IMPROVEMENTS IN DRYING TEA AND IN THE APPARATUS EMPLOYED THEREFOR.
Year: 1876

page_text: LETTERS PATENT to William Richard Middlemore Thomson, of 90, Buchanan
Street, Glasgow, in the County of Lanark, North Britain, Consulting Engineer,
for the Invention of "IMPROVEMENTS IN DRYING TEA AND IN THE APPARATUS
EMPLOYED THEREFOR. A communication from abroad by Francis William
Mackenzie, of Gelahating, Assam, in the Empire of India.
"
Sealed the 20th January 1877, and dated the 5th August 1876.
PROVISIONAL SPECIFICATION left by the said William Richard Middlemore
Thomson at the Office of the Commissioners of Patents on the 5th August
1876.
"IMPROVEMENTS IN
WILLIAM RICHARD MIDDLEMORE THOMSON, of 96, Buchanan Street, Glasgow, in
the County of Lanark, North Britain, Consulting Engineer.
DRYING TEA AND IN THE APPARATUS EMPLOYED THEREFOR." A communication
from abroad by Francis William Mackenzie, of Gelahating, Assam, in the Empire
of India.
This Invention relates essentially to the construction and use of apparatus for
drying tea in foreign tea plantations, and which is better adapted for the purpose
than the methods hitherto employed by tea planters.
When the green tea leaf is picked from the bushes it is spread out under cover
for about 24 hours to wither, and is then rolled by the usual rolling machines,
after which it is rolled by hand into balls and left for a short time to ferment.
The leaf in this state, being quite moist and gummy, is placed on wire trays over a
charcoal fire until the tea is perfectly dry and brittle, after which it is sorted
through different sized sieves and is ready for the market. The use of charcoal
fires, however, for drying tea is found in practice to be seriously objectionable;
1st, because charcoal is every day becoming dearer as timber for making it is
becoming scarcer; 2nd, it occupies all the best workmen on a plantation making it
during the cold season, when they might be more profitably employed; 3rd, the
number of fires in the tea house raise the temperature so much that even natives
can scarcely bear it; 4th, if the fire is too strong it burns the tea, and if not
sufficiently strong it does not dry the tea quick enough, does not stop fermentation
soon enough, and therefore produces a large quantity of useless red leaf which has
to be thrown out as waste. The object of the present Invention therefore is to
obviate these serious disadvantages, and it consists in passing a current of hot air
through trays of wire cloth, or perforated metal, or other material filled with tea

page_text: leaf, the current and temperature of the air being regulated to the required degree
The air is
by means under the control of the attendant in any ordinary manner.
heated by passing it through tubes, cells, or passages of metal, led or passing through
a large chamber containing steam, of a sufficiently high temperature, admitted by a
pipe or pipes from any adjacent steam boiler or generator.
The perforated trays are preferably ranged one above the other in any desired
number in the upper part of the chamber through which the air tubes or passages
ascend, a steam-tight division being formed between the upper and lower parts of
the large chamber, so that the air only is admitted to the upper part to pass
through the interstices of the trays to dry the tea. The trays are fitted by
preference into movable drawers or framics fitting air-tight into the upper chamber,
the drawer ends being constructed to overlap so that when a tray is withdrawn
from time to time for inspection, the end of the drawer closes the aperture of the
hot-air chamber sufficiently air tight so as not to disturb the upward current
through the other trays and the tea contained in them.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Richard Middlemore Thomson in the Great Seal Patent
Office on the 5th February 1877.
WILLIAM RICHARD MIDDLEMORE THOMSON, of 96, Buchanan Street, Glasgow, in
"IMPROVEMENTS IN
the County of Lanark, North Britain, Consulting Engineer.
DRYING TEA AND IN THE APPARATUS EMPLOYED THEREFOR." A communication
from abroad by Francis William Mackenzie, of Gelahating, Assam, in the Empire
of India.
This Invention relates essentially to the construction and use of apparatus for
drying tea in foreign tea plantations, and which is better adapted for the purpose
than the methods hitherto employed by tea planters.
When the green tea leaf is picked from the bushes it is spread out under cover
for about 24 hours to wither, and is then rolled by the usual rolling machines, after
which it is rolled by hand into balls, and left for a short time to ferment. The leaf
in this state, being quite moist and gummy, is placed in wire trays over a charcoal
fire until the tea is perfectly dry and brittle, after which it is sorted through different
sized sieves, and is ready for the market. The use of charcoal fires however for
drying tea is found in practice to be very seriously objectionable; 1st, because
charcoal is every day becoming dearer as timber for making it is becoming scarcer;
2nd, it occupies the best workmen on a plantation making it during the cold season,
when they might be more profitably employed; 3rd, the number of fires in a tea
house raises the temperature so much that evon natives can scarcely bear it; 4th,
if the fire is too strong it burns tho tea, and if not sufficiently strong it does not
dry the tea quick enough, and therefore does not stop the fermentation soon enough,
and thus produces a large quantity of useless red leaf, which has to be thrown out
as waste. The object of the present Invention, therefore, is to obviate these serious
disadvantages, and it consists in passing a current of hot air through trays of wire
cloth or perforated metal, or other material, spread over with the tea leaf, the
current and temperature of the air being regulated to the required degree by means
under the control of the attendant in any ordinary manner. The air is heated by
passing it through tubes, cells, or passages of metal led or passing through a large
chamber containing steam of a sufficiently high temperature admitted by a pipe or
pipes from any adjacent steam boiler or generator, or it may be exhaust steam from
a steam engine after it has done its work, which current of steam may be super-
heated in any ordinary manner, as by passing the pipes in a coil or otherwise
through a fire on their way to the close heating chamber surrounding the tubes for
heating the air current as it passes through them.
The perforated trays are preferably ranged one above the other in any desired

page_text: number in the upper part of or above the chamber through which the tubes or
passages ascend, steam-tight ends or divisions being formed at the ends of the
heating tubes and steam chainber between the upper and lower parts of the large
chamber, so that the heated air only is admitted to the upper part to pass through
the interstices of the tray to dry the tea placed in them. The drying trays con-
taining the tea are fitted by preference into movable drawers or frames fitting air-
tight into the upper part of the air chamber by making their ends to overlap the
front openings through which they slide, so that when a tray is withdrawn from
time to time for inspection the end of the drawer closes the said aperture of the
hot air chamber sufficiently air-tight as not to disturb the upward air current
through the other trays, and the tea contained in them.
And in order that the nature, novelty, and modo of performing this said Invention
may be properly understood, I shall now proceed to describe the several Figures on
the Sheet of Drawing which I have hereunto appended for the purpose of showing
the best modes and means I am at present aware of for putting the Invention into
effect or practice, the same reference letters indicating the same or like parts in all
the Figures where shown.
---
Figure 1 is a front elevation, and Figures 2 and 3 are a transverse section and a
longitudinal section respectively taken on the lines 1 - - 1 and 2 2 in Figures 3
and 2, all of an arrangement of machine for the drying of tea, constructed in
accordance with and illustrative of one modification of this said Invention.
Figure 4 is a plan view detached of one of the drying sieves or trays with par-
forated or wire gauze bottom for holding and drying the tea leaf thereon, while
Figure 5 is a general plan to a small scalo of a range of three of these ten drying
machines, showing the arrangement of their steam pipes S, 8, and drawing-off con-
densed steam or water pipes W, w.
Referring to these Figures 1, 2, 3, 4, and 5, each machine is constructed of a
rectangular open frame with corner angle iron pillars A secured together by
diagonal stays B, B¹, on the front and back and opposite sides respectively with
contral front and back supporting bars C and side pillars C, all supporting
horizontal slide rails or bars D, D', of T iron and angle iron respectively at
the centre and sides for carrying the four sets of sliding trays or drawers E over
each other near the top by the angle iron bearers E¹ on the sides of each drawer,
two sets being opened from the front and two at the back by the handles E¹, as
scen particularly in Figures 1 and 3. This upper part F containing the drawers E
is all closed in as a rectangular drying air chamber F by teak or other wood (or it
might be sheet iron) at the front and back F¹ and the sides F", and on the top at
G fitted with the ventilating openings G' and regulating slide doors g. The front
end of each drawer E overlaps the opening through which it slides at F"¹ all round,
so as when shut to close it air-tight, and the back end of each drawer may also be
made to do so to prevent the escape of hot air while it is drawn out for the
attendant inspecting and treating the tea leaf spread on the wire gauzo e secured
to a light angle iron round the inner side and bottom of these trays E, as seen
particularly in Figures 3 and 4.
In the centre below these four sets of drawers E a close steam heating cylindrical
chest H (closely fitted with vertical tubes h open right through from the bottom H¹
to the top H") is mounted on an open rectangular and diagonal frame I, I¹, some
little distance up from the ground, with a sliding tray i below it, and completely
closed in above on all sides by the angled boarding J from the rectangular base-
ment I to the sides F1, F", of the upper rectangular close chamber F containing the
tea drying drawers E.
The steam is admitted to the lower front part of each steam chest from the main
longitudinal pipe S by the service pipe and regulating tap s, so as to heat the
outside of all the tubes h, and the air passing up through them. The air enters
from the outside at the space i' between the tray i and bottom H¹ of the chest H,
and escapes at the top H of the vessel H, fitted above with an air spreading plate
or "baffle plate" j (preferably in the form of an inverted hollow cone), which

page_text: allows part of the air from the centre to pass right up, while it spreads or directs
the air from the outer tubes h towards the sides of the chambers F, as seen at j¹,
Figures 2 and 3, so as to diffuse it over the whole under surface of the trays E,
through the wire gauze e of which it passes as thus heated and spread, all as indi-
cated by the arrows in Figures 2 and 3, so as to dry and cut the tea leaf laid thereon
from time to time as required.
The air current is regulated by opening and closing the slides y more or less, and
controlling the escape of the moist air through the openings G¹ at top, the heat of
the air being regulated by the amount and temperature of the steam admitted to
the vessel H by the pipes S, s. Each vessel H is fitted with a condensed steam or
water escape pipe and tap w leading to the main escape pipe W fitted with a
drawing-off pipe W, and condensed steam or water trap at W" for the water
pipes W, w, of the whole set of drying machines 11, 21, 31, as seen particularly in the
general arrangement shown in Figure 5.
To prevent the waste of the small tea which passes down through the wire
gause e or perforated trays E it is conducted by the conical plate j down through
the tubes h, and by the narrow spaces or open corners J at the bottom of the
angled sides J (inclosing in the steam heating vessel H and lower part of the hot
air chamber F, F¹) so as to be deposited on to the lower "save all," tray, or slide i,
which is removed from time to time for the collection of this small tea. Instead of
the "baffle plate" ja small meshed "save all" tray may be used, which would
spread or diffuse the heated air below the trays E. The steam heating vessels H
and air drying chambers F may cach be fitted with a thermometer for indicating
the temperature of the steam and air in them, and thus enable the temperature to
be regulated as desired. The steam to be used may be conveyed by pipes S and s
from any ordinary high-pressure steam boiler direct, or after being superheated by
passing it through a heating coil or other ordinary superheating chamber before
reaching the pipes S, 8; or exhaust steain may be used after it has done its work
in a motive engine superheated, as described, before entering the pipes S, 8, and
vessel H.
Having now described the nature of my said Invention, and the manner of per-
forming the same, I have to state that I do not confine myself to the precise details
herein described or delineated, but what I consider novel and original and therefore
claim as the Invention secured to me by the herein-before in part recited Letters
Patent is,―
First. The general construction of tea drying machine, with close steam_heating
chest and its air current heating tubes h and close hot air drying chamber Faround
and above it, containing the leaf drying slide trays E, all substantially as herein
described in reference to and shown in the accompanying Drawings, or any mere
modification thereof.
Second. The construction and use of a close steam chest H or vessel with air
current heating tubes / supplied and heated by superheated exhaust steam, or by
high-pressure or superheated steam- direct from a steam boiler for the heating of
the air of tea-leaf drying machines, substantially as herein described in reference to
and shown in the accompanying Drawings, or any mere modification thereof.
In witness whereof, I, the said William Richard Middlemore Thomson, have
hereunto set my hand and seal, this Third day of February, in the year
of our Lord One thousand eight hundred and seventy-seven.
Witness,
JOHN BROWN,
Patent Agent,
96, Buchanan Street,
Glasgow.
W. R. M. THOMSON. (L.S.)