Abstract:
The invention is related to an ultrasonic welding device ( 5 ) comprising: an adapter frame ( 6 ); an ultrasonic horn ( 7 ) driven by a adapter frame mounted converter ( 8 ). A pick member ( 9 ) comprises grippers ( 11 - 14 ). Passive clamping means are provided with a press pad ( 10 ). Control means and activation means ( 15 ) are provided for controlled activation of the pick member ( 9 ) and the ultrasonic horn ( 7 ). The invention is further related to a method of operating said device.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to European patent application No. EP 12400009.2 filed Apr. 5, 2012, the disclosure of which is incorporated in its entirety by reference herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    (1) Field of the Invention 
         [0003]    The invention is related to an ultrasonic welding device with the features of the preamble of claim  1 . The invention is further related to a method of operating said device with the features of the preamble of claim  13 . 
         [0004]    (2) Description of Related Art 
         [0005]    Ultrasonic welding technology is used to weld elements to increase energy/time efficiency. 
         [0006]    The document CN101391343 A discloses an ultrasonic welding machine clamper fast conversion device, comprising a welding machine seat, a clamper, and additionally a welding head directional plate, a welding pad plate, a Y axis trimming plate and an X axis trimming plate with grooves of a locating pin of a locating plate, a trimming button and a bottom plate with a groove. 
         [0007]    The document U.S. 2008/0023529 A1 discloses an ultrasonic welding apparatus and method for detaching or effecting release of an ultrasonic welding tool stuck or attached to a weldment. The method includes the step of utilizing a mechanism mounted adjacent to the ultrasonic welding tool to hold the weldment in position during welding and/or while the ultrasonic welding tool is withdrawn and, if necessary, using the mechanism to detach the weldment from the ultrasonic welding tool. The method contemplates providing a twist, rotary or axial motion to one of the ultrasonic welding tool or weldment to effect release of the ultrasonic welding tool. The apparatus may include a clamp member having a distinct clamping area or pad located adjacent to the sonotrode or anvil of the ultrasonic welding tool. The clamp mechanism provides vibration control, noise mitigation, and a more uniform boundary condition during welding and facilitates part release upon the completion of the welding process. 
         [0008]    The document DE 3411933 A1 discloses an ultrasonic spot welding apparatus including a welding tip and a complimentary anvil, both mounted on a stationary welding frame and between which workpieces may be inserted for welding. The welding tip includes a vibratory reed adapted to introduce into and through the workpieces high frequency vibratory energy in order to effect a weld between the workpieces. 
         [0009]    The apparatus includes a reed stabilizer for clamping about and stabilizing the vibratory reed at its nodal point and clamping means for clamping the workpieces. The clamping means are mounted on a clamping frame which is pivotably mounted to the stationary welding frame. In an effort to reduce workpiece movement and produce consistent, strong welds, it has been found necessary to utilize a clamping system at or near the spot to be welded to tightly hold together the workpieces so as to prevent them from moving or twisting due to the powerful forces generated during the welding procedure. 
         [0010]    Additionally, control must be established over the mechanical waves and forces that are emitted from the working area so that these forces are not strong enough to damage those areas of the workpieces remote from the work spot. Absence of positive control over these forces has resulted in a degree of uncertainty with respect to the normal integrity of prior welds, bonds, mechanical attachments or stress concentrations. Clamping of the workpiece W is effected by movable collar clamp about the anvil and stationary collar clamp about the welding tip. Movable collar clamp is mounted on clamp housing which can be raised and lowered along rails by hydraulic clamp cylinders. Stationary collar clamp, which surrounds the welding tip, is mounted on clamping frame. 
         [0011]    The document U.S. Pat. No. 5,480,501 A discloses an ultrasonic apparatus and method for placing individual pillowed chips of light lock material in a cartridge. A vacuum plate mounted on a pivotable arm picks up a chip and releases it into a cartridge. The cartridge has a recessed area into which the pillowed edge of the chip fits. Once positioned with the cartridge, utilizing a tuck plate, the chip is sealed in place using an ultrasonic horn. 
         [0012]    The document GB 1219894 A discloses an ultrasonic welding apparatus with a vibrator for transmitting ultrasonic vibrations to the surface of a workpiece and mounted within a housing which includes an end portion resiliently connected to the body of the housing, the end portion extending coaxially around the tip of the vibrator such that, during a welding operation, when the tip is in contact with a workpiece, pressure is resiliently applied to the workpiece, around the area being welded, through the end portion. 
         [0013]    The document GB 1442251 A discloses ribbon segments made from heat fusible material and spliced by locating these segments in proper relationship for splicing, tensioning at least one of the segments, and splicing the segments while said at least one ribbon segment remains tensioned. 
       BRIEF SUMMARY OF THE INVENTION 
       [0014]    It is an object of the invention to provide an ultrasonic welding device to further automatize ultrasonic welding. It is a further object of the invention to provide a method of operating said device. 
         [0015]    The solution is provided with an ultrasonic welding device with the features of claim  1  and with a method of operating said device with the features of claim  13 . 
         [0016]    According to the invention an ultrasonic welding device is attached to an adapter frame. An ultrasonic horn of the ultrasonic welding device is driven by a converter arranged central with regard to said adapter frame. The adapter frame can be driven for moving said ultrasonic horn into engagement with a workpiece, particularly into engagement with a preform, to perform an ultrasonic welding operation on said workpiece to weld the preform to another fixed workpiece of fibre reinforced plastics (FRP) component, particularly another fixed preform. 
         [0017]    A pick member of the inventive ultrasonic welding device is provided for operative engagement with said workpieces, the pick member being resiliently mounted to said adapter frame. Passive clamping means at a press pad of the inventive ultrasonic welding device are resiliently mounted to said adapter frame alternatively to the pick member or the pick member combined with the passive clamping means at the press pad are resiliently mounted to said adapter frame. Control means and activation means are provided at the inventive ultrasonic welding device for controlled activation of the pick member and the ultrasonic horn for conveyance and a subsequent ultrasonic welding operation with said workpieces to weld the preform to the fixed workpiece of fibre reinforced plastics (FRP) component. 
         [0018]    The inventive ultrasonic welding device adds additional functionalities to an ultrasonic preform welding robot head allowing either pick-up or passive clamping or combined pick-up and passive clamping unilaterally from one side of any workpieces providing the advantage of free movements of the inventive ultrasonic welding device relative to fixed workpieces with varying dimensions thus avoiding the limitations for dimensions of workpieces resulting from ultrasonic welding devices of the state of the art, said ultrasonic welding devices of the state of the art allowing exclusively processing of movable workpieces, whereas the inventive ultrasonic welding devices allow free movements of the inventive ultrasonic welding device relative to fixed workpieces and thus ultrasonic welding of movable workpieces to fixed workpieces. These functionalities are perfectly complementing the ultrasonic horn in the creation of local welds. These local welds may be used advantageously to assemble binder preform elements or mount small preform patches onto big fixed preforms for local reinforcement of load critical areas in carbon fibre reinforced plastics (CFRP) components, such as applied for aircraft doors. 
         [0019]    The inventive ultrasonic welding device allows the integration of a pick-functionality with a further optional passive clamp functionality into the ultrasonic horn. The inventive ultrasonic welding device optionally avoids that a preform for welding needs to be carried and placed manually, which is expensive, time consuming and lacks reproducibility. The inventive ultrasonic welding device further avoids that a specific metal pattern—additionally to an underlying tool—are needed for every welding operation on the preform and allows dispense with the need to manually attach this pattern, which is time consuming, complex in geometry and thus expensive to manufacture. Thus the principal advantages of the invention are: integration of related functionalities into an ultrasonic welding device to save tooling costs and process time, —Reduction of tooling costs due to decreased complexity of passive clamping means and less parts, —Reduction of assembly preparation time, —Increase of automation of assembly process, —Increase of part quality and—substitution of more complex machinery. 
         [0020]    According to a preferred embodiment of the invention the pick member comprises a press pad, said press pad being preferably mounted to the adapter frame. The press pad provides stability and orientation to the grippers of the pick member. 
         [0021]    According to a further preferred embodiment of the invention the press pad is provided with clamping means. According to the invention said press pad with clamping means allows clamping of the preforms to be welded by means of the press pad to avoid cambering and/or yielding of the fixed workpieces of carbon fibre reinforced plastics (CFRP) components during ultrasonic weldment to the workpieces. 
         [0022]    According to a further preferred embodiment of the invention press pad comprises a central cut out for said ultrasonic horn allowing the press pad to hold on to the workpieces during welding. 
         [0023]    According to a further preferred embodiment of the invention the grippers are needle grippers or freezing grippers. 
         [0024]    According to a further preferred embodiment of the invention the activation means comprise pneumatic supply means. The pneumatic supply means supply pressurized air as bypass relative to the respective pneumatic grippers, to create negative pressure according to the Bernoulli rule at the centre under the respective pneumatic grippers for suction of the preforms to the respective pneumatic grippers. The pressurized air is deviated from a coupling of the inventive ultrasonic welding device. According to an alternative preferred embodiment of the invention the pneumatic supply means provide low pressure/vacuum to the respective pneumatic grippers for suction of the preforms to the respective pneumatic grippers. 
