An Improved Piston.
Year: 1891

page_text: Date of Application, 24th Sept., 1891
Complete Specification Left, 3rd June, 1892-Accepted, 9th July, 1892
PROVISIONAL
SPECIFICATION.
An Improved Piston.
I, CECIL GODFREY TINN, of Pontnewynydd, in the County of Monmouth,
Ironworks Manager, do hereby declare the nature of this invention to be as
follows:-
This invention relates to that class of pistons in which the packing rings are
expanded by steam acting behind them, the rings being expanded alternately
according to the stroke.
Under this invention the packing rings, which are approximately L-shaped, are
carried in corresponding recesses provided therefor in a carrier ring contained
between the piston head and the junk ring, and steam is admitted to act upon the
packing rings through diagonal or inclined channels provided at equal distances
apart in the piston head and in the junk ring. The steam channels in the piston
head and junk ring are situated towards the circumferences thereof and incline
from their respective outer faces towards their peripheries. At the inner ends the
steam passages communicate with recesses provided in the carrier ring, the said
recesses being behind a part of that limb of each packing ring which bears against
the cylinder. One face of each of the recesses last mentioned is so inclined that
the steam admitted by the inclined passages in the junk ring or the piston head,
according to the direction of the stroke, is deflected to exert an outward thrust
upon the said limb of the packing ring and thus to expand it against the cylinder.
The other limb of the ring extends back into the carrier ring, a space intervening
between its inner end and the carrier ring.
In a piston constructed and arranged as above described, liability to clogging the
steam passages with the lubricant and matter contained therein is reduced.
A further improvement comprised in this invention consists in splaying the ends
of the expansion rings and causing them to overlap. By this means a steam-tight
joint is obtained which is further maintained by the steam acting behind the
rings.
Dated the 23rd day of September 1891.
NICHOLAS WATTS,
Bristol Bank Buildings, Bristol, Agent.
COMPLETE
SPECIFICATION.
An Improved Piston.
I, CECIL GODFREY TINN, of Pontnewynydd, in the County of Monmouth,
Ironworks Manager, 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 :—
This invention relates to that class of pistons in which the packing rings are
expanded by steam acting behind them, the rings being expanded alternately
according to the stroke.
Under this invention the packing rings, which are of approximately L-shaped
section, are carried in recesses provided therefor in a carrier ring contained
between the piston head and the junk ring, and steam is admitted to act upon the
packing rings through passages provided at equal distances apart in the piston head
and in the junk ring. These steam passages admit steam to the rear of a part of
each packing ring. One face of each of the recesses in which the packing rings are
[P1

page_text: contained is so inclined that the steam admitted by the passages in the junk ring or
the piston head, according to the direction of the stroke, is deflected to exert an
outward thrust upon the said part of the packing ring and thus to expand the ring
against the cylinder.
In a piston constructed and arranged as above described, liability to clogging the
steam passages with the lubricant and matter contained therein is reduced.
Referring to the accompanying drawing,
Fig. 1 represents, partly in section and partly in side elevation, a piston con-
structed and fitted in accordance with this invention.
Fig. 2 represents a plan, the left-hand half being as seen from the junk ring face
of the piston, and the right-hand half as seen from behind the piston head.
The packing rings a are approximately L-shaped in section and are contained in
annular recesses provided for them in the carrier ring b. In the piston head c.and
the junk ring d are apertures e by which steam is admitted to bear upon a part of
the packing rings. When the steam is acting against the junk ring side of the
piston it is admitted by the apertures in the junk ring to the back of the packing
ring therein and expands it against the cylinder. The steam is directed to bear on;
the ring by the inclined face of the recess behind. Meantime, as the steam, pressure.
is withdrawn from the piston head side of the piston, the packing ring at that side
is free to contract and so reduce friction. Similarly, when the steam is acting at.
the opposite or piston head side, the packing ring, therein is expanded and that at
the junk ring side is free to contract.
At Fig. 3 is illustrated in section a modification in which the inclined faces: for
directing the steam upon the rings are provided on the, carrier ring..
A further modification is shown at Fig. 4. In this arrangement the piston body,
is in one piece and the packing rings are contained in recesses provided; therein.as
shown.
As under the steam pressure each ring a is in turn expanded, a part of the back
limb or stem thereof is exposed to the steam which; exerts on the exposed part of
the said stem a pressure in the direction of the axis of the cylinder, and thus
prevents escape of steam between the said limb and the carrier ring or; in the case
of a solid piston, between the said limb of the ring and the piston, body.
With pistons constructed and fitted with packing rings as above described
liability to clogging the steam passages with the lubricant. used in, cylinders is
lessened...
In the Provisional Specification left with my application for Letters Patent to
this invention it is set forth as a feature of this invention that the packing rings are
splayed and overlapped at the ends. I do not now consider this material and do
not therefore incorporate it as part of this invention.
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 :-
In a piston, the provision of packing rings such as a, approximately L-shaped in
section, carried in recesses provided in a carrier ring such as b. or in the piston, or
partly in both; the said packing rings being free to expand under steam: pressure.
admitted alternately to each by apertures in the junk ring and piston: head; or in
the piston body, the steam being directed by inclined faces to exert. an outward
thrust on the, rings, so that their outer faces are forced against the cylinder while at
the same time the back limbs or stems are forced by the steam against. the carrier.
ring or against the piston body, substantially as hereinbefore described and for the
purposes specified.
Dated this 31ot JOT of Mon 1902
NICHOLAS WATTS,
Bristol Bank Buildings, Bristol, Chartered Patent Agent.