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

page_text: Date of Application, 26th May, 1891-Accepted, 18th July, 1891
COMPLETE SPECIFICATION.
Improvements in Piston Valves for Steam and other Engines.
I, WILLIAM DE COURCY MAY, of Mount Airy Philadelphia in the State of
Pennsylvania, United States of America, Mechanical 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:-
In said drawings
Fig: 1 represents a central longitudinal section through the valve-chest and
pistons, showing also in section the adjacent side of the cylinder.
Fig. 2 is a top or plan view of the valve piston.
Heretofore in valves of this character where a large area is necessary in the
steam port it has been customary, either to use no packing ring in connection with
the piston, or in cases where such rings were used they were placed around the piston
itself and a liner or bushing was interposed between the piston and the adjacent
surface of the valve-chest. The former method of construction was liable to leak,
or if made with a sufficiently close joint to prevent leakage, the valve was liable to
stick, owing to unequal expansion of the seat, etc. The use of a liner was intended
to obviate this difficulty, but in order to retain the packing rings in position as they
respectively pass the opening of the annular port used it was necessary to provide
the liner with a series of bars extending across the port and leaving only the inter-
posed spaces between said bars for communication therewith. This reduced the
available area of the port usually about one-third, and consequently the dimensions
of the entire valve had to be increased. Furthermore, it was open to the objec-
tion that the liner was liable to crack at the bars and the cost of the structure as a
whole was considerably increased.
The object of my invention is to overcome these disadvantages and permit the
use of a packed piston in connection with this class of valves without increasing the
dimensions of the parts, or in any way complicating their structure. To this end I
mount packing rings on each side of the port scating them in the valve-chest itself,
and, to retain them in position after they are cleared by the piston, I provide the
latter with longitudinal wings of the same radial extent as the periphery of the valve
itself, and of such length that some portion of the wing shall always bear against
the packing rings, no matter what may be the position of the piston.
I will now proceed to describe my invention in its preferred form.
In the accompanying drawings, A represents the steam cylinder and B the piston
thereof, the valve-chest C being mounted upon the side of the cylinder, and being
provided with annular ports D, D', which communicate respectively at d, d', with
the upper and lower portions of the cylinder A. G represents the valve-rod upon
which the piston valves E, E', respectively are mounted in the proper relation to
said ports. The valve-chest communicates at 1 with the source of steam supply and
is provided with outlets H, H', arranged at top and bottom respectively.
Adjacent to the steam ports D, D₁, and on each side thereof, annular grooves are
formed upon the inner periphery of the valve-chest and in these grooves the packing
rings F, of the upper piston and F of the lower piston are seated, so as to
form a close joint with both pistons on both sides of each port. To maintain these
rings in position, as before stated, I provide the pistons E, E', with radial wings, e e¹,
respectively.
In the preferred form, these wings are arranged spirally or transversely to the
axis of the piston, as indicated by the dotted lines of Fig. 1, and as shown by the
shading in Fig. 2. The purpose of this is to obviate unequal wear upon the packing
rings, which otherwise might occur by the constant reciprocation of straight wings
at the same point only, and to produce the best result it is desirable that the top of

page_text: one wing should overlap or overhang the bottom of the next one so that all parts
shall be subject to the same amount of wear.
The operation of the device will be obvious from the foregoing description.
As the pistons reciprocate and open the ports they of course pass by the packing
ring upon one side or the other, but since the wings extend both directions to a
distance which conforms to the range of movement of the pistons, there is no
tendency of the rings to leave their seats, and thus the object sought for is
obtained.
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, the combination of a valve-chest having an annular port;
packing rings arranged on each side of said port; a piston mounted to reciprocate
in proper relation to said port and wings upon said piston adapted to bear against
said packing rings throughout the range of clearance movement of the piston, sub-
stantially as set forth.
2. In a piston-valve, the combination of a valve-chest having an annular port;
packing rings arranged on each side of said port; a piston mounted to reciprocate
in proper relation to said port and wings upou said piston adapted to bear against
said packing rings throughout the range of clearance movement of the piston,
said wings being inclined to the direction of movement of the piston, substantially
as set forth.
Dated this 5th day of May 1891
CARPMAEL & Co.,
Agents for the Applicant.