Abstract:
A carpet stretcher device has an automatic adjusting tube that changes length with telescoping motion of an inside tube and an outside tube. A housing is mounted on the outside tube, and at least one lever is connected to the housing. A hand lever controls the motion of a spring-loaded rotating arm with a locking button positioned within the housing to insert and remove the locking button from holes in the tubes. When lifted away from the housing, the hand lever releases the rotating arms, which rotate to remove the locking button from holes in the tubes and thereby allow the tubes to telescope. The carpet stretcher may also have a floor lever that retracts when the device contacts a floor surface and extends when the device is lifted off a floor surface. When extended, the floor lever also releases the rotating arms, thereby allowing the tubes to telescope.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 62/350,161, filed Jun. 14, 2016, which is incorporated by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    This invention relates generally to flooring tools, and in particular to adjusting a length of a carpet stretcher tool during use to install carpet. 
         [0003]    In residential construction, the installation of wall-to-wall carpeting first requires nailing carpet retaining wood strips to a subfloor, called tack strip. A tack strip is manufactured with metal pins that extend from the top surface of the wood strip to grip the back of the carpet and hold it in place. Tack strips are nailed down in close proximity to all the walls in the room. The carpet is first hooked at one wall, stretched across the length of the room, and then hooked on the tack strip at the opposite wall. The resulting tension in the stretched carpet keeps it hooked on the tack strip pins and thus flat on the floor. This prevents bumps and creases from forming in the carpet after it is installed, which could create a tripping hazard. 
         [0004]    To stretch the carpet across a room, a carpet stretcher tool is used.  FIG. 1  shows an assembled prior art carpet stretcher  10  including a power head  20 , automatic adjusting tube  30 , extension tube  40 , and tail block  50 . The tubes of the carpet stretcher  10  assemble in a telescoping manner across the length of the room. The power head  20  is placed within about 4 inches of a wall  60  at a slight angle. Power head  20  includes a receiving tube  21 , a leverage handle  22 , and a pin plate  23 . Pin plate  23  grips the carpet. The inside tube  31  of automatic adjusting tube  30  is inserted into the receiving tube  21  of the power head  20 . The inside tube  41  of the extension tube  40  is inserted in the outside tube  32  of the automatic adjusting tube  30 . A tail block  50  is inserted into the outside tube  42  of extension tube  40 . The tail block  50  is braced against wall  70 . When leverage handle  22  of power head is lowered (e.g., pushed down by hand), the carpet  80  will be stretched across room  100  in the direction of arrow  90 . 
         [0005]      FIG. 2  shows an exploded view of a prior art extension tube  40 , which includes inside tube  41 , outside tube  42 , and spring clips  43 . Spring clips  43  are inserted into both ends of inside tube  41 . Spring clip buttons  44  extend through inside tube holes  45 . When inside tube  41  is inserted into outside tube  42 , spring clip buttons  44  insert within adjustment holes  46  in the outside tube  42 , locking inside tube  41  and outside tube  42  at the particular extension. 
         [0006]    To unlock and adjust extension tube  40 , spring clip buttons  44  may be depressed using finger pressure. In this way, spring clip buttons  44  can be removed from adjustment holes  46  in outside tube  42 , unlocking outside tube  42  from inside tube  41 . Inside tube  41  and outside tube  42  can then be extended or retracted until spring clip buttons  44  align with another pair of adjustment holes  46  in outside tube  42 . At such point, spring clip buttons  44  insert within a pair of adjustment holes  46 , and inside tube  41  and outside tube  42  will again be locked at that extension position. Extension tube  40  can be further adjusted in length, but only by increments of the distance between adjustment holes  46  in outside tube  42 , which increment can be larger than desired in some cases. 
         [0007]    Furthermore, as inside tube  41  and outside tube  42  are extended and retracted, spring clip buttons  44  will tend to insert in adjustment holes  46  in outside tube  42 , and spring clip buttons  44  must be depressed if further adjustment is needed. For this reason, extension tube  40  does not provide a mechanism for automatic adjustment for either extension or retraction. Because this is inconvenient, extension tube  40  is normally used at one set extension so long as it is used in a particular room. 
         [0008]    As shown in  FIG. 1 , for ease of adjustment, an automatic adjusting tube  30  is used to adjust the overall length of carpet stretcher  10  in smaller increments. One such automatic adjusting tube is described in U.S. Pat. No. 4,577,837 to Berg, which describes a carpet stretcher with a tubular extension assembly including an inner tubular member that has a plurality of openings. An outer tubular member telescopes with the inner tubular member and also has openings. A housing is assembled onto the outer tubular member and holds a pair of levers that pivot on pins. The levers include lever actuating plungers on one end and locking plungers on their opposite ends. Berg&#39;s outer tubular member can be extended or retracted relative to the inner tubular member by depressing the lever activating plungers, typically using a thumb and forefinger. This removes the locking plungers from the openings of the inner tubular member. In addition, the outer tubular member can be extended automatically without depressing lever activating plungers by pushing back on the housing or the outer tubular member. This is due to the internal shaping of the housing with triangular blocks along with tension springs, which retain levers at an “oblique angle” relative to the axes of the tubes. This angle allows the outer tubular member to extend automatically in the direction of the tail block end of the carpet stretcher. When the outer tubular member is retracted (i.e., pulled back towards the power head end of the carpet stretcher), the locking plungers insert within openings of the inner tubular member, which locks the tubes. A similar motion of the outside tube also occurs when the leverage handle of the carpet stretcher is lowered. 
         [0009]    In use, the device of Berg is not ergonomic in certain respects. In the carpet stretching motion, a user normally kneels to the left of the carpet stretcher and lowers the leverage handle with the right hand. From this position, to adjust Berg&#39;s tubular extension assembly, the user must turn fully around to their right and use fingers to depress the activating plungers. The twisting motion can cause back strain, and repeatedly depressing the small lever activating plungers is tiring on the fingers, particularly with all the other button activation that is necessary to assemble, adjust, and then disassemble the carpet stretcher as it is moved from room to room on a jobsite. 
         [0010]    Furthermore, some motions in using the carpet stretcher are repetitive and could be more efficient if it were possible to extend and retract the tool on the fly. After each stretching motion, the carpet stretcher must be moved to stretch another section of the carpet. To do this, the user lifts the pin plate out of the carpet, typically by lifting at the leverage handle, then kicks the stretcher to the right utilizing the right leg. After moving the carpet stretcher, a new section of the carpet is stretched. 
         [0011]    As shown in  FIGS. 3 and 4 , extension and retraction of the carpet stretcher is frequently required in the direction of either the power head  20  end or the tail block  50  end because rooms frequently include that walls that jog in and out. In  FIG. 3 , room  110  includes a wall  111  that jogs outwardly at wall surface  112 . In the process of moving the carpet stretcher  10  to wall surface  112  (to the user&#39;s right), it would be desirable to simply to lift the pin plate  23  out of the carpet by lifting at leverage handle  22 , and then pulling forward on the leverage handle  22  to automatically extend the carpet stretcher  10 . As shown in  FIG. 4 , room  120  includes a wall  121  that jogs outwardly at wall surface  122 . In the process of moving the tail block  50  of carpet stretcher  10  to wall surface  122  (also to the user&#39;s right), it would be desirable simply to pull a handle connected to the automatic adjusting tube to automatically extend the tubes of the carpet stretcher until tail block  50  contacted wall surface  122 . Unfortunately, the tubular extension assembly of Berg has no suitable handle. 
         [0012]    Conversely, if it were necessary to reduce the length of the carpet stretcher  10  from the power head  20  end, it would be desirable to simply lift at leverage handle  22  to lift pin plate  23  out of the carpet and then pull back on leverage handle  22  to shorten it. If it were necessary to reduce the length of the stretcher from the tail block  50  end, it would be desirable simply to pull back on a handle to retract the tubes until tail block  50  could be braced against an opposite wall at a shorter distance. 
