DESCRIPTION UNITIZED BRAKE
TECHNICAL FIELD
[0001]
The present invention relates to a unitized brake.
BACKGROUND ART
[0002]
Heretofore, there has been known a unitized brake designed to drive a piston rod of a cylinder unit so as to swingingly move a brake lever to drive a brake shoe according to the swing movement, as disclosed in the following Patent Document 1. As shown in FIG. 8, in the unitized brake disclosed in this Document, a brake lever 101 is housed in a casing. The brake lever 101 has an intermediate portion which is swingably supported by a support shaft 102, and a top end which is pin-coupled to a distal end of a piston rod 106 of a cylinder unit 105. The cylinder unit 105 is provided with spring brake means and pneumatic brake means. The cylinder unit 105 is adapted to move the piston rod 106 forwardly or backwardly by an action of a spring force or a pneumatic pressure. Specifically, the cylinder unit 105 comprises a first cylinder 107 operable to drive the piston rod 106 by a pneumatic pressure, and a second cylinder 108 operable to drive the piston rod by a spring force. The cylinder unit 105 is further provided with a screw mechanism and clutch means 109 in order to make it possible to drive the piston rod 106 by any of the actions. The screw mechanism includes a multiple thread 106a provided in an outer peripheral surface of the piston rod 106, and a nut member 110 screwed with the multiple thread 106a. The clutch means 109 is used for switching between a rotatable mode and a retained mode of the nut member 110. For example, when the first cylinder 107 is actuated to move the piston rod 106 forwardly, the nut member 110 is in the rotatable mode to allow for a relative displacement of the piston rod 106 with respect to the second cylinder 108. Further, when the second cylinder 108 is actuated to move the piston rod 106 forwardly, the nut member 110 is locked by the clutch means 109. Thus, the piston rod 106 is moved while being coupled with the second cylinder 108. Then, when the piston rod 106 is moved forwardly or

backwardly, the brake lever 101 is swingingly moved, and a brake shoe is engaged with or disengaged from a wheel according to the swing movement.
[Patent Document 1] JP 2001-206213A [0003]
The unitized brake disclosed in the Patent Document 1 has the following problems. The distal end of the piston rod 106 and the top end of the brake lever 101 are pin-coupled together. Thus, during the forward or backward movement of the piston rod 106, the distal end of the piston rod 106 would receive a force in a direction perpendicular to an axial direction of the piston rod along with the swing movement of the brake lever 101. Consequently, during the forward or backward movement of the piston rod 106, the piston rod 106 receives a force causing a wobbling motion to give rise to a problem of an increase in resistance against driving of the piston rod 106. Moreover, the pin-connection between the distal end of the piston rod 106 and the top end of the brake lever 101 needs to be performed within the casing, that is, an operation for the pin-connection is performed through an opening formed in the casing, which gives rise to another problem that the operation becomes significantly vexatious and complicated.
DISCLOSURE OF THE INVENTION [0004]
It is therefore an object of the present invention to suppress a wobbling motion of a piston rod, while facilitating a reduction in time and effort for an assembling operation. [0005]
The present invention provides a unitized brake including: a cylinder unit having a piston rod; a brake lever adapted to be swingably moved about a support shaft according to a movement of the piston rod in an axial direction thereof; and a brake shoe holder adapted to be driven in conjunction with the brake lever. The unitized brake is characterized by comprising: a pair of wall portions provided in one of the piston rod and the brake lever and arranged in spaced-apart relation to each other in the axial direction of the piston rod; and an effort-point portion provided in a remaining one of the piston rod and the brake lever and disposed between the pair of wall portions, wherein the unitized brake is adapted, when either one of the wall portions is in

engagement with the effort-point portion according to the axial movement of the piston rod, to permit a relative displacement between the wall portion and the effort-point portion in a direction perpendicular to the axial direction, along with the swing movement of the brake lever.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006]
FIG. 1 is a sectional view showing an overall structure of a unitized brake according to one embodiment of the present invention.
FIG. 2A is a top view of a piston rod provided in the unitized brake in FIG. 1.
FIG. 2B is a side view of the piston rod.
FIG. 2C is a sectional view taken along the line IIc-IIc in FIG. 2B.
FIG. 2D is a perspective view partially showing the piston rod and a guide bar.
FIG. 3 is a sectional view of a brake lever, the piston rod and the guide bar which are provided in the unitized brake in FIG. 1.
FIG. 4 is a schematic diagram for explaining a piston rod and a brake lever which are provided in a unitized brake according to another embodiment of the present invention.
FIG. 5 is a schematic diagram for explaining a piston rod and a brake lever which are provided in a unitized brake according to yet another embodiment of the present invention.
FIG. 6 is a schematic diagram for explaining a piston rod and a brake lever which are provided in a unitized brake according to still another embodiment of the present invention.
FIGS. 7A and 7B are schematic diagrams for explaining a piston rod and a brake lever which are provided in a unitized brake according to yet still another embodiment of the present invention.
FIG. 8 is a sectional view of a conventional unitized brake.
BEST MODE FOR CARRYING OUT THE INVENTION
[0007]
With reference to the drawings, the best mode for carrying out the invention will now be specifically described. [0008]

FIG. 1 shows a unitized brake according to one embodiment of the present invention. The unitized brake 10 according to this embodiment is designed as brake equipment for railroad
vehicles. The unitized brake 10 comprises a casing 12 formed as a cast product having a
hollow structure. The casing 12 is formed with a fastening hole 14, and a bolt (not shown) can
be inserted into the fastening hole 14 to allow the casing 12 to be fixed to an carriage of a
railroad vehicle.
[0009]
A brake lever 18 is housed in the casing 12. The brake lever 18 is formed as a cast product,
and swingably supported by a support shaft 20 installed inside the casing 12 in a bridged manner.
More specifically, the brake lever 18 is installed in a posture extending in an upward-downward
direction.
[0010]
The support shaft 20 is disposed to an intermediate portion of the brake lever 18. The
brake lever 18 has an upper portion which is located above the support shaft 20 and formed as an
arm section 22, and a lower portion which is located below the support shaft 20 and formed with
a bearing hole 24.
[0011]
A spherical bearing 26 is fitted in the bearing hole 24. A sleeve rod 28 is fixed to an inner
race of the spherical bearing 26. The sleeve rod 28 is formed in a cylindrical shape, and an
inner peripheral surface thereof is formed with an internal thread. A pushrod 30 is screwed with the internal thread of the sleeve rod 28. This serves as a means capable of adjusting a protruding distance of the pushrod 30 relative to the sleeve rod 28. [0012]
The casing 12 is formed with a first upper opening 35, a second upper opening 36, and a lower opening 37. The first upper opening 35 is formed in an upper portion of a wheel-side sidewall 12a (sidewall on a left side in FIG. 1) of the casing 12. A cylinder unit 41 is attached to cover the first upper opening 35. The cylinder unit 41 comprises a piston rod 43. The cylinder unit 41 is operable to move the piston rod 43 in an axial direction of the piston rod 43 to swingingly move the brake lever 18. Details of the cylinder unit 41 will be described later. [0013]

The second upper opening 36 is formed in a top wall of the casing 12. The lower opening is formed in a lower portion of the wheel-side sidewall 12a. The pushrod 30 is disposed to protrude toward a wheel through the lower opening 37, and a brake shoe holder 45 is provided at a tip end of the pushrod 30. The brake shoe holder 45 is adapted to be moved forwardly and backwardly through the sleeve rod 28 and the pushrod 30 according to the swing movement of the brake lever 18. A brake shoe (not shown) is attached on the side of a front surface of the brake shoe holder 45. The brake shoe is adapted to apply a braking force to a wheel (not shown) of a railroad vehicle according to the swing movement of the brake lever 18. [0014]
The cylinder unit 41 includes a first cylinder 47 adapted to be actuated by a fluid pressure, such as compressed air, and a second cylinder 48 adapted to be actuated by a spring force. The first cylinder 47 is used for allowing the unitized brake 10 to function, for example, as a regular brake. The second cylinder 48 is used for allowing the unitized brake 10 to function, for example, as a parking brake. The two cylinders 47, 48 are configured to drive the common piston rod 43. This configuration will be specifically described below. [0015]
The first cylinder 47 comprises a first piston 47a connected to a base end of the piston rod 43, and a bottomed tubular-shaped first cylinder body 47b slidably receiving therein the first piston 47a. A cylinder packing made of an elastically deformable material, such as rubber, is attached to the first piston 47a. The first cylinder body 47b is provided with a first port 47c for selectively supplying and discharging a working fluid therethrough. A first actuation chamber 47d communicating with the first port 47c is defined inside the first cylinder body 47b. In response to a given braking operation, a working fluid, such as compressed air, is supplied to the first actuation chamber 47d. [0016]
The second cylinder 48 comprises a second piston 48a adapted to be movable in the axial direction of the piston rod 43 which penetrates therethrough, and a second cylinder body 48b slidably receiving therein the second piston 48a. The second cylinder body 48b has a drum portion 48c disposed outside an outer peripheral surface of a drum portion 47e of the first cylinder body 47b. The second piston 48a is adapted to be contactable with an edge of the

drum portion 47e of the first cylinder body 47b. A second actuation chamber 48d is defined between the second piston 48a and the wheel-side sidewall 12a of the casing 12, in such a manner as to allow a working fluid, such as compressed air, to be selectively supplied and discharged thereto and therefrom through a second port (not shown). Further, a spring member 48e is installed on an opposite side of the second actuation chamber 48d with respect to the second piston 48a. The spring member 48e is disposed between the drum portion 47e of the first cylinder body 47b and the drum portion 48c of the second cylinder body 48b, and pressedly compressed by a fluid pressure received in the second actuation chamber 48d. In a normal state, the working fluid is introduced into the second actuation chamber 48d, so that the spring member 48e is pressedly compressed. Then, in response to a given braking operation, the working fluid in the second actuation chamber 48d is discharged, so that the piston rod 43 is moved in a rightward direction in FIG. 1 (braking direction) by a spring force of the spring member 48e. [0017]
Further, a return spring member 47f is installed between the first piston 47a and the second piston 48a. The return spring member 47f presses the first piston 47a in a direction causing the first actuation chamber 47d to contract. When the working fluid is introduced into the first actuation chamber 47d, the return spring member 47f is pressedly compressed by the fluid pressure of the working fluid. In the normal state, no working fluid is introduced into the first actuation chamber 47d, so that the piston rod 43 is biased in a leftward direction in FIG. 1 (releasing direction) by a spring force of the return spring member 47f. Then, when the working fluid is introduced into the first actuation chamber 47d in response to the given braking operation, the piston rod 43 is moved in the braking direction. Subsequently, when the working fluid is discharged from the first actuation chamber 47d in response to a given brake-releasing operation, the piston rod 43 is returned to an initial position by the spring force of the return spring member 47f. [0018]
The piston rod 43 is disposed to extend in an approximately horizontal direction. The piston rod 43 includes a threaded section 51 which has a multiple thread formed in an outer peripheral surface thereof, and an extension section 52 extending from an edge of the threaded section 51 in the axial direction.

[0019]
The threaded section 51 is screwed with a nut member 54. The nut member 54 is inserted
into a through-hole formed in the second piston 48a, and rotatably supported by the second
piston 48a. The piston rod 43 is disposed to penetrate through the nut member 54.
[0020]
The cylinder unit 41 is provided with a clutch device 56 adapted to switch between a
rotatable mode and a retained mode of the nut member 54. The clutch device 56 is operable,
during driving of the first cylinder 47, to permit a rotation of the nut member 54, and, during
driving of the second cylinder 48, to lock the nut member 54.
[0021]
The clutch device 56 includes teeth arranged on an end surface thereof and adapted to be meshable with external teeth 54a provided on the nut member 54. In the normal state, the clutch device 56 is non-rotatably retained by an after-mentioned lock lever 59. [0022]
The clutch device 56 is located in a position toward a direction, with respect to the nut member 54, which the second piston 48e is biased by the spring member 48e. When the spring member 48e of the second piston 48a is pressedly compressed, the nut member 54 is spaced apart from the clutch device 56, and therefore the rotation of the nut member 54 is permitted. On the other hand, when the spring member 48e is stretched, the external teeth 54a of the nut member 54 are meshed with the teeth of the clutch device 56, so that the nut member 54 is non-rotatably retained. [0023]
The cylinder unit 41 is provided with a lock lever 59 which is adapted to allow the clutch device 56 to be switchably set to a lock state and an unlock state. The clutch device 56 has latch teeth provided in an outer peripheral surface thereof, and the lock lever 59 has a lock tooth 59a provided at an inner end thereof and adapted to be engageable with the latch tooth. The lock lever 59 is biased in a direction causing the lock tooth 59a to be engaged with the latch tooth by a biasing member 60. When the engagement between the latch tooth and the lock tooth 59a is released by pulling the lock lever 59 upwardly, the clutch device 56 becomes rotatable. The reason why the clutch device 56 has the structure capable of releasing the lock

state is to allow a spring-based brake to be manually released in case where the working fluid in the second actuation chamber 48d is discharged for some reason, and thereby the spring member 48e of the second cylinder 48 is stretched (in case where the spring-based brake is activated).
[0024]
The piston rod 43 is disposed to penetrate through the first upper opening 35 in such a manner that the extension section 52 is located inside the casing 12. As shown in FIGS. 2A to 2D, the piston rod 43 has an insertion hole 43a formed to extend over a range from a distal end of the extension section 52 to an intermediate position of the threaded section 51, and the extension section 52 is formed in a tubular shape. Each of the threaded section 51 and the extension section 52 is formed using a member having a circular shape in cross-section. [0025]
The extension section 52 includes a region formed by cutting out an outer peripheral wall thereof by a given distance in the axial direction. In the extension section 52, regions on both sides of the cutout serve as a pair of wall portions 61, 62 which is located in spaced-apart relation to each other in the axial direction of the piston rod 43. Further, a region having the cutout serves as a connection portion 63 which mutually connects the wall portions 61, 62. The connection portion 63 may be formed by partially removing the piston rod 43, for example, through cutting, after casting the piston rod 43, or may be simultaneously formed during casting of the piston rod 43. [0026]
One of the wall portions (first wall portion 61) has a contact surface adapted to come into contact with the brake lever 18 when the piston rod 43 is moved forwardly. The other wall portion (second wall portion) 62 has a contact surface adapted to come into contact with the brake lever 18 when the piston rod 43 is moved backwardly. Each of the two contact surfaces extends in a direction perpendicular to the axial direction of the piston rod 43. Further, a distance between the two contact surfaces is slightly greater than a size of an after-mentioned effort-point portion 65. This means that a space is defined between the two wall portions 61, 62, to allow the effort-point portion 65 to be inserted thereinto. [0027]

The connection portion 63 is formed to have a pair of flat surfaces 63a each serving as a side surface thereof. The two flat surfaces 63a are located in symmetrical relation with respect to an axis of the piston rod 43, and each of the flat surfaces 63a is formed as an approximately vertical surface parallel to the axis. The insertion hole 43a is opened in the connection portion 63. Specifically, a distance between the two flat surfaces 63a of the connection portion 63 (width or thickness of the connection portion 63) is less than a diameter of the insertion hole 43a, and therefore the insertion hole 43a is opened in each of the side surfaces of the connection portion 43a in such a manner as to separate each of the flat surfaces 63a into upper and lower regions. [0028]
The insertion hole 43a is formed to have a region increased in diameter, and a wear ring 43b is fitted in this large diameter region. [0029]
As shown in FIG. 3, the brake lever 18 is provided with an effort-point portion 65 in an upper end (tip end) thereof, i.e., in an upper end (tip end) of the arm section 22. The effort-point portion 65 is a region which receives a force from the piston rod 43 along with driving of the piston rod 43. The effort-point portion 65 is inserted between the wall portions 61, 62 of the piston rod 43 (see FIG. 1). The effort-point portion 65 has a pair of branch sub-portions 67, 67 formed by branching the arm section 22 into two regions. The two branch sub-portions 67, 67 are disposed in spaced-apart relation to each other by a distance sufficiently greater than the width of the connection portion 63 of the piston rod 43. [0030]
Each of the branch sub-portions 67, 67 is formed with a pin hole, and bearing pins 69 are inserted into the pin hole respectively. The bearing pin 69 protrudes inwardly from a corresponding one of the branch sub-portions 67, 67, and a roller bearing 70 is fitted on the protruding portion of the bearing pin 69. The roller bearing 70 has an outer diameter slightly less than the distance between the wall portions 61, 62 of the piston rod 43. The bearing pin 69 is provided as a means for reducing a sliding resistance between the brake lever 18 and an after-mentioned guide bar 72. The roller bearing 70 is provided as a means for reducing a sliding resistance between the brake lever 18 and the piston rod 43 (wall portions 61, 62).

[0031]
An inward surface of the roller bearing 70 is approximately flush with an inward surface of
the bearing pin 69. The connection portion 63 is disposed between the bearing pins 69. In
other words, the connection portion 63 is sandwiched between the pair of branch sub-portions 67,
67.
[0032]
A small gap is defined between each of the inward surfaces of the roller bearing 70 and the
bearing pin 69, and a corresponding one of the side surfaces 63 a of the connection portion 63.
The insertion hole 43a is opened in each of the side surfaces 63 a of the connection portion 63. Thus, the insertion hole 43a communicates with an outer space through the gap. Further, each of the flat-shaped side surfaces 63a of the connection portion 63 is located in adjacent relation to the inward surfaces of corresponding ones of the roller bearings 70 and the bearing pins 69. Thus, even if the piston rod 43 receives a force causing a rotation about the axis thereof, such a rotation will be stopped by the roller bearings 70 and the bearing pins 69a. [0033]
A guide bar 72 is inserted into the insertion hole 43a of the piston rod 43. The guide bar 72 is fixed to a side wall of the casing 12 on an opposite side of the wheel, through a base end thereof, and disposed in coaxial relation to the piston rod 43. Thus, when the piston rod 43 is moved in the axial direction, it is moved along the guide bar 72. During this movement, the aforementioned wear ring 43a functions as a slider relative to the guide bar 72. [0034]
The guide bar 72 is prepared by cutting a cross-sectionally circular-shaped member to form flat-shaped side surfaces thereon. Thus, the guide bar 72 is formed with a pair of flat-surface portions 72a. When the guide bar 72 is inserted into the insertion hole 43a of the piston rod 43, the flat-surface portions 72a become flush with the respective side surfaces 63a of the connection portion 63 of the piston rod. Therefore, even during the axial movement of the piston rod 43, the flat-surface portions 72a never interfere with the roller bearings 70 and the bearing pins 69. [0035]
In an operation of assembling the piston rod 43 and the brake lever 18, the guide bar 72 is first fixed inside the casing 12, and then the cylinder unit 41 is assembled to the casing 12. In

this process, the guide bar 72 is inserted into the insertion hole 43a of the piston rod 43 of the cylinder unit 41. Then, the brake lever 18 is assembled to the casing 18. In this process, the brake lever 18 is assembled to the piston rod 43 from therebelow to allow the effort-point portion 65 to be inserted between the wall portions 61, 62 of the piston rod 43. Although this assembling operation is performed through the second upper opening 36 of the casing 12, it can be completed by simply fitting the effort-point portion 65 of the brake lever 18 into the space between the wall portions 61, 62. Thus, even in the operation through the second upper opening 36, a risk that the operation becomes vexatious and complicated can be reduced. Specifically, the space between the pair of wall portions 61, 62 is opened downwardly, and therefore what is needed is to simply insert the effort-point portion 65 into the space from therebelow. [0036]
An operation of the unitized brake according to this embodiment will be described below. In a normal state, in the cylinder unit 41, no working fluid is supplied to the first actuation chamber 47b, and the working fluid is filled in the second actuation chamber 48d, so that the piston rod 43 is positioned on a left side in FIG. 1. Then, in response to a given braking operation, the working fluid is supplied to the first actuation chamber 47b to push the first piston 47a, or the working fluid in the second actuation chamber 48d is discharged to allow the spring force of the spring member 48e to push the second piston 48a. Consequently, the piston rod 43 is moved toward a right side in FIG. 2 (forwardly), while being guided by the guide bar 72. Then, the first wall portion 61, i.e., one of the pair of wall portions 61, 62 of the piston rod 43 on the side of the threaded section 51, pushes the effort-force portion 65 of the brake lever 18 to swingingly move the brake lever 18 about the support shaft 20. During the swing movement, the brake lever 18 is permitted to be displaced in a direction perpendicular to the movement direction of the piston rod 43. In other words, along with the axial movement of the piston rod 43, the brake lever 18 is displaceable in an upward-downward direction along the first wall portion 61. Thus, the piston rod 43 is linearly moved, while permitting an arc movement of the brake lever 18. [0037]
When the brake lever 18 is swingingly moved toward a right side in FIG. 1, the pushrod 30

is moved forwardly, i.e., toward the left side in FIG. 1, through the sleeve rod 28, in conjunction with the swing movement. Consequently, the brake shoe is pressed against a tread of a wheel (not shown) to apply a braking force to the wheel (not shown) of the railroad vehicle. [0038]
Then, in response to a given brake-releasing operation, the working fluid in the first actuation chamber 47d is discharged to allow the spring force of the return spring member 47f to move the first piston 47a toward the left side in FIG. 1, so that the piston rod 43 is moved backwardly, or the working fluid is supplied to the second actuation chamber 48d to move the second piston 48a toward the left side in FIG. 1, so that the piston rod 43 is moved backwardly. In either case, the pushrod 30 is moved backwardly, so that the brake shoe is moved away from the wheel to release a braking force. [0039]
As described above, in this embodiment, the effort-point portion 65 is engaged with either one of the wall portions 61, 62 according to the axial movement of the piston rod 43, and the brake lever 18 is swingingly moved by a force received from the piston rod 43. During the swing movement, a relative displacement between the wall portion (61, 62) and the effort-point portion 65 is permitted in a direction perpendicular to the axial direction. Thus, even though the piston rod 43 receives a force from the brake lever 18 in the direction perpendicular to the axial direction along with the swing movement of the brake lever 18, a load caused by the force can be relieved. This makes it possible to suppress a wobbling motion of the piston rod 43 during the forward or backward movement thereof. In addition, the effort-point portion 65 is disposed between the pair of wall portions 61, 62 to allow the brake lever 18 to be moved in conjunction with the piston rod 43. This eliminates a need for pin-connecting the piston rod 43 and the brake lever 18 as in conventional unitized brakes. Thus, in an assembling operation for the unitized brake 10, the effort-point portion 65 is simply inserted into the space between the pair of wall portions 61, 62. This makes it possible to reduce vexatiousness and complication in the assembling operation for the unitized brake 10. [0040]
In this embodiment, the wall portions 61, 62 are provided in the piston rod 43, and the effort-point portion 65 is provided in the brake lever 18. This makes it possible to suppress

