Improvements in Apparatus for Equalising the Pressure upon the Orankpins of Steam and other Engines.
Year: 1896

page_text: Date of Application, 27th Aug., 1896-Accepted, 19th Dec., 1886
Improvements in Apparatus for Equalising the Pressure upon the
Orankpins of Steam and other Engines.
A communication to me from CARL KÜSTER, Factory Manager, and JULIUS
KUSTER, Engineer, both of Piræus, in the Kingdom of Greece.
I, EDMUND EDWARDS, of the Firm of Edwards and Co. Patent Agents and
Engineers, of 65 and 66, Chancery Lane in the County of Middlesex, 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 and accompanying drawings that is to say :-
It is well known, that steam and other motive power engines working by means
of cranks have the disadvantage that the pressure upon the crank-pin constantly
varies, for two reasons. The first of these is, that from the working of the crank,
the effective power of the lever which it forms, continually varies in such a manner,
that even supposing a uniform pressure to be produced by the piston, the resulting
effect transmitted to the crank-pin must be much less effective as the crank-pin
approaches or leaves the dead points at the ends of the stroke. The second
reason depends upon the variable pressure of steam in the cylinder of the engine.
The present invention has for its object methods of equalizing the varying
pressure upon the crank-pin by interposing between the crank-shaft and the main
or fly-wheel shaft an intermediate gear for the purpose of shortening the length of
the lever formed by the crank when a greater pressure of steam is operating and
of lengthening the crank agaiu, as soon as the pressure of steam becomes less.
The dieadvantages of the cranks as hitherto ordinarily used in motive power
engines is illustrated in the accompanying drawings.
In Figure 1, the upper half of the circle indicating the path of the crank-pin is
divided into 20 equal parts (full lines being made use of). Supposing that the
speed of the crank-pin is uniform through its revolution the equal parts of the said
circumference may be considered as 20 equal spaces of time.
On the other hand the dotted lines of Figure 1 may indicate the division of half
the circumference, so as to represent the spaces of time, which the piston really
requires for completing half the revolution of the crank-pin. The straight line or
path taken by the inner end of the connecting rod during its to and fro motion may
also be divided in the same manner into parts corresponding with the motion of the
piston.
It will be gathered from this, that when the distance which the piston has passed
through when the cylinder is filled with 02 of steam, and after its having
passed of the whole stroke on the straight line, the crank-pin has already
In the same
travelled through 5.2 parts of its corresponding circular path.
manuer 2.66 spaces of time, which the crank-pin will pass through, correspond to
the first twentieth of the whole stroke, of the piston. Up to the tenth part of this
stroke, the number of spaces of time corresponding to one twentieth of the travel
of the crank-pin is continually diminishing, but after the tenth part has been passed
this number is again increasing, so that the last part of the piston's stroke (the
part between the 19th, and the 20th, division, and that nearest to the dead point),
corresponds to 3.2 spaces of time. The full steam-pressure works therefore only
for 5.2 spaces of time, whilst about 9 such spaces are wasted by the expansion of

page_text: steam and 6 of them are wasted either entirely or nearly so, without working at all
In practice these conditions are still worse, because the speed of the crank-pin-
here supposed to be uniform all through its path,-really undergoes many
variations.
All these disadvantages are overcome if both the crank shaft and fly-wheel shaft
(driving shaft) are separate and coupled to each other by non-circular wheels in
such a manner, that the crank-shaft operates with a substantial effect during those
spaces of time, in which the piston is exposed to full ateam-power. In order to
avoid loss of time, the arrangement should be so made that the working-effect of
the steam may be so much less during the other spaces of time.
Figure 2 shows a toothed wheel a fixed upon the crank-shaft C, working (by
means of the intermediate transmitting devices together with the toothed wheel b
which is concentrically fixed upon it) the intermediate shaft C. A toothed
wheel of the same size as that is excentrically fixed upon the spindle C, and
gears with a toothed wheel d, which is excentrically fixed upon the fly-wheel or
driving shaft, C'.
The greatest difference of the semi-diameters of these excentric wheels is in the
proportion of two to one. For indicating the division of spaces of time for the
excentric wheel d a semi-circle e concentrically arranged upon the fly-wheel
shaft C' is divided into ten equal parts. The shaft of the wheel d, being that of
the fly- or driving-wheel, is supposed to rotate with uniform speed. By connecting
the ten dividing points of the semi-circle e with the centre of the spindle C' by
meaus of straight lines, a division upon the semi-circumference of the excentric
wheel c is effected, which serves as a guide for the division of the semi-circumference
of the concentric wheel b.
The latter division, that is to say, is obtained when the dividing-points trans-
ferred from the wheel d to that care then connected by straight lines with the centre
of the intermediate shaft C (Figure 2), cutting thus-either directly or through
their prolongations-the circumference of the wheel b. The divisions thus obtained
are then transferred to the semi-circumference of the toothed wheel a', and from
thence by drawing the corresponding radii to the circumference a forming the path
of the crank-pin, in such a manner, that the narrowest part of the division is
numbered zero (0) and indicates the space of time equal to of the whole stroke
of the piston.
When the paths travelled over are indicated in this manner, the position of the
piston and the toothed wheel according to the above scheme and with reference to
Figure 1 is as follows:-
Supposing the part of the cylinder to be filled with steam, the path passed
through by the crank-pin would be indicated by 7-66 spaces of time, and, when
the next twentieth part is also filled--the said crank-pin will already stand ucar
the division which indicates ten twentieths or balf of the whole path.
By altering the position of the piston it would be possible by comparing the
indications to obtain a still more favourable result. This could, howover, only be
got by the adoption of a more minute division of the spaces of time about or near
the dead points of the crank.
But such a minute division would depend upon a more sensible friction between
the connecting-rod and the crank-pin, and this friction would have a bad effect
upon the working of the engine. If the proportion of excentricity of the wheels
used be somewhat increased, the correct division of the time spaces is made easier
but still more advantageous for such division would be the use of specially shaped
DOR-circular or irregularly shaped wheels, which would cause a less injurious
friction at a spot slightly distant from that where the position of the dead point
bas been passed. If such special shaped wheels are made use of, the best working
effect may be produced at the most favourable point of the path travelled by the
crank-pin.
Secondly, a similar result may be obtained, by constructing the crank-pin 80
that it is adjustable towards the centre of the fly- or driving-wheel shaft in such

page_text: a manner, that the crank-pin approaches nearer to the said centre during the
poriod of greatest pressure upon the crank-pin, and recedes from it when the
pressure diminishes.
As illustrated in Figure 18, this result is obtainable by introducing a stationary
guiding device o; or (referring to the Figures 13 to 19), the same result is again
attained by causing the crank-pin to slide in and out by means of an enforced
guiding apparatus, which will be more particularly described below. Both
arrangements may be made use of simultaneously, and if circumstances require,
a special provision may be made for each of them.
Figures 3 and 4 represent an engine having one cylinder. Upon the crank-
shaft, an elliptical wheel i is fixed gearing with an excentric wheel g fixed upon
the driving shaft h.
In Figures 5 and 6 a compound engine with two cylinders is illustrated, the
crank-shaft k of which, belonging to the high pressure cylinder is supported by
two bearings The said shaft is connected with the main driving shaft o by
means of two elliptical wheels m m which gear with two other similar elliptical
wheels n n in such a manner, that the motion of the crank-shaft is communicated
by the transmitting device at the same number of revolutions to the principal
shaft.
On the other hand the low pressure cylinder, or rather its crank-shaft p, is
connected to the driving-shaft o by means of an elliptical wheel 7 having teeth
inside and by the excentric wheel r, that is to say, by the transmitting device at
speeds in the proportion of 2 to 1.
It is thus possible for the low pressure cylinder to work at half the speed of the
high pressure cylinder.
Figure 9 shows a heart-shaped toothed wheel, and Figure 10 one of double
heart-shape. In both these cases the said wheels gear each with a second
corresponding wheel, thus working at the proportion of speed either of 1-1
or 2-1.
The Figures 7 and 8 represent the invention applied to a gas-motor, (or petroleum-
or benzine-motor) baring two cylindere, the fly-wheel shaft t having its bearings
above the crank-shaft and the driving force being transmitted by non-circular
wheels u, v.
The position shewn in the drawing is that occupied by the various parts
immediately after the explosion has been effected.
Such an arrangement has the advantage, that the cylinders may be fixed at their
usual level, whilst on the other hand the fly-wheel shaft may have its bearings at a
bigher level, so that the usually-required pit for it, can be dispensed with. Besides
this advantage, the invention allows the fly-wheel to be much less heavy and
therefore of smaller dimensions than las heretofore been necessary.
Figure 11 represents an excentric wheel A made adjustable as regards its
excentricity by wedges to or by screws. This is obtained by mounting the wheel A
upou an excentric D, which is fixed upon the shaft B.
By loosening these wedges it is possible to rotate the wheel A on the
excentric D and to fasten it afterwards in the desired position, by forcing in
the wedges again.
In case it should be desired to dispense with the excentric wheels, cranks may
be made use of, constructed in such a manner, that their lengths are shortened
during the period of high pressure, and are automatically lengthened again, whilst
the expansion of steam is going ou. This arrangement, however, does not influence
the working-effect so much, as that already described.
Figure 12 shews the simplest form of arrangement of such a crank. In this case,
its part E is guided in slot F made in a radial (longitudinal) direction in the
part of the wheel-boss, the sliding of the said part E being effected by its pin G
engaging with the fixed groove or cam-path e. Another form of such an
arrangement is illustrated in Figures 13 and 14, in which instead of the immovably
arranged groove e, an excentric H is made use of aud is caused to rotate in a

