GB2080453A - Piston anti-knock back assemblies - Google Patents
Piston anti-knock back assemblies Download PDFInfo
- Publication number
- GB2080453A GB2080453A GB8022587A GB8022587A GB2080453A GB 2080453 A GB2080453 A GB 2080453A GB 8022587 A GB8022587 A GB 8022587A GB 8022587 A GB8022587 A GB 8022587A GB 2080453 A GB2080453 A GB 2080453A
- Authority
- GB
- United Kingdom
- Prior art keywords
- ring
- piston
- cylinder bore
- main portion
- resilient
- 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.)
- Granted
Links
- 230000000712 assembly Effects 0.000 title description 7
- 238000000429 assembly Methods 0.000 title description 7
- 125000006850 spacer group Chemical group 0.000 claims abstract description 7
- 230000002093 peripheral effect Effects 0.000 claims description 12
- 239000012530 fluid Substances 0.000 claims description 6
- 238000007493 shaping process Methods 0.000 claims description 3
- 230000037431 insertion Effects 0.000 abstract 1
- 238000003780 insertion Methods 0.000 abstract 1
- 238000000034 method Methods 0.000 description 3
- 238000009434 installation Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
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
- F16D65/38—Slack adjusters
- F16D65/40—Slack adjusters mechanical
- F16D65/52—Slack adjusters mechanical self-acting in one direction for adjusting excessive play
- F16D65/54—Slack adjusters mechanical self-acting in one direction for adjusting excessive play by means of direct linear adjustment
-
- 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
- F16D2125/00—Components of actuators
- F16D2125/02—Fluid-pressure mechanisms
- F16D2125/06—Pistons
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Braking Arrangements (AREA)
- Pistons, Piston Rings, And Cylinders (AREA)
Abstract
A brake actuator 10 comprising a piston 12 slidably mounted within a cylinder bore 14 comprises an anti- knock back assembly 30 comprising an expanded resilient split ring 32 in frictional contact with a main portion 26 of bore 14 and loosely axially located in an annular groove 28 adjacent a conical head portion 22 of piston 12. The resilient ring 32, when unexpanded, is a sliding fit within the main portion 26 of bore 14, and the resilient ring is provided with abutment spacer means (shaped frustum or leg portion) which, when the ring is placed into contact with an end wall 20 of the cylinder bore 14, the plane of the ring is spaced far enough from wall 20 to allow insertion of the conical head 22 within the ring so as to expand the resilient ring over conical head portion 22 until it snaps into position in said annular groove 28. This gives frictional grip of ring 32 with bore 26, and ring also acts to adjust for friction surface wear to provide constant retraction distance (w-t). <IMAGE>
Description
SPECIFICATION
Piston anti-knock back assemblies
This invention relates to piston anti-knock back assemblies in hydraulically actuated brake assemblies, in particular in motor vehicle disc brake assemblies.
Hydraulically actuated motor vehicle disc brake assemblies usually have a brake actuator comprising a piston slidably mounted within a cylinder bore and operable to urge a friction surface into contact with a rotary disc surface on supply of hydraulic fluid under pressure to said cylinder bore. In such arrangements, it is desirable that the piston, upon release of the disc brake subsequent to application of the disc brake, should only retract within the cylinder bore a sufficient distance to ensure that the friction surface is out of contact with the rotary disc surface. Further retraction of the piston beyond this point is unnecessary, since it leads to a requirement for extended travel of a foot pedal associated with the disc brake assembly in order to apply the disc brake.It is desirable therefore to limit the extent to which the piston will retract upon release of the brake, even if exposed to a certain degree of knock-back of the piston within the cylinder due to the rotary disc used in the disc brake assembly not running completely true with respect to the disc brake assembly.
