US1956153A - Moving stairway - Google Patents

Description

April 24, 1 LINDQUIST ET AL 1,956j53 MOVING STAIRWAY Filed Sept. 22, 1932 10 Sheets-Sheet l UKCSUT N 8 a:

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s a lNVENiORS ATTO NEY April 24,1934. D. L. LINDQUIST ET AL 1,956,153

MOVING STAIRWAY Filed Sept. 22, 1932 10 Sheets-Sheet 2 M NVENTORS W ATTORNEY BY VII [III April 1934- D. LINDQUIST ET AL 1,956,153

MOVING STAIRWAY 10 Sheets- Sheet 3 Filed Sept. 22, 1932- i g I- I a-M Puvsmores ATTORNEY April 24, 1934. LlNDQUlST ET AL 1,956,153

MOVING STAIRWAY Filed Sept. 22, 1932' 10 Sheets-Sheet 4 b 4lb April 24,1934. D. L. LINDQUIST ET AL 1,956,153

MOVING STAIRWAY Filed Sept. 22, 1932 10 Sheets-Sheet 5 BYWJL' T y April 1934- D. L. LINDQUIST ET AL 1,956,153

MOVING STAIRWAY Filed Sept. 22, 1932' 10 Sheets-Sheet 7 {13M LLM L mm M INVENTORS By T1 ATTO-RNEY April 24,1934. D. 1.. LINDQUIST ET AL 1,956,153

MOVING STAIRWAY Filed Sept. 22, 1932 10 Sheets-Sheet 8 fi BY ATT(I)RNEY April 24, 1934. D. L. LINDQUIST ET AL MOVING STAIRWAY Filed Sept. 22, 1932 10 Sheets-Sheet 9 FIG. 28

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April .934. D. LINDQUIST ET AL 1,956,153

MOVING STQAIRWAY Filed Sept. 22, 1932 10 Shets-Sheet 1o INVENTORS BY ATTORNEY Patented Apr. 24, 1934 UNITED ,STATES PATENT OFFICE MOVING STAIRWAY ration of New Jersey Application September 22, 1932, Serial No. 634,338

25 Claims.

This invention relates to moving stairways.

It is the object of this invention to provide a moving stairway which is noiseless, is particularly adapted for high speed operation, and

5 is economical to manufacture, install and main-- tain.

Among the features of the moving stairway in accordance with this invention are the following:

Two equal-lengthed running gear chains, one at each side of the stairway, are connected at regular intervals by a series of uniformly spaced step axles, each step axle extending through corresponding hollow chain pins in the chains at opposite sides of the stairway. To each of such step axles, between the two running gear chains, is removably mounted a step, while on the portions of each of such step axles projecting out on either side of the stairway beyond the corresponding running gear chain are mounted two step wheels, for convenience hereafter identified as the chain wheels. A unitary endless loop is thereby formed of the two connected running gear chains, from which loop any step or number of steps may be removed and replaced with ease, and without opening up either running gear chain or removing the st p axle or axles con-, necting the running gear hains. Further, any one or more of the chain wheels on either side of the stairway may be removed and replaced with equal ease without opening up either running gear chain or removing any step axles. In addition, not only may uniformly pitched running gear chains be employed so thatthe sprocket wheels for such chains at the upper and lower landing are formed with uniform teeth, but the pitch of the running gear chains and the size of the chain wheels are not interdependent, so that the optimum size for each may be employed.

Tracks are provided for the chain wheels both while-the steps are on the upper and while on the return runs of the stairway, with each set of chain wheel tracks extending at least up to and slightly beyond the points at which the running gear chains engage with and disengage from the sprockets therefor at. the upper and lower landings. In this manner, it is assured that each step is supported by its chain wheels until after the support of such step is fully assumed by the sprocket wheels as a result of the engagement of the nmning gear chains therewith, and that the support of each step, prior to the termination of its support by the sprocket wheels, clue to the disengagement of the running gear chains therefrom, is fully resumed by its chain wheels.

In addition, it is preferred that the ends of the chain wheel tracks be adjustable vertically so as to insure that the running gear chains enter and leave the sprocket wheels therefor tangentially. As a result of these provisions, it has been found that the moving stairway is very quiet in operation.

Each step axle connecting the running gear chains at either side of the stairway is preferably free to rotate with respect to such chains, to the chain wheels mounted thereon, and to the step secured thereto. In the event, how- 'ever, that the step axles display a tendency to rotate with the chain wheels, due; for example, to a possible predominance of the friction between the chain wheels and the step axles over the friction between the chains and the step axles, such rotation of the step axles may be prevented, if desired, by suitably interlocking the chains to the step axles.

The two remaining step wheels for each step, for convenience hereafter identified as the trailer wheels, are located adjacent either side of such step and run upon trailer wheel tracks both while the steps are on the upper and while on the return runs of the stairway. To guide the trailer wheels while the steps are passing around the sprocket wheels at the upper and lower landings, substantially semi-circular guides, each with an inner and an outer track flange, are provided. At at least one of the two landings the inner track flange at one side of the stairway is flexibly supported through the medium of springs so that they urge such inner trackflange outwardly. A cramping action of the steps thereby results which takes up clearance and lost motion and eliminates knocks as the steps pass around the sprocket wheel. In the event such cramping action is employed at both the upper and lower landings, it is preferred that the cramping action be effected on one side of the stairway at one landing and on the other side of the stairway at the other landmg.

The chain wheel tracks are preferably cold rolled strips of steel clamped to suitable supports along the stairway, with the tracks at one side of the stairway having a groove formed therein so as to guide the corresponding set of chain wheels, and thus guide the steps. The trailer wheel tracks are either flat cold rolled steel strips clamped tosuitable supports along the stairway, or angle strips secured along the stairway through their vertical sides. By .means of this construction each track has a smooth, even surface over which roll the appropriate set of step wheels, irregularities such as bolt holes and bolt heads being particularly absent. Furthermore, such a track construction readily lends itself to fabrication in units prior to shipment from the factory, so that not only are erection costs of such track units small, but the complete track installation is accurately spaced and aligned.

The step wheels are preferably provided with a canvas or fabric tread formed of a series of canvas; or other fabric, squares radially supported around the circumference of a rotatable disc so that the edges of the squares constitute the rolling surface of each wheel. Noiseless wheels therefore result. In addition, due to the comparatively large coefficient of sliding friction between canvas, or such other fabric as is employed, and the tracks, it is assured that the step wheels roll upon the tracks, rather than slide thereon and develop fiat spots.

The frame of each step is formed of sheet material, such as steel, pressed into shape so as to provide a curved step riser and a portion upon which removable tread plates are mounted. Each tread plate is preferably die cast from zinc alloy, with the side walls of cleats formed therein. The resulting hollow cleats are filled with a suitable plastic stone, which, after hardening, provides a durable wearing surface for the cleats and one which can withstand considerable abuse. In addition, a completely fireproof step is obtained. If still longer life for the cleats is desired, a corrugated steel strip may be placed on edge in each cleat.

