WO2003078291A1

WO2003078291A1 - A gravity elevator

Info

Publication number: WO2003078291A1
Application number: PCT/IB2003/000917
Authority: WO
Inventors: Paolo Tagliabue
Original assignee: Negroni Automazioni S.R.L.
Priority date: 2002-03-15
Filing date: 2003-03-13
Publication date: 2003-09-25
Also published as: ITBO20020126A1; ITBO20020126A0; AU2003211396A1

Abstract

The invention pertains to a gravity elevator (1) for a multi-storey building, comprising: two tanks (11, 12), associated with the car (2) and the counterweight (5) of the elevator, containing a weight medium (10) that can be transferred by a transfer device (13) that varies the quantity of it contained in the tanks (11, 12); and a governor unit (9) that controls the speed and motion of the car (2) .The invention also pertains to a method for moving a car (2) of an elevator (1) by transferring a weight medium (10) from the car (2) to the counterweight (5), or vice versa, in such a way as to create an overbalance in the selected direction of movement, measuring the speed of the car (2), and keeping the speed of the car (2) within a preset limit using a brake (21) or motor-generator (23) .

Description

Description GRAVITY ELEVATOR

Technical field

The present invention relates to a gravity elevator and similar apparatus. The invention applies to elevators or hoists of different kinds provided they are equipped with counterweights and connecting cables or equivalent connecting means such as chains, etc. The present invention also relates to a method for moving an elevator car in a multi-storey building by the transfer of a weight .

More specifically, the invention pertains to improvements to elevators of the type comprising a car and a counterweight suspended by cables and where the car is moved from one floor of the building to another by transferring a weight from the car to the counterweight and vice versa. Preferably, the transfer or variation of the weight is accomplished by transferring a weight medium, for example a liquid, from one tank associated with the elevator car to another tank associated with the counterweight and vice versa or by varying the amount of liquid inside the tank or tanks .

Background art

An elevator of this type is disclosed in United States patent 182,280. United States patent 3,845,842 discloses an elevator system where the car and the counterweight both comprise a tank. The car and the counterweight are balanced by measuring the car load and transferring liquid from one tank to the other. With this arrangement, the power required to move the car from one floor to another using a pulley and cables can be provided by a smaller than usual electric motor.

Prior art solutions for gravity elevators cannot be applied to new installations and are not suitable for substituting existing installations because they require additional devices to be fitted in the lower part of the elevator shaft and cannot therefore meet current elevator safety regulations which require that the lower end of the elevator shaft be left free.

Other problems are due to the difficulty of controlling elevator car speed in prior art solutions. Moreover, in the solution described in US patent 3,845,842, the elevator still requires a motor-powered hoisting device to move the car from one floor to another.

Disclosure of the invention

The object of the present invention is to provide an improved gravity elevator that can be installed in any building and that is especially adapted to substitute existing installations, allowing the car to move quickly between floors and having a low power requirement.

Another object of the invention is to provide a method for moving an elevator car by the transfer of weights such that the car is caused to move promptly and quickly using a small amount of power. In accordance with one aspect of it, the present invention discloses a gravity elevator as defined in claim 1. The dependent claims embody preferred, advantageous forms of the invention. In accordance with another aspect of it, the present invention discloses a method as defined in claim 18 for moving an elevator car by the transfer of weights.

Description of the drawings

Preferred embodiments of the invention will now be described, without restricting the scope of the inventive concept, with reference to the accompanying drawings in which:

Figure 1 schematically shows a cross-sectional view of the gravity elevator according to the present invention;

Figure 2 is a schematic top view, with some parts cut away and others in cross section, of the gravity elevator of Figure 1; Figures 3 and 4 schematically show cross-sectional views of another two embodiments of the gravity elevator according to the present invention; Figures 5 to 10 show some constructional details of the gravity elevator illustrated in the drawings listed above; and

Figure 11 is a schematic axonometric view, w th some parts cut away and others in cross section, of another embodiment of the gravity elevator according to the present invention;

Detailed description of the preferred embodiments of the invention

With reference to the accompanying drawings, the numeral 1 denotes in its entirety the modular gravity elevator according to the present invention.

