SYSTEM AND METHOD FOR HYDRAULIC-PNEUMATIC DRIVE WITH ENERGY STORAGE FOR ELEVATORS

Abstract

A power drive for a passenger and/or cargo elevator—or any conveyance-using stored high pressure compressed air as a primary source, producing high pressure hydraulic fluid energy to move a servo-controlled hydraulic motor, mechanically connected to the hoisting mechanism of the elevator, is disclosed. The electric power driving the air compressor is not affected by the load of the elevator (e.g. number of passengers). The electric current is consumed to charge a high pressure air tank. The compressor is operated only when the elevator is in in a parked position, thus electric power consumption level is by no means correlated to the operational mode of the elevator motion.

Claims

1. A pneumatic-hydraulic system for driving an elevator cabin, comprising, a bi-directional hydraulic motor 24, configured to power motion of the elevator cabin; two pneu-hydraulic accumulators 16, 17, configured to feed hydraulic energy to the bi-directional hydraulic motor 24; two 3-way, 2-position pressure-compensated flow control valves 34, 35, each disposed between one of the hydraulic actuators 16, 17 and the bi-directional hydraulic motor 24, configured to alternately supply hydraulic fluid to a high-pressure line and a low-pressure return line; a pressurized air tank 8 configured to supply pressurized air to the pneu-hydraulic accumulators 16, 17; a multistage air compressor 3 configured to charge the pressurized air tank 8; and a compressor drive motor 2, configured to operate said compressor 3; wherein electric power consumption of the system and the cruising speed of the elevator cabin are substantially independent of the load of said cabin, including passengers and cargo riding in said cabin.

2. The system of claim 1, further comprising a weighing mechanism configured to measure said load during a brake release, after closing of doors of said elevator and before start of motion of said cabin, thereby determining an initial hydraulic pressure.

3. The system of claim 2, wherein said weighing mechanism comprises one or more elements in a group consisting of an axle torque sensor; measuring tension in a cable of said elevator; measuring pressure difference at two openings for the hydraulic fluid of the hydraulic motor; a strain sensor; a weight scale; a mechanical force gauge; a cylinder fluid pressure meter; a pressure difference gauge; an electric sensor; mechanical sensor; a magnetic sensor for load measurement; and any combination thereof.

4. The system of claim 2, further comprising a pressure regulating valve 580 (e.g. servo valve) and a controller 585; said controller 585 is configured to receive said load measurement (or computation or estimation by said controller) and to compute or estimate and control the size of an oil passage opening (e.g., with a solenoid) of said pressure regulating valve 580, said size such that to achieve said substantially load-independent cruising speed and an arrival time of said cabin to a pre-determined next destination is substantially independent of said load.

5. The system of claim 4, wherein said controller 585 is selected from a group consisting of an electric transducer, a potentiometer, a mechanical device (e.g. spring piston), and any combination thereof.

6. The system of claim 4, wherein said controller is further configured to set said oil passage opening to a maximum size before motion of said cabin and gradually reducing said size to said size that is said function of said load, and optionally wherein said maximum opening size is set before a second said brake release.

7. The system of claim 4, further comprising a microswitch actuation height-changing mechanism for the cabin of an elevator, comprising a floor of said cabin mounted on springs; a first rack, rigidly mounted to said cabin; a dual pinion comprising a small gear and a large gear, said small gear configured to roll along said first cabin rack; a second rack, said large gear configured to roll along said second rack; a microswitch activator, rigidly mounted on said second rack; wherein said microswitch activator is configured to activate a slow-down limit switch of said elevator, and said system thereby receives an early warning for control of a slow-down profile enabling said cabin to reach a next destination at an arrival time that is substantially independent of said load.

8. The system of claim 4, wherein said controller is configured to set a constant said opening size (e.g. by using a solenoid-controlled potentiometer forced to an initial voltage/current), according to the vertical direction of motion of said elevator and the assumption, independent of said load, that said load is the maximum load for said elevator; one-half the maximum load for said elevator; or a predetermined fraction of the maximum load for said elevator.

9. The system of claim 8, wherein said controller is configured to reverse the vertical direction of said elevator.

10. The system of claim 4, further comprising at least one speed sensor 539 configured to measure one or more of acceleration, deceleration, and velocity of said cabin.

11. The system of claim 10, wherein said speed sensor comprises one or more type in a group consisting of a mechanical sensor, mechanical linear or rotary encoder, electrical sensor, electrical linear or rotary encoder, magnetic sensor for velocity measurement, centrifugal speed sensor, pressure regulating valve, pressure-compensated flow control valve, or any combination thereof.

12. The system of claim 10, wherein said controller is further configured to receive said measurement from said speed sensor and adjust said opening size of said pressure regulating valve to maintain said constant cruising velocity.

13. The system of claim 12, wherein the cruise velocity and arrival time of said elevator to destinations of equal distance is substantially independent of said load.

14. The system of claim 1, wherein the speed of the hydraulic motor is controlled by two pressure-compensated hydraulic motor-flow control valves 21, 22 set primarily to a predetermined flow values by adjusting the required restriction in the fixed orifices of the hydraulic motor-flow control valves 21, 22; further wherein the cruise velocity of the hydraulic motor is fixed, pre-defined and not affected by the fluid pressure caused by the load weight.

15. The system of claim 1, wherein the more passengers and/or cargo are present in the cabin, the less mechanical and/or electric changes occur in the system (e.g., by removing flow-resistant elements such as a solenoid); e.g., piston movement of the two pressure-compensated flow control solenoid valves 34, 35 gets smaller with increasing total weight of the elevator cabin, including passengers and cargo.

16. The system of claim 15, wherein the flow control solenoid valves are used to hold the valves' pistons in maximal open/close state according to the total weight of the elevator's cabin and the vertical direction of motion.

17. The system of claim 1, wherein said system is switchable between three modes of operation: “Shabbat” mode, wherein the hydraulic motor operates by pressurized hydraulic liquid which is operated by pressurized air, which is supplied by said pressurized air tank and thereby said system has said load-independent electric power consumption. “Normal Electric” mode, wherein an electric motor drives the elevator without the hydraulic motor; and “Normal Hydraulic” mode, wherein the hydraulic motor is fed by a pump and drives the elevator without the electric motor.

18. The system of claim 1, further configured so that the hydraulic motor begins moving the elevator after a random time interval after closing of the elevator doors (e.g. the random time can be achieved by sending control commands to the hydraulic motor and/or the flow control valves at a random time in order to that the arrival time is within a predefined range; said random time and said predefined range substantially independent of said load.

19. The system of claim 18, wherein the random time delay is not less than a difference in time periods it takes the elevator to arrive at its next destination/floor when the cabin is empty (with no passengers and/or cargo) and with a full load.

20. The system of claim 1, further comprising a security valve configured to sense the velocity of said cabin; said system further configured, when said velocity exceeds an allowed limit (e.g. 20% above 1 m/s), to gradually close one or more hydraulic oil passages (e.g., in hydraulic motor, in the security valve, in the flow control valves) in said system until the elevator is fully stopped safety.

21. The system of claim 12, further configured such that when a counterweight of said elevator exceeds said load, said hydraulic motor begins in a neutral operation, enabling said elevator to initially operate by gravitational forces, and said hydraulic motor gradually engages (e.g., by adjustment of said flow control valves) such that said substantially load-independent cruising speed is maintained.

22. The system of claim 21, wherein said cruising speed is achieved in a predetermined time or predetermined cabin location after said initial gravitational operation.

23. A pneumatic-hydraulic method for driving an elevator, comprising steps of a. providing the pneumatic-hydraulic system of claim 1; b. operating a compressor when the conveyance is at rest; c. charging a pressurized tank with the compressor; d. supplying pressurized air to two pneu-hydraulic accumulators, by the pressurized tank; e. alternately supplying fluid to a high-pressure line and a low-pressure return line of the pneu-hydraulic accumulators; and f. powering motion of the conveyance, by fluid in the high pressure line. wherein electric power consumption of said system and the cruising speed of the elevator cabin are substantially independent of the load of said cabin, including passengers and cargo riding in said cabin.

24. The method of claim 23, further comprising a step of a weighing mechanism measuring said load during a brake release, after closing of doors of said elevator and before start of motion of said cabin, thereby determining an initial hydraulic pressure.

25. The method of claim 24, further comprising a step of selecting said weighing mechanism from one or more elements in a group consisting of an axle torque sensor; measuring tension in a cable of said elevator; measuring pressure difference at two openings for the hydraulic fluid of the hydraulic motor; a strain sensor; a weight scale; a mechanical force gauge; a cylinder fluid pressure meter; a pressure difference gauge; an electric sensor; mechanical sensor; a magnetic sensor for load measurement; and any combination thereof.

26. The method of claim 24, further comprising steps of a controller receiving (and/or computing or estimating) said load measurement, computing or estimating and controlling the size of an oil passage opening (e.g., with a solenoid) of a pressure regulating valve, said size such that to achieve said substantially load-independent cruising speed and an arrival time of said cabin to a pre-determined next destination is substantially independent of said load.

27. The method of claim 26, further comprising a step of selecting said controller from a group consisting of an electric transducer, a potentiometer, a mechanical device (e.g. spring piston), and any combination thereof.

28. The method of claim 26, further comprising steps of said controller to setting said oil passage opening to a maximum size before motion of said cabin and gradually reducing said size to said size that is said function of said load, and optionally wherein said maximum opening size is set before a second said brake release.

29. The method of claim 26, further comprising a microswitch actuation height-changing method comprising steps of, obtaining the system of claim 7; the microswitch activator activating a slow-down limit switch of said elevator, and said system thereby receiving an early warning for control of a slow-down profile enabling said cabin to reach a next destination at an arrival time that is substantially independent of said load.

30. The method of claim 26, further comprising a step of said controller is setting a constant opening size (e.g. by using a solenoid-controlled potentiometer forced to an initial voltage/current) of a servo valve, according to the vertical direction of motion of said elevator and the assumption, independent of said load, that said load is the maximum load for said elevator; one-half the maximum load for said elevator; or a predetermined fraction of the maximum load for said elevator.

31. The method of claim 30, further comprising a stop of said controller reversing the vertical direction of said elevator.

32. The method of claim 26, further comprising a step of at least one speed sensor measuring one or more of acceleration, deceleration, and velocity of said elevator cabin.

33. The method of claim 32, further comprising a step of selecting said speed sensor from one or more type in a group consisting of a mechanical sensor, mechanical linear or rotary encoder, electrical sensor, electrical linear or rotary encoder, magnetic sensor for velocity measurement, centrifugal speed sensor, pressure regulating valve, pressure-compensated flow control valve, or any combination thereof.

34. The method of claim 32, further comprising steps of said controller receiving said measurement from said speed sensor and adjusting said opening size of said pressure regulating valve to maintain said constant cruising velocity.

35. The method of claim 34, further comprising a step of said adjustment being such that the cruise velocity and arrival time of said elevator to destinations of equal distance is substantially independent of said load.

36. The method of claim 23, further comprising steps of two pressure-compensated hydraulic motor-flow control valves controlling the speed of said hydraulic motor to predetermined flow values by adjusting the required restriction in the fixed orifices of the hydraulic motor-flow control valves, whereby the cruise velocity of the hydraulic motor is fixed, pre-defined and not affected by the fluid pressure caused by the load weight.

37. The method of claim 23, further comprising a step of the more passengers and/or cargo are present in the cabin, less mechanical and/or electric changes occurring in the system (e.g., by removing flow-resistant elements such as a solenoid); e.g., piston movement of the two pressure-compensated flow control solenoid valves 34, 35 gets smaller with increasing total weight of the elevator cabin, including passengers and cargo.

38. The method of claim 37, further comprising a step of using the flow control solenoid valves to hold the valves' pistons in maximal open/close state according to the total weight of the elevator's cabin and the vertical direction of motion.

39. The method of claim 23, further comprising a step of switching said system between three modes of operation: “Shabbat” mode, wherein the hydraulic motor operates by pressurized hydraulic liquid which is operated by pressurized air, which is supplied by said pressurized air tank and thereby said system has said load-independent electric power consumption. “Normal Electric” mode, wherein an electric motor drives the elevator without the hydraulic motor; and “Normal Hydraulic” mode, wherein the hydraulic motor is fed by a pump and drives the elevator without the electric motor.

40. The method of claim 23, further comprising steps of the hydraulic motor beginning moving the elevator after a random time delay after closing of the elevator doors (e.g. the random time can be achieved by sending control commands to the hydraulic motor and/or the flow control valves at a random time in order to that the arrival time is within a predefined range; said random time and said predefined range substantially independent of said load.

41. The method of claim 40, further comprising a step of the random time delay being not less than a difference in time periods it takes the elevator to arrive at its next destination/floor when the cabin is empty (with no passengers and/or cargo) and with a full load.

42. The method of claim 23, further comprising steps of a security valve sensing the velocity of said cabin; and when said velocity exceeds an allowed limit (e.g. 20% above 1 m/s), gradually closing one or more hydraulic oil passages (e.g., in hydraulic motor, in the security valve, in the flow control valves) in said system until the elevator is fully stopped safety.

43. The method of claim 34, further comprising steps of, when a counterweight of said elevator exceeds said load, said hydraulic motor beginning in a neutral operation, enabling said elevator to initially operate by gravitational forces; and said hydraulic motor gradually engaging (e.g. by adjustment of said flow control valves) such that said substantially load-independent cruising speed is maintained.

44. The method of claim 43, further comprising a step of achieving said cruising speed in a predetermined time or predetermined cabin location after said initial gravitational operation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0087] FIG. 1 schematically illustrates a mechanical schematic diagram of a pneumatic-hydraulic drive system for an elevator, according to some embodiments of the invention.

[0088] FIG. 2 schematically illustrates a mechanical schematic diagram of a decelerator for a pneumatic-hydraulic elevator drive system, according to some embodiments of the invention.

[0089] FIG. 3 schematically illustrates a fully mechanical speed stabilizer controller for an elevator pneumatic-hydraulic drive system, according to some embodiments of the invention.

[0090] FIG. 4, shows steps of a pneumatic-hydraulic method for driving an elevator, according to some embodiments of the invention.

[0091] FIG. 5 schematically illustrates an electro-hydraulic servo system of a pneumatic-hydraulic drive system for an elevator, according to some embodiments of the invention.

[0092] FIG. 6 schematically illustrates a mechanically controlled servo system of a pneumatic-hydraulic drive system for an elevator, according to some embodiments of the invention.

[0093] FIG. 7 schematically illustrates pressurization of an oil tank of a pneumatic-hydraulic drive system for an elevator, according to some embodiments of the invention.

[0094] FIG. 8 illustrates a microswitch actuation height-changing mechanism for the cabin of an elevator, according to some embodiments of the invention.

LIST OF FEATURES IN THE DRAWINGS

[0095] 1 Compressor motor contactor [0096] 2 Compressor motor [0097] 3 High pressure air compressor [0098] 4 Compressor intake filter [0099] 5 Check valve 1 [0100] 6 Tank pressure manometer [0101] 7 Tank pressure electronic transducer [0102] 8 Main high pressure air tank [0103] 9 Drain cock [0104] 10 Check valve 2 [0105] 11-14 High-pressure 2-way, 2-position air solenoid valves [0106] 15 Air exhaust muffler [0107] 16-17 Air-over-oil piston accumulators [0108] 18-19 Magnetic proximity sensors for piston position [0109] 20 Up-down 4-way, 3-position closed center selector—solenoid operated [0110] 21-22 Pressure-compensated flow controllers with check valve, variable [0111] restrictor [0112] 23 Motor for restrictor area changing [0113] 24 Hydraulic motor—fixed displacement—2 rotation directions [0114] 25 Floor-level limit switch [0115] 26 Descending speed-lowering limit switch [0116] 27 Ascending speed-lowering limit switch [0117] 28 Electrically operated clutch [0118] 29 Main electric elevator motor [0119] 30 Main elevator hoisting gearbox [0120] 31 Elevator electrically operated brake [0121] 32 Cables wheel [0122] 33 Cabin [0123] 34-35 3-way, 2-position solenoid valves [0124] 36 Main control and relays box [0125] 37 Programmable logic controller (PLC) [0126] 38 Oil cooler (air over fins) [0127] 39 Shaft encoder [0128] 40 Oil micronic filter [0129] 41 Oil tank [0130] 42 Power supply [0131] 44 Differential pressure transducer [0132] 75 Gearbox [0133] 76 Electromagnetic clutch [0134] 77A-77B Spur gears [0135] 78A-78B Flow controllers [0136] 79 Torsion spring [0137] 302 Transmission (may be similar to spur gears 77A-77B) [0138] 303 Centrifugal mechanical speed contn [0139] 304 Preloaded spring [0140] 305 Sliding sleeve [0141] 306 Rack [0142] 307 Pinion [0143] 308-309 Small gear motor [0144] 310 Differential [0145] 520, 620, 720 Up/Down selector [0146] 524, 624 Hydraulic motor [0147] 526, 626 Hydraulic fluid leakage collector [0148] 539 Encoder [0149] 580 Electro-hydraulic servo valve [0150] 585 Controller [0151] 680 Mechanically operated servo valve [0152] 690 Mechanical speed governor [0153] 695 Mechanical velocity feedback link [0154] 738 Oil cooler [0155] 740 Micronic filter [0156] 741 Oil tank [0157] 792 Diaphragm [0158] 795 Air pressure reducer [0159] 800 Elevator cabin [0160] 805 Microswitch activator [0161] 810 Sliding track [0162] 815 Output rack [0163] 820 Pinion [0164] 825 Input rack [0165] 830 Springs

DETAILED DESCRIPTION OF THE INVENTION

[0166] The following description with the referenced drawings describe the present invention. The description and drawings are non-limiting. Some disclosed features may not appear in some embodiments of the invention. Furthermore, some embodiments of the invention may include additional undisclosed features.

[0167] The disclosure is made in reference to driving a Shabbat elevator. However, it is appreciated that a person skilled in the art may employ the teachings of the invention described herein to provide a drive system to power any conveyance, including a wheeled vehicle such as an automobile, a motorcycle, a scooter (e.g., a mobility scooter such “Kalnoit” scooters), a bicycle, a tricycle, or a wheelchair; an escalator; and a boat or ship.

[0168] Whether for driving an elevator or another conveyance, embodiments of the invention include drivers of conveyances intended for Shabbat use (i.e., the driver's electric power consumption is independent of weight load on the conveyance) and of conveyances intended for weekday use (i.e., the driver's electric power consumption is not necessarily independent of weight load on the conveyance).

[0169] It is furthermore appreciated that although this disclosure is made in reference to a pneumatically driven hydraulic system, the teachings of the invention described herein may be applied by a person skilled in the art to provide a hydraulically driven pneumatic system as well.

[0170] Reference is now made to FIG. 1, schematically illustrating a mechanical schematic diagram of a pneumatic-hydraulic drive system 100 (hereinafter also referred to as “drive system”) for an elevator, according to some embodiments of the invention.

[0171] Drive system 100 comprises a compressor drive motor 2, typically an electric motor, which drives an air compressor 3, typically a multi-stage compressor. Air compressor 3 charges a high-pressure air tank 8. One or more sensors 6, 7 monitor air pressure in air tank 8. A vent solenoid valve 9 enables evacuation of air tank 8 and system lines, if needed.

[0172] Compressed air is fed to a set of two pneu-hydraulic accumulators 16, 17, which can be piston type. The compressed air is fed via an array of four solenoid valves 11 12 13 14. An air chamber on one side of the piston of one accumulator 16, 17 is filled with high pressure air and the hydraulic chamber on the other side of the piston is filled with pressurized hydraulic fluid. At the same time, the other accumulator 17, 16 is vented, filled with low pressure hydraulic fluid is filling it from return line.

[0173] The pneu-hydraulic accumulators 16, 17 alternate in providing of high and low hydraulic pressure. When the fluid in the first accumulator 16, 17 is at a minimal level, magnetic sensors 18, 19 trigger valves 11, 12, 13, 14 to change position and to feed the other accumulator 17, 16 with high pressure air which causes feeding high pressure fluid to the system.

[0174] Flow control valves 34, 35 of each pneu-hydraulic accumulator 16, 17 assure permanent flow of hydraulic fluid in the pressure and return lines connected to hydraulic motor's 24 lines. Flow control valves 34, 35 can be pressure-compensated and can comprise 3-way, 2-position solenoid valves.

[0175] Hydraulic fluid is fed to a set of two motor-flow control valves 21, 22, preferably pressure compensated, connected to a bidirectional hydraulic motor 24. Hydraulic motor 24 is optionally mechanically connected via a clutch 28 to the shaft of the main gear of the hoisting mechanism of the elevator. Hydraulic motor speed is thereby fixed at a pre-defined level, and not affected by the fluid pressure caused by the load, neither in up nor down directions.

[0176] Hydraulic motor 24 may function as the only motor in the system driving the elevator. Alternatively, hydraulic motor 24 and a conventional electric motor are selectable, and the elevator could have the following modes of operation: [0177] “Normal Electric” mode—The electric motor drives the elevator without the hydraulic motor. [0178] “Normal Hydraulic” mode—The hydraulic motor is fed by a pump and drives the elevator without the electric motor. [0179] “Shabbat” mode—The hydraulic motor is fed as described in this document.

[0180] An encoder 39 is connected to the hoisting mechanism shaft. Its output is used as a velocity feedback to control and stabilize the deceleration stage of the motion of the elevator in both directions, up and down.

[0181] The return fluid is stored in an oil tank 41. The fluid is cooled by an air cooled heat exchanger 38 and filtered by a micronic filter 40. After passing through cooling and filtering, hydraulic fluid returns to accumulators 16, 17.

[0182] Stopping of the elevator cabin at each floor (station) is done by sensing its position by a limit switch 25 placed at floor level at all floors. Limit switch 25 cuts hydraulic power by centering a selector valve 20 and at the same time operating the electro-mechanical brake 31 of the hoisting gear.

[0183] In order to decelerate the cabin's velocity before total halting, two additional limit switches 26 27 mounted at predetermined distances (approximately 400 mm) from two sides of floor limit switch 25 (along elevator's track). When one of limit switches 26 27 is actuated, a small electric control motor 23 is operated, gradually closing the restrictor orifice openings of the flow controller 21 22, thus reducing hydraulic flow rate to the hydraulic motor 24 gradually. Upon reaching final stop, the cabin has a very low speed of approach. After reaching full stop, the control motor 23 returns the orifice openings to their originally set area to enable full speed motion continuation. In some embodiments, the time it takes to begin a deceleration process is random. Therefore the limit switches' operation and the elevator's cabin stopping process mechanism is not affected by the cabin load (not by passenger weight/count, cargo weight, nor direction of motion).

[0184] Reference is now made to FIG. 2, schematically illustrating a decelerator for a pneumatic-hydraulic elevator drive system, according to some embodiments of the invention. A mechanical connection of the shaft of main hydraulic motor 24 to the flow controllers' restrictors operates as follows:

[0185] The shaft of hydraulic motor 24 is connected to a small gearbox 75 which moves via electromagnetic clutch 76 and spur gears 77a 77b the restrictors of the flow controllers 78a 78b. Gearbox 75, furthermore, energizing a torsion spring 79. When the elevator's cabin actuates the deceleration limit switch, the clutch 75 is engaged and gradually closes restrictor passage orifices in flow controllers 78a 78b by rotating the gears 77a 77b. At the same time the spring 79 is energized. When the cabin reaches full stop and actuates the floor level limit switch, the clutch is de-energized and the spring's energy rotates the restrictors drive back to full opening position, ready for next acceleration movement of the cabin.

[0186] A differential pressure transducer 44 measures overload of the cabin is measured. When overload occurs, the pressure difference exceeds a predetermined limit. The elevator will not operate. An overload indication may be displayed.

[0187] A power supply 42 may convert the mains voltage (e.g. 220/110 volts 50/60 Hz) to the required voltages to feed a programmable logic controller PLC 37 and to optionally energize all sensors, relays and solenoid valves.

[0188] The hydraulic flow controllers 21, 22 serve to keep constant flow passing through them regardless the load, which varies according to passengers count and direction of motion (up or down).

[0189] The electro-mechanical clutch 28 connecting the hydraulic motor to hoisting gear electric motor shaft is engaged and transmits torque during hydraulic elevator operation.

[0190] When the elevator is moved by main electric motor 30, clutch 28 is disengaged and the pneumatic-hydraulic system is disabled, thereby cutting the hydraulic fluid supply, compressor drive motor 2 shuts down and vent valve 9 vents high pressure air tank 8.

[0191] Another optional feature of the system is a fully mechanical speed stabilizer controller which ensures that during all of the constant speed phase of motion, the elevator's speed in both directions (up & down) is not affected by the load.

[0192] Reference is now made to FIG. 3, schematically illustrating a speed-control embodiment. Two centrifugal mechanical speed controllers 303 are built of weights connected by arms to sliding sleeve 305 loaded by a preloaded spring 304. Upon increasing rotational speed, centrifugal force moves the sleeve with its rack 306, adding compression to the spring. Rack 306 turns a pinion 307 which is connected to corona wheel of a differential 310. Other sides of the differential wheels are connected to the hydraulic restrictor of the flow controller and to small gear motor 308 & 309 which is used to decelerate the cabin upon reaching station.

