CA1084431A - Hydraulic actuator for a drum brake - Google Patents
Hydraulic actuator for a drum brakeInfo
- Publication number
- CA1084431A CA1084431A CA306,121A CA306121A CA1084431A CA 1084431 A CA1084431 A CA 1084431A CA 306121 A CA306121 A CA 306121A CA 1084431 A CA1084431 A CA 1084431A
- Authority
- CA
- Canada
- Prior art keywords
- piston
- partition
- bore
- stepped bore
- hydraulic actuator
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D65/00—Parts or details
- F16D65/14—Actuating mechanisms for brakes; Means for initiating operation at a predetermined position
- F16D65/16—Actuating mechanisms for brakes; Means for initiating operation at a predetermined position arranged in or on the brake
- F16D65/22—Actuating mechanisms for brakes; Means for initiating operation at a predetermined position arranged in or on the brake adapted for pressing members apart, e.g. for drum brakes
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Braking Arrangements (AREA)
- Hydraulic Control Valves For Brake Systems (AREA)
Abstract
A HYDRAULIC ACTUATOR FOR A DRUM BRAKE
ABSTRACT OF THE DISCLOSURE
A drum brake assembly provides a pair of brake shoes which are movable by a hydraulic actuator to a braking position. The hydraulic actuator is carried by a backing plate and the pair of brake shoes is movable relative to the backing plate. A piston is slidably mounted within a bore on the hydraulic actuator and pressurized fluid communicated to the bore acts against the piston to move the piston and pair of brake shoes.
A partition is also disposed within the bore to substantially define a secondary chamber which receives pressurized fluid from the bore. The partition is movably disposed within the bore and resiliently engaged with the piston so that increased pressure within the bore is trans-mitted to the piston via tile partition and the resilient engagement.
Moreover, the partition controls venting of the secondary chamber so that upon contact of the pair of brake shoes with a drum, backlash or retraction of the pair of brake shoes is limited.
ABSTRACT OF THE DISCLOSURE
A drum brake assembly provides a pair of brake shoes which are movable by a hydraulic actuator to a braking position. The hydraulic actuator is carried by a backing plate and the pair of brake shoes is movable relative to the backing plate. A piston is slidably mounted within a bore on the hydraulic actuator and pressurized fluid communicated to the bore acts against the piston to move the piston and pair of brake shoes.
A partition is also disposed within the bore to substantially define a secondary chamber which receives pressurized fluid from the bore. The partition is movably disposed within the bore and resiliently engaged with the piston so that increased pressure within the bore is trans-mitted to the piston via tile partition and the resilient engagement.
Moreover, the partition controls venting of the secondary chamber so that upon contact of the pair of brake shoes with a drum, backlash or retraction of the pair of brake shoes is limited.
Description
BACKGROUND OF THE INVENTION
In a drum brake assembly a pair of brake shoes is urged -into engagement with a drum to retard the rotation of the latter.
A hydraulic actuator slidably carries a piston which abuts at least one of the pair of brake shoes and the piston is responsive to increases in pressure within the hydraulic actuator to move relative thereto, thereby moving the brake shoe into engagement with the drum.
The piston rests on a stop on the hydraulic actuator so that upon pressurization of the hydraulic actuator the piston moves away from the stop to urge the brake shoe into braking engagement with the drum. When contact between the drum and brake shoe is initially achieved, the pair of brake shoes frictionally grip the 3 rotating drum and the pair of brake shoes is rotated slightly in the direction of rotation of the drum until one of the brake shoes abuts the stop. Further pressurization of the hydraulic actuator at this time increases the braking forces between the pair of brake shoes and the drum to retard the rotation of the drum.
When the one brake shoe abuts the hydraulic actuator stop upon initial contact between the pair of brake shoes and the drum a clunking noise occurs as the impact between the stop and the piston can be quite large. Consequently, elimination of this clunking noise by simple means without interfering with brake bleeding or imposing a delay on normal brake application rates is believed to be an improvement over the state of the art.
SUMMARY OF THE INVENTION
The present invention relates to an improvement in a hydraulic actuator having a housing communicating pressurized fluid to a stepped bore therein via an inlet and a piston slidably disposed within the stepped bore engaging a brake shoe for urging the brake shoe from a normal position to a braking position when the pressure communicated to the bore is above a predetermined value, the improvement wherein a partition is movably disposed
In a drum brake assembly a pair of brake shoes is urged -into engagement with a drum to retard the rotation of the latter.
