EP2586739A1

EP2586739A1 - Brake release mechanism

Info

Publication number: EP2586739A1
Application number: EP10853667.3A
Authority: EP
Inventors: Yoshinori Tani
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2010-06-25
Filing date: 2010-06-25
Publication date: 2013-05-01
Also published as: JPWO2011161807A1; WO2011161807A1; CN102958820A; KR20130043641A

Abstract

Provided is a brake release mechanism capable of reducing effort required for a brake releasing operation. The brake release mechanism includes amovable lever (13) and a fixed lever (15) provided so as to be rotatable relative to each other, and a plurality of rolling bodies (17) provided between the levers. On one surface (13a) of a pair of surfaces of the levers which face each other, a plurality of supporting holes (19) are formed, and on another surface (15a) thereof, a plurality of elongated holes (21) each extending in an arc-like manner so as to enable the rolling bodies to move while rolling are formed. Each of the elongated holes is formed so that a depth for housing a corresponding one of the rolling bodies changes when the rolling bodies move along the elongated holes. A distance between both the levers in a direction of a relative rotation axis changes in accordance with the relative rotation of the levers. The brake release mechanism further includes a release bolt (43) which avoids securing a position of the fixed lever in the direction of the relative rotation axis and secures a position of the movable lever in the direction of the relative rotation axis. Through the rotation of the movable lever, the fixed lever applies a traveling force to a movable body in the direction of the relative rotation axis, to thereby release a brake.

Description

Technical Field

The present invention relates to a brake release mechanism for a hoisting-machine brake for an elevator.

Background Art

A brake for stopping a car is provided to a hoisting machine of an elevator. An electromagnetic coil is provided to the brake. During a normal operation in which the car is raised and lowered, the electromagnetic coil is energized. By an electromagnetic function, the hoisting-machine brake is placed in a released state. On the other hand, in case of emergency such as a power outage or an earthquake, the hoisting-machine brake is configured so that the energization is interrupted to automatically place the brake in a braking state. Therefore, as an operation after the car makes an emergency stop, the hoisting-machine brake is manually released to place the car in a state in which the car can be raised and lowered and then the car is moved to the nearest floor.
As a structure for manually releasing the hoisting-machine brake in the situation described above, there is a structure disclosed in Patent Literature 1. In this structure, a pin passes through a movable iron core constituting the brake. A distal end of the pin is screwed into a fixed iron core having an electromagnetic magnet. A head of the pin projects from a surface of the movable iron core, which is on the side opposite to the fixed iron core. When the brake is to be released, a wedge-like portion of a brake releaser is inserted between the head of the pin and the movable iron core. Through movement of the movable iron core toward the fixed iron core, a brake shoe supported by the movable iron core is separated from a braking surface of a rotor.
In a mode in which the brake is released by using the effects provided by the wedge as described above, however, the brake releaser is subjected to a large frictional force due to surface contact on the wedge-like portion over a wide area when the wedge-like portion is inserted between the head of the pin and the movable iron core. Therefore, enormous effort has been required for a brake releasing operation.

Citation List

Patent Literature

[PTL 1]: JP 2006-341942 A

Summary of Invention

Technical Problem

The present invention has been made in view of the problem described above, and therefore has an object to provide a brake release mechanism capable of reducing effort required for a manual brake releasing operation.

Solution to Problem

In order to achieve the above-mentioned object, according to the present invention, there is provided a brake release mechanism for a hoisting-machine brake for an elevator, the hoisting-machine brake including movable bodies for supporting brake shoes and a fixed base having electromagnetic coils for driving the movable bodies, the brake release mechanism including: a first member and a second member provided so as to be rotatable relative to each other; and a plurality of rolling bodies provided between the first member and the second member, in which: the brake release mechanism further includes: a plurality of supporting holes for partially housing the plurality of rolling bodies therein, the plurality of supporting holes being formed on one of a pair of surfaces of the first member and the second member, which face each other; and a plurality of elongated holes each extending in an arc-like manner so as to enable a corresponding one of the plurality of rolling bodies to move while rolling, the plurality of elongated holes being formed on another of the pair of surfaces ; the plurality of supporting holes respectively support the plurality of rolling bodies so as to enable the plurality of rolling bodies to spin by themselves and to move in synchronization with the plurality of supporting holes; each of the plurality of elongated holes is formed so that a depth for housing the corresponding one of the plurality of rolling bodies changes when the plurality of rolling bodies move along the plurality of elongated holes; each of the plurality of rolling bodies is housed in both a corresponding one of the plurality of supporting holes and a corresponding one of the plurality of elongated holes between the first member and the second member so that a distance between the first member and the second member in a direction of a relative rotation axis changes in accordance with the relative rotation of the first member and the second member; the brake release mechanism further includes a securing portion which avoids securing a position of one of the first member and the second member in the direction of the relative rotation axis and secures a position of another of the first member and the second member in the direction of the relative rotation axis; the securing portion is fixed to the fixed base; and the one of the first member and the second member is provided so as to apply a traveling force in the direction of the relative rotation axis to a corresponding one of the movable bodies.

Advantageous Effects of Invention

According to the brake release mechanism of the present invention, it is possible to reduce effort required for a manual brake releasing operation.

Brief Description of Drawings

[FIG. 1] A schematic view for illustrating an internal-expanding drum brake for an elevator hoisting-machine, which uses a brake release mechanism according to an embodiment of the present invention.
[FIG. 2] A view for illustrating a state in which a movable lever and a fixed lever, which constitute the brake release mechanism, are combined.
[FIG. 3] A view for illustrating a state as viewed from the arrow III in FIG. 2.
[FIG. 4] A sectional view taken along the line IV-IV in FIG. 3.
[FIG. 5] A plan view of the movable lever.
[FIG. 6] A sectional view taken along the line VI-VI in FIG. 5.
[FIG. 7] A plan view of the fixed lever.
[FIG. 8] A sectional view taken along the line VIII-VIII in FIG. 7, for illustrating an arc-like region extending along the line VIII-VIII which is developed in a planar form.
[FIG. 9] A view for illustrating the vicinity of one of collars in an enlarged manner in association with FIG. 2.
[FIG. 10] A view in the same mode as FIG. 1, for illustrating a state in which the brake release mechanism is assembled to a hoisting-machine brake.
[FIG. 11] A sectional view taken along the line XI-XI in FIG. 10.
[FIG. 12] A view for illustrating a plane taken along the line XII-XII in FIG. 10.

Description of Embodiment

Hereinafter, a brake release mechanism according to an embodiment of the present invention is described referring to the accompanying drawings. In the figures, the same reference symbols represent the same or corresponding parts.
FIG. 1 is a schematic view of an internal-expanding drum brake for an elevator hoisting-machine, which uses the brake release mechanism according to this embodiment. A hoisting-machine brake 1 includes a pair of movable bodies 3 and a fixed base 5.
The pair of movable bodies 3 are respectively provided on both sides of the fixed base 5 so as to sandwich the fixed base 5 therebetween. A projection 3a, to which a fixed lever described below is locked by hooking, is formed on each of the movable bodies 3. On the side of each of the movable bodies 3, which is opposite to the fixed base 5, a brake shoe 9 is provided so as to face an inner circumferential surface of a rotor 7. The brake shoes 9 are respectively supported by the corresponding movable bodies 3. An elastic body 11 is provided between each of the movable bodies 3 and the fixed base 5. In this manner, the pair of movable bodies 3 and the pair of brake shoes 9 are constantly biased toward the rotor 7 by elastic forces of the corresponding elastic bodies 11, respectively.
The fixed base 5 includes electromagnetic coils (not shown) in the vicinity of the pair of movable bodies 3. The pair of movable bodies 3 are driven by the electromagnetic coils. Specifically, when the electromagnetic coils are energized, the pair of movable bodies 3 are subjected to driving forces for attracting the movable bodies toward the fixed base 5 by electromagnetic forces thereof.
Next, the brake release mechanism according to this embodiment is described. FIG. 2 is a view for illustrating a state in which a movable lever and a fixed lever, which constitute the brake release mechanism, are combined. FIG. 3 is a view for illustrating a state as viewed from the arrow III in FIG. 2. FIG. 4 is a sectional view taken along the line IV-IV in FIG. 3. First, the brake release mechanism includes a movable lever (first member) 13, a fixed lever (second member) 15, and a plurality of rolling bodies 17.
The movable lever 13 and the fixed lever 15 are provided so as to be rotatable relative to each other. The plurality of (three in this embodiment) rolling bodies 17 are provided between the movable lever 13 and the fixed lever 15, and are formed as, for example, spherical bodies made of a bearing steel material in this embodiment. The same number of (three in this embodiment) supporting holes 19 as that of the rolling bodies are formed on one surface 13a of a pair of surfaces 13a and 15a of the movable lever 13 and the fixed lever 15, which face each other. The same number of (three in this embodiment) elongated holes 21 as that of the rolling bodies are formed on the another surface 15a. The supporting holes and the elongated holes are further described referring to other figures.
FIG. 5 is a plan view of the movable lever. FIG. 6 is a sectional view taken along the line VI-VI in FIG. 5. FIG. 7 is a plan view of the fixed lever. FIG. 8 is a sectional view taken along the line VIII-VIII in FIG. 7, for illustrating an arc-like region extending along the line VIII-VIII, which is developed in a planar form.
First, as illustrated in FIG. 5, the movable lever 13 includes a body portion 23 and a lever-piece portion 25. The body portion 23 is a circular disc-like portion provided about a rotation axis CL for the above-mentioned relative rotation. In a central portion of the body portion 23, a through hole 27 is formed. The lever-piece portion 25 is a portion extending in a radial direction for the relative rotation, and specifically, is a portion extending from the body portion 23 outward in a radial direction of the body portion 23 in this embodiment.
Each of the supporting holes 19 is a recess which is open on the above-mentioned one surface 13a of the body portion 23. Each of the supporting holes 19 has a form in which each of the rolling bodies 17 is partially housed, and for example, has a shape in accordance with an outer shape of each of the rolling bodies 17 (inner-surface shape similar to the outer shape of each of the rolling bodies). Specifically, each of the rolling bodies 17 is a spherical body in this embodiment, and hence the inner-surface shape of each of the supporting holes 19 is formed as a spherical surface shape. Moreover, a depth of each of the supporting holes 19 is a half of a diameter "d" of the spherical body forming each of the rolling bodies 17, as illustrated in FIG. 6, that is, d/2. As described above, in this embodiment, each of the supporting holes 19 is a semi-spherical recess. Because of the form of each of the supporting holes 19 described above, each of the supporting holes 19 supports a corresponding one of the rolling bodies 17 in a mode in which the rolling body cannot move in the hole but can spin by itself in the hole, in other words, in a mode in which the rolling body can move and spin by itself in synchronization with a corresponding one of the supporting holes.
The three supporting holes 19 are arranged on a circumference having a single radius about the center (relative rotation axis CL) of the body portion 23 in plan view. Further, each of the supporting holes 19 is separated from another adjacent one of the supporting holes 19 at an equiangular distance (120 degrees in this embodiment) in plan view.
On the other hand, as illustrated in FIG. 7, the fixed lever 15 includes a body portion 29 and a fixing-arm portion 31. The body portion 29 is a circular disc-like portion provided about the relative rotation axis CL. A through hole 33 is formed in a central portion of the body portion 29.
The fixing-arm portion 31 is a portion relating to the relative rotation, which extends in the radial direction, and specifically, is a portion extending outward in the radial direction of the body portion 29 from the body portion 29 in this embodiment. In the vicinity of a distal end of the fixing-arm portion 31, a pair of hooks 35 are provided. The pair of hooks 35 are a pair of protruding portions vertically standing on a surface opposite to the above-mentioned another surface 1.5a, on which the elongated holes 21 are formed, specifically, a surface on the side which faces a corresponding one of the movable bodies 3 at the time of completion of assembly. Then, when the brake is to be manually released, the above-mentioned projection 3a of the corresponding one of the movable bodies 3 is inserted between the pair of hooks 35.
Each of the elongated holes 21 is a recess which is open on the above-mentioned another surface 15a of the body portion 29. The elongated holes 21 have a form for partially housing the rolling bodies 17 therein and are arranged about the relative rotation axis CL, each extending in an arc-like shape. Further, as illustrated in FIG. 7, each of the elongated holes 21 has a shape which corresponds to a locus obtained when a circle is moved in an arc-like manner in plan view. An inner-surface shape of each of the elongated holes 21 corresponds to an outer shape of each of the rolling bodies 17, and specifically, is a shape which corresponds to a locus obtained when a spherical surface is moved in an arc-like manner in this embodiment, as illustrated in FIG. 8. A depth of each of the elongated holes 21 changes in accordance with the position in a direction in which each of the elongated holes 21 extends in the arc-like manner, as illustrated in FIG. 8. Specifically, each of the elongated holes 21 is formed so that a depth for housing a corresponding one of the rolling bodies 17 therein changes when the rolling body 17 moves along the elongated hole 21. In this embodiment, the relationship between a maximum depth Xmax of each of the elongated holes 21 and a minimum depth Xmin thereof which changes approximately linearly from the maximum depth is: $0 < Xmin < Xmax < d / 2$

with respect to the diameter "d" of each of the rolling bodies 17. With such a form of each of the elongated holes 21, each of the rolling bodies 17 can move along a direction in which the elongated holes 21 extend while rolling inside a corresponding one of the elongated holes 21. Moreover, the depth for housing each of the rolling bodies 17 (in other words, a height of a part of each of the rolling bodies 17, which is exposed from a corresponding one of the elongated holes 21) changes in accordance with the movement of the rolling bodies 17.
The three elongated holes 21 are arranged on a circumference having a single radius about the center (relative rotation axis CL) of the body portion 29 in plan view. Further, each of the elongated holes 21 is separated from another adjacent one of the elongated holes 21 at an equiangular distance (approximately 120 degrees between the centers of the elongated holes in the circumferential direction in this embodiment) in plan view.
Each of the rolling bodies 17 is partially housed in a corresponding one of the supporting holes 19 having the configuration described above on one side, and is partially housed in a corresponding one of the elongated holes 21 having the configuration described above on the other side. Specifically, each of the rolling bodies 17 is housed in both a corresponding one of the supporting holes 19 and a corresponding one of the elongated holes 21 between the movable bodies 3 and the fixed base 5. As a result, a distance between each of the movable bodies 3 and the fixed base 5 in the direction of the relative rotation axis CL varies in accordance with a rotating operation of the movable bodies 3 and the fixed base 5 relative to each other, specifically, in accordance with the positions of the rolling bodies 17 in the elongated holes 21.
The brake release mechanism according to this embodiment further includes a cover member and a plurality of collars. The cover member and the plurality of collars are described referring to FIGS. 2 and 9. FIG. 9 is a view for illustrating the vicinity of one of the collars in an enlarged manner in association with FIG. 2. As illustrated in FIGS. 2 and 9, a cover member 37 is provided so that the movable lever 13 is interposed between the cover member 37 and the fixed lever 15. Each of collars 39 is a cylindrical member and is provided between the cover member 37 and the fixed lever 15 so as to maintain a distance between the cover member 37 and the fixed lever 15. Through a hollow portion of each of the collars 39, a collar screw 41 is inserted. By the collar screws 41, the cover member 37 and the fixed lever 15 are connected to each other.
The brake release mechanism further includes a securing portion. For example, the securing portion does not secure the position of one of the movable lever 13 and the fixed lever 15 in the direction of the relative rotation axis CL but secures the position of another thereof in the direction of the relative rotation axis CL. In this embodiment, the securing portion is formed of a release bolt fixed to the fixed base 5. The securing portion is described referring to FIGS. 10 and 11.
FIG. 10 is a view in the same mode as that of FIG. 1, for illustrating a state in which the brake release mechanism is assembled to the hoisting-machine brake. FIG. 11 is a sectional view taken along the line XI-XI in FIG. 10. As is most clearly illustrated in FIG. 11, a release bolt 43 corresponding to the securing portion passes through the movable lever 13 and the fixed lever 15 so as to extend along the relative rotation axis CL, specifically, is inserted into the through holes 27 and 33 described above. A distal end of the release bolt 43 is screwed into the fixed base 5. A head of the release bolt 43 has a larger outer diameter than that of the through hole 27, and is exposed on an opposite surface 13b to the one surface 13a of the movable lever 13, on which the supporting holes 19 are formed, so as to sit on the opposite surface 13b. In a portion of the cover member 37 in the vicinity of the relative rotation axis CL, a hole for the escape of the head is provided so as not to prevent the head of the release bolt 43 from sitting on the opposite surface 13b.
Subsequently, the functions of the brake release mechanism according to this embodiment are described mainly referring to FIGS. 10 to 12. FIG. 12 is a view for illustrating a plane taken along the line XII-XII in FIG. 10. The movable lever 13 and the fixed lever 15 of the break release mechanism are provided on the side of each of the movable bodies 3, which is opposite to the fixed base 5, as illustrated in FIGS. 10 and 11. The movable lever 13 and the fixed lever 15 are provided to have the relation in which the fixed lever 15 is provided on the side closer to a corresponding one of the movable bodies 3. Further, as illustrated in FIGS. 10 to 12, the projection 3a of the corresponding one of the movable bodies 3 is inserted between the pair of hooks 35 of the fixed lever 15. Each of the rolling bodies 17 is located at the portion with the maximum depth Xmax in a corresponding one of the elongated holes 21. An example of a mounting procedure is described. First, the pair of hooks 35 of the fixed lever 15 are brought into engagement with the projection 3a of the corresponding one of the movable bodies 3. Subsequently, the release bolt 43 is inserted into the through holes 27 and 33 to be screwed into the fixed base 5. In this manner, the head of the release bolt 43 is brought into close abutment on the opposite surface 13b of the movable lever 13.
In a state described above, the movable lever 13 is rotated as indicated by the arrow R in FIG. 12. Then, the rotation of the fixed lever 15 in the direction of the relative rotation is blocked by the corresponding one of the movable bodies 3 due to the engagement between the hooks 35 and the projection 3a. Specifically, the fixed lever 15 does not rotate, but only the movable lever 13 rotates. Therefore, the relative rotation occurs between the movable lever 13 and the fixed lever 15.
When the relative rotation occurs between the movable lever 13 and the fixed lever 15, each of the rolling bodies 17 changes the position in synchronization with (together with) a corresponding one of the supporting holes 19 due to the arc-like movement of the supporting holes 19 provided on the rotating movable lever 13, and hence moves to the portion with the minimum depth Xmin while rolling inside a corresponding one of the elongatedholes 21. In this manner, through the movement of each of the rolling bodies 17 from the portion with the maximum depth Xmax to the portion with the minimum depth Xmin in a corresponding one of the elongated holes 21, the height of the part of each of the rolling bodies 17, which is exposed from the another surface 15a of the fixed lever 15, increases, to thereby increase the distance between the another surface 15a of the fixed lever 15 and the one surface 13a of the movable lever 13, specifically, the distance between the fixed lever 15 and the movable lever 13. Although the relative rotation is allowed for the movable lever 13, the movement thereof in the direction of the relative rotation axis CL (in particular, the movement in a direction away from the fixed base 5) is limited by the release bolt 43. Therefore, the increase in distance between the movable lever 13 and the fixed lever 15 appears as the movement of the fixed lever 15 in the direction of the relative rotation axis CL away from the movable lever 13. Therefore, the corresponding one of the movable bodies 3 is subjected to a pressing force in the direction of the relative rotation axis CL from the fixed lever 15 so as to move closer to the fixed base 5 against the elastic force of the elastic body 11. As a result, one of the brake shoes 9, which is provided integrally with the corresponding one of the movable bodies 3, separates from the inner circumferential surface of the rotor 7 to achieve the manual release of the brake.
The relative operation of the movable lever 13 and the fixed lever 15 is appropriately ensured by forming the collars 39 in the following mode. As illustrated in FIG. 9, it is appropriate to set a height "X" of each of the collars 39 so as to satisfy: $g + d - Xmin - a < X < (d - Xmax) + b - (d / 2)$

where "a" represents a depth of each of the supporting holes 19 of the movable lever 13, "b" represents a thickness of the movable lever 13, and "g" represents a distance of movement of each of the movable bodies 3, which is required to release the brake. With setting of the height of each of the collars 39 to the value X which satisfies the condition described above, the distance can be changed so that the movable lever 13 and the fixed lever 15 do not interfere with each other at the time of the brake releasing operation. In addition, even in a state in which the distance between the movable lever 13 and the fixed lever 15 increases to the maximum extent, the rolling bodies 17 interposed therebetween can be prevented from dropping off.
As described above, according to the brake release mechanism of this embodiment, for applying a brake releasing force to each of the movable bodies, a large frictional force due to surface contact over a wide area is advantageously prevented from being generated in a movable portion. More specifically, the friction generated due to the rotation of the movable lever can be absorbed by the rotation of the rolling bodies themselves. As aresult, effort required for the manual brake releasing operation can be significantly reduced. Moreover, the brake can be forcibly released by only applying a vertical turning force to the hoisting machine. Therefore, it is not necessary to provide a large space for the releasing operation on the side of the hoisting machine, which can lead to space saving of a hoistway and a machine room.
The present invention has been specifically described above referring to the preferred embodiment. However, it is apparent to those skilled in the art that various modified modes are possible based on the fundamental technological thought and teaching of the present invention.
As an example, there may be used any securing portion, which can provide the function of securing the position of one of the movable lever (first member) and the fixed lever (second member) in the direction of the relative rotation axis CL without securing the position of another thereof in the direction of the relative rotation axis CL. Therefore, the securing portion is not limited to a single independent member as in the embodiment described above as long as the function described above can be provided, and may be a part of the first member or the second member, a part of the fixed base, or a part of another element.

Reference Signs List

3 movable body, 5 fixed base, 9 brake shoe, 13 movable lever (first member, another of first member and second member), 13a one surface, 13b opposite surface, 15
fixed lever (second member, one of first member and second member), 15a another surface, 17 rolling body, 19
supporting hole, 21 elongated hole, 37 cover member, 39 collar, 43 release bolt (securing portion), CL
relative rotation axis

Claims

A brake release mechanism for a hoisting-machine brake for an elevator, the hoisting-machine brake including movable bodies for supporting brake shoes and a fixed base having electromagnetic coils for driving the movable bodies, the brake release mechanism comprising:
a first member and a second member provided so as to be rotatable relative to each other; and

a plurality of rolling bodies provided between the first member and the second member, wherein:
the brake release mechanism further comprises:
a plurality of supporting holes for partially housing the plurality of rolling bodies therein, the plurality of supporting holes being formed on one of a pair of surfaces of the first member and the second member, which face each other; and

a plurality of elongated holes each extending in an arc-like manner so as to enable a corresponding one of the plurality of rolling bodies to move while rolling, the plurality of elongated holes being formed on another of the pair of surfaces;

the plurality of supporting holes respectively support the plurality of rolling bodies so as to enable the plurality of rolling bodies to spin by themselves and to move in synchronization with the plurality of supporting holes;

each of the plurality of elongated holes is formed so that a depth for housing the corresponding one of the plurality of rolling bodies changes when the plurality of rolling bodies move along the plurality of elongated holes;

each of the plurality of rolling bodies is housed in both a corresponding one of the plurality of supporting holes and a corresponding one of the plurality of elongated holes between the first member and the second member so that a distance between the first member and the second member in a direction of a relative rotation axis changes in accordance with the relative rotation of the first member and the second member;

the brake release mechanism further comprises a securing portion which avoids securing a position of one of the first member and the second member in the direction of the relative rotation axis and secures a position of another of the first member and the second member in the direction of the relative rotation axis;

the securing portion is fixed to the fixed base; and

the one of the first member and the second member is provided so as to apply a traveling force in the direction of the relative rotation axis to a corresponding one of the movable bodies.
A brake release mechanism according to claim 1, wherein:
rotation of the one of the first member and the second member in a direction of the relative rotation is blocked by the corresponding one of the movable bodies; and

the plurality of elongated holes are formed on the one of the first member and the second member.
A brake release mechanism according to claim 1 or 2, wherein:
the another of the first member and the second member comprises a lever-piece portion extending in a radial direction for the relative rotation; and

the plurality of supporting holes are formed on the another of the first member and the second member.
A brake release mechanism according to any one of claims 1 to 3, wherein each of the plurality of rolling bodies comprises a spherical body.
A brake release mechanism according to claim 4, wherein:
at least three spherical bodies are provided as said spherical body; and

each of the plurality of supporting holes is separated from another adjacent one of the plurality of supporting holes at an equiangular distance.
A brake release mechanism according to any one of claims 1 to 5, wherein the first member and the second member are provided on a side of the corresponding one of the movable bodies opposite to the fixed base so that the one of the first member and the second member is located closer to the corresponding one of the movable bodies.
A brake release mechanism according to any one of claims 1 to 6, further comprising:
a cover member; and

a collar, wherein:
the cover member is provided so that the cover member and the one of the first member and the second member sandwich the another of the first member and the second member therebetween; and

the collar is provided between the cover member and the one of the first member and the second member so as to maintain a distance between the cover member and the one of the first member and the second member.
A brake release mechanism according to any one of claims 1 to 7, wherein:
the securing portion passes through the first member and the second member so as to extend along the relative rotation axis;

a distal end of the securing portion is screwed into the fixed base; and

a head of the securing portion is exposed on an opposite surface of the another of the first member and the second member, the opposite surface being located opposite to one surface on which the plurality of supporting holes or the plurality of elongated holes are formed, so that the head sits on the opposite surface.