EP4151579A1

EP4151579A1 - Variable stroke buffer for buffering a car or a counterweight of an elevator

Info

Publication number: EP4151579A1
Application number: EP21197923.2A
Authority: EP
Inventors: Juha Helenius
Original assignee: Kone Corp
Current assignee: Kone Corp
Priority date: 2021-09-21
Filing date: 2021-09-21
Publication date: 2023-03-22

Abstract

A variable stroke buffer for buffering a car or a counterweight moving in a hoistway of an elevator along a variable compression stroke comprises a buffer stand including a buffer, which is contactable by the car or the counterweight of a part of the hoistway at a decompressed position of the buffer stand and a control apparatus. The buffer stand is compressible by the buffer in a compressing direction, in which the compression stroke of the buffer stand is restricted to a compressed position, and in a decompressing direction, in which the buffer stand can decompress to the decompressed position. The control apparatus is configured to allow the compression stroke of the buffer stand in the compressing direction to a first compressed position corresponding to a first stroke, when the compression of the buffer stand is started at a first speed which is lower than a threshold speed. The control apparatus is further configured to limit the compression stroke of the buffer stand in the compressing direction to a second compressed position corresponding to a second stroke, when the compression of the buffer stand is started at a second speed which is higher than the threshold speed.

Description

The present invention relates to a variable stroke buffer for buffering a car or a counterweight of an elevator.
In conventional elevators, there is vertical clearance (headroom) between the top of a car (elevator cabin) and the top of a hoistway when the car is at the topmost landing. The headroom is dimensioned so that the car can never hit the top of the hoistway during a jump situation detailed below. In addition, the headroom forms a refuge space for fitters, which prevents them from being crushed between the car and the top of the hoistway. Minimum headrooms are defined e.g. in EN81-20.
The jump situation is a situation, in which a car surpasses the top landing, for example due to its inertia. The jump situation is illustrated in Figs. 9A to 9C, which show an elevator 80 having a hoistway 82 with a top landing 83, an elevator buffer 84 disposed in an elevator pit 85, a car 86 and a counterweight 88 connected to the car 86. Drive elements, cables, guide rails and other conventional components are omitted from the figures.
Fig. 9A shows a state, in which the car 86 approaches the top landing 83 while decelerating. Fig. 9B shows a state, in which the car 86 is situated at the top landing 83, and the elevator buffer 84 is compressed to a degree by the counterweight 88. During regular operation with low speeds and appropriate decelerations, the state of Fig. 9B would be a final state. However, when the car 86 approaches the top landing 83 with an excessive speed, for example due to machinery brake failure, the elevator buffer 84 may not be able to stop the counterweight 88 with an appropriate deceleration. In addition, the cables connecting the counterweight 88 and the car 86 can only absorb tensile forces, but not compressive forces. Therefore, even if the counterweight 88 is fully stopped at maximum compression of the elevator buffer 84, the car 86 may continue moving upward due to its inertia even after reaching the top landing 83. In both cases, the car 86 jumps as shown in Fig. 9C, that is, the car 86 surpasses the top landing 83 while moving upward and decelerating. Accordingly, after the jump, the car 86 reaches a speed of zero before heading downward towards the top landing 83. The position at which the top of the car 86 is located when the speed reaches zero defines a jump height, and the headroom provided in the elevator hoistway 82 has to account at least for the jump height that can be reasonably expected.
NHR (NoHeadRoom) is a new elevator concept without the conventional headroom. An elevator without the headroom is seen to have great business potential because it changes the interface between the building and the elevator. Because there is no need for headroom provision, architects and building designers have greater freedom of design.
However, due to missing headroom, the NHR elevator concept requires a new approach for preventing the car from hitting the top of the hoistway in a jump situation. Furthermore, refuge spaces for fitters must be provided in order to enable elevator assembly and maintenance.

SUMMARY OF THE INVENTION

In light of the above, the present invention has the goal to provide a simple and robust solution for preventing an elevator car from hitting the top of a hoistway with little or no headroom.
In order to address the above goal, the present inventors have conceived that instead of avoiding the jump situation, the elevator may be configured such that the jump situation is recognized and started earlier and allowed to occur without entering into a dedicated headroom. For example, simulations carried out by the inventors show that the jump height is 230 mm from 1.5 m/s speed. In this case, if the jump is started when the clearance between the car and the top of the hoistway is at least 230 mm and a car/counterweight speed is 1.5 m/s, the car will not hit the top of the hoistway. Accordingly, the headroom may be reduced or removed.
Hence, according to the present invention, the above goal is achieved by a variable stroke buffer for buffering a car or a counterweight moving in a hoistway of an elevator along a variable compression stroke, comprising a buffer stand including a buffer, which is contactable by the car or the counterweight or a part of the hoistway at a decompressed position of the buffer stand, and a control apparatus. The buffer stand is compressible by the buffer in a compressing direction, in which the compression stroke of the buffer stand is restricted to a compressed position, and in a decompressing direction, in which the buffer stand can decompress to the decompressed position. The control apparatus is configured to allow the compression stroke of the buffer stand in the compressing direction to a first compressed position corresponding to a first stroke, when the compression of the buffer stand is started at a first speed which is lower than a threshold speed. The control apparatus is further configured to limit the compression stroke of the buffer stand in the compressing direction to a second compressed position corresponding to a second stroke, when the compression of the buffer stand is started at a second speed which is higher than the threshold speed.
The variable stroke buffer can be provided to control car and/or counterweight motion at the top and/or bottom of the hoistway. The variable stroke buffer can be mounted on a stationary structure (e.g. on a floor of the elevator pit, at the top of the hoistway or on a guide rail), i.e. a part of the hoistway, or on a moving structure, i.e. the car or the counterweight. The above-described structure provides a variable stroke buffer whose stroke depends on a speed at which the car or the counterweight comes into contact with the variable stroke buffer and compresses the variable stroke buffer or a speed at which the variable stroke buffer comes into contact with the part of the hoistway thus compressing the variable stroke buffer.
If the initial compression speed corresponds to a nominal speed of the elevator car approaching the top landing (first speed) or is lower than that, the variable stroke buffer compresses fully and allows the car to go to the top landing.
If the initial compression speed is a second speed higher than the nominal speed of the elevator car approaching the top landing, the variable stroke buffer is automatically locked such that its stroke is reduced. Accordingly, the car or the counterweight contacting the buffer or the car or the counterweight having the buffer contacting the part of the hoistway is stopped by the variable stroke buffer after a smaller stroke.
For example, if the variable stroke buffer is contacted by the counterweight at the second speed, the counterweight is stopped after a reduced stroke of the variable stroke buffer and the car jump begins. The jump of the car is thus started from a lower position than would conventionally be the case. Hence, the car does not hit the top of the hoistway. Accordingly, the headroom can be reduced.
Since the car is subjected to its own inertia without further braking forces, the car average deceleration during the jump is 1g, which is the maximum value allowed by elevator codes. Hence, passenger safety is ensured.
If the variable stroke buffer is contacted by the car at the top of the hoistway, the car approaching at the second speed is stopped with a shorter stroke and thus within a shorter distance compared to a conventional buffer. Accordingly, the variable stroke buffer can replace a buffer with considerably longer stroke that has to account for both the first speed and the second speed. Also in this case, the headroom can be reduced.
If the variable stroke buffer is contacted by a part of the hoistway, the same principles apply, so long as it is taken into consideration whether the counterweight or the car is kinematically connected to the variable stroke buffer.
Consequently, the variable stroke buffer is designed so that a limitation of the stroke or a locking of the variable stroke buffer occurs early enough to prevent the car from hitting the top of the hoistway. Therefore, the car is reliably prevented from hitting the top of a hoistway with little or no headroom.
The variable stroke buffer may also be equipped with an oil level sensor and/or sensors detecting the position of the variable stroke buffer and a contact state between the variable stroke buffer and the car/counterweight/hoistway in order to ensure safe and reliable operation of the variable stroke buffer.
Preferably, the second stroke is shorter than the first stroke. Therefore, the variable stroke buffer can be applied in order to reduce the elevator headroom to a minimum as described above.
Preferably, the buffer stand comprises a hydraulic cylinder, the buffer stand is decompressible by a cylinder spring, and the buffer stand is configured to create a flow of hydraulic fluid through the control apparatus, wherein a flow rate of the flow and a compression speed of the buffer stand are interdependent, and the control apparatus is configured to control the flow of hydraulic fluid through the control apparatus according to the compression speed of the buffer stand.
Thereby, the variable stroke buffer stand can be implemented via well-known and well-studied components that are simple, robust and readily available. Accordingly, a simple, robust and inexpensive solution for a NHR elevator is provided.
Preferably, the control apparatus is configured to stop the flow of hydraulic fluid through the control apparatus so as to prevent further compression of the buffer stand when the compression of the buffer stand is started at the second speed.
Hydraulic fluids are incompressible. Accordingly, when the flow of the hydraulic fluid is stopped, the variable stroke buffer can be locked quickly and reliably.
Preferably, the control apparatus comprises a control mechanism capable of restricting and/or stopping the flow of hydraulic fluid.
Restricting the flow results in an increase in braking force applied by the variable stroke buffer stand (force necessary to continue compressing the variable stroke buffer stand). Stopping the flow locks the variable stroke buffer stand to its current position. There are numerous conventional hydraulic control mechanisms that can restrict and/or stop a fluid flow. Accordingly, with the above structure, a simple and inexpensive solution is provided for controlling the stroke of the variable stroke buffer.
Preferably, the control mechanism comprises a rupture valve or a pilot operated non-return valve. The control mechanism is preferably configured to allow the flow of hydraulic fluid through the control mechanism when the compression speed of the buffer stand is below the second speed, and to block the flow of hydraulic fluid when the compression speed of the buffer stand is above the second speed, whereby the flow of hydraulic fluid through the control apparatus is stopped so as to stop the compression of the buffer stand.
Thereby, a simple and robust variable stroke buffer is provided. In addition, rupture valves are maintenance-free and very reliable, while pilot operated non-return valves allow for high flexibility in terms of different configurations for different elevators.
Alternatively, the control mechanism comprises a 2/2-way directional control valve that is urged in an opening direction by a valve spring and that is urged in a closing direction by at least one of a hydraulic pressure, an electromagnet and a manual actuation.
By using a 2/2-way directional control valve, flexibility with respect to different configurations is increased. Furthermore, the 2/2-way directional control valve allows a more accurate control of hydraulic fluid flow, since it can be closed not only by the hydraulic fluid pressure, but also by external factors like a computer controlled electromagnet or manual actuation. Thereby, it is possible to lock the variable stroke buffer at a desired height, which is advantageous e.g. in locking the buffer stand for elevator maintenance.
Alternatively, a variable stroke buffer for buffering a car or a counterweight moving in a hoistway of an elevator along a variable compression stroke comprises a buffer stand including a buffer, which is contactable by the car or the counterweight or a part of the hoistway at a decompressed position of the buffer stand, and a control apparatus. The buffer stand is compressible by the buffer in a compressing direction, in which the compression stroke of the buffer stand is restricted to a compressed position, and in a decompressing direction, in which the buffer stand can decompress to the decompressed position. The buffer stand comprises a hydraulic cylinder, the buffer stand is decompressible by a cylinder spring, and the buffer stand is configured to create a flow of hydraulic fluid through the control apparatus, wherein a flow rate of the flow and a compression speed of the buffer stand are interdependent. The control apparatus comprises a throttle apparatus comprising a throttle valve configured to throttle the flow through the control mechanism.
Thereby, the deceleration can be finely adjusted such that high speeds of the counterweight/elevator car result in high decelerations thereof, while low speeds of the counterweight/elevator car result in low decelerations thereof. Hence, the counterweight/elevator car is decelerated to a larger extent in the beginning of the stroke thus reducing an unwanted jump of the elevator car.
Preferably, the buffer stand can be locked to a desired position by a shut-off valve that blocks the flow of hydraulic fluid in the control apparatus.
Thereby, it is possible to lock the variable stroke buffer at a desired height, which is advantageous e.g. in locking the buffer stand for elevator maintenance. Furthermore, the shut-off valve provides a simple and robust structure.
Preferably, the control mechanism receives a pilot pressure from a ramp monitoring device that comprises a movable piston and a spindle. When the ramp monitoring device is being compressed, a ramp monitoring hydraulic fluid flows from a first chamber of the ramp monitoring device to a second chamber of the ramp monitoring device through an opening whose cross-sectional area is defined by a piston hole cross-section and a spindle cross-section at a current compression position of the ramp monitoring device. A pressure of the ramp monitoring hydraulic fluid in the first chamber is dependent on the current compression position and a current compression speed of the ramp monitoring device. The pressure of the ramp monitoring hydraulic fluid in the first chamber is used as the pilot pressure for the control mechanism.
Thereby, the ramp monitoring device enables throughout the stroke thereof a continuous feedback of a position and a speed of the car or the counterweight that contacts the buffer or will contact the buffer or a position and a speed of the buffer coming into contact with the part of the hoistway. For example, the ramp monitoring device can be designed so that the pressure of the ramp monitoring hydraulic fluid in the first chamber remains below the value needed for closing a 2/2-way directional control valve if the car or the counterweight contacting the buffer or the variable stroke buffer contacting the part of the hoistway follows a desired position/speed ramp (relationship). If the speed is above a desired speed for a given position, the pressure of the ramp monitoring hydraulic fluid in the first chamber increases enough to close the 2/2-way directional control valve and the buffer stand is locked.
The strokes of the ramp monitoring device and the buffer stand can be partially or completely overlapping or subsequent. If the car or the counterweight or the part of the hoistway comes into contact with the ramp monitoring device before the buffer, the speed is monitored before contact. Accordingly, if the monitored speed is higher than a desired speed before contact, the buffer stand can be locked before the car or the counterweight or a part of the hoistway contacts the buffer.
Accordingly, the variable stroke buffer cannot only act in the case when an initial speed is a first speed or a second speed, but can monitor a desired position/speed ramp before and throughout the process of decelerating the car or the counterweight that is buffered by the variable stroke buffer.
Preferably, the control mechanism comprises a 2/2-way proportional directional control valve.
The 2/2-way proportional directional control valve can be completely open, completely closed or between the extreme positions. Accordingly, a more accurate control of hydraulic fluid flow is possible. In addition, intermediate closing positions act as a throttle mechanism, which is advantageous for increasing a braking force of the variable stroke buffer. Thereby, when an overspeed is monitored by the ramp monitoring device at a certain position, a braking force may be increased so as to slow down the car until it has settled into a desired position/speed ramp.
Preferably, the spindle has a variable cross-section.
Thereby, relationships between speeds and positions of the ramp monitoring device may be adjusted more finely. Alternatively, when the spindle has a constant cross-section, the ramp monitoring device has a simple configuration.
Preferably, an elevator is provided with a hoistway, a car movable in the hoistway, a counterweight movable in the hoistway and connected to the car and an elevator buffer comprising the variable stroke buffer as described above and being disposed in the hoistway, on the car or on the counterweight. The threshold speed preferably corresponds to the nominal speed of the car approaching the top landing.
With the above configuration and when the threshold speed is set according to the above, it is possible to provide an elevator with little or no headroom.
Furthermore, with the above structure, the variable stroke buffer and, if present, the ramp monitoring device will not become stuck (e.g. by rust), because they are always moved when car or counterweight is at the top or bottom landing.

BRIEF DESCRIPTION OF DRAWINGS

In the following, preferred embodiments of the invention are described with reference to the following drawings.

Fig. 1 shows a variable stroke buffer according to a first embodiment.
Fig. 2 shows a variable stroke buffer according to a second embodiment.
Fig. 3 shows a variable stroke buffer according to a third embodiment.
Fig. 4 shows a variable stroke buffer according to a fourth embodiment.
Fig. 5 shows a variable stroke buffer according to a fifth embodiment.
Fig. 6 shows a variable stroke buffer according to a sixth embodiment.
Fig. 7A shows a 2/2-way directional control valve opened by a spring and closed by hydraulic pressure.
Fig. 7B shows a 2/2-way directional control valve opened by a spring and closed by hydraulic pressure and/or an electromagnet.
Fig. 7C shows a 2/2-way directional control valve opened by a spring and closed by hydraulic pressure and/or manual actuation.
Fig. 7D shows a 2/2-way proportional directional control valve opened by a spring and closed by hydraulic pressure and/or an electromagnet.
Fig. 8A shows a ramp monitoring device according to the fifth embodiment.
Fig. 8B shows a modification of a spindle of the ramp monitoring device shown in Fig. 8A.
Fig. 8C shows another modification of a spindle of the ramp monitoring device shown in Fig. 8A.
Fig. 8D shows another modification of a spindle of the ramp monitoring device shown in Fig. 8A.
Fig. 9A shows a state, in which a car approaches a top landing while decelerating.
Fig. 9B shows a state, in which the car is situated at the top landing.
Fig. 9C shows a state, in which a jump situation has occurred.

DESCRIPTION OF PREFERRED EMBODIMENTS

First embodiment

Fig. 1 illustrates an embodiment of a variable stroke buffer 1 and its components.
The variable stroke buffer 1 comprises a buffer stand 10 having a buffer 12, a cylinder rod 13 connected to the buffer 12, a hydraulic cylinder 14, a cylinder piston 15 and a cylinder spring 16. The buffer 12 is a conventional buffer, for example a rubber element. The cylinder rod 13 is movable in a compressing direction C by a force applied to the buffer 12 and in an opposite decompressing direction D by a force applied to the rod 13 by the cylinder spring 16. The cylinder rod 13 is connected to the cylinder piston 15 so that the buffer 12, the cylinder rod 13 and the piston 15 move together in a vertical direction, wherein the movement changes a distance between a bottom of the hydraulic cylinder 14 and a top of the buffer 12. Accordingly, this movement together with a compression of the buffer 12 itself corresponds to a compression of the buffer stand 10.
The cylinder piston 15 moves within the hydraulic cylinder 14 and separates the hydraulic cylinder 14 into two chambers, namely an upper chamber 17 and a lower chamber 18. The chambers 17, 18 are filled with hydraulic fluid and sealed against each other by the piston 15. The cylinder piston 15 is biased towards a top position P0 (decompressed position) by the cylinder spring 16. The buffer stand 10 can be compressed to multiple compressed positions P1, P2 that will be detailed later.
The variable stroke buffer 1 further comprises a control apparatus. The control apparatus in this embodiment comprises a hydraulic circuit 130 having a shut-off valve 134 and a rupture valve 136 serving as a control mechanism 132. The shut-off valve 134 can be any conventional valve that allows or stops all flow therethrough. The rupture valve 136 can be any conventional rupture valve. For example, the rupture valve 136 may comprise a ball 136a biased away from an outlet 136c by a spring 136b. The hydraulic circuit 130 connects the chambers 17, 18 while throttling the flow of hydraulic fluid between the chambers 17, 18. As a result, the hydraulic pressure of the fluid inside the lower chamber 18 increases when the counterweight 88 contacts the buffer 12. The higher the speed of the counterweight 88, the higher the hydraulic pressure in the lower chamber 18 and the higher the hydraulic pressure acting on the ball 136a in the closing direction of the rupture valve 136. Accordingly, when a speed of the counterweight when arriving at the buffer is above a threshold speed, the hydraulic pressure acting on the ball 136a can overcome the spring force of the spring 136b so as to force the ball 136a towards the outlet 136c, thereby closing the outlet 136c.
The hydraulic circuit 130 receives hydraulic oil from each of the two chambers 17, 18 of the hydraulic cylinder 14, depending on a moving direction of the cylinder piston 15. When the cylinder piston 15 moves upward (when the buffer stand 10 is being decompressed), the upper chamber 17 feeds hydraulic fluid into the hydraulic circuit 130. When the cylinder piston 15 moves downward (when the buffer stand 10 is compressed), the lower chamber 18 feeds hydraulic fluid into the hydraulic circuit 130.
For example, when the buffer 12 is moved in the compressing direction C in Fig. 1, the cylinder rod 13 and the cylinder piston 15 move together with the buffer 12 so that the spring 16 in the lower chamber 18 of the hydraulic cylinder 14 is compressed according to the displacement of the cylinder piston 15. The generally incompressible hydraulic fluid is thereby fed into the hydraulic circuit 130. The amount of hydraulic fluid fed into the hydraulic circuit 130 is proportional to the displacement of the cylinder piston 15, and due to the incompressibility, the flow of the hydraulic fluid affects the displacement of the cylinder piston 15. The displacement and the speed of the cylinder piston 15 are interdependent (time derivative), and the same applies to flow rate of the hydraulic fluid. Accordingly, reducing a flow rate of the hydraulic fluid leads to a reduction of a speed v of the cylinder piston 15 and therefore the buffer stand 10, and stopping the flow altogether also stops the stroke of the cylinder piston 15 and therefore the buffer stand 10.
If the initial moving speed v of the cylinder piston 15 is less than or equal to the threshold value, the hydraulic fluid flows from the lower chamber 18 into the hydraulic circuit 130 through the rupture valve 136 and the shut-off valve 134, and is then fed into the upper chamber 17 of the hydraulic cylinder 14. Accordingly, the buffer stand 10 is allowed to compress such that its stroke S is a first stroke S1 from the decompressed position P0 to a lowest position P1 (first compressed position).
If the initial moving speed v of the cylinder piston 15 is above the threshold value, the ball 136a is moved against the urging force of the spring 136b until the outlet 136c is closed. Thus, the hydraulic circuit 130 is locked. Thereby, further displacement of the cylinder piston 15 is prevented, and the buffer stand 10 is also locked. Accordingly, the stroke S of the buffer stand 10 is reduced to a second stroke S2 from the decompressed position P0 to a second compressed position P2. In this embodiment, the second compressed position P2 is located higher than the first compressed position P1. Consequently, the second stroke S2 is smaller (shorter) than the first stroke S1.
With the above configuration, the control apparatus 130 is configured to allow the compression stroke S of the buffer stand 10 to be the first stroke S1, when the compression of the buffer stand 10 is started at a first speed v1 which is lower than the threshold. Furthermore, the control apparatus 130 limits the compression stroke S of the buffer stand 10 to the second stroke S2, when the compression of the buffer stand 10 is started at a second speed v2 which is higher than the threshold.
Thereby, a variable stroke buffer 1 is provided, whose stroke depends on a speed at which a counterweight (as an example for the car 86 or the counterweight 88 or the part of the hoistway 82 contacting the variable stroke buffer stand 10) comes into contact with the variable stroke buffer 1 and compresses the variable stroke buffer 1.
In addition, the cylinder piston 15 and thus the buffer stand 10 can be locked to a desired position (e.g. a top position) with the shut-off valve 134, which stops all flow through the hydraulic circuit 130. If the variable stroke buffer stand 10 is provided at the bottom of the elevator pit 85 and is locked at the top position for maintenance, and if the elevator 80 has a means to prevent lifting of the car when a counterweight is on the buffer (car stalling protection), refuge space for fitters is provided at the top of the car 86.
Further, the variable stroke buffer 1 may comprise a level sensor (not shown), such as an infrared liquid level sensor, monitoring the oil level in the first chamber 17, the second chamber 18 or in the hydraulic circuit 130. Furthermore, the variable stroke buffer 1 may comprise sensors (not shown) monitoring the position of the buffer 12, either directly or via the cylinder piston 15 or the cylinder rod 13, and monitoring a contact state between the buffer 12 and the counterweight 88. In order to monitor the position of the buffer 12 and the contact state between the buffer 12 and the counterweight 88 reliably, proximity switches can be employed. A first normally open proximity switch indicates the buffer 12 being at the top position P0 when closed. A second normally open proximity switch indicates a state of contact between the buffer 12 and the counterweight 88 when closed.
The first normally open proximity switch and the second normally open proximity switch are coupled in parallel in the elevator safety chain, i.e. a circuit of devices monitoring the safety status of the elevator and indicating by setting the safety chain in a non-conducting state that the status of the elevator is not safe. Said first and second proximity switches coupled in parallel keep the safety chain in a conducting state if either the buffer 12 is at the top position P0 (the first proximity sensor is closed) or the buffer 12 and the counterweight 88 contact each other (the second proximity sensor is closed), indicating that the buffer 12 is in normal operating condition. However, if the buffer 12 is not at the top position P0 and the buffer 12 and the counterweight 88 do not contact each other, the safety chain is open, due to the unsafe condition of the buffer stand 10 being jammed in a state that is not fully decompressed and it will, thus, not be able to decelerate the counterweight 88 the way it is meant to. Therefore, with one proximity sensor verifying complete decompression of buffer stand 10 and another proximity sensor verifying the contact of counterweight 88 and buffer 12, safe and reliable operation of the variable stroke buffer 1 can be ensured.
Accordingly, the first embodiment enables a simple and robust configuration for the variable stroke buffer 1.