page_text: reverse direction upon the crank-shaft C' by means of the bevel gear L, L', L
Through its strap I, this excentric H causes the part E of the crank, to move to
and fro. In order to avoid too great friction during the shortening or lengthening
of the said crank, tho parts E and F may be provided with steel friction rollers K
which by means of a system of levers M, M', M, are made to move at half the
speed of that with which the part E of the crank is caused to move in its longi-
tudinal direction. In case such a connecting-genr is to be applied to a single
acting motor engine worked by simple explosions, the excentric H should be
stationary, or the fixed groove e described in the form of arrangement shewn in
Figure 12 must be made of excentric or non-circular configuration.
For motors of this kind, that is to say, for motors, in which the crank ouly
sustains a single impulse during its complete revolution (and also when only one
cylinder is supposed to be made use.of, and where such a working-effect only takes
place every third revolution of the crank) the employment of cranks locking or
engaging with one another may be adopted, as illustrated in Figures 15 and 16.
In this case the shaft C of the fly-wheel is provided with a crank N having a
slot N with which the crank-pin O engagos, the latter being also connected to a
pin on the connecting rod as usual. The crank-pin O is carried by a second crank
ou a shaft or centre C parallel with, but not in line with, C
In order to make use of such a crank arrangement. in double-acting motor
engines, the revolving shaft or centre C must be movably arranged. As may be
seen in Figure 19, this can be effected by means of a guide P, in which the said
shaft C is caused to move to and fro by means of a sliding rod Q, lever R, and an
excentric rod S, driven by an excentric on the main shaft C'. The position of C
varies from the positions at the ends of its stroke in which (as shown) the crank-
piu O is nearest to the shaft C, to its central position concentric with C', in which
the crank-pin O is most remote from the latter.
Figures 17 and 18 illustrato a form of the invention in which the motion of the
piston is transmitted to the flywheel shaft C by the interposition of elliptical or
non-circular toothed wheels T, T', the crank being in this case supposed to be
of adjustable length.
The shortening of the crank N, or its lengthening, are effected by means of an
additional crank V, the latter being worked by the principal shaft C by means of
an endless chain W. This crank V rotates in direction contrary to that of the
crank N and also works, by means of a small rod V, the piu O' of the main
crank.
As illustrated in Figures 21 and 22, it is possible by means of this invention, to
cause two cylinders I and II of a compound steam engine (the first cylinder being
a high pressure one, and the second a low pressure one) to work the saine fly-wheel
shaft, each cylinder being provided with special connecting gear in accordance
with the invention. In this case the proper relations between the various trans-
mitting devices is solected in such a manner, that the piston of each cylinder works
during three-fourths of a complete revolutions of the fly wheel shaft, whilst the
remaining fourth of this revolution is used for the back-stroke of the piston.
Both the pistons working thus simultaneously during half the revolution of the
fly-wheel there are no objectionable dead points during the travel of the crank-pin.
If it is desirable to further apply the invention to motors having more than two
working oylinders, the same principles already described will lend to the right
construction of the connecting gears.
Consideration.
But moreover in such a case double-acting cylinders may be taken into
The various cylinders may then be united according to the
system of compound-engines, by making use of receivers or by dispensing with
the same.
In Figures 23 and 24, two high pressure cylinders and two low pressure cylinders
are combined, the first ones being arranged in front of the second ones.
With this motor engine it is supposed that the steam passes from chamber II
into that 111, whence it passes into chambers IV and V, working then in VI

page_text: when the piston returns back at great speed, the steam being afterwards condensed
in VII, when the speed of the piston will be diminished.
The chambers I and VIII not being used, the connecting rods may be jointed
directly to the piston.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what 1
claim is:-
In motive power engines, the methods of construction in which the effective
pressure upon the crank-pin is equalized by means of a connecting gear, consisting
of suitably shaped toothed wheels or of levers, interposed between the crank-shaft
and a separate main driving shaft, in such a manner and so constructed, that the
proper effective relation of the transmitting devices to each other, with regard to
the variations of effective pressure in the cylinder, is changed and modified during
the stroke of the said piston, and the effective action upon the main shaft is
equalized, substantially in the mauner and by the means described and illustrated.
Dated this 27th day of August 1896.
EDWARDS & Co.,
65 and 66 Chancery Lane, London, Agents for the Applicant.