Title of Invention

A SPRING BRAKE ACTUATOR WITH INTERNAL BREATHER FOR AN AUTOMOBILE BRAKING SYSTEM

Abstract

A spring breke actuator with internal breather, for an automobile braking system comprising a service brake diaphram chamber; a spring brake chamber;a ram assembly provided for the said chambers; and a service port, wherein valve means being normally open, when fitted in the assembly, such that duing application of the spring break, that vacuum created of the spring brake the spring chamber, causes air to flow from the service port through the open valve means into the spring side of the spring brake chamber to neutralize the vacuum; and such that duing release of the spring brake , the pressure build-up created within on the spring side of the spring chamber causes air chamber throughthesaid valve means to the service, to neutralize the pressure build-up.

Full Text

scl/hp This invention relates to a spring brake actuator with internal breather for an automobile braking system. Spring brake actuators are known to the art and comprise a diaphragm chamber for the application of the service brake of the vehicle and a spring chamber for the application of the spring brake/parking brake (hereinafter called the spring brake for the sake of brevity) of the vehicle. The known spring brake actuator is provided with a breather tube on the spring side of the spring brake chamber, for neutralising the partial vacuum produced on the spring side of the spring brake chamber, during application of the spring brake and for neutralising the pressure build-up produced on the spring side of the spring brake chamber/ during release of the spring brake. However this breather tube is prone to many disadvantages. It does not prevent dust and muddy water entering into the spring side of the spring brake chamber, and consequent corrosion and damage to the ram assembly, seal and power spring, thereby decreasing the service life of the said actuator as a whole. Internal breathing systems in spring brake actuators are also known. However such systems have the following disadvantages: The breathing system operates using pressure signal .applied at the service port. Since signal pressure is limited/ and less spring force is to be provided for operating the breather valve, this system is not robust enough against vibratory environment. On the other hand the spring brake actuator proposed herein eliminates, or at least greatly minimises, the above mentioned drawbacks associated with the known actuator. The breather valve in the actuator proposed herein is operated using mechanical spring force of the pushrod return spring and thus more force is available for operating the breather valve. The proposed actuator is thus more robust against vibration. Additionally, the breather provided in the proposed spring brake actuator is compact, cost effective and~ can be easily fitted to the stem of the conventional ram assembly. The major parts of the breather valve in the proposed system are preferably made from engineering plastic thus contributing to a lower cost structure. It is also highly reliable. In the spring brake actuator proposed herein, the breather valve is normally open under the force created by the push rod return spring in the service chamber, whenever the service brake is not applied. During application of the spring brake, the partial vacuum created on the spring side of the spring chamber causes air to flow from the service port through the open valve into the spring side of the spring brake chamber to neutralise the vacuum. Various of other features of the proposed spring brake actuator will be discernible from the following further description thereof given hereunder. The spring brake actuator with internal breather for an automobile braking system, according to this invention, comprises a service brake diaphragm chamber; a spring brake chamber; a ram assembly provided for the said chambers: and a service port, wherein two way valve means are provided in the stem of the ram assembly, said valve means being normally open, when fitted in the assembly, such that during application of the spring brake, the partial vacuum created on the spring side of the spring chamber, causes air to flow from the service port through the open valve means into the spring side of the spring brake chamber to neutralise the vacuum; and such that during release of the spring brake, the pressure build-up created within on the spring side of the spring chamber causes air to flow from the spring side of the spring brake chamber through the said valve means to the service port, to neutralise the pressure build-up. This invention will now be described with reference to the accompanying drawings, wherein Flg.l illustrates a sectional view of the known spring brake actuator Fig.2 illustrates by way of example and not by way of limitation, a sectional view of one of possible embodiments of the spring brake actuator according to this invention Fig.3 illustrates by way of example and not by way of limitation a separate view of the breather of the said embodiment Fig. 4 illustrates normal service brake application with the internal breather valve in closed condition. Fig. 5 illustrates by way of example .and not by way of limitation a sectional view of the said embodiment indicating the flow of air from the service port, through the breather and the stem of the ram assembly, into the spring side of the spring brake chamber when the ram moves irom lett to right in the direction of the arrow Z and Fig.6 illustrates by way of example and not by way of limitation a sectional view of the said embodiment indicating the flow of air from the spring side of the spring brake chamber, through the said stem and breather to the service port when the ram moves from right to left in the direction of the arrow Y The known spring brake actuator in Fig. 1 illustrates the breather tube T; the spring chamber C comprising the spring side D of the chamber C and the other side E of the chamber C; service brake chamber F with the diaphragm G, the ram assembly R power prmgs and service port P. The breather tube T is what may be called an "external breather", since it is external to the spring brake actuator. The said tube T is connected to the spring side D of the spring chamber C and allows air to go in and go out of the spring side D of the chamber C to neutralise the partial vacuum created therein (during application of the spring brake) and to neutralise the pressure build-up in the spring side D of the chamber C (during release of the spring brake). The disadvantages of the known actuator have already been stated above. From Figs. 2 to 6 of the accompanying drawings It will be seen that the embodiment of the spring brake actuator proposed herein has a spring chamber CI comprising the spring side Dl of the said chamber CI and the other side El of the said chamber CI; service brake chamber Fl with the diaphragm 61 and the ram assembly Rl, power spring SI and service port PI. Valve means V which serve as a breather are built into the ram assembly Rl and not fitted on to the spring side Dl of the spring chamber CI as in the case of the known actuator. The chamber Dl is closed at the point where the tube T is fitted in the conventional actuator. The function of the valve means V is to let in air into the chamber Dl whenever there is a partial vacuum created therein on the spring brake being applied and to let out air from the chamber Dl whenever pressure build-up is produced in the chamber. Dl on the spring brake being released. The valve means V are provided in the stem J of the ram assembly Rl. According to one of various possible forms the valve means V may take, such means will comprise a body K, bonded valve L, spring M, O-ring N and a spring guide Q. The said valve means will be normally open when fitted in the assembly, because the diaphragm Gl presses against the stem L of the valve means V by reason of the push plate U acting under the return spring W whenever there is no air pressure in the service chamber. Thus during application of the spring brake, the partial vacuum created in the chamber Dl causes air to flow from the service port PI, through the open valve means V into the chamber Dl, to neutralise the vacuum; and during release of the spring brake, the air pressure build-up produced in the chamber Dl causes air to flow from the chamber Dl through the said valve means V to the service port PI to neutralise the pressure build-up. The valve means V acts as an "internal" breather in the sense that it is provided within the actuator unlike the conventional breather, tube T which is "external" to the actuator. Consequently, the valve means V being "sheltered" within the actuator is less likely to suffer the drawbacks of the known breather T, since the possibility of extraneous matter such as dust and muddy water entering the actuator, particularly, the chamber Dl is remote. The terms and expressions in this specification are of description and not of limitation, there being no intention to exclude any equivalents of the features illustrated and described, but it is understood that various other embodiments of the spring brake actuator proposed herein are possible without departing from the scope and ambit of this invention. We Claim: 1. A spring brake actuator with internal breather, for an automobile braking system comprising a service brake diaphragm chamber; a spring brake chamber; a ram assembly provided for the said chambers; and a sendee port, wherein two way valve means are provided in the stem of the ram assembly, said valve means being normally open, when fitted in the assembly, such that during application of the spring brake, the partial vacuum created on the spring side of the spring chamber, causes air to flow from the service port through the open valve means into the spring side of the spring brake chamber to neutralise the vacuum; and such that during release of the spring brake, the pressure build-up created within on the spring side of the spring chamber causes air to flow from the spring side of the spring brake chamber through the said valve means to the service port to neutralise the pressure build-up. 2. A spring brake actuator as claimed in Claim 1 wherein the valve means comprise a body bonded valve, spring, O-ring and a spring guide 3. A spring brake actuator with internal breather for an automobile braking system substantially as herein described and illustrated in the accompanying drawings.

Documents:

976-mas-2002-abstract.pdf

976-mas-2002-claims duplicate.pdf

976-mas-2002-claims original.pdf

976-mas-2002-correspondance others.pdf

976-mas-2002-correspondance po.pdf

976-mas-2002-description complete duplicate.pdf

976-mas-2002-description complete original.pdf

976-mas-2002-drawings.pdf

976-mas-2002-form 1.pdf

976-mas-2002-form 26.pdf

976-mas-2002-other documents.pdf