Improvements in Tubes for Heating or for Interchange of Tempera- tures, and in Apparatus for Making the same.
Year: 1898

page_text: Date of Application, 13th May, 1898-Accepted, 6th Aug., 1898
Improvements in Tubes for Heating or for Interchange of Tempera-
tures, and in Apparatus for Making the same.
I, EUGENE MARIN, of Montlucon, in the Republic of France, 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:-
This invention has for its object various improvements in tubes for heating and
in tubes employed generally in apparatus used for interchange of temperature,
with the object of obtaining a maximum heating surface or exchange surface with
a minimum of space.
Take as an example the case of boiler tubes. Efforts have been made to increase
the heating surface without increasing the volume of the casing, and for this.
purpose ribbed or winged tubes have been employed which all have drawbacks. If
tubes having external ribs or wings be employed, the surface in contact with the
water is indeed increased but not the surface in contact with the flame, and
inversely if tubes with internal wings or ribs be employed the surface in contact
with the flame is increased but not the surface in contact with the water.
Tubes with external and internal ribs or wings have also been employed. By
this means both contact surfaces are indeed increased, but the quantity of material
is also increased in proportion to the said surfaces. The tubes are thus made too
heavy, the bases of the ribs form extra thicknesses, and the manufacture of the
same is rendered difficult.
Corrugated tubes have also been employed, which whilst possessing a constant
thickness increase but little the surfaces in contact unless the corrugations are
very accentuated, in which case the cleaning of the tubes is very difficult.
It is in order to avoid these drawbacks and to obtain a tube of equal thickness,
the internal and external surfaces of which are as far as possible symmetrical,
that I have adopted the system which I will now describe for enabling a rational
exchange of temperature which is a function not only of the difference of tempera-
ture but of the surfaces in contact internally and externally.
In the accompanying drawings,
Figure 1 is a longitudinal section of this improved tube and Figure 2 a trans-
verse section, the form being that usually known as a crescent:
Figure 3 is a transverse section of a modification corresponding to the so-called
double crescent form: Figure 4 is a sectional elevation; Figure 5 a horizontal
section and Figures 6 and 7 details of a modification of a machine for making the
tubes, whilst Figure 8 is a cross section on the line 1-2 of Figure 4 of the machine
for making the tube shown in Figures 1 and 2.
My process consists in causing a portion of the wall of the tube to bend in towards
the interior in such a way that the tube thus shaped whilst preserving the same
lateral surface occupies less space. I thus obtain a tube having a lateral surface,
that is to say a heating surface greater than that which a round tube of small

page_text: diameter would have without occupying more room than the latter. The shapes
and the transverse sections may be varied in many ways according to the require-
ments and the forms which it may be necessary to adopt. Figures 2 and 3 show
only two examples. It is easy to ascertain by a simple geometrical sketch that for
the same space occupied the surface in contact and the exchange surface is
increased in very considerable proportions. This increase may be easily varied
by modifying the form of the part bent in. It is necessary also to avoid angles
and to endeavour to have curves tangentially in the cross section so as to have
spaces easily cleaned. I have therefore in Figures, 2 and 3.adopted. circles, but
ellipses, parabolas or any other suitable curves may also be adopted.
According as the case may be, my tubes with a bent-in part may have the same
section along all its length in which case its corresponding supports on the furnace
plates will have the same profile, or it may have a cylindrical part at each
extremity which enables it to be utilized in existing furnaces and gives greater
facility for the rivetting of the plates. This is the case shown in Figure 1. In
practice the recessed or bent-in part should preferably be placed in the upper part
in order to avoid steam spaces.
These tubes having a recessed part with or without circular ends may be
obtained by any suitable method of manufacture, bending, screwing, boring, draw-
ing or the like.
As an example I will now describe a method for obtaining in a single operation
a tube with circular ends such as shown in Figures 1 and-2. This tube obtained
by selecting a tube of circular section larger than the section desired, depressing
or bending-in a part of the lateral wall along the major part of its length and
drawing the ends in order to bring them to the diameter of section finally required.
The apparatus comprises a ring or eye L into which a punch P actuated by an
hydraulic piston Q arranged in a cylinder R is adapted to be moved laterally.
The descending movement of the punch P corresponding to the action for deform-
ing the tube is obtained by the use of water under pressure arriving at S and
acting on the upper face of the piston Q. The return of the piston is obtained by
the action of a spring T.
The diameter of the ring or eye is equal to the final diameter of tube which it
is desired to obtain. The tube to be transformed which is of larger diameter is
drawn through this ring or eye. When the part of circular section has attained the
desired length the punch P is caused to descend and operate. This punch has an
external form corresponding to the form of the depression required to be made in
the tube. It acts by pressing the wall of the tube against a mandrel M held at
the end of a rod and having a recess of the internal form of the depression or
deformation to be made in the tube. The punch works in front of the ring or
eye L independently of the same.
After the tube has been deformed or rather shaped it passes through the ring
without being further worked. The rear of the mandrel which then comes into
the eye no longer acts except to regulate or adjust the shape of the tube.
When the shaped part has the desired length the punch is raised and the tube
is drawn into a circular section in the eye or drawing plate.
The hydraulic piston is moved automatically by suitable devices placed at the
side and on the bench to open and close the water supply. The punch and the
mandrel are of forms suited to the circumstances and according as it is desired
to increase or vary such and such advantage of the tube, such as the heating surface
or the part in the interior of the tube in contact with the heating gases. The
punch may thus assume any suitable form and I wish to reserve the right to replace
it by a roller of corresponding form as indicated in Figures 6 and 7.
This latter arrangement has the advantage of reducing the drawing action
exerted on the tube in order to bring it into its form. It is evident that
these tubes are not only suitable for boilers but also in all apparatus where there
is an interchange of temperature and more particularly to surface condensers and
apparatus for producing cold (refrigerating apparatus).

page_text: Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:-
-
1. Tubes for heating or for interchanging temperature having a maximum sur-
face of exchange with a minimum volume obtained by inwardly depressing a part
of the wall substantially as hereinbefore described and shown in Figures 1, 2 and 3
of the accompanying drawings.
2. For the production of tubes such as described a machine for forming a crescent
shaped tube, comprising a punch (P Figures 4 and 5) or a roller (Figures 6 and 7)
adapted to be actuated by a piston (Q) and returned by a spring (T), in com-
bination with an eye or ring (L) and a mandrel (M), substantially as hereinbefore
described and shown in the accompanying drawings.
1
1
100
1
1000
W. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.