One or more of the step frames is provided with an opening through the tread support so that, when the tread plates for such step or steps are removed, access may be had therethrough to the inner parts of the stairway.

The combplates at the upper and lower landings under which each step passes have their toothed ends vertically adjustable so thats the teeth may be made to mesh properly with the recesses between the cleats in the tread plates on the steps. This vertical adjustment is preferably obtained by rotating each combplate about its base end, where it is suitably supported to permit such rotation. In addition, the toothed end of each combplate is preferably secured to its adjustable supports so that it can quickly be released therefrom without the use of tools. Thus, in an emergency, the combplate can be quickly and readily raised to release anything that may have become wedged between the combplate and a step.

One brake is provided for the stairway and the driving motor, such brake being mounted between the two driving sprockets at the upper landing for the running gear chains, with the brake drum secured to the same shaft to which such two driving sprockets are secured. Such brakepreferably of the spring-applied, electromagnetically-released band type-is applied whenever the stairway is stopped, whether intentionally or by reason of the operation of any safety device. As a result of these provisions, a separate brake for the driving motor is unnecessary and space requirements at the upper landing are reduced. In addition, it is assured that the brake is in condition to respond effectively to the operation of any safety device at any time.

A member is provided at the upper landing extending laterally from the brake-which, being between the two sides of the steps, is enclosed by the loop of steps at the upper landing-to one side of the stairway outside the line of the steps.

move, as by turning an appropriate nut, the .otl1er end thereof actuates the brake mechanism so as. to release the brake. The stairway brake may thus be released exteriorly and without dismantling the stairway. This is of particular value in the event the brake, due to some accident thereto, falls to release when the step or steps having the access openings therein are elsewhere than directly over the brake. In such event, the brake may be released exteriorly by the member just described and then the stairway inched around until a step or steps having access openings therein come directly over the brake. Access may then be had to repair the brake.

Each handrail is maintained taut by means of a tensioning weight secured though the intermediary of a suitable flexible cable to the handrail tightener wheel. Slack is prevented from developing in the handrail by preventing upward movement of the tensioning weight, downward movement thereof, however, being freely permitted.

The two ends of each handrail are joined together by lapping the ends in steps, riveting them together with the rivets below the surface of the handrail, and vulcanizing'the joint. This produces a smooth joint which is nearly as strong as the handrail itself.

The balustrading along either side of the runway of the stairway isin units so constructed that the balustrading at any point along the stairway can be removed without disturbing the balustrading at any other point. The individual panels of the balustrating are preferably formed of two plys of thin sheet metal, such as steel, with one ply over each side of a relatively thin core of suitable material. The resulting balustrading is easy to manufacture and install, is fireproof, and is adaptable to varied architectural treatments.

The exposed exterior surfaces of the stairway are preferably encased, from the deckboard adjacent the handrail at one side of the stairway down around the bottom of the stairway truss and up to the deckboard adjacent the handrail at the other side of the stairway, by a monolithic enclosure, such as plaster, suitably supported from the stairway. A simple enclosure is thereby formed, and one which reduces the paneling to be furnished for each stairway to a In addition, such an enclosure is more fireproof, and has less tendency to vibrate, than wood paneling. In the event the stairway is located along a wall so that only one side and the bottom of the stairway are exposed, a monolithic enclosure is employed to encase such exterior surfaces of the stairway as are exposed, from the deckboard adjacent the handrail on the exposed side of the stairway down and around the bottom of the stairway truss.

The floor plates at the upper and lower landings are preferably metallic pans into which a composition flooring, such as artificial stone, is poured while it is in a plastic state. Preferably also, before the flooring hardens, a perforated sheet metal plate is pressed into the surface of the fioor plate so that it is flush with the edges thereof, excess flooring material being removed. a durable floor plate is thereby obtained, and one which lends itself readily to architectural treatment, since not only may various metals be employed for the exposed metal parts of the floor plates, including the perforated plate, but

'the perforations in the perforated plate may be out in any desired design.

The stairway is controlled for overspeed by means of a ball governor driven from the main drive shaft of the stairway at the upper landing. The contacts responsive to overspeed of the stairway are weighted to separate, but are maintained in engagement by. the action of a cam. In the event of overspeed the cam is moved so that it is inefiective to overcome the biasing weight for the overspeed, contacts. Normally, therefore, the contacts then separate. In the event the contacts do not separate, and the stairway continues to overspeed, provision is,made for causing the previously mentioned cam to positively effect the separation of the overspeed contacts. The arrangement is such that once the overspeed contacts separate, they do not reengage as the stairway slows down and stops, but must be reset manually, thereby insuring that the stairway is stopped, and is not started again, until after an experienced attendant has inspected the stairway. v

The governor also controls a second set of contacts. Such set is controlled so that the contacts are separated when the stairway is stationary and engage when the stairway attains a speed appropriately below normal full speed, remaining engaged while the stairway operates at normal full speed. Such contacts are utilized in the control system for the stairway in such a manner that if the stairway, while it is operating in the ascending direction, for example, stops due to the breaking of the driving chain, the brake is applied and the stairway prevented from moving in the decending direction due to the presence of passengers thereon.

Other features and advantages will become apparent from the specification taken in conjunction with the accompanying drawings.

In the drawings:

Figure 1 is a side elevation of a moving stairway according to this invention, with portions broken away to illustrate schematically certain portions thereof;

Figure 2 is a front elevation of a moving stairway from the lower landing, with certain portions thereof and of the adjacent building structure shown in section;

. Figure 3 is a vertical elevation of the upper landing, looking in the direction of the lower landing, with certain parts broken away;

Figure 4 is a vertical section of the moving stairway taken along the line 4-4 of Figure 3;

Figure 5 is a vertical section of the stairway taken along the line 5-5 of Figure 3, illustrating the stairway brake;

Figure 6 is a vertical section taken along the line 6-6 of Figure 5;

Figure '1 is a vertical elevation of the lower landing, looking in the direction of the upper landing, with certain parts broken away;

Figure 8 is a vertical section of the moving stairway taken along the line 8-8 of Figure 7;

Figure 9 is a section through the inclined portion of the moving stairway, at right angles thereto, looking in the direction of the upper landing; Figure 10 is an enlarged section showing the handrail and balustrade paneling and moulding; Figure 11 is a section through the balustrade paneling taken along the line 11-11 of Figure 10; Figure 12 is a plan View of one of the steps of the moving stairway;

'of the step Figure 13 is a vertical elevation of the step shown in Figure 12;

Figure 14 is a section taken along the line 14-14 of Figure 13;

Figure 15 is an enlarged detail illustrating a modified construction;

