Abstract:
A retractable tape measure having a flexible tape biased in a coiled position, and a housing sized to contain the flexible tape. The housing includes an opening through which a first end of the flexible tape extends, and a slot for positioning a locking mechanism. A tape biasing member operatively connects to the flexible tape to bias it in a retracted position. The locking mechanism controls the extension and retraction of the flexible tape from the housing. The mechanism includes a locking lever having a grip arm extending through the slot and a lock arm for contacting the flexible tape. A pin extends through the locking lever making the locking lever pivotable between an open position in which the flexible tape can move freely through the opening, a maintain position in which the flexible tape only exits freely through the opening, and a locked position to prevent the tape from moving relative to the opening. A lock biasing member biases the locking lever towards the locked position.

Description:
FIELD OF THE INVENTION 
     The present invention is directed generally to tape measures and, more particularly, a locking mechanism for controlling the extraction and retraction of a tape from a tape measure housing. 
     BACKGROUND OF THE INVENTION 
     Modern tape measures generally include a coiled tape that is spring biased towards a retracted position. A protective housing surrounds the tape and spring and includes an aperture through which a distal end of the tape extends. The distal end of the tape is pulled away from the housing during use, and when released, the spring pulls the tape back into the housing so that the tape assumes the retracted position. 
     Various types of locking mechanisms are utilized for maintaining the tape in any given extended position. Locking mechanisms usually bind the tape within the housing and are actuated by the user through a slide or push button positioned on an outer edge of the housing. Thus, the tape may be extracted to the desired length and a locking mechanism engaged to hold the tape at that distance. The locking mechanism may then be disengaged and the tape is retracted into the housing. 
     Many previous tape measures only provide for the locking mechanism to be either completely engaged or completely disengaged. These devices do not provide for any intermediate levels of control which may be advantageous in various environments. The lack of any intermediate level limits the functionality and environments in which the tape measure may be used. To overcome this problem, some tape measures are equipped with two separate locking mechanisms. One locking mechanism provides for a positive lock function, essentially mimicking the engaged and disengaged functionality of the previous models. The second locking mechanism provides a drag function which opposes the retraction or extraction of the tape relative to the housing, but typically at a lower grip force level than the “full” locking condition. However, each of the two locking mechanisms require separate elements which must be positioned within the housing. See for example U.S. Pat. No. 5,007,178. A two activator arrangement thus complicates the tape measure design, usually leading to a higher overall cost. Additionally, the housing must be larger to contain the tape and at least two separate locking mechanisms which is undesirable as hand tools must easily fit within the user&#39;s hands, attach to work belts, or be stored within limited spaces such as a crowded tool box. Other tape measures may have either, but not both types of braking mechanisms. 
     Therefore, there is a need for a tape measure having a single locking mechanism operable in three modes: a free mode characterized by a disengaged or open position in which the tape is free to retract or extend from the housing; a lock mode characterized by a lock position in which the tape is prevented from moving relative to the housing; and a maintain mode characterized by a maintain position in which the tape is prevented from retracting, but is allowed to extend relatively freely. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a tape measure having a variety of locking positions for controlling the retraction and extraction of a tape. The variety of positions allows a user to more easily handle and manipulate the tape to his or her advantage, especially when they are doing multiple tasks. 
     The tape measure includes a flexible tape subject to a bias towards a retracted position and a housing substantially surrounding the tape when it is in the retracted position. A locking lever is connected to the housing and includes a tip for selectively engaging the tape. The locking lever is positionable between at least three positions corresponding to the three functional modes. A free mode positions the locking lever and tip away from the tape for relatively free retraction and extraction of the tape from the housing. A lock mode engages the tip against the tape requiring increased force to extract or retract the tape relative to the housing. A maintain mode engages the tip against the tape to require force to retract the tape into the housing, but require little additional force with respect to the free mode for extraction. 
     Preferably, the locking lever pivots about an axis to accommodate the three modes. The locking lever includes a lock arm that extends to the tape, and a grip arm that extends outside the housing allowing for the user to control the modes. A tip is connected to the end of the lock arm for contacting the tape. The tip is constructed of a pliable material. In one embodiment, the tip is positioned off-center from the centerline of the lock arm in the lock mode for increased holding. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of a tape measure constructed in accordance with the present invention. 
     FIG. 2 is a partial perspective view illustrating the locking lever and tape. 
     FIG. 3 is a side view illustrating the tape biasing device. 
     FIG. 4A is a partial side view illustrating the locking mechanism in an open orientation. 
     FIG. 4B is a partial side view illustrating a locking mechanism in a maintained orientation. 
     FIG. 4C is a partial side view illustrating the locking mechanism in a lock orientation. 
     FIG. 5A is an end view illustrating the free mode wherein the tip is in the open position located above the tape. 
     FIG. 5B is an end view illustrating the lock mode wherein the tip is rotated to the locked position against the tape. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description, like reference characters designate like or corresponding parts throughout the several views. Also in the following description, it is to be understood that such terms as “forward”, “rearward”, “left”, “right”, “upwardly”, “downwardly”, and the like are words of convenience and are not to be construed as limiting terms. It should be understood that the illustrations are for the purpose of describing a preferred embodiment of the invention and are not intended to limit the invention thereto. 
     As illustrated in FIG. 1, a tape measure, generally designated  10 , is shown constructed according to the present invention. The tape measure  10  includes a coilable measuring tape  20  contained within a housing  30 . The tape  20  includes a proximal end positioned about a shaft  24  and a distal end  22  which extends through an opening  32  within the housing  30 . The distal end  22  is preferably equipped with a lip  26  to prevent it from being retracted into the housing  30 . A tape-biasing device  40  is operatively connected to the tape  20  to bias it towards a retracted orientation in which the lip  26  contacts the opening  32 . A locking mechanism  50  is selectively positionable between open, maintained, and locked positions to control the extraction and retraction of the tape  20  to and from the housing  30 . 
     The housing  30  extends around and protects the tape  20 , tape-biasing device  40 , and locking mechanism  50 . Housing  30  includes the opening  32  through which the tape distal end  22  extends, and a slot  34  having a first end  36  and second end  38  through which a part of the locking mechanism  50  extends. The slot  34  may further include detents  35  for maintaining the position of the locking mechanism  50 . Shafts and/or mounting components may be mounted on the housing inner edges for positioning the tape  20 , locking mechanism  50 , and tape biasing device  40 . The housing  30  is preferably sized to fit within a user&#39;s hand, and also conveniently stored on a work belt or toolbox. Housing  30  is preferably manufactured in a two-piece construction as illustrated in FIG. 1, and made from a durable material such as a hardened plastic. 
     The tape biasing device  40  urges the tape  20  into the retracted position within the housing  30 . In one embodiment best illustrated in FIG. 3, the device  40  includes a spring  42  positioned in two coils  44 ,  46 . Gears  48  are attached between coil  44  and the tape shaft  24  for transferring the spring biasing force to the attached tape  20 . When the tape distal end  22  is extracted from the housing  30 , the tape shaft  24  rotates causing rotation of the gears  48  thereby tightening the spring  42  onto the coil  44 . When the tape  20  is released, the spring  44  returns to coil  46  thereby rotating the gears  48  and causing retraction of the tape into the housing  30 . This type of tape biasing device is disclosed in U.S. Pat. No. 5,119,521 herein incorporated by reference in its entirety. One skilled in the art will understand that other types of biasing devices are available for retracting the tape  20  into the housing  30 , any of which may be used with the present invention. 
     The locking mechanism  50  includes a locking lever  52  and an optional lockbiasing member  53 . Locking lever  52  is best illustrated in FIG.  2  and includes a substantially L-shaped member having a grip arm  54  and a lock arm  56 . Grip arm  54  extends through the housing slot  34  and includes a gripping surface  55  positioned on the outside of the housing  30  for contact by the user. Preferably, the gripping surface  55  includes a contoured surface to prevent the user&#39;s hands or fingers from slipping. The lock arm  56  extends at an angle from the grip arm  54 . The lock arm  56  and grip arm  54  should be angled relative to one another such as between about 80°-110°, and preferably about 90°. In one embodiment, the grip arm  54  and lock arm  56  are constructed in a unitary manner. A guide member  59  may extend from the grip arm  54  for maintaining the orientation of the locking lever  52  within the housing slot  34  and cover the slot  34  to prevent debris from entering the housing  30  via the slot  34 . 
     The end of the locking arm  56  includes a tip  57  for contacting and controlling the retraction and extraction of the tape  20 . The tip  57  is preferably constructed of a high friction, pliable material such as a soft rubber to prevent the tape  20  from unintentionally slipping through the locking mechanism  50 . The tape  20  has a concave shape as it exits the housing  30  as illustrated in FIGS. 5A and 5B. Preferably, the radius of the tip  57  is less than the tape radius such that the tip  57  contacts a central area of the tape  20 . 
     Tip  57  has a compound radius, the apex of which is offset from a middle line of the locking arm  56  as illustrated in FIG.  4 A. This orientation provides the tip  57  with a cam-like action against the tape  20 . When the locking arm  56  moves beyond the vertical centerline CL of rotation in the locked position, as will be described below, the surface of the tip  57  does not recede from the tape  20 , as it would if the is tip  57  was centered on the locking arm  56 . In one embodiment, the apex of the tip  57  is about 0.030 inches offset clockwise from a middle line of the locking arm  56  as illustrated in FIG.  4 A. 
     The locking lever  52  is mounted within the housing  30  on an axle or pin  58  that extends from the inner edges of the housing  30 . This positioning allows the locking lever  52  to rotate between open, maintain, and locked positions as will be explained below. In one embodiment, the pin  58  is aligned substantially parallel with the shaft  24 . 
     The optional lock-biasing member  53  biases the locking lever  52  such that the tip  57  contacts the tape  20 . In the embodiment illustrated in FIGS. 1,  4 A,  4 B, and  4 C, the lock-biasing member  53  is a torsion spring having two ends and an inner coiled section. Preferably, mounts  37  extend from the grip arm  54  and the inner housing to contain the spring ends, and the coiled section is positioned around the pin  58 . 
     The use of the tape measure  10  in operation is illustrated in FIGS. 4A,  4 B, and  4 C. The lock-biasing member  53  maintains the locking lever  52  in the maintain position as illustrated in FIG. 4B when no external forces are applied. A force to overcome the lock bias is applied by the user to the gripping surface  55  in the direction of arrow  60  in FIG. 4A to move the locking lever  52  to the open position with the tip  57  removed from and not in contact with the tape  20 . The force applied by the tape-biasing device  40  pulls the tape  20  into a retracted orientation with the tape lip  26  contacting the housing  30  in proximity to the opening  32 . The maximum extent of rotation of the locking lever  52  may be controlled by the grip arm  54  contacting the slot first end  36  or a boss (not illustrated) extending from the housing. In the open position, a force of about 1.0 lbs. is required to extract the tape  20  from the housing  30 . This is necessary to overcome the retraction force applied by the tape biasing device  40 . 
     The maintain position illustrated in FIG. 4B allows the tape  20  to be extracted (also referred to as extended) from the housing  30 , but prevents unintentional retraction of the tape  20  into the housing. An angle θ is formed between a line extending through the center of the grip arm  54  and a centerline CL. 
     In the embodiments illustrated in FIGS. 4A-4C, the centerline CL is the line drawn between the locking mechanism pin  58  and the bottom of the case  30 . The centerline CL forms an imaginary line at about a ninety degree angle to the case bottom and through the center of the locking member pin  58 . In the maintain position, the grip arm  54  of the locking lever  52  is rotated (counter-clockwise in FIG. 4B) such that angle θ is roughly between about 5°-40°, and preferably about 30°. In some embodiments, the optional lock biasing device  53  applies a force to the locking lever  52  to hold the tape  20  between the tip  57  and housing  30 . Alternatively, the locking lever  52  may be held in the maintain position by other means, such as by detents and the like. With the locking lever  52  in the maintain position, a force of about 1.4 lbs. is necessary to extract the tape from the housing  30 , while the force necessary to push in, or retract the tape  20  into the housing  30  is about at least 7 lbs. This force is necessary to overcome the frictional contact between the tip  57  and the force applied to the tape  20  by the tape biasing device  40 . Retraction of the tape  20  into the housing  30  will tend to rotate the lever arm  52  in a counterclockwise direction, thereby lessening θ and increasing the gripping force exerted by the lever arm  52  and the housing  30 . Thus, in the maintain position, extension of the tape requires overcoming the retraction spring and some slight amount of drag from the frictional contact of the tip  57  while retraction requires overcoming an increasing amount of gripping force exerted by the lever arm  52  and the housing  30 . Thus, in the maintain position, the tape  20  may be easily pulled out (extended), but will not be pulled back into the housing  30  (retracted) when released by the user. The maintain position is preferably the default position when no external forces are applied to the tape  20  or locking mechanism  50 . 
     FIG. 4C illustrates the locking mechanism  50  in the locked position in which extraction and retraction of the tape  20  relative to the housing  30  is prevented. In this position, the locking lever  52  is further rotated counterclockwise by the user such that the tip  57  of the lock arm  56  clamps the tape  20  against the housing  30 . In one embodiment illustrated in FIG. 4C, the lock arm  56  rotates beyond the centerline CL resulting in a negative θ. In this embodiment, the locking lever  52  is mounted within the housing  30  such that the tip  57  of the lock arm  56  experiences maximum deformation after the lock arm  56  has rotated beyond the centerline CL due to the offset of the apex of the tip  57  relative to the locking arm  56 . The deformation may also be felt by the user as they contact the gripping surface  55  providing positive enforcement that the locking mechanism is in the locked position. In the locked position, the tip  57  of the lock arm  56  preferably remains at least partially deformed so as to substantially clamp the tape  20  between the tip  57  and the housing  30 . In one embodiment, the angle θ in the lock position is between about 0°-(−20°), and preferably about −12°. The maximum extent of angle θ may also be controlled by the grip arm  54  contacting the slot second end  38 , or a boss (not illustrated) may extend from the inner edge of the housing. In the locked position, about 15 lbs. of force is required to pull the tape  20  from the housing  30 . The push-in or retraction force is about at least 7 lbs. 
     In the locked position in which the locking arm  56  is rotated beyond the centerline CL, an over-center lock occurs. The force between the case bottom and the tip  57  serves to maintain the locking mechanism  50  in the same position because the force is directed at continuing the counter-clockwise rotation of the locking mechanism  50 . This prevents the locking mechanism  50  from inadvertently slipping out of the locked orientation. 
     FIGS. 5A and 5B illustrate the movement of the tip  57  relative to the tape. FIG. 5A illustrates the tip  57  in the open position located above the tape  20 . As is customary in the industry, the tape  20  has a concave shape as it extends from the housing  30 . The tip  57  preferably has a corresponding curved shape having a rounded edge that substantially conforms to the shape of the tape  20 . In the locked position illustrated in FIG. 5B, the tip  57  is placed firmly against the tape  20 . Preferably, the tip  57  contacts an inner portion of the tape such that the tape  20  maintains the concave shape while the tip deforms and holds the tape  20 . The housing  30  may further include a contact surface  31  which contacts the tape  20  opposite the tip  57 . In the maintain position, the tip  57  preferably rests against the tape  20 , but with less pressure than in the locked position. 
     Certain modifications and improvements will occur to those skilled in the art upon a reading of the foregoing description. In one embodiment, the grip arm  54  and lock arm  56  are separately constructed and connected together at an angle to form the locking lever  52 . It should be understood that all such modifications and improvements have been deleted herein for the sake of conciseness and readability, but are properly within the scope of the following claims.