US 4,359,869 A · Hydraulic power boost apparatus

Abstract

A hydraulic power boost apparatus for use with the braking system of an automotive vehicle includes a power piston cooperating with a slide valve to define a plurality of spool valves to regulate the flow of a pressurized fluid therethrough to selectively apply the fluid to boost the force applied to the power piston. A resilient member is positioned within the power piston blind bore to modulate the force transmitted from the slide valve to the power piston. The power piston also includes an annular ridge for engaging a mating annular ridge of the slide valve to limit the travel of the slide valve to prevent the resilient member from being deformed beyond its elastic limit.

Drawings

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Drawings

Claims10

Dependent claims

A hydraulic power boost apparatus in a brake system for an automotive vehicle comprising:

a booster housing communicating with a working fluid source and receiving therefrom a working fluid, which working fluid recirculates through a hydraulic circuit via said booster housing;
a power piston slidably disposed within the interior of said booster housing and movable along the longitudinal axis of said housing, said power piston being connected with a brake master cylinder which distributes pressurized fluid to each of individual wheel cylinders, said power piston cooperating with said booster housing to define a pressure chamber within said booster housing where a boost pressure is built up, and said power piston defining therein a longitudinally extending blind bore having a bottom adjacent said master cylinder;
an elastically deformable resilient member disposed at the bottom of said blind bore, said resilient member having a predetermined thickness;
a valve member disposed within said power piston and cooperating therewith to connect and disconnect said pressure chamber with respect to said fluid source in response to application and release of a brake pedal, which valve member is movable from an initial position in which it is spaced from said resilient member for disconnecting said pressure chamber from said fluid source, to a first position in which it abuts against said resilient member to push said power piston towards said master cylinder to connect said pressure chamber to said fluid source, and to a second position in which it deforms said resilient member to transmit a braking force applied to said brake pedal directly to said power piston;
and
a stroke limiting means for limiting the movement of said valve means beyond said second position, thereby preventing said resilient member from being deformed beyond its elastic limit.

3 more elements

A hydraulic power boost apparatus in a brake system for an automotive vehicle comprising:

a substantially cylindrical booster housing having inlet and outlet ports respectively communicating with a working fluid source in order to recirculate a working fluid through said housing;
a substantially cylindrical power piston slidably disposed within the interior of said booster housing and movable along the longitudinal axis of said booster housing, said power piston defining a blind bore adjacent a brake master cylinder and cooperating with said booster housing to define a pressure chamber within said booster housing, where a boost pressure is built up in response to application of a brake pedal, said power piston being connected with said brake master cylinder for transmitting the boost pressure thereto;
a substantially cylindrical valve member cooperatively disposed within said power piston and movable along the longitudinal axis of said power piston, said valve member defining a plurality of communication passages to direct the flow of working fluid within the internal periphery of said power piston, said valve member being cooperatively connected with said brake pedal through an input rod so that it establishes communication between said inlet port and said pressure chamber upon said brake pedal being depressed in order to build up the boost pressure;
a resilient member disposed within the interior of said power piston and facing one end of said valve member, said resilient member being provided with an annular projection on the surface facing said end of the valve member, said resilient member having a predetermined elastic limit beyond which it should not be compressed;
a radially extending shoulder extending from the internal periphery of said power piston;
a surface associated with and extending radially beyond the outer periphery of said valve member at a location opposing said shoulder, said surface being spaced from said shoulder at a given distance which limits the stroke of said valve member and thereby prevents said resilient member from being compressed beyond its elastic limit.

3 more elements

A hydraulic power boost apparatus in a brake system for an automotive vehicle comprising:

a substantially cylindrical booster housing having an inlet port and an outlet port respectively communicating with a working fluid source in order to recirculate the working fluid therethrough;
a substantially cylindrical power piston slidably disposed within the interior of said booster housing and movable along the longitudinal axis of said booster housing, said power piston dividing the interior of said booster housing into two chambers, one of which serves as a pressure chamber where the boost pressure is built up while a brake pedal is depressed, said power piston being cooperatively connected with a brake system master cylinder;
a substantially cylindrical valve member cooperatively disposed within said power piston and movable along the longitudinal axis of said power piston, said valve member defining a plurality of communication passages to direct the flow of working fluid within the internal periphery of said power piston, said valve member being cooperatively connected with said brake pedal through an operating rod so that it establishes communication between said inlet port and said pressure chamber via said cylindrical valve when the brake pedal is depressed;
a resilient member of substantially dish-shaped configuration having a circumferential projective section and central planar section, said circumferential projective section protruding toward the corresponding end of said valve member, which resilient member being disposed within said power piston and opposing to said corresponding end of said valve member so that it can be deformed by abutment of said valve member against the resilient member when the brake pedal is applied exceeding a given amount said resilient member having a predetermined elastic limit beyond which it should not be compressed by an allowable valve member stroke following contact of said resilient member by said valve member;
a means for limiting the valve member stroke toward said resilient member, which limit is determined so that the elastic limit of said resilient member is not exceeded, said means comprising a shoulder extending radially inwardly from the internal periphery of said power piston, and a surface associated with and extending radially outwardly beyond the outer periphery of said valve member at a location opposing said shoulder, said surface being spaced from said shoulder at a given distance which establishes the allowable valve member stroke.

2 more elements

Dependencies are inferred from the claim text.

Description4,368 words

Summary710 words

#1. Field of the Invention

#The present invention relates generally to a hydraulic power boost apparatus for use with an automotive vehicle, and more specifically to a hydraulic power boost apparatus having a means for limiting the travel of the slide valve within the apparatus to prevent damage to the resilient power cushion positioned within the apparatus.

#2. Description of the Prior Art

Brief description of the drawings7 figures

#The present invention will become more fully understood from the detailed description given below, and from the accompanying drawings of the preferred embodiment of the present invention, which, however, are not to be limitative of the present invention in any way, but are for the purpose of elucidation and explanation only.

#In the drawings:

#FIG. 1 is a diagramatical illustration of a hydraulic system to be applied to a fork lift truck employing a hydraulic booster according to the present invention;

Detailed description3,453 words

#Referring now to the drawings, particularly to FIG. 1, there is illustrated a general construction of a hydraulic system used on a fork-lift truck or the like. Working fluid is generally stored in a fluid reservoir 10. A fluid pump 12 communicates with the fluid reservoir 10 through a fluid suction passage 14. The fluid pump 12 is mechanically connected to an engine 16 such as an internal combustion engine to be driven thereby. The fluid pump 12 pressurizes the working fluid and feeds it to an inlet port 18 of a hydraulically operative boost mechanism 20. The hydraulic booster 20 cooperates with a brake pedal 21 and with a braking system master cylinder 22.

#In a fluid passage 24 connecting the fluid pump 12 to the hydraulic booster inlet port 18, there is provided a flow-priority valve 26. Through the flow-priority valve 26, the working fluid is also fed to a working section of the vehicle, for example, a lifter operating system 30, via a passage 36.

#The hydraulic lifter system 30 comprises control valves 32 and 34, communicating with a lifting cylinder 38 for lifting a fork of the vehicle (not shown), and a tilting cylinder 40 for tilting the fork to up the free end thereof, respectively. By shutting off the valves 32 and 34 and thereby stopping fluid pressure, the cylinders 38 and 40 return to inoperative position by gravity. Working fluid applied to the cylinders is then exhausted from the cylinders to the fluid reservoir 10 through the control valves and drain passages 42 and 44. Within the drain passage 44, there is provided with a micron-filter 46 for cleaning the working fluid flowing therethrough.

Facts

Application

06/173,316Filed 29 Jul 1980

Priority

JP 54-106057[U]2 Aug 1979

Granted

23 Nov 1982

Term ended

29 Jul 2000

Estimated · how

Pre-1995 term; greater of 17 years from grant or 20 years from filing when eligible. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification2 codes

B60T 13/163
Master cylinder mechanically coupled with booster: pilot valve provided inside booster piston
B60T
Vehicle brake control systems or parts thereof

Hydraulic power boost apparatus

Life of this patent

Hydraulic power boost apparatus

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims10

Description4,368 words

Drawings

Classification2 codes

Life of this patent

Description4,368 words