Abstract: A rotating type machine including a first moving member having a first surface and a second member having a second surface slidably interfacing with the first surface. The first and second surfaces have relative movement therebetween, and one of the first and second members is supported by the other member through the interface of their respective first and second surfaces. At least one of the first and second surfaces is provided with at least one recess therein. A liquid lubricant is provided between the first and second surfaces, and the lubricant is received in the recess. Relative to the surface in which the recess is provided, the recess has a maximum depth which ranges between about 0.00125 and 0.0060 inches, and a surface area which ranges between about 1.767×10−4 and 1.

Abstract: A well production apparatus includes a down-hole gear pump and a transport assembly to which the gear pump is attached. The transport assembly is formed from a string of modular pipe assemblies having one or more passages for carrying production fluid from the bottom of the well to the surface. The passages can be arranged in a side-by-side configuration, and include pressure and return lines for driving the gear pump. The gear pump includes a hydraulically driven motor that is ganged with a positive displacement gear set. Both the motor and the pumping section have ceramic wear surfaces, the ceramic being chosen to have coefficients of thermal expansion corresponding to the coefficients of thermal expansion of the gear sets. The pumps and rotors have ceramic bushings rather than ball or journal bearings, and are operable under abrasive conditions.

Abstract: An air compressor assembly of the rotary screw type. The air compressor assembly comprises a housing having an inlet end and a discharge end. An internal working chamber extends within the housing and terminates in a discharge end face at the discharge end of the housing. At least one rotor is mounted for rotation and axial movement within the working chamber. The rotor has a discharge end surface having a step defined thereon. A thrust piston extends from the rotor and is positioned within a thrust piston chamber. A pressure source is associated with the thrust piston chamber and is controllable between a high pressure condition and a reduced pressure condition to control the position of the rotor relative to the discharge end face. A method of mounting a rotor with a desired end clearance is also provided.

Abstract: An improved control over the pressure vented or tapped to a back pressure chamber in a scroll compressor is achieved by maintaining a vent hole closed for the majority of the operational cycle of the scroll compressor. The hole is preferably selectively exposed to a discharge pressure for a small portion of the cycle, and to an intermediate pressure for a second small portion of the cycle. Other than those two small portions, the hole is preferably closed. The invention reduces pulsation in the back pressure chamber and also reduces pumping losses caused by fluid moving into and out of the back pressure chamber through the hole. In one embodiment, grooves are formed in the fixed scroll member to communicate a selected intermediate pressure and a discharge pressure to locations on the base plate of the fixed scroll member. A vent hole in the wrap of the orbiting scroll member cyclically moves over the two grooves.

Abstract: The present invention is directed to an apparatus and method for determining vane wear in rotary vane pumps that operate using slideable vanes. A view port is formed in an end of the pump housing. The view port is dimensioned such that a width of the port represents a predetermined amount of vane length loss. The view port is positioned in relation to the slots such that an end of the vane not in engagement with the wall of the pump will appear in the port only after a predetermined amount of vane loss occurs, and relative to the slots and the vanes to allow a determination of vane length for each vane when the vane is in engagement with the wall.

Abstract: A trochoidal design rotary piston engine design has a rotary piston housing with a double curve inner contour and triangular type rotary pistons. Sliding bearings distribute lubricating oil from a pressure cycle into a high pressure circuit and a low pressure bypass circuit branches to the side parts and axial cooling channels of the rotary piston housing to supply the cooling oil.

Abstract: The location of center of mass of an orbiting scroll is optimized by adding or removing mass at certain strategic locations on the orbiting scroll member. The center of mass is optimized to reduce alternating torsional moment acting on Oldham coupling. Reduction in alternating torsional moment minimizes unwanted radiated sound caused by Oldham coupling chatter.

Abstract: A screw compressor having an unloader valve with a movable valve member, the unloader valve being capable of indicating when the valve member is installed incorrectly. The valve member is manufactured such that if it is installed incorrectly it provides a leakage path sufficiently large to be detected during full load testing of the compressor. When the screw compressor fails the load test, the compressor is partially disassembled, and the valve is reinstalled in the proper orientation and the compressor is re-tested. The valve member leakage path is provided while maintaining low costs for production and assembly of the compressor.

Abstract: A multiple-module, oil-flooded, rotary screw compressor wherein a plurality of compressor modules are driven by a single drive shaft. The modules are positioned in parallel so that a large volume of compressed air can be provided for use in equipment which continuously requires a large supply of such air. The compressor is configured so that each rotary screw compressor module includes a driven gear engaged with the same gear on the drive shaft. The compressor modules may share a common inlet cavity and a common outlet cavity.

Abstract: The present invention provides an adjustable rotor and/or stator, so that the interference fit and/or clearance can be adjusted. The rotor and/or stator are tapered to provide a difference in fit between the rotor and stator by longitudinal adjustment of their relative position. The relative longitudinal adjustment is achieved in response to a change in temperature and is matched to the taper angle of the stator/rotor to maintain a desired interference fit.

Abstract: An oil storage area (45a) is defined on the bottom of a motor chamber (45) of a scroll compressor (1). An oil transfer route (4a) is defined in the portion of a center housing (4) that corresponds to the storage area (45a). Lubricating oil L is separated from the discharged, compressed refrigerant by an oil separator (80) and the lubricating oil L is supplied to the rear side of a movable scroll (20) due to a pressure differential within the compressor (1). After lubricating slide contact portions of scroll walls (28, 30) of the fixed and movable scrolls (2, 20), the lubricating oil L is temporarily stored in the storage area (45a) and then is transferred due to a refrigerant pressure differential to the suction-side of a compression mechanism (21) via the oil transfer route (4a). The lubricating oil L is then transferred to the oil separator (80) together with the compressed refrigerant that is discharged from a compression chamber (32) of the compression mechanism (21).

Abstract: An oil storage area (45a) is defined on the bottom of a motor chamber (45) of a scroll compressor (1). An oil transfer route (4a) is defined in the portion of a center housing (4) that corresponds to the storage area (45a). Lubricating oil L is separated from the discharged, compressed refrigerant by an oil separator (80) and the lubricating oil L is supplied to the backside of a movable scroll (20) due to a pressure differential within the compress (1). After lubricating a bearing (10), the lubricating oil L is temporarily stored in the storage area (45a) and then is transferred due to a pressure differential to the suction-side of a compression mechanism (21) via the oil transfer route (4a). The lubricating oil L is then transferred to the oil separator (80) together with the compressed refrigerant that is discharged from a compression chamber (32) of the compression mechanism (21).

Abstract: A scroll-type compressor having a stationary scroll and a movable scroll is provided. A compression chamber is defined between a stationary scroll and a movable scroll. A refrigerant introducing passage formed in the movable scroll for introducing a refrigerant from the compression chamber to a driving mechanism. The compressed refrigerant including a lubricant introduced through the passage is affective to lubricate the driving mechanism. The compressor may also include a sump to collect the lubricant leaving the driving mechanism. Collected lubricant is reintroduced into the compression region via a suction region of the compressor.

Abstract: The present invention is directed to an apparatus and method for determining vane wear in rotary vane pumps that operate using slideable vanes. A view port is formed in an end of the pump housing. The view port is dimensioned such that a width of the port represents a predetermined amount of vane length loss. The view port is positioned in relation to the slots such that an end of the vane not in engagement with the wall of the pump will appear in the port only after a predetermined amount of vane loss occurs, and relative to the slots and the vanes to allow a determination of vane length for each vane when the vane is in engagement with the wall.

Abstract: A scroll compressor has a fixed scroll member, a movable scroll member, a housing. The housing is secured to the fixed scroll member. The housing accommodates the movable scroll member to define a back pressure chamber. Pressure in the back pressure chamber is applied to the back surface of a movable scroll base plate of the movable scroll member. The back pressure chamber communicates with a region through a communication passage. The region is lower in pressure than the back pressure chamber. The communication passage relieves the pressure in the back pressure chamber to the region. The communication passage includes a valve. The valve varies an opening amount of the communication passage due to difference between the pressure in the compression region in the predetermined period of a compression process of the gas, and the pressure in the back pressure chamber.

Abstract: The invention relates to a method for compressing a compressible medium, in which at least two displacement elements, each having at least one limiting face extending helically in the cross section, are orbited in relation to each other under formation of at least one chamber, the volume of the chamber being changed by the orbiting movement, performing a cycle with a suction phase, a compression phase and a discharge phase, the chamber being opened and forming a suction chamber during the suction phase.

Abstract: The present invention is directed to an apparatus and method for determining vane wear in rotary vane pumps that operate using slideable vanes. A view port is formed in an end of the pump housing. The view port is dimensioned such that a width of the port represents a predetermined amount of vane length loss. The view port is positioned in relation to the slots such that an end of the vane not in engagement with the wall of the pump will appear in the port only after a predetermined amount of vane loss occurs, and relative to the slots and the vanes to allow a determination of vane length for each vane when the vane is in engagement with the wall.

Abstract: Two slide valves are located in the discharge end bearing case of a multi-rotor screw machine and independently coact with the sun rotor of the multi-rotor screw machine for controlling capacity and Vi. Movement of the slide valves is in a plane perpendicular to the axis of the sun rotor.

Abstract: Scroll compressors are taught that include an outer peripheral portion (23) of a movable scroll member (20) disposed opposite of an end face (13) of a stationary scroll member (10). At least one end portion (20, 23) has a shape that prevents contact when the movable scroll member (20) bends or deforms under high pressure. The contact avoiding shape or structure may be, for example, a tapered portion, a recessed portion or a step shaped portion.

Abstract: A scroll type compressor includes a fixed scroll member, a movable scroll member, an inlet, a discharge port, a discharge valve, a first pressure region and a second pressure region. The inlet is formed through the fixed scroll base plate. The discharge port is formed through the movable scroll member. The discharge valve opens and closes the discharge port. The first pressure region and the second pressure region defined at opposite sides of the movable scroll member apply pressure to the movable scroll member. Gas introduced through the inlet is compressed and highly pressurized in accordance with the movable scroll member orbiting with respect to the fixed scroll member. The highly pressurized gas is discharged from a compression region via the discharge port and the discharge valve. The compressor is provided with a communication passage so as to intercommunicate the first pressure region and the second pressure region during a predetermined period of a compression cycle established by the gas.

Abstract: The present invention provides an adjustable rotor and/or stator, so that the interference fit and/or clearance can be adjusted. The rotor and/or stator are tapered to provide a difference in fit between the rotor and stator by longitudinal adjustment of their relative position. In one embodiment, the adjustment may occur while the PCP in mounted downhole in a wellbore. In another embodiment, the adjustment may occur automatically depending on sensor input of operating conditions of the PCP.

Abstract: A rotating type machine including a first moving member having a first surface and a second member having a second surface slidably interfacing with the first surface. The first and second surfaces have relative movement therebetween, and one of the first and second members is supported by the other member through the interface of their respective first and second surfaces. At least one of the first and second surfaces is provided with at least one recess therein. A liquid lubricant is provided between the first and second surfaces, and the lubricant is received in the recess. Relative to the surface in which the recess is provided, the recess has a maximum depth which ranges between about 0.00125 and 0.0060 inches, and a surface area which ranges between about 1.767×10−4 and 1.

Abstract: A variable pump or motor is providing including a housing with inlet and outlet ports and a vaned rotor. Spool ends are provided at either end of the rotor thereby enhancing the effective sealing of the pump and its overall efficiency. Piston actuators are also described. A sealing means is provided in conjunction with the use of a flexible belt wherein volumetric efficiency is substantially improved.

Abstract: A positive displacement fluid pump capable of an output flow rate can be varied from a maximum to zero at a given pump rotation speed. The pump is a variable-fluid-displacement-volume, gear pump having complement elements associated with pumping gears to provide end seals for a variable-length pumping chamber. A timing arrangement maintains both pumping gears always in synchronization, whether engaged or fully disengaged (zero pump output). And a follower provides effective sealing with a movable face of an axially-translating pumping gear.

Abstract: A gear pump for delivering liquid media has a pump housing with at least two bores, in which at least two meshing gears with tooth tips are contained. The gears are radially mounted by bearing surfaces which on one side consist of areas of the tooth tips and on the other side, of areas of the interior of the bores. This arrangement requires no slide bearings in the conventional sense, which results in a smaller number of pump parts and hence to reduced manufacturing costs.

Abstract: A method stabilizes the temperature in a gear pump lubricated with material to be delivered. At least one housing part has at least two slide bearings in which shafts are mounted and are lubricated by medium to be delivered. A medium is adjusted in a temperature stabilizer to a predetermined temperature and then flows firstly through the housing part and secondly through shafts and/or slide bearings to stabilize the temperature.

Abstract: An improved housing for scroll compressor has the end cap housing formed integrally with the fixed scroll member. The end cap housing is preferably welded to a tubular housing enclosing the scroll compressor. Most preferably, the end housing has inner and outer tubular portions and the tubular housing extends upwardly into a channel between the inner and outer tubular portions. A muffler is preferably formed integrally with the end cap and extends to a side of the end cap. The present invention further includes heat transfer fins extending from the end cap. The positioning of the muffler to the side decreases the overall length of the compressor. The use of the fins increases the efficiency of compression as heat is removed from the compression chambers. The use of the unique combined end cap and fixed scroll which is welded to the tubular housing simplifies assembly.

