Abstract: A controlled variable delivery external gear machine (VD-EGM). The VD-EGM includes a housing, an inlet, a drive gear, a driven gear, the drive gear configured to engage the driven gear in an angular mesh zone, an outlet, a first slider comprising a first longitudinal portion connected to a second longitudinal portion such that longitudinal forces applied to the first and second longitudinal portions substantially cancel each other thereby requiring between about 0 N to about 20 N to longitudinally moving the first slider, selective positioning of the first slider configured to vary net operational volumes of fluid communication between the inlet and the outlet, for a given rotational speed of the drive gear, and a first drive mechanism coupled to the first slider and configured to cause the first slider to slide in a longitudinal direction.

Abstract: A fluid gear pump comprising: a first gear including a concentrically disposed first hub portion and a plurality of first teeth; a second gear including a concentrically disposed second hub portion and a plurality of second teeth, wherein at a time in operation the plurality of first teeth and second teeth contact at first and second contact point to create a backlash volume; a first bearing abutting and coaxial to first hub portion; a second bearing abutting and coaxial to second hub portion; and a bridgeland connecting the first and second bearing, the bridgeland separates a low pressure side from a high pressure side, the bridgeland is located such that the backlash volume closes to the high pressure side and opens to the low pressure side when a rate of change of a volume measurement of the backlash volume is decreasing or about equal to zero.

Abstract: A rotary, self-priming, positive displacement pump is described. The pump may include a pump housing having a fluid inlet and outlet, first and second rotary impellers having vanes, an input shaft and drive gears synchronizing the impellers to avoid clash, and a dividing wall separating a pumping chamber from a chamber containing the drive gears. The dividing wall separates the pumping chamber from the gear chamber, partially supports impeller shafts, and is formed in a plurality of abutting manually separable sections. When manually pulled apart, the separable sections free the impeller shafts for manual removal, to facilitate manual service to the pump.

Abstract: A Roots-type blower may include first and second meshed, lobed rotors disposed in first and second chambers of a housing. Each lobe may have first and second axially facing end surfaces defining a twist angle that may be a function, at least partially, of the number of lobes on each rotor. A blower housing may include a bearing plate that may include one or more internal pressure relief ports. A pressure relief port may be configured to relieve fluid pressure from a trapping area that may form between first and second meshed rotors.

Abstract: A rotary device includes a first rotor rotatable about a first axis and having at its periphery a recess bounded by a curved surface, and a second rotor counter-rotatable to the first rotor about a second axis, parallel to the first axis, and having a radial lobe bounded by a curved surface, the first and second rotors being coupled for intermeshing rotation, wherein the first and second rotors of each section intermesh in such a manner that on rotation thereof, a transient chamber of variable volume is defined, the transient chamber having a progressively increasing or decreasing volume between the recess and lobe surfaces, the transient chamber being at least in part defined by the surfaces of the lobe and the recess; the ratio of the maximum radius of the lobe rotor and the maximum radius of the recess rotor being greater than 1.

Abstract: A bearing includes a bridge land geometry having a finger cut that defines a width ISW, a center of the width ISW displaced from a shaft axis a radial distance ISR, a ratio of ISW/ISR between 0.074-0.293, to reduce cavitation and pressure ripple.

Abstract: The subject matter of this specification can be embodied in, among other things, a method that includes a gear pump includes gears having a gear root diameter and teeth having an addendum and pressure angle. A housing includes a fluid inlet and discharge, bearings configured to position the gear teeth in intermeshing contact across a fluid dam. The fluid dam includes a first face arranged at an angle to a split line, spaced apart from a center line at the split line a first distance towards the inlet, and extending from the first gear root diameter away from the center line to the first gear root diameter, and a second face arranged approximately perpendicular to the split line, spaced apart from the center line at the split line a second distance towards the outlet, and extending between the first gear root diameter and the second gear root diameter.

Abstract: A fluid pump includes a housing that defines a suction chamber, a discharge chamber, and a barrier having a first height, wherein the barrier is configured to separate the suction chamber from the discharge chamber. The pump also includes meshed first and second gears rotatably disposed in the housing. The gears are configured to draw relatively low-pressure fluid from the suction chamber, transform the relatively low-pressure fluid into relatively high-pressure fluid, and release the relatively high-pressure fluid into the discharge chamber. The barrier includes first and second portions configured to accept the first and second gears respectively, and a bridge connecting the first and second portions. The bridge is disposed proximately to where the gears mesh and is configured to provide a transition from the first height to a second height to thereby generate gradual re-expansion of the fluid away from the bridge.

