IMPROVEMENTS IN THE MACHINERY FOR OBTAINING ROTARY MOTION BY THE ACTION OF TWO FORCES ON DIFFERENT CRANKS
Year: 1884

page_text: PROVISIONAL SPECIFICATION,
:
I, GEORGE SHANN, of 3 Park Row, Albert Gate, London, in the County
of Middlesex, Engineer, do hereby declare the nature of my invention for
IMPROVEMENTS IN THE MACHINERY FOR OBTAINING ROTARY MOTION BY THE
ACTION OF TWO FORCES ON DIFFERENT CRANKS, to be as follows:-
The cranks on which the two forces act, are not rigidly fixed on the same crank-
shaft, but are so connected together, by machinery for giving alternate quick and
slow motion, that while one crank is passing through that part of its revolution
during which it can be driven in the required direction by the action of that one of
the motive forces which more directly does work upon it, the other crank is
thereby made to revolve through an angle greater than two right angles. The
relative positions of the two cranks are so arranged that each is made to pass both
its dead centres in the time during which the motive force is acting directly on the
other. The quick-&-slow-motion connexion between the crank shafts can be
arranged in more than one way: I proceed to describe the particular arrangements
for which I now ask protection.
The two crank-shafts are placed with their axes in the same straight line, and
between them is hung an intermediate shaft with its axis parallel to, but not
coincident with, this straight line. Each end of the intermediate shaft carries a
lever having in it a radial slot; and the nearer end of the corresponding crank-
shaft carries a pin, fixed excentrically, fitting into and capable of sliding along, the
slot in the lever. The pins must be farther away from the line of the axes of the
crank-shafts than this line is from the axis of the intermediate shaft.
In the drawing, A, A¹ are the cranks; B, B¹, the levers on the intermediate shaft,
and C, C, the pins sliding in slots in B, B¹; the position shown is that assumed by
the machinery when the crank A is about the middle of its return stroke.
I include in this application arrangements which are mechanically equivalent to
the above; for example, one in which pins are carried excentrically on the ends
both of the crank shafts and of the intermediate shaft, these pins being connected
by means of a link of suitable length.
The invention above described is especially applicable to velocipedes, and to two-
cylinder engines which, like most gas-engines, have the power applied at one end.
of the cylinder only.

page_text: I GEORGE SHANN of 3 Park Row Albert Gate London in the County
of Middlesex Engineer do hereby declare the nature of my invention for
"IMPROVEMENTS IN THE MACHINERY FOR OBTAINING ROTARY MOTION BY THE
ACTION OF TWO FORCES ON DIFFERENT CRANKS" and in what manner the same
is to be performed, to be particularly described and ascertained in and by the
following statement:-
According to my Invention the cranks on which the two forces act, are not
'rigidly fixed on the same crank shaft, but are so connected together by an
arrangement or arrangements, that while either one of the cranks is passing
through that part of its revolution in which it can be driven in the required
direction by the action of the force which does work more directly upon it, the
other crank is thereby made to revolve through an angle greater than two right
angles. The relative positions of the two cranks are so arranged that each is made
to ass both its dead-centres in the time during which the motive force is acting
directly on the other.
Figure 1 of the accompanying drawing illustrates a manner in which the
connection between the two cranks may be made in carrying my Invention into
effect. The separate crank shafts A. A¹ are so hung that their axes are in the same
straight line and at their inner ends these shafts carry arms or levers a a¹ carrying
pins CC¹ having their centres not in the same straight line with the axes of the
crank shafts-Between the two crank shafts A. A¹ is hung an intermediate shaft D
having at its ends arms or levers B B¹ having in them radial slots in which the
pins CC are capable of turning and of moving longitudinally.
The axis of the intermediate shaft D is not in the same straight line as the axes
of the crank shafts A A¹, but is so placed in respect to it, that when either of the
cranks is passing through that part of its revolution in which it can be driven in
the required direction by the action of the motive force which more directly does
work upon it, the intermediate shaft D is driven at a greater angular velocity than
the said crank, but that the crank which is passing through its return stroke is on
the other hand driven at a greater angular velocity than the intermediate shaft.
The drawing represents the arrangement in plan representing the crank upon
which the force is being directly applied and y representing the crank which is
performing its return stroke for the time being.
I do not limit myself to the precise arrangement above described as my Invention
may be carried into effect by other equivalent arrangements substantially the same
in their action; for instance the slots may be in the arms or levers carried by the
crank shafts and the pins in the levers on the intermediate shaft, or the levers on
the cranks and on the intermediate shaft may be connected by means of a link of
suitable length, in place of the aforesaid pins and slots.
Figure 2 shows an arrangement wherein the connection between the ends of the
levers is effected in the case of each crank by a link as at c-Figure 3 shows a
spring connection in place of the said link e the spring being formed in one with or
attached to the levers.
The Invention is applicable more especially for tricycles but may be used for Gas
Engines or any other machines to which it is or may be applicable.

page_text: 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 hereinbefore described arrangement or arrangements whereby each of two
cranks combined for obtaining rotary motion, may be driven past its dead centres
by means of the force acting more directly on the other of the said cranks
substantially as hereinbefore described.