| 1. | A machine for stacking or destacking flat objects, such as lids for cans, one or more substantially box shaped cassettes being associated with the machine for receiving a stack of objects and having a longitudinal opening for insertion and discharge of the objects, c h a r a c t e r i z e d in that the machine has an elevator with lifting means cooperating with a level sensor so that the upper side of the stack in a cassette carried by the lifting means is kept substantially at a predetermined level, an object conveyor being provided for feeding objects to or picking up objects from the stack at this level, said lifting means being adapted to move the cassettes in elongation of each other in the direction of the stack when the cassettes are present in the vicinity of the object conveyor. |
| 2. | A machine according to claim 1, c h a r a c t e r i z e d in that the lifting means of the elevator com¬ prise a friction elevator which manipulates the cassette by friction against the sides of the cassette. |
| 3. | A machine according to claim 2, c h a r a c t e r i z e d in that the friction elevator comprises two belt assemblies arranged at their respective sides of the cassette, at least one of said belt assemblies being resiliently affected to engage the cassette, and that each belt assembly comprises an endless belt which is moved around two rollers whose common axial plane is parallel with the cassette sides in question, said belt being tightened with a third roller. |
| 4. | A machine according to claims 13, c h a r a c t e r i z e d in that the object conveyor is adapted to be moved clear of the cassettes fed in elongation of each other. |
| 5. | A machine according to claim 4, c h a r a c t e r¬ i z e d in that the end faces of the cassettes, dis¬ posed at each end of the stack, are formed with cuts allowing the object conveyor to pass through the cassettes. |
| 6. | A machine according to claims 15 and for stacking flat, magnetizable objects, c h a r a c t e r i z e d in that it has a shaftshaped buffer which is equipped with spreading magnets and which receives the objects from above, a roller being provided below the discharge end of said buffer, said roller having one or more dis¬ crete, ci cumferentially spaced magnetic poles on the surface and forming one end of a belt conveyor, whose other end is so positioned with respect to a receive cassette placed in the machine that the objects drop down into the cassette from this end of the conveyor. |
| 7. | A machine according to claim 6, c h a r a c t e r i z e d in that the roller consists of nonmagnetizable material and contains one or more radial bar magnets, and that one or more magnets are provided on the inner side of the upper belt extent of the belt conveyor to retain the transported objects on the belt. |
| 8. | A machine according to claims 15, where the flat objects are magnetizable, c h a r a c t e r i z e d in that the object conveyor is adapted to pick up objects from the stack and comprises a conveyor belt where the flat objects are fixed by means of magnetism. |
| 9. | A machine according to claims 15, c a r a c¬ t e r i z e d in that the object conveyor comprises a conveyor belt with a predetermined pattern of holes and a vacuum behind these holes. |
| 10. | A transport cassette for receiving at least one stack of flat objects such as lids for cans and intended for the machine according to claim 3, c h a r a c t e r¬ i z e d in that the cassette is substantially box shaped and provided with an opening extending in the direction of the stack, that the end faces of the cassette, disposed at each end of the stack, are formed with cuts so that the object conveyor can pass through the cassette when the cassette is fed in the direction of the stack, that the cassette is exteriorly provided with longitudinal tracks for cooperation with the end¬ less belt, and that respective projections and grooves, disposed with uniform modular spacing, are provided on the upper side and the underside. |
The invention concerns a machine for stacking or de¬ stacking flat objects, such as e.g. lids for cans, and of the type defined in the introductory portion of claim 1.
It is known that manipulation of e.g. lids for cans takes place in that an operator manually moves a stack of lids from the production machine to a box. When this box arrives at the factory where the cans are filled, another operator manually moves the lids from the box to a store on the machine. Since a machine can handle up to 400 cans/min., it requires in certain cases one operator per machine merely to provide it with lids. This is a great cost, and at the same time it must be considered a less interesting job. Therefore, great interest attaches to automatizing these operations.
The US Patent Specification 3 357 554 discloses a machine where the lids are stored in a long paper bag. This method is vitiated by the drawback that the objects rub against one another during transport of the hose. This mechanical wear is not desirable since it increases the probability of the lid surfaces being damaged, which may prevent hermetic sealing of the can.
NO 32715 discloses a machine for automatic filling of can lids in cassettes. This machine is inexpediently constructed since the structure does not enable con¬ tinuous flow of cassettes through the machine, which is necessary for a sufficient number of objects to be handled. The cassettes are moreover not expediently arranged with a view to automatic emptying, so it must be assumed that they are emptied manually.
The object of the invention is to provide a machine of the type defined in the introductory portion of claim 1, where the objects are stored and manipulated in an ex¬ pedient manner, and where the necessary manual labour is limited.
This is achieved as stated in the characterizing portion of claim 1 in that the objects are stored in cassettes which fix and protect the lids during transport, and which are moved in elongation of each other in the vicinity of an object conveyor.
When the machine is constructed as stated in claims 2-5, the cassettes will be fed expediently.
An object conveyor for filling a cassette as stated in claims 6-7 provides a very gentle manipulation of the objects during the stacking process. The buffer is pro¬ vided with spreading magnets so that air is present be- tween the objects, and the magnet fixation against a flexible belt on the conveyor entails that it is very unlikely that the objects will be damaged.
An object conveyor for emptying cassettes as stated in claims 8-9 involves very gentle manipulation of the ob¬ jects in the destacking process.
Claim 10 defines a cassette for use in the machine of claim 3.
The invention will be explained more fully below with reference to the drawing, in which
fig. 1 shows a cassette for storing flat objects,
fig. 2 is an outline diagram of the machine,
fig. 3 shows how the gripper cooperates with the cassette,
fig. 4 shows a preferred embodiment of the pick-up means,
fig. 5 shows a preferred embodiment of the feeding means.
Fig. 1 shows a cassette 9 for storing flat objects, e.g. lids for cans. Both ends of the cassette are formed with a cut 11, which enables an object conveyor to reach in¬ wardly over the flat object. Both sides of the cassette are formed with feed grooves 10, whose function will be explained in connection with fig. 2. Owing to practical stacking of the cassettes, they are moreover provided with knobs 12 on the upper edge and grooves 13 under the bottom so that they can be stacked in bond.
Fig. 2 shows a sketch of the actual machine. A feeder 20 feeds filled cassettes to an elevator 21 which lifts a cassette so that the lifting means 22 can grip it. The lifting means consist of two belts which are squeezed into the feed grooves 10 in the cassette. The location of the upper object in the cassette is constantly ad¬ justed so that there will be a suitable predetermined distance between it and the object conveyor 24. After emptying the cassette is pushed aside by a manipulator 23. Instead of lifting means 22 based on friction, the cassette may be manipulated by means of relaseable en¬ gagement means operating on the sides of the cassette or on the bottom of the cassette; the cassettes are merely to be movable in elongation of each other, and prefer¬ ably in immediate elongation.
Fig. 3 shows how the object conveyor 24 cooperates with the cassette 9.
Fig. 4 shows a preferred embodiment of an object con¬ veyor for picking up flat objects, and this pick-up means may be used when the objects are magnetic.
A belt 40 runs continuously, and an electromagnet 41 is positioned above the flat object. When the electro¬ magnet 41 is activated, the uppermost object is lifted and retained against the belt 40 which moves it past a number of permanent magnets 42 so that it is constantly engaged with the belt until it reaches a chute or a con¬ veyor belt where it drops down because the magnetic ef¬ fect is too small here.
In case of non-magnetic materials an embodiment of the pick-up means is conceivable where the objects are re¬ tained against the belt by means of a suction mechanism, the belt being provided with a suitable pattern of holes so that there will be a certain interval between suc¬ cessive manipulations.
Fig. 5 shows a preferred embodiment of an object con¬ veyor for feeding flat objects when these are magnet¬ izable. For filling the cassette, the machine operates as outlined in fig. 2, with the cassettes merely running in the opposite direction. Flat objects are fed e.g. from a can lid machine to a shaft-like buffer 50. The buffer is provided with spreading magnets 51 causing the plates to be magnetized so that poles with a common sign will be positioned on top of each other so that two suc- cessive plates reject each other while being retained in the buffer. At the discharge end of the buffer there is mounted a roller 52 equipped with one or more circum- ferentially distributed magnetic poles 53. The roller 52 forms one end of a belt conveyor 54 so that having been attracted by one of the magnetic poles 53 of the roller 52 an object from the buffer will continue via the belt conveyor 54 to its other end. The other end of the belt
conveyor is so positioned with respect to a receive cassette 9 that the object drops down into the cassette 9 from this end of the conveyor 54. Magnets 55 may be provided on the inner side of the upper extent of the belt conveyor to retain the transported objects against the belt.