Pipes and tubular conduits – With pressure compensators
Patent
1997-10-22
1999-08-24
Brinson, Patrick
Pipes and tubular conduits
With pressure compensators
138 30, 138109, 138113, 181255, F16L 5504
Patent
active
059412836
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a fluid supply conduit for attenuating the pressure pulses in the fluid, and particularly, though not exclusively, to a conduit for the hydraulic circuit of a vehicle power steering system.
BACKGROUND ART
As is known, in hydraulic systems in which the operating fluid is circulated by means of a pump, the pressure pulses generated by the pump are transmitted along the conduits and may give rise to undesired noise and vibration.
To reduce pulsation, conduits are currently used in which the path of the fluid is so devised as to produce reflected pressure waves which interfere with the incident waves; and by appropriately selecting the length of the wave paths, destructive interference of the waves is achieved to substantially eliminate pulsation at a given frequency.
In one known embodiment, the above conduits comprise an outer tube, and an inner tube extending a given length from an end fitting and defining an annular chamber with the outer tube. The fluid flows through the fitting into the inner tube, and, at the outlet of the inner tube, the incoming pressure waves interfere with the waves travelling along the annular chamber and reflected by the end wall of the chamber defined by the fitting. For interference to be destructive, the length of the annular chamber must be a quarter of the wavelength of the pressure waves.
With the above sizing of the inner tube, known conduits of the aforementioned type are "tuned" to a given frequency, whereas, in a real circuit, the pressure pulses are periodic but not purely sinusoidal with a well defined frequency, and may be divided into a number of frequency components comprising a fundamental or first harmonic component, and harmonic components of frequencies equal to multiples of the fundamental frequency. This therefore poses the problem of attenuating a number of components, typically the first two or three harmonics which present a much higher amplitude as compared with the harmonics of a higher order.
One way of doing this is to use a conduit comprising a number of elementary conduits of the above type in series with one another and each tuned to a respective frequency. Such a solution, however, results in an excessive total length of the conduit, and is therefore unsuitable for automotive applications in which size is a critical factor.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide a compact fluid supply conduit for attenuating a number of frequency components of the pressure pulses in the fluid.
According to the present invention, there is provided a fluid supply conduit for attenuating the pressure pulses in the fluid, and comprising an outer tube; at least one inner tube housed inside, and forming an annular chamber with, said outer tube; and fitting means fitted in sealed manner to said outer tube and supporting the inlet end of said inner tube; said fitting means presenting at least one opening for feeding said fluid into said inner tube, and defining a first reflecting surface at one axial end of said annular chamber; characterized in that it comprises means for closing the opposite end of said inner tube, and defining a second reflecting surface; and in that said inner tube presents at least one intermediate hole at predetermined distances from said first and from said second reflecting surface.
BRIEF DESCRIPTION OF DRAWINGS
A number of preferred, non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, in which:
FIG. 1 shows an axial section of a first conduit in accordance with the teachings of the present invention;
FIG. 2 shows an axial section of a second conduit in accordance with the teachings of the present invention;
FIG. 3 shows an axial section of a third conduit in accordance with the teachings of the present invention;
FIG. 4 shows an axial section of a fourth conduit in accordance with the teachings of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Number 1 in F
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patent: 4611633 (1986-09-01), Buchholz et al.
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patent: 5094271 (1992-03-01), Fritz et al.
patent: 5172729 (1992-12-01), Vantellini
patent: 5201343 (1993-04-01), Zimmermann et al.
patent: 5449866 (1995-09-01), Moss
patent: 5495711 (1996-03-01), Kalkman et al.
Brinson Patrick
Dayco Europe S.p.A
LandOfFree
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