Figure 16 is an enlarged plan view of a portion tread of the step illustrated in Figure 12;

Figure 1'1 is a section taken along the line 17-17 of Figure 16;

Figure 18 is an enlarged section taken along the line 18-18 of Figure 16;

Figure 19 is an enlarged plan view of a portion of a step tread illustrating a modified construction for the step tread; 1

Figure 20 is a section taken along the line 20-20 of Figure 19;

Figure 21 is an enlarged section taken along the line 21-21 of Figure 19;

Figure 22 is an enlarged fragmental side elevation of a step wheel;

Figure 23 is a section taken along the line 23-23 of Figure 22;

Figure 24 is a plan view of the lower landing, showing the combplate and the floor plates positioned thereat;

Figure 25 is an enlarged section of a floor plate taken along the line 25-25 of Figure 24;

Figure 26 is a plan view of a handrail joint before assembly;

Figure 27 is a plan view of a handrail joint assembled; v

Figure 28 is a plan view of a finished joint;

Figure 29 is a section, taken along the line 29-29 of Figure 27;

Figure 30 is a side elevation of a portion of the chain and trailer wheel tracks as viewed ,in ac- Numbers below 100 designate equipment illustrated in the wiring diagram, Figure 33. Certain of this equipment, however, is also illustrated in other figures.

Numbers between 100 and 199 designate details of certain special equipment, such as the governor illustrated in Figures 31 and 32.

Numbers 200 and above designate the remain= ing equipment. Numbers which differ by 400 units designate corresponding apparatus for the two sides of the stairway. Thus 208 designates the handrail at one side of the stairway and 608 the handrail at the other side of the stairway.

Referring to Figures 1 and 2, the moving stairway, generally designated 200, extends between a lower landing 201 and an upper landing 202. The moving stairway comprises an endless series of steps 203 driven by a motor 85, preferably located at the upper landing as' illustrated. Motor 85 operates through reduction gearing 204, driving chain 205 and sprocket 206, to drive the main drive shaft 207 of the moving stairway. By appropriate equipment, illustrated in subsequent figures, the steps 203 of the moving stairway are driven from drive shaft 207. Two endless mov- 630 at the left thereof.

ing handrails 208, 608, one at each side of the stairway, likewise are driven from drive shaft 207, as is also a governor, generally designated 210.

The moving stairway is mounted upon supporting framework in the form of a truss, generally designated 211, the construction of which is shown in Figure 1. The lower portion of the truss is secured to two crossbeams 212 and 213.,at the lower landing, while the upper portion of the truss is secured to a crossbeam 214 at the upper landing. These beams form supports for the truss, being secured to the building structure. When the driving motor 85, control panel 215 and reduction gearing 204 are positioned as shown in Figure 1, such equipment is mounted upon suitable framework 216 secured at one end towzrossbeam 214 and at the other end to a crossbeam 217. Preferably the truss 211 is enclosed, as by plaster 218 or other covering medium suitably mounted upon the framework of the truss. Similarly, the driving motor andthe equipment related thereto may be enclosed. Suitable access doors 220 may be provided at convenient points as illustrated, to afford access to the enclosed portions of the moving stairway. The stair well at the upper landing is protected by means of balustrading 221 secured to the floor of the upper landing. I

Beneath the framework of the truss 211, and between the truss and the plaster or other medium 218, there is provided a drip pan 222 extending the length of the truss. If desired, this drip pan may be formed of a plurality of removable sections, each overlapping the adjacent section so that oil or other lubricant drippings from the stairway do not seep through to the plaster 218. Asimilar drip pan 223 may be provided under the framework mounting the driving equipment.

The endless series of steps 203 is driven by two endless running gear chains, extending along either side of the steps. The relation of the two running gear chains to the steps and to the step rollers is most clearly shown in Figures 12 and 13. The single step illustrated, generally designated 203, is shown between a running gear. chain 230 at the right thereof and a running gear chain The two running gear chains are similar in construction, each being of the double link roller type, with uniformly S1. aced chain bushings or rollers, 231 for chain 230 and 631 for chain 630, of uniform outside diameter. At every third chain roller in each of the two running gear chains, the chain is provided with a hollow pin, such as pin 632 for chain 630. Connecting the two running gear chains at each of the points therein having such hollow pins, there is a step axle 233 extending across the stairway, through the hollow chain pins, and projecting out beyond each chain. Upon each such projecting portion of each step axle 233 is mounted a chainwheel, the chain wheels adjacent running gear chain 230 being designated 234 while the chain wheels adjacent running gear chain 630 are designated 634. At the extreme ends of each step'axle there are two collars 235 and 635, which are retained in position preferably by taper pins driven therethrough and through the step axle. The'ends of such pins are split, and after assembly are spread apart. It is preferred that each collar 235 and 635 be provided with asleeve extending through the chain wheel and on which the chain wheel rotates. This sleeve is of sufficient length and diameter to provide clearance for the chain wheel between the running gear chain and the collar.

As a. result of the foregoing construction, the two running gear chains 230 and 630 are connected together at every third chain link by the series of step axles 233 throughout the entire loops of the two running gear chains.

As shown in Figures 12 and 13, eachstep axle 233 is free to rotate with respect to the hollow chain pins and to-the chain wheels associated therewith. Preferably, the bore of the hollow chain pins is slightly larger than the diameter of step axles 233. This is to prevent binding of the step axles in the chainpins in the event there should be irregularities in the construction or movement of the running gear chains of such a nature that any hollow chain pin for one chain should not be in alignment with the corresponding hollow chain pin for the other chain.

Under certain conditions of design and operation, when'step axle 233 may have a tendency to rotate with the chain wheel and in the hollow chain pin, it may be desirable to prevent such rotation of step axle 233. Under such circumstances, hollow chain pin 632 and the sleeve extension of collar 635 may be constructed, as illustrated in Figure 15, with a lug-and-slot connection 636. Such lug-and-slot connection 636 is preferably employed, when employed, on only one side of the stairway.

In order to insure that the distance between adjacent step axles in the upper run of the stairway does not fall below a predetermined value, due, for example, to any tendency of a running gear chain to sag between adjacent step axles, the running gear chains are preferably of jackknife construction. This is illustrated for chain 230 in Figures 4 and 8, where links 240 and 242 are provided with extensions 246 and 248, respectively, and link 244 is provided with extensions 250 and 251. These extensions cooperate with stops 247, 249 and 252 on links 241, 243 and 245, respectively, to prevent fiexure of the chain links downwardly between adjacent step axles 233, while such chain links are on the upper run of the stairway. If desired, the stops and extensions may be so proportioned that when the chain links between adjacent step axles are in a straight line, there is a small clearance between each extension and its cooperating stop. Under normal conditions, with such a construction, the extensions do not engage the stops, so that any noise resulting from such engagement is eliminated.

Each step 203 comprises a step tread 254, a step frame 255 and two step yokes 256 and 656. The step frame is formed of suitable sheet material bent into the shape illustrated in Figure 14 so as to provide a tread support 257 and a curved riser 258. Step tread 254 is preferably made up of a plurality of tread plates each of which is bolted or otherwise secured to tread support 257 of the step frame. A small number of the steps, frequently two, in a complete moving stairway preferably have their tread plates secured to tread support 257 by means of screws so that the tread plates may be removed from such steps, and replaced thereon, from the exterior of the stairway. The step frames of such steps are formed with an opening therein, illustrated by the dot and dash outline 260 in Figure 12, so that access may be had to the under side of such steps and to the inner parts of the moving stairway when the tread plates have been removed. If desired, however, each step of the stairway may be constructedwith such opening therein, and with while the trailer'wheelsrollupon a track 274. screwed down tread plates. 1 These two tracks 273 and 274 curve away from The tread plates are preferably constructed each other as shown in Figure 4 was to graduwith cleat formations as illustrated in- Figures ally bring the steps into ahorizontal platform 6 12 and 13. The details of such tread plates will "formation when the. steps-move horizontally at A be discussed later in this description. the upperlandlng. The upthrust track for the l The two step yokes 256 and 656 are secured-to chain wheels 234 during the evolution of the steps the step frame near the sides of the step, as from a chair formation to a horizontal platform illustrated in Figures 13 and 14. These two step formation is a continuation of upthrust track yokes are conveniently die cast of appropriate 272, secured in .a suitable manner so that it is zinc alloy and formed with hubs 261- and 661,- possessed'with an gppropriate'curve, as illusrespectively, of bearings for step axle 233. Each trated. The steps thereafter are reversed in distep is secured to its step axle by means of bear rection as running gear chain 230 passes around ing caps 262 and 662 bolted to the hubs of the a sprocket 275 at the upper landing. While the step yokes. In the event it is desired to remove a steps are on the lower or return run of the instep, the two bearing caps 262 and 662 for such cline, the chain wheels roll on a track 276 while step are removed, whereupon such step'may be the trailer wheels roll on a track 277. During removed from the stairway as a unit. In so re'. this time the. upthrust track forthe chain wheels moving and replacing a step, it is to be noted is a track 278. As the steps near the lower landthat no part of the running gear chains 230, 630 is ing, chain wheels 234 roll upon a curved track disturbed. Each step is centered and maintained 279 and trailer wheels 264 roll upon a curved in position on its step axle 233 by'means of track 280, a track ,281 becoming the'upthrust .spacing sleeves 263 and 663. I track for the chain wheels. At the lower land- .At the trailer end of each of the two step ing, the direction of movement of the steps is yokes 256 and 656, there is mounted a short stub reversed as running gear chain 230 engages and shaft parallel to the step axle 233.- On each passes around a sprocket wheel 282. After the stub shaft there is provided a trailer wheel rolldirection of -movement of the steps has been reing in a plane just inside the adjacent side edge versed at the lower landing and the running gear of the step. The trailer wheel at the side of the chain disengages from sprocket 282, chain wheels step adjacent chain 230 is designated 264, while 234 roll upon a track 283 and trailer wheels 264 the trailer wheel at the side of the step adjacent roll upon a track 284. During this time a track chain 630 is designated 664. 285 is the upthrust track for chain wheels 234. In the illustrated embodiment of the moving Track 286 is a. short upthrust track provided for stairway, step yokes 256 and 656 are shaped as the trailer wheels. The initial portion of tracks illustrated in Figure 14 so that, when the step is 283 and 284 are horizontal so that the steps, as

on the upper incline run of the stairway, the they leave the lower landing, are initially in a trailer wheels roll on an inclined plane, indihorizontal platform formation. Tracks 283 and cated at 266 in Figure 14, which is parallel to 284 subsequently curve so that they gradually but below the inclined plane, indicated at 265, on bring the steps into stair formation as the steps which roll the chain wheels. With such illusenter upon the upper run of the incline. The trated construction, a perpendicular line-extendtwo steps whose'action has thus been traced are ing upwardly through the axis of the trailer then backin their initial illustrated position with wheels is just within the nose of the step. It the chain wheels on track 2'70 and the trailer is thus practically impossiblefor anyone to stand wheels on track 2'71. .1 near the nose of a step in such a manner that While the stairway has been in motion as dehe produces any appreciable turning moment scribed above, handrail 208 has also been in motending to rotate. the step clockwise about the tion. motion has been at substantially the v trailer wheels, as viewed in Figure 14. It lstheresame speed as that of the steps, due to the acfore practically impossible for anyone to stand tion of driving equipment for'the handrail that on the step in such-a manner that he lifts the is to be described in detail later. At this point chain wheels from the track along'. which they it is sufflcient to note that the handrail, while ro?l. In addition, as a result of thisconstructhe stairway is in motion as described above,

tion', the weight of a person standing on the step moves upwardly along a handrail guide 290, where a person normally would stand thereon around a newel wheel 291 at the upper landing, a is approximately equally distributed between the arounda take-up wheel 292 and a wheel 293 chain wheels and the trailer wheels. mounted in the balustrading at the upper land- Reference is now made to Figures 4 vand 8, ing, down along a handrail guide 294, around a which, when pieced togetherwith the lower left newel wheel 295 at the lower landing, and then hand corner of Figure 4 slightly overlapping the back along handrail guide 290. upper right hand comer of Figure 8, illustrate The equipment on the side of the moving stairin vertical section the stairway shown in Figure way not shown in Figures 4 and 8 operates in 1. For convenience, let it be assumed that the the same general fashion as the corresponding stairway is in motion in the ascending direction. equipment illustrated in Figures 4and 8. Cer- Two steps 203 are shown complete, in section, tain specific differences exist, however, but these in stair formation on the upper run of the inwill appear as the'description proceeds. cline near the lower left hand comer of Figure Reference is now made to Figure 9, in which 4. These two steps will be followed'as they move the equipment at both sides of the moving stairthrough a complete cycle and-return to their ilway is illustrated. It will be recalled that this lustrated position. figure is a section through the inclined portion of Whfle the steps are on the upper run of the the moving stairway, at right angles to the inincline, chain wheels 234 roll on a track 270 and cline, looking in the direction of the upper landthe trailer wheels 264 roll on a track 271. During. The framework of the truss 211 along the ing this time, the chain wheels are directly beinclined portion of the stairway includes side neath an upthrust track 2'72. Nearth'e upper members 224 and 624 spaced along longitudinal landing thechain wheels roll upon a track 273 members 7 229 and 629, respectively, at either 150 side of the stairway. Above each track bracket 227 and 627 (except near the lower landing, as shown ,in Figure 8), there is secured thereto and to the truss, a balustrade bracket 228 and 628,

respectively.

