Title:
DEVICE FOR RADIATION MEASUREMENTS ON MATERIAL WEBS
United States Patent 3806730
Abstract:
Apparatus is disclosed for the measurement of a variable parameter at different points distributed across the width of a web of material travelling lengthwise relative to the apparatus. The apparatus includes a first set of "light tubes" fixed in relation to said apparatus and extending from a light source transversely of the web of material with their output ends spaced across the width of the web of material. A second set of "light tubes" also is fixed in relation to said apparatus and extends from light sensitive means transversely of the web material with their input ends spaced across the width of the web of material. The input ends are respectively associated with corresponding light output ends of the light tubes of the first set.
US Patent References:
Apparatus for measuring and recording basis weight of paper and the like
Barker, Jr. - January 1966 - 3228282
Photoelectric apparatus for generating musical tones
Clark, Jr. - July 1960 - 2946253
Apparatus for measuring and recording basis weight of paper and the like
Barker, Jr. - January 1966 - 3228282
Photoelectric apparatus for generating musical tones
Clark, Jr. - July 1960 - 2946253
Inventors:
Tirkkonen, Erkki Tapio (Helsinki, SF)
Typpo, Pekka (Hiekkaharju, SF)
Typpo, Pekka (Hiekkaharju, SF)
Application Number:
05/369066
Publication Date:
04/23/1974
Filing Date:
06/11/1973
View Patent Images:
Export Citation:
Assignee:
Oy Nokia Ab (Helsinki, SF)
Primary Class:
Other Classes:
250/559.010, 250/359.100, 250/227.110
International Classes:
G01N21/89; G01N21/88; G01T1/16; G02B5/14; G01N21/30
Field of Search:
250/341,359,219DF,227,219D,219DC,219FT,219FR 350/96R
Primary Examiner:
Lawrence, James W.
Assistant Examiner:
Grigsby T. N.
Attorney, Agent or Firm:
Kelman, Kurt
Parent Case Data:
This is a continuation-in-part of our copending U.S. Pat. application Ser. No. 187,411, filed Oct. 7, 1971 pending in art unit 256.
Claims:
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows
1. Apparatus adapted for the measurement of a variable parameter at different points distributed across the width of a web of material travelling lengthwise relative to the said apparatus, comprising a first set of infrared radiation emitting tubes fixed in relation to said apparatus and mechanically combined to form a first rigid beam extending from a light source transversely across the full width of the web of material with their output ends spaced across the width of the web of material, and a second set of infrared radiation emitting tubes also fixed in relation to said apparatus and mechanically combined to form a second rigid beam extending from light sensitive means transversely across the full width of the web material with their input ends spaced across the width of the web of material and respectively associated with corresponding light output ends of the tubes of the first set, the length of each tube in the first set being so related to the length of the associated tube in the second set that the sum of their lengths is substantially the same for each such pair of tubes.
2. Apparatus as claimed in claim 1, wherein the first set of tubes is disposed on one side or face of said web and the second set of tubes is disposed on an opposite side or face of said web.
3. Apparatus as claimed in claim 1, wherein one of these beams is disposed above the web of material, and the other of these beams is disposed below the web of material.
4. Apparatus as claimed in claim 1, wherein the tubes have reflective inner surfaces.
5. Apparatus as claimed in claim 1, wherein the tubes are aluminum tubes having highly reflective inner surfaces.
6. Apparatus as claimed in claim 1 wherein the tubes are metal tubes having highly polished inner surfaces, and filled with an inert gas selected to inhibit deterioration of said polished surfaces.
7. Apparatus as climed in claim 1, wherein the tubes have reflective inner surfaces and filled with a transparent gas under a positive pressure, precluding the ingress of light obscuring gases.
1. Apparatus adapted for the measurement of a variable parameter at different points distributed across the width of a web of material travelling lengthwise relative to the said apparatus, comprising a first set of infrared radiation emitting tubes fixed in relation to said apparatus and mechanically combined to form a first rigid beam extending from a light source transversely across the full width of the web of material with their output ends spaced across the width of the web of material, and a second set of infrared radiation emitting tubes also fixed in relation to said apparatus and mechanically combined to form a second rigid beam extending from light sensitive means transversely across the full width of the web material with their input ends spaced across the width of the web of material and respectively associated with corresponding light output ends of the tubes of the first set, the length of each tube in the first set being so related to the length of the associated tube in the second set that the sum of their lengths is substantially the same for each such pair of tubes.
2. Apparatus as claimed in claim 1, wherein the first set of tubes is disposed on one side or face of said web and the second set of tubes is disposed on an opposite side or face of said web.
3. Apparatus as claimed in claim 1, wherein one of these beams is disposed above the web of material, and the other of these beams is disposed below the web of material.
4. Apparatus as claimed in claim 1, wherein the tubes have reflective inner surfaces.
5. Apparatus as claimed in claim 1, wherein the tubes are aluminum tubes having highly reflective inner surfaces.
6. Apparatus as claimed in claim 1 wherein the tubes are metal tubes having highly polished inner surfaces, and filled with an inert gas selected to inhibit deterioration of said polished surfaces.
7. Apparatus as climed in claim 1, wherein the tubes have reflective inner surfaces and filled with a transparent gas under a positive pressure, precluding the ingress of light obscuring gases.
Description:
This invention relates to an improvement in apparatus disclosed in U.S. Pat. application Ser. No. 135,201, now abandoned, by one of the joint inventors Erkki Tapio Tirkkonen. The apparatus is adapted for the measurement of a variable parameter at different points distributed across the width of the web of material travelling lengthwise relative to the apparatus.
The continuing development of paper making machines and the increase of their production speeds and web widths impose the necessity of elaborating ever faster measuring devices, by the aid of which the paper-making is also controlled. For successful control to be possible, one has to be able to measure the base weight and moisture content of the paper web with high accuracy and high speed at various points on the wire up to the take-up unit.
It is necessary to perform measurement over the entire width of the paper web, and the accuracy of differentiation should be as high as 10-20 mm. Moreover, it should be possible to determine the transversal profile within a short period, in order that the longitudinal displacement of the profile might be minimal. It would be advantageous, and in many instances indispensable, to perform the measurement without contact with the paper web. The equipment which has to be mounted on the paper machine should have as small weight as possible and it should take up a minimum of space.
Existing measuring devices do not meet the above requirements. This is true even of the more sophisticated types of measuring equipment previously available, while their cost is such that their use is not economic.
An object of the present invention is the provision of improved measuring apparatus which meets the above requirements, and which is both relatively simple in design and relatively cheap to provide.
According to the present invention, apparatus adapted for the measurement of a variable parameter at different points distributed across the width of a web of material travelling lengthwise relative to the said apparatus comprises a first set of so-called light tubes fixed in relation to said apparatus and extending from a light source transversely of the web of material with their output ends spaced across the width of the web of material, and a second set of so-called light tubes also fixed in relation to said apparatus and extending from light sensitive means transversely of the web material with their input ends spaced across the width of the web of material and respectively associated with corresponding light output ends of the light tubes of the first set.
The invention will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a perspective drawing of an arrangement of light tubes according to the present invention;
FIG. 2 is a diagrammatic representation of the arrangement of light tubes shown in FIG. 1;
FIGS. 3 through 6 are side elevations showing alternative endings for the light tubes; and
FIG. 7 is an underneath view of the arrangement of light tubes of FIGS. 1 and 2.
As explained in the aforesaid U.S. Pat. application Ser. No. 135,201, in order that a travelling web of paper may be examined for defects, a suitable "light" type of radiation is supplied to the inlet ends of an arrangement of light tubes, the output ends of which are spaced apart in the form of a line to emit light towards the web at a large number of spaced locations distributed across the width of the web. On the other side or face of the web, is a similar arrangment of light tubes with the output ends of the first light tubes opposite the input ends of the second light tubes. Radiation from the first light tubes passes through the web and enters the other light tubes which lead the light to a suitable detection apparatus.
Suitably the radiation used is infrared, and the light source consists of hologen lamps of 2 kilowatt each run at reduced voltage to produce a colour temperature of 2,500K. The exact colour temperature is not critical but should be kept above 2,100K.
The present invention is directed to the arrangement of the light tubes, and in general a first set of light tubes 1 is arranged above the web 3 of paper to be examined, and a second set of light tubes 5 is arranged below the web 3. As indicated in FIG. 1, light is fed into the left-hand end of the first set 1 through an adaptor 7, and light is withdrawn from the right-hand end of the second set 5 through an adaptor 9.
This feature has the advantage that for each combination of a light tube from the first set, and a light tube from the second set, the total transmission length can be kept the same. This feature is important in the preferred arrangment in which infrared absorption is used to measure a parameter. Thus a stationary infrared souce 11 is situated on one side of the web and a stationary infrared analyser 13 on the other side of the web.
In FIG. 2, for example, a light tube 15 of the first set 1 has its outlet end 15A arranged opposite an inlet end 17A of a light tube 17 of the second set, and it will be seen that the total length of light tube is the same as in the case of light tube 19 of the first set, which has its outlet end 19A arranged opposite inlet end 21A of light tube 21 of the second set.
The light tubes in the preferred embodiments of the invention shown consist of rectangular aluminum pipes with bright inside surfaces. A considerable number of light tubes is required, and the pipes forming the tubes are bonded together by epoxy cement to form a self-supporting beam structure. For example, each pipe can cover a section of 100 mm. of the width of the web, and the space between adjacent outlet ends in the first set can be minimal so that the whole width of the web is covered. During operation of the apparatus, the gap between the upper and lower beam is 70 mm., but the lower set of tubes is positioned by a hydraulic device, so that the beam consisting of the lower set of tubes can be lowered as a unit to increase the spacing from the beam formed by the upper set of light tubes to 500 mm., so facilitating threading of the web between the two sets of light tubes.