Second embodiment

A variable stroke buffer 2 according to a second embodiment shown in Fig. 2 includes the buffer stand 10 and a hydraulic circuit 230.
The hydraulic circuit 230 comprises a throttle valve 242, a non-return valve 244 in parallel with the throttle valve 242, a shut-off valve 234 identical to the shut-off valve 134 of the first embodiment, and a control mechanism 232 having a 2/2-way directional control valve 238.
A 2/2-way directional control valve is a valve that has an inlet and an outlet, as well as a means to open, close or regulate a flow amount through the valve. Examples for different ways to control 2/2-way directional control valves are shown in Figs. 7A to 7D. Fig. 7A shows a 2/2-way directional control valve opened by a spring and closed by hydraulic pressure. Fig. 7B shows a 2/2-way directional control valve opened by a spring and closed by hydraulic pressure and/or an electromagnet. Fig. 7C shows a 2/2-way directional control valve opened by a spring and closed by hydraulic pressure and/or manual actuation. Fig. 7D shows a 2/2-way proportional directional control valve opened by a spring and closed by hydraulic pressure and/or an electromagnet.
The 2/2-way directional control valve 238 according to the second embodiment is biased to an open position by a valve spring 240 and closed by a pilot pressure p, which is a pressure taken upstream of the throttle valve 242. When the pilot pressure p is below a threshold value, the 2/2-way directional control valve 238 remains open. When the pilot pressure p reaches a threshold value so as to overcome the spring force of the valve spring 240, the 2/2-way directional control valve 238 closes.
Accordingly, when the counterweight 88 hits the buffer 12 with a speed v being below the threshold, the pressure p upstream of the throttle valve 242 increases to a level not overcoming the spring force of the valve spring 240, such that the 2/2-way directional control valve 238 remains open and allows the first stroke S1.
When the counterweight 88 hits the buffer 12 with a speed v being above the threshold, the pressure p upstream of the throttle valve 242 increases to overcome the spring force of the valve spring 240, thus closing the 2/2-way directional control valve 238. The hydraulic circuit 230 and thereby the buffer stand 10 are locked, and the stroke S of the buffer stand 10 is limited to the second stroke S2.
When the counterweight 88 is moved away from the buffer 12, the pressure p is released such that hydraulic fluid can flow via the non-return valve 244 back into the lower chamber 18 of the hydraulic cylinder 14 without being throttled by the throttle valve 242. Accordingly, the buffer stand 10 can quickly decompress when the cylinder piston 15 moves upward assisted by the cylinder spring 16. The decompression of the buffer stand 10 is enabled regardless of whether the first stroke S1 or the second stroke S2 has been carried out.
The 2/2-way directional control valve 238 can alternatively be closed e.g. by an electromagnet or by manual actuation (as illustrated in Figs. 7B and 7C). The alternative closing methods are advantageous in locking the buffer stand for elevator maintenance. If the 2/2-way directional control valve 238 can be closed by electromagnet or manual actuation, the shut-off valve 234 can be omitted.
Accordingly, the second embodiment enables a simple and robust configuration for the variable stroke buffer 2.

Third embodiment

A variable stroke buffer 3 according to a third embodiment shown in Fig. 3 includes the buffer stand 10 and a hydraulic circuit 330.
The hydraulic circuit 330 comprises a throttle valve 342, a non-return valve 344 in parallel with the control valve 342, a shut-off valve 334 identical to the shut-off valve 134 of the first embodiment, and a control mechanism 332.
The control mechanism 332 has a pilot operated non-return valve 346 being arranged in series with the throttle valve 342 and in parallel with the non-return valve 344.
If the counterweight 88 hits the buffer 12 with a speed v above the threshold, the speed v of the buffer stand 10 becomes the second speed v2, and the pressure upstream of the throttle valve 342 increases enough so that the pilot operated non-return valve 346 is closed. Thereby, the buffer stand 10 is locked.
Accordingly, the third embodiment enables a simple and robust configuration for the variable stroke buffer 3.

Fourth embodiment

A variable stroke buffer 4 according to a fourth embodiment shown in Fig. 4 includes the buffer stand 10 and a hydraulic circuit 430.
The hydraulic circuit 430 comprises a throttle valve 442, a non-return valve 444 in parallel with the control valve 442, and a shut-off valve 434 identical to the shut-off valve 134 of the first embodiment. However, compared to the hydraulic circuit 330 of the third embodiment, the hydraulic circuit 430 of the fourth embodiment lacks the pilot operated non-return valve 346 or any other means to completely close the flow through the hydraulic circuit.
Therefore, the control mechanism 432 of the fourth embodiment is a throttle apparatus 448 that does not lock the buffer stand 10 depending on a compression speed v. The compression speed v of the buffer stand 10 is restricted by the throttle valve 442. Thereby, the deceleration can be finely adjusted such that high speeds of the counterweight/elevator car result in high decelerations thereof, while low speeds of the counterweight/elevator car result in low decelerations thereof. The second compressed position P2 gradually moves over time, allowing the buffer stand 10 to compress further and further at a decreasing compression speed.
As a result, the second stroke S2 in the variable stroke buffer 4 according to the fourth embodiment is not a predetermined or constant stroke, but is a timedependent stroke. Due to the throttling effect of increasing a braking force, headroom can be decreased compared to a conventional buffer stand.

Fifth embodiment

A variable stroke buffer 5 according to a fifth embodiment shown in Fig. 5 includes a control apparatus 530 with a control mechanism 532 comprising a 2/2-way directional control valve 538 and a valve spring 540, the latter being respectively the same as the 2/2-way directional control valve 238 and the valve spring 240 of the second embodiment.
The control apparatus 530 further comprises a ramp monitoring device 550 which controls the buffer stand compression via a pilot pressure p of a 2/2-way directional control valve 538. The ramp monitoring device 550 has a movable piston 552 and a spindle 554, and is partially filled with hydraulic fluid such as oil (ramp monitoring hydraulic fluid). In particular, a first chamber C₁ of the ramp monitoring device 550 is completely filled with oil and a second chamber C₂ of the ramp monitoring device 550 contains both oil and a compressible gas.
A working principle of the ramp monitoring device 550 will be explained with reference to Fig. 5 and Fig. 8A.
When the ramp monitoring device 550 is being compressed by the car 86 or the counterweight 88 or the part of the hoistway 82, the volume of the first chamber C₁ decreases. Due thereto, oil flows from the first chamber C₁ to the second chamber C₂ through an opening O whose cross-sectional area is defined by a piston hole diameter D₁ and a spindle diameter d_s at that position (Fig. 8A). In case the rate at which the volume of the first chamber C₁ is decreasing is larger than the flow rate of oil flowing from the first chamber C₁ to the second chamber C₂ through the opening O, the oil pressure in the first chamber C₁ increases in accordance with the speed of the car 86 or the counterweight 88 compressing the ramp monitoring device 550. That is, the higher the speed of the car 86 or the counterweight 88, the higher the pressure rise in the first chamber C₁.
Further, as described above, the second chamber C₂ contains both oil and a compressible gas. Additionally, the second chamber C₂ may have a breather. Thus, the second chamber C₂ is configured such that no pressure rise occurs in the second chamber C₂ due to oil flowing from the first chamber C₁ to the second chamber C₂ because the compressible gas in the second chamber C₂ can be compressed and additionally, the gas (air) pressure may be released through the breather. Therefore, the oil pressure in the first chamber C₁ is not affected by the amount of oil in the second chamber C₂, since the oil pressure in the second chamber C₂ is substantially constant regardless of the amount of oil, which has flown into the second chamber C₂.
The spindle 554 is a spindle 54A having a variable cross-section over the spindle position x_r, as shown in Figs. 8A to 8C. Thus, the pressure in the first chamber C₁ is dependent on both the position x_r and compression speed v_r of the ramp monitoring device 550, since the cross-sectional area of the opening O is dependent on the position x_r of the ramp monitoring device 550.
The pilot pressure p corresponds to the oil pressure in the first chamber C₁, since a hydraulic line connecting the ramp monitoring device 550 and the 2/2-way directional control valve 538 communicates with the first chamber C₁. Accordingly, the pilot pressure p(x_r,v_r) is dependent both on the position x_r and compression speed v_r of the ramp monitoring device 550.
Because the pilot pressure p(x_r,v_r) is dependent both on the position x_r and compression speed v_r of the ramp monitoring device 550, the ramp monitoring device 550 enables continuous monitoring of position/speed throughout a stroke SR of the ramp monitoring device 550 between a first extreme position P3 and a second extreme position P4 (Fig. 6). For example, the ramp monitoring device 550 can be designed so that the pilot pressure p(x_r,v_r) remains below a value needed for closing the 2/2-way directional control valve 538 if the car 86 or the counterweight 88 or the variable stroke buffer coming into contact with the part of the hoistway 82 follows a desired position/speed ramp, i.e. deceleration rate.
If the compression speed is too high at a given position, the pilot pressure p(x_r,v_r) increases enough to close the 2/2-way directional control valve 538. Thereby, the buffer stand 10 is locked.
The stroke SR of the ramp monitoring device 550 and the stroke S of the buffer stand 10 can be partially or completely overlapping or subsequent. If the car 86 or the counterweight 88 or the part of the hoistway 82 comes into contact with the ramp monitoring device 550 before coming into contact with the buffer 12 of the buffer stand 10, overspeed can be monitored and the buffer stand 10 can be locked before the car 86 or the counterweight 88 hits the buffer 12 or before the buffer 12 hits the part of the hoistway 82.
The spindle 554 is not limited to a circular cross-section as described above, and may have any other cross-sectional shape.
Further, the spindle 554 may be a spindle 54B having a constant cross-section, as shown in Fig. 8D. When the spindle has a constant cross-section, the ramp monitoring device has a simple configuration and reduced manufacturing costs. However, with such configuration of the spindle 54B, the pilot pressure p(x_r,v_r) is dependent only on the compression speed v_r of the ramp monitoring device 550.
The 2/2-way directional control valve 538 may also be closed with an electromagnet e.g. for elevator maintenance. Therefore, there is no need for a separate shut-off valve.

