JPS5926811B2 - Spring assembly for internally expanding brakes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spring assembly, and more particularly to a spring assembly for suppressing lifting of a brake shoe from a backing plate in an internally expandable brake.

One type of vehicle control device is an internally expandable brake.

This internally expandable brake generally includes a circular backing plate and a pair of arcuate brake shoes disposed on the backing plate to face each other along the circumferential direction of the backing plate.

Each brake shoe is pivotally supported on a backing plate, and a wheel cylinder or the like disposed between both brake shoes is mounted around the pivot axis on the radially outer side of the backing plate, that is, on the inner circumferential surface of the brake drum. will be expanded towards.

In order to suppress lifting of the brake shoes from the backing plate during pivoting of the brake shoes, internally expandable brakes generally include a spring assembly.

A conventional spring assembly of this type includes a generally U-shaped leaf spring having mutually opposing portions, and a pin for assembling the leaf spring at a predetermined location.

One end of the pin is provided with a head, and the other end is provided with a locking portion.

Further, each of the opposing portions of the leaf spring is provided with a th
A hole is provided to allow the part to pass through.

On the other hand, the backing plate is formed with a hole that allows the locking portion of the pin to pass through and prevents the head portion of the pin from passing through, and the brake shoe has a hole formed therein.

When assembling the spring assembly.

The leaf spring is disposed on the brake shoe such that the hole in the opposing portion of the leaf spring is aligned with a diameter hole in the backing plate and the brake shoe on the backing plate.

The pin is inserted into the hole so that its locking portion penetrates the hole from the backing play 1 side, and when the pin is inserted, the leaf spring is pressed so that the locking portion protrudes from the leaf spring. .

The pin whose other end protrudes from the leaf spring is rotated by the pressure of the leaf spring, and the other end of the pin, that is, the locking portion, is locked to the edge of the hole of the leaf spring.

As a result, the backing plate, brake shoe, and elastically deformed leaf spring are inserted between the head of the pin and the engaging part, and the restoring force of the leaf spring acting in the axial direction of the pin causes the Lifting of the brake shoe from backing play 1 is suppressed.

At this time, since the hole for receiving the pin of the brake shoe is a blank hole, the expansion of the brake shoe is not prevented by the pin.

By the way, relatively hard spring steel is used in the above-mentioned leaf spring in order to resist the large floating force acting on the brake shoes, and when assembling the leaf spring, one facing part should be turned toward the other facing part. It is necessary to press with great force.

For this reason, in the conventional strut assembly, the leaf spring may be deformed beyond its elastic limit due to the pressing force during assembly, or may become so-called sag.

This flattening of the leaf spring causes brake shoe flopping and brake shoe dragging, which causes premature wear of the brake lining and paper lock.

Accordingly, it is an object of the present invention to provide a spring assembly for an internally expandable brake that does not sometimes sag during assembly.

The present invention includes a leaf spring having a U-shape as a whole and having portions facing each other, and a pin for penetrating the both opposing portions of the leaf spring and assembling the leaf spring in a predetermined position in an elastically deformed state. , a pair of bent portions is formed by bending both side portions near the free ends of one of the opposing portions toward the other of the opposing portions, and when the leaf spring is assembled, the two opposing portions are sometimes brought close to each other. By bringing the protrusion formed by the pair of bent portions into contact with the other opposing portion when the one opposing portion is pressed, the assembly of the leaf spring exceeds the elastic limit of the leaf spring at the time. It is characterized by preventing deformation.

The features of the present invention will become clearer from the following description of the illustrated embodiments.

In FIG. 1, an internally expandable brake is shown generally at 10 and includes a spring assembly according to the present invention.

The brake 10 is a conventionally well-known leading brake.
It is a trailing shoe type and includes a circular backing plate 12 fixed to the vehicle body side and a brake drum (not shown) arranged around the outer periphery of the backing plate 1 and fixed to the axle side.

A pair of arc-shaped brake shoes 14 are arranged on the backing plate 12 so as to face each other in the circumferential direction of the backing plate 1-12.

A brake lining 16 is fixed to the outer circumference of each brake shoe 14, and a web 18 is formed along the brake shoe 14 on the inner circumference thereof.

An anchor block 20 is disposed between adjacent ends of the pair of brake shoes 14, and the anchor block 20 is fixed to the backing plate 12.

Both brake shoes 14 are brought into contact with an anchor block 20 at the end of each web 18 by the tension of a return spring 22 stretched between one end of the brake shoes 14, and are mounted on the backing plate 12 with the anchor block as a pivot. is pivotably supported on.

A wheel cylinder 24 is provided between the other ends of both brake shoes 14 for pushing and expanding the pair of brake shoes 14 with the anchor block 20 as a pivot toward the inner peripheral surface of the brake drum. The brake lining 16 of the brake shoe 14 is
is pressed against the inner peripheral surface of the brake drum, thereby applying braking to the brake drum.

Furthermore, in the illustrated example, the strut assembly 2 has a star wheel 26 and is extendable by rotation of the star wheel.
8 is provided between both brake shoes 14.

A parking brake lever 3 is also provided on the web 18 of one brake shoe 14 for pushing apart or expanding both brake shoes 14 via the strut assembly 28 regardless of the operation of the wheel cylinder 22.
0 is pivotally connected via a pin 32, into which a shoe clearance adjusting lever 34 for rotating the star wheel 26 of the strut assembly 28 is fitted.

This shoe clearance adjusting lever 34 is
As is well known in the art, the parking brake lever 32 is pivoted in conjunction with the pivoting of the parking brake lever 32, which pivots the star wheel 26 to rotate the strut assembly 28.
is expanded according to the amount of wear of the brake lining 16.

As a result, the shooter IJ 7 lance or brake 1
The gap between the brake lining 16 and the brake drum during non-operation is maintained constant regardless of wear of the brake lining 16.

A spring assembly 36 according to the present invention is applied to prevent the pair of brake shoes 14, which are pivoted about the anchor block 22 by the operation of the wheel cylinder 24 and the brake lever 30, from lifting off from the backing plate 12 when the pair of brake shoes 14 pivot. has been done.

The spring assembly 36 includes a pin 38 and a leaf spring 40, as shown in FIG.

The pin 38 includes a cylindrical stem portion 42, a circular head 44 consisting of an increased diameter portion formed at one end of the stem portion, and a circular head 44 formed at the other end of the stem portion 42 and extending radially outward of the stem portion. A locking part 4 consisting of a pair of protrusions protruding opposite to the
6.

Further, as shown in FIGS. 3 and 4, the leaf spring 40 has a U-shape as a whole, and near the free end of the portion 48 facing each other, the pin 38 is located at a specific rotational position. A slot 50 is formed to allow the stem portion 42 to pass through from the other end, that is, the locking portion 46 .

Furthermore, a protrusion 52 that projects toward the other opposing portion 48 is formed on one opposing portion 48 .

In the illustrated example, the protrusion 52 is formed by a pair of bent portions formed by partially bending both side portions near the free end of one opposing portion 48 toward the other free end.

This protrusion 52 has two opposing portions 48 close together (so that when a pressing force is applied to the leaf spring 40, the leaf spring 40 does not come into contact with the other facing portion 48 for a relatively small load).
The plate spring 40 acts as a stopper to prevent excessive deformation of the leaf spring 40 by coming into contact with the other opposing portion 48 in response to a large load that would cause an elastic limit.

Therefore, the leaf spring 40 will not be deformed to the point where it reaches its elastic limit due to the above-mentioned pressing force.

To assemble the spring assembly 36, as shown in FIG. 2, holes 54 and 56 are formed in the backing plate 12 and the web 18, respectively, to allow the locking portion 46 of the pin 38 to pass therethrough.

The hole 56 formed in the web 18 is a so-called blind hole and has an inside diameter sufficiently larger than the diameter of the stem portion 42 of the pin 38 so as not to prevent the aforementioned pivoting of the brake shoe.

When assembling the spring assembly, the leaf spring 4
0, the slot 50 provided in the opposing portion 48 is the backing play) 12 and the neck hole 54.5 of the web 18.
6, and the locking portion 46 thereof is inserted into the hole from the side of the backing plate 1, 12 so that the pin 38 passes through each member 12, 18 and 40.

