Improvements in Trip Valve Gear for Engines operated by Steam or other Expansive Fluid
Year: 1897

page_text: Date of Application, 7th Jan., 1897
Complete Specification Left, 6th Oct., 1897-Accepted, 4th Dec., 1897
66 Improvements in Trip Valve Gear for Engines operated by Steam
or other Expansive Fluid."
I JAMES MARSHALL of Britannia Iron Works Gainsborough in the County of
Lincoln Engineer do hereby declare the nature of this Invention to be as
follows:-
My Invention has for its object to provide a simple and efficient valve gear of
the kind known as trip gear which can be regulated by hand or automatically by a
governor.
According to my Invention the valve lever is operated by a bell-crank lever
centred to links which links turn on a pin which may be the same pin as that on
which the valve lever turns. The said links are operated by an eccentric on a
lay shaft or by other suitable means which will impart the requisite vibratory
movement to the links and in the bell crank lever carried thereby. One arm of
the said bell-crank lever is provided with a steel face piece the lower end of which
during the active stroke comes at the point of lead into contact with the upper
end of a steel face piece on the valve lever and the said valve lever operates the
valve spindle (through a cross-head connection therewith) to admit motive fluid.
The other arm of the said bell-crank lever extends at right angles inwards towards
the centre of the valve and the disengagement of the said bell-crank lever from
operative bearing on the valve lever is effected by the said arm coming into contact
with a stop carried by an arm on an eccentric strap embracing an eccentric or cam
actuated by the governor the last named arm and strap being so centered or arranged
that the impact of the bell-crank arm with the stop does not exert any back
pressure on the governor.
The valve lever, being thus released from contact with the bell-crank lever,
returns to its normal position and the valve is closed. On the upward stroke the
side of the steel face piece on the bell-crank lever slides against the side of the
steel face piece on the valve lever until it rises above it when the bell-crank lever
returns to such a position that the bottom of its steel face piece is over the top
of the steel face piece on the valve lever ready for again operating the valve on the
next down stroke. The degree of engagement of the bell-crank lever with the
valve lever is restricted by a stop on the links so situated that only a limited engage
ment of the steel faces takes place, the amount of such engagement being constant
for any point of cut-off. The stop which releases the bell-crank lever from engage-
ment with the valve lever is automatically varied in position by reason of the
governor acting on the eccentric or cam and so moving the arm of the strap
embracing the eccentric or cam so that the position of the stop carried by the said
arm (which stop may be an adjustable screw) and consequently the time of cut-off
by the valve are altered as required by the governor according to the action of the
engine. The point of cut-off may if desired be regulated by hand instead of

page_text: automatically by turning the shaft which carries the eccentric or cam by means
of a device such as a hand wheel and lever.
Dated this 7th day of January 1897
JOHNSONS & WILLCOX,
47 Lincolns Jun Fields London W.C. Agents.
66 Improvements in Trip Valve Gear for Engines operated by Steam
or other Expansive Fluid."
I, JAMES MARSHALL of Britannia Iron Works, Gainsborough in the County of
Lincoln, 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 Invention has for its object to provide a simple and efficient valve gear of
the kind known as trip gear which can be regulated by hand, or automatically
by a governor.
I will describe my invention with reference to the accompanying drawings.
Figure 1 shewing the gear in mid-position on the downward, or active, stroke;
and Figure 2 shewing it on the return stroke, after the release.
According to my invention the valve lifting lever A, is operated by a bell-crank
lever C, centered at C, to links M, which links turn on a pin by preference the same
pin K, as that on which the valve lifting lever A, turns. The said links M, are
operated by an eccentric on a lay shaft, (the connection with which is indicated
at N), or by other suitable means, which will impart the requisite vibratory move-
ment to the said links M and to the bell-crank lever C carried thereby. One arm
of the said bell-crank lever C is provided with a steel face-piece G, the lower part
of which, during the active stroke, comes, at the point of lead, into contact with the
upper part of a steel face-piece H, on the end of the valve lifting lever A, and, by
depressing the said end, operates the valve spindle P, (through a cross-head con-
nection therewith), and lifts the valve to admit motive fluid to the cylinder. The
other arm of the bell-crank lever C extends, as shewn, inwards towards the centre
of the valve, and the disengagement of the said bell-crank lever C, from operative
bearing on the face H, of the valve-lifting lever, is effected by a set pin D, on the
said arm C, coming into contact the steel faced stop-lug e formed on an eccentric
strap L, embracing an eccentric, or cam, E, actuated by the governor. The
eccentric strap L, is provided with jaws on the opposite side, which jaws embrace
a loose collar turning on a fulcrum pin R, the space between the embracing jaws
allowing of the lengthwise movement of the strap L under the action of the
eccentric or cam E. This arrangement compensates for the pressure exerted on
the stop-lug e by the bell-crank lever C and prevents back pressure from coming on
the governor.
On the release of the face G, from the face H, the bell-crank lever C returns to
its normal position and the valve closes. On the return, or upward, stroke, the
side of the steel face-piece G, on the bell-crank lever C slides against the inside
of the steel face-piece H, on the valve-lifting lever A, until the face-piece G, rises
above the face-piece H, when the bell-crank lever C, returns to such a position
that the bottom of the face-piece G, is over the top of the face-piece H, so that,
on the downward stroke, the valve-lifting lever A is again depressed and the valve
opened. The amount of engagement of the face-piece G, with the face-piece H,
is restricted by the stop F, on the links M, such amount of engagement being
constant for any point of cut-off. The stop-lug e, carried by the eccentric strap L,
''

page_text: which releases the bell-crank lever C, from engagement with the valve-lifting
lever A, is automatically varied in position by the governor acting, through a
shaft, or spindle, B, on the eccentric, or cam, E, to partially rotate it, in one, or the
other direction, so that the position of the said stop-lug e, and consequently the
length of time the valve remains open, and its point of closing, are determined
by the governor and thus the admission of motive fluid is regulated so as to main-
tain a constant speed of the engine under varying load. The stop-lug e, may be
an adjustable screw instead of the part 1) being adjustable as shewn.
In the case of engines having high and low pressure cylinders the gear on the
low pressure cylinder may be regulated by hand if desired by rotating the eccentric,
or cam, E, by a hand-wheel, or lever, or other suitable device.
In place of a pair of links M, one link only may be used; but it is preferred to
use a pair of links with the operating connection and levers between them.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed I declare that what I claim is:-
1. In trip valve gear operated by steam, or other expansive fluid, the combination
with the valve lever of a link, or links, operated from a moving part of the engine,
and turning on the same centre as the valve lever, and carrying a bell-crank lever
having an arm tending to fall towards the centre of the valve and another arm to
act upon the valve lever, a stop carried by the link, or links, determining the
amount of engagement between the bell-crank lever and valve lever, so as to be
constant for all points of cut-off, the said levers being arranged and acting sub-
stantially as, and for the purpose, hereinbefore described.
2. In trip gear for engines operated by steam, or other expansive fluid, the com-
bination, with the trip mechanism, of an eccentric, or cam, operated by the
governor and acting on a lever carrying a stop for releasing the trip lever, and so
supported, on the other side, as to prevent the tripping action exerting back
pressure on the governor; substantially as herein before described.
3. The arrangement and combination of parts constituting the trip gear as
hereinbefore described and illustrated in the accompanying drawings.
Dated this 6th day of October 1897.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.