US3737115A

US3737115A - Web-transisioning apparatus

Info

Publication number: US3737115A
Application number: US00143696A
Authority: US
Inventors: N Baker
Original assignee: Wilton James Ltd
Current assignee: Wilton James Ltd
Priority date: 1970-05-08
Filing date: 1971-05-10
Publication date: 1973-06-05
Anticipated expiration: 1990-06-05
Also published as: GB1305647A

Abstract

Apparatus for automatically tensioning a web of material being drawn from a reel, utilizing a belt engaging the side of the reel, the belt being in the form of a continuous loop contacting the reel surface and being driven in use of the apparatus to reduce the relative speed between the contacting surfaces of the belt and reel which might result in damage to the reel material, the belt being associated also with compensating means for maintaining a substantially constant tension throughout the life of the reel despite the gradual reduction in reel diameter.

Description

United States Patent 1 Baker 51 June 5,1973

[54] WEB-TRANSISIONING APPARATUS [75] Inventor: Noel John Baker, London, England [73] Assignee: Wilton-James Limited, Wembley,

England 22 Filed: May 10, 1971 21 Appl.No.: 143,696

[30] Foreign Application Priority Data May 8, 1970 Great Britain ..22,299/70 [52] US. Cl ..242/75.1, 242/7542 [51] Int. Cl. ..B65l'l 23/08 [58] Field of Search ..242/75.5, 75.42,

[56] 7 References Cited UNITED STATES PATENTS 2,892,597 6/1959 Schmidt ..242/7542 2,979,280 4/1961 Ralph ..242/75.42

Primary ExaminerGeorge F. Mautz Assistant ExaminerEdward J. McCarthy Attorney-Kirschstein, Kirschstein, Ottinger & Frank [57] ABSTRACT Apparatus for automatically tensioning a web of material being drawn from a reel, utilizing a belt engaging the side of the reel, the belt being in the form of a continuous loop contacting the reel surface and being driven in use of the apparatus to reduce the relative speed between the contacting surfaces of the belt and reel which might result in damage to the reel material, the belt being associatedalso with compensating means for maintaining a substantially constant tension throughout the life of the reel despite the gradual reduction in reel diameter.

7 Claims, 6 Drawing Figures 1 WEB-TRANSIS IONING APPARATUS This invention relates to web-tensioning apparatus of the kind comprising at least one tensioning belt arranged to engage the surface of a web-reel of material as the material is drawn from the reel in order to create a drag on the reel and hence impart a tension to the web, the invention being especially concerned with apparatus of this kind incorporating a tensioning device for varying the tension in the belt in order to control the tension in the web.

Such apparatus may, for example, form part of a fluid control system which automatically corrects for changes in web tension in order to maintain the tension in the web at a substantially constant value, the belt tensioning device in such an arrangement often being in the form of a piston and cylinder unit which is fed with fluid such as air at controlled pressures related to the tension in the web to effect the required degree of control.

It will, however, be observed that as the web of paper or like material is drawn from its reel the diameter of the reel decreases; as a result the angle of wrap of the tensioning belt around the reel also decreases, so that means are commonly provided for gradually increasing the fluid pressure as the reel becomes smaller in order to maintain the constant tension in the web. The pressure limits of the system needed to maintain a substantially constant tension in the web throughout the life of a reel in such an arrangement depend upon the initial and final diameters of the reel, and the required range of pressures can in some cases be considerable.

Also in such apparatus the tensioning belt is normally stationary. While this is generally satisfactory for most purposes it has not proved successful for some applications. Thus in the production of newspapers having colored or partially colored pages it is customary to print the colored matter separately, the printed or partially printed web being rewound into a reel which is subsequently fed into a printing press for insetting into the normal pages of newsprint. If, however, such preprinted matter lies on the surface of the web which contacts such a static tensioning belt it may be damaged as a result of the dragging effect of the belt, particularly where the web is drawn from the reel at high speed.

An object of the present invention is to provide a form of web tension control arrangement which is less subject to the above disadvantages.

According, therefore, to the invention in web tensioning apparatus of the kind referred to the tensioning belt is in the form of a continuous loop arranged to be driven at such speed in use of the apparatus as to reduce the relative speed between the contacting surfaces of web and the belt, the belt passes over at least one pulley which is movable to vary the tension in the belt under the control of a tensioning device, and compensating means are provided between the tensioning device and said pulley for varying the ratio between the tension applied by the tensioning device and the tension imparted to the belt, such that the increase in the tension of the belt for a given increase in tension applied by the tensioning device increases as the reel diameter decreases.

