Prior art disclosure It is well known in the art that the inversion valve along with the double check valve and relay valve is primarily used in truck and tractors equipped with spring brakes. This new inversion valve intergrades the above said three valves and enables a predetermined value of hold-off pressure to be maintained, keeping the spring brakes released. The hold-off pressure is usually varied from 4 bar to 7 bar. This valve enables exhaustion of air from the spring brakes, while parking the vehicle, thereby allowing application of the spring brakes.

This valve prevents compounding of the service brakes and the spring brakes and modulates application of the spring brakes in the event of failure in service brake circuit.

Summary of Invention The inventors have made great effort to provide a device, which meet the requirement of the industry and overcome the problem associated in the prior art.

To achieve the above object according to first aspect and'feature of the present invention there is provided a valve for the air brake systems to improve, the performance and efficiency.

According to. second_aspect_and feature of the invention in addition-to the first feature the invention comprises a novel valve, which is unique, rugged efficient and economical.

At the outset of the description which follows it is to be understood that ensuring description only illustrate a particular form of this invention. However, such particular form is only an exemplary embodiment without intending to imply any limitation on the scope of this invention. Accordingly, the description is to be understood as an exemplary embodiment and reading of the invention is not intended to be taken restrictively.

The above and other objects features and disadvantages will be clear from the following description of preferred embodiment taken in conjunction with accompanying drawings.

The foregoing description is outlined rather broadly preferred and alternative feature of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows.

Additional features of the invention will be described hereinafter that form the subject of 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 structures for carrying out the same purposes of the present invention. Those skilled in the art should realize such equivalent conception do not depart from the spirit and scope of the invention in its broadest form. <BR> <BR> <P>-T-he-inversion-valve-according to invention dispenses-with-the-need-to-utilise the known double check valve, the relay valve and the known inversion valve as separate devices in the air brake system. On the other hand, the inversion

vaive-proposed herein combines, in itself, _the_turlction_of_the known inversion valve, the double check valve and the relay valve as one integral unit.

Thus inversion valve according to invention is-com-pact and occupies less space. Servicing and maintenance is also rendered easier. The known three valves aforesaid of the existing system are also easily replaceable with the inversion valve proposed herein. The number of working parts of the known system, comprising the known inversion valve, the known double check valve and the known relay valve are more than those of this novel inversion valve.

This is because lesser number of components in the proposed inversion valve performs the functions of the known inversion valve, the double check valve and the relay valve put together. Further more in the proposed inversion valve the spring, loading the primary piston and the relay piston (also called the graduating spring), is"caged"that is to say that the entire spring assembly is in a caged condition and allowed to move along with the relay piston and the primary piston, even as it provides the necessary load to achieve the pressure- limiting function. This feature is unlike the known means of employing a graduating spring, wherein one end of the spring is made to rest on a stationary surface.

In a related invention known in the art, any air pressure at the primary service port acts upon the primary piston, after the air passes through a cross hole, and also directly upon the relay piston. To avoid the latter condition, which is unnecessary, this invention proposes a spring-loaded ring piston, surrounding the relay piston. The ring piston takes up such air pressure on itself, without permitting it to act on the relay piston directly.

Whenever any small pressure differential, or a fluctuating pressure differential,

between the air pressure at the secondary service port and a lower air pressure at the primary service port and a lower air pressure at the primary service port exits, this is taken up by the spring-loaded ring piston and not by the relay piston thereby avoiding unnecessary actuation of the relay piston.- Brief Description of Drawings This invention will now be described with reference to the accompanying drawings.

The accompanying drawings are intended to provide further understanding of invention and are incorporated in and constitute a part of invention. The drawings illustrate an embodiment of invention and together with the description illustrate principle of invention.

The drawings should not be taken as implying any necessary limitation on the essential scope of invention.

The drawings are given by way of non-limitative example to explain the nature of the invention.

For a more complete understanding of the instant invention reference is now made to the following description taken in conjunction with accompanying drawings.

-T-he-various-featu-re-of-novelty-ufhich-cfaracterise-the-in vention-a-re- pointed out specifically in the claims which a part of description. For a better understanding of the invention, its operating advantage, specific objects obtained--by-its use, reference-should-be-made-to-the-drawings-. and descriptive--- matter in which there are illustrated and described preferred embodiments of invention.

Referring now to drawings, where like numerals designate identical or- corresponding parts throughout the referred views.

Figure 1 shows in elevation of an--embodiment of inversion valve in spring brake released condition.

