IMPROVEMENTS IN ELLIPTIC SPRINGS
Year: 1885

page_text: COMPLETE
DIECIFICATION.
I, WILLIAM DAVISON, a subject of the Queen of Great Britain, residing at
Hoboken in the County of Hudson and State of New Jersey one of the United.
States of America Manufacturer, do hereby declare the nature of my invention
for IMPROVEMENTS IN ELLIPTIC SPRINGS and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement :-
My invention relates to elliptic and semi-elliptic springs made of plates of concavo-
convex form in cross section and arranged in the spring with the concave sides of the
plates on the outer or crowning side of the longitudinal bend and with the convex
sides on the longitudinally concave side of the spring, so that the edges of the
plates of the spring are subject to compression in service, and the tension is sus-
tained by the web of metal between the edges, by which the metal is disposed in
the spring so as to sustain the greatest weight of load for a given quantity of
metal in the spring.
My invention consists of the short outside or top plate of the spring constructed
with ends.extended beyond the edges of the band proportionately to the extension
of the ends of the intermediate plates, and being graduated from the flat upper
surface to the concave form of the same corresponding to that of the other plates.
And the invention also consists of the said top plate and the intermediate plates
constructed with points curved proportionately to the breadth and transverse
curvatures of the plates, all for graduating the spring better and making it more
substantial and durable than as heretofore constructed reference being made to the
accompanying drawings in which :
Fig 1 is a perspective view of a complete spring constructed with my improve-
ments.
Fig 2 is a transverse section of the upper member of the spring on the line xx.
Fig 3 is a transverse section of the top plate on the line y, y, of fig 4, and Fig 4
is a longitudinal section of the top plate on line z, z, fig 3, figs 2, 3 and 4 being on
a large scale.
I make a top plate of transversely convex form its whole length on the longi-
tudinal concave or inner side that is to fit in the concave outer side of the second
plate of the spring with the middle portion a, of said top plate flat on the upper or
outside and the end portions b, concave transversely and tapering in thickness from
the ends of the flat portion to the ends of the plate.

page_text: I also taper the edges of the said top plate to a point at the ends beginning back
of the ends a distance equal to the width of the plate and constructing said taper
edges on a curve the radius of which is the width of the plate, and I also construct
the points h of all the other plates of the spring except the main plate in the same
form which, together with the transverse concavo-convex curvatures of the plates
formed on the same radius, as represented in fig 2, and with the arrangement of
the plates in uniformity as to the distances between the ends of the superimposed
plates ensures almost perfect uniformity in the movements of the spring for given
weights in closing under the load.
I make the flat section a, of the top plate a little longer than the width of the
band d by which the plates are bound together so that the ends e of the flat section
will be extended beyond the ends of the band to separate these points for better
graduation and I also extend the ends of the said top plate beyond the ends of the
flat section a, so that the curves f of the taper ends vanish in the edges of the plate
at the points g, some distance from the ends e, while the taper of the thickness of
the plate, both along the edges and in the concaves b, extends from the points 1 to
the ends e, of said taper sections for graduation of said concave and tapered ends.
The plano-convex section a, of the top plate is about as much thicker than the
concavity to be filled by it in the second plate as the thickness of the other plates
of the spring so that from the edges of the band to about where the taper edges of
the points begin at g, the edges of the top plate rise about the same above the
second plate as the edges of the other plates are above the plates below them, and
from these points the ends of the top plate taper both in thickness and breadth in the
same measure as the ends of the other plates, I may however make the top plate
thinner in some cases.
These contrivances very greatly improve the spring in the uniformity of the load
carrying power, that is to say, by the fine graduation of the spring due to these
improvements, the load sustaining power of the metal is so uniformly distributed
throughout the whole spring, that each part has the requisite strength for its
position which will be readily understood when it is considered that where the top
plate terminates abruptly and without any graduation and also at or near the
edge of the band that the weakest part between said end of the top plate and the
end of the next plate below it will be directly at the end of said top plate, because
there is the greatest variation in the quantity of metal and being the weaket point
the deflection will here be the greatest and the metal will be subjected to the
greatest strain and to more than it would be with the same load if more evenly
graduated, whereas with the graduation which I effect with the graduated and
tapered ends which I make, the deflection is distributed along the spring so that
the metal is much less tried with the same amount of the load.
The same is true with the graduated ends of the intermediate plates, and it is
found in practice that the graduation of the ends of the plates by curves of the
same radius as that of the transverse concavity of the plates, gives better results in
springs having this concavo-convex form than any other shape of the ends.
Numerous tests of springs made with top plates as herein described and with
the taper points of the intermediate plates curved on the same radius as the points
of said top plates have invariably given practically the same extent of closing of
the spring for the same amount of additional weight throughout the whole range
from the beginning to the limit of the load.
When I speak of the top plate I mean the outer short plate of either half of an
elliptic spring whether said plate be at the top or bottom of the spring in use.
Having now particularly described and ascertained the nature of my invention
and in what manner the same is to be performed, I declare that what I claim is
1st The improved top plate for elliptic or semi-elliptic springs made with
concavo-convex intermediate and main plates having the plano-convex middle
section a, and concavo-convex and tapered ends substantially as described.
-
2ond The improved top plate for elliptic or semi-elliptic springs made with concavo
convex intermediate and main plates having the plano convex middle section a,

page_text: and concavo convex ends said ends being tapered at the edges on a radius equal
to the breadth of the plate substantially as described.
3rd The combination in an elliptic or semi-elliptic spring of a top plate having
the plano-convex middle section a, and concavo-convex pointed ends with inter-
mediate concavo-convex plates baving similarly pointed ends and a main plate of
concavo convex form with flat ends substantially as described.
4th The combination in an elliptic or semi-elliptic spring of a top plate having
the middle plano convex section a, and concavo convex tapered ends with edges f
formed on a radius equal to the width of the plate, intermediate plates also having
pointed ends formed on the said radius, and a main plate, snid intermediate and
main plates being concavo convex in cross section and the transverse curvatures
of all the plates being formed on a radius equal to the width of the plates sub-
stantially as described.
In witness whereof I, the said William Davison have hereunto set my band
this Fifteenth day of October in the year of our Lord 1884.