IMPROVEMENTS IN ROCK
Year: 1882

page_text: LETTERS PATENT to Howard Devenish Pearsall of Savile Row in the County
of Middlesex Civil Engineer for an invention of IMPROVEMENTS IN ROCK
PROVISIONAL SPECIFICATION left by the said Howard Devenish Pearsall
at the Office of the Commissioners of Patents on the 4th April 1882.
HOWARD DEVENISH PEARSALL of Savile Row, London, in the County of
Middlesex, Civil Engineer-IMPROVEMENTS IN ROCK DRILLING.
The use of certain explosive substances to give percussive action to a drill or
drills and the manner of so using them. I use a cylinder and piston or plunger
(mounted on any convenient carriage) the piston rod or plunger carrying the drill.
The forward stroke of the piston or plunger is caused by the explosion of certain
explosive substances which are fed in small quantities into the cylinder or into a
chamber communicating. The feeding is by preference automatically worked by
the piston itself when once started. The method of feeding is varied to suit the
particular form of explosion used. The chief forms used are gun cotton diluted
mixture with inert substance, or gunpowder, or combustible gas. Other explosive
substances may also be used.
The first way of using gun cotton or gunpowder is by 'making them into small
cartridges of the requisite strength with or without detonators and enclosing them
in a tube at intervals in the length of the tube about equal to the diameter of the
cylinder. This tube is passed through the cylinder across its end one cylinder-
diameter's length at a time in such a manner that a cartridge is always found in
place in the cylinder when the piston is making the return stroke. A small pro-
jection on the upper side of the piston will then strike the cartridge and cause its
explosion or it may be exploded in other ways.
Another way of feeding the explosion is to have a slot in the side of cylinder
extending throughout lower half (more or less) of its length. The explosive
being then wrapped in a tube of thin paper or other material is fed in at the slot
as the piston or plunger is returning, is caught by the said plunger and carried to
head of cylinder and is there exploded by the compression of air or gas which
Prias C631

page_text: takes place. The slot in this arrangement may be left always open and form
exhaust passage for the gases produced in the explosion. The unconsumed part
of the cartridge will also be blown out at the same time.
Another way of feeding is to have a hopper carrying the explosive in form of
powder or liquid and communicating with the cylinder by a tube closed by a
double stopcock or double valve which is opened and shut at every stroke thus
feeding in a measured quantity of the powder or liquid.
In the case of using combustible gas the gas is admitted into the cylinder together
with atmospheric air and exploded by any of the known methods for effecting such
an object in gas engines and elsewhere.
The return stroke is accomplished by any of the following methods. (1) on the
underside of the piston (ie. the side towards the drill) the piston rod passes
through a gland or stuffing box. A short distance from this end of the cylinder
there is a small opening in the side of the cylinder allowing communication with
the atmosphere so that at every back stroke of the piston the cylinder space on
the under side of the piston will be filled with air. Then in the forward stroke
some of this air will be expelled through said opening but some of it will will be
retained and forcibly compressed by the force of the forward stroke and so form a
cushion to prevent fracture of the machine and a spring which will throw the
piston back and so cause the return stroke. The strength of this spring can be
modified to any extent by the position and size of said opening in side of cylinder
so as to cause a back stroke of the exact extent required and for this purpose said
opening may be fitted in appropriate way with sliding valve, stopcock, or other
'contrivance.
(2) The compression of air for the return stroke may be otherwise accomplished
in the upper part of the cylinder, the cylinder having a partition in or about the
middle of its length through which passes a rod connecting the main piston or
plunger with another piston in the upper part of the cylinder.
In this case no
stuffing box is required to cylinder.
(3) The air cushion may also be dispensed with and return stroke accomplished
by hand or foot power or by springs or weights; or retaining the air cushion,
other power may be used to assist in making the return stroke.
A further modification consists in the application of the explosive power once
only in 2 or more strokes, the intervening strokes being made (1) by the momentum
of a fly wheel, or (2) by the reaction or expansion of air confined in either end of
the cylinder forming two powerful springs which absorb part of the force of the
original explosion and give it out again in the course of one or more strokes, or (3)
by the vaporisation of a small quantity of water injected into the cylinder and
vaporised by the beat produced by the previous explosion. This latter method
has the advantage of keeping the cylinder cool and lubricated and may be applied
to such an extent as that the cylinder shall never be much hotter than low pressure
steam.
'
In order to keep the cylinder cool. I also surround it with a large tube and
connect said tube with the exhaust pipe used in ventilating the drift or heading
where the work is being done.
This also effects the immediate removal of the gaseous products of explosion
without allowing them to mix at all with the general atmosphere of the
gallery.

page_text: · ŠPĒCIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Howard Devenish Pearsall in the Great Seal Patent Office on the
3rd October 1882.
:
'
HOWARD DEVENISH PEARSALL of Saville Row London in the County of
Middlesex, Civil Engineer. "IMPROVEMENTS IN ROCK DRILLING."
My invention relates to the use of certain explosive substances to give percussive
action to a drill or drills and the manner of so using them.
I use a cylinder and piston or plunger (mounted on any convenient carriage) the
piston rod or plunger carrying the drill. The forward stroke of the piston or
plunger is caused by the explosion of certain explosive substances which are fed in
small quantities into the cylinder or into a chamber communicating with it. The
feeding is by preference automatically worked by the piston itself when once
started. The method of feeding is varied to suit the particular form of explosives
used. The chief forms used are gun cotton diluted by a mixture with inert
substance, or gunpowder, or combustible gas. Other explosives and volatile oils
may also be used. According to one mode of using guncotton or gunpowder, they
are made into small cartridges of the requisite strength with or without detonators
and enclosed in a tube at intervals in the length of the tube about equal to the
diameter of the cylinder. This tube is passed through the cylinder across its end,
one cylinder-diameter's length at a time in such a manner that a cartridge is
always found in place. in the cylinder when the piston is making the return stroke.
A small projection on the upper side of the piston will then strike the cartridge
and cause its explosion, or it may be exploded in other ways. Another way of
feeding the explosive is. to have a slot in the side of the cylinder extending
throughout the lower balf (more or less) of its length. The explosive, being then
wrapped in a tube of thin paper or other material is fed in at the slot as the
piston or plunger is returning, is caught by the said plunger and carried to the
head of the cylinder and is there exploded by the compression of air or gas which
takes place. The slot in this arrangement may be left always open and form the
exhaust passage for the gases produced by the explosion. The unconsumed part
of the cartridge will also be blown out at the same time. Another way of feeding
is to have a hopper carrying explosives in the form of powder or liquid, and com-
municating with the cylinder by. a tube closed by a double stop cock or double
valve which is opened and shut at every stroke thus feeding in a measured quantity
of the powder or liquid. In the case of using combustible gas, the gas is admitted
into the cylinder together with atmospheric air and exploded by any of the known
methods for effecting such an object in gas engines and elsewhere.
The return stroke is accomplished by one of the following methods: (1) A piston
may be used instead of a mere plunger and on the underside of the piston (i.e. the
side toward the drill) the piston rod passes through a gland or stuffing box.
A short distance from this end of the cylinder there is a small opening in the side
of the cylinder allowing communication with the atmosphere so that at every back
stroke of the piston, the cylinder space on the underside of the piston will be filled
with air. Then on the forward stroke some of this air will be expelled through
the said opening but some will be retained and forcibly compressed by the force of
the forward stroke and so form a cushion to prevent fracture of the machine, and a
spring which will throw the piston back and so cause the return stroke. The
strength of this spring can be modified to any extent by the position and size of
the said opening in the side of the cylinder so as to cause a back stroke of the
exact extent required, and in order to so modify the positions and size of the said
opening it may be fitted with a sliding valve, stop cock, or other contrivance.

page_text: (2) The compression of air for the return stroke may be otherwise accomplished
in the upper part of the cylinder, the cylinder having a partition in or about the
middle of its length through which passes a rod connecting the main piston or
plunger with another plunger or piston in the upper part of the cylinder. In this
case no stuffing box is required to the cylinder. (3) The air cushion may be
dispensed with and the return stroke accomplished by hand or foot power or by
springs or weights; In this case a plunger only is used without a piston, or
retaining the air cushion, other power may be used to assist in making the return
stroke and for this method of working the drill a foot treadle has been devised as
shewn in the drawings. A further modification consists in the application of the
explosive power once in only two or more strokes, the intervening strokes being
made by the momentum of a flywheel or the reaction or expansion of air confined
in either end of the cylinder, forming 2 powerful springs which receive part of the
force of the original explosion and give it out again in the course of one or more
strokes, or it may be effected by the vaporisation of a small quantity of water, oil
or other fluid injected into the cylinder and vaporised by the heat produced by the
previous explosion. The latter method has the advantage of keeping the cylinder
cool and lubricated, and may be applied to such an extent that the cylinder shall
never be much hotter than low pressure steam, also in order to keep the cylinder
cool I surround it with a large tube and connect the said tube with the exhaust
pipe used in ventilating the drift or heading where the work is being done. This
will also effect the immediate removal of the gaseous products of explosion without
their being allowed to mix at all with the general atmosphere of the gallery.
Fig. 1 of the accompanyings is a side elevation shewing one construction and
arrangement of rock drill according to my invention, the back stroke being effected
by a treadle. Fig. 2 shews separately the mechanism for feeding the cartridges,
part of which is shewn in section to a larger scale at Fig. 3. A is the cylinder
titted with a plunger B to which is attached the drill B. At the side of the
cylinder is an open slot C by which the cartridges are introduced as will presently
be explained D is the treadle which on being pressed by the foot raises the arm E
and so causes the plunger B to make its back stroke. In order to allow for
variations in the position and attitude of the drill the arm E is not rigidly con-
nected to D but can be secured at various angles to it by inserting a pin through
a hole in E into one or other of the holes in a semicircular plate attached to D.
The plunger is linked by a rod F to a lever G which is fixed to a rocker H. This
rocker may have teeth or grooves at its circular ends to engage with teeth or
grooves on either of two lateral slides J and Q according as it is brought to bear
against the one or the other by moving a hand lever W, having its short arm X
linked by a rod Y to the axis of H, which passes through a slotted hole in the
framing. The slides J and Q are guided by the head N forming part of the frame.
3 is jointed to a lever K on which is fixed the magazine tube L which is charged
with cartridges through the funnel P as will be understood on reference to Fig. 2
in which is shewn in its middle position the dotted lines L' L indicating the
two extremes of its stroke.. Near the mouth of the tube L is mounted a rocking
shutter M shewn to an enlarged seale in Fig. 3, this shutter having an arm linked
to a fixed pin at O,. is moved by the rocking of L so as to permit issue of a
cartridge as L passes the slot C in the cylinder. The slide Q is attached to the
plunger of a pump R which draws by a pipe S water or other liquid in quantity
regulated by a cock or valve V and delivers it by a pipe T into the cylinder in
fine spray. Instead of employing a treadle to make the return stroke of the drill,
it may be effected by the elasticity of the air compressed in front of the piston P
as shewn in Fig. 4 or in front of a piston P2 attached to the plunger B as shewn
in Fig. 5, a cock Z being applied to adjust the air passage. Although no means
are shewn of causing the drill to revolve, it is to be understood that this can be
effected by any of the known means employed for percussive rock drills.
Having thus described the nature of my invention and in what manner the
same is to be performed, I claim:

page_text: First. Propelling the piston or plunger of a percussive rock drill by an explosive
admitted to and fired in the cylinder of the drill, as herein described.
Second. Effecting intermediate strokes by the vapour of a liquid admitted to
the heated cylinder, as described.
Third. The construction and arrangement of drill herein described with reference
to Figs. 1, 2 and 3.
In Witness whereof I the said Howard Devenish Pearsall have hereunto set
my hand and seal this thirteenth day of September in the year of our
Lord One thousand eight hundred and eighty two.
HOWARD DEVENISH PEARSALL. (L.S.)