Improvements in Sand Blast Apparatus.
Year: 1889

page_text: Date of Application, 21st Sept., 1889-Accepted, 4th Jan., 1890
Improvements in Sand Blast Apparatus.
I JEREMIAH EUGENE MATHEWSON of Bellefield Works, Shellield 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 :—
This invention relates more particularly to that class of sand blast apparatus in
which a jet of steam is used to propel the cutting material, and the object of the
invention is to increase the efficiency of the apparatus at present in use for grinding,
frosting, ornamenting, and perforating glass, stone, and other hard substances.
In some kinds of work, it is necessary that the sand employed shall remain
throughout the operation in a dry or comparatively dry state, and I have practically
secured this result by separating the steam from the stream of sand, at the moment
the latter is about to strike the work, by means of a counter current of air induced
by an exhaust. The steam condenses, and, while the addition of minute particles of
dust arising from the pulverisation of the sand and of the surface of the article
under treatment (which are also drawn away by the exhaust), collects in an inner
chamber, and obstructs the exhaust pipe, unless often removed. During removal,
some of the liquid is liable to be upset into the dry sand, and damp it, which will
produce a clogging of the apparatus.
I have also found, in practice, that the steam valve is liable to leak under certain
conditions which frequently arrive, and the water of condensation issues from the
steam jot, and, by capillary attraction, gets into the dry sand receptacle and damps
the sand.
Now, according to my present invention, I simplify and improve the apparatus, so
that I overcome the objections above enumerated.
In the accompanying drawings,-
Fig. 1 is a vertical section of the improved sand blast apparatus, in which steam is
used as the motor or propeller, and :-
Fig. 2 is a sectional plan of the same, taken in the line 1, 2, of Fig. 1.
A, A is the outer case of the apparatus, and B is a central steain drying chamber,
in communication with which is a pipe B, supplied with steam from any convenient
source.
The steam, as it leaves the pipe B', enters helical passages B2, situate in the centre
of the chamber B, and in passing through these passages, a whirling motion is imparted
to the steam, which it retains while passing up a straight pipe forming a continuation
of the steam passages.
The pipe is piorced with holes or slits, and as the whirling steam moves upwards,
any moisture which it contains will be thrown out laterally, and find its way into
the chamber B, whence it. will flow through a discharge pipe in the bottom of the
chamber.
'
The dry steam then passes up through the stean jet C, and the vertical blast
pipe C, and out at the bell mouth C², together with the sand which it has taken up
during its passage.
I will now explain how the sand is introduced to the steam blast.-Surrounding.
the bell-mouth pipe C, is an annular chamber D, which is a receptacle for the sand.
This chamber is formed partly by the outer casing A, and partly by the walls of the
inner exhaust chamber E, in the centre of which the pipe C is situated.
Opposite the mouth of the pipe. C, is an opening in the top of the exhaust
chamber, and, in a line therewith, there is a corresponding opening in the outer

page_text: casing A, over which opening, the glass or other surface to be operated upon is
laid, to be presented to the action of the sand blast.
The blast pipe C" terminates at the point c, and fitted on to the steam jet C, and
surrounding the open end of the pipe C, is a dish-shaped hopper c¹, for receiving
sand discharged into it by the tubes d, leading from the bottom of the chamber D.
As, therefore, the steam passes from the jet C, up the pipe C', it will draw with
it sand from the dish shaped hopper c', and discharge it onto the glass or other
surface submitted to its action.
From this surface, the sand will rebound, and fall back into the chamber D,
ready to find its way again into the hopper c', to be ejected from the pipe Cas
before.
The steam, on issuing from the pipe C², comes under the action of a counter
current of air produced by an exhaust, and is thus withdrawn froin the ascending
current of sand into the exhaust chamber E. This chamber E extends some
distance below the said chamber D and its tubes d, and nearly all round the
apparatus, as will be clearly seen in the drawing; thus I obtain a collecting chamber
of considerable extent, from which the mud and deposit can be withdrawn by the
door E¹, also below the chamber D, thus obviating any risk of wetting the dry sand.
The steam jet C is also outside the chamber E, as well as the chamber D, from both
of which it is effectually shut off, and any water of condensation will overflow at the
hopper c', and run out of the apparatus, without coming into contact with the
sand.
The abstraction of the steam from the sand current. is effected by an ordinary
steain jet exhauster F, steam being supplied to the jet by the pipe leading from
the bottom of the steam dryer B.
The jet of steam is discharged into a trunk F2, connected with the exhauster F, the
air being drawn into the apparatus through holes in the casing A, situate above the
sand chamber, and passing down the pipe F, with the steam, to the exhauster.
Instead of the steam jet exhauster, other means may be employed to produce a
vacuum. The jet C is fitted with a valve ce provided with a hand wheel c³, and fitted
to the tubes d, is a flat annular valve d', pierced with holes corresponding to the
tubes d, by which the discharge of steam by the jet C, and the supply of sand by
the tubes d, can be cut off as and when required.
The valve rests upon a ledge carried by the inner wall of the casing, and is
provided with a handle de, by which it can be partially rotated, to turn off or on
the sand. Access is obtained to the tube Cand other parts by the opening A* in the
casing A.
The pipe C', which sucks in the sand from the hopper c', is liable to rapid
deterioration, and I have found it desirable to make it easily removable. For this
purpose, I provide the pipe C' with an india-rubber ring C, which, when the pipe
is placed in position, is pushed up into the socket a of the casing A, and thus holds
the pipe securely in, and centrally of the socket.
To remove a worn pipe, the pipe is first pushed up a little into the bell-mouthed C².
It is next pulled to one side, to clear the hopper, and is then pulled away from the
ring, which can be afterwards removed.
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 in which steam is the motor, a blast pipe, as C¹, having
its open lower end entering a dish-shaped hopper supported by, or placed
immediately above the steam jet C, such hopper being supplied with sand in regulated
quantities, by gravitation, direct from the dry sand chamber, as set forth, whereby
the liability of the sand to come in contact with moisture from the condensed steam,
is. avoided.

page_text: 2. The arrangement of sand blast apparatus as described, in which the receptacle
for the condensed steam,and the mud arising from the pulverization of the sand, and of
the surface under treatment, is placed below the dry sand chamber and its connections,
for the purpose above fot forth.