This invention relates to a method and to a device for application of self adhesive labels onto sacks having filling tubes, and further to a ^■ _* conveyor especially designed to allow a label application also to the bottom side of a continously conveyed sack. ^" "•i To be able to fill the sacks with bulk material in a rational way a filling tube is often used in connection to one of the corners of the sack. This tube is folded and sealed after the filling. The impenetra¬ bility and the safety of the sealing methods used today are not satisfactory in sackfilling of e.g. corrosive bulk material as e.g. meta silicate, or of other dusting material as cement and ceramic materials. This is especially the case with smaller sacks where the filling tube is short making the sealing action inadequate. Besides giving a defective closure the existing closure methods are also very slow, among other things depending upon that the sacks often have to stand still for some seconds the closure performance. This means that a closuring capacity of just about 150 sacks/hour is common. Sealings with melt¬ ing glue cannot be used together with various existing bulk material as a chemical reaction can occur between the bulk material and the melting glue/heat. Moreover melting glue cannot be brought to the corner tips of the sack- in a simple way to assist in forming a complete closure.

Pre-glued sacks , i.e. sacks where glue strings are applied at one corner portion of the sack at the manufacturing of the sack, is often more expensive than conventional sacks and moreover they demand a special equipment to heaten the pre-glued portion, or in some other way carry out the closure of the pre-glued sack.

Furthermore there is a demand from shipping autorities and from transport organizations that bulk material harmful to the environ¬ ment shall be properly packed.

The main object of this invention is to obtain a method and a device to both rapidly (up to 1.000 sacks/hour), safely, exactly and ^* continously apply self adhesive labels onto sacks with filling tubes.

An other object of the invention is to obtain a closure technique which is not sensitive to different forms of the sack by being automatically adapted to these forms and also seal e.g. that part of the corner portion of the sack normally resting on the conveyor.

According to this invention these objects are obtained by the method and the device having the characterizing clauses mentioned in the claims.

By letting the label being carried onto an elastically resilient web at an applicator means it is possible to apply these labels onto sack during their conveying on a conveyor. Thus, this elastically resilient web at the applicator means and the label will be formed after the contour of the sack and will be safely adhered to the surface of the sack. An especially favourable adhesion of the label onto all sides of the corner of the sack is possible by using an upper and an lower guiding plate at the applicator means to press the label agaist the surface of the sack.

A retaining force onto the label provided by vaccum at the applicator means is so small that it in no ways prevents adaption to the sack and adhesion of the label onto the sack.

By having the applicator means working with label application onto sacks being moved this applicator mens is preferably given a move¬ ment being such that said means "catch up" the sack. The obtained relative motion between the sack and the applicator means will lead to an inturned deflection of the rubber web of the applicator means during the application of the web.

The vaccum used to hold the label is brought to the rubber web of the applicator means through conduits in such a way that these ends in the rubber web. The vaccum is controlled in such a way that there is no vaccum during the feeding of the label to the applicator means. The vaccum is immediately applied when the label has taken its correct position at the applicator means.

One embodiment of the invention will now be described by way of example with reference to the accompanying drawing, i.e. without a specific description of neither the device feeding the label nor the controU and transfer mechanism of the applicator means. This device and this mechanism are necessary to carry out the invention, but they are well known in different embodiments to the man skilled in the art.

Fig. 1 shows a diagrammatic view from above of a label applicator means in a label recieving position at the side of the sack conveyor,

Fig. 2 is a view corresponding to fig. 1 but where the label is correctly positioned at the applicator means and where this means has been brought back and turned in a direction towards the sack conveyor,

Fig. 3 a is a view corresponding to fig. 2 where the label applicator means har been brought forward over one corner of the sack for applying the label, and

Fig. 3b is a side view showing the upper and lower guiding plates applying a force to safely adhere the label onto the face of the sack.

In fig. 1 the label applicator means 1 with the rubber web 2 is in a waiting position where a label 3 carried by a web 4 i". fed to the applicator means 1. The feeding of the label 3 to the applicator means 1 and the loosening from the label web 4 occurs when the web 4 is brought around a non-cutting edge of a knive means 5 during a driving roller 6 and a counter pressur roller feeding of the web 4 from a supply roller to a collecting roller. As the label 3 can be made of stiff aluminium folie or of a stiff plastic film having a very strong adhering glue surface at its back side, i.e. the side being directed upwards when the label 3 is correctly positioned onto the applicator means, blowing nozzles 8a, 8b have been arranged on one hand towards the knife edge 8a and on the other hand towards the rubber web 2 (8b) of the applicator means 1 to assist in loosening the label from the label web and to press the label towards the rubber web. Brushing means 5a is arranged to slow down and to stretchen the label web 4 during its feeding. When the label is in a correct position at the applicator means, which is sensed by a transmitter, e.g. a photocell device 7, vaccum means is activated through conduits 9 and will suck the label onto the rubber web 2 of the applicator means.

A stationary transmitter, preferably a photocell 13 in connection to a conveyor 10 is shown just being passed by one corner of a sack 12 or by the trailing edge of a filling tube. This means that a signal is sent to an activating means (not shown) of the applicator means having the applicator means to start moving and takes in that • moment the position shown in fig. 2, i.e. the applicator means has been turned about 45° towards the sack conveyor 10, from where it is

directely brought against and onto/over the corner portion of the sack 12 as is shown in fig. 3a and fig. 3b. From fig. 3a is also shown that both the rubber web 2 of the applicator means 1 and the label 3 will hold a form- completely corresponding to the corner of the sack 12 (incL a collected filling tube, if any). This means that a safe closure of the sack opening/filling tube is obtained. The positions and the acting of the upper and lower guiding plates 14a and 14b, respectively, can be seen in fig. 3b. Thus by arranging the guiding plates it is possible to bring the label around and over all the sides bordering the corners - of the sack, whereby an adhesion of the label onto its sides is possible to obtain.

The invention is not restricted to the above described embodiment, but modifications can be made within the scoop of the appended claims.