Abstract: The required larger than normal pressure drop between the infeed and pump inlets of a positive displacement gear or lobe type pump pumping a high viscosity fluid such as pastry dough is obtained by the introduction of a vacuum inside the pump at or near the rotary nip points of the gear or lobe type pump to provide a means for the removal of any gas present in the vicinity of the nip point.

Abstract: Scroll compressors are taught that include an outer peripheral portion (23) of a movable scroll member (20) disposed opposite of an end face (13) of a stationary scroll member (10). At least one end portion (20, 23) has a shape that prevents contact when the movable scroll member (20) bends or deforms under high pressure. The contact avoiding shape or structure may be, for example, a tapered portion, a recessed portion or a step shaped portion.

Abstract: A reversible double-throw air motor utilizes a moveable cylinder casing to switch between forward and reverse operation. The cylinder casing rotates between its forward and reverse positions in response to movement of an externally accessible actuator, via a front bearing plate rotationally coupled to the cylinder casing. The actuator may be biased to the proper position by reaction forces generated within the motor. In some embodiments, the coupling of the front bearing plate to the cylinder casing allows for the cylinder casing to float, thereby enabling the cylinder casing to self-center about the rotor. In other optional embodiments, the front bearing plate is pressed against the cylinder casing during operation by air pressure. The resulting double-throw air motor is easy to use motor and may be economically produced.

Abstract: A rotary fluid machine, such as a pump or motor, is provided with a fluid flow control mechanism that allows the flow of fluid to be easily and precisely controlled. The device has a housing with a spherical interior in which primary and secondary vanes rotate, with the secondary vane reciprocating between open and closed positions. The primary and secondary vanes define fluid chambers within the housing that communicate with inlet and outlet ports of the device. An adjustable fixed shaft, about which the secondary vane rotates, allows the degree of communication to be varied between the inlet and outlet ports and the chambers formed by the primary and secondary vanes. In this way, the flow rate or fluid capacity of the device, and even the direction of fluid flow, can be changed.

Abstract: A scroll compressor having improved efficiencies includes a fixed plate having a spiral involute and an orbiting plate having a spiral involute wrap. The fixed and orbiting plates are positioned in a housing such that the spiral involute wraps mesh with each other to define chambers. A sealant being applied to tips and sides of said involute wraps, said sealant substantially closing any gaps between the tip of the involute wrap and the plat opposing the involute wrap. The sealant is chosen from the group consisting essentially of a grease, a dampening gel, and an epoxy. If a grease is used, then the grease is preferably a low vapor pressure grease. During assembly of the scroll compressor, the sealant is applied to tips and sides of the involute wraps. After the scroll compressor has been assembled, it is run to purge excess sealant, leaving sealant only in the gaps between the two scrolls.

Abstract: A scroll compressor which can be easily sealed and assembled is presented. Also a scroll compressor which can be sealed easily and at low cost is presented. It includes a cylindrical front casing with a bottom, a rear cover to be fitted to the inner circumference of the front casing, a fixed scroll having an end plate to be fitted to the inner circumference, a fitting portion to be fitted concentrically to the rear cover, and a spiral blade disposed at the opposite side of the fitting portion, a movable scroll engaged with the fixed scroll and swiveling at a specified radius of swivel, and a rotation preventive mechanism for preventing rotation of the movable scroll and permitting swivel motion only.

Abstract: A progressing cavity pump adapted for use in pumping liquid/solid mixtures with a solid content of about 50% has a single start helical rotor and a two start helical stator bore. The ratio of the eccentricity of the rotor to its minor diameter is about 1:4.9. The ratio of the eccentricity of the rotor to the stator lead is about 1:13.3. The pump may be truck mounted and used for pumping explosives.

Abstract: The invention comprises a progressive cavity pump for pumping a flowable explosive composition or other heat-sensitive material comprising an inlet and an outlet; a stator that is meltable at or above a selected maximum pump operation temperature; a rotor, and a drive shaft connecting the rotor to a power source; wherein the stator will melt above the selected temperature to prevent the generation of temperatures within the pump high enough to create a hazard. The invention also relates to a method of safely pumping a flowable explosive composition or other heat-sensitive material comprising the use of a progressive cavity pump having a stator that is meltable above a selected maximum pump operation temperature for the similar result.

