BACKGROUND OF THE INVENTION
[0001] The present invention is directed to a toric pump having an improved impeller which
minimizes internal leakage through the clearance gap between the impeller and pump
housing and which minimizes the noise generated by operation of the pump.
[0002] Toric pumps of the type with which the present invention is concerned employ a disk
like impeller having a series of radial vanes mounted around its periphery. The opposed
side surfaces of the impeller are flat, except for pockets between the vanes, and
the impeller is mounted within a pump housing having an internal chamber having opposite
side surfaces and a peripheral surface which closely enclose the impeller but allow
sufficient clearance such that the fluid can exit the impeller radially and then turn
forward or backward into the internal pump chambers of the housing. The chamber walls
are formed with an internal pump chamber or passage extending along an annular path
in operative relationship with the path of the impeller vanes at a constant radial
distance from the impeller axis from an inlet at one end of the toroidal passage to
an outlet at the opposite end. The circumferential extent of the toroidal passage
around the pump axis is less than 360°, and between the ends of the passage a relatively
narrow portion of the chamber side wall extends across the annular region traversed
by the toroidal chamber. This portion of the chamber side wall is called the stripper
and the stripper functions to deflect fluid being impelled through the pump chamber
by the impeller vanes into the pump outlet instead of being pumped back to the inlet.
[0003] During operation of the pump, as each vane advances past the outlet end of the pump
chamber to cross the stripper, the sudden reduction in the cross sectional area of
the chamber through which the vane is moving generates a discontinuity in the fluid
flow. Such a discontinuity occurs each time a vane passes across an edge of the stripper
and, there is thus a generation of a cyclic change of resistance to the rotation of
the impeller. Where the vanes are equally spaced around the impeller periphery, the
frequency of this cyclic reaction is directly proportional to the rotative speed of
the impeller, and at certain critical speeds, structural resonances or harmonics may
develop which generate noise. It has been recognized in the prior art that this problem
may be solved to some extent by varying the vane spacing around the periphery of the
impeller. However, variable vane spacing usually results in the creation of at least
some rotor imbalance which in turn leads to problems potentially more serious than
undesirable noise.
[0004] A second problem encountered by pumps of types described above results from the fact
that a slight clearance or gap must exist between the stationary pump housing surfaces
and the adjacent rotating surfaces of the impeller in order that the impeller can
freely rotate relative to the housing. Those portions of the chamber side surfaces
and the opposed side surfaces of the impeller which are located radially inwardly
of the toroidal pump chamber present a gap which extends the entire length of the
radially inner side of the circumferentially extending pump chamber. Pressure progressively
increases in this chamber from the inlet end to the outlet end, and the clearance
gap provides a path for leakage of fluid from high pressure regions of the chamber
to regions of lower pressure. Where the fluid being pumped is of low viscosity - i.e.,
air for example - this leakage can be substantial and substantially reduce the flow
delivered by the pump.
[0005] Prior art attempts to employ a labyrinth type seal to reduce this leakage have not,
in general been successful as demonstrated by the fact that very few, if any, commercially
available regenerative pumps employ such seals. Labyrinth seals rely upon a series
of restrictions separated by expansion chambers which are intended to enable the fluid
entering the chamber to expand to an increased volume or bulk which is in theory more
difficult to pass through the next following restriction. Where the fluid is of low
compressibility, such as a liquid, no expansion takes place and the presence of the
expansion chambers reduces the area available for restriction, thus reducing the effectiveness
of the seal. Where the pump of the type described above is employed to pump gasses,
the gasses are highly compressible, but the pumps typically develop only a relatively
small pressure differential between the inlet and outlet. Because of the relatively
small differential between the density of the compressible fluid at the inlet and
its density at the outlet, there is little opportunity for expansion of the gas in
the expansion chambers of a labyrinth seal. Further, most of the prior art effort
has focused on reducing leakage across the stripper between the inlet and outlet ends
of the chamber while ignoring the fact that leakage likewise may occur between points
in the chamber which are not necessarily closely adjacent the inlet or outlet.
[0006] The present invention is directed to a solution of the problems discussed above.
SUMMARY OF INVENTION
[0007] In accordance with the present invention, leakage through the gap between the opposed
side surfaces of the pump housing and impeller is minimized by forming a plurality
of concentrically arranged series of pockets in at least one of the opposed side surfaces.
Each series of pockets includes a plurality of pockets circumferentially spaced from
each other in a circular array about the impeller axis. The pockets of each series
are so located that the pockets of one series circumferentially overlap the space
between the pockets of the adjacent series. This arrangement assures that there is
no truly direct line path of flow through the gap between separated locations in the
pump chamber which open into the gap. Stated another way, any direct path through
the gap between two points opening into the pump chamber is interrupted by at least
one or more pockets so that the likelihood of establishing a continuous flow path
for leakage between the two points is minimal. This arrangement is the most effective
when the pockets are formed in the side surfaces of the impeller in that fluid which
enters a pocket enters a moving pocket which disrupts the normal path of flow.
[0008] Minimization of noise generated by the pump operation is accomplished by effectively
doubling the number of vanes on the impeller and operating the impeller at rotative
speeds such that noise which is generated is generated at frequencies above the audible
range. The rotor of the present invention is formed with an annular web at it outer
peripheral portion which lies in a general plane normal to the axis of rotation of
the impeller. Vanes project radially outwardly from opposite sides of the web and
are variably spaced from each other in a calculated mirror image pattern which is
duplicated, but angularly offset by 180° at opposite sides of the impeller. The vane
spacing and arrangement is such that no vane on one side of the rotor is in axial
alignment with a vane on the opposite side of the rotor. Effectively, this doubles
the total number of vanes and the axial extent of the individual vanes is reduced
so that the flow discontinuity created by the passage of a vane across a stripper
edge is minimized. By choosing the number of vanes to be located at one side of the
impeller web to be the largest odd number of vanes consistent with convenient fabrication
of the rotor (tooling or mold structure may establish a minimum limit to the spacing
between adjacent vanes) and selecting a calculated vane spacing sequence a geometrically
balanced impeller with variable vane spacing can be achieved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Other objects, features and advantages of the invention will become apparent by reference
to the following detailed description and drawings, in which:
Fig. 1 is a front view of a regenerative toric pump embodying the present invention;
Fig. 2 is a rear view showing the inner side of the pump housing cover of the pump
of Fig. 1;
Fig. 3 is a front view showing the interior side of the pump housing of the pump of
Fig. 1;
Fig. 4 is a cross sectional view taken on line 4-4 of Fig. 1;
Fig. 5 is a detailed cross sectional view taken on line 5-5 of Fig. 1;
Fig. 6 is a side view of the impeller employed in the pump of Fig. 1, showing the
front side of the impeller;
Fig. 7 is a detailed cross sectional view of the impeller taken on line 7-7 of Fig.
6;
Fig. 7A is an edge view of the impeller showing a portion of the outer periphery of
the impeller;
Fig. 8A is a schematic diagram illustrating the pattern of vane spacing employed at
the front side of the impeller; and
Fig. 8B is a schematic diagram illustrating the pattern of vane spacing employed on
the rear side of the impeller;
Fig. 9 is a front view showing the interior side of an alternate pump housing having
pockets defined therein;
Fig. 10 is a cut away cross sectional view taken on line 10-10 of Fig. 9, showing
the cover in place, with the impeller and drive shaft shown in phantom; and
Fig. 11 is an enlarged view of the impeller housing in the area designated by arrow
B in Fig. 10.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0010] Referring first to Figs. 1-5, a regenerative toric pump embodying the present invention
includes an impeller housing designated generally 20 and a housing cover designated
generally 22 fixedly and sealingly secured to each other as by bolts 24. For purposes
of orientation, that side of the pump on which the cover 22 is located will be referred
to as the front of the pump. Housing 20 is formed with a forwardly opening impeller
receiving recess having a flat bottom surface 26 and an annular recess 28 which, as
best seen in Fig. 3, extends circumferentially of the housing about a central housing
axis A from an inlet end 30 to an outlet end 32 which are separated from each other
by a stripper section 34 coplanar with the surface 26.
[0011] Cover 22 is formed with a flat rear face 36 and a similar annular recess 38 which
extends circumferentially from an inlet 40 opening from recess 38 forwardly through
the cover to an outlet 42 which likewise opens forwardly through cover 22, the inlet
and outlet ends of the annular recess 38 being separated from each other by a stripper
portion 44 coplanar with the flat rear face 36 of cover 22.
