DE2750780A1 - Palletised load stretch wrapping machine - has compensation mechanism for sheet irregularities caused by rectangular pallet - Google Patents

Abstract

The stretch-wrapping machine encloses palletised loads in sheet material. A compensation mechanism is provided to counteract the effect of irregularities caused when pulling the sheet off the storage roll, due to the rectangular shape of the pallet or the reducing roll diameter. Typically this can be effected by a jockey roller (4) on a swing arm, and on which a constant force acts. The braking torque on the storage roll (2) can also be reduced in a predetermined proportion to the deflection angle of the roller.

Description

Stretch film wrapping machine with compensation device

The invention relates to a stretch film wrapping machine for pallet loads with a compensation device, which automatically compensates for irregularities in the film removal compensates.

There is a method for securing pallet loads during transport in it to wrap a sheet of film around the loaded pallet. The slide is doing this elastically stretched so that the restoring force creates a firm cohesion both the load itself as well as between the load and the pallet. The wrapping can be done either horizontally or in a spiral.

The film wrapping is generally done so that the pallet on put a motor-driven turntable and the beginning of a rolled up Foil web is attached to the pallet. When the turntable rotates, it winds the film web around the pallet and around the load. The tension and with it the Stretching of the film web is caused by the rolling motion of the film roll is decelerated by a fixed or adjustable braking device.

Because the angular speed of the turntable and the braking torque of the film roll are generally constant during the wrapping of a pallet, This method has the following shortcomings: 1. As a result of the rectangular shape of the pallet the film requirement per unit of time when wrapping around an edge is greater than when breaking one side. Because the film roll at a constant braking torque not suddenly the Dispense the entire additionally required amount of film can, there is a greater stretch of film on the pallet edges.

2. Since the roll diameter is steadily decreasing as the film is unrolled, is formed from the tension of the film and the respective roll diameter Torque also continuously smaller. Since this torque is a constant Counteracts braking torque, the clamping force inevitably increases and thus the Stretching of the film.

To prevent the film web from tearing as a result of these two effects and to have a stretch reserve in the elastic range, must resilience and Elongation should be chosen from the outset to be lower than would be theoretically possible.

The invention has set itself the task of the two described To compensate for effects by a suitable device so that during the whole Wrapping process a uniform film tension and stretch is generated so that optimal use is made of the stretchability of the film and a reduction in the amount of film required is achieved per pallet load with the same strength.

According to the invention, this is achieved in that the film web guided around an articulated deflection roller between the film roll and the pallet to which a constant but adjustable force (e.g. compressed air, oil pressure, Weight) works. If the deflection roller against the Force is deflected from the central position, is controlled by a corresponding control (e.g. by means of pressure regulating valves or potentiometers) the braking torque by one value reduced, which is roughly proportional to the angle of deflection.

In this way it is achieved that a sudden need for film is achieved is covered immediately by deflecting the pulley when an edge is knocked in and that the film tension by a corresponding reduction of the braking torque is kept constant.

It is also within the meaning of the invention if instead of a pivotable one Deflection roller, the film roll itself is pivotably mounted.

Finally, it is possible to adjust the deflection angle of the pulley or of the film roll to convert it into an electrical value and a corresponding one stepless drive to vary the angular speed of the turntable.

The figure shows an exemplary embodiment. This means: 1 turntable with pallet 2 film roll 3 electromagnetic brake 4 swiveling deflection roll 5 Air cylinder 6 Chain wheel 7 Chain wheel with potentiometer The turntable 1 turns at constant angular velocity. This wraps itself on the pallet attached film web over the pivotable deflection roller 4 from the film roll 2. On the mounting arm of the pivoting pulley 4 there is a balance between the torque generated by the tension of the film web and the opposite directed torque applied by the piston rod side with constant pressure Compressed air cylinder 5 is generated.

When the film tension is increased, the deflection roller 4 swivels from their equilibrium position. The resulting shortening of the film web additional film is released for wrapping.

At the same time the chain wheel 6 is connected to the chain wheel 7 Potentiometer operated. This creates the electrical voltage and thus the braking torque reduced on the electromagnetic brake 3. The tension of the film web is reduced and a new equilibrium position of the pivotable pulley 4 is reached.

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Claims (6)

Claims 0 Stretch film wrapping machine for pallet loads characterized in that irregularities in the film removal caused by the rectangular shape the pallet and the decreasing outer diameter of the film roll, be compensated by an automatic compensation device. 2. Stretch film wrapping machine according to claim 1, characterized in that that the film web for the purpose of compensation around an articulated deflection roller, on which a constant force acts, is guided. 3. Stretch film wrapping machine according to claim 1 and 2, characterized in that that the braking torque on the film roll by one, in a fixed ratio to Deflection angle of the deflection roller standing value is reduced. 4. stretch film wrapping machine according to claim 1 and 2, characterized in that that the constant force is generated by a compressed air pressurized of all hydraulic cylinders is generated. 5. stretch film wrapping machine according to claim 1 to 3, characterized in that that to regulate the braking torque of an electromagnetic brake through the Deflection movement of the pulley operated potentiometer is used. 6. Stretch film wrapping machine according to claim 1, characterized in that that the film roll is articulated in such a way that an increase in the film tension a deflection movement and a reduction of the Braking torque causes.