Improvements in or connected with Crank Driving Mechanism.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
Improvements in or connected with Crank Driving Mechanism.
We, EBENEZER STANLEY BURCHETT, Professor of Geometry, and PHILIP
STEPHEN JAMES BURCHETT, Mechanical Engineer, both of 23, Ravenscourt Park,
Hammersmith, in the County of Middlesex, do hereby declare the nature of this
invention to be as follows:-
The object of our invention for, or in connection with, driving mechanism, is
to so construct same whereby there is gained a greater advantage in the use of
the power expended than heretofore; this is effected by automatically increasing
the length of the leverage of a crank when travelling in an acting or driving
direction, and similarly decreasing the length of the leverage of the crank during
its return or inactive travel.
According to our invention we mount in suitable bearings an axle, to which inay
be attached a wheel, called the driven wheel, and upon each side of the said bearing
we mount a fixed toothed chain wheel, having the same axis as the bearing, but
not rotating. Upon each end of the same axle we fix a compound crank composed
cf two members, one part being pivotally attached to the other part, while the
extremity of the second member, or extension of the crank, carries a crank pin or
pedal.
The pivot which carries the second member of the compound crank revolves
in a bearing in the first member, and the said pivot carries a chain wheel connected
by an endless chain to the stationary chain wheel before mentioned, and this
second member of the crank, and its crank pin, are thus controlled or guided in a
circular path.
Upon moving the 'crank pin, the axle and the driven wheel will be eccentric to the
circle travelled by the crank pin, the length of the leverage of the crank during
part of the stroke being considerably greater than during the other part of the
stroke, and the effective leverage is therefore considerably in excess of that usually
obtained.
In some cases the connection between the second member of the crank and the
fixed toothed wheel may be effected either by a series of toothed wheels in gear with
the fixed wheel on the bearing, or by two eccentrics and a strap in lieu of the
toothed wheels.
Our mechanism may be arranged having one, two, three or more cranks,
and is applicable to driving any rotary machines, and especially all type of veloci-
pedes and cycles, and pedal driven machinery.
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T... 1007
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page_text: Improvements in or connected with Crank Driving Mechanism.
We, EBENEZER STANLEY BURCHETT, Professor of Geometry, and PHILIP
STEPHEN JAMES BURCHETT, Mechanical Engineer, both of 23, Ravenscourt Park,
Hammersmith, 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:-
The object of our invention for, or in connection with, driving mechanism, is
to construct same whereby there is gained greater advantage in the use of
the power expended than heretofore; this is effected by automatically increasing
the length of the leverage of a crank when travelling in an acting or driving
.direction, and similarly decreasing the length of the leverage of the crank during
its return or inactive travel.
We will now proceed to describe our invention as applied to the driving
mechanism of a bicycle, with reference to the accompanying drawing, of which,
Fig. 1 is a plan of one side of such driving mechanism; Fig. 2 is a side elevation
and Fig. 3 a half end view of same.
Similar letters of reference refer to like parts in all the figures.
Referring to the drawing, A is the bottom bracket bearing tube of the frame
carrying the bearing for the crank axle A¹ to which latter is attached the sprocket
wheel C called the driving wheel all as usual. Now according to our invention we
mount upon each side of the bearing sleeve A. a fixed sprocket wheel C which
wheels Care arranged concentrically to the axle A' and are held in position by
arms D D¹ D³ extending from the framework of the bicycle.
Upon each end of the axle A¹ we fit. a compound crank, composed of two parts E
and F, the part F being fixed to a pivot pin G which latter passes through a
bearing H on the part E, while the extremity of the part F carries the crank pin
or pedal J. The part E is secured to the end of the axle A¹ by the cotter M or in
any usual manner.
The pin G which carries the second member F of the compound crank is free
to revolve in the bearing H which is situated in the end of the first member E as
aforesaid, and the said pin G carries on its inner end, and keyed thereto, a chain
wheel K which is the same diameter as the fixed chain wheels C, and the pairs of
chain wheels K and C on each side of the machine are connected together by endless
chains L.
By this means the cranks F will travel round the axis of the pin G but will be
always at a constant angle to the ground, the pin G at the same time travelling
round the axle A'; by this means the length of the leverage of the crank during
the downward part of the stṛcke is made considerably greater than during the
upward part, and the effective leverage is considerably in excess of that with cranks
as usually constructed.
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: :―
1. In crank driving mechanism, wherein the leverage of the crank on its down-
ward stroke is increased and reduced on its upward stroke, the compound cranks
composed of two parts, the one part being keyed to the axle and the other part
pivotted to the end of the first part and caused to travel round therewith, in
combination with, a stationary sprocket wheel fixed to the frame of the machine
concentrically with the pedal axle, and a second sprocket keyed to the end of the

page_text: pivot pin to which the outward part of the crank is fixed, which pin unites the two
portions of the crank, and an endless chain connecting the two sprocket wheels.
aforesaid for the purpose of keeping the outward portion of the crank at a constant
angle to the ground, and whereby the pedal is caused to describe a circular path,
and to move therein at an unvarying speed, substantially as described.
2. The general arrangement and construction of crank driving mechanism
combined and acting substantially as and for the purposes hereinbefore described
with reference to the accompanying drawings.
Pool VS
way
οοοτ πι
BREWER & SON,
London and Leeds, Agents for the Applicants.