Abstract:
A safety utility razor knife is normally maintained in a locked closed condition which protects the user or carrier from accidental injury by the blade. No action on the part of the user or carrier is required to lock the protective hood over the blade. The hood pivots into the open position, exposing the razor blade, when the knife is in use, and automatically self-locks the safety hood immediately after use, requiring no action or adjustment on the part of the user. The knife is designed for easy and convenient use in cutting cartons, and other materials, including but not limited to dry wall, floor coverings, and insulation, etc. The hood is unlocked by the user&#39;s thumb by moving a slide forward. The amount of blade exposed may be determined by a hood stop on the shoulder of the knife, or as regulated by the depth of cut cam action dial. This insures that only enough blade is exposed for the task at hand, i.e. when cutting a carton containing cereal boxes, only enough blade to cut the carton without damage to the cereal boxes is exposed. In addition, provisions may be made to control the depth of cut which is made by the safety utility razor knife.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of copending provisional patent application Ser. No. 60/251,758, filed Dec. 7, 2000, incorporated herein by reference. 
     
    
     
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
         [0002]    Not Applicable.  
         REFERENCE TO A “MICROFICHE APPENDIX” 
         [0003]    Not Applicable.  
         BACKGROUND OF THE INVENTION  
         [0004]    1. Field of the Invention  
           [0005]    This invention relates to knives with retractable safety sheaths or hoods.  
           [0006]    2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98  
           [0007]    This invention provides improvements in knives with retractable hoods. This invention provides a knife with a retractable hood with improved durability, reliability, and with a hood that provides enhanced safety and which automatically locks in the closed position.  
           [0008]    U.S. Pat. No. 2,376,887 discloses two embodiments of a package cutter having a pivoting mounted guard which covers exposed parts of the blade. The guard has two rearwardly projecting ears, one of which has an opening through which a pivot member is engaged and also has a spring which engages the pivot member and urges the guard to a blade covering position.  
           [0009]    U.S. Pat. No. 2,370,800 discloses a safety paper box cutter having a razor blade inserted through an opening of the body where the blade is retained bearing against a body end wall. The guard member is pivoted near the end of the body and is yieldingly held in the operating position by the spring.  
           [0010]    U.S. Pat. No. 2,743,523 discloses a carton opening knife with a razor blade which fits into a horizontally extending recess and is secured by a clip member having a run which contains the blade within the confines of the clip member when the clip is in repose.  
           [0011]    U.S. Pat. No. 3,781,988 discloses a safety paper carton opening blade holder in which a blade is retained by fingers and a guard is mounted on pivot trunnions above the blade. The guard is biased in a closed position by a spring.  
           [0012]    U.S. Pat. No. 4,531,286 discloses a carton cutting knife in which a razor blade is retained by detent means on the blade mounting extension and a blade guard is secured to the knife by a flexible attachment strap.  
           [0013]    U.S. Pat. No. 4,744,146 discloses an adjustable-blade safety knife with carton-cutting guide in which the blade is slidably-retained within the handle in the closed position and extends from the end of the handle in the open position and having a guide which constrains the blade to cut the side of the carton at a slightly inclined angle from the horizontal.  
           [0014]    U.S. Pat. No. 4,899,443 discloses a safety knife for cardboard with a longitudinally slidable knife blade holder spring-loaded in the direction of the knife handle. The normally retracted blade is extended for use by using a finger to slide a guide within an elongated passage in the blade holder until a stop is encountered.  
           [0015]    U.S. Pat. No. 5,241,750 discloses a utility razor safety knife with a normally closed hood which automatically self-locks in the closed position after use without action or adjustment by the operator. It is stabilized in its movement and biased toward the closed position by a yoke with springs attached. The disclosures of this patent are hereby incorporated by reference into this patent application.  
           [0016]    U.S. Pat. No. 5,943,780 discloses a cutter for fibrous compressible material such as insulation batting. The cutter has an elongated base with a slot for the blade which normally prevents exposure of the blade but which is depressed by contact with material to be cut and allows the blade to protrude through the slot. A safety bar prevents movement of the base unless the cutter is gripped by the user.  
           [0017]    The prior art inventions do not provide a safety knife with the reliable, durable, adjustable and efficient safety features of the present invention.  
         BRIEF SUMMARY OF THE INVENTION  
         [0018]    This invention is an improved safety utility razor knife of the type having a handle, a blade attached to the handle, a blade guard hood pivotally attached to the handle, the blade guard hood normally locked in the closed position by a locking plunger which is normally biased by a spring in the closed position. The locking plunger is released by a slide pushed forward from its resting position. Once a cut has been made and the cutter is lifted from the cut surface, the pressure dependent hood moves into the closed position and is automatically locked in that position by the locking plunger, regardless of the position of the slide. In order to move the hood to the open position and to cut again, the slide must be released and allowed to move to the closed, resting, position, then pushed forward into the open position, thereby unlocking the hood and allowing exposure of the blade and use of the knife.  
           [0019]    Such knives are used for cutting paper box cartons, opening packages, cutting sheet materials such as roofing and floor coverings and removing insulation from coated wires.  
           [0020]    The knife of this invention has the advantage of a “normally locked” hood, which insures that a knife which is not in actual use is in the safe configuration where the protective hood is locked in the closed protective position without any action on the part of the user or carrier.  
           [0021]    In the present invention the hood is biased in the closed position by a hood plunger pin which is urged by a spring to hold the hood in the closed position, thereby preventing exposure of the blade. A slide which is biased by a spring in the closed position retains the hood plunger pin in the closed position and retains the hood in the locked position. In addition, a locking plunger is normally biased in the locked position and provides a mechanism for locking the hood in the locked position.  
           [0022]    When it is desired to allow the hood to pivot upward with the exposure of the knife blade, the slide is pressed forward thereby allowing upward movement of the hood plunger pin into a groove in the slide. The upper surface of the groove slopes upward from the front to the back of the slide, thus allowing full upward movement of the hood plunger pin and full exposure of the knife blade when the slide is pressed fully into the forward position. In addition, pushing the slide forward causes the locking plunger to move backward, releasing the hood from the locked position. Completion of a cut and release of the knife from the cut surface allows the hood to snap into the closed position where it is immediately locked in the closed position by the locking plunger. This occurs despite the fact that the slide may be held in the forward position. The slide must be released and allowed to returned to the rearmost locked position and then pushed forward before the hood may be moved to the open position. This is an important safety feature which prevents injury associated with rapid cutting.  
           [0023]    Release of the slide by the knife user allows the slide to move immediately to the rear locked position with the positive locking of the hood in the closed position by both the hood plunger and by the locking plunger. The knife now can be used by pressing the slide forward to the open position and pressing the hood against the surface to be cut. The hood now is free to pivot, exposing the edge of the blade.  
           [0024]    In a second embodiment of the safety knife, the degree of retraction of the hood, and therefore the depth of cut of the blade, may be adjusted.  
           [0025]    It is an object of this invention to provide a safety knife having a number of different safety hood embodiments adopted for specific cutting tasks.  
           [0026]    It is an object of this invention to provide a safety knife wherein the retractable hood can be opened only by moving the slide from the closed position to the open position and pressing the hood against a surface to be cut, while the hood locks in the closed position when the knife is lifted from the cut surface regardless of the position of the slide.  
           [0027]    It is a further object of this invention to provide a safety knife wherein the blade is positively protected against exposure without the necessity of any action by the user.  
           [0028]    It is a further object of this invention to provide a safety knife wherein the hood is retained in the closed position by a positive locking mechanism and by a spring biasing the hood in the closed position.  
           [0029]    It is a further object of this invention to provide a safety knife wherein the hood is automatically locked in the closed position when the knife is lifted from the cut surface, whether the slide is in the open position or closed position.  
           [0030]    It is a further object of this invention to provide a safety knife wherein the biasing tension of the hood is adjustable.  
           [0031]    It is a further object of this invention to provide a safety knife wherein action by the user is required in order to allow exposure of the blade, thereby preventing accidental injury by the blade.  
           [0032]    It is a further object of this invention to provide a safety knife wherein the hood is transparent, thereby affording an improved view of the cutting surface for the user.  
           [0033]    It is a further object of this invention to provide a safety knife which is stabilized against tilting when resting on a surface.  
           [0034]    It is a further object of this invention to provide a safety knife wherein the hood accommodates a cable for use in slitting cable insulation.  
           [0035]    It is a further object of this invention to provide a safety knife which is stabilized to ensure a right-angle cut.  
           [0036]    It is a further object of this invention to provide a safety knife with an easily replaceable blade.  
           [0037]    It is a further object of this invention to provide a safety knife having a grip contoured to insure a firm grip by each finger of the gripping hand, thereby preventing slipping of the knife when in use.  
           [0038]    It is a further object of this invention to provide a safety knife wherein the amount of retraction of the hood, and thus the depth of the cut, may be controlled.  
           [0039]    It is a further object of this invention to provide a safety knife wherein the movement of the safety slide is stabilized by a rocker pin.  
           [0040]    It is a final objective of this invention to provide a safety knife which is safe, effective, reliable, durable, and inexpensive to manufacture without adverse effects on the environment. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0041]    [0041]FIG. 1 is a side view of the first embodiment safety knife.  
         [0042]    [0042]FIG. 2 is a side view of the first embodiment safety knife when the slide is in the rearmost closed position.  
         [0043]    [0043]FIG. 3 is a side view of the first embodiment safety knife when the slide is in the forward most open position.  
         [0044]    [0044]FIG. 4 is a side view of the first embodiment safety knife when the slide is in the forward most open position and the knife hood has been pressed against the surface to be cut and the hood is moved into the open position.  
         [0045]    [0045]FIG. 5 is a side view of the first embodiment safety knife when the slide is in the forward most open position and the knife hood has been released from the surface after cutting and the hood is moved into the closed position.  
         [0046]    [0046]FIG. 6A is a perspective view of the rocker hook.  
         [0047]    [0047]FIG. 6B is a side view of the rocker hook.  
         [0048]    [0048]FIG. 7A is a side view of the rocker.  
         [0049]    [0049]FIG. 7B is a front view of the rocker.  
         [0050]    [0050]FIG. 8A is a side view of the locking plunger.  
         [0051]    [0051]FIG. 8B is a side view of the locking plunger.  
         [0052]    [0052]FIG. 9 is a cross section view of the hood plunger assembly.  
         [0053]    [0053]FIG. 10A is a side view of the first embodiment hood.  
         [0054]    [0054]FIG. 10B is an end view of the first embodiment hood.  
         [0055]    [0055]FIG. 11A is a side view of the second embodiment hood.  
         [0056]    [0056]FIG. 11B is an end view of the second embodiment hood.  
         [0057]    [0057]FIG. 12A is a side view of the third embodiment hood.  
         [0058]    [0058]FIG. 12B is an end view of the third embodiment hood.  
         [0059]    [0059]FIG. 13A is a side view of the fourth embodiment hood.  
         [0060]    [0060]FIG. 13B is an end view of the fourth embodiment hood.  
         [0061]    [0061]FIG. 14 is a side view of the second embodiment safety knife.  
         [0062]    [0062]FIG. 15A is a side view of the control of the second embodiment safety knife.  
         [0063]    [0063]FIG. 15B is a side view of the detent of the second embodiment safety knife.  
         [0064]    [0064]FIG. 15C is a front view of the face of the depth control of the second embodiment safety knife.  
         [0065]    [0065]FIG. 16A is a cross section of FIG. 1 along line  2 - 2 .  
         [0066]    [0066]FIG. 16B is a cross section of FIG. 1 along line  2 - 2  showing the safety knife with the second embodiment hood. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0067]    [0067]FIG. 1 is a side view of the first embodiment safety knife. Visible in FIG. 1 are the handle  100  to which the blade  116  is attached, as well as the transparent hood  112  which covers the blade, and the slide  300  which is used to unlock the hood when the knife is in use.  
         [0068]    The handle  100  is extended to fit the hand of the user and consists of a front portion  101  and a gripping portion  102  at the rear end. The gripping portion  102  is shaped to accommodate either the left or right hand of the user and has four finger grip grooves  104  to insure a safe, firm, and comfortable fit in the user&#39;s hand. The handle accommodates users whether they are wearing gloves or not, and whether they have short or long finger nails.  
         [0069]    The front portion  101  includes a blade holder escutcheon (not visible in FIG. 1) which is a cut-out in the handle of approximate the shape of the blade and into which the blade fits with one end of the blade protruding from the end of the handle. The trapezoid shaped blade  116  is placed in the blade holder escutcheon and a blade retainer  200  of approximately the shape of the escutcheon covers a portion of the blade and retains the blade in place and provides firm strong reinforcement of the blade against breakage in use by forces lateral to the blade. The blade retainer  200  is attached to the handle by a blade screw  118  which extends through a hole in the blade and the blade holder into a tapped blade screw hole in the handle and retains both the blade  116  and blade retainer  200  in place. Two blade retainer pins  126  extend outward from the escutcheon portion of the handle. These blade retainer pins  126  extend through notches in the blade and into corresponding notches in the blade holder and are fixed in the side of the front portion  101  of the handle  100 . The blade retainer pins  126  serve to prevent the pivoting of the blade about the blade screw when the knife is in use. Alternatively, if the handle is injection molded, the blade retention pins may be integral with and extending from the side of the front portion  101  of the handle  100 . The sharp edge of the blade  119  extends along the entire bottom of the blade  116 .  
         [0070]    A transparent hood  112  extends around both sides of the blade and pivots about a  20  hood pivot screw  204 . Two hood pivot screws  204  may be used, one on either side of the handle  100 , each threaded into the handle. Alternatively, a single hood pivot screw  204  may extend through a threaded hole in the handle and retain the hood on either side of the handle. The use of a single hood pivot screw  204  facilitates the changing of the hood  202  or blade  116 .  
         [0071]    The top surface of the handle is generally flat with the exception of the front end where a T-shaped fin ( 360  in FIG. 16A) extends upward. The fin is used to secure the slide  300  to the top of the handle.  
         [0072]    A groove  103  is in the front end of the handle. The hood  202  rests on the lower edge of the groove when the hood is in the closed position. Hood  202  is held in the closed position by the hood plunger assembly  305  which is spring biased into the lowered position which holds the hood in the closed position until the hood is pressed into the open position during cutting. A locking plunger  312  extends from back side of the groove  103  and locks the hood in the closed position.  
         [0073]    In operation, the slide  300  is pushed toward the front of the knife by the user&#39;s thumb with the release of the hood plunger assembly  305  and locking plunger  312 , allowing the hood  202  to pivot upward with exposure of the cutting edge  119  of the blade  116 .  
         [0074]    FIGS.  2 - 5  depict the internal workings of the safety knife.  
         [0075]    [0075]FIG. 2 shows additional details on the slide  300 . FIGS.  2 - 5  are sagittal cross sections of the knife of FIG. 1. The slide  300  has an internal cavity  301 . A rocker hook  322  is a flat spring which is anchored at the front of the slide  330  and extends through the cavity  301  and has a loop  323  on one end. Additional detail on the structure of the rocker hook  322  is in FIGS. 6A and 6B. A rocker  310  extends into the cavity  301  and pivots about a pivot pin  311  embedded in the front part of the handle  101  and extending through a pivot hole approximately in the middle of the rocker. A rocker ball  325  is formed on one end of the rocker  310 . Additional detail on the structure of the rocker is in FIGS. 7A and 7B. A hood plunger assembly  305  extends through the top of the groove. The hood plunger assembly  305  is spring biased to extend down onto the top of the hood and bias the hood into the closed position. The top  329  of the hood plunger assembly  305  bears on the rocker hook  322 . Additional detail on the structure of the hood plunger assembly  305  is found in FIG. 9. The rocker ball  325  extends into a locking plunger slot  315  bored through the locking plunger  312 . A locking plunger spring  313  biases the locking plunger into the forward locked position. The locking plunger beveled end  317  bears on the top of the hood  202  and locks the hood into the locked position. Additional detail on the structure of the locking plunger is in FIGS. 8A and 8B. A slide plunger  304  extends from the top of the handle  101  into the cavity  301 . A slide spring  306  fits into a hole in the slide and bears on the slide plunger  304  and biases the slide to the rear closed position. The slide spring preferably consists of  22  coils of 0.012 inch musical wire. Movement of the slide is controlled by a slide travel pin which extends above the handle and into a slide groove  330 .  
         [0076]    [0076]FIG. 2 shows the knife in the closed locked position when the edge  119  of the blade  116  is covered and protected by the hood  202 . In this position, the slide  300  is biased by the slide spring  306  into the closed position where the slide travel pin  303  bears against the front side of the slide groove  330 . In the closed position of FIG. 2 the beveled end  317  of the locking plunger  312  extends over the top of the hood  202  and locks the hood in the closed position. The rocker  310  is pivoted so that the ball  325  is in the forward position in the locking plunger slot  315  and the top  331  of the rocker bears against the rocker hook  322 . The hood plunger assembly  305  extends against the top of the hood.  
         [0077]    [0077]FIG. 3 is the same as FIG. 2 except that the slide  300  has been pushed forward with the back of the slide groove  330  against the slide travel pin  303 . The slide spring  306  is compressed by the forward movement of the slide. The forward movement of the slide  300  causes the loop  323  on the end of the rocker hook  322  to engage the top  331  of the rocker  310  and causes the top  331  to move forward. The forward movement of the top  331  of the rocker  310  causes the rocker ball  325  to move toward the rear of the knife. Since the rocker ball  325  extends through a slot  315  in the locking plunger  312 , the locking plunger is moved to the rear of the knife, thereby moving the beveled end  317  of the locking plunger to the rear and freeing the hood  202  to move upward.  
         [0078]    [0078]FIG. 4 is the same as FIG. 3 except that the hood  202  has been displaced into the open position because the knife has been pressed against a surface being cut. Movement of the hood  202  into the open position exposes the sharp edge  119  of the knife  116 . The maximum exposure of the blade preferably is 0.300 inch. The upward movement of the hood  202  against the hood plunger assembly  305  causes the emergence of the top  329  of the hood plunger assembly  305  which displaces the rocker hook  322  upward. This causes the upward movement of the rocker hook loop  323  and releases the top  331  of the rocker  310 .  
         [0079]    [0079]FIG. 5 is the same as FIG. 4 except the knife has been lifted from the cut surface and the hood  202  has been moved by the spring in the hood plunger assembly  305  into the closed position which protects the blade. Since the top  331  of the rocker  310  was freed in FIG. 4, the rocker  310  pivots so that the top  331  moves to the rear of the knife and the ball  325  moves forward with the locking plunger  312 . The beveled end  317  of the locking plunger  312  is biased forward by the locking plunger spring  313  and locks the hood in the closed position. Thus the lifting of the knife from the cut surface causes the hood to close and lock in a safe position, despite the fact that the slide  300  is still in the forward position. In order to unlock the hood it is necessary to allow the slide to return to the rear locked position and then to push the slide forward into the unlocked position.  
         [0080]    [0080]FIGS. 6A and 6B provide more details on the rocker hook  322 .  
         [0081]    [0081]FIG. 6A is a perspective view which shows the rocker hook  322  comprised of the rocker hook body  336 , the rocker hook loop  323  at one end of the rocker hook, the rocker hook flange  332 , which at the other end of the rocker hook and is bent at approximately a right angle to the rocker hook body  336 , and on the side of the body opposite to that of the rocker hook loop  323 . A hole  334  in the rocker hook flange  332  is used to attach the rocker hook to the front of the slide  330  in FIG. 2 using a screw or other suitable fastener. The rocker hook is preferably 0.012 inch in width.  
         [0082]    [0082]FIG. 6B is a side view of the rocker hook  322 . Visible are the rocker hook body  336 , the rocker hook loop  323 , and the rocker hook flange  332 .  
         [0083]    [0083]FIGS. 7A and 7B provide more details on the rocker  310 .  
         [0084]    [0084]FIG. 7A is a side view of the rocker  310  showing the rocker top  331 , the hole  338  in the rocker for the pivot pin, and the rocker ball  325 . In a preferred embodiment the rocker top  331  upper surface is at an angle of approximately 65° to the body of the rocker  310 .  
         [0085]    [0085]FIG. 7B is a front view of the rocker  310  showing the rocker top  331  which is a T-shaped web like structure, and the rocker ball  325 .  
         [0086]    [0086]FIGS. 8A and 8B provide more details on the locking plunger  312 .  
         [0087]    [0087]FIG. 8A is a top view of the locking plunger  312  showing locking plunger slot  315  which extends through the locking plunger. The top bevel  319  located in the beveled end  317  is shown.  
         [0088]    [0088]FIG. 8B is a side view of the locking plunger  312  showing the beveled end  317 , the top bevel  319 , and the bottom bevel  321 . In a preferred embodiment the top bevel  319  is at an angle of approximately 50° to a plane perpendicular to the long axis of the locking plunger.  
         [0089]    [0089]FIG. 9 is a cross section of the hood plunger assembly  305 . The hood plunger is comprised of a hood plunger body  340  which has a hood plunger lower end  342  which bears on the top of the hood. The hood plunger body  340  is necked down to accommodate a hood plunger spring  346  which fits into a cylindrical hood plunger collar  344 . The hood plunger spring  346  preferably consists of  12  coils of 0.012 inch musical wire. The outer surface  348  of the hood plunger collar  344  is threaded. The top  329  of the hood plunger is preened so it is retained in the hood plunger collar  344 . The hood plunger spring  346  biases the hood plunger body  340  is a downward direction.  
         [0090]    [0090]FIG. 10A is a side view of the first embodiment hood  202 . FIG. 10A shows the top of the hood  206 , the left side of the hood  208 , and the hole  204  for the screw about which the hood pivots when it opens and closes.  
         [0091]    [0091]FIG. 10B is a end view of the first embodiment hood  202 . FIG. 10B shows the top of the hood  206 , the left side  208 , the right side  210 , the front of the hood  218 , the left bottom side  212 , the right bottom side  214 , and the opening for the blade  216 . The left bottom side is attached approximately perpendicularly to the left side and the right bottom side is attached approximately perpendicular to the right side.  
         [0092]    [0092]FIG. 11A is a side view of the second embodiment hood  222 . FIG. 11A shows the top of the hood  226 , the left side of the hood  228 , and the hole  224  for the screw about which the hood pivots when it opens and closes. The second embodiment hood is adapted for the removal of insulation from electrical wires and cables. In use, the length of the cable fits into the inverted-V shape of the bottom of the hood.  
         [0093]    [0093]FIG. 11B is a end view of the second embodiment hood  222 . FIG. 11B shows the top of the hood  226 , the left side  228 , the right side  230 , the front of the hood  238 , the left bottom side  232 , the right bottom side  234 , and the opening for the blade  236 . The left bottom side  232  is mounted at an angle of approximately 45° to the left side  228 . The right bottom side  234  is mounted at an angle of approximately 45° to to the right side  230 . The left bottom side  232  and right bottom side  234  form an inverted-V which accommodates a cable or wire to be stripped of a coating, such as an insulation coating.  
         [0094]    [0094]FIG. 12A is a side view of the third embodiment hood  242 . FIG. 12A shows the top of the hood  246 , the left side of the hood  248 , and the hole  244  for the screw about which the hood pivots when it opens and closes. A fin  254  is extended downwardly from the left side  248 .  
         [0095]    The third embodiment hood is designed for use in cutting along the top of a case. The fin  254  is placed against the side of a case and the cut is made along the top of the case at a uniform distance from the side of the case.  
         [0096]    [0096]FIG. 12B is a end view of the third embodiment hood  242 . FIG. 12B shows the top of the hood  246 , the left side  248 , the right side  250 , the front of the hood  258 , the left bottom side  252 , the right bottom side  254 , and the opening for the blade  256 . The fin  254  is shown extending down from the left side  248 .  
         [0097]    [0097]FIG. 13A is a side view of the fourth embodiment hood  262 . FIG. 13A shows the top of the hood  266 , the left side of the hood  268 , and the hole  264  for the screw about which the hood pivots when it opens and closes. The fourth embodiment hood  262  is adapted for case cutting. It includes the fin  278  as in the third embodiment and in addition a flange  280  which extends at an approximate right angle from the right side  270 . The flange  280  stabilizes the cutter when cutting the top of a case.  
         [0098]    [0098]FIG. 13B is a end view of the fourth embodiment hood  262 . FIG. 13B shows the top of the hood  266 , the left side  268 , the right side  270 , the front of the hood  278 , the left bottom side  272 , the right bottom side  274 , and the opening for the blade  276 . In addition, a fin  278  extends down from the left side  268 . A flange  280  extends from the right side  270  approximately perpendicular to the right side  270 .  
         [0099]    [0099]FIG. 14 is a side view of the second embodiment safety knife which is the same as the first embodiment safety knife of FIG. 1 except the second embodiment has the added feature of a mechanism which controls the depth of cut of the safety knife. The depth control  400  is a variable offset cam which is rotatively mounted on the side  101  of the handle  100  of the knife. The control  400  controls the movement of the hood  202  and thereby controls the depth of cut made by the blade  116 . Each of the six sides of the control  400  is at a different distance from the center of the control. Rotation of the control allows variation of the depth of cut. Indicia  402  on the face of the control indicate the depth of the cut. The maximum exposure of the blade preferably is 0.300 inch.  
         [0100]    [0100]FIG. 15A is a side view of the control  400 . The face  404  is a disk with unequal sides which is mounted on the control post  406 . The control post  406  is mounted on the side of the cutter. The back of the control has indentations  408  which interacts with a detent on the cutter for restricting free rotation of the control.  
         [0101]    [0101]FIG. 15B shows the detent  410  used to restrict free rotation of the depth control. The detent is inserted into a hole on the side of the cutter, a spring  412  biases the detent outward against an indentation ( 408  in FIG. 15A) and thereby restricts rotation of the depth control.  
         [0102]    [0102]FIG. 15C shows the face  404  of the depth control  400  and the indicta  402  used to indicate the depth of the cut.  
         [0103]    [0103]FIG. 16A is a cross section of FIG. 1 along line  2 - 2 . FIG. 16A shows the slide  300  and the cavity  301  in the slide as well as the screw  348  which retains the rocker hook. The left side  350  of the slide is shown along with the flange  352  at the bottom of the left side  350 . The right side  354  of the slide is shown along with the flange  356  at the bottom of the left side  354 . The slide fits over a T-shaped fin  360  which is mounted along the top of the safety knife handle. Visible in FIG. 16A is the blade  116  and screw  118  which secures the blade. The hood plunger assembly  305  is shown along with the beveled end  317  of the locking plunger. Also visible in FIG. 16A is the first embodiment hood  202  comprising a right side  210 , top  206 , left side  208 . The left bottom  212  is attached at approximately a right angle to the left side  208 . The right bottom  214  is attached at approximately a right angle to the right side  210 . The opening  216  for the blade is also visible.  
         [0104]    [0104]FIG. 16B is the same as FIG. 16A except that a second embodiment hood  222  is used rather than the first embodiment hood. Visible in FIG. 16B is the second embodiment hood  222  comprising a right side  230 , top  266 , left side  228 . The left bottom  232  is attached at approximately a 45° angle to the left side  228 . The right bottom  234  is attached at approximately a 45° angle to the right side  230 . The left side  232  and right side  234  form an inverted-V. The opening  236  for the blade is also visible.  
         [0105]    When the blade becomes dull, its life may be extended by reversing the blade in its mount in the handle, thereby exposing a unused portion of the blade for use. The first step in reversing the blade is to remove the hood. This is accomplished by removing the hood pivot screw ( 204  in FIG. 1) and pulling the hood forward and off the front end of the safety knife. The blade screw ( 118  in FIG. 1) is then removed, the blade holder ( 200  in FIG. 1) is removed, the blade  116  in FIG. 1) is removed and flipped over so the front end of the blade is at the rear of the escutcheon. The blade holder and screw are replace, along with the hood, and the safety knife is ready for use with a previously unused cutting surface available for use. After the entire blade is dulled, a similar process is used to replace the blade with an unused blade.  
         [0106]    The handle of the safety knife is constructed out of any strong, resilient, hard material, such as aluminum, steel, or plastic. A preferred material is plastic. If metal is used, the handle can be coated with a resilient material, such as rubber, in order to prevent and relieve user fatigue. Any suitable case cutter type blade may be used with the safety knife. The hood is made of any suitable hard, strong, transparent material, prefereable plastic, such as polymethylmethacrylate or polycarbonate. The rocker hook is made of any suitable resilient material, a preferred material is stainless steel. Other parts of the cutter are made of suitable metals.  
         [0107]    It will be apparent to those skilled in the art that the examples and embodiments described herein are by way of illustration and not of limitation, and that other examples may be used without departing from the spirit and scope of the present invention, as set forth in the appended claims.