Year: 1897

page_text: Date of Application, 11th Aug., 1897-Accepted, 11th Sept., 1897
I, JOHN OWDEN O'BRIEN, M.I.Mech. E., of the firm of W. P. Thompson & Co.,
of 6.Bank Street, Manchester, Liverpool, and London, in the Counties of Lancas-
ter and Middlesex respectively, Patent Agents (a communication from Charles
Rudolph, of 66 Rue du Theatre, Paris, in the Republic of France, Manufac-
turer), 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 invention relates to that class of metallic tubing which is formed by
twisting a strip of metal into a spiral shape in such a way that the various
spirals fasten into each other a cord or thread of rubber being placed between
the interlocking flanges of the spirals, in order to make them thoroughly water
tight. The object of the invention is to provide a simple and efficient method
of keeping the elastic cord in its place, and of preventing it from getting out of
the right position under any circumstances.
The invention consists essentially of inserting and keeping this elastic pack-
ing in a fold or groove made for the purpose in one of the flanges of the metal
band above mentioned, in such a way that the packing does not come into con-
tact with the interlocking flanges of the spirals, the displacements of which aris-
ing from the flexion of the tube or the internal pressure which it has to sup-
port, would have a tendency to force it either to the inside or the outside of
the tube, thus depriving it of its water tight capacity.
In fact in tubes of this description, as hitherto constructed, the cord of
packing is interposed between the interlocking flanges of the spirals, so that
when the tube is very much bent, or when it is subjected to very great internal
pressure, the packing being strongly compressed by the said flanges, is con-
tracted by reason of its natural elasticity, and escapes wholly or in part through
any interstices which will allow of its passage.
The invention will now be described in detail with reference to the accom-
panying drawings.
Fig. 1. Longitudinal section of the tube in its rectilinear position.
Fig. 2. Elevation with a portion in dongitudinal section of same tube in a
bent position.
Fig. 3. Enlarged sectional detail of the improved tube.
As will be clearly seen from Fig. 3, the metal band intended to form the tube
usually includes two parts a b c and c d e bent in contrary directions, in which
the flanges a and e serve to fasten the spirals to each other but in addition to one
of these flanges e for instance, the metal is turned in again, so as to form a kind
of trough or channel f g, to receive the elastic thread or packing x which, after

page_text: the metal band has been twisted is kept in this screw shaped position in such a
way as to form a close fitting joint on the almost plain surface 6 of the next spiral.
The result of this arrangement is that when the spirals of the tube are drawn
away from each other as shown at the upper parts M N of Fig. 2, the edge a of
one spiral meets the edge e of the next spiral, and when these spirals come
together (see the bottom part R S of Fig. 2) the face c of one of the spirals is
met either by the edge of the above mentioned groove, or by the flange a of
the next spiral according to the respective widths of which and d are made.
It will therefore be observed that in any case the pressure, which is produced
between the spirals by the bending of the tube or the internal pressure to which
it is subjected, is confined exclusively to the flanges of the spirals, that is to
say, metal comes against metal, and the packing which is kept between the
surfaces and g (which are preferably made slightly conical) of the groove
does not feel the pressure at all and is therefore not liable to be pushed out of
its enclosure and can slide on the very slightly inclined surface b situated at
the side of the opposite flange of the next spiral.
It will also be seen from Fig. 3 that the pressure of the fluid contained in the
tube, and which acts direct on the packing & fitted into the screw shaped
groove f g can have no other effect than to press it strongly against the sur-
face 6 of the next spiral and thus increase the tightness of the joint. When con-
structed as shown in Figs. 1 and 2, the metal band which serves to form the
tube is wound into a spiral shape in such a way that the parts b 6 of the spirals
are outside the tube, and the parts d d inside the tube; it must, however, be
understood that the winding may be done the reverse way, the parts d d of
the spirals then being outside, and the parts 6 6 inside, the results being the
same in both cases as can easily be ascertained on examining Fig. 3. It will also
be understood that the relative shapes and dimensions of the various parts of the
outline of the spirals and of the groove, which forms an integral part of them,
may vary within certain limits without affecting the principle of the invention.
Finally and as a consequence of the invention the packing a used, being fixed
in a special receptacle which keeps it in its place, the rubber thread hitherto used
may be replaced by a thread of asbestos covered with rubber or bitumen, or of
any other material which will suit the nature of the fluid contained in the tube
which may then be used not only for water or steam, but also for superheated
fluids, oils, petroleum or any other liquids or gases which affect indiarubber.
Having now particularly described and ascertained the nature of the said in-
vention and in what manner the same is to be performed, as communicated to
me by my foreign correspondent, I declare that what I claim is: -
1. In the construction of a flexible metal watertight tube, a metal strip com-
prising a channel or groove at one of the fastening edges to contain a water
tight packing, and an almost flat piece situated on the opposite side of the said
strip so that when the metal strip has been twisted into a screw shape to form
the successive spirals of the tube, the packing becomes fixed and is kept in the
groove of one of the spirals and forms a tight joint in the very slightly bent
part of the next spiral substantially as described.
2. In a watertight flexible metal tube made by twisting into a screw form a
metal strip shaped for the purpose; the combination with one of the fastening rims
of each spiral, of a screw shaped conical groove to contain a watertight packing
which can slide on to the slightly inclined surface of the next spiral, the abutting
of the spirals against each other, resulting from their respective displacements
being limited to the metallic parts of each spiral substantially as and for the
purpose described.
3. In a flexible metallic tube made by twisting a shaped metal strip into a
spiral form, fitted with a groove forming a continuation of one of the fastening
edges of the said strip, the combination with the said groove of a packing com-
posed of a cord or thread of asbestos or a material like asbestos which cannot be

page_text: injured, and the fibres of which are made to adhere together by an agglutinant
material such as tar or its equivalent substantially as and for the purpose
described.
Dated this 10th day of August 1897
WM. P. THOMPSON & Co.,
Manchester, Liverpool and London, Patent Agents.