Claims:We claim,
1. A tandem master cylinder (1000) for a motor vehicle comprising:
a master cylinder body (100) with a cylindrical bore (200),
a primary piston (500) and a secondary piston (600) situated within the cylindrical bore (200) and capable of sliding within the master cylinder body (100),
a brake fluid inlet bore (110) on the master cylinder body (100) opening into the cylindrical bore (200),
a brake fluid inlet bore (120) on the master cylinder body (100) opening into the cylindrical bore (200),
a brake fluid reservoir (700) connected to the brake fluid inlet bore (110), and the brake fluid inlet bore (120),
an outlet port (130) on the master cylinder body (100) connected to a brake pressure outlet tube (1100), and
characterized by,
an outlet passage (140) from the cylindrical bore (200) opening into a cavity (150) in a housing portion (160) of the master cylinder body (100).
2. The tandem master cylinder (1000) for a motor vehicle, as claimed in claim 1, wherein the housing portion (160) has a passage (168) from the cavity (150) to an outlet port (170).
3. The tandem master cylinder (1000) for a motor vehicle s claimed in claim 1, wherein the cavity (150) accommodates a brake pressure regulatory mechanism (800).
4. The tandem master cylinder (1000) for a motor vehicle, as claimed in claim 1, wherein the housing portion (160) has a connectivity hole (162) which opens into the cavity (150).
5. The tandem master cylinder (1000) for a motor vehicle, as claimed in claim 4, wherein the connectivity hole (162) is closed by a closing means (164).
6. The tandem master cylinder (1000) for a motor vehicle, as claimed in claim 5, wherein the closing means (164) is a screw with a seal.
7. The tandem master cylinder (1000) for a motor vehicle, as claimed in claim 5, wherein the closing means (164) is a pressed ball.
8. The tandem master cylinder (1000) for a motor vehicle, as claimed in claim 1, wherein the master cylinder body (100) and the housing portion (160) are housed as a single unit.
, Description:FIELD OF INVENTION
The invention is related to the tandem master cylinder for a three and four-wheeler motor vehicle. It more particularly relates to a tandem master cylinder with the capability to regulate its brake fluid pressure output.
BACKGROUND OF THE INVENTION
Every hydraulic system utilized in the industry is at risk of being rendered defunct by leakage of hydraulic fluid from it due to structural damage. This is true even for the hydraulic braking system utilized in motor vehicles. A typical braking system, forming part of state of the art, deals with this problem by utilizing a tandem master cylinder with at least two pistons for developing braking fluid pressure in two separate hydraulic braking circuits. This way if one braking circuit becomes ineffective due to structural damage, the other hydraulic braking circuit still remains functional. While this makes the braking system of motor vehicles more reliable and resilient, it still requires some amount of skill to use it so as to prevent the occurrence of wheel locking while braking. As such the tandem master cylinder still need to be provided along with another device that can regulate the rate at which braking fluid pressure is transmitted to the hydraulic braking circuit. Recognizing this need, designers are known to provide pressure control regulator valves in line with the outlets of a tandem master cylinder.
While providing pressure control regulator valves improves control of the driver over the motor vehicle, this addition necessitates the provision of additional mounting space and mounting points in the motor vehicle. This is normally not a serious issue in larger motor vehicles, but in smaller motor vehicles like three-wheelers, this poses a serious problem as space available for providing these devices is already very limited. Even if the pressure regulatory valves are provided by modification in structure to incorporate more mounting points, this will inevitably reduce space available for providing other features. As overall size of the vehicle cannot be increased beyond a point considering both economic and even engineering constraints, there exists a need for a tandem master cylinder which can accommodate a pressure control regulator valve within its structure and still be provided in the same mounting space and mounting points as provided for a conventional tandem master cylinder.
It is yet another objective of this invention to provide a tandem master cylinder which does not necessitate redesigning mounting points, thereby allowing it to be provided in vehicles that are already on the road.
It is still another objective of the invention to provide an economical tandem master cylinder allowing its wider utilization in any suitable motor vehicle.
SUMMARY OF THE INVENTION
A tandem master cylinder for a motor vehicle comprising a master cylinder body with a cylindrical bore, a primary piston and a secondary piston situated within the cylindrical bore and capable of sliding within the master cylinder body, a brake fluid inlet bore on the master cylinder body opening into the cylindrical bore, a brake fluid inlet bore on the master cylinder body opening into the cylindrical bore, a brake fluid reservoir connected to the brake fluid inlet bore, and the brake fluid inlet bore, an outlet port on the master cylinder body connected to a brake pressure outlet tube, and characterized by, an outlet passage from the cylindrical bore opening into a cavity in a housing portion of the master cylinder body.
Typically, the housing portion has a passage from the cavity to an outlet port.
Typically, the cavity accommodates a brake pressure regulatory mechanism.