[0012] As best seen in Figs. 4 and 5, when cover 22 is assembled upon housing 20, the flat
faces 26 and 36 of the housing and cover respectively are disposed in spaced parallel
relationship to each other by a distance which slightly exceeds the axial thickness
of a disk shaped impeller designated generally 46 (see Figs. 6 and 7) indicated in
broken line only in Figs. 4 and 5. Impeller 46 is received within the pump housing
for rotation about the axis A and is rotatively fixed upon the end of an impeller
drive shaft 48 rotatably mounted within a bore 50 coaxial with axis A of housing 20
as by a bearing 52. Impeller vanes 58, 60 respectively formed on the front and rear
sides of the impeller are operable upon rotation of the impeller to impel air along
the respective annular recesses of pump chambers 38, 28 in a well known manner. The
clearance between the opposite side surfaces of impeller 46 and the flat surfaces
26, 36 on the housing and cover is chosen to be sufficient so as to assure there will
be no contact between the rotating impeller and the fixed surfaces 26, 36 during operation
of the pump. For reasons to be explained in more detail below, it is desirable that
the impeller be driven at relatively high speeds of rotation - in the order of 10,000
rpm or higher - and any contact between the impeller and housing surfaces during operation
must be avoided.
[0013] Similarly, a relatively small gap or clearance between the outer peripheral surface
54 of the impeller and the opposed peripheral surface 34C, (Figs. 3 and 5) of the
stripper portion of the impeller receiving recess in housing 20 is required. Because
recess 28 in housing 22 is located at the rear side of the impeller, and the inlet
40 and outlet 42 of the pump enter the interior chamber through the cover at the front
side of impeller 46, recesses 28 and 38 are formed at their inlet ends 30, 40 with
radially outwardly extending enlarged portions 30A, 40A so that fluid entering through
inlet 40 can flow across the outer periphery 54 of impeller 46 via the enlargements
40A, 30A to the rear side of the impeller. Similar enlarged portions 32A, 42A are
formed at the outlet ends 32, 42 of the recesses 28, 38.
[0014] In the particular cover 22 shown in the drawings, external connections to inlet and
outlet 42 are made through a filter housing indicated in broken line at F in Figs.
4 and 5 which is seated upon a filter chamber defining formation designated generally
62 on the front side of cover 22. The filter F - filter chamber 62 arrangement provides
a convenient means for filtering incoming air when the pump is employed to pump air.
While the pump disclosed in the application drawings is specifically intended to supply
air as required to an automotive emission control system, the pump described has other
applications and is readily adapted for use in pumping liquid or fluids other than
air.
[0015] Regenerative toric pumps of the general type here disclosed are known in the prior
art and, as stated above, have two inherent problems in their design. The first of
these two problems is the generation of noise resulting from the cyclic passage of
the rotor vanes into and out of the restricted passage constituted by the opposed
stripper portions 34, 44 whose presence is required to deflect fluid from the annular
recess or pump chamber into the pump outlet. The second problem is that of leakage
of the fluid being pumped through the clearance gaps between the opposed surfaces
of the rotating impeller and pump housing.
[0016] The present invention addresses the problem of noise generation by employing a relatively
large number of vanes on the impeller which are arranged in a predetermined non uniformly
spaced pattern and by forming the stripper portion edges to extend along a non radially
inclined edge.
[0017] Referring now particularly to Fig. 3, it is seen that the edges 34A, 34B of the stripper
portion 34 of the pump housing do not lie on lines radial to axis A, such as lines
R1 and R2, but are instead inclined to those radial lines. As will be described in
more detail below, the various vanes 58, 60 of the impeller lie in general planes
which extend radially from axis A. In Fig. 3, which shows the front side of housing
20, the direction of rotation of the impeller would be in a counterclockwise direction
so that the vanes would advance air (or whatever fluid is being pumped) along the
annular recess 28 from inlet end 30 to outlet end 32. Because of the inclination of
edge 34B of the stripper to the radial line R2, as a vane on the impeller passes in
a counterclockwise direction from outlet end 32 of recess 28 into overlying relationship
with the stripper portion 34, the radially extending vane is inclined to the stripper
edge 34B so that as the vane advances from the relatively large passage defined by
the annular recess 28 into the relatively restricted passage defined by stripper portion
34, the entire vane does not attempt to enter this restricted passage simultaneously,
as would be the case if both the vane and edge 34B extended in a radial direction.
Effectively, the inclination of edge 34B to the radial line R2 slices air from the
vane edge, rather than chopping it as would be the case if edge 34B extended along
a radius from axis A. This arrangement cushions to some extent the fluid shock occasioned
by the transit of the vane from a relatively unrestricted passage into an extremely
restricted passage. A similar action occurs at edge 34A, and as is best seen in Fig.
2, the corresponding edges 44A and 44B of the opposed stripper portion 44 on cover
22 are inclined similarly to radial lines extending from the axis A.
[0018] Typically, the impeller 46 will be driven in rotation at a substantially constant
speed which, if the vanes are equally spaced about the impeller circumference, will
result in the passage of a vane edge across the edge of the stripper at a substantially
constant cyclic frequency. Noise generated will be of this frequency and its harmonics
and, when one of these frequencies approaches some natural frequency of the pump structure,
amplification of the noise can occur. The prior art has recognized that some noise
generation is inherent where an impeller with equally spaced vanes is driven at a
constant speed across a stripper, and that noise generation may be reduced by arranging
the vanes in a pattern in which the vanes are unequally spaced to avoid a constant
frequency generation situation. However, unequal spacing of the impeller vanes typically
creates other problems, such as impeller imbalance and increased manufacturing costs.
[0019] A second approach to minimizing the noise generation problem is to generate noise
at frequencies above the audible range which, for most persons means frequencies above
15,000 cycles per second. In that the frequency of noise generated by the pump is
essentially the product of the number of vanes on the impeller multiplied by the number
of impeller revolutions per second, high speed operation of an impeller with a relatively
large number of vanes offers the possibility of avoiding the generation of noise within
the audible range.
[0020] Both of these approaches are employed in the impeller of the present invention, with
special care being given to determining a pattern of variable vane spacing which also
results in a geometric balance of the impeller.
[0021] Referring first to the cross sectional view of Fig. 7, impeller 46 is formed with
an annular web 66 at its outer peripheral portion which lies in a general plane normal
to the impeller axis mid-way between the front and rear side surfaces of the impeller.
Vanes 58 project forwardly from the front side of web 66 and vanes 60 project rearwardly
from the rearward side of web 66. Referring now particularly to Fig. 6, which is a
front axis in angularly spaced relationship to each other. As best seen in Fig. 7,
the front edges 72 of the vanes 58 lie in the plane of the front surface 68 of the
impeller and the radially outer edges 74 of vanes 58 extend flush with the outer periphery
of web 66. Pockets 76 are formed between adjacent vanes 58. The vanes 60 which project
from the rearward face of web 66 are of a configuration similar to vanes 58.
[0022] For clarity of illustration, pockets 76 (see Fig. 7) defined by vanes 60, 58, as
shown in Fig. 4, appear to have a lesser radial dimension than the corresponding radial
dimension of pump chambers 38, 28. It should be recognized however that in practice,
the radial extent of pockets 76 and chambers 38, 28 preferably should be as nearly
equal as possible within the requirement for maintaining adequate clearance between
the outer peripheral surface 54 of the impeller and the opposed peripheral inner suface
34C of the impeller receiving recess in housing 20.
[0023] In Fig. 6, the vanes on the front face of the rotor are arranged in a pattern which
is determined in the following manner.
[0024] Rather than computing the space between adjacent vanes, which have a finite thickness,
it is somewhat simpler and more convenient to assume that the vanes are of zero thickness
and to compute the locations of the radial general planes which will bisect the space
betwen adjacent vanes.
[0025] The first step in the procedure is to select a total number of spaces between the
vanes at the front side of impeller 46. In order to assure that no vane on the front
side of the impeller will be directly aligned with a vane on the rear side of the
impeller, the number of spaces selected must be an odd number. The number chosen should
be as large as possible, taking into account limitations imposed by structural strength
requirements and the tooling and techniques employed to fabricate the impeller.
[0026] The number of spaces selectes is then divided into 360° to determine the size (angular
extent about the axis) of an average size space. To follow an exemplary calculation,
it will arbitrarily be assumed that 45 spaces are to be employed, in that this results
in an average space of 360° ÷ 45 or 8°.
[0027] The next step is to determine a maximum increment to be added or substracted from
an average space to determine the minimum and maximum space sizes. It will arbitrarily
be assumed
The next step is to determine a maximum increment to be added or subtracted from
an average space to determine the minimum and maximum space sizes. It will arbitrarily
be assumed that the maximum departure from the average space size of 8° will be ±
15% of 8° or 1.2°. This will give a maximum space size of 9.2° and a minimum space
size of 6.8°. The minimum space size should then be checked to be sure it can be achieved
by the tooling and techniques employed in fabricating the vanes. Typically, the impeller
is formed by an injection molding or die casting technique and the machining of the
mold or die cavity will be the determining factor.
[0028] With an odd number of spaces, the pattern of the vanes on the front face of impeller
46 will be established with respect to a reference line L (Fig. 8A) which extends
diametrically of the impeller and passes through the impeller axis. With an odd number
of spaces, the line L, as indicated in Fig. 8A, can be so located as to pass through
the central general plane of one vane 58A and bisect the space between the two vanes
58B and 58C at the opposite side of the impeller circumference.
