POWER TOOL AND GEAR UNIT FOR SUCH A POWER TOOL

Abstract

A handheld power tool includes a gear unit, which includes a gear input shaft, a gear output shaft, and a subassembly. The subassembly includes a sun gear co-rotating with the input shaft, an internal ring gear, and at least one planet gear arranged between the sun gear and the internal ring gear. The gear unit further includes a first freewheel clutch mechanism arranged to selectively provide a first torque transferring connection between the gear input shaft and the gear output shaft bypassing the gear unit subassembly when a drive shaft rotates in a first direction and a second freewheel clutch mechanism arranged to selectively provide a second torque transferring connection via the gear unit subassembly when the drive shaft rotates in a second, opposite direction.

Claims

1-14. (canceled)

15. A handheld power tool comprising a motor, an output shaft, and a gear unit arranged between the output shaft and a drive shaft connected to the motor, wherein the gear unit comprises: a gear input shaft adapted to be driven by the motor; a gear output shaft adapted to engage the output shaft; and a gear unit subassembly comprising: a sun gear arranged on and co-rotating with the gear input shaft, an outer element comprising an internal ring gear, at least one planet gear arranged between the sun gear and the internal ring gear, and adapted to transfer rotational movement therebetween, and a planet carrier, wherein the gear unit further comprises a first freewheel clutch mechanism and a second freewheel clutch mechanism, each adapted to selectively transfer torque to the gear output shaft, wherein the first freewheel clutch mechanism is arranged to selectively provide a first torque transferring connection between the gear input shaft and the gear output shaft bypassing the gear unit subassembly, wherein the second freewheel clutch mechanism is arranged to selectively provide a second torque transferring connection between the drive shaft and the gear output shaft via the gear unit subassembly, wherein the first freewheel clutch mechanism provides the torque transferring connection when the drive shaft rotates in a first direction, and the second freewheel clutch mechanism provides the second torque transferring connection when the drive shaft rotates in a second, opposite direction, and wherein the outer element of the gear unit subassembly comprises an outer cylindrical surface and, on an inside, comprises a first cylindrical portion adapted to receive a cylindrical outer surface of the second freewheel clutch mechanism and a second portion constituting the internal ring gear cooperating with the at least one planetary gear.

16. The handheld power tool according to claim 15, wherein the first freewheel clutch mechanism is arranged to engage the gear input shaft and the gear output shaft.

17. The handheld power tool according to claim 16, wherein the first freewheel clutch mechanism comprises a cylindrical element having a cylindrical outer surface and at least one movement transferring element arranged to engage the cylindrical element, wherein the cylindrical outer surface is fitted to the gear output shaft, and wherein the at least one movement transferring element is further adapted to engage an outer surface of the gear input shaft.

18. The handheld power tool according to claim 15, wherein the second freewheel clutch mechanism is arranged to engage the outer element and the gear output shaft.

19. The handheld power tool according to claim 18, wherein the second freewheel clutch mechanism comprises a cylindrical element having the cylindrical outer surface, and at least one movement transferring element arranged to engage the cylindrical element, wherein the cylindrical outer surface is fitted to the output element, and wherein the at least one movement transferring element is further adapted to engage an outer surface of the gear output shaft.

20. The handheld power tool according to claim 15, wherein at least one of the first and second freewheel clutch mechanism is a roller clutch.

21. The handheld power tool according to claim 15, further comprising a housing enclosing at least the motor and the gear unit, and wherein a rotational movement of the planet carrier is fixed with respect to the housing.

22. The handheld power tool according to claim 21, wherein the gear unit further comprises an outer sleeve, wherein the outer sleeve is fixedly arranged in the housing and wherein a rotational movement of the planet carrier is fixed with respect to the outer sleeve.

23. The handheld power tool according to claim 15, wherein the first and second freewheel clutch mechanisms are coaxially arranged.

24. The handheld power tool according to claim 23, wherein the first and second freewheel clutch mechanisms are arranged such that at least a partial axial overlap prevails between the first and second freewheel clutch mechanisms.

25. The handheld power tool according to claim 15, wherein a gear ratio of the gear unit, when the drive shaft is rotating in the first direction, is 1:1.

26. The handheld power tool according to claim 25, wherein the gear ratio, when the drive shaft is rotating in the second, opposite direction, differs from 1:1.

27. The handheld power tool according to claim 15, wherein the power tool is a power tool chosen from a group comprising a screw driver, a nut runner, a drill and a grinder.

28. A gear unit adapted for use in a handheld power tool comprising a motor, an output shaft, and a gear unit arranged between the output shaft and a drive shaft connected to the motor, wherein the gear unit comprises: a gear input shaft adapted to be driven by the motor; a gear output shaft adapted to engage the output shaft; and a gear unit subassembly, wherein the gear unit subassembly comprises: a sun gear arranged on and co-rotating with the input shaft, an outer element comprising an internal ring gear, at least one planet gear arranged between the sun gear and the internal ring gear, and adapted to transfer rotational movement therebetween, and a planet carrier, wherein the gear unit further comprises a first freewheel clutch mechanism and a second freewheel clutch mechanism, each adapted to selectively transfer torque to the gear output shaft, wherein the first freewheel clutch mechanism is arranged to selectively provide a first torque transferring connection between the gear input shaft and the gear output shaft bypassing the gear unit subassembly, wherein the second freewheel clutch mechanism is arranged to selectively provide a second torque transferring connection between the drive shaft and the gear output shaft via the gear unit subassembly, wherein the first freewheel clutch mechanism provides the torque transferring connection when the drive shaft rotates in a first direction, and the second freewheel clutch mechanism provides the second torque transferring connection when the drive shaft rotates in a second, opposite direction, and wherein the outer element comprises an outer cylindrical surface and, on an inside, comprises a first cylindrical portion adapted to receive an outer cylindrical surface on the second freewheel clutch mechanism and a second portion constituting the internal ring gear cooperating with the at least one planetary gear.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The invention will be described in the following illustrative and non-limiting detailed description of exemplary embodiments, with reference to the appended drawing, on which

[0043] FIG. 1a is a cross sectional view of an exemplary power tool according to one embodiment.

[0044] FIG. 2a is a cross sectional view of an exemplary gear unit of a power tool according to one embodiment.

[0045] FIG. 2b is a cross sectional view along section B-B of the exemplary gear unit shown in FIG. 2a.

[0046] FIG. 2c is a cross sectional view along section C-C of the exemplary gear unit shown in FIG. 2a.

[0047] All figures are schematic, not necessarily to scale and generally only show parts which are necessary in order to elucidate the invention, wherein other parts may be omitted or merely suggested.

DETAILED DESCRIPTION

[0048] FIG. 1 is a cross sectional view of an exemplary power tool 10 according to one embodiment, in this case a handheld angled battery powered tool 10. The tool comprises a motor (not shown), an output shaft 20 with which the gear unit may be adapted to engage, in the illustrated embodiment an output shaft 20 adapted to be connected to, or form part of, the bevel gear B at the front end of the tool, and a gear unit 30 arranged between the output shaft 20 and a drive shaft, or drive axle connected to said motor. The drive shaft is adapted to engage the axle 4 indicated in FIG. 1. Further, a housing 40 encloses the motor and gear unit.

[0049] The gear unit 30 will now be described in detail with reference to FIG. 2, a cross sectional view of an exemplary embodiment of the gear unit 30. The gear unit 30 shown in FIG. 2 comprises a gear input shaft 4 adapted to engage the drive shaft (not shown) and hence the motor at a first end A of the input shaft and a gear output shaft 1 adapted to engage the output shaft 20. Further, the gear unit 30 comprises a gear unit subassembly 30a. This subassembly 30a may also be referred to as a planetary gear 30a and comprises a sun gear wheel 4a formed integral with the input shaft 4, more particularly the cogs representing the wheel are formed in the circumferential surface of the shaft 4 as seen in FIG. 2. Alternatively, the sun wheel 4a may for example be a separate component press- or shrink fitted to the shaft 4. The subassembly further comprises an outer element 2, in the illustrated embodiment a cylindrical outer element 2 comprising an internal ring gear 2a. In the illustrated embodiment three planet gears 3,3′,3″ of which two may be seen in FIG. 2, are arranged between the sun gear and the internal ring gear 2a. The gear unit further comprises an outer sleeve 8 which is arranged in the housing 40. A planetary carrier 7, on which the planetary gears 3,3′,3″ are arranged, is fixedly attached to this outer sleeve 2. Hereby, the rotational movement of the planet carrier 7 is fixed with respect to the outer sleeve 2 and hence to the housing 40. The carrier comprises cogs along its circumference and is locked, i.e. fixed to the sleeve 2, by means of these cogs engaging corresponding structures 2b bf the sleeve 2.

[0050] The gear unit 30 further comprises a first freewheel clutch mechanism 5 and a second freewheel clutch mechanism 6 each adapted to selectively transfer torque to the gear output shaft 1. In the illustrated embodiment, these mechanisms are roller- or sprag clutches. In the following the term roller clutch will be used, i.e. a first roller clutch 5 and a second roller clutch 6. As such, they each comprise a respective cylindrical element 5;6 and transferring elements such as rollers (or sprags) 5b, 6b arranged there between (see fog 2b).

[0051] With regards to the first roller clutch, this roller clutch is arranged between the input shaft 4 and the gear output shaft 1 by means of an arrangement where an outer surface 5a of the cylindrical element 5 is fitted to the output shaft 1 whereas the transfer elements engage an outer surface of the input shaft 4. The second roller clutch 6 on the other hand is arranged between the outer cylindrical element 2 and the output shaft 1 by means of an arrangement wherein the transferring elements engage an outer surface of the output shaft 1 and wherein said outer cylindrical surface 6a is fitted to the outer element 2, in each case for example by means of press fitting. In order to allow for this arrangement, i.e. for the output shaft 1 to be able to receive the first and/or second roller clutch 5,6 in a particularly advantageous manner, the shaft 1 comprises an end portion 1a having the shape of a hollow cylinder having an open end such that the first roller clutch may be arranged on the inside of the hollow cylinder by means of the outer cylindrical surface 5a engaging an inner surface of the cylinder-shaped end portion and the second freewheel clutch mechanism may be arranged on the outside of the hollow cylinder, in this case by means of the transferring elements of the second clutch 6 engaging an outer surface of the cylinder-shaped end portion.

[0052] Further, as may be seen from FIG. 2a as well as in a perpendicular cross section in FIG. 2b, the first and second roller clutch 5,6 are coaxially arranged, and also arranged overlapping in an axial direction. FIG. 2b also show the roller element 5b,6b or sprags 5b,6b, of the respective freewheel mechanisms 5, 6. More particularly, the second freewheel 6 may in the illustrated embodiment be denoted an outer freewheel effectively enclosing the first, or inner, freewheel clutch 5. I.e. in the illustrated embodiment a total axial overlap prevails. The second, or outer roller clutch is hence also larger both in terms of diameter and axial length.

[0053] The first roller clutch 5 and at the second roller clutch 6 are arranged to provide a torque transferring connection between the input shaft 4 and the output shaft 1 depending on the rotation of orientation of the motor. This will be described in greater detail in the following as the functionality of the gear unit will be explained.

[0054] The functionality of the gear unit and hence the power tool is achieved by the gear unit 30 selectively providing a connection between the drive shaft (connected to the motor) and the output axle, i.e. between the gear input- and output shafts 4,1, either bypassing- or via the planetary gear mechanism depending on the direction of rotation of the motor and hence the drive axle.

[0055] This alternating force flow is in the illustrated embodiment of FIG. 2, achieved by means of the first and second freewheel roller clutch 5,6 which allows for the force flow to be redirected depending on the direction of rotation of the motor. More particularly, the output shaft 1 is in fact coupled to the input 4 both by means of the first roller clutch 5 and the second roller clutch 6, but the behavior of the clutches and hence the gear unit is governed by the direction of the motor according to the following.

[0056] As the gear input shaft is brought to rotate in a first direction, in this exemplary case a clock wise direction, the sun gear wheel 4a and the input axel 4 rotates along in the same direction. This in turn causes the planet gears 3,3′,3″ to rotate (in the opposite direction). The next component, the carrier 7, is fixedly arranged with respect to the sleeve 8 but the ring gear 2a of the outer element 2 engages the planet gears and hence the cylindrical outer element 2 as a whole is brought to rotate. The outer element 2 is turn connected to and hence effects a rotation of the cylindrical element 6 of the second roller clutch 6, in this case in a counter clockwise direction given the change of direction of rotation over the planetary gear assembly. The second roller clutch 6 is as mentioned above design not to transfer any torque when rotating in a counter clockwise direction and hence idles and no torque is transferred.

[0057] The first roller clutch, instead rotates in the clockwise direction of the input shaft 4 and hence indeed transfers torque when rotating in the clockwise direction. Hereby the rotational movement of the input shaft 4 is directly transferred to the output 2 and a 1:1 gear ratio is provided.

[0058] In the opposite case, i.e. if the gear input shafts is brought to rotate in the opposite direction, in this exemplary case a counter clock wise direction, the sun gear wheel and the input axel 4 off course also in this case rotates along, causing the planet gears 3,3′,3″ and hence the cylindrical outer element 2 as a whole to rotate which in turn effects the cylindrical element of the second roller clutch 6. In this case however, the second roller clutch 6 is brought into rotation in the clock wise direction in which the second roller clutch 6 does transfer torque and hence the rotational movement of the input shaft 4 is in this case transferred to the output 1 via the planetary gear and a gear ratio differing from 1:1 is provided. The first roller clutch on the other hand in this case idles and hence transfers no torque.

[0059] In both cases the output shaft 2 rotates in a clockwise direction.

[0060] In the illustrated embodiment an exemplary gear ratio of 1:5 is obtained using 9 teeth on the sun gear, 17 on the planet gears and 45 teeth on the ring gear.

[0061] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiment. The skilled person understands that many modifications, variations and alterations are conceivable within the scope as defined in the appended claims.

[0062] Additionally, variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, form a study of the drawings, the disclosure and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope of the claims.