IMPROVEMENTS IN PISTONS
Year: 1871

page_text: LETTERS PATENT to Paul Giffard, of Paris, Rue Pépinièrè, No. 12,
Civil Engineer, for the Invention of "IMPROVEMENTS IN PISTONS."
Sealed the 9th January 1872, and dated the 31st July 1871.
PROVISIONAL SPECIFICATION left by the said Paul Giffard at the
Office of the Commissioners of Patents, with his Petition, on the
31st July 1871.
I, Paul Giffard, of Paris, Rue Pépinièrè, No. 12, Civil Engineer,
do hereby declare the nature of the said Invention for "IMPROVEMENTS IN
PISTONS," to be as follows:-
My Invention consists in constructing pistons in the following
manner: The body of the piston is made smaller in diameter than
the cylinder in which it works; it is grooved on its circumference, and
in such groove is fitted loosely a flexible ring of india-rubber or other
suitable material, which ring may be made to act either simply as a

page_text: packing for producing a fluid or gas tight fit against the cylinder, or both
as a packing and as a valve for producing a suction or forcing action.
When employed simply as a packing the flexible ring is made of a
less thickness than the width of the groove in the piston, and a space
is left between the bottom of the groove and the inner circumference
of the ring, so that when the piston moves in one direction the ring
will by the counter pressure of the gas or fluid upon which the piston
acts be forced against the one edge or rim of the groove, thus allowing
the gas or fluid to have access past the other edge or rim of the groove
into the space between the bottom of the groove and the inner circum-
ference of the ring, whereby the latter will be pressed outwards against
the surface of the cylinder by the pressure of the gas or fluid. The
bottom of the groove is by preference made polygonal, while the ring
is circular, so as to give greater space between the two for the action
of the gas or fluid.
When the flexible ring is to act both as a packing and as a valve
the piston is, as before, made smaller in diameter than its cylinder, and
the one edge or rim of its groove is made of a less diameter than the
other, and holes are formed through the lesser rim so as to establish a
communication between the outside of the piston and the inside of the
groove. The flexible ring is, as before, of a less depth than the groove,
and a space also exists between the bottom of the groove and the inner
circumference of the ring, so that when by the one stroke of the piston
the ring is pressed against the lesser rim of the groove by the pressure
of the fluid or gas against which the piston acts, such fluid or gas will
find its way from the one side of the piston between the larger rim
and the ring into the space between the bottom of the groove and the
ring, whence it will escape through the before-mentioned holes to the
other side of the piston. On the return stroke of the piston the ring
will be pressed against the larger rim thereof, and the fluid or gas in
entering the groove will press the ring outwards against the cylinder
so as to form a fluid or gas tight packing, so that the fluid or gas that
before was caused to pass through the piston by the valve-like action
of the ring will now be forced out of the cylinder by the motion of the
piston.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Paul Giffard in the Great Seal Patent Office on
the 19th January 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, PAUL
GIFFARD, of Paris, Rue Pepinieré, No. 12, Civil Engineer, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Thirty-first day of July, in the year of
our Lord One thousand eight hundred and seventy-one, in the thirty-
fifth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Paul Giffard, Her special licence that I,
the said Paul Giffard, my executors, dministrators, and assigns, or
such others as I, the said Paul Giffard, my executors, administrators,
and assigns, should at any time agree with, and no others, from time
to time and at all times thereafter during the term therein expressed,
should and lawfully might make, use, exercise, and vend, within the
United Kingdom of Great Britain and Ireland, the Channel Islands,
and Isle of Man, an Invention for "IMPROVEMENTS IN PISTONS," upon the
condition (amongst others) that I, the said Paul Giffard, my executors
or administrators, by an instrument in writing under my, or their, or
one of their hands and seals, should particularly describe and ascertain
the nature of the said Invention, and in what manner the same was to
be performed, and cause the same to be filed in the Great Seal Patent
Office within six calendar months next and immediately after the date
of the said Letters Patent.
NOW KNOW YE, that I, the said Paul Giffard, do hereby declare
the nature of the said Invention, and in what manner the same is to
be performed, to be particularly described and ascertained in and by the
following statement thereof, reference being had to the accompanying
Sheet of Drawings, and to the figures and letters marked thereon, that
is to say :-
My Invention consists in constructing pistons in the following
manner-The body of the piston is made smaller in diameter than
the cylinder in which it works; it is grooved on its circumference, and
in such groove is fitted loosely a flexible ring of india-rubber or other
suitable material, which ring may be made to act either simply as a

page_text: packing for producing a fluid or gas tight fit against the cylinder, or both
as a packing and as a valve for producing a suction or forcing action.
When employed simply as a packing the flexible ring is made of a
less thickness than the width of the groove in the piston, and a space
is left between the bottom of the groove and the inner circumference
of the ring, so that when the piston moves in one direction the ring
will by the counter pressure of the gas or fluid upon which the piston
acts be forced against the one edge or rim of the groove, thus allowing
the gas or fluid to have access past the other edge or rim of the groove
into the space between the bottom of the groove and the inner circum-
ference of the ring, whereby the latter will be pressed outwards against
the surface of the cylinder by the pressure of the gas or fluid. The
bottom of the groove is by preference made polygonal, while the ring
is circular, so as to give greater space between the two for the action
of the gas or fluid.
When the flexible ring is to act both as a packing and as a valve
the piston is, as before, made smaller in diameter than its cylinder, and
the one edge or rim of its groove is made of a less diameter than the
other, and holes are formed through the lesser rim so as to establish a
communication between the outside of the piston and the inside of the
groove. The flexible ring is, as before, of a less depth than the groove,
and a space also exists between the bottom of the groove and the inner
circumference of the ring, so that when by the one stroke of the piston
the ring is pressed against the lesser rim of the groove by the pressure
of the fluid or gas against which the piston acts, such fluid or gas will
find its way from the one side of the piston between the larger rim
and the ring into the space between the bottom of the groove and the
ring, whence it will escape through the before-mentioned holes to the
other side of the piston. On the return stroke of the piston the ring
will be pressed against the larger rim thereof, and the fluid or gas in
entering the groove will press the ring outwards against the cylinder
50 as to form a fluid or gas tight packing, so that the fluid or gas that
before was caused to pass through the piston by the valve-like action
of the ring will now be forced out of the cylinder by the motion of the
piston.
DRAWINGS

page_text: and c made somewhat smaller in diameter than the cylinder in which
the piston works with a rounded groove for the reception of a packing
ring b. This ring is made of flexible material, such as caoutchouc,
leather, or woven fabric, and it may be strengthened by rings of steel
or other flexible metal worked into its body. It is made of such
dimensions as to fit at its outer circumference the cylinder in which
the piston works to have less width than the groove in the piston, and
to leave a space between its inner circumference and the bottom of
the groove.
At the one side of the Figure this ring is represented in
the position which it assumes when the piston is moving upwards (as
indicated by the arrow) so as to compress fluid above it. The pressure
of the fluid acting in the space left between the groove and the ring
forces the ring outwards so as to make it fit the cylinder, and downwards
against the lower flange of the piston so as to prevent passage of fluid
from the groove to the under side of the piston. The other side of
the Figure represents the position of the ring b when the piston is
descending as indicated by the arrow, the ring being in this case pressed
against the upper flange of the piston.
The bottom of the piston groove may be made polygonal as repre-
sented in the sectional plan Fig. 13, and in the elevation Fig. 12, in
which Figure the ring 6 is shewn in section. Such polygonal form of
groove gives greater space between the packing ring 6 and the hollow
of the piston for the access of fluid to press on the ring.
For pistons of large dimensions it is advantageous to strengthen the
flexible ring by a band of steel or other elastic metal. Fig. 5 repre-
sents a plan partly in section of such a strengthened ring; Fig. 6
represents a transverse section of the same; and Fig. 7 represents a
plan, and Fig. 8 an elevation of the metallic ring employed. The
metallic ring p is split as at q, and the flexible ring 6 is split obliquely
as at n. The ring 6 is formed with an internal groove, into which the
ring p is sprung in such a position that the points of division of the
two rings, namely q and n, do not coincide.
Fig. 15 illustrates diagrammatically the application of my Invention
to the purpose of packing for a piston rod or pump rod. a is the
main working cylinder fitted with its piston c, and 6 is a small cylinder
fixed on the cover of the main cylinder and communicating with it.
A small piston d is fixed on the piston rod and works in the small

page_text: cylinder b. The piston d being furnished with an elastic packing ring
such as I have described above, provides against leakage from the main
cylinder round the piston rod.
Figures 1, 2, 3, 4, 9, 10, and 11 shew the application of a flexible
ring such as I have described to the combined purpose of acting as a
valve as well as packing. Fig. 1 represents a piston in elevation with
a packing ring in section. Fig. 3 represents a half section of the
piston while ascending; and Fig. 4 represents it when descending, as
indicated respectively by the arrows. In these Figures the packing
ring is intended to act as a valve opening during the ascent of the 1
piston and closing during its descent; Figs. 9, 10, 11, are corre-
sponding views shewing the arrangement of parts when the packing
ring has to act as a valve opening during the descent of the piston
and closing during its ascent; Fig. 2 is a plan of the under side of
the piston shewn in Figure 1, and of the upper side of the piston 1
shewn in Fig. 9; in either case there are numerous holes o, which
may be either round holes or elongated slots communicating between
the space under the piston in Fig. 1, and between the space over the
piston in Fig. 9 and the interior of the groove in the piston. It
will be seen in Figs. 3 and 11 that the fluid which the piston tends 2
to compress by its movement in the one direction finds passage past
the flange of the piston a and the interior of the packing ring b
through the holes o. In Figs. 4 and 11 the pressure of the fluid
compressed by the movement of the piston communicated through the
holes o to the space within the ring 6 forces the ring outwards, so as 2
to make it to fit closely to the cylinder in which it works, and also forces
it against the flange a so as to prevent leakage.
Having thus described the nature of my Invention, and the manner
in which it is to be performed, I claim,-
First. The use of a flexible ring such as I have described for 3
the packing of pistons, the pressure of the fluid which acts on the
piston or on which the piston acts being utilized for expanding the
packing ring so as to make it fit the cylinder, substantially as herein
described.
Second. The use of a flexible packing ring and small piston in lieu 3

page_text: Third. The use of a flexible ring for the combined purpose of packing
and acting as a valve, substantially as herein described in reference to
Figs. 1, 2, 3, 4, 9, 10, and 11.
In witness whereof, I, the said Paul Giffard, have hereunto set
my hand and seal, this Fifth day of January, in the year of our
Lord One thousand eight hundred and seventy-two.
Witness,
CHARLES ARMENGAUD,
Civil Engineer,
23, Boulevard de Strasbourg,
à Paris.
PAUL GIFFARD. (L.S.)