US3583615A

US3583615A - Web guide apparatus

Info

Publication number: US3583615A
Application number: US864694A
Authority: US
Inventors: Robert W Ott Jr
Original assignee: ROCKFORD SERVO CORP
Current assignee: ROCKFORD SERVO CORP
Priority date: 1969-10-08
Filing date: 1969-10-08
Publication date: 1971-06-08
Anticipated expiration: 1988-06-08

Abstract

A web guide apparatus having swingably mounted arm assemblies for supporting a web guide roller for shifting movement in a direction crosswise of the path of web travel, in which the arm assemblies include a main arm swingably mounted on a stationary support and an auxiliary arm swingably mounted on the main arm, and mechanism for effecting swinging of the auxiliary arm relative to the main arm through an angle correlated with the angular movement of the main arm relative to the stationary support to move the roller in a path having a relatively flatter curvature than the arc defined by the main arm during its angular movement.

Description

United States Patent [72] Inventor Robert W. Ott, Jr.

Rockford, Ill. [21] Appl. No. 864,694 [22] Filed Oct. 8, 1969 [45] Patented June 8, 1971 [73] Assignee Rockford Servo Corporation Rockford, Ill.

[54] WEB GUIDE APPARATUS 16 Claims, 7 Drawing Figs.

{52] 11.8. C1 226/20, 226/21 [51] Int. Cl B65h 23/26 [50] Field of Search .I 226/15, 18, 19, 20, 21, 22, 23

[56] References Cited UNITED STATES PATENTS 2,722,415 11/1955 Wood,Jr. 226/23X Primary Examiner- Allen N. Knowles Attorney-Mc Canna, Morsbach, Pillote and Muir ABSTRACT: A web guide apparatus having swingably mounted arm assemblies for supporting a web guide roller for shifting movement in a direction crosswise of the path of web travel, in which the arm assemblies include a main arm swingably mounted on a stationary support and an auxiliary arm swingably mounted on the main arm, and mechanism for effecting swinging of the auxiliary arm relative to the main arm through an angle correlated with the angular movement of the main arm relative to the stationary support to move the roller in a path having a relatively flatter curvature than the arc defined by the main arm during its angular movement.

PATENTED JUN 8 I97l SHEET 1 BF 3 PATENTEDJUN 8I97| 3583615 SHEET 2 or 3 PATENTEU JUN 8l97| 3583615 SHEET 3 (IF 3 fwrwfwd WEB GUIDE APPARATUS BACKGROUND Web guide apparatus have heretofore been made which support the web guide roller for a combined longitudinal shifting and tilting movement of the web guide roll relative to the path of travel of the web. Longitudinal movement of the web guide roll in a direction transverse to the path of web travel, and opposite the direction of deviation of the web from the desired path, produces a relatively rapid correction of the path of travel of the web. However, if the factors which initially caused the web to move out ofthe desired path continue to exist, the web will tend to creep back out of position. Tilting of the roll as it is moved longitudinally applies a continuous correction to the traveling web and thus tends to maintain the traveling web on the corrected path. While the relationship between the longitudinal movement of the roller and the tilting movement of the roller will vary in different installations depending on factors such as the width of the web, speed of web travel, web tension, friction between the web and the guide roll, and stiffness of the web, it is frequently desirable to have the tilting of the web occur about a relatively large instantaneous are center, frequently of the order of the width of the web and more. In the prior web guide apparatus employing swingably mounted arms of the type shown in the US. Pat. to Wood, Jr. No. 2,722,415, the length of the instantaneous arc center about which the roller was tilted was controlled by the length of the support arms and, when guiding relatively wide webs, it was necessary to use very long support arms. The use of very long support arms not only markedly increases the space requirements of the web guide apparatus, but also markedly increases the problem of providing adequate support for the web guide roller at the outer ends of the arms.

The web guide assembly of the present invention employs an articulated arm assembly for supporting an end ofthe roller for movement through a path having an effective radius of curvature which is large as compared to the length of the arms employed in the articulated arm assembly. The articulated arm assembly includes a main arm swingably mounted on a stationary support, an auxiliary arm swingably mounted on the main arm for movement relative thereto, and a means for effecting swinging movement of the auxiliary arm relative to the main arm through an angle correlated with the angular movement of the main arm relative to the stationary support and such that the end of the web guide roller carried by the auxiliary support arm moves through a path having a flatter curvature than the path defined by the main arm during its swinging movement.

