JP2010265068A - Emergency stop device for elevator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an emergency stop device for an elevator reduced in excess deceleration in emergency braking without increasing the size of the device. <P>SOLUTION: The emergency stop device for braking a lift body by applying spring pressure to a guide rail with a pair of dampers sandwiching the guide rail includes dampers each having two braking surfaces and rotatable between an open position where the braking surface is spaced from the rail and a braking position where the braking surface is pressed to the rail. When braking power is not larger than a prescribed threshold, the damper is positioned in a first braking position for braking by the first braking surface, and when the braking power exceeds a prescribed threshold, the damper rotates and is positioned in a second braking position for braking by the second braking surface. The device is small in size and does not cause the excess deceleration in the emergency braking. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an emergency stop device for an elevator.

  In a conventional elevator emergency stop device, a housing that is horizontally displaceable with respect to a car is provided with a support rail and a rotating rail, and the guide rail that guides the car rotates with the support rail. It is arranged between the moving rails. The interval between the receiving rail and the rotating rail is configured to be reduced by the rotation in the vertical direction (in the vertical plane) per rotating rail. In response to the emergency stop signal, the housing is moved by the displacement drive mechanism in a direction in which the rotation rail hits the guide rail. When the contact with the guide rail comes into contact with the guide rail, it is rotated in the direction corresponding to the moving direction of the car, and the distance between the contact with the turn rail and the receiving rail becomes narrow, and the guide rail is gripped and braked. (For example, refer to Patent Document 1).

International Publication WO2008 / 099487 Pamphlet

In such an emergency stop device for an elevator, the direction of the pressing force against the guide rail passing through the center of the rotating shaft per rotating rail, the center of the rotating shaft per rotating rail, and the guide rail entering side per rotating rail When the angle between the straight line connecting the edges is θ, the friction coefficient μ _A with the guide rail per rotation rail is μ in order to maintain the surface contact with the guide rail per rotation rail. _It is necessary to satisfy _A ≦ tanθ.

However, during braking, the friction coefficient tends to increase during deceleration due to wear powder generated between the guide rail and the braking surface per rotating rail. When μ _A becomes large until the above formula is not satisfied, the rotation rail further rotates beyond the position where it comes into surface contact with the guide rail. In order to ensure that the contact of the rotating rail comes into surface contact with the guide rail, a slight gap Δd corresponding to machining tolerance is provided between the rotating rail and the stopper. This is because it rotates excessively by an angle corresponding to this gap.

  In such a state, the rotation rail hits the edge at the rail entry side edge portion with respect to the guide rail and the surface contact cannot be maintained, and the edge portion bites into the guide rail and digs up the guide rail. . In such a situation, the coefficient of friction increases rapidly, resulting in excessive deceleration immediately before stopping, causing the car to stop suddenly, and passengers feel anxiety and discomfort due to impact, and the guide rail is Damaged.

In order to prevent such a phenomenon, the position of the stopper per rotating rail can be adjusted, and the contact between the rotating rail and the stopper and the contact between the rotating rail and the guide rail occur simultaneously. Fine adjustments can also be made. However, this adjustment work is time-consuming work, and needs to be performed relatively frequently according to the wear of the brake pads, so that the workability of installation and maintenance inspection deteriorates. In addition, the perimeter of the rotating rail is lengthened in the direction of extending the guide rail, and the distance between the direction of the pressing force per the rotating rail described above and the direction of the guide rail entry side edge portion as viewed from the rotating shaft per rotating rail. If the angle θ is increased, it will be difficult to hit the edge even if the friction coefficient μ _A increases, but it is necessary to enlarge the rotating body and increase the mounting part in order to mount a large rotating rail per direction in the guide rail extending direction. Therefore, the emergency stop device becomes large.

  Accordingly, an object of the present invention is to provide an emergency stop device for an elevator that does not increase in size and does not cause excessive deceleration during deceleration and stop.

  According to this invention, the emergency stop device for an elevator is mounted on the lifting body guided by the guide rail, and the guide rail is clamped by the braking surfaces of the pair of brake elements by the pressing force of the elastic element, thereby moving the lifting body. In the emergency stop device for an elevator for braking, the first brake piece of the pair of brake pieces is braked by an open position in which a braking surface is separated from the guide rail, and the braking surface is pressed by the guide rail. A first braking surface and a second braking surface having a smaller coefficient of friction than the first braking surface, wherein the first brake element is at the braking position; When the braking force is less than or equal to a predetermined threshold, the first braking position where the braking by the first braking surface is mainly performed is performed, and when the braking force exceeds the predetermined threshold, further rotation from the first braking position is performed. Te, and it is characterized in that predominantly the second braking position the braking by the second braking surface is performed.

  According to the device of the present invention, it is possible to obtain an emergency stop device for an elevator that is small and does not generate excessive deceleration even when decelerating and stopping.

It is a schematic side view which shows the elevator provided with the emergency stop apparatus for elevators of this invention. It is a schematic plan view which shows the state which one Embodiment of the emergency stop apparatus for elevators shown in FIG. 1 exists in an open position. FIG. 3 is a partially enlarged view showing a first braking surface and a second braking surface of the first brake element of FIG. 2. FIG. 3 is a partially enlarged view showing a first braking surface and a second braking surface of the second brake element of FIG. 2. It is a schematic plan view which shows the state which the emergency stop apparatus for elevators shown in FIG. 2 exists in the 1st braking position by the 1st braking surface among braking positions. It is a schematic plan view which shows the state which the emergency stop apparatus for elevators shown in FIG. 2 exists in the 2nd braking position by the 2nd braking surface among braking positions. It is the schematic which shows 2nd Embodiment of the emergency stop apparatus for elevators of this invention. It is the schematic which shows 3rd Embodiment of the emergency stop apparatus for elevators of this invention. It is the schematic which shows 4th Embodiment of the emergency stop apparatus for elevators of this invention.

  Embodiments of the present invention will be described below.

Embodiment 1 FIG.
FIG. 1 shows a configuration diagram of an elevator. In the hoistway 1, a car 4 as a lifting body and a balancing weight 5 are attached to both ends of the main measure 3 wound around the sheave 2 a of the hoisting machine 2. The car 4 moves up and down along the guide rail 6 by rotating 2a. An elevator emergency stop device 7 according to the present invention for holding and braking the guide rail 6 in an emergency is provided below the car 4. A speed governor 9 is attached to the upper part of the hoistway 1 on a mounting base 8 assembled to the guide rail 6, and a tension wheel 10 is attached to the lower part of the hoistway 1. A governor rope 11 is wound around the tension wheel 10. The governor rope is connected to the emergency stop device 7 via the link mechanism 12. A rope gripping device 13 is assembled to the governor 9 in order to stop the circulation of the governor rope 11 when the speed of the car increases abnormally.

  Here, if the speed of the car 4 is increased due to some abnormality and the car 4 does not stop by the brake of the hoisting machine 2 (particularly when the main measure 3 is disconnected), the speed governor that detects the speed abnormality of the car 4 When the governor rope 11 is stopped by the rope gripping device 13, the link mechanism 12 is operated by the relative movement difference between the car 4 and the governor rope 11 to operate the emergency stop device 7.

  FIG. 2 is a schematic plan view showing the elevator emergency stop device 7 shown in FIG. 1 in the open position. FIGS. 3 and 4 show details of the braking surface, and FIGS. 5 and 6 show the elevator. The emergency stop device 7 is shown in the braking position.

  The elevator emergency stop device 7 has a base 14 mounted on a car 4 (or a counterweight 5 that is a lifting body) that is a lifting body guided by a guide rail 6. A frame 16 guided and supported by two guides 15 is provided so as to be movable in a right angle direction. On the frame 16, a first brake 17 and a second brake 18 that are disposed on both sides of the guide rail 6 and are paired are provided. An elastic device 19 such as a compression spring is provided between the base 14 and the frame 16. A stopper 20 is also provided between the base 14 and the frame 16 so that the position of the frame 16, that is, the positions of the first brake 17 and the second brake 18 can be adjusted with respect to the guide rail 6. . The elastic device 19 is for applying the frame 16 to the stopper 20, and an elastic element 37 on the second brake element 18 side, which will be described in detail later, is a pair of brake elements (the first brake element 17 and the second brake element 18. ), The guide rail 6 is clamped to brake the car 4.

  The first brake element 17 is a plate member having a pentagonal shape or a sector shape as a whole in plan view, and the opening angle of the fan is slightly smaller than 90 °. A portion corresponding to the top of the fan (an arcuate portion of the fan) that is supported so as to be able to rotate and that is arranged to face the guide rail 6 and is configured by three straight lines is the braking surface 22 of the first brake element 17. It has become. In the example shown in the drawing, the braking surface 22 is formed on the opposing surface 23 slightly parallel to the guide rail 6 with the first brake element 17 in the open position in FIG. A first braking surface 24 that is provided and pressed against the guide rail 6 when in the braking position shown in FIG. 5, and is pressed against the guide rail 6 instead of the first braking surface 24 when in the braking position shown in FIG. The second braking surface 25 is provided.

  The first braking surface 24 is a surface of a brake pad 26 made of heat-resistant steel or tool steel, which is fixed to both ends of the facing surface 23 and has a higher hardness and higher heat resistance than the guide rail 6. It is inclined with respect to. The second braking surface 25 is a surface of a copper alloy brake pad 27 that is fixed to the outer end portion of the brake pad 26 and has a surface that is lower in hardness than the guide rail 6 and has stable friction characteristics. A slight angle α is further inclined with respect to the braking surface 24.

  Due to such a configuration, a braking force due to friction acts between the first braking surface 24 and the guide rail 6 at the braking position shown in FIG. The power gradually increases, and when the braking force reaches a certain threshold value, the first brake element 17 is rotated clockwise around the first rotation shaft 21 to the second braking position in FIG. The second braking surface 25 comes into contact with the guide rail 6. Further, because of the minute angle α described above, the second braking surface 25 is not in contact with the guide rail 6 when the first braking surface 24 is in contact with the guide rail 6 as shown in FIG. As shown in FIG. 6, the first brake surface 24 is not in contact with the guide rail 6 when the first brake element 17 is further rotated and the second brake surface 25 is in contact with the guide rail 6. .

  The elevator emergency stop device 7 includes a drive device 28 that drives the first brake element 17 between the open position shown in FIG. 2 and the brake position shown in FIG. 5. The drive device 28 is, for example, an electromagnetic solenoid that operates in response to a braking signal, and is connected to the first brake member 17 by a rod 31 having a long hole 30 that fits into a pin 29 of the first brake member 17. The first brake element 17 is supported so as to be rotatable around a first rotating shaft 21 perpendicular to the extending direction of the guide rail 6 (up and down direction in FIG. 2) and the moving direction of the frame 16 (left and right direction in FIG. 2). Therefore, when the pin 29 is moved in the extending direction of the guide rail 6 by the drive device 28, the first brake element 17 is rotated and driven to the open position or the brake position. In order to limit the rotation range of the first brake element 17, a stopper 32 is provided on the frame 16.

  The second brake element 18 provided on the left side of the guide rail 6 of the frame 16 in FIG. 2 is an open position in which the braking surface 33 is separated from the guide rail 6 in accordance with the operation of the first brake element 17 (FIG. 2). And a braking position (FIGS. 5 and 6) in which the braking surface is pressed against the guide rail 6 and brakes, and the first braking surface 34 and the first The second braking surface 35 has a smaller friction coefficient than the first braking surface 34.

  In the illustrated example, the second brake element 18 is made of heat-resistant steel or tool steel having a surface having higher hardness and superior heat resistance than the guide rail 6, and the first brake surface 34 is the second brake element 18. The second braking surface 35 is the surface of the copper-based alloy brake pad 36 having a surface that is lower in hardness than the guide rail 6 and has a stable friction characteristic. The first braking surface 34 is parallel to the guide rail 6, and the second braking surface 35 is provided at both ends of the first braking surface 34, and is approximately equal to the angle α with respect to the first braking surface 34. It is tilted by a small angle.

