An Improved Frame for Rear-driving Safety Bicycles and other Cycles.
Year: 1890

page_text: Date of Application, 17th Mar., 1890
Complete Specification Left, 16th Dec., 1890-Accepted, 17th Jan., 1891
PROVISIONAL SPECIFICATION.
An Improved Frame for Rear-driving Safety Bicycles and other
Cycles.
I, JOHN BOYD DUNLOP, of 50 Gloucester Street, Belfast, Veterinary Surgeon, do
hereby declare the nature of this invention to be as follows:-
:-
This invention, which is based upon that described in the Specification accompanying
my application for Letters Patent No. 16119 dated 12th October 1889, has for its
object to produce a spring frame for safety bicycles and other cycles in which flexible
metallic bars or rols are employed to reduce vibration whilst maintaining the position
of the seat, relatively to the crank or driving axle, always constant.
The improved frame, according to my present invention, is simple in construction,
it being so arranged that the working joints or hinges usually employed in spring
frames are rendered unnecessary.
In accordance with my invention that portion of the frame to the rear of the
steering socket takes the form of the ordinary diamond frame with the stays (or fork)
I employ two
between the seat pillar socket and the axle of the rear wheel removed.
bars of flexible spring steel or similar material, the upper and front ends of which
are bolted, or otherwise secured, to a lug on the lower end of the steering socket, and
the other ends of the said bars are bolted or otherwise secured to lugs or brackets on
the bearing cases of the driving or crank axle. I also propose to employ two other
bars or the like of flexible spring steel, or similar material, the upper ends of which
are bolted to a lug on, or adjoining, the seat pillar socket, and the lower ends of said
bars are bolted, or otherwise secured, to lugs or brackets on the bearing cases of the
driving or crank axle.
The front fork is of the usual description. A tube, about 10 inclios in length, is
brased on the crown of the front fork, and placed, one inch, more, or less, in front of
the steering socket and parallel thereto. The said tube is connected, at its upper and
lower ends, to the steering post by means of flat, curved or bent springs of steel or
other similar material.
These springs are bent in a horizontal plane.
When desirable, the upper end of the tube on the fork crown, and the lower end
of the steering post, may be connected by means of an auxiliary suspension spiral
spring so as to minimise the jarring or vibration of the pilot or front wheel.
JAMES STEVENSON,
Gray's Inn Chambers, 20, High Holborn, London, W.C., Agent for Applicant.
COMPLETE SPECIFICATION.
An Improved Frame for Rear-driving Safety Bicycles and other
Cycles.
I, JOHN BOYD DUNLOP, of 50 Gloucester Street, Belfast, Veterinary Surgeon, do
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:—
This invention, which is based upon that described in the Specification accompanying
my former applications for Letters Patent 16,119 October 12th, 1889, 20,319
December 17th, 1889 has for its object to produce a spring frame for safety
bicycles and other cycles in which flexible metallic bars or rods are employed to reluce
vibration whilst maintaining the position of the seat, relatively to the central axis of
the steering post and that of the crank axle, always constant.
The improved frame according to my present invention is simple in construction,
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page_text: are rendered unnecessary.
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In the accompanying drawing
Figure 1 is a side elevation of my improved frame adapted to a rear driving safety
bicycle.
Figure 2 is also a side elevation of the frame shown detached and slightly modified
in form.
Figures 3 and 4 are plan views of the springs which connect the steering post with
the front fork; and,
Figures 5 and 6 are elevational detached views of the yielding or "springy" portion
of the supporting framework, hereinafter more particularly referred to.
