Title of Invention

SPRING WIND OFF TOOL FOR A DIAPHRAGM TYPE SPRING BRAKE ACTUATOR OF THE AIR BRAKE SYSTEM OF A MOTOR VEHICLE

Abstract

Spring wind off tool for a diaphragm type spring brake actuator of the air brake system of a motor vehicle, having a threaded bolt with nut and washer, the internal diameter of the washer being larger than the outer periphery of the threads on The bolt; and a locating member on the nut or matter engaging with the washer or nut for keeping the internal periphery of said washer always out of contact with the outer periphery of the threads on the bolt.

Full Text

This invention relates to the power spring wind off tool of a diaphragm type spring brake actuator used in air brake systems of commercial vehicles for applying and releasing the foundation brake. A powerful heavily loaded spring, called a power spring, is used in these actuators to apply a mechanical force on the brake drums of the vehicle for parking applications. To compress the spring (release of brakes) and release the spring (application of brakes) a diaphragm element operated with air pressure is used in these actuators. When the actuator or the foundation brake needs to be serviced, pneumatic pressure cannot be used to compress the power spring. In such cases a manual wind off tool, which is essentially a long threaded bolt with a washer and a nut, is used to compress the power spring and keep it in the compressed condition. This manual wind off tool has to withstand the forces of the power spring wind-off during multiple operations throughout the life of the actuator. Such diaphragm type spring brake actuators are known to the art. The normal mode of failure of the wind off tool is failure of the threads and damage to the washer after a few operations. This invention proposes, inter alia, a wind off tool by which damage to the threads and washer could be avoided and life of the tool increased. In the prior art wind off tool, the washer is not guided with respect to the threads, which results in the washer getting displaced and fouling with the threads causing consequent damage and failure. Furthermore, the wind off tool threads, washer and nut are made from unhardened steel, which also causes surface damage to me contact surfaces during Wind-off operations. Such prior art wind off tools allow only about 5 wind-off operations before occurrence of damage to the threads and washer, rendering the wind off tool unusable. The main feature of the present invention is that the washer of the wind-off tool is guided out of contact with the threads, thus preventing damage to the threads. Another feature of the present invention is that the contact surfaces of the wind off tool threads, nut and washer are hardened to resist friction and prevent damage to the surfaces due to repeated oration resulting in an average life span in excess of 25 operations. Referring to the accompanying drawings Figure 1 shows a cross section of a known double diaphragm spring brake actuator. Figure 2 shows the prior art construction of the wind-off tool. Figure 3 shows one of possible embodiments of the wind off tool according to this invention* by way of example, and not by way of limitation. With respect to figure I, the cylinder A. which is steel, and the aluminium body casting B along with rubber diaphragm C are joined together permanently by clamp ring Df achieved by plastically deforming I). This construction creates a chamber E, which is the spring chamber and a chamber F, which is the air chamber into which compressed air is charged or exhausted. A heavily loaded power spring G is supported and guided by a guide H which rests on the cylinder A. Another guide 1 rests on the diaphragm C. the diaphragm is attached to the spring side push rod J rigidly. The other end of the push rod J passes through two sealing rings K and a bearing L. In figure 1, the power spring is shown in manually woundup condition (brakes released condition). When the spring is released, the push rod J transmits the force from the spring Q through push plate I\ which rests against the service side of diaphragm M. The diaphragm M in turn transmits the force through push plate P and push rod Q to the foundation brake. The chamber 1SI for the service brake chamber is secured to the body B through detachable damp ring O. The return spring S rests on the spring seat R and helps in returning the push rod Q once the actuating force is removed. The gaiter T protects the service chamber from external dust. The wind off tool U is inserted into the unit, whenever the power spring is to be compressed manually (wind up). The feature I' in the spring guide I, engages with a pin like feature U' in the wind off tool. The nut V rests on the washer W which m turn rests on the cylinder A. The rotation of the nut V in one direction compresses the spring G and rotation in the other direction releases the spring. The dust cap X is assembled in the aperture X' in the cylinder A, when the spring is pneumatically compressed and the wind-off tool U, the nut Vand washer W are removed, which is the normal operating position of the actuator. Referring to figure 2, which depicts the prior art construction of the wind off tool, the nut V and washer W are free to move with respect to each other. When, therefore, the washer W is axially offset with respect to the thread of the wind-off tool U, the inner diameter of the washer can foul with the thread and cause damage to the threads. This will render the wind-off tool unusable after a few operations. Referring to figure 3, the wind-off tool proposed herein is shown along with the nut V. The said nut has a locating member, such as, for example, a spigot V the external periphery of which corresponds to the internal periphery of the washer W, whereby the washer gets located on the spigot of the nut as shown, thereby automatically aligning itself with the axis of the thread on the wind-off tool. The internal periphery of the washer being larger than the external periphery of the thread, the washer, located on the spigot is retained out of contact with the thread, during rotation of the nut. As an Alternative, the .washer will be provided with a locating member, such as, a collar, the internal periphery of which corresponds to the external periphery of the nut V, Thus, if the nut has a hexagonal shape, the periphery of the collar will have a matching hexagonal shape, such that the collar gets located on the nut, thereby automatically aligning itself with the axis of the thread on the wind-off tool, out of contact with the thread. It will be visualised that other forms of the locating member can be provided either on the nut or on the washer. This feature prevents the washer from coming into contact with the threads when the manual wind off of the power spring is carried out. Furthermore, in accordance with this invention, the contact surfaces of the threads on the wind-off tool, the nut and me washer are made of hardened metal, such as hardened steel, like surface nitrided steel. This reduces friction between the moving parts like the threads, the washer face, nut; and resists wear and tear on such parts. The terms and expressions herein are of description and not of limitation and do no exclude any equivalents of the features illustrated and described but it is understood that various other embodiments are possible without departing from the scope and ambit of this invention We claim 1. Spring wind off tool for a diaphragm type spring brake actuator of the air brake system of a motor vehicle, having a threaded bolt with nut and washer, the internal diameter of the washer being larger than the outer periphery of the threads on the bolt and a beating member on the nut or washer engaging with the washer or nut for keeping the internal periphery of said washer always out of: contact with the outer periphery of the threads on the bolt. 2. Spring wind off tool as claimed in claim 1, wherein the locating member is a spigot provided on the nut. 3. Spring wind off tool as claimed in Claim 1 wherein the locating member is a collar provided on the washer. 4. Spring wind off tool as claimed in any one of the preceding Claims wherein the contact surfaces of the said threads, nut and washer arc of made of hardened metal 5. Spring wind off tool for a diaphragm type spring brake actuator of the air brake system of a motor vehicle, substantially as herein described with reference to, and as illustrated in, the accompanying drawings.

Documents:

2-CHE-2008 AMENDED PAGES OF SPECIFICATION 28-08-2014.pdf

2-CHE-2008 EXAMINATION REPORT REPLY RECEIVED. 05-06-2014.pdf

2-CHE-2008 FORM-1 28-08-2014.pdf

2-CHE-2008 FORM-13 28-08-2014.pdf

2-CHE-2008 FORM-13 [1] 28-08-2014.pdf

2-CHE-2008 FORM-3 28-08-2014.pdf

2-CHE-2008 FORM-5 28-08-2014.pdf

2-CHE-2008 POWER OF ATTORNEY 28-08-2014.pdf

2-CHE-2008 POWER OF ATTORNEY.pdf

2-CHE-2008 ABSTRACT 01-01-2008.pdf

2-CHE-2008 CLAIMS 01-01-2008.pdf

2-CHE-2008 CORRESPONDENCE OTHERS 01-01-2008.pdf

2-CHE-2008 CORRESPONDENCE OTHERS 16-06-2008.pdf

2-CHE-2008 CORRESPONDENCE OTHERS 28-08-2014.pdf

2-CHE-2008 DESCRIPTION (COMPLETE) 01-01-2008.pdf

2-CHE-2008 DRAWINGS 01-01-2008.pdf

2-CHE-2008 FORM -2 16-06-2008.pdf

2-CHE-2008 FORM-1 01-01-2008.pdf

2-CHE-2008 FORM-1 16-06-2008.pdf

2-CHE-2008 FORM-18 01-01-2008.pdf

2-CHE-2008 FORM-6 16-06-2008.pdf

2-CHE-2008 POWER OF ATTORNEY 16-06-2008.pdf