Improvements in Trip Expansion Gear for Motive Power Engines.
Year: 1893

page_text: COMPLETE SPECIFICATION.
Improvements in Trip Expansion Gear for Motive Power Engines.
I, GEORGE THORNLEY of Waterloo Engineering Works Burton-on-Trent in the
County of Stafford, 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 means whereby the governor of motive
power engines provided with trip gear and operated by steam or other expansible
motive fluid is caused to vary in a more efficient and perfect manner than hitherto
the point in the stroke of the piston at which the steam or motive fluid is cut off.
According to my invention, I provide for acting upon the trip lever which opens
the valve, a longitudinally reciprocating circularly disposed projection, shaped so
that as it is moved round it presents a varying length to act on the trip lever
which opens the valve the time during which the valve remains open and conse-
quently the period of cut off of motive fluid to the cylinder, being in accordance
with the portion of the projection which is by its movement of partial rotation,
brought into position to act upon the trip lever. The longitudinal reciprocating
motion of the projection may be imparted to it from any suitable part of the engine,
such for instance as by an eccentric on the crank shaft of the engine. The
governor is connected to or geared with the device so that it imparts the move-
ment of partial rotation to the projection in such a way that as the speed of the
engine increases a portion of the projection of less length is brought by the
governor into position to act on the trip lever and as the speed of the engine
decreases a portion of the projection of greater length is brought by the governor
into such position.
As the most convenient form for the said projection is a short cylinder with
one of its ends in the form of a helix. I will refer to it as the helical projection.
In order that the nature of my invention and the manner in which the same
may be performed, may be well understood I will describe with reference to the
accompanying drawings an arrangement according to my invention as applied to a
double acting single cylinder engine, from which its applicability to other types of
engines will also be understood.
Figure 1 is a side view. Figure a plan and Figure 3 an end view of the engine,
with an arrangement according to my invention applied thereto.
Figures 4 and 5 shew in side view, and plan drawn to a larger scale, details of the
trip gear.
A are the weighted valve spindles, and B are the trip levers. They may be
constructed and connected together in any suitable way. In the arrangement
shewn the trip levers are centered at b to arms c secured to shafts C mounted in
brackets the said shafts having also secured to them arms c which engage by
rounded heads with openings formed in the valve rods A to receive them. The
brackets are extended to act as guides for the valve rods. Thus when the lower
ends of the trip levers B are acted upon in the directions of the arrows Figure 4
they raise the arm c and turn the shafts C so as to raise the arm c³ and
The said
lift the valve rods A to open the valves attached to the said rods.
operation of the trip levers is performed by the devices marked D constituting what
I have hereinbefore termed the helical projections. These helical projections are
formed on, or secured to, a rod E provided with sliders e, e³ which can be reciprocated
in bearings in brackets F. F' F. The rod E is connected to the slider et so
that it can have a rotary motion therein the slider being secured to the rod E and
being capable of a rotary motion in the bearing F and the rod E being capable of
a rotary motion in the bearings F' which bearings F' serve also to confine a toothed
e

page_text: which
wheel G which is connected to the rod E by a groove and feather connection so
that the said rod can move longitudinally through the said wheel G but so that
when the said wheel G is partially rotated it gives the same movement to the rod E
and helical projections D. The reciprocating movement is given to the rod E and
the parts carried by it by means of the eccentric H whose rod h is connected to one
end of the arm i secured to the shaft I which has also secured to it an arm
by the links e imparts the longitudinal motion to the rod E and its connections.
J is the governor acting on the lever j centered at and provided with a quad-
rantal rack gearing with the wheel G. It will be understood that when the
engine is at work the reciprocation of the helical projections D beneath the trip
levers B operates them to open the valves and that the time during which they are
open depends upon the length of the said projections which lie in their path. The
helical projections commence with an inclined circular part d and end with the
helical part 2. The part d (in the stroke which opens the valve) first comes in
contact with the trip levers and opens the valves and they are kept open till the
part of the helical projections which lies in the paths of the trip levers is passed
from beneath the trip levers when the said levers drop, or are forced by their
springs, into the position in which the valves are closed. The variation of the
cut off in accordance with the speed of the engine is effected by the governor as
the quadrantal rack partially rotates the wheel G and rod E and consequently
the helical projections D. and so brings a lesser and lesser length of the helical
projections into the path of the trip levers as the speed of the engine increases and
so the cut off is effected at a correspondingly earlier period. As the speed of the
engine slackens the reverse effect is of course produced. It will be understood
that the operation of the valves in the arrangement shewn takes place alternately.
From the foregoing description it will be evident that the details of the operating
mechanism can be considerably varied without departing from the nature of my
invention and that the invention may be applied to the operation of a valve or
valves by trip gear in either single or multiple cylinder engines and whether the
cylinders be single or double acting.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. In trip gear for engines operated by steam or other expansible motive agent a
projection for acting on the trip lever by the longitudinal reciprocating motion of
the said projection which is so formed and so operated by the governor that
portions of the projection of different lengths are brought into position to act on
the trip lever in accordance with the speed of the engine substantially as herein-
before described.
2. In trip gear for engines operated by steam or other expansible motive agent a
rod provided with what I have hereinbefore termed a helical projection (or with
helical projections) the said rod being also provided with means by which a longi-
tudinal reciprocating movement is imparted to it and being connected with the
governor so that movement of partial rotation is given to the said rod and pro-
jection or projections substantially as, and for the purpose, herein before described.
3. In engines operated by steam or other expansible motive agent the arrange-
ment of trip gear substantially as hereinbefore described and illustrated by the
accompanying drawings.
Dated the 5th dew of Ontahan 1000