CLIAMS:We claim:

1. An anti lock brake compatible master cylinder comprising;

a master cylinder machining (6);
a reservoir assy (1);
a primary compensation port (3);
a secondary compensation port (2);
a primary plunger (4) and a secondary plunger (8), a plunger bore including a closed wall, a fluid inlet located in the closed wall of the plunger bore, a front opening, and a cylindrical side wall;
a primary pressure seal (5);
a secondary pressure seal (7);

characterized in that the plunger bore includes a U type seal groove (9) including a front wall, a back wall, and a bottom, and located near the front opening of the plunger bore.

2. An anti lock brake compatible master cylinder as claimed in Claimed 1 wherein the master cylinder primary plunger (4) and secondary plunger (8) include sliding primary pressure seal (5) and secondary pressure seal (7) which separate fluid into various chambers in the master cylinder.

3. An anti lock brake compatible master cylinder as claimed in Claimed 1 wherein the U type seal groove (9) is of a height of 0.5 mm to 1.0 mm and width of 0.5 mm to 0.6 mm.

4. An anti lock brake compatible master cylinder as claimed in Claimed 1 wherein the U type seal groove (9) may include a seal of height of 3.85 mm to 4.15 mm and width of 4.65 mm to 4.95 mm, made of brake fluid resistant material and having low friction coating.

5. An anti lock brake compatible master cylinder as claimed in Claimed 1 wherein the U type seal groove (9) includes a dynamic inner sealing lip of a radius of 0.3 mm surrounding the plunger.

6. An anti lock brake compatible master cylinder as claimed in Claimed 1 wherein seal includes a rear face that is provided with a flat transverse surface forming a continuous annular ring, the outer wall shape of the seal being straight and the ends of the outer walls of the seal being blunted with a slight indent.

7. An anti lock brake compatible master cylinder as claimed in Claimed 1 wherein the seal contains circumferential grooves placed equidistantly on the central portion of the side walls of the seal to engage with the outside diameter of the plunger.

8. An anti lock brake compatible master cylinder as claimed in Claimed 1 wherein the plunger body includes an insert end portion serving as an insert port usable when the seal is assembled, and an attachment groove located on the axial line but away from the insert end portion to the other end side of the plunger body, the seal being fitted in the attachment groove in order to mutually seal the front and rear parts of the plunger body in its axial direction.

9. An anti lock brake compatible master cylinder as claimed in Claimed 1 wherein the end of the plunger includes a tapered portion at an area facing with the opening of the relief port on the side of the cylinder body, and this tapered portion is gradually enlarged in outside diameter from the insert end portion of the plunger body to the attachment groove.

10. An anti lock brake compatible master cylinder as claimed in Claimed 1 and working thereof wherein during brake pedal pulsation, during the motion of the plunger in the master cylinder, when pressure is applied fluid flows into the plunger bore, fluid pressure within the master cylinder chamber acts against the seal to deform the seal and move the seal along with the plunger, the seal shape, curvature and the presence of the circumferential grooves in the U type seal groove (9) produces an asymmetric pressure gradient which increases towards the master cylinder cavity, the radius depth of the seal and the seal geometry such that it assists in retracting the plunger, with no seal failure or tear or nibbling even though considerable pressure and heat may be generated.
,TagSPECI:TITLE
SIMPLE ANTI LOCK BRAKE COMPATIBLE MASTER CYLINDER

FIELD OF THE INVENTION
This invention generally relates to automobile engineering and particularly relates to a master cylinder. More particularly this invention relates to a simple, novel, antilock brake compatible master cylinder.

BACKGROUND OF THE INVENTION
In automobile engineering, the master cylinder is a control device that converts non-hydraulic force (commonly from a driver's foot) into hydraulic pressure. This device controls foundation brakes located at wheels. As plunger(s) move along the bore of the master cylinder, this movement is transferred through the hydraulic fluid, to result in a movement of the plungers in the foundation Brakes. The hydraulic pressure created by moving a plunger (inside the bore of the master cylinder) toward the foundation Brakes compresses the fluid evenly, but by varying the comparative surface-area of the master cylinder, one can vary the amount of force and displacement applied to each foundation, relative to the amount of force and displacement applied to the Master cylinder.

The most common vehicle uses of Master cylinders are in Brake and clutch systems. A reservoir above each master cylinder supplies the master cylinder with enough brake fluid to avoid air from entering the master cylinder. Most modern light trucks and passenger cars have one master cylinder for the brakes which contains two plungers. Each plunger in a master cylinder operates a brake circuit, and for modern light trucks and passenger cars, usually a brake circuit leads to a brake caliper or shoe on only two of the vehicle's wheels, and the other brake circuit provides brake-pressure to power the other two brakes.

The master cylinder is connected to the brake pedal via the booster pushrod. Of vehicle brake systems, an anti-lock brake system serves to prevent a slippage of wheels on a road surface by periodically intermitting supply of brake fluid to the wheels. Typically an antilock braking system master cylinder includes four main components: speed sensors, valves, a pump, and a controller. ¬
Speed sensors - The anti-lock braking system needs some way of knowing when a wheel is about to lock up. The speed sensors, which are located at each wheel, or in some cases in the differential, provide this information.
Valves - There is a valve in the brake line of each brake controlled by the ABS. On some systems, the valve has three positions: In position one, the valve is open; pressure from the master cylinder is passed right through to the brake. In position two, the valve blocks the line, isolating that brake from the master cylinder. This prevents the pressure from rising further should the driver push the brake pedal harder. In position three, the valve releases some of the pressure from the brake.
Pump - Since the valve is able to release pressure from the brakes, there has to be some way to put that pressure back. That is what the pump does; when a valve reduces the pressure in a line, the pump is there to get the pressure back up.
Controller - The controller is an ECU type unit in the car which receives information from each individual wheel speed sensor, in turn if a wheel loses traction the signal is sent to the controller, the controller will then limit the brake force (EBD) and activate the ABS modulator which actuates the braking valves on and off.

When the brake is applied, the primary plunger moves, which closes its compensating port. Fluid pressure in the primary circuit rises. It acts with the primary plunger spring, to move the secondary plunger forward, closing the secondary compensating port. Pressure builds in the secondary circuit. Pressure keeps building in both circuits, and applies the brakes in both circuits. If the secondary circuit fails, the secondary plunger is forced to the end of the cylinder. When it reaches the end, pressure builds in the primary circuit. If the primary circuit fails, the primary plunger contacts the secondary plunger, and pushes it to operate the secondary circuit.

In normal operation when the pedal is released, the springs in the master cylinder push the plungers back more quickly than the fluid can flow back from the wheel brake units. This creates a low pressure area in front of each plunger. Such low-pressures can cause air to be drawn into the system. To prevent this, there are recuperating grooves in the plungers and the seals. Fluid at atmospheric pressure flows through the inlet port, and past these grooves. When the primary and secondary plungers are returned fully, any extra fluid coming back from the brake units displaces fluid into the reservoir, through the compensating port. When the plunger has returned to the “rest” position, the seal is pulled off its seat by the action of the link and spring. This lets fluid still returning from the wheel units displace fluid back to the reservoir.

The concern of all the conventional master cylinders presently known in the art is short life and poor performance of the master cylinder due to the plunger seal nibbling due to brake pedal pulsation. Nine times out of ten master cylinders go bad because it has an internally leaking plunger seal that has undergone nibbling due to wear and tear arising out of usage. Further the plunger is angled in such a way and has a very sharp edge which can damage the rear plunger seal and reduce seal life. The worn out and cast off seal matter further creates a quantity of black rubber debris in the brake fluid. Further repeated 'nibbling' of the seal can cause premature seal failure. Thus seals have a well known tendency to break down and fail due to erosion and nibbling. Erosion is caused by the constant action and movement under varying pressures and conditions which the seal experiences. Nibbling is the breakdown of small pieces of the seal over time due to the pressure placed on the seal. Both the erosion and nibbling are enhanced in an anti lock brake system master cylinder due to the brake pedal pulsation.

Therefore it is the need of the hour in the industry to develop a cost effective and simple master cylinder that solves the problem of seal nibbling during ABS modulation and is compatible for both ABS and Non ABS Brake Systems.

Some of the prior art in this field reveal various improvement made over the years in the art in master cylinders for better working and efficacy.

Indian Patent No: 233521 discloses a master cylinder comprising a substantially axial body (12) inside a bore (14) whereof is mounted sliding at least an axial plunger, of the type wherein the bore (14) comprises two front and rear sealing means interposed between the plunger and the bore, the front sealing means delimiting in the bore (14) rear and front feeding chambers, of the type wherein the body (12) comprises a feeding conduit (42,48) connecting an external reservoir to the rear feeding chamber and emerging between the two sealing means.

Indian Patent Application No: 216532 claims a tandem hydraulic master cylinder mainly comprising a body (1) pierced with a bore, first and second inlets (2a, 2b) for a hydraulic fluid at low pressure, a primary plunger (3) and a secondary plunger (4) which slide respectively in first and second length sections (SI, S2) , a primary pressure chamber (5), a secondary pressure chamber (6), first and second upstream and downstream sealing cups (91a, 91b, 92a, 92b) , first and second resupply ducts (21, 22) and first and second outlet orifices (41 and 42) for the pressurized hydraulic fluid

Indian Patent Application No: 210194 describe a master cylinder compartment and caliper compartment being integrated as a single piece.

Indian Patent Application No: 1229/DEL/2008 claims a Brake master cylinder (10) for a motor vehicle, of the type which comprises a substantially axial body (12) inside a bore (14) of which at least one axial plunger is slideably mounted, of the type in which the bore (14) comprises two seals, front (30, 34) and rear, interposed between the plunger and the bore (14), the seals (30, 34) comprising three radially concentric lips accommodated in grooves (70, 72) in the bore (14), characterized in that front faces of the grooves (70, 72) are configured at least in part as a slope.

Indian Patent Application No: 1232/DEL/2008 describes a brake master cylinder- (10) for a motor vehicle, which comprises a substantially axial body (12) inside a bore (14) of which at least one axial plunger is slideably mounted, of the type in which the bore (14) comprises two front (30, 34) and rear seals, interposed between the plunger and the bore (14), the seals (30, 34) comprising three radially concentric lips accommodated in grooves (70, 72) in the bore (14), characterized in that the seals (30, 34) comprise central lips of reduced cross section.

Indian Patent Application No: 1233/DEL/2008 discloses a brake master cylinder (10) for a motor vehicle, of the type which comprises a substantially axial body (12) inside a bore (14) of which is slideably mounted at least one axial plunger, of the type in which the bore (14) comprises two seals, front and rear, interposed between the plunger and the bore (14), characterized in that it comprises at least one wide groove (66, 68) which is formed in the bore (14) in front of a groove (70, 72) for retaining the front seal, which extends at least in part around the plunger, and which communicates with said retaining groove (70, 72) and the hole in the plunger, in order to allow resupplies to occur with a high flow rate.

Indian Patent Application No: 153/MUMNP/2010 describes a master cylinder, ewherein a plunger is axially displaceable inside a guide sleeve and the plunger has a front recess in which a plunger-side end of a plunger rod is received.

Indian Patent Application No: 1546/DEL/2004 claims a combined master cylinder and dump valve including a body having a body bore, a brake port, a tank port, and a pressure port with each port being hydraulically connected with the body bore, a plunger slideable within the body bore and a plunger, the plunger delimiting a part of the body bore to define a master cylinder for pressurising the brake port, the plunger further including a plunger seal for isolating the pressure port from the tank port, and including a plunger bore.

Indian Patent Application No: 721/MUMNP/2012 discloses a hydraulic cylinder, in particular a master cylinder (1), comprising a device (7L, 7R) for fastening in an opening provided in the firewall (11)/chassis of a vehicle and elements for fastening in an opening of a wall of a pedal box (12), wherein the remaining opening between the master cylinder and the firewall is sealed by an elastic sealing element (7B).

Indian Patent Application No: 734/CHE/2008 claims a master cylinder capable of controlling an increase in an intruding amount of a cup seal while relieving a stress concentration therein to thereby prevent the cup seal from being damaged.

However none of the existing prior art discloses any anti lock brake master cylinder which structurally overcomes the problem of seal nibbling during the brake pedal pulsation of ABS modulation.

Therefore it is the need of the hour in the industry to develop a master cylinder that is simple in construction, cost effective, compatible for use with both anti lock brake and non anti lock brake systems, has less number of parts, weighs less, and is less expensive than a conventional anti lock brake system master cylinder.

The present invention attains this objective and addresses the major problem of the wear and tear of a plunger seal and the mixing of the residue from a worn seal into the brake fluid.

The present invention involves a master cylinder containing a novel plunger seal where new radius is provided for the sealing lip. Further a new seal formulation with higher hardness, higher modulus & higher tear strength has been used. The seal surface is coated with low friction coating. This will totally eliminate the seal nibbling during brake pedal pulsation in the anti lock brake system.

Further it will be apparent to those skilled in the art that the objects of this invention have been achieved by providing a novel compact ABS compatible master cylinder which is unique in nature unlike existing master cylinders as described in the above prior art. Various changes may be made in and without departing from the concept of the invention. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing and modifying other methods and structures for carrying out the same purpose of the present invention. Further, features of some stages disclosed in this application may be employed with features of other stages. Therefore, the scope of the invention is to be determined by the terminology of the following claims and the legal equivalents thereof.

OBJECTIVES OF THE INVENTION
This invention may be summarized, at least in part, with reference to its objects.
The foremost object of the present invention is to present a simple, compact anti lock brake compatible master cylinder.
Another object of the present invention is to provide a novel compact anti lock brake compatible master cylinder whereby the problem of seal nibbling is solved.
Another object of the present invention is to provide a simple and compact anti lock brake compatible master cylinder that is compatible for both ABS and Non ABS Brake Systems.
Another object of the present invention is to provide a novel compact anti lock brake compatible master cylinder that has less weight than conventional Antilock Brake master cylinders.
Another object of the present invention is to provide a simple anti lock brake compatible master cylinder that has less number of parts than a conventional Antilock Brake master cylinder.
Yet another object of the present invention is to provide a novel compact anti lock brake compatible master cylinder that is less expensive than a conventional anti lock brake master cylinder.
A further object of the present invention is to provide a novel compact anti lock brake compatible master cylinder with an enhanced performance quotient due to no seal nibbling or contamination of brake fluid with seal material debris.

Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention.

SUMMARY OF THE INVENTION
The present invention embodies a master cylinder that can be used in hydraulic braking systems of cars, SUVs, MUVs incorporated with anti lock braking system or non anti lock braking systems. The present invention consists of a master cylinder which is simple in construction and consists of a sliding seal, a compensating hole, and supply port compatible for usage in an anti lock braking system master cylinder.

.DESCRIPTION OF THE DRAWINGS
The advantages and features of the present invention will be more readily apparent by persons skilled in the art when considered in reference to the following description and when taken in conjunction with the accompanying drawings listed below
Figure 1 is a cross sectional diagram illustrating the present invention master cylinder.
Figure 2 is a cross sectional diagram of the present invention sliding seal.
Figure 3 is a cross sectional diagram of the present invention plunger.
Figure 4 is a cross sectional diagram of the present invention machining compensation port.

DETAILED DESCRIPTION
The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of particular applications of the invention and their requirements. The present invention can be configured as follows:

The master cylinder that can be used in hydraulic braking systems of cars, SUVs, MUVs incorporated with anti lock braking system or non anti lock braking systems. The present invention can be used for the production of a varied range of master cylinder assemblies, for heavy, medium and small vehicles.

In a preferred embodiment of the present invention, as illustrated in Figure 1 (MC Assy), the present invention consists of the master cylinder includes the machining (6), a reservoir assy (1), a primary compensation port (3), a secondary compensation port (2), a primary plunger (4), a secondary plunger (8), a primary pressure seal (5) and a secondary pressure seal (7), where the primary plunger (4) moves in response to application of the brake pedal. The plunger bore may include a fluid inlet, a closed wall, a front opening, and a cylindrical side wall that includes a compensating hole or cut-off hole, otherwise called the U type seal groove (9) located near the front opening. The master cylinder plunger (4) and (8) thus includes sliding pressure seals (5) and (7) which separate fluid into various chambers in the master cylinder. Typically, the fluid inlet is located in the closed wall of the plunger bore so that when pressure is applied the fluid will flow into the plunger bore.

