Patent Publication Number: US-2018036832-A1

Title: Vibration welding system and method

Description:
TECHNICAL FIELD 
     The present disclosure relates to a vibration welding system. 
     BACKGROUND 
     In a vibration welding process, adjacent surfaces of a clamped workpiece are joined using vibration energy. The transmission of vibration energy through the material of the workpiece creates surface friction and heat along interfacing workpiece surfaces. The heat causes interfacing surfaces to become malleable, which facilitates their bonding together at a resultant welded joint. 
     A vibration welding system preferably includes various interconnected welding devices, including a vibrating sonotrode/welding horn and an anvil assembly. The anvil assembly may include an anvil and a back plate, with the anvil being bolted or otherwise attached to a rigid support member via the back plate. A workpiece can be clamped between the horn and the anvil. The horn is then caused to vibrate at a calibrated frequency and amplitude in response to a high-frequency input signal from a controller. 
     SUMMARY 
     A vibration welding system for joining a wire to a substrate is disclosed, and includes a welding pad attached to a sonotrode and an anvil. The welding pad includes a plurality of first energy directors that are disposed in a first region and a plurality of second energy directors that are disposed in a second region. A channel is formed between the substrate and the first energy directors when the second energy directors are in contact with the substrate. The channel is configured to accommodate the portion of the wire, and has a depth that is less than a cross-sectional diameter of the portion of the wire. The portion of the wire and the substrate are clamped between the welding pad and the anvil during operation of the sonotrode. The first energy directors are disposed to urge the portion of the wire towards the substrate during the operation of the sonotrode to effect joining of the portion of the wire to the substrate. 
     The above features and advantages and other features and advantages of the present disclosure are readily apparent from the following detailed description of the best modes for carrying out the disclosure when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of an example vibration welding system that is specially configured to join elements of a workpiece that includes a wire and a substrate using ultrasonic vibration, in accordance with the disclosure; 
         FIGS. 2 and 3  schematically show cross-sectional side views of embodiments of a welding pad and anvil that may be employed in the vibration welding system described with reference to  FIG. 1  to join a workpiece that includes a wire and a substrate, in accordance with the disclosure; 
         FIG. 4  schematically shows a perspective side view of an embodiment of a welding pad and anvil that may be employed in the vibration welding system described with reference to  FIG. 1  to join a workpiece that includes a wire and a substrate, in accordance with the disclosure; 
         FIG. 5  schematically shows a cross-sectional side view of an embodiment of a welding pad and anvil that may be employed in the vibration welding system described with reference to  FIG. 1  to join a workpiece that includes a wire and a substrate, in accordance with the disclosure; 
         FIGS. 6-1 and 6-2  schematically show a cross-sectional side view and a corresponding cross-sectional end view, respectively, of another embodiment of a welding pad and anvil that may be employed in the vibration welding system described with reference to  FIG. 1  to join a workpiece that includes butted ends of a first wire and a second wire, and a cover sheet in accordance with the disclosure; and 
         FIG. 7  schematically shows a cross-sectional bottom-view of another embodiment of a welding pad that includes a first region having a channel and a second region, wherein the channel is a continuous arc that includes an insert point and an exit point on a side portion of the welding pad, in accordance with the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The components of the disclosed embodiments, as described and illustrated herein, may be arranged and designed in a variety of different configurations. Thus, the following detailed description is not intended to limit the scope of the disclosure, as claimed, but is merely representative of possible embodiments thereof. In addition, while numerous specific details are set forth in the following description in order to provide a thorough understanding of the embodiments disclosed herein, some embodiments can be practiced without some or all of these details. Moreover, for the purpose of clarity, certain technical material that is known in the related art has not been described in detail in order to avoid unnecessarily obscuring the disclosure. Furthermore, the drawings are in simplified form and are not to precise scale. For purposes of convenience and clarity only, directional terms such as top, bottom, left, right, up, over, above, below, beneath, rear, and front, may be used with respect to the drawings. These and similar directional terms are not to be construed to limit the scope of the disclosure in any manner. 
     Referring to the drawings, wherein like reference numbers refer to like components, a vibration welding system  10  is shown in  FIG. 1 . Those of ordinary skill in the art will appreciate that the vibration welding system  10  may operate at an ultrasonic frequency or within another frequency range without departing from the scope of the disclosure. The vibration welding system  10  described herein is specially configured to form a welded joint in a workpiece  40  that includes a portion of a wire  44  and a substrate  42  using ultrasonic vibration. The wire  44  is a single strand that is fabricated from a shape memory alloy (SMA) material, a high tensile strength material, or another suitable material, and is preferably cylindrically-shaped. One feature of the welded joint that is formed in the workpiece  40  is that the portion of the wire  44  that is joined to the substrate  42  retains its cross-sectional shape and is free from gouging, scoring or witness marks. 
     The vibration welding system  10  includes an anvil assembly  12  and a vibrating sonotrode or welding horn  24 . The anvil assembly  12  preferably includes a backplate  16  on which an anvil  14  is disposed, and the anvil  14  includes an anvil welding pad  18  having a welding surface  19 . The anvil assembly  12  provides a relatively stiff mass that is sufficient for opposing the welding horn  24  during the welding process. The welding surface  19  of the anvil welding pad  18  preferably has a knurled pattern in the form of, e.g., raised bumps, ridges, or any other textured pattern to provide traction for gripping the workpiece  40  during the welding process. 
     The welding horn  24  includes a welding power supply  30 , a converter  26 , a booster  28  and a welding pad  23 . The welding power supply  30  may include a welding controller  33  as part of the power supply (as shown) or as a separate device. The welding power supply  30  may be advantageously employed to transform available source power into a form that is more conducive to vibration welding to drive and control the vibration welding process. For instance, the power supply  30  may be electrically connected to any suitable energy source, e.g., a 50-60 Hz AC wall socket. In this instance the power supply  30  may include voltage rectifiers and inverters for generating a high-frequency waveform suitable for vibration welding. The power supply  30  and the welding controller  33  transform source power into a suitable power control signal having a predetermined waveform characteristic(s) suited for use in the vibration welding process, for example a frequency of several Hertz (Hz) to about 40 KHz, or higher frequencies depending on the particular application. The converter  26  may be in the form of a piezoelectric stack or another configuration that has the required mechanical structure for producing a mechanical vibration in response to the input signal (arrow  31 ). The booster  28  amplifies the amplitude of vibration of the input signal (arrow  31 ) at a calibrated frequency, and/or changes a direction of any applied clamping force between the welding horn  24  and the anvil  14 . The welding pad  23  includes a joining surface  25  that works in conjunction with the welding surface  19  of the anvil welding pad  18  to securely grip the workpiece  40  during the vibration welding process. 
     A wire feeder  50  may be disposed to supply to the vibration welding system  10  a portion of the wire  44  for joining to the substrate  42  as part of the workpiece  40 . The wire feeder  50  may have the capability to pre-bend, cut and insert the wire  44  into the vibration welding system  10  in one embodiment. Alternatively, the wire feeder  50  may include a continuous spool of the wire  44  that is fed through a channel in the welding horn  24  to form a desired shape prior to welding. The wire feeder  50  may insert the wire  44  into the vibration welding system  10  without bending it in one embodiment. In one embodiment, the welding controller  33  of the vibration welding system  10  including suitable positioning elements and sensors to control a position of the control of the welding horn  24  with regard to a position of the workpiece  40  to provide a wire guide for the wire feeder  50  prior to executing the welding process. In one embodiment, this can be in the form of a multi-step closing sequence, which permits closing of the welding horn  24  to the anvil  14  at a first, low level clamping pressure for wire guiding, and then closing of the welding horn  24  to the anvil  14  at a second, high level clamping pressure for vibration welding. 
     Embodiments of the welding pad and joining surface are described herein with reference to  FIG. 2 , et seq. In each of the embodiments, the welding pad includes a first region that may include a plurality of first energy directors that project from the welding pad, and a second region that includes a plurality of second energy directors that project from the welding pad. As used herein, the term “energy director” refers to a portion of material that projects orthogonally from the surface of the welding pad, and may be in the shape of a pyramid or another suitable three-dimensional shape, as described herein. Placement of the welding pad against the substrate generates a channel between the substrate and the first energy directors when the second energy directors are in contact with the substrate, wherein the channel is configured to accommodate a length portion of the wire. The channel has a depth that is preferably less than a cross-sectional diameter of the portion of the wire. When a portion of the wire and the substrate are clamped between the welding pad and the anvil during operation of the sonotrode, the first energy directors are disposed to urge the portion of the wire towards the substrate and the second energy directors are disposed to act upon the surface of the substrate to effect joining of the portion of the wire to the substrate. The primary function of the second energy directors is to propagate and concentrate the vibration energy that is generated by the welding horn  24  in a localized area of the surface of the substrate to soften and melt its material to facilitate forming of a welded joint between the wire and the substrate of the workpiece. 
       FIG. 2  schematically shows a cross-sectional side view of a first embodiment of a welding pad  220  and anvil  240  that may be employed in the vibration welding system  10  described with reference to  FIG. 1 . The welding pad  220  and anvil  240  may be advantageously employed to join a portion of the wire  44  to the substrate  42  of the workpiece  40  such that the wire  44  retains its cross-sectional shape and is free from gouging, scoring or witness marks in the resulting welded joint. The wire  44  is depicted as having a circular cross-section with a diameter  46 , which is one embodiment. The cross-sectional shape of the wire  44  may be any suitable shape, including, e.g., a square cross-section, an oval cross-section, a hexagonal cross-section, etc. 
     In this embodiment, the welding pad  220  includes a first region  222  that includes a plurality of first energy directors  224  and a second region  232  that includes a plurality of second energy directors  234 . In one embodiment, the first and second energy directors  224 ,  234  are formed by knurling, and may be in the form of a straight pattern, an angled pattern or a diamond-shaped pattern, and arranged in a coarse, medium or fine density. Alternatively, the first and second energy directors  224 ,  234  may be machined into the shape of hemispherical bodies, pyramids, truncated pyramids or other suitable shapes. 
     The first energy directors  224  and the second energy directors  234  project from the welding pad  220  at different heights in this embodiment, such that placement of the welding pad  220  against the substrate  42  generates a channel  228  between the substrate  42  and the opposed first energy directors  224  when the second energy directors  234  are in contact with the substrate  42 . The channel  228  is configured to accommodate a portion of the wire  44 . The channel  228  has a depth  230  that is preferably less than a cross-sectional diameter  46  of the portion of the wire  44  that is inserted or otherwise placed in the channel  228  prior to the workpiece  40  being clamped into the vibration welding system  10 . During vibration welding, the second energy directors  234  act upon the substrate  42  and the first energy directors  224  act upon the wire  44 . The action of the second energy directors  234  causes the substrate  42  to become malleable, and the clamping force acting upon the first energy directors  224  of the welding pad  220  and the anvil  240  urges the portion of the wire  44  into the malleable substrate  42  at a joining surface  226  to effect the joining. 
       FIG. 3  schematically shows a cross-sectional side view of another embodiment of a welding pad  320  and anvil  340  that may be employed in the vibration welding system  10  described with reference to  FIG. 1 . The welding pad  320  and anvil  340  may be advantageously employed to join the wire  44  to the substrate  42  of the workpiece  40  such that the wire  44  retains its cross-sectional shape in the finished workpiece  40  and is free from gouging, scoring or witness marks in the resulting welded joint. The wire  44  is depicted as having a circular cross-section with diameter  46 , which is one embodiment. The cross-sectional shape of the wire  44  may be any suitable shape, including, e.g., a square cross-section, an oval cross-section, a hexagonal cross-section, etc. In this embodiment, the welding pad  320  includes a first region  322  that includes a plurality of first energy directors  324  that project from the welding pad  320 , and a second region  332  that includes a plurality of second energy directors  334  that project from the welding pad  320 . 
     The first energy directors  324  and the second energy directors  334  project from the welding pad  320  at the same heights in this embodiment. The first energy directors  324  each include concave side portions  325 . The first energy directors  324  are situated such that opposed concave side portions  325  form a channel  328  between the substrate  40  and the first energy directors  324  when the second energy directors  334  are in contact with the substrate  42 . The channel  328  is configured to accommodate a portion of the wire  44 . The channel  328  has a depth  330  that is preferably less than a cross-sectional diameter  46  of the portion of the wire  44  that is inserted or otherwise placed in the channel  328  prior to the workpiece  40  being clamped into the vibration welding system  10 . During vibration welding, the second energy directors  334  act upon the substrate  42  and the concave side portions  325  of the first energy directors  324  act upon the wire  44 . The action of the second energy directors  334  causes the substrate  42  to become malleable, and the clamping force acting upon the concave side portions  325  of the first energy directors  324  of the welding pad  320  and the anvil  340  urges the portion of the wire  44  into the malleable substrate  42  at a joining surface  326  to effect the joining. 
       FIG. 4  schematically shows a perspective side view of another embodiment of a welding pad  420  and anvil  440  that may be employed in the vibration welding system  10  described with reference to  FIG. 1 . The welding pad  420  and anvil  440  may be advantageously employed to join a portion of the wire  44  to the substrate  42  of the workpiece  40  such that the wire  44  retains its cross-sectional shape in the finished workpiece  40  and is free from gouging, scoring or witness marks in the resulting welded joint. In this embodiment, the portion of the wire  44  that is joined to the substrate  42  may be arranged in a C-shape, or may otherwise double back on itself. 
     In this embodiment, the welding pad  420  includes a plurality of second energy directors  434  that project from a welding pad surface  426  of the welding pad  420 . The second energy directors  434  project to a common projection height relative to the welding pad  420  as it contacts the substrate  42  of the workpiece  40  when clamped into the vibration welding system  10 . In this embodiment, the welding pad surface  426  of the welding pad  420  functions to urge the wire  44  into the substrate  42  during vibration welding. 
     In this embodiment, the second energy directors  434  have frustoconical shapes, i.e., frustums that are arranged on the welding pad  420  such that the welding pad surface  426  is exposed on the surface of the welding pad  420 . Alternatively, the second energy directors  434  may have hemispherical shapes, or another suitable shape. A channel  428  having a C-shape or another suitable arrangement is preferably formed between the second energy directors  434  in the welding pad surface  426 , and the wire  44  can be threaded therethrough prior to welding. The depth that is associated with the second energy directors  434  is selected based upon a diameter of the wire  44 , and is preferably less than a diameter of the wire  44 . Preferably, the second energy directors  434  are disposed on the welding pad surface  426  such that the channel  428  is formed to accommodate the wire  44 . In one embodiment, the second energy directors  434  are formed by machining. During vibration welding, the second energy directors  434  act upon the substrate  42 , and the wire  44  is inserted in the channel  428 . In one embodiment, the wire  44  is preformed; alternatively, the wire  44  may be fed into the channel  428  with trimming of any extraneous portion. The action of the second energy directors  434  causes the substrate  42  to become malleable, and the clamping force acting upon the wire  44  from the welding pad surface  426  urges the wire  44  into the malleable substrate  42  to effect the joining. 
       FIG. 5  schematically shows a cross-sectional side view of another embodiment of a welding pad  520  and anvil  540  that may be employed in the vibration welding system  10  described with reference to  FIG. 1 . The welding pad  520  and anvil  540  may be advantageously employed to join a portion of the wire  44  to the substrate  42  of the workpiece  40  such that the wire  44  retains its cross-sectional shape in the finished workpiece  40  and is free from gouging, scoring or witness marks in the resulting welded joint. In this embodiment, the portion of the wire  44  that is joined to the substrate  42  may be arranged in a straight line, a C-shape, or otherwise doubles back on itself. The wire  44  is depicted as having a circular cross-section with diameter  46 , which is one embodiment. The cross-sectional shape of the wire  44  may be any suitable shape, including, e.g., a square cross-section, an oval cross-section, a hexagonal cross-section, etc. In this embodiment, the welding pad  520  includes a channel  522  that is annular to a portion of the cross-section of the wire  44  and is arranged to circumscribe the portion of the wire  44  that is being joined to the substrate  42 . A plurality of second energy directors  534  project from the welding pad  520 , and form a channel  528  that has a projection depth  530  relative to a joining surface  526  as it contacts the substrate  42  of the workpiece  40  when clamped into the vibration welding system  10 . The second energy directors  534  project to a common projection height relative to the welding pad  520  as it contacts the substrate  42  of the workpiece  40  when clamped into the vibration welding system  10 . In this embodiment, the welding pad  520  surrounding the channel  528  functions to urge the wire  44  into the substrate  42  during vibration welding. In this embodiment, the tips of the second energy directors  534  preferably have pyramid shapes, and are arranged on the welding pad  520  such that their tips contact the joining surface  526 . Alternatively, the second energy directors  534  may have another suitable shape. The wire  44  can be threaded through the channel  528  prior to welding. The projection depth  530  may be selected based upon the diameter  46  of the wire  44 . Preferably, the second energy directors  534  are disposed on the joining surface  526  such that the channel  528  is formed to accommodate the wire  44 . In one embodiment, the second energy directors  534  are formed by machining. During vibration welding, the second energy directors  534  act upon the substrate  42 , and the wire  44  is inserted in the channel  528 . In one embodiment, the wire  44  is preformed; alternatively, the wire  44  may be fed into the channel  528  with trimming of any extraneous portion. The action of the second energy directors  534  causes the substrate  42  to become malleable, and the clamping force acting upon the wire  44  urges the wire  44  into the malleable substrate  42  to effect the joining. 
