IMPROVEMENTS IN VARIABLE EXPANSION GEAR
Year: 1877

page_text: LETTERS PATENT to Gerard Wenzeslaus von Nawrocki, of the Firm of Brandt
and v. Nawrocki, of 2, Koch Strasse, Berlin, Germany, Patent Agents,
for the Invention of "IMPROVEMENTS IN VARIABLE EXPANSION GEAR."
communication from Carl H. A. Prött, of Brackwede, Germany.
A
Sealed the 8th February 1878, and dated the 10th August 1877.
PROVISIONAL SPECIFICATION left by the said Gerard Wenzeslaus von
Nawrocki at the Office of the Commissioners of Patents on the 10th August
.1877.
1
GERARD WENZESLAUS VON NAWROCKI, of the Firm of Brandt and v. Nawrocki,
of 2, Koch Strasse, Berlin, Germany, Patent Agents. "IMPROVEMENTS IN
VARIABLE EXPANSION GEAR." (A communication from Carl H. A. Prött, of
Brackwede, Germany.)
In this arrangement the expansion is varied automatically by the action of the
governor. The ports on the cylinder face and on the face of the slide valve are
inclined at an angle of 45° against the horizontal slide spindle; the slide valve is
circular and obtains a partly rotating as well as a reciprocating motion.
The slide valve is fixed on its spindle, which latter can turn in a sliding frame to
which it is connected, and which has two friction rollers actuated by a cam or cams
on the fly wheel shaft or other shaft connected thereto. The back of the slide valve
is formed like the front or face side, and works against a concave plate, the edges of
which suit the cylinder ports, and are perforated so that steam from the ports may
come to the back of said plate and hold it and the slide valve in equilibrium; a
wedge-formned plate or piece between the back of the just named plate and the
slide jacket cover serves to set it up to counteract the wear.
The slide valve is turned axially by lever connections to a sleeve which can slide on
a feather on the slide valve spindle, and is acuated by a cam sleeve on the fly wheel
shaft or cam shaft aforesaid.

page_text: The opening of the steam ports is commenced by the horizontal movement of the
slide valve from the cam, and is completed by the rotation; when one edge of the cam
sleeve passes a friction roller on a lever resting thereon, the lever will go down by
its own weight or be assisted by a spring; the slide valve is then turned in an
opposite direction, the port is closed, and the expansion begins.
The governor is by preference placed just over the fly wheel shaft or cam shaft,
and causes the cam sleeve to slide on the shaft by means of a bell-crank lever, thus
altering the expansion, according to the power required, the acting edge of the cam
sleeve having a screw or twist shape to suit.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Gerard Wenzeslaus von Nawrocki in the Great Seal Patent Office on
the 9th February 1878.
*
GERARD WENZESLAUS VON NAWROCKI, of the Firm of Brandt and v. Nawrocki,
of 2, Koch Strasse, Berlin, Germany, Patent Agents. IMPROVEMENTS' IN
VARIABLE EXPANSION GEAR." (A communication from Carl H. A. Prött, of
Brack wede, Germany.)
According to this Invention the expansion is varied automatically by the action of
the governor. The ports on the cylinder face and on the face of the slide valve 'are
inclined at an angle of 45° against the slide spindle; the slide valve is by preference
circular, with a partly rotating as well as a reciprocating motion, but various other.
forms of slide valve and movements of one and the same slide valves in different
directions may be applied.
The automatic variation of the grade of expansion by means of a governor may
also be carried out in various ways.
And in order that this Invention may be fully understood, I will now proceed to
describe the same with reference to one mode of carrying the same into effect, that
is, with a circular slide valve with partly rotating as well as reciprocating motion
applied to the cylinder of a horizontal engine.
Figure 1 is a vertical longitudinal section through the slide jacket with the slide
valve removed.
Figure 2, a horizontal longitudinal section through the slide valve, slide jacket, and
part of the cylinder.
Figure 3, a vertical cross section through cylinder, slide jacket, and slide.
And Figure 4, an end view of the slide gear, showing also part of the governor.
A is the slide valve which is fixed on its spindle a and is of cylindrical form, the
slide jacket being bored out cylindrically to suit; the ends of the slide valve are
inclined, and the cylinder admission ports b, b, and exhaust port c are of a corres-
ponding shape. As here shown the slide valve is formed similar to the "Rieder"
expansion valve. The back pressure on the slide valve may be obviated or lessened
in any well-known manner.
Or the back of the slide may work against a concave plate, the edges of which
suit the cylinder ports, and are perforated to admit steam from the ports to the back
of the plate, and thus produce equilibrium of pressure, a slightly wedge-shaped piece,
between the back of the plate and the slide jacket cover, serving to set it up to
counteract for wear.

page_text: The slide valve consists of an upper and a lower half which are held together by
means of a ring wave-shaped feathering plate a. The greater part of the steam
pressure is thus kept off the back surface of the slide valve.
The outer gear for imparting motion to the slide valve consists mainly of an
eccentric cam or other well-known appliance for such purpose; on, the fly wheel shaft
or on a shaft connected thereto, the eccentric imparts the reciprocating movement. The
slide valve is turned axially by lever connections H, H³, to a sleeve B, B, which can
slide on a feather on the slide valve spindle. When the engine is.to work expansively
the slide valve is turned axially until the inlet port is closed, as shown at Figure 2.
Before the other inlet port can be opened the slide valve must be turned back into
the position from which a straight movement results again. By this return rotation
the slide valve obtains a screw-like motion by the sliding on one another of the
screw-like surfaces or cams W, W, Figure 2, until the slide valve returns to its
middle position and the sraight motion must then follow.
Two of the screw-like faces or cams W are on the staple H, which is fixed on the
slide valve spindle, and the other two faces W are on the bosses B on the sleeve
through which the slide spindle passes. The middle position of the slide valve
corresponds to the highest position of the staple H. In this position the fork-shaped
lever H, situated between the bosses B and turning with the staple H, falls into the
latch K. From this point the slide valve moves in a straight direction until the
wedge K¹ comes against the inclines F on the staple H. The wedge K¹ is firmly
connected with the latch K, and can be shifted more or less in the guide by the
governor. The wedge K¹ will, by coming against the inclines F, be pressed back, the
latch K will be released, and the lever H, which is firmly connected to the slide
valve spindle, is pulled down by a spiral spring with air buffer.
In consequence of this the slide valve is turned so quickly that the inlet port can
be closed very quickly. The wedge K¹, operated by the governor, works in a notch
in the latch K and in the fork of the lever H¹; the front edge of the wedge is by
the governor drawn to or from the staple. The wedge thus comes against the inclines
F, F, of the staple sooner or later, and thereby an earlier or later cut-off is produced.
The raising and lowering of the wedge K¹ takes a very small force because it
inoves freely in the latch K; the governor therefore only requires to be of very small
size. It is also evident that the adjustment of the degree of expansion is done more
accurately than heretofore usually possible with other kinds of variable expansion
gear.
The following are the advantages of this arrangement:-The weight of the wedge
K' is very small, and during the whole of the play of same it takes the very least
power, so that the governor works almost without any load on it, and therefore varies
the expansion to the greatest exactitude. This expansion gear has also the advantage
that the so-called loss in ports is considerably reduced because the ports through the
main slide valve are done away with.
If the slide valve be divided, and if the ports be not in one line, but arranged as
indicated, the loss in ports is reduced even below that of the "Sulzer" expansion
gear.
The wear on the slide valve is extremely even, as the whole cylinder face is
traversed by the slide valve with each degree of cut-off, no ridges are therefore
formed on the face, and a kind of constant facing up action takes place by the
constant motion of the slide valve in varying directions. The wear on the outer
mechanism is likewise very slight as the power to work the slide is so very
small, and ample wearing surfaces may conveniently be provided which may be
hardened.
"
Because of the aforesaid advantages this expansion gear will be at least as good as
the "Corliss and other gearing, while it considerably exceeds them as regards
exactness of cut-off; by a small modification of the mechanism a cut-off of from
nothing to 9/10 is equally possible. Nevertheless, this expansion gear is not like
those above named, considerably dearer than the ordinary expansion slide gear, but

page_text: cheaper, and if the slide valve is not made as an equilibrium valve as here shown,
the cost is reduced to below that of the cheapest expansion gear variable by hand.
And having thus described and ascertained the nature of this Invention, I declare
that I claim, the construction of a slide valve having two movements in different
directions, the cut-off being automatically varied by means of a governor, all
substantially as set forth.
In witness whereof, I, the said Gerard Wenzeslaus von Nawrocki, have here-
unto set my hand and seal, this First day of February, in the year of
our Lord One thousand eight hundred and seventy-eight.
GERARD WENZESLAUS V. NAWROCKI. '(L.S.)