Self-braking gear and people conveyor comprising a self-braking gear

A self-braking gear (2) comprises: an input shaft (4), an output shaft (6), a braking mechanism (8), which is configured for braking the output shaft (6), and a planetary gear (10). The planetary gear (10), which is connected between the input shaft (4) and the output shaft (6), is configured to activate the braking mechanism (8) in order to brake the output shaft (6), when no torque is provided via the input shaft (4). The self-braking gear (2) may be employed in a people conveyor (50) such as an escalator.

The invention relates to a self-braking gear, in particular to a self-braking gear which is configured to be employed in a people conveyor. The invention further relates to a people conveyor comprising such a self-braking gear and to a method of operating such a people conveyor.

A people conveyor such as an escalator or a moving walkway typically comprises a chain of conveyance elements, such as pallets or steps, which are configured for conveying people, and a drive unit, which is configured for driving the chain of conveyance elements. Torque provided by the drive unit is transmitted to the chain of conveyance elements via transmission elements, which in particular may include chains and/or belts.

In particular in configurations in which the chain of conveyance elements extends between different levels of height, such as different floors of a building, there is a risk that the conveyance elements will move downwards in an uncontrolled manner in case the drive unit and/or at least one of the transmission elements fails.

It is desirable to avoid such an uncontrolled movement of the conveyance elements.

According to an exemplary embodiment of the invention a self-braking gear, which in particular may be employed in a people conveyor, comprises an input shaft, which is configured to be connected to a drive unit; an output shaft, which is configured to be connected to a load, such as a chain of conveyance elements; a braking mechanism, which is configured for braking the output shaft; and a planetary gear which is connected between the input shaft and the output shaft. The planetary gear is configured to activate the braking mechanism in order to brake the output shaft when no torque is provided via the input shaft.

A people conveyor according to an exemplary embodiment of the invention comprises a chain of conveyance elements which are configured for conveying people; a drive unit, which is configured for driving the chain of conveyance elements; and a self-braking gear according to an exemplary embodiment of the invention. The drive unit is connected to the input shaft of the self-braking gear and the chain of conveyance elements is connected to the output shaft of the self-braking gear.

A method of operating a people conveyor according to an exemplary embodiment of the invention includes operating the drive unit in order to drive the chain of conveyance elements via the self-braking gear.

A method of operating a people conveyor according to an exemplary embodiment of the invention also includes locking the chain of conveyance elements by means of the self-braking gear when no torque is provided via the input shaft, i.e. when the drive unit is not driving the chain of conveyance elements via the self-braking gear.

A self-braking gear according to an exemplary embodiment of the invention is configured to transmit torque from the input shaft to the output shaft in normal (driving) operation, i.e. when the chain of conveying elements is driven by torque provided by the drive unit.

In case, however, no torque is transmitted to the input shaft of the self-braking gear, e.g. due to a failure of the drive unit or at least one of the transmission elements, the braking mechanism is activated in order to brake the output shaft. Braking the output shaft avoids an uncontrolled and undesirable movement of the chain of conveying elements, which is mechanically connected to the output shaft.

A self-braking gear according to an exemplary embodiment of the invention may be realized in a configuration which may be integrated in a main drive shaft of a sprocket which is provided for driving the chain of conveying elements of a people conveyor. This allows to integrate the self-braking gear into a people conveyor without increasing the space which is necessary for the people conveyor. As a result, a self-braking gear according to an exemplary embodiment of the invention may be added easily to existing people conveyor designs.

FIG. 1shows a schematic side view of a people conveyor50extending between two landing portions51. In the embodiment shown inFIG. 1, the people conveyor50is an escalator comprising a plurality of steps53. The skilled person, however, will understand that exemplary embodiments of the invention may include different kinds of people conveyor50, in particular moving walkways comprising a plurality of pallets instead of steps53. The steps53are arranged as a chain of conveyance elements52. The chain of conveyance elements52is in engagement with a sprocket56which is mounted to a rotating shaft6. A drive unit54is configured for driving the rotating shaft6and in consequence the sprocket56and the chain of conveyance elements52via a transmission element58, which may be a chain or belt.

A self-braking gear2according to an exemplary embodiment of the invention, which is not visible inFIG. 1, is arranged within the rotating shaft6. The self-braking gear2will be described in more detail in the following with reference toFIGS. 2 to 8. The rotating shaft6in particular may be an output shaft6of the self-braking gear2. The transmission element58is connected to an input shaft4of the self-braking gear2. Thus, the torque provided by the drive unit54is transmitted via the transmission element58to the self-braking gear which transmits the torque via its output shaft6to the sprocket56.

In an alternative configuration, which is not shown in the figures, the input shaft of the self-braking gear2may be connected directly to an output shaft of the drive unit54.

FIGS. 2 and 3respectively show a perspective view of a self-braking gear2according to an exemplary embodiment of the invention, andFIG. 4shows a side view thereof.

The self-braking gear2comprises an input shaft4extending along an axis A through the self-braking gear2. The self-braking gear2further comprises an output shaft6in the form of a cylindrical cage enclosing the input shaft4. The axis of the cylindrical cage forming the output shaft6is coaxial with the axis A of the input shaft4.

The input shaft4is mechanically connected to a drive or motor, e.g. a drive unit54of a people conveyor50. The output shaft6is mechanically connected to a load, such as a chain of conveying elements52of a people conveyor50(seeFIG. 1).

A cycloidal gear drive40, which is shown on the left side ofFIGS. 2, 3, and 4, connects the input shaft4to the output shaft6of the self-braking gear2in order to allow to transmit torque from the input shaft4to the output shaft6. When the input shaft4is rotated by the drive or motor, the cycloidal gear drive40causes the output shaft6to rotate with a rotational speed that is lower than the rotational speed of the input shaft4.

The cycloidal gear drive40comprises braking mechanism8which is configured for braking the rotation of the output shaft6. The structures of the cycloidal gear drive40and of the braking mechanism8will be discussed in more detail further below with respect toFIG. 8.

The self-braking gear2further comprises a planetary gear10, which is depicted on the right side ofFIGS. 2, 3, and 4.

The planetary gear10is a self-locking gear, which locks in case no torque is delivered via the input shaft4, i.e. in case torque would be transferred “in reverse” from the output shaft6to the input shaft4of the self-braking gear2. Such a situation may occur when the drive or motor (drive unit54) does not work or the mechanical connection, e.g. the transmission element58, between the input shaft4and the drive or motor is damaged or destroyed.

In case the planetary gear10locks, a movable disk26, which is arranged in between the planetary gear10and the cycloidal gear drive40, is moved away from the planetary gear10towards the cycloidal gear drive40(from right to left inFIGS. 2, 3, and 4). This mechanism is described in more detail further below with reference toFIGS. 5 and 6.

A force amplifier30, which is arranged between said movable disk26and the cycloidal gear drive40amplifies the force provided by the movement of the movable disk26and activates the braking mechanism8of the cycloidal gear drive40in order to brake the output shaft6.

FIG. 5shows a perspective view of the planetary gear10, andFIG. 6shows a sectional view thereof along the axis A.

The planetary gear10comprises a first sun gear14. The first sun gear14is a spur gear which is fixed to the input shaft4(not shown inFIG. 5) so that the first sun gear14rotates integrally with the input shaft4. The first sun gear14is in engagement with a plurality of first planets (first planetary spur gears)16. Each of the first planets16is supported by a corresponding axle19of a planet carrier18, which is rotatable with respect to the input shaft4.

Friction pads15(seeFIG. 3) are elastically pressed by springs17or other elastic elements against the outer periphery of the planet carrier18. The springs17or other elastic elements are supported by the inner surface of the cylindrical cage forming the output shaft6.

Each axle19of the planet carrier18further supports a second planet (second planetary spur gear)20. Each second planet20is arranged coaxially with a corresponding first planet16. The first and second planets16,20may rotate independently of each other, even when supported by the same axle19.

In the exemplary embodiment shown inFIGS. 2 to 6, the planetary gear10comprises four first planets16and four second planets20, respectively. The skilled person, however, will understand that different numbers of first and second planets16,20may be employed as well.

The second planets20are in engagement with a second sun gear22, which is arranged coaxially with the input shaft4and the first sun gear14. The second sun gear22may rotate freely with respect to the input shaft4and the first sun gear14.

When the input shaft4rotates, the planet carrier18rotates around the axis A of the input shaft4so that the first and second planets16,20move along a circular orbit. The first and second sun gears14,22are located in the centers of said orbits, respectively. Due to the engagement with the sun gears14,22, the first and second planets16,20rotate around their respective axles19of the planet carrier18.

On the side of the second planets20, which is facing away from the first planets16(the left side inFIGS. 4 to 6), a conically formed eccentric shaft24is provided on the surface of each of the second planets20. The eccentric shafts24are spaced apart from centers of the second planets20in the radial direction. As a result, the eccentric shafts24move along an eccentric circular path around the respective axles19when the second planets20rotate around their respective axles19. As a result, the eccentric shafts24move along a cycloidal path when the planet carrier18and the second planets20rotate.

A movable plate26is arranged next to the second planets20on the side facing away from the first planets16and the planet carrier18.

The movable plate26is supported so that it is not able to rotate but may be shifted in the axial direction. A groove28, which is configured for receiving the eccentric shafts24, is formed on the surface27of the movable plate26facing towards the second planets20. The groove28is formed along a cycloidal track. In normal driving operation, i.e. when the input shaft4is driven so that torque is transmitted from the input shaft4to the output shaft6and the planetary gear10operates as it has been described before; the cycloidal track of the groove28coincides with the cycloidal path of the eccentric shafts24. Thus, in normal driving operation, the eccentric shafts24follow the cycloidal track of the groove2and there is no mechanical interaction between the eccentric shafts24and the movable plate26.

As mentioned before, the planetary gear10is designed as a self-locking gear, i.e. as a planetary gear10which locks in case no torque is provided via the input shaft4. Such a situation may result from a reverse/backward motion of the load, such as a chain of conveying elements52of a people conveyor50, when the provision of a driving force from the drive unit54is interrupted, e.g. because the drive unit54is stopped or the transmission element58is broken (seeFIG. 1).

The self-locking properties of the planetary gear10may result from friction between the sun gear14and the planets16. In order to enhance the efficiency and reliability of the self-locking properties, the first sun gear14and the first planets16may have a special self-locking design, e.g. a self-locking design as it has been proposed by A. Kapelevich et al. in “Direct Gear Design”, published on Mar. 22, 2013 by CRC Press (ISBN 9781439876183).

When the planetary gear10is locked, the eccentric shafts24no longer move along the cycloidal path which coincides with the path of the groove28formed within the surface27of the movable plate26. Instead, the eccentric shafts24are pressed against the sidewalls of the groove28. This mechanical interaction between the conically formed eccentric shafts24and the walls of the groove28causes the movable plate16to move (shift) in the axial direction away from the planetary gear10, i.e. to the left side inFIGS. 2 to 6. Said movement of the movable plate26results in an input force, which is input to the force amplifier30arranged in between the movable plate26and the cycloidal gear drive40.

FIG. 7shows an enlarged view of an exemplary embodiment of the force amplifier30. The skilled person will understand that alternative types of force amplifiers30, as they are known in the art, may be employed as well. The force amplifier30comprises a plurality of levers32, which interact in order to amplify an input force, which is input from the movable disk26to an input element34of the force amplifier30by pushing the input element34from right to left in the configuration shown inFIG. 7. The levers32are in particular arranged in a configuration in which they form a plurality of knee levers. An output element36of the force amplifier30acts on a braking element48of the brake mechanism8of the cycloidal gear drive40. This activates the brake mechanism8(seeFIG. 4).

FIG. 8shows a sectional view of the cycloidal gear drive40and the brake mechanism8.

The cycloidal gear drive40comprises two cyclo disks46extending parallel to each other orthogonally to the axis A of the input shaft4. The cyclo disks46are connected to the input shaft4via an eccentric bearing (not shown). As a result, the cyclo disks46perform an eccentric, cycloidal motion, when the input shaft4rotates.

The outer contour of each cyclo disk46has a cycloidal shape which unrolls on a ring of outer pins (outer ring)42when the input shaft4rotates.

A plurality of inner pins forming an inner ring44, which is connected to the output shaft6, extend parallel to the common axis A of the input and output shafts4,6through openings formed within the cyclo disks46. When the input shaft4rotates, the inner ring44and in consequence the output shaft6are rotated by the cyclo disks46with a rotational speed which is considerably smaller than the rotational speed of the input shaft4.

The cycloidal gear drive40further comprises a braking element48which extends parallel to the axis A of the input shaft4and which is arranged between the input shaft4and the cyclo disks46when viewed in the radial direction. The braking element48comprises conical outer surfaces49. The conical outer surfaces49are configured to lock the only degree of freedom between the input shaft4and the cyclo disks46when the braking element48is pushed in the axial direction towards the cycloidal gear drive40, i.e. to the left side inFIGS. 2 to 7, by the output element36of the force amplifier30when the planetary gear10is locked, as it has been described before.

In summary:

In normal driving operation, i.e. when torque is input via the input shaft4, the planetary gear10is not locked. In consequence, the conical eccentric shafts24provided on the side surfaces of the second planets20follow the cycloidal path of the groove28formed within the movable plate26. As a result, no axial forces are exerted on the movable disk26, the braking element48is not pushed into the cycloidal gear drive40and the braking mechanism8of the cycloidal gear drive40is not activated.

In braking operation, i.e. when no torque is provided via the input shaft4, the planetary gear10locks due to its self-locking properties. In consequence, there is a difference in the rotational speed between the output shaft6and the planet carrier18. The conical eccentric shafts24provided on the side surfaces of the second planets20no longer follow the cycloidal path of the groove28formed within the movable plate26. As a result, the conical eccentric shafts24are pressed against the walls of the groove28. Due to their conical shape, the eccentric shafts24push the movable plate26away from the planetary gear10towards the cycloidal gear drive40. This linear movement in the axial direction is amplified by the force amplifier30. The braking element48is pushed into the cycloidal gear drive40locking the only degree of freedom between the input shaft4and the cyclo disks46. This locking brakes the output shaft6, which is connected to the cyclo disks46via the inner ring44.

A number of optional features are set out in the following. These features may be realized in particular embodiments, alone or in combination with any of the other features.

In one embodiment the planetary gear may be configured to lock due to friction when no torque is provided via the input shaft. A planetary gear which locks due to friction is easy to implement at low costs.

In one embodiment at least some gears of the planetary gear, in particular the first sun gear and the first planets, may comprise self-locking tooth profiles in order to lock when no torque is provided via the input shaft. Providing gears with special, self-locking tooth profiles allows to enhance the reliability and efficiency of the self-locking feature.

In one embodiment the planetary gear may comprise a plurality of planets (planetary gears) and an eccentric shaft may be provided on one side of each planet. The eccentric shafts may extend parallel to the axis of the planets. Each of the eccentric shafts may have a conical (tapered) shape, with the thinner side of the conical shape facing away from the planet. The eccentric shafts may be arranged outside the centers of the planets, i.e. offset from the centers of the planets in the radial direction, so that they follow an eccentric cycloidal path when the planets rotate.

In one embodiment the self-braking gear may further comprise a movable disk, which is movable along an axial direction of the input shaft. A groove may be formed on a surface of the movable disk facing the planetary gear. Said groove in particular may be configured to receive the eccentric shafts provided on the planets.

The interaction of the conically shaped eccentric shafts provided on the planets and the groove formed on a surface of the movable disk allows to push the movable plate away from the planetary gear when the planetary gear is locked and the eccentric shafts do not follow the track provided by the groove. This movement of the movable disk may be used to activate the braking mechanism.

In one embodiment the planetary gear may comprise a force amplifier. The force amplifier may be configured to amplify the force, which is applied to the movable disk by the eccentric shafts, and to transfer the amplified force to the braking mechanism. Such a force amplifier allows to provide an increased braking force. This enhances the efficiency and the reliability of the breaking mechanism.

In one embodiment the force amplifier may comprise a plurality of levers which interact in order to amplify the force applied to the movable disk. A plurality of levers allows to realize an efficient and reliable force amplifier.

In one embodiment the self-braking gear may further comprise a cycloidal gear drive, which is configured for transmitting torque from the input shaft to the output shaft. A cycloidal gear drive provides a gear which needs only little space and which allows to provide a large reduction of the rotational speed in combination with a large increase of the torque.

In one embodiment the braking mechanism may be arranged within the cycloidal gear drive. The force amplifier may be located between the movable disk and the cycloidal gear drive. Such an arrangement allows for a very compact configuration which needs only little space and which may be integrated conveniently into the driving shaft of a people conveyor.

In one embodiment the people conveyor may be an escalator. The chain of conveyance elements may be a step chain comprising a plurality of steps. This provides a safe escalator in which an uncontrolled movement of the steps is reliably prevented.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition many modifications may be made to adopt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention include all embodiments falling within the scope of the dependent claims.

REFERENCES

4input shaft of the self-braking gear

6rotating shaft/output shaft of the self-braking gear

14first sun gear

19axles of the planet carrier

22second sun gear

27surface of the movable plate

28grove in the surface of the movable plate

32levers of the force amplifier

34input element of the force amplifier

36output element of the force amplifier

40cycloidal gear drive

42outer ring of the cycloidal gear drive

44inner ring of the cycloidal gear drive

49conical outer surfaces of the braking element

52chain of conveyance elements

A axis of the input (and output) shaft