Improved Driving Gear for Bicycles and other Machines Driven or Propelled by Crank Mechanism.
Year: 1898

page_text: Date of Application, 7th Nov., 1898 -Accepted, 2nd Sept., 1899
COMPLETE SPECIFICATION.
Improved Driving Gear for Bicycles and other Machines Driven or
Propelled by Crank Mechanism.
We, ROBERT VILE THOMPSON, of No. 450, Elizabeth Street, Melbourne, in the
Colony of Victoria, Engine Fitter, CHARLES ALBERT HORTON, of No. 575, Sydney
Road, Brunswick, near Melbourne, aforesaid, Engineer, and WILLIAM MURPHY,
of "Seaforth," Bond Street, Caulfield, near Melbourne, aforesaid, Gentleman, 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 follow-
ing statement:.
-
This invention relates to machinery driven by cranks and is especially applic-
able to bicycles and other velocipedes, its main object being to obtain a maxi-
mum rate of speed and a minimum expenditure of power.
Its essential feature consists in the use of cranks pivotally mounted on rigid
supports at any desired distance from or in front of the centre of the main
drive wheel or axle. These cranks are formed with longitudinal slots or grooves
engaging with projecting anti-friction rollers or with a stud or the like on the
side of a sprocket or other drive wheel mounted upon the axle or shaft of the
machine. These cranks are so arranged as to give a maximum leverage upon the
main drive wheel at those parts of the stroke where the maximum effect is
required or is obtainable whilst it gives a correspondingly reduced leverage on
the return stroke.
The invention as above stated is mainly applicable for the driving gear of
bicycles and other velocipedes, but in order that its application to other classes
of crank driven machinery may also be understood we will subsequently describe
it with reference to steam or other engines and pumping machinery.
In order that these various applications of our invention may be readily under-
stood we will describe them with the aid of the accompanying drawings in
which,
Figure 1 is a side elevation of part of an ordinary bicycle illustrating our
improved driving gear applied to it, and
Figure 2 is a horizontal section on line 2-2 Figure 1.
Figure 2 is a detail view illustrating a slight modification of a mechanical
detail.
Figure 3 is a side elevation of a steam engine illustrating the application of
our invention thereto whilst,―
Figures 4 and 5, are side and front elevations illustrating the application of
our invention to a pump.
The same letters of reference indicate the same or corresponding parts in all
the figures.
Referring to Figures 1 and 2, A represents a part of the frame of a bicycle,
and B B the cranks which are, according to this invention, pivotally mounted as
indicated at 6, upon rigid supports 61 secured to and projecting forwardly from
a fixed axle C which is mounted or secured within the ordinary barrel at the
lower part of the frame. Between the supports and each end of said barrel
are mounted two sprocket wheels I on ball bearings, as illustrated in Figure 2.

page_text: "
These sprocket wheels are fitted with laterally projecting antifriction rollers or
studs d which fit into and work within slots 2 in each of the cranks B. Or if
preferred in lieu of these slots recesses may be provided on the inner side of
the cranks to receive said rollers or the modification ilustrated in Figure 2"
may be employed the cranks being made solid, as shown, and passed through
eyes or lugs projecting from the sprocket wheel.
It will be evident that on the downstroke the crank or cranks will project
beyond the sprocket wheels and there will be considerable leverage exerted upon
said wheels whilst on the up stroke the leverage will be reduced. This result
is obtained without increasing the travel of the ends of the cranks. By this
means a much higher gear can be used than would otherwise be practicable,
and consequently a higher rate of speed can be attained without entailing a
greater expenditure of power than with ordinary gear.
The invention can be applied to a steam or other engine in a very simple
manner, as illustrated in Figure 3, the connecting rod being attached to a
crank B mounted upon a pin or stud 6 above the centre of the main shaft so
that at certain parts of the stroke the piston will exert its power upon said
shaft through the medium of the lever constituting the crank B and consequently
more power will be developed during that part of the stroke.
For pumping purposes the leverage available from the crank B might be
arranged to come into play when the greatest power is required. This will be
readily understood from the illustration of the application of the invention to
an ordinary hand pump as shewn in Figures 4 and 5 where the crank B is
pivoted or fulcrummed upon a rigid support 6 projecting from the fixed stud or
spindle C and engaging with a stud or pin projecting from the main fly wheel
of the pump. Motion can be imparted from this fly wheel to the pump rods by
means of an eccentric as shewn.
From the illustrations given above it will be obvious that our invention may
be applied to many different classes of machinery where an increase of power is
required during a part of the stroke.
Having now particularly described and ascertained the mature of our said
invention and in what manner the same is to be performed, we declare that what
we claim is:
-
1. The herein described driving gear for bicycles and other machines driven
or propelled by crank mechanism consisting of the various parts constructed
arranged and operating substantially as and for the purposes herein described
and explained and as illustrated in the accompanying drawings.
2. In driving gear for bicycles and other machines driven or propelled by crank
mechanism a crank (such as B) mounted upon a pin (such as 6) or other fixed
support at any desired distance from the centre of the sprocket or drive wheel
axle, and connected with said wheel by a pin or antifriction roller either working
within a slot or groove in said crank or else encircling said crank substantially
as herein described and explained and as illustrated in the accompanying draw-
ings.
Dated this Sixteenth day of August, One thousand sight hundred and
ninety-eight.
ROBERT VILE THOMPSON.
CHARLES ALBERT HORTON.
WILLIAM MURPHY.
G. F. Redfern & Co.,
4, South Street, Finsbury, London, Agents for the Applicants.