Device for switching operating mode for hand tool

[0001] The invention relates to a device for switching operating modes for an at least partially rotational and percussive hand tool machine such as a combi-hammer.

[0002] U.S. Pat. No. 4,236,588 discloses a hammer drill that comprises an external manually operated, axially displaceable sliding cylinder that is mounted rotationally and locked on the guide cylinder. The sliding cylinder is provided with a dog catch, which in a first operating mode fixes the guide cylinder locked against rotation relative to the housing, in a second operating mode freely rotational and in a third operating mode relative to a bevel gear.

[0003] DE4009762 discloses a chisel hammer having a two-part guide cylinder that can be rotationally adjustable and fixed using locking balls both engaging radially and a spring-biased, external axial manual displaceable sliding sleeve.

[0004] Torque limiters or overload clutches are used in the power transmission train for mechanically limiting unacceptable torque, in particular, for tool blockage.

[0005] DE3804414 discloses a drill hammer having a spring-biased overload clutch connected with the tool receptacle between the hollow driving guide cylinder containing an axially striking driving piston, said guide cylinder being locked against rotation, and a driving bevel gear mounted rotationally on the guide cylinder. The overload clutch can be snapped in again after its release on overload using an external manually operated, axially displaceable sliding sleeve.

[0006] JP9239675 discloses a drill hammer having an overload clutch comprising two opposing axially spring biased mutually interlocking coupling rings that are arranged between the hollow driving guide cylinder containing an axially impacting driving piston and a driving crown gear rotationally mounted on the guide cylinder and which is driven via an additional intermediate shaft having three external manually switchable operating modes.

[0007] The object of the invention is to provide a simple realization of an operating mode switching device manually switching a hand tool device in three operating modes and having a manual overload clutch.

[0008] This object is essentially achieved, in accordance with the invention, by a device for switching operating modes for an at least partially rotational and percussive hand tool machine with at least three operating modes having an overload clutch, which is disposed between a hollow, driving guide cylinder containing an axially impacting driving piston and a driving crown gear and which can be switched using an external manually switchable, axially displaceable switching member into different operating modes, whereby the guide cylinder is rotationally driven in at least one operating mode. The axially displaceable switching member rotationally form-lockingly engages in a freely rotating coupling ring of the overload clutch relative to the guide cylinder.

[0009] The driving coupling ring combines the operating mode switching device in a technically simple manner with a torque-dependent overload clutch by virtue of the axially displaceable switching member being rotationally form-lockingly engaged in the driving coupling ring of the overload clutch and thus results in a reduction of structural parts.

[0010] The overload clutch preferably comprises two opposing, axially spring biased friction lockingly interlocking coupling rings, whereby the springs may be configured in a structurally simple fashion around the guide cylinder.

[0011] Preferably, the driving coupling ring is pre-biased by the axial spring relative to the guide cylinder and mounted rotationally locked, and axially limited moveable relative to the guide cylinder, whereby the freely rotating driving coupling ring is in an axially fixed positioned.

[0012] Preferably, the axially displaceable switching device, which is preferably configured as a sliding sleeve, is rotationally form-lockingly connected with a driving coupling ring via radial projections and associated radially disposed grooves, whereby the engagement is axially freely moveable.

[0013] Preferably, the axially displaceable sliding sleeve can be rotationally form-lockingly connected at a first frontal end with a driving crown gear via radial projections and associated grooves, whereby one operating mode having a rotary drive such as “hammer drilling” can be switched.

[0014] Preferably, the axially displaceable sliding cylinder is shorter than the engaging distance between the driving crown gear and the locking ring fixed to the housing, whereby an operating mode fixed against rotation such as “chisel” can be switched.

[0015] Preferably, the axially displaceable sliding cylinder can be spring biased against the freely rotational coupling ring, whereby a synchronized switching between the operating modes relative to the rotationally form locking engagement is possible.

[0016] Preferably, the axially displaceable sliding sleeve is radially stepped, whereby the axial stop for the sliding spring is formed.

[0021] FIG. 1 shows a device for switching operating modes of a rotating and striking hand tool machine (not shown) comprising an overload clutch having a housing 1, which is arranged between a hollow driving guide cylinder 3 containing an axially striking impact piston 2 and a driving crown gear 4 that can be rotated on the guide cylinder 3, whereby a sliding cylinder 5 that is axially displaceable and externally manually switched using a handle, is rotationally form lockingly mounted in driving coupling ring 6 of the overload coupling freely rotating relative to the guide cylinder 3. The overload clutch comprises the driving coupling ring 6 fixed axially relative to the guide cylinder 3 and an axially limited displaceable mounted driving coupling ring 8 locked against rotation, wherein the coupling ring can be axially frictionally interlocked according to the claw principle. The axially displaceable, peripherally radially offset sliding cylinder 5 is rotationally form lockingly connected with the driving coupling ring 6 using radial projections 9 and associated radial grooves 10. In the illustrated operating mode with rotational drive, the axially offset sliding cylinder 5 is connected at a first frontal end 11 with the driving crown gear 4 using radial projection 9′ and associated grooves 10′.

[0022] FIG. 2, shows an operating mode with a rotation lock, wherein the axially displaceable sliding cylinder 5 is rotationally form lockingly connected at a second frontal end 12 with a locking ring 13 fixed to the housing using radial projection 9″ and associated grooves 10″.

[0023] In FIG. 3, the centrally positioned, axially displaceable sliding cylinder 5 is shorter than the engaging distance between the driving crown gear 4 and the locking ring 13, whereby in the illustrated freely rotating operating mode there is no engagement. The radially stepped sliding cylinder 5 is axially spring biased using a sliding spring 14 against the rotational freely rotating coupling ring 6.