Expansible chamber devices – Piston – With separable means for pivotally mounting connecting rod...
Reexamination Certificate
2000-05-25
2002-10-29
Look, Edward K. (Department: 3745)
Expansible chamber devices
Piston
With separable means for pivotally mounting connecting rod...
Reexamination Certificate
active
06470791
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to improvements in fluid-operated cylinder-and-piston assemblies in general, and more particularly to assemblies known as master cylinders. A master cylinder can be utilized, for example, in a motor vehicle where it can form part of a device such as a hydraulic brake or clutch.
As a rule, a master cylinder comprises a cylinder or housing defining a chamber for a reciprocable piston which can displace a column of liquid to thus actuate a brake or a clutch, e.g., by way of a so-called slave cylinder. “Modern Automotive Technology” (authored by James E. Duffy and published by The Goodheart-Willcox Company, Inc. of Tinley Park, Ill.) defines a master cylinder for a brake pedal assembly as a foot-operated pump that forces liquid into the brake lines and wheel cylinders. Its basic functions are to develop pressure, causing the wheel cylinder pistons to move toward rotors or drums; to help equalize the pressure required for braking after all of the shoes or pads produce sufficient friction; to keep the system full of fluid as the brake linings wear; and to maintain slight pressure to keep contaminants (such as air and/or water) from entering the system.
A master cylinder can be assembled with a brake pedal or with a clutch pedal to form part of a module which is ready to be installed in a motor vehicle, e.g., to apply brakes to the wheels or to engage or disengage a friction clutch. In many master cylinders, the brake pedal or clutch pedal is linked to a piston rod having a free end provided with a spherical head which is connected to and can swivel relative to the piston in the housing of the master cylinder. The module can be installed on a wall, e.g., between the space for the prime mover and the driver compartment. The piston can displace a column of liquid in order to cause the piston of a slave cylinder to expel liquid from the housing of the slave cylinder or to permit liquid to reenter the housing.
Reference may be had, for example, to published German patent application Ser. No. 196 08 132 A1 which describes and shows a conventional master cylinder. The latter comprises a housing made of a plastic material and defining a chamber for a plastic piston. The piston rod of the master cylinder has a spherical head which is form-lockingly connected with the piston. To this end, the piston is provided with a socket having a recess bounded by a concave surace and serving to receive the head of the piston rod (reference may be had to
FIG. 3
of the German published application). The piston is slotted axially in the region of the head of the piston rod so that the head can be readily introduced into the socket. A firm swiveling connection between the head of the piston rod and the piston is established by a sleeve which is slipped onto the slotted part of the piston so that the latter snugly surrounds the head and prevents separation of the spherical head from the piston.
A drawback of such master cylinders is that at least the slotted end of the piston and/or the head of the piston rod (also called push rod) must be made of a highly elastic material in order to permit the head of the piston rod to enter the cavity of the socket in the piston. As a rule, the head of the piston rod and/or the piston must be made of an elastomeric material, particularly a thermoplastic material which permits adequate deformation of the head and/or of the adjacent end of the piston and to thus permit insertion of the head into its socket. In many instances, the thermal expansion coefficient of a thermoplastic material is very high and actually too high because the stability of the piston is not sufficient for the intended purpose. In other words, the stability of the entire master cylinder is unsatisfactory for the intended purpose e.g., for use in a brake system or in combination with a clutch in the power train of a motor vehicle.
The manner in which an electronically controlled or operated master cylinder can regulate the operation of a clutch by way of a slave cylinder in the power train of a motor vehicle is described and shown, for example, in commonly owned U.S. Pat. No. 5,725,456 granted Mar. 10, 1998 to Robert FISCHER et al. for “METHOD OF REGULATING THE OPERATION OF A TORQUE TRANSMISSION APPARATUS”. The disclosure of the commonly owned priority application Ser. No. 197 52 076.6, as well as the disclosure of each U.S. and foreign patent and patent application identified in the specification of the present application are incorporated herein by reference.
OBJECTS OF THE INVENTION
An object of the present invention is to provide a master cylinder wherein the connection between the piston and the piston rod is more reliable than in heretofore known master cylinders.
Another object of the invention is to provide a relatively simple and inexpensive but higly reliable swivel joint between the piston and the spherical head of the piston rod or push rod in a master cylinder which is suitable for use in the power train between the prime mover (such as an internal combustion engine) and the wheels of a motor vehicle.
A further object of the invention is to provide a novel and improved arrangement which couples a female part to a spherical male part in such a way that the force with which a separation of the male part from the female part is opposed invariably exceeds a preselected lower threshold value irrespective of the orientation of male and female parts relative to each other.
An additional object of the invention is to provide a novel piston for use in the above outlined master cylinder.
Still another object of the invention is to provide a novel and improved reliable (but separable, if and when necessary) joint between the piston and the piston rod in the chamber of a housing forming part of a master cylinder for use in conjunction with the braking system or with a clutch in the power train of a motor vehicle.
A further object of the invention is to provide a master cylinder adapted to be utilized as a superior (e.g., longer-lasting) substitute for conventional master cylinders which are presently employed in the power trains of motor vehicles.
An additional object of the invention is to provide a master cylinder which constitutes a less expensive, more reliable, more compact and more readily assemblable and/or disassemblable substitute for presently known master cylinders.
Another object of the invention is to provide a novel and improved method of connecting the spherical head of a piston rod or push rod with the piston of a master cylinder.
Still another object of the invention is to provide a module wherein the piston and the spherical head of a piston rod are assembled with each other in a novel and improved way with freedom of swivelling movement relative to each other and in a condition of readiness for installation in the housing of a master cylinder for use in conjunction with the braking system or with a friction clutch in the power train of a motor vehicle.
A further object of the invention is to provide a module which forms part of a master cylinder and can be installed in the housing of a master cylinder in a simple and reliable manner, be it in conjunction with one or more brakes or in conjunction with a friction clutch.
An additional object of the invention is to provide a highly compact and lightweight master cylinder for use in the power train of a motor vehicle.
SUMMARY OF THE INVENTION
The invention is embodied in a cylinder and piston assembly, particularly in a master cylinder, which comprises a housing defining a chamber, a piston which is reciprocable in the chamber, a reciprocable piston rod including a spherical head extending into the chamber into engagement with one end of the piston, and means for articulately coupling the head to the one end of the piston. The coupling means includes a first section which engages the piston rod and a second section which is affixed to the piston.
The piston is or can be made of a plastic material, and at least a portion of the coupling means can consist of a metallic sheet material, i.e
Giese Peter
Meyer Gerhard
Schaaf Peter
Welter Roland
Winkelmann Ludwig
Darby & Darby
Kershteyn Igor
LuK Lamellen und Kupplungsbau Beteiligungs KG
LandOfFree
Master cylinder does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Master cylinder, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Master cylinder will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2946167