When inserting the pin 38, the opposing portions 48 of the leaf spring 40 are moved closer together (so that a pressing force is applied to the leaf spring 40, so that the locking portion 46 of the pin 38 is moved closer to the opposing portion 48 of the leaf spring 40). stand out.

In this state, the pin 38 is rotated, and the locking portion 46 is attached to the leaf spring 4.
0 slot 50.

As a result, as shown in FIG.
A leaf spring 40, which is elastically deformed together with the backing plate 12 and the web 18 of the brake shoe 14, is inserted between the engagement portion 1E and the engagement portion 46.

Therefore, since the restoring force of the leaf spring 40 acts in the axial direction of the pin 38, the brake shoe 14 is pressed toward the backing plate 12 by this restoring force.

When assembling this spring assembly 360, as described above, the protrusions 52 formed by the pair of bent portions provided on the opposing portions 48 of the leaf spring 40 restrict excessive deformation of the leaf spring 40, so that The leaf spring 40 does not undergo so-called sagging due to the pressing force during attachment.

Therefore, the return force of the leaf spring 40 is not reduced below a predetermined value due to fatigue of the leaf spring, and the leaf spring 40 can maintain a predetermined return force even after assembly.

Further, the projection 52, which is formed by the pair of bent portions, reinforces the one opposing portion 48 where the projection is provided, thereby making it easier to assemble the spring assembly 36.

That is, when inserting the pin 38 into the slot 50, a pressing force is applied to one opposing portion 48 in order to bring the opposing portion closer to the other opposing portion 48. In order to effectively act as a deforming force on the leaf spring 40, it is preferable that the pressing force be applied to the free end of the one opposing portion.

By the way, when a strong pressing force acts on the free end of the one opposing portion 48, the leaf spring 40 may cause local deflection in the longitudinal direction of the opposing portion 48 near the free end. The local deflection prevents effective deformation of the leaf spring for insertion of the pin 38, and the pin 38
makes insertion difficult.

However, the bending portion 52 prevents the above-mentioned local deflection by reinforcing the vicinity of the free end, making it easier to insert the pin 38, and thereby making it easier to assemble the spring assembly 36. becomes.

Therefore, according to the present invention, as described above, the assembly of the spring assembly prevents partial deflection of the leaf spring in the vicinity of the free end during assembly, and also prevents the leaf spring from sagging. This makes it possible to reliably suppress lifting of the brake shoe from the backing plate by the appropriate return force of the leaf spring of the spring assembly, and prevent the lifting of the brake shoe from dancing or dragging of the brake shoe due to the lifting of the brake shoe. , it is possible to reliably prevent phenomena such as premature wear of the brake lining and paper lock, thereby increasing the durability and reliability of the brake.

[Brief explanation of drawings]

FIG. 1 is a plan view showing a brake to which a spring assembly according to the present invention is applied, and FIG. 2 is a longitudinal sectional view taken along line 2--2 shown in FIG. Figure 3 is the first
4 is a plan view of the leaf spring of the spring assembly shown in FIG. 4, and FIG. 4 is a longitudinal cross-sectional view taken along line 4--4 shown in FIG. 3; 12: Backing plate, 14 brake shoes, 1
8: Web of brake shoe, 20 front cover block, 36: Spring assembly, 38: Pin, 402 leaf spring, 44: Head of pin, 46: Locking part of pin, 48: Opposing part of leaf spring , 52: Protrusion of leaf spring.

Claims (1)

[Claims] 1 A spring assembly for suppressing lifting of the brake shoes of an internally expandable brake including brake shoes pivotally mounted on a backing plate from above the backing plate, the spring assembly pressing the brake shoes toward the backing plate. and a pin passing through the backing plate, the brake shoe, and the spring and having a head at one end and a locking portion at the other end, the springs each having a slot for allowing the pin to pass therethrough. a generally U-shaped leaf spring having mutually opposing portions, one of the opposing portions having a cylindrical shape such that the opposing portions are close to each other in order to pass the pin into the slot; In order to prevent deformation exceeding the elastic limit of the leaf spring when the opposing portion of the plate spring is pressed, a protrusion that can come into contact with the other opposing portion is formed, and the protrusion A spring assembly for an internally expandable brake comprising a small bent portion formed by bending both side portions near the ends toward the other opposing portion.