TECHNICAL FIELD The invention relates to a picking member intended for taking hold of at least a first article in connection with fetching the arti- cle from a holding device arranged for storage and/or intermedi- ate storage of at least the first article and a second article close to each other. The articles at least partially comprise a mag- netizable material. The picking member further comprises a picking means arranged to take hold of the first article. The in- vention also relates to a method for fetching an article from a holding device, a separating magnet intended to facilitate for a picking member to take hold of at least a first article, and a ro- bot for fetching at least a first article from a holding device.

BACKGROUND OF THE INVENTION AND PRIOR ART In case of industrial manufacturing, articles, such as finished products, product parts, components, semi-manufactured prod- ucts, and/or tools, must often be fetched from a storage, an in- termediate storage or a machine, for example when assembling the product. The manufacturing is usually facilitated if the article can be fetched automatically. In particular, the manufacture is facilitated if the articles are fetched by an industrial robot. This since industrial robots have very broad areas of application and can deliver the articles to a desired location and/or control the continued machining or use of the article. Such articles are usu- ally at least partially manufactured in a magnetizable material, for example iron or a ferrous material.

One problem when fetching such articles is that it is sometimes difficult to fetch a desired number of articles. The articles are usually stored close to each other and it happens that the arti- cles stick together, for example due to dirt or due to the articles having very fine polished surfaces such that adhesive forces arise between them, which may cause that an article which is not to be fetched follows the article which is to be fetched during the fetching. Some articles may have a shape such that the arti- cles are difficult to take hold of and/or a shape such that it is hard to take hold of only one or a desired number of articles.

Thus the tolerances when fetching the articles are usually very small. If an incorrect number of articles are fetched the conse- quences may be severe. For example, there may be a defect in a manufactured product such that it must be rejected, alterna- tively there may arise a standstill in the production causing great costs. A further problem when fetching articles is that the arti- cles may easily be damaged, for example if a gripping tool grips too hard in or obliquely across the articles.

One method to alleviate the problems above is used during fetching of steel plates. The steel plates are stored lying on top of each other in a pile, they are flat, large and heavy, and are difficult to take hold of breadth-wise and lengthwise. The fetch- ing of the steel plates is facilitated by use of a separating mag- net to separate the steel plates. The separating magnet is placed along one edge or one corner of the steel plates and magnetizes the steel plates. The steel plates then obtain the same magnetic pole along their edges and therefore repel each other. The steel plates are bended upwards resembling a fan along the edge, such that the steel plates ends up at a distance from each other along the edge. The steel plates may thus eas- ily be gripped since their thickness is substantially smaller than their width or length. The steel plates thus still rest against each other with one end of the steel plates and are bended away from each other with the other end of the steel plates.

Such a separating magnet is difficult to use for fetching articles from a holding device. It takes a lot of energy to build up a mag- netic field for the separating magnet in an initial state. Therefore the separating magnet is not turned off but is turned on during the entire time that any articles are in the holding device. Light articles thus risk falling out of the holding device since, in differ- ence to the case with the steel plates, their weight usually are not sufficient to hold them in the holding device. Further, the separating magnet cannot be used for holding devices in which articles are taken in and out of the holding device horizontally since the articles then also risk falling out of the holding device.

Further, the positions of the articles in the holding device be- come undetermined which makes it difficult to achieve an effi- cient control for automatic fetching the articles. Furthermore the need for space for the storage is increased since the articles will be stored at a distance from each other. Further problems is that there is a risk for the articles being changed in shape by the separating magnet, since they are subjected to forces from the magnetism during the entire storage. Furthermore the articles are magnetized during a long time such that the articles remain magnetized even after that the articles have been fetched from the holding device, which magnetism may disturb subsequent processing steps.

One area in which fetching of articles is very important is when cutting thin plates into plate bands. The plates are cut by steel cutters arranged at fixed distances from each other by spacers in a cutting machine. The distances between the steel cutters determine the width of the plate bands. The steel cutters and the spacers are fetched from a number of holding devices each stor- ing one type of article. There are usually about 90 different spacers and steel cutters thus requiring 90 different holding de- vices. Some spacers are very thin which makes them very hard to take hold of. If an incorrect number of spacers are arranged in the cutting machine between two steel cutters it will thus mean that a plate band receives an incorrect width, meaning

that the band must be rejected. The known separating magnet for separating steel plates would not be efficient to use in this application either. It would take 90 different separating magnets to separate the articles in the holding devices. Further, since the holding devices each store several articles the separating mag- net must be made very long to separate all articles in the hold- ing devices such that the innermost article also can be fetched.

This would mean that the articles are stored at a distance from each other in the holding devices, which would waste space in the manufacturing plant. Further the spacers and the steel cut- ters would risk fatting out of their holding devices.

SUMMARY OF THE INVENTION One object of the present invention is to indicate a method which facilitates the fetching of articles and which solves at least some of the problems mentioned above.

This object is achieved with the method according to the pream- ble of claim 1 which is characterised in that a movable picking member comprising a separating magnet is brought close to the first article in the holding device such that the separating mag- net is brought close to both the first and the second articles, wherein the separating magnet generates a magnetic field at least partially magnetizing the magnetizable material of the first and the second articles such that the induced magnetism repels the first and the second articles away from each other, and that the picking member takes hold of the first article in such a way that the second article remains in the holding device.

By using a movable separating magnet moved together with the picking member only one separating magnet for fetching articles from several holding devices is needed. Thus large cost savings is obtained especially if the articles are to be fetched from a large number of different holding devices. To use only one sepa- rating magnet also decreases the need for controlling several

separating magnets which further decreases the cost and com- plexity during fetching. Since the separating magnet in fact only needs to separate the article which is to be fetched and the arti- cle which is to remain in the holding device and which is stored closest to the article which is to be fetched, and since the sepa- rating magnet easily can be brought close to precisely these ar- ticles, the size of the separating magnet can be decreased since the separating magnet only needs to be large enough to affect two articles at the time. Further the separating magnet can be made smaller since the degree of magnetization of the articles is inversely proportional to the square of the distance between the separating magnet and the articles, and the separating magnet may easily be brought very close to the articles. Thus the cost for the fetching is decreased further. Further the control of the separating magnet is facilitated since the separating magnet need not be adapted to simultaneously affect several articles to any higher degree.

Further, the risk that the articles are harmed during the fetching is decreased, since it is easier to leniently take hold of a lone article. By using a separating magnet when the picking member takes hold of the first article the sticking together of the first and the second articles with each other is counteracted. It is thus easier to take hold of only the first article without the second ar- ticle following during the fetching. Further it is easier to take hold of a desired number of articles since the articles are ar- ranged at a distance from each other such that a small dis- placement of the picking member does not cause fetching of an incorrect number of articles. Since the articles are not constantly affected by the magnetic field from the separating magnet, their positions in the holding device are easier to determine, allowing larger picking members with larger tolerances. Neither are the articles magnetized during a longer period of time by the sepa- rating magnet such that the magnetism of the articles decreases quickly. Neither are the articles subjected to long-term magnetic forces, which risk changing the shape of the articles. During the

fetching of the articles the first article is pushed towards the picking member by the force generated by the separating mag- net, which also facilitates for the picking member to take hold of the article.

Further the holding devices can be made more compact partly since there is no need for one separating magnet for each de- vice and partly because the articles in the holding device are stored closer to each other since no separating magnet con- stantly separates the articles. Further there is no risk that the articles are to fall out of the holding device, which makes the separating magnet useful to facilitate fetching of small and light articles also and for fetching articles in holding device arranged for horizontal insertion and removal of the articles.

According to one embodiment of the method according to the invention the separating magnet is brought to generate said magnetic field only during a short interval in connection with that the picking member takes hold of the first article. Advanta- geously said interval is shorter than or equal to 50 ms. Prefera- bly the interval is shorter than or equal to 30 ms. By generating said magnetic field only during a short interval the heat genera- tion in the separating magnet becomes smaller. Thus the sepa- rating magnet may be fed with a larger current without the sepa- rating magnet running the risk of being damaged by the gener- ated heat, which means that a larger magnetic field may be generated by the separating magnet without changing the size of the separating magnet. Thus a smaller separating magnet can be used making the picking member and the separating magnet easier to move close to the articles in the holding device. Fur- ther an impact effect is achieved with such a magnetic field, which is generated in short intervals, which makes the articles easier to separate from each other. By generating the magnetic field in short pulses or intervals it is also easy to adapt the separating magnet to separate articles with different size and weight. For example two light articles may be separated with

only one thrust while to heavy articles may be separated with two or several thrusts. The pulsating magnetic field also pushes the first article towards the picking member and the second arti- cle away from the picking member, making it easier for the pick- ing member to take hold of the first article. By the separating magnet only generating the magnetic field during a short interval the articles are not displaced while the separating magnet is brought close to the articles, which would have changed the po- sition of the articles in the holding device and make the control of the fetching more difficult. Further the magnetic field may be turned off before the picking member takes hold of the first arti- cle such that the fetching is not disturbed by the separating magnet. Further, the prejudice indicating that the energy loss becomes great when the separating magnet is activated repeat- edly is overcome. Further the magnetization of the articles is re- duced further, which in some applications is a very great advan- tage. Naturally the separating magnet may still be allowed to generate another weaker magnetic field, which does not affect the articles to any appreciable degree, outside said interval as well.

According to a further preferred embodiment of the method ac- cording to the invention the picking member is brought to take hold of said article by bringing a picking means of the picking member to generate a magnetic field attracting the first article.

Thus the risk that the picking member damages the article is re- duced, for example during mechanical picking of the article, which is advantageous for example during picking of articles with delicate shape. Further such a picking member may more easily take hold of articles with different shapes. Further, there are no mechanical tolerances to which the picking member must adhere, for the most part the picking member only needs to adapt the strength of the attracting magnetic field in order to take hold of a desired number of articles. It is also advanta- geous to take hold of the article magnetically when the articles

are pushed towards the picking member by the magnetic field generated by the separating magnet.

A further object of the invention is to indicate a separating mag- net facilitating fetching of articles and solving at least some of the problems mentioned in the prior art.

This object is achieved with the separating magnet according to the preamble of claim 6 and being characterised in that the separating magnet is adapted to be connected with and moved with the picking member. The separating magnet is thus ar- ranged to generate a magnetic field magnetizing the magnetiz- able material of the first and the second articles such that the induced magnetism repels the first and the second article away from each other in order to facilitate for the picking member to take hold of the first article in such a way that the second article remains in the holding device. Such a separating magnet shows the advantages described above in connection with the method according to the invention.

According to one embodiment of the separating magnet accord- ing to the invention the separating magnet comprises an even number of electrically conducting coils arranged to generate said magnetic field when an electric current is allowed to flow through the coils, the coils being arranged to form substantially closed magnetic circuits in pairs. Preferably each coil is oriented with one end against the articles such that each coil magnetizes the articles with one magnetic pole. By arranging the coils in pairs two of the coils will form a close magnetic circuit, meaning that a larger part of the magnetism generated by the coils is kept close to and passes through the coils. Thus losses from spreading of the magnetic field is decreased which gives a more efficient separating magnet. Further the coils are oriented such that each coil magnetizes one article with one magnetic pole. Thus each coil pair is arranged to magnetize the article with two magnetic poles such that the magnetism is conducted through

the articles. Thus the loss in efficiency due to further spreading of the magnetic field is decreased since the magnetizable mate- rial in the articles are good conductors of magnetism. Further the magnetization of the articles is increased such that the re- petting force between the articles is as large as possible.

According to a preferred embodiment the separating magnet ac- cording to the invention comprises a homogenous and continu- ous body of a magnetizable material, the body at least partially being positioned inside the coils of a coil pair in order to en- hance and conduct the magnetic field generated by the coil pair.

For example such a body may consist of an iron core positioned within both coils and connecting the coil pair at the back of the coil pair. Thus the magnetic field is conducted through this body at the back of the coil pair, further decreasing the losses due to the spreading of the magnetic field, since the magnetic field ef- fectively is conducted through the body. Further, such a mag- netizable body enhances the magnetic field generated by the coils because of magnetization of the iron core.

According to a further advantageous embodiment of the inven- tion the separating magnet comprises at least four electrically conducting coils arranged in two coil pairs, the coil pairs being oriented such that the two closest lying coils of the coil pairs generates the same magnetic pole in said first and second arti- cles. By the coils lying closest to each other and belonging to two different coil pairs generating the same pole the risk for the coils in different coil pairs to disturb each other in such a way that the magnetism of one coil pair is spread to another coil pair is decreased. This since two magnetic poles of the same kind repels each other's magnetic fields. The orientation of the coil pairs thus prevents spreading of the magnetic field between the coil pairs. The coils in each coil pair is thus adapted to each other such that substantially all the generated magnetic field is conducted only between the coils within a substantially closed magnetic circuit.

Preferably the separating magnet comprises a body of a mag- netizable material, preferably a ferrous material, as mentioned above and which is common for at least a major part of the coil pairs. Thus, the loss because of spreading of the magnetic field behind the coil pairs is much smaller and the separating magnet also becomes less expensive to produce. Preferably said mag- netizable body is homogenous since a homogenous body con- ducts the magnetism better.

According to a further advantageous embodiment of the inven- tion the separating magnet is arranged to be insertable in a by the articles at least partially enclosed space passing through the articles, wherein the separating magnet is arranged to generate said magnetic field outwardly from the separating magnet to- wards the articles. That the separating magnet is insertable in a space being enclosed by the articles and that the separating magnet is arranged to generate the magnetic field outwardly is advantageous since the holding device for the articles thus does not need to be shaped such that there is space for the separat- ing magnet at the side of the articles. Thus the articles may be stored closer to each other such that space may be saved which is advantageous for example in narrow factory premises. Thus the distances within the factory premises also becomes smaller such that faster movements of the articles is allowed.

According to a further preferred embodiment of the invention the separating magnet is adapted to only generate said magnetic field in a short interval in connection with that the picking mem- ber takes hold of the first article. Preferably the separating mag- net is adapted to generate said magnetic field in the form of one or several short pulses in connection with that the picking mem- ber takes hold of the first article. By feeding the separating magnet with a current only for a short interval or for a number of pulses, the heat generation within the separating magnet be- comes smaller. Thus the coils of the separating magnets may be

winded with a thinner wire and still be fed with the same current without the risk of damaging the winding. Thus the coils may be winded a larger number of turns since the wire is thinner and does not occupy as large space as a thicker wire. This gives the effect that a stronger magnetic field is obtained since the same current passes through the coils a larger number of turns.

A further object of the invention is to indicate a picking member intended to fetch at least a first article and which solves at least some of the problems mentioned of the prior art.

This object is achieved with the picking member according to the preamble of claim 10 and which is characterised in that the pick- ing member comprises a separating magnet arranged to gener- ate a magnetic field magnetizing the magnetizable material of the first and the second article such that the induced magnetism repels the first and the second article away from each other, wherein the picking member being arranged to take hold of the first article in such a way that the second article remains in said holding device. Such a picking member show the advantages described in connection with the method described above.

Preferably the separating magnet comprised by the picking member is arranged according to any of the claims 6-9. Such a picking member will thus show the advantages as given in the description of the separating magnet.

According to a preferred embodiment of the picking member said picking means is arranged to take hold of the first article to the picking member by generating a magnetic field attracting the first article. Such a picking member shows the advantages as indicated previously in the description of the method. Preferably the picking member is arranged to generate said magnetic field with different strength. If the article which the picking member is to take hold of is heavy the picking member thus generates a stronger magnetic field than if the article is light. Preferebly the

picking member is arranged to generate a magnetic field which is sufficiently weak not to attract the second article in such a way that the position of the second article in the holding device is not affected by the picking member.

According to a further embodiment of the picking member said picking means is arranged to release the first article by generat- ing a magnetic field during a short interval which repels the first article. Thus, the first article is released in a simple, fast and lenient way by the picking member. Since the picking member magnetizes the article during the holding of the article a polar change of the magnetic field generated by the picking member will repel the article away from the picking member. Further such a polar change, in which the magnetic field generated by the picking member changes pole, will demagnetize the article.

When an article comprising a magnetizable material is subjected to a magnetic field during a long time the article will retain the magnetization even after that the article has been removed from the magnetic field. By changing the pole of the magnetic field the article will be magnetized in an opposite way, which reduces the magnetization of the article.

According to a further preferred embodiment of the invention said separating magnet is arranged to generate said magnetic field substantially perpendicular relative to the magnetic field generated by the picking member. The articles are usually stored one behind the other along a line. A magnetic field gen- erated perpendicular to this line will generate the same mag- netic pole along the edge of the articles achieving a repelling force between the articles. A magnetic field generated in parallel with this line will generate a pole at the front of the article and an opposite pole at the back of the articles, wherein the articles instead will be attracting each other. Thus it is advantageous that the separating magnet generates the magnetic field sub- stantially perpendicular to the magnetic field generated by the picking member.

According to a further embodiment of the picking member the picking member comprises a control member arranged to control said separating magnet such that the separating magnet gener- ates said magnetic field only during a short interval in connec- tion with that the picking member takes hold of the first article.

Naturally the control member may control the separating magnet to generate another, weaker magnetic field outside of said inter- val also, which does not affect the articles to any appreciable degree and/or which does not cause any harmful heat genera- tion.

A further object with the invention is to indicate a robot intended to fetch an article and solving at least some of the problems mentioned of the prior art.

This object is achieved with a robot according to the preamble of claim 16 and which is characterised in that the robot comprises a robot arm and a picking member comprising a separating magnet, that the picking member and the separating magnet are connected with the robot arm to allow movement of the picking member and the separating magnet to a position close to the first and the second article, that the separating magnet is ar- ranged to generate a magnetic field magnetizing the magnetiz- able material of the first and the second article such that the in- duced magnetism repels the first and the second article away from each other and that the picking member is arranged to take hold of the first article in such a way that the second article re- mains in said holding device. This robot shows the advantages mentioned in connection with the method, separating magnet and picking member above. Preferably said separating magnet is arranged according to any of the claims 6-9. Preferably the picking member is also arranged according to any of the claims 10-15.

According to a preferred embodiment of the robot according to the invention, said articles are constituted by spacers and/or cutting tools for machining. Preferably the robot comprises a control member arranged to receive a signal about a desired type of article, to control the robot arm to move the picking member and the separating magnet to a holding device storing the desired type of article, to control the picking member and the separating magnet to take hold of one and only one article of the desired type, to control the robot arm to move the picking member to a delivery location and to control the picking member to release the article. The device is very advantageous to use in the application with articles, which are spacers and cutting tools for machining. A large number of different spacers and cutting tools, usually about 90 different types, must be possible to fetch by the robot. The different types are each stored in a holding device of its own. The fetching is facilitated by a robot compris- ing only one separating magnet, which can be used to facilitate the fetching of all these types. Further the articles are very sen- sitive and must not be damaged, since there is then a risk that the production of the plate bands fails. Further there is a large difference between the size of the articles since the spacers are dimensioned for different distances between the cutting tools, and since the articles are as sensitive the tolerances during picking of an article are very small. This makes the use of a ro- bot according to the invention, which solves these problems, very advantageous. Further the application is well suited for automatic fetching since large volumes of articles must be fetched, delivered and rigged in the correct order.

SHORT DESCRIPTION OF THE DRAWINGS The invention is now to be described by a number of non limiting examples of the invention and with reference to the attached drawings.

Fig. 1 shows a contact member comprising a separating mag- net.

Fig. 2 shows the magnetic field of a separating magnet and two articles when the separating magnet magnetizes the ar- ticles.

Fig. 3 shows a robot according to one embodiment of the in- vention when the invention is used in a suitable applica- tion.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS In Fig. 1 a picking member 1 according to the invention is shown comprising a separating magnet 3 according to the invention. In Fig. 1 is also shown a holding device 5 arranged for storing a first 7 and a second article 9 close to each other. The picking member 1 further comprises a picking means 2 arranged to take hold of the first article 7. The first 7 and the second article 9 at least partially comprises a magnetizable material, for example iron and/or a ferrous alloy. The articles 7,9 are in this example constituted by circular plates with a circular space 22 in the middle of the plates passing through the articles 7,9, but the shape of the articles may of course be varied greatly.

The picking member 1 is arranged to take hold of at least the first article 7 in connection with that the article 7 is fetched from the holding device 5. The picking member 1 is arranged to take hold of the first article in such a way that the second article 9 remains in the holding device 5. The picking member 1 com- prises the separating magnet 3, which is intended to facilitate for the picking member 1 to take hold of the first article 5. The separating magnet is then arranged to generate a magnetic field magnetizing the magnetizable material of the first 7 and the second article 9, such that the induced magnetism repels the first 7 and the second article 9 away from each other. Thus the

picking member 1 may more easily take hold of the first article 7 such that the second article 9 remains in the holding device 5, since the articles are separated from each other such that a dis- tance between them is formed. The functioning of the separating magnet 3 will now be described closer in connection with Fig. 2.

Since the picking member 1 comprises the separating magnet 3 the picking member 1 and the separating magnet 3 will be moved together. The picking member 1 is further adapted to be connected to a robot arm and for this purpose the picking mem- ber 1 comprises a connecting member 11 arranged at the back of the picking member 1. This connecting member 11 is only shown schematically herein, and may be arranged in any possi- ble way, for example in a way known to a man skilled in the art of industrial robots.

The picking member 1 further comprises a control member 13 arranged to control the separating magnet 3. The control mem- ber 13 comprises in this example electronic circuits and/or soft- ware to control the separating magnet 3. In this example the control member 13 is arranged in connection with the rest of the picking member 1 but in another example the control member 13 may be located at a distance from the other parts of the picking member 1. For example the picking member 13 may be located in connection with the control member for the robot to which the picking member 1 is connected.

The control member 13 is arranged to control said separating magnet 3 such that the separating magnet 3 only generates said magnetic field during a short interval in connection with that the picking member 1 takes hold of the first article 7. In this exam- ple the control member 13 controls the separating magnet 3 by controlling electrical currents through coils 15a-h of the separat- ing magnet 3. By the magnetic field being generated during a short interval, in this example an interval of 20 ms, an impact effect is achieved which easily can separate heavy articles 7,9.

Preferably the separating magnet 3 pushes the articles 7,9 apart in a horizontal direction, such that the articles 7,9 do not fall back onto each other again due to gravitational force. Fur- ther the first article 7 is pushed in a direction towards the pick- ing member 1 and the second article 9 is pushed in a direction away from the picking member 1.

The picking means 2 is arranged to take hold of the first article 7 by generating a magnetic field attracting the first article 7. Since the first article 7 comprises a magnetizable material the first ar- ticle 7 is magnetized by the picking means 2, such that the arti- cle 7 is attracted even though the articles 7 are not themselves magnetical. Further the picking means 2 is arranged to be able to release the first article, 7 by generating a magnetic field dur- ing a short interval, which repels the first article 7. This is a fast, efficient and lenient method to release the article. By letting the picking means 2 change the magnetic polarity, the picking mem- ber 2 will repel the article 7 instead of attracting it. In connection with this the article 7 is at least partially demagnetized.

In the following the separating magnet 3 and its function will be described closer with reference both to Fig. 1 and to Fig. 2.

The separating magnet 3 comprises eight coils 15a-h comprising an electrically conducting wire winded a number of turns. When a current is allowed to flow through the electrically conducting wire of the coils 15a-h a magnetic field is generated in the same way as for a solenoid according to prior art. The magnetic field generated by the coils 15e-h is shown in Fig. 2 by the help of flush lines. In this example the electrically conducted wire is winded with a circular cylindrical form, but the wire may equally well be winded according to some other geometrical shape. The separating magnet 3 further comprises a homogenous and con- tinuous body 17 of a magnetizable material, in this case an iron core 17 comprising eight protruding portions 18 around which each respective coil 15a-h is winded. That a coil 15a-h is winded

around an iron core 18 means that the magnetic field is consid- erably enhanced. To enhance the magnetic field generated by coils by an iron core is also well known.

The separating magnet 3 magnetizes the articles 7,9 such that the articles 7,9 at least temporarily become magnetic. Since the articles 7,9 are located close to each other and the separating magnet 3 magnetizes the articles 7,9 perpendicular relative to the contacting line of the articles 7,9, the articles 7,9 obtains the same magnetic poles in the same portions of the articles 7, 9. For example a north pole end of a coil 15a-h generates a south pole in both articles 7,9. Magnetic poles of the same kind repels each other and thus a repelling force will also be ob- tained between the articles 7,9. The articles 7,9 will thus repel each other and thus a separation of the articles 7,9 is achieved.

If the magnetization instead had been in parallel with the con- tacting line of the articles 7,9 an attractive force would be ob- tained instead.

In this example the separating magnet 3 comprises an even number of electrically conductive coils 15a-h, namely eight coils 15a-h, arranged to generate said magnetic field when an electric current is allowed to flow through the coils 15a-h. Each coil 15a- h comprises two ends, wherein one end is directed towards the articles 7,9 and one end is directed inwardly towards the body 17. This since the magnetic field generated by the coils 15a-h is strongest at the ends of the coils 15a-h. The coils 15a-h are thus oriented such that the coils 15a-h magnetizes the articles with one magnetic pole each.

The eight coils 15a-h are arranged in four coil pairs 19a-d. The coils 15a-h within the same coil pair 19a-d are arranged to con- stitute closed magnetic circuits. This is illustrated in Fig. 2 by the lines corresponding to the generated magnetic field forming closed circles passing only through two coils 15e-f, 15g-h each.

Thus the magnetic field is not spread out causing a larger part

of the magnetic field to be used to magnetize the articles 7,9.

The coils 15a-h within the same coil pair 19a-d are oriented such that the two coils 15a-h magnetizes the articles 7,9 with different magnetic poles. Thus the magnetic field generated by the two coils 15a-h in one coil pair 19a-d, is conducted around in a circuit between the coils 15a-h. Further the magnetic field is conducted through the articles 7,9. Since magnetizable materi- als are good conductors of magnetism the magnetic field thus becomes more concentrated within the articles 7,9. In the same way said magnetizable body 17 conducts the magnetic field on the back of the coil pairs 19a-d between the both coils of the coil pairs 19a-d, which decreases the loss of efficiency here as well.

Further, the coil pairs 19a-d are oriented such that the two clos- est lying coils 15f, 15g of the coil pairs 19a-d generates the same magnetic pole in said first 7 and second article 9. That is, the coils 15f, 15g of two different coil pairs 19a-d and lying clos- est to each other are oriented to generate the magnetic field in the same direction. Thus the magnetic fields generated by these coils 15b-g repel each other such that the leakage of the mag- netic field between two coil pairs 19a-d is decreased. Thus the risk for losses because of end effects of for example a group of coils is decreased, since the coil pairs in the middle 19b-c of such a group also forms substantially closed magnetic circuits.

In this example the magnetizable body 17, that is, the iron core 17, is common to all coil pairs 19a-d. Thus the magnetic field is conducted at the back of the coil pairs 19a-d through the same iron core which also gives smaller losses. Further the separating magnet 3 becomes less expensive and the body 17 conducts the magnetic field better since the body 17 is homogenous.

Further, the separating magnet 3 is with advantage adapted with its shape after the geometry of the articles. Preferably the sepa- rating magnet is moved such that the separating magnet 3 sub- stantially bear against the magnetizable material of the first 7

and the second article 9, such that the magnetization of the first 7 and the second article 9 is facilitated. Preferably the separat- ing magnet is a) so moved into such a position that the first 7 and the second 9 articles substantially are right in front of at least one magnetic pole in the magnetic field generated by the sepa- rating magnet 3. With this is meant that the coils of the separat- ing magnet 3 are directed such that one end of the coil is close to and substantially perpendicular towards the article. Thus it is ensured that as large part as possible of the magnetic field gen- erated by the coils 15 passes through the articles. As mentioned above it is important that the field is generated perpendicular toward the article. Otherwise the field becomes attracting in- stead of separating.

The separating magnet 3 is in this example further shaped to be insertable into a by the articles 7,9 at least partially enclosed space 22 passing through the articles 7,9, wherein the separat- ing magnet 3 is arranged to generate said magnetic field out- wardly from the separating magnet 3 towards the articles 7,9.

Thus less space is demanded around the articles 7,9 in the holding device allowing a more compact storage of the articles.

The separating magnet is further arranged to generate the mag- netic field in a direction radially outwardly and is arranged to substantially bear against and/or to be very close to the articles' 7,9 inner sides of said space 22. In another example of the in- vention the separating magnet may instead be shaped to at least partially enclose at least two articles in said holding de- vice. The separating magnet is then advantageously arranged to generate said magnetic field in a direction inwardly towards the enclosed articles. Such an arrangement of the separating mag- net is advantageous for example if the articles are small.

In the following the picking means 2 and the picking of the first article 7 by the picking member 1 by generation of a magnetic field attracting the first article 7 is to be described closer. The picking means 2 thus comprises several coils 21 arranged to

generate a magnetic field. Further the picking means 2 com- prises cylindrical bodies 23, one body 23 for each coil 21, of a magnetizable material, in this example of iron. The bodies 23 are thus arranged within the coils 21 and are arranged to pro- trude a short distance outside the coils 21. The cylindrical bod- ies 23 thus conducts the magnetic field generated by the coils 21 towards the first article 7. When the picking member 1 takes hold of the first article 7 the coils 21 generate a magnetic field attracting the first article 7 such that the first article 7 is drawn towards the picking member 1 and the picking means 2. The first article 7 will thus bear against and be held against the ends of the cylindrical bodies 23. In this example the magnetic field is generated independently of the magnetic field generated by the separating magnet 3. In another example of the invention the picking member generates a magnetic field attracting the poles generated by the separating magnet in the first article. Thus the picking means does not need to magnetize the first article by itself which saves time when the picking member takes hold of the first article. The draw back is however that the second arti- cle also risks to be attracted by the picking member. Preferably the picking means 2 generate said magnetic field during sub- stantially all the time that the picking member 1 holds the first article 7. This to ensure that the article 7 remains bonded to the picking member 1 until the picking member 1 is to release the article.

When the picking member 1 releases the first article 7 the pick- ing means 2 is brought to generate a magnetic field during a short interval which repels the first article 7. This is simply achieved by changing the direction of the current in the coils 21. Thus the first article 7 is also at lest partially demagnetized by the repelling magnetic field. Preferably the taking member 1 comprises a control member 25 arranged to control the picking means 2 and the voltage across the coils 21 in order to achieve the magnetic field, both the picking of the first article 7 and dur- ing the release. The control member 25 is in this example inte-

grated with the control member 13 controlling the separating magnet 3, but it can also be arranged separately.

In this example the picking means 2 is adapted according to the shape of the articles 7,9. Thus the coils 21 of the picking means 2 are arranged in a circle adapted according to the size of the articles 7,9. The separating magnet 3 is further arranged in front of the picking means 2 and is adapted to said space 22 within the articles 7,9. Further the separating magnet 3 is in- sertable into the space 22 of the articles 7,9. The picking mem- ber 1 also comprises an inner space 27 arranged to allow en- trance of a protruding part of the holding device. In this example the articles 7,9 are hung up on a peg 5, wherein the peg 5 is allowed room in the space 27 during picking of the articles 7, 9.

The picking member 1 is also provided with a notch 24 arranged to connect a detector to the picking member 1. The detector may for example be arranged to measure the distance between the picking member 1 and the first article 7 in order to facilitate for the picking member 1 to take hold of the first article 7. The de- tector may thus be an optical detector such as a film camera.

Alternatively the detector may measure the distance for example with laser light or microwaves. In order to further increase the adaptability of the picking member to different kinds of holding devices the separating magnet may be displaceable in parallel with the length of the picking member. Naturally the separating magnet may also be displaceable in some other direction and even in several directions at the same time.

The picking member 1 is further arranged to fetch several arti- cles at the same time, wherein the separating magnet separates articles further inside in for example a pile of articles. Thus, for example, three or four articles may be picked by the picking member at the same time. The magnetism attracting the first ar- ticle will also attract the other articles, which are to be picked, since the magnetism is conducted through the first article and the magnetic field is generated in parallel with the storing of the

articles. The separating magnet 3 thus only separates the article which is not to be picked and the article bearing against the ar- ticle which is not to be picked.

In Fig. 3 a robot 40 according to the invention is shown during use within a preferred application. A number of holding devices 42 are shown in the figure holding several articles 44 of different types. The articles 44 are sorted such that each holding device 42 holds articles 44 of a certain type. A rigging magazine 46 is also shown in the figure, to which the articles 44 is to be deliv- ered.

The articles 44 are constituted by spacers 48 and steel cutters 50. The spacers and the steel cutters are intended to be used for cutting bands out of plates. The bands are cut with different widths by rigging spacers with different thicknesses between the steel cutters 50 in the rigging magazine 46. After the rigging magazine 46 has been loaded with a full set of articles of spac- ers and steel cutters the rigging magazine transfers the whole set to a machine which cuts plates with the set. The rigging magazine 46 thus comprises four arms 52 on which the articles are delivered by the robot 40. When an arm has been loaded with a full set of steel cutters and spacers the rigging magazine 46 is thus turned such that a set may be transferred to the in- tended machine. When the steel cutters and the articles has fin- ished being used in the machine they return to an arm 52 where after the robot 40 fetches the articles from the arms 52, sorts them and returns them to the holding devices 42.

The robot 40 comprises a robot arm 41 and a picking member 56, similar to the picking member 1 described in connection with the figures 1 and 2. The picking member 56 thus comprises a separating magnet 58 and is connected with the robot arm 41.

The robot 40 further comprises a control member 54 which in this example is arranged for controlling both the robot 40, pick- ing member 56 and the separating magnet 58. The control

member 54 is further arranged to also control the robot arm 41 and the movement of the picking member 56.

During fetching of said articles 44 a signal is received by the control member 54 from an external unit comprising information about a desired type of article 44. The signal can for example be received from an entering member into which an operator may enter which articles are desired and in which order. The control member 54 controls the robot 40 and thus the picking member 56 which is movable by the robot arm 41 to a holding device 42 storing articles 44 of the article type which is first desired.

After that the control member 54 controls the picking member 56 to take hold of a first article. The picking member 56 takes hold of the article by bringing the picking member 56 close to the first article and by bringing the separating magnet 58 close to the first and the second article, which is stored close to the first ar- ticle. Thereafter the separating magnet 58 generates a magnetic field at least partially magnetizing the magneitzable material of the first and the second article such that the induced magnetism repels the first and the second article away from each other. At the same time the picking member 56 takes hold of the first arti- cle in such a way that the second article remains in the holding device. The separating member 54 brings the separating magnet 58 to generate said magnetic field only during a short interval in connection with that the picking member 56 takes hold of the first article 44. In this example the separating magnet 58 is brought to generate said magnetic field in the form of one or several short pulses in connection with that the picking member 56 takes hold of the first article.

In this example the picking member 56 takes hold of the article by the picking member 56 generating a magnetic field attracting the first article. Thus the control member 54 is arranged to con- trol the picking member 56 and the separating magnet 58 to generate magnetic fields such that one and only one article of a

desired article type is fetched. Thereafter the control member 54 controls the robot arm 41 to move the picking member 56 with the picked article to the rigging machine 46 and to deliver the article on an arm 52. The control member 54 thus controls the picking member 56 to release the article by generating a mag- netic field with an opposite polarity in comparison to the previ- ous field, such that the article is repelled away from the picking member 56.

The articles 44 comprise, as the articles described in connection with Fig. 1 and Fig. 2, a space passing through the articles 44.

During picking of the articles 44 the separating magnet 58 is in- serted into the space enclosed by the articles 44. The separat- ing magnet 58 is then brought to generate said magnetic field in a direction outwardly from the separating magnet 58. Thus the holding devices 42 can be arranged closer than if the separating magnet 58 is brought close to the article 44 from the outside of the articles 44. The articles 44 are further arranged such that the enclosed space comprises two openings on each side of the articles, wherein the articles are stored in the holding device such that the openings are next to each other. Thus the spaces of the articles 44 constitute a large common, connected space.

The separating magnet 58 is thus inserted into the common, connected space.

After delivery of the article to the rigging machine 46 the control member 54 controls the robot 40 to pick a second article of an- other desired article type, and so on until one arm 52 of the rig- ging machine 46 is completely loaded with the desired articles.

Thereafter the rigging machine 46 is turned and the set with the desired articles is forwarded to a desired machine for cutting plates to plate bands.

In another example of the robot the separating magnet may in- stead be moved towards the outside of said articles. The sepa- rating magnet then generates the magnetic field in a direction

towards the articles. Preferably the separating magnet is then arranged to at least partially enclose the circumference of the first and the second articles. The separating magnet then gen- erate said magnetic field in a direction inwardly towards the arti- cles. Thus it is achieved that a magnetic field is generated which is as strong as possible, such that it is ensured that a sufficient separation between the first and the second article is achieved.

Preferably the separating magnet is in this case moved such that the separating magnet bear against the outside of said arti- cles. Thus the efficiency losses of the magnetic field is reduced since the magnetic field directly passes from the separating magnet to the magnetizable material of the article and does not need to pass through the air which is a bad conductor of mag- netism.

Other areas of application for a robot provided with a picking member comprising a separating magnet can for example be during punching, mounting, picking, sorting, transporting of arti- cles and/or some other application in which it is suitable that a robot fetches product parts or tools comprising a magnetizable material such as iron.

The invention is not limited to the embodiments shown but can be varied freely within the framework of the following claims. For example the picking member may be provided with two or more separating magnets and/or picking means, for example of vary- ing strength.