US3542496A - Dishwasher pump - Google Patents

Description

United States Patent [72] Inventors Richard P-BEIgESOIl 3,359,907 12/1967 Bochan 103/3 Lambs Grove; 3,364,860 1/1968 Matzen 103/3 Charles W. Burkland; Thomas R. Smith, 1,635,786 7/1927 Holmes 103/96 Newton, Iowa 3,374,744 3/1968 Toma 103/96 1 1 1 738,282 FOREIGN PATENTS [221 Flled 3133: 678,531 l/l964 Canada 103 3 [451 patiamed 1 678,669 4 1951 Great Britain 103/3 [73] Asslgnee The Maytag Company Newton Iowa Primary Examiner-William L. Freeh a corporation of Delaware Attorney-William G. Landwier ABSTRACT: A pumping apparatus is disclosed that includes a [54] DISHWASHER PUMP housing defining a pump cavity having a central axis and an Claims6 Drawing FigS inlet and outlet spaced apart axially and extending substantially tangentially from radially outwardly disposed portions of [52] US. Cl 417/423, the cavity Ah n is rotatahh/ operable within the cavity 4l5/143,4l5/71,4l5/l 8,415/208 for pumping fluid from the inlet along a ramp means in a [5]] InLCl ..F04b 17/00, spitalhke path toward the Outlet This pump i f l in a F04b 1/00 reversible dual pumping assembly in turn useful in a dishwash- Field of Search l03/3.4, 96, m pumping System where the pump embodying the featumS 2(a) 3; 230/42 of the instant invention, is operable for effecting a relatively low positive pressure head at the outlet in one direction of [56] References cued rotation and a relatively high pressure head at the outlet in the UNITED STATES PATENTS opposite direction of rotation while the other pump effects 2,764,096 9/1956 Engstrom 103/3 unidirectional fluid flow therethrough in both directions of 3,301,]88 l/l967 Belonger 103/3 rotation.

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a c: O Q 64 25 63 L w- /o r 4 3 Patented Nov. 24, 1970 3,542,496

Sheet 2 of2 INVENToas RICHARD R BRGESON CHARLES W BUQKLAND THOMA$ [2. SMITH gkamm DISHWASHER PUMP BACKGROUND OF THE INVENTION 1. Field of the Invention:

This invention relates to pumps and more specifically to a pump structure having ,an inlet and outlet axiallyspaced apart for achieving a unique fluid flow between the inlet and the outlet.

2. Description ofthe Prior Art Prior art has shown pumps operable for effecting a relatively low rate of pumping in one direction and a relatively high rate of pumping in the opposite direction. Generally these pumps have been of. the centrifugal type with the inlet disposed substantially axially with respect to the pump cavity and the outlet disposed substantially tangentially with respect to the cavity.

Other prior art has shown turbine-type pumps having an inlet and outlet disposed tangentially to the cavity and both in a plane juxtaposed the impeller. This type of pump is operable for effecting relatively equal flow in either direction.

SUMMARY OF THE INVENTION and outlet and a unique fluid control means wherein the pump assembly is operable for effecting a first relatively high-pressure head in a first direction and a second substantially lower pressure head in the second direction.

The above objectives are realized in a pump assembly including a housing defining a cavity having a substantially central axis and having an inlet and outlet axially spaced apart and extending nonradially from the cavity. An impeller is rotatably operable within the cavity for inducing pumping from said inlet along a ramp means in a spirallike path toward the outlet in a first direction of rotation. I

Operation of the device and further objects and advantages thereof will become evident as the description proceeds and from an examination of the accompanying two pages of drawings which illustrate a preferred embodiment of the invention and in which similar numerals refer to similar parts throughout the several views.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of the motor and pump assembly embodying the pump structure of the instant invention with the section view beingtaken substantially along the longitudinal axis of the pump assembly;

FIG. 2 is a schematic drawing showing relative flow patterns of a dishwashing apparatus having a pump assembly embodying the instant invention;

FIG. 3 is a cross-sectional view of a first pump portion as taken along lines 3-3 of FIG. 1;

FIG. 4 is a cross-sectional view of a second pump portion embodying elements of the instant invention as taken along lines 4 of FIG. 1;

FIG. 5 is an enlarged fragmentary sectional view of the central axis portion showing constructional details of the pump assembly of FIG. 1; and

FIG. 6 is a diagrammatic view showing the development of a portion of the second pump cavity.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, there is shown a dual pump assembly including a motor 10 and a first pump 11 and a second pump 12. The motor-driven dual pump assembly 13 shown in FIG. 1

is useful in a dishwashing fluid system as shown schematically in FIG. 2. The dishwasher fluid system is operable for providing a washing fluid to the dishwashing chamber 15 and in cludes a rotatable lower spray arm 16 and a spray nozzle 19 rotatable with the spray arm 16 for spraying washing fluid onto the articles within the chamber 15. The fluid recirculated into the washing chamber 15 by the spray arm 16 and spray nozzle 19 is collected in a sump area 20.

Filter means located in the sump area 20 is self-cleaning and continuously operable for removing particles from the fluid in the sump area 20 as fluid is drawn through the pump II for recirculation to the spray arm I6 and. nozzle 19. The filter means includes acylindrical filter screen 21 having fine mesh openings. Fluid flow from the sump 24) through a first stage filter plate 24 and the filter screen 21 passes through the filtered fluid conduit 25 to the pump 11 and is forced through a recirculation conduit 26 toward the recirculation spray arm 16 and nozzle 19 and the upper spray means 2']. An auxiliary spray arm 28 located within the filter screen 21 is also opera ble for receiving a portion of the fluid from the recirculation conduit 26 and for spraying fluid on the downstream side of the filter screen 21 to remove particles collected on the upstream side thereof. Further constructional and operational details ofa filter of this type may be found in the U.S. Pat. No. 3,090,391 issued to H. J. Kaldenberg et al., May 2 l, 1963, and assigned to the assignee of the instant invention.

Means are provided for supplying fluid to the washing chamber from an external source. The normal fluid level at rest is shown by a broken line 29 in FIG. 2.

Referring to FIG. 2, the sump area 220 communicates with the inlets of two effectively separate pumps 11 and 12 which are part of the combined dual pump assembly. Though shown below the sump 20 in FIG. 2, to more clearly illustrate the fluid system by diagrammatic means, the pumping assembly 13 is positioned adjacent the bottom wall 30 of the washing chamber 15 at substantially the same general elevation as the sump 20. The inlet 31 of the first pump 11, operable for recirculating fluid to the washing chamber I5, is connected to the sump 20 at a position within the filter screen 21 so as to i receive filtered fluid from the sump area 20 for recirculation to the washing chamber 15. This fluid path includes a filtered fluid conduit 25 connecting the sump area 20 to the inlet 31 of the recirculation pump 11 and a recirculation conduit 26 connecting the outlet 32 of the recirculation pump 11 to the lower spray conduit 34, the upper spray conduit 35 and the auxiliary spray conduit 36.

The second pump 12 embodying the instant invention and operable for draining fluid from the washing chamber I5, is connected to the sump 20 at an upstream position from the filter screen 21 so as to receive unfiltered fluid and particles which have collected outside the filter screen 21 during the recirculation of fluid to the washing chamber 15. The drain pump inlet 39 is connected to the sump 20 by the unfiltered fluid conduit 40. A drain conduit 41 extends from the outlet 44 of the drain pump 12 to an external drain. A portion of the drain conduit 41 is elevated above the pump assembly 13 an the lower portion of the washing chamber 15. Y

The pump assembly 13 is driven by a fractional horsepower reversible motor 10 of the type commonly used in household appliances and includes an end bell 45 and a sidewall portion 46 that are connected to the pump housing 60 by a plurality of through bolts 49. The motor stator 50 is carried by the sidewall portion 46 while the armature 51 and shaft 54 are rotatably supported by a first bearing 55 in the end bell 45 and a second bearing 56 retained within a portion of the pump housing 60. The pump housing 60 includes a substantially cylindrical outer portion 61 engageable with the motor sidewall 46 at one end and a pump cover 63 at the other end and further includes aninner portion 64 defining a pair of pump cavities 65, 66 and adapted to receive one end of the armature shaft 54. The motor 10 and pump assembly 13 may be mounted on a dishwashing apparatus through resilient mounts 59 and a bracket 67 attachable to a cabinet panel 62 and washing chamber bottom wall 30 as indicated in FIGS. 3 and 4.

Referring to the central portion 64 of the pump housing 60, as best shown in FIGS. 1 and 5, the end of the armature shaft 54 is rotatively supported by the second bearing 56 and extends into the cavities 65, 66 of the pump housing 60. The second bearing 56 is clamped between a portion of the pump housing 60 and a mounting plate 68 that is in turn secured to the pump housing 60. A retaining ring 69 is axially secured to the shaft 54 and bears against the motor side of bearing 56 to locate the shaft 54 axially with respect to the pump housing 60. The shaft 54 extending into the pump housing 60 is adapted, as by a double-D section, to receive and rotate a pair of impellers 70, 71. The drain pump impeller 71 includes a longitudinally extending hub 73 engageable with a washer 74 abutting the inner race 75 of the second bearing 56 for properly locating the drain impeller 71 within the second pump cavity 66. The recirculation impeller 70 is also mounted on the shaft 54 and includes a hub portion 76 abutting one end of the drain impeller hub 73 to properly locate the recirculation impeller 70 within the first pump cavity 65. A screw member 78 axially retains the two impellers on the shaft 54.

A sealing system is included in the pump assembly 13 to prevent leakage of fluid from either of the pump cavities 65 or 66 into the bearing or the motor areas. There is an annular seal 79 beneath the head of the screw 78 that secures the impellers 70 and 71 to the shaft 54 for preventing leakage around the screw head and through the central mounting opening of the first impeller 70. A second annular seal 80 is provided at the mating juncture of the hubs 76 and 73 of the first and second impellers 70 and 71 to prevent leakage at this point. These two annular seals 79 and 80 are effective for providing a seal between surfaces that rotate as a unit. A seal assembly 81 for preventing leakage at the junction of relatively rotatable members is provided to the left of the second impeller 71. This seal assembly 81 includes a resilient portion 83 sealingly engageable with an annular recess in the housing 60 and further includes a seal ring 84 fixed to this resilient portion 83 and biased by acoil spring 85 toward a wear ring 86 carried by the impeller 71. The wear ring 86 secured to the second impeller 71 is mounted within a recess of the impeller by a resilient cushion member 88.

The housing 60 further defines a fluid vent 89 from the central portion 64 of the pump housing 60 in the area to the left of the seal assembly 81 and extending from the seal area outwardly through the outer portion of thepump housing 60 to allow escape of fluids that might bypass the seal arrangement.

The recirculation pump 11, comprising the first cavity 65 and the recirculation impeller 70 disposed therein, is operable for recirculating fluid to the washing chamber and is shown in FIGS. 1 and 3. This pump 11 is defined at least in part by the pump cover 63 and includes an inlet 31 disposed substantially coaxially with the axis of rotation of the pump assembly 13 and connected to the sump through the filtered fluid conduit 25. The cavity 65 is in the form ofa volute terminating in a substantially tangentially extending outlet 32 connected in 7 turn to the recirculation conduit 26. The recirculation impeller 70 includes a flange portion 90 extending outwardly from the hub 76 and a plurality of arcuate-shaped vanes 91 mounted on one side ofthe flange portion 90. The radially inward portion of the vanes 70 define a central eye 93 coaxially alined with the recirculation pump inlet 31.

The recirculation pump 11 is operable in a clockwise direction as shown in FIG. 3 to effect, through centrifugal pumping, a pressure differential between the inlet 31 and the outlet 32 of the recirculation pump 11 of approximately inches of mercury with a fluid flow rate of g.p.m. In the reverse, or counterclockwise, direction of rotation, the recirculation pump 11 is operable for pumping fluid from the inlet 31 to the outlet 32 with a pressure differential of approximately 3 inches of mercury.

