Hand-held power tool

Patent metadata

Field	Value
Publication number	US-9539708-B2
Application number	US-201214356515-A
Country	US
Kind code	B2
Filing date	Oct 17, 2012
Priority date	Nov 7, 2011
Publication date	Jan 10, 2017
Grant date	Jan 10, 2017

Abstract

A hand-held power tool has a motor, a tool holder, and a percussion mechanism disposed between the motor and the tool holder in the drive train. The percussion mechanism includes a first shaft and a second shaft. A magnetically conductive ring gear is connected to the first shaft. An inner wall of the ring gear is eccentric to an axis of the second shaft. A magnetically conductive impeller is connected to the second shaft and is arranged to rotate within the ring gear. The impeller is spaced from the ring gear by a first air gap in a first position while being spaced from the ring gear by a second air gap in a second position, the first air gap being smaller than the second one. A magnet array is arranged coaxially to the second shaft. A magnetorheological fluid fills a cavity between the ring gear and the impeller.

First claim

What is claimed is:

1. A hand-held power tool comprising:
a motor;
a tool holder; and
a percussion mechanism connected in a drive train between the motor and the tool holder, the percussion mechanism including:
a first shaft,
a second shaft,
a hollow wheel connected to the first shaft and whose inside wall is not rotation-symmetrical with respect to an axis of the second shaft,
an impeller connected to a second shaft and rotatably situated within the hollow wheel,
a magnet situated coaxially to the second shaft, and
a magnetorheological fluid filling a cavity between the hollow wheel and the impeller,
in a first position, the impeller being spaced apart from the hollow wheel by a first air gap, and in a second position, the impeller being spaced apart from the hollow wheel by a second air gap, the first air gap being smaller than the second air gap, and
the impeller and the hollow wheel being made of a magnetically conductive material.

2. The hand-held power tool as recited in claim 1 wherein the inner wall includes one or multiple pole shoes projecting toward the axis.

3. The hand-held power tool as recited in claim 2 wherein the number of pole shoes is equal to the number of vanes of the impeller.

4. The hand-held power tool as recited in claim 1 wherein a magnetic back iron extends from a side of the magnet facing away from the hollow wheel to the hollow wheel.

5. The hand-held power tool as recited in claim 1 wherein the second shaft is made of a magnetically conductive material.

6. The hand-held power tool as recited in claim 1 wherein the hollow wheel is closed along the axis by a cover and a bottom toward a chamber in which the impeller and the magnetorheological fluid are situated.

7. The hand-held power tool as recited in claim 1 wherein the magnet is attached to a housing of the hand-held power tool or to the second shaft.

8. The hand-held power tool as recited in claim 1 wherein the magnet includes a solenoid and a settable power source, and further comprising an operating element for setting a current delivered by the power source.

9. The hand-held power tool as recited in claim 1 wherein the magnet includes a solenoid and a settable power source, and a control unit increases a current flow from the power source when the impeller approaches the first position.

10. The hand-held power tool as recited in claim 9 wherein the control unit reduces the current flow after a predefined time period after which the impeller approaches the first position.

Assignees

• Hilti Ag

Inventors

• Hoop Alexander
• Binder Albert
• Wierer Michael
• Profunser Dieter

Classifications

• F16D2037/002

  characterised by a single substantially axial gap in which the fluid or medium consisting of small particles is arranged · CPC title

• F16D37/02

  the particles being magnetisable · CPC title

• F16D5/00

  Impulse couplings, i.e. couplings that alternately accelerate and decelerate the driven member · CPC title

• B25B21/02 Primary

  with means for imparting impact to screwdriver blade or nut socket · CPC title