[0029] The next step is to locate, through one 180° clockwise displacement from the reference
vane 58A location the angular displacement from line L of the radial lines L1, L2,
etc., which bisect the successive spaces in a clockwise direction from line L1 through
180°, assuming all spaces are of the average size. Since the average size of the spaces
is 8°, line L1 of Fig. 8A will be displaced an angle a₁ from line L of 4°, line L2
will be displaced from line L1 by an angle a₂ 12°, subsequent lines L3, L4, etc.,
(not shown) will be displaced from the preceding line by 8° increments. The angles
a₁, a₂ will be used in calculating the individual spacings.
[0030] For reasons which will become apparent, it is desired that the spaces in the first
90° of displacement clockwise from line L will be approximately, but not precisely
symmetrically disposed with respect to the respective spaces in that quadrant between
a 90° displacement from line L and a 180° displacement from line L. Therefore, it
is convenient if the variation in space sizing follows some periodic function which
will result in an increase in the space sizing through the first 90° from line L and
a decrease in space sizing through the next 90°. One obvious choice of such a function
is a sine or cosine function.
[0031] The sizes of the respective spaces clockwise from reference vane 58A through the
first 180° as viewed in Fig. 6 may be determined by the following relationship:
where n = a number of the space counting clockwise from reference vane 58A, S = the
angular extent of the "space" - i.e., the angular displacement between the general
planes of two adjacent vanes, a
n = the angle between line L1 and the center line of space S
n if all spaces were of the average size - i.e.,
, where B is the average space (8° in the example given above) and D = the maximum
increment to be added to or subtracted from the average space size - D= 1.2° in the
example give above.
[0032] The above formulation is but one of many which can be employed for computing a variable
spacing between adjacent vanes. The foregoing formulation establishes a vane spacing
pattern in which the vane spaces are of a minimum size adjacent reference vane 58A,
increase progressively through the first 90° from line L1 and then decrease progressively
to vane 58C.
[0033] The foregoing explanation has been concerned solely with determining the spacing
of the vanes over the first 180° clockwise from reference vane 58A. The spacing of
the vanes at the opposite side of the line L which bisects reference vane 58A and
the space between vanes 58B and 58C is precisely the same pattern except the spacing
progression commences at vane 58A and proceeds counterclockwise as viewed in Figs.
6 and 8A through 180° from vane 58A. In other words, the pattern of vanes 58 to the
right of line L of Fig. 8A is a precise mirror image of the vane spacing at the opposite
side of line L. As viewed from the front, as in Fig. 6, the vane spacing or the pattern
in which the vanes 58 are arranged about the impeller axis is geometrically balanced
on opposite sides of a vertical line passing through the impeller axis as viewed in
Fig. 6. To compensate for any imbalance on opposite sides of a horizontal line passing
through the impeller axis, as might arise in the manufacturing of the impeller, the
vanes 60 at the rear side of impeller 46 are arranged in precisely the same pattern
as the vanes 58 on the front side with the overall pattern displaced 180° about the
impeller axis. Thus, the vanes at the rear face of the impeller include a reference
vane 60A from which the vane spacing progressively increases and decreases in the
same amounts as that of the vanes 58 with the reference vane 60A being located at
the six o'clock position as viewed in Fig. 8B as compared to the 12 o'clock position
of the reference vane 58A on the front side of the impeller.
[0034] This arrangement achieves two important results. First it achieves a geometric balance
of the impeller as a whole on opposite sides of both a vertical and a horizontal plane
passing through the impeller axis, and second, as viewed in Fig. 7A, it assures that
none of the vanes 58 at the front side of the impeller will be axially aligned with
any of the vanes 60 at the rear side of the impeller. Effectively, as far as the generation
of noise is concerned, this latter arrangement presents twice as many vanes as would
be the case if vanes 58 and 60 were axially aligned because with the disclosed arrangement,
when a vane 58 at the front side of the impeller is passing across an edge of the
stripper portion, there is no vane 60 aligned with the edge of the stripper portion.
[0035] In the case of a 3 1/2 inch diameter impeller with 59 vanes on each side, as shown
in the drawings, the frequency at which a vane edge - either an edge of a front vane
58 or a rear vane 60 - will pass an edge of the stripper portion will exceed 15,000
cycles per second if the speed of rotation of the impeller exceeds approximately 8400
rpm. Suitable motors for driving an impeller of a 3 1/2 inch diameter at speeds of
up to 20,000 rpm in an air pumping application are readily available from a number
of commercial sources.
[0036] The problem of leakage through the clearance gap between the opposed side surfaces
of the impeller and pump housing is usually believed to involve flow across the stripper
portions 34, 44 of the pump in that the highest pressure differential within the pump
exists between that side of the stripper facing the outlet and that side of the stripper
facing the inlet. Most of the prior art efforts directed to reduction of gap leakage
losses are concerned with leakage across the stripper, but overlook the fact that
significant leakage can occur across the main housing surfaces 26 and 36 as, for example,
across the surface 36 between points P1 and P2 (Fig. 2). While the distances leakage
of this latter type must traverse are much greater normally than across the stripper,
and the pressure differential is much lower than the pressure differential across
the stripper, the circumferential extent of the gap through which leakage may pass
is substantially greater.
[0037] In accordance with the present invention, the opposed side surfaces of the impeller
radially inwardly of the impeller vanes are formed with concentric series of recesses
or pockets such as 80, 82, 84. These pockets 80, 82 and 84 provide expansion chambers
into which fluid flowing through the gap between the impeller side surfaces and housing
side surfaces can flow. As compared to leakage flow across opposed flat or unrecessed
surfaces, fluid flowing into the recessed pockets 80, 82 and 84, is carried along
with the pocket by rotation of the impeller and, at a high speed of rotation of the
impeller will eventually be discharged from the pocket at some random location and
in a direction which normally will have some radially outwardly directed component
of movement as well as a component of movement directed in general toward a high pressure
region of the pump chamber. Effectively, this arrangement prevents the formation of
any organized continuous flow path through the gap.
[0038] As shown in Fig. 6, the pockets 80, 82 and 84 are elongated circumferentially of
the impeller and each circular array of pockets has a uniform length proportional
to the radial distance between the pockets and the impeller axis. The circumferential
length of the pockets 80, 82 and 84 in any circular array exceeds the space between
the pockets in a next adjacent circular array. If an imaginary line were drawn on
Fig. 6 extending radially from the impeller axis to bisect the space between two adjacent
pockets of one circular array, the imaginary line would also circumferentially bisect
a pocket in an adjacent circular array.
[0039] The pocket arrangement disclosed provides further advantages from the manufacturing
standpoint where the impeller is molded from a thermoplastic or lightweight metal
such as aluminum. The amount of gap leakage is essentially dependent upon the magnitude
of the gap between the side faces of the impeller and the respective opposed housing
side wall surfaces 26 and 36. If the side surfaces 68, 70 of the impeller were not
formed with the pockets 80, 82, 84, uneven cooling of the impeller in the mold normally
would result in an uneven - i.e., a non-flat side surface of the impeller. By forming
the pockets 80, 82, 84 as shown, a more uniform rate of cooling of the annular portion
of the impeller radially inwardly of the vanes is achieved, and those portions of
the side surfaces between the pockets will be formed as a flat surface which enables
a minimum clearance gap to be established.
[0040] The pattern of the pockets as viewed in Fig. 6 also facilitates an even radially
outward flow of the molten plastic or metal which flows into the impeller forming
mold at the center of the impeller.
[0041] One preferential arrangement of the pockets 80, 82, 84 is that shown in Fig. 6 in
which the pockets extend in concentric circular patterns in uniformly circumferentially
spaced relationship within the circular pattern. The circumferential length and location
of the pockets angularly about the impeller axis varies for each concentric circular
array of pockets with the pockets 82 circumferentially overlapping the space between
adjacent pockets 80 of the next inner most ring, and with the pockets 84 of the outer
most ring similarly circumferentially overlapping the spaces between adjacent pockets
82 of the next inner most ring. This arrangement effectively positions one or more
pockets in any direct path of flow across the faces 26 or 36 of the housing which
might extend between any two points in the pump chamber such as P1 and P2 of Fig.
2 which are sufficiently spaced from each other to develop any substantial pressure
differential.
[0042] The configuration and location of the pockets 80, 82, and 84 may take any of several
alternative forms which may be chosen in accordance with the structural requirements
of the impeller and the tooling and fabrication techniques employed to form the pockets.
Generally speaking, it is desired that a plurality of concentric rings of pockets
in which the pockets in the respective rings circumferentially, symmetrically overlap
the spaces between the pockets in adjacent rings be employed, and the arrangement
shown in the drawings is but one example of such a preferred arrangement.
[0043] While the pockets may advantageously be formed in the impeller as described above,
where the construction of the impeller makes this impractical, or if desired by the
manufacturer and/or end user, the pockets may be formed in the housing and cover in
the surfaces 26, 36. One such embodiment is shown in Figs. 9-11. An alternate housing
is designated generally as 120 and an alternate housing cover is designated as 122.
The opposed housing side wall surfaces 26, 36, radially inwardly of annular recesses
28, 38, respectively, are formed with concentric series of recesses or pockets such
as 180, 182, 184, as best seen in Fig. 10. The structure and advantages of pockets
180, 182 and 184 are as described above in relation to pockets 80, 82 and 84. It is
to be understood that pockets 180, 182, 184 may be formed in either housing 120 or
cover 122 or both, and that impeller 46 may be formed without any pockets whatsoever
formed therein. Further, any combination is possible: the pockets may be formed in
one side face of the impeller 46 and one side wall surface of the housing; pockets
can be in both side faces of impeller 46 and one side wall surface of the housing,
etc. As such, in the preferred embodiments, the pockets may advantageously be formed
in neither, one or both of the side wall surfaces 26, 36 of the housing in addition
to, or in lieu of the pockets formed in impeller 46.
[0044] While exemplary embodiments of the invention have been described above in detail,
it will be apparent to those skilled in the art the disclosed embodiments may be modified.
Therefore, the foregoing description is to be considered exemplary rather than limiting,
and the true scope of the invention is that defined in the following claims:
1. In a toric pump including a pump housing having an internal impeller receiving chamber
defined in part by a pair of spaced parallel side wall surfaces, a disk-like pump
impeller mounted in said impeller chamber between said side wall surfaces for rotation
about an axis normal to said side wall surfaces, opposed annular recesses in said
side wall surfaces defining a toric pump chamber extending circumferentially of said
axis from an inlet end to an outlet end, said impeller having planar side faces in
opposed facing relationship to the respective side wall surfaces of said impeller
chamber and a plurality of vanes at opposite sides of said impeller lying in respective
general planes radiating from said axis for driving fluid in said pump chamber from
said inlet end to said outlet end, said inlet and outlet ends of said recesses being
separated from each other by stripper portions on said housing co-planar with the
respective side wall surfaces of said impeller chamber and defining a restricted passage
for said vanes while inhibiting flow of fluid from said outlet through said restricted
passage;
the improvement wherein said planar side faces of said impeller radially inwardly
of said vanes are spaced from the respective opposed side wall surfaces of said impeller
chamber by a clearance gap of a width sufficient to accommodate free rotation of said
impeller relative to said housing and insufficient to accommodate any substantial
flow of fluid through said clearance gap, means defining a plurality of pockets in
certain of said side faces of said impeller and said housing side wall surfaces, arranged
in at least two circular arrays at different radial distances from the impeller axis,
the pockets in each circular array being uniformly circumferentially spaced from each
other with the spaces between the pockets of one circular array being radially aligned
with the pockets of the other circular array.
2. The invention defined in claim 1 wherein said means defining a plurality of pockets
are located in at least one of said housing side wall surfaces.
3. The invention defined in claim 2 wherein said plurality of pockets are located in
both of said housing side wall surfaces, the pockets in each housing side wall surface
being separated axially from one another, preventing direct axial fluid flow communication
between the pockets in opposite side wall surfaces.
4. The invention defined in claim 2 wherein the vanes at one side of said impeller lie
in radial general planes which are non-uniformly angularly spaced about said axis
at one side of said impeller in a pattern such that a first radial plane bisects a
first vane at said one side of said impeller and bisects the space between two adjacent
vanes at said one side of said impeller at a location 180° from said first vane, the
vanes at said one side of said impeller located at one side of said first radial plane
being non-uniformly angularly spaced in a mirror image relationship to the non-uniform
spacing between the vanes at said one side of said impeller located at the other side
of said first radial plane, the vanes at the opposite side of said impeller being
arranged in the same non-uniform angular spacing as the vanes at said one side of
said impeller with the vanes at said opposite side being angularly displaced 180°
about said axis from the respective corresponding vanes at said one side.
5. The invention defined in claim 1 wherein said means defining a plurality of pockets
are located in at least one of said housing side wall surfaces and in at least one
of said impeller side faces, the pockets in said at least one side wall surface and
impellar side face being separated axially from one another, preventing direct axial
fluid flow communication between the pockets in opposite side faces and side wall
surfaces.
6. The invention defined in claim 1 wherein said pockets are elongated circumferentially
of said impeller, the pockets of each circular array being of a uniform length proportional
to the radial distance between the pockets and the impeller axis.
7. The invention defined in claim 1 wherein the circumferential length of the pockets
in any circular array exceeds the space between the pockets in a next adjacent circular
array.
8. The invention defined in claim 7 wherein an imaginary line extending radially from
said impeller axis to bisect the space between two adjacent pockets of one circular
array also circumferentially bisects a pocket in an adjacent circular array.
9. The invention defined in claim 1 wherein the vanes at one side of said impeller lie
in radial general planes which are non-uniformly angularly spaced about said axis
at one side of said impeller in a pattern such that a first radial plane bisects a
first vane at said one side of said impeller and bisects the space between two adjacent
vanes at said one side of said impeller at a location 180° from said first vane, the
vanes at said one side of said impeller located at one side of said first radial plane
being non-uniformly angularly spaced in a mirror image relationship to the non-uniform
spacing between the vanes at said one side of said impeller located at the other side
of said first radial plane, the vanes at the opposite side of said impeller being
arranged in the same non-uniform angular spacing as the vanes at said one side of
said impeller with the vanes at said opposite side being angularly displaced 180°
about said axis from the respective corresponding vanes at said one side.
10. In a toric pump including a pump housing having an internal impeller receiving chamber
defined in part by a pair of spaced parallel side wall surfaces, a disk-like pump
impeller mounted in said impeller chamber between said side wall surfaces for rotation
about an axis normal to said side wall surfaces, opposed annular recesses in said
side wall surfaces defining a toric pump chamber extending circumferentially of said
axis from an inlet end to an outlet end, said impeller having planar side faces in
opposed facing relationship to the respective side wall surfaces of said impeller
chamber and a plurality of vanes at opposite sides of said impeller lying in respective
general planes radiating from said axis for driving fluid in said pump chamber from
said inlet end to said outlet end, said inlet and outlet ends of said recesses being
separated from each other by stripper portions on said housing co-planar with the
respective side wall surfaces of said impeller chamber and defining a restricted passage
for said vanes while inhibiting flow of fluid from said outlet through said restricted
passage;
the improvement wherein said planar side faces of said impeller radially inwardly
of said vanes are spaced from the respective opposed side wall surfaces of said impeller
chamber by a clearance gap of a width sufficient to accommodate free rotation of said
impeller relative to said housing and insufficient to accommodate any substantial
flow of fluid through said clearance gap, means defining a plurality of pockets in
at least one of said housing side wall surfaces, arranged in at least two circular
arrays at different radial distances from the impeller axis, the pockets in each circular
array being uniformly circumferentially spaced from each other with the spaces between
the pockets of one circular array being radially aligned with the pockets of the other
circular array, wherein the circumferential length of the pockets in any circular
array exceeds the space between the pockets in a next adjacent circular array.
11. In a toric pump including a pump housing having an internal impeller receiving chamber
defined in part by a pair of spaced parallel side wall surfaces, a disk-like pump
impeller mounted in said impeller chamber between said side wall surfaces for rotation
about an axis normal to said side wall surfaces, opposed annular recesses in said
side wall surfaces defining a toric pump chamber extending circumferentially of said
axis from an inlet end to an outlet end, said impeller having planar side faces in
opposed facing relationship to the respective side wall surfaces of said impeller
chamber and a plurality of vanes at opposite sides of said impeller lying in respective
general planes radiating from said axis for driving fluid in said pump chamber from
said inlet end to said outlet end, said inlet and outlet ends of said recesses being
separated from each other by stripper portions on said housing co-planar with the
respective side wall surfaces of said impeller chamber and defining a restricted passage
for said vanes while inhibiting flow of fluid from said outlet through said restricted
passage;
the improvement wherein said planar side faces of said impeller radially inwardly
of said vanes are spaced from the respective opposed side wall surfaces of said impeller
chamber by a clearance gap of a width sufficient to accommodate free rotation of said
impeller relative to said housing and insufficient to accommodate any substantial
flow of fluid through said clearance gap, means defining a plurality of pockets in
at least one of said housing side wall surfaces and in at least one of said impeller
side faces, arranged in at least two circular arrays at different radial distances
from the impeller axis, the pockets in each circular array being uniformly circumferentially
spaced from each other with the spaces between the pockets of one circular array being
radially aligned with the pockets of the other circular array, the pockets in said
at least one housing side wall surface and impeller side face being separated axially
from one another, preventing direct axial fluid flow communication between the pockets
in opposite housing side wall surfaces and impeller side faces, wherein said pockets
are elongated circumferentially of said impeller, the pockets of each circular array
being of a uniform length proportional to the radial distance between the pockets
and the impeller axis.