Patent Publication Number: US-2010107421-A1

Title: Convertible cutting instrument

Description:
BACKGROUND OF INVENTION 
     1. Field of Invention 
     Embodiments of the invention relate to cutting instruments that are convertible between a dual-blade configuration and a single-blade configuration. 
     2. Discussion of Related Art 
     A typical dual-blade cutting instrument, such as a pair of scissors or shears, includes two blades pivotally coupled to each other. Each of the two blades is further coupled to a handle, so that a user may cause the two blades to rotate toward each other by grasping the handles. As the two blades rotate toward each other, an object placed between the blades, e.g., a piece of cloth or paper, is sheared by the sharp edges of the blades. Such a dual-blade cutting instrument allows the user to control the curvature of the cut by turning the object in relation to the blades or by turning the blades in relation to the object. It may also allow a user to cut relatively hard objects, such as metal wires and tree branches, by squeezing the handles together. 
     A typical single-blade cutting instrument, such as a knife, comprises a single blade attached to a handle, so that a user may use the blade to chop, slit, or stab objects by grasping the handle. Such a single-blade cutting instrument allows the user to make cuts quickly and efficiently, although the user may have less control over the shape of the cut. 
     As explained above, dual-blade and single-blade cutting instruments are useful in different ways. It is advantageous to provide a cutting instrument that is convertible between a dual-blade configuration and a single-blade configuration, so that the user may obtain greater utility from a single tool. Several variants of a scissors and knife combination have been proposed, e.g., in U.S. Pat. Nos. 1,771,031, 3,835,533, and 4,528,707. 
     SUMMARY OF INVENTION 
     Various embodiments of the invention relate to a convertible cutting instrument with improved safety. In accordance with some embodiments of the invention, a convertible cutting instrument is operable as a pair of scissors in a dual-blade configuration and as a knife in a single-blade configuration. When in the dual-blade configuration, the convertible cutting instrument may comprise no outwardly facing cutting edges. The convertible cutting instrument may further comprise one or more safety mechanisms adapted to prevent the cutting instrument from entering into the single-blade configuration until the safety mechanism is released. Methods for converting a convertible cutting instrument between a dual-blade configuration and a single-blade configuration are also described. 
     One embodiment of the invention is directed to a convertible cutting instrument comprising a first blade, the first blade comprising a first cutting edge and a first outer edge opposite the first cutting edge, and a second blade pivotally coupled to the first blade, the second blade comprising a second cutting edge and a second outer edge opposite the second cutting edge. When the first and second blades are in an open position, the first blade is angularly displaced from the second blade with the first and second cutting edges facing inward. When the first and second blades are in a closed position, the first and second blades substantially overlap and the first cutting edge does not extend beyond the second outer edge. The convertible cutting instrument further comprises a conversion mechanism to convert the cutting instrument from a dual-blade configuration, in which the first and second blades are movable between the open position and the closed position to perform a cutting operation, to a single-blade configuration, in which the first cutting edge extends at least partially beyond the second outer edge to form an outwardly facing cutting edge. 
     Another embodiment of the invention is directed to a method for using a cutting instrument comprising first and second blades pivotally coupled to each other, the first blade comprising a first cutting edge and a first outer edge opposite the first cutting edge, and the second blade comprising a second cutting edge and a second outer edge opposite the second cutting edge. The method comprises cutting an object using the first and second cutting edges by rotating the first and second blades toward each other in a scissors-like motion, and converting the cutting instrument from a dual-blade configuration to a single-blade configuration by displacing the first blade in relation to the second blade to expose at least a portion of the first cutting edge. 
     A further embodiment of the invention is directed to a convertible cutting instrument comprising a first blade comprising a first cutting edge and a first outer edge opposite the first cutting edge, the first outer edge being substantially blunt; a first handle attached to the first blade; a second blade pivotally coupled to the first blade, the second blade comprising a second cutting edge and a second outer edge opposite the second cutting edge, the second outer edge being substantially blunt; and a second handle attached to the second blade. The first and second blades are adapted to rotate in relation to each other. The first and second cutting edges face each other when the first and second blades are in an open position, in which the first and second blades are angularly displaced from each other. The first and second cutting edges are adapted to shear an object placed between the first and second blades when the first and second blades rotate from the open position to a closed position, in which the first and second blades are substantially overlapping and the first cutting edge does not extend beyond the second outer edge. The convertible cutting instrument further comprises a bias mechanism adapted to bias the first and second blades into the closed position, and a conversion mechanism that, when actuated, overcomes the bias mechanism and causes the first and second blades to enter into a single blade configuration, wherein the first cutting edge extends beyond the second outer edge to form an outwardly facing cutting edge. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1A  is a side view of a prior convertible cutting instrument with blades in an open position; 
         FIG. 1B  is a side view of the convertible cutting instrument of  FIG. 1A  with blades in a closed position; 
         FIG. 2A  is a perspective view of a convertible cutting instrument in accordance with an exemplary embodiment of the invention; 
         FIGS. 2B-F  are side views of the convertible cutting instrument shown in  FIG. 2A , partially cut away to illustrate a lock mechanism; 
         FIG. 2G  is a side view of an alternative embodiment of the convertible cutting instrument shown in  FIG. 2A , partially cut away to illustrate an alternative lock mechanism; 
       FIG.  3 SA is a perspective view of a convertible cutting instrument in accordance with another embodiment of the invention; 
         FIGS. 3B-C  are side views of the convertible cutting instrument of  FIG. 3A , partially cut away to illustrate a conversion mechanism; 
         FIG. 3D  is a side view of the convertible cutting instrument of  FIG. 3A , shown in a single-blade configuration; and 
         FIG. 3E  is a side view of the convertible cutting instrument of  FIG. 3A , partially cut away to illustrate a safety mechanism. 
     
    
    
     DETAILED DESCRIPTION 
     Applicant has appreciated that prior designs of convertible cutting instruments disclosed in U.S. Pat. Nos. 1,771,031, 3,835,533, and 4,528,707 have features that lead to some disadvantages. These features will be discussed below with reference to  FIGS. 1A-B , which illustrate an example of the convertible cutting instrument of U.S. Pat. No. 4,528,707. 
       FIG. 1A  shows convertible cutting instrument  100  with blades  110  and  120 , which are pivotally coupled at a hinge  130 , in an open position. The blades  110  and  120  are respectively coupled to handles  150  and  140 . The blade  110  comprises a single cutting edge  115 , while the blade  120  comprises two opposite cutting edges  125   a - b.  When using the instrument  100  as a pair of scissors, a user squeezes the handles  140  and  150  together, thereby causing the blades  110  and  120  to rotate toward each other to cut an object placed between the cutting edges  115  and  125   a.    
       FIG. 1B  shows the blades  110  and  120  of cutting instrument  100  in a closed position, in which both cutting edges  125   a - b  are exposed. The cutting instrument  100  may be used as a knife in this position, with cutting edges  125   a - b  forming cutting edges of the knife. 
     Applicant has appreciated a drawback of this type of design; namely, an outwardly facing cutting edge is exposed at all times. For example, the cutting edge  125   b  is outwardly facing and is exposed both when the blades are in the open position shown in  FIG. 1A  and when the blades are in the closed position shown in  FIG. 1B . To avoid potential injuries caused by the cutting edge  125   b,  a user may need to take greater care while handling the instrument  100 , as if handling a knife. For example, a sheath may be needed to prevent accidental contact with the cutting edge  125   b  when the blades of the instrument are in the closed position. By contrast, a conventional pair of scissors has no exposed outwardly facing blades, and therefore is safer to handle. 
     Embodiments described herein relate to a convertible cutting instrument with improved safety. In particular, some embodiments of the invention relate to a convertible cutting instrument that may be safely handled when the blades are in a closed position, with no exposed cutting edges. Some further embodiments of the invention relate to a convertible cutting instrument that comprises only two cutting edges, both of which are inwardly facing when the cutting instrument is in a dual-blade configuration. This may render the cutting instrument safer for use as a pair of scissors or shears. 
       FIGS. 2A-F  show an exemplary embodiment of a convertible cutting instrument  200  having a conversion mechanism that converts an inwardly facing cutting edge into an outwardly facing cutting edge, so that the cutting instrument  200  may be used as a knife. The cutting instrument  200  comprises blades  210  and  220 . The blades  210  and  220  are pivotally coupled with each other at a hinge  280 , and are attached respectively to handles  250  and  240 . In the illustrated embodiment, the handle  240  is straight, while the handle  250  forms a loop through which a user may place one or more thumb and/or fingers. However, it should be appreciated that the invention is not limited to the particular handle configuration shown, and that each handle may be straight, looped, or have some other configuration. 
     The cutting instrument  200  is convertible between a dual-blade configuration in which the cutting instrument is operable as shears, and a single-blade configuration in which the cutting instrument is operable as a knife. In the dual-blade configuration, the blades  210  and  220  of the cutting instrument  200  are movable between an open position and a closed position. The dual-blade configuration is shown in  FIGS. 2A and 2B . 
       FIG. 2A  shows the blades  210  and  220  of the cutting instrument  200  in a closed position, and  FIG. 2B  shows the blades  210  and  220  of the cutting instrument  200  in an open position. As shown, the blade  210  comprises two edges: an outer edge  212  and a cutting edge  215 . Similarly, the blade  220  comprises an outer edge  222  and a cutting edge  225 . In this embodiment, the cutting instrument  200  also comprises a lock button  260 , which will be described in greater detail below. 
     In the open position shown in  FIG. 2B , the two blades  210  and  220  are rotated away from each other, exposing at least a portion of each of cutting edges  215  and  225 . The cutting edges  215  and  225  face inward, towards each other. The cutting instrument  200  comprises a spring  285  as shown in  FIG. 2B  to bias the blades  210  and  220  of the cutting instrument  200  into the open position. Alternative bias mechanisms are possible, such as an elastic material, or the bias mechanism may be omitted so that no bias force is imposed on the blades or handles. Further, the bias mechanism may be applied as a pulling force and/or as a pushing force, and may be coupled to one or both of the blades  210  and  220  and/or one or both of the handles  240  and  250 . 
     An object to be cut, e.g., a piece of paper or cloth, may be placed in the opening formed between the cutting edges  215  and  225  when the blades  210  and  220  are in the open position. To cut the object, a user of the cutting instrument  200  may squeeze the handles  240  and  250  together in a suitable way, causing the cutting edges  215  and  225  to rotate toward each other in a scissors-like motion. The object placed between the cutting edges  215  and  225  may be sheared as the cutting edges  215  and  225  rotate past each other, or otherwise when at least one cutting edge penetrates the object. 
     The user may continue to squeeze the handles  240  and  250  until the blades  210  and  220  at least substantially overlap, e.g., as in the closed position shown in  FIG. 2A . The footprint of the pair of blades may be minimized, and the blade  220  may be obscured from view by the blade  210  as shown in  FIG. 2A . However, it should be appreciated that the invention is not limited in this respect. For example, in other embodiments, the outer edge  222  may remain slightly below the cutting edge  215  when the blades  210  and  220  are in the closed position. Furthermore, the outer edge  222  may be substantially blunt and may serve as a shield that prevents potential injuries that may be caused by the cutting edge  215 . Similarly, the outer edge  212  may be above the cutting edge  225  when the blades  210  and  220  are in the closed position, and may serve as a shield for the cutting edge  225 . 
     As explained above, the blades  210  and  220  are biased into an open position in which the blades are angularly displaced with respect to each other and the cutting edges  215  and  225  are exposed. To overcome the bias without the need for continuously applied force by a user, a lock mechanism may be employed. In the embodiment illustrated in  FIGS. 2A-F , a lock mechanism prevents blades  210  and  220  from entering an open position (e.g., as shown in  FIG. 2B ) until the lock mechanism is released. As shown in  FIG. 2C , the lock mechanism comprises an aperture  270  formed on the blade  210  and a lock button  260  located on the handle  240 . The lock button  260  may be adapted to slide back and forth within a lock button chamber  265  formed on the handle  240 . For example,  FIGS. 2C-D  show the lock button  260  positioned at the back of the lock button chamber  265 , and  FIGS. 2E-F  show the lock button  260  positioned at the front of the lock button chamber  265 . 
     The lock button  260  and the lock button chamber  265  may be configured to enable at least a portion of the lock button  260  to become lodged within the aperture  270  to engage the lock mechanism. For example, starting from the configuration shown in  FIG. 2D , the lock button  260  may be pushed forward so that a portion of the lock button  260  enters the aperture  270 , and the lock button  260  and the aperture  270  form a male-female mating connection. This results in the configuration shown in  FIG. 2E , in which the portion of the lock button  260  lodged within the aperture  270  prevents the blades  210  and  220  from rotating into the open position. To release the lock, the lock button  260  may be pushed back so that the lodged portion exits the aperture  270 , returning the cutting instrument  200  to the configuration shown in  FIG. 2D  and allowing the blade  210  to rotate in relation to the blade  220 . When a bias mechanism such as the spring  285  is included in the cutting instrument  200 , as shown in  FIG. 2B , the blades  210  and  220  may automatically rotate away from each other as soon as the lodged portion of the lock button  260  exits the aperture  270  and the lock mechanism is released. 
     It should be appreciated that the invention is not limited to the particular lock and/or bias mechanisms shown in  FIGS. 2A-F , as many other alternative lock and/or bias mechanisms may also be suitable. For example, the aperture  270  may be located at a different location on the blade  210 , or on the handle  250 . One such alternative embodiment will be described in further detail below in connection with  FIG. 2G . Also, the lock mechanism may comprise one or more mechanisms (e.g., springs) to bias the lock mechanism into either the released configuration (e.g.,  FIG. 2D ) or the engaged configuration (e.g.,  FIG. 2E ). 
     Turning to  FIG. 2F , the cutting instrument  200  is shown in a single-blade configuration. To configure the cutting instrument  200  in this manner, the user may squeeze the handles  240  and  250  further toward each other, starting from the position shown in  FIG. 2E  wherein the blades  210  and  220  are in the closed position. The rotation may cause the blade  220  to rotate beyond the blade  210 , thereby exposing the cutting edge  225 . In  FIG. 2F , the cutting edge  225  is exposed at least partially above the blade  210  and the cutting edge  215  is exposed at least partially below the blade  220 . In this configuration, the cutting instrument  200  may be used as a knife, with the exposed cutting edges  225  and  215  forming the cutting edges of the knife. Alternatively, the single-blade configuration may include only one exposed cutting edge, such as one of cutting edge  225  or cutting edge  215 . 
     To maintain the single-blade configuration, the lock mechanism described above may be actuated and a continuous squeezing force may be applied to the handles  240  and  250 . Alternatively, a lock mechanism may be employed to lock the cutting instrument  200  in the single-blade configuration such that no squeezing force needs to be applied by the user. 
     It should be appreciated that the conversion between the dual-blade configuration and the single-blade configuration may be accomplished in various ways other than that described above. For example, the cutting instrument may further comprise a conversion button, and the relative rotation of the blades  210  and  220  may be caused by applying pressure on the conversion button, instead of or in addition to squeezing the handles  240  and  250  toward each other. One such embodiment will be described in greater detail in connection with  FIGS. 3A-E . Furthermore, the cutting edges of the single-blade configuration may be exposed by means other than by rotating the blades  210  and  220  with respect to each other. For example, the cutting instrument  200  may comprise a mechanism to displace, vertically and/or horizontally, at least one of the blades  210  and  220  in relation to the other. 
     As discussed above and illustrated in  FIGS. 2A-F , the blades  210  and  220  of the cutting instrument  200  are biased into an open position and a lock mechanism is used to overcome the bias. In the embodiment shown in  FIGS. 2C-F , the lock mechanism comprises an aperture  270  formed on the blade  210  and a lock button  260  located on the handle  240 , where a portion of the lock button  260  is adapted to become lodged within the aperture  270  to engage the lock mechanism. 
       FIG. 2G , illustrates an alternative lock mechanism that may also be used to overcome a bias force. Particularly,  FIG. 2G  shows a cutting instrument  200 ′ having a lock button  290  adapted to engage/release the lock mechanism by sliding between two detents formed on a handle  250 ′ of the cutting instrument  200 ′. The cutting instrument  200 ′ comprises two blades  210 ′ and  220 ′ that are pivotally coupled to each other at a hinge  280 ′. The blade  210 ′ is coupled to the handle  250 ′, on which two detents  297  and  298  are formed. The detent  298  is located near the hinge  280 ′ and the detent  297  is located further away from the hinge  280 ′. 
     As shown in  FIG. 2G , a portion  291  of the lock button  290  rests upon the detent  297  when the lock mechanism is released. In this configuration, the detent  297  may prevent the blades  210 ′ and  220 ′ from rotating past each other to enter into a single blade configuration similar to that shown in  FIG. 2F . To engage the lock mechanism, a user may push the lock button  290  forward so that the portion  291  enters a cavity  296  bounded at least partially by the detent  298 . The cavity  296  may be configured so that, whenever the portion  291  occupies a sufficient portion of the cavity  296 , the detent  298  prevents the blades  210  and  220  from rotating into an open position similar to that shown in  FIG. 2B . To release the lock mechanism, the lock button  260  may be pushed backward so that the portion  291  exits the cavity  296 , returning the cutting instrument  200 ′ to the configuration shown in  FIG. 2G  and allowing the blades  210 ′ and  220 ′ to rotate into an open position. 
       FIGS. 3A-E  illustrate another embodiment of the invention. According to this embodiment, a cutting instrument  300  is convertible between a dual-blade configuration in which the cutting instrument is operable as scissors, and a single-blade configuration in which the cutting instrument is operable as a knife. The convertible cutting instrument  300  comprises blades  310  and  320  that are pivotally coupled at a hinge  380  and are respectively attached to handles  350  and  340 . Each of the handles  340  and  350  forms a loop through which a user may place one or more thumb and/or fingers. The blade  310  comprises a cutting edge  315  and an outer edge  312 , and the blade  320  comprises a cutting edge  325  and an outer edge  322 . 
     In the dual-blade configuration, the blades  310  and  320  of the cutting instrument  300  are movable between an open position and a closed position. The dual-blade configuration is shown in  FIGS. 3A and 3B .  FIG. 3A  shows the blades  310  and  320  of the cutting instrument  300  in a closed position, and  FIG. 3B  shows the blades  310  and  320  of the cutting instrument  300  in an open position. 
     As shown in  FIG. 3A , the blades  310  and  320  are in a closed position, with the blades  310  and  320  substantially, though not completely, overlapping. In particular, the cutting edge  315  is slightly above the outer edge  322 . As discussed above, when the blades are in such a configuration, the outer edge  322  may serve as a shield to prevent potential injuries caused by the cutting edge  315 , although the invention is not limited to the illustrated positions of the blades  310  and  320  or to the use of an outer edge as a shield for a cutting edge. Further, the blades may alternatively completely overlap in the closed configuration, and the blades may have the same footprint. 
     In the embodiment illustrated in  FIGS. 3A-E , the handle  340  comprises a conversion button  390  to convert the cutting instrument  300  between a dual-blade configuration and a single-blade configuration. The conversion button  390  will be discussed in greater detail below in connection with  FIGS. 3B-C . The handles  340  and  350  further comprise a safety mechanism to prevent the cutting instrument  300  from entering the single-blade configuration until the safety mechanism is released. The safety mechanism comprises a leaf spring component  355  formed on the handle  350  and a detent  345  formed on the handle  340 , so that the detent  345  comes into contact with the leaf spring component  355  as the handles  340  and  350  are squeezed toward each other. The safety mechanism will be described in greater detail in connection with  FIGS. 3D-E  below. 
       FIG. 3B  shows the blades  310  and  320  of the cutting instrument  300  in an open position, illustrating the conversion button  390 . The conversion button  390  is housed in a conversion button chamber  393  formed within the handle  340  and is adapted to slide back and forth within the conversion button chamber  393 . As described in connection with  FIG. 3C , a user may push the conversion button  390  forward to convert the cutting instrument  300  from a dual-blade configuration (e.g., as shown in  FIG. 3A ) to a single-blade configuration (e.g., as shown in  FIG. 3D ). 
     The cutting instrument is shown in  FIG. 3C  with the handle  340  removed to illustrate the operation of the conversion button  390 . As discussed above, the conversion button  390  is adapted to move from the front of the conversion button chamber  393  to the back of the conversion button chamber  393 , and vice versa. As shown in  FIG. 3C , the handle  350  comprises a detent  397  and, when the conversion button  390  is at the back of the chamber  393 , a bottom portion  391  of the conversion button  390  is in contact with the detent  397 . In such a configuration, the detent  397  prevents the handles  340  and  350  from rotating further toward each other, thereby preventing the blades  310  and  320  from entering into a single-blade configuration (e.g., as shown in  FIG. 3D ). 
     When the bottom portion  391  of the conversion button  390  is moved from the back of the chamber  393  to the front of the chamber, the bottom portion is no longer in contact with the detent  397 , and the handles  340  and  350  are capable of rotating toward each other when a suitable torque is applied, thereby entering the blades  310  and  320  into the single-blade configuration. The torque may be applied in a number of different ways, as the invention is not limited in that regard. For example, a user may apply a force on the conversion button  390  at a suitable angle, so that the conversion button is moved from the back of the chamber  393  to the front of the chamber  393  and, at the same time, a torque is produced to rotate the handle  340  towards the handle  350 . Alternatively, or additionally, the user may squeeze the handles  340  and  350  together when applying a force to move the conversion button  390  from the back of the chamber  393  to the front of the chamber  393 . 
     Also shown in  FIG. 3C  is a spiral spring  395  coupled to the conversion button  390  to bias the conversion button  390  to the back of the chamber  393 . When a force is applied to move the conversion button  390  from the back of the chamber  393  to the front of the chamber  393 , the spiral spring  395  compresses against a front wall of chamber  393  to allow the movement of the conversion button  390 . When no force is applied to the conversion button  390 , the spiral spring  395  maintains the conversion button  390  in the back of the chamber  393 , where the detent  397  prevents the handles  340  and  350  from rotating further toward each other and thereby prevents the blades  310  and  320  from entering into the single-blade configuration. 
     When a bias mechanism such as the spiral spring  395  is used, the user may need to apply force to the conversion button  390  continuously in order to maintain the cutting instrument  300  in the single-blade configuration. When the user releases the force, the cutting instrument  300  may automatically return to the dual-blade configuration. In particular, the blades  310  and  320  may return to the closed position. When a bias mechanism is not used, the cutting instrument  300  may remain in the single-blade configuration until the user applies a suitable force to return the conversion button  390  to the back of the chamber  393 . As a further alternative, the cutting instrument  300  may comprise a lock mechanism that maintains the cutting instrument  300  in the single-blade configuration until the lock mechanism is released. 
       FIG. 3D  shows the cutting instrument  300  in a single-blade configuration. To configure the cutting instrument  300  in this manner, the user may squeeze the handles  340  and  350  together, causing the detent  345  to compress the leaf spring component  355 , as shown in  FIG. 3D . The leaf spring component  355  is shown in its entirety in  FIG. 3E , which shows the cutting instrument  300  with the handle  350  removed. As shown in  FIG. 3E , the leaf spring component  355  is coupled to the handle  350  via a mount  355   a,  and comprises a leaf spring  355   b  that is compressed by the detent  345  when the handles  340  and  350  are squeezed together. 
     The squeezing of the handles  340  and  350 , in conjunction with pushing the conversion button  390  forward, allows the blades  310  and  320  to rotate past each other to expose at least a portion of at least one of the cutting edges  315  and  325 . For example, as shown in  FIG. 3D , the cutting edge  325  rises at least partially above the outer edge  312 , forming a cutting edge of a knife. Similarly, the cutting edge  315  extends at least partially below the outer edge  322  (obscured by the blade  310 ), forming another cutting edge of the knife. 
     As the user releases the handles  340  and  350 , the leaf spring  355   b  returns to an uncompressed state, causing the blades  310  and  320  to return to the closed position, e.g., as shown in  FIG. 3A . In this embodiment, the cutting edge  325  retracts to a position slightly below the outer edge  312 , and the cutting edge  315  retracts to a position slightly above the outer edge  322 . Thus, the detent  345  and the leaf spring component  355  form a safety mechanism that biases the blades  310  and  320  into the closed position, so that the cutting instrument  300  may enter the single-blade configuration only when the user applies pressure to squeeze the handles  340  and  350  together. Alternatively, the cutting instrument  300  could be configured such that a user does not need to apply a force to maintain the cutting instrument in the single-blade configuration. 
     It should be appreciated that, while a safety feature may be desirable, the invention is not limited to the inclusion of a safety feature. In an embodiment without a safety mechanism, it may be sufficient to activate a conversion mechanism (e.g., by holding the conversion button  390  forward) in order to convert the cutting instrument  300  to the single-blade configuration. 
     It should also be appreciated that the invention is not limited to the particular conversion and/or safety mechanisms shown in  FIGS. 3A-E , as many other suitable conversion and/or safety mechanisms may be used. For example, the cutting instrument  300  may comprise a lock mechanism that, when engaged, prevents the cutting instrument from entering the single-blade configuration. 
     The convertible cutting instruments described herein may by formed using any suitable materials. For example, the blades  210 ,  220 ,  310 , and  320  may be formed of steel (e.g., SK-5 steel), and the buttons  260  and  390  may be formed of one or more suitable plastic materials. The handles  240 ,  250 ,  340  and  350  may comprise plastic cores and thermoplastic rubber (TPR) outer casings. However, it should be appreciated that these are merely illustrative examples, as the invention is not limited to the materials used in forming various parts of a convertible cutting instrument. 
     Having thus described several aspects of some embodiments of this invention, it is to be appreciated that the present invention is not limited in its application to the details of construction and the arrangement of components set forth in the foregoing description or illustrated in the drawings. Various alterations, modifications, and improvements may readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only. 
     Further, although certain advantages of the devices and methods described herein have been expressed, these advantages are provided merely to illustrate potential applications, etc., of such devices and methods, and do not define necessary features of the invention. The phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having,” “containing,” “involving,” and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.