Abstract:
A locking tool includes a handle; an elongated tool blade having a body and a tang. The tool blade has a tang spline opening formed therein which defines an annular array of alternate spline teeth and splined slots. A transversely-extending lock member has a spline ring with an annular array of alternate spline ribs and spline grooves formed thereon complementary to the tang spline opening, and is translatable between a locked position and a released position. The tool blade is attached to the handle by the locking member such that when the lock member is in said released position, the tool blade is freely pivotable about the locking member. When the lock member is in the locked position, the spline ring engages the tang spline opening such that the tool blade is retained in one of a plurality of predetermined angular positions relative to the handle.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates generally to a folding tool, and more particularly to a folding knife which locks in multiple positions.  
         [0002]     Folding tools, particularly including knifes and other cutting implements, are well known. A folding knife typically includes a blade which is pivotally mounted to a handle so that it can swing between an open position and a closed position in which the cutting edge is covered by the handle to protect both the user from injury and the blade from damage. It is also known to provide such knives with a lock to prevent inadvertent closing of the blade during use. However, such locks fail to provide both multiple positions and easy release of the blade.  
         [0003]     Accordingly, there is a need for a folding tool which can be securely locked into a plurality of positions.  
       BRIEF SUMMARY OF THE INVENTION  
       [0004]     The above-mentioned need is met by the present invention, which according to one aspect provides a folding tool, including: a handle having front and rear ends; an elongated tool blade having a body and a tang, the tool blade having a tang spline opening formed therein which defines an annular array of alternate spline teeth and splined slots; and a transversely-extending lock member having a spline ring with an annular array of alternate spline ribs and spline grooves formed thereon complementary to the tang spline opening, the lock member translatable between a locked position and a released position The tool blade is attached to the handle by the locking member such that when the lock member is in the released position, the tool blade is freely pivotable about the locking member, and when the lock member is in the lock position, the spline ring engages the tang spline opening such that the tool blade is retained in one of a plurality of predetermined angular positions relative to the handle.  
         [0005]     According to another aspect of the invention, the folding tool further includes a spring which urges the lock member towards the locked position.  
         [0006]     According to another aspect of the invention, the tool blade is a knife blade having a cutting edge.  
         [0007]     According to another aspect of the invention, the handle includes at least one spline opening disposed coaxially with the lock member, the spline opening having an annular array of alternate spline teeth and spline slot formed thereon complementary to the lock ring, wherein the spline opening engages the spline ring when the lock member is in the locked position.  
         [0008]     According to another aspect of the invention the handle includes spaced-apart left and elongated frames, and each of the frames includes a frame spline opening having an annular array of alternate spline teeth and spline slot formed thereon complementary to the spline ring.  
         [0009]     According to another aspect of the invention, the spline ring of the lock member engages each of the frame spline openings when the lock member is in the locked position.  
         [0010]     According to another aspect of the invention, the locking member includes two spaced-apart spline rings each having an annular array of alternate spline ribs and spline grooves formed thereon complementary to the tang spline opening, wherein one of the spline rings engages one of the frame spline openings, and the other of the spline rings engages the other of the frame spline openings, when the lock member is in the locked position.  
         [0011]     According to another aspect of the invention, a folding tool includes: a handle including a pair of spaced-apart left and right frames each having front and rear ends, wherein at least one of the frames includes a frame spline opening disposed at the front end thereof, the spline opening having an annular array of alternate spline teeth and spline slot formed thereon; an elongated tool blade having a body and a tang, the tool blade having a tang spline opening formed therein which defines an annular array of alternate spline teeth and splined slots identical to the spline opening; and a transversely-extending lock member. The lock member includes: at least one having a spline ring with an annular array of alternate spline ribs and spline grooves formed thereon complementary to the tang spline opening and the spline opening; and at least one central shaft having a cylindrical outer surface, wherein the lock member is disposed between the left and right frames such that the spline ring engages at least one of the frame spline openings. The lock member is translatable between a locked position and a released position. The tool blade is attached to the handle by the locking member such that when the lock member is in the released position, the tool blade is freely pivotable about the central shaft of the locking member, and when the lock member is in the lock position, the spline ring engages the tang spline opening such that the tool blade is retained in one of a plurality of predetermined angular positions relative to the handle.  
         [0012]     According to another aspect of the invention, the folding tool further includes a spring which urges the lock member towards the locked position.  
         [0013]     According to another aspect of the invention, the spring is carried between the lock member and a side plate which covers one of the spline openings.  
         [0014]     According to another aspect of the invention, each of the frames includes a frame spline opening having an annular array of alternate spline teeth and spline slot formed thereon complementary to the spline ring.  
         [0015]     According to another aspect of the invention, the spline ring of the lock member engages both of the frame spline openings when the lock member is in the locked position.  
         [0016]     According to another aspect of the invention, the locking member includes two spaced-apart spline rings each having an annular array of alternate spline ribs and spline grooves formed thereon complementary to the tang spline opening, wherein one of the spline rings engages one of the frame spline openings, and the other of the spline rings engages the other of the frame spline openings, when the lock member is in the locked position. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     The invention may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which:  
         [0018]      FIG. 1  is a side view of an exemplary folding tool constructed according to the present invention;  
         [0019]      FIG. 2  is a top view of the folding tool of  FIG. 1 ;  
         [0020]      FIG. 3  is an enlarged side view of  FIG. 2  showing a locking mechanism of the folding tool in greater detail;  
         [0021]      FIG. 4  is a top view of the locking mechanism shown in  FIG. 3 ;  
         [0022]      FIG. 5  is an exploded perspective view showing the components of the folding tool of  FIG. 1 ;  
         [0023]      FIG. 6  is a side view of an exemplary folding tool constructed according to an alternative embodiment of the present invention;  
         [0024]      FIG. 7  is a top view of the folding tool of  FIG. 6 ;  
         [0025]      FIG. 8  is an enlarged side view of  FIG. 7  showing a locking mechanism of the folding tool in greater detail;  
         [0026]      FIG. 9  is a top view of the locking mechanism shown in  FIG. 9 ;  
         [0027]      FIG. 10  is an exploded perspective view showing the components of the folding tool of  FIG. 6 ;  
         [0028]      FIG. 11  is a side view of an exemplary folding tool constructed according to an alternative embodiment of the present invention;  
         [0029]      FIG. 12  is a top view of the folding tool of  FIG. 11 ;  
         [0030]      FIG. 13  is an enlarged side view of  FIG. 11  showing a locking mechanism of the folding tool in greater detail;  
         [0031]      FIG. 14  is a top view of the locking mechanism shown in  FIG. 13 ;  
         [0032]      FIG. 15  is an exploded perspective view showing the components of the folding tool of  FIG. 11 ;  
         [0033]      FIG. 16  is a side view showing an alternative tool blade for use with the present invention;  
         [0034]      FIG. 17  is a side view showing another alternative tool blade for use with the present invention;  
         [0035]      FIG. 18  is a side view showing yet another alternative tool blade for use with the present invention; and  
         [0036]      FIG. 19  is an exploded perspective view showing an alternative folding tool. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0037]     Referring to the drawings wherein identical reference numerals denote the same elements throughout the various views,  FIG. 1  illustrates a representative folding tool, generally designated  10 , constructed according to an embodiment of the present invention. The basic components of the folding tool  10  are a tool blade  12 , a handle  14 , and a locking mechanism  16 . In the illustrated example, the tool blade  12  is a knife blade having an inner end or tang  18 , a body  20 , an elongated cutting edge  22 , and a pointed distal end  24  disposed opposite the tang  18 . As shown in  FIG. 5 , a tang spline opening  26  is formed in the tang  18 . The tang spline opening  26  includes a circumferential array of spline slots  28  which define an outer diameter D 1 . The tang spline slots  28  alternate with radially-inwardly extending tang spline teeth  30  that define an inner diameter D 2 .  
         [0038]     The handle  14  comprises left and right frames  32  and  34 , respectively. The construction of the left and right frames  32  and  34  may be substantially similar in dimensions and material to prior art folding tools. For example, the left and right frames  32  and  34  may be formed from stamped or machined steel. The left frame  32  is generally planar and has a forward end  36  and a rear end  38 . The left frame  32  has a left frame spline opening  40  formed therein at the front end  36 . The left frame spline opening  40  is substantially the same in size and shape to the tang spline opening  26 , and includes alternating spline teeth  42  and spline slots  44 . A raised, inwardly-protruding left bearing ring  46 , the purpose of which is explained below, is formed around the left frame spline opening  40 .  
         [0039]     The right frame  34  is generally planar and has a front end  48  and a rear end  50 . The right frame  34  has a right frame spline opening  52  formed therein at the front end  48 . The right frame spline opening  52  is substantially the same in size and shape to the tang spline opening  26 , and includes spline teeth  54  and alternating spline slots  56 . A raised, inwardly-protruding right bearing ring  58 , the purpose of which is explained below, is formed around the right frame spline opening  52 .  
         [0040]     A lock member  60  is provided which is a generally cylindrical member having a left end  62  and a right end  64 . The lock member  60  includes, in left-to-right order, a cylindrical release button  66 , a left spline ring  68 , a central shaft  70 , and a right spline ring  72 . The lock member  60  may be integrally formed from steel or a similar material. The release button  66  has an outside diameter smaller than the inside diameter D 2  of the tang spline opening  26 . If desired, the release button  66  may include a reduced diameter portion (not shown) specifically for being pressed by a user. This may be more aesthetically pleasing than a large diameter button. The left spline ring  68  includes a circumferential array of left spline ribs  74  which define an outer diameter slightly smaller than the outer diameter D 1 . The left spline ribs  74  alternate with radially-inwardly extending left spline grooves  76  that define an inner diameter slightly smaller than the inner diameter D 2 . The central shaft  70  has an outer diameter slightly smaller than the inner diameter D 2 . The right spline ring  72  includes a circumferential array of right spline ribs  78  which define an outer diameter slightly smaller than the outer diameter D 1 . The right spline ribs  78  alternate with radially-inwardly extending right spline grooves  80  that define an inner diameter slightly smaller than the inner diameter D 2 . Chamfered surfaces, shown in exemplary form at  82 , may be provided at the ends of the spline ribs  78  to ease operation of the lock member  60 .  
         [0041]     The folding tool  10  is assembled as follows. The lock member  60  is inserted into the right frame  34  so that the right spline ring  72  engages the right frame spline opening  52 . A right side plate  84  is attached to the outside of the right frame  34  with the illustrated rivets  86  or other suitable means. The right side plate  84  includes a cup  88  which covers the right spline opening  52  and retains a spring  90 , such as the illustrated coil spring, between the right frame  34  and the right side plate  84 . In the illustrated example, the right side plate  84  is a unitary member which comprises both the cup  88  and a spring clip  92  (see  FIG. 2 ) suitable for holding the folding tool  10  to a user&#39;s pocket or belt.  
         [0042]     The tang spline opening  26  of the tool blade  12  fits over the lock member  60 . The left frame spline opening  40  fits over the lock member  60  as well. A retainer plate  94  fits over the outer surface of the left frame  32  to retain the lock member  60  in position. The retainer plate  94  is attached to the left frame  32  by the illustrated rivets  98  or other suitable means, and includes an opening  96  therein through which the release button  66  passes. A left side plate  100  is attached to the left frame  32  as well. It may be made of a material suitable for decorative or grip-enhancing purposes, such as rubber, plastic, wood, etc.  
         [0043]      FIGS. 2, 3 , and  4  show the folding tool  10  in the assembled condition, with the tool blade  12  clamped tightly between the left and right bearing rings  46  and  58  to prevent wobbling or lateral movement. It is noted that the bearing rings  46  and  58  need not be distinct ring-like structures as shown. For example, the thickness of the left and right frames  32  and  34  could simply be increased to bear against the sides of the tool blade  12 . An optional stop pin  102  extends laterally between the left and right frames  32  and  34  and engages an optional step  104  in the tang  18  to provide a bearing point for the tool blade  12  in a fully opened position. The left and right frames  32  and  34  are attached to each other by suitable means such as the plurality of struts  106 .  
         [0044]     In the locked position, shown in  FIG. 4 , the spring  90  urges the lock member  60  leftwards so that the release button  66  protrudes through the opening  96  in the retainer plate  94 . The left spline ribs  74  and left spline grooves  76  of the left spline ring  68  engage the spline slots  44  and spline teeth  42 , respectively, of the left frame spline opening  40 . The right spline ribs  78  and right spline grooves  80  of the right spline ring  72  engage the spline slots  28  and spline teeth  30 , respectively, of the tang spline opening  26 , and also engage the spline slots  56  and spline teeth  54 , respectively, of the right frame spline opening  52 . In this condition, the tool blade  12  is solidly locked against pivoting motion in either the open or closed directions.  
         [0045]     The tool blade  12  is released by depressing the release button  66 , moving the lock member  60  to the right against the spring  90 . This causes the left spline ring  68  to disengage the left frame spline opening  40 , and the right spline ring  72  to disengage the tang spline opening  26 . The spline teeth  30  of the tang spline opening  26  thus ride on the central shaft  70 . In this condition a user can freely swing the tool blade  12  inwards or outwards to the desired position. The user keeps the release button  66  depressed until the tool blade  12  is disposed at or near the correct angular position, and then releases the release button  66 . The spring  90  urges the lock member  60  leftwards. As the tool blade  12  is brought into alignment at the desired working position, the lock member  60  moves fully to the locked position, described above. The tool blade  12  is thus locked against any further pivoting motion until the release button  66  is again depressed, and the user may safely work with the folding tool  10  knowing that the tool blade  12  will neither open further nor close accidentally.  
         [0046]     As shown in  FIG. 1 , the tool blade  12  can be locked in a number of different positions, represented by dashed lines. In the illustrated example there are eight locking positions including “fully” open (i.e. parallel to the handle  14 ), shown at “A”, open 135°, shown at “B”, open 90°, shown at “C”, open 45°, shown at “D”, and fully closed (not shown). If the stop pin  102  is not used the tool blade  12  can be locked in additional positions around a full circle. Examples of these positions are shown at “E”, “F”, and “G”. The number of positions as well as the angular orientation of each position may be varied to suit a particular application by suitable modification of the lock member  60 , tang spline opening  26 , left frame spline opening  40 , and right frame spline opening  52 . These positions greatly add to the utility of the folding tool  10 . Of course, the folding tool  10  may be used in a conventional manner when the tool blade  12  is at position A or fully closed. When the tool blade  12  is placed in positions B or C, is it useful for making cuts on vertical or horizontal surfaces while placing the user&#39;s hand in a comfortable position. Finally, when placed in position D, the tool blade  12  may be used to make cuts while preventing unwanted damage or injury. For example, in this position, the tool blade  12  may be used to cut carpeting without damaging the subflooring, or to sever a seat belt in the event of a car accident.  
         [0047]      FIGS. 6-10  illustrate an alternative folding tool  110 . The folding tool  110  is substantially similar to the folding tool  10  described above and has a tool blade  112 , a handle  114 , and a locking mechanism  116 . It differs from the folding tool  10  principally in the design of the locking mechanism  116 . In the illustrated example, the tool blade  112  is a knife blade having an inner end or tang  118 , a body  120 , an elongated cutting edge  122 , and a pointed distal end  124  disposed opposite the tang  118 . As shown in  FIG. 10 , a tang spine opening  26  is formed in the tang  118 . The tang spline opening  26  includes a circumferential array of spline slots  128  which define an outer diameter D 1 . The tang spline slots  128  alternate with radially-inwardly extending tang spline teeth  130  that define an inner diameter D 2 .  
         [0048]     The handle  114  comprises left and right frames  132  and  134 , respectively. The construction of the left and right frames  132  and  134  may be substantially similar in dimensions and material to prior art folding tools. For example, the left and right frames  132  and  134  may be formed from stamped or machined steel. The left frame  132  is generally planar and has a front end  136  and a rear end  138 . The left frame  132  has a left frame opening  140  formed therein at the front end  136 .  
         [0049]     The right frame  134  is generally planar and has a front end  148  and a rear end  150 . The right frame  134  has a right frame spline opening  152  formed therein at the front end  148 . The right frame spline opening  152  is substantially the same in size and shape to the tang spline opening  26 , and includes spline teeth  154  and alternating spline slots  156 . A raised, inwardly-protruding right bearing ring  158 , the purpose of which is explained below, is formed around the right frame spline opening  152 .  
         [0050]     A lock member  160  is provided which is a generally cylindrical member having a left end  162  and a right end  164 . The lock member  160  includes, in left-to-right order, a release button  166  disposed at the end of a central shaft  170 , and a spline ring  172 . The lock member  160  may be integrally formed from steel or a similar material. The central shaft  170  has an outer diameter slightly smaller than the inner diameter D 2 . The spline ring  172  includes a circumferential array of spline ribs  178  which define an outer diameter slightly smaller than the outer diameter D 1 . The spline ribs  178  alternate with radially-inwardly extending spline grooves  180  that define an inner diameter slightly smaller than the inner diameter D 2 . Chamfered surfaces, shown in exemplary form at  182 , may be provided at the ends of the spline ribs  178  to ease operation of the lock member  160 .  
         [0051]     The folding tool  110  is assembled as follows. The lock member  160  is inserted into the right frame  134  so that the spline ring engages the right spline opening  152 . A right side plate  184  is attached to the outside of the right frame  134  with the illustrated rivets  186  or other suitable means. The right side plate  184  includes a cup  188  which covers the right spline opening  152  and retains a spring  190 , such as the illustrated coil spring, between the right frame  134  and the right side plate  184 . In the illustrated example, the right side plate  184  is a unitary member which comprises both the cup  188  and a spring clip  192  (see  FIG. 7 ) suitable for holding the folding tool  110  to a user&#39;s pocket or belt.  
         [0052]     The tang spline opening  126  of the tool blade  112  fits over the lock member  160 . The left frame opening  140  fits over the release button  166  and central shaft  170  of the lock member  160  to retain the lock member  160  in position. A left side plate  200  is attached to the left frame  132  as well. It may be made of a material suitable for decorative or grip-enhancing purposes, such as rubber, plastic, wood, etc.  
         [0053]      FIGS. 7, 8 , and  9  show the folding tool  110  in the assembled condition, with the tool blade  112  clamped tightly between the left frame  132  and right bearing ring  158  to prevent wobbling or lateral movement. It is noted that the bearing ring  158  need not be a distinct ring-like structure as shown. For example, the thickness of the right frame  134  could simply be increased to bear against the side of the tool blade  12 . An optional stop pin  202  extends laterally between the left and right frames  132  and  134  and engages an optional step  204  in the tang  118  to provide a bearing point for the tool blade  112  in a fully opened position. The left and right frames  132  and  134  are attached to each other by suitable means such as the plurality of struts  206 .  
         [0054]     In the locked position, shown in  FIG. 9 , the spring  190  urges the lock member  160  leftwards so that the release button  166  protrudes through the opening  140  in the left frame  132 . The spline ribs  178  and spline grooves  180  of the spline ring  172  engage the spline slots  128  and spline teeth  130 , respectively, of the tang spline opening  26 , and also engage the spline slots  156  and spline teeth  154 , respectively, of the right frame spline opening  152 . In this condition, the tool blade  112  is solidly locked against pivoting motion in either the open or closed directions.  
         [0055]     The tool blade  112  is released by depressing the release button  166 , moving the lock member  160  to the right against the spring  190 . This causes the spline ring  172  to disengage the tang spline opening  26 . The spline teeth  130  of the tang spline opening  126  thus ride on the central shaft  170 . In this condition a user can freely swing the tool blade  112  inwards or outwards to the desired position. The user keeps the release button  166  depressed until the tool blade  112  is disposed at or near the correct angular position, and then releases the release button  166 . The spring  190  urges the lock member  160  leftwards. As the tool blade  112  is brought into alignment at the desired working position, the lock member  160  moves fully to the locked position, described above. The tool blade  112  is thus locked against any further pivoting motion until the release button  166  is again depressed, and the user may safely work with the folding tool  110  knowing that the tool blade  112  will neither open further nor close accidentally.  
         [0056]     As shown in  FIG. 6 , the tool blade  112  can be locked in a number of different positions, denoted “A” through “D” and represented by dashed lines, in the same manner as for the folding tool  10  described above, and may also be locked in a fully closed position (not shown).  
         [0057]      FIGS. 10-15  illustrate another alternative folding tool  210 . Again, the folding tool  210  is substantially similar to the folding tool  10  described above and has a tool blade  212 , a handle  214 , and a locking mechanism  216 . Like the folding tool  110 , it differs from the folding tool  10  principally in the design of the locking mechanism  216 . In the illustrated example, the tool blade  212  is a knife blade having an inner end or tang  218 , a body  220 , an elongated cutting edge  122 , and a pointed distal end  124  disposed opposite the tang  218 . As shown in  FIG. 15 , a tang spline opening  226  is formed in the tang  218 . The tang spline opening  226  includes a circumferential array of spline slots  228  which define an outer diameter D 1 . The tang spline slots  228  alternate with radially-inwardly extending tang spline teeth  230  that define an inner diameter D 2 .  
         [0058]     The handle  214  comprises left and right frames  232  and  234 , respectively. The construction of the left and right frames  232  and  234  may be substantially similar in dimensions and material to prior art folding tools. For example, the left and right frames  232  and  234  may be formed from stamped or machined steel. The left frame  232  is generally planar and has a front end  236  and a rear end  238 . The left frame  232  has a left frame spline opening  240  formed therein at the front end  236 . The left frame spline opening  240  is substantially the same in size and shape to the tang spline opening  226 , and includes alternating spline teeth  242  and spline slots  244 .  
         [0059]     The right frame  234  is generally planar and has a front end  248  and a rear end  250 . The right frame  234  has a right frame spline opening  252  formed therein at the front end  248 . The right frame spline opening  252  is substantially the same in size and shape to the tang spline opening  226 , and includes spline teeth  254  and alternating spline slots  256 .  
         [0060]     A lock member  260  is provided which is a generally cylindrical member having a left end  262  and a right end  264 . The lock member  260  includes, in left-to-right order, a release button  266  disposed at the end of a central shaft  170 , and a spline ring  272 . The lock member  260  may be integrally formed from steel or a similar material. The central shaft  270  has an outer diameter slightly smaller than the inner diameter D 2 . The spline ring  272  includes a circumferential array of spline ribs  278  which define an outer diameter slightly smaller than the outer diameter D 1 . The spline ribs  278  alternate with radially-inwardly extending spline grooves  280  that define an inner diameter slightly smaller than the inner diameter D 2 . Chamfered surfaces, shown in exemplary form at  282 , may be provided to ease operation of the lock member  260 . The main difference in the lock member  260  and the lock member  160  is that the spline ring  278  is substantially longer than the spline ring  178 .  
         [0061]     The folding tool  210  is assembled as follows. The lock member  260  is inserted into the right frame  234  so that the spline ring engages the right spline opening  252 . A right side plate  284  is attached to the outside of the right frame  234  with the illustrated rivets  286  or other suitable means. The right side plate  284  includes a cup  288  which covers the right spline opening  252  and retains a spring  290 , such as the illustrated coil spring, between the right frame  234  and the right side plate  284 . In the illustrated example, the right side plate  284  is a unitary member which comprises both the cup  288  and a spring clip  292  (see  FIG. 11 ) suitable for holding the folding tool  210  to a user&#39;s pocket or belt.  
         [0062]     The tang spline opening  226  of the tool blade  212  fits over the lock member  260 . The left frame spline opening  240  fits over the lock member  260  as well. A retainer plate  294  fits over the outer surface of the left frame  232  to retain the lock member  260  in position. The retainer plate  294  is attached to the left frame  232  by the illustrated rivets  298  or other suitable means, and includes an opening therein  296  through which the release button  266  passes. A left side plate  300  is attached to the left frame  232  as well. It may be made of a material suitable for decorative or grip-enhancing purposes, such as rubber, plastic, wood, etc.  
         [0063]      FIGS. 11, 12 , and  13  show the folding tool  210  in the assembled condition, with the tool blade  212  clamped tightly between the left and right frames  232  and  234  to prevent wobbling or lateral movement. An optional stop pin  302  extends laterally between the left and right frames  232  and  234  and engages an optional step  304  in the tang  218  to provide a bearing point for the tool blade  212  in a fully opened position. The left and right frames  232  and  234  are attached to each other by suitable means such as the plurality of struts  306 .  
         [0064]     In the locked position, shown in  FIG. 14 , the spring  290  urges the lock member  260  leftwards so that the release button  266  protrudes through the opening  296  in the retainer plate  294 . The spline ribs  278  and spline grooves  280  of the spline ring  272  engage the spline slots  242  and spline teeth  244 , respectively, of the left frame spline opening  240 . The spline ribs  278  and spline grooves  280  of the spline ring  272  engage the spline slots  228  and spline teeth  230 , respectively, of the tang spline opening  226 , and also engage the spline slots  256  and spline teeth  254 , respectively, of the right frame spline opening  252 . In this condition, the tool blade  212  is solidly locked against pivoting motion in either the open or closed directions.  
         [0065]     The tool blade  212  is released by depressing the release button  266 , moving the lock member  260  to the right against the spring  290 . This causes the spline ring  272  to disengage the left frame spline opening  240  and the tang spline opening  226 . The cup  288  is made deep enough to accommodate this motion of the lock member  260 . The spline teeth  230  of the tang opening  226  thus ride on the central shaft  270 . In this condition a user can freely swing the tool blade  212  inwards or outwards to the desired position. The user keeps the release button  266  depressed until the tool blade  212  is disposed at or near the correct angular position, and then releases the release button  266 . The spring  290  urges the lock member  260  leftwards. As the tool blade  212  is brought into alignment at the desired working position, the lock member  260  moves fully to the locked position, described above. The tool blade  212  is thus locked against any further pivoting motion until the release button  266  is again depressed, and the user may safely work with the folding tool  210  knowing that the tool blade  212  will neither open further nor close accidentally.  
         [0066]     As shown in  FIG. 10 , the tool blade  212  can be locked in a number of different positions, denoted “A” through “D” and represented by dashed lines, in the same manner as for the folding tool  10  described above, and may also be locked in a fully closed position (not shown).  
         [0067]      FIGS. 16, 17 , and  18  depict variations of a tool blade, which are suitable for use with any of the folding tool embodiments  10 ,  110 , or  210  described above. As can be seen, the tool blade need not be a cutting blade, but may be any tool useful for a working purpose. For example,  FIG. 16  illustrates a tool blade  312  which includes a holder  314  for disposable, single-sided razor blades  316  of a known type. This kind of tool blade  312  may be useful for carpet-laying work and the like.  FIG. 17  illustrates a general-purpose tool blade  412  having a stub  414  which can engage various tools such as a screwdriver, wrench, or the like.  FIG. 18  illustrates yet another tool blade  612  in the form of a cutting blade so-called “sheep&#39;s-foot” profile.  
         [0068]      FIG. 19  illustrates another alternative folding tool  510 . The folding tool  510  is substantially similar to the folding tool  210  described above and has a tool blade  512 . It differs from the folding tool  210  principally in the design of the locking mechanism. In the illustrated example, the tool blade  512  is a knife blade including a tang spline opening  526  formed in the tang  518  thereof. The tang spline opening  526  includes a circumferential array of spline slots  528  which define an outer diameter D 1 . The tang spline slots  528  alternate with radially-inwardly extending tang spline teeth  530  that define an inner diameter D 2 .  
         [0069]     The handle comprises left and right frames  532  and  534 , respectively. The construction of the left and right frames  532  and  534  may be substantially similar in dimensions and material to prior art folding tools. For example, the left and right frames  532  and  534  may be formed from stamped or machined steel. The left frame  532  is generally planar and has a front end  536  and a rear end  538 . The left frame  532  has a left frame spline opening  540  formed therein at the front end  536 . The left frame spline opening  540  is substantially the same in size and shape to the tang spline opening  526 , and includes alternating spline teeth  542  and spline slots  544 . However, some portion of the left frame spline opening  540  is a continuous surface without any spline structure. In the illustrated example approximately one-half of the left frame spline opening  540  is a simple semi-circular shape.  
         [0070]     The right frame  534  is generally planar and has a front end  548  and a rear end  550 . The right frame  534  has a right frame spline opening  552  formed therein at the front end  548 . The right frame spline opening  552  is substantially the same in size and shape to the tang spline opening  526 , and includes spline teeth  554  and alternating spline slots  556 . However, some portion of the right frame spline opening  552  is a continuous surface without any spline structure. In the illustrated example approximately one-half of the right frame spline opening  552  is a simple semi-circular shape.  
         [0071]     A lock member  560  is provided which taken together is generally semi-cylindrical member having a left end  562  and a right end  564 . The lock member  560  includes, in left-to-right order, a release button  566  disposed at the end of a central shaft  570 , and a spline ring  572 . The lock member  560  may be integrally formed from steel or a similar material. The central shaft  570  has an outer diameter slightly smaller than the inner diameter D 2 . The spline ring  572  includes a circumferential array of spline ribs  578  which define an outer diameter slightly smaller than the outer diameter D 1 . The spline ribs  578  alternate with radially-inwardly extending spline grooves  280  that define an inner diameter slightly smaller than the inner diameter D 2 . Chamfered surfaces, shown in exemplary form at  582 , may be provided to ease operation of the lock member  560 . A semi-cylindrical cross-shaft  601  is disposed next to the lock member  560  and has an outer diameter slightly smaller than the inner diameter D 2 .  
         [0072]     The folding tool  510  is assembled as follows. The lock member  560  is inserted into the right frame  534  so that the spline ring engages the right spline opening  552 . A right side plate  584  is attached to the outside of the right frame  534  with the illustrated rivets  586  or other suitable means. The right side plate  584  includes a cup  588  which covers the right spline opening  552  and retains a spring  590 , such as the illustrated coil spring, between the right frame  534  and the right side plate  584 .  
         [0073]     The tang spline opening  526  of the tool blade  512  fits over the lock member  560 . The left frame spline opening  540  fits over the lock member  560  as well. A retainer plate  594  fits over the outer surface of the left frame  532  to retain the lock member  560  in position. The retainer plate  594  is attached to the left frame  532  by the illustrated rivets  598  or other suitable means, and includes an opening therein  596  through which the release button  266  passes. A left side plate  600  is attached to the left frame  532  as well. It may be made of a material suitable for decorative or grip-enhancing purposes, such as rubber, plastic, wood, etc.  
         [0074]     In this embodiment, the cross-shaft  601  engages the non-splined portions of the left and right frame spline openings  540  and  552 , described above. It cooperates with the lock member  560  to form a shaft for the tool blade  512  to rotate above when the lock member is in the released position. However, the cross-shaft  601  does not move with the lock member  560 . Thus, the user only depresses the lock member  560  in order to release the tool blade  512 . The cross-member  601  serves to align the various components of the folding tool  510 . If desired, it may also be used as a fastener to hold the folding tool  510  together. For example, the ends of the cross-shaft  601  may be made of a size selected to create an interference fit with the left and right frame spline openings  540  and  552 , or it could be brazed to the left and right frames  532  and  534 , or the ends of the cross-shaft  601  could be peened over the outsides of the frame spline openings in a fashion similar to a rivet.  
         [0075]     The foregoing has described a folding tool. While specific embodiments of the present invention have been described, it will be apparent to those skilled in the art that various modifications thereto can be made without departing from the spirit and scope of the invention. For example, while the lock members  60 ,  160 , and  260 , the tool blade tang spline openings  26 ,  126 , and  226 , and the frame spline openings  40 ,  52 ,  152 ,  240 , and  252  have all been depicted in the illustrated examples as having spline structures disposed around their full circumference, the spline structures may be formed only part way around one or more of these elements, so long as at least one pair of complementary spline elements are engaged in the desired locking positions such that the tool blade is prevented from rotation relative to the handle. Accordingly, the foregoing description of the preferred embodiment of the invention and the best mode for practicing the invention are provided for the purpose of illustration only and not for the purpose of limitation, the invention being defined by the claims.