Sixth embodiment

The variable stroke buffers 1 to 5 of the first to fifth embodiments are provided at the bottom of the hoistway 82 (in the pit). By contrast, a variable stroke buffer 6 according to a sixth embodiment shown in Fig. 6 is provided at the top of the hoistway 82. Accordingly, a buffer 12 of a buffer stand 10 and a ramp monitoring device 650 come into contact with a car.
The variable stroke buffer 6 includes the ramp monitoring device 650 which controls the buffer stand 10 via a 2/2-way proportional directional control valve 656. The ramp monitoring device 650 according to the sixth embodiment is the same as the ramp monitoring device 550 according to the fifth embodiment. The buffer stand 10 of the sixth embodiment is the same as the buffer stand 10 according to the first to fifth embodiment.
The 2/2-way proportional directional control valve 656 can be completely open, completely closed or between the extreme positions. The 2/2-way proportional directional control valve 656 is normally held open by a valve spring 640 and can be completely or partially closed via an oil pressure or an electromagnet.
If the car 86 approaches the top landing 83 (see Fig. 9A) with a desired position/speed ramp, the pressure produced by ramp monitoring device 650 remains so low that the 2/2-way proportional directional control valve 656 is completely open. Therefore, the buffer stand 10 can carry out the first stroke S1. If the car 86 has overspeed at a given position x_r, the pressure increases enough to partially close the 2/2-way proportional directional control valve 656. This results in an increasing buffer force P that slows down the car 86 until it has settled to the desired position/speed ramp. In other words, the variable stroke buffer 6 having the ramp monitoring device 650 coupled with the 2/2-way proportional directional control valve 656 operates like a hydraulic P-controller (proportional controller) for a position/speed ramp of the car 86.
In addition, if the 2/2-way proportional directional control valve 656 can be completely closed by an electromagnet or by manual actuation, the buffer stand 10 can be locked e.g. to the bottom position (first extreme position P3), and refuge space can be reliably provided at the top of the car for maintenance and the like.
Further, the variable stroke buffer 6 also includes the normally open proximity switches similar to the variable stroke buffer 1 according to the first embodiment. However, in contrast to the variable stroke buffer 1 according to the first embodiment, in the variable stroke buffer 6, the second normally open proximity switch indicates a state of contact between the buffer 12 and the car 86 when closed.
In the sixth embodiment, the ramp monitoring device 650 is mounted on the top of the hoistway 82. The working principle of the ramp monitoring device 650 of the sixth embodiment is basically the same as that of the ramp monitoring device 550 of the fifth embodiment. Accordingly, when the ramp monitoring device 650 is being compressed by the car 86, the volume of the first chamber C₁ decreases. In order to obtain a functionality of the ramp monitoring device 650 similar to that of the ramp monitoring device 550, the first chamber C₁ of the ramp monitoring device 650 is completely filled with oil so that when the volume of the first chamber C₁ decreases, oil flows from the first chamber C₁ to the second chamber C₂ through the opening O. Further, since in the ramp monitoring device 650 the second chamber C₂ is located below the first chamber C₁ in the gravity direction, both the first chamber C₁ and the second chamber C₂ are completely filled with oil.
In the ramp monitoring device 550 of the fifth embodiment, the second chamber C₂ contains both oil and a compressible gas and may have a breather. In this manner, the second chamber C₂ of the ramp monitoring device 550 is configured such that no pressure rise occurs in the second chamber C₂ due to oil flowing from the first chamber C₁ to the second chamber C₂. However, since in the ramp monitoring device 650 the second chamber C₂ is completely filled with oil, such simple pressure relief arrangement cannot be employed. Therefore, the pressure relief arrangement for the second chamber C₂ of the ramp monitoring device 650 of the sixth embodiment differs from that of the ramp monitoring device 550 of the fifth embodiment.
Therefore, the spindle 654 of the ramp monitoring device 650 is hollow and the lower end of the spindle 654 that projects into the second chamber C₂ is open towards the second chamber C₂. Further, the spindle 654 is at least partially filled with a compressible gas. Additionally, the other end of the spindle 654 may be open and connected to a breather, thus providing a connection between the second chamber C₂ and the breather. Consequently, when an amount of oil flows from the first chamber C₁ to the second chamber C₂ of the ramp monitoring device 650, a corresponding amount of oil can flow from the second chamber C₂ into the spindle 654. A pressure rise does not occur in the second chamber C₂ and in the spindle 654, since the compressible gas in the spindle 654 can be compressed and additionally, the gas (air) pressure may be released through the breather. Thus, also in the ramp monitoring device 650 the oil pressure in the first chamber C₁ is not affected by the amount of oil flowing from the first chamber C₁ to the second chamber C₂, since the oil pressure in the second chamber C₂ is substantially constant regardless of the amount of oil, which has flown into the second chamber C₂.
The remaining structures and functions of the variable stroke buffer 6 according to the sixth embodiment are the same as those of the variable stroke buffer 5 according to the fifth embodiment.

Further modifications

The hydraulic circuits 130, 230, 330, 430, 530, 630 are examples for control apparatuses that utilize hydraulic principles and work as passive structures dynamically controlled solely by hydraulic pressures and flows. However, the control apparatus is not limited thereto, and instead of passively, the hydraulic components may be controlled actively, for example by solenoid valves paired with pressure and/or flow sensors.

Industrial applicability

The above-described variable stroke buffer that prevents an elevator car from hitting the top of the hoistway is applicable for general use elevators and especially for NHR elevators. The variable stroke buffer can also be used to provide refuge space for fitters e.g. during maintenance. The variable stroke buffer is simple and robust and applies readily available common hydraulic components.

Claims

Variable stroke buffer (1; 2; 3; 5; 6) for buffering a car (86) or a counterweight (88) moving in a hoistway (82) of an elevator (80) along a variable compression stroke (S), comprising
a buffer stand (10) including a buffer (12), which is contactable by the car (86) or the counterweight (88) or a part of the hoistway (82) at a decompressed position (P0) of the buffer stand (10); and

a control apparatus (130; 230; 330; 530; 630); wherein

the buffer stand (10) is compressible by the buffer (12) in a compressing direction (C), in which the compression stroke (S) of the buffer stand (10) is restricted to a compressed position (P1, P2), and in a decompressing direction (D), in which the buffer stand (10) can decompress to the decompressed position (P0); and

the control apparatus (130; 230; 330; 530; 630) is configured to:
allow the compression stroke (S) of the buffer stand (10) in the compressing direction (C) to a first compressed position (P1) corresponding to a first stroke (S1), when the compression of the buffer stand (10) is started at a first speed (v1) which is lower than a threshold speed, and

limit the compression stroke (S) of the buffer stand (10) in the compressing direction (C) to a second compressed position (P2) corresponding to a second stroke (S2), when the compression of the buffer stand (10) is started at a second speed (v2) which is higher than the threshold speed.
Variable stroke buffer (1; 2; 3; 5; 6) according to claim 1, wherein the second stroke (S2) is shorter than the first stroke (S1).
Variable stroke buffer (1; 2; 3; 5; 6) according to claim 1 or 2, wherein
the buffer stand (10) comprises a hydraulic cylinder (14);

the buffer stand (10) is decompressible by a cylinder spring (16);

the buffer stand (10) is configured to create a flow of hydraulic fluid through the control apparatus (130; 230; 330; 530; 630), wherein a flow rate of the flow and a compression speed (v) of the buffer stand (10) are interdependent; and

the control apparatus (130; 230; 330; 530; 630) is configured to control the flow of hydraulic fluid through the control apparatus (130; 230; 330; 530; 630) according to the compression speed (v) of the buffer stand (10).
Variable stroke buffer (1; 2; 3; 5; 6) according to claim 3, wherein
the control apparatus (130; 230; 330; 530; 630) is configured to stop the flow of hydraulic fluid through the control apparatus (130; 230; 330; 530; 630) so as to prevent further compression of the buffer stand (10) when the compression of the buffer stand (10) is started at the second speed (v2).
Variable stroke buffer (1; 2; 3; 5; 6) according to claim 3 or 4, wherein
the control apparatus (130; 230; 330; 530; 630) comprises a control mechanism (132; 232; 332; 532; 632) capable of restricting and/or stopping the flow of hydraulic fluid.
Variable stroke buffer (1; 2; 3; 5; 6) according to claim 5, wherein
the control mechanism (132; 332) comprises a rupture valve (136) or a pilot operated non-return valve (346); and

the control mechanism (132; 332) is configured to:
allow the flow of hydraulic fluid through the control mechanism (132; 232; 332; 532; 632) when the compression speed (v) of the buffer stand (10) is below the second speed (v2), and

block the flow of hydraulic fluid so when the compression speed (v) of the buffer stand (10) is above the second speed (v2), whereby the flow of hydraulic fluid through the control apparatus (130; 330) is stopped so as to stop the compression of the buffer stand (10).
Variable stroke buffer (2; 5; 6) according to claim 5, wherein
the control mechanism (232; 532; 632) comprises a 2/2-way directional control valve (238; 538; 638) that is urged in an opening direction by a valve spring (240; 540; 640) and that is urged in a closing direction by at least one of a hydraulic pressure, an electromagnet and a manual actuation.
Variable stroke buffer (4) for buffering a car (86) or a counterweight (88) moving in a hoistway (82) of an elevator (80) along a variable compression stroke (S), comprising
a buffer stand (10) including a buffer (12), which is contactable by the car (86) or the counterweight (88) or a part of the hoistway (82) at a decompressed position (P0) of the buffer stand (10); and

a control apparatus (430); wherein

the buffer stand (10) is compressible by the buffer (12) in a compressing direction (C), in which the compression stroke (S) of the buffer stand (10) is restricted to a compressed position (P1, P2), and in a decompressing direction (D), in which the buffer stand (10) can decompress to the decompressed position (P0);

the buffer stand (10) comprises a hydraulic cylinder (14);

the buffer stand (10) is configured to create a flow of hydraulic fluid through the control apparatus (430), wherein a flow rate of the flow and a compression speed (v) of the buffer stand (10) are interdependent; and

the control apparatus (430) comprises a throttle apparatus (448) comprising a throttle valve (442) configured to throttle the flow through the control mechanism (430).
Variable stroke buffer (1; 2; 3; 4) according to claim one of claims 3 to 8, wherein the buffer stand (10) can be locked to a desired position by a shut-off valve (134; 234; 334; 434) that blocks the flow of hydraulic fluid in the control apparatus (130; 230; 330; 430).
Variable stroke buffer (5; 6) according to one of claims 5 to 8, wherein the control mechanism (532; 632) receives a pilot pressure from a ramp monitoring device (550; 650) that comprises
a movable piston (552; 652), and

a spindle (554; 654); wherein

the ramp monitoring device (550; 650) is configured such that
when the ramp monitoring device (550; 650) is being compressed, a ramp monitoring hydraulic fluid flows from a first chamber (C₁) of the ramp monitoring device (550; 650) to a second chamber (C₂) of the ramp monitoring device (550; 650) through an opening (O) whose cross-sectional area is defined by a piston hole cross-section and a spindle cross-section at a current compression position (x_r) of the ramp monitoring device (550; 650), and

a pressure of the ramp monitoring hydraulic fluid in the first chamber (C₁) is dependent on the current compression position (x_r) and a current compression speed (v_r) of the ramp monitoring device (550; 650); and wherein

the pressure of the ramp monitoring hydraulic fluid in the first chamber (C₁) is used as the pilot pressure for the control mechanism (532; 632).
Variable stroke buffer (6) according to claim 10, wherein
the control mechanism (632) comprises a 2/2-way proportional directional control valve (656).
Variable stroke buffer (5; 6) according to claim 10 or 11, wherein the spindle (554; 654) has a variable cross-section.
Elevator (80) comprising:
a hoistway (82),

a car (86) movable in the hoistway (82),

a counterweight (88) movable in the hoistway (82) and connected to the car (86); and

an elevator buffer (84) comprising the variable stroke buffer (1; 2; 3; 4; 5; 6) as set forth in one of claims 1 to 12, the elevator buffer (84) being disposed in the hoistway (82), on the car (86) or on the counterweight (88), wherein
the threshold speed (v1) corresponds to the nominal speed of the car (86) approaching the top landing (83).