EP2024150B1 - Portable power tool having a tool driven in an oscillating and pendulous manner - Google Patents

Description

The invention relates to a hand tool according to the preamble of claim 1.

Pendulum jigsaws are known in which the saw blade exerts an oscillating movement along its longitudinal axis, wherein this oscillating movement is superimposed on a pendulum movement to engage a sawtooth blade of the saw blade in the cutting stroke with the workpiece and lift something off the workpiece during the backward stroke.

From the GB 1 093 032 A and from the US 2005/210687 A1 Hand tool machines of the type mentioned are also already known, which are also pendulum jigsaws. In these jigsaws, the pivot axis is located beyond a received in a tool holder end face of a sawing tool in the oscillating tool holder, so that the oscillating together with the tool holder sawing tool performs a pendulum motion about the pivot axis. However, with such an arrangement of the pivot axis, the deflection of the tool is always greatest at its free end remote from the tool holder.

Although it is possible to sever workpieces with these and other jigsaws, it is not possible to produce or process grooves in workpieces. In addition, the known jigsaws can only be equipped with saw blades and used for cutting workpieces, but are not suitable for other material processing methods, such as grinding or scraping.

Proceeding from this, the present invention seeks to improve a hand tool of the type mentioned in that they are relatively low not only to cut workpieces, but also to produce joints and recesses in the workpieces, and that they can be equipped not only with a sawing tool but also with different cutting tools and grinding and scraping tools, so that the hand tool to carry out a variety of different work and therefore has a great versatility.

This object is achieved in that the pivot axis between two angularly arranged lever arms of a two-armed lever is arranged, one of which carries the tool and the other forms a push rod of a Geradschubkurbel. As a result, the tool oscillates during its oscillating movement about the pivot axis which moves along the path of motion, preferably at a significant distance from a machining edge, for example a sawtooth or knife edge, or a machining surface, for example a grinding surface , The tool is arranged and aligned in this generally parallel.

According to a preferred embodiment of the invention, a first end of the push rod is pivotally guided about the pivot axis along the movement path, while the opposite second end of the push rod is articulated eccentrically on a drive crank rotationally driven drive crank, so that it describes a circular path during operation of the drive motor.

The longitudinal axis of the lever arm serving as a tool carrier is preferably aligned at right angles to the longitudinal axis of the push rod, while the machining edge or surface of the tool is preferably aligned at right angles to the longitudinal axis of the serving as a tool carrier lever arm. However, deviations from these angles are possible.

To suppress vibrations, the tool carrier and / or the tool preferably has mass balancing devices which are expediently arranged at least partially on the side of the pivot axis opposite the machining edge or machining surface of the tool.

With the machine tool according to the invention a continuous jerk-free immersion of the tool into a workpiece and a machining of the workpiece to corners and edges is possible, especially if the machining edge of the tool according to an advantageous embodiment of the invention after attachment of the tool on the tool carrier T-shaped opposite sides over the tool carrier protrudes. If the tool is designed cranked according to a further advantageous embodiment of the invention, also a clearing or editing of grooves with a predetermined by the cranking maximum depth is possible.

The tool, and in particular a sawing tool, may alternatively have either a straight, a convex or a concave machining edge, so that workpieces with a convex or concave shape can be optimally machined by selecting a correspondingly adapted tool. The pendulum motion of such a tool also ensures a clean cut and minimizes the tendency to jamming due to the good clearance of the kerf.

A further preferred embodiment of the invention provides that in particular sawing, cutting or scraping tools have an elongated machining edge or cutting edge, which is aligned after attachment to the tool carrier generally parallel to a longitudinal axis of the power tool and arranged at a lateral distance from this, which for a favorable center of gravity of the machine tool sogt and a comfortable handling and one-handed operation allows.

Advantageously, the machine tool can also comprise a receptacle for the tool, which can be mounted rotated by 180 degrees in different orientation on the tool carrier, so that an adaptation of the machine tool to right and left-handers and processing to every corner is possible.

Brief description of the drawings

• Fig. 1 eine perspektivische Ansicht einer Handwerkzeugmaschine;
• Fig. 2 eine schematische Darstellung eines Getriebemodells der Handwerkzeugmaschine;
• Fig. 3a und 3b eine Seitenansicht bzw. eine Querschnittsansicht von Zähnen eines an der Werkzeugmaschine in Fig. 1 angebrachten Sägewerkzeugs;
• Fig. 4a bis 4c Seitenansichten alternativer Zahnformen von Zähnen des Sägewerkzeugs;
• Figuren 5 bis 17 Bewegungsbahnen von Zähnen des an der Werkzeugmaschine angebrachten Sägewerkzeugs in Abhängigkeit verschiedenen Parametern der Werkzeugmaschine und des Sägewerkzeugs.

