US3039714A - Pneumatic web control device - Google Patents

Description

June 19, 1962 L. CAMPBELL ETAL 3,039,714

PNEUMATIC WEB CONTROL DEVICE 3 Sheets-Sheet 1 Filed Jan. 15. 1958 FIG. I

INVENTORS ALBERT L. PETERSON LEONARD CAMPBELL EMQ M m,@amn

PA A ZRNEYS FLOATING ROLLE DERS TENSION CYLINDER PRESSU BUILD CYLI N m T s F o E m T June 19, 1962 CAMPBELL ETAL 3,039,714

PNEUMATIC WEB CONTROL DEVICE Filed Jan. 15, 1958 FIG. 3

3 Sheets-Sheet 2 NTROL VALVE I 2 PER AIR MOTOR INVENTORS ALBERT L. PETERSO LEONARD CAMPBELL ATT RNEYS June 19, 1962 CAMPBELL ETAL 3,039,714

PNEUMATIC WEB CONTROL DEVICE Filed Jan. 15. 1958 5 Sheets-Sheet 3 INVENTORS ALBERT L.PETERSON LEONARD CAMPBELL ATTOR EY S I United States Patent Ofiflce 3,639,714 Patented June 19, 19-62 3,039,714 PNEUMATIC WEB CONTROL DEVICE Leonard Campbell, New Brunswick, and Albert L. Peterson, Westfield, N.J., assignors to Wood Newspaper Machinery Corporation, Plainfield, N.J., a corporation of Virginia Filed Jan. 15, 1958, Ser. No. 709,152 6 Claims. (Cl. 242-7542) This invention relates generally to a pneumatic Web control device and more particularly to an automatic web tensioning device incorporating a floating roller for maintaining substantially constant tension in a running web, pneumatic braking means actuated by movement of the floating roller for braking a rotating supply roll, and rate means for adjusting the characteristics of response of the brake means to the movement of the floating roller.

A prime requirement of high speed printing presses such as used in printing newspapers, is that the running web of paper passing to the printing press be kept at a substantially constant tension. If, for any reason, the tension of the web increases considerably, there is dang r that the Web will break. On the other hand, if the tension of the web decreases below a predetermined value, there is danger that the web will bunch up before entering the press. This latter condition will usually occur when the web is supplied from a rotating supply roll, which, due to its heavy mass, will tend to run ahead of the press if the press speed drops suddenly and if the floating roller and tensioning device are incapable of overcoming the change in tension of the running web.

The weight of a floating roller and the pivoted arm to which it is attached becomes an important factor in maintaining constant web tension when the pivoted arm moves beyond its vertical axis running through its pivot point. Thus, in application Serial No. 624,790 entitled, Web Tensioning Device, filed November 28, 1956, by A. L. Peterson, there is disclosed a spring for overcoming the weight of the floating roller and the arm to which it is mounted when the arm swings beyond its vertical axis. This application further discloses an electrical relay system incorporated in the brake control of the press Which will apply braking force to the rotating supply roll be fore the brakes of the press are actuated in order to compensate for the inertia of the rotating supply roll during an emergency stop of the press.

We propose in our present invention to eliminate the separate spring shown in the previously mentioned application which compensates for the weight of the roller and arm by utilizing a balance spring included in a pneumatic control valve. We further propose to provide for an easily adjustable rate means for varying the speed of response, amount and duration of reaction means used to return the floating roller to an original position so that substantially constant tension may be maintained on a web even during emergency stop of a web handling machine without the necessity of incorporating a phased electrical relay system between the brakes of the machine and the supply roll.

Broadly, We propose to use a variable pneumatic pressure control valve which has therein a pressurized reaction chamber having a flexible diaphragm at one end for overcoming the force necessary to depress a spring biased inlet valve contained in the control valve which allows pressurized air to be admitted to a tension cylinder and which returns the control valve to a balanced state. The tension cylinder in turn exerts pressure on a tension belt which passes over the rotating supply roll. A floating roller mounted on a pivoted arm is positioned between the machine and the rotating supply roll so that the running web will pass over its surface. The pivoted arm is urged in one direction by means of a reference force air motor and is pulled in the opposite direction by the tension of the web on the floating roller. Movement of the arm will actuate the control valve to allow air to be either exhausted from the tension cylin der or to be admitted thereto from a source of pressure.

Conduit means connect the reaction chamber of the control valve either with the tension cylinder or with a control pressure outlet port of the control valve so that pneumatic pressure in the reaction chamber will cause the flexible diaphragm to move and to compensate and oppose the force necessary to actuate the control valve. Rate of flow means are provided in the conduit for adjusting rate of flow of pressure air into the reaction chamber in order that the period and amount of response between application of braking force on the supply roll and return of the control valve to its balance position may be varied. The overall effect of such a system is to apply an initially greater pressure in the tension cylinder than is normally needed to maintain constant tension.

Referring to the drawings which illustrate a preferred embodiment of our invention,

FIG. 1 is a schematic view illustrating the position of the different parts of the web tensioning device with respect to supply rolls;

FIG. 2. is a graph illustrating pressure built up in the tension cylinder with regard to receipt of a stop signal by the press;

FIG. 3 is an enlarged side view of the floating roller and associated parts shown in FIG. 1;

FIG. 4 is an enlarged cross-sectional view of the control valve shown in FIG. 3; and

FIG. 5 is a partial View of FIG. 4 ilustrating a slightly different embodiment of means for varying the rate of response of the brake means incorporated in the tensioning device.

Referring initially to FIG. 1, supply rolls 1, 2 and 3 supply a web 4 to a web handling machine, normally a printing press, not shown. As illustrated in FIG. 1, web 4 is initially run off supply roll 1, while supply rolls 2 and 3 are reserve rolls which may swing in to paste onto web 4 when roll 1 is exhausted. A tension belt 5 passes over a portion of supply roll 1 so that when tension of the belt is increased by movement of the piston 6 in tension cylinder 7, a braking force will be imparted to the rotating roll. Tension cylinder 7 is in turn connected by conduit 8 to a control valve denoted generally by the numeral 9 in FIG. 3.

A floating roller 10 mounted on a pivoted arm 11 is placed between the rotating supply roll and the web handling machine and serves to provide a measure of constant tension in the running web. The arm 11, as shown in FIG. 3, is urged in a counterclockwise direction by means of a reference force air motor 12 which is connected by means of a conduit 13 to manual pressure con trol valve 14. Arm 11 is urged in a clockwise direction by the tension existing in the running web 4. A conventional damper 15 serves to slow the movement of the arm 11 about the pivot point 16 and to reduce hunting of the arm. The control valve 9, air motor 12, damper 15, and the linkage connecting these parts with the arm 11 are all incased within a housing 80.

Control valve 9 is actuated by movement of the floating roller 10 and arm 11 through link 20 and arm 21. Arm 21 is pivoted about the point 22 so that when the floating roller and arm 11 move in a counterclockwise direction, arm 21 will rotate about point 22 to depress a piston 30 which is slidable in housing 31 of the control valve 9. Roller 32 is mounted on the end of arm 21 in order to reduce friction of contact between the arm and the piston. Adjustable stops 33 and 33' limit movement of the arm 21 while adjustable stops 34 and 34' limit movement of arm 11 by hearing on portion 35 and 3-5 thereof.

Control valve 9 has a flexible diaphragm 40 having therein an aperture through which a tube 41 is fixedly attached. Piston 30 is biased outwardly of the housing by means of control spring 42 and is movable with respect to tube 41. Spring 42 is of such strength as to balance; the effect of gravity on floating roller 1%) and arm 11 when the arm swings beyond its vertical axis. Piston '30, housing 31, flexible diaphragm 40 and tube 41 all cooperate to form an exhaust chamber 43 which is connected to a conduit not shown, which in turn leads to atmospheric pressure.

The side of the diaphragm opposite spring 42 forms with housing 31 and tube 41 a reaction chamber 44 which has therein a spring 45 biasing said diaphragm to the left as shown in FIG. 4 against the force of spring 42. Reaction chamber 44 is connected by means of conduit 4-3 to tension cylinder 7 as shown in FIG. 1 so that pressure buildup in the chamber is dependent on pressure in the tension cylinder. A rate valve 47 in conduit 46 varies the rate of pressure build-up in the reaction chamber.

Tube 41 terminates at one end in an exhaust valve seat 50 which is adapted to be sealed by valve face 51 of slidable poppet 52. Poppet 52 has on the end opposite that of face 51 a valve face 53 which cooperates with seat 54 to form an inlet valve. Poppet 52 is biased to the left as shown in FIG. 4 by means of spring 55. The space between valve faces '51 and 53 comprises a pressure chamber 56 which is connected by means of conduit 8 with tension cylinder 7. Inlet valve 53 opens into conduit 57 which is connected to a source of pressure, not shown. The pressure chamber 56 is sealed from the exhaust chamher by means of ring '58 carried in the lower half of housing 31 and through which tube 41 may slide when moved by diaphragm 49.

A slightly modified form of the invention is shown in FIG. Where a conduit 60 connecting pressure chamber 56 with reaction chamber 44. Conduit 60 has therein an adjustable rate valve 61 to vary the rate of pressure buildup in the reaction chamber until it equals the pressure in the pressure chamber. It is to be understood that the size of the pressure chamber 62 varies with the length of conduit 60 and with the desired rate of pressure build-up in the reaction chamber. When this form of the invention is used, conduit 69 is, in effect, substituted for conduit 46.

The operation of the device to maintain substantially constant tension in the web throughout all phases of press operation is readily apparent by referring to FIGS. 1, 3 and 4. A desired pressure to give a desired tension in the web is initially set in the system by means of manual pressure control 14. This in turn will impart pressure in reference loading air motor 12 which will move arm 11 in a counterclockwise direction to put tension into web 4.

Arm 11 will move to the left under the influence of pressure in the air motor. This in turn will move link 20 and arm 21 so at to depress piston 30 in the control valve. Depression of piston 30 will in turn exert a force on control spring 42 causing flexible diaphragm 40 and 41 to move in a right hand direction from a neutral position as shown in FIG. 4. This movement of tube 41 will bring exhaust seat 59 into contact with exhaust face 51 of the poppet 52 to close the exhaust port. Further movement of the tube 41 will depress poppet 52 against spring 55 to open the inlet port and so allow admission of pneumatic pressure from conduit 57 into the chamber 56. Increase of pressure in pressure chamber 56 will in turn be transmitted to the tension cylinder 7 through conduit 8 to cause piston 6 to move to the left to increase the tension in tension belt 5 and so exert a braking force on the rotating supply roll 1. As a result the rotating supply roll will slow down and so tend to increase the tension in the moving web which will cause arm 11 and floating roller to move back in a clockwise direction.

' The weight of floating roller 1t) and arm 11 have an increasing moment about the pivot point 16 as they move to the left. Under static or slow changing conditions, this moment is balanced by the compression of spring 42 when flexible diaphragm 40 is in a neutral or nearly neutral position, as shown in FIG. 4, and when control valve 9 is in a balanced position neither delivering to nor exhausting appreciable amounts of air from cylinder 7.

However, when the change in tension is appreciable and such that the flexible diaphragm is moved rapidly to the right as shown in FIG. 4, the spring 42 must be compressed to a shorter length in order to generate a force suflicient to balance the moment due to the weight of the arm 11 and roller 10 in their new position. This is accomplished by having pressure build-up in the reaction chamber 44 to eventually equal that in the tension cylinder 6 or, as shown in alternate embodiment, the pressurized chamber 62, which will cause diaphragm 46 to return to its original position and so compress spring 42.

Any delay in pressure build-up in conduits 46 or 60 Will in turn cause a delay in pressure build-up in the reaction chamber and a consequent delay in the spring 42 being able to produce a balancing force. This delay in producing a balancing force will result in the roller continuing its movement to the left under the force of the air motor and increasing moment. The result is that the diaphragm will move even further to the right and so allow even more pressure build-up in the tension cylinder.

This motion of the floating roller might be considered as a self energizing action which tends to increase the amount of air flow to the tension cylinder and thus speed up the corrective action. Further, the falling over of the floating roller tends to take up web loop rapidly as tension of the web decreases.

It can be cited that the reverse of the above operation can occur if there is an increase in tension. The self energizing action can occur but in the opposite sense. In other words, the floating roller becomes lighter and the corrective action is sped up from the tension cylinder.

When tension in the web has been increased by application of braking force on the rotating supply roll and after the pressure in the reaction chamber is equal to that in the tension cylinder or chamber 62, the arm 11 and roller will move to the right. Spring 45 and pressure in reaction chamber 44 will then move diaphragm 40 to the left back to the neutral position. Any further movement of the diaphragm to the left, will open the exhaust port so allowing pressure to exahust from tension cylinder 7 to decrease tension in the web.

If the web handling machine speeds up momentarily, the tension of the web will increase so causing arm 11 to rotate in a clockwise direction. This will in turn allow piston 30 to move outwardly of the control valve and to let the flexible diaphragm 40 and tube 41 move to the left under the influence of pressure in the reaction chamber 44 and spring 45 with the result that the exhaust valve will open while the inlet valve remains closed. Pressure in the tension cylinder and thus braking of the supply rolls will, therefore, decrease to compensate for the increase of tension in the web due to the increase in machine speed.

If there is an emergency stop of the machine so that the tension in web 4 drops sharply, it is obvious that floating roller 10 will move quickly to the left in order to compensate for the sharp decrease in tension. This in turn will move piston 30 violently against spring 42 and flexible diaphragm 40 and so cause the tube 41 to open the inlet port at valve 53 to allow a large amount of pressure build-up in the tension cylinders. There will be a momentary period of time before pressure in the reaction chamber 44 will build up to equal the pressure exerted in the tension cylinder, as shown in FIG. 4, or the pressure chamber, as shown in FIG. 3, due to the pressure drop across either rate control valves 47 or 61. During the period while pressure in the reaction chamber is building up, maximum pressure will be exerted on the tension cylinder while at the same time the floating roller will be seeking its maximum pressure or tension position. The net result of incorporating a rate control means in the control valve is that pressure build-up in the tension cylinders may be accelerated with relation to receipt of a stop signal by the web handling machine. This feature is shown in FIG. 2 which is a graph illustrating rate of pressure build-up in tension cylinders with respect to receipt of a stop signal by a press. It is seen from an inspection of FIG. 2, that pressure builds up in the tension cylinder faster when rate control means are provided.

We have found that by incorporating a tension control device such as disclosed, that substantially constant tension may be maintained on a moving web under all conditions of web handling machine operating speeds. The rate control means disclosed provides a practical and eflicient means of varying the rate of braking force to be applied to a rotating supply roll with the movement of a floating roller while at the same time compensating for the inertia of the heavy rotating supply roll.

Having described our invention, reference should now be had to the claims which follow for determining the scope thereof.

We claim:

1. A web tensioning device for controlling tension of a web running from a rotating supply roll to a web han dling machine under all running speeds, comprising a vertically extending floating roller pivoted for rotation about its lower end contacting said web to measure and maintain substantially constant tension in said movable Web, a variable pressure control valve connected to a source of pressure and actuated by movement of said floating roller, a pressure chamber in said control valve, a reaction chamber in said control valve communicating with said pressure chamber, a flexible diaphragm comprising one side wall of said reaction chamber, a control spring bearing on said diaphragm and positioned between said diaphragm and said floating roller to compensate for change of effective Weight of said floating roller due to movement beyond the vertical axis, pressure operated braking means operable by actuation of said variable pressure control valve for exerting braking force on said rotating supply roll, and rate control means for varying the rate of pressure build up in said reaction chamber when said variable pressure control valve is actuated by movement of said floating roller.

2. A web tensioning device controlling tension of a web running from a rotating supply roll to a press, comprising a floating roll contacting said web, a vertically extending arm pivoted for rotation about a fulcrum at its lower end and having said roller mounted on one end thereof, motor means urging said arm and roller in a direction about said fulcrum to increase tension in said web, a variable pressure control valve connected to a source of pressure and actuated by movement of said floating roller and arm about said fulcrum, a pressure chamber in said control valve, a reaction chamber in said control valve commuting with said pressure chamber, a flexible diaphragm comprising one side of said reaction chamber, a control spring bearing on said diaphragm and positioned between said diaphragm and said arm to compensate for change of moments due to change of position of said arm and roller about said fulcrum, pressure operated braking means operable by actuation of said variable control valve for exerting braking force on said rotating supply roll, and rate control means for varying the rate of pressure build up in said reaction chamber when said variable pressure control valve is actuated by movement of said arm to increase pressure in said pressure chamber; pressure build up in said reaction chamber causing said diaphgram to move against said control spring to return said variable pressure control valve to a neutral position.

3. A web tensioning device according to claim 2 wherein said reaction chamber connects by a conduit to said pressure chamber and said rate control means are interposed in said conduit.

4. A web tensioning device according to claim 2 wherein said braking means comprises a pneumatic tension cylinder in communication with said pressure chamber whereby admission of pressure in said pressure chamber increases pneumatic pressure in said cylinder to increase braking force on said rotating supply roll.

5. A web tensioning device according to claim 4 wherein said reaction chamber connects by a conduit to said tension cylinder and said rate control means are interposed in said conduit.

6. In a web tensioning device for controlling tension of a web running from a rotating supply roll to a press by means of a floating roller mounted on a vertically extending arm movable about a fulcrum located on the lower end of said arm wherein movement of said arm in response to change of tension in said web varies braking force applied to said rotating supply roll; the improvement comprising a variable pressure control valve having therein a pressure chamber, an exhaust chamber and a reaction chamber, a piston movable in said exhaust chamber and in response to movement of said arm, a first spring urging said piston outwardly of said exhaust chamber to balance moments due to the weights of said arm and roller when out of vertical alignment, a flexible diaphragm separating said exhaust chamber and said reaction chamber and bearing on said first spring, a second spring in said reaction chamber urging said diaphragm in a direction opposite to said first spring, a movable poppet having thereon an exhaust face and an inlet face, an exhaust seat fixedly positioned with respect to said flexible diaphragm adapted to engage said exhaust face, an inlet seat fixedly positioned with respect to said housing and adapted to engage with said inlet face, a third spring biasing said poppet to seat said inlet face on said inlet seat, conduit means connecting said pressure chamber with said reaction chamber, and rate control means interposed in said conduit means for varying the rate of pressure build up from said pressure chamber to said reaction chamber.

References Cited in the file of this patent UNITED STATES PATENTS Germany July 21, 1952

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