WO1993009908A1 - Friction welding apparatus - Google Patents

Friction welding apparatus Download PDF

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Publication number
WO1993009908A1
WO1993009908A1 PCT/SE1992/000791 SE9200791W WO9309908A1 WO 1993009908 A1 WO1993009908 A1 WO 1993009908A1 SE 9200791 W SE9200791 W SE 9200791W WO 9309908 A1 WO9309908 A1 WO 9309908A1
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WO
WIPO (PCT)
Prior art keywords
welding
chuck
steel body
stud
engagement
Prior art date
Application number
PCT/SE1992/000791
Other languages
French (fr)
Inventor
Tore Skog
Original Assignee
Tore Skog
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tore Skog filed Critical Tore Skog
Publication of WO1993009908A1 publication Critical patent/WO1993009908A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
    • B23K20/12—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding
    • B23K20/129—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding specially adapted for particular articles or workpieces

Definitions

  • the present invention relates to apparatus for welding welding studs onto a steel body to form a cooperating construction.
  • Rust and scaling must be removed from the surface of the girder prior to welding and the porcelain ring must be removed after welding. Resistance welding is performed manually. Because of the vast number of welding studs required, the manual work is extremely monotonous an the risk of stress injuries is considerable. Furthermore, all the welding spots must be accurately marked on the steel girder for manually performed resistance welding, which also increases manufacturing costs.
  • Portable devices for friction welding are also known but these can only be used for friction welding objects of smaller dimension than welding studs, i.e. smaller than 10 mm, since larger objects require higher torque and higher friction-producing pressure.
  • the object of the present invention is to eliminate the heavy manual welding work and provide an apparatus for welding welding studs onto a steel body which permits automatic welding using the friction-welding technique and which gives welding joints of sufficient strength.
  • the apparatus according to the invention is characterized in that it comprises a rotatably journalled spindle means with vertical axis of rotation, supported by a stand; that the apparatus is arranged to be moved stepwise in relation to the steel body by an actuator to a new welding position and to be fixed in relation to the steel body in each such welding position by means of locking members; that the apparatus also includes drive means to rotate the spindle means about its axis of rotation, said spindle means comprising a chuck located at its lower end to clamp a welding stud to be welded by means of friction welding, so that the welding stud and spindle means form a rotating unit without relative movement of rotation therebetween; supply means to supply welding studs to engagement position for the chuck; and pressure means arranged to press the welding stud clamped by the chuck against the steel
  • the joint surface is heated to "welding temperature", i.e. a little above forging temperature, about 1200°C, by rotating the welding at high speed while being simultaneously pressed against the girder with high pressure.
  • the material in the joint surface is plasticized and is forced by the rotation to the periphery where it forms a unitary "swelling".
  • the vigorous plasticization of the material causes the removal of impurities and surface oxides from the joint surface. Rust and scaling must be removed from the joint surface but moisture does not affect the welding result. Since the joint surfaces are pressed tightly together no air can penetrate to oxidize the material.
  • friction welding produces a weld joint with fine-grained structure, free from pores, oxides and inclusions, thus contributing to reduced sensitivity to fatigue failures.
  • Casting structures with brittle segregations and pores deteriorating the mechanical properties of the material can thus be avoided. Since only small volumes of material are heated the energy consumption is low, only 10-20% of the energy consumed for resistance welding under equivalent conditions.
  • friction-welding structural welding-steel the parameters of number of revolutions, time and pressure can be varied within a relatively large interval without jeopardizing the strength of the joint.
  • Figure 1 is a side view of an apparatus for friction welding welding studs onto a steel girder.
  • Figure 2 is an end view of the apparatus according to Figure 1, seen from the left.
  • Figure 3 is a view along the line III-III in Figure 2.
  • Figure 4 is a view in vertical longitudinal section of a locking element included in the apparatus according to Figure 1.
  • Figure 5 is a cross-sectional view of the locking element according to Figure 4.
  • Figure 6 is a view in horisontal longitudinal section of the locking element according to Figure 4.
  • Figure 7 is an end view of the welding apparatus according to Figure 1, seen from the right.
  • Figure 8 is a view in horizontal section of a support plate of the stand of the apparatus, and a hydraulic cylinder for transverse displacement of the spindle of the apparatus holding the welding stud.
  • Figure 9 is a cross-sectional view along the line IX-IX in Figure 8.
  • Figure 10 is a view in vertical cross section of a bearing housing and spindle of the apparatus according to Figure 1, and shows the spindle in raised position.
  • Figure 11 is a cross-sectional view along the line XI-XI in Figure 10.
  • Figure 12 is a view similar to that according to Figure 10 but showing the spindle in lowered welding position.
  • Figure 13 is a view from above of a pivotable thrust bearing housing carried by the bearing housing according to Figure 10.
  • Figure 14 is a view in cross section of a supply device for new welding studs, carried by the thrust bearing housing according to Figure 13.
  • Figures 15, 16, 17 and 18 are side views of parts of the apparatus according to Figure 1 and illustrate the stepwise movement of the apparatus in various stages after the first welding stud has been welded on according to Figure 1.
  • FIG. 1 shows schematically from the side an apparatus for automatically friction-welding a welding stud 1 onto a steel body 2, which in the embodiment shown consists of a steel girder, of a cooperating construction.
  • the steel girder has a flat welding surface.
  • the fully automated apparatus which can thus be designated a welding robot, comprises a stand 3 having a vertical support plate 4, a horizontal frame-shaped upperpart 5 and a horizontal lower part 6.
  • the upper and lower stand parts 5, 6 are rigidly joined to the vertical support plate 4.
  • a tank 7 is rigidly mounted on the upper stand part 5.
  • the tank 7 is equipped with filter, accumulator and electric- hydraulic valves (not shown).
  • An electric motor 8 is mounted on the top of the tank 7 to drive a hydraulic pump 9 via a coupling 10.
  • the upper stand part 5 has two parallel rods 11, 12, each supporting a sleeve 13, 14 that can be fixed on the rod.
  • the lower stand part 6 has two parallel rods 15, 16 which are joined together by means of a horizontal crossbar 17.
  • the crossbar 17 is located at a predetermined distance from the support plate 4 of the stand.
  • the connection between the crossbar 17 and rods 15, 16 may be lockable allowing said distance to be adjusted to each particular operating situation.
  • the upper and lower stand parts 5, 6 are joined together by two vertical stays 18, 19, these being secured to said crossbar 17 and the sleeves 13, 14.
  • the sleeves 13, 14 can be secured to respective rods 11, 12 by suitable locking members, such as screws, to give the stand 3 increased stability.
  • connection support 36 intended for connection to one end of the steel girder 2 in a linear relationship, to produce a stable unit.
  • the connection support comprises a short beam 36, the top of which lies in the same plane as the upper side of the steel girder 2.
  • the connection beam 36 is provided with two rows of pre-welded welding studs la, lb, lc. Id with four welding studs in each row and a pitch corresponding to that of the welding studs 1 to be welded onto the steel girder 2.
  • a step-feed cylinder 21 is secured by its front end to said crossbar 17 and extends rearwards past the free ends of the rods 15, 16.
  • the step-feed cylinder 21 is parallel with the rods 15, 16 and at an equal distance from the rods, i.e. it coincides with the vertical centre plane of the apparatus.
  • the plunger 22 of the step-feed cylinder is secured by its front end to a yoke 23 located parallel with the crossbar 17 and in its starting position is located close to and outside this as shown in Figure 3.
  • Each rod 15, 16 of the lower stand part 6 carries a locking device comprising a sleeve-shaped locking element 24, 25 rigidly mounted to the yoke 23 via a connection piece 26.
  • the locking sleeves 24, 25 are slidably journalled on the rods 15, 16, and each has a lower part provided with groove 27 running longitudinally through it, open at the bottom and with T-shaped cross section to fit the dimension of the welding stud 1 so that the head 28 and shaft 29 of the stud 1 can be received in the groove 27 to be moved freely into or out of the groove 27 when the step-feed cylinder 21 is connected during specific operating conditions of the apparatus.
  • the locking sleeve 24, 25 is provided with opposite, arc-shaped recesses 30, 31 arranged to receive the head 28 of the welding stud 1 to achieve locking engagement when the locking sleeve 24, 25 is displaced up to an upper position during another operating condition of the apparatus.
  • the locking means also comprises a rear clamping cylinder 32, 33 arranged on the lower side of each rod 15, 16 and slightly outside the vertical centre plane of the rod 15, 16 so as not to be impeded by the welding studs 1 when the locking sleeve 24, 25 is moved forward along the rod 15, 16 in relation to the stand 3.
  • the clamping cylinder 32, 33 is rigidly mounted to said connection piece 26 and its piston rod 34, 35 is directed downwardly so that its free end can be pressed initially against the connection beam 36 and later against the girder 2.
  • the rear clamping cylinder 32, 33 is provided with a support roller 37, 38 arranged to be in contact with and run along the connection beam 36 and steel girder 2, respectively when the piston rod 34, 35 is withdrawn and no longer in contact with said supports 36 and 2. When the support roller 37, 38 is in contact with the support 36, 2 the head 28 of the welding stud 1 runs free from the surrounding surfaces 30, 31 of the groove 27.
  • each forward locking device includes a clamping cylinder 42, 43 rigidly fitted to the stand 3 via a connection piece 44.
  • the clamping cylinder 42, 43 is arranged on the lower side of the rod 15, 16 and slightly below the vertical centre plane of the rod 15, 16 so as not to be impeded by the welding studs 1 upon movement of the stand 3 forwards in relation to the rear locking arrangement.
  • the piston rod 45, 46 of the clamping cylinder 43, 33 is directed downwardly so that its free end can press against the stationary support 36, 2.
  • the clamping cylinder 43, 44 is provided with a support roller 47, 48 arranged to be in contact with and run along the support 36 when the piston rod 45, 46 is withdrawn an no longer in contact with the support 36, 2. When the support roller 47, 48 is in contact with the support 36, 2 the head 28 of the welding stud 1 runs free from the surrounding surfaces of the groove 41.
  • a bearing housing 60 rests on the side of the support plate 4 of the stand facing away from the rods 11, 12,
  • the bearing housing 60 is displaceable transversely to the direction of movement of the apparatus along the steel girder 2 to be set in various welding posisitions, namely a central position and two side positions in order to produce three parallel rows of welding studs 1.
  • the bearing housing 60 is mounted on the support plate 4 by means of a linear bearing element 61 comprising two engagement parts 52, 53 with dovetail-shaped cross section and with cooperating sliding surfaces.
  • Displacement of the bearing housing 60 along the bearing element 61 is effected by an actuator 64 (see Figure 8) which consists in the embodiment shown of a hydraulic cylinder 65 with a piston rod 66 running through it, the opposite ends being attached to side plates 67, 68 which are in turn secured to the support plate 4.
  • the cylinder 65 is rigidly connected to the bearing housing 60.
  • Two support rollers 69 are located at the upper part of the bearing housing 60 (see Figure 1), resting on and rolling along a horizontal support rail 70 arranged in the vertical long side of the support plate 4 facing the bearing housing 60.
  • the bearing housing 60 contains a rotation cylinder 80 journalled on the inside of the bearing housing by means of ball bearings 81 in order to rotate inside the bearing housing 60.
  • the rotation cylinder is secured against axial movement by means of top and bottom rings 82, 83 screwed into the ends of the bearing housing 60.
  • a belt pulley 84 is rigidly mounted to the upper part of the rotation cylinder 80.
  • the belt pulley 84 forms part of a transmission to drive, amongst other things, the rotation cylinder 80, the transmission also comprising a hydraulic drive motor 85 (see Figure 1) and a plurality of V-belts 86 which drive the belt pulley 84 of the rotation cylinder 80 via the belt pulley 87 of the hydraulic motor 85.
  • the hydraulic motor 85 is supported by brackets 88 secured to the bearing housing 60 and protruding from the side of the bearing housing 60 facing away from the stand 3.
  • the rotation cylinder 80 receives and supports a spindle 89, coaxial with the rotation cylinder and axially displaceable in relation to the rotation cylinder 80 to assume an upper charging position as shown in Figure 10 and a lower welding position as shown in Figure 12.
  • the spindle 89 is connected to the rotation cylinder 80 to rotate therewith as a rotating unit about the axis of rotation 90.
  • the spindle 89 comprises an outer sleeve 91, an inner sleeve 92 and an intermediate sleeve 93, the latter being located between the outer and inner sleeves 91, 92.
  • the spindle 89 is provided at its lower end with a support ring 94, secured to the lower end of the outer sleeve 91 and having an inner conical surface 95.
  • a chuck 96 comprising a plurality of clamping aws 97, the upper ends of the jaws and the lower end of the intermediate sleeve 93 being provided with cooperating connection means 79 that permit radial displacement of the clamping jaws 97 between an outer rest position according to Figure 10 and an inner operative position according to Figure 12.
  • the chuck 96 is thus supported by the intermediate sleeve 93.
  • the cooperating connection means consist of T-shaped elements shaped in the upper end part of the chuck 96 and corresponding T-shaped radial slots or grooves shaped in the lower end part of the intermediate sleeve 93.
  • One of the functions of the sleeve 93 is to control the clamping jaws 97.
  • the outer sleeve 91 and rotation cylinder 80 are provided on their facing surfaces with cooperating engagement members 98 allowing common rotation of the outer sleeve 91 and rotation cylinder 80, as well as axial displacement of the outer sleeve 91 in relation to the rotation cylinder 80.
  • these engagement members 98 may consist of axial grooves and cams formed in the opposing sides to cooperate with each other.
  • the inner sleeve 92 is rigidly mounted to the intermediate sleeve 93 and is slightly shorter than this at the lower end. The sleeves 92 and 93 thus form an inner unit for joint displacement.
  • Similar cooperating engagement members 99 are arranged on facing sides of the intermediate sleeve 93 and the outer sleeve 91, said engagement members 99 allowing joint rotation of the two sleeves 93, 91 and axial displacement of the sleeve unit 92, 93 in relation to the rotation cylinder 80.
  • These engagement members 99 may also consist of axial grooves and cams produced in the facing sides of the sleeves.
  • the spindle 89 is provided at its upper end with a circular lifting plate 100 secured to the end of the intermediate sleeve 93 and provided with a circular inlet 101 having a diameter somewhat greater than the diameter of the stud head 28 so that this can pass down unhindered through the inlet 101.
  • the spindle 89 is provided with a vertical cavity 102 through which the welding studs pass standing one on top of the other in a vertical column, and which is defined by the lifting plate 100, sleeves 92, 93, chuck 96 and support ring 94 in that order (see Figure 10).
  • the axial displacement of the spindle 89 is achieved by means of an actuator consisting in the embodiment shown of two hydraulic cylinders 103, 104 arranged one of each side of the bearing housing 60, as can be seen more clearly in Figure 7.
  • the piston rods 105, 106 of each hydraulic cylinder extend vertically upwards and support a feeder 107, 108 which is arranged during the welding step to go free from the lifting plate 100 as illustrated in Figure 12.
  • the two hydraulic cylinders 103, 104 support between them a pressure device 110 in the form of a thrust bearing housing comprising a bearing housing 121, a pressure plate 122 and a thrust bearing 123.
  • the pressure plate 122 is mounted on the bearing housing 121 by means of an outer ring 124, the pressure plate 122 cooperating in sliding manner with the ring 124.
  • the thrust bearing housing 110 is arranged to be moved down by the piston rods 105, 106 to an operative position, its pressure plate 122 pressing with predetermined pressure against the lifting plate 100 of the spindle 89 and against the head 28 of the upper welding stud 1. This pressure is then transmitted to the lower stud le through the row or column of welding studs located in the axial central cavity 102 of the spindle 89.
  • the thrust bearing housing 110 thus permits the pressure plate 122 in this pressing position to rotate together with the rotation cylinder 80 and spindle 89 as a unitary rotation body.
  • the outer sleeve 91 is surrounded by a rubber ring 71 resting on the upper side of the belt pulley 84 and acting as a buffer.
  • the dampening ring 71 is arranged to form a resilient seat for an annular support flange 72 carried by upper end of the outer sleeve 91.
  • the function of the dampening ring 71 is to resiliently lift the outer sleeve 91 and its lower support ring 94 so that the clamping jaws 97 are brought into strong abutment against the head of the welding stud and at the same time centre the stud (see Figure 12).
  • the dampening ring 71 shall also absorb differences in the length of the welding studs ( ⁇ 0.2 mm) and enable the thrust bearing housing 110 to maintain the pressure exerted by it via its pressure plate 122 on the vertical row of welding studs.
  • Said support flange 72 on the upper end of the outer sleeve 91 forms the seat for a plurality of axial compression springs 73, the function of which is to prevent the outer sleeve 91 from moving upwards during the first part of the lifting phase when the feeders 107, 108 have been brought into engagement with the lifting plate 100 and the sleeve unit 92, 93 is lifted in relation to the outer sleeve 91 retained by the compression springs 73, so that the chuck 96 is released from its engagement with the welding stud le which is now welded to the steel girder 2.
  • Said thrust bearing housing 110 is arranged to assume an inoperative upper position at a distance above the lifting plate 100 that corresponds to the distance between the lifting plate 100 and the feeders 107, 108 when the thrust bearing housing 110 is in operative lower position.
  • the thrust bearing housing 110 is also pivotable journalled on one of the piston rods 105, to assume a locked position upon engagement with the other piston rod 106 and a position swung aside as shown by unbroken and broken lines, respectively, in Figure 13. Swinging of the thrust bearing housing 110 is effected by a hydraulic cylinder 111 journalled eccentrically on the thrust bearing housing 110 in relation to the piston rod 105 constituting the pivot axis.
  • the thrust bearing housing 110 On the side of the thrust bearing housing 110 facing away from that on which the hydraulic cylinder 111 is arranged, the thrust bearing housing supports a stud-feed cylinder 112. This cylinder is provided with a downwardly directed pressing arm 113 with an electromagnet 115 arranged to be activated when the thrust bearing housing 110 is in its swung-in position so that a welding stud 1 is picked up by the electromagnet 115 from an adjacent magazine 114.
