After being manufactured, a number of different objects, particularly packaging for foodstuffs, are placed in stacks. These stacks can be transported to a store or a shop, where they are offered to consumers. In order to hold down costs, it is desirable for this placing of the objects in stacks to be performed in a fast and inexpensive manner. The stacking of the objects is therefore usually carried out automatically with packing machines which stack the objects in transportable shelves or trolleys which are then transported to a store or a shop. An example of objects which are placed in stacks is milk bottles which are placed in shelf trolleys in a dairy. These shelf trolleys are then driven to cold storage in a shop, where the consumers pick the milk bottles directly from the stack.

When placing objects in shelf trolleys or other storage units with a packing machine, the objects are placed in layers. Based on the requirement for a stable positioning of the objects, it would be desirable to place each layer of objects on a separate base, for example in the form of a shelf. Based on the requirement for a fast and inexpensive positioning of the objects, and based on the requirement that the same shelf trolley or other storage unit should preferably be used for objects of different height, however, it is desirable to stack the layers of objects directly on top of one another, thus forming a connected stack of objects. In practice, a compromise will often have to be made between these two requirements, for example by every second or every third layer being placed on a shelf or another fixed base, and the intermediate layers being placed on top of these layers which are placed on the fixed base.

In order to achieve adequate stability, it is also often necessary in addition to place a loose support sheet or a support plate under the layers of objects which are not placed on a fixed base. This support sheet may be made of cardboard.

A commonly-used material for the support sheet, however, is a corrugated plastic sheet.

The loose support sheets can be placed manually on top of the underlying layer of objects before the next layer of objects is placed in the stack. This is relatively problem-free, but involves unwanted costs. Consequently, it is desirable to be able to place the support sheets automatically in the stack.

Automatic placing of support sheets in the stack, however, is not altogether without problems, since a shelf trolley or another storage unit is often provided with stiffeners which prevent access from the side. If the shelf trolleys are open at the top, the support sheets can be dropped down from above, but since the support sheets have a large surface and are made of a light material, the air may cause them to slide laterally out of the correct position. It is often not possible to fit support sheets from above either, since the shelf trolleys or the storage units are often provided with fixed shelves which prevent access from above. Automatic placing of support sheets in the stack is further complicated by the fact that the vertical position for placing the support sheet is constantly altered as the shelf trolley or the storage unit is filled with new layers of objects.

The object of the invention is to provide a method for placing support sheets under layers of objects in a stack, and devices for placing support sheets under layers of objects in a stack.

The object is achieved with a method and devices of the type mentioned in the introduction which are characterized by the features which are indicated in the claims.

The invention will presumably have its primary application in packing machines employed in the food industry for stacking drink cartons, preserving jars, tins, bottles, cardboard boxes and plastic boxes, but it should be understood that the invention has general application in any location where objects are stacked in layers.

The invention will now be explained in more detail in connection with a packing machine which is employed in a dairy, with reference to the accompanying drawings, in which: fig. 1 is a schematic illustration of a packing machine for placing an arrangement of objects in a stack of objects in a shelf trolley, fig. 2 illustrates the packing machine in fig. 1 with a support sheet placed under the arrangement of objects,

fig. 3 illustrates the packing machine in fig. 1 after the arrangement of objects and the support sheet have been passed in over the stack, fig. 4 illustrates the packing machine in fig. 1 with the arrangement of objects and the support sheet placed in the stack, while their support in the packing machine is in the process of being passed out of the shelf trolley, fig. 5 is a schematic illustration of a packing machine with a store of support sheets, as a support sheet is in the process of being passed into a stack of objects, fig. 6 illustrates the packing machine in fig. 5 after the support sheet has been passed into the stack, fig. 7 illustrates the packing machine in fig. 5 as a new support sheet is in the process of being supplied from the store of support sheets, fig. 8 illustrates the packing machine in fig. 5 as this new support sheet is in the process of being passed into the stack of objects, and fig. 9 illustrates a packing machine with a store of support sheets, where the support sheets are passed from the store to an intermediate position before being passed into the packing machine.

Fig. 1 is a schematic illustration of a packing machine for stacking objects.

The packing machine is employed in a dairy, and the objects are milk bottles 17 which are stacked in a stack 7 in a shelf trolley 19.

The packing machine comprises a drawer 2 which in fig. 1 is illustrated in a loading position 5, with an arrangement 3 of bottles 17 standing on a support 4 in the drawer 2. Fig. 1 shows only one row of bottles 17, but there will normally be several rows behind one another, for example between four and eight rows, with the result that the arrangement 3 of bottles is rectangular.

The drawer 2 is horizontally movable forwards and backwards in a direction of feed F and opposite F respectively, between the loading position 5 and a stacking position 6 (see fig. 3) where the arrangement 3 of bottles is located immediately above the stack 7, inside the shelf trolley 19.

The drawer's 2 horizontal mobility is achieved by the drawer 2 being attached in a conveyor bracket 21 which is slidingly or rollingly mounted in conveyor rails or a conveyor table 15, and which can be moved forwards and backwards

in direction F and opposite F by one or more actuators, which may comprise hydraulic or pneumatic cylinders, chain drives, belt drives, electrical linear actuators or other kinds of movement devices. The conveyor rails 15 in turn are supported by a base 14.

The shelf trolley 19 has a bottom 8 and three shelves 20,20', 20", whereof at least the middle shelf 20"is of a type which can be tilted up, thus enabling the shelf trolley 19 to be adapted for placing several types of objects. A first layer 1 of bottles is placed on the bottom 8 of the shelf trolley, and a second layer 1' of bottles is placed on top of the first layer 1. In order to ensure adequate stability in the second layer 1'of bottles, a support sheet 10 is placed between the first layer 1 and the second layer 1'of bottles. A third layer 1"of bottles is placed on the bottom shelf 20 without any underlying support sheet 10.

The packing machine comprises a holder 9 for retaining the arrangement 3 of bottles 17 in the stacking position 6 when the drawer 2 is moved away from the stacking position 6, with the result that the arrangement 3 of bottles is thereby pushed out of the drawer 2. The holder 9 is movable by means of a not shown mechanism, which may comprise an articulated mechanism or a linear actuator which can move the holder 9 between an inactivated position illustrated in fig. 1, where the holder 9 has no function, and the position where it restrains the arrangement 3 of bottles 17 (see fig. 3).

The packing machine further comprises non-illustrated devices for relative vertical positioning in the direction V and opposite V of the drawer 2 relative to the stack 7 or the stack's base, i. e. the bottom 8 of the shelf trolley. The devices for relative vertical positioning may be composed of an elevator, either for the shelf trolley 19 or for the drawer 2, and possibly also the conveyor rails 15 and the base 14.

The relative vertical positioning of the drawer 2 relative to the shelf trolley 19 is controlled dependent on how many layers of bottles 17 are already stacked in the stack 7. By means of this vertical positioning, the drawer 2 is inserted into the shelf trolley 19 at the correct height for placing the arrangement 3 of bottles either on the base 8, on one of the shelves 20,20', 20", or as the top layer in the stack 7.

A transporter 18 for insertion of more bottles 17 is located on the other side of the drawer 2 relative to the shelf trolley 19. After an arrangement 3 of bottles 17 has been transferred from the drawer 2 to the shelf trolley 19 when the

drawer is located in the stacking position 6, a new arrangement 3 of bottles 17 is loaded into the drawer 2 from the transporter 18 when the drawer is located in the loading position 5.

The packing machine also comprises non-illustrated pushers, guides, support surfaces and brackets for conveying the bottles 17, which is known in the prior art, and which for reasons of clarity is not illustrated in the figures. In addition, the packing machine comprises devices for operation and control of various movable parts, typically comprising electrically or pneumatically driven actuators and an electronic control unit of a type which is capable of receiving, storing and transmitting information and processing it according to established algorithms and instructions from an operator.

Fig. 2 illustrates the packing machine in the same position as in fig. 1, but in this case a support sheet 10 is placed under the bottles'17 position in the drawer 2. In the illustrated embodiment the support sheet 10 is placed on a support 11 for the support sheet. A pusher 12 abuts against the side of the support sheet 10 facing away from the stack 7. The pusher 12 is movable in the direction F and opposite F by means of a non-illustrated mechanism, which may comprise an electrical linear actuator, a belt drive or a pneumatic or hydraulic cylinder.

In fig. 3 the drawer 2 is moved to the stacking position 6, and the arrangement 3 of objects is located immediately above the stack 7. The middle shelf 20'in the shelf trolley 19 is not shown in figure 3, since this shelf is tilted up to the side in order to make space for the arrangement 3. The holder 9 is moved to a position where it abuts against the bottles 17 which are located nearest the packing machine. Relative to the drawer 2, the pusher 12 is pushed slightly forwards in the direction F, which has resulted in the support sheet 10 also being moved slightly forwards in the direction F.

In fig. 4 the drawer 2 is moved slightly away from the stacking position 6 towards the loading position 5, opposite the direction F. Relative to the stack 7, the holder 9 has retained the position it had in fig. 3, and the holder 9 thereby pushes the bottles in the arrangement 3 out of the drawer 2. Relative to the stack 7, the pusher 12 has also retained the position it had in fig. 3, and the pusher 12 thereby pushes the support sheet 10 out of its support 11 down on to the third layer 1"of bottles. The bottles in the arrangement 3 thereby slide

down on to the support sheet 10, thereby forming a fourth layer 1"'in the stack 7.

The drawer 2 is then moved back to the loading position 5 for loading a new arrangement 3 of bottles from the transporter 18. By means of a relative vertical positioning of the shelf trolley 19 and the drawer 2 with the said devices, the drawer 2 is positioned in the direction V to a height where the next arrangement 3 of bottles will be able to be inserted as the next layer in the stack 7.

The feeding of the support sheet 10 in the direction F before the drawer 2 is moved away from the stacking position 6, which was described with reference to fig. 3, is a preferred embodiment of the invention, resulting in a controlled and repeatable positioning of the support sheet 10 relative to the layers 1", 1"' of bottles. It is also entirely possible, however, to use the invention without feeding in the support sheet in this way before the drawer is moved away from the stacking position.

The supports 4,11 for the arrangement 3 of objects may be designed in different ways, being composed, for example, of corrugated or perforated plates, grids, rails or rods. To obtain a robust construction of the packing machine, however, it is preferred that the drawer 2 has a double bottom, where the support 4 for the objects 17 is composed of an upper bottom and the support 11 for the support sheet 10 is composed of a lower bottom.

In the embodiment illustrated in figs. 1-4 the support sheet 10 is placed on the support 11 when the drawer 2 is located in the loading position 5. Here the support sheet 10 can be placed on the support 11 before, simultaneously with or after the arrangement 3 of bottles is placed on its support 4. The support sheet 10, however, may also be placed on the support 11 when the drawer 2 is located outside the loading position 5, before or after the arrangement 3 of bottles is placed on the support 4. The support sheet 10 can be inserted in the drawer 2 from one of the sides, or from the front or the back relative to the direction of feed F.

In a second embodiment of the invention, where there is no separate support for the support sheet 10, the support sheet 10 is placed on the objects'or the bottles'support 4 in the drawer 2, and the bottles 17 are placed on top of the support sheet 10 when the drawer 2 is located in the loading position 5. In this case the drawer 2 has a graduation or lip between the objects'support 4 and the

transporter 18. This graduation or lip faces the bottles'support 4, and the support sheet 10 is placed in such a manner that the edge of the support sheet is located on a level below the edge of the graduation or lip. The bottles 17 can thereby be inserted horizontally in the drawer 2 from the transporter 18 without colliding with the edge of the support sheet 10. When the drawer 2 is located in the stacking position 6, and the holder 9 restrains the arrangement 3 of bottles, friction between the underside of the bottles 17 and the support sheet 10 will contribute to retain the support sheet in the stacking position 6 when the drawer 2 is moved away from the stacking position.

In order to ensure that the friction between the underside of the bottles 17 and the support sheet 10 is sufficiently great to retain the support sheet in the stacking position 6, the support 4 in the drawer 2 in this embodiment of the invention can be coated with a low-friction coating, such as teflon. In order to further ensure that the support sheet 10 remains in the stacking position 6 when the drawer 2 is retracted, the support 4 in the drawer 2 may be composed of a number of rollers of very small diameter and with longitudinal directions across the drawer's 2 direction of feed F, and possibly with an external conveyer belt. The support sheet 10 will thereby be easily removed from the drawer 2 when the drawer 2 is moved away from the stacking position 6.

These rollers or the conveyer belt may be driven by a drive device which is activated when the drawer 2 is moved away from the stacking position, thus further ensuring that the support sheet 10 remains in the stacking position 6 when the drawer 2 is moved away from the stacking position. Alternatively, in this embodiment of the invention too, the drawer may have a separate pusher for the support sheet, which may be combined with the graduation or lip which ensures the collision-free insertion of the objects from the transporter 18.

Figs. 5-8 illustrate a preferred embodiment of the packing machine, where it is combined with a store 13 of a stack of support sheets 10. The objects and the stack of objects are not shown.

In fig. 5 the drawer 2 has been moved along the conveyor rails 15 in the direction F, and is located in the stacking position 6. The support 4 for objects is illustrated partly cut away in order to show the support sheet 10 and its support 11. The store 13 of support sheets is located beside the conveyor rails 15.

In fig. 6 the drawer 2 has been moved back along the conveyor rails 15 in the direction opposite F, and the support sheet 10 has remained in the stacking position 6.

In fig. 7 the drawer 2 is still located in the loading position 5, and a new support sheet 10 has been inserted in the drawer on top of the support 11, under the support 4 for the objects. Yet another support sheet 10'lies ready to be inserted in the drawer 2 from the store 13 in a direction S. The feeding of the support sheets 10 from the store 13 is performed by non-illustrated pushers and transporters, which are controlled by the said electronic control unit.

In fig. 8 the drawer 2 is again fed in the direction F to the stacking position 6, and the new support sheet 10'lies ready to be placed in a stack. The drawer 2 will then be moved back to the loading position 5 for the insertion of a new support sheet 10.

Fig. 9 illustrates a preferred embodiment of the packing machine according to the invention, which is particularly advantageous when the support sheets have corrugations. In this case the support sheets 10 are composed of sheets of plastic or cardboard with corrugations 16 of a thickness of the order of 3 mm, which is advantageous with regard to the strength and rigidity of the support sheets.

The corrugations extend in the direction of feed F, and an expulsion of a support sheet from the store 13 as illustrated in figs. 5-8 will be impossible in practice, since when they are located in the stack in the store 13, the support sheets 10 are locked together in a horizontal direction across the corrugations 16, which horizontal direction is parallel with the direction S.

In the embodiment in fig. 9 the support sheets 10 are removed from the store 13 in a direction P across the direction S, or more specifically perpendicular to the direction S, whereupon the support sheets 10 are inserted in the drawer 2 in the direction S, and into the stack in the direction F, as explained with reference to figs. 5-8. The direction P coincides with the direction of the corrugations 16, thus enabling the removal of only one support sheet at a time from the store 13. The problem regarding the impossibility of pushing support sheets one by one out of the store 13 across the corrugations 16 is thereby solved.

In the above, the invention has been explained with regard to placing a support sheet under a layer of objects which are placed on top of a second layer of objects. It should be understood, however, that the support sheet can also be placed under layers of objects which are placed on fixed bases, which may be expedient, for example if the fixed base is composed of a grid with apertures which are so large that the objects would not stand steady without the support sheet. Another example of a case where it may be desirable to place a support sheet under a layer of objects placed on a fixed base is when packing goods in cardboard boxes. The bottom of the cardboard box, which can be said to form a fixed base, may be too weak to be capable of supporting the weight of the objects on its own, if the weight is not distributed by means of the support sheet. This latter problem applies particularly in cases where the cardboard box may be exposed to moisture after long-term storage, with the result that the strength of the cardboard box is impaired.