The gravity elevator 1 comprises a car 2 connected to a mechanical supporting arch 3 that slides in car guides 4 attached to the structure of the building in which the elevator is installed. The gravity elevator 1 further comprises a counterweight 5 that slides in respective counterweight guides 6. The car 2 and the counterweight 5 are connected by cables 7 positioned on opposite sides of a transmission pulley 8, the latter being in turn connected to a governor unit 9.

The above refers to an exemplary form of the elevator according to the invention, it being understood that the inventive concept can be embodied in other different forms, all falling within the scope of its protection.

Another embodiment of the invention is shown in Figure 3 in which the car 2 of the elevator 1 is supported at the bottom by a double transmission system with car pulleys 2a positioned under the car and with the transmission pulley 8 and governor unit 9 positioned above it within the elevator shaft. This makes it possible to install the gravity elevator 1 even in confined spaces, for example where there is no room above the elevator shaft.

In another embodiment, shown in Figure 4, the car 2 of the elevator 1 is connected to the counterweight 5 by an idle transmission pulley and the transmission pulley 8 and the governor unit 9 are located at the lower end of the elevator shaft. Figure 11 illustrates yet another embodiment of the invention in which the transmission pulley 8 and the governor unit 9 are mounted directly on the guides 4 and 6 of the car 2 and of the counterweight 5. This embodiment is made possible by the fact that the transmission pulley 8 and the governor unit 9 are compact .

This solution is especially advantageous for installations in existing buildings, where an elevator was not originally contemplated, because it does not require a machine room separate from the elevator shaft. Moreover, the transmission pulley 8 and the governor unit 9 do not need to be mounted on a load-bearing floor slab of the building, while they themselves support the car 2 and the counterweight 5.

The transmission system of the pulley 8 is such that movements of the car 2 and of the counterweight 5 cause the pulley 8 to rotate but without making the cables 7 slide on the surface of the pulley 8. The pulley 8 is connected to the governor unit 9 that controls the speed at which the elevator car moves. The governor unit 9 acts on the pulley 8 in such a way as to slow the car 2 and, if necessary, it may also detect its movements, as explained in more detail below.

For movement of the car 2, there is a weight medium 10, for example water with suitable additives to prevent freezing, reduce evaporation and increase mass per unit volume, and at least one tank located on the car or on the counterweight. By changing the quantity of the weight medium 10 in the tank, the weight of the car 2 can be made to overbalance that of the counterweight 5 or vice versa, increasing the corresponding weight force in such a way as to cause the car 2 to move in one direction or the other.

Preferably, there are two tanks: a tank 11 for the car and a tank 12 for the counterweight, so that changes of weight in the two tanks are faster because the weight of one tank can be increased while that of the other is simultaneously decreased, which means that the movements of the car 2 are also quicker. For the weight changes in the two tanks, the car tank 11 and the counterweight tank 12 are connected to each other by a device 13 for transferring the weight medium 10. The transfer device 13 may consist of piping 14 and one or two pumps 15, 16.

The pumps 15, 16 may be of any type suitable for transferring the weight medium 10, which, as stated above, is usually water with additives, from one height to another in a short space of time. In the case of moderate height differences, multi-stage centrifugal pumps may be used, while positive- displacement pumps may be used for greater height differences. The car tank 11 may be positioned below the car, as shown in

Figure 1, or on one side of it, in an unused space, as shown in Figure 2, or above the car (not illustrated) . In the same way, the counterweight tank 12 may be positioned below the fixed part 5a of the counterweight (this position not being illustrated) or above it, as illustrated in the drawings.

When the difference in height between the car tank 11 and the counterweight tank 12 is limited in relation to pump capacity, a single, two-way pump 15 may be used, mounted close to, and preferably under, one of the two tanks 11, 12, or at a fixed intermediate position, as shown in Figure 4.

For greater height differences between the car tank 11 and the counterweight tank 12, two pumps 15, 16 must be used, each mounted close to, and preferably at the bottom of, the corresponding tank 11, 12. This means that each pump 15, 16 operates in one direction only as a force pump of the weight medium 10, thus preventing problems due to suction height, cavitation, and so on.

The governor unit 9 comprises a car 2 parking brake 17, a force sensor 18 connected to the reaction point of the brake 17, a speed sensor 19 and a sensor 20 for detecting the motion of the pulley 8, a car 2 speed control brake 21 and a controller 22 connected to all these components.

