Piston pump for liquefied gas

Abstract

A fuel supply system for a vehicle uses a multi-piston LPG injunction pump which pumps fluid from a storage tank to an engine. The multi-piston pump uses the vehicle's pneumatic air system, wherein the pressurized air of this system alternatingly drives at least two pistons of the piston pump. Each piston moves through a pumping stroke and a return stroke wherein one piston moves through a pumping stroke, while the opposite piston moves through a return stroke. The pump includes barrier fluid chambers surrounding each of the pistons wherein during a pumping stroke of one piston, a first barrier fluid chamber associated with the one piston decreases in volume as the piston displaces through its pumping stroke. This reduction in volume of the barrier chamber drives the barrier fluid out of the first barrier fluid chamber into a second barrier fluid chamber associated with the second piston. By driving the barrier fluid into this second chamber, this pressurizes the second chamber and effects the displacing movement of the second piston through its return stroke as the barrier fluid chamber increases in volume through the movement of the second piston.

What is claimed: 
     
         1 . A multi-piston pump for pumping an engine fluid in a vehicle comprising:
 a pump housing defining at least first and second piston bores which are separated from each other, each of said piston bores comprising a housing shoulder which faces axially, said piston bores having opposite ends wherein said housing has a drive fluid connector opening into each of said piston bores at said first end, an inlet port opening into each of said piston bores for supplying the engine fluid to said second end, and an outlet port opening into each of said piston bores for discharging said engine fluid from said second end to an engine of the vehicle;   at least first and second pistons slidably received within said first and second piston bores respectively so as to each reciprocate axially in opposite axial directions along a pumping stroke and an opposite return stroke, each of said first and second pistons having a piston shoulder facing axially, said piston shoulders and said bore shoulders facing toward each other in opposing relation and being spaced apart to define first and second barrier fluid chambers between said first and second pistons and said first and second piston bores wherein a volume of each of said first and second barrier fluid chambers decreases and increases respectively during movement of said piston through said pumping stroke and said return stroke, said first and second barrier fluid chambers being fluidly connected together wherein said first and second barrier fluid chambers contain a barrier fluid such that decreasing the volume of one said first and second barrier fluid chambers displaces said barrier fluid into and increases the volume of the other of said first and second barrier fluid chambers to fluidly displace the piston within said other of said first and second barrier fluid chambers through the return stroke thereof;   a control system for alternatingly pressurizing said first and second piston bores with a drive fluid at said first ends through said drive fluid connectors to alternatingly drive one or the other of said first and second pistons through the respective pumping stroke thereof while the other of said first and second pistons is driven simultaneously through the return stroke thereof by the displacement of said barrier fluid between said first and second barrier fluid chambers, said control system successively pressurizing one of said first and second piston bores and then the other to reciprocate said first and second pistons through their respective pumping and return strokes.   
     
     
         2 . The pump according to  claim 1 , wherein said outlet port in one said piston bore opens during the pumping stroke of the piston therein for pumping of the engine fluid out of said pump while said inlet port in the other said piston bore opens during the simultaneous return stroke of the piston therein to recharge said other piston bore with said engine fluid. 
     
     
         3 . The pump according to  claim 1 , wherein each of said piston bores is defined by a stepped interior bore surface which comprises a first bore section having a major bore width, and a second bore section having a minor bore width smaller than said major bore width. 
     
     
         4 . The pump according to  claim 3 , wherein said bore shoulder is located axially between said first and second bore sections and extends widthwise from said first bore section to said second bore section. 
     
     
         5 . The pump according to  claim 3 , wherein each of said piston bores is defined by first and second piston sections which have respective major and minor piston widths proximate to said first and second widths of said piston bores. 
     
     
         6 . The pump according to  claim 5 , wherein said piston shoulder is located axially between said first and second piston sections and extends widthwise from said first piston section to said second piston section. 
     
     
         7 . The pump according to  claim 1 , wherein said barrier fluid is an incompressible liquid. 
     
     
         8 . The pump according to  claim 1 , wherein said control system comprises a control valve connected to said drive fluid connectors of said first and second piston bores and being operable between first and second operative conditions, said control valve in said first operative condition pressurizing said first piston bore and depressurizing said second piston bore to respectively move said first and second pistons through their respective pumping and return strokes, and then being switched to said second operative condition and depressurizing said first piston bore and pressurizing said second piston bore to respectively move said first and second pistons through their respective return and pumping strokes. 
     
     
         9 . The pump according to  claim 8 , wherein said second ends of said piston bores include respective proximity sensors for detecting the approach of each of said pistons during said pumping stroke thereof and switching said control valve between said first and second operative conditions. 
     
     
         10 . The pump according to  claim 8 , wherein each of said piston bore includes a drive fluid discharge passageway which defines a restricted flow of drive fluid being discharged from said piston bore during said return stroke, said discharge passageway restricting said restricted flow of said drive flow to control a rate of movement of said piston through said return stroke. 
     
     
         11 . The pump according to  claim 1 , wherein said barrier fluid separates said drive fluid from said engine fluid to define a barrier against leakage of said engine fluid into said drive fluid. 
     
