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(11) | EP 1 741 508 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Circular saw blade |
| (57) The disc (10) for a circular sawing machine, in particular for cutting materials
such as wood, plywood, plastic and PVC, comprises a peripheral rim (16) provided with
a plurality of teeth (18a-f) having respective cutting edges (20a-f) and delimited
by an outer circumference (C1) passing through the cutting edges (20a-f) of the teeth
(18a-f).
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[0001] The present invention relates to a disc for a circular sawing machine, in particular for cutting materials such as wood, plywood, plastic and PVC.
[0003] These discs, which are typically made of steel, during use are subject to a high degree of frictional contact with the material to be cut, and consequent overheating, in particular as regards the side faces, the teeth and their tangential flanks.
[0004] In order to solve these problems, discs having teeth alternately inclined with respect to their side faces are known, but this arrangement causes vibrations and "wobbling" of the disc, making it less controllable and resulting in a less precise cutting action. Moreover these discs must have an absolutely equal number of teeth in order for them to function correctly and are also likely to seize during cutting of the material.
[0005] An object of the invention is to overcome the abovementioned problems and drawbacks of the known art by providing a disc having a reduced frictional contact with the material to be cut, a low degree of overheating and a high cutting precision.
[0006] These and other objects are achieved by a disc of the type specified above and having the features defined in the appended Claim 1.
[0007] The invention relates furthermore to a circular sawing machine according to the accompanying Claim 22.
[0008] Further features of the invention will emerge during the course of the detailed description which follows, provided by way of a non-limiting example with reference to the drawings, in which:
Figure 1 is a side view of a disc for a circular sawing machine, according to the known art;
Figure 2 is a partial view of a portion of the disc shown in Figure 1;
Figure 3 is a side view of a variation of embodiment of a disc according to the invention; and
Figure 4 is a partial front view of the periphery of the disc along the arrow IV of Figures 1 and 3.
[0009] With reference to Figure 1, 10 denotes in general a steel disc able to be connected to a circular sawing machine, in particular of the portable type (not shown) and suitable for the cutting of materials such as wood, plywood, plastic and PVC. The disc 10 comprises an inner portion 12 having a central hole 14 intended to be connected to a motor of the sawing machine by means of coupling and transmission means of the type known per se.
[0010] This disc 10 has along its perimetral portion a peripheral ring 16 provided with six teeth 18a-f having respective cutting edges 20a-f. This peripheral ring 16 is delimited by an outer circumference C1 passing through the cutting edges 20a-f produced by means of incisions 21a-f of substantially circular shape formed between pairs of consecutive teeth 18a-f. The teeth 18a-f need not necessarily be six in number, but their number may preferably range between two and twenty. The outer circumference C1 conveniently has its centre 01 at the centre of rotation O of the disc 10, in this case coinciding with the centre of the hole 14.
[0011] An intermediate ring 22 is situated between the peripheral ring 16 and the inner portion 12 of the disc 10, and defines an intermediate circumference C2, bordering with the peripheral ring 16, and an inner circumference C3, bordering with the inner portion 12. The outer, intermediate and inner circumferences C1, C2, C3 have their respective centres 01, 02, 03 coinciding with the centre of rotation O of the disc 10, but the abovementioned centres may also be located in positions different from each other in the region defined by the inner portion 12.
[0012] The intermediate ring 22 has on its surface three openings conveniently in the form of slots 24a-c passing through the side faces of the disc 10 and shaped in the form of circular ring segments having a respective outer edge 26a-c defined by an arc of the intermediate circumference C2 and a respective inner edge 28a-c defined by an arc of the inner circumference C3. These slots are situated around the inner portion 12, advantageously but not necessarily are angularly equidistant on the intermediate ring 22, are substantially equidistant from the centre 01 of the outer circumference C1 and may be of any number and have forms different from those of the slots 24a-c, for example circular or generally polygonal holes. In further embodiments (not shown) the number of openings or slots may advantageously coincide with the number of teeth.
