US2944401A - Hydraulic elevator leveling system - Google Patents

Description

July 12, 1960 w. BECK HYDRAULIC ELEvAToR LEVELING SYSTEM Filed oct. 29, 195s ZfzUe/EZW 1M.: .5,4% ai..

Y 2,944,401r I HYDRAULIC ELEVATOR LEVELING SYSTEM v Walter Beck, Moline, Ill., assignor, by mesne assignments, to Montgomery Elevator Company, a corporation of Delaware Filed oa. 29, 1956, ser. No. 618,800

z claims. (creo-52) This invention relates to a hydraulic elevator mechanism, andinparticular it relates to such a mechanism which includes means for reducing variations inleveling speed of the elevator in .the up direction due to diierences in elevator loading.

Leveling of hydraulic elevators in the up direction has. always presented a serious problem in the fart. For manyj years the commonest arrangement was to .use asingle speed electric motor drivingA oneliquid. pump, and the' controls were such .that .there was no slowdown or speed reduction as the elevator approached `a.oorr atwhich it'k was to stop in the other direction. This necessitated. thiat Vthe stopping switches or iloorseleotor contacts `besofset that the elevator-would carry fullload up .tothe o'o'r, go*V a short distance above the licorv due` toinertia of.the"`` motor, pump, etc., and then settle'back'lto' iloor levell If the controls are setto carry arull loadto floor level, an empty car nraygo 8 or lOinches past floor level.

An improvement on thisY system consists 4in providingh an up leveling bypass valve Iwhich `opens when the elett/afv Itor'is la 'shortdistance below the oorlevel fatwhich a stop is to be made, so that the over-travel ofthe elevator would lbe reduced.

This improvement, however, also has'some disadvan! ftages. When ythe bypass valve opens to initiate the vup leveling operation, it inmediately makes the system sensitive to di'erences in .back pressure due to changesinfthe load 'on the elevator car, because it is obvious thaltthe higher the hack pressure the more rapid will be lthe out-y ow through the bypass. Typical .pressure variations may range from 100 p.s.i. when the elevator car .is emptyj= and 300 psi. when the car is fully loaded. Testreadings ona hydraulic elevator mechanism includingan up level-'1 A ing .bypass valve showed that with full load on ftliecai' the speed during leveling was abo-'ut 5 feet per minute, while'. with the ycar empty the speed was 30 feet per minute..

1 the llleight'in the elevator car 'and the internal peculiari;

ties of the regulator valve itself. Using a commercially' available flow regulator valve which was not specially designed to compensateior external variations in the system, the variation in up 'leveling speed was brought .to a

minimumrof'lZ feet per minute and a maximum of 18 feety per minute. vWhenfthe flow regulator valve is specia1ly, tted to the system in which it is used, this variation may be reduced substantially .to zero.

The invention is illustrated in the preferred embodi` mentfin thev accompanying drawings in which:

Fig. 1 is Ia schematic piping, valve and control circuit' layout for a hydraulic elevator system embodying the invention; and

Fig. 2 is a central longitudinal sectional view of a flow regulator valve which is suitable for inclusion in .the

system of Fig. 1.

.Referring to the drawings in greater detail, the elevatorl system includes a liquid reservoir 10, a hydraulic cy1in der 11, an elevator plunger 12 slda'bily mounted in the 1- cylinder and surmounted by Van elevator car 13, together with suitable piping, valves and pump mechanism for moving hydraulic fluid between the reservoir 10 and thek cylinder 11.- Y l A kA main oilsupply Vline 114 connects the reservoir |10 Y if'. with a positivedisplacement pump 15 which pumpshyspeed.

draulic fluid intoia manifold 16, through a shockless check valve 17, Aand Ithrough a second manifold 18 into' the cylinder 11.` The 'pump 15 is provided with apulley ISabyfmeans of which the pump may be driven by a belt 15b connect-ed -t-o a suitable electric motor (not shown).f Atypicalfsmall install-ation would have a pump 15 adapted to deliver 50 gal-lons per minute when opl era-ted olf ta'n 1800 r.p.m.vmotor at the correct operating Control of elevator movement is effected by a pressure controlled, normally open starting valve 19, a main down valve 20 and a down leveling valve 21, all of lwhich areA provided 'with suitable communications into a ,returnl manifold 22 from which a return line 23 car-ries hydraulic A-uid back tothe reservoir |10'. ILeveling of the elevator Obviously, this is a very undesirable situation .in provid'- w ing accurate leveling of the car at a floor. Y

In accordance with' the present invention fthe-'bypass line for up leveling is provided with a flow regulator valve of a type in which passages 'forl passingiliquid through :the valve havetheir area changed bymovement'l of a valve lpiston so that .the liquid Vwhich-.may pass through the valve varies inversely :with the hack pressure'i in the system which is exerted on the valve piston. With such 'a ilow regulator valve inthebypa'ss line, increased load on the elevator car moves the piston .in a direction to'.

when moving` in the up direction isefrected by means of up leveling bypass means, indicated generally at 24,

which' includes a bypass line 25 which is controlled hy` a solenoid 'bypass vala/e126 and, in Ithe illustrated system,

. abattery of three ilow regulator valves 27, 28 |and 29 `whichrare positioned between an inflow .bypass manifold 370'` and an outflow bypass manifold 31; The bypass valve means '24' perm-its hydraulic uid to be selectively by-lv, passed from the manifold 16 back to the liquid reservoir 10 through the bypass line 25, Ithe manifold 22 and thev return line 23. One or more yflow regulator valves may be required, depending on the capacity of the hydraulicf system land of the valves.

The down valves 20 and 21 and the bypass valve 26. A. are :all 'providedwith operating solenoids, numbered refv spectively 20a,[21aj 'and,26a, vand the solenoids arealli controlled by conventional electric control components.'y

Briefly, the electrical control components may include,

as diagrarnmatically.illustrated in Fig. 1 of the drawing,

l a4 normally open switch 50 whichV is closedv by a suitable reduce the available liquid passage area so that the Avol,R

urne of-liquid which mayipass through the ilow regulator valve is smaller when the pressure .due -to elevator car loading is greater. between maximum and minimum speed ofthe car during up leveling. Y t, 1

Proper design of the ilow regulator valve Itoy substantially eliminate variations in elevator leveling speed due to differences in elevator load` requires that ,theilow This Itends toreduce the difference;

regulator valve bedesigned to compensatefor flow variaf tions in lthe system which are due to factors other' than magnetic device'51 (seev Beck Patent 2,843,697) when. elevator car, 13 ascends to ya vpredetermined position;- VThe closing of switch -50V connects solenoid 26a of the' bypass valve 26 across power` supply leads, 'L1 and L2.,- and, thus, opens valve 26 to permit iluid to flow through" bypass manifold 30, the ow regulator` valves, and'return line 23.

, The operation of valve solenoids a and 21a to open' valves 20v and 21 and e'ect a descent of elevator ear', 13 is controlled by avnorrnally open switch 52. .Switch l E52 comprises herein the normally open contacts of'a con! Patented July 12, 1960I stant pressure push button yunit which contacts close when the push .button is Adepressed for Ydown service and open when the push button vis released. Conventionally, such a push button unit is 4maintained in the depressed position by .ftheoperator until the elevator reaches :a point slightly iaboye :the preselected floor level at which it is intended :the elevator :he stopped. The yclosingof switch 52 connects :solenoid 26a .across power supply leads lLi and l2 :and concurrently energizes a relay coil vv53 'Lto close normally y.open :contacts 54 associated .therewith and thereby connect solenoid ,21 also across `power supply leads L1 and L2. Thus, the main descent .operation -of the elevator car is .eifected .by concurrent opening of valves 20 and ,21.

When the ,elevator car reaches .a point .slightly above the selected vfloor level .and :the voperator :releases the :push button to .openswitch :52, valve solenoid 20a is ,de-.energized. While coil 53 is simultaneously de-energized ito open contacts 54, an alternative circuit tomaintain valve solenoid 21u :energized iis established `to maintain waive 21 open and thereby lower the car slowly ato rthe :preselected floor level. This alternative circuit is established through `a normally open switch 56 :closed by a magnetic device 5'5 on the elevator car (-similar to magnetic device 5,-1) and connected in series with ,a relay Icoil 58 controlling normally open relay contacts 59, which :relay contacts, when closed by Vthe energization of coil `58., bypass contacts 54 to energize solenoid 21a. When the elevator car reaches the selected floor level, magnet-ic device 55 allows switch :56 to open land thereby de-energize coil 5,8., fwhereupon -contacts 59 open and solenoid 21a opens toclose valve 21.

Similarly, v.operation -of the motor to drive thegpump 15 is leffected through conventional elevator control .com-

ponents.

In operation, assuming Vthe plunger 12 to be .at the bottom of its travel and rthe elevator car 13 to be positioned .at .the lowest -loor level which it serves, operation of the elevator car starting control starts up the motor to Aoperate the pump 15 which pumps ,liquid from the reservoir into the manifold )16, and against the check valve 1.7. The start-ing valve 19 is normally `opemwhile the down valves 2.0 and 21 and the bypass valve 26 are normal-ly closed; so that at the .start of .operation liquid from .the pump goes through the starting valve 19 into the return manifold 22. With ydevelopment of pressure in the system, the stmting valve gradually closes through the operation of pressure valve control head 19a so that liquid passes through the vcheck -valve 17 and into the cyl-inder 11 to start raising the elevator plunger 12. When pressure in the system drops due .to cutting off the pump motor, the check valve A17 closes .to ymaintain the plunger in the position which it ,has reached during pump operation.

When it is desired to move the elevator down, the electric elevator controls open both the down valves 20 and 21 so as to permit rapid llow of .liquid from the cylinder 11 into the manifold 22, and back .to Y.the reservoir 10 through the return line 23. When the elevator car gets within a short distance of a floor at which it is to stop in the down direction, the elevator controls close the main down valve 20, but leave the down leveling valve 21 open. The main down valve closes gradually, and when the elevator reaches floor level the down leveling valve also becomes fully closed so that -the elevator may stop .at floor level. The leveling problem heretofore noted in up operation does not occur when the ,elevator is mov-ing down, 'because control of Aelevator travel through the two down travel valves ,20 Aand 21 permits accurate leveling of the elevator car at any floor regardless of the load on the car.

The present invention is directed particularly to the up leveling bypass means v24J which provides `a relatively uniform up travel leveling speed regardless .of variations in elevator loading.

When .the elevator car approaches a Vdoor at which it is to stop, the control circuit operates as previously described *toppen 'the ynormally closed solenoid lbypass valve 26, so the liquid may pass through the manifold 30, the flow regulator valves 27, 2S and 29, the manifold 31 and the bypass line 25. It is obvious that the rate of flow of liquid through the bypass means 24 will vary with the load in the elevator car 13, which will necessarily produce a variation in back pressure .in .the

'- system. Thus, 'with a '-heavy load -on Vthe car, the develing .speed of the elevator will be very low, -due to the rapid flow of liquid through the `bypass means, while if the elevator is empty, or very lightly loaded, the .small back pressure will produce a relatively Slow ow through the bypass means 24 Vand a Acorrespondingly rapid travel of the elevator in the ,leveling zone. This speed variation is eliminated by the ow regulator valves 27, 28 and 29, all of which are structurally alike, so that only the valve 27 will be described in detail with reference to Figure '2.

The flow regulator valve `27 consists of a mai-n valve body 32 which includes a hollow, internally Ithreaded inlet portion V33, -a hollow casing portion 34 of smaller external diameter than the inlet portion, and a hollow, internally threaded outlet lpor-tion 35 of intermediate outside diameter. The casing portion 34 has a cavity 34a which is in direct communicationY with the -hollow inlet portion 33, but which is vseparated from direct communication -with'the hollow outlet portion 35 of the body by a transverse -wall 34h. At l,one end of the casing portion 34 is .a group .of radiallyV extending liquidV outow passages 36 which communicate -vvith an annular vvmanifold `37 :the `inner wall of twhich is-dened by the casing 34^Sand the .outer wall of which is defined by an outer sleeve 38 which seats on an external shoulder 33a of the inlet portion .33 of the `valve body 32. A snap rring 39 engages the other .end of the sleeve and is seated ina recess in .the .outlet end portion 35 of the valve body. From the annular manifold 37 -liquid may pass through a :second group Eof liquid .passages 4.0 Awhich opens .directly into .an .outlet ,bore :35a of the outlet end portion 35 of the valve body 32. Thus, liquid may flow into the lhollow ,inlet portion 33, through .the liquid passages 36, the annular manifold .37, the liquid passages 40 and out through :the outlet bore 35a.

Control of .the flow .of liquid `through .the ow regulator `valve is effected by 'means of a cup-like valve piston 41 which has an end wall 4Z provided with an axial opening 43 and a group of radially extending liquid `ports 44. A snap -ring 45 in the hollow inlet pipe portion 33 acts as a seat for .the valve piston 41, against which the piston is resiliently urged by a valve spring 46 in the chamber 34a. When the valve piston 41 is seated on the Y ange 45 the liquid ports i4 are precisely aligned with the liquid outlet passages 36 `in Vthe casing ,34, so that in this position of the Vvalve piston a maximum Vflow of liquid through the iiow regulator valve is permitted. The spring 46 `is so calibrated `as yto retain the valve piston 4l on the ring 45 when there is a minimum load the elevator car 13. Increase in the load onthe elevator car 13 .produces an increasing backl pressure against the end wall 4'2 of the valve piston 41, land moves the vvalve piston in such a manner as to lreduce the effective area of the liquid flow passages 36. Thus., the available outflow passage area varies linversely with respect to :the

back pressure on the lpiston end .-wall 42 caused by the load in the elevator car 13. Y

The system shown in the patent drawings uses three ow `regulator valves so that each vmay be of relatively small capacity, and between them they are adequate to carry the total volume of liquid adapted to be bypassed through the solenoid bypass valve Z6.

The system is valso provided with an over pressure relief 'valve 47, l'in the conventional manner, which is set to open at a pressure about 10% above 'the normal operating pressure for the system, vso that if there is any failure of the normal operating valves-the relief valve will prevent damage to the system.

The foregoing detailed description is given for clearness of understanding only and no unnecessary limitations are to be understood therefrom, as some modifications will be obvious to those skilled in the art.

I claim:

1. In an operating system for controlling the delivery of liquid to the cylinder and plunger of a hydraulic elevator to control its ascent from station to station and its leveling at a station in the course of such ascent: a constant delivery pump to delivery liquid under pressure; a bypass line; a normally closed bypass valve between said pump and said bypass line; means for opening said bypass valve to admit liquid to said 'bypass line when the rising plunger reaches a predetermined point at which a reduced rate of rise is desired; and a flow regulator valve in said line downstream from the bypassrvalve, said flow regulator valve having a liquid passage and means for modifying the available area of said passage 6 inversely with respect to back pressure at the pump outlet, whereby the rate at which liquid is bypassed remains substantially constant with variations in said back pressure.

` 2. The mechanism yof claim 1 in which the ow regulator valve includes a longitudinally movable valve piston and spring means urging said piston to a position at which the liquid passage in the valve is fully open, said spring means being calibrated to permit movement of the piston to reduce the available area of the liquid passage Iwhen back pressure on the piston exceeds a predetermined minimum value.

References Cited in the file of this patent UNITED STATES PATENTS Moran Nov. 6, 1951

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