Improvements in Pistons for Steam Engines.
Year: 1888

page_text: Date of Application, 16th Jan., 1888
Specification Accepted, 17th Feb., 1888
Improvements in Pistons for Steam Engines.
I, DAVID JOHN MORGAN, of Bute Docks, Cardiff, in the County of Glamorgan,
Engineer, do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by the
following statement :—
My invention relates to improvements in the method of constructing the pistons of
steam engines and relates to methods according to which the piston will be capable
of fitting more tightly against the cylinder sides, and be at the same time less likely
to allow steam to pass through it than are the various kinds of self expanding pistons
known, or in use, up to the present time.
The importance of a piston fitting the cylinder absolutely steam-tight, and at the
same time presenting no ways along which the steam can leak through, cannot be
over estimated, or receive too much attention; especially in the case of marine engines:
and, although there have, from time to time, appeared numerous ingenious devices,
more or less practicable, for the purpose of keeping a piston steam-tight under all the
circumstances under which it must work, the increased pressures at which steam is
now being used demands a construction of piston endowed with a greater degree of
sensitiveness, and capacity for adjusting itself to the task of resisting said pressures,
than was required in the self-adjusting piston previously used.
It is obvious that a piston adapted, in virtue of the. automatically expanding devices
with which it is fitted, to resist a given pressure; may, and very likely will, leak if
the pressure be doubled: for, if the said double pressure were not practicable, or
apparently probable, or even possible, in the opinion of the designer of the piston at
the time he designed it, he would naturally confine himself to adapting his piston to
resist the pressure with which he was at the time familar. As a consequence, he
would unconsciously allow to creep into the construction he adopted certain latent
defects which would assume a practical existence as soon as the piston is subjected to
a double pressure.
I wish to point out, that it is possible to improve a piston in the direction of fitting

page_text: the cylinder tightly, at a sacrifice of capacity for working smoothly. Thus one
advantage may be more than counterbalanced by a greater disadvantage; for it is
well known to all practical engineers, that an increase of friction between the piston
and cylinder will send up the coal-consumption more rapidly than an economy in
steam will help to keep it down, besides increasing the wear and tear of the engine.
The essential features of this invention are rings of a channel-section expanded
radially by internal springs; intermediate ring or rings of a section adapted to the
double purpose of keeping the aforesaid rings apart; and the providing suitable
grooves for them; as well as further springs which force the intermediate rings
outward radially against the piston-flange and the junk-ring respectively.
According to my invention, therefore, steam is prevented by the channel-section
rings from leaking past the piston, and by the inner rings from leaking through it.
In order that my invention, and the means by which the same is to be carried into
practical effect, may be thoroughly understood, I will now describe the same in detail,
referring in so doing to the accompanying drawings which are to be taken as part
of this specification and read therewith, and in which like parts are marked with the
same reference letter.
Fig. 1 is a sectional plan of a piston constructed according to my invention.
Fig. 2 is a sectional elevation taken on the line Y-Z of Fig. 1.
Fig. 3 is a plan of an alternative device for adjusting the strength of the spring of
a channel-section piston-ring; and
Fig. 4 is a sectional elevation of a modified form of intermediate ring with its
spring.
A is the body of the piston; B, the piston-flange; and C the junk ring. D, Dare
rings of a channel-section. Two only are illustrated in the figures, but I do not
confine myself to this number.
E is a ring of a T section, the back, e, of which extends from the piston flange to
the junk-ring. Its web, e¹, parts the two rings D, D, and forms, with the flange and
junk ring, suitable grooves to receive the said rings.
The ring, E, may be saw-cut in only one place, as is done with common piston-
rings, or into segments as may be desirable to meet the special conditions of any
particular case.
F is a spring of any suitable kind that is capable of expanding the ring, E, radially
from the piston body.
G is a spring of similar construction in each recess between a ring, D. and the
ring, E. Both springs, F and G, are drawn as of a wavy pattern, but I wish it to be
distinctly understood that I do not confine myself to rings of this pattern.
The ends, g, of each spring, G, are bent outwards for the purpose of forming abut-
ments between which a spiral, or other equivalent form of spring, H, is placed for the
purpose of adjusting the strength of the spring, G, and increasing its sensitiveness.
Liners, g', may also be used between the spiral spring, H, and the abutments, g, for
the purpose of perfecting the adjustment.
Instead of using a spring, H, for the purpose of adjusting the spring, G; I may
use a stud, 1, furnished with two pairs of nuts, as illustrated in Figure 3. The ends
of the stud are passed through eyes in respective spring-ends, g; and the necessary
adjustment of the spring G against the bore of the cylinder is effected by moving the
pairs of nuts either further from, or nearer to, the centre of the stud.
Figure 2 illustrates the ring, E, as of a solid T-section; but a useful modification
of this is illustrated in Figure 4. Instead of making this ring of a solid T-section,
I sometimes, and preferably, use two rings, e¹, e¹, of an angle section. Their adjacent
faces are grooved out as shown in the figure, so that when they are brought together
they produce a T with an annular cavity, e, in the web thereof. This cavity receives
a spring, e³, of any suitable kind capable of discharging the desiderated function of
said spring, which is to force the two angle rings apart with the result of keeping
each angle-ring and channel-ring tight against the piston flange, or junk ring, as the
case may be.

page_text: 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. The combination with the expansible rings of a steam engine piston, of an inner
ring of a T-section, the web of which separates the said expansible rings; substantially
as described with reference to the accompanying figures.
2. The combination in a steam engine piston of expansible rings; inner ring of
T-section, the web of which separates the said expansible rings; and a spring adapted
to expand the said T-ring; substantially as herein described with reference to the
accompanying drawings.
3. The combination in a steam engine piston of expansible channel-section rings;
internal rings of an angle section placed together relatively to each other so as to form
a T-section, the web of which separates the said expansible rings; an annular groove
formed within the said web; a spring within the said web adapted to force one anglo
section ring towards the junk-ring, and the other towards the piston-flange; and
internal springs adapted to expand the said angle-section rings radially; substantially
as described with reference to the accompanying drawings.
4. The combination in a steam engine piston of junk ring, piston flange, two angle
section rings, and a spring adapted to force them towards the junk-ring and piston-
flange respectively.
PHILLIPS & LEIGH,
Patent Agents,
22, Southampton Buildings,
Chancery Lane, W.C.,
Agents for the Applicant.