Title of Invention

BRAKE CHAMBER OF A MOTOR VEHICLE

Abstract

This invention relates to brake chamber diaphragms used in brake actuators in the air brake system. The Brake chamber diaphragms are designed to achieve desired output characteristics, wherein the diaphragm depth and the profile is optimized with the stroke of the brake chamber such that the ratio of 3. Diaphragm profile depth to the stroke and 4. Diaphragm depth to the pressure plate depth is made critical, wherein the diaphragm depth being the distance between the push plate seating face of the diaphragm to the clamping region and stroke being the maximum travel of the piston assembly upon application of air pressure. Higher ratio is better for achieving flat force output characteristics but leads to increased air consumption, which is not desirable. By optimizing the ratio of stroke to diaphragm profile depth, and the ratio of pressure plate depth to the diaphragm depth the desired force output characteristic is achieved.

Full Text

Field of invention * This invention relates to brake chamber diaphragms used in brake actuators in the air brake system of motor vehicles. In the conventional construction of the brake chamber, the force output drops significantly at higher strokes as compared to mid stroke. This leads to the requirement of frequent adjustment of the brake shoe clearance for reducing the stroke of the brake chamber for effective braking. To overcome this problem, brake chambers with larger stroke have to be used. This in turn increases the cost and the size of the actuator. The object of the current invention is to overcome the aforesaid problem. The solution resides in optimizing the design parameters of the diaphragm in order to avoid the drop in force output at the higher end of the stroke. Prior art Brake chambers are known to the prior art. However the prior art has the following disadvantages. 1. The force output of the prior art products is low at higher strokes and this leads to ineffective braking at higher strokes (which happens due to wear of the brake shoes) and thereby requires frequent adjustment of brake shoe clearance for effective braking. To overcome this problem the prior art products require longer strokes, which makes the products bulky and thereby increasing the cost of the products. 2. Certain other prior art brake chambers specify constant or flatter output force characteristics for a limited stroke but these prior art chambers also characterize lower output force near to full stroke. 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 device to improve, efficiency, According to second aspect and feature of the invention in addition to the first feature the invention comprises a device, which is unique, rugged efficient, economical. At the outset of the description, which follows it, is to be understood that ensuing description only illustrates 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. This invention relates to brake chamber diaphragms used in brake actuators in the air brake system. The Brake chamber diaphragms are designed to achieve desired output characteristics, wherein the diaphragm depth and the profile is optimized with the stroke of the brake chamber such that the ratio of 1. Diaphragm profile depth to the stroke and 2. Diaphragm depth to the pressure plate depth are made critical, wherein the diaphragm depth being the distance between the push plate seating face of the diaphragm to the clamping region and stroke being the maximum travel of the piston assembly upon application of air pressure. Higher ratio is better for achieving a constant force output characteristic but leads to increased air consumption, which is not desirable. By optimizing the ratio of stroke to diaphragm profile depth, and the ratio of pressure plate depth to the diaphragm depth the desired force output characteristic is achieved. Brief description of 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. The various features of novelty which characterize the invention are pointed out specifically in the claims which forms 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 are illustrated and described, the preferred embodiments of invention. Referring now to drawings, where like numerals designate identical or corresponding parts throughout the referred views. Figure-1 of the drawings shows in cross section the brake chamber Figure-2 of the drawings shows the flexing of the diaphragm across the stroke Figure-3 of the drawings shows the diaphragm and pressure plate dimensions. Figure-4 of the drawings shows the output force characteristics of a conventional brake chamber Figure-5 of the drawings shows the output force characteristics of the conventional along with the novel force output characteristics of the brake chamber with the current invention. Detailed description of preferred embodiment of invention The Brake Chamber consists of a pressure plate (1) with a facility of air inlet connection, (A), Non pressure plate (2), Piston assembly (3), diaphragm (4) clamped between the non-pressure plate and the pressure plate using a clamp ring (5), and a return spring (6). It is used in the compressed air brake system to generate the braking force required for stopping or decelerating the vehicle. When air pressure is applied through the port (A), the diaphragm deflects and pushes the piston assembly (3) against the return spring (6) in the direction of (B) and output force is generated. The output force is proportional to the effective diaphragm diameter (C), which is dependent on the stroke (S) of the brake chamber, shown in figure-1 As mentioned, the force output of the brake chamber is dependent on the effective area of the diaphragm. The effective area of the diaphragm keeps varying due to the stroke and the flexing pattern of the diaphragm. The flexing pattern of the diaphragm is dependent on the applied air pressure and the stroke 'S' of the brake chamber. An approximate flexing pattern of the diaphragm at various strokes i.e. 0, 1/4S, 1/2S, 3/48 and S is shown in figure-2. It can be seen from figure-2 that the diaphragm flexing pattern keeps varying and the effective area changes correspondingly leading to a non-linear and non-uniform force output characteristics. Thereby the force output at full strokes is lower than at mid stroke. Such a condition is not desirable because this will require frequent adjustment of the brake shoe clearance to maintain the stroke of the brake chamber at mid stroke during brake application. The unique feature of this invention is to overcome this problem. This is done by making the following parameters critical 1. Ratio of diaphragm profile length (E) to Stroke (S) 2. Ratio of diaphragm depth (F) to Pressure plate depth,(G) The above parameters are explained in the figure-3. Figure-3 shows in detail the various critical parameters such as diaphragm profile length (E) Pressure plate depth (G) and diaphragm depth (F). Higher ratio of the diaphragm profile length (E) to stroke (S) is desirable for achieving minimum variation across the stroke. Higher ratio increases the air consumption, which is not desirable. By optimizing the ratio of stroke to diaphragm depth, the desired output characteristic with minimal variation is achieved. A higher ratio of diaphragm depth to the pressure plate depth is desirable to improve the effective diaphragm area at higher strokes. But higher ratio induces difficulty in assembly and clamping of the Pressure plate and Non-pressure plate. Based on the above considerations, an optimum ratio has been arrived at to ensure uniform output characteristics across the total stroke of the brake chamber. The typical ratio of the diaphragm profile depth to the stroke of the chamber is 0.55 to 0.65 and the ratio of the pressure plate depth to the diaphragm depth is 0.8 to 0.9, which enables the construction to achieve the objective of providing output force with reduced variation as the stroke of the brake chamber changes. The output characteristic of a known brake chamber is shown in figure-4. The variation in the force output level between the initial and final stroke is indicated by V1. The force output curve is denoted by Q. It is evident from figure-4 that there is an extreme variation in the output level, which is not desirable. Applying the invention, the force output characteristics are indicated in figure-5, the force output is denoted by curve P in dotted lines, where in the variation is minimized. This leads to various benefits, which are outlined in the objects of the invention. The variation V1 of a conventional brake chamber and V2 of the novel brake chamber is shown in the figure. It can be clearly seen that there is a significant reduction in the amount of variation. These results are based on the actual performance data. The invention has been explained in relation 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 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. We claim 1. A brake chamber of a motor vehicle, which comprises a brake chamber diaphragm (4) incorporated between the pressure plate (1) and the non pressure plate (2) and joined together with a clamp ring (5), the diaphragm bearing on one side of a piston assembly (3) to provide a mechanical output force dependent on the pressure acting through the port provision (A) and a spring (6) bearing on the reverse side of the said piston assembly to provide the restoring force for the piston assembly when the pressure acting on the port provision (A) is removed or depleted, characterized by the construction of the said diaphragm (4) such that the ratio of the linear dimension of the flexing portion of the said diaphragm (E) to the stroke (5) and the ratio of the depth of the said pressure plate(G) to the depth of the said diaphragm (F) are adjusted to provide a force output with low variation with respect to the stoke (S) of the brake chamber 2. A brake chamber of a motor vehicle as claimed in claim 1 ^ lCoH^^A«ars^^^;^the ratio of the dimensions E/S is between 0.55 and 0,65 \. 3. A brake chamber of a motor vehicle as claimed in claims 1 and 2 wKwfc£5*3^ V" the ratio of dimensions G/F is between 0.8 and 0.9 4. A brake chamber of a motor vehicle as described in claims 1 to 3 and as described in the complete specification and as illustrated by way of drawings.

Documents:

1070-che-2003-abstract.pdf

1070-che-2003-claims duplicate.pdf

1070-che-2003-claims original.pdf

1070-che-2003-correspondence others.pdf

1070-che-2003-correspondence po.pdf

1070-che-2003-description complete duplicate.pdf

1070-che-2003-description complete original.pdf

1070-che-2003-drawings.pdf

1070-che-2003-form 1.pdf

1070-che-2003-form 19.pdf