IMPROVEMENTS IN MUFFLES OR OVENS TO BE EMPLOYED IN THE MANU- FACTURE OF LOOKING GLASSES OR MIRRORS
Year: 1864

page_text: PROVISIONAL SPECIFICATION left by John Henry Johnson at the Office.
of the Commissioners of Patents, with his Petition, on the 5th
October 1864. A communication from abroad, by the Society Randal
Cresswell, Alfred Tavernier, and Edouard Dodé, of Paris, in the Empire
of France.
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of
Middlesex, Gentleman, do hereby declare the nature of the said Inven-
tion for "IMPROVEMENTS IN MUFFLES OR OVENS TO BE EMPLOYED IN THE MANU-
FACTURE OF LOOKING GLASSES OR MIRRORS," a communication to me from
abroad by the Society Randal Cresswell, Alfred Tavernier, and Edouard Dodé,
of Paris, in the Empire of France, to be as follows :-
This.Invention relates to the construction and arrangement of muffles or
ovens intended to be employed in the heating of sheets or plates of glass
after they have been coated or covered with the composition or substance
described in the Provisional Specification filed by me in the Office of the
Commissioners of Patents, on the 18th day of June last, No. 1520, with
respect to an Invention of "Improvements in the Manufacture of Looking
Glasses, Mirrors, and other Reflecting Surfaces," communicated to me by
Edouard Dodé, of Paris, in the Empire of France..
According to this Invention, the muffle or oven in which the coated sheets
or plates of glass are to be heated has its sides constructed of cast iron panels

page_text: which are removable so as to be built up and form a muffle or oven of any
required height according to the size of the sheets of glass to be introduced.
To facilitate the accurate fitting of one panel on to another it is proposed
to tongue and groove them on their edges, by which means a close joint is
obtained, and the smoke from the furnace is effectually excluded from the
interior of the muffle. The top and bottom of this muffle may be each com-
posed of one single plate of cast iron having its edges turned up and tongued
or grooved to receive the panels which constitute the sides of the muffle.
-This-muffle-is-supported-upon-a bed-of-fire-clay which is itself supported on-
brick arches forming the roof of the furnace beneath. The sheets of glass
are introduced into the muffle on the front side thereof, whilst the furnace
is lighted, and fed with fuel from the opposite side. The closed muffle above
described is surrounded by brickwork, a space being left all around between
the exterior of the muffle and the inner face of the walls for the free circulation
of the heat and products of combustion from the furnace, whilst the products
of combustion pass off through perforations in an arched roof constructed
some little distance above the top of the muffle and entering a chamber above,
whence they pass off to the chimney. One or more pipes are fitted into the
top of the muffle and lead through the arched roof into the chamber above it
in order to carry off any fumes arising from the composition applied to the
sheets of glass in the muffle. Other pipes or s
spy holes are fitted into the
front of the muffle and pass through the brickwork, whereby the progress of
the heating operation may be watched. The sheets or plates of glass may
either be placed directly inside the glass muffle (the panels in' the front of
which are to be removed for that purpose) or they may be inserted into skeleton
frames or holders which are placed inside the muffle and provided with
horizontal racks or notched bars at proper heights to receive the edges of the
sheets of glass which are placed inside the frames in a vertical-position side by
side, the notched plates; serving to keep them upright 'in their. proper
places. These frames may be made of various sizes to suit different. sized
plates and several of them may be placed inside the muffle either side.by.side
or in tiers.
:
By using moveable horizontal division plates the skeleton frames.may each
be subdivided into two or more compartments in height. Or, in lieu of these
frames, the panels of the muffle may have cast upon them.or. secured thereto,
the requisite notched bars or racks for holding the sheets of glass in their
proper vertical position. Whilst the glass is being introduced, the front end-
of the furnace is closed up by a temporary stopper of fire-clay, and after the

page_text: muffle has been charged the front panels are replaced, the stopper removed,
and the brickwork or wall rebuilt up to the full height of the muffle. Valves
or regulating doors are formed in the wall behind the muffle for the
of facilitating the cooling of the same and regulating its temperature.
purpose