  In order to enable the second brake element 18 to be rotated in this manner, the second rotation of the second brake element 18 on the support block 38 elastically supported by the wall-like rising portion 16a of the frame 16 via the elastic body 37 which is a disc spring. Supported by a shaft 39. As shown in FIG. 5, when the second brake element 18 is in the first braking position, the first braking surface 34 comes into contact with the guide rail 6 and braking is mainly performed by the first braking surface. When the braking force between them exceeds a predetermined threshold value, which will be described later, it further rotates from the first braking position around the rotation shaft 39 to the second braking position as shown in FIG. 34 is inclined with respect to the guide rail 6, and the second braking surface 35 comes into contact with the guide rail so that braking by the second braking surface is mainly performed. In order to regulate the moving direction of the support block 38, a guide 40 is provided on the frame 16.

  Due to such a configuration, during braking, the braking force between the first braking surface 34 and the guide rail 6 at the braking position shown in FIG. When the threshold value is reached, the second brake element 18 is rotated counterclockwise about the second rotation shaft 39 to the second braking position in FIG. 6, and the second braking surface 35 faces the guide rail 6. You will win. Further, because of the above-described minute angle between the first braking surface 34 and the second braking surface 35, the second braking surface 34 is in contact with the guide rail 6 as shown in FIG. In the state where the braking surface 35 is not in contact with the guide rail 6 and the second braking element 18 is rotated and the second braking surface 35 is in contact with the guide rail 6 as shown in FIG. One braking surface 34 is not in contact with the guide rail 6.

  In the elevator emergency stop device 7 in the open position shown in FIG. 2, the drive device 28 is actuated by the braking signal, the rod 31 is pulled up, and the first brake 17 is moved clockwise around the first rotating shaft 21. First, the first brake 17 is brought into point contact with the guide rail 6 at the edge A (FIGS. 3 and 5) of the brake pad 26, and further rotated to resist the acting force of the elastic device 19 when the first brake 17 is rotated. The first brake face 24 of the first brake piece 17 and the first brake face 34 of the second brake piece 18 are brought into surface contact with the guide rail 6 together with the second brake piece 18. In this state, the first braking surface 24 is in surface contact in a range from the edge portion A to the edge portion B at the boundary with the second braking surface 25, and the second braking surface 25 is guided only by the edge portion B. It is in contact with the rail 6. Since most of the pressing force F by the elastic element 37 acts on the first braking surface 24 located on the center side of the rotating shaft 21, the braking force by the first brake element 17 at the initial stage of braking is the first braking force. It occurs at one braking surface 24. Further, the braking force by the second brake element 18 is generated at the first braking surface 34. The pressing force F is such that the first brake 17 rotates and the edge portion A of the first braking surface 24 hits the guide rail 6, and further rotates so that the first braking surface 24 comes into contact with the surface and the second brake 18 is The elastic element 37 is compressed by being pushed into the left side in the figure with respect to the frame 16.

  Here, at the braking position of FIG. 5, the end of the first braking surface 24 of the first brake element 17 on the entry side of the guide rail 6, that is, the boundary between the first braking surface 24 and the second braking surface 25. The point B is defined as B, the end of the second braking surface 25 on the guide rail 6 entry side is defined as C, and the pressing direction of the pressing force F of the elastic device 19 and the edge B serving as the end are formed around the rotation shaft 21. Let β be the angle. Further, when the friction coefficient of the first braking surface 24 of the first brake element 17 is μ24, the angle β is constant during the braking period, but the friction coefficient μ24 increases due to the engagement of wear powder and the like, and μ24 ≦ The expression of tan (β) is not satisfied, and the first brake 17 starts to rotate further clockwise, and most of the pressing force F starts to act on the second brake 18. That is, the braking force value generated by the friction coefficient μ24 that does not satisfy the expression of μ24 ≦ tan (β) is used as a threshold value (in this example, the angle β is constant), and the braking from the first braking surface 24 to the second braking surface 25. Shift to braking by. At this time, the first brake element 17 further rotates by an angle corresponding to the size of the minute gap G provided between the portion corresponding to the main frame of the fan and the stopper 32, contacts the stopper 32 and stops there. To do. This minute gap is provided for reasons of production or assembly adjustment of an emergency stop device for an elevator.

  Such a state is shown in FIG. In FIG. 6, the edge portion C on the guide rail entry side of the second braking surface 25 starts to contact the guide rail 6. However, since the friction coefficient μ25 of the second braking surface 25 is lower than the friction coefficient μ24 of the first braking surface 24, the frictional force generated by the second braking surface 25 causes the first braking element 17 to rotate clockwise. The counterclockwise rotational force generated when the pressing force F pushes the edge portion C becomes larger, and the edge portion C does not contact the point of contact with the point C by rotating further clockwise. Even if point contact occurs, since the edge portion C has a lower hardness than the guide rail 6, the edge portion C is not deformed and the edge portion C does not bite into the guide rail 6. Therefore, an excessive increase in braking force can be prevented, and a shock at the time of braking stop can be eased to ensure passenger comfort.

  Further, also on the second brake element 18 side, the edge part on the entry side of the guide rail 6 of the first brake surface 34 of the second brake element 18, that is, between the first brake surface 34 and the second brake surface 35. The boundary point is D, the edge portion of the second braking surface 35 is E, the angle between the pressing direction of the pressing force F of the elastic device 19 and the edge portion D around the second shaft 39 is γ, and Assuming that the friction coefficient of the first braking surface 34 is μ34, when the friction coefficient μ34 increases and does not satisfy μ34 ≦ tan (γ), the second brake element 18 is counteracted around the second shaft 39. Try to rotate clockwise. That is, the braking force value generated by the friction coefficient μ34 that does not satisfy the expression μ34 ≦ tan (γ) is used as a threshold value (in this example, the angle γ is constant), and braking from the first braking surface 34 to the second braking surface 35 is performed. Shift to braking by.

  Therefore, as shown in FIG. 6, the first braking surface 34 of the second brake element 18 is once separated from the guide rail 6, and the second braking surface 35 comes into contact with the guide rail 6 and starts braking. However, since the friction coefficient μ35 of the second braking surface 35 is smaller than the friction coefficient μ34 of the first braking surface 34, the second brake element 18 rotates the shaft 39 counterclockwise by the frictional force of the second braking surface 35. The force that the pressing force F acts on the edge portion D to rotate in the clockwise direction is larger than the force, and the edge portion E is less hard than the guide rail 6 and does not bite. For this reason, the first braking surface 34 of the second brake element 18 comes into contact with the guide rail 6 again. At this time, since the first braking surface 34 is once separated from the guide rail 6 and the wear powder that has digged in is discharged, the excessively increased friction coefficient μ 34 is removed and returned to the original size. Then, braking is started again at the first braking surface 34.

  The angle β when shifting from braking by the first braking surface 24 of the first brake element 17 to braking by the second braking surface 25 is the angle γ when shifting to braking by the second braking surface 35 of the second brake element 18. Further, the material of the second braking surface 25 of the first brake element 17 and the material of the second braking surface 35 of the second brake element 18 are the same, and the friction coefficient is made equal. For this reason, a predetermined threshold for the braking force acting between the first braking surface 24 of the first brake element 17 and the guide rail 6 and the distance between the first braking surface 34 of the second brake element 18 and the guide rail 6 are set. There is a difference in magnitude between the braking force acting on the brake and a predetermined threshold value, the timing for limiting excessive braking force is shifted, and the braking force increases excessively when stopping emergency braking. Can be softened. Such a relationship between the threshold values of the braking force is realized by changing the coefficient of friction between the first braking surface 24 of the first braking element 17 and the first braking surface 34 of the second braking element 18 by changing the material or the surface condition. You can also

  In the drawing, various angles and dimensions are exaggerated for explanation. For example, the angle between the first braking surface 34 and the second braking surface 35 of the second brake element 18 is actually the same. It is minute. For this reason, the biting into the guide rail 6 at the edge portion D of the first braking surface 34 can be suppressed. Therefore, an excessive increase in the braking force due to the biting of the edge portion D during deceleration can be prevented, and the impact at the time of emergency braking stop can be mitigated.

Embodiment 2. FIG.
In the elevator emergency stop device 7 shown in FIG. 7, both the first brake 17 and the second brake 18 are connected to the drive device 28, and are configured to be rotationally driven in response to the brake signal. ing. That is, the first brake element 17 is pivotally supported by the rotating shaft 21 on the dedicated frame 16 guided on the guide 15 and biased toward the guide rail 6 by the elastic element 37, and the second brake element 18. Are arranged in the same manner as the first brake element 17 with the guide rail 6 interposed therebetween. Both the first brake 17 and the second brake 18 are supported on a dedicated frame 16.

  Also in the emergency stop device for elevator 7, both the first brake element 17 and the second brake element 18 can rotate between the open position and the brake position, and the braking force exceeds a predetermined threshold value at the brake position. When this occurs, it can be further rotated from the first braking position to the second braking position, and the impact at the time of emergency stop can be reduced.

Embodiment 3 FIG.
In the elevator emergency stop device 7 shown in FIG. 8, the second brake element 18 of the first brake element 17 and the second brake element 18 that form a pair has a uniform braking surface 33. In other words, the second brake element 18 is supported on the frame 16 by the elastic element 37 so as to be elastically movable in the direction of separating from and coming into contact with the guide rail 6. Is flat and has a uniform coefficient of friction, and is not supported so as to be able to rotate in the extending direction of the guide rail 6. Other configurations are the same as those shown in FIGS.

  As described above, as a configuration in which the present invention is applied only to the first brake element 17 on the driving side, the second brake element 18 can be extended in the extending direction of the guide rail 6 without increasing the outer shape as compared with the driving side. Therefore, it is possible to prevent the edge portion from biting into the guide rail 6 with a compact and simple structure.

Embodiment 4 FIG.
In the elevator emergency stop device 7 shown in FIG. 9, the first brake 17 is brought into contact with the guide rail 6 via the frame 16 driven by the drive element 41, and the guide rail 6 and the emergency stop device are brought into contact with each other. 7 is configured to be rotationally driven from the open position to the braking position by relative movement with respect to the position 7. The second brake element 18 may be the same as that shown in FIG.

  That is, the frame 16 that slides on the guide 15 is biased by the drive element 41 in a direction in which the first brake 17 on the guide 15 contacts the guide rail 6. During normal operation, the frame 16 is held by the electromagnetic solenoid 42 at an open position where the first brake element 17 is separated from the guide rail 6. When the electromagnetic solenoid 42 is deenergized by a braking signal, the frame 16 is elastic. The first brake 17 is brought into contact with the guide rail 6 by the action force of the first contact, and is rotated by the relative movement with the emergency stop device 7 so that the first brake 17 is subjected to the first braking. The surface 24 brakes the guide rail 6 with the first brake surface 34 of the second brake element 18 interposed therebetween.

  Other configurations, for example, the relationship between the first braking surface 24 and the second braking surface 25, and the replacement of the braking surface that performs the braking action by the threshold of the braking force are the same as those shown in FIGS.

  The elevator emergency stop apparatus illustrated and described above is merely an example, and various modifications can be made, and the features of each specific example can be used altogether or selectively combined. For example, the material of the first braking surface 24 and the second braking surface 25 of the first brake member 17 and the material of the first braking surface 34 and the second braking surface 35 of the second brake member 18 are the second braking surface 25. And the friction coefficient of 35 is smaller than the friction coefficient of the first braking surfaces 24 and 34, the hardness of the guide rail 6 is smaller than the hardness of the first braking surfaces 24 and 34, and the hardness of the second braking surfaces 25 and 35. However, the material may be different as long as it is large.

  The present invention can be used for an emergency stop device for an elevator.

  4, 5 Elevator, 6 Guide rail, 16 Frame, 17, 18 Brake (17 1st brake, 18 2nd brake), 19 Elastic device, 22, 33 Brake surface, 24 First brake 1st Brake surface, 25 Second brake surface of the first brake element, 28 Drive device, 34 First brake surface of the second brake element, 35 Second brake surface of the second brake element, 37 Elastic element, 41 Drive element.

Claims (11)

In an emergency stop device for an elevator that is mounted on a lifting body guided by a guide rail and brakes the lifting body by clamping the guide rail by a braking surface of a pair of brake elements by a pressing force by an elastic element,
The first brake element of the pair of brake elements is rotatable between an open position where the braking surface is separated from the guide rail and a braking position where the braking surface is pressed by the guide rail to brake. And having a first braking surface and a second braking surface having a smaller coefficient of friction than the first braking surface,
When the braking force is less than or equal to a predetermined threshold at the braking position, the first brake element is at a first braking position where braking by the first braking surface is mainly performed, and when the braking force exceeds a predetermined threshold, The elevator emergency stop device further rotates from the first braking position to become a second braking position where braking by the second braking surface is mainly performed. The second brake of the pair of brakes is in an open position where the braking surface is separated from the guide rail in response to the operation of the first brake, and the braking surface of the second brake is A first braking surface and a second braking surface having a friction coefficient smaller than that of the first braking surface, wherein the first braking surface is movable between the braking position pressed by the guide rail and braked;
When the braking force is less than or equal to a predetermined threshold at the braking position, the second brake element is in a first braking position where braking by the first braking surface is mainly performed, and when the braking force exceeds a predetermined threshold, 2. The emergency stop device for an elevator according to claim 1, wherein the emergency stop device for an elevator according to claim 1, wherein the emergency stop device is turned from the first braking position to a second braking position where braking is mainly performed by the second braking surface.   When the second brake element is rotatable between the open position and the brake position and the braking force exceeds a predetermined threshold at the brake position, the second brake element further rotates from the first brake position. The emergency stop device for an elevator according to claim 1, wherein the second braking position is reached.   The emergency stop device for an elevator according to claim 1, wherein the second brake element of the pair of brake elements has a uniform braking surface.   The second braking surface is disposed at a slight angle with respect to the first braking surface so as not to contact the guide rail when the first braking surface is in contact with the guide rail. The emergency stop device for an elevator according to any one of claims 1 to 4, wherein the elevator emergency stop device is provided.   The first braking surface is a surface having higher hardness and heat resistance than the guide rail, and the second braking surface is a surface having lower hardness than the guide rail and stable friction characteristics. The emergency stop device for an elevator according to any one of claims 1 to 5.   The elevator emergency according to any one of claims 1 to 6, wherein the first braking surface is a surface of heat-resistant steel or tool steel, and the second braking surface is a surface of a copper-based alloy. Stop device.   The pair of brake elements are disposed opposite to each other across the guide rail, and the predetermined threshold for the braking force acting between the first brake surface of the first brake element and the guide rail, The difference in magnitude is provided between the predetermined threshold value for the braking force acting between the first braking surface of the second brake element and the guide rail. An emergency stop device for an elevator according to claim 1.   A frame that is movable in a direction perpendicular to an extension direction of the guide rail and supports the brake element; an elastic element that biases the frame in a direction in which the first brake element contacts the guide rail; and The emergency stop device for an elevator according to any one of claims 1 to 8, further comprising a drive device that drives the first brake element between the open position and the brake position.   The first brake element is supported so as to be rotatable about a first axis perpendicular to the extending direction of the guide rail and the moving direction of the frame, and is rotated by the driving element to move the first brake element from the open position. The emergency stop device for an elevator according to claim 9, wherein the emergency stop device is driven to a braking position.   The first brake element is brought into contact with the guide rail via the frame driven by the drive element, and is driven to rotate from the open position to the brake position by mutual movement of the guide rail and the emergency stop device. The elevator emergency stop device according to claim 9.

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