Apparatus for detecting electrically conductive particles using a gas permeable, but liquid impermeable surface

Claim 2

Apparatus for detecting electrically conductive particles comprising an electrically insulating surface supporting and impermeable to electrically non-conductive particulate material and electrically conductive particles contained therein, said surface being also impermeable to liquids, but permeable to gases, a first network of electrically conductive elongated first elements extending longitudinally across and recessed in said surface, said first network being at a defined electric potential, and connected to one terminal of an electric energy source; a second network of electrically conductive elongated second elements extending longitudinally across and recessed in said surface, being separated from said first network by insulating spaces, at an electric potential different from that of the first network, and connected to another terminal of the electric energy source, so that electrically conductive particles deposited at said surface form a bridge over an insulating space between said first network and said second network and close a circuit from said one terminal and said first network through said bridge to said second network and said other terminal, said circuit including means for indicating a current.

Claim 3

Apparatus for detecting electrically conductive particles comprising a surface supporting and impermeable to electrically non-conductive particulate material and electrically conductive particles contained therein, a first network of electrically conductive first elements extending across said surface, said first network being at a defined electric potential, and connected to one terminal of an electric energy source; a second network of electrically conductive second elements extending across said surface, being separated from said first network by insulating spaces, at an electric potential different from that of the first network, and connected to another terminal of the electric energy source, so that electrically conductive particles deposited at said surface form a bridge over an insulating space between said first network and said second network and close a circuit from said one terminal and said first network through said bridge to said second network and said other terminal, said circuit including means for indicating a current, said first and second elements comprise electrically conductive laminae of a laminated magnet, the odd and even numbered laminae alternately connected to said two terminals of said electric energy source, said insulating spaces comprising the insulation between said laminae, so that electrically conductive particles forming a bridge across an insulating space between said odd numbered laminae connected to said one terminal and said even numbered laminae connected to said other terminal of said electric energy source, close an electric circuit from said one terminal and said odd numbered laminae through said bridge to said even numbered laminae and said other terminal.

Claim 4

Apparatus for detecting electrically conductive particles comprising a surface supporting and impermeable to electrically non-conductive particulate material and electrically conductive particles contained therein, a first network of electrically conductive first elements extending across said surface, said first network being at a defined electric potential, and connected to one terminal of an electric energy source; a second network of electrically conductive second elements extending across said surface, being separated from said first network by insulating spaces, at an electric potential different from that of the first network, and connected to another terminal of the electric energy source, so that electrically conductive particles deposited at said surface form a bridge over an insulating space between said first network and said second network and close a circuit from said one terminal and said first network through said bridge to said second network and said other terminal, said circuit including means for indicating a current, said first and second elements comprise electrically conductive laminae of a laminated magnet, the odd and even numbered laminae alternately connected to said two terminals of said electric energy source, said insulating spaces comprising the insulation between said laminae, so that electrically conductive particles forming a bridge across an insulating space between said odd numbered laminae connected to said one terminal and said even numbered laminae connected to said other terminal of said electric energy source, close an electric circuit from said one terminal and said odd numbered laminae through said bridge to said even numbered laminae and said other terminal.

Claim 5

Apparatus for detecting electrically conductive particles as claimed in claim 2 wherein the insulation between said odd numbered laminae and said even numbered laminae extends to a level below said surface formed by said laminated magnet.

Claim 6

Apparatus for detecting electrically conductive particles as claimed in claim 2 wherein an opening extends through said laminated magnet traversing said laminae, said opening being connected to means for introducing a gas, the insulation between said laminae recessed in an area between said opening and the upper edges of said laminae, so that gas introduced into said opening flows through said area between said laminae.

Claim 7

Apparatus for detecting electrically conductive particles as claimed in claim 4 wherein said opening has a gas-permeable electrically non-conductive liner with passages smaller than the size of the smallest particles of said particulate material and of said electrically conductive particles, so that said particles are prevented from getting from said surface between said laminae through said liner into said opening.

Claim 8

Apparatus for detecting electrically conductive particles as claimed in claim 2 wherein the upper edges of the laminae on one pole of said laminated magnet form one area of said surface, and the upper edges of the laminae on the other pole of said laminated magnet form another area of said surface, the portion of said surface between said areas descending in height toward said areas, so that magnetic, electrically conductive particles are pulled by magnetic and gravity forces toward one of said areas where they form a bridge across said insulation between odd and even numbered laminae on one of said poles, and non-magnetic, electrically conductive particles are pulled by gravity forces toward one of said areas where they form a bridge across said insulation between odd and even numbered laminae on one of said poles.

Claim 9

Apparatus for detecting electrically conductive particles as claimed in claim 6 wherein the upper edges of the laminae in said one area decrease in height toward said other area and the upper edges of the laminae in said other area decrease in height toward said one area.

Claim 10

Apparatus for detecting electrically conductive particles as claimed in claim 2 wherein said laminae of said magnet form areas of the surface supporting the particulate material and electrically conductive particles contained therein, said laminated magnet carries a primary winding connected to the terminals of an electric voltage source, and a secondary winding connected to means for indicating a current, so that metal particles in the particulate material at said laminae change the magnetic field of the laminated magnet and the induced electric current through the secondary winding and the current indicating means.

Claim 11

Apparatus for detecting electrically conductive particles as claimed in claim 8 wherein a second magnet, the comparative magnet carries a separate primary winding, the primary comparative winding, connected to the terminals of the alternating voltage source to which is connected the primary winding of the laminated magnet forming areas of the surface supporting the particulate material, said comparative magnet having a separate secondary winding, the secondary comparative winding, the secondary windings of said laminated magnet and of said comparative magnet connected in opposition and in series in a secondary circuit to said means for indicating a current, their induced voltages adjusted to cancel each other resulting in zero voltage, so that an electrically conductive particle changing the magnetic field of said laminated magnet supporting the particulate material changes the voltage induced in said secondary wInding, thus ceasing to balance the voltage induced in said secondary comparative winding, resulting in a voltage and a current in said secondary circuit through the current indicating means thus indicating the presence of said particle.

Claim 12

Apparatus for detecting electrically conductive particles as claimed in claim 8 wherein a second laminated magnet, the comparative magnet, has laminae extending across and forming other areas of said surface supporting the particulate material and electrically conductive particles contained therein, said laminae alternately connected to two terminals of an electric energy source, said comparative magnet having a primary winding, the primary comparative winding, connected to the terminals of the electric voltage source, and a secondary winding, the secondary comparative winding, said primary comparative winding inducing into said secondary comparative winding a voltage changed by particles changing the magnetic field of said comparative magnet, the secondary windings of said magnet and of said comparative magnet connected in opposition and in series in a secondary circuit to said means for indicating a current, their induced voltages adjusted to cancel out each other thus resulting in zero voltage, so that an electrically conductive particle changing the magnetic field of one of said magnets changes the voltage induced in the secondary winding thereof, thus ceasing to balance the voltage induced in the secondary winding of the other of said magnets, and resulting in a voltage and a current in said secondary circuit through the current indicating means thus indicating the presence of said particle.

Claim 13

Apparatus for detecting electrically conductive particles as claimed in claim 1 wherein said electrically conductive first elements extend across the surface supporting and impermeable to the particulate material and are spaced from each other, said electrically conductive second elements extending across said surface and being spaced from each other and from said first elements.

Claim 14

Apparatus for detecting electrically conductive particles as claimed in claim 11 wherein means are provided for introducing a gas through said surface into said particulate material, so that electrically conductive particles settle to said surface and form a bridge between said first elements and said second elements.

Claim 15

Apparatus for detecting electrically conductive particles as claimed in claim 1 wherein said first network and said second network comprise conductive material connected to the surface by a method selected from the methods of printing and bonding.

Claim 16

Apparatus for detecting electrically conductive particles as claimed in claim 13 wherein means are provided for introducing a gas through said surface into said particulate material, so that electrically conductive particles settle to said surface and form a bridge between said first network and said second network.

Claim 17

Apparatus for detecting electrically conductive particles as claimed in claim 14 wherein said first network and said second network comprise gas-permeable material, so that gas is introduced through the gas-permeable surface supporting and impermeable to the particulate material, and through said gas-permeable first and second network into said particulate material.

Claim 18

Apparatus for detecting electrically conductive particles comprising an electrically conductive surface supporting and impermeable to electrically non-conductive particulate material containing electrically conductive particles, said surface being impermeable to liquids, but permeable to gases and at a defined electric potential and connected to one terminal of an electric energy source, a network of electrically conductive elongated elements extending longitudinally across said surface, being insulated from said surface, and at an electric potential different from the potential of said surface, and connected to an oTher terminal of said electric energy source, so that electrically conductive particles forming a bridge between said network and said surface close a circuit from said one terminal and said surface through said bridge to said network and said other terminal, said circuit including means for indicating a current.

Claim 19

Apparatus for detecting electrically conductive particles comprising an electrically conductive surface supporting and impermeable to electrically non-conductive particulate material containing electrically conductive particles, said surface being impermeable to liquids, but permeable to gases and at a defined electric potential and connected to one terminal of an electric energy source, a network of electrically conductive elongated elements extending longitudinally across said surface, being insulated from said surface, and at an electric potential different from the potential of said surface, and connected to an oTher terminal of said electric energy source, so that electrically conductive particles forming a bridge between said network and said surface close a circuit from said one terminal and said surface through said bridge to said network and said other terminal, said circuit including means for indicating a current.

Claim 20

Apparatus for detecting electrically conductive particles as claimed in claim 16 wherein said network extends across and above said surface, and is insulated from said surface by a space therebetween.

Claim 21

Apparatus for detecting electrically conductive particles as claimed in claim 17 wherein said network of conductive elements are spaced a distance smaller than the largest conductive particle from the surface supporting and impermeable to the particulate material, so that electrically conductive particles forming a bridge between said surface and one of said elements close said circuit.

Claim 22

Apparatus for detecting electrically conductive particles as claimed in claim 16 wherein said network is recessed in said surface and is insulated from said surface by insulating material.

Claim 23

Apparatus for detecting electrically conductive particles as claimed in claim 16 wherein means are provided for introducing a gas through said surface into said particulate material, so that electrically conductive particles settle to said surface and form a bridge between said surface and said network.

Claim 24

Apparatus for detecting electrically conductive particles as claimed in claim 20 wherein said network, and said insulating material are also gas-permeable, means being provided for introducing a gas through said surface, network and insulation into said particulate material.

Claim 25

Apparatus for detecting electrically conductive particles as claimed in claim 16 wherein said network is attached to said surface by an adhesive forming said insulation.

Claim 26

Apparatus for detecting electrically conductive particles as claimed in claim 22 wherein means are provided for introducing a gas through said surface into said particulate material.