EP0174171B1 - Supercharger with reduced noise - Google Patents
Supercharger with reduced noise Download PDFInfo
- Publication number
- EP0174171B1 EP0174171B1 EP19850306198 EP85306198A EP0174171B1 EP 0174171 B1 EP0174171 B1 EP 0174171B1 EP 19850306198 EP19850306198 EP 19850306198 EP 85306198 A EP85306198 A EP 85306198A EP 0174171 B1 EP0174171 B1 EP 0174171B1
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- EP
- European Patent Office
- Prior art keywords
- lobes
- rotor
- blower
- backflow
- outlet port
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
- F04C18/08—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
- F04C18/12—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type
- F04C18/14—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons
- F04C18/16—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons with helical teeth, e.g. chevron-shaped, screw type
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
- F04C29/0021—Systems for the equilibration of forces acting on the pump
- F04C29/0035—Equalization of pressure pulses
Definitions
- EP-A-0176269 and 0176268 European Applications published as EP-A-0176269 and 0176268. These applications are assigned to the assignee of this application, and all are incorporated herein by reference.
- This invention relates to rotary compressors or blowers, particularly to blowers of the backflow type. More specifically, the present invention relates to reducing airborne noise associated wityh Roots-type blowers employed as superchargers for internal combustion engines.
- Rotary blowers particularly Roots-type blowers are characterized by noisy operation.
- the blower noise may be roughly classified into two groups: solid borne noise caused by rotation of timing gears and rotor shaft bearings subjected to fluctuating loads, and fluid borne noise caused byfluid flow characteristics such as rapid changes in fluid velocity. Fluctuating fluid flow contributes to both solid and fluid borne noise.
- Roots-type blowers are similar to gear-type pumps in that both employ toothed or lobed rotors meshingly disposed in transversely overlapping cylindrical chambers. Top lands of the lobes sealingly cooperate with the inner surfaces of the cylindrical chambers to trap and transfer volumes of fluid between adjacent lobes on each rotor. Roots-type blowers are used almost exclusively to pump or transfer volumes of compressible fluids, such as air, from an inlet receiver chamber to an outlet receiver chamber. Normally, the inlet chamber continuously communicates with an inlet port and the outlet chamber continuously communicates with an outlet port. The inlet and outlet ports often have a transverse width nominally equal to the transverse distance between the axes of the rotors.
- each receiver chamber volume is defined by the inner boundary of the associated port, the meshing interface of the lobes, and sealing lines between the top lands of the lobes and cylindrical wall surfaces.
- the inlet receiver chamber expands and contracts between maximum and minimum volumes while the outlet receiver chamber contracts and expands between like minimum and maximum volumes.
- transfer volumes are moved to the outlet receiver chamber without compression of the air therein by mechanical reduction of the transfer volume size. If outlet port air pressure is greater than the air pressure in the transfer volume, outlet port air rushes or backflows into the volumes as they become exposed to or merged into the outlet receiver chamber. Backflow continues until pressure equalization is reached.
- backflow blower in which compression is realized by way of this backflow is hereinafter called a backflow blower.
- Nonuniform displacement is caused by cyclic variations in the rate of volume change of the receiver chamber due to meshing geometry of the lobes and due to trapped volumes between the meshing lobes.
- first and second trapped volumes are formed.
- the first trapped volumes contain outlet port or receiver chamber air which is abruptly removed from the outlet receiver chamber as the lobes move into mesh and abruptly returned or carried back to the inlet receiver chamber as the lobes move out of mesh.
- the trapped volumes are further sources of airborne noise and inefficiency for both straight and helical lobed rotors.
- both the first and second trapped volumes are formed along the entire length of the lobes, whereas with helical lobes rotors, the trapped volumes are formed along only a portion of the length of the lobes with a resulting decrease in the degrading effects on noise and efficiency.
- the first trapped volumes contain outlet port air and decrease in size from a maximum to a minimum, with a resulting compressing of the fluid therein.
- the second trapped volumes are substantially void of fluid and increase in size from a minimum to a maximum with a resulting vacuum tending expansion of fluid therein. The resulting compression of air in the first trapped volumes, which are subsequently expanded back into the inlet port, and expansion of the second trapped volumes are sources of airborne noise and inefficiencies.
- Nonuniform displacement, due to trapped volumes, is of little or no concern with respect to the Hallett blower since the lobe profiles therein inherently minimize the size of the trapped volumes.
- lobe profiles in combination with the helical twist, can be difficult to accurately manufacture and accurately time with respect to each other when the blowers are assembled.
- Hallett also addressed the backflow problem and proposed reducing the initial rate of backflow to reduce the instantaneous magnitude of the backflow pulses. This was done by a mismatched or rectangular shaped outlet port having two sides parallel to the rotor axes and, therefore, skewed relative to the traversing top lands of the helical lobes.
- US ⁇ A ⁇ 2,463,080 to Beier is considered the State of the Art and discloses a related backflow solution for a straight lobe blower by employing a triangular outlet port having two sides skewed relative to the rotor axes and, therefore, mismatched relative to the traversing lands of the straight lobes.
- the Weatherston blower provides preflow of outlet receiver chamber air to the transfer volumes via. circumferentially disposed, arcuate channels or slots formed in the inner surface of the cylindrical walls which sealingly. cooperate with the top lands of the rotor lobes. The top lands and channels cooperate to define orifices for directing outlet receiver chamber air into the transfer volumes.
- the arc or setback length of the channels determines the beginning of preflow.
- Weatherston suggests the use of additional channels of lesser setback length to hold the rate of preflow relatively constant as pressure in the transfer volumes increases.
- the Weatherston preflow arrangement which is analogous to backflow, is believed theoretically capable of providing a relatively constant preflow rate for predetermined blower speeds and differential pressures. However, to obtain relatively constant preflow, several channels of different setback length would be necessary. Further, accurate and consistent forming of the several channels on the interior surface of the cylindrical walls is, at best, an added manufacturing cost.
- An object of the present invention is to provide a rotary blower of the backflow type for compressible fluids which is relatively free of airborne noises due to nonuniform displacement.
- Another object of the present invention is to provide a rotary blower of the backflow type for compressible fluids wherein backflow is relatively constant when the blower operates at predetermined speeds and differential pressures.
