EP1418031A2

EP1418031A2 - Tool for working wood and its derivatives

Info

Publication number: EP1418031A2
Application number: EP03005692A
Authority: EP
Inventors: Piergiorgio Pozzo
Original assignee: Pozzo SpA
Current assignee: Pozzo SpA
Priority date: 2002-11-06
Filing date: 2003-03-13
Publication date: 2004-05-12
Also published as: EP1418031A3; ITUD20020234A1

Abstract

Tool (10) for working wood or its derivatives, comprising at least a support element (11) provided peripherally with a plurality of radial housing seatings (12). Each of the housing seatings (12) houses a cutting blade (15) and an associated clamping element (16). Each housing seating (12) comprises at least a bottom surface (21) and a lateral reference surface (22) for the cutting blade (15). The clamping element (16) comprises at least a thrust element (19) that acts on a lateral surface (26) of the cutting blade (15) in order to keep the cutting blade (15) against the reference surface (22). The angle between the bottom surface (21) and the reference surface (22) is obtuse and the thrust element (19) contacts the bottom surface (21) in order to slide with respect thereto.

Description

FIELD OF THE INVENTION

The present invention concerns a tool, such as for example a milling cutter or cutter, or similar, for working wood and its derivatives. The tool comprises a support element, or head, substantially cylindrical in shape, with which two or more cutting blades are radially associated, and clamping devices to clamp the latter onto the head of the tool. To be more exact, each clamping device is able to keep the cutting diameter of the tool constant, even after any operation to sharpen the cutting blades.

BACKGROUND OF THE INVENTION

It is known that tools for working wood and its derivatives normally comprise a support element, or tool body, which is provided radially with a plurality of housing seatings, inside which an equal number of cutting blades is arranged. To be more exact, each blade rests on a fixed shoulder made in the seating, on a bottom surface.
Moreover, to guarantee a solid coupling of the tool head and each cutting blade, in each of said seatings a clamping device is mounted, which comprises a thrust element, called wedge, which, thrust by a threaded grub screw, acts against a plane lateral surface, or face, of the cutting blade, keeping the latter positioned inside the relative seating.
Each thrust element is also provided with a clamping element that, during use, is normally inserted in a corresponding hollow made in the cutting blade, to prevent the latter from emerging radially from the tool head.
Each cutting blade is also provided with an upper surface, or back, shaped so as to define the cutting edge of the blade. The face and the back of the blade form a clearance angle γ, normally less than 90° and defining the cutting part of the blade, by means of which the shavings are removed.
The normal use of the tools leads to a progressive loss of the edge on the cutting part of the blades, and a consequent need to periodically sharpen the blades.
This sharpening operation is performed, in known manner, by removing material from the face of the blade, so as to restore the cutting edge of the blade, keeping the clearance angle γ unchanged.
This sharpening method, however, leads to a progressive reduction in the height of the blade and, considering the positioning of the latter on the fixed shoulder, to a consequent proportionate reduction in the cutting diameter of the tool.
This reduction in diameter entails a lack of precision in the working steps, even in the range of 1 mm.
Sometimes, to recover this reduction in diameter due to the sharpening of the cutting blades, action is taken directly on the working assembly on which the tool is assembled. However, this means re-setting the working parameters of the whole machine tool on which the working assembly is assembled, with a consequent increase in work times and associated production costs.
The Applicant has studied, devised and embodied the present invention to overcome these shortcomings of the state of the art and to obtain other advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the main claim, while the dependent claims describe other innovative characteristics of the present invention.
One purpose of the present invention is to achieve a tool for working wood and its derivatives, which allows to keep the nominal cutting diameter of the tool substantially constant, irrespective of the number of times the cutting blades are sharpened and the reduction in thickness and height of the blades due to the sharpening processes.
In accordance with this purpose, a tool for working wood or its derivatives, according to the present invention, comprises at least a support element provided peripherally with a plurality of radial housing seatings to house a corresponding plurality of cutting blades, provided with respective cutting edges. Each housing seating comprises at least a bottom surface and a lateral reference surface for a corresponding cutting blade.
The tool according to the present invention also comprises, for every housing seating, a clamping device that comprises at least a thrust element that acts on a lateral surface of the cutting blade in order to keep the latter against the aforesaid reference surface of the housing seating. The thrust element is provided with a clamping element that, during use, is normally inserted in a corresponding hollow, or hole, in the cutting blade in order to prevent reciprocal movements of the thrust element and the cutting blade.
According to a characteristic feature of the present invention, the bottom surface and the reference surface of the housing seating form an obtuse angle between them, greater than 90° by a determinate angular value ε. Moreover, the lower part of the thrust element contacts the bottom surface of the housing seating in order to be able to slide with respect thereto. In this way, every time it moves towards the reference surface of the housing seating, the thrust element is also displaced radially towards the outside of the housing seating itself.
The angular value ε is a function of the sum of the clearance angle γ and the hook angle α. By hook angle α we mean the angle that the lateral surface of the cutting blade, considered in the vertical position, forms with respect to a radius of the support element passing through the cutting edge of the cutting blade.
Moreover, the thrust element comprises a shoulder that cooperates with a lower surface of the cutting blade, so that to every radial displacement of the thrust element corresponds an analogous radial displacement of the cutting blade.
After every sharpening of the cutting blade, in order to attach it to the support element, first the thrust element and the cutting blade are coupled together, then the thrust element is taken into contact with the bottom surface of the housing seating, and then the thrust element is thrust towards the reference surface of the housing seating, by means of any threaded element, such as a grub screw or suchlike.
This operation causes the thrust element to slide along the bottom surface of the housing seating, which causes a simultaneous and consequent longitudinal movement of the cutting blade with respect to the reference surface of the housing seating.
Said longitudinal displacement is a function of the angular value ε, and therefore allows to automatically recover the reduction in height of the cutting blade, due to the sharpening thereof, keeping the nominal cutting diameter of the tool constant.
Since the cutting edges of the cutting blades develop on different cutting diameters, this entails that the corresponding hook angle α changes from point to point. Consequently, in the logic of the present invention, as can easily be understood, this entails that the correction made to the radial position of the cutting blade with respect to the tool body obtains variations in diameter which vary from point to point of the cutting edge. In any case, this variation, even in the most extreme case, is in the range of 0.1 mm over the entire cutting diameter, and is easily accepted for the most recurrent workings made with this type of tool.
A similar variation can obviously be obtained even when the cutting edge is not aligned with the axis of rotation of the tool, but forms with the latter an angle other than zero, so as to form what, in technical terms, is called axial angle. In this case too, the variation is in any case negligible.

BRIEF DESCRIPTION OF THE DRAWINGS

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:

fig. 1 is a plane view of a tool for working wood according to the present invention;
fig. 2 shows a detail of a conventional tool for working wood;
fig. 3 shows an enlarged detail of the tool in fig. 1;
fig. 4 shows an enlarged detail of fig. 3;
fig. 5 shows a variant of fig. 3;
fig. 6 shows a table of calculations of the values of inclination of the bottom surface of the housing seating in fig. 3;
fig. 7 shows a front section along the radius X of fig. 3.

DETAILED DESCRIPTION OF A PREFERENTIAL FORM OF EMBODIMENT

With reference to fig. 1, a tool 10 for working wood according to the present invention comprises a substantially cylindrical support element 11, provided peripherally with a plurality of housing seatings 12, in this case three, identical to each other and each able to house inside itself a cutting blade 15 and a corresponding clamping device 16. Every clamping device 16 comprises a thrust element 19 associated with an attachment grub screw 18, to attach the cutting blade 15 inside the respective housing seating 12.
On the support element 11, in correspondence with every housing seating 12, there is a through hole 17, threaded at the end, inside which the attachment grub screw 18 is able to be screwed.
The support element 11 is also provided with a central hole 20 to be coupled with a relative drive shaft, of a conventional type and not shown in the drawings.
Each cutting blade 15 (figs. 1 and 3) comprises a cutting edge 30, by means of which the shavings are removed, a plane surface 25, a lateral surface or face 26 substantially parallel to the plane surface 25, a bottom surface 27 which at the lower part connects the plane surface 25 to the face 26, and an upper surface or back 29, inclined with respect to the face 26 by a determinate angle β, the tool's cutting angle.
The edge where the back 29 and face 26 of the cutting blade 15 intersect defines the cutting edge 30, which can have the most disparate shapes.
The face 26 of each cutting blade 15 is inclined by a hook angle α with respect to a radius X of the support element 11, passing through the cutting edge 30.
Each cutting blade 15 also comprises a transverse hole 32, inside which a mating pin 33 is able to be arranged, in order to prevent the cutting blade 15, during the working steps and due to the thrust exerted by centrifugal force, from coming out, even only partly, from its housing seating 12.
In order to better clarify the characteristic and innovative features of the present invention, and purely to serve as a comparison, we shall now describe a conventional housing seating 112 (fig. 2) of a tool 110 for working wood.
The seating 112 substantially comprises a bottom surface 121 and a lateral reference surface 122 substantially orthogonal to each other.
The cutting blade 15 rests with the plane surface 25 against the reference surface 122 of the seating 112, while the face 26 cooperates with a thrust element 119 to keep the plane surface 25 against the reference surface 122. The cutting blade 15 also rests with its lower surface 27 on a shoulder 128 made in correspondence with the bottom surface 121 of the seating 112.
The cutting edge 30 is sharpened by removing material from the face 26 of the cutting blade 15, thus also entailing a reduction in thickness of the latter and a corresponding reduction in height of the blade 15 by a value Δh. In order to compensate for this reduction in thickness, the attachment grub screw 18 is screwed in further, so that the thrust element 119 is moved towards the reference surface 122, until the plane surface 25 of the cutting blade 15 stops against said reference surface 122.
In this way, however, the reduction in height Δh of the cutting blade 15 is not compensated for at all, and this has the effect of a consequent reduction in the diameter of the tool 110, which causes the disadvantages described above.
On the contrary, the tool 10 according to the present invention comprises, for every housing seating 12 (figs. 3 and 4), a bottom surface 21, a lateral reference surface 22 and a surface 23 opposite and substantially parallel to the reference surface 22.
The bottom surface 21 forms an obtuse angle with the reference surface 22. The amplitude of said obtuse angle is greater than 90° by a determinate angular value ε. This angular value ε is a function of the hook angle α and the clearance angle γ: it does not depend, except to a negligible extent, either on the height of the cutting blade 15 or on the cutting diameter of the tool 10.
To give an example, for a tool 10 having a cutting diameter of 200 mm and a clearance angle γ of 20°, the angular value ε, in proportion to the value of the hook angle α, is the one shown in the table in fig. 6.
The thrust element 19 comprises a lower surface 31 that contacts the bottom surface 21 of the housing seating 12, and a shoulder 28 on which the lower surface 27 of the blade 15 rests. The lower surface 31 is advantageously plane, as shown in figs. 1, 3, 4 and 5, but it could also be pointed, in which case it would contact the bottom surface 21 only along a segment parallel to the lateral reference surface 22.
The tool 10 as described heretofore functions as follows.
Each cutting blade 15, after every sharpening process, is coupled with the thrust element 19 so that the lower surface 27 rests on the shoulder 28, the pin 33 is completely inserted into the transverse hole 32, and the face 26 is in contact against the thrust element 19.
Then the attachment grub screw 18 is screwed in until the cutting blade 15, thrust by the thrust element 19, goes into contact with the reference surface 22 of the housing seating 12. The thrust element 19, sliding with its lower surface 31 along the bottom surface 21 of the housing seating 12, also moves radially with respect to the support element 11 and also thrusts the cutting blade 15 towards the outside.
The outward movement of the cutting blade 15 is a function of the angular value ε, and allows to compensate for the reduction in height of the cutting blade 15 after every sharpening operation, keeping the cutting diameter of the tool 10 constant, in accordance with the purpose of the present invention.
It is clear that modifications and/or additions of parts may be made to the tool 10 as described heretofore without departing from the field and scope of the present invention.
For example, according to a variant shown in fig. 5, instead of the threaded grub screw 18 a threaded stud screw 34 may be provided, with its longitudinal axis substantially parallel to the face 26 of the cutting blade 15, and provided with a wedge-shaped or ogival profile 35 by means of which pressure can be exerted on the thrust element 19 in order to take the cutting blade 15 against the reference surface 22.
Moreover, depending on the width of the cutting blade 15, which normally varies from 5 to 100 mm, instead of a single threaded grub screw 18 several threaded screws 18 may be provided (fig. 7), to improve the pressure and grip of the thrust element 19 against the cutting blade 15.
It is also clear that, although the present invention has been described with reference to specific examples, the person of skill in the art shall certainly be able to embody other forms of tool for working wood, all of which shall come within the field and scope of the invention.

Claims

Tool for working wood or its derivatives, comprising at least a support element (11) provided peripherally with a plurality of radial housing seatings (12) each able to house a cutting blade (15) and associated clamping means (16), wherein each of said housing seatings (12) comprises at least a bottom surface (21) and a lateral reference surface (22) for said cutting blade (15), and wherein said clamping means (16) comprise at least a thrust element (19) able to act on a lateral surface (26) of said cutting blade (15) in order to keep said cutting blade (15) against said reference surface (22), characterized in that the angle between said bottom surface (21) and said reference surface (22) is obtuse and in that said thrust element (19) contacts said bottom surface (21) to slide with respect thereto.
Tool as in claim 1, characterized in that the amplitude of said obtuse angle is greater by 90° than a determinate angular value (ε).
Tool as in claim 1 or 2, wherein said lateral surface (26) of said cutting blade (15) is inclined by a hook angle (α), with respect to a radius (X) of said support element (11) passing through the cutting edge (30) of said cutting blade (15), and wherein said cutting blade (15) defines a determinate clearance angle (γ), characterized in that the amplitude of said obtuse angle is a function of the sum of said hook angle (α) with said clearance angle (γ).
Tool as in claims 2 and 3, characterized in that, for a clearance angle (γ) of 20°, for a cutting diameter of about 200 mm and for a value of said hook angle (α) of between about 5° and 40°, said angular value (ε) is between about 20° and about 45°.
Tool as in any claim hereinbefore, characterized in that said thrust element (19) comprises a lower surface (31) which is substantially parallel to said bottom surface (21) of said housing seating (12).
Tool as in any claim hereinbefore, characterized in that said thrust element (19) comprises a shoulder (28) able to support a bottom surface (27) of said cutting blade (15), so as to thrust said cutting blade (15) longitudinally along said reference surface (22) according to the position of said thrust element (19) with respect to said bottom wall (21) of said housing seating (12).
Tool as in any claim hereinbefore, characterized in that said clamping means (16) comprise at least a threaded element (18) able to exert a desired pressure against said thrust element (19).
Tool as in claim 7, characterized in that said threaded element comprises an attachment grub screw (18) inserted in a corresponding through hole (17) made in said support element (11).
Tool as in claim 7, characterized in that said threaded element comprises a threaded stud screw (34) provided with a wedge-shaped profile (35) able to act against said thrust element (19).