Improvements in Positive Motion Gear for Lift Valves.
Year: 1889

page_text: Date of Application, 14th Dec., 1889-Accepted, 18th Jan., 1890
COMPLETE SPECIFICATION.
Improvements in Positive Motion Gear for Lift Valves.
We, CARL GEORG ADOLF FREDERKING, and JOHANNES THEODOR WILLIAM
SCHUBERT, both of No. 34, Brühl, Leipsic, in the kingdom of Saxony, Engineers,
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 :-
Our invention relates to the gear for operating lift-valves employed for controlling
the admission of steam and gas-mixture to the cylinders of power-engines and for
other like purposes, and it consists in improved means for positively actuating such
valves and for keeping them down on their seats while they are to interrupt the
passage of fluid.
The main parts of the improved gear are a movable frame connected to the valve
and having, transversely to its line of motion, two parallel inner surfaces, and an
oscillating cam-disk or two such disks combined, the said disk or disks being paired
with the frame and having a particular form to be described in the following.
In the annexed drawings fig. 1 is a sectional view showing the valve-gear applied
to a steam-engine. vv are two valves, r r the aforesaid frames and cc the cam-
disks, the frames being movable in straight lines between guides, while the cam-disks
are operated by an eccentric e through the medium of rods t and levers 7. In the
arrangement represented by fig. 2 the operating mechanism of the cam-disk consists
in a rack gearing with a toothed bow. Fig. 3 shows the valve-stem s connected to
the frame by means of a frame g, a slide-block gl and a lever d pivoted at d¹, so
that the frame swings in an arc of a circle. Fig. 4 is a detail view of the valve-
motion with single disk of the simplest form, the disk being represented in its
medium position by a full line, and in its extreme positions to the right and to the
left by broken lines. The position of the frame r corresponding to the right-hand
position of the disk is indicated by hatching. Fig. 5 shows the valve-gear provided
with a single cam-disk c of modified form, the parts being represented in different
positions as in fig. 4. Fig. 6 is a detail front view of the arrangement with two
combined cam-disks c¹ c³, and fig. 7 a sectional side-view corresponding thereto. Fig. 8
is a like side-view of the same gear with the modification that there are two like
disks arranged on either side of the disk c¹, in view of distributing the pressure
of the former equally on both sides of the frame. Figs. 9 and 10 show the valve-
gear with two cam-disks and an oscillating frame r applied to one of the inlet valvės
of a steam-engine.
Referring to fig. 5, e and e¹ are the parallel inner surfaces of the frame r, on which
the cam-disk c acts, and a is its centre of oscillation. The operative peripheral
portions of the disk are composed of four arcs of circles, viz., the two arcs 3, 21
and 1, 1' drawn about the centre of oscillation a, and the arcs 1, 2 and 3, 3¹ drawn
about a point b, which is situated together with the points 1 and 3 of the arcs on
one straight line drawn through the centre of oscillation a. The sums of the radii a 1
and a 3 are equal to the sums of the radii 63 and 61 and to the distance between the
frame-surfaces e e', but the proportion between the radii a 3 and a 1, and that between
the radii 63 and 61 are variable independently of each other.
It will be seen that by this construction a cam-disk is obtained in which all lines
drawn from any point of the arc 3, 2¹ through the centre of oscillation a to the are 1, 11
and all lines drawn from any point of the arc 1, 2 through the point 6 to any point
of the arc 3, 31, are equal. Therefore, if the disc oscillates from the position shown
by full dark lines, to the left or back, the arcs 1, 1' and 3, 2', having their common
centre in the axis of oscillation, will slide on the respective frame-surfaces without
shifting the frame, which is consequently maintained stationary ; and, as this position
rn
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page_text: of the frame corresponds to the closing position of the valve, the latter will be kept
closed. If, on the other hand, the disk oscillates from the aforesaid position to the
right, the arc 1, 2 causes the frame and the valve to be raised, very gradually at first
and then with, increasing, speed, the arc 3, 3¹ meanwhile sliding on the frame-
surface e and keeping the frame in positive connection with the disk. Upon the
disk returning from its extreme right-hand position, it causes the frame and the valve
to descend with decreasing speed and finally closes the valve gently.
The cam-disk having the described form has an operative range of angular motion
of 120 degrees. The portions 2, 21 and 11, 3¹ of its periphery are inoperative and
may be formed in any suitable manner. In view of preventing the parts of the
gear from being strained, especially when the valve-rod s expands after having been
adjusted in cold state, the spring f is inserted between the said rod and the frame r.
In the arrangement shown by fig. 3, this spring is placed between the valve-rod s
I and the frame g. (See also fig. 9).
In the foregoing it was stated that the proportions between the radii a 1 and a 3 on
one hand, and between the radii 61 and 63 on the other hand are variable. In
fact the radii a 1 and 63 may be reduced to zero, the arcs 1, 1 and 3, 31 being
thereby contracted to a point, while the radii a 3 and 61 become equal to the distance
between the surfaces e and e¹. The form of disk thus obtained is shown by fig. 4.
The axis of oscillation a of the same coincides with the point 1.
The
In the arrangement of the gear represented by figs. 6 to 10, the operative arcs of
the disk described with reference to fig. 5, are distributed on two disks c¹ and c...
Thus in fig. 6 the disk c¹ is formed with the arcs 1, 2 and 1, 1, and it cooperates
I with the frame-surface e, while the disk c² which acts on the surface e¹, is formed with
the arcs 3, 21 and 3, 3', the arcs 1, 11 and 3, 2¹ being drawn about the centre of
oscillation a and the arcs 1, 2 and 3, 3¹ about the point b, as in the first case.
operative range of angular motion of which these combined disks are capable,
amounts to 270 degrees, whereof 90° may be utilized for the period in which the
valve is opened and closed, and 180° for the period in which it is maintained closed.
According as the angles of oscillation are smaller, the operative portions of the disks
may be reduced in length. Likewise the operative portions of the disks described
with reference to figs. 4 and 5, may be made shorter if the angle of oscillation of
these disks is to be less than 120 degrees.
:
The disks c¹ and and the framer belonging thereto may be arranged as shown
by fig. 7, the disk c² being keyed on the shaft w sideward of the centerline of the
valve-rod s. Preferably, however, two like disks c 2, fig. 8 are employed, placed at
either side of the disk c¹, all lateral strain on the valve-rod being thereby avoided.
The described gear presents the following advantages. It prevents the valve
connected therewith from opening accidentally, or from leaking, as otherwise often
occurs with valves subject to concussions, for instance on steam-vessels. No delay
in the closing of the valve can take place, and the valve can never be thrown open
too far, which is of special importance in engines running at high speed, or in case
the valve is to be opened but for a very short period, for instance in steam engines
with high expansion and in four-period gas-engines. As no weights or springs are
employed, the pressure thereof on the operating mechanism is done away with, and
the power required for actuating the valve as well as the wear of the parts are less.
Finally, the valve is started from its seat and lowered upon the same. gently and
without shock.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :
In a positive-motion-gear for operating lift-valves, the combination of a movable
frame connected to the valve and having two parallel inner surfaces e e¹ transverse
to its line of motion, and a cam-disk c or two combined disks cc, the said disk or
disks oscillating on a centre a and in contact with the surfaces e e¹, and the operative
peripheral portions of the disk or disks being formed according to four arcs of circles,

page_text: viz., the arcs 3, 21 and 1, 1' drawn about the centre of oscillation a, and the arcs 1, 2
and 3, 3' drawn about a point b situated on the line 1 a 3, the proportions between
the radii a 1 and a 3, and between the radii 61 and 63 being variable independently
of each other, so that the radii a 1 and 63 may become zero, and the arcs 1, 11
and 3, 3¹ be each contracted to a point, substantially as described.
Dated the Ninth day of December 1889
J. H. JOHNSON & Co.,
Agents.