Title of Invention

APPARATUS FOR DETERMINING PRECISE PROCESS TENSIONS FOR WEB MATERIAL

Abstract The present invention discloses an appartatus for determining precise process tensions for web material, particularly, moving webs of flexible materials such as paper, plastics, films, metals, foils, boards, wires and cables as required in different processing zones of machines, that process or onvert such materials,The apparatus includies means to impart stretch and strain to the web material and means for calculating such stress and strain and thereby calculate the precise process tensions for said web material.
Full Text

Field of invention
The present invention relates to an apparatus for determining precise process tensions for web material. In particular, the present invention relates to an apparatus for determining correct tension values, for moving webs of flexible materials such as paper, plastics, films, metals, foils, boards, wires and cables as required in different processing zones of machines, that process or convert such materials. The invention generally relates to a means for providing quick quality checks on parent materials for the purpose of ensuring consistency of raw materials and their fitness for use. Background of the invention
It is a widely known fact, that among the more important factors, contributing to the final product quality and product consistency of processing or converting flexible materials, the most important factor is the tension, at which these materials are required to be processed.
It is therefore, important that an operator is aware of the web tension to be set by the machine within each of the processing zones thereof in order to produce quality products with minimum wastage of material and human resources. Once these tension values are known to the machine operator, there exists today, many forms of control systems that provide for on-line measurements and control of tension as demanded by the operator. Therefore, it becomes extremely important for the operator to have a means of knowing the correct tension values or "set tension" required for the type of material and the process involved.
The set tension depends on material composition, properties, thickness and width of the web. Thus, in the case of high-speed winding of Copper or Aluminium wires, the correct winding tension depends on the wire thickness and the annealing process it has undergone. Another example, is the importance of tension in unwinding, processing or rewinding of webs of plastics, paper or metal foils undergoing a converting process such as printing, coating, laminating or slitting operations. To the applicants' knowledge, there exists no consistent or scientifically measurable means to accurately determine the "set Tension" values of a given material.
In the prior art, "set tension" is normally determined by employing some empirical tables. A typical example of such empirical table is the "Tappi Tables" for

web processing and similar Tension Tables, for wires and cables. Such tables give some broad guidelines on typical tension values for commonly used materials. At best, these tables provide the machine operators with a starting point to finally arrive at an appropriate tension value, by a process of trial and error, often at the expense of production time and wastage of raw materials.
Typically, the prior art methods employing empirical tables involve the following cumbersome, and often, inaccurate steps for determining the applicable value of "set tension" of a given material:
1. verification of the type of material, for eg., low density or high density
polyethylene, Polyester, BOPP, Aluminium foil, paper or as the case may be.
2. measurement and verification of the thickness of the material to be
processed.
3. a search to determine if the material is included in standard Tables (example Tappi Tables) and if so, read the recommended tension value from this Table, which gives a broad range of tension value for commonly used materials, in terms of tension per Linear inch per unit thickness or gauge.
4. multiplication of the value so obtained, by the thickness and width of the material to be processed, to obtain approximate values of Tension to be set, as a starting point.
While, the above method provides an operator with some guidance in respect of the "set tension" of the material in question, the recommended unit tension for any material given in such tables is usually not one figure but a range of values from a minimum to maximum value. The range of values, recommended in such tables itself is so vast (sometimes a ratio of up to 1:3) that that operator choice necessarily has to be purely judgmental and irrational and would tend to vary from operator to operator.
The operator therefore, has to rely on his experience and skill to determine the correct tension values in different machine zones based on a process of trial and error. Deciding the tension values finally, in each of the zones, require considerable operator skill and process knowledge and machine characteristics.
The prior art methods thus suffer from the following main disadvantages: 1. the machine operator is expected to have precise knowledge of the material to
be processed. Any mistake made at this staee. can result in significant
process rejections.

2. the process of finding the recommended "tension" is tedious, time consuming and operator dependent.
3. final tension setting becomes judgmental and subjective. Considerable amount of material wastage could be expected by this method before consistent and acceptable quality of processing can be achieved.
4. variations between different batches of raw materials from the same source or different sources cannot be accounted for by this method. Marginal tension adjustments of "tension setting" during "reel changes" of parent material is often required to obtain consistent quality of processed materials.
5. setting of correct tension is a reactive process and not a proactive methodology based on scientifically verifiable measurements.
Objects of the invention
Accordingly, it is an object of the present invention to provide an apparatus for determining precise process tensions for web material.
It is yet another object of the present invention to provide an apparatus for determining correct tension values for moving webs of flexible materials such as paper, plastics, films, metals, foils, boards, wires and cables as required in different processing zones of machines, that process or convert such materials.
It is still another object of the present invention to provide an efficient, compact and relatively inexpensive apparatus based on sound scientific measurements, with little chance for human error.
It is still another object of the present invention to provide a quick, reliable and accurate pre-check on the properties and thickness of the web material in question.
It is yet another object of the present invention to provide an apparatus for computing and displaying correct "set tension" values appropriate for the material to be processed and for each processing zone of any web processing or converting machine.
It is yet another important object of the present invention to provide an apparatus to determine the correct tension, regardless of any prior knowledge of its material properties, material name or thickness.
It is still another object of the present invention to provide an apparatus capable of determining any changes needed in set tension, before every reel is

processed, thereby accounting for marginal changes due to tolerances in material properties, production variations and thickness changes.
It is a further object of the present invention to provide an apparatus capable of automatically downloading correct values periodically to one or more tension control systems associated with the machine
It is another object of the present invention to provide a means of segregating bad quality raw materials before reel changing.
It is another object of the present invention to have a provision to fine tune and pre-calibrate the apparatus to suit individual preferences or machine characteristics, in the form of a "Machine Constant" which, (being a one time data entry) accordingly, modifies the tension values for any proprietary reasons.
It is yet another object of the present invention to provide a means for regular verification for incoming materials for their material consistency, thickness and fitness for use. Summary of the invention
The above and other objects of the present invention are achieved by the novel apparatus of the present invention, which is simple in construction and easy to use.
The invention is based on the finding that there exists a common denominator (independent of the material variations), which forms a reliable basis for determining the correct tension setting for a particular process. The present apparatus is based on a novel concept that the primary objective of correct tension setting is, in fact, to provide a definite material "strain" which is optimal, for any given process. Thus tension becomes a dependent variable that needs to be set in order to obtain a definite and pre-defined strain value, which is unique for any given production process.
In scientific terms, "Strain" is defined as the elongation of the material per unit length, and is dimensionless.
Strain = AL/L where. A L refers to the change in length on original length L.
It is a well-established engineering principle that the mechanical properties of almost all materials can be expressed by its Stress-Strain characteristics. Therefore, depending on the material properties, a definite value of stress would be needed to produce the desired strain, as needed for a process.

Stress is defined as the force per unit area or tension per unit area experienced by the material.
"Stress" is popularly expressed in terms of kg(f)/ mm2 or pounds per inch2. In S.I system of units, strain is expressed in terms of Pascals ( N/m2)
Within the limits of proportionality, all materials exhibit a linear relationship between its stress and strain values, as defined by its Young's Modulus, which is the ratio of Stress to Strain, ... a constant, within the proportionality limits of the material.
The invention, in its present form, enables an operator to quickly prepare a sample of material from its parent roll and to subject this sample to a mechanical test that quickly evaluates its Young's modulus, forming the basis for automatic computation of tension, appropriate for a pre-defined process.
Accordingly, the present invention provides an apparatus for determining precise process tensions for a web material which comprises a pair of rollers mounted on a support between which said web material to be tested is firmly attached, said pair of rollers consisting of a first roller means which is fixedly mounted on a support, a moveable roller means moveably mounted at a distance from said first roller means, a moveable shaft means on which said moveable roller is mounted, means for applying tension to the fixed material connected to said moveable roller, said tension applying means causing said moveable roller to rotate thereby causing said web material to stretch and impart tension thereto, a means of sensing the angular movement of said moveable shaft caused by the stretching of said web material, thereby providing a measurement of the strain of said web material, and a second means of sensing the torsional stress induced in said shaft due to the torque transmitted by it, thereby providing data for measurement of the stress of said web material, a computing means for receiving the above data in respect of strain and stress and calculating the precise process tension for the said web material.
In an embodiment of the invention, the sensing of angular movement is accomplished without the use of an angle sensor by moving the movable shaft in definite and pre-defined angular steps, by a stepper motor, controlled according to a programme.

In another embodiment of the invention, a torque sensor, preferably a transducer is used to measure the stress induced in the specimen material.
In another embodiment, the tension applying means comprises of an electrically operated stepper motor which is attached to said roller means by a mechanical coupling means, so that an angular movement of the stepper motor results in a torque on said moveable shaft, the said torque causing said moveable roller to rotate thereby causing said web material to stretch by a value based on the material property of said web material.
Preferably, the roller shafts have slots thereon through which the ends of the web material are inserted. In an embodiment of the invention, the ends of said web material are held in place by screws.
In a preferred embodiment, the pair of rollers are mounted on a frame.
In another preferred embodiment of the invention, a means for preparing said web material for testing is mounted on said frame.
The means for preparing sample preferably consists of a support means for supporting a length of said web material, one or more pressure pads connected to said support for holding said web material firmly on said support and a pair of rotary knife means for cutting said length of web material to a predetermined sample size. Preferably, said pressure pads are spring loaded to hold the material firmly in place during the cutting operation. Brief description of the drawings
The present invention will now be described in greater detail with reference to the accompanying drawings wherein:
Fig. 1 shows a web material, which is the result of excessive tension on the substrate or inadequate tension of the laminating film.
Fig. 2 shows the reverse of Fig. 1, resulting due to excessive tension of the laminating film or inadequate tension of the substrate.
Fig. 3 shows the case of perfectly laminated material, resulting from correct settings of tensions in the two webs, as they enter the laminating roll
Fig. 4 shows a schematic view of the apparatus of the present invention. Fig. 5 illustrates mounting of the sample web material to be tested on the apparatus of the present invention.
Fig. 6 depicts a sub assembly, mounted on the apparatus shown in Fig. 4 for preparing a sample web material to be tested.

Detailed description of the invention.
As will be apparent to one skilled in the art, there exists today, a wide range and diversity of industrial machines for processing or converting flexible materials such as paper, films, foils and wires. Such machines, in general, may include one or more processing zones or sections such as unwind sections, processing sections and rewind sections. The quality of the final product depends, to a large extent, on the correct setting of tension values which may be different for different sections and different for different materials processed.
An example of a simple laminating machine will highlight the importance of tension setting on the final product quality and highlight typical difficulties presently experienced by machine operators, in deciding the optimum tension value for each and every job.
Figs. 1 to 3 shows a simplest case of tension setting in the processing section of a laminating machine typically used for laminating two different materials, for eg., to laminate a thin Polyester film on a substrate, which is a relatively thick Aluminium foil. In the example shown in the drawings, both webs are of same width. Lamination of these materials, takes place as they pass between a pair of driven rollers, that press them together, with an adhesive in between, as it transports the two webs, that enter this section, from different web paths. Each of the webs have to enter the laminating section, at correct tension, so that the final laminated product is produced with proper adhesion and without "curling", which often spoiling the quality of final laminated product.
The importance of tension setting becomes apparent from figures 1, 2 8B 3, which show the dependence of tension on curling in the machine direction.
Figure 1 is a result of excessive tension on the substrate or inadequate tension of the laminating film.
Figure 2 shows the reverse case, resulting due to excessive tension of the laminating film or inadequate tension of the substrate.
Figure 3 shows the case of perfectly laminated material, resulting from correct settings of tensions in the two webs, as they enter the laminating roll
There is today no scientific means or method available to a machine operator to predict the correct tension to be set in order to achieve perfect product quality. The present invention aims at filling this gap by a technique, hitherto unfamiliar to the industry and as explained hereinafter.

The novelty of the present invention will be evident from the following explanations on the principle and method of measurement, employed in the present apparatus.
A close study of the wide divergence of tension values for different materials and different batches of raw materials reveals that there exists a common denominator (independent of the material variations) which can form a reliable basis for determining the correct tension setting, for a particular process. The present apparatus is based on a novel concept that the primary objective of correct tension setting is in fact, to provide a definite material "strain" which is optimal, for any given process. Thus, tension becomes a dependent variable that needs to be set in order to obtain a definite and pre-defined strain value, which is unique for any given production process.
The invention, in its present form, enables an operator to quickly prepare a sample of material, from its parent roll and to subject this sample to a mechanical test that quickly evaluates its Young's modulus, forming the basis for automatic computation of tension, appropriate for a pre-defined process.
Referring next to Fig. 4, there is illustrated the basic constructional details of the apparatus in the form of a schematic showing the key elements and their locations.
A specimen (18) of material of known width is first anchored to a fixed roller (1) and stretched across to a free roller (2), to which the other end is firmly attached. By turning the free roller (2) therefore, one can induce a stretch in the specimen and create a tension, according to the torque exerted on this free shaft. This shaft ( 20) can be seen freely supported on two anti-friction bearings (3) on either ends of the shaft. The profile of anchoring elements as explained is typical for webs, in sheet or tape forms. For wires and cables, the anchoring elements can be in the form of pulleys, having dimensions, appropriate to account for the flexibility of the materials
Although the method of attaching the web to the shafts can take many forms, the method of fixing adopted in the apparatus, in its present form, is explained with reference to figure 5
The ends of the specimen (18) can be inserted in between slots (19) provided on both shafts (20) and firmly held in place by screwing in the knob (21) as shown.

The hand-operated knob (21) can be seen to actuate a "moving jaw" (22) which grips the specimen (18) firmly in place.
The method of applying an adjustable torque to the shaft, in order to tension the specimen can take many forms. In the present embodiment of this invention, torquing is accomplished by means of an electrically operated Stepper motor (5) shown in figure 4. The stepper motor provides an electrical means to gradually tension the specimen in controlled incremental steps. The angular rotation of the stepper motor can be seen to cause a corresponding movement of the free roller (2) and, in turn, to set up a tension, that depends on the Young's modulus of the material of the specimen
The amount of stretch that results is governed by the diameter of the movable roller and the angular movement of the movable roller caused by the stepper motor. The value of strain on the specimen web material depends on the initial free length "L" of the specimen between the two anchoring points. This method provides a reliable and accurate information of the value of strain experienced by the specimen material, for any step movement of the stepper motor. An automatic compensation, for marginal angular strain experienced by the shafts, due to application of torque, is also accounted for, in evaluating the value of material strain. This compensation is done in the digital computing circuits explained hereinafter.
The value of stress experienced on the specimen as a consequence of the said strain depends on the material property, defined by its Young's modulus.
The tension that the specimen is subjected to due to the application of torque is also monitored by means of a built-in torque sensor (4). The torque sensing, in its present form, is by means of strain-sensitive gauges, bonded on a mechanical structure, mounted in-line with the free roller, as shown in the figure 4. The strain gauges, when excited by an external voltage, therefore outputs a signal proportional to the torsional stress induced in the torque sensor due to the torque transmitted by it to the specimen. Thus, the tension induced in the specimen can be directly measured by the output signal from this torque transducer.
Controlling the stretch and thereby controlling the strain in the specimen is accomplished by gradually moving the stepper motor in controlled angular steps by electrical pulses applied to the stepper motor in appropriate directions.

It is necessary to first prepare a specimen from parent material, with, specified width and length. Although this operation can be done externally and independently, a provision is included in the present form of this apparatus to quickly prepare a sample of required dimensions.
A sub-assembly (6), shown mounted on top in Figure (4) consists of a means for cutting and other provisions needed to prepare a specimen of desired length and width.
The details of this construction are shown in Figure-6.
A safety hood (8) shown in fig (6) is first lifted to expose the cutter assembly. The wide web of parent material, from which the sample has to be extracted is next placed on top of the flat bed of this assembly.
When the hood is closed, the material is held in place, by a number of pressure pads (9) inside the hood.
A pair of rotary cutters, (12) are shown in fig (6) [Detail-A ], the function of which is to simultaneously cut two sides to form a long strip of specimen from a wide-width web of the parent material. Both sides of a light-weight carriage, (10) moving on a precision guide, (11) carries a pair of rotary cutters (12) on either side. A linear stroke of the carriage from left to right therefore cuts through any flexible material that is placed in the path of the rotary cutters. The said carriage is driven by a long endless belt (13) to which the said carriage is attached. In one embodiment of this apparatus, the motive power to the belt is by means of another stepper motor (14) which, in turn, is driven at controlled speeds and directions, through an associated electronic drive forming part of the control circuit. Thus, the belt and the carriage attached to it, can be stroked to and fro from its home position to cut through the material and extract a sample of defined width and length.. In the present embodiment of this apparatus, the cutter assembly is designed to extract a sample of approximately 25 mm width and 800 mm length.
The thickness measuring device (15), located inside the bottom flat bed of the cutter assembly is shown separately, in detail, in figure-6. When the hood is closed after placement of the material for the cutting operation, the thickness gauge is also activated. The deflection of the cantilever beam (16), can be seen to be a function of material thickness that is sand-witched between a fixed pad, (23) attached to the top side of the hood, and a measuring button(24) attached to the end of the

cantilevered beam (16) of the thickness gauge. In the absence of any material, the deflection of the beam will be minimum corresponding to zero thickness of the material. Depending on the thickness of the material, the deflection of the cantilever beam will gradually increase to a maximum value limited by the clearance between the fixed pad and the bottom flat bed. In the present embodiment of this apparatus this clearance is chosen as 0.5 mm, being the maximum thickness proposed to be measured in a particular model of apparatus. Deflection of the cantilever beam, is therefore a measure of the material thickness. Strain sensitive gauges (17) bonded on the cantilever beam and excited by conventional measuring techniques, thus provide a means of measuring the resulting deflection and therefore the material thickness.
The signals from the torque and thickness sensors, described above are connected to a digital computing and control circuit associated with the apparatus, shown as (7) in figure (4).
Although the complexity, sophistication and features of the control and monitoring system can be configured in a variety of ways, the essential features would remain the same as incorporated in the present embodiment of this apparatus.
After the specimen is mounted and anchored as explained, the operator initiates the test, by actuating a " START" button. This causes the stepper motor to turn the free roller and thereby tighten the specimen in a longitudinal direction. The amount of stretch with each step movement of the stepper motor is known from the radius of the movable roller. The torque, as measured by the torque sensor, for every step change in angular roatation, therefore provides a set of values of stress, corresponding to every incremental strain values. Computation of the ratio of stress to strain, directly yields the value of the characteristic property of the specimen as fully described below:
The digital controller and associated circuits derive data corresponding to above referred signals from the torque sensor as well as from the angle of rotation as determined by electronic pulses causing the movements of the stepper motor and manipulates these data to compute the value of Young's modulus of the material specimen, under test. The thickness of snecimen, as measured during the

sample preparation is also available for the purpose of computation. The only additional data entry needed by the operator would be the width of the material, from which the sample was extracted.
Data needed for computation are from the following sources.
1. Signals from the torque sensor captured at regular intervals during controlled tensioning of specimen as explained above
2. The data received from in-built thickness measuring transducer.
3. The data entry by operator specifying the width of the parent web from which the specimen was extracted.
The control circuit firstly computes the Young's modulus of the material within its limits of proportionality. This computation is done by manipulating the data received from the torque sensor and a pulse counting circuit in the control circuit, during the test cycle.
The digital controller computes the incremental strain of the test specimen and resulting stress values in the specimen material. The average value of the ratio of stress to strain is computed which yields the value of Young's modulus of the test specimen.
The strain value (i.e. the stretch per unit length) for any particular process is process dependent and not material dependent. As an example, if the application is for winding a material on a core, it can be said that a perfect and tight winding is obtained if strain on the material is maintained approximately 1.5 mm for every 1000 mm of material length. The correct tension at which the material is to be wound for a re-winding operation, therefore, is that tension which is necessary to produce a strain of approximately 1.5/1000. Variations on this value to suit individual preferences or special process requirements can be accommodated in the form of a machine constant, for example as a one time entry into the computing software.
In general, designating an acceptable strain ( AL/L) as V for any given process.
The stress needed to produce this strain = £.E
Where "E", refers to the Young's modulus of the material, computed as explained in the foregoing sections.

