IMPROVEMENTS IN FURNACES TO BE USED IN THE MANUFACTURE OF CHROMATES
Year: 1876

page_text: LETTERS PATENT to James Mactear, of Glasgow, in the County of Lanark,
North Britain, Chemist, for the Invention of "IMPROVEMENTS IN FURNACES
TO BE USED IN THE MANUFACTURE OF CHROMATES."
Sealed the 7th October 1876, and dated the 10th July 1876.
PROVISIONAL SPECIFICATION left by the said James Mactear at the Office
of the Commissioners of Patents on the 10th July 1876.
JAMES MACTEAR, of Glasgow, in the County of Lanark, North Britain, Chemist.
"IMPROVEMENTS IN FURNACES TO BE USED IN THE MANUFACTURE OF CHROMATES."
This Invention relates to the employment in the manufacture of chromates of a
furnace constructed with improvements which cause the decomposition of the
chrome ore to be effected in a more economical, efficient, and expeditious manne
than heretofore.
The furnace to which the improvements are applied is of the kind having a
horizontal circular revolving bottom, and the Invention consists principally in
providing for the withdrawal of the finished charges of materials down through
the centre of the furnace bottom. The form of the discharge opening and of the
closing detail or valve may be varied, but in a preferable modification a cylindrical
aperture is formed quite through the bottom and lining, and is cased with iron,
and a similar opening, but larger in size, is formed through or partly through the
roof or arch of the furnace. The closing detail is an iron cylinder jacketed with
fire-clay or other refractory material, and when in the closing position rests on the
surface of the bottom lining round the central discharge aperture. Air is allowed
to pass up through the discharge aperture and through the valve or closing detail
so as to prevent the metal parts from being overheated. The discharge aperture
is opened to the interior of the furnace by raising the valve into the opening or
recess in the centre of the roof or furnace arch, and the contents of the furnace
may then be discharged into a wagon under the furnace, or into any suitable
receptacle. The fire gases are led into the furnace space between the revolving
bottom and roof, by preference through openings at one side, and pass towards the
opposite side, finding egress by two flues separated a short distance from each other,
whilst stirring apparatus is arranged by preference in the part of the furnace space
between the two exit flues.

page_text: The stiring apparatus may be of any known suitable kind, but preference is
given to au improved arrangement in which a row of vertical spindles in a radial
plane are carried in a frame fitted so that it can be lowered or raised by pinions
and racks. The spindles are driven by spur or other gearing, so that the alternate
ones rotate in opposite directions, and each has fixed at its lower end a cross bar
formed or fitted with two prongs to project down into the materials. The circles
described by the several pairs of prongs intersect each other and a very efficient
stirring action is thereby obtained.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said James Mactear in the Great Seal Patent Office on the 8th January
1877.
JAMES MACTEAR, of Glasgow, in the County of Lanark, North Britain, Chemist.
" IMPROVEMENTS IN FURNACES TO BE USED IN THE MANUFACTURE OF CHROMATES."
"
...
My said Invention relates to the employment in the manufacture of chromates of
a furnace constructed with improvements which cause the decomposition of the
chrome ore to be effected, in a more economical, efficient, and expeditious manner
than heretofore.
སྒྱུ!་
The furnace to which my improvements are applied is of the kind having a
horizontal circular revolving bottom, and my Invention consists principally in
providing for the withdrawal of the finished charges of materials down through
the centre of the furnace bottom. In a modification of my improved furnace, which
I prefer, the fire gases are led into the furnace space between the revolving bottom
and roof through openings at one side and pass towards the opposite side, finding
egress by two flues separated a short distance from each other, whilst stirring
apparatus is arranged in the part of the furnace space between the two exit flues.
And in order that my said Invention and the. manner, of performing the same
may be properly understood I hereunto "append a Sheet of explanatory Drawings
to be herein-after referred to, and representing a furnace as constructed with one
modification of my improvements. In these Drawings the same reference numerals
are used to mark the same or like parts wherever they are repeated...
.
Figure 1 of the Drawings is a horizontal section of. the furnace, and Figure 2 is
a corresponding vertical section.
The circular furnace bottom-1 consists of plate iron lined with fire-brick, and is
fixed on frame pieces 2, which are fitted with wheels 3 arranged to run on a circular
flanged tram plate 4 fixed beneath the furnace. The furnace bottom 1 is made
with a raised rim 5, and is, covered by a roof or arch:6 of fire-brick carried by arc-
shaped girders 7, which are supported on pillars 8, indicated by dotted lines in
Figure 1. Two fire-places 9 conimunicate by a passage 10 with the reverberatory
chamber or space enclosed between the roof or arch 6 and the circular bottom,
and after the fire gases have acted in that chamber they pass off by two exit flues
11 nearly opposite to the inlet passage 10. For charging the furnace one or more
openings (not shown in the Drawings), which are closed whilst the furnace is in
operation, are provided at any convenient part of the roof or arch 6. ----
--
The discharge aperture. is a cylindrical or nearly cylindrical opening 12 made
quite through the bottom 1 and its lining at the centre, and this opening 12 is
fitted with an iron casing 13, which projects below the bottom. A' somewhat
larger opening 14 is formed through the roof or arch 6, and is fitted with an iron
lining.
The closing detail is an iron cylinder 15, which is jacketed with fire-brick or other
refractory material, and when in the closing position, as shown in Figure 2, rests
on the top edge of the iron lining of the discharge opening 12 in the furnace
bottom, whilst its upper part closes the opening 14 in the roof 6.

page_text: The cylindrical closing detail or valve 15 is made with two sets of arms 16, 17, to
the upper set of which there is attached an eye bolt for the connection of a chain
18 for raising the valve, whilst to the lower set 17 there is attached a spindle 19
which passes through a guide 20 fixed by arms in the opening 12 below. Air is
allowed to pass up through the discharge opening 12, and through the valve 15, so
as to prevent the metal parts from becoming overheated.
The discharge aperture 12 is opened to the interior of the furnace chamber by
raising the cylindrical valve 15 into the opening or recess 14 in the roof or arch 6,
and the contents of the furnace may then be discharged into a wagon placed
beneath the furnace, or into any suitable receptacle.
The stirring apparatus is arranged to act between the central valve 15 and the
outer rim 5 of the furnace bottom at the part between the two exit flues 11, and
it comprises a set of forks 21 fixed on the lower ends of vertical shafts 22, which
are held in a frame 23 and geared together by spur wheels 24 at their upper ends
so as to rotate in alternate directions, the forks 21, which are disposed diametrically,
being arranged so as not to interfere with each other, although they are large
enough to work over overlapping areas.
The stirring apparatus can be raised out of action or lowered more or less as may
be required, the frame 23 being fitted to slide in vertical guides 25 on a fixed
framing, and being formed with vertical racks 26 with which there gear pinions
on a horizontal shaft 27 arranged to be turned by means of a crank handle.
The driving power is applied to the outermost of the vertical stirrer shafts 22,
which is elongated to pass up through a bevil wheel 28, to which it is geared by a
groove and feather, admitting of its vertical movement with the frame 23. The
bevil wheel 28 gears with a bevil wheel on a short horizontal shaft 29 driven as
herein-after described.
The finished charges of materials may be pushed towards the central discharge
outlet 12 by means of scrapers or other implements worked by hand through the
openings herein-before referred to as for charging in the materials. I, however,
prefer to use mechanical discharging apparatus of the kind shown in the Drawings,
and which comprises a series of pushers or scrapers 30 attached to an endless chain
31 carried and moved by pulleys 32 on the lower ends of vertical shafts 33, 34.
These shafts 33, 34, are carried by a frame 35, which is fitted to work in
vertical guides 36, and has racks 37 on it in gear with pinions 38 on a horizontal
shaft 39 so that it can be raised or lowered as required by means of a crank
handle. The discharging apparatus is worked by means of one 33 of the vertical
shafts, which is elongated to pass up through a bevil wheel 40 connected to it
by a groove and feather to admit of the vertical movement of the frame 35. The
bevil wheel 40 is in gear with a bevil wheel 41 on a horizontal shaft 42, which
has also on it a spur wheel 43 gearing with a spur wheel 44 on the horizontal shaft.
29 of the stirring apparatus. The shaft 42 has on it clutches in connection with
the wheels 41 and 43, so that either can be put into or out from gear as required,
and this shaft 42 is itself driven by bevil wheels 45 from a vertical shaft 46
geared by bevil wheels 47 to the shaft 48, which imparts rotation to the furnace
bottom and is driven by means of a pulley and belt or otherwise from any
suitable prime mover. The furnace bottom 1 is turned by means of a pinion 49
on the shaft 48 and gearing with a circular rack 50 fixed to the framing of the
furnace bottom. A gutter 51 is formed round the outside of the rim 5 of the
furnace bottom to contain loose materials from the inside of the furnace, or sand,
into which the vertical flange of the girders 7 dips so as to form a closed connec-
tion between the rotating bottom 1 and fixed roof or arch 6 of the furnace as
usual in furnaces with rotating bottoms.
Having thus particularly described my said Invention, and the manner of
performing the same, I have to state that I do not restrict myself to the precise
details berein-before described and shown in the accompanying Drawings, as the
forms of the discharge opening and closing details and the arrangements of the
stirring and discharging apparatus may be greatly varied; but that what I believe

page_text: to be novel and original, and claim as the Invention secured to me by the herein-
before in part recited Letters Patent; is the application and use in the manufacture
of chromates of a furnace formed with a revolving bottom having a central
discharge opening, substantially as herein-before described.
In witness whereof, I, the said James Mactcar, have hereunto set my hand and
seal, this Sixth day of January, in the year of our Lord One thousand eight
hundred and seventy-seven.
Witness,
EDMUND HUNT,
Patent Agent,
Glasgow.
JAMES MACTEAR. (L.S.)