Year: 1898

page_text: Date of Application, 26th Feb., 1898-Accepted, 2nd Apr., 1898
I, ROBERT FÖRSTER, of Kottbus, in the Empire of Germany, Manufacturer, 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:
Numerous attempts have been made to construct a valve gear for steam engines
allowing of a rapid opening of the steam inlet passages but all such gears are more
or less extremely complicated so that their use is expensive and little suitable in
practice.
The valve gear or motion which forms the object of the present invention may be
easily introduced into any old engine having valve gear and allows the steam inlet
ports of same being rapidly opened and slowly closed.
A valve motion having the improved arrangement is shown diagrammatically in
the accompanying drawings, in Figures 1 to 4, for a steam engine which has only one
slide valve, a so called shell valve, and in Figure 5 for one having two slide valves,
that is to say a so-called expansion valve gear.
a is the fly wheel shaft of a steam engine, and b a crank connected with the steam
piston or rather the connecting rod. c is the eccentric which imparts its reciproca-
ting movement to the slide valve or shell valve. In order that the valve gear may
receive a rapid movement for opening the steam inlet passages, a spur wheel d of
suitable diameter and number of teeth is mounted on the flywheel shaft a and
beneath it a second spur wheel e of exactly half the diameter of the spur-wheel d is
arranged on a separate shaft e¹, so that for one revolution of the wheel d the wheel e
makes two revolutions. The eccentric c is connected by means of an eccentric rod f
with a slotted lever g which is revolubly arranged on a shaft g¹ suitably connected
with the machine frame, which rod f engages with a stud or sliding block h mounted
in said lever. On an extension g¹¹ of the lever a slide rod which is not further shown
engages. A link i runs downwards from the stud h of the lever and is connected
with an elbow lever k pivoted on a shaft which elbow lever is further connected
with the spur wheel e by means of a rod m.
The arrangement works in the following way :-
In the position shown in Figure 1, as may be gathered from the position of the
crank b, it is assumed that the steam piston is at the left hand dead point and the
slide is about to open the left hand steam port which may be gathered from
the position of the eccentric rod f.
When the crank b travels further to the right, the rod m by means of the gear
wheels de will be rapidly drawn round and by the intermediary of the elbow lever k
and link the stud h of the slotted lever and therewith the eccentric rod f will be
drawn downwards in the slot of the lever, so that the leverage for the movement of
the slide becomes larger and thereby a rapid opening of the left hand steam inlet
passage is attained. The position is maintained until the parts assume the position
shown in Figure 2, and the piston stands in the middle of the cylinder. On the
further rotation, a lifting of the stud h is then produced as shown in Figure 3, and

page_text: the left hand steam inlet passage is slowly closed. In the position shown in Figure 3,
the crank b has reached its extreme right hand position and the piston stands at the
first dead point. When then the crank 6 moves into the position shown in Figure 4,
the slide is moved quickly to the left, by the renewed descent of the stud h, and
opens the right hand steam inlet passage whereby the steam piston is driven to the
left.
On the further rotation of the crank b out of the position shown in Figure 4
into that shown in Figure 1, the right hand steam inlet passage is slowly closed and
the crank band steam piston come gradually again to the left hand-dead point
position, Figure 1, whereupon the movements are repeated.
If in a slide or expansion valve gear it be desired to produce also a rapid closing of
the expansion slide and thus to attain variable charges, it is only necessary, as shown
in Figure 5, to connect a slotted levert with the rod of this slide and to allow the
eccentric rod n belonging to such slide to engage the stud o. The engine governor r
is then connected with the stud o of the link by means of link 8, two armed lever q
and a rod p in such a way that the stud is drawn down on the outward movement of
the governor balls and a rapid movement is imparted to the expansion slide connected
with the lever t.,
The movement of the governor takes place from the flywheel shaft a by means of
a belt pulley on the shaft of a bevel wheel u arranged in the fork shaped support of
the governor, and engaging with a second bevel wheel ¹ firmly connected with the
spindle of the governor.
The use of a rapid movement of the valves in steam engines is thus easily
rendered possible by the arrangements herein before described and they work very
precisely.
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. In steam engines having a slide valve, a valve gear for producing a rapid opening
of the steam inlet ports, consisting of a slotted lever (g) connected with the slide rod
and pivotally suspended at one end and a stud or sliding block (h) arranged in the
slot of said lever and connected by a series of levers and links (i k m) with a pair of
gear wheels (de) so proportioned that one wheel (e) makes twice as many revolutions
as the other wheel (d) in gear therewith, substantially as herein before set forth.
2. A modification of the valve gear herein before described to adapt it to work with
two slides, characterised by the distributing slide being operated by the mechanism
herein before described and the expansion slide being similarly connected with a
slotted lever (t) pivotally suspended by one end, the stud (0) or sliding block mounted
in the slot of said lever being connected with the eccentric rod (n) and the governor (r)
by means of a link and lever gear (o q p) so that on the balls of the regulator flying
out, the expansion slide is also more quickly closed, substantially as hereinbefore
described.