Improvements in Sand Blast Apparatus.
Year: 1892

page_text: Date of Application, 29th Jan., 1892
Complete Specification Left, 14th Oct., 1892-Accepted, 3rd Dec., 1892
PROVISIONAL SPECIFICATION.
Improvements in Sand Blast Apparatus.
I, JEREMIAH EUGENE MATHEWSON of 265, Upperthorpe, Sheffield, in the
County of York do hereby declare the nature of this invention to be as
follows:-
In sand blast apparatus as heretofore constructed, the following devices or their
equivalents have been considered necessary for the proper working of the process.
(1) A reservoir to hold a supply of sand which sand after being projected against
the article under operation, is collected and returned to the said reservoir to be used
over again.
(2) An apparatus to regulate the flow or feed of sand from the said reservoir.
(3) A settling chamber in which the spent sand is separated from the air and
deposited at the bottom thereof.
(4) An elevator or its equivalent to return the spent sand from the settling
chamber back to the said reservoir in order to be used over again.
(5) A means of escape of all the spent air after being separated from the sand in
the settling chamber.
In my improved system these contrivances are mainly dispensed with thus making
the apparatus more simple and less expensive.
My invention consists in constructing the apparatus so that the spent sand after
striking the object under operation shall not be allowed to separate or settle from
the air which propelled it, but both shall immediately pass mixed together back
into the blower, pump, or exhausting apparatus, and then be driven from it into the
tube leading to the blast pipe, through which the mixture is propelled at a
maximum velocity against the object under operation, and thence again passes back
into the pump &c. so as to make a continuous automatic circulation of the same air
and sand, their velocity being renewed by the action of the blowing or exhausting
apparatus, at each circuit.
:
By causing the propelling blast to be created by means of a partial vacuum, any
leakage at the joints of the doors or openings (through which the articles to be
operated upon are introduced into the working chamber) will be inwards thus
avoiding dust in the atmosphere of the working room. A suitable outlet and sand
trap are provided in the pipe conducting the sand laden air from the exhausting
apparatus to the blast pipe, for the escape of surplus air caused by leakage &c.,
into the working chamber or its connections. The surplus air carries with it the
finest dust resulting from pulverization but any useful sand is retained by the sand
trap and either thrown back into the, current or into the small sand reservoir
hereinafter mentioned or into other convenient receptacle. When using a
propelling blast created by a pressure of air, an outlet and sand trap is provided in
the pipe leading from the blower to the blast pipe through which outlet a small
amount of the mixed air, sand and dust, is allowed to escape. This loss of air
creates a partial vacuum in the working chamber and the conducting pipe and this
again causes the leakage through the joints in the working chamber to be inward
as before. It will thus be seen that the blast may be created either by a partial
vacuum or by pressure above the atmosphere, or by a combination of the two
systems, as may be found convenient. As the sand laden air would quickly cut
away any rubbing surfaces, I prefer to use a frictionless blowing or exhausting
apparatus of the type described in my Patent No. 11,552/87 or its equivalent.
The tubes conveying the sand laden air should be of such size shape and direction
as to avoid as much as possible the separation of the sand and air, at the same time
keeping the velocity as low as possible in order to cause the least possible friction.

page_text: The diameter of the conducting pipe compared with that of the blast pipe, should
be arranged according to the size of the sand used. A small sand reservoir is
provided from which sand is introduced automatically or otherwise to make up for
that pulverized and carried off by-the. surplus air escape.
To diminish wear, the surfaces exposed to the currents of sand laden air may
advantageously he kept covered with the elastic compound of glue and glycerine or
its equivalent.
Dated this 28th day of January One thousand eight hundred and
COMPLETE SPECIFICATION..
Improvements in Sand Blast Apparatus.
I JEREMIAH EUGENE MATHEWSON, Engineer, residing at No. 265 Upper-
thorpe Sheffield in the County of York do hereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
In sand blast apparatus as heretofore constructed, the following devices or their
equivalents have been considered necessary for the proper working of the process.
(1) A reservoir to hold a supply of sand, which sand after being projected
against the article under operation, is collected and returned to the said reservoir,
to be used over again.
(2) An apparatus to regulate the flow or feed of sand from the said reservoir.
(3) A settling chamber in which the spent sand is separated from the air and
deposited at the bottom thereof.
(4) An elevator or its equivalent, to return the spent sand from the settling
chamber, back to the said reservoir, in order to be used over again.
(5) A means of escape of all the spent air after being separated from the sand
in the settling chamber.
In my improved system these contrivances are mainly dispensed with; thus
making the apparatus more simple and less expensive.
My invention consists in constructing the apparatus so that the spent sand, after
striking the object under operation shall not be allowed to separate or settle from
the air which propelled it, but both shall immediately pass, mixed together, into
the blowing, exhausting or propelling apparatus and then to be driven from it
into the tube leading to the blast pipe, through which the mixture is driven at a
maximum velocity against the object under operation, and thence again passes
back into the propelling apparatus, so as to make a continuous automatic
circulation of the same air and sand, their velocity being renewed by the action of
the propelling apparatus at each circuit. By causing the blast to be created by
means of a partial vacuum, any leakage at the joints of the doors or other openings
into the working chamber, will be inwards, thus avoiding dust in the atmosphere of
the working room.
A suitable outlet and sand trap is provided in the pipe conducting the sand laden
air from the propelling apparatus to the blast pipe, for the escape of surplus air
caused by leakage into the working chamber or its connections. The escaping
sand laden air carries with it fine dust, resulting from pulverization; but the
useful sand is retained by the sand trap, and either thrown back into the current,
or into the small sand reservoir hereinafter mentionel, while the dust is carried
away by the current of air.
The blast may be created by a partial vacuum or by pressure above the
atmosphere, or by a combination of the two systems as may be found convenient.
As the sand laden air would quickly cut away any rubbing surfaces, I prefer to use
a frictionless blowing or exhausting apparatus, of the type described in
No. 11552, 1887, or its equivalent.
my Patent,

page_text: The tubes conveying the sand laden air, should be such size, shape and direction,
as to avoid as much as possible, the separation of the sand and air, at the same
time keeping the velocity as low as possible in order to cause the least possible
friction. The diameter of the conducting pipe, compared with that of the blast
pipe, should be arranged according to the size of the sand used. A small sand
reservoir is provided, from which sand is introduced automatically or otherwise, to
make up for the loss from pulverization &c. To diminish wear, the surfaces
exposed to the currents of sand laden air, may advantageously be kept covered
with the elastic compound of glue and glycerine, or its equivalent.
The following is a method of carrying my invention into effect, using a blast
created by a partial vacuum,-
Referring to the annexed drawing,
Fig. 1. is a side elevation, partly sectional, of the apparatus.
Fig. 2. is a plan thereof.
The same letters refer to the same parts in each figure.
A is an ordinary centrifugal fan or air propelling apparatus, by the action of
which, a partial vacuum is created at its inlet L, thereby causing the air in the
conducting pipe B, working chamber C, blast pipe E, and conducting pipe D, to
flow rapidly toward said inlet. The outlet M, of the propelling apparatus, being
connected with the pipe D leading to the blast pipe, a continuous circulation of the
air within is set up. A quantity of sand from the hopper H, about equal in
weight to the air in circulation, is then allowed to mingle with the current. The
stream of sand laden air issuing with great velocity from the blast pipe E, strikes
against the sheet of glass F, or other object under operation, held or moved about
over the hole G in the working chamber. The blast pipe E, is from one third to
one quarter of the diameter of the conducting pipes, and the velocity of the
current through it, depends upon the degree of vacuum maintained by the pro-
pelling apparatus, in the working chamber C. I is a sand trap and surplus air
escape.
The escaping air carrying with it some useful sand, and dust, (from the
pulverization of the sand and glass) passes through the centrifugal separator,
whereby the usable sand is arrested and again put into circulation, while the
useless dust is carried off by the surplus air. H is a hopper with a movable
plug K, to supply fresh sand to the circulating current of sand laden air when
needed.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is,
1. In a sand blast apparatus, the continuous automatic circulation of sand laden
air, from the air propelling machine to the working chamber, and thence back to
the propelling machine.
2. The combination with a sand blast apparatus having a continuous circulation
of sand laden air, of any one or more of the following devices.
3. A partial vacuum, or a pressure above the atmosphere in one side or part of
the apparatus, or a vacuum in one side and pressure in the other, to cause the
circulation of sand laden air.
4. An escape for the surplus air, caused by leakage accidental or otherwise, into
the apparatus.
5. A settling chamber or sand trap, for the purpose of arresting usable sand
carried out by the escaping surplus air.
6. A hopper to supply fresh sand to the circulating current of sand laden air.
All substantially as described.
J. E. MATHEWSON.