Such an apparatus for applying a banderole is disclosed in the European patent publication EP-B-0 741 656. This prior art banding machine is provided with the conveyor unit embodied as conveyor belt, connected with suction means for holding the band material. The suction OOOOOmeans comprise a vacuum pump whose suction side is connected with the conveyor belt by means of an under- pressure channel surrounding the conveyor belt. The con- veyor belt is provided with openings that are thus in com- munication with the suction side of the vacuum pump. Due to the pressure difference over the conveyor belt, the band material adheres to the conveyor belt, allowing the conveyor belt to take the band material around the product space. The transport unit may also be formed by a plural- ity of mutually spaced conveyors cords. However, the force holding the band material to the conveyor unit in the form of the conveyor belt or cords is brought about indirectly by means of pressure difference, and the magnitude of said force, as well as the pressure difference will be deter- mined by the degree of friction between the band material

and the conveyor unit. In addition to the friction coeffi- cient between band material and conveyor unit, the degree of friction will also be determined by the contact surface between the conveyor unit and the band material, which contact surface will be limited due to the necessity of openings in the conveyors unit. To allow the prior art banding machine to work properly it is further essential that the sides of the band material join on to the walls of the under-pressure channel. If this is not the case, the pressure difference will decrease, resulting in a re- duction in the force holding the band material to the con- veyor unit. The necessary presence of openings in the con- veyor unit will also increase the elasticity of the con- veyor unit. This will result in the occurrence of slip be- tween band material and conveyor unit, involving consider- able inaccuracy as the band material is taken around the product space, which is further amplified by the elastic- ity of the conveyor unit.

It is the object of the invention to eliminate the above-cited drawbacks of the prior art banding ma- chine. To this end the invention provides a banding ma- chine of the type mentioned in the preamble, which is pro- vided with means for generating electrostatic attraction between the band material being supplied and the conveyor unit. The electrostatic attraction produces a direct hold- ing force causing the band material to adhere to the con- veyor unit, the magnitude of the holding force being vari- able by the degree of electrostatic attraction. The occur- rence of slip between the band material and conveyor unit will be extremely unlikely, and the conveyor belt to be used need only possess very little elasticity. As a result the band material can be supplied in very exact amounts so that, for example, a precisely determined length of band material can be applied around a product. This is of par- ticular importance with products that due to a tensile force become deformed in the banderole. Further, due to the greater adhesive force, the rate of conveying the band material around the product space may be increased, allow-

ing the application of a banderole around the product or products to proceed more quickly, and reducing the proc- essing costs.

In a preferred embodiment that is simple to real- ize, in that the conveyor unit is connected to earth po- tential and an electrode, connected to a high voltage, is positioned in the vicinity of the trajectory to be fol- lowed by the band material. Due to these measures the con- veyor unit and the band material receive different charges, generating an electrostatic attraction that causes the band material to adhere to the conveyor unit.

Preferably the electrode is positioned in the vi- cinity of the starting point of the trajectory around the product space so that the electrostatic attraction is al- ready effective from this starting point.

In a preferred embodiment the conveyor unit is connected at various positions along the trajectory around the product space to earth potential, and/or is provided with a number of electrodes that are connected to high voltage and are positioned in the vicinity of and distrib- uted over the trajectory around the product space. This is a simple manner for ensuring the electrostatic charge dif- ference between the band material and the conveyor unit over the trajectory around the product space.

In an embodiment of the banding machine in which the trajectory around the product space comprises a plu- rality of segments, it is preferred for each segment to include at least one electrode, with the electrode (s) of each subsequent segment, viewed in the transport direction of the band material around the product space, having an opposite charge in relation to the electrode (s) of a pre- ceding segment. Practice has proven that in this manner each segment acquires an exceedingly good adhesion between the band material and the conveyor unit. In an optimal situation an electrode is positioned in the vicinity of the starting point of each segment.

The invention will now be explained in more de- tail with reference to the accompanying drawing, in which

identical reference numbers designate similar parts, and in which: -Figure 1, shows a longitudinal cross section of an embodiment of the banding machine according to the in- vention; and -Figure 2, shows a cross section along the line A-A according to Figure 1.

The longitudinal cross section in Figure 1 of an embodiment of the banding machine according to the inven- tion shows band material made of, for example, plastic or paper that is supplied by means of a feed mechanism 10 from, for example, a feeding roller (not shown). The band material 1 is fed to an endless conveyor belt 20 as unit for conveying the band material 1 around a product space 30. Guide rollers 40 guide the conveyor belt 20 around the product space 30. It is remarked that not all the guide rollers shown are provided with the reference number 40.

The band material 1 is taken by the conveyor belt 20 in the direction of the arrows D over a trajectory around the product space 30, until the end of the band material reaches a mechanism 50, by means of which the end of the band material 1 can be held. The conveyor belt 20 and the guide rollers 40 are mounted between two parallel walls 80. A detail of this is shown in Figure 2. One or several of the guide rollers 40 are driven by a motor (not shown in the Figures) connected with a control. A motor that is not shown also drives the feed mechanism 10.