A hydraulic actuator slidably carries a piston which abuts at least one of the pair of brake shoes and the piston is responsive to increases in pressure within the hydraulic actuator to move relative thereto, thereby moving the brake shoe into engagement with the drum.
The piston rests on a stop on the hydraulic actuator so that upon pressurization of the hydraulic actuator the piston moves away from the stop to urge the brake shoe into braking engagement with the drum. When contact between the drum and brake shoe is initially achieved, the pair of brake shoes frictionally grip the 3 rotating drum and the pair of brake shoes is rotated slightly in the direction of rotation of the drum until one of the brake shoes abuts the stop. Further pressurization of the hydraulic actuator at this time increases the braking forces between the pair of brake shoes and the drum to retard the rotation of the drum.
When the one brake shoe abuts the hydraulic actuator stop upon initial contact between the pair of brake shoes and the drum a clunking noise occurs as the impact between the stop and the piston can be quite large. Consequently, elimination of this clunking noise by simple means without interfering with brake bleeding or imposing a delay on normal brake application rates is believed to be an improvement over the state of the art.
SUMMARY OF THE INVENTION
The present invention relates to an improvement in a hydraulic actuator having a housing communicating pressurized fluid to a stepped bore therein via an inlet and a piston slidably disposed within the stepped bore engaging a brake shoe for urging the brake shoe from a normal position to a braking position when the pressure communicated to the bore is above a predetermined value, the improvement wherein a partition is movably disposed
- 2 -rwl~3 ~~
-^` 1084431 within the stepped bore, the partition being connected to the piston by resilient means and being movable within the stepped bore in response to pressurized fluid therein for transmitting the force created by the pressurized fluid within the stepped bore during braking to the piston, the partition being biased by the resilient means into engagement with a shoulder defined by the stepped bore and also cooperating with the piston to substantially define a secondary chamber communicating with the inlet via a restrictive passage substantially defined by the partition, the piston including a portion in abutment with the housing when the :
brake shoe is in the normal position, the fluid pressure within the secondary chamber increasing as the brake shoe moves from the braking position to the normal position and the partition is in engagement with the shoulder, and the partition regulating reduction of the increased fluid pressure in the secondary chamber as the brake shoe moves from the braking position to the normal position in order to provide for gradual retraction of the piston portion into abutment with the housing, so as to substantially eliminate noise when the piston portion abuts the housing. -. .
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a front side view of a drum brake assembly;
and Figure 2 is a partial cross-sectional view of the encircled portion of Figure 1.
DETAILED DESCRIPTION
In Figure 1 a drum brake assembly generally referred to as reference numeral 10 includes a backing plate 12 which supports a hydraulic actuator 14 via fastener pins 16. A pair of brake shoes at 18 and 20 carry an adjustment mechanism at 22 opposite the hydraulic actuator 14 while hold-down springs at 24 support the pair of brake shoes on the backing rw/~
' 10~4431 plate 12. In addition, return springs at 26 retaTn the pair of brake shoes adjacent the hydraulic actuator 14.
Turning to F7gure 2, it is seen that the hydraulic actuator 14 comprises a houslng 30 havTng a right stepped bore 32 forming a shoulder 34.
A piston 36 is slidably disposed wTthTn the stepped bore 32 and Ts engaged wTth the brake shoe 18. The pTston 36 Tncludes a plate 38 whTch Ts rTgidly secured to the pTston 36 and provided wTth a radTal flange at 40 opposTng the end of the housing, thereby limiting retractTon of the pTston 36 wTthTn the stepped bore 32. Although the descrTptTon hereTn proceeds wTth refer-10 ence to the rTght stepped bore 32 and the pTston 36, it is clear that thehousing 30 Tncludes a simTlar left stepped bore and pTston.
In accordance wTth the TnventTon, a partitTon 44 is movably disposed wTthin the stepped bore 32 and is normally maTntaTned Tn abutment wTth the shoulder 311 by rr~ans of a resTlient member 46. The partTtTon 44 cooperates wTth the plston 36 to substant1ally define a secondary chamber 48 whTch receT~es the resTlient member 46. A restrTctTon passage at 50 communTcates the secondary chamber 48 wTth an Tnlet port 52 so that pressurTzed fluTd communlcated to the steppped bore 32 vTa the Tnlet port 52 wTll be communTcated to the secondary chamber 48 vTa the restrTc-20 tTon passage 50.
MODE OF OPEi~ATlON
When a brake applTcation Ts effected, pressurlzed fluTd Ts com-municated to the stepped bore 32 via the Tnlet port 52. ThTs pressurized fluid Is communTcated to the secondary chamber 48 via the restrTctTon passage 50 wherein the pTston 36 Ts movable Tn response to the pressurTzed fluld wlthTn the secondary chamber 48 Tn order to urge the brake shoe 18 Tnto frictTonal engagement wTth a drum 54. If the pressure of the pres surtzed fluid communTcated to the stepped bore 32 is ai~ove a predeter-mTned value, the force generated thereby Ts sufficient to move the partT-30 tTon away from the shoulder 34 to contract the resTlTent member 46, )89L431 thereby transmitttng the increase in the pressure of the pressurized fluidto the ptston 36 upon a brake applicatTon, and also communicating the increased pressurized fluid to the secondary chamber 48 via a clearance between the stepped bore 32 and the partition 44.
When the pair of brake shoes initially contact the rotating drum 54, the brake shoes frictTonally grip the drum so that the brake shoes are rotated slightly in the direction of the rotating drum. This reaction by the pair of brake shoes causes the brake shoe 18 to force the piston 36 to retract within the stepped bore 32. Consequently, the pressure of the '0 pressurtzed fluid wlthin the secondary chamber is increased to ~ove the partition 44 in abutment with the shoulder 34. Thereafter, the increase in the pressure of the pressurTzed fluld with;n the secondary chamber 48 opposes any retraction of the ptston 36 so that the flange 40 attached to the piston will not impact against the end of the houslng 30. However, as the Increased pressurlzed fluTd withln the secondary chamber 48 ts vented vla restr7cted passage 50 to the stepped bore 32 the piston 36 gradually retracts wlthin the stepped bore 32 until the flange 40 abuts the end of the houslng, thereby stopping retraction of the piston 36.
After this initlal contact, further brakTng increases the pressure of pressurlzed fluld communicated through the inlet port 52 to urge the left piston (not shown) to move the pair of brake shoes into tighter frictional engagement wlth the rotating drum in order to retard the rotation o~ the latter. At this ttme the piston 36 and the flange 40 act as an anchor to oppose rotatlon of the brake shoe 18, directly, and the brake shoe 20, indirectly, via adjustment means 22, with the rotating drum 54.
If the drum 54 is rotating in a clockwise direction, opposite to the dlrection illustrated in FTgure 1, then the initTal contact between the pair of brake shoes and the drum will cause the brake shoe 20 to urge a left plston (not shown) in a left stepped bore (not shown) to retract
-^` 1084431 within the stepped bore, the partition being connected to the piston by resilient means and being movable within the stepped bore in response to pressurized fluid therein for transmitting the force created by the pressurized fluid within the stepped bore during braking to the piston, the partition being biased by the resilient means into engagement with a shoulder defined by the stepped bore and also cooperating with the piston to substantially define a secondary chamber communicating with the inlet via a restrictive passage substantially defined by the partition, the piston including a portion in abutment with the housing when the :
brake shoe is in the normal position, the fluid pressure within the secondary chamber increasing as the brake shoe moves from the braking position to the normal position and the partition is in engagement with the shoulder, and the partition regulating reduction of the increased fluid pressure in the secondary chamber as the brake shoe moves from the braking position to the normal position in order to provide for gradual retraction of the piston portion into abutment with the housing, so as to substantially eliminate noise when the piston portion abuts the housing. -. .
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a front side view of a drum brake assembly;
and Figure 2 is a partial cross-sectional view of the encircled portion of Figure 1.
DETAILED DESCRIPTION
In Figure 1 a drum brake assembly generally referred to as reference numeral 10 includes a backing plate 12 which supports a hydraulic actuator 14 via fastener pins 16. A pair of brake shoes at 18 and 20 carry an adjustment mechanism at 22 opposite the hydraulic actuator 14 while hold-down springs at 24 support the pair of brake shoes on the backing rw/~
' 10~4431 plate 12. In addition, return springs at 26 retaTn the pair of brake shoes adjacent the hydraulic actuator 14.
Turning to F7gure 2, it is seen that the hydraulic actuator 14 comprises a houslng 30 havTng a right stepped bore 32 forming a shoulder 34.
A piston 36 is slidably disposed wTthTn the stepped bore 32 and Ts engaged wTth the brake shoe 18. The pTston 36 Tncludes a plate 38 whTch Ts rTgidly secured to the pTston 36 and provided wTth a radTal flange at 40 opposTng the end of the housing, thereby limiting retractTon of the pTston 36 wTthTn the stepped bore 32. Although the descrTptTon hereTn proceeds wTth refer-10 ence to the rTght stepped bore 32 and the pTston 36, it is clear that thehousing 30 Tncludes a simTlar left stepped bore and pTston.
In accordance wTth the TnventTon, a partitTon 44 is movably disposed wTthin the stepped bore 32 and is normally maTntaTned Tn abutment wTth the shoulder 311 by rr~ans of a resTlient member 46. The partTtTon 44 cooperates wTth the plston 36 to substant1ally define a secondary chamber 48 whTch receT~es the resTlient member 46. A restrTctTon passage at 50 communTcates the secondary chamber 48 wTth an Tnlet port 52 so that pressurTzed fluTd communlcated to the steppped bore 32 vTa the Tnlet port 52 wTll be communTcated to the secondary chamber 48 vTa the restrTc-20 tTon passage 50.
MODE OF OPEi~ATlON
When a brake applTcation Ts effected, pressurlzed fluTd Ts com-municated to the stepped bore 32 via the Tnlet port 52. ThTs pressurized fluid Is communTcated to the secondary chamber 48 via the restrTctTon passage 50 wherein the pTston 36 Ts movable Tn response to the pressurTzed fluld wlthTn the secondary chamber 48 Tn order to urge the brake shoe 18 Tnto frictTonal engagement wTth a drum 54. If the pressure of the pres surtzed fluid communTcated to the stepped bore 32 is ai~ove a predeter-mTned value, the force generated thereby Ts sufficient to move the partT-30 tTon away from the shoulder 34 to contract the resTlTent member 46, )89L431 thereby transmitttng the increase in the pressure of the pressurized fluidto the ptston 36 upon a brake applicatTon, and also communicating the increased pressurized fluid to the secondary chamber 48 via a clearance between the stepped bore 32 and the partition 44.
When the pair of brake shoes initially contact the rotating drum 54, the brake shoes frictTonally grip the drum so that the brake shoes are rotated slightly in the direction of the rotating drum. This reaction by the pair of brake shoes causes the brake shoe 18 to force the piston 36 to retract within the stepped bore 32. Consequently, the pressure of the '0 pressurtzed fluid wlthin the secondary chamber is increased to ~ove the partition 44 in abutment with the shoulder 34. Thereafter, the increase in the pressure of the pressurTzed fluld with;n the secondary chamber 48 opposes any retraction of the ptston 36 so that the flange 40 attached to the piston will not impact against the end of the houslng 30. However, as the Increased pressurlzed fluTd withln the secondary chamber 48 ts vented vla restr7cted passage 50 to the stepped bore 32 the piston 36 gradually retracts wlthin the stepped bore 32 until the flange 40 abuts the end of the houslng, thereby stopping retraction of the piston 36.
After this initlal contact, further brakTng increases the pressure of pressurlzed fluld communicated through the inlet port 52 to urge the left piston (not shown) to move the pair of brake shoes into tighter frictional engagement wlth the rotating drum in order to retard the rotation o~ the latter. At this ttme the piston 36 and the flange 40 act as an anchor to oppose rotatlon of the brake shoe 18, directly, and the brake shoe 20, indirectly, via adjustment means 22, with the rotating drum 54.
If the drum 54 is rotating in a clockwise direction, opposite to the dlrection illustrated in FTgure 1, then the initTal contact between the pair of brake shoes and the drum will cause the brake shoe 20 to urge a left plston (not shown) in a left stepped bore (not shown) to retract
3 therein in a similar manner as the right piston 36. Moreover, a similar - 10~4431 partition (not shown) is movably disposed within the left stepped bore to control the retraction of the left piston upon initial contact of the pair of brake shoes with the clockwise rotating drum.
Although venting of the secondary chamber 48 is provided by the restricted passage 50, it is possible for the partition 44 to form a restricted passage with the shoulder 34, thereby eliminating the necessTty for the passage 50.
It is a1so apparent that many alternatives and/or modifications to the present invention are posslble by those skilled in the art. Accord-Ingly, these alternatlves and/or modifications are intended to fall withinthe scope of the appended claims.
. . ., , : . ~ .
.
Although venting of the secondary chamber 48 is provided by the restricted passage 50, it is possible for the partition 44 to form a restricted passage with the shoulder 34, thereby eliminating the necessTty for the passage 50.
It is a1so apparent that many alternatives and/or modifications to the present invention are posslble by those skilled in the art. Accord-Ingly, these alternatlves and/or modifications are intended to fall withinthe scope of the appended claims.
. . ., , : . ~ .
.
Claims
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a hydraulic actuator having a housing communicating pressurized fluid to a stepped bore therein via an inlet and a piston slidably disposed within the stepped bore engaging a brake shoe for urging the brake shoe from a normal position to a braking position when the pressure communicated to the bore is above a predetermined value, the improvement wherein a partition is movably disposed within the stepped bore, said partition being connected to the piston by resilient means and being movable within the stepped bore in response to pressurized fluid therein for transmitting the force created by the pressurized fluid within the stepped bore during braking to the piston, said partition being biased by said resilient means into engagement with a shoulder defined by the stepped bore and also cooperating with said piston to substantially define a secondary chamber communicating with the inlet via a restrictive passage substantially defined by said partition, the piston including a portion in abutment with the housing when the brake shoe is in the normal position, the fluid pressure within the secondary chamber increasing as the brake shoe moves from the braking position to the normal position and the partition is in engagement with the shoulder, and said partition regulating reduction of the increased fluid pressure in the secondary chamber as the brake shoe moves from the braking position to the normal position in order to provide for gradual retraction of said piston portion into abutment with the housing, so as to substantially eliminate noise when the piston portion abuts the housing.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US83353177A | 1977-09-15 | 1977-09-15 | |
| US833,531 | 1977-09-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1084431A true CA1084431A (en) | 1980-08-26 |
Family
ID=25264668
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA306,121A Expired CA1084431A (en) | 1977-09-15 | 1978-06-23 | Hydraulic actuator for a drum brake |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS5453759A (en) |
| AU (1) | AU3920478A (en) |
| CA (1) | CA1084431A (en) |
| DE (1) | DE2837340A1 (en) |
| FR (1) | FR2403489A1 (en) |
| GB (1) | GB2004326A (en) |
| IT (1) | IT1098567B (en) |
| TR (1) | TR20806A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| MX153781A (en) * | 1980-08-28 | 1987-01-09 | Kelsey Hayes Co | IMPROVEMENTS IN HYDRAULIC PISTON FOR AUTOMOBILE BRAKE SYSTEMS |
| DE102017123978B3 (en) | 2017-10-16 | 2019-02-28 | Saf-Holland Gmbh | Drum brake with angular piston arrangement |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB413089A (en) * | 1933-04-13 | 1934-07-12 | Rover Co Ltd | Motor-vehicle brakes |
| US2189134A (en) * | 1935-12-28 | 1940-02-06 | Joseph M Sachs | Hydraulic brake |
| US2575963A (en) * | 1949-08-11 | 1951-11-20 | Lambert & Brake Corp | Hydraulic disk brake and actuator means therefor |
| FR1097744A (en) * | 1953-04-23 | 1955-07-08 | Bendix Aviat Corp | Brake improvements |
| US3147825A (en) * | 1961-12-06 | 1964-09-08 | Ford Motor Co | Automotive brake having servo assist fluid distributing means |
-
1978
- 1978-06-23 CA CA306,121A patent/CA1084431A/en not_active Expired
- 1978-08-14 GB GB7833182A patent/GB2004326A/en not_active Withdrawn
- 1978-08-24 AU AU39204/78A patent/AU3920478A/en active Pending
- 1978-08-26 DE DE19782837340 patent/DE2837340A1/en not_active Withdrawn
- 1978-09-01 TR TR20806A patent/TR20806A/en unknown
- 1978-09-11 FR FR7825990A patent/FR2403489A1/en not_active Withdrawn
- 1978-09-12 IT IT27534/78A patent/IT1098567B/en active
- 1978-09-14 JP JP11242778A patent/JPS5453759A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| GB2004326A (en) | 1979-03-28 |
| IT7827534A0 (en) | 1978-09-12 |
| AU3920478A (en) | 1980-02-28 |
| IT1098567B (en) | 1985-09-07 |
| DE2837340A1 (en) | 1979-03-29 |
| TR20806A (en) | 1982-09-03 |
| JPS5453759A (en) | 1979-04-27 |
| FR2403489A1 (en) | 1979-04-13 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |