AU604215B2 - Device for maintaining tension range - Google Patents

Description

COMMONWEALTH OF AUSTRAL A Patent Act 1952 C1 1 COMPLETE S P E C IF I

(ORIGINAL)

CATION

6 3' t Class Int. Class Application Number Lodged Complete Specification Lodged Accepted Published

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Priority 2 October 1985 Related Art Name of Applicant Address of Applicant Actual Inventor/s Address for Service COLGATE-PALMOLIVE COMPANY 300 Park Avenue, New York, N.Y.

10022, United States of America SDennis Elmore F.B. RICE CO., Patent Attorneys, 28A Montague Street, BALMAIN 2041.

Complete Specification for the invention entitled: DEVICE FOR MAINTAINING TENSION RANGE The following statement is a full description of this invention including the best method of performing it known to us/FW:- I r- -2- FIELD OF THE INVENTION This invention relates to control of tension on web materials and, more particularly, to the maintenance of an operating tension range by incrementing downstream stretch ratios.

DESCRIPTION OF THE PRIOR ART Diaper machines now in use are arranged to laminate two different materials together, including a top sheet, which is usually of a non--woven hydrophillic material and a backsheet, which is generally of a waterproof film, such as polyethylene or polypropylene. These materials each have distinctly different characteristics and each modulus of elasticity is different from the other.

4 The prior art shows ase of control systems to achieve constant tension on individual or all materials to be laminated and required operator skill and careful monitoring of quality of the final laminate. This is disclosed in an article entitled

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"The Art of Roll to Roll Adhesive Laminating," as published in Converter magazine, December, 1981.

Load cells and dancer arms have been used in the past to control the tension on a web being fed as disclosed in United States Patent No. 2,753,128, as well as Japanese Patent No. 44-12163 and British Patent No. 1,371,760.

Uniced States Patent No. 2,627,296 to Secrest discloses an apparatus including means for adjusting the tension in a web of fabric.

J United States Patent No. 3,239,161 to Dutro et al discloses a drive control mechanism which dispenses an elongated web of material with the speed and tension thereof being adjustable.

The United States Patent No. 3,510,374 to Walker discloses a control apparatus for sensing a property of a moving web and adjusting the moving web so that the desired property is uniform throughout the web.

United States Patent No. 3,107,679 to Pawlowski discloses an automatic tension control device which utilizes either pneumatic or electrical circuitry to maintain the tension in a web of material substantially constant.

United States Patent No. 3,762,125 to Prena discloses a device for controlling the lamination of one material onto another material which utilizes a photocell which is responsive to indicia on the film which sends the information to a control box of a clutch, which controls the stretch rollers, to thereby keep the two webs lined up with one another.

United States Patent No. 4,347,993 to Leonard discloses a tension monitoring and controlling means which includes a controller responsive to outputs of the tension sensing transducer thereof a reference tension selector for controlling torque applied to the tension control roll to thereby control the web tension.

SUMMARY OF THE INVENTION The present invention provides means for obtaining an operating tension range by incrementing downstream stretch ratios and has for an object to group correction devices under one detector and logic control system to minimize hardware.

It is a further object of the present invention to maintain line operating tensions within a desirable range automatically thereby improving output capacity and improving operating efficiency and reducing scrap levels.

T, -rpqpn- invpnt-inn J s an extension of my invention set forth in the co-pending application called "Stretch Control of Materials to be.Laminated or Joined." A diaper machine consists of two unwinding systems, one for a top sheet and one for a botm sheet. These systems are or can be tension controlled (or stretc controlled as in -my pr-evious- -application) the-bala-n-ce-o-f-t-he ing sectian -4- I- 7 7~ i 4a A diaper machine consists of two unwinding systems, one for a top sheet and one for a bottom sheet. These systems are or can be tension controlled; the balance of the converting section j i

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I MPMM of the line is inherently a stretching process between pull stations. This involved modulation of the two unwind tensions in order to prestretch both sheets equally. A problem with this previous concept was that when a more inelastic material was used, the devices would increase the unwind tension or socalled pre-tension in order to stretch the sheet to a target value. As this inelastic material (loaded with higher pretension) passed into a later stretching zone of the machine, the additional stretching also created a higher additional tension increment than on the more elastic materi.ls. Essentially then an inelastic material leads to higher downstream tensions by these two multiplier effects. This invention envisages a control logic routine whereby a downstream commercially available web tension detector would be used to initiate a correction in the stretching ratio between downstream pull stations. Whenever the downstream tension detector detects a minimum tension or maximum tension condition, a routine would be enacted to adjust the speed of the most downstream pulling unit in that zone in a preset incremental amount, in a direction and impact on the stretching ratio to bring tension back within the desired operating range; it is envisaged that the stretching ratio may be less than 1.0. This pulling unit speed change causes a change in the number of product lengths in the subject zone of the machine. Zones are defined by the location of pulling units. Within each zone there can be a number of mechanisms which are, or must be, in synchronization registration with the web. It is foreseen due to the predictable registration shift caused by the aforementioned pulling unit speed change, that all registered mechanisms in that zone can be phase shifted olu o rnoA cck aab i_ (in proportion to their distance (in web -ath) from the upstream pulling unit. The logic of registration change for any following zones is, however, based upon a fixed registration adjustment for all registered mechanisms (rather than a varying adjustment as described for the subject zone) The basis for this fixed correction is also calculated from the 1i percentage of spee d change made in the original zone multiplied times the total length of the web path in that zone. The adjustments can be verified with a feed-back signal from a single photo eye scanned near the end of the zone or can be based on the photo eye scanner reading itself with suitable prograniming per the above logic.

It is to be noted that variations in friction or drag within the machine cause registration drifts and, in the absence of a concurrent speed change, these can be monitored or tracked due to their effect on the number of fractional product lengths within a zone of the machine as a result of the change in the tension profile exerted in the web in the zone where friction/drag has varied. This can be done by monitoring one photoeye sensor versus the machine cycle position or by monitoring the differential readings between two photo eye registration sensors, one at the end of the subject zone and the other in the preceding zone. Once a variation in drag 2"' -6- 7 fi has been so identified, the logic for phase adjustment of registered mechanisms is accomplished in a similar manner to the phase shift logic previously described following a pulling unit speed change.

The present invention relates to a device for maintaining an operating tension range on two different materials comprising: a first material supply roll, means for unwinding a first web material from said first supply roll, a second supply roll, means for unwinding a second web material from said second supply roll, sensing means downstream of both unwinding means for sensing the tension on said first and second web materials, adjustment means downstream of said sensing means for adjusting the tension of said first and second web materials, microprocessor means for controlling said adjustment means to maintain a predetermined range of tension on said first and second web materials according to input to said microprocessor means from said sensing means.

BRIEF DESCRIPTION OF THE DRAWING The Fig. is a schematic diagram of the present invention.

t6 K eIAC; DETAILED DESCRIPTION OF THE INVENTION With continuing reference to the accor;panying drawing, reference numerals 10 and 12 generally designate FYI OAt er't O-U.

unwinding arrangements for two matierl differing characteristics. A supply roll 14 for material 16 is provided and an unwind motor 18 drives an endless belt assembly 20 for initially unwinding web 16 from supply roll 14.

The web 16 is entrained about idler roller 22 and thence about roller 24 mounted on the dancer arm 26 pivotally mounted at 28.

The tension force exerted on the web by the dancer arm 26 is controlled by a compressed air pressure regulator operating an air cylinder 27 connected through its piston to the dancer arm 26. The speed of the endless belt 20, which serves as the unwind, is automatically modulated by the rotary sensor at 28 in order to maintain the dancer arm 26 in a mid position.

After passing about the roller 24 on the dancer arm 26, the web passes over rollers 30, 32, 34 and thence to rollers 36, 38 and 42. Roller 38 is connected to the load cell A photoelectric cell 44 senses the registration timing/position of web 16 and provides an input to the logic control or micro processor The web 16 then passes to the downstream pull station 52 driven by motor 54, whose speed is controlled by microprocessor 50. The motor 54 receives its input at 56.

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-8- The other unwinding assembly 12 is made up of a supply roll 60 for the web material 62 initially unwinding tension thereon being afforded by the endless belt 64 driven by the unwind motor 66.

The web 62 passes over roller 68 and is thence entrained on roller 70 mounted on the dancer arm 72, which is mounted at 74 for pivotal movement and which is monitored by a rotational sensor or potentiometer The web 62 thence passes over rollers 82 and 84 as it passes to the first pull station 86 before in turn passing over rollers 36, 38 and 42 and thence to the downstream pull station 52.

0000 0°0 Thus it will be seen that the tension or stretch S on the webs 16 and/or 62 are in fact controlled by the speed oe of unwinding in connection with the modulus of elasticity of the web material 16 and/or 62 and the inputs to the micro- 0 processor o oe 0 0 0 0 4 -9-

Claims (3)

1. 2. A device according to claim 1, wherein said means for unwinding said first web material includes a sensing means for measuring the stretch on said first web material after it has passed from said supply roll.
2. 3. A device according to claim i, where said means for unwinding said first web material includes a pneumatically operated dancer arm means for applying tension on said first web material.
3. 4. A device according to claim 1, wherein said means for unwinding said first and second web materials respectively include pneumatically operated dancer arm means for selectively applying tension on each of said first web material and said second web material. A device for maintaining an operating tension range on two different materials as hereinbefore described with reference to the drawing. DATED this 3 day of September 1990 COLGATE-PALMOLIVE COMPANY Patent Attorneys for the Applicant: F.B. RICE CO.