Improvements in Apparatus for the Drying or other Treatment of Tea Leaf, Tobacco Leaf, Coffee, Grain, Malt, Fruits, and other Sub- stances by Means of a Current of Hot or Dry Air or Mixed Gas or Gases and Air.
Year: 1897

page_text: end. The air current through the web chamber thus passes in a serpentine course
down and up through the whole length of the web from end to end of the web
chambers, and the number of times it so passes through the web may be arranged
to suit requirements as to size and power of apparatus required and the descrip-
tion of work to be done.
:
Improvements in Apparatus for the Drying or other Treatment of Tea
Leaf, Tobacco Leaf, Coffee, Grain, Malt, Fruits, and other Sub-
stances by Means of a Current of Hot or Dry Air or Mixed Gas or
Gases and Air.
I, SAMUEL CLELAND DAVIDSON, of Sirocco Engineering Works, Belfast, Ireland,
Merchant, do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by
the following statement:-
=
My invention has reference to apparatus for the drying or other treatment of
tea leaf, tobacco leaf, coffee, grain, malt, fruits and other substances by means of
a current of hot or dry air or mixed gas or gases and air.
The chief features of the invention are the passing of a current of hot or dry
nir, or mixed gas or gases and air twice or oftener through the tea or tobacco leaf
or other substance as this is being carried by a travelling web of foraminous
material through a chamber or enclosure (hereinafter called the web chamber)
the current passing alternately downward and upward through the web; a special
construction of the web chamber whereby the said current is caused to follow a
serpentine course so as to pass through the web downward and upward alternately
and whereby the distribution of the current is approximately equalised' over the
whole area of the web; a special disposition or location relatively to the web
chamber of a current-producing fan and air duets whereby the current from the
air inlet end of the web chamber up to an intermediate point of same is an exhaust
or suction current and the current through the remainder of the web chamber is
a pressure blast; and the general construction and arrangement of the whole
apparatus.
Having stated the chief features of the invention I will now describe an
apparatus in which the invention is embodied.
The body of the apparatus consists of a horizontal box or enclosure being what
I call the web chamber mounted on a suitable stand or legs, and divided inter-
nally into upper and lower compartments by a web of any suitable foraminous
material such as wire web which is arranged to pass through the web chamber
from end to end and about midway between top and bottom. This web is mounted
upon and moved by two revolving drums one at each end and outside of the web
chamber, and so adjusted thereto that the under surface of the web returns below
the bottom and outside the chamber as shown. The upper and lower compartments
of the web chamber are also divided into sub-compartments by means of cross
partitions so arranged that when a current of air is passed through the web cham-
ber from either of its ends to its centre as in one modification hereinafter described
or from end to end as in another modification, it must necessarily pass alternately
down and up as a serpentine-like current through the web dividing the upper end

page_text: and lower compartments. In order to equalise the distribution of this current
over the whole area of each soction of the web which is exposed thereto I insert.
in each of the sub-compartments formed by the cross partitions a perforated plate
either above or below the section of the web through which the current is to pass
in its course from one sub-compartment above to another below or vice versa. The
said distributing plates have their perforations so arranged that the current in
passing through same is evenly distributed over the next intervening surface of
the web, the area of perforations through the said plate being for this purpose less
at the end which is towards the advancing current than towards the further end
where the same may consist of one large oblong opening or the plate itself may
be terminated so as to leave an open space equivalent to the said oblong opening.
To create the current through the web chamber I employ a fan mounted accord-
ing to one modification preferably on top of, and over the two central sub-
compartments above the web, and I connect the eye of the fan by a port and duct
to one of these sub-compartments and the nozzle to the other so that the fan will
draw the air out of the sub-compartment connected to the eye of the fan by suction
and propel it into the other which is connected to the nozzle of the fan.
The effect of employing the fan in this way is that from the air inlet end of the
web chamber to the fan, the air current is created by exhaust or suction and from
the fan to the opposite end by pressure blast. Above the top sub-compartment
at the suction end of the web chamber I fit a supply duct to be connected with
any suitable apparatus or stove for producing hot or dried air, gases or mixed
gas and air (hereinafter referred to as the air current) and I preferably make the
bottom of such supply duct with a perforated plate to distribute the air evenly
over the top surface of the section of the web below same. In working the
apparatus the tea or tobacco leaf or other material to be treated is fed on to
the exposed upper surface of the web at the feed end, and the web being in motion
the leaf or material is carried thereby through the web chamber. The suction of the
fan draws the air firstly down through the web and the material thereon into the
sub-compartment below same, which is double the length of the first or inlet onc
on top, and as its passage along this sub-compartment is blocked by the cross-
partition forming its further end the current now passes upward through a
second perforated plate, below the next section of the web through which the
current passes to evenly distribute it over the bottom of same, after which the
current may, if the apparatus be required of larger size be made to take further
down and up courses through the web in which case the web would be equiva-
lently longer, but I usually construct the apparatus so as to let the current then
go into the fan out of the top of the second upper sub-compartment, and after
passing through the fan it is then reintroduced by pressure blast into the top of
the third upper sub-compartment through a perforated distributing plate and
driven down through the section of web then below same to the second of the
lower sub-compartments, and then through another perforated distributing plate
to the bottom of the next section of the web, and after passing upwards through
same I usually then allow the air to escape.
Either end of the machine may he made the feed end, according to the direction
in which the web drums are revolved, but usually the most economical results
are obtained by making the feed end that at which the air escapes after its transit
through the web chamber. The material fully dried or treated is carried over the
end drum and thereby discharged off the web, after which the web is brushed
clean of any adhering leaf or material by a revolving brush for this purpose. The
web drums may be driven in any suitable manner to give the web the proper
speed of movement.
In the accompanying drawings:-
Figure 1 is a central longitudinal section, but with the fan shown in elevation,
of an apparatus constructed in accordance with this invention.
.

page_text: Figure 4 is a view on a larger scale of the perforated distributing plate O..
In these figures,-A is the endless woven wire web carried on the two revolving
drums B B and supported between same by the rollers C: A is the web chamber
through which the upper portion of the wire web A on which the material to be
treated is carried travels in the direction indicated by the arrow. This chamber
is divided into upper and lower compartments by the web A, which compartments
are further divided into sub-compartments D E F G and H by the cross parti-
tions E and F, but the number of these sub-compartments may be increased
according to requirements. I and I are openings in the ends of the compart-
ments and H for the entrance and exit respectively of the wire web. K is the
air heating apparatus or stove; it is connected to the top of the upper sub-
compartment H by an air duct L. M is a fan mounted' upon the top of the upper
sub-compartment F. This fan draws the hot air (supplied by the stove K)
through the duct L, down through the perforated plate N into the upper sub-
compartiment H, and through the wire web A with the material thereon into the
lower sub-compartment G, thence through the perforated plate 0 (shown separ-
ately in Figure 4) and again through the wire web A into the upper sub-compart-
ment F, then through the air ducts P P into the eye of the fan M, the air is then
delivered under pressure into the pressure duct Qdown through the perforated
plate R into the upper sub-compartment E again through the wire web A into
the lower sub-compartment D and through the perforated plate S (which is the
same as the plate O shown in Figure 4) and up again through the wire web A
after which it escapes into the open air. The bearings T T of the shaft carrying
the drum B at the feed end of the machine are fitted with adjusting screws U U¹
so that the web A may be kept sufficiently, strained for satisfactory working.
V is a rotary brush for removing any material clinging to the wire web A
WW are inspection and cleaning doors.
The web A is driven by means of the drum B¹ at the delivery end of the
machine, by any suitable gear; that shown is an arrangement of worm gear-
ing, a bed, operated by the driving pulleys e.
By utilising as above-described both exhaust and pressure blast of the fan for
passing the air current through the web chamber, less power is required to drive
the fan for passing a given volume of air current through the web chamber than
if either suction or pressure alone were employed for this purpose. I may, how-
ever, alternatively use either pressure blast or suction alone and especially for
small machines, in which case I preferably work with the exhaust fan, and in
one modification, place the suction port in the last lower sub-compartment of the
web chamber, and employ this as the feed end, and mount the inlet air duct in
this case as in the hereinbefore previously described modification on top of the
upper sub-compartment at opposite end, which in this case would be delivery
end. The air current through the web chamber thus passes in a serpentine course
down and up through the whole length of the web from end to end of the web
chambers the part of the partition E' which is above the web being dispensed with,
and the number of times the current passes through the web may be arranged
to suit requirements as to size and power of apparatus required and the description
of work to be done.
Having now particularly described and ascertained the nature of my said in-
vention and in what manner the same is to be performed, I declare that what
I claim is:
1. In apparatus for drying or treating tea leaf, tobacco leaf, coffee, grain, malt,
fruit or other substances by a current of hot or dry air or mixed gas or gases and
air, having a drying chamber, a carrying web travelling horizontally from end to
end of said chamber approximately midway between the top and bottom of same,
openings at opposite ends of said chamber respectively for the entrance and exit
of the web and the substance it carries and transverse partitions in said chamber
substantially as set forth, inclined perforated plates disposed across the compart-

page_text: ments in said chamber and having the area of the perforations less at the end
which is towards the advancing current than towards the further end, whereby
the current of air or of gas and air is distributed equally over the whole area of the
web in said compartments, substantially as hereinbefore described.
2: In apparatus for drying or treating tea leaf, tobacco leaf, coffee, grain, malt,
fruit or other substances by a current of hot or dry air or mixed gas or gases and
air, the combination with a drying chamber and a carrying web travelling hori-
zontally from end to end of said chamber approximately midway between the
top and bottom of same, said chamber having at opposite ends openings respec-
tively for the entrance and exit of the web and the substance it carries, of a fan
and air ducts disposed relatively to the drying chamber substantially as shown,
whereby the current from the air inlet end of the drying chamber up to an inter-
mediate point of same is an exhaust or suction current and the current through
the remainder of said chamber is a pressure blast, substantially as liereinbefore
described.
3. The general arrangement or combination of parts constituting an improved
apparatus for drying or treating tea leaf, tobacco leaf, coffee, grain, malt, fruit or
other substances by a current of hot or dry air, or mixed gas or gases and air
substantially as hereinbefore described and shown in the accompanying drawings.
Dated this 23rd day of March 1898.
J. C. MEWBURN & ELLIS,
55 and 56,, Chancery Lane, London, Chartered Patent Agents.