DESC:FORM 2
The Patent Act 1970
(39 of 1970)
and
The Patent Rules, 2005

COMPELETE SPECIFICATION
(See Section 10 and Rule 13)

TITLE OF THE INVENTION
“MASTER CYLINDER FOR TWO WHEELER BRAKING SYSTEM AND THE PROCESS OF MANUFACTURING THEREOF”

Endurance Technologies Limited
E-92, M.I.D.C. Industrial Area, Waluj,
Aurangabad – 431136, Maharashtra, India

The following specification describes the nature of the invention and the manner in which it is to be performed.

Field of Invention

The present invention relates to a master cylinder for two / three wheeler braking unit. More particularly, the present invention relates to the master cylinder with a uniquely profiled sleeve and having a master cylinder bore devoid of any casting surface irregularities such as blow holes, pits, porosity etc. and the process of manufacturing the same.

Background of the Invention

The master cylinders are employed in the motor vehicles to transform the mechanical force into the hydraulic force in order achieve the function of braking. The said master cylinders for use with hydraulic brake systems in motor vehicles and the like are formed by casting wherein the reservoir is cored out followed by the machining of the internal surface of the master cylinder bore. Due to machining, the interior of the master cylinder bore wears down within a relatively short time, thereby causing a gap between the piston and the master cylinder wall. Further the casting process has its own inherited drawback as it is difficult to cast the metal without having pits on the interior surface of the master cylinder bore. Also, it is observed that the brake fluid causes the pits to become enlarged over the time, which causes the leakage of the fluid from the master cylinder thus reducing the overall life of the master cylinder thereby.

Several attempts have been made by the industry experts to address the challenge by insert molding a pre-machined sleeve with the master cylinder body to function as an internal bore of the master cylinder. One of the conventional solution has been disclosed in U.K. Patent Application No. 2194833, wherein molding a master cylinder housing around a tubular sleeve has been described. However, the tubular sleeve disclosed in the said patent application does not have any positive locking means to facilitate the locking of the sleeve during the molding. This may cause the rotation of the sleeve inside the mold resulting in a poor adhesive bond between the sleeve and the master cylinder housing.

Thus, there is a long pending demand for having a master cylinder which addresses the aforementioned technical challenges and is free of casting surface irregularities wherein the said master cylinder eliminates the drawbacks of the prior-art yet imparting at par operational performance.

Objectives of the Present Invention

The main object of the present invention is to provide master cylinder for a braking unit of a two / three wheeled vehicle.

Another main object of the present invention is to provide a master cylinder having a master cylinder bore free of any casting surface irregularities such as blow holes, pits, porosity etc.

Another objective of the present invention is to provide a master cylinder having an embedded metallic sleeve acting as the master cylinder bore with uniform surface finish.

Still another objective of the present invention is to provide a master cylinder formed by casting the metal around a preformed, machined sleeve.

Still another objective of the present invention is to provide a method of manufacturing a master cylinder involving the surface pre-treatment of the metallic sleeve and processes involved in molding thereof.

Yet another objective of the present invention is to provide a master cylinder being able to meet first time right manufacturing.

Brief Description of Drawings

This invention is illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein and advantages thereof will be better understood from the following description when read with reference to the following drawings, wherein

Figure 1 discloses the cut-sectional view of the master cylinder casted with the embedded metallic sleeve as per the present invention.

Figure 2a and 2b describes the front view and cut-sectional view of the metallic sleeve of the present invention.

Figure 3 discloses the cut-sectional view of the machined master cylinder with the embedded metallic sleeve as per the present invention.
Figure 4 discloses the process flow diagram of anodizing of the metallic sleeve as per the present invention.

Detailed Description of the Present Invention

The invention will now be described in detail with reference to the accompanying drawings which must not be viewed as restricting the scope and ambit of the invention.

Referring to Fig. 1, the master cylinder (200) is configured to have a master cylinder body (50) casted around a preformed metallic sleeve (100) and Fig. 3 shows the master cylinder (250) formed by machining the casted master cylinder (200) as will be described hereinafter in detail. The casting process is selected from well-known casting methods such as gravity die casting (GDC), pressure die casting (PDC) preferably high pressure die casting (HPDC). The master cylinder body is made of aluminum alloys preferably EOS Aluminum alloy (AlSi10Mg) and the metallic sleeve is made of Aluminum / Steel.

Referring to Fig. 2a and 2b, the metallic sleeve (100) is a hollow cylindrical tube configured to have a locking groove (G1) formed at a proximal end (E1) and a locking groove (G2) formed at a distal end (E2) of the said metallic sleeve (100). The locking grooves (G1 and G2) of the metallic sleeve (100) are formed by any conventional machining process in such a manner that the formation of the said grooves (G1 and G2) renders the metallic sleeve (100) to have a proximal solid portion (P1), an intermediate solid portion (P2) and a distal solid portion (P3). The locking groove (G1) and the locking groove (G2) are configured to have the profiles selected from a rectangular profile, a helix profile, and any other profile as may be obvious to a person skilled in the art for facilitating the proper adhesion between two metallic bodies during molding process. The said locking grooves (G1 and G2) facilitates the adhesion of the master cylinder body (50) casting material with the metallic sleeve (100) so as to inhibit the axial displacement of the metallic sleeve (100) within the finished master cylinder (250) (refer Fig. 3) during operation of the said master cylinder (250) under working conditions. Also, the locking grooves (G1 and G2) helps arresting the metallic sleeve (100) during the casting process so as to avoid the rotation or slip movement of the said metallic sleeve (100). Further, the proximal solid portion (P1), an intermediate solid portion (P2) and a distal solid portion (P3) of the metallic sleeve (100) are formed so as to maintain the below mentioned empirical relations in order to carry out the said invention:
?(6a/((a + x) ))= k l/l'

x/a =c
Where,
a is the length of the proximal / distal solid portion of the metallic sleeve
x is the length of the locking grooves of the metallic sleeve
l is the length of the metallic sleeve
l’ is the length of the intermediate solid portion of the metallic sleeve
k is correction constant wherein k = 1.0 to 1.2
c is the empirical constant wherein c = 1.5 to 1.75

It is to be noted the length “l” of the intermediate solid portion, length “a” of the proximal / distal solid portion and the length “x” of the locking grooves need to be maintained as per the above mentioned relations so as have the proper tolerance for providing the machined replenishing hole (230) and supply port (220) as required in the finished casted master cylinder (250).

The metallic sleeve (100) as described above is formed by any suitable manufacturing method viz. additive manufacturing or subtractive manufacturing. The said metallic sleeve (100) is pre-treated for improving the surface properties of the said metallic sleeve (100). The pre-treatment process includes shot blasting and anodizing wherein the shot blasting is performed at a shot blasting machine for 5-10 min for removing the contamination on metal substrates and/or changing the coarseness or smoothness of the surface before anodizing. Whereas, the anodizing is performed for enhancing the adhesion of the said metallic sleeve with the master cylinder body material during casting.

The anodizing process of the metallic sleeve includes the sequential steps viz. (i) material inspection; (ii) degreasing; (iii) etching; (iv) rinsing; (v) de-smutting; (vi) rinsing; (vii) oxsilan coating; (viii) rinsing; (ix) cold sealing; (x) rinsing; and (xi) air drying.

The material inspection is performed for identification of the any dents, damage, scratch, excess oil/dust present in the metallic sleeve. The inspection is performed visually by the operator and the part is rejected in case of any of the defects identified as mentioned above. After passing the quality check, the metallic sleeve (100) is sent for degreasing wherein the degreasing is performed in a hot mild alkaline solution at a preferable temperature. The pointage of the solution is in the range of 10-30 ml and the spray pressure is in the range of 0.5 to 2.0 kg/cm2. The maximum oil content after degreasing should be preferably in the range of 1.5 to 6.5 gm/lit. After degreasing the metallic sleeve (100) is sent for etching in an etching tank. The pointage of the etching solution is preferably in the range of 10-80 g/L. The etching process is then followed by rinsing wherein the metallic sleeve is rinsed in a basic water solution. After rinsing, the metallic sleeve (100) is sent for de-smutting process in a mineral inorganic acid having the pointage value in the range of 180-200 g/L. The de-smutting is required for removing the excess alloyed metals from the surface of the metallic sleeve (100) after rinsing. The de-smutting process is further followed by water rinsing wherein the pH range of the water is in the range of 3.0 to 7.5.

The metallic sleeve (100) is then sent for oxsilan coating after water rinsing at a preferable temperature range and voltage range. The metallic sleeve is then further sent for water rinsing. The metallic sleeve (100) at this stage is sent for cold sealing for a specific time period wherein the cold sealing solution has a specific pointage value and the pH value. The cold sealing process is then further followed by the process of water rinsing wherein the pH range of the water is within the range of 3.5 to 8.5. The metallic sleeve (100) is then finally subjected to air drying wherein the sleeve is allowed to cool naturally.

