Title of Invention

A COMBINED KEY AND RETAINER FOR A VACUUM BRAKE BOOSTER OF THE BRAKING SYSTEM OF A MOTOR VECHILE

Abstract

ABSTRACT A combined key and retainer device for a vacuum brake booster of the braking system of a motor vehicle. In which the valve body of the said booster has a slot for Inserting a key to engage with a groove on a piston housed within the valve body, the portions of the key, when Inserted Into the slot protruding out of the body, the key being provided with a retainer to prevent the key from working Itself loose and thus getting disengaged from the groove, wherein the key Is of the pronged type with no rubber bushes on Its surface and the retainer Is a disc having a central hole, the rim of the disc having a bent configuration all around to define a peripheral channel on one side of the disc, the channel being made of a flexible material whereby the part of the valve body provided with the slot Is receivable through the hole until the key Is positioned against the channel, to enable the channel to be manually urged over and around the said protruding portions of the key. In _a snap-fit, for not only receiving the said portions within the channel and thus preventing the key from getting disengaged from the groove but also for preventing the key from coming Into contact with the rear housing.

Full Text

This invention relates to a combined key and retainer device for a vacuum brake booster of the braking system of a motor vehicle. A vacuum brake booster (also called a vacuum brake valve) is employed in motor vehicles using a hydraulic braking system, such as light commercial vehicles/ sport utility vehicles and passenger cars to make braking more effective. The vacuum booster multiplies or boosts the force applied on the brake pedal, by the vehicle operator, and delivers such force as the output of the booster, thereby improving the comfort level of the operator during braking. The output force of the booster is delivered through a long and slender member called the putout rod. A hydraulic master cylinder is fitted at one end of the vacuum brake booster and the push out rod -of the booster will be butting against the input plunger of the master cylinder. Thus, any force output of the booster will be acting on the input piston of the master cylinder. This will in turn pressurize fluid in the hydraulic brake system to effect braking. The multiplication or boosting of the input force is a result of net force acting on a rigid but movable disc due to atmospheric air pressure on one side and vacuum on the other side. The level of boosting is decided by the air pressure differential maintained across the disc The ratio of output force to input force within the boosting range is called the boost ratio. A typical vacuum brake booster consists of a leak proof enclosure in which a hollow body containing a valve mechanism and a boosting mechanism are located. The input force from the brake pedal is transferred to a valve body through a plunger attached to a piston. A key engages with a groove in the piston. The rigid disc and pushout rod are attached to the valve body on the output side. This Invention relates to a combined key and retainer device for the valve body comprised in the vacuum brake booster. The key performs several important functions. The key is Inserted into and across the valve body througn a slot provided tor it. Inside the body, the key engages with a groove provided on the piston, thus preventing the piston from coming out of the body. The two ends of the key project out of the body and Is held In a retainer which butts against the rear housing surface. Thus, when the booster Is fully evacuated and In the brake un-applled condition, the key and the retainer together press against the rear housing and while doing so the piston will slightly move Inside the body and keep the Inlet valve closed. In case the Inlet valve slightly opens In the process It will result In a small differential pressure across the wall and the valve body moves slightly towards the front housing thereby closing the exhaust valve. The key has to be retained In Its position Inside the valve body to work effectively. However, It should also be sufficiently free to move "in the axial direction to facilitate the opening and closing of the inlet and exhaust valves. Devices for securing the key in its position are known to the art. Two Of such known devices are a sneet metal clamp which envelops the valve body and holds the key; a pronged key for gripping the piston. In such known devices rubber bushes are fixed on the key surface to prevent metal to metal contact when the key butts against the rear housing surface of the vacuum brake booster. In this invention a retainer has been proposed which grips the key in a snap-fit. This arrangement has several advantages over the existing methods. It is easy to assemble and dls-assemble. It is easy to manufacture (can be made out of moulded plastic) It prevents metal to metal contact of key with the rear housing. The combined key and retainer device for a vacuum brake booster of the braking system of a motor vehicle according to this invention, in which the valve body of the said booster has a slot for inserting a key to engage with a groove on a piston housed within the valve body, the portions of the key, when inserted into the slot protruding out of the hody, the key being provided wlth a retainer to prevent the key from . working itseif loose and thus getting disengaged from the groove, wherein the key is ot the pronged type with no rubber bushes on its surface and the retainer is a disc having a central hole, the rim of the disc having a bent configuration all around to define a peripheral channel on one side of the disc, the channel being made of a flexible material whereby the part of the valve body provided with the slot is receivable through the hole until the dine is positioned against the channel, to enable the channel to be manually urged over and around the said protruding portions of the key, in a snap-fit, for not only receiving the said portions within the channel and thus preventing the key from getting disengaged from the groove but also for preventing the key from coming into contact with the rear housing. This invention will now be described with reference to the accompanying drawings which illustrate by way of example, and not by way of limitation one of various possible embodiment of the combined key and retainer proposed herein. Fig. 1 Illustrating a vacuum brake booster showing the location of the known version of a pronged key Kl. Fig.2 Illustrating the known version of a pronged key Kl used for the booster with rubber bushes U thereon Fig.3 Illustrating a version of a pronged key K2 according to the said embodiment without rubber bushes thereon Fig.4 Illustrating a perspective view of the retainer depleting the central hole and the channel formed around the rim Fig.5 Illustrating In a cut-away view the key of Fig.3 being located within the retainer of Fig. 4 In snap-fit Fig. 6 Illustrating the valve body with the slot Fig.7 Illustrating the valve body being received within the hole In the retainer Fig. 8 Illustrating the retainer being ideated against the key K2 just before engaging with each other In a snap fit Fig. 9 Illustrating the retainer-surrounding the said protruding portions of the key K2 and engaged therewith In a snap-fit. The valve body B has a slot S for inserting the key K2 to engage with a groove G on a piston P housed within the body B. When the key K2 is inserted into the slot s to engage with the groove G on the piston P, portions E of the key K2 protrude out of the body. The booster referred to herein above is of the known kind and for the purposes of this invention it is not necessary to go into the working details thereof except to describe the invention which relates to the combined key and retainer. The key K2 is provided with a retainer to prevent the key from working itself loose in the slot S and thus getting disengaged from the groove G. In the embodiment illustrated, the retainer is a disc D having a central hole o. The rim R of the disc has a bent configuration all around to define a channel c on one side of the disc. The part of the valve body provided with the slot S is receivable through the hole 0 until the key C2is positioned adjacent the channel C. The channel C, which is made of a flexible material, is now manually urged over and around the said protruding portions of the key K2 In a snap-fit. This results not only In snugly receiving the said portions of the periphery of the key In a grip fit, within the channel, and thus preventing the key from getting disengaged from the groove, but also In the key K2 being prevented from coming Into contact with the surtface of the rear housing, since the wall w of the disc D Is Interposed between the rear housing and the key K2. As already stated, unlike the known key Kl Illustrated In Fig.2, the key K2 proposed herein (Fig.3) does not have any rubber bushes thereon for the reasons that no part of the key comes Into contact with the rear housing. The terms and expressions herein are of description and not of limitation since this Invention Is not confined to the embodiment herein described and Illustrated, but It Is understood 'that various other embodiments of the combined key and retainer proposed herein are possible" without departing from the scope and ambit of this Invention. We Claim: 1. A combined key and retainer device for a vacuum brake booster of the braking system of a motor vehicle. In which the valve body of the said booster has a slot for Inserting a key to engage with a groove on a piston housed within the valve body, the portions of the key, when Inserted Into the slot protruding out of the body, the key being provided- with a retainer to prevent the key from working Itself loose and thus getting disengaged from the groove, wherein the key Is of the pronged type with no rubber bushes on Its surface and the retainer Is a disc having a central hole, the rim of the disc having a bent configuration all around to define a peripheral channel on one side of the disc, the channel being made of a flexible material whereby the part of the valve body provided with the slot Is receivable through the hole until the Key Is positioned against the channel, to enable the channel to be manually urged over and around the said protruding portions of the key. In a snap-fit, for hot only receiving the said portions within the channel and thus preventing the key from getting disengaged from the groove but also for preventing the key from coming Into contact with the rear housing. 2. A combined key and retainer device for a vacuum brake booster of the braking system of a motor vehicle, substantially as herein described and as Illustrated In Figs. 3 to 9 of the accompanying drawings. Dated this the 23rd day of December 2002

Documents:

985-mas-2002 abstract-duplicate.pdf

985-mas-2002 abstract.pdf

985-mas-2002 claims-duplicate.pdf

985-mas-2002 claims.pdf

985-mas-2002 correspondence-others.pdf

985-mas-2002 correspondence-po.pdf

985-mas-2002 description(complete)-duplicate.pdf

985-mas-2002 description(complete).pdf

985-mas-2002 drawings-duplicate.pdf

985-mas-2002 drawings.pdf

985-mas-2002 form-1.pdf

985-mas-2002 form-19.pdf

985-mas-2002 form-26.pdf