WORK TOOL DRIVE UNIT FOR A CUTTING BLADE OF A HANDHELD WORK APPARATUS, AND HANDHELD WORK APPARATUS HAVING THE WORK TOOL DRIVE UNIT

Abstract

A work tool drive unit for a cutting blade of a handheld work apparatus includes an electric motor configured to rotate a drive pinion, a gearbox, a planetary gear arranged in the gearbox, with a single ring gear, a single planetary carrier and planets driven by the drive pinion, an eccentric shaft driven by the planetary gear and is configured to drive at least one cutting tool. The planets each have a first peripheral section and a second peripheral section. The first peripheral section is in engagement exclusively with the drive pinion, and the second peripheral section is in engagement exclusively with the ring gear. The work tool drive unit has an oscillating weight which is connected fixedly to the drive pinion for conjoint rotation.

Claims

1. A work tool drive unit for a cutting blade of a handheld work apparatus, the work tool drive unit comprising: an electric motor configured to rotate a drive pinion at a drive rotational speed; a gearbox; a planetary gear arranged in said gearbox and said planetary gear including a single ring gear, a single planetary carrier and planets driven by said drive pinion; an eccentric shaft driven by said planetary gear at an output rotational speed and being configured to drive at least one cutting tool in an oscillating manner; said planets each having a first peripheral section and a second peripheral section; wherein a first diameter of said first peripheral section is greater than a second diameter of said second peripheral section; wherein said first peripheral section is in engagement exclusively with said drive pinion and said second peripheral section is in engagement exclusively with said ring gear; and, an oscillating weight connected fixedly to said drive pinion for conjoint rotation.

2. The work tool drive unit of claim 1, wherein said drive pinion has a third peripheral section and a fourth peripheral section; said fourth peripheral section is in engagement with said first peripheral section; said third peripheral section has a diameter increased in comparison with said fourth peripheral section; and said third peripheral section forms said oscillating weight, at least partially.

3. The work tool drive unit of claim 1, wherein said electric motor, said planetary gear and said eccentric shaft are arranged coaxially with respect to one another.

4. The work tool drive unit of claim 1, wherein said gearbox has a pot-shaped gear receiving chamber and a cover; and, said cover covers said gear receiving chamber in an axial direction.

5. The work tool drive unit of claim 4, wherein said electric motor is arranged on said cover.

6. The work tool drive unit of claim 4, wherein said ring gear is at a spacing (a) from said cover; and, said spacing (a) is bridged by a hold-down.

7. The work tool drive unit of claim 1, wherein said ring gear has a fifth peripheral section and a sixth peripheral section; said fifth peripheral section is in engagement with said second peripheral sections of said planets; and, a bearing position for the planetary carrier of said planetary gear is arranged on said sixth peripheral section.

8. The work tool drive unit of claim 1, wherein said planetary gear has a transmission ratio lying in a value range between 4 and 13.

9. The work tool drive unit of claim 1, wherein said gearbox has a cylindrical circumferential wall with an internal diameter (d.sub.20) and a length (l.sub.20) measured in an axial direction; said length (l.sub.20) is at most 50% of said internal diameter (d.sub.20); and, said internal diameter (d.sub.20) lies radially outside a cam arranged on said eccentric shaft.

10. The work tool drive unit of claim 1, wherein said first peripheral section and said second peripheral section are configured in one piece.

11. A handheld work apparatus comprising a work tool drive unit including: an electric motor configured to rotate a drive pinion at a drive rotational speed; a gearbox; a planetary gear arranged in said gearbox and said planetary gear including a single ring gear, a single planetary carrier and planets driven by said drive pinion; an eccentric shaft driven by said planetary gear at an output rotational speed and being configured to drive at least one cutting tool in an oscillating manner; said planets each having a first peripheral section and a second peripheral section; wherein a first diameter of said first peripheral section is greater than a second diameter of said second peripheral section; wherein said first peripheral section is in engagement exclusively with said drive pinion and said second peripheral section is in engagement exclusively with said ring gear; an oscillating weight connected fixedly to said drive pinion for conjoint rotation; a handle unit for holding and guiding the work apparatus; an energy source for feeding the electric motor; and, cutting blades movable relative to one another and of which at least one cutting blade is driven by said eccentric shaft.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0028] The invention will now be described with reference to the drawings wherein:

[0029] FIG. 1 shows a perspective view of a work apparatus with a work tool drive unit according to the disclosure,

[0030] FIG. 2 shows a longitudinal section through the work tool drive unit of the work apparatus from FIG. 1 along the sectional line II-Il in FIG. 3,

[0031] FIG. 3 shows a detailed view of the region Z from FIG. 2,

[0032] FIG. 4 shows a cross section through the work tool drive unit of the work apparatus from FIG. 1 along the sectional line IV-IV in FIG. 2; and,

[0033] FIG. 5 shows a side view of the work apparatus from FIG. 1 in a partially assembled state.

DETAILED DESCRIPTION

[0034] FIG. 1 shows a handheld work apparatus 100 in an embodiment as a hedge trimmer. The work apparatus 100 includes a handle unit 110 for holding and guiding the work apparatus 100, and a work tool drive unit 1 for driving the cutting blade of the work apparatus 100. In the embodiment, a first handle 111 with an operator controlled element 113 for controlling the work tool drive unit 1 and a second handle 112 are arranged on the handle unit 110, between which handles a receptacle 118 (shown using dashed lines) for a rechargeable battery pack which can be removed without tools is configured as energy source 120 for the work tool drive unit 1. The receptacle 118 can also be arranged at other positions of the handle unit 110, in particular below the rear first handle 111 which is remote from the tool. The rechargeable battery pack can be arranged completely within the receptacle 118 or can protrude completely or partially out of it. The work tool drive unit 1 is connected to the handle unit 110 via anti-vibration elements (not shown). A rigid attachment of the work tool drive unit 1 to the handle unit 110 is also possible.

[0035] FIG. 2 shows the work tool drive unit 1 with cutting blades 131, 132 of the work apparatus 100 which are arranged thereon. The work tool drive unit 1 includes a gearbox 14 with a pot-shaped gear receiving chamber 18 and a cover 16 which covers the gear receiving chamber 18 in an axial direction. A planetary gear 30 is arranged in the gear receiving chamber 18. An electric motor 3 is arranged on the cover 16, which electric motor is configured as an internal rotor motor in the embodiment and protrudes with its rotor shaft 5 into the gear receiving chamber 18. The drive pinion 10 is arranged fixedly on the rotor shaft 5 of the electric motor 3 for conjoint rotation. The electric motor 3 drives the drive pinion 10 at a drive rotational speed. The drive rotational speed is, in particular, at least 12,000 revolutions per minute, in particular at least 20,000 revolutions per minute. A through opening 24 is configured on a base 22 of the gear receiving chamber 18. An eccentric shaft 50 protrudes through the through opening 24. The eccentric shaft 50 is driven by a planetary carrier 34 of the planetary gear 30 at an output rotational speed. The eccentric shaft 50 is supported at its first end indirectly by the planetary carrier 34 on a first bearing position 56 on the sixth peripheral section 46 of the ring gear 36. The eccentric shaft 50 is supported at its second end on a second bearing position 57. The rotor shaft 5 and the eccentric shaft 50 lie coaxially with respect to a central axis 80 of the planetary gear 30. The rotational axis of the drive pinion 10 forms the central axis 80 of the planetary gear 30.

[0036] Cams 51, 52 for driving the cutting blades 131, 132 are arranged on the eccentric shaft 50 between the first bearing position 56 and the second bearing position 57. In the embodiment, a first cam 51 for driving a first cutting blade 131 and a second cam 52 for driving a second cutting blade 132 are arranged on the eccentric shaft 50. In the embodiment, the eccentric shaft 50, the first cam 51, the second cam 52 and the planetary carrier 34 are configured in one part with one another. It is also possible, however, for one or both cams 51, 52 to be configured separately from the eccentric shaft 50 and, instead, to be connected fixedly to it for conjoint rotation. Independently of this or in addition to this, it is possible for the eccentric shaft 50 to be configured separately from the planetary carrier 34 and, instead, to be connected fixedly to it for conjoint rotation. The second bearing position 57 of the eccentric shaft 50 is arranged in a second cover 62. The second cover 62 closes a blade chamber 60. The first cam 51 and the second cam 52 and in each case one drive end, arranged on the circumference thereof, of the first cutting blade 131 and the second cutting blade 132 are situated in the blade chamber 60.

[0037] FIG. 3 shows the planetary gear 30 from FIG. 2 in detail. The planetary gear 30 is driven by a drive pinion 10. The drive pinion 10 is seated on the rotor shaft 5 of the electric motor 3. In the embodiment, the planetary gear 30 has three planets 32 (FIG. 4). A different number of planets 32 can also be expedient. The planets 32 each have a first peripheral section 41 and a second peripheral section 42. A first diameter di of the first peripheral section 41 is greater than a second diameter d2 of the second peripheral section 42. The first peripheral section 41 of the planet 32 is driven by the drive pinion 10. The second peripheral section 42 of the planet 32 meshes with a fifth peripheral section 45 of a ring gear 36 of the planetary gear 30. The ring gear 36 has an internal diameter d.sub.5 on the fifth peripheral section 45. The ring gear 36 includes a sixth peripheral section 46, on the internal diameter d.sub.6 of which the first bearing position 56 of the eccentric shaft 50 is configured. Projections 37 are configured on the ring gear 36 on an outer circumference of the ring gear 36, by which projections 37 the ring gear 36 is centered in the gear receiving chamber 18 and is fixed against rotation with respect to the gearbox 14. Grooves 21 (FIG. 4) are arranged in the circumferential wall 20 of the gear receiving chamber 18, into which grooves 21 the projections 37 protrude. The ring gear 36 is fixed in the axial direction by hold-downs 28. The hold-downs 28 bridge an axial spacing a between the cover 16 and an end face of the ring gear 36 which faces the cover. The hold-downs 28 are arranged in the grooves 21 of the gearbox 14. The hold-downs 28 are manufactured from a plastic material in the embodiment. The ring gear 36 is manufactured, in particular, from a plastic material. Even if hold-downs 28 which are configured separately from the ring gear 36 are shown in the embodiment, it is readily possible for them to be of integral configuration with the ring gear. The properties which are described for the separate hold-downs 28 also apply to hold-downs which are configured integrally with the ring gear.

[0038] In the embodiment, the drive pinion 10 has a third peripheral section 43 and a fourth peripheral section 44. The fourth peripheral section 44 meshes with the planets 32. The third peripheral section 43 has a diameter d.sub.3 which is increased in comparison with the diameter d.sub.4 of the fourth peripheral section 44, and is configured as an oscillating weight 7. The third peripheral section 43 and the fourth peripheral section 44 are connected fixedly to one another for conjoint rotation. In the embodiment, the third peripheral section 43 and the fourth peripheral section 44 are configured as a component formed from the same material. It can also be provided that the third peripheral section 43 and the fourth peripheral section 44 are joined to one another, in order to form the drive pinion 10. The drive pinion 10 is arranged in the gearbox 14. A thrust washer 26 divides the gear receiving chamber 18 in such a way that the planetary gear 30 and the oscillating weight 7 are arranged on different sides of the thrust washer 26. The oscillating weight 7 is arranged between the cover 16 and the thrust washer 26. The third peripheral section 43 has an axial length l.sub.3 which is arranged completely between the cover 16 and the thrust washer 26. The thrust washer 26 lies on a shoulder of the hold-down 28. The cover 16 has an (in particular, peripheral) collar, against which the thrust washer 26 bears. The thrust washer 26 is clamped, in particular, between the hold-down 28 and the collar.

[0039] In the embodiment, the first peripheral section 41 and the second peripheral section 42 of the planet 32 are configured in one piece, in particular from the same material. The planet 32 is produced by a sintering method. In the interior of the planet 32, an anti-friction bearing extends over the first peripheral section 41 and the second peripheral section 42, to which anti-friction bearing the planet 32 is attached rotatably on the planetary carrier 34.

[0040] Toothing systems are configured in each case on the first peripheral section 41 and the second peripheral section 42 of the planet 32 and the fourth peripheral section 44, interacting with the former, of the drive pinion 10 and the fifth peripheral section 45 of the ring gear 36.

[0041] The number of teeth of the fourth peripheral section 44 lies, in particular, between 7 and 20, very particularly between 10 and 15; in the embodiment, it is 13. The number of teeth of the first peripheral section 41 lies, in particular, between 15 and 40, very particularly between 23 and 33; in the embodiment, it is 28. The number of teeth of the second peripheral section 42 lies, in particular, between 10 and 26, very particularly between 15 and 22; in the embodiment, it is 18. The number of teeth of the fifth peripheral section 45 lies, in particular, between 30 and 90, very particularly between 48 and 72; in the embodiment, it is 61. Here, the numbers of teeth are adapted to one another in such a way that the result is a transmission ratio of the planetary gear 30 of between 7 and 10. In the embodiment, the planetary gear 30 has a transmission ratio of approximately 8.

[0042] In the embodiment, the internal diameter d.sub.20 (FIG. 4) of the circumferential wall 20 of the gear receiving chamber 18 is approximately 60 mm, and the axial length l.sub.20 of the circumferential wall 20 of the gear receiving chamber 18 is approximately 24 mm. Accordingly, the axial length l.sub.20 of the circumferential wall 20 is approximately 40% of the internal diameter d.sub.20 of the circumferential wall 20. As a result, the gearbox 14 is particularly flat.

[0043] The planets 32 have an axial length l.sub.32 which corresponds at most to 50% of the first diameter d.sub.1. As a result, the planets 32 are particularly flat. The axial length of the fifth peripheral section 45 of the ring gear 36 is at most 10% of the internal diameter d.sub.5 of the ring gear 36 on the fifth peripheral section 45. As a result, the fifth peripheral section 45 is particularly flat. The ring gear 36 has an axial minimum length l.sub.36 for support on the gearbox 14. The axial minimum length l.sub.36 is greater than the axial length l.sub.5 of the fifth peripheral section 45. The axial length l.sub.5 of the fifth peripheral section 45 is, in particular, shorter than the axial length l.sub.1 of the first peripheral section 41, the axial length l.sub.2 of the second peripheral section 42, the axial length l.sub.4 of the fourth peripheral section 44 and/or the axial length l.sub.6 of the sixth peripheral section 46. At least one part of the axial length l.sub.6 of the sixth peripheral section 46 contributes to the support on the gearbox 14. The sixth peripheral section 46 of the ring gear 36 surrounds the planetary carrier 34. In this way, the same axial installation space is used particularly efficiently for the support of both the ring gear 36 and the planetary carrier 34 on the gearbox 14. As a result, the planetary gear 30 is of particularly flat configuration.

[0044] FIG. 4 shows a part of the work tool drive unit 1 in the viewing direction along the central axis 80 directly below the thrust washer 26. The first peripheral sections 41 of the three planets 32 in the embodiment mesh with the fourth peripheral section 44 of the drive pinion 10. The grooves 21 for receiving the hold-downs 28 are arranged in the circumferential wall 20 of the gearbox 14. Four grooves 21 are provided in the embodiment; a different number of grooves, in particular three, can also be expedient. The grooves 21 are distributed over the circumference of the circumferential wall 20, in particular, at a uniform angular spacing. The first diameter d.sub.1 of the first circumferential section 41 of the planet 32 can be maximized by receiving the hold-downs 28 in the grooves 21, without the planet 32 colliding with the hold-down 28 during circulation.

[0045] FIG. 5 shows the blade chamber 60 in the viewing direction along the central axis 80 in a partially assembled state of the work tool drive unit 1. The second cover 62 and the second cutting blade 132 are removed. As can be seen, the first cam 51 bears against the drive end of the first cutting blade 131. In the illustration, the first cutting blade 131 is situated in an end position and would again move closer to the central axis 80 in the case of further rotation of the eccentric shaft 50. An end face 35, facing the first cam 51, of the planetary carrier 34 protrudes radially beyond the first cam 51 in every direction. There is a minimum overhang b of the end face 35 with respect to the first cam 51 even in the end positions. As a result, regardless of the position in which the first cam 51 is situated, the end face 35 serves as a supporting surface for the drive end of the first cutting blade 131. The diameter d.sub.35 of the end face 35 is illustrated using dashed lines, with the result that it becomes visible that the first cutting blade 131 can always (that is, also in the end positions) be supported on the planetary carrier 34. In the case of jamming of the cutting blade 131, it is therefore reliably ensured that the drive end of the first cutting blade 131 cannot lift up axially from the periphery of the first cam 51. The diameter d.sub.35, increased in comparison with the prior art, of the end face 35 of the planetary carrier 34 supports the drive end axially and thus avoids releasing of the drive end from the cam 51. Additional securing means which hold the first cutting blade 131 axially in position and avoid sliding off from the first cam 51 can be dispensed with. The configuration of the planetary carrier 34 with a diameter d.sub.35 of the end face 35 which lies radially completely outside the first cam 51 and therefore forms a supporting surface for a drive end of a first cutting blade 131 is an independent inventive concept which can also be implemented independently of the remaining configuration of the planetary gear 30. In particular, a planetary carrier which is configured in this way can also be used in a multiple-stage planetary gear in the last stage, that is, on the gear output side.

[0046] The handheld work apparatus can also have cutting blades which, instead of an oscillating translational relative movement, carry out an oscillating rotational relative movement with respect to one another. Here, at least one cutting blade is driven indirectly by the eccentric shaft.

[0047] It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.