DESCRIPTION
CLEARANCE ADJUSTMENT DEVICE FOR A BRAKE CYLINDER, AND BRAKE
CYLINDER WITH THE SAME
TECHNICAL FIELD
[0001]
The present invention relates to a clearance adjustment
device and a brake cylinder with the same, the clearance
adjustment device keeping a clearance of a vehicle braking
device at brake release constant in a brake cylinder including
a push rod for operating the vehicle braking device.
BACKGROUND ART
[0002]
Regarding such a type of clearance adjustment devices,
Patent Document 1 discloses a cylinder that includes an output
piston provided with a push rod connected to a brake shoe for
braking a wheel tread, and a friction ring assembly in which
one elastic ring is placed between two discs to be expanded
outward in a radius direction and friction slide resistance
between the expanded ring and an inner surface of the cylinder
is increased. In addition, Patent Document 1 discloses that
the output piston and the friction ring assembly move in
accordance with the wear amount when the brake shoe wears down
during operation of a brake, the friction ring assembly does

not move, at loosening of the brake, due to large slide
resistance, and consequently a proper clearance between the
brake shoe and the wheel tread can be secured.
[0003]
In addition, Patent Document 1 discloses that the two discs
are connected to each other, and when a desired slide resistance
cannot be obtained due to wearing of an outer circumference of
the elastic ring, the slide resistance can be adjusted by
tightening an adjusting screw.
Patent Document 1: Japanese Published Examined Patent
Application No. H06-67725 (Claim 1, Fig. 2)
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0004]
However, in the constitution disclosed in Patent Document
1, since slide resistance is generated only by frictional force
between a flat cylinder inner circumferential surface and an
elastic ring surface, it easily becomes unstable by the surface
condition and wearing down of the cylinder inner circumferential
surface, wearing down of the elastic ring surface, and the like.
In addition, adjustment with the adjusting screw makes
adjustment and control of the slide resistance complicated, and,
also in this point, the constitution should be improved.
Means for Solving the Problem, and Effect of the Same

[0005]
In view of the above problem, the present invention aims
at easily adjusting and controlling slide resistance with a
simple constitution, and next, means for solving the problems
and an effect of the means will be described.
[0006]
The present invention provides a clearance adjustment
device for a brake cylinder constituted as follows. That is,
the clearance adjustment device includes a push rod and a guide
member which is attached to the push rod and movable together
with the push rod. An uneven surface is provided in an outer
surface of the push rod, the uneven surface having recesses and
projections alternately arranged in a moving direction of the
push rod. At least, a space for opening the uneven surface side
of the guide member is formed in the member, and an elastic member
is arranged in the space. The elastic member is deformed to
be engaged with the uneven surface, and thus the guide member
and the push rod are connected to each other. When force over
a predetermined value is applied to the guide member, the elastic
member is deformed to get over the projections of the uneven
surface, and thus the push rod is displaced in relation to the
guide member.
[0007]
Since the elastic member is thus deformed and engaged
(bitten), frictional force or connection force between the push

rod and the guide member can be stabilized.
[0008]
In the clearance adjustment device for a brake cylinder,
it is preferable that the elastic member is an O-ring.
[0009]
Compared with an elastic member having a rectangular cross
section, the O-ring having a circular cross section is easily
engaged with (bitten into) the recess, and thus the frictional
force or connection force can be stabilized.
[0010]
In the clearance adjustment device for a brake cylinder,
it is preferable to provide a plurality of O-rings for being
engaged with the uneven surface.
[0011]
Thus, compared with the case where an O-ring is singly
provided, the frictional force or connection force between the
push rod and the guide member can be further stabilized.
[0012]
In the clearance adjustment device for a brake cylinder,
it is preferable to provide a backup ring between each of the
plurality of O-rings.
[0013]
Thus, the O-ring is prevented from entering the inside of
the adjacent O-ring or getting over the outside of the adjacent
O-ring, and the push rod and the guide member can be securely

connected to each other by the frictional force.
[0014]
In the clearance adjustment device for a brake cylinder,
it is preferable to provide, in the space, an energizing spring
for pushing the O-rings to one side in an axis direction.
[0015]
Thus, since the O-rings are securely deformed by the
energizing spring so as to be crushed in the axis direction even
if a slight error arises in the size or the like of the space
housing the O-rings, the frictional force or connection force
between the push rod and the guide member can be stabilized.
[0016]
In view of another point, the present invention provides
a brake cylinder with the clearance adjustment device.
[0017]
Thus, a compact brake cylinder can be obtained which has
a clearance adjusting function of easily adjusting and
controlling the slide resistance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018]
Fig. 1 is an entire cross sectional view of a brake cylinder
with a clearance adjustment device of a first embodiment, the
brake cylinder in a brake non-operating state;
Fig. 2 is an enlarged cross sectional view of O-rings

arranged on a guide member;
Fig. 3 is an entire cross sectional view of the brake
non-operating state after clearance adjustment;
Fig. 4 is a cross sectional view of a brake cylinder with
a clearance adjustment device of a second embodiment, the brake
cylinder in a brake non-operating state; and
Fig. 5 is an entire cross sectional view of the brake
cylinder in the brake non-operating state after clearance
adjustment.
REFERENCE NUMERALS
[0019]
1, 101: Brake cylinder
8: Push rod
12: Uneven surface
22: Guide member
24: Clearance adjustment device
27: O-ring housing space
29: Backup ring
31: Energizing spring
BEST MODE FOR CARRYING OUT THE INVENTION
[0020]
First, a brake cylinder with a clearance adjustment device
of a first embodiment will be described with reference to Fig.

1. Fig. 1 is an entire cross sectional view of the brake cylinder
of the first embodiment in a brake non-operating state. Fig.
2 is an enlarged cross sectional view of O-rings arranged on
a guide member. Fig. 3 is an entire cross sectional view of
the brake non-operating state after clearance adjustment. In
the embodiment, the O-ring is cited as an elastic member, the
O-ring being available, and having a relatively high dimensional
precision and a substantially circular cross section having a
diameter of approximately 5 mm. However, such an elastic member
is applicable that has an elliptical or rectangular cross
section and is mainly made of rubber and the like.
[0021]
As shown in Fig. 1, a brake cylinder 1 includes a main body
3 forming an inner space 2. The main body 3 includes a casing
4 and a cover 5 as main components.
[0022]
The casing 4 is in a substantial cup shape with a bottom
(cylindrical shape), and the cover 5 is fixed with a bolt 6 so
that the opening side of the casing 4 is closed. Thus, the inner
space 2 is formed. In addition, a piston 7 is arranged so as
to partition the inner space into two parts, airtightly engaged
with an inner circumferential surface of the casing 4, and
slidable in an axis direction.
[0023]
A base end of a push rod 8 is fixed to the piston 7 via

a flange plate 9 and a bolt 10. The push rod 8 is inserted into
an insertion hole 11 formed in the cover 5 to project outside
of the main body 3, and a brake block of a vehicle braking device
(not shown) is connected to a top end of the push rod 8.
[0024]
An uneven surface 12 is formed in an outer circumferential
surface of the push rod. 8, the surface 12 having recesses and
projections alternately arranged in an axis direction of the
push rod 8 (moving direction of the push rod 8). A height
difference between the recess and projection of the uneven
surface 12 is approximately 0.3 mm. In addition, a dust-proof
flexible bellows cover 13 is provided between the cover 5 and
the push rod 8 so as to cover an opening of the insertion hole
11.
[0025]
On one side of the spaces, into which the inner space 2
is partitioned by the piston 7, is formed a pressurizing chamber
14, and the pressurizing chamber 14 communicates with a
feed/discharge port 15 for pressurized air (pressurized fluid) ,
which is formed in the cover 3 (casing 4). A cup packing 16
is attached to the piston 7 so that the airtightness of the
pressurizing chamber 14 is raised.
[0026]
A ring-shaped spring receiving projection 17 is projected
toward an axial center at one end of the axis direction of the

insertion hole 11 formed in the cover 5. On the other hand,
a cover 18 is fixed to the inner surface side of the cover 5
via a bolt 19, and on the bolt 19, a ring-shaped regulating
projection 20 is projected toward the axial center. A coil
spring-shaped returning spring 21 and a flange 23 of a guide
member 22 described below are arranged between the spring
receiving projection 17 and the regulating projection 20.
[0027]
The guide member 22 is a main component of a clearance
adjustment device 24 of the embodiment and has a substantially-
cylindrical shape, and the push rod 8 is inserted in a shaft
hole thereof. A ring-shaped receiving projection 25 is
projected from an inner circumferential surface of one end of
the guide member 22 in the axis direction, and a locking ring
26 is engaged with an inner circumferential surface of the other
end thereof in the axis direction. Thus, an 0-ring housing space
27 is formed between the receiving projection 25 and the locking
ring 26 on the inner circumferential side of the guide member
22. The O-ring housing space 27 is in a shape for opening the
uneven surface 12 side of the push rod 8 which the space 27 faces.
[0028]
The guide member 22 is arranged so as to extend over the
inner space 2 of the main body 3 and the inside of the insertion
hole 11, and movable in the axis direction of the push rod 8.
The ring-shaped flange 23 is projected on the outer side of the

guide member 22, the returning spring 21 is interposed between
the flange 23 and the spring receiving projection 17, and the
guide member 22 is constantly energized to the base end side
of the push rod 8.
[0029]
The regulating projection 20 prevents the guide member 22,
which is pushed in a base end direction of the push rod 8 by
the returning spring 21, from over-advancing to the base end
from a predetermined position. In addition, when the guide
member 22 moves by a predetermined distance with advancing of
the push rod 8, the spring receiving projection 17 comes into
contact with the guide member 22 and serves as a locking
projection for regulating over-movement of the guide member 22.
[0030]
Fig. 2 is an enlarged view of a main part of the O-ring
housing space 27. As shown in Fig. 2, a plurality of (three)
0-rings 28 as elastic members and a plurality of (three) backup
rings 29 are alternately arranged inside the O-ring housing
space 27. Each backup ring 29 is interposed between the adjacent
0-rings 28. In addition, an energizing spring 31 is arranged
between the backup ring 29 positioned at the end and a spring
receiving ring 30 arranged on the locking ring 26 side, the
energizing spring 31 for pushing the O-rings 28 and the backup
rings 29 against the receiving projection 25 side (to the advance
side of the push rod 8) . By the elastic force of the energizing

spring 31, each O-ring 28 is elastically deformed so as to be
crushed in the axis direction, the inner circumferential side
thereof is expanded, and the O-ring is bitten into and engaged
with the recess of the uneven surface 12 of the push rod 8. Thus,
the guide member 22 and the push rod 8 are connected to each
other to integrally move.
[0031]
Based on the above constitution, in Fig. 1, the
feed/discharge port 15 is in a state, where no pressurized air
is fed, the piston 7 is positioned at a stroke end, and the push
rod 8 is in a retreating state (non-operation position). In
addition, the guide member 22 is fixed to the outer
circumferential surface of the push rod 8 via the O-rings 28,
and the flange 23 thereof is brought into contact with the
regulating projection 20 by the returning spring 21.
[0032]
When pressurized air is fed to the feed/discharge 15 in
this state, the piston 7 moves leftward in Fig. 1, and the push
rod 8 moves leftward as shown by a chain line and pushes an
inputting part of the vehicle braking device (not shown) to
operate a brake. Since the returning spring 21 pushes the flange
23 of the guide member 22 when the pressurized air is discharged
from the feed/discharge 15, the push rod 8, with which the guide
member 22 is engaged, returns rightward in Fig. 1 and a brake
operation state is returned to a brake release state shown in

Fig. 1.
[0033]
On the other hand, if the brake block of the vehicle braking
device (not shown) wears down with long time use, a stroke of
the push rod 8 necessary for operating the brake is slowly
increased. When the push rod 8 advances at a large stroke and
the guide member 22 comes into contact with the spring receiving
projection 17, the spring receiving projection 17 applies a
large returning force to the guide member 22. Consequently,
the 0-rings 28 are deformed to get over the projections of the
uneven surface 12, and the push rod 8 is shifted (displaced)
in relation to the guide member 22 in accordance with the
remaining advancing strokes of the push rod 8. Since the wear
amount of the brake block for each brake operation is extremely
small, the displacement amount of the push rod for each brake
operation is also generally as small as an interval between the
projections of the uneven surface 12.
[0034]
Accordingly, when the brake is then released, the return
distance of the push rod 8 and the piston 7 is reduced (the
clearance distance on the vehicle braking device side is
reduced) by the displacement amount, and thus the vehicle
braking device can be operated at a constant stroke of the push
rod 8 from the next time. Fig. 3 shows an example of a brake
non-operation position in a state where the vehicle braking

device wears down by a considerable amount and the clearance
distance is adjusted by the clearance adjustment device 24.
Compared with the non-operation position shown in Fig. 1, it
is revealed that the push rod 8 and the piston 7 move to the
advancing side by a considerable distance.
[0035]
As described above, the clearance adjustment device 24 of
the brake cylinder 1 of the embodiment includes the push rod
8 and the guide member 22 which is attached to the push rod 8
and movable together with the push rod 8. The uneven surface
12 is provided in the outer circumferential surface of the push
rod 8, and the uneven surface 12 has recesses and projections
alternately arranged in the moving direction of the push rod
8. In addition, the O-ring housing space 27 for opening the
uneven surface 12 side is formed in the member 22, the O-rings
28 are arranged in the O-ring housing space 27, and the guide
member 22 and the; push rod 8 are connected to each other by
engagement of the O-rings 28 with the uneven surface 12. When
the clearance distance of the braking device becomes large, the
guide member 22 comes into contact with the projection 17 and
a large retuning force is applied to the guide member 22 from
the projection 17, the O-rings 28 are deformed to get over the
projections of the uneven surface 12, and thus the push rod 8
is displaced in relation to the guide member 22.
[0036]

Accordingly, the inner circumferential surfaces of the
O-rings 28 are deformed and engaged with (bitten into) the uneven
surface 12 of the push rod 8, and thus clearance adjustment for
the braking device can be securely performed and a frictional
force or connection force between the push rod 8 and the guide
member 22 can be stabilized. Thus, the compact brake cylinder
1 can be obtained which has a clearance adjusting function of
easily adjusting and controlling slide resistance.
[0037]
In addition, in the embodiment, since the O-rings 28 are
employed as elastic members in the embodiment, the each elastic
member of the embodiment is further easily engaged with (bitten
into) the recesses in comparison with an elastic member having,
for example, a rectangular cross section, and the frictional
force or connection force can be stabilized.
[0038]
In addition, in the embodiment, a plurality of O-rings 28
for being engaged with the uneven surface are provided.
Therefore, the frictional force or connection force between the
push rod 8 and the guide member 22 can be further stabilized.
[0039]
Furthermore, since the backup ring 29 is provided between
each of the plurality of O-rings 28, the each O-ring 28 is
prevented from entering the inside of the adjacent O-ring or
getting over the outside of the adjacent O-ring 28, and the push

rod 8 and the guide member 22 can be securely connected to each
other by the frictional force.
[0040]
Furthermore, in the embodiment, the energizing spring 31
which pushes the O-rings 28 to one side in the axis direction
is provided. Accordingly, even if a slight dimensional error
arises regarding, for example, the width of the 0-ring 28 or
a engagement position of the locking ring 26, the O-rings 28
are securely deformed by the energizing spring 31 so as to be
crushed in the axis direction, and thus the frictional force
or connection force between the push rod 8 and the guide member
22 can be stabilized.
[0041]
Next, a brake cylinder with a clearance adjustment device
of a second embodiment will be described with reference to Fig.
4 . In the second embodiment, the same symbols are, in principle,
attached to members the same as, or similar to the members of
the first embodiment, and description thereof will be omitted.
Fig. 4 is a cross sectional view of the brake cylinder provided
with the clearance adjustment device of the second embodiment
in a brake non-operating state, and Fig. 5 is an entire cross
sectional view of the brake cylinder being in the brake
non-operating state after clearance adjustment.
[0042]
In a brake cylinder 101, a base end of an outer cylinder

41 is fixed to the piston 7, which is arranged in the casing
4, via the flange plate 9 and the bolt 10. A head flange 42
is housed inside of the base end of the outer cylinder 41. A
taper-shaped narrowing part 43 is formed in an inner
circumferential surface at an axis end of the outer cylinder
41, and the taper-shaped narrowing part 43 allows an oblique
outer edge of the head flange 42 to be pushed to the top end
side (advancing side of the push rod 8) . In addition, a pushing
pin 44 is provided on the outer cylinder 41 so as to project
inward, and a tip of the pushing pin 44 is adapted to push the
head flange 42 to the base end side (retreating side of the push
rod 8). The pressurizing chamber 14 partition-formed by the
piston 7 communicates with the feed/discharge port 15 formed
on the cover 5 side.
[0043]
A base end of a shaft rod 45 is attached to the head flange
42, and a male screw 46 is engraved on an outer circumferential
surface of the shaft rod 45. In addition, the push rod 8 is
cylindrically formed, a female screw 47 is engraved on an inner
circumferential surface of a shaft hole of the push rod 8, and
the male screw 46 of the shaft rod 45 is screwed in the female
screw 47. Similar to the first embodiment, the uneven surface
12 is provided in the outer circumferential surface of the push
rod 8, and the surface 12 has recesses and projections
alternately arranged in the moving direction of the push rod

[0044]
Furthermore, the cylindrical guide member 22 is rotatably
supported outside of the shaft rod 45 via a thrust bearing 48.
The guide member 2:2 has a shaft hole with a stage, into which
the push rod 8 is inserted, and the 0-ring housing space 27 is
provided in a part which is formed in a large diameter shape
of the shaft hole. The 0-ring housing space 27 is formed between
a bottom part 49 (with a stage) of the large diametrical hole
and the locking ring 26 engaged with an opening of the large
diametrical hole, and the inside (a side of the push rod 8 which
faces the uneven surface 12) of the space 27 is opened.
[0045]
In the O-ring housing space 27, a plurality (four) of
O-rings 28 are arranged in the axis direction, and the backup
ring 29 is arranged at each end of the each O-ring 28 (between
the adjacent O-rings 28). The energizing spring 31 (shown in
Fig. 1) provided in the first embodiment is not provided in the
second embodiment. Instead, positions of the large diametrical
bottom 49 and the locking ring 26 are set in accordance with
the width of the each O-ring 28 so that the O-rings 28 are
elastically deformed so as to be slightly crushed in the axis
direction between the bottom 49 and the locking ring 26. Thus,
the O-rings 28 are expanded to the inner circumference side to
be engaged with the uneven surface 12 of the outer

circumferential surface of the push rod 8.
[0046]
A rotation-proof bolt 50 is tightened into the cover 5 of
the main body 3, and a tip thereof is inserted into a long hole
51 provided in the outer cylinder 41 and a long hole-shaped
groove 52 provided on the guide member 22. Thus, the outer
cylinder 41 and the guide member 22 are prevented from rotating.
[0047]
In addition, a regulating body 53 is projected from the
guide member 22 in a radius direction, and inserted into a long
hole 54 provided in the outer cylinder 41. On the other hand,
a stroke adjusting bolt 55 is tightened into the cover 5. When
the guide member 22 moves to the advancing side by a
predetermined stroke, the regulating body 53 comes into contact
with a tip of the stroke adjusting bolt 55, and over-movement
to the advancing side is regulated. The stroke adjusting bolt
55 is rotated so that a tip position thereof can be adjusted.
[0048]
The returning spring 21 for energizing the piston 7 in the
retreating direction is interposed between the cover 5 and the
piston 7. In addition, an energizing spring 56 is interposed
between the head flange 42 and the guide member 22.
[0049]
Based on the above constitution, when pressurized air is
fed to the feed/discharge port 15 from the non-operating state

shown in Fig. 4, the piston 7 is pushed, against the returning
spring 21, leftward in Fig. 4, and thus the outer cylinder 41
fixed to the piston 7 moves leftward. Then, the narrowing part
43 formed on the inner circumferential surface of the base end
of the outer cylinder 41 pushes the outer edge of the head flange
42, and thus the head flange 42 also moves leftward in Fig. 4
and the push rod 8 connected to the shaft rod 45 also moves
leftward. At this time, both the head flange 42 and the shaft
rod 45 do not rotate, but these are simply pushed by the outer
cylinder 41. The push rod 8 is thus pushed and advances leftward
in Fig. 4 (together with the outer cylinder 41 and the guide
member 22), and operates the vehicle braking device.
[0050]
When the pressurized air is then discharged from the
feed/discharge port 15, the piston 7 is pushed rightward in Fig.
4 by the returning spring 21, and thus the outer cylinder 41
is pulled rightward. Thus, the head flange 42 is pushed by the
pushing pin 44, and the shaft rod 45 and the push rod 8 connected
thereto are pulled rightward to retreat. Thus, the operating
state is returned to the non-operating state shown in Fig. 4.
[0051]
On the other hand, if the braking surface of the brake block
of the vehicle braking device (not shown) wears down with long
time use, the stroke of the push rod 8 necessary for operating
the brake is increased, and a stroke of the guide member 22

connected to the push rod 8 via the O-rings 28 is also increased.
When the stroke exceeds a stroke regulated by the stroke
adjusting bolt 55, the regulating body 53 comes into contact
with the tip of the stroke adjusting bolt 55, and thus a large
returning force is applied to the guide member 22 . Accordingly,
after the regulating body 53 comes into contact with the tip
of the stroke adjusting bolt 55, the O-rings 28 are deformed
and get over the projections of the uneven surface 12, and thus
the push rod 8 is shifted (displaced) , in the advancing direction,
in relation to the guide member 22 in accordance with the
remaining strokes of the push rod 8.
[0052]
When the pressurized air is then discharged from the
feed/discharge port 15 and the brake is released, the piston
7 is returned rightward in the figure by the returning spring
21, and the head flange 42 is pushed rightward by the pushing
pin 44 of the outer cylinder 41 pulled by the piston. Then,
the head flange 42 rotates together with the shaft rod 45, the
shaft rod 45 is pulled out from the push rod 8, and the
displacement of the push rod 8 in the advancing direction
relative to the guide member 22 is offset by the screw movement.
Consequently, when the piston 7 returns to the non-operating
position shown in Fig. 4, the push rod 8 projects in the advancing
direction by the displacement amount.
[0053]

The clearance of the vehicle braking device is thus
adjusted, and the vehicle braking device can be operated at a
constant stroke of the push rod 8 from the next time. Fig. 5
shows a brake non-operating position in a state where the vehicle
braking device wears down by a considerable amount and the
clearance distance is adjusted by the clearance adjustment
device 24. It is revealed that the push rod 8 moves to the top
end side by a considerable distance from the non-operating
position shown in Fig. 4.
[0054]
In addition, as is evident from a comparison of Fig. 5 and
Fig. 3, in comparison with the first embodiment, the position
of the piston 7 in the second embodiment is not changed even
if the vehicle braking device wears down. Accordingly, there
is an advantage that the pressurized air amount necessary for
operating the brake can be reduced even in the wear-down state
of the vehicle braking device.
[0055]
The preferred embodiments of the present invention have
been described above. However, the above constitutions can be
modified as follows, for example.
[0056]
In the first embodiment, an energizing spring 31 may be
omitted which energizes and compresses the O-rings 28 to one
side in the axis direction. In addition, in the second

embodiment, an energizing spring for energizing the O-rings 28
can be provided. In addition, the number of O-rings 28 can be
increased or decreased in both the embodiments.
[0057]
A backup ring 29 arranged between the adjacent O-rings 28
may be omitted. However, in terms of preventing the O-ring 28
from getting into or over the adjacent O-ring 28, it is
preferable to interpose the backup ring 29 therebetween

CLAIMS
1. A clearance adjustment device for a brake cylinder,
comprising:
a push rod; and
a guide member which is attached to the push rod and movable
together with the push rod,
wherein an uneven surface is provided in an outer surface
of the push rod, the uneven surface having recesses and
projections alternately arranged in a moving direction of the
push rod,
a space for opening the uneven surface side is formed in
the guide member and an elastic member is arranged in the space,
the elastic member is deformed and engaged with the uneven
surface so that the guide member and the push rod are connected
to each other, and
when a force exceeding a predetermined value is applied
to the guide member, the elastic member is deformed and get over
projections of the uneven surface, and thus the push rod is
displaced in relation to the guide member.
2. The clearance adjustment device for a brake cylinder
according to claim 1, wherein the elastic member is an O-ring.
3. The clearance adjustment device for a brake cylinder
according to claim 2, wherein a plurality of the O-rings are

provided which are engaged with the uneven surface.
4. The clearance adjustment device for a brake cylinder
according to claim 3, wherein a backup ring is interposed between
each of the plurality of O-rings.
5. The clearance adjustment device for a brake cylinder
according to claim 2 or 3, wherein an energizing spring for
pushing the O-rings to one side in an axis direction is provided
in the space.
6. A brake cylinder comprising the clearance adjustment
device for a brake: cylinder according to claim 1.

In a clearance adjustment device for a brake cylinder including a push rod for operating a vehicle braking device, and a guide member which is attached to the push rod and movable
together with the push rod, a frictional force (connection force) between the push rod and the guide member is stably obtained. An uneven surface 12 is provided in an outer surface of
a push rod 8, and the uneven surface 12 has recesses and projections alternately arranged in a moving direction of the rod 8. An O-ring housing space 27 for opening the uneven surface
12 side is formed in the guide member 22, and O-rings 28 are arranged in the space 27. The O-rings 28 are compressed in an axis direction to be engaged with the uneven surface 12, and
thus the guide member 22 and the push rod 8 are connected to each other. When a stroke of the push rod 8 is increased by wearing down of a brake and the guide member 22 comes into contact
with a projection 17, the O-rings 28 are deformed by a returning force applied to the guide member 22 so as to get over projections
of the uneven surface 12, the push rod 8 is displaced in relation to the guide member 22, and thus a clearance is adjusted.