Improved Cut-off Mechanism for the Slide-valves of Steam and other Motive Power Engines.
Year: 1890

page_text: Date of Application, 13th Feb., 1890
Complete Specification Left, 13th Nov., 1890-Accepted, 13th Dec., 1890
PROVISIONAL DIEUITUATION.
Improved Cut-off Mechanism for the Slide-valves of Steam and other
Motive Power Engines.
+
I, THOMAS METCALFE, of St. James' Ironworks, Moss Street, Bradford, in the
County of York, Engineer, do hereby declare the nature of this invention to be as
follows:
This invention relates to certain improvements in the cut off mechanism for the slide
valves of steam and other motive power engines, and consists in combining with a
slide valve a cut off plate, and actuating the whole through one eccentric rod in the
manner as hereinafter described.
At the back of the slide valve I have a cut off plate, and I cast the slide valve
with a projection which carries a pin on which 1 pivot an arm or lever attached
to the cut off plate. I couple up to the slide valve an eccentric rod in the ordinary
way, and in order to effect the cut off I have at the back of the cut off plate a shaft
carrying two stop pieces, one at each side, which arrest the motion of the lever
attached to the cut off plate, and cause the latter to travel in the opposite direction to
the main slide valve, thus closing the valve and cutting off the pressure to the cylinder.
The position of the stop pieces on the shaft I regulate by the governors, or if the
engine is not required to be automatic the same can be regulated by hand.
Dated this 19th day of February 1800
J. SIDNEY CRITCHLEY,
Agent for the Applicant.
COMPLETE SPECIFICATION.
Improved Cut-off Mechanism for the Slide-valves of Steam and other
Motive Power Engines.
1, THOMAS METCALFE, of St. James'. Ironworks, Moss Street, Bradford, in the
County of York, 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:-
This invention relates to certain improvements in the cut off mechanism for the
slide valves of steam and other motive power engines, and consists in combining with
a slide valve a cut off plate and actuating the whole through one eccentric rod in the
manner as hereinafter described.
In order to elucidate my invention I append sheets of drawings marked with letters
of reference, and in every figure of the drawings like letters denote like parts.
Fig., 1 represents a section of a slide valve and cut off plate for a steam or other
motive power engine, with a partial section of the steam and exhaust ports in con-
nection therewith, arranged according to my invention.
Fig. 2 represents an end view of the valve and cut off arrangement,
Fig. 3 a plan of same, and
Fig. 4 a plan of the valve without the cut off plate.
The scale of the drawings is half full size, the valve as drawn being suitable for
a steam cylinder nine inches in diameter.
The letter A indicates the slide valve of an ordinary steam engine with one eccentric
and rod, having steam ports A' A', and exhaust port A constructed after the usual
fashion with the exception that I have at the back of same two projections or
arms B B. The letter C marks a cut off plate the back of which is toothed and into
which gears a toothed segment D pivotted on a pin E attached to the projections B B
of the valve A. F is the valve spindle and G a shaft which receives a circular motion

page_text: from the governors of the engine through a lever G'. H H are two stop pieces fixed
onto the shaft E by set screws, and K K are inclined projections cast onto the
segment D and arranged so as to come into contact with stop pieces H H in the
manner as hereinafter described.
In operation the action of the arrangement is as follows. The valve A is being
drawn say from left to right, the cut off plate C being also carried in the same
direction by means of the toothed segment D until the inclined projection on the
toothed segment is drawn to and comes into contact with the stop piece H on the
shaft G, when the horizontal motion with the slide valve A is arrested and the segment
oscillates on the pin E giving to the cut off plate Ca contrary motion to the valve A,
thereby closing the port and cutting off the steam to the cylinder. The exact period
at which the steam is cut off depends on the position of the stop pieces H H relative
to the inclined projections K K. It will easily be seen that as the shaft E is turned
in either direction by the rise or fall of the governors of the engine, the stop
pieces H H are faced opposite varying parts of the inclined projections K K, thus the
horizontal motion of the toothel.segment is arrested sooner or later according to
what part of the inclined projections K K strike against the stop pieces H H.
Figs. 5. 6. 7 & 8 show the same arrangement of cut off applied with a circular cut
off plate, Fig. 5 being a section of the arrangement similar to Fig. 1, Fig. 6 an end
view, Fig. 7 a plan and Fig. 8 a plan of the valve without the cut off plate.
In this instance the back of the slide valve A is made concave, and the cut off
plate C pivotted onto the pin E by means of an arm or lever, the centre of the pin E
being taken as the centre of the radius of the face of the cut off plate. The arm
connecting the cut off plate C to the pin E is fitted with inclined projections similar
to the segment D to meet the stop pieces H H on a shaft G, in the manner and for
the
purpose previously set forth.
Fig. 9 shows another modification of the toothed segment, in place of which I show
a slotted lever L pivotted on the pin E, into the slotted end of which fits a pin P
attached to the cut off plate C.
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 I
claim is :-
In combination with the slide valve of a steam or other motive power engine, a cut
off plate attached to the slide valve by means of a toothed segment or lever, and
appliances for changing the horizontal motion of the toothed segment or lever into an
oscillating motion, substantially in the manner as shown and described and for the
purpose herein set forth.
In combination with the slide valve of a steam or other motive power engine, a cut
off plate attached to the slide valve, and appliances for changing the horizontal motion
of the cut off plate into an oscillating motion substantially in the manner as shown
and described, and for the purpose herein set forth.
Dated this 10th day of November 1890.
J. S. CRITCHLEY,
Agent for the Applicant.