Abstract:
A novel two-stage clamp used in testing a device-under-test (DUT) is herein presented. The two-stage clamp provides two sequential actuations via one linear force, and includes clamps moving in multiple different directions. The two-stage clamp uniquely uses the DUT being clamped to provide the linkage and timing for the two-stage actuation of clamps moving in three different directions.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates generally to electrical device testing, and more particularly to a two-stage device-under-test (DUT) clamp with DUT-linked double action for testing an electrical device. 
   Final level test of electrical devices often involves insertion probing of one or more receptacles, pressing buttons, and/or activating switches on the device. For example, a cellular phone often includes a receptacle configured as an array of signal points on the device under test (hereinafter referred to as the “system connector”), an audio receptacle into which a headset audio plug is inserted or a charger receptacle into which an A/C charger plug is inserted to charge up the device, and a numeric keypad comprising a set of buttons used for dialing. During final level test, the functionality of each of these features of the phone must be tested prior to shipping. 
   Accordingly, various tests are performed on the device (hereinafter referred to as “device under test” or “DUT”). Typically at least one or more tests require insertion probing of one or more of the DUT receptacles. Insertion probing involves the insertion of a probe into a mating DUT receptacle such that the probe and DUT receptacle make electrical contact. The electrical contact is the means through which the probe stimulates and/or receives measurement signals from the DUT. In addition, automated button pressing is required to test the operation of the keypad. Typical final level testing of electronic devices is performed in an automated environment, often using robotic actuators. 
   In order to accurately test a DUT in such an automated environment, several conditions must be met. First, accurate location of the DUT relative the testing probes is required for proper probing and button location. Second, the fixture that holds the DUT must firmly lock the DUT into position in order to ensure accurate probing/button-pressing force, to prevent cosmetic damage to the DUT, and to prevent the DUT from moving around during test resulting in electrical and RF signal loss and falsely failing tests. 
   In order to meet these requirements, the DUT is typically clamped into a known position relative the robotic tester. 
   Some prior art clamping solutions attempt to clamp the DUT against a fixture from the top of the DUT. However, oftentimes this configuration is not available as a clamping option due to risk of cosmetic damage to the DUT being clamped. 
   DUT clamps that clamp from below the DUT typically require the clamp walls to be parallel and opposing each other, and that the linear motion of the clamp be perpendicular to the wall planes. This configuration may not be feasible with certain DUT designs. 
   In addition, some prior art clamping solutions often use separate actuators for performing individual clamping motions. However, more actuators add complexity, cost, and tester space. 
   Finally, some prior art clamping solutions use custom-made link parts, adding complexity to the design. 
   Accordingly, although the idea of clamping a DUT is itself conceptually straightforward, the design of a clamping mechanism that is used for the purpose of fixing a DUT in place for insertion probing and button-pressing testing requires several important considerations. First, the DUT must be accurately located within the clamp to allow small probe points (e.g., the pins of a system connector) to be accurately probed. Second, clamping should be performed without risk of cosmetic damage to the DUT. Finally, the clamp should be designed with minimal complexity, cost, and space. 
   SUMMARY OF THE INVENTION 
   The present invention is a two-stage device-under-test (DUT) clamp with DUT-linked action. The preferred embodiment of the invention uniquely provides a two-stage clamp that provides two sequential actuations via one linear force, with clamps moving in multiple different directions. The clamp of the invention uniquely uses the DUT being clamped to provide the linkage and timing for the two-stage actuation of clamps moving in three different directions. 
   The present invention addresses three common problems when designing a clamp for such a DUT. This assembly is able to clamp a DUT with limited clamping features in the battery grave. Additionally, this assembly can clamp a DUT with clamping features on non-parallel faces of the DUT, and faces non-perpendicular to the linear actuation motion. The assembly also uses less space than conventional multiple direction clamping mechanisms as well as multiple actuation clamping mechanisms. 
   In an illustrative embodiment of the invention, the DUT is a wireless phone that is charged in a battery grave. The assembly locates and clamps the DUT from within the battery grave. Using the battery grave increases DUT location accuracy and at the same time minimizes the risk of cosmetic damage to the DUT case. 
   The clamp design of the invention requires only one linear actuator, which, using the DUT as part of the linkage, actuates three different clamping motions in three different directions. The multiple clamping forces lock the DUT firmly in place for probing and button pushing in all directions without risk of any movement of the DUT. 
   The invention is ideal for use in a test fixture during final level device test in which the DUT requires some insertion probing of a receptacle and/or button-pushing or switch activation. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of this invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: 
       FIG. 1  is an isometric view of a clamping assembly implemented in accordance with the invention; 
       FIG. 2  is a rear isometric view of an example cellular phone DUT; 
       FIG. 3  is a rear isometric view of the clamping assembly of  FIG. 1 and a  DUT positioned over the clamping assembly, with the clamp disengaged; 
       FIG. 4  is a rear view of the clamping assembly of  FIG. 1 and a  DUT positioned over the clamping assembly with the clamp disengaged; 
       FIG. 5  is a rear view of the clamping assembly of  FIG. 1 and a  DUT positioned over the clamping assembly with the first actuation stage completed wherein the front clamp is engaged and the rear clamp is disengaged; 
       FIG. 6  is a rear view of the clamping assembly of  FIG. 1 and a  DUT positioned over the clamping assembly with both actuation stages completed wherein both the front clamp and rear clamp are engaged; and 
       FIG. 7  is a flowchart of a method for clamping a DUT. 
   

   DETAILED DESCRIPTION 
   Turning now to the drawings,  FIG. 1  illustrates a preferred embodiment of a two-stage device-under-test (DUT) clamp assembly  10  with DUT-linked double action for testing an electrical device  30 , hereinafter device under test (DUT). As illustrated, the clamp assembly  10  includes a datum tower  12 , an active clamp  14 , and two rotating clamps  22   a ,  22   b . The datum tower  12  is stationary, and the active clamp  14  moves in a linear motion relative the datum tower  12  as indicated by arrow A. The rotating clamps  22   a ,  22   b  rotate in opposite directions through a plane parallel to the plane defined by the linear motion (indicated by arrow A) of the active clamp  14 . In the preferred embodiment, the rotating clamps  22   a ,  22   b  rotate 30° around respective clamp pivots  25   a ,  25   b , implemented with a pin as shown. Each of the datum tower  12 , active clamp  14 , and rotating clamps  22   a ,  22   b  are positioned within the DUT battery grave  32  when the DUT  30  is loaded on the clamp assembly  10 . 
     FIG. 2  shows a rear isometric view of an example DUT  30 , in this example a cellular phone. The DUT  30  itself is encased in a DUT case  40 . As used herein, the front  41  of the DUT case  40  is considered the face of the cellular phone on which the keypad (not shown) is accessible, the rear  42  of the DUT case  40  is considered the side of the cellular phone where the battery grave  32  is accessible, the top  43  of the DUT case  40  is considered the face of the cellular phone located at the top of the case when the numbers/letters on the keypad are upright, the bottom  44  of the DUT case  40  is considered the face of the cellular phone located at the bottom of the case when the numbers/letters on the keypad are upright, the right  45  of the DUT case  40  is considered the right side face of the cellular phone when looking at the front face  41 , and the left  46  of the DUT case  40  is considered the left side face of the cellular phone when looking at the front face  41 . 
   As shown in  FIG. 2 , the DUT case  40  includes a battery grave  32  on the bottom rear of the DUT case  40 . The battery grave  32  is formed as a sunken box within the DUT case  40 , including a battery grave floor  31  parallel to the front  41  and rear  42  faces of the DUT case  40  and sunk approximately ⅜ inch below the rear face  42  of the DUT case  40 , two side walls  34   a ,  34   b  parallel to the right  45  and left  46  faces of the DUT case  40 , and a top wall  36  parallel to the top face  43  of the DUT case  40 . During use, the purpose of the battery grave  32  is to seat one or more batteries (not shown) in electrical contact with the DUT circuitry to provide power to the DUT  30 . When the batteries are seated in position, a cover (not shown) is attached over the battery grave  32  to protect the batteries and to prevent them from falling out of the DUT case  40  during use. During test, the cover is removed and the battery grave  32  is empty of batteries. 
   The features of the battery grave  32  that allow the cover to snap into place and remain fixed in position are used in the present invention to clamp the DUT  30  into place for DUT final level test. To this end, the DUT  30  includes a pair of flanges  35   a ,  35   b  located at the top wall  36  of the battery grave  32  that project over a portion of the battery grave  32  flush with the rear face  42  of the DUT case  40 . The DUT case  40  also includes a pair of slots  38   a ,  38   b , one each located at the bottom of the respective side walls  34   a ,  34   b  of the battery grave  32 . 
   Turning now to the clamp assembly  10 , shown in  FIG. 1 , the active clamp  14  includes a block  11  that supports a pair of tabs  15   a ,  15   b  located at the end (hereinafter “clamping end”) of the block  11  that are designed to be inserted into the battery grave  32  of the DUT case  40 . These tabs  15   a ,  15   b  are designed to slide beneath the pair of flanges  35   a ,  35   b  at the top wall  36  of the DUT battery grave  32  when the active clamp  14  is actuated. 
   The datum tower  12  is a stationary block that supports a pair of rotating clamps  20   a ,  20   b  that are designed to fit within the respective slots  38   a ,  38   b  on the side walls  34   a ,  34   b  of the battery grave  32  when rotated into final engagement position, as discussed hereinafter. 
   Operation of the clamp assembly  10  is now described in conjunction with  FIGS. 3 ,  4 ,  5 , and  6 . In operation, the DUT  30  encased in DUT case  40  is loaded over the clamping end of both the datum tower  12  and active clamp  14  such that the clamping end of the clamp assembly  10  is positioned within the battery grave  32  of the DUT case  40 , as shown in  FIGS. 3 and 4 .  FIG. 3  is an isometric view of the positioning of the DUT case  40  over the clamp assembly  10  prior to engagement of the clamps.  FIG. 4  shows the rear,view of the DUT case  40  with the clamp assembly  10  in position for engagement but as yet disengaged. As shown in  FIGS. 3 and 4 , in preparation for engagement of the clamp assembly  10  with the DUT  30 , active clamp tabs  15   a ,  15   b  are positioned in proximity to and facing the respective battery grave top wall flanges  35   a ,  35   b  of the DUT case  40 , and rotating clamps  20   a ,  20   b  are positioned in proximity to but not inserted in the respective side wall slots  38   a ,  38   b  of the DUT case  40  near the bottom of the DUT battery grave  32 . The active clamp tabs  15   a ,  15   b  and rotating clamps  20   a ,  20   b  are each positioned within the battery grave  32  such that the clamping end of the active clamp  14  and datum tower  12  abut against the floor  31  of the battery grave  32 . At this point, the active clamp tabs  15   a ,  15   b  are not yet underneath the battery grave top wall flanges  35   a ,  35   b , and the rotating clamps  20   a ,  20   b  are in their non-rotated position and therefore not inserted in the respective DUT case slots  38   a ,  38   b.    
     FIG. 5  illustrates the first stage of actuation of engagement of the DUT case  40  by the clamp assembly  10 . In operation, once the battery grave  32  of the DUT  30  is positioned over the clamping end of the assembly  10 , as shown in  FIGS. 3 and 4 , a linear actuator  13  (pneumatic or otherwise, but attachable to block arm  16  which is in turn attached to block  11 ) then actuates the active clamp  14 , moving it linearly along the path indicated by arrow A in the direction toward the top wall  36  of the battery grave  32 . This causes the active clamp tabs  15   a ,  15   b  to begin moving under the battery grave top wall flanges  35   a ,  35   b . Actuation of the active clamp  14  continues until the active clamp tabs  15   a ,  15   b  engage the battery grave top wall  36 , whereupon the ends of the active clamp tabs  15   a ,  15   b  are positioned underneath the battery grave top wall flanges  35   a ,  35   b . This action clamps the top wall  36  of the DUT case  40 , as shown in  FIG. 5 , and the first stage of actuation in which the active clamp  14  is engaged and the rotating clamps  20   a ,  20   b  are still disengaged is complete.  FIG. 7 , step  101  describes the first stage of actuation. 
   Once the active clamp  14  is engaged, the second stage of actuation begins as described in  FIG. 7 , step  102 . To this end, after the active clamp  14  engages the front wall  36  of the DUT battery grave  32 , the actuator (not shown) continues to move the active clamp  14  forward in the same direction, thereby moving the DUT  30  forward with it. Because the datum tower  12  holding the rotating clamps  20   a ,  20   b  remains stationary, notches  37   a ,  37   b  near the bottom of the battery grave  32  engage the rotating clamp engagement members  22   a ,  22   b  of the rotating clamps  20   a ,  20   b . As the actuator continues to move the DUT linearly along the same direction, the notches  37   a ,  37   b  continue to further engage the rotating clamps  20   a ,  20   b , causing the rotating clamps  20   a ,  20   b  to rotate such that the rotating clamp hooks  24   a ,  24   b  respectively rotate outward towards the side walls  34   a ,  34   b  of the battery grave  32  and into the slots  38   a ,  38   b  in the side walls  34   a ,  34   b  of the DUT&#39;s battery grave  32 . The actuator continues to move the DUT  30  linearly forward until the rotating clamps  20   a ,  20   b  are fully within the respective slots  38   a ,  38   b  of the battery grave  32 , as illustrated in FIG.  6 . At this point both stages of actuation of the clamp assembly  10  is complete, and all clamps  15   a ,  15   b ,  20   a ,  20   b  are fully engaged with the DUT case  40 . 
   As illustrated, the DUT case  40  is clamped in three different directions (i.e., one on the top wall of the battery grave  32  and one on either of the side walls  34   a ,  34   b  of the battery grave  32 ) and movement of the DUT  30  in any direction is prevented. 
   To release the DUT  30  from the clamp assembly  10 , the actuator moves ( FIG. 7 , step  103 ) the active clamp  14  in the reverse linear direction to disengage the active clamp tabs  15   a ,  15   b  from underneath the flanges  35   a ,  35   b  of the top wall  36  of the DUT battery grave  32 . Springs (not shown) which bias the rotating clamps  20   a ,  20   b  to their original non-rotated position rotate the rotating clamps out of the slots  38   a ,  38   b , and the DUT  30  may be removed from the clamp assembly  10 . 
   It is clear from the above detailed description that the present invention offers several advantages over prior art clamping techniques. First, the clamp requires only one actuator and one actuating motion yet clamps in multiple directions, including on non-parallel faces of the DUT. Secondly, the clamp traps and clamps the DUT from the rear, using features already present in the DUT. This prevents cosmetic damage to the DUT case, and simplifies the DUT case design since additional features and design are not required for clamping. Finally, the DUT itself is used as the linkage between two clamp actuation stages. 
   Although this preferred embodiment of the present invention has been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. It is also possible that other benefits or uses of the currently disclosed invention will become apparent over time.