Abstract:
An automatic locking mechanism for use in a power return tape measure includes a user-accessible actuator, a brake element, and a biasing member normally urging the brake element into contact with the tape drum. In a locked position, the brake element wedges against the drum. The actuator displaces inwardly to move the brake element out of contact with the drum. A rotatable coupler/member may convert pivoting motion of the actuator into brake member translation. The coupler may include first and second arms that respectively contact the actuator and the brake element. The coupler may further include a cammed outer surface that contacts the drum in the locked position. The cammed surface rotates out of contact with the drum in the release position. The cammed surface of the rotatable member may be used independently of, or in conjunction with, the brake element. Related methods are also described.

Description:
[0001]    This application claims benefit of U.S. Provisional Application No. 60/821,989, filed 10 Aug. 2006, the disclosure of which is incorporated herein by reference. 
     
     BACKGROUND 
       [0002]    The present invention is directed generally to tape measures (or “tape rules”) of the type commonly used to measure linear distances. Conventionally, these devices include a flexible tape blade, with distance markings thereon, that can be extended from a housing to measure linear distances. Generally, the tape blade in these devices is constantly subjected to a retraction bias (e.g., from a retraction spring) for pulling the tape blade back into the housing. As such, modern tape measures typically incorporate some type of locking feature to selectively hold the blade in an extended position. Typically, these features require positive engagement in that they are actuated after the tape blade is extended. In other types of tape measures, the locking feature is automatic. That is, once the tape blade is pulled out to an extended position, the tape blade automatically remains in that position until a release mechanism is actuated to allow the return spring to pull the tape blade back into the housing. These latter types of tape measures are sometimes referred to as “auto-lock” tape measures. 
         [0003]    Conventional auto-lock tape measure designs often use a locking mechanism that pinches the tape blade at or near the opening where the tape blade exits the housing. However a pinching force applied to the tape blade imparts friction and undesirable wear on the tape blade. Further, the tape blade is a flexible member and may not provide an optimal braking surface on which to apply a locking force. In addition, the interior of the housing adjacent to the tape blade opening, and thus the locking mechanism, may be susceptible to dirt or foreign object contamination. Accordingly, conventional auto-lock designs may not be ideal in all circumstances. As such, there remains a need for alternative auto-lock locking mechanism designs; advantageously, designs that provide robust and consistent locking forces over extended use. 
       SUMMARY 
       [0004]    In one illustrative embodiment, the tape measure provides an automatic locking mechanism including an externally accessible actuator, a brake, and a biasing member normally urging the brake into contact with the tape drum. The brake may occupy a first locked position in contact with the drum. The actuator may be displaceable towards the interior of the housing to move the brake to a second release position out of contact with the drum. 
         [0005]    The locking mechanism may include a rotatable coupler that converts motion of the actuator into brake member motion. The coupler may have first and second arms that contact the actuator and the brake, respectively. In one embodiment, the rotation of the coupler causes the brake to move in a substantially linear direction, into and out of wedged contact with the tape drum. The coupler may optionally or alternatively further include a cammed outer surface that contacts the drum in the locked position, and rotates out of contact with the drum in the release position. 
         [0006]    In another illustrative embodiment, the tape measure provides an automatic locking mechanism including an externally accessible actuator, a rotatable member including a cammed outer surface, with the cammed outer surface biased into contact with the tape drum. Inward movement of the actuator causes the rotatable member to rotate, which causes the cammed surface to rotate to a release position out of engagement with the tape drum. 
         [0007]    The various aspects of the various embodiments may be used alone or in any combination, as is desired. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  shows a perspective view of a tape measure incorporating an automatic locking mechanism according to one embodiment. 
           [0009]      FIG. 2  shows a side view of the tape measure of  FIG. 1 . 
           [0010]      FIG. 3  shows a perspective view of the interior of the tape measure of  FIG. 1 . 
           [0011]      FIG. 4  shows a side view of the tape measure of  FIG. 1  with a shell portion removed to expose the interior thereof. 
           [0012]      FIG. 5  shows a perspective view of one embodiment of an actuator. 
           [0013]      FIG. 6  shows a perspective view of one embodiment of a coupler. 
           [0014]      FIG. 7  shows one embodiment of a brake. 
           [0015]      FIG. 8A  shows a detail view of one embodiment of a locking mechanism in a locked state. 
           [0016]      FIG. 8B  shows a detail view of one embodiment of a locking mechanism in a release state. 
           [0017]      FIG. 9  shows a detail view of a portion of a tape measure housing suitable for use with the tape measure of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The various embodiments disclosed herein are directed to a tape measure including an auto-lock function. As illustrated in  FIG. 1 , a tape measure, generally designated  10 , is shown constructed according to one embodiment. The tape measure  10  includes a housing  12 , a coilable measuring tape blade  20 , and an end hook assembly  30 . The housing  12  includes an opposing pair of sidewalls  14  and an interconnecting peripheral wall  16  which help define an internal chamber (not labeled) that houses the coiled portion of the tape  20 . The housing  12  typically has a generally squarish shape with rounded corners, but any shape known in the art may be employed, and is preferably sized to fit within a user&#39;s hand and/or conveniently stored on a work belt or in a toolbox. The housing  12  may be formed by two mating shells  22 ,  24 , each including a respective sidewall  14  and a portion of the interconnecting peripheral wall  16 . The housing  12  houses, among other items, a suitable tape-biasing device (e.g., retraction spring  45 ) and portions of the blade auto-locking mechanism  50  described in greater detail below. The housing  12  typically includes an opening  18  near its lower-front corner that connects to the internal chamber. The distal end of the tape  20  extends through this opening  18  for selective deployment therefrom. A belt clip  19  may be attached to a side of the housing  12  and may take any form known in the art, such as the conventional modified “R” shape well known in the art. As the general design and operation of power-return tape measures are well known in the art, additional detailed discussion thereof is omitted herein for brevity. However, additional discussion may be found in U.S. Pat. Nos. 4,976,048 and 6,718,649, and U.S. Patent Application Publication 2003/0233762, which are incorporated herein by reference. 
         [0019]    The end hook assembly  30  may include a hook member  32  that extends downward in a direction substantially perpendicular to the tape blade  20 . Conventional end hooks serve several functions such as allowing users to pull the tape blade  20  from the housing  12  and engaging the end of a surface while measuring a workpiece. In the illustrated embodiment, the end hook assembly  30  further comprises a magnetic structure such as that disclosed in commonly assigned U.S. patent application Ser. No. 11/243,197, filed Oct. 4, 2005, the contents of which are incorporated herein by reference. The exemplary tape end hook assembly  30 , or simply end hook, includes a hook member  32 , a bezel  35 , one or more magnets  36   a ,  36   b , and a fastener  34 . The fastener  34  secures the bezel  35  to the hook member  32  and further secures the magnets  36   a ,  36   b  between the bezel  35  and the hook member  32 . The magnetic structure provides flexibility in attaching the end hook assembly  30  to a measurement surface via magnetic and/or mechanical means. 
         [0020]    As suggested above, the tape measure  10  includes an auto-locking mechanism  50 , one embodiment of which is shown in  FIG. 3 . As suggested above, the locking mechanism  50  automatically holds the tape blade  20  in an extended position when the tape blade  20  is pulled from the housing  12 . The locking mechanism  50  illustrated in  FIG. 3  includes an actuator  40 , a coupler  52 , and a brake  54 . The actuator  40  can be pushed inward relative to the housing  12  by a user to retract the tape blade  20 . When actuator  40  is pushed inward by the user, actuator  40  rotates coupler  52  about pivot axis C, which in turn releases brake  54 . Additional details regarding the operation of locking mechanism  50  are provided below. Notably, locking mechanism  50  is disposed towards the rear of housing  12 , away from opening  18  and away from dirt that may enter opening  18 . Further, this rearward location of locking mechanism  50  avoids undesirable interference with tape motion and/or shock absorption mechanisms (not shown) that may be disposed near opening  18 . 
         [0021]    The actuator  40  is disposed towards bottom  42  of the tape measure  10 .  FIG. 2  further illustrates that the actuator  40  is recessed relative to surfaces  42   a ,  42   b  that help form the bottom  42  of the tape measure  10 . That is, if the tape measure  10  is placed at rest upon a surface such as a table or bench, the tape measure  10  will rest upon surfaces  42   a ,  42   b  because these surfaces protrude the furthest in the “bottom” direction. Furthermore, if the tape measure  10  is positioned with surfaces  42   a ,  42   b  resting on a substantially flat work surface, a downward force applied to the housing  12  in the direction of the arrow labeled F will not inadvertently cause the tape blade  20  to retract into the housing  12 . Instead, a localized displacement force applied to the actuator  40  in the direction of arrow R causes the tape blade  20  to retract into the housing  12 . A user can apply this release force R with their fingers, which may be optimally positioned on or proximate to actuator  40  when the user grasps the tape measure  10  in a conventional manner. 
         [0022]      FIGS. 3-4  depict different views of the locking mechanism  50 . Specifically,  FIG. 3  shows a perspective view of the lower rear corner of the tape measure  10 , with the tape blade  20  slightly extended.  FIG. 4  shows a side view of the tape measure with the tape blade  20  retracted. Also,  FIGS. 8A-8B  show a detailed representation of the locking mechanism  50  according to the DETAIL VIII callout in  FIG. 4 .  FIGS. 8A-8B  show the locking mechanism  50  in the locked and released states, respectively. In  FIGS. 8A-8B , shell  22  is removed, exposing the internal workings of the tape measure  10 . The blade winding drum (or “reel”)  44  is rotatably mounted in the housing  12  and typically takes a commonly known bobbin-like form with two parallel flanges  46  and an intervening core (not visible). The tape blade  20  is wound about the drum  44  in a convolute coil. The inner portion of the drum  44  provides a central cavity for substantially housing retraction spring  45  (see dashed line representation in  FIG. 4 ). The retraction spring  45  is anchored on one end to the drum  44  and at the other end to a post  48 , which may be a separate member or integrally formed with the shell  24 . The post  48  is generally not rotatable whereas the drum  44  is free to rotate about the post  48  and about axis D. As such, the retraction spring  45  provides a bias to retract the tape blade  20  when the locking mechanism  50  is released. 
         [0023]    As suggested, the actuator  40  is moveably supported by the housing  12 . The actuator  40  is operatively coupled to coupler  52 , which in turn, is operatively coupled to brake  54 .  FIGS. 5-7  show respective views of the actuator  40 , coupler  52 , and brake  54 . The brake  54  is normally disposed in contact with the drum  44 . When a release force R is applied to actuator  40 , coupler  52  is displaced (counter-clockwise in  FIG. 4 ), thereby producing a corresponding displacement of brake  54  (downward in  FIG. 4 ). The displacement that is produced as a result of applied release force R tends to move the brake  54  at least temporarily out of contact with the drum  44 , thereby allowing the retraction spring  45  to retract the tape blade  20 . 
         [0024]    A biasing member  56  urges the brake  54  into contact with one or both of the drum flanges  46 . In the depicted embodiment, the biasing member  56  is a coiled compression spring. Other types of biasing members may be used, including for example, leaf springs, torsion springs, and tension springs. The spring  56  advantageously urges the brake  54  into simultaneous contact with the drum  44  and the housing  12 . More specifically, as shown in  FIG. 3 , the spring  56  may advantageously urge the brake  54  into contact with drum flanges  46  and a locking boss  58  that protrudes inwardly from peripheral wall  16  of housing  12 . Note that in an alternative approach, locking boss  58  may protrude from a sidewall  14  of the housing. Alternatively, the brake  54  may be wedged between a sidewall  14  itself and the drum flanges  46 . In such embodiments, brake  54  is normally wedged between drum  44  and some portion of housing  12 , which prevents drum  44  from rotating in a retraction direction. 
         [0025]    The actuator  40  may be pivotally mounted proximate bottom  42  of tape measure  10 . The actuator  40  of  FIG. 5  includes a generally flattened and elongated body  68 , with pivot apertures  60  disposed towards the actuator&#39;s forward end  63 . The pivot apertures  60  are aligned along a common pivot axis X. While two pivot apertures  60  are shown, an alternative embodiment may incorporate a single aperture extending a distance that is less than, greater than, or equal to the width of actuator  40 . The pivot apertures  60  engage a corresponding pivot boss  62  that is disposed towards a forward end of housing  12  near opening  18  in each of the shells  22 ,  24 . Of course, the male/female relationship of this connection may be reversed, as is desired. As the release force R is applied to actuator  40 , the rear end  64  of actuator  40  moves inward towards drum  44 . This inward displacement, in turn, causes coupler  52  to move brake  54  towards a released position. In an alternative embodiment, the actuator  40  is implemented as a push button instead of the substantially cantilevered embodiment illustrated. 
         [0026]    As shown in  FIG. 4 , coupler  52  may be mounted to pivot boss  66  so as to rotate about axis C. Pivot boss  66  is disposed towards a rear of the housing  12 , away from forward opening  18 , and is therefore disposed rearward of the drum&#39;s rotation axis D.  FIG. 6  shows a perspective view of one embodiment of coupler  52 . The coupler  52  of  FIG. 6  includes a cylindrical body  76  with a laterally extending first arm  78  that contacts a bearing surface  70  on actuator  40 . The bearing surface  70  may be a single surface or, as shown in  FIG. 5 , may be comprised of multiple surfaces. In  FIG. 5 , three substantially parallel ribs  74  protrude from the body  68  towards the interior of the housing  12  to form the bearing surface  70 . Further, the ribs  74  extend substantially parallel to one another in a direction substantially perpendicular to the pivot axis X. The first arm  78  of coupler  52  contacts bearing surface  70 . Consequently, as the actuator  40  displaces inwards under the influence of a release force R, bearing surface  70  pushes first arm  78  and causes coupler cylindrical body  76  to rotate about pivot boss  66 . 
         [0027]    The coupler  52  of  FIG. 6  further includes a laterally extending second arm  80  that engages brake  54 . Thus, as the cylindrical body  76  rotates about pivot boss  66 , the second arm  80  displaces brake  54  against the urging force provided by spring  56 . Thus, application of release force R moves the brake  54  out of simultaneous contact with the housing  12  and drum  44 , thereby allowing the tape blade  20  to retract into the housing  12 . As release force R is removed, spring  56  tends to displace brake  54  back into simultaneous contact with drum  44  and housing  12 . This once again locks the drum  44  relative to housing  12 . Furthermore, the movement of brake  54  to the locked position rotates coupler  52 , which in turn pushes actuator  40  outward. The actuator  40  may include a stop tab  72  that engages the housing  12  to limit the extent to which the actuator  40  is pushed outward. 
         [0028]    The second arm  80  advantageously fits within a corresponding aperture  82  in brake  54 . Further, second arm  80  may be curved slightly to maintain engagement with the brake aperture  82 . At each interface (i.e., between coupler  52  and actuator  40  and between coupler  52  and brake  54 ), there is sliding contact between the parts, which tends to reduce the overall size of the brake mechanism  50 . Further, the sliding interfaces tend to limit the extent to which motion of the parts is constrained. However, it should be noted that the interface either between coupler  52  and release lever  40  or between coupler  52  and brake  54  may take other forms, such as a ball and socket joint. 
         [0029]    The brake  54  shown in  FIG. 7  includes at least one, and advantageously a pair, of brake pads  84  that extend laterally from a brake body  86 . Alternatively, the brake body  86  could be formed with a width that is equal to or greater than brake pads  84 . In any event, brake pads  84  are spaced so that they align with the flanges  46  on tape drum  44 . Furthermore, as shown in  FIGS. 8A-8B , the brake pads  84  may be tapered or curved to better engage the curved drum flanges  46 . Due to their configuration, brake pads  84  tend to become less engaged with the drum  44  when the drum  44  rotates in one direction (clockwise in  FIGS. 8A-B ) corresponding to the tape blade  20  being pulled out, but tend to become more engaged with drum  44  when the drum  44  rotates in the opposite direction (counter-clockwise in  FIG. 8A-B ) corresponding to the tape blade  20  being retracted. The brake  54  and/or flanges  46  may be advantageously constructed from wear resistant materials such as Delrin, PTFE, or ultra-high molecular weight polyethylene. This is not to suggest that these are required materials or that some amount of wear is not advantageous. For instance, as the brake pads  84  and/or the flanges  46  wear over time, their mating surfaces may tend to conform to one another providing increased surface contact and increased locking capacity. 
         [0030]    As indicated above, the coupler  52  includes a generally cylindrical body  76 . The cylindrical body  76  is hollow and is sized to fit on pivot boss  66 . In one embodiment, the cylindrical body  76  includes a substantially fixed outer diameter (excluding arms  78 , 80 ). However, in the illustrated embodiment, the cylindrical body  76  includes a cam feature  88  that protrudes outward from cylindrical body  76 . The cam feature  88  extends from a first end  90  that is substantially flush with the remainder of the cylindrical body  76  towards a second end  92  that protrudes a greatest amount from the cylindrical body  76 . In one embodiment, the second end  92  of cam feature  88  protrudes from the cylindrical body  76  by an amount sufficient to contact drum flange  46  when the locking mechanism  50  is locked as shown in  FIG. 8A . Accordingly, when the locking mechanism  50  is locked, the coupler  52  and the brake  54  both contact a given flange  46  of the drum  44  at locations circumferentially spaced from one another, thus providing a two-point friction lock. However, once release force R is applied as shown in  FIG. 8B , coupler  52  rotates as indicated by the arrow labeled A so that the second end  92  of cam feature  88  rotates out of contact with flange  46  and cam feature first end  90  rotates to face flange  46 . However, because cam feature first end  90  protrudes by a smaller amount from cylindrical body  76 , coupler  52  does not engage flange  46 . Furthermore, as described above, coupler  52  rotation tends to pull brake  54  out of contact with flange  46 . Therefore, when release force R is applied as shown in  FIG. 8B , the drum  44  is free to rotate (in the clockwise direction in the views shown) to retract the tape blade  20 . Note that the rotating motion A of coupler  52  tends to produce a corresponding linear motion of brake  54  as indicated by arrow B. 
         [0031]    The brake  54  and the cam feature  88  are advantageously tapered to allow rotation of drum  44  in the extension direction while resisting rotation in the retraction direction. For instance, tapered brake pads  84  are shaped and oriented such that interference between the brake  54 , the housing  12 , and the drum  44  normally increases when the drum  44  rotates in the retraction direction (such as under the influence of retraction spring  45 ). Conversely, tapered brake pads  84  provide a decreasing interference between the brake  54 , the housing  12 , and the drum  44  when the drum  44  rotates in the extension direction. Generally, a similar effect is achieved by the tapered cam feature  88  on the coupler  52 . That is, the cam feature  88  is advantageously shaped and oriented to provide greater resistance to rotation of drum  44  in the retraction direction, and less (or advantageously essentially none) resistance to rotations of drum  44  in the extension direction. 
         [0032]    It is believed that the brake pads  84  and the cam feature  88  are each independently sufficient to prevent rotation of the drum  44  in the retraction direction. Therefore, in addition to the illustrated embodiments, the locking mechanism  50  may include only one of these locking features. For instance, in one embodiment, the locking mechanism  50  may include brake pads  84  on the brake  54  and no cam feature  88  on coupler  52 . In an alternative embodiment, the locking mechanism  50  may include the cam feature  88  on coupler  52 , with either no brake pads  84  on brake  54  or no brake  54 . In such arrangements, the coupler  52  may be more properly thought of as a rotatable member  54 , and may be alternatively referred to thereas. The rotatable member  54  should be biased to rotate into the engaged position, such as directly or indirectly by spring  56 , or by some other means such as a torsion spring (not shown) between pivot boss  66  and body  76 , a resilient connector (not shown) between pivot boss  66  and body  76 , or other rotational biasing means known in the mechanical arts. Any of these alternative embodiments may be sufficient to achieve the desired auto-lock function. 
         [0033]      FIG. 9  shows shell  24  with locking mechanism  50  and drum  44  removed for clarity, and illustrates exemplary geometry within the tape housing  12  that may be used to secure the various components of the locking mechanism  50 . Generally, each of the mating shells  22 ,  24  may include similar geometry, mirrored about the center plane of housing  12 , perpendicular to axis D. The pivot boss  66  onto which coupler  52  is installed is located proximate to brake channel  94 . The brake channel  94  may be formed as a slot in which the brake  54  resides and moves. However, in the embodiment shown, opposed channel bosses  96 , 98  form the brake channel  94  to limit the range of motion for the brake  54 . A first set of channel bosses  96  limits forward and backward motion, but permit up and down motion of the brake  54 . Similarly, the second set of channel bosses  98  limits lateral motion, but also permit up and down motion of the brake  54 . As suggested, these bosses  96 , 98  cooperate with corresponding bosses in the unillustrated mating shell  22  to further constrain the motion of the brake  54 . The tape housing  12  also includes a seat  100  for spring  56 . The seat  100  may be formed as a post, a recess, a hook, or other retaining feature intended to constrain spring  56 . The seat  100  further provides resistance against which spring  56  can urge brake  54  into contact with drum  44  and locking boss  58 . 
         [0034]    It should be understood that the tape measures  10  of the present invention may also include other features, such as shock-absorbing bumpers proximate the opening  18 , specially coated blades, reinforced hooks, and like, all of which are known in the art. 
         [0035]    The present invention may be carried out in other specific ways than those herein set forth without departing from the scope and essential characteristics of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.