Brake cable mounting structure for a drum brake

Brakes – Wheel – Transversely movable

Reexamination Certificate

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Details

C188S079550, C188S00200R, C188S325000, C188S078000

Reexamination Certificate

active

06412609

ABSTRACT:

BACKGROUND OF INVENTION
1. Field of the Invention
This invention relates to a drum brake comprising a mechanical expander spreading a pair of brake shoes apart. More specifically, this invention relates to a brake cable mounting structure which enables remote operation of the mechanical expander.
2. Description of Related Art
One known brake cable mounting structure for the drum brake is disclosed in the Japanese Patent Application Unexamined Publication Number 6-337027 filed by this applicant.
FIGS. 4-7
explain a drum brake device employing this kind of the brake cable mounting structure. As depicted in
FIG. 4
, a pair of brake shoes
110
,
120
are moveably mounted on a back plate
100
with shoe holding devices
111
,
121
. Lower adjacent ends of the brake shoes
110
,
120
abut against a supporting portion
201
of an almost L-shaped anchor
200
while upper adjacent ends thereof are connected via an adjuster
130
. An upper shoe return spring
160
is extended between the upper adjacent ends of the brake shoes
10
,
120
and a lower shoe return spring
160
is extended between the lower adjacent ends thereof, maintaining the abutment of the two brake shoes
110
,
120
against the adjuster
130
and the anchor
200
.
A mechanical expander
300
comprising a brake lever
320
; a strut
330
; and a lever pin
310
, is positioned adjacent to the supporting portion
201
of the anchor
200
between the brake shoes
110
,
120
(see FIG.
4
). As depicted in
FIG. 5
, the brake lever
320
comprising two facing long plates has a notched groove
321
formed at the superimposing portion on the right side of the plates being functionally engaged with the right brake shoe
110
. An arc-shaped groove
322
formed on the forked legs on the left side of the plates receives a cable end nipple
420
of a brake cable
400
. The strut
330
, integrally formed from a deformed piece of plate, comprises two facing plate portions connected on their upper edges by a bridge
332
and positioned between the brake shoes
110
,
120
. A notched groove
331
formed at the superimposing portion on the left side of the strut
330
is functionally engaged with the left brake shoe
120
.
The brake lever
320
is inserted from the opposite side of the bridge
332
into a space formed between the facing plate portions of the strut
330
, and upper right ends of the brake lever
320
is pivotally supported relative to the strut
330
with the lever pin
310
as depicted in FIG.
5
.
As is evident from
FIG. 5
, clockwise rotation of the brake lever
320
with respect to the lever pin
310
is restricted when the brake lever
320
abuts against the bridge
332
of the strut
330
. A guide pipe
500
and the brake cable
400
, which act as a remote force transmitting member, pass through the back plate
100
to engage the cable end nipple
420
with the arc-shaped groove
322
as an input force portion of the brake lever
320
. The guide pipe
500
depicted in
FIGS. 5-7
is so designed that the overhanging portion
501
, integrally formed on the intermediate portion thereof, contacts a back of an anchor seat
202
of the anchor
200
. An upper end
502
of the guide pipe
500
penetrated through a hole on the anchor seat
202
and projected outwardly from the surface of the anchor seat
202
is widened in opposite directions; therefore, the guide pipe
500
is integrated with the anchor seat
202
of the anchor
200
. The widened end
502
of the guide pipe
500
is designed to be partially widened toward each side of the brake shoes
110
,
120
. However, the widened end shape is not limited to the above described one and may be a widened shape in the direction as long as it can secure the thickness thereof in the direction to the supporting portion
201
of the anchor
200
without becoming an obstacle to components of the drum brake.
The brake cable
400
is comprised of an outer casing
430
, an inner cable
410
and so on. A large diameter portion of a casing cap
431
, fixed at an end of the outer casing
430
, abuts against an outer opening end of the guide pipe
500
. A small diameter portion of the casing cap
431
fits into a bore of the guide pipe
500
. Then, the brake cable
400
is retained on the guide pipe
500
by a wire spring clip
440
. A means to retain the casing cap
431
on the guide pipe
500
may be utilized until the operational end (not shown) of the brake cable
400
is attached on a corresponding member. As an alternative, the casing cap
431
may be press fit into the bore of the guide pipe
500
instead of using the spring clip
440
.
The inner cable
410
is slidably inserted into the outer casing
430
, and the topside thereof projected out from the casing cap
431
is passed through the guide pipe
500
as shown in
FIG. 5. A
pin portion of the cable end nipple
420
secured on the tip of the inner cable
410
is connected on the arc-shaped groove
322
of the brake lever
320
. A dust boot
411
with bellows is positioned and connected between the casing cap
431
and the cable end nipple
420
, performing a water proof function into the outer casing
430
. To be lower in weight than the drum brake, a relatively lighter plate material forms the back plate
100
. A back plate stiffener
105
is provided only at the
110
area from the central portion to the portion around the anchor
200
on the back plate
100
where required certain high strength and is substantially integrated with the back plate
100
such as by welding.
The back plate
100
and the stiffener
105
are fixed on the brake fixing part
150
(e.g., nonrotatable part on an axle member of the vehicle) having almost same outline of the mounting surface as the stiffener
101
by four fixing bolts
140
,
140
,
141
,
141
and corresponding nuts (not shown in Figures). Each of the two bolts
140
,
140
at the anchor
200
side has a serration
142
on its intermediate portion. The serrations
142
,
142
are pre-press-forced into the back plate
100
and the back plate stiffener
105
, thereby temporary fixing the anchor seat
202
of the anchor
200
and slidably supporting the right side of the brake lever
320
and the left side of the strut
330
on the vertexes of the fixing bolts
140
,
140
. Finally, the anchor
200
will be firmly fixed to the brake fixing part
150
.
Brake operation of the above-explained structured device is explained below. If the operation side of the inner cable
410
(not shown in the figure) is pulled, the intermediate portion of the curved outer casing
430
tends to be deformed to a straight line shape. The casing cap
431
is supported by the guide pipe and the other side of the outer casing
430
(not shown in the figure) are supported by the corresponding member in order to prevent this deformation, thereby transmitting the pulling force onto the cable end nipple
420
.
As the pulling force is transmitted to the arc-shaped groove
322
functioning as the input force portion of the brake lever
320
, the brake lever
320
rotates counterclockwise in
FIG. 5
with respect to the lever pin
310
to move the brake shoe
110
outward, and that reaction force urges the strut
330
to push the brake shoe
120
via the lever pin
310
. If such a pressing force overcomes a tension of the shoe return springs
160
,
160
, both brake shoes
110
,
120
spread apart at the point of abutment on the adjuster
130
, thereby making a frictional engagement with the brake drum, not shown in the figure.
In
FIG. 4
, when the brake drum (not shown in the figure) rotates clockwise, the brake shoe
110
is abutted by the supporting portion
201
of the anchor
200
, and the left brake shoe
120
becomes supported by the adjuster
130
, thereby generating a braking force. Contrary, the brake drum rotates counterclockwise, the brake shoe
120
is abutted by the supporting portion
201
of the anchor
200
, and the brake shoe
110
is abutted by the adjuster
130
, thereby generating a braking force. Accordingly, both brake shoes
110
,
120
have a self-servo function even if the bra

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