Measuring and testing – With fluid pressure – Fluid pressure brake system or unit
Reissue Patent
1999-09-30
2001-05-01
McCall, Eric S. (Department: 2855)
Measuring and testing
With fluid pressure
Fluid pressure brake system or unit
C073S049700, C073S168000
Reissue Patent
active
RE037151
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to hydraulic apparatus in general and more particularly to a hydraulic control apparatus comprising a hydraulic master cylinder and a hydraulic slave cylinder for operating a mechanism remotely located from the master cylinder [the hydraulic control apparatus being prefilled with hydraulic fluid and pretested prior to shipment to a motor vehicle manufacturer for installation in a motor vehicle].
It is known to prefill with hydraulic fluid a motor vehicle clutch control apparatus comprising a master cylinder, a reservoir of hydraulic fluid and a slave cylinder for operating the throw out bearing of a mechanical diaphragm spring clutch. Such prefilled hydraulic control apparatus are shown, for example, in U.S. Pat. Nos. 4,407,125, 4,599,860, 4,503,678, 4,506,507, 4,959,960, and 4,993,259, all assigned to the assignee of the present invention.
As is well known, prefilling with hydraulic fluid and pretesting hydraulic apparatus for operating motor vehicle mechanisms such as mechanical clutches presents the many advantages, for the motor vehicle manufacturer, of receiving a fully assembled mechanism comprising all of the components filled with hydraulic fluid and pretested for proper operation ready to install on a motor vehicle on the assembly line without requiring that the components be installed, separately connected by way of a flexible conduit, and filled after installation with hydraulic fluid while being purged of any atmospheric air contained in the apparatus.
Fast, efficient and accurate prefilling and testing of the hydraulic apparatus is critical to the commercialization of such prefilled controlled apparatus. Various filling and testing methods are disclosed in the above-identified patents assigned to applicant's assignee.
Specifically, in U.S. Pat. No. 4,407,125, liquid is supplied through the open top of the reservoir until the liquid bleeds out of a bleed port in the slave cylinder whereupon the filling is terminated.
In U.S. Pat. Nos. 4,506,507 and 4,503,678, a port is provided in a side wall of the reservoir, vacuum is applied to the system through the port to evacuate the system, liquid is introduced into the system through the port, and the port is thereafter sealed with a plug which serves to allow flow of hydraulic fluid out of the reservoir upon excess pressure but prevents reverse flow.
In U.S. Pat. No. 4,959,960, the apparatus is filled by the use of a filling head which is fitted into the open top of the reservoir and which includes a nozzle portion having an exterior surface enclosing a volume which approximates the volume of the diaphragm so that, following filling of the apparatus, removal of the filling head, and reinsertion of the diaphragm, the apparatus is automatically placed in the totally filled condition. In U.S. Pat. No. 4,993,259, the system is closed to substantially preclude escape of hydraulic fluid from the cylinder bore through the conduit means, a predetermined force is applied to the piston to urge the piston to move in the cylinder bore, and the magnitude of the movement of the piston in the cylinder bore in response to the predetermined force is measured to determine the acceptability or unacceptability of the unit under test.
Whereas the filling and testing methods disclosed in these patents have proven to be generally satisfactory, there continues to be a need to improve the apparatus and methodology of filling and testing to provide more reliable, less expensive, and faster filling and testing.
SUMMARY OF THE INVENTION
This invention is directed to the provision of improved method and apparatus for testing the integrity of a fluid pressure apparatus.
More specifically, this invention is directed to the provision of improved method and apparatus for filling, and testing the integrity of, a fluid pressure apparatus.
Yet more specifically, this invention is directed to the provision of an improved method and apparatus for
prefilling
filling and testing
a hydraulic control apparatus.
The invention methodology relates to the testing and filling of a fluid pressure apparatus having a fluid pressure chamber. For example, the fluid pressure apparatus may comprise a hydraulic control apparatus including a slave cylinder; a conduit connected to one end of the inlet port and the slave cylinder; a master cylinder connected at its discharge port to the other end of the conduit; and a reservoir assembly associated with the master cylinder.
According to the invention, the mass of the fluid in the chamber of the fluid pressure apparatus is gradually varied; the pressure in the chamber is noted at successive times as the mass is varied, whereby to generate successive pressure
reading
readings
; a signature is created from the pressure
reading
readings
; and the signature is compared to a known stored signature of a satisfactory apparatus. This methodology provides a convenient means of readily determining the integrity of the apparatus under test.
According to one aspect of the invention methodology, the step of gradually varying the mass of fluid in the chamber comprises evacuating air from the chamber to gradually reduce the pressure in the chamber. This evacuation step, which precedes the filling step, is thus utilized to test the integrity of the apparatus.
According to another aspect of the invention methodology, the step of gradually varying the mass of fluid in the chamber comprises gradually filling the chamber with a fluid. According to this aspect of the invention methodology, the filling step, following the evacuating step, is utilized to provide a further determination with respect to the integrity of the apparatus.
According to a more specific aspect of the invention methodology, the step of gradually varying the mass of fluid in the chamber comprises evacuating air from the chamber to gradually reduce the pressure in the chamber, and thereafter filling the chamber with a fluid; the step of noting the pressure in the chamber at successive times comprises noting the pressure in the chamber at successive times as the chamber is evacuated and thereafter noting the pressure in the chamber at successive times as the chamber is filled; the step of creating a signature from the pressure readings comprises creating a vacuum signature as the chamber is evacuated and creating a fill signature as the chamber is thereafter filled; and the step of comparing the signature to a known storage signature comprises comparing the vacuum signature to a known stored vacuum signature and thereafter comparing the fill signature to a second known stored fill signature.
The invention methodology may be applied to various types of fluid pressure systems and apparatus both prefilled and postfilled.
REFERENCES:
patent: 4959960 (1990-10-01), LaFountain
patent: 4993259 (1991-02-01), LaFountain
SAE International; “Automotive Engineering” article entitled Testing Method Modernized pp. 37-38, Jun. 1992.*
“Signature Analysis” (5 pages) advertising brochure.*
“Engine Test Systems” 1 page advertisement by Proel Systems USA.
Automotive Products
McCall Eric S.
Young & Basile
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