Abstract:
A rotatable tool for chip removing machining, including a basic body having front and rear ends between which a first center axis extends with which an envelope surface is concentric, the front end including a jaw delimited by two torque-transferring drivers and an intermediate bottom in which a center hole extending axially inside the basic body mouths, and a bore for a locking screw extending radially between the center hole and the envelope surface. A loose top has front and rear ends between which a second center axis extends, in the extension of which a pin protruding from the rear end extends that is delimited by a free end surface and an envelope surface in which a shoulder surface is included for the locking screw arranged in the radial bore. A countersink axially spaced apart from the end surface is formed in the envelope surface of the pin of the loose top for the receipt of a snap-in member arranged along the inside of the center hole to provisionally clamp the pin in the center hole when the locking screw is not tightened.

Description:
[0001]    This application claims priority under 35 U.S.C. §119 to Swedish Patent Application No. 0950850-8, filed on Nov. 10, 2009, which is incorporated by reference herein in its entirety. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to a rotatably tool for chip removing machining of the type that includes, on one hand, a basic body having front and rear ends between which a first center axis extends with which an envelope surface is concentric, the front end including a jaw delimited by two torque-transferring drivers and an intermediate bottom in which a center hole extending axially inside the basic body mouths, and a bore for a locking screw extending radially between the center hole and the envelope surface, and on the other hand a loose top that includes front and rear ends between which a second center axis extends, in the extension of which a pin protruding from the rear end extends that is delimited by a free end surface and an envelope surface in which a shoulder surface is included for a locking screw arranged in the radial bore. The invention also relates generally to a loose top and a basic body as such. Tools of the kind in question are suitable for chip removing or cutting machining (drilling and milling, respectively) of workpieces of metal, such as steel, cast iron, aluminium, titanium, yellow metals, etc. The tools may also be used for the machining of composite material of different types. 
       BACKGROUND OF THE INVENTION 
       [0003]    More recently, drilling tools as well as milling tools have been developed, e.g., in the form of shank-end mills, which, contrary to integral solid tools, are composed of two parts, viz. a basic body and a head detachably connected with the same and thereby being replaceable, and in which head the requisite cutting edges are included. In such a way, the major part of the tool can be manufactured from a comparatively inexpensive material having a moderate modulus of elasticity, such as steel, while a smaller part, viz. the head, can be manufactured from a harder and more expensive material, such as cemented carbide, cermet, ceramics and the like, which gives the requisite cutting edges a good chip-removing capacity, good machining precision and long service life. In other words, the head forms a wear part that can be discarded after wear-out, while the basic body can be re-used several times (e.g., 10 to 20 replacements). A now recognized denomination of such cutting edge-carrying heads is “loose tops”, which henceforth will be used in this document. 
         [0004]    Drilling tools as well as milling tools of the loose top type may be divided into a plurality of different categories depending on the ideas on which the designs are based. To one of these categories tools belong that are based on the use of a basic body and a loose top of the type initially mentioned, i.e., a basic body having a front jaw and a hole mouthing in the bottom of the jaw, into which hole a pin of the loose top can be inserted in order to center the loose top. This tool design presupposes that the loose top is mounted and dismounted by being inserted axially into and out of, respectively, the jaw of the basic body. An example of a tool of this type realized in the form of a drill is disclosed in U.S. Pat. No. 6,012,881 (see also U.S. Pat. No. 6,109,841). Other examples are disclosed in Swedish patent applications SE 0900844-2 and SE 0900845-9. 
         [0005]    Drills of the loose top type are often mounted projecting vertically downward, or at least directed generally downward, from the holder in the driving machine, which in turn is situated above a table on which a workpiece can be placed. For time-saving reasons, it is desirable upon replacement of the loose tops to dismount the individual, worn loose top directly from the basic body clamped in the holder of the machine, i.e., without first needing to detach the proper basic body from the holder. In an analogous way, the replacing, fresh loose top is mounted directly in the basic body remaining in the holder. In other words, the basic body is detached from the holder of the machine only when the same has worn out or alternatively when it should be replaced by a drill having another dimension. 
         [0006]    Previously known drills of the type that requires axial movement of the loose top into and out of a downwardly open jaw in the basic body, present in this respect annoying problems for the operator. Thus, it is required that the operator when mounting holds the loose top with one hand, while the other hand tightens the locking screw. However, the drill is often situated deep inside the machine, and therefore the operator has to lean or bend far in over the subjacent table. To overcome this posture in a convenient and reliable way, the operator would theoretically need an additional hand to lean against the table. A compromise between these three incompatible desires will therefore in practice be that the operator leans one arm against the table and uses the hand of this arm to passably retain the loose top in the jaw, while the hand of the other arm is utilized to tighten the locking screw. However, such compromises are most unsatisfactory, not only in respect of the ergonomics of the operator, but also in respect of the possibility of quickly and distinctly mounting the loose top in the correct position. In this connection, it should be pointed out that if the operator loses the grip of the loose top before this has been fixed properly, the loose top may come loose and disappear down into the machine; which is something that in turn may give rise to a time-consuming search operation. 
         [0007]    In U.S. Pat. No. 4,950,108, a loose top drill is disclosed in which the loose top is fixed in the front end of a basic body by two axial locking screws, which are tightened in a threaded, axial hole each, which mouths in the front end of the basic body. In the interface between the loose top and the basic body, a male member is arranged, which per se is spring-loaded, but which consists of a centering pin that does not have any capability of provisionally clamping the loose top before some one of the two locking screws has been tightened. 
         [0008]    The present invention aims at obviating the above-mentioned problems and at providing an improved tool of the kind in question. Therefore, an object of the invention is to provide a loose top tool, the loose top of which can be mounted in and dismounted out of, respectively, the jaw in a basic body of the tool in a convenient, quick and reliable way. In particular, the requisite replacement of loose tops should be possible to be carried out without neither the worn loose top nor the new and fresh one running an obvious risk of being lost in or adjacent to the drilling machine in question. In addition, unintentional incorrect mounting of the loose top should efficiently be counteracted. 
       SUMMARY OF THE INVENTION 
       [0009]    In an embodiment, the invention provides a rotatable tool for chip removing machining, including a basic body having front and rear ends between which a first center axis extends with which an envelope surface is concentric, the front end including a jaw delimited by two torque-transferring drivers and an intermediate bottom in which a center hole extending axially inside the basic body mouths, and a bore for a locking screw extending radially between the center hole and the envelope surface. A loose top has front and rear ends between which a second center axis extends, in the extension of which a pin protruding from the rear end extends that is delimited by a free end surface and an envelope surface in which a shoulder surface is included for the locking screw arranged in the radial bore. A countersink axially spaced apart from the end surface is formed in the envelope surface of the pin of the loose top for the receipt of a snap-in member arranged along the inside of the center hole to provisionally clamp the pin in the center hole when the locking screw is not tightened. 
         [0010]    In another embodiment, the invention provides a loose top for rotatable tools for chip removing machining, including front and rear ends between which a center axis extends, in the extension of which a pin protruding from the rear end extends that is delimited by a free end surface and an envelope surface in which a shoulder surface is included for a locking screw. A countersink axially spaced apart from the end surface is formed in the envelope surface of the pin for receipt of a snap-in member in a co-operating basic body of the tool. 
         [0011]    In yet another embodiment, the invention provides a basic body for rotatable tools for chip removing machining, including front and rear ends between which a center axis extends with which an envelope surface is concentric, the front end including a jaw delimited by two torque-transferring drivers and an intermediate bottom in which a center hole extending inside the basic body mouths for the receipt of a pin on a co-operating loose top, and a bore for a locking screw extending radially between the center hole and the envelope surface. A snap-in member spaced apart from the bore for the locking screw is arranged on the inside of the center hole to provisionally clamp the pin of the loose top in the center hole when the locking screw is not tightened. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate the presently preferred embodiments of the invention, and together with the general description given above and the detailed description given below, serve to explain features of the invention. 
           [0013]      FIG. 1  is a partly sectioned perspective view of a loose top tool in the form of a drill, the basic body and loose top of which are shown in a composed, operative state; 
           [0014]      FIG. 2  is an exploded perspective view showing the loose top separated from the basic body; 
           [0015]      FIG. 3  is an enlarged exploded view showing a jaw included in the basic body in top perspective view and the loose top in bottom perspective view; 
           [0016]      FIG. 4  is a partial side view showing a front part of the basic body; 
           [0017]      FIG. 5  is a cross section V-V in  FIG. 4 ; and 
           [0018]      FIG. 6  is an exploded view corresponding to  FIG. 3 , which illustrates an alternative embodiment of a loose top drill. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0019]    In the drawings, the invention has been exemplified in the form of drilling tools in two different embodiments, viz. a first embodiment according to  FIGS. 1-5  and a second one according to  FIG. 6 . The drilling tool shown in  FIGS. 1 and 2  includes a basic body  1  and a loose top  2  in which the requisite cutting edges  3  are included. In its composed, operative state according to  FIG. 1 , the tool is rotatable around a center axis designated C, more precisely in the direction of rotation R. In  FIG. 2 , it is seen that the basic body  1  includes front and rear ends  4 ,  5  between which a center axis C 1  specific to the basic body extends. In the backward direction from the front end  4 , a cylindrical envelope surface  6  extends in which two chip flutes  7  are countersunk, which in this case are helicoidal, but which also may be straight. In the example, the chip flutes  7  end in a collar included in a rear part  8  intended to be attached in the driving holder of the drilling machine in question. 
         [0020]    Also the loose top  2  includes front and rear ends  9 ,  10  and an own center axis C 2 , with which two envelope part surfaces  11  are concentric. In the loose top, two chip flute sections  12  are also included, which form extensions of the chip flutes  7  of the basic body, when the loose top is mounted onto the basic body. If the loose top  2  is centered correctly in relation to the basic body, the individual center axes C 1  and C 2  coincide with the center axis C of the composed drilling tool. 
         [0021]    Since the major part of the basic body  1  lacks interest in connection with the invention, henceforth only the front end portion thereof will be illustrated together with the loose top  2 , more precisely on an enlarged scale in  FIGS. 3-5 . 
         [0022]    As is seen in  FIG. 3 , a jaw  13  is formed in the front part of the basic body  1  and delimited by two diametrically spaced-apart drivers  14   a ,  14   b  as well as by an intermediate bottom  15  in the form of a plane surface. In the bottom surface  15 , which in this case serves as an axial support surface for the loose top, a center hole  16  mouths in which a centering pin  17  is insertable that protrudes axially backward from the rear end  10  of the loose top  1 , which rear end  10  has the shape of a plane axial contact surface that can be pressed against the bottom surface  15  of the jaw. The drivers  14   a ,  14   b  include non-compliant lugs, in contrast to elastically compliant branches. The insides  18   a ,  18   b  of the drivers  14   a ,  14   b  form side support surfaces for two opposite side contact surfaces  19   a ,  19   b  of the loose top  2 . In this case, the hole wall of the center hole  16  is cylindrical and extends axially so far into the basic body  1  that a radial hole or bore  20  (see also  FIG. 5 ) can mouth therein with one end thereof. This radial bore  20 , the opposite end of which mouths in the envelope surface  6 , includes a female thread that can co-operate with a male thread  26  of a locking screw  21 , which is movable in and out of the bore  20  and serves as a tightening device for the pin  17 . 
         [0023]    Like the center hole  16 , the centering pin  17  has a generally cylindrical basic shape. More precisely, the centering pin  17  is delimited by a cylindrical envelope surface  22  and a plane end surface  23 . Between the envelope surface  22  and the end surface  23 , a conical transition surface  24  may advantageously be formed to facilitate the insertion of the centering pin into the center hole  16 . In an analogous way, a conical, ring-shaped surface  25  is formed between the plane bottom surface  15  of the jaw  13  and the center hole  16 . 
         [0024]    In  FIG. 3 , it is shown how the male thread  26  of the locking screw  21  extends essentially along the entire length of the locking screw, more precisely between a rear or outer end  27  in which a key grip  28  is formed, and a front or inner end  29 . As is seen in  FIG. 2 , said front end includes a plane, circular end surface  30  and a conical transition surface  31  between the end surface  30  and the thread  26 . 
         [0025]    In  FIG. 3 , it is furthermore seen that the pin  17  of the loose top includes a shoulder surface  32  that is surrounded by two inclined chamfer surfaces  33   a ,  33   b . All these surfaces  32 ,  33   a  and  33   b  may be plane, the obtuse angle between the surfaces  32  and  33   a  advantageously being approximately equally great as the angle between the front end surface  30  of the locking screw and the conical transition surface  31 . The surfaces  32 ,  33   a  and  33   b  together delimit a chute that opens in the envelope surface of the pin  17 . 
         [0026]    When the loose top  2  is to be mounted in the jaw  13 , the same is inserted between the drivers  14   a ,  14   b , the centering pin  17  being inserted into the center hole  16  until the rear end surface  10  of the loose top is pressed against the bottom surface  15  of the jaw. In this state, the locking screw  21  is somewhat unscrewed from the bore  20 . As is seen in  FIG. 5 , the shoulder surface  32  of the centering pin  17  is initially inclined in relation to the front end surface  30  of the locking screw (see also  FIG. 2 ). When the locking screw is tightened with the purpose of fixing the loose top, the contact between the front end surface  30  of the locking screw and the shoulder surface  32  will therefore ensure a turning of the centering pin and thereby the loose top in its entirety. In such a way, the side contact surfaces  19   a ,  19   b  of the loose top are pressed against the side support surfaces  18   a ,  18   b  on the insides of the drivers  14   a ,  14   b . Simultaneously, the contact between the cone surface  31  of the locking screw and the chamfer surface  33   a  of the centering pin entails that an axial tensile force, which presses the end surface  10  of the loose top against the bottom surface  15  of the jaw  13 , is applied to the centering pin. In other words, the axial clamping of the loose top is in this case ensured by the engagement of the locking screw in the chute in the centering pin. 
         [0027]    It should be evident that if the drilling tool is vertically mounted in a machine with the jaw  13  opening downward, the loose top  2  has to, in one way or the other, be retained in the jaw  13  before the locking screw  21  finally is tightened. As has been mentioned by way of introduction, this has previously been effected in a manual way by the hand that has not been occupied by tightening the locking screw (with the accompanying disadvantages). 
         [0028]    In accordance with the invention, a provisional clamping is ensured of the loose top in connection with mounting and dismounting in a mechanical way instead of a manual one, more precisely by the loose top being attached by snap action in the jaw. For this purpose, a snap-in member designated  34  is arranged at the center hole of the basic body  1 , which snap-in member, on one hand, can yield, and on the other hand engage a countersink  35  in the centering pin  17  of the loose top. In the shown embodiment, the snap-in member  34  is a lock body in the form of a ball that is mounted in a cartridge  36  together with a spring  37  (see  FIG. 5 ). More precisely, the spring  37  is a compression spring, which always aims to press out the ball toward an end position and against the action of which the ball can be pressed into the cartridge. The cartridge  36 , and thereby the ball  34 , is mounted in a second bore  38 , which extends between the envelope surface  6  of the basic body and the center hole  16 . This second bore  38  is advantageously placed approximately diametrically opposite the first bore  20 . Although the cartridge can be mounted in various ways in the bore  38 , in the example, a threaded joint is preferred that includes a male thread  39  outside the cartridge and a female thread in the bore  38 . In such a way, the cartridge can easily be dismounted from the bore, e.g., in connection with possible damage. 
         [0029]    The countersink  35  in the centering pin  17  of the loose top is advantageously a long narrow groove that extends peripherally along the envelope surface  22  of the centering pin and is spaced apart from the end surface  23 . By the fact that the groove has a certain, peripheral length extension, the minimal turning of the centering pin, which arises when the locking screw  21  is tightened, will not entail that the ball  34  loses its engagement with the groove. 
         [0030]    The cartridge  36  is mounted in such a way that the ball  34  normally projects one or a few tenth of a millimeter from the inside of the center hole  16 . Simultaneously, the inner end  29  of the locking screw  21  is distanced from the center hole (although the same may be situated near the same). When the centering pin is inserted into the center hole  16 , the ball  34  is pressed away against the action of the spring  37  until the groove  35  is located on a level with the ball. In this state, the ball provides for a provisional clamping of the centering pin—and thereby the loose top—after which final fixation of the loose top can be effected by tightening the locking screw  21 . 
         [0031]    It should be pointed out that the spring force, by which the ball  34  is actuated, may be very moderate. Therefore, when dismounting the loose top, after the loosening of the locking screw  21 , the spring force does not offer any appreciable resistance to manual, axial retraction of the loose top from the jaw  13 . 
         [0032]    A fundamental advantage of the invention is that the operator only has to use one hand for the proper mounting and dismounting operation, while the other hand can be utilized for other purposes, e.g., to support the upper part of the body when required. Replacement of the loose top is facilitated even if the basic body would be mounted in another way than vertically in a co-operating machine, e.g., horizontally, as well as when the same not at all is applied in any machine. In the last-mentioned case, the provisional snap-in fastening of the loose top makes that the operator can use one of the hands to fix the basic body, while the other is utilized to tighten the locking screw. 
         [0033]    Reference is now made to  FIG. 6  which illustrates an alternative tool embodiment, which differs from the previously described embodiment only in respect of how the loose top is locked in the jaw  13  of the basic body. Thus, in this case, the shoulder surface  32  of the centering pin  17  for the locking screw  21  extends all the way along the length extension of the centering pin. In addition, two side contact surfaces  19   a ,  19   b  of the loose top  2  are inclined in relation to each other (and not parallel as in the preceding example), and co-operate with likewise inclined side support surfaces  18   a ,  18   b  on the insides of the drivers  14   a ,  14   b . When the locking screw  21  is tightened against the shoulder surface  32 , the loose top is turned so that the side contact surfaces  19   a ,  19   b  are pressed against the side support surfaces  18   a ,  18   b , which by the inclination thereof form a dovetail groove that prevents axial retraction of the loose top from the jaw. 
         [0034]    Another difference between this embodiment and the preceding one is that axial contact surfaces  40   a ,  40   b  of the loose top  2  are pressed against axial support surfaces  41   a ,  41   b  formed on the front ends of the drivers  14   a ,  14   b  instead of in the bottom of the jaw  13 . In other respects, the provisional snap-in fastening of the loose top is analogous to the previously described one in that a spring-loaded ball  34  in a cartridge  36  can engage a groove  35  on the centering pin  17  of the loose top. 
         [0035]    It should be noted that two flushing fluid channels  42  running inside the basic body  1  co-operate with two through channels  43  in the loose top  2 . In the embodiment according to  FIGS. 1-5 , the corresponding channels  42  mouth directly in the envelope surface of the basic body without being extended through the loose top. In both cases, however, the channels  42  formed in the basic body are in a satisfactory way spaced apart from the two radial bores  20 ,  38 . 
         [0036]    While the invention has been disclosed with reference to certain preferred embodiments, numerous modifications, alterations, and changes to the described embodiments are possible without departing from the sphere and scope of the invention, as defined in the appended claims and their equivalents thereof. For example, instead of a ball loaded by a spring, also other spring-loaded lock bodies may accordingly be a possibility, e.g., plugs. Also other snap-in members than spring-loaded lock bodies may be used to realize the invention. For instance, it is possible to mount a resilient leaf, or another member, in the inside of the center hole, which leaf, on one hand, can engage a groove or a countersink in the centering pin of the loose top, and on the other hand yield in connection with mounting and dismounting of the loose top. The invention may furthermore be applied to other rotatable cutting tools than drills, e.g., milling cutters, such as shank-end mills. In conclusion, it should be emphasized that the yielding snap-in member according to the invention does not have any operatively fixing function, in that reliable fixation of the loose top is carried out exclusively by the locking screw. In other words, the diminutive force exerted on the ball by the exemplified spring is entirely inadequate to resist the cutting forces acting on the loose top during the rotation of the tool. Accordingly, it is intended that the invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims.