Improvements in Electric Meters.
Year: 1899

page_text: Date of Application, 16th May, 1899-Accepted, 24th June 1899
COMPLETE SPECIFICATION (AMENDED).
Improvements in Electric Meters.
I, HANS OTTO SWOBODA, Electrical Engineer, of 78, East 91st Street, New York
City, Borough of Manhattan, State of New York, United States of America,
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 relates to electric meters of the type which are known as "maximum
current meters" and consists essentially of a strip of metal having a known linear
co-efficient of expansion when traversed by an electric current; a lever actuated by a
spring under tension, and a loosely mounted index needle arranged to be moved by
the lever to such a position on a scale as will indicate the maximum electric current
transmitted through the, meter within any given period of time and to be left in such
position when the lever moves backward or to its original position.
My invention further relates to the combination with a meter mechanism
consisting of the parts as set forth, of a device which will compensate for any change
in linear dimensions of the strip, traversed by the electric current, and due to the
variations in temperature of the locality in which the meter is situated.
In the accompanying drawings, which will serve to illustrate my invention
Figure 1 is a front view.
Figure 2, a vertical section taken on line XX of Figure 1.
Figure 3, is a similar section and illustrates the meter provided with a compensating
device.
In the drawings, A, represents the base of the case. B, body of the case, and which
is usually formed of metal. C, scale, which inay be divided in any suitable inanner.
The scale is usually made of transparent material. D, expansion strip. This 'strip
may be of any metal having a known co-efficient expansion, when influenced by the
passage through it of electric current.
For practical purposes I prefer to make this strip of à composite material known in
the arts as "platinoid." The strip is connected at one end to an adjusting screw E,
and at the other end to a horizontally mounted shaft F. Also mounted on the shaft
is a lever G, which, in its normal position, lies to the left and in front of the index
needle H, which latter is loosely mounted upon the shaft I, supported in the bracket J.
Also mounted upon the shaft F is an arm K, to which is connected the helical spring L,
connected at its opposite end to the body of the case at M.
When no current is traversing the meter the index needle H is at zero, to the left
of the scale, and the strip D is under tension from the spring L. When a current is
transmitted through the meter the strip D, expands, in proportion to the current
transmitted, thus permitting, the tension exerted by the spring 1, to move the lever
arm G to the right and with it the index needle H. The degree of movement of the
ndex needle H will of course depend upon the current traversing the strip D. When
he current is cut off or decreases, the strip D contracts and exerts tension upon the
haft F, thereby gradually returning the lever arm G to its original position, but
eaving the index needle H at the point to which it has been moved,

page_text: In Figure 3, N indicates a compensating device, which consists of a strip of metal
of determined length, supported at one end by the bracket O. This strip may be made
of any metal, so long as its co-efficient of expansion corresponds to that of the strip D;
or, in other words, that it shall have such a degree of expansion as will permit the
strip D, to exert the same degree of tension upon the shaft F and against the action
of the spring L, and irrespective of the temperature of the locality in which the
instrument is placed.
I am aware that electric meters have been made in which an index pointer has
been moved by the expansion and contraction of a metallic strip, but in such meters
the index finger has been moved in both directions and therefore the device only
served to indicate the current at the moment. Whereas, in the present device, the
index needle always indicates the maximum current transmitted within a given
period. I am also aware that, in maximum-current electric meters, it has previously
been proposed to employ, first, a thermometer heated by the electric current, secondly,
a loose pointer actuated by a moving part of the meter, and thirdly, a detaining
device and a detainable device in connection with a moving part of the meter, and I
wish it to be understood that I lay no claim to the use of either of these arrangements
.generally.
:
Manifestly, the mechanism introduced between the expansible strip and the pointer
can be changed from that shown and described without materially effecting the intent.
of my invention.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. In an electric meter, the combination of an expansible strip, a loosely mounted
index needle, and means interposed between the two, actuated by the expansion of
said strip which will move the needle to such a point as will indicate the maximum
electric current which has traversed the strip within a given time.
2. In an electric meter, the combination of an expansible strip, a shaft with which
said expansible strip is connected, a lever mounted on said shaft, a device acting to
rotate such shaft, and a loosely mounted index needle.
3. In an electric meter, the combination of an expansible strip, a temperature
compensating device connected to said strip, a loosely mounted pointer, and means
interposed between the two, actuated by the expansion of said strip which will nove
the needle to such a point, as will indicate the maximum electric current which has
traversed the strip within a given time.
4. In an electric meter, the combination of an expansible strip, a shaft, and a
device tending to rotate such shaft, a lever on said shaft, and a loosely mounted index
needle.
HERBERT HADDAN & Co.,
18, Buckingham Street, Strand, London, W.C., Agents to Applicant.