Improvements in Steam Engines for Rolling Mills and other . Reversible Machines.
Year: 1896

page_text: Date of Application, 1st Dec., 1896-Accepted, 13th Feb., 1897
COMPLETE SPECIFICATION.
Improvements in Steam Engines for Rolling Mills and other
. Reversible Machines.
I, CLEMENS KIESSELBACH, Mechanical Engineer, of Rath, near Düsseldorf, in
the German Empire, 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 :-
In the case of rolling mills operated by reversing engines, which, as is well-
known, have no fly-wheels, the attendant must be able to start slowly with the mill
running empty.
On the other hand he must be able also to start with a full load, or with the full
capacity of the engine.
The use of compound engines meets with the obstacle. that, when the valve for
the admission of fresh steam is closed, the engine continues to run for a few
revolutions with steam from the receivers which are deprived of steam. Sub-
sequently the admission valve for fresh steam may be slowly opened as far as may
be required to drive the mill without load; but the full working capacity can only
be reached, when the receiver has been refilled. The frequent reversal of compound
engines, however, has the drawback that the reversing action will entail the loss of
large quantities of steam, and that the refilling of the receiver may require
a separate manipulation on the part of the attendant, who is already fully
occupied.
If, however, he stops the engine by placing the reversing lever in its mid-position,
the receiver steam will not be lost; but, owing to the absence of a fly-wheel, it
would not be possible to start smoothly with the engine working at "no load,"
because on reversing, the full pressure of the receiver would enter the large
cylinder..
What has been stated above applies also to the use of triple expansion engines.
To avoid all these drawbacks, I place between the receiver and the large
cylinder or cylinders one or more stop-valves which are coupled with the stop-valve
for fresh steam. Consequently, if the fresh steam be cut off, the communication
between the receiver and the large cylinder. is interrupted also; if the admission
valve for fresh steam be opened, the receiver is opened also. The large cylinder
may therefore be controlled just like the small cylinder.
In starting at "no load," the steam flowing from the receiver to the large cylinder
will be throttled; in starting at "full load," the receiver steam is immediately
caused to, act in the large cylinder with its full pressure, without requiring any
special attention on the part of the machinist. In cases, where the coupled valves
would be too difficult to work by hand, they may be set in motion by steam power
under the control of an attendant.
In the accompanying drawings,
Fig. 1 represents a compound engine embodying my invention, the high pressure
and the low pressure cylinder being parallel to each other, and the receiver between
the cylinders.

page_text: Fig. 6 is a section of a lifting valve, and a side view of the corresponding valve
seat spread out into a straight line.
Fig. 7 is a section and plan of a slide valve.
Fig. 8 is a diagram hereafter explained.
In Figs. 1 and 2, d-indicates the high pressure cylinders and D the low pressure
cylinders; a indicates the valves for admitting fresh steam to the valve chests of
the high pressure cylinders; b, b, the valves for stopping the flow of steam from
the receivers to the low pressure cylinders. The valves a and 6 of the same engine
are coupled together by means of levers and connecting rods c.
Owing to the peculiar working of reversible rolling mill engines, the full steam
pressure cannot, as a rule, be utilized; the fresh steam must be considerably
throttled.
Fig. 5 is a "rankinised" working diagram of a tandem reversing engine for
unthrottled steam.
Fig. 4 is a similar indicator diagram when working with moderately throttled
steam.
To render the latter diagram possible, the steam should not be throttled to
any considerable extent between the small and the large cylinder. Should' such
throttling occur, it would entail a loss of steam-pressure and consequently an
increase in the consumption of steam per horse power.
Fig. 3 is a "rankinised " diagram, for the case, that the engine runs without
load, and that the fresh steam, as well as the receiver steam, is much throttled
before it enters the cylinder.
This diagram shows particularly the effect of the throttle valve inserted between
the receiver and the large cylinder, and explains how it is possible with this valve
to start the engine slowly, while the receiver is full. From the above explanation
it is clear that the principal requirement consists in not throttling the receiver
steam, while the fresh steam is throttled moderately; but if much throttling is
necessary, for instance when the engine runs without load, to throttle the fresh
steam and the receiver steam equally. The full opening should take place for the
fresh steam and for receiver steam simultaneously.
Figs. 6, 7 and 8 show two throttling devices for receiver steam, which satisfy the
said requirements.. The lifting or sliding from a to c takes place simultaneously
with the full opening of the fresh steam valve, but the valve is fully opened
already at the point b. The edge of the valve seat has recesses e, in order to
shorten the line of steam admission before the complete closing of the valve.
The diagram Fig. 8 serves to represent graphically the effect of throttling. The
line.a-b corresponds to the full opening of the throttle valve, and at the same
time, to the height to which the fresh steam valve will be lifted when opened fully.
a-9 represents, the full stroke of the throttle lever. If the latter performs this
stroke on the opening of the throttle valve, the fresh steam opens uniformly along
the line.bh-g, from zero to full way. While the throttle valve for fresh steam
opens fully, that is. to say, by the length a-b, the throttle valve for the receiver
steam is opened excessively, that is to say, by the length b-c.
If subsequently the throttle lever be turned from a to g, the receiver throttle is
not closed immediately, that is, not before the point m has been reached, 'because
the shifting from c to k will not entail a réduction of the sectional area. From
that point, however, until the point n is reached, the throttling takes place very
rapidly..
From n-g the throttling is much retarded, because the way n-g corresponds to
the depth of the recess e.
It is clear from an examination of Fig. 8, that the fresh steam may be throttled
very considerably, while the receiver steam remains completely unthrottled, and
also that during the period of "no load the admission of steam diminishes
uniformly. The latter is necessary, as otherwise the receiver throttle would: 'be
opened too far, so that the receiver steam would be lost, without being sufficiently
replaced by fresh steam.

page_text: Instead of lifting valves or slide valves, as illustrated by Figs. 6 and 7, piston
valves, cocks, double-beat valves, or similar contrivances may be employed to attain
the same result.
Having now particularly described and ascertained the nature of our said
invention and in what mauner the same is to be performed, we declare that what
we claim is ;-
1. A reversible compound engine for rolling mills and analogous machines,
comprising in its construction a valve or valves inserted between the receiver and
the large cylinder, the said valve or valves being coupled with the admission or
throttle valve for fresh steam in such a manner that on the starting of the engine
they admit receiver steam to the large cylinder simultaneously with the admission
of fresh steam to the small cylinder, substantially as described.
2. In reversible compound engines for rolling mills and analogous machines, a
throttle or shut-off valve inserted between the receiver and the low pressure
cylinder and coupled together with the admission or throttle valve for fresh steam,
the said valve and valve gear being so arranged that, on the starting of the engine,
the receiver valve opens more rapidly than the fresh steam valve, and is then kept
fully open while the fresh steam valve continues to open, so that the high pressure
cylinder is working with throttled fresh steam, while the low pressure cylinder is
working with unthrottled receiver steam, substantially as described.
Dated this 30th day of November 1896.
FAIRFAX & WETTER,
433, Strand, London, Agents.