Abstract:
A retractable knife includes an elongate handle and a blade holder slidingly mounted within the handle for sliding movements between a retracted position and an extended position. The blade holder is configured for receiving. A manually operable blade lock is formed on the holder and including a release member rotatably mounted on the blade holder. The release member having a first portion projecting beyond the handle and positioned to be actuated by a finger of a user while holding the handle. A second portion is movable with the first portion between a locking position in which the second portion is received with a notch of a blade and a releasing position in which the second position is removed from the blade notch to a position outside the notch of the blade. A spring normally rotates the release member to move the second portion to the locking position. Actuation of the release member by the finger of the user to overcome the spring moves the second portion to the releasing position and releases the blade.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally related to a hand tools, and more specifically to a retractable utility knife with a quick release blade mechanism. 
     2. Description of the Prior Art 
     Conventional utility knives have various types of structures including fixed, foldable and retractable. They are generally used to cut paper, fabric, and leather. The Chinese Patent Application No. 93208241.6 (Publication Date: Jun. 22, 1994) disclosed “a retractable rope-cut utility knife”, in which a blade stored in a handle is extended out step by step by moving a slider. However, it is not convenient to replace the blade. The Chinese Patent Application No. 03223149.0 (Publication Date: Dec. 24, 2003) disclosed “a combined utility knife”. It is convenient to replace a blade by arranging the blade in a groove of the handle assembly and using a top cover in connection with a lock member. However, the following problems exist. The structure is complex; when replacing a blade, a user needs to release the lock member first and then rotate the top cover, which is complicated and inconvenient. The Chinese Patent Application No. 20042010202117.2 (Publication Date: Feb. 8, 2006) disclosed “a utility knife” in which a blade is arranged in a mounting groove of a handle assembly and a fixing hole is provided in the handle assembly. A bolt anchored in the fixing hole secures the blade. This utility knife is also disadvantageous because extra tools are used when the blade is replaced. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the invention to provide a retractable utility knife which does not include the disadvantages inherent in prior art utility knives. 
     It is another object of the invention to provide a retractable utility knife that is simple in construction and economical to manufacture. 
     It is still another object of the invention to provide a retractable utility knife as in the previous objects which permits one hand operation for releasing a blade from a retractable utility knife. 
     It is yet another object of the invention to provide a retractable utility knife of the type under discussion that is easy and convenient to use. 
     It is a further object of the invention to provide a retractable utility knife as suggested in the previous objects that is ergonomically configured to allow a blade to be released with the thumb of a user while the blade is being held in the same hand of the user. 
     It is still a further object to provide a utility knife as in the previous objects that has a slim profile and easy to store and transport. 
     In order to achieve the above objects, as well as others which will become apparent hereafter, a retractable utility knife in accordance with the present invention includes an elongate handle generally defining an axis. A blade holder is slidingly mounted within the handle for sliding movements relative to the handle along the axis between a retracted position and an extended position. The blade holder is configured for receiving at least a portion of a blade provided with one edge formed as a cutting edge and an opposing edge formed with a notch. A manually operable blade lock is formed on the blade holder and includes a release member rotatably mounted on the blade holder. The release member has a first portion projecting beyond the blade holder and positioned to be actuated by a finger of a user while holding the handle. A second portion of the release member is arranged to move with the first portion and moveable between a locking position in which the second portion is received within the notch of the blade and a releasing position in which the second portion is removed from and is positioned beyond the notch of the blade. Biasing means in the form of a spring is provided for normally rotating the release member to move the second portion to the locking position. In this manner, actuation of the release member by the finger of the user to overcome the biasing forces of the spring moves the second portion to the releasing position and the blade can be quickly and conveniently removed from the blade holder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects and features of the present invention may become clear from the following description taken in conjunction with the preferred embodiments thereof with reference to the accompanying drawings, in which: 
         FIG. 1  is a bottom plan view of a retractable utility knife in accordance with the invention, shown with the blade and blade carriage in an extended position; 
         FIG. 2  is a right side elevational view of the utility knife shown in  FIG. 1 ; 
         FIG. 3  is a rear side elevational view of the utility knife shown in  FIGS. 1-2 ; 
         FIG. 4  is an exploded perspective view of the handle forming part of the retractable utility knife shown in  FIGS. 1-3 ; 
         FIG. 5  is a perspective view of a utility blade of the type that can be used with the retractable utility knife; 
         FIG. 6  is a right side elevational view of the carriage slidably mounted within the handle of the retractable utility knife, showing the details of a release button when it is in its upwardly extended, carriage-locking position; 
         FIG. 7  is similar to  FIG. 6 , but showing the reverse side of the carriage and further showing a cover plate removed from the forward or front end of the carriage to illustrate the details of the locking and releasing disk and the manner in which it is biased and used to selectively lock or release a blade received within the carriage or blade holder; 
         FIG. 8  is a side elevational view of the cover plate removed from the carriage and normally covering the blade locking and releasing mechanism shown in  FIG. 7 ; and 
         FIG. 9  is a perspective view of a flat strip receivable within a transverse through hole or slot in the release button shown in  FIGS. 6 and 7  for selectively engaging indents within the handle for selectively locking or releasing the carriage from longitudinal sliding movements relative to the handle. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     Referring know specifically to the Figures, in which identical or similar parts are designated by the same reference numerals throughout, and first referring to  FIGS. 1-4 , a retractable utility knife in accordance with the present invention is generally designated by the reference numeral  10 . 
     The retractable utility knife  10  includes a handle  11 , an exploded view of which is shown in  FIG. 4 . The handle  11  is generally elongate, as shown, and generally defines an axis A along its length direction. The handle  11  is preferably ergonomically configured to provide a comfortable grip by a user using the utility knife. 
     The handle  11  is formed of an inner frame  12  which includes spaced right and left plates or rails  12   a ,  12   b  separated a suitable or desired distance by means of a bridging strip  12   c , shown in  FIGS. 2 and 3 . In the presently preferred embodiment, the plates or rails  12   a ,  12   b  are spaced approximately 0.25″ apart. The inner frame  12  is, in accordance with the present invention, formed of stainless steel, although other rigid materials can be used. Since the bridging strip  12   c  is formed at the remote end of the handle  11 , suitable spacers, to be described, are provided for maintaining the right and left plates or rails  12   a,    12   b  at a fixed spacing from each other. Preferably, the inner facing surfaces of the plates or rails  12   a ,  12   b  are polished to provide smooth surfaces that minimize sliding friction. 
     A right cover  14  is mounted on the right plate or rail  12   a , the right cover being provided with a beveled edge  14   a , as shown, and exposed right surface  14   b . Similarly, a left cover  16  is provided with a bevel  16   a  and exhibits a left surface  16   b  when mounted on the left plate or rail  12   b . The right and/or left covers  14 ,  16  are preferably provided with suitable ornamentation  16   c , as suggested in  FIG. 4 . 
     A gap or space  18  resulting between the right and left rails or plates  12   a ,  12   b  is maintained at a desired spacing by means of spacers  20  of the type shown in  FIGS. 1  and  4 . Any suitable number of spacers may be provided to maintain the inner frame essentially fixed or rigid and the gap or space  18  uniform. In the presently preferred embodiment the spacing between the inner, facing surfaces of the plates or rails  12   a ,  12   b  is approximately 3/16″. 
     Mounted for sliding movements within the inner frame  12 , or between the right and left plates or rails  12   a ,  12   b  is a blade holder or carriage  22  that is received within the gap or space  18  of the inner frame  12  for sliding movements relative to the frame  12  and the handle  11  essentially along the length direction or axis A of the handle  11 . The carriage is preferably formed of stainless steel, although other comparable materials can also be used. The lateral right and left surfaces of the carriage facing the inner surfaces of the rails or plates  12   a ,  12   b  are preferably polished to provide smooth surfaces to minimize sliding friction with the smooth, polished, facing surfaces of the rails or plates. The thickness or transverse dimension of the carriage  22  is selected to allow the carriage to be received within the gap or space  18  to allow free longitudinal sliding movements without any significant lateral play. Preferably, a suitable lubricant, such as oil or silicone-based lubricants, are applied between the frame  12  and the carriage  22  to provide smooth movements involving little friction. 
     The carriage or blade holder  22  is provided with a receiving cavity for receiving at least a portion of a blade of the type generally shown in  FIG. 5 . The blade  24  is a conventional trapezoidal-shaped utility knife blade of the type commonly used in numerous utility knives. The blade is typically formed along its lower or larger base with a cutting edge  24   a , while the opposing upper or shorter base is formed with at least one notch  24   c . Typically, such blades are provided with two spaced notches  24   c  as shown so that with most utility knives in which these blades are used they can be reversed and utilized irrespective of which pointed edge extends beyond the utility knife during use. 
     Referring specifically to  FIGS. 6-9 , the carriage or blade holder  22  is shown formed of a solid block portion  22   a , at the rear or proximate end of the carriage  22 , while the forward or remote end of the carriage  22  is provided with the blade receiving cavity  22   b , in which material has been removed, as shown, to provide various cavities or recesses to be described. The forward or remote edge  22   c  is inclined to expose a triangular section of the blade  24  when it is exposed outside of the carriage during use. 
     Referring specifically to  FIG. 7 , the front or remote portion  22   b  of the carriage  22  is formed with a number of cavities having different depths. Thus, along the upper and lower edges there are provided mounting strips on which a cover plate  48  can be attached to enclose the various cavities or recesses shown in  FIG. 8 . The cover plate  48  is shown in  FIG. 8 . 
     The upper mounting strip  25  forms a step or upper guide edge  28  while the lower mounting strip  25  forms a lower step or upper guide edge  30 , the guide edges being parallel to each other and together define a guide surface  26  against which one surface of the blade  24  can slide. Additional bosses, such as boss  26   a , can be provided whose outer surfaces are co-extensive with the guide surface  26  to provide support and facilitate sliding movements of the blade relative to the guide surface  26 . 
     Referring to  FIG. 6 , a circular recess  23  is provided in the face or outer surface of the carriage  22 , as shown, the radial distance of the center of the circular recess being less than its radius from the upper edge of the carriage, as shown, so that an upper arc of the circular recess  23  forms an opening through the upper edge of the carriage. A circular release disk  32  is rotatably mounted on a suitable pivot pin  34  ( FIG. 7 ) so that at least a portion of the release disk extends or projects above the upper edge of the carriage as shown. Preferably, the portion of the release disk  32  that projects above the upper edge of the carriage is provided with a ribbed or knurled edge, as shown, to facilitate gripping with a finger of a user. 
     Referring to  FIG. 7 , a cutout or opening  36   a , shown as an arcuate cavity, is provided behind the release disk  32  and, similarly, a second cutout  36   b  is provided somewhat diametrically opposite to the cutout  36   a . A biasing finger  38 , attached to or forming a part of the release disk  32  projects through the cutout  36   b . However, the biasing finger  38  does not project beyond the guide surface  26  so as not to interfere with any blade supported on the guide surface  26 . A suitable biasing member is provided for engaging the biasing finger  38 . The biasing member in  FIG. 7  is shown to be a leaf spring  40  having the fixed end  40   a  received within a recess  42  and a moveable or free end  40   b  that engages the biasing finger  38  and urges the biasing finger  38  upwardly, as shown in  FIG. 7 , to rotate the release disk  32  in a generally clockwise direction. 
     A stop finger  44  projects transversely from the release disk  32  into the arcuate cutout  36   a . However, the stop finger  44  projects beyond the guide surface  26  by a distance that is substantially equal to the thickness of the blade  24 . The stop pin or finger  44  is configured so that in a locking position of the blade, as shown in  FIG. 7 , the stop finger or pin  44  is received within one of the notches  24   c  which fixes the position of the blade and prevents it from moving longitudinally along the steps or guide edges  28 ,  30  relative to the carriage  22 . It will be evident that when a user places his or her finger, typically the thumb, on the release disk  32  and pulls the projecting top edge of the disk and urges the disk towards the proximate or towards the rear of the handle  11 , the release disk rotates in a counterclockwise direction, as viewed in  FIG. 7 , against the biasing forces of the spring  40 . The spring  40  is selected to bias the release disk  32  to its normal locking position although readily rotatable to an unlocking position, when the stop pin or finger  44  is elevated or lifted out of one of the notches  24   c  of the blade without too much force or resistance. Like the biasing finger  38 , the spring  40  is placed within a cavity below the plane of the guide surface  26  so that the movements of the spring and the biasing finger  38  do not contact and do not interfere with the members of the blade. 
     When assembled, the cover plate  48  can be positioned over the recessed portions  22   b  of the carriage, at which time the tabs  46  are received within the recesses  48   a  of the cover plate and suitable fasteners can be used to secure the cover plate to the rest of the carriage. The thickness of the steps  28 ,  30  substantially correspond to the thickness of the blade so that when a cover plate  48  is secured onto the mounting strips  25  a receiving space is maintained for allowing a blade to be slidably inserted or removed from the carriage or blade holder  22  when the release disk  32  is rotated in a counterclockwise direction to lift the stop finger or pin  44  to avoid interference with the free movements of the blade. 
     Referring to  FIGS. 6 and 7 , the rear or proximate end of the carriage is provided with a T-shaped slot that includes a lower narrow slot  50  and a wide upper slot  52 , both slots being substantially aligned along a direction that is generally normal or perpendicular to the lengthwise direction or axis A of the handle  11 . A release button  54 , which may be formed of a slip resistant material, such as rubber or rubber-like material, is formed with a downwardly depending post or stem  56 . The axial length of the release button  54  is somewhat less than the width of the wide slot  52  while the axial or lengthwise dimension of the narrow slot  50  is somewhat greater than the dimension of the stem, as shown, so that the stem  56  can be received within the narrow slot  50  with some clearance and, likewise, the release button  54  can be received with some clearance within the wide slot  52 . In this way, the release button  54  can move downwardly or upwardly within the slots of the resulting T-shaped slot. A suitable spring  60 , such as helical spring, is arranged between the lower most surface of the narrow slot  50  and captured between that surface and the stem  56  so that the helical spring  60  normally biases or urges the release button  54  to move in an upward direction, although a downward pressure on the release button  54  by a user can move the release button downwardly into the wide slot  52  against the action of the spring. 
     A transverse slot  58  is formed within the post or stem  56  though with which a transverse bar or pin  62  may be inserted, as shown in  FIG. 6 . Referring to  FIG. 4 , the right and left rails  12   a ,  12   b  are provided with upper tracks  64  that extend along the longitudinal direction along the axis A of the handle. Similarly, corresponding lower tracks  66  are provided in each of the rails or plates  12   a ,  12   b  that are parallel to the upper tracks  64 . At least two indents are provided in the upper tracks  64 , extending in an upper direction away from the lower tracks  66  as shown in  FIG. 4 . In the embodiment shown, a single front indent  68  is provided at the front or remote end of the upper tracks  64  and two spaced rear indents  70  are provided at the rear or proximate ends of the upper tracks. Referring to  FIG. 9 , a transverse bar or pin  62 , when placed within the slot  58 , is dimensioned to project to each side of the stem or post  56  to be receivable within the upper tracks  64  for sliding movements within the upper tracks. The location of the slot  58  and, therefore, the transverse bar or pin  62  is selected so that when the helical spring  60  urges the stem  56  upwardly this biases the bar or pin  62  upwardly and, when juxtaposed against one of the indents  68 ,  70 , the bar or pin  62  will be urged into an indent below which it is placed. It should be evident that once the bar or pin  62  is received within one of the indents  68 ,  70  this locks the carriage  22  from longitudinal sliding movements along the axis A of the carriage. However, when the release button  54  is pressed downwardly, against the action of the spring  60 , the bar or pin  62  is urged out of a recess in which it has been positioned, at which time a longitudinal or axial force on the release button forwardly or rearwardly causes the carriage or blade holder  22  to slide forwardly or rearwardly, depending on the direction of the force applied by the user&#39;s thumb. This allows a user to selectively lock the carriage, and any blade secured therein by the release disk  32 , to slide forwardly to an extended position shown in  FIGS. 1-3  or rearwardly, at which time the carriage or blade holder is locked or secured in its retracted position. 
     To facilitate sliding and to stabilize the movements of the carriage between extended and retracted positions, there are provided upper holes  72  and lower holes  74  in the carriage through which suitable stabilizing pins  75  (one shown in  FIG. 8 ) may extend, pins dimensioned to be received within the tracks  64 ,  66  with some but little clearance. Two upper holes  72  and two lower holes  74  are shown in  FIG. 7 , these holes being arranged along substantially parallel lines spaced to correspond to the spacing between the speed tracks  64 ,  66 . This ensures that the carriage moves longitudinally along the handle  11  with a smooth stable motion and without any rotational movement components. 
     Suitable fasteners, such as screws or rivets may be used to secure the cover plate  48  to the carriage and the covers  14 ,  16  to the inner frame  12 . The specific fasteners used are not critical for purposes of the invention. 
     In the embodiment illustrated, there is also provided an optional spring clip  76  secured to the right cover  14  by means of rivets or screw  78 . 
     By making the release button  54  from an elastameric or other non-slip resistant material this makes it easier for a user to push the release button downwardly and rearwardly or downwardly and forwardly without slippage. 
     With the retractable knife disclosed the utility knife has a carriage or blade holder  22  that, with the blade fixed thereon, can be fully retracted within the handle  11  or extended as shown in  FIG. 1-3 . It will be appreciated that once the carriage or blade holder is fully retracted within the handle the overall length of the utility knife becomes significantly shorter than the extended length. The design makes it possible to make the utility knife relatively slim and short and portable both within a tool box or tool bag, on the person, clipped to a belt, etc. Movements of the carriage from a retracted to extended positions, as well as quick release of the blade by rotation of the release disk are all one hand operations. 
     While the invention has been shown and described in connection with a preferred form of an embodiment it will be understood that modifications may be made without the departure from the scope or spirit of the invention.