GB2025373A - Apparatus for intermittent feeding of webs from supply rolls - Google Patents

Abstract

The apparatus comprises, a conveyor roller (4) which is disposed between the supply roll (2) from which the web (1) is wound off, and a pair of tongs (15) advancing the web intermittently. The web (1) is moved over rollers (6, 10, 12, 7, 11) for the purpose of forming buffer loops (20). The conveyor roller (4) is releasably connected to a drive wheel (38) by way of a planetary gear (37) comprising a brake drum (36). The loop lever (9) actuates, by way of a control cam (22), a control lever (23) for tightening and slackening a brake belt (35). When the brake belt (35) is tightened, the drive wheel drives the conveying shaft (4) so that the buffer loops (20) become longer and the control cam (22) finally slackens the brake belt (35) by way of the control lever (23). The conveying roller (4) then comes to a stop with the brake drum (38) idling, until the brake belt (35) is tightened again as a result of shortening of the buffer loops (20). <IMAGE>

Description

SPECIFICATION Apparatus for off-winding a web of sheet material from a supply roll in steps The invention relates to apparatus for offwinding a web of sheet material from a supply roll in steps. In a particular apparatus of this kind a conveying roller is present between a memberfor advancing the web, and the supply roll. The web forms buffer loops between the conveying roller and the advance member, the length of which loops influences the position of a control element which, when the length of the loops is short, connects the conveying roller to a drive element, but disconnects it therefrom when the length of the loops is great. Apparatus of this kind is described in German Patent Specification No.

605,481, where the control element actuates a lock coupling, and this results in the conveying roller starting up and stopping in a jerky manner.

This jerky action has a deleterious effect upon the web of sheet material conveyed by this roller and on the service-life of the apparatus. Thus, the known apparatus is not suitable for applying relatively large conveying forces such as are necessary for the off-winding of wide webs of sheet material, from which wrapping materials for the packaging of articles, for example, are to be cut off. The above-mentioned Patent Specification, for example, deals with the advance and severing of a narrow strip of paper for the purpose of forming labels.

Much more complex solutions have also been proposed which use, for example, D.C. motors and electrical, pneumatic or hydraulic actuating and monitoring elements as described in British Patent Specification No. 1,452,219 and in U.S. Patent Specification No. 3,937,1 12. These more recent installations achieve their object only at very considerable expense.

The present invention seeks to provide an improved off-winding apparatus of the kind referred to.

According to the invention there is provided apparatus for off-winding a web of sheet material from a supply roll in steps, a conveying roller being present between a member for advancing the web, and the supply roll, and the web forming buffer loops between the conveying roller and the advance member, the length of which loops influences the position of a control element which, when the length Of the loops is short, connects the conveying roller to a drive element, but disconnects it therefrom when the length of the loops is great, wherein the conveying roller is releasably connected to the drive element by way of a planetary gear, the planet wheels of which are mounted in a brake drum which is associated with a brake belt, the belt being tightened or slackened by said control element so as to connect the conveying roller t6 the drive element or to release it therefrom.

The invention will further be described with reference to the accompanying drawings of which Figure 1 is a schematic layout diagram of an off-winding apparatus in accordance with the invention; Figure 2 is a view of the planetary gear and brake arrangement of the apparatus of Figure 1; and Figure 3 is a section along line Ill-Ill of Figure 2.

The off-winding apparatus illustrated in Figure 1 can serve for off-winding a web 1 of paper or other sheet material from a supply roll 2, the shaft 3 of which is mounted on the frame of the apparatus. The supply roll 2 is braked in the usual manner so that it can be rapidly brought to a stop in the event of absence of a pull-off force applied to the web 1. The web 1 is looped round a conveying roller 4 of fixed location which supplies this pull-off force, and the web is then guided around two rollers 5 and 6 of fixed location and thence to a movable roller 7 which is mounted on a lever 9 which swings about a point 8.

From the roller 7, the web 1 passes around a roller 10 fixed location, a movable roller 11 also mounted on the lever 9, and a roller 12 of fixed location on to a bench 1 3. From the bench the web passes to a pair of pull-off tongs 1 5 between two blades 14 movable in opposite directions. The tongs 1 5 can be reciprocated in the directions indicated by the double-headed arrow 16, and their stroke is so adjusted that, during each working cycle of the apparatus, the blades 1 4 sever a portion 1 7 from the web 1. The tongs 1 5 then pass through the separated blades 14' so as to grip the web 1 again in the position 15', and to pull it forward so that the blades 14 can cut off a further portion 17, this series of movements being repetitive.After each severing operation, a clamp 19, pivoted at 1 8, prevents the free end of the web from being drawn backwards to any appreciable extent by the tension in the web 1 , the clamp locking the web 1 on to the bench 13. The.

portions 1 7 are passed by any suitable means to a packaging machine to be used as wrapping sheets, though they can, of course, be used for other purposes.

As the web 1 is being moved around the rollers 6, 7, 10, 11 and 12, it forms three loops 20 between them. The lever 9 is urged by a tension spring 21 to tension the loops 20. Thus, the length of the loop alters, and therefore also the length of web between the rollers 6 and 12. If less material is severed from the leading end of the web than is wound off from the supply roll 2 by the conveying roller 4, then the loops 20 increase in length, since the lever 9 swings out into the position 9'. Thus, the loops 20 serve as buffers. Provision then has to be made for returning the lever 9 to its original position; the conveying roller 4 must therefore be stopped so that it no longer applies tensile force to the web 1.This is achieved in that when the swung-out position 9' is reached, a control cam 22 secured to the lever 9 actuates a stopping lever 23 as will be described in detail. As long as the conveying roller 4 is rotating in the direction indicated by the arrow 24, it continues to apply tensile force to the web 1, since a pressure applying roller 25 is provided which provides the necessary friction even when the tension in the web 1 is low downstream of the conveying roller 4. The pressure-applying roller 25 is mounted on a lever 27 which can be swung about the point 26 and is held in the pressure-applying position by a spring 28.

Figure 2 shows, at 22', the.swung-out position of the control cam 22, and, at 23' the operative position of the stopping lever 23. The stopping lever 23 is pivotably mounted on a pin 29 and carries a feeler 30 which is held in contact with the control cam 22 by a tension spring 31.

Secured to the lever 23 is an asymmetrical rocker 32, to which are firmly connected the two ends 33 and 34 of a brake belt 35 which passes round a brake drum 36. Since the end 33 is at a greater distance from the pin 29 than is the end 34, then when the lever 23 is swung in the direction indicated by the arrow 49, the belt 35 is slackened whereas when the lever is swung in the opposite direction, the belt is tightened. By way of a planetary gear 37 comprising the drum 36, the conveying roller is so connected to a drive sprocket 38 that it always rotates when the drum 36 is fully braked by the belt 35.On the other hand, when the belt 35 is slackened -- this corresponding to the position 23' of the stopping lever 23 and the swung-out position 9' of the "loop lever" 9-the conveying roller 4 does not rotate so that the loop lever 9 returns to its initial position in which the loops are short. This mode of operation of the planetary gear 37 will be seen from the following more detailed description.

The conveying roller 4 is secured on a shaft 39 which is mounted at 40 in a wall 41 of the frame of the apparatus. The wall 41 also serves for securing the pin 29 on which is mounted the rocker 32 connected to the stopping lever 23, said wall also carrying further parts of fixed location.

The wall 41 has been omitted from Figure 1 since it would to some extent mask elements of importance in the operation of the apparatus.

Loosely mounted on the front end of the shaft 39 is the sprocket 38, which is caused to rotate continually by an endless chain 42. The sprocket 38 is formed integrally with a first sun wheel S1. A second sun wheel S2, however, is mounted on the shaft 39. The sun wheel S1 meshes with the first planet wheel P 1 , which is rotatable on a pin 44 secured to a wall 43 of the drum. The planet wheel P1 also meshes with a second planet wheel P2, which is likewise rotatable about a pin 45 mounted in the wall 43 of the drum and which on the other hand, also meshes with the second sun wheel S2. The drum 36 has a hub 46 which is freely rotatable on a hub 47 of the sun wheel S2.

When the drum 36 is fully braked by the brake belt 35, the continually rotating drive sprocket 38 drives the shaft 39 through the gearwheels S1, P 1, P2 and S2, and thus drives the conveying roller 39. The directions of rotation of these gearwheels are indicated in Figure 2 by arrows, and it can be seen that the sun wheel S2 drives the conveying roller 4 in the direction necessary for winding the web 1 off the supply roll 2. When the brake belt 35 is slackened however, the peripheral force applied by the sun wheel S1 to the planet wheel P 1 does not cause this wheel P 1 to rotate, on the one hand, because of the frictional resistance of the following gearwheels, and, on the other, because of the braking of the conveying roller 4 caused by the pressureapplying roller 25 and the braked supply roll 2.

The peripheral force applied to the planet wheel P 1 acts, by way of its pin 44, on the drum 36 which then rotates in the idle condition on the hub 37 of the sun wheel S2 in the direction indicated by the arrow 48.

By using a suitable shape and setting of the control cam 22 and by selecting an appropriate length for the brake belt and so on, the conveying roller 4 can be stopped and started up in a very gentle manner, so that only very slight strain is suffered by the web 1 of sheet material.

Furthermore, the reversal points in the movement of the loop lever 9 can be selected to give maximum advantage. The apparatus, which need use no electrical, pneumatic or hydraulic elements, is able to apply large off-winding forces even when constructed from relatively small elements of small mass. These purely mechanical elements are subjected to very little wear, so that a very reliable mode of operation can be expected over a lengthy service-life.

As shown in Figures 2 and 3, the two planet wheels P 1 and P2 are of different size as are also the sun wheels So and S2. However, these wheel sizes are shown in the drawing only to keep the pitch circles of the sun wheels S1 and S2 separate from each other and to show the directions of rotation of the wheels. In fact, from the point of view of manufacture, it is more advantageous for the pitch circles of the wheels P1 and P2 to be the same as each other, and this also applies as regards the wheels S1 and S2.

Claims (6)

1. Apparatus for off-winding a web of sheet material from a supply roll in steps, a conveying roller being present between a member for advancing the web, and the supply roll, and the web forming buffer loops between the conveying roller and the advance member, the length of which loops influences the position of a control element which, when the length of the loops is short, connects the conveying roller to a drive element, but disconnects it therefrom when the length of the loops is great, wherein the conveying roller is releasably connected to the drive element by way of a planetary gear, the planet wheels of which are mounted in a brake drum which is associated with a brake belt, the belt being tightened or slackened by said control element so as to connect the conveying roller to the drive element or to release it therefrom.

2. Apparatus according to Ciaim 1, wherein a drive wheel is mounted loosely on a shaft to which the conveying roller is firmly connected; a first sun wheel is firmly connected to the drive wheel, and a second sun wheel is firmly connected to said shaft; the sun wheels are each connected to one of the planet wheels and the latter mesh with each other, and the brake drum is mounted to rotate relatively to the shaft.

3. Apparatus according to either of the preceding claims, wherein the said control element is a lever, which is displaced by means of a control cam, the cam being swung by a springbiassed lever, which carries reversing rollers for forming the buffer loops.

4. Apparatus according to any of the preceding claims, wherein the web of sheet material is urged against the conveying roller by a pressureapplying roller.

5. Apparatus according to Claim 2, wherein the two planet wheels have like pitch circles as do the two sun wheels.

6. Apparatus substantially as hereinbefore described with reference to the accompanying drawings.