FASTENING DEVICE FOR MILLING TOOLS AND THE LIKE, ADAPTABLE FOR VARIOUS HOLDER SIZES

Abstract: The invention relates to a fastening device or mounting of a tool holder (2) at a mandrel (1) or the like rotatable holder for example at boring machines and the like. The mandrel (1) presents a central trunnion (4) having an axial threaded bore (6) and this trunnion is used as a support for a sleeve (9) which according to the invention is slided over the trunnion (4) and presenting an external circumferential V-groove (10) and at its inner end recesses (8) complementary to the wedge means (5) of the mandrel. A fastening screw (16) is insertable in the axial threaded bore and having a head (17) engaging the outer end face of the sleeve (9). The tool holder has an opposite central opening on each side communicating with recesses (8) for the wedge and the portion of the tool holder to surround the sleeve having a number of radial locking screws with conical inner ends adapted to engage the V-groove of the sleeve.

Description: '/ FASTENING DEVICE FOR MILLING TOOLS AND THE LIKE, ADAPTABLE FOR VARIOUS HOLDER SIZES. Technical field of the invention This invention relates to a fastening device for the fastening of to a milling tool mandrel or the like rotatable carrier for example at boring or milling machines or the like. Background of the invention SE,B, 409 832 discloses a device for the fastening of a tool holder wherein an axial screw is tightened rigidly in a bore of the centre trunnion of the mandrel, said screw having a saucer like head with obliquely arranged lower side and serving as fastener for a tool holder pushed onto and over said trunnion and screw and having radially arranged locking screws with conical ends displaceable to engage the obliquely arranged lower side of the head of the screw. The intention behind the known device was to facilitate the changing of tools earlier performed by manipulating a locking screw accessible from the opposite end of the tool holder forcing same into and out from the threaded bore at the mandrel trunnion. By utilizing as suggested a central holding screw having a saucer shaped head with an inwardly inclined inner side the loosening and fastening operations are facilitated, but by moving the area of engagement for the locking elements or screws so far away axially from the cooperating axial abutment faces, the stability is endangered. This especially if the tool holder sleeve to be slided onto the mandrel trunnion is toe short, which occurs as different makers have different dimensions. The axially acting moment of the inclined surface engaging conical ends of the locking screws, will be insufficient to press the sleeve with sufficient force against the abutment face of the mandrel especially when the points of the locking screws meet the axially oriented fastening screw shank. The localization of the locking screws outside the rigid and stable mandrel trunnion might result in a heavy wear because of the leverage occurring between the tool holder and mandrel on the operation of the milling tool. The object of the invention It has been noted that the axial dimension of the central trunnion at milling machine mandrels and the like might deviate from the measure decided and even if the deviation is relatively seen very small, it might result in that the tool holder cannot engage the abutment face properly. Similarly it occurs that the sleeve portion of the tool holder does not meet the requirements of dimension and is either too long or too short axially. The drawbacks mentioned above concerning the known device is the more pronounced if also the dimensions of the cooperating parts are faulty. One aspect of this invention is to bring about a fastening device which independently of deviations from given dimensions ensures a stable fastening. Summary of the invention The invention is based on a milling machine mandrel trunnion having a threaded central bore and this trunnion is used as support for a spec fic sleeve according to the invention. The sleeve has a circumferential V-groove and also, at its one end face recesses adapted to the locking wedge of the mandrel. A fastening screw having an essentially flat disc like head is adapted to be threaded into the central trunnion bore until its head engages the outer end face of the sleeve pressing the sleeve inwardly towards the opposite facing end surface of the mandrel. The tool holder or the like has a central opening closely fitting onto the sleeve and at the inner end of the holder communicating with the recesses for a locking wedge, the tool holder body also presents three radially arranged threaded bores directed towards the centre of the central opening for locking screws having a conical inner end, said screws adapted to engage the V-groove of the sleeve secured onto the mandrel trunnion. Brief description of the drawings One embodiment of the device according to the invention will be described in detail in the following with references to the attached drawing, which schematically and in a sectional view shows a portion of a milling machine mandrel and a portion of a tool holder with the fastening device according to the invention. A detailed description of a preferred embodiment In the embodiment shown a milling machine mandrel is designated 1, a tool holder designated 2 and the whole unit with 3. At the one end of the mandrel 1 there is a central trunnion 4 and diametrically over the end face of the mandrel there is a wedge means 5 having one section on each side of the trunnion 4. The trunnion 4 has a concentrically arranged threaded bore 6. The tool holder has at its one end a concentrically arranged cylindrical bore 7 and radially therefrom extends recesses 8 intended to cooperate with and engage the wedge means 5. According to the invention there is a cylindrical sleeve 9 having an inner diameter d j _ corresponding to the outer diameter of the central mandrel 4 and an outer diameter d corresponding to the inner diameter of the cylindrical bore 7 of the tool holder 2. The outside of the sleeve 9 presents a c rcumferential V-groove 10 which is localized a distance A from the end face of the mandrel surrounding the trunnion. The portion 11 of the tool holder enclosing the sleeve 9 and also the trunnion presents a number of threaded bores 12 and into such are locking screws 13 having a conical end portion 1^ inserted. On inserting, the screws 13 will engage groove 10 and thereby lock the sleeve and tool holder together. The sleeve 9 is in turn connected to the mandrel by the configuration related engagement between the sleeve having recesses 15 complementary to the wedge 5 and the engagement between the outer face of the mandrel or trunnion and the inside of the sleeve, and in axial direction by the engagement from a tightening screw 16 having a specifically adapted head 17, the circumferential portion thereof engaging the end face 18 of the sleeve. ' As can be seen the axial length of the sleeve 9 is larger than the axial length of the trunnion 4. This ensures under all circumstances a stable and rigid mounting of the sleeve. The sleeve 9 has a length so adapted that it covers even the largest deviations in length at trunnions meaning that you do not have to risk that the screw head 17 will engage the end of the trunnion before pressing the sleeve 9 completely or to desired extent towards the end face of the mandrel 1. This means that the measure A earlier mentioned, i.e. from the end face of the mandrel to the radial central plane of the V-groove, always is equal even if the mandrel or trunnion 4 deviates from standard. The sleeves can be delivered in given and standardized outer diameter sizes d v adapted to the inner diameter of the tool holder. The diameter of the trunnion of existing mandrels serves as a base value on determining the inner diameter d. of the sleeve 9 and naturally also an individual machining may take place on side. As the measure A is to be identic or one and the same, at all sleeves and tool holders the fastening device may be used as fitting part and be changed between different tool holders and mandrels. In order to reach a stable and rigid fastening, the point of each of the locking screws on threading in, has to meet the side of the V-groove 10 remote from the mandrel in order to - on proceeding the threading - allow the conical screw ends, simultaneously as they move radially inwardly in the groove, to displace themselves and also the tool holder 2 towards the mandrel 1. In order to achieve this and the desired tightening force, the measure A must be equal with or greater than the measure B, so that the points of each of the screws -initially is localized further from the end face of the mandrel than the centre plane of the V-groove of the sleeve 9 already secured to the end face of the mandrel by means of the screw 16.

Claims: C L A I M 1. Fastening device for tool holders and the like at mandrels and similar rotatable machine parts, wherein the mandrel has a central protruding trunnion and adjacent the root portion of the same arranged wedge means and the tool holder has a central opening intended to receive a central trunnion and lateral recesses intended to cooperate with the wedge means and in its hollow portion radial bores for screw means intended to engage inclined abutment portions at the trunnion, c h a r a c t e r i z e d by that the fastening means includes a cylindrical sleeve (9) having an inner diameter (d j i) corresponding to the outer diameter of the trunnion (4) and an outer diameter (d ) corresponding to the inner diameter of the opening (7) at the tool holder (2) and with radial recesses (15) at one end adapted to the wedge means (5), and at the opposite end, a radial circumferential abutment surface and also an external circumferential essentially V-shaped groove (10), that a screw (16) having a head (17) adapted to the axially facing abutment surface of the sleeve is by threading insertable into a per εe known axial and central threaded bore (6) at the trunnion (4) for pressing the sleeve (9) against the end face of the mandrel surrounding the trunnion (4) and establishing a rigid engagement against turning between the wedge and the recesses, that the screws (13) arranged in the threaded radial bores (12) of the hollow tool holder portion surrounding the sleeve have conical inner ends (14) arranged on lightening to engage both sides of the V-shaped groove (10) in order to position the tool holder in both axial directions, that the axial, length of the sleeve (9) is at least equal and preferrably greater than any possible axial length of the central trunnion (4) at available mandrels and that the axial distance between the radial plane through the V-groove (10) of the sleeve and the abutment end face of the mandrel closely corresponds with determined axial distance between the end face of the tool holder and a radial plane through the centre of the said screws.

Inventors: MIHIC WLAJKO, MIHIC, WLAJKO
Applicants: MIRCONA AB
Application year: 1992
Main classification: B23Q3
IPC codes: B23B31, B23C5