Improvements relating to Hydrostatic Weighing-machines, and to Gauges for use in connection therewith.
Year: 1892

page_text: Date of Application, 7th May, 1892-Accepted, 13th Aug., 1892
Improvements relating to Hydrostatic Weighing-machines, and to
Gauges for use in connection therewith.
We, EDWIN ALFRED HOAD, Manufacturer, and JOHN JACKSON, Engineer,
both of Suffolk House, Laurence Pountney Hill, in the City of London, 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:-
Our invention relates chiefly to hydrostatic weighing-machines, weigh-bridges
and the like of the kind or class described in the Specifications of the following
former Letters Patent granted to us, viz. :-No. 6338 dated 14th April 1891 and
No. 20,880 dated 30th November 1891, and to pressure-gauges for use in connection
therewith.
Our present improvements are, however, applicable to other hydrostatic weighing-
machines and gauges.
The accuracy of hydrostatic weighing-machines is liable to be impaired by the
expansion and contraction of the liquid therein, due to changes in the temperature
of the same, the said machines, when affected by such changes of temperature,
indicating either more or less than the actual weight of any load applied thereto,
according to whether the liquid is expanded or contracted.
To obviate this defect or inconvenience, we provide suitable means for
compensating for such expansion and contraction of the liquid. We find it
advantageous for this purpose to combine, with the weighing-machine, means
whereby the cubic capacity of the space in which the liquid is enclosed, may be
varied at will.
In weighing-machines of the kind or class described in our said former Specifi-
cations, it is desirable, in order to obtain the requisite strength and flexibility of
the diaphragm, that the outer portion of the latter should be stiffer than the central
portion thereof. To attain this result, we find it advantageous to combine, with
the diaphragm, a strengthening ring or annular piece the external diameter of
which is approximately equal to the diameter of the diaphragm, and the internal
diameter of which is such as to leave a suitable area of the central portion of the
said diaphragm unsupported by the said ring or annular piece.
We have found, moreover, that, when the machine is provided with a pressure-
gauge of the usual construction in which the movement of the needle or pointer is
arrested, on its return to zero, by a fixed pin or stud, the said needle or
pointer is liable to injury should the load on the machine be suddenly removed,
the said needle or pointer, in such case, striking the fixed pin or stud with
great force.
To obviate the liability to injury in this manner, we provide the gauge with a
suitable spring or cushion, so arranged that the needle or pointer, when it returns
with undesirable rapidity, will move back beyond the zero and will act upon the
said spring or cushion, and the latter, by its reaction, will then move the needle or
pointer forward to zero. The shock or concussion to which the needle or pointer
is subjected will thus be diminished sufficiently to avoid injury to the said needle
or pointer.
In the accompanying drawing, we have shown how our said invention may be
conveniently and advantageously carried into practice :
Figure is a front elevation and

page_text: Figure 2 a side elevation, partly in vertical central section, showing a hydrostatic
weighing-machine having our present improvements applied thereto..
Figure 3 is a section on the line r, z, Figure 2, showing a detail of
construction.
Figure 4 is a vertical central section, drawn to an enlarged scale, showing a
flexible diaphragm and a strengthening ring combined therewith, and
Figure 5 is a front elevation, also drawn to an enlarged scale, illustrating one
form of our cushion for the pointer of the gauge.
Like letters indicate corresponding parts throughout the drawing.
a is the hermetically sealed vessel or box in which the glycerine or other liquid
is enclosed; is the pressure-gauge; c is the loop or frame for suspending the
machine from a crane-chain or other suitable support. Other parts of the machine
are marked with reference letters corresponding to those used for the same parts in
our said former Specification No. 6338.
7 is a cylindrical chamber provided with a piston m, which is attached to an
adjusting screw n extending through a tapped hole in the cylinder-cover l', and
provided with a milled wheel n' to facilitate its adjustment. The said cylinder
communicates with the interior of the vessel or box a by means of a pipe or
passage p provided with an adjustable stop-valve 9, and both the vessel or box a
and the cylinder are to be filled with liquid.
To compensate for changes of volume of the liquid due to variations of temperature,
the valvey is opened and the piston m is then moved or adjusted, by means of the
screw, either downward or upward, according to whether expansion or contraction
of the liquid has been caused by the variation of temperature, until the pointer of
the gauge is brought to zero. The valve being then tightly closed, the machine
is ready for weighing accurately the loads placed thereon.
q
The vessel or box a is filled with liquid before closing it. The regulating
cylinder may be charged with liquid by screwing the piston m down to the end of
its stroke or movement, connecting the said cylinder through the nipple / with a
receptacle containing the liquid, and then raising the piston and thus drawing the
liquid into the said cylinder, the passage through the nipple being then closed by
screwing a cap or cover upon the said nipple. A suitable valve may, if necessary,
be provided for permitting the escape of air from the said vessel or box a.
In Figure 4, we have illustrated our improved device for strengthening or
supporting the diaphragm whilst preserving the requisite flexibility of the same.
a is the corrugated diaphragm and is a correspondingly corrugated ring or
anuular piece of metal, which we place over the said diaphragm and secure
therewith between the top of the vessel or box a and the holding-down flange
attached thereto.
The device which we have shown in the drawings for diminishing the shock or
concussion imparted to the needle or pointer of the gauge on its return to zero,
comprises a small plungers fitted to slide in a casing s in which is enclosed a weak
spiral spring bearing at one end against the said casing and at its other
end against a shoulder on the said plunger s so that it tends to push the latter
out of the said casing. The said plunger is retained in the casing s¹ by the
lock-nuts s³.
As may be seen in Figure 1, the pointer of the gauge, when' at zero, is just
clear of the spring plunger s. If the said pointer, after it has been turned to any
point of the graduated dial, should from any cause be allowed to return too
suddenly to zero, it will strike the plungers and more or less compress the springs,
the said pointer moving back a short distance beyond the zero; the spring will
then, by its reaction, move the said pointer forward to the zero. The pointer will
thus be returned to zero without injurious shock or concussion.
Although we have described our present improvements more particularly as
applied to machines such as we have described in our said former Specifications,
yet it is obvious that the said improvements may be advantageously applied to
other machines.

page_text: Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
:-
First. The combination, with a hydrostatic weighing-machine, of an adjustable
device whereby the cubic capacity of the space for the liquid may be varied at will,
for the purpose above specified.
Second. The combination, with the vessel or box for containing the liquid, of the
cylinder provided with the adjustable piston and communicating with the interior
of the said vessel or box by means of a pipe or passage governed by an
adjustable valve, substantially as herein before described and for the purpose
specified.
Third. The combination, with the diaphragm, of the strengthening or supporting
ring, substantially as, and for the purpose, above specified.
Fourth. The combination, with the index or pointer of a gauge, of a spring or
cushion for diminishing the shock or concussion imparted to the same on the sudden
return thereof to zero, substantially as herein before described.
Dated the 7th day of May 1892.
D. YOUNG & Co.,
11 & 12, Southampton Buildings, London, W.C., Agents for the Applicants.