Abstract: In a gear pump according to the present invention, a wall surface portion of a casing (2) includes a drive side partition surface (41) on which tooth crests (11) of a drive gear (10) slide, a driven side partition surface (42) on which tooth crests (21) of a driven gear (20) slide, a suction side inner peripheral surface (43) that connects the drive side partition surface (41) and the driven side partition surface (42) on a suction chamber (3) side, and a discharge side inner peripheral surface (44) that connects the drive side partition surface (41) and the driven side partition surface (42) on a discharge chamber (4) side.

Abstract: A pump includes a pump body defining first and second cavities. First and second rotors are disposed in the first and second cavities between an inlet passage and an outlet passage and are in sealing relationship with each other during rotation of the rotors. A drive transmission mechanism is coupled to the first and second rotors for rotating the rotors in opposite directions. During a revolution of the first rotor, a vane projecting from the first rotor emerges from a recess of the second rotor, passes the inlet passage and the outlet passage, and enters a recess of the second rotor, while the inlet passage remains sealed from the outlet passage.

Abstract: Positive-displacement auxiliary pumping systems for use in pump apparatus of different configurations are disclosed. The positive-displacement auxiliary pumping systems are included in positive-displacement rotary pumps having a casing defining a pumping cavity, an inlet port connected to the pumping cavity, a discharge port connected to the pumping cavity, and a positive-displacement auxiliary pumping port connected to the pumping cavity. Pumping elements move within the pumping cavity of the casing and define a collapsing pocket that maintains fluid communication with the positive-displacement auxiliary pumping port after the collapsing pocket is no longer in fluid communication with the discharge port.

Abstract: A single-screw compressor includes a screw rotor including a spiral groove, a casing, and a gate rotor. The gate rotor includes a plurality of radial gates configured to mesh with the spiral groove. A clearance between one of the gates disposed in the spiral groove and a wall surface of a discharge side portion of the spiral groove is larger than a clearance between the gate disposed in the spiral groove and a wall surface of a suction side portion of the spiral groove. The wall surface of the discharge side portion of the spiral groove is a portion extending from a predetermined position of the spiral groove at a certain point in a compression phase to the terminal end of the spiral groove. The wall surface of the suction side portion of the spiral groove being a portion other than the discharge side portion.

Abstract: An improved geared hydraulic apparatus, comprising a pair of meshing gearwheels, mounted to be reciprocally rotatable in a casing between an inlet side and an outlet side for a fluid having, in use, a substantially transverse flow with respect to the axes of rotation of the gearwheels. The meshing gearwheels create, during their reciprocal rotation, progressive meshing configurations between respective co-operating teeth. In at least one of said progressive meshing configurations is defined, in at least one cross-section of the gearwheels, at least one closed area between respective fluid entrapment teeth. The closed area decreases until it is substantially cancelled out at and around at least one other, separate progressive meshing configuration between the aforesaid respective co-operating teeth.

Abstract: A hydraulic device has an inlet side and an outlet side and includes two meshing cogwheels. Each cogwheel has external oblique teeth and is arranged between an inlet side and an outlet side. At least one control groove is provided on an end side of the cogwheels. The control groove periodically produces a pressure equalizing connection during the rotation of the cogwheels.

Abstract: Roots-type blowers with helical cycloidal rotors exhibit variation in leakback flow with angular position intrinsic to these rotor geometries. Calibration of individual blowers using a combination of high-resolution alignment and enhanced detection of residual noise phenomena permits noise in as-produced blowers to be significantly attenuated. Intrinsic lower limits of noise induced by leakback variation are associated with manufacturing tolerances, necessary clearances, and particular geometric considerations. Gross alignment errors (excluding contact between rotors) produce a characteristic noise pulse rate that is three times the shaft rate. Proper alignment suppresses this and reveals a pulse sequence at double this rate and at about half of the amplitude of faulty alignment. The novel process explains the error mechanisms and defines repeatable calibration methods for a mass-production environment, introducing appropriate gauges and methods for the task.

Abstract: A gear pump comprises a drive gear being mounted for rotation about a first axis and having a plurality of gear teeth at a radially outer location. A driven gear is mounted for rotation about a second axis, and having a plurality of teeth at a radially outer location. The drive gear teeth engage the driven gear teeth at a contact face to cause the driven gear to rotate. Slots are formed in the contact face of one of the drive and driven gear teeth.

