U.S. patent number 3,672,066 [Application Number 05/085,568] was granted by the patent office on 1972-06-27 for microwave drying apparatus.
This patent grant is currently assigned to Bechtel International Corporation. Invention is credited to Erik W. Stephansen.
United States Patent |
3,672,066 |
Stephansen |
June 27, 1972 |
MICROWAVE DRYING APPARATUS
Abstract
A device is provided for drying a continuous web or sheet of
material passing through a drying zone. The device includes two air
cushions which face each other and force the sheet of material
passing through the drying zone to stay midway between opposite
microwave drying units. Further, to prevent wrinkling of the sheet
material, the air cushions are provided by spaced slots extending
at an angle to the path of travel of the sheet to ensure that
streaking of a coating on the sheet is obviated.
Inventors: |
Stephansen; Erik W. (Foster
City, CA) |
Assignee: |
Bechtel International
Corporation (N/A)
|
Family
ID: |
22192490 |
Appl.
No.: |
05/085,568 |
Filed: |
October 30, 1970 |
Current U.S.
Class: |
34/265;
219/693 |
Current CPC
Class: |
D06C
7/00 (20130101); F26B 13/104 (20130101); H05B
6/78 (20130101); F26B 3/343 (20130101); F26B
3/34 (20130101); D06C 2700/09 (20130101); H05B
2206/046 (20130101) |
Current International
Class: |
D06C
7/00 (20060101); F26B 13/20 (20060101); F26B
3/32 (20060101); F26B 13/10 (20060101); F26B
3/34 (20060101); H05B 6/78 (20060101); B01k
005/00 () |
Field of
Search: |
;34/1,156 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Dority, Jr.; Carroll B.
Claims
I claim:
1. In an apparatus for drying a moving web of a sheet material
moving in one direction through the apparatus, the apparatus
including at opposite edges of the moving web and in spaced
relation thereto opposite first and second end walls extending
parallel to said direction, a top wall and a bottom wall extending
between said end walls generally parallel to the plane of the web
of sheet material and on opposite sides thereof, a third and a
fourth wall extending from each said top and bottom wall toward
said web of sheet material and between said end walls to provide a
gas duct, means for supplying gas to said duct for discharging gas
against said web, a fifth wall extending from said first end wall
toward the second end wall and spaced therefrom to provide a
waveguide, a sixth and a seventh wall extending from the first end
wall toward the second end wall to provide a gas exhaust duct and
an extension of the waveguide, and means for feeding microwave
energy into said wave guide.
2. In an apparatus for drying a moving web of sheet material as in
claim 1, an eighth wall extending from the second end wall toward
and spaced from the first end wall between the fifth and sixth
walls to continue the waveguide with the fifth wall.
3. In an apparatus for drying a moving web of sheet material as in
claim 2, wherein said sixth and seventh walls are spaced from the
second end wall and are closed at their ends adjacent the second
end wall, a top plate covering the sixth and seventh walls and
having a plurality of apertures therein through which the gas is
exhausted, said sixth wall defining a continuation of the waveguide
with the eighth wall.
4. In an apparatus for drying a moving web of sheet material as in
claim 3, wherein gas distribution means comprising slot means is in
said gas discharge duct between said third and fourth walls to
evenly distribute gas against said web.
5. In an apparatus for drying a moving web of sheet material as in
claim 4, wherein said gas distribution means comprises an
upstanding flange extending longitudinally in equally spaced
relationship between said third and fourth walls, a cover supported
on said flange in spaced relation between the third and fourth
walls and in the plane of the upper ends of the third and fourth
walls to define longitudinally extending slots between the opposite
edges of the cover and the adjacent edges of the upper ends of the
third and fourth walls, a plurality of slots in said cover disposed
at an angle to the direction of movement of said web and at an
angle to the third and fourth walls so that gas is released
angularly across the web of sheet material to prevent streaking or
wrinkling of said web of sheet material as it is moved through said
drying apparatus.
6. In an apparatus for drying a moving web of sheet material as in
claim 5, wherein a plurality of gas discharge ducts, waveguides and
exhaust ducts are alternately arranged in said drying apparatus.
Description
BACKGROUND OF THE INVENTION
The simultaneous application of a gas to a sheet of material
undergoing drying by microwave energy is known and one can refer to
prior U.S. Pat. Nos. 3,449,836, 3,475,827 and 3,491,457. In these
and other prior art devices, however, the gas impingement was such
that gas was not effective to maintain the web spaced equally
between the opposite waveguides providing the microwave energy
application.
SUMMARY OF THE INVENTION
It is in general the broad object of the present invention to
provide an improved drier for a continuous web of material by
microwave energy in which opposite and equal air cushions are
provided on opposite sides of the web to hold the web in a
centralized position as it passes through the opposite waveguides
of the microwave drier.
A further object of the present invention is to provide air
cushions so spaced and provided that wrinkling of the web or of a
coating on the web is obviated.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an embodiment of the apparatus for
practicing the present invention.
FIG. 2 is a section taken transversely through the means providing
the opposite air cushions.
FIG. 3 is a perspective view showing the air outlet means provided
at an angle to the run of the web.
FIG. 4 is a top plan view of one-half of the microwave drier
assembly.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In the description which follows, it is assumed that a coated or a
partially dry web is being dried by the combined action of
microwave energy and jets of a drying gas such as air, nitrogen or
superheated steam applied to a web of the sheet material indicated
at 10. The web 10 is drawn through the drier by means well known to
those skilled in the art and therefore is not illustrated. The
movement of the web can be in the direction indicated by the arrow
or in the opposite direction.
The drier comprises upper and lower sections indicated at 11 and
12. These sections are alike so a description of one will suffice.
The drier sections 11 and 12 are spaced apart about a quarter of an
inch to minimize the tendency for dust or lint which may accumulate
between the two halves to cause arcing. Each drier section includes
a plurality of waveguides and a plurality of gas distribution means
and gas collection means. Basically, each drier section includes
opposite parallel end walls 13 and 14 joined together by walls 16
and 17 which provide a first duct through which the drying gas is
passed for release against the web. A wall 18 also extends from end
wall 14 toward the opposite end wall 13 but is spaced therefrom. A
wall 19 extends from the end wall 13 toward the end wall 14 but is
also spaced therefrom. Extending from wall 14 are parallel walls 21
and 22 which extend toward end wall 13, the end of these walls
being closed as at 23 and by a top plate 24 provided with a
plurality of apertures 26 through which the drying gas is
exhausted. Angular guide plates 27 are provided at the junction of
each of the aforementioned walls with an end wall to direct the
flow of the microwaves through the drier.
A source 31 of microwave energy is provided to feed the spaced
waveguides through line 32 into the waveguide provided by walls 17
and 18. The generator 31 can be any well-known source of RF energy
and in one practical embodiment of the invention the energy source
consisted of a Klystron and associated power supply operating at
2,450 mHz. Suitably the RF generator operates at a frequency from
about 300 to 30,000 mHz. Thus the ISM allocated frequencies of 915;
2,450; 5,800 and 22,125 mHz are suitable.
The microwave energy is fed into the waveguides provided
sequentially, for example, by walls 17 and 18, 18 and 19, 19 and
21, 22 and 19, 19 and 18, and 18 and 16 to pass through the drying
section. At the terminal end 33 of the waveguide a dummy load 34 is
provided to absorb excess energy and, in case of a web break, to
absorb total energy input. The microwave energy is introduced
through a split microwave tee, one half being on the upper section
11 and the other half being on the lower section 12. The usual
microwave tuning devices are included and since these are well
known they are neither described nor shown.
In accordance with the present invention, there is provided in
conjunction with and between walls 16 and 17 (FIGS. 2 and 3) an air
distribution device, generally indicated at 36, which includes a
base 37 having an upstanding flange 38 provided centrally thereof
and providing a support for a cover 39 which fits in spaced
relation between walls 16 and 17 and in the plane of the upper ends
of the walls and fitting close to the edges of the walls so that
air can escape between the cover and the walls, as is shown in FIG.
2, and through slots 41 provided in the cover 39.
As appears in FIG. 2, the air release occurs on opposite sides of
the sheet and under conditions such that the forces applied by the
opposite air streams to the sheet are opposite and equal. Further
and in accordance with the preferred embodiment, the slots 41 are
at an angle to the run of walls 16 and 17 so that the air is
released angularly across the sheet. This prevents streaking of any
coating which may have been applied to the sheet. If the web is not
coated or if streaking is not objectionable, the slots can extend
parallel to the run of the sheet. The air is supplied by a fan 46
through a manifold 47 connected by line 48 to each of the air
inlets. If desired, the air may be heated and filtered. The air is
exhausted through outlets 49.
* * * * *