Year: 1887

page_text: Date of Application, 7th May, 1887
Specification Accepted, 7th June, 1887.
We, JOHN BENJAMIN PITCHFORD, residing at No. 807 Haight Street, and
WILLIAM THOMPSON GARRATT, residing at No. 405 Sixth Street, both of the city
and county of San Francisco, and State of California, one of the United States of
America, Gentlemen, 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:—
Our invention relates to a non-detaching cut-off valve-gear applied to engine-
valves.
It consists of an equalizing lever suspended and swinging from a point near its
middle, upon a pin or arm projecting from and imparting motion to a rotary valve.
One end of this equalizing lever is connected with a disk or rock-plate receiving
motion from the main eccentric, and the other end is connected through an inter-
vening bell-crank lever with the adjustable cut-off eccentric, so that a compound
motion is given to the equalizing lever, and through it transmitted to the rotary
valve which is thus opened to admit steam up to the point where it is desired to
cut-off, and then is rapidly closed.
Referring to the accompanying drawings,
Figure 1 is a side elevation of the rear side of the engine, showing the valve-gear
and also the governor upon the engine shaft.
Figure 2 is a vertical section taken through the engine cylinder, the steam and
exhaust valves with the relative positions of the connecting rods, equalizing levers, and
other parts shown in heavy black lines.
Figure 3 is a plan view of the engine.
Figure 4 is an enlarged vertical longitudinal section taken through the cylinder so
as to show the steam and exhaust ports, operating levers, connecting rods, etc., at one
end only of the cylinder, showing also the rock-plate which is actuated from the main
eccentric, and showing the various positions of the parts at different times, in dotted
lines.
Figure 5 is a perspective view of the equalizing lever, the rocker-arm by which it
is connected with the valve-stem, and upon which it is centrally fulcrumed; also the
bell-crank lever with which it is connected, and which receives motion from the cut-off
eccentric

page_text: A is an engine-cylinder, which in the present case is shown in a horizontal position
having the cylindrical oscillating steam valves B, lying in chambers horizontally and
transversely above the ends of the cylinder, and the exhaust valves C, in a like manner.
extending horizontally and transversely below the ends of the cylinder, each of the
valves covering ports or passages communicating with the interior, so that steam may
be admitted alternately to the opposite ends of the cylinder by the steam valves, and
exhausted therefrom in the same manner by the exhaust valves.
D is a disk, having a central spindle, upon which it oscillates, and motion is
communicated to it by the rod E, which extends from a pin on one side of the disk to
a pin upon the rock-lever or arm F. The latter, which is fulcrumed at its lower end,
is connected by an eccentric rod, indicated at G, (Figure 1), with the main eccentric
upon the engine shaft, so that when the engine is in motion the disk D receives an
oscillating motion.
The exhaust valves have rocker-arms connected with the lower part of this disk by
links H, so as to receive a regular oscillating motion by which they are opened to
allow steam to escape, and closed at the proper time when steam is being admitted
through the steam valves.
The steam valves B, which are more plainly shown in Figure 4, illustrating one end
of the cylinder and valve-chambers in section, oscillate within a chamber which
receives steam from the inlet I, and by means of the oscillation of the valves, steam
is admitted to the cylinder through ports J, as shown, and its admission is cut off by
the closing of these ports.
This is effected as follows:-
Upon the stem K, which extends outward through the end of the valve-chamber,
is fixed a rocker-arm L, having a pin at its outer end, upon which is hung an
equalizing lever M, these parts being plainly shown in Figure 5.
The lower end of this equalizing lever is connected with the rocker-plate D, by
means of a rod N, and the upper end of the equalizing lever is connected by a rod Ŏ
with one arm of a bell-crank lever P, which is fulcrumed just above the cylinder.
There is one equalizing lever and a bell-crank lever connected with each of the
steam valves, as shown in Figure 1, and the opposite arms of the bell-crank levers are
connected together by a rod Q, so that they will move in unison, the corresponding
arms of the bell-crank levers being connected by a rod R with a rock-lever S, which is
fulcrumed to the frame.
This lever is connected by a rod T, with the cut-off eccentric, and through it
motion is transmitted to the bell-crank levers P, in such a manner that they will act
through the equalizing levers M, upon the valve and close it at the proper time. The
cut-off eccentric is fitted to turn upon the engine shaft U, (Figure 1), and is
connected with a centrifugally acting governor, shown but not here described, by the
action of which this eccentric is either advanced or retracted so as to vary its action
upon the bell-crank levers and valves to correspond with the work of the engine and
its increased or decreased speed.
The operation of the device will then be as follows:-
The piston being at one end of the cylinder and ready to take the steam, the upper
end of the equalizing lever M will be held approximately stationary by reason of the
position of the bell-crank lever and the rock-plate D operated by the main eccentric,
will, through its connection with the lower end of the lever M, rotate the valves
sufficiently to open the ports and admit steam to the cylinder, the continued move-
ment of the engine shaft moves the main and cut-off eccentrics; but the peculiar
movement of the bell-crank lever P, about its fulcrum is such as to retain the valve
fully open up to the point where it is desired to cut off steam.
.
The bell-crank lever P, will then have reached such a point that its further move-
ment operates in conjunction with the equalizing lever and the disk D, to suddenly
close the valve and cut off the admission of steam.
It will be seen that the cut-off eccentric can be advanced about a quarter of a turn,
or during the period of over half the stroke, without moving the lower end of the
equalizing lever a sufficient amount to materially alter the position of the steam valve;

page_text: this depending upon the position of the bell-crank lever P, which moves in such a
manner that the arm connected with the equalizing lever only travels over a distance
equal to half the difference between the versed sine of the arc described by the lever
and that of the swinging link.
This movement is so slight that the main valve is not moved by the cut-off eccentric
during a period of half of the stroke of the piston, unless the action of the governor
advances the cut-off eccentric.
It will thus be seen that the last part of the arc moved through by the bell-crank
lever, imparts nearly all the motion that is given to the equalizing lever, and this
motion is comparatively rapid, so that the steam is cut off at once.
By means of this device, a range of cut-off can be obtained from zero to
three-fourths of the stroke.
Having now particularly described and ascertained the nature of our said invention,
and in what manner the same is to be performed, we declare that what we claim is
1. A lever suspended and swinging on an arm fixed to the steam valve-stem of an
engine, a connection between one end of this lever and an ordinary eccentric or rock-
plate, connections between the other ends of said lever and a variable or adjustable
eccentric operated by a governor, and a lever or disk interposed between the variable
eccentric and said lever-end, whereby the position of the suspended lever is changed
and accelerated motion is imparted to the valve in the latter part of its movement,
substantially as described.
2. In an engine, a bell-crank or arm turning on a fixed center, connected with an
eccentric by which it is caused to reciprocate, in combination with a swinging link
connecting the other arm, with one end of a lever suspended and swinging on a pin
connected with a steam valve-stem, said connection being such that the bell-crank or
arm imparts little or no motion to the lever in the first portion of its movement, and
causes accelerated motion at the last part of its movement to close the steam valve
quickly, substantially as described.
3. In an engine, a rotary valve and an equalizing arm or lever, having its central
portion swinging upon a pin on the rocker-arm by which the valve is moved, a fixed
eccentric imparting motion to the opposite end of the equalizing lever through any
suitable connections, another eccentric imparting motion to the opposite end of the
equalizing lever through a bell-crank arm or disk turning on a fixed center, and
imparting an irregular motion to the end of the equalizing lever with which it is
connected, substantially as described.
4. In an engine, a rotary or oscillating valve having an equalizing lever centrally
suspended and swinging upon the pin of its rocker-arm, a bell-crank arm or disk and
link through which motion is communicated to one end of the equalizing lever, in
combination with the eccentric or eccentrics loosely mounted upon a shaft driven by
the engine, and the governor connected with said eccentric or eccentrics, and operating
substantially as described.
2
1005