Improved Variable Expansion Gear for Steam Engines.
Year: 1888

page_text: Date of Application, 22nd Dec., 1888
Complete Specification Left, 21st Sept., 1889-Accepted, 23rd Nov., 1889
PROVISIONAL SPECIFICATION.
Improved Variable Expansion Gear for Steam Engines.
I, GEORG ANDREAS FRANKE, of St. Margarethen, No. 63, Mühlhausen, Thuringia,
Germany, Engineer, do hereby declare the nature of this invention to be as
follows:-
The present invention relates to a valve gear for steam engines, steam pumps, steam
hammers, etc., in which there is no steam pressure upon the backs of the slide valves
so that they may be considered to be balanced and the lubricant may be supplied
direct to the slide valve face. An important advantage is that the steam-tight valve
chest covers, stuffing boxes, glands, and valve rods, which are necessary in ordinary
valve gears, may be dispensed with. Another advantage is in the simplification of
the expansion or cut-off slide valve by the use of two cut-off plates adjusted by a
wedge controlled by the governor. This valve gear may be operated in the usual
manner by means of eccentrics, but elliptical gear may be employed to move the
slide valves, quickly at the points of admission and cut-off.
In the annexed drawings, illustrating the valve gear, figure i is a side elevation of
a horizontal steam engine provided with the improved valve gear, and figure 2 is a
plan of the same in section on the line A B of figure 3. Figure 3 is a cross-section on
the line CD of figure 2 through the cylinder and the slide valves. Figure 4 is a
cross-section on the line (D of figure 5 which is a longitudinal section on the
line A B of figure 4, these figures being drawn on a larger scale. Figure 6 is a
rear face view of the two cut-off plates and their operating wedge controlled by the
governor. Figure 7 is a face view, and figure 8 a plan, of the elliptical gear for
operating the valve connecting rods.
The main slide valve and the variable expansion valve with the adjustable cut-off
plates are contained in an open ended chest connected at d to a face stiffened by
ribs c at the under side of the cylinder. The bottom of the steam chest contains the
steam inlet and exhaust passages fg opening at the under side of the expansion and
main valves respectively, as shewn, this downward direction of the exhaust favoring
the carrying away of water of condensation. h is the main slide valve of the form
shewn in figures 4 and 5, and having ports i leading to the exhaust passage opening at
the underside of the valve and the two live steam "passages k¹ leading through the
valve. This valve is coupled directly to the eccentric rod 1. is the expansion
valve of the form shewn in figures 4 and 5, having a passage m² opening at the under-
side of the valve and leading to ports in the adjustable cut-off plates. It is coupled
directly to the eccentric rod n. Between the main and expansion valves are the two
cut-off plates O, and 0 provided with through ports p p. These two cut-off plates
work in a recess at the back of the main valve and constitute an adjustable working
face of the expansion valve to which they are connected as hereafter described. In
the back of each plate is a groove, the two grooves 9 7' (figure 6) being inclined in
opposite directions at an acute angle to the vertical in which engage guide ribs r
and on a wedge s which is moved up and down by the governor through the
medium of a connecting rod t. This wedge has a third guide rib u received in a
vertical or transverse slot in the cut-off valve. By the rising or lowering of the
wedge, the cut-off plates are adjusted closer together or farther apart whereby the
steam is cut off sooner or later to the main valve by the direct influence of
the governor and a variable rate of expansion in the engine cylinder is obtained.
In order to hold the two valves up to their seats, a packing wedge (figure 4) is
applied to the inclined back of the expansion valve and abuts against the rear
side of the steam chest. It is forced downwards by pressure screws y acting
through springs z whereby to maintain an elastic pressure and hold the two valyes

page_text: tight against their respective seats both in the direction of the ports leading to the
cylinder and those in the bottom of the valve chest. The valve chest is covered by a
cover w which fits in a groove. in the cylinder and is fixed to the rear wall of the
valve chest. All the rubbing surfaces of the main and cut-off valves are provided on
their upper surfaces with lubricating grooves from which extend lateral grooves to
the valve faces in order to keep the surfaces well oiled.
The valve connecting rods and n may be operated in the usual manner or by
means of the elliptical wheels A and B, the former being keyed on the crank shaft
whilst the latter is on a separate shaft on which also are keyed the eccentrics CD
which operate the main and expansion valves. The employment of the elliptical
wheels in combination with the eccentrics effects a quick, admission and cut-off,
Dated this 22nd day of December 1888.
G. A. FRANKE,
By A. M. & Wm. Clark,
53, Chancery Lane, London, Patent Agents.
COMPLETE SPECIFICATION.
Improved Variable Expansion Gear for Steam Engines.
I, GEORG ANDREAS FRANKE, of St. Margarethen No. 63, Mühlhausen, Thuringia,
Germany, Engineer, 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 :-
The present invention relates to a valve gear for steam engines, steam-pumps,
steam-hammers, etc., in which, owing to the special construction, there is no steam-
pressure upon the backs of the slide-valves and they may therefore be considered to
be balanced and by distributing lubricating grooves in the slide-valve face the
lubricant may be supplied directly (and without using any special lubricator) to the
slide-valve faces.
By means of my invention, the stuffing-boxes which are necessary in ordinary
valve-gears now used may be dispensed with, and all the advantages of a variable
expansion valve-motion is afforded without necessitating the use of special mechanism.
As, by this improved construction, the slide valves have no steam pressure on them it
is possible to increase their size and consequently the area of their ports without
increasing the friction of the valves and necessitating more power to operate them.
This is a very important advantage inasmuch as, owing to the increased area of the
ports the same result is obtained as in a precision valve motion. Owing to the
construction of the slide valves and to the manner of guiding them, countersteam can
be given as is necessary in locomotives.
The Invention is illustrated in the accompanying drawings, in which figures 1 to 4
show the improved construction of valves of my invention while figures 5 to 7 shew
the mechanism for operating them.
Figure 1 is a sectional plan view of the valve chest and cylinder, on line A-A
figure 2 which is a transverse section on lines B-B, C-C, figure 1. Figure 3 is a
vertical longitudinal section on lines D-D figure 2 and F-F figure 1. Figure 4 is
a section on line E-E figure 3. Figure 5 is a side elevation, and figure 6 a plan,
of the valve gear while figure 7 is a section on line G-G figure 5.
.:
is the engine cylinder, the valve chest cast in one therewith as usual, e the
slide-valve, and d the expansion valve. is a wedge at the back of the valve c having
'a spring and adjusting screws by means of which the valve is held against its
working faces. is the steam inlet which opens to the expansion valve d and has a
flaring mouth i, as seen in figure 2. The valve dis flat and is fitted to slide between
the wall of the upper portion of the valve chest and the upper face of the distribu-
ting valve c and it has a steam inlet leading to ports through which steam
passes to opposite ends of the valve . The cross-section of the valve c is shewn in
figure 2 and on its upper face it is provided with guides m m in which the expansion

page_text: valve d is fitted to slide. nn are steam admission ports in the distribution valve c
and oo are the exhaust ports communicating with the passage o in the rear or
inclined side of the valve through which the exhaust steam passes through a passage p
in the wedge to the exhaust pipe q at the underside of the valve chest. To provide
for the escape of the water of condensation in the cylinder the exhaust ports are on
a lovel with the lowermost part of the bore of the cylinder. The wedgo with its
pressure screws and spring g serve to keep the two valves in contact and hold them
up to their seats. The valves may be operated in the usual manner but preferably by
means of the gear represented in sheet 2, to which however no claim is here made.
The valves c and d are actuated by the eccentrics v and we keyed on the crank shaft u,
the valve e being actuated by the eccentric (see figure 6) and rod a, while the
valve is actuated indirectly by the eccentric w, so as to provide for variable
admission of steam. The eccentric w is connected to the valve by means of an
oscillating lever pivoted to a bracket y on the bed of the engine and having an
arm integral therewith which arm is connected by rod a' with the valve d and
slotted to receive a block d¹ to which the eccentric rod c is connected. The stroke of
the expansion valve is determined by the position of the block d¹ in the slotted
lever and this position is controlled by the governor which is connected to the
rod c by the link so that the lead of the expansion valve with respect to the
distribution valve is reduced or increased.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
A valve gear for steam engines, steam-pumps, steam-hammers, and the like, which
is characterized by the arrangement of two balanced slide-valves provided with the
necessary passages for the admission and cut-off of the steam-the steam passing
through the expansion slide valve to the main slide valve and thence laterally to the
cylinder and from the latter through the main slide valve to the atmosphere; the
valves being of the form described and shown in the drawings and working within
the steam cliest, as described, and the two valves being pressed one upon the other
and upon their seats by means of a wedge, substantially as set forth and shewn in the
accompanying drawings.
Dated this 21st day of September 1880.
G. A. FRANKE.
By A. M. & Wm. Clark,
53, Chancery Lane, London, Pateni Agents.