IMPROVEMENTS IN WEIGHING APPARATUS
Year: 1876

page_text: LETTERS PATENT to William Thomson, of Glasgow, in the County of Lanark,
North Britain, Engineer, for the Invention of "IMPROVEMENTS IN WEIGHING
APPARATUS."
Sealed the 15th February 1876, and dated the 22nd February 1876.
PROVISIONAL SPECIFICATION left by the said William Thomson at tho
Office of the Commissioners of Patents on the 22nd February 1876.
WILLIAM THOMSON, of Glasgow, in the County of Lanark, North Britain,
Engineer. "IMPROVEMENTS IN WEIGHING APPARATUS."
This Invention, which relates to improvements in apparatus for ascertaining the
weights of bodies, has reference to that class of apparatus known as the "steel-
yard."
In the steelyard as hitherto constructed it has been essential, owing to the form
of the apparatus, that the knife edges or centres are at a considerable distance
apart, such distance increasing with the size of the apparatus, and on this account
it has been compulsory to use very long levers and large counterbalances or to
compound the levers.
Under the present Invention the knife edges or centres of suspension are fixed
respectively at the inside and outside of the central box or shell of the apparatus,
and in the same horizontal plane, but in vertical planes which are capable of being
adjusted close to or in the same vertical line, or to any required distance on either
side thereof.
For the purpose of indicating the weight of a body suspended to the machine
various arrangements may be used by which a lever, finger, or pointer, situated
either horizontally, vertically, or at any intermediate angle, and moving round the
weighing centre, either pulls a spring balance, or lifts weights, or moves directly
over the face of a divided dial or quadrant.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Thomson in the Great Seal Patent Office on the 21st August
1876.
WILLIAM THOMSON, of Glasgow, in the County of Lanark, North Britain,
Engineer. "IMPROVEMENTS IN WEIGHING APPARATUS."
My said Invention, which relates to improvements in apparatus for ascertaining
the weights of bodies, has reference to that class of apparatus known as the "steel-
yard."
In the steelyard as hitherto constructed it has been essential, owing to the form
of the apparatus, to place the knife edges or centres at a considerable distance
apart, such distance increasing with the size of the apparatus, and on this account
it has been compulsory to use very long levers and large counterbalances or to
compound the levers.
Under my said Invention these defects are obviated by an improved arrangement
of the knife edges or centres of suspension of the weighing apparatus.
And in order that my said Invention may be properly understood, I now proceed
more particularly to set forth the system, mode, or manner in or under which the
same is or may be used or practically carried into effect, reference being had to
the annexed Sheet of Drawings and to the letters and figures marked thereon, that
is to say
On the Sheet of Drawings hereunto appended Figure 1 is a side elevation, and
Figure 2 a plan of one form of the improved weighing apparatus constructed in
accordance with my said Invention; Figure 3 is a section of the apparatus on the
line a, b, Figure 2.
As shewn by these Figures the apparatus consists of two side links or frames A,
through the lower part of which a bar or rod B formed with a knife edge passes.
The knife edge of the bar or rod carries within the side links or frame the centre
link C, from which the load or body to be weighed is suspended. Between brackets
or projections c, formed at one end of the side links or frame A, a flat bar D placed
horizontally is held rigidly by a screw bolt, or equivalent means, and the outer end
of the said bar is formed with a projecting head d, on which an indicating line e
is made. To counterbalance the said bar a weight F is supported in brackets at
the opposite end of the links or frame A. The steelyard E, which passes through
a slot in the head of the bar D, is secured by a screw bolt to brackets or projections
formed on a shell or box G, which is supported by knife edges of attached to the
said shell or box, the said knife edges acting against bearings g inserted in each of
the side links A. The suspending link H of the apparatus bears against a knife
edge h, formed on a bar passing through the interior of the box or shell G, and
which knife edge, as is seen at Figure 3 of the Drawings, is in the same horizontal
plane as the knife edges fat the exterior of the said box or shell G. Whilst in
the same horizontal plane the knife edges and are not in the same vertical
plane, one being situated at the side of the other. This distance, looking vertically,
may be increased or diminished as desired by making the knife edges fadjustable,
and this may either be effected by forming the bevil or inclination at one side of
each block f greater than that at the other side, or the adjustment may be effected
by making the slot in the pieces m projecting from tlie sides of the box or shell G
at right angles to the position shewn on the Drawings, and sliding the blocks f
backwards and forwards in the said slots, pinching pins being provided to hold the
blocks when adjusted in position.
