Abstract:
A metal cutting tool assembly comprising a rigid holder blade, an insert receiving slot formed in a leading end of the holder blade and defined between a resiliently displaceable clamping jaw formed integrally with the holder blade and rigid base jaw forming part of the holder blade, spaced apart displacement and supporting surfaces respectively formed in or on the clamping jaw and the holder, and a slot opening key, with a pair of spaced apart projecting prongs of the key adapted to engage the surfaces. At least one of the prongs is displaceable with respect to the holder blade so as resiliently to displace the clamping jaw outwardly with respect to the base jaw into an opening position for insertion or removal of an insert.

Description:
FIELD OF THE INVENTION 
     This invention relates to metal cutting tool assemblies of the kind wherein an exchangeable cutting insert is releasably retained in an insert retaining slot formed in a holder blade. The invention relates particularly to such a cutting tool assembly wherein the insert is retainably clamped within the retaining slot between a resiliently displaceable clamping jaw and a rigid base jaw without the use of additional mechanical clamping means such as clamping screws or the like. 
     BACKGROUND OF THE INVENTION 
     One known form of cutting tool assembly of the kind to which the invention relates involves the so-called “wedge clamping” of the insert in the insert retaining slot. Here, the insert, having a single cutting edge, is provided with a wedge-shaped body which forcibly inserted and is retained within a correspondingly wedge-shaped retaining slot, the actual clamping of the insert within the slot being effected by the resilient outward displacement of the clamping jaw as a result of the forced insertion of the insert into the slot. With this type of cutting tool assembly, the resilient displacement of the jaw is effected by the insertion of the insert into the slot, but when it is desired to remove the insert, special means have to be provided for mechanically ejecting the insert from the slot, these means involving the direct exertion of an ejection pressure on the insert. It will be understood that both the insertion and removal of the insert is accompanied by significant friction with consequent wear on the blade jaws which are, in general, of a much softer material than that of the insert. 
     Alternatively, it is known (GB 1379637) to introduce into and clamp an insert within an insert retaining slot by first of all mechanically displacing outwardly a resiliently clamping jaw, introducing the insert into the slot and then allowing the jaw to spring back on to the insert in a clamping position. When it is desired to remove the insert from the slot, the clamping jaw is again displaced outwardly, allowing for the removal of the insert. The outward displacement of the jaw is effected using a mechanical key which is displaced in frictional contact with the inside of the clamping jaw, thereby leading to frictional wear of the jaw and/or the key. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a new and improved metal cutting tool assembly in which the above-referred-to disadvantages are substantially reduced or overcome. 
     According to the present invention, there is provided a metal cutting tool assembly comprising a rigid holder blade; an insert receiving slot formed in a leading end of the holder blade and defined between a resiliently displaceable clamping jaw formed integrally with said holder blade and rigid base jaw forming part of the holder blade; spaced apart displacement and supporting surfaces respectively formed in or on said clamping jaw and said holder; and a slot opening key, a pair of spaced apart projecting prongs of said key adapted to engage said surfaces, at least one of said prongs being displaceable with respect to said holder blade so as resiliently to displace said clamping jaw outwardly with respect to said base jaw into an opening position for insertion or removal of an insert. 
     Preferably, there is formed in the holder blade an extension slot communicating with said insert receiving slot and extending rearwardly thereof. There can be formed in the clamping jaw forwardly of said extension slot a clamping jaw aperture, said displacement surface being constituted by a rim of said clamping jaw aperture. 
     In accordance with one preferred embodiment of the present invention, the supporting surface is formed on an upper surface of said clamping jaw adjacent said extension slot, one of said prongs being adapted to project into said clamping jaw aperture whilst the other of said prongs bears on said supporting surface, whereby a levering displacement of said one prong with respect to the other prong results in the outward displacement of said clamping jaw. 
     Alternatively, and in accordance with another preferred embodiment of the present invention, the supporting surface is formed in said base jaw, said supporting surface being constituted by a rim of said base jaw aperture and wherein said opening key is provided with means for displacing said prongs apart whereby, with said prongs projecting respectively into said clamping jaw and base jaw apertures, displacement apart of said prongs results in said outward displacement of said clamping jaw. 
     Thus, with a cutting tool assembly in accordance with the present invention, displacement of the clamping jaw, whether effected by a levering action or by way of a direct, linearly directed displacement, is not accompanied by any direct contact, either with the insert or with the inner surface of the clamping jaw, and in this way damage thereto is avoided or minimized. Furthermore, introduction into and removal of the insert from the slot is not accompanied by any frictional resistance by the opposite jaw surfaces and there is therefore avoided frictional wear of these surfaces leading to an extended life of the holder blade as a whole. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the present invention and to show how the same may be put into practice by way of example, reference will now be made to the accompanying drawings, in which: 
         FIG. 1  is a side elevation of a holder blade of a cutting tool assembly in accordance with the present invention; 
         FIG. 2  is a side elevation showing the retention of a cutting insert in the holder blade shown in  FIG. 1 ; 
         FIG. 3  is a perspective view of the cutting tool assembly shown in  FIG. 2 , together with an associated retaining slot opening key; 
         FIG. 4  is a similar view to that shown in  FIG. 3 , with a modified form of retaining slot opening key; 
         FIG. 5  is a side elevation of a further form of holder blade for a cutting tool in accordance with the present invention; 
         FIG. 6  is a perspective view of the holder blade shown in  FIG. 5  and a cutting insert clampingly retained therein, together with an appropriately mounted retaining slot opening key; 
         FIG. 7  is a perspective view of a further form of cutting tool assembly in accordance with the present invention, with an associated retaining slot opening key; and 
         FIG. 8  is a perspective view of a still further form of cutting tool assembly in accordance with the present invention, with an associated retaining slot opening key. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     As seen in  FIG. 1  of the drawings, a holder blade  1  for a metal cutting tool assembly in accordance with the present invention comprises a rigid body portion  2  with which are formed integrally a clamping jaw  3  and a base jaw  4 . The clamping jaw  3  is coupled to the body portion  2  via a relatively narrow neck portion  5 , thereby allowing for a limited degree of flexible resilience of the clamping jaw  3  with respect to the body portion  2  and with respect to the base jaw  4 , the latter forming a rigid whole with the body portion  2 . 
     As can be seen in dotted lines in  FIG. 1  of the drawings, the clamping jaw  3 , in its unstressed position, has its forward tip  6  directed downwardly towards the base jaw  4  and is spaced therefrom by a distance h 1 . 
     In order to allow for the introduction of an insert  7  (shown in  FIG. 2  of the drawings) having a height h 2 , the clamping jaw  3  must be displaced upwardly in the direction of the arrow  8  ( FIG. 1 ) so that its forward tip  6  is spaced from the base jaw  4  by a distance h 3  where h 3&gt; h 2 . As seen in  FIG. 1  of the drawings, there is formed in a leading end of the holder blade  1 , and defined between opposite surfaces of the damping jaw  3  and base jaw  4 , an insert retaining slot  9 , a rear end of which communicates with a rearwardly extending extension  10  of the slot  9  and a lower, curved aperture  11 . As can be seen in  FIG. 2  of the drawings, the location of the extension  10  is such as to be bordered by the narrow neck portion  5  of the clamping jaw. The lower, curved aperture  11  is provided so as to ensure that the lower, innermost edge of the insert is properly located within the aperture  11  without encountering the slot wall. The retained insert  7  is abutted by an abutment  12  of the body portion  2 , and the upper, innermost edge of the insert is located within the extension  10 . In this way there is prevented possibly damaging abutment of the inner edges of the insert with the body portion. 
     As can furthermore be seen in  FIG. 2  of the drawings, with the insert  7  clampingly retained within the insert retaining slot  9 , the clamping jaw  3  bears clampingly downwardly on the upper surface of the insert  7  in the direction of the arrow  13 . 
     There is formed in the clamping jaw  3 , forwardly of the neck portion  5 , a throughgoing aperture  14 , whilst there is formed in the base jaw  4 , adjacent a front edge thereof, a throughgoing aperture  15 . 
     Reference will now be made to  FIG. 3  of the drawings, for a detailed description of an insert retaining slot opening key  21  and the manner in which it is used in order to open the insert retaining slot so as to allow for the introduction of the insert. As seen in  FIG. 3  of the drawings, the retaining slot opening key  21  comprises a body  22  having a pair of integrally formed legs  23 a,  23 b from which respectively project a pair of spaced-apart prongs  24 a,  24 b. 
     Located between the legs  23 a,  23 b and bearing against them is a wedge-like spacer  25  having a throughgoing threaded bare  26  through which extends a screw  27 , an upper end of which remote from the spacer  25  is coupled to a turning handle  28 . 
     Rotation of the turning handle  28  in the direction of the arrow  29  results in an inwardly-directed displacement of the spacer  25 , thereby giving rise to an outwardly-directed displacement of the legs  23 a,  23 b and a consequent outwardly-directed displacement of the prongs  24 a,  24 b in the direction of the arrows  30 a,  30 b. 
     If now, and prior to the rotation of the handle  28  so as to cause the outward displacement of the prongs  24 a,  24 b, the latter are inserted in the apertures  15 ,  14  and rotation of the handle  28  takes place in the direction of the arrow  29 , it will be readily seen that there occurs an outwardly-directed displacement of the clamping jaw  3 . As a consequence, the clamping jaw  3  effectively pivots about its narrow neck portion  5 , thereby increasing the spacing between the clamping jaw  3  and the base jaw  4  and allowing for the introduction or removal of the insert  7 . Rotation of the handle  28  in the opposite direction allows for the clamping jaw  3  to return into a clamped position, thereby clampingly retaining the insert in position. 
       FIG. 4  shows a modified form of turning key  33  having a fixed projecting prong  34 a and an eccentrically rotatable projecting prong  34 b which is coupled to a turning handle  35 , rotation of which in one sense gives rise to widening the spacing between the prongs  34 a,  34 b and rotation in the other sense from this widened spacing results in a return to the original spacing. 
     If now, as before, the prongs  34 a,  34 b are positioned within the apertures  15 ,  14 , rotation of the handle in one sense gives rise to an outwardly-directed displacement of the clamping jaw, allowing for the insertion or removal of the insert. 
     It will be appreciated that, in the embodiments shown in  FIGS. 3 and 4  of the drawings, a rim of the aperture  14  in the clamping jaw  3  constitutes a clamping jaw displacement surface, whilst a rim of the aperture  15  in the base jaw  4  constitutes a support surface. 
     Reference will now be made to  FIGS. 5 and 6  of the drawings where, as can be seen, the clamping and base jaws define between them, as before, an insert retaining slot which communicates with a rearwardly-directed extension  10  and a lower, curved aperture  11 . 
     As before, there is formed in the clamping jaw  3  a throughgoing aperture  14 , but in this embodiment there is not formed any through-going aperture in the base jaw  4 . As seen in  FIG. 6  of the drawings, a turning key  41  is formed with a pair of spaced-apart, fixed cylindrical prongs  42 ,  42 b with the prong  42 a extending through the aperture  14  whilst the prong  42 b rests on an upper fulcrum surface of the Bolder blade  1 . If now the key is rotated in the direction of the arrow  43 , it can be seen that there will be a levering displacement outwardly of the clamping jaw  3  with respect to the prong  42 b. In this embodiment, the rim of the aperture  14  serves as a displacement surface whilst the holder blade  1 , upon which rests the prong  42 , serves as a supporting fulcrum surface. 
     In a modified embodiment shown in  FIG. 7  of the drawings, a rearwardly-directed extension  10 ′ of the insert retaining slot  9  is shaped to receive the prong  42 b of the key  41 , with the other prong  43 a extends through the aperture  14 . Here again, upon rotation of the key  41  in the direction of the arrow, a levering outward displacement of the clamping jaw is effected with respect to the prong  42 b. In the case of this embodiment, the rim of the aperture  14  again constitutes a displacing surface whilst the rim of the extension  10 ′ constitutes a supporting fulcrum surface. 
     In a still further modification shown in  FIG. 8  of the drawings, an additional aperture is formed in an upper portion of the body portion  2  of the holder, adjacent to and spaced from the aperture  14  and displaced inwardly with respect to the slot extension. If now the prongs  42 a,  42 b are inserted in the apertures  14 ,  45  and the key is rotated in the direction of the arrow, levering outward displacement of the clamping jaw is effected about the fulcrum constituted by the prong  42 b, with the rim of the aperture  14  constituting a displacement surface and the rim of the aperture  45  constituting a supporting fulcrum surface. 
     Whilst in the embodiments specifically described above clamping retention of a cutting insert having substantially parallel upper and lower surfaces has been described, it will be readily appreciated that the present invention can be extended to the so-called “wedge clamping” of inserts having a wedge-shaped body portion arranged to be retained within a corresponding wedge-shaped slot formed in the holder blade. 
     It will be furthermore understood that the present invention is not restricted to any particular kind of cutting insert such as, for example, the cutting insert specifically illustrated, but is readily applicable to other forms of cutting inserts.