Various important objects of this invention are to provide a web guide apparatus employing a swingably mounted arms assembly for supporting the web guide roller for movement laterally of the web while tilting the guide roller relative to the path of web travel, which is adapted to support the web guide roller for movement about a relatively large instantaneous arc center; which is compact and occupies a minimum of space; which provides firm support for the web guide roller during movement relative to the path of web travel; which can be adjusted to vary the instantaneous arc center about which the roller moves; and which can be economically fabricated and installed.

These, together with other objects and advantages of this invention will become apparent from the following description when taken in connection with the accompanying drawings wherein:

FIG. 1 is a fragmentary isometric view of a web guide apparatus embodying the present invention;

FIG. 2 is a fragmentary plan view of the web guide apparatus shown in H0. 1;

FIG. 3 is a fragmentary plan view of the web guide apparatus illustrating the paths defined by different points on the web guide apparatus during movement of the same relative to the path of web travel;

FIG. 4 is a diagrammatic view illustrating different moved positions ofa web guide apparatus constructed in accordance with the present invention;

FIG. 5 is a fragmentary plan view ofa further modified form of web guide apparatus embodying the present invention;

FIG. 6 is a fragmentary plan view ofa modified form of web guide apparatus embodying the present invention;

FIG. 7 is a fragmentary sectional view taken on the plane 7-7 of FIG. 6.

Referring to FIGS. l-3 there is shown a web guide apparatus l0 embodying the present invention for laterally guiding a web W at a point intermediate its ends to maintain the webalong a preselected path P of web travel. The web guide apparatus includes one or more web engaging rollers herein shown as a pair of rollers R1 and R2 disposed in running engagement with the web. In the form shown, the web passes under one roller R1 and over a second roller R2 to maintain the web in frictional engagement with the rollers, it being understood that the web could be arranged to pass over or under both rollers or that a single roller could be used if the web guide apparatus is offset from a plane through the rollers 8 and 9 at the inlet and exit side of the web guide apparatus a distance such that the web tension is sufficient to maintain adequate frictional engagement between the web and the roller or rollers.

lt is well known that a cylindrical roll extending transversely to a web and in frictional engagement therewith will, if shifted in a direction lengthwise of the roll axis, tend to draw the traveling web in the direction of axial movement of the roll. Thus, if a guide roll is shifted in a direction opposite the direction of deviation of the traveling web from its correct path, the guide roll will tend to return the web to its correct path. This provides a rapid correction of the deviation of the web from the desired path of travel. However, if the forces that initially cause the web to deviate from the desired path, continue to exist, the web will tend to move back out of the desired path of travel and thus necessitate continued endwise movement of the roll.

lt is also noted that a traveling web in frictional engagement with a cylindrical roll will tend to move at right angles to the axis of the rotating roll and that, if the axis of the cylindrical roll is inclined with respect to the path of travel of the web, the web will tend to move toward the end of the roll which is first contacted by the traveling web. This tendency of the web to move toward the end of the inclined roll continues as the web travels over the roll and is limited only by the slippage between the web and the roll. Thus, the traveling web will tend to move toward the end of the inclined roll until the other forces acting on the web are sufficient to overcome the traction between the web and the roll and cause the web to slip on the roll.

The present invention relates to an improved apparatus for supporting the web guide roll for endwise movement of the roll in a direction laterally of the path of web travel to provide a rapid correction of the web travel, as well as tilting of the web guide roller relative to the path of web travel to apply a continuing correction to the traveling web which tends to maintain the traveling web in the corrected path. The relationship between the amount of endwise movement and the amount of tilting movement necessary for correction of the path of travel of the web varies in different installations dependent on various factors such as the width of the web, web tension, stiffness of the web, speed of the web, and frictional engagement of the web with the roll. However, it is generally desirable to tilt the web guide roller about a relatively large instantaneous radius of curvature, for example, an effective instantaneous radius corresponding to the width of the web and sometimes more.

