Improvements in Pneumatic Percussion Tools.
Year: 1889

page_text: Date of Application, 23rd July, 1889
Complete Specification Left, 22nd Apr., 1890--Accepted, 28th June, 1890
PROVISIONAL
SPECIFICATION.
Improvements in Pneumatic Percussion Tools.
We, THOMAS THORP of Whitefield near Manchester in the County of Lancaster
Architect and Engineer, and WILLIAM JOHN CROSSLEY of Openshaw near Man-
chester in the County of Lancaster, Engineer, do hereby declare the nature of this
invention to be as follows:-
Our invention relates to pneumatic percussion tools of the kind described in the
Specifications No. 13,687 of 1884, No. 7685 of 1886 and No. 16,077 of 1887.
In these tools a piston having within it a transverse slide valve, is moved rapidly
to and fro by compressed air or other fluid under pressure alternately admitted to and
discharged from the ends of the cylinder in which the piston works, through ports
and passages governed by the slide valve which is itself moved to and fro transversely
by the fluid pressure as the piston approaches each end of its stroke. The piston, at
each forward stroke, strikes the end of a tool holder, which, during each back stroke of
the piston is retracted by a spring, and the chisel, punch or other tool held in the
holder is thus caused to make short but rapidly repeated strokes against the stone,
metal or other material to which the tool is applied.
According to one of our present improvements, instead of making the piston strike
against the tool holder with the full area of its face we make a head, of considerably
smaller diameter than the piston itself, project from the end of the piston into the bore
in which the tool holder, which is of corresponding diameter, moves to and fro. The
steel of which this projecting head consists, owing to its comparatively small size, can
be hardened more easily and completely than the body of the piston which is of con-
siderably larger sectional area, and the part subjected to the blows is thus rendered
more durable and less liable to deformation. Moreover, a considerable economy of
the working fluid is thus obtained, because the fluid which effects the back stroke of
the piston has to fill only the annular space around the projecting piston head.
According to another improvement, instead of fixing the handle rigidly to the
cylinder, we fit it to slide in a socket in which there a helical spring pressing the
handle outwards against a transverse stop pin.
This spring deadens the recoil of the apparatus, and relieves the hand and arm of
the operator from the shocks to which they are subjected when the handle is rigidly
fixed to the cylinder. The handle, thus arranged to slide, and subject to the action of
the spring, has its stem formed as a piston valve or formed as a slide valve with a
passage through its stem, so arranged that when the handle is pushed in against the
spring, so as to press the tool against the work on which it operates, there is a clear
passage for working fluid to pass to the cylinder ports or for the discharge fluid to
pass from the cylinder ports, keeping the tool at work; but when the handle is
relieved from pressure, the spring pushing its stem outwards, closes the passage, and
the tool thereupon ceases to work.
Instead of making this piston or slide valve as part of the stem of the handle, it
may be a separate piston or slide valve urged by a spring to close the passage unless
when it is pressed by hand in opposition to the spring so as to open the passage, and
thus the tool is kept working only while the valve stein is pressed.
Tlated this 22nd day of T.... 1000
ABEL & IMRAY,
Agents for the Applicants.

page_text: Improvements in Pneumatic Percussion Toois.
We, THOMAS THORP of Whitefield near Manchester in the County of Lancaster,
Architect and Engineer, and WILLIAM JOHN CROSSLEY of Openshaw near Manchester
in the County of Lancaster, 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 :-
Our invention relates to pneumatic percussion tools of the kind described in the
Specifications No 13687 of 1881 No. 7685 of 1886 and No. 16077 of 1887.
In these tools a piston having within it a transverse slide valve, is moved rapidly
to and fro by compressed air or other fluid under pressure alternately admitted to and
discharged from the ends of the cylinder in which the piston works, through ports and
passages governed by the slide valve which is itself moved to and fro transversely by
the fluid pressure as the piston approaches each end of its stroke. The piston, at
each forward stroke, strikes the end of a tool holder, which, during each back stroke
of the piston is retracted by a spring, and the chisel, punch or other tool held in the
holder is thus caused to make short but rapidly repeated strokes against the stone,
metal or other material to which the tool is applied.
According to one of our present improvements, instead of making the piston strike
against the tool holder with the full area of its face we make a head of considerably
smaller diameter than the piston itself project from the end of the piston into the
bore in which the tool holder, which is of corresponding diameter moves to and fro.
The steel of which this projecting head consists, owing to its comparatively small
size, can be hardened more easily and completely than the body of the piston which
is of considerably larger sectional area, and the part subjected to the blows is thus
rendered more durable and less liable to deformation. Moreover a considerable
economy of the working fluid is thus obtained, because the fluid which effects the
back stroke of the piston has to fill only the annular space around the projecting
piston head. According to another improvement, instead of fixing the handle rigidly
to the cylinder, we fit it to slide in a socket in which there is a helical spring pressing
the handle outwards against a transverse stop pin. This spring deadens the recoil of the
apparatus, and relieves the hand and arm of the operator from the shocks to which
they are subjected when the handle is rigidly fixed to the cylinder. The handle, thus
arranged to slide and subject to the action of the spring, has its stem formed as a
piston valve or formed as a slide valve with a passage through its stem, so arranged
that when the handle is pushed in against the spring so as to press the tool against
the work on which it operates, there is a clear passage for working fluid to pass to
the cylinder ports and for the discharge fluid to pass from the cylinder ports, keeping
the tool at work; but when the handle is relieved from pressure, the spring pushing
its stem outwards closes this passage, and the tool thereupon ceases to work.
Instead of making this piston or slide valve as part of the stem of the handle,
it, may be a sepurate piston or slide valve urged by a spring to close the passage
unless when it is pressed by hand in opposition to the spring so as to open the
passage, and thus the tool is kept working only while the valve stem is pressed.
Figs. 1 and 2 of the accompanying drawings are longitudinal sections on planes at
right angles to one another of a pneumatic percussion tool with our improvements
applied thereto. Fig. 3 is a transverse section through the slide valve." A is the
outer casing and B the cylinder having grooves and ports to form air passages as
described in the previous Specifications above referred to. The piston P, within
which works the transverse slide valve S, is made of smaller diameter in its front
part p which strikes the stem T of the tool.
Owing to the reduced diameter of the steel part p it can be better hardened, and
the fluid required to effect the back stroke of the piston is only that necessary to
fill the annular space around p.
The hinder part of the casing A is so shaped as to

page_text: form a handle H which can be held by the fingers while the thumb is pressed
against a projecting knob K. This knob has attached to it a piston slide valve k,
which, in the position shewn in Fig. 2 (to which position it is urged by a spring
against a stop pin) closes the outlet passage O for the discharge of the working
fluid which has performed work in the cylinder, and consequently stops the action
of the apparatus.
But when the knob K is pressed inwards by the thumb of the
operator, the passage O is opened and, as fluid under pressure is supplied to the
inlet I, the piston is caused to reciprocate giving a succession of rapid strokes to
the stem T of the tool. The spring which urges the knob K outward sustains the
recoil which occurs when the piston makes its forward stroke and so relieves the
operator's hand from the successive shocks.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed we declare that what we
claim in respect of pneumatic percussion tools of the kind described in the
Specifications No. 13687 of 1884 No. 7685 of 1886 and No. 16077 of 1877, is
1. Making the striking end p of the piston of smaller diameter than the body P of
the piston, substantially as and for the purpose set forth.
2. In combination with the handle and outlet passage for discharge of the working
fluid, a spring valve arranged and operating substantially as described.
Dated this 21st day of April 1890.
ABEL & IMRAY,
Agents for the Applicants.