Improvements in Balanced Pistons for Steam Engines.
Year: 1892

page_text: Date of Application, 19th Apr., 1892-Accepted, 21st May,
1892
COMPLETE SPECIFICATION.
Improvements in Balanced Pistons for Steam Engines.
I, WILLIAM JAMES THOMAS, of Sausalito, in the County of Marin, State of
California, United States of America, Machinist, do hereby declare the nature of
my invention and in what manner the same is to be perforined, to be particularly
described and ascertained in and by the following statement :-
This invention relates to that improvement in balancing pistons for which Letters
Patent of the United Kingdom of Great Britain and Ireland were issued to me
and dated the 18th day of June 1889, No. 10,001 and it embraces improvements in
the construction of the packing rings and in the arrangement of steam ports and
passages in the piston. The object of these improvements is to simplify the
construction of the parts and to ensure a better supply and perfect control of the
steam pressure by which the balancing is effected.
I proceed to attain the desired end and object and produce these improvements
by the construction and arrangement of the parts represented in the accompanying
drawings, in which :-
Figure 1. is a side elevation of a balanced piston to which my improvements are
applied the top and bottom portions of the surrounding cylinder being shown
portions of the surrounding cylinder being shown in section.
Figure 2 is a longitudinal section through the piston in a vertical plane.
Figure 3 is a top view of the piston.
Figures 4, 5 and 6 illustrate the manner of forming the lap and joint of the
packing ring.
XY indicate the top and bottom sides of the cylinder; A is the piston, and B B
are the packing rings. C is the steam chamber or hollow space in the piston and
DE are ports and passages opening into the space C through the piston.
The packing rings are set obliquely the same as in my former Patent No. 10001
but the passage D is carried from the outside into the steam space C through that
part of the face or rim of the piston which lies between the two rings at or near
the top side of the piston where the two packing rings approach the nearest to
each other. The inlet is common to the two packing-rings and steam is admitted
through it into the piston-chamber C from one groove or the other according to
the direction of the travel of the piston, that is, from the pressure side of the
piston.
The Packing rings are fitted closely in the piston-grooves and the steam from the
pressure side passes around the leading or foremost ring and so into the space
between the two rings where the inlet Ď is located.
The general action or operation of the rings is the same as in my former Patent:
the packing rings have sufficient play in the grooves to let the steam from the
pressure side pass into the space C, and in being shifted by the movement of the
piston from one side of its grooves to the other side, the leading ring admits steam
while the other ring which is between the exhaust side of the piston and the steam
inlet is pressed closely against the outer side of its own groove to shut off the
inlet D and the space C from the exhaust. The two rings thus acting alternately
maintain a regular and uniform degree of pressure in the space under the piston
between the two rings and the bottom of the cylinder. The inlet D serves to give
quick inlet of live steam directly to the space under the piston, but in addition to
that supply it will be noticed that the steam pressure after passing the joint of the
ring into the space between the two rings above the piston is free to pass around
the circumference between the piston and the walls of the cylinder and so finds its

page_text: way into the space under the piston. The admission and supply of live steam
into the space under the piston is more direct and quick, however, through the
ports D E.
The joint of the packing-ring is constructed to give suitable passage for the
steam both between the ring and the bottom of the groove and the inner side of
the groove when the steam pressure is against the outer side of the ring, but the
outside face of the ring is flush and produces a close joint when the outside face of
the ring is seated against the outer side of its groove. The joint Dx is flush or
continuous on the outer face as well as on the top or working face, but it is cut
away or broken on the bottom and on the inner side. It is also expansible to
accommodate itself to the elasticity of the ring.
In constructing this joint a solid ring is first finished on the sides and top face and the
parts for the joint are formed as shown in Figures 4 and 5 by cutting or milling them
out of the solid metal. The portion from 1 to 2 is cut away on the inner or bottom
face, the portion from 3 to 4 is cut away across the ring on the outer face and the
part from 5 to 6 is cut away on the side face for about one half the thickness of the
metal the portion of metal from 1 to 2 being removed to a corresponding amount
on the opposite face. After these operations the ring is cut through at the
line x y across the milled and cut-away portions, and the lap is produced by rolling
the two end portions for about one third of the circumference: this is done
by passing the ends between revolving rollers which are placed in relative
position as indicated by the dotted lines, Figure 5. By this means a close
expansible joint is obtained, and the ring when finished and sprung into place will
be cylindrical. Snap-rings with lap-joints produced by other modes of construction
will not be true circles and therefore not so well adapted for my purpose.
To illustrate the action of the steam in the piston, if the pressure be on the
right side of the piston, as shown in Figures 1, 2 and 3, the right hand ring B will
be forced against the inner edge of the groove into the piston, and a space or
passage for the steam will be opened by the lateral movement of the ring between
the ring and the outer edge of the groove, as seen in Figure 3 through which
the steam will pass under the cut-away portion 1 to 2, and thence out
through the cut-away portion 5 to 6 (see Figures 5 and 6) into the space between
the rings.
The ring B on the left of the piston being pressed against the
side of its groove will at the same time make a tight joint all around against
the outer edge of the groove by reason of the continuous unbroken contact
of the ring with the said outer edge, as may be seen in Figure 3, and as will be clearly
indicated by the side elevation of the ring shown in Figure 6. No steam there-
fore can pass this left-hand ring when the pressure is upon the right of the
piston. When the pressure is shifted to the left of the piston the conditions of
the rings will be reversed as will be readily understood.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what I
claim is :-
1. In a balanced piston for steam engines a piston having obliquely set packing-
ring grooves, a steam-space or chamber and passages communicating with the
outside through the opposite faces of the piston and between the said grooves, in
combination with packing-rings having lapping ends with flush outer faces and
cut-away portions on the bottom and at the inner sides, constructed and arranged
for operation substantially as described.
2. A packing-ring for steam pistons having a lap-joint with a tongue or reduced
end-portion which is cut-away on the bottom of the ring and on the inner face,
and a recessed end adapted to take the said tongue and form a lap-joint as
described.
3. In a balanced piston the combination with the hollow body of the piston
having peripheral openings and annular circumferential grooves as described, of a 5

page_text: pair of packing rings each having a lap-joint said rings being of less width than
the width of the grooves and each lap-joint being formed of one recessed end and
one reduced end of the ring, said reduced end lying in said recess and making a
tight joint all around in the groove when pressed against its outer edge as
described.
Dated this 10th day of Anvil 1000
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant