GB2071802A - Improvements relating to movement control devices - Google Patents

Abstract

As sheet material (1) unwinds from a roll (3) the size of the roller decreases and allows a biased follower arm (4) to move towards the roll centre. The arm (4) carries a bracket (7) on which is mounted a control member (8) from which extends a plunger (9) into contact with the surface of a cam (10). The control member, eg a potentiometer or valve, will act on a brake or clutch device associated with the roll (3) so as to ensure a constant run speed for the material (1). The cam (10) can be moved to various positions so as to modify the extent to which the plunger (9) projects from the control member (8), as it moves around the cam. In alternative embodiments the cam is adjustably mounted on the arm and coacts with a fixed but adjustable control member or it determines the pivot point of a lever which transmits movements of the arm to the control member. <IMAGE>

Description

SPECIFICATION Improvements relating to movement control devices This invention relates to devices which can produce a variable output in response to the movement of an arm, the output being used to control the operation of a member which is associated with the arm movement. A particular application is in the field of tension controllers used to control the operation of unwind brakes or rewind clutches on reels for wound webs.

In many such installations the unwind stand is fitted with a pneumatic brake controlled manually by the operator. Failure of the operator to adjust the air pressure energising the brake as the reel unwinds, will cause an increase in tension with possible web breakage or slippage of reel on core shaft. Also as rotation speed increases, overheating and damage to brake can occur.

Where rewind shaft is driven through pneumatic clutch, the converse situation can occur.

Clutch pressure and torque must be increased as the reel diameter builds up. Incorrect setting of a manually controlled system can result in too high a setting at the start of winding with possible breakage or clutch damage. Insufficient torque will cause loss of tension, and possible failure to complete winding of the reel.

It is an object of this invention to provide a device which will enable tension controllers to be operated in such a way that the tension may be maintained at a constant level even though the diameter of the reel being wound is constantly increasing or decreasing.

Accordingly, this invention provides a variable output device whose output will be a function of the position of a pivotally mounted arm and comprising the arm, a cam, a control member whose output depends upon the po.- sition ofsa plunger extending therefrom into contact with the surface of the cam, the cam being movable with respect to a reference position to a state whereby, as the arm rotates about its pivot point, the cam provides a varying path for the plunger.

Where such a device is used as a tension controller the arm will be the arm which follows the surface of the reel as the reel diameter changes and the control member will control the operation of the brake or clutch associated with the reel during unwinding or winding respectively.

It may be desirable to be able to set the cam in a neutral position in which movement of the arm will not alter the position of the plunger as the plunger moves relative to the cam surface.

The device could be so arranged that the cam is mounted on the arm but is adjustable with respect to the arm and acts on the control member which is fixed to a stationary part of the apparatus. Preferably, however, the control member is carried by the arm and the cam is mounted about a pivot point which is displaced from that of the arm. With this latter form of arrangement the cam can be a circular cam. Ideally the position of the control member relative to the arm will be adjustable so that a predetermined minimum operational value of the control member can be set into the device. Thus the control member could be slidably adjustable on a bracket extending from the arm.

Where the control member is to be used to control an electrical or an electronic circuit (for example to determine the speed of a motor) the control member could be a potentiometer whose resistence value varies with movement of the plunger. Alternatively the control member can be a pneumatic or hydraulic pressure control valve. The control valve could then control the applied pressure of a brake or clutch device.

Ideally, the arm is lightly biassed against rotation. This biassing can be provided by a ram whose operation can be reversed to withdraw the arm in a direction opposite to the biassing direction. The means for reversing operation of the ram is preferably linked with means for switching off the control member.

It is also preferred that the degree of biassing applied to the arm should be adjustable.

From a further aspect, the invention provides a variable output device whose output will be a function of the position of a pivotally mounted arm and comprising the arm, a control member whose output depends upon the position of a plunger extending therefrom, a cam controlled member in contact with the plunger, the arm being linked with the control member or the cam controlled member, the cam being movable to a position which will cause varying movement of the plunger as the arm rotates about its pivot point.

Such a device may generally take one of the forms defined above. As an alternative, the cam controlled member could be a lever whose pivot is a cam whose position is adjustable with respect to the lever, the arm and the plunger being in contact with opposite ends of the lever.

The invention may be performed in various ways and preferred embodiments thereof will now be described with reference to the accompanying drawings, in which: Figure 1 is a representation of one preferred tension controller of this invention; Figure 2 is an enlarged detail of the device shown in Fig. 1; Figure 3 shows the operational relationship between parts of the device illustrated in Figs.

1 and 2; Figure 4 is a cross-section on lines IV-IV of Fig. 3; Figure 5 illustrates a pneumatic circuit for use with the tension controller of Figs. 1 to 4; and Figures 6 and 7 illustrate very diagrammatically alternative types of tension controller constructions according to the invention.

As shown in Fig. 1 paper or other web material 1 is wound onto a central reel 2 to form a roll 3. As the roll increases in diameter an arm 4, bearing on the roll surface by means of a ball 5, will rotate about a fixed pivot point 6. Depending from the arm 4 is a bracket 7 carrying a pressure regulating valve 8 from which projects a plunger 9 which bears against the surface of a circular cam 10.

As the arm 4 moves from the initial, dashed outline, position 4A into the position shown in solid lines the plunger 9 will slide around the surface of the cam 10.

As shown in Fig. 2 the cam 10 is pivotally mounted about a pivot point 11 so that it may be moved from the position shown in solid outline where it is concentric with the pivot point 6 of the arm 4 to a new position whereby it provides a path for the plunger 9 which is not centred on the pivot point 6.

Thus as the arm 4 rotates about the pivot point 6 the plunger will be caused to enter further into the body of the valve 8 thus providing a variable output from the valve.

Constructional details of the device can be seen more clearly from Figs. 3 and 4. The plunger 9 carries a roller 1 2 whose rotational centre may be aligned with the axis of the pivot point 11 of the cam 1 0. The arm 4 (not shown) is carried by the plate 1 3 attached to a collar 14 mounted about the pivot shaft 6.

A ram 1 5 is provided to apply a light biassing pressure to the arm 4 so as to hold it against the surface of the roll 3. The ram 1 5 is mounted between pins 1 6 and 1 7 within a casing 1 8 holding the operational parts of the device. A hand wheel 1 9 is mounted on a shaft 20 projecting through the casing 18, the shaft 20 having a screwthread passing through a pivotally mounted collar 21. The end of the shaft 20 is attached to the cam 10 so that, as the wheel 1 9 is turned, the shaft 20 will move inwards or outwards to alter the position of the cam 10 about its pivot 11.

The extent to which the cam 10 is displaced will determine the response of the valve 8 to movement of the arm 4. Thus an infinitely proportional control of the degree of valve output can be achieved to control the operation of a brake or clutch so as to ensure that the tension applied to the web 1 will remain constant at all times. Where tapered tension characteristics are required to allow the tension to be reduced proportionally during the winding operation to prevent the telescoping of reels of delicate or slippery material, this can readily be achieved by adjusting the cam to ensure that a lower final tension will be created than the initial tension. This facility can also be used to compensate for clutches having non-linear characteristics.An initial minimum pressure for the valve 8 (for example to overcome the resistance of any pull-off springs fitted to the brake or clutch) may be achieved by varying the basic position of the valve relative to the bracket 7. This can be achieved by allowing the valve 8 to be slidably adjusted on the bracket 7.

Fig. 5 shows the pneumatic circuit which incorporates the valve 8 and the ram 1 5.

Pressure is applied to a brake and brake pressure gauge 23 through the line 22 in a control box 24. An on/off control switch 25 (shown in the off position) allows pressurised air to be supplied from a source 26 to the valve 8 which will perform a pressure regulation function to balance the pressure in line 22 to a desired value. As the plunder 9 of the valve 8 moves in or out due to movement of the arm 4, the pressure regulation will vary the pressure applied to the brake 22 as required to ensure the required tension. The line 27 from the switch 25 (when in the on position) is also supplied to an arm pressure regulation valve 28 having a manual control which can be varied from the outside of. the control box 24. This will modify the pressure applied by the arm 4 against the roll 3.When the switch 25 is moved to the off condition the ram 1 5 will be operated in the opposite direction via the line 29 to move the arm 4 away from the roll (for example for removal of a complete roll) and at the same time pressure in the line 22 will be bled through the valve 8 and the line 27 exhaust, thus disconnecting the brake. Flow restrictors 29 are provided in the lines to the ram 1 5 to ensure a positive response when the switch 25 is moved to the on condition, whilst the restrictors operate to bieed off the air from the ram 1 5 when the switch 25 is moved to the off condition.

The modified arrangement shown diagrammatically in Fig. 6 has a cam 30 carried by the bracket 7 mounted on the arm 4 whilst the valve 8 is mounted adjustably to the casing 1 8. As the arm 4 rotates the surface of the cam 30 will cause the plunger 9 to move in or out.

In another alternative arrangement shown in Fig. 7, a cam 31 is provided in the form of an adjustable pivot point for a lever 32 which is operated on by an extension 33 depending from the arm 4. The other end of the lever 32 operates on the plunger 9 of the valve 8 which is adjustably attached to the casing 18.

For heavy duty applications, e.g. metal coiling, the follower arm can be mounted on a separate shaft and bearings with a toothed belt or shaft connections to the shaft of the sensor unit. An adjustable follower arm may be provided to allow for most reel sizes. This arm will feature a nylon ball roller running on sealed ball bearings which may be mounted in one of two positions allowing the arm to operate in line or at right angles to the reel axis.

It will readily be appreciated that the variable output device of this invention may be employed to control pneumatic or electric variable speed motors associated with brakes or clutches, enabling automatic adjustment of air pressure or voltage to the motor to be achieved to ensure optimum drive and tension characteristics for a web being wound off or onto a reel.

Claims (12)

1. A variable output device whose output will be a function of the position of a pivotally mounted arm and comprising the arm, a control member whose output depends upon the position of a plunger extending therefrom, a cam controlled member in contact with the plunger, the arm being linked with the control member or the cam controlled members, and wherein the cam of the cam controlled member is movable to positions which will each cause varying movement of the plunger as the arm rotates about its pivot point.

2. A device according to claim 1, wherein the cam controlled member is a surface on the cam which is contacted by said plunger.

3. A device according to claim 2, wherein the cam can be set in a neutral position in which movement of the arm will not alter the position of the plunger as the plunger moves relative to the cam surface.

4. A device according to claim 2 or claim 3, wherein the control member is carried by the arm and the cam is mounted about a pivot point which is displaced from that of the arm.

5. A device according to claim 2 or claim 3, wherein the cam is carried by the arm and is movable relative to its mounting on the arm.

6. A device according to claim 1, wherein the cam controlled member is a lever whose pivot is a cam whose position is adjustable with respect to the lever, the arm and the plunger of the control member being in contact with opposite ends of the lever.

7. A device according to any one of claims 1 to 6, wherein the position of the control member relative to its mounting is adjustable.

8. A device according to claim 7, wherein the control member is slidably adjustable on a bracket comprising the mounting.

9. A device according to any one of claims 1 to 8, wherein the control member is a potentiometer whose resistence value varies with movement of the plunger.

1 0. A device according to any one of claims 1 to 8, wherein the control member is a pneumatic or hydraulic pressure control valve.

11. A device according to claim 10, wherein the control valve controls the applied pressure of a brake or clutch device.

12. A device according to any one of claims 1 to 11, wherein the arm is lightly biased against rotation.

1 3. A device according to claim 12, wherein biasing is provided by a ram whose- operation can be reversed to withdraw the arm in a direction opposite to the biasing direction.

1 4. A device according to claim 13, wherein means for reversing operation of the ram is linked with means for switching off the control member.

1 5. A device according to any one of claims 1 2 to 14, wherein the degree of bias applied to the arm is adjustable.

1 6. A variable output device substantially as herein described with reference to the accompanying drawings.