A DIOPTICAL METALLIC LEVEL INDICATOR OR LIQUID GAUGE
Year: 1863

page_text: LETTERS PATENT to Désiré François Leblanc, of 3, Percy Street,
Bedford Square, in the County of Middlesex, for the Invention of "A
DIOPTICAL METALLIC LEVEL INDICATOR OR LIQUID GAUGE."-A communi-
cation from abroad by Ferdinand Philippe Edouard Carré, Engineer, of
. Paris.
PROVISIONAL SPECIFICATION left by the said Désiré François Leblauc
at the Office of the Commissioners of Patents, with his Petition, on the
15th January 1863.
I, DÉSIRÉ FRANÇOIS LEBLANC, of 3, Percy Street, Bedford Square, in the
County of Middlesex, do hereby declare the nature of the said Invention for
"A DIOPTICAL METALLIC LEVEL INDICATOR OR LIQUID GAUGE," being a commu-
nication to me from abroad by Ferdinand Philippe Edouard Carré, Engineer,
of Paris, to be as follows:-
The glass tube indicators or gauges used to shew the level of the liquid in
steam boilers and other receivers placed under pressure, have two principal
defects, viz., their frequent breaking, which causes numerous accidents to
happen, and the darkening of their sides, which renders their indications almost
imperceivable.
To obviate at once both of these defects the following combination is
intended :-
Let us consider a rather thick sided glass tube half filled with water, we
shall readily note the wide difference in refraction which exists (between the
full portion of it and the empty part thereof; and now let there be a screen
provided with a circular hole of about two-thirds of the outside diameter of
this tube placed behind that portion of it which is full of water, and this

page_text: circular hole will appear in the form of an ellipse, having its great or transverse
axis perpendicular to the axis of the tube, whilst on the sanie screen being
removed behind the empty portion of the tube the ellipse assumes a rather
lengthened form, having then its great or transverse axis parallel to that of
the tube.
It follows from this, first, that such a screen may be of avail to know (when
no solution of continuity appears in the tube) whether this is quite empty or
quite full.
And secondly, that, however darkened its sides may be, unless they are
altogether opaque, it will always be possible for any one to ascertain with its
aid the presence or the absence of the liquid inside.
A metallic tube pierced from end to end with circular holes opposite each
other on two or three alternate diameters, and encasing the glass tube, may
therefore become at once both a protection against its breakages and their
effects, and a means of more distinctly shewing the height of the liquid
inside.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Désiré François Leblanc in the Great Seal Patent
Office on the 15th July 1863.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, DÉSIRÉ
FRANÇOIS LEBLANC, of 3, Percy Street, Bedford Square, in the County of
Middlesex, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fifteenth day of January, in the year of our Lord
One thousand eight hundred and sixty-three, in the twenty-sixth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said Désiré François Leblanc, Her special licence that I, the said
Désiré François Leblanc, my executors, administrators, and assigns, or such
others as I, the said Désiré François Leblanc, 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 "A DIOPTICAL METALLIC LEVEL INDICATOR OR LIQUID GAUGE,"
a communication to me from abroad by Ferdinand Philippe Edouard
Carré, Engineer, of Paris, upon the condition (amongst others) that I,
the said Désiré François Leblanc, my executors or administrators, by an

page_text: instrument in writing under my, or their, or one of their hands and
seals, should particularly describe and ascertain the nature of the said Inven-
tion, 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 Désiré François Leblanc, 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 :-
The glass tube indicators or gauges used to show the level of the liquid in
steam boilers and other receivers placed under pressure have two principal
defects, viz., their frequent breaking, which causes numerous accidents to
happen, and the darkening of their sides, which renders their indications almost
imperceivable.
To obviate at once both of these defects the following combination is
intended :-
Let us consider a rather thick sided glass tube half filled with water, we
shall readily note the wide difference in refraction, which exists between the
full portion of it and the empty part thereof; and now let there be a screen
provided with a circular hole of about two-thirds of the outside diameter of
this tube placed behind that portion of it which is full of water, and this
circular hole will appear in the form of an ellipse, having its great or transverse
axis perpendicular to the axis of the tube, whilst on the same screen being
removed behind the empty portion of the tube the ellipse assumes a rather
lengthened form, having then its great or transverse axis parallel to that of the
tube.
•
It follows from this, first, that such a screen may be of avail to know-
when no solution of continuity appears in the tube- whether this is quite
empty or quite full.
And secondly, that, however darkened its sides may be, unless they are alto-
gether opaque, it will always be possible for any one to ascertain with its
aid the presence or the absence of the liquid inside.
A metallic tube pierced from end to end with circular holes opposite to
each other on two or three alternate diameters, and encasing the glass tube,
may therefore become at once both a protection against breakages and their
effects, and a means of more distinctly shewing the height of the liquid
inside.
Such is the nature and object of the said Invention for "A Dioptical
Metallic Level Indicator or Liquid Gauge," but essentially consisting in the

page_text: application of the combined dioptical properties of glass and water to the con-
struction of a liquid gauge that should possess such requisites to clearness of
indication and security of service as have never been as yet attained, it is
susceptible of any form; for example, a glass tube consisting of several short
ones may be advantageously substituted for that of one piece, and lenses for
either of them.
Again, a casing made of any 'flexible matter, as vulcanized or hardened
india-rubber, or simply sheets of paper or cloth, impregnated with siccative
greasy substances, rolled several times and stuck on the glass tube, may also
be used, with the same purpose, if not with the same result, instead of the
metallic casing.
Being given a quadrangular opaque tube, the sides of which are pierced
with two circular holes opposite to each other; if you fix in each of them a
plano-concavel ens, whose concavity faces the axis of the tube, and whose focus
lies a little behind the opposite side; the hole that faces the lens which is
looked at will appear greatly reduced in diameter, the tube being empty;
whilst, on the same being filled with water, the index of refraction of this being
pretty nearly the same as that of glass, the concavity of the lens is found to be
almost annulled by the convexity of the water, and the opposite hole reappears
with its nearly full diameter. The crown glass gives the maximum of diffe-
rential effect.
Such being the nature and object of the said Invention for "A Dioptical
Metallic Level Indicator or Liquid Gauge," I will proceed to describe the
manner in which the same is to be or may be performed or carried into prac-
tical effect;. and in order that the same may be distinctly understood, I have
annexed hereunto one Sheet of Drawings illustrative thereof, and have marked
the same with figures and letters of reference, corresponding with those of the
following explanation thereof, (Figures 1, 3, 4, and 5, are full size; Figure 2
half size; and Figure 6 an enlarged view,) that is to say:―
Figure 1 of the annexed Drawings represents a glass tube enveloped in a
metallic casing pierced with circular holes opposite to each other. The
metallic casing may be simply a non-adhesive case surrounding the glass tube,
but it is better to have it fixed thereon, by means of a mastic or cement, such
.as that of ceruse and minium, oxychloride of zinc, and such like.
A is the glass tube; B, the metallic casing; c, the mastic; d, the holes of
the casing; e, the outline and direction of the ellipse, as seen in the empty
part of the tube; e¹, the same as seen in the part occupied by the liquid.
Figure 2 represents a sort of forcing pump or press that serves to fix the
glass tube and the metallic casing together.

