Anti-lock braking arrangement for an elevator and method for controlling same

Abstract

A braking arrangement for an elevator arrangement includes a speed sensor arrangement for generating an over-speed signal of a moving component of the elevator arrangement, a hydraulic brake arrangement for generating a braking action of the moving component upon application of a hydraulic pressure and an actuator arrangement for generating and applying the hydraulic pressure to the hydraulic brake arrangement. The braking arrangement includes a control connected to the speed sensor arrangement and in response to the over-speed signal initiating an ABS braking process by controlling the actuator arrangement to repeatedly increase and decrease the hydraulic pressure to the hydraulic brake arrangement with a repetition time interval that is successively extended during the ABS braking process. The braking arrangement enables safe and reliable deceleration of the moving component, such as a car or a counterweight, while avoiding an excessive jerk by smoothly increasing the braking action.

Claims

1. A braking arrangement for an elevator arrangement, comprising: a speed sensor arrangement for generating an over-speed signal upon detecting an over-speed of a moving component of the elevator arrangement; a hydraulic brake arrangement for generating a braking action of the moving component upon application of a hydraulic pressure; an actuator arrangement for generating and applying the hydraulic pressure to the hydraulic brake arrangement; a control for controlling the actuator arrangement, the control being connected to the speed sensor arrangement; and wherein the control, upon receiving the over-speed signal from the speed sensor arrangement, initiates an ABS braking process by controlling the actuator arrangement to repeatedly increase and decrease the hydraulic pressure to the hydraulic brake arrangement with a repetition time interval, wherein the repetition time interval is successively extended by the control during the ABS braking process.

2. The braking arrangement according to claim 1 wherein the actuator arrangement repeatedly increases and decreases the hydraulic pressure within the repetition time interval being of less than 50 ms.

3. The braking arrangement according to claim 1 wherein the actuator arrangement includes a piston and a motor and wherein the actuator arrangement increases the hydraulic pressure by a stroke of the piston driven by the motor and decreases the hydraulic pressure by a return stroke of the piston driven by the motor.

4. The braking arrangement according to claim 1 wherein the control at least doubles the repetition time interval during the ABS braking process.

5. The braking arrangement according to claim 1 wherein the repetition time interval extends non-linearly.

6. The braking arrangement according to claim 1 wherein a pattern with which the repetition time interval extends during the ABS braking process is predetermined.

7. The braking arrangement according to claim 1 wherein a pattern with which the repetition time interval extends during the ABS braking process is based on a feedback signal to the control indicating a current velocity of the moving component.

8. The braking arrangement according to claim 7 wherein the feedback signal is provided by the speed sensor arrangement.

9. The braking arrangement according to claim 1 wherein the speed sensor arrangement includes a roller and a detector, the roller being arranged and adapted for rotating upon motion of the moving component and the detector being arranged and adapted for detecting rotating motion of the roller.

10. The braking arrangement according to claim 9 wherein the detector detects the rotating motion of the roller contactlessly.

11. The braking arrangement according to claim 9 wherein the detector is an optical detector.

12. The braking arrangement according to claim 1 wherein the speed sensor arrangement is fixed to the moving component of the elevator arrangement.

13. The braking arrangement according to claim 1 wherein the hydraulic brake arrangement includes at least one brake pad and a brake cylinder that, upon application of the hydraulic pressure, presses the at least one brake pad against a static component of the elevator arrangement.

14. The braking arrangement according to claim 13 wherein the static component of the elevator arrangement is a guide rail for guiding the moving component during its motion.

15. The braking arrangement according to claim 1 wherein the hydraulic brake arrangement is fixed to the moving component of the elevator arrangement.

16. A method for controlling a braking arrangement for an elevator arrangement comprising the steps of: operating a speed sensor arrangement to generate an over-speed signal upon detecting an over-speed of a moving component of the elevator arrangement; operating a hydraulic brake arrangement to generate a braking action of the moving component upon application of a hydraulic pressure; operating an actuator arrangement to generate and apply the hydraulic pressure to the hydraulic brake arrangement; and initiating an ABS braking process, upon receiving the over-speed signal from the speed sensor arrangement, by controlling the actuator arrangement to repeatedly increase and decrease the hydraulic pressure to the hydraulic brake arrangement with a repetition time interval, wherein the repetition time interval is successively extended during the ABS braking process.

17. A computer program product comprising computer readable instructions which are adapted to, when executed by a programmable control, perform the method according to claim 16.

18. A non-transitory computer readable medium comprising the computer program product according to claim 17 stored thereon.

Description

DESCRIPTION OF THE DRAWINGS

(1) In the following, advantageous embodiments of the invention will be described with reference to the enclosed drawings. However, neither the drawings nor the description shall be interpreted as limiting the invention.

(2) FIG. 1 shows an elevator arrangement.

(3) FIG. 2 shows a principle view of a braking arrangement according to an embodiment of the present invention.

(4) FIG. 3 shows a side view of a speed sensor arrangement for a braking arrangement according to an embodiment of the present invention.

(5) FIG. 4 shows a top view onto the speed sensor arrangement of FIG. 3.

(6) FIG. 5 visualized a time-dependent development of a braking action realized with a braking arrangement according to an embodiment of the present invention.

(7) The figures are only schematic and not to scale. Same reference signs refer to same or similar features.

DETAILED DESCRIPTION

(8) FIG. 1 shows an elevator arrangement 1 in which a braking arrangement according to an embodiment of the present invention may be applied. The elevator arrangement 1 comprises two moving components 3, 5. A first moving component 3 is an elevator car, a second moving component 5 is a counterweight. Both moving components 3, 5 are supported by a suspension means 7 which may be for example one or more ropes or belts. Ends of the suspension means 7 are fixed to fixation structures 9, 11 at a top of an elevator shaft 13. The suspension means 7 may be moved by a traction sheave 15 driven by an engine 17 such that both moving components 3, 5 may be displaced vertically and in opposite directions within the elevator shaft 13. Conventionally, it is common practice to provide a load sensor 22 either in the car 3 (as in the current example) or at the rope fixation structures 9, 11 to determine whether an overload condition develops for example if too many passengers try to board the elevator car 3 from a given landing. If such an overload occurs an alarm generally sounds in the car 3 and the elevator 1 is prevented from moving until the loading of the car 3 is within the permitted thresholds.

(9) During travel, the moving components 3, 5 are typically guided by one or more guide rails 19 which may be attached for example to walls of the elevator shaft 13 or to the brackets which are attached to the walls. Such guide rails 19 may be mechanically stable metal profiles having for example a T-shaped cross-section such that guide rollers or guide shoes attached the moving components 3, 5 may roll or slide along the guide rails 19.

(10) In order to be able to fulfil safety requirements, one or more braking arrangements 21 may be included into the elevator arrangement 1. In accordance with an embodiment of the present invention, such braking arrangement comprises a speed sensor arrangement 23, a hydraulic brake arrangement 25 and an actuator arrangement 27. Furthermore, a controller is provided for controlling the actuator arrangement 27 to thereby enabling controlling a braking process for decelerating the moving component 3, 5 for example in case of an emergency.

(11) Details of an embodiment of the braking arrangement 21 will be described with reference to FIG. 2.

(12) The speed sensor arrangement 23 is adapted for measuring a velocity of at least one of the moving components 3, 5. At least, an over-speed condition of the moving component 3, 5 shall be detectable by the speed sensor arrangement 23 which, thereupon, generates an over-speed signal. This over-speed signal indicates that the monitored moving component 3, 5 exceeds a predetermined speed limit such that it may be in an over-speed condition which may be potentially dangerous.

(13) Such information about the occurrence of an over-speed condition is transmitted to the control 29 of the elevator arrangement 1 by submitting a specific over-speed signal.

(14) Upon receiving such over-speed signal, the control 29 controls the actuator arrangement 27 such that hydraulic pressure is generated and applied to the hydraulic brake arrangement 25. For such purpose, the actuator arrangement 27 comprises a motor 39 such as an electric motor via which a master cylinder 33 connected to the hydraulic brake arrangement 25 may be actuated. For example, the actuator arrangement 27 comprises a piston (not shown) and the electric motor 39 allows consistent actuation times as little as only a few milliseconds of variance in cycle times. The master cylinder 33 comprises a piston and spring arrangement 35. Furthermore, the master cylinder 33 is connected to a hydraulic reservoir 37 via for example two ports, i.e. an inlet port 36 and a compensating port 38. During operation, hydraulic fluid may flow through or into the reservoir 37 based on operating conditions during a braking process.

(15) An outlet of the master cylinder 33 is connected via one or more hydraulic fluid lines 31 to one or more brake cylinders 41. Each brake cylinder 41 comprises one or more brake pads 43. In the example of FIG. 1, each brake cylinder 41 comprises two brake pads 43 arranged at opposite sides inside the brake cylinder 41 such that a portion of the T-shaped guide rail 19 lies in between the two brake pads 43. Furthermore, the brake pads 43 of a brake cylinder 41 are connected with each other via a caliper 45.

(16) Upon an application of hydraulic pressure through the hydraulic fluid lines 31 to the brake cylinder 41, the brake pads 43 are pressed into mechanical contact with the intermittently arranged portion of the guide rail 19 forming a static component within the elevator arrangement. As the brake pads 43 are typically made of a high friction material, pressing the brake pads 43 into mechanical contact with the intermittently arranged portion of the guide rail 19 will generally result in a braking action onto a moving component 3, 5 to which the hydraulic brake arrangement 25 is attached.

(17) However, in order to avoid excessively high braking forces acting onto the moving component 3, 5 upon initiating a braking process, which excessive braking forces could otherwise result in excessive jerk onto the moving component 3, 5, the hydraulic pressure applied to the hydraulic brake arrangement 25 is not abruptly raised to a maximum level. Instead, the control 29, upon receiving the over-speed signal from the speed sensor arrangement 23, progressively increases a braking action generated by the hydraulic brake arrangement by initiating a specific braking process which is called herein ABS braking process.

(18) For such purpose, the control 29 controls the actuator arrangement 27 such as to repeatedly increase and decrease the hydraulic pressure to the hydraulic brake arrangement 25. Therein, the control 29 extends a repetition time interval during the ABS braking process. This may mean that the variable velocity motor 39 presses and releases the piston 35 of the master cylinder 33 in very short time intervals at the beginning of the ABS braking process whereas, successively, the time intervals with which the piston 35 is pressed and released will gradually increase in the course of the ABS braking process. In other words, a stroke with the piston 35 and a return-stroke thereof may follow each other at short time intervals at the beginning of the ABS braking process and such stroke, and optionally also the release in the return-stroke, may become longer and longer during the progression of the ABS braking process.

(19) Accordingly, with the repetition of increasing and decreasing hydraulic pressure onto the hydraulic brake arrangement 35 and successively increasing repetition time intervals, the ABS braking process starts with a relatively low braking action and may then quickly but smoothly increase the braking action by increasing the high pressure time intervals applied to the hydraulic brake arrangement.

(20) In other words, due to an increase/decrease in hydraulic pressure, the brake pads 43 of the brake cylinders 41 will get repeatedly engaged and disengaged against a surface of the guide rail 19, thereby causing braking and brake release actions which will reduce the velocity of the moving component 3, 5. A velocity of the actuator piston will reduce as the braking/brake-releasing continues. With reduced velocity of the actuator piston, a time for braking action, i.e. the braking pads 43 being pressed against the guide rails 19, will increase. Eventually, this frictional force between the brake pads 43 and the guide rails 19 will bring the moving component 3, 5 to stop.

(21) FIG. 5 shows a schematic diagram illustrating the development over time t of the braking action B during an ABS braking process effected by the braking arrangement 21 according to an embodiment of the present invention.

(22) An over-speed of the moving component 3, 5 is detected at the point in time t.sub.0. Upon receiving the corresponding over-speed signal from the speed sensor arrangement 23, the control 29 initiates the ABS braking process by controlling the actuator arrangement 27 to increase the hydraulic pressure applied to the hydraulic brake arrangement 25. However, this hydraulic pressure is not increased up to a maximum value and held there but, instead, already after a very short time period of for example only a few milliseconds, the hydraulic pressure is already released again, for example by reversing a stroke of the actuator arrangement's 27 motor 39 to a counter-stroke. Such increase and decrease of the hydraulic pressure applied to the hydraulic brake arrangement 25 is repeated many times.

