Liquid purification or separation – With alarm – indicator – register – recorder – signal or... – Fluid pressure responsive
Patent
1991-07-19
1993-02-23
Dawson, Robert A.
Liquid purification or separation
With alarm, indicator, register, recorder, signal or...
Fluid pressure responsive
73744, 116267, 116272, 116DIG42, 210 94, 267282, G01L 1904
Patent
active
051887282
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a clogging display for a fluids filter and comprising means detecting pressure variations at the ports, i.e. the upstream and downstream sides, of said filter.
It is known that the random impurities stopped by a filter impede proper fluid flow and operation of the devices downstream of said filter, progressively leading to clogging. This clogging entails a pressure differential between its ports and accordingly clogging displays comprise means detecting pressure differentials between upstream and downstream. However such pressure differentials are not caused solely by the clogging impurities, sometimes they are also due to the fluid's grade (viscosity) which often is temperature sensitive.
For a viscous liquid such as a hydrocarbon or an oil, the viscosity increases as the temperature drops, causing a substantial pressure differential across the filter ports, which the clogging display is meant to monitor, even in the absence of impurities. In that instance the display mistakes the viscosity effect for clogging.
Attempts already have been carried out to remedy this drawback, for instance in the disclosures of a number of patents such as U.S. Pat. No. 2,942,572 filed on Jun. 17, 1958 (David B PALL) and the French patent 2,558,255 filed on Jan. 12, 1984 (Facet Enterprises Inc.), namely using either a bimetallic element or a deforming split ring sensitive to the temperature of the fluid. These devices deform perpendicularly to the axis of its sliding elements and are arranged to reduce the cross-section preserved to one of these elements when the temperature is below a given value. In that instance mechanical locking of said sliding element may take place. As a result the clogging display may be inoperative at these lower temperatures.
These devices present difficulties both as regards manufacture and installing them in the display, and they are expensive. Their operation is susceptible to malfunctions.
In order to remedy these drawbacks and to improve such displays, the inventor developed a clogging display for a fluid filter of the species comprising a case with a cavity, i.e. a case, and made of a non-magnetic material, further a piston moving inside a suitable housing unit of said case, a magnet mounted on the piston and a magnet-position detector, where this clogging display is characterized in that it comprises a magnet or a magnet-equipped holder affixed to the piston head and moving in the same axis relative to said piston as a function of opposing forces, and a coiled spring made of a shape-memory alloy (SMA) which is stiff above a specified temperature and compliant below, and means for mounting the SMA spring in such a way that above a specified temperature it shall rigidly join the magnet support to the piston.
Several embodiment modes of the invention are feasible, for instance with or without mechanical flag.
In the instance of a clogging display with a sliding flag, the object of the invention is a clogging display for a fluid filter comprising a substantially cylindrical and non-magnetic case of one or more components equipped with external fasteners, said case comprising boreholes and matching boreholes on the same axis and determining two so-called upper and lower housings each open at an opposite end of the cylinder: together with its fastener inside said housing which is at atmospheric pressure, and at its bottom with the downstream and receives: chamber of its housing, chamber of the so-called lower housing moreover includes a coiled shape-memory alloy (SMA) spring which is rigid at high temperature and compliant at low temperature and with the same straight axis as the piston and which at low temperature can be compressed by a trivial force, said SMA spring being mounted in such a way as to rigidly join, or not, the magnet to the piston depending on the temperature being high, or not. The SMA spring is located between a stop solidly joined to the magnet and a stop solidly joined to the piston. When hot and because of its stiffness, the SMA spring rigidly connects t
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Pottier Philippe
Tertre Dominique
Traonvoez Jean-Michel
Dawson Robert A.
Drodge Joseph
Le Bozec et Gautier
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