In the embodiments illustrated, a pair of articulated arm as semblies 11 are provided for supporting opposite ends of the web guide roller for simultaneous lateral and tilting movement. It is to be understood, however, that in some applications it is possible to use a single articulated arm assembly to support one end of the web guide roller, provided the other end is supported for axial sliding and swiveling movement to accommodate the endwise and tilting movement of the guide roller produced by the articulated arm assembly at the other end of the guide roller.

The articulated arm assemblies 13 each included a main support arm 13 mounted on a stationary support base I2 for swinging movement about an axis AI; an auxiliary support arm 14 swingably mounted on a respective main support arm I3 for swinging movement relative thereto about an axis A2, and a roller mounting means 15 mounting one end of the roller or rollers on the auxiliary support arm 14 for pivotal movement relative thereto about a third axis A3. The arm assemblies also include a means 16 for controlling relative angular movement between the main and auxiliary arms to effect movement of the auxiliary arms relative to the respective main arm through an angle correlated with the angular movement of the main arm relative to the stationary support. As is conventional in web guide apparatus, a means is provided for sensing the position of the web and for automatically shifting the web guide apparatus in a direction to correct deviation of the web from the desired path of web travel. As diagrammatically shown in FIG. 1, this means includes at least one web edge sensor 18 arranged to sense the lateral position of the web, a roller shifting mechanism 19 for moving the roller, and a power unit 21 which is responsive to the signal produced by the sensor I8 and which actuates the roller shifting mechanism 19 to move the roller in a direction to correct the deviation of the web from the desired path of web travel. The roller shifting mechanism 19 is herein shown in the form of a linear actuator such as a cylinder having a movable member or piston 23 and provision is made for connecting the movable member to the web guide apparatus to shift the rollers in a direction opposite the deviation of the web from the desired path of web travel. In the form shown in FIGS. 1 and 2, the movable member 23 of the mechanism 19' is operatively connected by a clevis 45 to one of the main arms 13 to shift the main and auxiliary arms along with the roller assembly, it being apparent from the following description that the movable actuator can be otherwise connected to the auxiliary arm 14 or to the web guide rollers directly to effect movement of the latter. As shown, the

cylinder of the roller shifting mechanism is swivelly connected at to the stationary support to accommodate the swinging of the main arm 13 relative to the stationary support.

The geometry of the arm assemblies 11 and the overall web guide apparatus will be better understood by reference to the diagrammatic illustration in FIG. 4 of a presently preferred arrangement of the main and auxiliary arms. As shown in that view, the pivot points a] of the main arms 13 are located at relatively opposite sides of the path Pof web travel and the arms 13 are swingable in a plane crosswise of the path of web travel. The main arms 13 diverge in the direction of advance of the web relative to the path of web travel and in the diagrammatic illustration herein diverge at an angle of about 15. The pivots points a2 at the outer ends of the main arm 13 are movable through an arcuate path designed cl, as the main arm is swinging about the pivots points al. The auxiliary arms 14 move with .the main arm and the control mechanism 16 operates to swing the auxiliary arms relative to the main arms during angular movement of the latter. In the diagrammatic illustration of FIG. 4, the auxiliary arms extend from the pivot points a2 toward the pivot points a] when the web guide roll R1 is disposed perpendicular to the path of travel P of the web. It is desired that the pivot points a3 at which the roll is supported on the auxiliary arms move through a path having a relatively flatter curvature than the arcuate path cl of the arms 13 and the control mechanism 16 is arranged to swing the auxiliary arms 14 about the pivot points a2 relative to the respective main arm in an angular sense opposite the angular sense of movement of the respective main arm. Stated otherwise, when the main arm 13 moves in a clockwise direction about the pivot point al, the control mechanism swings the auxiliary arm 14 in a counterclockwise direction about the pivot point 02 and vice versa, so that the motion imparted to the auxiliary arm due to swinging of the main arm about its pivot is amplified by the auxiliary arm and applied to the pivot point a3 to increase the lateral motion ofthe rollers. However, since the arc defined by the auxiliary arm 14 as it swings about pivot point a2 is opposite the are defined by the arm 13 asit swings about point al, the resultant motion in point a3 in a direction lengthwise of the web is reduced. As a result, the pivot point a3 on the auxiliary arm moves through an arc having a relatively flatter curvature than the arc cl of the main arm.

