BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to means for attaching saw blades to power tools, and in particular to a device that can secure blades of various designs and thicknesses to the driving member of a reciprocating saw.  
           [0002]    The frictional forces encountered by saw blades used in reciprocating tools such as scroll saws, jigsaws or saber saws necessitate a secure blade clamping mechanism. Early blade clamp designs required the use of an additional tool for securing the blade and placed limitations on the shape or features of compatible saw blades. Subsequently, various improvements in this area have focused on simplifying blade mounting and removal and increasing the saw blade compatibility while maintaining a secure clamp. Still many of these designs suffer from problems such as insufficient clamping strength, requirement for excessive user force, complexity in design and manufacture, and limitations on the shape of compatible saw blades.  
         BRIEF SUMMARY OF THE INVENTION  
         [0003]    It is an object of this invention to describe the design of a blade clamp of simple construction that is compatible with and readily mounted to a variety of reciprocating saws.  
           [0004]    It is a further object of this invention that this blade clamp provides a secure clamping mechanism yet permits rapid, toolless mounting of saw blades while maintaining compatibility with multiple blade designs.  
           [0005]    It is a further object of this invention to describe a blade clamp body comprising all of the elements necessary to secure a blade, such that the design can function apart from and be refined independently of other features or mounting means such as the driving member of a reciprocating tool.  
           [0006]    These objects are achieved by providing a design wherein the operating means for securing and releasing the blade are one in the same. A wedging member is coupled with a spring-biased operating means such that in the rest state, the operating means urges the wedging member into a clamping position. The user may readily handle the operating means to overcome the biasing force thereby directly moving the wedging member, allowing insertion or removal of a saw blade.  
           [0007]    The blade-receiving cavity is designed such that a multitude of blade shapes and thicknesses can be accommodated. Blade mounting is intuitive and can be performed quickly and easily without compromising clamping strength. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    A better understanding of the invention, and of the various embodiments thereof, may be derived from the following description and the accompanying drawings in which:  
         [0009]    [0009]FIG. 1 is a schematic representation of a jigsaw incorporating the first embodiment of the invention.  
         [0010]    [0010]FIG. 2 is a longitudinal cross-sectional view of just the blade clamp body of the first embodiment.  
         [0011]    [0011]FIG. 3 is a perspective view of two saw blades mountable in the present invention.  
         [0012]    [0012]FIG. 4 is a cross-sectional view of the first embodiment of the blade clamp in the rest state.  
         [0013]    [0013]FIG. 5 is a side view of the functional end of the blade clamp with a blade in the clamping position. Certain features of the invention and the saw blade not visible in this view are identified by dashed lines to indicate their position relative to the visible features.  
         [0014]    [0014]FIG. 6 is a perspective view of the first embodiment of this invention. In a like fashion to the previous figure, a feature of the invention, in this case the general outline of the clamp body  12 , is identified by dashed lines.  
         [0015]    [0015]FIG. 7 is a longitudinal cross-sectional view of the first embodiment of the blade clamp in the releasing position. The plane visualized is located laterally with respect to and parallel to the plane of symmetry.  
         [0016]    [0016]FIG. 8 is a perspective view of a cross-section of the blade clamp body and driving member of the second embodiment of this invention.  
         [0017]    [0017]FIG. 9 is a cross-sectional view of the blade clamp body and the wedging member of the second embodiment.  
         [0018]    [0018]FIG. 10 is a perspective view of the second embodiment of the invention in the clamping position with a mounted saw blade and fastened to the driving member. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    The present invention is applicable to reciprocating saws in general, including those commonly known as jigsaws, saber saws, or scroll saws. A schematic version of a jigsaw  2  is pictured in FIG. 1 exemplifying the common elements of these saws, which generally include an operator handle  4 , a driving member  6  and a housing  8 . The housing  8  contains a motor and a gear for driving the reciprocating movement of the driving member  6 . A blade clamp, shown generally as  10 , may be fastened to the driving member  6  using any of a variety of methods well-known in the art. Alternatively, the driving member  6  and blade clamp  10  may comprise a single contiguous entity.  
         [0020]    Cross-sectional views of a clamp body  12  of a first embodiment of the blade clamp  10  are shown in FIGS. 2 and 4, revealing a blade-receiving cavity  14  which is defined by two parallel side faces  16  and  18 , a grooved longitudinal face  20  and an abutment  22 . The spacing between the two side faces  16  and  18  permits mounting of blades of various thickness. A generally V-shaped groove runs along the entire length of the grooved longitudinal face  20 . Optionally, the grooved longitudinal face  20  may be further characterized by a notch  24  which may be generally rectangular in shape as shown in FIG. 2.  
         [0021]    Two examples of reciprocating saw blades compatible with this blade clamp design are illustrated in FIG. 3. A first blade  26  has a generally rectangular mounting portion  28  and a region bearing cutting teeth  30 . A generally rectangular mounting portion  32  of a second blade  34  has rectangular lateral extensions  36  and  38 , one of which is receivable by the notch  24  when the blade  34  is inserted into the cavity  14 . Additional blade features such as an aperture  40  are not relevant to the mounting or clamping of the blade  34  to the blade clamp  10 .  
         [0022]    In this embodiment (as shown in FIGS. 2, 4 and  5 ), slots  42  and  44  pass through the side faces  16  and  18  respectively and are slanted with respect to a longitudinal axis  46  of the clamp body  12  forming first inclined surfaces  48  and  49  and second inclined surfaces  50  and  51 .  
         [0023]    As shown most clearly in FIGS. 4, 5 and  6 , a sleeve  52  surrounds the blade-receiving portion of the clamp body  12  in close proximity but freely movable generally along the longitudinal axis  46 . An angled protrusion  56  of the sleeve  52  (best visualized in FIG. 5) creates a rear cavity  58  between a rear internal face  60  of the sleeve  52  and a rear face  62  of the clamp body  12 . This cavity  58  permits nonlinear movement of the sleeve  52  with respect to the long axis  46  of the clamp body, as seen in FIG. 7 and described below. An equivalent functionality would be provided for if either the rear face  62  or the rear internal face  60  were inclined with respect to this long axis  46  in the region that the sleeve  52  straddles the clamp body  12 . A first internal abutment  68  of the sleeve  52  cooperates with a protruding abutment  70  of the clamp body  12  to create a front cavity  72 . A biasing means, such as a coil spring  74  or alternatively a globule of elastomeric material  76  is positioned in the front cavity  72  and tends to move the sleeve  52  along the longitudinal axis  46  away from the driving member  6 .  
         [0024]    Clamping of a saw blade  26  into the blade-receiving cavity  14  is accomplished by a wedging member, in this case a cylindrically-shaped pin  78 , passing through the slots  42  and  44  as well as through paired apertures  80  and  82  in the sleeve  52 . The pin  78  is preferably maintained within the apertures  80  and  82  using disc-shaped extensions  84  and  86  (see FIG. 4), such attachment permitting free rotation of the pin  78 .  
         [0025]    In a rest position of the blade clamp  10  pictured in FIG. 6, the sleeve  52  which is freely slidable along the clamp body  12  has been moved by the spring  74  until a second internal abutment  88  (see FIG. 5) of the sleeve  52  comes into contact with the protruding abutment  70  of the clamp body  12 .  
         [0026]    To mount a blade, the sleeve  52  is moved against the force of the spring  74  or elastomeric material  76  as illustrated in FIG. 7. With respect to the longitudinal axis  46 , the pin  78  is thereby moved axially towards the abutment  22 . At the same time, it is biased away from the grooved longitudinal face  20  by the second inclined surfaces  50  and  51 , enlarging the available access to the blade-receiving cavity  14 . The sleeve  52  moves primarily axially as well, but a front portion  90  of the rear internal face  60  is also driven towards rear face  62  of the clamp body  12  (see FIG. 7). Movement of the sleeve  52  may be facilitated by an arcuate surface  92  on the sleeve  52  suited for manual manipulation by a user of the blade clamp  10 . Alternatively the sleeve may include a manually gripable element  94  to serve the same purpose as schematically illustrated in FIG. 5.  
         [0027]    In a releasing position of the blade clamp  10  pictured in FIG. 7, the operator may insert the mounting portion  28  of a saw blade  26  into the cavity  14  bringing a top edge  96  of the blade into contact with the abutment  22 . A saw blade  34  with rectangular extensions  36  and  38  of the proper dimensions will be received by the notch  24  in the blade-receiving cavity  14 , allowing a first edge  98  of the blade  34  to rest against the grooved longitudinal face  20 . A saw blade without extensions  26  is similarly inserted into the cavity  14  until it rests against the abutment  22  and grooved longitudinal face  20 . Either blade type tends to be centered with respect to the blade receiving cavity  14  when it is received by the grooved longitudinal face  20 .  
         [0028]    Once the user withdraws the force acting against the spring  74 , the sleeve  52  moves generally along the longitudinal axis  46 . As a result, the pin  78  is urged into contact with the second edge  100  of the saw blade  26  by the first inclined surfaces  48  and  49 , thereby securely wedging the blade against the grooved longitudinal face  20 . This state (see FIG. 5) is considered the clamping position.  
         [0029]    Such wedging action by the pin  78  provides a secure clamping action. During the downstroke of reciprocation by the driving member  6 , the blade  26  is driven into and its movement prohibited by the abutment  22 . During the upstroke, even as frictional forces tend to pull the blade out of the cavity  14 , the friction of the pin  78  on the blade  26  will tend to move the pin  78  along the first inclined surfaces  48  and  49 , thereby increasing the clamping force on the saw blade  26 . Use of a saw blade  34  with lateral extensions  36  and  38  provides additional clamping security.  
         [0030]    A second and preferred embodiment of the blade clamp is pictured in FIG. 810. In this case, a clamp body  400  includes means  402  and  404  for attaching to the driving member  6 , although the clamp body  400  and driving member  6  may also be contiguous. As in the first embodiment, a blade-receiving cavity  406  is defined by two side faces  408  and  410 , a grooved longitudinal face  412 , and an abutment  413 , which may optionally be grooved or partially grooved. However, the blade-receiving cavity  406  is partially defined by parallel second and third longitudinal faces  414  and  415 . In addition, the blade-receiving cavity  406  is configured to receive less of the mounting portion  32  of an inserted blade  34 . As a consequence, saw blade  34  is compatible with this blade-receiving cavity  406  since the rectangular lateral extensions  36  and  38  of saw blade  34  do not enter the blade-receiving cavity  406  when the mounting portion  32  is mounted so as to come in contact with the abutment  413 .  
         [0031]    Slots  416  and  418  pass through the side faces  408  and  410  respectively and are inclined with respect to a longitudinal axis  420  of the the clamp body  400  forming first inclined surface  422  plus second inclined surfaces  424  and  425 . The second inclined surfaces  424  and  425  may optionally be interrupted by curved openings  426  and  427  (see FIGS. 8 and 10) which facilitate assembly of the invention by allowing insertion of a wedging member  428 . The wedging member  428  passes through the slots  416  and  418  as seen in FIG. 9. Like the grooved longitudinal face  412  or optionally the abutment  413 , the wedging member  428  may be circumferentially grooved as an additional means to center an inserted blade within the blade-receiving cavity  406 . The protruding ends  429  and  431  of the wedging member  428  incorporate a disc shape to retain the wedging member  428  within the clamp body  400  and allow it to freely rotate about its axis of symmetry. The optional curved openings  426  and  427  are fashioned such that the disc-shaped aspects of the wedging member  428  may pass through the slots  416  and  418  during assembly.  
         [0032]    The function mediated by the sleeve  52  in the first embodiment is carried out by two L-shaped levers  430  and  432  which straddle the clamp body  400  and are physically linked at one extremity by a joining element with a front aspect  434  and a top aspect  435 . The other extremity of each lever may be fork-shaped (as in FIG. 10) or rather have an elongate slot (not pictured) so as to fit about the protruding ends  429  and  431  of the wedging member  428 . The levers  430  and  432  are secured to and free to pivot about two protrusions  436  and  438  that pass through cavities in the corners of each lever. This pivot point lends the user a mechanical advantage when manipulating the front aspect of the joining element  434  to move the wedging member  428  during the mounting or releasing of a blade. The extremities of the L-shaped levers are designed with either a fork shape or an elongate slot so that the lever may freely rotate while coupled to the wedging member  428  even though the arc of rotation is not consistent with the linear path of travel of the wedging member  428  through the slots  416  and  418 .  
         [0033]    Free rotation of the levers  430  and  432  is influenced by a biasing means, in this case a coil spring  440 , that is secured between a cylindrical element  442  on the clamp body  400  and the front aspect of the joining element  434  (see FIG. 10) which functions similarly to the internal abutment  68  of the sleeve  52  of the first embodiment. This front aspect  434  may include a lip  443  to further secure the coil spring  440 . The coil spring  440  is retained in place by mating with the cylindrical element  442  which is shaped such that it can protrude into the interior of the coil spring  440  itself. Elastomeric material, if it were used in place of a coil spring, is ideally configured to mate with the cylindrical element  442  as well. The coil spring  440  acts on the joining element to pivot the levers such that the acute angle between the long axis  444  of levers  430  and  432  and the long axis  420  of the clamp body  400  is increased. In a manner similar to the sleeve  52  of the first embodiment, the biasing action of the spring  440  has the effect of causing the forked regions of the levers  430  and  432  to urge the wedging member  428  to move within the inclined slots  416  and  418  such that the wedging member  428  is driven towards the grooved longitudinal face  412  and away from the abutment  413 .  
         [0034]    To mount a saw blade  26  or  34 , a user presses the front aspect of the joining element  434  to directly counteract the force of the coil spring  440  on the levers  430  and  432 . The forked region of each lever urges the wedging member  428  to move within the inclined slots  416  and  418 , thereby freeing up the blade-receiving cavity  406 . After inserting a saw blade  26  or  34 , releasing the force on the front aspect of the joining element  434  allows the coil spring to rotate the levers  430  and  432  such that the wedging member  428  is pressed by the first inclined surface  422  into the second edge  100  of the mounted saw blade  26  or  34 . In a like fashion to the first embodiment, this provides a secure clamping action.  
         [0035]    The invention is not intended to be limited to the particular embodiments shown, but rather to include such alternatives, modifications and equivalents as one skilled in the art would appreciate to be within the spirit and scope of the invention as described by the appended claims
A toolless blade clamp for a reciprocating saw is disclosed comprised of a clamp body that defines a cavity for receiving a saw blade, a wedging member that traverses the cavity, operating means that is coupled with the wedging member and biasing means that acts on the operating means. In a clamping position, the operating means urges the wedging member into contact with an edge of a saw blade to securely clamp it within the cavity. In a releasing position, the operating means is manually urged by the user to bring the wedging member free of the cavity to allow insertion or removal of the saw blade.