The drain pump 12, comprising the second pump cavity 66 and the drain impeller 71, is shown in section in FIG. 4 and is disposed to the left of the first pump cavity 65 as viewed in FIG. 1. A fragmentary portion of the impeller 71 is shown in FIG. 4 but the portion removed has the same general shape as that shown in FIG. 4. The second volute cavity 66 is relatively smaller in diameter than the first cavity 65 and the difference between the smallest and largest radius of the volute is less than that for the first cavity 65. A dam or fluid cutoff 94 projects into the cavity 66 to a position adjacent the impeller 71 for directing fluid from the cavity 66 into the outlet 44.

The inlet 39 for the drain pump 12 is directed inwardly toward the pump cavity 66 along a line extending substantially tangentially with respect to a portion of the cavity 66 radially spaced outwardly from the axis of the shaft 54. The inlet 39 lies in a plane substantially normal to the axis of rotation. The outlet 44 of the drain pump 12 is also disposed substantially tangentially to an outer portion of the cavity 66 and also lies in a plane substantially normal to the axis of rotation. These two planes, however, are axially spaced apart as best seen in FIG. 1. The fluid from the sump 20 flows through the inlet 39 and enters the second pump cavity 66 at a position that is radially displaced from the axis a distance substantially similar to that of the impeller vanes and axially displaced to the left of the im peller 71 as shown in FIGS. 1 and 5. The fluid is pumped from the inlet 39 through the second pump cavity 66 toward the tangentially extending outlet 44 disposed angularly from the inlet 39.

As previously noted, the inlet 39 for the pump cavity 66 is displaced to the left of the impeller as viewed in FIG. 1 or below the impeller as viewed in FIG. 4. It is necessary, therefore, to move the fluid axially within the pump cavity 66. To accomplish this axial movement of the fluid from the inlet 39 to the outlet 44, the pump cavity 66 includes a ramp means as indicated in FIG. 4 and more clearly shown in the ramp development of FIG. 6.

The ramp means extends from the leftmost position of the inlet 39 in FIG. 5 to the first plane 101 and then'up a beveled step 104 to a plateau 105 extending arcuately around a large portion of the annular groove 106 and terminating in a first incline portion 109 disposed for axially moving the fluid to a shelf 110 alined with the leftmost portion of the outlet 44. A second incline portion 111 extends back to the first plane 101.

This ramp means is more specifically shown in the ramp development of FIG. 6 in which the broken line 114 is the broken line 114 shown in FIG. 4. The ramp development extending toward the left from the broken line 114 shows the ramp construction of thesecond pump cavity 66 as it extends progressively in a counterclockwise direction in FIG. 4. FIG. 6 shows the first plane 101, the beveled step 104, the plateau 105, and the first and second incline portions 109 and 111. This ramp means is operable for influencing the direction of fluid so as to move the fluid from the inlet axial position 100 to the outlet axial position 110 upon rotation of the impeller 71 in the counterclockwise direction.

It may be seen that, with the drain pump 12 rotating in a counterclockwise direction, the fluid is pumped from the inlet 39 through the second pump cavity 66 to the axially displaced and tangentially extending outlet 44 disposed angularly from the inlet 39 so that the fluid tends to move around the axis substantially circumferentially a distance approximating a full circle. Thus the fluid moves generally along what will be termed a spirallike path from the inlet 39 toward the outlet 44 and may include helical and spiral characteristics.

A combination of the second incline portion 111 and the beveled step 104 adjacent the broken line 114 effectively provides a recess or pocket at the point of entry of the inlet 39 into the pump cavity 66 cooperable with the cutoff 94 to provide a unique valve means for facilitating achievement of an efficient pumping operation in the counterclockwise direction while also facilitating achievement of a static condition at the outlet 44 with the pump operating in the clockwise direction, as in the recirculation operation. This second incline portion 111 and beveled step portion 104 disposed adjacent the first plane 101 at the inlet 39 effectively function, in cooperation with the cutoff 94, as a one-way valve within the drain pump 12.

The drain pump impeller 71 is operable in the same direction as the impeller 70 of the recirculation pump 11 and during operation of the pump assembly 13 in a clockwise direction, the drain pump maintains a substantially static con- 7 dition in the drain conduit 41 of approximately 6 to 14 inches of water while permitting a relatively small amount of fluid flow from the second cavity 66 toward the unfiltered fluid conduit 40 through the inlet 39. The fluid flowing toward the unfiltered fluid conduit 40 is that fluid which bypasses a cavity divider member 119 and effectively flows downhill from the pump inlet 39 toward the sump 20.

In the reverse direction of rotation, or in the counterclockwise direction, as during the drain operation, the drain pump 12 is operable for effecting a pressure head in the drain conduit 41 of approximately 3.5 feet of water with the flow of 4.5 g.p.m. through a drain hose of approximately seven-six teenth inch diameter.

Referring again to FIG. 2, the relative fluid flow effected by the pumping system is shown schematically. In this diagram, the pumping effected by the pumping assembly 13 operating in the clockwise direction is shown in full line arrows. The pumping effected during counterclockwise rotation of the pumping assembly is shown in broken line arrows. More specifically, FIG. 2 indicates that clockwise rotation of pump 11 will effect movement of fluids from sump through filtered fluid conduit toward inlet 31 and then pass through outlet 32 and be directed toward the lower spray conduit 34, upper spray conduit 35, and auxiliary spray conduit 36. It has been indicated above that clockwise rotation of drain pump 12 will effect a substantially static pressure in the drain conduit 41 to prevent suction of fluids therefrom and thus no flow arrows are shown for clockwise rotation of pump 12. It has also been indicated above, though not shown schematically in FIG. 2, that a small amount of fluid will bypass the divider member 119 and flowin a generally downhill direction from the inlet 39 of the second pump 12 toward sump 20.

Counterclockwise rotation of the pumping assembly 13 will effect continued flow through pump. 11 in the same relative pattern as effected in the clockwise rotation of pump 11. The pumping efficiency, however, will be at a lower level as indicated hereinabove. The.counterclockwise rotation of the second pump 12 effects a substantially increased pressure at the outlet 44 and a draining of fluid from sump 20 through unfiltered fluid conduit 40, through pump 12 and through drain conduit 41 to the external drain as shown by broken line arrows in FIG. 2.

Thus it is seen that the drain pump 12 is operable for effecting a relatively low pressure head at the outlet 44 due to the valve means in the cavity 66 and the resulting inefficient operation of the pump 12 in pumping fluid from the inlet 39 toward the outlet 44 with the impeller 71 rotating in a clockwise direction opposite to that tending to create the spiral path from the inlet 39 to the outlet 44. [n the counterclockwise direction, however, the fluid is drawn in the inlet 39 and passes through the spirallike path toward the outlet 44 with a greatly improved pumping efficiency to maintain a relatively high pressure head at the outlet 44. In this counterclockwise direction, the outlet receives both a velocity head and a pressure head.

Disposed within the pump housing 60 between the first and second cavities 65 and 66 is the annular divider member 119 connected to the housing 60 by a plurality of screw members 120. A flange portion 121 extends inwardly between the first and second impellers 70 and 71 and terminates in a lip portion 124 adjacent the hub 76 of the first impeller 70. As best shown in FIG. 5, the annular lip portion 124 terminates at a position spaced from the periphery of the impeller hub 76 to define an annular orifice 125 between the first and second pump cavities 65 and 66. This relatively small annular orifice 125 achieves a degree of pressure control and limits fluid flow between the two cavities 65 and'66 while avoiding contact between the stationary divider 119 and rotatable impeller hub 76. The lip portion 124 being in close proximity to the hub 76 also prevents passage of particles from the drain pump 66 cavity into the recirculating pump cavity 65 during operation ofthe pump assembly 13.

It has been found that a small fluid flow through the annular orifice 125 and the drain pump cavity 66 toward the drain pump inlet 39, as previously mentioned, is beneficial in securing a more rapid response of the drain pump 12 in initiating fluid flow from the sump 20 upon reversal in direction of rotation. It is believed that the improved operation results from a condition wherein less air is trapped in the drain pump circuit. The fluid flow through the annular orifice 125 during operation of the pump assembly 13 in the recirculation direction maintains the drain pump circuit substantially full of fluid rather than air and therefore the time required to purge the air from the drain pump 12 upon reversal in direction of rotation is substantially eliminated.

It is noted that the recirculation pump 11 is operable for maintaining a relatively high fluid pressure in a portion of the first pump cavity 65 and in the absence ofthe divider member 119 the high pressure would be transmitted at least in part to the drain pump cavity 66. Tests on the preferred embodiment have shown that without the divider 119 between the first and second pump cavities 65 and 66 the operation of the pump 13 in the clockwise direction will effect recirculation of fluid to the recirculation conduit 26 but will at the same time effect drainage of fluid from the sump 20 toward the drain conduit 41. The divider 119 thus effectively serves as a pressure orifice for controlling pressure differentials and fluid flow between the cavities.

Tests have also shown that the relative size of conduits 40 and 41 are important in maintaining proper operation of pump 12 in the clockwise direction. In an operable embodiment tested, the unfiltered fluid conduit 40 is three-fourth inch ID. and the drain conduit 41 is seven-sixteenth inch l.D.

It has been shown in the foregoing description that the instant invention provides a pump structure having unique operational characteristics useful in a bidirectional pump assembly for effecting a relatively low-pressure head at the outlet in one direction of rotation and a relatively high-pressure head at the outlet in the opposite clockwise direction of rotation. This improved mode of operation is achieved at least in part through the relative axial spacing of the inlet and outlet 39 and 44 with respect to the impeller 71 and also the the construction of the ramp and valve means in the cavity 66. The spacing provides an annular space between the inlet 39 and the impeller 71 effective for achieving a spirallike fluid flow in a first counterclockwise direction while achieving a very low level pumping in the opposite direction. This pump structure 12 is especially useful in a dual pump assembly 13 for a dishwashing apparatus to achieve an improved fluid system therefore. Further constructional and operational details of a dishwashing apparatus embodying the pumpingapparatus of the instant invention are contained in a copending application filed by Thomas R. Smith and Stewart W. Faust, entitled Fluid Control System, Ser. No. 738,277, filed June 19, 1968, and assigned to the assignee of the instant application.

In the drawings and specification, there has been set forth a preferred embodiment of the invention and although specific terms are employed, these are used in a generic and descriptive sense only and not for purposes of limitation. Changes in form and the proportion of parts as well as the substitution of equivalents are contemplated as circumstances may suggest or render expedient, without departing from the spirit or scope of this invention as further defined in the following claims.

We claim:

1. A pump comprising: housing means defining a pump cavity having a substantially central axis; means defining an inlet directed substantially tangentially inwardly to an inlet portion of said cavity radially spaced from said axis; means defining an outlet directed substantially tangentially outwardly from an outlet portion of said cavity that is radially spaced from said axis and axially spaced from said inlet portion; an impeller disposed within said cavity axially adjacent said outlet and rotatable about said axis; bidirectional drive means operable for driving said impeller in first and second directions; and fluid control means including valve means formed within said cavity between said inlet and said outlet, said fluid control means further including ramp means and a fluid cutoff projecting into said cavity adjacent said outlet and juxtaposed said impeller for diverting said fluid from a spirallike path into said outlet in said first direction of rotation. said fluid control means being operable in the first direction of rotation of said impeller for effecting flow of fluid from said inlet toward said outlet and operable in the second direction of rotation of said impeller for substantially preventing fluid flow through the pump.

2. A pump comprising: first housing means defining a first pump cavity and an ingress and egress associated therewith; a first impeller rotatively operable about an axis and disposed within said first cavity for effecting a pumping action therethrough; second housing means defining a second pump cavity juxtaposed said first pump cavity and further defining an inlet and an outlet for said second pump cavity, said inlet being directed substantially tangentially inwardly to an inlet portion of said second pump cavity, said outlet being axially spaced from said inlet and directed substantially tangentially from an outlet portion of said second cavity; a second impeller disposed with said second cavity juxtaposed-said outlet portion; fluid control means including directional-responsive combination valve and'ramp means within said cavity between said inlet and said outlet and operable on fluid within said cavity; and bidirectional drive means operable for driving said impellers in first and second directions, said first impellers being operable in said first and second directions for effecting flow of fluid from said ingress to said egress, said second impeller being cooperable with said directional-responsive combination valve and ramp means in said first direction for effecting a relatively high rate of fluid flow from said inlet toward said outlet along a spirallike path and in said second direction for substantially preventing fluid flow through said second cavity.

3. A pump as definedin claim 2 wherein said first and second housing means are integrally connected and wherein said drive means includes a shaft member to which said impellers are rotatively fixed for effecting common rotation of said impellers by said drive means.

4. A pump as defined in claim 3 wherein a divider separates said pump cavities and defines an annular orifice adjacent said shaft member and effectively controlling fluid pressures between said cavities.

5. A pump comprising: housing means defining a pump cavity having a substantially central axis, said housing means including a generally annular cavity-defining end wall portion .disposed about said axis; means defining an inlet directed substantially tangentially inwardly to an inlet portion of said cavity radially spaced from said axis; means defining an outlet directed substantially tangentially outwardly from an outlet portion'of said cavity that is radially spaced from said axis and axially spaced from said inlet portion; an impeller disposed within said cavity and rotatable about said axis; bidirectional drive means operable for'driving said impeller in first and second directions; and fluid control means including a generally annular groove portion disposed radially inwardly of said annular end wall portion and recessed in said housing means for'fluid communication with said inlet, said fluid control means further including directionally responsive valve means in said groove portion whereby said fluid control means is operable inthe first direction of rotation of said impeller for effecting flow of fluid from said inlet toward said outlet and operable in the second direction of rotation of said impeller for substantially preventing fluid flow through the pump.

6. A pump as defined in claim 5 wherein the radial spacing of said outlet portion from said axis exceeds the radial spacing of said inlet portion from srud axis and wherein the outlet portion is disposed approximately 360 from said inlet portion whereby flow from said inlet to said outlet is along a spirallike path.

7. A pump as defined in claim 5 wherein said impeller includes vanes constructed and disposed to effect greater pumping in said first direction than in said second direction.

8. A pump comprising: housing means defining a pump cavity having a substantially central axis; means defining an inlet directed substantially tangentially inwardly to an inlet portion of said cavity radially spaced from said axis; means defining an outlet directed substantially tangentially outwardly from an outlet portion of said cavity that is radially spaced from said axis and axially spaced from said inlet portion; fluid control means including valve means, said fluid control means being formed within said cavity between said inlet and said outlet and operable for effecting the flow of fluid within said cavity; an impeller disposed within said cavity and rotatable about said axis; and bidirectional drive means operable for driving said impeller in first and second directions, said valve means including ramp means comprising progressively a step, an arcuate plateau, andanincline and being directionally responsive whereby said pump is operable in the first direction of rotation of said impeller for effecting flow of fluid from said inlet toward said outlet and operable in the second direction of rotation of said impeller for substantially preventing fluid flow through the pump.

9 A pump as defined in claim 8 wherein said valve means and ramp means extend approximately 360 around said axis between said inlet portion and said outlet portion and wherein said incline occupies an acute arcuate portion thereof.

10. A pump as defined in claim 8 wherein said valve means includes progressively a recess, a step, an arcuate plateau, an incline, and a fluid cutoff adjacent said impeller and is responsive to rotation of said impeller in said first direction for effecting a spirallike flow of fluid from said inlet toward said outlet and wherein said recess and said cutoff are operative in said second direction of rotation of said impeller for substantially preventing fluid flow through the pump.

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