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The present invention is concerned with equipment by means of which the numbers of boxes in incomplete stacks of boxes fed forwards on a conveyor can be increased to a certain desired number of boxes.
Equipments of this type are used in various shipping departments, warehouses and equivalent in which quantities of merchandise are supplied for delivery as collected or packed into box-like units of equal size, or stored as box stacks of certain height. As examples might be mentioned bakeries and wholesale companies, from which merchandise is delivered every day to retail stores. Goods of this sort are delivered as packed into boxes developed for this purpose. In such a case, some retail ' storekeeper may receive, e.g., three boxes of a certain merchandise and four boxes of some other merchandise. The said quantities of merchandise are collected and delivered to the shipping department either as two successive stacks of boxes, which, thus, contain three boxes and four boxes, respectively, or, alternatively, as one stack of boxes containing seven boxes. In order to take advantage of the full capacity of the transport vehicle, it would, however, be advantageous if. all the stacks of boxes to be trans¬ ported were of a height of, e.g., ten boxes. This is of course possible, e.g., so that the lorry driver completes the incomplete stacks of boxes in connection with the loading out of a stack of boxes destined to some other delivery destination. Such a procedure, however, requires an abundance of human work and, above all, it makes the operations in the shipping department slow. In order to eliminate this problem, various equip- ments have been developed which automatically equalize the stacks of boxes arriving at the shipping line so that they contain a certain maximum number of boxes.
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However, it is a drawback of these prior-art equipments that, at the equalizing stage of the stacks, they handle the boxes one by one, which procedure does not permit a rapid and smooth equalizing operation. An essential improvement has been obtained for the said problem of equalization of stacks of boxes by means of the equipment in accordance with the present invention, whose characteristics come out from the attached patent claim. The invention and the operation of the equipment in accordance with the invention will be described with the aid of the attached drawing, wherein the operation of the equipment is illustrated as steps I to VI. The equipment in accordance with the inven¬ tion is intended for the handling of stacks of boxes carried forwards on an appropriate conveyor, e.g., to a loading point, so that a desired equal number of boxes is received for each stack. The conveyor may be a roll conveyor, on which the box stacks arrive from the box-packaging stage.
The equipment in accordance with the inven¬ tion includes two pairs of lifting arms 2 and 4 of op¬ posite directions, supported by an appropriate support structure 1 _■ which said pairs of lifting arms have been provided in view of grasping some box in the stacks of boxes and in view of lifting the said box (and the boxes placed on that box) . The support struc¬ ture 1 may consist of columns placed at both sides of the conveyor, the top ends of the columns being con¬ nected together by means of a transverse beam. This supporting frame structure is provided with means for lifting and lowering the pairs of lifting arms as well as with appropriate sensing members in themselves known, such as limit switches, photocells, and equivalent for controlling the operation of the pairs of lifting arms by means of logic circuits.
Step I shows an operation situation in which a box stack 5 is coming to transportation, which stack comprises four boxes, and thereinafter a stack 6 that comprises five boxes. In the example case, a number of boxes favourable in view of the . transportation is, however, 10 boxes per stack.
The first box stack 5 is stopped by means of j control means included in the equipment at the so-called equalizing position, and the following stack 6 at the so-called completing position. The pairs of lifting arms are at this stage in their lower positions. The first pair of lifting arms 2 receives a command from its control circuit to grasp the box of stack 5 that is at the leve.l of the pair of lifting arms (always the lowermost box in the stack). Hereupon the pairs of lifting arms start rising (while the pair of lifting arms 4 is open) . The lifting movement goes on until the topmost box in the first box stack 5 meets a limit stop 3, which is a sensing member and placed at the height corresponding to the desired number of boxes in each stack. The limit stop 3 transmits the corresponding information to the control circuit, whereby the other pair of lifting arms 4 receives the grasping command. This said situation is shown in step II of the attached drawing.
In this situation, the stack 6 at the equalizing position, however, comprised five boxes only, so that the pair of lifting arms 4 had by-passed the stack 6 at the stage when it received its grasping command. Under these circumstances, the pair of lifting arms had to "grasp nothing" . The next step of operation is a further movement of the lifting arms upwards by about half the height of a box; the signifi¬ cance of this movement will be explained later. After this movement step, the conveyor on which the stacks of boxes rest, or a shifting member included in the equip¬ ment, receives a command to move the box stack 6 placed
in the feeding position to the equalizing position, whereby it becomes placed underneath the raised stack of boxes 5. After the box stack 6 has reached its position in the equalizing position, the lifting arms receive a command to be lowered. The lowering movement goes on until the lowermost box in the box stack 5 has been lowered onto the topmost box in the box stack 6. At this stage, the pair of lifting arms 2 receives a command to be opened, whereby a stack of nine boxes has been obtained in the equalizing position, as comes out from the right stack of boxes in step III.
The next box stack 7 coming on the conveyor comprises six boxes. This stack of boxes is stopped at the feeding position. Thereupon the lowered pair of lifting arms 2 receives an operating command to grasp the combined stack of boxes 5,6 placed in the equalizing position, the lowermost box of the stack. After the grasping stage, the pair of lifting arms, as well as the other pair of lifting arms 4 moving together with it in the vertical direction, receive the command to rise. After the topmost box in the combined stack of boxes 5,6 has reached the limit stop 3, the other pair of lifting arms 4 again receives a command to grasp, whereat it grasps the box at that time placed at its level. This is the second box from the bottom in the stack 7, for the combined stack 5,6 had risen by the missing one box only before the topmost box • met the limit stop 3. Hereupon the grasping arms 2 and 4 still rise by an additional half the height of a box in the way described above in order that the topmost boxes in the box stack 7 should definitely rise apart from the lowermost box in the stack, which lowermost box is, in this case, not subject to the lifting effect of the arms 4. After the detaching lifting stage, the operation goes on in the way described above, i.e. the conveyor is started and shifts the lowermost box in
the stack 7 to the equalizing position, onto which box " the lifting arms 2 then lower the combined stack 5,6. The result is a full-height stack of ten boxes, which is passed further, e.g., to the transport vehicle or to the warehouse shelf. The stack 7, from which the lowermost box was removed, is lowered onto the con¬ veyor as supported on the arms 4, which arms release their grasp after they have reached their bottom posi¬ tion, whereupon the reduced stack 7 is transferred to the equalizing position. This situation is shown in step V of the drawing, wherein a new stack 8 to be equalized is also shown as arriving in the equipment, by means of which said stack 8 the remaining number of boxes in stack 7 is increased in accordance with step VI.
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