GB2188037A

GB2188037A - Apparatus for intermittently pull advancing a sheeting web

Info

Publication number: GB2188037A
Application number: GB08705294A
Authority: GB
Inventors: Fritz Achelpohl
Original assignee: Windmoeller and Hoelscher KG
Current assignee: Windmoeller and Hoelscher KG
Priority date: 1986-03-14
Filing date: 1987-03-06
Publication date: 1987-09-23
Also published as: DE3608625A1; DK132687A; IT8704804A0; DE3608625C2; IT1207745B; GB8705294D0; DK132687D0

Abstract

Apparatus for intermittently pull advancing a sheeting web, such as a tubular or semi-tubular web of synthetic thermoplastics material, which is to be fed to a succeeding transverse welding and transverse severing apparatus of a bagmaking machine, comprises an intermittently rotatably drivable pair of feed rollers (2,3) including an upper roller (3). The feed rollers (2,3) are connected to belt pulleys, cogged belt pulleys or chain sprockets, and a belt (5) or a chain is trained in S shape around said pulleys or sprockets rotatably to drive them jointly in mutually opposite directions. In one aspect of the invention the upper roller (3) is pivoted to the machine frame (1) by being mounted on those ends of parallel links (4) which are the forward end to the direction of travel of the sheeting web (12), at least one of which links (4) is biased by resilient means (15). In another aspect of the invention the upper roller (3) is mounted in at least substantially vertically displaceable bearings, at least one of which is biased by resilient means and in each case the belt (5) or chain extends at such an angle to the belt pulley or the chain sprocket associated with the upper roller (3) that the forces acting on the roller as a result of the driving belt or chain act to press the upper roller (3) more tightly against lower roller (2) preventing slippage of the web between the rollers. <IMAGE>

Description

SPECIFICATION Apparatus for intermittently pull advancing a sheeting web This invention relates to apparatus for intermittently pull advancing a sheeting web, such as a tubular or semitubular web of synthetic thermoplastics material, which is to be fed to a succeeding transverse welding and transverse severing apparatus of a bagmaking machine. Such a known apparatus includes an intermittently rotatably drivable pair of feed rollers of which the upper roller is pivotally connected to a frame of the apparatus by being mounted on those ends of parallel links which are the forward ends in the direction of travel of the sheeting web, with at least one of the links being biased by resilient means.

German Patent Specification 19 66 161 discloses such an apparatus in which the links carrying the upper roller are biased upwardly by compression springs, which tend to lift the upper roller from the lower one, and pneumatic cylinders are provided for urging the links in a vertical direction against the action of the compression springs so that the upper roller of the pair of feed rollers is urged against the lower roller of said pair and the required frictional contact with the sheeting web gripped between the feed rollers is established. To ensure that the sheeting web will be intermittently advanced in steps of equal length, slip between the feed rollers and the sheeting web must be avoided.Practice has shown that in the known apparatus there may be slip between the sheeting web and the feed rollers as the latter are accelerated and that the upper feed roller may vibrate at high cycle rates.

There is thus a need for a generally improved apparatus for intermittently pull advancing a sheeting web in which the gripping pressure between the feed rollers and the sheeting web can be increased during the accelerating phase so that the risk of slip will be reduced.

According to a first aspect of the present invention there is provided an apparatus for intermittently pull advancing a sheeting web, such as a tubular or semitubular web of synthetic thermoplastics material, which is to be fed to a succeeding transverse welding and transverse severing apparatus of a bagmaking machine, including an intermittently rotatably drivable pair of feed rollers of which the one which is uppermost in operation of the apparatus is pivotally mounted by being mounted on those ends of parallel links which are the forward ends in the direction of travel of the sheeting web, with at least one of the links being biased by resilient means to urge said one feed roller towards the other roller, wherein the feed rollers are connected to belt pulleys, cogged belt pulleys or chain sprockets, a belt or a chain is trained in S shaped around said pulleys or sprockets rotatably to drive the feed rollers jointly in mutually opposite directions, and the arrangement being such that in operation the resultant of the forces in the incoming or outgoing belt or chain courses which serve rotatably to drive said one feed roller extends above the pivotal axis of the links which carry said one feed roller.

