IMPROVEMENTS IN BRIDGES
Year: 1858

page_text: LETTERS PATENT to Michael Kenney, of Queen Street, Dublin, Mechanical
Engineer, for the Invention of "IMPROVEMENTS IN BRIDGES."
PROVISIONAL SPECIFICATION left by the said Michael Kenney at the
Office of the Commissioners of Patents, with his Petition, on the
22nd December 1858.
I, MICHAEL KENNEY, of Queen Street, Dublin, Mechanical Engineer, do
hereby declare the nature of the said Invention for "IMPROVEMENTS IN
BRIDGES," to be as follows:-
This Invention relates to that class of bridges in which the length of road-
way of necessity exceeds the width of the opening which they are employed to
span, and which bridges are withdrawn longitudinally in the direction of the
roadway, for the purpose of enabling greater height to be obtained below, and
also to permit of a clear passage being effected along the line of way spanned
by the bridge when-closed.
This class of bridges are usually designated as sliding or rolling bridges,
and are substitutes for swing or swivel bridges.
My improvements consist in so constructing a rolling bridge that it shall be
perfectly balanced, and require but little power to open and close it, and that

page_text: whilst it is closed and in use it is perfectly secure, and the roadway and
approaches are made, as it were, continuous and unbroken, and when opened
or withdrawn, the tail or balance end is drawn over the ground line or
approach on the balance or withdrawing side, and without injury thereto. The
travelling of the bridge in and out may be effected by means of a rack or
racks, or other well-known or similar means.
run.
These improvements are effected by constructing the roadway or longitudinal
framing of the bridge as a double incline platform; the platform is mounted
upon bearing rollers, which, if the bridge were free to rise and fall, would
enable it to do so, it being balanced thereon; thus, upon withdrawing the
bridge or moving it backward or forward, the power required is chiefly that
which is alone necessary to overcome the friction of the rollers with their load
running over the rails. The top face of the pit over which or in which the
bridges moves backward and forward is level, and it may have two or more
edge rails, railway bars, or tram plates arranged longitudinally therein or
thereon, and upon which the central bearing wheels supporting the bridge will
The platform. or framed roadway may be trussed on the top sides of the
longitudinal beams or trellis girders, or a bow and string or other such con-
trivance may be adopted to give stability or stiffness, and to resist longitudinal
flexure. For the purpose of opening and closing the bridge, I prefer to employ
racks and pinions, and when I do so I apply them in the following manner:-
On the under side of each side I fit a rack, which takes into a corresponding
pinion projecting above the line of the face of the pit, and motion may be
communicated to the, pinions whereupon the tail end of the bridge is drawn
inward, and projected above the level of the ground line along which the 'under
side of the platform moves, and wheels or rollers may be fitted to the extreme
tail end of the bridge platform, as there should in like manner be a roller at
the opposite or outer and overhanging end of the platform, for enabling the
platform to come to rest and take its bearing upon the opposite abutment
when it has been projected across or moved into its proper position; where it
When the bridge is
may be secured by locking wedges, or by other means.
in situ, the central bearing rollers or wheels approach nearly to the face of the
supporting wall, pier, or abutment, on the side upon which the balanced or
tail end of the bridge runs, and the top side of the platform at each end
becomes level with the ground line of each approach. The platform of the
bridge itself forming a double incline of slight elevation, the centre of its
length being the highest part of the roadway.
No distinct lifting of the tail end of the bridge is needful according to my
Invention, as I enabled by means of suitably formed terminations to the rack

page_text: or racks, or other equivalents, to produce the necessary elevation and travelling
motion as a continuous operation, and which may be performed by a very
much less amount of labour than heretofore has been necessary for the purpose
of working sliding or travelling bridges.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Michael Kenney in the Great Seal Patent Office on the
22nd June 1859.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, MICHAEL
KENNEY, of Queen, Street, Dublin, Mechanical Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-second day of December, in the year of our
Lord One thousand eight hundred and fifty-eight, in the twenty-second year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Michael Kenney, Her special licence that I, the said Michael Kenney,
my executors, administrators, and assigns, or such others as I, the said Michael
Kenney, my executors, administrators, and assigns, should, at any time agree
with, and no others, from time to time and at all times thereafter during
the term therein expressed, should and lawfully might make, use, exercise,
and vend, within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for IMPROVEMENTS IN
BRIDGES," upon the condition (amongst others) that I, the said Michael Kenney,
by an instrument in writing under my hand and seal, should particularly
describe and ascertain the nature of the said Invention, and in what manner
the same was to be performed, and cause the same to be filed in the Great
Seal Patent Office within six calender months next and immediately after the
date of the said Letters Patent.
NOW KNOW. YE, that I, the said Michael Kenney, do hereby declare the
nature of my said Invention, and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following statement
and the accompanying Drawings:-
This Invention relates to that class of bridges which in the length of
roadway, of necessity exceeds the width of the opening which they are
employed to span, and which bridges are withdrawn longitudinally in the
direction of the roadway, for the purpose of enabling greater height to be
obtained below, and also to permit of a clear passage being effected along the
line of way spanned by the bridge when closed. These bridges are usually

page_text: designated as sliding or rolling bridges, and are substituted for swing or
swivel bridges.
My improvements consist in so constructing a rolling bridge that it shall
be perfectly balanced and require but little power to open and close it, and
that, whilst it is closed and in use, it is perfectly secure, and the roadway
and approaches are made as it were continuous and unbroken, and when
opened or withdrawn, the tail or balance end is drawn over the ground line
or approach on the balance or withdrawing side, and without injury thereto.
The travelling of the bridge in and out may be effected by means of a rack
or racks, or other well-known or similar means.
These improvements, as applied to road traffic bridges, are effected by
constructing the roadway or the longitudinal framing of the bridge as a
double incline platform; the platform is mounted upon bearing rollers, which
if the bridge were free to rise and fall, would enable it to do so, it being
balanced thereon; thus, upon withdrawing the bridge, or moving it backward
and forward, the power required is chiefly that which is alone necessary to
overcome the friction of the roliers, with their load running over the rails.
The top face of the pit over which or in which the bridge moves backward
and forward is level, and it may have two or more edge rails, railway bars,
or tram plates arranged longitudinally therein or thereon, and upon which the
central bearing wheels supporting the bridge will run. The platform or
framed roadway may be trussed on the top sides of the longitudinal beams
or trellis girders, or a bow & string or other such contrivance may be
adopted to give stability or stiffness and to resist longitudinal flexure, and the
roadway or bridge platform may be quite level instead of being cambered
and the necessary amount of rigidity may be given by the girders or trussing.
For the purpose of opening and closing the bridge, I prefer to employ
racks and pinions, and I apply them in the following manner :-On the
under side of each side frame or longitudinal girder, I fit a rack or its
equivalent which takes into a corresponding pinion wheel or its equivalent
projecting above the line of the face of the pit, and notion may be commu-
nicated to the pinions; the tail end of the bridge is drawn inward, and
projected above the level of the ground line, along which the under side of the
platform moves, and wheels or rollers may be fitted to the extreme tail end
of the bridge platform, as there should in 'like manner be a roller at the
opposite or outer and overhanging end of the platform, for enabling the
platform to come to rest, and take its bearing upon the opposite abutment,
when it has been projected across or moved into its proper position, where
it may be secured by locking wedges, cams, or by other means. When the

page_text: bridge is in sitû the central bearing rollers or wheels approach nearly to the
face of the supporting wall, pier, or abutment, on the side upon which the
balanced or tail end of the bridge runs, and the top side of the platform at
each end becomes level with the ground line of each approach; the platform
of the bridge itself either forming a double incline of slight elevation, the
centre of its length being the highest part of the roadway, or it may be level
as before mentioned. In the several views Figs. 1, 3, and 5, of Sheet 1, no
distinct operation of first lifting the tail end of the bridge is needed, as I am
enabled by means of suitably formed curved terminations to the rack or
racks, (or their mechanical equivalents,) to produce the necessary elevation
and travelling motion as a continuous operation, and which may be performed
by a very much less amount of labour than heretofore has been necessary for
the purpose of working sliding or travelling bridges.
In the two Sheets of Drawings hereunto attached, Fig. 1 is a longitudinal
sectional view of a bridge constructed according to this Invention with three
longitudinal wrought-iron girders, the platform being formed of a series of
wrought-iron transverse iron girders, the floor or platform being slightly
cambered up in the centre of its length; it is supported at its inner or tail end,
at or near to the centre of its length, by a carriage having an axle or transverse
shaft, upon which the bearing wheels are mounted, which run upon the
longitudinal rails provided for them in the tail pit. Fig. 2 is a transverse
section of Fig. 1, taken on the line A, B, and exhibits the three longitudinal
girders forming two roadways, and the overhanging handrail forming sideways
or footpaths, the three pairs of bearing rollers or wheels mounted on the
axle, which is shewn as supported in three carriages secured to the under side
of the platform, each being fixed immediately under each longitudinal girder;
a section of the pit is also shewn with the six bearing and guiding rails;
Fig. 3 is a transverse section of Fig. 1, taken on the line A, C, and shews
the platform and terminations of the three girders in the land end of pit, and
it also shows the two curved ends of the racks, as well as the pinions, which
take into and raise them, and draw them onward and inward; Fig. 4 is also
a transverse section of Fig. 1, but taken on the line A, D, and exhibits a
mode of locking or securing the outer or overhanging end of the bridge upon
its being projected across the opening it is employed to span.
In this view
an arrangement of wedges is shewn as being actuated or propelled by means
of a right and left hand screw upon a cross shaft, this shaft being rotated
or caused to revolve by means of a handle, and the pair of mitre wheels as
shewn, the wedges being separated or withdrawn when it is desired to release
the bridge, and when the bridge has again been projected across, a bearing is

