Abstrict This invention discloses a device usable as a pump or a compressor
or a flow meter that includes a plurality of flaps having a substantially
"comma-shaped" cross section assembled in a parallel arrangement
wherein the flaps are respectively pivotable about a plurality of
pivoting axes axisymmetrically positioned about the central axis
of the assembly of the flaps. The outer boundary of the cross section
of the assembly of the flaps takes a substantially circular configuration
when all of the flaps are pivoted to the fully retracted position.
The assembly of the flaps is rotatably disposed eccentrically within
a cylindrical cavity having a cross section of a circle or ellipse
or other configuration of smooth perimeter which cylindrical cavity
includes a fluid inlet and outlet disposed at two substantially
diametrically opposite positions across a plane including the central
axis of the assembly of the flaps and the central axis of the cylindrical
cavity.
Claims I claim:
1. A fluid handling device comprising in combination:
(a) a body including a cylindrical cavity having a cylindrical
wall and two closed ends, said cylindrical cavity including a first
port disposed through a portion of said cylindrical wall and a second
port disposed through another portion of said cylindrical wall;
(b) a first end disc disposed adjacent to one closed end of said
cylindrical cavity and rotatable about an axis of rotation parallel
to and offset from the geometric central axis of said cylindrical
cavity;
(c) a second end disc disposed adjacent to the other closed end
of said cylindrical cavity and rotatable about said axis of rotation;
and
(d) a plurality of flaps disposed parallel to and about said axis
of rotation intermediate said first and second end discs within
said cylindrical cavity, each of said plurality of flaps having
a first convex cylindrical surface of a first radius disposed parallel
and adjacent to said axis of rotation; a second convex cylindrical
surface smoothly extending from one boundary of said first convex
cylindrical surface wherein at least a portion of said second convex
cylindrical surface is generated by a second radius greater than
said first radius, and a concave cylindrical surface smoothly extending
from the other boundary of said first convex cylindrical surface
and merging with said second convex cylindrical surface in an accute
angle providing a substantially sharp edge wherein combination of
said cylindrical surfaces provides a cross section of said flap
having a first edge of a substantially round geometry and a second
edge of a substantially pointed crescent geometry, each of said
plurality of flaps supported by said first and second end discs
in a substantially rotationally symmetric pattern about said axis
of rotation and pivotably about an axis of pivoting coinciding with
the origin of said first radius; wherein said concave cylindrical
surface of one flap accomodates said first convex cylindrical surface
of another flap adjacent to said one flap enabling said flaps to
fold into a position wherein at least a portion of said second convex
cylindrical surface substantially coincides with a hypothetical
circular cylindrical surface concentrically disposed about said
axis of rotation;
wherein the minimum distance from said axis of rotation to said
cylindrical wall of the cylindrical cavity is substantially equal
to said second radius of the second convex cylindrical surface of
the flap, and the maximum distance from said axis of rotation to
said cylindrical wall is less than the sum of distance between said
axis of rotation and said axis of pivoting and the distance between
said axis of pivoting and said second edge of the flap.
2. The combination as set forth in claim 1 wherein said combination
includes means for rotating said first and second end discs.
3. The combination as set forth in claim 2 wherein said first edge
of the flaps adjacent to one another is substantially in contact
with one another.
4. The combination as set forth in claim 2 wherein said combination
includes a sealing means coaxially disposed with said axis of rotation
and substantially in contact with said first edges of the flaps.
5. The combination as set forth in claim 2 wherein said first and
second end discs are connected to one another by a rigid elongated
member coaxially disposed with said axis of rotation.
6. The combination as set forth in claim 2 wherein said combination
includes magnet imbedded in said second edge of the flaps and said
cylindrical wall of the cylindrical cavity includes magnetically
reacting material.
7. The combination as set forth in claim 2 wherein said combination
includes rollers rotatably affixed to said flaps adjacent to the
second edge of said flaps for limiting the sliding contact between
the second edge of the flaps and the cylindrical wall of said cylindrical
cavity.
8. The combination as set forth in claim 2 wherein said combination
includes means for measuring the rate of rotation of said first
and second end discs as a measure of fluid flow moving through said
first and second ports.
9. The combination as set forth in claim 1 wherein said combination
includes means for measuring the rate of rotation of said first
and second end discs as a measure of fluid flow moving through said
first and second ports.
10. The combination as set forth in claim 9 wherein said first
edge of the flaps adjacent to one another is substantially in contact
with one another.
11. The combination as set forth in claim 9 wherein said combination
includes a sealing means coaxially disposed with said axis of rotation
and substantially in contact with said first edges of the flaps.
12. The combination as set forth in claim 9 wherein said first
and second end discs are connected to one another by a rigid elongated
member coaxially disposed with said axis of rotation.
13. The combination as set forth in claim 9 wherein said combination
includes magnet imbedded in said second edge of the flaps and said
cylindrical wall of the cylindrical cavity includes magnetically
reacting material.
14. The combination as set forth in claim 9 wherein said combination
includes rollers rotatably affixed to said flaps adjacent to the
second edge of said flaps for limiting the sliding contact between
the second edge of the flaps and the cylindrical wall of said cylindrical
cavity.
15. A fluid flow measuring device comprising in combination:
(a) a body including a cylindrical cavity having a cylindrical
wall and two closed ends, said cylindrical cavity including a first
port disposed through a portion of said cylindrical wall and a second
port disposed through another portion of said cylindrical wall;
(b) a first annular groove disposed in the first closed end of
said cylindrical cavity coaxially about an axis of rotation parallel
to and offset from the geometric central axis of said cylindrical
cavity;
(c) a second annular groove disposed in the second closed end of
said cylindrical cavity coaxially about said axis of rotation;
(d) a plurality of flaps disposed parallel to and about said axis
of rotation intermediate said first and second closed ends within
said cylindrical cavity, each of said plurality of flaps having
a first convex cylindrical surface of a first radius disposed parallel
and adjacent to said axis of rotation; a second convex cylindrical
surface smoothly extending from one boundary of said first convex
cylindrical surface wherein at least a portion of said second convex
cylindrical surface is generated by a second radius greater than
said first radius; and a concave cylindrical surface smoothly extending
from the other boundary of said first convex cylindrical surface
and merging with said second convex cylindrical surface in an accute
angle providing a substantially sharp edge wherein combination of
said cylindrical surfaces provides a cross section of said flap
having a first edge of a substantially round geometry and a second
edge of a substantially pointed crescent geometry, each of said
plurality of flaps supported by said first and second annular grooves
orbitably and pivotably receiving a pair of protrusions respectively
extending from the two extremities of said flap in a coaxial relationship
with the origin of said first radius; wherein said concave cylindrical
surface of one flap accomodates said first convex cylindrical surface
of another flap adjacent to said one flap enabling said flaps to
fold into a position wherein at least a portion of said second convex
cylindrical surface substantially coincides with a hypothetical
circular cylindrical surface concentrically disposed about said
axis of rotation;
wherein the minimum distance from said axis of rotation to said
cylindrical wall of the cylindrical cavity is substantially equal
to said second radius of the second convex cylindrical surface of
the flap, and the maximum distance from said axis of rotation to
said cylindrical wall is less than the sum of distance between said
axis of rotation and said protrusion and the distance between said
protrusion and said second edge of the flap.
16. The combination as set forth in claim 15 wherein said combination
includes means for counting the rate of rotation of said flaps about
said axis of rotation as a measure of fluid flow flowing through
said first and second ports.
17. The combination as set forth in claim 16 wherein said first
edges of adjacent flaps are substantially in contact with one another.
18. The combination as set forth in claim 17 wherein an elongated
member extending from said first closed end to said second closed
end of the cylindrical cavity and disposed coaxially with said axis
of rotation is simultaneously in contact with said first edges of
the flaps.
19. The combination as set forth in claim 16 wherein each of said
protrusions comprises a roller extending from the extremity of said
flap.
20. The combination as set forth in claim 19 wherein said first
edges of adjacent flaps are substantially in contact with one another.
21. The combination as set forth in claim 20 wherein an elongated
member extending from said first closed end to said second closed
end of the cylindrical cavity and disposed coaxially with said axis
of rotation is simultaneously in contact with said first edges of
the flaps.
Description BACKGROUND OF THE INVENTION
In the present day fluid handling technology, the sliding vane
pump or compressor is widely employed as a fluid moving device as
well as a fluid flow measuring device. The sliding vane pump or
compressor comprises a plurality of vanes slidably engaging a plurality
of radial slits included in a circular rotor cylinder that is rotatably
disposed eccentrically within a circular cylindrical cavity having
a fluid inlet and outlet. The sliding movements of the vanes relative
to the slits are subjected to a high friction, which creates not
only wear and tear on the vanes as well as the slits but also the
excessive power consumption by the pumps or compressors and the
high pressure drop in case of flow meters. The arrangement of the
vanes slidably retained in the slits of the rotor has an inherent
weakness in the structural rigidity and strength that limits the
application of vane pumps or compressors to moderately low pressures.
