IMPROVEMENTS IN PISTONS
Year: 1881

page_text: PROVISIONAL SPECIFICATION left by Alexander Melville Clark at the
Office of the Commissioners of Patents on the 14th March 1881. A communi-
cation from abroad by Henry Waterman, of Brooklyn, in the County of Kings,
State of New York, United States of America.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of
Middlesex, Patent Agent. "IMPROVEMENTS IN PISTONS." [A communication
from abroad by Henry Waterman, of Brooklyn, in the County of Kings, State of
New York, United States of America.]
The object of this Invention is to construct a light hollow piston possessing
all the advantages of a solid piston, and capable of accurate and easy adjustment.
The piston is of the ordinary hollow split ring kind, and the Invention consists
of a curved segmental plate having a hemispherical socket in its concave face, which
plate is pressed outward against the inner ring by a block that is provided with
a central hemispherical stud which fits in the plate socket, said plate and block
being pressed outward by shims or backing pieces driven between them and the
piston hub; and the Invention further consists of an elastic concavo-convex circular
plate laid between the follower and edge of the outer rings, which plate being
pressed down by the follower serves to hold the rings down in position.
The piston consists of an end cast plate provided with a central hub bored for
attachment on the end of a piston rod, and provided on one side with two lateral
lugs. On the face of the plate, near its edge, are set edgeways, one above and upon
the other, two diagonally split rings of steel or other suitable metal, and inside these
rings is placed a split ring, whose width equals the width of the two rings together.
In three sides of the hub are screwed adjusting screws provided with check nuts,
the heads of which screws press on vertical flat plates which bear out against the
inner circumference of the inner ring to hold the rings out in position. By holding
the nuts and turning the screws, the said rings may be expanded to fit more closely
in a steam cylinder, or may be allowed to contract as may be desired. This method
of adjustment of the rings by screws is superior to the usual spring adjustment,
being more rigid and durable, and less affected by the erosive action of the steam ;
but for the lower side of the piston, where a more rigid adjustment is required, a
device is applied consisting of a curved segmental plate provided with a central

page_text: hemispherical socket in its concave face, and having a vertical slot in its concave
face, said plate being fitted with its convex face against the inner surface of the
inner ring, its slot permitting it to be set over a key which passes through the rings
to assist in holding them in position. Between the lugs of the hub is placed a loose
block having a hemispherical stud or boss on one face, which is fitted in the Bocket
of the plate, and this block is forced outward against the plate, and the latter
against the ring with any desired force by means of shims or backing pieces that
are driven back of said block between it and the hub, said shims being held laterally
by the lugs. The boss and socket form in effect a ball and socket joint that permits
the plate to adjust itself more nicely and accurately to the ring, and the combined
hub, plate, block, and sims form as solid and inelastic a backing for the rings as
is afforded by a solid piston. Shims of greater or less thickness can be introduced
between the lugs to press the rings outward as far as may be desired.
The concavo-convex plate is of thin sheet metal, and is so shaped for the sake of
elasticity. It is of equal diameter with the rings, and is placed on top of the piston
so as to extend over the upper edge of the upper ring. The follower is then
placed on top of the plate, and both plate and follower are held down in place upon
the rings by bolts that pass through corresponding holes in said follower and plate
into the hub, whereby the piston is made complete.
The elastic plate serves to hold the rings down without rattling, and also to make!
a tight joint between the edges of the said rings and the follower.