     
         12 . A multi-piston pump for pumping an engine fluid in a vehicle comprising:
 a pump housing having an outer wall defining at least first and second piston bores which are separated internally from each other by a housing wall, each of said piston bores comprising a stepped interior bore surface defined by a first bore section having a major bore width, a second bore section having a minor bore width smaller than said major bore width, and a housing shoulder which is located axially between said first and second bore sections and extends widthwise from said first bore section to said second bore section so as to face axially, said piston bores having opposite ends wherein said housing has a drive fluid connector opening into each of said piston bores at said first end, an inlet port opening into each of said piston bores at said second end for receiving an engine fluid, and an outlet port opening into each of said piston bores at said second end for discharging said engine fluid to an engine of the vehicle;   at least first and second pistons slidably received within said first and second piston bores respectively so as to each reciprocate axially in opposite axial directions along a pumping stroke and an opposite return stroke, each of said first and second pistons having first and second piston sections which have respective major and minor piston widths proximate to said first and second widths of said piston bores and have a piston shoulder, said piston shoulder being located axially between said first and second piston sections and extending widthwise from said first piston section to said second piston section so as to face axially, said piston shoulders and said bore shoulders facing toward each other in opposing relation and being axially spaced apart to define first and second barrier fluid chambers between said first and second pistons and said first and second piston bores, said first and second barrier fluid chambers being fluidly connected together by at least one balancing passage extending through said housing wall wherein said first and second barrier fluid chambers contain a barrier fluid such that decreasing a volume of one said first and second barrier fluid chambers displaces said barrier fluid into and increases a volume of the other of said first and second barrier fluid chambers,   a control system for alternatingly pressurizing said first and second piston bores through said drive fluid connectors with a drive fluid, wherein one of said first and second pistons is alternatingly driven through the respective pumping stroke thereof by said control system while the other of said first and second pistons is driven simultaneously through the return stroke thereof by the displacement of said barrier fluid between said first and second barrier fluid chambers, said control system successively pressurizing one of said first and second piston bores and then the other to reciprocate said first and second piston through their pumping and return strokes;   said outlet port in one said piston bore opening during the pumping stroke of the piston therein for pumping of the engine fluid out of said pump and said inlet port in the other said piston bore opening during the simultaneous return stroke of the piston therein to recharge said other piston bore with said engine fluid.   
     
     
         13 . The pump according to  claim 12 , wherein said barrier fluid is an incompressible liquid. 
     
     
         14 . The pump according to  claim 13 , wherein said barrier fluid effects displacement of each of the first and second pistons through the respective return stroke thereof. 
     
     
         15 . The pump according to  claim 12 , wherein said control system includes an overpressure detector for detecting excessive pressure of said barrier fluid indicating leakage of said engine fluid or said drive fluid into said barrier fluid chambers. 
     
     
         16 . The pump according to  claim 12 , wherein said control system comprises a four-way valve connected to said drive fluid connectors of said first and second piston bores for pressurizing said first piston bore and depressurizing said second piston bore in a first operative condition to respectively move said first and second pistons through their respective pumping and return strokes, and then depressurizing said first piston bore and pressurizing said second piston bore in a second operative condition to respectively move said first and second pistons through their respective return and pumping strokes. 
     
     
         17 . The pump according to  claim 16 , wherein said second ends of said piston bores include respective proximity sensors for detecting the approach of each of said pistons during said pumping stroke thereof and switching said four-way valve between said first and second operative conditions. 
     
     
         18 . The pump according to  claim 12 , wherein said drive fluid is pressurized air supplied by a vehicle air supply system. 
     
     
         19 . A multi-piston pump for pumping an engine fluid in a vehicle comprising:
 a pump housing defining at least first and second piston bores which are separated from each other, each of said piston bores comprising a housing shoulder which faces axially, said piston bores having opposite first and second ends wherein said housing has an inlet port opening into each of said piston bores for supplying the engine fluid to said second end, and an outlet port opening into each of said piston bores for discharging said engine fluid from said second end to an engine of the vehicle;   at least first and second pistons slidably received within said first and second piston bores respectively so as to each reciprocate axially in opposite axial directions along a pumping stroke and an opposite return stroke, each of said first and second pistons having a inner pumping side and an outer side disposed within said second and first ends of said first and second piston bores, and having a piston shoulder axially between said inner pumping side and said outer side wherein said piston shoulder faces axially, said piston shoulders and said bore shoulders facing toward each other in opposing relation and being spaced apart to define first and second barrier fluid chambers between said first and second pistons and said first and second piston bores wherein a volume of each of said first and second barrier fluid chambers decreases and increases respectively during movement of said piston through said pumping stroke and said return stroke, said barrier fluid chambers axially separating said inner pumping side from said outer side of said first and second pistons, said first and second barrier fluid chambers being fluidly connected together by a balancing passage extending through said housing wherein said first and second barrier fluid chambers contain a barrier fluid such that decreasing a volume of one said first and second barrier fluid chambers displaces said barrier fluid into and increases a volume of the other of said first and second barrier fluid chambers;   said first and second pistons including respective axially spaced seals on opposite sides of said barrier fluid chambers which sealingly separate said barrier fluid chambers from said inner pumping side of said pistons and said outer side thereof, said seals sealing against leakage of said engine fluid being pumped into said barrier fluid chambers; and   a control system having a drive system to alternatingly drive one or the other of said first and second pistons through the respective pumping stroke thereof while the other of said first and second pistons is driven simultaneously through the return stroke thereof.   
     
     
         20 . The pump according to  claim 19 , wherein said barrier fluid is an incompressible liquid. 
     
     
         21 . The pump according to  claim 20 , wherein said barrier fluid lubricates said seals. 
     
     
         22 . The pump according to  claim 19 , wherein said control system includes an overpressure detector for detecting excessive pressure of said barrier fluid indicating leakage of said engine fluid into said barrier fluid chambers. 
     
     
         23 . The pump according to  claim 19 , wherein said control system includes a contaminant sensor in communication with said barrier fluid to detect leakage of said engine fluid into said barrier fluid chambers. 
     
     
         24 . The pump according to  claim 19 , wherein said pump includes a drive fluid connector opening into each of said piston bores at said first end, and said control system pressurizes said first and second piston bores with a drive fluid which drives one of said pistons through said pumping stroke thereof, while said barrier fluid fluidly displaces the piston within said other of said piston bores through said return stroke. 
     
     
         25 . The pump according to  claim 24 , wherein said drive fluid comprises pressurized air supplied by a vehicle air supply system, and said control system successively pressurizes one of said first and second piston bores and then the other to reciprocate said first and second pistons through their pumping and return strokes, said control system comprising a control valve connected to said first and second piston bores for pressurizing said first piston bore and depressurizing said second piston bore in a first operative condition to respectively move said first and second pistons through their respective pumping and return strokes, and then depressurizing said first piston bore and pressurizing said second piston bore in a second operative condition to respectively move said first and second pistons through their respective return and pumping strokes 
     
     
         26 . The pump according to  claim 25 , wherein said seals seal against leakage of any leaked engine fluid within said barrier fluid out of said barrier fluid chambers to said outer sides of said pistons. 
     
     
         27 . The pump according to  claim 26 , wherein said control system includes a contaminant sensor in communication with said drive fluid to detect leakage of said engine fluid into said drive fluid. 
     
     
         28 . A piston pump for pumping an engine fluid in a vehicle comprising:
 a pump housing defining at least one piston bore comprising a housing shoulder which faces axially, said piston bore having opposite first and second ends wherein said housing has an inlet port opening into each said piston bore for supplying the engine fluid to said second end, and an outlet port opening into each said piston bore for discharging said engine fluid from said second end to an engine of the vehicle;   a piston slidably received within each said piston bore so as to reciprocate axially in opposite axial directions along a pumping stroke and an opposite return stroke, said piston having an inner pumping side and an outer side disposed within said second and first ends of said piston bore, and having a piston shoulder axially between said inner pumping side and said outer side wherein said piston shoulder faces axially, said piston shoulder and said bore shoulder of each said piston facing toward each other in opposing relation and being spaced apart to define a respective barrier fluid chamber between each said piston and said respective piston bore wherein a volume of said barrier fluid chamber decreases and increases respectively during movement of said piston through said pumping stroke and said return stroke, said barrier fluid chamber including a barrier fluid disparate from said engine fluid and axially separating said inner pumping side from said outer side of said piston, said pump including a barrier fluid passage for accommodating displacement of said barrier fluid into and out of said barrier fluid chamber;   each said piston including respective axially spaced seals on opposite sides of said barrier fluid chamber which sealingly separates said barrier fluid chamber from said inner pumping side of said piston and said outer side thereof, said seals sealing said engine fluid being pumped against leakage into said barrier fluid chamber; and   a control system having a drive system to alternatingly drive one or the other of said first and second pistons through the respective pumping stroke thereof while the other of said first and second pistons is driven simultaneously through the return stroke thereof.   
     
     
         29 . The pump according to  claim 28 , wherein a plurality of said pistons and said piston bores are provided which define respective barrier fluid chambers fluidly connected together by a balancing passage extending through said housing wherein decreasing a volume of one said barrier fluid chambers displaces said barrier fluid into and increases a volume of the other of said barrier fluid chambers 
     
     
         30 . The pump according to  claim 29 , wherein said barrier fluid lubricates said seals. 
     
     
         31 . The pump according to  claim 28 , wherein said control system includes an overpressure detector for detecting excessive pressure of said barrier fluid indicating leakage of said engine fluid into said barrier fluid chamber. 
     
     
         32 . The pump according to  claim 28 , wherein said control system includes a contaminant sensor in communication with said barrier fluid to detect leakage of said engine fluid into said barrier fluid chambers. 
     
     
         33 . The pump according to  claim 29 , wherein said seals seal against leakage of any leaked engine fluid within said barrier fluid out of said barrier fluid chambers to said outer sides of said pistons.