[0193] There are two identical mechanical speed controllers, one serves for upwards elevator movement and the other for downwards movement.

[0194] An elevator employing drive system 100 may be switchable between three modes of operation: [0195] “Normal Electric” mode—An electric motor is driving the elevator without the hydraulic motor; and [0196] “Normal Hydraulic” mode—The hydraulic motor is fed by a pump and drives the elevator without the electric motor. [0197] “Shabbat” mode, wherein the hydraulic motor operates with load-independent electric power consumption, substantially as described;

[0198] In Shabbat mode, the hydraulic motor may be configured to begin moving the elevator after a random time interval after closing of the elevator doors. The random time delay should be not less than the difference in time periods it takes the elevator to arrive at its next destination/floor when the cabin is empty (with no passengers and/or cargo) and with a full load. Such a mechanism decouples the connection between the time it takes the elevator to arrive at its next velocity deceleration process starting point and activating the limit switches placed at each floor and the weight of passengers and/or cargo. In this manner, activation of the limit switches will not occur earlier than it would have occurred without the random time delay.

[0199] The system is configured so that the time periods it takes the elevator to arrive its next destination/floor is not dependent on the load. These time periods will not get shorter when the load increases or decreases.

Additional Embodiments

[0200] In some embodiments, the time it takes the elevator's cabin to reach the velocity deceleration process starting point is always random. Therefore the limit switches' operation and the elevator's cabin stopping process mechanism is not affected by the elevator's load (passengers count, cargo weight, and direction of motion).

[0201] In some embodiments, stopping the elevator's cabin is performed by decreasing the hydraulic pressure to the hydraulic motor and at the same time operating the electromechanical brake of the hoisting gear. This way the cabin's velocity is decelerated gradually until full stop. This deceleration sets a soft stop of the cabin motion, without overshooting or shock.

[0202] Upon stopping at a floor station, the mechanism is returned to its initial state in order to enable driving the elevator's cabin to next floor (e.g. using solenoid, energized torsion spring etc.).

[0203] In some embodiments, a central control unit synchronizes and operates the flow of high pressure compressed air from the air tank to the accumulators.

[0204] When one accumulator is under high air pressure, its hydraulic fluid is transferred to the hydraulic motor while the other accumulator is vented without pressure and is being filled with hydraulic fluid.

[0205] In some embodiments, when one of the accumulators is with minimal fluid quantity and level, the position of its piston is sensed by proximity sensor.

[0206] In some embodiments, signals of malfunctioning of the system are displayed and serve to shut down the operation of the elevator in case of a major fault.

[0207] Major faults might be: filter high differential pressure, high fluid temperature, low air pressure, too low or too high motor speed, sensors and transducers malfunction, etc.

[0208] In some embodiments, in case of a system malfunction during a Shabbat or holiday, any technical treatment of the system (e.g. opening the controller, opening the engine etc.) will be recorded in a log. In some embodiments, a person presence detection element is then activated. If there are no people in the elevator cabin and such a technical treatment was carried out, the elevator's driving system is disabled. This feature can helps to avoid desecration of the Shabbat or holiday, as use of the elevator is forbidden if it was repaired on Shabbat or a holiday.

[0209] In some embodiments, the system further includes an acoustic and/or visual indicator. The indicator is activated before and during closing of the elevator door(s). The indicator alerts persons near the elevator that the doors are about to or are now closing. The alert helps one avoid desecration Shabbat or holiday caused by entering the elevator during the time the doors are closing (which typically triggers a sensor and door-opening mechanism, or may affect the electric power consumption of the door-closing mechanism). The alerting element can be a buzzer, vocal time indication, stop light, count-down time display, etc.

[0210] In some embodiments, the system further comprises a hydraulic dummy load whose applied force is about equal to the maximum load weight of the elevator. The dummy load is added to the load of the system to cause the system to produce its maximum hydraulic power. The system is later removes the dummy load, allowing the system to reach said constant velocity. The dummy load may added to the system at the beginning of each movement of the elevator and disconnected a short period of time afterwards.

[0211] Reference is now made to FIG. 4, showing steps of a pneumatic-hydraulic method 400 for driving an elevator, wherein the electric power consumption of method 400 and the speed of the elevator cabin, and travel time between floors are independent of the weight of passengers and cargo riding in the elevator.

