GB2138405A

GB2138405A - Belt driven reel unwinding device

Info

Publication number: GB2138405A
Application number: GB08307255A
Authority: GB
Inventors: Harry Cunnington
Original assignee: Norcros Investments Ltd
Current assignee: Norcros Investments Ltd
Priority date: 1983-03-16
Filing date: 1983-03-16
Publication date: 1984-10-24
Also published as: GB8307255D0; GB2138405B

Abstract

A powered web unwind device comprises a web reel mounting (10), a light-weight sensor (18, 20) for sensing the configuration of an unwind loop downstream of the web reel mounting and a driven toothed belt (32) contacting the periphery of the web. The belt (32) is driven intermittently in dependence upon the location of the light-weight sensor (18, 20). The linear velocity of the web is maintained constant irrespective of the reel diameter at any given instant and the sensor and corresponding intermittent operation of the motor merely serve to ensure that the actual velocity is closely matched to the desired velocity. <IMAGE>

Description

SPECIFICATION Web unwinding devices This invention relates to web unwinding de vices as incorporated in machines such as overprinters and label applicators to ensure even unwinding of a web- despite inertia prob lems which are sometimes encountered with reels of web material of large diameter.

Although primarily intended for relatively small machines such as overprinters and label applicators, it is believed that the invention can also be applied to advantage in larger size machines such as those generally employed in the packaging and printing industries, includ ing the newspaper industry.

Reels of web material whether paper or plastics can be unwound ready for use by a powered unwind mounting but the inertia effect of such large reels can result in uneven unwinding particularly at start-up of the machine. Proposals to overcome this problem have inciuded the provision of anti-snatch devices but although these may overcome the inertia problems they do not eliminate the basic difficulty that the overall installation of the unwind mounting device is bulky and often expensive in comparison with the overall cost of the machine.

It is also important that the powered unwind device shall provide a constant linear velocity in the unwound web irrespective of the peripheral diameter of the reel as the unwinding progresses.

According to the present invention there is provided a powered web unwind device comprising a web reel mounting, means for sensing the configuration of an unwind loop downstream of the web reel mounting and a toothed belt drive which can be driven by an electric motor and which is arranged to contact the periphery of the web of the reel in driving relationship, and motor means coupled to the belt drive, the motor means being capable of being energized by the said sensing means when the loop achieves a predetermined configuration.

A powered web unwind mounting device embodying the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawing, the sole Figure of which is a side elevation of the mounting.

The mounting comprises an arm of L-shape 10, which can, conveniently, replace a web reel mounting arm of cdnventional constructiomn when incorporated in an overprinter, an applicator or other web consuming machine.

The arm 10 will, of course, be sufficiently robust to support a web reel 1 2 appropriate to the machine in question. The horizontal limb of the arm 10 carries a reel holder 14 which ensures concentricity of the reel in relation to its rotational axis. A suitable holder is described and claimed in our co-pending appli cation of today's date (reference "Scissors Reel"). The holder will be mounted on the face of the arm 10 corresponding to the upper surface of the paper.

The horizontal limb of the arm 10 also carries a pivot pin 1 6 (broken lines) mounting a lightweight sensing member 18 having an end portion 20 through which a loop 22 being unwound from the reel passes. The sensing member 18 may be counterbalanced to improve sensitivity and a connection is made with a micro-switch 24 mounted on the face of the arm 10, corresponding to the underside of the paper.

The upstanding limb 26 of the arm 10 supports for rotation on its face corresponding to the underside of the paper a gear-wheel 28 (broken lines) and mounted on the shaft rotatably supported in the upstanding limb 26 is a toothed pulley 30 meshing with a toothed belt 32 which also meshes with a further toothed pulley 34 rotatably mounted adjacent a free end of an arm 36 pivotally mounted about the same axis of rotation as the gearwheel 28. As shown, the arm 36 is biased downwardly by a helical tension spring 38 and as will be apparent from the drawing one run of the belt 32 is in tangential, pressure contact with the periphery of the reel 1 2.

The gear-wheel 28 meshes with a pinion 40 driven by a shaded-pole electric motor (not shown).

The spring 38 is so mounted in relation to the pivotal arm 36 and the upstanding limb 26 of the arm 10 that it can act as an overcentre control for the pivotal arm 36 thus facilitating mounting a fresh reel 1 2.

The operation of the web reel mounting device is very straightforward. Provided that the loop 22 holds the lightweight sensor 20 in an upper position the motor will remain energized and the reel 1 2 is driven frictionally throughout the pay-out operation by the belt 32. Although the reel progressively diminishes in diameter, the motor is energized intermittently at a constant rate so that effectively the configuration of the loop 22 remains of substantially constant shape, and in other words, the linear pay-out rate also remains constant because it is required that the velocity of the web through the machine must be constant. This advantageous operation arises because the belt linear velocity remains constant at the transverse contact line with the web and the web is thus driven at a constant linear velocity irrespective of the reel diameter at any instant.

It will be readily apparent that the amount of power consumed and the size of motor required is kept to a minimum by using the device in accordance with the invention. The use of a reel mounnting 1 4 that ensures precise concentricity will avoid cyclic variations in the linear pay-out velocity. The gear ing ratio will be such that for normal operation the motor is energized for a major part of the operating time. For heavy reels, such as those used in wrapping and packaging machines, the reel mounting 14 may be supported between two arms 10.

Claims

1. A powered web unwind device comprising a web reel mounting, means for sensing the configuration of an unwind loop of the web downstream of the web reel mounting, a toothed belt drive drivable by an electric motor controlled by the sensing means and which is arranged to contact in tangential driving relationship the periphery of the web on the reel and means for energizing the motor controlled by the sensing means so that the motor is energized only while the web loop maintains a predetermined configuration and the linear velocity of the web downstream of the loop is kept substantially constant.

2. A powered web unwind device comprising a web reel mounting, means for contacting and thereby sensing the configuration of an unwind loop of the web lying downstream of the web reel mounting, a toothed drive belt overlying and in tangential driving relation with the periphery of the web reel with the smooth face of the belt contacting the periphery, an electric motor controlled by the sensing means and arranged to drive the belt through a toothed wheel meshing with the belt and means for energizing the motor controlled by the sensing means so that the motor is energized only while the web loop maintains a predetermined configuration and hence the linear velocity of the web downstream of the loop is kept substantially constant.

3. A device according to claim 1 or claim 2, wherein biasing means serve to hold the belt against the web reel periphery.

4. A device according to any one of claims 1 to 3 wherein the belt is mounted on two spaced toothed wheels carried by an arm pivoted on the web reel mounting.

5. A device according to any one of the preceding claims wherein the sensing means includes an L-shaped arm pivoted at one point on the web reel mounting and carrying an end portion lightly contacting the web at said loop, a further portion extending from the pivot serving to activate a micro-switch in the motor circuit.

6. A device according to any one of the preceding dates wherein the web reel mounting is of L-shape with one arm supporting the web reel and the other arm supporting the electric motor and the drive to the belt.

7. A web unwind device substantially as hereinbefore described with reference by the accompanying drawing.

8. An overprinter or other printing machine incorporating a device according to any one of the preceding claims.