US3842943A

US3842943A - Hydraulic elevator

Info

Publication number: US3842943A
Application number: US00341372A
Authority: US
Inventors: M Takenoshita; H Yumino; I Nakamura; F Fujisawa
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1972-03-15
Filing date: 1973-03-15
Publication date: 1974-10-22
Anticipated expiration: 1991-10-22
Also published as: JPS5326378B2; DE2312959A1; JPS4894136A

Abstract

A hydraulic elevator is constructed so that acceleration and rated speed running in both ascent and descent are controlled by adjusting the quantity of the working oil flowing from an oil pump, with deceleration during at least the descent being controlled by throttling an oil passage carrying the discharging oil from the working chamber of the hydraulic elevator through a throttle valve. The oil pump is preferably a positive pump having a constant delivery for a constant given speed.

Description

United States Patent 1191 Nakamura et al.

1 1 HYDRAULIC ELEVATOR [75] Inventors: Ichiro Nakamura, Katsuta; Fumio Fujisawa, Mito; Mitsuaki Takenoshita; Hiroshi Yumino, both of Katsuta, all of Japan [73] Assignee: Hitachi, Ltd., Tokyo, Japan [22] Filed: Mar. 15, 1973 21 App]. No.: 341,372

[30] Foreign Application Priority Data Mar. 15, 1972 Japan 47-25700 [52] US. Cl 187/28, 60/477, 91/454, 187/17, 187/38 [51] Int. Cl B66b l/24 [58] Field of Search 187/28, 17, 38, 68, 29 A; 91/469, 454, 455, 457; 60/413, 477

[56] References Cited UNITED STATES PATENTS 2,737,l97 3/1956 Jaseph 187/17 2,913,070 11/1959 Nyberg 187/29 A 3,020,891 2/1962 Jaseph 187/38 3,057,160 10/1962 Russell et al 187/17 3,105,573 10/1963 Leveski 187/38 3,120,880 2/1964 Jaseph 187/17 3,570,243 3/1971 Comer et al. 187/28 Primary ExaminerRlchard A. Schacher Assistant Examiner-Jeffrey Nase Attorney, Agent, or FirmThomas E. Beall, Jr.

[ 5 7 ABSTRACT A hydraulic elevator is constructed so that acceleration and rated speed running in both ascent and descent are controlled by adjusting the quantity of the working oil flowing from an oil pump, with deceleration during at least the descent being controlled by throttling an oil passage carrying the discharging oil from the working chamber of the hydraulic elevator through a throttle valve. The oil pump is preferably a positive pump having a constant delivery for a constant given speed.

20 Claims, 10 Drawing Figures HYDRAULIC ELEVATOR BACKGROUND OF THE INVENTION The present invention relates to hydraulic elevators, particularly where the speed control of the hydraulic elevator is constructed so that the ascent or descent of the load supporting surface is controlled by the supply or discharge of liquid to or from an expansible chamber defined by. a cylinder and piston pair arranged to drive the load supporting surface of the elevator.

In prior elevators of this type, speed control for the hydraulic elevator has been accomplished during ascent of the elevator by throttling the quantity of fluid flowing from the oil pump into the expansible chamber and during descent of the elevator by throttling the quantity of fluid being discharged from the expansible chamber, with each being conducted by a throttle valve. With this system, there is energy loss of pressurized fluid, oil, that is discharged from the oil pump into an oil reservoir or storage tank during ascent of the elevator, and during descent of the elevator there is further energy loss of pressurized oil discharging the expansible chamber through the throttle into the oil reservoir or tank. These energy losses appear to manifest themselves as heat.

During the ascent of such an elevator, the elevator loses energy during acceleration and deceleration, and the amount of energy loss is equal to the product of the difference between the amount of oil flowing from the oil pump and the amount of oil supplied into the expansible chamber times the pressure of the oil in the expansible chamber.

Accordingly, the heat generated by the energy loss over a period of time varies with the number of starts and stops of the elevator, which correspond to the number of accelerations and decelerations; as the number of starts and stops become greater, the amount of heat being produced by energy loss correspondingly increases.

During descent of the elevator, the energy losses that exist during running of the elevator are equal to the product of quality of oil discharging from the expansible chamber times the pressure of the oil within the expansible chamber. In this case, the amount of heat produced by the energy loss is greatly influenced by the running distance in addition to the number of times that the elevator starts and stops over a given period. As the number of starts and stops become greater and the running distance is longer, the amount of heat being produced correspondingly increases.

If the amount of heat being produced over a given period of time becomes relatively great, it will have the following undesirable influences upon the various characteristics of the elevator, namely:

1. As the oil temperature becomes higher, the lifetime of the working oil used in the elevator correspondingly becomes shorter. Therere, the elevator must be provided with an oil cooler, which accordingly will increase the cost of the elevator and produce other difficulties.

2. The viscosity of the working oil will vary according to variations of its temperature. With viscosity variations, the pressure drop across the throttle valve will correspondingly vary, and accordingly the running characteristics of the elevator do not remain constant.

Due to the variations of the pressure drop produced as mentioned above by the corresponding variations in viscosity of the working oil, the time in which the elevator is running at the landing operation speed varies, which will. greatly reduce the comfort of the designed ride.

4. Because of the above-mentioned variation of pressure drops, when the elevator stops at a floor inv a building, the difference between the height of the floor of the carriage and height of the floor of the building will thus vary accordingly. Therefore, the safety of the elevator becomes quite low.

These and other affects show that an increase in oil temperature is quite undesirable in a hydraulic elevator.

In conventional speed control for hydraulic elevators, the abovementioned heat generation of the working oil has been considered to be unavoidable, and th following method has been applied thereto.

In the case where it may be predicted that the number of times the elevator is in operation over a predetermined period of time and correspondingly the amount of heat generated by losses over this time are to be relatively small, the landing position of the elevator may be adjusted by anticipating the variation of the landing operation times to the variations of the landing speed.

In the case where it may be anticipated that the quantity of heat generated or the heat losses will become relatively great because of the corresponding high number of times, longer running distances and the like over a predetermined period of time, a cooler for cooling the working oil may be provided. Such coolers may be of the air-cool type or the water-cool type, which choice is usually dependent upon the conditions within the building. However, since water supply or change of air is occasionally not sufficient according to the conditions of the building, cooling is correspondingly occasionally not sufficient for the working oil of the elevator.

As a means of solving the heat generation problem due to losses during throttling, it has been further proposed to employ a constant delivery oil pump that will produce a quantity of oil pumped that is proportional to its rotational speed to be used to vary the speed of the elevator. In such a system wherein the constant delivery oil pump is used for the speed control of the elevator, very little heat is generated since the working oil is not being throttled. According to this system, the speed control at the time of acceleration and rated speed of the elevator in both cases of ascent and descent of the elevator is accomplished without any great amount of trouble. However, considerable troubles appear when such a system is used during deceleration of the elevator, particularly during descent of the elevator.

Namely, slow-down of the elevator speed, deceleration, greatly influences the performance of landing with respect to a floor, and it is very difficult to control the slow-down speed of the elevator by the adjustment of the amount of working oil flowing from the pump by controlling the speed of the constant delivery pump. In the case where slowdown of the elevator speed during descent is controlled through the pump, the motor being driven by the pump must generate forces corresponding to the braking forces required by the pump and the force due to the pressure of the working oil in the expansible chamber, therefore, a defect of such a system is that the motor drivingly being driven by the pump generates a large quantity'of heat that is being induced therein by losses. There are a corresponding great number of disadvantages resulting from the generation of such a large quantity of heat within an electric motor.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a hydraulic elevator in which the temperature elevation of the working oil is quite small, while avoiding the disadvantages mentioned above. A simple hydraulic circuit is employed for controlling the speed of the elevator, while providing a comfortable ride without shocks.

Particularly, a hydraulic elevator is constructed so that acceleration and rated speed running during both ascent and descent is controlled by the amount of fluid being pumped, and further deceleration during at least the descent of the elevator, is controlled by throttling the oil as it passes through a throttle valve.

BRIEF DESCRIPTION OF THE DRAWINGS Further objects, features and advantages of the present invention will become more clear from the following description of a preferred embodiment of the present invention as shown in the following drawing, wherein:

FIGS. 1 through 4 each disclose a diagrammatic view of a variation of a hydraulic elevator according to the present invention;

FIGS. 5A, 58, 6A, 6B, are graphic views showing the relationship between the quantity of working oil flowing and the running conditions of the hydraulic elevator according to the present invention, along with the heat being generated thereby; and

FIGS. 7A and 7B are graphic views showing the heat generation and the relationship between the quantity of working oil flowing and the running conditions of a conventional hydraulic elevator.

DETAILED DESCRIPTION OF THE INVENTION Although different variations of the present invention are shown in different Figures, many of the elements employed therein are common and correspondingly will be provided with the same numerals so that they need only be described in detail once with respect to their structure and operation.

The hydraulic elevator as shown in FIG. 1 includes a cage 37 having therein a load supporting surface, a cage driving means comprising a cylinder 41 and a plunger 39 forming therebetween an expansible chamber and mounting the cage 37 on the top of the plunger 39, oil reservoirs or

tanks

9a and 9b for providing a source of working oil, an oil pump 55, a motor 3 for driving the pump 55, in inertia disk or fly wheel 53 for increasing the inertia of the rotary parts including the rotor of the motor 3 and the rotating working member of the pump 55, an accumulator 57 for absorbing fluctuations of the working oil, various valves, and oil passages all interconnected in a fluid circuit to be described below in function.

The pump 55 is a positive pump that will have a constant delivery for each pumping speed, so that the quantity of oil pumped is proportional to the speed at which the pump is driven by the motor 3 through the inertia disk 53. The pump inlet sucks oil from the oil tank 9a through a strainer 7. The working oil flows from the pump 55 under pressure to the change-over valve 61 through an oil passage 13. The pressurized working oil is delivered to the cylinder 41 of the elevator expansible chamber through the pilot type check valve 19, which valve is constructed so as to open in one direction under pressure as an ordinary check valve and further to open for flow in either direction when actuated by pressurized oil in its pilot line 29. The change-over valve 61 has three valve blocks 61a 61b, 610, each of which has two oil passages for switching the direction of flow for the working oil. One passage 65 of the change-over valve 61 leads to a throttle valve 45. The throttle valve 45 has the block 45a and the block 45b, with movement of the valve between the two blocks being gradual with the change between the two blocks providing a correspondingly gradually changing throttle orifice in the line 65 varying continuously from thefull blockage of fully aligned block 45b to the full opening of fully aligned block 45a, to correspondingly gradually increase or decrease the quantity of working oil flowing through the line 65 depending upon the direction of movement of the valve blocks. A further oil passage 63 of the change-over valve 61 fluid communicates with the passage between the pump 55 and the strainer 7.

The pilot type check vlave 19 is disposed in fluid communication between the change-over valve 61 and the accumulator 57, inthe oil passage 47. The pilot oil for controlling the opening of the pilottype check valve 19 is controlled by the change-over valve 31, which has a block 31a for providing communication between the pilot acuator of the check valve 19 and the oil reservoir or tank 9b for venting, and further has a block 31b for providing pressurized oil communication between the pressurized oil passage 35 in direct communication with the chamber 41 and the pilot actuator of the pilot check valve 19; thus, the pilot check valve 19 may be either vented through passage 29, block 31a, passage 33 and oil tank 9b or it may be pressurized through passage 29, block 31b, passage 43, and passage 35 leading to the pressurized working chamber of the cylinder 41. A relief valve 11 will relieve excess pressure from the line 13 to the oil tank 9a. The accumulator 57 communicates with the remainder of the system through a restrictive orifice or throttle resistance 59.

Operation of the device according to FIG. 1 during ascent of the elevator, will be described below.

The normal positions for the various valves and movable elements of the system are as they are shown in FIG. 1. Particularly, the normal state for each of the electromagnetically operated change-over

valves

61 and 31, and the throttle valve 45 is in each case that the block 61a, 31a and 45b is respectively connected with the

oil passage

13, 47, 63 and 65, the

oil passages

29, 33 and 43, and the oil passages 65, all as shown in the position of FIG. 1.

To start the ascent of the cage 37 of the hydraulic elevator, the block 61a of the electromagnetic changeover valve 61 is replaced in position by the block 610 so as to allow the oil passage 13 to communicate di rectly with both the

oil passages

47 and 65 by energizing the electromagnet 61e provided for driving the valve 61 in accordance with a control signal produced for the ascent of the elevator. Afterward, the oil pump 55 is driven in its normal pumping direction through the inertia disk 53 by rotation of the motor 3 in its normal driving direction. Thereby, the oil pump 55 sucks the working oil from the oil tank 9a through the strainer 7 and delivers it under pressure into the oil passage 13. The working oil under pressure is introduced to the pilot type check valve 19 through the block 61c of the change-over valve 61 and the 'oil passage 47. When the pressure of the working oil in the oil passage 47 becomes higher than the pressure of the working oil in the passage 35, the working oil automatically opens the pilot type check valve 19, which here is acting as an ordinary check valve, and the working oil is thereby delivered to the cylinder 41 through the oil passage 35 to raise the plunger 39 with the cage 37 thereon and expand the working expansible chamber.

In order to accelerate the inertia system comprising the inertia disk 53, the oil pump 55, the cage 37 and the plunger 39, the starting torque of the motor 3 is chosen so that the acceleration of the cage 37 during the starting of the ascent of the elevator falls within the predetermined range of acceleration allowed in view of the comfort desired for the ride of the elevator. Acceleration of the pumping speed will produce :1 corresponding acceleration of the elevator cage ascent speed, due to the positive displacement nature of the pump 55.

A control device 3a is used to determine the starting torque of the motor 3, which is by means of controlling the voltage supplied to the motor 3, with the starting voltage being lower than the rated voltage of the motor 3. Thus, the quantity of the working oil flowing from the oil pump 55 during acceleration of the elevator can be set to the working oil quantity desired so that the elevator will have the desired acceleration, all as controlled by the voltage supplied the motor 3 by the volt age control means 3a. Accordingly as the flow of oil from the pump 55 increases proportionately to the in crease in motor'speed and pump speed, the cage 37 is accelerated.

On the other hand, since the starting voltage is lower than the rated voltage, in the case of running the elevator at the rated speed, the variation of slip of the motor 3 becomes large according to the variation of the load of the elevator. For improvement of this phenomena,

when the rpm of the motor 3 approaches the rated rpm of the motor 3, the input voltage as determined by the control means 3a for the motor 3 is switched over to the rated voltage of the motor 3 so that slip of the motor does not greatly vary in accordance with load variations.

In the case where the motor 3 is running at its rated speed, the working oil flows from the oil pump 55 at its rate of delivery to correspondingly move the carriage 37' at its rated speed.

When the cage 37 approaches the floor or level where it isto stop, the control motor 25 is driven with a slow-down signal from a control pannel to gradually and continuously change the throttle valve from block 4512 tothe block 45a so as to correspondingly gradually increase the quantity of oil that is returned from the pump through line 13, change-over valve block 61c, and line 65 to the oil reservoir tank from the oil pump 55. As the quantity of the. workingoil passsing through the throttle valve 45 increases as the block 45a moves check valve 19, the quantity of oil passing through the pilot type check valve 19 becomes zero as the pilot type check valve is automatically closed to hold the cage 37 at the desired position. That is, the elevator will decelerate with movement of the throttle valve from the position of block 45b being aligned with passage 65 gradually to the position of block 45a being aligned with the passage 65. When the elevator cage 37 has stopped, the motor 3 will be stopped rapidly by electrical or mechanical braking, and at the same time the electromagnetic change-over valve 61 is returned to its normal position by de-energizing the electromagnet 6le; thereafter, the throttle valve is returned to its normal position after it has been removed from the fluid circuit by the change-over valve 61, that is, the throttle valve 45 is moved by its motor 25 to where the block 45b instead of the block 45a is aligned fully with the passage 65, which is accomplished with a suitable signal from the control to operate the motor 25 in the reverse direction to its normal throttling direction.

Operation of the hydraulic elevator according to FIG. 1 during descent will be set forth below.

In starting the descent of the elevator, the change over valve 31 is operated by suitable signal from the control to its electromagnet 310 to replace the block 31a with the block 31b. Thereby, the oil passage 29 from the pilot check valve 19 will be in pressurized fluid communication with the oil passage 43 which with the passage 35 leads to the cylinder 41; accordingly, the pilot type check valve 19 will be opened to allow the oil passage 13 to communicate with the oil passage 35 through the block 61a of. the electromagnetic change-over valve 61, the oil passage 47, and the pilot opened check valve 19. With this arrangement, oil discharging from the cylinder 41 will flow through the oil pump in the direction reverse to its normal rotary pumping direction, which normal direction is the pumping direction of the oil pump as driven by the motor3 through the inertia disk during ascent of the elevator. The pump 55, rotating in reverse, will drive or be driven by the motor 3 through the inertia disk 53, which motor 3 will be energized. At the same time as starting of the motor 3, the control motor 25 is driven to change the throttle valve 45 from the block 45b to the block 45a in the above mentioned gradual continuous manner of decreased throttling. In this manner, the oil from the expansible chamber of the cylinder 41 is discharged into the oil tank through the oil pump 55 and the strainer 7. As the speed of the pump 55 increases, the speed of the descent of the cage 37 correspondingly increases, that is, as the pump 55 acting as a turbine accelerates, the descent of the cage 37 will correspondingly accelerate.

When the cage 37 is running downwardly at its rated speed, the oil pump 55 is driven as a hydraulic motor or turbine by the working oil discharging from the cylinder 41. However, as the pump is braked by the regenerative braking of the motor 3, the speed of the oil pump is held constant at the desired rate of descent speed.

When the cage. approaches the floor or level at which it is to stopduring the descent while running at its rate of descent speed, a slow-down signal for the elevator will be provided to the electromagnetic valve 61 to change it from the block 6lato the block 61b, by energizing the electromagnet 61d, to allow the oil passage 47 to communicate with the oil passage 65 and to allow the oil passage 13 to communicate with the oil passage 63. As previously mentioned, the controlled motor 25 was started when the descent of the elevator was started, so that by the time it is desired to decelerate the descent of the elevator, the block 45a of the throttle valve 45 is in full alignment with the oil passage 65, so that when change-over occurs with block 61b replacing block 61a, the working oil which has been discharging the cylinder 41 through the oil pump 55 will thereafter be discharged into the oil tank 9a through the throttle valve 45a to start the deceleration of the descent; at the same time, the working oil from the oil pump 55 is circulated through the passage 13, the block 61b, and the passage 63 and the motor 3 may be stopped by electrical or mechanical braking so that the motor may be returned to its normal rest position for the next operation.

At the same time as the electromagnetic change-over valve 61 is changed from the block 61a to the block 61b to start the deceleration of the descent, the control motor 25 of the throttle valve 45 is actuated-to gradually change the throttle valve 45 from the block 45a to the block 45b to correspondingly gradually increase the throttling of the fluid being discharged from the cylinder 41. Thereby, the flow of the working oil returning to the oil tank 9a through the throttle valve 45 from the cylinder 41 will correspondingly decrease with the increased throttling so that the speed of the cage 37 will slow down, that is so that the descent of the cage 37 will be decelerated. When the throttle valve 45 has completely changed from the block 45a to the block 45b, the cage 37 will stop.

After the cage 37 has stopped as mentioned above, the pilot type check valve 19 is closed by de-energizing the electromagnet 31c of the change-over valve 31 to return the change-over valve 31 to the normal position, that is to change from the block 31c to the block 31a and thereby vent the pilot of the pilot valve 19. Thus, the pilot valve 19 will close and-the cage 37 will be held at the position where it has stopped. Thereafter, the appropriate electromagnet of thechange-over valve 61 is de-energized to return its valve to its normal position. It is'noted that the throttle valve 45 has already returned to its normal position and the motor 3 has already stopped, which is its normal position.

The block 45a of the throttle valve 45 is so constructed that the pressure drop across it when the working oil is passing therethrough is fairly lower than the pressure within the cylinder 41 at the time when the elevator has no load. Thereby, when the elevator is running downward or descending at its rated speed, although the electromagnetic change-over valve 61 is changed from the block 61a to the block 61b to introduce the working oil from the cylinder 41 to the throttle valve 45, the cage 37 does not freely fall and does not spoil the comfort of the ride designed characteristics of the elevator.

The accumulator 57 is in communication with the oil passage 35 and thus the expansible chamber of the elevator through the restriction 59 to keep the comfort of the ride by absorption of hydraulic impulses or shocks induced at the time of the motor starting the voltage change-over, or the electromagnetic valves changeovers.

The hydraulic elevator as shown in FIG. 2 differs from the previously described elevator of FIG. I in that the electromagnetic change-over valve 61 of FIG. I has been replaced by the electromagnetic change-over valve 61' of FIG. 2, so that the throttle valve 45 operates only during deceleration of the elevator during its descent, and deceleration of the elevator during its ascent is accomplished solely by electrically or mechanically braking the motor 3. Otherwise, the construction and operation of the corresponding elements are the same as those mentioned above. The operation of the hydraulic elevator according to FIG. 2 will be briefly described below.

The normal condition of the electromagnetic valve 61' is as shown in FIG. 2 wherein the block 61a communicates with the

oil passages

13, 65, 47 and 63.

For the ascent of the elevator of FIG. 2, the oil pump 55 is driven by the motor 3 through the inertia disk 53. Because of the oil pump, the working oil is delivered under pressure to the pilot type check valve 19 from the oil tank 19a through the strainer 7, the oil passage 13, the valve block 6l'a and the oil passage 47. When the pressure in the oil passage is higher than the pressure within the oil passage 35, the pilot type check valve 19 will automatically open as an ordinary check valve, and the working oil under pressure will be supplied to the cylinder 41 through the oil passage 35. As the flow of the working oil from the oil pump 55 increases proportionately with the speed that the oil pump 55 is being driven, the speed of the cage 37 will correspondingly increase, that is, with acceleration of the pump 55, the cage 37 will correspondingly accelerate. When the speed of the oil pump 55 has reached its rated speed, the cage 37 will be running at its rated speed.

For the slow-down or deceleration of the elevator ascent, the speed of the motor 3 will be decreased by mechanical braking or by dynamic braking obtained by impressing a dc voltage upon the motor 3. The motor is easily braked by small braking force for deceleration of the ascent due to the gravity affects of the cage 37 and the piston 39, so that the heat produced by braking the motor 3 is negligible and the capacity of the braking system for the motor 3 may be relatively small.

For descent of the elevator according to FIG. 2, the operation of the hydraulic circuit and speed control is the same as the operation of the elevator previously described with respect to FIG. 1; therefor, further description will be omitted and reference may be made to the description and operation of FIG. 1 for corresponding elements and function.

The hydraulic elevator as shown in FIG. 3 will be described below.

As the construction of the element between the oil passage 147 and the cage 137 is similar to that shown in FIG. 1 for corresponding elements, the construction of the remainder of the elements will be discussed in detail below. That is, structure corresponding to that of previous Figures will not be described again and reference may be made above with respect to its operation.

In FIG. 3, the oil pump 155, which is again of the pilot type check valve 119. The change-over valve 169 is provided with an electromagnet operator 169C to block the passage 163 with the valve block 169a or provide for free flow through the passage 163 with the valve block 16% to bypass the oil pump 155. A throttle valve 145 and a change-over valve 167 are fluid connected by an oil passage 175. An oil passage 165 of the throttle valve 145 is connected with the oil passage 147, and an oil passage 173 from the change-over valve 167 is connected with the oil passage 113 at the position adjacent to the oil pump 155. The change-over valve 167 has a block 167a in which the working oil can pass through, a block 167b for changing an oil passage and an electromagnet 167C to effect the change of these two blocks. The change-over-valve 169 has a block 169a to check the oil or prevent its flow and a block 16% to pass the oil therethrough, and an electromagent 169c to affect the change of these two blocks. The throttle valve 145 has a block 145a to pass oil, a block 145b to check oil, and a control motor 125 to gradually change the valve between these two blocks.

First, the operation of the hydraulic elevator will be described with respect to the construction of FIG. 3. The normal position of each of the change-over

valves

131, 167, and 169, and the throttle valve 145 are as shown in their positions of FIG. 3. I

For the ascent of the elevator according to FIG. 3, upon the receipt of a suitable instruction or signal from ,the control pannel or circuit, the control motor 125 is ,driven to change the throttle valve 145 from the block 1450 to the block 145b, at the same time, themotor 103 is energized to rotatably drive the oil pump 155. With rotation of the pump 155, the working oil will flow from the oil pump into the

oil passages

113 and 173 under pressure. The working oil supplied under pressure to the oil passage 173 is checked by the block 145b of the throttle 145, and the working oil supplied under pressure to the oil passage 113 will automatically open the check valve 171 to permit the flow of oil under pressure into the oil passage 147 when the pressure in the oil passage 113 becomes higher than the pressure within the oil passage 147. When the pressure of the working oil within the oil passage 147 becomes higher than the pressure of the oil within the passage 135, the working oil will automatically open the pilot type check valve 119 to permit the flow of the oil under pressure into the cylinder 141 through the oil passage 135. Thereby, the plunger 139 with the cage 137 will ascend. As the speed of the oil pump 155 increases, the speed of the cage 137 will correspondingly increase. That is, when the oil pump 155 is accelerated, the cage 137 will accelerate. When the speed of the oil pump 155 reaches its rated speed, the cage will be running at its rated speed.

After the above, an instruction for the slow-down of the elevator will be provided to the circuit of FIG. 3

when it is desired to stop the ascent of the elevator. For such a signal, the change-over valve 167 will be changed from the block 1670 to the block 1671) through energizing the electromagnet 1676 of the changeover valve 167 to allow the oil passage 175 to communicate with the oil passage 177. At this time, the control motor of the throttle valve 145 will be driven to gradually change the throttle valve 145 from the block 145b to the block 1450, that is to decrease its throttling. Thereby, part of the working oil from the oil pump 155 will be gradually discharged through the oil passage 165, the throttle valve 145 the oil passage 175, the change-over valve 167 and the oil passage 177 to the oil reservoir or tank 109a; at the same time, another part of the working oil from the oil pump 155is supplied into the cylinder 14]. The quantity or flow of the working oil discharged into the oil tank 109a will be increased by gradually enlarging the oil passage of the throttle valve 145 as the control motor 125 changes from the block 1451) to the block 145a and reduces the throttling action; accordingly, the speed of the cage 137 will slow down or decelerate as the flow of oil into the cylinder 141 decreases. When the throttle valve 145 has completely achieved the displacementof the block 145a, the pressure of the oil passage 147 becomes lower than the pressure within the cylinder 141, and accordingly, the pilot type check valve 119 is auto matically closed to keep the position where the cage 137 has stopped. Thereafter, the motor103 is stopped by electric or mechanical braking. After this, the change-over valve 167 is de-energized to return it to its normal position.

