Gm Global Technolgoy Operations, Inc.

John R Coleman

Malvin L Schubert

Cecil C Pugh

Dwight W McDaniel

A dual acting master cylinder and reservoir assembly includes a pair of bayonets on the reservoir that are received within primary and secondary bosses of the master cylinder. The bayonets each include disks within their central openings wherein each disk has a control orifice for controlling the pressure rise in the associated primary and secondary braking circuits during the initial filling process of the master cylinder and reservoir assembly. Through means of the control orifices, the initial filling process of the braking system through the reservoir is effected while minimizing pressure differential establishment across the secondary piston.

Master cylinder reservoir assembly

A master cylinder assembly in which the plastic reservoir has mounting tubes fitting about mounting bosses or into recesses of mounting bosses of a master cylinder body. The tube outer ends have elastic seals integrally formed thereon which engage a wall surface of the mounting bosses in sealing relation. The seals may be lip type or O-ring type seals.

Integral reservoir seal of a master cylinder

A reservoir diaphragm for a vehicle brake master cylinder fluid reservoir has a passage in communication with the atmosphere defined between the reservoir cover and diaphragm. The diaphragm has a slot receiving a projection from the cover to normally form a seal. The seal prevents pasage of air between the reservoir and the passageway when the reservoir substantially equals the atmospheric pressure. The diaphragm is movable with respect to the projection to open the seal when the pressure in the reservoir is less than the atmosphere thereby allowing air from the atmosphere to enter the reservoir.

Venting master cylinder reservoir diaphragm

A diaphragm for a vented master cylinder reservoir which further includes means for opening the slit thereby assuring venting of the master cylinder reservoir is provided. The slit opening means are configured in such a manner that contact of the slit opening means with the master cylinder cap will cause the diaphragm to be stressed and to elastically deform, therefore assuring the opening of the venting slit.

Assured venting master cylinder diaphragm apparatus and method

A dual master cylinder for a vehicle brake system includes a housing having a housing bore with a open end and a closed end. The open end has a piston stop. Two pistons are reciprocably received in the housing bore and define therewith a first pressurizing chamber between the pistons and a second pressurizing chamber between the second piston and the housing bore closed end. Each piston has a piston cavity opening into the respective pressurizing chamber. A first locator member and a second locator member are respectively received in the pressurizing chambers and slidably mounted in the piston cavities of the respective pistons. The first locator member projects into engagement with the rear wall of the second piston and the second locator member projects into engagement with the housing to establish the pistons at respective normal rest positions enabling fluid communication through the port between the fluid reservoir and the respective chambers. A detent associated with each of the locator members permit the collapse of the locator members within the respective piston cavity upon a first occurring forward movement of the pistons forward of the respective normal rest positions, and further acts to retain the locator members in their respective collapsed states. With the locator members remaining in the cavities, the pistons are freed for fore and aft reciprocable movement within the housing during subsequent operation of the master cylinder.

Master cylinder with collapsible piston locator

A dipstick in the brake fluid reservoir of a brake system of the type having one or more pistons carrying a seal of elastomeric material subject to swelling upon exposure to the presence of a foreign fluid other than brake fluid. A piece of elastomeric material of the same type as the elastomeric material of the piston seal is mounted on the dip stick at a level thereon to be consistently submerged in the brake fluid whereby the presence of the seal swelling foreign fluid in the brake fluid reservoir will be detectable by examination of the piece of elastomeric material upon removal of the dip stick from the reservoir.

Master cylinder dip stick

An apparatus is provided for connecting a master cylinder to a brake booster of the type which has a shell with a planar front surface and a plurality of threaded studs displayed about the bore and projecting from the planar front surface. The master cyliner has a necked down end portion defining a shoulder facing the booster. The master cylinder has a circumferential extending groove provided in the necked down end portion and spaced longitudinally from the shoulder. An adapter has a central aperture to receive the necked down end portion of the master cylinder and a plurality of apertures which register with the plurality of threaded studs. A lock ring or other locking device is received in the groove of the master cylinder and effective to lock the adapter to the master cylinder and in engagement with the shoulder. A plurality of threaded nuts are installed on the threaded studs to retain the adapter in engagement with the planar surface of the booster shell.

Master cylinder attachment adapter

A master cylinder having pistons sliding through high pressure lip seals during operation. When the pistons are at rest during release, the seals are in an open position relative to the pistons sufficient to permit the passage of fluid therepast for compensation. The open positions are attained by providing piston portions of smaller diameter than the high pressure seals. These piston portions may be at least parts of piston beveled edge surfaces, or such edge surfaces in conjunction with notches or grooves which are of smaller diameter than the high pressure lip seals. The notches or grooves may extend circumferentially completely around the pistons, or may be arcuately extending circumferentially spaced notches or grooves.

Center compensating tandem master cylinder with seals in cylinder wall

In order to accommodate all of the tolerances along the bore centerline plane of the reservoir mount for a master cylinder, the reservoir bayonets or projections extending into the boss bores of the master cylinder body are at a reduced diameter established by worst case tolerancing. This results in greater side-to-side clearance perpendicular to the bore center-line than is desired in many instances, giving a relatively loose reservoir fit. To reduce this side-to-side clearance, locally raised ribs or the like are added to the reservoir mount bayonets to better match the diameter in the machined body reservoir bosses provided by the boss reservoir mounting surfaces. The clearance is reduced by locally increasing the diameter of the reservoir bayonet mounts based on worst case tolerancing considering only one reservoir mounting member and its associated mounting boss independently of the other mounting member and its associated mounting boss.

Master cylinder with reservoir mounting arrangement

A master cylinder assembly has a low pressure, high volume displacement quick take-up chamber and a high pressure, low volume displacement pressurizing chamber formed by a stepped bore and a stepped piston. A compensation control and blow-off valve unit has a peripheral lip seal type valve providing compensation flow on brake release but preventing flow from the quick take-up chamber during brake apply. A normally closed check valve can open to provide communication between the quick take-up pressurizing chamber and the fluid reservoir. When the pressurizing cup for the high pressure chamber closes its compensation port, the check valve is subjected to the pressure in the quick take-up pressurizing chamber. Initial fluid flow is obtained from the quick take-up chamber past the pressurizing cup into the high pressure chamber. At a predetermined pressure level, arranged to be sufficient to take up lining clearance and initially apply the vehicle brakes, the pressure in the quick take-up chamber opens the normally closed check valve so that fluid from the quick take-up chamber then flows to the reservoir without further pressure buildup in that chamber. As the master cylinder is released, compensation fluid can flow past the peripheral compensation valve to both chambers. When the master cylinder is returned to the fully released position, the check valve is closed. A fluid flow restrictive orifice is provided which bypasses the normally closed check valve to provide a continuous fluid path controlled leak from the quick take-up chamber to the fluid reservoir.

Valve assembly

A quick take-up valve in a quick take-up master cylinder assembly which reduces fluid flow noise and restriction caused by fluid flowing in one mode of operation through an incipiently or substantially closed valve spring coil stack. The check valve arrangement has a coil compression limiting device and also has the outlet orifice so positioned as not to require fluid flow through the check valve spring coils while the check valve is open.

Quick take-up master cylinder with check valve assembly

The lip of a cup seal for use in a master cylinder incorporates a semi-torus of material extending axially outward from the outer peripheral end of the seal lip. The added material is positioned immediately adjacent, but slightly radially inward from, the sharp lip edge. This added material prevents the lip from hanging up on the edges of compensation ports which open into the master cylinder bore, particularly during initial installation.

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Dayton, OH, United States of America

John R Coleman