WO1988006991A1

WO1988006991A1 - Manually operable booster for vehicular braking systems

Info

Publication number: WO1988006991A1
Application number: PCT/US1988/000686
Authority: WO
Inventors: Carl D. Russell
Original assignee: R & R Research Corporation
Priority date: 1987-03-09
Filing date: 1988-03-08
Publication date: 1988-09-22

Abstract

An apparatus (50), (100), (33), and (38), (41) providing a method for applying manual forces in one movement to initiate mechanical forces which are increased by hydraulic forces in providing a booster to the master cylinder (MC) needed in automotive and truck braking.

Description

MANUALLY OPERABLE BOOSTER FOR VEHICULAR BREAKING SYSTEMS

FIELD OF THE INVENTION

The invention relates to a new and useful improvement in the technique for manually boosting brake pressures. PRIOR ART

The closest prior art known is U. S. Patent 2,915,878, issued December 8, 1959, to O. HRAMOFF for Self-contained Booster Cylinder. However, this patent requires foreign actuators, such as air pressure or hydraulic pressure actuators to function, and further requires systems components throughout to accommodate such pressures. It is unacceptable for use as a vehicular booster because the pressure pumps and lines are subject to failures which could render the vehicular braking system useless, or worse. Further, the patent includes no sealing for high pressure liquids, also fatal to braking systems. SUMMARY OF THE INVENTION

A cylindrical housing includes a power primary piston connected to a manually operable vehicular brake pedal. A small diameter centerbore piston is affixed to the primary piston and extends axially of the housing.

A housing divider axially receives the centerbore piston and forms a first chamber between it and the primary piston. The first chamber is connected by a normally open resiliently biased valve and valve passageway, including the hollow centerbore piston to a second chamber formed by an output piston, serving as an output rod for actuating the vehicular master cylinder.

A low pressure compr.ession chamber is in liquid communication with the first chamber through a spring biased opening. As the manual brake pedal pressure is increased, the pressure in the system increases sufficiently to overcome the resilient bias and close the valve. Further pressure against the primary piston then must overcome the compression chamber spring biased opening in order for liquid to enter because the resilient valve is now closed. A flexible diaphragm and air chamber in the compression chamber permits further brake pedal pressure and movement of the primary piston. The compression chamber accommodates the overflow for direct brake pedal force against the primary piston, and the fluid trapped in the hollow centerbore piston and in the second chamber. Thus, the input piston force has been transferred to the small diameter bore, thereby multiplying the force applied to the vehicular master cylinder by the output piston approximately by 15 to 1. Prior to the boosting effect, the brake shoes were positioned by light brake pressure via the liquid connection. DETAILED DISCRIPTION OF THE DRAWINGS

The single figure shows a split view of the booster apparatus with the liquid passages closed for liquids in the first and second chambers to permit the centerbore piston to exert substantially boosted force against the master cylinder. DISCRIPTION OF A PREFERRED EMBODIMENT

The cylindrical housing 18 is preferably comprised of a heavy walled aluminum cylinder, finished for receiving pistons. The housing or cylinder 18 has (e.g.) an internal diameter of 5.08 cm and is 8.89.cm in length. It has lock ring grooves

18' ', 0.098 cm from the outer left end.

Pistons 14 and 33 are fitted in cylinder 18 for sliding and O-rings 14' and 33' are provided for sealing. Chamber A is formed between piston 14 and divider plate 28.

Form end cylinder 32 with a 5.72 cm inside diameter, heavy wall aluminum, press in bushing 32' finished for sliding piston 33. Provide flange 34 for securing to the vehicle brake master cylinder housing MC. Secure divider plate- 28 by pressing bushing 32'.

Piston 14 is 5.08 cm in diameter and piston 14 and associated structure is 9.21 cm long of steel. The outer end 12 of the piston is reduced to 3.33 cm diameter and extends outward for 3.175 cm. Provide a finished centerbore

1.59 cm in diameter 4.13 cm deep. The piston flange is

0.79 cm long, finished for sliding in cylinder 18, sealed with O-ring 14'. Reduce the outer diameter to 2.54 cm for 1.9 cm, forming valve 200 housing. Further reduce to 1.27 cm. diameter extending 3.175 cm long forming centerbore piston 6. Provide groove for O-ring 28'. Centerbore 0.476 cm diameter through 1.27 cm diameter extension. Form clearance around valve 200 and seat 200'. Provide four orifices 6', equally spaced around the base of the piston 14 into cylinder 12.

Divider plate 28, with its 1.27 cm long cylinder 24, is made of steel. Finish inside diameter of cylinder 24 to slide centerbore piston 6, and seal with O-ring 28'.

Divider plate 28 and bushing 32' seal to cylinder 32 with O-ring 32' .

Valve Piston 100 and valve 200 are formed of brass, finished for sliding in cylinder 12, fitted with O-ring 100' for sealing. Attached valve 200 is finished for seating and sealing in seat

200'.

Valve spring 10 is 1.27 cm diameter, 2.54 cm long with 1.587 kg tension. Slidable disk 5 is 0.317 cm thick, fitted to float in cylinder 12.

