Improvements in or relating to Automatic Control Mechanism for Fluid-pressure Motors.
Year: 1895

page_text: Date of Application, 31st Dec., 1895-Accepted, 3rd Oct., 1896
Improvements in or relating to Automatic Control Mechanism for
Fluid-pressure Motors.
A communication from JAMES BEDFORD STANWOOD, of Reading Road, near
Linton, Cincinnati, Ohio, U.S.A., Director of The Technical School,
Cincinnati.
I, ALFRED JULIUS BOULT, of 323 High Holborn, in the County of Middlesex,
Chartered Patent Agent, 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:-
This invention relates to improvements in the steam engine; its object being to
obtain a better regulation of its action in the varying conditions of its use in actual
service in the industrial arts, and a more economical use of the steam power
employed; to which end it consists in the combination with the engine, of means
whereby the regulation of speed, the adjustment of steam pressure, and the degree
of expansion behind the working piston, are automatically controlled by one and
the same element, the engine governor.
Heretofore, the speed of the engine has been controlled either (1) by a regulating
valve in the steam-supply pipe, actuated by a governor (the expansion being
determined by fixed proportions of parts); or, (2) by mechanism under control of
the governor which admits steam to the cylinder at or approximately at boiler
pressure, and automatically cuts off the supply at such period of the piston-stroke
as to maintain a nearly constant speed for light and heavy loads.
Experience proves, however, that for a cylinder of given proportions, there is a.
narrow range of cut-off points (or corresponding ratios of expansion) which give
or permit a maximum economical result in the proportion of steam used to the
work done; and that any earlier or later cut-off (or larger or smaller ratios of
expansion) increase the amount of steam used per horse-power delivered.
The severe demands made upon steam-engines employed to drive electric light
and power plants, etc. which require quick adjustments of power to widely varying
conditions of load, make it extremely desirable to maintain a steam economy as
high as possible for these conditions.
To meet this demand my correspondent has devised a system whereby both the
pressure of steam delivered to the engine and the determination of the point of
cut-off, are controlled automatically by the same means used to regulate the speed of
the engine; so that the range of cut-off, (or the corresponding ratios of expansion)
may be kept within economical limits under great variations of load.
The invention is especially advantageous as applied to compound or multi-
cylinder expansion engines, inasmuch as early cut-offs in the primary cylinder of
the series frequently cause so great a number of expansions, as to render the
operation of the machine not only wasteful, but (with some forms of valve motion)
impracticable.
By automatically reducing the initial steam-pressure the stresses upon the engine
working under light loads are greatly reduced; and this corresponds to the practice
of many engineers, who, under similar circumstances, reduce the initial pressure
by manipulating the throttle valve of the supply pipe. On the other hand, by
automatically delaying the cut-off (reducing the ratio of expansion) heavier loads
can be carried than under a fixed cut-off; thus increasing the range of power.
in connection with the forms of valve-gear of the Corliss type; the utilization
of the speed-governor to control both cut-off and supply regulation, tends,

page_text: moreover, to prevent excessive speed through failure of either of the operating
mechanisms singly.
The invention is illustrated in the accompanying drawings in which,
Figure 1 is a partial side elevation of a tandem compound engine of the
Corliss type, showing the invention applied thereto in connection with a
governor ";
"ball-
Figure 2 is a plan and Figure 3 a corresponding elevation of a parallel-cylinder
compound engine, showing the application of the invention thereto, in connection
with a 66
shaft-governor ";
Figure 4 is a detail perspective view of the bell-crank detached ;
Figure 5 is an enlarged elevation and Figure 6 an axial cross section of a shaft-
governor, showing details of construction, and adaptation of the invention thereto;
and
Figure 7 is a diagram showing the relative arcs of movement of the governor
and eccentrics.
Referring now to the drawings herewith-(illustrating the application of the
invention to two different types of engine, namely ;-(1), those in which the
governor acts directly upon the admission valve to control the cut-off; and (2),
those in which the governor acts upon the eccentric or valve-mover)-in the type
shown in Fig. 1, the governor A is connected to the admission valve-gear a aa aj
(which is of the usual construction and requires no formal description), to control
the point of cut-off in the working cylinders C C¹.
In this type of engines, is added a regulating-valve B (which, for this
purpose is so 'constructed, as to be delicately balanced) in the supply pipe
adjacent to the primary cylinder C and connect it, (as by bell-cranks 66', and
connecting rod 62) to the governor A, in such manner, that with light loads
the earliest practical cut-off is determined by the governor and the steam-
admission-aperture is also correspondingly reduced. The regulation and setting
of these connections, will of course depend upon the nature of the service to
which the engine is devoted; but it will be seen, that by a setting of the devices
which permits maximum boiler-pressure in the primary cylinder, in case of heavier
loads and a reduction of initial pressure for the lighter loads, the range of working
variations can be constrained to fall constantly within the best limits of expansion
and greater economy will result.
In the type of engine illustrated in Figs. 2 and 3, where the eccentric is con-
trolled either as to its amount of eccentricity or its radial position upon the shaft,
by a governor, the regulating valve B, is connected mediately to the governor by
a grooved collar f, carried loosely upon the shaft, and threaded upon the extended
hub C2, of the oscillating rotating plate C, forming part of the connections
between the governor and the eccentric e. (Fig. 6.) A convenient construction of
the mechanism connecting the governor with the regulating valve, is shown in
Figs. 2, 3 and 4, in the bell-cranks, gg carried upon suitable fixed brackets, and
connected by a rod g 2.
The collar has a "slot-and-feather" connection with the shaft S, as indicated
by dotted lines at p, (Fig. 6), whereby it is held in fixed radial relation with the
shaft, and is moved longitudinally upon the shaft by the rotation of the hub C2.
The construction and action of the governor in other respects is as follows;-
The main pulley D upon the shaft S, carries pivoted near its periphery two
arms d' d 2, connected by links d 3 d4 respectively, to opposite ends of an oscil-
lating plate c, centred upon the shaft S, and provided with a hub having .an
eccentric portion c¹ and a further extension c2 concentric with the shaft S, as
described.
h
A strap-link upon the eccentric c¹ has a pivotal connection with.the main
eccentric e, which is swung upon an arm or plate i pivotally connected to the main
pulley at .
The arms d¹ d2 are provided with adjustable weights w, and springs in the
usual manner.

