Improvements in Metallic Wedges or Keys for Railways.
Year: 1894

page_text: Date f Application (in United Kingdom), 13th Nov., 1894
Complete Specification Left, 13th Nov., 1894-Accepted, 15th Dec., 1894
COMPLETE SPECIFICATION.
Improvements in Metallic Wedges or Keys for Railways.
I, PIERRE COLOMBIER of 61, Rue de la Roquette Paris in the Republic of
France, Metal Founder, 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 :----
Up to the present the metallic wedges or keys employed or experimented with
by railway companies for fixing the rails in their chairs have, besides real
advantages, drawbacks of various kinds according to their shape or conformation.
For instance, the following defects may be found in them-
1st. One of the surfaces of contact forms too great an angle to the other;
2nd. The load supported by the wedge or key after tightening is unequally
distributed along its length;
3rd. During the tightening, one or more points of contact between the flexible
branches of the wedge or key arrest the action of the spring and hence there are
frequent breakages, either of the chair, or of the key;
4th. The keys when removed after a continuous period of compression never
resume exactly their original form.
The improved metallic wedges or keys which I have designed have a
rectangular tightening section, the action of resistance is equally distributed over
all the surface under pressure, and the bends are about equal at the two ends of
the key.
I have shown in the accompanying drawings two different forms of keys fulfilling
these conditions, but it is evident that the curves and sinuosities of the branches
of the wedges or keys are capable of being varied without these keys ceasing to
present the essential characteristics defined in the preceding paragraph.
Figure 1 of the drawing shows a longitudinal section of a wedge or key arranged
according to my invention;
Figure 2 is a corresponding plan view; and
Figure 3 a transverse section;
Figures 4 and 5 show a longitudinal section and a plan view of a modified form
of key.
My improved key is made of steel and may have the form either of a united
band or of a strip of any suitable section having for instance slots and internal
projections for diminishing its weight, whilst retaining sufficient strength.
The edges are preferably rounded instead of being sharp.
The face be, Figures 1 and 4, in contact with the chair is slightly curved, whilst
the face df which touches the rail is straight. The shape of the parts a b c d as
well as the play which exists between the points ij allow the key to be easily
inserted. The loop g h 1 may be straight as shown in full lines in Figures 1 and 4
or may be curved as indicated by the dotted lines.

page_text: This wedge or key is combined in such a way that however it may be compressed
the points b b d d never come in contact, whilst the contact between the points i j
ensures an equivalent pressure in the direction b d to that which is exerted in
the direction ef that is to say, that the two extremities of the key are equally
elastic.
It is thus easy to see that the strain transmitted to the chair will be distributed
over all the supporting surface and not on one side as is the case with conical or
hollow keys, the resistance of which is unequal at the two extremities.
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 :-
An improved metallic wedge or key having equal bends at the two extremities
and with rectangular tightening sections, and a power of resistance equally
distributed over all the surface under pressure substantially as hereinbefore
described with reference to the two specimens shown as an example in the
accompanying drawings.
Dated this 19th day of November 1894.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant..