Year: 1886

page_text: I, CHARLES HENRY TWIST of 22 Sutton Place, in the City and State of New York,
United States of America, 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 following statement:-
In the use of springs for wagons, cars, and other vehicles requiring elliptic, half
elliptic and half springs, that is springs which are not elliptical or half elliptical in
shape but such as side-bar springs, platform springs &c., certain difficulties have been
experienced owing to the want of a proper distribution of the strength and elasticity
of the metal from which such springs are made. Springs which possoss the necessary
strength, have been found to want more elasticity than was consistent with the form
into which the metal was shaped; and, so too, springs which have been made suffi-
ciently elastic, have lacked strength. Elliptic and half elliptic and half springs in
which the leaves are flat may be made sufficiently elastic, but when so the centre
of the spring, which of necessity must bear the weight, is generally wanting in
strength, and consequently such springs usually break, midway, between the ends.
In springs having their leaves made concave, or concavo-convex in cross-section,
there is sufficient strength in the centro, but as the concavity and convexity have
heretofore been made to extend from one end of the leaf to the other, the ends of
the leaves do not have sufficient elasticity, and consequently, as the strain is conveyed
from the mid-portion to the ends where the yield must eventually take place, the
want of sufficient elasticity causes such springs to break near the ends. And, not
only so, the pressure upon such a spring causes the leaves to "buckle" and flatten out
in places when bent beyond a straight line, or the reverse of their original shape or
curvature.
The object of my invention is to secure a more perfect combination and distribution
of strength and elasticity in the construction of elliptic, half elliptic and half springs

page_text: than has heretofore been attainable, and it consists in the construction of one or more
leaves with the central or mid-portion made concavo-convex in cross section, and
which is made to taper from such concavo-convex shape to a flat surface, the ends
being made flat, and further in the construction and arrangement of the leaves when
the spring is made up of a number of leaves as hereinafter more fully described and
claimed.
In the drawings Figure 1 is a side elevation of an elliptic spring, each half of which
is composed of several leaves which are concavo-convex in cross section at the centre
or mid-portion, as appears in Figure 2, which is a sectional view taken on the
line,, of Figure 1. Figure 3 is a cross section taken on the line z, z, of Figure 1,
and shows the flat surface of the ends of the two lower leaves of the spring. Figure 4,
is a cross section taken on the line y, y, of Figure 1, and shows the leaves of the
spring less concave than at the centre, but not quite flat, but this figure shows the
manner in which the leaves taper from the concave to the flat form by gradually
becoming more and more flattened until they reach a flat surface, in which shape the
ends are made. Figure 5, is a central cross section of a modified form of spring and
shows the main or longest leaf, as being made plano-concave in form at the centre
while the other leaves are concavo-convex, but each leaf in such spring tapers into a
flat surface at the ends, as do those of the spring shown in Figure 1, and its cross
sections Figures 3 and 4.
Figure 6, is a central cross section of another modification, and shows a spring in
which the main or longest leaf is made flat its entire length, while the next leaf is
plano-concave like the main leaf of the spring shown in Figure 5.
In the drawings I have shown a spring composed of five leaves a, b, c, d, e, but the
number of leaves is an immaterial matter, and is to be regulated by the requirements
which are to be met in its practical use. Where several leaves are used they may be
placed together one upon another and secured in the ordinary way. In making the
leaves, however, and in preparing them for use, I make the mid-portion concavo-
convex in cross section, and from a certain distance on each side of the centre I taper
them so that they gradually pass from a concavo-convex form to a flat surface, the
ends being made flat. This shape may be given by a die or suitable tools, and, of
course each leaf will begin to taper at practically the same distance from the centre, so
that a snug fit of one leaf upon another may be obtained. This will make the flat
portion of the main loaf longer than that on any other leaf, and consequently some of
the shorter leaves may not reach a flat surface at the ends, especially if there be many
leaves in the spring, but this will not impair the elasticity which will be carried on the
longer leaves and terminate in a yielding at the ends, to which point the strain will
extend in any event. The main leaf and the one next to it are the ones which must
he depended upon for the most elasticity and they of course have the greatest amount
of flat surface.
In making a single leaf spring I may use one leaf which is concavo-convex in the
centre and which tapers to a flat surface at the ends or I may use a leaf which is
plano-concave, that is having one flat side while the other is made concave.
So also in using a number of leaves to compose the spring I may make the
main leaf plano-concave as shown in Figure 5, or I may have a flat main
leaf as shown in Figure 6, in which case the second leaf is inade plano-concave
and the others concavo-convex. Or if the spring to be constructed is a heavy
one containing a large number of leaves, I may use several flat leaves, always putting
a leaf plano-concave in shape between the flat leaves and the concavo-convex shaped
leaves. In each case, however, the leaves which furnish the elasticity are made flat at
the ends. The other leaves which furnish the necessary strength in the centre being
shorter may not taper sufficiently to remove the concavo-convex surface.
By making a spring in the manner explained I am enabled to combine the desirable
elements of a spring having concavo-convex leaves, which give strength in the centre,
with the yielding qualities at the ends of a spring having flat leaves, thus making a
more durable spring without increasing the cost.

page_text: Having now particularly described and ascertained the nature of my said invention,
and in what manner the same is to be performed, I declare that what I claim is :-
First. A vehicle spring having one or more leaves, which are concavo-convex in
cross section midway between the ends, the same being made to taper toward the ends
from a concavo-convex surface to a flat surface, and the ends whereof are flat,
substantially as and for the purpose set forth.
Second. In a vehicle spring a leaf made plano-concave in cross section midway
between the ends, the concave surface whereof is made to taper into a flat surface, the
ends of such leaf being made flat, substantially as described.
Third. A vehicle spring, having its longest leaf made flat, and a leaf above the
same made plano-concave in cross section, midway between the ends, the concave
surface of said leaf being made to taper into a flat surface at the ends, substantially as
described.
HERBERT J. ALLISON,
Agent for the Applicant.