IMPROVEMENTS IN CUSHIONING THE PISTON AND WORKING THE VALVE OF DIRECT-ACTING STEAM ENGINES
Year: 1874

page_text: LETTERS PATENT to Martin Benson, of No. 9, Southampton Buildings,
London, for the Invention of " IMPROVEMENTS IN CUSHIONING THE
PISTON AND WORKING THE VALVE OF DIRECT-ACTING STEAM ENGINES."—A
communication from abroad by Ezra Cope and James Riley
Maxwell, of Hamilton, Ohio, United States of North America.
COMPLETE SPECIFICATION filed by the said Martin .Benson at
the Office of the Commissioners of Patents, with his Petition and
Declaration, on the 28th March 1874, pursuant to the 9th Section
of the Patent Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, MARTIN
BENSON, of No. 9, Southampton Buildings, London, send greeting:
WHEREAS I am in possession of an Invention for "IMPROVEMENTS
IN CUSHIONING THE PISTON AND WORKING THE VALVE OF DIRECT-ACTING STEAM
ENGINES," and have petitioned Her Majesty to grant unto me, my
executors, administrators, and assigns, Her Royal Letters Patent for the
same, and have made solemn Declaration that it has been communicated

page_text: to me from abroad by Ezra Cope and. James Riley Maxwell, of
Hamilton, Ohio, United States of North America.
NOW KNOW YE, that I, the said Martin Benson, do hereby declare
that the following Complete Specification, under my hand and seal
fully describes and ascertains the nature of the said Invention, and
in what manner the same is to be performed in and by the following
statement :-
My improvement relates to direct-acting steam engines for working
reciprocating pumps, and can be used for other purposes requiring a
reciprocating motion, and is supplemental to my Patent dated
September 15th 1868, No. 2831, for improvements in constructing,
arranging, and working steam pumping machinery, and consists in the
arrangement and structure of inlet and outlet steam ports and passages
for cushioning the piston in terminating its stroke at each end of the
cylinder, also in the structure and arrangement of cams or levers, and
rods for moving the steam valve by hand when first starting the engine
if required.
The piston of the engine is made sufficiently longer than its stroke in
order to cover steam ports and passages at all times leading into and out
of the centre of the cylinder shell, for admitting steam into and out of
the interior of the piston through suitable steam [ports and passages
made therein. The piston is provided with steam ports and passages
and a cylindrical chamber in its centre in which the main valve works,
for admitting steam to and from the ends of the main steam cylinder
through suitable steam ports for giving motion to the piston similar to
that described in my Patent dated September 15th 1868, herein-before
mentioned.
In order to give a fuller understanding of the said Invention reference
will be made to the accompanying Drawings herewith annexed, forming
part of this Specification by the letters and figures marked thereon.
Similar letters of reference marked on each Figure refer to corresponding
parts.
Fig. 1 is a longitudinal vertical section through the cylinder A,
piston B, valve C, and arrangement of parts for moving the valve when
first starting the engine.
Fig. 2 is a longitudinal horizontal section through the cylinder, piston.

