US5121631A — Shielded level sensing system

Claim 1

Independent Claim 195 words

A shielded level sensing system for sensing with improved reliability the level of a medium stored in a storage container of low dielectric constant material, said sensing system comprising: a conducting sensing member to be secured to a predetermined portion of the container exterior; means for securing said sensing member to the container exterior; circuit means, having a source of electrical power and operatively interconnected with said sensing member, for energizing said sensing member so as to emanate an electrostatic field therefrom, which emanating field will vary in accordance with the level of the medium in the container, said circuit means including sensing means for sensing variations of said electrostatic field and outputting signals to be interpreted as indications of the level of the medium in accordance with such sensed variations; and electrostatic shield means, associated with said sensing member, for reducing influence on said emanating electrostatic field other than variations caused by changes in the level of the medium in the container, wherein said electrostatic shield means includes insulating material receiving said sensing member on one area thereof and conducting material received on areas of said insulating material other than said one area thereof.

Claim 2

Dependent Claim 195 words

A shielded level sensing system for sensing with improved reliability the level of a medium stored in a storage container of low dielectric constant material, said sensing system comprising: a conducting sensing member to be secured to a predetermined portion of the container exterior; means for securing said sensing member to the container exterior; circuit means, having a source of electrical power and operatively interconnected with said sensing member, for energizing said sensing member so as to emanate an electrostatic field therefrom, which emanating field will vary in accordance with the level of the medium in the container, said circuit means including sensing means for sensing variations of said electrostatic field and outputting signals to be interpreted as indications of the level of the medium in accordance with such sensed variations; and electrostatic shield means, associated with said sensing member, for reducing influence on said emanating electrostatic field other than variations caused by changes in the level of the medium in the container, wherein said electrostatic shield means includes insulating material receiving said sensing member on one area thereof and conducting material received on areas of said insulating material other than said one area thereof.

Claim 3

Dependent Claim 153 words

A shielded level sensing system as in claim 1, wherein: said sensing member comprises a single, unitary member, and said predetermined portion of the container exterior comprises the height of such container for a distance corresponding to the full range of the different levels to be sensed for the stored medium; said sensing system circuit means further includes means for indicating the level of the medium in the container responsive to signals output from said sensing means, and said circuit means includes an oscillator detector circuit with a variable amplitude output; and said sensing member is associated with said oscillator detector circuit as a capacitor component thereof such that variations in said electrostatic field are adapted to correspondingly vary the amplitude of said output of said oscillator detector circuit, so that a change in the amplitude of the output of said circuit means indicates a change in the level of the stored medium.

Claim 4

Dependent Claim 32 words

A shielded level sensing system as in claim 2, wherein said means for indicating are connected with said oscillator detector circuit output and are positioned relatively remote from said oscillator detector circuit.

Claim 5

Dependent Claim 34 words

A shielded level sensing system as in claim 1, wherein said sensing member comprises a copper strip, and said means for securing comprises adhesive materials interposed between said sensing member and the container exterior.

Claim 6

Dependent Claim 21 words

A shielded level sensing system as in claim 1, wherein said conducting sensing member further includes a coating of plastic material.

Claim 7

Dependent Claim 20 words

A shielded level sensing system as in claim 1, wherein said circuit means is insulatingly mounted on said sensing member.

Claim 8

Dependent Claim 54 words

A shielded level sensing system as in claim 1, wherein said electrostatic shield means insulating material includes an insulating member generally comprising a polyhedron along one face of which is received said sensing member, and over other faces of which is received said conducting material including a conducting wire mesh commonly connected to ground.

Claim 9

Dependent Claim 29 words

A shielded level sensing system as in claim 7, wherein said polyhedron comprises a parallelepiped and said wire mesh is received other three faces of said insulating member parallelepiped.

Claim 10

Dependent Claim 58 words

A shielded level sensing system as in claim 1, wherein said electrostatic shield means insulating material includes an insulating member generally comprising a polyhedron along one face of which is received said sensing member, and over other faces of which is received said conducting material including at least two parallel conducting wires which are commonly connected to ground.

Claim 11

Dependent Claim 34 words

A shield level sensing system as in claim 9, wherein said polyhedron comprises a parallelepiped and said conducting wires comprise a plurality of parallel wires received over three faces of said insulating member parallelepiped.

Claim 12

Dependent Claim 58 words

A shielded level sensing system as in claim 1, wherein said electrostatic shield means insulating material comprises a member received along the length of said sensing member, and said electrostatic shield means conducting material comprises one of a conducting wire mesh and at least two parallel conducting wires supported on said insulating material member and connected to ground.

Claim 13

Dependent Claim 48 words

A shielded level sensing system as in claim 11, wherein said insulating material member includes a notch defined along one side thereof with said sensing member received in such notch so that such side of said insulating material member may be generally supported against the stored container exterior.

Claim 14

Dependent Claim 37 words

A shielded level sensing system as in claim 11, wherein said insulating material member has a thickness in a range generally from about three times to about five times greater than the thickness of said sensing member.

Claim 15

Dependent Claim 40 words

A shielded level sensing system as in claim 13, wherein the thickness of said insulating material member in a direction normal to the plane of intersection of such member and said sensing member is generally about one-fourth of an inch.

Claim 16

Dependent Claim 15 words

A shielded level sensing system as in claim 11, wherein said insulating material comprises foam.

Claim 17

Dependent Claim 44 words

A shielded level sensing system as in claim 11, wherein said conducting material of said electrostatic shield means comprises brass, and wherein said conducting material is relatively smaller than the cross-sectional size of said sensing member so as not to interfere with operation thereof.

Claim 18

Dependent Claim 168 words

An improved level sensing system for determining the level of a stored medium in a container comprising nonconducting material, said system comprising: a metallic strip situated on the exterior of the container and having a length approximately equal to the range of potential stored medium levels to be sensed; circuit means having a source of electrical energy connected to said strip and arranged for inducing an electrical characteristic therein which varies in response to the range of levels to be determined; indicating means, connected to said circuit means and responsive to variations of said electrical characteristic, for indicating the level of the stored medium in accordance with such variations; and shielding means, associated with said strip, for shielding said strip from electrical influences external to changes in the level of the stored medium to be indicated, so that improved reliability of the indicating level is provided; wherein said shielding means comprises insulating material with said metallic strip received thereon and conducting material also received on said insulating material.

Claim 19

Dependent Claim 168 words

An improved level sensing system for determining the level of a stored medium in a container comprising nonconducting material, said system comprising: a metallic strip situated on the exterior of the container and having a length approximately equal to the range of potential stored medium levels to be sensed; circuit means having a source of electrical energy connected to said strip and arranged for inducing an electrical characteristic therein which varies in response to the range of levels to be determined; indicating means, connected to said circuit means and responsive to variations of said electrical characteristic, for indicating the level of the stored medium in accordance with such variations; and shielding means, associated with said strip, for shielding said strip from electrical influences external to changes in the level of the stored medium to be indicated, so that improved reliability of the indicating level is provided; wherein said shielding means comprises insulating material with said metallic strip received thereon and conducting material also received on said insulating material.

Claim 20

Dependent Claim 122 words

An improved level sensing system as in claim 17, wherein: said metallic strip comprises a single, unitary stick-on strip detachably applied to the container exterior surface; said circuit means includes means for producing an output which fluctuates in direct proportion with the level of stored medium in the container; said indicating means is responsive to variations of said circuit means output; and further wherein said circuit means includes a variable amplitude output oscillator detector circuit with changes in said electrical characteristic of said metallic strip connected thereto correspondingly varying the output amplitude of said oscillator detector circuit, so that a change in said output amplitude of said circuit means output results in a change in the indicated level of the stored medium.

Claim 21

Dependent Claim 18 words

An improved level sensing system as in claim 17, wherein said metallic strip is encapsulated with nonconducting material.

Claim 22

Dependent Claim 52 words

An improved level sensing system as in claim 17, wherein said shielding means comprises a polyhedron of said insulating material with said metallic strip received along one face thereof, and said conducting material comprises a relatively fine conducting wire mesh connected to ground and received over three other faces of said polyhedron.

Claim 23

Dependent Claim 84 words

An improved level sensing system as in claim 17, wherein said shielding means comprises a polyhedron of said insulating material with said metallic strip received along one face thereof, and said conducting material comprises a plurality of parallel, relatively fine conducting wires commonly connected to ground and received over three other faces of said polyhedron, said conducting wires each being generally parallel with said metallic strip, of relatively smaller diameter than said metallic strip, and of generally the same length as said metallic strip.

Claim 24

Dependent Claim 33 words

An improved level sensing system as in claim 17, wherein said shielding means insulating material includes a polyhedron of said insulating material having a longitudinal notch therein for receipt of said metallic strip.

Claim 25

Dependent Claim 30 words

An improved level sensing system as in claim 17, wherein the thickness of said shielding means is approximately three to five times greater than the thickness of said metallic strip.

Claim 26

Dependent Claim 177 words

An improved sensing system with shielding for relatively more reliably determining the level of a stored medium in a storage container made from conducting material, comprising: a sensing circuit having an oscillator detector circuit and a source of electrical energy for energizing the same, said oscillator detector circuit including an electrode arranged for varying the output amplitude of such oscillator detector circuit in accordance with the electrostatic field emanating from such electrode, said electrode being applied to the container exterior surface along a line generally parallel to the direction of movement of the level of the stored medium through its range of movement within the storage container; and an electrostatic shielding circuit, including an insulator receiving said electrode and at least a pair of generally parallel, grounded conductors received on said insulator and generally about the same length as said electrode, so that the electrostatic field emanating from said electrode will vary in accordance with the level of the stored medium throughout its range of movement within the storage container without excessive influences from external electrostatic sources.

Claim 27

Dependent Claim 177 words

An improved sensing system with shielding for relatively more reliably determining the level of a stored medium in a storage container made from conducting material, comprising: a sensing circuit having an oscillator detector circuit and a source of electrical energy for energizing the same, said oscillator detector circuit including an electrode arranged for varying the output amplitude of such oscillator detector circuit in accordance with the electrostatic field emanating from such electrode, said electrode being applied to the container exterior surface along a line generally parallel to the direction of movement of the level of the stored medium through its range of movement within the storage container; and an electrostatic shielding circuit, including an insulator receiving said electrode and at least a pair of generally parallel, grounded conductors received on said insulator and generally about the same length as said electrode, so that the electrostatic field emanating from said electrode will vary in accordance with the level of the stored medium throughout its range of movement within the storage container without excessive influences from external electrostatic sources.

Claim 28

Dependent Claim 135 words

An improved sensing system as in claim 24, wherein: said sensing circuit oscillator detector circuit includes a variable amplitude output which amplitude changes according to changes in the level of the stored medium, and said electrode includes a single unitary electrode comprising a capacitor component of said oscillator detector circuit for varying the output of said oscillator detector circuit proportionately with variations of the emanating electrostatic field, said electrode being detachably applied to the container exterior; and wherein said sensing system further includes an indicator device responsive to changes in said oscillator detector circuit output, so that said indicator device indicates the level of the stored medium in accordance with corresponding variations in the electrostatic field emanating from said electrode due to variations of the level of the stored medium throughout its range of movement.

Claim 29

Dependent Claim 16 words

An improved sensing system as in claim 24, wherein said electrode is encapsulated with nonconducting material.

Claim 30

Dependent Claim 15 words

An improved sensing system as in claim 24, wherein said insulator comprises a foam parallelepiped.

Claim 31

Dependent Claim 41 words

An improved sensing system as in claim 27, wherein said pair of generally parallel conductors comprise part of a plurality of parallel, commonly grounded relatively fine wire conductors situated on three sides of said parallelepiped and generally parallel to said electrode.

Claim 32

Dependent Claim 28 words

An improved sensing system as in claim 28, wherein said plurality of relatively fine wire conductors are generally evenly mutually spaced along said three sides of said parallelepiped.

Claim 33

Dependent Claim 25 words

An improved sensing system as in claim 24, wherein said electrode is at least partially embedded within the face of one side of said insulator.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1995-06-16	1995-12-16	1996-06-16	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1999-06-16	1999-12-16	2000-06-16	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2003-06-16	2003-12-16	2004-06-16	$7700.00	Window Closed / Lapsed

Shielded level sensing system

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