Improvements in Piston Slide Valves for Steam and other Engines.
Year: 1891

page_text: e of Application, 15th June, 1891-Accepted, 20th Feb., 1892
COMPLETE SPECIFICATION.
Improvements in Piston Slide Valves for Steam and other Engines.
1, WILLIAM CUMMING of Adelaide in the Colony of South Australia Marine
Engineer on board the steamship Innamincka 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 pistons slide valves which have a piston
body, junk ring, and packing ring with necessary studs, bolts etc. and also in pistons
slide valves of small diameter in which the body of piston and packing ring are in
one and may be constructed to suit that class of valve chamber in which steam
from the boiler is admitted direct to each end of the chamber or if desired in the
case of large piston valves the steam admitted at one end of the valve chamber can be
allowed to pass through an orifice in the body of the piston to the other end of the
chamber whilst retaining my said improvement.
In this invention I dispense entirely with springs and use no material for packing
other than the packing ring hereafter described. This piston valve will prove
superior to any other kind at present in use in many respects. Thus where spring
rings are employed within the junk rings and piston flanges the points of admission
and cut off greatly alter as the valve chamber. wears and the rings ultimately
become the cutting off and admission edges of the valves instead of the top and
bottom of the piston as originally intended thus causing steam to be admitted and
exhausted earlier than it should be.
When spring packing rings are used they are compressed under their normal
diameter by steam pressure in the cylinder ports, every time they pass said ports
and thus the friction on the chamber is not uniform and it wears unevenly. The
above together with the waste of power caused by steam leakage after wear has
taken place and the necessity for frequent renewals of parts in spring rings of valve
pistons, constitute serious disadvantages all of which are obviated by the use of my
invention.
A further improvement in the construction of piston valves with my packing
ring is that the ring is allowed lateral movement on the piston so that it always
maintains its true position in valve chamber even should the valve rod wear out of
its true line. It is also apparent that with my valve piston friction is reduced to a
minimum thereby firstly releasing the valve gearing from the weight caused by the
friction of spring rings, and secondly requiring very little lubrication thus
economising lubricant and also avoiding the injurious results which follow when
decomposed lubricant passes through into the boilers. Piston valves fitted with
my rings are applicable to chambers whether fitted with ordinary steam ports or
with diagonally ribbed ports whereas where narrow spring rings are employed
diagonally ribbed ports only can be used.
My piston valves work with so little friction that they wear much more slowly
than ordinary types, besides always wearing uniformly throughout the stroke. The
use of my valve allows the chamber at any time to be rebored and no part will
require to be renewed since the packing ring merely requires to be enlarged (by
addition of lining between the sections) sufficiently to allow of its being again
turned down to the proper diameter.
Referring now to the accompanying sheet of drawings which shows a piston valve
containing my said improvements.
Figure 1 shows a side elevation of the same.
Figure 2 a vertical sectional elevation through the middle of the valve,

page_text: Figure 4 a plan view of the valve when half of the junk ring has been removed.
The same letters of reference indicate corresponding parts in all the figures.
A shows the piston rod; B the piston body, C the junk ring secured to the piston
body by studs and nits C¹. D the packing ring in sections D',' D', D³, and D
having internal flanges D³ secured firmly together by bolts and nuts Dª.
An essential feature of my invention lies in dividing the packing ring into a
number of equal sections (in practice the best results following when there are four
or more such sections) and then inserting between the flanges before bolting them
together a lining sheet of any suitable thin material so as to increase the size of
the ring as a whole to any extent required for the purposes before stated.
Thus the packing ring however often worn down can be always easily adjusted to
fit the valve chamber accurately. In the case of very small valve pistons where a
separate packing ring is not used the piston edge itself fitting, I apply my invention
by dividing the piston itself into four or more sectors and I compensate for wear
by inserting lining material between the sectors which are then bolted together.
Another advantageous feature in my invention consists as will be seen in the
drawing, in making the packing ring D extend longitudinally from the top to the
bottom of the piston, so as to form the admission and cut off edges of the valve thus
maintaining always the same lead and lap for both steam and exhaust sides of piston
as originally allowed.
It will be evident that the said improved valve piston may be similarly used in
other engines besides steam engines.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. In a piston valve, a packing ring divided into a number of sections bolted
together and having any required thickness of lining inserted between said sections
to secure an accurate adjustment and to compensate for wear, substantially as
described.
2. An improved piston valve packing ring constructed to extend longitudinally
from the top to the bottom of the piston and form permanent admission and cutting
off edges substantially as herein described.
3. An improved piston valve of the class having no separate packing ring, formed
by dividing the piston in a number of sectors or equivalent divisions and adjusting
the same together with any required thickness of lining between substantially as
and for the purposes specified.
Dated this 15th day of June 1891
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.