         [0025]    According to a further preferred embodiment of the invention the press pad is symmetrically mounted with regard to said ultrasonic horn by respective spring legs to four pneumatic grippers integrated into the mounting means. 
         [0026]    According to a further preferred embodiment of the invention the press pad comprises a clamping ring or a preferably entirely clamping surface. 
         [0027]    According to a further preferred embodiment of the invention the adapter frame is adjustable relative to the ultrasonic horn to allow adjustment of the distance between the press pad and said ultrasonic horn and thus to allow changes of the pressure of the press pad on the workpieces during welding. 
         [0028]    According to a further preferred embodiment of the invention the ultrasonic welding device is operated manually relative to fixed workpieces. 
         [0029]    According to a preferred embodiment of the invention the method of operating first moves said ultrasonic welding device with the pick element towards the preform element to be welded. The pick element with the grippers is activated by a control unit to grip the preform element. The ultrasonic welding device moves the preform element to the weld position at the fixed preform. Once the weld position reached the ultrasonic horn is driven into contact with the preform element till exerting some pressure to the preform. Ultrasound is induced through the ultrasonic horn to the preform element to be welded and the weld is accomplished. 
         [0030]    According to a further preferred embodiment of the invention the distance of the press pad relative to the ultrasonic horn is adjustable to allow changes of the pressure from the press pad to the preform during welding, said variable pressure being controllable by means of the mounting means being conceived as spring legs. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0031]    A preferred embodiment of the invention is presented with reference to the following description and the attached drawings. 
           [0032]      FIG. 1  shows a spherical view of small preforms mounted onto an aircraft&#39;s door edge member according to the state of the art, 
           [0033]      FIG. 2  shows a spherical view of an ultrasonic welding device according to the invention, 
           [0034]      FIG. 3  shows a further spherical view from a different point of view of an ultrasonic welding device according to the invention, and 
           [0035]      FIG. 4  shows a spherical view of a manual ultrasonic welding device according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0036]    According to  FIG. 1  workpieces, such as small patches of preforms  1 ,  2 ,  3  are attached to a fixed preform  4  on a tooling as further workpiece made of carbon fibre reinforced plastics (CFRP) components. Said preforms  1 - 4  are defined as composite elements of partly or fully impregnated fabric material. 
         [0037]    According to  FIGS. 2 and 3  an ultrasonic welding device  5  is mounted inside an adapter frame  6 . Control means (not shown) are provided for control of said ultrasonic welding device  5 . An ultrasonic horn  7  is actuated by activation means  15  comprising a converter  8  of the ultrasonic welding device  5 . The ultrasonic horn  7  is oriented parallel to said adapter frame  6 . The adapter frame  6  is mounted to two opposed surfaces of the converter  8  with adjustment means  19  allowing adjustment of the adapter frame  6  parallel to said ultrasonic horn  7 . 
         [0038]    A pick member  9  is mounted to said adapter frame  6  with the ultrasonic horn  7  centrally inside. The pick member  9  comprises a press pad  10 , four rectangular arranged pneumatic grippers  11 - 14 , pneumatic supply means  15  with four separate supply lines integrated into spring legs  18  with essentially equal lengths from the respective pneumatic supply means  15  to the respective pneumatic grippers  11 - 14 . The pneumatic supply means  15  supply pressurized air to bypass the respective pneumatic grippers  11 - 14  and to create negative pressure according to the Bernoulli rule at the centre under the respective pneumatic grippers  11 - 14  for suction of the preforms  1 ,  2 ,  3  to the respective pneumatic grippers  11 - 14 . 
         [0039]    The four separate spring legs  18  are conceived respectively as resilient mounting means for the press pad  10  to the adapter frame  6 . Instead of the pneumatic grippers  11 - 14 , needle grippers or freezing grippers could be used with correspondingly adapted supply means  15 . The press pad  10  stands over the ultrasonic horn  7  with the ultrasonic horn  7  being central relative to a rectangular cut out  16  in the press pad  10 . 
         [0040]    Passive clamp means, e. g. a central clamp ring  17  or a clamping surface, are provided coaxial to the rectangular cut out  16  in the press pad  10 . The clamp ring  17  or the clamping surface are made of tacky cork for improved adherence. Passive clamping functionality is provided by moving the adapter frame  6  towards the workpieces  1 ,  2 ,  3  and the fixed workpiece  4  at the tooling and the reactive forces from the workpieces  1 ,  2 ,  3  and the fixed workpiece  4  at the tooling provide the clamping pressure at the press pad  10  as a function of the stiffness and the predetermined spring stroke of the four separate spring legs  18  said spring stroke being determined by the distance of the press pad  10  to the ultrasonic horn  7 . 