In accordance with my invention, that part of the frame to the rear of the steering
socket assumes a form somewhat analogous to that of an ordinary diamond frame,
with the stays, support or fork, between the seat pillar socket and the axle of the rear
wheel, removed. The frame comprises a rigid tube A firmly bolted, brazed or other-
wise united to the upper end of the steering socket B, or steering centre neck pin, and
extending horizontally, or nearly so, rearwards to the seat pillar socket C to which it
is also firmly secured. Two bars a, a', of flexible spring steel, are bolted, or otherwise
secured, at their lower ends, to lugs or brackets formed on the crank axle bearing
case F. and, at their upper ouds, to a lug or bracket formed on the rigid tube A
adjacent to the seat pillar socket (). The spring bars a. a', may extend upwards from
the crank axle case at any desired angle; and may be made to pass on each side of
the rear wheel, and be attached to a fork E projecting from the seat pillar socket C.
in place of being attached to the tube A, as shown in Figure 2. Two other bars b. b),
also of spring steel. are secured by their rear ends to lugs or brackets on the crank
axle case F, the anterior ends of said bars being bolted to a lug on the lower end of
the steering socket B. The rear horizontal rigid fork c is made sufficiently strong to
hear all strain on the rear wheel. A tube d is brazed or similarly secured on the
crown of the front fork, and is placed an inch or so, more or less, in front of the
swering socket B, and parallel thereto. The tube d is connected at its upper end to
the steering pillar B₁, by means of the two flat bars of spring steel D', curved or bent
angularly in a horizontal or inclined plane. Figure 3. Said tube d is also connected.
at its lower end, to the steering post B₁ by two similar springs D. The ends of the
surings D, D, are preferably bolted to lugs or brackets formed on the steering post B¹
and tube d. These springs are disposed one on each side of the steering post and tube,
as shown in Figures 1 and 3; they may however entirely or partly surround the
steering post and tube, in which latter case, one spring of each pair would be slightly
above or below the other, Figure 4.
It will be seen that the spring bars a, a, and b, & Figures 1, 2, and 5, form the
sides of two triangles with the crank axle bearing case F as a base, common to both;
therefore, the points where a, a', and b,, meet are maintained perpendicularly to
the centre of the crank axle case F, whilst the bars a, a', and b, b', by their lower
ends maintain the crank axle case F parallelwise to the axles of the front and rear
wheels on account of the absence of the usual rigid support or forked stay between
the seat pillar socket and the axle of the rear wheel, the spring bars a, a', and b, b³,
being subjected to a bending strain; the flexibility of the said spring steel bars
permitting the crank axle case to sink and slightly rotate on its own axis when the
weight of the rider is thrown on the machine and when vertical motion is imparted
to the rear end of the horizontal fork owing to the rise and fall of the rear wheel
caused by the inequalities of the road or other surface. When it is desirable to have
the crank axle case movable for the purpose of adjusting the chain I may join the
lower ends of said bars a, a and b, to lugs on a bar or tube near to the crank
axle and parallel thereto.
When it is found necessary to increase the width of the base of the triangular
portion of the frame, the lug on the crank axle case farthest from the chain wheel may
be placed at an increased distance from the centre of the axle case relatively to the
lug adjoining the chain wheel.

page_text: A single spring bar, tapering in width from the top or front end to the lower or
rear end Figure 6-might be substituted in lieu of the duplicate bars a, a, b, b',
and may be bifurcated if so desired.
The springs or curved bars D, D', at the front of the machine, permit of an easy
vertical motion, whereby the vibration from the front wheel is considerably lessened.
These springs might be placed lower down, on each side of the wheel, in which case
the steering post would be provided with a forked extension, each member of which
would be connected, by means of said springs, to a tube running parallel to such
forked extension and resting on each end of the axle of the front wheel, the tube d
being dispensed with. I may bend said springs or bars D, D', in other forms but
they are preferably bent so as to be as near as practicable in a plane when the rider
is supported on the machine. These curved springs act as stays or links as well as
springs. It is important that said springs D, D¹, should be placed one above
another with a considerable space between them as shown so as to maintain the
tube d, and socket B parallel to one another. In the case of a lady's bicycle, the
springs a a', might be inade shorter and the tube A curved downwards in the centre
to correspond.
.
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 :-
First. A spring or flexible frame for cycles with bars a, a and b, b', substantially
as described and shown and for the purposes specified.
Second. In combination with a spring or rigid frame the employment of bent or
curved steel bars D, D₁ placed one above another and connecting the steering post
and front fork together substantially as described and shown.
Dated this 16th day of December 1890
JAMES STEVENSON,
Gray's Inn Chambers, 20, High Holborn, W.C., Agent for Applicant.