IMPROVE- MENTS IN PISTONS."
Year: 1868

page_text: LETTERS PATENT to Mark Havenhand and John Allen, both of
Dronfield, in the County of Derby, for the Invention of "IMPROVE-
MENTS IN PISTONS."
PROVISIONAL SPECIFICATION left by the said Mark Havenhand
and John Allen at the Office of the Commissioners of Patents, with
their Petition, on the 26th March 1868.
We, MARK HAVENHAND and JOHN ALLEN, both of Dronfield, in
the County of Derby, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN PISTONS," to be as follows:-
The object of our Invention is to keep the sides of pistons steam-
tight against their cylinders, and to compensate for wear produced in
the parts by friction. For this purpose we employ angle pieces or
wedges, which are kept pressed outwards by springs, the points of these
wedges coming between the adjacent end surfaces of two half rings.
These surfaces are inclined to correspond with the inclines of the wedges,
and they are grooved or undercut to receive corresponding tongues or
ribs on the inclines of the wedges. The springs which bear against the

page_text: backs of the wedges may have their other bearings either against cach
other or against a ring or diamond-shaped block on the piston rod.
When a diamond-shaped block is employed it is preferred to be loose on
the rod so as to be free to move round thereon together with the wedges,
springs, and half rings. As the periphery of the half rings wears by
friction the springs force out the wedges, so as to move the adjacent
surfaces of the half rings from each other, the points or narrow edges of
the wedges and their tongues filling up the spaces so formed. Instead of
employing two half rings as before explained the circle may be composed
of three or other convenient number of pieces which will together make
up a ring, the wedges being of corresponding number. The whole of
the parts are enclosed between a top and a bottom cover.
One or
more rings acted on by the wedges as before explained may be
employed.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Mark Havenhand and John Allen in the Great
Seal Patent Office on the 26th September 1868.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, MARK
HAVENHAND and JOHN ALLEN, both of Dronfield, in the County of
Derby, send greeting..
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-sixth day of March, in the year
of our Lord One thousand eight hundred and sixty-eight, in the thirty-
first year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto us, the said Mark Havenhand and John Allen,
Her special licence that we, the said Mark Havenhand and John
Allen, our executors, administrators, and assigns, or such others
as we, the said Mark Havenhand and John Allen, 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
yend, 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 we, the said Mark

page_text: Havenhand and John Allen, or one of us, our executors or adminis-
trators, by an instrument in writing under our, or one of our, or their,
or one of their hands and scals, 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 we, the said Mark Havenhand and John
Allen, 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 thereof, reference being
had to the Drawings hereunto annexed, that is to say :-
The object of our Invention is to keep the sides of pistons steam-
tight against their cylinders and to compensate for wear produced in the
parts by friction. For this purpose we employ angle pieces which are
kept pressed outwards by springs, the points of these angle pieces
coming between the adjacent end surfaces of two half rings. These
surfaces are inclined to correspond with the inclines of the angle pieces,
and they are grooved or undercut to receive corresponding tongues or
ribs on the inclines of the angle pieces. The springs which bear against
the backs of the angle pieces may have their other bearings either
against each other or against a ring or a diamond-shaped block on the
piston rod. When a diamond-shaped block is employed it is preferred
to be loose on the rod, so as to be free to move round thereon together
with the angle pieces, springs, and half rings. As the periphery of the
half rings wears by friction the springs force out the angle pieces, so as
to move the adjacent surfaces of the half rings from. each other, the
points or narrow edges of the angle picces and their tongues. filling up
the spaces so formed. Instead of employing two half rings as before
explained the circle may be composed of three or other convenient
number of pieces which will together make up a ring, the angle pieces
being of corresponding number. The whole of the parts are enclosed
between a top and a bottom cover. One or more rings acted on by the
angle pieces as before explained may be employed.
Figure 1 of the accompanying Drawings is a plan or top view with
the top cover removed; Figure 2, an edge view; and Figure 3, a
section through the line x, x, of Figure 1 of a piston constructed.
according to our Invention.

page_text: a is the piston rod; b, the piston block; c, the bottom cover; and d,
the top cover secured to the block 6 by screws e, e, or otherwise; f, f
are two half rings held between the top and bottom covers; g, g, are
two angle pieces, the points of which come between the adjacent
end surfaces of the two half rings as shown. These surfaces are under-
cut, as seen at h, to receive corresponding tongues or ribs i on the
inclines of the angle pieces. If desired, grooves (as in Figure 5) may
be substituted for the undercuts h; k is a ring fitting loosely round
the block 6 and provided with projections 1, 1; m, m, are two springs
which bear against the backs of the angle pieces g, g, to which they are
preferably attached by screws n, n; the ends of these springs bear
against the ring k as shown, while the projections 1, 1, act as stops to
keep all the parts in their relative positions. The half rings f, f, angle
pieces g, g, springs m, m, and ring k are all free to turn together round
the block b, but their relative positions remain the same.
In Figures 4 and 5 we show a piston constructed the same as that
represented in Figures 1, 2, 3, except that a diamond-shaped piece k¹ is
substituted for the ring k and projections 1, 1, and instead of the end
surfaces of the half rings f,f, being undercut they are grooved as seen at
h', the angle pieces g, g, being formed to correspond. If desired the
diamond piece k¹ may be a part of or fastened to the block b, but we
prefer it to be loose thereon. This diamond piece forms inclined planes
for the ends of the springs to rest on, and while these planes give great
elasticity to the half rings they also equalize the pressure of the springs
from the commencement of the wear of the rings until they are worn
out; the same may be said of the central ring k, Figure 1.
When we employ two or more sets of angle pieces and other parts in
the same piston we find it desirable to keep the sets in the same relative
position and to make them as it were break joint; the manner in which
this may be effected will be understood on reference to Figures 6 and 7,
Figure 6 being a top view of one set of angle pieces and other parts
provided with recesses o, o, in the diamond-shaped piece k', and Figure 7
being a top view of the other set of angle pieces and other parts
provided with projections p, p, on the diamond-shaped piece to take into
the recesses o, o, Figure 6. It will be seen that the angle pieces g, g, of
Figure 6 will be at right angles to those of Figure 7, and that while the
two sets of angle pieces and other parts are free to turn in the cylinder
they all turn together, thereby retaining their relative position. This

page_text: mode of combining the sets of angle pieces and other parts of course
applies to the arrangement shown in Figures 1, 2, and 3.
cases instead of employing two springs m, m, one for each angle piece, we
employ one oval spring represented detached at m³, Figure 8, and we
spring it into its place, as seen in Figure 9, so that its tendency to
resume its normal shape will produce the necessary pressure at the
back of the angle pieces. This oval spring m¹ is formed with projections
q, q, to take or fit into corresponding holes in the backs of the angle
pieces. We find it preferable in all cases to make the angle pieces
right angled.
And having now described the nature of our said Invention, and in
what manner the same is to be performed, we declare that we claim as
our "Improvements in Pistons,"
First. The employment of angle pieces in combination with half
rings or portions of rings in such manner that the angle pieces are
moved outwards in proportion to the wear of the half rings or portions
of rings, substantially in the manner and for the purpose herein-before
described and represented in the accompanying Drawings.
Second. The employment of a central ring or of a diamond piece to
form the bearings for the springs which act against the backs of the
angle pieces, substantially as herein-before described and represented in
the accompanying Drawings.
Third. The combination or combinations of parts of pistons, sub-
stantially as herein-before described and represented in the accompanying
Drawings.
In witness whereof, we, the said Mark Havenhand and John
Allen, have hereunto set our hands and seals, this Twenty-
fourth day of September, One thousand eight hundred and sixty-
eight.
MARK HAVENHAND. (L.S.)
JOHN ALLEN.
(L.S.)