Gas separation: processes – Deflecting – Centrifugal force
Reexamination Certificate
2001-12-19
2004-04-13
Hopkins, Robert A. (Department: 1724)
Gas separation: processes
Deflecting
Centrifugal force
C055S416000, C055S429000, C055S438000, C055SDIG003
Reexamination Certificate
active
06719830
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates initially, and thus generally, to an improved vacuum cleaner. More specifically, the present invention relates to an improved vacuum cleaner that utilizes a cylindrical vortex flow such that the air pressure within the dust collector is above air pressure in the separation chamber. The high pressure maintains the cylindrical vortex flow pattern without preventing dust particles from traveling straight into the dust collector. Moreover, the present invention's impeller serves the dual purpose of both moving fluid through the system and creating a cylindrical vortex by spinning air at the blade speed of the impeller. Thus, the dual purpose impeller provides both efficiency and simplicity to the separator. The present invention eliminates the need for vacuum bags, HEPA filters, or liquid baths. Further, straightening vanes in the outlet air flow provide non-rotating air to the vacuum cleaner nozzle. The present invention provides non-rotating, substantially dust-free air to the vacuum cleaner nozzle. The preferred embodiment utilizes a toroidal vortex vacuum cleaner nozzle. However other nozzles or application of straightened airflow are possible.
BACKGROUND OF THE INVENTION
The use of vortex forces is known in various arts, including the separation of matter from liquid and gas effluent flow streams, the removal of contaminated air from a region and the propulsion of objects. However, cylindrical vortex flow has not previously been provided in a bagless vacuum device having light weight and high efficiency.
The prior art is strikingly devoid of references dealing with toroidal vortices in a vacuum cleaner application. However, an Australian reference has some similarities. This Australian reference does not approach the scope of the present invention, but it is worth discussing its key features of operation so that one skilled in the art can readily see how its shortcomings are overcome by the present invention disclosed herein.
In discussing Day International Publication number WO 00/19881 (the “Day publication”), an explanation of the Coanda effect is required. This is the ability for a jet of air to follow around a curved surface. It is usually referred to without explanation, but is generally understood provided that one makes use of “momentum” theory: a system based on Newton's laws of motion. Utilizing the “momentum” theory instead of Bernoulli's principles provide a simpler understanding of the Coanda effect.
FIG. 1
shows the establishment of the Coanda effect. In (A) air is blown out horizontally from a nozzle
100
with constant speed V. The nozzle
100
is placed adjacent to a curved surface
102
. Where the air jet
101
touches the curved surface
102
at point
103
, the air between the jet
101
and the surface
102
as it curves away is pulled into the moving airstream both by air friction and the reduced air pressure in the jet stream, which can be derived using Bernoulli's principles. As the air is carried away, the pressure at point
103
drops. There is now a pressure differential across the jet stream so the stream is forced to bend down, as in (B). The contact point
104
has moved to the right. As air is continuously being pulled away at point
104
, the jet continues to be pulled down to the curved surface
102
. The process continues as in (C) until the air jet velocity V is reduced by air and surface friction.
FIG. 2
shows the steady state Coanda effect dynamics. Air is ejected horizontally from a nozzle
200
with speed represented by vector
201
tangentially to a curved surface
203
. The air follows the surface
203
with a mean radius
204
. Air, having mass, tries to move in a straight line in conformance with the law of conservation of momentum. However, it is deflected around by a pressure difference across the flow
202
. The pressure on the outside is atmospheric, and that on the inside of the airstream at the curved surface is atmospheric minus
V
2
/R where
is the density of the air.
The vacuum cleaner Coanda application of the Day publication has an annular jet
300
with a spherical surface
301
, as shown in FIG.
3
. The air may be ejected sideways radially, or may have a spin to it as shown with both radial and tangential components of velocity. Such an arrangement has many applications and is the basis for various “flying saucer” designs.
The simplest coanda nozzle
402
described in the Day publication is shown in FIG.
4
. Generally, the nozzle
402
comprises a forward housing
407
, rear housing
408
and central divider
403
. Air is delivered by a fan to an air delivery duct
400
and led through the input nozzle
401
to an output nozzle
402
. At this point the airflow cross section is reduced so that air flowing through the nozzle
402
does so at high speed. The air may also have a rotational component, as there is no provision for straightening the airflow after it leaves the air pumping fan. The central divider
403
swells out in the terminating region of the output nozzle
402
and has a smoothly curved surface
404
for the air to flow around into the air return duct using the Coanda effect.
Air in the space below the Coanda surface moves at high speed and is at a lower than ambient pressure. Thus dust in the region is swept up
405
into the airflow
409
and carried into the air return duct
406
. For dust to be carried up this duct, the pressure must be low and a steady flow rate must be maintained. After passing through a dust collection system the air is sent through a fan back to the air delivery duct. Constriction of the airflow by the output nozzle leads to a pressure above ambient in this duct ahead of the jet. In sum, air pressure within the system is above ambient in the air delivery duct and below ambient in the air return duct.
Coanda attraction to a curved surface is not perfect. As shown in
FIG. 5
, not all the air issuing from the output nozzle is turned around to enter the air return duct. An outer layer of air proceeds in a straight fashion
501
. When the nozzle is close to the floor, this stray air will be deflected to move horizontally parallel to the floor and should be picked up by the air return duct if the pressure there is sufficiently low. In this case, the system may be considered sealed; no air enters or leaves, and all the air leaving the output nozzle is returned.
When the nozzle is high above the ground, however, there is nothing to turn stray air
501
around into the air return duct and it proceeds out of the nozzle area. Outside air
502
, with a low energy level is sucked into the air return to make up the loss. The system is no longer sealed. An example of what happens then is that dust underneath and ahead of the nozzle is blown away. In a bagless system such as this, where fine dust is not completely spun out of the airflow but recirculates around the coanda nozzle, some of this dust will be returned to the surrounding air.
Air leakage is exacerbated by rotation in the air delivery duct caused by the pumping fan. Air leaving the output nozzle rotates so that centrifugal force spreads out the airflow into a cone. This results in the generation of a larger amount of stray air. Air rotation can be eliminated by adding flow straightening vanes to the air delivery duct, but these are neither mentioned nor illustrated in the Day publication.
A side and bottom view of an annular Coanda nozzle
600
is shown in FIG.
6
. This is a symmetrical version of the nozzle shown in FIG.
4
. Generally, the nozzle
600
comprises outer housing
602
, air delivery duct
601
, air return duct
605
, flow spreader
603
and annular Coanda nozzle
604
. Air passes down though the central air delivery duct
601
, and is guided out sideways by a flow spreader
603
to flow over an annular curved surface
604
by the Coanda effect, and is collected through the air return duct
605
by a tubular outer housing
602
.
This arrangement suffers from the previously described shortcomings in that air strays away from the Coanda
Illingworth Lewis
Reinfeld David
Hopkins Robert A.
Vortex Holding Company
Ward & Olivo
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