Abstract: A journal bearing comprises a body having a central longitudinal axis, a cylindrical inner surface coaxially disposed around the longitudinal axis and defining an axial bore, and an outer surface including a peripheral planar section. A lateral face is disposed on an end of the body, and extends between the outer and inner surfaces of the body. A feed channel is formed in the lateral face at an acute angle with respect to the planar section and in an inward direction with respect to the axial bore. A first end of the feed channel communicates with the outer surface of the bearing at a location proximate to the planar section, and a second end of the feed channel communicates with the axial bore. A pocket is formed in the inner surface of the bearing in communication with the second end of the feed channel and extends along a substantially helical path from the lateral face of the bearing. At least a portion of the pocket has a width of greater magnitude than a corresponding depth of the portion.

Abstract: Rotary pump apparatus includes a pump housing having a drive gear and a driven gear positioned in the interior of the housing. A fluid-flow passageway provides fluid to a volumetrically changing space located between meshing gear teeth to prevent the pressure in the space from dropping below the vapor pressure of the fluid.

Abstract: Upon starting instruction of a compressor before the compressor is started, a pressurized water jet line 20 is opened and pressurized water is jetted to the inside of the compressor. By this manner, a dry operation with rotors and a mechanical seal kept in a dry state is definitely prevented and the compressor can be started even after it is stopped for a long hour. Further, the compressed air is supplied to the inside of the water tank, and the water from the water tank is jetted to the inside of the compressor by its pressure. The compressed air ejected from the water tank is cooled below a saturation temperature of water content and the water content thereof is condensed and separated. The separated water content is supplied to the inside of the compressor, and an excess circulating water is discharged from the water tank. Thus, a long hour continuous operation can be performed without replenishing water.

Abstract: A compressor system for creating essentially liquid-free fluid flows includes a screw compressor that has an inlet port for receiving a low pressure gas stream, a main lubrication injection port for receiving an injection branch of a filtered lubrication stream, an inlet bearing lubrication port for receiving an inlet branch of the filtered lubrication stream, a discharge bearing and seal lubrication port for receiving a discharge branch of the filtered lubrication stream, a prime mover for powering the rotary screw compressor and a discharge port for discharging a high pressure compressed gas mixture stream from the compressor. The system further includes a separator for receiving the compressed gas mixture stream from the compressor. The separator has at least a primary and a secondary coalescer devices connected in series, such that the primary coalescer device has a smaller surface area than the secondary coalescer device.

Abstract: Methods of sealing a planetary rotor engine, and the resulting seals, are described which improve the engine's efficiency and solves each of three main problem areas. A first method and resulting dynamic seal for sealing the rotor face surfaces as they translate across one another to constantly reform the contact between each other includes the key step of moving the shaft centerlines of each of the rotors, thereby radially positioning the rotors along diametric axes at positions which compensate for varying thermodynamic conditions (e.g. thermal expansion or contraction of rotor materials). A second method and resulting dynamic seal for effectively minimizing leakage between the end space formed between the rotor end and the case includes the key step of introducing a surface depression of any shape on one, or both, of the rotor end and opposing casing, thereby eliminating the need for a frictional seal and, in essence, forming a pressure wave plug.

Abstract: A scroll hydraulic machine comprising a housing having a key groove, a fixed scroll disposed in said housing, a swirling scroll having a key groove disposed in said housing, engaging with said fixed scroll, and moving in a swirling motion, and an Oldham ring provided with a swirling key engaging, in a freely sliding manner, with said key groove formed on said swirling scroll, and a fixed key engaging, in a freely sliding manner, with the key groove formed on said housing, and Sn plated on at least one side surface of the swirling key and the fixed key.

Abstract: Rotary fluid compressor comprises a stator housing and a crankshaft rotatable about an axis of rotation and having a crank pin offset relative to the axis of rotation. A rotor is disposed by a bearing assembly on the crank pin for orbiting motion about the axis of rotation in the stator housing. An annular spring is assembled between the bearing assembly and either the rotor or the crank pin with the spring radially compressed to an extent to provide a controlled spring preload that, in combination with a controlled spring rate, maintains radial sealing force between the rotor and the stator housing between preselected minimum and maximum design values.

Abstract: This invention provides a scroll type compressor employing an Oldham coupling producing little vibration or noise and in which components thereof are easy to produce by means of a lathe. The Oldham coupling blocks a rotation of a movable scroll member 4. A direction of a reciprocation of the Oldham coupling 16 coincides with a minor axis of an elliptic circulating orbit of the movable scroll member 4. When a total mass of the movable scroll member 4 and parts circulating elliptically together therewith is ma, a mass of an Oldham ring 16 is mb, a radius of a minor axis of an elliptic circulating orbit is R.sub.Y and a radius of a major axis of the elliptic circulating orbit is R.sub.X, a relation of R.sub.X =(1+mb/ma)R.sub.Y is established.

Abstract: The invention provides a rotary-vane machine having a stationary shell including a casing member (2), a camming ring (4) having an internal, noncircular camming surface (6), and a flange member (8); a rotor (10) including at least two first vanes (12) fixedly attached to, or integral with, the rotor (10), a first cover plate (14) fixedly attachable to the rotor (10); a second cover plate (16) fixedly attachable to the rotor and integral with a first shaft (22) supported on its free end by bearing (26) mounted in the casing (2), and being provided with at least four ports (a) for access or egress of a working medium; a second shaft (23) supported by a first bearing (28) accommodated in the first cover plate (14) and by a second bearing (30) accommodated in the second cover plate (16); at least two second vanes (38) fixedly attached to the second shaft (23) and oscillatably accommodated within the rotor (10), and defining, together with the rotor (10), the first vanes (12) and the first and second cover plates

Abstract: A scroll compressor of the type having a cantilever mounted shaft is provided with a carbon crank case bearing. The carbon bearing insures that the shaft will be quickly worn away should there be shaft misalignment.

Abstract: A gas blower and method according to which the gas is introduced into the inlet of a housing where it is pressurized by rotating impellers. The pressurized gas is directed to a discharge plenum from which a first portion of the gas is discharged. The remaining portion of the gas is passed from the discharge plenum through a plurality of openings to a recirculating chamber for recirculating the gas back to the housing. The gas is passed from the recirculating chamber back to the housing through two radially-spaced sets of angularly-spaced openings formed in the housing.

Abstract: This design utilizes spherical balls that function as pumping members and also function as bearing loads. The housing includes channels that are used to convert rotary motion to true linear reciprocating motion relative to the center of operation by use of modified involute profile curves. The channels have an enlarged radius of curvature, four (4) contact point designs, and an arch design depending upon application and loads, etc. A variable vane shaft and variable seal plug have a make-before-break design that eliminates damaging high pressure spikes due to the trapped fluid. The vane is used to vary and control pumping arc by directing the high and low pressures. A rotor disclosed has an angle and slots that are designed to align with tangent of the involute curve. The variable displacement disclosed herein is varied by varying the pumping arc thereby causing more or less fluid to be pumped from inlet pressure to inlet pressure which actually affects displacement and input power required.

Abstract: A positive displacement rotary pump with an improved impeller design integrating a replaceable wiper insert. The impeller generally has or more lobes and an equal number of conjugate surfaces. Each lobe has a cavity which holds a wiper blade. The wiper blade improves efficiency by making a seal with a pump chamber or the conjugate surface on the other impeller as it rotates. The wiper is pressed radially outward from a central axis of the impeller by a biasing means such as a spring.

Abstract: A gear pump is provided with a drive gear rotated via a drive shaft; a slave gear; a gear housing containing a gear chamber housing these gears therein; and a pump housing composed of a cylindrical housing main body with a bottom which contains the gear housing for serving as a low pressurized chamber, the inside of which communicates with the gear chamber, and an opening being defined thereon, and a covering member for closing the opening, wherein an eccentric pitted portion being eccentric with respect to the axis of the drive shaft is defined on the covering member, and the fluid return port is allowed to face to the eccentric pitted portion to function the eccentric pitted portion as a return fluid passage for return fluid, whereby it is possible to reduce a size of the gear pump without accompanying any cavitation.

Abstract: A suction pump (22) suitable for use in a fuel dispensing system (20) or other fluid delivery system for volatile liquids. The suction pump includes a pump casing that defines a pump chamber (52) with inlet and outlet ports. A rotor (54) with vanes (58) is seated in the pump chamber. The vanes define fluid cavities (96a, 96b, 96c, . . . 96f) that rotate between the inlet and outlet ports. During each turn of the rotor, each fluid cavity passes through a section of the pump chamber in which it is isolated from both the inlet port and outlet port. A bleed duct (102) extends from the outlet port. A bleed port (104) extends from the bleed duct to the section of the pump chamber that defines the isolated position of the fluid cavities. During operation of the pump, pressurized fluid discharged from the outlet port flows through the bleed duct and bleed port into the isolated fluid cavity.