Improvements in or connected with Crank Driving Mechanism.
Year: 1896

page_text: Date of Application, 18th June, 1896
Complete Specification Left, 18th Mar., 1397-Accepted, 15th May, 1897
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
construct same whereby there is gained a greater advantage in the use of the power
expended than heretofore; this is effected by increasing the length of the leverage of
a crank when travelling in an acting or driving direction, and the length of the
leverage of the crank is decreased during its return or inactive travel.
According to our invention we mount in suitable bearings an axle, to which may be
attached a wheel hereinafter called the driven wheel, the said axle having upon it a
projecting boss or hosses formed with a broad groove or slot therein at right angles to
the axis of the driven wheel.
Free to move in a longitudinal direction within the boss groove, is a sliding crank,
which sliding crank carries a crank pin or pedal on the one side and a guide-block or
sliding clip upon the opposite side.
Carried in any suitable manner is a fixed or stationary guide ring, circular or
otherwise, placed eccentrically to the axis of the driven wheel, engaging with which
is the before mentioned guide block or sliding clip.
By our invention the travel of the crank pin or pedal is guided by the above fixed
ring, the crank pin or pedal being carried upon the sliding crank passing through the
groove in the axle boss as aforesaid and free to slide longitudinally therein.
Upon moving the crank pin, the axle and the driven wheel will be eccentric to the
axis of the driven wheel, the length of the leverage of the crank during part of the
stroke being considerably greater than that during the other part of the stroke, and
the length of the effective leverage being considerably in excess of that usually
obtained.
Our mechanism may be arranged having one, two, three or more cranks, and is
applicable to driving any rotary machines, and especially all types of velocipedes
and cycles.
BREWER & SON,
London and Leeds, Agents for the Applicants.
COMPLETE 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, and in
what manner the same is to be performed to be particularly described and ascertained
in and by the following statement :-
Many attempts have been made to increase the leverage of velocipede cranks, during

page_text: the effective part of the stroke and to decrease the leverage during the return motion,
but such arrangement have involved the employment of a considerable bearing surface
between the moving parts, and the number of moving parts have been greatly
increased with the result, that the friction in and cost of production of such driving
mechanism is a feature of great disadvantage.
Our invention refers to an arrangement which comprises upon each side of the
machine a single crank, with a pedal attached at its outer end; the pedal end of the
crank is pivotally fixed to a small guide block or clip, which latter embraces and is
adapted to be travelled around a stationary ring, the latter being fixed to the
framework of the machine eccentrically to the driven wheel axle. The cranks at the
end opposite to the pedal, are arranged to slide through a slot or groove in, and at
right angles to the axis of the pedal shaft.
In order that our invention may be readily understood, we have appended illustrative
drawings shewing means whereby our invention may be carried into effect.
Fig. 1 is a side elevation of the mechanism complete.
Fig. 2 is a plan of the parts shewn at Fig. 1.
Fig. 3 is an enlarged side elevation of the guide block, also shewing a portion of the
crank and stationary ring.
Fig. 3 is a sectional plan taken upon the line x y of Fig. 3.
Fig. 4 is an inverted sectional plan taken upon the line X Y of Fig. 3.
Fig. 5 is a plan view of Fig. 3 with the crank removed.
Fig. 6 is a sectional end elevation taken upon the line X! Y' of Fig. 3.
Fig. 7 is an end sectional view taken upon the line X2 Y2 of Fig. 3, the crank
being removed.
Fig. 8 is a vertical longitudinal elevation partly in section, of the guide block
hereinafter more fully described.
Fig. 9 is a back elevation of Fig. 3.
Fig. 10 is an enlarged side elevation of the guide, fitted to the end of the axis of
the pedal shaft through which the crank slides.
Fig. 11 is an end elevation of Fig. 10.
Fig. 12 is a front elevation of the back part of the guide, Fig. 10, when all the
detachable parts have been removed therefrom.
Fig. 13 is an end elevation of Fig. 12.
Fig. 14 is a sectional side clevation taken upon the line X3 Y3 of Fig. 10.
Fig. 15 is a sectional side view taken upon the line X Y of Fig. 11.
With reference to Figs. 1 and 2 of the drawings we have illustrated our mechanisin
and so much of a velocipede frame, as is necessary to illustrate the application thereto
of mechanism constructed and arranged according to our invention.
The driven wheel A is keyed upon or secured to an axle, which passes through and
is carried in suitable bearings, within the bottom bracket B, of the velocipede
framework in the example shewn the mechanism fitted on both sides of the axle
is similar, it will therefore be sufficient if that upon one end only is described.
C is the guide, fixed to the axle, the said guide having at right angles thereto, a
broad groove or slot formed therein. Free to move in a longitudinal direction within
the groove of the guide C, is the sliding crank D, which latter carries the pedal
pin E, upon which is mounted the pedal F.
G is the stationary guide ring, carried by and fixed to the framework of the machine,
engaging with which guide ring G is the guide block or sliding clip H.
Thus it will be seen that upon the front pedal F being depressed by the foot of an
operator in the direction indicated by the arrow, the leverage of the crank would be
considerably longer during its descent than during its return and upward movement
to that position in which it is now shewn. During the circular rotation of the pedals F,
the latter travel eccentrically to the axis of the driven wheel A, the length of the
stroke required being equal to the diameter of the guide ring G, while the leverage
at certain parts of the descent is much greater than the radius of travel of
the pedals.
Illustrated at Figs. 3 to 9 we have shewn (drawn to a larger scale than at

page_text: Figs. 1 and 2), the construction and arrangement of the head of the crank D, and
also the guide block or sliding clip H.
The head of the sliding crank D is formed to receive a bush D' which latter is
clamped in position by means of the screw D2 which draws the embracing parts of
the crank end tightly around such bush; a longitudinally adjustable cone D³ screws
within the bush B'.
The guide block or sliding clip H is built up of a number of parts, which consist
of a front plate H' from which projects a pin H2 having a ball race cut therein
to receive balls J, Fig. 4 which latter are held in position by the adjustable core D³
and the bush D¹ carried by the head of the crank D, and the balls also retain the said
crank D in position as is clearly seen at Fig. 4.
Arranged one above and one below the ring G, are two plates H3 and H' which
are held by rivets H to two plates H. Each of the plates H are constructed
with a projecting part H', which is arranged concentrically within the recessed
parts of the plates H³ H*.
These pairs of plates H³ H and H H are held in contact with the front plate H¹
by means of bolts which are extensions of the rivets H, and when so arranged in
position they form upper and lower channels for the reception of balls which bear
against the ring G on one side, and the central parts H' on the other side, the
channels or grooves away from the ring G, (best seen at Fig. 8) are return passages,
so that when the guide block H is travelling around the ring G, the balls move
along the surface of the said ring G and pass again to the front by way of the
return channel.
Provision is made for the adjustment of the bearing by means of the screws K K
which bear upon the two upper bolts H which latter pass through slotted holes in the
plate H', and thereby the bolts H³, together with the pair of plates H³ H®, may be
adjusted to suit requirements.
We will now proceed to explain the construction of the guide located in the end
of the axle of the wheel A, which guide C we have illustrated at Figs. 10 to 15
inclusive on a larger scale than that shewn at Figs. 1 and 2.
A plate is provided having a projecting boss C which takes and is fixed onto
the axle of the driven wheel A. The plate which is shewn at Figs. 12 and 13, is
formed with a projecting part 3 around which is fitted and secured in position
by screws L Fig. 11, a recessed plate C, the two when secured together forming a
channel or race to receive balls.
Similar channels are formed at the opposite parts of the plate but in this case
the central part C is composed of two parts held together by screws M Figs. 10 and 15,
and a surrounding plate C having a recessed part is secured by the overlapping
of the plates C C³×
In this manner we have a groove adapted to receive the crank D, the said
groove having balls arranged in contact on each side of the crank D, and return
channels for the said balls.
Adjusting means are provided as shewn at Fig. 15 wherein screws N are fitted
into the projecting lip and act upon the plate C, as also on plates C³ C¹³* for
the reason that the said three plates are secured together.
We are aware that it is not broadly new to provide mechanism whereby the length
of leverage of each crank is greater during the effective portion of the stroke than
it is during the ineffective portion. We are also aware that it has been proposed in
printed patent specifications some years ago to fit the cranks to slide during the
revolution in bearing boxes upon the ends of the driven shaft, and we are also
aware that it is not new to provide eccentric discs or plates fixed to the frame of
the machine, the circular straps of which are pivotally connected to the cranks and
whereby the latter are slidden in the guide blocks upon the ends of the pedal axle
to increase and decrease the acting length of the cranks.
Further we are aware that it is not new to provide a fixed eccentric disc upon
each side of the machine, the disc having a circular eccentric strap, and an arm

page_text: extending therefrom and pivotally connected with the axis of a pedal whereby the
position of the latter is changed relatively to the axis of the driven shaft during its
revolution, such having been patented in the United States of America several years
ago. Ball bearings having return passages for the balls are well known, and it has
further been proposed some years ago to arrange such bearings between slide blocks
and guides in velocipedes:
Having now particularly described and ascertained. the nature of our invention
and in what manner the same is to be performed we declare that what we claim
as our improvements in driving mechanism for velocipedes where the length of
leverage of the cranks is automatically increased during the effective part of the
travel, and decreased during the ineffective part of the travel, to be as follows:-
1. The combination with a pedal crank adapted to be slidden lengthwise through
a slot or guido formed in or fixed to the end of the crank shaft and at right angles
to the axis thereof; of a ring fixed to the framework of the machine in a plane
parallel to the plane of travel of the crank, and set eccentrically to the crank shaft,
a short segmental block or clip to embrace the outer and inner peripheries of the
fixed ring, and to hold onto and be travelled round the said fixed ring, and a pivotal
connection between the clip and the pedal end of the crank, the effective length of
leverage of the said crank being governed by the eccentricity of the fixed ring, and
whereby the crank is supported at one end by its bearing in the crank axle, and at
the other end directly against the fixed ring, substantially as set forth.
2. The combination with the driving mechanism as claimed by Claim 1, of the
particular arrangement and general construction of the short segmental blocks and
parts connected therewith, together with the ball bearings therefor having the return
channels for the balls, substantially as and for the purposes described and illustrated
with reference to Figs. 3 to 9 of the accompanying drawings.
3. The combination with the driving mechanism as claimed by Claim 1, of the
particular arrangement and general construction of the parts composing the guides
upon the ends of the crank shaft, through which the cranks slide, together with the
ball bearings therefor having the return channels for the balls, substantially as and
for the purposes described and illustrated with particular reference to Figs. 10 to 15
of the accompanying drawings.
4. The general arrangement of combination of parts composing our improvements in
driving gear for velocipedes, arranged and acting substantially as and for the purposes
described and illustrated with reference to the accompanying drawings.
this 10th day of
BREWER & SON,
London and Leeds, Agents for the Applicants.
BREWER & SON,
London and Leeds, Agents for the Applicants.