Improvements in Motors for Tools or other like Reciprocating Mechanism.
Year: 1899

page_text: Date of Application, 17th Nov., 1899-Accepted, 24th Feb., 1900
COMPLETE SPECIFICATION.
Improvements in Motors for Tools or other like Reciprocating
Mechanism.
I, CHESTER BIDWELL ALBREE, of the City of Allegheny, in the County, of
Allegheny, and State of Pennsylvania, United States of America, residing at
187, Western Avenue, in said City of Allegheny, Mechanical 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, reference being had to the accompanying drawings:
My invention relates to the class of pneumatic tools, rock drills, and other
mechanism of the reciprocatory type, and is designed to provide simple means
for permitting variable stroke of the reciprocating part, so that the piston will
be reversed automatically even when it is stopped before the limit of its stroke.
The facility which my apparatus possesses in this regard is of very great im-
portance in the work to which such tools are ordinarily put.
Fig. 1 of the accompanying drawings, shows in vertical longitudinal section,
a motor constructed in accordance with my invention and adapted to be operated
with compressed air. Fig. 2 is a like view showing the parts in the position
which they occupy when the piston is at the end of its back stroke. Fig. 3 is
a view illustrating a modification. Fig. 4 is a vertical sectional view showing
the application of my invention to a compound motor: and Fig. 5 is a like view
showing that modification with the piston at the other end of its stroke.
In Fig. 1, 2 represents the cylinder having a cylinder head 3, and a piston 4,.
of two diameters 4, 4', which at its end has a socket T designed to receive the
tool or other instrument which it is used for operating. 5 is the inlet port
connected with a source of motive fluid, for example, compressed air. The
piston has a hollow passage 6 extending through it, preferably cylindrical in
form, and in that passage is a valve 7 which fits neatly therein, but can slide
back and forth as hereinafter explained. 8, 8 are exhaust ports leading from
the hollow piston, and 9, 9, are ports leading through the hollow piston, aš
shown. The valve 7, is formed with openings constituting ports 10 adapted to
register with the exhaust ports 8 when the valve is in the position shown in
Fig. 1 and with ports 11 adapted to register with the ports 9 when the valve
is in its other position shown in Fig. 2. 12 is a stop at the end of the hollow
passage of the piston, adapted to limit the back motion of the sliding valve.
When the
The operation is as follows: The parts being in the position shown in Fig. 1
motive fluid is admitted through the port 5, and entering the cylinder at the
sinaller diameter of the piston, forces the piston back to the rear end of the
cylinder, the air which is back of the piston being displaced through the
passage 6, hollow valve 7 and exhaust port S to the atmosphere.
piston reaches the end of its backstroke and is stopped by engagement with the
head 3, the valve 7 is caused by its inertia to move back into the position shown
in Fig. 2, thus closing the exhaust ports 8, and putting the ports 9 into com-
munication with the interior of the hollow valve by way of the ports 11 which
then register therewith. Thereupon, the air passes through the ports 9, 11,

page_text: valve 7 and passage 6 to the cylinder back of the piston, thus tending to
equalize the pressure therein with the pressure at the other end of the piston,
and by reason of the differential area, the piston is forced forward. When it
reaches the end of its outstroke, or if for any reason, as is very common in tools
of this class, its motion should be checked by coming in contact with some
obstacle before the end of its normal outstroke is reached, the valve 7 is caused
by its inertia to move forward into the position shown in Fig. 1 and thereupon
the rear end of the cylinder is cut off from the inlet and put into communication
with the exhaust, and the compressed air acting on the differential area of the
piston, forces it back, the cycle of operation being thus continued. The
automatic character of the work and the certainty with which the motor will
reverse, although checked short of the full limit of its outstroke, renders the
apparatus perfectly adapted to varied uses of the character above mentioned.
In Fig. 3 I show a modification of my invention in which the smaller diameter 4¹
of the piston is enclosed by a portion of the cylinder, and the exhaust, instead
of taking place directly from the hollow piston to the atmosphere, passes into a
space or recess 13 formed on the interior surface of the cylinder and communi-
cating with the exhaust ports 14.
The modification shown in Figs. 4 and 5 is designed to illustrate the applica-
tion of my invention to a compound motor wherein the motive fluid acts at
high pressure to move the piston in one direction and then expansively at a
lower pressure to move it in the opposite direction.
In these Figs. 4 and 5, A represents the cylinder, having two portions A, A¹
of different diameter, and B is the inlet port opening into the larger portion A
of the cylinder. D is the exhaust port communicating with an annular space C
in the smaller diameter of the cylinder. The piston E has two portions E
and E of different diameters, fitting respectively within the portions A, A¹
of the cylinder, and around the larger portion E is an annular recess of sufficient
length to constitute a port, which is always in communication with the inlet
port B in every position of the stroke of the piston. It will be understood that
the shape of the ports B and F may be reversed, the port B being elongated
and the port F being a single opening, and the same is true of the relations
between the ports and L hereinafter described. G is a passage which is
formed lengthwise through the piston, having ports H communicating with the
annular port F, and ports L communicating with the annular ports C adapted
by reason of the length of the ports C to be in communication therewith at every
portion of the stroke of the piston. Ports J also lead from the passage G.
to the outer surface of the piston, at or near the shoulder K at the junction of
the large and small diameters of the piston. The passage G is preferably
cylindrical and it contains a hollow sliding inertia valve M which fits neatly
therein, but is free to slide back and forth. It has an external annular recess N,
constituting a port of sufficient length to register with and connect the ports H
and J when the valve is at the outer end of the passage G as shown in Fig. 4.
It has also a port O leading from the interior to the exterior of the valve,
and adapted to register with the ports J, when the valve is at the inner end
of the passage G, as illustrated in Fig. 5. The valve has ports P leading from
its interior to its exterior surface, and adapted to register with ports L when
the valve is at the outer end of the passage G as shown in Fig. 4.
The valve has also an exterior annular space Q so situate that it does not
register with any two of the ports L, J, or H at any position of the valve.
Therefore it does not serve as a port, but its purpose is to contain coiled
springs S. S1, the adjacent ends of which bear against. a ring R, which is fixed
to the interior of the passage G of the piston. The other end of the springs
bear against the valve at the ends of the annular space Q, and these springs are
so related to each other in strength, that normally they hold the valve in the
position shown in Fig. 4, but they are sufficiently flexible to allow the valve
to be moved by inertia to the other end of its stroke, in the manner explained

page_text: below. The piston has a socket or holder T adapted to the tool which is intended
to be used with it, and the cylinder has a suitable head V. At the end of.
the
passage G is a stop U adapted to limit the motion of the valve, and between
the cylinder head and the piston is a spring W, which is adapted to return the
piston automatically to the outer end of the stroke when the cylinder is dis-
connected from power, in order to put the parts in position. for starting, as
explained below.
The operation is as follows:-The parts being in the position shown in Fig. 4
io start the motor, compressed air is admitted through the port B, and thence
passes through the passage F, and ports H, passage N, and ports J to the
shoulder of differential area K on the piston, and forces the piston to the rear
end of the cylinder, the air contained in the rear portion of the cylinder being
displaced through the passage G, hollow valve M, ports P and L and passage C
to the exhaust port. When the piston strikes the rear end of the cylinder, its
motion is checked thereby, and the valve M, by reason of its inertia moves back
in the passage G until it is stopped by the stop U. The parts are then in the
position shown in Fig. 5 in which the inlet ports B and H are cut off from com-
munication with the working space of the cylinder and the space A² of the
cylinder at the shoulder K is put into communication with the rear of the
cylinder by way of the ports J, O and hollow valve passage M; the exhaust
ports being cut off from communication with the interior of the valve by the
disconnection of the ports L and P. Thereupon the air under pressure which is
contained in the space A2 flows to the rear end of the piston, and by reason of
its expansion, forces the piston outward, the air pressure per square inch decreas-
ing, as the motion of the piston continues and as the volume of the space in
which the motive fluid can expand increases. When the forward motion of
the piston is checked either by striking the end of the cylinder, or by the
striking of the tool against some object before the end of the normal stroke
is reached, the valve M continues to move by reason of its inertia until it
reaches the end of the passage G whereupon the valve is brought again into
position shown in Fig. 4, another supply of motive fluid is admitted from the
inlet B into the space A2, and any motive fluid remaining under pressure at
the back end of the piston exhausts through the ports P, L, and D, the motion
of the piston being thus reversed and the operation repeated, as above described.
In order to insure the starting of the piston, it is necessary that the passage N
should be in register with the ports J and H and also that the piston should be
at the outer end of its stroke. This is not always the position of the parts when
the motive fluid is cut off, and if the apparatus should come to rest, with the
piston at the rear end of its stroke it must be moved to the other end in order
to make it possible to start the apparatus. Great convenience is effected by
doing this automatically.
The necessary automatic motion of the valve to its outer position, is effected
by the springs S, SI, which may be either in tension or compression, and which,
as above explained normally hold the valve in the position of Fig. 4. The
spring W when the motive fluid is turned off, presses the piston automatically to
the outer end of its stroke, so that no matter at what portion of the stroke the
piston may be stopped it will immediately assume the position required for
starting. When the cylinder is vertical, or nearly so, with the piston extending
downwardly, is spring is not necessary, for the automatic return of the piston
will be effected by gravity.
The arrangement of the ports and passages, shown in Figs. 4 and 5 may be
varied or more than one inertia valve may be employed without departure from
the scope of my invention, an essential feature of which is the combination with
the other parts recited in the claims, of an inertia valve tubular in form and
therefore balanced in its action, said tubular valve controlling a port affording
communication between the spaces at the smaller and larger piston areas res-
pectively, and controlling also a separate exhaust port. For example, the parts
'

page_text: may be arranged so that the motive fluid will act at high pressure to move the
piston outwardly, and will perform the backward stroke by expansion.
The springs controlling the valve M may be placed inside of the valve, or at
its ends, or may be otherwise arranged to perform the function above explained.
My invention may be modified in other respects which will be suggested to
those skilled in the art by the foregoing description.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is: --
1. A motor having a piston with differential areas, a tubular valve carried by
the piston and adapted to be moved by inertia when the motion of the piston is
checked, a port affording communication between the spaces at the smaller and
larger piston areas, said port being controlled by the tubular valve and a separate
exhaust port also controlled by said valve, substantially as described.
2. A motor having a piston with differential areas, a tubular valve carried in
a cavity therein and adapted to move from one end to the other of the cavity
by inertia when the motion of the piston is checked, a port or. ports in the
body of the piston leading into the valve cavity and communicating thereby
with the portion of the cylinder adjacent to the larger piston area, said inertia
valve having a port adapted to register with said ports and to open and close
the same alternately to control the exhaust of the motive fluid from the larger
piston area chamber, substantially as described.
Dated this Sixteenth day of November 1899.
W. B. JOHNSON,
4, Clayton Square, Liverpool, Agent.