Next, the operation of the hydraulic elevator according to FIG. 3 during the descent will be described below.

During descent of the elevator as shown in FIG. 3, the change-over valve 131 is energized according to an instruction or signal of descent to displace the block 131b to the position of the block 131a. Thereby, the working oil from the cylinder 141 is introduced to the pilot of the pilot type check valve 119 to correspondingly open the pilot type check valve 119 and to allow the passage of oil from oil passage directly to the oil passage 147. As the throttle valve is in its normal position, the working oil from the cylinder 141 is introduced to the oil pump through the check valve 119, the throttle valve 145, and the change-over valve 167. Thereafter, the motor 103 is driven in the direction inversed to the normal direction, the normal direction being defined as that of ascent of the elevator, to rotate the inertia disk 153 and the oil pump 155. Thereby, the working oil from the cylinder 141 is discharged into the oil tank 9a through the

oil passages

135, 147, and 165, the throttle valve 145, the changeover valve 167', the oil passage 173, the oil pump 155, and the strainer 107 to accelerate the cage 137 in descent.

When the oil pump 155 has reached its rated speed, the cage 137 will be descending at its rated speed, that is at a steady speed.

For the slow-down of the elevator to reach or stop at a particular level, a suitable instruction is provided as a signal for the slow-down, and the control motor 125 with the throttle valve 145 is driven to gradually displace the block l45b to the position of the block 145a. At the same time, the motor 103 is gradually braked. As the pressure within the oil passage 147 becomes higher than that in the cylinder 141 with the resistance increased against the working oil flowing in through throttle valve 145, the flow of the working oil through the throttle valve 145 decreases. In the case where the decrease in the flow of working oil is greater than the degree of slow-down of the motor 103, the interior of the

oil passage

173 and 175 will tend to be pumped out and become vacuous so that the oil pump 155 would be in danger of being broken. To prevent this, the block 169a of the change-over valve 169 is displaced to the position of the block 16% by energizing the electromagnet 169C to supply the working oil from the oil tank 9a to the oil pump 155 as it slows down.

When the throttle valve 145 has completely accomplished the displacement of the block 145!) to the posi tion where fluid will no longer be discharged from the cylinder 141 and the elevator thereby stopped, the pilot type check valve 119 will be closed with deenergization of the electromagnet 1310 by a suitable signal.

At the approximately same time as the displacement of the block 145b of the throttle valve 145 has been accomplished, the motor 103 will stop. Then the changeover valve 169 will be returned to the normal position by de-energizing its electromagnet 169C, and at the same time, the throttle valve 145 will be returned to its normal position by rotating the control motor 125 in the direction reverse to the rotary direction at the slowdown of the elevator. Thereby, operation of the descent of the elevator will be completed.

Most of the structure function of the hydraulic elevator as shown in FIG. 4 is similar to that previously described, with corresponding parts being provided with similar numerals.

In FIG. 4, the cage 237 is provided with a plunger 239 and the cylinder 241 for its operation, which are in turn in communication with the oil passage 235, the accumulator 257, the orifice 259, the pilot type check valve 219, an oil passage 229, an electromagnetic change-over valve 231, an oil reservoir tank 209b, an oil passage 233, and an oil passage 243, all of which correspond to the similar elements as set forth in FIG. 1 with a corresponding operation as previously described in FIG. 1.

An oil pump 255, which is also of the positive displacement type with constant delivery for constant speed, is connected with a motor 203 through an inertia disk 253. The suction side of the oil pump 255 is connected with the strainer 207 leading to the oil tank 209a, and the pressure side of the oil pump is connected with the throttle valve 245 through an oil passage 213. The throttle valve 245 by itself corresponds to the throttle valve 45 in FIG. 1. The throttle valve 245 and the pilot type check valve 219 are fluid interconnected by an oil passage 247. A by-pass comprising a check valve 249, an oil passage 251a and an oil passage 251b, is provided so as to by-pass the oil pump 255. A relief valve 211 is provided in parallel with the check valve 249 to relieve excess pressure in the system.

The normal state of the change-over valve 231 is as shown with the block 231a thereof connected with

oil passage

229, 243 and 233 as shown in FIG. 4. The normal state of the throttle valve 245 is with the block 245a thereof in communication with the

oil passages

213 and 247.

For the ascent of the elevator as shown in FIG. 4, a suitable instruction or signal is provided for the ascent of the elevator to operate the motor 203 to drive it in the normal direction to rotate the oil pump 255 and the inertia disk 253. Thus, the oil pump will suck the working oil from the oil tank 209a through the strainer 207 and discharge it under pressure into the oil passage 213. The working oil from the oil pump is introduced to the oil passage 247 through the block 245a of the throttle valve 245. When the pressure within the oil passage 247 becomes higher than the pressure within the oil passage 235, the working oil automatically opens the check valve 219 so that the oil may flow into the cylinder 241 to elevate the cage 237.

The starting torque of the motor 203 to accelerate the inertia disk 253, the oil pump 255, the motor 203, the cage 237 and the plunger or piston 239, is so determined that the acceleration of the cage 237 at the start of the ascent falls within the allowable accelration that has been predetermined in view of the comfort desired for the ride of the elevator. The starting torque is determined by the voltage control means 203a, as in all of the preceding embodiments, so that the voltage of their motor at starting is lower than the rated motor voltage. As the motor 203 is running with input voltage lower than the rated voltage, slip of the motor 203 varies largely with variation of the load of the elevator, which appears to be a large variation of the rated speed of the elevator. To prevent this phenomena, when the speed of the motor 203 approaches its rated speed, the input voltage is changed to the rated voltage of the motor 203 by the voltage control means 203a, so as not to largely vary the slip or the slip rate of the motor according to variation of the load on the elevator.

When the motor 203 is running at its rated speed, the oil pump 255 will be pumping at its rated flow rate, so that the cage 237 will be ascending at its rated steady speed.

When the cage 237 approaches a floor or level where it is to stop, an instruction or signal for slow-down of the elevator will be given. Accordingly, the input voltage of the motor 203 is switched off and the dc voltage is impressed on the motor 203 to brake it, which braking is known as dynamic braking. The gravity of the cage 237, the plunger 239, and the passage resistance of the working oil flowing to the cylinder will further act as a brake force on the inertial system comprising the cage, the plunger, the working oil flowing t0 the cylinder, the pump and the inertia disk. Accordingly, the dc voltage corresponding to the braking force required for the motor in addition to that produced by the above-mentioned gravity and passage resistance is relatively small and may be provided quite easily. Therefore, the motor 203 does not generate much heat during this braking and does not produce a great amount of noise by braking due to supplying the small dc voltage to the motor 203 to slow down or decelerate the descent. The braking of the motor 203 obtained by supplying the dc voltage serves to accurately align the elevator at the desired position where it stops. When the motor 203 is stopped, the flow of the working oil passing through the pilot type check valve 219 becomes zero and the pilot type check valve 219 automatically closes to hold the cage 237 at the position wherein the cage stopped.

For the descent of the elevator as shown in FIG. 4, the electromagnet 2310 of the change-over valve 231 is energized according to an instruction or signal for the descent of the elevator to change the valve 231 from the block 231a to the block 231b. Thereby, the working oil from the cylinder 241 is directly communicated with the pilot of the pilot type check valve 219 through the

oil passages

243 and 229 to open the pilot type check valve 219. Thereby, the cylinder 241 and the oil pump 255 are placed in direct fluid communication for discharge of working oil from the cylinder 241 through the

passages

235, 247 and 213. After this, the motor 203 is driven to rotate the oil pump 255 and the inertia disk 253 in their reverse direction. The oil pump 255 sucks the Working oil from the cylinder 241 and discharges the working oil into the oil tank 209a through the strainer 207. The descent will accelerate until the rated speed of descent is obtained.

After this, when it is desired to stop the descent, a signal for slow-down of the descent is provided to the control motor 225 of the throttle valve 245, to gradually change the block 245a to the block 245b. When the oil passage from the cylinder is slightly throttled by the throttle valve 245 (when the pressure in the oil passage 213 becomes a little less than in the cylinder 241), the input voltage of the motor 203 is switched off and the dc voltage is applied to the motor 203 to brake the motor 203. Slow-down and stopping of the cage 237 are accomplished by the throttle valve 245, a rotary system comprising the inertia disk 253, the oil pump 255, and the motor 203 is braked by braking the motor 203 with the dc voltage applied to the motor 203. Therefore, a small dc voltage is supplied to the motor 203 that is just for braking the motor 203, and it is not necessary to slow the speed of the rotary system proportional to the deceleration of the cage speed. If the rate of slow-down of the rotary system is greater than that of the cage 237, the oil pump 255 is driven by the working oil from the cylinder 241. If the rate of slow down of the rotary system is less than that of the cage 237, the oil pump 255 sucks the working oil from the oil tank 209a through the oil psssages 251b and 251a and the check valve 249, and discharges into the oil tank through the strainer 207. Thus, the rate of slowdown ordeceleration of the descent of the cage 237 is under the control of the throttle valve 245.

When the block 245a of the throttle valve 245 has been displaced to the position of the block 245b, the change-over valve 231 is de-energized to displace the block 231b to the position of the block 231a. Thereby, the pilot or the pilot type check valve 219 is discharged or vented to thereby close the pilot type check valve 219. Thus, the cage 237 will be held at the fixed position. Thereafter, the control motor 225 will be driven to displace block 245b to the position of the block 245a to return it to its normal position. As the motor 203 is stopped, the cage will also stop at about the same time. Thus, the elevator will be returned to its normal rest position awaiting the next instruction.

In the various Figures, voltage control means 3a, 103a and 203a have been shown to accomplish the voltage control mentioned throughout the description, which is applicable to all of the Figures and accomplished preferably by means of variable resistance.

According to the present invention, the temperature elevation of the working oil is very small. This important point will be further discussed and made clear with respect to the following Figures that compare the conventional elevator with the elevator of the present invention.

Heat generation for the hydraulic elevator according to FIG. 1 appears only during slow-down, that is deceleration, in both ascent and descent of the elevator. The amount of this heat generation corresponds to the hatched portions in FIGS. 5a and 5b.

In all of the FIGS. 5 through 7, Op equals the quantity of working oil flowing from the positive displacement oil pump, for example 55 in FIG. 1.

Qcy equals the quantity of working oil supplied into the cylinder, for example 41 in FIG. 1.

Qv equals QP minus Qcy equals the quantity of the working oil discharged into the oiltank through the throttle valve, for example, 45 in FIG. 1.

Accordingly, the energy loss is equal to the amount of the product obtained by multiplying Qv by the pressure in the cylinder, Fe. The energy loss is as heat generation.

The heat generation of the hydraulic elevator as shown in FIG. 2, FIG. 3 and FIG. 4 appears only at slow-down or deceleration in the descent of the cage, as shown in FIGS. 6A and 68.

FIG. 7A and FIG. 7B show the heat generation of the conventional elevator which has already been described with respect to the background of the present invention.

With the elevator according to the present invention operating under its hardest conditions or between two floors with a running length of the elevator being 3 meters and a rated speed of 45 meters per minute, heat generation of the elevator according to the present invention represents 17 to 25 percent of the heat generated according to the conventional type of hydraulic elevator.

In the modifications of the hydraulic elevator according to the present invention as shown in FIGS. 1 4, a suitable inertia disk or fly wheel is utilized in order to properly accelerate the elevator or the cage, however, since the invention is also achieved by controlling the speed of the motor by other means, the invention is not limited to such a fly wheel or inertia disk or the control of the pump motor speed by the means specifically defined.

While a preferred embodiment of the present invention has been set forth with several modifications, further modifications, embodiments and variations are contemplated within the spirit and scope of the present invention as defined by the following claims.

We claim:

1. A hydraulic elevator comprising: a load support for allowing persons or objects to be carried thereby; expansible chamber means being drivingly connected to said load support for moving said load support upwardly during expansion and downwardly during discharge; variable capacity pump means for supplying fluid under pressure into said expansible chamber during upward movement of the elevator through means for conducting said fluid from said pump means; means drivingly connected to said pump means for controlling the flow rate of fluid pumped through controlling the capacity of said pump means to control the speed of ascent of the elevator; throttle means for throttling the flow of fluid from said expansible chamber; means for discharging fluid from said expansible chamber, said discharging means including means for controlling the speed of descent of the elevator through controlling the flow of fluid discharged from said expansible chamber, which means for controlling the speed of descent comprises said pump means, said means for controlling the flow of fluid and said throttle means.

2. A hydraulic elevator as defined in claim 1, wherein said throttle means controls the deceleration of said elevator at least during descent by varying the throttling of the working fluid discharging from said expansible chamber; and only said means for controlling the flow rate being operative to control both the acceleration and steady running speed of said elevator during descent without throttling by controlling the flow rate through said pump means from said expansible chamber means.