The incoming and outgoing belt or chain courses which are trained around the driving pulley or the driving sprocket associated with the upper feed roller will exert tensile and drive forces on said upper feed roller and the tensile force in the outgoing courses will be stronger by the driving force than the tensile force in the incoming course. With reference to the horizontal center plane of the upper feed roller the two incoming and outgoing courses are approximately arranged in mirror symmetry so that the resulting belt or chain force has a line of action which is adjacent to or includes an acute angle with the center plane.That resulting belt or chain force has a component which extends through the pivotal axis of the links which carry the upper feed roller and for this reason is ineffective and has a vertical component which acts in the plane that contains the axes of rotation of the two feed rollers. In dependence on the position of the resultant the vertical component will be upwardly or downwardly directed. In accordance with the invention that vertical component is used to increase the gripping force that is exerted by the feed rollers on the sheeting web. As a result, in accordance with the invention the gripping force will be increased by a vertical component when the resultant of the belt or chain forces extends above the pivotal axis of the links. Such a position of the pivotal axis can be achieved, e.g., if the links consist of bell crank levers.

Because owing to the frictional force and the pulling force acting on the sheeting web the tensile force in the outgoing course of the belt or chain will always exceed the tensile force in the incoming course, the arrangement may be such that the belt or chain forces can be utilized in a simple manner to increase the gripping forces. During an acceleration the tensile forces in the outgoing course are increased by the accelerating forces of the upper feed roller so that said tensile forces may assume substantiai values and there will be a large vertical component of force, which will increase the gripping force and will prevent a slip just in the critical acceleration phase.

According to a second aspect of the present invention there is provided an apparatus for intermittently pull advancing a sheeting web, such as a tubular or semitubular web of synthetic thermoplastics material, which is to be fed to a succeeding transverse welding and transverse severing apparatus of a bagmaking machine, including an intermittently rotatably drivable pair of feed rollers of which the one which is uppermost in operation of the apparatus is mounted in at least substantially vertically displaceable bearings, at least one of which is biased by resilient means, wherein the feed rollers are connected to belt pulleys, cogged belt pulleys or chain sprockets, a belt or a chain is trained in S shape around said pulleys or sprockets rotatably to drive them jointly in mutually opposite directions and the arrangement being such that the uppermost course of the belt or chain extends at such an angle to the belt pulley or the chain sprocket associated with said one feed roller that the vertically directed component of the force exerted by the incoming course is smaller than the vertically directed component of the force exerted by the outgoing course.

In this case the horizontally directed components of the belt or chain forces will be compensated by the vertical guidance so that only the vertical forces can become effective and are used in accordance with the invention to increase the clamping force.

The angle at which the incoming course extends will influence the location and magnitude of the resulting belt or chain force and that angle can be influenced by a deflecting upper roller or wheel. The axis of the upper deflecting wheel or roller suitably extends adjacent to the plane which contains the axes of rotation of the feed rollers.

For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying single figure drawing which diagrammatically shows in a side elevation feed rollers of the apparatus of the invention in conjunction with a severing and welding apparatus for removing bags from a tubular or semitubular web by hot wire welding.

As shown in Figure 1 of the accompanying drawings, apparatus of the invention for intermittently pull advancing a sheeting web has a lower roller 2 of a pair of feed rollers, mounted between two side walls of a frame of a bagmaking machine. Only one of said side walls is shown and is designated 1. The upper roller 3 is mounted on two links in the form of beli crank levers 4, which are pivotaily connected to the side walls 1 at those ends of the levers which are remote from the upper roller 3. The feed rollers 2, 3 of the pair are driven by a cogged vee belt 5, which is trained in S shape around a deflecting roller 6 and around the feed rollers 2, 3.

The belt forces exerted during normal operation of the rollers 2, 3 are represented by dotted lines, just as the associated resultant force R. It is apparent from the drawing that the resultant R is spaced a distance a from the pivot points 1'. As the pivot point 1' is disposed below the resultant R, a moment or force will be exerted which urges the upper roller 3 against the lower roller 2. The belt forces will increase during an acceleration of the rollers 2, 3. Said belt forces are indicated in phantom. The resultant R' which is then obtained is also spaced a distance ai above the pivot point 1'. Because the distance a' exceeds the distance a, the upper roller 3 will exert a stronger contact pressure force on the lower roller 2 during the acceleration phase.

This will eliminate a risk of slip, particularly during the acceleration phase.

Because the belt forces alone are not sufficient to urge the upper roller against the lower roller with an adequate gripping force, a compression spring 15 is provided, which biases the bell crank levers 4 in a sense to increase the gripping force of the feed rollers. The compression spring 15 is gripped between a spring abutment 16 and the bellcrank lever 4.

The initial stress of the compression spring 15 can be increased by an adjusting screw 17, which has been screwed into a bracket 18, which is fixed to the frame. The upper feed roller 3 can be lifted from the lower feed roller 2 by a pivotal movement imparted to the bell crank levers 4 in the counterclockwise sense. This can be effected by a rotation of eccentric cams 19, which act on the underside of the ball crank levers 4. Said eccentric cams can be rotated by any desired drive means, not shown.

In known manner the upper and lower rollers 2, 3 are provided with peripheral annular grooves 9, 10, through which an air-blasting rake 11 protrudes in the direction of travel. By that rake, the web 12 is perfectly guided to the welding jaw 13 and the cooperating roller.

In a second aspect of the invention, not illustrated, the apparatus of the invention has a pair of feed rollers of which the one which is uppermost in operation of the apparatus is mounted in at least substantially vertically displaceable bearings, at least one of which is biassed by resilient means. In this aspect the uppermost course of the belt or chain extends at such an angle to the belt pulley or the chain sprocket associated with the upper feed roller that the vertically directed component of the force exerted by the incoming belt course is smaller than the vertically directed component of the force exerted by the outgoing belt course.

Claims

1. Apparatus for intermittently pull advancing a sheeting web, such as a tubular or semitubular web of synthetic thermoplastics material, which is to be fed to a succeeding transverse welding and transverse severing apparatus of a bagmaking machine, including an intermittently rotatably drivable pair of feed rollers of which the one which is uppermost in operation of the apparatus is pivotally mounted by being mounted on those ends of parallel links which are the forward ends in the direction of travel of the sheeting web, with at least one of the links being biased by resilient means to urge said one feed roller towards the other roller, wherein the feed rol lers are connected to belt pulleys, cogged belt pulleys or chain sprockets, a belt or a chain is trained in S shaped around said pulleys or sprockets rotatably to drive the feed rollers jointly in mutually opposite directions, and the arrangement being such that in operation the resultant of the forces in the incoming or outgoing belt or chain courses which serve rotatably to drive said one feed roller extends above the pivotal axis of the links which carry said one feed roller.

2. Apparatus according to claim 1, including a deflecting wheel or roller located, in operation of the apparatus, upwardly of said one feed roller, which deflecting wheel or roller has an axis of rotation adjacent to the plane which contains the axes of rotation of the feed rollers.

3. Apparatus according to claim 1, wherein the links are bell crank levers.

4. Apparatus for intermittently pull advancing a sheeting web, such as a tubular or semitubular web of synthetic thermoplastics material, which is to be fed to a succeeding transverse welding and transverse severing apparatus of a bagmaking machine, including an intermittently rotatably drivable pair of feed rollers of which the one which is uppermost in operation of the apparatus is mounted in at least substantially vertically displaceable bearings, at least one of which is biased by resilient means, wherein the feed rollers are connected to belt pulleys, cogged belt pulleys or chain sprockets, a belt or a chain is trained in S shape around said pulleys or sprockets rotatably to drive them jointley in mutually opposite directions and the arrangement being such that the uppermost course of the belt or chain extends at such an angle to the belt pulley or the chain sprocket associated with said one feed roller that the vertically directed component of the force exerted by the incoming course is smaller than the vertically directed component of the force exerted by the outgoing course.

5. Apparatus according to claim 4, including a deflecting wheel or 15 roller located, in operation of the apparatus upwardly of said one feed roller, which deflecting wheel or roller has an axis of rotation adjacent to the plane which contains the axes of rotation of the feed rollers.

6. Apparatus for intermittently pull advancing a sheeting web, such as a tubular or semitubular web of synthetic thermoplastics material, which is to be fed to a succeeding transverse welding and transverse severing apparatus of a bagmaking machine, substantially as hereinbefore described with reference to or as shown in the accompanying drawing.