Improvements in Trip Expansion Gear of Steam or other Fluid- pressure Engines.
Year: 1889

page_text: Date of Application, 30th Nov., 1889
Complete Specification Left, 28th Aug., 1890-Accepted, 29th Nov., 1890
PROVISIONAL SPECIFICATION.
Improvements in Trip Expansion Gear of Steam or other Fluid-
pressure Engines.
We JOHN COCHRANE of Grahamston Engine Works, Barrhead in the County of
Renfrew Engineer, and WILLIAM CAMERON of Maryport in the County of Cumber-
land Mechanical Engineer do hereby declare the nature of our invention to be as
follows:-
This invention relates to that class of valve gear in which the steam and exhaust
valves are operated by one eccentric. The object of our invention being to simplify
and to obtain a greater range of expansion than heretofore.
To attain these ends when our invention is used without a wrist plate we couple
the exhaust valve lever which is keyed on the valve trunnion to the eccentric in the
usual way and connect the exhaust valve lever by a short link to a lever pivoted on
the steam valve trunnion or its bracket. On this lever we hang a latch which gears
with a suitable block fixed to a lever keyed on the steam valve trunnion.
The latch bears on a projection carried by a lever hung on the exhaust valve
bracket or otherwise. This lever is under the control of the governor and as the
position of the governor varies the projection causes the latch to be liberated at an
earlier or later period of the stroke.
Upon the latch being released the valve is caused to close the port in the usual
way.
If the latch is released from the block only during the period in which the steam
valve is opening the port which is the usual practice the greatest possible range that
can be obtained is from zero to of the stroke.
In order to lengthen this range so as to be more suitable for triple or quadruple
expansion engines, we cause the latch to be liberated from its block during the
period in which the valve is closing as well as in that in which it is opening the
port.
To liberate the latch during the closing of the port, we mount on the before-
mentioned lever (which is hung on the exhaust valve trunnion or other convenient
place and which carries the projection that liberates the latch during the opening of
the port if allowed by the governor) an oscillating lever also carrying a projection.
This lever is caused to oscillate by the eccentric through suitable connections. The
point from which the motion is taken and the connections are so arranged that the
projection is carried away from the latch during the opening of the valve allowing
the fixed projection to liberate the latch.
If however the load on the engine is such that the steam is required to be admitted
for a longer period of the stroke than about 3, the governor places the fixed
projection in such a position that the latch will not be liberated during the opening
period and upon the return or closing period the oscillating lever will bring up its
projection. which will cause the liberation.
The oscillating lever being hung on the lever which is under the control of the
governor it follows that the period in which liberation occurs during the closing of
the port will also depend upon the position of the governor balls.
When we use a wrist plate we couple the lever on which the latch is. hung to a
in fixed in the plate and hang the lever that is under governor control and which
arries the oscillating lever and projection, in a convenient position instead of on the
xhaust valve bracket.
The valves we use may be Corliss or they may be of the grid type moved longi-
tudinally or obliquely by the partial rotation of their trunnions..

page_text: The steam valves are closed upon liberation by springs or weights and brought to
rest by air cushions in the usual way.
Two steam and two exhaust valves are required, the above description refers
to one half the gear but stands good for the remaining half it being similar.
f
Dated thioth
AL
11000
"
JOHN COCHRANE.
WM. CAMERON.
COMPLETE SPECIFICATION.
Improvements in Trip Expansion Gear of Steam or other Fluid-
pressure Engines.
We, WILLIAM CAMERON of Maryport in the County of Cumberland, Mechanical
Engineer and JOHN COCHRANE Engineer, Grahamston Engine Works Barrhead in
the County of Renfrew 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 that class of valve gear in which the steam and exhaust
valves are operated by one eccentric. The object of the invention being to simplify
and to obtain a greater range of expansion than heretofore.
"The valves I use with this gear are of the Corliss type.
To attain these ends we couple the exhaust valve lever which is keyed on the valve
trunnion to the eccentric in the usual way and connect the exhaust valve lever by a
short link to a lever pivoted on the steam valve trunnion or its bracket.
"
On this lever we hang a latch which gears with a suitable block fixed to a lever
keyed on the steam valve trunnion.
The latch bears" on a projection carried by a lever hung on the exhaust valve
bracket or otherwise.. This lever is under the control of the governor and as the
position of the governor balls vary the projection causes the latch to be liberated at
an earlier or later period of the stroke. Upon the latch being liberated the valve is
caused to close the port or ports in the usual way.
If the latch is released from the block during the period in which the steam valve
is opening the port which is the usual practice the greatest possible range that can be.
obtained is from zero to of the stroke.
To lengthen this range so as to be more suitable for triple and quadruple
expansion engines we cause the latch to be liberated from its block during the
period in which the valve is closing as well as in that in which it is opening
the port.
In order to liberate the latch during the closing of the port, we mount on the
beforemention lever which is hung on the exhaust valve trunnion or other convenient
position and which carries the projection that liberates the latch during the
opening of the port if allowed by the governor) an oscillating lever also carrying a
.projection.
This lever is caused to oscillate by the eccentric or by some other part of the engine
mechanism having a suitable movement through suitable connections. The point
from which the motion is taken and the connections are so arranged that the pro-
jection is carried away from the latch during the opening of the port allowing the
fixed projection (that is the projection not carried by the oscillating lever to liberate
the latch.
If however the load on the engine is such that steam is required to be admitted
further than about 3 of the stroke the governor places the fixed projection in such a
position that it does not cause the liberation of the latch during the opening perid
and upon the return or closing period the oscillating lever will bring up its projection
which will cause the liberation."
When we use a wrist plate we couple the lever on which the latch is hung to a in
in the wrist plate and hang the lever which is under the governor control and which
carries the oscillating lever with its projection or pin in a convenient position instead
3

page_text: of on the exhaust valve bracket. The exhaust valves being placed on the other side
of the axis of the cylinder.
In order that this invention may be better understood, we will proceed to describe
the annexed drawings.
Fig. 1 on Sheet 1 shows an arrangement of this gear.
Fig. 2 Sheet 1 shows an enlarged view of the valve levers and oscillating lever.
Fig. 3 Sheet 1 shows a side elevation of the steam valve trunnion or spindle with
the lever carried thereon.
Fig. 4 Sheet. 1 show a side elevation of the exhaust valve trunnion or spindle with
its lever also the lever which is under the governor control and the oscillating lever
carried by it.
Referring to Fig. 1 Sheet 1, the following description will show the action of the
gear and will relate to that half of the gear on the right hand of the drawings that is
to one steam and one exhaust valve and to their connections the action of the other
half being precisely similar.
The piston is supposed to be just completing its stroke and travelling towards the
crank end of the cylinder. The eccentric moves the exhaust lever A through its
connections and closes the exhaust port this motion is communicated by the link C to
the lever B which is mounted loosely on the boss of the steam valve lever D which is
keyed on the valve spindle or trunnion. This lever B has the latch E hung at its
lower end. This latch E at a little before the commencement of the return stroke of
the piston will have engaged with the latch block F which is secured to the valve
lever D. The movement of the eccentric is thus transmitted to the steam valve which
is just about to open the steam port to cushion the piston.
The movement of the piston will now be reversed and steam will continue to be
admitted until the latch E is release from its block F when the valve will at once
close the steam ports.
The release is caused by two distinct arrangements one of which is used for the
earlier periods of cut off from zero to 3 and the other from to of the stroke.
If the load on the engine be such that the governor balls are running above their
mean plane of revolution the steam may be cut off anywhere from zero to this is
caused by the projection 9, cast on or secured to the trip lever h which is under.
governor control. The latch E bears on the projection 9 during the period in which
the steam valve is opening its port and accordingly as the governor balls place the
projection g the latch will be released from its block sooner or later in the range from
zero to of the stroke.
If however the load on the engine is such that the governor balls are running under
their mean plane of revolution steam may be required to be admitted anywhere up
to of the stroke. It will be understood that the valve is opening up to 8 of the
stroke and from the valve is returning and closing the port.
The means whereby we obtain a variable cut-off from 3 to 7 is by hanging an
oscillating or vibrating lever on a pin carried by the trip lever h.
The oscillating lever i is oscillated by the eccentric through the bell-crank ? and the
coupling rods.
I prefer this means of actuating the lever but it may be operated from any.
suitable part of the engine mechanism or by another motor running at a suitable
speed.
The oscillating lever i has at its other extremity a pin or projection K which may
engage with the free end of the latch E at any period during the closing of the valve
depending upon the position of the governor balls and cause its release from its
block F. After the latch E is released from its block F the valve is closed by a
spring or weight and cushioned by a dashpot in the usual way. During the
return stroke of the piston and while the exhaust valve has opened its port the
oscillating lever i has moved away its pin or projection from the latch E allowing it
to engage with its block F ready for again opening the steam port and is still away
from it during the earlier periods of the stroke allowing the projection g to release the
atch if allowed to do so by the governor,

page_text: It will be seen that this extended range is of the utmost important as it allows a
greater range in the load or boiler pressure.
Figs. 1, 2, 3 & 4 Sheet 2 show a modification of the oscillating lever applied to the
well known Wheellock gear.
In the Wheellock gear the greatest range of variable cut off is under 3 of the stroke
and by the application of this invention the range can be extended to of the stroke.
This gear is operated by connecting the exhaust valve lever A to the eccentric and
transmitting this movement to the steam valve lever B by the latch E hung on the
exhaust lever A and which gears with the latch block F. The duration of this con-
nection depending upon the position of the projection g which is cast on or secured to
the trip lever . The lever h being under governor control. The tail of the latch E
bearing on the projection during the opening of the valve. The release of the
latch E from its block F can take place sooner or later from zero to accordingly as
the governor places the projection g. If the load on the engine is such as requires
steam to be admitted for a longer period than 3 of the stroke with a variable
expansion which is of the utmost importance more especially in triple and quadruple
expansion engines where the normal cut off in the high pressure cylinder should be
about of the stroke. To obtain such a variable cut off from 3 to or during the
period in which the steam valve is closing the port, I mount an oscillating lever i on
or in connection with the trip lever h, so that any movement communicated by the
governor to the trip lever is communicated to the oscillating lever i.
I prefer to oscillate the lever i through the bell crank which is moved by the
eccentric.
For the purpose of illustrating this invention we show the oscillating lever i
mounted on a sliding piece ; which is suitably guided and connected to the trip
lover h so that sliding piece j and consequently the oscillating lever i is moved by
the trip lever in an approximately vertical direction.
The oscillating lever i has a pin or projection K fixed in its other extremity which
comes in contact with the tail of the latch E and causes it to be released from its
latch block F. As the motion which the oscillating lever i receives from the eccentric
or other suitable source is constant, the moment in which the projection or pin K
will act on the latch E will depend upon the position in which the governor has
placed the sliding piece ; which carries the oscillating lever i.
It will be seen that the pin K of the oscillating lever i moves away from the tail of
the latch E during the early periods of cut off allowing the projection g to determine
the periods from zero to when the governor balls are running above their normal
plane of revolution. On the governor balls running below their normal plane of
revolution the sliding piece j is moved down by the governor carrying with it the
oscillating lever i, and the lower the sliding piece j has been placed the nearer must
the oscillating lever i approach the limit of its travei before its pin or projection K
acts on the tail of the latch E. This takes place during that part of the stroke in
which the steam valve is closing its port. On the latch being liberated from its block
the valve is closed by a spring or weight and is brought to rest by a dashpot in the
usual way.
Fig. 1, 2, 3 Sheet 3 show a modification of the gear shown by Fig. 1, 2 3 & 4
Sheet 1. The steam valves are placed at the top corners of the cylinder casting and
the exhaust valves at the bottom. The valves are worked from a wrist plate in the
usual way. The action of this arrangement is identical with that shown by Fig. 1,
2, 3 & 4 Sheet 1. The difference in this arrangement being that the trip lever h is
hung on a suitable pin carried by the cylinder or other suitable support instead of
heing carried on the exhaust valve trunnion bracket.
It will be readily seen that the point of release of the latch from the block in this
invention can be fixed by hand by means of suitable mechanism instead of being
automatically varied by the governor.
We are aware that the oscillating lever can be applied to other modifications or
arrangements of similar gears, but we consider that we have shown sufficient to
illustrate its action

page_text: Having now described the nature of my invention and ascertained how the same
is to be performed we declare that what we claim is
1st. In a trip expansion gear an oscillating lever, oscillated by the eccentric or
other suitable source substantially for the purpose set forth.
2nd. In a trip expansion gear the combination of a trip lever with a projection and
an oscillating lever having a suitable pin or projection both being under the governor
control substantially as and for the purpose set forth.
3rd. In a trip expansion gear the combination of a trip lever with a projection an
oscillating lever having a pin or projection and a bell crank substantially as shown
and described in reference to Figs. 1, 2, 3, 4 Sheets 1 & 2 of the annexed
drawings.
4tb. The combination of parts with and without an oscillating lever substantially
as shown and described in reference to Fig. 1, 2, 3, 4 Sheet 1 of the annexed
drawings.
5th. The combination of parts in a trip expansion gear substantially as shown
and described in reference to Fig. 1, 2, & 3 Sheet 3 of the annexed drawings.
Dated this 26th day of August 1890.
JOHN COCHRANE.
WM. CAMERON.