EP2142343A1

EP2142343A1 - Hand tool

Info

Publication number: EP2142343A1
Application number: EP08708786A
Authority: EP
Inventors: Aldo Di Nicolantonio
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2007-03-28
Filing date: 2008-02-07
Publication date: 2010-01-13
Anticipated expiration: 2028-02-07
Also published as: ATE540783T1; JP2010522644A; DE102007014756A1; EP2142343B1; US20090321102A1; WO2008116689A1; CN101657301B; CN101657301A; JP5080635B2

Abstract

The invention relates to a hand tool (1), particularly electric hand tool, having a drive (5), a tool shaft (3), a first overload clutch (14) and a transmission (6), which comprises a first and at least one second gear wheel unit (7, 8), said gear wheel units being operable alternatively to transmit torque. According to the invention, at least one second overload clutch (18) is provided and is permanently and exclusively operatively connected to the first gear wheel unit (7).

Description

description

title

hand tool

State of the art

The invention relates to a hand tool, in particular an electric hand tool, preferably a drill, a hammer drill or a cordless screwdriver according to the preamble of claim 1.

Hand tools with a, in particular designed as an electric motor drive, are well known. For working with different materials and / or tools, in particular drilling tools, it is known to equip hand tools with a, in particular designed as a two-speed spur gear transmission gear. To protect the user against high reaction moments of the hand tool and to protect the transmission gear against overuse, it is known to arrange an overload clutch as a torque limiting device in the drive train, with which the maximum transmitted to the tool shaft and / or the rotationally driven tool torque is limited. When a maximum torque (release torque) is exceeded, the power flow between the drive (electric motor) and the tool shaft rotatably driven tool as soon as possible interrupted, whereby the operator, the hand tool and the workpiece to be machined or product are protected. A disadvantage of the known hand tools is that regardless of the choice of gear ratio always the same maximum torque is transmitted. A choice between different maximum torques for different gear ratios is not possible if the overload clutch is arranged on the tool spindle. If the overload clutch is on a countershaft, the transmitted torque is determined by the transmission ratio. An independent choice of triggering torque is not possible.

In addition to the known hand tools with a single, non-adjustable overload clutch hand tools with an adjustable overload clutch are known by means of which the maximum torque to be transmitted to the task to be done is customizable. For varying the torque while the spring force of a force acting on a coupling part of the overload clutch, in particular a form-locking locking clutch closing spring is varied. A disadvantage of this type of hand tools is on the one hand, that the adjustable overload clutch is susceptible to interference due to their relatively complex structure and on the other hand that two different switches with separate shift linkages are to operate for the operation of the transmission gear and to select the triggering torque.

DISCLOSURE OF THE INVENTION Technical Problem

The invention is therefore based on the object to provide an alternative design of a hand tool, can be reliably selected with only one switch between at least two different, maximum transmittable torques. Technical solution

The invention is based on the idea of providing at least one second overload clutch in addition to the first overload clutch and assigning it exclusively to a first gear unit so that the second overload clutch is automatically activated when the first gear unit is connected to the drive train for torque transmission purposes. In other words, the second overload clutch with the first gear unit forms a functional unit that can be activated or deactivated exclusively as a whole. This makes it possible, by means of a single switch, in particular rotary switch, to change to the first gear unit with the tuned to this second, in particular non-adjustable, overload clutch. A separate switch for switching between the overload clutches is not needed with advantage. If the first gear unit is switched over to the second gear unit by means of the single switch, the second overload clutch is automatically deactivated or displaced out of the drive train. It is within the scope of the invention to provide, in addition to the first and the second overload clutch, further overload clutches and preferably to associate each overload clutch with a separate gear unit.

Under gear unit according to the invention, both a single, in particular designed as a spur gear transmission gear, as well as several mutually rotatably coupled gears, which are arranged exclusively rotatable together understood. It is advantageous if different gears of a gear unit have a different diameter, so that an overload clutch can be effective at different translations.

Advantageously, the at least two overload clutches are dimensioned differently, so that different sized maximum torques can be transmitted. Preferably, the maximum torque to be transmitted, so the triggering torque of the first overload clutch, greater than that of the second overload clutch.

An advantage is an arrangement in which at least two gears of the first gear unit have different diameters and at least one gear of the second gear unit has the same diameter as at least one of the gears of the first gear unit. This makes it possible to realize the same gear ratio with two gear units, the respective effective triggering torques are different. For example, it is possible to use diamond drill bits with large diameters at a low speed on the tool shaft and at the same time a low release torque. By changing the gear units, however, the same diameter of the active gear on the other hand, the same low speed can be realized with a high release torque, which, for example, long wood screws are easily screwed.

With regard to the arrangement of the first overload clutch, there are different possibilities. For example, the first overload clutch may be permanently and exclusively operatively connected to the second gear unit. In such an arrangement, both overload clutches are used exclusively alternatively. When choosing the first tooth By means of the single switch, the second overload clutch is automatically active, wherein by switching to the second gear unit, only the first overload clutch, which forms a functional unit with the second gear unit, is active.

In addition, it is conceivable to associate the first overload clutch of all gear units, so preferably arrange them in the drive train such that it is always active torque limiting active. Optionally, a Ü bridging device for the first overload clutch can be provided. In the embodiment with acting on all gear units first overload clutch, it is of significant advantage if the first overload clutch is harder than the second overload clutch. In this case, for example, the first overload clutch can be designed as a form-locking latching coupling and the second overloading clutch as a frictionally engaging clutch.

If the first overload clutch is assigned to all or one group of gear units, it is preferred that when the second gear unit is operated to transmit torque, only the first overload clutch is active. If the first gear unit is switched by means of the single switch, the second overload clutch operatively connected to the first gear unit is additionally automatically activated, so that the triggering torque of the weaker, second overload clutch can be transmitted overall only as maximum torque. In the configuration described, the second gear unit is not exclusively associated with an overload clutch. However, embodiments are also conceivable in which the second overload clutch acts on all gear wheel torque-limiting and a plurality of gear units are each configured with its own overload clutch.

For manufacturing and assembly reasons, it is advantageous if the gear units transmitting torque at different times are arranged on a motor shaft or a countershaft arranged in the drive train between the motor shaft and the tool shaft. Preferably, the countershaft is driven by the motor shaft via a spur gear. In the embodiment described last, it is advantageous if the first gear unit is assigned to this spur gear, that acts on all disposed on the countershaft gear units.

In order to activate the different gear units, of which at least one is permanently associated with an overload clutch, it is conceivable to associate on the tool shaft of each gear unit at least one output gear unit and at least one output gear, whereby by adjusting an axially displaceable wedge between the different output gear units and thus between the different gear units can be selected. By means of the wedge while a rotationally fixed connection between the selected output gear unit and the tool shaft is made. Non-selected driven gear units are rotatable relative to the tool shaft and thus not torque transmitting, so arranged outside the drive train. In the described configuration, the gear units are rotatably connected to the countershaft. Likewise is it is conceivable to arrange the output gear unit rotationally fixed on the tool shaft and to select, for example, by means of an axially adjustable wedge directly between the axially adjacent gear units.

According to an alternative embodiment, it is conceivable to provide at least one driven gear unit connected to the tool shaft in a rotationally fixed manner but axially adjustable relative to the tool shaft. Preferably, a plurality of different sized output gears as output gear unit rotatably coupled to each other. By axial adjustment of this output gear unit thus formed can be selected between the different gear units, wherein at least one of the gear units fixed one ne overload clutch is assigned.

Brief description of the drawings

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings; these show in:

1a is a schematic representation of a hand tool with a two-speed transmission and with two overload clutches,

FIG. 1b shows a switch for simultaneously setting the gear ratio and the maximum torque to be transmitted for the hand tool shown in FIG. 1a, FIG.

2a shows an alternative hand tool with a transmission gear and two overload clutches,

FIG. 2b shows an operating switch belonging to the hand tool according to FIG. 2a, FIG.

Fig. 3a shows an alternative hand tool with a transmission gear and two overload clutches and

Fig. 3b shows a switch for a hand tool according to Fig. 3a.

Embodiments of the invention

In the figures, the same components and components with the same function with the same reference numerals. FIG. 1 schematically shows a hand tool 1, for example a power drill.

The drive train 2 of the hand tool 1 comprises a tool shaft 3 which carries a tool, for example a drill chuck with drill, at its left-hand end in the drawing plane (not shown). Parallel to the tool shaft 3, a motor shaft 4 of a designed as an electric motor drive 5 is arranged. The torque transmission between the motor shaft 4 and the tool shaft 3 via a transmission gear 6 with a single gear existing first gear unit 7 and a axially spaced apart second gear unit 8. Here, the first gear unit 7 is a single gear consisting of the first output gear unit 9th and the second gear unit 8, a second, consisting of a single gear output gear unit 10 assigned.

By means of an axially adjustable wedge 11, either the first or the second output gear unit 9, 10 is rotationally fixed, i. torque transmitting, connectable to the tool shaft 3. By means of the wedge 11, a positive connection is produced via corresponding driving balls 12, 13. In Fig. Ia, the second driven gear unit 10 is rotatably connected to the tool shaft 3, whereas the first driven gear unit 9 is rotatable relative to the tool shaft 3.

The second gear unit 8 is exclusively associated with a first overload clutch 14 designed as a friction clutch, by means of which the torque is transmitted from the motor shaft to the second gear unit 8, wherein the first overload clutch 14 transmits the maximum limited torque limit. The first overload clutch 14 comprises a movable in the axial direction relative to the motor shaft 4 and rotatably connected to the motor shaft 4 Reibteller 15 which is spring-loaded via springs 16 in the direction of the second gear unit 8. The first overload clutch 14 only ever active torque transmitting or limiting active when the second gear unit 8 is operated to transmit torque.

For switching between the second gear unit 8 and the first gear unit 7, a switch 17 designed as a rotary switch is provided (see FIG. 1b). This is from the switch position shown (K2, 14), in which the first overload clutch 14 is active and a power flow K2 is realized (active second gear unit 8), in a rotated by 90 ° switch position (Kl, 18), whereby (means a shift linkage, not shown) of the wedge 11 is moved in the drawing plane to the left. In this switch position, only the first output gear unit 9 is non-rotatably connected to the tool shaft (positively locking), so that the first gear unit 7 with an associated second overload clutch 18 is active in transmitting torque. The second overload clutch 18 is also provided with a Reibteller 19 which is spring-loaded by means of springs 20 in the axial direction of the first gear unit 7. Alternatively, the first or the second overload clutch (14, 18), for example, be designed as a positive locking detent coupling. In the second switch position, the force flux K1 is active via the tool shaft 3, the friction plate 19, the first gear unit 7, the first output gear unit 9 and the tool shaft 3 to the tool, not shown. Both overload clutches 14, 18 are exclusively alternative, in each case together with the associated gear unit 7, 8 active. By switching between the two gear units 7, 8 is simultaneously selected between two different loaned maximum torques, preferably by means of the first overload clutch 14, a higher maximum torque is transferable.

In Fig. 2a, an alternative embodiment of a hand tool 1 is shown. The also designed as an electric motor drive 5 drives the motor shaft 4 rotating. On the motor shaft 4 is seated a first spur gear 21 which cooperates with a second spur gear 22 to transmit torque. The second spur gear 22 is arranged coaxially to a countershaft 23, wherein the torque is transmitted from the second spur gear 22 to the countershaft 23 via a first overload clutch 14 designed as a positive-locking detent clutch.

On the countershaft 23 sits non-rotatably consisting of a single gear second gear unit 8 and a first gear unit 7 with two different sized, rotatably coupled to each other gears 7a, 7b. The first gear unit 7 is associated with a second overload clutch 18 (friction clutch).

Each gearwheel 7a, 7b of the first gearwheel unit 7 is assigned an output gearwheel unit 9a, 9b, each consisting of an output gearwheel, which can be operated independently of one another to transmit torque. The second gear unit 8 is associated with a driven gear unit 10 with a single output gear. By adjusting a wedge, not shown, is alternatively between the three output gear units 9a, 9b, 10 selectable. The first overload clutch 14 is designed harder than the second overload clutch 18th

In the switch position shown in Fig. 2b (Kl, 18) of the power flow Kl of the drive 5 via the spur gears 21, 22, the first overload clutch 14, the countershaft 23, the gear 7a, the output gear unit 9a and the tool shaft 3 is active. As can be seen from FIG. 2a, the first overload clutch 14 is assigned to both gear units 7, 8, ie to be permanently torque-transmitting or torque-limiting active.

In the switch position shown (Kl, 18) a high speed of the tool shaft 3 with low release torque (second overload clutch 18) is realized. This setting is suitable, for example, for drilling with diamond drill bits with small to medium diameters.

Upon activation of the gears 7a or 7b, i. The first gear unit 7 are both overload clutches 14, 18 cumulatively active and it is therefore only the triggering torque of the weaker, second overload clutch 18 effective.

In the second switch position (K2, 18), the second power flow K2 via the second gear 7b of the first gear unit 7 is realized. Thus, a low speed of the tool shaft 3 is realized with a low release torque. This setting is suitable, for example, for drilling with diamond drill bits with very large diameters. In the third shift position (K3, 14), the power flow K3 extends via the second gear unit 8 and the output gear unit 10, wherein the second gear unit 8 is non-rotatably mounted on the countershaft 23 without an overload clutch. Here, only the first overload clutch 14 is active with a high release torque. The diameter of the gear 7b of the first gear unit 7 corresponds to the diameter of the gear of the second gear unit 8. Thus, low speeds of the tool shaft 3 can be realized with a high release torque, which is suitable for example for turning very large, long wood screws.

In the exemplary embodiment according to FIGS. 3 a and 3 b, a single output gear unit 9 is provided on the tool shaft 3 with two gearwheels 24, 25 coupled to one another in a rotationally fixed manner. The output gear unit 9 is axially adjustable by means of the switch 17 shown in Fig. 3b and a shift linkage, not shown, on the tool shaft 3 and rotatably connected in each adjustment position with the Werkzeugwel- Ie 3.

The second gear unit 8 without its own overload clutch and the first gear unit 7 with two gear wheels 7a, 7b are rotatably mounted on the countershaft 23, the diameter of the gear 7a of the first gear unit 7 corresponding to the diameter of the gearwheel of the second gear unit 8. The first gear unit 7 is the second, designed as a friction clutch overload clutch 18 exclusively assigned. From the motor shaft 4 driven by the drive 5, the torque is transmitted to the countershaft 23 via the two spur gears 21, 22 and via the first overload clutch 14 assigned to the second spur gear 22. In the switch position shown (FIG. 3b) (K1, FIG. 14), the force flux K1 initially extends via the spur gears 21, 22 and the first overload clutch 14 to the countershaft 23 and from there via the second gear unit 8 connected in a rotationally fixed manner to the countershaft 23 the first, larger gear 24 of the output gear unit 9 and from there to the tool shaft 3. In this switch position, a low speed of the tool shaft 3 is combined with a hard release torque (first overload clutch 14). This setting is suitable, for example, for screwing in large, long wood screws.

In a second switch position (K2, 18), in which the gear 24 cooperates with the gear 7a, also a low speed on the tool shaft, but with a soft release torque (second overload clutch 18) is realized. This setting is suitable, for example, for diamond drill bits with a very large diameter.

In the third switching position (K3, 18) high speeds are combined on the tool shaft 3 with a soft release torque. This setting is suitable for diamond drill bits with small to medium diameters.

Claims

claims

1. hand tool (1), in particular electric hand tool, with a drive (5), with a tool shaft (3), with a first overload clutch (14), and with a transmission gear (6) having a first and at least one second gear unit (7, 8), wherein the gear units (7, 8) are alternatively operable to transmit torque, characterized in that at least one second overload clutch (18) is provided, which is permanently and exclusively with the first gear unit (7) operatively connected.

2. Hand tool according to claim 1, characterized in that the overload clutches (14, 18) of different large maximum torques are designed to transmit, preferably that the first overload clutch (14) is harder than the second overload clutch (18).

3. hand tool (1) according to one of claims 1 or 2, characterized in that at least two gears (7a, 7b) of the first gear unit (7) have different diameters, and that the second gear unit (8) at least one gear (8a, 8b) whose diameter corresponds at least approximately to the diameter of one of the toothed wheels (7a, 7b) of the first gear unit (7).

4. Hand tool according to one of the preceding claims, characterized in that the first overload clutch (14) is permanently and exclusively with the second gear unit (8) operatively connected.

5. Hand tool according to one of claims 1 to 3, characterized in that the first overload clutch (14) all or a group of gear units (7, 8) is associated.

6. Hand tool according to claim 5, characterized in that the first overload clutch (14) in the drive train (2) between the drive (5) and the tool shaft (3), in particular between one of the drive (5) driven motor shaft (4) and a Countershaft (23) is arranged.

7. Hand tool according to one of claims 5 or 6, characterized in that the second gear unit (8) overload clutch-free formed or provided with a third overload clutch.

8. Hand tool according to one of the preceding claims, characterized in that the gear units (7, 8) are arranged on a countershaft (23).

9. Hand tool according to claim 8, characterized in that each of the gear units (7, 8) at least one rotatably with the tool shaft (3), in particular by means of an axially adjustable wedge (11), connectable driven gear unit (9, 9a, 9b, 10) is assigned.

10. A hand tool according to claim 8, characterized in that at least one rotatably connected to the tool shaft (3) and axially relative to the tool shaft (3) adjustable driven gear unit (9, 9a, 9b, 10) is provided.