page_text: piston, and valve, showing the inlet and outlet steam ports leading to
the interior of the piston, also a section of the parts for moving the
valve..
Fig. 4 is a separate view of the main piston showing the face or
working portion of it provided with the main and auxiliary steam ports
and channels.
Fig. 5 is a face view of the cam or lever employed for moving the
valve C by hand.
b, b, are two main exhaust ports and channels made in the under
side of the piston (see Fig. 4) for exhausting the steam from the ends of
the cylinder by means of the valve C, and made so that they will.
overrun their corresponding ports 6", 6", in the main cylinder shell,
owing to each port terminating some distance from the ends of the
piston as represented, and thereby prevent the remaining steam and
vapour escaping from the ends of the cylinder, which cushions the piston
as it terminates its stroke. The piston is supposed to be moving to the
left-hand end of the cylinder, and when it carries the channel port 6' in
the piston past its corresponding exhaust port in the cylinder shell it
cuts off communication from the end of the cylinder from which steam
is being exhausted, and thereby hems in the remaining steam and
vapour and effectually cushions the piston; in the mean time the exhaust
port or channel 6 is in position for communicating with and exhausting
the steam from the opposite end of the main cylinder by the changing of
the main valve C.
The channels or exhaust ports b, ', in the piston are reduced at
their opposite ends m, m, (see Fig. 4), so as to form mear slots or grooves,
or instead of grooves they may be made V shaped in order to allow a
certain amount of escape to prevent the piston at slow speeds from
balancing on the cushion, which would prevent the piston from moving
far enough to allow the supplementary exhaust ports f, f, to come in
communication with the exhaust port in the centre of the cylinder shell,
for exhausting the steam from the end of the valve chamber for moving
the valve C, and thereby stop the motion of the piston B. The ports or
3 channels b, ¹, can be made to cushion the piston at such parts of its
stroke as may be desired, and thereby at all times prevent the piston
from striking the cylinder ends,

page_text: If desired steam may be admitted for additional cushioning from
behind the advancing piston just as the exhaust is cut-off by means of
the ports g, g', in the piston, and ports and passages h, h¹, h¹¹, h¹¹, in the
cylinder shell. The ports 9 and g¹ can be so arranged so that the
further advance of the piston will carry them over and beyond the
ports h, h, and thereby cut off the admission of steam and retain it in
the end of the cylinder; in such cases care must be taken to adjust the
exhaust ports f, f¹, leading into the ends of the valve chamber to suit
the motion of the piston, so as to cause the valve C to move promptly
and at the right time; if it does not, the cushioned steam will exceed the
boiler pressure and stop the motion of the piston.
The valve C and its seat or face in the piston B have each four ports,
as more fully represented by Fig. 1. The outside ports c, c', in the
valve C are steam ports, and the inside ports d, d, are exhaust ports. In
the present position of the valve C in Fig. 1 these ports are showing the
steam exhausting from the left-hand end of the cylinder through the
ports a and d, over and beyond the port 6 into the port 6', while steam
is entering the right-hand end of the cylinder through the port c¹ in the
valve, and a¹ in the piston.
The following is a description of the working of the engine:-Steam is
admitted to the interior of the piston by the inlet steam passage S
through the cylinder shell, and has constant access to the interior of the
piston between its ends B, B, and to the piston valve C, and its ends
through the small ports e, e¹. It has also free access when the valve C
is in proper position to the main cylinder A through the ports c, c¹, in
the valve C, and a, a', in the piston, as fully represented in Fig. 1. In
the present position of the valve steam passes through the port c¹ and
passage a¹ into the right-hand end of the cylinder, and is exhausting
from the left-hand end, causing the piston B, B, to move to the left-hand
end of the cylinder, until the auxiliary port f¹ leading into the end of
the valve chamber communicates with the main exhaust port 6" in the
cylinder shell, which exhausts the steam from the right-hand end of the
valve chamber, and causes the valve C to move towards the end by
the pressure of steam acting on the opposite end; the valve is then in the
position to exhaust the steam from the right-hand end of the cylinder,
and admit steam to the left-hand end of the cylinder by means of the
port c, c', and d, d, in the valve, and a, a¹, in the piston, as before
described, and thereby a constant reciprocal motion of the piston is

page_text: produced. The valve C is moved on the negative principal, similar to
that described in my Patent dated 2rd December 1872, No. 3617, by
exhausting the steam from the ends of the valve chamber through the
exhaust ports f, f, which causes the steam that enters the valve
chamber from the interior of the valve through the small ports e, e¹, in
the end of the valve to expand in the opposite end of the valve chamber,
from which steam is being exhausted by one of the ports for f¹, as the
case may be, to suit the motion of the piston and thereby move the valve,
or if desired the ends of the valve chamber may be provided with both
inlet and exhaust steam ports for moving the valve on the positive
principal, similar to that before described in my Patent dated 15th
September 1868, herein-before mentioned.
The throttle valve J, Fig. 3, in the exhaust pipe or channel is for
regulating or equaliseing the motion of the main piston when the engine
is made to perform unequal duties; for instance, when the cylinder is
placed in a vertical position for working, the down stroke of the piston.
would move quicker than the up stroke, but by throttleing the exhaust
of the down stroke with the valve J it could be regulated to move at the
same speed as the up stroke, or in cases where the engine is made to
work two pumps of unequal dimentions one attached to each end of the
piston, the throttle valve J can be employed to throttle the exhaust from
the end of the cylinder having the least duty to perform, and thereby
regulate or equalise the motion of the piston, so it would move with the
same velocity in both directions.
The following is a description of the parts employed for moving the
main valve C by hand, either while the engine is in motion or when at
rest. D, Figs. 1, 3, and 5, is a long segment representing about one-
third of a wheel provided with teeth, and is operated by the sector E,
shaft G, and lever H, the sector E is provided with teeth and gear into
the segment D as fully represented by Fig. 3. The segment is as much
longer than the stroke of the piston B as the thickness of the sector E,
and necessary clearance may require to prevent the piston from striking
the sector. The teeth on the segment extend along its whole length and
it is swung on the pin D¹ in order to give it a free vibratory lateral
motion, the pin D¹ is supported by the piston ends B, B, and passes
through the bos of the segment D as represented in Figs. 1 and 3. The
cam-shaped surface i, i, is cast or otherwise attached to the segment D
below the pin D¹ at or near the centre of its length as represented by

page_text: Fig. 5, which fully shows the proper form of the cam or groove with
the present position of ports. When the lever or handle H is in a
vertical position, the cam i, i, is in its central position which allows the
main valve C free motion endwise. As the lever H is turned to the
right or to the left the cam i, ¹, is also turned and made to act on the
valve C for moving it through the medium of the pin F secured to
the top of the valve. The points of the cam are made so as not to stand
opposite each other for the purpose of moving the valve beyond its
centre each way sufficient to admit and exhaust steam from either end
of the cylinder by moving them to the right or to the left. This is of 1
great importance in some cases where it is desired to start the engine in
the least possible time; for instance, when used for fire engine purposes
it enables the opperator to work the water out of the cylinder and heat it
sooner, by admitting steam alternately in and out of each end of the
cylinder until the parts of the machine is warmed sufficient to commence ]
working.
As a rule if desired the engine can be made to work without using
the parts for moving the valve, as it has no tendency to stick, and
commonly is constructed so that the ports in the valve and piston have no
lead or lap, which makes it most impossible for the valve to stop at any 2
point of its movement to prevent steam from entering one end of the
cylinder and thereby move the piston.
Having described the nature of my Invention, and manner of working.
the same, I would have it understood that I do not confine myself to the
exact form and arrangement of exhaust steam ports and channels in
the piston and cylinder of the engine for cushioning the main piston, as
they may be varied in form and arrangement to suit the size of the
engine to which they are applied, and extent of cushioning required, nor
do I confine myself to the exact form and arrangement of parts for
moving the valve by hand in the piston when the piston is made a
longer than the stroke of the engine, as it is necessary to change them
to suit the size and position of the engine to which they are applied.
What I claim is,―
First. The exhaust ports or channels 6, 61, in the piston, and their
corresponding ports 6", 6", in the cylinder, or their equivalents for a
cutting-off the exhaust. steam communication from the ends of the
cylinder as the piston is terminating its stroke at each end of the

page_text: cylinder for cushioning the piston B, B, in the manner herein-before
described.
Second. The segment D, pin D¹, sector E, shaft G, cam i, i, and pin F,
or their equivalents for moving the valve C by hand in the piston B, B,
in the manner and for the purposes herein-before described.
In witness whereof, I, the said Martin Benson, have hereunto set
my hand and seal, this Twenty-eighth day of March, in the year
of our Lord One thousand eight hundred and seventy-four.