Piston anti-knock back assemblies are known in which there is an annular member loosely mounted upon a piston of a piston and cylinder arrangement, with the annular member being in frictional contact with the cylinder bore. Thus, in operation of the brake, the piston is advanced along the cylinder bore, taking the annular member with it, until application of the brake pad associated with the piston takes place with the member to be braked. Upon release of the brake, the piston retracts within the cylinder bore by an amount governed by the clearance between the piston and the annular member retained thereon, and is then prevented from further retraction within the cylinder bore. An example of such a piston anti-knock back assembly is disclosed in
British patent specification number 865 048.The piston anti-knock back assembly disclosed in this patent, although effective, requires that the piston should be of a somewhat complicated two part structure in order to retain the annular member loosely engaged therewith.
A piston anti-knock back assembly according to the present invention comprises, in a disc brake assembly having a brake actuator comprising a piston slidably mounted within a cylinder bore and operable to urge a friction surface into contact with a rotary disc surface upon supply of hydraulic fluid under pressure to said cylinder bore, said cylinder bore having an enlarged stepped section therein adjacent the end wall of the cylinder bore, an expanded resilient split ring in frictional contact with a main portion of the cylinder bore and loosely axially located in an annular groove adjacent the head of said piston by expanding said
ring over a conical frustum of the piston head until
said ring snaps into position in said annular
groove, the ring, when unexpanded, being a
sliding fit within the main portion of the cylinder
bore and having abutment spacer means on one
side of the ring which, when the unexpanded ring
is inserted into the cylinder bore as far as said
stepped section of the bore, contacts said cylinder
end wall and maintains the plane of the ring far
enough from the cylinder end wall to allow the
conical frustum of the piston head to be thrust
through the ring to locate the ring in position in
said annular groove
Preferably the piston anti-knock back assembly
according to the present invention is one in which
the width of the annular groove in the piston
exceeds the axial thickness of the resilient ring by
a predetermined amount such that retraction of
the piston can occur sufficiently to remove said
friction surface from rubbing contact with said
rotary disc surface until further retraction of said
piston is restrained by said frictional contact
between said ring and said cylinder bore.
In a preferred embodiment of the invention, the
abutment spacer means on the resilient ring is
provided by shaping the outer peripheral portion of
the resilient ring into a frustum of a hollow cone.
Alternatively, the abutment spacer means on the
resilient ring can comprise at least three leg
portions extending from said one side of the ring
axially of said ring and equispaced about the inner
perimeter of said ring.
Advantageously, the outer periphery of the
resilient ring has a sharp edge, which, when the
ring is expanded into frictional contact with the
main portion of the cylinder bore, tends to dig in to said main portion of the cylinder bore when the piston is retracted within said cylinder bore.
Alternatively, the outer periphery of the resilient
ring can be provided with a serrated edge, which, when the ring is expanded into frictional engagement with the main portion of the cylinder bore, tends to dig in to said main portion of the cylinder bore when the piston is retracted within said cylinder bore.
The invention and how it may be performed are hereinafter particularly described with reference to the accompanying drawings, in which: Figure 1 is a partial cross sectional view of a brake actuator of a disc brake assembly incorporating an anti-knock back assembly according to the present invention; and
Figures 2 to 4 show similar views of a partial cross section of the brake actuator shown in
Figure 1, demonstrating the procedure for mounting the anti-knock back assembly in place upon the piston of the brake actuator shown in
Figure 1.
As can be seen in Figure 1, a brake actuator 10 of a disc brake assembly (not shown) comprises a piston 1 2 slidably mounted within a cylinder bore
14, and operable to urge a friction surface (not shown) connected to an open end 1 6 of the piston 1 2 into contact with a rotary disc surface (not shown) upon supply of hydraulic fluid under pressure to a chamber 18 formed between an end wall 20 of the cylinder bore 14 and a head portion 22 of the piston 12. An annular seal 24 prevents loss of hydraulic fluid from the chamber 18 past the piston 12 and a main portion 26 of the cylinder bore 14. The cylinder bore 14 has an enlarged stepped section 28 formed therein adjacent the end wall 20 of the cylinder bore, for a purpose that will be made apparent later in this description.
The head portion 22 of the piston 12 is formed as a conical frustum, and there is an annular groove 28 formed in the piston 12 adjacent the maximum diameter portion of the conical head portion 22 of the piston 12. Annular groove 28 is of a predetermined width (w), as will be discussed hereinafter in the description. As can be seen in
Figure 2 of the accompanying drawings, the conical head portion 22 has a predetermined maximum diameter d2 and a predetermined minimum diameter d1.
Referring again to Figure 1 of the drawings, the brake actuator 10 is provided with a piston antiknock back assembly 30 which comprises an expanded resilient split ring 32 which is loosely axially located in the annular groove 28 behind the conical head portion 22 of the piston 12. The outer peripheral portion of the resilient ring 32 is shaped into a frustum of a hollow cone, and is in frictional contact with the main portion 26 of the cylinder bore. The thickness of the split ring 32 is designated by t, as shown in Figure 2 of the drawings. The thickness t of the resilient ring 32 is smaller than the width wofthe annular groove 28 by a predetermined amount, which corresponds to the desired distance of retraction of the piston 12 within the cylinder bore 14 upon release of the disc brake.The outer conical peripheral portion of the resilient ring 32 is provided with a sharp edge which tends to dig in to said main portion 26 of the cylinder bore when the piston is retracted within the cylinder bore. Consequently, the coefficient of friction existing between the outer peripheral portion of the resilient ring 32 and the main portion 26 of the cylinder bore is much larger than the coefficient of friction existing between the inner surface of the slit ring 32 and the base of the annular groove 28. Consequently, during retraction of the piston upon release of the disc brake, relative movement can occur between the piston 12 and the split ring 32 until the distance (w - t) is taken up and the edge of the groove 28 abuts upon the side of the split ring 32.This relative movement is just sufficient to remove the friction surface associated with the piston 12 from rubbing contact with said rotary disc surface. Any further retraction of the piston 12 within the cylinder bore 14 is opposed by the frictional contact of the outer peripheral portion of the resilient ring with the main portion 26 of the cylinder bore 14. The slope of the outer conical peripheral portion of the resilient ring 32 relative to the main portion 26 of the cylinder bore 14 ensures that the frictional contact between this outer conical peripheral portion of the ring 32 and the main portion 26 of the cylinder bore is greater in the direction of retraction of the piston than it is in the opposite direction.Consequently, when wear of the friction surface associated with the piston 12 takes place, this is compensated for by relative movement taking place between the resilient ring 32 and the main portion 26 of the cylinder bore during application of hydraulic pressure to chamber 1 8 during application of the disc brake. Upon release of the disc brake, the resilient ring remains in its new position, and the retraction movement of the piston 12 is restored to the predetermined distance (w-- t),
Installation of the piston anti-knock back assembly 30 in position upon the piston 12 is a simple procedure indicated schematically in
Figures 2 to 4 of the accompanying drawings. The resilient ring 32, when unexpanded, is a sliding fit within the main portion 26 of the cylinder bore 14.
Accordingly, to install the resilient split ring 32 in position within the annular groove 28 of the piston 12, the resilient split ring 32 is first placed in the cylinder bore 14 so that the outer conical peripheral portion of this ring contacts the cylinder end wall 20 as shown in Figure 2. This outer conical peripheral portion maintains the plane of the resilient split ring 32 a predetermined distance from the cylinder end wall 20, which predeterrhined distance is greater than the height of the conical head portion 22 of piston 12.The internal diameter d3 of the resilient split ring 32 is less than d2, and greater than d,. Piston 12 is then inserted within the main portion 26 of the cylinder bore 14 and pushed down this main portion 26 until the conical head portion 22 of the piston 12 is inserted within the resilient split ring 32, as shown in Figure 3 of the drawings. Further inward pressure on piston 12 causes the conical head portion 22 to expand the resilient split ring 32 until this resilient split ring snaps into position in said annular groove 28.The diameter of the base of the annular groove 28 is greater than d3 by a predetermined amount sufficient to ensure that the resilient split ring 32 stays expanded by an amount sufficient to give the desired frictional contact between the outer conical peripheral portion of the resilient split ring and the main portion 26 of the cylinder bore. The enlarged stepped section 28 of the cylinder bore 14 is provided to allow room for the resilient split ring to expand as it is forced over the conical head portion 22 of the piston 12 and into position in the annular groove 28, as shown in Figure 4 of the drawings. Pressurisation of the chamber 18 with hydraulic fluid then moves the piston 12 out of the a cylinder bore 14 until the friction surface r associated with piston 12 comes into contact withy the rotary disc surface. During this process, the expanded resilient split ring 32 leaves the enlarged step section 28 of cylinder bore 14 and is placed in'frictional contact with the main portion 26 of the cylinder bore. The movement of the piston 12 relative to the cylinder bore 14 during this brake apply movement effectively positions the resilient split ring 32 in the correct position within the cylinder bore 14 to act as a piston antiknock back assembly.
If desired, the resilient split ring can be shaped with at least three leg portions extending axially from one side of, and equi-spaced about the perimeter of, the resilient split ring, instead of shaping the outer peripheral portion of the resilient split ring into a frustum of a hollow cone.
In such an instance, each leg portion would be of a longer length than the depth of the conical head portion 22 of piston 12. Similarly, if desired, the outer periphery of the expanded ring can have a serrated edge portion to increase the degree of frictional contact between the outer periphery and the main portion 26 of the cylinder bore.
A piston anti-knock back assembly according to the present invention is a simple, yet effective, assembly for obtaining a desired piston anti-knock back arrangement in a disc brake assembly.
Claims (7)
1. A piston anti-knock back assembly in a disc brake assembly having a brake actuator comprising a piston slidably mounted within a cylinder bore and operable to urge a friction surface into contact with a rotary disc surface upon supply of hydraulic fluid under pressure to said cylinder bore, said cylinder bore having an enlarged stepped section therein adjacent the end wall of the cylinder bore, said anti-knock back assembly comprising an expanded resilient split ring in frictional contact with a main portion of the cylinder bore, and loosely axially located in an annular groove adjacent the head of said piston by expanding said ring over a conical frustum of the piston head until said ring snaps into position in said annular groove, the ring, when unexpanded, being a sliding fit within the main portion of the cylinder bore and having abutment spacer means on one side of the ring which, when the unexpanded ring is inserted in the cylinder bore as far as said stepped section of the bore, contacts said cylinder end wall and maintains the plane of the ring far enough from the cylinder end wall to allow the conical frustum of the piston head to be thrust through the ring to locate the ring in position in said annular groove.
2. A piston anti-knock back assembly according to claim 1, in which the width of the annular groove in the piston exceeds the axial thickness of the resilient ring by a predetermined amount such that retraction of the piston can occur sufficientiy to remove said friction surface from rubbing contact with said rotary disc surface until further retraction of said piston is restrained by said frictional contact between said ring and said cylinder bore.
3. A piston anti-knock back assembly according to claim 1 or 2, in which the abutment spacer means on said ring is provided by shaping the outer peripheral portion of the resilient ring into a frustum of a hollow cone.
4. A piston anti-knock back assembly according to claim 1 or 2, in which the abutment spacer means on said ring comprises at least three leg portions extending from said one side of the ring axially of said ring and equispaced about the inner perimeter of said ring.
5. A piston anti-knock back assembly according to any one of the preceding claims, in which the outer periphery of the expanded ring in frictional contact with the main portion of the cylinder bore has a sharp edge tending to dig in to said main portion when the piston is retracted within said cylinder bore.
6. A piston anti-knock back assembly according to any one of claims 1 to 4, in which the outer periphery of the expanded ring in frictional contact with the main portion of the cylinder bore has a serrated edge tending to dig in to said main portion when the piston is retracted within said cylinder bore.
7. A piston anti-knock back assembly substantially as hereinbefore particularly described and as shown in Figures 1 to 4 of the accompanying drawings.
Priority Applications (9)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8022587A GB2080453B (en) | 1980-07-10 | 1980-07-10 | Piston anti-knock back assemblies |
| AU71802/81A AU544866B2 (en) | 1980-07-10 | 1981-06-12 | Piston anti-knock back assemblies |
| DE19813125273 DE3125273A1 (en) | 1980-07-10 | 1981-06-25 | HYDRAULIC BRAKE PISTON |
| BR8104302A BR8104302A (en) | 1980-07-10 | 1981-07-06 | PISTON REAR SHOCK ASSEMBLY |
| IT48849/81A IT1171370B (en) | 1980-07-10 | 1981-07-07 | IMPROVEMENT IN DISC BRAKE PISTON ARRANGEMENTS |
| FR8113413A FR2486615A1 (en) | 1980-07-10 | 1981-07-08 | ANTI-HAMMER PISTON DEVICE FOR BRAKE CYLINDER |
| ES503802A ES8204102A1 (en) | 1980-07-10 | 1981-07-09 | Piston anti-knock back assemblies |
| JP56107244A JPS5790428A (en) | 1980-07-10 | 1981-07-10 | Knocking back preventing assembly for piston |
| BE0/205387A BE889596A (en) | 1980-07-10 | 1981-07-10 | BACKFLOW DEVICE FOR PISTON |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8022587A GB2080453B (en) | 1980-07-10 | 1980-07-10 | Piston anti-knock back assemblies |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2080453A true GB2080453A (en) | 1982-02-03 |
| GB2080453B GB2080453B (en) | 1983-11-09 |
Family
ID=10514672
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8022587A Expired GB2080453B (en) | 1980-07-10 | 1980-07-10 | Piston anti-knock back assemblies |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS5790428A (en) |
| AU (1) | AU544866B2 (en) |
| BE (1) | BE889596A (en) |
| BR (1) | BR8104302A (en) |
| DE (1) | DE3125273A1 (en) |
| ES (1) | ES8204102A1 (en) |
| FR (1) | FR2486615A1 (en) |
| GB (1) | GB2080453B (en) |
| IT (1) | IT1171370B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2117464A (en) * | 1982-03-27 | 1983-10-12 | Automotive Products Plc | Disc brakes |
| EP0413112A1 (en) * | 1989-07-19 | 1991-02-20 | Knorr-Bremse Ag | Vehicle brake hydraulic cylinder |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115199680B (en) * | 2022-07-08 | 2024-03-19 | 潍柴动力股份有限公司 | Forced brake release device and method for walking motor |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB865048A (en) * | 1956-11-07 | 1961-04-12 | Zapadoceske Autodruzstvo V Plz | An hydraulic braking system |
-
1980
- 1980-07-10 GB GB8022587A patent/GB2080453B/en not_active Expired
-
1981
- 1981-06-12 AU AU71802/81A patent/AU544866B2/en not_active Ceased
- 1981-06-25 DE DE19813125273 patent/DE3125273A1/en not_active Withdrawn
- 1981-07-06 BR BR8104302A patent/BR8104302A/en unknown
- 1981-07-07 IT IT48849/81A patent/IT1171370B/en active
- 1981-07-08 FR FR8113413A patent/FR2486615A1/en active Granted
- 1981-07-09 ES ES503802A patent/ES8204102A1/en not_active Expired
- 1981-07-10 BE BE0/205387A patent/BE889596A/en not_active IP Right Cessation
- 1981-07-10 JP JP56107244A patent/JPS5790428A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2117464A (en) * | 1982-03-27 | 1983-10-12 | Automotive Products Plc | Disc brakes |
| EP0413112A1 (en) * | 1989-07-19 | 1991-02-20 | Knorr-Bremse Ag | Vehicle brake hydraulic cylinder |
Also Published As
| Publication number | Publication date |
|---|---|
| BE889596A (en) | 1981-11-03 |
| GB2080453B (en) | 1983-11-09 |
| FR2486615B1 (en) | 1985-03-22 |
| BR8104302A (en) | 1982-03-23 |
| IT1171370B (en) | 1987-06-10 |
| ES503802A0 (en) | 1982-04-16 |
| AU7180281A (en) | 1982-01-14 |
| ES8204102A1 (en) | 1982-04-16 |
| FR2486615A1 (en) | 1982-01-15 |
| IT8148849A0 (en) | 1981-07-07 |
| DE3125273A1 (en) | 1982-07-08 |
| JPS5790428A (en) | 1982-06-05 |
| AU544866B2 (en) | 1985-06-20 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19920710 |