Inductive-capacitive probe in machine for handling sheetlike material

Claim 2

In a machine for feeding a stream of sheets of sheet material to a sensing station which includes an electrically conductive member, apparatus for detecting a misfeed of said sheets at said sensing station comprising: a sensing probe at said sensing station comprising capacitive electrode means cooperating with said conductive member to form a capacitor for sensing sheet material between said electrode means and said conductive member, and compensation means responsive to vibration induced changes in distance between the electrode and the conductive member for compensating for the variations of the capacitance reaction between the electrode and the conductive member caused by said changes in distance.

Claim 3

In a machine according to claim 1, wherein said compensation means comprises a coil whose impedance varies inversely with said capacitive reactance changes but is substantially unaffected by the sheetlike material at the sensing station.

Claim 4

A machine for handling sheetlike material comprising a support, means for advancing the material along a predetermined path across said support at a sensing station, said support being of electrically conductive material, a sensing probe, means for supporting said sensing probe at said sensing station on the opposite side of said path from said support, said probe having a capacitive electrode spaced from said path by an airgap and in confronting relationship to said support, said capacitive electrode and said support coacting to provide opposite plates of a capacitor between which the sheetlike material is advanced, said capacitor having a capacitive reactance which varies with the thickness of the sheetlike material on the support opposite the probe and with the spacing between said electrode and said support, said probe also including a coil means and means for supporting said coil means in a confronting relationship to said support so that one side of the sheetlike material faces said coil means and the opposite side faces said support, said coil means having an impedance which is substantially unaffected by the presence of sheetlike material on said support opposite the probe but which varies with changes in the spacing between said coil means and said support, said variation of said impedance of said coil means due to spacing changes being inversely related to the changes in the capacitive reactance of said capacitor caused by such spacing changes.

Claim 5

A machine for handling sheetlike material comprising a support, means for advancing the material along a predetermined path across said support at a sensing station, said support being of electrically conductive material, a sensing probe, means for supporting said sensing probe at said sensing station on the opposite side of said path from said support, said probe having a capacitive electrode spaced from said path by an airgap and in confronting relationship to said support, said capacitive electrode and said support coacting to provide opposite plates of a capacitor between which the sheetlike material is advanced, said capacitor having a capacitive reactance which varies with the thickness of the sheetlike material on the support opposite the probe and with the spacing between said electrode and said support, said probe also including a coil means and means for supporting said coil means in a confronting relationship to said support so that one side of the sheetlike material faces said coil means and the opposite side faces said support, said coil means having an impedance which is substantially unaffected by the presence of sheetlike material on said support opposite the probe but which varies with changes in the spacing between said coil means and said support, said variation of said impedance of said coil means due to spacing changes being inversely related to the changes in the capacitive reactance of said capacitor caused by such spacing changes.

Claim 6

A machine according to claim 3, and further comprising means for selectively adjusting the spacing between said capacitive electrode and said coil means in the probe.

Claim 7

A machine according to claim 3, wherein said capacitor and said coil means are connected electrically to provide an LC circuit, and further comprising means for detecting changes in the impedance of said LC circuit.

Claim 8

A machine according to claim 5, wherein one end of said coil means is directly connected to said capacitive probe electrode and the opposite end of said coil is connected directly to said support.

Claim 9

In combination: a sheet or web handling machine comprising a printing press, an electrically conductive support and means for advancing sheet or web material along a predetermined path across said electrically conductive support at a sensing station; and a sensing probe, means for supporting said sensing probe at said sensing station on the opposite side of said path in which said material advances from said support, said probe including a capacitive electrode, and means for supporting said capacitive electrode at a location spaced from said path by an airgap and in confronting relationship to said support, said capacitive electrode and said support coacting to provide opposite plates of a capacitor, said capacitor having a capacitive reactance which varies with the thickness of the sheet or web material on the support opposite the probe and with the spacing between said electrode and said support, said probe further including a coil means and means for supporting said coil means in a spaced, confronting relationship to said support so that one side of said material faces said support, said coil means having an impedance which is substantially unaffected by sheet or web material on the support opposite the probe but which varies with changes in the spacing between the coil means and the support, said variation of said impedance of said coil means due to spacing changes being inversely related to the changes in the capacitive reactance of said capacitor caused by such spacing changes.

Claim 10

In combination: a sheet or web handling machine comprising a printing press, an electrically conductive support and means for advancing sheet or web material along a predetermined path across said electrically conductive support at a sensing station; and a sensing probe, means for supporting said sensing probe at said sensing station on the opposite side of said path in which said material advances from said support, said probe including a capacitive electrode, and means for supporting said capacitive electrode at a location spaced from said path by an airgap and in confronting relationship to said support, said capacitive electrode and said support coacting to provide opposite plates of a capacitor, said capacitor having a capacitive reactance which varies with the thickness of the sheet or web material on the support opposite the probe and with the spacing between said electrode and said support, said probe further including a coil means and means for supporting said coil means in a spaced, confronting relationship to said support so that one side of said material faces said support, said coil means having an impedance which is substantially unaffected by sheet or web material on the support opposite the probe but which varies with changes in the spacing between the coil means and the support, said variation of said impedance of said coil means due to spacing changes being inversely related to the changes in the capacitive reactance of said capacitor caused by such spacing changes.

Claim 11

The combination of claim 7, wherein said capacitor and said coil means are connected electrically to provide an LC circuit, and further comprising means for detecting changes in the impedance of said LC circuit.

Claim 12

The combination of claim 8, wherein one end of said coil means is directly connected to said capacitive probe electrode and the opposite end of said coil means is connected directly to the support means.

Claim 13

The combination of claim 9, and further comprising means for selectively adjusting the position of said coil means with respect to said capacitive electrode in the probe.