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(11) | EP 1 574 308 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Milling tool |
| (57) Milling tool (10) comprising a main body (11), at least a blade (12) and at least
a clamping element (13), including a threaded hole (23) for the insertion of screw
means (14), and arranged in a hollow (15) made in the main body (11), in order to
clamp, by means of the screw means (14), the blade (12) against a wall (17) of the
hollow (15). The clamping element (13) has a front surface (25) arranged in abutment
on the blade (12), a part of the front surface (25) is inclined, in use, by an angle
(α) with respect to a plane (A) orthogonal to the axis (x) of the threaded hole (23). |
FIELD OF THE INVENTION
[0001] The present invention concerns a milling tool, used essentially but not only for working wood, comprising a main body able to be made to rotate and on the periphery of which one or more blades are mounted.
BACKGROUND OF THE INVENTION
[0002] Milling tools are known, comprising a main body able to be made to rotate and on the periphery of which one or more blades are mounted, with a substantially radial arrangement, by means of which the desired working is performed. Each blade is removably associated with the main body in correspondence with a relative hollow, by means of a clamping element or block, and by at least one screw that clamps it under pressure against a wall of said hollow.
[0003] In consideration of the fact that the blades must be periodically replaced, it is important that the milling tools allow rapid and easy operations to assemble and disassemble the blades, in any case guaranteeing a precise and stable clamping thereof onto the main body, also considering the extremely high cutting speeds and the relative centrifugal forces generated. The solutions for clamping the blades that have been proposed until now have not been considered satisfactory by businessmen working in this field, because these solutions either guarantee the desired reliability in clamping the blades, with the disadvantage of long and laborious operations to assemble/dis-assemble them, or they simplify and speed up the assembly/dis-assembly operations without guaranteeing a secure positioning and clamping of the blades.
[0004] Another disadvantage of conventional milling tools is the difficulty of discharging the chip removed by the blades during working; this causes chip, resins or dust to infiltrate into the fissures present on the bottom of the hollows, between the blocks and the main body. It is therefore necessary to carry out periodic operations to clean the tool, especially when the latter is made to work at the highest speeds or with considerable cutting depth.
[0005] One purpose of the present invention is to achieve a milling tool which will allow a precise, self-centering positioning together with a stable clamping of the blades with respect to the main body, at the same time allowing rapid and easy operations to assemble/dis-assemble said blades.
[0006] The present Applicant has devised and embodied this invention to overcome the shortcomings of the state of the art, to achieve these purposes and to obtain other advantages.
SUMMARY OF THE INVENTION
[0007] The present invention is set forth and characterized in the main claim, while the dependent claims describe other innovative characteristics of the invention.
[0008] The milling tool according to the invention comprises a main body able to be made to rotate, at least a blade and at least a clamping element, or block, able to clamp the blade removably, in cooperation with screw means, onto the periphery of the main body.
[0009] The clamping element is arranged between a first and a second wall of a hollow on the main body, clamping the blade, thanks to the screw means, against the second wall. The hollow has a discharge surface, open on the outside of the main body and as an extension of the first wall, able to facilitate the discharge of the chip.
[0010] The clamping element has a threaded hole inside which the screw means are screwed; the latter act as a draw rod to determine the clamping thrust on the blade by the block.
[0011] According to the invention, the clamping element has a front surface able to be arranged in abutment on the blade, in order to exert the clamping thrust, in an inclined position with respect to the second wall of the hollow. In a preferential embodiment, at least part of the front surface is inclined by an angle of between 0.5° and 5°, advantageously between 1° and 2°, with respect to a plane orthogonal to the axis of the threaded hole, in order to guarantee a secure contact with the upper part of the blade.
[0012] In a preferential embodiment, the front surface of the clamping element has a progressively decreasing section, going towards the end which, in use, is external, so as to ensure a certain level of flexibility and elasticity which ensure a more effective clamping of the relative blade.
[0013] The main body has, on the same axis, at least a through hole and a blind hole communicating with the hollow, with respect to which holes the threaded hole is able to be aligned; the screw means are able to pass through the through hole and be inserted with the end in the blind hole, so as to facilitate the correct positioning of the clamping element on which they are to be screwed. Advantageously, the blind hole is open on the first wall of the hollow, while the through hole is open on the second wall of the hollow and communicates with a channel accessible from outside so as to insert and screw in the screw means.
[0014] According to another preferential embodiment, in correspondence with its lower end the clamping element has a protrusion facing towards the second wall of the hollow against which the blade is clamped. This protrusion is defined by two segments of surface at an angle to each other, with an angle of between about 70° and 110°, and is able to cooperate with a mating recess, also of an angled shape and substantially of the same angle, made at the base of the second wall.
