U.S. patent application number 09/737756 was filed with the patent office on 2001-06-21 for brake cable mounting structure for a drum brake.
Invention is credited to Asai, Seiji.
Application Number | 20010004035 09/737756 |
Document ID | / |
Family ID | 18457884 |
Filed Date | 2001-06-21 |
United States Patent
Application |
20010004035 |
Kind Code |
A1 |
Asai, Seiji |
June 21, 2001 |
Brake cable mounting structure for a drum brake
Abstract
A brake cable mounting structure for a drum brake, in which even
if the distance from the brake mounting surface to the center of
the brake shoes in the width direction is short, the layout of the
brake cable mounting section and the mechanical expander is
efficient and effectively provided. Further, the anchor only need
to support the braking force, thereby making the device smaller and
lighter. The brake cable mounting structure of this invention is
characterized in that the inner cable of the brake cable extends
out from the brake; and the guide pipe on which the outer casing of
the brake cable is integrally fixed with the back plate.
Inventors: |
Asai, Seiji; (Okazaki-shi,
JP) |
Correspondence
Address: |
Liniak, Berenato, Longacre & White
Ste 240
6550 Rock Spring Drive
Bethesda
MD
20817
US
|
Family ID: |
18457884 |
Appl. No.: |
09/737756 |
Filed: |
December 18, 2000 |
Current U.S.
Class: |
188/79.51 ;
188/205R |
Current CPC
Class: |
F16D 2125/565 20130101;
F16D 2125/62 20130101; F16D 2125/68 20130101; F16D 65/22 20130101;
F16D 51/50 20130101 |
Class at
Publication: |
188/79.51 ;
188/205.00R |
International
Class: |
F16D 051/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 16, 1999 |
JP |
11-358165 |
Claims
What is claimed is:
1. A brake cable mounting structure for a drum brake comprising: a
mechanical expander having an input force portion, said expander
disposed adjacent to a pair of adjacent facing ends of brake shoes
moveably mounted on a back plate so as to actuate said brake shoes;
a brake cable having an inner cable connected with said input force
portion of said mechanical expander and having an outer casing; and
a guide pipe for guiding said inner cable to pass out of said drum
brake, said outer casing being attached to said guide pipe, wherein
said guide pipe is fixed on said back plate.
2. The brake cable mounting structure for a drum brake as claimed
in claim 1 wherein a guide pipe fixing portion of said back plate
is designed to be a convex shape toward a brake fixing part
side.
3. The brake cable mounting structure for a drum brake as claimed
in claim 1 wherein said guide pipe penetrates through a guide pipe
insertion hole of said back plate and projects outwardly from said
guide pipe fixing portion, a large diameter overhanging portion
provided on an intermediate portion of said guide pipe contacts
said back plate at said brake fixing part side, a projected
outwardly end tip of said guide pipe is formed to be a widened end,
and said guide pipe is securely fixed on said back plate between
said overhanging portion and said widened end.
4. The brake cable mounting structure for a drum brake as claimed
in claim 1, wherein said back plate is configured to be integrated
by superposing an independently formed back plate body and a back
plate stiffener.
5. The brake cable mounting structure for a drum brake as claimed
in claim 1, wherein an anchor supporting one adjacent ends of both
brake shoes is positioned adjacent to said mechanical expander.
Description
BACKGROUND OF INVENTION
[0001] 1. Field of the Invention
[0002] 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.
[0003] 2. Description of Related Art
[0004] 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 110, 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.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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 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.
[0010] The back plate 100 and the stiffener 105 are fixed on the
brake fixing part 150 (e.g., non-rotatable 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.
[0011] 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.
[0012] 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.
[0013] 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 brake drum rotates in either
direction, i.e., functioning as a duo-servo (DS) type drum
brake.
[0014] The above-conventional drum brake suffers from the following
drawbacks and deficiencies.
[0015] The guide pipe 500 is designed so that the overhanging
portion 501 contacts the back (the back plate 100 side) of the
anchor seat 202 of the anchor 200, and the upper portion thereof is
penetrated through the hole on the anchor seat 202. The known end
portion 502 is widened at the terminal end of the guide pipe 500.
With this structure, an effective stroke of the brake cable 400 is
restricted by a gap between the lower end surface of the brake
lever 320 and the widened end 502 of the guide pipe 500. If the
distance (brake off-set) H from the brake mounting surface to the
center of the brake shoes 110, 120 is too short, it becomes
difficult to design the layout of the brake cable mounting section
and of the mechanical expander 300.
[0016] The overall length of the guide pipe 500 must be longer,
which is another disadvantage when considering the cost of
manufacturing.
[0017] During the brake operation, the anchor 200 receives the
brake force of the brake shoes 110, 120 and the operational
reaction force on the outer casing 430 via the guide pipe 500.
Therefore, the anchor 200 needs to be stronger which is another
disadvantage in considering the weight and cost.
SUMMARY AND OBJECT OF THE INVENTION
[0018] This invention improves upon the aforementioned problems in
the prior art and provides a brake cable mounting structure for a
drum brake, in which even if the distance from the brake mounting
surface to the center of the brake shoes in the width direction is
short, an efficient and effective layout of the brake cable
mounting section and the mechanical expander is facilitated.
Further, the load acting on the anchor may be reduced, which
eliminates the uncertainty of the anchor strength.
[0019] With this invention, no projection on the anchor seat toward
the mechanical expander side (i.e., widened end of the guide pipe
in the conventional part) is necessary; therefore the range of the
effective stroke of the brake cable is increased. Accordingly, even
if the distance from the brake fixing portion to the brake shoe
center in the width direction, i.e., brake off-set, is short, the
layout of the brake mounting section and the mechanical expander is
facilitated.
[0020] Further, an operational reaction force during the parking
brake operation is supported by the back plate. Hence, the anchor
supports the braking force, which enables to be designed smaller
and lighter.
[0021] A widened end of the guide pipe is positioned in the pocket,
thus, a through hole for the inner cable with the cable end nipple
opened on the anchor seat may be made smaller which also reduces
the size of the anchor.
[0022] Since the guide pipe is mounted on the back plate, the
overall length of the guide pipe is reduced, which also reduces the
cost of manufacturing the device.
[0023] The objectives and advantages of this invention are achieved
by a brake cable mounting structure for a drum brake comprising a
mechanical expander having an input force portion, where the
expander is disposed adjacent to a pair of adjacent facing ends of
brake shoes moveably mounted on a back plate so as to actuate said
brake shoes. The mounting structure also comprises a brake cable
having an inner cable is connected with said input force portion of
the mechanical expander and the brake cable has an outer casing.
The mounting structure further comprises a guide pipe guides the
inner cable to pass out of said drum brake, where the outer casing
is attached to said guide pipe, and where the guide pipe is fixed
on said back plate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The above and other objects of the present invention will
become readily apparent by reference to the following detailed
description when considered in conjunction with the accompanying
drawings wherein:
[0025] FIG. 1 is an explanation view of the brake actuating part of
first embodiment;
[0026] FIG. 2 is a cross-section view of FIG. 1 taken along the
line II-II;
[0027] FIG. 3 is an explanation view of the brake actuating part of
second embodiment;
[0028] FIG. 4 is a plan view of the conventional drum brake
device;
[0029] FIG. 5 is a cross-section view of FIG. 4 taken along the
line V-V;
[0030] FIG. 6 is a cross-section view of FIG. 5 taken along the
line VI-VI; and
[0031] FIG. 7 is an exploded view of the brake actuating part.
DETAILED DESCRIPTION OF THE INVENTION
[0032] Embodiments of this invention are explained with reference
to the following figures. Here, except for the guide pipe fixing
portion, the rest of components of the drum brake and the brake
operation are similar to the conventional device illustrated in
FIGS. 4-7, hence the similarly parts or the similar portions are
numbered as same as the conventional device, while the explanation
of those components will be omitted.
[0033] As shown in FIGS. 1 and 2, first invention includes a guide
pipe 510 for guiding a brake cable 400 out of a drum brake fixing
on a back plate 600.
