Measuring and testing – Volume or rate of flow – Using differential pressure
Reexamination Certificate
1999-11-23
2002-01-15
Patel, Harshad (Department: 2855)
Measuring and testing
Volume or rate of flow
Using differential pressure
C073S861570, C340S607000
Reexamination Certificate
active
06338278
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
A flow detector to detect and monitor the flow of fluid through a conduit.
2. Description of the Prior Art U.S. Pat. No. 4,183,029 shows an ink filter clogging sensor and indicator for a ink filter disposed in an ink supply conduit. A first and second electrode are disposed in the conduit upstream and downstream of the filter respectively. A sensor means measures an electrical parameter such as the electrical resistance, capacitance or the like between the electrodes which varies as a function of the degree of clogging of the filter. An indicator such as a light analog meter or the like indicates the magnitude of the electrical parameter and thereby indicate the degree of clogging of the filter.
U.S. Pat. No. 2,826,754 teaches an oil failure indicator apparatus. The outlet of the indicator mechanism is connected to a fluid line leading to a device to which the fluid under pressure is delivered. The fluid from the line enters the inlet port and is admitted to the axial bore in a piston. Since the only outlet is through radial passages so long as these passages are located within the bore, fluid cannot pass through the interior chamber to the outlet port. However, whenever sufficient pressure is built up by the pump, the resistance of the spring will be overcome, and the piston will move until the radial passages enter the interior chamber. Since this chamber is of greater diameter than that of the bore, fluid will then pass outwardly through the passages into the chamber and thence through the outlet port. It will be understood that so long as sufficient pressure exists in the line to overcome the resistance of the spring no current can flow from the battery to the lamp, inasmuch as the contact disk is normally insulated by the washers which are connected to the grounded side of the battery. However, if the pressure in the line should fall below the value necessary to maintain the piston in the position shown, or if for any reason there should be a stoppage in the line, the spring will return the piston until the axial bore engages with the annular portion of the contact which will complete the circuit for lighting the lamp, or actuating any other type of warning device which may be in the circuit.
U.S. Pat. No. 2,772,409 comprises a pressure responsive flow indicator for use between a relief valve and an outlet pipe, including a housing containing a movable plug, fluid inlet and outlet openings in the housing at opposite ends of the plug, means urging the plug resiliently in one directions, means to operate a warning device when the plug is moved in the opposite direction, and a conduit through the plug and/or between the plug and the housing.
U.S. Pat. No. 4,181,835 shows a gas flow indicator including an open-ended cylinder, a piston constrained within the cylinder to move between the ends thereof, and a reed switch positioned on the outside of the cylinder for responding to the position of a magnet secured to the piston. The piston is closed adjacent the output aperture of the cylinder and is open adjacent the input aperture of the cylinder for defining a basin within the piston. A spring is positioned between the piston and the output aperture for forcing the piston away from the output aperture. Gas flowing in through the input aperture forces the piston toward the output aperture. An indication of the state of gas flow through the cylinder is provided in accordance with whether the switch is open or closed.
U.S. Pat. No. 2,826,754 relates to fluid circulating systems responsive to a change of pressure in an oil circulating system for automobiles, diesel engines, oil burners and the like whereby a warning such as a signal lamp, a buzzer or other device will be actuated as a result of a predetermined change in such pressure.
U.S. Pat. No. 4,423,751 describes a “snap action” early warning bypass valve assembly responsive to fluid pressure differentials and/or low pressure that functions as both an electrical switch to provide an indication of low pressure or an impending fluid bypass and as a mechanical valve to actually implement the fluid bypass. The valve assembly includes a sealing piston supported by a retaining surface having a central bore formed therein. The sealing piston contains a bypass aperture and is shaped to present a differential sealing area to fluid circulating within the central bore. A spring-biased bypass disc covers the bypass aperture to present a central sealing area to fluid within the central bore. A first pressure differential acting simultaneously across the central and differential sealing areas forces piston into contact with an electrical terminal pin thus energizing an alarm circuit. A second, greater pressure differential acting across the central sealing area alone pushes the bypass disc away from the bypass aperture to complete the bypass operation. A low pressure sensing means including a low pressure piston biased to a no alarm position by spring and to an alarm position by spring is responsive to fluid pressure in a bypass conduit below a predetermined level to energize the same alarm circuit.
U.S. Pat. No. 4,663,613 shows a tub supplied with hot water through a water circulation system including a pump, a water filter and an electric flow-through heater energized through an electric contactor upon closure thereof. A user of the tub is urged to service the water circulation system upon clogging thereof. For this purpose, water flow fluctuations occurring in the circulation system upon restrictions of the water circulation system are sensed and closure of the contactor is precluded for a time interval of predetermined duration in response to a sensing of water flow fluctuations. That predetermined duration is made sufficiently short for a resumption of the heater energization through reclosure of the contactor if the fluctuations are only transient, but sufficiently long to effect the reduction of water temperature in the tub supplied through the heater by restricting reclosure of the contractor as long as the fluctuations continue, so as to indicate to the user of the tub through the reduced water temperature a need to service the water circulation system.
U.S. Pat. No. 2,803,718 comprises a spring-loaded, pressure-responsive piston operatively connected to a snap-acting electric switch, provides all the desirable characteristics in a light, compact unit capable of easy manufacture. The switch embodies means for limiting the movement of the piston so that a momentary high pressure surge will not damage the mechanism, as frequently occurs in the previous Bourdon or diaphragm type pressure devices. The same movement limiting means enables the switch to respond to a pressure stimulus almost instantaneously, there being no necessity for the piston to travel through a relatively long path to reach its proper operating point.
French 1,449,240 is an additional example of the prior art.
SUMMARY OF THE INVENTION
The present invention relates to a flow detector to detect and monitor the intermittent flow of fluid through a conduit to monitor the progressive life cycle of a filter element or other device operatively coupled to the conduit. The flow detector is operatively coupled to a power source and a flow detection monitor including a logic circuit and a signal device. The logic circuit monitors the progressive number and total duration of intermittent flow events occurring within the conduit over time and compares this data with predetermined values relating to the life cycle performance of the filter element or other structure or device.
The flow detector comprises a first flow detection element comprising a bias such as conductive coil spring operatively engaging a fluid flow control disposed within a housing having an inlet section, a flow detection section and an outlet section. The fluid flow control comprises a piston slidably disposed within a cylinder formed in the flow detection section of the housing. The conductive coil spring is compressed between the piston and a second flow
Fisher III Arthur W.
Patel Harshad
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