IMPROVEMENT IN PROCESS AND COMPOSITION FOR THE MANUFACTURE OF THE MASTIC OF ASPHALTUM
Year: 1874

page_text: LETTERS PATENT to Robert Skinner, of San Francisco, in the County
of San Francisco, and State of California, one of the United States
of America, Gentleman, for the Invention of an "IMPROVEMENT IN
PROCESS AND COMPOSITION FOR THE MANUFACTURE OF THE MASTIC OF
ASPHALTUM."
COMPLETE SPECIFICATION filed by the said Robert Skinner at
the Office of the Commissioners of Patents, with his Petition and
· Declaration, on the 19th September 1874, pursuant to the 9th
Section of the Patent Law Amendment Act, 1852.
COMPLETE SPECIFICATION filed by the said Robert Skinner at
.
the Office of the Commissioners of Patents, with his Petition and
Declaration, on the 19th September 1874, pursuant to the 9th
Section of the Patent Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ROBERT
SKINNER, of San Francisco, in the County of San Francisco, and State
of California, one of the United States of America, Gentleman, send
greeting.

page_text: "
WHEREAS I am in possession of an Invention for "IMPROVEMENT IN
PROCESS AND COMPOSITION FOR THE MANUFACTURE OF THE MASTIC OF ASPHALTUM,'
and have petitioned Her Majesty to grant unto me, my executors,
administrators, and assigns, Her Royal Letters Patent for the same,
and have made solemn Declaration that I verily believe myself to be the
true and first Inventor thereof.
NOW KNOW YE, that I, the said Robert Skinner, do hereby declare
that the following Complete Specification, under my hand and seal,
fully discribes and ascertains the nature of the said Invention, and in
what manner the same is to be performed, in and by the following
statement, that is to say:-
My said Invention relates to a new composition of matter for the
production or manufacture of the mastic of asphalte, useful for roofing,
flooring, building, footpaths, roadways, reservoirs, docks, sea walls,
fortifications, and other purposes.
Before describing it intelligently it is necessary to refer to the
indefinite use of the terms bitumen, asphalte, asphaltum, and stone.
Bitumen is applied to various products from the gascous to the vitriform.
Asphaltum and asphalte are indifferently applied to pure bitumen of
several grades, to bituminous limestone, bituminous sandstone, and to
various conglomerates of bitumen with sand, gravel, stone, &c. Stone
is applied indiscriminately to carbonates, sulphates, silex, ect.
In my composition I use 80 per cent. of pulverized carbonate of lime,
limestone, chalk, or shells. The finer it is pulverized the better, but I
have found that the siftings through a No. 20 screen will answer my
purpose. I feed the pulverized carbonate into one end of an iron
jacketed trough about sixteen feet long. The trough is placed
horizontally, and contains a horizontal conveyer made with a hollow
shaft. Hot air or steam is introduced into the jacket and shaft for
the purpose of expelling the water from the carbonate by raising its
temperature above 212° Fahrenheit; at the same time I avoid a degree
of heat that will expel the carbonic acid from the carbonate and change
it into quicklime. As the pulverized carbonate is carried along the
trough to a point where it becomes anhydrous I combine with it two
per cent. of vegetable or mineral tar (the latter is preferable), previously

page_text: heated to a degree sufficient to expel the water from it. This saturates
and coats the pulverized carbonate, which is discharged by the conveyer
into a combined mixer and conveyer, into which is fed 18 per cent. of a
different form of bitumen, such as found for example in a compact form
on Hancock's Rancho, Los Angeles County, State of California, one of
the United States of America.
The manner of combining the last-described bitumen with the
saturated and coated granules of the carbonate is an important part
of my Invention, and may be described as follows, to wit:-I reduce
the bitumen to a pulverized condition by means of rapidly rotating
machinery before mixing it, and use an adjustable feed in the proceeds.
I am aware that materials classed under the indefinite names of bitumen
and asphaltum have been pulverized by machinery before combining
them with other substances, but the quality of bitumen to which I refer
has never been used as an admixture with other materials, without being
liquified by heat, and in this respect my process differs essentially from
all others. The combined mixer and conveyer is in the form of a
covered and jacketed trough, designed to control the temperature of the
materials as they are being incorporated and discharged. It contains a
horizontal shaft with arms, the action of which is comparable to that of
a sausage meat cutting and mixing machine.
The temperature of the materials is graduated by the common
appliances of hot or cold air, hot or cold water, or of steam passing
through the said jacket, so that said materials, while they are intimately
combined, shall be discharged at a compressible temperature, and the
combination may be formed into tiles, blocks, curbing, etc., by means of
pressure, or be spread over surfaces and solidified to the desirable
degree by means of tamps, heated irons, or rollers, such as are in
common use in working other bituminous compounds. .
:
:
It should here be observed that by decreasing the proportion of the
powdered carbonate the temper of the product is softened, and its quality
of resisting heat is impaired, whereas by increasing the proportion of
the carbonate the product is made harder, and resists a greater degree of
beat.
In order to distinguish my Invention from all others of a similar
eláss; although not identical, I would here state that I do not evaporato

page_text: materials described under a sufficient degree of heat to incorporate the
constituents.
In witness whereof, I, the said Robert Skinner, have hereunto
set my hand and seal, this Thirty-first day of August, A.D.
1874.