Under another arrangement slots may be made horizontally in the sides of the
box or shell G, and the blocks m noved backwards and forwards therein when it
is desired to adjust the position of the knife edges f, or pins or projections formed
on or fixed to the sides of the said box or shell may pass through horizontal slots
made in the pieces m, the said pieces being held to the adjusted position by
pinching nuts, or the adjustment of the knife edges f and relatively with each

page_text: other may be effected by other suitable means. By means of this arrangement of
the knife edges f and h they may be brought close together or separated apart in a
vertical plane as may be desired, and the necessity of employing very long levers
and large counterbalances or of compounding the levers of the weighing apparatus
in the manner hitherto adopted is thereby obviated. At the end of the box or
shell G, opposite to that whereat the steelyard E is carried, a screwed rod or bar L
is fixed, a weight N being placed thereon, as seen at Figures 1 and 2 of the Draw-
ings. This weight is employed to counterbalance the weight of the steelyard E,
and of the "tare," that is, of the chain or other apparatus by which the load or
body to be weighed is suspended from the link C, the said weight N being adjusted
for that purpose on the rod or bar L until the upper edge of the steelyard is in line
with the part marked e of the flat bar D; a nut O retains the weight N in the
position to which it has been adjusted.
In weighing with the apparatus herein-before described, the weights are sus-
pended from the hook P at the free end of the steelyard, a one pound weight being
hung from the said hook for every one hundredweight of the load or body sus-
pended from the link C, and the intermediate number of pounds within one quarter
of a hundredweight ascertained by shifting the movable weight R along the gradu.
ated scale of the steelyard until the box or shell G, by moving round the weighing
centre f, brings the upper edge of the steelyard to a level with the line e, Figure 1.
It is manifest that by increasing or diminishing the length of the steelyard E the
amount of weight necessary to be suspended from the hook P thereof, in order to
counterbalance or nearly to counterbalance the weight of the load hung from tho
link C, may be varied inversely with the length of the lever. I therefore do not
confine myself to the proportion of weight relatively with the load herein-before
specified, nor do I restrict myself to employ the arrangement of steelyard and
indicating apparatus shewn on the Drawings, as in lieu thereof a finger, or pointer,
or analogous apparatus may be employed, the said apparatus being situated either
horizontally, vertically, or at any intermediate angle and acted upon by the load
suspended from the link C, so as to move round the weighing centre and raise
weights, pull a spring balance, or otherwise act against a determined resistance.
With this arrangement a divided dial, or quadrant, or other suitable form of
graduated scale is, in conjunction with the finger or pointer, employed to shew the
weight of the load or body suspended from the link C.
Having now described and particularly ascertained the nature of my said Inven-
tion, and the system, mode, or manner in or under which the same is or may be
used or practically carried into effect, I would observe in conclusion that what I
consider to be novel and original, and therefore claim as the Invention secured to
me by the herein-before in part recited Letters Patent is, the new or improved
weighing apparatus herein-before described, wherein the knife edges or centres ƒ
and are situated at the exterior and interior respectively of a box or shell C,
and in the same horizontal plane but in vertical planes which are capable of being
adjusted close to or at a short distance apart from each other, substantially as
and for the purpose set forth and illustrated on the Sheet of Drawings hereunto
appended.
In witness whereof, I, the said William Thomson, have hereunto set my
hand and seal, this Eleventh day of August One thousand eight hundred
WILLIAM THOMSON. (L.S.)