[0212] Method 400 comprises steps of [0213] a. providing a pneumatic-hydraulic drive system for an elevator of the invention 405; [0214] b. operating a compressor when the elevator is at rest 410; [0215] c. charging a pressurized tank with the compressor 415; [0216] d. supplying pressurized air to two pneu-hydraulic accumulators, by the pressurized tank 420; [0217] e. alternately supplying fluid to a high-pressure line and a low-pressure return line of the pneu-hydraulic accumulators 425; and [0218] f. powering vertical motion of the elevator, by fluid in the high pressure line 430.

[0219] Reference is now made to FIG. 5, schematically illustrating an electro-hydraulic (EH) servo system of a pneumatic-hydraulic drive system for an elevator, according to some embodiments of the invention.

[0220] During a momentary brake release before the start of motion of the elevator cabin, a controller 585 receives the weight of the cabin from a weighing mechanism (not shown). The weighing mechanism can be an axle torque sensor; measuring tension in a cable of said elevator; measuring pressure difference at two openings for the hydraulic fluid of the hydraulic motor; a strain sensor; a weight scale; a mechanical force gauge; a pressure difference gauge and any combination thereof.

[0221] The controller 585 sets the size of an oil passage opening of a pressure regulating valve 580 as a function of said load measurement, such that an arrival time of the elevator to a pre-determined next destination is independent of the measured load.

[0222] Optionally, the controller sets the opening size independently of load measurement, according to the maximum load of the elevator or half the maximum load of the elevator.

[0223] Upon initial motion of the elevator, a speed sensor 539 measures the velocity of the elevator cabin. In the embodiment shown, the speed sensor comprises a rotary encoder, giving a rotational velocity of an elevator hoisting shaft, from which the controller can determine linear velocity proportional to the rotational velocity. In other embodiments, the speed sensor 539 is a linear encoder, magnetic speed sensor, centrifugal speed sensor, pressure regulating valve, pressure-compensated flow control valve, or any combination thereof.

[0224] Reference is now made to FIG. 6, schematically illustrating a mechanically controlled servo system of a pneumatic-hydraulic drive system for an elevator, according to some embodiments of the invention. The mechanical speed governor 690 is described in relation to FIG. 3. It is connected, by a mechanical velocity feedback link 695 (a lever, in the embodiment shown), to a mechanically operated servo valve 680. The servo valve 680 accordingly adjusts speed of the hydraulic motor 624. Optionally, the lines between the servo valve 680 and motor 624 pass through other elements such up/down selector valve 620, which do not necessarily contribute a feedback response.

[0225] Reference is now made to FIG. 7, schematically illustrating pressurization of a return oil tank 741 of a pneumatic-hydraulic drive system for an elevator, according to some embodiments of the invention.

[0226] Air from an air tank (not shown) applies pressure to a diaphragm 792 of the oil tank 741. A pressure reducer 795, preferably of 3 bars, is placed along the line from the air tank to the oil tank 741.

[0227] Pressurization of the return oil tank 741 assures safe hydraulic fluid filling of the accumulators 16-17 (see FIG. 1).

[0228] Reference is now made to FIG. 8, illustrating a microswitch actuation height-changing mechanism for the cabin of an elevator, according to some embodiments of the invention.

[0229] The floor 828 of an elevator cabin 800 is mounted on springs 830. A first cabin rack 825 is fixed to the elevator cabin 800. Generally, the first rack 825 is mounted to the front wall of the cabin. The weight of passengers 832 on the floor 828 causes a downward translation of the first rack 825.

[0230] The small gear of a dual pinon 820 rolls along the first rack 825. The large gear of the dual pinion rolls along a second rack 815. The second rack 815 is translated upward with the downward translation of the first rack 825. The translation magnitude of the second rack is amplified is amplified by the gear ratio of the large and small gears of the dual pinion 820.

[0231] A microswitch activator 805 is mounted on the second rack, on the side opposite to the teeth. The activator 805 can be a detent or a magnetic activator. The activator 805 activates an external slow-down limit switch (not shown) located in the elevator shaft.

[0232] With greater weight in the cabin, during upwards motion, the limit switch is activated earlier, giving the controller 585, 685 an earlier warning needed to adjust the slow-down profile (oil passage opening as a function of time) of the servo valve 580, 680 (see FIGS. 5 and 6), such that the arrival time at the next floor is independent of the cabin load. A similar rack-and-pinion design may be employed for downward motion.