A ventilator adapted to project a uniform air curtain of high velocity
and of high pressure. The ventilator is in the form of an elongated
air pump in which a rotor shaft is mounted eccentrically within
an open coil helix lining the tubular casing of a stator assembly
having parallel intake and outlet slots extending the full length
of the casing. The shaft is provided with centrifugal vanes which
are caused by centrifugal force to engage the convolution of the
helix and to slide therealong, whereby the helix functions to engage
the vanes without interfering with the flow of air into the pump
and its ejection through the outlet.
1. An air curtain-projecting ventilator formed by an elongated
air pump comprising:
A. a stator assembly formed by a tubular casing having a relatively
broad intake slot an a narrower outlet slot in parallel relation
thereto, the slots extending longitudinally the full length of the
casing, and an open-coil helix lining the casing, the convolutions
of the helix bridging the slots to define grids thereacross which
in no way interfere with the flow of air through the slots;
B. a rotor shaft mounted eccentrically within the helix and extending
the length thereof, said shaft being driven at high speed; and
C. a set of extensible vanes supported on said shaft, said vanes
when extended by centrifugal force being caused to engage the convolutions
of said helix and to slide therealong in an uninterrupted circular
path whereby the helix functions to encage the vanes within the
casing without interfering with the incoming flow of air through
said intake slot and its ejection through said outlet slot to produce
a high velocity air curtain.
2. A ventilator as set forth in claim 1, wherein said shaft is
supported at either end of said casing by bearings and extends beyond
one of said bearings to terminate in a drive pulley.
3. A ventilator as set forth in claim 1, wherein said vanes are
constituted by a set of rigid blades which are slidably received
in slots formed in the shaft, the free ends of the blades engaging
the convolutions of said helix.
4. A ventilator as set forth in claim 3, wherein shaft slots are
in the pattern of an equilateral triangle.
5. A ventilator as set forth in claim 1, wherein said helix is
formed of solid wire.
6. A ventilator as set forth in claim 5, wherein said wire is stainless
7. A ventilator as set forth in claim 1, wherein said helix is
formed of a tubular pipe through which a fluid may be conducted
to produce a heat exchanger to heat or cool the air in said casing.
8. A ventilator as set forth in claim 1, wherein said casing, said
helix and said shaft have corresponding curvatures to define a curvilinear
9. A ventilator as set forth in claim 1, wherein said vanes are
formed by flexible inelastic sheets which are attached at one end
to said shaft, a portion of said vanes being wound on said shaft
when the vanes are extended.
10. A ventilator as set forth in claim 9, wherein said vanes terminate
in weighted cords.
11. A ventilator as set forth in claim 1, wherein said helix is
formed of a tube of permeable material to carry a lubricating fluid.
BACKGROUND OF INVENTION
This invention relates generally to an air curtain-projecting ventilator,
and more particularly to a ventilator whose rotor is provided with
centrifugal vanes operating within the confines of an open-coil
helix lining the tubular casing of a stator assembly having longitudinally
extending intake and outlet slots to generate a uniform air curtain
of high velocity.
In my prior U.S. Pat. No. 3,350,994 isued Nov. 7, 1967, there is
disclosed a ventilating system which projects and air curtain by
means of a tubular casing having a rotor mounted eccentrically therein,
the rotor extending the full length of the casing and being provided
with outstretched vanes or wings whose free edges are tracked to
run adjacent to the inner surface of the casing. The casing is formed
with a large intake opening and a narrow outlet parallel thereto,
so that as air passes through the intake, it is collected by the
vanes, compressed thereby and forced out through the outlet at great
This ventilator functions as an efficient centrifugal air pump
to produce an air curtain which is fully effective throughout the
entire length of the outlet. On the intake or suction side of the
air pump, one may install heating, cooling, and air filter elements
to condition the air.
Such air curtain-projecting ventilators have many practical applications
and are useful wherever it is necessary to thermally or otherwise
isolate a given region, such as the interior of a building from
the exterior, without interposing a physical barrier in the entrance
thereto. For example, where a working station is to be maintained
in a clean atmosphere, one may use an air curtain to isolate this
station from a surrounding contaminated atmosphere.
The difficulty experienced with a ventilating air pump structure
of the type disclosed in my prior patent is that the intake and
outlet slots formed in the casing constitute structural gaps in
the support for the centrifugal blades of the rotor. Because of
these gaps, it becomes necessary to track the vanes at their opposing
ends to maintain the free edges of the vanes slightly spaced from
the surface of the casing. However, because the vanes are subjected
to centrifugal force and are retained only at their ends, they tend
to bow and thereby strike the surface of the casing. The resultant
knocking action of the vanes produces objectionable noise and degrades
the efficiency of the system.
Another factor which has to a degree militated against the success
of an air-curtain projecting air pump of the type disclosed in my
prior patent is that the centrifugal blades, because of the bowing
effect previously mentioned, make contact along their edges with
the curved inner surface of the casing, thereby giving rise to a
relatively high degree of friction and loss of operating efficiency.
SUMMARY OF INVENTION
In view of the foregoing, it is the main object of this invention
to provide an improved ventilator for projecting a uniform air curtain
of high velocity.
More particularly, it is an object of this invention to provide
a ventilator of the above type which is constituted by an air pump
whose rotor shaft is provided with centrifugal vanes operating within
the confines of an open-coil helix which lines the tubular casing
of a stator assembly having longitudinally-extending intake and
outlet slots whereby air drawn into the intake slot is collected,
compressed and ejected at high velocity through the outlet slot.
Among the significant features of an air pump in accordance with
the invention are that the pump operates with high efficiency in
a virtually noiseless fashion and that friction is minimized, so
that the power requirements are relatively low. The air curtain
projected from the air pump is substantially laminar throughout
its entire length, and the structure of the pump is such that it
may be readily installed either horizontally or vertically, no ducts
being required. Moreover, the air pump requires little maintenance
and may be manufactured at low cost.
Briefly stated, these objects are attained in an elongated air
pump in which a rotor shaft is mounted eccentrically within an open-coil
helix that lines the tubular casing of a stator assembly having
parallel intake and outlet slots extending the full length of the
casing, the shaft being driven at high speed.
The shaft is provided with centrifugal vanes or wings which are
initially retracted and in the course of shaft rotation are caused
to extend outwardly to engage the convolutions of the helix and
to slide therealong, whereby the helix functions to encage the vanes
within the casing without interfering with the incoming flow of
air and its ejection from the pump through the outlet slot.
OUTLINE OF DRAWINGS
For a better understanding of the invention as well as other objects
and further features thereof, reference is made to the following
detailed description to be read in conjunction with the accompanying
FIG. 1 is a side view of one preferred embodiment of an air curtain-projecting
ventilator in accordance with the invention;
FIG. 2 is a longitudinal section taken through a portion of the
FIG. 3 is a transverse section taken through the ventilator;
FIG. 4 is a separate view of the helix which is included in the
FIG. 5 is an alternative form of helix formed by a hollow pipe;
FIG. 6 is a side view of a modification of the first embodiment
of the ventilator;
FIG. 7 is a side view of a second preferred embodiment of an air
curtain-projecting ventilator in accordance with the invention;
FIG. 8 is a longitudinal section taken through the second ventilator,
with the helical liner omitted;
FIG. 9 is a transverse section taken through the second ventilator;
FIG. 10 is a side view of a modification of the second embodiment.
DESCRIPTION OF INVENTION
Referring now to FIGS. 1 to 4, there is shown a preferred embodiment
of an air curtain-projecting ventilator in accordance with the invention.
The ventilator is in the form of an elongated air pump that includes
a stator assembly constituted by a straight-line tubular casing
10 having a relatively large intake slot 11 and a narrower outlet
slot 12 in parallel relation thereto, both slots extending longitudinally
along the full length of the casing.
Lining the casing 10 is an open-coil helix 13 which is fabricated
of polished steel wire or other material having a low coefficient
of friction, such as Teflon. The convolutions of helix 13 are well
separated from each other, the helix defining a cage within the
casing which creates grids bridging the intake and outlet slots.
Mounted eccentrically within the stator assembly adjacent the intake
and outlet slots is a rotor shaft 14 supporting a set of three centrifugal
vanes or blades 15. The blades are freely slidable in slots formed
in the rotor, the slots being cut in the pattern of an equilateral
triangle so that in their retracted positions the blades fully occupy
the slot with their inner edges touching the adjacent blade to limit
further retraction thereof. Rotor shaft 14 is supported at either
end of the casing by bearings 16 and 17. One end of the rotor shaft
terminated in a pulley 18 having a motor-driven endless belt 19
looped thereover to rotate the rotor shaft at high speed. As a consequence,
blades 15 are caused by centrifugal force to slide outwardly and
press against the convolutions of helix 13.
When blades 15 are outwardly extended by centrifugal force to engage
the convolutions of the helix, they serve to effectively divide
the stator assembly into three air compartments whose volumes are
unequal and vary with the angular position of the rotor shaft. Because
the edges of the blades make contact not with the inner surface
of casing 10, but with the convolutions of the helix, sliding contact
is effected along a series of distinct points rather than along
a broad area, thereby minimizing friction.
Since these convolutions extend across the gaps in the casing created
by the intake and outlet slots, the gaps are bridged by grids which
in no way interfere with the flow of air into and out of the air
pump and yet maintain continuity in the circular path traversed
by the rotating blades. Thus there are no irregularities encountered
by the blades in the course of shaft rotation, and the system operates
at a relatively low noise level, as compared to prior art structures.
As best seen in FIG. 3, air entering the relatively broad inlet
11 is collected by the centrifugal blades 15 and is compressed in
the compartments defined thereby, the air being ejected at high
velocity through the narrower outlet 12 to project a uniform air
curtain therefrom. the slots are provided with flanges which are
angled to direct the air flow.
In helix 13 shown in FIG. 4, the coil is formed of solid wire,
whereas in the alternative form shown in FIG. 5, coil 13' is formed
of tubular piping material. Hence the helix may be used to convey
a refrigerant or a heated fluid in heat exhange relationship with
the air in the air pump, thereby obviating the need for heating
or cooling elements in advance of the intake, as in prior art structures.
Alternatively, the helix may be used to conduct a lubricant through
the casing which serves to coat the surface engaged by the blades
through minute apertures in the tubing. Alternatively, the tube
may made of oil-permeable material. Also, while three blades have
been shown, in practice any suitable number thereof may be used.
Since the convolutions of helix 13 are physically in contact with
the inner surface of casing 10, there is no leakage path in the
air pump despite the separation of the blade edges from the surface
of the casing. The casing may be reinforced by oppositely-disposed
strips 10A and 10B, as shown in FIG. 3.
Modification of First Embodiment
In the air pump illustrated in FIG. 6, the structure has an arcuate
formation whereby the resulant air curtain has a converging pattern.
In this instance, rotor 14', which is supported at either end by
main bearings 16 and 17 within a casing 20, is constituted by a
series of articulated segments supported by intermediate bearings
21. The open coil helix 22 which lines the casing has a corresponding
In all other respects, this curvilinear air pump functions in the
same manner as that shown in FIG. 1, air sucked into the intake
being projected at high velocity through the outlet slot.
In the air pump disclosed in FIGS. 7, 8 and 9, the structure is
essentialy the same as that of the first embodiment, the stator
assembly being constituted by a casing 10 having a broad intake
slot 11 and a parallel narrow outlet slot 12, the casing being lined
by an open coil helix 13 to bridge the gaps.
However, in this embodiment, rotor shaft 23 eccentrically mounted
within the stator assembly and adjacent the slots is provided with
a set of three vanes 24 of flexible, inelastic material, which are
anchored on the shaft at equidistant points. In practice, the vanes
may be formed of plastic or fabric sheeting. Each vane terminates
at its free end in a weighted cord 25 which runs the full length
of the vane and engages the convolutions of the helix.
Each vane 24 has a breadth that is greater than the straight line
distance between its point of attachment to rotor shaft 23 and the
convolutions of helix 13. As a result, when the rotor shaft turns
to create a centrifugal force, a reserve portion of each vane is
wound on the shaft and the remaining or active portion of the vane
is extended outwardly to divide the casing into air compartments.
Because the rotor shaft is mounted eccentrically within the helix,
the radial distance between the surface of the shaft at any point
therein and the helix varies as a function of shaft angle.
In lieu of weighted cords which make sliding contact with the convolutions
of the helix, use may be made of a bead of Teflon or other low coefficient
material for the same purpose. The weight at the ends of vance 24
is sufficient to produce the centrifugal force which causes the
vane ends to engage the helix. Rotor shaft 23 acts as a control
pulley, which in the course of its rotation more or less winds a
portion of each blade on its surface. It is for this reason that
with rotation of the shaft, each vane 24 has its active portion
extended to the limit imposed by its weighted cord 25 or bead within
helix 13. But since the cord or bead slides along the convolutions
of the helix, the resultant resistance causes the active part of
the vane to assume a tangential position relative to the rotor shaft.
This tangential projection of the active portion of the vanes occurs
throughout the closed circuit rotary cycle in accordance with the
distance of the rotary shaft relative to the helix. Thus in the
course of each rotary cycle, each vane undergoes an extension to
the degree limited by the helix, the relation between the reserve
portion of the vane wound on the rotor shaft and the active portion
extending tangentially from the shaft varying with angle. As a consequence,
the volume of the air compartments defined by the blades varies
from a minimum to a maximum value to provide a highly efficient
centrifugal air pump.
Modification of Second Embodiment
In the air pump illustrated in FIG. 10, the structure has an arcuate
rather than a rectilinear formation, and rotor 26, which is supported
at either end by main bearings 27 and 28, is constituted by a series
of articulated segments supported by intermediate bearings 29. Open
coil helix 30 which lines the casing has a corresponding curvature.
The air pump in all other respects functions in the same manner
as that in FIGS. 7 to 9 to suck in air through its longitudinally-extending
intake and to expel the air through the outlet slot to produce an
air curtain of high velocity.
Because an elongated air-curtain projecting ventilator according
to the invention acts as a positive displacement pump and in a manner
similar to an air compressor, the air curtain projected thereby
is not only at a high velocity but also is at high pressure. Hence
there are practical applications for this ventilaor for which conventional
air curtain-projecting devices are unsuitable. For example, the
high-pressure, high-velocity air curtain may be caused to impinge
on a water stream to effect aeration thereof. Or the air curtain
may be used in a Hovercraft or other air elevated platforms to provide
the necessary elevating force. Thus an array of elongated air-curtain
projecting ventilators may be mounted on the undersurface of the
platform to produce a very powerful air stream for elevating the
While there have been shown and described preferred embodiments
of an air curtain-projecting ventilator in accordance with the invention,
it will be appreciated that many changes and modifications may be
made therein without, however, departing from the essential spirit
thereof. For example, while an articulated rotor shaft has been
shown for a curvi-linear ventilator, this shaft may be formed of
flexible material and bent to the desired curvature.