Apparatus for measuring a characteristic of sheet materials

Claim 2

Apparatus for measuring the moisture content of a sheet of material having substantial radiation diffusing and absorbing properties, said apparatus including means defining a path for said sheet material and comprising: a radiation source positioned on one side of said path and emitting one spectral band of radiation that is relatively sensitive to absorption by water and another spectral band that is relative insensitive to absorption by water, both of said bands being sensitive to absorption and diffusion by said sheet material; a radiation detector adjacent said path for receiving a portion of said radiation after it has impinged upon sheet material in said path and for converting said received radiation to an electrical signal; and means positioned with respect to said source, detector, and path and cooperating with said sheet material to cause substantial and repeated diffusion including reflection of substantially all of said radiation as it travels from said source to said detector to prevent direct transmission of any substantial amount of radiation from said source to said detector wherebY said electrical signal is proportional to the moisture and whereby said moisture measurement is substantially independent of fluctuations in diffusion or absorption by said sheet material.

Claim 3

Apparatus as in claim 1 where said source and detector are located on opposite sides of said path and where said means cooperating with said sheet material includes a pair of translucent sheets composed of diffusing material, one of said sheets being positioned between said source and said path and the other of said sheets being positioned between said detector and said path.

Claim 4

Apparatus as in claim 2 where said source and detector have respective axes of radiation and detection which are colinear.

Claim 5

Apparatus as in claim 2 where said source and detector have respective axes of radiation and detection which are laterally offset from one another with respect to said path.

Claim 6

Apparatus as in claim 2 where said sheets have a reflective backing except in proximity to said source and detector.

Claim 7

Apparatus as in claim 2 where said means defining a path for said sheet material includes a pair of substantially parallel plates each having an aperture therein said apertures being respectively coupled to said radiation source and detector, said translucent sheets being respectively coextensive with said apertures.

Claim 8

Apparatus as in claim 1 where said means defining a path for said sheet material includes at least one plate substantially parallel to said path and where said means cooperating with said sheet material includes a specular reflecting surface on the side of said plate adjacent said path.

Claim 9

Apparatus as in claim 1 where said means defining a path for said sheet material includes at least one plate substantially parallel to said path and where said means cooperating with said sheet material includes a non-specular reflecting surface on the side of said plate adjacent said path.

Claim 10

Apparatus as in claim 7 where said plate includes a pair of apertures respectively coupled to said radiation source and detector.

Claim 11

Apparatus as in claim 8 where said plate includes a pair of apertures respectively coupled to said radiation source and detector.

Claim 12

Apparatus as in claim 1 where said means defining a path for said sheet material includes a pair of substantially parallel plates such plates being located on opposite sides of and substantially parallel to said path each having an aperture therein said apertures being respectively coupled to said radiation source and detector, and where said means cooperating with said sheet material includes specular reflecting surfaces on the side of said plates adjacent said path and where said source and detector are laterally offset from one another with respect to said path.

Claim 13

Apparatus as in claim 1 where said means defining a path for said sheet material includes a pair of substantially parallel plates such plates being located on opposite sides of and substantially parallel to said path each having an aperture therein said apertures being respectively coupled to said radiation source and detector, and where said means cooperating with said sheet material includes non-specular reflecting surfaces on the side of said plates adjacent said path and where said source and detector are laterally offset from one another with respect to said path.

Claim 14

Apparatus as in claim 1 where said sheet material is paper.

Claim 15

Apparatus as in claim 13 where said one spectral band of radiation sensitive to water is centered around 1.94 microns and said other band is centered around 1.7 microns.

Claim 16

Apparatus for measuring the moisture content of a sheet material having substantial radiation diffusing and absorbing properties, said apparatus including means defining a path for said sheet material comprising: a radiation source positioned on one side of said path and emitting one spectral band of radiation that is relatively sensitive to absorption by water and another spectral band that is relatively insensitivE to absorption by water, both of said bands being sensitive to absorption and diffusion by said sheet; a radiation detector adjacent said path for receiving a portion of said radiation after it has impinged upon sheet material in said path and for converting said received radiation to an electrical signal; and means positioned with respect to said source, detector, and path and cooperating with said sheet material to cause substantial and repeated diffusion including reflection of substantially all of said radiation as it travels from said source to said detector to prevent direct transmission of any substantial amount of radiation from said source to said detector whereby said electrical signal is proportional to the moisture and whereby said moisture measurement is substantially independent of fluctuations in diffusion or absorption by said sheet material, said means comprising radiation diffusing material adjacent said path in a position to intercept all radiation travelling from said source to said detector.

Claim 17

Apparatus for measuring the moisture content of a sheet material having substantial radiation diffusing and absorbing properties, said apparatus including means defining a path for said sheet material comprising: a radiation source positioned on one side of said path and emitting one spectral band of radiation that is relatively sensitive to absorption by water and another spectral band that is relatively insensitivE to absorption by water, both of said bands being sensitive to absorption and diffusion by said sheet; a radiation detector adjacent said path for receiving a portion of said radiation after it has impinged upon sheet material in said path and for converting said received radiation to an electrical signal; and means positioned with respect to said source, detector, and path and cooperating with said sheet material to cause substantial and repeated diffusion including reflection of substantially all of said radiation as it travels from said source to said detector to prevent direct transmission of any substantial amount of radiation from said source to said detector whereby said electrical signal is proportional to the moisture and whereby said moisture measurement is substantially independent of fluctuations in diffusion or absorption by said sheet material, said means comprising radiation diffusing material adjacent said path in a position to intercept all radiation travelling from said source to said detector.

Claim 18

Apparatus as in claim 15 where said path defining means comprises spaced members having surfaces between which said sheet is passed.

Claim 19

Apparatus as in claim 16 where said spaced members include apertures to which said source and detector are coupled.

Claim 20

Apparatus as in claim 17 where said radiation diffusing material is contiguous to at least one of said surfaces and covers at least one of said apertures.

Claim 21

Apparatus as in claim 18 where said source and detector are coupled to apertures on opposite sides of said path of said sheet material.

Claim 22

Apparatus as in claim 19 where said source aperture is laterally offset from said detector aperture with respect to said path.

Claim 23

Apparatus as in claim 19 where said source and detector apertures are aligned.

Claim 24

Apparatus as in claim 21 where said radiation diffusing material is coextensive with said source and detector apertures.

Claim 25

Apparatus as in claim 18 where said radiation diffusing material consists of translucent quartz having a reflective backing except at said apertures.

Claim 26

Apparatus as in claim 15 where said sheet material is paper.

Claim 27

Apparatus as in claim 24 where said one spectral band of radiation sensitive to water is centered around 1.94 microns and said other band is centered around 1.7 microns.

Claim 28

In a method for measuring the moisture content of a sheet of material of which the basis weight varies randomly and has an unknown moisture content by the use of a source and detector with the source providing first and second spectral bands of radiation with the radiation being of the type so that at least a portion of each of the spectral bands is absorbed and diffused by the sheet material regardless of the moisture content of the sheet material and said radiation also being of the type so that moisture in said sheet material will cause substantially more of the radiation from one of said spectral bands of radiation to be absorbed than from the other spectral band of radiation, said method comprising moving the sheet material along a path, causing radiation in both of said spectral bands coming from said source on one side of the path to strike one side of said sheet material, using the detector adjacent the path for receiving a portion of the radiation from both of said spectral bands after the radiation from both the spectral bands has impinged upon the sheet material in said path and for converting the received radiation to an electrical signal, causing substantial and repeated diffusion including reflection of substantially all of the radiation from both of said spectral bands striking said one side of said sheet material prior to receiving portions thereof by the detector and preventing direct transmission of any substantial amount of radiation from the source to the detector whereby the electrical signal is proportional to the moisture and whereby the moisture measurement is substantially independent of fluctuations in diffusion or absorption by said shEet material.

Claim 29

In a method for measuring the moisture content of a sheet of material of which the basis weight varies randomly and has an unknown moisture content by the use of a source and detector with the source providing first and second spectral bands of radiation with the radiation being of the type so that at least a portion of each of the spectral bands is absorbed and diffused by the sheet material regardless of the moisture content of the sheet material and said radiation also being of the type so that moisture in said sheet material will cause substantially more of the radiation from one of said spectral bands of radiation to be absorbed than from the other spectral band of radiation, said method comprising moving the sheet material along a path, causing radiation in both of said spectral bands coming from said source on one side of the path to strike one side of said sheet material, using the detector adjacent the path for receiving a portion of the radiation from both of said spectral bands after the radiation from both the spectral bands has impinged upon the sheet material in said path and for converting the received radiation to an electrical signal, causing substantial and repeated diffusion including reflection of substantially all of the radiation from both of said spectral bands striking said one side of said sheet material prior to receiving portions thereof by the detector and preventing direct transmission of any substantial amount of radiation from the source to the detector whereby the electrical signal is proportional to the moisture and whereby the moisture measurement is substantially independent of fluctuations in diffusion or absorption by said shEet material.

Claim 30

A method as in claim 26 together with the step utilizing a ratio of the radiation in one of said spectral bands in comparison to the radiation in the other spectral band to ascertain the moisture content in the sheet of material to provide a measurement thereof which is relatively insensitive to the basis weight of the sheet of material.