         [0013]    What is needed therefore is an automatic adjustment mechanism for a tube of a carpet stretcher that provides automatic extension or retraction in the direction of either the power head or tail block ends, rather than just automatic extension towards the tail block end as prior art devices like Berg&#39;s. The process of extension and retraction is desirably activated at convenient gripping surfaces on the carpet stretcher, such as at the leverage handle and some added handle attached to the automatic adjusting tube. 
       SUMMARY 
       [0014]    In various embodiments of the invention, an automatic adjusting tube for a carpet stretcher comprises an inside tube, an outside tube, a housing mounted on the outside tube, and at least one lever connected to the housing. The lever is usable to control the motion of a spring-loaded rotating arm with a locking button positioned within the housing to insert and remove the locking button from holes in the inside tube. In one embodiment, a hand lever hinges on a fulcrum on the housing to control a pair of spring-loaded rotating arms with locking buttons. The hand lever begins from a retracted (or lowered) position. At this position, the hand lever releases the rotating arms, and the rotating arms rotate, being urged by a pair of springs. If the holes in the outside tube and the inside tube are aligned, the rotation of the rotating arms cause the locking buttons to extend through holes in the outside tube and insert within the holes in the inside tube. 
         [0015]    When the lever is raised into an extended (or raised) position, this rotates the rotating arms to remove the locking buttons from the holes in the inside tube. With the hand lever extended, the automatic adjustment tube can be automatically extended or retracted by pushing or pulling on the hand lever so long as it is raised. When the hand lever is again retracted from the extended position, if the holes in the outside tube and the inside tube are aligned, the rotating arms will again rotate to extend through holes in the outside tube and insert within the holes in the inside tube. In one embodiment, with the hand lever in a retracted position, the rotating arms and locking buttons are at an oblique angle in relation to the long axes of the outside tube and inside tube, so that if the outside tube is pushed back to extend it the outside tube extends automatically. 
         [0016]    In another embodiment, a floor lever hinges on a fulcrum on the housing to control a pair of spring loaded rotating arms with locking buttons. The floor lever retracts when the device contacts a floor surface and extends when the device is lifted off a floor surface. When the device is connected to the power head of the carpet stretcher and both are laid on a floor surface, the floor lever retracts, which releases the rotating arms to rotate, being urged by a pair of springs. If the holes in the outside tube and the inside tube are aligned, the rotation of the rotating arms causes the locking buttons to extend through holes in the outside tube and insert within the holes in the inside tube. 
         [0017]    If the power head is lifted off a floor surface, the floor lever extends, which rotates the rotating arms to remove the locking buttons from holes in the inside tube. With the floor lever extended, the automatic adjusting tube can be automatically extended or retracted by pushing or pulling on the power head, preferably at the leverage handle. When the power head is lowered to the floor, the floor lever contacts the floor and retracts. If the holes in the outside tube and the inside tube are aligned, the rotating arms rotate to insert the locking buttons within the holes of the inside tube, being urged by a pair of springs. In one embodiment, with the floor lever in a retracted position, the rotating arms and locking buttons are at an oblique angle in relation to the long axes of the outside tube and inside tube, so that if the outside tube is pushed back to extend it, the outside tube will extend automatically. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  shows an assembled prior art carpet stretcher in a room. 
           [0019]      FIG. 2  shows an exploded view of an extension tube of a prior art carpet stretcher. 
           [0020]      FIGS. 3 and 4  show the extension and retraction of prior art carpet stretchers for example rooms including walls that jog in and out. 
           [0021]      FIG. 5  is an exploded view of an automatic adjustment tube for a carpet stretcher, in accordance with an embodiment of the invention. 
           [0022]      FIG. 6  is an assembled view of an automatic adjustment tube for a carpet stretcher, with a hand lever in a retracted position, in accordance with an embodiment of the invention. 
           [0023]      FIG. 7  is a cross sectional view of the automatic adjustment tube of  FIG. 6  with the hand lever in the retracted position, along line A-A. 
           [0024]      FIG. 8  is an assembled view of automatic adjustment tube for a carpet stretcher, with the hand lever in an extended position, in accordance with an embodiment of the invention. 
           [0025]      FIG. 9  is a cross sectional view of the automatic adjustment tube of  FIG. 8  with the hand lever in the extended position, along line B-B. 
           [0026]      FIG. 10  is an assembled view of an automatic adjustment tube for a carpet stretcher, with a floor lever in a retracted position, in accordance with an embodiment of the invention. 
           [0027]      FIG. 11  is a cross sectional view of the automatic adjustment tube of  FIG. 10  with the floor lever in the retracted position, along line C-C. 
           [0028]      FIG. 12  is an assembled view of the automatic adjustment tube of  FIG. 10 , with the floor lever in an extended position, in accordance with an embodiment of the invention. 
           [0029]      FIG. 13  is a cross sectional view of the automatic adjustment tube of  FIG. 12  with the floor lever in the extended position, along line D-D. 
           [0030]      FIG. 14  is an assembled view of an automatic adjustment tube for a carpet stretcher, with the hand lever in an extended position, in accordance with an embodiment of the invention. 
           [0031]      FIG. 15  is a cross sectional view of an automatic adjustment tube of  FIG. 14  with the hand lever in an extended position, along line E-E. 
           [0032]      FIG. 16  is an assembled view of an automatic adjustment tube for a carpet stretcher, with the floor lever in an extended position, in accordance with an embodiment of the invention. 
           [0033]      FIG. 17  is a cross sectional view on an automatic adjustment tube  FIG. 16  with the floor lever in an extended position, along line F-F. 
       
    
    
       [0034]    The figures depict various embodiments of the present invention for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the invention described herein. 
       DETAILED DESCRIPTION 
       [0035]    As shown in  FIG. 5 , automatic adjusting tube  1000  includes outside tube  1020 , inside tube  1040 , hand lever  1100 , housing top  1200 , rotating arm  1510  with locking button  1511 , rotating arm  1520  with locking button  1521 , rotating arm springs  1512 ,  1522 , housing bottom  1300 , floor lever  1400 , floor lever springs  1702 ,  1704  that activate floor lever  1400 , and lock pin  1600  to lock floor lever  1400  in a retracted position. 
         [0036]    Hand lever  1100  pivots on housing top  1200  at its hand lever holes  1102 ,  1104 . Bushings  1106 ,  1108  are inserted into hand lever holes  1102 ,  1104 , and fasteners  1110 ,  1112  are passed through bushings  1106 ,  1108  and fastened into housing top lever holes  1202 ,  1204 . Hand lever arms  1114 ,  1116  are inserted into hand lever arm slots  1214 ,  1216  in housing top  1200 . Hand lever spring arm  1119  is inserted into spring arm slot  1219  of housing top  1200 . Hand lever retracting spring  1121  is inserted into a hand lever spring holding cavity  1221  in housing top  1200 . Hand lever retracting spring  1121  contacts the back of hand lever spring arm  1119  to retract it against housing top  1200  when released by the user. 
         [0037]    Floor lever  1400  pivots on housing bottom  1300  at its floor lever holes  1402 ,  1404 . Bushings  1406 ,  1408  are inserted into floor lever holes  1402 ,  1404 . Fasteners  1410 ,  1412  are passed through bushings  1406 ,  1408  and fastened into holes  1302 ,  1304  of housing bottom  1300 . Floor lever arms  1414 ,  1416  insert into floor lever arm slots  1314 ,  1316  in housing bottom  1300 . A locking arm  1419  inserts into a locking arm slot  1319  in housing bottom half  1300 . Locking arm  1419  includes a locking arm hole  1421  formed in conjunction with a locking arm radial slot  1423 . 
         [0038]    Lock pin  1600  along with ball spring  1330  and ball  1331  create a locking mechanism for floor lever  1400  that operates in two positions. Ball spring  1330  and ball  1331  insert within a ball blind hole  1332  in housing bottom  1300 . Lock pin  1600  inserts into lock pin hole  1321  of bottom half  1300 , with end  1611  entering first (pull ring  1609  not yet installed). Lock pin  1600  has an inner large diameter  1601 , inner groove  1602 , outer groove  1604 , middle small diameter  1605 , and outer medium diameter  1607 . Lock pin  1600  passes over ball spring  1330  and ball  1331 , holding these inside ball blind hole  1332 . Lock pin  1600  extends through locking arm hole  1421  in locking arm  1419  when floor lever  1400  is in a retracted position. Inner large diameter  1601  of lock pin  1600  is larger in diameter than lock pin hole  1321  in housing bottom  1300 , thus preventing lock pin  1600  from pulling out. Once lock pin  1600  is assembled in this manner, pull ring  1609  is installed on lock pin  1600 . 
         [0039]    When lock pin  1600  is in an outer position, ball  1331  is pressured upward by ball spring  1330  and enters an inner groove  1602  of lock pin  1600 . With lock pin  1600  in this outer position and floor lever  1400  retracted, middle small diameter  1605  of lock pin  1600  aligns with locking arm hole  1421  of locking arm  1419 . Middle small diameter  1605  of lock pin  1600  is smaller in dimension than the width of locking arm radial slot  1423 . Thus, as floor lever  1400  pivots downward to extend, middle small diameter  1605  of lock pin  1600  will pass within locking arm radial slot  1423 , permitting floor lever  1400  to extend. 
         [0040]    With floor lever  1400  is retracted, and lock pin  1600  is in an inner position, ball  1331  enters outer groove  1604 , and outer medium diameter  1607  of lock pin  1600  aligns with locking arm hole  1421 . Outer medium diameter  1607  of lock pin  1600  is larger in dimension than the width of locking arm radial slot  1423 . This prevents floor lever  1400  from extending, if desired, for reasons to be explained below. 
         [0041]    Floor lever  1400  is urged to extend by floor lever springs  1702 ,  1704 . Floor lever springs  1702 ,  1704  are inserted into plungers  1706 ,  1708  which pass through plunger holes  1346 ,  1348 . Plungers  1706 ,  1708  contact a top surface  1420  of floor lever  1400 , producing pressure on floor lever  1400  to extend it. 
         [0042]    Outer tube  1020  is positioned in the midsection  1350  of housing bottom  1300  with a boss  1351  extending into a bottom positioning hole  1021  in outer tube  1020 . Rotating arms  1510 ,  1520  are inserted into cavities  1362 ,  1364  of housing bottom  1300 . Rotating arm springs  1512 ,  1522  are inserted behind rotating arms  1510 ,  1520 . When holes  1022 ,  1024  in outside tube  1020  are in alignment with adjustment holes  1042 ,  1044  of inside tube  1040 , rotating arm springs  1512 ,  1522  urge locking buttons  1511 ,  1521  to extend through holes  1022 ,  1024  in outer tube  1020  and insert into adjustment holes  1042 ,  1044  in inner tube  1040 . 
         [0043]    Housing top  1200  is positioned on top of outer tube  1020  at midsection  1250  with a boss  1251  inserting into a top positioning hole  1025  in outer tube  1020 . Fasteners  1260  pass through holes  1261  in housing top  1200  into holes  1360  in housing bottom  1300  to fasten housing top  1200  to housing bottom  1300 . 
         [0044]      FIG. 6  shows the assembled adjustment tube  1000 , with hand lever  1100  retracted, floor lever  1400  retracted, and section A-A taken in a plane that illustrates the position of hand lever arms  1114 ,  1116  ( FIG. 7 ). In  FIG. 7 , section A-A shows that with hand lever  1100  retracted, hand lever arms  1114 ,  1116  also retract, releasing rotating arms  1510 ,  1520  to rotate, being urged by rotating arm springs  1512 ,  1522 . As rotating arms  1510 ,  1520  rotate, locking buttons  1511 ,  1521  extend through holes  1022 ,  1024  in outside tube  1020  and insert within adjustment holes  1042 ,  1044  in inside tube  1040 . Holes  1022 ,  1024  in outside tube  1020  and adjustment holes  1042 ,  1044  in inside tube  1040  are aligned. 
         [0045]      FIG. 8  shows the assembled adjustment extension tube  1000 , with hand lever  1100  extended, floor lever  1400  retracted, and section B-B taken in a plane that illustrates the position of hand lever arms  1114 ,  1116  ( FIG. 9 ) and rotating arms  1510 ,  1520  ( FIG. 9 ). In  FIG. 9 , section B-B shows that with hand lever  1100  extended, hand lever arms  1114 ,  1116  also extend, which rotates rotating arms  1510 ,  1520  to a position where locking buttons  1511 ,  1521  are removed from adjustment holes  1042 ,  1044  in inside tube  1040 . Holes  1022 ,  1024  in outside tube  1020  and adjustment holes  1042 ,  1044  in inside tube  1040  are aligned. 
         [0046]      FIG. 10  shows the assembled automatic adjustment tube  1000 , with hand lever  1100  retracted, floor lever  1400  retracted, and section C-C taken in a plane that illustrates the position of floor lever arms  1414 ,  1416  ( FIG. 11 ) and rotating arms  1510 ,  1520  ( FIG. 11 ). In  FIG. 11 , section C-C shows that with floor lever  1400  retracted, floor lever arms  1414 ,  1416  also retract, releasing rotating arms  1510 ,  1520  to rotate, being urged by rotating arm springs  1512 ,  1522 . As rotating arms  1510 ,  1520  rotate, locking buttons  1511 ,  1521  extend through holes  1022 ,  1024  in outside tube  1020  and into adjustment holes  1042 ,  1044  in inside tube  1040 . Holes  1022 ,  1024  in outside tube  1020  and adjustment holes  1042 ,  1044  in inside tube  1040  are aligned. 
         [0047]      FIG. 12  shows the assembled automatic adjustment tube  1000 , with hand lever  1100  retracted, floor lever  1400  extended, and section D-D taken in a plane that illustrates the position of floor lever arms  1414 ,  1416  ( FIG. 13 ) and rotating arms  1510 ,  1520  ( FIG. 13 ). In  FIG. 13 , section D-D shows that with floor lever  1400  extended, floor lever arms  1414 ,  1416  also extend, which rotates rotating arms  1510 ,  1520  to a position where locking buttons  1511 ,  1521  are removed from adjustment holes  1042 ,  1044  in inside tube  1040 . Holes  1022 ,  1024  in outside tube  1020  and adjustment holes  1042 ,  1044  in inside tube  1040  are aligned. 
         [0048]      FIG. 7  shows that rotating arm  1510  includes bend  1514 , and rotating arm  1520  includes bend  1524 . Housing top  1200  includes contours  1224 ,  1226  and housing bottom  1300  ( FIG. 11 ) includes contours  1324 ,  1326  ( FIG. 11 ). The contours  1224 ,  1226  and  1324 ,  1326  ( FIG. 11 ) correspond in shape and together form fulcrums for rotating arm  1510 ,  1520  at bends  1514 ,  1524 . Contours  1224 ,  1226  and  1324 ,  1326  ( FIG. 11 ) additionally permit button legs  1515 ,  1525  of rotating arms  1510 ,  1520  to rotate to an oblique angle in relation to a long axis  1005  of automatic adjustment tube  1000 , being urged by rotating arm springs  1512 ,  1522 . This oblique angle combines with the oblong shape of holes  1022 ,  1024  ( FIG. 5 ) in outside tube  1020  (longer horizontally than circular adjustment holes  1042 ,  1042  in inside tube  1040 — FIG. 5 ) and the rounded ends of locking buttons  1511 ,  1521  to allow automatic adjustment tube  1000  to always extend automatically. The difference in shape between holes  1022 ,  1024  ( FIG. 5 ) in outside tube  1020  and adjustment holes  1042 ,  1044  in inside tube  1040  wedges locking buttons  1511 ,  1521  out of these holes as they move past each other. The rounded ends of locking buttons  1511 ,  1521  also force locking buttons  1511 ,  1521  out of adjustment holes  1042 ,  1044  in inside tube  1040 . As shown in  FIG. 6 , if a user pushes back on housing  1225  or pushes on outside tube  1020 , automatic adjustment tube  1000  will extend automatically in the direction of arrow  1007  ( FIG. 7 ) even when hand lever  1100  ( FIG. 6 ) and floor lever  1400  ( FIG. 6 ) are not extended. 
         [0049]    As shown in  FIG. 5 , automatic adjustment tube  1000  includes a spring clip  1043  comparable to prior art spring clip  43  ( FIG. 2 ). Spring clip  1043  is inserted at a distal end of inside tube  1040  as shown. The buttons of spring clip  1043  insert within end holes  1046 ,  1048  which are horizontal in orientation and in the same plane as adjustment holes  1042 ,  1044  of inside tube  1040 . Spring clip  1043  is used to lock automatic adjustment tube  1000  with a receiving tube of a carpet stretcher (e.g., the receiving tube  21  shown in  FIG. 1 ). 
         [0050]    As shown in  FIG. 5 , automatic adjustment tube  1000  additionally includes safety spring clip  1045 . Inside tube  1040  includes inside tube safety lock holes  1047 ,  1049 , and outside tube  1020  includes outside tube safety lock holes  1026 ,  1028 . Inside tube safety lock holes  1047 ,  1049  and outside tube safety lock holes  1026 ,  1028  are both vertically oriented. Safety spring clip  1045  is inserted at the proximal end of inside tube  1040  as shown. The buttons of safety spring clip  1045  are inserted within inside tube safety lock holes  1047 ,  1049 . 
         [0051]    The normal range of adjustment for automatic adjustment tube  1000  is the hole pattern  1041  of adjustment holes  1042 ,  1044  in inside tube  1040 . If the locking buttons  1511 ,  1521  move beyond hole pattern  1041  (forming a plurality of holes) in the direction of inside tube safety lock holes  1047 ,  1049 , the buttons of safety spring clip  1045  will insert within safety holes  1026 ,  1028  of outside tube  1020 , preventing inside tube  1040  from coming apart from outside tube  1020 . Hole pattern  1041  of adjustment holes  1042 ,  1044  are horizontally oriented, whereas inside tube safety lock holes  1047 ,  1049  and outside tube safety lock holes  1026 ,  1028  are vertically oriented in a different plane. 
         [0052]    As shown in  FIG. 5 , automatic adjustment tube  1000  includes lock pin  1600 . Lock pin  1600  allows the user to prevent floor lever  1400  from automatically extending and unlocking if automatic adjustment tube  1000  is lifted off the floor. This may desirable for example when carpet stretcher is disassembled and automatic adjustment tube  1000  is lifted off the floor to be carried to another room. 
         [0053]    Automatic adjustment tube  1000  can be automatically extended or retracted in the direction of tail block end  50  ( FIG. 1 ) end by lifting hand lever  1100  and pushing or pulling on it. Hand lever  1100  forms a large ergonomic handle surface  1125  to grasp and push or pull. With this large handle surface  1125 , the user can more easily adjust automatic adjustment tube  1000  simply by reaching back and grasping at large handle surface  1125 . Floor lever  1400  permits the power head of the stretcher to be extended or retracted efficiently in conjunction with the normal operating motion of lifting the power head of the carpet stretcher as required each time a new section of carpet is stretched. Floor lever  1400  can be locked in a retracted position if necessary for example for convenient carrying of the automatic adjustment tube  1000  from room to room on the jobsite. 
         [0054]    In one embodiment, the hand lever of the automatic adjustment tube extends a reduced distance from the housing, moving the the rounded ends of the locking buttons in a direction outward of the adjustment holes in the inside tube, but not completely removing the locking buttons from the adjustment holes in the inside tube.  FIG. 14  shows automatic extension tube  2000  with hand lever  2100  extended a reduced distance from housing  2225  and a section E-E taken in a plane that illustrates locking buttons  2511 ,  2521  ( FIG. 15 ) having moved in a direction outward of adjustment holes  2042 ,  2044  ( FIG. 15 ) in inside tube  2040  ( FIG. 15 ), but not completely removed from adjustment holes  2042 ,  2044  ( FIG. 15 ). In  FIG. 15 , Section E-E shows that due to the rounded ends on locking buttons  2511 ,  2521 , locking buttons  2511 ,  2521  need not be completely removed from adjustment holes  2042 ,  2044  for outside tube  2020  and inside tube  2040  to extend and retract. This is because the rounded ends on locking buttons  2511 ,  2521  cause locking buttons  2511 ,  2521  to move out of  2042 ,  2044  when outside tube  2020  and inside tube  2040  are extended or retracted. 
         [0055]    In another embodiment, the floor lever of the automatic adjustment tube extends a reduced distance from the housing, moving the rounded ends of the locking buttons in a direction outward of the adjustment holes in the inside tube, but not completely removing the locking buttons from the adjustment holes in the inside tube.  FIG. 16  shows automatic tension tube  3000  with floor lever  3400  extended a reduced distance from housing  3225  and a section F-F taken in a plane that illustrates locking buttons  3511 ,  3521  ( FIG. 17 ) having moved in a direction outward of adjustment holes  3042 ,  3044  ( FIG. 17 ) in inside tube  3040  ( FIG. 17 ), but not completely removed from adjustment holes  3042 ,  3044  ( FIG. 17 ). In  FIG. 17 , Section F-F shows that due to the rounded ends on locking buttons  3511 ,  3521 , locking buttons  3511 ,  3521  need not be completely removed from adjustment holes  3042 ,  3044  for outside tube  3020  and inside tube  3040  to extend and retract. This is because the rounded ends on locking buttons  3511 ,  3521  cause locking buttons  3511 ,  3521  to move out of  3042 ,  3044  when outside tube  3020  and inside tube  3040  are extended or retracted. 
         [0056]    The embodiment of  FIGS. 8 and 9 and 12 and 13  also show locking buttons  1511 ,  1521  moving in a direction outward of adjustment holes  1042 ,  1044 . In  FIG. 8 , hand lever  1100  extends to rotate rotating arms  1510 ,  1520  ( FIG. 9 ) to move locking buttons  1511 ,  1521  ( FIG. 9 ) in the same direction outward of adjustment holes  1042 ,  1044  ( FIG. 9 ). In  FIG. 12 , floor lever  1400  extends to rotate rotating arms  1510 ,  1520  ( FIG. 13 ) to move locking buttons  1511 ,  1521  in the same direction outward of adjustment holes  1042 ,  1044 . 
         [0057]    The foregoing description of the embodiments of the invention has been presented for the purpose of illustration; it is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Persons skilled in the relevant art can appreciate that many modifications and variations are possible in light of the above disclosure. Finally, the language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based hereon. Accordingly, the disclosure of the embodiments of the invention is intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims. 
         [0058]    The present illustrated embodiments can be characterized in a number of ways. First, the device could be sold as part of a complete carpet stretcher, as shown in  FIG. 1 , having an improved automatic extension tube illustrated in any of  FIG. 5-15  or set out in this detailed description. The device is connectable to prior art carpet stretcher tools as shown in  FIG. 1  and could be sold separately as an accessory for prior art carpet stretcher tools. In addition, the device is connectable to prior art extension tubes as shown in  FIG. 2  and could be sold as a part of set of tubes. The device could be sold with or without a carrying case. Alternatively, the device could be sold disassembled. The elements would remain the same, but would require assembly by the user prior to use.