GB2383387A

GB2383387A - An electric tool gear shifter has detent springs cooperating with grooves

Info

Publication number: GB2383387A
Application number: GB0226046A
Authority: GB
Inventors: Josh Davis
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2001-11-16
Filing date: 2002-11-07
Publication date: 2003-06-25
Anticipated expiration: 2022-11-07
Also published as: GB0226046D0; CN1419997A; DE10156392B4; CN1317108C; JP2003205478A; DE10156392A1; GB2383387B

Abstract

Gear shift apparatus comprises a shift slide 9 which is connected via a changing bow 18 to a gear unit, eg planetary gearing, having a number of gear speeds. The shift slide 9 has bearing rails 14, 15 which are guided in an electric tool housing 8 by guide planes 10, 11 that support, via lugs 25, 26, detent springs 23, 24 so that the shift slide is pressed into a frictional connection with the guides 10, 11. Guide planes 10, 11 are provided with grooves 27, 28, the number of which corresponds to the number of gear speeds, and into which the detent springs 23, 24 latch upon attainment of a respective shift position of the shift slide 9. In another embodiment the grooves 27, 28 are provided in the shift slide 9 and the detent springs are supported on the bearing rails 14, 15.

Description

Gear shift apparatus for a multi-speed gear unit of an electric tool

Prior art

The present invention relates to a gear shift apparatus for a multi-speed gear unit of an electric tool, comprising a shift slide, which is mounted displaceably on the tool housing, is movable into a plurality of shift positions and is in working connection with a displaceable part of the gear unit, wherein means of guiding the shift slide are disposed in the tool housing.

Such a gear shift apparatus for a multi-speed gear unit of an electric tool is known from DE 39 04 085 Al . Fastened to the shift slide mounted displaceably in the tool housing is a bow, which engages into an axially displaceable shift gear forming part of the gear unit. The shift bow possesses the property of a spring element and therefore has the effect that, upon actuation of the shift slide, the displaceable shift gear engages with its gearing into a fixed gear wheel as soon as the next tooth/tooth space position between the shift gear and the gear wheel is reached. Said known shift slide has no means of allowing it to latch in a clearly detectable manner into one or the other shift position. Advantages of the invention

In the initially described gear shift apparatus for a multi-speed gear unit of an electric tool, according to claim 1 there is fastened either to the shift slide or to the guide means for the shift slide at least one detent spring, which establishes a friction-locking connection between the shift slide and the guide means. The guide means or the shift slide is provided with grooves, the number of which corresponds to the number of gear speeds of the gear unit and into which the detent spring latches upon attainment of the respective shift position of the shift slide. The detent spring is a technically very simple means of providing the shift slide with as many stable latching positions as there are gear speeds. The shift slide is held securely in each shift position of the shift slide, in which one of a plurality of gears of the multispeed gear unit is engaged, thereby preventing unintentional jumping of the gear unit out of the respective engaged gear. In addition, from the latching of the detent spring into the respective groove the user may clearly sense that a desired gear of the gear unit has been engaged.

Advantageous embodiments and developments of the invention emerge from the sub-claims.

It is expedient that the shift slide is guided by at least one of its two longitudinal sides extending parallel to the direction of displacement between two guide planes, and that disposed between the at least one longitudinal side of the shift slide and the guide plane extending at its underside and/or the guide plane extending at its upper side is at least one detent spring, which on the one hand is fastened to the shift slide and on the other hand is supported on the respective guide plane, which is provided with the grooves for the detent spring.

In an advantageous manner the shift slide has on both longitudinal sides bearing rails, to the underside of each of which at least one detent spring is fastened, wherein each of the bearing rails is supported by its detent spring on a guide plane, which is disposed on the tool housing and provided with grooves.

Drawings

There now follows a detailed description of several embodiments of the invention, which are illustrated in the drawings. The drawings show in: Figure 1 a cross section through a gear unit of an electric tool with a shift slide for changing the gear of the gear unit,

Figure 2 a longitudinal section through a part of the machine housing having a shift slide inserted therein and Figure 3 a perspective view of a shift slide from the underside thereof.

Description of an embodiment

Figure 1 shows a cross section through a planetary gear unit of an electric tool, e.g. a drilling screwdriver. The planetary gear unit in a known manner, such as emerges from DE 39 04 085 Al, comprises a sun wheel 1, which is connected non-rotatably to a drive shaft 2 of an electric motor, a plurality of planet wheels 3, 4 and 5 meshing with the sun wheel 1, and a ring gear 6, which surrounds the planet wheels and the sun wheel and with which the planet wheels 3, 4, 5 mesh. The entire gear unit is enclosed in a gearbox 7. The ring gear 6 is mounted so as to be displaceable in axial direction of the drive shaft 2. Said axially displaceable ring gear 6 is used to change the gear of the e.g. two-speed planetary gear unit.

In a first position the ring gear 6 is in mesh with nonillustrated gearing on the gearbox 7 and is therefore held locked against rotation, and the planet wheels 3, 4 and 5 driven by the sun wheel 1 rotate in the internal gearing of the ring gear 6. In a second position the ring gear is not held at the gearbox 7 but co-rotates with the planet wheels 3, 4 and 5. Depending on which of the two described positions the ring gear 6 occupies, a different rotational speed is transmitted from the drive shaft 2 to a nonillustrated spindle of the electric tool.

Figure 1 also shows in a cutout manner the tool housing 8, in which the gear unit is accommodated.

The axial displacement of the ring gear 6 into one or the other of the two gears of the gear unit is effected by means of a shift slide 9, whic is displaceable in axial direction on the tool housing 8. The shift slide 9 is guided e.g. at each of its two longitudinal sides between a bottom guide plane 10, 11 and a top guide plane 12, 13, wherein the shift slide 9 on each of its two longitudinal sides has a bearing rail 14, 15, which is supported on the bottom guide plane 10, 11. On its upper side the shift slide 9 has a handle 17, which protrudes from an opening 16 of the tool housing 8 and enables the user of the electric tool to actuate the shift slide 9. Connected to the shift slide is a bow 18 manufactured e.g. from a wire, which with its two arms partially embraces the gearbox 7 and engages into the gear unit through mutually opposing holes 19 and 20 in the gearbox 7 so that the ends 21 and 22 of the bow 18 grasp the ring gear 6 in the gearbox 7. The bow ends 21 and 22 may engage e.g. into a non-illustrated groove in the outer wall of the ring gear 6. Thus, via the bow 18 an axial force exerted upon the shift slide 9 may be transmitted to the ring gear 6. The ring gear 6 is accordingly, as a result of actuation of the shift slide 9, displaced axially into the one or the other gear position.

The top guide planes 12 and 13 provided on the tool housing

8 are preferably positioned and shaped in such a way that they rest on the upper side of the shift slide 9, close to the handle 17 of the latter. By virtue of the shift slide

9 being pressed with its upper side against the top guide planes 12 and 13 of the tool housing 8 a high degree of sealing is achievable to prevent dirt from penetrating through the opening 16 into the interior of the tool housing 8.

The shift slide 9 is to latch clearly into each of its gear positions . On the one hand, this is to allow the user to sense that the desired gear position has been reached and, on the other hand, with latching-in of the shift slide 9 the ring gear 6 is to be held securely in the selected gear position so as to prevent self-release from said position . The means whereby said requirements may be met are shown in Figures 2 and 3 , in which the same reference characters have been used for the parts described in connection with Figure 1.

Figure 2 shows a longitudinal section through the region of the electric tool, in which the shift slide 9 is situated, and Figure 3 shows a perspective view of the shift slide 9 alone, from the underside thereof. The two views in Figure 2 and Figure 3 clearly show that detent springs 23, 24 are fastened to the underside of the two bearing rails 14, 15 disposed on the longitudinal sides of the shift slide 9.

Both detent springs 23, 24 have a detent lug 25, 26, which is bent in an outward direction, i.e. away from the respective bearing rail 14, 15. The detent springs 23, 24 are supported by their detent lug 25, 26 on the bottom guide plane 10, 11 formed on the tool housing 8. In said case, by virtue of the spring action of the detent springs 23, 24 the shift slide 9 is pressed out towards the opening 16 in the tool housing 8, with the result that the shift slide 9 is pressed with its upper side against the top guide planes 12, 13 on the tool housing 8. The resulting close contact between the shift slide 9 and the tool housing 8 ensures that the opening 16 in the tool housing 8 is efficiently sealed to prevent the penetration of dirt.

As many grooves 27, 28 as the gear unit has gear speeds are introduced in the bottom guide planes 10, 11 of the tool housing 8, along which the detent lugs 25, 26 of the detent springs 23, 24 slide during displacement of the shift slide 9. The grooves 27, 28 are moreover positioned in such a way that, at each shift position reached by the shift slide 9, the detent springs 23, 24 latch with their detent lugs 25, 26 into an associated groove 27, 28. In the illustrated embodiment, two grooves 27, 28 are provided for a two-speed gear unit. The invention is however not limited to a two-speed gear unit, the point being that as many grooves are to be disposed in the guide planes 10, 11 as the gear unit has gears.

In a departure from the illustrated embodiment, the detent springs 23, 24 may alternatively be disposed between the bearing rails 14, 15 and the top guide planes 12, 13. Furthermore, the individual detent springs 23, 24 may alternatively have more than only one detent lug. This accordingly entails the provision of a plurality of grooves in the guide planes contacted by the detent springs 23, 24. Improved locking of the shift slide in each shift position is achieved when a plurality of detent lugs latch into a plurality of grooves in each shift position. The same effect may be achieved when a plurality of detent springs are disposed in each bearing rail 14, 15 of the shift slide 9 and there are a corresponding number of grooves in the guide planes 10, 11 and/or 12, 13 of the tool housing 8.

The latching of the shift slide 9 in the individual gear positions is achievable equally by the kinematic reversal of detent springs 23, 24 and grooves 27, 28 of the embodiment illustrated in Figures 2, 3. I.e. the detent springs 23, 24 may be fastened in the bottom and/or top guide planes 10, 11, 12, 13 of the tool housing 8 and the associated grooves 27, 28 may be introduced into the bearing rails 14, 15 of the shift slide 9.

The actual inventive idea, which is to use detent springs 23, 24 to realize detent positions for the shift slide 9, which correspond to the gears, is independent of the design of the gear unit used in the electric tool, which may for example take the form of a planetary gear unit as described above.

Claims

Claims 1. Gear shift apparatus for a multi-speed gear unit of an electric tool, comprising a shift slide (9), which is mounted displaceably on the tool housing (8), is movable into a plurality of shift positions and is in working connection with a displaceable part (6) of the gear unit, wherein means (10, ..., 13) of guiding the shift slide (9) are disposed in the tool housing (8), characterized in that fastened to the shift slide (9) or to the guide means (10, ..., 13) is at least one detent spring (23, 24), which establishes a frictionlocking connection between the shift slide (9) and the guide means (10, ..., 13) , and that the guide means (10, ..., 13) or the shift slide (9) is provided with grooves (27, 28) , the number of which corresponds to the number of gear speeds of the gear unit and into which the detent spring (23, 24) latches upon attainment of the respective shift position of the shift slide (9) .
2. Gear shift apparatus according to claim 1, characterized in that the shift slide (9) is guided by at least one of its two longitudinal sides extending parallel to the direction of displacement between two guide planes (10, 11; 12, 13), and that disposed between the at least one longitudinal side of the shift slide (9) and the guide plane (10, 11) extending at its underside and/or the guide plane (12, 13) extending at its upper side is at least one detent spring (23, 24), which on the one hand is fastened to the shift slide (9) and on the other hand is supported on the respective guide plane (10, 11, 12, 13), which is provided with the grooves (27, 28) for the detent spring (23, 24) .
3. Gear shift apparatus according to claim 1, characterized in that the shift slide (9) has on both longitudinal sides bearing rails (14, 15), to the underside of each of which at least one detent spring (23, 24) is fastened, and that each of the bearing rails (14, 15) is supported by its detent spring (23, 24) on a guide plane (10, 11), which is disposed on the tool housing (8) and provided with grooves (27, 28) . Gear shift apparatus substantially as herein described with reference to the accompanying drawings.