Instrument for Measuring the Average Pressures of Indicator Diagrams.
Year: 1887

page_text: PROVISIONAL SPECIFICATION.
Instrument for Measuring the Average Pressures of Indicator
Diagrams.
WALTER BAGSHAW of Victoria Foundry Batley, Yorkshire, Mechanical Engineer
do hereby declare the nature of this invention to be as follows :-
My invention consists in a diagrammeter or instrument for measuring the average
pressure of a diagram without calculation. This instrument has two legs like a pair
of compasses, on the joint of which is placed a graduated dial worked by a ratchet,
which said ratchet is fastened to one leg of the pair at such a distance from the joint-
as to move any desired fractional part of the total movement at the extremities when
the legs are opened. An index pointer on the dial shows at a glance the fractional
part, preferably one tenth, of either one or more openings of the legs. Thus, to
obtain the average pressure of a diagram divided into ten parts, it is only necessary
to open the legs of the instrument to the length of each division in turn, whereby the
dial will be moved one tenth by each successive opening, and will show the average
length or pressure of the ten divisions.
Dated this 20sh law of
11007

page_text: Diagrams.
WALTER BAGSHAW Victoria Foundry Batley Yorkshire 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 :-
My invention consists in a diagrammeter or instrument for measuring the average
pressure of a diagram without calculation. This instrument has two legs like a pair
of compasses on the joint of which is placed a graduated dial worked by a ratchet,
which said ratchet is fastened to one leg of the pair at such a distance from the joint
as to move any desired fractional part of the total movement at the extremities when
the legs are opened.
An index pointer on the dial shows at a glance the fractional part, preferably one
tenth, of either one or more openings of the legs. Thus, to obtain the average
pressure of a diagram divided into ten parts, it is only necessary to open the legs of
the instrument to the length of each division in turn, whereby the dial will be moved
one tenth by each successive opening, and will show the average length or pressure
of the ten divisions.
a
Fig. 1 shows the front and fig. 2 the side of the instrument. The two legs a
and are jointed at e by a pin, on which is placed the graduated dial d having
radius of that of the legs, though of course other proportions may be adopted,
and on the leg ba spring ratchet e is attached as shown, so that when the legs are
opened, the dial is moved the opening at the points.
On the opposite side of dial a spring prevents any movement of dial in a backward
direction whilst the legs are being closed for another operation.
When 10 openings of the legs have been made, the pointer shows the average
length or pressure at a glance.
The divisions on the dial may be made to correspond with any given scale, the dial
being replaced as often as desired by others with different markings or one dial may
be made to answer for any scale by projecting the divisions on to a linear scale like
au ordinary measuring rule, to which ordinary indicator scales may be applied, and
the pressures read off. The error arising from the difference between the arcs and
the chords measured is so very slight as to be inappreciable in any diagram.
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
An instrument for measuring the average pressure of indicator diagrams substantially
as set forth.
Dated this 2nd day of August 1888
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