In a preferred embodiment of the present invention, the U type seal groove (9) may include a seal so that upon inserting the plunger into the bore, an interference fit between the plunger and the seal is created so that fluid leakage out of the front opening is prevented. The height of the seal may be 3.85 mm to 4.15 mm and the width of the seal may be 4.65 mm to 4.95 mm. The seal may be made of any material that is resistant to brake fluid. The material formulation of the seal is such that it has higher hardness, higher modulus & higher tear strength. The seal is further coated with low friction coating. The U type seal groove (9) may include a front wall, a back wall, and a bottom. The U type seal groove (9) may be 0.5 mm to 1.0 mm in height and 0.5 mm to 0.6 mm in width, this being smaller than the conventional compensating hole diameter.

In a preferred embodiment of the present invention, as shown in Figure 2, the U type seal groove (9) includes a dynamic inner sealing lip surrounding the plunger, a radius of 0.3 is provided for the seal lip. The radius depth of the seal may be deep enough so that the seal geometry assists in retracting the plunger, but no so deep that the cut causes the seal to fail and/or tear.

It can be seen from Figure 2 that the seal is generally of an annular configuration including a specific cross-sectional configuration. In a preferred embodiment of the present invention, as shown in Figure 2, the outer wall shape of the seal may be straight, as opposed to the conventional seal outer wall shape of one step and one slope. This shape is invented to meet and negate the problems of uni-directional and bi-directional pressure, low friction, seal nibbling, port passing, and zero-drift scenarios.

In a preferred embodiment of the present invention, as shown in Figure 2 (Seal drawing), the ends of the outer walls of the seal are blunted instead of the conventional sharp shape and there is a slight indent. This prevents chipping off of the seal end and reduces friction between the cut-off hole and the seal. The seal includes a rear face that is provided with a flat transverse surface forming a continuous annular ring.

In a preferred embodiment of the present invention, as shown in Figure 2 (Seal drawing), there are circumferential grooves in the seal placed equidistantly on the side walls of the seal. These grooves are situated on the central portion of the side walls of the seal which engages the outside diameter of the plunger. This provides high stability of the seal during operating cycles, eliminating rocking and pumping effects of brake pedal pulsation.

In a preferred embodiment of the present invention, as shown in Figure 3 (Plunger drawing), the plunger body includes an insert end portion serving as an insert port usable when the seal is assembled, and an attachment groove located on the axial line but away from the insert end portion to the other end side of the plunger body. The seal is fitted in the attachment groove in order to mutually seal the front and rear parts of the plunger body in its axial direction. Further by changing the configuration of the end of the plunger adjacent to the attachment groove, the wear and tear of the seal during plunger motion to and fro, is eliminated. Thus the end of the plunger includes a tapered portion at an area facing with the opening of the relief port on the side of the cylinder body, and this tapered portion is gradually enlarged in outside diameter from the insert end portion of the plunger body to the attachment groove. The tapered portion of the plunger end is thus designed to reduced the flowing resistance of the brake fluid during brake pedal pulsation and thus eliminate seal nibbling.

During brake pedal pulsation in an anti lock brake system, during the motion of the plunger in the master cylinder, fluid pressure within the master cylinder chamber acts against the seal to deform the seal and move the seal along with the plunger. In the U type seal groove (9), the seal shape, curvature and the presence of the circumferential grooves produce an asymmetric pressure gradient which increases towards the master cylinder cavity. The above shape of the seal, seal material and the compensating hole ensures that seal nibbling does not arise, even though considerable pressure and heat may be generated The present invention thus results in less friction, better flow of brake fluid and less wear and tear or seal nibbling.

While there has been shown and described what is considered to be preferred embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention be not limited to the exact forms described and illustrated, but should be constructed to cover all modifications that may fall within the scope of the appended claims.

It will be apparent to those skilled in the art that the objects of this invention have been achieved by providing the above invention. However various changes may be made in the structure of the invention without departing from the concept of the invention. Therefore, the scope of the invention is to be determined by the terminology of the following claims and the legal equivalents thereof.