Year: 1886

page_text: We URBAIN ANDRÉ CHAUVEAU, and JACQUES. GUSTAVE JOURDAN, Engineers
both of 86 Rue Royale, Brussels, Belgium 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 our invention is to produce a moro perfect gauge for indicating
the pressures of steam, compressed air, and other elements, than heretofore. To
accomplish this we employ a plunger working in a case containing enough mercury
to support the said plunger in equilibrium or nearly so, the plunger being con-
nected to a piston on which the steam or other element presses such amount of
pressure being communicated by levers or other means and indicated by a pointer
on a dial all as hereafter described, and the invention will be best understood by
reference to the accompanying drawings.
Figure 1 is an elevation or front view of a pressure gauge constructed according
to our invention.
Figure 2 is a section on the line y y of Figure 1.
Figure 3 is a transverse section on the line x, x of Figure 4, and
Figure 4 is a plan with the case in section.
:
In a tube or cylinder T we place a quantity of mercury, sufficient so that when
the plunger P is put in as far as P 1, the mercury rises to the height M―S.
The diameters of the tube T and the plunger P are optional, as well as their
shape, but the arrangement which we prefer is that indicated in the drawings
namely; the form of the cylinder, and secondly, that the relation of the section
between the tube and the plunger be as 2 to 1.
The weight of the plunger must be in perfect equilibrium with the column of
mercury so that when the plunger descends to P'1, the column of mercury rises
to MS. This weight can be ascertained by different means, by, for example, the
density of the metal of which the plunger is made, or by external overcharge.
A lever L fulcrummed at A on a bracket from the cylinder T is attached at its
other end to the plunger P by a hinge as best seen in the plan view Figure 4. The
steam, or other element, the pressure of which is to be indicated by the apparatus,
enters at the tube B into a chamber D where there is a small piston E covered by
an india rubber washer F or diaphragm which, while leaving the piston E free
to move prevents the steam or gas from escaping from the box D and passing the
FDA

page_text: piston E. The piston rod of the piston E transmits the pressure contained in the
chamber D to the lever L' which by means of the connecting rod G transmits it to
the lever L. This transmission of pressure can be effected directly (by the piston.
rod of the piston E to the lever L) but there would have been a difficulty in con-
struction, because of the excessive proximity of the fulcrum of the lever L with the
fulcrum which would attach the piston rod of the piston E with the lever L.
The action is as follows: when the pressure passing by the tube B acts on the
piston E its action is felt on the lever L³ connecting rod G and lever L, and
the latter in rising lifts the plunger P partly out of the mercury, which falls the
same distance as the plunger has risen, because the latter is of the same section as
that of the mercury at MS; the weight of the part of the plunger which is raised
multiplied by 20 (because of the levers L and L¹ namely divided by 5 for L and
by 4 for L¹) will equal the pressure exerted at E by the steam, and any suitable
needle or pointer as for example that shewn in the drawings is employed to indicate
the pressure on a dial as at E.
The plunger P must not rise above PS at its highest position and the lowest
level of the mercury must not be lower than M1 so that the plunger P is always
immersed to the depth of M 1 to P—S.
It is at this space that we form a flange on the inside part of the tube or
cylinder T. The object of this flange is to guide. the plunger P and also by leaving
sufficient play it permits the mercury to pass but only in small quantities at a
time, and so prevents the oscillations of the mercury-from any jerk and thus com-
municating such jerk to the indicating needle by means of the motion that would
be so given to the plunger P. A screw V may be used which can be pressed at
will on to the top of the plunger P keeping the mercury in the tube or cylinder T
thus saving the necessity of emptying the tube, when the gauge is taken down and
refilling it again when it is wanted to be used.
Instead of the levers, the movement can be obtained by, for example, racks with
tooth wheels, so that the action of the plunger can be employed in the inverse
sense, that is the plunger may be balanced in the atmosphere in such manner so.as
to annul its weight and it may be plunged into instead of withdrawn from the
mercury so that its volume will cause the plunger to rise. In either case the result
of the pressure will be clearly indicated and either method can be employed at
will, but we prefer the form of apparatus as shewn in the drawings.
If it was not for the enormous difference in the density and the question of
evaporation, water or any other liquid would produce the same effect, but in
practice we find mercury to be most suitable.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim is:
First. In pressure gauges the application of the difference of weight of bodies in
the atmosphere or when immersed in mercury and then afterwards plunging or
withdrawing them from the mercury substantially as herein before described with
reference to the accompanying drawings.
Second. The particular construction and arrangement of mechanism for pressure
gauges substantially as and for the purposes herein before described with reference
to the accompanying drawings.