Abstract: A pump comprises a driving rotor and a driven rotor that are positioned in a housing such that, as the driving rotor and the driven rotor rotate, the teeth of the driving rotor and the teeth of the driven rotor mesh to form a positive displacement seal. The teeth of the driving rotor and the driven rotor are configured such that seals between the inlet side and the discharge side of the pump are formed between only the leading surfaces of the teeth of the driving rotor and the trailing surfaces of the teeth of the driven rotor.

Abstract: A gear pump comprises a first gear to be connected to a source of drive, and having a first plurality of gear teeth. A second gear has a second plurality of teeth engaged with the first gear teeth. The first gear teeth contact the second gear's teeth on a contact face, causing the second gear to rotate. The first plurality of teeth is greater than the second plurality of teeth.

Abstract: A low noise gear set for use generally and preferably with a power plant having an engine driving a pump connected to a low pressure fluid source, generating high pressure fluid at an output. The idle gear meshes with the drive gear along two points of the profile of the corresponding gears. The first point being the root of one gear tooth meshing with the tip of the opposite gear tooth creating an initial first contact point and a subsequent second point along the profile when the teeth are disengaging at the first point and engaging at the second point, forming a sealed area, allowing the fluid to hydrostatically escape between the points.

Abstract: A Roots-type blower with helical cycloidal rotors features relief recesses in the chamber walls, isolated from the input and output ports. The relief recesses counter variation in leakback flow with angular position intrinsic to helical cycloidal rotors, attenuating a noise source.

Abstract: The invention concerns a hydraulic machine with a set of teeth, having a toothed ring with an inner toothing and a gear wheel with an outer toothing, the gear wheel rotating and orbiting in the toothed ring, the inner toothing and the outer toothing touching each other in contact areas, thus separating pressure chambers, and with a valve arrangement controlling a connection between a connection arrangement having a high pressure connection and a low pressure connection, and the pressure chambers. It is endeavoured to achieve a stable operation, particularly with low speeds. For this purpose, each contact area is provided with an opening, which, at the time when a pressure chamber reaches an extreme value of its volume, produces a short-circuiting with the neighbouring pressure chamber.

Abstract: A gear pump is provided and includes an inlet port which terminates, in the pumping direction of the rotor set, in a radially inwardly extending ramp portion. The ramp portion operates to direct working fluid from an inlet radially inwardly into a pumping chamber of the rotor set which is passing over the ramp portion. By closing the pumping chamber at a radially inwardly point, the filling efficiency of the pumping chamber is improved, reducing cavitation and/or operating noise of the pump.

Abstract: A gear pump for operating with reduced likelihood of cavitation occurrences in the fluid being pumped thereby, the pump having a pair of gears each supported on a corresponding one of a pair of gear with teeth provided in each gear that mesh with at least one tooth of the other when such teeth have been rotated into a meshing region in the gear plane, and with one of the gear shafts being rotatably connectable to a motor. Bearing structures rotatably support corresponding ones of each of the pair of gear shafts with the bearing structures having bearing surfaces adjacent those gear sides. A pressurized fluid passageway is provided in at least one of the bearing structures across from the meshing region and extending between surface openings at the bearing surface of that bearing structure that are positioned on opposite sides of an alignment axis in that bearing surface, the surface openings being separated from one another by at least the width of a tooth provided in the pair of gears.

Abstract: A screw compressor rotatably accommodates, within a casing including a suction port and a delivery port, a pair of female and male rotors under the meshed state and compresses gas in the state where a liquid is mixed by pouring the liquid to the gas confined within a working chamber formed with both rotors and the casing. On the wall surface of the casing opposing to the rotor delivery end, a recessed part is provided. The working chamber is communicated with the recessed part immediately before isolating from the delivery port and this communication is maintained until a volume of the working chamber substantially becomes zero. Thereby, the screw compressor can be control increase in power consumption, vibration, and noise.

Abstract: In a screw vacuum pump 30, equal lead screws each in the range of 1 to 4 leads are added on the discharge side of male and female screw rotors (4) and (5) having a continuously changing screw gear helix angle, at a final lead angle of the male and female unequal lead screw rotors on the discharge side that continuously change in helix angle following the advance of the screw gear helix.

Abstract: An oil pump includes a pump cover covering a recess in a side face of a pump body to form a gear compartment therebetween. A drive gear and a rotatably driven gear are meshed and mounted in the gear compartment. Working spaces R are formed by the engagement of the meshed gear teeth. Discharge ports are formed in both the pump body and the pump cover in communication with the gear compartment. A notch is formed in the pump body at the bottom of the gear compartment and extends from the front end of the discharge port in the pump body to the rear end of a discharge area for the working spaces. Another notch is formed in the inner side face of the pump cover, and extends from the front end of the discharge port in the cover to the rear end of the discharge area.

Abstract: According to one embodiment of the invention, an engine system comprises a housing, an outer gerotor, an inner gerotor, a tip inlet port, a face inlet port, and a tip outlet port. The housing has a first sidewall, a second sidewall, a first endwall, and a second endwall. The outer gerotor is at least partially disposed in the housing and at least partially defines an outer gerotor chamber. The inner gerotor is at least partially disposed within the outer gerotor chamber. The tip inlet port is formed in the first sidewall and allows fluid to enter the outer gerotor chamber. The face inlet port is formed in the first endwall and allows fluid to enter the outer gerotor chamber. The tip outlet port is formed in the second sidewall and allows fluid to exit the outer gerotor chamber.

Abstract: An external toothed wheel pump, comprising a delivery chamber comprising an inlet and an outlet for a fluid; a first feed wheel and a second feed wheel which can be rotationally driven for delivering the fluid and are in a toothed engagement with each other which separates the outlet from the inlet; and sealing surfaces which axially face the feed wheels and form axial sealing gaps with the feed wheels, wherein at least one of the sealing surfaces comprises a relieving pocket on a high-pressure side of the delivery chamber only and except for the relieving pocket, extends circumferentially up to at least the root circle and tip circle of the axially facing feed wheel.

Abstract: A screw vacuum pump includes a gas working chamber formed by a male screw rotor and a female screw rotor respectively including unequal lead screws engaging each other and having a lead angle that continuously changes with the advance of helix and a stator receiving therein both rotors. The stator is provided with a gas inlet port and a gas outlet port that can communicate with one end portion and the other end portion of the working chamber, respectively. The male screw rotor and the female screw rotor have unequal lead screws each of which is formed into a perpendicular-to-axis cross-sectional shape that changes following a continuous change in lead angle with the advance of helix. Alternatively, one of the male screw rotor and the female screw rotor has the unequal lead screw formed into a perpendicular-to-axis cross-sectional shape that is constant. Another has the unequal lead screw formed into a perpendicular-to-axis cross-sectional shape that changes.

Abstract: A double-screw compressor for supplying gas, such as air, to a gas consumer, is provided. The double-screw compressor includes two interacting rotors for compressing the gas and a toothed gearing. The toothed gearing includes a gearing housing with two opposite end walls made of a first material. Two gearwheels made of a second material which has a thermal expansion coefficient different from the thermal expansion coefficient of the first material are mounted in the end walls. In order to reduce the effect of the temperature on the backlash, both gearwheels are designed with one and the same pressure angle which is smaller than 15°.

Abstract: A trochoid oil pump, which enables the endurance to be increased and the reduction of discharge pulsations and noise to be achieved, and in which those results can be realized with a very simple structure. An interdental space constituted by an inner rotor and an outer rotor having trochoid tooth profile or substantially trochoid tooth profile starts a compression stroke in the location of a partition section between an intake port and a discharge portion, and a linking gap L is composed by the interdental space and a preceding adjacent interdental space realized in a discharge stroke. The linking gap expands gradually from the start of compression stroke to the discharge stroke.

Abstract: A pump comprises a driving rotor and a driven rotor that are positioned in a housing such that, as the driving rotor and the driven rotor rotate, the teeth of the driving rotor and the teeth of the driven rotor mesh to form a positive displacement seal. The teeth of the driving rotor and the driven rotor are configured such that seals between the inlet side and the discharge side of the pump are formed between only the leading surfaces of the teeth of the driving rotor and the trailing surfaces of the teeth of the driven rotor.

Abstract: A hydraulic pump is provided that reduces or eliminates unwanted noise, local pressure waves, pressure pulsations or cavitation and the like through use of pressure and suction chambers that are in substantial fluid isolation except for a backflow connection with a predetermined flow cross section to the suction chamber.

Abstract: A seal assembly for the protection of a static seal device for use in a vacuum pump. The seal assembly comprising at least two components which are sealingly connected together, an o-ring seal, which is engaged between the two components to prevent transfer of fluid to and from the pump between these two components and a fluid channel. The fluid channel being in the plane of the o-ring and located between the o-ring seal and a process gas flow path. The fluid channel provides a path for a barrier gas to be routed when the apparatus is in use. The channel being connectable to an external source of barrier fluid and having an outlet in fluid communication with the pump swept volume.

Abstract: A scroll compressor with a backflow-proof mechanism. The scroll compressor comprises a slider disposed on a scroll couple, forming several enclosed spaces. The slider is raised by the working fluid in the spaces, preventing liquid leakage from a high-pressure chamber to a low-pressure chamber, when the scroll compressor starts. The slider descends when the compression ratio of the scroll compressor is exceeded. Thus, the pressure is released, and the performance of the scroll compressor is improved. The slider of the invention further comprises a floating element to prevent reversal of pressurized fluid and damage to the scroll couple.

Abstract: It is an object of the present invention to provide a trochoid type oil pump in which erosion of the rotor surfaces caused by cavitation is minimized, vibration and noise are reduced, and the structure is greatly simplified. The trochoid type oil pump of the present invention comprises a rotor chamber which has an intake port and a discharge port, an outer rotor, an inner rotor, and shallow grooves which are formed on the side of the initial end portion of the discharge port on the circular circumference of the track of the positions of the bottom portions of the teeth created by the rotation of the outer rotor. In a state in which the sealed spaces formed by the outer rotor, the inner rotor and a partition part between the final end portion of the intake port and the initial end portion of the discharge port are reduced in volume from the maximum volume, the sealed spaces Sa are caused to communicate with the shallow grooves.

Abstract: A screw compressor comprises a casing, and a male and a female rotor formed with axially twisted screw grooves and accommodated in the casing, the both rotors being rotated by timing gears fixed to the respective rotors while a desired minute gap is kept therebetween, and a method of manufacturing rotors therefor. In the screw compressor, the male and female rotors formed with axially twisted screw grooves in the casing comprise concave stripes having a minute depth and provided on the respective screw grooves to extend along directions of twist thereof, and leakage of a compressed air is less to give a high compression efficiency.

Abstract: A bottom portion of an intake port is provided with a sloped bottom surface formed of a plane such that sloped bottom surface approaches the side surfaces of external teeth and internal teeth from an upstream side to a downstream side in rotational direction of two rotors. Fluid that flows in the intake port is regulated by the sloped bottom surface and smoothly guided into individual inter-teeth chambers that are expanding. Since the sloped bottom surface on the bottom portion of the intake port is formed of a plane without spiral or twisting, design and manufacturing of a gear pump is extremely easy.

Abstract: At a boundary area between a high-pressure portion in which a discharge port of a fuel pump is disposed and a low-pressure portion in which an intake port is disposed, a pressure relief groove extending along the boundary area is formed so as to be communicated with the outside of the pump by pressure relief hole. Alternatively, a slit is formed communicated with the outside. Accordingly, a fuel at a high-pressure area portion can be drained with reliability. Further, by communicating the above pressure relief groove with a positioning pin insertion port, a single hole can serve both as a positioning pin insertion hole and a pressure relief hole.

Abstract: An internal/external gear pump includes a wear plate disposed between the gear members and at least one sidewall of the pump. The wear plate has a recess formed therein having a substantially constant depth and width. The recess extends into the full mesh point between the gear members of the pump to provide a flow path from the full mesh point to an inlet side or suction port of the pump.

Abstract: A feedpump for discharging a string of a viscous medium containing solid particles. The feedpump includes a casing and two gearwheels drivable to execute an oppositely directed rotation and arranged in the casing so as in each case to form and maintain gaps relative to both walls of the casing and to one another. The gaps have a size adapted to the size of the particles in the viscous medium.

Abstract: An oil pump includes suction and discharge chambers formed in a sidewall of a housing, and a maximum-volume-side partition area formed with the sidewall of the housing on a trajectory of pump houses and at a position where each pump house has a maximum volume, wherein the maximum-volume-side partition area creates a section where any pump house spreads over neither of the suction and discharge chambers. A plurality of channels is arranged in the discharge chamber at an end thereof, each channel having a predetermined length and extending to the maximum-volume-side partition area.

Abstract: A method for the metered discharge of a string of a viscous medium, in particular of an abrasive medium containing solid particles, via a nozzle, in which the quantity of the medium is discharged as a function of the speed of the nozzle and is increased or reduced as a function of the acceleration or deceleration of the nozzle.

Abstract: An oil pump includes suction and discharge chambers formed in a sidewall of a housing, and a maximum-volume-side partition area formed with the sidewall of the housing on a trajectory of pump houses and at a position where each pump house has a maximum volume, wherein the maximum-volume-side partition area creates a section where any pump house spreads over neither of the suction and discharge chambers. A plurality of channels is arranged in the discharge chamber at an end thereof, each channel having a predetermined length and extending to the maximum-volume-side partition area.

Abstract: A gear pump includes a pair of gears accommodated in a gear chamber. When the inside pressure of a trap region which is changed with the rotation of the gears becomes substantially equal to the inside pressure of an inlet chamber, the communication state is switched from a state in which communication between the trap region and the first and second relief channels is blocked to a state in which the trap region communicates with the second relief channel. With the inside pressure of the trap region being substantially equal to the inside pressure of the inlet chamber, the trap region is opened to the inlet chamber.

Abstract: In a Roots displacement fluid machine (5) comprising rotors (15, 17) meshed with each other in a tooth trace (57, 59) formed in parallel to a rotating central axis, and a casing (13) having a rotor chamber (33) rotatably receiving the rotors (15, 17), a fluid inlet port for a fluid and a fluid outlet port, an inclined surface (67) forming an angle .theta. with respect to an opposing surface (65) of the rotor chamber (33) is disposed at least in a tip end of the end portion of the rotor (15), and a gap (69) is formed with respect to the opposing surface (65).

Abstract: The invention relates to a fluid-conveying machine, in particular, a pump having a component rotating in a stationary housing part inside an annular gap. The stationary housing part separates an interior having a higher product pressure from an exterior having a lower pressure. A rotating component is mounted in an external bearing which is sealed with respect to the interior via a sealing system. In order to improve the sealing, the invention provides that the annular gap is formed between two sliding bearing shells which comprise extremely hard, wear-resistant materials and, in accordance with the operating principle of a radial sliding bearing, form a first pressure-reducing stage. A feedback device, which feeds back the leakage from this first sealing stage into the conveying process of the machine, is connected downstream of the first pressure-reducing stage. A second sealing stage is arranged axially downstream of the feedback device.

Abstract: A pump or motor 10 provides a housing 20 which carries one or more elliptical drivers 40 which rotate freely with an axle which is rotatably carried by the housing. One V-shaped rocker 60 is associated with each elliptical driver, and moves in an oscillatory motion in response to being driven by the associated elliptical driver. When used as a motor, fluid entering the housing tends to apply pressure to one side of the elliptical driver, while the other side is shielded from pressure by the V-shaped rocker. Uneven pressure causes the elliptical driver to rotate. As the elliptical driver rotates, the V-shaped rocker oscillates in a period manner at twice the frequency of the elliptical driver. The vertical height of the V-shaped is determined by an adjustable support 80, which allows regulation over the friction level and fluid seal between the rocker and the elliptical drive, and which allows adjustment to compensate for wear of the surfaces of contact between the rocker and the elliptical driver.

Abstract: A crescent pump including a housing having an inlet port and a discharge port, a driving gear, and a driven gear meshing with driving gear in a gap between the inlet and the discharge ports. External and internal troughs on the driving and the driven gears define pump chambers. A stationary crescent-body has a pair of arc-shaped walls which cooperate with the tips of the external and the internal gear teeth thereon in defining fluid seals. The edges of an inlet ramp at an upstream end of the crescent body and the edges of a discharge ramp at a downstream end of the crescent body define inner and outer upstream and downstream metering orifices which close and open in complementary fashion to maintain constant the rate of fluid leakage from the discharge port toward the inlet port. A pair of shaped metering grooves in the pump housing cooperate in defining a flow path between the discharge port and the inlet port through a succession of trapped volumes between the driving and the driven gears.

Abstract: A filling member-less internal-gear unit has a casing with a bearing ring which is accommodated movably in a bore in the casing transversely with respect to its axis but non-rotatably. An internally toothed annular gear is rotatably mounted in the bearing ring and meshes with a pinion rotatably mounted in the casing. The bearing ring is pivotable relative to the bore in the casing about a pivot axis parallel to its axis. The pivot axis is so disposed that the ring portion of the bearing ring, which is associated with the engagement-free annular gear region, is moved at least approximately radially towards the pinion axis by the hydraulic pressure forces acting on the annular gear in the pressure chamber.