structural complexity of the brake lever 18. [0041]
In this embodiment, the effort-point portion 65 is formed to have the pair of branch sub-portions 67, 67 branched in such a manner as to sandwich the connection portion 63 therebetween. Thus, the branch sub-portions 67, 67 are disposed on respective ones of both sides of the connection portion 63, so that a force of the piston rod 43 can be transmitted to the brake lever 18 in a balanced manner. In addition, the piston rod 43 and the brake lever 18 can be assembled together by simply inserting the effort-point portion 65 into the space between the pair of wall portions 61, 62 of the piston rod 43 in such a manner as to sandwich the connection portion 63 between the pair of branch sub-portions 67, 67. Thus, in combination with the structure where the pair of wall portions 61, 62 are mutually connected by the connection portion 63, time and effort for the assembling operation can be reduced. [0042]
In this embodiment, the connection portion 63 is formed to have the pair of flat-shaped side surfaces 63a contactable with respective ones of the branch sub-portions 67, 67. Thus, even if the piston rod 43 receives a force causing a rotation about the axis thereof, the side surfaces 63a come into contact with the respective ones of the branch sub-portions 67, 67 to prevent the rotation of the piston rod 43 about the axis. [0043]
In this embodiment, the guide bar 72 fixed inside the casing 12 is inserted into the insertion hole 43 of the piston rod 43. Thus, even if the piston rod 43 receives a frictional force with the brake lever 18 which causes a wobbling motion of the piston rod 43, the guide bar 72 prevents such a wobbling motion. This makes it possible to prevent vibration of the piston rod 43 to effectively reduce a sliding resistance of the piston rod 43 relative to the nut member 54. [0044]
In this embodiment, the insertion hole 43a is opened in the side surfaces 63a of the connection portion 63 of the piston rod 43. Thus, during the forward or backward movement of the piston rod 43, air can be supplied into the insertion hole 43a or discharged from inside the insertion hole 43a. This makes it possible to reduce a difference between respective characteristics during an operation of applying a braking force and during an operation of

reducing the braking force. [0045]
In this embodiment, when the nut member 54 in the rotatable mode, a relative position of the piston rod 43 with respect to the piston 48a of the second cylinder 48 is changed according to a rotation of the nut member 54. Thus, the piston rod 43 can be moved in the axial direction while locking the second piston 48a. Further, the piston rod 43 can be moved together the second piston 48a by non-rotatably retaining the nut member 54. Thus, this embodiment is compatible with a dual braking system. [0046]
It is understood that the present invention is not limited to the above embodiment, but various changes and modifications may be made therein without departing from the spirit and scope of the present invention. For example, although the above embodiment has been described based on the structure where the cylinder unit 41 comprises the first cylinder 47 and the second cylinder 48, the present invention is not limited thereto, but the cylinder unit may be provided with only the first cylinder 47. [0047]
Further, although the above embodiment has been described based on the structure provided with the guide bar 72, the guide bar 72 may be omitted. [0048]
For example, in a structure where the guide bar 72 is omitted, the extension section 52 of the piston rod 43 may comprise a pushing portion 52a and a hook member 52b, as shown in FIG. 4. This structure will be specifically described below. The pushing portion 52a is disposed in coaxial relation to the threaded section 51 to extend linearly from the threaded section 51. Although the hook member 52b is also provided to extend from the threaded section 51, it extends to reach an opposite side of the brake lever 18 while passing around the top end (effort-point portion 65) of the brake lever 18. A distal end of the pushing portion 52a makes up a first wall portion 61, and a distal end of the hook member 52 makes up a second wall portion 62. The effort-point portion 65 is disposed between the two wall portions 61, 62. The first wall portion 61 is operable, when the piston rod 43 is moved forwardly, to push the effort-point portion 65. The second wall portion 62 is operable, when the piston rod 43 is

moved backwardly, to push the effort-point portion 65. The hook member 52b has an intermediate portion formed in a curved shape to avoid interference with the effort-point portion 65 even if the effort-point portion 65 is moved upwardly during a swing movement of the brake lever 18. Further, a tubular-shaped guide member 75 is fitted on the piston rod 43. The guide member 75 is disposed to come into contact with the casing 12 to prevent the piston rod 43 from vibrating by a force received from the brake lever 18 during the swing movement of the brake lever 18. [0049]
In the above embodiment, the effort-point portion 65 is made up of a plurality of elements including the roller bearings 70 provided in the top end of the brake lever 18. Alternatively, as shown in FIG. 5, the effort-point portion 65 may consist only of a bearing pin 77 provided in a top end of the brake lever 18. Specifically, the top end of the brake lever 18 is formed in a cylindrical shape having a pin hole, and the bearing pin 77 is inserted into the pin hole. Further, the extension section 52 of the piston rod 43 is provided with a hook member 78 which is formed in a shape covering the top end of the brake lever 18 from thereabove. The hook member 78 has a cutout 79 formed to define a pair of wall portions 61, 62 which sandwich the bearing pin 77 therebetween. The cutout 79 is also formed in a shape which allows the hook member 78 to avoid interference with the bearing pin 77 even if the bearing pin 77 is moved upwardly during a swing movement of the brake lever 18. [0050]
Although the structure in the above embodiment comprises the pair of wall portions 61, 62 provided in the piston rod 43, and the effort-point portion 65 provided in the brake lever 18, the present invention is not limited thereto. For example, a structure as shown in FIG. 6 may be employed. In this structure, the extension section 52 of the piston rod 43 is formed with a pin hole, and a bearing pin 81 is inserted into the pin hole in such a manner as to protrude laterally from the extension section 52. The bearing pin 81 serves as the effort-point portion 65. Further, the brake lever 18 has a hook portion 82 formed to extend from the top end thereof toward the threaded section 51. The hook portion 82 has a cutout 82a formed to have an open lower end, and the bearing pin 81 is disposed within the cutout 82a. In the hook portion 82, regions on both sides of the cutout 82a serve as a pair of wall portions 61, 62. In this structure,

during a swing movement of the brake lever 18, the pair of wall portions 61, 62 themselves are moved upwardly and downwardly. Thus, the cutout 82a is formed in a shape capable of preventing the bearing pin 81 from getting out of the cutout 82a even during the upward or downward movement of the hook portion 82. [0051]
In the structure illustrated in FIG. 6, the hook portion 82 is integrally formed with the brake lever 18. In contrast, a structure illustrated in FIGS. 7A and 7B, a hook member 84 as a separate component is attached to a top end of the brake lever 18. A pair of the hook members 84 is disposed to sandwich therebetween a roller bearing 70 provided on the top end of the brake lever 18. Further, the top end of the brake lever 18 is formed as a pair of branch sub-portions 67, 67, and each of the hook members 82 is disposed between the branch sub-portions 67, 67. The roller bearing 70 is disposed between the hook members 82. During the forward movement of the piston rod 43, the roller bearing 70 is pushed by a distal edge of the extension section 52. Further, during the backward movement of the piston rod 43, the bearing pin 81 penetrating though the extension section 52 is engaged with the hook member 84. Thus, the distal edge of the extension section 52 and the hook members 84 serve as a pair of wall portions 61, 62. In this structure, the branch sub-portions 67, 67 of the brake lever 18 extends toward the threaded section 51 to reach a position capable of sandwiching the extension section 52 therebetween. Thus, the branch sub-portions 67, 67 of the brake lever 18 also serve as a means to prevent a rotation of the piston rod 43.
[SUMMARY OF EMBODIMENTS]
A summary of the above embodiments will be described below. [0052]
(1) In the above embodiments, either one of a pair of wall portions is engaged with an effort-point portion according to a movement of a piston rod in an axial direction thereof, and a brake lever is swingingly moved by a force received from the piston rod. During the swing movement, a relative displacement between the wall portion and the effort-point portion in a direction perpendicular to the axial direction is permitted. Thus, even though the piston rod receives a force from the brake lever in the direction perpendicular to the axial direction along

with the swing movement of the brake lever, the force can be relieved. This makes it possible to suppress a wobbling motion of the piston rod with would otherwise be caused by such a force during a forward or backward movement thereof. In addition, the effort-point portion is disposed between the pair of wall portions to allow the brake lever to be moved in conjunction with the piston rod. This eliminates a need for pin-connecting the piston rod and the brake lever as in conventional unitized brakes. Thus, in an assembling operation for a unitized brake, the effort-point portion is simply inserted into a space between the pair of wall portions. This makes it possible to reduce vexatiousness and complication in the assembling operation for the unitized brake. [0053]
(2) The pair of wall portions may be provided in the piston rod, and the effort-point
portion may be provided in the brake lever. This embodiment makes it possible to suppress
structural complexity of the brake lever.
[0054]
(3) Preferably, in the above embodiment, a connection portion is provided between the
pair of wall portions to mutually connect the pair of wall portions, wherein the effort-point
portion has a pair of branch sub-portions branched in such a manner as to sandwich the
connection portion therebetween. In this embodiment, the branch sub-portions are disposed on
respective ones of both sides of the connection portion, so that a force of the piston rod can be
transmitted to the brake lever in a balanced manner. In addition, the piston rod and the brake
lever can be assembled together by simply inserting the effort-point portion into the space
between the pair of wall portions of the piston rod in such a manner as to sandwich the
connection portion between the pair of branch sub-portions. Thus, in combination with the
structure where the pair of wall portions are mutually connected by the connection portion, time
and effort for the assembling operation can be reduced.
[0055]
(4) When the cylinder unit includes a cylinder body, a piston installed in the cylinder body
slidably relative to the cylinder body in the axial direction of the piston rod, and a nut member
rotatably supported relative to the piston, wherein the piston rod includes a threaded section
which has a multiple thread formed in an outer peripheral surface thereof and screwed with the

nut member, and an extension section formed to extend from an edge of the threaded section in the axial direction and provided with the pair of wall portions, the connection portion is preferably formed to have a pair of flat surfaces which allow respective ones of the pair of branch sub-portions to come into contact therewith. In this embodiment, even if the piston rod receives a force causing a rotation about an axis thereof, the flat surfaces of the connection portion come into contact with respective ones of the branch sub-portions to prevent the rotation of the piston rod about the axis. This allows the branch sub-portions and the connection portion to function as a means to prevent a rotation of the piston rod. [0056]
(5) The cylinder unit may include a first cylinder operable to drive the piston rod by a
fluid pressure, and a second cylinder operable to drive the piston rod by a spring force, wherein
the nut member may be rotatably supported relative to a piston of the second cylinder, and the
unitized brake may be provided with a clutch device adapted to switching between a rotatable
mode and a retained mode of the nut member. In this embodiment, when the nut member in the
rotatable mode, a relative position of the piston rod with respect to the piston of the second
cylinder is changed according to a rotation of the nut member. Thus, the piston rod can be
moved in the axial direction while locking the piston of the second cylinder. Further, the piston
rod can be moved together the piston of the second cylinder by non-rotatably retaining the nut
member. Thus, this embodiment is compatible with a dual braking system.
[0057]
(6) The piston rod may have an insertion hole formed therein to extend in the axial
direction, wherein the unitized brake includes a guide bar inserted into the insertion hole while
being supported by a casing of the unitized brake. In this embodiment, even if the piston rod
receives a frictional force with the brake lever which causes a wobbling motion of the piston rod,
the guide bar suppresses such a wobbling motion. This makes it possible to prevent vibration
of the piston rod.
[0058]
(7) Preferably, the insertion hole is opened in a surface of a tubular portion of the piston
rod. In this embodiment, during the forward or backward movement of the piston rod, air can
be supplied into the insertion hole or discharged from inside the insertion hole. This makes it

possible to reduce a difference between respective characteristics during an operation of
applying a braking force and during an operation of reducing the braking force.
[0059]
As described above, the above embodiments make it possible to suppress a wobbling motion of the piston rod, while facilitating a reduction in time and effort for the assembling operation.

CLAIMS
1. A unitized brake including: a cylinder unit having a piston rod; a brake lever adapted to be swingably moved about a support shaft according to a movement of the piston rod in an axial direction thereof; and a brake shoe holder adapted to be driven in conjunction with the brake lever, the unitized brake being characterized by comprising:
a pair of wall portions provided in one of the piston rod and the brake lever and arranged in spaced-apart relation to each other in the axial direction of the piston rod; and
an effort-point portion provided in a remaining one of the piston rod and the brake lever and disposed between the pair of wall portions,
wherein the unitized brake is adapted, when either one of the wall portions is in engagement with the effort-point portion according to the axial movement of the piston rod, to permit a relative displacement between the wall portion and the effort-point portion in a direction perpendicular to the axial direction, along with the swing movement of the brake lever.
2. The unitized brake as defined in claim 1, wherein:
the pair of wall portions are provided in the piston rod; and the effort-point portion is provided in the brake lever.
3. The unitized brake as defined in claim 2, which includes a connection portion provided between the pair of wall portions to mutually connect the pair of wall portions, wherein the effort-point portion has a pair of branch sub-portions branched in such a manner as to sandwich the connection portion therebetween.
4. The unitized brake as defined in claim 3, wherein the cylinder unit includes: a cylinder body; a piston installed in the cylinder body slidably relative to the cylinder body in the axial direction of the piston rod; and a nut member rotatably supported relative to the piston, wherein:
the piston rod includes a threaded section which has a multiple thread formed in an outer peripheral surface thereof and screwed with the nut member, and an extension section formed to extend from an edge of the threaded section in the axial direction and provided with the pair of

wall portions; and
the connection portion is formed to have a pair of flat surfaces which allow respective ones of the pair of branch sub-portions to come into contact therewith.
5. The unitized brake as defined in claim 4, wherein the cylinder unit includes a first cylinder
operable to drive the piston rod by a fluid pressure, and a second cylinder operable to drive the
piston rod by a spring force, wherein:
the nut member is rotatably supported relative to a piston of the second cylinder; and the unitized brake is provided with a clutch device adapted to switching between a rotatable mode and a retained mode of the nut member.
6. The unitized brake as defined in any one of claims 1 to 5, wherein the piston rod has an insertion hole formed therein to extend in the axial direction, wherein the unitized brake includes a guide bar inserted into the insertion hole while being supported by a casing of the unitized brake.
7. The unitized brake as defined in claim 6, wherein the insertion hole is opened in a surface of a tubular portion of the piston rod.

[PROBLEMS] A unit brake in which rocking of a piston rod is suppressed and which can be assembled with reduced labor. [MEANS FOR SOLVING PROBLEMS] The unit brake has a pair of wall sections (61,62) arranged on the piston rod (43) so as to be spaced from each other in the direction of the axis of the piston rod (43), and also has a power point section (65) provided on a brake lever (18), between the pair of wall sections (61, 62). With either one of the wall sections (61, 62) and the power point section (65) engaged with each other by axial movement of the piston rod (43), relative movement that occurs between the wall section (61, 62) and the power point section (65) in the direction perpendicular to the axial direction and is caused by rocking of the brake lever (18) is permitted.