(23) However, the repetition time interval T.sub.n is not held constant but increases successively during the ABS braking process. In other words, a repetition time interval T.sub.n is shorter than a succeeding repetition time interval T.sub.n+1. Due to such increasingly long repetition time intervals T.sub.n, a braking action generated by the hydraulic brake arrangement 25 and therefore a deceleration of the moving component 3, 5 successively increases over time.

(24) Therein, a pattern or time development with which the repetition time intervals T.sub.n are successively extended during the ABS braking process may follow a predetermined pattern, i.e. may be independent of actual conditions for example within the elevator arrangement 1 and/or the braking arrangement 21.

(25) Alternatively, a pattern with which the repetition time intervals T.sub.n extend during the ABS braking process may be adapted based on a feedback signal indicating a current velocity of the moving component, such feedback signal being provided for example by the speed sensor arrangement 23. Accordingly, with such feedback option, the control 29 may control the actuator arrangement 27 such that the braking action generated by the hydraulic brake arrangement 25 may be adapted for example as the speed of the moving component 3, 5 reduces. In other words, based on signals from the speed sensor arrangement 23 a real-time feedback signal may be provided to the control 29 which, in turn, may control for example the variable velocity of the actuator piston within the actuator arrangement 27.

(26) Furthermore, as shown in FIG. 2, a signal representing the actual load within the car 3 derived from load sensor 22 can also be fed into the control 29. In this case the control 29 can additionally determine the actual load unbalance between the moving components 3, 5. Using the load signal from the load sensor 22 and the velocity signal from the speed sensor arrangement 23, the control 29 can instruct an appropriate braking action to be delivered by actuator arrangement 27. For example, if the control 29 determines that the car 3 is heavily loaded and travelling downwards at a high speed it can instruct a stronger braking action. On the contrary, if the control 29 determines that the car 3 is unloaded and travelling downwards at low speed, it can instruct weaker braking action.

(27) FIGS. 3 and 4 show a side view and a top view onto a speed sensor arrangement 23 which may be used for a braking arrangement 21 according to an embodiment of the present invention.

(28) The speed sensor arrangement 23 is fixedly attached to the moving component 3, 5 such as for example to a body of an elevator car. For example, a mounting housing 47 may be screwed, bolted, welded or fixed in other ways to the moving component 3, 5. The speed sensor arrangement 23 may comprise a spring loaded roller 53 which is pressed against a static component within the elevator arrangement 1 such as for example to the guide rail 19 such that it rotates upon moving the moving component 3, 5. For such purpose, the roller 53 is attached to the mounting housing 47 via a screw spring arrangement including a screw 49 and a spring 51 such as to keep the roller 53 tensioned against the guide rail 19.

(29) In the example shown in FIGS. 3 and 4, a toothed wheel 55 is connected to the roller 53 such that it rotates together with the roller 53. The rotation of such toothed wheel 55 may be detected with a speed sensor 57. Preferably, such speed sensor 57 determines the rotation velocity of the toothed wheel 55 contactlessly. For example, the speed sensor 57 may comprise an optical detector such as a photodiode. Such optical detector may detect optical characteristics such as optical reflectance variations or optical transmission variations upon rotation of the toothed wheel 55 and a signal indicating the rotation velocity of the toothed wheel 55 may be derived therefrom.

(30) It may be noted that, while the exemplary speed sensor arrangement 23 shown in FIGS. 3 and 4 may be advantageous in that it enables continuous reliable velocity detection for the moving component 3, 5, various other examples of speed sensor arrangements may be applied for determining an over-speed condition of the moving component and generating the over-speed signal.

(31) Finally, it should be noted that terms such as comprising do not exclude other elements or steps and that term such as a or an do not exclude a plurality. Also elements described in association with different embodiments may be combined.

(32) In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.