Patent Description:
As disclosed by <CIT>, lasers have previously been used for mechanically joining aluminum and/or magnesium elements using self-piercing rivets with preheating. Documents <CIT>, <CIT>, <CIT> and <CIT> were cited. Document <CIT> is considered to represent the closest prior art, but falls under Art. <NUM>(<NUM>) EPC, hence is not relevant to the question of inventive step.

Use of lasers for heating in metallic joining processing must be carried out in a light-safe manner so that no scattered radiation from an intense laser beam causes damage to an operator. Previously such processing has been performed in a processing station that is secured against operator access during use so there is no exposure of operators to the laser beams.

The invention provides an improved method for securing a clinch nut to a sheet of AHSS, according to claim <NUM>.

As per a method embodiment, for securing a clinch nut to a sheet of AHSS pierce clinch nuts are fed to the nut ram.

As per a method embodiment, the indexing member is either moved in a rectilinear manner between the heating position and the joining position or pivotally moved between the heating position and the joining position.

As per a method embodiment, the temperature of the AHSS sheet is sensed at its work location from above or below the AHSS sheet.

As per a method embodiment, the controller operates a plurality of the joining assemblies spaced from each other; the controller also operates a parallel kinematic machine (PKM) including: a first support; a tripod having three extendable and retractable struts mounted and extending away from the first support in a converging manner toward each other; and a second support mounted by the three struts spaced from the first support to mount the nut ram that cooperates with the clinch die under the operation of the controller to provide the attachment of the clinch nut to the AHSS sheet; and wherein perpendicular rails mount the PKM for movement under its operation of the controller in horizontal directions that are perpendicular to each other to cooperate with the joining assemblies to provide attaching of pierce clinch nuts to the AHSS sheet at different locations.

As per a method embodiment, the joining assembly and the nut ram are operated between a floor and an upper beam of a framework mounted on the floor.

As per a method embodiment, the joining assembly is operated below the AHSS sheet and the nut ram is operated above the AHSS sheet.

As per a method embodiment, the controller operates a plurality of the joining assemblies mounted on the floor spaced from each other; and a nut ram assembly mounts a plurality of the nut rams and under the operation of the controller cooperates with the joining assemblies to simultaneously provide attaching of pierce clinch nuts to the AHSS sheet at different locations.

As per a method embodiment, one end of a C frame supports the joining assembly and another end of the C frame supports the nut ram that cooperates with the clinch die under the operation of the controller to provide attaching of a clinch nut to the AHSS sheet, and wherein a robot moves the C frame under operation of the controller to provide the attaching of the clinch nut to the AHSS sheet at different locations.

The objects, features and advantages of the present invention are readily apparent from the following detailed description of the preferred embodiments when taken in connection with the referenced drawings.

As required, detailed embodiments and latest mode of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments and modes of operation are merely exemplary of the invention that may be embodied in various and alternative forms and modes. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention that is defined in the appended claims.

With reference to <FIG>, <FIG> and <FIG>, three different embodiments of apparatus <NUM> are illustrated for providing a method of the invention for providing an assembly <NUM> of a pierce clinch nut <NUM>, having an extended pierce form <NUM> and a threaded hole <NUM> therethrough and is secured by a clinch interlock as is hereinafter described to a sheet of AHSS <NUM> as shown in <FIG>. Both the apparatus for providing the method of the invention and the method of the invention will be described in an integrated manner to facilitate an understanding of different aspects of the method of the invention. Also, the AHSS sheet <NUM> has a tensile strength of at least <NUM> mega Pascal or higher. Such, AHSS has particular utility for use in vehicle body-in-white assembly of structural components such as pillars and roof headers. This enables these vehicle structural components to have a relatively thin gauge and thus lightweight construction that enhances vehicle energy efficiency and provides improved occupant safety. Because of the extreme hardness and lack of elongation, i.e. approx. below <NUM> percent, AHSS sheets are generally not workable using conventional mechanical joining methods.

The embodiments of the apparatus <NUM> shown in <FIG> are each disclosed as being within a light-safe work station <NUM> that can be controlled so no operation of laser heating that is involved can be performed unless human access thereof it prevented. However, the work stations <NUM> can be configured so human access thereto during the operation can be permitted as it is hereinafter more fully described. The embodiments of the apparatus <NUM> respectively shown in <FIG>, <FIG> and <FIG> are each mounted on a horizontal support <NUM> such as a "floor", a "factory floor", a "pedestal" or a "floor pedestal" all of which will be covered in connection with reference numeral <NUM> for purposes of this application. The different embodiments of the apparatus <NUM> respectively shown in <FIG>, <FIG> and <FIG> are more specifically identified as 20a, 20b and 20c and may be operated singularly or in combination that will be discussed in providing the assembly <NUM> show in <FIG> with one or more clinch nuts <NUM> secured to the AHSS sheet <NUM> so as to facilitate connection of another component to the AHSS sheet by use of a threaded fastener such as a threaded bolt, threaded stud or the like received by its threaded hole <NUM>.

Each of the work stations <NUM> shown in <FIG> includes at least one joining assembly <NUM>, a plurality of which joining assemblies are part of the embodiments 20a and 20b of <FIG> and <FIG>, and only a single joining assembly with the embodiment of apparatus 20c shown in <FIG>. Each of the embodiments of the apparatus includes a base <NUM> and an indexing member <NUM> mounted on the base for movement parallel to the AHSS sheet <NUM>. The indexing member moves between a heating position where a heating opening <NUM> is located and a joining position where a clinch die <NUM> is spaced from each other along a direction parallel to the AHSS sheet <NUM>. An actuator <NUM> moves the indexing member <NUM> between the heating position shown in <FIG> and <FIG> where its heating opening <NUM> is aligned with a work location <NUM> of the AHSS sheet <NUM> and a joining position shown in <FIG> and <FIG> where a clinch die <NUM> located within the indexing member is aligned with the work location <NUM>.

A laser assembly <NUM> of each embodiment fires a laser beam <NUM> as illustrated in <FIG> through the heating opening <NUM> of the indexing member <NUM> while in the heating position to provide heating of the AHSS sheet <NUM>. Such heating makes the heated work location <NUM> of the AHSS sheet <NUM> more ductile to permit the piercing of the hole and attachment of the clinch nut to the AHSS sheet. Each embodiment of the apparatus <NUM> includes a nut ram <NUM> to which the pierce clinch nuts <NUM> are cyclically fed and which cooperates with the clinch die <NUM> by movement toward each other to attach each clinch nut to the AHSS sheet <NUM> thereby clinching it to the heated work location <NUM> of the AHSS sheet as shown in <FIG> so that a threaded fastener as previously discussed can be connected to the AHSS sheet.

Each embodiment of the apparatus <NUM> shown in <FIG> includes a controller <NUM> that operates the joining assembly <NUM> and the nut ram <NUM> and any other necessary components of the apparatus to provide the attachment of clinch nuts <NUM> to the AHSS sheet <NUM> as the assembly <NUM> shown in <FIG>.

As best illustrated in <FIG> and shown to some extent in <FIG>, each embodiment of the disclosed apparatus is provided with its joining assembly <NUM> including an enclosure <NUM> defining a light-safe chamber <NUM> partially defined by the base <NUM>. The laser assembly <NUM> fires the laser beam <NUM> through an opening <NUM> in the base <NUM> as well as through the heating opening <NUM> in the indexing member <NUM> while the indexing member <NUM> is in the heating position to provide the heating of the work location <NUM> of the AHSS sheet <NUM>. The mounting of AHSS sheet to the index member <NUM> on the base <NUM> as shown in <FIG> is light-safe to prevent excessive radiation emissions from escaping from the light-safe chamber. Further, a detector assembly <NUM> is operated by the controller <NUM> to only permit operation of the laser assembly <NUM> when the AHSS sheet <NUM> is in light-safe contact with the indexing member <NUM> around its heating opening <NUM>. As such, operators can then have safe access to the work station <NUM> for any necessary operational, repair or maintenance function, even when the apparatus is performing the clinch nut attachment as described, without any operator being subjected to any harmful scattered radiation from the laser beam.

As best illustrated in <FIG>, each of the embodiments of the joining assembly <NUM> has its detection assembly <NUM> including a source <NUM> for providing pressurized gas to the light-safe chamber <NUM> of the joining assembly as well as including sensors <NUM> and <NUM> between which a detector <NUM> is located to detect a predetermined gas movement between the sensors which is indicative of a lack of light-safe contact with the indexing member around its heating opening <NUM> with the AHSS sheet <NUM> in order to provide a signal to the controller <NUM> that prevents the laser assembly <NUM> from the laser beam <NUM> when the laser is activated. The laser is supplied from a laser generator <NUM> to a collimator <NUM> that fires the laser beam <NUM> through the base opening <NUM> and the heating opening <NUM> of the indexing member to the work location <NUM> of the AHSS sheet <NUM> as previously described.

The clinch nuts attached by the apparatus and method are disclosed as pierce clinch nuts <NUM> that pierce through and form an interlock connection with the AHSS sheet <NUM> as is hereinafter more fully described, with the laser heating providing the AHSS sheet <NUM> with sufficient ductility to permit the piercing of the hole and attachment of the clinch nut.

As illustrated in <FIG>, the joining assembly <NUM> includes a slideway <NUM> that supports the indexing member <NUM> on the base <NUM> for rectilinear movement, in a light-safe manner as discussed above, between its heating position shown in <FIG> and its joining position shown in <FIG> under the operation of the actuator <NUM> which may be of any suitable type such as an air cylinder or a solenoid directly connected or through a linkage to the indexing member.

It is also possible as shown in <FIG> for the joining assembly <NUM> to have its indexing member <NUM> supported on the base <NUM> by a pivotal connection <NUM> for pivotal movement, in a light-safe manner as discussed above, between its heating position of <FIG> and its joining position of <FIG>. Furthermore, as also shown in <FIG>, the indexing member may include a die insert <NUM> that allows the clinch die <NUM> to be replaced due to wear or for switching the types of clinch nut utilized for the construction of the clinch dies needed for the production of jobs being performed.

As also shown in <FIG>, the joining assembly includes a temperature sensor <NUM> for sensing the temperature of the work location <NUM> of the AHSS sheet <NUM> from either top or bottom side of the AHSS sheet through the heating opening <NUM> of the indexing member <NUM>. This temperature sensing may be used to determine the extent of heating for performing any production job being executed. As shown in the embodiment of <FIG> whose structure and operation is described later, it is also possible for the temperature sensor <NUM> to sense the temperature of work location <NUM> from above on its side that faces away from the indexing member of the joining assembly <NUM>. With either embodiment, it is also possible for the sensed temperature to control the extent of laser heating by operation of the controller <NUM> if such control is warranted.

With reference to <FIG>, the embodiment of apparatus 20a includes a plurality of the joining assemblies <NUM> mounted on the horizontal support <NUM> provided by the factory floor. Laser heating provided by the apparatus 20a heats the AHSS sheet <NUM> to provide the mechanical joining of the clinch nut to the AHSS sheet as is hereinafter more fully described. The laser generator <NUM> through a beam splitter feeding fiber optic cables <NUM> feeds the laser to the laser collimators (identified as <NUM> in <FIG>) to selectively provide heating at a plurality of work locations respectively aligned with the plurality of joining assemblies <NUM>.

Apparatus 20a shown in <FIG> also includes a parallel kinematic machine (referred to as a PKM) <NUM> that is mounted by a schematically illustrated carriage supported riser <NUM> on horizontal rails <NUM> and <NUM> that extend in perpendicular directions to each other on a framework <NUM> that is itself supported on the factory floor <NUM> and has an upper beam <NUM> on which the support is provided. The PKM <NUM> supports the nut ram <NUM> that cooperates with the clinch die <NUM> (<FIG>) of the joining assembly <NUM> to provide the joining by piercing a hole and clinching the clinch nut to the AHSS sheet, and the nut ram <NUM> is movable in horizontal directions perpendicular to each other along the rails <NUM> and <NUM> to different work locations while the operation of struts of the PKM by extension and retraction moves the nut ram <NUM> provides the clinch nut attachments. Furthermore, the nut ram <NUM> cyclically feeds pierce cinch nuts <NUM> for the joining operation. A feeder <NUM> shown on the riser <NUM> cyclically feeds the pierce clinch nuts <NUM> to the nut ram <NUM> and may be of any conventional type such as the feeders disclosed by the <CIT> of Mark A. Savoy et al. entitled PROGRAMMABLE APPARATUS AND METHOD FOR VEHICLE BODY PANEL AND CLINCH NUT ATTACHMENT or by the <CIT> of Phillip J. Morgan entitled VEHICLE BODY SHEET METAL CLINCH NUT FEEDER. This pierce clinch nut feeding is shown in <FIG> held between spring fingers <NUM> and against a positioning stop <NUM> of the nut ram <NUM>.

With continuing reference to <FIG>, the riser <NUM> of PKM <NUM> connects a first support <NUM> thereof to the carriage <NUM> that is supported for movement in perpendicular directions by the perpendicular rails <NUM> and <NUM> to a selected position under operation of the controller <NUM>. Extendable and retractable struts <NUM> of the PKM <NUM> project from the first support <NUM> to a second support <NUM> to provide a tripod <NUM> arrangement with the second support mounting the nut ram <NUM> for rotation and angular positioning that permits the operation at any required orientation in cooperation with the joining assembly <NUM> as previously described. The struts <NUM> may be extendable and retractable in any suitable manner such as disclosed by <CIT>. under the title WORK STATION AND METHOD FOR JOINING METALLIC SHEETS. More specifically, the struts <NUM> may each be embodied by a roller screw having: an upper end pivotally connected to the first support <NUM> of the PKM and a lower end pivotally connected to the second support <NUM>, an elongated screw, a nut including a planet carrier and a plurality of threaded rollers rotatable on the planet carrier and meshed with the screw such that relative rotation between the screw and the nut changes the length of the strut as disclosed in the referenced application.

With reference to <FIG>, the embodiment of the apparatus 20b includes at least one joining assembly <NUM> mounted on the factory floor <NUM>. With a single joining assembly <NUM>, the AHSS sheet <NUM> is positionally indexed to provide clinch nut connection at different locations. It is also possible for this embodiment like the embodiment of <FIG> to have a plurality of the joining assemblies <NUM> mounted on the factory floor <NUM> and fed by the laser generator <NUM> through the cables <NUM>. These joining assemblies <NUM> are operated by the controller <NUM> in cooperation with a nut ram assembly <NUM> including a platen <NUM> that supports one or a plurality of the nut rams <NUM>, each of which that has a nut feeder <NUM>. The platen <NUM> is movable vertically by one or a plurality of operators <NUM> supported on framework <NUM> at its upper beam <NUM> for vertical to provide the piercing and clinching for attachment of the clinch nuts as shown in <FIG>. When there is a single joining assembly <NUM> this embodiment will perform one clinch nut piercing at a time with a single nut ram <NUM>. The AHSS sheet <NUM> can then be horizontally indexed as needed to perform the pierce clinch nut connection at other locations. Furthermore, when there are a plurality of the joining assemblies <NUM>, this embodiment can sequentially pierce a hole and clinch the clinch nut <NUM> to the AHSS sheet <NUM> at each joining assembly. Also, each nut ram <NUM> of this embodiment can be angularly operated on platen <NUM> as needed by cams to control their angularity of operation relative to the vertical movement provided by the operator <NUM>.

With reference to <FIG> and <FIG>, the apparatus 20c includes a C frame <NUM> having one end <NUM> supporting the joining assembly <NUM> where in a laser beam is provided to heat the AHSS sheet <NUM>, and the C frame <NUM> has another end <NUM> that supports the nut ram <NUM>. More specifically, a housing <NUM> of the C frame <NUM> supports the laser collimator <NUM> and, as shown best in <FIG>, has its laser beam <NUM> projecting downwardly from the collimator toward a first mirror <NUM> within the light-safe chamber <NUM> defined by the housing. That first mirror <NUM> reflects the laser beam <NUM> at a <NUM> degree angle horizontally toward a second mirror <NUM> for reflection <NUM> degrees upwardly toward the indexing member <NUM> which functions generally the same as the previously described embodiment of <FIG> by pivoting between its heating position and its joining position. Extension and retraction of the piston connecting rod <NUM> of actuator <NUM> in this embodiment pivots the indexing member <NUM> about pivotal connection <NUM> to move between the heating position and the joining position.

With further reference to <FIG>, the apparatus 22c includes a roller screw <NUM> that moves the nut ram <NUM> vertically, and a robot <NUM> shown in <FIG> supports and moves the C frame <NUM> to and from different locations.

The pierce clinching operation of each embodiment begins as shown in <FIG> with clinch die <NUM> located in the indexing member <NUM> while the indexing member is in the joining position shown in <FIG>. While in this position, the chamber <NUM> remains light-safe since the clinch die <NUM> mounted in the indexing member <NUM> is covering the opening <NUM>. The indexing member then moves to the heating position so that the AHSS sheet can be heated by the laser beam. Actuation of the nut ram <NUM> as shown in <FIG> brings the piercing form <NUM> of the clinch nut <NUM> into contact with the heated AHSS sheet <NUM>. Continuing downward motion of the nut ram <NUM> moves pierce form <NUM> into the AHSS sheet to create a pierced hole as shown in <FIG>. The pierced slug is discarded through an opening in the clinch die <NUM>. Simultaneous with the creation of the hole in the AHSS sheet, as the nut ram <NUM> continues downward the heated AHSS sheet <NUM> area surrounding the opening of the clinch die <NUM> starts to flow into an undercut <NUM> of the clinch nut <NUM> as shown in <FIG>. As the nut ram <NUM> reaches the end of its downward movement the AHSS sheet <NUM> continues to flow into the undercut so as to create an interlock <NUM> and completely fill the area of the undercut <NUM> and securely attach the clinch nut <NUM> to the AHSS sheet <NUM> as shown in <FIG> and <FIG>. Thereafter the ram <NUM> is moved upward to its start position where after the cycle repeats itself.

It is to be understood that the piercing form <NUM> may be of a configuration i.e. round, square, oblong or contoured.

During vehicle body assembly for which this invention has particular utility, the sheet <NUM> of AHSS to which the clinch nut <NUM> is attached will normally have a thickness of <NUM> to <NUM> millimeters and will be heated to an approximate temperature of <NUM>° to <NUM>° C. The heating time depends on the thickness but will normally be about <NUM> to <NUM> seconds and the indexing time will be about <NUM> to <NUM> of a second, the time to perform the attachment of the clinch will be about <NUM> to <NUM> seconds and the laser will be of any type of laser that is able to accomplish these functions as stated. Further, even if operators are located within station <NUM> as shown in <FIG>, the operation will be light-safe due to the containment of scattered radiation from the laser beam as described. Furthermore, the laser utilized may be a fiber laser or a diode laser. Also, during the laser heating and mechanical joining, any suitable but not shown clamping or the like may be used to position the AHSS sheet <NUM> for the operation.

The controller <NUM> shown and described above in connection with <FIG> is configured to provide the operation shown by the flow chart <NUM> of <FIG>. As described above, this operation begins by step <NUM> as the indexing member is moved to the heating position and continues with step <NUM> as the laser provides the light-safe heating of the work location of the AHSS sheet. The following movement of the indexing member to the joining position as shown by step <NUM> is then followed by the nut ram and die operation of step <NUM> to connect the clinch nut to the sheet of AHSS.

Claim 1:
A method for securing a clinch nut (<NUM>) to a sheet of AHSS (<NUM>) comprising:
positioning an AHSS sheet (<NUM>) adjacent a joining assembly (<NUM>) including an indexing member (<NUM>) movable parallel to the AHSS sheet and having a heating opening (<NUM>) and a clinch die (<NUM>) spaced from each other along a direction parallel to the AHSS sheet;
firing a laser beam (<NUM>) through the heating opening (<NUM>) of the indexing member (<NUM>) at a heating position thereof to heat a work location of the AHSS sheet;
moving the indexing member (<NUM>) parallel to the AHSS sheet to a joining position where its clinch die (<NUM>) is aligned with the work location of the AHSS sheet; and
using a controller (<NUM>) to operate a nut ram (<NUM>) to which clinch nuts, each of which has a threaded opening, are fed to align with the clinch die when the indexing member (<NUM>) is in the joining position to attach a clinch nut to the AHSS sheet at its heated work location so a threaded fastener can be connected to the clinch nut; wherein the laser beam (<NUM>) is fired from within a light-safe chamber (<NUM>) through an opening (<NUM>) in said chamber (<NUM>) and then through the heating opening (<NUM>) of the indexing member (<NUM>) while in the heating position to provide the heating of the work location of the AHSS sheet, and wherein the laser beam firing is only permitted by the controller (<NUM>) when presence of the AHSS sheet is detected closing the heating opening (<NUM>) of the indexing member (<NUM>) around its heating opening (<NUM>) with light-safe contact.