Improvements in Steam and other Engines and Pumps.
Year: 1892

page_text: Date of Application, 30th Sept., 1892
Complete Specification Left, 28th June, 1893-Accepted, 5th Aug., 1893
PROVISIONAL SPECIFICATION.
Improvements in Steam and other Engines and Pumps.
I WILFRID L. SPENCE, of The Elms, Seymour Grove, Manchester, Civil
Engineer, do hereby declare the nature of this invention to be as follows:-
My improvements relate to steam and other engines, pumps, &c., and have
reference to that class of engine known as the "Central Valve," i.e., in which the
piston or pistons is or are carried by a hollow trunk or piston rod through which
the slide valves work.
Hitherto such engines while possessing many advantages over all other types for
quick running have laboured under three main disadvanges. (a). The point of
cut-off is fixed and cannot conveniently be altered automatically so as to vary the
ratio of expansion. (b). The central valve being actuated from the outer or crank
shaft end of the cylinder must, from the nature of the case, be solid and is therefore
subjected to the full pressure of steam at the inside end while the outer end has
only the exhaust pressure against it. The valve is consequently unbalanced.
(c). A certain complication, accompanied by increased cost of manufacture, is
inevitable from the desire to have all strains acting along straight lines (there are
three connecting rods on one crank pin to each line of cylinders).
actuated from the
In my improved engine the central valve is retained but
back or inner end of the cylinder or line of cylinders. The requisite motion may
be communicated to the valve spindle in several ways but I prefer one or other of
the two following
-
Method A. At one or both ends of the crank shaft, (preferably outside the
closed crank chamber if such is used), I place a flywheel governor of the well
known shifting eccentric type. The eccentric will have an equivalent radius
differing slightly from that of the crank pin and it will have the requisite lead so
that the valve travel is in advance of, and may be greater or less than that of the
piston and trunk. A connecting rod conveys the eccentric motion to a beam or
rocking lever, mounted over the cylinder or line of cylinders, which in its turn
actuates the valve by a spindle or trunk passing through a packed gland into the
steam dome surmounting the engine.
Method B. A reciprocating movement is communicated to the valve, by a disc
or arm oscillating in a vertical plane, about a horizontal axis, to which it is con-
nected by a short link. A spring is so arranged that when this arm has been
turned, (by coming in contact at certain parts of the stroke with one or other of
two stops or tappets), through a given angular distance on either side of a dead
point it will pull the arm over and amplify the movement already imparted. This
gear is carried preferably by a projection from the main trunk, thus moving in
unison with it. The lines of action of the spring and the positions of the limiting
stops are so arranged that, in the one case, the valve is opened to exhaust just as
the piston is completing the down stroke, and in the other, the valve is closed to
exhaust, for compression, and then opened to steam at about three-fourths of the
up stroke and on completion of the same respectively. Thus from a straight line
motion I am enabled to obtain the effect of an eccentric with lead. If desired the
two tappets may be so arranged on a spindle that their relative or absolute positions
can be adjusted to vary the point of cut-off.
In order to have the valve balanced so far as steam pressure is concerned I
construct it with a central steam way through from end to end so that the pressure
on the lower may be at least equal to that on the upper surface. By enlarging the
section a little at the outer, and by reducing it somewhat at the inner end the
gravity also of the valve may be compensated. I sometimes find it convenient to

page_text: do this by continuing the latter end as a small trunk passing steam tight through a
packing ring in the end of the main piston trunk.
If it is desired to have the steam always cut off at a fixed point it may be
accomplished by the method described in the Specification of P. W. Willans,
No. 13769, 1884. This is by closing the upper or inside end of the trunk and
admitting steam through ports in the sides thereof, which ports by passing into and
through a packing ring shut off the steam at any predetermined point.
Dated this 30th day of September 1892.
COMPLETE SPECIFICATION.
Improvements in Steam and other Engines and Pumps.
I, WILFRID L. SPENCE of 9, Newark Drive, Pollokshields, N.B., Civil
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 improvements relate to steam and other engines, pumps and meters and have
reference to that class of engine known as the "Central Valve," i.e., in which the
piston, or pistons, is or are carried by a hollow trunk through which the slide valve
works.
.
Hitherto such engines, while possessing advantages over all other types for quick
running, have laboured under three main disadvantages: (a) The point of cut off
is fixed and cannot conveniently be altered automatically so as to vary the ratio of
expansion; (b) The central valve, heing actuated from the outer or crank. shaft
end of the cylinder, must from the nature of the case be closed at this end and it is
therefore subjected to the full pressure of steam tending to force it in one direction.
The valve is consequently unbalanced; (c) A certain complication accompanied by
increased cost of manufacture is inevitable if the valve is actuated by a straight
rod: The eccentric being in the middle of the crank pin with main connecting rods
on each side of it.
In my improved engine the central valve is retained but it is actuated from the
back or inner end of the cylinder or line of cylinders. The requisite motion may
be communicated to the valve in several ways but I prefer the following which is
quite suitable for high speed steam and other engines.
At one or both ends of the crank shaft (preferably, but not necessarily, outside
the closed crank chamber if such is used) is placed a flywheel governor of the well
known shifting eccentric type. The eccentric may have an equivalent radius
differing but slightly from that of the crank pin and it will have the requisite lead
so that the relative motions of the valve and piston are such as usually obtain in
engines of this class. An eccentric rod transmits the motion to a beam or rocking
lever mounted over the cylinder or line of cylinders which in its turn actuates the
valve by a spindle or trunk passing through a gland into the steam dome or chest
surmounting the top cylinder.
It will be seen that by this method of operating the central valve the hollow
piston rod need not be open to the crank chamber with its exhaust, or atmospheric,
pressure. Hence by having a steam passage through the valve from end to end
and communicating with the steam chest the valve may be balanced so far as steam
pressure is concerned.
Similarly by proportioning the diameter of the valve trunk, where it passes out
of the steam chest, to the diameter within the piston rod a perfect balance, or any
desired constancy of unidirectional pressure, may be arranged.
If it is desired to have the steam always cut off at a fixed point as
maximum it
may be accomplished by the method described in the Specification of P. W. Willans,
No. 13769, 1884. This by closing the upper or inside end of the trunk in any
appropriate way and admitting steam through ports in the sides thereof, which

page_text: ports by passing into and through a packing ring shut off the steam at any
predetermined point.
My improved construction, doing away with the necessity for an eccentric on the
crank pin and two main connecting rods, is both simpler and stronger than previous
designs, and by employing a flywheel governor as indicated the engine becomes, by
reason of the variable cut off, very much more economical at light loads.
It will be obvious that my improvements are equally applicable to single or
double acting, simple or compound engines either horizontal or vertical, and that
they are not limited to a single line of cylinders.
In the accompanying drawing which is intended merely to indicate the principle,
V is the valve trunk actuated by a rocking arm A, through a link L. E is the
eccentric rod provided with a ball and socket joint at B. The main trunk M,
carries a piston P, and passes into the steam dome or chest C.
I have abandoned the constructions described in my Provisional Specification
under "Method B" and make no claim thereto.
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 1
claim is
1. In a central valve engine the combination with an eccentric or equivalent
device on the crank shaft of means for transmitting the motion of the same to the
valve through the back or inner end of the cylinder or line of cylinders, sub-
stantially as described.
2. In a central valve engine the combination with a flywheel governor of the
shifting eccentric type mounted on the crank shaft of a valve operated by the
same through the back or inner end of the cylinder or line of cylinders, substantially
as described.
3. My improvements in central valve engines substantially as described.
1000
WILFRID L. SPENCE.