Bolt joining method and tools therefor

Abstract

A method for carrying out a stud joining process by a tool performing a working step on a workpiece and the working step is carried out while taking into account at least one parameter value which is selected from a set of values, and the working step is to be carried out at a certain position on the workpiece, and the position determines the parameter value. The method comprises the steps of: storing the parameter value for the position in an RFID transponder; locating the RFID transponder on the workpiece in the region of the position before the working step is carried out, reading the parameter value out from the RFID transponder with an RFID communication device associated with the tool.

Claims

1. A method for carrying out a stud joining process by a working step on a workpiece by means of a tool, and the working step is carried out while taking into account at least one parameter value which is selected from a set of values, and the working step is to be carried out at a first position on the workpiece, and the first position determines the parameter value, wherein the method comprises the steps of: storing the parameter value for the first position in an RFID transponder; providing a positioning device including a plurality of positioners for defining a plurality of positions on the workpiece; securing the RFID transponder to a first positioner on the positioning device: locating the positioning device temporarily on the workpiece with the RFID transponder in the region of the first position before the working step is carried out; and reading the parameter value out from the RFID transponder with an RFID communication device associated with the tool.

2. A method according to claim 1 and further comprising the step of securing the RFID transponder to a holding device before the step of locating the RFID transponder on the positioning device.

3. A method according to claim 1 and further comprising the steps of: transmitting the read-out parameter value to a control device; and setting the tool on the basis of the read-out parameter value.

4. A method according claim 1 and further comprising the step of providing the RFID transponder with a coil arranged concentrically around a processing axis.

5. A stud joining tool for carrying out a stud joining process by a working step on a workpiece, and the working step is carried out while taking into account at least one parameter value which is selected from a set of values, and the working step is to be carried out at a certain position on the workpiece, and the position determines the parameter value, and wherein the tool comprises: a stud holding device defining a processing axis; an RFID communication device located in a working region of the tool and operable for at least one of reading out a parameter value from an RFID transponder and for writing a parameter value into an RFID transponder, and wherein the RFID communication device is mounted on the tool so as to be movable relative to the stud holding device in a direction parallel to the processing axis.

6. A stud joining tool according to claim 5 and further comprising a control device connected to the RFID communication device and operable for setting a tool parameter according to a parameter value read-out from the RFID transponder.

7. A stud joining tool according to claim 5, wherein the RFID communication device includes a coil arranged concentrically about a processing axis in such a way that communication with the RFID transponder can be effected substantially independently of a rotary position of the tool about the processing axis.

8. A positioning device for carrying out a stud joining process by a working step on a workpiece, and the working step is carried out while taking into account at least one parameter value which is selected from a set of values, and the working step is to be carried out at a certain position on the workpiece, and the position determines the parameter value, and wherein the positioning device comprises: a plurality of positioners operable for defining a plurality of positions on the workpiece; a bushing located at a first positioner; and an RFID transponder located in the bushing.

9. A positioning device according to claim 8, wherein the bushing includes: an outer sleeve; an inner ring connected to the outer sleeve; and wherein the RFID transponder is integrated into the inner ring.

10. A positioning device according to claim 8, wherein the RFID transponder includes a coil arranged concentrically to a longitudinal axis of the bushing.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) Exemplary embodiments of the invention are shown in the drawing and are described in more detail below. In the drawing:

(2) FIG. 1 shows a schematic cross-sectional view of a joining arrangement having a stud joining tool according to an embodiment of the present invention;

(3) FIG. 2 shows a schematic illustration of a positioning device;

(4) FIG. 3 shows a perspective sectional view of a bushing for a positioning device of the type shown in FIG. 2;

(5) FIG. 4 shows a sectional view through a further embodiment of a bushing for a positioning device of the type shown in FIG. 2; and

(6) FIG. 5 shows a cross-sectional view of a joining arrangement with a further embodiment of a stud joining tool according to the invention and of a positioning device according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) A joining arrangement in the form of a stud welding arrangement is designated generally by 10 in FIG. 1. The joining arrangement 10 serves to join a stud 12 to a workpiece 14 in the form of a sheet or the like in one working step. The joining operation is effected in this case preferably in such a way that an integral connection, such as a welded or adhesively bonded connection, is set up between the stud 12 and the workpiece 14. The joining operation is carried out only from one side of the workpiece 14.

(8) The joining arrangement 10 has a joining tool 20 in the form of a stud welding gun. The joining tool 20 has a handle 22 and is connected via a schematically indicated supply line 24 to a power source and possibly to a control device.

(9) In the region of a head, the joining tool 20 has a holding device 26 for holding a stud 12. The holding device 26 is surrounded by a mouthpiece 28, which can be connected, for example, rigidly to the housing of the joining tool 20. The holding device 26 can be displaceable in the axial direction relative to the housing. Furthermore, the holding device 26 is preferably driven in the axial direction by means of a mechanical or electromechanical device.

(10) To carry out a stud welding operation, as a rule the stud 12 is first of all put onto the workpiece 14 and then the mouthpiece 28 comes down on the workpiece 14. A pilot current, which flows via the workpiece 14 and the stud 12, is then switched on. Subsequently, the stud 12 is lifted from the workpiece 14, such that an arc is produced between the stud 12 and the workpiece 14. The current is then increased to a welding current, such that those surfaces of stud 12 and workpiece 14 which are opposite one another are fused. In a last step, the stud 12 is lowered again onto the workpiece 14, such that the molten pools intermix and the arc is short-circuited. The welding current is switched off. The complete molten pool solidifies, such that the stud 12 is integrally connected to the workpiece 14. In a stud adhesive-bonding process, it is normal practice to heat a layer of adhesive on that side of the stud 12 which faces the workpiece 14 before the stud 12 is lowered onto the workpiece 14.

(11) To carry out such a joining process, the joining tool 20 is positioned with respect to an intended position 30 at the workpiece 14.

(12) To carry out a plurality of such joining processes one after the other, during which different studs 12 are joined one after the other to the same workpiece 14 or different workpieces 14, it may be necessary to set the respective joining parameters differently for the individual processes. As a rule, the joining parameters are stored for the individual welding processes in a control device which is connected to the joining tool 20.

(13) In order to be able to select the suitable set of joining parameters automatically, an RFID transponder 32 has been arranged in the region of the position 30. In the illustration of FIG. 1, the transponder 32 is arranged on that side of the workpiece 14 which is opposite the joining location. As a rule, this embodiment is only relevant when the workpiece 14 is not made of a metallic material. As an alternative, the transponder 32 can also be arranged next to the position 30 or the joining location on the top side of the workpiece 14. The transponder 32 is in this case preferably arranged temporarily, such that the workpiece 14 can then be further processed or delivered without the transponder 32. Stored in the RFID transponder 32 is a parameter value which is selected from a range of values and contains the joining parameters or a reference to the joining parameters in the control device which are to be set for the joining process to be carried out at this position 30.

(14) An RFID communication device 34 is provided on the joining tool 20. As shown in FIG. 1, the RFID communication device 34 is preferably arranged in the region of the mouthpiece 28 of the joining tool 20. The RFID communication device 34 is connected to a control device 36 of the joining tool 20. Alternatively, the RFID communication device 34 can be connected to a control device which is connected to the tool 20 via the supply line 24.

(15) When the mouthpiece 28 is put onto the workpiece 14, before the joining process is actually carried out, the RFID communication device 34 reads the parameter value from the transponder 32 and transmits this parameter value to the control device 36. With reference to the parameter value, the control device 36 selects the joining parameters relevant to this position and accordingly sets the joining tool 20. Furthermore, an energy supply source can also be set with reference to this parameter value, said energy supply source being connected to the joining tool 20 via the supply line 24. Finally, the type of stud 12 which is to be joined in the working step and is possibly fed automatically to the tool 20 can be alternatively or additionally selected via the parameter value.

(16) The joining process is then carried out with reference to the joining parameters selected automatically in this way. Manual selection errors of incorrect joining parameters can be avoided as a result.

(17) For the correct positioning of the joining tool 20 with respect to the joining position 30, it is known to mount a positioning device 38 at the workpiece 14 beforehand. The positioning device 38 is attached to the workpiece 14 at schematically indicated attachment points 40, 41, for example in the form of screwed connections or by clamping connections or the like. The connection should at any rate also be easily releasable again, since the positioning device 38 is secured only temporarily to the workpiece 14.

(18) Furthermore, the positioning device 38 is preferably mounted at a distance 42 from the surface of the workpiece 14.

(19) The positioning device 38 has a positioner in the form of a bushing 44. The bushing 44 defines a joining axis 46 which, when the positioning device 38 is attached, is disposed exactly and perpendicularly at the position 30 on the surface of the workpiece 14.

(20) To carry out the joining process, the mouthpiece 28 is inserted into the bushing 44 and then put onto the top side of the workpiece 14. As a result, it can be ensured that the stud 12 is joined to the workpiece 14 at the correct position 30.

(21) When such a positioning device 38 is used, it is preferred to secure the RFID transponder 32 to the positioning device 38. It is especially preferred to secure a transponder to the positioning device 38 in the region of the bushing 44, as schematically shown in FIG. 1 at 32. In this case, on account of the close proximity between the mouthpiece 28 and the bushing 44 during the joining process, reliable recognition and reading-out of the transponder 32 by means of the RFID communication device 34 can be ensured.

(22) Shown in FIG. 2 is a further embodiment of a positioning device 38. The positioning device 38 has a plurality of bushings 44a, 44b, 44c, 44d which are rigidly connected to one another by struts. Furthermore, the positioning device 38 has a plurality of stirrups or clamping devices 48, 50 for securing the positioning device 38 to the workpiece 14.

(23) The bushings 44a-44d define respective joining axes 46a-46d, which define a plurality of different positions 30 on the workpiece 14.

(24) Although not shown in FIG. 2 for reasons of clarity, a transponder 32 is preferably arranged on at least one of the bushings 44a-44d, as shown at 32 in FIG. 1. Such a transponder 32 is preferably arranged on each bushing 44a-44d. The transponders 32 of the bushings 44a-44d define, via the parameter value stored therein, in each case the joining parameter or the set of joining parameters which are to be used when carrying out the joining processes in the region of the respective bushings 44a-44d.

(25) FIG. 3 shows a preferred embodiment of a bushing 44, as can be used, for example, in the positioning device 38 for each of the bushings 44a-44d.

(26) The bushing 44 of FIG. 3 has an outer sleeve 54 made of a metallic material. The outer sleeve 54 has a shoulder 56 at a first longitudinal end, such that the outer sleeve 54 can be inserted into a preformed bore in a positioning device 38. Furthermore, a notch 58 for fixing the bushing 44 to a positioning device is formed on the outer circumference of the outer sleeve 54.

(27) Furthermore, the bushing 44 has an inner ring 60. The inner ring 60 is preferably made of a non-metallic and non-magnetic material, such as, for example, plastic or synthetic resin. For example, the inner ring 60 can be formed by casting a synthetic resin compound.

(28) A top side of the inner ring 60 is flush with the top side of the outer sleeve 54. An underside of the inner ring 60 is in alignment with a radially inwardly projecting section of the outer sleeve 54. An inside diameter of the radially projecting section of the outer sleeve 54 and an inside diameter of the inner ring 60 are coaxial to one another and jointly form a bore 66.

(29) Integrated into the inner ring 60 is an electronic component in the form of a transponder chip 62, which has a memory for storing the parameter value. In general, each transponder chip 62 has a unique ID worldwide, which can represent a reference to a parameter value. Furthermore, the chip 62 is connected to a coil 64 which forms an aerial of the transponder 32. The transponder 32 is preferably a passive transponder and does not have an independent energy supply source. The read-out operation is effected by the RFID communication device 34 supplying energy to the chip 62 by an inductive coupling with the coil 64, said chip 62 reading out the memory by means of this energy and transmitting in turn the parameter value stored therein via an inductive coupling between the coil 64 and the RFID communication device 34. As a result, the transponder 32 can be read out. The transponder 32 can also be of the active type, which is fed from a battery.

(30) The coil 64 is preferably formed concentrically to the inner ring 60 and is jointly integrated with the chip 62 connected thereto into the inner ring 60, preferably cast therein. As a result of the concentric arrangement of the coil 64, it is possible to set up a communication with an RFID communication device which is substantially independent of a relative rotary position of the tool 20 about the joining axis 46.

(31) On the top side of the inner ring 60, an insertion taper 68 is provided in the region of the inside diameter in order to be able to insert the mouthpiece 28 more easily into the bore 66.

(32) Shown in FIG. 4 is a further preferred embodiment of a bushing 44, which with regard to construction and functioning generally corresponds to the bushing 44 of FIG. 3. The same elements are therefore provided with the same reference numerals. The differences are essentially explained below.

(33) It can thus be seen that the inner ring 60 of the bushing 44 is of multi-piece design, which can be advantageous from the production point of view. To be more precise, the inner ring 60 has a first ring part 70, which is arranged at the inner circumference of the outer sleeve 54, and a second ring part 72. The second ring part 72 forms, together with the first ring part 70, a casting cavity and forms with its inner circumference the bore 66. The casting cavity is filled with a casting compound 74 in which the RFID transponder is integrated, in particular cast. The coil 64 arranged rotationally symmetrically relative to the joining axis 46 permits a communication with an RFID communication device independently of the relative rotary position.

(34) In the bushing 44, the ring parts 70, 72 are arranged in such a way that they are jointly flush with a top side of the outer sleeve 54. The casting compound 74 in this case bears against a shoulder (not designated in any more detail) of the outer sleeve 54.

(35) The first and second ring parts 70, 72 are preferably electrically and magnetically non-conductive components and are preferably made of a plastic, for example by the injection moulding process.

(36) FIG. 5 shows an alternative embodiment of a joining arrangement 10. With regard to construction and functioning, said joining arrangement 10 generally corresponds to the joining arrangement 10 of FIG. 1. The same elements are therefore provided with the same reference numerals. The differences are essentially explained below.

(37) Inserted into the positioning device 38 is a bushing 44 which, with regard to construction and functioning, generally corresponds to the bushing 44 of FIG. 4. The same elements are therefore provided with the same reference numerals. In contrast to the bushing 44 of FIG. 4, the bushing 44 has yet a third ring part 76, which is arranged at the inner circumference of the inner ring 60. This third ring part encloses with the outer sleeve 54 an annular space, into which the inner ring 60 is inserted. The third ring part 76 can in this case likewise be made of a plastic, for example by an injection moulding process, but can, if need be, also be made of a metallic material in order to increase the abrasion resistance.

(38) In the bushing 44, a casting cavity which is open towards the top side of the bushing 44 is formed by the first ring part 70 and the second ring part 72. Consequently, the casting compound 74 forms part of the top side of the bushing 44.

(39) In the bushings 44 and 44 of FIGS. 4 and 5, the inner ring 60 or 60 can be produced separately and can then be connected to the outer sleeve 54, for example by pressing, adhesive bonding or the like.

(40) As shown in FIG. 5, a distance 42 is provided between the positioning device 38 and a top side of the workpiece (sheet) 14. In a positioning device having a plurality of bushings, this distance 42 can vary from bushing to bushing.

(41) In the joining tool 20 shown in FIG. 5, provision is therefore made for the RFID communication device 34 to be mounted on the joining tool 20 so as to be movable in a direction parallel to the joining axis 46. To be more precise, the RFID communication device 34 is secured to a slide 80 which is axially movable relative to the mouthpiece 28 of the joining tool 20. The maximum stroke of the slide 80 is shown at 82 in FIG. 5.

(42) The RFID communication device 34 has a coil 84 as aerial, which is arranged concentrically around the mouthpiece 28 and preferably has a diameter which is equal to the diameter of the coil 64 of the RFID transponder. When the mouthpiece 28 is inserted into the bore 66 of the bushing 44, the RFID communication device 34 comes into contact with the top side of the bushing 44. Different distances 42 from bushing to bushing can be compensated for by the axial displaceability of the slide 80.

(43) The coil 84 is preferably likewise cast in a casting compound 86 which has been accommodated in a cavity of a sleeve component 88, which is connected to the slide 80, or is formed by the slide 80. During a movement relative to the mouthpiece 28 or the housing of the joining tool 20, the slide 80 can be guided on the mouthpiece 28 and/or on housing parts 91, 92 and/or on one or more guide rods 89. The latter can also serve as anti-rotation locking means.

(44) Furthermore, the slide 80, as shown, can be preloaded elastically in the joining direction by means of a spring device 90 (consisting of one or more springs). As a result, it can be ensured that the RFID communication device 34 is also pressed onto the top side of the bushing 44 irrespective of the distance 42 or other ambient conditions in order to minimize an air gap in between. As a result, the communication reliability can be increased. In the ideal case, the casting compounds 86, 74 bear directly against one another, such that no air gap at all is formed. Consequently, an inductive coupling between the coils 64, 84 can be realized with a lower magnetic resistance. It goes without saying that this equally applies if not only a casting compound but possibly also sections of other non-metallic or non-conductive elements, such as sections of the ring parts 70, 72 for example, are arranged between the coils 64, 84.

(45) It will be appreciated by persons skilled in the art that the above embodiments have been described by way of example only, and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims.