Improvements in Valve-gear.
Year: 1889

page_text: Date of Application, 25th Mar., 1889
Complete Specification Left, 24th Dec., 1889-Accepted, 25th Jan., 1890
PROVISIONAL SPECIFICATION.
Improvements in Valve-gear.
I, WILLIAM RUSSELL CUMMINS of 6 Bredalbane Street, Glasgow, in the County of
Lanark, Scotland Engineer do hereby declare the nature of this invention to be as
follows:-
29 2
A single eccentric is keyed on the engine shaft. The eccentric rod end is connected
to the valve by a system of levers forming a kind of parallel motion, in order to main-
" and
tain equality of "lead." The different motions required for "ahead," astern
any intermediate "gear are obtained by swinging the eccentric rod end through a
suitable angle as described more fully hereafter. The gear is applicable to any form
of marine, locomotive or other engine requiring to be reversed or to work with
different rates of expansion. The present description applies to a marine engine.
The different motions required for "ahead" gear,
astern gear "mid" gear and
for any other intermediate gear are obtained by means of a single eccentric keyed to
the engine shaft.
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The end of the eccentric rod, which is made as short as conveniently possible, is
guided, approximately in the direction of a line passing through the centre of the
shaft, by means of a short link, one end of which is connected to the eccentric rod
end and the other is pivoted on an arm, centred on the shaft, which arm is controlled by
any suitable arrangement of reversing gear.
gear the
The eccentric is keyed to the shaft, in such a manner, that, in "mid"
motion of the eccentric rod end is synchronous, or practically synchronous with the
motion of the piston.
For the "ahead" motion, the above mentioned arm centred on the shaft is rotated
by the reversing gear through an angle corresponding to the "angle of advance" of
an ordinary eccentric producing the required motion. The eccentric rod, being
connected to the arm by the before mentioned short guide link, is of course rotated
through the same, or nearly the same, angle.
For the "astern" motion the arm is rotated through a similar angle in the opposite
direction.
Intermediate motions are obtained by rotating the arm, in the proper direction,
through a suitable angle.
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The motion of the eccentric rod end is transmitted to the valve by a modified
parallel motion" in order to maintain equality of "lead" or approximate equality
of "lead" for the "ahead and astern motions, and for any intermediate
motion.
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The parallel motion is preferably of the following description.
A beam, which may be straight or bent, has one extremity connected to the eccentric
rod end. The other extremity is connected to a fixed point on the framework of the
engine by a rod of suitable length. From the middle point or an intermediate point
of the beam a rod is led away, either directly to the valve spindle, or if more con-
venient, to an arm on a rocking shaft, the valve spindle being worked off another
arm on said shaft.
In either case, the length of the rod connecting the extremity of the beam with
the fixed point; the position of the fixed point; and the relative positions of the
eccentric rod and beam, are so arranged, that, when the piston is at the beginning or end
of its stroke, and the eccentric rod end is rotated, by means of the arm, from the
"ahead" to the "astern" position, then the path described by the middle point, or
intermediate point, of the beam, as the case may be, will be an arc, or approximate
to an arc of a circle of radius equal to the length of the rod connecting said

page_text: point to the valve spindle, or to the arm on the rocking shaft as the case
may be.
The parallel motion may also be arranged by connecting the middle or inter-
mediate point of the beam, to the fixed point by a rod of suitable length and leading
a rod from the extremity of the beain to the valve 'spindle or to the arm on the
rocking shaft.
COMPLETE SPECIFICATION.
Improvements in Valve-gear.
1, WILLIAM RUSSELL CUMMINS of 40 Perth Road Dunilee formerly of
6, Bredalbane Street, Glasgow, in the County of Lanark, 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 various motions required for "ahead," "astern," or other intermediate motions are
obtained by means of a single eccentric (see Figs. 1, 2 & 3) keyed upon the engine
shaft B. The end D of the eccentric rod, which is made as short as conveniently possible
is guided, approximately in the direction of a line passing through the centre of the
shaft B, by means of a short link C, one end of which is connected to the eccentric
rod end D and the other is pivoted on an arm E centred on the engine shäft, or 'on a
point near to the centre of the engine shaft.
The arm E is controlled by any suitable arrangement of reversing gear.
The eccentric A is keyed on the shaft B in such a manner that in mid gear the
motion of the eccentric rod end D is synchronous or practically 'synchronous with the
motion of the piston..
For the "ahead "motion the above mentioned arm E controlled by the reversing
gear is rotated through an angle corresponding or nearly corresponding to the "angle
of advance" of an ordinary eccentric producing the required motions.
For the "astern" motion the arm E is rotated through a similar angle in the
opposite direction.
The motion of the eccentric rod end D is transmitted to the valve spindle L by a
modified parallel motion in order to secure equality or 'approximate equality of
"lead" for the "ahead" "astern" and intermediate motions.
The parallel motion is preferably of the following description.
A beam F. (see Figs. 1 and 2) which may be straight or bent; 'has one' extremity
connected to the eccentric rod end D.
The other extremity is connected to a fixed point G'on the framework of 'the'engine
by a rod H of suitable length. From the middle or an intermediate point J of the
beam a rod K is led away either directly to the valve spindle L (see Fig.41) ör
if more convenient to an arm M (see Fig. 2) on a rocking shaft N; the valve
spindle L being worked off another arm O on 'the shaft N.
In either case, the length of the rod H connecting the end of the beain and the
fixed point G, the position of 'the fixed point G, and the relative positions of the
eccentric rod and beam F are so arranged that, when the piston 'is "at 'the commence-
ment of its stroke and the eccentric rod end D is rotated from the "ahead" to the
"astern" position, then the path described by the middle gudgeon J of the beain F,
will be an are or approximate to an arc of a circle of radius equal to the 'length of the
rod K connecting said gudgeon J to the valve spindle L (see Fig. 1) or to the arm M
of the rocking shaft N (see Fig. 2) as the case may be.
The parallel motion may also be arranged by connecting the "middle gudgeon J
(see Fig. 3) to the fixed point G by a rod H of suitable length and leading a rod from
the other extremity of the beam Feither direct to the valve spindle "as shewn by
Fig. 3 or if more convenient to an arm M'on'a rocking 'sliaft N (as shewn in-"Fig. 2)

page_text: astern
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the valve spindle being worked off another arm O on said shaft. In either case the
length of the rod H connecting the middle gudgeon of the beam F with the fixed
point G, the position of the fixed point G, and the relative positions of the
eccentric rod & beam F are so arranged that, when the piston is at the commencement
of its stroke & the eccentric rod end D is rotated from the "ahead" to the "
position, then the path described by the extremity of the beam F will be an arc, or
approximate to an are of a circle of radius equal to the length of the rod K connecting
the extremity of the beam F with the valve spindle L (see fig. 3) or with the arm M
(see fig. 2) of the rocking shaft N, as the case may he.
Having now particularly described & ascertained the nature of my said
Invention, and in what manner the same is to be performed, I declare that what
I claim is:
The combination of the single eccentric A, having its rod rotated through the
K angle of advance" to give the various motions of "ahead "astern" & intermediate
motions, with the modified "parallel motions," substantially as described, to maintain
approximate equality of "lead" for said ahead," astern and intermediate
motions.
Datad this "2ed ov
Desam 1000
"
W. R. CUMMINS,
Applicant.