DE2201407A1 - Device for measuring or testing a property, in particular the thickness of a sheet-like material - Google Patents

Description

M. 71 162 Wdm / Wa

HAMBURG 13 T2. 1. Ύ &

INNOCENTIASTRASSE 30 TELEFON 45 2139

Measurex Corporation,
Santa Clara, Caliph. (7th St.A.)

Device for measuring or testing a property, in particular the thickness, of a sheet material.

For this registration, the priority is derived from the corresponding one Application in U.S.A. Serial No. Io6 55o of January 14, 1971 claimed.

The invention relates to a device for measuring or testing a certain property, in particular the thickness of an object to be examined in the form of a sheet Material such as paper. Facilities of this type are commonly referred to as throat gauges. The invention specifically relates to the measurement of the thickness of a sheet material moving linearly at high speed in web form during its production or immediately after it.

To measure the thickness of a sheet-like material such as paper, attempts have already been made to use snap gauges and to compare them to the fluttering and scuffing movements of the paper. as well as to adapt to the extremely high ambient temperatures, dlο occur with IlGrstellun ;; = ^e jpror.eß the paper. Such snap gauges used opti *> ohj to sense the thickness of the paper

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and acoustic devices or the measurement of electrical or magnetic properties.

Some earlier gauges of this type required abutting or overlapping the sheet material Parts. In order for a corresponding flexibility and the necessary adaptation to the camber and the skew of a To ensure the paper web and, moreover, to keep the frictional forces that are effective on the paper web as small as possible, Attempts have been made with various mechanical articulation devices as well as with storage on air cushions. Neither of these devices, however, has been entirely satisfactory since they are either overly sensitive to ambient temperature or were unable to fully follow the fold and skew of the paper.

Another difficulty in measuring the thickness of paper in the form of a continuous web is that the standards for paper thickness prescribed by the Technical Association of the Pulp and Paper Industry (TAPPI) and set out in Standards Bulletin T411OS-44 provide that the paper should be measured under a pressure of 0.56 kg / cm. It has been extreme so far difficult to carry out measurements with devices working on a moving paper web exactly in accordance with the TAPPI standards.

The invention is based on the object of creating a device of the type mentioned at the outset, duroh the oino certain property of a sheet-like material like his

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Thickness can be continuously measured or checked that is also temperature stable and the movements of the leaf-shaped Material is able to follow better.

A new device of the type in question which is suitable for solving this problem is characterized according to the invention through two air chambers, each with a larger opening, the be kept closed by two flexible membranes or thin plates, each with at least one corrugation, polygamy are arranged opposite one another in such a way that a gap is formed between them, into which the sheet-shaped examination is easy to introduce and on which measuring devices for measuring a certain property of the material to be examined are attached, and by a compressed air source to generate a Pressure in the two chambers, which is slightly greater than the pressure in the environment, around the two membranes on top of each other to move out and the measuring device for contact with the Bring the material to be examined.

The invention is explained in more detail below with reference to the drawings, for example. Show it

Fig. 1 is a perspective view of part of an embodiment of a device according to the invention,
FIG. 2 is an enlarged sectional view of part of FIG. 1;

Fig. 2A is the side view of a cover plate to supplement Fig. 2,

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Pig. j5 shows a cross section approximately along line 5-5

of Fig. 2,
4 is an enlarged cross-sectional view of a

Part of Fig. 1 and
Figure 5 is an electrical equivalent schematic of part of a device according to the invention.

The, as Fig. 1 shows, designed in the manner of a throat gauge Device according to the invention is used in connection with a scanner which extends in the longitudinal direction moving sheet-like web coated for example paper in the area of a paper machine. The in Flg. 1 shown The scanner generally consists of a frame with two spaced beams, an upper one Beam 11 and a lower 12 on which the carriage 13 and 14 are performed. The slide IjJ carries the upper part 16 and the carriage 14 the lower part 17 of a kind of throat gauge. The parts 16 and 17 are arranged opposite one another that they form a gap 18 through which the sheet-shaped Material whose thickness is to be measured moves freely.

Although the arrangement shown in Fig. 2 only recognize the snap gauge parts l6 and 17 for the paper thickness measurement can, but the carriages 15 and 14 can also normally additional arrangements for measuring basis weight, moisture content and other properties of the sheet material. In addition, the measuring

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teach according to the invention itself modified in the catfish become that * other properties can also be measured.

In Fig. 2 the upper part 16 is the thickness measuring device according to the invention shown in cross section. It contains a chamber 16 with a larger opening 22, which passes through a flexible thin-walled plate or membrane 2j5 held closed 1st. The flexible thin-walled plate or membrane (which will be explained in more detail with reference to Pig. 4) is a rubber membrane, as it is for example wont be used for the purposes of pumps. Such a membrane has at least one annular corrugation or groove 24 which allows the central part of the membrane to move easily when it is for example by a piston or, as in the present case Trap is moved by air pressure and vacuum. Of course, other designs can also be used, such as for example a membrane with a horseshoe-shaped corrugation.

The part ΐβ of the gauge is on the carriage 13 through a circular plastic insert ring 26 held, the a part of the chamber 21 contains. The carriage 13 is in Plates 13a and 13b divided in order to provide greater resistance to resistance as soon as temperature fluctuations occur. It is also the reason for using the plastic in the case the ring 26. The membrane 23 is held against the ring, which also forms part of the larger opening 22,

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namely by a retaining ring 27, which by a machine screw 23 (only one shown) is attached to the edge of the membrane 23 between brackets or hoops 29 and 31 to be clamped. The ring 26 also includes a V-shaped Shoulder 32 facing corrugation or groove 24, to limit inward movement of the diaphragm 23.

A source of compressed air is used to generate an air pressure in the chamber 2L and a corresponding chamber in the lower part 17 (Piß x 1) of the device, which is greater than the ambient air pressure, in order to thereby create the flexible membrane 23 and the to move corresponding membranes in the lower part 17 towards one another and to bring them into contact with the moving specimen, namely the paper or other sheet-like material. In addition, a vacuum can also be established in the chamber 21 and the corresponding chamber of the lower part 17 in order to bring about a rapid retraction movement of the membrane. The details of the air source are shown in FIGS. The pressure or the vacuum is supplied by a motor-driven blower % (FIG. 3). The fan has an air inlet 37 and an air outlet 38. The fan 36 is accommodated in a housing 39 which is coupled to the slide 13 and the ring 26, which has the opening 22, and a part of the chamber 21. An upper part 21a of this chamber is shown in broken lines.

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The fan 56 is preferably one of the turbulent or gyroscopic type and provides a pressure of about 5.74 to 5.61 torr (2-5 inches of water or 0.1 psi = 0.007

kg / cm). A suitable blower is, for example, type no. ES2A-1 the manufacturer Rotron Incorporated in Woodstock im New York State. The fan 56 is in a housing 59 arranged and its air inlet 57 is connected to a vacuum space 41, which is located in the front part of the housing 59, while a pressure chamber 42 is arranged in the rear part of the housing.

These two spaces are in communication with the air chamber 21 through a piston arrangement, the two cylinders 46 and 47 with pistons 48 and 49, respectively. The lower ends the cylinders 46 and 47 are, as shown in Fig. 5, connected directly to the upper part 21a of the air chamber. In the middle part of each of these cylinders there are several openings 51 and 52 respectively are provided for each cylinder. The openings 51 are in direct connection with the vacuum chamber 41, the openings 52 with the pressure chamber 42, specifically via an opening 5o. The pistons 48 and 49 are driven by a rotary solenoid 54 can be moved back and forth so that the openings 51 and 52 alternate be connected to the air chamber 21. This creates pressure or vacuum in the chamber 21 as required taken care of. The upper parts of the pistons 46 and 47 are attached to the Cavity 56 connected, which also contains the rotary electromagnet, and this is with a sieve

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provided opening 57 * as shown in Fig. 2A, which the cover plate 5δ for covering the front of the housing 39 forms.

The opening 57 is connected to the free atmosphere in the surrounding area with a cover 6l, which is held on the carriage 13 and the entire housing surrounds. 39 The cover 6l is cleaned with dry nitrogen through the channel 15 in the achlitten in order to slit the device against the corrosive atmosphere of the surroundings. However, there are enough leaks to keep the atmosphere within cover 61 at ambient pressure. The cover 61 contains membranes 62 and 6.5 of the same construction as the membrane 23 for connection with the outside atmosphere and for almost instantaneous equalization of the pressure in the container, for example if the membrane 23 is suddenly compressed by a movement of the sheet-shaped material to be examined. These membranes are necessary because at the low pressure, namely 0.007 kg / cm, which is used here, the air can be relatively incompressible.

The lower part 17 of the measuring gauge according to I? Ig. 1 has in essentially the same structure as previously described for the upper part 16. The only significant one The difference in the two parts is still to be found treating magnetic circuit.

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In order to rejoin the size of the pressure, the pressure chamber 42 also contains a force control device on the back of the housing 39.This includes a rotatable disk 64 with openings 66 of different sizes, which can optionally be rotated into a position in which they fit with the opening 57 match in the housing 39, so as to allow the penetration of some air from the pressure space 42 into the surrounding atmosphere in the cover 6l. This creates a regulation of the maximum pressure that can build up in the pressure chamber 42. The force acting on the sheet-shaped material to be examined can therefore be adjusted so that it also adapts to particularly fine paper which is easy to tear. In addition, unequal forces on the opposing membranes, which result from differences in the fans or the structure of the membranes, can be compensated. The maximum pressure is also adjustable by changing the voltage supplied to the fan motors.

The magnetic devices are attached centrally to the two flexible membranes 23 and 23 ¹ , as shown in FIG. 4, so that a gap 18 is formed into which the paper or other sheet-like material can be inserted. The membrane 23 ¹ forms part of the lower part 17 of the measuring gauge. The magnetic circuit includes a U-shaped core 71 made of Perrit material with two legs 72 and 73 * which carry coils or windings 74 and 75. A support shoe 76 having a flat surface 77 for contacting the sheet-like material

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is attached to the membrane 2j>. The shoe Υβ contains a first opening 78 through which a ferrite leg 72 extends and is fastened in the opening by an essentially rigid adhesive such as an epoxy adhesive. In a second opening 79 of the shoe 76, the leg 73 is fastened by a rubber-like adhesive such as, for example, a rubber or rubber that vulcanizes at room temperature (RTV). The core 71 can have many other shapes as well. The use of a U-shaped core should, however, be preferred in order to prevent warping of the support shoe. The shoe 76 consists of a highly wear-resistant material, such as ruby or sapphire, which is stable in terms of its dimensions. Such a material ensures a flatness which is less than 0.0025 mm, even with the most extreme temperature fluctuations.

Coupled to the membrane 2j5 'is a support shoe 8l which is made of ferrite and has a flat surface 82 for contact with the sheet-like material. Thus L3t uin in siüh closed circle FLIR the magnetic flux formed by the U-shaped ferrite core 71 'of the gap 18 and the Ferritschuh 8l. The shoe 81 is larger in diameter than the shoe 76 to compensate for any misalignment. The ferrite is a ceramic material that is also stable in its dimensions, albeit a little less than ruby. However, a single ferrite crystal would

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the filüi'jjio stability 'like ruby g-3w "ihrl.'ii:; U: in.

The magnetic circuit is excited by an oscillator, as shown in Fig. 5>, fed by a voltage source V. The oscillator contains an amplifier 85 together with a feedback circuit with the inductive windings 7 ^, 73 and a capacitor C. This arrangement forms an oscillator whose resonance frequency, labeled f ~, at the output terminal is determined by the inductance L of the winding 7 ^, 75. This inductance in turn is determined by the gap distance lo, which is equal to the diameter of the sheet-like material. The output frequency of the oscillator geniäa Fic · b is therefore a measure of the quality of the sheet-like material. This can be proven as follows. The resonance frequency is for the oscillator

f = 1 (1)

R äiTf ¹

The inductance L is determined by

L = ¹ ^ - (2)

φ - φ _λ + φ ₂ (5)

where <f> is the main flux in the gap and <p "is the leakage flux, which is assumed to be constant. Therefore

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-it-

♦ ι ⁼ ΊΓΤΤζ "(5)

Where G is the gap worlds or the thickness of the leaf-like length Materials in Mel and KL a constant for correcting the reluctance, i.e. the magnetic resistance in the ferrite. Substituting equation (2), (3), (4) and (5) into equation (l) gives

_f . ι (6)

VG + K ^d where K combines all constants. A solution after

G yields

f ²

¹ row

(7)

Thus, the thickness of the sheet-like material G is proportional to the resonance frequency f "of the oscillator. Additionally will set a constant T for each particular type of sheet-like material or paper to be milled, to simulate the required 0.56 kg / cm (8 pounds per square inch), as is the standard TAPPI-Mefl method is equivalent to. The invention thus enables continuous reading of a TAPPI standard Thickness measurement result. The final equation useful for computing purposes is

G = t i: - K, + τ] YES (MoI-MolRef) + lj

(8th)

Count

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Here, K ^ / Count is used to convert f _R into a digital count, taken over a setting time interval, T is the TAPPI correction, Moi is the actual moisture and MoiRef is the moisture reference value for the sheet-like material. The latter values are available from a moisture meter. A is a constant for a given type of sheet-like material.

As can also be seen from FIG. 4, bearing rings 84 and 84 ', which are made of stainless steel and come into contact with the sheet-like material ^{, are additionally attached to the membranes 2j5 and 2J5 1.} These ensure additional stability of the sheet-type material against tilting. Each friction ring contains an associated rear support plate 86 and 38 '. These rings are arranged in the same plane as the shoes and have the effect that the central parts of the membranes act as zero-distance membranes, whereby the force of the carrying shoes is kept constant on the sheet-like material to be examined, for example paper, regardless of the position of the material to be examined in the total gap between the ring 27 (Fig. 2) and the opposite ring on the lower part of the measuring gauge.

In order to dissipate any electrostatic charge that may build up on the measuring gauge, a grounded one is required Plate 87 opposite the ferrite shoe 82 and a plate 88

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provided in connection with the shoe 76. In addition, for example, the ruby shoe "(S itself can be metallized in order to prevent the build-up of a charge. Another possibility is to use electrically conductive rubber or the like for the material of the membranes.

The use of membrane structures with corrugations or grooves 24, 24 'results in a kind of pivot mounting of the support shoes 76 and 8l, with their pivot points being practical lie in the same plane as their flat surfaces 77 and 32, which touch the sheet-shaped material to be examined. This is a property of the flexible thin-walled Materials for the rubber membranes. Such a structure is vastly superior to complicated rigid ones Articulated devices that would not allow a pivot point of this type. One such pivotable bracket is almost ideal for shoes 76 and 8l, as it enables to be moved freely from the paper or other sheet-like material to be examined, which is essentially is in the same plane as the pivot points. This fulfills a main purpose of the invention, which is a measuring device with improved accuracy of the pole position to create the movement of the sheet-like specimen.

Particularly good temperature stability is achieved in part through the use of a temperature- stable material such as ruby for the shoe 76, in which the ferrite grain 71 is arranged, and also reduces the use of

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Rubber from IiTV-Ty ρ to Defest I £ urr. the. Gchonkela T3 in the ufX'nun ^ 79, the thermal beans? Odor of the ochuheu Yo.

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Claims (1)

220H07 - 16 claims 1. Device for measuring or testing a certain property, in particular the thickness of an object to be examined in the form of a sheet-like material such as paper, characterized by two air chambers with one each larger opening, which is closed by two flexible thin walls or membranes, each with at least one corrugation are held, which are arranged opposite each other that a gap is formed between them, in the the material to be examined can be monitored, and on which measuring devices for measuring a certain property of the material to be examined, and by a compressed air source to generate a pressure in the two chambers that is slightly greater than the pressure in the surrounding area, to move the two membranes towards each other and the measuring devices for contact with the material to be examined bring to. 2. Device according to claim 1 for measuring the thickness of the specimen which has a certain moisture content having, characterized by a device for comparing this moisture content with a Humidity reference value to correct the measured Thickness. 209831/0702 - ir - 3. Device according to claim 1, characterized in that that the measuring device has a magnetic circuit, part of which is attached to one membrane and another part to the other membrane to provide a magnetic flux path To be formed over the gap mentioned, which is variable depending on the thickness of the sheet-shaped material to be examined. 4. Device according to claim j5, characterized in that that the magnetic device has a U-shaped core contains magnetic material on which windings are attached and the two legs of which extend through openings in a shoe that is attached to the one membrane is and made of a highly wear-resistant in terms of eelner Dimensions stable material, and that the magnetic device continues to be a disk made of magnetic Contains material that is attached to the second membrane so that a path for magnetic flux from the legs of the U-shaped core from over the gap and through the disc runs through it. 5. Device according to claim 4, characterized in that that the one magnetic core leg in one opening of the shoe by a relatively rigid adhesive and the other leg is fastened in the other opening of the shoe by a rubber-like adhesive. 6. Device according to claim 4, characterized in that the shoe consists of ruby. 209 8 31/0702 220U07 - 18 - 7. Device according to claim J>, characterized in that a support ring is attached to each of the two membranes so that the two rings opposite one another and lay against the sheet-shaped material to be examined and that these two support rings are arranged in such a position that they touch the sheet-shaped material to be examined in essentially the same plane as the parts of the magnetic circuit. 8. Device according to claim 3, characterized in that that each of the two chambers has an additional opening that leads to the outer atmosphere and that the interior wall flexible plate or membrane has at least one annular corrugation or groove. 9. Device according to claim 8, characterized in that that the connection opening opens into a cover, which each of the two chambers and their additional Connecting opening surrounds, and that each of the two hoods has at least one flexible thin-walled plate or membrane for connection with the surrounding atmosphere. lo. Device according to claim ^, characterized in that that the magnetic circuit has a first, centrally attached to a membrane part as a source of the magnetic Flux and a second part attached to the second membrane to complete the magnetic flux path out of the 209831/0702 first part over the mentioned gap to the second part showing. 11. Device according to claim lo, characterized in that that the second part has a larger diameter than the first to compensate for misalignment. 12. Device according to claim 3, characterized by an oscillator, the resonance frequency of which is determined by a feedback loop, which is connected to a winding Contains excitation of the magnetic circuit. IJ. Device according to claim 12, characterized in that that the resonance frequency in an adjustable via an Time interval taken digital count is convertible. 14. Device for measuring or testing a certain property, in particular the thickness of an object to be examined in the form of a sheet-like material such as paper, which is designed approximately in the manner of a throat gauge, characterized by a magnetic circuit with two fixed parts made of magnetic material, one as a source of the magnetic flux serving part and an armature, which are attached to the two legs of the throat gauge in such a way that a gap permeated by the magnetic flux remains between the two through which the sheet-shaped material to be examined can be passed, one part of the magnetic circuit being supported by a support shoe one level 209831/0702 - 2ο - Area for touching the specimen is surrounded and the second part likewise has a carrying shoe which touches the material to be examined with a flat surface and both carrying shoes can be pivoted about pivot points which lie in the planes of contact, so that the one penetrating the gap Magnetic flux is variable according to the thickness of the sheet-shaped material to be examined. 15 · Device according to claim 14, characterized in that the pivotable holder is provided by two flexible, thin-walled Plates or membranes are formed, each having at least one corrugation or groove. ΐβ. Device according to claim l4, characterized in that that the carrying shoes are both made of material which is stable in terms of its dimensions. 209831/0702