Each track bracket is formed witha shoulder 296 or 696, and to each shoulder is fastened, as by clamps 297 or 697,, a track for the chain wheels on the corresponding side of the stairway, track 270 being for chain wheels 234 and track 670 being for chain wheels 634. Suitable sounddeadening shims may be interposed between the tracks and the shoulders. Tracks 270 and 670 are cold rolled strips of metal, such as steel, with track 270 preferably being rolled with a groove therein as illustrated so as to guide chain wheels 234, and thus to guide the steps. There is secured to track 270, between each two adjacent track brackets, one or more (customarily two) separator brackets 298. Similar separator brackets 698 are secured to track 670. Preferably these separator brackets are welded to the underside of tracks 270 and 670. The other ends of these separator brackets are secured to the tracks for the trailer wheels, track 271 being for trailer wheels 264 and track 671 being for trailer wheels 664. As with tracks 270 and 670, it is preferred to weld the underside of tracks 271 and 671 to the separator brackets. The upthrust track 272 for chain wheels 234 is an angle strip the vertical side of which is secured, as by bolts, to track bracket 227. Upthrust track 672 for chain wheels 634 is similarly constructed and mounted.

Near the base of each track bracket 227 and 627 there is formed another shoulder, 300 and 700, respectively, to which tracks 276 and 676, similar to tracks 270 and 670, respectively, are secured in a -manner similar thereto. Tracks 276 and 676 arev tracks for chain wheels 234 and 634, respectively, during the travel of the steps on the return run of the stairway. Upthrust tracks for chain wheels 234 and 634 are angle strips 278 and. 678, respectively, similar to upthrust tracks 272 and 672, and secured to the track brackets in a similar manner. The tracks for trailer wheels 264 and 664 are angle strips 277 and 677, respectively, the vertical sides of which are secured, as by countersunk bolts, to the track brackets.

The track strips are preferably furnished and installed in standard lengths, except for the length of each track of the upper run on'the inclined portion of the stairway nearest the upper landing, which length is made variable to suit the particular installation, and also is provided with an allowance for field cuts. It is also preferred to secure trailer wheel tracks 271 and 671 to their respective chain wheel tracks 270 and 670 by means of the separator brackets 298 and 698 before the tracks leave the factory, thereby forming a chain and trailer wheel track unit. It is thus insured that the. proper spacing between these tracks exists. A side elevation of a portion of a chain and trailer wheel track unit, such as of tracks 270 and 271, together with a separator bracket 298, is illustrated in Figure 30. Separator brackets 299 at the ends of each 3 11 are formed of standard separator brackets 298 from which a portion of the flange on one side of the center rib has been removed. Adjacent chain and trailer wheel track units are joined by bolting together adjoining separator brackets 299, as shown in Figure 30. Adjacent lengths of chain wheel tracks 276 and 676 are joined in a manner similar to joint 302, illustrated in Figure 8 as the joint between chain wheel track 276 and chain wheel track 279. Adjacent lengths of upthrust tracks and othertracks formed from angles are joined by splice bars welded at one side of the joint and bolted at the other, as indicated at 303 in Figure 8. I

As a result of the foregoing track construction, there is provided a track system free from projections and depressions in the track surfaces on which the chain and trailer wheels operate, so

that as a result the steps move along the stairway smoothly, easily and quietly.

Continuing the description by referring to Figure 9, and also to Figures 10 and 11, there is, extending along each side of the stairway and secured to the top of each balustrade bracket, a handrail support, support 305 being secured to balustrade brackets 228 and support 705 being secured to balustrade brackets 628. These supports are preferably formed of sheet material and shaped as illustrated. The base .edge further removed from the center of the stairway fits into a slot in the balustade bracket, while the other base edge is suitably secured to the balustrade bracket, preferably by countersunk bolts. A guide, 290 for support 305 and 690 for support 705, is formed and secured to the corresponding handrail support as illustrated. Handrail 208 fits over and runs upon guide channel 290, while handrail 608 fits over and runs upon guide channel 690. Guides 294 and 694 support and guide handrails 208 and 608, respectively, on the return portions of their loops.

The stairway illustrated in Figures 2 and 9 is located so that one side thereof (the left) is adjacent a wall, while its other side (the right) is exposed. The space between the wall and handrail support 305. is spanned by a deckboard 306. Deckboard 306 is retained in place by moulding strips 307 and 308, bolts projecting from the underside of which extend through the deckboard and through suitable longitudinal strips 309 and 310 appropriately secured to each balustrade bracket 228. In an analogous fashion, deckboard 706 at the otherside of the stairway spans the area between handrail support 705 and stairway enclosure 218. Stairway enclosure 218 is preferably of plaster applied to metal lathing extending along the side of the stairway from the bottom of the truss to deckboard 706. The metal lathing may be fastened to a lattice-work composed of channels 312 and 313, channels312 being appropriately secured to the balustrade brackets and extending from the top of each balustrade bracket to below the bottom of the truss, and channels 313 being small longitudinal channels appropriately secured to channels 312. The underside of the stairway may similarly be enclosed with plaster, the lattice-work for the metal lathing for such enclosure being supported from the lower ends of channels 312 at one side of the stairway, and suitable angles 314 at the other side of the stairway.

In the event the stairway is located so that both' sides of it are exposed, instead of only one side as illustrated in Figures 2 and 9, both sides of the stairway may be enclosed with plaster, from the IOU deckboards to below the bottom of the truss, in a manner similar tothat described for the one exposed side of the illustrated stairway. In such instance, the framework supporting the plaster below the bottom of the truss is secured to the lower ends of channels 312 extending down each side of the stairway. As a result of this construction, there is a monolithic enclosure for the exthe stairway, down around the bottomof the terior of the-stairway extending from the deckboard at the top of the balustrade on one side of stairway and onto the deckboard at the top of the baiustrade on the other side of the stairway. Such an enclosure is readily made, presents a pleasing appearance, is cheaper to install and is more fireproof than panel work and has considerably less tendency to vibrate, and transmit sound than panel work..

For similar reasons, it is preferred to employ a continuous monolithic enclosure for the exteriorly exposed parts of the stairway when the stairway is located along a wall, as illustrated in Figtires 2 and 9.-

'Along each side of the runway of the strairway is the balustrading, generally designated 316 and 716. Inasmuch as the balustrading is similar on both sides of the stairway, only that for the left hand side of Figure 9 (balustrading 316) is described in detail. Figure 10 is an enlargement of such baiustrade to show details thereof. Each baiustrade bracket 228 is provided with three shoulders 317, 318 and 319. The lower shoulder, 317, is provided with a slot therein, while the two upper shoulders, 318 and 319, have secured thereto angle strips 320 and 321, respectively,-which extend along the stairway. Assuming that the balustrading is being installed, a panel 323 is inserted adjacent the sides of the steps so that a hook 324 thereon fits in the slot in shoulder 317. The top edge of panel 323 is secured to angle strip 320 by a moulding strip 325, as illustrated in Figure 10. Moulding strip 325-has a recess therein and into this recess is inserted the lower edge of a second panel 326. The upper edge of this panel rests against angle strip 321 and is secured thereto by a moulding strip 327, as illustrated inFigure r0. Moulding strip 327 is formedwith a recess at any point along the incline, the balustrading adjacent such point may be readily removed without disturbing the balustrading at other parts of the stairway.

It is preferred that the joints between adjacent panels 328, in view of the relative length of such joints, be protected with an H section 322 as illustrated in Figure 11. The joints between adjacent sections of panels 323 and of panels 326 may be simple butt joints.

The panels themselves are preferably formed of two thin sheets'or plys of metal, such as steel, between which is a core of one or more plys of wood or other suitable material. The core is preferably fireproofed if it is not of material inherently fireproof. The exposed ply of metal may be given a suitable surface finish, or, if desired, formed of such material that it inherently cured tothe track carriage at the upper landing,

has the desired appearance. If a wood surface is" desired, the exposed ply or metalmay be provided with a thin veneer of the appropriate wood. The moulding strips are also preferably formed of metal. The balustrading is thus not only fireproof but adaptable architecturally to its surroundings with comparative ease.

Referring now to Figures 3 and 4, which illustrate the upper landing equipment, main drive shaft 207 is driven from the motor by means of the engagement of driving chain 205 with sprock- J et 206. Sprocket 2061s a ring, on which suitable teeth are formed, secured to ashoulder on sprocket 275 for running gear 230. A similar sprocket 675, without sprocket ring 206, is provided for runninggear chain, 630. Sprocket 675. is driven by sprocket. 275 by virtue of the factthat both sprockets are keyed to main drive shaft 207.

The chain wheel tracks 273 and 673 extend to a point slightly beyond the center line of the main drive shaft so that each step 203 is supported-by chain wheel tracks 273 and 673 until running gear chains 230 and 630 seat in sprockets 275/ and 675, respectively. The ends of chain wheel tracks 273 and 673 are supported by brackets 336 and 736, respectively, which are mounted upon the truss by means of a suitable angle, a plate and one or more bolts, such as 337, 338 and 340, respectively, for bracket 336. As illustrated in Figure 3, bracket 336 is preferably threaded, and securable in adjusted position by clamping belt 341, so as to provide a vertical adjustment for track 273. In a similar manner the end of track 673 is vertically adjustable. By means of such adjustments, the running gear chains may be led tangentially onto sprockets 275 and 675. The ends of the chain wheel upthrust tracks 272 and 672 are also preferably made vertically adjustable by virtue" of removable shims positioned between them and their supports, such 115 as 342 for track 272. .Chain wheel tracks 273 and 673 are narrowed down to the width of the chain wheels adjacent the two sprocket wheels so as to provide appropriate clearances between the tracks and the sprocket wheels.

While the steps are reversed in direction as they pass around sprocket wheels 275 and 675, step axles 233 are supported thereby due to the fact that the chain .bushings of the running gear chains seat at the bottom of the tooth formations 125 g .-in' the sprocket'wheelsa Chain wheels 234 and 634, during this time, overhang sprocket wheels 275 and 675, respectively. End thrust tracks are provided for the chain wheelswhile the steps pass around sprocket wheels 275 and 675, one such track, 343, being. shown in Figure 4.

The upper landing is provided with a track carriage in which are formed horizontal track formations for the trailer wheels, track forma-' tions 344 and 345 for trailer wheels 264 being illustrated in Figure 4. Track formation 344 is above the center line of drive shaft 207 and track formation 345 is below the center line of thedrive shaft 207. To guide the trailer wheels while the steps pass around sprocket wheels 275 and 675,

a semi-circular track connectsthe upper and lower horizontal track formations at each side of the stairway. For trailer wheels 664, such semi-circular'track isa unitary member 746, se-

and provided with an inner track 747 and an outer track 748 for the trailer wheels 664, as illustrated in Figure 3. The semi-circular track for trailer wheels 264 is composed of two elements. The first element is member 350 secured to the track 13 urge member 351 to a normal position in which the base portions of the member are separated from the track-carriage. This separation or clearance, indicated at 353 in Figure 4, is subject to being taken up by movement of member 351 against the action of springs 352.

The foregoing construction of the semi-circular tracks at the upper landing, by which the trailer wheels (264) at one side of the stairway are urged outwardly by member 351 while the trailer wheels (664) at the other side of the stairway are guided by a fixed semi-circular track, results in wedging the steps as they pass around sprocket wheels 275 and 675 so that a quiet reversal of, movement of the steps is thereby effected. Such a construction, among other things, eliminates the slap which tends to occur when the trailer wheels I change their bearing surface from the inner semicircular track to the outer semi-circular track when the stairway is operating in the ascending direction, and vice versa when it is operating in the descending direction.

Chain wheel tracks 276 and 6'76 extend past the centerline of main drive shaft 207, as illustrated for track 276 in Figure 4, so that when the running gear chains disengage from sprockets 2'75 and 675, the steps are already supported by the chain wheels on tracks 276 and 676. The ends of chain wheel tracks 276 and 676 are vertically adjustable by means of suitable shims positioned between such ends and their supports so that the running gear chains may be caused to disengage tangentially from sprockets 275 and 675.

The upper landing is provided with a combplate 360 having combs or teeth 361 which project into the spaces between the cleats of the step treads as the steps pass under the combplate. The base end of the combplate is tongue and grooved to a floor plate 362, while the toothed end is supported" on suitable shoulders 363 and 763 on pins 364 and 764, respectively, one at each side of the stairway. Pins 364 and 764 are preferably threaded into their respective supporting members so as to provide a vertical adjustment for the teeth of combplate 360. Preferably, also, the stems of the pins above shoulders 363 and 763 are such that the combplate may be raised upwardly off such pins. Normally wedges 365 and 765, extending through suitable slots in pins 364 and 764, respectively, retain the combplate against pin shoulders 363 and 763. As a result of such construction, in the event of an umbrella end or other body becoming snagged between the teeth of the combplate and a step, the combplate may be raised, the obstruction removed, the combplate replaced and operation of the stairway resumed, all in a minimum of time. In practice, it is customary to provide, proximate to each of the wedges 365 and 765, a small hammer, by means of which one may release the combplate vvithout other tools, and without waiting for the building engineer.

