Improvements in Pneumatic and like Impact Tools.
Year: 1896

page_text: Date of Application, 17th Dec., 1896-Accepted, 20th Mar., 1897
COMPLETE SPECIFICATION.
Improvements in Pneumatic and like Impact Tools.
1 JOHN FRANKLIN CLEMENT of 2147 Bainbridge Street, in the City and
County of Philadelphia, State of Pennsylvania, one of the United States of
America, Doctor of Dental Surgery, 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 impact tools of the valveless class and has for one of its
objects to prevent side pressure upon the reciprocating piston or hammer, a
further object being to arrest the reciprocation of the hammer except when the
tool is at work, a further object being to facilitate the handling of the tool by the
workman, and a still further object being to adapt the tool for use with different
kinds of chisels or cutting tools.
These objects I attain in the manner hereinafter set forth, reference being had
to the accompanying drawings, in which,
Figure 1 is a longitudinal section of an impact tool constructed in accordance
with my
invention.
Figure 2 is a similar view showing the piston or hammer in a different
position.
Figure 3 is a transverse section on the line 3-3, Figure 1; and
Figure 4 is a view of a special form of hammer constituting part of my
invention.
In Figures 1, 2, and 3, A represents the cylinder of the tool which has at the
rear end a cap B firmly secured thereto by screwing it into the end of the
cylinder, a spring plug a carried by the cap and adapted to an opening in
the cylinder serving to prevent the unscrewing of the said cap until the said
plug has been first pushed inward so as to be free from engagement with the
cylinder.
The cap is bored out centrally to receive the enlarged forward end of the
stem 6 of a handle F, the said stem being seated upon a block or washer b¹ of
rubber or other elastic material placed at the inner end of the opening in the cap,
which block is slightly compressed by the stem of the handle, the latter being
retained in longitudinal position to insure such compression by means of an annular
washer 62 of elastic material bearing upon the shoulder formed by the enlargement
of the stem 6 and retained in position by an annular retainer Ď screwed into the
outer end of the cap B.
By this means the handle F is connected to the cylinder A so as to prevent its
movement in a longitudinal direction, but yet free to turn in the cylinder to suit
the convenience of the workman using the tool, the elastic cushions preventing any
shock or jar from being transmitted to the handle.
Snugly fitting in the bore of the cylinder is the reciprocating piston or hammer G
which has extending transversely through it an opening f which is always in
communication with an inlet port i in one side of the cylinder, this inlet
port communicating in any suitable manner with a supply of motive fluid under
pressure.
In the present instance the tool is intended for used with compressed air and
the inlet port i is in communication with a nozzle to which the air conveyor
pipe is directly applied, but any other available means of conveying the motive
fluid to the inlet port i may be adopted without departing from my invention.

