IMPROVEMENTS IN THE MANUFACTURE OF CRUCIBLES AND POTS IN WHICH METALS OR OTHER SUBSTANCES MAY BE MELTED
Year: 1865

page_text: LETTERS PATENT to George Nimmo, of Jersey City, in the State of New
Jersey, United States of America, for the Invention of "IMPROVEMENTS IN
THE MANUFACTURE OF CRUCIBLES AND POTS IN WHICH METALS OR OTHER
SUBSTANCES MAY BE MELTED."
Sealed the 2nd May 1865, and dated the 6th March 1865.
PROVISIONAL SPECIFICATION left by the said George Nimmo at the
Office of the Commissioners of Patents, with his Petition, on the 6th
March 1865.
I, GEORGE NIMMO, of Jersey City, in the State of New Jersey, United
States of America, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN THE MANUFACTURE OF CRUCIBLES AND POTS IN WHICH METALS
OR OTHER SUBSTANCES MAY BE MELTED," to be as follows:-
I employ a horizontal revolving head formed with a socket into which I
place a mould with a cavity of the external size and shape of the crucible or
pot to be formed; this mould is to be made of plaster or other porous material
that will absorb moisture from the pot or crucible formed within it. I have a
number of such moulds, and after one has been used in the revolving head
aforesaid, and the crucible formed in it, the mould and crucible are lifted off
the head and set aside to dry and another mould placed in the revolving head.
The porous nature of the mould causes an absorption of moisture from the
crucible or pot so that the pot contracts and separates easily from the mould,
and is to be dried or baked as usual. In order to spread the plumbago or
other crucible material evenly around in said mould I have a curved rib or

page_text: spreader, formed of metal or other smooth material, the shape of the interior
of the mould, or of one side of said interior; this is affixed to a handle or lever
set in slides or supports. The material for forming the pot or crucible is placed
in the plaster or porous mould and the said mould revolved by the head, and
the aforesaid rib or spreader pressed down upon the material, which operation
spreads, forms, and consolidates the material into a crucible or pot.
In the manufacture of black lead or plumbago pots or crucibles I find a
great advantage in making use of old plumbago crucibles or pots ground up
and introduced into the plastic mixture for the pots, or in place of old ground
pots to use calcined plumbago. The heat in calcining drives off the gases and
other foreign substances, so that the pots or crucibles are much less liable to
crack in the baking or when in use for melting than the pots made of crude
plumbago.
The compound which I find practically to be in the best proportion for the
mixture is about one measure of fine sand, one and a half measures of German
clay, and half a measure of china clay mixed with four measures of calcined
plumbago or old ground black lead pots, or a mixture of the two, these
produce a strong pot less liable to crack than heretofore.
°
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said George Nimmo in the Great Seal Patent Office on the 5th
September 1865.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
NIMMO, of Jersey City, in the State of New Jersey, United States of America,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Sixth day of March, in, the year of our Lord One
thousand eight hundred and sixty-five, in the twenty-eighth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
George Nimmo, Her special license that I, the said George Nimmo, my ex-
ecutors, administrators, and assigns, or such others. as I, the said George
Nimmo, my executors, administrators, and assigns, should at. any time. agree
with, and no others, from time to time and at all times thereafter during the
term therein expressed, should and lawfully might make, use, exercise, and
vend, within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN THE MANUFACTURE
QP CRUCIBLES AND POTS IN WHICH METALS OR OTHER SUBSTANCES MAY BE MELTED,"

page_text: upon the condition (amongst others) that I, the said George Nimmo, by an
instrument in writing under my hand and seal, should particularly describe
and ascertain the nature of the said Invention, and in what manner the
same was to be performed, and cause the same to be filed in the Great Seal
Patent Office within six calendar months next and immediately after the date
of the said Letters Patent.
NOW KNOW YE, that I, the said George Nimmo, do hereby declare the
nature of my said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement, reference being had to the Drawing hereunto annexed, and to
the letters and figures marked thereon (that is to say):
:-
Fig. 1 is a plan of my machine for molding erucibles; and
2 is a sectional elevation of the same.
Difficulty has heretofore been experienced in removing the crucibles from
the mold in consequence of the adhesive nature of the black lead compound or
mixture employed for such crucibles. The amount of water also that is
required to make the mixture sufficiently plastic causes the material frequently
to crack and break in shrinking as it dries.
The nature of my said Invention consists in the manufacture of crucibles in
a plaster mold, which gives shape to the pot externally and absorbs the
moisture from the pot, causing it to dry uniformly and at the same time shrink
away from the mold so as to separate easily, the plaster mold preventing the
air acting upon the outside of the pot until after the moisture has been mostly
absorbed prevents the pot from splitting or cracking from unequal contraction
in drying. I mount my plaster mold in a revolving chuck and employ a rib
attached to a lever for spreading the plastic crucible material on the inside of
the mold and at the same time hardening, consolidating, and polishing the
crucible on the inside by means of the said rib.
In the Drawing a is a bed carrying the vertical spindle b, on the upper end
of which is the hollow chuck c into which the plaster mold & fits, and these
parts are revolved by a belt to a wheel e and crank f, see Fig. 1, or by any
other competent means. Near the chuck c is an upright frame g with rollers
h, h, over which the chain or rope passes, on one end of which is the counter-
weight k, and on the other the lever 1, having a handle m at one end and
carrying the rib n. This lever is guided by the upright frame 9, and when
not in use is drawn up by the weight k. The crucible material is placed in
the plaster mold d and partially spread by hand or by a conical moller; the
back end of the lever is then brought beneath the stop or fulcrum o and
pressed down until the lever reaches a stop p. The rib n on the lever

page_text: smooths, compresses, hardens, and polishes the interior of the mold, forming a
perfect crucible possessing great strength and beauty, at the same time there
is great uniformity in the crucibles made in this manner. The crucible and
mold are to be lifted off the chuck and another mold introduced in the chuck,
and the operation repeated. The crucible and mold are set aside, and when
the plaster of the mold has absorbed the moisture from the crucible, and the
crucible has contracted away from the mold and become sufficiently dry to be
exposed to the air without risk of cracking the crucible is to be removed and
dried in any usual manner, and may afterwards be baked or burned.
In the manufacture of black lead or plumbago crucibles it has been usual
heretofore to mold the black lead with certain proportions of clay and sand
and then bake and burn the pots previous to sending them to market. This
requires the use of costly kilns that will subject the pots to the heat necessary
for driving off the gases that are formed in the said material by the action of
heat, and this baking operation has to be performed with great care to prevent
the crucibles flying or breaking; and the said crucibles often crack and break
when subjected to the heat necessary for melting steel, &c., and the pots, after
being used from three to five heats on steel, and from eighteen to thirty on
brass, are valueless. The nature of this portion of my said Invention consists
in the use of calcined plumbago with a proper admixture of clay and sand,
whereby I am enabled to produce crucibles adapted to use after drying without
requiring to be first burnt, care being taken not to heat the crucibles too
suddenly at the first.
The calcining of the black lead previous to mixing drives off the gaseous
materials that ordinarily cause the pots to crack and break, hence said pots
are merchantable when dried instead of requiring burning in costly kilns, and
are much more durable in use than those made from uncalcined plumbago.
I have found practically that calcined black lead or old black lead crucibles,
when ground up finely and mixed with about one measure of fire sand and
one and a half measures of German clay and half a measure of china clay to
four measures of black lead, will form about the best proportion for molding
into crucibles to be dried simply before using. The said proportion of four
measures of black lead being composed entirely of old crucibles ground, or of
one half or one quarter part of new calcined black lead mixed with such old
ground crucibles. If desired, the crucibles might be burned after drying
previous to sending to market, in which case they may be subjected to an
ordinary open fire without the use of a kiln. Uncalcined black lead may be
used in a small proportion.
What I claim and desire to secure by Letters Patent is,-

page_text: First, manufacturing crucibles in a plaster mold in the manner and for the
purposes specified.
Second, I claim lever l and rib n, applied in the manner specified, to form
the interior of a crucible contained within a revolving mold, as set forth.
Third, I claim the combination of the revolving chuck c, plaster mold d,
lever l, and rib n, as and for the purposes specified.
Fourth, I claim mounting the lever and rib n in the frame g, in the
manner specified, in combination with the counterpoise k, fulcrum o, and stopp,
for determining the size of the interior of the crucible, as specified.
Fifth, I claim the manufacture of crucibles from calcined plumbago, in the
manner and for the purposes specified.
In witness whereof, I, the said George Nimmo, have hereunto set my
hand and seal, this Seventh day of August, A.D. One thousand eight
hundred and sixty-five.
Vitnesses,
LEMUEL W. SERRELL,
121, Nassau St., New York.
JAS. E. SERRELL, jr.,
121, Nassau St., New York.
GEORGE NIMMO. (L.S.)