US 3,956,760 A · Liquid level gauge

Abstract

A device for indicating the presence or absence of liquid at a single level in a tank, comprising a sealed cylindrical housing having one end wall permanently fixed and the other end wall removable. The housing has an internal shoulder against which the removable wall is seated. The latter has an annular recess extending about its periphery in which there is disposed an O-ring, adapted to sealingly engage the housing wall adjacent the shoulder and thus effect a watertight seal therewith. The removable wall is connected to the fixed end wall by means of draft screws and sealing nuts, the screws having spacers which mount two printed circuit boards in spaced relation with one another inside the housing. The removable end wall also carries at its outer side two concentric, conductor tubes on feed-through insulators, constituting a probe whose conductive or capacitive characteristics vary according to whether the tubes are submerged or dry. The circuitry employed with the probe is disposed inside the housing and includes a signal generator for applying signals to one part of the probe, and amplifier circuitry for receiving signals from another part of the probe. Means are provided for selecting either a.c. or d.c. signals at the output of the generator, enabling the gauge to be used with either dielectric fluids or conductive fluids respectively. The arrangement is such that an especially compact and rugged assemblage is realized, with the supply and signal leads which extend from the housing all being characterized by very low impedance, thus making them highly immune to stray pick-up, hum and the like.

Claims13

Dependent claims

A device for indicating the presence or absence of either dielectric or conductive liquids at substantially a single level in a tank, comprising in combination:

a. signal generating-means for producing an a.c. signal on an output line,
b. means providing a signal of substantially constant potential level on said output line,
c. an immersion probe comprising substantially concentric inner and outer, insulatedly-mounted conductive tubes, one of said tubes being connected to receive signals from said output line, said probe being adapted to couple an a.c. signal when immersed in a dielectric liquid, and to couple a d.c. signal when immersed in a conductive liquid,
d. means for selecting one or the other of said signals to be operable on the output line,
e. a rectifier and filter circuit having input terminals connected to receive signals produced in the other of said tubes, said circuit being adapted to convert received a.c. signals to d.c. signals, and being adapted to pass received d.c. signals, and
f. an indicator device responsive to signals from said rectifier and filter circuit.

3 more elements

A device for indicating the presence or absence of liquid at substantially a single level in a tank, comprising in combination:

a. a substantially cylindrical housing,
b. said housing having a fixed end wall carrying a sealed electrical receptacle,
c. the other end of the housing having an annular internal shoulder,
d. a removable, circular, sealed end wall disposed at said other end and adapted to abut the shoulder,
e. said removable wall having an annular recess at its periphery,
f. an O-ring received in the annular recess, adapted to be flattened when the removable wall is carried in the end of the housing, and to engage a wall of the recess and the inner wall of the housing adjacent the shoulder thererof to thereby form a watertight seal,
g. electrical circuitry carried at the inner side of the removable end wall, said circuitry being adapted for connection to the sealed receptacle on the first-mentioned sealed wall,
h. a probe unit adapted for immersion in the liquid being gauged, said unit comprising substantially concentric hollow tubes insulated from one another and insulatedly carried by the removable end wall,
i. means providing electrical connections between said probe unit and said electrical circuitry,
j. draft means carried by the removable end wall and extending through the housing and through the first-mentioned end wall for securing the removable wall in the housing, and
k. nuts with seals carried by said draft means and engaging the fixed end wall of the housing so as to seal the same against leakage.

8 more elements

Dependencies are inferred from the claim text.

Liquid level gauge

Life of this patent

Liquid level gauge

Life of this patent

Abstract

Claims13