A product or several stacked products (not shown in the Figures) may be introduced into the product space 30. When the band material 1 has been taken around the product space and its ends are held by the mechanism 50, the rotation direction of the feed mechanism 10, and op- tionally of the conveyor belt 20, are reversed. The band material 1 will, at least at the sides and top of the product space 30, become detached from the conveyor belt 20 and, due to the fact that the end of the band material 1 is held by the mechanisms 50, will become tightened around the product or products. After completion of this

process, the portion of the band material 1 applied around the product or products is cut by means of a cutter incor- porated in the mechanisms 50 such that the two ends of the portion of band material 1 surrounding the product or products overlap, after which the two ends can, for exam- ple, be welded together by means of sealing means incorpo- rated in the mechanism 50. The product or products are thus provided with a banderole made from the band material 1 and may be conveyed from the product space 30, after which a following cycle may commence.

When the band material 1 is supplied by the feed mechanism 10, one end of the band material 1 is brought near the conveyor belt 20 in order to be taken over the trajectory around the product space 30. At the beginning of this trajectory, an electrode 60 is provided in the vi- cinity of the trajectory. In the exemplary embodiment shown, said electrode 60 is put on a negative high voltage as indicated by the minus sign in Figure 1. The guide roller 40 for the conveyor belt 20, which is located in the vicinity of said electrode 60, is connected with earth potential, as indicated by an earthing sign in Figure 1, so that the conveyor belt 20 is also connected with earth potential. As a result, opposite, attracting electrostatic charges will now be applied to the conveyor belt 20 and the band material 1, effectuating an electrostatic attrac- tion between the supplied band material 1 and the conveyor belt 20. The band material 1 thus adheres to the conveyor belt 20, whereby the conveyor belt 20 takes the band mate- rial 1 with.

The materials used for the band material 1 and the conveyor belt 20 have to be selected for their suit- ability to sustain an electrostatic charge. In the embodi- ments illustrated, the band material 1 and the conveyor belt 20 comprise materials with electrically insulating properties such as, for example, plastic, paper and rub- ber.

In the embodiments illustrated, the trajectory around the product space 30 is formed by four segments: in

succession a horizontal lower first segment, a vertical second segment, a horizontal upper third segment, and a vertical fourth segment. Successive segments are somewhat spaced out, forming (in the exemplary embodiment shown) a corner of 90°. These corners are provided with permanent corner guides 70 for the band material 1.

At the same time, the corner guides 70 loosen the band material 1 from the conveyor belt 20 to allow trans- fer to a following segment. This is only schematically shown in Figure 1. In order to achieve for each segment an exceptionally good adhesion between the band material 1 and the conveyor belt 20, an electrode 60 is placed at the beginning of a following segment, connected with a high voltage having an opposite charge to that of the high voltage of the electrode 60 belonging to the preceding segment. In Figure 1, a plus or minus sign indicates whether an electrode is connected to a positive or nega- tive high voltage. In the vicinity of the electrode of each segment a guide roller 40 is provided for the con- veyor belt 20, which guide roller 40 is earthed. In Figure 1, this is indicated by means of an earthing sign.

In the embodiment illustrated, the mechanism 50 and the feed mechanism 10 are arranged at the left under the product space 30. Alternatively it is possible to po- sition the same approximately in the middle under the product space 30. The horizontal lower portion of the tra- jectory around the product space 30, will then consist of two different segments each of which possibly having its own electrode and earthed guide roller for the conveyor belt 20.

Figure 2, shows a cross section along the line A- A according to Figure 1. The Figure shows two parallel walls 80 between which the various guide rollers 40 and the conveyor belt 20 are arranged. In Figure 2 only one guide roller 40 is visible. A table 85 is connected with the side walls 80, on which the product or products can be placed. In Figure 2, the conveyor belt 20 is shown to run

round the guide roller 40 and at its upper side the band material 1 can be seen.

One of the side walls 80 is provided with an opening for an electrode 60. The electrode 60 shown is connected with a negative pole of a schematically repre- sented high voltage source 90, whose positive pole which is connected with the earth potential, is connected with the axle 45 of the guide roller 40, which axle 45 is elec- trically connected to the guide roller 40. Both the guide roller 40 connected with the earth potential, and its axle 45 are made of electrically conductive material. The sides 41 of said guide roller 40 enclosing the conveyor belt are made of an insulating material.

High voltage sources are generally known in the field of technology and will not be further explained. In practice, a high a voltage source 90 having a high voltage in the order of 20 kV has been shown to suffice. Depending on the specific application, it is possible to choose a high voltage of another order. Since no, or hardly any electrical current will be passing, a voltage source 90 of a low capacity may be chosen. This is also preferable with a view to safety.

The above-described embodiment should not be un- derstood to limit the invention. The banding machine ac- cording to the invention can be realized in a diversity of embodiments, all within the scope of the claims. One pos- sible variant within the framework of the invention is a banding machine that is equipped such that during opera- tion the band material being supplied is earthed and that an electrode connected with a high voltage is positioned in the vicinity of the conveyor belt.