Abstract:
A compact, folding tool permitting the exchange of implement sets, including one or more quick release mechanisms that are easily removed from a handle to release interchangeable implements; the tool further accommodating implement sets including different types and quantities of implements which are inhibited from rotating by an adjustable clamping force produced by the quick release mechanisms and optionally including over travel stops to obstruct implement rotation, or may rely solely on the clamping force provided by the quick release mechanisms to stabilize implements for use.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to a provisional application, U.S. Ser. No. 61/647,668, filed May 16, 2012, entitled Folding Interchangeable Implement Apparatus, by Richards, Todd, which is hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates generally to compact folding multi implement tools. More specifically, it relates to an apparatus with rotating, interchangeable implements retained in a common handle by a quick release cam locking mechanism. 
         [0004]    2. Description of the Related Art 
         [0005]    Portable, multi-implement tools such as foldable pocketknives are well known in the prior art. In addition to a set of cutting blades, such tools commonly include other implements such as saws, files, screwdrivers, scissors, etc., that can be individually unfolded from a handle. Traditionally, the implement set was permanently joined to the tool by pins or other swiveling or pivoting type fasteners. More recently however, such tools have incorporated removable fastener mechanisms to allow the tool to be disassembled and the implements replaced or substituted with those having a different function. While many are designed to be disassembled by removing small bolts or screws, alternate mechanism have been proposed that function without the need of additional tools. 
         [0006]    One such tool is in U.S. Pat. No. 7,926,136, issued Apr. 19, 2011 to Yale, et. al. The tool includes a pivoting holder that is described as a socket for receiving the base portion of numerous implements. The connection between the holder and the implement is maintained by a latch mechanism that may be released for replacing implements 
         [0007]    In another type of interchangeable implement tool, the bases of the implements have hooked ends for coupling with a fixed pin inside the handle portion of the device. The individual implements may be detached from the handle by positioning them in a slightly opened position and them pushing them free from the fixed pin. Such a tool is thoroughly described in U.S. Pat. App. No. 2008/0086,822 filed on Oct. 18, 2007, by Elsener. 
         [0008]    Another interchangeable multifunction tool is described in U.S. Pat. No. 8,087,173 issued on Jan. 3, 2012 to Tang, et al. The tool includes a key and keyway type cam mechanism to sandwich one or more implement plate layers between a pair of side plates. Each implement layer comprises a segment of the cam mechanism, an implement, and a carrying plate. Different implement layers may be combined to vary the kind and number of implements housed between the side plates and the keys are designed to be manipulated by hand. 
         [0009]    While interchangeable implement tools have the potential to tailor function more precisely than traditional fixed implement tools, the demand for fixed implement tools remains high. Despite many years of development, improved devices that make changing implements foolproof and convenient have not yet been identified. Some require careful manipulation and may be hazardous when pushing against small or sharp implement ends. Others have not been embraced because they are far too complicated to operate or require too many sophisticated parts. 
         [0010]    Improvements in interchangeable implement tools are needed to provide updated function and convenience particularly as new implement pieces are devised. Therefore, it would be desirable to provide a foldable tool with exchangeable implements having a mechanism that is simple and easy to operate for replacing worn implements or tailoring function to a user&#39;s needs. 
       SUMMARY OF THE INVENTION 
       [0011]    It is an advantage of the present invention to provide a foldable tool apparatus with implements that are safely and easily manipulated while being exchanged. 
         [0012]    It is an advantage of the present invention to provide a foldable tool apparatus with interchangeable implements that are firmly secured by a simple quick release mechanism. 
         [0013]    It is also an advantage of the present invention to provide a foldable tool apparatus that is tailored in function by adding, removing, or exchanging implements. 
         [0014]    It is still another advantage of the present invention to provide an interchangeable tool apparatus having parts with standardized dimensions that may be exchanged or used with additional components to assemble multifunction tools having implements of different lengths and sizes. 
         [0015]    These and further advantages are found in various embodiments of the inventive concept of the foldable tool as are herein shown, described, and claimed. 
         [0016]    The present invention provides a portable, foldable tool apparatus having a set of interchangeable implements. The tool is readily assembled or disassembled for exchanging implements and other components. When assembled, the tool is held together and its implements are made secure in a handle by at least one quick release mechanism. The mechanism comprises a shaft that is hinged at one end to a cam lever and fitted at the other with a removable retainer. The shaft is an improvement over conventional implement axles found in traditional folding tools because it is easily removed from the handle. Implements of the tool comprise a base end having a void opposite the working instrument end. The shaft of the quick release mechanism is positioned through the voids so that the implements are pivotally connected to the remainder of the tool. The cam lever may be moved about its hinge between a raised and a lowered position to affect tension on the shaft. In the lowered position, the amount of tension is such that enough friction is produced on the sides of the implement bases to inhibit the implements from pivoting about the shaft. The foldable tool may comprise one or more quick release mechanisms at various places in a handle, serving to facilitate a simple and easy exchange of implements. 
         [0017]    In an exemplary embodiment of the inventive concept, the tool comprises a quick release mechanism joined with a handle having a pair of side plates that are continuous with a back plate in between. The mechanism of the tool includes a cam lever hinged to one end of a shaft. The shaft is positioned through the handle side plates and limited in axial movement by a removable retainer at its opposite end. The shaft of the quick release mechanism is also positioned through voids of multiple implements nested between the side plates and serves as a pivot for the implements. The cam lever of the mechanism further comprises an integral cam in close proximity to the hinge. The cam profile is oriented with respect to the cam lever such that when the cam lever is in the lowered position a higher portion of the profile is in contact with a side plate, thereby increasing tension on the shaft and compressing the side plates and implements with enough force to immobilize the implements with respect to their rotation about the shaft. 
         [0018]    When the cam lever is in the raised position, the high portion of the cam profile is moved away from the side plate and tension in the mechanism shaft is minimized. In this position, the implements may be easily rotated about the shaft for positioning, or the retainer may be removed and the shaft retracted from the handle and implements to disassemble the tool. Upon reassembly, different implements may be exchanged for those removed, or a spacer of the same dimension as one of the removed implement bases may be substituted to reduce the quantity of implements housed by the tool. With the cam lever in the lowered position, implements residing on a sufficiently tensioned shaft are immobilized in any position whether between or beyond the side plates. 
         [0019]    The back plate portion of the handle limits the rotation of the implements about the shaft to approximately 180 degrees and provides an obstruction to implement rotation in addition to the clamping force provided by the quick release mechanism. In related embodiments, implement base dimensions are sized in multiples of a common fraction of the distance between the side plates. Further embodiments also comprise one or more tabs on the handle to maintain cam levers in alignment with the side plates. In still other related embodiments, the back plate includes a stop which inhibits the rotation of one or more implements at a position that is well before the implement has rotated 180 degrees from its nested position. 
         [0020]    In another aspect of the inventive concept, the folding interchangeable implement tool is without a back plate and implements of the tool rotate about a relaxed shaft of a quick release mechanism in either direction for a full 360 degrees. In preferred embodiments, the shaft of the mechanism is extendable so that a range of distances may be accomplished between parallel side plates and different numbers of implements may be housed without requiring spacers or considering the dimensions of the implement bases. 
         [0021]    In still another aspect of the inventive concept, the tool comprises twin side plate pairs, each pair having a quick release mechanism and an implement set residing on the mechanism shaft. One of the implements is a component adapted to fit together with the implement component of the other side plate pair. With the implement components fitted together in an operative position, the side plates function together as a handle for the implement. 
         [0022]    In a further aspect of the inventive concept a tool comprises a quick release mechanism with an oversized cam lever and a set of implements among one or more side plates. To make the implements more accessible, at least one of the side plates is minimized in proportion to the implements. To adequately house the implements, the oversized lever rests in close proximity to the implements when moved to its lowered position. In one embodiment of this aspect of the inventive concept, a unitary side plate is flanked by a set of implements on both sides and penetrated by shafts of quick release mechanisms at both ends. The mechanisms both comprise oversize cam levers that when in the lowered position rest along the implements on both sides of the tool. Preferably, embodiments of this aspect of the inventive concept comprise implement sets that are without sharp or pointed damaging surfaces, or include cam levers that are sufficiently sized to significantly conceal such damaging surfaces when the implements are folded closed along the implements as the tool is carried or used. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is a side view of an interchangeable implement tool having a quick release mechanism. 
           [0024]      FIG. 2  is a side view of a portion of an interchangeable implement tool with a cam lever in a raised position. 
           [0025]      FIG. 3A  is an isometric view of a quick release mechanism having a bifurcated cam lever. 
           [0026]      FIG. 3B  is an elevation view of a quick release mechanism having a bifurcated shaft which differs by 90 degrees. 
           [0027]      FIG. 3C  consists of elevation views of a quick release mechanism having a unilateral hinge pin which differs by 90 degrees. 
           [0028]      FIG. 4A  is a side view of an interchangeable implement tool having a continuous back plate handle and implement sets retained by quick release mechanisms at both ends. 
           [0029]      FIG. 4B  is perspective view of the tool shown in  FIG. 4 . 
           [0030]      FIG. 5  is a side view of an interchangeable implement tool having two quick release mechanisms with oversized cam levers. 
           [0031]      FIG. 6  is a representation of a portion of an interchangeable implement tool before and after an implement set is exchanged. 
           [0032]      FIG. 7  is a combination of three views of an interchangeable implement tool having implements in different configurations. 
           [0033]      FIG. 8  is side view of an interchangeable implement tool having dual side plate pairs for operating a first class lever implement. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    An embodiment of an elongated folding interchangeable implement apparatus is shown in  FIG. 1 . The apparatus includes a handle and a set of implements that are pivotally connected and retained inside the handle by a quick release mechanism according to the inventive concept. The quick release mechanism is comprised of a cam lever  02  that is moveable between a lowered and a raised position. The cam lever  02  is hinged to one end of a substantially inelastic shaft  04  that penetrates the handle and the implement set. The shaft functions as an implement axle and is fitted at the end opposite the cam lever with a threaded retainer  06  to be tensioned when the cam lever  02  is in the lowered position as shown. When the cam lever is moved to the raised position, the implements may easily rotate about the shaft of the quick release mechanism for stowing in the handle or exposing instrument ends. 
         [0035]    The handle of the apparatus is comprised of an upper  08  and a lower side plate  10 . Voids through each side plate at a first end  12  of the handle are coaxial and adapted for commonly receiving the removable shaft  04  of the quick release mechanism. A rivet  14  having a shoulder that is approximately the same width as the implement set is used to secure the side plates at the second end  16  of the handle. 
         [0036]    The implement set of the apparatus shown in  FIG. 1  includes a knife implement  18  and a crosshead screwdriver implement  20 , both having an instrument end and a flattened base end. Each of the implement base ends have substantially the same dimensions and include through voids which are aligned to be coaxial with the voids of handle side plates. The base ends  22  are sandwiched between the handle side plates and are loosely penetrated by the shaft of the quick release mechanism so as to allow the implements to rotate about the shaft  04  when the retainer is sufficiently loosened or the cam lever  02  is placed in the raised position. 
         [0037]    The cam lever  02  of quick release mechanism includes a bifurcated end having branches that span the shaft  04  and which are hingedly connected to opposite sides of the shaft by a hinge pin  24 . Together, the furcations, the pin, and the proximate end of the shaft form a hinge joint  26 . Each branch, e.g., furcation of the lever further includes a cam profile  28  having a higher portion  30  positioned against the upper side plate  08  when the cam lever  02  is placed in the lowered position, i.e., adjacent and superimposed upon the upper side plate as shown in  FIG. 1 . The threaded retainer  06  of the quick release mechanism is positioned outside the lower side plate  10  and is greater in diameter than the side plate voids. The end of the shaft  04  opposite the hinge pin  24  is threaded and maintained in position with respect to the lower side plate  10  by the retainer as the cam lever  02  is moved from the raised to the lowered position. 
         [0038]    The base ends  22  of the implements are pivotally connected to the shaft  04  of quick release mechanism and are in sliding contact with one another as well as with one of the side plates. Aligned with the side plates in the lowered position, the cam lever  02  functions together with the retainer  06  to tension the shaft and urge the side plates and implements together in the direction of the retainer, thereby increasing friction and inhibiting the implements from rotating about the shaft. When inhibited from being rotated or held in a particular position of rotation about the shaft, the implements are referred to herein as immobilized. 
         [0039]    Operating the quick release mechanism is simple. To immobilize the implements, the retainer  06  should be adjusted to coordinate with the cam lever  02  to produce adequate clamping action against the implements and side plates. The clamping action may be varied from an amount that merely inhibits rotation of the implements slightly to an amount that substantially inhibits rotation. If insufficient friction is produced by a particular adjustment of the retainer, the cam lever is raised and the retainer moved closer to the hinged end of the quick release mechanism shaft. In contrast, should the position of the retainer be such that the cam lever is unable to be folded against the handle e.g., adjacent to the upper side plate  08 , the retainer should be adjusted so that it is located further from the hinge end of the shaft. 
         [0040]    As shown in  FIG. 1 , implements of the apparatus are substantially inhibited from rotating. An exposed instrument end of the knife implement  18  is made operable and may be utilized by grasping the handle side plates. So long as adequate friction exists, the knife implement  18  will remain static with respect to the handle rather than rotate about the shaft  04  of the quick release mechanism. After work with the knife implement is completed, the cam lever  02  is raised to release tension from the shaft  04 , and the knife implement rotated to nest between the side plates, alongside the cross-head screwdriver  20 . If working with the screwdriver is desired, the screwdriver is rotated to an exposed position that is suitable for the work and the cam lever  02  is again lowered to immobilize the instruments. If instead, work with the apparatus is completed, the cam lever  02  is lowered against the handle while the implement instrument ends are positioned between side plates to prevent the implements from becoming exposed while the apparatus is carried or stored. 
         [0041]    It should be noted that as described herein the term, “raised position” includes positions of the cam lever  02  which when pivoted from the lowered position are before or after the cam lever is perpendicular to the handle so long as the high portion  30  of the cam profile  28  is pivoted off the handle side plate  08  or away from pointing in the direction of quick release mechanism shaft retainer  06 . 
         [0042]    In addition to providing clamping force for immobilizing the implements, the quick release mechanism is advantageous for substituting or renewing implements. Should it be desirable to exchange the implements shown in  FIG. 1  for others compatible with the apparatus, the implements are easily freed from the handle by disassembling the quick release mechanism. With the cam lever  02  in the raised position, the retainer  06  is simply threaded loose from the shaft  04  and the shaft is withdrawn from the side plates and implements. The same type of sharpened or otherwise renewed implements may be substituted for the original knife  18  and screw driver  20  implements or a different type of implement set may be assembled to nest within the handle to provide a different functional pair. As an alternative, other implement sets may be chosen having from one to several implements, so long as the total width of the base ends in the set is approximately the same as the width of the two base ends  22  of the original implement set. 
         [0043]    Referring now to the inventive concept in general, persons skilled in the art will recognize that the quick release mechanism and rivet shown in  FIG. 1  function to limit the number of implements the handle of apparatus may retain. However, in another embodiment of the present inventive concept, handle side plates accommodate any one of numerous quick release mechanisms having various different shaft lengths and a rivet component is made removable from between the side plates to be exchanged for rivets having different shoulder widths. When longer shaft lengths and rivet shoulders are selected, more implements may be connected with the handle to provide additional function as needed. 
         [0044]    Quick release mechanisms according to the concept of the present invention may be comprised of different types of retainers, hinge joints, and cam adjustment components so long as the mechanism incorporates a shaft that pivotally connects an implement set to a handle and releasably provides clamping force to the outside of side plates that is sufficient to immobilize implements through the action of a hinged lever. Mechanisms may be capable of providing minimal to very significant clamping force depending on the design. In some embodiments of the inventive concept, quick release mechanisms having levers in the lowered position maintain shafts under tension as implements are moved from between the handles to exposed positions as the immobilizing effect of the mechanism merely provides moderate resistance to rotation. Such mechanisms and methods of operation are particularly functional with handles providing over travel stops. In other embodiments, quick release mechanisms are substantially robust and adjusted to provide significant clamping force that substantially inhibits implements from rotating and therefore must have cam levers raised to rotate implements. 
         [0045]    Acceptable quick release mechanism may incorporate one or more washers along their shafts, outside the side plates, for transferring clamping forces to the apparatus handle. In some embodiments, an interchangeable implement tool includes a quick release mechanism having a specialized washer located at the hinged end of the shaft outside the side plate. The specialized washer includes a cupped recess adapted to slide against a cam profile of the lever when the lever is moved about the hinge. 
         [0046]    Retainers of interchangeable implement tools according to the inventive concept, function to maintain the position of a quick release mechanism shaft outside their neighboring side plate as the shaft is pulled from the opposite end by action of the cam lever. Shaft extending retainers providing substantial variations in shaft length are preferable in the sense that they allow for the interchange of implement sets having substantially different widths. The extending retainers may be threaded for providing adjustment at different lengths or in alternate embodiments may take the form of removable pins, clips, or the like, being fastened at multiple positions along the end of a quick release mechanism shaft adapted for receiving the retainer opposite a lever hinge joint. In preferred non-adjustable embodiments, the non-adjustable retainers are matched with handles and implement sets that together comprise pre-determined widths. In such embodiments, thicker replacement handle side plates may be used to compensate for wear or lack of adjustment in the quick release mechanism. 
         [0047]    In certain embodiments of interchangeable implement tools having quick release mechanisms with shaft extending retainers, retainers may be designed as elongated nuts having threads that engage the shaft over a long portion to prevent the shaft from protruding from the nut when the mechanism is made part of an apparatus with an implement set having a narrow width. In a portion of a preferred embodiment as shown in  FIG. 2 , an apparatus is comprised of a quick release mechanism having a threaded shaft  04  and retainer  06 . The quick release mechanism is itself situated in a handle  36  having a lower and an upper side plate  08 . The shaft is shown hinged at one end to a raised cam lever  02 , placing no tension on the shaft. The extending retainer is threaded upon the shaft opposite the hinge joint  26  and includes a threaded tube  32  facing the hinge pin  24  that is made round and narrow to fit within side plate and implement base end voids. The threaded tube  32  of the retainer serves as the pivot upon which the implements rotate and is generally hidden by the implements and handle. Opposite the tube, an exposed portion of the retainer has a diameter greater than the voids, offering a retainer shoulder  34  to maintain the exposed portion outside the handle  36 . 
         [0048]    As the number of installed implements for the tool in  FIG. 2  is changed, movement of the threaded retainer to different positions along the shaft  04  is compensated for by the void nearest the hinge joint  26 , allowing more or less of the threaded tube to enter the upper side plate  08 . If the set of implements is desired to be changed for one having a greater width, bushings having an outer diameter roughly the same as the narrowed portion of the retainer and an inner diameter roughly the same as the threaded portion of the shaft may be placed along the shaft within implement voids to provide stability. If instead a narrower implement set is fitted in the handle, a greater portion of the threaded tube  32  penetrates the upper side plate  08 , effectively making the shaft of the mechanism extendable in length and providing variation between the cam profile  28  and the effective shoulder of the retainer  06 . The extendable shaft allows the mechanism to clamp implements between side plates over a wider range of distances, expanding the possible combinations of implement sets retained by the handle. 
         [0049]    Hinge joints of tools according to the inventive concept include a cam lever and retainer at opposite ends of a substantially inelastic shaft and function by turning a higher portion of a cam in the direction of a retainer to produce an implement immobilizing clamping force. Shown in  FIG. 3  is a quick release mechanism of the inventive concept separated from an apparatus handle. The mechanism includes a hinge joint  26  having a cam lever  02  with a bifurcated end. The furcations  35  of the lever span the shaft  04  of the quick release mechanism and are connected to the same by a hinge pin  24 . The lever  02  is moveable between a raised and a lowered position and incorporates a cam profile  28  in proximity to the hinge joint  26 . 
         [0050]    Preferably the amount of clamping force transferred by a hinge joint is made adjustable. For example, the hinge joint shown with the remainder of a quick release mechanism in  FIG. 3A  includes a cam lever that coordinates with an adjustable retainer to vary the amount of clamping force. The cam lever is pivotally connected to the shaft and includes a cam profile. The cam profile  28  is oriented such that when the lever is in the lowered position a high portion  30  of the profile would be pressed against the outside of an apparatus handle side plate. At the opposite end of the shaft, an adjustable retainer  06 , in the form of a threaded thumb nut, moves throughout a range of adjustments along a threaded portion of the quick release mechanism shaft  04 . If, after assembly with a compatible handle and implement set, the force produced by the mechanism is insufficient to immobilize the implements, the hinge joint is adjusted by moving the position of the retainer closer to the cam profile. The adjustment is most easily accomplished while the cam lever is raised and will result in increasing the potential tension on the shaft when the lever is again moved to the lowered position. 
         [0051]    Other acceptable hinge joints comprise a cam lever  02  with a single cam profile  28  that pivots on an offset bifurcated shaft  04 , an embodiment of which is shown with a knurled adjustable retainer  06  in multiple views in  FIG. 3B . In other embodiments, a quick release mechanism shaft may be angled approximately 90 degrees near the proximity of a hinge joint  26  to form a hinge pin or, as shown in two views in  FIG. 3B , may at the same location support a hinge pin  24  which protrudes unilaterally from only one side of the shaft  04  to support a pivoting lever  02 . In this embodiment, the cam lever  02  pivots asymmetrically with respect to the mechanism shaft  04  to urge the cam profile  28  against the handle and provide clamping force in coordination with the retainer  06  at an opposite end of the shaft  04 . Bifurcated shaft and unilateral hinge joint designs are compatible with adjustable or non-adjustable retainers to oppose the forces they produce at opposite ends of their respective quick release mechanism shafts. 
         [0052]    In accordance with the inventive concept, alternate views of an interchangeable implement apparatus having first and second quick release mechanism pivotally connecting a first and second implement set to opposite ends of a common handle  36  are shown in  FIGS. 4A and 4B . Sides of the implement sets  44  are in sliding contact with side plates of the handle. The two mechanisms of the apparatus each include a hinge joint and are shown with cam levers  02  in their lowered positions, superjacent to the side plates and providing tension to the mechanism shafts. The handle ends each include a pair of coaxial voids sized to accommodate the quick release mechanism shafts. Implements of the implement sets have base end voids and are retained between the handle side plates by the shafts traversing through the handle and implement voids. With clamping forces from the mechanisms released, the implements freely pivot about the shafts from nested positions between the handle side plates to fully exposed and extended positions. 
         [0053]    As shown in  FIG. 4A , one implement from each set  44  is immobilized in an exposed position and another from each set is immobilized with its instrument end nested between the handle side plates. 
         [0054]    Like the first quick release mechanism  38 , the second quick release mechanism  40  includes a second quick release mechanism shaft  42  that is non-extendable. The second shaft  42  retains a second implement set on the second end of the handle. The second mechanism  40  is situated along the handle, inverted and parallel to the first quick release mechanism, at a sufficient spacing to avoid interferences between the rotating implement sets. 
         [0055]    The quick release cam levers  02  are hinged to the shafts opposite adjustable threaded retainers  06 . The cam levers include cam profiles  28  adjacent to the side plates and opposed on the shafts by the retainers  06  which are adjusted to provide sufficient tension to immobilize the implements when the cam profiles are made to urge the side plates by action of the cam levers. 
         [0056]    The quick release mechanisms also include cupped washers  46  placed along the shafts between the cam levers and the side plates. The washers  46  have through voids that allow them the travel along the shafts, transferring force from the cam profiles  28  to each side plate. 
         [0057]    Protruding from the side plates and contacting the cam levers opposite each hinged end is a tab  48 . The tabs prevent the quick release mechanism shafts from rotating in the handle and secure the levers adjacent to and in alignment with the side plates. 
         [0058]    In still another embodiment, an interchangeable implement tool comprises a first  38  and second  40  quick release mechanism as shown in  FIG. 5 . The mechanisms function to retain implements between two side plates of a handle  36  and are easily removed from the remainder of the tool for exchanging implements. The mechanisms comprise adjustable retainers  06  on shafts  04  that traverse voids in the handle side plates and implements and that are hinged at opposite ends to oversized cam levers. When the cam levers  02  are placed in the lowered position as shown, the cam lever of the first mechanism  38  covers the retainer of the second mechanism  40  and the lever of the second mechanism  40  covers the retainer of the first  38 . The large cam levers serve to enclose implements of the implement sets  44  stowed in the handle and provide a gripping structure such that side plates may be minimized. In related embodiments, a single side plate may be used for the purpose of joining two quick release mechanisms retaining separate implement sets, and stowed implements may also serve as part of a handle. 
         [0059]    Referring now generally to tools of the inventive concept, cam levers may be slotted to accept handle tabs for the purpose of keeping the levers secure. Also, other components in addition to tabs may serve as tab means to keep cam levers of interchangeable implement tools of the inventive concept in alignment with the handle side plates. Such components might include magnets or channels in the handle or the like, so long as the components engage the cam levers in the lowered position and inhibit the levers from becoming misaligned. In another embodiment, two quick release mechanisms may be arranged in a handle having cam levers on the same side of the tool so that the levers mechanically interface when placed in a lowered position against the handle. 
         [0060]    Referring again to the tool shown in  FIGS. 4A and 4B , the handle is further comprised of back plate  50  continuous with the two handle side plates. The back plate  50  spans between and is perpendicular to the side plates along the full length of the handle, behind the folded implements as shown in  FIG. 4A . 
         [0061]    As shown in  FIG. 4B , the back plate  50  of the apparatus extends along the length of the handle  36 , significantly enclosing the implements between the side plates and providing graduations  49  on its outside surface for measuring. With the cam levers in the raised position, each of the implements easily rotates approximately 180 degrees around one of the shafts of the quick release mechanisms before contacting one of two over travel stops  52 , integral with the back plate  50  and in proximity to the implement base ends of each set. While lowering the levers with the retainers properly adjusted immobilizes the instruments to some extent, maximum resistance to implement rotation is achieved by rotating an implement to be used against one of the stops. 
         [0062]    In the embodiment of the inventive concept shown in  FIGS. 4A and 4B  all implements of both sets are stopped by the back plate ends. However, in other embodiments according to the inventive concept not shown, a partial back plate may be used to allow some of the implements to be more or less limited from rotating or not affected by the back plate at all. Alternatively, over travel stops may be designed to originate from a side plate rather than a back plate. 
         [0063]    The embodiment of an apparatus shown in  FIGS. 4A and 4B  is fitting for severe use, since the stops  52  essentially prevent fully extended implements from rotating when subjected to forces that would otherwise cause the tool to fold. However, because of the back plate, distances between the side plates along the inside of the handle are substantially fixed. Therefore, implements of the apparatus sets may be interchanged with others, but only so long as the set widths remain substantially constant. 
         [0064]    Implements of the sets shown in  FIGS. 4A and 4B  are standard sized, having base ends of a particular width. The implements are easily removed from the apparatus by removing the retainers from the quick release mechanisms and withdrawing the shafts from the handle side plates. Once the mechanisms are removed, individual implements may be exchanged but the number of standard sized implements in each set must remain the same unless spacers, capable of making sufficient friction contact with neighboring components and approximately the width of standard sized base ends are incorporated into the set. Alternatively, non-standard implements, having wider or narrower base ends may be incorporated into the sets to vary the number of implements on either side of the handle. 
         [0065]    In general, embodiments having continuous back plate handles preferably also comprise sets of implements with base ends having widths that are multiples of a common fraction of the distance between side plates to maximize the combinations of implements that might be installed. Shown in  FIG. 6  is one end of interchangeable implement tool apparatus having a handle with a back plate  50  and a quick release mechanism according to the inventive concept. The figure shows the tool as it appears both before and after the implement set  44  is changed. In both instances the total distance between the side plates remains substantially the same and equal to the width of the implement sets. The total side plate distance  54  before the implement change is equal to “D” and the tool comprises three implements having base ends that are ⅙, 2/6, and 3/6 of D in width. After the implement set change, the side plate distance  54  remains the same and the set instead comprises four implements having base ends that are ⅙ and another that is 2/6 of D. 
         [0066]    Referring again to the inventive concept more generally, tools may comprise a single or multiple quick release mechanisms retaining interchangeable implements in a single handle side plate pair. Handles with a quick release mechanism at one end may be also include a conventional implement axle and implement rotation inhibitor permanently fixed between the handle side plates to secure rotating but non-interchangeable implements at an opposite end. In interchangeable implement tools incorporating these features, fixed implement axles are particularly appropriate for mainstay implements such as knife blades, etc., since such implements are likely to be desired in the selection of implements for the tool. In addition, conventional rotation inhibiting components such as spring stops may be directly combined with exchangeable implements retained by quick release mechanism shafts for limiting rotation. 
         [0067]    Shown in different implement configurations in  FIG. 7  is an interchangeable implement tool having separate upper  08  and lower  10  handle side plates fitted with a quick release mechanism  38  at one end. The mechanism includes a cam lever  02  hinged to a shaft  04  which penetrates voids in the side plates and is fitted on the opposite end by a removable retainer  06 . Along the shaft  04  and nested between the side plates is a removable implement set  44 . Side plate ends opposite the quick release mechanism are fixed together by a permanent rivet  56  and only the quick release mechanism shaft serves as an implement axle for the tool. 
         [0068]    The implement set  44  includes implements base ends  58  that are in sliding contact with one another, and instrument ends that function as a knife blade and a cross-head screwdriver. In configurations  7 A and  7 B the screwdriver  20  is shown in an exposed position, with its instrument end approximately 90 degrees from between the side plates. The retainer  06  (out of view in  7 B) is adjusted so that the mechanism provides substantial clamping force to the side plates when the cam lever  02  is in the lowered position, immobilizing the screwdriver implement  20  in the exposed position as shown. Although not fully extended and without encountering an over travel stop, the screwdriver  20  of the tool is useful for driving screws in obstructed spaces while in this position. 
         [0069]    With the lever moved to the raised position, the instrument end of the screwdriver may be rotated between the handle of the tool and the knife implement  18  extended. As shown by configuration  7 C, the tool is viewed from the opposite side with the screwdriver implement  20  stowed, the knife implement  18  instrument end rotated to an exposed position, and the cam lever (not shown in  7 C) placed in the lowered position. In configurations  7 A and  7 C, a stop spring  60 , fixed to the upper handle side plate  08  in alignment with the knife implement  18  makes contact with the base end  58  of the knife implement to limit rotation of the implement. 
         [0070]    In general, the mechanism of the interchangeable implement tool shown in  FIG. 7  may be adjusted differently depending upon the needs of the user. The mechanism may instead be adjusted to at all times provide only minimal clamping force so that the screwdriver may be rotated between stowed and exposed positions with the cam lever  02  remaining lowered. Alternatively, the retainer may be adjusted more loosely or tightly so that the over travel stop function of the spring  60  functions with or without assistance from the clamping force of the quick release mechanism  38 , to immobile the knife implement  18  for use. 
         [0071]    Aspects of the inventive concept are applicable to complex embodiments of folding tools. Shown in  FIG. 8 , a compact, interchangeable implement tool comprises two handle side plate pairs. Each of the pairs includes two quick release mechanisms at opposite ends and each mechanism retains an implement set that rotates about a mechanism shaft. The implement sets rotate between the handle side plates when the mechanisms are not producing substantial clamping force. However, a back plate (not shown) that is continuous with each of the handle side plate pairs includes over travel stops  52  at each end, to limit the rotation of implements to approximately 180 degrees. 
         [0072]    Four quick release mechanisms, each having a cam lever  02  hinged to a shaft  04  opposite a threaded retainer  06  serve as implement axles on the first ends  12  and the second ends  16  of the handle side plate pairs. Shown in the lowered position, the levers  02  are secured adjacent to each side plate by tabs  48  protruding from the side plate pairs. The levers  02  are moveable between raised and lowered positions and include integral cam profiles (not shown). When the levers are placed in the lowered position, as shown, the mechanisms function to produce clamping forces on the outside of the side plate pairs. 
         [0073]    Within each of the implement sets retained between the first ends  12  of the side plate pairs is a single jaw  62  of a pliers. The jaws  62  are pivotally joined together at a fulcrum  64 , forming a complete first class lever implement that is operable as a set of pliers when the jaws  62  are extended from their respective handle side plate pairs, as shown. The jaws  62  are limited in rotation by contact with the back plates at their base ends  22  and are further immobilized by clamping action from the quick release mechanisms. When the jaws  62  are in the extended position, the side plate pairs function together as a handle  36  for squeezing, as the jaws are urged to pivot around the fulcrum  64 . 
         [0074]    In alternate embodiments, one or more of the quick release mechanism shafts shown or described in  FIG. 8  may be substituted by a non-removable implement axel. In other embodiments, a different first class lever implement such as a wire cutter or scissors may have components retained in separate side plate handle pairs. In further alternate embodiments, pivoting components of first class lever implements housed in separate side plate pairs may be adapted to be disjoined from the one another so that side plate pairs may be separated for storage or carry. 
         [0075]    Specific embodiments shown or described are intended to be exemplary rather than limiting. Additional embodiments combining features and details of the disclosure herein are now made obvious to persons skilled in the art and understood to be in keeping with the spirit and scope of the inventive concept and appended claims.