Sheet coating thickness measuring apparatus

Claim 2

A sheet thickness measuring apparatus comprising: a light beam source (4); a shaft (2) for supporting a sheet (1) which partly surrounds said shaft and whose thickness is to be measured; a light shading plate (3) positioned in a plane including the central axis of said shaft (2) and passing through the contact area between the surface of said shaft and the sheet (1) to be measured, and which forms a slit (30) of a predetermined width between the surface of said shaft and the edge thereof; a scanning apparatus including a scanner (6) for scanning at a constant speed a light beam irradiated from said light beam source (4) towards said slit (30) in a plane which crosses the sheet to be measured supported by said shaft within said slit, and a photoelectric conversion device (7) which receives the light beam through said slit (30), converts it into electric signals and outputs them; a timer (9) for measuring the signal output duration of said photoelectric conversion device (7); and an arithmetic means (10) which detects the clearance between the surface of the sheet (1) supported by said shaft (2) and the edge of said light shading plate (3), on the basis of a measuring result by said timer and the scanning speed of the light beam by said scanning apparatus and determines the sheet thickness by subtracting the detected result from said slit width.

Claim 3

A sheet thickness measuring apparatus comprising a light beam source (4), which irradiates at least two light beams; a shaft (2) for supporting a sheet (1) which partly surrounds said shaft (-2) and whose thickness is to be measured; a light shading plate (3) positioned on a plane including the central axis of said shaft (2) and passing through the contact area between the surface of said shaft (2) and the sheet (1) to be measured, and forms a slit (30) of a predetermined width between the surface of said shaft and the edge thereof; a scanning apparatus including a scanner (6) for scanning at a constant speed, one of the two light beams being irradiated from said light beam source (4) toward said slit (30) in a plane which crosses the sheet (1) to be measured supported by said shaft (2) within said slit and the other one toward said slit on another plane which crosses said shaft within said slit at a portion which does not support the sheet to be measured, and a photoelectric conversion device (4) which receives the light beam through said slit, converts it into electric signals and outputs them; a timer (9) for measuring the signal outputting duration of said photoelectric conversion device; and an arithmetic means (10) which detects the clearance between the surface of the sheet (1) to be measured supported by said shaft (2) and the edge of said light shading plate (3) and the clearance between the surface of said shaft (2) and the edge of said light shading plate (3) on the basis of measuring result by said timer (9) and the scanning speed of the light beam by said scanning apparatus (6) and determines the sheet thickness (1) by calculating the difference of said both clearances.

Claim 4

A sheet thickness measuring apparatus comprising a light beam source (4), which irradiates at least two light beams; a shaft (2) for supporting a sheet (1) which partly surrounds said shaft (-2) and whose thickness is to be measured; a light shading plate (3) positioned on a plane including the central axis of said shaft (2) and passing through the contact area between the surface of said shaft (2) and the sheet (1) to be measured, and forms a slit (30) of a predetermined width between the surface of said shaft and the edge thereof; a scanning apparatus including a scanner (6) for scanning at a constant speed, one of the two light beams being irradiated from said light beam source (4) toward said slit (30) in a plane which crosses the sheet (1) to be measured supported by said shaft (2) within said slit and the other one toward said slit on another plane which crosses said shaft within said slit at a portion which does not support the sheet to be measured, and a photoelectric conversion device (4) which receives the light beam through said slit, converts it into electric signals and outputs them; a timer (9) for measuring the signal outputting duration of said photoelectric conversion device; and an arithmetic means (10) which detects the clearance between the surface of the sheet (1) to be measured supported by said shaft (2) and the edge of said light shading plate (3) and the clearance between the surface of said shaft (2) and the edge of said light shading plate (3) on the basis of measuring result by said timer (9) and the scanning speed of the light beam by said scanning apparatus (6) and determines the sheet thickness (1) by calculating the difference of said both clearances.

Claim 5

A sheet thickness measuring apparatus comprising a light beam source (4), which irradiates at least two light beams, a shaft (2) for supporting a sheet which partly surrounds said shaft (2) and whose coating thickness is to be measured; a light shading plate (3) positioned in a plane including the central axis of said shaft and passing through the contact area between the surface of said shaft (2) and the sheet (1) whose sheet thickness is to be measured, and forms a slit (30) of a predetermined width between the surface of said shaft (2) and the edge thereof; A scanning apparatus including a scanner (6) for scanning at a constant speed one of two light beams irradiated from said light beam source toward said slit (30) in a plane which crosses the sheet at a coating portion supported by said shaft (2) within said slit and the other one toward said slit (30) in another plane which crosses the sheet (1) at a non-coating portion within said slit and a photoelectric conversion device (7) which receives the light beam through said slit (30), converts it into electric signals and outputs them; a timer (9) for measuring the signal outputting duration of said photoelectric conversion device (7); and an arithmetic means (10) which detects the clearance between the surface of the coating portion of the sheet supported by said shaft (2) and the edge of said light shading plate (3) and the clearance between the surface of the non-coating portion of the sheet (1) and the edge of said light shading plate (3) on the basis of a measuring result by said timer and the scanning speed of the light beam by said scanning apparatus (6) and determines the coating thickness by calculating the difference of said both clearances.

Claim 6

A sheet thickness measuring apparatus comprising a light beam source (4), which irradiates at least two light beams, a shaft (2) for supporting a sheet which partly surrounds said shaft (2) and whose coating thickness is to be measured; a light shading plate (3) positioned in a plane including the central axis of said shaft and passing through the contact area between the surface of said shaft (2) and the sheet (1) whose sheet thickness is to be measured, and forms a slit (30) of a predetermined width between the surface of said shaft (2) and the edge thereof; A scanning apparatus including a scanner (6) for scanning at a constant speed one of two light beams irradiated from said light beam source toward said slit (30) in a plane which crosses the sheet at a coating portion supported by said shaft (2) within said slit and the other one toward said slit (30) in another plane which crosses the sheet (1) at a non-coating portion within said slit and a photoelectric conversion device (7) which receives the light beam through said slit (30), converts it into electric signals and outputs them; a timer (9) for measuring the signal outputting duration of said photoelectric conversion device (7); and an arithmetic means (10) which detects the clearance between the surface of the coating portion of the sheet supported by said shaft (2) and the edge of said light shading plate (3) and the clearance between the surface of the non-coating portion of the sheet (1) and the edge of said light shading plate (3) on the basis of a measuring result by said timer and the scanning speed of the light beam by said scanning apparatus (6) and determines the coating thickness by calculating the difference of said both clearances.

Claim 7

A sheet thickness measuring apparatus comprising; a light beam source (4); a shaft (2) for supporting a sheet (1) which partly surrounds said shaft (2) and whose thickness (1) is to be measured; a light shading plate (3) having a reference slit (31) of reference width extending parallel to the axial direction of said shaft, positioned in a plane including the central axis of said shaft and passing through the contact area between the surface of said shaft and the sheet to be measured, forming a slit of a predetermined width between the surface of said shaft and the edge thereof; a scanning apparatus including a scanner (6) for scanning at a constant speed a light beam irradiated from said light beam source (6) toward said slit (30) and said reference slit (31) in a plane which crosses said reference slit (31) and the sheet to be measured supported by said shaft within said slit (30) and photoelectric conversion devices (7a,7b) which receive the light beams through said slit (30) and said reference slit (31), convert them into electric signals and output them respectively; . timers (9a,9b) for measuring the signal output duration of said photoelectric conversion devices (7a,7b) respectively; and an arithmetic means (10) which determines the sheet thickness on the basis of the ratio of a measured result by said timers (9a,9b) and said reference slit width (31).

Claim 8

A sheet thickness measuring apparatus comprising; a light beam source (4); a shaft (2) for supporting a sheet (1) which partly surrounds said shaft (2) and whose thickness (1) is to be measured; a light shading plate (3) having a reference slit (31) of reference width extending parallel to the axial direction of said shaft, positioned in a plane including the central axis of said shaft and passing through the contact area between the surface of said shaft and the sheet to be measured, forming a slit of a predetermined width between the surface of said shaft and the edge thereof; a scanning apparatus including a scanner (6) for scanning at a constant speed a light beam irradiated from said light beam source (6) toward said slit (30) and said reference slit (31) in a plane which crosses said reference slit (31) and the sheet to be measured supported by said shaft within said slit (30) and photoelectric conversion devices (7a,7b) which receive the light beams through said slit (30) and said reference slit (31), convert them into electric signals and output them respectively; . timers (9a,9b) for measuring the signal output duration of said photoelectric conversion devices (7a,7b) respectively; and an arithmetic means (10) which determines the sheet thickness on the basis of the ratio of a measured result by said timers (9a,9b) and said reference slit width (31).

Claim 9

A sheet thickness measuring apparatus as set forth in any preceding claim, wherein said scanning apparatus comprises a light receiving slit (70) at the light receiving surface of said photoelectric conversion device (7), of an appropriate width in the longitudinal direction crossing at right angles to the scanning direction of the light beam and said scanner (6) is positioned at the front focal point of a first lens (52), said slit (30) is positioned at the back focal point of said first lens and also at the front focal point of a second lens (55), and said light receiving slit (70) is positioned at the back focal point of said second lens (55) respectively so that the light beam is projected through said light receiving slit (90) onto the photoelectric conversion device (7).

Claim 10

A sheet thickness measuring apparatus as set forth in any preceding claim, wherein said timer (9) measures the outputs of said photoelectric conversion device (7) which are converted into rectangular waveforms by using the means value of the maximum and minimum outputs thereof as a threshold value.

Claim 11

A sheet thickness measuring apparatus as set forth in any preceding claim, wherein rotating speed of said shaft (2) is controlled corresponding to the transferring speed of the sheet (1) whose thickness is to be measured.

Claim 12

A sheet thickness measuring apparatus as set forth in any preceding claim, wherein said light beam is a coherent light.

Claim 13

A sheet thickness measuring apparatus as set forth in any preceding claim, wherein said coherent light is a laser beam.

Claim 14

A sheet thickness measuring apparatus as set forth in claim 2 or 3 wherein said light beam source (4) irradiates two light beams by branching one light beam.