[0034] In this embodiment, the back plate 600 is not formed out of
a superposed-steel plate but is formed of a steel sheet, which is
fixed on a brake fixing part 150 (e.g., non-rotatable part on an
axle member of the vehicle) by bolts 140, 140, 141, 141.
Simultaneously, an anchor 200 is firmly fixed to the brake fixing
part 150 by the bolts 140, 140.
[0035] A guide pipe 510 is fixed on a guide pipe fixing portion 601
on the back plate 600, wherein the guide pipe fixing portion 601
has a insertion hole 602 for the insertion of a guide pipe 510 as
well as a funnel shape portion protruding into a notched groove 151
of the brake fixing part 150.
[0036] One end of the guide pipe 510 penetrates through the
insertion hole 602 of the back plate 600 from the brake fixing part
150 side, and an overhanging portion 511 integrally formed on the
intermediate portion thereof contacts a back of the guide pipe
fixing portion 601. An end of the guide pipe 510, projected
outwardly from the guide pipe fixing portion 601 at the anchor 200
side, is formed to be a widened end 512. Therefore, the guide pipe
510 is significantly integrated with the back plate 600.
[0037] An operational reaction force generated during the parking
brake operation is supported and absorbed by the back plate 600 via
the guide pipe 510. Hence, the anchor 200 only needs to bear a
braking force, which enables to be designed smaller and lighter.
The widened end 512 of the guide pipe 510 may be positioned in a
pocket of the guide pipe fixing portion 601 on the back plate 600.
Hence, the widened end 512 of the guide pipe 510 does not need to
be projected out from the anchor seat 202 of the anchor 200 toward
the mechanical expander 300 unlike the conventional art. Therefore,
the range of effective stroke of the brake cable 400 is increased.
Accordingly, this structure is effective even if the distance from
the brake fixing portion to the brake shoe center in the width
direction, i.e., brake off-set, is short.
[0038] For the structure of installing the outer casing 430 on the
guide pipe 510 in this invention, the large diameter portion of the
casing cap 431 of the outer casing 430 contacts the outer opening
end surface of the guide pipe 510 and at the same time the small
diameter top portion thereof fits into the bore of the guide pipe
510. After that, the brake cable 400 is fixed on the guide pipe 510
by a wire spring clip 440. However, the brake cable 400 once
properly attached is securely affixed to the operational end (not
shown) of the brake cable 400 on the corresponding member.
Therefore, the casing cap 431 may be press fit into the bore of the
guide pipe 510 instead of using the spring clip 440. The diameter
of a through hole 210 formed on the anchor seat 202 of the anchor
200 only need penetrate through the inner cable 410 with the cable
end nipple 420; thus may be designed smaller, thereby further
reducing the size of the anchor seat 202.
[0039] The overhanging portion 511 of the guide pipe 510 may be
formed by expanding the intermediate portion of the guide pipe 510
outwardly. An independent flat washer-like ring may be jointed over
the guide pipe 510 instead of the overhanging portion 511 as shown
to add the large diameter overhanging portion on the guide pipe
510. Besides the above-described means to fix the guide pipe 510 on
the back plate 600, the guide pipe 510 may be fixed by other
suitable means such as being welded on the back plate 600.
[0040] The guide pipe fixing portion 601 on the back plate 600 may
be designed to be a flat, where a diameter of the inner cable
through hole 210 of the anchor 200 may be made large to store the
widened end 512 of the guide pipe 510.
[0041] FIG. 3 shows a case where a back plate is configured in
combination of an independently formed back plate body 700
superimposed on an independent back plate stiffener 705 as a
reinforcing plate supporting the back plate body 700.
[0042] This second embodiment describes in case which a spacer 800
is sandwiched between the brake fixing part 150 and the back plate
stiffener 705, where the anchor 200, the back plate body 700, the
back plate stiffener 705, and the spacers 800, 800 are fixed on the
brake fixing part 150 by the bolts 140, 140. The spacers 800, 800
may be omitted without substantially reducing the
effectiveness.
[0043] The guide pipe fixing portion 706 of the guide pipe 520 in
this second embodiment is different from the first embodiment in
that the guide pipe fixing portion 706 is formed only on the back
plate stiffener 705. That is, the guide pipe fixing portion 706 is
positioned in a space between two spacers 800 and 800 and is
designed to be a funnel shape portion protruding toward the brake
fixing part 150. Further, the guide pipe insertion hole 707 is
opened on the back plate stiffener 705 for the installation of the
guide pipe 520. A portion of the back plate body 700 adjacent to
the guide pipe insertion hole 707 is a flat and has a through hole
703 for an inner cable 410 with a cable end nipple 420 to be
penetrated through.
[0044] One end of the guide pipe 520 penetrates through the
insertion hole 707 of the back plate stiffener 705 from the brake
fixing part 150 side, and an overhanging portion 521 contact a back
of the guide pipe fixing portion 706. An end of the guide pipe 520,
projected outwardly from the guide pipe fixing portion 706 at the
anchor 200 side, is formed to be a widened end. Therefore, the
guide pipe 520 integrated with or fixed relative to the back plate
stiffener 705.
[0045] Accordingly, the widened end 522 of the guide pipe 520 may
be positioned in the pocket of the guide pipe fixing portion 706 on
the back plate stiffener 705. Hence, the widened end 522 of the
guide pipe 520 does not need to projected out from the anchor seat
202 of the anchor 200 toward the mechanical expander unlike the
conventional art.
[0046] Although it is not shown in FIG. 3, a funnel shape portion
may be formed on the back plate body 700 for fixing the guide pipe
520, and alternatively, funnel shape portions may be formed both on
the back plate body 700 and the back plate stiffener 705 for fixing
the guide pipe 520 without difficulty.
[0047] The above-described embodiments employ a brake cable
mounting structure for a duo-servo (DS) type drum brake device
where one adjacent facing ends of a pair of brake shoes 110, 120 is
supported by the anchor 200, while the other adjacent facing ends
thereof is connected via the adjuster 130. However, this invention
is not limited to the application in the DS type. For example, a
fixed anchor as shown in the German Utility Mode Gazette No.
DE7116427 may be employed instead of the conventional adjuster 130
as appeared in FIG. 4, which enables the brake cable mounting
structure of this invention to be used in a leading-trailing (LT)
type drum brake device.
[0048] Alternatively, the brake cable fixing device of this
invention may be applied in a dual mode drum brake as shown in the
U.S. Pat. No. 5,720,367 which functions as the LT type drum brake
when a service brake is in operation but functions as the DS type
when a parking brake is in operation. Basically, the brake cable
mounting structure of this invention is applicable to any drum
brake device with the mechanical expander 300 and the guide pipe
510, 520.
[0049] Because of the particular structure described above, this
invention has the following effects.
[0050] No projection on the anchor seat toward the mechanical
expander side (i.e., widened end of the guide pipe in the
conventional part) is necessary; therefore the range of the
effective stroke of the brake cable is increased. Accordingly, even
if the distance from the brake fixing portion to the brake shoe
center in the width direction, i.e., brake off-set, is short, the
layout of the brake mounting section and the mechanical expander is
facilitated.
[0051] An operational reaction force during the parking brake
operation is supported by the back plate. Hence, the anchor
supports the braking force, which enables to be designed smaller
and lighter.
[0052] Widened end of the guide pipe is positioned in the pocket,
thus, a through hole for the inner cable with the cable end nipple
opened on the anchor seat may be made smaller which also reduces
the size of the anchor.
[0053] Since the guide pipe is mounted on the back plate, the
overall length of the guide pipe is reduced, which also reduces the
cost of manufacturing the device.
[0054] It is readily apparent that the above-described embodiments
have the advantage of wide commercial utility. It should be
understood that the specific form of the invention hereinabove
described is intended to be representative only, as certain
modifications within the scope of these teachings will be apparent
to those skilled in the art. Accordingly, reference should be made
to the following claims in determining the full scope of the
invention.
* * * * *