CA1110194A - Escalator - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An escalator for transporting passengers between upper and lower landings. The escalator includes a fly-wheel, an overrunning clutch, and a fail-safe friction brake. The overrunning clutch and brake, when actuated applies a braking torque only when the escalator is moving such that it would transport passengers from the upper to the lower landing. The inertia of the flywheel and the braking torque of the brake are predetermined to provide the desired range of deceleration, when the escalator stops in either travel direction, regardless of load.

Description

ESCALATOR
BACKGROUND OF THE IN ENTION
Field of the Invention: ~_ The invention relates in general to escalators, and more specif.ica'L'ly to arrangements for stopping an escal.ator.
DescrLpt:ion o~ the Pr:ior Art:
R~lle 804.3 of the ANS'I A17.1-1978 Safety Code for Escalators states that an "escalator shall be provided with an electrically released, mechanically applied bralce capa-ble o~ stopping an up or down traveling escalator with anyload up to brake design load".
The maximum braking eEort i.s required to stop a -fully .Loaded esca:Lator going down, ancl thus the brake is si2ed accordi.ng'Ly. I;'or example, the brake torque is selec-ted to provide some min:imum val-ue of deceleration, such as about 1 ft/sec2, when an escalator with rated load is stopped while transporting passengers from an upper landing to a lower landing. Thus, any other condition than a fully l.oaded escalator golng down wil.l result in a higher rate of deceleration. The highest rate of deceleration, or an : escalator w-ith a fixed braking torclue, would occur when a ~ul-ly loade~l escala-tor is stopped whl.le transporting pas-'' ~ ,.

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2 4~,031 sengers from -the lower landing to the upper landing. This rate may -t~pically be about 8 to 10 ft/sec2.
The prior art has disclosed many different ar-rangements which adjus-t the braking effort~ in order to decrease the range between the minimum and maximum rates of decelera-tion, by taking such things as speed, load and/or travel direction into acco~t. For example~ the braking effort may be adjusted (a) according to the load, (b) ac-cording to speed, such as in response to an error signal which is responsive to the difference between the actual and desired speeds of the escalator while decelerating, or (c) in response to travel direction. In general, such con-trolled braking arrangements adcl ,substantially to the cost of an escalator, as well as to the main-terlance thereo~, because o~ the more complex mechanical and/or elec-trical apparatus requlred.
It would be desirable to provide a new and im-proved stopping arrangement for an escalator which enables an escalator to be stopped within a selected range of de-celeratlon rates, wlthout requiring the speed, load ortravel direction of the escalator to be sensed.
Copendirlg Canadian appllcatlon Serial No. 336,520, ~iled September ~7, 1979, in the name of H. A. Wehrli, III, entitled "Escalator" which application is also assigned to the same assignee as the present application, discloses such an escalator, which will decelerate and stop within a predetermined much smaller r~lge of deceleration than typical prior ar-t escalator~ which apply a fixed braking torque. In the arrangement of this copending application, a predetermined value of iner , -: ~
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t:ia is added to -the escalator drive apparatus, and a brak~
is selected which has about a 50~/~ higher torque rating than the typical prior art escalatox. The added inertia and braking torque are calculated to prc~vide the desired range of decelera-tion for all loads in either -travel direction.
T'he present invention improves upon the arrange-ment of this copending application by rcducing the amount of inertia required to be added to the escala-tor system, and by reducing the amount of brake torque required to be added, for any like range of deceleration.
SUMMARY OF T~IE XNVENTION
Briefly, the present invenl::ion is a new and im p-roved esca'lator or electr:ic stairway wh:ich utilizes an overrunning clutcl^l w:ith a ~ail-saEe brake, w:ith the over--running clutc'h coupling the brake to decelerate the esca-lator only when the direction of the escalator is such that passengers would be transported ~rom the upper to the lower landing. Thus, the brake 3 when actuated, applies its rated braking torque only when the escalator is operati-ng in its 2a down direction. It appl:ies no braking eEfort to the esca-:Lator iE it :is belng opera-ted in the up d:irection. Once an up running st,airway stops, however, the clutch will auto-matically couple the brake to the drive mechanism to pre-vent reversal of the escalator.
In addition to providing an overrunning clutch, inertia is added to the drive system of the escalator.
Inertia is needed to (1~ keep a fully loaded escalator traveling in the up direction Erom stopping too quickly, and (2) to keep an unloaded escalator traveling in the downward direction from stopping too quickly. However, .,, ,......... ,, .. , ,, .. , .,,- . ,~ ............ .. ..

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since there is no braking effort applied by the brake to an up-running escalator~ the maximum deceleration will be applied in situa~ion (2) above, in which an unloaded esca-lator is stopped while traveling in a downward direction.
If inertia is provided to satisfy the seconcl condition, it will also satisfy the first condition. The amoun-t of inertia required is less than that which would be required to be added in the hereinbefore mentioned copending appli-~ cation, however, and thus the brake torque of the brake to be used with the overrunning clutch, and to be applied to a down traveling escalator, is not as large as required -in the copending application. The brake is sixed to prevent a ful:Ly loaded escalator traveling in the clownward direction from exceeding a predetermined stopping cliatance.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention may be better understood~, and fur-ther advantages and uses thereo:E more readily apparent, when considered in view of the following detailed descrip-tion of exemplary embodiments, taken with the accompanying drawings in which:
F:igure 1 is an elevat:ional view of an escalator which may be constructed according to the teachings of the invention;
Figure 2 is a plan view of a drlve ~nit for an escalator constructed according to the teachings of the invention; and Figure 3 is a schematic diagram which illustrates a control circuit for the escalator of Figure 1.
DESCRIPTION OF PREFERRED EMBODIMENT
Referring now to the drawings, and to Figure 1 in .. . . ~ ~ .
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:' '' ' . ~ ; ' particular, there is shown an escalator 10 of the type which may utili~e the teachings o-f the invention. Esca-lator 10 employs a conveyor 12 for transporting passengers between a first or lower lancli.ng 14 and a second or upper landing 16. The conveyor 12 is of the endless type, having an upper load bearing run 18 on which the passengers stand while being transported between the landings, and a lower return run 20.
A balustrade 22 is disposed above the conveyor 12 for guiding a continuous, flexible handrail 24. The balus-trade guides the handrail 24 as it moves about a closed loop which includes an upper run 26 during which a surface of the handrail 24 may be grasped by passengers as -they are transported along the COrlVeyor 12, ancl a :lower return run 28. The handrail 2~ is guided around the balustrade by suitable guide means, such as a T-shaped guide member which is located within the C-shaped cross-section of the hand-rail 2~.
Conveyor 12 includes a plural-ity of steps 36, only a few of which are shown in Figure 1. The steps are each clampecl to a step axle and they move in a closed path, with the cvnveyor 12 being clriven in a conventional manner, such as illustrated in U.S. Patent 3,414,109~ or the con-veyor 12 may be clriven by a modular drive arrangement, such as disclosed in U.S. Patent 3,677,388, both of which are assigned to the same assignee as -the present application.
For purposes of example, the modular drive arrangement is shown in Figure 1.
As disclosed in U.S. Patent 3,677,38g, -the con-veyor 1~ includes an endless belt 30 having ~i:rst and .
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second sides, with eaeh side being formed of -toothed links, 38, in~erconneeted by step axles to which the steps 36 are connected. The steps 36 are supporlecl by main and trailer rollers l10 and 42, respectively, at opposi-te sides of the endless be].t 30. The main and trailer rollers cooperate with support and gu:ide tracks 46 and ~8, respeetively, to guide the steps 36 in the endless path or loop and cause artieula~i.on of the s~eps between platform and step modes at the proper locations. The st.eps 36 are drïven by a 10modular dri.ve unit 52 which includes sprocket wheels and a drive chain for engaging the L~e~h links 38. The modular ; drive unit 52 includes a handrail dri.ve pulley S4 on eaeh side o~ the conveyor whic`h dr:i.ves Lhe hanclra:il drive wnit 56.
I;':igure 2 i.s a plan view of the drive wnit 52 shown in Figure 1., with the drive unit 52 shown in Figure 2 being construeted according to the teaehings of the inven-tion. In general, drive unit 52 ineludes a drive motor 60, such as a three-phase, 60 H~. induetion motor, a gear 20. redueer 62, driven sproeket wheels 64 and 66, and idler sproeket wheels 68 and 70. The gear recl-leer 62, whieh may be a eommercia:l 36.2:1 gear reducer, has an input shaft 72 and an output sha:Et 74. The drive motor 60 has a motor shaft 76. The motor shaft 76 is coupled to the input shaft 72 of the gear reducer 62 by any suitable means, sueh as via pulleys 78 and 80 and a timing belt 82. A broken belt switch 84 monitors the integrity o:E the belt 82.
The out~put shaft 74 of gear redueer 62 is eon nected to the drive sproekets 64 and 66, and eaeh driven 30sprocke-t is coup].ed with an idler sprocket Vi.cl a drive .

chain 86. As illustrated~ the drive chain may have three strands, with the outer two strands engaging teeth on the sprockets, and with the inner strand engaging the teeth on the toothed links 38, -to drive the end:Less belt 30 about its g-uided loop.
According to the teachings of the invention, a fail-safe friction brake 90, and an overrunning clutch 91, are mounted on inpu-t shaft 72 of the gear reducer 62.
Brake 90, whi.ch is electrically released and mechanically applied, may be of any suitable type, such as the caliper brake described in the hereinbe:Eore-mentioned U.S. Patent

3,677,388, or i.t ~ay be oE the plate t:ype i1.lustrated in Eigure 2. In the p.late type, a first plate member~is rotatab:le in ~esponse to clutch 91, ancl a seconcl plate 9~, which is non-rotatable, is pulled back away from the rotat-able plate 92 electrically, against a pressure from a spring or permanent rnagnet. If electrical power connected to the brake is disconnected, the brake sets automatically due to the pressure from the spring or permanent magnet, and i.s thus "fail-safe".
Even though the brake 90 is set when it is de-sirecl to stop the escalator, regardless of the travel direction of the escalator, clutch 91 is arranged to sl.ip if shaft 72 is turning i.n the direction which causes the escalator to transport passengers from the lower landing 14 to the upper landing 16. If shaft 72 is turning in the opposi.te direction at the time brake 90 is released, i.e.;
in a direction to transport passengers from the upper to the lower landi.ng, the clutch 91 is engaged and the brake .90 applies i-ts predetermined torque to stop the escalator.

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If -the brake 90 is applied while the escalator is running in the up direction, clutch 9l slips until the escalator coasts to a stop. If the escalator stops ancl then starts `
-to t.rave] in the downward directiorl, the clutch 91 will automat:ically cease to slip and the brake 90 will be applied to hold the escalator in the stopped condition. The over-running clutch 91 may be oE any desired type 3 such as the roller or sprag t~pes.
As will be hereinafter explainecl, a flywheel 100 is added to the drive unit 52, with the flywheel 100 being preferably applied to that element of the drive which has the greatest rotat:ional speecl. T'he stored energy or momen-hlm provi.de(l by a E'Lyw'hee:l increases wit'h,t'he square oE the rotati,ona:l, spee(l. Th~ls, I)y apply,ing the Elyw'hee:l. to that element having the greatest rotational speed, the si~e or mass of the f:Lywheel is minin-li,zed.
If there is a reduction in the pulley arrangemen-t 78 'and 80 between the drive motor 60 and the reducer 62, the preferable loca-tion -for the flywheel is that illus-trated in E'igure l, i.e., on the motor shaEt 76. If thereiS tlO reduction i,n th:is pu:Lley arrangement, i.e., the arrangernent is 1:], the fl~wheel may be applied to the input sha:Et 72 of the reducer 62. Or~ the inertia required may be divided and applied to both -the motor shaft 76 and to the reducer inpu~ shaf-t 72. ~ile -the flywheel 100 is indicated as being a separa-te component, the 1ywheel 100 may be des:igned as part of the pulley 78, the pulley 80, or both.
I'he fvllowing relationship applies to the drive unit 52 and escala-to:r arrangernent shown in Figures 1 and 2:

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(R~ducer Ratio x B~ake Torque) -~ Passenger I.oad (1) decel~ration = In~rtia of ~scalator When the escalator is traveling i.n the upward direction, the passenger load is positive, and the braking torque applied by the brake is zero. When the escalator is moving in the downward direction, the passenger load is negative, bwt always smaller than the brake torque in order that the brake be capable of holding a full load of passen-gers. Thus, when the escalator is moving in the upward direction, the escalator coasts to a stop. By eliminating the braking effort from the brake in the upward travel direction, a fully loaded stairway going up will deeelerate more slowly than an empty escalator going down. Therefore, it. is only necessary to consider an unloaclecl escalator travel.ing in the downward direction, and a loaded escalator traveling in the downward direction, in considering and selecting the inertia and brake sizes.
The value of the inertia required -to be added to an escalator in order to meet the requirements -that an ...
unloaded escalator, when traveling down, will not deceler-ate faster than the maximum desired cleceleration, may be determined from the Eollowing relationship:

(2) Requirecl Inertia ~ ~esire~--e~rera ~

The desired deceleration range in the above rela-tionship is determined by subtracting the mlnimum desired deceleration from the maximum desired deceleration. The amounk of inertia required -to be added by the flywheel 100 is the difference be-tween the calculated required inertia for the escalator sys~em, and the ~ctuaL iner~ia of the .:
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escalator before such a flywheel is acided thereto. This relationship is given as follows:
(3) Flywheel iner~ia = Required Inertia - Actual Inertia.
'I`he brake torque required ~o meet the re~uire-ments that a loaded escalc~tor traveling in the downward direction wlll not exceed a predeterrnined braking distance, -is given by the following relationsh.ip:

(4) Brake Torque ~ R quired Inertia x Maximum Deceleration The Ratlo of Gear ~educer ''~

The flywheel and brake siæes were calculated for ~o typical prior art esccnlators ha~ing a ~lodular drive, for a 20 ft. ri,se. The values were ca'Lculated on the basis that the f'lywhee:L is mountecl on the motor d-ri~e shaft, ancl the brake :LS moLInLed on l.he inpuL s~haft oE the speecl reducer.
The calculations were made for- a deceleration range of 1 to ft./sec.2, and also for a range of 1 to 2 ft./sec.2.
TABLE ~[
ESCALATOR S~E'EED FLYWHEEL BRA~
PM) ~ F__)___ _ __ (Et~
D c. Ran~e - Ft/~cc Dec. R.~nge -_/ ec.
:L to ~ 1 to 2 ]. to 4 1 to 2 ~ .. _ ~_ ____ __ _~
3_" W:i(lttl 0.~ 5.2 6~.5 93.5 120 2 . 2 9 . 9 60 . 5 93 . 5 90/120 4.1521. 7 60.5 93.5 48" Width 1 . 7 ~ . 2 91 140 120 3 . 6 15 91 140 90/120 7 . 7 34 91 140 A steel flywheel having a diameter of six inches ' , ancl a thickness of one inch has an inertia of .25 lbs/ft2, f~r example, while a steel flywheel ten inches in diameter . . ; . . .
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and khree inches thick has an inertia of 6.5 Ibs/f-t2.
In determining flywheel size, an average braking torque is assumed from rated speecl to zero speed. While the brake utilized in the invention is a fixed brake, the braking -torque applied by a fixed brake ~ay vary with the speed of rotation. If the braking torque characteristic of the particular brake selected does not increase appreciably at -the lower rpm of the drive motor 9 the calculated size of the flywheel may be used without change. However, if the brake torque vs. speed characteris-tic of the bra'ke selected is such that the brake torque inc-reases substantia'lly in vc~ at the lower rpm's, the .qctual. size r~!quire(l for the f'lywhee'l Inay be 'L.lrgei- than ca'lcll'lat:e(l~ in order to prevent the ~naximum deceleral:ion value from being exceeded. The amount of the increase in ~he flywheel size, o~er tha-t calculated, will depend upon the particular characteristics of the brake utili~ed.
Practi.cal experience has also shown that some variation in system co~ponents is to be expected. The bralce torque, gearing eft':iciency, drclg, etc., can all contribute to this variation. Thus, it is preferable to speiEy a brake which is abo-ut 10% larger than the calcu-lated value, with some adjustment means on the brake to provide, Eor exampleS a +0-20% torque range. Then, by rl~nning the escalator in the downward'direc-tion ~ith no load, the exact 'brake torque for each escalator can be obtained by adjusting the brake torque until the desired stopp:ing dis-tance is ob-tained. This adjus-tment then will generate the desired deceleration range, regardless of load n or travel direc-tion.

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Figure 3 is a schematic diagram which illustrates.
a con~rol arrangemen-t which may be used. A safe-ty relay SFR is connected between conductors lO2 ancl 104, which are connected to a source of electrical potenti.al via a string of safety contacts, shown generally as saEety circui.ts 106.
The safety circuits may include contacts from the broken belt swi-tch 8LI, switches responsive to broken step links 38, skirt safety switches, step up-thrust switches, broken drive chain switches, under/overspeed switch, maintenance switches, and t.he like.
I~ the safe~y ci.rcuits :106 i.nclicate there is no malfunct:i.orl i.n t'he ~seala~,or systcm, :re:l.ay SF~. w:i.ll `~e energi.zecl ancl~ closes a contclct SF~-l i n the c:ircuit o:f a control re:Lay CR. A start push button -108 eompletes a series circuit between conductors 102 and lOh which also inc:l.udes the coil of t'he control relay CR, and con-tact SFR-l. A seal-in contact CR-l of rel.ay CR ancl a stop push button 110 are serially connected across the start push button 108.
'rhe dri.ve motor 60 :is connected to a source 112 o electr:ical potential via a contactc)r :I.14 which includes an operating coil 116. The operating coil 116 is conneeted ,`~
between conductors 102 and 104 via a normally open contaet CR-2 of the control relay CR.
The brake coil BK of brake 90 is connected be-tween conductors 102 and lOl~ vi.a a normally open contact CR-3 of control relay CR, and the saety circuits 106.
Thus~ if the safe-ty circuits 106 are all closed, the sa-fety relay SF will be energizecl and its contact SFR-:L will be closed. Actuation of the s~.art push buttoll lOg will then .: : . . ~

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cause control relay CR to pick `up and seal-in via its, contact CR-l. Contact CR-2 will close to pick up contactor 114 to energize the drive motor, and contact CR-3 will close to energize the brake coil BK and disengage the brake.
If the stop push button 110 is depressed while the escalator is operating, relay CR will drop and its contact CR-2 and its contact CR-3 will both open to deener-gize the drive motor 60, and to engage the brake 90~ respec-tively. The same result will occur if any contact of the safety ci.rcuits 106 opens, as relay SFR will drop to open its contact SFR-l, to clrop the cc)nt:rol. relay CR.

Claims (4)

We claim as our invention:

1. An escalator for transporting up to a predetermined full load of passengers, at a predetermined rated speed, in a selected travel direction between spaced upper and lower landings, comprising:
a conveyor having inertia, drive means for moving said conveyor at the rated speed, means for selectively energizing and deenergizing said drive means, said means including a drive motor having a motor shaft, and a speed reducer having input and output shafts, with the output shaft of said drive motor being coupled to the input shaft of said speed reducer, and with the output shaft of said speed reducer being coupled to the conveyor, braking means including an overrunning clutch and a brake, said brake being applied when said drive means is deenergized, regardless of the travel direction, said overrunning clutch operatively coupling said brake to said conveyor only when said conveyor is moving in the down travel direction, to apply a predetermined braking force to said conveyor, only in the down travel direction of the conveyor, when said drive means is deenergized, and inertia means adding a predetermined value of inertia to the inertia of said conveyor, said predetermined value of inertia being selected such that when added to the inertia of said conveyor the sum is proportional to the maximum rated load of passengers divided by the difference between the maximum and minimum desired rates of deceleration, to limit the maximum deceleration of the conveyor when it is unloaded, traveling in the down travel direction, and the drive means is deenergized, said predetermined braking force being selected in response to the inertia of the conveyor plus the pre-determined value of the inertia of said inertia means when transporting the predetermined full load of passengers from the upper to the lower landing times the predetermined maximum desired deceleration, divided by the ratio of the speed reducer, to provide a predetermined minimum decele-ration when the conveyor is transporting the predetermined full load of passengers from the upper to the lower landing, and the drive means is deenergized.

2. The escalator of claim 1 wherein the inertia means is coupled to the motor shaft.

3. The escalator of claim 1 wherein the braking means applies the predetermined braking force to the input shaft of the speed reducer.

4. The escalator of claim 1 wherein the inertia means is coupled to the motor shaft, and the braking means applies the predetermined braking force to the input shaft of the speed reducer.