INTEGRATED POSITIVE DISPLACEMENT PUMP MOTOR ASSEMBLY FOR FUEL DISPENSING Background of the Invention The present invention relates to an integrated, positive displacement pump-motor assembly. The pump-motor apparatus incorporates a filtering section adjacent the pump intake portion, and a cyclone gas separator adjacent the pump discharge section. Because the components of the apparatus are mounted in an explosion-proof housing, the pump-motor assembly is particularly suitable for use in dispensing liquid hydrocarbon fuels such as gasoline.

The delivery of gasoline or diesel fuel to motor vehicles is normally accomplished by means of fuel dispensers (popularly referred to as"gas pumps") which are connected, via piping, to fuel storage tanks (usually underground in the United States but may be above ground). In operation, activation of a switch on a fuel dispenser activates an electrically-powered pump, causing fuel to move toward the fuel dispenser. Opening a valve in a nozzle at the end of a dispensing hose attached to the fuel dispenser allows fuel to be delivered from the storage tank into a motor vehicle's fuel tank.

Metering apparatus in the fuel dispenser measures the quantity of fuel being delivered.

Two general classes of pump-motor assemblies are used in fuel- dispensing apparatus: 1) Centrifugal pump-motor assemblies are often employed in situations where the pump-motor assembly is submerged beneath the fuel in an underground fuel storage tank. These underground assemblies can supply fuel to a plurality of fuel dispensers and operate by pushing fuel upward into piping connecting the storage tank with the fuel dispensers. (2) Positive-displacement pump-motor assemblies are normally mounted above- ground, most often at the delivery end of piping connecting the fuel storage tank with the fuel dispenser. When mounted within the fuel dispensing cabinet, these pumps can serve one or two fuel-dispensing hoses. The present invention

is directed to pump-motor assemblies of the second (positive-displacement) type.

Because they are in contact with flammable materials, pump-motor assemblies used in fuel-dispensing apparatus must be designed to minimize the possibility of fire and explosion. Additionally, the process of conveying fuel from one location to another can introduce gases (e. g., air) into the fuel. While liquid gasoline is relatively safe, gasoline/air mixtures can be explosive.

Moreover, gasoline is not inexpensive; the presence of entrained air in gasoline results in a customer paying a higher per unit price than is justified. Because of this, international standards have been developed to regulate the amount of air and other entrained gases present in fuel. One internationally-recognized body which has promulgated such standards is the Organisation Internationale De Metrologie Legale (OIML). ODAL Recommendation 117 applies to liquid fuel dispensing apparatus, and specifies that dispensing equipment be capable of delivering a fuel such as gasoline at a level < 0.5% accuracy. For a liquid such as diesel fuel, the required accuracy is < 1.0%.

Heretofore, cyclone chambers and other methods have been used to remove such entrained air with some success. However, the efficiency of these air-removal systems is rate-dependant, and conventional devices are often incapable of meeting the OIML standards at delivery rates which exceed 10 gallons (40 liters) per minute. Because a fuel pump supplying two hoses on a fuel dispensing cabinet may be required to deliver fuel at a rate of 20 gallons (80 liters) per minute, and even higher flows for dispensers having a single nozzle, there is the need for a better air-removal systems.

The fuel dispensing process is generally initiated by a customer or attendant removing the dispensing nozzle from a cradle on the dispensing cabinet and activating a switch which activates a pump and causes fuel to move into the dispenser. After the dispensing nozzle is placed into an automobile's or similar vehicle's fuel intake port, and a valve on the nozzle is opened, fuel will flow into the vehicle or tank. In order to avoid excessive pressure build-up

during the period between pump-activation and nozzle valve opening, fuel pumping systems can be equipped with one or more pressure-regulated bypass valves which allow the fuel to re-circulate until the nozzle valve is opened.

Lastly, fuel-dispensing systems typically contain filters to remove any particulate material from the liquid prior to its being delivered to a vehicle fuel tank.

Summary Of The Invention The present invention describes an integrated, pump-motor apparatus for transporting flammable liquids such as gasoline or diesel fuel. In a preferred embodiment, the apparatus incorporates the following elements into a single, explosion-proof structure: 1) an explosion-proof electrical motor; 2) a positive displacement pump; 3) a vapor (air) and liquid separator; 4) a settling chamber and shut-off valve; 5) a suction line filter; 6) a pressure-regulated bypass valve which opens to allow fuel re-circulation within the assembly while fuel is not being dispensed; 7) a two-way output check valve which keeps the meter and hose filled with liquid and protects against excessive pressure build-up in the customer side of the system as well as too low a pressure; and 8) a means of detecting whether the air content exceeds a pre-set level. These elements are arranged in a single, compact package which can be easily and safely mounted within a fuel dispensing system without the need for extra piping, belts and pulleys, and added wiring.

A main casting or pump-head section of the pump-motor assembly functions both as the end bell of the electric motor section and as the inboard pump head. This pump-head section includes suction (intake) and discharge ports, suction line filtering, cyclone air and liquid separation, an output valve (preferably, two-way), and pressure bypass features.

Because of the explosive nature of the liquid being handled, safety regulations mandate that the pump must stand off of the motor at the shaft entrance a specified distance and that a flame path be provided. The design of

the apparatus of the present invention takes advantage of the space resulting from this distance requirement, utilizing this area for the pump's inlet and discharge ports where suction and discharge piping are connected to the pump.

The pumping elements of the pump-motor assembly can be easily serviced by removing the outboard pump-head cover without disturbing the electric motor, the driving mechanism, or the suction and discharge piping.

Similarly, the filter, pressure-bypass and air-separator sections of the apparatus are equipped with caps and covers which permit servicing of these elements without disassembling the entire pump-motor assembly.

The first element of the pump motor assembly is an explosion-proof motor having a rotatable shaft extending from one end thereof. Explosion- proof motors suitable for this application are available from Franklin Electric Company, Bluffton, Indiana. The motor shaft should be long enough to extend through the pump-head section of the assembly. Alternatively, the motor shaft can be coupled to a separate pump shaft by conventional means. The explosion-proof motor is attached to the pump-head section in a manner which eliminates or minimizes the migration of liquid or vapor into the motor unit (e. g., by using seals or the like between the motor unit and the pump head).

The pump-head section comprises a rotary positive displacement pump.

Such pumps operate by maintaining a time-continuous liquid seal between inlet suction and outlet discharge ports by the action and position of the pumping elements, and by maintaining close running clearances. Liquids enter a pumping chamber through one or more intake or suction ports and leave through one or more discharge ports which are maintained in liquid-tight connection to an external fluid system. One boundary of the pumping chamber is formed by the endplate or pump-head cover.

The pumping action of rotary displacement pumps operates as follows: The rotating and stationary elements of the pump act to define a volume in the pumping chamber, sealed from the pump discharge port and open to the pump intake port, which grows as the pump rotating element rotates. Next, the

pump elements establish a seal between the pump intake and some of this volume, and there is a time (however short) when this volume is not open to either the intake or discharge parts of the pump chamber. Then the seal to the discharge port of the chamber is opened, and the volume open to the discharge port is constricted by the cooperative action of the moving and stationary elements of the pump. Thus, the action of rotary displacement pumps is: 1) closed-to-discharge, open-to-intake; 2) closed-to-discharge, closed-to-intake; and 3) open-to-discharge, closed-to-intake.

Rotary displacement pumps come in several different types, including gear pumps, multiple-rotor screw pumps, circumferential piston pumps, lobe pumps, rigid rotor vane pumps, rotary piston pumps and flexible member pumps. While each of these types could be adapted to the apparatus of the present invention, gear and vane pumps are especially preferred.

Adjustment to the pumping capacity of positive displacement pumps can be made by either changing the speed of rotation of the pump motor, by changing the length of the pumping elements, or by adjusting valving. By using various combinations of different-length gear elements, the capacity of the pump can be varied over a wide range. Because these gear elements are housed in an easily-removable housing, modifying pump capacity by changing the size of the gear elements is relatively simple.

In a preferred embodiment, the gear set comprises inner and outer gear assemblies (a"gerotor set"). The inner gear assembly is concentrically coupled to the motor shaft. It has been found that an inner gear having eight teeth in combination with an outer gear having nine teeth provides an especially effective gear set for use in the present invention.

The gear set is preferably manufactured of sintered metal, the outer gear having a comparatively large outside diameter. The inner gear is manufactured with a smaller than normal inside diameter to fit to the available motor shaft diameter. In a preferred embodiment, the motor shaft extends through the gear set and a shaft seal, into a ball bearing positioned in the pump

head; however, a ball bearing may not be necessary in all cases. The rigidity and precision of ball bearings, in conjunction with the machining accuracy achieved by having the ball bearing assembly and the gear set fit in one component (the pump-head housing), provides an accurate alignment of the gear set, thus increasing performance and longevity.

As noted above, a sealing element is required around the rotating shaft of the motor where it extends into the fluid containing cavity of the pump. In the preferred embodiment, the seal is within the space between the small diameter motor shaft and the large diameter inboard bearing. This shortens the overall length of the pump motor assembly.

In normal operation, the rotating positive displacement pump carries liquid from a liquid source (e. g., a fuel storage tank) which is connected, via piping, to a main pump input port at the base of the pump-motor apparatus.

Liquid entering into the main input port is carried through a fuel filter to an intake passage in the pump head to the pump suction port, and is expelled through the pump discharge port into a liquid discharge passageway which communicates with a cyclone separator (described below) which removes air and other gases from the liquid. Fuel or other liquid exiting the cyclone chamber is directed to the liquid exit or main discharge port at the top of the pump-motor apparatus. The main discharge port is connected, via piping, to metering apparatus, and ultimately to a fuel dispensing hose or the like.

The pump-motor apparatus incorporates features to prevent excessive pressure build-up while the pump is running, but fuel is not being delivered (e. g., the interval between pump activation and the activation of the valve on the fuel-dispensing hose. The pump-head unit contains a liquid bypass passage which interconnects the liquid intake and liquid discharge portions of the pump.

The liquid bypass passage is closed by a normally-closed bypass valve.

However, if excessive pressure begins to build up within the pump-head unit because fuel is not flowing out of the main discharge port, the bypass valve will open and fuel will be transported through the bypass passage, back to the pump

suction port. Recirculation of liquid in this manner will continue until liquid begins to flow out of the main pump discharge port.

As part of the integration of the pump air and liquid separation system, the pump discharge port feeds directly into an air separation inlet of a vertically-disposed first cyclone separator within the pump-motor assembly.

Fuel enters the air separation inlet in such a manner that a high velocity centrifuge is established in the form of a cyclone. This cyclone is of such a velocity that the liquid outward pressure forces all vapors, gases, and air to the center of the cyclone in a vortex. This separation of liquid and gases (air) allows for the liquid to exit the dynamic air separation system through a liquid outlet port of the cyclone separator, and allows the vapors or gases (with a small percentage of liquid) to proceed through a vortex finder located in the center of the first cyclone separator to a vapor outlet or exit port at the top of the vortex finder.

The liquid, which has been purged of gases and vapors proceeds from the liquid outlet port of the first cyclone air separator chamber to the pump outlet port and/or liquid bypass passage. The separated gases and/or vapors proceed from the vortex finder, out of the first cyclone separator, to a static air separator chamber or sump. In a preferred embodiment, this sump is an integral part of the pump-motor assembly which is mounted above the motor, at a higher elevation than the first cyclone separator.

Although most of the entrained gas (air) in the fuel is removed in the first cyclone air separation chamber, some air-containing fuel will pass into the sump. At the sump or static air separator entrance, a second, horizontally- disposed high velocity centrifuge is used for further separation of liquid from air. The centrifuge or second cyclone separator, the inlet of which is located adjacenct to the inlet of the static sump, is adapted to provide a low velocity discharge into the static sump cavity, as well as minimizing potential foaming of the fuel.

The static sump is designed to maximize the length of the travel path of fuel exiting the second cyclone separator in order to allow adequate time for further air and liquid separation. In a preferred embodiment, the static sump contains internal vertical walls or partitions which form a labyrinth between the discharge outlet of the second cyclone separator and a liquid outlet in the bottom of the static sump. This liquid outlet is interconnected, via tubing, interconnected casting or the like, to the inlet side of the pump-motor assembly, allowing air-purged fuel to be recycled.

The separated air is discharged through an orifice or vapor outlet in the top of the static sump. Optimally, the discharged air is not discharged to the atmosphere, but is fed, via tubing, through a venturi which is designed to measure the volume or flow of air exiting the separation compartments. The measurement can be made with a pressure sensor, flow meter, or similar technique. This measured value, typically an electronic signal, is compared with a preset calibration point, a measure of inlet air or vapor, or an accumulated total value which, if exceeded, indicates the unit is experiencing air leakage, or a similar phenomenon which indicates that the system is non- OIML compliant. If this measurement shows that the system is non-compliant, the pump-motor assembly is either shut down or the output flow is adjusted by some means to a level which allows the assembly to operate within OIML limits. This could include reducing the output flow rate, controlling the dispenser valving, or similar techniques obvious to those familiar with this technology.

Brief Description Of The Drawings Further features and advantages of the present invention will be apparent from the following detailed description of a preferred embodiment with reference to the accompanying figures wherein: FIG. 1 is a perspective view of a first embodiment of a pump-motor apparatus in accordance with the present invention;

FIG. 2 is a partially-exploded perspective view of the pump-head portion of the apparatus of FIG. 1; FIG. 3 is a fully-exploded view showing the apparatus of FIG. 2 in greater detail; FIG. 4 is a side elevational view of the pump-motor assembly of FIG. 1; FIG. 5 is a front view of the apparatus of FIG. 1; FIG. 6 is a perspective view, partly in phantom, showing the construction of the cyclone air separator employed in the apparatus of FIG. 1; FIG. 7 is a partial sectional view of the apparatus of FIG. 5, showing the interior of the pump-head casting ; FIG. 8 is a perspective view of a second embodiment of a pump-motor apparatus in accordance with the present invention; FIG. 9 is a partially-exploded perspective view of the of the apparatus of FIG. 8, showing elements of the pump-head and motor, but omitting the tubing that interconnects parts of the pump-motor assembly; FIG. 10 is a side elevational view of the pump-motor assembly of FIG.

8; FIG. 11 is a front view of the apparatus of FIG. 8; FIG. 12 is a sectional view taken along 12-12 of FIG 8 and shows the first cyclone separator integrated into the main casting; FIG. 13 is a partially-exploded perspective view of the apparatus of FIG. 8, showing the pump-head casting and several valves of the pump-motor assembly, but omitting the motor and elements of the pump-head assembly; FIG. 14 is a partially-exploded perspective view of portions of the fuel- inlet section of the apparatus of FIG. 8, showing the fuel filter; FIG. 15 is a sectional view of the valve assembly utilized in the fuel outlet port of the apparatus of FIG 8 ; FIG. 16 is a partially-exploded perspective view of elements of the static sump unit employed in the apparatus of FIG. 8;

FIG. 17 is a partially-exploded perspective view of the float valve assembly shown in FIG. 16; FIG. 18 is a partially-exploded perspective view of the of the interior of the static sump of FIG 16, showing the connection of the second cyclone separator to the static sump inlet; FIG. 19 is a partially-exploded perspective view of elements of the second cyclone separator of FIG. 18; FIG. 20 is a sectional view through the inlet of the second cyclone separator of FIG. 18, but having a different type of bypass valve; FIG. 21 is a rear view of the pump-head section of the apparatus of FIG. 8; FIG. 22 is a sectional view taken through 22-22 of FIG. 8; and FIG. 23 is a front elevational view of the pump-motor apparatus of FIG. 8, showing portions of the pump-head interior in phantom.

Detailed Description Of The Preferred Embodiment Figures 1 through 7 depict one embodiment of an integrated (i. e., unitary or integral) pump-motor assembly or apparatus 5 in accordance with the present invention which includes an explosion-proof motor section 10 joined to a pump-head section 11. Pump-head section 11 functions as an end bell for motor 10, and includes as part of the pump-head structure: i) a main casing or casting 30 having a front face 12 (FIG. 3) for mounting a positive displacement pump 39; ii) a filter region 13; iii) a pressure bypass section 14; and iv) a vertically-extending cyclone separation chamber 15.

Pump-head section 11 has a main pump inlet port 16 and a main pump outlet port 17 for interconnection to tubing or pipes (not shown). When used to dispense fuel, the liquid pathway downstream of outlet port 17 terminates in a fuel delivery hose and dispensing nozzle (not shown). When motor 10 is in operation, fuel is drawn into port 16, passes through filter region 13 into the positive displacement pump region 12. Fuel exiting pump region 12 passes

through a liquid discharge passageway 35 in pump-head section 11 into a bottom inlet 18 of the cyclone separation chamber 15. Fuel exits separation chamber 15 through a top liquid outlet 36 which is connected to a top orifice 37 of pump-head section 11.

If fuel is in the process of being delivered to a vehicle, fuel will flow out of the pump motor assembly 5 through outlet port 17. If fuel is not being delivered (i. e., the fuel nozzle valve is closed), pressure will build up within pump-head section 11, a bypass valve or piston 19 (FIG. 3) in bypass section 14 will open, and fuel will re-circulate within pump-head section 11 through a bypass passage 38 (FIG. 7).

FIG. 2 depicts pump-head section 11 (with motor 10 not connected), and with a pump-head end plate 20 removed from a gear housing 21 to expose a portion of positive displacement pump 39. Mounted within pump gear housing 21 is a two-piece gerotor set 22 comprising an outer gear 23 and an inner gear 24. Outer gear 23 is surrounded by an outer bearing 40. Inner gear 24 is supported by a shaft bushing 25 which extends outwardly from the inner gear. Bushing 25, in turn, surrounds a motor shaft (not shown). Inner gear 24 is shrink-fitted to bushing 24 by heating the gear prior to mounting it on the bushing. Bushing 25 cooperates with a larger-diameter carbon-graphite bearing 26 and a recess portion 27 of end plate 20 to form a motor shaft journal.

Referring now to FIGS. 2,3 and 5, in its fully-assembled position (FIG.

5), end plate 20 is mounted to front face 12 by internally threaded bolts 28 which extend through gear housing 21. An outer o-ring seal 29 assists in providing a fluid-tight structure. When sealed in this manner, plate 20 and gear housing 21 serve as an end housing 41 for positive displacement pump 39.

FIG. 3 shows the elements of pump-head section 11 in considerable detail. As illustrated in the drawing, vapor separation region 15 is a separate structure attached to central pump-head casting 30 by bolts (not shown).

Pump-head casting 30 has front face 12 and fuel filter region 13 integral with

the casting. Front face 12 includes an arcuate suction port 31, an arcuate discharge port 32, and a motor shaft passageway 33. The combination of moveable gears 23,24 (FIG. 2), stationary ports 31,32, and end housing 41 produces a negative pressure at fuel inlet port 16 when the motor 10 is activated.

As depicted in FIG. 3, shaft bushing 25 has a key section 34 which is adapted to mate with a corresponding element on the motor shaft (not shown) to secure the bushing to the shaft.

FIG. 3 also shows details of fuel filter region 13, pressure bypass region 14 and vapor separation region 15. Fuel filter region 13 contains a fuel filter 42 which can be easily removed for cleaning by removing a treaded filter cap 43.

Note that valve 19 in pressure bypass region 14 is biased to a normally closed position by a spring 50, closing liquid bypass passage 38. The area of the face of valve 19 and the size of spring 50 are selected so that valve 19 will open if pressure within apparatus 5 exceeds predetermined limits.

FIGS. 8 through 23 depict a second embodiment of an integrated pump-motor apparatus 105 in accordance with the present invention which includes an explosion-proof motor section 110 having a motor shaft 179 (FIG.

22) and a pump-head section 111. Pump-head section 111 has a rear face 170 (FIGS. 21 & 22) for attachment to motor 110 so that pump head section 111 functions as an end bell for motor 110, and provides a flame path so that explosive vapors in pump-head section 111 are isolated from motor 110.

A stand or base 176 supports pump-motor assembly 105. A hook 177 at the top of assembly 105 allows it to be moved into position within (for example) a fuel dispensing cabinet (not shown).

Pump-head section 111 includes: i) a main casting 130 having a front face 112 (FIG. 9) for mounting a positive displacement pump 139; ii) a fuel filter region 113 extending above a fuel inlet port 116; iii) a pressure bypass section 114 (FIGS. 13 & 22); iv) a vertically-extending first cyclone separation

chamber 115, and v) an upper sump chamber 140. In this embodiment, first cyclone air separator 115 is integral with main casting 130 (FIG 12).

In operation, liquid enters into pump head section 111 through fuel inlet port 116, passes through fuel filter section 113 and positive displacement pump 139 to first cyclone separation chamber 115 where entrained air and other gases are removed, and moves out of pump head section 111 through a pump outlet port 117 at the top of head section 111. Pump outlet port 117 is connected, via pipes and/or hoses (not shown) to a liquid dispensing valve such as that in a gasoline dispensing nozzle. In order to avoid pressure build-up within pump-motor apparatus 105, pressure bypass section 114 of pump-head 111 is equipped with a liquid discharge passageway 135 (FIG. 12) which is blocked by a normally-closed pressure discharge valve 119. Liquid discharge passageway 135 interconnects the pump-intake and pump discharge sections of positive displacement pump 139. When liquid is unable to exit through pump outlet port 117 (e. g., the gasoline dispensing nozzle is closed), pressure discharge valve 119 will open, allowing liquid to recirculate within pump head 111 through passageway 135.

FIG. 9 depicts integrated pump-motor apparatus 105 with components of positive displacement pump 139, motor 110, and upper sump chamber 140 removed. Motor 110 has a cooling fan 171 covered by a fan cowl 172. Lag bolts 173 join motor 110 to pump-head section 111. Upper sump 140 is attached to brackets 174 on motor 110 to anchor sump 140 to the pump-motor apparatus.

Portions of positive displacement pump 139 have been exploded outwardly from main casting front face 112 to show the fixed and movable elements of pump 139. Referring to FIGS. 9,13 & 22, main casting front face 112 includes an arcuate suction port 131, an arcuate discharge port 132, and a motor shaft passageway 133 which surrounds a front end 178 of motor shaft 179. Suction port 131 and discharge port 132 form stationary elements of displacement pump 139, as does a pump gear housing 121 which is mounted to

front face 112 by housing bolts 128. An outer o-ring seal 129 around the periphery of gear housing 121 ensures an air-tight fitting between front face 112 and housing 121.

Mounted within pump gear housing 121 is a two-piece gerotor set 122 comprising an outer gear 123 and an inner gear 124. Inner gear 124 has a notch 126 which fits a raised keyway 125 on motor shaft front end 178, forcing inner gear 124 to rotate with motor shaft 179. Outer gear 123, which has nine interior teeth, is eccentrically mounted around inner gear 124, which has eight exterior teeth. As a consequence, the rotation of inner gear 124 also causes outer gear 123 to rotate.

Pump gear housing 121 also contains an outer, motor shaft bearing assembly 180, a front spring 181 and a back snap ring 182 surrounding motor shaft front end portion 178. A pump head end plate 120 is secured to housing 121 to close the housing assembly. When motor 110 is activated, the combination of moveable gears 123,124, stationary ports 131,132, and stationary gear housing 121 produces a partial vacuum or negative pressure at fuel inlet port 116, drawing liquid into pump-head section 121.

Referring now to FIGS. 12-14 & 23, liquid entering into pump-motor apparatus 105 through fluid inlet port 116 passes through a flapper valve 160 into fuel filter region 113. Region 113 contains a removable fuel filter 161 which is secured to a threaded fuel filter cap 162 by a clip 163. This design allows filter 161 to be properly centered in filter region 113, and allows the filter to be easily removed for cleaning or replacement. Flapper valve 160 is closed when motor 110 is not running, ensuring that liquid remains in pump- motor apparatus 105.

Propelled by rotating gears 123,124 of displacement pump 139, filtered liquid exits fuel filter region 113 and is carried, via a liquid intake passageway 164 (FIGS. 13 & 23) in main casting 130, through suction port 131 and discharge port 132 to a liquid discharge passageway 165 (FIG. 23) in the

opposite side of main casting 130. Liquid discharge passageway 165 is connected to a bottom inlet 166 of first cyclone air separation chamber 115.

Referring now to FIGS. 12 & 13, cyclone air separation chamber 115 is adapted to remove any air or other gases entrained in the liquid. Separation chamber 115 has a lower portion 190, and an upper portion 191. The cross- sectional area of lower portion 190 is smaller than that of upper portion 191.

As a result, fuel or other liquid exiting lower portion 190 is propelled upward, in a spiral, so that air and gases are forced to the center of the rising fluid in chamber 191. Suspended from the top of chamber 115 is a centrally disposed vortex finder 141. Air and air-rich liquid is forced into the vortex finder; and air-free liquid is directed to a top liquid outlet 167 at the top of cyclone air separation chamber 115 where it passes into an upper chamber 168 in casting 130.

The bottom of cyclone air separation chamber 115 is closed by a plug 192. Vortex finder 141 is suspended from a threaded closure cap 193, and a cyclone chamber seal 194 ensures that chamber 115 is air-tight. Vortex finder 141 terminates in a vapor outlet port 142 in the center of closure cap 193.

Referring still to FIGS. 12 & 13, gas-purged liquid entering upper chamber 168 from cyclone separation chamber 167 has two potential avenues to travel: out of pump-head 111 through pump outlet port 117 ; or recirculation through liquid discharge passageway 135 of pump-head pressure bypass section 114. Which avenue will be taken depends on conditions downstream of the pump-motor apparatus.

Pump outlet port 117 is blocked by an outlet check valve 150 which is mounted in a top outlet valve housing 151 that is attached to the top of casting 130 by outlet housing bolts 154. An outlet seal 153 ensures that the fit between casting 130 and housing 151 is liquid and air-tight. An outlet bias spring 152 in housing 151 holds valve 150 in a normally closed position, ensuring that fuel does not flow backward into pump-motor assembly 105 when the fuel dispenser is in the off condition. However, when the pressure

downstream of outlet port 117 drops (e. g., a nozzle in a fuel dispensing hose is opened), outlet check valve 150 will open and the fuel or other flammable liquid will exit pump-motor apparatus 105 through a metering apparatus to a vehicle gas tank or the like.

Referring to FIGS. 12 & 15, outlet check valve 150 contains a safety valve 155 at its center to provide an outlet for liquid if pressure downstream of outlet port 117 exceeds a predetermined level (e. g., dynamic pressure pulses at automatic shut-off, thermal expansion of liquid in pipes and hoses when the fuel dispenser is in direct sunlight, etc.). Safety valve 155 takes the form of a Schroeder valve. With outlet check valve 150 seated (in the closed position), a channel 156 in outlet check valve 150 is also closed by safety valve 155. In the event that the pressure exceeds a predetermined limit, Schroeder valve 155 will open, allowing fuel to pass back into pump-head section 111.

As described above, when liquid is moving out of pump outlet port 117, bypass passageway 135 in pressure bypass section 114 is blocked by normally- closed pressure bypass valve 119. However, if flow through outlet port 117 is blocked, pressure bypass valve 119 will open, allowing liquid to recirculate until flow through outlet port 117 resumes. Details of pressure bypass section 114 are shown in FIGS. 12 & 13. Bypass valve 119 has upper and lower sections 195,196 biased apart by a spring 199. An adjusting screw 197 of upper valve section 195 fits in a channel in a top guide piece 198. A bottom stem 299 of lower valve section 196 fits within a guide channel 200 in casting 130. In the normally-closed position shown in FIG. 12, liquid in upper chamber 168 is blocked from entering liquid bypass passageway 135; however, with motor 110 running, and flow out of port 117 blocked, pressure bypass valve 119 will open.

As described above, air and some liquid is funneled out of first cyclone separation chamber 115, through vortex finder 141, to a vapor outlet port 142 at the top of chamber 115. Referring now to FIGS. 8,11 & 12, a vapor tube

148 at the top of sump chamber 140 connects vapor outlet port 142 to a sump chamber inlet port 143 in the top plate 144 of sump chamber 140.

FIGS 16-20 depict the interior 145 of sump 140 which is a generally rectangular structure having front and back walls 212,213, a pair of sidewalls 214,215, and a sump bottom 216 (FIGS. 8 & 22). Mounted immediately below sump inlet port 143, to a bottom surface 137 of plate 144, is an inlet head 146 of a second cyclone air separator 147. Second cyclone separator 147 is secured to bottom surface 137 by mounting bolts 138, and an inlet gasket 126. Inlet head 146 has a small diameter countersunk hole 136 which communicates directly with sump inlet port 143 and receives the gas and liquid output from first cyclone separator 115. Inlet hole 136 is sized to restrict the flow of the air/liquid mixture carried from first cyclone air separator 115 through vapor tube 148. As a consequence, the air/gas mixture passes through hole 136 at high velocity, into a larger diameter cylindrical chamber 149 within inlet head 146. The tangential orientation between hole 136 and cylindrical chamber 149, combined with the high velocity of the entering air/liquid mixture, sets up a cyclone action in the second cyclone air separator 147, forcing air, gases and vapor bubbles toward the center. This spinning flow continues through second separator center section 201 and tubing elbow 202, beginning the dissipation of any foam in the mixture entering the sump.

Because a large quantity of foam is eliminated during passage of liquid through second cyclone air separator 147, the internal volume of sump interior 145 can be reduced.

Elbow 202 straightens out the spinning flow and allows the mixture to enter sump 140 at a lower velocity. An outlet 203 of second cyclone air separator 147 is directed against a flat surface such as side wall 214 of sump 140 rather than directly into the liquid pool, thus minimizing the generation of new foam as liquid exits second separator 147.

Referring now to FIGS. 8,17 & 17, the interior 145 of sump 140 is equipped with a plurality of interior baffles 204a, 204b, 204c and 204d

extending upwardly from sump bottom 216 which force the liquid moving through sump interior 145 to flow over an extended pathway, facilitating the further removal of any entrained air. Sump 140 has a sump liquid outlet port 159 (FIG. 8) in sump bottom 216. Outlet port 159 is connected to an exterior drainage tube 158 which returns the air-purged liquid to pump-head section 111, above fuel inlet port 116.

Referring now to FIGS. 8,16 & 17, the interior of sump 140 contains a float valve 205 mounted to side wall 215 of sump 140 by a cotter pin 206.

Float valve 205 is connected to a normally-closed needle valve 207 which closes liquid outlet port 159 (FIG. 8) at the base of sump 140 until the level of liquid in sump 140 exceeds a predetermined height, thus ensuring that air from the sump is not carried back into pump-head section 111 through drainage tube 158.

Air and other gases which are removed from the fuel pass out of the pump-motor assembly through a sump vapor exit port 208. Although vapor exit port 208 is shown as being open to the atmosphere, ideally, gases are not discharged into the atmosphere, but pass through a venturi (not shown) which is designed to measure the volume or flow of air exiting the separation compartments through exit port 208 of sump 140. The gas-flow measurement can be made with a pressure sensor, flow meter, or similar technique. This measured value is used to compare against a preset calibration point, a measure of inlet air or vapor, or an accumulated total value which, if exceeded, indicates that the unit or system is experiencing air leakage, liquid and air separation or similar phenomena which may allow the system to be non-OIML compliant. In the event that the measurement falls outside the preset range, pump-motor apparatus 105 is either shut down or the outlet flow is reduced by some means to ensure that the system is operating within OIML limits. This could include reducing the outlet flow controlling the dispenser valving to reduce flow, or similar techniques obvious to those familiar with the technology.

FIG. 22 shows the interior of pump-motor apparatus 105, especially the interconnection of pump-head section 111 to motor 110. Motor shaft 179 extends through a rear bearing assembly 210 into the center of pump-head section 111. Motor shaft front end 178 extends outwardly from motor casting front face 112 into positive displacement pump 129. The distance between rear bearing assembly 210 and front face 112 defines a flame path within apparatus 105, ensuring that any sparks which might be generated within motor 110 do not reach the explosive liquid in pump 129. A weep hole 209 within pump casting 130 extends downwardly from shaft 179, behind a casting front seal 211. Weep hole 209 functions as a drainage port in the event that liquid in pump 129 seeps behind seal 211.

Other features of the invention will be apparent to those of ordinary skill in the art in light of the above description and the detailed drawings.