Abstract:
A barrel lock for locking various utilities devices such as valves, meters, or enclosures associated with the control or distribution of gas, water or electricity includes a shank with a single driven ball that can be forced radially outward from the shank to lock onto a cap-like retainer such that the utilities device is restrained between the retainer and an enlarged head of the shank. Preferably, only a single driven ball is used to concentrate the clamping force at a single point, thereby creating an exceptionally high clamping pressure. For even greater clamping force, an accurately and strategically positioned end stop allows a drive ball to push against the driven ball at an extremely shallow angle of attack while preventing the two balls from accidentally toggling over center and irreversibly locking up. The barrel lock has infinite variable adjustment in an axial direction to fit a wide variety of devices.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The subject invention generally pertains to barrel locks and more specifically to a barrel lock actuated by a ball and mandrel. 
   2. Description of Related Art 
   Barrel locks are typically used for preventing unauthorized personnel from tampering with public utility devices such as valves and meters for gas, water and electricity. 
   Many barrel locks comprise a shank with a head at one end and a locking mechanism at the opposite end. The locking mechanism typically includes two or more balls that can be forced to protrude radially outward beyond the outside diameter of the shank. A mandrel inside the shank, and actuated by a separate key, forces the balls outward or allows the balls to retract depending on which direction the mandrel is rotated. 
   To lock a utilities device, the device requires a feature for receiving the barrel lock. A gas valve, for instance, may include a tab extending from the valve&#39;s housing and another one extending from the valve&#39;s handle. Each tab would have a hole so that when the handle is rotated to a closed position, the holes become aligned to receive the shank of the barrel lock, which inhibits the handle from rotating the valve back open. 
   To prevent someone from simply withdrawing the shank from within the holes, the end of the shank with the locking mechanism protrudes beyond the two tabs, and a close-fitting, cap-like retainer is placed over that end of the shank and locked there. In order to place the retainer on the end of the shank, the balls first need to be retracted within the shank, due to the close fitting clearance between the outside diameter of the shank and the inside diameter of the retainer. Once the retainer is on the end of the shank, the key is used to rotate the mandrel, which forces the balls outward to extend into an annular groove that is inside the retainer, thereby locking the retainer to the shank and capturing the two tabs between the retainer and the head of the barrel lock. 
   There is a problem, however, with such barrel locks. There are a wide variety of utilities devices but not nearly as many different size barrel locks, so in some applications, the barrel lock may not fit as tightly as it should. Excessive axial clearance may exist underneath the shank&#39;s head or between one of the valve&#39;s tabs and the retainer. If sufficiently large, such clearance could allow a pry bar to be inserted underneath the head or the retainer to force the barrel lock apart. 
   To address this problem, some retainers have two axially spaced apart annular grooves, so the axial distance between the head and the retainer is determined by which groove is selected to receive the balls of the locking mechanism. Although this provides some adjustability, the discrete steps of adjustment are far too crude to effectively solve the problem. Consequently, a need still exists for an adjustable barrel lock that can tightly fit a wide variety of devices. 
   SUMMARY OF THE INVENTION 
   To provide a better barrel lock, an object of some embodiments is to provide a barrel lock with infinite axial adjustment. 
   Another object of some embodiments is to maximize a barrel lock&#39;s radial thrust by having one ball drive another to an extremely shallow angle made possible by providing the drive ball with an accurately and strategically positioned end stop. 
   Another object of some embodiments is to provide a barrel lock with an angled end stop for the drive ball so that the driven ball is forced radially outward an extra distance in reaction to the drive ball encountering the end stop&#39;s angled surface. 
   Another object of some embodiments is to enable a barrel lock to form its own ball-locking dimple for infinite axial adjustment, and later allow the barrel lock to be withdrawn and reinstalled using the same dimple or forming another one at a different axial location. 
   Another object of some embodiments is to use the rotational movement of a drive ball and a driven ball to help draw the shank of the barrel lock into its retainer. 