The curvature of the patch c2 can be varied by changing different parameters of the articulated arm assembly. In the diagrammatic form shown in FIG. 4, the control mechanism 16 is arranged to swing the auxiliary arm 14 relative to the main arm 13 through an angle which is approximately twice the angular movement of the main arm 13 relative to the support. The curvature of the resultant path 02 can be varied by changing the length of the main and

auxiliary arms

13 and 14 as well as the ratio of the length of the auxiliary arm relative to the main arm; by changing the ratio between the angular movement of the auxiliary arm in relation to the angular movement of the main arm; by changing the angular position of the auxiliary arm relative to the main arm when the roller R1 is in its normal position perpendicular to the path of web travel, and by changing the initial angular position between the main arm and the path of travel of the web, that is the angular relation between the main arm and the path of travel of the web, when the roller RI is perpendicular to the path of web travel. As will be apparent from FIG. 4, the effective instantaneous radius of curvature of the path 02 will decrease and approach the radius of curvature of the path cl, as the distance between the pivot point a3 and the pivot point 02 is decreased. Conversely, the radius of curvature of the path c2 will increase and become a straight line, as the distance between the pivot point a3 and the pivot point a2 is increased so as to equal the distance between the pivot points al and 02. The lines c3 in FIG. 4 illustrate the resultant path of travel of the pivot point a3, when the distance between the pivot point a3 and the pivot point a2 is equal to the distance between the pivot points a1 and a2. As will be seen, the paths c3 are perpendicular to the lines through the pivot points al and a2, when the main arms 13 are in their normal position supporting the web guide roller perpendicular to the path of travel of the web. It will also be understood that the inclination of the tangent to the curved paths such as 02, can be respectively increased and decreased by changing the angle which the main arms define with the path of travel, when the main arms are in their normal position. The curvature of the resultant path of travel of the pivot point a3 can also be varied by changing the ratio of the angular movement of the auxiliary arm in relation to the angular movement of the main arm. In general, it is considered preferable to maintain the ratio of angular movement of the auxiliary arm relative to angular movement of the main arm greater than 1:] and less than above 2:1. As the ratio approaches 1:1, the curvature of the path defined by the point a3 approaches that of the path defined by the point a2 but is displaced from the path defined by the point a2 by the length of the auxiliary arm.

Referring more specifically to the embodiment shown in FIGS. l3, of the main arm 13 is shown formed with spaced

knuckles

31 and 32 which are rotatably supported on a pintle 33 secured to the stationary support. The spaced knuckles provide a stable pivotal support for the main arm and the auxiliary arm is similarly formed with spaced portions 34 and 35 which overlie opposite sides of the main arm and are swingably connected thereto by a pivot pin 36. As shown, the main arm is formed with a generally L-shaped configuration to provide clearance for the auxiliary arm during swinging movement of the main and auxiliary arms relative to each other. A pair of rollers R1 and R2 are utilized in the embodiment illustrated and these rollers are supported by a roller mounting bracket IS on the auxiliary arms for swinging movement relative thereto about a pivot axis :13. As shown, the bracket 15 is attached to the auxiliary arms by pivot pins 38 and the roller shafts 39 are mounted on the bracket at relatively opposite sides of the pivot pin. As will be readily understood, the rollers can be rotatably supported on the shafts 39 by suitable bearings (not shown) or, alternatively, the roller shafts 39 can be rotatably supported on the roller mounting bracket 15, to rotatably mount the rollers.

In the embodiment of FIGS. 1-3, the control of angular movement of the auxiliary arms relative to the main arms during movement of the main arms relative to the support is effected by

sector wheels

41 and 42 and a belt means 43. One sector wheel 41 is located at the pivot axis al and mounted so as to be nonrotatable relative to the stationary support 12. The second sector wheel 42 is located at the pivot axis a2 and is mounted so as to be nonrotatable with relation to the auxiliary arm 14. The belt means 43 nonrotatably interconnects the sector wheels so as to rotate the sector wheel 42 in response to angular movement of the main arm relative to the stationary support. The sector wheels can be of various different constructions and may, for example, be sprockets or pulleys and the belt means can be in the forms of a sprocket chain, toothed timing belt, or a cable. Since the main and auxiliary arms do not swing through a complete circle, the sector wheels can be semicircles if desired and, moreover, the belt means does not have to be a continuous belt but can be one or more flexible sections which interconnect the

sector wheels

41 and 42 but are terminally attached thereto at points so arranged as to not interfere with the angular motion.

The movable member 23 of the actuator for moving the rollers can be connected to the rollers in any desired manner to move the same. In the form shown in FIGS. l3, the actuator is connected through a clevis 45 to one of the main arms 13. As is well understood by those skilled in the art, the power unit 21 is arranged in relation to the sensor 18 and the roller shifting mechanism 19 so that, when the web deviates in one direction such as to the right as viewed in FIGS. 1-3, the roller shifting mechanism is operated to move the rollers in the relatively opposite direction, that is to the left so as to tend to correct the path of web travel. The main arms 13 diverge in the direction of advance of the web, as shown in FIGS. 2 and 3, so that the resultant path of travel of the points 03 have instantaneous arc centers located in advance of the inlet side of the web guide apparatus whereby the roller, during endwise movement, is simultaneously canted or tilted in a direction correiated with the endwise movement of the roller to tend to maintain the web in the corrected path.

A web guide apparatus having a modified form of control apparatus for regulating angular movement of the auxiliary arms relative to the main arms, as shown in FIG. 5. The arms assemblies are generally similar to that shown in FIG. 1 and like numerals are used to designate corresponding parts. In this embodiment, however, a lever 42a is nonrotatably connected to each auxiliary arm 14 and, as shown, extends laterally of the respective auxiliary arm adjacent the pivot point a2. A means is provided for connecting the lever to the stationary support 12 to effect swinging of the latter in response to angular movement ofthe main arms 13. As shown, this means includes a link 43a pivotally connected at one end as by pin 48 to the lever 42a and at the other end as by pin 49 to the stationary support 12. The length of the lever 42a between the pivot point 02 and the pin 48 is made less than the spacing between the pivot point a1 and the pin 49 so that, dur ing angular movement of the main arms 13 about the point al, the lever 42a is moved through an angle correlated with and greater than the angular movement of the respective main arm 13. The ratio is preferably about 2: 1 so that the auxiliary arm moves relative to the main arm through an angle about twice the angular movement of the main arm relative to the stationary support. The ratio of angular movement can be selectively adjusted as by use ofdifferent mounting holes in the base or in the lever 42a, as shown.

A modified form of web guide roller assembly is illustrated in FIGS. 6 and 7 adapted for use in applications involving somewhat higher loading of the web guide rollers. The arm assemblies are each supported on the stationary supports by a mounting bracket 51 having upper and lower legs 51a and 52a which nonrotatably support the opposite ends of a shaft 53. Each main arm 53 is swingably supported on a respective shaft as by bearing 54 and a second shaft 55 is rotatably supported at the outer ends of the respective main arm 53 as by bearing 56. Each auxiliary arm 57 is nonrotatably connected to its respective shaft 55 and has a pivot shaft 58 rotatably supported by bearings 59 at the outer ends of the auxiliary arm. A roller mounting bracket 61 is secured to the shaft 58 and supports the rollers R1 and R2 at relatively opposite sides of the shaft 58. Sector wheels 62 and 63 are nonrotatably attached to the stationary shaft 53 and to the rotatable shaft 55 respectively as by locking screws 62a and 63a and are interconnected by a belt means 64 to rotate the shaft 55 and hence swing the auxiliary arms 57 relative to the main arms 53 during angular movement of the latter. In this embodiment, the movable member 23 of the roller shifting mechanism 19 is directly connected to one of the roller mounting brackets 61 to move the rollers crosswise of the path of travel of the web. The geometry of the arm assembly is similar to that described in connection with FIG. 4 and the arm assemblies cause tilting of the rollers R1 and R2 during movement of the rollers in a direction crosswise of the web.

From the foregoing it is believed that the construction and operation of the web guide apparatus will be readily understood. The articulated arm assemblies support the web guide roller for simultaneous lateral and tilting movement relative to the path of travel of the web. The auxiliary arms swing through an angle correlated with the angular movement of the main arms and such that the resultant path of travel of the points a3 corresponding to the end of the guide rollers, has a flatter curvature than the arcs a2 defined by the main arms. This arrangement enables supporting of the web guide roller for movement about a large instantaneous arc center without requiring corresponding long support arcs. The articulated arm assemblies are thus more compact and provide a more stable support for the web guide rollers than can be achieved with single arm assemblies having a corresponding large radius of curvature.

What I claim is:

1. In an apparatus for guiding a traveling web of material along a preselected path of travel including at least one web guide roller in running engagement with the web, means mounting said roller for shifting movement relative to a stationary support in a direction crosswise of the path of web travel, and means responsive to deviation of the web from the desired path of web travel for shifting the roller in a direction to correct the path of web travel, the improvement wherein said roller mounting means includes a first arm means swingably mounted on said stationary support for movement about a first arc center, second arm means swingably mounted on said first arm means for movement relative thereto about a second arc center spaced from said first are center, roller attaching means pivotally mounting one end of said roller on said second arm means for pivotal movement relative thereto about a third pivot axis spaced from said second arc center, said roller shifting means including control means for simultaneously moving said first arm means relative to said stationary support through a first angle while moving said second arm means relative to said first arm means through a second angle correlated with said first angle such that the resultant path of movement of said third pivot axis relative to the stationary support has a flatter curvature than the path defined by said second arc center as said first arm means moves through said first angle about said first arc center.

2. A web guide apparatus according to claim 1 wherein said control means effects angular movement of the second arm means relative to the first arm means at a rate greater than the rate of angular movement of said first arm means relative to said support means.

3. A web guide apparatus according to claim 1 wherein said second arm means extends from said second arc center in a direction generally toward said first arc center during at least a portion of the angular movement of said second arm means through said second angle.

4. A web guide apparatus according to claim 1 wherein the distance between said third pivot axis on said second arm means and said second arc center is no greater than the distance between said second are center and said first arc center.

5. A web guide apparatus according to claim 1 wherein said control means includes a first sector wheel at said first arc center nonrotatable relative to said support means, a second sector wheel at said second arc center nonrotatable relative to said second arm means, and belt means connecting said first and second sector wheels to rotate the second sector wheel in response to angular movement of said first arm means relative to said support means.

6. A web guide apparatus according to claim 5 wherein said first sector wheel has a diameter greater than said second sector wheel.

7. A web guide apparatus according to claim 1 wherein said control means includes a lever nonrotatably connected to said second arm means, and means connected to said stationary support and engaging said lever for swinging said second arm means relative to said first arm means in response to angular movement of said first arm means relative to said stationary support.

8. A web guide apparatus according to claim 1 wherein said control means includes a lever nonrotatably connected to said second arm means and link means pivotally connected at one end to said lever and at the other end to said stationary support for swinging said second arm means relative to said first arm means in response to angular movement of said first arm means relative to said stationary support.

9. An apparatus for guiding a traveling web during advance in one direction along a preselected path relative to a stationary support comprising, a pair of main support arms and means for swingably mounting said arms on said stationary support for movement relative thereto about first pivot axes adjacent opposite sides of the web, an auxiliary support arm swingably mounted on each main support arm for movement relative thereto about a second pivot axis spaced from the pivot axis of its main support arm, at least one web guide roller extending between said auxiliary support arms and means mounting opposite ends of said roller on said auxiliary support arms for swinging movement relative thereto about third pivot axes each spaced from a respective one of said second pivot axes, means responsive to deviation of said web from said web from said preselected path of web travel for shifting said roller in a direction to correct the path of web travel, said last-mentioned means including control means for simultaneously moving said main support arms relative to said stationary support through a first angle while moving said auxiliary support arms relative to its respective main support arm through a second angle greater than said first angle such that the resultant paths of movement of said third pivot axes relative to said stationary support have a flatter curvature than the paths defined by said second pivot axes as said main support arms move through said first angle about said first arc centers thereof.

10. A web guide apparatus according to claim 9 wherein said control means moves said auxiliary support arms in a clockwise direction about said second pivot axis in response to counterclockwise movement of said main support arms about said first pivot axis and vice versa.

line through the first and second pivot axes on each main surpport arm iverges relative to the direction of advance oft e web when the roller is perpendicular to said preselected path of web travel.

13. A web guide apparatus according to claim 12 wherein said auxiliary support arms extend from said second pivot axis generally toward said first pivot axis during at least a portion of the angular movement of said auxiliary support arms through said second angle.

14. A web guide apparatus according to claim 9 wherein said control means includes a first sector wheel at each of said first pivot axes nonrotatable with respect to said stationary support, a second sector wheel at each of said second pivot axes nonrotatable relative to the respective auxiliary support arms, and belt means connecting respective ones of said first and second sector wheels to rotate said second sector wheels in response to angular movement of said main support arms relative to said stationary support, said first sector wheels having a diameter greater than the respective second sector wheels.

15. A web guide apparatus according to claim 9 wherein said control means includes a lever nonrotatably connected to each of said auxiliary support arms, and means connected to said levers and to said stationary support for swinging said auxiliary support arms relative to the respective main support arms in response to angular movement of said main support arms relative to said stationary support.

16. An apparatus for guiding a traveling web along a preselected path relative to a stationary support comprising, at least one web guide roller and first and second arm assemblies for supporting opposite ends of said roller, each arm assembly including a main support arm swingably mounted on said stationary support for movement relative to the stationary support about a first pivot axis and an auxiliary arm swingably mounted on the main arm for movement relative thereto about a second pivot axis spaced from the first pivot axis, a roller mounting bracket pivotally mounted on each auxiliary support arm for swinging movement relative thereto about a third pivot axis spaced from the second pivot axis of the respective auxiliary arm, means on the roller mounting brackets rotatably supporting the end of the roller thereon with the roller extending between the arm assemblies, means responsive to deviation of said web from said preselected path of web travel for shifting said roller in a direction to correct the path of web travel, said last-mentioned means including control means responsive to movement of said main support arms in one angular direction through a first angle relative to said stationary support for moving said auxiliary support arms relative to the respective main arm in the relatively opposite angular direction through a second angle greater than said first angle, said second angle being correlated with said first angle such that the resultant motion of said third pivot point produced by swinging of said main arm relative to said stationary support through said first angle and swinging of said auxiliary arm relative to said main arm through said second angle has a flatter curvature than the path defined by said second pivot axis during swinging of said main arm through said first angle.

Claims

1. In an apparatus for guiding a traveling web of material along a preselected path of travel including at least one web guide roller in running engagement with the web, means mounting said roller for shifting movement relative to a stationary support in a direction crosswise of the path of web travel, and means responsive to deviation of the web from the desired path of web travel for shifting the roller in a direction to correct the path of web travel, the improvement wherein said roller mounting means includes a first arm means swingably mounted on said stationary support for movement about a first arc center, second arm means swingably mounted on said first arm means for movement relative thereto about a second arc center spaced from said first arc center, roller attaching means pivotally mounting one end of said roller on said second arm means for pivotal movement relative thereto about a third pivot axis spaced from said second arc center, said roller shifting means including control means for simultaneously moving said first arm means relative to said stationary support through a first angle while moving said second arm means relative to said first arm means through a second angle correlated with said first angle such that the resultant path of movement of said third pivot axis relative to the stationary support has a flatter curvature than the path defined by said second arc center as said first arm means moves through said first angle about said first arc center.

4. A web guide apparatus according to claim 1 wherein the distance between said third pivot axis on said second arm means and said second arc center is no greater than the distance between said second arc center and said first arc center.

11. A web guide apparatus according to claim 9 wherein said auxiliary support arms extend from said second pivot axis in a direction generally toward said first pivot axis during at least a portion of the angular movement of said auxiliary support arms through said second angle.

12. A web guide apparatus according to claim 9 wherein said main support arms are constructed and arranged so that a line through the first and second pivot axes on each main support arm diverges relative to the direction of advance of the web when the roller is perpendicular to said preselected path of web travel.