Power plants – Pressure fluid source and motor – Pulsator
Reexamination Certificate
2002-02-12
2004-08-03
Lopez, F. Daniel (Department: 3745)
Power plants
Pressure fluid source and motor
Pulsator
C060S588000
Reexamination Certificate
active
06769254
ABSTRACT:
CROSS-REFERENCE TO RELATED CASES
This application claims the priority of the commonly owned copending German patent application Serial No. 101 06 416.0 filed Feb. 12, 2001. The disclosure of the aforementioned copending German priority application, as well as that of each US and foreign patent and patent application identified in the specification of the present application, is incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to improvements in fluid operated systems, especially hydraulic systems, which employ cylinder and piston units. Examples of such units (also called hydraulic or pneumatic cylinders) are so-called slave cylinders and master cylinders which are utilized in the power trains of numerous motor vehicles, e.g., to engage and/or disengage a friction clutch between the prime mover (such as an internal combustion engine) and the change-speed transmission which latter selects the speed and the direction of movement of the vehicle.
As a rule, the piston of the master cylinder of the clutch actuating system in the power train of a motor vehicle is set up to furnish (when necessary or desired) a pressurized fluid to the housing (cylinder) of the slave cylinder by way of one or more conduits, and the piston in the cylinder or housing of the slave cylinder causes a lever, a fork or another suitable actuator or implement to engage or disengage the friction clutch so that the latter establishes or interrupts a torque transmitting connection between the rotary output element (such as a camshaft or a crankshaft) of the prime mover and the rotary input shaft of the transmission.
Published German patent application No. 44 05 581 discloses a master cylinder which employs a one-piece piston having a complex undercut portion for reception of an insert which defines a socket for one (spherical or dome-shaped) end portion of a piston rod. The piston is made of a plastic material by resorting to complex and hence expensive injection molding tools, or of a metallic material in a time-consuming operation by employing material removing implements.
The peripheral surface of the piston in a conventional master or slave cylinder cooperates with the internal surface of the housing to serve as a guide surface for the piston as well as to prevent leakage of hydraulic fluid from the chamber (such as a plenum chamber) of the cylinder. In the absence of a special treatment, the internal surface of the housing and/or the external surface of the piston undergoes pronounced wear after a relatively short period of use with attendant leakage as a result of the development of undesirable clearances and/or due to pronounced wear upon or total destruction of the seal or seals which is or are provided between the housing and the piston.
It is customary to provide a fluid reservoir or tank above or on top of the master cylinder (also called clutch cylinder). Such reservoir contains a supply of brake fluid or another suitable hydraulic fluid which is forced by the piston into the housing of the slave cylinder when the piston of the master cylinder is displaced in its housing in order to change the condition of the friction clutch. As a rule, the housing of the master cylinder is provided with a machined channel, groove or anoter suitable passage to establish a path for the flow of hydraulic fluid between the aforementioned fluid reservoir or tank and the chamber in the housing of the master cylinder when the piston is idle. The passage must be reliably sealed from the surrounding atmosphere during the entire useful life of the master cylinder which involves additional work and contributes to the cost of such hydraulic system.
A further drawback of presently known master cylinder-slave cylinder combinations is that they cannot compensate for the development of subatmospheric pressures in the housing of the master cylinder during retraction of its piston, i.e., such hydraulic systems are incapable of ensuring or of adequately ensuring satisfactory drawing of hydraulic fluid into the chamber which is defined by the housing of the master cylinder and its piston in order to prevent the development of cavitation while the piston is caused to return to its idle or starting position in which the pressure of fluid in the master cylinder assumes its lowest value.
OBJECTS OF THE INVENTION
An object of this invention is to provide a simple, inexpensive and long-lasting fluid-operated system, especially a hydraulic system, which employs at least one cylinder and piston unit and can be utilized with advantage in the power trains of motor vehicles as well as for numerous other purposes.
Another object of our invention is to provide a hydraulic system of the above outlined character which can be assembled and/or otherwise attended to by semiskilled persons.
A further object of the present invention is to provide a novel and improved method of making the piston and/or the housing of the cylinder and piston unit for use in a hydraulic system which is or which can be employed in a power train, e.g., to actuate the friction clutch and/or the brake(s) in the power train of an automobile or another motor vehicle.
An additional object of the instant invention is to provide novel and improved articulate connections between the pistons and piston rods in the cylinder and piston units which can serve as master cylinders or slave cylinders in the power trains of motor vehicles, such as passenger cars, trucks, suburban vehicles and many others.
Still another object of this invention is to provide a master cylinder or a slave cylinder which employs or which can operate properly by employing fewer sealing rings, sealing lips and/or other types of sealing elements than heretofore known cylinders.
A further object of our invention is to provide a master cylinder or a slave cylinder which can reliably draw oil or another hydraulic fluid into the chamber of its housing during each retraction of the piston to or toward its starting position.
Another object of the present invention is to provide a novel and improved method of articulately anchoring the piston rod in the socket of the piston or another part of a hydraulic cylinder and piston unit, for example, in the power train of a motor vehicle.
An additional object of the invention is to provide novel and improved means for mounting one or more seals in the housing of a hydraulic cylinder and piston unit of the above outlined character.
Still another object of the instant invention is to provide a novel and improved piston for use in a hydraulic cylinder and piston unit.
A further object of the invention is to provide a novel and improved housing or cylinder for use in a hydraulic cylinder and piston unit, particularly in the power train of a passenger car or another combustion engine-driven or otherwise power-driven conveyance.
Another object of the invention is to provide a novel and improved method of reducing the extent of wear upon and of prolonging the useful life of the piston and/or housing and/or sealing means and/or other constituents of hydraulic cylinder and piston units.
An additional object of the invention is to provide a novel and improved method of constructing, configurating and assembling the constituents of a master cylinder or a slave cylinder in such a way that they are automatically locked to each other as soon as they are properly positioned relative to one another.
Still another object of our invention is to construct the constituents of a master cylinder, a slave cylinder or another fluid-operated or fluid conveying and/or compressing cylinder and piston unit in such a way that they are automatically limited or confined to requisite (permissible) movements with and/or relative to each other as soon as their assembly with one another and/or with one or more additional constituents is completed.
An additional object of our instant invention is to provide a power train, particularly for use in motor vehicles, which embodies one or more master cylinders and/or slave cylinders with pistons, piston rods, seals and other con
Grabenstätter Jan
Heller Jean-Francois
Panther Urban
Rammhofer Thomas
Welter Roland
Darby & Darby
Lopez F. Daniel
LuK Lamellen und Kupplungsbau Beteiligungs KG
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