Abstract:
The invention consists of an industrial robot comprising a control system and a manipulator provided with a tool. The manipulator is provided with a number of moveable arms relative to one another, and an attachment of a tool. The attachment of a tool includes a carrying organ, which carries the tool while assembling. A locking ring locks the tool to the manipulator after centring of the tool. A method of doing the same is also included.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to an industrial robot comprising a control system and a manipulator with a tool and a method for such an industrial robot. The invention especially relates to a manipulator with a plurality of arms which are movable relative to each other and which include a tool attachment for attachment of the tool. In particular, the invention relates to a manipulator with a turn disk including the tool attachment.  
       BACKGROUND ART  
       [0002]     Most industrial robots are intended to work with a tool that is supported by a manipulator. Such a tool is attached to the outer arm of the manipulator and may include a plurality of operating possibilities. These tools often have a considerable weight, which implies that the mounting of the tool to the manipulator entails complicated and heavy work. The mounting work also comprises operations that require very high precision during the mounting. It is a condition for the subsequent work with the manipulator that a correct position for the tool is obtained.  
         [0003]     According to WO 99/50032, a device for attaching a tool to a manipulator is previously known. The task of the known device is to offer simpler mounting which entails a minimum of downtime for a process. Despite the rapid mounting, the method involves an operation when the tool has to be kept in place and at the same time in the correct position while a fixing member is being applied. It is thus desirable to eliminate the need to have to support and guide the tool simultaneously during the mounting.  
         [0004]     In the process industry, a plurality of solutions for automatic tool changing are known. These systems often comprise a device for centring and guiding the tool as well as a system for automatic locking of the tool to the robot. The known systems often provide inferior precision and involve an extensive and costly system for the actual tool-changing operation. The automatic systems must also include functions and magazines for storing and handling tools that are not in operation. When attaching heavier tools, the automatic systems are not suitable since such tools often also require an extensive connection of process media, such as current, control signals, cooling liquids, etc.  
         [0005]     From GB 2 120 634 A, a coupling between a robot and a tool is previously known for automatic tool changing without the intervention of an operator. The task of the known coupling is to provide a simple, light and reliable detachable coupling for this purpose. The coupling comprises a first part that is attached to the robot and a second part that is attached to the tool. The first part comprises a locking device in the form of a pneumatic piston with a transverse pin that is adapted to penetrate an elongated hole provided in the second part. After the piston has penetrated the hole, the first part is oriented in relation to the second part by rotating the first part in relation to the second part. During this rotary movement, also the transverse pin is given such a position that, during a tightening movement of the piston, the pin will rest against the rear side of the first part. The locking operation is then completed by bringing the piston, by the force from the pneumatic arrangement, to pull the second part towards it.  
         [0006]     The known device thus requires process media, in the form of pneumatics, to function. The known method also means that the tool is first oriented and then hooked and locked. The known coupling and method are thus not suited for attaching a heavy tool with great precision.  
       SUMMARY OF THE INVENTION  
       [0007]     The object of the present invention is to suggest ways and means of providing a method and a device which, when mounting a tool on a manipulator, simplify the work of the operator and relieve the operator of the weight of the tool itself. Another object of the invention is to offer a simple and cost-effective system for manual mounting of a tool.  
         [0008]     These objects are achieved according to the invention by an industrial robot according to the characteristic features described in the characterizing portion of the independent claim  1  and with a method according to the characteristic features described in the characterizing portion of the independent method claim  9 . Advantageous embodiments are described in the characterizing portions of the dependent claims.  
         [0009]     According to the invention, the manipulator comprises a tool attachment including a member for supporting the tool before it is fixed to the manipulator. The supporting member is adapted to carry the weight of the tool such that the manipulator supports the tool during the mounting. The work is carried out in such a way that the tool is lifted by the operator and hooked onto the supporting member. The lifting operation may be carried out completely manually or with a lifting device such as, for example, a crane or a travelling crane. The operation can also be carried out by hooking the robot onto the tool and by lifting the tool to an operator position for fixing. At the same moment that the tool is hooked onto the supporting member, the weight of the tool is transferred to the manipulator. Thus, any lifting devices may then be immediately removed and the tool be completely freely accessible for the mounting work. The continued work comprises centring the tool to a predetermined position and fixing it, in this position, to the tool attachment and hence to the manipulator.  
         [0010]     According to the invention, the supporting member comprises a hook that is fixed to a first structural part and an aperture that is adapted to receive the hook arranged in a second structural part. Here, the first structural part may be the tool attachment and the second structural part the actual tool, or inversely. The designation hook is here to be given a broad meaning of a member adapted to be detachably attached to another member. Thus, a hook may be an elongated object that is partly curved. A hook also comprises a stud with a lower part and a head where the dimension of the head is larger than that of the lower part. The designation aperture for the reception of the hook is also to be given a broad meaning of a hole or a slot that completely or partly surrounds the hook. The function of the aperture is to allow introducing the hook in an unloaded state but to prevent the hook from being pulled out, under loading, through the aperture.  
         [0011]     To assist in the centring of the tool, according to the invention, the tool attachment comprises one or more guide members. In one embodiment, this is implemented by means of a stud, which is adapted to fit into a hole. The stud is thus arranged in a first structural part, which may be the tool, and the hole in a second structural part, which may be the tool attachment. The stud is thus arranged either in the tool or in the tool attachment. The hole corresponding to the stud is arranged in the structural part opposite to the stud. In an advantageous embodiment, the stud is made slightly conical, whereby the structural parts, when being brought together, are allowed to be displaced relative to each other in the lateral direction so as to achieve the correct position when the stud has completely penetrated the hole. The penetration of the stud here means that the structural parts, by the force between the stud and the hole, simultaneously with the threading on, are displaced to the desired position.  
         [0012]     In another embodiment, the guide member is designed to form a so-called dovetail joint, in which case the joint at the same time acts as the supporting member. In a further embodiment, either the tool or the tool attachment includes studs which are provided with heads and which are inserted into corresponding holes comprising a round section and an elongated section, usually referred to as “keyholes”. In this embodiment, the tool is first brought to be supported by the studs provided with heads. The tool is then brought to adopt the correct position through a rotational operation, whereby the studs penetrate into the narrower part of the keyholes. In one preferred embodiment, the elongated part of the holes is arranged wedge-shaped in the direction of rotation.  
         [0013]     The invention also comprises a coupling, by which the tool in its correct position is fixed to the manipulator. According to a preferred embodiment, the coupling comprises a mechanical joint, whereby a surrounding ring comprising two semicircular parts is brought, by tensioning, to fix the tool to the tool attachment. The tool and the tool attachment are adapted to meet each other with a respective disc with the same diameter. Those edges of the discs which are facing away from each other are chamfered. A coupling comprising a clamping ring with a trapezoidal inner groove is brought to surround the two discs. The trapezoidal surfaces of the grooves grip over the chamfered edges of the discs like a key joint and bring the discs to be pressed against each other when the ring applies a surrounding force around the discs. In one embodiment, the ring halves are equipped with flanges at their ends. A coupling brings the flanges of the two halves against each other, whereby the surrounding force arises. In one embodiment, the coupling is a screw joint and in another an eccentric lock in which a small lever arm first clamps the clamping ring and then fixes it.  
         [0014]     In an additional embodiment, the coupling is in the form of a plurality of studs arranged in one of the plates, which studs penetrate into holes in the other plate. The studs are provided with tapering webs limited by accurately adjusted conical portions. When the studs are inserted into the holes, a pin adapted for each stud is brought, in a plane normal to the stud, to penetrate into and make contact with the web. In a further embodiment, the coupling is a screw joint that directly clamps the two plates together.  
         [0015]     In still another embodiment, the tool attachment comprises a locking device that prevents the hook from loosening. Such a locking device comprises, for example, a pin that is arranged in a direction transversely to the extent of the hook and hence blocks the possibility of the hook to move. In another embodiment, the locking device comprises a catch device which, after the hook has reached its supporting position, is folded out and prevents the supported part from moving.  
         [0016]     In case of special tools, such as, for example, a spot welding gun, fault currents, traversing the manipulator, sometimes arise. These fault currents often lead to damage, above all in bearings. The damage arises as recesses in bearing races and leads to extensive and time-consuming repair work. In an additional embodiment, therefore, the tool is galvanically separated from the manipulator. An insulating barrier is then arranged at the section between the tool and the manipulator. In an advantageous embodiment, this barrier is arranged as a disc of insulating material between the tool and the tool attachment. In another advantageous embodiment, the barrier is arranged as an insulating coupling between the turn disc and the tool attachment.  
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0017]     The invention will be explained in greater detail by description of embodiments with reference to the accompanying drawing, wherein  
         [0018]      FIG. 1  is a device according to the invention comprising a tool attachment, belonging to a manipulator (not shown), said tool attachment having a hook for relieving and a guide pin for guiding, and an only partly shown tool,  
         [0019]      FIG. 2  is an advantageous embodiments of the device with a groove,  
         [0020]      FIG. 3  is another embodiment of the device with two supporting and guide pins penetrating two corresponding “keyholes”,  
         [0021]      FIG. 4  is a further embodiment of the device with a centre stud and a guide pin,  
         [0022]      FIG. 5  is an additional embodiment of the device with a dovetail joint,  
         [0023]      FIG. 6  is still another embodiment of the device with a dovetail joint,  
         [0024]      FIG. 7  is yet another embodiment of the device with a screw joint,  
         [0025]      FIG. 8  is a further embodiment of the invention with studs provided with webs with transverse pins for fixing,  
         [0026]      FIG. 9  is an embodiment of the device with a locking device in the form of a pin preventing the hook from loosening,  
         [0027]      FIG. 10  is an embodiment of the device with a locking device in the form of a catch preventing the hook from loosening,  
         [0028]      FIG. 11  is an embodiment of the device with a locking device in the form of a pin preventing the hook from loosening, and  
         [0029]      FIG. 12  is an embodiment of the device with a locking device in the form of a stud penetrating a hole that prevents the hook from loosening 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0030]     The device according to  FIG. 1  comprises a tool attachment  1  that is an integrated part of the outermost arm of a manipulator (not shown) that together with a control system constitutes an industrial robot. Further, the device comprises a tool  2 , which in the figure is exemplified by a circular plate. In the example shown, the tool attachment comprises a slot  3  and a guide spindle  4 . The tool comprises, partly concealed, a hook  5  and a hole  6 . In a first step, the hook  5  is adapted to engage with the slot  3  such that the whole weight of the tool is brought to be supported by the tool attachment. In a second step, the guide spindle  4  is adapted to be inserted into the hole  6 , such that the tool is centred into the right position relative to the operating point of the manipulator. In an advantageous embodiment, the hook exhibits a bent outer part which is brought to hook into the rear side of the slot. In the example the slot has parallel sides with a trumpet-shaped opening to facilitate receiving the hook. However, the groove may, of course, also be slightly conical to assist in centring the tool. Similarly, instead of having a bent outer part, the hook may be provided with a head with a larger diameter than the slot so that this head prevents the hook from sliding through the slot.  
         [0031]     The tool attachment  1  and the tool  2  are shown in the example as circular plates of equal size. Each plate has a chamfered edge so that the plates, when being assembled, exhibit a common trapezoidal edge portion. A clamping ring  7  in two halves  7   a  and  7   b  are adapted to grip over the trapezoidal edge portion. To this end, the inner side of the clamping ring is designed with a trapezoidal groove with a narrower shape such that, like a key joint, it surrounds the edges of the two discs with clamping force. Thus, when the tool is suspended, such that its weight is supported by the manipulator, and centred, such that the operating point of the tool coincides with the operating point of the manipulator, the coupling is fixed by the clamping ring  7 . The two halves  7   a  and  7   b  of the clamping ring are pressed against each other with a screw joint or the like.  
         [0032]     The device of  FIG. 2  includes the same parts as in  FIG. 1  but here the tool attachment  1  comprises a recess that forms a first hook line  8  arranged across the disc. In a corresponding way, the tool comprises a second hook line  9  that is adapted to engage with the first hook line. The hook lines are arranged in this example to form a coupling where, in a first step, the weight of the tool is transferred to the manipulator and where, in a second step, the tool is brought, by sliding between the hook lines, to be centred and finally fixed with the clamping ring  7 .  
         [0033]     The device of  FIG. 3  also includes the same parts as in  FIG. 1 . In this example, the tool attachment comprises two key-shaped holes  10   a  and  10   b . Intended to be inserted into these holes, the tool comprises two studs  11   a  and  11   b  (concealed in the example), each having a head with a larger diameter than the stud itself. When mounting, the studs are thus inserted into the corresponding holes, whereby the weight is transferred. In a second step, the tool is centred by rotating the tool such that the studs slide into the narrower part of the keyhole. Fixing is performed as above.  
         [0034]     The device of  FIG. 4  shows a further embodiment of the invention with the same parts as in  FIG. 1 . Here, the tool  2  comprises a supporting member in the form of a coarse stud  12 . For receiving this stud, the tool attachment comprises a hole  13 . In this example, the tool also comprises a guide spindle  14  adapted to penetrate into a hole  15  comprised in the tool attachment. The device shown also comprises an insulating barrier in the form of a disc  24  of an insulating material that galvanically separates the tool from the manipulator. Also the guide spindle and the clamping ring must, in this embodiment, be manufactured of insulating material.  
         [0035]     A further example is the device of  FIG. 5  in which the supporting member and the guide member consist of a dovetail joint. Here, the tool attachment comprises a dovetail slot  16  in the form of an elongated recess with a wider bottom than the orifice. The tool comprises a dovetail  17  in the form of a projecting portion with two opposing plane sides, diverging outwardly. The mounting is performed such that the dovetail is introduced from the side into the dovetail slot. When the dovetail has been inserted a certain distance, the manipulator assumes the weight of the tool. Then the tool is moved laterally so as to be centred, whereupon it is fixed. An additional variant of the device with a dovetail joint is shown in  FIG. 6 . Here, the parts have the same designations as in  FIG. 5 . The difference is that the dovetail joint is only arranged along part of the tool and the tool attachment, respectively. This means that the mounting is made from above.  
         [0036]     The device according to  FIG. 7  shows a coupling comprising a plurality of screws  18  that are arranged in holes in the tool and that are each engaged with a threaded hole  19  in the tool attachment. Otherwise, the embodiment corresponds to that shown in  FIG. 1 . The supporting of the tool is thus attended to by a hook  5  that engages into the slot  3 . The centring is attended to by a hole  6  provided in the tool, the hole being adapted to receive a guide spindle  4  arranged in the tool attachment.  
         [0037]      FIG. 8  shows the device with a different design of a coupling. Two studs  20  with a trapezoidal web  21  are arranged in the tool attachment. Corresponding holes (concealed) are arranged in the tool. In the same way as in  FIG. 1 , the device is provided with a hook  5  and a guide spindle  4  for supporting and centring the tool. During mounting, the studs  20  are inserted into the corresponding holes. The tool comprises a pin  22  arranged on either side and running in a normal plane to holes  23  provided for the studs. Each pin is adapted to penetrate from the side into the stud  20  and to make contact with the web  21  of the stud, thus obtaining fixing.  
         [0038]     For safety reasons it is of great interest that the tool be retained in its lifted position, even if the robot, inadvertently or through malfunction, should happen to rotate the turn disc.  FIGS. 9 and 12  show a plurality of embodiments of a locking device that prevent the hook from loosening.  FIG. 9  shows a hook  5  that, after having penetrated into the groove  3 , is locked by a pin  25 . In  FIG. 10 , the locking device is instead shaped as a catch device  26  that, when being unfolded, grasps the lower edge of the first part  1 . An additional example of a locking device is shown in  FIG. 11  where a pin provided with a handle is arranged in a groove where it locks the movement of the hook. Finally,  FIG. 12  also shows a further solution where the locking operation is achieved in that a stud  28  in the second part  2 , when fastening the hook  5 , penetrates into a hole  29  in the first part.  
         [0039]     Although advantageous, the invention is not limited to the embodiments shown. Thus, the various parts of the device may, for example, be made from a plurality of different materials. The design of the supporting device, the centring device and the locking device may also adopt various embodiments with regard to design and material choice.