Abstract:
A spring-assisted folding knife, including a one-piece knife blade having a proximal end and including a receiver on one side of its proximal end having a through bore; a blade insert made of a separate piece of material than the blade having a rear surface configured to be seated into the receiver, an opposite front surface, and a central bore extending between the rear surface and the front surface; and a coil spring received on the rear surface of the blade insert, the coil spring having a first end secured to the blade insert and an opposite second end secured to a fixed rigid surface of the knife.

Description:
FIELD 
     This disclosure relates to the field of folding knives. More particularly, this disclosure relates to improvements in the design of knives that utilizes a coil spring and a cam insert separate from the blade and are particularly useful for the manufacture of knives having blades formed of materials other than metal. 
     BACKGROUND 
     Improvement is desired in the design of spring assisted folding knives. Conventionally, spring assisted knives utilize components that are substantially exposed to the elements, which can undesirably affect the performance of the knife especially in opening. 
     Conventional spring assisted knives also typically utilize metal blades. However, the use of non-metal blades for knifes, such as blades made of ceramic or plastic, is often desired but blades of such non-metal materials are not suited for use with conventional spring assist structures. The present disclosure advantageously relates to a spring assisted knife that may use non-metal knife blades. 
     SUMMARY 
     The above and other needs are met by an improved spring-assisted folding knife. 
     In one embodiment, the knife includes a one-piece knife blade having a proximal end and including a receiver on one side of its proximal end having a through bore; a blade insert including a separate piece of material than the blade having a rear surface configured to be seated into the receiver, an opposite front surface, and a central bore extending between the rear surface and the front surface. 
     A coil spring is received on the rear surface of the blade insert, the coil spring having a first end secured to the blade insert and an opposite second end secured to a fixed rigid surface of the knife. A pivot extends through the through bore of the blade, the central bore of the insert, and the coil spring. The coil spring serves to assist opening of the blade of the knife from a closed position to an open position. 
     In another aspect, the blade is made of a ceramic or other non-metal material. The structure of the disclosure also provides additional advantages, such as location of the drive mechanism in a cavity in the handle so as to be protected from exposure to dirt and other elements that are detrimental to conventional spring-assisted knives. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantages of the disclosure are apparent by reference to the detailed description when considered in conjunction with the figures, which are not to scale so as to more clearly show the details, wherein like reference numbers indicate like elements throughout the several views, and wherein: 
         FIG. 1  is an exploded perspective view of a knife according to the disclosure. 
         FIGS. 2 and 3  show a blade of the knife of  FIG. 1 . 
         FIGS. 4 and 5  show a blade insert of the knife of  FIG. 1 . 
         FIG. 6  shows a coil spring of the knife of  FIG. 1 , and  FIG. 7  shows the coil spring installed within the blade insert of  FIGS. 4 and 5 . 
         FIGS. 8 and 9  show liners of the knife of  FIG. 1 , with  FIG. 9  shown receiving a portion of the coil spring of  FIGS. 6 and 7 . 
         FIG. 10  shows a rocker component of the knife of  FIG. 1 , and  FIG. 11  shows the rocker component located within the liner of  FIG. 8 , with a compression spring installed. 
         FIG. 12  shows a handle of the knife of  FIG. 1  configured to cooperate with the rocker and liner of  FIG. 11 . 
         FIG. 13  is an assembled view of the knife of  FIG. 1 , with a blade of the knife in an open position. 
         FIG. 14  is an assembled view of the knife of  FIG. 1 , with a blade of the knife in a closed position. 
         FIG. 15  illustrates operation of the knife between the open position and the closed position. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to the drawings, and initially to  FIG. 1 , the disclosure relates to a spring-assisted knife  10  having as major components a blade  12  having thumb screw  12   a  and a cutting surface  12   b , a blade insert  14 , a coil spring  16 , liners  18   a  and  18   b , a rocker arm  20 , a compression spring  22 , blade pivot members  24   a  and  24   b , and handle members  26   a  and  26   b . Additional structure of the knife  10  that facilitates assembly includes washers  30  and  32 , spacers  34 , latch button  36   a , latch  36   b , and latch screw  36   c , and blade stop  38 . 
     With reference to  FIGS. 2 and 3 , the blade  12  may advantageously be made of a non-metal material such as ceramic. In this regard, it is noted that ceramic and other non-metal blades have conventionally been unsuitable for implementation into a spring-assisted knife. The disclosure overcomes the prior unsuitability by combining a non-metal blade with the blade insert  14  to provide improved strength characteristics and suitability for providing a spring-assisted knife. 
     The blade  12  includes a receiver  40  on one side of its proximal end configured to fittingly receive the blade insert  14  and seat the blade insert  14  such that as the blade  12  and the blade insert  14  do not move relative to one another. The opposite side of the blade has a recess  42  to seat the washer  32 . A bore  44  extends through the receiver  40  and the recess  42 . Aperture  46  is located along an upper edge of the blade  12  to receive the thumb screw  12   a . The proximal end of the blade  12  is rounded and the step-down from the upper edge of the blade to the proximal end of the blade defines a shoulder  48  configured for abutting the blade stop  38  of the knife  10  to define the fully open position of the blade  12 . A notch  50  is defined on the rounded proximal end of the blade  12  for contacting a portion of the liner  18   b  for locking the blade  12  in the fully open position, as explained more fully below. 
     With reference to  FIGS. 4 and 5 , the blade insert  14  is preferably made of metal, such as stainless steel, and is generally doughnut-shaped having a rear surface  60  that is configured to be seated into the receiver  40  and an opposite front surface  62 . A central bore  64  extends between the rear surface  60  and the front surface  62 . The rear surface  60  includes an annular recess  66  configured to receive the spring  16  and having an aperture  68  for engaging a free end  70  of the spring  16  ( FIGS. 6 and 7 ). The front surface  62  of the blade insert  14  includes a raised cam surface  72  having a projecting lobe  74  adjacent a detent  76 . 
     The spring  16  is a coil spring having the free end  70  and an opposite free end  80 . The relatively flat portion of the spring  16  adjacent the end  70  is received by the annular recess  66 , with the free end  70  inserted into the aperture  68 . The spring characteristics are selected to provide spring-assisted opening of the knife  10  and will depend upon the size of the blade, weight of the blade, and other characteristics of the knife. 
     With reference to  FIG. 8 , the liner  18   a  is made of a flat rigid material such as aluminum plate and includes a cutout  90  having a substantially circular portion  90   a  configured to accept the blade insert  14 , an adjoining elongate portion  90   b  configured to accept the rocker arm  20 . A recess  90   c  is located below the elongate portion  90   b  for receiving the compression spring  22 . Apertures  92  are located through the liner  18   a  for receiving one side of the spacers  34 . Aperture  94  is located to receive a small projection of the latch plate  36   b . Groove  96  is located to receive and permit sliding of the latch screw  36   c  when it is connected to the latch plate  36   b . Aperture  98  is located to receive one side of the blade stop  38 . 
     With reference to  FIG. 9 , the liner  18   b  is made of a rigid flat material such as aluminum plate and is configured to have the same profile as the liner  18   a . The liner  18   b  includes the apertures  92  and  98  for receiving the other sides of the spacers  34  and the blade stop  38 , respectively. A circular cutout  100  is located in alignment with the circular portion  90   a  of the liner  18   a  for passage of the blade pivot member  24   b  and location proximate the spring  16  when it is mounted on the blade insert  14 . A linear recess  102  is located adjacent the cutout  100  for receiving the end  80  of the spring  16 , it being understood that the liner  18   b  provides a fixed rigid surface to which the end  80  of the spring is secured. An elongate stepped slot  104  is cut through a lower portion of the liner  18   b  to define a lock plate  106 . It will be appreciated that the lock  106  is unflexed so as to bear against the back-side of the lobe  74  and thereby lock the blade  12  against closing. To close the blade  12 , a user must first manually move or flex the lock  106  outwardly so as to permit the blade insert  14  to pass and once again maintain the lock  106  in the flexed state. 
     With reference to  FIG. 10 , the rocker  20  is preferably made of metal and includes a central pivot lobe  110  and pivot aperture  112 , with a cam engagement end  114  and an opposite spring engagement end  116 . As shown in  FIG. 11 , one side of the rocker  20  is received in the elongate portion  90   b  of the liner  18   a  with sufficient operational clearance, with the spring  22  installed on the spring engagement end  116  of the rocker  20  and received in the recess  90   c  of the liner  18   a.    
     As shown in  FIG. 12 , the handle  26   a  includes a recess  120  on an inner surface thereof configured to receive the other side of the rocker  20  with sufficient operational clearance. A pivot  122  extends from the handle  26   a  for engaging the pivot aperture  112  to permit pivoting of the rocker  20 . The handle  26   a  also includes a latch recess  124 , a latch button aperture  126 , a washer recess  128 , and a pivot member aperture  130 . 
     With reference to  FIG. 13 , the assembled knife  10  is shown in the open orientation.  FIG. 14  shows the knife  10  in the closed orientation. The assembled knife  10  is configured with the blade insert  14  seated in the receiver  40  on one side of the blade  12  and the spring  16  on the opposite side of the blade  12 , seated in the annular recess  66  of the blade insert  14 , with the pivot members  24   a  and  24   b  secured together and bearing against the handles to provide a pivot point about which the blade  12  pivots between the open and closed positions. The free end  80  of the spring  16  is seated in the linear recess  102  of the liner  18   b  and provides an anchor point for tensioning of the spring  16 . Opening of the blade  12  will decrease tension of the spring  16 , while closing of the blade  12  will increase the tension of the spring  16 . The rocker  20  in combination with the spring  22  and the lobe  74  and detent  76  of the blade insert  14  serve to urge the blade  12  to remain in the closed position. However, this may be overcome by a user intentionally urging the blade  12  away from the closed position, with the tension of the coil spring  16  thereafter serving to assist in the opening of the knife to position the blade  12  in the open position, as halted by contact of the shoulder  48  of the blade  12  against the blade stop  38 . As an additional feature to help maintain the blade  12  against accidental opening, the latch  36   b , operated by the button  36   a , is positioned to abut the blade insert  14  when the blade  12  is in the closed position to provide a latching feature. The latch  36   b  is easily moved out of engagement with the blade insert  14  by moving the button  36   a.    
     For example, with reference to  FIG. 15 , movement of the blade  12  from the open position to the closed position is depicted. An open position of the knife  10  is shown as position A. As will be appreciated, the shoulder  48  of the blade  12  is against the blade stop  38 . In addition, it will be understood that the lock  106  is in a flexed or biased state to bear against a portion of the blade insert  14  when the blade is in the closed position and throughout opening of the blade until just prior to the blade  12  becoming fully opened. When the blade  12  is fully opened, the blade insert  14  has rotated so as to have the back-side of the lobe pass by the lock  106  such that there is no portion of the blade insert  14  available to maintain the lock  106  in its flexed position. Thus, the lock  106  becomes unflexed and bears against the back-side of the lobe  74  and thereby locks the blade  12  against closing. When the blade  12  is in the fully open position (A), the rocker  20  does not interfere with opening or closing of the blade  12 . 
     To close the blade  12 , a user must first manually move or flex the lock  106  outwardly so as to permit the blade insert  14  to pass and once again maintain the lock  106  in the flexed state. Once closure of the blade  12  begins, as represented by position B, the user is applying pressure to close the blade  12  and is thereby increasing the tension of the spring  16 . As will be appreciated, the cam engagement end  114  of the rocker  20  is approaching the lobe  74  as the blade  12  begins to close as shown in position B, at which point the cutting surface of the blade  12  is just beginning to enter again into the enclosed space of the handles, representing about 130 degrees of closure, 180 degrees representing full closure. In this position, the rocker  20  does not interfere with opening or closing of the blade  12 . 
     In the next position C, representing about 160 degrees of closure of the blade  12 , it will be noted that the cam engagement end  114  of the rocker  20  is a the highest point of the lobe  74  and that any further rotation of the blade  12  toward closure will position the cam engagement end  114  of the rocker  20  past the lobe  74 . With the cam engagement end  114  past the lobe  74 , the rocker  20  does not interfere with closing of the blade  12 , but will resist opening of the blade  12 . 
     In the fully closed blade position D, representing 180 degrees of closure, the cam engagement end  114  is urged by the spring  22  against the detent  76  of the blade insert  14  to provide a closed position force and a user must exert force sufficient to overcome the closed position force to open the blade. As the blade  12  is opened from the closed position D to the open position A, it will be understood that once the blade  12  is urged past the position C, such that the cam end  114  of the rocker  20  is past the lobe  74  as represented by position B, the tension of the coil spring  16  will exert an opening force to quickly open the blade  12  to the open position A. 
     As will be appreciated, the use of a blade insert such as the blade insert  14  enables provision of a spring-assisted knife for blades that are not made of metal. However, the blade insert  14  may be used with a metal blade, and provides additional advantages, such as location of the drive mechanism, e.g., the coil spring  16  behind the blade  12  in a cavity in the handle so as to be protected from exposure to dirt and other elements that are detrimental to conventional spring-assisted knives. 
     The foregoing description of preferred embodiments for this disclosure has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments are chosen and described in an effort to provide the best illustrations of the principles of the disclosure and its practical application, and to thereby enable one of ordinary skill in the art to utilize the disclosure in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the disclosure as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.