Abstract:
A utility knife has a disposable blade cartridge in its handle that has front and rear blade compartments. Each compartment is sized to store a plurality of blades in side-by-side relation. Fresh blades are disposed in the front compartment and one end of each is advanced one at a time substantially out of the compartment into operative position by a carrier that is controlled by an actuator on the handle. When the active blade is to be replaced, it is moved by the carrier into the rear compartment, and a new blade may then be withdrawn from the front compartment into the operative position. The active blade when not in use is partially withdrawn into the front compartment. The cartridge is reversed when the one end of all the blades in the front compartment are used, placing what was the rear compartment at the front, and the unused end of each blade is advanced into the operative position and when used they are each moved to the rear compartment. When all are used, a new cartridge replaces the old in the knife

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to utility knives and more particularly comprises a utility knife with an automatic blade loading system that enables the user to change blades without touching them so as to achieve maximum safety, speed and convenience in the operation of the device. This application claims the benefits of applicant&#39;s earlier filed, copending provisional application Serial No. 60/307,285 filed Jul. 23, 2001 and incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    Utility knives are widely used for a number of different purposes and are a very popular and handy tool. Conventionally, utility knives use a thin double-ended blade that in use extends out one end of the knife case. When the cutting end becomes dull or otherwise unsuited for continued use, the blade is reversed so that its other end extends out of the case. In most utility knives, reversal of the blade requires handling of it, and because the blades are very sharp, thin, and not particularly easy to handle, accidents frequently occur. It is also difficult to properly mount the blade within the components in the case.  
           [0003]    A number of utility knives have been developed that employ cartridges that hold a plurality of blades, some of which enable the user to change the blade with a reduced risk of cutting ones self, but none have proved to be entirely satisfactory. Some require a very large case to receive the cartridge, which detracts from the comfort of using the tool. And none of the prior art tools known to applicant provide total protection against accidental injury when reversing or changing the blade. Many of those knives have non-traditional shapes so as to limit their appeal to those who frequently use them.  
         SUMMARY OF THE INVENTION  
         [0004]    In accordance with the present invention, the utility knife has a cartridge that may contain as many as  20  or more blades fully enclosed in it and that may be mounted in the case without the user coming into contact with any of the blades. In accordance with one embodiment of the invention, the cartridge is initially packaged with all the blades in one compartment stacked close together, side-by-side. The blades may be extended from the cartridge and the case, one at a time to an operative position wherein one end of the blade is exposed, and when not in use the blade may be fully withdrawn into the case. An actuator mounted on the case controls a carrier that engages the blades in the cartridge one at a time and slides them to the operative position wherein one end of the blade extends from the case as well as to a number of retracted positions within the case..  
           [0005]    In accordance with another aspect of the present invention, the cartridge has two compartments, one of which when the cartridge is initially loaded, contains all of the blades, and the other compartment is empty. After one end of each blade has been used and is to be replaced, the used blade is moved into the second compartment and thereafter, the next blade in the first compartment is moved into position for continued use of the knife. This sequence is followed for each of the blades in the first compartment until one end of each blade is used and all are deposited in the second compartment. Thereafter, the cartridge is repositioned in the case so that the second compartment is close to the operative end of the case and all of the blades may be withdrawn in sequence from the second compartment. When the cartridge is repositioned in the case, the blades in the second compartment are positioned so that the unused ends of the blades are moved one at a time into the operative position. In sequence, each of the blades in the second compartment is extended to the operative position exposing the unused end and when the second end is worn, the blade is deposited in the first compartment now at the rear of the case. When both ends of all the blades are used, the cartridge is discarded and a new one inserted in the case.  
           [0006]    In accordance with another aspect of the present invention, the carrier which moves through the cartridge and case to position the blades one at a time in the operative position and alternate retracted positions, is operated by an actuator that remains locked in position until the actuator lock is released to allow the actuator to move longitudinally in the case. As the actuator is attached to the carrier, the carrier cannot move without movement of the actuator, and only the actuator is accessible to move the carrier and the blades.  
           [0007]    The various aspects of the present invention will be better understood and appreciated from the following detailed description of one embodiment thereof shown in the accompanying drawings, in which:  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a top plan view of a utility knife in accordance with one embodiment of the invention;  
         [0009]    [0009]FIG. 2 is a side elevation view of the utility knife shown in FIG. 1;  
         [0010]    [0010]FIG. 3 is a vertical cross-sectional view of the knife taken along section line  3 - 3  in FIG. 1;  
         [0011]    [0011]FIG. 4 is a horizontal cross-sectional view of the knife taken along section line  4 - 4  in FIG. 2;  
         [0012]    [0012]FIGS. 5, 6 and  7  are cross-sectional views of the knife taken along the corresponding section lines in FIG. 2, respectively;  
         [0013]    [0013]FIG. 8 is a perspective view of a spring that in accordance with an embodiment of the invention serves as a latch for the door in the case through which the cartridges are inserted and removed from the case;  
         [0014]    [0014]FIG. 9 is a perspective view of one half of the blade cartridge, the full cartridge being made up of two identical halves, in accordance with another aspect of this invention;  
         [0015]    [0015]FIG. 10 is a perspective view of an assembled cartridge made up of two identical halves, one shown in FIG. 9;  
         [0016]    [0016]FIG. 11 is a side elevation view of one half of a cartridge showing blades disposed in each of the compartments;  
         [0017]    [0017]FIG. 12 is a perspective view of the cartridge similar to FIG. 10 and showing the carrier and actuator subassembly mounted on it;  
         [0018]    [0018]FIG. 13 is side elevation view of one embodiment of a blade constructed in accordance with one aspect of the invention and which may be packaged with other identical blades in the cartridge;  
         [0019]    [0019]FIG. 14 is a side elevation view of another blade that may be packaged with other like blades in the cartridge and used in the knife of this invention;  
         [0020]    [0020]FIG. 15 is an end perspective view of a blade, carrier and actuator assembly;  
         [0021]    [0021]FIG. 16 is a side perspective view of the assembly shown in FIG. 15;  
         [0022]    [0022]FIG. 17 is a perspective view of the actuator but viewed from the side opposite that of FIG. 16;  
         [0023]    [0023]FIG. 18 is a perspective view of the carrier showing the face thereof hidden by the blade in FIG. 16 and opposite the side shown in FIG. 17;  
         [0024]    [0024]FIGS. 19 and 20 are detailed horizontal cross-sectional views respectively showing the support forming part of the carrier and engaging a blade as in FIG. 16 and retracted and not engaging a blade;  
         [0025]    [0025]FIGS. 21 and 22 are perspective views of the actuator in its unlocked and locked positions, respectively;  
         [0026]    [0026]FIG. 23 is a horizontal cross-sectional view of the knife case and actuator taken along section line  23 - 23  in FIG. 2 and showing the locking arrangement for the actuator and carrier;  
         [0027]    FIGS.  24 - 28  are vertical cross-sectional views similar to FIG. 3 on a reduced scale and illustrating the carrier, actuator and blades in various positions in the knife case;  
         [0028]    [0028]FIG. 29 is an enlarged, fragmentary, horizontal, cross-sectional view of the front end of the knife showing the carrier and a blade advanced to the operative position;  
         [0029]    [0029]FIG. 30 is a view similar to FIG. 29 and showing the carrier moved rearwardly in the case toward the rear compartment to deposit a used blade in it;  
         [0030]    [0030]FIG. 31 is a view similar to FIG. 30 showing the carrier moved further back with the used blade toward the rear compartment;  
         [0031]    [0031]FIG. 32 is a view similar to FIG. 31 showing the used blade yet further back in the rear compartment about to deposit the used blade in it;  
         [0032]    [0032]FIG. 33 is a view similar to FIG. 32 and showing the empty carrier approaching a new blade in the front compartment;  
         [0033]    [0033]FIG. 34 is a view similar to FIGS.  29 - 33  and showing the carrier empty and moving rearwardly in the case to pick up the first blade in the front compartment after a new cartridge has been inserted in the case or the cartridge has been reversed;  
         [0034]    [0034]FIGS. 35 and 36 are enlarged, fragmentary horizontal cross-sectional views of an alternative knife construction showing the carrier moving a used blade into the rear (used blade) compartment beside previously stored blades in that compartment;  
         [0035]    [0035]FIG. 37 is a vertical side elevation view of a cartridge half and having a blade restrictor in the front compartment for preventing new blades from inadvertently moving rearwardly into the passageway between the compartments toward the used blade compartment but permits the blade to move to the slot in the front of the knife;  
         [0036]    [0036]FIG. 38 is a fragmentary elevation view partly in section showing a gate that controls the movement of blades through the passageway from the front to the rear compartment;  
         [0037]    FIGS.  39 - 41  are fragmentary cross-sectional views of the gate guarding the passageway between the compartments and respectively showing the gate closed, in the process of being opened, and fully opened allowing a blade into the rear compartment 
     
    
     DETAILED DESCRIPTION  
       [0038]    The utility knife of the present invention includes a case  40 , a blade cartridge  42  containing a number of blades  44 , a carrier  46  movable within the case  40  and through the cartridge  42 , and an actuator  48  connected to the carrier and accessibly mounted on the case  40 . As is described in detail below, the cartridge in a preferred embodiment of the invention contains a pair of compartments and is initially filled with all of the new blades in the same compartment, while the other compartment is empty. The blades are withdrawn from the new blade compartment one at a time so that one end of each blade may be sequentially used, and after each blade requires replacement, it is deposited in the other compartment. When all of the blades have been transferred to the other compartment, the cartridge is reversed in the case and the unused edges of the blades are sequentially used and then deposited in what becomes the used blade compartment when the cartridge is reversed. In this manner, one edge of each blade is used as the active cutting implement in the utility knife, and when all the blades have one used edge, the cartridge is reversed so as to place the unused edges in position to be used in sequence. These various components are described separately below along with their interaction with the other components in the assembly.  
         [0039]    Case  40   
         [0040]    The case  40  is particularly illustrated in FIGS.  1 - 8 . The case in the illustrated embodiment typically is a metal casting such as die casting of aluminum or zinc and is composed of two halves or shells  60  and  62  that may be secured together by any one or more of a variety of different fasteners such as screws, hook-like fingers, snaps, etc. to form an elongated housing for the utility knife components as well as a handle for operating the knife. In FIGS. 1 and 5- 7 , parting lines  64  along the top and bottom are suggested representing the mating edges of the two halves  60  and  62  of the case. In this description the end  66  of the case will sometimes be identified as the front end while the other end  68  will sometimes be identified as the back end of the case. The parting line  64  of the case runs longitudinally from end-to-end, and in the usual orientation of the case illustrated, is in a vertical plane. The front end of the case  66  has a blade slot  70  (see FIG. 4) through which individual blades may be extended to an operative position by the carrier  46  and through which the blade may be withdrawn into the case and into the cartridge  42  when not in use. It should be understood that while the case in the illustrated embodiment is composed of two half shells split longitudinally along the approximate center line of the case, the case may be made up of a different number of parts and the various components may be assembled in a variety of different ways.  
         [0041]    As shown in FIGS. 2, 6 and  7 , the case shell  60  includes a door  72  through which access is gained to its interior chamber  100 . The door may be mounted on the case shell  60  by many different ways. For example, the bottom  74  of the door may be provided with prongs  73  that are received in recesses  77  in the bottom of the shell  60  as shown in FIGS. 6 and 7 to secure the bottom of the door in place. The top of the door may be held in place by a latch  76  at the top of the door that releasably engages the edge of the door opening in the shell  60 . One embodiment of a latch is suggested in FIGS. 6 and 8. The latch  76  is shown in the form of a spring mounted on a post  78  on the inside of the door  72 , and having a free arm  80  that engages the edge  82  of the door opening in shell  60 . Many other and different types of closures may be employed, but they should not interfere with the grasping of the case as a handle when the knife is being used and should not accidentally or inadvertently open particularly during use. The door may be removable or not, but must at least open sufficiently wide so as to enable the cartridge  42  to be conveniently and easily inserted into and removed from the case interior chamber  100 . The door as one alternative may be hinged to the case, and any form of latch may be used in combination with the hinge for releasably holding the door closed. Many other arrangements for holding the door in place may be used as well.  
         [0042]    A slot  90  (see FIG. 1) is provided in the top  92  of the case and extends longitudinally a substantial portion of the case length and serves as a slide track for the actuator  48 . As shown in FIGS.  6 - 8 , the slot  90  opens into a chamber  93  below which is a channel  94  that receives the shoulders  96  of the carrier  46 .  
         [0043]    The case  40  and more particularly its shells  60  and  62  define the large chamber  100  that receives the cartridge  42  and carrier  46 . The shell  62  is provided with shoulders  102  on its inner surface (see FIGS. 6 and 7) that conform to the shape of the cartridge  42  so as to provide a firm seat for it. The bottom  74  of the door also has a shoulder  106  that provides further support for the cartridge  42  when the cartridge is in place in the chamber  100 .  
         [0044]    Cartridge  42   
         [0045]    The cartridge  42  is shown in FIGS.  9 - 12 . The cartridge  42  in accordance with this embodiment is made up of two identical halves  120  that may be injection molded of a plastic material such as nylon or be made of any other suitable material. Each half has a bottom wall  122 , top wall  124 , side or outside wall  125  and upwardly converging end walls  126  and  127 . The cartridge is assembled by joining the edges of the top, bottom and end walls and with the side walls generally parallel to one another. The cartridge  42  includes a pair of compartments  128  and  130  that are sometimes called front and rear compartments and/or new and used blades compartments. The two compartments are identical as they are used interchangeably depending upon the orientation of the cartridge  42  in the case  40 . As has been stated above, the cartridge is initially filled with new blades in one compartment and the other compartment is empty but receives each blade after it&#39;s outside edge is worn. In this description, the edges of the blades  44  that are extended out of the compartments are sometimes called the outside edges as they lie close to the adjacent end walls  126  and  127  of the compartments. Furthermore, when all of the new blades in front compartment  128  are used and deposited in the rear compartment  130 , the cartridge is reversed in the case so that the unused edge of each of the used blades may be utilized.  
         [0046]    The two halves  120  that make up the cartridge may be connected together edge-to-edge by flexible interengageable hook-like tabs  132  and flanges  134  formed as integral parts of the case halves. The tabs and flanges are clearly shown in FIG. 9. When the identical halves  120  are placed edge-to-edge, the barbed tabs  132  engage the flanges  134  to hold the halves  120  together. Tabs and flanges  132  and  134  are provided along the edges of the bottom and top walls  122  and  124  and the end walls  126  and  127  to hold the cartridge in its assembled form. The tabs and flanges  132  and  134  are typical of a variety of different types of fasteners that may be employed to retain the two halves of the cartridge together. As it is intended that the cartridge be disposable under ordinary circumstances, and there is no need to open it after it is initially filled with blades, the tabs and flanges or whatever other means may be employed to assemble the cartridge halves together need not be releasable. Rather, once a cartridge is filled with blades by the manufacturer, there is no need ever to reopen the cartridge.  
         [0047]    To assure proper alignment of the two halves  120  of the cartridge  42  when it is assembled, offsets  136  and recesses  138  are provided along the edge of the bottom wall  122 , and end walls  126  and  127 . The offsets and recesses in the bottom wall of the cartridge and in each of the compartments create an irregular longitudinal mating edge where the two halves  120  meet. This arrangement prevents the sharp bottom edges of the blades described below from getting caught in what otherwise would be a straight parting line in the cartridge floor. The tabs  136  and recesses  138  also serve to maintain the planar configuration of the floor formed by the edge-to-edge bottom walls  122 . The two compartments  128  and  130  are separated and defined in part by a V-shaped wall  150  that may include additional tabs  132  and flanges  134  or other structure to facilitate the connection of the two halves. One side of each V-shaped wall  150  converges upwardly with the adjacent end wall  126  or  127  so as to configure the compartments  128  and  130  to complement the shape of the blades  44 . This is shown particularly in FIG. 11.  
         [0048]    It should be noted that end wall  126  of each cartridge half  120  includes a slot  154  adjacent the side wall  125  and through which the operative blade is extended while the other end wall  127  does not have such a slot (see FIG. 10). Therefore, when the two halves  120  are assembled, the slots at each end of the cartridge are on opposite sides adjacent different side walls  125 , that is, they are not longitudinally aligned with one another but each is aligned with the slot  70  in the case when placed at the operative end of the case.  
         [0049]    A restrictor  152  is shown in FIG. 11 provided in the top wall  124  of compartment  130  for preventing certain movements of the blades. Specifically, the restrictor  152  prevents the blades in that compartment from moving into the center passageway of the cartridge that joins the two compartments or into the slot  154 . This function is described in more detail in connection with the movement of the blades  44  in the cartridge  42 .  
         [0050]    Blades  44   
         [0051]    The blades  44  (two embodiments shown in FIGS. 13 and 14) may take many different forms but in outline generally conform to the shape of conventional utility blades that are so widely used. The blades  44  may have straight cutting edges as conventional utility blades or may have “hook” style cutting edges that is also fairly well known in the utility knife industry as illustrated in FIG. 14. The blade in FIG. 13 includes a long cutting edge  170 , upwardly converging side edges  172  and an upper edge  174  while the blade  44   a  in FIG. 14 has two hooks  170   a , one at each end of its long edge, and upwardly converging side edges  172   a  and top edge  174   a . Specifically referencing the blade  44  of FIG. 13, a notch  176  is provided in the center of the upper edge  174  sized to receive the restrictor  152  formed in the upper wall  124  of the compartments  128  and  130  of the cartridge. The restrictor limits certain motions of the blade as is described more fully below. Slots  178  in the side edges  172  are engaged by the carrier so as to selectively lift the blade when moving in either direction and pushes the blades in the operative direction toward the case front  66 . Opening  180  at the approximate center of the blade body is engaged by a support in the carrier when the blade is moved in the cartridge and case between operative and inoperative or stored positions. Specifically, the support lifts the blade when moving either toward the operative or retracted positions but pushes the blade while moving the blade away from the operative position. As in conventional utility blades, the corners  182  of the cutting edge  170  are the principal portions of the blade that are utilized during conventional cutting operations. One corner  182  (the outside corner) of each blade is used as each is extended from the front compartment  128  of the cartridge  42  out the blade slot  70  in the case, while the other cutting corner  182  remains protected in the cartridge. After the one corner  182  of each blade from the front compartment is worn and each blade is moved to the rear compartment, the cartridge  42  is reversed in the case so that the unused corners  182  of the blades in the blade compartment  130  may then be utilized. The unused inside corners of the blades in the front compartment become the outside corners when the blades are moved to the rear compartment.  
         [0052]    It will be noted in FIG. 11 that the corner  186  of the compartment  130  is enlarged to provide additional protection for the corner  182  of the blades when each is contained within a compartment of the cartridge. Both corners in each compartment of the cartridge are preferably enlarged in that fashion so as to provide further protection for the blade  44  and eliminate binding of the blade corners in the light corners of the compartments.  
         [0053]    It will be appreciated that the “hook” blade of FIG. 14 will function just as the utility blade  44  of FIG. 13 within the cartridge and move in it from one compartment to the other as the outside hooks are used.  
         [0054]    Carrier  46   
         [0055]    The carrier  46  shown in FIGS. 6, 7,  12  and  15 - 20  transports the blades  44  one at a time to the various stored and operative positions in the case  40  and cartridge  42 . The actuator  48  is shown in the FIGS. 12, 15 and  16  to be attached to the carrier  48 , and the two move together as the blade  44  moves from one position to another. The carrier includes the upper panel  96  shown disposed in a horizontal plane within the channel  94  in the case (see FIGS.  5 - 7 ) and has a depending body  190  that actually engages the blades. The body  190  has an offset portion  192  that defines with panel  193  an upper channel  194  that receives an upper rail  196  (see FIGS. 6 and 7) forming part of the cartridge  42 . The body  190  of the carrier also includes a second offset portion  198  that defines a second lower channel  200  that receives a lower rail  212  in the side of the cartridge  42 . The interlocking relationship of the rails  196  and  212  with the carrier channels  194  and  200  assures that the carrier precisely engages the blades and moves each from one end of the case to the other and out the case through the slot  70  at the front end of the case during its transitions in use. An enlarged longitudinal slot  210  formed on the side wall  125  of the cartridge receives the panel  193  of the body  190  so as to provide further support and guidance for the carrier as it moves longitudinally in the case. Note that the rails  196  and  212 , channels  194  and  200 , and slot  210  are duplicated on both sides of the assembled cartridge  42 .  
         [0056]    The outside surface  220  of the central portion  202  of the carrier body  190  (the surface facing away from the cartridge) carries a flat metal spring  222  (see FIGS. 17, 19 and  20 ) supported on the surface by an anchor pin  224 . The spring  222  bears against a support  226  pivotally mounted on a hinge  228  provided on the carrier  46 . The hinge  228  includes a pivot post  229  supported by bosses  231  in turn mounted on the panel  192  and offset portion  198 . In FIGS. 19 and 20 the two positions of the support  226  are shown. In FIG. 20 the support is shown seated on the edge  349  of the opening  350  in the panel  193  with its side portion  232  disposed in the hole  180  of the blade. In FIG. 19, the support is moved away from the blade  44  (the side portion is withdrawn from the hole  180 ) against the bias of the spring  222 . As described more fully below, the squared edge  276  of the support engages the side of the hole  180  in the blade to move the blade rearwardly in the case to either of its retracted positions. As shown in FIGS. 19 and 20 the side portion  232  of the support  226  away from the squared edge  276  is rounded so that the support can be deflected against the bias of the spring  222  and ride over the blade surface until it snapes into the hole  180  as the support moves forwardly from the rear to the front compartment as it is picking up the next blade.  
         [0057]    In FIGS. 6 and 7, the configuration of the cartridge is shown to be the same on both sides so that when the cartridge is reversed in the case with the other outside wall  125  facing the carrier, the carrier can move into the cartridge and engage the blades one at a time and move them through the cartridge and case between the rear compartment and the very front of the case with the blade extending out of the case  40  through slot  70  in its operative position.  
         [0058]    Referring to FIGS. 16 and 18, the panel  193  carries a lifter and pusher combination  270  that engages the end edge  172  and slot  178  of the blade  44 . The surface  272  of the pusher/lifter is positioned at the rear edge of the blade to push the blade in a forward direction (to the right as viewed in FIG. 16) as the carrier moves in that direction. Similarly, the flange portion  274  of the pusher/lifter combination also is positioned to push the blade in that direction as it bears against the inner end of slot  178  in the blade, and it also lifts the blade by engaging the top of the slot  178 . The support  226  urged into position by the spring  222  also serves to lift the blade when positioned in the blade central hole  180  and the edge  276  of the support bears against the rear edge of the hole so as to push the blade rearwardly with respect to the case and cartridge as the carrier moves in that direction.  
         [0059]    Actuator  48   
         [0060]    The actuator  48  is shown in FIGS. 15, 16, and  21 - 23  mounted on the panel  96  of the carrier. In FIGS. 15 and 16 the actuator lock is shown in its unlocked and locked condition, respectively. The actuator includes a rocker  250  supported by an axle  252  mounted in cavities  254  on the opposed walls  255  of arms  256  that are part of the frame of the actuator. The rocker  250  includes a stop  258  that when moved to the lower position shown in FIG. 22 is disposed between the ends  262  of spring arms  260  and prevents the arms from flexing toward one another. The ends  262  of the arms register with the racks  264  formed along the sides of the slot  90  in the case as shown in FIG. 23. When the rocker is moved to the position shown in FIG. 21 so that the stop  258  is out from between the ends  262  of the spring arms  260 , the ends  262  are free to move toward one another and essentially run over the teeth of the ratchet sections  264  in the slot  90  and allow the actuator  48  to move along the top of the case and carry the carrier  46  with it. However, when the rocker  250  is in the position of FIG. 22, the actuator  48  cannot move, and the carrier is also locked.  
         [0061]    In FIG. 23 the ratchet sections  264  are shown to have several locking stations  266 ,  268  and  270 . In addition, a fourth locking station  272  is established by the barbs  274  spaced from the rear end  275  of slot  90 . When the ends  262  of the springs  260  are disposed in any of the stations  266 ,  268 ,  270 , or  272  and the stop  258  of the rocker is lowered to a position between the ends  262  as shown in FIG. 22, the actuator is locked in that position and cannot move, and the carrier and blade are locked as well. Thus, in order to move the carrier  46  so as to move a blade, the actuator rocker must be placed in the position shown in FIG. 21.  
         [0062]    Preferably the rocker is biased to the locking position of FIG. 22 and for that purpose, the rocker carries an extension  273  that bears against the spring arm component  260  and acts as a spring to urge the rocker to pivot counterclockwise on its axle  252  as viewed in FIGS. 21 and 22 and move the stop between the spring arms  262 .  
         [0063]    Movement of Carrier in Operation of Utility Knife  
         [0064]    In FIGS.  24 - 28  the various positions of the carrier are shown that allow the cartridge to be replaced and that sequentially move new blades from the front compartment to the operative position, retracted position and finally to the rear compartment when each worn blade requires replacement. In FIG. 24 the cartridge  42  is shown with all of the blades  44  in the rear or used blade compartment R—no blades are in the front new blade compartment F. In this situation, the cartridge  42  must either be replaced as required when both corners  182  of each blade  44  have been used, or reversed with the compartment R at the front of the case when just one corner of each blade is worn. To reverse or replace the cartridge, the carrier  46  must be moved to the front of the case  40  fully detached from and out of the cartridge  42  as shown in FIG. 24. If the cartridge  42  of FIG. 5A is reversed, chamber R would be disposed at the front end of the case and chamber F would be disposed at the rear. As a result, all of the blades  44  in compartment R would be disposed at the front end of the case  40  with the unused ends  182 R of the blades at the front end of the case, and the compartment F at the rear would again be empty. The same, of course, would be true if the cartridge  42  were replaced with a new one.  
         [0065]    In FIG. 25 the carrier  46  is shown in position to engage the first blade  44  in the front compartment by means of the support  226  and the pusher/lifter  270  of the carrier as described above in connection with FIGS.  16 - 20 . The pusher/lifter  270  engages the rear slot  178  in the rear side edge  172  of the blade. When the blade is engaged in that fashion, the carrier may be moved towards the front end  66  of the case and that motion carries the blade with it toward the slot  70  in the case  40 . In FIG. 26 the blade  44  is shown partially removed from the front compartment of the cartridge, but is contained fully within the case, and in FIG. 27 the blade is shown in its operative position extending almost entirely out of the cartridge and its leading cutting edge  182 L is fully exposed beyond the slot  70  in the case. The carrier as it moves toward the back end  68  of the case pushes the blade with it by virtue of the engagement of the squared edge  276  of the support  226  with the rear edge of the hole  180  in the blade. It should be noted that to move the blade from one position to another, the rocker  250  of the actuator  48  must be in the unlocked position. However, when the blade is not to move such as when it is in use, the rocker  250  is placed under the influence of spring  273  in the locking position of FIG. 22 so as to prevent the carrier  46  from moving.  
         [0066]    If the forward cutting edge  182 L of the blade  44  is not worn and the knife is not to be used for a period of time, the carrier  46  may be returned to the position shown in FIG. 26 and the actuator should be locked so that the blade  44  and particularly its leading edge  182 L is fully contained within the case so as not to be exposed and cause accidental injury. When the utility knife is to be used again, the carrier may again be moved in a forward direction by unlocking the actuator, so as to expose the working end  182 L of the blade as shown in FIG. 27. When the utility blade forward cutting edge  182 L is no longer suitable for performing its intended cutting function, the blade is moved to the rear compartment by sliding the actuator  48  and carrier  46  to the position shown in FIG. 28. In that manner, the blade is deposited in the rear used blade compartment, and the carrier may then be moved forward to the position shown in FIG. 25 to pick up the next blade in order in the front or new blade compartment. The carrier may be locked in any one of the positions illustrated in FIGS.  24 - 28  by the ratchet-like mechanism provided in the actuator and slot  90  in the top of the case as shown in FIG. 23, all as described in detail below.  
         [0067]    Interaction of Cartridge  42  Blade  44  and Carrier  46 A  
         [0068]    The interaction of the cartridge  42 , carrier  46 , and blade  44  as illustrated in FIGS.  29 - 41  enables the utility knife to function in the manner shown in FIGS. 24 through 28. In FIG. 6 the support  226  is shown with its outer portion  232  disposed in the hole  180  of the blade  44 , and the blade extends out of the opening  70  in the front end  66  of the case. The carrier moves the blade to that position by virtue of the connection between the pusher/lifter  270  on the carrier and the slot  178  in the blade shown in FIG. 16. The rear end of the blade is shown disposed in the slot  154  in the cartridge, which is wide enough to allow only one blade at a time to pass through it. Thus, only one blade at a time can be moved from the front compartment of the cartridge to the operative position shown in FIG. 29. The rear corner  182  of the blade remains in the front compartment of the cartridge to prevent the next blade in the stack of blades in the front compartment from moving into a position that would block the blade path (slot  154 ) when the carrier retracts the operative blade into the cartridge either in the position suggested in FIG. 26 or rearwardly thereof anywhere back to the position shown in FIG. 28. The blade  44  carried by the carrier is held in position by the blade guides  314  shown in FIGS. 3, 4,  25  and  27 . The guides which form part of the case hold the active blade against the carrier when the carrier is outside the cartridge.  
         [0069]    In FIGS. 30 and 31 the carrier is shown moving the blade  44  through center passageway  316  that connects the front and rear compartments F and R in the cartridge. The edge  276  of the support  226  is shown bearing against the rear edge  318  of the hole  180  so as to move the blade in the rearward direction. The center passageway  316  is also wide enough to receive only one blade at a time. The center passageway  316  is shown in FIG. 26 between the side wall  125  of the cartridge  42  and a wall  150   a  that joins the ends of the cartridge V-shaped wall  150 .  
         [0070]    The used blades in the rear compartment are held out of the way of incoming blade  44  by means of springs  320 . The springs  320  may be formed as an integral part of the cartridge. In FIG. 31, the blade  44  engaged by the carrier  46  is shown entering the rear compartment of the cartridge. As the blade enters the compartment it temporarily displaces the first spring  320  out of the way so as to enable the blade on the carrier to enter. The rearmost spring  320  assists in displacing the other blades in the rear compartment.  
         [0071]    In FIG. 32 the blade  44  is shown carried by the carrier further back in the rear compartment, pushed along by the edge  276  of support  226  bearing against the rear edge  318  of the blade hole  180 . When the carrier and blade  44  are completely through the passage  316  and therefore free of the frictional binding effect of the center blade passageway  316  on the end of the blade, the springs  320  eject the blade  44  off the carrier and particularly off the support  226 . The springs  320  are returned to their biased position to hold the used blades in the rear compartment out of the path of the next blade to be deposited in that compartment as in FIG. 30. The carrier  46  is then free of the blade deposited in the rear compartment and can move forward toward the new blade compartment to engage the next blade in the stack. If there are no more blades in the new compartment, the carrier may be moved to the forwardmost position as shown in FIG. 24 so that the cartridge may be replaced or reversed.  
         [0072]    In FIG. 33 the carrier  46  is shown moving in the direction of the new blade compartment to engage the next blade in order. The hinge mounted support  226  is displaced against the bias of spring  222  as it encounters the next blade  44  in the new blade compartment F. The support  226  remains displaced as shown in FIG. 10 until it is aligned with the hole  180  in the next blade and is forced into the hole by the bias of the spring  222 . At the same time, the pusher/lifter  270  at the rear end of the carrier  46  engages the slot  178  in the blade (see FIG. 16) so that the carrier may move the blade out of the front compartment to the operative position when it is to be used.  
         [0073]    When the blade  44  is to be withdrawn fully into the cartridge  42 , no interference can be encountered from the other blades in the front compartment because the rear corner  182 R has not been withdrawn from it (see FIG. 27) and therefore it maintains the displacement of those blades in the compartment.  
         [0074]    If the carrier is positioned as shown in FIG. 5A and does not carry a blade, (the cartridge has either been reversed or replaced), the wedge  334  on the rear of the carrier displaces the blades in the front compartment F to allow the carrier to enter and engage the first blade in the stack. This action is shown in FIG. 34. The wedge  334  is also shown in FIGS. 16, 19 and  20 .  
         [0075]    A pressure spring  340  bears against the rear of the stack of blades in each compartment (see FIGS.  30 - 34 ) and continuously yieldably pushes both stacks toward the carrier  46  to insure proper engagement. The spring is mounted on a post  342  on the rear shell  62  of case  40  and retained in place by lock washer  344 .  
         [0076]    In FIGS. 35 and 36, an alternative construction is shown to displace the blades in the rear compartment out of the path of the incoming used blade and to free the incoming blade from the carrier  46  and the edge  276  of support  226 . For this purpose, a ramp  370  and support surface  372  are provided in the side wall  125  and replace the springs  320  shown in FIGS.  30 - 32 . In FIG. 35 the rear ends of the carrier  46  and blade  44  are shown approaching ramp  370 , and the blades already in the compartment are displaced away from the path of the blade by the surface  372 . Continued rearward travel of the carrier and its blade causes the blade to assume the orientation of the surface  372  and allows the carrier to move freely in the opposite or forward direction. There is nothing on the forward curved surface of the support  226  to engage the blade and to interfere with the forward movement and the support  226  will not drag the blade with it.  
         [0077]    When the cartridge  42  with the blades  44  in the rear compartment is out of the case, the spring  340  which remains in the case is not available to urge the blades into the position shown in FIGS. 35 and 36, and the front most blade in the stack may lodge in the center passageway  316 . To prevent that from occurring, a restrictor  374  formed as an integral part of the top wall  125  of the cartridge (see FIG. 37) engages the notch  176  in the top edge of the blade. The restrictor  374  acts as a flexible finger to allow a blade to enter the compartment through the center passageway  316  but not to leave the compartment through it.  
         [0078]    Another embodiment of the invention is shown in FIGS.  38 - 41 . In accordance therewith a gate system is employed to further insure that an additional blade is not drawn into the center passageway  316  between walls  150   a  and  125  when a blade is being moved through the front compartment toward that passageway on the way to the used blade compartment. The gate system includes a gate  400  formed as an integral part of each cartridge half  120 . The gate is carried on a live hinge  402  that positions the free end  404  of the gate in the center passageway  316  (see FIG. 39) but allows it to move inward out of the passageway at the urging of the wedge  334  on the rear end of the carrier (see FIG. 40). A front elevation of the gate  400  and hinge  402  is shown in FIG. 31. In FIG. 34 the gate  400  is fully open allowing the blade  44  and carrier  46  to pass through the passageway  316  on its way to the rear compartment.  
         [0079]    In the foregoing description the invention has been directed to a utility knife using traditional sized blades customarily approximately 0.025 inches in thickness. In such an application of this invention the passageways  154  and  316  may be approximately 0.037 inches, less than the thickness of two blades (0.050 inches) and nevertheless providing enough clearance to allow one blade at a time to comfortably pass through them. It should be appreciated that the invention has wider application than simply with utility knives and the invention is not to be limited to that specific use.  
         [0080]    In the foregoing description many components have been described as being integrally formed together with other components in the knife. For example, certain springs, ramps, gates, etc. have been described as being integral with the main parts  120  of the cartridge  46 . However, it is important to recognize that these and other components may be fabricated as separate parts and subsequently be assembled together to form the cartridge. The same applies to the various parts of the case  40 , carrier  46  and actuator  48 . While parts may have been characterized in the description as being integral with one another, the present invention is not confined to that specific form as it is within the scope of the invention to separately fabricate the parts and subsequently assemble them together.  
         [0081]    Upon viewing this or other descriptions of the invention and/or a reduction to practice thereof, those skilled in the art will recognize that many variations may be made of the embodiments of the invention viewed by them. Therefore, it is not intended that the breadth of the invention be limited to the specific embodiments illustrated and described. Rather, the breadth of the invention is to be determined by the appended claims and their equivalents.