Improvements in Cranks of Varying Length.
Year: 1894

page_text: Date of Application, 4th June, 1894
Complete Specification Left, 4th Mar., 1895-Accepted, 6th Apr., 1895
Improvements in Cranks of Varying Length.
I, HENRI JOSEPH FÉLIX GUILLOU, of 31 Boulevard Henri IV, Paris, in the
Republic of France, Engineer do, hereby declare the nature of this invention to be
as follows:-
This invention has for its object novel methods of varying the effective length
of the cranks of steam engines, or other cranks or levers of the like kind, so
that the crank pin of such crank, instead of describing a circle concentric with
the axis of rotation, shall describe an ellipse or a circle excentric to such axis of
rotation.
In order to put my invention in operation, I form in, or connected with the
crank, two grooves or recesses, one parallel with the length of the crank, and the
other at right angles to the first and parallel with the plane in which the crank
revolves.
In the first groove or recess slides a block which carries the axis of the crank
pin, whilst in the second one a similar block slides, which serves as a guide to a
circular cam or excentric which is let into a recess in its thickness. The object of
this cam is to regulate as it turns the effective length of the crank. The axis of
the crank pin is fixed to the end of a connecting rod, and turns in its sliding block,
and determines the rotation of the cam or excentric by means of toothed wheels,
arranged and geared together so that the cam makes two revolutions for one
revolution of the crank.
It will be seen that in this way, during one complete revolution of the crank, the
effective radius of the latter will be lengthened twice and at equal intervals so that
the crank pin will describe an elliptical path the longer diameter of which is of any
determined greater length than the shorter diameter, the difference being dependent
upon the radius or excentricity of the cam or excentric.
In order to make the crank pin describe an excentric path instead of an
elliptical one, the toothed gear is omitted the movement of the cam being regulated
by the axis of the crank pin, to which it is fixed and which then describes an
excentric circle.
If the improved apparatus is to be applied to a double acting steam or other
engine, I arrange the crank so that the longer axis of the ellipse is at right angles
to the axis of the cylinder.
The travel of the piston and the consumption of steam will remain the same as in
an ordinary engine, but the leverage of the crank is increased at the points where it
is most effective. The power of the engine is therefore increased in exact proportion
to the lengthening of the crank.
If it is desired to modify the power given out by a revolving shaft, as for
instance in the case of a double-acting pump driven by a crank, the latter is so
arranged that the longer axis of the ellipse is in a line parallel with the centre of
the cylinder.
The second method of construction above described, in which the toothed gear is
omitted is applicable to single-acting engines such as gas engines, petroleum or
carbonic acid engines, velocipedes and the like.
In such cases it is only necessary to increase the effective length of the crank
during the semi-revolution corresponding with the out stroke of the piston. In

page_text: the return stroke it is often desirable to shorten the length of the crank, as
where (in gas engines) such return stroke effects the compression of the explosive
mixture.
The improved apparatus is applicable generally to all cases in which an
alternating backward and forward movement is to be transferred to a continuous
movement of rotation, or vice vered, and by its use an economy of 20 to 40 per cent.
is effected as compared with engines or apparatus in which cranks of fixed effective
length are used.
Improvements in Cranks of Varying Length.
I, HENRI JOSEPH FÉLIX GUILLOU, of 31, Boulevard Henri IV, Paris, in the
Republic of France, 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 and accompanying drawing, that is
to say:
My invention has for its object novel methods of varying the effective length
of the cranks of steam engines, or other cranks or levers of the like kind, so that
the crank pin of such crank, instead of describing a circle concentric with the
axis of rotation, shall describe an ellipse or a circle excentric to such axis of
rotation.
The accompanying drawing is in illustration of my invention;
Figure 1 being a side view of a crank constructed according to my invention;
Figure 2 a front view;
Figure 3 a view of the opposite side to Figure 1;
Figure 4 the ellipse described by the crank pin in one method of construction;
Figure 5 a modified method of construction, in which a circle excentric to the axis
of rotation is described; and
Figure 6 shews an excentric circle described by such method of construction.
In the case of the ellipse (Figures 1, 2, 3 and 4), A is the body of the crank, fixed
upon a revolving shaft in the ordinary way.
I form in, or connected with the crank, two grooves or recesses, one parallel with
the length of the crank, and the other at right angles to the first, and parallel with
the plane in which the crank revolves.
a
In the first groove or recess slides a block B, which carries the axis C of the crank
pin, whilst in the second one a similar block D slides, which serves as guide to a
circular cam or excentric E which is let into a recess in its thickness. The object
of this cam is to regulate, as it turns, the effective length of the crank. The axis C
of the crank pin is fixed to the end of a connecting rod, and turns in its sliding
block B, and determines the rotation of the cam or excentric by means of toothed
wheels F, F, arranged and geared together so that the cam makes two revolutions
for one revolution of the crank.
It will be seen that, in this way, during one complete revolution of the crank, the
effective radius of the latter will be lengthened twice and at equal intervals, so
that the crank pin C will describe an elliptical path O, the longer diameter of which
is of about 40 per cent. greater length than the shorter diameter, the difference being
dependent upon the radius or excentricity of the cam or excentric, (which may be
varied as desired).
In order to make the crank pin describe an excentric path (Figures 5 and 6) instead
of an elliptical one, the toothed gear F, F' is omitted, the movement of the cam E'

page_text: being effected by the axis of the crank pin C¹ to which it is fixed, and which then
describes an excentric circle O¹.
If the improved apparatus is to be applied to a double acting steam or other
engine, I arrange the crank so that the longer axis of the ellipse is at right angles
to the axis of the cylinder.
The stroke of the piston and the consumption of steam will remain the same as in
an ordinary engine, of which the length of the crank is 0,6 Figure 4, but the
leverage of the crank is increased at the points where it is most effective, to O, a,
instead of O, b. The power of the engine is therefore increased in exact proportion
to the lengthening of the crank, at the proper times.
If it is desired to modify the power given out by a revolving shaft, as, for
instance, in the case of a double-acting pump driven by a crank, the latter is so
arranged that the longer axis of the ellipse is in a line parallel with the centre of
the cylinder.
The second method of construction above described, in which the toothed gear is
omitted, is applicable to single-acting engines such as gas engines, petroleum, or
carbonic acid engines, velocipedes and the like.
In such cases it is only necessary to increase the effective length of the crank
during the semi-revolution corresponding with the out-stroke of the piston. In
the return stroke it is often desirable to shorten the length of the crank, as
where (in gas engines) such return stroke effects the compression of the explosive
mixture.
This result is obtained by the second form of variable crank illustrated in
Figure 6, the length of which is O¹ a¹, in the outstroke, and O¹ 61, in the return
stroke.
The improved apparatus is applicable generally to all cases in which an alternating
backward and forward movement is to be transformed to a continuous movement of
rotation, or vice versa, and by its use an economy of 20 to 40 per cent. is effected as
compared with engines or apparatus in which cranks of fixed effective length are
used. The apparatus may be varied more or less according to the purpose to which
it is to be applied.
Having now particularly described and 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, in a crank fixed upon a shaft, of the grooves or recesses at
right angles to each other, the first groove or recess being provided with a
sliding block, carrying a crank pin and operated backward and forward by an
excentric cam contained in a recess in a sliding block working in the second
groove or recess, the cam being actuated by toothed wheels, which toothed wheels
inay in some cases be omitted, substantially in the manner and for the purpose
described and illustrated.
Dated this 4th day of March 1895.
EDWARDS & Co.,
65 and 66, Chancery Lane, London, Agents for the Applicant.