IMPROVEMENTS IN OR APPLICABLE TO SLIDE VALVES OF STEAM ENGINES."
Year: 1881

page_text: LETTERS PATENT to Edmund Pilkington, of Pendleton, in the County of
Lancaster, Engineer, for an Invention of "IMPROVEMENTS IN OR APPLICABLE
TO SLIDE VALVES OF STEAM ENGINES."
PROVISIONAL SPECIFICATION left by the said Edmund Pilkington at the
Office of the Commissioners of Patents on the 11th February 1881.
EDMUND PILKINGTON, of Pendleton, in the County of Lancaster, Engineer.
"IMPROVEMENTS IN OR APPLICABLE TO SLIDE VALVES OF STEAM ENGINES."
These improvements relate to the application of a simple and efficient cut-off
to new or existing slide valves, whereby the cut off of steam can be effected
instantly, and varied to the greatest nicety.
In performing my Invention I dispense with the laps at each end of the slide
valve, and in place thereof I arrange a supplementary slide working on the existing
valve free, and which is carried along by the slide valve, and acts as the lap, a
given amount of play or space being left between the two valves to supply the
required quantity of steam to the port, and which slide is arranged to follow the
valve, and then to cut off the steam supply at any required point in the stroke
of the engine. This supplementary slide can be either arranged to act automatically
or moved by the steam; or it can be geared by adjustable mechanism to a rocking
arm controlled by the ordinary eccentric, or in any other convenient manner, and
the cut off can also be regulated by and be under the the control of the governor.
By the application of these improvements considerable pressure is taken off the
back of the slide valve, and hence less power is required to operate such valve.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Edmund Pilkington in the Great Seal Patent Office on the
11th August 1881.
"
EDMUND PILKINGTON, of Pendleton, in the County of Lancaster. IMPROVE-
MENTS IN OR APPLICABLE TO SLIDE-VALVES OF STEAM-ENGINES."
These improvements relate to the application of a simple and efficient cut off to
new or existing slide valves, whereby the cut off of steam can be effected instantly,
and varied to the greatest nicety. In performing my Invention I dispose with the
lap at each end of the slide valve, and in place thereof I arrange a supplementary
slide working on the existing valve free, and which is carried along by the slide valve,
and acts as the lap, a given amount of play or space being left between the two
valves to supply the required quantity of steam to the port, and which slide is
arranged to follow the valve, and then to cut off the steam supply at any required
point in the stroke of the engine. This supplementary slide can be either arranged
to act automatically or moved by the steam; or it can be geared by adjustable
mechanism to a rocking arm controlled by the ordinary eccentric, or in any other
convenient manner, and the cut off can also be regulated by and be under the
control of the governor. By the application of these improvements considerable
pressure is taken off the back of the slide valve, and hence less power is required
to operate such valve.
And in order that this my said Invention may be the more readily understood
and carried into practical effect I have hereunto annexed two Sheets of Drawings
illustrative of my improvements, and I will now proceed to describe the same with
the assistance of the figures and letters of reference marked thereon. The same
letters of reference being used to denote similar parts in the several views.
Fig. 1 is a side sectional view of so much of the slide valve box of a steam
engine as is necessary to explain my improvements, which are shewn applied
thereto.
In Fig. 1, A is the main valve worked in the ordinary manner from the
rocking shaft B, but having little or no lap, as illustrated; C is the supplementary
valve, which forms the subject of this Invention, and consists of two slides C and C
connected together by a strap C³ passing behind the main valve, as seen best in plan,
Fig. 2. It will be obvious that these slides C' and C² might be connected together
by other arrangements than the one illustrated. For instance, the strap C³ might be
carried over the main valve when the height of the valve box would admit. A certain
amount of play or space is allowed between the main valve A and the supple-
mentary valve C sufficient to supply the cylinder with the proper quantity of steam
and no more. It will be observed that as the main valve A moves it will carry
the supplementary valve along with it, and the cut off action might be produced in
two ways, first, by varying the stroke of the main valve A, in which case the cut off
would be determined by the time of the traverse of the space between the main
valve and supplementary valve over the ports D, or the main valve might have
sufficient movement given to it to ensure the proper action of the exhaust and the
cut off effected by the supplementary valve being made to overtake the main
valve. It is this last arrangement which is illustrated in the Drawing. The
rocking arm B¹ is extended and drives a cut off rod E from a centre F, adjustable
by means of the worm G, under control of the hand wheel H. At the other
extremity of this rod E is a finger piece I working in a box J, keyed upon a
spindle K connected to the supplementary valve C through the gland L. It will
be apparent from the Drawing that the supplementary valve would overtake the
main valve as soon as the finger piece I comes in contact with the ends j of the

page_text: box J by reason of the increased throw of the cut off rod E centered at a higher
point above the rocking shaft than the main valve, and that the period of cut off
might be varied by altering the throw of the cut off rod by means of the hand
wheel H. In order to render the cut off automatic under the control of the governor
I shape the finger piece I and the ends of the box J as illustrated, and arrange a
bow! M on a lever N pivoted upon the slotted pedestal and guide piece O rising from
the valve chest cover operated by the governor rod P, so that as the governor rises
and falls it shall vary the extent which the finger piece I projects into the box J,
and consequently vary the time at which the cut off valve overtakes the main
valve. Fig. 3 is a side elevation, and Fig. 4 an end elevation of my Invention
applied to a vertical engine. The main valve is worked in the ordinary manner
by the valve rod a, depending from the guide bar b; c is a lever centered at d in
the main frame e, and which is caused to reciprocate by being connected to the
guide bat f. The shorter arm of this lever drives the rod g, link h, and finger
piece i; j is a box working in guide K, and connected to the supplementary valve
by the rod l. The period of cut off is varied by the double armed lever m, n,
working in the link h, throwing the finger piece i further in or out of the box j
under the control of the governor rod o. The finger piece and box should be
serrated, as shown, to prevent slip. The weight of the supplementary valve and
rod is counterpoised by the spring p resting upon the extension q projecting from
the guide bar b, and bearing against the adjustable piece r fixed on the supple-
mentary valve rod l. By this means the supplementary valve moves with the
main valve until the finger piece i comes in contact with the box j, and effects an
accelerated movement of the supplementary valve. In Fig. 5 I illustrate a plan,
and in Fig. 6 a side sectional view of my improved supplementary valve formed as
a plate to lie under the main slide valve, and having openings through the same to
give the same action as in the previous modification. I find it advantageous to
use this form of plate valve for vertical and other descriptions of engines in which
the supplementary valve might otherwise have a tendency to slip the weight of the
slide valve upon this plate valve, serving to obviate this tendency. In conclusion
I would observe that these improvements are applicable to all classes of steam
engines in which a slide valve is employed, that by their application the cut off of
steam can be effected instantly, and varied to the greatest nicety, and at the samo
time less power is required to work the slide valve owing to its diminished area.
Having thus particularly described and ascertained the nature of this my said
Invention, together with the best methods with which I am acquainted for
carrying the same into practical effect, I wish it to be distinctly understood that I
do not confine myself to the methods of actuating my improved supplementary
valve hereinbefore described and illustrated on the accompanying Drawings, nor to
the relative proportions or dimensions of the several parts, as the same may be
considerably varied without departing from the Invention, but what I claim is,
1st. The improvements in slide valves of steam engines, substantially as and
for the purposes hereinbefore described and illustrated on the accompanying
Drawings.
2nd. The use and application of a supplementary slide or valve in the valve box
of steam engines, substantially as hereinbefore described and illustrated on the
accompanying Drawings.
In witness whereof, I, the said Edmund Pilkington, have hereunto set my