IMPROVEMENTS IN FURNACE DOORS
Year: 1883

page_text: LETTERS PATENT to William Douglass, of Blaydon,-on-Tyne, in the County
of Durham, Engineer for an Invention of IMPROVEMENTS IN FURNACE DOORS
-
LSANNE
PROVISIONAL SPECIFICATION left by the said William Douglass at the
Office of the Commissioners of Patents on the 3rd July 1883.
$6
WILLIAM DOUGLASS of Blaydon on Tyne in the County of Durham, Engineer,
IMPROVEMENTS IN FURNACE DOORS AND FRONTS
»
This invention relates in the first place to an improved mode of manufacture of
the fronts and doors of furnaces, and, secondly, to certain mechanical appliances for
closing the doors or setting them open to any required extent.
I form the front plate and the door, separately, by stamping each out of a plate
of any malleable metal, preferably mild steel, in moulds formed to give the desired
shape, by hydraulic or other pressure. The moulds are made to give any desired
flanged or beaded form to the front or door with either plain or corrugated surfaces
and to provide for protecting fire clay linings being inserted when required.
The hinges may in some cases be formed on the door by stamping but I prefer
to fit them by rivetting or bolting to the door either on the inside or outside.
To fasten the door close, or to open it to any desired extent, I fit to it a lever
latch of simple construction having its fulcrum on a stud fixed to the door near
the hinged side and its longer arm having a heavy knob on the end and working
freely in a slot or guide. The shorter arm of this latch forms a "pawl" which
engages with teeth or slots in a ratchet fixed to the front plate, concentric with the
hinge pin, so that when the door is closed or when opened to any desired extent,
the tail end of the lever latch, by the weight of the knob on longer arm, is forced
into one of the slots in the: ratchet and the door securely held. The projecting
knob enables the door to be opened for firing or other purposes, partially opened
for the admission of air or completely closed, with the greatest ease by the stoker
who only requires to raise the knob (which can be done with his shovel) to
disengage the tail end from the ratchet slots into one of which it engages on the
knob being released and fixes the door fully open, partially open or closed. The
door may be fitted with "baffle" plates or other means of protecting it from the
heat and with adjustable air inlets.

page_text: When the door is closed as shewn on all the Figures the heavy knob S keeps the
outer end of the latch lever O down and by the action of the lever on its fulcrum
forces the tail piece or "pawl" N into one of the notches in boss L, thus keeping
the door closed but when it is desired to open the door, the Stoker with the point
of his shovel, raises the knob S and draws it towards him till it is sufficiently open
either in position shewn by dotted lines N° 1 half open or N° 2 full open or thrown
back as in No 3 when by releasing the knob its weight causes it to bring down the
latch lever O and press the "pawl" N into one of the notches in boss L when it is
securely held until desired to be closed.
Having now fully described my invention and illustrated the manner in which
it may be practically applied although I do not confine myself to details of
construction or application. I claim as novel and secured to me by Letters
Patent.
Firstly. The construction of furnace fronts and doors by stamping them (by
hydraulic or other pressure) in moulds formed to give them the required shape, from
sheets or plates of steel iron or other malleable metal, substantially as shewn and
described.
Secondly. The application to furnace doors of any shape (whether stamped cast or
otherwise constructed) of a lever latch with a tail piece forming a "pawl" engaging
with notches formed in a fixed boss on front plate concentric to the hinge pin so as
to secure the door closed, open or in any required intermediate position, constructed
and operating substantially as shewn and described.
In witness whereof I the said William Douglass have hereunto set my hand
and seal this first day of January in the year of our Lord one thousand eight
hundred and eighty four.
TATTENT 122
DOUGLASS