IMPROVE- MENTS IN SWING BRIDGES ADAPTED FOR CROSSING LINES OF RAILWAYS AND OTHER WAYS
Year: 1862

page_text: PROVISIONAL SPECIFICATION left by Alexander Black at the Office
of the Commissioners of Patents, with his Petition, on the 10th April
.1862.
I, ALEXANDER BLACK, of Banbridge, in the County of Down, Ireland,
Law Clerk, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN SWING BRIDGES ADAPTED FOR CROSSING LINES OF RAILWAYS AND OTHER
WAYS," to be as follows:-
This Invention is designed for rendering the crossing of lines of railways,
especially at the junctions of different railway lines more safe and convenient
for passengers, railway servants, and luggage than heretofore, and consists in
so constructing a bridge for that purpose, as that it shall be capable of being
readily and easily moved or swung from its original transverse position into a
longitudinal position between two lines of rails or permanent ways, and thus
allow railway trains to pass clear of said bridge. This improved bridge is so
constructed as to close or fold up into a very small compass, by arranging
and combining together the several parts thereof in the following manner; for
example, I fix two strong iron pillars or standards into the ground between
two lines of railway or double permanent ways, said pillars being fixed out of
the central line, one to the right hand, and the other pillar to the left hand,
or diagonally with respect to the railways for the purpose hereafter described,
the upper ends of said pillars are formed each with a tubular recess or long
cylindrical hole into each of which a pivot or spindle is adapted so as to revolve
therein. These pivots carry strong castings or wrought-iron girders equal in
length to the width between the opposite platforms of the railway, allowing

page_text: the ends to project into suitable angular grooves, hewn in the curb stones of
the opposite platforms by means of which the extremities of the said girders
are supported when the bridge is in its transverse position across the railways,
which two girders are connected together by transom ties or cross pieces of
metal hinged thereto by their ends, a longitudinal groove or recess being
formed in each of said girders on the inner sides to receive said transom ties
when the bridge is folded and the girders are closed to the inner edges of each
other. I hinge a series of floor plates to the upper inner edges of the aforesaid
girders, and form a roadway or passage; each of said series of plates being
formed half the width of the distance between the aforesaid girders when they
are separated and distended or pushed asunder to the full extent the transom
ties will admit of, said plates rest upon the several transoms and thus form a
solid and substantial bridge on a level with and extending from the platform
situate at one side of a railway station and across the permanent or railways
to the platform situate at the other and opposite side of the railway
station. When it is required to change the position of this improved bridge
to enable trains to pass on the lines of rails or permanent ways, the same may
be effected by lifting or turning up the several hinged plates aforesaid, and
resting them against the hand rail affixed to each girder, the girders are then
moved on their pivots, which may be easily done, say, by two men, the effect of
which is to bring the two girders close together, the transom ties occupying
the recesses therein, so that the bridge then only occupies in breath a space
equal to the width of the two girders aforesaid, the action being somewhat
similar in principle to the well known "parallel rule" used by draughtsmen
in delineating or making drawings. By thus making the bridge to move on
two main swivels or supports when folded up or closed, the girders or folded
parts cannot be otherwise than parallel or nearly so to the lines of rails' or
permanent ways between which they are situate provided the pillar supports
or standards are fixed in proper relative positions and occupying but little
breadth of space offer no obstruction to the passage of railway trains along
the lines of rails or permanent ways.