page_text: A, body of the pump or barrel, wherein the mastic or cement is placed; B,
piston, furnished at its lower end with a circular leather plate, rectangularly
bent back upon itself B¹, and set in motion by a screw b. Compressed by the
piston, the mastic runs into two tubes C, fitted to the bottom of the barrel with
ball-and-socket joints c. These tubes end in two opposite cylindrical seg-
ments c', capable of enclosing about ten centimeters in length of the metallic
casing, which is so placed in them that its holes should correspond with their
orifices, through both of which holes and orifices the mastic is forced between
the glass tube and its casing. A cramp d, provided with screws d², d¹¹, which
press the lower extremeties of the tubes C, serves to bring the segments.close
to the casing intended for being cemented. Corner plates d³, d, embracing
the rectangular prominences c" of the tubes, keep them in front of each other.
A spring E. thrusts the segments back when the screw d' gets loosened.
Indicators of unlimited length and best fitted to resist expansion will be
obtained by using short glass tubes joined end to end. For this purpose
it is necessary that each joint should correspond with the middle of a spaco
without holes, so long as the sealing should prevent leakage.
The mastic of ceruse and minium, by reason of its solidifying slowly in a
cold place, appears to be the most suitable one to employ. The complete
solidification is obtained by its being exposed for two or three hours to a tem-
perature of from two hundred to two hundred and fifty degrees centigrade.
All mastics that solidify slowly in a cold place and quickly in a hot one may
likewise be advantageously used. Coloured mastics, and above all those colored
with black, render more distinct the perception of the optical phenomenon.
3 The glass tube extends a little beyond the metallic casing, in order to obtain
a hermetical joint, in case the sealing of its extremities to its casing should not
be quite water-tight, and thus to prevent acids and other agents from attacking
the metal or the mastic. This disposition, however, is not indispensable, and
in most cases the glass tube will be level with its casing.
Figure 3 represents a special mode of fastening together, end to end, the
fragments of a compound glass tube. Each joint is made with a ring of vul-
canized india-rubber. The fragments are compressed by means of screws a,
which enter into the extremities of the casing, and press down the platines a¹.
The superfluity of india-rubber in the interior of the glass tube is prevented
5 by placing therein about each joint a short thin metallic tube, as in b, and by
sloping the ends of the fragments externally, as in 6¹.
Figure 4 represents the section of an indicator, provided with lenses.
A, metallic body; A¹, tubulatures, capable of receiving cocks; a, a¹, a¹¹,
plano-concave lenses. There are many means of fixing the lenses in the holes ;

page_text: they may be screwed with an oily mastic, as in a¹, or simply sealed with a
mastic, specially that of cast iron in brimmed holes, as in a", or only hot fixed
by means of a sufficiently fusible enamel, provided that the glass made use of
be of a dilatation pretty nearly the same as that of the metal employed, which
should be little dilatable itself, such as cast iron, iron, steel. I do not mention
platinum because of its high price.
Lenses may also be placed on thinner tubes by means of tubulatures, A,
Figure 5, into which they are fixed, either with a mastic or with india-rubber,
by means of a screw cap. They may likewise be sealed with an enamel into
very thin tubulatures which will attenuate the effects of expansion. By
enamelling the cast iron, iron, and steel tubes, they will thoroughly be kept
from oxydation.
Figure 6 represents an enlarged view of a mode of fixing the lenses in the
tubulatures, which mode may be applied either to the tubes, Figure 4, or those
Figure 5.
A, lens; B, side of the tube; c, externally screwed tubulature; c', matter
of the joint, which matter may be, according to the case, either a ring of
vulcanized india-rubber, or amianth, impregnated with mastic, or simply oiled
hemp for both low and mean pressures; c", metallic ring that compresses the
joint; d, screwed cap, screwing on the metallic ring.
Having now described the nature and object of the said Invention for "A
Dioptical Metallic Level Indicator or Liquid Guage," together with the
manner in which the same is to be or may be performed or carried into prac-
tical effect, I would remark in conclusion that I claim as the Invention com-
municated to me by the aforesaid Ferdinand Philippe Edouard Carré, the
dioptical metallic level indicator or liquid gauge herein-before described and
illustrated in the Drawings, or any mere modification or imitation thereof.
In witness whereof, I, the said Désiré François Leblanc, have hereunto
set my hand and seal, this Fourteenth day of July, in the year of our
Lord One thousand eight hundred and sixty-three.
DESIRE FRANÇOIS. LEBLANC. (Ls.)