Fluid handling – With repair – tapping – assembly – or disassembly means – Assembling – disassembling – or removing cartridge type valve
Patent
1994-07-11
1995-06-27
Rivell, John
Fluid handling
With repair, tapping, assembly, or disassembly means
Assembling, disassembling, or removing cartridge type valve
13762524, 91375A, B62D 5083
Patent
active
054271347
DESCRIPTION:
BRIEF SUMMARY
This invention relates to rotary valves and more particularly to rotary valves for hydraulic power steering of vehicles.
Typically such valves include an input-shaft, usually connected to the steering wheel of the vehicle by a flexible joint, and having in its outer periphery a plurality of blind ended, longitudinally extending slots separated by lands. Journalled on the input-shaft is a sleeve member having in its bore a similar array of longitudinally extending slots matching those of the input-shaft, but in underlap relationship thereto, the slots of the one being wider than the lands of the other so defining a set of longitudinally extending orifices which open and close when relative rotation occurs between the input-shaft and the sleeve.
Drilled passages in the input-shaft and sleeve, together with circumferential grooves in the periphery of the sleeve, serve to communicate oil between the slots in the input-shaft and sleeve, an engine driven oil pump, and right-hand and left-hand hydraulic assist cylinder chambers incorporated in the steering gear.
A torsion bar incorporated in the input-shaft serves to urge the input-shaft and sleeve towards a neutral, centered condition when no power assistance is required. When torque is applied by the driver to the steering wheel, the torsion bar deflects, allowing relative rotation of the sleeve and input-shaft from the neutral condition, so directing oil to the right-hand and left-hand assist cylinder chambers.
The general method of operation of such rotary valves is well known in the art of power steering design and so will not be described in any greater detail in this specification. An excellent description of this operation is contained in U.S. Pat. No. 3,022,722 (Zeigler), commonly held as being the "original" patent disclosing the rotary valve concept.
It is a requirement of operation of a steering gear that the left and right turn operation of the hydraulic assist be as nearly as possible identical, and this symmetry of operation can only be determined at assembly of the steering valve components.
Great accuracy is required in adjusting the exact position of the torsion bar relative to the input shaft to ensure this symmetry and once this position is determined, it must be retained for the life of the steering gear.
According to the most common present practice, the torsion bar is secured to the input shaft by a pin pressed through a hole drilled and reamed through in a hydraulic "balance" or "trimming" machine.
In one such machine, both the input shaft and the torsion bar are independently clamped to a drive mechanism capable of making fine angular adjustments of one relative to the other. This whole drive mechanism however, must be capable of being rotated and have precisely determined input torques, or angles depending on the system used, applied thereto while the resulting pressure in left and right turn cylinders are noted. When precise balance has been achieved, the drive mechanism stops rotating and the entire valve assembly and drive mechanism is moved in the "trimming" machine successively into stations or positions where the above referenced drilling and reaming is performed, and a further station at which a pin is pressed into the hole.
It frequently happens that during these various operations, the precise adjustment is disturbed and it is found on inspection of the completed steering gear or valve assembly that valve operation is no longer symmetrical. This requires that the assembly be extensively reworked at great cost and inconvenience. Furthermore, it is an undesirable feature of this existing method that, on a precise machine such as the trimming machine just described, involving sensing devices for both pressure and input torque or angle, and supplied with carefully monitored flow of oil at regulated pressure and flow, that drilling and reaming operations are carried out with the danger of contaminating the machine system.
Several attempts have been made to solve this problem, and to avoid the scrappage which occurs when asymmetry is
REFERENCES:
patent: 4385898 (1983-05-01), Jordan
patent: 4428399 (1984-01-01), Masuda et al.
patent: 4966192 (1990-10-01), Umeda
patent: 5230273 (1993-07-01), Fraley, jr.
James N. Kirby Products Pty Limited
Rivell John
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