- Another object of the present invention is to provide a rotary blower of the backflow type for compressible fluids wherein nonuniform displacement, due to meshing geometry and trapped volumes, is substantially eliminated.
- US-A-2463080 discloses the pre-characterizing portion of Claim 1 but can undesirably restrict outflow.
- a rotary blower of the backflow type includes a housing defining inlet and outlet ports and a chamber containing first and second meshed lobes rotors for transferring volumes of relatively low- pressure inlet port fluid, via spaces between adjacent, unmeshed lobes, to relatively highpressure outlet port fluid, which alternately backflows into each volume in response to alternate and initial travesing of wall surfaces, defining traversely opposite boundaries of the outlet port.
- the outlet port longitudinal and traverse boundaries and the expanding orifices form a somewhat hourglass port shape.
- FIGURES 1-4 illustrate a rotary pump or blower 10 of the Roots-type.
- blowers are used almost exclusively to pump or transfer volumes of compressible fluid, such as air, from an inlet port to an outlet port without compressing the transfer volumes prior to exposure to the outlet port.
- the rotors operate somewhat like gear-type pumps, i.e., as the rotor teeth or lobes move out of mesh, air flows into volumes or spaces defined by adjacent lobes on each rotor. The air in the volumes is then trapped therein at substantially inlet pressure when the top lands of the trailing lobe of each transfer volume moves into a sealing relation with the cylindrical wall surfaces of the associated chamber.
- the volumes of air are transferred or exposed to outlet air when the top land of the leading lobe of each volume moves out of sealing relation with the cylindrical wall surfaces by traversing the boundary of the outlet port. If the volume of the transfer volumes remains constant during the trip from inlet to outlet, the air therein remains at inlet pressure, i.e., transfer volume air pressure remains constant if the top lands of the leading lobes traverse the outlet port boundary before the volumes are squeezed by virtue of remeshing of the lobes. Hence, if air pressure at the discharge port is greater than inlet port presure, outlet port air rushes or backflows into the transfer volumes as the top lands of the leading lobes traverse the outlet port boundary.
- Blower 10 includes a housing assembly 12, a pair of lobed rotors 14, 16, and an input drive pulley 18.
- Housing assembly 12 as viewed in FIGURE 1, includes a center section 20, left and right end sections 22, 24 secured to opposite ends of the center section by a plurality of bolts 26, and an outlet duct member 28 secured to the center section by a plurality of unshown bolts.
- the housing assembly and rotors are preferably formed from a lightweight material such as aluminum.
- the center section and end 24 define a pair of generally cylindrical working chambers 32, 34 circumferentially defined by cylindrical wall portions or surfaces 20a, 20b, an end wall surface indicated by phantom line 20c in FIGURE 1, and an end wall surface 24a. Chambers 32, 34 traversely overlap or intersect at cusps 20d, 20e, as seen in FIGURE 2. Openings 36, 38 in the bottom and top of center section 20 respectively define the transverse and longitudinal boundaries of inlet and outlet ports.
- Rotors 14,16 respectively include three circumferentially spaced apart helical teeth or lobes 14a, 14b, 14c and 16a, 16b, 16c of modified involute profile with an end-to-end twist of 60°.
- the lobes of teeth mesh and preferably do not touch.
- a sealing interface between meshing lobes 14c, 16c is represented by point M in FIGURE 2.
- Interface or point M moves along the lobe profiles as the lobes progress through each mesh cycle and may be defined in several places as shown in FIGURE 7.
- the lobes also include top lands 14d, 14e, 14f, and 16d, 16e, 16f.
- Rotors 14, 16 are respectively mounted for rotation in cylindrical chambers 32, 34 about axes coincident with the longitudinally extending, transversely spaced apart, parallel axes of the cylindrical chambers. Such mountings are well-known in the art. Hence, it should suffice to say that unshown shaft ends extending from and fixed to the rotors are supported by unshown bearings carried by end wall 20c and end section 24. Bearings for carrying the shaft ends extending rightwardly into end section 24 are carried by outwardly projecting bosses 24b, 24c.
- the rotors may be mounted and timed as shown in EP-A-0135256 and incorporated herein by reference.
- Rotor 16 is directly driven by pulley 18 which is fixed to the left end of a shaft 40.
- Shaft 40 is either connected to or an extension of the shaft end extending from the left end of rotor-16.
- Rotor 14 is driven in a conventional manner by unshown timing gears fixed to the shaft ends extending from the left ends of the rotors.
- the timing gears are of the substantially no backlash type and are disposed in a chamber defined by a portion 22a of end section 22.
- the rotors have three circumferentially spaced lobes of modified involute profile with an end-to-end helical twist of 60°.
- Rotors with other than three lobes, with different profiles and with different twist angles, may be used to practice certain aspects or features of the inventions disclosed herein.
- the lobes are preferably provided with a helical twist from end-to-end which is substantially equal to the relation 360°/2n, where n equals the number of lobes per rotor.
- involute profiles are also preferred since such profiles are more readily and accurately formed than most other profiles; this is particularly true for helically twisted lobes.
- involute profiles are preferred since they have been more readily and accurately timed during supercharger assembly.
- inlet receiver chamber 36a is defined by portions of the cylindrical wall surfaces disposed between top lands 14e, 16e and the lobe surfaces extending from the top lands to the interface M of meshing lobes 14c, 16c.
- Interface M defines the point or points of closest contact between the meshing lobes.
- outlet receiver chamber 38a is defined by portions of the cylindrical wall surfaces disposed between, top lands 14d, 16d and the lobe surfaces extending from the top lands to the interface M of meshing lobes 14c, 16c.
- meshing interface M moves along the lobe profile and is often defined at several places such as illustrated in FIGURES 6 and 7.
- the cylindrical wall surfaces defining both the inlet and outlet receiver chambers include those surface portions which were removed to define the inlet and outlet ports.
- Transfer volume 32a is defined by adjacent lobes 14a, 14b and the portion of cylindrical wall surfaces 20a disposed between top lands 14d, 14e.
- transfer volume 34a is defined by adjacent lobes 16a, 16b and the portion of cylindrical wall surface 20b disposed between top lands 16d, 16e. As the rotors turn, transfer volumes 32a, 34a are reformed between subsequent pairs of adjacent lobes.
- Inlet port 36 is provided with an opening shaped substantially like an isosceles trapezoid by wall surfaces 20f, 20g, 20h, 20i defined by housing section 20.
- Wall surfaces 20f, 20h define the longitudinal extent of the port and wall surfaces 20g, 20i define the transverse boundaries or extent of the port.
- the isosceles sides or wall surfaces 20g, 20i are matched or substantially parallel to the traversing top lands of the lobes.
- the top lands of the helically twisted lobes in both FIGURES 3 and 4 are schematically illustrated as being straight for simplicity herein. As viewed in FIGURES 3 and 4, such lands actually have a curvature.
- Wall surfaces 20g, 20i may be curved to more closely conform to the helical twist of the top lands.
- Outlet port 38 is provided with a somewhat T-shaped opening by wall surfaces 20m, 20n, 20p, 20r, 20s, 20t:defined by housing section 20.
- the top surface of housing 20 includes a recess 20wto provide an increased flow area for outlet duct 28.
- Wall surfaces 20m, 20r are parallel and define the longitudinal extent or boundaries of the port.
- Wall surfaces 20p, 20s and their projections to surface 20m define the transverse boundaries or extent of the port for outflow of most air from the blower.
- Wall surfaces 20p, 20s are also parallel and may be spaced farther apart than shown herein if additional outlet port area is needed to prevent a pressure drop or back pressure across the outlet port.
- the expanding orifices control the rate of back flow air into the transfer volumes.
- Orifices 42, 44 are designed to expand at a rate operative to maintain a substantially constant backflow rate of air into the transfer volumes when the blower operates at predetermined speed and differential pressure relationships.
- Apexes 20x, 20z are respectively spaced approximately 60 rotational degrees from surfaces 20p, 20s and are alternately transversed by the top lands of the associated lobes.
- inlet port wall surfaces 20g, 20i and the apexes allow the top lands of the trailing lobes of each transfer volume to move into sealing relation with the cylindrical wall surfaces before backflow starts and allows a full 60° rotation of the lobes for backflow.
- curves S and H illustrate cyclic variations in volumetric displacement over 60° periods of rotor rotation.
- the variations are illustrated herein in terms of degrees of rotation but may be illustrated in terms of time.
- Such cyclic variations are due to the meshing geometry of the rotor lobes which effect the rate of change of volume of the outlet receiver chamber 38a. Since the inlet and outlet receiver chamber volumes vary at substantially the same rate and merely inverse to each other, the curves for outlet receiver chamber 38a should suffice to illustrate the rate of volume change for both chambers.
- Curve S illustrates the rate of change for a blower having three straight lobes of modified involute profile per rotor and curve H for a blower having three 60° helical twist lobes of modified involute profile per rotor.
- the absolute value of rate-of-change is approximately 7% of theoretical displacement for straight lobe rotors while there is no variation in the rate of displacement for 60° helical lobes.
- the rate of volume change or uniform displacement for both straight and helical lobes is due in part to the meshing geometry of the lobes.
- the meshing relationship of the lobes is the same along the entire length of the lobes, i.e., the meshing relationship at any cross section or incremental volume along the meshing lobes is the same.
- interface or point M of FIGURE 2 is the same along the entire length of the meshing lobes, and a line through the points is straight and parallel to the rotor axis.
- a rate of volume change, due to meshing geometry is the same and additive for all incremental . volumes along the entire length of the meshing lobes.
- Volumes of fluid trapped between meshing lobes are another cause or source affecting the rate of cyclic volume change of the receiver chambers.
- the trapped volumes are abruptly removed from the outlet receiver chamber and abruptly returned or carried back to the inlet receiver chamber.
- the trapped volumes also reduce blower displacement and pumping efficiency.
- Curves ST and HT in the graph of FIGURE 5 respectively illustrate the rate of cyclic volume change of the outlet receiver chamber due to trapped volumes for straight and 60° helical twist lobes. As may be seen the rate of volume change, as a percentage of theoretical displacement due to trapped volumes is approximately 4.5 times greater for straight lobes.
- the total rate of volume change of the receiver chamber is obtained by adding the associated curves for meshing geometry and trapped volume together.
- FIGURES 6 and 7 therein is shown areas trapped between adjacent lobes 14a, 14c and 16c.
- the areas may be thought of as incremental volumes when they have a small depth.
- the areas for meshing relationship of FIGURE 6 represents a maximum incremental volume TV 1 .
- incremental volume TV decreases in size while a second incremental volume TV 2 is formed which increases in size.
- each maximum incremental volume TV 1 is formed along the entire length of the meshing lobes at substantially the same instant.
- each incremental volume TV 2 is formed along the entire length of the meshing lobes at substantially the same instant.
- the individual sums ⁇ TV 1 and rTV 2 of the incremental volumes define or form trapped volumes.
- ⁇ TV 1 and ⁇ TV 2 contribute to airborne noise and reduced blower efficiency. Both, particularly ⁇ TV 1 , cause substantial rates of volume change as illustrated in the graph of FIGURE 5.
- the carryback of fluid in ⁇ TV 1 and the respective decrease and increase in the size of 7-TV, and 2:TV2 directly reduce blower efficiency.
- Helical lobes greatly reduce the size of TV, and TV 2 ; this may be illustrated with reference to FIGURE 6, which is an end view of the rightward end of the rotors.
- FIGURE 6 is an end view of the rightward end of the rotors.
- incremental volume TV, at the rightward end of meshing lobes 14a, 14c and 16c is not trapped and subsequent incremental volumes TV, from right-to-left are not trapped until the leftward end of lobes 14a, 14c and 16c move into the same meshing relationship.
- For 60° twist lobes this does not occur until the rotors turn an additional 60°.
- each successive incremental volume TV, from right-to-left decreases in size while still in communication with the outlet receiver chamber.
- the number of trapped incremental volumes TV is greatly reduced. Further, the total volume of this number of trapped incremental volumes is less than the total volume of a comparable number of straight lobe incremental volumes since trapped incremental volumes with helical lobes vary in cross-sectional area from a minimum to a maximum.
