Improvements in or connected with Weighing Apparatus.
Year: 1896

page_text: Date of Application, 15th Feb., 1896
Complete Specification Left, 12th Nov., 1896-Accepted, 19th Dec., 1893
PROVISIONAL SPECIFICATION.
Improvements in or connected with Weighing Apparatus.
I, GEORGE HENRY, DENISON, of 25 North Street, Leeds, in the County of
York, Engineer, do hereby declare the nature of this invention to be as follows:-
This invention relates to, and is connected with, the indicating mechanism of
weighing machines such as are self acting or partially so; and the improvements
consist in the employment of a plunger or the like working in a vessel containing
mercury, which is used as a resistance to the load instead of a spring or other
device; the object of the invention being to provide a true and reliable indication
of the weight, and this, as far as possible, automatically-preferably wholly so.
The principle underlying the invention is the use of the fluid pressure of the
mercury tending to lift or float a more or less immersed plunger, and indicating the
results.
By preference I make the plunger of a hollow cylindrical shape, closed at its
lower end, but with one or more small holes through which the mercury may obtain
access to the interior of the plunger; somewhat after the manner of a "cataract"
in its steadying action.
The rise and fall of the plunger may be magnified as desired so as to render a
small movement visible.
Dated this 14th day of February 1896.
WM. SNOWDON,
9 Old Bank Chambers, Leeds, Agent for the Applicant.
paratus.
I, GEORGE HENRY DENISON, of 25, North Street, Leeds, in the County of
York, 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 relates to, and is connected with, the indicating mechanism of
weighing machines such as are self-acting, or partially so; and the improvements
consist in the employment of a plunger or the like working in a vessel containing
mercury, which is used as a resistance to the load instead of a spring or other
device; the object of the invention being to provide a true and reliable indication
of the weight, and this, as far as possible, automatically.
The principles cr chief characteristics underlying the invention are the use of
the fluid pressure of the mercury tending to lift or float a more or less immersed
plunger; the indication of the results promptly; and on a magnified scale.
By preference I make the plunger of a hollow cylindrical shape, closed at its
lower end, but with one or more small holes through which the mercury may
D7

page_text: obtain access to the interior of the plunger, with the object of producing a steadying
action, somewhat after the manner of a "cataract" or "dash-pot."
The rise and fall of the plunger may be magnified as desired, so as to render a
small movement visible.
In order to describe my invention fully, I have annexed three sheets of
drawings.
Fig. 1 is a front elevation of such parts of a weighing machine as are necessary
to a full understanding of the mode of carrying out my invention (the appliance
being shown attached to the steelyard, etc.), whilst Fig. 2 is an end elevation
corresponding with Fig. 1.
Fig. 3 is an enlarged section, in end view, of the plunger in its bath of mercury,
and Fig. 4 is a variation in detail, which is referred to later.
The same letters refer to the same parts or their equivalents in all the figures.
A is the steelyard, whose fulcrum is at B on the pillar B', a sliding weight C
being mounted as usual.
At the end of the steelyard is a hanging link D D, to which is attached the
plunger E, as shown more fully on a larger scale in Fig. 3. Here, in Fig. 3,
a a are the knife edges, on which the link D D hangs, the cross bar d¹ being
made to support the rod e¹ of the plunger E. The foot of the rod e' fits into, and is
secured in, the head of the plunger.
The mercury bath F, which is fixed to the secondary standard G, has a lid as
shown, and a further protecting cover is attached to the rod e', for keeping dust out
of the bath.
In order that the exact mean level of the mercury in its bath need not be adhered
to strictly, I make the plunger of uniform shape, and of equal cross section, so that
equal amounts of mercury may be displaced by equal movements of the steelyard,
and for facility of manufacture, I make the said plunger take a circular form.
For an important reason to which I refer later, I further prefer to make it hollow,
with the base of the hollow body closed by a diaphragm e, through which a small
hole runs.
Another hole (or its equivalent) is run through the enlarged part of the
supporting rod at e, for admitting air to the interior of the plunger.
From what has been described, it follows that upon a load being placed on the
machine, the steelyard plunger is proportionately withdrawn from the mercury, the
amount of its withdrawal being a measure of the load.
In order to magnify small movements, I place at a suitable distance along the
steelyard, a light link h', which actuates a balanced bell-crank lever H, mounted
on a suitable pivot. The longer leg of this lever indicates on a suitable scale g'
the extent to which the steelyard is noved, and thus measures the load.
As here arranged, the scale is laid out on an upward prolongation of the
secondary standard, a tie g2 steadying the whole in its relationship to the
pillar B
When iny machine is used for weighing more or less uniform loads, such as are
met with at a colliery, for instance, when weighing the "corves" laden with coal,
a second arm of the steelyard (not shown) may be made to carry a weight
representing the tare weight of the "corves"; the weight C is then fixed for the
minimum weight, and the index, worked by the mercury balance, is arranged, and
the scale made, to denote all excess over the said minimumn. In this way the net
result is displayed automatically on the index.
Previous reference has been made to the importance of making the plunger
parallel, so as to displace equal portions of mercury for equal movements of the
steelyard, etc., and also to the fact that the base of the hollow plunger is made solid,
except for a central hole or so.
The special object of this is to obtain a "cataract" or "dash-pot" action from
this base. Seeing that the mercury has to flow in and out of the interior through
the small hole e³, it follows that any tendency to an undue vibration of the
steelyard is at once checked, and the pointer H promptly brought to an exact

page_text: reading. Of course it is essential that no portion of the base be drawn to the
surface of the mercury, and also that no part of the foot of the rod el should touch
the mercury.
Fig. 4 shows in sectional elevation a variation in the mode of using the
mercury bath.
Here the bath F is attached to, and moves with, the steelyard A;
and the plunger E is fixed to the secondary standard G; the resulting action being
practically the same as before.
From this, it also follows that the plunger, for all practical purposes, may be
rigidly attached to the steelyard in such an arrangement as that in Fig. 1, instead
of being suspended by the link D D.
Variations in the mode of magnifying the amount of displacement of the mercury
may be made without departing from the spirit of the invention, as for instance,
a rack, in connection with the plunger, may actuate a pinion on the axis of a
pointer.
Although I attach great importance to the plunger forming its own dash-pot,
nevertheless an independent dash-pot could be arranged, but I do not advocate any
such arrangement. Without a dash-pot the steelyard would vibrate too much for
a prompt reading of the index.
Although not shown on the drawings the steelyard is fitted with the usual devices
for balancing the unloaded machine; and details may be arranged to vary the
relative distance apart of the knife edges of the steelyard for ease of adjustment
when necessary.
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. The improved method of weighing by means of a plunger moving in a bath of
mercury, the amount of displacement being automatically magnified and displayed
on a suitable scale; in, and after, the manner set forth herein, and shown on the
drawings.
2. In a weighing machine using a bath of mercury as a resistance, the combination
of a plunger and a dash-pot diaphragm in one device; in, and after, the manner set
forth herein, and shown on the drawings.
3. The general arrangement of a weighing machine steelyard balanced by a
plunger moving in a bath of mercury and automatically indicating the weight
on a magnified scale; substantially as described herein, and shown on the
drawings.
4. In a weighing machine having a steelyard balanced by a plunger moving in a
bath of mercury and automatically displaying the result on a magnified scale, the
plan of attaching the bath to the steelyard, whilst fixing the plunger to the
Secondary standard, as set forth herein, and shown, in Fig. 4, on the drawings.
5. In a weighing machine having a plunger moving in a bath of mercury and
automatically displaying the result on a magnified scale, the plan of attaching the
olunger rigidly to the steelyard, with the bath fixed on the secondary standard,
ubstantially as described herein.
Dated this 11th
T
WM. SNOWDON,
9, Old Bank Chambers, Leeds, Agent for the Applicant.