A reduction in the relative speed of the contacting surfaces of the web and belt to a sufficiently low value enables the apparatus to be safely used for controlling the tension in a preprinted web without risk of damage to the printed material.

In addition the variation in the ratio of the tension applied by the tensioning device and that imparted to the belt as the reel diameter decreases effectively narrows the pressure limits normally required for the control system, and by a suitable designing the compensating means it becomes possible to maintain a substantially constant tension in the web for a given cylinder pressure throughout the life of a reel.

The compensating means may be provided by a pivoted cam to which a torque is arranged to be applied by the belt tensioning device and around which a strap connected to a carriage supporting the movable pulley is arrangedto be wrapped as the cam is rotated to increase the tension in the belt, the shape of the cam being such that the radius at which the cam acts on the strap to create the tension in the belt is reduced the further the strap is wrapped around the cam.

Preferably in such an arrangement the strap is secured to the cam surface and the cam is rigidly attached to a pulley, the belt tensioning device being arranged to apply a torque to the pulley. The tensioning device may, for example, comprise a pneumatic piston and cylinder unit operable by air pressure controlled automatically in response to variations in web tension, the piston being coupled to a further strap wrapped around the pulley in such a manner that an increase in the pressure of fluid supplied to the cylinder produces a rotation of the pulley and hence of the cam in such a direction as to cause the first strap to be wrapped further round the surface of the cam.

In an alternative arrangement a movable pulley around which the belt passes is supported eccentrically between a pair of coaxial gear wheels movable along cooperating parallel racks, the belt tensioning device acting on the gear wheels to produce a movement of the latter along the racks, and the eccentric disposition of the movable pulley being such that the distance between its axis of rotation and the plane containing the pitch line of the racks decreases as' the gear wheels are moved in the direction of increasing tension.

It will be seen that for a given increase in tension applied by the belt tensioning device a greater tension will be imparted to the belt when the distance between the axis of rotation of the movable pulley and the plane containing the racks is small, compared with that imparted to the belt when this distance is larger. I

Consequently by arranging for the distance between the pulley axis and the plane of the racks to be greatest when the belts contact'a full reel, and for this distance to decrease as the reel diameter is reduced, it is possible to maintain a substantially constant tension in the web with little or no change in control pressure throughout the reel life.

The tensioning device in this arrangement is also conveniently provided by a pneumatic piston and cylinder unit operable by air pressure control automatically in response to variations in web tension.

A single gear wheel and rack, with the pulley carried eccentrically by the single gear wheel could in some cases replace the two coaxial gear wheels of the arrangement above described.

In a further arrangement the movable pulley may be supported by an arm in which is itself pivotably supported by a carrier member movable under the control of the tensioning device, the apparatus including cam means acting on the arm to produce a pivoting movement thereof as the carrier member is moved by the tensioning device in a manner such that movement of the carrier member in the direction of increasing tension causes the ratio of the tension imparted to the belt to that applied by the tensioning device to the carrier member to be gradually increased.

Various other forms of compensating means capable of varying the ratio between the tension applied by the tensioning device and that imparted to the belt in the appropriate sense as the reel diameter is reduced may similarly be employed.

In general a number of tensioning straps will be employed each with an associated tensioning device and compensating means.

In order that the invention may be readily understood three different embodiments of web tensioning apparatus in accordance with the invention will now be described by accompanying schematic drawings.

In the drawing FIGS. 1 and 2 represents diagrammatically and not to scale a side view and an end view of a reel stand incorporating one form of web tensioning apparatus in accordance with the invention,

FIG. 3 represents a side view of a similar reel-stand incorporating the second fonn of web-tensioning apparatus,

FIG. 4 illustrates a plan view in part section of part of the web-tensioning apparatus of FIG. 3, and

FIGS. 5 and 6 represent also diagrammatically, a sectional side view and end view of part of the third webtensioning apparatus.

Referring first to FIGS. 1 and 2, these illustrate a reel-stand 1 comprising a three-armed spider 2 consisting, in known manner, of two spaced members 3 (FIG. 2) mounted on a common shaft 4 and each having three support arms 5 for supporting a running reel and replacement reels. The spider is capable of being rotated to bring a replacement reel R1 into the running positions R2 when the web 6 on the running reel has nearly expired, means (not shown) of any suitable kind being associated with the reel-stand for severing the expiring web and joining the end of the new web to the severed end of the expiring web when the replacement reel has been run up to the appropriate speed.

The reel-stand incorporates web-tensioning apparatus comprising four tensioning belts 7 arranged to engage the surface of the running reel, and means are provided for automatically varying the tension in the belts inorder to control the tension in the web 6 as will subsequently be explained. Each belt is in the form of a continuous loop supported by a system of pulleys P1 to P6, one of which pulleys (P1) is arranged to be driven for example by an electric motor M0 in use of the apparatus at a rate such that the region of the belt 7 which contacts the surface of the running reel travels at a speed which is only slightly less than the peripheral speed of the reel. Control means C responsive to web speed may be used to control the speed of the motor, although the latter may be arranged to operate in synchronism with the motor or motors driving the press or other machine into which the web is drawn, the size of the pulley P1 or the gearing between the motor Mo and the pulley being selected to obtain the desired relative speed between the belt 7 and the web 6.

In an alternative arrangement the motor Mo may be omitted, the pulley P1 being driven by a main machine motor through suitable gearing.

The pulley P2 is supported by a carriage 8 which is movable in guide slots 9 in a support frame 10, in such a manner as to control the tension in the belt, the tension being increased by a downward movement of the carriage 8 and decreased by an upward movement of the carriage. I

The carriage 8 has attached to it one end of a strap 12 which passes downwards from the carriage around a fixed pulley 13 and is attached at its opposite end to a cam 14 in such a manner that rotation of the cam in one or other direction about its axis wraps the strap around or unwraps it from the cam surface.

A drive pulley 15 is rigidly secured to the shaft carrying the cam 14 to one side of the cam and a further strap 16 is attached to the periphery of the pulley 15, this further strap passing around a further pulley 17 carried by a piston 18 working within a pneumatic cylinder 19. In use of the apparatus the pressure of air supplied to the cylinders 19 associated with the respective tensioning belts is controlled in response to signals from a monitoring unit M, of any suitable kind, responsive to variations in the tension of the web, in such a sense as to tend to maintain the web tension approximately constant. I

The monitoring unit M conveniently comprises a piston and cylinder unit 41 having its piston connected to one end of an arm 42 fixed at approximately its center to a shaft 43 to which are attached further arms 44 carrying a roller 45 around which the web 6 passes as shown in FIG. 1.

In use of the apparatus air at a preselected controllable pressure is supplied to the piston. and cylinder unit 41 in such a sense as to urge the arm 42 and hence the arms 44 in a direction which opposes and counterbalances the web tension forces acting on the roller 45. There is also provided a variable-output-pressure lever operated valve 46 fed from a constant pressure source, the operating lever of the valve also being coupled to the arm 42 so that the output pressure is proportional to the arm and

roller assembly

42, 44, 45 which will vary as a result of variation in web tension.

The output pressure of the valve 46 is applied to the pneumatic cylinder 19 in such a sense as to compensate for web tension changes. I 1

Thus if the web tension tends to decrease, the pressure of air supplied to the cylinders 19 increases forcing the respective pistons outwards and causing the straps 16 to rotate the pulleys 15 and cams 14, this causing the straps 12 to be wrapped further around the respective cams and urging the carriages 8 downwards, thereby increasing the'tension in the belts 7 and exerting an increased drag on the running reel to restore the tension in the web. Similarly an increase in web tension results in a reduction in the pressure of air supplied to the cylinders 19, and as a result the carriages are permitted to move upwards to reduce the tension in the belts 7 as the straps 12 are unwrapped from the respective cams.

It will be seen that sincev each drive pulley 15 is of constant radius, the torque applied to the drive pulley in order to increase the web tension will be proportional to the pressure of air supplied to the respective cylinder 19. This torque will rotate the pulley to cause the strap 12 to be wrapped further round the surface of the respective cam, and the latter is so shaped that as the angle of wrap is increased the radius at which the strap 12 is acted upon by the torque in the drive pulley 15 decreases and hence the tension applied to the respective tensioning belt 7 will increase at a continuously greater rate than the tension applied to the strap In this way the tension in the belts 7 is increased gradually as the web is drawn from the reel so as to compensate for the reduction in reel diameter, and by suitable choice of cam it is possible to maintain a substantially constant tension in the web for a given cylinder pressure throughout the life of the reel.

In the second embodiment illustrated in FIGS. 3 and 4, the tensioning belts 7 similarly pass around a system of pulleys P11 and P17, the pulley P11 being driven in order to drive the belts at a slightly slow speed than the periphery of the running reel as in the embodiment previously described; the movable pulley P2 of the previous embodiment is in this case replaced by a pulley P12 which is supported eccentrically between two coaxial gear wheels 22 on a shaft 23 about which it is free to rotate.

The gear wheels 22 are supported in contact with a respective pair of racks 25 by a carriage 24, the carriage being constrained to move in a direction parallel to the direction of the racks by means of a pair of guide grooves 26 in a support frame 30 in which rollers 27 mounted at the sides of the carriage engage. The carriage is connected to the end of a piston 28 working within a pneumatic cylinder 29, and in use of the arrangement the pressure of air supplied to the cylinders 29 associated with the respective tensioning belts is controlled in response to signals from a monitoring unit M in dependence upon the tension in the web in such a sense as to maintain the web tension approximately constant, as in the embodiment illustrated in FIGS. 1 and 2.

Thus the arrangement is such that an increase in the pressure of air supplied to a cylinder 29, resulting from a reduction in web tension urges the piston 28 inwards imparting a greater tension to the respective belt 7. At the same time the rotation of the gears along the racks results in the axis of the pulley P2 approaching the plane containing the pitch lines of the racks 25. The path of the pulley axis is indicated by thebroken line A and it will be seen that if the distance from the pulley axis to the plane of the racks is greater than the pitch circle radius of the gears the tension in the belts for a given tension in the piston rod will be less than if this distance is smaller than the pitch circle radius of the gears; then as the piston moves inwards to compensate for the reduction in web tension resulting from the decrease in reel diameter the tension applied to the belt for a given increase in cylinder pressure will gradually increase, becoming a maximum at the minimum reel diameter. The axis of the pulley P12 is offset from the axis of the gear wheels 22 by an amount such that the tension in the web substantially corresponds to a given cylinder pressure throughout the complete life of the reel.

The third embodiment is illustrated in part in FIGS. 5 and 6 and in this embodiment each of the belts 7 (shown only in part) passes around a series of pulleys arranged to maintain part of the belt in contact with the running reel as in the arrangements previously described. A pulley P22 replaces the pulleys P2 and P12 of the previous embodiments and is carried between two arms of a frame 31 pivotably supported by a spindle 32 carried by a carriage 33. The carriage 33 is secured to a piston 34 working within a pneumatic cylinder 35, and is constrained to move along a straight path perpendicular to the spindle and defined by a pair of grooves accommodating rollers 35 carried by the ends of the spindle. Further rollers 36 are mounted at the upper end of the frame and engage a pair of plate cams 37, the plates being so shaped that as the piston is forced inwards to compensate for the decrease in reel diameters the frame is pivoted by a gradually increasing amount in a direction tending to increase the tension in the belt 7 for a given movement of the carriage, and such that the tension in the web corresponds approximately to a given cylinder pressure throughout the life of a reel as in the arrangements previously described.

I claim:

1. Apparatus for tensioning a web of material as it is drawn from a reel of the material, comprising a. at least one tensioning belt engageable with the surface of the reel in order to create a drag and hence tension the web,

i. which belt is in the form of a continuous loop drivable at a speed such as to reduce the relative speed between the contacting surfaces of the belt and the reel,

b. a movable pulley around which the belt passes,

c. a tensioning device controlling the movement of the pulley so as to vary the tension in the belt and control the web tension, and 1 d. compensating means between the tensioning de vice and the pulley capable of modifying the force applied to the pulley in response to changes in the output of the tensioning device,

i. so as to vary the ratio between the tension applied by the tensioning device and that imparted to the belt by the pulley,

ii. in a sense which produces a greater increase in belt tension for a given increase in tension applied by the'tensioning device, as the reel diameter decreases.

2. A web tensioning apparatus according to claim 1 wherein the compensating means includes a pivoted cam to which a torque is arranged to be applied by the tensioning device, a carriage supporting the movable pulley, a strap connected to the carriage, said strap being arranged to be wrapped around the pivoted cam as the cam is rotated to increase the tension in the belt, the distance of the active part of the cam surface from the cam pivot decreasing as a cam is rotated to tighten the strap, thereby increasing the tension in the strap for a given applied turning force as the reel diameter decreases.

3. A web tensioning apparatus according to claim 2 wherein the strap is secured to the cam surface, wherein a further pulley is provided and the cam is rigidly attached to said further pulley and wherein the belt tensioning device is arranged to apply a torque to the further pulley.

4. A web tensioning apparatus according to claim 3 wherein the belt tensioning device comprises a pneumatic piston and cylinder unit operable by air pressure controlled automatically in response to variations in web tensioning, wherein a further strap is provided, said piston being coupled to said further strap, said further strap being wrapped around the further pulley in such a manner that an increase in the pressure of fluid supplied to the cylinder produces a rotation of the further pulley and hence of the cam in such a direction as to cause the first strap to be wrapped further around the surface of the cam.

5. A web tensioning apparatusaccording to claim 1 wherein the compensating means comprises a gear wheel and a rack, said gear wheel being movable along said rack under the control of the tensioning device, the movable pulley being eccentrically supported by the gear wheel so that the distance between the axis of rotation of the pulley and the pitch line of the rack decreases as the gear wheel is moved in the direction which increases the tension in the belt.

6. A web tensioning apparatus according to claim 1 wherein the compensating means comprises a pair of coaxial gear wheels and cooperating parallel racks, said gear wheels being movable along said racks, the belt tensioning device acting on the gear wheels to produce a movement of the latter along the racks, the movable pulley being eccentrically supported by the gear wheels in a manner such that the distance between the axis of rotation of the pulley and the plane containing the pitch line of the rack decreases as the gear wheels are moved in the direction which increases the tension in the belt.

7. A web tensioning apparatus according to claim 1 wherein the compensating means comprises an arm and a carrier member, the arm being pivotally supported by the carrier member, said carrier member being movable under the control of the tensioning device, the movable pulley being supported by the arm, and wherein the apparatus further includes cam means acting on the arm to produce a pivoting movement thereof as a carrier member is moved by the tensioning device in a manner such that a movement of the carrier member in the direction which increases the tension in the belt causes the ratio of the tension imparted to the belt, to that applied by the tensioning device to the carrier member, to be gradually increased.

UNITED STATES PATENT OFFICE I I a CERTIFICATE OF CORRECTION Patent No. ,737,115 Dated June S 1973 Inventor(s) NOEL JOHN BAKER It is certified that error appears in the above-identified patent Y and that said Letters Patent are hereby corrected .as shown below:

On the cover sheet [54] and column 1,, line 1,

"Web-Transisioning Apparatus" should read Web-Tensioning Apparatus.

Signed and sealed this 22nd day of January 1974'.

(SEAL) Attest:

EDWARD M.FLET( IHER,JR.. RENE D. TEGTMEYER I Attestlng Offlcer Acting Commissioner of Patents

Claims

1. Apparatus for tensioning a web of material as it is drawn from a reel of the material, comprising a. at least one tensioning belt engageable with the surface of the reel in order to create a drag and hence tension the web, i. which belt is in the form of a continuous loop drivable at a speed such as to reduce the relative speed between the contacting surfaces of the belt and the reel, b. a movable pulley around which the belt passes, c. a tensioning device controlling the movement of the pulley so as to vary the tension in the belt and control the web tension, and d. compensating means between the tensioning device and the pulley capable of modifying the force applied to the pulley in response to changes in the output of the tensioning device, i. so as to vary the ratio between the tension applied by the tensioning device and that imparted to the belt by the pulley, ii. in a sense which produces a greater increase in belt tension for a given increase in tension applied by the tensioning device, as the reel diameter decreases.

5. A web tensioning apparatus according to claim 1 wherein the compensating means comprises a gear wheel and a rack, said gear wheel being movable along said rack under the control of the tensioning device, the movable pulley being eccentrically supported by the gear wheel so that the distance between the axis of rotation of the pulley and the pitch line of the rack decreases as the gear wheel is moved in the direction which increases the tension in the belt.