WO2003080483A1

WO2003080483A1 - Apparatus, device and method for handling of product units

Info

Publication number: WO2003080483A1
Application number: PCT/DK2003/000204
Authority: WO
Inventors: Erik Lund Jepsen; Peter Folkmann; Klaus Thoegersen
Original assignee: Slagteriernes Forskningsinstitut
Priority date: 2002-03-27
Filing date: 2003-03-26
Publication date: 2003-10-02
Also published as: AU2003218633A1; DK200200471A

Abstract

An apparatus for handling of products, e.g. slaughterhouse products, comprises an elevator device (10), which has a lifting column (14) and a lowering column (15). Each of the columns has a plurality of product support units (12) placed above each other and a mutual vertical distance, lifting means (22) for stepwise and simultaneous movement of the support units in the lifting column inupwards direction to predetermined stop positions, and lowering devices (22) for stepwise and simultaneous movement of the support units in the lowering column in downwards direction to other stop positions. There are a first transfer device (18) to transfer a support unit in the top stop position in the lifting column to the lowering column and a second transfer device (19) to transfer a support unit in the bottom stop position in the lowering column to the lifting column. The apparatus also comprises a supply conveyor (16) for supply of one or several product units to a support unit, which is located in a predetermined stop position in the elevator device, and at least two removal conveyors (17) to receive product units from support units, which are located in predetermined stop positions opposite the conveyors.

Description

Apparatus, device and method for handling of product units

The invention relates to an apparatus, a device and a method for handling of product units.

A very high number of different apparatuses for sorting and separation of product units into groups are known. During the transportation of products from one production or processing place to a storage or packing place these apparatuses can for instance sort and separate the product units into product groups of particular sizes and categories.

The present invention provides an apparatus, a device and a method which are suitable for such s orting a nd se paration, a nd w hich a re v ery flexible a nd u niversal, a nd h ave o nly a relatively small need for space.

The apparatus according to the invention for handling of product units comprises:

- an elevator device which has a lifting column and a lowering column, each of which has a plurality of product support units which are placed above each other and at a mutual vertical distance, lifting means for stepwise and simultaneous movement of the support units in the lifting c olumn in upwards direction to predetermined stop p ositions, and lowering means for stepwise and simultaneous m ovement of the support units in the lowering column in downwards direction to other stop positions, a first transfer device to transfer a support unit in the top stop position in the lifting column to the lowering column, and a second transfer device to transfer a support unit in the bottom stop position in the lowering column to the lifting column, - a supply conveyor for supply of one or several product units to a support unit which is located in a predetermined stop position in the elevator device, and

- at least two removal conveyors to receive product units from support units which are located in predetermined stop positions opposite the conveyors.

Product units which are supplied to the elevator device by the supply conveyor in random order and/or at random time intervals can be delivered, by suitable control of the elevator device, to the removal conveyors in a desired sequence, a desired grade and/or at desired intervals in distance. In proportion to its capacity the elevator device being used requires very little space as far as base size is concerned.

The support units in the elevator device can have any suitable shape with a support surface for the product units. In a preferred embodiment each of the support units comprises a conveyor, preferably a conveyor belt, and in this instance the support surface can be formed by the upper run of the conveyor belt. The product units can in this way be moved on to and out from the support surfaces by activation of the conveyors with these support surfaces. In other embodiments the product units can be carried from the supply conveyor to the support surfaces in the elevator device and from these to the removal conveyors by means of push devices, which can for example be activated by means of pneumatic or hydraulic cylinders.

The lifting and lowering means of the elevator device can be of any suitable type which ensures that the support units - also by transfer from one column to the other - are moved in such a way that the product units can remain supported by these. In the preferred embodiment the lifting and lowering means comprise flexible, continuous chains, straps or belts, which are provided with carriers to carry the support units. The carriers can for example have the shape of rollers or brackets with upwards-turning support surfaces, which can fit tightly against the underneath of protruding flaps or flanges designed on the support units. In order to increase the stability of the support units during their upwards and downwards movements in the columns of the elevator device the support units can be designed with rollers or other contact devices designed to have a sliding fit against vertical guide rails or guide surfaces.

The support units in the two columns can for example be carried by a total of eight vertically running, continuous, flexible chains, straps or belts placed in the respective four corners of each column. Alternatively, a total of six continuous, flexible chains, straps or belts can be used, two of these, which are located between the two bordering columns, are common to the support units in these columns. In the preferred embodiment the support units are carried by a first and a second continuous chain, strap or belt, each of which has a first and a second vertical run, and wherein each support unit in the lifting column is carried by carriers on the first run of the first and the second flexible chain, strap or belt respectively, whereas each support unit in the lowering column is carried by carriers on the second run of the first and the second flexible chain, strap or belt respectively. In this embodiment the continuous chains, straps or belts will carry each of the support units by only two corners located diagonally opposite each other. Therefore, it is appropriate to stabilize the vertical, translatory movements of the support units along the lifting column and the lowering column respectively by means of vertical guidance means.

The first and second transfer means can comprise any suitable type of pushing or pulling devices. In an advantageous embodiment, however, each of them comprises horizontal guidance means and shifting devices, such as hydraulic or pneumatic cylinders, to shift a support unit along these guidance means, hi the embodiment most preferred at present the horizontal guidance means comprise a roller conveyor or rails to support rollers mounted on the support units. These shifting devices preferably comprise a chain, a strap or a belt, which is provided with carriers.

The apparatus according to the invention can preferably comprise a second elevator device which corresponds to the first elevator device mentioned, and which is placed opposite the end of the removal conveyors away from the first elevator device, so that it can receive product units from there on support units which are located in predetermined stop positions in the second elevator device, and a discharge conveyor to remove product units successively from the second elevator device from a support unit which is located in a certain stop position. In this way a buffer system can be provided with high capacity and flexibility for a given room height.

In principle the mutual movements of the various conveyors of the apparatus can be controlled manually, but in practice the control will take place fully or semi-automatically. Thus, the apparatus according to the invention appropriately comprises an electronic control device to control the mutual movements of the conveyors and the lifting and lowering means of the elevator device or devices.

The apparatus according to the invention is suitable for sorting of the product units, which are handled by the apparatus. Such a sorting can be controlled by an operator, but preferably it is made by means of a control device which is designed to control the movements, at a signal about the category of a supplied product unit, so that only product units of the same category are moved from the first elevator device onto a given removal conveyor. The control device can for example be designed to perform sorting on the basis of weight, volume, colour and/or outline, and the signal can come from suitable electronic sources, e.g. a sensor, which reads a marking of the individual product units, or a computer, which contains information of the properties or identity of the individual product units.

The removal conveyors can appropriately be placed above each other and/or next to each other, and each of them can comprise several conveyors that lie in line, in order to achieve a capacity of the desired size. In that way each of the conveyors can for example accumulate product units which come from the elevator device, e.g. in such a way that groups of product are built up, each with a predetermined number of product units of a given category. Thus, the electronic control device can be designed to control the mutual movements for the conveyors and for the lifting and lowering means of the elevator device or devices such that product units from the removal conveyors are carried to a destination in groups of a predetermined number of product units of the same category. This destination can for instance be a packing or storage place.

The invention also relates to an elevator device for handling of product units, which device comprises a lifting column and a lowering column, each of which has a plurality of product support units placed above each other and at a mutual vertical distance, lifting means for stepwise and simultaneous movement of the support units in the lifting column in upwards direction to predetermined stop positions, and lowering means for stepwise and simultaneous movement of the support units in the lowering column in downwards direction to other stop positions, a first transfer device to transfer a support unit in the top stop position in the lifting column to the lowering column, and a second transfer device to transfer a support unit in the bottom stop position in the lowering column to the lifting column.

The invention also relates to a method for handling of product units, which method comprises:

- transport on a supply conveyor of one or several product units to a product support unit placed in a predetermined stop position in an elevator device, which elevator device has a lifting column and a lowering column, each of which has a plurality of product support units placed above each other and at a mutual vertical distance, lifting means for stepwise and simultaneous movement of the support units in the lifting column in upwards direction to predetermined stop positions, and lowering means for stepwise and simultaneous movement of the support units in the lowering column in downwards direction to other stop positions, a first transfer device to transfer a support unit in the top stop position in the lifting column to the lowering column, and a second transfer device to transfer a support unit in the bottom stop position in the lowering column to the lifting column, - transport in the elevator device of the support unit with product unit/units to a stop position opposite one of several removal conveyors, - transport of product unit/units from the support unit, which is located opposite the removal conveyor, to this conveyor.

As explained above, product units from the removal conveyors can favourably be supplied to a s econd e levator d evice c orresponding t o the first e levator d evice. According t o this embodiment product units are carried from the removal conveyors to support units in a second elevator device of a construction corresponding to the first elevator device, and after transport on support units in the second elevator device they are carried from this by means of a discharge conveyor, which is placed opposite a stop position of the support units in the second elevator device.

hi a preferred embodiment the mutual movements for the conveyors and the lifting and lowering means of the elevator device are controlled by a signal about the category of the product unit which is carried from the supply conveyor to a support unit in the elevator device, so that only product units of the same category are carried from the elevator device onto a given removal conveyor.

Furthermore, the mutual movements of the different conveyors and elevator devices are preferably controlled in such a way that the discharge conveyor carries product units from the second elevator device to a destination in groups of a predetermined number of products of the same category. The product units in question can be of any type, e.g. pieces of meat or other cut parts of carcasses. Thus, the apparatus, the device and the method according to the invention can advantageously be used in slaughterhouses to transport various cuts, such as hams, middles, fore-ends etc., from a place where carcasses of pigs or other animals are cut to temporary destinations, e.g. places packing or suspension places. The apparatus can for instance be designed in such a way that the products are carried to each destination in groups with a predetermined number of the same cuts and of the same grade.

The invention will be explained in detail in the following, with reference to the drawings, in which

fig. 1 seen in perspective shows part of a apparatus according to the invention with an elevator device of the paternoster type, figs. 2-6 seen from the side illustrate the functioning of the elevator device, - fig. 7 seen in perspective shows how the support units in a preferred embodiment of the elevator device are supported by only two continuous chains or straps, fig. 8 seen in perspective shows a second embodiment of the elevator device with six continuous chains or straps, fig. 9 seen in perspective shows a third embodiment of the elevator device with eight continuous chains or straps,

- fig. 10 seen from the side shows an embodiment of a apparatus according to the invention with two elevator devices,

- fig. 11 shows the apparatus shown in fig. 10 seen from above, and

- fig. 12 illustrates how a apparatus of the type shown in figs. 10 and 11 can be used for sorting of two different product types in different qualities.

The apparatus in fig. 1 comprises an elevator device 10 with a housing 11, in which eight product support units 12 are placed, each of which comprises a short conveyor belt 13, the top side of which constitutes the support surface of the support unit. The support units 12 are placed at mutual vertical distance above each other in two columns, namely a lifting column 14 and a lowering column 15. By means of lifting and lowering means, which will be described in further detail in connection with figs. 7-9, the units 12 are moved stepwise upwards in the lifting column 14 and stepwise downwards in the lowering column 15, as is indicated by anows in fig. 1. Product units (not shown), e.g. hams and/or other cuts, are supplied to the elevator device 10 from a cutting or production place by means of a supply conveyor 16. The product units are transported away from the elevator device 10 by means of removal conveyors 17, which also serve as temporary storage place for the units. It is 5 also possible, of cause, to use two or more supply conveyors, which can carry the product units to support units in determined stop positions in the lifting column 14 and/or the lowering column 15. The removal conveyors 17 are placed, as indicated in fig. 1, above and next to each other opposite the stop positions of the six middle support units.

10 The support unit 12 in the top end of the lifting column 14 can be transferred to the top end of the lowering column 15 by means of transfer devices 18, and correspondingly the bottom support unit 12 in the lowering column 15 can be transferred to the bottom end of the lifting column 14 by means of other transfer devices 19. These transfer devices can, as indicated in figs. 2-7, comprise guide rails or roller conveyor 20 (see fig. 7) to support the support units

15 12 during their horizontal movement from one column to the other, and movement devices in the form of horizontally running, motor-driven, continuous chains, straps or belts 21. The functioning of the elevator device 10 will now be explained in further detail with reference to figs. 2-6.

20 In fig. 2 the units 12 stand still and the units indicated by 2, 3, 4, 6, 7 and 8 can independently of each other if desired be emptied of product units by means of the bordering removal conveyors 17. If/when a support unit opposite the conveyor 16 is free, one or several product units can be carried from the conveyor 16 onto the support unit. In fig. 3 the units 12 are in motion, as is indicated by arrows, and therefore products cannot be

25 supplied to or removed from the units, h fig. 4 the units 12 stand still again during their stepwise movement to different stop positions, and one or several of the units 12 indicated by 1, 2, 3, 5, 6 and 7 can if desired be emptied of products by means of the conveyors 17. One or several new product units can be carried onto an empty support unit opposite the conveyor 16. In fig. 5 the top support unit 12 in the lifting column 14 is carried by means of

30 the top transfer device 18 to the top end of the lowering column 15, and the bottom support unit 12 in the lowering column 15 is carried by means of the bottom transfer devices 19 to the bottom end of the lifting column 14, as is indicated by means of arrows. Finally, fig. 6 illustrates the same situation as fig. 2, but all of the units 12 have been moved one step forwards. During this working cycle a control device ensures that a product unit of a certain category is delivered to one of the conveyors 17 each time a support unit with the product is opposite a c onveyor, w hich i s i ntended for t he c ategory i n q uestion. T he w orking c ycle described above can now be repeated. After a number of runs a predetermined number of product units of a certain category are now accumulated on a removal conveyor, e.g. corresponding to the number of hooks on a transport element, such as a Christmas tree for suspension of meat cuts. These product units can now be run out of the apparatus, for instance for suspension on a transport element or for packing. During the working cycle new product units are supplied all the time to empty support units opposite the conveyor 16.

Figs. 7-9 show how the above-mentioned lifting and lowering means, which stepwise move the support units 12 upwards through the lifting column 14 and downwards through the lowering column 15, can be designed, h the construction shown in fig. 7 all of the support units 12 are suspended in two continuous chains, straps placed at a distance from each other and displaced sideways, e.g. toothed straps or belts 22, which are provided with carriers 23, which are designed to mesh with protruding flaps 24 on the support units 12. These flaps 24 are shaped and placed in such a way that they fit tightly against the roller conveyor 20 when the unit 12 in question is to be transfened from one column 14 to the second column 15. As appears from fig. 7, each unit 12, with flaps 24 located diagonally at a distance from each other, is supported by carriers 23 on the downwards or upwards runs respectively of the two continuous chains, straps or belts 22. The movements of the units 12 can be stabilized by allowing them to fit tightly against vertical, not shown, guide rails or guide surfaces.

Fig. 8 illustrates a construction where the lifting and the lowering devices comprise six chains, straps or belts 22. Each of the units 12 is supported at all of its four corners, but the two chains, straps or belts which are located between the lifting column 14 and the lowering column 15 are common to the units 12 in these columns, since the units 12 in the lifting column 14 fit tightly a gainst carriers on the upwards run of the chains, while the units in the lowering column 15 fit tightly a gainst carriers on the downwards run of the chains.

Fig. 9 shows a construction where the lifting and lowering devices comprise eight vertically running continuous chains, straps or belts 22. Each of the units 12 in each of the columns 14 and 15 is supported at its four corners by carriers on four of the chains, straps or belts

22.

The apparatus in figs. 10 and 11 comprises in addition to an elevator device 10 a second 5 corresponding elevator device 26 of the paternoster type. The apparatus is suitable for grading of product units which are supplied by the conveyor 16 and which are delivered in a g raded s tate to a d ischarge c onveyor 27. T he i ntervening conveyors 17, w hich c an b e placed side by side and also above each other, will carry products from the lifting and lowering columns 14, 15 of the elevator device 10 to the lifting and lowering columns 14,

10 15 of the elevator device 26. The products, which are supplied to the elevator device 10 are sorted according to type of product and/or quality, and are placed according to predetermined c riteria o n t he different c onveyors 17. It i s for example p ossible to p lace product units of a predetermined type and quality on the respective conveyors 17. When a product group with a predetermined number o f product units o f the prescribed type and

15 quality or grade has been collected on a conveyor 17, this group is transfened via the second elevator device 26 to the discharge conveyor 27, which will carry it to a predetermined destination. Of cause it is also possible, according to predetermined criteria, to have the products delivered to the discharge conveyor 27 in any desired number, in any order, and/or in any pattern desired. If desired, there can be one or several further discharge 0 conveyors, e.g. if the apparatus is to serve several packing places or product types (as described in connection with fig. 12).

The different conveyors and elevator devices can be driven by common or separate motors 25 (only shown in figs. 8-10). These motors can be controlled by an electronic control 5 device not shown, which can receive control signals from different sensors or feelers placed at suitable places in the apparatus, or from a computer unit which keeps track of the identity and position of the product units. Control signals can also be sent to the control device from one or several measuring devices, which can perform a classification on the basis of for instance weight, volume, outline and/or further appearance. 0

Fig. 12 illustrates schematically how a apparatus according to the invention will be able to sort two different types of product which are supplied two by two to the elevator device 10 by means of the supply conveyor 16, both according to type of product and quality. The products can for instance comprise two types of meat cuts belonging together, such as pork bellies and loins, which are transported two by two on the conveyor 16 with the bellies immediately in front of the loin. The illustration to the left in fig. 12 shows the elevator device 10 with the lifting column 14, where support units 12 at different levels marked with 1-4 each are located opposite one removal conveyor 17, and the lowering column 15, where support units 12 at different levels marked with 5-8 each are also located opposite one conveyor 17.

Product sets, each consisting of a belly and a corresponding loin, are carried in succession by the supply conveyor 16 onto the support unit 12, which is located at level 2, which in fig. 12 is shaded and indicated by "belly-loin/IN". The conveyors 17, which are located at the levels 2-5 can for example be intended for collection of bellies of four different grades, and the conveyors at the levels 6-8 and 1 can, as indicated in fig. 12, be intended for collection of loins of four different grades or qualities. During a working cycle corresponding to the one illustrated in figs. 2-6 the product set is carried to the one of the levels 3-5 which corresponds to the relevant grade for the belly. The conveyor 13 of the support unit 12 is then activated, so that the belly is carried onto the conveyor 17 at the relevant level. If the grade conesponds to the one at level 2, no working cycle will be performed, since the support unit lies immediately opposite the relevant conveyor. In this case the belly is transferred to the conveyor 17 without rotation of the support units. During the further working cycle the support unit 12 with the loin is carried on to the one of the levels 6-8 and 1 which corresponds to the grade of the loin in question, and the loin is here transfened to the conveyor at this level. During the performance of the working cycle bellies and loins on other support units are transfened to the conveyors 17 when they are opposite a conveyor conesponding to the grade/product type.

The support units are filled with new sets of belly/loin as they enter level 2. When a predetermined number of bellies or loins of a given grade have been accumulated on one of the conveyors 17 in this way, the group of products is transfened successively from the conveyor 17 to the elevator device 26, which is illustrated to the right in fig. 12. A predetermined number of loins, which are accumulated on the conveyor 17, e.g. at level 1, are carried successively onto the support units 12 of the elevator device 26 at level 1 and are then transported on to level 6, which communicates with one of the discharge conveyors 27 and which in fig. 12 is indicated by "loin/OUT". Then the discharge conveyor transports the predetermined number of loins of one and the same grade as a whole group of product to a predetermined destination. Conespondingly, bellies on a conveyor 17 can be transported by means of the elevator device 26 to a second discharge conveyor, which is located opposite the position "belly/OUT".

It is clear that groups of products of the same type and grade, which are collected on the other conveyors 17, can be carried in a similar way to a destination via the elevator device 26 and the discharge conveyor 27.

Claims

1. Apparatus for handling of product units, which apparatus comprises:

- an elevator device (10) which has a lifting column (14) and a lowering column (15), each of which has a plurality of product support units (12) which are placed above each other and at a mutual vertical distance, lifting means (22) for stepwise and simultaneous movement of the support units in the lifting column in upwards direction to predetermined stop positions, and lowering means (22) for stepwise and simultaneous movement of the support units in the lowering column in downwards direction to other stop positions, a first transfer device (18) to transfer a support unit in the top stop position in the lifting column to the lowering column, and a second transfer device (19) to transfer a support unit in the bottom stop position in the lowering column to the lifting column, - a supply conveyor (16) for supply of one or several product units to a support unit which is located in a predetermined stop position in the elevator device, and - at least two removal conveyors (17) to receive product units from support units which are located in predetermined stop positions opposite the conveyors (17).

2. Apparatus according to claim 1, wherein each of the support units comprises a conveyor, preferably a conveyor belt (13).

3. Apparatus according to claim 1 or 2, wherein the lifting and lowering means (22) comprise flexible, continuous chains, straps or belts which are provided with carriers (23) to cany the support units.

4. Apparatus according to claim 3, wherein the support units in the two columns are carried by a first and a second continuous, flexible chain, strap or belt (22), each of which has a first and a second vertical run and wherein each support unit in the lifting column is carried by carriers on the first run of the first and the second flexible chain, strap or belt respectively, while each support unit in the lowering column is carried by carriers on the second run of the first and the second flexible chain, strap or belt respectively.

5. Apparatus according to claim 4, comprising vertical guidance means to stabilize the vertical, translatory movements of the support units along the lifting column and the lowering column respectively.

6. Apparatus according to any of the claims 1-5, wherein the first and second transfer means each comprises horizontal guidance means (20) and shifting devices (21) to shift a support unit along these guidance means.

7. Apparatus according to claim 6, wherein the horizontal guidance means comprise a roller conveyor or rails to support rollers mounted on the support units.

8. Apparatus according to claim 6 or 7, wherein the shifting devices comprise a chain, a strap or a belt (22) which is provided with carriers.

9. Apparatus according to any of the claims 1-8, comprising a second elevator device (26), which conesponds to the mentioned first elevator device (10) and which is placed at the end of the removal conveyors away from the first elevator device (10), so that it can receive product units from there on support units (12) which are located in predetermined stop positions in the second elevator device (26), and a discharge conveyor (27) to carry product units away successively from the second elevator device from a support unit which is located in a particular stop position.

10. Apparatus according to any of the claims 1-9, which apparatus comprises an electronic control device to control the mutual movements for the conveyors and the lifting and lowering means of the elevator device or devices.

11. Apparatus according to claim 10, wherein the control device is designed to control the movements, on basis of a signal about the category of a supplied product unit so that only product units of the same category are carried from the first elevator device (10) onto a given removal conveyor (17).

12. Apparatus according to claims 9 and 11, wherein the electronic control device is designed to control the mutual movements for the conveyors and the lifting and lowering means of the elevator devices, so that product units on the removal conveyors (17) are carried to a destination in groups of a predetermined number of product units of the same category.

5 13. Apparatus according to any of the claims 1-12, wherein the removal conveyors (17) are placed above each other and/or next to each other, and possibly each comprises several conveyors in line.

14. E levator d evice ( 10) for h andling o f p roduct u nits, w hich d evice c omprises a 1 ifting 10 column (14) and a lowering column (15), each of which has a plurality of product support units (12) placed above each other and at a mutual vertical distance, lifting means (22) for stepwise and simultaneous movement of the support units in the lifting column in upwards direction to predetermined stop positions, and lowering means (22) for stepwise and simultaneous movement of the support units in the lowering column in downwards 15 direction to other stop positions, a first transfer device (18) to transfer a support unit in the top stop position in the lifting column to the lowering column, and a second transfer device (19) to transfer a support unit in the bottom stop position in the lowering column to the lifting column.

20 15. Method for handling of product units, which method comprises:

- transport on a supply conveyor (16) of one or several product units to a product support unit (12) placed in a predetermined stop position in an elevator device (10), which elevator device has a lifting column (14) and a lowering column (15), each of which has

25 a plurality of product support units (12) placed above each other and at a mutual vertical distance, lifting means (22) for stepwise and simultaneous movement of the support units in the lifting c olumn in upwards direction to predetermined stop p ositions, and lowering means (22) for stepwise and simultaneous movement of the support units in the lowering column in downwards direction to other stop positions, a first transfer

30 device (18) to transfer a support unit in the top stop position in the lifting column to the lowering column, and a second transfer device (19) to transfer a support unit in the bottom stop position in the lowering column to the lifting column, - transport in the elevator device of the support unit (12) with product unit/units to a stop position opposite one of several removal conveyors (17),

- transport of product unit/units from the support unit (12), which is located opposite the removal conveyor (17), to this conveyor.

16. Method according to claim 15, wherein product units from the removal conveyors (17) are carried to support units (12) in a second elevator device (26) of a design conesponding to the first elevator device (10) and after transport on support units in the second elevator device (26) are carried from this by means of a discharge conveyor (27), which is placed opposite a stop position of the support units in the second elevator device (26).

17. Method according to any of the claims 15-16, wherein the mutual movements for the conveyors and the lifting and lowering means of the elevator device are controlled by a signal about the category of the product unit which is carried from the supply conveyor (16) to a support unit (12) in the first elevator device (10), so that only product units of the same category are carried from the elevator device (10) onto a given removal conveyor (17).

18. Method according to claims 16 and 17, wherein the mutual movements of the different conveyors and elevator devices are controlled in such a way that the discharge conveyor (27) carries product units from the second elevator device (26) to a destination in groups of a predetermined number of products of the same category.

19. Method according to any of the claims 15-18, wherein the product units are pieces of meat or other cut parts of carcasses.