US3292500A

US3292500A - Hydraulic elevator

Info

Publication number: US3292500A
Authority: US
Inventors: Daniel W Risk
Original assignee: COAST ELEVATOR CO
Current assignee: COAST ELEVATOR CO
Priority date: 1965-09-17
Filing date: 1965-09-17
Publication date: 1966-12-20
Anticipated expiration: 1983-12-20
Also published as: GB1148455A; DE1456344A1

Description

Dec. 20, 1966 D. w. RISK 3,

HYDRAULIC ELEVATOR Filed Sept. 17, 1965 $1. gal

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ATTORNEY United States Patent 3,292,500 HYDRAULIC ELEVATOR Daniel W. Risk, Los Angeles, Calif., assignor to Coast Elevator Company, Los Angeles, Calif., a corporation of California Filed Sept. 17, 1965, Ser. No. 488,064 6 Claims. (Cl. 91-449) This invention relates to hydraulic elevator systems in general, and relates more specifically to an hydraulic control system for supply of fluid under pressure for the upward movement of an elevator.

Hydraulic elevator systems generally employ positive displacement supply pumps, with a conduit from the pump to the elevator ram. Prior practice has been to provide a release or by-pass line and a meter-out system to allow a certain quantity of the fluid to bypass and thus establish the speed of operation of the elevator. All not by-passed to the sump would be theoretically available to the elevator ram.

It has been found that such meter-out control system is seriously defective in that temperature conditions, among other factors, affect the metering system and cause the car to stop short, or overshoot the proper stopping position.

Accordingly, it is the object of this invention to provide a metering-in system, whereby the supply of fluid is controlled to assure a suflicient quantity of fluid to bring the car to the proper floor under all circumstances.

It is a further object of this invention to control the supply of fluid to the elevator, such that the flow will never stop until the actual source is completely cut oil.

In accordance with these and other objects which will become apparent hereinafter, a preferred form of the present invention is disclosed in the accompanying drawing wherein:

FIGURE 1 is a schematic hydraulic system operating according to the principles of this invention;

FIGURE 2 is a graphic representation of the rate of flow to the elevator ram with respect to distance travelled between a starting and destination level of an elevator under one type of incorrect fluid supply;

FIGURE 3 is a similar graph under a second type of defective supply; and

FIGURE 4 is a .graph of the rate of flow with respect to distance travelled under the control of the present inven-tion.

FIGURE 1 of the drawing illustrates a system which will supply oil for the elevating direction of the car. A separate system controls the descent.

In the FIGURE 1, the hydraulic ram of the elevator is represented by the piston and cylinder assembly 10. A source of fluid under pressure is supplied by positive displacement pump 12. A transport conduit 14 is connected to deliver the driving power by delivering fluid under pressure from the pump 12 to the piston and cylinder system 10.

A by-pass system 16 includes a variable flow by-pass valve 18, whereby fluid may be by-passed through a line 20 and out through pipe 22 to a sump 24.

The valve '18 may be of any of a number of suitable 3,292,500 Patented Dec. 20, 1966 bodiment of this invention operates on the principle of an expandable fluid chamber, the illustrated embodiment is purely diagrammatic for illustration of principles.

As thus described, the illustrated valve will cause a complete closing of by-pass flow whenever piston 26 is to the extreme left in FIGURE 1.

By like token, when the dominating forces are able to move the piston 26 to the extreme right, then the passageway of the valve 18 is opened completely. In the drawing, a stop 30 is provided in the piston chamber 27 in order to limit the opening movement of piston 26 to useful limits.

A supply line 32, shown to lead from the bypass line 20, and thus effectively connected to pressure Within the main transport conduit 14, supplies fluid to the cylinder chamber 27 through a needle valve control 34.

Thus, if the chamber 27 is closed against exhaust of fluid, then the supply of fluid through line 32 will'bui-ld up a total pressure within chamber 27. This chamber pressure will create a piston force urging valve 18 to close. However, the same pressure is applied to the opposite side of piston 26. For this reason, the piston 26 has an extension 26A of smaller area operating in a throat 27A to create an unbalance, urging the valve 18 closed under static fluid pressure conditions. If line pressure is removed, then only spring 28 is operative and will open valve 18 fully.

Assuming, therefore, that the chamber 27 has been depressurized, and the spring 28 has completely opened the valve 18, then under such conditions, whenever the pump 12 begins to operate, the fluid output will find a ready escape through the valve 18 and will not supply pressure to the system 10 sufliciently to cause upward movement. However, pressure is available in any condruit of flowing fluid, and back pressure is created even though valve 18 is open. Very quickly, therefore, fluid by-passing through line 20 will begin to supply pressure to the chamber 27, and the piston 26 will move against the action of spring 28. The first such movement will cause an increase of pressure in line 20, and, thereby, accelerate the process.

Refer to the FIGS. 2 to 4. These graphs illustrate comparison of flow rate delivered to the piston and cylinder assembly 10 with respect to car position between a starting location and a leveling oil at a destination, after commencement of operation of the positive displacement pump 12. The graphs are broken to indicate that the car may travel further than one level before stopping. In all instances, the curve begins slowly, because as the piston 26 first starts to close the by-pass system valve 18, the pressure gradually builds up on the elevator piston 10 until movement begins. Because closing of the bypass valve 18 increases the pressure in chamber 27, which in turn closes the by-pa'ss valve further, the action is cumulative. In a short period of time, represented by position A on the charts, the elevator has gained considerable speed, because the volume of supply has beeninc'reased rapidly.. 4

Note, therefore, that the curve beyond position A begins to taper'oif untilit reaches a maximum at position B. This condition is-broughtv about by reason of the fact that as the valve comes into the range of being completely closed, the actual increase in volume rate delivered to the elevator 10 will be comparatively-small with respect to the period of time involved to bring the valve completely closed.

The entire output of the pump 12 is thereafter delivered to the elevator 10 until it is desired to bring the elevator to a stop at a particular floor.

Referring now to the FIGURE 1, an exhaust line 36 is shown to drain fluid from the chamber 27 to the sump 3 24. Therefore, so long as the line 36 is closed, pressure can be built up 'in chamber 27 by supply of fluid through the line 32.. If the exhaust line 36 is opened to sump 24, and is unrestricted, the pressure will bleed away from the chamber 27 faster than it can be supplied through the needle valve 34. In this event, the pressure upon 26A and the force of spring 28 soon takes over and moves the piston 26 into the chamber 27. This action, of course, opens the valve 18 and allows by-pass of fluid. is at this portion of the operation that control becomes critical.

reaches the floor where it should stop, and, thus, will overshoot and will need to return. This situation is indicated in FIGURE 2. The position D in all of the graphs indicates the distance between travel limits at which time the source of fluid under pressure is completely stopped. However, at the time the source is cut off in FIGURE 2, the elevator is traveling and will have some degree of overshooting. Thus, the volume rate curve goes negative in FIGURE 2 to suggest the required direction reversal.

On the other hand, if the by-pass action is too great, then the elevator will come to a stop short of position D, as illustrated in FIGURE 3. This situation is brought about by the fact that the fluid is bled off through the by-pass to such an extent that elevating force is lacking before the proper floor position has been reached.

According to this invention, the supply of fluid to the hydraulic elevator is maintained at a slow and steady pace .after normal de-accelerat'ion, until the floor position is obtained. Thus, the curve of FIGURE 4 shows a slow flat curve end from an intermediate position C substantially to the floor position, and regardless of the condition of the hydraulic fluid, or the by-pass valve, movement upwardly is assured until such time as the pump 12 is brought to a stop, or a dump valve by-passes all supply. By maintaining a slow and uniform travel, stopping will be almost instantaneous when the supply is stopped. Thus, the elevator may be caused to travel until it reaches the proper level, whereupon a cut-off switch stops the supply, causing the elevator to come to a smooth and exact stop at floor levels.

In the FIGURE 1, a solenoid operated on-off valve 38 is indicated as being the primary control factor in opening and closing line 36. This control valve 38 operates in response to the position of the elevator after a control system has been set up by a passenger operating a button to indicate the floor desired, or a person on a floor signaling for the elevator. That is, as the elevator approaches the floor where it is to stop, a pre-set device operates to open the valve 38 and bleed off the pressure in the chamber 27. This causes the de-acceleration shown in each of the three graphs between positions C and D.

A flow-responsive device 40 is provided to sense the flow of fluid through the transport conduit 14, and modulate flow in line 36 accordingly.

The drawing, being diagrammatic only, is limited to symbols of basic elements. A check valve 44 is urged by a spring 46 to close and prevent reverse flow in conduit 14.

This check valve serves the dual function of a drive to operate valve 48.

When the flow is rapid in conduit 14, the valve 44 opens the valve 48 to its maximum extent, and, therefore, line 36 is openwhile the elevator is ascending. Nevertheless, the chamber 27 is closed by valve 38 and will accumulate fluid under pressure.

After the valve 38 has been opened, and flow of fluid through the transport conduit 14 begins to slacken, the

check valve 44 within the conduit 14 will begin to close and valve 48 line 36 will then move toward its closed'position, thus slowing the flow of fluid through line 36. The degree of slowing and time that slowing begins is dependent upon the setting of the spring 46 in relationship with the desired fluid control.

By placing a modulating valve in the line 36, in control of a sensing device in line 14, the modulating valve will gradually close ofl the flow through line 36, and, therefore, the rate of discharge from the chamber 27 is decreased in relationship to the decreased flow in conduit 14. Thus, the function of the device 40 is to cause a decreasing rate of discharge from chamber 27 more than to actually close oil the line 36. However, under extreme conditions of flow reduction in line 14, the sensor may cause the flow control 40 to completely close off line Accordingly, regardless of the fact that line 36 is open to sump pressure insofar as control by the valve 38 is concerned, the rate of flow in the transport conduit 14 ultinratcly determines the degree of bleed-off in the line 36.

Thus, by slowing down the discharge rate through the line 36, the piston 26 may be stopped against further opening of the by-pass valve, and if maintained closed sufliciently long, it is possible for the pressure to build up in the line 36 and reverse the by-pass valve 18. That is, if the line 36 is closed by the device 40 to a degree greater than the input through line 32, the by-pass valve will begin to close.

The relationship between the pressures in the line 32 and the discharge through line 36 is a moment-by-moment relationship, subject to a continuing flow and adjustment which will assure a continuous flow of fluid to the hydraulic cylinder 10, albeit at a predetermined rate.

Thereafter, when the elevator reaches its proper floor, the car activates a control which causes an electrical control system to turn off the pump 12, and at such time, the flow stops completely in the line 14 and the elevator'will come to a smooth and accurate stop.

While the instant invention has been shown and described herein in what is conceived to be the best mode contemplated, it is recognized that departures maybe made therefrom within the scope of the invention which is, therefore, not to be limited to the details disclosed herein, but is to be afforded the full scope of the invention as hereinafter claimed.

What is claimed is:

1. In a hydraulic system having supply means for supplying fluid under pressure,

utilizing means for utilizing said fluid under pressure,

transport conduit means for transporting said fluid under pressure from said supply means to said utilizing means, bypass conduit means for depriving said utilizing means of a variable proportion of said fluid supplied from said supply means,

bypass valve means in said bypass conduit means for variably controlling the deprivation of said fluid from said utilizing means,

pressure responsive means for controlling said bypass valve means, and

pressure supply means for supplying pressure to said pressure responsive means, the combination comprising:

pressure relief means independent of pressure in said transport conduit means for relieving pressure applied to said pressure responsive means, and

flow means responsive to flow in said transport conduit means for controlling said pressure relief means, thereby to control said bypass valve means-and thus control the amount of fluid bypassed by said bypass conduit means.

