US4402656A — Control of tubular film size

Claim 1

Independent Claim 277 words

Control apparatus for maintaining a desired circumference of a longitudinally extending thin-walled expanded plastic tube extruded from an annular die, comprising: internal cooling air supply means connected to the interior of said tube for supplying a continuous flow of cooling air to said interior; exhaust means for exhausting warmed air from said interior; deviation sensing means for sensing the deviation in position of two or more circumferentially-spaced portions of the wall of said tube, said deviation sensing means including two or more energy-beam sensors positioned so as not to make physical contact with said wall and means for providing a variable electrical output for each said wall portion that is directly dependent upon the deviation in position of said portion, over a range of positions, from a predetermined set point, said output having a multiplicity of different output levels, each said level corresponding to a different said deviation in position; control means for processing said electrical outputs to compute therefrom a difference signal representative of the change of the circumference of the tube from said desired circumference; and said deviation sensing means and said control means including means for making said difference signal insensitive to transverse sway of said tube, said sway leaving the tube circumference unchanged, valve means responsive to said difference signal for adjusting the open position of said valve means for controlling said continuous flow of air to the interior of said tube to reduce said difference signal, thereby to restore the circumference of the tube toward the desired value, whereby the size of the tube can be precisely controlled without physical contact with the tube and in the presence of the tube sway.

Claim 2

Dependent Claim 277 words

Control apparatus for maintaining a desired circumference of a longitudinally extending thin-walled expanded plastic tube extruded from an annular die, comprising: internal cooling air supply means connected to the interior of said tube for supplying a continuous flow of cooling air to said interior; exhaust means for exhausting warmed air from said interior; deviation sensing means for sensing the deviation in position of two or more circumferentially-spaced portions of the wall of said tube, said deviation sensing means including two or more energy-beam sensors positioned so as not to make physical contact with said wall and means for providing a variable electrical output for each said wall portion that is directly dependent upon the deviation in position of said portion, over a range of positions, from a predetermined set point, said output having a multiplicity of different output levels, each said level corresponding to a different said deviation in position; control means for processing said electrical outputs to compute therefrom a difference signal representative of the change of the circumference of the tube from said desired circumference; and said deviation sensing means and said control means including means for making said difference signal insensitive to transverse sway of said tube, said sway leaving the tube circumference unchanged, valve means responsive to said difference signal for adjusting the open position of said valve means for controlling said continuous flow of air to the interior of said tube to reduce said difference signal, thereby to restore the circumference of the tube toward the desired value, whereby the size of the tube can be precisely controlled without physical contact with the tube and in the presence of the tube sway.

Claim 3

Dependent Claim 85 words

The control apparatus of claim 1 wherein said means for making said difference signal independent of sway includes means for making each said electrical output be substantially linearly proportional to the deviation in position of each portion over a range of positions from a predetermined set point, and said control means includes means for processing said electrical outputs to compute a difference signal dependent upon the relative distances between said wall portions, whereby the size of the tube can be controlled substantially independently of sway.

Claim 4

Dependent Claim 138 words

The control apparatus of claim 1 wherein each said sensor includes an optical transmitter for projecting an optical beam generally tangentially of said longitudinally extending tube wall, with the region of tangency corresponding to said wall portion, said beam having a substantial transverse cross sectional dimension in the direction of the radius of the tube, extending to each side of a predetermined position, to define said range of positions for the corresponding wall portion, and an optical detector for receiving said optical beam at a position beyond said region of tangency, each of said multiplicity of electrical output levels derived from said detector by said deviation sensing means corresponding to a different percentage by which the respective beam is occluded by the respective wall portion, and said control means computes said difference signal by summing said electrical outputs.

Claim 5

Dependent Claim 40 words

The control apparatus of claim 3 wherein each optical transmitter includes means for projecting a beam with uniform beam energy incrementally along said transverse direction, and each optical detector includes photocell means to convert the beam into said electrical output.

Claim 6

Dependent Claim 57 words

The control apparatus of claim 4 wherein said transmitter includes a light source, a lens, and masking means for varying the height of said beam in the direction parallel to the longitudinal axis of said tube at zones transversely outward from its center to correct for transverse nonuniformity in beam energy produced by said filament and lens.

Claim 7

Dependent Claim 43 words

The control apparatus of claim 1 or 2 wherein said control means includes means for producing said difference signal as an analog value and said valve means includes means for producing a change in said flow of air proportional to said analog signal.

Claim 8

Dependent Claim 104 words

The control apparatus of claim 3 wherein there are two said wall portions diametrically opposed one on either side of said tube, each said beam has a tapering cross section along the beam length, the direction of taper of the two beams being oppositely directed so that if sway occurs in the direction of beam length, to the extent one beam is occluded more due to such sway, the other is occluded less, said control means computes the difference between the electrical outputs for said two portions as said difference signal, said signal being independent of sway in the direction parallel to said beams.

Claim 9

Dependent Claim 49 words

The control apparatus of claim 2 wherein said deviation sensing means includes a plurality of supports each supporting one said sensor, said supports being moveable dependently between a plurality of different radial positions with respect to said tube wall to establish different selected set points for different size tubes.

Claim 10

Dependent Claim 62 words

The control apparatus of claim 8 wherein said supports comprise pivotal arms adapted to pivot in transverse planes relative to said tube, and coupling means for causing said arms to pivot in unison, whereby the transverse position of all said optical sensor assemblies with respect to said tube wall can be adjusted by making a single adjustment of said coupled pivoting arms.

Claim 11

Dependent Claim 145 words

The apparatus of claim 8 or 9 wherein each said sensor includes an optical transmitter for projecting an optical beam generally tangentially of said longitudinally extending tube wall, with the region of tangency corresponding to said wall portion associated with said sensor, and an optical detector for receiving said optical beam, the electrical output derived from each said optical detector being linearly proportional to the percentage by which the respective beam is occluded by the respective wall portions, and said control means includes means for summing said electrical outputs to compute said difference signal, whereby said supports can be adjusted such that, when said tube has said desired circumference, said beams are partially occluded by said wall portions at said regions of tangency and such that changes in the sum of the percentage occlusion of said beams is respresentative of the change in said circumference.

Claim 12

Dependent Claim 47 words

The control apparatus of claim 8 further comprising means for adjusting the longitudinal location of said sensors along said tube, said means including a support ring surrounding said tube, said supports extending from locations spaced around said support ring, and means for longitudinally moving said support ring.

Claim 13

Dependent Claim 47 words

The control apparatus of claim 10 further comprising means for adjusting the longitudinal location of said sensors along said tube, said means including a support ring surrounding said tube, said supports extending from locations spaced around said support ring, and means for longitudinally moving said support ring.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1986-09-05	1987-03-07	1987-09-06	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1990-09-05	1991-03-07	1991-09-06	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1994-09-05	1995-03-07	1995-09-06	$7700.00	Window Closed / Lapsed

Control of tubular film size

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