Figure 2 shows in elevation of an embodiment of inversion valve in balanced condition.

Figure 3 shows in elevation of an embodiment of inversion valve in spring brake applied condition.

Figure 4 shows in elevation of an embodiment of inversion valve in anti- compounding mode Figure 5 shows in elevation of an embodiment of inversion valve in primary failed condition for applying spring brakes.

Detailed Description of Preferred Embodiment of Invention The inversion valve along with the double check valve and relay valve is primarily used in trucks or tractors equipped with spring brakes. The new inversion valve intergrades the above said three valves and is used in dual air brake system for performing the following four functions.

1. During normal operation this valve permits a particular value of hold-off pressure to the spring brakes thereby keeping it released.

This hold-off pressure can be varied from-4-bar to 7 bar.

2. During parking of the vehicle, this valve quickly exhausts air from the spring brakes thereby allowing a fast application of the spring brakes.

3. Prevents compounding of service brake and spring brake 4. Modulates application of spring brakes in the event of a failure in the primary service circuit.

The inversion valve for the air brake system of a motor vehicle comprises a valve body provided with a spring brake control port, a primary service port, a secondary service port, a reservoir port, a delivery port and an exhaust port; the valve body housing a primary piston and spring loaded relay piston; a diaphragm valve for the spring brake control port and an air chamber provided above the primary piston; a spring-loaded inlet/exhaust valve, the arrangement being such that whenever the inlet/exhaust valve is open, pressurised air enters the reservoir port and leaves at the delivery port until, at a predetermined pressure, the inlet valve closes under such pressure preventing further passage of air to the delivery port, while maintaining the exhaust port closed. The air in the chamber is depleted, by operation of the part control valve of the vehicle, the primary piston, and along with it the relay piston, under -the the airhead load beneath the relay piston, move upward, thereby opening the

exhaust port and allowing the air from the delivery port to pass. out. Jttfough. tbe- inlet/exhaust valve and the exhaust port, thus applying the spring brakes. When the service brakes are applied, with the spring brakes also applied, the diaphragm valve-is-deflected by the pressurised air entering the primary-service port to seal the spring brake control port and allow such air into the air chamber, causing the primary piston and the relay piston to move downward, to open the inlet/exhaust valve, allowing air to flow from the reservoir port to the delivery port, thus releasing the spring brakes. Whenever failure of the primary brake circuit occurs, air entering the secondary service port acts on the relay piston causing the relay piston to move upwards and thus allowing air from the delivery port to pass through the exhaust, applying the spring brakes. When the spring brakes are released and the service brakes are applied, air of substantially the same pressure enters through the primary and secondary service ports on either side of the relay piston, thus leaving the relay piston unaffected.

The invention further comprises a spring-loaded ring piston, (7) and the spring (8).

The ring piston surrounds the relay piston (5) and is located in. the space provided in the valve body (1) adjacent the relay piston (5). The ring piston is moveable in the space between a first stop on the valve body and a second stop on the relay piston (5). The stop R thus moves with the relay piston (5).

The ring piston (7) moves independently of the relay piston.

From the foregoing construction, it will be observed that (i) Whenever air pressure is present at the primary service port (P1) it is taken up by the spring-loaded ring piston, and not by the relay piston,

(ii) the ring piston moving downwards while taking up such pressure.

(iii) Whenever air pressure exists at the secondary service port (P2), it is initially taken up by the ring'piston (7), to move it upwards until contact takes place between the ring piston (7) and the second stop to move the relay piston (5) also upwards.

(iv) Any pressure differential between the air pressure at the secondary service port (P2) and a lower air pressure at the primary service port (P1), is taken up by the spring-loaded ring piston (7) and not by the relay piston (5).

The provision of the spring-loaded piston (7) renders the inversion valve according to the present invention more stable, since the relay valve does not unnecessarily expose itself to air pressures affecting its performance.

Spring brakes released When the system is being charged, air pressure enters the reservoir port (B) and is present in the cavity beneath the inlet/exhaust valve (6). The inlet/exhaust valve (6) is in contact with the inlet valve seat in the body (1) thus preventing passage of air to delivery as well as through the exhaust (D).

When the full system pressure is reached, the'park control valve'can be operated to release the spring brakes. The park control valve is a manually operated on/off valve. Shifting the park control valve to the'on'condition ensures continuous supply of air pressure at the spring brake control port (A) of the inversion valve. Pressurised air at the spring brake control port (A), deflects the diaphragm (2), and flows into the cavity on top of the primary piston (3)-through-the-cr-oss-hole (1 provided in-the valve-body T-his-air-pressure forces the primary piston

(3) (3)-to-mnve-downward and contact the relay piston_ (5> Ihe_relay piston (5) then moves downward and contacts the inlet/exhaust valve (6). Further movement of the relay piston (5) opens the inlet passage thereby allowing air to flow-from-the reservoir port (B) to the delivery--ports-- (C). Consequently the spring brakes are released. At the same time the exhaust valve seat in the relay piston (5) prevents loss of air through exhaust (D).

The limiting value of the hold-off pressure (or pressure at the delivery ports) to the spring brakes can be varied between 4 bar and 7 bar by caging the graduating spring (4) load on the relay piston (5) with the help of the adjustment screw (9). The air pressure that is communicated to the delivery ports (C) also acts on the underside of the relay piston (5). When the airhead load on the relay piston (5) equals the load exerted by the graduating spring (4), the valve is in the'balanced'condition. In this condition the inlet valve seat and the exhaust valve seat are in the same plane thereby preventing further flow of air to delivery ports (C) and at the same time preventing loss of air through exhaust (D).

Spring brakes applied The park control valve is switched to the'off'position to apply the parking brakes. Consequently, air pressure at the spring brake control port (A) and on top of the primary piston (3) is exhausted through the park control valve. The primary piston (3) then moves upward. Airhead load beneath the relay piston forces it to move upward thereby opening the exhaust passage and sealing the inlet. Air from the delivery ports (C) is then exhausted thereby applying the spring brakes.

Service brakes appliedLwith-parking brakes applied (Anti-compounding) Application of service brakes provides air pressure at the primary service port (P1) and secondary service port (P2). There is no air pressure in the spring brake control port (A) since the spring brakes are applied. Air entering-the primary service port (P1) deflects the diaphragm (2) in the double check valve and seals the passage in the spring brake control port (A). Air then flows through the cross hole (H) provided in the body (1) to the top of the primary piston. This air pressure forces the primary piston (3) to move downward and contact the relay piston (5). The relay piston (5) then moves downward and contacts the inlet/exhaust valve (6). Further movement of the relay piston (5) opens the inlet passage thereby allowing air to flow from the reservoir port to the delivery ports (C). Consequently the spring brakes are released thereby preventing the compounding of the service brake and the parking brake.

Continuous application of the service brakes results in the'balanced'condition explained earlier.

Air that enters the valve body through the primary service ports (P1) and secondary service port (P2) gets neutralised since the pressure and sealing areas on the top and bottom of the relay piston (5) are essentially equal.

Application of service brakes with primary in failed condition (Modulated application) In the event of failure in the primary circuit, air pressure, upon application of service brakes will be available only in. the secondary service port (P2).

However, air pressure will be available at the spring brake control port (A) and consequently the delivery ports (C) thereby keeping the spring brakes released.

Air that enters the valve through the secondary service port (P2) acts beneath

the relay piston (5) and forcesthe-reiay-pjston to move upward thereby exhausting air from the delivery ports (C) and applying the spring brakes. The air released from the spring brakes will be proportional to the pressure at secondary service port (P2) thus providing-the driver with a modulated application of the spring brakes.

Service brakes applied with spring brakes released During normal running of the vehicle spring brakes are in the released condition. Service brake applications made will result in air pressure entering the valve through the primary service port (P1) and secondary service port (P2). However, this will not have any impact on the functioning of the valve since the pressure and sealing areas on the top and bottom of the relay piston (5) are essentially equal.

Pressure limiting is achieved by caging the spring Limitation of hold-off pressure to the spring brakes is achieved by caging the graduating spring (4) in the relay piston (5) and primary piston (3). Normally in such applications one end of the graduating spring is always made to rest on a stationary surface. The unique feature in this invention is that the entire spring assembly is in a caged condition and allowed to move along with the relay piston even as it provides the necessary load to achieve the pressure-limiting function.

The invention has been explained in relatioin to specific embodiment. It is inferred that the foregoing description is only illustrative of the present invention and it is not intended that the invention be limited or restrictive <BR> -thereto-.-- Many-other-specific-embodiments-of-the present-invention-will-be- apparent to one skilled in the art from the foregoing disclosure. All substitution,

alterations and modification of the present-invention-which-come within the scope of the following claims are to which the present invention is readily susceptible without departing from the spirit of the invention.

The scope of the invention should therefore be determined not with reference to the above description but should be determined with reference to appended claims along with full scope of equivalents to which such claims are entitled.