Improvements in Automatic Cut-off Mechanism for the Slide Valves of Steam and other Engines.
Year: 1890

page_text: Date of Application, 1st Oct., 1890
Complete Specification Left, 1st July, 1891-Accepted, 1st Aug., 1891
PROVISIONAL SPECIFICATION.
Improvements in Automatic Cut-off Mechanism for the Slide Valves
of Steam and other Engines.
We, GEORGE FLETCHER, of Masson Works, Litchurch, in the County of Derby,
Engineer, and WILLIAM PRICE ABELL, of Essequebo, British Guiana, and Tooley
Park, in the County of Leicester, Mechanical Engineer, do hereby declare the
nature of this invention to be as follows:-
Our invention relates to cut-off mechanism for steam, compressed air and other
engines, and consists in combining with the slide valves of such an engine a valve
and appliances as hereinafter described.
A suitable arrangement for carrying our invention into practice is as follows,
that is to say, we mount on the top or back of the ordinary slide valve a double
ended valve (advantageously in the form of a bobbin) which is free to slide upon a
rod or other guide between two seats or ports at either end of the said slide valve.
By such sliding of the double ended valve, one of the steam ports in the slide valve
can be closed, and the other at the same time opened.
Near the centre of this double ended valve we fix a wedge or cam, which is
moved by the engine in such a manner that during the travel of the main slide
valve the double ended valve will impinge against it, the amount of movement
varying with the position of the cam, as determined and regulated by the governor.
So long as the engine is nearly at its normal speed, the steam is cut off at proper
times by the action of the double ended valve and the cam or wedge, but when the
speed of the engine increases the governor operates the cam or wedge, and gives it
such a position that the steam is cut off earlier by reducing the length of the travel
of the double ended valve.
Instead of employing a double ended valve, we may use separate valves in such a
manner that as the main slide valve completes its stroke, it carries alternately each
cut-off valve against a projection or stud in such a manner as to open the valve
actually in contact, thus leaving it in position for full admission of steam at the
commencement of the stroke; this takes place at each end alternately.
We can also open these valves, if desired, by allowing their ends to project and
come in contact with a fixed wedge in either end of the steam chest; the closing of
the valves being determined by the varying position of the cam or lever, or wedge
actuated by the governor.
•
Cones or cylinders are sometimes used to encircle the valves, in order that the
steam is directed past the said valves in such a manner that its velocity assists in
closing the same.
COMPLETE SPECIFICATION.
Improvements in Automatic Cut-off Mechanism for the Slide Valves
of Steam and other Engines.
We, GEORGE FLETCHER, of Masson Works, Litchurch, in the County of Derby,
Engineer, and WILLIAM PRICE ABELL, of Essequebo, British Guiana, and Tooley
Park, in the County of Leicester, 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 :-
Our invention relates to automatic cut-off mechanism of the kind forming the

page_text: subject of British Letters Patent granted to one of us dated November 4th 1884
No. 14577 and of United States Letters Patent dated November 18 1884
No. 308181 granted to J. H. Man and in which cut-off valves adapted to be closed
by differential pressure are employed.
The object of our present invention is to provide improved means for controlling
the movements of such valves and principally to effect the positive opening of the.
same, and to this end it comprises the improvements hereinafter described.
In the accompanying drawings:
Figures 1 and 2 are an elevation and sectional plan of a valve-chest and a slide-
valve provided with our improvements:
Figure 3 is a view similar to Figure 2 illustrating a slight modification:
Figures 4 and 5 are a sectional elevation and transverse section respectively,
illustrating another modification :
Figure 6 is a sectional plan shewing a slide-valve provided with two cut-off valves
having double faces and double seats:
Figure 7 is an elevation shewing an arrangement of slide-valve and cut-off valve
suitable for a vertical engine; and,
Figure 8 is an elevation shewing another arrangement of valve suitable for a
vertical engine :
Figures 9 and 10 are a sectional elevation and transverse section respectively
shewing a slide-valve provided with two cut-off valves of similar construction but
arranged in a different manner to those shewn in Figure 6:
Figure 11 is a sectional plan shewing a slide-valve provided with a single cut-off
valve having double faces and double seats.
Similar letters of reference indicate corresponding parts in the several
figures.
a, a indicate the slide-valves, b, b passages therein through which the motive fluid
passes to the induction ports of the cylinder, c, c the cut-off valves for controlling
the flow of motive fluid through the said passages, and d, d cam-surfaces or tappets
or stops which regulate the operation of the cut-off valves.
As shewn in Figures 1 and 2 the cut-off valve c, which is provided with a recess
between its two faces, is adapted to slide upon a spindle e so as to close one or the
other of the ports or openings f communicating with the passages b, and the tappet d
which projects into the said recess is of a wedge or cam-shape and is mounted upon
a shaft g in such a manner that, by rotating the said shaft g, the tappet can be
moved according to the cut-off required. This shaft g is connected with the
governor of the engine so that the position of the tappet d is regulated according to
the speed of the engine.
When the slide-valve is in motion and the cut-off valve c rests loosely on the
spindle e it will travel in the same direction as the slide-valve until one of its ends
comes into contact with the tappet d; during the further movement of the slide-
valve the spindle e slides through the cut-off valve until the seat around one of the
openings of a passage b comes so close to the said valve that the velocity of the
steam or air flowing into the passage, together with the difference of pressure in
the passage and in the valve-chest, causes one end of the cut-off valve to close
against its seat to cut off the supply of motive fluid; the valve will then remain
closed and travel with the slide-valve until the motion of the latter is reversed.
On the return stroke the other end of the cut-off valve comes into contact with the
tappet, thereby drawing the end of the valve, first referred to, away from its seat
and so on, the same movements taking place alternately at opposite ends of
the valve.
When the tappet is in such a position that only the thin end or apex comes into
contact with the valve, the said cut-off valve will come to rest later than if it came
into contact with the wider part of the said tappet, thereby allowing a longer
period of time to elapse and consequently a greater portion of the piston stroke to
be performed before the motive fluid is cut-off.
In the modification of our invention shewn in Figure 3, the arrangement is