3. The hydraulic elevator as defined in claim 1, including passage means for conducting substantially all of the fluid discharging from said expansible chamber means through said throttle means during deceleration of the elevator descent.

4. The hydraulic elevator as defined in claim 3, wherein said passage means further conducts all of the fluid discharged from said expansible chamber through said pump means and by-passes said throttle means during acceleration of the elevator descent and during steady running speed of the elevator descent.

5. The hydraulic elevator as defined in claim 4, wherein said passage means further conducts all of the working fluid through said pump means to said expansible chamber during acceleration of the elevator ascent and during steady running of the elevator ascent, and further by-passing said throttle means.

6. The hydraulic elevator as defined in claim 5, wherein said passage means further conducts all of the fluid from said pump means to said expansible chamber by-passing said throttle means during deceleration of the elevator ascent.

7. The hydraulic elevator as defined in claim 5, wherein said passage means further conducts fluid from said pump means to both said throttle means and said expansible chamber means during deceleration of said elevator ascent; and said throttle means varying the throttling of the working fluid passing therethrough and discharging the throttled fluid away from said expansible chamber means during deceleration of the elevator ascent.

8. The hydraulic elevator as defined in claim 1, wherein said throttle means during deceleration of said elevator at descent has a maximum pressure differential of the working fluid being throttled that is a little less than the pressure within the expansible chamber of theelevator under no load conditions.

9. The hydraulic elevator as defined in claim 1, wherein said pump means includes a variable speed positive displacement pump having a constant fluid deliveryfor each speed of operation, power means for driving said'pump, and a fly wheel drivingly connected with said power means and pump; said pump means delivering all of its fluid to said expansible chamber during acceleration of ascent to correspondingly determine the acceleration of said elevator during ascent.

10. The hydraulic elevator as defined in claim 9, wherein said power means is an electric motor having means for controlling its starting voltage with a variable resistance to correspondingly control the starting torque of said motor.

11. The hydraulic elevator as defined in claim 1, wherein said pump means includes a variable speed positive displacement pump having a constant fluid delivery for each speed of operation and power means for driving said pump.

12. A hydraulic elevator, comprising: a load support for allowing persons or objects to be carried thereby; expansible chamber means being drivingly connected to said load support for moving said load support upwardly with expansion and downwardly with discharge; a positive displacement pump means having a constant fluid delivery for each corresponding constant speed of operation, an inlet and an outlet; liquid storage tank means for providing a supply in reserve of working liquid therein; first liquid passage means establishing liquid communication from said liquid tank means through said pump means to said expansible chamber means; check valve means operatively mounted within said first liquid passage means between said pump means outlet and said expansible chamber means for normally permitting the flow of liquid only from said pump means to said expansible chamber means only when the pressure of the working liquid flowing from said pump means is higher than a predetermined pressure; flow means for freely passing liquid in either direction between said pump means outlet and said expansible chamber regardless of pressure upon being selectively actuated by a predetermined signal; changeover valve means further connected within said first liquid passage means between said check valve means and said pump means; throttle valve means having an outlet connected to said tank means and and an inlet; second liquid passage means providing fluid communication between said change-over valve means, liquid storage tank means and throttle valve means in parallel with said pump means; said change-over valve means having one position for supplying all of the working liquid from said pump means into and out of said expansible chamber when the pressure of the working liquid from said pump means is greater than said'predetermined pressure to pass through said check valve and blocking fluid communication between said expansible chamber and throttle means at least during acceleration of ascent and descent of the elevator; and said change-over valve means having a second position for conducting the working liquid from said expansible chamber means during discharge into said liquid tank means through both said pump means and said throttle valve means in parallel at least during deceleration of the descent of the elevator.

13. The hydraulic elevator as defined in claim 12 wherein said change-over valve means further conducts a portion of the working liquid from the outlet of said pump means and returns it to said liquid tank means through said throttle valve means, and said throttle valve means gradually increases the throttling of the working liquid passing through said throttle valve during deceleration of the elevator ascent.

14. A hydraulic elevator, comprising: a load support for allowing persons or objects to be carried thereby; expansible chamber means being drivingly connected to said load support for moving said load support upwardly with expansion and downwardly with discharge; a positive displacement pump means having a constant delivery for a corresponding constant speed, an inlet and an outlet; liquid storage tank means for providing a supply in reserve of working liquid therein; first liquid passage means establishing liquid communication from said liquid tank means through said pump means to said expansible chamber; first check valve means operatively mounted within said liquid passage means between said pump means outlet and said expansible chamber means for normally permitting the flow of liquid only from said pump means to said expansible chamber means only when the pressure of theworking liquid flowing from said pump means is higher than a predetermined pressure; flow means freely passing liquid in either direction between said pump means and said expansible chamber regardless of pressure upon being selectively actuated by a predetermined signal; second check valve means in fluid communication between said first check valve means and said pump means outlet within said first passage means for permitting liquid from said first check valve means to communicate with said pump means only when pressure of the working liquid from said pump means is higher than a predetermined pressure; throttle valve means parallel with said first passage means; change-over valve means; second liquid passage means conducting liquid from between said first and second check valve means to said liquid tank means through said throttle valve means and said change-over valve means; third liquid passage means for conducting liquid between said second liquid passage means and said pump means through said change-over valve means; said changeover valve means, passage means and check valve means supplying all of the liquid through said pump means to and from said expansible chamber through said first and second check valve means at least during both acceleration and rated running of ascent and descent, respectively of the elevator; and said changeover valve means and passage means conducting the working liquid from said expansible chamber and discharging it into said liquid tank through said changeover check valve means, both said throttle valve means and said pump means in parallel, and said first check valve means at least during deceleration of descent of the elevator.

15. A hydraulic elevator as defined in claim 14, further being provided with a change-over valve for bypassing liquid around said pump means.

16. A hydraulic elevator, comprising: a load support for allowing persons or objects to be carried thereby; expansible chamber means being drivingly connected to said load support for moving said load support upwardly with expansion and downwardly with discharge; positive displacement pump means having a constant delivery for a corresponding constant speed, an inlet and outlet; liquid storage tank means for providing a supply in reserve of working liquid therein; liquid pas sage means establishing liquid communication from said liquid tank means through said positive pump means to said expansible chamber means; check valve means operatively mounted within said liquid passage means between said pump means outlet and said expansible chamber means for normally permitting the flow of liquid only from said pump means to said expansible chamber means only when the pressure of the working liquid flowing from said pump means is higher than a predetermined pressure; flow means freely passing liquid in either direction between said pump means and said expansible chamber regardless of pressure upon being selectively actuated by a predetermined signal; variable throttle valve means in liquid communication between said check valve means and said pump means outlet; meansfor controlling the speed of the elevator by correspondingly controlling the flow of liquid into and out of said expansible chamber at least during acceleration and rated running of both ascent and descent of the elevator by only controlling the pumping of the liquid with said pump means without throttling; and said means for further controlling at least the deceleration of the descent speed of "the elevator by controlling the discharge of liquid from said expansible chamber through said pump means and said throttle valve means with throttling.

17. A method of controlling the ascent and descent of a hydraulic elevator having an expansible chamber for driving the elevator load platform upwardly and downwardly, comprising the steps of: supplying fluid under pressure to said expansible chamber during ascent by means of a variable capacity pump; controlling the acceleration and running steady speed of said elevator solely by controlling the flow rate of said pump and providing the entire output of said pump to said expansible chamber; discharging all of the fluid from said expansible chamber reversely through said pump during at least acceleration and running steady speed of the elevator descent; controlling the acceleration and running steady speed of descent by solely controlling the flow rate of fluid passing through said pump while conducting all of the fluid being discharged from the expansible chamber through the pump; and controlling the deceleration of descent by variably throttling at least some of the fluid being discharged from said expansible chamber.

18. The method of claim 17, wherein said step of controlling the deceleration of descent further passes at least some of the fluid discharged from said expansible chamber reversely through said pump and further controls the rate of flow of said pump.

19. The method of claim 18, including the further step of controlling the deceleration of elevator ascent by throttling at least some of the fluid discharged from said pump.

20. The method of claim 17, including the further step of controlling the deceleration of elevator ascent by throttling at least some of the fluid discharged from said pump.

Claims

8. The hydraulic elevator as defined in claim 1, wherein said throttle means during deceleration of said elevator at descent has a maximum pressure differential of the working fluid being throttled that is a little less than the pressure within the expansible chamber of the elevator under no load conditions.

9. The hydraulic elevator as defined in claim 1, wherein said pump means includes A variable speed positive displacement pump having a constant fluid delivery for each speed of operation, power means for driving said pump, and a fly wheel drivingly connected with said power means and pump; said pump means delivering all of its fluid to said expansible chamber during acceleration of ascent to correspondingly determine the acceleration of said elevator during ascent.

12. A hydraulic elevator, comprising: a load support for allowing persons or objects to be carried thereby; expansible chamber means being drivingly connected to said load support for moving said load support upwardly with expansion and downwardly with discharge; a positive displacement pump means having a constant fluid delivery for each corresponding constant speed of operation, an inlet and an outlet; liquid storage tank means for providing a supply in reserve of working liquid therein; first liquid passage means establishing liquid communication from said liquid tank means through said pump means to said expansible chamber means; check valve means operatively mounted within said first liquid passage means between said pump means outlet and said expansible chamber means for normally permitting the flow of liquid only from said pump means to said expansible chamber means only when the pressure of the working liquid flowing from said pump means is higher than a predetermined pressure; flow means for freely passing liquid in either direction between said pump means outlet and said expansible chamber regardless of pressure upon being selectively actuated by a predetermined signal; change-over valve means further connected within said first liquid passage means between said check valve means and said pump means; throttle valve means having an outlet connected to said tank means and and an inlet; second liquid passage means providing fluid communication between said change-over valve means, liquid storage tank means and throttle valve means in parallel with said pump means; said change-over valve means having one position for supplying all of the working liquid from said pump means into and out of said expansible chamber when the pressure of the working liquid from said pump means is greater than said predetermined pressure to pass through said check valve and blocking fluid communication between said expansible chamber and throttle means at least during acceleration of ascent and descent of the elevator; and said change-over valve means having a second position for conducting the working liquid from said expansible chamber means during discharge into said liquid tank means through both said pump means and said throttle valve means in parallel at least during deceleration of the descent of the elevator.

14. A hydraulic elevator, comprising: a load support for allowing persons or objects to be carried thereby; expansible chamber means being drivingly connected to said load support for moving said load support upwardly with expansion and downwardly with discharge; a positive displacement pump means having a constant delivery for a corresponding constant speed, an inlet and an outlet; liquid storage tank means for proviDing a supply in reserve of working liquid therein; first liquid passage means establishing liquid communication from said liquid tank means through said pump means to said expansible chamber; first check valve means operatively mounted within said liquid passage means between said pump means outlet and said expansible chamber means for normally permitting the flow of liquid only from said pump means to said expansible chamber means only when the pressure of the working liquid flowing from said pump means is higher than a predetermined pressure; flow means freely passing liquid in either direction between said pump means and said expansible chamber regardless of pressure upon being selectively actuated by a predetermined signal; second check valve means in fluid communication between said first check valve means and said pump means outlet within said first passage means for permitting liquid from said first check valve means to communicate with said pump means only when pressure of the working liquid from said pump means is higher than a predetermined pressure; throttle valve means parallel with said first passage means; change-over valve means; second liquid passage means conducting liquid from between said first and second check valve means to said liquid tank means through said throttle valve means and said change-over valve means; third liquid passage means for conducting liquid between said second liquid passage means and said pump means through said change-over valve means; said change-over valve means, passage means and check valve means supplying all of the liquid through said pump means to and from said expansible chamber through said first and second check valve means at least during both acceleration and rated running of ascent and descent, respectively of the elevator; and said change-over valve means and passage means conducting the working liquid from said expansible chamber and discharging it into said liquid tank through said change-over check valve means, both said throttle valve means and said pump means in parallel, and said first check valve means at least during deceleration of descent of the elevator.

15. A hydraulic elevator as defined in claim 14, further being provided with a change-over valve for by-passing liquid around said pump means.

16. A hydraulic elevator, comprising: a load support for allowing persons or objects to be carried thereby; expansible chamber means being drivingly connected to said load support for moving said load support upwardly with expansion and downwardly with discharge; positive displacement pump means having a constant delivery for a corresponding constant speed, an inlet and outlet; liquid storage tank means for providing a supply in reserve of working liquid therein; liquid passage means establishing liquid communication from said liquid tank means through said positive pump means to said expansible chamber means; check valve means operatively mounted within said liquid passage means between said pump means outlet and said expansible chamber means for normally permitting the flow of liquid only from said pump means to said expansible chamber means only when the pressure of the working liquid flowing from said pump means is higher than a predetermined pressure; flow means freely passing liquid in either direction between said pump means and said expansible chamber regardless of pressure upon being selectively actuated by a predetermined signal; variable throttle valve means in liquid communication between said check valve means and said pump means outlet; means for controlling the speed of the elevator by correspondingly controlling the flow of liquid into and out of said expansible chamber at least during acceleration and rated running of both ascent and descent of the elevator by only controlling the pumping of the liquid with said pump means without throttling; and said means for further controlling at least the deceleration of the descent speed of the elevator by controlling the discharge of liquid from said expansiblE chamber through said pump means and said throttle valve means with throttling.