End cap 4 is made of steel, 0.95 cm thick, and 3.33 cm diameter. Attach with countersunk screws, tap for brake pedal eye bolt 2.

Eye bolt 2 is a 0.953 N.F. thread length determined on installation, and interconnected link 2' extends to brake pedal 50.

Lock nut 3 holds eye bolt 2 in position on assembly and installation.

Fill entire system with liquid, filling chambers A, B and C through sealable filler passage 35, as well as passages 6'' and 6' and valve 200 spaces. Pressure on foot pedal 50 moves piston 14 inward which causes liquid to move from chamber A into hollow centerbore piston 6, via liquid tubular passage or orifice 6' and open valve 200 due to movement of output piston 33. Valve 200 is held away from valve seat 200' by spring 10 bias of (e.g.) 1.415 Kg for cars and trucks require a heavier spring (e.g.) 4.08 Kg. With valve 200 open, the liquid passes into the passage 6', hollow centerbore 6'' and thence through cylinder 24 via centerbore 26 into chamber C.

In this manner, the same forces are applied to piston 33 as manual forces are applied to brake pedal 50 and thence to piston 14. This causes piston 33 to move out.

As chamber C is expanded, the outward movement of piston 33 applies force to a load (Brake Master Cylinder, MC) and this force is increased to close the brake shoes to the disks or drums to a point where forces are required to be increased to exert more power, causing a build-up of pressure as further manual forces are applied to piston 14 to exert more force on piston 33 to a point where the manual pressure is increasing the pressure in chamber A and liquid passages 26 aforementioned extending into chamber C.

As further manual force is applied to piston 14, with output piston 33 against, the master cylinder to offer resistance, increasing the pressure to 16 psi in the aforementioned parts to a point to overcome the spring 10 bias against valve piston 100 to cause piston 100 to move outward to a point of closing valve 200 against valve seat 200'.

At this point no liquid will pass from chamber A to chamber C. However, as further manual force is applied to piston 14, the pressure build-up in chamber A will cause ball valve 36 to open by collapsing spring 37 (e.g. 9.07 Kg ) and force the non- compressible liquids between closed valve 200 and piston 33 in chamber C to move piston 33 outward as piston 6 increasing the braking. This allows the foot pedal to directly drive piston 6, compounding the pressure available for the vehicle's brake cylinders. This increased pressure between piston 33 and valve 100 is applied in further sealing the valve 100. SUMMARY

The liquid reserve housing 38 straddles or otherwise attaches to cylindrical housing 18 with liquid communication established via passage 39.

Thus, when the pressure is increased in chamber A to e.g. 9.07 Kg , ball 36 is raised from its valve seat 39' to permit the liquid (oil, brake fluid or other liquid suitably non-corrosive) from chamber A to exit passageway 39 via slit 40 into chamber B which is already full so flexible diaphragm 41 (rubber or the like) is caused to expand to its dotted position against the entrapped air in air chamber B', which is maintained at about 15 p.s.i. via air valve 42. Housing 38 may be fabricated of aluminum, and is equipped with the sealable valve filler 35 at the top of chamber B.

Air pressure switch 43 is attached to the air reservoir portion of housing 38 to signal the driver when pressure is depleted, indicating a need for instant attention to the braking system.

When the pressure against brake pedal 50 is eliminated or reduced, the diaphragm, urged by air pressure, returns the fluid to chamber A. The return passages include inlet in tube 44, ball valve 45, passage 46 back to passageway 39 as piston 33 is returned by the spring in the master cylinder. Resilient spring 10 opens valve 200, when the pressure is thus released.

A conventional brake foot pedal exhibits an approximate 3 to 1 mechanical advantage ratio over the pivital connection 2'. Applying a force on the foot pedal will result in an equal pressure on pistons 14 and 33 (each which are 2 inches in diameter). At approximately 7.257 Kg force on the foot pedal valve 200 is closed by piston 100 due to 0.3417 Kg/cm inchamber A, (also in chamber C, 26, 6" and 6') effective against 1.587 Kg spring 10 which firms the vehicular brake shoes to the drums and disks. At this point, centerbore piston 6 {being 1.27 cm in diameter) becomes the driving force and develops a 16 to 1 ratio in passage 6'', 26 and chamber C, which responds at this ratio. This ratio results from the cross section of 1.27 cm bore 26 and the larger 5.08 cm bore in chamber C at output piston 33. Additional manual force on the brake foot pedal multiplies the additional manual force by 3:1 mechanical leverage, enhanced by the 16:1 ratio providing a 48 to 1 ratio. As a result with approximately 29.94 Kg force on the brake foot pedal, more than

683.596 Kg/cm² can be exhibited on the vehicular brake master cylinder piston. Thus, 29.937 - 7.257 = 22.68 x 21.77 = 1088.641 Kg most vehicles require 907.19 to 1360.79 maximum braking Kgs. The above diameters may be made to accommodate pressures for vehicles of any kind, including trucks.