Access is obtained to wedges 365 and 765, which are positioned inside the balustrading, by virtue of the fact that a portion of the bottom panels 323 and 723 is hinged, as shown at 766 for panel 723 in Figure 3. The doors thereby formed extend the length of the combplate so that the combplate may be raised without interference fromthe bottom panels.

carriage and having formed therein the outer Handrails 208 and 608 are driven at the upper landing from sprockets 368 and 768 on main drive shaft 207, handrail208 being driven by a chain 369 which engages sprocket 368 and then-extends up into upper landing balustrade 370, and handrail 608 being similarly driven by a chain 769 which engages sprocket 768 and then extends up into upper landing balustrade 770'. Inasmuch as the drives for the two handrails are similar, further details of the drive are described only for handrail 20s, illustrated in Figure 4.

Chain 369 engages a sprocket wheel 371 keyed to a shaft 372 on which newel wheel 291 is also keyed. Shaft 372 issuitably supported by a newel stand 373 which also supports one end of a channel 374, channel 374 being also supported'by upper balustrade bracket 375. Wheel 293 and a sprocket 376, suitably connected thereto, are rotatably mounted upon channel 374. Chain 369 engages sprockets 371 and 376 to drive the handrail, the diameters of sprockets 371 and 376 being properly proportioned with respect to the diameters of wheels 291 and 293, respectively, so that the circumferential speed of wheels 291 and 293 is the same. An adjustable tightener sprocket 377 is provided for chain 369.

Tightener wheel 292 is rotatably mounted on a carriage 380 which is arranged to slide along two rods, 381 and 382, parallel to channel 374, the

spacing between rod 382 and the plane of the channel being made greater than the spacing between rod 381 and the plane of the channel so that tightener wheel 292 tilts, and thus guides the handrail from the vertical plane of newel wheel 291 to the vertical plane of wheel 293. Rods 381 and 382 are secured at one end to upper balustrade bracket 375, and at the other end to channel 374. Tightener wheel 292 is urged in the direction to maintain tension in handrail 208 by means of a vertically movable weight 383, such weight being connected to carriage 380 by a cable 384 as illustrated in Figure 4.

Preferably a device, such as dog 385 and ratchet teeth 386 formed on the side of weight 383, is employed to prevent upward movement of the weight while permitting free downward movement thereof. Weight 383 thus automatically moves tightener wheel 292 to take up stretch and other elongationsrin the handrail and thus serves to keep the handrail taut. By preventing upward movement of weight 383, slack in the handrail is prevented from developing. example, when the normal motion of the handrail is prevented or retarded at a point removed from the handrail drive, while the handrail continues to be driven by the handrail drive (i. e., while the slippage point is not yet reached at both newel wheel 291 and wheel 293), the handrail drive tends to cause tightener wheel 292 to move so that slack results in the handrail. Such slack is objectionable for many reasons, of which one is that the handrail slack may become entangled with other moving .parts of the stairway, and another is that when the means obstructing the normal motion of the handrail is removed after weight 383 has been, raised and slack developed, the falling back of weight 383 to its initial position in taking up the handrail slack may causethe handrail to break. By preventing upward movement of'weight 383, as in the manner illustrated, so as to prevent movement of tightener wheel 292 in the direction that de- ,velops handrail slack, handrail slack under such conditions is thereby prevented.

It is preferred that the hitch between cable 384 and weight 383 includes a spring 387. v This spring permitssuch small oscillations of tightener wheel 292 as may occur during normal operation of the stairway without causing undue strain upon the handrail.

The handrail drive for each handrail is enclosed within the balustrading at the upper land ing. The top cover piece of such balustrading is preferably removable so as to afford access to the handrail drive. The balustrading 316 and 716, extending along the sides of the runway in the inclined portion of the stairway, is continued along the horizontal portion thereof at the upper landing. The individual panels of such bal-' ustrading, and their manner of support, are substantially identical with that described for the panels along the inclined portion of the stairway, so that the details of such balustrading at the upper landing have not been shown; As mentioned before, however, the lower panels at each side of the upper landing are provided with a hinged section, as indicated by hinges 766 in panel 723.

The upper portion of the balustrading 316 and 716 at each side :of the stairway adjacent the newel wheels rests against the exterior portion of a newel frame for the corresponding newel wheel. This is illustrated in Figure 3, where balustrading 716 rests against exterior portion 791 of newel frame 790. Newel frame 790 is supported upon newel stand 773, as by bolts 792. exterior portion 791 of newel frame 790 are separated by a portion of the circumference of newel wheel 691 which projects through the newel frame. Exterior portion 791 of the newel frame is secured to the interior; portion thereof at the points where the newel wheel ceases to project through the newel frame. Such points are illustrated in Figure 4 for newel wheel 291 and interior and exterior portions 393 and 391, respectively, of newel frame 390, where one such point,

designated 394, is adjacent the transition of handrail 208 from guide 290 to newel wheel 291, and the other, designated shoulder 395, is adjacent the entry of'handra'l 208 into'the upper landing balustrading. upper'landing newel frame is formed to provide a support for the circular handrail brush, brush 396 for handrail 208 beingillustrated in Figures 3- and 4. In addition, shoulder 395 of newel frame 390 is preferably formed with a, suitable recess in which is mounted a set of control buttons for the stairway, generally designated 397. There are three individual buttons-in such set, one, 23, for starting the stairway in the ascending direction, a second, 46, for starting the stairway in the descending direction, and a third, 40, for stopping the stairway. Ihe three individual control buttons comprising set 397 are shown only in the wiring diagram, Figure 33. All three control buttons are protected by a hinged cover 398 secured to a cover plate 399. The first two buttons are preferably operable only with keys in the possession of proper attendants. The third, or stop button, directly under the cup formation in hinged cover 398, may be operated by anyone should occasion require it.

The newel frames may be .made of any suitable metal or alloy so that their exposed surfaces match the metal mouldings, or otherwise be subject to architectural treatment.

Main drive shaft 207 is provided with a brake, generally designated 90, positioned on the shaft between sprockets 275 and 675. Brake 90, as

The interior portion 793 and the Such shoulder for each 9 illustrated in Figures 8, 5 and 6, is of the band type, operating on brake drum401 keyed to shaft 207, and is applied by the action of spring 402 raising arm 403. Arm 403 is pivotally supported upon a bracket 404, which in turn is secured to crossbeam 405 of the upper landing drive assembly. A brake magnet 79, when energized, releases the brake by depressing arm 403 against the action of spring 402. Arm 403 actuates a brake switch 73, the functions of g a lip of crossbeam 405. A vertically extending rod 411,is pivotally secured to such end of member 408, as by a pin 412 passing through an eyeformed on rod 411. The upper end of rod 411 passes through a chord angle 413 of the truss, and is provided with a threaded nut 4l4bearing against angle 413, and with one or more lock nuts.

It is to be noted that the end or member 408 to which rod 411 is secured extends out beyond the vertical plane, indicated at 415 in Figure 6,

including the side edges of steps 203.

