Year: 1888

page_text: I JEREMIAH EUGENE MATHEWSON of Bellefield Works, Sheffield, in the County
of York, Engineer, do hereby declare the nature of this invention to be as
follows:-
This invention relates to improvements in the apparatus employed with what is now
known as the "sand blast" for sharpening and otherwise operating upon files and
rasps and for cutting other hard substances.
In apparatus of the kind as at prosent employed, it has been found necessary to use
nozzle tubes, by which the stream of sand or cutting medium to be propelled, is, so to
speak, confined within limits for such a length of time as may be required to give it,
by means of the propelling medium (steam or air), a high velocity, in order to produce
the cutting effect on the article under treatment.
The result of this confining action is that the nozzle tubes are cut through or worn
away in a short time, in some cases only half an hour, but always within a few hours,
which renders continuous working a comparatively expensive operation, from the
constant renewals that have to take place."
Now the object of the present invention is to obviate these inconveniences, and
produce an apparatus in which the required velocity will be given to the cutting
imedium immediately it leaves the supply pipe, and without the intervention of a
nozzle tube.
In carrying out my invention, I take a sand supply pipe of any suitable or convenient
section and dimensions, and I place it inside a steam or propelling medium pipe, so
that the ends of the two pipes will be in the same or nearly the same plane, with a steam
space all round the sand pipe.
The steam pipe I so arrange that the line of its inner walls, if prolonged, will meet
at a short distance in front of the sand pipe. In this manner, the issuing streams of
steam or air will converge and meet in front of the sand pipe, and cause a vacuum in

page_text: that pipe, which will draw or suck out a stream of sand. The sand will be immediately
caught up by the propelling medium, and will be propelled with great force onto the
article to be cut.
An almost similar effect will be produced by having the inner walls of the steam
pipe parallel, and by withdrawing the sand pipe, so that its end will be a short distance
in rear of the outlet of the steam pipe. As steam expands on issuing from a pipe, and
in this case it cannot expand outwardly, the ring of steam contracts, and practically
becomes solid a short distance in front of the sand pipe, producing the effect (more or
less) mentioned above.
By these means the sand mingles at once with the propelling medium, and the
necessity for what I may call a mixing tube" is obviated.

page_text: COMPLETE SPECIFICATION.
Improvements in Sand Blast Apparatus.
I JEREMIAH EUGENE MATHEWSON of Bellefield Works, Sheffield in the County of
York, Engineer 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 the sand blastapparatusas heretofore constructed, the rapid destruction of thenozzle
in which the propelling fluid and the sand or cutting material are mingled before
passing out of the apparatus, has proved a great obstacle to the economical success of
the process of sharpening files, and cutting stone, glass, metals, and other substances
by the sand blast. The drawback experienced in the working of the process is due
not merely to the necessity for frequently renewing the nozzles, but also to the fact
that the cutting action, which is at its maximum of efficiency at or soon after the starting
of the blast, becomes less and less efficient as the operation proceeds.
Now the object of the present invention is to remove these serious disadvantages
and thereby to effect an important economy both in the cost of maintenance of the
apparatus, and in the power and time required to produce a certain quantity of
work. It is well known that the abrasion of the nozzles is due to the sand
or other cutting material receiving its impulse while contained within the
.nozzle.
By a series of experiments I have discovered that if the streams of propelling fluid
and sand or cutting material are kept apart until they leave the blast pipe, and if the
steam or air, on leaving the mouth piece, is caused to converge either to a central
point or to a line in front of the mouth piece, and there strike the issuing stream of
sand, a perfect mingling of the sand with the steam or air will take place, and no
cutting action will occur until the sand blast meets the work.
'
I may use in carrying out my invention either a circular mouth piece or a broad flat
mouth piece, or forms intermediate of these, according to the work in hand, with the
like beneficial result.-I will first describe the invention as applied to a flat mouth
piece, and afterwards to a round mouth piece.
In the accompanying drawings,
Fig. 1 shows in plan view,
Fig. 2 in longitudinal section, and
Fig. 3 in front or end view, a mouth piece such as I employ in finishing and
sharpening files and rasps, and working over broad surfaces.
Figs. 4 and 5 show in longitudinal section and end view, a circular mouth piece
suitable for general work, such as cutting, frosting, and ornamenting glass and inetallic
surfaces, or boring holes in glass and other materials; and
Fig. 6 is a diagram which illustrates the action of the invention.
Before describing the construction of the mouthpieces, I will, by reference to the
diagram Fig. 6, explain the manner in which the cutting material and the steam or
air blast are mingled at and beyond a point clear of the mouth piece...
W

page_text: In this diagram, 1 is the passage for the cutting material, and 2, 2, are passages (on
opposite sides of the passage 1) for the steam or air under pressure to pass out and
converge in a plane indicated by the line 3, 3 in advance of the passage 1.-The
streams of steam or air, in thus converging, will form a slight vacuum in front of the
passage 1, facilitate the feed of the cutting material, and cause it to mingle with the
impelling fluid, as indicated by the dots in the diagram. Thus, the mingling, instead
of taking place, as heretofore, within the nozzle or mouthpiece, and in contact with
the metal, will occur in front of the mouthpiece, and thereby the abrading action so
detrimental to the efficiency of the apparatus will be avoided.
In Figs. 1, 2, and 3, A is a casting forming the main portion of the mouth piece, and
BB are plates bolted to opposite sides of the mouth piece. In this casting A, there is
cored out a steam passage, a, which diverges from a cylindrical to a forked shape at a¹.
This forking of the steam passage is produced by a transverse wall of metal which
constitutes the back of a chamber C that opens in the form of a slit c at the front of
the mouth piece. Access is obtained to this chamber by side openings in the
casting A, for the purpose of inserting therein a sand tube D, connected with a
reservoir for the sand or other cutting material. This tube D is preferably tapered
towards its closed end, and at its back is formed a rib which enters a transverse slot
cut in the back of the chamber, to ensure its proper insertion in the mouthpiece. The
front of this tube D has a longitudinal opening covered by a flattened tube or
parallel lips & closed at their ends. Thus, a passage is formed for conducting the sand
from the tube D to the slit or exit opening c in the chamber C.
By this mode of fitting the tube in placo, as little metallic contact as possible is
established between the chamber and the tube. The object of this arrangement is to
prevent the heat of the impelling fluid from so acting upon the cutting material (when
wet sand or mud is used), as to choke the action of the apparatus.
The plates B B fit close upon slightly raised ribs at the sides of the casting A, and
form at their back and sides, steam tight joints with the casting. These plates converge
slightly towards the front of the mouthpiece, and serve to form extension passages bb
from which the impelling fluid issues in thin streams, converging at an angle of some
.15 degrees towards the plane of progress of the stream of sand or cutting material,
where they meet the same, and mingle therewith as above explained with reference to
Fig. 6. The chamber C terminates in a straight mouth c parallel with the exit
-openings of the steam passages bb.-The mouth of the passage c is flush with the exit
ends of the passages 6 b, but its width is somewhat less than the width of those
passages.
For the purpose of delivering the sand or cutting material freely from the mouth
piece, I employ pressure (by gravitation or otherwise) to ensure the steady feed of the
material through the apparatus; and to provide against injury to the mouth cof the
chamber C, any bruising or notching of which would detract from the evenness of
the stream, I form the plates B with lips, which overhang the openings for the issue
of the steam without interfering with its travel. This provision, it will be understood
is simply a guard for maintaining the efficiency of the apparatus against rough
usage.
EE are detachable plates set at opposite ends of the outlet passages bb to prevent
air entering between the streams of steam and interfering with the steady flow of the
cutting material.-These plates, which are made preferably of steel, are held in place
against the plates B by binding screws, which pass through screwed lugs formed on
the casting A.
F is a loop cast in one with the mouth piece A,and intended to receive a "feeler "G,
which beds upon a raised portion of the upper plate B, and serves as a support
and testing piece for the file or rasp presented to the action of the sand blast.
In the circular portion of the passage a, a screw is cut to allow of the mouth piece
being secured to the steam supply pipe. When steam is delivered to the mouth piece
and sand or other cutting material is admitted to the pipe D,a jet of mingled steam
and sand will be formed beyond the mouth piece, of a shape roughly corresponding,
when striking the work; to the exit end of the mouth piece.-For.general work I use

page_text: a circular mouth piece, the size of which will depend upon the work it is required to
perform. Thus, when a jet corresponding more or less with a pencil point is required,
I propose to employ a circular mouthpiece with an air exit of about one third
the diameter of that shown at Figs. 4 and 5, or say of an inch outside
diameter.
In this case, an annular jet is formed, which surrounds the extruded feed of cutting
material, and strikes it at a point beyond the mouthpiece, mingling with the cutting
material, and producing an incisive jet, the diameter of which will increase according
to the distance from the point of concentration at which the jet strikes the
work.
In Figs. 4 and 5 H is a straight tube in communication with a reservoir of dry sand
or other cutting material, which is supplied by gravitation to the tube H. This tube
fits into the centre of a tubular casting I, which terminates on a level with the exit
end of the tube H, and is supplied with steam or air under pressure through a
branch I' in communication with a steam boiler, or an air pump, or a reservoir of
compressed air, as the case may be. The stean or air entering the tubular casting I,
surrounds the tube H, and passes out in the form of a hollow tapering jet, drawing
with it a stream of sand or cutting material, which meets the steam or air at a point
in advance of the mouthpiece, as in the first described arrangement. Here the sand
and the steam or air unite, and mingling as illustrated in the diagram Fig. 6, form a
cutting blast, which, when presented to a metallic or other surface, will abrade it.
either evenly, or in the form of lines, or hard or softened shadows, the distance
between the point of concentration of steam or air and sand, and the surface of the
plate under treatment, being varied to produce these varying results, according to the
nature of the work in hand.
I may remark that by slightly retracting the sand tube H within the tube I, when
that tube takes a cylindrical form at its exit end, a converging jet may be obtained to
operate upon the protruded sand or cutting material. But the efficiency of this
arrangement, as compared with that just described, is not such as to recommend its
adoption.
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. The means above described for ensuring the combination or mingling of the
cutting material and the impelling fluid with each other, beyond or clear of the
mouthpiece, for the purpose above set forth.
2. The construction of flat jet mouthpieces with converging steam or air passages
placed at opposite sides of the passage for the extruded cutting material, such
passages all terminating in the same plane, as and for the purpose above
described.
3. In circular mouth-pieces for sand blast apparatus, a tapering annular steam or
air passage surrounding the passage for the extruded cutting material,and terminating
in the same plane therewith, such annular passage serving to concentrate the jet of
impelling fluid, which then mixes with the cutting material at a point in front of and
clear of the mouthpiece.
Dated this 22nd day of September 1888