Web Edge Guide System

Abstract

Apparatus for limiting the maximum lateral web shift initiated by a web guiding system to a predetermined safe amount. A first web edge sensor adjacent the supply roll senses deviations from a normal web edge position and generates a correction signal which causes a servo-drive system to axially move the web supply roll in a direction to return the web to its normal position. A second web edge sensor longitudinally spaced along the web from the first sensor senses the web edge, and in response thereto positions stop members which limit corrective lateral shift of the first edge sensor to a predetermined safe amount.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the manufacture and processing of webs such as paper, plastic, film and the like. More particularly, the invention relates to means for continuously monitoring the lateral shift of the edge of a web from a normal desired position, and safely returning the web to the normal position.

2. Description of the Prior Art

In the production and processing of continuous webs, it is well known that web rolls are not wound with even intensity across the entire width of the roll, and that the tightness of winding may vary from side to side as the web unwinds. For this and other reasons, there is sometimes a stronger pull in one section of the web, which causes the web to move from side to side on the machine thereby producing uneven cuts or uneven transport of the web. Previous attempts to force the web to run in a selected straight path have incorporated a mechanical finger which operates gearing to shift the roll so as to keep the edge of the web in a straight line. Such mechanisms suffer from a slow response time because of the relatively massive control equipment required. Attempts to improve the tracking of the web material by controlling the position of the feed roll by a servo system actuated by a pneumatic sensor operated by the edge of the web have resulted in faster response times. However, too fast a response time can cause distortion of the web particularly when the amount of the correction introducted in the position of the feed roll is too large, thereby causing wrinkling or creasing of the web. This condition exists primarily during start-up of a machine due to the threading of the web by the operator in an off-normal or off-centered position.

SUMMARY OF THE INVENTION

In accordance with a preferred embodiment of the invention, a web edge guide system is disclosed of extremely simple construction which overcomes many of the prior art problems. The system is provided with stop members, which are sensitive to the position of the web edge, and which act to limit the amount of axial corrective movement imparted to the web supply roll. A first movable sensing means is provided for imparting axial corrective movement to the supply roll for returning the web to a normal position. A second movable sensing means senses the web edge, and in response thereto sets stop members for limiting the amount of corrective action permitted by the first sensing means to correct the position of the web edge. As the web gradually returns to its normal position, the first sensing means gradually returns the supply roll and web to its normal web edge position. The rate of return of the web edge to the normal web edge position is governed by adjustment of the limit stop members and by the rate of web travel.

It is, therefore, an object of this invention to limit the maximum amount of lateral shift correction applied to a transported web to a predetermined safe amount.

A further object of this invention is to provide an edge guide system which minimizes distortion of a web as it is unwound from a supply roll by limiting corrective movement of the supply roll.

A still further object of this invention is to provide an edge guide system wherein the allowable maximum lateral shift correction applied to the web may be quickly and easily changed, and in which the position of the web edge may be easily adjusted.

The invention and its objects and advantages will become more apparent from the detailed description of the preferred embodiment presented below.

BRIEF DESCRIPTION OF THE DRAWINGS

In the detailed description of the preferred embodiment of the invention presented below, reference is made to the accompanying drawings, in which:

FIG. 1 illustrates a schematic and diagrammatic representation of the web edge guide system of the present invention;

FIG. 2 is an enlarged, side elevational view, partly in section, of a web edge positioning device incorporated in the guide system of FIG. 1;

FIG. 3 is a schematic representation of the web edge guide system in relation to a misaligned web illustrating how the corrective lateral shifting of the supply roll is limited;

FIG. 4 is a view similar to FIG. 3 illustrating gradual return of the web to its normal position; and

FIG. 5 is a view similar to FIGS. 3 and 4 illustrating the edge guide system and web in their normal position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Because web production and transport equipment is well known, the present description will be directed in particular to elements forming part of, or cooperating more directly with, apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described herein may take various forms well known to those skilled in the art.

With reference to FIG. 1, a web supply roll 10 is utilized to supply a web 12 to any form of web processing equipment. Web supply roll 10 is mounted on a supply core 14, and web 12 from roll 10 is trained over a first idler roller 16, a second idler roller 18 and a web drive drum 24, preferably arranged at different elevations. Supply core 14 and idler rollers 16 and 18 are mounted on a single supply frame 20. A movable idler roller 22 is positioned substantially half-way between idler roller 18 and web drive drum 24.

A first web edge detector indicated generally at 26 includes a pneumatic sensor 27 of any suitable type of which the sensor shown in U. S. Pat. No. 1,982,685 is exemplary. Sensor 27 is mounted on a laterally movable arm 28 for sensing the position of the edge of web 12, and depending on the position of arm 28, generating an input signal through any suitable signal generating circuit for driving a servo drive 30. Servo drive 30 serves to axially position frame 20 containing thereon supply core 14 and idler rollers 16 and 18. A torque shaft 32 coupled by any suitable means such as gears 29, 31 to arms 28, 33 respectively via racks, not shown, axially positions idler roller 22 relative to frame 20 to prevent slippage between roller 22 and web 12. For the configuration shown in FIG. 1, this positioning structure is designed to move roller 22 one-half the distance that the pneumatic sensor 27 is moved by any suitable apparatus to be explained hereinafter.

In operation, sensor 27 will detect any deviation of the position of the web edge from the normal position, and will cause servo-drive 30 to move frame 20 in a direction tending to return the web edge to its normal position.

A web edge positioner 34 is provided to position one edge of web 12 at a desired or normal position. The web edge positioner 34 which is shown in detail in FIG. 2 comprises a frame 90 for rotatably supporting a shaft 91 which is coupled to gear 29. A worm wheel 92 having a radially spaced stop pin 94 is rotatably mounted on shaft 91, and is rotatably driven by a worm 93 coupled to a hand crank 38. A collar 95 having a radially extending pin 96 is secured to shaft 91. An inner sleeve 97 is rotatably mounted on shaft 91, and in turn rotatably supports an outer sleeve 98. An adjusting collar 99 is rotatably mounted on sleeve 97 and adapted to be locked thereto by set screw 100. The collar 99 and sleeve 98 are provided with bores 101, 102 respectively for receiving the ends of a helical spring 103 encircling sleeve 98. By adjusting collar 99 and locking it to inner sleeve 97 with set screw 100, spring 103 can be rotationally preloaded to rotatably urge sleeves 97 and 98 toward one another, causing stop lugs 104, 105 on sleeves 98, 97 respectively to engage pin 94. Normally, pin 94 on wheel 92 is turned by crank 38 for moving shaft 91 and pin 96 by lugs 104, 105 for aligning sensor 27 in register with a desired position of the web edge. In such position, flange 44 is arranged substantially centrally of stop screws 72, 74. In operation, as flange 44 is forced away from its normal position by one of the limit stop screws 72 or 74, axial movement is imparted to arm 28 which rotates shaft 32 through gear 29. Rotation of shaft 32 causes shaft 91, collar 95 and pin 96 to be rotated. This, in turn, causes rotation of one of the stop lugs 104, 105 and its corresponding sleeve 98, 97 causing further tensioning of spring 103. Tensioned spring 103 continues to apply a torque on pin 96 forcing arm 28 to return to its normal position when no longer restrained by one of the limit stop screws 72, 74. This position is reached when both of the stop lugs 104, 105 bear against stop pin 94. By moving stop pin 94 through worm wheel 92 and worm 93, the position of shaft 91 and the normal running position of the web edge can be changed at will.

A second web edge detector indicated generally at 52 and longitudinally spaced along the web from detector 27 includes a pneumatic sensor 54 mounted on an arm 56 guided by any suitable means for axial movement to sense the web edge near drive drum 24. One end of arm 56 is threaded and mounted on a threaded spindle 58 journaled for rotation in bearings 109, 110. Spindle 58 is rotated by servo-drive 60 through belt 106 and pulleys 107 and 108 for axially positioning arm 56 and sensor 54. The servo-drive 60 is coupled to sensor 54 and controlled by any suitable electrical or hydraulic means to continuously locate or position sensor 54 over the edge of web 12. By means of a second belt 111 and pulleys 112 and 113, servo-drive 60 rotates another threaded spindle 114 journaled for rotation in bearings 115, 116 for axially moving a frame 66 of a limiting device generally indicated at 64 for limiting lateral corrective movement of sensor 27 to a predetermined amount. Frame 66 is provided with integral depending fingers 68, 70, through which adjustable threaded limit stop screws 72, 74 respectively extend. In a normal position of the web edge guide system, sensors 27, 54 are in register with a desired normal web edge position, and limiting device 64 is adjustably positioned with flange 44 extending substantially between limit stop screws 72 and 74 as best seen schematically in FIG. 5.

If web 12 is initially threaded over rollers 16, 18 and 22 and drive drum 24 in a misaligned condition, and transport of the web commenced, edge sensor 54 will indicate a misaligned position to servo-drive 60 which thereby repositions arm 56 until sensor 54 is centered over the web edge as seen in FIG. 3. The operation of servo-drive 60 simultaneously causes movement of limiting device 64 in the same direction as arm 56, thereby moving fingers 68, 70 and screws 72, 74 off-center with respect to flange 44. If the initial misalignment of web 12 is large enough, a limit screw 72 or 74, depending on the direction of the misalignment, will engage flange 44 and move arm 28 and sensor 27 out of its normal position. Such movement also imparts movement to shaft 91, pin 96 and one of the lugs 104, 105 against the bias of spring 103. The maximum allowable lateral movement of flange 44 and sensor 27 is pre-set by limiting device 64 and limit screws 72 and 74, and is generally substantially half the distance between the ends of the two limit screws minus the width of arm flange 44. The maximum allowable lateral movement of sensor 27 depends on the characteristics of web 12, and the physical layout of the machine between supply frame 20 and web drive drum 24. In general, the movement should be large, but not so large that web 12 wrinkles or creases as it moves from supply roll 10 to web drive drum 24. The pneumatic sensor 27 senses the misalignment and transmits a signal to servo-drive 30, which in turn axially moves from 20 core 14, rollers 16 and 18 and supply roll 10 in a direction to reposition the edge of web 12 under sensor 27.

A few seconds after web transport is commenced, the web will tend to decrease its offset between roller 18 and drive drum 24 due to the corrective action of servo-drive 30, among other reasons, as best seen in FIG. 4. Sensor 54 will sense this decrease and signal servo-drive 60 to reposition both edge detector 52 and limiting device 64 to the new web edge position. Spring 103 forces pin 96 and shaft 91 in a direction moving sensor 27 toward the web edge consistent with limit screw 72. This process continues until the web edge and sensors 27, 54 are in register with the normal web edge position as seen in FIG. 5. In this position, lugs 104, 105 are in engagement with pin 94 and shaft 91 positioned to locate flange 44 substantially in the center of limit stops 72 and 74.

During continued transport of web 12, the edge guide system of this invention will limit the corrections introduced in the web position to those pre-set by adjustable limit stop screws 72, 74, thereby limiting the maximum angle by which the web can deviate from a straight line. Since limit stops 72, 74 are each adjustable, they can be repositioned to vary the amount of lateral shift in the web edge. Sensor 27 and servo-drive 30 should be calibrated and adjusted such that flange 44 is centered between stop lugs 72, 74 when the web is transported through the machine in a straight line.

It is also possible to incorporate pilot lights 76, 78 into limiting device 64 to indicate an initial web misaligned condition and thereby assist in proper threading of the web through the machine. One terminal of each of pilot lights 76, 78 is connected to one terminal of battery 80, and the other terminal of battery 80 connected to flange 44, formed from a conductive material. The outer terminals of pilot lights 76, 78 are respectively connected to one of the limit stops 72, 74. An electrical circuit will be completed whenever flange 44 contacts one of the limit stops 72, 74 and the respective pilot light is lit, indicating this fact to the operator.

The invention has been described in detail with particular reference to a preferred embodiment thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Claims

I claim:

1. Apparatus for detecting and correcting the lateral position of a longitudinally travelling web, said apparatus comprising:

first means for sensing the lateral position of said web at a first position and in response thereto for correctively laterally displacing said web, if misaligned, to a predetermined lateral position at said first position;

second means for sensing the lateral position of said web at a second position, said second position being spaced apart from said first position along the longitudinal dimension of said web; and

means interconnecting said first and second means for limiting the maximum corrective lateral displacement imparted to said web by said first mans to a predetermined amount.

2. The invention according to claim 1 wherein said first means comprises a movable sensing member, a sensor on said sensing member, and a pair of opposed resilient members coupled to said sensing member for biasing said sensor to a predetermined position corresponding to said predetermined lateral position of said web.

3. The invention according to claim 2 wherein said inter-connecting means comprises means for preventing movement of said sensing member to said predetermined position so long as the lateral displacement of said web between said first and second positions is at least as great as said predetermined maximum amount of displacement.

4. The invention according to claim 3 wherein said movement preventing means includes stop members responsive to said second means, said stop members being positionable within the path of movement of said sensing member for preventing movement thereof.

5. The invention according to claim 2 wherein said inter-connecting means comprises a pair of opposed stop members, one of said stop members being positionable within the path of movement of said sensing member to prevent movement of said sensing member to its predetermined position whenever the lateral displacement of said web between said first and second positions is at least as great as said predetermined maximum amount of lateral displacement.

6. The invention according to claim 5 wherein said inter-connecting means further comprises a pair of signal lights, each of said signal lights being responsive to movement of one of said stop members to a position wherein it prevents movement of said sensing member.

7. The invention according to claim 1 wherein said inter-connecting means comprises means for indicating whenever the lateral displacement of said web between said first and second positions is at least as great as said predetermined maximum amount of lateral displacement.

8. The invention according to claim 7 wherein said indicating means comprises a pair of signal lights.

9. The invention according to claim 1 wherein said inter-connecting means comprises a pair of opposed stop members, said stop members being responsive to said second means for movement to a position whereby said stop members inhibit repositioning of said web to said predetermined lateral position so long as the lateral displacement of said web between said first and second positions is at least as great as said predetermined maximum amount of lateral displacement.

10. The invention according to claim 9 wherein said first means comprises means responsive to movement of said stop members to said inhibiting position for partially repositioning said web.

11. The invention according to claim 10 wherein said first means comprises a movable sensing arm, a sensor on said arm, and a pair of opposed resilient members coupled to said arm for biasing said arm and sensor towards a predetermined position corresponding to said predetermined lateral position of said web, said stop members preventing movement of said arm to its predetermined position whenever said stop members are in said inhibiting position.

12. The invention according to claim 11 wherein said inter-connecting means further comprises a pair of signal lights, each of said signal lights being responsive to movement of one of said stop members to said inhibiting position.

13. Apparatus for detecting the lateral position of a longitudinally travelling web and for moving said web to a predetermined lateral position without exceeding a predetermined maximum amount of lateral displacement, said apparatus comprising:

first and second movable sensing arms, said arms sensing the lateral position of said web at first and second positions, said sensing positions being spaced apart from each other along the longitudinal dimension of said web;

a pair of opposed resilient members coupled to said first arm for biasing said first arm towards a predetermined position corresponding to said predetermined lateral position of said web;

means responsive to the position of said first arm for moving said web towards said predetermined lateral position; and

a pair of opposed stop members, said stop members being responsive to the position of said web at said second position for movement to a position within the path of movement of said first arm to prevent movement of said first arm to its predetermined position whenever the lateral displacement of said web between said first and second positions is at least as great as said predetermined maximum amount of displacement.

14. The invention according to claim 13 wherein said apparatus further comprises a pair of signal lights being responsive to movement of one of said stop members to its movement preventing position.