rail to the other and being arranged along the center of each rail at that side 28 which opposes the other rail. The corresponding side edges of the sheets 20, 21 which comprise the door project through the slots 26 into the rails on opposite sides of the doorway, as best illustrated in FIG. 2.

To guide and permit sliding movement of the sheets. 20, 21 along these slots 26 of the two rails 22, the vertical part 23 of each rail is lined with one or more lubricous graphite blocks 29 having a longitudinal slot 3® in one side which is in register with and preferably considerably narrower than the slot 26 in its rail, the width of the slot 30 being preferably sufficient to snugly receive the edges of the sheets 20, 21 for free sliding movement therealong.

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A slotted lubricous graphite block 33 similar to the slotted graphite block 29 and having a similar slot 34 lines the upper horizontal portion 25 of the rail 22. The curved portion 24 of the rail is shown as lined with a plurality of lubricous graphite blocks 35 slotted as at 36 and which are substantially identical in cross section to the graphite blocks 29, 33 but are in the form of short lengths and are arranged in successive contacting relation with wedge-shaped spaces 37 therebetween.

The slots 30, 34 and 36 of the graphite blocks 29, 33' and 35 form a continuous slideway for the opposite edges of the sheets 20, 21 comprising the door so that the door can be manually slid along this way from the vertically closed position shown in FIG. 1 to a horizontal open position in which it is contained within the upper portion 25 and curved portion 24 of the two rails 22 and contained within the slots 34 and 36 of the graphite blocks 33 and 35 therein. If desired the series of blocks 35 can be held in position in the curved portion 24 by projections 38 from the opposite ends of the curved rail portion 24 into the endmost of the blocks 35. These projections can be produced in any suitable manner as by drilling a hole through the rail into each end block 35 and then applying weld metal to the hole to form the projection which extends into the block 35. It will be seen that by this arrangement the straight rail sections 23 and 25 can be separated from the connecting curved rail section 24 without having any of the graphite blocks 35 fall out of the curved rail portions.

As previously indicated, the door is essentially composed of two face-to-face sheets 28, 21 of laterally manually flexible material which are rigid in the direction of their broad surfaces so as to be capable of being pushed or drawn around the curved ways providing by the slots 36 contained within the graphite blocks 35 mounted in the curved portion 24 of each side rail. These sheets can be sheet metal and by providing them in the form of two sheets in face-to-face relation, they are rendered more readily flexible laterally than if they were a single sheet of the same thickness while at the same time they jointly have both the thickness and planar rigidity to be readily pushed along the rails and also to resist blows against their exterior surfaces such as are bound to happen in handling and transporting cargo. These two sheets can also be made of other material having the necessary lateral flexibility and planar rigidity such as flexible sheet plastics.

It is desirable that the sheets have sliding contact with each other in their direction of movement so as to provide a slight differential in length of the two sheets in rounding the curving portion 24 of each track, the outer sheet 20 having a greater curvature than the inner sheet 21 in this movement. For this purpose, while the sheets 26, 21 can be of the same length in their direction of travel, one sheet is preferably offset with reference to the other so that the outer sheet has, say, an offset 40 at its lower end and the inner sheet 21 has a similar offset 48 at its upper end. Cross bars 42 preferably enclose these opposite ends of the door and are each secured to the corresponding offset 48 by a row of rivets 43. Desirably, these cross bars 42 are of double tubular form in cross section to provide an inner tube 44 and an outer tube 45 separated by a longitudinal slot 46 which receives the ends of the door and through the walls of which slot the fastening rivets 43 extend. It will be noted that at each end of the door, the end of the non-riveted sheet stops short of the rivet as indicated at 48 in FIG. 3, this permitting the slight differential surface movement required when the two face-to-face sheets round the curve 24. If desired, the sheets 20, 21 can be secured together midway between their cross bars 42 as indicated by the rivets 49, FIG. 1, so as to positively hold these two sheets in the specific offset relation illustrated. A lubricant can be applied to the opposing surfaces of the two sheets.

While the lubricous graphite blocks 29, 33 and 35 pro vide adequate ways for guiding the sheets 20, 21 to follow the changes in direction of the side rails 22, they are not adequate to hold these sheets in centered relation between these two rails. Thus, there would be nothing to prevent these sheets from, say; creeping to the right or left with the result that their edges would cut deeper and deeper into the graphite blocks at one side of the body and ultimately work themselves free from the opposite rail. To avoid this, a thrust bearing, indicated generally at 5®, is provided at each end of each cross bar 42 to engage those faces 28 of the rails 22 which oppose each other, thereby to positively hold these bars, and hence the sheets 20, 21 connecting these bars, in centered relation with reference to the two rails. Such thrust bearings can be of any form but each is shown as being in the form of a single graphite block 51 set into each end of each of the cross bars 42 for the door, as best illustrated in FIG. 2, and projecting from the cross bar a sufficient distance to snugly encounter the corresponding face 28 of each rail. These graphite blocks 51 can be held in place in any suitable manner as by inward projections 52 from the cross bar. As with the projections 38, a simple way of providing the projections 52 is to drill holes through the ends of the cross bars 42 and into the graphite blocks 51 and then apply a bit of molten weld, metal to fill these holes and also weld to the metal of the cross bars 42.

_ It will be seen that while the slots 30, 34 and 36- provide an adequate weather seal along the vertical sides of the closed door and while the engagement of its bottom cross bar of the door with the sill 18 provides an adequate weather seal at the bottom of the door, a substantial. space is left at the top of the door between it and the cross frame bar 19. To provide a weather seal across this space, a rubber strap 53 is secured to the underside of the cross frame bar 19 to extend the full width of the doorway and to have a flap or squeegee-like extension toward the door and which engages the exterior face of the outer panel 20. This flap or extension sweeps along the door as it opens or closes and provides a flexible seal against wind, rain, snow or dirt being driven into the body through the space between the door and the upper cross bar 19 of the door opening.

The door can be provided at its lower end with a handle 54 which is shown as being secured to the outside of the door and hence is secured only to the outside sheet 20 of the door so as to avoid interference with the movement of the inside sheet 21- thereof.

In the operation of the form of the invention shown in FIGS. 1-5, to open the door the operator seizes the handle 54 and lifts the same, this causing the opposite vertical edges of the two face-to-face flexible metal or plastic panels to move along the slots 38 and 36 of the lubricous graphite blocks 29 and 35 of the vertical and curved portions 23, 24 respectively of the two side rails 22. The advancing ends of these side edges of the two face-to-face sheets 20, 21 are guided to enter the slots 34 of the graphite blocks 33 of the horizontal section 25 of the two rails 22. When the handle reaches the top of the door opening, the door is supported by the graphite blocks 33 and 35 contained within the upper horizontal portions 25 and the curved portions 24 of these rails.

During this movement, the flap or squeegee extension 53 of the rubber strap across the top cross bar 19 of the door frame sweeps against the outside face of the door so as to provide a continuous weather seal. Also, during this movement, the door is held in centered relation between, the two rails 22 by the graphite thrust bearing blocks 51 secured to project from each end of each cross bar 42 of the door into engagement with the opposing faces 28 of the side rails 22. By making the door of two sheets of flexible material instead of one, greater lateral flexibility is provided in rounding the curved portions 24 of the rails than if a single sheet having the same thickness as the two sheets were, provided while at the same time the door is made sufficiently thick so as to be

3,129,752

G and have sliding contact with one of the lubricous strips 69. Instead of the upper and lower cross bars used with the form of the invention shown in FIGS. 1-5, the upper and lower edges of the sheets 69, 61 of the door are 5 shown as bent around the end edge of the end slats, as indicated at 78, thereby to provide a rounding nose at both the top and bottom of the door and which nose is sufficiently flexible to permit the slight expansion of the sheets relative to each other due to the differential in cur10 vature in rounding the curved portions 64 of the rails.

Instead of graphite blocks to provide thrust bearings at each of the four corners of the door, these thrust bearings are each in the form of a ball 79 provided at each of the four corners of the door to engage the face 68 of the 15 corresponding rail and hold the door in centered relation to these rails as it is moved from open to closed position and vice versa. These balls are shown as held within a body 88 in which these balls are freely revolvable and each of these bodies is shown as secured within a socket 81. Each socket is shown as having a flange 82 by means of which the socket can be screwed, as indicated at 83, to each end of these top and bottom end slats 71 for the door.

A particular feature of the form of the invention shown 25 in FIGS. 6-9, is that the door is counterbalanced. For this purpose a pair of long helical tension springs 85, 85α are arranged side by side within each of the tubular rails 62 along the inside of the inner sheet 61 of the door as best shown in FIG. 6. One end each spring 85, 85α is fixed to a bracket 86 which is in turn secured to the lowermost corner of the door against corresponding bottom slat 71 as by a rivet 88 as shown in FIGS. 6 and 8. The opposite end of each spring 85, 85α is shown as secured to an eye 89, or other suitable fastening, to an end head 90 at the free end extremity of the horizontal upper section 65 of the corresponding rail 62. At the curved portion 64 of each rail each pair of springs passes around a series of pairs of rollers 91 each pair being journalled on a pin 92 suitably secured to the corresponding side wall 12 of the body as best shown in FIG. 9. The inner or shorter curving side of each curved track section 64 is provided with a slot 93 through which these rollers project to support the corresponding portion of the pairs of springs 85, 85α in general conformity with the curved section 64 of the track as best illustrated in FIG. 7.

In the use of the form of the invention shown in FIGS. 6-9, the door is manually raised and lowered and in doing so the flexible sheets 60 and 61 and wooden cross slats 71 move between and in contact with the lubricous strips 69 which are preferably impregnated with a lubricant to insure easy movement of these parts along these strips. These strips are arranged longitudinally in the side rails 62 on opposite sides of the slot 66 through which the sides of the door project into these slots and to hold the door in centered relation while moving along these rails, the thrust bearings, each in the form of the ball 79, are provided at each of the four corners of the door to engage the opposing faces 68 of the rails and thereby prevent displacement of the door to the right or left with reference to its rails.

The wooden slats 71 add considerably to the weight of the door in providing protection against heavy blows and to compensate for this weight the pairs of counterbalance springs 85, 85α are provided. As the door lowers, these pairs of springs are stretched out, their intermediate portions travelling over the arcuately arranged pairs of rollers 91 so that the strain upon the springs is distributed along all of the coils thereof and not concentrated at the ends of the springs attached to the door. It will also be particularly noted that the pairs of springs are completely housed, and that the counterbalancing mechanism is essentially contained within the same rails which support and guide the door in its opening and closing movement.

The use of the helical springs 85, 85α in pairs and in side-by-side relation is an important feature of the inven5 completely rigid in the direction of its broad faces and also sufficiently thick to withstand accidental blows against its sides such as are incident to doors for cargo carriers.

In the form of the invention illustrated in FIGS. 6-8, the truck body is the same as illustrated in FIGS. 1-5, and hence the same reference numerals have been employed. The form of the invention shown in FIGS. 6-8 is designed for a much heavier and sturdier door, the door being both counter-balanced and also being provided with wooden slats to withstand blows from cargo handling against the door which otherwise might dent or bend the simple two-ply door construction shown in FIGS. 1-5.

As with the form of the invention shown in FIGS. 1-5, the body of the door comprises two sheets 60 and 61 arranged in face-to-face relation with each other and made of flexible metal or plastic so that they can manually be moved to track around a curve, but at the same time are rigid in the direction of their broad faces so that they can neither be pushed or pulled around such curves. 20 Also as with the form of the invention shown in FIGS. 1-5, the opposite vertical edges of this door are constrained to move along rails 62 at opposite sides of the door and body, each of these rails having a bottom vertical part 63 secured along the vertical sides of the doorway 16 and leading to an upper curved part 64 which curves toward the front of the truck body and which leads to a horizontal top part 65, arranged in closely spaced relation below the roof 13 of the body. As with the form of the invention shown in FIGS. 1-5 each of these ³θ rails 62 is of C-shaped tubular form in cross section, having a longitudinal slot 66 in that wall or face 68 which opposes the opposite rail.

The vertical edges of the flexible sheets 6®, 61 project through these slots 66 into the interiors of the two rails 62 and are shown as guided between a pair of lubricous strips 69 set into suitable grooves 70 at opposite sides of the slot 66 to have portions projecting into this slot to engage the opposite sides of the door as hereinafter set forth. These strips or pieces 69 can be made of any lubricous material to have the required firmness, strength and lubricity to guide the door along the curved and straight portions of the side rails with minimum manual effort. For example, the strips can be made of wood fiber with, say 20% impregnated graphite. These 45 strips could have about the same hardness as conventional hardboard panels, with graphite added. Alternately these strips could, of course, be made of various other materials.

To provide increased protection to the door from shift- θθ ing cargo within, the door is shown as being provided with horizontal wooden slats 71 covering its inside face. These slats are shown as having longitudinal grooves 72 provided in their opposing longitudinal edges, and each pair of grooves slidingly receives a strip of metal 73 having bent ends 74 engaging the ends of the slats to prevent longitudinal displacement of these strips. It will be apparent that these strips maintain substantial alinement of the slats while permitting edge separation thereof when passing around the curved portion of the rail, as well as permitting the slats to come into closely spaced edge to edge relation on traversing the vertical and horizontal portions of the rails. In addition, to permit of free travel around the curved sections 64 of the two rails, the faces 75 of these slats which oppose the sheets 60, 61 are preferably rounded to conform to this curvature as best illustrated in FIG. 7.

Each slat is preferably secured at its center by a line of rivets 76 to the inside sheet 61 thereby to leave the outside sheet 60 free to move along the inside sheet in conforming to the differential in curvature between these two sheets when rounding the curved portions 64 of the rails. For strength the slats 71 preferably extend the full width of the sheets 60, 61 and are interposed between

3,129,752 tion. Thus a single spring 85 at each side of the door could not be made to stand up, the springs breaking down under service conditions. The use of a pair of springs 85, 85α at each side of the door travelling around the pairs of rollers 86 as shown provides a complete solution to 5 this fundamental defect. Apparently the problem had to do with the much larger diameter spring required when the use of only one spring at each side of the door was attempted. Thus while the combined torsional forces from both stretching the spring and bending the spring around j 0 a curve resulted in rapid breakdown of the larger diameter single springs, this result was wholly eliminated when the pair of smaller diameter springs 85, as shown, were substituted.

With the smaller diameter springs so arranged side-by- 15 side in pairs at each side of the door, danger is present, however, of having the coils of the springs intermesh with each other and, on contracting, causing failure of the springs to operate. To avoid this, as best illustrated in FIG. 8, the coils of one spring 85 are arranged so as to be 20 pitched in one direction, say clockwise, while the coils of the companion spring 85α are arranged to be pitched in the opopsite direction, say counter-clockwise. In this manner, with the degree of separation of the coils which obtains under actual service conditions, the coils of one 25 spring cannot intermesh with the coils of the other and hence the danger of the springs becoming tangled together and becoming inoperative is eliminated.

In the form of the invention shown in FIGS. 10 and 11 the truck body is the same as illustrated in the preceding 30 figures and the same reference numerals have therefore been employed. The form of the invention shown in FIGS. 10 and 11 illustrates a modification of the invention in which the manually laterally flexible sheet, which is the principal component of the door, is in the form of 35 a horizontally corrugated sheet. The purpose of such corrugations is, of course, to give transverse strength to the door without the use of wooden slats as with the form of the invention as shown in FIGS. 6-9, and at the same time without interfering with the easy flexing of 40 the door while travelling around the arcuate or curved portion of its rails.

For this purpose, the door is shown as including two manually flexible corrugated sheet metal or plastic sheets 100 and 101, these sheets being arranged in interfitting, 45 face-to-face relation with their corrugations mating and extending horizontally. As with the other forms of the invention, each rail 102 is of tubular form and of Cshaped form in cross section to provide a slot 103 in its side face 104, these slotted side faces 104 of the two 50 rails opposing each other and receiving the opposite ends of the corrugated sheets ICO, 101. To guide the corrugated sheets, each rail can be lined with blocks 105 of graphite, similar to graphite blocks in the form of the invention shown in FIGS. 1-5. Also, to hold the 55 doorway centered thrust bearings 106 are provided at each of its four corners to engage the face 104. The thrust bearings 106 can each take the form shown in FIGS. 6-9, namely a ball 108 revolvably contained within a bracket 109 secured to the inner sheet 101. The sheets 00 100, 101 can be joined at their opposite ends by a bead 110, this being shown as formed by bending one of the sheets around the other as shown in FIG. 10.

With the form of the invention shown in FIGS. 12 and 13, the truck body is the same as shown in conjunc- 65 tion with the other forms of the invention and the same reference numerals have been applied. The form of the invention shown in FIGS. 12 and 13 is particularly characterized by the use of wooden slats on the exterior of the door as compared with the interior wooden slats shown 70 in the form of the invention illustrated in FIGS. 6-9.

The main body of the door is shown as being in the form of a single flexible sheet 115 of metal or plastic to the exterior of which a plurality of horizontal wooden slats 116, quite similar to slats 71 of FIGS. 6-9, are 75 secured in closely spaced vertical relation as by rivets 118 passing through the center of each slat and anchoring in the sheet 115. As with the other forms of the invention, this door is slid along side rails indicated generally at 119 of tubular form and C-shaped in cross section to provide longitudinal slots 12® in that side 121 of each rail which opposes the opposite rail. The opposite edges of the door project into these slots of the two rails and are contained within and slide along a slot 122 in a block 123 of graphite or lubricant impregnated material. The blocks 123 can be of the same form as the graphite blocks used in the form of the invention illustrated in FIGS. 1-5. One side of the graphite blocks 123 engages the inner face of the flexible sheet 115 and the other side of these graphite blocks engages the outer faces 125 of the wooden slats 116 at the opposite extremities thereof. To this end the outer faces 125 of these -wooden slats, at least at their extremities which engage the graphite blocks 123, are curved so as to have full surface contact with the graphite blocks 123, when travelling around the curved part of the rail as illustrated in FIG. 12. To maintain the door in centered relation between the rails 119, every tenth or so slat 116 is made longer than the others to project further at its opposite ends and have sliding contact with the bottoms of the grooves 122.

When used on the exterior, it is also desirable to provide a weather seal between the several slats. Such a weather seal can be of any form but is shown as being in the form of a strip of metal 126 like strips 73 of FIGS. 6-9, slidingly fitted in longitudinal grooves 128 provided in the opposing edges of the succession of wooden slats 116 and having bent ends 129 engaging the ends of the slats to prevent longitudinal displacement of these sealing strips. It will be seen that these strips, like strips 73 of FIGS. 6-9, prevent cocking of the slats, while permitting edge separation of the wooden slats 116 when passing around the curved portion of the rail as well as permitting these slats to come into closely spaced edge-to-edge relation on traversing the vertical and horizontal portions of the rail.

In the form of the invention illustrated in FIG. 14, the body is the same as with the other forms of the invention and the same reference numerals have been applied. As with the form of the invention shown in FIGS. 1-5, the door illustrated in FIG. 14 is composed of two sheets 130, 131 of flexible metal or plastic arranged in face-toface relation with each other so as to be manually flexible laterally but to be stable or rigid in the direction of their broad faces. As with the other forms of the invention illustrated, the opposite edges of the sheets 130, 131 are guided in a rail 132 secured to the truck body and along which the sheets slide. The rail 132 is of C-shaped form in cross section to provide a longitudinal slot 133, the slots of the two rails opposing each other and the opposite edges of the sheets 130, 131 being contained within these slots. Each rail 132 is shown as being in the form of a thick walled metal extrusion as compared with the other forms of the invention illustrated wherein sheet metal is used, and this extrusion is shown as having an enlarged through bore 134 extending along inner end of the slot 133. This bore and the slot 133 are lined with a sheet 135 of material having a high degree of lubricity, such as nylon, which is inherently lubricous although any other lubricous liner could be used.

In the slot 133 this liner slidingly engages the outer sides of the sheets 130, 131 and provides a way along which these sheets are guided. This liner tightly embraces a large wire 136 which serves to anchor the same in position. The rail can readily be produced by spreading the jaws of the rail, inserting the liner 135 and wire 136, and then bringing the jaws together to clamp the wire 136 and thereby securely hold the liner 135 in operative position.

In other respects, the form of the invention illustrated in FIG. 14 can follow that form of the invention illustrated in FIGS. 1-5.

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From the foregoing, it will be seen that the present invention provides a very simple door particularly a sliding door in which the principal elements are one or more sheets which are laterally manually flexible but rigid in the direction of their broad surfaces so as to be capable 5 of being pushed or drawn along or around curved rails. It will also be seen that the door can be centered by the provision of simple thrust bearings at each of its corners and which travel along and engage the opposing sides of the rails in which the edges of the door are contained. 10 It will also be noted that a simple guide and support for these sheets are provided by a pair of side rails which are C-shaped in cross section to provide opposing slots containing the opposite vertical edges of the sheets and by the use of suitable lubricous blocks or strips within the 15 rails to engage and slidingly support the sheets. It will also be noted that the door can be given the required resistance to impacts either by the addition of wooden slats or by corrugating the same, and that it can be rendered counterbalanced by a simple extensible spring 20 housed within the tubular rails, this latter feature also being applicable to doors of a construction other than illustrated.