AN IMPROVED PISTON
Year: 1861

page_text: LETTERS PATENT to William Hobson, Engineer, and Thomas Cavill, Mill-
wright, both of Sheffield, in the County of York, for the Invention of
"AN IMPROVED PISTON."
Sealed the 17th December 1861, and dated the 21st June 1861.
PROVISIONAL SPECIFICATION left by the said William Hobson and
Thomas Cavill, at the Office of the Commissioners of Patents, with
their Petition, on the 21st June 1861.
We, WILLIAM HOBSON, Engineer, and THOMAS CAVILL, Millwright, both
of Sheffield, in the County of York, do hereby declare the nature of the said
Invention for "AN IMPROVED PISTON," to be as follows:-
The object of this Invention is to secure for engine pistons a resilient
surface or packing capable of adjusting itself to the wear and tear of the
cylinder. On the block of the piston we propose, between the top and
bottom plates, to secure two or more rings of cast iron, brass, or other metal;
these rings are formed with indentations on the convex side, and are disjointed
at one point; the abutting ends at this point are formed to admit of the
introduction of a wedge pointing outwards from the piston block. This wedge
is acted upon by a spiral spring, and advances or recedes as the condition of
the cylinder demands the distension or otherwise of the packing.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Hobson and Thomas Cavill in the Great Seal
Patent Office on the 21st December 1861.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, WILLIAM
HOBSON, Engineer, and THOMAS CAVILL, Millwright, both of Sheffield, in the
County of York, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-first day of June, in the year of our Lord
One thousand eight hundred and sixty-one, in the twenty-fifth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
us, the said William Hobson and Thomas Cavill, Her special license that
we, the said William Hobson and Thomas Cavill, our executors, adminis-
trators, and assigns, or such others as we, the said William Hobson and
Thomas Cavill, our 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 "AN IMPROVED PISTON," upon the
condition (amongst others) that we, the said William Hobson and Thomas
Cavill, by an instrument in writing under our hands and seals, should par-
ticularly 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 imme-
diately after the date of the said Letters Patent.
NOW KNOW YE, that we, the said William Hobson and Thomas Cavill,
do hereby declare the nature of our said 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 Drawings here-
unto annexed, that is to say:-
The object of this Invention is to secure for engine pistons a resilient
surface or packing capable of adjusting itself to the wear and tear of the
cylinder. On the block of the piston we purpose, between the top and bottom
plates, to secure two or more rings of cast iron, brass, or other metal; theso
rings are formed with indentations on the concave side, and are disjoined at
one point; the abutting ends at this point are formed to admit of the intro-
duction of a wedge pointing outwards from the piston block. The wedge is
acted upon by a spiral spring, and advances or recedes as the condition of the
cylinder demands the distension or otherwise of the packing.

page_text: We will now proceed to describe the accompanying Drawings, which
represent a piston constructed according to our said Invention. The same
parts in each Figure are indicated by the same letters of reference.
Figure 1 is a view of the end of the piston; Figure 2 is a view of the
periphery, shewing the packing; Figure 3 is a horizontal section on the
line a, b, (Figure 2), and Figure 4 is a vertical section on the line c, d,
(Figure 3).
Between the top and sole plates the rings or packing A, A, are shewn in
position; two only aro shewn, but more may be introduced if desired. The
joint B is formed to admit of a wedge C, which is acted upon by the spring D
and distends the packing to the full bore of the cylinder; the indentations
e, c, e, secures equality of pressure, and the adaptation of the packing to the
ordinary wear and tear of the cylinder.
Having now described and particularly ascertained the nature of our said
Invention, and the manner in which the same is or may be carried into effect,
we would observe that what we claim and desire to have secured to us by the
above in part recited Letters Patent, is, the peculiar packing rings and the
mode of securing their distension, substantially as herein-before set forth and
delineated on the accompanying Drawings.
In witness whereof, we, the said William Hobson and Thomas Cavill,
have hereunto set our hands and seals, this Twentieth day of December,
in the year of our Lord One thousand eight hundred and sixty-one.
Witness,
T. F. CASHIN.
W. HOBSON.
(L.S.)
THOMAS CAVILL. (L.S.)