Fall arrest devices, and related methods

Abstract

A fall arrest device comprises a casing with an entry hole for the wire rope, and an exit hole for the wire rope, and a clamping mechanism and an overspeed detector arranged inside the casing. The speed detection mechanism comprises a driven roller arranged to be driven by the wire rope. The driven roller has one or more selected areas to be detected by a sensor, and the device further comprises a motion indicator configured to receive a signal from the sensor when the sensor detects one of the selected areas. The motion indicator is configured to give different indications depending on whether or not the signal is received from the sensor, and such indications are detectable from outside the casing. Methods for operating such a fall arrest device and method for retrofitting fall arrest devices are also disclosed.

Claims

1. A fall arrest device configured to be mounted around a wire rope of an elevator, the fall arrest device comprising a casing with an entry hole for the wire rope, and an exit hole for the wire rope, and a clamping mechanism and an overspeed detector arranged inside the casing, the overspeed detector comprising a driven roller arranged to be driven by the wire rope and wherein the clamping mechanism is configured to clamp the wire rope if the overspeed detector detects a speed of the driven roller above a predetermined threshold, wherein the driven roller has one or more selected areas to be detected by a sensor, and the device further comprising a motion indicator configured to receive a signal from the sensor when the sensor detects one of the selected areas, and the motion indicator is configured to give different indications depending on whether or not the signal is received from the sensor, such indications being detectable from outside the casing.

2. The fall arrest device according to claim 1, wherein the sensor inside the casing is a photoelectric sensor.

3. The fall arrest device according to claim 1, wherein the sensor inside the casing is an inductive sensor.

4. The fall arrest device according to claim 1, wherein the sensor is a color sensor or a contrast sensor.

5. The fall arrest device according to claim 4, wherein the overspeed detector further comprises a pressure roller configured to force the wire rope and the driven roller into contact.

6. The fall arrest device according to claim 1, wherein the overspeed detector further comprises a pressure roller configured to force the wire rope and the driven roller into contact.

7. The fall arrest device according to claim 6, wherein the overspeed detector is a centrifugal speed detection mechanism.

8. The fall arrest device according to claim 1, wherein the overspeed detector is a centrifugal speed detection mechanism.

9. The fall arrest device according to claim 8, wherein the motion indicator is a light.

10. The fall arrest device according to claim 1, wherein the motion indicator is a light.

11. The fall arrest device according to claim 10, wherein the wire rope is a hoisting wire rope of the elevator.

12. The fall arrest device according to claim 1, wherein the wire rope is a hoisting wire rope of the elevator.

13. The fall arrest device according to claim 12, wherein the casing further comprises an inspection window for viewing the speed detection mechanism.

14. The fall arrest device according to claim 1, wherein the casing further comprises an inspection window for viewing the speed detection mechanism.

15. An elevator system comprising the fall arrest device according to claim 1, and the elevator.

16. A wind turbine comprising the elevator system according to claim 15.

17. A method for operating the elevator according to claim 15, wherein the elevator is operated by a traction mechanism, and the method comprising deriving an estimated speed of the wire rope from the speed of the driven roller, deriving an actual speed of the wire rope from the traction mechanism, and comparing the estimated speed with the actual speed, and issuing a warning signal if a difference between the actual speed and the estimated speed is higher than a predetermined threshold.

18. The method for retrofitting a fall arrest device comprising a casing with an entry hole for a wire rope, and an exit hole for a wire rope, and a clamping mechanism and an overspeed detector arranged inside the casing, the overspeed detector comprising a driven roller arranged to be driven by the wire rope and wherein the clamping mechanism is configured to clamp the wire rope if the overspeed detector detects a speed of the driven roller above a predetermined threshold, the method comprising: providing a sensor configured to detect selected areas of the driven roller, and providing a motion indicator configured to receive a signal from the sensor when the sensor detects one of the selected areas, wherein the motion indicator is configured to give different indications depending on whether or not the signal is received from the sensor, and such indications being detectable from outside the casing.

19. The method according to claim 18, further comprising making selected areas of the driven roller detectable by the sensor.

20. A method according to claim 19, wherein making one or more selected areas of the driven roller detectable by the sensor includes providing one or more of a reflective foil, reflective paint, reflective coating or reflective sticker on the selected areas.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Non-limiting examples of the present disclosure will be described in the following, with reference to the appended drawings, in which:

(2) FIG. 1 is a perspective view of an example of a fall-arrest device;

(3) FIGS. 2a-2c show longitudinal cross-sectional views and a cross-sectional top view of a fall arrest device which may the same or similar to the fall-arrest device shown in FIG. 1; and

(4) FIGS. 3a-3c schematically illustrate an example of a fall arrest device including an additional sensing mechanism and a motion indicator.

DETAILED DESCRIPTION OF EXAMPLES

(5) In these figures the same reference signs have been used to designate matching elements.

(6) FIG. 1 schematically illustrates a fall arrest device. The fall arrest device 10 of FIG. 1 is mounted on an elevator, and the fall arrest device comprises a housing 13 having an upper wire rope entry 12, an unlocking lever 4 and an inspection window 51. The housing further comprises a lower wire rope exit 14. Also indicated in FIG. 1 is an emergency locking lever 38. The wire rope 5 passes through the fall arrest device 10.

(7) FIGS. 2a-2c schematically illustrate cross-sectional views of a safety device 10 similar to the one shown in FIG. 1. In the interior of the housing of the safety device 10, at least one safety mechanism is provided. The safety mechanism acts on the wire rope, and therefore may be subject to wear. In particular, the parts and components that are substantially constantly in contact with the wire rope may be subject to wear.

(8) FIG. 2b illustrates an entry hole 12 for a wire rope. The wire rope passes in between the clamping jaws 8, 9 of upper clamp 6 and lower clamp 7. In normal operation, the clamping jaws are open, and there is substantially no contact between the wire rope and the clamping jaws. The jaws are in normal operation prevented from closing by blocking element 59. If in operation, an overspeed of the wire rope is detected (this indicates that the elevator to which the safety device is mounted is falling), the overspeed detector trips which moves the blocking element 59 and allows the jaws 6, 7 to close. The elevator is thus prevented from falling.

(9) The overspeed detection and trip mechanism may comprise a first driven roller 48 which is in contact with the wire rope. As the wire rope moves, the roller 48 is driven and rotates. The first driven roller 48 is operatively coupled with the driven roller of the centrifugal overspeed detector 55 shown in FIG. 2a. Both the driven roller 48 and the driven roller of the overspeed detector 55 may be mounted on the same axle of shaft.

(10) The overspeed detector 55 may comprise a plurality of weights 53, which are configured to move outwards as the detector rotates due to the centrifugal forces acting on them. If the driven roller rotates too fast (i.e. this may indicate an unsafe condition caused by e.g. a traction hoist malfunction and/or electromagnetic brake malfunction), the weights 53 move outwardly to such an extent that the detector trips: the weights contact lever 57, which releases the blocking element 59 from its original position. When the detector trips, as explained before, the clamping jaws close down and the elevator comes to a halt.

(11) In order to ensure that the first driven roller 48 is in fact driven by the movement of the wire rope, a pressure roller 50 may force both of them in contact with each other. Reference sign 49 indicates the space between the first driven roller 48 and the pressure roller 50 through which the wire rope passes. Both the pressure roller 50 and the driven roller 48 are constantly in contact with the tensioned wire rope. The contact between the wire rope and the rollers may result in wear of the grooves along the perimeters of the rollers. As a result of wear, the driven roller may not be driven at all by the wire rope, or may not rotate at the correct speed. Either one of these situations can be dangerous as they both compromise the correct functioning of the overspeed detector.

(12) FIGS. 3a-3c show schematic views inside the casing of a fall arrest device such as the one described with reference to FIG. 1 and FIGS. 2a-2c. Even though in the following reference will be made to such a fall arrest device, it should be clear that a similar teaching may be applied to different kinds of fall arrest devices: e.g. the clamping mechanism may be different from the one described before, and the overspeed detector may be different. The overspeed detector might be a centrifugal overspeed detector, but does not necessarily need to be of this type.

(13) The wire rope, either directly or indirectly, drives the driven roller of the centrifugal overspeed detector. In this example, a photocell detector 66 is used. The photocell detector 66 according to this example has a light transmitter, and a light receiver. The photocell detector is connected to a connector 60 through an electric, data or fiber cable 63.

(14) Connector 60 may be connected to an indicator, such as e.g. a light, in particular a LED. This light may be mounted on the outside of casing 13 of the safety device but may also be installed in a suitable location on the elevator. In a further example, it may also be located remotely in a position in which it is visible to operating personnel. In one example, the indicator may be mounted to an inside wall of a wind turbine tower.

(15) Selected parts 58 of e.g. the perimeter of the driven roller of the centrifugal overspeed detector 55 or of the centrifugal elements 53 may be made to be reflective using a foil or paint, or other. Alternatively, selected parts of the driven roller of the centrifugal overspeed detector may be made to be non-reflective.

(16) As a result, selected parts 58 of the driven roller of the centrifugal overspeed detector will reflect light received from the transmitter to the receiver, whereas other parts of the driven roller will not reflect the light. As the driven roller rotates, it continuously receives alternating signals of light, and no light, or reflective and non-reflective. The detector 66 thus selectively turns the indicator on and off repeatedly. Such a transmission of the alternating signals may be through an electric, data or fiber cable 63 or may be wireless.

(17) The indicator may give a visual indication (a light), an audible indication, or a combination of these each time a light signal is received (or alternatively, each time, a no-light signal is received). As a result, the motion indicator will give continuously alternating indications when the driven roller is rotating. This may easily be noted by personnel, even if no direct access to the fall arrest device is available. A flashing light may easily be detected from a distance and even in circumstances of relative darkness.

(18) In this particular example, selected parts of a driven roller of the centrifugal speed detector were detected. This driven roller is not in direct contact with the wire rope, but instead is indirectly driven as it is operatively coupled with the first driven roller 48. In other examples, selected parts or areas of the first driven roller may be detected in a similar manner as described before.

(19) Furthermore, in this particular example, reference was made to a photocell detector based on the presence or absence of reflection, but alternative sensors might be used. In another example, sensors suitable for determining the colour of a surface may be used. The centrifugal elements may then be distinguished from other parts of the driven roller based on their colour.

(20) One other example of a sensor that may be used is an inductive sensor. Selected portions or areas of the driven roller or centrifugal elements may be made from a different material. The inductive sensor may thus again receive alternating signals, material A, material B, or simply positive and negative. Each of these examples of sensors take up little space in a fall arrest device and make retrofitting existing fall arrest devices with the additional described capability possible. Depending on the type of sensor used, existing fall arrest devices may be simply retrofitted by installing the sensor and connecting the indicator with the sensor.

(21) In other cases, specific portions or areas of the driven roller are made detectable, and/or others non-detectable. A suitable sensor inside the casing and a motion indicator giving indications that are visible or hearable from the outside of the casing may be easily incorporated.

(22) Although only a number of examples have been disclosed herein, other alternatives, modifications, uses and/or equivalents thereof are possible. Furthermore, all possible combinations of the described examples are also covered. Thus, the scope of the present disclosure should not be limited by particular examples, but should be determined only by a fair reading of the claims that follow.