         [0041]    The distance of the press pad  10  relative to the ultrasonic horn  7  is adjustable with screws  19  interacting with longitudinal slits  23  for mounting said adapter frame  6  to the converter  8 . 
         [0042]    The control means control the pneumatic supply means  15 . 
         [0043]    According to  FIG. 4  corresponding features are referred with the same references. An ultrasonic welding device  20  is manually operated. The press pad  21  and the cut out  22  are circular and the press pad  21  is resiliently mounted to the adapter frame  6  by means of three spring legs  24 . 
         [0044]    The ultrasonic horn  7  is centrally arranged relative to the spring legs  24 . A mechanical link  25  transfers mechanical ultrasound vibrations from a generator (not shown) to the ultrasonic horn  7 . 
       Method of Operating the Ultrasonic Welding Device 
       [0045]    The screws  19  fixing the adapter frame  6  to the converter  8  are untightened and the adapter frame  6  is moved along the longitudinal slits  23  to adjust the distance between the ultrasonic horn  7  and the press pad  10  and/or the grippers. The adapter frame  6  is fixed to the converter  8  by the screws  19 . 
         [0046]    First said ultrasonic welding device  5  with the pick member  9  is moved towards the workpieces  1 ,  2  or  3 , such as preforms, to be welded. Coordinates of the ultrasonic welding device  5  relative to the workpieces  1 ,  2 ,  3  or the fixed workpiece  4  at the tooling are available in the control unit for control of said ultrasonic welding device  5  with the pick member  9 . The grippers  11 - 14  at the pick member  9  are activated by the control means and the workpieces  1 ,  2  or  3  are gripped by means of the grippers  11 - 14  as soon as the grippers  11 - 14  have reached the workpieces  1 ,  2  or  3 . 
         [0047]    The workpieces  1 ,  2 ,  3  are moved to a weld position at a fixed workpiece  4  of a CFRP tooling by means of the ultrasonic welding device  5 . Coordinates of the weld position are available in the control unit for control of said ultrasonic welding device  5  with the pick member  9 . 
         [0048]    Pressure is applied by means of the pick member  9  via the press pad  10  of the ultrasonic welding device  5  to the workpieces  1 ,  2 ,  3  and the fixed workpiece  4  at the tooling to be welded once the workpieces  1 ,  2  or  3  have reached their weld position. The spring legs  18  give way to the pressure via the press pad  10  and the ultrasonic horn  7  is moved through the cut out  16  in the press pad  10  till exerting some pressure of up to  10  bar to the workpieces  1 ,  2 ,  3  and the fixed workpiece  4  at the tooling. Ultrasound is introduced from the converter  8  through the ultrasonic horn  7  to the workpieces  1 ,  2 ,  3  and the fixed workpiece  4  at the tooling to be welded till the weld is accomplished. 
         [0049]    Subsequently the ultrasonic welding device  5  is available for a new pick and weld operation. 
         [0050]    Alternatively the press pad  21  of the hand guided ultrasonic welding device  20  is manually positioned on workpieces  1 ,  2 ,  3  and the fixed workpiece  4  at the tooling (not shown). The press pad  21  of the hand guided ultrasonic welding device  20  is manually pressed against the workpieces  1 ,  2 ,  3  and the fixed workpiece  4  at the tooling such that the spring legs  24  are compressed and the ultrasonic horn  7  can move relative to the spring legs  24 . The ultrasonic horn  7  is guided along leading members, integrated into a break through with a certain guiding length of the adapter frame  6  and ensuring orientation of said ultrasonic horn  7 . Said ultrasonic horn  7  is driven through the cut-out  22  in said press pad  21  by manual force to the adapter frame  6  compressing said three spring legs  24 . The ultrasonic horn  7  is brought to contact with the preform, ultrasound is induced and a local bond between workpieces  1 ,  2 ,  3  and a fixed workpiece  4  on the tooling to be welded is created. 
       REFERENCE LIST 
       [0000]    
       
           1  preform 
           2  preform 
           3  preform (workpieces) 
           4  fixed preform on tooling 
           5  ultrasonic welding device 
           6  adapter frame 
           7  ultrasonic horn 
           8  converter 
           9  pick member 
           10  press pad 
           11  pneumatic gripper 
           12  pneumatic gripper 
           13  pneumatic gripper 
           14  pneumatic gripper 
           15  supply means 
           16  cut out 
           17  clamp ring 
           18  spring legs 
           19  adjustment means 
           20  ultrasonic welding device 
           21  press pad 
           22  cut out 
           23  gripper 
           24  spring legs 
           25  mechanical link