The primary object of the present invention is to provide the flap
pump-flow meter that includes all the advantages of the operating
principles of the sliding vane pump-flow meter without accompanying
the disadvantages of the sliding vane pump-flow meter.
Another object is to provide a positive displacement rotary pump
of a high efficiency and capable of delivering a high pressure head.
A further object is to provide a positive displacement rotary pump
of a compact and light weight construction.
Yet another object is to provide a positive displacement rotary
flow meter of a high sensitivity and great accuracy that is applicable
to high pressure fluid flow.
Yet a further object is to provide a positive displacement rotary
flow meter of a compact construction including simple elements.
These and other objects of the present invention will become clear
as the description thereof proceeds.
BRIEF DESCRIPTION OF THE FIGURES
The present invention may be described with a greater clarity and
specificity by referring to the following figures:
FIG. 1 illustrates a cross section of an embodiment of the flap
pump-flow meter of the present invention.
FIG. 2 illustrates another cross section of the flap pump-flow
meter shown in FIG. 1.
FIG. 3 illustrates a cross section of the body of another embodiment
of the flap flow meter, which cross section is taken along a plane
equivalent to that shown in FIG. 1.
FIG. 4 illustrates an end view of the flap usable in conjunction
with the body shown in FIG. 3.
FIG. 5 illustrates another view of the flap shown in FIG. 4.
FIG. 6 illustrates a further embodiment of the construction of
the flap shown in FIGS. 4 and 5.
FIG. 7 illustrates a cross section of a further embodiment of the
flap pump-flow meter of the present invention.
FIG. 8 illustrates another cross section of the flap pump-flow
meter shown in FIG. 7.
FIG. 9 illustrates a cross section of an embodiment of the assembly
of the flaps usable in conjuction with the flap pump-flow meter
of the present invention.
FIG. 10 illustrates a cross section of another embodiment of the
assembly of the flaps.
FIG. 11 illustrates a cross section of a further embodiment of
the assembly of the flaps.
FIG. 12 illustrates a cross section of yet another embodiment of
the assembly of the flaps.
FIG. 13 illustrates a cross section of yet a further embodiment
of the assembly of the flaps.
DESCRIPTION OF ILLUSTRATED EMBODIMENTS
In FIG. 1 there is illustrated a cross section of an embodiment
of the flap pump-flow meter constructed in accordance with the principles
of the present invention, which cross section is taken along a plane
including the central axis of the fluid inlet and the outlet and
perpendicular to the axis of rotation of the rotor assembly including
a plurality of the flaps. The body 1 of the flap pump-flow meter
1 includes a cylindrical cavity 2 having a smoothly contoured side
wall 3 and two closed ends. The cross section of the cylindrical
cavity 2 may be a circle or an ellipse or any other shape of a smoothly
contoured perimeter. A pair of flow ports 4 and 5 are disposed through
the side wall 3 of the cylindrical cavity 2 at two substantially
diametrically opposite positions. The extremities of the flow ports
4 and 5 include adapting means 6 and 7 respectively, for connecting
the flap pump-flow meter to a pipe line. A plurality of the flaps
8 9 10 etc. are disposed within the cylindrical cavity 2 wherein
each of the flaps is rotatable about the central axis 11 of the
assembly of the flaps and pivotable about the pivoting axis 12 of
each flap that coincides with the center of the circle including
the substantially semicircular leading edge or head portion 13 of
the cross section of the flap. The crescent trailing edge or tail
portion 14 of the cross section of the flap includes a substantially
pointed edge, where the convex and concave edges of the cross section
of the flap merge. The center line 11 of the assembly of the flaps
8 9 10 etc. is located eccentrically from the center line of
the cylindrical cavity 2 wherein the minimum distance between the
center line 11 of the assembly of the flaps and the wall of the
cylindrical cavity 2 is substantially equal to the radius of the
circle including the outer perimeter of the assembly of the flaps
at the fully retracted position and the maximum distance therebetween
is substantially less than the distance from the center line 11
of the assembly of the flaps to the tip of the trailing edge of
the flap at the fully extended position. The pivoting centers of
the flaps coinciding with the center of the circle including the
semicircular leading edge of the cross section of the flaps are
axixymmetrically located about the central axis of 11 of the assembly
of the flaps and spaced from each other in such a way that the semicircular
loading edges of the flaps are in contact with each other in a leak
proof rolling contact. The trailing edges of the flaps 8 9 10
etc. may include magnetic bars 15 16 17 etc. imbeded in the trailing
edges of the flaps, respectively, in order to establish a constant
sliding contact between the trailing edge of the flaps and the side
wall 3 of the cylindrical cavity 2. Of course, the side wall 3 of
the cylindrical cavity 2 must include a ferro-magnetic material
in order to make the magnet-tipped flap effective. The arrangement
shown in FIG. 1 includes means for rotating the assembly of the
flaps about the central axis thereof when the assembly functions
as a pump or compressor, while it may include a sensor 18 that counts
the frequency of the trailing edges of the flaps passing thereby
when it functions as a flow meter. It should be noticed that the
flow ports 4 and 5 are disposed in the pattern of mirror image to
one another with respect to a plane including the central axis of
the assembly of the flaps and the central axis of the cylindrical
cavity 2. The flaps may be made hollow in order to reduce the mass
and the centrifugal force resulting therefrom.
In FIG. 2 there is illustrated a cross section of the arrangement
shown in FIG. 1 taken along plane 2--2 as shown in FIG. 1. In this
particular embodiment each flap includes a pair of stub shafts 19
and 20 extending from two extremities thereof in line with the pivoting
axis coinciding with the center of the circle including the substantially
semicircular leading edge of the cross section of the flap, which
rotatably engage the holes 21 22 etc. respectively included in
a pair of the circular discs 23 and 24 rotatably supported by a
pair of stub shafts 25 and 26 extending therefrom in the coaxial
relationship and supported by the bearings 27 and 28 secured to
the end walls of the cylindrical cavity 2. It should be noticed
that the circular discs 23 and 24 are respectively disposed in two
counter bores respectively included in two end walls of the cylindrical
cavity wherein the inside end face of the circular discs 23 and
24 are flush to the natural end wall of the cylindrical cavity 2.
It should be understood that the components assembled to a pump
of flow meter as shown in FIGS. 1 and 2 must have the precise dimensions
whereby the interfaces therebetween do not provide any gap through
which the fluid may creep and leak. The circular discs 23 and 24
rotatable about the central axis 11 of the assembly of the flaps
enables the flaps 8 9 10 etc. to rotate about the central axis
11 while the pivotable support of the flaps by the circular discs
23 and 24 enablesthe flaps to pivot about the pivoting axis coinciding
with the center of the circle including the substantially semicircular
leading edge of the cross section of the flap. When the arrangement
shown in FIGS. 1 and 2 is used as a pump or compressor the stube
shafts 25 and 26 should be made to extend through the end walls
of the cylindrical cavity 2 in a leak-proof manner and coupled to
a power input shaft. When the arrangement shown in FIGS. 1 and 2
is used as a flow meter, it should include a counter that counts
the frequency of the flaps passing thereby. It is not difficult
at all to realize from FIG. 1 that, when the assembly of the flaps
is rotated in the clockwise direction by means of an external power
input, the fluid will be forcibly moved from the right hand side
port 5 to the left hand side port 4 and, consequently, it is a pump
or compressor. When the fluid moves from the left hand side port
4 to the right hand side port 5 under a pressure gradient, the assembly
of the flap will rotate in the counter clockwise direction at a
rotational speed proportional to the rate of flow of the fluid and,
consequently, it is a positive displacement flow meter. The particular
embodiment shown in FIG. 2 is one of many arrangements providing
the kinematical functions for the flaps as illustrated in FIG. 1.
In FIG. 3 there is illustrated a cross section of the body of an
embodiment of the flap flow meter operating under the same principles
as illustrated in FIG. 1 which cross section is taken along the
same plane as the plane 2--2 shown in FIG. 1. The body 29 of the
flow meter shown in FIG. 3 includes a cylindrical cavity 30 equivalent
to the cylindrical cavity 2 shown in FIG. 1. Two end walls 31 and
32 of the cylindrical cavity 30 respectively includes a pair of
annular grooves 33 and 34 having semicircular cross section. The
common central axis 35 of the two annular grooves 33 and 34 are
off set from the central axis of the cylindrical cavity 30. The
two fluid ports including the port 36 shown in FIG. 3 is arranged
in the same way as illustrated in FIG. 1.
In FIG. 4 there is illustrated an end view of the flap having a
substantially semicircular leading edge 37 two hemispherical extremities
38 and 39 having the same radius as the semicircular leading edge
37 and a substantially crescent trailing edge 40 which combination
has essentially the same cross section as that of the flaps shown
in FIG. 1.
In FIG. 5 there is illustrated another view of the flap shown in
FIG. 4 viewed through plane 5--5 as shown in FIG. 4 which may be
constructed with a solid or a hollow core as shown in FIG. 1. The
radius of the hemispherical extremities 38 and 39 are closely matched
to the radius of the cross section of the annular grooves 33 and
34 shown in FIG. 3 whereby the flaps shown in FIGS. 4 and 5 confined
within the cylindrical cavity 30 shown in FIG. 3 are rotatable about
the rotating axis 35 and pivotable about the pivoting axis passing
through the center of two hemispherical extremities of the flap
as two hemispherical extremities of the flaps slidably and rotatably
engage two annular grooves 33 and 34 in a substantially leak-proof
manner. The radius of the annular groove measured from the rotating
axis 35 may be proportioned to the radius of the substantially semicircular
leading edge of the flap in such a way that the semicircular leading
edges of adjacent flaps confined within the cylindrical cavity 30
establish a leak-proof sliding contact. In such a case the midsection
of the central cylindrical member 41 coaxially disposed with the
rotating axis 35 can be omitted. It should be understood that, in
practice, the body of flow meter shown in FIG. 3 should be a two
piece construction whereby the flaps can be confined therein after
the body and flaps are manufactured separately.
In FIG. 6 there is illustrated another embodiment for constructing
the flap of one-piece construction shown in FIGS. 4 and 5. The cylindrical
construction of the flap with a substantially semicircular leading
edge 42 and a crescent trailing edge 43 is provided with two hemispherical
extremities by a pair of hemispherical members 44 and 45 rotatably
connected to the cylindrical flap, wherein the hemispherical members
are rotatable relative to the cylindrical flap about the pivoting
axis coinciding with the centers of the two hemispherical members
and the center line of the semicircular leading edge of the flap.
The construction of the flap shown in FIG. 6 has an advantage over
the construction of the flap shown in FIG. 5 in view that the rotating
movement of two hemispherical ends 44 and 45 relative to the cylindrical
midsection of the flap eliminates the localized wear on the hemispherical
ends of the flap.
In FIG. 7 there is illustrated a cross section of a further embodiment
of the flap pump-flow meter having essentially the same construction
as that shown in FIG. 1 with two exceptions being that, firstly,
the flaps 46 47 48 49 etc. are not in contact to each other
in contrast to the flaps 8 9 10 etc. shown in FIG. 1 and, secondly,
a seal including a plurality of sets of lips 52 53 54 55 etc.
supported by the shaft 51 is simultaneously in contact with the
substantially semicircular leading edges of the flaps. It should
be mentioned that the number of flaps employed in each arrangement
is merely a matter of design, as the arrangement shown in FIG. 1
may include more than three flaps, while that of FIG. 7 may include
three or more than four flaps. It is also a matter of design to
construct the flap with a solid or hollow core. The magnetic bars
imbeded in the trailing edge of the flaps as shown in FIG. 1 are
usually not required in pumps as the centrifugal force generated
by the high rate of rotation of the assembly of the flaps ensures
the sliding contact between the trailing edges of the flaps and
the cylindrical walls of the cylindrical cavity.
In FIG. 8 there is illustrated a cross section of the flap pump-flow
meter shown in FIG. 7 taken along plane 8--8 as shown in FIG. 7.
The arrangements illustrated in FIG. 8 is similar to that of FIG.
2 with a few exceptions. The two circular discs 56 and 57 rotatably
and pivotably supporting the flaps are nonrotatably connected to
the shaft 51 having at least one extremity extending through the
end wall of the cylindrical cavity in leak-proof manner, as facilitated
by a sealing means such as the packed seal 58 for coupling thereof
with a power input shaft. The bearings 59 and 60 are respectively
isolated from the medium being pumped by the annular seals 61 and
62. It should be understood that the construction illustrated in
FIGS. 7 and 8 may be used as a flow meter wherein the amount of
the volume flow is measured by measuring the speed of rotation of
the shaft 51. In general, the construction shown in FIGS. 2 or 3
is more suitable for a flow meter compared with that of FIG. 8
as the former arrangement operates with much less frictional resistance.
In FIG. 9 there is illustrated a cross section of the assembly
of the flaps 63 64 65 etc. wherein the assembly itself is rotatable
about the central axis 66 thereof and each of the flaps 63 64
65 etc. is respectively pivotable about each of the pivoting axis
67 68 69 etc., each of which coincides with the center of the
circle including the substantially semicircular leading edge of
each of the flaps 63 64 65 etc. The outer perimeter of the assembly
of the flaps takes on a substantially circular configuration when
all of the flaps are pivoted to the fully retracted position. In
this arrangement, the pivoting axis 67 68 69 etc. are axisymmetrically
positioned about the central axis 66 wherein the semicircular leading
edges of the flaps are under a leak-proof slidable contact therebetween.
The radius of the circle including the outer perimeter of the assembly
of the flaps at the fully retracted position is substantially equal
to the distance between the central axis 66 and the pivoting axis
67 plus the radius of the semicircular leading edge of the flap.
The assembly of the flaps shown in FIG. 9 is essentially the same
one as that employed in the flap pump-flow meter shown in FIG. 1
with the exceptions of the hollow core and the magnetic bar included
therein. It is easy to realize that less or more than three flaps
can be assembled into an assembly similar to that shown in FIG.
9.
In FIG. 10 there is illustrated a cross section of another assembly
of flaps 70 71 72 etc. constructed essentially in the same way
as that of FIG. 9 with one exception being that the radius of the
circle including the outer perimeter of the assembly of the flaps
at the fully retracted position is significantly greater than the
distance between the central axis of assembly and the pivoting axis
of the flap plus the radius of the semicircular leading edge of
the flap.
In FIG. 11 there is illustrated a cross section of a further assembly
of the flaps 73 74 75 76 etc. wherein the pivoting axis 77
78 79 80 etc. are axisymmetrically located about the central
axis 81 of the assembly in such a way that the semicircular leading
edges of the flap are not in contact to each other. A seal 82 including
a plurality of sets of lips mounted on the central shaft 83 is simultaneously
in contact with all of the semicircular leading edges of the flaps.
The outer perimeter of the assembly of the flaps at the fully retracted
position takes on a circular configuration as defined in conjunction
with FIG. 9 or 10. The assembly of the flaps shown in FIG. 11 is
essentially the same one as that included in the flap pump-flow
meter shown in FIG. 7 which assembly may include the flaps of less
or greater number than four.
In FIG. 12 there is illustrated a cross section of yet another
assembly of the plurality of flaps 84 etc. pivotable about the
pivoting axis 85 etc. coinciding with the center of the circle
including the substantially semicircular leading edge of the flap,
which assembly is rotatable about the central axis 86 thereof. The
creeping movement of the fluid across the assembly is checked by
the leak-proof sliding contact between the substantially semicircular
leading edges of the flaps as well as by the seal 87 including a
plurality of sets of the lips mounted on the drum 88 coaxially affixed
to the central shaft 89 which seal is simultaneously in contact
with all of the semicircular leading edges of the flaps. The assembly
of the flaps of this combination is particularly suitable for constructing
a flap pump.
In FIG. 13 there is illustrated a cross section of yet a further
assembly of the flaps 100 etc. assembled essentially in the same
construction as that shown in FIG. 12 with two exception being that,
firstly, the substantially semicircular leading edges of the flaps
are not in contact to each other and, secondly, the tips of the
crescent trailing edges of the flaps include the circular cylindrical
rollers 101 etc, rotatably secured to the flaps, respectively.
The outer perimeter of the assembly of the flaps including the trailing
edge rollers takes on a substantially circular configuration when
all of the flaps are pivoted to the fully retracted position. It
should be mentioned that the trailing edge rollers as shown in FIG.
13 may be included in other assemblies of the flaps such as those
shown in FIGS. 9 10 11 and 12. The magnetic bars and the hollow
cores of the flaps as shown in FIG. 1 may be incorporated into those
flap assemblies shown in FIGS. 9 through 13. It should be understood
that the outer perimeter of the assembly of the flaps at the fully
retracted position need not be of an exact circle, as it is sufficient
that the tip of the crescent trailing edge of each flap or a point
on the convex edge of the crescent trailing edge of each flap lies
on a common circle when all the flaps are pivoted to the fully retracted
position.
While the principles of the present invention have now been made
clear by the illustrative embodiments, it will be immediately obvious
to those skilled in the art many modifications in the structures,
arrangements, proportion, elements and materials which are particularly
adapted to the specific working environments and operating conditions
in the practice of the invention without departing from those principles.
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