Claims

WHAT IS CLAIMED IS:

1. A vehicular booster for substantially increasing the manual force applied to the brake foot pedal through liquid pressure for application to the master cylinder, comprising in combination; a cylindrical housing; a power input piston slidably mounted in the housing and adapted for movement from the brake pedal; a hollow centerbore piston affixed to the input piston axially of the housing; an output piston slidably mounted in the housing and a divider wall adjacent to the output, piston for collectively defining a first chamber between the input piston and the wall and second chamber between the wall and the output piston with the latter in liquid communication with the centerbore piston via the end thereof remote from the input piston; pressure sealing valve means supported within the housing for controlling liquid flow between the first and second chambers; and, a liquid overflow and return reservoir means comprising reservoir valve means in communication with the first chamber; said pressure sealing valve means comprising resilient means normally maintaining said pressure sealing valve means open for said communication until sufficient braking force has been applied to the brake pedal to compress the spring a predetermined amount to cause the liquid pressure in the first chamber to overcome the resilient means to close the valve means, providing a direct liquid connection between the brake pedal and the output piston, the brake pedal force being multiplied by a factor approximately equal to the ratio of the area of the output piston divided by the area of the centerbore piston, and the pressure sealing valve means being held tightly closed by the increased pressure in said second chamber; said reservoir valve means permitting further increasing of the braking pressure by opening to receive overflow liquid from the first chamber after the pressure sealing valve means close.

2. The booster of Claim 1., wherein: said housing comprises a liquid sealed multi-compartment including the first chamber, second chamber, hollow centerbore piston, and overflow reservoir; said reservoir being expandible to receive overflow liquid from said first chamber.

3. The booster of Claim 2., wherein: the valve means are disposed within the hollow centerbore piston with the liquid pressure locking the valve means closed when the brake pedal force overcomes the pressure sealing resilient means.

4. The booster of Claim 1., wherein: said wall comprises a cylindrical axial portion for receiving and guiding the centerbore piston and a diametrical portion affixed to the housing; said diametrical portion and the interior of the cylindrical axial portion comprising said wall for the second chamber for cooperation with the output piston.

5. The booster of Claim 4., wherein: said pressure sealing valve means comprises a valve seat in the centerbore piston; a valve disposed in the centerbore piston and connected to a valve piston normally biased to an open valve position by the resilient means effective against the valve piston; and, liquid openings from the first chamber to the valve piston on a side thereof opposite the resilient means to permit increasing liquid pressure to drive the valve piston to compress the resilient means and close the valve means with further increasing liquid pressure being effective to increase the liquid forces holding the valve against the valve seat.

6. A vehicular booster for substantially increasing the liquid brake pressure force applied to the vehicular master cylinder as a result of the manual force applied to the brake foot pedal, comprising in combination; a cylindrical housing adapted for attachment to a vehicle frame; a power input piston slidably mounted in the housing and adapted for axial movement from the brake pedal; a hollow centerbore piston affixed to the input piston axially of the housing and having a diameter small relative to the diameter of the housing; a wall across the housing forming a first chamber with the input piston;. an output piston slidably mounted in the housing for forming a second chamber, together with the wall, in liquid communication with the centerbore piston via the end thereof remote from the input piston;

Pressure sealing valve means supported within the housing with a valve and valve seat in the centerbore piston for controlling liquid flow between the first and second chambers via the centerbore piston; and, an expandible overflow reservoir means in communication with the first chamber; said pressure sealing valve means comprising resilient means normally maintaining said valve open for said communication until sufficient braking force has been applied to the brake pedal to cause the liquid pressure in the housing to overcome the resilient means to close the valve, providing a direct liquid connection between the brake pedal and the output piston, the brake pedal force being multiplied by a factor approximately equal to the ratio of the area of the output piston divided by the area of the centerbore piston, and the liquid pressure within the centerbore piston increasing the sealing of the valve against the valve seat with further incr«eise of braking pressure causing transfer of liquid overflow from the first chamber to the reservoir means.

7. The booster of Claim 6, wherein: said wall extending across the housing having an axial extension to mate with the centerbore piston in liquid-tight slidable engagement therewith.

8. The method of controlling liquid to boost manual braking force applied to a vehicular braking pedal at the master cylinder piston, comprising the steps of: applying said braking force to a piston of given size in a first chamber of fluid to establish a liquid path through a valve, via a second hollow piston of substantially reduced size relative to said first mentioned piston, to a chamber including an output piston for driving the master cylinder piston to bring the brake shoes into contact with the brake drums; and, closing the valve to transfer the force to the small piston thereby multiplying the brake force applied to the master cylinder piston.

9. The method of controlling liquid to boost manual braking force applied to a vehicular braking pedal at the master cylinder piston and via the brake shoes to the brake drums, comprising the steps of: using the liquid to bring the brake shoes into contact with the brake drums; and, entrapping the liquid and using the entrapped liquid to compress the brake shoes against the brake drums.

10. The method of controlling a body of liquid to boost manual braking force applied to a vehicular braking pedal at the master cylinder piston and via the brake shoes to the brake drums, comprising the steps of: using a body of fluid effective against the piston to bring the brake shoes into contact with the brake drums; and, using a smaller body of entrapped fluid against the piston to enhance the braking force at the master cylinder.