The metallic sleeve (100) as treated by the above mentioned process is then placed in the mold of the high pressure die casting (HPDC) in such a manner that a core pin of a diameter smaller than the inner diameter of the metallic sleeve (100) is positioned within the sleeve (100). The molten metal is poured in the mold at a preferable range of temperature ranging from 520 to 750 °C. The said molten metal is preferably an aluminum alloy more preferably AlSi10Mg. The core pin is removed from the mold after the casting is cooled to get the master cylinder (200) having the master cylinder body (50) integrally casted with the metallic sleeve (100).

The master cylinder (250) is formed by machining the casted master cylinder (200) obtained from the casting wherein the said master cylinder (250) has a fluid reservoir (210), a machined bore (100B), a supply port (220) and a replenishing hole (230) as shown in Fig. 3. The supply port (220) and replenishing hole (230) are formed by drilling the bottom surface of the fluid reservoir (210) in a manner such that the said supply port (220) and replenishing hole (230) maintains a fluidic connection with the bore (100B) and the fluid reservoir (210).

The master cylinder (250) of the present invention eliminates the problems of the conventional casting methods such as blow holes, pits, porosity. Also, the master cylinder bore (100B) of the metallic sleeve (100) has an excellent surface finish ranging from 5 micron to 10 micron. Thus, the said master cylinder (250) can be used for longer period of life without having the need to replace master cylinder.

The master cylinder (250) of the present invention provides the following technical advantages that contributes to the advancement of technology:
Eliminates the problem of pits, blow holes and porosity as compared to the convention casting methods.
Eliminates the tool trial lead time.
Provides the first time right manufacturing.
Reduces machining cycle time.
It reduces the tool cost modification thus reducing the overall effective cost of the system.

It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
,CLAIMS:We Claim

A master cylinder (250) for two wheeler braking system of a vehicle comprising of a master cylinder (200) having a master cylinder body (50) casted around a preformed metallic sleeve (100) wherein,
the said metallic sleeve (100) is a hollow cylindrical tube configured to have a locking groove (G1) formed at a proximal end (E1) and a locking groove (G2) formed at a distal end (E2) of the said metallic sleeve (100);
the master cylinder (250) is formed by machining the casted master cylinder (200) obtained from the casting wherein the said master cylinder (250) has a fluid reservoir (210), a machined bore (100B), supply port (220) and replenishing hole (230); and
the said supply port (220) and replenishing hole (230) are formed by drilling the bottom surface of the fluid reservoir (210) so that the said supply port (220) and replenishing hole (230) maintains a fluidic connection with the bore (100B) and the fluid reservoir (210).

The master cylinder (250) for two wheeler braking system of a vehicle as claimed in claim 1, wherein
the locking grooves (G1 and G2) of the metallic sleeve (100) are formed by any conventional machining process in such a manner that the formation of the said grooves (G1 and G2) renders the metallic sleeve (100) to have a proximal solid portion (P1), an intermediate solid portion (P2) and a distal solid portion (P3); and
the said locking groove (G1 and G2) are configured to have a profile selected from a rectangular profile, a helix profile wherein the said locking grooves (G1 and G2) facilitates the adhesion of the master cylinder body (50) casting material with the metallic sleeve (100) so as to inhibit the axial displacement of the metallic sleeve (100) within the finished master cylinder (250) during operation of the said master cylinder (250) under working conditions.

The master cylinder (250) for two wheeler braking system of a vehicle as claimed in claim 2, wherein
the proximal solid portion (P1), an intermediate solid portion (P2) and a distal solid portion (P3) of the metallic sleeve (100) are formed in accordance with the below described relations:
?(6a/((a + x) ))= k l/l' and x/a =c
where,
a is the length of the proximal / distal solid portion of the metallic sleeve, x is the length of the locking grooves of the metallic sleeve, l is the length of the metallic sleeve, l’ is the length of the intermediate solid portion of the metallic sleeve, k is correction constant wherein ranging from 1.0-1.2 and c is the empirical constant ranging from 1.5-1.75.

A process of manufacturing a master cylinder (250) for two wheeler braking system of a vehicle comprising a set of sequential steps of:
pre-treatment of a metallic sleeve (100) for improving its surface wherein the pre-treatment process includes shot blasting and anodizing; wherein said anodizing process of the metallic sleeve (100) follows the sequential steps of (i) material inspection, (ii) degreasing, (iii) etching, (iv) rinsing, (v) de-smutting, (vi) rinsing, (vii) oxsilan coating, (viii) rinsing, (ix) cold sealing, (x) rinsing, and (xi) air drying;
the said metallic sleeve (100) is placed in the mold of the high pressure die casting (HPDC) in such a manner that a core pin of a diameter smaller than the inner diameter of the metallic sleeve (100) is positioned within the sleeve (100) and the molten metal is poured in the mold at the temperature ranging from 520 to 750 °C wherein the said molten metal is selected from AlSi10Mg;
the said core pin is removed from the mold after the casting is cooled to get the master cylinder (200) having the master cylinder body (50) integrally casted with the metallic sleeve (100); and
forming of the the master cylinder (250) by machining the casted master cylinder (200) obtained from the casting wherein the said master cylinder (250) has a fluid reservoir (210), a machined bore (100B), supply port (220) and replenishing hole (230).

The process of manufacturing a master cylinder (250) for two wheeler braking system of a vehicle as claimed in claim 4, wherein
the shot blasting is performed at a shot blasting machine for 5 to 10 mins for removing the contamination on metal substrates and/or changing the coarseness or smoothness of the surface before anodizing; and
the anodizing is performed for enhancing the adhesion of the metallic sleeve (100) with the master cylinder body (50) material during casting.

The process of manufacturing a master cylinder (250) for two wheeler braking system of a vehicle as claimed in claim 5, wherein
the material inspection is performed for identification of the any dents, damage, scratch, excess oil/dust present in the metallic sleeve (100) wherein the inspection is performed visually by the operator and the part is rejected in case of any of the defects identified;
the metallic sleeve (100) is sent for degreasing wherein the degreasing is performed in a hot mild alkaline solution wherein the pointage of the solution is in the range of 10-30 ml and the spray pressure is in the range of 0.5 to 2.0 kg/cm2 and the maximum oil content after degreasing should be preferably in the range of 1.5 to 6.5 gm/lit;
after degreasing the metallic sleeve (100) is sent for etching in an etching tank wherein the pointage of the etching solution is in the range of 10-80 g/L;
the etching process is followed by rinsing wherein the metallic sleeve is rinsed in a basic water solution;
after rinsing, the metallic sleeve (100) is sent for de-smutting process in a mineral inorganic acid having the pointage value in the range of 180-200 g/L wherein the de-smutting is required for removing the excess alloyed metals from the surface of the metallic sleeve (100) after rinsing; and
the de-smutting process is followed by water rinsing wherein the pH range of the water is in range of 3.0 to 7.5.

The process of manufacturing a master cylinder (250) for two wheeler braking system of a vehicle as claimed in claim 6, wherein
the metallic sleeve (100) is sent for oxsilan coating after water rinsing wherein the said coating is performed for 90 minutes at a preferable temperature range of 10 to 25 °C and voltage range of 10 to 25 V;
the metallic sleeve is then further sent for water rinsing for a period of 1.0 to 4.0 mins wherein the pH range of the water is within the range of 4.0 to 7.5 and the metallic sleeve (100) at this stage is sent for cold sealing for 40 minutes wherein the cold sealing solution has a pointage value in the range of 5.0 to 9.0 g/L and the pH value in the range of 5.0 to 8.0;
the said cold sealing process is further followed by the process of water rinsing for a period of 1.0 to 4.0 mins wherein the pH range of the water is within the range of 4.0 to 7.5 and the metallic sleeve (100) is then finally subjected to air drying for a period 10-30 minutes wherein the sleeve is allowed to cool naturally.

The process of manufacturing a master cylinder (250) for two wheeler braking system of a vehicle as claimed in claim 7, wherein the master cylinder bore (100B) of the metallic sleeve (100) is configured to have surface finish ranging from 5 microns to 10 microns and the said metallic sleeve (100) is made of Aluminum / Steel.

The process of manufacturing a master cylinder (250) for two wheeler braking system of a vehicle as claimed in any of the above claims, wherein the casting process is selected from gravity die casting (GDC), pressure die casting (PDC) and high pressure die casting (HPDC).

Dated this 16th day of Jan. 2025

Sahastrarashmi Pund
Head – IPR
Endurance Technologies Ltd.

To,
The Controller of Patents,
The Patent Office, at Mumbai