Year: 1888

page_text: Date of Application, 23rd June, 1888
Complete Specification Left, 23rd Mar., 1889
Complete Specification Accepted. 27th Apr. 1839
I WILLIAM FORD of 57 Duke Street Liverpool in the County of Lancaster
Engineer do hereby declare the nature of this invention to be as follows:-
My invention relates to pistons for steam and other fluid pressure motors, air and
gas compressors, pumps and such like machines, and consists in improved arrangements
for expanding the piston rings and keeping them tight in the cylinder by the pressure
of the steam or other fluid.
I make the piston in the ordinary manner with two rings of rectangular section
slit and turned to the diameter of the cylinder after being drawn together to close
the slit, so that the rings spring outwards. Inside these rings I place another ring as
broad as the two outer rings together and made in the same manner. By preference
I turn the inside of the rings excentrically to the outside so that they are thicker at
one side and place the thickest part of the inner ring against the thinnest part of the
outer rings. I screw or attach to one or to both ends or covers of the piston one
or more valves, which may be of any ordinary suitable kind arranged so as to open
inwards into the annular space between the piston rings and the boss of the piston,
and load these valves with springs or weights directly or through levers. When steam
or other fluid under pressure is admitted to the cylinder, these valves will be opened
by the pressure and steam or other fluid will enter the piston until the fluid pressure
upon the valve or valves inside the piston added to the pressure of the springs or
weights upon the valve or valves equals the pressure upon them from the outside or
in the cylinder. By this arrangement the pressure inside the piston, which acts upon
the rings and expands them, will be equal to the maximum pressure in the cylinder
less the pressure of the springs or weights upon the valve or valves, all pressures
being reduced to the unit of area and by adjusting the springs or weights the fluid
pressure expanding the rings can be regulated so as not to exceed the pressure

page_text: required in combination with the springing of the piston rings themselves for keeping
said rings tight, and thereby the friction of the piston can be reduced to the least
practicable amount. When the piston has once been filled with fluid of the pressure
herein before indicated, no further fluid enters the piston unless the pressure inside
the piston becomes reduced by leakages or otherwise, when a further quantity of
fluid will enter the piston again through the valve or valves. Ordinarily I use
only one valve on one end of the piston, but more valves may be used on one end or
on both ends.

page_text: Improvements in Pistons.
I, WILLIAM FORD, of 57, Duke Street, Liverpool, 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 :-
My invention relates to pistons for steam and other fluid pressure motors, air and
gas compressors, pumps and such like machines, and consists in improved arrangements
for expanding the piston rings and keeping them tight in the cylinder by the pressure
of the steam or other fluid.
I make the piston in the ordinary manner with two rings slit and turned to the
diameter of the cylinder after being drawn together to close the slit, so that the rings
spring outwards. Inside these rings I place another ring as broad as the two outer
rings together and made in the same manner. By preference I turn the inside of the
rings excentrically to the outside so that they are thicker at one side and place the
thickest part of the inner ring against the thinnest part of the outer rings. I'screw or
attach to one or to both ends or covers of the piston one or more valves, which may
be of any ordinary suitable kind arranged so as to open inwards into the annular
spaco between the piston rings and the boss of the piston, and load these valves with
springs or weights directly or through levers. When steam or other fluid under
pressure is admitted to the cylinder, these valves will be opened by the pressure and
steam or other fluid will enter the piston until the fluid pressure upon the valve or
valves inside the piston added to the pressure of the springs or weights upon the
valve or valves equals the pressure upon them from the outside or in the cylinder.
By this arrangement the pressure inside the piston, which acts upon the rings and
expands them, will be equal to the maximum pressure in the cylinder less the pressure
of the springs or weights upon the valve or valves, all pressures being reduced to the
unit of area, and by adjusting the springs or weights the fluid pressure expanding the
rings can be regulated so as not to exceed the pressure required in combination with
the springing of the piston rings themselves for keeping said rings tight and thereby
When the
the friction of the piston can be reduced to the least practicable amount.
piston has once been filled with fluid of the pressure hereinbefore indicated, no further
fluid enters the piston unless the pressure inside the piston becomes reduced by
leakages or otherwise, when a further quantity of fluid will enter the piston again
through the valve or valves. Ordinarily I use only one valve or one end of the piston,
but more valves may be used on one end or on both ends.
The drawings appended hereunto shows a piston made in accordance with my
invention, partly in section. The rings a a are shewn with tapering section, and the
expansion ring b with a double inclination to press the rings against the piston ends c
Into the end ca valve
and c¹, but the rings may be made in any other ordinary way.
seating d is fixed, with a valve e opening inwards, having wings f to guide it as usual.
The valves have
Into the cover c¹ a similar valve seating d¹ is fixed with a valve e¹.

page_text: stems g g cast to their tops, one of which is guided in the other. Between the two
valves e and e¹ a strong helical spring his placed, which keeps them closed. When
steam is admitted to either end of the cylinder in which the piston moves, one of the
valves is opened by the steam pressure and steam enters the piston until its pressure
inside the piston combined with the spring pressure equals the pressure in the cylinder.
By making the spring h of the required strength, the pressure inside the piston can
be limited as desired. For instance, if a pressure of 20 pounds to the square inch
upon the ring b combined with the elasticity of the rings a a and b sufficed for
keeping the piston tight; while the steam pressure in the cylinder were 80 pounds,
the spring h would be made of such strength that it exercises a pressure of 60 pounds
to the square inch upon the valves. On admission of steam to the cylinder, one of
the valves would open and let steam into the piston, and as soon as the pressure inside
the piston reaches 20 pounds, the valve would close. By regulating the pressure
of the spring, the pressure on the inside of the ring and consequently the pressure
of the rings a a on the cylinder can be regulated to the least pressure required
for keeping the piston tight in the cylinder and consequently all unnecessary excess of
friction can be avoided.
I do not confine myself to the kind of valve and method of loading the same shewn
on the drawing, but any suitable ordinarily used kind of valve or method of loading
the same may be applied, and one valve in one end of the piston, or several valves in
one or both piston ends may be used. I am aware that steam has been admitted
behind piston rings for expanding them previously to this my invention, but without
regulation of the pressure of such steam.
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,
In pistons for steam or other fluid pressure motors, air and gas compressors, pumps
and such like machines.
Firstly. The expansion of the piston rings by means of the fluid admitted behind
said rings at a reduced pressure through one or several loaded valves arranged in one
or both ends of the piston, substantially as herein described.
Secondly. The arrangement of one or several loaded valves opening inwards in one
or both ends of the piston, substantially as herein described and illustrated by the
drawing and for the purpose set forth.
Dated this 22nd day of March 1889.