An Improved Method of Laying Wires and Cables in Pipes or Conduits.
Year: 1891

page_text: Data of Application, 28th Oct., 1891
Complete Specification Left, 27th July, 1892-Accepted, 1st Oct., 1892
PROVISIONAL SPECIFICATION.
An Improved Method of Laying Wires and Cables in Pipes or
Conduits.
I, ALFRED ROSLING BENNETT, of 22, St. Albans Road, Harlesden,
London, N.W., Electrical Engineer do hereby declare the nature of this inven-
tion to be as follows:-
The object of my invention is to facilitate the passing of wires and cables
containing electrical conductors through pipes and conduits having occasional
openings, as when an iron pipe is laid beneath the surface of the street with man-
holes or joint-boxes for the purpose of giving access to the ends of the various
sections at intervals, in the manner commonly practised.
In the following description of my invention the word pipe includes all other
forms of channel or conduit of uniform section adapted to contain wires or cables,
and the word cable comprises all descriptions of wires and conductors.
Heretofore the common practice has been to drag or draw the cable through the
pipe by means of a strong wire previously laid to which the cable is attached.
The length of pipe which can be laid uninterruptedly when this plan is adopted is
very short as the friction of drawing in is great and the application of excessive
force is apt to damage the cable.
According to my invention the draw wire is dispensed with and replaced by
steam, compressed air or other gas, or hydraulic power, acting on a piston which
fits true to the interior of the pipe and has attached to it the cable to be laid.
The piston may be of metal or leather or any suitable material. It may take
the form of a short hose or pipe closed at one end only so that the propelling
medium may enter and by distending it from the inside cause it to fit close to the
pipe. Or it may be closed at both ends and made tight with junk rings, india-
rubber rolling rings, leathers or other common devices. The piston should prefer-
ably be flexible to enable it to traverse bends and curves.
To the closed or solid end of the piston a wire, chain, swivel or other suitable
appliance is fixed to which the cable to be drawn in is attached.
At the forwarding end of the pipe a strong closed chamber is provided having a
steam, air or water-tight connection with the pipe on the one side and on the other
a stuffing-box fitting closely round the cable to be drawn. The chamber has also
an opening through which the propelling medium is admitted.
The method adopted is to place the piston in the pipe with its solid end in
advance. The cable is passed through the closed chamber and attached to the
wire or other coupling fixed to the piston. The tight connection between the
chamber and pipe is then made and the packing ring or collar of the stuffing-box
adjusted round the cable so that while the cable may pass the stuffing-box the
compressed air or other propelling medium will not escape. The propelling
medium, steam, compressed air or other gas or water or other liquid under pressure,
is then admitted to the closed chamber and by pressing on the piston will force it
through the pipe, drawing the cable after it. If air or water is used the power
may be applied by an air or force pump worked by hand. If the propelling
medium is steam from a boiler or compressed air from a reservoir the amount
admitted to the chamber and the consequent speed of the piston should be capable
of regulation by a throttle-valve or otherwise.
Dated this Twenty-seventh day of October 1891.

page_text: COMPLETE SPECIFICATION
An Improved Method of Laying Wires and Cables in Pipes or
Conduits.
ALFRED ROSLING BENNETT, 22, St. Alban's Road, Harlesden, London, N.W.,
Electrical Engineer, 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 :-
The object of my invention is to facilitate the passing of wires and cables
containing electrical conductors through pipes and conduits having occasional
openings, such as when an iron pipe is laid beneath the surface of the street with
man-holes or joint-boxes for the purpose of giving access to the ends of the various
sections at intervals, in the manner commonly practised.
In the following description of my invention the word pipe includes all other
forms of channel or conduit of uniform section adapted to contain wires or cables,
and the word cable comprises all descriptions of wires and conductors.
Heretofore the common practice has been to drag or draw the cable through the
pipe by means of a strong wire previously laid, to which the cable is attached.
The length of pipe which can be laid uninterruptedly when this plan is adopted is
very short, as the friction of drawing in is great and the unequal application of
excessive force is apt to damage the cable.
According to my invention the draw wire is dispensed with and replaced by
steam, compressed air, or other gas, or hydraulic power, acting on a piston which
fits true to the interior of the pipe and has attached to it the cable to be laid.
The piston may be of metal or leather or any suitable material. It may take
the form of a short hose or pipe closed at one end only so that the propelling
medium may enter and by distending it from the inside cause it to fit close to the
pipe. Or it may be closed at both ends and made tight with junk rings, india-
rubber rolling rings, leathers or other ordinary devices. The piston should prefer-
ably be flexible to enable it to traverse bends and curves.
To the closed or solid end of the piston a wire, chain, swivel or other suitable
appliance is fixed to which the cable to be drawn in is attached.
A
At the forwarding end of the pipe a strong closed chamber is provided having
steam, air, or water-tight connection with the pipe on the one side and on the other
a stuffing-box fitting closely round the cable to be drawn. The chamber has also
an opening through which the propelling medium is admitted.
The method adopted is to place the piston in the pipe and attach it securely to
the cable after the latter has been passed through the closed chamber. The tight
connection between the chamber and pipe is then made and the packing ring or
collar of the stuffing-box adjusted round the cable so that while the latter may pass
the stuffing-box the compressed air or other propelling medium will not escape.
The propelling medium, steam, compressed air, or gas or water or other liquid
under pressure, is then admitted to the closed chamber and by pressing on the
piston will force it through the pipe, drawing the cable after it. If air or water
is used the power may be applied by an air or force pump worked by hand. If the
propelling medium is steam from a boiler or compressed air from a reservoir the
amount admitted to the chamber and the consequent speed of the piston should be
capable of regulation by a throttle-valve or otherwise.
I shall now describe one effective method of carrying out my invention. In the
accompanying drawings
Figure 1 represents a cable C about to be drawn into the underground pipe K
through the box or opening in the ground M.
The cable C is represented as having been placed in position ready for the
admission of pressure. through the inlet or supply pipe F and is attached to the
piston P by means of a short chain L. The mouth of the pipe K is in communi-
cation with the outlet N of the pressure chamber R by means of a strong flexible

page_text: hose or pipe T. The cable C lies within this flexible pipe and is continued through
the pressure chamber R and the gland or stuffing-box D to the outer air where it
is coiled or wound on a drum ready for running off. The flexible pipe rests in
rounded and grooved guides H¹ H' designed to control the course of the cable.
The lower guide H' is specially intended to fend the cable off the sharp edge of
the pipe K and with that view its position is adjustable by means of the vertical
bar or rod X, the lever Y and adjustable weight Z shown in Figure 1. The
downward pressure is obtained by the action of the lever and weight on the pin O.
To the bar or rod X is attached the guide H' which may be of either wood or
metal, grooved as described. Lateral displacement is prevented by wooden wedges
or blocks or other suitable packing, and by the pin O' shown in Figure 1 at the
short end of the lever Y. The details of the guiding arrangement, lettered as in
Figure 1, are shown in Figure 3.
The pressure chamber should be preferably of circular section and may be of
cast iron and generally resemble the cylinder of a steam-engine, but it may also be
built up of iron plates rivetted together. It may vary greatly in size and, as
drawn in Figures 4 and 5 may consist of a length of metal tube or a metal casting
only slightly greater than the cable in diameter. In the variations shown in
Figures 4 and 5, which are intended for direct connection with the pipe K, thus
dispensing with the flexible pipe T, the reference letters indicate the same parts as
in Figure 1.
V is a safety valve and G a pressure gauge attached to the pressure chamber R
which is supported on a bed-plate E. On establishing a connection between the
supply pipe and a reservoir containing compressed air or gas, steam, water or
other liquid under pressure, or on pumping air or liquid into the said supply pipe
the piston P is acted upon and if the pressure admitted is sufficient to overcome the
resistance due to the friction of the piston and to the friction and weight of the
cable C the said piston will move forward and draw the cable after it. The pressure
admitted may be regulated by a throttle-valve on the supply pipe F or on the
boiler or reservoir to which it is attached. It will be understood that when the
box or opening in the ground M is sufficiently large the flexible pipe T may be
dispensed with since in that case the pressure chamber R may be placed in the box
and the outlet N connected directly to the mouth of the pipe K. In all cases the
area of the cable C should be smaller than that of the pipe K in order that the
propelling medium may pass it and act on the piston P.
In Figure 2 is drawn one suitable form of piston. In this figure the body of the
piston, which is made of vulcanized india-rubber, is indicated by P, while B is an
iron bolt which passes right through the piston and has fixed to it behind the
Bwivel S to which the cable is connected by the chain L. A metal washer W
intervenes between the head of the bolt B and P, the india-rubber body of the
piston. The piston is made concave behind and accurately fitting in the cavity is
placed the circular metallic plate I which is convex in front and flat behind and
has a circular hole in its centre to enable it to be slipped over the bolt B. The
pressure acting on the flat side of L forces the convex front of that plate into the
concave cavity in the india-rubber body of the piston and by compressing it against
the washer W, causes it to bulge and fill the pipe, thus preventing any escape of
the propelling medium past the piston. When the pipe K contains curves or is not
perfectly regular in diameter it will be advantageous to employ two pistons as
drawn in Figure 2 connected by six or eight inches of chain, for which purpose the
head of the bolt B in the second piston should be made with an eye or hook to
receive the chain from the first. Any pressure escaping past one piston would then
encounter the other.
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 :-

page_text: or liquid pressure admitted behind suitable pistons which are attached to such
cables or conductors so as to draw them.
2. The combination and application to the laying of cables and conductors in the
manner aforesaid of the several mechanical devices and appliances set forth, all
substantially as described and drawn.
Dated this Twenty-seventh day of July 1892.