page_text: Referring now to the diagram, Fig. 7, it will be observed that, the governor
oscillates the rotating plate c, which action moves the centre c¹ of the intermediate
eccentric from c3 to c 4. By this action the pivotal connection h¹ of the strap h,
is moved to h2, and shifts the centre x', of the main eccentric to 2, an angular
arc equal to ' h 2. At the same time the rotation of the oscillating plate c with
its eccentric h, through the are c3 c4, rotates the hub e2, which shifts longitu-
dinally the collar f, and operates the valve B, through connections g g g 2. The
relation of these movements, it will be observed, is substantially the same as the
relation of the movements of the crank-pins of the connections before described;
and produces a like result, namely;-that in heavy loads where the tendency of the
engine is to slow speed, the cut-off practically governs; whereas, in light loads
where the tendency is to high speed, the regulating throttle governs.
It will be observed from the relative setting of the bell-crank-connections of
the governor, in Fig. 1, which form an intermediate oscillating connection between
the governor and (1) the adjustable cut-off mechanism, and (2) the supply valve,
that the immediate effect of the governor is, primarily, on the distributing valve-
connections, a; at which relative period the action of the governor upon the valve B,
is very slight. The two arms of the bell cranks are set in such radial relations,
that, as the governor increases its speed, the range of controlling action upon the
cut-off valve diminishes; while the range of controlling action upon the regulating
valve B, increases. It follows that the controlling action of the governor upon
these two, is, in a degree, successive, the regulating valve being in the first part
of the governor movement, practically wide-open and exercising no control upon
the movement of the engine; whereas, in the higher range of speed of the
governor, it exercises a direct control.
Thus, in light loads upon the engine, where speed increases, the regulating valve
controls, while in heavy loads where speed becomes reduced, the cut-off is lengthened
and thus controls the engine. And this method of control is found to be not only
more effective in controlling the movements of the engine, but conserves economy
of steam, in a higher degree.
Having now particularly described and ascertained the nature of the said inven-
tion as communicated to me by my foreign correspondent, and in what manner the
same is to be performed, I declare that what I claim is :-
1. In a steam engine the combination of a variable cut-off mechanism and a
regulating admission valve with one and the same moving element or governor in
such relations that with increased loads where the tendency is to reduced speed
the cut-off mechanism is actuated to delay the point of cut-off (thus increasing
the period of steam admission) and with diminished load where the tendency is to
a higher speed the steam admission period is shortened and the admission valve
actuated to reduce the steam-supply, substantially as set forth.
2. The combination in a steain-engine with the main shaft and a centrifugal
governor actuated thereby of adjustable cut-off mechanism and a regulating valve
in the supply-passage both connected to and operated simultaneously with and by
the said governor substantially as set forth.
3. The combination in a steam engine of an adjustable cut-off mechanism and a
regulating valve in the steam supply passage both connected to and controlled
by a centrifugal governor and an intermediate rotating connecting device between
the governor and the adjustable cut-off mechanism, and between the governor. and
regulating valve in the steam-supply passage so connected as to automatically
adjust the degree of their operation that the cut-off is delayed under high initial
pressure with heavy loads and the cut-off is shortened and initial pressure is
reduced with light loads substantially as set forth.
Dated this 21st day of December 1895.