       FIGS. 6-1 and 6-2  schematically show a cross-sectional side view and a corresponding cross-sectional end view of another embodiment of a welding pad  620  and anvil  640  that may be employed in the vibration welding system  10  described with reference to  FIG. 1 . The welding pad  620  and anvil  640  may be advantageously employed to join a workpiece  650  that includes butt-joined ends of a portion of a first wire  652  and a portion of a second wire  654 , and a substrate that is in the form of a cover sheet  656 . The first and second wires  652 ,  654  may be opposite ends of a single strand of cable, thus forming a continuous loop, or alternatively, may be ends of two different strands. The cover sheet  656  may be fabricated as a cylindrical tube forming an inner portion that has first and second ends into which the first and second wires  652 ,  654 , respectively, may be inserted. The vibration welding system  10  joins the first and second wires  652 ,  654  employing the cover sheet  656  such that first and second wires  652 ,  654  both retain their respective cross-sectional shapes in the finished workpiece  650  and are free from gouging, scoring or witness marks in the resulting welded joint. 
     In this embodiment, the welding pad  620  includes a first channel  628  that is annular to a portion of the cross-section of the first wire  652  and is arranged to circumscribe the portion of the cross-section of the first wire  652 . The anvil  640  includes a second channel  629  that is preferably oriented in an opposed manner to the first channel  628 . Together the first channel  628  and the second channel  629  circumscribe an outer circumference of the cover sheet  656  and the first and second wires  652 ,  654 . 
     A plurality of inwardly-directed first energy directors  624  are circumferentially disposed on the first channel  628  and the second channel  629 , wherein the first energy directors  624  contact the cover sheet  656  and one of the first and second wires  652 ,  654 . A plurality of inwardly-directed second energy directors  634  are circumferentially disposed on the first channel  628  and the second channel  629 , wherein the first energy directors  624  contact only the cover sheet  656 , and are located between the joined ends of the first and second wires  652 ,  654 . 
     The first energy directors  624  project to a common projection height relative to the cover sheet  656  and one of the first and second wires  652 ,  654  when the workpiece  650  is clamped into the vibration welding system  10 . 
     The first energy directors  624  may have any suitable shapes. During vibration welding, the first energy directors  624  act upon the cover sheet  656  and one of the first and second wires  652 ,  654 . The action of the first energy directors  624  causes the cover sheet  656  and the first and second wires  652 ,  654  to become malleable, and the clamping force urges the joining of the cover sheet  656  and one of the first and second wires  652 ,  654 . The second energy director  634  urges the cover sheet  656  into any gap that exists between the butted portions of the first and second wires  652 ,  654 . 
       FIG. 7  schematically shows a cross-sectional bottom-view of another embodiment of a welding pad  720  that includes a first region  722  that includes a channel  728  and a second region  732 . The channel  728  is disposed to accommodate a portion of the wire  44 . The second region  732  is a knurled surface. The channel  728  is formed therein as a continuous arc that preferably includes an insert point and an exit point on a side portion of the welding pad  720 . The face of the welding pad  720  is disposed to physically contact a substrate (not shown) to effect vibration welding of the portion of the wire  44  thereto. This configuration permits a wire feeder, e.g., the wire feeder  50  described with reference to  FIG. 1 , to feed a portion of the wire  44  into the channel  728 , with the portion of the wire  44  bending in the continuous arc and emerging at the exit point. The sonotrode (not shown) can be activated to effect vibration welding of the portion of the wire  44  to the substrate employing the second region  732  to effect the vibration welding with normal force applied to the portion of the wire  44  via the channel  728 . The wire feeder  50  can include a device that trims any excess wire after the vibration welding is completed. 
     While the best modes for carrying out the disclosure have been described in detail, those familiar with the art to which this disclosure relates will recognize various alternative designs and embodiments for practicing the disclosure within the scope of the appended claims.