Typically, the housing portion has a connectivity hole which opens into the cavity.
Typically, the connectivity hole is closed by a closing means.
Typically, the closing means can be a screw with a seal or a pressed ball.
Typically, the master cylinder body and the housing portion are housed as a single unit.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 discloses a vertical cut section diagram of a conventional tandem master cylinder
Figure 2 discloses a vertical cut section diagram of a tandem master cylinder in accordance with the first embodiment of the present invention
Figure 3 discloses a vertical cut section diagram of a tandem master cylinder in accordance with the second embodiment of the present invention
Figure 4 discloses another vertical cut section diagram of a tandem master cylinder in accordance with the second embodiment of the present invention

DETAILED DESCRIPTION OF THE INVENTION
The preferred embodiments of the tandem master cylinder will now be described in detail with accompanying drawings. The preferred embodiments must not be viewed as restricting the scope and ambit of the disclosure.
A conventional tandem master cylinder (999) (refer Figure 1) for a motor vehicle comprises of a master cylinder body (100) with an opening (200), a primary piston (500) and a secondary piston (600) situated within the opening (200) and capable of sliding within the master cylinder body (100). Brake fluid inlet (110) and (120) opening into the bore (200) is provided for connecting the brake fluid reservoir (700) with the hydraulic braking circuits corresponding to the primary piston (500) and secondary piston (600) respectively. An outlet port (130) is provided for transmitting pressure developed by the movement of the primary piston (500) via a brake pressure outlet tube (1100) to a first hydraulic brake circuit. Another outlet port (135) (not visible in Figure 1) is provided for transmitting the pressure developed by movement of the secondary piston (600) via a brake pressure tube (1200) into the second hydraulic brake circuit. The way the conventional tandem master cylinder (999) functions is well known and does not require any detailed description. The conventional tandem master cylinder (999) cannot accommodate any brake pressure regulator valve /mechanism within its structure. This limitation of the conventional tandem master cylinder (999) does not allow it to be readily utilised along with a brake pressure regulator valve/mechanism in a three-wheeled motor vehicle.
This limitation of the conventional tandem master cylinder (999) is overcome by the embodiments of the tandem master cylinder (1000), as shown in Figure 2 and Figures 3 and 4. It may be noted here that similar parts have been given the same numbers in all the figures. The tandem master cylinder (1000) (as shown in Figure 2) comprises a master cylinder body (100) with a cylindrical bore (200), a primary piston (500) and a secondary piston (600) situated within the cylindrical bore (200). As in a conventional tandem master cylinder (999) in the tandem master cylinder (1000), the brake fluid inlet (110) and (120) opening into the bore (200) are provided for connecting the brake fluid reservoir (700) with the hydraulic braking circuits corresponding to the primary piston (500) and secondary piston (600) respectively. As shown in figure 2, the outlet port (130) on the master cylinder body (100) opens into the bore (200).
The outlet bore (130) transmits the pressure developed by movement of the primary piston (500) into the first hydraulic brake circuit of the motor vehicle via a brake pressure outlet tube (1100) (not shown in Figure 2) connected to it. The master cylinder body (100) of the tandem master cylinder (1000) also has an outlet passage (140) from the cylindrical bore (200) opening into a cavity (150) in a housing portion (160) of the master cylinder body (100). The housing portion (160) further has a passage (168) from the cavity (150) to an outlet port (170) (refer figure 2). The outlet port (170) transmits the pressure developed by movement of the secondary piston (600) into the other brake hydraulic circuit of the motor vehicle via a brake pressure outlet tube (1200) (not shown in Figure 2) connected to it. The opening (166) in the cavity (150) is closed using a suitable bolt once a brake pressure control regulator mechanism (800) has been assembled within the cavity (150). Using a bolt for closing the opening (166) allows the brake pressure regulatory mechanism (800) to be serviced as and when required. A cap may also be pressed into the opening (166) to close it. The cap cannot be removed after it is pressed into the opening (166). The brake pressure control regulator mechanism (800) in general comprises a seal, a spring, and two pistons. Other arrangements may be also be developed in the future to perform the function of the brake pressure control regulator mechanism (800). Such mechanisms may also be accommodated in the cavity (150) of the housing portion (160).
In the tandem master cylinder (1000) shown in Figure 2, the pressure developed by movement of the secondary piston (600) is transmitted to the cavity (150) via the outlet (140). The brake pressure control regulator mechanism (800), therefore, controls and regulates pressure developed by the secondary piston (600) in the first embodiment of the tandem master cylinder (1000). This controls and regulates the rate at which pressure rises in the hydraulic brake circuit connected to the outlet port (170) via a brake outlet tube (1200) (not shown in Figure 2).
The second embodiment of the tandem master cylinder (1000) as shown in Figure 3 and 4 comprises of a master cylinder body (100) with a cylindrical bore (200), a primary piston (500) and a secondary piston (600) situated within the cylindrical bore (200). As in a conventional tandem master cylinder (999) in the tandem master cylinder (1000), the brake fluid inlet (110) and (120) (not visible in Figure 3 and 4) opening into the bore (200) are provided for connecting the brake fluid reservoir (700) with the hydraulic braking circuits corresponding to the primary piston (500) and secondary piston (600) respectively. The outlet port (130) on the master cylinder body (100) opens into the bore (200).
In the second embodiment as shown in Figure 3 and 4, the outlet bore (130) transmits the pressure developed by the secondary piston (600) into the second hydraulic brake circuit of the motor vehicle via a brake pressure outlet tube (1200) (not shown in Figure 3 and 4). The master cylinder body (100) of the tandem master cylinder (1000) also has an outlet passage (140) from the cylindrical bore (200) opening into a cavity (150) in a housing portion (160) of the master cylinder body (100). The housing portion (160) further has a passage (168) from the cavity (150) to an outlet port (170). As in the first embodiment (shown in Figure 2) in the second embodiment (shown in figure 3 and 4) as well, the opening (166) in the cavity (150) is closed using a suitable bolt once a brake pressure control regulator mechanism (800) has been assembled within the cavity (150). Using a bolt for closing the opening (166) allows servicing of the brake pressure regulatory mechanism (800) as and when needed. A cap may also be pressed into the opening (166) in order to close it. The cap cannot be removed after it is pressed into the opening (166). The brake pressure control regulator mechanism (800) provided in the second embodiment also, in general, comprises a seal, a spring, and two pistons. Other mechanisms may be also be developed in the future to perform the function of the brake pressure control regulator mechanism (800). Such mechanisms may also be accommodated in the cavity (150) of the housing portion (160) of the second embodiment of the tandem master cylinder (1000). The outlet port (170) transmits the pressure developed by the primary piston (500) into the first hydraulic brake circuit of the motor vehicle via a brake pressure outlet tube (1100) (not shown in Figure 3 and 4).
Furthermore, it may be noted from the construction shown in Figure 3 and 4 that the outlet portion (140) (proceeding from the cylindrical bore (200) opening into a cavity (150) in a housing portion (160) of the master cylinder body (100)) functions to provide an outlet for pressure developed by movement of the primary piston (500). Same as the housing portion (160) of the first embodiment shown in Figure 2, the second embodiment is shown in Figures 3, and 4 also has a passage (168) from the cavity (150) to an outlet port (170). The outlet port (170) transmits the pressure developed by movement of the primary piston (500) into the first hydraulic brake circuit of the motor vehicle via a brake pressure outlet tube (1100) (not shown in Figure 3 and 4).
Specifically, in the second embodiment of the tandem master cylinder (1000) the as shown in Figures 3 and 4, the housing portion (160) has a connectivity hole (162), which opens into the cavity (150). The connectivity hole (162) is closed by a closing means (164). The closing means (164) can be a screw provided along with a seal (refer figure 3). The closing means (164) can also be a ball of a suitable material pressed into the connectivity hole (162) (see figure 4). The existence of the connectivity hole (162) in the second embodiment of the tandem master cylinder (1000) is necessitated by the unique alignment of the housing portion (160) with respect to the master cylinder body (100). The alignment as shown in Figures 3 and 4, does not allow machining of the outlet portion (140) to happen without creating the connectivity hole (162).
In both of the embodiments of the tandem master cylinder (1000), as shown in Figures 2 and Figures 3 and 4, the master cylinder body (100) and the housing portion (160) are housed as a single unit on the motor vehicle. The disclosed embodiments of the tandem master cylinder (1000), therefore, provide a compact structure capable of accommodating a brake pressure regulator valve/mechanism within its structure. The construction of the embodiments of the tandem master cylinder (1000) also makes it easier to bleed air out of the hydraulic brake circuits during installation.
The tandem master cylinder (1000) can be attached within a motor vehicle body in place of a conventional tandem master cylinder (999) without necessarily having to redesign the mounting points provided. It is, therefore comparably more economical to utilize than a traditional tandem master cylinder and the brake pressure regulator valve/mechanism attached separately to the motor vehicle body and connected via suitable connecting pipes. This allows it to be readily utilized in motor vehicles already on the road as well.
List of reference numbers

100…..Master cylinder body
110…..Brake fluid inlet bore
120…..Brake fluid inlet bore
130…..Outlet port
140…..Outlet passage
150…..Cavity
160…..Housing portion
162…..Connectivity hole
164…..Closing means
166…..Opening
168…..Passage
170…..Outlet port
200…..Cylindrical bore
500…..Primary piston
600…..Secondary piston
700…..Brake fluid reservoir
800…..Brake pressure control regulator mechanism
999…..Conventional tandem master cylinder
1000….Tandem master cylinder