2. The system of claim 1 wherein said pressure relief means comprises bleed-off conduit means with valve means therein responsive to said flow.

3. The system of claim 2 wherein said bleed-off conduit means leads to a region of pressure substantially less than the pressure in said transport conduit means.

4. The system of claim 1 wherein said flow means comprises velocity sensing means interposed in the flow of fluid through said transport conduit means.

5. In a hydraulic system having:

supply means for supplying fluid under pressure,

utilizing means for utilizing said fluid under pressure,

transport conduit means for transporting said fluid under pressure from said supply means to said utilizing means,

variable bypass conduit means for depriving said utilizing means of a variable proportion of said fluid supplied from said supply means,

the combination including:

flow sensing means interposed in the flow of said fluid in said transport conduit means, for sensing the flow velocity of said fluid from said supply means to said utilizing means, and

control means controlled by said flow sensing means in response to said flow velocity sensed by said flow sensing means for controlling the extent to which said variable bypass conduit means deprives said utilizing means of said fluid.

6. In a hydraulic system having fluid supply means,

fluid utilizing means,

conduit means for transporting fluid from said supply means to said utilizing means,

bypass conduit means for depriving said utilizing means valve means in said bypass conduit means operable to control the bypass of fluid away from said utilizing means,

control means for operating said valve means in accordance with fluid pressure applied thereto,

conduit means for supplying fluid pressure to said control means,

the combination comprising:

bleed conduit means for removing fluid pressure from said control means,

variable opening valve means in said bleed conduit means for variably controlling the removal of pressure from said control means,

flow sensing means for sensing flow in said transport conduit means, and for actuating said variable opening valve means in accordance with fluid flow thus sensed, and

shut-off valve means in said bleed conduit means for opening and closing said bleed conduit means.

References Cited by the Examiner UNITED STATES PATENTS 2,737,197 3/1956 Jaseph.

2,953,902 9/1960 Arbogast.

3,057,160 10/1962 Russell.

3,171,432 3/1965 Bard 137486 EVON C. BLUNK, Primary Examiner.

H. C. HORNSBY, Examiner.

Claims

1. IN A HYDRAULIC SYSTEM HAVING SUPPLY MEANS FOR SUPPLYING FLUID UNDER PRESSURE, UTILIZING MEANS FOR UTILIZING SAID FLUID UNDER PRESSURE, TRANSPORT CONDUIT MEANS FOR TRANSPORTING SAID FLUID UNDER PRESSURE FROM SAID SUPPLY MEANS TO SAID UTILIZING MEANS, BYPASS CONDUIT MEANS FOR DEPRIVING SAID UTILIZING MEANS OF A VARIABLE PROPORTION OF SAID FLUID SUPPLIED FROM SAID SUPPLY MEANS, BYPASS VALVE MEANS IN SAID BYPASS CONDUIT MEANS FOR VARIABLY CONTROLLING THE DEPRIVATION OF SAID FLUID FROM SAID UTILIZING MEANS, PRESSURE RESPONSIVE MEANS FOR CONTROLLING SAID BYPASS VALVE MEANS, AND PRESSURE SUPPLY MEANS FOR SUPPLYING PRESSURE TO SAID PRESSURE RESPONSIVE MEANS, THE COMBINATION COMPRISING: PRESSURE RELIEF MEANS INDEPENDENT OF PRESSURE IN SAID TRANSPORT CONDUIT MEANS FOR RELIEVING PRESSURE APPLIED TO SAID PRESSURE RESPONSIVE MEANS, AND FLOW MEANS RESPONSIVE TO FLOW IN SAID TRANSPORT CONDUIT MEANS FOR CONTROLLING SAID PRESSURE RELIEF MEANS, THEREBY FOR CONTROL SAID BYPASS VALVE MEANS AND THUS CONTROL THE AMOUNT OF FLUID BYPASSED BY SAID BYPASS CONDUIT MEANS.