WO2013178243A1

WO2013178243A1 - Rotation transfer arrangement

Info

Publication number: WO2013178243A1
Application number: PCT/EP2012/059958
Authority: WO
Inventors: Daniel KNOPF; Martin Breuninger; Martin Lugert
Original assignee: Husqvarna Ab
Priority date: 2012-05-29
Filing date: 2012-05-29
Publication date: 2013-12-05
Also published as: DE112012006451T5

Abstract

A rotation transfer arrangement, such as could be used with a power tool such as a hedgetrimmer, comprising: a shaft (2) supported at a first end, typically with a torque-applying member such as a motor (1) coupled thereto; a first rotation transfer member such as a pinion gear (3) on the shaft (2); a second rotation transfer member such as a wheel gear (4) engaging the first rotation transfer member (3), in which the first rotation transfer member (3) has a distal end (11) distal from the first end of the shaft (2), the arrangement further comprising a support member (6) comprising a sleeve (7) at least partly surrounding the first rotation transfer member (3) and provided with an aperture (9) through which the first rotation transfer member (3) contacts the second rotation transfer member (4), the sleeve (7) supporting the distal end (11) of the first rotation transfer member (3).

Description

ROTATION TRANSFER ARRANGEMENT

This invention relates to a rotation transfer arrangement, such as may, non- exclusively, be used in power tools such as hedgetrimmers.

Hedgetrimmers and other power tools (such as drills, screwdrivers, chainsaws, trimmers, pumps etc) comprising a motor powering one or more driven elements are well known. Typically, a relatively high speed motor is used, with a gearbox used to reduce the speed of rotation but increase the torque felt at the driven elements. A common arrangement is to have a pinion gear pressed onto the output shaft of the motor, engaging with a wheel gear mounted adjacent to the pinion gear.

It is generally desirable to support the pinion gear against the radial and tangential forces exerted on it by the wheel gear. The aim of such a support is to ensure a good contact of the pinion gear with the wheel gear, with little play and to prevent deformation of the motor shaft.

One potential arrangement is to provide a bearing, such as a ball bearing, on the motor side of the point of transmission of force (the point of transmission of force being where the pinion gear and wheel gears mesh). One might suppose that providing an ideal play-free bearing at that point would provide the necessary support against deformation of the shaft. However, competing against that aim, in a practical installation providing a bearing with low play at that point can lead to a static over- determination of the output shaft, which can lead to high power consumption and even breakage of the output shaft. As such, in order to avoid this static over- determination of the output shaft, and to improve the ease of assembly, it is desirable for this reason to have the bearing supporting the pinion gear have as large a play as possible. These two aims evidently conflict.

Treating the point where the output shaft exits the motor as a pivot point of the output shaft, it can be seen that, as the bearing is on the motor side of the point where the forces on the pinion gear are transmitted to the wheel gear (the point of transmission), in order to keep the deformation of the output shaft small, a relatively small play must be provided at the bearing supporting the pinion gear. Another potential arrangement is to provide a bearing at the distal end of the pinion gear (that is, the end of the pinion gear farthest from the motor); typically this might comprise a sinter bearing, wherein a sintered block on the axis of the output shaft is used to support the distal end of the pinion gear. This provides a longer lever from the motor to the bearing supporting the pinion gear, thus meaning that, for the same deformation of the shaft, the play at the distal end bearing can be more than in the first arrangement, thus allowing for easier assembly and lower risk of static over- determination, whilst still compensating for the same level of deformation of the shaft. Alternatively, a bearing having the same level of play as in the first arrangement could be used, with less deformation of the shaft, or a compromise between the two situations. However, this second arrangement is not an efficient use of space, as a bearing has to be provided in the space past the distal end of the pinion gear. According to a first aspect of the invention, there is provided a rotation transfer arrangement, comprising:

a shaft supported at a first end thereof;

a first rotation transfer member on the shaft; and

a second rotation transfer member engaging the first rotation transfer member; in which the first rotation transfer member has a distal end distal from the first end of the shaft, the arrangement further comprising a support member comprising a sleeve at least partly surrounding the first rotation transfer member and provided with an aperture through which the first rotation transfer member contacts the second rotation transfer member, the sleeve supporting the distal end of the first rotation transfer member.

As such, by having the sleeve support the distal end of the first rotation transfer member, for the same level of deformation of the shaft, more play can be allowed for in the support member than would be the case if it were on the proximal side of the first rotation transfer member. Because a sleeve surrounding the first rotation transfer member is used to support the first rotation transfer member, less space is needed on the distal side of the first rotation transfer member.

In the preferred embodiment, the arrangement further comprises a torque-applying member coupled to the first end of the shaft. The shaft may be clamped against radial movement by the torque applying member. The torque-applying member will typically be a motor, but could also be a brake.

Typically, the first and second rotation transfer member will each comprise a gear; as such, the first rotation transfer member may comprise a pinion gear, and the second rotation transfer member may comprise a wheel gear meshing with the pinion gear, typically through the aperture. Alternatively, the first and second rotation transfer members may be pulleys contacting one another through a belt passing through the aperture.

The sleeve may support the distal end of the first rotation transfer member through a bearing. The bearing may comprise a friction bearing comprising a surface on which the first rotation transfer member rubs. The bearing may only extend circumferentially around part of the distal end of the first rotation transfer member; the region where the bearing does not extend typically aligns with the aperture. The bearing can therefore be dispensed with in the region adjacent to the aperture, as the force from the second rotation transfer member on the pinion will largely be outwards away from the second rotation transfer member (at least in the case of the rotation transfer members comprising gears), and so little support will be needed on the side of the first rotation transfer member adjacent to the second rotation transfer member and so to the aperture. Where the rotation transfer members comprise pulleys, the forces between the rotation transfer members will be reversed, and so the aperture may be provided on the side of the sleeve opposite to the second rotation transfer member. Alternatively, the bearing may comprise a ball or roller bearing.

The arrangement may be provided with a housing supporting the shaft and the second rotation transfer member relative to one another, and typically also the torque- applying member. The support member may be fixed to the housing, or to the torque- applying member.

The first rotation transfer member may be pressed onto the shaft or otherwise fixed thereon; it may be formed as part of the shaft. The aperture may extend circumferentially only around a portion of the first rotation transfer member; typically, the angle of the aperture which is open will be around 90 to 180 degrees. The aperture may typically have a thickness along an axis of the shaft at least as thick as the second rotation transfer member.

The sleeve will generally be of cylindrical form.

Typically, the motor will be an electric motor. The arrangement will preferably be for a handheld power tool, such as a hedgetrimmer.

According to a second aspect of the invention, there is provided a support member for a first rotation transfer member, comprising a cylindrical sleeve having an internal bore with an aperture therein to allow access by a second rotation transfer member to a first rotation transfer member, the internal bore having a first end and a second end, the second end having a bearing for an end of the first rotation transfer member.

Typically, the first end will be larger in diameter than the second end. The support may have any of the optional features recited with reference to the first aspect of the invention.

According to a third aspect of the invention, there is provided an electric power tool, comprising a housing and a rotation transfer arrangement according to the first aspect of the invention within the housing, having a motor as the torque-applying member. Typically, the support member will be fixed relative to the motor or the housing, typically at a point closer to the motor than the distal end of the first rotation transfer member.

Such a tool will allow for the space at the distal end of the first rotation transfer member to be used more efficiently, whilst still allowing the distal end of the first rotation transfer member to be supported.

Typically, the power tool will be a hedgetrimmer, drilling machine, cordless screwdriver, chainsaw, trimmer, grass shear, blower, lawn mower or water pump. There now follows, by way of example only, description of embodiments of the invention described with reference to the accompanying drawings, in which:

Figure 1 shows a side elevation of a motor arrangement for use in a hedgetrimmer in accordance with a first embodiment of the invention;

Figure 2 shows a perspective view of a support member used in the motor arrangement of Figure 1 ; Figure 3 shows a cross section through the motor arrangement of Figure 1 ;

Figure 4 shows an exploded perspective view of the motor arrangement of Figure 1 in a hedgetrimmer; Figure 5 shows a partial cross section through a motor arrangement according to a second embodiment of the invention;

Figure 6 shows a perspective view of the motor arrangement of Figure 5; Figure 7 shows a cross section through a motor arrangement according to a third embodiment of the invention; and

Figure 8 shows a perspective view of the motor arrangement of Figure 7. A rotation transfer arrangement in accordance with a first embodiment of the invention is shown in Figures 1 to 5 of the accompanying drawings. The arrangement comprises a motor 1 having an output shaft 2. On the output shaft 2 is pressed a first rotation transfer member of the form of a pinion gear 3. The pinion gear 3 engages a second rotation transfer member of the form of a wheel gear 4 rotatably mounted on a drive shaft 5 parallel to the output shaft 2. Given that the wheel gear 4 is larger in diameter than the pinion gear 3, the drive shaft 5 will rotate at a lower speed than the output shaft 2 of the motor; this rotation can be put to whatever use is desired. As discussed above, the pinion gear 3 is pressed onto the output shaft 2 of the motor 1. This defines a distal end 1 1 of the pinion gear, being the end furthest from the motor. The pinion gear 3 is provided with a cylindrical peg 12 at its distal end 1 1. In order to support the pinion gear 3, a support member 6 is provided. This comprises a cylindrical sleeve 7 having an internal bore 8 in which the pinion gear 3 fits. The sleeve 7 has an aperture 9 formed therein to enable the wheel gear 4 to engage the pinion gear 3 when the pinion gear 3 is received within the bore 8. The sleeve 7 terminates in a section of reduced internal diameter 10. The diameter reduces to match that of the peg 12. The peg 12 is supported in this section 10, and can rub against bearing surface 13, which forms a friction bearing. The positioning of the peg 12 in the section 10 therefore provides support for the pinion gear 3 against both radial and tangential forces applied by the wheel gear 4.

Furthermore, as the support for the pinion gear 3 is at the distal end 1 1 of the pinion gear 3, the support member is close to the wheel gear 4 but as far as possible from the motor 1. This means that, in order to provide a given limited bending deformation of the output shaft 2, a larger play can be allowed at the support of the pinion gear 3 at section 10 of the support 6 than if the bearing were to be located on the motor side of the point of transmission of force.

The support member 6 also has a collar 14 which is wider than the sleeve 7. As shown in Figure 4 of the accompanying drawings, this collar also fits over the pinion gear 3, but is received within a housing 15 of the apparatus in which the motor arrangement is used; here, the apparatus is a hedgetrimmer. The collar 14 is a press fit within a corresponding recess 16 in the housing 15, although the collar 14 could equally well be screwed, bolted or otherwise fixed to the housing 15 in any convenient way. Given that the housing 15 also supports the motor and the wheel gear, all of the components will be suitably supported relative to one another.

It is also to be noted that, not least because the collar 14 is supported in the recess 16 closer to the motor than the distal end 1 1 of the pinion gear 3, there is no need to provide any further support to the pinion gear 3 farther from the motor than the distal end 1 1 of the pinion gear 3. This means that the area 17 below the pinion gear 3 can be used for other purposes; in this example of a hedge trimmer, the space can be used to house the reciprocating gears 18 that convert the rotational movement of the drive shaft 5 into linear reciprocating movement of the hedgetrimmer blades 19.

A motor arrangement according to a second embodiment of the invention is shown in Figures 5 and 6 of the accompanying drawings. In this embodiment, equivalent integers to those of the first embodiment have been given corresponding reference numerals, raised by 50.

In this embodiment, rather than using gears to transfer the rotational motion of the output shaft of the motor 51 , a system of belts and pulleys is used. The first rotation transfer member 53 mounted on the output shaft 52 comprises a first pulley 53a, whereas the second rotation transfer member 54 comprises a second pulley 54a. A belt 70 connects the first and second pulleys 53, 54 so that rotational motion of the first pulley 53a drives the belt 70 so as to drive the second pulley 54a.

In order to provide support for the first rotation transfer member, a sleeve 57 is provided over the first rotation transfer member 53, mounted on housing 65. As in the previous embodiment, the sleeve has an aperture 59 through which the belt 70 engages the first pulley. The sleeve 59 also has a recess 60 providing location for a peg 62 formed in the end of the first rotation transfer member 53 distal from the motor 51. When the first rotation transfer member rotates, the peg can rub against bearing surface 63, which forms a friction bearing. The positioning of the peg 72 in the recess 60 therefore provides support for the first rotation transfer member 53 against both radial and tangential forces applied by the belt 70 at a point as far from the motor 51 as possible.

It is to be noted that the aperture 59 is on the opposite side of the first rotation transfer member 53 to the second rotation transfer member 54. This is because that is where the belt 70 will engage the first pulley 53a. In an alternative third embodiment shown in Figures 7 and 8 of the accompanying drawings (in which reference numerals have been raised by a further 30 with respect to the second embodiment), it is possible for the aperture 89 to be on the side of the first rotation transfer member 53 directed towards the second rotation transfer member 54, but for the belt 100 still to contact the first pulley on the far side thereof. In both the second and third embodiments, the radial forces acting on the first and second rotation transfer members 53, 54; 83, 84 will tend to bias the rotation transfer members 53, 54; 83, 84 together (as the belt 70; 100 will be in tension), whereas in the first embodiment the radial forces on the first and second rotation transfer members 3, 4 will tend to bias those members apart.

Claims

1. A rotation transfer arrangement, comprising:

a shaft supported at a first end thereof;

a first rotation transfer member on the shaft; and

a second rotation transfer member engaging the first rotation transfer member; in which the first rotation transfer member has a distal end distal from the first end of the shaft, the rotation transfer arrangement further comprising a support member comprising a sleeve at least partly surrounding the first rotation transfer member and provided with an aperture through which the first rotation transfer member contacts the second rotation transfer member, the sleeve supporting the distal end of the first rotation transfer member.

2. The rotation transfer arrangement of claim 1 , further comprising a torque- applying member coupled to the first end of the shaft.

3. The rotation transfer arrangement of claim 2, in which the shaft is clamped against radial movement by the torque applying member.

4. The rotation transfer arrangement of claim 2 or claim 3, in which the torque- applying member is a motor.

5. The rotation transfer arrangement of claim 2 or claim 3, in which the torque- applying member is arranged to rotationally brake the output shaft..

6. The rotation transfer arrangement of any preceding claim, in which the sleeve supports the distal end of the first rotation transfer member through a bearing.

7. The rotation transfer arrangement of claim 6, in which the bearing comprises a friction bearing comprising a surface on which the first rotation transfer member rubs.

8. The rotation transfer arrangement of claim 6 or claim 7, in which the bearing only extends circumferentially around part of the distal end of the first rotation transfer member.

9. The rotation transfer arrangement of claim 8, in which the region where the bearing does not extend aligns with the aperture.

10. The rotation transfer arrangement of claim 2, provided with a housing supporting the torque-applying member and the second rotation transfer member relative to one another, the support member being fixed to at least one of the housing and the torque-applying member.

1 1. The rotation transfer arrangement of claim 10, in which the support member is fixed relative to the motor or the housing at a point closer to the motor than the distal end of the first rotation transfer member.

12. The rotation transfer arrangement of any preceding claim, in which the first and second rotation transfer members each comprise a gear, the gears meshing through the aperture.

13. The rotation transfer arrangement of any of claims 1 to 1 1 , in which the first and second rotation transfer members each comprise a pulley, the pulleys contacting one another through a belt passing through the aperture.

14. A support member for a first rotation transfer member, comprising a cylindrical sleeve having an internal bore with an aperture therein to allow access by a second rotation transfer member to the first rotation transfer member, the internal bore having a first end and a second end, the second end having a bearing for an end of the first rotation transfer member.

15. The support member of claim 14, in which the first end is larger in diameter than the second end.

16. An electric power tool, comprising a housing and a rotation transfer arrangement according to claim 4 within the housing.

17. The tool of claim 15, in which the support member is fixed relative to the motor or the housing.

18. The tool of claim 17, in which the support member is fixed relative to the motor or the housing at a point closer to the motor than the distal end of the first rotation transfer member.

19. The tool of any of claims 16 to 18, being a tool selected from the group comprising a hedgetrimmer, a drilling machine, a cordless screwdriver, a chainsaw, a trimmer, a grass shear, a blower, a lawn mower and a water pump.