Improvements in Sand Blast Machines.
Year: 1891

page_text: Date of Application, 1st Sept., 1891
Complete Specification Left, 31st May, 1892-Accepted, 2nd July, 1892
PROVISIONAL SPECIFICATION.
Improvements in Sand Blast Machines.
I, JEREMIAH EUGENE MATHEWSON, of Bellefield Works, Sheffield, Engineer,
do hereby declare the nature of this invention to be as follows:-
My invention relates to that class of sand blast machines in which the sand is
propelled in an upward direction by a current of air: In such machines the sand,
after it has struck the object operated on, is generally collected in a settling.
chamber and made to run back by gravity, so as to be again used to feed the blast.
As heretofore made, the settling chamber, or greater portion of it, has been placed
above the object 'operated on, so that the spent air and sand move. through it in an
upward direction towards the escape pipe, and consequently the tendency of the
Band' to separate and settle from the air, is in some degree hindered by the upward
motion of the air, and the settlement can only be produced by making this motion
very slow and the chamber large and high. Also the blast pipe has to be made
much longer than would otherwise be necessary, so that the sand may run by
gravity to the mouth of the blast pipe. This extra length of blast pipe.beyond
what is necessary to allow the current of air to impart its velocity to the sand is
hurtful; in that it increases the friction and wear of the pipe and diminishes the
efficient velocity of the sand. ·
"
1
11
"
My invention consists in placing the settling chamber, or the greater part of it,
below the level of the object operated on, and causing the spent air and sand to
enter its upper part in a tangential direction, and to travel spirally downwards 80
as to give a whirling or centrifugal motion to the current of air and sand. The
settling chamber is preferably circular in cross section and its shape is generally
cylindrical, or conical with the small end downward. The sand is thrown outward
by the centrifugal force against the inside surface of the chamber. I arrange an
interior tube to lead upward from near the bottom of the chamber to the outlet, so
that 'the spent air, after depositing its sand, turns upwards through this tube and
escapes to the open air.
"
In order to avoid the inconvenience of a blast pipe longer than is required to
allow the current of air to impart its velocity to the sand, it is necessary that the
feed sand should be lifted by some means from the outlet. at the bottom of the
settling chamber to the lower or bell-mouthed end of the blast pipe. One part of
my invention consists in lifting this sand by means of a slow induced current of air,
created in the' sand feeding tube by inserting its upper end. a regulated, distance
into the lower or bell mouthed end of the blast pipe. The sand is made to fall by
gravity from the outlet'in the bottom of the settling chamber into the lower end
of the sand feeding tube and is there picked up by the slow induced current of air
and carried by it into the lower end of the blast pipe where it mixes with the rapid
current of air and receives its efficient velocity.
I
'
I prefer to give velocity to the air which propels the sand by means of a partial
vacuum, but I do not confine myself thereto. The advantage of the improved
construction is; that the machine is smaller, cheaper to make and.more convenient
to use.
L21
1001

page_text: COMPLÈTE SPECIFICATION.
Improvements in Sand Blast Machines:
I, JEREMIAH EUGENE MATHEWSON, of Bellefield Works, Sheffield, 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:-
My invention relates to that class of sand blast machines in which the sand is
propelled in an upward direction by a current of air.
In such machines the sand after it has struck the object operated on is generally
collected in a settling chamber and made to run back by gravity so as to be again
used to feed the blast.
As heretofore made the settling chamber, or the greater portion of it, has been
placed above the object operated on so that the spent air and sand move through
it in an upward direction, towards the escape pipe, and consequently the tendency
of the sand to separate and settle from the air is in some degree hindered by the
upward motion of the air, and the settlement can only be produced by making this
motion very slow, and the chamber large and high.
Also the blast pipe has to be made much lunger than would otherwise be necessary,
Bo that the sand may run by gravity to the mouth of the blast pipe.
This extra length of blast pipe beyond what is necessary to allow the current of
air to impart its velocity to the sand is hurtful, in that it increases the friction and
wear of the pipe and diminishes the efficient velocity of the sand.
My invention consists in causing the spent air and sand to enter the upper part
of the settling chamber in a tangential direction and to travel spirally downwards
so as to give a whirling or centrifugal motion to the current of air and sand: The
- settling chambor is preferably circular in cross section and its shape is generally
cylindrical or conical with the small end downwards.
The sand is thrown outward by the centrifugal force against the inside surface
of the chamber.
I arrange an interior tube to lead upward from near the bottom of the chamber
to the outlet, so that the spent air after depositing its sand turns upward through
this tube and escapes to the open air.
In order to avoid the inconvenience of a blast pipe longer than is necessary to
allow the current of air to impart its velocity to the sand, it is necessary that the
feed sand should be lifted by some means from the outlet at the bottom of the
settling chamber to the lower or bell mouthed end of the blast pipe. One part of
my invention consists in lifting this sand by means of a slow induced current of air
created in the sand feeding tube by inserting its upper end a regulated distance
into the lower or bell mouthed end of the blast pipe. The sand is made to fall by
gravity, in a regulated quantity, from the outlet in the bottom of the settling
chamber into the lower end of the sand feeding tube and is there picked up by the
slow induced current of air and carried by it into the lower end of the blast pipe
where it mixes with the rapid current of air, and receives its efficient velocity. I
prefer to give velocity to the air which propels the sand by means of a partial
vacuum, but I do not confine myself thereto. The advantages of the improved
construction are that the machine is smaller, cheaper to make and more convenient
to use.
The following is a method of carrying my invention into effect.
Referring to the annexed drawings,
Fig. 1. is a vertical section of a sand blast machine suitable for operating on flat
or curved glass, metal, stone or other material, tablets, sheets, bottles, globes and
similar objects.
Fig. 2. is a cross section of same through the line a, b, showing half the cover
cut away.
The same numbers refer to the same narts in each figure.

page_text: 1, 1, is the sand settling chamber, made preferably of a sheet iron cylinder with
cast iron ends and communicating at its top, by the pipe 2, with any suitable air
exhausting apparatus capable of maintaining a vacuum of from half a pound to
two pounds per square inch in the chamber 1, 1, during the operation. Chamber 1, 1,
has a conical bottom 3, which is kept full of sand, and from its centre descends the
pipe 4, about two inches in bore, and of a length proportioned to the vacuum
employed, say about eighteen inches long for. each pound of vacuum.
The bottom of 4, is closed by the sand valve 5, which is provided with a sliding
plate 18, to regulate the flow of sand into the horizontal pipe 7, where it is picked
up by the current of air entering at 8, and is carried through the tube 6, into the
tube 9, the end of which is inserted a regulated distance into the trumpet mouth of
the collar 10, which forms the entrance to the vertical tube 11. A strong current
of air rushes from the side oponings of 10, into the tube 11, and induces a moderate
current of air through the tube 7, 6, 9, which picks up and carries the sand dropped
through the valve 5. The requisite working velocity is imparted to the sand in
the tube 11, so that it strikes the object 12, which is held and moved about on the
hole 15. The sand rebounding from the object is carried sideways by the current
of spent air into the outer zone 16, of chamber 1, 1, which it enters tangentially,
as shown in Fig. 2, and descends in a spiral course to the bottom of tube 13, into
which the air and fine dust turn upwards, and are drawn into the tube 2, and thence
into the air exhausting apparatus, and are finally thrown into the open air, while
the coarse sand settles at 17, in the bottom of chamber 1, 1, and is again used.
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-
In sand blast machines in which the sand is propelled by a current of air, the
following devices either singly and separately or in combinations of any two or
more of them-viz.
1. Causing the spent air and sand to enter the settling chamber near its upper
end in a tangential direction and to travel spirally downward so as to give them a
centrifugal motion.
2. Causing the spent air to pass out of the settling chamber, after it has
deposited the coarser parts of its sand, through a central tube leading into the
exhausting machine.
3. Raising the feed sand to the mouth of the blast pipe by means of an induced
current of air created by inserting the upper end of the sand feeding pipe a
regulated distance into the lower or bell mouthed end of the blast pipe.
All substantially as described.
Dated this AL 1
1000