[0015] During the assembly step, the precise coupling in shape of the angled protrusion of the clamping element and the angled recess of the hollow guarantees a precise self-centering and stable positioning without play, which prevents any kind of oscillation or unwanted movement of the clamping element. Moreover, this coupling in shape of the protrusion and the recess contributes to preventing the axial detachment of the clamping element even in the inactive position of the tool with the clamping screw partly loosened.
[0016] In a preferential embodiment, the clamping element has positioning and centering means able to cooperate with mating coupling means present on the blade, in order to facilitate the correct arrangement of the latter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] These and other characteristics of the present invention will become apparent from the following description of a preferential form of embodiment, given as a non-restrictive example with reference to the attached drawings wherein:
- figs. 1a and 1b show two three-dimensional views of the tool respectively in its assembled condition and in exploded condition;
- figs. 2, 3 and 4 show a sectioned detail of a milling tool according to the invention respectively in the assembled and dis-assembled condition and during the disassembly step;
- figs. 5, 6 and 7 show variants respectively of figs. 2, 3 and 4;
- fig. 8 shows a detail of the block of the tool according to the invention.
DETAILED DESCRIPTION OF SOME PREFERENTIAL FORMS OF EMBODIMENT OF THE INVENTION
[0018] In the attached figures, the number 10 denotes in its entirety the milling tool according to the invention, which comprises a main body 11, able to be made to rotate, and two blades 12 removably mounted on its periphery by means of relative clamping blocks 13 and screws 14.
[0019] The main body 11 has corresponding hollows 15 on the periphery, arranged radially, in correspondence with each of which a block 13 can be inserted in order to clamp a mating blade 12. Each hollow 15 defines a first 16 and a second 17 wall, substantially parallel to each other, a bottom 18 and a discharge surface 19, arranged as an extension of the first wall 16 and open towards the outside of the main body 11, in order to facilitate the discharge of the chip from the hollow 15.
[0020] The second wall 17 has a recess 17a and a tooth 17b in correspondence with which the blade 12 is positioned. Laterally to each hollow 15 there is a channel 20 open towards the outside of the main body 11 and communicating with the hollow 15, in correspondence with the second wall 17 by means of a through hole 21.
[0022] The block 13 is inserted between the first wall 16 and the second wall 17, resting on the bottom 18, and has a threaded through hole 23 which is aligned with the through hole 21 and the blind hole 22. In its segment facing towards the outside of the hollow 15, the block 13 also has a front surface 25 able to be arranged in abutment on the blade 12, and a rear connecting surface 26, partly curvilinear, able to be arranged in continuity with the discharge surface 19 of the hollow 15.
[0023] In a preferential embodiment, the connecting surface 26 has a progressively decreasing section from the inside to the outside of the block 13, so as to confer characteristics of flexibility and elasticity which improve the clamping properties thereof when the block 13 is clamped onto the blade 12.
[0024] At one end of the connecting surface 26, and in an opposite position with respect to the position of the blade 12, the block 13 has an edge 24 protruding laterally, facing towards the discharge surface 19 and able to be at least partly superimposed on the edge between the discharge surface 19 and the first wall 16; in correspondence with the front surface 25, the block 13 has one or more pins 27, two in the case shown here, able to be inserted into mating holes 28 present on the blade 12 to prevent it from accidentally coming out.
[0025] Advantageously, the portion of the front surface 25 arranged towards the outside with respect to the threaded hole 23, that is, the one on which the pins 27 are found, is angled by an angle α, with an amplitude of about 1°, with respect to the plane "A" orthogonal to the axis "x" of the threaded hole 23 (fig. 8).
[0026] In its innermost segment, in the terminal lower part of the front surface 25, the block 13 has a protrusion 29 which, in the solution shown in figs. 2+4, is able to couple with the second wall 17.
[0027] The screw 14 has a head 14a, advantageously with a "Torx" type impression, a smooth rear segment 14b and a smooth front segment 14d and a threaded central segment 14c; the rear segment 14b and the front segment 14d are respectively housed in the through hole 21 and the blind hole 22, while the central segment 14c is screwed inside the threaded hole 23 of the block 13.
[0028] A blade 12 is clamped inside the relative hollow 15 as follows. The block 13 is put inside the hollow 15, resting on the bottom 18 so as to align the threaded hole 23 with the holes 21 and 22 of the main body 11. Subsequently the blade 12 is inserted between the front surface 25 of the block 13 and the recess 17a of the second wall 17, resting on the tooth 17b, so that the pins 27 are inserted into the mating holes 28, univocally determining the correct positioning of the blade 12. Then, through the channel 20, the screw 14 is inserted into the through hole 21 and screwed with the central segment 14c inside the threaded hole 23, while the front segment 14d is inserted inside the blind hole 22, promoting the correct positioning of the block 13.
[0029] By screwing the screw 14 , which acts as a draw rod, the block 13 is brought near the second wall 17, with a consequent thrust of the blade 12 on the recess 17a (figs. 3 and 6). In this step, the type of screw 14 used allows a high clamping torque to be applied; moreover, the fact that the protrusion 29 rests on the second wall 17 and that the front surface 25 is inclined guarantees the progressive distribution of a great pressure of the block 13 on the entire surface of the blade 12, contributing to making the clamping of the latter more stable and secure.
[0030] In the solution shown in figs. 5+7, the protrusion 29 couples, during the assembly step, with a mating cavity 17c made partly on the bottom 18 and partly on the second wall 17. To be more exact, in this solution, both the protrusion 29 and the cavity 17c are defined by respective segments of wall that form between them an angle α preferably between 70° and 110°, advantageously around 90°.
[0031] The presence of the angled protrusion 29 and the corresponding angled cavity 17c facilitates the self-centering and self-positioning of the block 13; during the assembly step the coupling of the relative mating angled surfaces determines, when the screw 14 is tightened, the stable positioning of the block 13 in the hollow 15, without play and in a secure position. In the assembled position, the block 13 is prevented from making any movement of oscillation or rotation since the respective angled segments that form the protrusion 29 and the cavity 17c do not allow any type of oscillatory movement.
[0032] Moreover, the coupling of the protrusion 29 and the cavity 17c prevents the radial detachment of the block 13, and hence of the blade 12, even in the inactive condition when the screw 14 is partly loosened.
[0033] The inclination of the front surface 25 with respect to the second wall 17 of the main body 11, together with the variability of the section that increases the elasticity thereof, prevents dust or resin from depositing between the blade 12 and the block 13. The position of the channel 20 behind the blade 12 does not communicate directly with the hollow 15 and reduces the risk of chip deposit inside it, making the interventions on the screw 14 easier.
[0034] In order to release the blade 12, it is sufficient to unscrew the screw 14, so that the block 13 moves towards the first wall 16, freeing the blade 12 which can thus be removed (figs. 4 and 7). The only partial unscrewing of the screw 14 in any case allows to keep the block 13 constrained to the main body 11, without any danger of the block 13 falling, thus allowing to remove the blade 12 more easily.
[0035] Modifications and/or additions of parts may be made to the milling tool 10 as described heretofore, without departing from the field and scope of the present invention. The block 13 can have any conformation whatsoever and can have positioning and centering means other than pins 27. The front surface 25 could be orthogonal to the axis "x" of the threaded hole 23 in all its extension, inclining with respect to the second wall 17 of the main body 11 due to the effect of the abutment on the latter by the protrusion 29, which acts as a fulcrum, when the screw 14 is screwed in. Instead of the screw 14 the use of a grub screw or dowel can be provided.
1. Milling tool comprising a main body (11), at least a blade (12) and at least a clamping
element (13), including a threaded hole (23) for the insertion of screw means (14),
and able to be arranged in a hollow (15), having a first wall (16) and a second wall
(17), made in said main body (11), in order to clamp said blade (12) against said
second wall (17) of the hollow (15) by means of said screw means (14), said clamping
element (13) having a front surface (25) able to be arranged in abutment on said blade
(12), characterized in that at least a part of said front surface (25) is inclined, in use, by an angle (α) with
respect to a plane (A) orthogonal to the axis (x) of said threaded hole (23).
2. Tool as in claim 1, characterized in that said angle (α) has an amplitude of between 0.5° and 5°.
3. Tool as in claim 1, characterized in that said clamping element (13) has a connecting surface (26), opposite with respect to
said front surface (25), with a progressively decreasing section from the inside towards
the outside of said clamping element (13).
4. Tool as in any claim hereinbefore, characterized in that said main body (11), on the same axis, has at least a through hole (21) and a blind
hole (22) communicating with said hollow (15), with respect to which holes (21, 22)
said threaded hole (23) is able to be aligned, said screw means (14) being able to
pass through said through hole (21) and to be inserted with its end (14d) in said
blind hole (22).
5. Tool as in claim 4, characterized in that said through hole (21) is open on said second wall (17) and said blind hole (22)
is open on said first wall (16).
6. Tool as in any claim hereinbefore, characterized in that said clamping element (13) includes an angled protrusion (29) able to cooperate with
a mating angled shaping (17c) of said second wall (17) made in proximity with the
bottom (18) of said hollow (15).
7. Tool as in any claim hereinbefore, characterized in that said clamping element (13) includes positioning and centering means (27) able to
cooperate with mating coupling means (28) present on said blade (12).
8. Tool as in claim 7, characterized in that said positioning and centering means (27) comprise pin means able to be inserted
in mating holes (28) made on said blade (12).