ENERGY STORAGE FOR ELEVATORS

FIELD OF THE INVENTION

The invention relates to a system for providing operating power to an elevator (of the type typically used for passengers and/or cargo in buildings); and in particular 5 to a pneumatic energy storage system used to drive a hydraulic system, as an alternative or as an add-on to an electro-mechanical system.

BACKGROUND OF THE INVENTION

There are religious Jewish communities whose religious traditions forbid one to use electricity or operate electrically-powered appliances, including passenger 10 elevators, on Saturday and Jewish holydays.

Elevators designed for such communities operate automatically, stopping at each floor and opening and closing the doors at predetermined time intervals. Such elevators are colloquially called“Shabbat elevators.”

Some Jewish communities further demand that, on these holy days, the electric 15 power consumption is not directly affected by the weight of the passengers. This need has encouraged the development of load-independent electric-power consumption Shabbat elevators.

US20140364272A1 discloses a system, including a transportation device, configured to operate under at least a first condition and a second condition, wherein 20 the transportation device is configured to operate without a human induced change in an electrical current during the second condition. A disengageable motor is configured to operate the transportation device under the first condition and coupled to the transportation device. A disengageable energy storage device is configured to operate the transportation device under the second condition and coupled to the transportation 25 device, wherein the disengageable energy storage device may be automatically recharged by a charging device when the energy storage device is disengaged. A mechanical processing unit mechanically controls the motion of the transportation device. The present invention advances the technology of Shabbat elevators, as further 30 described herein.

SUMMARY OF THE INVENTION

There are two important considerations for designing Shabbat elevators:

According to an aspect of the invention, electric power consumed by an elevator drive system (e.g. from the electric grid and/or generator and/or batteries etc.) is not 35 directly affected by the weight of the passengers and/or cargo (hereinafter,“the load”) in the elevator cabin. The electric power consumption does not increase when the total load increases, for example when there are more passengers

Additionally, according to an aspect of the invention, the weight of the load does not influence the timing of any electric actuators or electric sensors. Such an 40 influence would cause a passenger entering or leaving the elevator to hasten the activation time of the actuator or sensor, which is tantamount to using electricity on the holy day. Therefore, for example, factors such as cabin velocity that influence the timing of sensors, such as a floor- level limit switch, should not be influenced by the weight of the cabin load— i.e., that the speed of the elevator cabin should be the same 45 whether the cabin is empty, partially loaded, or fully loaded.

The present invention provides a power system for elevators that stores pneumatic energy of high-pressure compressed air to drive the elevator via hydraulic means, while electric power is drawn from mains only when the elevator is not in motion. When the elevator is in use, electric power is disconnected and the elevator is 50 moved by compressed air energy. When the elevator is stopped, an air compressor is operated drawing constant electric power to charge an air tank.

The pneumatic-hydraulic system consumes electric power to drive the compressor only when the elevator is not in motion, thus there is no correlation between the load and motion of the elevator and the electric current consumed by the pneumatic 55 system.

(It should be noted that an increased frequency, under higher loading levels, of charges by an electric compressor motor is not forbidden according to most rabbinic authorities, because (in some embodiments) the charges occur during indeterminate periods when the cabin is not in motion and therefore do not constitute direct usage of 60 electricity.)

The pneumatic-hydraulic system may also serve as emergency operational power source in cases when electricity is disconnected.

It is within the scope of the invention to provide a pneumatic -hydraulic drive system for a conveyance whose electric power consumption is unaffected by weight 65 load carried on the conveyance, the system comprising a. a bi-directional hydraulic motor, configured to power motion of a

conveyance;

b. two pneu-hydraulic accumulators configured to feed hydraulic energy to the

bi-directional hydraulic motor; 70 c. two 3-way, 2-position pressure-compensated flow control solenoid valves each disposed between one of the hydraulic actuators, and the bi-directional hydraulic motor, configured to alternately supply hydraulic fluid to a high- pressure line and a low-pressure return line;

d. a pressurized air tank configured to supply pressurized air to the pneu- 75 hydraulic accumulators;

e. a multistage air compressor configured to charge the pressurized air tank; and

f. a compressor drive motor, configured to operate the compressor when the

conveyance is at rest. 80 wherein electric power consumption of the system and speed of the conveyance are independent of the weight of passengers and cargo riding in the conveyance.

It is further within the scope of the invention to provide the previous pneumatic- hydraulic drive system, wherein the conveyance is a Shabbat elevator, a regular elevator, an automobile, a motorcycle, a scooter, a bicycle, a tricycle, a wheelchair, an 85 escalator, a boat, or a ship.

It is further within the scope of the invention to provide a pneumatic -hydraulic drive system for an elevator whose electric power consumption is unaffected by weight load carried in the elevator, the system comprising a. a bi-directional hydraulic motor, configured to power vertical motion of an 90 elevator;

b. two pneu-hydraulic accumulators configured to feed hydraulic energy to the

bi-directional hydraulic motor;

c. two 3-way, 2-position pressure-compensated flow control solenoid valves

each disposed between one of the hydraulic actuators, and the bi-directional 95 hydraulic motor, configured to alternately supply high and low pressure return-line fluid;

d. a pressurized air tank configured to supply pressurized air to the pneu- hydraulic accumulators,;

e. a multistage air compressor configured to charge the pressurized air tank; 100 and

f. a compressor drive motor, configured to operate the compressor when the

elevator is at rest. wherein electric power consumption of the system, speed of the elevator cabin, and travel time between floors are independent of the weight of passengers and 105 cargo riding in the elevator cabin.

It is further within the scope of the invention to provide the previous pneumatic- hydraulic drive system, wherein energy for the vertical motion of the elevator between different floors and/or along a specific floor is provided by any combination of a. the bi-directional hydraulic motor or an electric motor; 110 b. the weight of the elevator cabin and its load; and

c. the weight of the elevator’s counterweight.

It is within the scope of the invention to provide any of the above pneumatic- hydraulic drive systems for an elevator, wherein the compressor drive motor is configured to operate only when the elevator is at rest. 115

It is further within the scope of the invention to provide any of the above pneumatic -hydraulic drive systems for an elevator, further configured, after release of an electro-magnetic brake of the elevator and before start of the hydraulic motor, to sense the impending movement direction of the elevator by, for example, sensing the hydraulic liquid pressure. 120 It is further within the scope of the invention to provide the previous pneumatic- hydraulic drive system for an elevator, further configured to employ the movement direction data to compute the extent to which each of the following elements are used for driving the elevator cabin: a. the bi-directional hydraulic motor or an electric motor; 125 b. the weight of the elevator cabin and its load; and

c. the weight of the elevator’s counterweight.

It is further within the scope of the invention to provide any of the above pneumatic -hydraulic drive systems for an elevator, further comprising a velocity- control subsystem comprising one or more encoders for velocity control of the elevator 130 cabin; the encoders configured to measure one or of acceleration, deceleration, and velocity of the elevator.

It is further within the scope of the invention to provide the previous pneumatic- hydraulic drive system for an elevator, wherein the velocity-control encoders comprise one or more type in a group consisting of mechanical, electrical, centrifugal element, 135 servo valve, and pressure compensated flow control valve.

It is further within the scope of the invention to provide any one the previous two pneumatic -hydraulic drive systems for an elevator, wherein the velocity-control subsystem is forced to either a partially or fully opened or closed state (e.g. by using solenoid) as currently needed, thus the more passengers and/or cargo are present in the 140 elevator's cabin the less mechanical and/or electric changes occur in the system (e.g. by removing the preventive elements).

It is further within the scope of the invention to provide any of the three previous pneumatic -hydraulic drive systems for an elevator, wherein the velocity-control subsystem is further configured to compensate for leaks of the hydraulic fluid in the 145 system, e.g. for the purpose of controlling the elevator's cabin velocity.

It is further within the scope of the invention to provide any of the above pneumatic -hydraulic drive systems for an elevator, wherein at the beginning of cabin motion from rest, the hydraulic engine starts at full power.