The sensors 19, 20 are associated with the pulley 8 and the cables 7 are wound around the pulley 8 n such a way, as mentioned above, that they cannot slide on the surface of it. Thus, the movements and speed of the car 2 correspond to equivalent rotations and angular velocity of the pulley 8, meaning that the sensors 19 and 20 register and convert the movements and speed of the car 2 into an analog or digital electrical signal. Figure 8 shows an embodiment of the governor unit 9 in which the speed and motion sensors 19 and 20 are separate and consist of customary analog or digital sensors . Alternatively, the two sensors 19 and 20 may be combined into one sensor unit consisting, for example, of an encoder. Further, the car 2 motion sensor 20 may consist of a set of sensors 20a, for example, close to each landing and which may be simple electromechanical contacts, that is to say, switches or similar components, arranged vertically along the elevator shaft in such a way as to be actuated by the car 2 as it moves up and down .

The brakes 17, 21 of the embodiment shown in Figure 8 and the parking brake 17 of the embodiment of Figure 9 are shoe brakes, although it will be understood that any other suitable type of brakes may be used such as, for example, disc brakes, drum brakes or electrical metal powder brakes.

Figure 6, on the other hand, shows a parking brake 17 that operates directly on the cables 7, but the brake works in the same way as the other types of brake that operate on the pulley 8.

Figures 1 and from 5 to 7 show the position of the force sensor 18 in different embodiments. In the embodiments shown in Figures 5 and 6, the force sensor 18 is fitted between the reaction bar of the brake block or of the brake caliper of the parking brake 17. When the parking brake 17 is applied, for example, when the car 2 is stopped at a landing, the force sensor 18 detects the weight force overbalance between the car 2 and the counterweight 5. In the embodiment of Figure 7, the parking brake 17 operates directly on the cables 7 and, in this case, too, is positioned at the reaction point of the brake 17 itself so as to detect the weight force overbalance between the car 2 and the counterweight 5. In the embodiment shown in Figure 1, the force sensor 18a is divided into parts located, respectively, between the cables 7 and between the car 2 and the counterweight 5. In this case, too, the weight force of the car 2 and of the counterweight 5 is detected, so as to create a weight force overbalance between the car 2 and the counterweight 5.

In yet another embodiment, which is not illustrated, the two sensors 18a of the embodiment of Figure 1, fitted to the connections on the cables 7 at the car and at the counterweight 5, may be substituted with a force sensor located under the car tank 11, which is in turn located under the car floor. Thus, it is possible to detect both the weight force due to the car load and the weight force due to the weight medium 10 inside the car tank 11. With reference to Figure 1, this embodiment contemplates the provision of the sensor 18 between the supporting arch 3 and the car 2, which in turn also includes the car tank 11. According to this embodiment, the counterweight tank 12 also has a force sensor under it which detects the weight force of the weight medium 10 inside the counterweight tank 12.

Figure 10 shows another embodiment of the means for detecting the weight force of the car 2 or of the counterweight 5. In this instance, the cables are diverted by a pulley 18b and the force at the ends of the diverted section of the cables 7 is measured by a sensor 18a similar to that of Figure 1.

Figure 9 shows another embodiment of the governor unit 9 in which the speed is controlled by a motor-generator 23 instead of a brake . The arrangement of the reaction point of the brakes 21 or of the casing of the motor-generator 23, in the case of the embodiment of Figure 9, is substantially the same as that shown in Figures 5 and 6.

The force sensor connected to the control brake 21 provides a signal proportional to the braking torque, whilst the force sensor connected to the motor-generator 23 provides a signal proportional to the braking torque or to the torque created by the acceleration applied by the motor-generator 23 to the car 2, as explained in more detail below. Advantageously, and as illustrated in Figures 8 and 9, the two brakes 17, 21 or the brake 17 and the motor-generator 23 may be connected to the same sensor 18. In this case, only the sensor 18 detects the weight force overbalance between the car 2 and -the counterweight 5 under static and dynamic conditions. The force sensor 18 converts the force due to braking of the two brakes 17 and 21 - or the reaction force due to the torque of the motor-generator 23 - into an electrical signal proportional to the intensity of the force, or as stated above, the weight force overbalance between the car 2 and the counterweight 5. The sensor 18 may be of the analog or digital type and, in one preferred embodiment, may consist of a load cell capable of reacting in both push and pull directions.

The operation of the gravity elevator 1 according to the present invention is described below.

Operating conditions can be divided broadly into the following three main categories: (i) car 2 leaving or arriving at the bottom landing of the building; (ii) car 2 leaving or arriving at the top landing of the building; (iii) car 2 leaving or arriving at an intermediate landing of the building.

In the first case (i) the elevator car 2 can only go up, the parking brake 17 holds the car at the landing and the governor unit 9 has already transferred all the weight medium 10 to the tank 12 of the counterweight 5. Thus, irrespective of the load in the car 2, the weight of the counterweight 5 overbalances that of the car 2 by the highest possible amount, so as to create the maximum weight force for the car 2 to go up. When the destination landing is selected, either from the control panel in the car 2 or from one of the other floors, the signal related to that landing is sent to the governor unit 9 which releases the parking brake 17 and allows the car 2 to accelerate freely until it reaches the maximum speed it was designed for. Usually, this speed is reached before the car reaches the next landing after the one it left from.

The car 2 is then maintained at a constant speed by operation of the speed control brake 21, which is suitably modulated by the controller 22, the latter receiving as input the signal related to the speed at which the pulley 8 is rotating and, hence, the speed at which the car 2 is travelling. This provides a control system of the feedback, that is to say, closed loop, type so that the speed of the car 2 is controlled accurately and safely. If necessary, the speed of the car 2 may be controlled even during the initial acceleration stage. Thus, if the acceleration of the car 2 is too high, the speed control brake 21 may be applied by the controller 22, which is receiving the speed increase signal from the speed sensor 19. To increase the response speed of the controller 22, an acceleration sensor (not illustrated) may be provided to apply the car 2 acceleration value directly to the controller 22.

In the embodiment of Figure 9, the motor-generator 23 may, on the basis of the acceleration signal, either slow the car 2 in the same way as the speed control brake 21, or it may operate actively to increase the acceleration of the car 2 and to increase the response speed of the elevator 1 on starting.

It should be emphasised that the power consumption of all the stages described up to now is practically zero: both the acceleration and steady-state speed of the car 2 are achieved by the weight force overbalance between the car 2 and the counterweight 5. Even when the motor-generator 23 operates actively, power consumption is limited not only because of its short duration but also because the motor-generator 23 is low- powered compared to conventional elevators with car and fixed counterweight since it must never overcome the difference in weight between the car and the counterweight or vice versa, but must only provide a faster response when the elevator starts moving.

Even the transfer of the weight medium 10 from one tank to the other may be effected by a relatively small pump, for example, an electric pump with a 1.5 kilowatt motor, and for short spaces of time. Even the operation of the speed control brake 21 and of the controller 22 involves limited power consumption.

Furthermore, in the embodiment of Figure 9, the motor- generator 23, when it is used as a speed control brake, generates electricity that may be stored in a battery (not illustrated) . The battery may then be used instead of the mains to power the system for a certain length of time, thus further reducing power consumption.

If elevator operation is software-based and permits calls to different landings of the building to be stored and executed sequentially, the governor unit 9, when there are different calls to different landings in progress, may decide either to transfer the weight medium 10 from the counterweight tank 12 to the car tank 11 or to leave the weights unchanged, depending on which landings are still to be served.

The transfer of the weight medium 10 from one tank to the other facilitates the elevator slowing action of the speed control brake 21. However, in the case of operation with a motor-generator 23, this transfer may be avoided and power consumption is thus reduced. Even in the case of software-based operation without storage of calls, the weights of the two tanks 11, 12 are left unchanged and no weight medium 10 is transferred because the system does not know in advance what landings the elevator will serve next.

Whatever the type of operation of the elevator 1, when the car 2 approaches the landing at the top floor of the building, the controller 22 transfers all the weight medium 10 to the counterweight tank 12. When the car 2 is approaching the top floor, the speed control brake 21 also starts slowing it down and stops it completely when it reaches the landing. When the car 2 is stationary, the parking brake 17 is applied and the speed control brake 21 released. During operation of the speed control brake 21, the braking torque is continuously detected by the sensor 18 - or by another sensor - and the resulting signal is sent to the controller 22 for better speed control.

For detecting the position of the car 2, the invention contemplates the provision of the motion sensor 20 which, as stated above, may be embodied in several different forms. Whatever its form, the car 2 position signal is sent to the controller 22 which processes it in the specified ways.

In the second case (ii) , that is to say, when the car 2 is leaving or arriving at the top landing of the building, the situation corresponds to that of the last stage of the first case described above.

In this second case (ii) the elevator car 2 can only go down, the parking brake 17 holds the car at the landing and, as described above, the governor unit 9 has already transferred all the weight medium 10 to the car tank 11. Thus, irrespective of the load in the car 2, the weight of car 2 overbalances that of the counterweight 5 by the highest possible amount, so as to create the maximum weight force for the car 2 to go down.

As in the previous case, when the destination landing is selected, either from the control panel in the car 2 or from one of the other floors, the signal related to that landing is sent to the governor unit 9 which releases the parking brake 17 and allows the car 2 to accelerate, either freely or assisted by the brake 21 or the motor-generator 23, until it reaches the maximum speed it was designed for. All the subsequent speed control stages until the car 2 stops at the destination landing are performed in substantially the same way as in the first case (i) where the car starts at the bottom floor of the building.

In the third case (111) , which will now be described, the car 2 leaves from or arrives, or is stopped at, an intermediate landing of the building.

If the operating system of the elevator 1 ascertains that the intermediate landing at which the car 2 is stopping at is not the last landing to be served but that the direction of the car 2 does not have to be reversed, then the overbalanced condition between the weights of the car 2 and of the counterweight 5 s left unchanged because the car 2 has to continue moving in the same direction, up or down, past the intermediate landing it s about to stop at.

This situation can therefore be likened to one of the two cases (1) or (11) described above, in which the car can go only up or only down.

If the operating system of the elevator 1 ascertains that the landing to be served after the one it is currently stopping at requires the car 2 to reverse its direction of travel, then, as the car 2 approaches the current landing, the controller 22 begins transferring all the weight medium 10 from one tank to the other. In this way, the elevator 1 is ready to start moving the car 2 in the opposite direction.

If the operating system of the elevator 1 is unable to ascertain whether the intermediate landing it is stopping at is the last stop or not, or if that intermediate landing is the last stop, and the car 2 is to remain at that landing for an indefinite length of time, then the controller 22 balances the weight of the car 2 with that of the counterweight 5. Thus, since the weights of the car 2 and of the counterweight 5 are already balanced, the system is ready to start transferring the weight medium 10 promptly from one tank to the other when the elevator 1 is used next .

During the stop at the intermediate landing, the parking brake 17 is applied and the controller 22 is able to detect the loads of the car 2 and of the counterweight 5 through the sensor or sensors 18. When the car 2 is stationary at the intermediate landing and the load n the car 2 changes, the controller 22 transfers from one tank to the other an amount of weight medium 10 corresponding to the change in the load. This weight transfer is performed quickly because the power of the pumps 15, 16 is such that they can rapidly compensate for weight variations due, for example, to a person entering or leaving the car 2.

When the destination landing is selected, either from the control panel in the car 2 or from one of the other floors, the controller 22 can transfer the weight medium 10 from one tank to the other, in such manner as to create the overbalance required to move the car 2 up or down. From this moment, the situation can be likened to one of the two cases (i) or (11) described above.

In this case, too, the waiting time is usually short. The time needed to create the overbalance necessary to move the car 2 is comparable to the time taken to close the doors of the elevator 1 car 2.

To increase the response speed of the elevator 1, as mentioned above, the parking brake 17 can be released as soon as an initial overbalance in the weights has been created, without waiting for all the weight medium 10 to be transferred from one tank to the other.

Moreover, a motor-generator 23 may be used to assist the starting of the car 2 even if transfer of the weight medium 10 has not been completed. The weights of a preferred embodiment of the elevator according to the present invention are given below:

Weight of car (including cables) : 600 kg. Car load-bearing capacity (weight of 6 persons) : 480 kg.

The volume of the car tank must create a weight equal to one half of the car load-bearing capacity plus an additional volume needed to create the overbalance of forces. As an approximate indication, the additional volume may be such as to create an additional weight equal to 15% of the weight created by the car tank. For simplicity, the weight medium may consist of water with a weight per unit volume of 1 kg per litre.

Therefore, the volume of the car tank is 240 litres, plus 15%, which adds up to 276 litres. The counterweight, on the other hand, must be equal in weight to the weight of the car plus one half of the load-bearing capacity of the car, and therefore:

Weight of counterweight (including cables) : 840 kg.

The volume of the counterweight tank must be equal to that of the car tank, that is to say, 276 litres.

As regards the pumps for transferring the weight medium, the following can be said: a pump with a 1.5 kW electric motor has the following specifications : head: 15 m water column; flow rate: 360 litres per minute.

It follows that the maximum time needed to transfer the full volume of liquid is 276/360 x 60 = approximately 46 seconds; and to transfer half the volume - in a situation where the car is at an intermediate floor - approximately 23 seconds. Obviously, shorter times can be achieved using higher capacity pumps and it should also be remembered that these values refer to the elevator working under the most onerous conditions.

The invention achieves important advantages . The gravity elevator according to the present invention is compact and can therefore be installed in confined spaces .

More specifically, since there is no hoist, the transmission pulley 8 need not be installed in a machine room separate from the elevator shaft. Compared to other prior art solutions, where a gearless motor, is coupled directly to the transmission pulley, less space is occupied in a radial direction because motors of this kind must be larger in diameter than the transmission pulley itself.

Even the version with the motor-generator 23 is less cumbersome because the motor-generator does not have to overcome a difference in weight force between the car and the counterweight but only the inertia of the car when the car starts moving so as to improve the response speed of the system.

The operating system of the gravity elevator according to the present invention is such that the car always starts promptly and smoothly. In particular, in the solution with the speed control brake, the car can start moving as soon as the weight of the car overbalances that of the counterweight (or vice versa) by even the smallest amount, and, in the solution with motor- generator, the car can start moving as soon as the command is given without even waiting for the overbalance to be created.

The gravity elevator according to the present invention has a very low power requirement since the movement of the car is created by the weight difference between the car and the counterweight. The speed of the car is independent of the power used by the elevator.

In addition, the motor-generator 23 makes it possible to recover power during the stages in which the car is slowed.

Hence, in the event of substitution of an existing elevator installation, it is not necessary to increase the power input required of the electrical line but, on the contrary, it may be reduced and it is also possible, for example, to change from a three-phase power supply to a single-phase power supply.

The weight medium 10 used for weight transfer may consist simply of water (plus suitable additives), which is more economical and easier to dispose of than the hydraulic fluid used in oil-hydraulic elevator installations, and which also greatly simplifies maintenance.

It will be understood that the invention can be adapted and modified in several ways without thereby departing from the scope of the inventive concept. Moreover, all the details of the invention may be substituted by technically equivalent elements. List of reference characters

1 gravity elevator

2 elevator car 2a car pulley 3 car supporting arch

4 car guides

5 counterweight

5a fixed mass section of counterweight

6 counterweight guides 7 cables

8 transmission pulley

9 governor unit

10 weight medium

11 car tank 12 counterweight tank

13 device for transferring weight medium 10

14 piping 15, 16 pumps

17 parking brake 18 force sensor

18a force sensor on cables 7

18b pulley for diverting force sensor 18a

19 speed sensor

20 motion sensor 20a set of vertical motion sensors

21 speed control brake

22 controller

23 motor-generator

Claims

1. A gravity elevator (1) for a multi-storey building, comprising: a car (2) and a counterweight (5) connected to each other by cables (7); a transmission pulley (8) around which the cables (7) are looped; at least one tank (11, 12) associated with the car (2) or the counterweight (5) and containing a weight medium (10); and a device (13) for transferring the weight medium (10) in such a way as to vary the amount of the weight medium (10) contained n the tank (11, 12), the elevator being characterised in that it comprises a governor unit (9) that controls the speed and motion of the car (2) in such manner that the car (2) can vary its speed from zero to a predetermined maximum value and can move from one floor of the building to another as a result of the weight difference between the car (2) and the counterweight (5).

2. The gravity elevator according to claim 1, characterised in that the governor unit (9) comprises a brake (21) for controlling the speed and acceleration of the car (2).

3. The gravity elevator according to claim 1, characterised in that the governor unit (9) comprises a motor-generator (23) for controlling the speed and acceleration of the car (2) .

4. The gravity elevator according to one of the foregoing claims, characterised in that the governor unit (9) comprises a parking brake (17) to hold the car (2) at the landing it has stopped at when the car (2) is not required to move.

5. The gravity elevator according to one of the foregoing claims, characterised in that the governor unit (9) comprises a speed sensor (19) to detect the speed at which the car (2) is travelling.

6. The gravity elevator according to one of the foregoing claims, characterised in that the governor unit (9) comprises at least one motion sensor (20, 20a) to detect the position of the car (2) .

7. The gravity elevator according to one of the foregoing claims, characterised in that the governor unit (9) comprises an acceleration sensor to detect the acceleration of the car (2).

8. The gravity elevator according to one of the foregoing claims, characterised in that the governor unit (9) comprises a controller (22) which controls the car (2) and which is operatively connected to the speed control brake (21) , or to the motor-generator (23), and/or to the parking brake (17), and/or to the speed sensor (19), and/or to the motion sensor (20, 20a) and/or to the acceleration sensor, so as to detect and/or control the speed, stops, motion and acceleration of the car (2), respectively.

9. The gravity elevator according to one of the foregoing claims, characterised in that the device (13) for transferring the weight medium (10) comprises piping (14) and at least one pump (15, 16).

10. The gravity elevator according to one of the foregoing claims, characterised in that the device (13) for transferring the weight medium (10) comprises two force type pumps (15, 16).

11. The gravity elevator according to any of the foregoing claims from 2 to 10, characterised in that the speed control brake (21) is equipped with a force sensor (18) capable of detecting the braking torque and/or the weight force overbalance between the car (2) and the counterweight (5) .

12. The gravity elevator according to any of the foregoing claims from 3 to 10, characterised in that the speed control motor- generator (23) is equipped with a force sensor (18), fitted to the casing of the motor-generator (23) and capable of detecting the braking torque or the acceleration torque.

13. The gravity elevator according to any of the foregoing claims from 4 to 12, characterised in that the parking brake (17) is equipped with a force sensor (18) capable of detecting the braking torque and/or the weight force overbalance between the car (2) and the counterweight (5).

14. The gravity elevator according to one of the foregoing claims, characterised in that it comprises at least one force sensor (18a) associated with the cables (7) and designed to detect the braking torque and/or the weight force overbalance between the car (2) and the counterweight (5).

15. The gravity elevator according to claim 13, characterised in that the parking brake (17) , the speed control brake (21) or the motor-generator (23) have a single force sensor (18) that detects the weight force overbalance between the car (2) and the counterweight (5) under both static and dynamic conditions.

16. The gravity elevator according to any of the foregoing claims from 5 to 13, characterised in that the speed sensor (19) and the motion sensor (20) are made as a single unit.

17. The gravity elevator according to claim 16, characterised in that the speed sensor (19) and the motion sensor (20) are embodied in a single encoder.

18. A method for moving a car (2) of an elevator (1) in a multistorey building by the transfer of weight, the elevator (1) being equipped with cables (7) connecting the car (2) and a counterweight (5), the method comprising the steps of: keeping the car (2) stationary at a landing; selecting a car (2) direction of movement; detecting the weight forces of the car (2) and of the counterweight (5); transferring a weight medium (10) from the car (2) to the counterweight (5), or vice versa, in such manner as to create an overbalance in the selected direction of motion; releasing the car (2) so that it can move freely; the method being characterised in that it further comprises the following steps: detecting the speed at which the car (2) is travelling; and controlling the speed of the car (2) using a brake (21) or a motor-generator (23) so that it does not exceed a predetermined value.

19. The movement method according to claim 18, characterised in that it comprises the following steps: detecting the position of the car (2) ; ascertaining the final destination landing to be served by the car ( 2 ) ; ascertaining whether the car (2) has to reverse its direction or whether the destination landing is at the top or bottom floor of the building; transferring the weight medium (10) from the car (2) to the counterweight (5), or vice versa, n such manner as to create an overbalance in the direction of travel opposite the current direction of travel when the car (2) approaches the destination landing, thus making the car (2) ready for the next run.

20. The movement method according to claim 18, characterised in that it comprises the following steps: detecting the position of the car (2); stopping the car (2); transferring the weight medium (10) from the car (2) to the counterweight (5), or vice versa, in such manner as to create a weight force balance between the car (2) and the counterweight (5) so that the car (2) is ready for the next run, whose direction cannot be ascertained.