Knowing the thickness of the web and its width, the tension required to produce this stress value across the cross section of the web would provide information on the tension value needed for that process.
The digital computation of "set tension", appropriate for any given process is thus made available to the operator, regardless of any prior knowledge of the material or its properties. It is clear from above, that the only information needed to be furnished by the operator is the width of the material to be processed for a specified process.
The software for the digital processor and control circuits is so designed that the type of processing can be selected from the menu from a number of preprogrammed process options and machines, limited only by the computer memory made available in the apparatus.
The elements shown in the apparatus need not be in the same sequence as shown in the preferred embodiments. They can be interchanged in a variety of ways, without functionally altering the performance.
It will be apparent to those skilled in the art, that many modifications, variations and other uses for the apparatus according to the invention are possible. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of this invention are deemed to be covered under this invention which is limited only by the claims that follow.
The apparatus of the present invention as described in the following section displays, inter alia, the following advantages:
1. The apparatus can display various values of tension, for different sections of a machine, as can be programmed into its memory.
2. The apparatus displays the tension values in preferred engineering units for example in terms of Pounds or kg. (if web width is entered by the operator ) or in terms of tension per unit width of material
3. The default values of tension as displayed, can be modified by the user (in
terms of a "machine constant") for proprietary reasons or meeting the needs of
special processes.
4. The band of acceptability of material for a change in tension setting is
user selectable.

5. The apparatus can be programmed to cater to the requirements of a number of different machines and machine sections, having different processing zones.
6. Thickness measurement too is automatic. Other than the width of material to be processed, there is no need for the operator to provide data on the nature of material or its thickness or gauge.
7. The apparatus has inbuilt communication facility, to digitally transmit (for loading or refreshing) computed tension data to one or more automatic tension control systems, associated with the machine. .




WE CLAIM:
1. An apparatus for determining precise process tensions for a web material which comprises a pair of rollers mounted on a support between which said web material to be tested is firmly attached, said pair of rollers consisting of a first roller means which is fixedly mounted on a support, a moveable roller means moveably mounted at a distance from said first roller means, a moveable shaft means on which said moveable roller is mounted, means for applying stretch to the fixed material connected to said moveable roller, said stretch applying means causing said moveable roller to rotate thereby causing said web material to stretch and impart tension thereto, one or more sensor means connected to said moveable shaft, to derive data of incremental values of elongation of said web material, and resulting tension values in the web material, a computing means for receiving respectively said signals in respect of strain and stress data and calculating the precise process tensions for said web material.
2. An apparatus as claimed in claim 1 wherein said stretch inducing means is a electric Stepper motor.
3. An apparatus as claimed in claim 1 wherein said sensor is a torque sensor, preferably a strain sensitive transducer.
4. An apparatus as claimed in any preceding claim wherein the roller shafts have slots thereon through which the ends of the web material are inserted. In an embodiment of the invention, the ends of said web material are held in place by screws.
5. An apparatus as claimed in any preceding claim wherein said pair of rollers are mounted on a frame.
6. An apparatus as claimed in any preceding claim wherein a means for preparing said web material for testing is mounted on said frame.
7. An apparatus as claimed in claim 6 wherein said means for preparing consists of a support means for supporting a length of said web material, one or more pressure pads for holding said web material firmly on said support and a rotary knife means for cutting said length of web material to a predetermined sample size.

8. An apparatus for determining precise process tensions for a web material substantially as herein described with reference to and as illustrated in the accompanying drawings.


Documents:

991-mas-2002-claims.pdf

991-mas-2002-correspondence others.pdf

991-mas-2002-correspondence po.pdf

991-mas-2002-description complete.pdf

991-mas-2002-drawings.pdf

991-mas-2002-form 1.pdf

991-mas-2002-form 26.pdf

991-mas-2002-form 3.pdf

991-mas-2002-form 9.pdf


Patent Number 193861
Indian Patent Application Number 991/MAS/2002
PG Journal Number 30/2009
Publication Date 24-Jul-2009
Grant Date 21-Mar-2005
Date of Filing 30-Dec-2002
Name of Patentee M/S. DYNASPEDE INTEGRATED SYSTEMS PVT. LTD
Applicant Address 136-A, SIPCOT HOSUR, TAMILNADU 635126
Inventors:
# Inventor's Name Inventor's Address
1 BALGOPAL C 136-A, SIPCOT HOSUR TAMILNADU 635 126
PCT International Classification Number 87
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA