Abstract:
A utility knife has a blade carriage having a blade-receiving bay and moveable horizontally to move a cutting blade disposed in the bay from a retracted position to a deployed position. A locking mechanism is operative to releasably couple the cutting blade to the carriage and includes a lock plate having an blade-engagement element and moveable by non-pivoting, generally vertical displacement between a locked position and an unlocked position. An actuator engages the locking mechanism and moves the locking mechanism from the locked position to the unlocked position. The actuator may move from a first position to a second position in unlocking the locking mechanism, optionally vertically, with the second position being not closer to the midline of the utility knife than the first position. The blade-receiving bay may face the side of the housing that supports the actuator for the locking mechanism.

Description:
BACKGROUND OF THE INVENTION 
   The present invention is directed generally to utility knives, and more particularly to a utility knife having a releasable blade locking mechanism. 
   Modern utility knives typically include a housing, a moveable blade carriage, and a cutting blade. The blade carriage is mounted in the housing so as slide back and forth inside the housing. The cutting blade is coupled to the blade carriage so as to move between an extended or deployed cutting position (carriage forward) and a retracted position (carriage back). The cutting blade typically has a trapezoid shape with a razor sharp cutting edge along the long lower side and two small U-shaped notches along an opposing shorter upper side for mating the cutting blade to the blade carriage. 
   In use, the sharp edge of the cutting blade may become dulled, or the blade may break, or the blade may otherwise need to be replaced. As such, it is common for utility knives to allow the blade to be replaced. In very simple utility knives, the housing may be formed of two halves that are joined together by a central screw. Replacement of the blade in such devices requires the screw to be removed, the housing halves separated to expose the blade carriage, removal and replacement of the blade, and then re-assembly of the housing. Such an arrangement is shown, for example, in U.S. Pat. Nos. 5,099,578 and 3,192,624. Other utility knives use modified versions of this concept, with housing halves that pivot with respect to one another, or other means to hold the housing halves together. Nevertheless, the manipulation of the housing required to change the cutting blades is less than ideal with such designs. Accordingly, some designs have been proposed that use a “quick release” mechanism that allows the cutting blade to be replaced via the front slit in the housing. Examples of such designs are shown in U.S. Pat. Nos. 6,829,827 and 6,553,674. However, even these quick-release mechanisms have proven less than ideal, and there remains a need for alternative utility knife designs that allow for easy cutting blade replacement. 
   SUMMARY OF THE INVENTION 
   In one embodiment, the present invention is directed to a utility knife comprising: an outer housing having a top, a bottom, and first and second lateral sidewalls extending between the top and bottom; the sidewalls being longer than the top and bottom in cross-section; the housing further having a forward opening; a blade carriage having a blade-receiving bay; the blade carriage moveable horizontally in the housing to move a cutting blade disposed in the bay from a retracted position to a deployed position, the cutting blade extending through the forward opening in the deployed position; a locking mechanism operative to releasably couple the cutting blade to the carriage; the locking mechanism connected to the carriage for horizontal movement therewith; wherein the locking mechanism comprises a lock plate having an blade-engagement element; the locking plate moveable by non-pivoting, generally vertical displacement between a locked position operative to couple the cutting blade to the carriage for horizontal movement therewith and an unlocked position wherein the cutting blade may be removed from the carriage; the locking mechanism biased toward the locked position; a first actuator moveable by a user to engage the locking mechanism and move the locking mechanism from the locked position to the unlocked position. The first actuator may mount to the housing first sidewall and move generally vertically to engage the locking mechanism and move the locking mechanism from the locked position to the unlocked position. The carriage may further comprises a second actuator biased to an upward position for engaging the housing so as to retain the carriage in a selected horizontal position relative to the housing. The lock plate may comprise first and second portions, the second portion disposed at an angle to the first portion so as to overlie the blade-receiving bay; wherein the blade-engagement element comprises a protrusion disposed on an underside of the second portion toward the blade-receiving bay; wherein the second portion is disposed vertically farther upward with respect to the carriage in the unlocked position than in the locked position. The first portion may extend generally vertically. The locking mechanism may further comprise a spring biasing the lock plate toward the locked position. The blade-receiving bay may be disposed toward the first sidewall. The housing may further comprise a front slit, wherein the cutting blade may be inserted into the blade-receiving bay via the front slit. The first actuator may comprise a body having an external section and an internal section, relative to the housing; the internal section having a protrusion for engaging the underside of the second portion of the lock plate; the body biased downward relative to the housing. Combinations of the above are also possible. 
   In another embodiment, the present invention provides a utility knife comprising: an outer housing having a top, a bottom, and first and second lateral sidewalls extending between the top and bottom; the sidewalls being longer than the top and bottom in cross-section; the housing further having a forward opening and a longitudinally extending midline; a blade carriage having a blade-receiving bay; the blade carriage moveable horizontally in the housing to move a cutting blade disposed in the bay from a retracted position to a deployed position, the cutting blade extending through the forward opening in the deployed position; a locking mechanism operative to releasably couple the cutting blade to the carriage; the locking mechanism connected to the carriage for horizontal movement therewith; the locking mechanism moveable generally vertically between a locked position operative to couple the cutting blade to the carriage for horizontal movement therewith and an unlocked position wherein the cutting blade may be removed from the carriage; the locking mechanism biased toward the locked position; a first actuator mounted to the first sidewall of the housing; the first actuator vertically moveable by a user to engage the locking mechanism and move the locking mechanism from the locked position to the unlocked position; wherein the first actuator moves from a first position to a second position in moving the locking mechanism from the locked position to the unlocked position, the second position being not closer to the midline than the first position. The first actuator may move generally parallel to the first sidewall in moving from the first position to the second position. The second position of the first actuator may be farther from the midline than the first position of the first actuator. The carriage may further comprise a second actuator biased to an upward position for engaging the housing so as to retain the carriage in a selected horizontal position relative to the housing. The lock mechanism may comprise a lock plate having a protrusion and first and second portions, the second portion disposed at an angle to the first portion so as to overlie the blade-receiving bay; wherein the protrusion is disposed on an underside of the second portion toward the blade-receiving bay and is disposed vertically farther upward with respect to the carriage in the unlocked position than in the locked position. The locking plate may move by non-pivoting, generally vertical displacement between the locked position and the unlocked position. The blade-receiving bay may be disposed toward the first sidewall. The first actuator may comprise a body having an external section and an internal section, relative to the housing; the internal section having a protrusion for engaging the underside of the second portion of the lock plate; the body biased downward relative to the housing. Combinations of the above are also possible. 
   In another embodiments, the present invention provides utility knife comprising: an outer housing having a top, a bottom, and first and second lateral sidewalls extending between the top and bottom; the sidewalls being longer than the top and bottom in cross-section; the housing further having a forward opening; a blade carriage having a blade-receiving bay disposed toward the first sidewall; the blade carriage moveable horizontally in the housing to move a cutting blade disposed in the bay from a retracted position to a deployed position, the cutting blade extending through the forward opening in the deployed position; a locking mechanism operative to releasably couple the cutting blade to the carriage; the locking mechanism connected to the carriage for horizontal movement therewith; the locking mechanism moveable generally vertically between a locked position operative to couple the cutting blade to the carriage for horizontal movement therewith and an unlocked position wherein the cutting blade may be removed from the carriage; the locking mechanism biased toward the locked position; a first actuator mounted to the first sidewall of the housing; the first actuator vertically moveable by a user to engage the locking mechanism and move the locking mechanism from the locked position to the unlocked position. The first sidewall may include a side opening oriented toward the blade carriage; wherein the first actuator extends through the side opening, and/or the first may be disposed to the left of the second sidewall when viewed the housing is viewed from the rear. The lock mechanism may comprise a lock plate having a protrusion and first and second portions, the second portion disposed at an angle to the first portion so as to overlie the blade-receiving bay; wherein the protrusion is disposed on an underside of the second portion toward the blade-receiving bay and is disposed vertically farther upward with respect to the carriage in the unlocked position than in the locked position. The locking plate may move by non-pivoting, generally vertical displacement between the locked position and the unlocked position. The housing may have a longitudinally extending midline and wherein the second position of the first actuator is farther from the midline than the first position of the first actuator. Combinations of the above are also possible. 
   In another embodiment, the present invention provides a utility knife comprising: an outer housing having a top, a bottom, and first and second lateral sidewalls extending between the top and bottom; the sidewalls being longer than the top and bottom in cross-section; the housing further having a forward opening; a blade carriage having a blade-receiving bay; the blade carriage moveable horizontally in the housing to move a cutting blade disposed in the bay from a retracted position to a deployed position, the cutting blade extending through the forward opening in the deployed position; a locking means operative to releasably couple the cutting blade to the carriage; the locking means moveable between a locked position operative to couple the cutting blade to the carriage for horizontal movement therewith and an unlocked position wherein the cutting blade may be removed from the carriage; the locking mechanism biased toward the locked position; the locking means connected to the carriage for horizontal movement therewith; a first actuator moveable by a user to move the locking means from the locked position to the unlocked position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is shows one embodiment of a utility knife constructed in accordance with the present invention with a blade storage arm moved to an open position. 
       FIG. 2  shows an exploded view of the utility knife of  FIG. 1  with the blade storage arm moved to a closed position. 
       FIGS. 3A–3B  shows some operational components of the embodiment of  FIG. 1  in the locked position and the release position, respectively, with the housing removed. 
       FIG. 4  shows a side perspective view of a blade mated to a blade carriage. 
       FIG. 5  shows a portion of a releasable locking mechanism. 
       FIG. 6  shows a release actuator suitable for use with the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In one illustrative embodiment, the present invention provides a utility knife having a novel releasable blade locking mechanism that allows the associated cutting blade to be replaced easily. 
   As illustrated in  FIG. 1 , a utility knife, generally designated  10 , is shown constructed according to the present invention. The knife  10  includes a housing  20 , a blade carriage  30 , and a locking mechanism  60  for coupling a cutting blade  5  to the blade carriage  30 . The housing  20  includes a top  21 , a bottom  24 , and two lateral sidewalls  26  disposed between the top  21  and bottom  24 . When viewed in cross-section, the sidewalls  26  are longer than the top  21  and bottom  24 , and it is intended that the sidewalls  26  be disposed generally parallel to the planar side surfaces of the cutting blade  5 . The housing  20  is generally elongate, with a theoretical midline  25  extending longitudinally front to back, midway between the sidewalls  26 . The housing  20  may be formed of respective halves  20   a ,  20   b  that part generally along a plane that includes the midline  25  and are joined together by suitable means, such as by screws  12  or snap-fitting. The outer profile of the housing  20  should be shaped so as to fit comfortably in a user&#39;s hand. The housing  20  should be formed of a suitably strong material, such as steel or hard plastic, but the housing  20  may include areas  27  of soft elastomeric material on the exterior surfaces as is desired in order to increase comfort and/or to increase grip. As is conventional, the front portion of the housing  20  includes a front slit  29  sized so as to accommodate a cutting blade  5  extending therethrough. 
   The blade carriage  30  is slidably disposed in the housing  20 . The blade carriage  30  includes a main body  32  defining a blade-receiving bay  40  and a carriage positioning actuator  50 . The blade-receiving bay  40  is adapted to accept and support the cutting blade  5 . While a wide variety of configurations for blade-receiving bay  40  are possible, the blade-receiving bay  40  typically has a generally U-shaped profile opening to the side (typically, the left side when viewed from the rear), with a vertical retaining wall  46 , a bottom support wall  42 , and a top retaining wall  44 . When the cutting blade  5  is mated to carriage  30 , a rearward portion of the cutting edge of blade  5  rests against the bottom support wall  42 , the generally planar side of the blade  5  rests against retaining wall  46 , and the upper edge of the blade  5  is disposed proximate the upper retaining wall  44 . The carriage positioning actuator  50  mounts to a rearward portion of the blade carriage main body  32  and typically comprises a spring biased button having a cap  52  and a post  56 . The post  56  extends through a longitudinal slot  22  formed in the housing top  21 , and the cap  52  resides outside the housing  20  or in a recess in the housing top  21 . The post  56  includes a laterally extending pin  58  that engages with corresponding indentions (not shown) on the interior of the housing  20  proximate the slot  22 . Depressing the cap  52  moves the pin  58  out of engagement with the indentions, and allows the carriage  30  to slide back and forth horizontally to the desired position relative to the housing  20 . The lower portion of the post  56  is disposed in a retaining structure  34  formed on the carriage main body  32  and the biasing spring  59  for the carriage positioning actuator  50  may be disposed in this retaining structure  34  if desired. As the construction and general operation of blade carriages and positioning actuators are well known in the field of utility knives, further details are omitted herein for brevity. 
   The locking mechanism  60  is supported by, and travels with, the blade carriage  30 . The locking mechanism includes a generally L-shaped lock plate  62  (locking means). The long leg  70  of the lock plate  62  extends generally parallel to retaining wall  46 , on the side of the blade carriage  30  opposite the blade-receiving bay  40 . The short leg  64  of the lock plate  62  extends generally perpendicular to the long leg  70 . The upper retaining wall  44  of the blade-receiving bay  40  includes a gap  45 , and the short leg  64  of the lock plate  62  extends laterally into this gap  45  so as to overlie an upper portion of the blade-receiving bay  40 . A protrusion  66  extends downwardly from the underside of the short leg  64 . This protrusion  66  is intended to engage one of the notches  8  on the cutting blade  5  so as to couple the cutting blade  5  to the blade carriage  30 , as discussed further below, and therefore may be referred to as the locking protrusion. At least a portion of the upper side of the short leg  64  is positioned so as to underlie the cap  52  of the carriage positioning actuator  50  and a compression spring  76  extends therebetween to bias the lock plate  62  downward relative to the blade carriage  30 . There may be small bosses  68 ,  54  on the top of the lock plate  62  and the underside of the cap  52  to aid in seating and retaining bias spring  76 . The long leg  70  of lock plate  62  is advantageously relatively smooth on the outboard side (facing away from the blade-receiving bay  40 ), while the inboard side of the long leg  70  may be smooth, but advantageously includes a shoulder  72  that is intended to abut against the carriage  30  to limit the downward movement of the lock plate  62 . The long leg  70  is slidably captured by a suitable retaining arm  36  on the outboard side of the blade carriage  30  so that the lock plate  62  moves in a non-pivoting fashion relative to the carriage  30 , with the relevant displacement being in a generally vertical direction. Thus, the lock plate  62  moves horizontally with the blade carriage  30 , but is allowed to move up and down vertically with respect to the blade carriage  30 . 
   A release button  80  is mounted to one of the sidewalls  26  of the housing  20  and acts as an actuator for the locking mechanism  60 . The button  80  includes an exterior portion  82  and an interior portion  84 . The exterior portion  82  is accessible to the user and advantageously has the general shape of a rectangle, but other shapes are also possible. The outer surface of the exterior portion  82  may be textured, such as with ridges, raised dots, or the like. The exterior portion  82  of the button  80  advantageously fits at least partially in a recess in the housing&#39;s sidewall  26 . The innermost wall of the recess includes an opening  28  to the interior of the housing  20 , and the button  80  extends through this opening  28 . Advantageously, this opening  28  is smaller than the exterior portion  82  of the button  80  so as to be concealed thereby. The interior portion  84  of the button  80  includes guide flanges  86  and a central engaging section  90 . The guide flanges  86  engage the inside of the sidewall  26  to constrain the movement of the button  80  to be a sliding motion up and down, rather than back and forth or in and out. The central engaging section  90  of  FIG. 6  includes a longer upright flange  92  disposed forward of a shorter platform  94 . The tip of the upright flange  92  is intended to engage the underside of the short leg  64  of lock plate  62 . The top of the platform  94  is intended to engage the underside of the locking protrusion  66 . Thus, together, the top of the platform  94  and the tip of the flange  92  comprise an two-part engagement surface  96 . Advantageously, the vertical distance between the tip of the flange  92  and the top of the platform  94  is such that they engage their respective portions of the lock plate  62  at the same time when the button  80  is displaced upward sufficiently. Further, the location of the flange  92  forward of the platform  94  allows button  80  to avoid interfering with the lock plate&#39;s forward movement to bring the blade carriage  30  into alignment with the button  80 , but still provides redundant, and spaced apart, points of contact with the lock plate  62 . It is believed that this spacing allows the lock plate  62  to be displaced by the button  80  with a minimum of binding, thereby insuring smooth operation. The central engaging section  90  may be braced as is desired to provide sufficient rigidity and support. The interior portion  84  may also include a short boss or pin  98  for accepting spring  99  that biases button  80  downward relative to housing  20 . Thus, unless actuated by a user, the button  80  is in a lower, unengaged position, but can be slidably moved to an upper engaged position by a user. In moving from the unengaged position to the engaged position, the button  80  may advantageously move in a plane that is generally parallel to the sidewall  26 . Thus, the button  80  in the engaged position is generally no closer to the midline  25  of the housing  20  than in the unengaged position, and advantageously farther away therefrom. 
   As is conventional, the blade carriage  30  is slidably disposed in the housing  20 , and moves horizontally back and forth between a retracted position (back) and a deployed position (forward). The interaction of pin  58  on carriage positioning actuator  50  and the indentions on the interior of the housing  20  proximate the slot  22  allow for the carriage  30  to be retained in the desired horizontal position. Thus, the cutting blade  5 , when coupled to the blade carriage  30 , may be extended from the housing  20  for use and retracted into the housing  20  for storage. 
   The locking mechanism  60  acts to couple cutting blade  5  to blade carriage  30 . In the locked position, lock plate  62  is in its downward position and locking protrusion  66  is disposed in one of the notches  8  in the upper edge of cutting blade  5 . Thus, horizontal movement of the blade carriage  30  is conveyed via the lock plate  62  to the cutting blade  5 , causing the carriage  30 , locking mechanism  60 , and blade  5  to all travel back and forth together. When it is desired to remove the blade  5 , such as for replacement or to change cutting ends of the blade  5 , the carriage  30  is moved forward to the fully deployed position. In this position, the lock plate  62  is generally aligned with the button  80 , with the engaging surface  96  positioned underneath short leg  64 . The user then slides the button  80  upward, bringing the engaging surface  96  into contact with the underside of the short leg  64  and forcing the lock plate  62  upward. Movement of the button  80  to the fully up position displaces the lock plate  62  upward enough so that the locking protrusion  66  on the underside of the short leg  64  is higher than the top of the cutting blade  5  (i.e., outside the notch  8 ), thereby decoupling the blade  5  from the carriage  30 . The user may then simply pull the blade  5  out front slit  29  of housing  20 . If desired, a new blade  5  may then be inserted into blade-receiving bay  40  of blade carriage  30  by inserting the blade  5  through front slit  29 . When the blade  5  is sufficiently inserted, the user may release button  80 , which is then urged downward by spring  99 . The downward movement of the button  80  allows spring  76  to force lock plate  62  downward, so that locking protrusion  66  is thereby positioned in one of the cutting blade&#39;s notches  8 , coupling the blade  5  to carriage  30 . If desired, it may be advantageous for the blade-receiving bay  40  of blade carriage  30  to include a rear wall  48  positioned so as to facilitate alignment of the locking protrusion  66  with notch  8 , although such is not required in all embodiments. The new blade  5  may then be retracted into the housing  20  in a conventional fashion. 
   As can be seen, the action of the locking mechanism  60  and release button  80  allow replacement of cutting blades  5  without requiring the utility knife&#39;s housing  20  to be disassembled and re-assembled. Instead, the simple vertical sliding movement of the release button  80 , with the blade carriage  30  in the correct position, allows the cutting blade  5  to be very quickly changed with minimal effort. Indeed, in most embodiments, the release button  80  is disposed through the hole  28  in the housing sidewall  26  that faces the blade-receiving bay  40  of the blade carriage  30 . This arrangement allows the blade  5  changing operation to be easily carried out by pressing the release button  80  with the user&#39;s thumb while the utility knife  10  is grasped in the conventional fashion in the user&#39;s hand (forward portion of the utility knife  10  extending out from thumb/forefinger area of the user&#39;s hand). Having the blade-receiving bay  40  thus oriented toward the user during the blade changing operation allows the user to more easily mate the blade  5  to carriage  30 . Further, because most users are right-handed, the sidewall  26  of the housing  20  associated with the release button  80  is advantageously the left sidewall of housing  20  (when viewed from the rear of the utility knife). 
   It should be noted that the central surface  96  and guide flanges  86  of release button  80  are advantageously sized so as to avoid obstructing the blade-receiving bay  40 . That is, they are spaced laterally from the plane of retaining wall  46  of blade-receiving bay  40  a sufficient distance to allow a cutting blade  5  to be easily inserted into the blade-receiving bay  40  via the front slit  29 , and for the combination of the blade carriage  30  and the blade  5  to slide back and forth without interference. However, the lateral extent of the central engaging section  96  and/or guide flanges  86  may also be advantageously sized to butt against the upper retaining wall  44 , or other portion of the blade carriage  30 , when the release button  80  and the locking mechanism  60  are not properly horizontally aligned so as to prevent the substantial up/down movement of the release button  80  until the release button  80  and the locking mechanism  60  are properly horizontally aligned. 
   In some embodiments, the utility knife  10  may include a storage area for storing replacement blades  5 . Any one of the numerous spare or used blade storage approaches known in the art may be used. By way of no-limiting example, the utility knife  10  may include a storage arm  14  that pivots in and out of a rear portion of the top  21  of housing  20  and is configured to hold several spare blades  5 . Such a pivoting storage arm  14  may include suitable detents or other means to prevent inadvertent opening, magnets to secure the spare blades, and other means known in the art to facilitate convenient spare blade storage. 
   The discussion above has assumed that the release button  80  and the locking mechanism  60  are properly aligned when the blade carriage  30  is at its forwardmost position. However, such is not required, and the relevant aligned position may be at some forward point along the carriage&#39;s travel prior to the forwardmost position, but this is believed to be an inferior arrangement. 
   While it is believed advantageous if the utility knife  10  of the present invention has housing halves  20   a ,  20   b  that are not separable by the user, such is not required in all embodiments. For example, provisions can be made to allow the user to separate the housing halves  20   a ,  20   b  if desired, such as by removal of screw  12 . 
   The present invention may, of course, be carried out in other specific ways than those herein set forth without departing from the 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.