CERTAIN IMPROVEMENTS IN METALLIC PISTONS
Year: 1858

page_text: LETTERS PATENT to Joseph Smethurst, of the firm of Messieurs Martin
and Smethurst, of Guide Bridge, in the County of Lancaster, Engineers,
for the Invention of "CERTAIN IMPROVEMENTS IN METALLIC PISTONS."
PROVISIONAL SPECIFICATION left by the said Joseph Smethurst at the
Office of the Commissioners of Patents, with his Petition, on the 27th
December 1858.
I, JOSEPH SMETHURST, of the firm of Messieurs Martin and Smethurst, of
Guide Bridge, in the County of Lancaster, Engineers, do hereby declare the
nature of the said Invention for "CERTAIN IMPROVEMENTS IN METALLIC PISTONS,"
to be as follows:-
The object of my Invention is to render metallic pistons more elastic, and
easier to adjust than heretofore. In performing my Invention, I make use of
two packing rings, the inner circumferences of which are bevelled to fit a
wedge ring, which is cut through in one place, or made in two or more parts,
and is acted upon by an excentric spring ring. I prefer to make the spring
ring of cast iron, and it must be cut through at one part. The spring ring.
must first be turned rather more in diameter than the internal diameter of the
wedge ring or segments, to give the requisite elasticity. These pistons can be.
used either with or without adjusting screws to act on the wedge ring. or.
segments.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Joseph Smethurst in the Great Seal Patent Office on the
22nd June 1859.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOSEPH
SMETHURST, of the firm of Messieurs Martin and Smethurst, of Guide Bridge,
in the County of Lancaster, Engineers, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-seventh day of December, in the year of our
Lord One thousand eight hundred and fifty-eight, in the twenty-second year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Joseph Smethurst, Her special licence that I, the said Joseph
Smethurst, my executors, administrators, and assigns, or such others as I, the
said Joseph Smethurst, my executors, administrators, and assigns, should at
any time agree with, and no others, from time to time and at all times there-
after 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
"CERTAIN IMPROVEMENTS IN METALLIC PISTONS," upon the condition (amongst
others) that I, the said Joseph Smethurst, 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 Joseph Smethurst, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the fol-.
lowing statement (that is to say) :-
The object of my Invention is to render metallic pistons more elastic and
easier to adjust than heretofore. In performing my Invention, I make use of
two packing rings, the inner circumferences of which are bevelled to fit a
wedge ring, which is cut through in one place, or made in two or more parts,;
and is acted upon by an excentric spring ring. I prefer to make the spring:
ring of cast iron, and it must be cut through at one part. The spring ring
must first be turned rather more in diameter than the internal diameter of the s
wedge ring or segments, to give the requisite elasticity. These pistons can be
used either with or without adjusting screws to act on the wedge ring or
segments.

page_text: But in order that my Invention may be fully understood and readily
carried into operation, I will proceed to describe the accompanying Sheet of
Drawings, reference being had to the figures and letters marked thereon.
Fig. 1 in an elevation of my improved piston; Fig. 2 is a transverse
section; Fig. 3 is a plan of the same with the lid removed. a is the body or
block of the piston; b, b, are the packing rings, which are bevelled in the
usual manner to fit the wedge ring c; this wedge ring may be cut into four
parts, as shown in Fig. 3, or, if preferred, it is only cut through in one place,
or it may be cut into two or any greater number of parts, according to the
diameter of the piston. The segments or wedge ring c is acted upon by the
excentric spring ring d, which, like the packing and wedge ring or segments,
I prefer to make of cast iron. The spring ring is only cut through in one
place, and it is turned rather larger in its outside diameter than the internal
diameter of the wedge ring or segments, so that when the parts forming the
piston are in their places, and the piston is within the cylinder in which it has
to work, the requisite elasticity is given. These pistons may be used either
with or without adjusting screws, to act on the wedge ring or segment c. By
means of these improvements in metallic pistons, they are rendered more
elastic and easier to adjust than those hitherto generally employed, and the
spring ring being detached from the wedge ring or segments, and supported
by the body or block of the piston, obviates the injurious knocking common to
most metallic pistons.
Having thus stated the nature of my Invention, and described the manner
of carrying the same into operation, I wish it to be understood that I make
no claim to the wedge ring c, nor to the peculiar shape of the packing rings b;
but what I do claim is, the combination of the excentric spring ring d with
the wedge ring or segments c and packing rings b, as shewn and described.
In witness whereof, I, the said Joseph Smethurst, have hereunto set my
hand and seal, this Twenty-first day of June, in the year of our Lord
One thousand eight hundred and fifty-nine.
JOSEPH SMETHURST. (L.S.)