   Another object of some embodiments is using the binding nature of hardened steel to help lock a retainer to a shank of a barrel lock. 
   Another object of some embodiments is to adjust the axial spacing between the retainer and the head of the barrel lock&#39;s shank by rotating the shank relative to the retainer, and then locking the shank in place by rotating a mandrel inside the shank. 
   Another object of some embodiments is to provide the shank with a thread-biting tooth that can engage internal threads or a spiral groove inside the retainer to help lock the shank and retainer together. 
   Another object of some embodiments is to provide a retainer with a spiral groove into which a driven ball can be forced. The ball engaging the spiral groove provides three functions: 1) it provides a way to axially adjust the barrel lock, 2) it helps hold the shank and retainer together, and 3) it gets progressively tighter as the barrel lock is driven to its locked position. 
   Another object of some embodiments is to screw a shank into a retainer to axially adjust and clamp a barrel lock, and then rotate a mandrel inside the shank to lock the retainer and shank in position. 
   Another object of some embodiments is to use a barrel lock to lock the door of an electrical enclosure, wherein the barrel lock draws the door progressively tighter as the barrel lock it driven to its locked position. 
   Another object of some embodiment is to push a single driven ball into engagement with a retainer so as to concentrate the contact pressure against the retainer, whereby the concentrated pressure promotes desirable binding and/or dimpling that helps lock the device. 
   Another object of some embodiment is to maximize the radial thrust of the driven ball by minimizing the ratio of the driven ball&#39;s radial movement to the corresponding rotation of the ball-driving mandrel. 
   Another object of some embodiments it to promote dimpling of the retainer by making the retainer softer than the driven ball, yet make both of them of steel for security. 
   One or more of these and/or other objects of the invention are provided by a high pressure, radially extendable ball style barrel lock that includes a shank that fits into a retainer. The barrel lock includes a feature that makes the lock infinitely adjustable (as opposed to incrementally) within a limited range of adjustability. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross-sectional view taken along a longitudinal centerline of a barrel lock that is about to secure two parts. 
       FIG. 2  is a cross-sectional view similar to  FIG. 1  but showing the barrel lock assembled but not yet secured. 
       FIG. 3  is a cross-sectional view similar to  FIG. 2  but showing the barrel lock secured. 
       FIG. 4  is a cross-sectional view similar to  FIGS. 1-3  but showing the shank being removed after having once been locked onto its retainer. 
       FIG. 5  is an enlarged view of  FIG. 3  showing various angles and dimensions. 
       FIG. 6  is similar to  FIG. 5  but showing relative motion of the parts. 
       FIG. 7  is a cross-sectional view similar to  FIG. 3  but showing another barrel lock embodiment. 
       FIG. 8  is a cross-sectional view similar to  FIGS. 3 and 7  but showing yet another barrel lock embodiment. 
       FIG. 8   a  shows one possible arrangement for the balls of the barrel lock of  FIG. 8 . 
       FIG. 8   b  shows another possible arrangement for the balls of the barrel lock of  FIG. 8 . 
       FIG. 9  is a cross-sectional view of another barrel lock embodiment in an unlocked position. 
       FIG. 10  is a cross-sectional view similar to  FIG. 9  but showing the barrel lock in a locked position. 
       FIG. 11  is a cross-sectional view of another barrel lock embodiment in an unlocked position. 
       FIG. 12  is a cross-sectional view similar to  FIG. 11  but showing the barrel lock in a lightly tightened position. 
       FIG. 13  is a cross-sectional view similar to  FIG. 12  but showing the barrel lock in a firmly locked position. 
       FIG. 14  is a cross-sectional view of another barrel lock showing its shank about to be inserted into its retainer. 
       FIG. 15  is a cross-sectional view similar to  FIG. 13  but showing the shank being screwed into its retainer to axially adjust the barrel lock. 
       FIG. 16  is a cross-sectional view similar to  FIGS. 13 and 14  but showing the shank locked into its retainer. 
       FIG. 17  is a cross-sectional view of yet another barrel lock with its driven ball in a retracted position. 
       FIG. 18  is a cross-sectional view similar to  FIG. 16  but showing the driven ball in an intermediate position. 
       FIG. 19  is a cross-sectional view similar to  FIG. 17  but showing the driven ball in an extended position. 
       FIG. 20  is a perspective view of a retainer and clip used in the barrel lock of  FIGS. 17-19 . 
       FIG. 21  is a cross-sectional view corresponding to  FIG. 19  but showing more of the box. 
       FIG. 22  is a cross-sectional view corresponding to  FIG. 17  but showing more of the box. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A barrel lock  10 , shown in  FIGS. 1-6 , comprises a shank  12  and a retainer  14  that can be locked together to limit the relative movement of two parts  16  and  18  of a utilities device  20 . Examples of device  20  include, but are not limited to, a valve, meter, or enclosure associated with the control or distribution of gas, water or electricity. 
   For the sake of example, the invention will be described with reference to device  20  being a valve that has a first tab (part  16 ) rigidly extending from a body of the valve and a second tab (part  18 ) extending from the valve&#39;s handle, which is used for operating the valve. Parts  16  and  18  each have a hole  22  and  24  that when aligned allow shank  12  to be inserted through the holes. Inserting shank  12  through the tabs&#39; holes inhibits the valve&#39;s operation, and locking retainer  14  onto shank  12  prevents unauthorized removal of shank  12 . For security, both shank  12  and retainer  14  are preferably made of steel or some other tamper resistant metal. 
   In some embodiments of the invention, shank  12  comprises a head  26  at an upper end  28  of the shank, and a locking mechanism  30  at a lower end  32 . Upper end  28  is open to a shank bore  34  inside the shank. A drive ball  36 , a driven ball  38  (both preferably made of tamper resistant steel), and a drive pin  40  can be disposed inside shank  12  by inserting them through upper end  28 . Drive pin  40  has a threaded portion  42  between a drive end  44  and a driven end  46  of pin  40 . The pin&#39;s threaded portion  42  screws into a threaded bore  48  of shank  12 . Driven ball  38  can move within a side hole  50  in shank  12 , and drive ball  36  is situated between driven ball  38  and drive end  44 . Turning pin  40 , via a key removably attached to driven end  46  (see U.S. Pat. No. 5,542,273), forces driven ball  38  to protrude radially outward from within shank  12  or allows driven ball  38  to retract, depending on which direction pin  40  is rotated. Drive ball  36  significantly increases the outward thrust of driven ball  38  for reasons that will be explained later. O-rings  52  and  54  can be added to protect the inner workings of shank  12  from dirt, moisture and other contaminants. Additional basic information that may apply to barrel lock  10  can be found in U.S. Pat. No. 5,542,273, which is specifically incorporated by reference herein. 
     FIGS. 1-4  could be considered a typical sequence of operation of barrel lock  10 . In  FIG. 1 , parts  16  and  18  are aligned at the valve&#39;s closed position so that shank  12  can be inserted through holes  22  and  24 . Shank  12  is inserted through the holes, and retainer  14  is placed over the shank&#39;s lower end  32 . In order to do this, drive pin  40  may need to be partially unscrewed to an unlock position ( FIGS. 1 ,  2  and  4 ) away from lower end  32  so that driven ball  38  can retract to a retracted position ( FIGS. 1 ,  2  and  3 ) to provide the necessary annular clearance between a maximum outside diameter  56  of shank  12  and a minimum inside diameter  58  or throat diameter of retainer  14 . 
     FIG. 2  shows barrel lock  10  installed but not yet locked. To lock shank  12  in place, pin  40  is screwed farther into shank  12  to a lock position ( FIG. 3 ) to push drive ball  36  toward lower end  32 , thereby forcing drive ball  36  to push driven ball  38  outward to an extended position ( FIG. 3 ) against an inner wall  60  of retainer  14 . Driven ball  38  pressing against retainer  14  forces shank  12  to tilt relative to retainer  14 . The relative tilting between shank  12  and retainer  14  can also be seen in  FIG. 5 , which shows a longitudinal centerline  86  of pin  40  being at a slight angle  89  to a longitudinal centerline  87  of retainer  14 . In some cases, a backside  62  of shank  12  may need to be relieved or beveled to provide sufficient radial clearance between shank  12  an inner bore diameter  64  of retainer  14  so that shank  12  has room to tilt within retainer  14 . Tilting shank  12  to the strained position of  FIG. 3  creates a two-point binding action (frictional binding forces at points  66  and  68 ) between shank  12  and a throat  70  of retainer  14 . 
   In cases where driven ball  38  is driven with sufficient force and is perhaps harder than inner wall  60 , driven ball  38  may even form a beneficial dimple  72  ( FIG. 4 ) in wall  60 . Driven ball  38  extending into dimple  72  and/or shank  12  binding against throat  70  helps lock shank  12  to retainer  14 . Even if unauthorized personnel attempts to pry or otherwise forcibly pull shank  12  out from within retainer  14  while driven ball  38  is still extended, ball  38  may eventually catch on a step  74  between bore diameter  64  and the smaller throat diameter  58 , which would greatly increase the force required to completely separate shank  12  and retainer  14 . 
   To properly unlock barrel lock  10 , pin  40  is rotated in a direction that moves pin  40  away from lower end  32 . This allows driven ball  38  to retract so that shank  12  can tilt back to its relaxed position of  FIG. 4  and be readily removed from within retainer  14 , as indicated by arrow  76 . In future use, dimple  72  can be reused, or driven ball  38  can form another dimple. 
   When locking shank  12  to retainer  14 , one or more interesting phenomena come into play, such as 1) an extremely high radial thrust of driven ball  38 , 2) the high binding force created between shank  12  and throat  70 , 3) an axial drawing action made possible by the rotation of a single driven ball  38 , and 4) an end stop  78  with an optional angled cam surface  80  that in some cases provides driven ball  38  with extra radial push as drive ball  36  engages surface  80 . 
   Referring to  FIG. 5 , which is an enlarged view of  FIG. 3 , the extremely high radial thrust of driven ball  38  is created by having a very low ratio of the driven ball&#39;s radial movement to the corresponding rotation of drive pin  40 . In some cases, a 90-degree rotation of pin  40  moves driven ball  38  less than 0.004-inches somewhat near the driven ball&#39;s end of outward travel. This low ratio and high thrust is partially due to a very acute, predetermined minimum angle  81  created between a ball-to-ball line  82  and a radial line  84  that is perpendicular to longitudinal centerline  86  of drive pin  40 . The predetermined minimum angle  81  is preferably less than 15-degrees and in some cases is less than 6-degrees. 
   To achieve the mechanical advantage of such a low angle of attack while preventing balls  36  and  38  from irreversibly locking up by toggling over center (i.e., angle  81  getting too close to zero degrees), end stop  78  is strategically and accurately situated within shank  12 . In some embodiments, end stop  78 , which in this example includes the optional tapered surface  80 , is created by drilling side hole  50 . In other words, a portion of end stop  78  is simply an extension of hole  50 . If desired, tapered surface  80  can be created by drilling bore  34  in shank  12 , wherein the tapered surface  80  corresponds to the point of the drill used for drilling bore  34 . Drive ball  36  is preferably, but not necessarily, larger than driven ball  38  so that when both balls  36  and  38  lie against side hole  50  (i.e., both balls are against the far left vertical side of hole  50  and end stop  78  as viewed in  FIG. 5 ), the center points of balls  36  and  38  will not be parallel to that far left vertical side of hole  50  and end stop  78 , thus the balls are still prevented from toggling over center and locking up. Under normal operation, drive ball  36  stops moving deeper into bore  34  upon engaging tapered surface  80  of end stop  78 , as shown in  FIG. 5 . Under worn or otherwise unusual conditions, pin  40  might continue pushing drive ball  36  along surface  80  until ball  36  solidly abuts the far left side of hole  50  and end stop  78 . Drive ball  36  moving along surface  80  toward the far left side of end stop  78  forces driven ball  38  to protrude a little farther out through side hole  50 . 
   Although end stop  78  is shown to engage drive ball  36 , it is also well within the scope of the invention to have the end stop be some other feature that engages pin  40  rather than ball  36 . The end stop, for example, could be where a shoulder or protrusion on pin  40  could engage a complementary shoulder on shank  12  to limit the axial travel of pin  40  and thus limit the travel of ball  36 , wherein the complementary shoulder would serve as the end stop instead of end stop  78 . End stop  78  and the complementary shoulder could be used as alternatives of each other or they could both be used in the same barrel lock. As another alternative to end stop  78  and the complementary shoulder, or in addition to them, internal threads  48  of shank  12  could bottom out on external threads  42 , thereby providing an end stop that would limit the axial travel of pin  40  and thus limit the travel of ball  36 . 
   Still referring to  FIG. 5 , the ratio of a first distance  88  between driven ball  38  and throat  70  and a second distance  90  of the axial length of throat  70  is relatively large to provide a mechanical leverage advantage that creates a significant two-point binding force between shank  12  and throat  70  even if the radial thrust of driven ball  38  is relatively low. The radial thrust of driven ball  38 , however, is not low, but instead the force is quite high for the reasons explained in the previous paragraph; therefore, the two-point binding force is tremendous. 
   Referring to  FIG. 6 , driven ball  38  not only helps bind shank  12  to retainer  14 , ball  38  may also actually help draw shank  12  in an axial direction  92  into retainer  14  as pin  40  is screwed into shank  12 . As pin  40  forces drive ball  36  to roll along one side of bore  34 , drive ball  36  may roll in a counterclockwise direction  94 . Friction between balls  36  and  38 , thus urges driven ball  38  to rotate in a clockwise direction  96 . As driven ball  38  rolls in clockwise direction  96  along inner wall  60 , the traction between driven ball  38  and wall  60  tends to draw shank  12  further into retainer  14 , thereby tightly clamping parts  16  and  18  between head  26  and retainer  14 . 
   In comparing  FIGS. 5 and 6 , it should be noted the effect that angled cam surface  80  has on balls  36  and  38 . As pin  40  is screwed into shank  12 , pin  40  initially pushes drive ball  36  in a generally straight line along bore  34 . After drive ball  36  reaches angled surface  80  of end stop  78 , surface  80  redirects drive ball  36  more directly toward side hole  50 , whereby drive ball  36  gives driven ball  38  an extra push through side hole  50  just before drive ball  36  reaches an ultimate termination point  98  of end stop  78 . Giving driven ball  38  an extra push near the end of its travel increases the extent to which driven ball  38  can protrude from shank  12 , which can increase the relative tilting and binding between shank  12  and retainer  14 . 
     FIG. 7  shows a retainer  100  whose inner wall  102  (retainer bore) and/or throat  104  has a Brinell hardness of at least 230. With such hardness, it may not be necessary for driven ball  38  to form a dimple in retainer  100 . Instead, shank  12  can be locked to retainer  100  solely by binding forces created between shank  12  and throat  104  as driven ball  38  forces shank  12  to tilt relative to retainer  100 . 
     FIG. 8  shows an alternate barrel lock  106  that includes two or more driven balls  38  that lock a retainer  108  to a shank  110  by forming a corresponding two or more dimples  112 . To prevent balls  38  and  36  from locking over center, the axial movement of drive ball  36  can be limited by a generally linear end stop  114  that prevents pin  40  from forcing ball  36  directly between and inline with balls  38  (i.e., all three balls being inline). When driven balls  38  are directly opposed and distributed 180-degrees about a centerline  105  of ball  36 , as shown in  FIG. 8   a , the linearity of end stop  114  can be created by the side wall of a through hole that is drilled to create the two side holes through which driven balls  38  protrude. Since ball  36  is preferably larger than driven balls  38 , the center points of the three balls will be displaced out of collinear alignment when all three balls are up against end stop  114 . 
   In some cases, however, it may be desirable to have driven balls  38  nonconcentrically distributed about centerline  105  at, for example, 120-degrees apart as shown in  FIG. 8   b . Multiple driven balls that can each protrude a given distance can provide shank  110  with an overall greater change in its extendable outside dimension, whereby the stepped throat of retainer  108  could possibly be omitted and replaced by providing retainer  108  with a tapered bore whose diameter increases with its depth. Having driven balls  38  distributed nonconcentrically, can provide shank  110  with a tilting or binding effect that was explained with reference to barrel lock  10  of  FIGS. 1-6 . 
     FIGS. 9 and 10  show a barrel lock  116  whose shank  118  includes a tooth  120  for engaging internal threads  122  or some other type of spiral groove within a retainer  124 .  FIG. 9  shows barrel lock  116  in its unlocked position where driven ball  38  is retracted so that shank  118  can be readily inserted or removed from within retainer  124 . In the locked position, as shown in  FIG. 10 , driven ball  38  is pushed outward against threads  122 , which tilts shank  118  and forces tooth  120  into positive engagement with threads  122 , thereby preventing shank  118  from being withdrawn from within retainer  124 . To adjust the axial spacing between a head  126  of shank  118  and an open end of retainer  124 , drive pin  40  can be just lightly tightened initially so that driven ball  38  and tooth  120  only lightly engage threads  122 . Light engagement with threads  122  allows shank  118  and retainer  124  to be screwed together so that head  126  and retainer  124  clamp against parts  16  and  18 . Once barrel lock  116  is axially adjusted, it can be locked in place by tightening drive pin  118 . 
   A barrel lock  128  of  FIGS. 11-13  is similar to barrel lock  116 ; however, lock  128  includes a retainer  130  with a spiral groove  132  that is coarser than threads  122 , and shank  134  does not necessarily have a tooth for engaging groove  132 . Barrel lock  128  is shown unlocked in  FIG. 11 , snug in  FIG. 12 , and tightly locked in  FIG. 13 . 
   To operate barrel lock  128 , driven ball  38  can be retracted so that shank  134  can be inserted into retainer  130 , as shown in  FIG. 11 . Next, drive pin  40  is lightly tightened to gently extend driven ball  38  partially into groove  132 . To adjust the axial spacing between head  126  and an open face  136  of retainer  130 , shank  134  can be rotated to effectively screw shank  134  into retainer  130 , thereby minimizing the axial gap between barrel lock  128  and parts  16  and  18 . Once barrel lock  128  is adjusted axially ( FIG. 12 ), drive pin  40  can be tightened so that driven ball  38  “bites” into or tightly grips retainer  130  ( FIG. 13 ). A surface  129  is preferably tapered to prevent that surface from biting into ball  38  and to enhance the ball&#39;s ability to draw shank  134  into retainer  130 . 
   If initially shank  134  is just snuggly screwed into retainer  130  while driven ball  38  is only partially extending into groove  132  ( FIG. 12 ), subsequent final tightening of drive pin  40  forces driven ball  38  farther into groove  132  ( FIG. 13 ), which draws retainer  130  and head  126  more tightly together in the axial direction. In addition, barrel lock  128  could incorporate the dimpling effect of the other embodiments described herein. It is also well within the scope of the invention to modify retainer  130  to use a tilting or binding effect between shank  134  and retainer  130  to help hold the two together. 
   In the illustrated embodiment, however, retainer  130  does not include a throat for binding or for preventing shank  134  from being forcibly pried out from with retainer  130 . Instead, retainer  130  includes an obstruction  138  that limits how far driven ball  138  can travel along groove  132 , thereby limiting an extent to which shank  134  can withdraw from within retainer  130 . For barrel lock  128 , obstruction  138  is simply where groove  132  ends; however, obstruction  138  should not limited to this particular example. 
   In another embodiment, shown in  FIGS. 14-16 , a barrel lock  140  includes a retainer  144  with internal threads  142  and a shank  148  with external threads  146 , so the two can be screwed together to adjust the axial distance between retainer  144  and a head  150  of shank  148 . Once adjusted, a drive pin  152  acts upon drive ball  36  to force driven ball  38  tightly up against a retainer bore  154  in a manner similar to that of barrel lock  10 . The point at which driven ball  38  engages retainer bore  154  is preferably spaced apart from the threads to prevent driven ball  38  from damaging internal threads  142 .  FIG. 13  shows shank  148  and retainer  144  being assembled,  FIG. 14  shows shank  148  being rotated relative to retainer  144  to adjust the axial spacing between retainer  144  and head  150 , and  FIG. 16  shows barrel lock  140  adjusted and locked in position. 
     FIGS. 17-22  show how a barrel lock  156  can be used to lock a door panel  158  tightly closed against a box  160 , such as conventional electrical enclosures, which are well known to those of ordinary skill in the art. Box  160  and door panel  158  correspond to parts  16  and  18  of the other embodiments. In this example, a clip  162  with two openings  164  helps hold a rectangular retainer  166  adjacent to a flange  168  that frames an access opening  170  of box  160 . Retainer  166  includes a retainer bore  172  with a shoulder  174 . 
   Before panel  158  can be locked shut, box  160  needs a hole  176  in flange  168 , and panel  158  needs a similar corresponding hole  178 . Holes  176  and  178  should be located so that they come into alignment with each other when the door is closed. If box  160  and panel  158  were not originally manufactured with such holes, they can be readily added using a conventional drill or punch. 
   To lock door panel  158  shut, door  158  is closed with a front face  180  of clip  162  being situated between door  158  and flange  168 . A bottom flange  182  of clip  162  can extend underneath or along some side wall  161  of box  160 . Flange  182  is preferably harder than the material of box  160  and door  158  to inhibit the door and box from being forcibly pried open. Retainer  162  can be held between front face  180  and a back face  184  of clip  162 . When door panel  158  is closed, as shown in  FIGS. 18 ,  19 , and  21 , a series of inline through holes is created by holes  178 ,  176 , openings  164 , and retainer bore  172 . A shank  186  with its driven ball  38  in a retracted position, as shown in  FIGS. 17 and 22 , can be inserted (or removed) through the series of holes. A drive pin  188  can be screwed into shank  186  to force driven ball  38  to an intermediate position ( FIG. 18 ). At the intermediate position, driven ball  38  lightly engages shoulder  174  such that barrel lock  156  exerts a first pressure that pulls door panel  158  closed, but not very tightly. Additional turning of drive pin  188  forces driven ball  38  to protrude farther out to an extended position ( FIGS. 19 and 21 ) so that driven ball  38  presses harder against shoulder  174 , which causes barrel lock  156  to exert a second, greater pressure that more forcefully pulls door panel  158  closed. Shoulder  174  is preferably a chamfer whose angled surface promotes an axial door-closing force that increases as ball  38  extends radially. 
   Although the invention is described with respect to a preferred embodiment, modifications thereto will be apparent to those of ordinary skill in the art. Therefore, the scope of the invention is to be determined by reference to the following claims: