Patent Publication Number: US-8966768-B2

Title: Ball bearing assembly for folding knife or tool

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of U.S. Provisional Application No. 61/450,071 filed Mar. 7, 2011, which is incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure concerns embodiments of a ball bearing assembly for use in a tool having a pivotable tool element, such as a folding knife having a pivotable knife blade. 
     BACKGROUND 
     A folding knife connects the blade to the handle through a pivot, allowing the blade to fold into the handle. Folding knives are attractive to many users as compared to a fixed blade knife because they are lightweight, versatile and easily carried. Folding knives utilize a variety of folding mechanisms. However, most designs and systems used for folding have proven to be expensive, unsafe, and mechanically unreliable. For example, prior ball bearing systems for folding knives utilize balls disposed in annular races machined directly into the side panels of the handle. Unfortunately, it is difficult to manufacture the side panels of the handle with a high degree of planarity. As such, the balls are susceptible to binding after repeated use. Moreover, if the side panels are made of a relatively softer metal than the balls, the bearing races wear relatively quickly. 
     SUMMARY 
     Disclosed herein is a folding tool, such as a folding knife which includes a ball bearing assembly which addresses the problems of the prior art because the races are manufactured with a high degree of planarity and precision. When mounted on pivots, the races are maintained in precise parallel alignment with respect to each other. The blade which is mounted on the shaft of the races therefore can be maintained in precise parallel alignment with the races to ensure there is even contact between the blade and the balls of both bearings. In addition, the balls and the races desirably can be made of materials with similar hardness to reduce wear. For example, the balls and the races can be made of hardened steel, while the side panels and liners of the handle can be made of a relatively softer material, such as aluminum. 
     In one representative embodiment of the present disclosure, a folding tool comprises a handle, a tool element and a ball bearing assembly. In some embodiments, the handle portion includes a first side panel with a first side panel inner surface and a second side panel with a second side panel inner surface. In some embodiments, a tool element is pivotably connected to the handle portion and comprises a tang; the tool element being pivotable relative to the handle portion between a closed position and an open position. In some embodiments, the bearing assembly is disposed in the handle portion and comprises a first bearing race and a second bearing race, wherein each race comprises a ball housing in which a plurality of balls partially reside therein. In some embodiments, the plurality of balls of each housing are positioned to contact an adjacent side surface of the tang thereby allowing the plurality of balls to roll along opposing sides of the tang as the tool element is pivoted from the open position to the closed position or the closed position to the open position. 
     In some representative embodiments, the folding tool further comprises a first side panel liner and a second side panel liner wherein the first side panel liner is positioned adjacent to the first side panel inner surface and the second side panel liner is positioned adjacent to the second side panel inner surface. 
     In some representative embodiments, the first side panel inner surface includes a recessed portion and the second side panel inner surface includes a recessed portion for receiving the first side panel liner and the second side panel liner, respectively. 
     In some representative embodiments, the bearing assembly comprises a shaft extending through the tang and opposite end portions on which the bearing races are mounted. 
     In some representative embodiments, the first race and second race each further include a flange extending radially outwardly from an inner end of the ball housing and a head portion extending axially from an outer end of the ball housing. 
     In some representative embodiments, the flange has a diameter greater than the opening in the first side panel liner and the second side panel liner. 
     In some representative embodiments, the bearing assembly further comprises a first screw for securing the first race to the first side panel and a second screw for securing the second race to the second side panel. 
     In some representative embodiments, each ball housing comprises a groove for receiving the plurality of balls. For example, each groove has a surface which corresponds to the curvature of the ball of the plurality of balls. 
     In some representative embodiments, the tool element is a knife blade. 
     In some representative embodiments, the ball housing comprises a first material and the first side panel and second side panel comprise a second material, the first material being harder than the second material. For example, the ball housings are made of steel and the first side panel and the second side panel are made of aluminum. 
     In some representative embodiments, the plurality of balls and the ball housing are made of the same material. 
     In some representative embodiments, the tang comprises an oversized tang portion that extends outwardly through an upper edge of the handle portion when the tool element is in the closed position. 
     In some representative embodiments, the folding tool further comprises a biasing element configured to apply an opening force to the blade. 
     In some representative embodiments, a method of operating a folding tool, such as a folding knife is disclosed. In some representative embodiments, the method comprises providing a folding knife comprising: a handle portion; a blade pivotably connected to the handle portion and including a tang; and a ball bearing assembly disposed in the handle portion and comprising a first bearing race and a second bearing race each race having a ball housing in which a plurality of balls partially reside therein. The method also comprises when the blade is in a closed position, applying an opening force to the blade to displace the blade from the closed position, thereby allowing the plurality of balls within each ball housing to roll along opposing sides of the tang of the blade as the blade pivots from the closed position to an open position. 
     In some representative embodiments, a folding knife is provided. In some representative embodiments, the folding knife comprises a handle, a blade and a ball bearing assembly. In some representative embodiments, the folding knife comprises a handle portion including a first side panel with a first side panel inner surface and a second side panel with a second side panel inner surface and a first side panel liner and a second side panel liner wherein the first side panel liner is positioned adjacent to the first side panel inner surface and the second side panel liner is positioned adjacent to the second side panel inner surface. In some representative embodiments, the blade is pivotably connected to the handle portion and comprises a tang, a bottom surface including a sharpened edge, and an upper surface opposite the bottom surface, the blade being pivotable relative to the handle portion between a closed position and an open position wherein the sharpened edge is exposed for use. In some representative embodiments, the bearing assembly is positioned between the first side panel and the second side panel, wherein the tang of the blade, the first side panel liner and the second side panel liner each include an opening for mounting the bearing assembly and the bearing assembly comprises a first bearing race and a second bearing race, wherein each bearing race comprises a ball housing; and a first screw for securing the first race of the first side panel and a second screw for securing the second race of the second side panel; and a plurality of balls residing partially within each ball housing, wherein the plurality of balls are positioned to contact an adjacent side surface of the tang thereby allowing the plurality of balls to roll along opposing sides of the tang as the blade is pivoted from the open position to the closed position or the closed position to the open position. 
     The foregoing and other features and advantages will become more apparent from the following detailed description of several embodiments, which proceeds with reference to the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a folding knife, according to one embodiment, showing the blade of the knife in its extended position. 
         FIG. 2  is a side view of the folding knife of  FIG. 1  in a collapsed, folded position. 
         FIG. 3  is a side view of the folding knife of  FIG. 1  showing the blade of the knife in its extended position. 
         FIG. 4  is a plan view of the bottom of the folding knife shown in  FIG. 3 . 
         FIG. 5  is an exploded, perspective view of the folding knife of  FIG. 1 . 
         FIG. 6  is a perspective view of a side panel of the handle. 
         FIG. 7  is a side elevation view of the folding knife of  FIG. 1  in the collapsed, folded position with one of the side panels removed. 
         FIG. 8  is a side elevation view of the folding knife of  FIG. 1  in the extended, open position with one of the side panels removed. 
         FIG. 9  is a partial cross-sectional view of the folding knife shown in  FIG. 8 . 
         FIG. 10  is an exploded, perspective view of a ball bearing assembly. 
         FIG. 11  is a side view of the inner face of one of the races of the bearing assembly with a shaft inserted in the central opening of the race. 
         FIG. 12  is a side view of the inner face of one of the races of the bearing assembly. 
         FIG. 13  is a cross-sectional view of one of the races of the bearing assembly. 
     
    
    
     DETAILED DESCRIPTION 
     Referring first to  FIGS. 1 and 2 , there is shown a folding knife  10 , according to one embodiment, comprising a handle  12  and a knife blade  14 . The blade  14  is pivotably coupled to the handle  12  for pivoting movement about a pivot axis  16  (shown in  FIGS. 4 and 5 ) between an open position (shown in  FIGS. 1 and 3 ) and a closed position wherein the blade is at least partially stored inside the handle (shown in  FIGS. 2 and 7 ). The blade  14  in the illustrated embodiment is coupled to the handle  12  via a bearing assembly  18  (FIGS.  5  and  9 - 13 ), which is described in greater detail below. The blade  14  has a “bottom” surface  76  that includes a sharpened edge  78  (referred to as the sharpened side or edge of the blade) and an “upper” surface  80  (referred to as the non-sharpened side or edge of the blade). The knife  10  can be provided with a clip  72  secured to the handle portion  12  so that the knife can be clipped onto a belt, a pocket, etc. 
     As best shown in  FIGS. 4 and 5 , the handle  12  can comprise first and second side panels  20 ,  22  (also referred to as right and left side portions of the handle) that can be coupled to each other by one or more spacers  24 . The handle  12  can also include first and second liners  26 ,  28  ( FIG. 5 ) positioned adjacent inner surfaces of side panels  20 ,  22 , respectively. The side panels  20 ,  22  can be formed with recessed portions on their inner surfaces (such as recess  21  on side panel  20  shown in  FIG. 6 ) that are sized to receive the first and second liners  26 ,  28 , respectively. As best shown in  FIG. 5 , each liner  26 ,  28  is formed with a respective opening  30  for mounting the bearing assembly  18 , as further described below. As best shown in  FIG. 8 , the liner  26  can be formed with a locking arm, or leaf spring,  32  for holding the blade  14  in its open position, as known in the art. The locking arm  32  is normally biased into a locking position wherein the free end of the locking arm  32  engages a rear edge portion  35  of the tang  70  of the blade so as to resist inadvertent closure of the blade. The locking arm  32  can be released from its locked position by moving the free end of the locking arm laterally away from the rear edge  35  of the handle toward the side panel  20  allowing the blade  14  to be folded into the handle  12  as shown in  FIG. 7 . As shown in  FIG. 5 , a pin  41  can be positioned a slot  39  in the blade  14  to control the swing of the blade  14  and a detent  47  can be provided in the blade  14  so in operation the detent  47  assists in retaining the blade  14  in a closed position. 
     In certain embodiments, the locking arm is provided with a tab  37  (as shown in  FIG. 5 ). For example, the tab can include a raised head, which is used to press against the back end of the tang  70  of the blade  14  when the blade  14  is being extended from the handle. The tab  37  can be released/unlocked by applying manual pressure to the tab  37  causing it to be released and allowing the blade  14  to be folded into the handle  12  (shown in  FIG. 7 ). 
     In certain embodiments, the knife  10  can be an assisted-opening knife or an automatic knife, and therefore includes a biasing element  86 , such as a spring operatively connected to the blade, which applies an opening force to the blade. The biasing element of an assisted-opening knife is operable to apply an opening force to the blade after manual pressure is applied to the blade to pivot the blade from the closed position  20  to an intermediate position between the closed and open positions. When the blade reaches the intermediate position, the force exerted by the biasing element causes the blade to further pivot from the intermediate position to the open position. Spring configurations for assisted-opening knives are disclosed in U.S. Pat. No. 6,834,432 and U.S. Pat. No. 6,145,202, which are incorporated herein by reference. 
     As best shown in  FIG. 2 , the tang  70  can include an oversized tang portion  84  (sometimes referred to as a “flipper”) that extends outwardly from the upper longitudinal edge of the handle portion  12  when the blade is in the closed position. The oversized tang portion can be used to open the blade. For example, the blade can be opened by applying sufficient manual pressure to the oversized tang portion (in the general direction of arrow  86  in  FIG. 2 ), such as by pressing on the oversized tang portion with a finger, to pivot the blade to the intermediate position, at which point the biasing element can further pivot the blade to the open position. 
     In embodiments where the knife comprises an automatic knife, the knife can include a biasing element, such as a spring, that applies an opening force to the blade that is strong enough to cause the blade to pivot from the closed position to the open position. The automatic knife can comprise a blade-locking element (such as a cross-bolt) that retains the blade in the closed position against the opening force of the biasing element. When the blade-locking element is activated by a user to release the blade, the biasing element causes the blade to open. 
       FIG. 8  is a side elevation view of the folding knife of  FIG. 1  in the extended, open position with one of the side panels removed.  FIG. 9  is a partial cross-sectional view of the bottom of the folding knife shown in  FIG. 8  illustrating the bearing assembly  18  including first and second bearing races  34 ,  36 , respectively. 
       FIG. 10  is an exploded view of the bearing assembly  18 . The bearing assembly  18  in the illustrated configuration includes first and second bearing races  34 ,  36 , respectively, and first and second pivot elements  38 ,  40 , respectively (also referred to as pivot screws). Each race  34 ,  36  houses a plurality of balls  42 . The first  20  race  34  includes a shaft  44  that extends through an opening in the tang  70  of the blade  14 . Although the shaft  44  is shown as an integral component of the first race  34 , it can be a separate component that is secured to the race  34 . For example, the shaft  44  can be press fit into a central opening in the race  34 . Each race  34 ,  36  in the illustrated embodiment includes a ball housing  46 , an annular lip or flange  48  extending radially  25  outwardly from the inner end of the ball housing  46 , and a head portion  50  extending axially from the outer end of the ball housing  46 . The head portion  50  of each race includes a flat surface  51  corresponding with a flat surface in the opening  30  of an adjacent side panel  20 ,  22  (as shown in  FIG. 5 ). 
     Referring to  FIG. 9 , when the knife is assembled, the ball housing  46  of each race is disposed in a respective opening  30  of a corresponding liner  26 ,  28 , and the annular lip  48 , which has a diameter greater than opening  30 , bears against the inner surface of the corresponding liner  26 ,  28 . The head portion  50  of each race extends into a corresponding opening of an adjacent side panel  20 ,  22  of the handle. The shaft  44  extends from the inner end of the ball housing  46  of race  34  through an opening in the blade tang, and into a central opening  52  of race  36 . The races  34 ,  36  can be held in place by pivot elements  38 ,  40 . For example, the shaft  44  can have a threaded bore, and each pivot element  38 ,  40  can have a respective head portion  64  and a threaded pin  54  extending therefrom. When the knife is assembled, the pins  54  are tightened into opposite ends of the threaded bore of the shaft  44 , and the head portions  64  can bear against the outer surfaces of the side panels  20 ,  22 . The knife handle  12  is assembled by securing the side panel  20  to side panel  22  by a plurality of screws  74 . As shown in  FIG. 5 , two screws  74  are threaded through openings in side panel  20 ,  22  and then through corresponding openings in liners  26 ,  28  into spacers  24 . The clip can comprise an elongated body having one or more openings for receiving one or more fasteners can be mounted onto the outer surface of the side panel  20  or  22  of the handle portion  12  by positioning the one or more fasteners (such as a pair of screws  74  as shown in  FIG. 5 ) through the one or more openings in the body of the clip which align with corresponding openings in the outer surface of side panel  20 ,  22 . Other retaining mechanisms in lieu of or in addition to a screw can be used to secure the clip  72  to the handle portion  12  of the knife  10 , including, but not limited to, a ball and detent retaining mechanism disclosed in U.S. patent application Ser. No. 12/429,051 which is hereby incorporated by reference. 
     As shown in  FIGS. 11-13 , the balls  42  of each race are disposed in an annular slot or groove  58  formed in each ball housing  46 . The groove  58  can have a radiused  25  surface  60  that corresponds to the curvature of the balls  42 . The balls  42  reside partially outside of their respective ball housing and are positioned to contact an adjacent side surface of the blade tang  70 . The balls  42  therefore can roll along the opposing sides of the blade tang  70  as the blade is pivoted from the open position to the closed position, and vice versa, to minimize friction on the sides of the blade. The opposing sides of the blade contacted by the balls are those sides that extend from the “upper” edge  80  to the lower edge  76  of the blade perpendicular to the pivot axis  16 . As can be appreciated, the opening force or inertia required to begin pivoting the blade from its closed position can be significantly reduced due to reduced friction of the blade. Even without a biasing element that applies an opening force to the blade, it is possible to fully open the blade from the closed position by applying manual pressure to the oversized tang portion  84 . For example, the knife can be opened by placing the knife in the hand with the non-sharpening edge of the blade facing away from the palm, and then exerting  10  manual pressure on the oversized tang portion  84  with the forefinger. 
     In certain embodiments, the balls  42  are not disposed in annular races machined directly into the first side panel  20  and the second side panel  22  of the handle  12 . 
     A significant advantage of the bearing assembly  18  is that the dimensions and tolerances of the races  34 ,  36  can be tightly controlled to ensure that there is even and consistent contact between the balls  42  and the sides of the blade. Prior ball bearing systems for folding knives utilize balls disposed in annular races machined directly into the side panels of the handle. Unfortunately, it is difficult to manufacture the side panels of the handle with a high degree of planarity. As such, the balls can be susceptible to binding after repeated use. Moreover, if the side panels are made of a relatively softer metal than the balls, the bearing races can wear relatively quickly. In contrast, the bearing assembly  18  addresses the problems of the prior art because the races  34 ,  36  can be manufactured with a high degree of planarity and precision. When mounted on pivots  38 ,  40 , the races  34 ,  36  can be maintained in precise parallel alignment with respect to each other. The blade  14 , which is mounted on shaft  44  of the races, therefore can be maintained in precise parallel alignment with the races to ensure there is even contact between the blade and the balls of both bearings. In addition, the balls and the races desirably can be made of materials with similar hardness to reduce wear. For example, the balls and the races can be made of hardened steel, while the side panels and liners of the handle can be made of a relatively softer material, such as aluminum. As can be appreciated, the choice of material for the side panels and liners of the handle does not affect the operation and durability of the bearing assembly because the balls are contained within respective races of similar hardness. 
     In particular embodiments, the knife  10  can be provided with different sized bearings. In other words, one side of the handle can be provided with a relatively larger race and balls compared to the other side of the handle. 
     In certain embodiments, such as depicted in  FIG. 13 , the annular grooves  58  in races  34 ,  36  can be covered by a cover  66  to help seal the races and prevent the ingress of particulate matter into the grooves  58 . The cover  66  can be formed with a plurality of openings  68 , each aligned with a respective ball  42  to allow the balls to contact the sides of the blade through the cover. The cover  66  can be made of a low-friction, polymeric material, such as Mylar™. 
     The bearing assembly  18  can be used in devices other than folding knives. In particular, the bearing assembly can be adapted for use in various types of hand tools that have a tool element that is pivotably connected to a handle. In one implementation, for example, a hand tool can have a construction similar to that of folding knife  10 , except that the blade  14  is replaced with a different type of tool element, such as a file, a screwdriver blade, a saw blade, a bottle opener, etc. In another implementation, the bearing assembly  18  can be adapted to form the pivot of a pair of scissors. 
     In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrated embodiments are only preferred examples of the invention and should not be taken as limiting the scope of the invention. Rather, the scope of the invention is defined by the following claims. I therefore claim as my invention all that comes within the scope and spirit of these claims.