The invention will be explained in more detail in some embodiments with reference to the accompanying drawings. Show it:

• Fig. 1 a perspective view of a power tool;
• Fig. 2 a schematic representation of a transmission model of the power tool;
• Fig. 3a and 3b a side view and a cross-sectional view of teeth of a machine tool in Fig. 1 attached sawing tool;
• Fig. 4a to 4c Side views of alternative tooth shapes of teeth of the sawing tool;
• FIGS. 5 to 17 Trajectories of teeth of the attached to the machine tool sawing tool depending on various parameters of the machine tool and the sawing tool.

Embodiments of the invention

In the Fig. 1 shown hand tool 2 is used for material processing by sawing, grinding or scraping and emergency repairs. The hand tool 2 is in Fig. 1 shown in the form of a equipped with a cranked sawing tool 4 off-grid battery device, but may also be designed with a grinding or scraping tool or as an electrical appliance with a cable for connection to a power grid.

How best in Fig. 1 illustrated, the machine tool 2 consists of a closed, substantially elongated cylindrical plastic housing 6, a arranged at one end of the housing 6 removable battery pack 8, arranged at the other end of the housing 6 processing head 10 with a laterally arranged tool holder 12 for exchangeable attachment of Tool 4, a housed in the interior of the housing 6 electric drive motor (not visible) and arranged between the drive motor and the tool holder 12 thrust crank 14, the in Fig. 2 is shown schematically together with the tool 4.

The slider crank drive 14 consists essentially of a drive crank via an angular reduction gear about a rotation axis 16 rotatably driven drive crank 18, an angled two-armed lever 20, one lever arm 22 serves as a tool carrier 12 and carries the tool 4, and the other lever arm 24, the push rod of Thrust crank 14 forms, and a guide slot 26 for a between the two lever arms 22, 24 arranged part 28 of the lever 20th

The drive crank 18 may be formed as an eccentric disc with an eccentric to the rotation axis 16 arranged pin 30 for articulation of the one end of the push rod 24 and directly on the free end of an output shaft of the reduction gear (not shown) sit, the eccentricity e of the pin 30 in conjunction with the speed of the drive crank 18 is an essential parameter for the length of the path of movement of an oscillating movement of a workpiece engaging in a sawtooth cutting edge 32 of Fig. 1 Sawing tool 4 or a corresponding machining edge or machining surface of another tool, for example, a grinding surface or grinding edge of a grinding tool is shown, and also their pendulum motion and their speed of movement determined.

The guide slot 26 is formed as a linear guide, in which a sliding block 34 in a to a longitudinal axis 36 (FIG. Fig. 1 ) of the machine tool 2 parallel axis 44 is longitudinally displaceable movable, but in principle, a curved path of movement is possible. The sliding block 34 and the lever 20 are connected by a pivot joint 38, the pivot axis 40 is aligned perpendicular to the longitudinal axis 36 of the machine tool 2, as in Fig. 1 shown.

The two lever arms 22, 24 of the lever 20 are aligned perpendicular to each other, wherein serving as a push rod lever arm 24 has a length of L1 and is hinged at its free end on the pin 30 of the drive crank 18 so that this End of the lever arm 24 describes a circular path about the axis of rotation 16. Serving as a tool carrier 12 lever arm 22 is so matched to the associated tools, such as the tool 4, that the machining edge or processing surface, such as the Sägezahnschneide 32, arranged at a distance L2 from the pivot axis 40 of the pivot joint 38 and approximately parallel to the longitudinal axis 36th the machine tool 2 is aligned. In this case, the machining edge or machining surface of the tool 4 projects beyond the tool carrier 12 to both sides, so that it encloses an angle α with the machining edge or machining surface. At the in Fig. 2 illustrated transmission model is this angle α = 90 °, as well as the enclosed by the two lever arms 22, 24 angle β, but the two angles α, β can assume other values.

As in Fig. 1 shown, the sawing tool 4 is provided to avoid vibrations on the sawtooth edge 32 opposite side of the pivot axis 40 with a mass balance portion 42 which is tuned with respect to its position and its mass to the oscillating overall system of tool 4 and lever 20. The mass balance portion 42 may either be part of the tool 4, as in FIG Fig. 1 represented, or alternatively at least partially by a tool on the support 12 mounted mass balance element (not shown) are formed, for example, in the manufacture of the lever 20 integrally formed as a die-cast part on the lever arm 22, that it is beyond the pivot axis 40. In this case, however, 4 additional measures for mass balance must be made to differently shaped or sized tools, since the mass balance element of the tool carrier 22 only provides for a basic balance.

The slider crank drive 14 serves to detach the tool 4, which is detachably fastened to the tool carrier 12, in an oscillating movement parallel to the longitudinal axis 36 of the machine tool 2 (double arrow A in FIG Fig. 1 ) and to offset this movement a pendulum or pivoting movement about the pivot axis 40 (double arrow B in Fig. 1 ) to superimpose.

While in known purely rotating or oscillating sawing tools each sawtooth passes through an identical trajectory, there are in the machine tool 2 and the specific tools for the machine tool 2, such as the sawing tool 4, a set of parameters that determine the motion of each tooth or other machining tool of each part of the machining edge or surface.

With regard to the machine tool 2, these parameters are essentially the eccentricity e, the length L1 of the push rod 24 or the distance between the axis of rotation of the pin 30 and the pivot axis 40, and the angle β between the two lever arms 22, 24 of the lever 20th , and a possible distance a between the axis of rotation 16 of the drive crank 18 and the rectilinear trajectory 44 of the pivot axis 40, resulting from the parameters L1 and 2e, a maximum pendulum angle γ of the tool 4 according to the following relationship: $$\mathrm{tan\; \gamma }\mathrm{=}\mathrm{2}\mathrm{e}\mathrm{/}\mathrm{L}\mathrm{1}$$

With regard to the tool 4 or the tool 4 attached to the machine tool 2, these parameters are essentially the distance L2 between the pivot axis 40 and the sawtooth edge 32 or the machining edge or surface of the tool 4, the angle α between the longitudinal axis of the tool Tool holder 12 and the machining edge or surface of the tool 4, the tool width Wa, as well as the shape of an envelope of the individual teeth of the sawtooth edge 32 and the individual points on the processing edge or surface, said envelope even, convex, as in Fig. 1 shown, or even may be concave, the latter, for example, in a sawing tool for cutting through pipes or round rods. The shape of the envelope is defined by its radius of curvature Rw, which is ∞ at plane envelopes.

The determination of the individual quantities depends on the demands placed on the machine tool 2, e.g. By increasing the eccentricity e and decreasing the ratio of L1 / L2 in conjunction with a sawing tool 4 having an aggressive tooth shape, high cutting performance can be achieved in sawing suitable materials.

The FIGS. 3a and 3b as well as the Figures 4a, 4b and 4c show various shapes of teeth 46, 48, 50 of the sawtooth cutting edge 32 of different sawing tools 4, with which the machine tool 2 can be equipped. The FIGS. 3a and FIGS. 4b and 4c show a sawtooth cutting edge 32 in which all or part of the saw teeth 46 are formed as pointed teeth. This tooth form is with cut free cut in milled or ground design, as in Fig. 3b shown, universally applicable, since it cuts equally well in both directions and prevents jamming of the tool 4. In contrast to the triangular-shaped pointed tooth 46 with a strongly negative rake angle, teeth 48, 50 with a more aggressive tooth form, ie with a positive rake angle, can be used for a high sawing progress, for example when sawing wood or plastic, as in FIG Fig. 4a shown when these teeth 48 and 50 are effective in both cutting directions. In order to exploit the advantages of the good cutting of teeth 46, it is also possible to use combinations of pointed teeth 46 and teeth forms 48, 50 with a positive rake angle, as illustrated by two examples in FIG Fig. 4b and Fig. 4c shown.

