IMPROVEMENTS IN VALVE GEAR FOR STEAM ENGINES
Year: 1885

page_text: I, FERDINAND BOSSHARDT of the firm of Bosshardt & Grant, Mechanical &
Consulting Engineers & Patent Solicitors of 24 & 32 Bulls Head Exchange
Chambers Market Place Manchester in the County of Lancaster do hereby declare
the nature of my invention for "IMPROVEMENTS IN VALVE GEAR FOR STEAM
ENGINES which has been communicated to me from abroad by Johann Rudolf
Frikart of 122 Rue Nationale, Lille in the Republic of France Engineer and
in what manner the same is to be performed to be particularly described &
ascertained in and by the following statement :-
"
My invention relates to improvements in steam engines where the distribution
of steam takes place by means of four rotary valves.
Most engines of this kind on account of their arrangement of gearing permit
only an admittance of steam between 0 to 1/3 part of the stroke of the piston.
The gearing described hereinafter permits according to the position of the governor
connected therewith, a feed from 0 to 10 part of the stroke of the piston, which
peculiarity is of great importance in compound steam engines.
And in order that my invention may be more fully understood I have caused to
be appended hereunto one sheet of drawings marked with letters of reference
indicating like parts in various figures.
Fig 1 on the annexed drawing is a side elevation of the valve gearing and
connection with the governor of the steam engine.
Fig 2 is a plan partly in section.
Fig 3 is a cross section at +. +.
Figs 4, 5 and 6 explain the action of the system of levers connected with the
governor.
Fig 7. is an end view and Fig 8 partly side view and section of part of the
valve gear.
In carrying out my invention the shaft A which may be driven direct or indirect
from the crank shaft of the engine, carries on its end the bevel wheel B, see Figs 1
and 2. which imparts motion to the bevel wheel C.
The wheel C is fixed on a short shaft y which carries on its end near the centre
of the engine a small crank X.
D...

page_text: The shaft y is carried by the box-shaped casing 2, which latter carrying also
the governor column, is securely fastened to the bed of the engine by means of
bolts.
A second pair of wheels, see dotted lines Fig 3, serves to impart motion to the
governor.
The four valves see Fig 1 receive their motion in the first place from an
oscillating disc F. suspended on the centre of the cylinder, which disc receives
its symmetrical swinging by means of the rod D. from the already-named crank.
The two bottom or eduction valves are securely connected to the disc F while
the two top or inlet valves are only kept in their positions by means of a spring.
On the spindle of the inlet valve the crank arm k is keyed, see Figs 7 and 8
which by means of a rod is connected to the air buffer contained in the air
cylinder G.
A spring presses this air buffer and causes the valve to be closed thereby.
The oscillating disc F acts on a double lever H¹ which latter revolves freely on
the bush E.
The other arm of the lever H carries the piece J capable of rotating on the stud,
see Fig 7.
4.
This piece J is provided with an adjustable projection and forms a lever L.
The crank arm k keyed on the valve spindle is also provided with a projection
which at certain times is caught by the piece J, thereby causing the opening of
the valve.
The adjustment of the piece J is caused by two independent motions its centre
of vibration being set swinging partly by means of the lever H, the disc F and the
crank arm X and partly by the adjustable projection J sliding by means of the
levers L and M at a certain time from the crank arm k, and the longer the valve
remains open, the larger the amount of feed will be.
3, a frame P
One of these
The hereinafter described system of levers causes a connection between the
piece J and the governor of the engine for the purpose of automatic governing.
The governor column carries on its two arms, see Figs 1, 2 and
which latter provided with pivots t, t, swings in the said two arms.
pivots carries a lever N. which by means of a connecting rod D is set into
vibration.
It will be easily understood that in this manner the motion of the frame P and
the disc F will not be the same.
In reality when the disc is in its middle position, the frame has nearly arrived
at the end of its travel. This arrangement substitutes therefore two crank arms
or eccentrics keyed on differently and I consider this arrangement as the simplest
to obtain a large amount of feed controlled by the governor.
On the column of the governor a ring O is moving, which by means of the
rods 8, 8, is connected with the governor and therefore rising and descending with
the same.
This ring O carries on each side a stud which carries the bell crank levers Q, Q.
These bell crank levers are partly connected with the frame P and being capable
of sliding in a bracket arranged on each side of the frame and partly by carrying
the rods, T, T, which extend to the levers M M.
Figs 4, 5 and 6 explain the action of the system of levers.
The frame P makes its regular swing, while the bell crank levers Q, Q, according
to the position of the stud o will alter their positions.
A displacement of the circle described by the levers M M is thereby caused in
such a manner, that when the governor rises the levers M M will get near the
cylinder middle and when the governor falls the same will go distant.
By this symmetrical movement the curve which is described by the point of the
piece J will get nearer to or more distant from the centre of the crank arm k and
the piece J slides sooner or later off k, which causes the variable from the governor
depending, admission of steam.

page_text: To prevent damaging shocks a small spring R is inserted between the levers L
and M.
The rod U when descending pushes with its shoulder against the brass bush V
which latter contains the spring which when rising will compress the spring R by
means of the nut W.
It will be understood that when the engine is set, in such a manner, that the
highest position of the governor will correspond with the feed 0, and the lowest
position will not cause the piece J to leave the crank arm k, any suitable admission
from 0 to the whole amount of. the feed of the cylinder can be obtained by means
of the described gearing mechanism.
Having now described and ascertained the nature of my said invention and in
what manner the same is to be performed I would have it to be understood that
I claim
A valve gear for steam engines with rotary valves which permits variable
amounts of feed from 0 to 9/10 part of the stroke of the piston consisting for this
purpose of the following principal parts:
1st The catch or piece J, the point of which on account, partly of the oscillation
of the lever H and partly of the irregular motion of the lever M describes an
elliptical curve and thereby remaining always securely connected with the releasing
mechanism, according the position of the governor, causing the valve crank arm k
sooner or later to be released.
2nd The swinging frame P which by means of the bell crank lever Q the rod T
and the lever M impart a motion which is dependent on the governor and causes
thereby the variable feeding.