Attitude compensating liquid content indicator

A liquid container is provided with paired variable resistors fluidly connected to the container at opposite ends of the bottom thereof. The resistors are electrically interconnected in series, and the output comprising the sum of the resistances is directly received by an electric current-responsive measuring device. Each of the resistors is weight-responsive and varies individually according to local liquid depth, however, the total resistance for a particular quantity of liquid in the container is always constant. The indicator of the present invention is particularly useful for measuring liquid content in containers subject to movement and change in attitude, such as, for example, gasoline tanks in motor vehicles.

BACKGROUND OF THE INVENTION 
The present invention relates to a liquid lever meter which will provide an 
accurate reading regardless of tilts or changes in horizontal attitude. 
Prior art efforts in the present area include such patents as U.S. Pat. No. 
1,285,145 and U.S. Pat. No. 3,640,134. 
The prior art, as represented by the above, suffers from such shortcomings 
as the use of non-continuous variable resistances and cmplexity of circuit 
design which, typically, involves a measurement of differences in 
resistances and not, as in the present case, a sum of pressure variable 
resistances. These shortcomings in the prior art have limited the 
usefulness of such approaches because of the poor accuracy, limited 
reliability, and high cost of manufacture which they have involved. The 
present invention represents a response to these shortcomings in the art. 
SUMMARY OF THE INVENTION 
An indicator for measuring the liquid content of a container is provided 
which comprises a weight-responsive attitude correcting sensing assembly 
comprising paired weight-responsive variable resistors disposed in fluid 
connection with the bottom of the container. The resistors are located at 
opposite ends of the container and are electrically connected to each 
other in series. The total resistance developed by the sensing assembly, 
comprised of the sum of the resistances of the individual variable 
resistors, remains constant for a particular quantity of liquid at all 
times regardless of the distribution of the liquid within the container. 
The sensing assembly is directly electrically connected to an electric 
current-responsive meter calibrated to indicate liquid content. The 
indicator of the present invention is operated by connection to an 
appropriate voltage supply, such as a storage battery or the like. The 
exact construction of the meter useful in accordance with the present 
invention may vary, and in one embodiment, may include meters adapted to 
compensate for variations in the output of the voltage supply.

DETAILED DESCRIPTION OF THE INVENTION 
The present apparatus is a liquid content indication which measure the 
volume of liquid in a container independent of the disposition of the 
liquid contained therein. 
The present invention involves the use of two variable weight-responsive 
resistors in electrical series connection, and controlled by 
weight-sensitive elements which are fluidly connected to the bottom of the 
liquid container. 
Referring now to FIG. 1, weight-responsive resistors 10 and 12 are 
positioned at opposite ends of liquid container 17 such that a change from 
the horizontal, with its consequential shifting of the contained liquid to 
the low side, will cause a decrease in value at the low-side resistor, 
said decrease being equal to an increase in value at the high-side 
resistor. The sum of the two resistance values obtained through their 
series connection will of course remain constant, this constant value 
being established by the value read from the tank when in its horizontal 
position. 
In a first embodiment illustrated in FIG. 1, the weight-sensitive elements 
14 and 16 may comprise Bourdon tube gauges. A Bourdon tube gauge is 
essentially a metal tube having a flattened oval section which is bent to 
a curve, the free end 13 being closed and the fixed end open to the 
pressure. The pressure tends to straighten the bent tube, and its 
consequent movement is communicated by means of a linkage 15a, a toothed 
sector 15b and a pinion 15c, to the axis of a needle or pointer 15d 
comprising a rheostat arm which, by its movement along rheostat 15e, 
varies the output of resistor 10. Resistor 12 is identical in construction 
to resistor 10 and operates in the same manner. Inasmuch as the Bourdon 
tube gauge responds to the weight pressure of the liquid, the present 
measuring device will not be affected by changes in atmospheric pressure 
upon the surface of the liquid. In other words, a Bourdon tube gauge 
responds only to the specific gravity of the liquid within the container 
17 and, accordingly, variations in atmospheric pressure will not produce 
any noticeable effect upon the mechanical output of the electric 
current-responsive meter attached thereto. 
As an alternative to the use of Bourdon tube gauges, other weight-sensitive 
devices, such as aneroid bellows, may be advantageously utilized. 
Referring now to FIG. 2, an alternate weight-responsive sensing assembly 
is schematically shown, which comprises paired aneroid bellows 11 and 19, 
which operate essentially as Bourdon tubes 14 and 16. Thus, each of the 
bellows units is connected by a similar mechanical linkage to a rheostat 
which operates in a manner comparable to that disclosed with respect to 
the Bourdon tubes, above. Accordingly, increased liquid weight impinging 
on the bellows results in an expansion thereof which moves the rheostat 
arm to reduce the resistance output of the rheostat. As illustrataed 
herein, bellows 19 is mechanically connected to an identical rheostat 
linkage, and the respective rheostats are electrically connected in the 
same manner illustrated in FIG. 1. 
With further regard to FIG. 1, there is provided an electric-current 
responsive meter calibrated to indicate liquid content and schematically 
represented by fuel gauge 18 which is compensated with respect to possible 
changes in output from an emf or battery 20. 
Such meter structure is well known in the art as illustrated in U.S. Pat. 
No. 2,004,421 to Smulski, the disclosure of which is incorporated herein 
by reference. As indicated earlier, however, the invention is not limited 
to the employment of the meter represented in FIG. 1 and disclosed in 
Smulski, but rather encompasses all metering devices which are operable in 
response to variations in electric current. 
As noted earlier, the indicator of the present invention is useful as a 
fuel meter. In this regard, as fuel is consumed, decreasing in total 
volume the fuel contained, the compensated sum of the resistances of the 
two measuring elements will be affected such that the total resistance 
will be proportionately increased, therein decreasing the total amount of 
current passing through the circuit of the meter 18. Thus, the meter 
reading will always bear a direct linear proportionality to the liquid 
level in the container 17. 
While there have been herein shown and described the preferred embodiments 
of the present invention, it will be understood that the invention may be 
embodied otherwise than as herein specifically illustrated or described 
and that within said embodiments certain changes in the detail and 
construction, and the form of arrangement of the parts may be made without 
departing from the underlying idea or principles of the invention within 
the scope of the appended claims.