The FIGS. 5 to 17 show trajectories of tips of teeth 46, 48, 50 at different points on the sawtooth cutting 32 differently shaped, mounted on the machine tool 2 sawing tools 4 in response to L1, Rw and the angle 90 ° -α, ie the tilt angle of the sawtooth cutting edge 32 of the sawing tool 4 with respect to the longitudinal axis 36 of the machine tool 2, wherein to limit the many possible trajectories e = 20 mm, L2 = 100 mm, Wa = 100 mm and β = 90 ° were set as constants. For clarity, three individual tooth tips or points in the middle of the sawtooth cutting edge 32 as well as at the opposite ends of the same are usually considered. Table 1 L1 rw 90 ° -α a figure 200 ∞ 0 ° 0 5 200 ∞ 0 ° 0 5a 200 ∞ 15 ° 0 6 200 100 0 ° 0 7 200 200 0 ° 0 8th 200 200 0 ° 0 8a 200 200 0 ° 0 8b 200 200 15 ° 0 9 100 200 0 ° 0 10 100 200 0 ° 0 10a 100 ∞ 0 ° 0 11 200 70 concave 0 ° 20 12 200 70 concave 0 ° 0 13 200 70 convex 0 ° 0 14 200 70 convex 0 ° 20 15 200 ∞ 0 ° 20 16 200 200 0 ° 20 17

• die Bahnkurven sämtlicher Zahnspitzen weisen eine elliptische oder quasi-elliptische Kurvenform auf;
• die Bahnkurven von Punkten beiderseits der Mitte weisen entgegengesetzte Bewegungsrichtungen auf;
• die Bahnkurven von Punkten in der Mitte und an den beiden entgegengesetzten Enden der Sägezahnschneide 32 haben gleichgroße Schwingweiten in Richtung der oszillierenden Bewegung, die zur Exzentrizität e proportional sind;
• die Amplituden der Bahnkurven senkrecht zur Richtung der oszillierenden Bewegung werden in Richtung der Mitte der Sägezahnschneide 32 kleiner;
• die Mitte der Sägezahnschneide 32 bewegt sich auf einer schleifenförmigen Kurvenbahn;
• die Mitte der Sägezahnschneide 32 fällt in der Regel nicht mit dem Wendepunkt der Kurvenbahn zusammen;
• die Kurvenformen sind grundsätzlich nicht symmetrisch zu einer Mittelachse des Werkzeugs 4, nähern sich aber mit größer werdendem Verhältnis L1/L2 einer symmetrischen Form an;
• entlang der Kurvenbahnen erreichen die Zähne am linken und rechten Scheitelpunkt ihre geringste Geschwindigkeit und am oberen und unteren Scheitelpunkt ihre höchste Geschwindigkeit.
• während eines Umlaufs durch die Kurvenbahn leistet der Zahn im oberen Teil der Kurvenbahn "aktive" Zerspanarbeit und im unteren Teil der Kurvenbahn "passive" Zerspanarbeit, das heißt dieser letztere Teil der Kurvenbahn wird überwiegend zum Ausräumen der Schnittfuge und zum Abtransport der Späne genutzt. Für die Zähne im mittleren Teil der Sägezahnschneide überwiegt wegen der annähernd geradlinigen Bewegung die reine Zerspanung.
• annähernd gleiche Kurven für Punkte rechts und links der Mitte der Sägezahnschneide erhält man unter den Vorraussetzungen L1 > L2, wobei für L1 als Mindestwert L1 = L2 angestrebt werden sollte, α = 90°, β = 90° sowie a = 0. Dabei spielt es keine Rolle, ob die Werkzeugform, d.h. die Hüllkurve der Zahnspitzen, gerade, konvex oder konkav ausgeführt ist.

As is clear from the FIGS. 5 to 17 can be seen, the trajectories of the tooth tips at different points of the sawtooth cutting edge 32 for different combinations of L1, Rw, α and a have some similarities:

• the trajectories of all tooth tips have an elliptical or quasi-elliptic curve shape;
• the trajectories of points on both sides of the middle have opposite directions of movement;
• the trajectories of points in the middle and at the two opposite ends of the sawtooth cutting edge 32 have equally large oscillations in the direction of the oscillating motion, which are proportional to the eccentricity e;
• the amplitudes of the trajectories perpendicular to the direction of the oscillating motion become smaller in the direction of the center of the sawtooth cutting edge 32;
• the center of the sawtooth cutting edge 32 moves on a loop-shaped curved path;
• the center of the sawtooth cutting edge 32 does not coincide generally with the inflection point of the cam track;
• the waveforms are basically not symmetrical to a central axis of the tool 4, but approach with increasing ratio L1 / L2 of a symmetrical shape;
• Along the curved paths, the teeth reach their lowest speed at the left and right vertex and their highest speed at the top and bottom vertex.
• during one revolution through the curved path, the tooth makes "active" machining work in the upper part of the curved path and "passive" machining in the lower part of the curved path, ie this latter part of the curved path is used predominantly for clearing out the kerf and for removing the chips. For the teeth in the middle part of the sawtooth cutting, the pure machining predominates because of the approximately rectilinear motion.
• Approximately equal curves for points to the right and left of the center of the sawtooth are obtained under the prerequisites L1> L2, where L1 should be the minimum value L1 = L2, α = 90 °, β = 90 ° and a = 0 It does not matter whether the tool shape, ie the tooth tip envelope, is straight, convex or concave.

Decisive for the length of the curved paths of the individual teeth is primarily the eccentricity e, whose determination is to be made in dependence on the desired conditions of use. However, the lengths of the trajectories can also be influenced by the ratio L1 / L2, with L1 <L2, the trajectories are extended, as in the FIGS. 10, 10a and 11 shown.

When the angle α is changed or the distance a between the rotation axis 16 of the drive crank 18 and the pivot axis 40 is set greater than zero, the loop curves of the tooth tips in the center of the sawtooth edge 32 change into flat ellipses, as in FIGS Figures 9 . 12 and 15 to 17 shown. By introducing a distance a also obtained geometrically unequal curves for points to the right and left of the center of the Sägezahnschneide 32, as in the Figures 12 and 15 to 17 shown.

In FIG. 8a the trajectories of each one point in the middle and at the two opposite ends of the Sägezahnschneide 32 for a revolution of the drive crank 16 in eight individual substeps are shown, wherein like numerals indicate the position of the three points at the same time points. Combining these points with each other results in their trajectories.

The FIGS. 12 to 17 In addition to the trajectories of three points in the middle and at the two opposite ends of the sawtooth cutting edge 32, trajectories of further points in the right part of the sawtooth cutting edge 32 are shown. Fig. 8b and Fig. 10a only show trajectories of points in the right part of the sawtooth cutting edge 32.

Claims (14)

1. Portable power tool having a drive motor and a tool (4) which is driven by the drive motor and which performs an oscillating movement during operation of the drive motor, a pendulous movement being superimposed on said oscillating movement, wherein the tool (4) moves in a pendulum fashion about a pivot axis (40) which moves in a reciprocating manner along a path (44) of movement, characterized in that the pivot axis (40) is arranged between two lever arms (22, 24), arranged at an angle to one another, of a two-armed lever (20), wherein the one lever arm (22) carries the tool (4) and the other lever arm (24) forms a connecting rod of a slider crank.
2. Portable power tool according to Claim 1, characterized in that the path (44) of movement is rectilinear and is oriented substantially parallel to a machining edge (32) or machining surface of the tool (4).
3. Portable power tool according to Claim 1 or 2, characterized in that the pivot axis (40) is at a significant lateral distance from a machining edge (32) or machining surface of the tool (4).
4. Portable power tool according to one of the preceding claims, characterized in that one end of the connecting rod (24) is pivotably guided about the pivot axis (40) along the path (44) of movement.
5. Portable power tool according to one of the preceding claims, characterized in that one end of the connecting rod (24) is eccentrically linked to a drive crank (18) rotationally driven by the drive motor, such that said end describes a circular path during operation of the drive motor.
6. Portable power tool according to Claim 5, characterized in that the centre of the circular path lies on the rectilinear path (44) of movement.
7. Portable power tool according to Claim 5, characterized in that the centre of the circular path is laterally offset with respect to the rectilinear path (44) of movement.
8. Portable power tool according to one of the preceding claims, characterized in that the tool (4) can be interchangeably fastened to the lever arm (22) serving as tool carrier (12).
9. Portable power tool according to one of the preceding claims, characterized in that the lever (20) or the tool (4) has mass balancing devices for suppressing vibrations.
10. Portable power tool according to one of the preceding claims, characterized in that the power tool (2) can be optionally fitted with a sawing, cutting, grinding or scraping tool.
11. Portable power tool according to one of the preceding claims, characterized in that the tool (4) has an elongated machining edge (32) which, after being fastened to the power tool (2), is generally oriented parallel to a longitudinal axis (36) of the power tool (2) and is arranged at a lateral distance therefrom.
12. Portable power tool according to one of the preceding claims, characterized in that the tool (4) is cranked.
13. Portable power tool according to one of the preceding claims, characterized in that the tool (4) has a convexly or concavely curved machining edge (32).
14. Portable power tool according to one of the preceding claims, characterized by a tool receptacle which can be rotated by 180° and fastened in different orientations on the power tool (2).

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