Background of the invention The plastic containers (baskets or trays) of the type with which this invention is concerned are provided with a pair of arms in the form of metal or plastic rods located at both ends of the square or oblong, open-topped container so that each arm, known as a bale arm, extends along an upper edge of the side of the container, each end of the bale arm being located in a respective recess or slot located in the body of the basket. The arrangement is such that the bale arm can be moved between at least two positions. In the first position, the bale arm lies outside the open top of the container. With the two bale arms in this first position, then two or more containers may be stacked in a"nested'"configuration with one container lying almost wholly within another lower container. The bale arms are used in this position when the containers are empty and are to be returned to their source. In this way, a stack of containers will take up a minimum amount of space.

When the bale arms are in a position other than that for nested stacking, they extend across the container at a position spaced inwardly from their respective end walls.

Accordingly, when containers are stacked one upon another they are each seated on the bale arms of the next lower container and are in a"denested"configuration. The

bale arms are then said to be"inboard"whereas when they are in their"nesting" position they are stated to be"outboard".

Some containers allow only a single inboard position for the bale arm. Others are designed such that there are two or more inboard positions which differ from each other by the height of the bale arm relative to the container. In a first inboard position, the bale arm may be located at the height of the upper edge of the container.

In the second inboard position, the bale arm may be located well below the upper edge of the container. The first inboard position will be used when the container is substantially full of the product to be transported. The second inboard position may be used when the container is substantially less than full.

Whether the containers are empty, partially full of goods or wholly full of goods, they are transported in stacks. A stack of fully loaded containers may comprise about 9 to 12 containers. A stack of unloaded nested containers may comprise 25 or more containers. In order to load containers with goods, it is necessary to destack a stack of nesting containers and, similarly, in order to transport loaded or partially loaded containers, it is necessary to stack them.

Such destacking and stacking operations may be performed manually. This is time consuming and also, for loaded or partially loaded containers, work which requires considerable strength and dexterity, particularly when handling the uppermost containers in the stack. Co-pending patent application 9919937. 4 discloses apparatus and a method for automatic stacking and destacking of containers of the type with which this invention is concerned.

The containers of the type with which this invention is concerned are typically transferred over short distances in single stacks on wheeled supports known as dollies. Over longer distances, or where substantial quantities of goods are being moved, the containers are moved on larger pallets which may be loaded on vehicles and/or transported by means of fork lift trucks. The containers are arranged on the

pallet in a plurality of stacked layers, each stack typically comprising 9 containers (See Figure 1). Typically there may be five stacks arranged in a three by two formation, that is to say, each layer comprises three containers arranged side-by-side with long sides adjacent and two further containers arranged end to end with long sides adjacent the short sides of the first three containers (See Figure 2a). In this example two containers are in line longitudinally and three further pallets are in line transversely, the five containers being arranged into a rectangle of dimensions 1200mm x 1000mm.

Alternatively the stacks may be arranged in a three by three formation wherein each layer comprises three containers arranged side-by-side or in line longitudinally, with long sides adjacent and three further containers also arranged side-by-side with short sides adjacent the short sides of the first three containers (See Figure 2b). The dimension of the rectangle formed is also 1200mm x 1 000mm.

Loading or unloading stacks of containers onto or off a pallet (See Figure 3) has hitherto been carried out manually. Considerable time is required to undertake such an operation. With loaded containers, considerable strength and dexterity are also required.

Statement of the invention According to the present invention there is provided apparatus for transferring containers between a conveyor on which the containers are arranged in stacks in an in-line formation, and a pallet, on which the stacks are arranged in an out-of-line formation, the apparatus comprising means for converting the formation of said stacks between an in-line formation and said out-of-line formation, a station for accommodating said stacks in said out-of line formation, means located at said station for raising said stacks such that the base of the lowermost container of each stack is at a height greater than the height of a pallet, means for feeding a pallet to or from a position directly below said raised stacks and means for positioning said plurality of stacks on said pallet or for removing said pallet from below said stacks.

Reference will be made hereinafter to the loading of full or partially full containers from a conveyor on to a pallet but it should be understood that apparatus of the invention may be used to transfer empty containers from a conveyor to a pallet or indeed may carry out an unloading operation (pallet to conveyor) whether of full, partially full or empty containers. Indeed a single apparatus may be adjustable so that it carries out any of these operations as desired.

The present invention also provides a method for transferring containers between a conveyor on which the containers are arranged in stacks in an in-line formation, and a pallet, on which the stacks are arranged in an out-of-line formation, the apparatus comprising means for converting the formation of said stacks between an in-line formation and said out-of-line formation, a station for accommodating said stacks in said out-of line formation, means located at said station for raising said stacks such that the base of the lowermost container of each stack is at a height greater than the height of a pallet, means for feeding a pallet to or from a position directly below said raised stacks and means for positioning said plurality of stacks on said pallet or from removing said pallet from below said stacks.

Brief description of the drawings Figure 1 illustrates side. front, plan and perspective views of a typical stack of nine containers.

Figures 2a and 2b illustrate a plan view of containers arranged in a typical five and a typical six format.

Figure 3 is a perspective sketch of a typical five format of 600mm x 400mm containers loaded onto a 1200mm x 1 000mm pallet.

Figure 4 is a plan view of the apparatus according to the present invention.

Figure 5 is a diagrammatic view showing apparatus of the present invention Figure 6a is a diagrammatic view of that part of the apparatus shown in Figure 5 concerned with lifting the stacks of containers.

Figure 6b is a front elevation of that part of the apparatus shown in Figure 6a concerned with lifting the stacks of containers.

Detailed description of the invention Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings.

Referring to Figure 2a of the accompanying drawings, there is illustrated a typical formation of a layer of containers 1 as they are located on the pallet. In this example, each container has a length of 600mm and a width of 400mm and they are arranged in a three by two formation or format with two pallets in line longitudinally and three further pallets in line transversely, the five containers being arranged into a rectangle of dimensions 1200mm x 1 000mm.

When full of goods, such as packets of frozen food or packaged or loose vegetables, the containers may be arranged in the above described formation on a pallet with the stacks being at least nine layers high. As a result the pallet carries a considerable weight and height of containers.

In order to load a pallet with stacks of containers in the above described five formation, apparatus of the invention, such as that described with reference to figures 4 to 6, may be used. Referring particularly to Figure 4, three stacks of containers are fed one by one, with short sides leading, by means of feed conveyor 1 to a formation converting station 3. Upon reaching station 3 each of the first three stacks is fed, long side leading, to associate conveyor 4 which runs substantially perpendicular to

conveyor 1 and extends into adjacent station 11. At station 11 each of the three stacks are bought to a standstill at positions 5,7 and 9.

The forth stack of containers is fed with short sides leading to station 3 and onto turn- table 13. On the turntable the stack of containers is indexed through 90° and a further movement, effected by a feed conveyor 15 which runs parallel to conveyor 4, carries the stack of containers, short side leading, to the position indicated at 17 in station 11.

A fifth stack of containers is then fed with short sides leading to station 3 and onto turntable 13. This stack of containers is also indexed through 90° and then fed, short side leading. to the position indicated at 19 in station 11.

Before reaching station 11, each stack of containers fed to conveyor 15 follows a curved path as a result of a bifurcation in the adjacent conveyors 1 and 15. The three in-line stacks of containers are separated from the two in-line stacks by a central partition 21. As a result the formation of the five stacks at station 11 is substantially that of the three by two formation required for loading on to the pallet.

Conveyors 4 and 15 have two inwardly inclined guide arms 5 mounted down each side of the stack feed conveyor.

Referring to Figures 5,6a and 6b, station 11 is provided with a container lifting mechanism 23 including arms or lifting platforms 25 which are welded to a support frame 27 running through four upright channels 29 positioned at each corner of station 11 and also central partition 21. Lifting platforms 25 are arranged along the length of the frame in each upright channel and also on each side of partition 21.

These lifting platforms are arranged at the same level as each other and are capable of being lifted and lowered together and also extended and retracted in a direction towards and away from the containers.

In addition to feed conveyors 4 and 15 which transport stacks of containers from station 3 to station 11, there is located a further pair of feed conveyors 30 and 31 which extend from station 11 in a direction away from station 3. These feed conveyors may be raised or lowered above or below the level of the first-mentioned feed conveyors and are used to transport a pallet into and out of station 11.

Once five stacks of containers are situated within station 11 in the three by two formation, the lifting mechanism is operated. The lifting platforms 25 are located below the upper lip or rims 33 of the first layer of containers and with these lifting platforms extended towards the containers, they are raised, thereby raising the stacks of containers above the feed conveyors on which they previously rested. The stacks of containers are raised until the bottom of the lower level of containers is at a height above the feed conveyors greater than the height of a pallet.

Pallet feed conveyors 30 and 31 on which a pallet rests is now raised to a level just above the feed conveyors used to transport the containers. The pallet feed conveyor is then operated to feed the pallet into station 11 below the uplifted stacks of containers. The lift mechanism is then operated to lower the stacks of containers on to the pallet, following which the lift platforms are retracted. The pallet feed conveyor is then operated in the reverse direction in order to drive the pallet out of station 11.

Due to the presence of partition 21 within station 11, the set of three in-line stacks of containers is at this stage separated from the other set of two stacks. In the desired formation on a pallet, the stacks of containers are located in substantially abutting relationship. In order to achieve this guides (not shown) may be mounted down each side of the pallet feed conveyor and inclined inwardly in a direction away from station 11. As a result the two sets of stacks of containers are moved close together as the pallet proceeds between the inclined guides. The pallet comes to a standstill beyond these guides and may then be accessed by a fork lift truck for further transportation.