IMPROVEMENTS IN THE CON- SMD HARLAN " PRO
Year: 1855

page_text: LETTERS PATENT to Samuel John Pittar, of 10, Lisle Street, Leicester
Square, Civil Engineer, for the Invention of "IMPROVEMENTS IN THE CON-
SMD HARLAN
"
PROVISIONAL SPECIFICATION left by the said Samuel John Pittar at the
Office of the Commissioners of Patents, with his Petition, on the 21st
July 1855.
I, SAMUEL JOHN PITTAR, of 10. Lisle Street, Leicester Square, Civil
Engineer, do hereby declare the nature of the Invention for "IMPROVEMENTS
IN THE CONSTRUCTION OF BRIDGES" to be as follows:-
This Invention consists of constructing bridges by combining several
systems of diagonal bracings with posts or perpendiculars in such manner,
that a weight coming on one of the systems of which a truss-formed bridge
consists when constructed according to this Invention, is not only transferred
over that one system, but over and through the whole of the systems before it
is brought to the piers. For this purpose a number of parallel perpendicu-
lars or posts are employed, which are connected together at their tops from

page_text: pier to pier by suitable bars; then by means of a tension rod or rods pro-
ceeding from each pier to the lower end of a central perpendicular or post,
one system of triangular framing or bracing is produced. The space on either
side of such central perpendicular or post and between it and the pier is then
divided into another system by diagonal tension rods, which connect the end
of the bridge with the lower end of a post or perpendicular, which is inter-
mediate of the pier and the central post or perpendicular, before mentioned.
and also the lower end of this intermediate post or perpendicular with the
upper end of the central post or perpendicular of the bridge, and if the bridge
be of considerable length the intermediate space may be divided into another
system or more of triangular framings or bracings, similar to those above
described. And then another system of triangular framings or bracings is
produced by means of tension rods, which proceed from the ends of the bridge
to the lower ends of the posts or perpendiculars nearest thereto, and from the
lower ends of such posts or perpendiculars to the upper ends of the next posts
or perpendiculars, and from the upper ends of those posts or perpendiculars to
the lower ends of the next post or perpendicular, and so on to the central
post or perpendicular first mentioned, by which means each pair of neigh-
boring posts or perpendiculars will be tied together with diagonal tension
rods, which cross each other intermediate of the two posts or uprights, in
addition to the other tension rods, above described. And in some construc-
tions the piers are carried to a height to receive suspending rods, chains,
or wires, which proceed from the upper parts of such piers to the parts of
the bridge, by which the parts of a bridge on either side of a pier balance
each other.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Samuel John Pittar in the Great Seal Patent Office on
the 21st January 1856.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, SAMUEL
JOHN PITTAR, of 10, Lisle Street, Leicester Square, Civil Engineer, send 3
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-first day of July, in the year of our Lord One
thousand eight hundred and fifty-five, in the nineteenth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said s

page_text: Samuel John Pittar, Her special licence that I, the said Samuel John Pittar,
my executors, administrators, and assigns, or such others as I, the said Samuel
John Pittar, 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
THE CONSTRUCTION OF BRIDGES," (partly a communication.) upon the condition
(amongst others) that I, the said Samuel John Pittar, my executors or
administrators, by an instrument in writing under my, or their, or one of their
hands and seals, 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 calendar
months next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Samuel John Pittar, do hereby declare
the nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement thereof:-
This Invention consists of constructing bridges by combining several
systems of diagonal bracings with posts or perpendiculars in such manner,
that a weight coming on one of the systems of which a truss-formed bridge
consists when constructed according to this Invention, is not only transferred
over that one system, but over and through the whole of the systems before it
is brought to the piers. For this purpose a number of parallel perpendiculars
or posts are employed, which are connected together at their tops from pier to
pier by suitable bars, then by means of a tension rod or rods proceeding from
cach pier to the lower end of a central perpendicular or post, one system of
triangular framing or bracing is produced. The space on either side of such
central perpendicular or post and between it and the pier is then divided into
another system by diagonal tension rods, which connect the end of the bridge
with the lower end of a post or perpendicular which is intermediate of the
pier and the central post or perpendicular before mentioned, and also the lower
end of this intermediate post or perpendicular with the upper end of the
central post or perpendicular of the bridge, and if the bridge be of consider-
able length, the intermediate space may be divided into another system or
more of triangular framings or bracings, similar to those above described.
And then another system of triangular framings or bracings is produced by
means of tension rods, which proceed from the ends of the bridge to the lower

page_text: ends of the post or perpendicular nearest thereto, and from the lower ends of
such posts or perpendiculars to the upper ends of the next posts or perpendi-
culars, and from the upper ends of those posts or perpendiculars to the lower
ends of the next post or perpendicular, and so on to the central post or per-
pendicular first mentioned, by which means each pair of neighbouring posts or
perpendiculars will be tied together with diagonal tension rods, which cross
cach other intermediate of the two posts or uprights, in addition to the other
tension rods above described. And in some constructions the piers are carried
to a height to receive suspending rods, chains, or wires which proceed from
the upper parts of such piers to parts of the bridge, by which the parts of a
bridge on either side of a pier balance each other.
Having thus described the nature of the said Invention, I will proceed to
describe more fully the manner of performing the same.
DESCRIPTION OF THE DRAWINGS.
Plate 1 shews the application of the improvement to bridges where the
roadway is above the truss; Figure 1 representing a side elevation; 2, a plan;
3, a cross section, and 4 to 15, details of different parts.
Plates 2 show the application of the improvement to bridges where the
truss is above the roadway; Figure 1 representing a Diagram of the whole
truss; 2, an elevation of a part of the truss; 3, a plan of the top of that
part 4, a plan of floor; 5, a front view; 6, a cross section; 7 to 13, details
of the bridge.
In cach Plate similar letters of reference in the several Figures denote the
same part of the bridge.
The nature of the Invention consists in combining different "
systems" of g
triangular bracings, in the manner hereafter to be described, so that a weight
coming on one of the "systems" of the "truss," is not only carried over one
or more other "systems" before it is carried back to the "abutment," but the
foot of the post of each triangle shall be capable of setting vertically and
moving to the side, so that the "tension rods of each "system" of the s
triangular bracing will be strained equally when the bridge settles under a
superincumbent weight.
To enable others skilled in the art to use the Invention, I will proceed to
describe the same-and-its-operation.
In Plate 1, A, A, represents stretchers of cast or wrought iron, consisting of a
a number of hollow pipes, connected as shown in the Drawing, their heads or
ends resting on the abutment W. The middle point of the stretcher A (see

page_text: Figure 1, Plate 1,) I support by the suspension bars B, B, through the post C.
The details of the connection between the stretcher A. (see Figure 1, Plate 1,)
post C, and suspension bars B, B3, being set forth in the Drawing, and not
being essential to the understanding of the Invention, will not require here any
particular description.
I then, by suspension rods B', B', and post C', support two points inter-
mediate between the central point and the abutment, forming the second
triangular "system;" then by rods B", B", and posts C", I support four points
between the abutment posts C' and posts C', forming the third triangular
"system" and in this manner I multiply the "systems" according to the span
of the bridge, supporting first the central point by suspension rods running to
the abutments, then making this central point a point of support for two other
systems, which intermediate points in their turn may become points of support
for other systems.
Plate 2 shows the Invention as applied to bridges with the truss above the
roadway; where B, B, is the first "system" of suspension rods; B'. B', the
second system; B", B", the third system, and so on; the several systems being
distinctly shewn by the various colored lines in Figure 1 of that Plate. The
operation of the improved truss is as follows:-The pressure of a load at any
point of the truss is diffused over the entire truss, and transmitted through one
or more of the various systems of which the truss is composed, before being
carried to the abutments. For instance, a pressure coming upon the bridge
at X, Figure 1, Plate 1, will be received by system 3, and a portion of that
pressure transmitted by suspension rods B" to system 2, and a portion from
thence by rod B' to system 1, whence, by suspension rods B, B, it is carried
to the abutments, the weight having been diffused over the entire space. The
operation will be the same, no matter how many triangular systems may be
used in the truss.
The sinking of a portion of the truss by a superincumbent weight, or by
changes in the condition of the material used in construction, from effects of
temperature, will not cause the several parts of the truss to deviate from their
mutual adjustment; and herein consists the important advantage of my In-
vention, as wrought and cast iron may be combined in the same truss without
danger, as will be seen by reference to Diagram X, Plate 1, where the point
a of system 1 settles, as indicated by the letter a; the two triangles of system 2
will change their position, as shewn by the red lines 2, 2; the points b, b, of
system 2 not only setting vertically, but moving horizontally, as indicated in
the Diagram. Now, although the position, as shewn by red lines, system 2,

page_text: has changed, there have been no changes in the triangles themselves, and
therefore their bearing capacity is still the same as it was before the settling
of point a.
What is here illustrated for two systems is equally true for
trusses composed of any number of triangular systems combined on this plan.
This advantage of permitting the foot of the post to move to the side when the
bridge settles would not obtain, were the foot of the post in the second system
to rest upon the tension chord of the post of the first system, as heretofore used,
the freedom of movement allowed to the foot of the post of each system pro-
ducing the beneficial result due to the Invention.
The construction set forth in the Drawings are but two of the applications
of the Invention, and must not be considered as confining it in any respect, as
any suitable material may be used in construction, and a great variety of forms
given to the parts. The stretchers may be octagon, square, round, or of any
other form, and either of wood, wrought or cast iron; the posts may be of
any desired form of cross section, and the suspension bars may be either wire
cable or wrought-iron bars. Moreover, upright trusses may be constructed,
as above described, for inverted ones, by the substitution of struts for sus-
pension bars or ties for the stretchers and suspension rods for the posts, the
same law governing the combination in this case as will obtain in the cases
described.
The points supported need not necessarily be arranged and chosen as above
set forth, the general rule being to support a point at or near the middle of the
space by system 1, the first intermediate points by system 2, whether these
points are in the middle between the first supported point and the abutments
or not, and further intermediate points by system 3, and so on.
Figure 1 represents a Diagram of the construction of bridge where the
piers are carried to a height to receive suspending rods, chains, or wires which
proceed from the upper parts of such piers to parts of the bridge, by which the
posts of a bridge on either side of a pier balance each other.
I do not claim as new the manner in which the central point is supported,
nor do I claim the combination of a series of triangular bracings in such a
manner that one system of triangles is supported by and dependent on the
other merely, as I am aware that this has been done before both in trusses
for bridges and roofs; but what I do claim as of the Invention, and as different
-from-any-method-of-bracing and strengthening bridge trusses heretofore known,
is, the method of combining the different systems of triangular bracings above
described, so that a weight coming on one of the systems of the truss is not
only transferred over one or more other systems before it is carried back to the

page_text: abutments, but the foot of the post in each triangle being unconnected with
the tension rods of the other triangular bracings, can settle vertically as well as
move to the side, so that the tension rods of each system of the triangular
bracings will be strained equally when the bridge settles under a superin-
cumbent weight, which would not be the case if the foot of the post in the
second system of triangular bracings rested on the tension chord of the post in
the first system, as heretofore used, and herein consists the improvements for
which I have obtained Letters Patent.
In witness whereof, I, the said Samuel John Pittar, have hereunto set
my hand and seal, this Twenty-first day of January, in the year of
our Lord One thousand eight hundred and fifty-six.
Witness,
S. CARPMAEL.
SAM. JOHN PITTAR. (L.S.)