US3464644A - Device for winding off flexible material - Google Patents

Description

Sept. 2, 1969 R T ETAL 3,464,644

DEVICE FOR WINDING OFF FLEXIBLE MATERIAL Filed May 12, 1967 INVENTORS (J's/m KARA m AT'A j TEVAN C. L EBONOI/IC ATTORNEY United States Patent 3,464,644 DEVICE FOR WINDING OFF FLEXIBLE MATERIAL Jean Karamata and Stevan Celebonovic, Geneva, Switzerland, assignors to Rolpa S.a.r.l., Carouge-Geneva, Switzerland, a corporation of Switzerland Filed May 12, 1967, Ser. No. 638,092 Int. Cl. B65h 25/22 US. Cl. 24275.43 8 Claims ABSTRACT OF THE DISCLOSURE A device for unwinding flexible material rolled on a rotary support, said material acting on a movable member operatively connected to a brake acting on the support, wherein an arm is located at such a point that it is subjected to a force varying in relation with the radius of the winding of the material on said support, said variable force controlling the braking action of said brake.

Background of the invention In the different technical fields, it is often desirable to wind off some flexible material rolled on a rotary support so that the tension to which the material is subjected remains constant. It is necessary that the tension of the material is not influenced by the variations of the speed of the unrolling, or by the variation of the diameter of the rolling up on the rotary support, the diameter is continually diminishing with the winding 011 of the material.

The simple devices which permit an unrolling at a reasonably constant tension, include an arm which acts on the brake of the rotary support, the wound off material running over a cylinder or over a wheel held by the free end of said arm so that said arm is displaced more or less according to the tension of the body. The brake is maintained tight by a spring or something similar, and the tension of he wound off material acts so that the brake is loosened with an alternative action of the spring. As soon as the tension of the material falls under a determined value, the brake tightens while, when the tension becomes too great, the brake is loosened. Such devices are, for example, being used on rolling machinesto make electric windings.

In such devices, a variation of braking of the rotary support is controlled by the variation of the tension of the body in such a way that a constant tension of the body which is being unwound cannot be obtained.

In order to obtin a constant tension, much more complicated devices have been developed, including electronic devices which yield excellent results but which are also very costly.

The present invention is directed to a very simple device which permits obtaining an extremely constant tension of the material which is being wound off from the rotary support.

Summary of the invention This invention relates to a device for winding off a length of flexible material rolled on a rotary support. When the material leaves the support, it acts on an arm, the displacements of which influence a brake retaining the material on the rotary support in order to make the tension of the material reasonably constant. Such device is characterized by the fact that the arm is placed so as to be subjected to a force which depends on the radius of the material rolled on the rotary support, which force is conveyed to the brake.

3,464,644 Patented Sept. 2, 1969 Brief description of the drawing Description of the preferred embodiment With reference to FIG. 1, the device includes a frame comprising two metal plates 1 and 2 which are parallel and connected with each other by cross-bars 3. The material which is to be wound ofl is a roll of paper 4 carried by an axle 5 which is rotatable within two bushings 6 and 7 respectively, which are secured to the metal plates 1 and 2.

The paper is wound off from roll 4 in the form of a strip 8 passing over a roller 9. The strip of paper is pulled by a take-up device, not shown, for feeding a machine which can be used for example, to make rolls formed by several strips placed one over the other, or a machine dispensing paper in sheets.

The roller 9 is fixed in such a way as to rotate on an axle member 10 journaled in bearings 11 and 11 attached to the metal plates 1 and 2. The axle member 10 includes an arm 13, the position of which depends on the position of the roller 9. The arm 13 is connected by a rod 12 at right angles thereto to an arm 14 the movement of which is controlled by a piston 29 of a hydraulic system 15 for regulating the braking free of a "brake 16.

The brake 16 is a well known type of disk brake in which a disk 17 fixed on the end of the axle 5, runs through a slot in a block 18 which includes two shoes, not shown in FIG. 1, which are subject to the action of hydraulic fluid in the system 15 in order to exert the desired braking force on the disk 17.

The block 18 is slidably on the shaft 19 and its position can be adjusted in a manner parallel to the axis of the roll 4 by means of a screw 20 which has a knob 21 rigid therewith. Thus, by adjusting the position of the brake 16, the axial position of the roll 4 can be adjusted with great accuracy.

FIG. 2 shows diagrammatically the circuit of the hydraulic circuit which controls the brake 16. The circuit includes a first cylinder 22 which communicates through a pipe 23 with a second cylinder 24. The cylinder 22 is closed by a piston 25 which exercises a constant pressure on the liquid which fills the cylinders 22 and 24 and the pipe 23 under the effect of the weight 26 connected to the end of a lever 27 which acts on the piston 25. The pressure existing in the cylinder 24 is conveyed into a third cylinder 28 by means of a double acting piston 29. The liquid which is subject to the pressure of the piston 20 exerts a force on a shoe 30 which slides in a cylinder in the block 18. Said last-mentioned cylinder is connected with the cylinder 28 by a pipe 31 which communicates further with a cylinder 32 which is closed by a piston 33, which piston can be displaced by means of a screw 34.

The double acting piston 29 is connected with the end of the arm 14 which is secured by means of rod 12 to the arm 13 of axle 10 which carries the roller 9. The axis of the roller 9 is disposed on a line parallel to the axis of rod 12 connected to arm 13 and parallel to the axis of the roll 4.

The above described arrangement permits obtaining a constant tension of the strip of paper 8 when it is wound off the roll 4 as can be seen from the following considerations:

The forces which act on the piston 29 are the followmg:

(l) The force F, due to the pressure exercised by the piston 25, pushes the piston 29 towards the right, as

I X (cos ai) C G,

where r=rs, s being the radius of the roll 9.

Thus the resultant force Y acting on piston 29 is as follows:

The couple of braking M is proportional to Y and to the distance d which marks the radial distance between the axle S and the brake 16. That couple is as follows:

Where K is a constant depending on the type of brake utilized, on the dimensions of the pistons, of the coefficient of friction of the brake etc. The couple of braking is equal to the couple exercised on the axle by the tension X of the strip on the roll 4 of the the radius r which gives the following relation:

1" 1) X1 -KYd-Kd[FX(cos 01- By transforming the Equation 3 in order to obtain X, it results:

b s 1 Kb In the Equation 4, the only variable is r, so that it is possible to obtain that the tension X remains constant by cancelling the factor of r, i.e.:

1 fi d ac It is therefore necessary to construct the device as to a d T E 6 When the condition 6 is fulfilled, the Equation 4 becomes:

cos n+ (7) oralso:

a F 'ggi i As can be seen it is sufiicient to fix the initial force F, due to the pressure of the piston 25 in order to determine the tension X which one wishes to obtain on the strip 8 which is being wound ofi from the roll 4. Otherwise, the variation of the radius of the roll 4 automatically controls the modifications which have to be made in the braking in order to maintain constant the tension X of the strip. On account-of the very weak elasticity of the hydraulic control, the forces acting on the roller 9 are conveyed to the double acting piston 29 without the roller 9 being displaced appreciably. When the wear which shows up after a certain time on the brake 16 causes too great a displacement of the roller 9 in relation to its ideal posi- 4 tion, it is easy to return the roll into the desired position by tightening the screw 34.

The described construction can of course be easily modified so that the displacements of the roller 9 have practically no influence on the tension X of the tape. In fact, it is suificient, on one hand, to place the revolving point-of the arms'13, 14 on the axis of the axle 5 and, on the other hand, to place the cylinder 35 so that the angle a is nil. In that way, the angle which the tape 8 coming out of roll 4 forms with the arms will be constant because the point of connection of the arms corresponds with the axis of the roll 4. Furthermore, displacements of substantial magnitude of roller 9 cause only a very small variation of the angle a. The pressure exerted on the arms fixed in this manner will be, to a great extent, independent of the position of said arms.

It is understood that the principle of the device described can be applied to different technical fields. Its use seems particularly indicated in the case of winding mechanisms for electric Wires or for textile fibres as well as for braking paper rolls in printing presses.

The device described can be modified and, particularly, the double piston can be replaced by two elastic tubes connected to the arm 14. By an appropriate choice of the dimensions of the whole arrangement and the distances a, b and c, it is possible to obtain a simple correspondence between the pressure in the cylinder 22 and the force of traction to be exercised on the strip 8. For example, it is possible to obtain a force of traction of 1 kg. on the strip 8 for a pressure of 1 kg./cm.

As another solution, the same result can be obtained by using a braking device including two brakes, one of which can be regulated so as to furnish a constant braking force, while the other will be connected with roll 9 so as to furnish a braking force which will be proportional to the result of the forces which act on roll 9.

The constant pressure exerted on the face of piston 29 by the liquid which is subject to the weight 26 can also be obtained mechanically by a spring which acts directly on the piston 29. It should be noted that in such case, like in the one represented in the drawing, the force due to the tension of the strip is opposed to the constant force, which is very advantageous in order to obtain a good compensation of the dynamic effects. In fact, when the traction exerted on the tape 8 ceases suddenly, the tension of the tape becomes nil, and all the constant force acting on the piston 29 becomes available in order to assure the braking of roll 4. In that way, that roll is blocked almost immediately.

It is understood that the described principle of regulating can also be realised with the same efficiency by providing a mechanical connection between the roller 9 and the brake. The brake can be of any type, such as a brakeshoe directly acting on axle 5. At any rate, it seems-preferable, in the latter case, that the shoe includes a portion which enters into at least one ridge in form of a-V pro- 7 vided on the axle 5, so that, by displacing the shoe sidewards, the axial position of the axle 5 can be fixed at the same time.

til)

In any case, it is of advantage to build in a shock absorber, preferably a hydraulic one, in order to resist the rapid displacements which could arise on roller 9 by the sudden variations of the tension of the strip. Such varia tions happen, in fact, when the roller has a slight defect in its centralizing, and it is preferable to avoid a condition where the variations exert a reaction on the braking force.

We claim:

. 1. In a device for maintaining constant tension on a rotary support from which a roll of strip material is being unwound, a hinged arm on which the material leaving the support exerts a force proportional to the tension of the material and the function of the relative diameter of the roll of material on the rotary support, a brake acting on said rotary support, said arm being subjected to a return force and acting on said brake, said device characterized by the fact that said return force is selected so as to balance the action of the constant component of the forces exerted by the material on said arm for a given unwinding tension, the length of said arm and the location of its hinge axis being selected as a function of the braking coefiicient, so that the component of the forces, which is variable depending on the diameter of the winding, produces a braking torque equal to the product of the tension on the elongated body and the radius of the roll of material.

2. A device as claimed in claim 1, including a roller connected with said arm, said material being in contact with said roller, said roller located substantially in a plane defined by the axis of the roll of strip material and the hinge axis of said arm.

3. A device as claimed in claim 2, wherein the distance between the rotary support and the point of action of the strip material on said arm is determined in terms of the relation of transmittal of the force exerted on the arm against the brake and is dependent on the constant of the brake.

4. A device as claimed in claim 3, wherein the brake is hydraulic and said arm acts on a piston controlling the hydraulic circuit of said brake, said piston being subjected to a substantially constant force opposite to and higher than that applied by the arm.

5. A device as claimed in claim 4, including a second hydraulic circuit adapted to produce the substantially constant force acting on the control piston.

6. A device as claimed in claim 4, wherein a weight applies said substantially constant force to said control piston.

7. A device as claimed in claim 4, wherein said hydraulic circuit acting On the brake comprises an adjustable piston for wear take-up of the brake.

8. A device as claimed in claim 1, wherein said brake is a disc brake and the shoes of said brake are carried by an adjustable block which is movable in parallelism with the axis of the rotary support, said support being rotatably and slidably mounted in bearing means so that the axial position of the rotary support is set by the position of the brake block.

References Cited UNITED STATES PATENTS 1,859,577 5/1932 Armbrecht 242--75.43 1,884,183 10/1932 Pearson 24275.43 2,965,326 12/1960 Rockstrom 24275.43

NATHAN L. MINTZ, Primary Examiner

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