Fluent material handling – with receiver or receiver coacting mea – Diverse fluid containing pressure filling systems involving... – Filling with exhausting the receiver
Reexamination Certificate
1999-06-24
2001-05-01
Maust, Timothy L. (Department: 3751)
Fluent material handling, with receiver or receiver coacting mea
Diverse fluid containing pressure filling systems involving...
Filling with exhausting the receiver
C141S051000, C141S083000, C141S094000, C141S285000, C141S290000, C141S302000, C095S008000, C095S012000, C073S023200
Reexamination Certificate
active
06223789
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to vapor recovery systems for use in fuel dispenser applications, and, more particularly, to apparatus for detecting hydrocarbon emissions discharged during refueling activity and for regulating the intake flow of pumped vapors using an adjustable valve that is controlled in accordance with the sensed hydrocarbon concentration.
2. Description of the Related Art
The dispensing of fuel into the gasoline tank of a motor vehicle during refueling operations causes the displacement of volatilized fuel vapors by the incoming fuel resulting in their forcible discharge from the tank. These effluent vapor emissions must be captured or otherwise collected to prevent their escape into the surrounding environment as a contaminant. Vacuum-assisted stage II vapor recovery systems serve to recover hydrocarbon vapors displaced from vehicle fuel tanks during fuel dispensing operations. The released vapors are collected using a vapor pump that draws vapor emissions along a vapor recovery line leading to a storage facility where recovered vapors are subject to some form of treatment process such as recycling or combustion.
Optimal efficiency of the vapor recovery system results when vapor is collected at a rate that corresponds as closely as possible to the instantaneous rate of effluent vapor discharge, allowing minimal excess air to be retrieved. Conventional vacuum-assist systems employ apparatus that accomplishes such flow rate control by adjusting the operating speed of the vapor pump to create an equalization between the recovered vapor flow rate and the liquid fuel dispensing rate. These systems rely upon transducers and other sensing devices for measuring the relevant flow rates. However, this approach to flow rate equalization based on flow rate measurements and adjustments to the vapor pump operating speed may not provide the required precision needed to accurately evaluate the compositional content of the discharge environment because no direct measurement is obtained of the concentration of hydrocarbon in the effluent vapor stream. The hydrocarbon concentration is the only true measure of the suitability of an effluent vapor stream for collection and recovery.
The challenge encountered by all such vacuum-assisted vapor recovery systems involves therefore the selection of a suitable vapor monitoring device capable of dynamically sensing the presence of hydrocarbon components and generating a signal that accurately measures the detected hydrocarbon. One limitation experienced by conventional detection apparatus involves an inability to sense hydrocarbon in both its vapor and liquid state. This deficiency is pronounced when the refueling operation occurs during temperature and pressure conditions favorable to the condensation of gaseous hydrocarbon. The failure to adequately remove the hydrocarbon condensate from the detection surface of a sensing device leads to false readings and an overall corruption of the sensing measurement data, resulting in an unreliable control mechanism for regulating the vapor pump.
Implementing changes to the vapor recovery rate by adjusting the vapor pump operating speed itself presents certain disadvantages because it requires continuous variations to the cycling frequency of the vapor pump motor. This aperiodic operation may necessitate at times certain wide-ranging fluctuations in the motor frequency that could lead to excessive wear and eventually premature breakdown.
SUMMARY OF THE INVENTION
The invention comprises, in one form thereof, an apparatus for determining the actual content of hydrocarbon in the effluent vapor stream and for regulating the vapor flow of hydrocarbon effluents by controlling an adjustable valve configured at the intake side of the vapor pump in accordance with the measured hydrocarbon content. A hydrocarbon sensor is used to conduct hydrocarbon measurements. The hydrocarbon sensor may be, for example, a fiber-optic sensor, an oxygen sensor an adsorption resistor sensor, or a crystal oscillation sensor. The sensors may be disposed in front of each vapor pump or in a common vapor header, so long as the sensor is upstream of the vapor pump. A solenoid assembly is provided to activate the valve in response to the sensor measurement data. Operating conditions characterized by a low hydrocarbon or high oxygen measurement will cause the solenoid assembly to close the vapor input to the vapor pump, or the vapor output from the vapor pump, prompting the vapor pump to enter into an internal recirculation mode. The vapor flow rate is effectively varied without requiring any change in the pump operating speed.
The invention comprises, in another form thereof, a system for recovering hydrocarbon vapor effluents from a fuel storage container for use with a fuel delivery system, including a vapor transfer means, a sensor means, and a valve means. The vapor transfer means generates a vapor drawing action effective in communicating vapor between an inlet port and an outlet port thereof. The sensor means, which is disposed in effluent-detecting relationship to the fuel storage container and is upstream of the vapor transfer means, provides a measurement indicative of the hydrocarbon content in the hydrocarbon effluents. The valve means, which is disposed in vapor communicating relationship at an inlet port thereof to the fuel storage container and is disposed in vapor communicating relationship at an outlet port thereof to the inlet port of the vapor transfer means, controllably regulates the vapor flow of hydrocarbon effluents to the vapor transfer means in accordance with the hydrocarbon content measurement provided by the sensor means.
The sensor means includes, in one form thereof, a crystal oscillator means disposed for exposure to hydrocarbon effluents from the fuel storage container and operative to generate a resonant frequency signal having an oscillation frequency that is representative of a hydrocarbon content within vapors exposed thereto. The oscillation frequency exhibits a frequency shift relative to a fundamental resonant frequency that is determined by the hydrocarbon content within vapors exposed to the crystal oscillator means. The crystal oscillator means includes, in one form thereof, a resonant crystal structure including at least one portion thereof formed of a material capable of interacting with hydrocarbon and inducing the frequency shift upon occurrence of the hydrocarbon interaction. The vapor recovery system further includes a reference crystal oscillator means for generating a reference frequency signal at the fundamental resonance frequency; a mixing means for generating a beat signal representing the frequency differential between the resonant frequency signal from the crystal oscillator means and the reference frequency signal from the reference crystal oscillator means; and a means for coupling the beat signal to the valve means to effect vapor flow regulation therein.
The valve means includes, in one form thereof, an adjustable valve element and a solenoid assembly for controllably activating the valve element in accordance with the hydrocarbon content measurement provided by the sensor means. There is further provided a solenoid control signal means that is responsive to the resonant frequency signal provided by the crystal oscillator means for generating a solenoid control signal representative of the hydrocarbon content within vapors exposed to the crystal oscillator means. A means is provided for coupling the solenoid control signal to the solenoid assembly to effect control thereof. The vapor transfer means includes, in one form thereof, a vapor pump.
The vapor recovery system preferably includes a thermal applicator means for applying thermal energy to the crystal oscillator means to enable removal of hydrocarbon liquid therefrom.
The sensor means includes, in another form thereof, an oxygen sensor means for sensing an oxygen content within vapors exposed thereto, and an analysis means for determining a hydrocarb
Knuth Randall J.
Maust Timothy L.
Tokheim Corporation
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