IM- PROVEMENTS IN PERCUSSIVE ENGINES
Year: 1874

page_text: LETTERS PATENT to John Darlington, of 2, Coleman Street Buildings,
1
.
Moorgate Street, in the City of London, for the Invention of "IM-
PROVEMENTS IN PERCUSSIVE ENGINES."
PROVISIONAL SPECIFICATION left by the said John Darlington at the
Office of the Commissioners of Patents, with his Petition, on the
15th May 1874.
I, JOHN DARLINGTON, of 2, Coleman Street Buildings, Moorgate
Street, in the City of London, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN. PERCUSSIVE ENGINES," to be as
follows:-
My improvements in percussive engines are directly applicable to the
stamping of ores, minerals, or stone, to the dressing of stone, to the
beating of flax, riveting plates, sharpening mine tools, planishing and
hammering metals, and to the boring of rocks in which the length of
stroke and intensity of blow have frequently to be varied.

page_text: The percussive engine itself has no valve, but consists of a cylinder
so contrived that the movement of the piston or cylinder across
passages, and portways set in one or the other admits and discharges
the fluid pressure so as to effect a sharp quick reciprocating move-
ment.
5
In the case of a single-acting engine the pressure fluid is kept con-
stantly on the smaller area of the piston, and by the movement of the
piston within the cylinder, the pressure fluid is admitted by means of a
long passage to the upper side of the piston, which piston is then
subjected to a return movement and passes an outlet through which the 1
pressure fluid is exhausted..
In a double-acting engine the pressure fluid is alternately admitted
to and exhausted from both sides of the piston by passing two
induction passages and two exhaust portways formed in the cylinder.
In a modification of the single-acting engine the cylinder is formed 1
of a slightly larger diameter than the piston at the back end, and has
also a groove or recess formed near the middle of its length, which
recess is in connection with the exhaust portway..
The piston itself has induction and exhaust passages formed in it,
which passages alternately communicate with the enlarged parts or 2
passages of the cylinder and admit the fluid pressure to and exhaust it
from the superior area of the piston.
In a modification of the double-acting engine the piston is made of
sufficient length to have two grooves or recesses formed in it which
communicate with two sets of passages in the body of the piston itself. 2
These said grooves at either end of the piston stroke come opposite to
portways in the cylinder, two induction portways and one exhaust port-
way placing one end of the cylinder in communication with one pressure
portway by means of one set of passages and corresponding grooves in
the body of the piston, at the same time as the opposite end is.opened 30
to the exhaust portway by means of the other set of passages and the
corresponding groove.
. Instead of moving the piston in these several arrangement of ports
and passages the cylinder may be moved, and one end of the cylinder
fitted with a head suitable for delivering the required blow....
3

page_text: When it is required to turn the piston, as in rock or coal boring
apparatus, the end of the piston may be formed into a turbine, and
the induction passage or exhaust port fitted with turbine wings
accordingly; or a ratchet wheel may be placed within the cylinder with
an oval and slightly twisted bar, the latter entering a suitable nut, set
in the head of the piston, the ratchet wheel itself being detained in ono
direction by a detent formed so as to drop into the teeth without the use
of a spring.
For the purpose of lightening the piston and augmenting the volume
of steam to the cylinder, the piston may be made partly hollow; and
for working the pressure fluid at various rates of expansion a sliding
block or piston may be fitted in the end of the cylinder, or the piston
itself provided with a shifting ring, or made with a suitable "cover or
length above the exhaust passage, over and above the depth of the
piston when its opposite length is in line with the admission passage and
has cut off the supply of pressure fluid.
"
For the purpose of obtaining various lengths of stroke and weight
of blow the relative areas of the cylinder and piston are varied, as also
the cover of the piston, either separately or in combination one with
another.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Darlington in the Great Seal Patent Office
on the 14th November 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
DARLINGTON, of 2, Coleman Street Buildings, Moorgate Street, in the
City of London, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Fifteenth day of May, in the year of our
Lord One thousand eight hundred and seventy-four, in the thirty-
seventh year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said John Darlington, Her special license
that I, the said John Darlington, my executors, administrators, and
assigns, or such others as I, the said John Darlington, my exccutors,.
administrators, or assigns, should at any time agree with, and no,
J

page_text: In the modification of the single-acting engine the cylinder is formed
of a slightly larger diameter than the piston at the back end, and has also
a groove or recess formed near the middle of its length, which recess is
in connection with the exhaust portway.
The piston itself has also induction and exhaust passages formed in it,
which passages alternately communicate with the enlarged parts or
passages of the cylinder and admit the fluid pressure to and exhaust it
from the superior area of the piston.
In a modification of a double-acting engine the piston is made of
sufficient length to have two grooves or recesses formed in it which
communicate with two sets of passages in the body of the piston itself.
The said grooves at either end of the piston stroke come opposite two
portways in the cylinder, two induction portways and one exhaust port-
way, placing one end of the cylinder in communication with one pressure
portway by means of one set of passages and corresponding grooves in
the body of the piston, at the same time as the opposite end is opened to
the exhaust portway by means of the other set of passages and the
corresponding groove.
Instead of moving the piston in the several arrangements of ports
and passages the cylinder may be moved, and one end of the cylinder
fitted with a head suitable for delivering the required blow.
.
When it is required to turn the piston as in rock or coal-boring
apparatus, the end of the piston may be formed into a turbine, and
the induction passage or exhaust port fitted with turbine wings.
accordingly; or a ratchet wheel may be placed within the cylinder
with an oval and slightly twisted bar, the latter entering a suitable nut
set in the head of the piston, the ratchet wheel itself being detained in
one direction by a detent formed so as to drop into the teeth without the
use of a spring.
For the purpose of lightening the piston and augmenting the volume
of steam to the cylinder the piston may be made partly hollow, and for
working the pressure fluid at various rates of expansion a sliding block
or piston may be fitted in the end of the cylinder, or the piston itself
provided with a shifting ring, or made with a suitable "cover" or
length above the exhaust passage, over and above the depth of the
piston when its opposite end is in line with the admission passage and
has cut off the supply of pressure fluid.

page_text: For the purpose of obtaining various lengths of stroke and weights
of blow, the relative area of the cylinder, piston, and piston rod are
varied, as also the cover or lap of the piston, either separately or in com-
bination one with another.
. And in order that my said Invention may be fully understood, I shall
now proceed more particularly to describe the same, and for that
purpose shall refer to the several Figures on the annexed two Sheets of
Drawings, the same letters of reference indicating corresponding parts
in all the corresponding Figures.
Figure 1 (Sheet 1) of my Drawings is a sectional elevation of one of
my improved percussive engines applied to the stamping of ores and
minerals.
Figure 2 is a front elevation of a pair of such percussive engines and
a sectional front elevation of the stamping box.
The cylinder A is mounted on wrought iron or other suitable
bearers B, and is formed with an ordinary inlet port c through which
the motive fluid enters a long induction passage d with two portways e
and fand an outlet or exhaust port g. The body of the piston h is of
such a length that the induction port d and the exhaust port g are
thereby alternately uncovered, admitting the motive fluid from the
space j in front of the piston / to the space i behind the piston, where
acting on the full or larger area it forces the piston ḥ towards the front
of the cylinder A, the piston in its passage uncovering the exhaust
port and releasing the pressure from the back of the piston h, which
allows the constant pressure on the smaller area in front of the piston h
to effect the back stroke. By fixing the piston h and allowing the
cylinder to have a reciprocating movement a corresponding action
may be obtained.*
I
The rotation of the piston for rock-boring purposes is shewn on
Sheet 2, where Figure 3 is a sectional view of a piston formed with a
turbine top; Figure 4 is a plan view of the turbine top on the line x, x,
in Figure 3; and Figure 5, a plan view of a ratchet wheel and escape-
ment pawl. k is the turbine with its guide wings, and 7 is the exhaust
passage fitted with bucket curves.
-
The action is as follows:-When the quick curves k of the turbine 3
come opposite to the bucket curves 7 the steam contained within the

page_text: cylinder passes through the quick curves, and by impinging on the
bucket curves set in the exhaust passage, a slight rotatory movement is
imparted to the piston.
In Figure 5, m is a ratchet wheel; n, an escapement pawl; o, an
oval bar slightly twisted in its length. The ratchet wheel m and
escapement pawl n are fixed within the cylinder cover, whilst the
oval and slightly twisted bar o extends from the centre of the ratchet
wheel m into the piston. During the backward motion of the piston
the ratchet wheel m is detained by the escapement pawl n acting
without a spring, and the piston is turned by its motion along the
twisted bar o; but during the forward stroke the ratchet wheel m is frec
to move, and is turned in the opposite direction by the piston acting
through the twisted bar o.
Figure 6 represents the section of a percussive engine with the piston
and rod made partly hollow, and a sliding block or piston p fitted into
the rear end of the cylinder.
The piston cover or "lap.". q is also shown in Figures 1 and 6, being
that portion of the piston extending from the upper edge of the exhaust
portway to the top of the piston; p' is the hollow portion of the piston
and rod. By thus lightening the piston a higher velocity can be imparted
to it by a given pressure of steam than if it were of full weight, whilst
the hollow space p¹ within the piston and rod serves as a steam chamber
for modifying the main pressure of the steam as well as the intensity of
the blow. By depressing or raising the sliding block or piston p at the
rear end of the cylinder, the volume of steam to operate on the piston
can also be lessened or increased.
When it is requisite to increase the length of stroke it can be effected
either by lining up, renewing, or otherwise extending the piston, and so
lengthening the cover or "lap" q on the piston, or by lessening the
return area in proportion to the forward area, or by modifying one
with the other.
When intensity of blow is the principal object, then the cover or lap
of the piston may be lengthened so as to give the piston a longer stroke,
whilst the return or lesser area of the piston can be limited to an extent
just sufficient to carry the piston across the induction portway, when it
will be subject to the action of the pressure fluid.

page_text: Having now described and particularly ascertained the nature of my
said Invention and the manner in which the same is or may be used or
carried into effect, I would observe in conclusion that what I consider
to be novel and original, and therefore claim as the Invention secured
to me by the herein-before in part recited Letters Patent is,―
First. In percussive engines applied to rock boring, the turning
of the piston by means of an oval and slightly twisted bar in com-
bination with an escapement paul and ratchet wheel, substantially as
herein-before described and illustrated by my Drawings.
Secondly. The application and use of a sliding block or piston in the
rear end of the cylinder of percussive engines, and making the piston
and rod more or less hollow, substantially as and for the purpose herein.
before described and illustrated by my Drawings.
M
Thirdly. Varying the length of cover or "lap" of the pistons of rock
boring and percussive engines, substantially as and for the purpose
herein-before described and illustrated by my Drawings.
.
In witness whereof, I, the said John Darlington, have to this my
Specification set my hand and seal, this Fifth day of November,
One thousand eight hundred and seventy-four.