US2327315A - Closure for building constructions - Google Patents

Description

Aug 17, 1943 MICHELMAN CLOSURE FOR BUILD INC CONSTRUCIIONS '5 Sheets-Sheet 2 Filed Dec. 2, 1941 Aug. 17, 1943. N. M ICHELMAN CLOSURE FOR BUILDING CONSTRUCTIONS Filed m;

2, 1941 5 Sheets-Shee 3 ATTOQNEY.

Aug. 17, 1943. N, MICHELMAN CLOSURE FOR BUILDI NG CONSTRUCTIONS 5 sheets-sheet 4 Filed Dec. 2, 1941 A'TTORN EY.

Aug. 17, 1943. V N. MICHELMAN CLOSURE FOR BUILDI NG CONSTRUCTIONS Filed Dec. 2, 1941 5 Sheets-Sheet 5 a INVENTOR.

ATTORNEY.

Patented Aug. 17, 1943 UNITED STATES PATEN T OFFICE" 2,327,315 oLosUnn FOR BUILDING CONSTRUCTIONS Nathan Michelman, Brooklyn, N. Y. Application December 2, 1941, Serial No. 421,272 12 Claims. (01. loo-191) This invention relates generally to closures, as doors, in building constructions and is more particularly directed to improvements in doors of the so-called sliding types, which are elevated to open position, as employed in wharves, warehouses and other industrial buildings, to afford access to loading platforms and storage space.

, While the invention, as will be manifest from the description, is susceptible of a wide range of application, in various other constructions, including aircraft hangars, garages and similar structures, where maximum clearances are-essential, for the purposes of this disclosure, I have elected to present my invention asit may be practiced in the construction and operansnior covered or enclosed piers or wharves. However; this is merely illustrative and is not to be construed in any sense as a limitation of the scope of utility of my invention.

In pier or wharf construction, doors of the general type of my invention are extensively'used to close the openings which are provided in thesides of the pier superstructure} whereby cargo .or freight may be transferred to and from vessels docked alongside the pier, the floor offthe pier constituting the loading platform to and from which the freight is usually swung by a crane, operated from the vessel. To facilitate'such loading and unloading operations, the openings in the pier wall are usually arranged closetogether; the closures or doors therefor, which are customarily of the aforesaid sliding type, being adapted to, be moved upwardly in yarious ways for storage above the head of an opening, so that the maximum head-room is attained. However,

ing the abuse to which they may be subjected in operation by unskilled hands.

Therefore, the primary object of this invention is to provide a door or'closure of the sliding type referred to and a cooperating door or openingdefini'ngframe for use in wharf, warehouse and use of such devices, especially in the erection and the advantages of the maximum head-room or clearance are, to an extent, offset by the limitations to the movement of the boom of the crane, which are presented by the side frames or jambs of the doorways O-r openings, in'm-any instances it being necessary to deposit the freight on'the apron of the pier before'an opening, or just within the opening, where the superstructureis flush with the stringpiece of the pier, or removal to the interior of the wharf by stevedores. This, obviously, slows an unloading operation and the same, of course, applied to leading, the freight being moved by hand to a position within the opening or just beyond, to be picked uplbythe crane.

Further, the door constructionsand their opcrating mechanisms are not of that simple yet rugged design which is requisite to'the performance of their primary function and at the same time insure dependable operation, notwithstanduse of piers or wharves.

More specifically, it is an important object of this invention to provide a slidable door, construc tion, as aforesaid, and doorway-forming means, with which the door coacts to form a closure, having movable side frame members or socalled J'ambs, which normally function to guidethe door in its closing movement and retainlitin closed position, but which, when" the door 'is raised to its open position, are actuatable to a position above the head-line of the'fram of the opening, to present an opening having a span in excess of the normal width of the door frame and the door matable therewith. "Thus, where a series of doors, with their respective doorways, are juxtaposed along the side of a wharf or building, the entire side of the wharf or building may be free of vertical obstructions between the headline of the doorways or openings and the flooror'platform of the pier, affording a boom of a crane a virtually unlimited freedom of movement in swinging freight into the pier shed, for deposit in positions which, because of the obstructions offered by the fixed doorways of existing constructions, are far beyond the effective zone of operation of the boom. I Another important object of this invention is to provide a door construction in which a door embodying upper and lower sections of the requisite rugged construction, may be readilyoperated by the unskilled tog open and closed positions, with the expenditure of a minimum of actuating energy'and'with-a degree of dependability that insures ehicient service and low maintenance costs;

Other objects and advantages flowing from the practicing of my invention will become'evident as the description proceeds, not only as employed in wharf construction and operation, but in other appllcationsto which it readily lends itself, as hereinbeforepointed out.

" For the purpose of this disclosure, in the accompanying drawings, Lhaveshown a preferred embodiment of my improved door construction invention, showing schematically the upper and lower series of doors in closed position.

Figure 2 is a view similar to Figure 1, in which the doors of both decks have been raised or elevated, with the doorway frame members of the upper deck in their normal positions, while those of the lower deck are variously shown as raised and in movement to the latter position.

Figure 3 is a rear elevation of a door of a.

series, illustrating the actuating and control mechanism. ,7

Figure 4 is a side elevation, partly in section, showing the relationship of the upper and lower sections of a door in closed position.

Figure 5 is a view similar to Figure 4, in which the two door sections are 'in registration for movement as a unit to their stowedposition, the latter and an intermediate position in the movement of the mated door sections, being shown in dotted lines. V

Figure 6 is an enlarged sectional detail of the mounting for one end of a torsion spring, a component of the actuating mechanism.

Figure '7 is a detail of the mounting of the opposite end of the spring of the preceding figure, showing the cable-receiving drum.

Figure 8 is a detail view, partly in section, of a tension spring and cooperating means function therewith, as, control media. I

Fig. 9 is a horizontal crOss-sectionlof the guide roller of the lower section of the door.

Figure 10 is a top plan view, partlyin section, along lines lU-IE! of Figure 5, showing the guide roller of the upper section and the means for interconnecting the two door sections. v V, v Figure 11 is a view in elevation, showinga shiftablevertical'member of the doorway frame and cooperating door track, together with the means for actuating such member to and from normal position, the extreme raised and an intermediate position of said .member being indicated in dotted lines.

Figure 12 is a detail of the hinge connection between the door frame member and the door track thereabove. v

Figure 13 is a detail, partly in section, along line l3-l3 of Figure 11 of the hanger and carriage which function in the movement of the door frame member; and.

Figures 14 and 15 are respectively side and rear elevational views of lower portionsof the door frame members and cooperating means for locking such members to the floor of the pier, in normal door-supporting position, Figure 14 being a detail, partly in section, along lines I l-I4 of Figure 15. e f

Referring now to the drawings in detaiLin which like characters of reference are employed to designate similar parts in the severalv views, the door embodies an upper'section l, which may be provided with lights 8, and 'a lower section 9, preferably of a paneled or other solid construction, the two sections. being rectangular and of corresponding dimensions. Each end of the upper door-section is faced with a channel member IE}, extending from the top to the bottom thereof, which. coacts with the flange H of the angle piece l2 fixed to the adjacent end of the lower door-section to maintain the two door-sections in association for liding movement of the lower section relatively to the upper one, as hereinafter described, the lower edge of the upper door-section overlapping the upper edge of the lower section, when the two sections are in their closure-forming position (see Figure 4).

Mounted on a laterally extending shaft l3 on each end of the upper door-section, adjacent the top edge thereof, is a roller l4, while a roller 15 is rotatably supported from a fitting l6 fixed to each of the ends of the lower door-section, at the base thereof, to locate the roller lioutwardly of the face of the doorsection, with its axis parallel thereto (see Figure 9). These rollers 14 and I5, are adapted to be entered in and traverse the tracks or guideways 18 and 19 which form the opposite vertical side members of a doorway frame, the upper ends of said members being aligned with the contiguous end of the curved continuation 20 of the door track 2|, supported parallel to the ceiling of the pier shed, as by suitable hangers, generally indicated at 22 and 23.

The aforesaid'guideways may comprise single channels of the appropriate width and depth, or each may be formed by utilizing two shallow channels assembled in parallel, with their flanges in oppositely spaced relation, as at [8a and 18b, the channels being rigidly connected by a series of vertically spaced tie plates 180, the outer surface of the web of the channel 18a forming the outer face of the frame member of which it is a component, as clearly shown in Figure 14. Obviously, the formation of the vertical frame members in this manner provides a lighter and more economical construction, without sacrificing strength'or rigidity.

As will be evident, each doorway or opening includes the fixed header 24, formed by the pier wall or otherwise, and 'two vertical side-forming members It and I9, the upper door-section I normally being in alignment therewith, while the 'lower'door-section 9 is disposed to the'rear or inwardly thereof, with their abutting edges overlapped, as previously explained. (Figure 4.)

Each vertical door-frame member, at its upper end is hingedly connected to the adjacent end of the door track 2!i2 l the hinge, preferably, being of the spring type and acting to urge the frame member rearwardly out of alignment with the end of the door track to which it is connected (see Figures 4 and 12) for the purposes which will be explained.

Supported in parallel to the pier ceiling is a track 25, extending rearwardly from th outer wall of the pier, preferably of the cross-sectional configuration shown in Figure 13, in which is mounted for travel a carriage 26, carrying a dependent arm 2'! terminating in a bifurcated'portion 28, forming a mounting for a pulley 29. A cable 39, connected to the hinged door-frame member, adjacent its lower end, is reeved through this pulley 29 to traverse a second pulley 3| adjacent the inner end of said track 25, forwinding upon a mechanically or manually actuatable drum or reel 32, supported from a fixed surface, as a column 0 of the pier shed structure.

Preferably set into the floor I of the pier and appropriately anchored thereto. is a shoe 34 adapted to cooperate with each adjacent pair of hinged door-frame members. This shoeembodies a toe-piece 35, with parallel sides 36 and 3?, having'inclined top surfaces, the base of the shoe being provided'with'laterally spaced vertical bores or slots 38, for the reception of the slide bolts to and 4e, rigidly fastened to the web portions of adjoining hinged door-frame mem hers is and E9, to interlock such members with said shoe and rigidly retain them in their normal vertical door-supporting position, with their upper ends in alignment with the door tracks 20, 26, with which they are respectively connected, as heretofore described.

It will be understood from the foregoing, that each door, embodying the 'upperand lower sections 7 and 9, is locatable in closure-forming position between a pair of appropriatelyspaced vertical doonframe members I3 and IS, the gap therebetween corresponding approximately to the width of a the door; also, that a vertical member l8 of one door-frame or opening, immediately adjoins the vertical member IQ of the frame of the adjacent doorway, such immediately adjoining frame members #8 and [9 being interloclzable with the aforementioned common shoe, independently of each other, for reasons which will become obvious.

As will be observed from Figure 3, door-section 'i is supported between the cooperating vertical members '13 and 59 of the doorway and in engagement therewith, through the medium of the guide rollers I5, by tension spring ii and 52, connected by a turnbuckle l3 and located above and parallel to the top of said door-section,

the upper the outer ends of said springs having cables and ii: fixed thereto, which pass through grooved pulleys it and '27 and are in turn secured to the inner faces of the respective end-forming members of said door-section and centrally of -the top and bottom ,edges thereof, as indicated at t3 and 49. Each of ,the pulleys, and i? is swivelly mounted on a shaft or pin 56, horizontally sup,- portedin the lugs 51 and 52 of th bracket 53 bolted-or otherwise secured to the pier structure, in juxtaposition to the upperend of a vertical door-frame member, for radial movement under the; guidance of its tracking cable, as the door sections shift from one to another of their extreme positions in operation, the aforesaid tension springs contributing to the counteraction of inertia forces in th initiation of movement of the door-sections, from their extreme positions and acting to retardatively control their movement to such extreme positions, as hereinafter will be more fully explained. a

In superposed relation to the aforesaid tension springs 1i and 42 is a shaft 55, journaled in bearings 55 and 53, on one end of which is keyed a drum of a truncated conical configuration, having a spiral peripheral cable-receiving groove 58, a similar drum 5% being fixed to said shaft adjacent its other end, with which a gear til}, like: wise keyed to said shaft, is associated, said gear being adapted to be driven from an electric motor 6|, through suitable intermediate, gearing, generally indicated at 62, it being understood that the latter gearing may vary to meet installation and operatingrequirements.

A pair of "axially spaced torsion springs 63 and M, concentric with said shaft 54, are each supported at their adjacent ends from a bracket 65 attached to the pier wall onthe vertical center line of the doorway, by afitting embodying ahub portiontfi and concentric flange 6.1, longitudinally slotted; seat 68, for the reception of the end 01' the spring, as shown in Figure 6, the hubbeing bolted to the annulus 69 of the bracket, in spaced relation'theretojas at 10, foraxial alignment of scribed-and the two the bore -H of-said fitting with the-bore T2 of the-"bearing member" ?3. Th diazm'eter of the aligned bores?! and 12 is such'as to allow sum c'ient. tolerance for the shaft to rotate freely therein. The endof each spring adjacent a drum is positively connected to the shaft 5!, as by a sleeve l lpinned to the shaft, as at 15, and provided with" an enlarged portion 7'5, slotted, gas at 'F'L'the end of the spring being shaped to enter said slotxandaemb'r'ace said sleeve, as shown in Figure 7, it being m'anifest'that in the rotationof the shaftin one direction, the torque of the shaft will be effective thereon to compress oriwind the espective springs, while th rotative movement of the shaft in the reverse direction will be controlled in proportion to the load and the decrease in tension of the springs as they expand or unwind. I l

The lower door-section 9 is supported and operated by means of a pair of cables as at 18 and 79, which are connected to the end-forming members thereof, as at 80 and 8|, approximately centrally of the top and bottom edges of the door-section, and to, the drums 51 and 59 respectively;- Any suitable meansmay be employed for anchoring the ends of the cables extending, upwardly. to the drums in the convolutions thereof of largest diameter, so that as the drums revolve in one direction the cables will wind in the spiral grooves thereof toward the groove of smallest diameter, while the revolution of the drums in the reverse direction will cause the cable to unwind or traverse the cable toward the groove of greatest diameter, the latter rotative movementof the drums occurring when the doors position, during which movement the springs 63 and 64 are woundor compressed, as hereinafter will become evident. Assumingthat the vertical door-frame memthe' floor of the pier as dedoor-sections I and 9 are in closed positionwith therespective abutting edges 7 sections in superimposed overlapped, the operation of the motor 60, through the interconnected gearing will drive the shaft 54 to rotate the drums 51 and 59, keyed thereto, initiatingthe winding of the respective cables 18 and 79.150 raise the lower door section 9, its guide rollers 45 traversing the tracks formed by;the,door-frame members I8 and 19 until the extending arms [6 at the base of said door-section impinge against the lower edge of springs 4| and 42, connected to the upper doorsection bythe cables, 44 and 45 at this point contribute'to counteract the inertia of the upper door-section by generating a lifting impulse and initiating movement of the upper door-section in unis n with the lifted lower door-section; and

seotionzwill enter the curved-portion 20 of the,

door track, while the guide rollers l5 of the lower door-section are still engaged with the vertical side members of thedoor-frame, the lifting force continuing effective upon the lower end of the lower door-section until its rollers .l5 enter the curved portion of the door track for the final dispositionof the superimposed door-sections in alignment with the horizontal portion of, the door-track, with the rollers 14 and I5 of both sections in engagement therewith. As the doorsection movesto this latter position, the tension springs 4| andAZ again become efiective to yieldingly retardthe movement of the door-sections to their extreme or final position in association with the" horizontal track portion 2|, it being evident from Figure 5, that as the. mated doorsections assume the position of angularity with respect to the vertical and horizontal guideways shown in dotted lines, springs 4| and 42 will have assumed their normal degree of tension, but as the mated doors progress toward their extreme position on the horizontal portion 2! of the door track the tension of the springs will be gradually increased, with a concomitant increase in the resistance to the movement of the door-section longitudinally of the track.

As has been stated, the torsion springs are compressed or wound up, as the door-sections are lowered or moved to closing position and it may be pointed out that as the drums rotate to raise the door-sections, as just explained, the tension of these springs decrease, as they unwind or expand, with the raising of the lower door-section, while the weight of the door-section remains constant throughout its movement as a unit, it being evident that the decreasing efiective radius of the drums as the cables progress through the smaller diameter spirals, results in a correspondingly decreasing leverage, which lessens the load or force of the door-section so that it will be counterbalanced throughout its movement. While the'load is greatly increased as the lower door-sectionengages the upper door-section and in the initial movement of the two sections as a unit, which, to an extent is offset by the action of the tension springs M and 42, as set forth, at this period of operation the cables 18 and"!!! are progressing into the minor diameter grooves or convolutions to proportionately decrease the leverage through which the multiplied weight acts, so that the load which is a resultant of such weight will be properly counterbalanced by the springs 63 and 64, it being manifest that as the mated door-sections approach the horizontal the weight diminishes further, as the efiective efiort becomes relatively negligible.

When the door-sections have been elevated to their extreme position, in the horizontal portion Zlof the door track, as just described, the vertical door-frame members, .as desired may be swingably elevated to a position parallel thereto, following their disconnection from the shoes 34, to which they are normally bolted, by the actuation of the reels 32,the winding of the cables 30 thereon, producing an upward radial movement of the door-frame. members on their respective hinge lines, as the carriages 26 respond to the cable movement through their dependent pulleys 29 and traverse their tracks to their ulti mate positions in proximity to the pulleys3l at the end of the tracks, with the frame-members disposedbelow and parallel to the track 25. As will be understood, any frame member may be raised independently of the others. For instance where onlytwo adjacent doors may be opened for a particular loading or unloading operation, the adjoining frame members 18 and I9, one forming a part of each doorway maybe raised to provide an unobstructed opening having a span equivalent to the overall width of two doorways, plus the width of the two doorway members that are raised.

. It is obvious that various changes and modifications may be made to the details of construction without departing from the general spirit of the invention as set forth in the appended claims.

I claim:

1. In a closure for a doorway, an upper and a lower door-section, means for moving said lower section in a vertical path to a position in superimposed relation to said upper section and for moving both of said sections as a unit to an extreme open position, torsion spring means connected to said lower section for counter-balancing the movement of said lower section and the movement of the two sections as a unit to said extreme open position, and tension spring means separate from said counterbalancing means for generating lifting efiort in the initiation of movement or" the upper section toward open position, said separate spring means being efiective in a part of the conjoint movement of the two sections to the latter position, to yieldingly retard such conjoint movement.

2. Ina closure for a doorway, an upper doorforming section and a lower-door-forming section, tension spring means for supporting said upper section within the doorway, in closing position, means for moving said lower section in a vertical path to a position in superimposed engagement with said upper section and for moving both of said sections as a unit from such vertical path to a horizontal position above said doorway, torsion spring means for counterbalancing the lower section and the two sections as a unit in their movement to and in such horizontal position, said upper door-section supporting spring means acting to generate a lifting impulse effective to cushion the movement of the lower section into engagement with the upper section, for the inititation of movement of the upper section in unison with the engaging movement of the lower section and to retard the movement of the two sections in a final stage of their actuation in said horizontal position.

3. In a closure for a doorway, an upper doorforming section and a lower door-forming section, tension spring means for supporting said upper section within the doorway, in closing position, means for moving said lower section in a vertical path to a position in superimposed engagement with said upper section and for moving both of said sections as a unit from such vertical path to a horizontal position above said doorway, means for guiding said sections in their vertical and horizontal movement, including (20-,

operating fixed and relatively movable elements, torsion spring means for counterbalancing the lower section and the two sections as a unit in their movement to and in such horizontal position, said upper section supporting means coacting with said moving means in the engagement of said upper section by said lower section to generat a lifting impulse efiective in initiating vertical movement of said upper section in unison with the movement of the lower section into engagement therewith.

4. A sliding closure for a doorway, including upper and lower door-closure sections, trackways lowersection along said 'for guiding said sections invrvertical movement and. retaining them ing position, trackways section, said lower section being adapted to engage with and pick up said upper section for, con tinuing movement of the two sections as a unit,

in the sustainedoperation ofsaid moving means,

V and both sections intheir and counterbalancing torsion springs for controlling the movement of said sections, said 7 spring suspension means reacting to the pick-up engagement of said, upper section by the lower one; to generate lifting efiort and initiate movement of said upper door-section;

, 5. A'sliding closure for a, doorway, upper and lower door-closure sections, trackways for guidingsaid sections'in vertical movementand retaining them in cooperating closure.- forming position, trackways for guiding said sections from their vertical path. of movement to and 1 in-a horizontal path of movement, tension spring includin 1 means for suspending saidupper section between said vertical'trackways, means for elevatingsaid lower section to a position in supe p relation to said upper section, said lower section being adapted to engage and pick up said upper section for continuing movement of the two sections as a unit in a continuous operation of said moving means, and counterbalancing torsion springs efiective in controlling the movement of said sections, said spring suspension means reacting to the impelling effort applied to said upper section by the pick-up engagement of the lower section therewith, to generate lifting efi'ort effective to decrease the load imposed upon said lower section. I

6. A closure for a doorway, door section and a lower door for guiding said sections in vertical movement and retaining them in associated closure-forming position, trackways for guiding said sections from their vertical path of movement toand in a horizontal path of movement, tension spring means including an upper for suspending said upper section between said" said lower to a posivertical trackways, means for moving section along said verticaltrackways tion in superimposed relation to said upper section, said lower section being adapted to engage with and pick up said upper section for continuing movement of the two sections as a unit in the continuous operation of said moving means and ccunterbalancing torsion springs associated with said moving means for controlling the movement of said sections, said spring suspension means coacting with said counterbalancing springs in response to the impact of the pick-up engagement of the lower door-section with the upper one to overcome the inertia forces and main constant the lifting effort produced by said moving means.

'7. In a closure for a doorway, an upper doorforming section and a lower door-forming section, tension means for supporting said upper section in a closure-forming position in the doorway, and for generating a lifting impulse in the initiation of movement of said upper section, means for moving said lower section in a vertical path to a position in superimposed relation to said upper section and for moving both of said sections as a unit in and from such vertical path to a horizontal position above said doorway,

section, trackways and from the I vertical to position; said side-defining members being movwhen said sections are from their appropriately laterally guiding the movement of said sections vertically the aforesaid, horizontal able relative to the guiding portions thereabove in association with-said latter portions, and torsion, spring means connected to said lower. section for counterbalancing said lowersection; in its individual movement conjoining movement to and in: such horizontaljposition; V, l

sliding door" construction, including a doorway havin relatively vertically spaced permanent surfaces, definingthebase and head thereof, and, vertical side-definlngmembers in laterally spaced relationi normally locatabie between said vertically spaced surfaces, means having portions calmed with su ported parallel ;to the head, surface, vsaid said vertical members members being connected to such alined portions for relative movement, devices for detachably interlocking said vertical members with said base surface, said members being adapted to cooperate with sal means to form and lower door-forming sections associated therewith forsliding movement to a vertical closurejdorming p sitionand to a position in association with said means and independent of said vertical members to open said doorway, as defined by said head and base surfaces and said members, said vertical members being shiftable said door-section guiding positions to locate-them above said doorway head-defining surface, whereby the normal rectilineal outline of'the doorway will be interrupted.

9, A sliding door construction, including a doorway formed by relatively vertically spaced ous guideways for the movement of door-forming sections associated with said members to and from open and closed positions,'and means for actuating said vertical members to the aforesaid horizontal position when such door-forming sections are disassociated therefrom and associated with said supporting members.

10. A doorway formed by relatively vertically spaced permanent surfaces, defining the head and base thereof and side-defining members in spaced relation, said members being hingedly mounted in juxtaposition to said head-forming surface for movement from their doorway-side-forming positions to a horizontal position in association with said headforming surface, means carried by said members for detachably connecting said members to said base surface to retain them in their doorway frame defining positions and means for elevating said members to said horizontal position, when disconnected from said base member, to

means, including members defining the sides of the doorway and alined portions the-reabove, said In'embers and saidlalined portions coasting for uideways. for upper adapted to coact disrupt the rectilineal outline of said doorway, normally formed by said head and top surface and said side-defining members cooperating therewith.

11. A sliding door construction, including a doorway formed by relatively vertically spaced permanentsurfaces, defining the head'and base thereof, and side defining members in laterally connected to said alined means," and means for actuating said members on said hinge connections to-raise them to a position substantially parallel to said alined guideway continuationforming means, when the door-forming sections are supported horizontally from said latter means. s 7

12. In a closure for a doorway, an upper and a lower closure-forming section, trackways for up said upper guiding said sections in vertical movement and retaining them in associated closure-forming position, with abutting portions thereof overlapped, trackways having portions alined with said vertical trackways and conformed'to guide said-door sections from their vertical path of movement'to and in a horizontal path of movement, tension spring means functioning as the sole support of said upper section between said vertical trackways, means comprising a conical drum-and cable assembly for moving said lower section from closure-forming position longitudinally of said vertical trackways to a position in superimposed relation to said upper section, said lower section being adapted to engage and pick section from its closure-forming position for continuing-movement of the two sections as a unit between said vertical trackways to a position in arrested supported engagement with said horizontal trackways to clear said doorway, and counterbalancing torsion spring means connected to said lower door section effective in controlling the movement of saidsections in their transposition from doorway closing to doorway opening positions, said vertical trackway members bein displaceable at will from their guideway forming positions'when said door-forming sections are horizontally supported;

' NATHAN MICHELMAN.

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