The interiors of the pipes forming the light tubes are filled with an inert gas, for example, argon, under a slight positive pressure. One result of this is that light obscuring gases cannot enter the pipes to affect the light transmission while the use of an inert gas reduces to a minimum oxidation of the bright inner surfaces of the light tubes.
As will be clear from FIGS. 3 through 7, there are several ways in which the light tubes can be formed and arranged, and the arrangement adopted must depend upon the number of light tubes to be used. In FIG. 7, five light tube unit stacks are arranged side by side, and each light tube unit will provide three light tubes. In each stack of light tube units, the number of light tube units can be selected as desired, the resulting increase in height of the beam increasing the stiffness of the beam and thus being an advantage rather than a disadvantage.
In the arrangement shown in FIG. 4, a group of three light tubes 41 terminate at a planar mirror 43 so that each light tube delivers light to, or receives light from, only the appropriate part of the web 3 through a suitable window 45.
In the arrangement shown in FIG. 5, each light tube 51 is complete in itself, and at its inlet or outlet end at the web is provided with its own mirror surface 53 so that the outlet ends of the light tubes are directed at the web 3 through a suitable window 55.
In the arrangement shown in FIG. 6, each of a group of light tubes 61 terminates at a planar mirror 63, but in this case the reverse side of the mirror is also a mirror surface. In this way, light from the upper two of the three light tubes experiences multiple reflections between the light tube and the web 3, passing through a suitable window 65.
The arrangement of the light tubes in the beam 1 can be similar to the arrangement of the light tubes in the beam 5, or somewhat different arrangements can be used, as desired.
It will be seen that the apparatus described above makes use of a relatively cheap form of light tube; the light tubes are combined as a beam to provide a self-supporting arrangement; and the total length of each transmission path between light source and analyser is either the same or very nearly equal to that of the other transmission paths.
In the practical fabrication of the light tubes, it will be found convenient to provide the structure of the light tubes over the full length of the beam, and in each light tube insert a deflecting mirror and a window at the appropriate points. In this way the beam will have the general appearance indicated in FIG. 1, and will be of uniform rigidity and will be free from undesirable external ledges and projections. The light tubes described are so cheap to manufacture that no serious additional expense is involved in extending them across the full width of the web.
Since, in each beam, light travels along each light tube from one end and then leaves the light tube, if desired the remaining part of the light tube can be used for the return of light reflected from the surface of the web. This can be useful when the examination of the web which is required is to be carried out by the use of reflected light, rather than by transmitted light.
The continuing development of paper making machines and the increase of their production speeds and web widths impose the necessity of elaborating ever faster measuring devices, by the aid of which the paper-making is also controlled. For successful control to be possible, one has to be able to measure the base weight and moisture content of the paper web with high accuracy and high speed at various points on the wire up to the take-up unit.
It is necessary to perform measurement over the entire width of the paper web, and the accuracy of differentiation should be as high as 10-20 mm. Moreover, it should be possible to determine the transversal profile within a short period, in order that the longitudinal displacement of the profile might be minimal. It would be advantageous, and in many instances indispensable, to perform the measurement without contact with the paper web. The equipment which has to be mounted on the paper machine should have as small weight as possible and it should take up a minimum of space.
Existing measuring devices do not meet the above requirements. This is true even of the more sophisticated types of measuring equipment previously available, while their cost is such that their use is not economic.
An object of the present invention is the provision of improved measuring apparatus which meets the above requirements, and which is both relatively simple in design and relatively cheap to provide.
According to the present invention, apparatus adapted for the measurement of a variable parameter at different points distributed across the width of a web of material travelling lengthwise relative to the said apparatus comprises a first set of so-called light tubes fixed in relation to said apparatus and extending from a light source transversely of the web of material with their output ends spaced across the width of the web of material, and a second set of so-called light tubes also fixed in relation to said apparatus and extending from light sensitive means transversely of the web material with their input ends spaced across the width of the web of material and respectively associated with corresponding light output ends of the light tubes of the first set.
The invention will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a perspective drawing of an arrangement of light tubes according to the present invention;
FIG. 2 is a diagrammatic representation of the arrangement of light tubes shown in FIG. 1;
FIGS. 3 through 6 are side elevations showing alternative endings for the light tubes; and
FIG. 7 is an underneath view of the arrangement of light tubes of FIGS. 1 and 2.