page_text: In one side of the cylinder opposite that having the inlet port i are two double-
ended conveyor ports m and n, the rear end of the rear port m communicating
with the rear end of the cylinder and the forward end of the forward port n
communicating with the forward end of said cylinder. In the cylinder are also
formed two exhaust ports a and t, the port a serving to permit of the escape of
motive fluid from the rear end of the cylinder, and the port t providing for the
escape of motive fluid from the forward end of the cylinder, these ports, by
preference, being independent of each other and each consisting of inner and outer
radial portions connected by a longitudinal passage, so that while they provide for
the free escape of motive fluid from the cylinder they will prevent the access of
sand, metal chips, or other foreign matters into the cylinder.
The rear exhaust port is preferably of less area than the forward exhaust port so
as to provide for a freer escape of motive fluid from the front end of the cylinder
than from the rear end of the same.
The piston or hammer G has a forwardly projecting stem G which is guided in
the forward end of the cylinder and acts upon the inner end of the stem or
shank H of the chisel or other tool which is being used, the latter being
guided in an opening at the forward end of the cylinder to which it fits with
reasonable snugness.
The stem G when projected, enters a chamber d which is of slightly greater
diameter than the opening in which the said stem is guided, and has a lateral vent d'
so as to prevent the possibility of any cushioning of the blow by the compression
of air in advance of the hammer stem.
In the lower portion of the piston G is formed a right-angled opening w, one
portion of which extends to the forward end of the piston, while the other
portion extends to one side of the piston in line laterally with the lower exhaust
port t.
The operation of the tool is as follows:-
When the parts are in the position shown in Figure 2, the piston G is at the
rear end of its stroke, the port t is uncovered so as to permit the free escape of
motive fluid from the forward end of the cylinder, and the forward end of the port "n
is in communication with the transverse passage f of the piston so that motive
fluid flows freely from the inlet port i through the said passage and thence through
the port m to the rear end of the cylinder in order to drive the pistou forward.
After the projecting stem G¹ of the piston has delivered its blow upon the inner
end of the tool stem H, the parts are in the position shewn in Figure 1, the exhaust
port s being now open so as to permit of the escape of motive Huid from the rear
end of the cylinder and the forward port being in communication with the
transverse passage f of the piston so that motive fluid is directed to the forward end
of the cylinder in order to drive the piston rearward therein, this rearward
movement continuing until the parts again assume the position shown in Figure 2
in readiness for a repetition of the before described operations.
When the cutting tool is not being used or is not pressed firmly against the work,
the piston or hammer G will, on its forward movement, meet with no resistance, or
less than the normal amount of resistance from the tool, and hence will pass forward
beyond its normal point, thus opening communication between the passage in the
piston and the exhaust port t. The air which had entered the forward end of the
cylinder before the piston completed its excessive forward stroke, escapes therefrom
through the passage w and exhaust port t so that after the port i is closed by the
forward movement of the pistou there is no pressure in the forward end of the
cylinder to drive the said piston rearward, hence the parts will remain inoperative
until the tool is again pressed upon the work with sufficient force to move the piston
backward to such an extent as to again open the inlet port i.
In the construction shown in Figure 4 the piston G'is provided with a detachable
stem G which is intended to be of such length that its forward end will project
beyond the cylinder so that it can be adapted to a socket at the end of the tool
stem as shown by dotted lines, the forward end of the stem Gaiso, by preference,

page_text: having a socket formed in it, so that it can be applied to an ordinary tool stem as
well, if desired.
By forming a passage directly through the piston from one side to the other for
the conveyance of motive fluid from the inlet port to the conveyor ports of the
cylinder I avoid side pressure which invariably results when the passage is in the
form of an annular groove in the piston and which is due to the impingement of
the motive fluid upon the central or reduced portion of the piston. I therefore
reduce the friction upon the piston and facilitate the reciprocation of the same and
at the same time prevent wear of either piston or cylinder due to the lateral
pressure upon the said piston.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. The combination in an impact tool, of a cylinder having an inlet port, and
conveyor ports, one of the latter communicating with one end of the cylinder and
the other with the opposite end of the same, a piston reciprocating in the said
cylinder and having an opening transversely through it which serves to convey the
motive fluid from-the-inlet port to the conveyor ports alternately as the piston is
reciprocated, whereby side pressure upon the piston is prevented, substantially as
hereinbefore described.
2. The combination in an impact tool, of a cylinder having an inlet port, and
conveyor ports, one of the latter communicating with one end of the cylinder, and
the other with the opposite end of the said cylinder, and exhaust ports for the
opposite ends of the cylinder, a piston reciprocating in the said cylinder and serving
by its movements to direct motive fluid first to one end of the cylinder, and then to
the other end of the same, and an escape passage formed in the said piston serving
to open communication between the forward end of the cylinder and the forward
exhaust port, on excessive forward movement of the piston in the cylinder,
substantially as herein before described.
3. The combination in an impact tool, of a cylinder, a piston reciprocating
therein, and a stem detachable from the said piston, and projecting forwardly
beyond the cylinder, the said stem being constructed at its forward end for the
reception of a tool stem, substantially as hereinbefore described.
4. The combination of the cylinder, with the handle confined longitudinally to
the cylinder, but free to turn independently thereof, substantially as hereinbefore
described.
5. The combination of the cylinder, with the handle having an elastic longitudinal
connection with the cylinder but free to turn in respect to the cylinder, substantially
as hereinbefore described.
6. The combination of the cylinder, with the handle having a stem with enlarged
end, elastic blocks or washers engaging the forward and rear portions of said
enlargement of the stem, and a confining ring for said rear washer, substantially as
hereinbefore described.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.