Abstract:
A folding knife includes an elongated blade and an elongated handle. The elongated handle includes a releasable locking engagement for holding the blade.

Description:
BACKGROUND 
       [0001]    The invention relates to a folding knife. In this specification the term “folding knife” must be interpreted sufficiently broadly to mean any type of a folding tool having an elongate workpiece, such as, for example, a blade, a shank or a stem. Furthermore, any reference in this specification to an “elongate blade” must be interpreted to mean any elongate workpiece such as, for example, a blade, a shank or a stem. 
       SUMMARY 
       [0002]    According to the invention there is provided a folding knife including: 
         [0003]    an elongate blade having a free end and an opposite handle mounting end, the blade defining a longitudinal axis which extends between said ends, the blade defining a cam-receiving aperture having a generally circular profile and a blade notch which is disposed adjacent to and which opens into the cam-receiving aperture; 
         [0004]    an elongate handle having a free end and an opposite blade mounting end, the handle defining a longitudinal axis which extends between said ends, the handle including a locking formation for releasable engagement with the blade notch of the blade; 
         [0005]    a disc-shaped cam having a generally circular peripheral outer edge, which is pivotally mounted to the handle in an arrangement permitting pivotal displacement of the cam relative to the handle about a pivot axis which is offset from a centre of the cam, the cam being received within the cam-receiving aperture of the blade in an arrangement permitting rotation of the cam within the cam-receiving aperture, thereby providing for mounting of the blade to the cam and rotational displacement of the blade relative to the handle between a folded condition wherein the blade is folded onto the handle and an extended condition wherein the longitudinal axes of the blade and the handle are substantially aligned, the cam defining a cam notch in which the locking formation of the handle can be received, thereby permitting linear displacement of the cam and the blade relative to the handle when the locking formation is received in the cam notch; 
         [0006]    a cam mechanism for regulating said linear displacement of the cam relative to the handle, the cam mechanism including biasing means for biasing the cam and thereby the blade mounted thereto, in a predetermined linear direction relative to the handle; and an abutment formation which is fixed to the handle against which the biasing means abuts and is placed under tension when the cam is displaced in said predetermined linear direction, 
         [0007]    the configuration of the cam and the relative positions of the blade notch and the locking formation being such that when the blade is in the extended position, the locking formation is releasably captured in the blade notch, with a peripheral edge of the cam blocking the release of the locking formation, displacement of the blade into its folded condition from its extended condition, being achieved’ by exerting a force on the blade against the force of the biasing means so as to displace the blade notch in said linear direction away from the locking formation while rotating the blade relative to the cam so as to bring the cam notch into register with the blade notch thereby permitting the locking formation to be received within the cam notch so as to release the locking formation from the blade notch and permit rotation of the blade relative to the cam. 
         [0008]    The handle may include a stop formation against which the blade abuts in its extended condition and in its folded condition, the stop formation acting as a stop for preventing further rotational displacement of the blade beyond its extended condition when displacing the blade from its folded condition and for preventing further rotational displacement of the blade beyond its folded condition when displacing the blade from its extended condition. 
         [0009]    The blade may define a second blade notch in which the stop formation is received when the blade is in its extended condition. More specifically, the second blade notch may be defined in an edge of the handle mounting end of the blade. 
         [0010]    The folding knife may define a third blade notch which is disposed adjacent to and which opens into the cam-receiving aperture, the third blade notch being disposed substantially diametrically opposite the blade notch such that the locking formation is releasably captured in the third blade notch when the blade is in the folded condition. 
         [0011]    The locking formation and the additional locking formation of the handle may be positioned relative to one another such the locking formation is located relatively closer to the longitudinal axis of the handle than the additional locking formation, thereby providing for the position of the locking formation and the additional locking formation to be laterally offset from one another. Furthermore, the locking formation may be positioned relatively closer to the blade mounting end of the handle than the additional locking formation, thereby providing for the positions of the locking formation and the additional locking formation to be longitudinally offset. 
         [0012]    The folding knife may include a pair of covers wherein each cover of the pair of covers is disposed at a side of the cam-receiving aperture for closing off the side thereby retaining and covering the cam and the cam mechanism within the cam-receiving aperture. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    Further features of the invention are described hereinafter by way of a non-limiting example of the invention, with reference to and as illustrated in the accompanying schematic drawings. In the drawings:  FIG. 1  shows an exploded perspective view of a folding knife in accordance with the invention; 
           [0014]      FIG. 2  shows a side view of the folding knife of  FIG. 1 ; 
           [0015]      FIG. 3  shows a fragmentary enlarged plan view of the folding knife of  FIG. 1 , shown with a blade of the folding knife in its extended condition; 
           [0016]      FIG. 4  shows a fragmentary enlarged plan view of the folding knife of  FIG. 1 , shown with the blade being rotated relative to the handle from its extended condition into its folded condition; 
           [0017]      FIG. 5  shows a fragmentary enlarged plan view of the folding knife of  FIG. 1 , shown with the blade being further rotated relative to the handle from its extended condition into its folded condition; and 
           [0018]      FIG. 6  shows a fragmentary enlarged plan view of the folding knife of  FIG. 1 , shown with the blade of the folding knife in its folded condition. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    With reference to the drawings, a folding knife in accordance with the invention, is designated generally by the reference numeral  10 . 
         [0020]    The folding knife  10  includes a blade  12 , a handle  14 , a cam  16 , a cam mechanism  18  and a pair of disc-shaped bearing covers  20 . 
         [0021]    The blade  12  has an elongate configuration having a free end  22  and an opposite handle mounting end  24  and defines a longitudinal axis A which extends between the ends  22  and  24 . The blade  12  defines a cam-receiving aperture  28  having a generally circular configuration, in which the cam  16  is received. The cam-receiving aperture  28  has a centre C when viewed in plan view and defines an axis of rotation through the centre about which the blade  12  is rotatable. The cam is rotatably mounted within the cam-receiving aperture. The blade defines a first blade notch  30 , a second blade notch  32  and a third blade notch  33 . The first blade notch  30  is defined adjacent the cam-receiving aperture  28  and opens into the cam-receiving formation. The second blade notch  32  is defined in an edge of the blade at its handle mounting end  24 . The third blade notch  33  is disposed diametrically opposite the first blade notch  30  adjacent the cam-receiving aperture  28  and opens into the cam-receiving aperture. The blade further defines a serrated thumb grip  34  and a cut-out  35 . 
         [0022]    The handle  14  has an elongate configuration having a free end  36  and an opposite blade mounting end  38 , and defines a longitudinal axis B which extends between the free end  36  and the opposite blade mounting end  38 . The handle includes two handle halves  40 . The handle halves  40 . 1  and  40 . 2  include inner liner plate  42 . 1  and  42 . 2 , respectively, and a relatively thicker outer cover plate  44 . The blade  12  is rotatably received between the handle halves. The folding knife is assembled such that the handle halves are spaced apart so as to define a gap within which the blade is received. The handle half  40 . 1  additionally defines a locking formation in the form of a locking pin  48 , a stop formation in the form of a stop pin  50  and a pivot pin  52 . The inner liner plate  42 . 1  additionally includes a pair of inwardly extending spacer bushes  53  which define internally screw threaded bores at opposite ends thereof. The handle halves  40 . 1  and  40 . 2  are connected to one another by means of screws  46  which are received in countersunk holes defined in the outer plates  44  and aligned holes defined in the associated inner plates  42 . The spacer bushes  53  space the handle halves from one another so as to define an internal space within which the blade is received in a folded condition thereof. More specifically, the screws  46  are screwed into the threaded bores defined in the ends of the spacer bushes  53 . 
         [0023]    The cam  16  has a disc-like configuration and is configured to be pivotally mounted to the handle  14  in an arrangement permitting linear displacement of the cam  16  relative to the handle  14 , as will be described in more detail below. The cam  16  comprises a cam body defining a cam notch  54 , a pivot-receiving aperture  56  and a bell-shaped cam mechanism-receiving aperture  58  in which the cam mechanism  18  is received. The cam body has a generally circular peripheral outer edge which is received within the cam-receiving aperture  28  of the blade  12  in a contact fit permitting rotation of the cam  16  within the cam-receiving aperture  28  of the blade —  The cam notch  54  is dimensioned and configured for receiving the locking pin  48  therein. The pivot-receiving aperture  56  is configured for receiving the pivot pin  52  therein, for pivotally mounting the cam  16  to the handle  14  at a position which is offset a distance ‘X’ from the centre C of the cam  16  when the cam is viewed in plan view (see  FIG. 3 ). 
         [0024]    The cam mechanism  18  is configured for regulating linear displacement of the cam  16  and includes an abutment formation in the form of an abutment pin  60  and biasing means in the form of a torsion spring  62 . As is most clearly shown in  FIG. 1 , the abutment pin  60  includes a central disc  64  and two cylindrical end pin sections  66  which extend outwardly from opposite ends of the central disc  64 . A central passage  68  extends centrally through the abutment pin  60 . The central passage  68  is threaded at its opposite ends, with openings of the passage being defined at free ends of the end pin sections. The abutment pin  60  is received within a part of the cam mechanism-receiving aperture  58  of the cam  16  and is fixed to the handle halves  40  by means of screws. The spring  62  is received in the cam mechanism-receiving aperture  58  and is shaped so as to conform to the shape of part of the aperture  58  against which the spring abuts. The spring  62  also abuts against the abutment pin  60 , causing the spring  62  to be placed under tension when the cam  16  is displaced in a linear direction as is explained hereinbelow. 
         [0025]    The bearing covers  20  are in the form of relatively thin plates and have a circular configuration when viewed in plan view. Each bearing covers  20  has three holes  70 . 1 ,  70 . 2 ,  70 . 3  defined therein. Each bearing cover  20  has a circular outer profile, the diameter of the retaining disc being slightly larger than the diameter of the cam-receiving aperture  28  of the blade  12 . The holes  70 . 2  of the covers  20  each receive a different one of the cylindrical end pin sections  66  of the abutment pin  60  therethrough. Locking pin  48  and pivot pin  52  are received in the holes  70 . 1  and  70 . 3 . The bearing covers  20  thus close off opposite sides of the cam-receiving aperture  28  thereby retaining the cam and the cam mechanism within the cam-receiving aperture and preventing the ingress of dirt. 
         [0026]    Each liner plate  42  also defines holes  71 . 1 ,  71 . 2  and  71 . 3  which are in register with the holes  70 . 1 ,  70 . 2  and  70 . 3  of the retaining discs  20  and in which the loading pin  48 , pivot pin  52  and end pin section  62 , respectively, are received. The bearing covers  20  and the liner plates  42  are screwed onto the abutment pin  60  by means of screws  73 . 1  and  73 . 2  which are screwed into the threaded ends of the end pin sections  66  thereby securing the bearing covers to the sides of the cam-receiving aperture  28 . The screws  73 . 1  and  73 . 2  are tightened to a required torque such that outer peripheral portions of the bearing covers bear against portions of the blade  12  surrounding the cam-receiving aperture, thereby preventing the ingress of dirt into the cam-receiving aperture and the blade notch  30 . 
         [0027]    In use, it will be appreciated that when the cam  16  is mounted to the blade  12 , the contact fit between the cam and the cam-receiving aperture  28  of the blade permits rotation of the cam within the cam-receiving aperture  28  of the blade  12 , thereby providing for rotational displacement of the blade  12  between a folded condition (as shown in  FIG. 6 ) wherein it is folded onto the handle  14  so as to be received between the handle halves  40  and an extended condition (as shown in  FIGS. 2 and 3 ) wherein the longitudinal axis A of the blade  12  and the longitudinal axis  13  of the handle  14  are aligned. 
         [0028]    The configuration of the cam and the relative positions of the first blade notch  30  and of the locking pin  48  are such that when the blade  14  is in its extended condition, the locking pin is releasably captured in the first blade notch  30 , with a peripheral edge of the cam blocking the release of the locking pin as is shown in  FIG. 3 . The blade  12  is released so as to permit displacement into its folded condition, by exerting a force on the blade  12  against the force of the spring  62  so as to displace the blade  12  in a linear direction ‘F’ as shown in  FIG. 3  relative to the handle  14 . This causes the second blade notch  32  to be displaced away from the stop pin  50  and the first blade notch  30  to be displaced away from the locking pin  48 . The blade is then slightly rotated relative to the cam  16  so as to bring the cam notch  54  into register with the first blade notch  30 . This allows the locking pin  48  to be released from the first blade notch  30  and received within the cam notch  54 , as is shown in  FIG. 4  of the drawings. 
         [0029]    Rotation of the blade into its folded condition from its extended condition is permitted when the locking pin  48  is received in the cam notch  54  and in the third blade notch  33 . Spring pressure provided by spring  62  releasably holds the locking pin  48  in the blade notch  33  thereby preventing the blade from opening accidentally when in the folded condition. In the folded condition of the blade, the stop pin  50  is received in the cut-out  35  thereby preventing further rotation of the blade. 
         [0030]    In order to displace the blade from its folded condition into its extended condition, thumb pressure is exerted on the thumb grip  34  of the blade for commencing rotation of the blade into its extended condition. The pressure exerted on the thumb grip causes the blade notch  33  to be displaced away from the locking pin  48  thereby allowing rotation of the blade. The blade is further rotated until the first blade notch  30  is aligned with the locking pin  48  and the locking pin is releasably captured into the blade notch  30  under the action of the spring  62 . In this position, the stop pin  50  is received in the second blade notch  32 , preventing further rotation of the blade. 
         [0031]    The locking pin  48  and the stop pin  50  are positioned relative to one another such that the locking pin is relatively closer to the longitudinal axis B of the handle  14  and the pins are thus laterally offset from one another. Furthermore, the locking pin  48  is positioned relatively closer to the blade mounting end  38  of the handle than the stop pin  50  and the pins are also longitudinally offset from one another. Offsetting of the locking pin and stop pin as described above, provides for the blade to be securely held in its extended position. 
         [0032]    In use, it will be appreciated that as the bearing covers  20  are larger in diameter than the diameter of the cam-receiving aperture  28  of the blade  12 , the bearing covers  20  are effective in preventing particulate material such as dust and/or dirt from entering into the cam-receiving aperture  28  and hampering the operation of the cam mechanism  18  and displacement of the cam  16 . More particularly, the screws  73 . 1  and  73 . 2  holding the bearing covers  20  to the abutment pin  60  are tightened to a required torque, such that outer peripheral portions of the bearing covers  20  bear against portions of the blade  12  surrounding the cam-receiving aperture  28  and the blade notch  30 , thereby to keep particulate material out of the cam-receiving aperture  28  and blade notch  30 , in use. The bearing covers  20  also provide bearing surfaces against which the blade bears during rotation of the blade between its extended and folded conditions. The bearing covers  20  also serve to space the blade from inner sides of the inner liner plates thereby protecting the blade from rubbing against the inner liner plates when the blade is rotated. 
         [0033]    It will be appreciated that the exact configuration of the folding knife  10 , in accordance with the invention may vary greatly while still incorporating the essential features of the invention as described hereinabove.