Improvements in Apparatus for Drying Tea or other Vegetable Substances or other Material.
Year: 1893

page_text: Date of Application, 12th Jan., 1893-Accepted, 18th Feb., 1893
VUMI LEIE DUIFICATION.
Improvements in Apparatus for Drying Tea or other Vegetable
Substances or other Material.
I, SAMUEL CLELAND DAVIDSON of Sirocco 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 :-
This invention has reference to drying apparatus of the type in which the tea
or other material to be dried is exposed on superimposed sieves or perforated
trays in a drying chamber to the action of a current of heated or otherwise
dried air which is drawn or forced in either a downward or upward direction
through the trays and the material thereon, the trays being capable of being
intermittently moved up (or down) as a column in the drying chamber and the
uppermost tray (or lowermost tray as the case may be) being withdrawn after
each intermittent movement and a fresh tray introduced at the bottom (or top)
of the series.
The improvements relate more particularly to the form of drying apparatus
described in a former Specification No. 12844 of 1888 (which apparatus is now
generally known as the "Down Draft Sirocco Drier").
The said Specification described the combination of a lifting arrangement
whereby the superimposed trays are moved simultaneously in rotation order from
bottom to top of the drying chamber, and of a set of pawls or equivalent devices
for catching and holding the set of superimposed trays after each lift.
According to the present invention instead of a single set of pawls for catching
and holding the entire set or column of superimposed trays after each lift as in
the apparatus described in the said Specification two or more sets of pawls are
employed and are so arranged as to support the column or set of superimposed
trays in two or more divisions or sections and so that each upper division or
section is held clear of, and therefore does not rest upon, the trays of the division
or section next below. And further the drying chamber is provided with a door
or port opposite the top tray of each under division or section of trays. These
improvements allow the top tray of either of the lower divisions to be removed
and again returned to position and if required the material thereon shaken up
and turned. Consequently. a more even and satisfactory drying of the material
is effected than when the trays and the material thereon are passed the whole
way from the bottom to the top of the column or vice versa as they must neces-
sarily be when the apparatus is constructed as described in the said former
Specification.
Figures 1 to 4 represent a drying apparatus constructed according to my inven-
tion with two sets of pawls for supporting the superimposed trays in two divisions
or sections; the apparatus shown in these figures is arranged for the trays with
the damp material on them to be inserted at the bottom of the column and to
be moved up in consecutive order to the top where they are taken out.
Figures 5 and 6 represent the adaptation of my invention to a drying apparatus
n which the trays with the damp. material on them are inserted at the top of
he column and, moved down in consecutive order to the bottom where they are
aken out.
Referring first to Figures 1 to 4, Figure 1 is a front elevation of the apparatus,
portion..of the front plate of the drying chamber. being broken away to show
he two sets of pawls and how they engage under and support the column of
rays inɛ.two divisions or sections...

page_text: Figure 2 is a transverse section of the apparatus,
Figure 3 an end elevation and Figure 4 a sectional plan.
The tray lifting appliance is shown at its lowest point of travel. a is the
drying chamber, bb the trays, c c bars or battens on the top of the tray frames
to support the next upper tray at the required distance. d'inlet for the supply
of heated or dried air over the top of the trays, e exhaust fan, driving shaft
of same, exhaust air passage from below the trays in the drying chamber to
the eye of the fan; h valve box controlling the admission of exhaust air to fan
in accordance with the movements of the tray lifts; the tray lifts which are
raised and lowered as required by means of the beam levers jj actuated by the
hand lever k through the intermediation of the lever l. m is a rod and n a link
connecting the tray lift with the valve of the exhaust air passage so that this
is closed when the lift is down and the tray inlet port open and vice versa.
o is the tray inlet port and p the shutter of same, q is the tray outlet port
and the shutter of same. r is the lower set of pawls which support the
under section of the trays. s is a manhole door for giving access to the space
below the column of trays. All the above parts marked respectively with the
reference letters a to s are practically the same as described in the said prior
Specification. t is the upper set of pawls which according to the present inven-
tion is employed to support the upper section or division of trays clear above
the top tray of the lower section. is a port in the drying chamber opposite
the top tray of the lower section and vis à door to the said port. The upper
set of pawls like the lower set are pushed back by the trays during the
upward movement, and when the trays have sufficiently passed them the pawls
drop again into place so that when the tray lift is again lowered the pawls
receive and support the trays which have just passed them. In order that the
upper set of pawls t may support the upper division of the column of trays so ag
to be sufficiently clear of the top tray of the lower division, as seen in Figure 1,
to allow the same to be moved freely out of and into the drying chamber
through the port u, these pawls are so placed relatively to the lower pawls
that they support and engage the trays above them a little before the lower
division of trays is engaged and supported by the lower pawls r.
The upward
movement of the tray lift must therefore be sufficient to push the bottom tray
of the upper division past its supporting pawls t after the bottom tray of the
lower division has passed the pawls r. Figure 7 is a detail view showing
on a larger scale one of the pawls r or t used in the apparatus represented in
Figures 1 to 4.
+
Referring now to the modification shown in Figures 5 and 6 in which the trays
have to be moved in consecutive order downwards instead of upwards as in the con-
struction shown in Figures 1 to 4, instead of the tray frames pushing back the pawls,
metal bars or straps w w are employed moving in guides outside the drying
chamber and connected through slots in the side of the chamber to cross bars y
forming part of the tray lift appliance, so that the up and down movement of the
tray lift gives a corresponding movement to the bars w. These are arranged
to engage with the pawls and t at the outer side of the drying chamber, so that
just as the tray lift touches and takes the weight of the column of trays off the
pawls, the bars w begin to push the pawls back, and these when their points are
quite withdrawn from below the trays tilt back further clear of same and remain in
this position until the bars w in returning down again past the lower projections of
the pawls tumble them back into their normal position for supporting the trays
after the tray that had been resting upon them has passed on down below them, and
they then engage under and support the next descending tray above them. The
top set of pawls t are situated so as to do this a little in advance of the lower pawls r
so that the trays of the lower division drop away sufficiently from the bottom tray
of the upper division to allow of the top tray of the lower division being freely
moved out of and into the drying chamber as required through the port u.
Figures 8 and 9 are detail views showing on a larger scale one of the pawls rort

page_text: used in the apparatus represented in Figures 5 and 6. In Figure 8 the pawl is seen
engaged with the trays resting on it previous to its being tilted back by the up
stroke of the bar w. In Figure 9 the pawl is seen in its tilted back position previous
to its being again brought into gear by the downstroke of the bar w.
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. In drying apparatus in which a number of superimposed and perforated trays
or sieves are employed for exposing the material to be dried therein to either an
upward or downward current of heated or dried air, and which trays are moved by
a mechanical arrangement in consecutive order either from bottom to top or from
top to bottom of drying chamber, the employment of two or more sets of pawls
for so supporting the trays that a number of same in the upper part of the column
are supported as an upper division or section, at a sufficient distance above, and
clear of, the top tray of the division or section immediately below same to allow of
said top tray of the lower division being freely moved out of or into the drying
chamber through a port or door provided for the purpose, all substantially as
hereinbefore described and represented in the accompanying drawings.
2. The combination or combinations of parts substantially as hereinbefore
described and represented in the accompanying drawings forming improved
apparatus working as set forth for drying tea or other vegetable substances or other
material.
Dated this 11th day of January 1802
J. C. MEWBURN,
55 & 56, Chancery Lane, London, Chartered Patent Agent.