Abstract:
A powered utility knife has a housing defining a handle surface and an internal cavity. A shuttle plate assembly disposed for movement relative to the internal cavity, with a first surface in sliding engagement with an interior wall of the cavity includes a motor mounted to the shuttle plate and a blade carrier with a surface in sliding engagement with the shuttle plate. A drive assembly associated with the motor imparts effective cutting motion to a blade on the blade carrier. An activator protruding through a slot in the housing is configured for slidable translation along the slot to cause lateral movement of the shuttle plate assembly within the cavity. The blade, with the shuttle plate assembly in extended position, has a first portion protruding through a blade slot at the end of the housing, and with the shuttle plate assembly in retracted position, the blade is retracted within the cavity. A power source is connected to the motor, and a power switch is in communication between the power source and motor.

Description:
BACKGROUND  
       [0001]     This application claims benefit from U.S. Provisional Patent Application No. 60/609,781, filed Sep. 14, 2004, now pending, and U.S. Provisional Patent Application No. 60/616,698, filed Oct. 7, 2004, now pending. The complete disclosures of both applications are incorporated herein by reference.  
         [0002]     The present disclosure relates to powered utility knives.  
         [0003]     A conventional manual utility knife typically includes an axially elongated housing or case that also serves as a handle, a blade holder moveably mounted in the case, and a blade mounted upon the blade holder. The blade holder may be fixed relative to the body by a spring-biased tab that can be disengaged to permit movement of the blade holder to extend the blade from the case, e.g. for cutting, and to retract the blade into the case, e.g. for safe storage. To replace a blade, the case is usually disassembled to allow the blade to be removed from the blade holder. A replacement blade, which may be stored in a cavity in the handle provided for that purpose, is installed on the blade holder, and the utility knife case is then reassembled.  
       SUMMARY  
       [0004]     The present disclosure provides a powered utility knife.  
         [0005]     The disclosure can be implemented to realize one or more of the following advantages.  
         [0006]     The utility knife of the present disclosure has the benefit of motorized power that shuttles the blade back and forth rapidly for more efficient cutting of various materials commonly cut with manual utility knives. In addition, the power feature allows this utility knife to cut materials not previously feasible to be cut with a manual utility knife.  
         [0007]     The motor of the disclosed utility knife can be powered by a combination of options, such as rechargeable or replaceable batteries or by an electrical corded connection. A battery or battery cartridge can be recharged while engaged with the knife housing or the battery cartridge can be removed for recharging while an alternate battery cartridge is engaged for used.  
         [0008]     In one example, the blade of the disclosed utility knife can be extended beyond the knife housing and locked into one of a number of cutting positions. The blade can also be retracted so that the blade is fully contained within the knife housing to allow safe handling of the utility knife without risk of the user being cut. The extending and retracting of the blade is accomplished by moving an automatic locking activator located on the top of the knife housing axially, forward or backwards.  
         [0009]     Some of the disclosed utility knives have a blade-change-door to expedite changing of blades. Power is “on” only while the operator is depressing the power switch, or when safety limit switches or other safety electrical disconnect circuits contained within the utility knives are not actuated, thus providing a multiplicity of concurrent safety features.  
         [0010]     The power feature enables this utility knife to cut a greater variety of materials, including materials not feasible to cut, with a manual utility knife. A variety of blades with different cutting edges have also been designed for use with this utility knife to make further advantage of the power feature.  
         [0011]     In another implementation, the disclosed powered utility knife has many of the features described above; however, the non-retractable blade is fixedly mounted to extend at the end of the housing. This implementation of the utility knife also has multiple concurrent safety features to protect against power being inadvertently activated during blade changing.  
         [0012]     In another implementation, the disclosed utility knife has a blade powered in cutting motion by a vibrating motor. This utility knife has many of the features of the implementations described above. A non-retractable blade is fixedly mounted to extend at the end of the housing. The vibrating motor, secured to a fixed motor plate by a motor bracket assembly, causes the extended blade to vibrate in an effective cutting fashion.  
         [0013]     In still another implementation, the disclosed utility knife includes a retractable motor plate and vibrating motor. The retractable motor plate allows manual retraction or extension of the blade relative to the knife housing. The vibrating motor, secured to the motor plate by a motor bracket assembly, causes the blade, when extended blade, to vibrate in an effective cutting fashion.  
         [0014]     Utility knives described herein may also permit the blade to be reversed, allowing use, in turn, of both front and rear end segments of the cutting edge of a single blade. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0015]      FIGS. 1 and 2  are top and side views, respectively, of a powered utility knife of the disclosure.  
         [0016]      FIG. 3  is a side view of a drive worm gear and driven gear assembly for a powered utility knife of the disclosure.  
         [0017]      FIGS. 4 and 5  are side section views of the powered utility knife of  FIG. 1 , with the blade in retracted position and with the blade in extended position, respectively.  
         [0018]      FIGS. 6 and 7  are top section views of the powered utility knife of  FIG. 1 , with the blade in retracted position, as in  FIG. 4 , and with the blade in extended position, as in  FIG. 5 , respectively.  
         [0019]      FIGS. 8 and 9  are end section and side section view, respectively, of another implementation of a powered utility knife of the disclosure, with sliding electrical connection between contacts mounted to the shuttle plate and to the utility knife housing.  
         [0020]      FIG. 10  is a partial side view of a powered utility knife of  FIG. 1 , with the utility knife door removed and the utility knife blade fully positioned in the door aperture for removal.  
         [0021]      FIG. 11  is an end section view of a powered utility knife of the disclosure with a retractable shuttle plate.  
         [0022]      FIGS. 12 and 13  are partial side section views of a powered utility knife with the utility knife blade carrier moved to its maximum forward shuttle stroke position, and with the utility knife blade carrier moved to its rearward shuttle stroke position, respectively.  
         [0023]      FIG. 14  is a partial side section view of the powered utility knife of  FIGS. 12 and 13  with a utility knife blade mounted to the utility knife blade carrier.  
         [0024]      FIGS. 15 and 16  are exterior face plan and interior face plan views, respectively, of a powered utility knife door of the disclosure; and  
         [0025]      FIG. 17  is an end section view of the powered utility knife door, taken at the line  17 - 17  of  FIG. 16 .  
         [0026]      FIGS. 18 and 19  are fragmentary side section views of a powered utility knife of the disclosure, with a first safety limit switch open, to interrupt power, due to retraction of the shuttle plate, and with the first safety limit switch closed, to permit flow of power, due to extension of the shuttle plate, respectively.  
         [0027]      FIG. 20  is a partial side view of the powered utility knife of  FIG. 2 , showing a segment of the utility knife door; and  
         [0028]      FIGS. 21 and 22  are end section views, both taken at the line A-A of  FIG. 20 , with the utility knife door in closed position, and with the utility knife door in open position, respectively.  
         [0029]      FIGS. 23 and 24  are partial side views of an interior wall of the powered utility knife of  FIG. 2  showing a segment of the utility knife door aperture, with the door removed, and with the door in place, respectively.  
         [0030]      FIGS. 25, 26  and  27  are top plan, side and end views, respectively, of an activator for a powered utility knife of the disclosure.  
         [0031]      FIGS. 28 and 30  are side section views, taken at the line J-J of  FIG. 25 , of an activator for a powered utility knife of the disclosure, shown in locked mode and shown in unlocked mode, respectively.  
         [0032]      FIGS. 29 and 31  are end section views, taken at the line K-K of  FIG. 25 , of an activator for a powered utility knife of the disclosure, shown in locked mode, as in  FIG. 28 , and shown in unlocked mode, as in  FIG. 30 , respectively.  
         [0033]      FIG. 32  is a top section view of the activator for a powered utility knife of the disclosure.  
         [0034]      FIGS. 33 and 34  are side views of the rear end portion of a powered utility knife of the disclosure, showing a removable battery cartridge engaged with the housing, and showing the battery cartridge disengaged from the housing, respectively.  
         [0035]     FIGS.  35  to  40  are side plan views of various implementations of utility knife blade configurations for use in powered utility knives of the disclosure.  
         [0036]      FIG. 41  is a side view of a powered utility knife of the disclosure having a fixed (non-retractable) blade carrier and blade.  
         [0037]      FIG. 42  is a side section view of the powered utility knife of  FIG. 41  having a fixed (non-retractable) blade.  
         [0038]      FIGS. 43 and 44  are top section views of the powered utility knife of  FIG. 41 , with the blade release button depressed and with the blade release button returned to normal operating position, respectively.  
         [0039]      FIGS. 45 and 46  are end section views of the powered utility knife of  FIG. 41 , with the blade release button depressed, as in  FIG. 43 , and with the blade release button returned to normal operating position, as in  FIG. 44 , respectively.  
         [0040]     FIGS.  47  to  53  are side plan views of other implementations of utility knife blade configurations for use in powered utility knives of the disclosure.  
         [0041]     FIGS.  54  to  57  are side plan views of still other implementations of utility knife blade configurations for use in powered utility knives of the disclosure.  
         [0042]      FIGS. 54A  to  57 A are side plan views of implementations of utility knife blade carriers of the disclosure configured to receive utility knife blades having the configurations of FIGS.  54  to  57 , respectively.  
         [0043]      FIG. 58  is a side section view of another implementation of a powered utility knife of the disclosure, in which a fixed (non-retractable) blade is driven in a vibrating cutting action; while  
         [0044]      FIGS. 59 and 60  are end section views with the blade support locking the utility blade in place, and with the blade support in position for blade removal, respectively.  
         [0045]      FIGS. 61 and 62  are side section views of still another implementation of a powered utility knife of the disclosure, in which a moveable (retractable) blade is driven in a vibrating cutting action, with the blade shown retracted ( FIG. 61 ) and extended ( FIG. 62 ), and  
         [0046]      FIG. 63  is an end section view of the retractable blade mechanism.  
         [0047]      FIG. 64  is a side view of a motor assembly for a powered utility knife of the disclosure, and  
         [0048]      FIG. 65  is a top view of the motor assembly of  FIG. 64 .  
         [0049]      FIGS. 66 and 67  are side and top views, respectively, of a bevel gear drive assembly for a powered utility knife of the disclosure.  
         [0050]      FIGS. 68 and 69  are side section views of a powered utility knife of the disclosure equipped with a bevel gear drive assembly and a retractable utility knife blade, showing the blade in retracted position and in extended position, respectively.  
         [0051]      FIG. 70  is a side section view of a powered utility knife of the disclosure equipped with a bevel gear drive assembly and a fixed utility knife blade.  
         [0052]      FIG. 71  is a side view and  FIG. 72  is a top view of a variable length cutting stroke assembly for a powered utility knife of the disclosure.  
         [0053]      FIGS. 73 and 74  are side views of a powered utility knife of the disclosure equipped with implementations of bracket accessories for steadying and/or aligning the utility knife blade during use. 
     
    
       [0054]     Like reference numbers and designations in the various drawings indicate like elements.  
       DETAILED DESCRIPTION  
       [0055]     Referring to  FIGS. 1 and 2 , one implementation of a powered utility knife  1000  of the disclosure has an exterior configuration that includes an activator  1  for extending and locking a utility knife blade  38  for cutting in one or a number of alternative positions extending from a utility knife case or housing  53 . For safety purposes, the activator  1  also retracts the blade  38  axially into the case  53 , including for changing the blade. The utility knife case is ergonomically designed to provide leverage when a user applies pressure for cutting. A power switch  10  is ergonomically located for actuating the blade cutting motion, and for holding the power switch in actuating position while the user applies cutting pressure. The power switch  10  is activated only while pressure is applied by the user&#39;s finger. Once the power switch  10  is released, power to the utility knife ceases. The utility knife housing has a door  5  for ease of blade changes. In one particular implementation, described in more detail below, the utility knife is powered by batteries, which may be rechargeable and/or replaceable. In other implementations, the utility knife is powered by an external power cord and/or by a combination of battery and external power.  
         [0056]     Trigger  80  is depressed to unlock activator  1 , allowing the activator to be moved axially along the utility knife housing. When the trigger is released, the activator returns to its locking position at that location. The activator is attached to a retractable shuttle plate  19  within the utility knife housing, and travels in an activator slot  94 . Forward movement of the activator (toward end  110 ) manually moves retractable shuttle plate  19  axially forward to extend blade  38  to a desired cutting position. When the activator  1  is moved toward a rearward position, the blade  38  is retracted. At the rearmost position of the activator, the blade is completely retracted into knife housing  53 .  
         [0057]     The utility knife housing is formed by utility knife case left portion  2  and utility knife case right portion  3 , which are joined together by a case fastener, e.g. a screw (not shown). The spring-loaded door  5 , e.g. for replacement of the blade, is opened by applying downward pressure upon latch release  6 . Pressing and holding spring loaded power switch  10  inwardly activates power to the knife, while releasing the power switch deactivates power to the knife.  
         [0058]     Referring to  FIG. 3 , the utility knife has a drive system the includes a motor  12 , bearing assembly  14 , worm gear  16 , shuttle cam  36  and cam arm  18 , which permit rapid shuttling of the knife blade back and forth for power cutting.  
         [0059]     As seen in  FIG. 4 , when activator  1  is moved rearwardly, the blade  38  is retracted into the knife housing, and safely locked. Case left portion  2  is shown with retractable shuttle plate  19  manually retracted by activator  1  to the rear of its range of travel, retracting the blade  38  fully into the housing.  
         [0060]     Power switch  10  is mounted to post  33 . Battery  7  provides power to the drive system when activated by the user pressing and holding the spring-loaded power switch inwards. Motor  12  is mounted to retractable shuttle plate  19  by motor bracket  13 . Bearing assembly  14  is a component of retractable shuttle plate  19 . Cam post  28 , which is attached to carrier  32  on which the blade  38  is mounted, defines a cam arm attachment hole  37 .  
         [0061]     Battery contact  8  transmits power (e.g., battery power) through wiring to switch  10 , motor  12 , limit switch  11  and power contacts  90  of a safety switch mounted to door  5 . Limit switch  11  is a safety device that interrupts the electrical circuit when retractable shuttle plate  19  is manually retracted (as shown). Blade  38  can then be inserted or removed without actuation of power, even if power switch  10  is inadvertently pressed to “on” position. Other safety devices that may incorporated into the powered utility knife are described below.  
         [0062]     As shown on  FIG. 5 , when activator  1  is moved forward, the blade  38  is extended through a blade opening at the front of the knife housing  53 , and then locked for cutting. Here, the retractable shuttle plate  19  is shown moved to its maximum forward position, extending blade  38  to a cutting position (different degrees of blade extension may be selected). As described above, retractable shuttle plate  19  is locked in any position to which the activator  1  is moved by release of the activator  1 , which causes the spring-loaded trigger  80  to be urged upwards by trigger springs  81 , automatically locking the activator against further movement. Limit switch  11  is now in open position and power is applied when the power switch  10  is pressed. Upon actuation of the power switch, cam arm  18 , held in place by cam arm bracket  402  and cam arm fastener  411 , moves back and forth, shuttling carrier  32  back and forth in cutting action on shuttle plate guide rails  20 . A series of ball bearings  112  in ball bearing cage  405  allow the carrier  32  to operate efficiently with minimal friction when articulating back and forth in the power cutting mode, even while considerable force is being applied to the utility knife during the cutting process with blade  38 . Force applied to case left  2  and case right  3  is transmitted directly to shuttle plate shoulders  41  of retractable shuttle plate  19 . Simultaneously, blade  38 , extended in the cutting position, pushes carrier  32  upwards so that ball bearings  112  in ball bearing cage  405  above carrier  32 , now in contact with the underside of retractable shuttle plate  19  and the underside of case left  2  and case right  3 , permit the carrier  32  to easily move back and forth in the power cutting mode.  
         [0063]     The motor  12 , powered by battery  7 , drives the drive worm gear  16 , which in turn drives driven gear  17 . Cam arm  18  is attached to driven gear  17  by engagement upon mounting pin  45  of cam drive post  44  and attached to retractable shuttle plate  19  engagement of cam arm attachment hole  37  upon cam arm post  28 . Rotation of the driven gear moves the cam arm back and forth, which in turn move blade carrier  32  back and forth in cutting motion. In one implementation, battery  7  is recharged through battery recharging port  46 .  
         [0064]     Referring to  FIG. 6 , retractable shuttle plate  19  is manually moved to its rearmost position by means of activator  1 , retracting the blade  38  completely within knife housing  53 . Lower blade support  48  on door  5  and lower blade support  30  on knife case right portion  3  together hold blade  38  securely to carrier  32  during all phases of carrier  32  travel.  
         [0065]     In  FIG. 7 , retractable shuttle plate  19  is manually moved forward by means of activator  1  to extend the blade  38  to its cutting positions. Lower blade support  30  and door-mounted lower blade support  48  securely hold blade  38  against carrier  32 .  
         [0066]     In one implementation of the powered utility knife  1001  of the disclosure, sliding electrical contacts are provided for the shuttle plate, to eliminate folding and unfolding of electrical wires as the shuttle plate and motor move back and forth as the utility knife blade is extended and retracted. Referring to  FIGS. 8 and 9 , fixed electrical contact strips  426  and  427  are mounted to the inside wall  424  of the utility knife housing  425 . Upper and lower sliding electrical contacts  428  and  429  are mounted to the rear bearing assembly housing  443  by sliding electrical contact fasteners  430 . Upper motor contact wire  431  completes the electrical circuit between upper sliding electrical contact  428  and upper motor electrical contact  433 . Lower motor contact wire  432  completes the electrical circuit between lower sliding electrical contact  429  and lower motor electrical contact  434 . When the utility knife blade is extended or retracted, retractable shuttle plate shoulders  41  ride in shuttle plate channels  42 , moving motor  12  forward and rearward, and moving upper and lower sliding electrical contacts  428  and  429  along fixed electrical contact strips  426  and  427 , which are, in turn, connected to battery  7  (power source). Upper fixed electrical contact strip  426  is electrically connected to battery charging module  435 , which connects to battery  7  and power switch  10 . Lower fixed electrical contact strip  427  is connected through door  5  power breaker  89  to wiring leading to battery charging module  435  and battery  7 .  
         [0067]     Referring next to  FIG. 10 , the activator  1  is moved to rearward along the exterior of the case  53 . With the retractable shuttle plate  19  manually moved to its rearmost position, blade  38  is positioned fully within the aperture of door  5  and exposed for removal. The door  5  is shown removed for access to the blade  38 . The aperture of door  5  is wide enough to accommodate the range of positions over which the shuttle mechanism may have stopped the carrier  32  and blade  38  in its powered cutting motion when shuttle plate  19  is fully retracted. Thus, the entire blade  38  is accessible for removal and/or insertion.  
         [0068]     As a safety feature, when the door  5  is opened power contacts  90  are removed from contact with door-mounted power breaker  89 , interrupting the electrical circuit. A user changing the blade is thus protected from having the power started, e.g. should he or she inadvertently press power switch  10 , since while the door  5  is open for changing blade  38 , interruption in the electrical circuit restricts the motor  12  from actuation to move the carrier  32  with the blade  38 .  
         [0069]     As an additional safety precaution, when the retractable shuttle plate  19  carrying motor  12  is retracted to bring the blade into line with door  5  for blade changing, lower sliding electrical contact  429  runs beyond the end of the relatively shorter lower fixed electrical contact strip  427 , thereby interrupting the electrical connection as the blade is position placed inline with door  5 .  
         [0070]     A further safety precaution is provided by contact of retractable shuttle plate  19 , when fully retracted, with limit switch  11  to interrupt the circuit, as described below in more detail with reference to  FIGS. 18 and 19 .  
         [0071]     Referring to  FIG. 11 , the retractable shuttle plate  19  moves back and forth in channel  42 . Articulating carrier  32  rides on guide rails  20  and  39  when power shuttling back and forth in cutting motion. The activator  1  is shown in a locked position with trigger  80  in an “up” position, placing trigger lock  84  between locking arms  104 . This restricts dislodgement of locking shoulders  103  from locking pocket  86 . Door upper blade support  50  and door lower blade support  48  hold blade  38  securely against carrier  32 . Shuttle plate shoulder  41  rides within shuttle plate support channel  42  when manually moving the retractable shuttle plate  19  forward and rearward. Retractable shuttle plate  19  defines shuttle plate guide rails  20 ,  39  that extend forward of the body of the main shuttle plate  19  to supporting carrier  32  in a fashion that allows carrier  32  to ride securely back and forth within carrier rails  105 . Plastic guide rails  20 ,  39  serve as the primary movement contact surfaces and reduce friction, allowing power shuttling of carrier  32  to slide easily back and forth. Loading and/or removing blade  38  from the utility knife is achieved efficiently by use of a blade tray  79  and blade loading assist  25 . Door hinge prong  58  is positioned on and behind prong engager  75  when door  5  is attached to knife case right portion  3 . Door latch  54  secures the door closed by latch spring  55  forcing door latch  54  up behind latch lock  106 .  
         [0072]     In  FIG. 12 , the power assembly has the cam arm  18  in its extended position, moving carrier  32  to its maximum forward shuttle stroke position of its back and forth powered cutting movement. The power feature moves the carrier  32  back and forth along shuttle plate guide rails  20  of shuttle plate  19 .  
         [0073]     In  FIG. 13 , the power assembly has the cam arm  18  in its retracted stroke position, moving carrier  32  to its rearward powered shuttle stroke position of its back and forth powered cutting movement.  
         [0074]     Referring to  FIG. 14 , the power assembly of  FIGS. 12 and 13  is shown with blade  38  attached to carrier  32 . The carrier  32  defines an upper side engager  441  and a middle blade pusher  22 , which engage rear surface of the blade  38  when pushing the blade  38  in its forward cutting direction. Upper blade engager  26  and blade loading assist  25  extend through apertures in a center region of the blade  38  and push blade  38  in both forward and rearward cutting directions. Blade tray  79  assists in positioning of the blade  38  when loading blade  38  onto the carrier  32 .  
         [0075]     As shown in  FIG. 15 , door  5  has door release  6  in a locked position. Pushing spring-loaded release  6  downward unlocks door  5 . Door hinge prongs  58  attach a lower portion of door  5  to prong engager  75  on knife case right portion  3  and pivot the door  5  upwards to close, engaging door latch  54  to latch lock  106  to lock the door  5  in place.  
         [0076]     As shown in  FIG. 16 , the door latch  54  has a latch spring  55  urging the door latch  54  upwards. The latch spring is mounted to spring post  57 . Door upper blade support  50  and door lower blade support  48  hold blade  38  securely against the carrier  32 . Power breaker  89  is attached to door extension  92  and completes the electrical circuit when engaged between contacts  90  of the safety switch assembly.  
         [0077]     Referring next to  FIG. 17 , the details of door latch  54 , latch release  6 , latch spring  55 , spring post  57 , door upper blade support  50 , door lower support  48 , latch retaining plate  56 , which holds latch assembly in place, and door hinge  58  are more fully illustrated.  
         [0078]     Power to the utility knife is always off unless and until the user presses and holds the power switch  10 . However, as a safety precaution, to minimize or eliminate any possibility that the power may be actuated inadvertently, such as during blade changing, additional safety features are provided.  
         [0079]     Referring to  FIGS. 18 and 19 , a first safety limit switch  11  interrupts the electrical circuit when the retractable shuttle plate  19  is manually retracted into the utility knife housing by movement of the activator  1 . In  FIG. 18 , activator  1  has moved retractable shuttle plate  19  to the rear, retracting the blade inside the utility knife housing, where the shuttle plate shoulder compresses plunger return spring  437  and pushes limit switch plunger  436  into engagement with limit switch  11 , to open limit switch  11 , thereby interrupting all electrical connections, including any electrical connection to power switch  10 . This restricts actuation of the knife blade, should the user inadvertently hit the power switch  10  while blade is being changed.  
         [0080]     Referring next to  FIG. 19 , when the activator  1  has moved shuttle plate  19  forward to the extend blade from the utility knife housing, the plunger return spring is extended, pulling the limit switch plunger forward and allowing limit switch  11  to close, completing the circuit for connection of all electrical power.  
         [0081]     Referring next to FIGS.  20  to  22 , a second safety limit switch interrupts the electrical circuit when the utility knife door  5  ( FIG. 2 ) is open, removing power breaker  89  from electrical contact with power contact  90 .  FIG. 20  shows a fragmentary cross-section of utility knife case right portion  3  of the utility knife shown in  FIG. 2  with a utility knife door  5  having a door extension  92 . In  FIG. 21 , the utility knife door  5  is closed, and power breaker  89 , mounted on door extension  92 , completes the electrical circuit between power contacts  90 , which are fastened to case right portion  3  of the utility knife housing by contact posts  88 . Power wires  93  are attached to contact posts  88  to bring power from battery  7  to power contacts  90 . In  FIG. 22 , the utility knife door is open, and power breaker  89  at the inside of utility knife case right portion  3  of the utility knife housing is pulled away from power contacts  90 , interrupting the electrical circuit. The power breaker  89  is mounted to door extension  92  by breaker posts  91 .  
         [0082]     We refer next to  FIGS. 23 and 24 , in which a fragmentary section of the inner surface of utility knife case right portion  3  of the utility knife housing, including a portion of the utility knife door aperture, is shown. In  FIG. 23 , the utility knife door is removed, illustrating power contacts  90  attached by contact posts  88 . Power wires  93 , also attached to contact posts  88 , provide electrical power to power contacts  90 . While the door  5  is removed, as shown, the electrical circuit is interrupted. In  FIG. 24 , the utility knife door  5  is replaced, with power breaker  89 , attached to door extension  92 , completing an electrical circuit between power contacts  90 .  
         [0083]     As shown in FIGS.  25  to  31 , the activator  1  has an automatic locking function. Activator  1  is attached to retractable shuttle plate  19  to move the shuttle plate  19 , with the carrier  32  and blade  38 , forward so that the blade  38  extends to optional cutting positions outside the knife housing  53 . When the activator  1  is moved is rearwards, it retracts the blade  38  completely inside the knife housing  53 . When the user&#39;s finger is applied to the activator  1  to move it forward or backwards, a trigger  80  on top of the activator  1  is pressed downward, unlocking the activator  1  so it is free to move. Once the blade  38  is moved to its desired position, the activator  1  automatically locks in that position when the user releases the activator  1  and trigger  80 .  
         [0084]      FIGS. 25, 26  and  27  show a top view, side view and end view, respectively, of the activators and the trigger  80 .  
         [0085]      FIGS. 28 and 29  show cross-sections of side and end views, respectively, of the activator assembly in locked mode. Activator  1  includes trigger  80  biased upwards by trigger springs  81  into the locked position. Trigger lock  84  is positioned between locking arms  104  of locking spring  82 , restricting any movement inward, thereby freezing locking shoulders  103  in locking pockets  86 . This restricts activator  1  and retractable shuttle plate  19  from being moved forward or backwards. Activator  1  is anchored by activator anchor points  85  in retractable shuttle plate  19  and held into position by case left portion  2  and case right portion  3  of the utility knife housing.  
         [0086]      FIGS. 30 and 31  show cross-section side and end views, respectively, of the activator assembly in unlocked mode. Activator  1  includes trigger  80  pressed downward to unlock locking arms  104  by compressing trigger springs  81 . Moving trigger lock  84  from between locking arms  104 , into region  107 , allows the pliable locking arms  104  to bend inward as locking spring  82  is pushed by activator  1  as it is adjusted backwards or forwards.  
         [0087]     As shown in  FIGS. 29 and 32 , the pliable locking arms  104  are restrained from bending towards one another by trigger lock  84 , thereby engaging the locking shoulders  103  in locking pockets  86 . Locking spring  82  is attached to the activator  1  by retractable shuttle plate post  98 , activator anchor point  85 , case right portion  3  and case left portion  2 . When locking spring  82  is locked into locking pockets  86 , the retractable shuttle plate  19 , carrier  32  and blade  38  are all locked in place. There are a number of locking pockets  86  defined by the knife case right portion  3  and knife case left portion  2  into and out of which the locking shoulders  103  articulate as they pass. Once the blade  38  is moved to its desired position, activator  1  is released, allowing trigger  80  to be urged upwards by trigger springs  80 , raising trigger lock  84  to a position between locking arms  104  of locking spring  82 . This restricts locking shoulders  103  from moving out of the locking pockets  86  of that location.  
         [0088]     As shown in  FIG. 32 , the activator  1  is now locked in place. Locking shoulders  103  are engaged in locking pockets  86 . The ends of the pliable locking arms  104  are restrained from bending towards one another by trigger lock  84 , thereby locking shoulders  103  in locking pockets  86 . When locking spring  82  is locked into locking pockets  86 , retractable shuttle plate  19 , carrier  32  and blade  38  are all locked in place.  
         [0089]     Referring now to  FIGS. 33 and 34 , in one particular implementation, the utility knife is powered by batteries, which can be rechargeable and/or replaceable. In this implementation, a battery cartridge  40  is engaged with the utility knife housing  403  by battery cover  4  ( FIG. 33 ). The battery cartridge  40  is removed by gripping the battery cover  4  and pulling it axially rearward to disengage the battery cover from the utility knife housing.  
         [0090]     Referring to  FIGS. 35-39 , a number of particular style blades are provided, including for use with the power utility knife of the disclosure. The blades have particular cutting features suited for different cutting applications.  
         [0091]     In  FIG. 35 , blade  96  defines a sharp cutting edge along its bottom and curved or angled ends. To assist in keeping the blades  96  firmly attached to carrier  32  during its rapid powered shuttling back and forth, each blade  96  defines a loading assist opening  52  that receives blade support  64 , and notch  442  that receives side engager  441 .  
         [0092]     In  FIG. 36 , blade  35  defines a sharp serrated detail along bottom edge. To assist in keeping blades  35  firmly attached to carrier  63  during its rapid powered shuttling back and forth, each blade  35  defines a loading assist opening  52  that receives blade support  64 , and notch  442  that receives side engager  441 .  
         [0093]     In  FIG. 37 , alternate blade  38  defines a bottom edge with two different details on each side of centerline  166 , i.e. angled saw teeth  162  and straight Sharpe edge  164  with beveled end  168  with saw teeth on the bevel and a sharp angled end  169 . To assist in keeping the saw teeth blades  38  firmly attached to carrier  63  during its rapid powered shuttling back and forth, each blade  38  defines a notch loading assist opening  52  that receives blade support  64 , and notch  442  that receives side engager  441 .  
         [0094]     In  FIG. 38 , another alternative blade  121  has sharp teeth  449  along the bottom edge. The tooth design of the teeth  449  is configured in such a manner that the aggressive cutting edge of each tooth is always facing inward during its articulating cutting stroke. This is achieved by having a mirror image of the tooth profiled on each side of a centerline  448  of the blade. When the blade  121  is rotated to utilize the unused half of the blade  121 , the aggressive cutting edge of the teeth  449  are again facing inward during the cutting stroke. To assist in keeping the blades  121  firmly attached to carrier  63  during its rapid powered shuttling back and forth, each blade  121  defines a loading assist opening  52  that receives blade support  64 , and notch  442  that receives side engager  441 .  
         [0095]     In  FIG. 39 , another alternative blade  122  defines a cutting edge with two different details on each side of centerline  451  angled saw teeth  452  and coarse teeth  453  with angled ends  454  and  455  containing saw teeth. To assist in keeping the blade  122  firmly attached to carrier  63  during its rapid power shuttling back and forth, each blade defines a loading assist opening  52  that receives blade support  64 , and notch  442  that receives side engager  441 .  
         [0096]     In  FIG. 40 , another alternative blade  456  defines a semicircular cutting edge  457 ,  458  at each end of the blade. To assist in keeping the blade  456  firmly attached to carrier  63  during its rapid power shuttling back and forth, each blade  456  defines a loading assist opening  52  that receives blade support  64 , and notch  442  that receives side engager  441 .  
         [0097]     Referring to  FIG. 41 , an alternative powered utility knife  1100  of the disclosure has a nonretractable blade. Knife housing  59  has blade  61  extending through blade opening  109  at the front end of knife housing  59 . Power switch  10 , when pressed and held inward, actuates the motor to shuttle carrier and blade  61  rapidly back and forth in cutting motion. Blade changing is accomplished by pressing blade release button  65 , which releases blade  61  so it can manually be pulled out of the front of knife housing  59  through blade opening  109 . Release button  65  is also connected to safety switch  76 , mounted on bracket  102 . The safety switch interrupts the electrical circuit when release button  65  is pressed inward. After removal, the blade  61  can be either turned end-for-end to expose a new cutting edge or it can be replaced with a new blade. The blade is inserted through blade opening  109  and engaged and locked by blade support  64 .  
         [0098]     As shown in  FIG. 42 , the fixed shuttle plate is fastened to the utility knife is fastened to case left portion  66  and case right portion  60  by shuttle plate anchor points  97 . The drive system may be as described above. The shuttle plate  62  is fixed in one position while the motor-driven components shuttle carrier  63  rapidly back and forth on fixed shuttle plate guide rails  77  in powered cutting motion.  
         [0099]      FIGS. 43 and 44  illustrate the simultaneous function of release button  65  with power disconnect safety switch and the blade release assembly, which is shown in the circuit breaking and blade removal modes respectively. Blade support  64  is long enough to so that release wheel  68  makes proper contact with blade support  64  when carrier is at both forward and rearward limit of power driven shuttle stroke.  
         [0100]     In  FIG. 43 , release button  65  is pressed inward, moving blade support  64  back by pivoting on blade support pivot pin  74 . Rotation of release wheel  68  on wheel support  101  allows blade  61  to slide between the wheel and support  64  when blade  61  is pulled out of the front of knife housing  59  through blade opening  109 . Release button  65  is attached to switch plunger  99  of safety switch  76  and release shaft  100  attached to spring compressor  70 . Safety switch  76  is shown in the circuit breaking position while blade  61  is being removed or inserted. Safety switch  76  interrupts any power that may have been inadvertently actuated while blade  61  is being removed or inserted.  
         [0101]     In  FIG. 44 , button spring  67  has returned blade changing release button  65  and safety switch  76  to their normal operating positions. Support spring  69  returns support  64  back to its normal position to lock blade  61  in place on carrier  63 . Support pusher  78  urges blade in rearward direction, and side engager  441  and middle blade pusher  22  urge the blade in a forward direction during cutting. Safety switch  76 , shown in circuit connected position, is wired directly to battery  7 . Carrier  63  shuttles back and forth on shuttle plate guide rails  77  and shuttle plate channel  108  in powered cutting motion.  
         [0102]     In  FIG. 45 , release button  65  is shown in normal operating position. Blade  61  is locked in place by blade support  64 , which is held in position by support spring  69 . Upper support rib  72  and lower support rib  73  hold blade  61  securely against carrier  63 . Release button  65  is attached to release shaft  100 , which is attached to spring compressor  70 . Button spring  67  moves spring compressor  70  outwards, moving release button  65  and release wheel  68  away from blade support  64  for normal operating mode.  
         [0103]     In  FIG. 46 , release button  65  is shown pressed inward to release the blade for removal and to insert a blade. Release button  65  is pressed inward, displacing blade support  64  so that blade  61  can be pulled out of, or inserted into, knife housing  59 . Release wheel  68  rotates, allowing blade  61  to slide between the wheel and blade support  64 . When button  65  is released, spring  67  pushes up against button spring compressor  70 , returning release button back to normal position. Spring bracket  71 , containing spring  67 , is attached to knife case right portion  60 . Alternative release mechanisms may be employed; for example, release button  65  may be replaced with a button that slides over switch plunger  99  and release shaft  100  to realize an equivalent mechanical action.  
         [0104]     A series of ball bearings  404  in ball bearing cage  405  allow carrier  63  to operate efficiently with minimal friction when carrier  63  is articulating back and forth in the powered cutting mode, even when considerable force is applied to the knife blade  61  during cutting. Force applied to the knife housing is transmitted to ball bearings  404  in ball bearing cage  405  riding between the top of reciprocating carrier  63  and the underside of knife case left portion  66  and knife case right portion  60 , to permit the carrier  63  to easily roll back and forth while in the powered cutting mode.  
         [0105]     Additional blade embodiments are shown in FIGS.  47  to  53  (with reference to the carrier shown in  FIGS. 4 and 5 ):  
         [0106]     In  FIG. 47 , preferred blade  117  has a sharp cutting edge  125  along the bottom edge. The sharp angled ends  129  of the blade  117  enable the reciprocating blade  117  to make a smooth entry into the material being cut. To aid in keeping the blade  117  firmly aligned on carrier  32  during its rapid powered shuttling back and forth, each blade defines an upper blade notch  124  that engages upper blade engager  26 , a loading assist opening  116  that engages preferred loading assist  25 , and a notch  442  that receives side engager  441 .  
         [0107]     In  FIG. 48 , preferred blade  118  has two different details on each side of centerline  459  angled saw teeth  460  and straight sharp edge  461 . To aid in keeping the blade  118  firmly aligned on carrier  32  during its rapid powered shuttling back and forth, each blade defines an upper blade notch  124  that engages preferred upper blade engager  26 , a loading assist opening  116  that engages loading assist  25 , and a notch  442  that receives side engager  441 .  
         [0108]     In  FIG. 49 , preferred blade  119  defines sharp teeth  127  along the bottom edge. The tooth design of the teeth  127  is configured in such a manner that the aggressive cutting edge of each tooth is always facing inward during its articulating cutting stroke. This is achieved by having a mirror image of the tooth profiled on each side of a centerline  462  of the blade  119 . When the blade  119  is rotated to utilize the unused half of the blade  119 , the aggressive cutting edge of the teeth  127  are again facing inward during the cutting stroke. To aid in keeping the blade  119  firmly aligned on carrier  32  during its rapid powered shuttling back and forth, each blade defines an upper blade notch  124  that engages upper blade engager  26 , a loading assist opening  116  that engages loading assist  25 , and a notch  442  that receives side engager  441 .  
         [0109]     In  FIG. 50 , a preferred blade  120  defines a sharp serrated detail  128  along a bottom edge. The angled end with sharp teeth  131  and sharp rounded end  446  of the blade  120  enable the reciprocating blade  120  to make a smooth entry into the material being cut. To aid in keeping the blade  120  firmly aligned on carrier  32  during its rapid powered shuttling back and forth, each blade defines an upper blade notch  124  that engages upper blade engager  26 , a notch  442  that receives side engager  441 , and a loading assist opening  116  that engages preferred loading assist  25 .  
         [0110]     In  FIG. 51 , a preferred blade  150  defines a bottom with two different details  152 ,  154  on each side of a centerline  156  the straight sharp bottom edge  152  and saw teeth  154  with sharp angled end  158 , and sharp angled end with sharp teeth  159 . To aid in keeping the blade  150  firmly aligned on carrier  32  during its rapid powered shuttling back and forth, each blade defines an upper blade notch  124  that engages upper blade engager  26 , a notch  442  that receives side engager  441 , and a loading assist opening  116  that engages preferred loading assist  25 .  
         [0111]     In  FIG. 52 , a preferred blade edge  160  defines two different details on each side of centerline  465  angled saw teeth  468  and coarse teeth  469  with angled, ends  466  and  470  containing saw teeth. To aid in keeping the blade  160  firmly aligned on carrier  32  during its rapid powered shuttling back and forth, each blade defines an upper blade notch  124  that engages upper blade engager  26 , a notch  442  that receives side engager  441 , and a loading assist opening  116  that engages loading assist  25 .  
         [0112]     In  FIG. 53 , a preferred blade  477  defines a semicircular cutting edge  471  and  472  at each end. To aid in keeping blades  447  firmly aligned on carrier  32  during its rapid powered shuttling back and forth, each blade defines an upper blade notch  124  that engages preferred upper blade engager  26 , a notch  442  that receives side engager  441 , and loading assist opening  116  that engages loading assist  25 .  
         [0113]     In  FIG. 54 , utility knife blade  473  defines a blade edge with sharp teeth  481  along the bottom edge. The tooth design of the teeth  481  is configured in such a manner that the aggressive cutting edge of each tooth is always facing inward during its articulating cutting stroke. This is achieved by providing a mirror image of the tooth profiled on each side of a centerline  401  of the blade  473 . When the blade  473  is rotated to utilize the unused half of the blade  473 , the aggressive cutting edge of the teeth  481  are again facing inward during the cutting stroke. To aid in keeping the blades  473  firmly aligned on carrier  495  during its rapid powered shuttling back and forth, each blade defines an upper blade notch  124  that engages upper blade engager  26 , loading assist opening  116  that engages loading assist  25 , and corner notch  443  that engages corner notch engager  485 . Referring to  FIG. 54A , a utility knife blade carrier  495  is configured for receiving utility knife blade  473 . In particular, carrier  495  has a corner notch engager  485  configured and positioned to engage corner notch  443  of utility knife blade  473 .  
         [0114]     In  FIG. 55 , utility knife blade  474  has sharp teeth  482  along the bottom edge. The tooth design of the teeth  482  is configured in such a manner that the aggressive cutting edge of each tooth is always facing inward during its articulating cutting stroke. This is achieved by providing a mirror image of the tooth profiled on each side of a centerline of the blade  474 . When the blade  474  is rotated to utilize the unused half of the blade  474 , the aggressive cutting edge of the teeth  482  are again facing inward during the cutting stroke. To aid in keeping the blades  474  firmly aligned on carrier  496  during its rapid powered shuttling back and forth, each blade defines an upper blade notch  124  that engages upper blade engager  26 , a loading assist opening  116  that engages preferred loading assist  25 , long side notch  444  that engages upper side notch engager  487  and lower side notch engager  488  ( FIG. 55A ). Referring further to  FIG. 55A , a utility knife blade carrier  496  is configured for receiving utility knife blade  474 . In particular, carrier  496  has an upper side engager  487  and a lower side engager  488  configured and positioned to engage long side notch  444  of utility knife blade  474 .  
         [0115]     In  FIG. 56 , utility knife blade  475  has sharp teeth  483  defined along the bottom edge. The tooth design of the teeth  483  is configured in such a manner that the aggressive cutting edge of each tooth is always facing inward during its articulating cutting stroke. This is achieved by providing a mirror image of the tooth profiled on each side of a centerline  479  of the blade  475 . When the blade  475  is rotated to utilize the unused half of the blade  475 , the aggressive cutting edge of the teeth  483  are again facing inward during the cutting stroke. To aid in keeping the blades  475  firmly aligned on carrier  497  during its rapid powered shuttling back and forth, each blade defines a load assist opening  52  that receives blade load assist  64 , and a corner notch  445  that engages corner notch engager  490  ( FIG. 56A ). Referring further to  FIG. 56A , a utility knife blade carrier  497  is configured for receiving utility knife blade  475 . In particular, carrier  497  has a corner notch engager  408  configured and positioned to engage corner notch  445  of utility knife blade  475 .  
