Improvements in Chain Driving Gear for Velocipedes.
Year: 1889

page_text: Date of Application, 29th Aug., 1889
Complete Specification Left, 28th May, 1890-Accepted, 19th July, 1890
PROVISIONAL SPECIFICATION.
Improvements in Chain Driving Gear for Velocipedes.
I, ARCHIBALD SHARP, Engineer, of 26 Melrose Gardens, West Kensington Park
in the County of Middlesex, do hereby declare the nature of this invention to be as
follows:-
My said invention relates to a method of tightening the chain, and to a method of
constructing the crank bracket in chain-driven velocipedes.
For providing a means of adjusting the chain, the upper and lower forks of the
driving wheel have each an eye hole formed at the end for the reception of the wheel
spindle. The opposite ends of the forks are attached to the frame by hinge joints.
The lower fork, which is approximately parallel to the line joining the chain wheels'
centres and which is attached at one end to the crank bracket and at the other end to
the driving wheel spindle, is made so that its length may be adjustable. This adjust-
ment may be made by forming each side of the fork in two pieces united by a right-
and-left-handed screw, the turning of which screw will make an alteration in the
distance between the chain wheels; or by a single screw fitting into the end of each
tube forming one side of the fork, the said screw having an eye formed on its
opposite end for attachment to the crank bracket by a pin passing through the said
eye.
The crank bracket consists of a short piece of tube, through which the crank asle
passes, screwed internally at each end for the reception of the 'cones' forming part
of the ball bearing. In double frame' velocipedes, encircling this tube at each end
is fixed a ring having projections or snugs to provide for the fixing of the crank
bracket to the different parts of the frame. In single frame' velocipedes a corres-
ponding ring will be placed at the middle of the aforesaid tube, for fixing to the
single members of the frame; the two rings at the ends being still required to provide
for the attachment of the lower fork.
Dated this Twenty-eighth day of August 1889
COMPLETE SPECIFICATION.
Improvements in Chain Driving Gear for Velocipedes.
I, ARCHIBALD SHARP, Engineer, of 26 Melrose Gardens, West Kensington Park,
London, 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:-
My said invention relates to an improved method of tightening the chain, and to a
method of constructing the crank bracket in chain driven velocipedes.
The upper and lower forks of the driving wheel are attached to the frame by the
bolts a and b fig. 1, and the lower fork can be altered in length to provide a chain
tightening adjustment. The upper fork being hinged to the frame by the bolt a is
free to adjust itself to a new position corresponding to the altered length of the lower
fork. This alteration can be made by having a screw c on each of the two tubes k
which form the lower fork, the end of the said screw being attached to the frame by
the bolt d. The wheel spindle is, as usual, threaded through holes in the back ends of
the forks.
When the angle P fig. 1 is nearly a right angle a small alteration in the length of
the lower fork will make no appreciable alteration in the angle Q. In this case the
following method may be used for adjusting the length of lower fork :-e is a
right and left handed screw (see lower part of fig. 3). One end is screwed into the

page_text: The
projection of the crank bracket and the other into the end of the tube k.
screw when properly adjusted may be fixed in position by a lock nut; or
alternatively, by the ferrule the bore of which is hexagonal. This hexagon fits that
of the screw and an equal hexagon formed either on the end of the tube / or on the
projection from the crank bracket. To make an adjustment the ferrule g is moved
9
along tube and the screw e is turned by a spanner into the desired position, the
ferrule is then moved back to cover the hexagons one and f. The ferrule may
be retained in position by a pin or spring.
The crank bracket (figs. 2 & 3) consists of a short piece of tube / into the ends
of which the cones forming part of the ball bearings are fixed either by screwing or
brazing. Encircling this tube at each end is a ring m with projections 2, y, z, for the
attachment of the bracket to the different members of the frame. Figures 2 and 3
shew the arrangement for 'double frame velocipedes; for single frame velocipedes
there will be another similar ring near the middle of tube h.
Having now particularly described and ascertained the nature of my said Inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is,
1- The method of forming a chain tightening gear by altering the length of
the lower fork, while the crank bracket is immovably fixed to the frame, the upper
fork being attached by a bolt to the frame so as to allow of said alteration to
take place without straining the frame; substantially as described above.
2 The two combinations for altering length of lower fork as described and
illustrated in figures 2 and 3.
3-The method of forming a crank bracket by a short length of tube encircled by
rings with suitable projections for attachment to the frame.
Dated this Twenty-eighth day May 1890.