Improvements in Trip Expansion_Gear of Steam or other Fluid Pressure Engines.
Year: 1889

page_text: Date of Application, 19th June, 1889-Accepted, 20th July, 1889
COMPLETE SPECIFICATION.
Improvements in Trip Expansion_Gear of Steam or other Fluid
Pressure Engines.
We, JOHN COCHRANE, Engineer Grahamston Engine Works, Barrhead in the
County of Renfrewshire and WILLIAM CAMERON, Mechanical Engineer of Maryport
in the County of Cumberland do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement :-
This gear is of that class described in patent No. 6773 of 1889 the original of which
was exhibited in the Glasgow Exhibition in the
The object of the present invention is to obtain equality of liberation, a long range
year 1887.
of expansion, a large surface of contact between the latch and the projection on
muff when the Engine is steaming to the earlier points of cut off, and to be able to
dispense with a wrist plate.
We obtain these important results by the use of an eccentric pieco on which
we hang a lever or disc, we prefer however to use a lever which we call a box
lever.
On this lever is hung a latch and trip. lever. The latch at a certain period of an
oscillation engages with a projection on a muff. This muff is securely fixed to the
valve spindle or trunion so that any movement of the muff is transmitted to the
valve. The trip lever liberates the latch from the muff and allows the valve to
close.
The before mentioned eccentric piece is securely fixed to or may be in one
piece with the valve bracket or bonnet through which the valve spindle or trunion
passes.
By hanging the box lever on this eccentric piece the centre on which the box lever
oscillates does not coincide with the valve trunion centre on which the muff is fixed
but lies outside of it.
By suitably determining the amount of eccentricity which we give the eccentric
piece and the proper angle at which the centre must lie we get the desired equality of
liberation and also a suitable normal cut off, that is, the point at which the latch
is liberated from its muff when the governor balls are in their normal plane of
revolution lies very approximately equidistant between the points at which the
Hovernor trips or liberates the latch from its muff when the governor balls are at
their maximum and mimimum radii which corresponds with Zero and of the
stroke.
We also obtain another very important result with this arrangement when we
dispense with a wrist plate that is we get a very quick opening of the valve which is
open fully three fourths of its width when the piston has travelled one fourth of its
stroke.
This quick opening when combined with a suitable amount of compression gives
excellent results.
The box lever as before stated is oscillated by an eccentric which movement is
transmitted to the valve when the latch is in gear with its muff. When the latch is
disengaged the box lever can continue its outward stroke and on the completion of its
inward stroke the. latch will fall into gear with the muff ready to open the port on
the commencement of the outward movement.
On the latch being released the valve closes the port and is brought to rest by
weights or springs and a dashpot in the usual way. In order to liberate the latch
from its muff we hang on a pin fixed in the box lever at a suitable distance from the
free end of the latch, a lever hereafter called the trip lever. This lever has two arms

page_text: +
one of which formed in a suitable manner bears on the latch at its free end the other
is connected by a swinging link to a lever which is coupled to and is under the control
of the governor so that any movement of the governor balls caused by variation of
load or fluid pressure is transmitted to the trip levet. This movement causes the
latch to be liberated from its muff at an earlier or later period of the stroke as the
case may be.
It is to be understood that one eccentric piece with a box lever, latch muff and
trip lever are required for each induction valve. The valves are preferably of that
class know as corliss valves.
We would have it understood that the eccentric movement of the lever on
which the latch or detent and trip lever is hung in relation to the muff or its
equivalent can be applied to other combinations than those shown in the annexed
drawings without departing from our invention.
In order that our invention may be better understood we proceed to describe the
annexed drawings.
:
Fig. 1 Sheet 1 shows a front elvevation of the improved gear with a cheek of the
box lever removed to show more clearly the various parts.
Fig. Sheet. 1 is an end elevation in section showing the box lever A hung on the
eccentric piece L. Fig. 3 Sheet 1 is a front elevation of the box lever A with a
check, the latch muff and trip lever removed. Fig. 4 Sheet 1 is a front elevation of
the valve bonnet or bracket showing the eccentric piece L in position. Fig. 5 Sheet 1
is a part sectional plan showing the eccentric piece L.
Refering to Fig. 1 Sheet 1 which shows the latch B in gear with the projec-
tion of the muff D and the trip lever E the short arm 1 of which bears on the free
end of the latch B while the long arm 2 is connected by a swinging link K to a lever
coupled to the governor in the usual way.
The action of the gear is as follows
On the eccentric moving the lever A in the direction which will open the port.'
The latch B being in gear with the projection of the muff B, the opening of the port
continues until the latch is released froin the muff.
The release of the muff B is caused by the arm 1 of the trip lever E lifting the
latch B. In order to get a suitable movement of the arm 1 we hang the trip lever E
on the box lever A and connect arm 2 by a swinging link to a lever. As the box
lever A moves so as to open the valve, the point of supension of the trip lever E
is carried round in a arc while the end of the arm 2 of the trip lever E describes
an arc whose radius is the length of the connecting link The result of these
movements when properly proportioned is that the arm 1 of the trip lever which
bears on the latch B liberates it from the muff at of the stroke when the governor
balls are in their minimum plane of revolution and at Zero when in their maximum
plane. As will be seen in the annexed drawings the box lever A moves on a
centre G while the muff with valve move round a centre F. The result of this
eccentric movement of the box lever A relatively to the muff D is to equalize the
points of release that is by suitably determining the amount of eccentricity we
get the normal point of release to take place while the governor balls are runing
in their normal plane of revolution.
Figs. 1, 2, 3, 4 Sheet 2. show a modification of the improved Gear the action
of which is identical with that shown in Sheet 1 as the same letters are used to
indicate similiar parts the description of that shown in Sheet 1 holds good for this
gear.
Figs. 4 5 6 & 7 Sheet 2 show another modification.
Fig. 5 Sheet 2. is a side elevation of the box lever A with a cheek removed to
show the latch B in gear with the projection of the muff D and the trip lever E.
The latch B has two arms on one of which the arm of the trip lever bears, the
arm 2 being coupled by a swinging link to a lever coupled to the governor in the usual
We hang the latch B from the vertical so that it may fall into gear at the
proper time by its own weight. By placing a suitable spring under the arm 3 of the
way.

page_text: latch we
can cause it to gear at the proper time independent of the action of
gravity.
Fig. 6 Sheet 2 is an end elevation in section showing the box lever A hung on its
eccentric piece L.
Fig. 7 Sheet 2 shows an end elevation of the eccentric piece L in the valve bracket
or bonnet.
Fig. 4 Sheet 2 shows the eccentric piece L in the valve bracket or bonnet and the
niuff B on the valve spindle or trunion.
The action of this gear is identical with that described in connection with Sheet 1.
Wo would have it known that all these combination give good results when used in
connection with a wrist plate.
Having now described our invention and shown how the same is to be performed
we declare that what we claim is
1st. A trip expansion gear where the lever on its equivalent on which the latch or
detent and trip lever is hung oscillates on a centre which does not coincide with the
centre of oscillation of the muff or its equivalent.
2nd. A trip expansion gear consisting of an eccentric piece on which the box lever
or its equivalent oscillates, a box lever carrying a latch and trip lever, and a muff with a
suitable projection substantially as shown and described in relation to Figs. 1, 2,
3 and Sheet 1 of the annexed drawings.
3rd. A trip expansion gear consisting of an eccentric piece on which the box lever
or its equivalent oscillates a box lever carrying a latch and trip lever, and a muff
with a suitable projection substantially as shown and described in relation to Figs. 1,
2, 3 & 4 Sheet 2 of the annexed drawings.
4th. A trip expansion gear consisting of an eccentric piece on which the box
lever or its equivalent oscillates, a box lever carrying a latch having two arms a
trip lever, and a muff with a suitable projection substantially as shown and described
in relation to Figs. 4, 5, 6 and 7 Sheet 2 of the annexed drawings.
D
1101 Jan of La 1880
JOHN COCHRANE.
WM. CAMERON.