MENTS IN ROLLER BEARINGS FOR BRIDGES AND OTHER STRUCTURES
Year: 1884

page_text: "
I, JOHN ALEXANDER MCDONALD of Sydney in the Colony of New South Wales,
Civil Engineer, do hereby declare the nature of my invention for IMPROVE-
MENTS IN ROLLER BEARINGS FOR BRIDGES AND OTHER STRUCTURES" and in what
manner the same is to be performed to be particularly described and ascertained
in and by the following statement:-
It is customary to place bearing rollers between the superstructure and the
foundations of bridges, arches, viaducts, aqueducts, pipes and other structures so as
to allow such structures to expand and contract at changes of temperature or from
other causes. Now my invention has been devised so that such bearing rollers
may have a much larger diameter and yet at the same time take up no larger or
very little larger space on the bearing plate relatively than the rollers hitherto
used.
My improvements in bearing rollers for bridges and other structures consist in
their peculiar construction and in connecting two or more of them in series.
The peculiar construction of my bearing rollers is that of a flat or parallel portion
of a cylinder about its diameter, or in other words, a cross section of the roller
shows a portion of a circle from which two equal and parallel segments have been
taken. When a large bearing surface is required I use two or more of these rollers
connected together by a link or links so that each one in the series shall have the
same movement.
But in order that my invention may be clearly understood reference will now be
made to the drawing herewith in which Figure 1 shows a cross section of one of
my rollers-Figure 2 side elevation of the same. Figure 3 shows end elevation of
a group or series of six rollers when in their mean position while Figure 4 is a
similar view after the superstructure has made its maximum movement in one
direction. A is the roller-B connecting links-C the bearing' plate or saddle of a
superstructure and D the bed plate for the same on its foundation. A' A¹ in
Figure 2 are recesses in the body of the rollers. A very slight variation in the
length of the superstructure caused by change of temperature & will revolve or
move rollers A and their larger diameter prevents or tends to prevent the bearing
plate C and the bed plates D from being crushed on the lines of pressure. The
connecting links B ensure that all the rollers move at the one time.

page_text: The rollers may in some cases be placed in a box or frame or be sunk in masonry
and may also sometimes have a shoulder or groove on their curved edge or end to
work in a corresponding groove or shoulder on the bearing plates and so tend to
prevent lateral movement of the superstructure. For bridges generally I prefer
that these rollers should be say from eighteen inches to twenty-four inches in
diameter and that the width of their face should be slightly in excess of the
Daximum amount of movement caused by the expansion and contraction of the
superstructure. The length and number of rollers required in each bearing I prefer
to calculate by allowing say one ton weight on every linear inch of the total length
of all the rollers. I prefer the rollers to be of, cast iron and I sometimes reduce
their weight by recessing the flat faces or by coring them out.
Having thus particularly described and ascertained the nature of my said
invention and the manner of performing same I would have it understood that I do
not confine myself to any particular dimensions or proportions to or in which my
rollers may be made nor to any particular material of which they may be
constructed but what I believe to be new and therefore claim as my improvements
in bearing rollers for bridges and other structures is-
First. Making the said rollers of a flat portion of a cylinder about its diameter,
that is of a cylinder from which two equal and parallel solid segments have been
taken substantially as herein described and explained.
Second. The combination of two or more of said flat bearing roller's connected by
a link or links to form a yielding bearing substantially as herein described and
explained.
Dated this 29th day of August One thousand eight hundred and eighty four.
Witnesses,
FRED WALSH.
EDGAR FUSSELL
JOHN A. McDONALD.