- the number of trapped incremental volumes TV 2 and their total volume is the same as described for incremental volumes TV,. However, their formation sequence occurs in the reverse order, i.e., when incremental volume TV 2 starts to form and expand at the right end of the lobes, it and subsequent incremental volumes TV 2 are trapped until the right end of the lobes moves to the meshing relationship shown in FIGURE 8; from thereon all incremental volumes TV 2 are in constant communication with the inlet receiver chamber.
- Outlet port 138 is provided with a somewhat hourglass shaped opening by wall surfaces 120m, 120n, 120p, 120q defined by housing section 20'.
- the top surface of housing 20' includes a recess 20w' to provide an increased flow area for outlet duct 28.
- Spaced apart wall surfaces 120m, 120p extend transverse to the rotational axes of the rotors and define the longitudinal extent or boundaries of the port.
- Spaced apart wall surfaces 120n, 120q extend between wall surfaces 120m, 120p and define the transverse boundaries of the port.
- Wall surfaces 120n, 120q respectively include surface portions 120r, 120s convergently extending from wall surface 120p toward wall surface 120m and surface portions 120t, 120u convergently extending from wall surface 120m to points of intersection with portions 120r, 120s.
- Surface portions 120t, 120u and wall surface 120m cooperate with the top lands of the rotor lobes to provide expanding orifices 142, 144 which begin at apexes 120x, 120z and which are alternately active.
- the expanding orifices control the rate of backflow air into the transfer volumes.
- Orifices 142, 144 may be designed to expand at a rate operative to maintain a substantially constant backflow rate of air into the transfer volumes when the blower operates at predetermined speed and differential pressure relationships. When such relationships exist, the traversing lands will be traversing surface portions 120r, 120s at the instant backflow ceases.
- Apexes 120x, 120z are respectively spaced approximately 60 rotational degrees from the intersections 142a, 144a of surface portions 120t, 120r and 120s, 120u, and are alternately traversed by the top lands of the associated lobes.
- the spacing between inlet port wall surfaces 120g, 120i and the apexes allows the top lands of the trailing lobes of each transfer volume to move into sealing relation with the cylindrical wall surfaces before backflow starts and allows a full 60° rotation of the lobes for backflow.
- Apexes 120x, 120z may be positioned to allow backflow slightly before the top lands .of the trailing lobes of each transfer volume move into sealing relation with cylindrical wall surfaces 20a, 20b, thereby providing a slight overlap between the beginning and ending of backflow to ensure a smooth and continuous transition of backflow from one transfer volume to the next.
- outlet port 138 effectively divides the port into controlled backflow areas and an unrestricted outflow area.
- the exact shape of outlet port may vary substantially from what is illustrated herein yet still provide substantial advantages.
- the angles or inclination of surface portions 120t, 120u with wall surface 20m may be greater or less than as shown herein.
Description
- The invention of this application relates to European Applications published as EP-A-0176269 and 0176268. These applications are assigned to the assignee of this application, and all are incorporated herein by reference.
- This invention relates to rotary compressors or blowers, particularly to blowers of the backflow type. More specifically, the present invention relates to reducing airborne noise associated wityh Roots-type blowers employed as superchargers for internal combustion engines.
- Rotary blowers particularly Roots-type blowers are characterized by noisy operation. The blower noise may be roughly classified into two groups: solid borne noise caused by rotation of timing gears and rotor shaft bearings subjected to fluctuating loads, and fluid borne noise caused byfluid flow characteristics such as rapid changes in fluid velocity. Fluctuating fluid flow contributes to both solid and fluid borne noise.
- As is well-known, Roots-type blowers are similar to gear-type pumps in that both employ toothed or lobed rotors meshingly disposed in transversely overlapping cylindrical chambers. Top lands of the lobes sealingly cooperate with the inner surfaces of the cylindrical chambers to trap and transfer volumes of fluid between adjacent lobes on each rotor. Roots-type blowers are used almost exclusively to pump or transfer volumes of compressible fluids, such as air, from an inlet receiver chamber to an outlet receiver chamber. Normally, the inlet chamber continuously communicates with an inlet port and the outlet chamber continuously communicates with an outlet port. The inlet and outlet ports often have a transverse width nominally equal to the transverse distance between the axes of the rotors. Hence, the cylindrical wall surfaces on either side of the ports are nominally 180° in arc length. Each receiver chamber volume is defined by the inner boundary of the associated port, the meshing interface of the lobes, and sealing lines between the top lands of the lobes and cylindrical wall surfaces. The inlet receiver chamber expands and contracts between maximum and minimum volumes while the outlet receiver chamber contracts and expands between like minimum and maximum volumes. In most Roots-type blowers, transfer volumes are moved to the outlet receiver chamber without compression of the air therein by mechanical reduction of the transfer volume size. If outlet port air pressure is greater than the air pressure in the transfer volume, outlet port air rushes or backflows into the volumes as they become exposed to or merged into the outlet receiver chamber. Backflow continues until pressure equalization is reached. The amount of backflow air and rate of backflow are, of course, a function of pressure differential. Backflow into one transfer volume which ceases before backflow starts into the next transfer volume, or which varies in rate, is said to be cyclic and is a known major source of airborne noise. A blower in which compression is realized by way of this backflow is hereinafter called a backflow blower.
- Another major source of airborne noise is cyclic variations in volumetric displacement or nonuniform displacement of the blower. Nonuniform displacement is caused by cyclic variations in the rate of volume change of the receiver chamber due to meshing geometry of the lobes and due to trapped volumes between the meshing lobes. During each mesh of the lobes first and second trapped volumes are formed. The first trapped volumes contain outlet port or receiver chamber air which is abruptly removed from the outlet receiver chamber as the lobes move into mesh and abruptly returned or carried back to the inlet receiver chamber as the lobes move out of mesh. As the differential pressure between the receiver chambers increases, so does the mass of carry-over air to the inlet receiver chamber with corresponding increases in the rate of volume change in the receiver chambers and corresponding increases in airborne noise. Further, blower efficiency decreases as the mass of carry-over air increases.
- The trapped volumes are further sources of airborne noise and inefficiency for both straight and helical lobed rotors. With straight lobed rotors, both the first and second trapped volumes are formed along the entire length of the lobes, whereas with helical lobes rotors, the trapped volumes are formed along only a portion of the length of the lobes with a resulting decrease in the degrading effects on noise and efficiency. The first trapped volumes contain outlet port air and decrease in size from a maximum to a minimum, with a resulting compressing of the fluid therein. The second trapped volumes are substantially void of fluid and increase in size from a minimum to a maximum with a resulting vacuum tending expansion of fluid therein. The resulting compression of air in the first trapped volumes, which are subsequently expanded back into the inlet port, and expansion of the second trapped volumes are sources of airborne noise and inefficiencies.
- Many prior art patents have addressed the problems of airborne noise. For example, it has long been known that nonuniform displacement, due to meshing geometry, is greater when rotor lobes are straight or parallel to the rotor axes and that substantially uniform displacement is provided when the rotor lobes are helically twisted. US-A-2,014,932 to Hallett teaches substantially uniform displacements with a Roots-type blower having two rotors and three 60° helical twist lobes per rotor. Theoretically, such helical lobes could or would provide uniform displacement were it not for cyclic backflow and trapped volumes. Nonuniform displacement, due to trapped volumes, is of little or no concern with respect to the Hallett blower since the lobe profiles therein inherently minimize the size of the trapped volumes. However, such lobe profiles, in combination with the helical twist, can be difficult to accurately manufacture and accurately time with respect to each other when the blowers are assembled.
- Hallett also addressed the backflow problem and proposed reducing the initial rate of backflow to reduce the instantaneous magnitude of the backflow pulses. This was done by a mismatched or rectangular shaped outlet port having two sides parallel to the rotor axes and, therefore, skewed relative to the traversing top lands of the helical lobes. US―A―2,463,080 to Beier is considered the State of the Art and discloses a related backflow solution for a straight lobe blower by employing a triangular outlet port having two sides skewed relative to the rotor axes and, therefore, mismatched relative to the traversing lands of the straight lobes. The arrangement of Hallett and Beier slowed the initial rate of backflow into the transfer volume and therefore reduced the instantaneous magnitude of the backflow. However, both of these arrangements inherently limit or restrict outlet port area available for outflow of air following backflow. Hence, the outlet ports, which slow the initial backflow rate, can undesirably restrict the outflow of air and thereby contribute to airborne noise and inefficiencies. However, neither teaches nor suggests controlling the rate of backflow so as to obtain a continuous and constant rate of backflow.
- Several other prior art U.S. Patents have also addressed the backflow problem by preflowing outlet port or receiver chamber air into the transfer volumes before the lands of the leading lobe of each transfer volume traverses the outer boundary of the outlet port. In some of these patents, preflow is provided by passages of fixed flow area through the cylindrical walls of the housing sealing cooperating with the top lands of the rotor lobes. Since the passages are of fixed flow area, the rate of preflow decreases with decreasing differential pressure. Hence, the rate of preflow is not constant.
- US-A-4,215,977 to Weatherston discloses preflow and purports to provide a Roots-type blower having uniform displacement. However, the lobes of Weatherston are straight and, therefore, believed incapable of providing uniform displacement due to meshing geometry.
- The Weatherston blower provides preflow of outlet receiver chamber air to the transfer volumes via. circumferentially disposed, arcuate channels or slots formed in the inner surface of the cylindrical walls which sealingly. cooperate with the top lands of the rotor lobes. The top lands and channels cooperate to define orifices for directing outlet receiver chamber air into the transfer volumes. The arc or setback length of the channels determines the beginning of preflow. Weatherston suggests the use of additional channels of lesser setback length to hold the rate of preflow relatively constant as pressure in the transfer volumes increases. The Weatherston preflow arrangement, which is analogous to backflow, is believed theoretically capable of providing a relatively constant preflow rate for predetermined blower speeds and differential pressures. However, to obtain relatively constant preflow, several channels of different setback length would be necessary. Further, accurate and consistent forming of the several channels on the interior surface of the cylindrical walls is, at best, an added manufacturing cost.
- An object of the present invention is to provide a rotary blower of the backflow type for compressible fluids which is relatively free of airborne noises due to nonuniform displacement.
- Another object of the present invention is to provide a rotary blower of the backflow type for compressible fluids wherein backflow is relatively constant when the blower operates at predetermined speeds and differential pressures.
- Another object of the present invention is to provide a rotary blower of the backflow type for compressible fluids wherein nonuniform displacement, due to meshing geometry and trapped volumes, is substantially eliminated. US-A-2463080 discloses the pre-characterizing portion of Claim 1 but can undesirably restrict outflow.
- According to an important feature of the present invention set out in Claim 1, a rotary blower of the backflow type includes a housing defining inlet and outlet ports and a chamber containing first and second meshed lobes rotors for transferring volumes of relatively low- pressure inlet port fluid, via spaces between adjacent, unmeshed lobes, to relatively highpressure outlet port fluid, which alternately backflows into each volume in response to alternate and initial travesing of wall surfaces, defining traversely opposite boundaries of the outlet port. The subject matter of Claim 1 is insofar different that
- the inlet port is a single opening extending through at least a portion of one of the cusps and with the first and second transverse boundaries thereof disposed on opposite sides of the one cusp;
- the outlet port is a single opening extending through at least a portion of the other cusp and with the first and second transverse boundaries thereof disposed on opposite sides of the other cusp; and
- the first and second backflow means are respectively defined by V-shaped extensions of the outlet port first and second transverse boundaries, each V-shaped extension extending counter to the direction of rotation of the respective rotor and with an apex of each V-shaped extension defining the maximum extension of each and with each apex being positioned for traversal by the top land of the lead lobe of the respective upcoming transfer volume of the associated rotor at approximately the same time the top land of the lead lobe of the preceding transfer volume of the other rotor traverses the outlet port transverse boundary associated therewith, whereby said backflow means are alternately operative at predetermined rotor speeds and pressure differential relationships to maintain a substantially constant backflow rate into each of the transfer volumes.
- According to another feature of the present invention, the outlet port longitudinal and traverse boundaries and the expanding orifices form a somewhat hourglass port shape.
-
- FIGURE 1 is a side elevational view of the Roots-type blower;
- FIGURE 2 is a schematic sectional view of the blower looking along line 2-2 FIGURE 1;
- FIGURE 3 is a bottom view of a portion of the blower looking in the direction of arrow 3 in FIGURE 1;
- FIGURE 4 is a top view of a portion of the blower looking along line 4-4 of FIGURE 1;
- FIGURE 5 is a graph illustrating operational characteristics of the blower;
- FIGURES 6 and 8 are reduced views of the blower section of FIGURE 2 with the meshing relationships of the rotors therein varied; and
- FIGURE 9 illustrates an alternate shape of the outlet port of FIGURE 4.
- FIGURES 1-4 illustrate a rotary pump or
blower 10 of the Roots-type. As previously mentioned, such blowers are used almost exclusively to pump or transfer volumes of compressible fluid, such as air, from an inlet port to an outlet port without compressing the transfer volumes prior to exposure to the outlet port. The rotors operate somewhat like gear-type pumps, i.e., as the rotor teeth or lobes move out of mesh, air flows into volumes or spaces defined by adjacent lobes on each rotor. The air in the volumes is then trapped therein at substantially inlet pressure when the top lands of the trailing lobe of each transfer volume moves into a sealing relation with the cylindrical wall surfaces of the associated chamber. The volumes of air are transferred or exposed to outlet air when the top land of the leading lobe of each volume moves out of sealing relation with the cylindrical wall surfaces by traversing the boundary of the outlet port. If the volume of the transfer volumes remains constant during the trip from inlet to outlet, the air therein remains at inlet pressure, i.e., transfer volume air pressure remains constant if the top lands of the leading lobes traverse the outlet port boundary before the volumes are squeezed by virtue of remeshing of the lobes. Hence, if air pressure at the discharge port is greater than inlet port presure, outlet port air rushes or backflows into the transfer volumes as the top lands of the leading lobes traverse the outlet port boundary. -
Blower 10 includes ahousing assembly 12, a pair oflobed rotors 14, 16, and an input drive pulley 18.Housing assembly 12, as viewed in FIGURE 1, includes acenter section 20, left andright end sections 22, 24 secured to opposite ends of the center section by a plurality of bolts 26, and anoutlet duct member 28 secured to the center section by a plurality of unshown bolts. The housing assembly and rotors are preferably formed from a lightweight material such as aluminum. The center section and end 24 define a pair of generally cylindrical workingchambers surfaces 20a, 20b, an end wall surface indicated by phantom line 20c in FIGURE 1, and an end wall surface 24a.Chambers Openings center section 20 respectively define the transverse and longitudinal boundaries of inlet and outlet ports. -
Rotors 14,16 respectively include three circumferentially spaced apart helical teeth or lobes 14a, 14b, 14c and 16a, 16b, 16c of modified involute profile with an end-to-end twist of 60°. The lobes of teeth mesh and preferably do not touch. A sealing interface between meshing lobes 14c, 16c is represented by point M in FIGURE 2. Interface or point M moves along the lobe profiles as the lobes progress through each mesh cycle and may be defined in several places as shown in FIGURE 7. The lobes also includetop lands Rotors 14, 16 are respectively mounted for rotation incylindrical chambers end section 24. Bearings for carrying the shaft ends extending rightwardly intoend section 24 are carried by outwardly projecting bosses 24b, 24c. The rotors may be mounted and timed as shown in EP-A-0135256 and incorporated herein by reference. Rotor 16 is directly driven by pulley 18 which is fixed to the left end of ashaft 40.Shaft 40 is either connected to or an extension of the shaft end extending from the left end of rotor-16.Rotor 14 is driven in a conventional manner by unshown timing gears fixed to the shaft ends extending from the left ends of the rotors. The timing gears are of the substantially no backlash type and are disposed in a chamber defined by a portion 22a of end section 22. - The rotors, as previously mentioned, have three circumferentially spaced lobes of modified involute profile with an end-to-end helical twist of 60°. Rotors with other than three lobes, with different profiles and with different twist angles, may be used to practice certain aspects or features of the inventions disclosed herein. However, to obtain uniform displacement based on meshing geometry and trapped volumes, the lobes are preferably provided with a helical twist from end-to-end which is substantially equal to the relation 360°/2n, where n equals the number of lobes per rotor. Further, involute profiles are also preferred since such profiles are more readily and accurately formed than most other profiles; this is particularly true for helically twisted lobes. Still further, involute profiles are preferred since they have been more readily and accurately timed during supercharger assembly.
- As may be seen in FIGURE 2, the rotor lobes and cylindrical wall surfaces sealingly cooperate to define an inlet receiver chamber 36a, an
outlet receiver chamber 38a, and transfer volumes 32a, 34a. For the rotor positions of FIGURE 2, inlet receiver chamber 36a is defined by portions of the cylindrical wall surfaces disposed betweentop lands outlet receiver chamber 38a is defined by portions of the cylindrical wall surfaces disposed between, top lands 14d, 16d and the lobe surfaces extending from the top lands to the interface M of meshing lobes 14c, 16c. During each meshing cycle and as previously mentioned, meshing interface M moves along the lobe profile and is often defined at several places such as illustrated in FIGURES 6 and 7. The cylindrical wall surfaces defining both the inlet and outlet receiver chambers include those surface portions which were removed to define the inlet and outlet ports. Transfer volume 32a is defined by adjacent lobes 14a, 14b and the portion of cylindrical wall surfaces 20a disposed betweentop lands 14d, 14e. Likewise, transfer volume 34a is defined by adjacent lobes 16a, 16b and the portion of cylindrical wall surface 20b disposed betweentop lands 16d, 16e. As the rotors turn, transfer volumes 32a, 34a are reformed between subsequent pairs of adjacent lobes. -
Inlet port 36 is provided with an opening shaped substantially like an isosceles trapezoid by wall surfaces 20f, 20g, 20h, 20i defined byhousing section 20. Wall surfaces 20f, 20h define the longitudinal extent of the port and wall surfaces 20g, 20i define the transverse boundaries or extent of the port. The isosceles sides or wall surfaces 20g, 20i are matched or substantially parallel to the traversing top lands of the lobes. The top lands of the helically twisted lobes in both FIGURES 3 and 4 are schematically illustrated as being straight for simplicity herein. As viewed in FIGURES 3 and 4, such lands actually have a curvature. Wall surfaces 20g, 20i may be curved to more closely conform to the helical twist of the top lands. -
Outlet port 38 is provided with a somewhat T-shaped opening by wall surfaces 20m, 20n, 20p, 20r, 20s, 20t:defined byhousing section 20. The top surface ofhousing 20 includes a recess 20wto provide an increased flow area foroutlet duct 28. Wall surfaces 20m, 20r are parallel and define the longitudinal extent or boundaries of the port. Wall surfaces 20p, 20s and their projections to surface 20m define the transverse boundaries or extent of the port for outflow of most air from the blower. Wall surfaces 20p, 20s are also parallel and may be spaced farther apart than shown herein if additional outlet port area is needed to prevent a pressure drop or back pressure across the outlet port. Diagonal wall surfaces 20n, 20t, which converge with transverse extensions of wall surface 20m atapexes 20x, 20z to form V-shaped backflow means 42, 44 which define expanding orifices in combination with the transversing top lands of the lobes. The expanding orifices control the rate of back flow air into the transfer volumes.Orifices Apexes 20x, 20z are respectively spaced approximately 60 rotational degrees from surfaces 20p, 20s and are alternately transversed by the top lands of the associated lobes. The spacing between inlet port wall surfaces 20g, 20i and the apexes allows the top lands of the trailing lobes of each transfer volume to move into sealing relation with the cylindrical wall surfaces before backflow starts and allows a full 60° rotation of the lobes for backflow. - Looking now for a moment at the graph of FIGURE 5, therein curves S and H illustrate cyclic variations in volumetric displacement over 60° periods of rotor rotation. The variations are illustrated herein in terms of degrees of rotation but may be illustrated in terms of time. Such cyclic variations are due to the meshing geometry of the rotor lobes which effect the rate of change of volume of the
outlet receiver chamber 38a. Since the inlet and outlet receiver chamber volumes vary at substantially the same rate and merely inverse to each other, the curves foroutlet receiver chamber 38a should suffice to illustrate the rate of volume change for both chambers. Curve S illustrates the rate of change for a blower having three straight lobes of modified involute profile per rotor and curve H for a blower having three 60° helical twist lobes of modified involute profile per rotor. As may be seen, the absolute value of rate-of-change is approximately 7% of theoretical displacement for straight lobe rotors while there is no variation in the rate of displacement for 60° helical lobes. - The rate of volume change or uniform displacement for both straight and helical lobes, as previously mentioned, is due in part to the meshing geometry of the lobes. For straight lobes, the meshing relationship of the lobes is the same along the entire length of the lobes, i.e., the meshing relationship at any cross section or incremental volume along the meshing lobes is the same. For example, interface or point M of FIGURE 2 is the same along the entire length of the meshing lobes, and a line through the points is straight and parallel to the rotor axis. Hence, a rate of volume change, due to meshing geometry, is the same and additive for all incremental . volumes along the entire length of the meshing lobes. This is not the case for helical lobes formed according to the relation 360°/2n. For three lobe rotors having 60° helical lobes, the meshing relationship varies along the entire length of the meshing lobes over a 60° period. For example, if the meshing lobes were divided into 60 incremental volumes along their length, 60 different meshing relationships would exist at any given time, and a specific meshing relationship, such as illustrated in FIGURE 2, would first occur at one end of the meshing lobes and then be sequentially repeated for each incremental volume as the rotors turn through 60 rotational degrees. If the meshing relationship of an incremental volume at one end of meshing lobes tends to increase the rate of volume change, the meshing relationship of the incremental volume at the other end of the meshing lobes tends to decrease the rate of volume change an equal amount. This additive- substractive or canceling relationship exists along the entire length of the meshing lobes and thereby cancels rates of volume change or provides uniform displacement with respect to meshing geometry.
- Volumes of fluid trapped between meshing lobes are another cause or source affecting the rate of cyclic volume change of the receiver chambers. The trapped volumes are abruptly removed from the outlet receiver chamber and abruptly returned or carried back to the inlet receiver chamber. The trapped volumes also reduce blower displacement and pumping efficiency. Curves ST and HT in the graph of FIGURE 5 respectively illustrate the rate of cyclic volume change of the outlet receiver chamber due to trapped volumes for straight and 60° helical twist lobes. As may be seen the rate of volume change, as a percentage of theoretical displacement due to trapped volumes is approximately 4.5 times greater for straight lobes. The total rate of volume change of the receiver chamber is obtained by adding the associated curves for meshing geometry and trapped volume together.
- Looking briefly at the rightward end of the rotors, as illustrated in FIGURES 6 and 7, therein is shown areas trapped between adjacent lobes 14a, 14c and 16c. The areas may be thought of as incremental volumes when they have a small depth. The areas for meshing relationship of FIGURE 6 represents a maximum incremental volume TV1. With reference to FIGURE 7, as the rotors turn, incremental volume TV,, decreases in size while a second incremental volume TV2 is formed which increases in size.
- For straight lobe rotors, each maximum incremental volume TV1 is formed along the entire length of the meshing lobes at substantially the same instant. Likewise, each incremental volume TV2 is formed along the entire length of the meshing lobes at substantially the same instant. Hence, the individual sums ΣTV1 and rTV2 of the incremental volumes define or form trapped volumes. ΣTV1 and ΣTV2 contribute to airborne noise and reduced blower efficiency. Both, particularly ΣTV1, cause substantial rates of volume change as illustrated in the graph of FIGURE 5. The carryback of fluid in ΣTV1 and the respective decrease and increase in the size of 7-TV, and 2:TV2 directly reduce blower efficiency.
- Helical lobes greatly reduce the size of TV, and TV2; this may be illustrated with reference to FIGURE 6, which is an end view of the rightward end of the rotors. With helical lobes, incremental volume TV, at the rightward end of meshing lobes 14a, 14c and 16c is not trapped and subsequent incremental volumes TV, from right-to-left are not trapped until the leftward end of lobes 14a, 14c and 16c move into the same meshing relationship. For 60° twist lobes this does not occur until the rotors turn an additional 60°. During this 60° period, each successive incremental volume TV, from right-to-left decreases in size while still in communication with the outlet receiver chamber. Hence, the number of trapped incremental volumes TV, is greatly reduced. Further, the total volume of this number of trapped incremental volumes is less than the total volume of a comparable number of straight lobe incremental volumes since trapped incremental volumes with helical lobes vary in cross-sectional area from a minimum to a maximum. The number of trapped incremental volumes TV2 and their total volume is the same as described for incremental volumes TV,. However, their formation sequence occurs in the reverse order, i.e., when incremental volume TV2 starts to form and expand at the right end of the lobes, it and subsequent incremental volumes TV2 are trapped until the right end of the lobes moves to the meshing relationship shown in FIGURE 8; from thereon all incremental volumes TV2 are in constant communication with the inlet receiver chamber.
- Looking now at the alternately shaped
outlet port 138 of FIGURE 9, therein components identical to components of FIGURE 4 are provided with the same reference numeral, suffixed with a prime.Outlet port 138 is provided with a somewhat hourglass shaped opening by wall surfaces 120m, 120n, 120p, 120q defined by housing section 20'. The top surface of housing 20' includes arecess 20w' to provide an increased flow area foroutlet duct 28. Spaced apart wall surfaces 120m, 120p extend transverse to the rotational axes of the rotors and define the longitudinal extent or boundaries of the port. Spaced apart wall surfaces 120n, 120q extend between wall surfaces 120m, 120p and define the transverse boundaries of the port. Wall surfaces 120n, 120q respectively include surface portions 120r, 120s convergently extending from wall surface 120p toward wall surface 120m and surface portions 120t, 120u convergently extending from wall surface 120m to points of intersection with portions 120r, 120s. Surface portions 120t, 120u and wall surface 120m cooperate with the top lands of the rotor lobes to provide expandingorifices 142, 144 which begin atapexes 120x, 120z and which are alternately active. The expanding orifices control the rate of backflow air into the transfer volumes.Orifices 142, 144 may be designed to expand at a rate operative to maintain a substantially constant backflow rate of air into the transfer volumes when the blower operates at predetermined speed and differential pressure relationships. When such relationships exist, the traversing lands will be traversing surface portions 120r, 120s at the instant backflow ceases. -
Apexes 120x, 120z are respectively spaced approximately 60 rotational degrees from the intersections 142a, 144a of surface portions 120t, 120r and 120s, 120u, and are alternately traversed by the top lands of the associated lobes. The spacing between inlet port wall surfaces 120g, 120i and the apexes allows the top lands of the trailing lobes of each transfer volume to move into sealing relation with the cylindrical wall surfaces before backflow starts and allows a full 60° rotation of the lobes for backflow.Apexes 120x, 120z may be positioned to allow backflow slightly before the top lands .of the trailing lobes of each transfer volume move into sealing relation with cylindrical wall surfaces 20a, 20b, thereby providing a slight overlap between the beginning and ending of backflow to ensure a smooth and continuous transition of backflow from one transfer volume to the next. - While expanding
orifices inlet port 36, the top lands of the helically twisted lobes in are schematically illustrated as being straight for simplicity herein. Such lands actually have a curvature. Hence, surface portions 120r, 120s may be curved to more closely conform to the curvature of the helical twist of the top lands. - The hourglass shape of
outlet port 138 effectively divides the port into controlled backflow areas and an unrestricted outflow area. The exact shape of outlet port may vary substantially from what is illustrated herein yet still provide substantial advantages. For example, the angles or inclination of surface portions 120t, 120u with wall surface 20m may be greater or less than as shown herein.
Claims (11)
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US647072 | 1984-09-04 | ||
US06/647,071 US4564346A (en) | 1984-09-04 | 1984-09-04 | Supercharger with hourglass outlet port |
US647071 | 1984-09-04 | ||
US06/647,072 US4564345A (en) | 1984-09-04 | 1984-09-04 | Supercharger with reduced noise |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0174171A2 EP0174171A2 (en) | 1986-03-12 |
EP0174171A3 EP0174171A3 (en) | 1987-03-18 |
EP0174171B1 true EP0174171B1 (en) | 1990-03-07 |
Family
ID=27095079
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19850306198 Expired EP0174171B1 (en) | 1984-09-04 | 1985-09-02 | Supercharger with reduced noise |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP0174171B1 (en) |
DE (1) | DE3576390D1 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0458134A1 (en) * | 1990-05-25 | 1991-11-27 | Eaton Corporation | Inlet port opening for a Roots-type blower |
EP0458135A1 (en) * | 1990-05-25 | 1991-11-27 | Eaton Corporation | Roots-type blower with improved inlet |
EP1286053A1 (en) | 2001-08-21 | 2003-02-26 | Ford Global Technologies, Inc., A subsidiary of Ford Motor Company | Rotary pump with backflow |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2028414A (en) * | 1933-05-19 | 1936-01-21 | Fairbanks Morse & Co | Fluid displacement device |
US2701683A (en) * | 1951-12-15 | 1955-02-08 | Read Standard Corp | Interengaging rotor blower |
AT242855B (en) * | 1962-02-21 | 1965-10-11 | Polysius Gmbh | Roots blower |
US3667874A (en) * | 1970-07-24 | 1972-06-06 | Cornell Aeronautical Labor Inc | Two-stage compressor having interengaging rotary members |
DE3238015C2 (en) * | 1982-10-13 | 1986-07-31 | Aerzener Maschinenfabrik Gmbh, 3251 Aerzen | Roots compressor |
-
1985
- 1985-09-02 DE DE8585306198T patent/DE3576390D1/en not_active Expired - Lifetime
- 1985-09-02 EP EP19850306198 patent/EP0174171B1/en not_active Expired
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0458134A1 (en) * | 1990-05-25 | 1991-11-27 | Eaton Corporation | Inlet port opening for a Roots-type blower |
EP0458135A1 (en) * | 1990-05-25 | 1991-11-27 | Eaton Corporation | Roots-type blower with improved inlet |
EP1286053A1 (en) | 2001-08-21 | 2003-02-26 | Ford Global Technologies, Inc., A subsidiary of Ford Motor Company | Rotary pump with backflow |
US6589034B2 (en) | 2001-08-21 | 2003-07-08 | Ford Global Technologies, Inc. | Backflow orifice for controlling noise generated by a rotary compressor |
Also Published As
Publication number | Publication date |
---|---|
EP0174171A2 (en) | 1986-03-12 |
DE3576390D1 (en) | 1990-04-12 |
EP0174171A3 (en) | 1987-03-18 |
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