         [0116]     In  FIG. 57 , utility knife blade  476  defines sharp teeth  484  along the bottom edge. The tooth design of the teeth  484  is configured in such a manner that the aggressive cutting edge of each tooth is always facing inward during its articulating cutting stroke. This is achieved by providing a mirror image of the tooth profiled on each side of a centerline of the blade  476 . When the blade  476  is rotated to utilize the unused half of the blade  476 , the aggressive cutting edge of the teeth  484  are again facing inward during the cutting stroke. To aid in keeping the blades  476  firmly aligned on carrier  490  during its rapid powered shuttling back and forth, each blade defines a load assist opening  52  that receives a blade load assist  64 , and a long side notch  447  that engages an upper side notch engager  492  and a lower side notch engager  493  ( FIG. 57A ). Referring further to  FIG. 57A , a utility knife blade carrier  490  is configured for receiving utility knife blade  476 . In particular, carrier  490  has an upper side engager  492  and a lower side engager  493  configured and positioned to engage long side notch  447  of utility knife blade  476 .  
         [0117]     Referring now to  FIGS. 58, 59  and  60 , in another implementation of a powered utility knife  1200  of this disclosure, the utility knife blade  206  is caused to vibrate in an effective cutting fashion by means of a vibrating motor  202 . Utility knife  1200  has many of the features described above. In addition, shuttle plate  204  is maintained in fixed position and the blade  206  is non-retractable relative to the utility knife housing  208 . The vibrating motor  202  is secured to the fixed motor plate  204 , e.g., by a motor bracket assembly  210 . The vibrating motor  202  may include a counterweight  212 . In  FIGS. 59 and 60 , the non-retractable blade  206  is shown in end section views with release wheel  68  and blade support  64  locking the blade in place ( FIG. 59 ) and with the release wheel  68  and blade support  64  in position to remove or insert the blade ( FIG. 60 ). This mechanism has been described in more detail above, with reference to FIGS.  42  to  45 .  
         [0118]     In another implementation, shown in  FIGS. 61, 62  and  63 , a powered utility knife  1250  of the disclosure having a utility knife blade that is caused to vibrate in effective cutting fashion has a retractable motor plate  252  and vibrating motor  254 . The vibrating motor  254  is secured to the retractable motor plate  252  by a motor bracket assembly  260 . The retractable motor plate  252  thus allows manual retraction of the blade  256  into the utility knife housing  258  ( FIG. 61 ) and allows extension of the blade  256  out of the utility knife housing  258  ( FIG. 62 ). The retractable blade mechanism is also shown in end view in  FIG. 63 . The vibrating utility knife typically would not be equipped with the ball bearing  112  and ball bearing cage  405  assembly described above for support of the reciprocating back and forth cutting motion of the blade. In one particular implementation, the vibrating motor  254  causes an extended blade  256  to vibrate axially as the extended blade  256  is rapidly shuttled back and forth by a drive system (not shown). In one implementation, shown in  FIGS. 64 and 65 , an exemplary vibrating motor assembly  300  includes a vibrating motor  302  and a counterweight  304 .  
         [0119]     A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made. For example, the blade change details described with reference to  FIGS. 43 and 44  for use in a powered utility knife for a non-retractable blade may be used also in a powered utility knife with a retractable blade.  
         [0120]     Also, referring to FIGS.  66  to  71 , the worm gear drive  16  and driven gear  17 , described above with reference, e.g., to  FIG. 3 , may be replaced with a bevel drive gear  409  and bevel driven gear  410  ( FIGS. 66 and 67 ), including for powered utility knives of the disclosure having a retractable utility knife blade ( FIGS. 68 and 69 ) and for powered utility knives of the disclosure having a fixed utility knife blade ( FIG. 70 ).  
         [0121]     Also, utility knives of the disclosure may be provided with a variable length cutting stroke assembly to allow a user to change the length of the back and forth cutting stroke of the utility knife blade mounted on the blade carrier  500 . Referring to  FIGS. 71 and 72 , motor  12  drives a bevel drive gear  413 , which drives a bevel driven gear  450 , which is part of stroke selector plate  412  turned by gear  450 , mounted by gear hub  463  to rotating shaft  464 . Adjustable crank pin  406  can be located in any of a number of different stroke adjustment holes  491  to vary the length of the cutting stroke. Crank pin knob  494  is used to move the crank pin  406  to a desired position within the adjustable cam  489  slot. Spring connector arm  414  springs back when crank pin  406  is pulled out of stroke adjustment hole  491 , by means of crank pin knob  494 , and rotated on spring connecting arm  414  which pivots on connecting arm pivot pin  400  allowing movement to other adjustment locations within the adjustment cam  489  slot. Crank pin slot  499  allows crank pin knob  494  and crank pin  406  to slide back and forth to accommodate various radial requirements when rotating on spring connecting arm  414 . In the event that the stroke adjustment hole is not within an adjustment cam slot  489  opening when adjustment is made, the V-groove follower  407  is positioned on the radial V groove  498  between the desired stroke adjustment holes  491 . When motor  12  is started, the stroke selector plate is turned by the driven bevel gear  450  and the V-groove follower  407  follows the V-grove  498  until the desired stroke adjustment hole  491  is rotated under the adjustment cam  489  opening, at which time crank pin  406  is pushed into stroke adjustment hole  491  by spring connecting arm  414 , causing adjustment cam  489  to move connection plate  467  back and forth at the desired stroke length. Reducing the cutting stroke length reduces the cutting speed and increases the force applied. Relatively shorter cutting strokes may be used for cutting small detail and/or small parts. Increasing the cutting stroke length increases the cutting speed. Relatively longer cutting stroke may be used in cutting larger and/or thicker work pieces.  
         [0122]     Also, powered utility knives of the disclosure may be provided with accessories in the form of support brackets constructed for mounting to the utility knife housing, e.g. by engagement with pockets provided at each side of the blade opening, for the purpose of steadying or aligning the utility knife and blade for cutting is special situations. Referring to  FIG. 73 , an adjustable angle steadying bracket  415  defines a blade slot  418  in the center bracket for receiving the blade  38 . Adjustable bracket arm supports  417  firmly attach the bracket to the utility knife housing  420  by engagement into support arm pockets  419  on each side of blade  38 . Adjustable bracket lock  416  may be rotated clockwise to loosen or counterclockwise to lock the support, thus enabling the user to adjust the desired angle of adjustable bracket  415 . Referring to  FIG. 74 , a non-adjustable support bracket  421 , formed, e.g. of a continuous metal rod, has bracket support arms  423  at each end that engage the utility knife housing  420  in support arm pockets  419  on each side of blade  38 . Bracket stop  422  rests against the utility knife housing  420  for support when the user applies pressure to the knife during use.  
         [0123]     These and other implementations are within the scope of the following claims.