AUTOMATIC NON-DETACHING CUT-OFF FOR STEAM ENGINES
Year: 1885

page_text: We, JOHN BENJAMIN PITCHFORD, and WILLIAM THOMPSON GARRATT, both of
the City and County of San Francisco State of California, one of the United
States of America, Gentlemen do hereby declare the nature of our invention for
"AUTOMATIC NON-DETACHING CUT-OFF FOR STEAM ENGINES 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 certain improvements in Steam-engines and the cut-off
mechanism therefor. It consists of an equalizing arm or lever which is so con-
nected with the valve-stem of the engine that movement may be imparted to the
valve from two different sources at the same or at different times as may be required
for the purpose of opening and closing the valves and admitting and cutting off
steam to suit the load of the engine.
The equalizing lever has its swinging center attached to the valve-stem in such
a manner that the main eccentric can impart motion to one end of it, while another
cam or eccentric can impart motion to the other, so that the period of the cut-off
can be made to take place at any time from zero up to three-quarters of a stroke
without the use of any letting go or detaching device.
A cam or eccentric can be set to close the valve at stated periods, or it can be
made to close the valve automatically, by the varying speed of the engine acting
upon two swinging weights connected with toothed racks which engage a pinion
attached to the cut-off cam and turning it on the engine-shaft, so that when the
speed of the engine becomes too great, the weights by their centrifugal force move
outward, acting through the racks and pinion to cause the cam to advance so as to
bring the point of cut-off earlier in contact with the levers, the operation being
reversed when the engine runs too slowly.
Referring to the accompanying drawings for a more complete explanation of this
invention,
Figure 1 is a side elevation, showing our invention applied to an engine having
two rotary valves, each of which admits and exhausts steam; showing also the
reversing links.
Figure 2 is a section taken through the longitudinal axis of the cylinder, and
transversely to the valves.
Figure 3 is a view of the governing device.

page_text: Figure 4 is a perspective view of the equanizing rever, showing its
with the rocker-arm of the valve-stem.
Connec
Figure 5 is a side elevation, showing our invention applied to a " Corliss" engine.
Figure 6 is a plan or top view of the same.
The main feature of this invention consists in an equalizing lever swinging on
a pin at the outer end of the valve-stem rocker-arm, to which it is attached at
a point between its two ends.
The motion of an eccentric is imparted to one end of the lever, and the motion
of a cam is imparted to the other end of the lever, and the movement imparted to
the valve can be the result of the cam and eccentric in conjunction, the cam and
eccentric neutralizing each other, or the movement of the eccentric alone, and these
results can be accomplished automatically or by adjustment.
A is the steam cylinder having a transverse valve at each end. B is the engine-
frame. C is the pillow-block. D shows the path of the crank-pin. E shows the
position of the cross-head pin. F is the main reversing link, which is connected
to the forward and back eccentrics by the rods G G. The cut-off cam is represented
by H. Rollers 11' on the ends of levers K K¹ ruu in the groove of the cam.
The levers K K¹ are suspended on pins L L' near their centers, and the lower
ends are connected by rods M M to the cut-off reversing links N, which vibrate on
the pin O at their centers.
The link-blocks in the links N are connected by the rods P P to the lower end
of the equalizing or cut-off levers QQ, and these levers swing on pins R which are
fitted in arms U attached to the valve-stem.
The top ends of the cut-off levers QQ are attached to the sliding-block S by the
rods T T.
Figure 2 shows a longitudinal section in which A is an engine-cylinder, b the
piston, and c the piston-rod, d is the steam-chest with the inlet d', and e is the
exhaust-chamber which discharges at f. The valves g extend transversely through
chambers, so formed at each end between the steam and exhaust chambers that
the valves by their oscillation may open communication from the steam-chambers
to the cylinder through the port i and passage j, and when turned to the proper
point will open communication between the cylinder and the exhaust-chamber by
means of the curved passage k forined upon one side of the cylinder.
The valves are oscillated by rocker-arms U fixed to stems projecting through
stuffing-boxes in the ends of the valve-chambers.
Figure 3 shows the governing device by which the speed of an engine can be
controlled automatically. A gear a which is made in one piece with or connected
to the cam H, turns loosely with it on the engine-shaft, being controlled by
engaging with the toothed racks a at the end of the swinging levers t t. These
levers are pivoted upon the rim of the disc u, and having weights V V upon them,
are caused to move apart when the accelerated speed of the engine produces
sufficient centrifugal force.
When the speed of the engine is increased, the weights fly from the center and
pull the racks a which engage the pinion s, thus turning it and the cam on the
shaft in such a manner as to advance the point of cut-off.
When the speed is reduced, the arms tare drawn inward by the action of the
springs W, which have one end attached to the arms t, and the others to the peri-
phery of the disk at opposite sides. The arms t act upon the racks a and through
them upon the gear 8, thus rotating the cam backwards and changing the point
of cut-off.
In figures 5 and 6 the invention is shown as applied to that class known as the
"Corliss" engine, in which independent steam and exhaust valves are employed at
the ends of the cylinder. These valves have rocker-arms which are connected
with a disc, receiving motion from an eccentric upon the main shaft in the usual
manner.
In our invention the equalizing levers Q have their centres journaled upon the
crank-pins R of the rocker-arms U, the lower ends being connected with the disc,

page_text: while the upper ends are connected by the rods T with the levers J, which are
operated by means of the cam H upon the main or engine-shaft.
In this case the levers J are pivoted at the bottom to the pillow-block or engine-
frame as shown at m, and rollers n are journaled upon the levers J between their
points of suspension at n and the upper ends to which the rods T are attached.
These rollers are fitted to travel in the groove of the cam H shown at Figure 7,
and as the cam revolves upon its axis, the levers J are caused to reciprocate so as
to operate the equalizing levers Q and cut off steam at the desired point. In this
case the construction of the cam is such that but a single groove or channel is
necessary, as the rollers n lie upon opposite sides of the axis, and the cam is so
constructed that both rollers may be operated upon in the proper manner as the
cam rotates.
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. In a steam-engine valve-gear, an equalizing arm or lever swinging on the
crank or rocker-arm pin of a rotary valve at a point between its two ends, one end
being connected to and receiving motion from an eccentric, and the other end being
connected to and receiving motion in an opposite direction from a cam.
2. In a steam-engine valve-gear with two rotary steam inlet-valves, an equalizing
lever or arm, swinging or pivoted upon a pin between its two ends, one end being
attached by non-detaching connections to the eccentric, and the other end being
attached by non-detaching connections to a cam.
3. In a "Corliss" engine valve-gear with two steam valves; two levers swinging
on pins between their two ends attached to separate rotary valve-stems operating
valves at each end of the cylinder, one end of each lever being connected with
an eccentric with non-detaching connections, and the other end of each lever being
connected and moved from a cam by non-detaching connections, both valves being
operated by the same eccentric and one cam.
4. An engine valve-gear, having two main steam inlet valves, controlled by the
action of one eccentric for the admission of the steam, and one cam for cutting off
the steam without having separate cut-off valves, by means of swinging levers
pivoted at or near their centers on the valve-stems with one of their ends attached
to the eccentric, and the other ends attached to the cam, all connections having
hold of the valve, and non-detaching, substantially as described.
5. A reversible engine valve-gear, with two steam inlet-valves operated by two
eccentrics through a link motion conuected to one end of swinging levers upon the
valve-stems, while the other ends of the levers are connected to links which receive
motion from a cut-off cam.
6. A reversible engine, with two steam inlet valves operated by eccentrics to run
in either direction with a reversible cut-off motion operated by one cam, all the
connections retaining hold of the valve and being non-detaching.
7. An engine with swinging levers as described, connected to an eccentric and a
cam, the cam being moved on the shaft by the toothed racks engaging in the pinion
for the purpose of making the cut-off automatic.
8. The device with a cam set on the engine-shaft to cut off at a given point.