IMPROVEMENTS IN AND RELATING TO VALVE GEARING FOR STEAM ENGINES
Year: 1885

page_text: I JOHN THOM of 8 Storey Square Barrow in Furness in the County of Lancaster
Engineer do hereby declare the nature of my invention for IMPROVEMENTS IN
AND RELATING TO VALVE GEARING FOR STEAM ENGINES to be as follows:-
My invention consists in working the valves of connecting rod engines, without
eccentrics, thereby improving the actions of. the valve motions, and obtaining the
same amount of lead at all grades of expansion.
For connecting rod engines my invention consists in working the valve from the
connecting rod and cross head, or any vertical moving part attached to piston rod.
Fig. I shows the lever connected to piston rod cross head, to work on a sliding
fulcrum, at correct distance from pin on lever carrying rocking link to obtain the
linear advance of the valve The opening of the valve for steam inlet is obtained
through rocking the link by the rod joined to connecting rod and lever on link.
The lever or rod next cylinder to be longer (if necessary) than the one next
crank shaft, so that line drawn from centre of eye in valve spindle, would cut
through centre of pin on lever for carrying link, and centre of pin on lever for
rocking link from connecting rod if rod instead of being joined to connecting rod,
was worked up and down on centre line of engines at proper distance from
cross head; this is necessary that valve may have equal opening at both ends
(or nearly so) and dispenses with the rods or levers necessary to correct angularity
of connecting rod. This gear can be arranged to cut off steam with inside edges of
valve, by putting sliding fulcrum at end of lever, and pin for carrying link inside.
The lever on link for rocking same may be placed next cylinder if more
Buitable.
In reversing the rod connecting valve spindle to block in or on rocking link, is
moved to the opposite end of link
This gear can be arranged to work from air pump lever or similar levers with
fixed fulcrum.

page_text: JOHN THOM Engineer 8 Storey Square Barrow in. Furness County of Lancaster
do bereby declare the nature of my invention for IMPROVEMENTS IN AND RELATING
TO VALVE GEARING FOR STEAM ENGINES, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
My invention consists in working the slide valves of steam engines from the
connecting rod and crosshead, or any vertical moving part attached to the
piston rod.
Fig 1 shews a lever 1 connected to piston rod crosshead to work on a sliding
fulcrum 2, at a correct distance from più. on lever, which carries the rocking, link 3
to obtain the linear advance of the valve.
The opening of the valve for steam inlet is obtained, through rocking the link
by the rod 4 joined to connecting rod, and lever on link..
The lever or rod 1 next to the cylinder to be made longer than the one, next' to
crankshaft, so that a line drawn from centre of eye in valve spindle would' cut
through centre of pin on lever for carrying link, and centre of pin on lever for
rocking link from connecting rod, if rod instead of being joined to connecting rod,
was worked up and down, on centre line of engine at a proper distance from
crosshead. This is necessary that valve may have equal openings at both ends.
Fig. 2. shews a method of working the valves, by a motion derived from the
pump levers and connecting rod of an engine. In this arrangement the pump
levers, give the linear advance, and the rod 1 attached to the connecting rod, at
one end; and to a link 2 attached to rocking link 3, and the radius link 4 at the
other, gives the motion for steam inlet. The linear advance motion derived from
the pump levers, acting through link 2, makes the necessary correction for the
angularity of rod on link attached to connecting rod of engine. The radius link 4
may be substituted' by a straight sliding block at joint 5. The methods shewn
both by Fig. 1 and Fig. 2 may be used' for valves cutting off, with inside or
outside edges with slight modifications of detail!
Referring to the accompanying drawings Fig. 1 shews an elevation of a marine
engine. The lever 1 is attached direct to the piston rod' crosshead, at one end, and
to a sliding fulcrum 2 at the other. The point at which' the lever works, on the
crosshead, is so determined that a line drawn through the centre of eye of spindle
working the slide valve, would cut througli centre of pin; on the lever 1, for
carrying rocking link 3, and centre of pin on lever of rocking link to which is
attached the rod or link 4-worked by connecting rod, if the rod or link 4) instead
of being joined to the connecting rod, was worked up, and down on centre line of
engine, at a proper distance from the crosshead.
By constructing the gear in this way equal' openings to steam, at the slide valve
may be obtained.
The motion of the valve may be reversed by sliding the block, to which the
valve spindle connecting rod is attached along the curved rocking link 3, and the

page_text: cut off, may be varied, by altering the position of the sliding block in the
curved link.
Fig. 2 shews an elevation of a marine engine, with the valves worked by a
motion derived from the connecting rod, and air pump lever. The curved rocking
link 3, works on a pin, fixed at a point, on the pump lever suitable for giving the
lap and lead, the steam opening being given, by the motion derived from the
connecting rod through the rod or lever 1 acting on a link 2 which works in the
centre, on a pin attached to the rocking link 3, the opposite end of this link 2
being guided, by a radius link 4 fixed to a bracket, on the condenser. By the
combined action of the links 2 and 4, with the motion from the pump lever, equal
openings of the valve to steam may be obtained. The motion of the valve is
reversed in a similar manner, to gear described in the paragraph relating to Fig. 1.
Having now particularly described, and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:
1. Working a rocking link from a fixed point on the connecting rod of an engine
without any intervening link or links by a rod attached direct to connecting rod
at one end, and lever on rocking link at the other.
2. Working this rod in combination with a lever, fixed direct to the cross head
at one end, and working in a sliding fulcrum at the other. The point at which
the lever joins the crosshead giving the required correction for the angularity of
the rod attached to the connecting rod.
3. The combination as shewn in Fig. 2 by which the linear advance motion is
used to correct the angularity of the rod attached to the connecting rod by which
equal openings at each end of valve for steam inlet, may be obtained, as sub-
stantially described in the foregoing specification.