Improvements in Apparatus for Withering or Limping Tea Leaf in the Course of its Manufacture into Black Tea, or for the Final Drying or Finishing of Tea Preparatory to its being Packed into Chests.
Year: 1895

page_text: Date of Application, 11th Mar., 1895-Accepted, 20th Apr., 1895
COMPLETE SPECIFICATION.
Improvements in Apparatus for Withering or Limping Tea Leaf in
the Course of its Manufacture into Black Tea, or for the Final
Drying or Finishing of Tea Preparatory to its being Packed into
Chests.
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 :-
The improvements have reference to the revolving drum or cylinder apparatus
for withering tea leaf as described in the Specification of my previous British
Patent No. 9965 of 1894 and which Specification for brevity of description is
hereinafter referred to as the previous Specification.
In the practical working of the drum or cylinder described in the previous
Specification and illustrated in Figures 11, 12, 13 and 14 thereof, the air current
had a tendency to carry the leaf or tea as the case might be from the air inlet end
of the drum and accumulate it at the air outlet end, and one of the objects of the
hereinafter described improvements is to effect the circulation of the air current
through the drum without the aforesaid tendency of accumulating the leaf or tea
more at one end of the drum than another.
According to one method of carrying the improvements into effect the inlet and
outlet air ports through which the circulating flow and return currents pass
through the drum are enclosed with short open-ended cylinders formed preferably
of perforated sheet metal of somewhat larger diameter than said air ports, and
the length of which is ordinarily equal to about half of their diameter. One
end of each enclosing cylinder is secured to the end of the drum concentrically
with the air port enclosed by it, and the perforated sides and interior open
end of each of these short cylinders are covered with wire gauze, or other
foraminous material, whereby the inflow air current is diffused as a fine spray
from the inlet port into the drum, without directly impinging against the leaf
or tea therein, the horizontal lifting shelves within the drum, (as described in
the previous Specification) being only of sufficient depth to lift the leaf or tea
to such a height in the drum that when falling it would not drop across the
line of the inflow air current, and the wire gauze screen on the outlet port
prevents the leaf or tea being drawn away along with the return current; or
alternatively the perforated plate and gauze screen may be applied completely
across each end of the drum, in front of the air inlet and outlet ports, in such
a manner as to form false ends to the drum, and to enclose an air space between
same and the actual ends of the drum. Or according to another method of
carrying the improvements into effect the flow and return air conduit pipes may
be continued through the inlet and outlet ports of the drum, so as not to
revolve with the drum, and to meet about half way between its ends, at which
meeting point the flow pipe is separated from the return by a baffle plate or
diaphragm, which is placed either between the ends of the pipes, at right angles
thereto, or inclined so as to better deflect the inflow current through an opening
which is preferably in the upper side of the connecting tube, and which opening
is covered by a roof-shaped hood extending partly or entirely the length of the
cylinder, and having a long narrow open space between its lower edges and the
surface of the tube or pipe, the total area of which is equal to that of the inflow

page_text: opening in
the connecting pipe so as to cause an equal diffusion of the air
current along the whole length of said openings on both sides of the hood.
The opening for the return current is preferably in the lower side of the return
end of the tube, and is covered by an inverted roof-shaped hood of equal length
to the upper hood, and having an opening along its apex, the total area of
which is the same as said opening for admitting the return current into the
outlet end of the connecting pipe.
The accompanying drawings will enable the invention and the mauner of
carrying it into effect to be fully understood.
Figure 1 is a plan of an apparatus constructed according to one modification of
the invention.
Figure 2 is a front elevation of same with the rotating cylinder in central
longitudinal section.
Figure 3 is an end elevation of the same.
Figure 4 is a cross section on line 4--4 of Figure 2.
Figure 5 is a front elevation, with the cylinder in section, of another modification
of the apparatus.
Figure 6 is a cross section at 6-6 of same.
Referring to Figures 1 to 4, A is the horizontal rotating cylinder or drum; it has
an iron tyre or ri on each end; B B are standards upon which it is mounted,
C is an air inlet port at one end and D is an air outlet port at the other end of the
cylinder. E is an air heating apparatus and F the fan, C¹ is the inflow air conduit
tube leading from the fan F to the air inlet port C, D' the return air conduit tube
leading from the air outlet port D to the air heating apparatus E and E¹ is an air
conduit tube leading from the air heating apparatus E to the fan F.
L L are
doors or ports of any suitable construction in the side of the cylinder for use in
charging and emptying same. M M are longitudinal ledges or shelves fitted to the
interior circumference of the cylinder. NN are air chambers enclosed within
short cylinders N' fitted one at each end of the cylinder A; they are of larger
diameter than the inlet and outlet ports C and D and are concentric therewith;
they are each covered at the inner end with a screen O of gauze or other foraminous
material secured to the cylinder N' by an angle iron ring O. P is a door or valve
in the tube D'. There is a thermometer on the flow tube and also one on the
return tube.
The cylinder A and the fan F may be rotated by any suitable means, the
drawings shew the cylinder rotated by means of friction rollers G G acting on
the tyre or rim at the opposite ends of same, these rollers being mounted on
shafts H and H, one of which H may be driven from the main shaft I of an
engine K by means of a belt which passes over a pulley R on said shaft, and
over a pulley S on the shaft H.
The fan is also shown as driven from the main shaft I by means of a belt T
passing over a pulley U on this shaft and over a pulley V on the fan shaft.
The cylinder A is preferably made of galvanized sheet iron. The air heating
apparatus E is preferably fitted with steam pipes, but it may also be in the form of
a hot air stove or other suitable means of heating air. The air heating appliance
is preferably situated as shown, but it may be placed between the fan and the air
inflow end of the cylinder, if so desired.
Instead of the air chambers N N being formed of short cylinders covered at their
inner euds with foraminous screens as above described the foraminous screens
may extend quite across the drum A as shown in dotted lines at O' in Figure 2
so as to constitute false ends and form chambers between themselves and the actual
cylinder ends; the short cylinders N¹ N¹ as seen in Figure 2 that form the sides
of the chambers are in this case dispensed with.
In the modification illustrated in Figures 5 and 6 the flow and return air
chambers N N of Figures 1 to 4 are replaced by the longitudinal tube W
constructed as a continuation of the inflow and return tubes or attached as a
fixture to the end standards B B so as to form a continuation of the inflow and

page_text: return pipes right through the cylinder A with a diaphragm X in it about midway
between the ends of the cylinder and either diagonally or (as shown) at right
angles across the tube W so as to completely block the direct passage of the
circulating air current through the tube and deflect the inflow current through
an opening Y in the upper side of the tube W of equivalent area to that of a cross
section of the tube itself and surmounted by a roof shaped cover or hood a with
closed ends but with a space c between it and the top surface of the tube W,
leaving a narrow longitudinal opening & extending the whole length of the roof
shaped hood, the total area of which openings should be about the same or only
slightly in excess of the cross section area of the tube, and from which the inflow
air current is thus diffused into the cylinder A equally over its whole length. On
the inner side of the tube W there is on opening Z leading into the return current
end of the tube and situated midway between the ends of the cylinder A. This
opening Z is covered by an inverted roof shaped hood a' with closed ends 6' and
a space e between it and the tube similar to that in the top hood a. The hood a¹
is fitted close to the tube W along its sides, but has an opening d¹ the full length
of its inverted apex, the area of which should be equal to or only slightly in excess
of that in the tube W in order that it may admit the return current evenly all
along its entire length to the return tube W.
When using the machine for the purpose of withering tea leaf the temperature
of the inflow air which is preferably employed is at or about 110 degrees Fahrenheit
but for the final drying or finishing of tea preparatory to packing for which the
apparatus is also applicable a temperature of about 160 to 180 degrees Fahrenheit
is preferably employed. The leaf or tea has merely to be emptied into the drum
through the door provided for this purpose, the drum is then caused to revolve
at the rate of about 10 to 15 revolutions per minute, and the horizontal shelves
inside the drum cause the leaf to rise a short distance up the sides and fall there-
from, or roll over upon itself, back again into the bottom of the drum, while at
same time the fan causes the flow and return circulation of the air current through
the drum and heating apparatus as hereinbefore described, practically the same
air being returned over and over again through the heater and through the drum
until the leaf has become sufficiently "withered" or (in the case where the
apparatus is employed for finally drying or finishing tea) until the tea is raised to
a temperature of about 150 to 160 degrees Fahrenheit. This apparatus is par-
ticularly suitable for the finishing (or "facing" as it is sometimes called) of green
tea, to which it imparts the peculiar bloom that is sought for with this quality of tea.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:-
1. The construction of rotating drums or cylinders for withering tea leaf (as
described in the previous Specification) or for the final drying or finishing of tea
preparatory to packing, with air chambers inside the drum over the inlet and
outlet ports for the circulating flow and return air current that passes through the
drum the said air chambers being formed by short cylinders constructed with
perforated plate, wire web, gauze or other foraminous material, or alternatively
by screens of foraminous material extending right across each end of the drum,
so as to form false ends thereto whereby the inflow of the air current in the drum
becomes diffused as a fine spray, and also the tea leaf or tea is prevented from
being carried away in the outflowing return air current, all substantially as and
for the purposes hereinbefore described and represented in Figures 1 to 4 of the
accompanying drawings.
2. The construction of rotating drums or cylinders for withering tea leaf (as
described in the previous Specification) or for the final drying or finishing of tea
preparatory to packing, with a stationary connecting tube passing through the
drum or cylinder between the inlet and outlet ports, for the circulating flow and
return current with a divisional diaphragm in said connecting tube and an opening

page_text: therefrom into the drum covered by a hood, so attached to the connecting tube
that a long narrow space is left between it and the tube for evenly distributing the
air into the drum, and another opening on the return tube side of said diaphragm
covered by a hood with a long narrow space between it and said connecting tube
for effecting an even outflow from the drum of the return air current, all sub-
stantially as and for the purposes hereinbefore described and represented in
Figures 5 and 6 of the accompanying drawings.
3. The general combinations or arrangements of parts substantially as and for
the purposes herein before described and represented in the accompanying drawings
forming improved apparatus for withering tea leaf or for the final drying or
finishing of tea preparatory to packing.
Dated this 11th day of March 1895.
J. C. MEWBURN & ELLIS,
55 and 56, Chancery Lane, London, Chartered Patent Agents.