JPH0535769B2 - - Google Patents

Abstract

PURPOSE:To facilitate lay-out of parts shifted to the central part of a backing plate by using a piston as a reaction force transmitting member when a parking lever is operated. CONSTITUTION:A pair of pistons 5a, 5b are incorporated in a wheel cylinder 5, and a push rod 8 is disposed between the inner end portions of both pistons 5a, 5b. A lever member 6b is clamped between the outer end portion of one piston 5a and a brake shoe 2, and the middle portion of the lever member 6b is fixed to the forward end of a shaft of a parking lever 6. When the parking lever 6 is turned, the lever member 6b is turned, so that one end portion of the lever member 6b moves one brake shoe 2, and the other end portion of the lever member 6b transmits reaction force to the other brake shoe 3 to be moved through one piston 5a, the push rod 8 and the other piston 5b.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a parking device for an LT (leading trailing) brake.

(Prior Art) A conventional LT brake parking device will be explained based on FIG. 5.

1 is a bucking plate, 2 and 3 are respective brake shoes, 4 is an anchor that supports one end of both brake shoes 2 and 3, and 5 is a pair interposed between the other ends of both brake shoes 2 and 3. It is a double-acting wheel cylinder having a piston of 1, and by introducing pressure oil, the other ends of both brake shoes 2 and 3 are expanded, and both brake shoes 2 and 3 are connected to the inner periphery of the drum 12. It slides into contact with the surface and operates as a regular brake. Reference numeral 16 denotes a parking lever, which is pivotally supported by a pin 3a fixed to the other brake shoe 3. Reference numeral 10 denotes a strut, which is located closer to the center of the bucking plate 1 than the wheel cylinder 5. One end engages the other brake shoe 3 and the parking lever 16, and the other end engages the other brake shoe 3 and the parking lever 16. It is locked to shoe 2.

By applying a pull to the parking cable 16a connected to one end of the parking lever 16, the parking lever 16 rotates around the pin 3a, and the reaction force is transmitted to one brake shoe 2 through the strut 10. , and presses both brake shoes 2 and 3 against the inner circumferential surface of the drum 12 to generate braking force.

(Problem to be Solved by the Invention) When the parking lever is operated, one brake shoe comes into contact with the inner circumferential surface of the drum, and because the strut is used to transmit the reaction force, the brake plate is pushed closer to the center of the drum. The layout of the parts at the bottom of the diagram of the brake cylinder was cramped.

(Means for Solving the Problems) The present invention uses a piston to transmit reaction force in order to solve the above problems, and the configuration of the first invention is as follows.

In a parking device for an LT brake, which has a double-acting wheel cylinder having a pair of pistons, a pair of brake shoes, an anchor, and a shoe return spring on a bucking plate, a push rod is placed between the inner ends of both pistons. A lever member is interposed between the outer end of one of the pistons and the brake shoe, and the intermediate portion of the lever member is
This is a parking device for the LT brake, which is placed on the outside of the bucking plate and fixed to the tip of the shaft of the parking lever, which is rotatably supported by the bucking plate.

Further, the second invention is as follows.

In a parking device for an LT brake, which has a double-acting wheel cylinder having a pair of pistons, a pair of brake shoes, an anchor, and a shoe return spring on a bucking plate, a push rod is placed between the inner ends of both pistons. is provided, and the inner surface of one end of the parking lever is brought into contact with the outer end of either one of the pistons together with the brake shoe, and is positioned radially outward of the parking plate from the locking position of the parking lever. This is a parking device for LT brakes in which a through hole is provided at the location where the brake shoe is installed, and the through hole is engaged with a pin fixed to the web of the brake shoe.

(Function) In the first invention, when the parking lever is rotated, the lever member is rotated by the rotation of the shaft of the parking lever, and one end of the lever member moves one brake shoe of the drum. While making contact with the inner peripheral surface, the other end of the lever member pushes one piston into the wheel cylinder, transmits a reaction force to the other brake shoe via the push rod and the other piston, and pushes the other brake shoe. The parking brake is applied by bringing the brake into contact with the inner peripheral surface of the drum.

Further, in the second invention, the parking lever rotates about the inner surface of one end, which is the part that locks onto the one piston, as a fulcrum, and operates the brake shoe via a pin fixed to the web of one brake shoe. The brake shoe is brought into contact with the inner peripheral surface of the drum, and the reaction force is transmitted to the other brake shoe via the push rod and the other piston, and the other brake shoe is brought into contact with the inner peripheral surface of the drum. The parking brake is applied.

(Embodiment) A first embodiment of a parking device for an LT brake according to the present invention will be described based on FIGS. 1 to 3.

1 is a bucking plate, 2 and 3 are brake shoes, 4 is an anchor fixed to the bucking plate 1, 7 is a shoe return spring, and 12 is a drum.