page_text: substantially the same as that hereinbefore described, except that guide-flanges h
are arranged around the openings to the passages b, in order to direct the steam or
air so as to flow over the edges of the ends of the cut-off valves rather than to flow
into the said openings from all directions, thereby ensuring a greater sensitiveness
and more immediate action than would otherwise be obtained.
In Figures 4 and 5 the tappet d instead of being connected to the rotary
spindle y,
is connected directly to the governor-spindle by which it is raised and
lowered, the bottom end of the said tappet being held in position by means of a
guide-bracket . The action of the valve in this case is the same as that herein-
before described.
In the arrangement shewn in Figure 6, instead of using a single valve as herein-
before described, we employ two cut-off valves, one in connection with each passage b.
In this case the closing of the valves is effected by the use of a double ended
lever m, the inclination of which regulates the point at which the closing shall take
place. The opening of the cut-off valves is effected by means of the adjustable
steps d, d in the walls of the valve-chest.
In the arrangement shewn in Figure 7 which especially applicable for use in a
vertical cylinder engine the cut-off valve is represented as moving in a line at right
angles to the line of motion of the slide-valve. The tappet d is in this case similar
in construction to the lever m described with reference to Figure 6, but the valve c
instead of striking directly upon the ends of the said tappet strikes the same upon
the sides and then slides along it.
In the arrangement shewn in Figure 8, which also represents a slide-valve having,
a cut-off valve moving in a line at right angles to the line of motion, the tappet d is
at one end of a bell-crank lever which is free to move upon a pin or stud n fixed to
the slide-valve. The end of the bell-crank lever which does not serve as the tappet
is slotted as at o and is free to move about a movable pin p. When the slide-
valve a is in a central position, the tappet end of the bell-crank lever will be in a
vertical position and the slotted end in a horizontal position, and, if a reciprocating
motion is given to the slide-valve, the tappet end of the said lever will deviate to
the right hand side of the vertical line when the valve is moved upwards and the
left hand side when the valve is moving downwards. The amount of deviation
depends on the distance of the pin p from the vertical centre line of the slide-valve
thus determining the position of the cut-off valve. The pin p is moved in the slot o
by means of the governor.
In the arrangement shewn in Figures 9 and 10 the slide-valve a is provided with
two cut-off valves c, e arranged and operating at right angles to the line of motion
of the slide-valve. Each valve c is provided with a spindle e projecting through
the top of one of the passages b, b, and the inclined surfaces d, d are stationary, the
spindles of the cut-off valves during the reciprocation impinging against the said
inclined surfaces whereby the valves c, c are caused to open; g is a spindle connected
to the engine governor and having a sleeve 9 free to slide upon it, so as to move
with the valve a but working on a feather-key so as to turn with the said spindle.
Integral with the sleeve 9 are two small levers r, which, when the spindle
turned by the governor, adjust the position of the cut-off valves c, c so that the
pressure of steam closes them, the two faces of each valve being of different areas
to enable this to be effected. When the slide-valve a in moving nears one end of
the valve-chest the spindle e nearest the said end comes into contact with the
inclined surface d also at the said end and causes its valve c to open, the amount of
such opening being controlled by one of the levers r.
9 is
In the arrangement shewn in Figure 11 the cut-off valve is provided at each end
with double faces c, c and double seats and is operated upon by a cam or tappet d
similarly to the valve shewn in Figure 1. In this arrangement, however, the steam
flows into the passages b, b past the two faces c and c at each end of the valve as
in the arrangement shewn in Figures 6, 9, and 10.
Having now particularly described and ascertained the nature of our said

page_text: invention and in what manner the same is to be performed, we declare that what
we claim is :
1. The combination with the slide-valve (or each of the slide-valves if two or
more are employed) of a steam or compressed air engine, such slide-valve being
provided with a cut-off valve or valves of the kind hereinbefore described adapted
to be closed by differential pressure, and a cam-surface or tappet against which the
said cut-off valve or valves comes or come in contact during the reciprocation of the
slide-valve, and which serves to effect the opening of such cut-off valve or valves
after it or they has or have been closed by the differential pressure, substantially as
described.
2. The combination with a slide-valve having a cut-off valve operated by
differential pressures, of a cam-surface or tappet for positively opening such valve,
the said cam-surface or tappet being connected with the engine governor, substan-
tially as, and for the purpose, described.
3. A slide-valve provided with two cut-off valves having double faces and double
seats and adapted to come into contact with stops at each end of the valve-chest,
substantially as described.
4. The combination with a slide-valve having a cut-off valve or valves, of a
tappet in the form of a cam, inclined surface or lever, substantially as, and for the
purpose, set forth.
5. The combination with a slide-valve having cut-off valves adapted to be
operated as described, of flanges for directing the motive fluid into the openings
covered by the said cut-off valves, substantially as described.
Dated the 1st day of July 1891
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicants.