EP1349692A1

EP1349692A1 - Sawing tool for a manual circular sawing machine with coaxial saw blades that can be driven in opposite direction

Info

Publication number: EP1349692A1
Application number: EP01978200A
Authority: EP
Inventors: Albrecht Hofmann; Ivo Gruber; Thomas Schomisch; Christian Walker
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2000-12-02
Filing date: 2001-09-29
Publication date: 2003-10-08
Also published as: WO2002043911A1; US20030136242A1; DE10059969A1; JP2004513798A

Abstract

The invention relates to a sawing tool for a manual circular sawing machine comprising two coaxial saw blades (11, 11') that can be driven in opposite direction and that can rotate immediately past each other. The invention aims at enabling a constructionally simple generation of an axial force in each of the saw blades (11, 11'), said force preventing the saw blades (11, 11') from pushing apart during the cutting process. The front cutting edge (161, 161') of each major cutting edge (16, 16') rotating in the direction of rotation lies on a plane extending through the axis of the saw blades (18, 18'). The major cutting edges (16, 16') are slanted in the direction of the axis of the saw blades (18, 81') in such a manner that they tilt from the sides of the blades of the saw blades (11, 11') that face each other to the sides of the blades that are opposite each other.

Description

SAWING TOOL FOR A HAND CIRCULAR SAWING MACHINE WITH ANOTHER DRIVELY DRIVABLE, COAXI AL SAW BLADES

State of the art

The invention relates to a sawing tool for a circular saw machine with two directly past one another in opposite directions drivable rotating _f ,, coaxial saw blades of the type defined in the preamble of claim 1.

Such sawing tools have the advantage that, when working with the hand-held circular saw machine, the reaction forces and moments are eliminated by the counter-rotation of the two saw blades and the machine is easy to operate and easy for the user to operate. To achieve optimal cutting results, it is important that the two saw blades are not axially pressed apart by the cutting forces acting in the cut. In order to avoid this, an axial force must be exerted on the toothing area engaging in the workpiece during the cutting process are applied, which counteracts the cutting force components that try to push the saw blades apart.

In a known sawing tool of the type mentioned at the outset (WO 89/00474), the main sheaths of the saw teeth are inclined against the saw blade plane in order to generate such an axial force which counteracts the saw blades being pushed apart, the corner edges of the main cutting edges located further forward in the direction of rotation of the saw blades Blade sides of the saw blades lie directly facing each other. This creates an axially directed force component due to the cutting force of the main cutting edge, which axially holds the toothing areas of the saw blades together in the cutting area.

Advantages of the invention

The sawing tool according to the invention in each of its embodiments according to claims 1, 2, 3, 6 and 8 has the basic advantage that an axial force component is present in the work case, which at least presses the tooth areas of the two saw blades in the workpiece engagement, and also the Another advantage that this force component is achieved with inexpensive manufacturing technology measures, so that the

Production costs for the sawing tool can be reduced.

In the embodiment according to claim 1, the cutting edges, which are at the front in the direction of rotation, lie in a plane running through the coaxial saw blade axes

Main blades that slant to the outer sides of the saw blade fall off, much easier to produce than beveled main cutting edges, the front cutting edge of which has an acute angle with a plane running through the saw blade axis, since the cutting bevel does not have to be made tooth by tooth, but can be ground in with a rotating saw blade.

In the embodiment of the invention as claimed in claim 2, the outer rounding of the two saw blades, which in turn generates an axial force component inward, in addition to the production-related advantage described above, also provides a higher level of security against cutting edge breakouts, which occur especially in hand-held machines due to vibrations.

In the embodiment of the invention according to claim 3, the axial force component is not generated by the feed of the saw tool, but the teeth of the saw blades are pressed together by an elastic prestress, so that the saw blades resiliently abut each other in the area of their teeth with a small spring constant. This spring force holds the saw blades together in the cut and counteracts the saw blades being pushed apart during work. Such an axial preload can be implemented in various ways, e.g. with the constructive measures specified in claim 4 or claim 5.

The embodiment of the invention according to claim 6 has the advantage that no modifications to the to generate the axial force component for the cohesion of the saw blades Saw blades must be made so that conventional, inexpensive saw blades can be used. Due to the slight inclination of the saw blades or the saw blade axes, which intersect in the plane of symmetry of the saw tool, part of the toothing on the two saw blades is pressed together, which leads to an inward axial force component that holds the saw blades together in the cut.

According to an advantageous development of the embodiment according to claim 6, the outer blade surfaces of the master blades of the two saw blades, which face away from one another, are set back somewhat from the outer secondary cutting edges turned away from one another. As a result, despite the slight inclination of the saw blades, there is no or only very slight friction of the saw tool on the cut inner surfaces of the workpiece cut.

In the embodiment of the invention according to claim 8, the axial force component for holding the saw blades together in the case of work is achieved in that the secondary cutting edges lying on mutually facing blade sides are set outwards relative to the master blades so that the plane in which the secondary cutting edges lie with the Master blade includes the smallest possible helix angle. As a result, the corner angle between the main and outer minor cutting edge is as large as possible, but still less than 90 °, which leads to a strong, axial cohesion of the saw blades in the work case than with a larger helix angle of the minor cutting edges. The above-described embodiments of the sawing tool according to the invention are further optimized with regard to an improved cutting result if, according to a preferred embodiment of the invention, means are provided on each saw blade for forcing air guidance for toothing, as a result of which very good cooling of the saw blades in the work situation and thus besides one improved cutting result and a long service life of the saw blades is achieved.

According to an advantageous further development, the air guiding means have through bores made in the master blades, which are preferably arranged equidistantly on a circle of dividers concentric to the saw blade axis. Air swirling around the teeth is achieved through these through holes.

According to an advantageous further development, the air guiding means have wing-shaped spokes which are formed in the master blades in the radial direction. The spokes can have a constant or a continuously increasing cross-section. The cross-sectional profile of the spokes can be angular, the spokes being inclined to the plane of the saw blade, or can be optimized in terms of flow and be designed like an airplane wing.

According to another development, the

Air guiding means in the master blade of the one saw blade, pairs of radially spaced through bores offset from one another by preferably the same circumferential angle, and in the The main blade of the other saw blade is offset from one another by preferably the same circumferential angle, extending in the radial direction, elongated holes or grooves which overlap the pairs of holes when the two saw blades rotate. If grooves are provided instead of elongated holes, the amount of air conveyed per revolution of the saw blades is higher, since the air cannot escape laterally - as with an elongated hole. The holes can be made at an angle in the master blades, so that the hole axes are inclined to the saw blade level. In the same way, the end regions of the grooves or elongated holes are made obliquely. This further supports the airflow.

According to an alternative further development, the air guiding means in the main blade of the one saw blade are preferably offset through holes arranged on the divider circle by preferably the same circumferential angle and radially extending elongated holes are arranged on the master blade of the other saw blade and are offset in the master blade circumference

Open the tooth gap and, when the two saw blades rotate, overlap the through holes with their end area facing away from the mouth. In this case, the tooth gap base of the toothing of the saw blade having the through bores is preferably drawn inward more deeply than in the other saw blade. Instead of the elongated holes, identically arranged grooves can be provided.

A further optimization of the sawing tools presented in the direction of an improvement in the cutting result is achieved if, according to an advantageous embodiment of the Invention in the toothing of the two saw blades that in the direction of rotation behind the main cutting edges of the main cutting edge free surfaces receive a contour that starts from the main cutting edge and rises again towards the following tooth. The rising contour reduces the maximum possible feed per tooth, which reduces vibrations. With the reduction of the feed rate, the maximum will be

Feed speed is reduced, but the advantage of vibration reduction outweighs the limited performance of hand-held circular saws and the comparatively flexible guidance of the machine by the user.

drawing

The invention is explained in more detail in the following description with reference to exemplary embodiments shown in the drawing. In a schematic representation:

1 is a plan view of a sawing tool with two circular saw blades rotating in opposite directions,

Fig. 2 is a section along the line II - II in Fig. 1, Fig. 3 is an enlarged view of the detail

III in Fig. 1,

4 is a top view of the development of the toothing in the direction IV in FIG. 3,

5 shows a section along the line V - V in FIG. 3, 6 shows the same representation as in FIG. 5 of a sawing tool according to a further exemplary embodiment,

7 is a side view of a sawing tool according to a third embodiment,

8 is a side view of a sawing tool according to a fourth embodiment,

9 is a side view of a sawing tool according to a fifth embodiment,

10 is an enlarged view of section X in Fig. 9,

11 shows the same representation as in FIGS. 5 and 6 of a sawing tool according to a sixth exemplary embodiment,

12 shows a plan view of the master blade of one to 14 saw blades of the sawing tool in FIGS. 1-6 according to three exemplary embodiments,

Fig. 15 is a section along the line XV - XV in

Fig. 13,

16 shows the same representation as in FIG. 15 according to a further exemplary embodiment, 17 shows a longitudinal section of the master blades of a sawing tool according to FIGS. 1-6 with a cut along the line XVII - XVII in FIG. 19 in two variants,

18 is a plan view in the direction of arrow XVIII in FIG. 17,

19 is a plan view in the direction of arrow IXX in FIG. 17

Fig. 20 is a partial plan view of a

Sawing tool according to another

Embodiment,

Fig. 21 is a partial plan view of a

Saw blade of a sawing tool according to a further embodiment.

Description of the embodiments

The sawing tool for a hand-held circular sawing machine shown in FIGS. 1-5 in different views and sections has two coaxial circular saw blades rotating in opposite directions, which can be driven in opposite directions, in the following

Saw blades 11, 12 called, which, after being clamped in the tool holder of a hand-held circular saw machine, not shown here, are each connected in a rotationally fixed manner to one of two concentrically arranged, counter-rotating drive spindles. Each saw blade 11 or 11 'has a master blade 12 or 12 ^! and a the master sheet 12 or 12 'enclosing, with this one-piece toothing 13 or 13' from a plurality of equidistantly arranged teeth 14 or 14 'radially protruding from the main blade 12, 12'. In Fig. 1, only four teeth 14, 14 'of the circumferential teeth 13, 13' are shown and the rest of the saw blade 11 is indicated with a circle running along the tooth tips. Each tooth 14 or 14 'has a main cutting edge 16 or 16' pointing in the direction of rotation 15 or 15 '(FIG. 4) and two secondary cutting edges 17 or 17' running radially to the side thereof. Main cutting edges 16 and 16 'and secondary cutting edges 17 and 17' meet at the cutting edges. The outer secondary cutting edges 17 and 17 'which face away from one another when the saw blades 11, 11' are adjacent to one another, are set slightly against the respective main blade 12 or 12 ', so that the outer cutting edges formed by main cutting edges 16, 16' and outer secondary cutting edges 17, 17 ' Project axially beyond the outer surface of the respective master sheet 12 or 12 '. As shown in FIGS. 4 and 5, each of the cutting edges 161 and 161 'of the main cutting edges 16 and 16', which is at the front in the direction of rotation, lies in a plane running through the saw blade axis 18 and 18 ', at the same time the main cutting edges 17, 17' in the direction of the saw blade axis 18 or 18 ^! are so beveled that the main cutting edges 17, 17 'fall from the mutually facing blade sides of the saw blades 11, 11' towards the mutually facing blade sides. The

The helix angle of the main cutting edges 17 and 17 'is marked in FIG. 5 with α and α' and is of the same size for both saw blades 11, 11 ^r . This helix angle α or α 'is applied to the main cutting edges 16 and 16' by a compressive force F _D , which is caused by the user pressure and half with the compressive force F _D ι and F _D2 . acts, generates an axial force F _Ai and F _A2 , which is equal to ^ F _D e tan α. This axial force ensures with increasing pressure F _D. αen the user exerts on the machine and the sawing tool on average, for increasing axial cohesion of the two saw blades 11, 11 '.

In the modified embodiment of the sawing tool according to FIG. 6, this axial force F _A ι or F _A2 , which counteracts the pushing apart of the two saw blades 11, 11 'in the cutting area, by rounding off the transition from the main cutting edge 16 or 16' of the secondary cutting edge 17 or 17 'obtained when the saw blades 11, 11' lie against one another. The rounding of the cutting edge transition also brings greater security against cutting edge corner breakouts, which occur especially on hand-held machines as a result of vibrations.

In the exemplary embodiments of the sawing tool according to FIGS. 7 and 8, the axial force for holding the saw blades 11, 11 'together is achieved in the case of work by axially prestressing the saw blades 11, 11'. The two saw blades 11, 11 'lie axially against one another in the region of their toothing 13, 13 ^r with a small spring constant. In the embodiment of Fig. 7, the elastic bias in the axial direction is achieved in that the

Master blades 12, 12 'of the two saw blades 11, 11' have a tapering, to a certain extent conical shape towards the blade sides facing away from one another, which is obtained after the manufacturing process by a forging process. 7, the saw blades 11, 11 ^! solid in her relaxed position and dashed in her Clamping position shown in the tool holder of the hand-held circular saw, in which they receive the elastic preload.

In FIG. 8, the master blades 12, 12 'of the two saw blades 11, 11 "are reduced from the facing blade sides to achieve the elastic prestress, and each master blade 12 or 12' stands in the direction of the other master blade 12 'or 12 a clamping hub 19 or 19. The height of the clamping hubs 19, 19 'is dimensioned in such a way that at the end it goes back behind the plane of the adjacent inner cutting edges 17, 17'. The saw blades 11, 11 'lying against one another without pretensioning are shown in FIG 8. If the sawing tool is clamped into the tool holder of the hand-held circular sawing machine, the two saw blades 11, 11 'assume the position shown in broken lines in Fig. 8, whereby the teeth 13, 13' of the two saw blades 11, 11 'are pressed axially against one another become.

In the exemplary embodiment of the sawing tool according to FIG. 9, the axial force which prevents the saw blades 11, 11 'from being pushed apart in the case of work is generated by inclining the saw blades 11, 11'. The two saw blades 11, 11 'are at a small acute angle ß against each other so that the saw blade axes 18, 18' intersect in the plane of symmetry 20 of the saw tool. As a result, the teeth 14, 14 'within a partial area of the λerzahnungen 13, 13 ^! of the two saw blades 11, 11 * axially pressed together in the region of their secondary cutting edges 17, 17 '. In Fig. 10 this is The adjacent cutting edges 17, 17 'lying against one another are shown enlarged during the engagement in a workpiece 21. As can be clearly seen, the outer blade surfaces of the rake blades 12, 12 'which face away from one another are set back somewhat from the outer secondary cutters 17, 17' which face away from one another, so that there is little or no lateral friction on the cut edges over the depth of cut. Inner surfaces 221, 222 of the cut 22 occur in the workpiece 21.

In the exemplary embodiment of the sawing tool according to FIG. 11, the axial force F _Ai or F _{A2 is} achieved by large corner angles between the main cutting edge 16 or 16 'and the outer secondary cutting edge 17 or 17'. This corner angle is chosen as large as possible, but always smaller than 90 °. For this purpose, the secondary cutting edges 17 and 17 'lying on opposite sides of the blade are positioned relative to the main blade 12 and 12' in such a way that the plane in which the outer secondary cutting edges 17 and 17 'lie, with the associated master blade 12 or 12' includes the smallest possible helix angle γ or γ '. The helix angle γ, γ 'on the two

Saw blades 11, 11 'are selected to be the same size; in comparison, the inclined position of the outer secondary cutting edge 17, as is customary in conventional saw blades, is shown in broken lines in FIG. 11. The helix angle γ * is significantly larger than the helix angle γ of the novel saw blade 11.

On all the sawing tools described, means for forcing an air flow to the toothing 13 or 13 'are provided on each saw blade 11 or 11'. According to the exemplary embodiments in FIGS. 12 to 20, these air guidance means are realized differently. In all cases, however, in the case of saw blades 11, 11 'rotating in opposite directions, air is guided radially outwards from the inside to the toothings 13, 13' of the saw blades 11, 11 'and thereby cooling in the tooth area and good heat dissipation from the saw blades 11, 11'. reached. The air guiding means are formed in the master blades 12, 12 'of the two saw blades, so that only the master blades 12 and 12 * are shown in the exemplary embodiments of FIGS. 12 to 19 of the saw blades 11, 11'.

In the exemplary embodiment of FIG. 12, the master blade 12 has through holes 23 which are preferably arranged in an aquidistant manner on a part of the saw blade axis 18 which is concentric. The not visible master sheet 12 'of the saw blade 11' has identical holes. Due to the rotating through bores 23 and 23 'passing through each other, air swirling is achieved in sawing operation, which causes a cooling effect on the toothings 13, 13' and on the master blades 12, 12 '.

In the exemplary embodiments according to FIGS. 13 and 14, spokes 24 and 25 are formed in the master page 12 of the saw blade 11, which extend in the radial direction and in the exemplary embodiment of FIG. 13 have a constant cross section over their length, while in the exemplary embodiment of FIG 14 have a continuously increasing cross-section towards the outside. As the sectional view in FIG. 15 shows, the spokes 24 have a rectangular profile and are positioned in relation to the plane of the saw blade so that they rotate the air inward like a scoop conduct. In a modification of the spokes 24, as shown in FIG. 16, the spokes 24 have a flow-optimized profile similar to the profile of an aircraft wing. Here too, the master blade 12 'of the other saw blade 11', which is not shown in FIGS. 13-16, is of identical design.

In the two exemplary embodiments of a cooling air supply to the toothings 13, 13 'of the saw blades 11, 11' shown in FIGS. 17-19, the air guiding means arranged in the master blades 12, 12 'are, on the one hand, by pairs offset in the one master blade 12 by the same circumferential angle from one another of radially spaced through bores 26 and on the other hand in the main blade 12 'of the other saw blade 11' by the same

Circumferential angles spaced apart from one another and extending in the radial direction are realized, which, when the two saw blades 11, 11 'rotate, intersect the pairs of through bores 26 with their end region. A modification is shown in the lower part of FIGS. 17-19. In this case, the elongated holes are replaced by grooves 28 placed in the same place, as can be seen in section in FIG. 17 and in dashed lines in a concealed top view in FIG. 19. When the two saw blades 11, 11 'rotate against one another, there is an air suction from inside to outside which cools the toothings 13, 13'. If grooves 28 are provided instead of elongated holes 27, the amount of air conveyed per revolution is higher, since no lateral escape of the air is possible, as is the case with elongated holes 27. In a further modification - as is also indicated in FIGS. 17-19 below - these are

Through holes 26 with oblique to the sheet plane Axes executed and the grooves 28 beveled in the end region. This also supports the air flow to the toothings 13, 13 '. A beveling of the ends of the elongated holes 27 acts in the same way.

In the exemplary embodiment of the sawing tool shown in FIG. 20, in which the toothings 13, 13 'are designed as described above, air guide means for the air supply to the toothings 13, 13' are again provided in the master blades 12, 12 '. For this purpose, through holes 29 arranged in the master blade 12 of the one saw blade 11, offset by the same circumferential angle from one another on a divider circle, and in the master blade 12 'of the other saw blade 11' offset by the same circumferential angle, radially extending elongated holes 30. The

Elongated holes 30 each open into a tooth space 31 on the circumference of the master blade and are dimensioned so long that when the two saw blades 11, 11 'rotate, their end region facing away from the mouth intersects the through bores 29. As shown in FIG. 20, the tooth space base 311 of the saw blade 11 having the through bores 29 is drawn radially lower than the tooth space base 311 'in the toothing 13' of the other saw blade 11 ^τ . Instead of the elongated holes 30, grooves of the same design can also be provided. 20 of the toothings 13,

13 'only three teeth 14 and 14' are shown and the rest of the teeth 13, 13 'indicated by the pitch circles 131, 131'.

To reduce vibration during hand sawing, all toothings 13, 13 ′ are advantageously designed as shown in FIG. 21 is shown in detail for a saw blade 11. The main cutting edge free areas 32 lying behind the main cutting edges 16 in the direction of rotation are given a contour which starts from the main cutting edge 16 and rises again towards the subsequent tooth 14. This increase reduces the maximum possible feed per tooth 14, which is determined by the dimension z in FIG. 21. Although this reduction also reduces the maximum feed rate, the advantage of vibration reduction outweighs the limited performance of hand-held circular saws and the comparatively flexible guidance by the user.

Claims

Expectations

1. Sawing tool for a hand-held circular saw machine with two coaxial saw blades (11, 11 ') which rotate directly past one another and can be driven in opposite directions, each of which has a master blade (12, 12') and a toothing (13, 13) surrounding the master blade (12, 12 ') ') from a multiplicity of teeth (14, 14') which are arranged in an equidistant manner one behind the other and protrude radially from the main blade (12, 12 '), each of which has a main cutting edge (16, 16 ") pointing in the direction of rotation and two laterally adjoining, has radially extending secondary cutting edges (17, 17 '), characterized in that on each saw blade (11, 11') the cutting edge (161, 161 ') of each main cutting edge (16, 16'), which is the front in the direction of rotation, in one through the saw blade axis (18, 18 ') extending plane and the main cutting edges (16, 16') in the direction of

Saw blade axes (18, 18 ') are beveled in such a way that the main cutting edges (16, 16') drop from the facing blade sides of the saw blades (11, 11 ') towards the facing blade sides.

2. Saw tool according to the preamble of claim 1, characterized in that on each saw blade (11, 11 ') the main cutting edges (16, 16') parallel to the saw blade axis (18, 18 ') and the transitions from the main cutting edges (16, 16 ') are rounded off at least to the outer secondary sheaths (17, 17') lying on opposite sides of the sheet.

3. Saw tool according to the preamble of claim 1, characterized in that the saw blades (11, 11 ') resiliently axially in the region of their teeth (13, 13') with a small spring constant.

4. Saw tool according to claim 3, characterized in that the master blades (12, 12 ') of the two saw blades

(11, 11 ') have a conical shape which tapers towards the opposite sides of the blade, which is preferably achieved by a forging process which follows the saw blade production process.

5. Saw tool according to claim 3, characterized in that in the two saw blades (11, 11 ') the axial thickness of the master blades (12, 12') is reduced from the mutually facing blade sides and of the master blades (12, 12 ') a coaxial clamping hub (19, 19 ^! ) protrudes on facing blade surfaces, the free end of which axially recedes behind the facing, inner minor cutting edges (17, 17 ') of the teeth (14, 14').

6. Saw tool according to the preamble of claim 1, characterized in that the two saw blades (11, 11 ') with intersecting saw blade axes (18, 18') in the plane of symmetry (20) of the saw tool at a small acute angle (ß) against each other are set up in such a way that the teeth (14, 14 ') of the two saw blades (11, 11') lie axially against one another within a partial area of their toothing (13, 13 ').

7. Sawing tool according to claim 6, characterized in that the facing away from the outer blade surfaces of the master blades ^' (12, 12') of the two saw blades (11, 11 ') with respect to the facing away from each other, minor cutting edges (17, 17') set back somewhat are.

8. Sawing tool according to the preamble of claim 1, characterized in that at least the outer secondary cutting edges (17, 17 ') lying on opposite sides of the blade (17, 17') are adjusted relative to the master blades (12, 12 ') so that the plane in which the outer minor cutting edges (17, 17 ') lie, with the main blade (12, 12') enclosing the smallest possible helix angle (γ, γ ^! ).

9. Sawing tool according to one of claims 1-8, characterized in that means are provided on each saw blade (11, 11 ') for forcing an air duct for toothing (13, 13').

10. Sawing tool according to one of claims 1-9, characterized in that in the toothing (13, 13 ') of the The main cutting edge free flats (32) in the direction of rotation of the main saw blades (11, 11 ') behind the main cutting edges (16, 16') have a contour which starts from the main cutting edge (16, 16 ') and leads to the following tooth (14, 14 ') increases again.