  • the inner sleeve 92 of the spindle 89 is provided internally with a plurality of plate springs 116 arranged in several vertical rows, e.g. three rows, in order to centre the welding studs 1 in the sleeve 92 and retain them therein so that they do not unintentionally fall down and out of the spring 89 when this is lifted.
  • the column of welding studs is displaced in downward direction when a new welding stud is fed in by the stud- feed cylinder 112.
  • the bearing housing 60 with its spindle 89 is secured in its central position in relation to the support plate 4 by means of a cylinder 117 (see Figure 1), the piston rod of this cylinder pressing against and locking the transverse slide 63 of the bearing housing 60.
  • Adjustment screws 118 are arranged in the side plates 67, 68 to form a stop for the cylinder 64 so that its stroke length can be regulated, and thereby the positions of the two outer rows of studs.
  • Two hydraulic cylinders for fine adjustment of the end positions for the cylinder 64 are designated 119.
  • the side plates 67, 68 which support the piston rod 66 are mounted on the support plate 4 by means of bolts 120 with gaps therebetween to enable said fine adjustment.
  • Each clamping j w 97 is provided on its inner side with a plurality of narrow axial ridges and grooves located at least within the cylindrical cavity part of the chuck 96.
  • the peripheral, cylindrical surface of the head 28 of the welding stud is provided with corresponding narrow axial ridges and grooves. These ridges and grooves are formed in conjunction with cold upsetting the welding stud.
  • the opposing ridges and grooves form cooperating engagement members 75, 76 (see Figure 12) which form such a strong joint that the welding stud becomes a rotating unit with the chuck 96, i.e. no relative rotary movement can occur between the head 28 of the welding stud and the chuck 96. Without these engagement members 75, 76, or similar means producing the same locking effect, i.e. if the surfaces were smooth, there would be a risk of the surfaces being welded together during the welding operation.
  • the apparatus is equipped with a suitable control unit comprising suitable computer equipment with monitoring and control programs, to control the various operating cylinders, motors, welding stages, welding parameters, etc.
  • Figures 1 and 2 show a position when the welding stud le is welded to the steel girder 2.
  • the piston rods 105 and 106 are engaged to lift the spindle 89 and the associated chuck 96 and support ring 94 to the position shown in Figures 10 and 15:
  • the rear clamping cylinders 32, 33 are then engaged so that their piston rods 34, 35 are retracted to be out of the way of the auxiliary support 36 used initially, and instead the rear support rollers 37, 38 will rest against the auxiliary support 36 as shown in Figure 16.
  • the heads 28 of the welding studs will be released from the vertical side recesses 30, 31 of the grooves 27 in the two sleeves 24, 25, as illustrated by the position of the welding stud indicated by the upper broken line in Figure 5.
  • the step-feed cylinder 21 is then connected in for its piston rod 22 to move the yoke 23 forwards in relation to the transverse stay 17, and thus also the sleeves 24, 25 joined to the yoke 23.
  • the movement is determined to be one pitch so that the sleeves 24, 25 will surround the heads 28 of the next pair of welding studs, as shown in Figure 15, after which the clamping cylinders 32, 33 are activated so that their piston rods 34, 35 once again press against the auxiliary support 36 and the sleeves 24, 25 are thereby locked to the welding studs.
  • the forward clamping cylinders 42, 43 are engaged so that their piston rods 45, 46 are free from the auxiliary support 36 and the supporting function is instead taken over by the support rollers 47, 48.
  • the locking engagement between the locking elements 39, 40 and welding studs Id is released and the step-feed cylinder 21 can again be activated to move the locking elements 39, 40 to the welding studs le first welded to the steel girder 2. Movement is effected by the transverse stay 17, and thus the whole stand 3, being pulled forward by the piston rod 22 towards the yoke 23 which is now secured in relation to the auxiliary support 36, thanks to the locking engagement between the sleeves 24, 25 and the welding studs.
  • FIG. 18 shows the stage when the spindle 89 is about to be moved forward one pitch to the next welding spot after the welding stud If has been welded on, the spindle 89 has been lifted, the rear sleeves 24, 25 have ⁇ been moved forward to the third pair of welding studs lc and locked fast thereto and the forward locking elements 39, 40 have been released from the fifth pair of welding studs le at the same time as the forward support rollers 47, 48 have been brought into rolling position on the welding girder.
  • the friction welding produces a welding joint comprising an annular bead 77.
  • the new welding stud is now axially aligned with the axis of rotation 90 of the spindle and at any rate with the vertical passage formed by the cavities 101, 102.
  • Cylinder 112 is then activated so that the arm 113 feeds the stud down into the central passage 101, 102, after which the electromagnet 115 is deactivated to release the welding stud 1.
  • the welding stud is fed down by the cylinder 112 the row of welding studs is pressed down through the central cavity 102 until the lowermost welding stud is caught by the chuck 96.
  • the electromagnet 115 When the electromagnet 115 has been deactivated to release the uppermost welding stud, the electromagnet 115 is raised to its starting position and the thrust bearing housing 110 is swung back to its engagement position with the piston rod 106. In the next phase the hydraulic cylinders 103, 104 are engaged to move the thrust bearing housing 110 downwards into contact with the lifting plate 100 to press this and the intermediate sleeve 93 with associated chuck 96 in downward direction.
  • the lifting plate 100 is brought into contact with the compression springs supported by the outer sleeve 91 on the spindle 89 so that the spindle is pressed downwards during the continued movement of the thrust bearing housing 110 during which the support flange 72 of the outer sleeve 91 comes into contact with the dampening ring 71 as illustrated in Figure 12.
  • the support ring 94 on the sleeve 91 is thus moved out of the rotation cylinder 80 by the thrust bearing housing 110.
  • the thrust bearing cylinder 110 acts on the chuck 96 via the lifting plate 100 and the intermediate sleeve 93 so that the clamping jaws 97 press with sufficient wedge force against both the support ring 94 and the head 28 of the welding stud so that the spindle 89 and welding stud 1 form a rotating unit when the hydraulic motor 85 is activated.
  • the thrust bearing cylinder 110 presses the row of welding studs against the steel girder with a pressure that can be increased to a high predetermined value. The pressure increase is possible since the dampening ring 71 permits compression so that the entire spindle 89 can be pressed down further in relation to the column of welding studs 1.
  • Phase 1 Heating phase. During this phase, when the torque requirement is greatest, the contact surfaces to be welded together are heated.
  • the drive motor 85 is operative throughout. Phase time: about 1 second.
  • Phase 2 Fusing phase.
  • the drive motor 85 is disconnected and the friction-producing pressure is increased.
  • Phase time about 2 seconds.
  • Phase 3 Stabilizing phase. The friction-producing pressure is kept constant even after rotation has ceased entirely. Phase time: about 2-3 seconds.
  • a combination of the continuous method and the inertia method, giving the modified friction welding method as described above, has the advantages that the oscillating mass need not be as large as when using only the inertia method and that the cycle time becomes shorter. Retardation can be achieved without the use of a mechanically or electrically influenced brake.
  • the method of automatically welding the welding studs 1 onto the steel girder 2 thus comprises the following main steps: welding is performed by means of friction welding using said apparatus comprising a spindle means 89 rotating about a vertical axis 90 and carrying the welding stud 1 to be friction welded; the apparatus is displaced stepwise in relation to the steel body 2 to a new welding position for the spindle means 89 and is fixed in relation to the steel body in each such welding position; the spindle means 89 and welding stud 1 are caused to rotate at predetermined speed; an initially low pressure is applied on the welding stud via the spindle means 89 so that the welding stud 1 with said speed is brought into friction-producing surface contact with the steel body 2 during an initial heating phase; an increased pressure is then applied on the welding stud via the spindle means 89, the friction thereby increasing and the welding stud 1 being welded to the steel body 2.
  • the spindle means 89 rotates preferably together with the rotation cylinder, the latter being rotatably journalled in the bearing housing.
  • the heating phase is preferably followed by a fusing phase during which the friction-producing pressure is increased so that rotation is gradually retarded and finally ceases, and then by a stabilizing phase during which the final pressure from the fusing phase is maintained in order to stabilize the friction-welded joint.
  • the heating phase preferably lasts for about 1 second, the fusing phase for about 2 seconds and the stabilizing phase for about 2-3 seconds.
  • the apparatus can be supported by a suitable support means, i.e. one or more rails or the like, extending along the steel girder.
  • a suitable support means i.e. one or more rails or the like, extending along the steel girder.
  • the apparatus is arranged to be locked to the support means in each welding position by means of a suitable locking member comprising a brake, for instance, so that the apparatus is fixed in relation to the steel girder, and each time a welding stud has been friction welded, after release of the locking member, to be moved one pitch step forward to a new welding position with the help of suitable actuator.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Pressure Welding/Diffusion-Bonding (AREA)

Abstract

Apparatus for welding welding studs (1) onto a steel body (2) to form a cooperating construction is described. According to the invention the apparatus comprises a rotatably journalled spindle (89) with vertical axis of rotation (90), supported by a stand (3) and arranged to be moved stepwise in relation to the steel body (2) by an actuating cylinder (21) to a new welding position and to be fixed in relation to the steel body (2) in each such welding position. The apparatus also includes drive equipment (85, 86) to rotate the spindle (89) about its axis of rotation (90), said spindle (89) comprising a chuck (96) located at its lower end to clamp a welding stud (1) to be welded by friction welding, so that the welding stud (1) and a spindle (89) form a rotating unit without relative movement of rotation therebetween. Supply members (110, 111, 112, 115) supply welding studs (1) to engagement position for the chuck (96). Furthermore, pressure members (103, 104, 110) are arranged to press the welding stud (1) clamped by the chuck (96) against the steel body (2) to generate friction therebetween.

Description

FRICTION WELDING APPARATUS.
The present invention relates to apparatus for welding welding studs onto a steel body to form a cooperating construction.
In a cooperating construction different materials have been joined to function statically as one unit. The advantages of the various materials are utilized in as favourable a manner as possible. One of the most usual applications is where a steel girder cooperates with a concrete slab, a combination girder. In order to ensure cooperation between the concrete slab and the steel girder mechanical shear connectors must be fitted on the upper flange of the steel girder to transmit the flow of horizontal shearing forces between concrete slab and steel girder and to prevent vertical separation. A usual form of mechanical shear connectors consists of welding studs welded onto the steel girder by resistance welding. In resistance welding the material is heated to melting temperature in the joint surface between welding stud and girder so that a "melt bath" is formed which is surrounded by a porcelain ring and into which the stud is depressed. This melt bath, having casting structure, may contain brittle segregations and pores which deteriorate the mechanical properties of the material. Extensive sample welds and destructive tests must be performed in order to ensure a good welding result. Resistance welding requires extremely high current and thus entails high energy consumption. A welding stud with 10 mm diameter requires 400-500 ampere and a welding stud with 22 mm diameter requires 1600-2000 ampere. In both cases strong magnetic fields are produced which cause disturbance in the surroundings. Rust and scaling must be removed from the surface of the girder prior to welding and the porcelain ring must be removed after welding. Resistance welding is performed manually. Because of the vast number of welding studs required, the manual work is extremely monotonous an the risk of stress injuries is considerable. Furthermore, all the welding spots must be accurately marked on the steel girder for manually performed resistance welding, which also increases manufacturing costs.
For other welding applications, i.e. when welding objects other than welding studs onto surfaces other than steel girders, it is known to use a friction welding technique which can be performed in two different ways generally designated continuous friction welding and friction welding using the inertia method. In the case of continuous friction welding the drive motor is connected until sufficient upset has been achieved. Thereafter the drive motor is disconnected and rotation of the object being welded is quickly stopped. With the inertia method a specific amoun of energy is stored in a flywheel, and a higher friction-producing pressure than in the continuous method is applied on the welding object in order to retard its rotation. The rate of revolution is also higher than in the continuous method. As mentioned, neither of these two methods has been used for welding studs onto a steel girder.
Portable devices for friction welding are also known but these can only be used for friction welding objects of smaller dimension than welding studs, i.e. smaller than 10 mm, since larger objects require higher torque and higher friction-producing pressure.
The object of the present invention is to eliminate the heavy manual welding work and provide an apparatus for welding welding studs onto a steel body which permits automatic welding using the friction-welding technique and which gives welding joints of sufficient strength. The apparatus according to the invention is characterized in that it comprises a rotatably journalled spindle means with vertical axis of rotation, supported by a stand; that the apparatus is arranged to be moved stepwise in relation to the steel body by an actuator to a new welding position and to be fixed in relation to the steel body in each such welding position by means of locking members; that the apparatus also includes drive means to rotate the spindle means about its axis of rotation, said spindle means comprising a chuck located at its lower end to clamp a welding stud to be welded by means of friction welding, so that the welding stud and spindle means form a rotating unit without relative movement of rotation therebetween; supply means to supply welding studs to engagement position for the chuck; and pressure means arranged to press the welding stud clamped by the chuck against the steel body to generate friction therebetween.
During friction welding the joint surface is heated to "welding temperature", i.e. a little above forging temperature, about 1200°C, by rotating the welding at high speed while being simultaneously pressed against the girder with high pressure. The material in the joint surface is plasticized and is forced by the rotation to the periphery where it forms a unitary "swelling". The vigorous plasticization of the material causes the removal of impurities and surface oxides from the joint surface. Rust and scaling must be removed from the joint surface but moisture does not affect the welding result. Since the joint surfaces are pressed tightly together no air can penetrate to oxidize the material.
Contrary to resistance welding, friction welding produces a weld joint with fine-grained structure, free from pores, oxides and inclusions, thus contributing to reduced sensitivity to fatigue failures. Casting structures with brittle segregations and pores deteriorating the mechanical properties of the material can thus be avoided. Since only small volumes of material are heated the energy consumption is low, only 10-20% of the energy consumed for resistance welding under equivalent conditions. When friction-welding structural welding-steel the parameters of number of revolutions, time and pressure can be varied within a relatively large interval without jeopardizing the strength of the joint.
The invention will be be described further by way of example with reference to the following drawings.
Figure 1 is a side view of an apparatus for friction welding welding studs onto a steel girder.
Figure 2 is an end view of the apparatus according to Figure 1, seen from the left.
Figure 3 is a view along the line III-III in Figure 2.
Figure 4 is a view in vertical longitudinal section of a locking element included in the apparatus according to Figure 1.
Figure 5 is a cross-sectional view of the locking element according to Figure 4.
Figure 6 is a view in horisontal longitudinal section of the locking element according to Figure 4.
Figure 7 is an end view of the welding apparatus according to Figure 1, seen from the right.
Figure 8 is a view in horizontal section of a support plate of the stand of the apparatus, and a hydraulic cylinder for transverse displacement of the spindle of the apparatus holding the welding stud. Figure 9 is a cross-sectional view along the line IX-IX in Figure 8.
Figure 10 is a view in vertical cross section of a bearing housing and spindle of the apparatus according to Figure 1, and shows the spindle in raised position.
Figure 11 is a cross-sectional view along the line XI-XI in Figure 10.
Figure 12 is a view similar to that according to Figure 10 but showing the spindle in lowered welding position.
Figure 13 is a view from above of a pivotable thrust bearing housing carried by the bearing housing according to Figure 10.
Figure 14 is a view in cross section of a supply device for new welding studs, carried by the thrust bearing housing according to Figure 13.
Figures 15, 16, 17 and 18 are side views of parts of the apparatus according to Figure 1 and illustrate the stepwise movement of the apparatus in various stages after the first welding stud has been welded on according to Figure 1.
Figure 1 shows schematically from the side an apparatus for automatically friction-welding a welding stud 1 onto a steel body 2, which in the embodiment shown consists of a steel girder, of a cooperating construction. The steel girder has a flat welding surface. The fully automated apparatus, which can thus be designated a welding robot, comprises a stand 3 having a vertical support plate 4, a horizontal frame-shaped upperpart 5 and a horizontal lower part 6. The upper and lower stand parts 5, 6 are rigidly joined to the vertical support plate 4. A tank 7 is rigidly mounted on the upper stand part 5. The tank 7 is equipped with filter, accumulator and electric- hydraulic valves (not shown). An electric motor 8 is mounted on the top of the tank 7 to drive a hydraulic pump 9 via a coupling 10. The upper stand part 5 has two parallel rods 11, 12, each supporting a sleeve 13, 14 that can be fixed on the rod. Similarly, the lower stand part 6 has two parallel rods 15, 16 which are joined together by means of a horizontal crossbar 17. The crossbar 17 is located at a predetermined distance from the support plate 4 of the stand. The connection between the crossbar 17 and rods 15, 16 may be lockable allowing said distance to be adjusted to each particular operating situation. The upper and lower stand parts 5, 6 are joined together by two vertical stays 18, 19, these being secured to said crossbar 17 and the sleeves 13, 14. The sleeves 13, 14 can be secured to respective rods 11, 12 by suitable locking members, such as screws, to give the stand 3 increased stability.
The apparatus includes a special connection support 36 intended for connection to one end of the steel girder 2 in a linear relationship, to produce a stable unit. In the embodiment shown the connection support comprises a short beam 36, the top of which lies in the same plane as the upper side of the steel girder 2. The connection beam 36 is provided with two rows of pre-welded welding studs la, lb, lc. Id with four welding studs in each row and a pitch corresponding to that of the welding studs 1 to be welded onto the steel girder 2.
A step-feed cylinder 21 is secured by its front end to said crossbar 17 and extends rearwards past the free ends of the rods 15, 16. The step-feed cylinder 21 is parallel with the rods 15, 16 and at an equal distance from the rods, i.e. it coincides with the vertical centre plane of the apparatus. The plunger 22 of the step-feed cylinder is secured by its front end to a yoke 23 located parallel with the crossbar 17 and in its starting position is located close to and outside this as shown in Figure 3. Each rod 15, 16 of the lower stand part 6 carries a locking device comprising a sleeve-shaped locking element 24, 25 rigidly mounted to the yoke 23 via a connection piece 26. The locking sleeves 24, 25 are slidably journalled on the rods 15, 16, and each has a lower part provided with groove 27 running longitudinally through it, open at the bottom and with T-shaped cross section to fit the dimension of the welding stud 1 so that the head 28 and shaft 29 of the stud 1 can be received in the groove 27 to be moved freely into or out of the groove 27 when the step-feed cylinder 21 is connected during specific operating conditions of the apparatus. Inside the groove 27 the locking sleeve 24, 25 is provided with opposite, arc-shaped recesses 30, 31 arranged to receive the head 28 of the welding stud 1 to achieve locking engagement when the locking sleeve 24, 25 is displaced up to an upper position during another operating condition of the apparatus. The locking means also comprises a rear clamping cylinder 32, 33 arranged on the lower side of each rod 15, 16 and slightly outside the vertical centre plane of the rod 15, 16 so as not to be impeded by the welding studs 1 when the locking sleeve 24, 25 is moved forward along the rod 15, 16 in relation to the stand 3. The clamping cylinder 32, 33 is rigidly mounted to said connection piece 26 and its piston rod 34, 35 is directed downwardly so that its free end can be pressed initially against the connection beam 36 and later against the girder 2. The rear clamping cylinder 32, 33 is provided with a support roller 37, 38 arranged to be in contact with and run along the connection beam 36 and steel girder 2, respectively when the piston rod 34, 35 is withdrawn and no longer in contact with said supports 36 and 2. When the support roller 37, 38 is in contact with the support 36, 2 the head 28 of the welding stud 1 runs free from the surrounding surfaces 30, 31 of the groove 27.
Two substantially similar locking devices are arranged on the support plate 4 except that their locking elements 39, 40 are rigidly connected to the stand 3. The locking elements 39, 40 are rigidly mounted to the lower side of the support plate 4. Each locking element 39, 40 is provided with a T-shaped groove 41 running longitudinally along and through it, similar to the groove 27 in the locking sleeve 24, 25 and located at the same level as this. In the same way as the groove 27, said groove 41 has two recesses (not shown) located opposite each other to receive the head 28 of the stud 1 and effect locking engagement. Similarly, each forward locking device includes a clamping cylinder 42, 43 rigidly fitted to the stand 3 via a connection piece 44. The clamping cylinder 42, 43 is arranged on the lower side of the rod 15, 16 and slightly below the vertical centre plane of the rod 15, 16 so as not to be impeded by the welding studs 1 upon movement of the stand 3 forwards in relation to the rear locking arrangement. The piston rod 45, 46 of the clamping cylinder 43, 33 is directed downwardly so that its free end can press against the stationary support 36, 2. The clamping cylinder 43, 44 is provided with a support roller 47, 48 arranged to be in contact with and run along the support 36 when the piston rod 45, 46 is withdrawn an no longer in contact with the support 36, 2. When the support roller 47, 48 is in contact with the support 36, 2 the head 28 of the welding stud 1 runs free from the surrounding surfaces of the groove 41.
A bearing housing 60 rests on the side of the support plate 4 of the stand facing away from the rods 11, 12,
15, 16. In the embodiment shown the bearing housing 60 is displaceable transversely to the direction of movement of the apparatus along the steel girder 2 to be set in various welding posisitions, namely a central position and two side positions in order to produce three parallel rows of welding studs 1. For this purpose the bearing housing 60 is mounted on the support plate 4 by means of a linear bearing element 61 comprising two engagement parts 52, 53 with dovetail-shaped cross section and with cooperating sliding surfaces. Displacement of the bearing housing 60 along the bearing element 61 is effected by an actuator 64 (see Figure 8) which consists in the embodiment shown of a hydraulic cylinder 65 with a piston rod 66 running through it, the opposite ends being attached to side plates 67, 68 which are in turn secured to the support plate 4. The cylinder 65 is rigidly connected to the bearing housing 60. Two support rollers 69 are located at the upper part of the bearing housing 60 (see Figure 1), resting on and rolling along a horizontal support rail 70 arranged in the vertical long side of the support plate 4 facing the bearing housing 60.
As can be seen more clearly in Figures 10 and 12, the bearing housing 60 contains a rotation cylinder 80 journalled on the inside of the bearing housing by means of ball bearings 81 in order to rotate inside the bearing housing 60. The rotation cylinder is secured against axial movement by means of top and bottom rings 82, 83 screwed into the ends of the bearing housing 60. A belt pulley 84 is rigidly mounted to the upper part of the rotation cylinder 80. The belt pulley 84 forms part of a transmission to drive, amongst other things, the rotation cylinder 80, the transmission also comprising a hydraulic drive motor 85 (see Figure 1) and a plurality of V-belts 86 which drive the belt pulley 84 of the rotation cylinder 80 via the belt pulley 87 of the hydraulic motor 85. The hydraulic motor 85 is supported by brackets 88 secured to the bearing housing 60 and protruding from the side of the bearing housing 60 facing away from the stand 3.
The rotation cylinder 80 receives and supports a spindle 89, coaxial with the rotation cylinder and axially displaceable in relation to the rotation cylinder 80 to assume an upper charging position as shown in Figure 10 and a lower welding position as shown in Figure 12. The spindle 89 is connected to the rotation cylinder 80 to rotate therewith as a rotating unit about the axis of rotation 90. The spindle 89 comprises an outer sleeve 91, an inner sleeve 92 and an intermediate sleeve 93, the latter being located between the outer and inner sleeves 91, 92. The spindle 89 is provided at its lower end with a support ring 94, secured to the lower end of the outer sleeve 91 and having an inner conical surface 95. It is also provided with a chuck 96 comprising a plurality of clamping aws 97, the upper ends of the jaws and the lower end of the intermediate sleeve 93 being provided with cooperating connection means 79 that permit radial displacement of the clamping jaws 97 between an outer rest position according to Figure 10 and an inner operative position according to Figure 12. The chuck 96 is thus supported by the intermediate sleeve 93. The cooperating connection means consist of T-shaped elements shaped in the upper end part of the chuck 96 and corresponding T-shaped radial slots or grooves shaped in the lower end part of the intermediate sleeve 93. One of the functions of the sleeve 93 is to control the clamping jaws 97.
The outer sleeve 91 and rotation cylinder 80 are provided on their facing surfaces with cooperating engagement members 98 allowing common rotation of the outer sleeve 91 and rotation cylinder 80, as well as axial displacement of the outer sleeve 91 in relation to the rotation cylinder 80. As in the shown embodiment, these engagement members 98 may consist of axial grooves and cams formed in the opposing sides to cooperate with each other. The inner sleeve 92 is rigidly mounted to the intermediate sleeve 93 and is slightly shorter than this at the lower end. The sleeves 92 and 93 thus form an inner unit for joint displacement. Similar cooperating engagement members 99 are arranged on facing sides of the intermediate sleeve 93 and the outer sleeve 91, said engagement members 99 allowing joint rotation of the two sleeves 93, 91 and axial displacement of the sleeve unit 92, 93 in relation to the rotation cylinder 80. These engagement members 99 may also consist of axial grooves and cams produced in the facing sides of the sleeves.
The spindle 89 is provided at its upper end with a circular lifting plate 100 secured to the end of the intermediate sleeve 93 and provided with a circular inlet 101 having a diameter somewhat greater than the diameter of the stud head 28 so that this can pass down unhindered through the inlet 101. The spindle 89 is provided with a vertical cavity 102 through which the welding studs pass standing one on top of the other in a vertical column, and which is defined by the lifting plate 100, sleeves 92, 93, chuck 96 and support ring 94 in that order (see Figure 10).
The axial displacement of the spindle 89 is achieved by means of an actuator consisting in the embodiment shown of two hydraulic cylinders 103, 104 arranged one of each side of the bearing housing 60, as can be seen more clearly in Figure 7. The piston rods 105, 106 of each hydraulic cylinder extend vertically upwards and support a feeder 107, 108 which is arranged during the welding step to go free from the lifting plate 100 as illustrated in Figure 12. When the hydraulic cylinders 103, 104 are connected after a completed welding step, the upwardly moving feeders 107, 108 will be brought into contact with the lifting plate 100 of the spindle 89 to lift this and the sleeve unit 92, 93 so that the chuck 96 is retracted into the lower support ring 94 thereby running free from the welding stud le. Said engagement members 99 have limited axial extension so that they form a stop 109, preventing further relative axial movement when the chuck 96 is retracted in the support ring 94. Upon continued upward movement of the feeders 107, 108 the outer sleeve 91 will also be lifted, together with the intermediate sleeve 93 until the lower support ring 94 of the spindle 89 has reached an upper resting position in which it is free from the welding stud le as shown in Figure 10.
The two hydraulic cylinders 103, 104 support between them a pressure device 110 in the form of a thrust bearing housing comprising a bearing housing 121, a pressure plate 122 and a thrust bearing 123. The pressure plate 122 is mounted on the bearing housing 121 by means of an outer ring 124, the pressure plate 122 cooperating in sliding manner with the ring 124. The thrust bearing housing 110 is arranged to be moved down by the piston rods 105, 106 to an operative position, its pressure plate 122 pressing with predetermined pressure against the lifting plate 100 of the spindle 89 and against the head 28 of the upper welding stud 1. This pressure is then transmitted to the lower stud le through the row or column of welding studs located in the axial central cavity 102 of the spindle 89. The thrust bearing housing 110 thus permits the pressure plate 122 in this pressing position to rotate together with the rotation cylinder 80 and spindle 89 as a unitary rotation body. The outer sleeve 91 is surrounded by a rubber ring 71 resting on the upper side of the belt pulley 84 and acting as a buffer. The dampening ring 71 is arranged to form a resilient seat for an annular support flange 72 carried by upper end of the outer sleeve 91. The function of the dampening ring 71 is to resiliently lift the outer sleeve 91 and its lower support ring 94 so that the clamping jaws 97 are brought into strong abutment against the head of the welding stud and at the same time centre the stud (see Figure 12). The dampening ring 71 shall also absorb differences in the length of the welding studs (±0.2 mm) and enable the thrust bearing housing 110 to maintain the pressure exerted by it via its pressure plate 122 on the vertical row of welding studs.
Said support flange 72 on the upper end of the outer sleeve 91 forms the seat for a plurality of axial compression springs 73, the function of which is to prevent the outer sleeve 91 from moving upwards during the first part of the lifting phase when the feeders 107, 108 have been brought into engagement with the lifting plate 100 and the sleeve unit 92, 93 is lifted in relation to the outer sleeve 91 retained by the compression springs 73, so that the chuck 96 is released from its engagement with the welding stud le which is now welded to the steel girder 2.
Said thrust bearing housing 110 is arranged to assume an inoperative upper position at a distance above the lifting plate 100 that corresponds to the distance between the lifting plate 100 and the feeders 107, 108 when the thrust bearing housing 110 is in operative lower position. The thrust bearing housing 110 is also pivotable journalled on one of the piston rods 105, to assume a locked position upon engagement with the other piston rod 106 and a position swung aside as shown by unbroken and broken lines, respectively, in Figure 13. Swinging of the thrust bearing housing 110 is effected by a hydraulic cylinder 111 journalled eccentrically on the thrust bearing housing 110 in relation to the piston rod 105 constituting the pivot axis. On the side of the thrust bearing housing 110 facing away from that on which the hydraulic cylinder 111 is arranged, the thrust bearing housing supports a stud-feed cylinder 112. This cylinder is provided with a downwardly directed pressing arm 113 with an electromagnet 115 arranged to be activated when the thrust bearing housing 110 is in its swung-in position so that a welding stud 1 is picked up by the electromagnet 115 from an adjacent magazine 114.
The inner sleeve 92 of the spindle 89 is provided internally with a plurality of plate springs 116 arranged in several vertical rows, e.g. three rows, in order to centre the welding studs 1 in the sleeve 92 and retain them therein so that they do not unintentionally fall down and out of the spring 89 when this is lifted. The column of welding studs is displaced in downward direction when a new welding stud is fed in by the stud- feed cylinder 112.
When a central row of welding studs 1 is to be welded, the bearing housing 60 with its spindle 89 is secured in its central position in relation to the support plate 4 by means of a cylinder 117 (see Figure 1), the piston rod of this cylinder pressing against and locking the transverse slide 63 of the bearing housing 60. Adjustment screws 118 (see Figure 8, only one shown) are arranged in the side plates 67, 68 to form a stop for the cylinder 64 so that its stroke length can be regulated, and thereby the positions of the two outer rows of studs. Two hydraulic cylinders for fine adjustment of the end positions for the cylinder 64 are designated 119. The side plates 67, 68 which support the piston rod 66 are mounted on the support plate 4 by means of bolts 120 with gaps therebetween to enable said fine adjustment.
Each clamping j w 97 is provided on its inner side with a plurality of narrow axial ridges and grooves located at least within the cylindrical cavity part of the chuck 96. The peripheral, cylindrical surface of the head 28 of the welding stud is provided with corresponding narrow axial ridges and grooves. These ridges and grooves are formed in conjunction with cold upsetting the welding stud. The opposing ridges and grooves form cooperating engagement members 75, 76 (see Figure 12) which form such a strong joint that the welding stud becomes a rotating unit with the chuck 96, i.e. no relative rotary movement can occur between the head 28 of the welding stud and the chuck 96. Without these engagement members 75, 76, or similar means producing the same locking effect, i.e. if the surfaces were smooth, there would be a risk of the surfaces being welded together during the welding operation.
In order to achieve fully automatic friction welding, the apparatus is equipped with a suitable control unit comprising suitable computer equipment with monitoring and control programs, to control the various operating cylinders, motors, welding stages, welding parameters, etc.
The welding apparatus described above operates in the following automatic manner. Figures 1 and 2 show a position when the welding stud le is welded to the steel girder 2. The piston rods 105 and 106 are engaged to lift the spindle 89 and the associated chuck 96 and support ring 94 to the position shown in Figures 10 and 15: The rear clamping cylinders 32, 33 are then engaged so that their piston rods 34, 35 are retracted to be out of the way of the auxiliary support 36 used initially, and instead the rear support rollers 37, 38 will rest against the auxiliary support 36 as shown in Figure 16. At the same time the heads 28 of the welding studs will be released from the vertical side recesses 30, 31 of the grooves 27 in the two sleeves 24, 25, as illustrated by the position of the welding stud indicated by the upper broken line in Figure 5. The step-feed cylinder 21 is then connected in for its piston rod 22 to move the yoke 23 forwards in relation to the transverse stay 17, and thus also the sleeves 24, 25 joined to the yoke 23. The movement is determined to be one pitch so that the sleeves 24, 25 will surround the heads 28 of the next pair of welding studs, as shown in Figure 15, after which the clamping cylinders 32, 33 are activated so that their piston rods 34, 35 once again press against the auxiliary support 36 and the sleeves 24, 25 are thereby locked to the welding studs. In the next stage the forward clamping cylinders 42, 43 are engaged so that their piston rods 45, 46 are free from the auxiliary support 36 and the supporting function is instead taken over by the support rollers 47, 48. The locking engagement between the locking elements 39, 40 and welding studs Id is released and the step-feed cylinder 21 can again be activated to move the locking elements 39, 40 to the welding studs le first welded to the steel girder 2. Movement is effected by the transverse stay 17, and thus the whole stand 3, being pulled forward by the piston rod 22 towards the yoke 23 which is now secured in relation to the auxiliary support 36, thanks to the locking engagement between the sleeves 24, 25 and the welding studs. The clamping cylinders 42, 43 are thereafter re-activated so that the forward locking elements 39, 40 also assist in locking the apparatus since they come into locking engagement with the welding studs le as illustrated in Figure 17. The apparatus is now in a position to friction weld a new welding stud If. Figure 18 shows the stage when the spindle 89 is about to be moved forward one pitch to the next welding spot after the welding stud If has been welded on, the spindle 89 has been lifted, the rear sleeves 24, 25 have^ been moved forward to the third pair of welding studs lc and locked fast thereto and the forward locking elements 39, 40 have been released from the fifth pair of welding studs le at the same time as the forward support rollers 47, 48 have been brought into rolling position on the welding girder. The friction welding produces a welding joint comprising an annular bead 77.
When a welding stud has been friction welded, e.g. welding stud le, feeding of the studs is initiated by the electromagnet 115 being activated to magnetically grip the next welding stud in the store 114. Simultaneously the hydraulic cylinders 103, 104 are activated to lift the spindle 89 and thrust bearing housing 110, whereupon the whole spindle 89 is lifted to a first position where its lower end is free from the welding stud 1 and then, in the same stroke, the intermediate sleeve 93 and inner sleeve 92 are lifted to an upper position according to Figure 10 in order to feed-in a new welding stud 1. Also simultaneously the hydraulic cylinder 111 is activated to swing the thrust bearing housing 110 an angle of 47°. The new welding stud is now axially aligned with the axis of rotation 90 of the spindle and at any rate with the vertical passage formed by the cavities 101, 102. Cylinder 112 is then activated so that the arm 113 feeds the stud down into the central passage 101, 102, after which the electromagnet 115 is deactivated to release the welding stud 1. When the welding stud is fed down by the cylinder 112 the row of welding studs is pressed down through the central cavity 102 until the lowermost welding stud is caught by the chuck 96. When the electromagnet 115 has been deactivated to release the uppermost welding stud, the electromagnet 115 is raised to its starting position and the thrust bearing housing 110 is swung back to its engagement position with the piston rod 106. In the next phase the hydraulic cylinders 103, 104 are engaged to move the thrust bearing housing 110 downwards into contact with the lifting plate 100 to press this and the intermediate sleeve 93 with associated chuck 96 in downward direction. During this movement the lifting plate 100 is brought into contact with the compression springs supported by the outer sleeve 91 on the spindle 89 so that the spindle is pressed downwards during the continued movement of the thrust bearing housing 110 during which the support flange 72 of the outer sleeve 91 comes into contact with the dampening ring 71 as illustrated in Figure 12. The support ring 94 on the sleeve 91 is thus moved out of the rotation cylinder 80 by the thrust bearing housing 110. At the same time the thrust bearing cylinder 110 acts on the chuck 96 via the lifting plate 100 and the intermediate sleeve 93 so that the clamping jaws 97 press with sufficient wedge force against both the support ring 94 and the head 28 of the welding stud so that the spindle 89 and welding stud 1 form a rotating unit when the hydraulic motor 85 is activated. At the same time the thrust bearing cylinder 110 presses the row of welding studs against the steel girder with a pressure that can be increased to a high predetermined value. The pressure increase is possible since the dampening ring 71 permits compression so that the entire spindle 89 can be pressed down further in relation to the column of welding studs 1.
To obtain welding joints of requisite high strength the friction welding is performed in accordance with a specifically modified method which in principle constitutes a combination of the friction welding methods described in the introduction. The modified method according to the invention can be divided into the following three phases:
Phase 1: Heating phase. During this phase, when the torque requirement is greatest, the contact surfaces to be welded together are heated. The drive motor 85 is operative throughout. Phase time: about 1 second.
Phase 2: Fusing phase. The drive motor 85 is disconnected and the friction-producing pressure is increased. During this phase the energy containing in the rotating mass is consumed and most of it is converted to friction heat. The friction causes the rotation to gradually decrease and finally cease. Phase time: about 2 seconds.
Phase 3: Stabilizing phase. The friction-producing pressure is kept constant even after rotation has ceased entirely. Phase time: about 2-3 seconds.
A combination of the continuous method and the inertia method, giving the modified friction welding method as described above, has the advantages that the oscillating mass need not be as large as when using only the inertia method and that the cycle time becomes shorter. Retardation can be achieved without the use of a mechanically or electrically influenced brake.
The method of automatically welding the welding studs 1 onto the steel girder 2 thus comprises the following main steps: welding is performed by means of friction welding using said apparatus comprising a spindle means 89 rotating about a vertical axis 90 and carrying the welding stud 1 to be friction welded; the apparatus is displaced stepwise in relation to the steel body 2 to a new welding position for the spindle means 89 and is fixed in relation to the steel body in each such welding position; the spindle means 89 and welding stud 1 are caused to rotate at predetermined speed; an initially low pressure is applied on the welding stud via the spindle means 89 so that the welding stud 1 with said speed is brought into friction-producing surface contact with the steel body 2 during an initial heating phase; an increased pressure is then applied on the welding stud via the spindle means 89, the friction thereby increasing and the welding stud 1 being welded to the steel body 2. The spindle means 89 rotates preferably together with the rotation cylinder, the latter being rotatably journalled in the bearing housing. The heating phase is preferably followed by a fusing phase during which the friction-producing pressure is increased so that rotation is gradually retarded and finally ceases, and then by a stabilizing phase during which the final pressure from the fusing phase is maintained in order to stabilize the friction-welded joint.
The heating phase preferably lasts for about 1 second, the fusing phase for about 2 seconds and the stabilizing phase for about 2-3 seconds.
Instead of being secured to the steel girder and locked to the welding studs, according to another embodiment the apparatus can be supported by a suitable support means, i.e. one or more rails or the like, extending along the steel girder. In this case the apparatus is arranged to be locked to the support means in each welding position by means of a suitable locking member comprising a brake, for instance, so that the apparatus is fixed in relation to the steel girder, and each time a welding stud has been friction welded, after release of the locking member, to be moved one pitch step forward to a new welding position with the help of suitable actuator.
Although central feeding of the welding studs through the spindle is preferred, they could be supplied to the welding spot or the spindle in some other manner, e.g. laterally.

Claims

C L A I M S
1. Apparatus for welding welding studs (1) onto a steel body (2) to form a cooperating construction, characterized in that it comprises a rotatably journalled spindle means (89) with vertical axis of rotation (90), supported by a stand(3); that the apparatus is arranged to be moved stepwise in relation to the steel body (2) by an actuator (21) to a new welding position and to be fixed in relation to the steel body (2) in each such welding position by means of locking members (24, 25, 32, 33; 39, 40, 42, 43); that the apparatus also includes drive means (85, 86) to rotate the spindle means (89) about its axis of rotation (90), said spindle means (89) comprising a chuck (96) located at its lower end to clamp a welding stud (1) to be welded by means of friction welding, so that the welding stud (1) and spindle means (89) form a rotating unit without relative movement of rotation therebetween; supply means (110, 111, 112, 115) to supply welding studs (1) to engagement position for the chuck (96); and pressure means (103, 104, 110) arranged to press the welding stud (1) clamped by the chuck (96) against the steel body (2) to generate friction therebetween.
2. Apparatus as claimed in claim 1, characterized in that the spindle means has a vertical central cavity (102) running through it and that the supply means (110, 111, 112, 115) are arranged to supply welding studs (1) to the upper end of said central cavity (102) and to feed welding studs through said central cavity.
3. Apparatus as claimed in claim 2, characterized in that the supply means for the supply of welding studs includes a cylinder (112) provided with a support element (113, 115) to carry a welding stud collected from a magazine (114), that the support element (113, 115) is arranged to be moved vertically so that, when coaxial with the central cavity (102) of the spindle means, it presses the collected welding stud down into the cavity, at the same time pressing down a continuous row of welding studs present in the central cavity, in order to bring the lowermost welding stud into engagement position for the chuck (96).
4. Apparatus as claimed in claim 3, characterized in that the support element includes an electromagnet (115).
5. Apparatus as claimed in claim 3 or 4, characterized in that the pressure means comprises a horizontal disc¬ shaped pressing device (110) pivotable between a first and a second position and carrying said support element (113, 115) which in the first position of the pressing device (110) is aligned with said magazine (114) and in its second position is aligned with the central cavity (102) of the spindle means (89).
6. Apparatus as claimed in claim 5, characterized in that the pressure means comprises an actuator (103, 104) for vertical movement of the pressing device (110) between an upper position and a lower position, and that the pressing device (110) is arranged by means of the control means to press the welding stud (1) clamped by the chuck (96) against the steel body (2) via the row of welding studs in the central cavity (102).
7. Apparatus as claimed in claim 6, characterized in that the actuator comprises two cylinders (103, 104) arranged one on each side of the spindle means (89), the piston rods (105, 106) of said cylinders carrying said pressing device (110) which at one part is pivotably journalled at one of the piston rods (105) and with an opposite part is in detachable engagement with the other piston rod (106) in order to permit horizontal and vertical movement of the pressing device (110).
8. Apparatus as claimed in any of claims 5-7, characterized in that the pressure device is in the form of a thrust bearing housing (110) comprising a bearing housing (121), a pressure plate (122) for cooperation with the spindle means (89) and a thrust bearing (123) permitting common rotation of the pressure plate (122) with the spindle means (89) in surface contact position with each other.
9. Apparatus as claimed in any of claims 2-8, characterized in that the spindle means (89) is arranged in a coaxial rotation cylinder (80), rotatably journalled in a coaxial bearing housing (60) connected to the stand (3), that the spindle means (89) comprises an outer sleeve unit (91, 94), that the outer sleeve unit (91) of the spindle means (89) and rotation cylinder (80) are provided on their facing cylindrical surfaces with cooperating engagement members (98) arranged to permit both common rotation of the spindle means (89) and rotation cylinder (80) and also axial displacement of the spindle means (89) in relation to the rotation cylinder (80) between a lower position (Figure 12) for friction welding and an upper position (Figure 10) disengaged from a welding stud which has been welded.
10. Apparatus as claimed in claim 9, characterized in that the rotation cylinder (80) comprises an annular belt pulley (84) arranged conically at its upper end and located outside the bearing housing (60), and that said drive means comprises a motor (85) supported by the bearing housing (60), the belt pulley (87) of which is connected to the belt pulley (84) of the rotation cylinder (80) by means of one or more belts (86).
11. Apparatus as claimed in claim 9 or 10 in combination with claim 6 or 7, characterized in that a horizontal lifting plate (100) is provided at the upper end of the spindle means (89), and that the actuators (103, 104) are provided with feeders (107, 108) arranged to be brought into engagement with the lifting plate (100) upon activation of the actuators (103, 104) to raise the spindle means (89) to said upper position.
12. Apparatus as claimed in claim 11, characterized in that the spindle means (89) comprises an inner sleeve unit (92, 93) carrying at its lower end said chuck (96) and at its upper end said lifting plate (100), that the cylindrical surfaces of the inner sleeve unit (92, 93) and the outer sleeve unit (91, 94) are provided with cooperating engagement members (99) arranged to permit both common rotation of the inner sleeve unit (92, 93) and the outer sleeve unit (91, 94) and also axial displacement of the inner sleeve unit (92, 93) in relation to the outer sleeve unit (91, 94) between a lower position in which the chuck (96) carried by the inner sleeve unit (92, 93) is in engagement with the welding stud for friction welding and an upper position in which the chuck (96) is disengaged from the welding stud which has been welded in the previous welding step.
13. Apparatus as claimed in claim 12, characterized in that the cooperating engagement members (99) of the sleeve units (92, 93; 91, 94) have a stop (109) which limits the relative axial displacement between the sleeve units corresponding to the distance between said lower and upper positions of the chuck (96), and that when said stop has been reached after said relative displacement, the sleeve units will be moved axially together thereby being caused to assume said upper position of the spindle means (89) in which the chuck (96) is retracted into the outer sleeve unit (91, 94).
14. Apparatus as claimed in claim 13, characterized in that the outer sleeve unit comprises a first sleeve (91) and a support ring (94) supported thereby, the inner side of said ring being conical to provide wedge engagement with the correspondingly conical clamping jaws (97) of the chuck (96), said clamping jaws (97) being arranged by the action of said wedge engagement to clamp the enclosed head (28) of the welding stud (1).
15. Apparatus as claimed in claim 14, characterized in that the clamp jaws (97) are suspended in the first sleeve (91) with the aid of connection means (79) arranged to permit radial movement of the clamping jaws (97) into engagement with the welding stud or disengagement from said welding stud.
16. Apparatus as claimed in any of claims 1-15, characterized in that the inner surface of the chuck (96) and the peripheral surface of the head (28) of the welding stud are provided with cooperating engagement members (75, 76) arranged, when in operative position during rotation of the spindle means (89), to prevent relative rotation between chuck (96) and welding stud (11).
17. Apparatus as claimed in any of claims 11-16, characterized in that the outer sleeve unit (91, 94) comprises a support flange (72) supporting a plurality of compression springs (73) arranged to cooperate with the lifting plate (100) in order, in compressed state, to temporarily retain the outer sleeve unit (91, 94) during the initial stage of lifting when the inner sleeve unit (92, 93) is raised in order to release the chuck (96) from the welded welding stud.
18. Apparatus as claimed in claim 17, characterized in that a ring (71) of a resilient material such as rubber is arranged to rest on the upper side of the belt pulley (84) during the friction-welding phase in order to yieldingly cooperate with said support flange (72) to exert a lifting action on the outer sleeve unit (91, 94) in order to increase the wedge engagement between support ring (94) and chuck (96) resulting in increased engagement between chuck (96) and welding stud, to centre the welding stud, and also to compensate for differences in length of the welding studs to ensure that the thrust bearing housing (110) always exerts sufficient pressure on the row of welding studs with the steel body (2) as counter member.
19. Apparatus as claimed in any of claims 12-18, characterized in that the inner sleeve unit (92, 93) is provided with a plurality of spring members (116) arranged at several points in the central cavity (102) for spring abutment against the welding studs (1), centering the welding studs therein and providing spring retention.
20. Apparatus as claimed in any of claims 1-19, characterized in that the stand (3) comprises a vertical support plate (4) located transversely to the direction of movement of the apparatus, that the bearing housing (60) of the spindle means (89) is journalled in the support plate (4) for transverse movement between two or more welding spots to obtain an equivalent number of parallel rows of welding studs welded onto the steel body (2).
21. Apparatus as claimed in any of claims 1-20, characterized in that it is supported by a support member extending along the steel body (2), the apparatus being arranged to be locked to the support member at each welding position with the aid of said locking means for securing the apparatus in relation to the steel body, and also to be moved by said actuator one step forwards to a new welding position on the steel body each time a welding stud has been friction welded.
22. Apparatus as claimed in any of claims 1-20, characterized in that it comprises said locking members (24, 25, 32, 33; 39, 40, 42, 43) to secure it in relation to the steel body (2) to be brought into locking engagement with the steel body or welding studs welded thereto, and also said actuator (21) for stepwise displacement in relation to the steel body (2).
23. Apparatus as claimed in claim 2, characterized in that the locking members comprise rear locking means (24, 25, 32, 33) in relation to the direction of movement of the apparatus and front locking device (39, 40, 42, 43) in relation to the direction of movement of the apparatus, and possibly one or more intermediate locking device resting on the stand (3).
24. Apparatus as claimed in claim 23 in combination with claim 20, characterized in that the stand (3) comprises a part (6) located in the vicinity of the steel body (2), that the front locking device (39, 40, 42, 43) are arranged close to the transverse support plate (4) of the stand (3) to rigidly support this and/or said stand part (6) joined to the support plate (4) and extending rearwards from the spindle means (89), that the rear locking device (24, 25, 32, 33) are spaced from the support plate (4) and journalled in the stand part (6) to be moved between a rear position and a front position in relation to the front locking device (39, 40, 42, 43) by means of said actuator (21) for stepwise feeding of the spindle means in forward direction when the rear locking device (24, 25, 32, 33) move away from the front locking device (39, 40, 42, 43) and are in locking engagement with at least one welding stud, while the front locking device (39, 40, 42, 43) are free from such locking engagement.
25. Apparatus as claimed in claim 24, characterized in that each locking device comprises at least one locking element (24, 25; 39, 40) provided with a T-shaped, groove aligned with the movement of the apparatus and running through to receive or release the head (28) of a welding stud, and at least one clamping cylinder (32, 33; 42, 43), the piston rod (34, 35; 45, 46) of which is arranged to be pressed against the steel body (2) to bring the locking element (24, 25; 39, 40) and a welding stud received therein into locking engagement with each other, a roller means (37, 38; 47, 48) arranged to run on the steel body (2) when said piston rod (34, 35; 45, 46) is not in contact with the steel body (2), and that the actuator for stepwise displacement of the apparatus comprises at least one power cylinder (21) which is rigidly mounted by its cylinder housing to said stand part (6) and by its piston rod (22) to said rear locking device in order to alternately push the rear locking device away and pull it towards itself in order to effect stepwise feeding of the apparatus.
26. Apparatus as claimed in claim 25, characterized in that the stand part (3) comprises two horizontal, parallel rods (15, 16) and that the rear locking device comprises two sleeve-shaped locking elements (24, 25) arranged slidably, one on each of said rods (15, 16).
27. Apparatus as claimed in any of claims 1-26, characterized in that it comprises a connection support (36) for unitary connection to the steel body at one end thereof, said connection support (36) being pre-welded with a plurality of welding studs (la-Id) with predetermined pitch, said locking members (24, 25, 32, 33; 39, 40, 42, 43) being arranged to be brought into engagement with the welding studs (la-Id) welded to the connection support until a sufficient number of welding studs (1) have been welded onto the steel body (2).
PCT/SE1992/000791 1991-11-21 1992-11-18 Friction welding apparatus WO1993009908A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9103446-2 1991-11-21
SE9103446A SE469513B (en) 1991-11-21 1991-11-21 DEVICE FOR FRENCH WELDING OF WELDING Bolts

Publications (1)

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WO1993009908A1 true WO1993009908A1 (en) 1993-05-27

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PCT/SE1992/000791 WO1993009908A1 (en) 1991-11-21 1992-11-18 Friction welding apparatus

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WO (1) WO1993009908A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103737172A (en) * 2014-01-09 2014-04-23 威海联桥精密机械有限公司 Dynamic detection mechanism for feed pressure
US20220193817A1 (en) * 2019-07-31 2022-06-23 Fusematic Corporation A multi-position clamp for friction welding operations

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106769469B (en) * 2016-12-30 2023-03-14 中国科学院合肥物质科学研究院 Automatic equipment for detecting yield strength of valve friction welding

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Publication number Priority date Publication date Assignee Title
WO1986006665A1 (en) * 1985-05-10 1986-11-20 Thomson Welding & Inspection Limited Friction welding
EP0397387A2 (en) * 1989-05-06 1990-11-14 ROLLS-ROYCE plc Friction welding

Patent Citations (2)

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Publication number Priority date Publication date Assignee Title
WO1986006665A1 (en) * 1985-05-10 1986-11-20 Thomson Welding & Inspection Limited Friction welding
EP0397387A2 (en) * 1989-05-06 1990-11-14 ROLLS-ROYCE plc Friction welding

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103737172A (en) * 2014-01-09 2014-04-23 威海联桥精密机械有限公司 Dynamic detection mechanism for feed pressure
US20220193817A1 (en) * 2019-07-31 2022-06-23 Fusematic Corporation A multi-position clamp for friction welding operations
US11858062B2 (en) * 2019-07-31 2024-01-02 Fusematic Corporation Multi-position clamp for friction welding operations

Also Published As

Publication number Publication date
SE469513B (en) 1993-07-19
SE9103446L (en) 1993-05-22
SE9103446D0 (en) 1991-11-21

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