FORM 2
THE Patent Act, 1970
(39 of 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)
Integral reservoir cap for master cylinder
Endurance Technologies Pvt Ltd R&D, E 93, MIDC Industrial Area, Waluj, Aurangabad, Maharashtra-431136
The following specification describes the invention

FIELD OF THE INVENTION
[001] The present subject matter described herein, in general, relates to improved
master cylinder of hydraulic disc brake, more specifically, the present subject matter relates to an integral reservoir cap assembly of master cylinder of hydraulic disc brake.
BACKGROUND OF THE INVENTION
[002] Generally, a master cylinder-reservoir assembly for front disc brake in two and
three wheelers comprises a housing provided with bore with piston, primary lip seal, a secondary lip seal, a piston return spring, an internal cir-clip, a protection boot, filler union and grommet. A separate hydraulic reservoir assembly comprises a reservoir body, a reservoir cap and a diaphragm. The master cylinder assembly and the oil reservoir assembly are connected through reservoir tube with the help of hose clamp at both ends. Piston connected with pushrod connected by fork can be operated by actuating the operating pedal. Pressing or actuating the brake pedal moves a push rod in the master cylinder. A piston that is mounted on the push rod exerts force against the fluid in the master cylinder bore. The pressure created displaces fluid through the hose connected to master cylinder and a caliper to each of the wheels and applies the brakes. The assembly is secured through mounting holes on the motorcycle at a suitable location such as swing arm, etc.
[003] Traditionally used hydraulic reservoir assemblies require a number of parts
which involves additional material cost and adds to weight. A reservoir cap is made up of aluminum casting involving additional costs in powder coatings and heat treatment of material. Casting defects like blow holes, cracks and shrinkages lead to poor quality of parts which is highly undesirable. Over tightening of traditionally used reservoir cap screws may lead to damage of reservoir cap and seal cap. Also in the current art with side vent holes in reservoir cap and seal cap, chances of entrapment of external water or dust particles inside vent hole paths are more.
[004] It is, therefore, a principle object of this invention to eliminate the aforesaid
drawbacks of the prior art, and to provide improved and inexpensive integral reservoir cap assembly for brake master cylinder.
[005] It is yet another object of this invention to provide fail proof design of
reservoir cap screw.

SUMMARY OF THE INVENTION
[006] In one embodiment, reservoir assembly of a master cylinder for hydraulic
brake system of two-wheeler is disclosed. The assembly comprises reservoir with side walls, diaphragm and an integrated reservoir cap. Integrated reservoir cap further comprises seal cap and a reservoir cap. The air flow passage is provided on integrated reservoir cap to allow diaphragm to be at atmospheric pressure.
[007] Additionally, plurality of stepped collar screws is provided for fastening
diaphragm and integrated reservoir cap with walls of reservoir assembly. The stepped collar screws are designed to have screw head depth limiter to prevent further advance of the screws when the screw head has reached the desired depth in a work piece.
BRIEF DESCRIPTION OF THE DRAWINGS
[008] The present invention will become more fully understood from the detailed
description given herein below and the accompanying drawings which are given by way of
illustration only and thus are not limitative of the present invention.
[009] Figure 1 illustrates a reseivoir assembly of master cylinder for hydraulic disc
brake found in prior art.
[0010] Figure 2 shows a cross sectional view of reservoir assembly with individual
components found in prior art.
[0011] Figure 3 shows a cross sectional view of improved reservoir assembly
according to the embodiments of the present invention.
[0012] Figure 4 shows a cross sectional view of reservoir assembly with integral
reservoir cap according to the embodiments of the present invention.
[0013] . Figure 5 shows a cross sectional view of, integral reservoir cap having side vent
hole and air flow path
[0014] Figure 6 shows a cross sectional view of improved reservoir cap screw.
DETAILED DESCRIPTION OF THE INVENTION

[0015] In the drawings, a first embodiment of a master cylinder 100 of hydraulic
braking system for a vehicle, such as a motorcycle, constructed in accordance with the invention is illustrated in Figure 1. For convenience, the master cylinder 100 will be described in connection with a motorcycle. However, the master cylinder 100 can also be used with other vehicles, such as bicycles, mopeds, snowmobiles, scooter, ATVs, and the like, or any other vehicle using a hand-operated lever. Therefore, the disclosure should not be limited to master cylinders for use with motorcycles.
[0016] The master cylinder 100 is actuated by a lever 114, which is coupled to the
master cylinder 100 by a push rod 116. Actuation of the lever 114 pushes the push rod 116
axially of the master cylinder 100 to cause hydraulic fluid (e.g., any incompressible fluid used
to generate pressure) to flow into the caliper (not shown) via a brake line (not shown) coupled
to the master cylinder 100 via an inlet/outlet port 118 of the master cylinder 100.
[0017] The master cylinder 100 includes a body that is generally L-shaped. The
master cylinder further comprises reservoir assembly having reservoir side walls 108 which are closed by a reservoir cap 102 commonly made of aluminum. The reservoir cap 102 is secured to reservoir walls 108 by a plurality of reservoir cap screws 110. A seal cap 104 is made up of non-metal elements such as plastic and is interposed between the upper portion of the reservoir walls 108 and reservoir cap 102. An elastomeric diaphragm 106 acting as a flexible wall is removably attached to seal cap 104, thereby defining the interior of said reservoir assembly.
[0018] Referring also to Figure 2, the diaphragm 106 also includes a central cavity
120 on a backside. This central cavity 120 permits expansion and contraction of the
diaphragm 106 during operation. Contraction of the diaphragm 106 further accommodates
fluid expansion in the master cylinder 100. Expansion of the diaphragm 106 permits
movement of fluid from the reservoir assembly tothe master cylinder 100.
[0019] An improved low cost design of master cylinder for hydraulic disc brake is
described with reference to figures attached herewith. The master cylinder reservoir assembly 300 is particularly adapted for use in conjunction with the hydraulic disc brake system (not shown) of a vehicle such as motorcycle or the like. The reservoir assembly 300 is mounted on the vehicular handlebar (not shown). The reservoir assembly 300 is particularly adapted to

hold the brake fluid required to generate braking force, in a manner which will become more apparent as this description proceeds.
[0020] Referring to Figures 3 and 4, master cylinder reservoir assembly 300 is
illustrated according to the embodiments of the present invention. The reservoir assembly 300 as whole constitutes a box structure configured approximately as a rectangle. In one embodiment, the reservoir assembly 300 comprises of integrated reservoir cap 302, which is formed by integration of two separate components, reservoir cap and seal cap. The single piece design of integrated reservoir cap 302 replaces the existing twin component assembly of separate reservoir cap and seal cap (102, 104 in Figure 2). The integrated reservoir cap 302 is formed from a molded plastic having relatively good strength and resistant to chemicals and solvent, particularly hydraulic brake fluid. The reservoir assembly 300 is made of a bellow-like pressure- compensation diaphragm 304 located between the reservoir cap 302 and side walls 108 of reservoir assembly 300. The diaphragm is constructed from a flexible material, such as thin rubber, or the like. The reservoir cap 302 along with the diaphragm 304 is fixed to the side walls 108 of reservoir assembly 300 by stepped screws 310.
[0021] Referring to Figure 5, reservoir cap 302 with at least one side vent opening 402
is illustrated according the embodiments of the present invention. Side vent opening 402
allows diaphragm to be at atmospheric pressure. With decrease in hydraulic brake fluid level,
air pushes the diaphragm 304 via the side vent opening 402 in the reservoir cap 302. This is
automatically done because the side vent opening 402 is open to atmospheric pressure.
[0022] Referring additionally to Figures 4 and 6, the reservoir cap 302 includes two
bores for receiving fasteners, such as screws 310, which are also received in corresponding
bores in said diaphragm. The screws 310 are designed to have a screw head depth limiter,
according to the present invention. The screws 310 have stepped collar 504 which rests on the
master cylinder face (112 in Figure 3), and prevents further advance of the screws when the
screw head has reached the desired depth in the work piece. This eliminates the chances of
over-tightening of screws 310 and further squeezing of the reservoir cap 302.
[0023] It is understood that the various preferred embodiments are shown and
described above to illustrate different possible features of the invention and the varying ways in which these features may be combined. Apart from combining the different features of the

above embodiments in varying ways, other modifications are also considered to be within the scope of the invention,
[0024] The invention is not intended to be limited to the preferred embodiments
described above, but rather is intended to be limited only by the claims set out below. Thus, the invention encompasses all alternate embodiments that fall literally or equivalently within the scope of these claims.

CLAIMS
We claim:
1. A reservoir assembly of a master cylinder for a hydraulic brake system of a two-wheeler comprising a reservoir with sidewalls, a diaphragm and an integrated reservoir cap.
2. The reservoir assembly as claimed in claim 1, wherein said integrated reservoir cap comprises a seal cap and a reservoir cap.
3. The reservoir assembly as claimed in claim 1, wherein a plurality of stepped collar screws are provided for fastening said diaphragm and integrated reservoir cap with said side walls of reservoir assembly.
4. The reservoir assembly as claimed in claim 1, wherein an air flow passage is provided on the said integrated reservoir cap.
5. A two-wheeler having said reservoir assembly as claimed in claim 1.
6. A reservoir system as herein substantially described and illustrated with reference to the accompanying drawings.