In the normal position of the parts, with the outer end of member 408 resting on crossbeam 405, a nut 416 secured to rod 406 is spaced from arm 403.so that arm 403 does not engage it during normal application and release of the brake. When rod 411 is raised, however, as by screwing nut 414 down on rod 411, member 408 is rotated so as to cause nut 416 on rod 406 to engage arm 403 and depress such arm, thereby mechanically releasing the brake. Resort may be had to this simple manner of releasing brake 90 from outside the loop of steps 203 in the event it jams or for any cause refuses to release when the brake magnet is energized or in the event the brake magnet burns out. The starting can then be inched along until the two or more steps having the removable tread plates come opposite the brake so that access may be had to the brake through such steps, or by removing such steps, in order to repair the brake. In the absence of this external release for brake 90, access could be obtained to the brake, and the brake repaired and released, only with considerable difiiculty and with appreciable dismantling of the stairway.

The upper landing equipment is preferably constructed into three principal assembly units, these being the main drive unit and the two handrail drive units. The main drive unit comprises all the equipment mounted upon or about main drive shaft 207, including the brake, the track carriages, and the crossbeam. The handrail drive unit for each side of the stairwaycomprises the newel stand, the upper balustrade bracket, the channel supported by such stand and bracket, and the equipment mounted on such stand, bracket and channel, the newel frames excepted. These three principal assembly units are shipped complete from the factory, so that as a result there is a minimum of field work in aligning and installing the upper landing equipment. Upper landing curved tracks 273 and 274 are also preferably shipped from the factory in an assembled unit, being secured together by suitable separator members 418 welded to the undersides of the stairway.

Referring now to Figures 7 and 8, which illustrate the lower landing equipment, running gear chains 230 and 630 engage two sprocket wheels 282 and682, respectively, while the direction of travel of the steps is reversed at the lower landing. Shaft 420, to which sprocket wheels 282 and 682 are keyed, turns in suitable bearings at either side of the stairway, such bearings being supported upon a carriage generally designated 421. Carriage 421 is provided with rollers 422 and 822 rolling upon tracks 423 and 823, respectively, at each side of the stairway so'that it has a horizontal movement in the line of the stairway. Running gear chains 230 and 630 are maintained under tension as a result of carriage 421 being urged leftwardly, as viewed in Figure 8, this being effected by weights 424 and 824, oneat each side of the stairway. Weight 424 is formed on the end of an arm 425 that is pivotally mounted at 426 upon the truss. To a short bell crank lever extension of arm 425 is secured a rod 427, rod 427 being connected, preferably Surrounding rod 430, and maintained in po-' sition by suitable nuts, is a collar 431. A bell crank lever 432, pivotally supported upon a plate secured to lower newel stand 433, has the end of one of its arms pivotally secured to collar 431. The end of the other of its arms is formed so as to straddle a tripper arm 434. Tripper arm 434 is provided with a shoulder by means of which a switch arm 435, pivotally supported at 436, is maintained in raised position. When tripper arm 434 is actuated so as to remove its shoulder as a support for switch arm 435, switch 435 rotates downwardly about its pivot and actuates a carriage safety switch 42, the contacts of which are enclosed within the box illustrated. Appreciable movement of the forked end of bell crank lever 432 in either direction from its normal position mechanically actuates tripper arm 434, so that as a consequence, any appreciable movement in either direction of weight 424 and thus of the corresponding side of carriage 421, from its normal position, causes the operation of carriage safety switch 42.

Similarly, any appreciable movement from its normal position, in either direction, of the side of carriage 421 to which weight 824 is secured, results in operating a corresponding carriage safety switch, 43, for that side of the stairway.

The operating mechanisms for the carriage safety switches are initially adjusted so that, as long as carriage 421 remains in its position determined by the length of the running gear chains and by the tension therein imparted by weights 424 and 824, the switches are not operated. In the event either or both sides of the carriage move appreciably from this normal position due, for

example, to the breaking of one or both running" gear chains, or to the snagging of a 'chain or step-the resulting motion of the carriage, whether forward or backward, causes the operation of the appropriate carriaggesafety switch. y means of instrumentalitiesto' described-later, the operation of either carriage safety switch effects i the stopping of the stairway.

- Preferably the carriage safety switches are required tofbe reset manually. This insures that the stairway will not be restarted until the proper attendant is summonedand has made an inspection and has repaired the trouble;

Carriage 421 is provided with horizontal track formations for the trailer wheels, track formations 437 and 438 for trailer wheels 264 being illuctrated in Figure 8. Track formation 437 is '-above the centerline of shaft 420 and track formation 438 is below the centerline of shaft 420. To guide the trailer wheels while the steps pass around sprocket wheels 282 and682, a semi-circular track connects the upper and lower horizontal track formations at each side of the stairway. "For trailer wheels 264, such semi-circular track is a unitary member 440, similar in coristruction and function to unitarymember 746 for trailer wheels 664 at the upper landing. Memher 440 is secured to the lower carriage 421 and is provided with an inner track 441 and an outer track 442 for trailer wheels 264. The semi-cir- -cular track for trailer wheels 664 at the lower landing is preferably composed of two elements 843 and 844, similar in construction and function to the twoelements 350 and-351, respectively, for trailer wheels 264 at the upper landing. In this manner quiet operation is assured as the steps pass around the sprockets at the lower landing as well as when they pass around the sprockets at the upper landing.

It will be noted that the movable semi-circular member, 351, at the upper landing engages trailer wheels 264, while the movable semi-circular member, 844,. at the lower landing engages trailer wheels 664. The wedging action of the steps is thus effected at one side of the stairway at the upper landing and at the other side of the stairway at the lower landing. This is the preferiged arrangement. If desired, however, such wedging action may be effected at either landing only, or on the same side of the stairway when provided at both landings.

The end of trailer 'wheel track 280 fits into an appropriate slot alongside the-lower track of lower horizontal track formation 438 so as to provide a continuous support for trailer wheels 264 regardless of the position of the movable lower carriage 421. A similar provision is made for the joint between the lower track of upper horizon-' tal track formation 437 and trailer wheel track 284, and for the joint between chain wheel track 283 and chain wheel track 445 carried by the carriage, as well as for the three corresponding joints at the other side of the stairway.

Also movable with carriage 421 is a short track 446 for chain wheels 234. One end of this track is secured to carriage 421 so that track 446 is a continuation of track 445. The other end of track 446 rests on a bracket 447 bolted to an angle 448. Bracket 447 extends through a plate 450 and is provided with adjusting nuts threaded thereto. Bracket 447 is secured to the truss by means of one or more bolts 451 passing through plate 450, the truss, and angle 448. Bracket 447 is secured on the truss after carriage 421 is installed and its normal position ascertained, bracket 447 being'positioned so as to support track 446 near its free end when in its normal position. Track 446 is of such a length that its

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