It is further within the scope of the invention to provide any of the above 150 pneumatic -hydraulic drive systems for an elevator, wherein the speed of the hydraulic motor is controlled by two pressure compensated motor-flow control valves, set primarily to a predetermined flow values by adjusting the required restriction in the fixed orifices of the motor- flow control valves,.

It is further within the scope of the invention to provide any of the above 155 pneumatic -hydraulic drive systems for an elevator, wherein piston movement of the two pressure-compensated flow control solenoid valves gets smaller with increasing total weight of the elevator cabin, including passengers and cargo.

It is further within the scope of the invention to provide any of the above pneumatic -hydraulic drive systems for an elevator, wherein the solenoid is used to hold 160 the valves’ pistons in maximal open / close state according to the total weight of the elevator’s cabin and the movement direction (up / down).

It is further within the scope of the invention to provide any of the above pneumatic -hydraulic drive systems for an elevator, backed up with either a mechanical or electric encoder connected to the main gear's shaft of the hoisting mechanism of the 165 elevator, e.g. for safety purposes.

It is further within the scope of the invention to provide any of the above pneumatic -hydraulic drive systems for an elevator, wherein the elevator is switchable between three modes of operation

• Shabbat mode, wherein the hydraulic motor operates with load-independent 170 electric power consumption;

• "Normal Electric" mode, wherein an electric motor is 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. 175

It is further within the scope of the invention to provide the previous pneumatic- hydraulic drive system for an elevator, further configured so that in Shabbat mode the hydraulic motor might begin moving the elevator after a random time interval after closing of the elevator doors.

It is further within the scope of the invention to provide either of the previous 180 two pneumatic -hydraulic drive systems for an elevator, 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.

It is further within the scope of the invention to provide any of the above 185 pneumatic -hydraulic drive systems for an elevator, wherein stopping the elevator's cabin at a floor (story) level is performed using a plurality of limit switches.

It is further within the scope of the invention to provide the previous pneumatic- hydraulic drive system for an elevator, wherein the limit switches comprise electric, magnetic, photoelectric, mechanical, pneumatic, or hydraulic switches or any 190 combination thereof.

It is further within the scope of the invention to provide either of the previous two pneumatic-hydraulic drive systems for an elevator, wherein the time it takes to begin a deceleration process is random; the timing of the limit switches’ operation and of the elevator’s cabin stopping process mechanism is thereby not affected by the load 195 weight or by the direction of motion.

It is further within the scope of the invention to provide any of the above pneumatic -hydraulic drive systems for an elevator, wherein 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 200 cabin's velocity may be decelerated gradually until full stop. This deceleration may set a soft stop of the cabin motion (without overshooting or shock).

It is further within the scope of the invention to provide any of the above pneumatic -hydraulic drive systems for an elevator, wherein a central control unit synchronizes and operates the flow of high pressure compressed air from the air tank 205 to the accumulators, whereby 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 hydraulic fluid return line fills this accumulator. When one of the accumulators is with minimal fluid quantity and level, the position of its piston is sensed by proximity sensor commanding switching of air and fluid from the 210 other accumulator.

It is further within the scope of the invention to provide any of the above pneumatic -hydraulic drive systems for an elevator, wherein a main control unit operates the cooling system of the hydraulic fluid by energizing air fan blowing air through liquid to air heat exchanger, thus keeping hydraulic fluid at constant temperature. 215

It is further within the scope of the invention to provide any of the above pneumatic -hydraulic drive systems for an elevator, wherein signals of malfunctioning of the system are displayed and serve to shut down the operation of the elevator in case of a major fault.

It is further within the scope of the invention to provide the previous pneumatic- 220 hydraulic drive system for an elevator, further configured, upon the malfunctioning signal, to record in a log an attempt to repair the malfunction.

It is further within the scope of the invention to provide the previous pneumatic- hydraulic drive system for an elevator, further comprising a person presence detector in the elevator cabin, activated upon the attempt to repair the malfunction, wherein if 225 no person presence is sensed, the system is configured to disable the elevator’s driving system.

It is further within the scope of the invention to provide any of the above pneumatic -hydraulic drive systems for an elevator, further comprising a mechanical speed stabilizer. 230

It is further within the scope of the invention to provide the previous pneumatic- hydraulic drive system for an elevator, wherein the mechanical speed stabilizer operates by centrifugal speed controller and via a gear system and moves the restrictors of the hydraulic flow controllers to bring the hydraulic motor to constant speed regardless of the load. 235

It is further within the scope of the invention to provide any of the above pneumatic -hydraulic drive systems for an elevator, wherein the time periods it takes the elevator to arrive at its next destination / floor is not dependent on the weight of the passengers and/or cargo.

It is further within the scope of the invention to provide any of the above 240 pneumatic -hydraulic drive systems for an elevator, further comprising an acoustic and/or visual indicator activated before and during closing of the elevator doors. It is further within the scope of the invention to provide the previous pneumatic- hydraulic drive system for an elevator, wherein the indicator is selected from a group consisting of a buzzer, a vocal time indication, a stop light, a count-down time display, 245 or any combination thereof.

It is further within the scope of the invention to provide the previous pneumatic- hydraulic drive system for an elevator, further configured for rescuing passengers in case of an emergency situation, such as a blackout.

It is further within the scope of the invention to provide the previous pneumatic- 250 hydraulic drive system for an elevator, further comprising a hydraulic dummy load whose applied force is about equal to the maximum load weight of the elevator; wherein the dummy load is added to the load of the system to cause the system to produce its maximum hydraulic power; and wherein the system is further configured to remove the dummy load, allowing the system to reach said constant velocity. 255

It is further within the scope of the invention to provide a pneumatic -hydraulic method for driving a conveyance, wherein electric power consumption is unaffected by weight load carried on the conveyance, the method comprising steps of a. providing a pneumatic-hydraulic drive system for a conveyance;

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.

It is further within the scope of the invention to provide a pneumatic -hydraulic method for driving an elevator, wherein electric power consumption is unaffected by 260 weight load carried in the elevator, the method comprising steps of a. providing a pneumatic-hydraulic drive system for an elevator;

b. operating a compressor when the elevator 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 vertical motion of the elevator, by fluid in the high pressure line.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 illustrates a mechanical schematic diagram of a pneumatic -hydraulic drive system for an elevator, according to some embodiments of the invention.

Fig. 2 illustrates a mechanical schematic diagram of a decelerator for a 265 pneumatic -hydraulic elevator drive system, according to some embodiments of the invention.

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

Fig. 4, shows steps of a pneumatic -hydraulic method for driving an elevator, 270 according to some embodiments of the invention.

Fist of Features in the Drawings

1 Compressor motor contactor

2 Compressor motor

3 High pressure air compressor 275

4 Compressor intake filter

5 Check valve 1

6 Tank pressure manometer

7 Tank pressure electronic transducer

8 Main high pressure air tank 280

9 Drain cock

10 Check valve 2

11-14 High-pressure 2-way, 2-position air solenoid valves

15 Air exhaust muffler

16-17 Air-over-oil piston accumulators 285 8-19 Magnetic proximity sensors for piston position

20 Up-down 4-way, 3-position closed center selector - solenoid operated

1-22 Pressure-compensated flow controllers with check valve, variable

restrictor

23 Motor for restrictor area changing 290

24 Hydraulic motor - fixed displacement - 2 rotation directions

25 Floor-level limit switch

26 Descending speed-lowering limit switch

27 Ascending speed-lowering limit switch

28 Electrically operated clutch 295

29 Main electric elevator motor

30 Main elevator hoisting gearbox

31 Elevator electrically operated brake

32 Cables wheel

33 Cabin 3004-35 3-way, 2-position solenoid valves

36 Main control and relays box

37 Programmable logic controller (PLC)

38 Oil cooler (air over fins)

39 Shaft encoder 305

40 Oil micronic filter

41 Low-pressure oil tank

42 Power supply

43 Differential pressure transducer

75 Gearbox 310

76 Electromagnetic clutch

A-77B Spur gears

A-78B Flow controllers

79 Torsion spring

302 Transmission (may be similar to spur gears 77A-77B) 315

303 Centrifugal mechanical speed controllers 304 Preloaded spring

305 Sliding sleeve

306 Rack

307 Pinion 320 308-309 Small gear motor

310 Differential

DETAILED DESCRIPTION OF THE INVENTION

The following description with the referenced drawings describe the present invention. The description and drawing are non-limiting. Some disclosed features may 325 not appear in some embodiments of the invention. Furthermore, some embodiments of the invention may include additional undisclosed features.

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 330 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.

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 335 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).

It is furthermore appreciated that although this disclosure is made in reference to a pneumatically driven hydraulic system, the teachings of the invention described 340 herein may be applied by a person skilled in the art to provide a hydraulically driven pneumatic system as well.

Reference is now made to Fig. 1, 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. 345 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. 350

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 355 vented, filled with low pressure hydraulic fluid is filling it from return line.

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 360 fluid to the system.

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. 365

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 370 load, neither in up nor down directions.

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:

• "Normal Electric" mode - The electric motor drives the elevator without the 375 hydraulic motor. • "Normal Hydraulic" mode - The hydraulic motor is fed by a pump and drives the elevator without the electric motor.

• "Shabbat" mode - The hydraulic motor is fed as described in this document.

An encoder 39 is connected to the hoisting mechanism shaft. Its output is used 380 as a velocity feedback to control and stabilize the deceleration stage of the motion of the elevator in both directions, up and down.

The return fluid is stored in a low pressure 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. 385

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.

In order to decelerate the cabin's velocity before total halting, two additional 390 limit switches 2627 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 395 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 400 direction of motion).

Reference is now made to Fig. 2 Another possible embodiment of the invention uses a mechanical connection of the shaft of main hydraulic motor 24 to the flow controllers’ restrictors as shown in Fig. 2 and operates as follows:

The shaft of hydraulic motor 24 is connected to a small gearbox 75 which moves 405 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 410 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.

A differential pressure transducer 44 measures overload of the cabin is measured. When overload occurs, the pressure difference exceeds a predetermined 415 limit. The elevator will not operate. An overload indication may be displayed.

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.

The hydraulic flow controllers 21, 22 serve to keep constant flow passing 420 through them regardless the load, which varies according to passengers count and direction of motion (up or down).

The electro-mechanical clutch 28 connecting the hydraulic motor to hoisting gear electric motor shaft is engaged and transmits torque during hydraulic elevator operation. 425

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.

Another optional feature of the system is a fully mechanical speed stabilizer 430 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.

Reference is now made to Fig. 3, showing 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, 435 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. 440

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

An elevator employing drive system 100 may be switchable between three modes of operation:

• "Normal Electric" mode - An electric motor is driving the elevator 445 without the hydraulic motor; and

• "Normal Hydraulic" mode - The hydraulic motor is fed by a pump and

drives the elevator without the electric motor.

• “Shabbat” mode, wherein the hydraulic motor operates with load- independent electric power consumption, substantially as described; 450

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 455 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.

The system is configures so that the time periods it takes the elevator to arrive 460 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

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’ 465 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). 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 470 decelerated gradually until full stop. This deceleration sets a soft stop of the cabin motion, without overshooting or shock.

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.). 475

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

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. 480

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.

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.

Major faults might be: filter high differential pressure, high fluid temperature, 485 low air pressure, too low or too high motor speed, sensors and transducers malfunction, etc.

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 490 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.

In some embodiments, the system further includes an acoustic and/or visual 495 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- 500 closing mechanism). The alerting element can be a buzzer, vocal time indication, stop light, count-down time display, etc.

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 505 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.

Reference is now made to Fig. 4, showing steps of a pneumatic -hydraulic 510 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.

Method 400 comprising steps of a. providing a pneumatic-hydraulic drive system for an elevator of the 515 invention 405;

b. operating a compressor when the elevator is at rest 410;

c. charging a pressurized tank with the compressor 415;

d. supplying pressurized air to two pneu -hydraulic accumulators, by the

pressurized tank 420; 520 e. alternately supplying fluid to a high-pressure line and a low-pressure return

line of the pneu -hydraulic accumulators 425; and

f. powering vertical motion of the elevator, by fluid in the high pressure line

430.