page_text: formed, and the end of the bridge is secured by the wedges being brought
together.
Figs. 5, 6, and 7 are transverse views respectively, somewhat similar to
Figs. 2, 3, and 4, but of a bridge having two longitudinal girders instead of
three as in the previous views; Fig. 5 is a transverse section taken on the
ground line of the tail pit, and shows the curved ends of the racks and the
pinions or wheels which take into them; Fig. 6 is a section taken at or near
to the centre of the length of the longitudinal girders; in this view two single
rails are shewn, the two bearing wheels running thereon being mounted on a
cross shaft or axle as before, but it is supported in four bearings or carriages,
each bearing wheel being shewn as mounted between the cheeks of a double
carriage; Fig. 7 is a transverse sectional view of a double girder bridge at the
point of the overhanging or locking end, and shews another arrangement or
mode of locking and supporting by means of two cams mounted upon a cross
shaft...
In the illustrations of this Invention which I have already given the opening
and closing of the bridge is effected by means of a handle or handles fixed in
any convenient position on the ground line or at the inner end of the tail pit;
but in the following illustrations in Sheet 2 will be described arrangements for
giving motion to the toothed wheels or pinions taking into the racks laid on the
bottom of the tail pit by means of a handle or handles fitted upon the bridge
at or near the centre of its length. I have also referred to the bridges being
constructed of wrought iron, but they may, of course, be built or constructed
of wood, wholly or in part, and may have either one, two, or more racks, and
with or without curved inner ends, as equivalent means can be employed for
the purpose of raising the inner or tail end of a bridge constructed according
to this Invention; and as I prefer for some purposes, as in the case of
railway bridges, where great weights have to pass over at high speeds, and
where, therefore, very great steadiness and absence of vibrations are of the
greatest importance, to employ a different arrangement or mode of raising the
end of the bridge in the course of withdrawing or opening it.
In Sheet 2, Fig. 1, is a longitudinal section of a balance rolling bridge
intended more particularly for roadways over dock entrances, and in such like
situations, the floor as well as the under side of the platform being cambered
upward in the centre in the direction of its length, and instead of mounting the
bridge at or near to its centre upon two or more bearing wheels fitted upon the
same cross shaft or axle, I have shewn a carriage or frame which is supported
upon three, four, five, or more wheels, two or more of which may be flanched or
flat faced bearing wheels running upon rails, whilst one or more of the bearing

page_text: wheels
may be toothed wheels taking into the racks or rack bars laid in the
tail pit, parallel to the plain bearing and guide rails. This carriage or frame
carries the bridge, a saddle piece being provided on the under side of the
platform at or near to the centre of the length of the bridge; this saddle is
so constructed that the ends of the bridge are permitted to rise and fall freely
to a limited extent when unsupported, a transverse trunnion piece or edge
bar being provided between the under side of the platform or the saddle
and the top side of the carriage or travelling frame; by this arrangement the
same action is allowed or provided for as that which is permitted by the
use of one line of bearing wheels mounted and applied as in Sheet 1,
Figs. 1 to 7.
The carriage or travelling frame has mounted upon it the wheel gearing by
which the toothed wheels or pinions taking into the racks or rack rails are
rotated or set in motion for the purpose of moving the bridge in or out, or back
and forth, as may be required from the floor or roadway of the bridge either by
oue or more bandles applied at the sides of the longitudinal girders, within the
thickness of which some or all of the spur wheels or other gearing may be
placed. Thus the toothed bearing and motion wheels taking into the racks or
rack rails at their bottom sides, are geared at their top sides with, and
are driven by the motion wheels, rotated by the crank handles. An
arrangement of gearing for this purpose is shewn dotted in in Fig. 1.
Instead of applying the racks to the under side of the bridge, platform, or
roadway, in the Figures 1, 2, 3, and 4, Sheet 2, I lay the rack or racks hori-
zontally in the tail pit; the inner end of each rack may either be curved
upward or a separate piece of rack may be set up against the end of the
tail pit, and the pinion working into this end piece of curved or vertical
rack may be fixed to the end of the bridge platform, and be actuated from the
centre of the bridge by a handle and gearing connected with the travelling
gear, or it may be separate therefrom; but by way of combining as many
variations of details in the mode of raising and traversing bridges constructed
and worked according to this Invention, I have shewn in Figs. 1 and 2
another mode of raising the inner end of balanced rolling bridges, as in reference
to the said Figures it will be seen that, instead of a pinion or small toothed
wheel (or two or more thereof) being attached to the tail end of the bridge
platform, I have arranged a roller or a line of rollers without teeth, which are
intended to run on plates or rails laid on the approach level with the roadway,
the end of the bridge being raised or tipped up by the turning of a fixed
pinion acting upon a vertically sliding rack, the pinions being turned, the rack

page_text: is caused to rise, and lifts the end of the bridge when the traversing gear is set
in motion, and the bridge, as shewn in Fig. 1, is moved or caused to move
inward over the pit into the position shewn in Fig. 2, Sheet 2, which thus
permits of the waterway or opening which the bridge is intended to span being
used unimpeded thereby.
In Figs. 1 and 2, (Sheet 2), locking cams are shewn as applied for
supporting and securing the overhanging or outer end of the balance rolling
bridge when it is closed and in its proper place.
In. Figs. 1, 2, 3, and 4, (Sheet 2), the power employed for moving or
opening and closing each of the bridges is applied in the centre of their
length.
Figs. 3 and 4 are side elevations in section (or longitudinal sections) of the
same bridge intended for carrying a railway; Fig. 3 shewing it closed and in its
proper place, and Fig. 4 shewing it opened to permit of the free passage of ships,
barges, or other vessels along the line of canal, or through the dock entrance
or other watercourse over which it is supposed to be applied. In Fig. 3 the
longitudinal sectional view of a balance rolling bridge has a level floor and is
supposed to have its platform laid with a single or double line of rails for a
railway; it is shewn as fitted with the opening and closing machinery or
gearing in the centre of the bridge, (as in Figs. 1 and 2, Sheet 1,) and a novel
arrangement or contrivance is shewn at the approach at the tail pit end of
the bridge by which a hinged platform piece for carrying the lines of metals or
railway bars to make good the connection between the land side and the bridge
end is raised and lowered; and it also shews the traversing wedge packings
under the moveable end of platform when the same is raised into its place, the
bridge being in sitû. The cams for locking the bridge at the opposite end are
also shewn. The platform piece before mentioned is in Figs. 3 and 4 shewn
as being raised and lowered by a segment rack and pinion, which action may
either be performed from the centre of the bridge as a preliminary (but as the
first part of a continuous) operation, or it may be set in motion by an
independent handle, as may be most convenient. I prefer to employ in
connection with the apparatus last described one or more incline metals or
rails for causing the end of the bridge to ascend or to rise sufficiently whilst being
opened or withdrawn, and down which it would travel when being closed, a
small roller or friction wheel being fitted to the end of the bridge over each
incline rail so laid.
Having now described my said Invention of " Improvements in Bridges,"
and illustrated some of its applications, as also some of the modes of working

page_text: bridges as shewn in the two Sheets of Drawings hereunto annexed, I claim
the mode or method of constructing and working balance rolling bridges as
herein described.
In witness whereof, I, the said Michael Kenney, have hereunto set my
hand and seal, this Twentieth day of June, One thousand eight
hundred and fifty-nine.
Witness,
JOSEPH RUSSELL,
32, Queen Street,
Dublin.
MICHAEL KENNEY. (L.S.)