Improvements in Apparatus for Withering or Limping Tea Leaf in the Course of its Manufacture into Black Tea.
Year: 1897

page_text: Date of Application, 15th Jan., 1897
Complete Specification Left, 15th Oct., 1897-Accepted, 27th Nov., 1897
Improvements in Apparatus for Withering or Limping Tea Leaf in
the Course of its Manufacture into Black Tea.
I, SAMUEL CLELAND DAVIDSON of Sirocco Engineering Works, Belfast, Ireland,
Merchant, do hereby declare the nature of this invention to be as follows:
In the Specification of a former Patent No. 9965 of 1894 I described a process
or method of withering or limping tea leaf during its manufacture into black
tea, the said process consisting in causing an artificially induced or mechanically
moved current of warm air saturated or nearly saturated with aqueous
vapor to flow or circulate through or amongst the leaf, whereby a moist
warmth is imparted to the leaf which efficiently limps or withers it
without at same time permitting any practical loss by evaporation of
the moisture contained in its cells, and the preservation of
which
moisture in the cells of the leaf renders the subsequent processes of its manufac-
ture into black tea more easily performed and a better quality of black tea
obtainable therefrom.
In the said Specification and also in the Specifications of subsequent l'atents
No. 5123 of 1895 and 21905 of 1895 I further described apparatus for carrying
out the said process, the said apparatus being so constructed and arranged that
the required production and maintenance of the combined conditions of satura-
tion and warmth of the air used were effected by having a revolving drum or
chamber in which the leaf is being withered made approximately air-tight in
respect of the outside atmosphere to prevent any of the contained air escaping
therefrom to the outside atmosphere or vice versa, and by circulating the thus
confined air over and over again by means of a fan or other equivalent air pro-
pelling appliance, or by an induced current caused by the action of heat operating
through conduit pipes in or connected with the drum or otherwise through the
drum and amongst the damp leaf therein and through any suitable air heating
appliance or apparatus connected therewith, so that the moisture rising from the
leaf cannot escape from and is consequently retained in the air of the revolving
drum, whereby a vapor bath saturation of the air therein is produced and main-
tained in combination with sufficient warmth to effect the withering of the leaf.
I have found in practice that in apparatus of the kind above referred to it is
very desirable to admit a certain or regulated amount of fresh air, preferably
in the latter part of the withering operation of each charge, to provide for the
supply of oxygen to the leaf in order to oxidate it, because oxidation at this
stage of the process of manufacture of black tea considerably improves the quality
of the black tea obtained, and it is the object of the present invention to so
construct the apparatus that a quantity, variable at will, of the moisture-laden
air shall be discharged continuously or occasionally from the apparatus, and an
equivalent volume of fresh atmospheric air admitted in place thereof.
For the purpose of my invention I fit the apparatus, preferably in the pipe
through which the moisture-laden air returns from the withering drum to the

page_text: air heater, with a moist air outlet valve so arranged as to, so to speak, cut out
a portion of the current of moist air as it flows at considerable speed through
the pipe and I also provide a fresh air. inlet, preferably in the form of a valve
likewise situated in the same pipe as the-moist air outlet valve, to admit a volume
of fresh air equivalent to the amount of moist air discharged:
A convenient way of carrying out my invention is to fit diametrically opposite
to each other in the wall of the said pipe, two flap, valves connected so as to move
together, one of these valves, namely the moist air outlet valve opening inwards,
and the other, the fresh air inlet valve, opening outwards. The nibist air outlet
valve is hinged at the side which is furthest from the withering drum so that when
open it presents itself at an angle with its inner edge to the current of moist air,
and consequently divides the current, one portion passing through the opening
of the valve and being thus discharged outside the apparatus, while the remaining
portion passes on through the pipe to the air heater, being joined by a fresh
amount of fresh air which enters through the inlet valve. This fresh air inlet
valve is preferably hinged like the moist air outlet valve, but this is not important
as it has not to cut or divide a current. The valves may be conveniently worked
by means of a quadrant bar attached to one or other of them, this bar having a
series of holes or notches to engage with a pin or catch, and thereby allow of
the valves being adjusted to any required extent of opening.
Dated this 15th day of January 1897
J. C. MEWBURN & ELLIS,
55 and 56 Chancery Lane, London, Chartered Patent Agents.
Improvements in Apparatus for Withering or Limping Tea Leaf in
the Course of its Manufacture into Black Tea.
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
by the following statement:-
In the Specification of a former Patent No. 9965 of 1894 I described a process
or method of withering or limping tea leaf during its manufacture into black
tea, the said process consisting in causing an artificially induced or mechanically
moved current of warm air saturated or nearly saturated with aqueous
vapor to flow or circulate through or amongst the leaf, whereby a moist
warmth is imparted to the leaf which efficiently limps or withers it
without at same time permitting any practical loss by evaporation of
the moisture contained in its cells, and the preservation of
moisture in the cells of the leaf renders the subsequent processes of its manufac-
ture into black tea more easily performed, and a better quality of black tea
obtainable therefrom.
which
In the said Specification and also in the Specifications of subsequent Patents
No. 5123 of 1895 and 21905 of 1895 I further described apparatus for carrying
out the said process, the said apparatus being so constructed and arranged that
the required production and maintenance of the combined conditions of satura-
tion and warmth of the air used were effected by having a revolving drum or
chamber in which the leaf is being withered made approximately air-tight in
respect of the outside, atmosphere to prevent any of the contained air escaping
therefrom to the outside atmosphere or vice versa, and by circulating the thus

page_text: confined air over and over again by means of a fan or other equivalent air pro
pelling appliance or by an induced current caused by the action of heat operating
through conduit pipes in or connected with the drum or otherwise through the
drum and amongst the damp leaf therein and through any suitable air heating
appliance or apparatus connected therewith, so that the moisture rising from the
leaf cannot escape from and is consequently retained in the air of the revolving.
drum, whereby a vapor bath saturation of the air therein is produced and main-
tained in combination with sufficient warmth to effect the withering of the leaf.
I have found in practice that in apparatus of the kind above referred to it is
very desirable to admit a certain or regulated amount of fresh air, preferably.
in the latter part of the withering operation of each charge, to provide for the
supply of oxygen to the leaf in order to oxidate it, because oxidation at this
stage of the process of manufacture of black tea considerably improves the quality
of the black tea obtained, and it is the object of the present invention to so
construct the apparatus that a quantity variable at will of the moisture-laden
air shall be discharged continuously or occasionally from the apparatus, and an
equivalent volume of fresh atmospheric air admitted in place thereof.
For the purpose of the present invention I fit the apparatus preferably in the pipe
through which the moisture-laden air returns from the withering drum to the
air heater with a moist air outlet valve so arranged as to, so to speak, cut out
a portion of the current of moist air as it flows at considerable speed through
the pipe; and I also provide a fresh air inlet, preferably in the form of a valve
likewise situated in the same pipe as the moist air outlet valve to admit a volume
of fresh air equivalent to the amount of moist air discharged.
A convenient way of carrying out the invention is to fit diametrically opposite
to each other in the wall of the said pipe, two flap valves connected so as to move
together, one of these valves, namely the moist air outlet valve opening inwards,
and the other, the fresh air inlet valve, opening outwards. The moist air outlet,
valve is hinged at the side which is furthest from the withering drum so that when
open it presents itself at an angle with its inner edge to the current of moist air,
and consequently divides this current, one portion passing through the opening
of the valve and being thus discharged outside the apparatus, while the remaining
portion passes on through the pipe to the air heater, being joined by a fresh
amount of fresh air which enters through the inlet valve. This fresh air inlet
valve is preferably hinged like the moist air outlet valve, but this is not important
as it has not to cut or divide a current. The valves may be conveniently worked
by means of a quadrant bar attached to one or other of them, this bar having a
series, of holes or notches to engage with a pin or catch, and thereby allow
the valves being adjusted to any required extent of opening.
In the accompanying drawings Figure 1 is a plan of the apparatus illustrated
in the Specification of Patent No. 21905 of 1895 but provided with means in
accordance with this invention in its preferred form for cutting out a portion of
the circulating current of moist warm air and admitting an equal volume of
fresh air.
Figure 2 is a front elevation with the rotating drum in section.
Figure 3 is an end elevation showing the exhaust or return air duct or pipe
with the combined cut-out and fresh air inlet valves fitted therein.
Figure 4 is a plan on a larger scale of the valve box with the combined cut out
and fresh air inlet valves.
Figure 5 is a longitudinal section on the line 5 5 of Figure 4.
Figure 6 is a cross section on the line 66 of Figure 4.
A is the rotating drum mounted on standards B B. C is the air inlet port at
E is the air
one end and D the air outlet port at the other end of the drum.
heating apparatus and F the fan. C¹ is the inflow air conduit pipe leading from
the fan to the air inlet port C. D is the return air conduit pipe leading from the
air outlet port D to the air heating apparatus E. E' is an air conduit funnel or

page_text: tube leading from the air heating apparatus E to the fan F. All the above
parts are the same as in the apparatus described in the said former Specification.
G is a valve box which for the purpose of the present invention is fitted in
the return air conduit pipe D'. H is the cut-out valve fitted according to the
present invention for exhausting a portion of the circulating air from the pipe D.
and. I is the fresh air inlet valve for admitting an equivalent volume of fresh air.
K is a connecting link between H and I whereby these two valves open and
close equally and simultaneously. L is a quadrant by which the amount of
opening given to the valves H and I is regulated. The valve box G is so
mounted in and forms part of the return pipe D¹ that the air current from the
rotating drum A to the heater E and fan F passes through the valve box as
indicated by the arrows.
The action is as follows:-Upon the valves H and I being worked, the exhaust
valve H opens inwards so that its edge faces the return air current, and thereby
cuts out of the valve box a certain quantity of air in accordance with the extent
of opening given thereto; fresh air equivalent in volume to the exhaust air thus
cut out by the valve H is simultaneously admitted by the inlet valve I which
by means of the link K connecting it with the valve H is opened outwards to a
corresponding extent.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what I
claim is:-
1. In apparatus of the kind herein referred to for withering or limping tea leaf
in a revolving drum or chamber by means of a current of moist warm air caused
to circulate through the same, means whereby a regulated quantity of the exhaust
warm air can be cut out and an equal volume of fresh air admitted, substantially
as and for the purpose herein before described.
2. In apparatus of the kind herein referred to, the combination or arrangement
in the return pipe D' of the valve box G, the cut out valve H, and the fresh air
inlet valve I connected with the said valve H so as to open and close simultaneously
therewith, substantially as and for the purpose herein before described.
Dated this 15th day of October 1897.
J. C. MEWBURN & ELLIS,
55 and 56 Chancery Lane, London, Chartered Patent Agents.