Patent Publication Number: US-2017348863-A1

Title: Knife apparatus with interchangeable blades

Description:
TECHNICAL FIELD 
     The present disclosure generally relates to a knife apparatus having interchangeable blades and specifically relates to a knife apparatus with a secure locking letch mechanism for retaining interchangeable blades. 
     BACKGROUND 
     Knives are an indispensable tool for workers and sportsmen across many fields and disciplines. A wide array of different knives are used for different purposes, and their differently sized and shaped blades are usually their most defining features. For outdoor applications, different blades are commonly used for cutting rope and cord, skinning, carving wood, dressing a downed animal, cutting food, and various other activities. Each blade may be especially suited for each task to maximize efficiency and preserve blade life. 
     However, the advantages of the specialization of each blade are counterbalanced by the disadvantages of needing different knives to perform different tasks. Having to carry and keep track of multiple knives can be space- and time-consuming. For outdoorsmen, the weight of carrying many knives in a pack can also be burdensome. 
     Therefore, knives have been developed that have interchangeable blades. With these kinds of knives, the user may use a particular blade for one specialized function and then remove the blade from a blade holder on the knife and exchange it for a blade or tool used for another function. These knives are also popular when used with utility razor blades that are used and then discarded when the blade dulls. 
     Although interchangeable-blade knives are easier to transport than multiple knives for different tasks, they also tend to be less reliable than single-purpose knives. The interchangeable blade retaining mechanisms can be loose in holding the blades, particularly when the blade is subjected to extreme force or unusual loading conditions. Blades that can potentially disconnect from the blade holders interfere with blade usage and can promote breakage of the blades and their holding mechanisms. Accordingly, there is a need for improvements to interchangeable-blade knives. 
     SUMMARY 
     One aspect of the present disclosure relates to a knife having an interchangeable blade. The knife may comprise a handle, a latch assembly connected to the handle, and a blade. The latch assembly may comprise a slot and a rocker positioned in the slot, with the rocker being rotatable within the slot between a first rocker position and a second rocker position and with the second rocker position being rotated relative to the first rocker position. The latch assembly may also comprise a rocker locking member extending across the slot, with the rocker locking member being movable between a locked position preventing rotation of the rocker between the first and second rocker positions and an unlocked position permitting rotation of the rocker between the first and second rocker positions. The blade may comprise a proximal end positioned in the slot and a back edge having a notch, with the rocker being positioned in the notch when the rocker is in the first rocker position, the blade being prevented from removal from the slot when the rocker is in the first rocker position, and the blade being removable from the slot when the rocker is in the second rocker position. 
     In some embodiments the latch assembly and blade are foldable into the handle. The rocker locking member may be a button and may be biased to the first rocker position by a compliant member. The rocker locking member may also comprise a first diameter portion and a second diameter portion, with the first diameter portion being aligned with the rocker in the slot when the rocker locking member is in the locked position and with the second diameter portion being aligned with the rocker in the slot when the rocker locking member is in the unlocked position. In that case, the first diameter portion may have a greater diameter than the second diameter portion. The rocker locking member may also be positioned on a thumbstud. 
     The rocker may comprise a pivot point in the slot that is positioned distal to the rocker locking member. The blade may further comprise a longitudinally-extending notch, and the latch assembly may further comprise a retaining member in the slot with the retaining member being positioned in the longitudinally-extending notch of the blade. The blade may further comprise a hook portion and the latch assembly may comprise a retention plate, with the hook extending around at least two sides of the retention plate. In some arrangements, the proximal end of the blade has a trapezoidal shape and the latch assembly has a trapezoidal hollow, with the trapezoidal shape being fitted into the trapezoidal hollow. 
     Another aspect of the disclosure relates to a knife having a removable blade and dual-stage locking mechanism. The knife may comprise a handle, a latch assembly, and a blade. The latch assembly may comprise a slot, a first latch, and a second latch, with the first latch being translatable relative to the slot and with the second latch being rotatable relative to the slot. A blade may be retained in the slot, with the blade being removable from the slot upon sequential actuation the first latch followed by the second latch. 
     In some configurations, the first latch may lock the position of the second latch. The second latch may also retain the blade in the slot. The first latch may be a biased pin extending through the slot. The second latch may be a rocker at least partially positioned in a notch in the blade. 
     Yet another aspect of the disclosure relates to a method of securing an interchangeable blade to a knife handle, wherein the method may comprise providing a knife, with the knife having a handle, a latch assembly, and a blade. The latch assembly may be connected to the handle, and the latch assembly may comprise a slot in which the blade is positioned. The latch assembly may also comprise a rocker and a rocker locking member, with the rocker retaining the blade in the slot. The method may further comprise actuating the rocker locking member to unlock the rocker relative to the blade, rocking the rocker away from the blade while actuating the rocker locking member, and removing the blade from the slot. 
     In some embodiments, actuating the rocker locking member may comprise pushing the rocker locking member laterally and at least partially through the slot. The method may also include inserting a second blade into the slot while rocking the rocker, rotating the rocker toward the second blade while actuating the rocker locking member, and deactuating the rocker locking member to lock the rocker relative to the second blade. 
     Still another aspect of the disclosure relates to an interchangeable blade for a knife, with the interchangeable blade comprising a lateral face, a belly edge, and a spine edge. The spine edge may be positioned opposite the belly edge. A first recess may be recessed into the spine edge in a first direction and a second recess may be recessed into the spine edge in a second direction, with the first direction being positioned non-parallel to the second direction. 
     In some arrangements, the first direction may extend toward the belly edge. The blade may also further comprise a heel portion comprising a rear edge and the belly edge may comprise a heel edge at the heel portion. The heel edge may extend at an acute angle relative to the rear edge. The spine edge may comprise a protrusion extending at least partially around the second recess. In some embodiments, the second direction may be parallel to a major longitudinal axis of the interchangeable blade and the first direction may be perpendicular to the second direction. The belly edge may comprise a sharpened gut hook blade. 
     The above summary of the present invention is not intended to describe each embodiment or every implementation of the present invention. The Figures and the detailed description that follow more particularly exemplify one or more preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings and figures illustrate a number of exemplary embodiments and are part of the specification. Together with the present description, these drawings demonstrate and explain various principles of this disclosure. A further understanding of the nature and advantages of the present invention may be realized by reference to the following drawings. In the appended figures, similar components or features may have the same reference label. 
         FIG. 1A  is a perspective view of a knife according to an embodiment of the present disclosure. 
         FIG. 1B  is a perspective view of the knife of  FIG. 1A  with the blade removed. 
         FIG. 2  is a perspective view of the knife of  FIG. 1A  in a folded configuration. 
         FIG. 3  is a side view of an interchangeable blade according to an embodiment of the present disclosure. 
         FIG. 4A  is a section view of a latch assembly according to an embodiment of the present disclosure. 
         FIG. 4B  is a section view of the latch assembly of  FIG. 4A  with a blade inserted. 
         FIG. 4C  is a section view of the latch assembly of  FIG. 4B  with a rocker rotated. 
         FIG. 5A  is a section view of the latch assembly of  FIG. 4A  taken through section lines  5 A- 5 A shown in  FIG. 4A . 
         FIG. 5B  is a section view of the latch assembly of  FIG. 4B  taken through section lines  5 B- 5 B shown in  FIG. 4B . 
         FIG. 5C  is a section view of the latch assembly of  FIG. 4C  taken through section lines  5 C- 5 C shown in  FIG. 4C . 
         FIGS. 6A-6C  show side views of interchangeable tools according to embodiments of the present disclosure. 
         FIG. 7  shows a section view of a latch assembly with a blade inserted. 
     
    
    
     While the embodiments described herein are susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, the exemplary embodiments described herein are not intended to be limited to the particular forms disclosed. Rather, the instant disclosure covers all modifications, equivalents, and alternatives falling within the scope of the appended claims. 
     DETAILED DESCRIPTION 
     The present disclosure generally relates to a knife apparatus having a secured interchangeable blade or other interchangeable tool. The knife may comprise a handle and a latch assembly. A blade may be positioned in a slot in the latch assembly and may be held in place in the slot by a rocker that is also positioned in the slot. The blade may also be held in the slot by a pin that is positioned within a hook-shaped or curled portion of the blade. The rocker may comprise a lever that is retained in place by a spring and a button that is operable as a thumbstud. When the blade is in use, the button may prevent the rocker from being inadvertently pivoted, and the blade therefore remains locked securely in place by a portion of the rocker. When the blade needs to be removed or exchanged, the button may be depressed and the rocker may be able to pivot into a space where a portion of the button was previously blocking the movement of the rocker. Accordingly, while the button is depressed, the rocker may be pivoted out of the way of the blade, and the blade may be easily removed and exchanged. 
     The rocker (i.e., lock back lever) may have a pushing side and a blade engagement side separated by a pivot point. The pushing side may be at the proximal end of the rocker and may be biased in a generally upward direction by a torsion spring. In its resting position, the torsion spring may be extended and the pushing side of the lever may be in a raised position generally aligned with the back edge of the blade holder (i.e., latch assembly). In this position, the blade engagement side of the lever may be held in a downward position at its distal end where it is configured to engage with an interchangeable blade. To actuate the lever, a user may press on the pushing side of the rocker. Since the lever is pivotally connected to the blade holder, depressing the pushing side may cause the blade engagement side to move away from a notch in the blade. However, the presence of the secondary lock button or pin prevents a user from being able to depress the pushing side of the rocker unless the lock button is simultaneously pressed. The secondary lock button may also be spring loaded. In its resting position, a thicker section of the lock button lies under the pushing side of the lever and prevents the lever from being depressed. In other words, the thicker section of the lock button serves as an obstruction to rotation of the lever. However, the secondary lock button may also include a narrow section, and when the lock button is depressed, the narrow section may align with the lever. Accordingly, when the narrow section is so aligned, the pushing side of the lever may rotate into a space created within the blade holder due to the thicker section of the lock button moving out of the way of the lever. 
     In operation, to change blades out, a user may depress the secondary lock button and then depress the pushing side of the lever. The extra space in the blade holder that is provided by the narrow section on the lock button may then allow the pushing side of the lever to rotate and drop, thereby raising the blade engagement side of the lever and releasing the blade. Once the blade engagement side of the lever is raised, a user can easily extract the blade from the blade holder. The inclusion of the secondary lock button may therefore prevent the inadvertent release of the blade by pressing the lever alone. 
     The reverse actions may be used to insert a new blade into the blade holder. Namely, a user may depress the pushing side of the lock lever while simultaneously pushing the secondary lock button. This aligns the narrow section of the secondary lock button with the lock back lever so that the pushing side of the lever has room to pivot and raise the blade engagement side of the lever. A user can then insert a new blade into the blade holder and release the lock back lever (which, because of the torsion spring, will return to its resting position) and the secondary lock button (which also, because it is spring loaded, will return to its resting position). The blade is thereby secured in place. 
     These features may strengthen the retaining mechanism of the knife apparatuses of the present disclosure by ensuring that the interchangeable blade or other tool contacts four or more differently-facing surfaces of the blade. Thus, the blade may be subjected to unusual loading patterns and forces applied from many different directions without being dislodged from the retaining mechanism. Additionally, the latch assembly may be implemented in folding or fixed-blade knives and with a wide variety of different blade and tool sizes and types, including, for example, utility razor blades and gut hooks. 
     As used herein, a “proximal” portion of a blade or tool connected to a knife is the part of the blade or tool that is closest to the handle, and a “distal” portion of a blade or tool is the part of the blade that is farthest from the handle. Thus, a proximal direction is a direction parallel to a longitudinal axis of the blade and/or handle and extends from a middle portion of the blade toward the handle. A distal direction is a direction parallel to the longitudinal axis of the blade and/or handle and extends away from a middle portion of the blade away from the handle. 
     The present description provides examples, and is not limiting of the scope, applicability, or configuration set forth in the claims. Thus, it will be understood that changes may be made in the function and arrangement of elements discussed without departing from the spirit and scope of the disclosure, and various embodiments may omit, substitute, or add other procedures or components as appropriate. For instance, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, features described with respect to certain embodiments may be combined in other embodiments. 
     Turning now to the figures in detail,  FIGS. 1A-2  show a knife  100  according to an embodiment of the present disclosure. The knife  100  may comprise a handle  102 , a blade  104 , and a latch assembly  106 .  FIG. 1A  shows the knife  100  unfolded,  FIG. 1B  shows the knife  100  unfolded with the blade  104  removed, and  FIG. 2  shows the knife  100  folded with a blade  104  attached. 
     The handle  102  may comprise a pommel end  108  and a pivot end  110 . The pivot end  110  may comprise a pivot pin  112  that extends through the pivot end  110  and through the latch assembly  106 . Using the pivot pin  112 , the latch assembly  106  may pivot between the unfolded positions of  FIGS. 1A-1B  and the folded position of  FIG. 2 . The latch assembly  106  may comprise a first side plate  114  and a second side plate  116 . A slot  118  may be positioned between the first and second side plates  114 ,  116 . See  FIG. 1B . The blade  104  may be positioned and removably retained in the slot  118  between the first and second side plates  114 ,  116 . A thumbstud  120  may be provided to facilitate folding and unfolding the blade  104  and latch assembly  106 . In some embodiments, a thumbstud  120  may be omitted, wherein the lock pin  322  may be shortened to have its button portion  400  closer to the first side plate  114 . See also  FIGS. 5A-5C . 
       FIG. 3  shows a blade  104  separated from the latch assembly  106  and handle  102 . The blade  104  shown in  FIG. 3  is a single-edged blade, but other types of blades and tools may be used. See also  FIGS. 6A-6C . Thus, the blade  104  shown is intended as an example illustrating one type of device that is possible to connect to the latch assembly  106 . The blade  104  may comprise a distal point  200 , a tip  202 , a cheek  204 , a sharpened edge  206  (i.e., belly edge), a blade spine  208  (i.e., the blade back at the tip  202 ), a heel  210 , a dull edge  212 , a rear edge  214 , and a latching portion  216 . The cheek  204  of the blade  104  is the side face of the blade  104 . It may comprise a flat, broad surface in comparison to the back or spine of the blade  104 . In some embodiments, the cheek  204  may comprise a grind or beveled surface. The grind or beveled surface may be part of the cheek  204 . A perpendicular plane extending through the cheek  204  may divide the blade  104  in a longitudinal direction between the dull edge  212  and the blade spine  208  (or latch spine  218 ). In various embodiments, the sharpened edge  206  may not be sharpened, such as in a blade  104  that functions as a crescent wrench or can opener. The sharpened edge  206  may also comprise serrations, may be entirely straight instead of belly-shaped, or may have other irregular shapes. Thus, the sharpened edge  106  may be alternatively referred to as any edge opposite the spine  208 / 218  of the blade  104  relative to the cheek  204 , whether or not that edge is sharp and straight. 
     The latching portion  216  may comprise a latch spine  218 , a spine notch  220 , and a longitudinal notch  222 . The longitudinal notch  222  may be formed in part by the latch spine  218  and in part by a retention hook portion  224  that extends proximally from the blade spine  208  and is dorsally spaced from the latch spine  218 . The blade spine  208  may also be spaced dorsally away from the latch spine  218  (i.e., the latch spine  218  may be ventrally spaced from the blade spine  208 ). For convenient reference in describing the features of the knife  100 , a dorsal direction extends upward along the Y-direction, and a ventral direction extends downward along the Y-direction. 
     The spine notch  220  and the longitudinal notch  222  may extend into the blade  104  in different, perpendicular directions. The spine notch  220  may be recessed vertically downward into the latch spine  218  along axis B 1 , and the longitudinal notch  222  may extend into the blade along a longitudinal direction that is perpendicular to the downward direction, i.e., along axis B 2 . The longitudinal direction may be along the major axis of the blade  104  and parallel to the X-direction in  FIG. 3 . 
     The retention hook portion  224  may be positioned at a location that is at about the midpoint of the blade  104 . Thus, the heel  210  and the tip  202  may be longitudinally positioned on each side of the retention hook portion  224 . The retention hook portion  224  may beneficially be positioned at or near the center of the blade  104  along the longitudinal axis/major axis of the blade  104  so that when forces are applied to the blade  104  that pull the tip  202  of the blade downward relative to the heel  210 , the retention hook portion  224  may provide an anchor point for the blade  104  against the latch assembly  106 . Specifically, contact between the retention hook portion  224  and at least two sides of the retainer plate  306  (see, e.g., the dorsal and ventral sides of the retainer plate  306  in  FIG. 4B ) may prevent the blade  104  from being dislodged from the latch assembly  106  if the tip  202  is rotated downward relative to the heel  210  since the anchor point is closer to the tip  202  than to the heel  210 . This feature may be beneficial when a gut hook tool  500  (see  FIG. 6A ) is used since pulling on a sharpened gut hook blade  501  may apply downward stress on the tip that would be unusual for other cutting blades (e.g., blade  104  or tools  502 ,  504 ). See also  FIGS. 6A-6C . 
     The spine notch  220  may be referred to as a recess in the latch spine  218  (or spine edge) of the blade  104 . The spine notch  220  may be generally U-shaped with a curved, semicircular end surface  220 - a  and parallel side surfaces  220 - b ,  220 - c . The longitudinal notch  222  may also be referred to as a recess in the spine edge of the blade  104 , wherein the spine edge includes a back edge  219  of the retention hook portion  224  and the latch spine  218 . Alternatively, the longitudinal notch  222  may be referred to as a recess extending longitudinally into the back edge  219  of the retention hook portion  224 . 
     The longitudinal notch  222  may be generally U-shaped with a curved, semicircular end surface  222 - a  and parallel side surfaces  222 - b ,  222 - c . One of the side surfaces  222 - c  may be coincident with and/or an extension of the latch spine  218 . The side surfaces  222 - b ,  222 - c  of the longitudinal notch  222  may be parallel to the longitudinal axis of the blade  104  (e.g., parallel to the X-direction), and the side surfaces  220 - b ,  220 - c  of the spine notch  220  may be perpendicular to the longitudinal axis of the blade  104 . Thus, the direction that the spine notch  220  or longitudinal notch  222  extends into the blade  104  may be defined as the direction parallel to their respective side surfaces  220 - b ,  220 - c  or  222 - b ,  222 - c . Alternatively, the direction that the spine notch  220  or longitudinal notch  222  extends into the blade  104  may be defined as being along an axis that bisects the notch  220 ,  222 , such as, for example, axis B 1  or axis B 2  in  FIG. 3 . In yet another example embodiment, the direction that a notch extends into the blade  104  may be defined as being along an axis that extends through a centroid of the notch and its most recessed end surface. Axes B 1  and B 2  would also meet this requirement for notches  220  and  222 , respectively. 
     The end surface of a recess or notch may be defined as the portion of the recess that is most recessed relative to the immediately adjacent portions of the edge from which the side surfaces of the recess or notch extends. In the case of spine notch  220 , the end surface  220 - a  is the end surface since it is most recessed relative to each portion of the latch spine  218  that connects to the side surfaces  220 - b ,  220 - c . Likewise, the end surface  222 - a  of longitudinal notch  222  is the end surface since it is most recessed relative to the portion of the latch spine  218  and the back edge  219  that connect to side surfaces  222 - b ,  222 - c . The back edge  219  of the retention hook portion  224  may be oriented perpendicular to the spine edge  218  and perpendicular to the blade spine  208 , at least where the blade spine  208  is immediately adjacent to the back edge  219 . 
     In some embodiments, at least one of the spine notch  220  and the longitudinal notch  222  may be a square recess, wherein the end surface  220 - a  or  222 - a  has a square or rectangular shape rather than a semicircular shape. Similarly, the spine notch  220  and longitudinal notch  222  may have hexagonal, octagonal, trapezoidal, or other polygonal recessed shapes. Each of the spine notch  220  and the longitudinal notch  222  may have boundaries in three directions that are defined by the blade  104 . For example, the spine notch  220  has its boundaries defined by three surfaces: end surface  220 - a  and each side surface  220 - b ,  200 - c . In other embodiments, the spine notch  220  may have its boundaries defined by two surfaces (i.e., a V-shaped notch). In that case, the spine notch  220  would still have boundaries in three directions since the sides of the V-shape would define sidewalls in two opposing directions and the point where the two sides of the V-shape intersect would define a sidewall in another direction that is perpendicular to the two opposing directions. Similarly, the longitudinal notch  222  may be referred to as having boundaries in three directions since a pair of axes that perpendicularly intersect within the longitudinal notch  222  would separately intersect each of three surfaces  222 - a ,  222 - b ,  222 - c . The same pair of axes, if positioned in the spine notch  220 , would also intersect three surfaces  220 - a ,  220 - b ,  200 - c.    
       FIG. 4A  shows a view of the latch assembly  106  with the first side plate  114  removed to expose the internal components of the latch assembly  106 . Thus, the interior of the slot  118  is also shown. A core plate  300  may be positioned between the first and second side plates  114 ,  116 . Thus, the pivot pin  112  may extend through the first and second side plates  114 ,  116  and the core plate  300 . The first and second side plates  114 ,  116  and core plate  300  may be connected to each other, such as by a plurality of fasteners (e.g., rivets), a welding, adhesive, or other fastening method providing a secure fit of the plates to each other. 
     The slot  118  in the latch assembly  106  may be formed on lateral sides by the first and second side plates  114 ,  116  and on its rear, top, and bottom sides by the core plate  300 . Thus, the slot  118  may include a forward blade retention void  304 , as shown in  FIG. 4A . The blade  104  may be inserted into and releasably retained within the forward blade retention void  304 , as shown in  FIGS. 4B and 4C . 
     The latch assembly  106  may also comprise a retainer plate  306  positioned forward of the core plate  300  between the first and second side plates  114 ,  116 . The retainer plate  306  may also be attached to the first and second side plates  114 ,  116  in a manner similar to the connection between the core plate  300  and the first and second side plates  114 ,  116 . The retainer plate  306  may comprise a pin portion  308  that extends longitudinally within the slot  118  (i.e., it may extend along the X-direction shown in  FIGS. 4A-4C ). 
     A rocker  310  may be positioned in the slot  118  rearward of the retainer plate  306 . The rocker  310  may be alternatively referred to as a lever or pivotable member because it is pivotable around a rocker pivot pin  312 . The rocker  310  may comprise a forward end  314  and a rearward end  316  that are divided from each other by the rocker pivot pin  312 . The forward end  314  may comprise a latch hook  318  or protrusion. The rearward end  316  may contact a rocker biasing member  320  attached to the core plate  300  and may, in certain configurations, contact a lock pin  322  extending through the thumbstud  120 . 
     The lock pin  322  may be laterally movable in a perpendicular direction (i.e., parallel to axis Z in  FIGS. 5A-5C ) through the core plate  300  and first and second side plates  114 ,  116 . In other words, the lock pin  322  may be translatable through the core plate  300  and first and second side plates  114 ,  116  since it can translate relative to those plates. In a first position, the lock pin  322  may have a first diameter aligned with the rocker  310  that is a first size, as shown by lock pin portion  322 - a . See  FIGS. 4A and 5A . In a second position, the lock pin  322  may have a second diameter aligned with the rocker  310  that is a second, smaller size, as shown by lock pin portion  322 - b . See  FIGS. 4B and 5B ; see also  FIGS. 5A-5C  and their related descriptions below. 
     At a rest position, the rocker  310  may be positioned as shown in  FIGS. 4A and 4B . The major longitudinal axis of the rocker  310  extending between the forward and rearward ends  314 ,  316  may be substantially parallel to the longitudinal axis of the latch assembly  106  (i.e., parallel to axis X). The rocker  310  may be biased into the rest position by the rocker biasing member  320  contacting the underside of the rearward end  316  of the rocker  310 . Thus, the rocker biasing member  320  may apply a vertically-upward-oriented force (i.e., parallel to axis Y) to the rearward end  316  of the rocker  310 . As a result, the rocker  310  may be biased to rotate counter-clockwise around the rocker pivot pin  312 , thereby driving the forward end  314  of the rocker  310  downward toward the blade  104 . The latch hook  318  is therefore rotated to a rest position oriented substantially parallel to the Y-direction and perpendicular to the pin portion  308  of the retainer plate  306  when in the rest position. 
     As shown in  FIG. 4B , the blade  104  may be positioned in the blade retention void  304  in the slot  118  when the rocker  310  is in the rest position. The blade  104  may be securely held in the slot  118  due to multiple points of interfering surface contact between the latch assembly  106  and the blade  104 . With reference to  FIGS. 3, 4A, and 4B , the pin portion  308  of the retainer plate  306  may be positioned within the longitudinal notch  222  of the blade  104 . Downwardly-directed movement of the blade  104  relative to the slot  118  (i.e., downward movement along the Y-direction in  FIG. 4B ) may be prevented by contact between the retention hook portion  224  and the upper side of the retainer plate  306  and/or contact between the dull edge  212  of the blade  104  and a ventral support surface  326  on the core plate  300 . Upwardly-directed movement of the blade  104  relative to the slot  118  may be prevented by contact between the latch spine  218  and the retainer plate  306 , contact between the latch spine  218  and a latch spine support surface  328  on the core plate  300  (see  FIG. 4A ), and/or contact between the rear edge  214  and a rear edge support surface  330  on the core plate  300  (see  FIG. 4A ). Inwardly- or proximally-directed movement of the blade  104  relative to the slot  118  (i.e., to the right along the X-direction in  FIG. 4B ) may be prevented by contact between the rear edge  214  and the rear edge support surface  330 , contact between the longitudinal notch  222  and retention hook portion  224 , and/or contact between spine notch  220  and the latch hook  318 . Outwardly- or distally-directed movement of the blade  104  relative to the slot  118  (i.e., to the right along the X-direction) may be prevented by contact between the spine notch  220  and the latch hook  318 . Accordingly, the blade  104  may be secured in the slot  118  in four directions along the X-Y plane (i.e., a plane between the cheeks  204  of the blade  104 ). The blade  104  may also be held in place in the lateral directions by contact with the inner surfaces of the first and second side plates  114 ,  116 . This all-around contact between the blade  104  and the latch assembly  106  may help prevent the blade from dislodging while in use. 
     The dull edge  212 , rear edge  214 , and rear portion of the latch spine  218  may collectively be part of the heel  210  of the blade  104  and may collectively form a trapezoidal shape, wherein the dull edge  212  and portions of the sharpened edge  206  may form one side of the trapezoidal shape, and those edges  206 ,  212  may be parallel to the latch spine  218 , which forms another side of the trapezoidal shape. The rear edge  214  forms a non-parallel side of the trapezoidal shape since it extends along angle A relative to the dull edge  212  (see  FIG. 3 ). A corresponding trapezoidal-shaped hollow is formed in the slot  118  by the core plate  300 . As shown in  FIG. 4A , the ventral support surface  326 , latch spine support surface  328 , and rear edge support surface  330  form a trapezoidal-shaped hollow. The rear edge support surface  330  may extend from the ventral support surface  326  at angle A as well. The trapezoidal shape of the heel  210  of the blade  104  may have a shape closely fitting into the correspondingly-sized trapezoidal-shaped hollow of the core plate  300 . For example, the heel  210  may contact the ventral support surface  326 , latch spine support surface  328 , and rear edge support surface  330  simultaneously. 
     The blade  104  may also be secured against rotating out of the slot  118  by the various points of contact with the latch assembly  106  described above. For example, a counter-clockwise moment applied to the blade  104  (e.g., by a force applied downward at the tip  202  of the blade  104 ) may be prevented from rotating the blade  104  out of the slot  118  due to the blade  104  having at least two coordinating contact points with the latch assembly  106 . In this example, the contact points may be the contact between the retention hook portion  224  and the retainer plate  306  and the contact between the rear edge  214  and the rear edge support surface  330  of the core plate  300 . These coordinating contact points may apply a resultant moment to the blade  104  that prevents rotational movement relative to the latch assembly  106 , thereby holding the blade  104  in place while it is in use. Similarly, a clockwise moment applied to the blade  104  may be prevented from rotating the blade  104  relative to the slot  118  due to coordinating contact points between the blade  104  and latch assembly  106 . For example, a first contact point may be between the dull edge  212  of the blade  104  and the ventral support surface  326 , and a second contact point may be between the latch spine  218  and the retainer plate  306  or the latch spine support surface  328 . 
     The blade  104  may be released from the latch assembly  106  when desired. Pressure may be applied to the spine of the rocker  310  at a detent  324  in the latch assembly  106  (see  FIGS. 1A-2 ), and the force applied to the rocker  310  may overcome the biasing force applied by the rocker biasing member  320  to cause the rocker  310  to rotate, as shown in  FIG. 4C . When the rocker  310  is rotated away from the blade  104 , the latch hook  318  may be rotated away from the spine notch  220 . Accordingly, the latch hook  318  may be moved clear of the blade  104 , and the blade  104  may therefore no longer have any interfering contact with that latch assembly  106  that would prevent the blade  104  from being drawn longitudinally and distally (i.e., along the X-direction) out of the slot  118 . After removal of the blade  104 , the force on the rocker  310  at the detent  324  may be removed, and the rocker  310  may be biased back into the position shown in  FIG. 4A . 
     In order to help avoid inadvertent or unintentional removal of the blade  104  from the latch assembly  106 , the front end  314  of the rocker  310  may be prevented from rotating away from the blade  104  under normal use of the knife  100 , even if a force is applied to the rocker  310  at the detent  324  during use.  FIGS. 5A-5C  illustrate how the lock pin  322  (i.e., rocker locking member) may be used to control movement of the rocker  310 .  FIGS. 5A-5C  illustrate section views through the lock pin  322 , thumbstud  120 , and detent  324  of the latch assembly  106 . 
     The lock pin  322  may extend through the thumbstud  120  and the first and second side plates  114 ,  116 . The lock pin  322  may comprise a button portion  400  that extends out of the thumbstud  120 . The lock pin  322  may also comprise a shaft  402  with a threaded portion  404  and a nut  406  on the threaded portion  404 . The lock pin  322  may therefore comprise a lock pin portion  322 - a  having a first diameter (i.e., the diameter of nut  406 ) and a lock pin portion  322 - b  having a second diameter (i.e., the diameter of shaft  402 ). The first diameter may be larger than the second diameter and may be located on an external end of the lock pin  322  (i.e., the end with threaded portion  404 ) relative to the second diameter. In some embodiments, the lock pin  322  may comprise a single integral piece, wherein the shaft  402  and nut  406  are formed as a single monolithic piece or are welded or adhered to each other. 
     The shaft  402  and nut  406  may be biased to a rest position shown in  FIG. 5A  by a pin biasing member  408  within the thumbstud  120 . The pin biasing member  408  may be a coil spring that contacts an inner surface of the button portion  400  of the lock pin  322  and an inner surface of the thumbstud  120 . In the rest position, the nut  406  is at least partially positioned in a rocker slot  332  between the first and second side plates  114 ,  116 , and the rocker  310  is positioned adjacent to and above the nut  406  in the rocker slot  332 . The slot  118  and rocker slot  332  may collectively be part of an overall slot between the first and second side plates  114 ,  116  in which the core plate  300  and retainer plate  306  are also positioned. 
     With the lock pin  322  in the rest position, when the rocker  310  is pressed downward at the detent  324 , the rocker  310  rotates into contact with the outer surface of the nut  406  and is therefore prevented from rotating very far (if at all) within the rocker slot  332 . The nut  406  interferes with the rotation, and the rocker  310  is therefore unable to rotate sufficiently to move from the position shown in  FIG. 4B  to the position shown in  FIG. 4C  or from the position shown in  FIG. 5A  to the position shown in  FIG. 5C . As a result, the latch hook  318  may be prevented from moving out of the spine notch  220  of the blade  104 , so the blade remains secured by the rocker  310 . 
     The lock pin  322  may be pressed toward the first side plate  114  by applying a lateral force to the button portion  400 , as shown in  FIG. 5B . When the lock pin  322  is pressed inward, the pin biasing member  408  may compress and the nut  406  may move out of the rocker slot  332 . The shaft  402  of the lock pin  322  may therefore be exposed to the rocker slot  332 . Because the shaft  402  has a smaller diameter than the nut  406 , the rocker  310  may no longer be as inhibited from rotation within the rocker slot  332  due to contact with the outer diameter of the lock pin  322 . Accordingly, if the lock pin  322  is pressed inward, the rocker  310  may simultaneously be rotated around the rocker pivot pin  312 , as shown in  FIGS. 4C and 5C . The rocker  310  may rotate downward along the Y-direction between the thumbstud  120  and the nut  406 , and in that position it has rotated far enough to be able to rotate the latch hook  318  out of the spine notch  220 , thereby releasing the blade  104 . 
     The latch assembly  106  may be referred to as having a dual-locking or two-step sequential latch since the lock pin  322  and rocker  310  may both need to be manipulated in sequence in order for the latch hook  318  to release the blade  104 . The lock pin  322  and rocker  310  may also be operated to insert a blade  104  into the slot  118 . In other words, the latch hook  318  may prevent insertion of a blade  104  until the latch hook  318  is pivoted out of the way of the blade  104 . The lock pin  322  may need to be simultaneously actuated with the rocker  310  for the locking mechanism to allow insertion or removal of the blade  104 . In other words, the lock pin  322  may need to remain actuated while the rocker  310  is actuated, even though the lock pin  322  should be actuated sequentially prior to actuation of the rocker  310 . 
     Because the blade  104  may be interchangeable, a variety of blades or other tools may be used and retained in the slot  118 .  FIGS. 6A-6C  show some examples of other tools  500 ,  502 ,  504  that may be used in place of blade  104 . Tool  500  is a gut hook, tool  502  is a narrow blade, and tool  504  is a utility blade/razor blade. These tools  500 ,  502 ,  504  may each comprise a rear edge  514  and a latch spine  518  having a spine notch  520 . Tools  500  and  502  may also comprise a longitudinal notch  522 , a retention hook portion  524 , and a dull edge  512 . Tool  500  may comprise a recessed hook-shaped cutting surface  501 , and tool  504  may comprise a sharpened edge  540  in the heel  510  area. 
     Accordingly, when the tools  500 ,  502  are inserted into the slot  118  of a latch assembly  106 , they may fit in the same manner as the blade  104 . When tool  504  is inserted into the slot  118 , it may not engage the top surface of retainer plate  306 , but may engage the bottom surface of the retainer plate  306  and the latch hook  318 .  FIG. 7  shows the tool  504  held in the latch assembly  106 . Tool  504  may also be reversibly insertable into the slot  118 , wherein either end of the tool  504  may be inserted into the slot  118  with the other end extending outward. The other tools  500 ,  502  and blade  104  may only have one orientation in which they may be retained in the slot  118 . Tool  504  may comprise two spine notches  520 ,  521  that facilitate its reversibility. Thus, either of the spine notches  520 ,  521  may be engaged with the latch hook  318 , depending on which end of the tool  504  is inserted into the latch assembly  106 . In some arrangements, tool  504  may be a conventional utility razor blade. Thus, the knife  100  may use conventional utility razor blades in addition to other tools. The blade  104  and tools  500 ,  502  may each have a heel angle A equivalent to an end angle A′ of a conventional utility razor blade. See  FIGS. 3 and 6A-6C . 
     Some aspects of the present disclosure relate to methods for making and using a knife having an interchangeable blade and a latch assembly. One method may include providing the knife (e.g., knife  100 ), actuating a rocker locking member (e.g.,  322 ) to unlock a rocker (e.g.,  310 ) or lever relative to the blade (e.g., blade  104 ), rocking the rocker away from the blade while actuating the rocker locking member, and removing the blade from a slot (e.g.,  118 ) in the knife. Actuating the rocker locking member may comprise pushing the rocker locking member laterally and at least partially through the slot. For example, actuating the rocker locking member may comprise pushing a button or pin feature into the broad side or cheek of the knife. The method may also comprise inserting a second blade into the slot while rocking the rocker, rotating the rocker toward the second blade while actuating the rocker locking member, and deactuating the rocker locking member to lock the rocker relative to the second blade. In one example embodiment, the blade  104  may be removed from knife  100  and tool  500  may be inserted into the knife  100  in place of blade  104  by inserting the tool  500  into the slot  118  while rocking the rocker  310  and then rotating the rocker  310  toward the tool  500  while actuating the lock pin  322 . The lock pin  322  may then be deactuated (i.e., released or let return to a rest or low-potential-energy position) to keep the rocker  310  in position to retain the tool  500 . Accordingly, the knife may have interchangeable blades wherein the blades are removable and replaceable with other compatible blades or tools. 
     Various inventions have been described herein with reference to certain specific embodiments and examples. However, they will be recognized by those skilled in the art that many variations are possible without departing from the scope and spirit of the inventions disclosed herein, in that those inventions set forth in the claims below are intended to cover all variations and modifications of the inventions disclosed without departing from the spirit of the inventions. The terms “including:” and “having” come as used in the specification and claims shall have the same meaning as the term “comprising.”