[0013] Experimental tests carried out by the Applicant have shown that the disc 10 has a particularly satisfactory performance if at least one of the following conditions is satisfied:
- the ratio between the radius of the inner circumference C3 and the radius of the outer circumference C1 is between 0.2 and 0.8;
- the ratio between the radius of the intermediate circumference C2 and the radius of the outer circumference C1 is between 0.4 and 0.95; and
- the ratio between the overall area of the slots 24a-c and the area of the outer circumference C1 is between 0.05 and 0.6
[0014] With reference in particular to Figures 1 and 2, the teeth 18a-f comprise respective tangential flanks 30a-f, which have profiles delimited externally by respective circumferential arcs, of which in Fig. 2 only the circumferential arc A relating to the tangential flank 30b of the tooth 18b is shown. The embodiment shown in Figures 1 and 2 shows the tangential flank 30b with a profile coinciding with the circumferential arc A, while the variant of Figure 3 (which will be described below) shows the abovementioned profile formed by two chords subtending said circumferential arc A. However it is possible to envisage other variations of embodiment characterized by other forms for the profile of the tangential flanks.
[0015] The centre K of the circumferential arc A is situated in a region lying between the outer circumference C1 and the diametral axes D1, D2 of the latter passing respectively through the two cutting edges 20a, 20b between which said circumferential arc A is situated. The abovementioned region has been highlighted in Figure 2 by means of oblique lines. This positioning of the centre K results in a form of the tooth 18b which is particularly advantageous in terms of the cutting performance of the disc 10.
[0016] With reference to Figure 1, it can be noted how the tangential flanks 30a-f are shaped as portions of curved sides (interrupted by the incisions 21a-f) of a regular polygon, which in this case is a hexagon, inscribed inside the outer circumference C1 and having the vertices at the angular points consisting of the cutting edges 20a-f of the teeth 18a-f. This configuration makes it possible to perform a particularly precise and efficient cut since the free space lying between the outer circumference C1 and the curvilinear polygonal form generated by the tangential flanks 30a-f reduces friction phenomena, preventing undesirable wobbling of the disc 10.
[0017] Figure 3 shows an alternative variation of embodiment of the tangential flanks 30a-f of the disc 10. The same reference numbers and letters are associated with elements similar to those described and illustrated in the embodiment previously illustrated in Figures 1 and 2.
[0018] In a directional sense opposite to a direction of rotation R of the disc 10, the tangential flank 30b comprises a leading portion or working chord 32 adjacent to the respective cutting edge 20b of the tooth 18b, and a terminal portion or clearance chord 34 adjacent to the following tooth 18a. The working and clearance chords 32, 24 are consecutive, subtending the arc A, and intersect themselves at an edge 36.
[0019] With reference to Figure 3, still in a directional sense opposite to a direction of rotation R of the disc 10, the radial distance d of the points of the clearance chord 34, with respect to the centre 01 of the outer circumference C1, has a decreasing progression starting from the maximum distance dmax of the edge 36. Therefore, during rotation of the disc 10, the clearance chord 34 of the tangential flank 30b does not cut into the object to be cut. An interval is therefore created between the two consecutive incisions of the cutting edges 20b and 20a, preventing further friction of the tooth 18b with the material to be cut and consequent overheating of the periphery of this tooth.
[0020] As is obvious, the working and clearance portions 32, 34 need not necessarily be straight chords or segments subtending the arc A, but may also have different forms, for example curvilinear forms.
[0021] The reduction in friction and overheating, as a result of the configuration of the disc 10 in accordance with both the embodiments shown, allows shaping of the teeth 18a-f in such a way that they lie in a plane Π parallel to the side faces of said disc 10, as shown in Figure 4 for the teeth 18e, 18f only. This measure allows greater cutting precision compared to the applications of the known art, which have the teeth alternately inclined with respect to the plane II. Consequently it is no longer necessary to adopt an even number of teeth, which is an essential condition for correct operation of discs with alternately inclined teeth, but the disc 10 could also have an odd number thereof (variant not shown).
[0022] Obviously, without modifying the principle of the invention, the embodiments and the constructional details may be widely varied with respect to what has been described and illustrated purely by way of a non-limiting example, without thereby departing from the scope of the invention as defined in the appended claims.
1. Disc (10) for a circular sawing machine, in particular for cutting materials such
as wood, plywood, plastic and PVC, able to be connected by means of coupling and transmission
means to a motor of said sawing machine,
characterized in that it comprises:
characterized in that it comprises:
a peripheral ring (16) provided with a plurality of teeth (18a-f) having respective cutting edges (20a-f), and delimited by an outer circumference (C1) passing through the cutting edges (20a-f) of said teeth (18a-f).
2. Disc according to Claim 1, also comprising an inner portion (12) able to be connected
by means of the coupling and transmission means to the motor of said sawing machine
and
an intermediate circular ring (22) situated between the peripheral ring (16) and the inner portion (12) and having a plurality of openings (24a-c) situated around said inner portion (12).
an intermediate circular ring (22) situated between the peripheral ring (16) and the inner portion (12) and having a plurality of openings (24a-c) situated around said inner portion (12).
3. Disc according to any one of the preceding claims, wherein the intermediate ring (22)
defines respectively an intermediate circumference (C2) and an inner circumference
(C3) having the respective centres at a first and a second point (02, 03) of the inner
portion (12) of said disc (10), and the openings comprise at least one slot (24a-c)
shaped in the manner of a circular ring sector having an outer edge (26a-c) defined
by an arc of the intermediate circumference (C2) and an inner edge (28a-c) defined
by an arc of the inner circumference (C3).
4. Disc according to Claim 3, wherein said first and second point (02, 03) coincide with
each other.
5. Disc according to Claim 4, wherein said first and second point (02, 03) coincide with
the centre (01) of the outer circumference.
6. Disc according to any one of Claims 3 to 5, wherein the ratio between the radius of
the inner circumference (C3) and the radius of the outer circumference (C1) is between
0.2 and 0.8.
7. Disc according to any one of Claims 3 to 6, wherein the ratio between the intermediate
circumference (C2) and the radius of the outer circumference (C1) is between 0.4 and
0.95.
8. Disc according to any one of Claims 3 to 7, wherein said openings (24a-c) are substantially
equidistant from the centre of the outer circumference (01).
9. Disc according to any one of Claims 2 to 8, wherein said openings (24a-c) are angularly
equidistant on the intermediate ring (22).
10. Disc according to any one of Claims 2 to 9, wherein the ratio between the overall
area of said openings (24a-c) and the area of the outer circumference (C1) is between
0.05 and 0.6.
11. Disc according to any one of Claims 2 to 10, wherein the number of openings (24a-c)
is equal to the number of teeth (18a-f).
12. Disc according to any one of the preceding claims, wherein said teeth (18a-f) comprise
a respective tangential flank (30a-f), the profile of which is delimited externally
by a corresponding circumferential arc (A) having the centre (K) located in a region
lying between said outer circumference (C1) and the diametral axes (D1, D2) of the
latter passing through the cutting edges (20a, 20b) between which said circumferential
arc (A) is situated.
13. Disc according to Claim 12, wherein at least one tangential flank (30a-f) has a profile
coinciding with the respective circumferential arc (A).
14. Disc according to Claim 13, wherein said tangential flanks (30a-f) define portions
of curved sides of a regular polygon inscribed in the outer circumference (C1) and
having the vertices at the abovementioned cutting edges (20a-f).
15. Disc according to Claim 12, wherein the profile of at least one tangential flank (30b),
in a directional sense opposite to a direction of rotation (R) of the disc (10), comprises:
- a leading working portion (32) adjacent to the respective cutting edge (20b) of the associated tooth (18b); and
- a terminal clearance portion (34) which is adjacent to the following tooth (18a), and the radial distance (d) of its points with respect to the centre of the outer circumference (C1) is decreasing.
16. Disc according to Claim 15, wherein the working portion of said tangential flank (30b)
comprises a working chord (32) subtending the respective circumferential arc (A).
17. Disc according to Claim 15 or 16, wherein the clearance portion of said tangential
flank (30b) comprises a clearance chord (34) subtending the respective circumferential
arc (A).
18. Disc according to Claims 16 and 17, wherein which said working and clearance chords
are two consecutive segments (32, 34).
19. Disc according to any one of the preceding claims, wherein the number of teeth (18a-f)
ranges between two and twenty.
20. Disc according to any one of the preceding claims, wherein the number of teeth (18a-f)
is odd.
21. Disc according to any one of the preceding claims, wherein said teeth (18a-f) lie
in a plane (II) parallel to the side faces of the disc (10).
22. Sawing machine comprising a motor able to be connected by means of coupling/transmission
means to a disc (10) according to any one of the preceding claims.