Field of the invention The invention relates to a device for manipulating work pieces. The invention also relates to a system utilizing the above-mentioned device.

Background of the invention In various systems of prior art, particularly manufacturing systems, work pieces are manipulated in various ways by means of pallets. The work pieces are connected to the pallet which is used as a transfer platform and is positioned carefully, for example, at a machine tool but, if necessary, also at various stations, such as a storage station or a loading station. By means of the positioning, the location and the position of the work piece are also known precisely, because the work piece, in turn, is connected in a specific location, that is, a place or position, and alignment, in relation to the pallet.

The pallets constitute a significant part of the whole system, also because of the investment costs, and particularly if the number of pallets increases with an increase in the production numbers of work pieces or in the system.

Next, we shall discuss a specific system. In the manufacture of bearings, it is typical to manipulate bearing billets which are annular pieces with a diameter ranging, for example, from 400 to 4000 mm. It is thus obvious that specific properties are required of the pallets, so that bearing billets with a varying diameter can be reliably fixed to them, or a respective pallet has to be used for each diameter range. In any case, the situation gives rise to high investment costs, particularly for pallets.

Brief summary of the invention

It is an aim of the invention to eliminate above-presented problems. The device for manipulating work pieces according to the invention is presented in claim 1 . The system according to the invention is presented in claim 12. The presented solution makes it possible to abandon the use of pallets. The presented solution makes it possible to employ the same device for positioning varying work pieces, but without movable elements for transferring the work piece in the device itself. In particular, the presented solution makes it possible to manipulate annular work pieces with a large diameter range, particularly e.g. bearing billets, without more specific limitations on the exact dimensions of the bearing billet.

In spite of this, the presented solution makes it possible to position the work piece, for example a bearing billet, and particularly to center it at a desired point with respect to the center line. The positioning takes place without any actions that the device would exert on the work piece and which would move the work piece in relation to the device. In an initial situation, the device is accurately positioned, in its position and alignment, with respect to the work piece by means of centering members in the initial station of the work piece; the device grips the work piece, keeps it in its place in the device, and delivers the work piece to the target station by means of centering members in the target station. The position of the work piece in relation to the centering members of the target station remains fully identical with the position of the work piece in relation to the centering members of the initial station. The device comprises centering members which are intended to be, if necessary, in a functional connection with the centering members of the target station or the initial station so that the position of the work piece is maintained in all stations, or in the device. The target station or the initial station may be, for example, a loading station, to which the work piece is delivered or from which it is received into the system, by utilizing, for example, a stacker crane and its fork; or a station which is functionally connected to a machine tool and to which the work piece is delivered to, or from which it is received from the machine tool, again by utilizing, for example, a stacker crane. The target station or the initial station may also be a storage location of a storage in the system, to which location the work piece is delivered or from which it is received, again by utilizing e.g. a stacker crane.

In an example, the device utilizes a magnetic plate, whose planar surface engages a surface of the work piece. An advantage is that the other exterior and interior surfaces of the work piece remain free. The only requirement of the work piece is an equivalent surface that is placed against the magnetic plate. The dimensions of the work piece, for example the diameter of a bearing billet, may thus vary even to a great extent. The same aim can also achieved with a vacuum gripper.

Description of the drawings

In the following, the invention will be described by means of examples and with reference to the appended drawings, in which

Fig. 1 shows a device according to an example, seen from the side, when manipulating a bearing billet with a large diameter; Fig. 2 shows a device according to an example, seen from the side, when manipulating a bearing billet with a small diameter;

Fig. 3 shows the device of Fig. 2 when gripping a work piece; Fig. 4 shows the device of Fig. 2 engaging a work piece and released from the centering members of a initial station or a target station; and

Fig. 5 shows a system in a reduced principle view and seen from above, the system comprising several stations and utilizing a device for transferring work pieces.

Detailed description of the invention

The numbering of parts shown in Fig. 1 also relates to the examples shown in Figs. 2 to 4 and the corresponding parts therein. Figure 1 shows an example of a device 1 . The device 1 for manipulating work pieces comprises a magnetic gripper 3 which engages a work piece 8 on the basis of a magnetic holding force. The gripper 3 preferably also comprises members for controlling the magnetic holding force, so that the work piece can be held or delivered by the gripper 3.

In the example of Fig. 1 , the gripper 3 is a planar surface enabling a gripping surface that is as large as possible, particularly for work pieces 8 of variable sizes. In the device 1 of Fig. 1 , the planar surface faces down and the work piece 8 is held under the planar surface and the device 1 .

A centering member 5 extends further out from the gripping surface of the gripper 3, away from the gripper 3, at a predetermined location in relation to the gripping surface. In this example, the centering member 5 is in a fixed position in relation to the gripping surface and the plane defined by it, that is, said planar surface. In other words, the axis X1 defined by the centering member 5 and transverse to the gripping surface is not movable. In the example of Fig. 1 , the centering member 5 extends downwards. The example of Fig. 1 also has an additional feature in that the centering member 5 is movably connected to the gripper 3 by a fastening sleeve 6. The fastening sleeve 6 secures that the centering member 5 is only movable in the direction of the axis X1 defined by the centering member 5 but not in the lateral direction. Consequently, the centering member 5 is only movable in a direction transverse to the gripping surface. The movable centering member 5 makes it possible to manipulate work pieces of different thicknesses. The centering member 5 can also be functionally connected to a backing member 7 in a station 9 when the device 1 is moving transversely towards the station 9. In the case of a low work piece, the centering member 5 may be con- nected to the backing member 7 already before the gripping surface of the gripper 3 is placed against the work piece 8, and simultaneously the centering member 5 yields, in this case in the direction of the axis X1 . An advantage is that the work piece does not need to be elevated or connected to such a height in the station 9 that corresponds to the height of the centering member 5. When manipulating the thickest possible work piece, the center- ing member 5 is connected to the backing member 7 simultaneously when the gripping surface of the gripper 3 is placed against the work piece 8.

The backing member 7 and the centering member 5 are functionally con- nected to each other, for example in such a way that the axis X1 defined by the centering member 5 is always placed in the same location, that is, place or position, and alignment in relation to the backing member 7. The principle is that the backing member 7 and the centering member 5 always center each other to a predetermined position and alignment in relation to each other. In many cases, said axis X1 coincides with the axis X2 defined by the backing member 7. Said axis X2, in turn, is transverse to that plane of the station 9, parallel to which the work piece is lying, or the surface, on which the work piece is lying. In this example, the backing member 7 is in a fixed position to said plane or surface. In other words, the backing member 7 and the axis X2 defined by it are not movable.

In some examples, the backing member 7 and the centering member 5 are tubular, annular or conical, or circular in cross-section and symmetrically closed in shape, so that the axes defined by them are simultaneously their symmetry axes or central axes.

Because the backing member 7 and the centering member 5 are always placed in the same position in relation to each other, then also the gripper 3 of the device 1 , with its gripping surface, is always placed in the same posi- tion in relation to the station 9. Thus, the work piece 8 always remains in the same position in relation to the backing member 7 and the centering member 5, irrespective of whether the piece is in the station 9 or in the device 1 .

Preferably, the work piece comprises two parallel surfaces, against which the gripping surface of the device 1 and the station 9 are placed. Thus, said surfaces are parallel to the planar surface of the gripper 3.

As shown in Fig. 1 , the work piece 8 is annular, in this example particularly a bearing billet having two said parallel surfaces and being penetrated by the centering member 5a preferably placed on the central line or axis defined by the bearing billet. The presented device 1 also makes it possible that the central line or axis of the work piece may deviate from the line or axis defined by the centering member 5 or the backing member 7. However, the centering mentioned in this description is involved, because the center line or axis is in a predetermined location and is not changed even if the work piece is moved from the initial station to the target station. Corresponding features are found in other annular work pieces as well. It should be noted that the centering member 5 is separate from the work piece and allows a transfer of the work piece in the gripper 3 or a change in the location of the work piece with respect to the centering member. In the case of the annular work piece of Fig. 1 , a rotation of the work piece is also allowed. The backing member 7 functions in a similar way. The centering member 5 and the backing member

7 are not in contact with the work piece, nor do they control the work piece but the gripper that engages the work piece. The station 9 in Fig. 1 is an initial station where the work piece 8 is centered or positioned carefully for the first time and always in the same way, particularly in relation to the backing member 7. In this example, the members for positioning and centering comprise a support or supports 1 1 which rest on top of a fastener 10 or are connected to it. In this example, the fastener 10 is magnetic. It is not necessary to position the work piece 8 in a corresponding manner in the other stations, to which the device 1 transfers the work piece 8, but it will suffice to provide them with a centering member 5 only.

According to the example shown in Fig. 1 , the device 1 can be connected, for example, to a fork 2 provided, for example, in a stacker crane. The device 1 may also be part of a lifting and transfer device for transferring work pieces between stations. In the presented example, the device 1 comprises a frame 12 connected to the fork 2. The stacker crane moves the device 1 and simultaneously also the work piece 8 from one station to another.

Figure 3 shows an example, in which the device 1 is gripping the work piece

8 of Fig. 2. It can be seen in the figure that the centering member 5 is movable in the mounting sleeve 6 and through the gripping surface. At this stage, a magnetic holding force is effective on the work piece 8, which remains engaged by the device 1 , so that the work piece 8 can be lifted up from the station 9, as shown in Fig. 4. During the lifting, the centering member 5 moves in the mounting sleeve 6 and finally detaches from the backing member 7. The return of the centering member 5 to the position shown in Fig. 1 can be assisted by a returning force effective on the centering member 5. The returning force is generated, for example, by a spring in the mounting sleeve 6. After this, the work piece 8 can be transferred to another station, and said station does not comprise members for positioning the work piece but merely the backing member 7. The delivery of the work piece 8 to the station takes place in the reverse order: first Fig. 4, then Fig. 3, and finally according to Fig. 2.

Figure 5 shows a principle of a system utilizing said device 1 . The system comprises a storage 14 with stations 15 used as storage locations for work pieces. The system further comprises at least one machine tool 16 with a station 17 for a work piece. Furthermore, the system comprises at least one station 13 which is used as a loading station. A stacker crane or another lifting and transfer apparatus 18 is capable of transferring work pieces from one station to another. The apparatus 18 comprises the device 1 described above. The apparatus 18 is capable of manipulating or transferring the device 1 in such a way that a work piece can be placed in a station. Accord- ing to another alternative, the device 1 is configured to perform the movements by which the placement of the piece into a station is possible.

A centering member 5 (Fig. 1 ) is utilized in at least two of the following: the station 13, the station 15, and the station 17, which are thus also equipped with the necessary backing members 7 (Fig. 1 ). At least one of said stations is also equipped with members for positioning and centering the work piece, which members are represented by supports 1 1 in Fig. 5. In the example of Fig. 5, all the stations 13, 15 and 17 comprise backing members 7, and the station 13 comprises said supports 1 1 . However, the supports 1 1 are not indispensable, because the positioning and centering can also be performed by measuring and transferring the work piece if needed, for example by transferring it to the center of the station. The measurement can be based on a dial gauge, a laser, a pneumatic gauge, a camera, or another corresponding system. However, the positioning and centering of the work piece always have to be performed in at least one of said stations so that the position and alignment of the work piece are known. In an example, the centering member 5 and the backing members 7 are based on shapes which correspond to each other and center each other. Thus, in a particular example, they have surfaces which follow a conical shape and are placed against each other. The centering member 5 and the backing member 7 act as female and male elements which are placed within each other and control precisely the mutual position of each other. In the example of Fig. 1 , the centering member 5 is a female element, but alternatively, it can be constructed to match the shape of the backing member 7 wherein it acts as a male element.

In an example, a vacuum gripper is used instead of a magnetic gripper. The gripper of the vacuum gripper comprises contact members based on vacuum, for example suction pads or ejectors which define a plane that cor- responds to the gripping surface or plane defined by the gripper 3 of Fig. 1 . The surface of the work piece is placed parallel to said plane and is engaged by the contact members. When a sufficient number of contact members are provided in a sufficiently large area, the same gripper can be used for gripping work pieces whose dimensions vary even to a great extent.

In selecting a vacuum gripper, one should make sure that the position of the work piece does not change in such a way that it would cause inaccuracy in centering the work piece. In other words, holding the work piece in the gripper and delivering it from the gripper are performed in such a way that the piece does not simultaneously move away from its center alignment or change its position.

In an example, the plane defined by the gripper 3 is horizontal, and the work piece 8 is supported under the device 1 . The work piece is lying on the sta- tion and is lifted from it after the gripper has grabbed it by a vertical movement. Also, the station is preferably horizontal. The centering member 5 and the backing members 7 move towards each other and are coupled to each other by a vertical movement of the device 1 . The movement takes place, for example, in the direction of the axis X1 . The line or axis defined by the cen- tering member 5 and the backing member 7 and in relation to which the work piece is centered, is vertical. The apparatus 18, to which the device 1 is con- nected and which carries the device 1 and simultaneously also the work piece, performs a rough positioning to bring the work piece at the station. The more accurate positioning is performed by the device 1 . According to one alternative, the apparatus 18, for example the fork of a stacker crane or another lifting and transferring apparatus, allows a movement between the device 1 and the apparatus 18, caused by the centering of the device 1 , if this is necessary. In the presented example, the gripper 3 can move by flexible elements 4 in relation to the frame 12 and thereby also in relation to the fork 2. The flexible elements make it possible that the gripper 3 can accu- rately find its way to the target station without a corresponding accurate positioning of the frame 12 of the lifting apparatus and the fork 2 of the stacker crane.

In an example, the centering member 5 comprises a conical recess, a partly conical recess, or an inner annular surface that forms part of the inner surface of a conical surface area. The annular surface opens and expands away from the device 1 , for example downwards. The backing members 7, in turn, comprise a conical, partly conical or outer annular surface that forms part of the outer surface of a conical surface area. The annular surface tapers away from the station 9, towards the device 1 , for example upwards. Said annular surfaces are placed against each other. The centering member 5 and the backing member 7 are placed against each other, and thanks to their matching shapes, they are locked into each other in such a way that their mutual movement in the lateral direction, for example in the horizontal direction, is prevented.

The invention is not limited solely to the above-presented examples, but it can be applied within the scope of the appended claims.