As shown in FIG. 2, a pair of pistons 5a and 5b are built into the wheel cylinder 5, and the inner ends of both pistons 5a and 5b have holes 5a' and 5b' facing each other in the axial direction. Each end of the push rod 8 is inserted into each hole 5a', 5b'. When both brake shoes 2 and 3 return to their original positions due to the tensile force of the shoe return spring 7, each end of the push rod 8 comes into contact with the bottom of each hole 5a' and 5b', and Even if the lining is worn out and it is time to replace it, the tips of the push rods 8 will not escape from the holes 5a', 5b'. Note that one end of the push rod 8 is fixed to the inner end surface of either one of the pistons 5a or 5b, and when both brake shoes 2, 3 return to their original positions, the other end of the push rod 8 is fixed to the inner end surface of one of the pistons 5a or 5b. 5
It may be made to abut on the inner end surface of a. Alternatively, the pistons 5a and 5b may be in direct contact with each other. And, at the tip of one piston 5a,
A recess 5a'' is provided in which an upper projection 6b' of a lever member to be described later can be engaged.

Reference numeral 6 denotes a parking lever, and as shown in FIG. 3, a shaft 6a, which is located outside the bucking plate 1 and fixed to the parking lever 6, is rotatably supported by the bucking plate 1. A lever member 6b fixed to the tip of the shaft 6a is interposed between one piston 5a and one brake shoe 2, and an upper projection 6b' provided at one end of the lever member 6b is attached to one piston 5a. The lower protrusion 6b'' engaged with the recess 5a'' at the tip and provided at the other end of the opposite surface is
Recess 2 provided at the tip of one brake shoe 2
It is engaged with a.

Next, the effect will be explained.

If you pull the parking cable 6c provided at the end of the parking lever 6, the parking lever 6
rotates the shaft 6a and the lever member 6b, and moves one brake shoe 2 to the drum 1 using the lower protrusion 6b''.
At the same time, the piston 5a is pushed into the wheel cylinder 5 by the projection 6b', and the other brake shoe 3 is brought into contact with the inner peripheral surface of the drum 12 via the push rod and the other piston 5b. When connected, it acts as a parking brake.

A second embodiment will be described based on FIG.

The same symbols as in FIG. 1 indicate the same parts. That is, 1
is a bucking plate, 2 and 3 are brake shoes, 4 is an anchor, 5 is a wheel cylinder, 7 is a shoe return spring, and 12 is a drum. Both ends of a push rod 8 are inserted into both pistons 5a and 5b built into the wheel cylinder 5, as in the first embodiment. The other brake shoe 3 has its one end surface 3a in contact with the tip of the other piston 5b, and the parking lever 6' also has a
The inner surface 6'a of one end thereof is brought into contact and locked. A through hole 6'b is provided at a location radially outward of the parking plate from the locking position of the parking lever 6', and the through hole 6'b is fixed to the web of the brake shoe. The pin 3b is engaged with the pin 3b. Note that 6'c is a parking cable.

Next, the effect will be explained.

When the parking cable 6'c is pulled, the parking lever 6' rotates around the inner surface 6'a of one end, which is the part that locks onto the piston 5b, and connects the other brake shoe 3 to the drum via the pin 3b. 1
2 and the reaction force is applied to the push rod 8.
The brake force is transmitted to one brake shoe 2 via one piston 5a, and one brake shoe 2 is brought into contact with the inner circumferential surface of the drum 12 to perform a parking brake action.

(Effects of the Invention) As understood from the above explanation, in the LT brake parking device of the present invention,
By using the piston as a reaction force transmitting member when the parking lever is activated, the strut can be omitted and the layout of the parts near the center of the bucking plate becomes easier.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway view showing a first embodiment of the present invention, FIG. 2 is a sectional view showing the inside of the wheel cylinder, and FIG. 3 is a cross-sectional view showing the parking lever and lever member. The partial sectional view, Figure 4, is
FIG. 5, which is a diagram showing the second embodiment of the present invention, is a diagram showing a conventional example. 1: Bucking plate, 2, 3: Brake shoe, 4: Anchor, 5: Wheel cylinder, 5
a, 5b: Piston, 5a', 5b': Hole, 6,
6': parking lever, 6a: shaft, 6b: lever member, 6b': ten part projection, 6b'': lower projection, 7: shoe return spring, 8: push rod, 12: drum.

Claims (1)

[Claims] 1. A double-acting wheel cylinder having a pair of pistons, a pair of brake shoes, an anchor,
In a parking device for an LT brake that has a shoe return spring on a bucking plate, a push rod is provided between the inner ends of both pistons, and a lever member is provided between the outer end of one of the pistons and the brake shoe. The intermediate part of the lever member is fixed to the tip of the shaft of a parking lever that is arranged outside the bucking plate and rotatably supported by the bucking plate.
LT brake parking device. 2. A double-acting wheel cylinder having a pair of pistons, a pair of brake shoes, an anchor,
In a parking device for an LT brake that has a shoe return spring on the bucking plate, a push rod is provided between the inner ends of both pistons, and the outer end of either piston is attached with a brake shoe and a push rod inside one end of the parking lever. The side surfaces are brought into contact and locked, and a through hole is provided at a location radially outward of the bucking plate from the locking position of the parking lever, and the through hole is fixed to the web of the brake shoe. A parking device for LT brakes that is characterized by engaging a pin.