As explained in the aforesaid U.S. Pat. application Ser. No. 135,201, in order that a travelling web of paper may be examined for defects, a suitable "light" type of radiation is supplied to the inlet ends of an arrangement of light tubes, the output ends of which are spaced apart in the form of a line to emit light towards the web at a large number of spaced locations distributed across the width of the web. On the other side or face of the web, is a similar arrangment of light tubes with the output ends of the first light tubes opposite the input ends of the second light tubes. Radiation from the first light tubes passes through the web and enters the other light tubes which lead the light to a suitable detection apparatus.
Suitably the radiation used is infrared, and the light source consists of hologen lamps of 2 kilowatt each run at reduced voltage to produce a colour temperature of 2,500K. The exact colour temperature is not critical but should be kept above 2,100K.
The present invention is directed to the arrangement of the light tubes, and in general a first set of light tubes 1 is arranged above the web 3 of paper to be examined, and a second set of light tubes 5 is arranged below the web 3. As indicated in FIG. 1, light is fed into the left-hand end of the first set 1 through an adaptor 7, and light is withdrawn from the right-hand end of the second set 5 through an adaptor 9.
This feature has the advantage that for each combination of a light tube from the first set, and a light tube from the second set, the total transmission length can be kept the same. This feature is important in the preferred arrangment in which infrared absorption is used to measure a parameter. Thus a stationary infrared souce 11 is situated on one side of the web and a stationary infrared analyser 13 on the other side of the web.
In FIG. 2, for example, a light tube 15 of the first set 1 has its outlet end 15A arranged opposite an inlet end 17A of a light tube 17 of the second set, and it will be seen that the total length of light tube is the same as in the case of light tube 19 of the first set, which has its outlet end 19A arranged opposite inlet end 21A of light tube 21 of the second set.
The light tubes in the preferred embodiments of the invention shown consist of rectangular aluminum pipes with bright inside surfaces. A considerable number of light tubes is required, and the pipes forming the tubes are bonded together by epoxy cement to form a self-supporting beam structure. For example, each pipe can cover a section of 100 mm. of the width of the web, and the space between adjacent outlet ends in the first set can be minimal so that the whole width of the web is covered. During operation of the apparatus, the gap between the upper and lower beam is 70 mm., but the lower set of tubes is positioned by a hydraulic device, so that the beam consisting of the lower set of tubes can be lowered as a unit to increase the spacing from the beam formed by the upper set of light tubes to 500 mm., so facilitating threading of the web between the two sets of light tubes.
The interiors of the pipes forming the light tubes are filled with an inert gas, for example, argon, under a slight positive pressure. One result of this is that light obscuring gases cannot enter the pipes to affect the light transmission while the use of an inert gas reduces to a minimum oxidation of the bright inner surfaces of the light tubes.
As will be clear from FIGS. 3 through 7, there are several ways in which the light tubes can be formed and arranged, and the arrangement adopted must depend upon the number of light tubes to be used. In FIG. 7, five light tube unit stacks are arranged side by side, and each light tube unit will provide three light tubes. In each stack of light tube units, the number of light tube units can be selected as desired, the resulting increase in height of the beam increasing the stiffness of the beam and thus being an advantage rather than a disadvantage.
In the arrangement shown in FIG. 4, a group of three light tubes 41 terminate at a planar mirror 43 so that each light tube delivers light to, or receives light from, only the appropriate part of the web 3 through a suitable window 45.
In the arrangement shown in FIG. 5, each light tube 51 is complete in itself, and at its inlet or outlet end at the web is provided with its own mirror surface 53 so that the outlet ends of the light tubes are directed at the web 3 through a suitable window 55.
In the arrangement shown in FIG. 6, each of a group of light tubes 61 terminates at a planar mirror 63, but in this case the reverse side of the mirror is also a mirror surface. In this way, light from the upper two of the three light tubes experiences multiple reflections between the light tube and the web 3, passing through a suitable window 65.
The arrangement of the light tubes in the beam 1 can be similar to the arrangement of the light tubes in the beam 5, or somewhat different arrangements can be used, as desired.
It will be seen that the apparatus described above makes use of a relatively cheap form of light tube; the light tubes are combined as a beam to provide a self-supporting arrangement; and the total length of each transmission path between light source and analyser is either the same or very nearly equal to that of the other transmission paths.
In the practical fabrication of the light tubes, it will be found convenient to provide the structure of the light tubes over the full length of the beam, and in each light tube insert a deflecting mirror and a window at the appropriate points. In this way the beam will have the general appearance indicated in FIG. 1, and will be of uniform rigidity and will be free from undesirable external ledges and projections. The light tubes described are so cheap to manufacture that no serious additional expense is involved in extending them across the full width of the web.
Since, in each beam, light travels along each light tube from one end and then leaves the light tube, if desired the remaining part of the light tube can be used for the return of light reflected from the surface of the web. This can be useful when the examination of the web which is required is to be carried out by the use of reflected light, rather than by transmitted light.