AN IMPROVED WEIGHING APPARATUS
Year: 1867

page_text: PROVISIONAL SPECIFICATION left by Joseph Alvin Munn at tho Office
of the Commissioners of Patents, with his Petition, on the 7th December
1867.
I, JOSEPH ALVIN MUNN, of the City and State of New York, United
States of America, now of No. 15, Commercial Street, in the County of
Middlesex, do hereby declare the nature of the said Invention for "AN
IMPROVED WEIGHING APPARATUS," to be as follows:-
My Invention relates to a weighing apparatus wherein flat springs are used
in connection with a dial to measure the weight, such apparatus being more
especially adapted for use in kitchens, grocers' shops, and other places where
small articles or quantities of materials or goods are weighed, and the object of
the said Invention is to produce a cheap, accurate, and reliable scale for such
and similar purposes.
The said Invention consists, first, in the employment of a flat spring or
springs with edges concave or so curved that they shall gradually decrease in
width from the ends towards the centre, thereby insuring the bending of the.
said springs in lengthened curves, and preventing their breaking off at the
ends or points of suspension; secondly, in the combination with the said flat
spring or springs of adjustable short pieces for increasing or diminishing the

page_text: length and consequently the stiffness of the spring or springs to make their
action conform to that of the pointer on the dial, so that the latter shall
indicate correctly; thirdly, in the combination with the said flat springs and
dial of a set screw for adjusting the rack to set the pointer on the said dial at
the proper position, whereby any slight variation in the position of the pointer
when at rest may be corrected.
A cast-iron frame is provided, to which the other parts of the machine are
secured. Projecting lugs or seats are formed on a post which rises from this
frame; the flat springs are secured to these lugs by screws passing through
caps. The adjustable pieces are placed under the end of the springs, the
screws passing through long apertures or slots in the said pieces; these slots
permit the pieces to be moved outward to strengthen or stiffen the springs, or
to be moved inward to render them weaker and more pliable. By this means
any slight variations in the quality of springs made for the scales may be
readily corrected and one uniform dial may be used, the springs being made
to conform thereto. In moving the adjustable piece outward the spring or
that portion of it which is capable of motion is shortened and more power is
required to move it a given distance, and in moving the said piece inward the
spring is lengthened and the amount of power required to bend it reduced.
The springs are secured at the other end to lugs on a movable bar, on which
the tray or basin is supported. The adjustable pieces are not required at
this end of the springs as their employment at one end of the same is
sufficient. The dial is sccured to a part of the frame, and the pointer is
properly arranged in front of the said dial. The said pointer turns on a
spindle which passes through the dial, and is supported to turn in suitable
bearings. A pinion is fixed on the spindle of the pointer, which pinion gears
into a toothed rack. The latter is arranged to slide through a slot in a
support rivetted to the movable bar, and is held by an adjusting screw at
a proper height in the said support so as to move therewith and with the
said bar. The said screw works in a lug on the rack, and bears against a
projection on the bar. By arranging this rack to rise and fall with the tray,
and by gearing the said rack into the pinion which turns the pointer, the
weight of the article in the tray is indicated on the dial. The said pointer is
adjusted to the zero point on the dial when there is no weight on the tray by
means of the adjusting screw. Instead of forming the springs with.concave
edges to cause them to bend and prevent their breaking, the same object may
be accomplished by making the said springs thickest at their ends, but this
would be a more expensive mode of construction, and I prefer to make them

page_text: as first described. A projection is cast or fixed on the frame to act as a stop
and support. for the bar which carries the tray; when the scale is loaded
beyond its capacity the said bar is stopped by this projection which thus
prevents injury to the springs from such overloading.