Claims:1. A master cylinder assembly (1000) for a motor vehicle comprising:
• a brake lever (101),
• a brake fluid reservoir (102),
• a master piston (109) within a master cylinder bore (108),
• a non-return valve pin (105) and a stopper bolt (104),
• a non-return valve spring (107) and a valve cover (110),
wherein said non-return valve pin (105) has an oil flow path (124) on the non-return valve pin stem (105a).
2. The master cylinder assembly (1000) for a motor vehicle as claimed in claim 1, wherein said non-return valve pin leg (105a) has ‘D’ shaped cross section with minimum of two edges.
3. The master cylinder assembly (1000) for a motor vehicle as claimed in claim 1, wherein said non-return valve pin leg (105a) has a groove with minimum of two edges.
4. The master cylinder assembly (1000) for a motor vehicle as claimed in claim 1, wherein said non-return valve pin leg (105a) has ‘D’ shaped cross section formed by metal removal whose area ranges from 0.15-0.8mm2.
5. The master cylinder assembly (1000) for a motor vehicle as claimed in claim 1, wherein said non-return valve pin leg (105a) has groove formed by metal removal whose area ranges from 0.15-0.8mm2.

6. The master cylinder assembly (1000) for a motor vehicle as claimed in claim 1, wherein ratio of area of the removed part A2 to the existing part of said non-return valve pin leg (105a) A1 ranges from 1:8 to 1:25.
, Description:
FIELD OF INVENTION
The present invention relates to a master cylinder assembly of a hydraulic drum or disk brake. More specifically the present invention deals with the structure of the non-return valve in the master cylinder of a hydraulic drum or disk brake.

BACKGROUND OF INVENTION
A vehicle master cylinder converts the brake pressure so applied to hydraulic pressure by feeding brake fluid into the brake circuit and controlling this according to the mechanical force. It multiples the force applied by the vehicle rider on the brake lever and transmits the same to the hydraulic circuit. The whole arrangement of the brake master cylinder, along with its intricate components plays the vital role in transferring the brake pressure to the wheels.
In the whole arrangement, non-return valve in the master cylinder plays an integrated role in the oil transfer mechanism during the retraction of the brake force. Thus the smooth functioning and proper arrangement of the valve is essential so as to ensure non sponginess of the brake and also its durability. The effective area of oil flow is the major decisive factor of oil feeding performance.
In the prior art EP 0518 375 B1, the master cylinder arrangement comprises of a non-return valve stem which is of reduced diameter at the edges so as to let the oil flow. This might result in the decreased strength of the valve and thus the durability is a point of concern in the prior art.
Hence, in light of the various limitations in the prior art there is a requirement of a brake master cylinder which can be manufactured with uncomplicated structures.
Thus the first objective of the present invention is to provide a master cylinder which has a non-return valve with a ‘D’ shaped cross section or a non-return valve with groove on it.
Second objective of the present invention is to provide a brake master cylinder which allows delicate control of braking force.
Third objective of the invention is to provide the smooth functioning of the brake master cylinder.
The fourth objective of the present invention is to provide optimal braking force.
The fifth or the final objective of the invention is to manufacture brake master cylinder which is easy to manufacture and also economic.
BRIEF DESCRIPTION OF THE INVENTION
In order to achieve the above objects, the present invention provides a non-return valve pin in the hydraulic brake master cylinder which has ‘D’ shaped cross section or groove in the non-return valve pin leg. The surface with minimum of two edges of the non-return valve pin helps let the adequate oil flow in the master cylinder. It can be easily manufactured even for lower dimension master cylinders which are normally used for two wheelers. The oil this portion of the stem of the non-return valve helps generate required amount of hydraulic pressure for brake application.
Although the subject matter has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments are possible. As such, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiment contained therein.
BRIEF DESCRIPTION OF THE DRAWINGS
Other aspects of the invention will become apparent by consideration of the accompanying drawings and their description stated below, which are merely illustrative of a preferred embodiment of the invention and do not limit in any way the nature and scope of the invention.
Figure 1 illustrates the brake master cylinder assembly in accordance with the present invention.
Figure 2a illustrates the isometric view of the non-return valve pin and also the non-return valve pin head in accordance with the present invention.
Figure 2b illustrates the isometric view of the non-return valve pin and also the non-return valve pin head in accordance with the present invention.
Figure 3 illustrates the view of the positioning of the non-return valve and the path of oil flow through the same in accordance with the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
The invention will now be described with reference to the accompanying drawings which do not limit the scope and ambit of the invention. The description provided is purely by way of example and illustration.
Figure 1 depicts the master cylinder assembly (1000) in accordance with the present invention. The whole arrangement comprises a brake lever (101), which works to activate the brake mechanism when force is applied to it by the rider of the vehicle. As the brake lever (101) is actuated, the force of actuation gets transferred to the piston actuator (103), which thereafter transfers the force to the master piston (109). The linear forward movement of the master piston (109) also moves the primary lip seal (112) and the secondary lip seal (116) along with it. This, in turn, displaces the O-ring (114) towards the non-return valve pinhead (105b) and releases the compressed non-return valve spring (107). This movement thereby closes the oil flow path (124). The vacant space created due to the master piston (109) movement lets the hydraulic fluid pass from the fluid reservoir (102) to the master cylinder bore (108) via the replenishing hole (120). The pressure generated also forces the piston return spring (106), which thereby transfers the force to the caliper via the outlet port (118).
Figures 2a and 2b depict the non-return valve pin (105), which is the novel component in accordance with the present invention. The non-return valve pin (105) has a non-return valve pin leg (105a) and a non-return valve pinhead (105b). The non-return valve pin leg (105a) has a ‘D’ shaped cross-section or groove or a serration of any suitable shape, which is formed by the metal removal and has a cross-section A2 which ranges from 0.15-0.8mm2. In other words, the area of the metal removed (A2) to the area of the existing non-return valve stem ranges from 1:8 to 1:25. This structure helps oil flow through the surface of the non-return valve pin leg (105a) during the retracement of the brake force and thereby prevents cavitation and helps in oil feeding performance.
Figure 3 depicts the positioning of the non-return valve pin (105) in the master cylinder assembly (1000) in accordance with the present invention. The image clearly shows that the removal of the material forms the non-return valve pin leg (105a) lets the optimum amount of oil flow via the oil flow path (124). This oil flow path (124) gets closed at the time of the actuation of the brake lever (101) by the movement of the master piston (109), which in turn moves the O-ring (114) towards the non-return valve pinhead (105b). During brake retraction, the oil in the master cylinder bore (108) fills up the space between the non-return valve pinhead (105b) and the O-ring (114) via the oil flow path (124) and thereby prevents brake sponginess or cavitation.
The technical advancements offered by the present disclosure include:
• The present invention results in easy adjustment or ease of fit of the non-return valve in a master cylinder with dimensional constraint.
• The present invention ensures a smooth supply of brake oil during brake operation and prevents fluctuation of a piston therein.
• Oil bleeding is prevented by creating the path for optimum oil flow.
• Increased durability of non-return valve pin by preventing excess oil flow.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

LIST OF REFERENCE NUMERAL
101- Brake Lever
102- Fluid Reservoir
103- Piston Actuator
104- Stopper Bolt
105- Non-Return Valve Pin
105a- Non-Return Valve Pin Leg
105b- Non-Return Valve Pin Head
106 - Piston Return Spring
107- Non-Return Valve Spring
108- Master Cylinder Bore
109- Master Piston
110- Non-Return Valve Cover
112- Primary Lip Seal
114- O-ring
116- Secondary Seal
118- Outlet Port
120- Replenishing Hole
122- Pressurised Fluid Chamber
124- Oil Flow Path
1000- Master Cylinder Assembly