Power tool with magneto-pneumatic striking mechanism

Patent metadata

Field	Value
Publication number	US-10792799-B2
Application number	US-201313916184-A
Country	US
Kind code	B2
Filing date	Jun 12, 2013
Priority date	Jun 15, 2012
Publication date	Oct 6, 2020
Grant date	Oct 6, 2020

Abstract

A power tool 1 including a bit socket 6 which is configured to hold a chiseling bit 7 so that the latter can move along an axis of movement 3 . A magneto-pneumatic striking mechanism 2 includes a primary drive 22 that is arranged around the axis of movement 3 and that has a first magnet coil 46 , a permanently and radially magnetizable ring magnet 42 and a second magnet coil 47 arranged consecutively in the striking direction 5 . On the axis of movement 3 , inside the magnet coils 46, 47 , the striking mechanism 2 has a striker 4 and a striking block 13 arranged consecutively in the striking direction 5 . An air cushion 23 acts upon the striker 4 in the striking direction 5.

First claim

What is claimed is:

1. A power tool comprising:
a bit socket configured to hold a chiseling bit movable along an axis of movement; and
a magneto-pneumatic striking mechanism including a primary drive arranged around the axis of movement and having a first magnet coil, a ring magnet and a second magnet coil arranged consecutively in a striking direction, and, on the axis of movement, inside the magnet coils, the striking mechanism having a striker and a striking block arranged consecutively in the striking direction, and the striking mechanism having an air cushion acting upon the striker in the striking direction, the ring magnet being permanently magnetic and magnetized radially relative to the axis of movement
wherein a field strength of the ring magnet is above 1 Tesla.

2. The power tool as recited in claim 1 wherein the ring magnet includes a plurality of permanent magnets all facing the axis of movement with a same magnetic pole.

3. The power tool as recited in claim 1 wherein a current fed into the first magnet coil and a second current fed into the second magnet coil have a same direction of rotation around the axis of movement.

4. The power tool as recited in claim 1 further comprising a control unit actuating the first and second magnet coils in alternating phases, a first magnetic field generated by the first magnet coil inside the first magnet coil being superimposed with the magnetic field of the ring magnet constructively in a first phase and destructively in a second phase, while a second magnetic field generated by the second magnet coil inside the second magnet coil is superimposed with the magnetic field of the ring magnet destructively in the first phase and constructively in the second phase.

5. The power tool as recited in claim 1 wherein the striker is made of a soft- magnetic material.

6. The power tool as recited in claim 1 further comprising a stationary closure closing off the air cushion opposite from the striking direction.

7. The power tool as recited in claim 1 wherein the striking block projects into the second magnet coil or into a yoke adjoining the second magnet coil in the striking direction.

8. The power tool as recited in claim 7 wherein the striking block is made of a soft-magnetic material.

9. The power tool as recited in claim 1 wherein, in every position, the striker partially overlaps at least one of the first and second magnet coils, and partially the ring magnet.

10. The power tool as recited in claim 1 wherein a first length of the first magnet coil is smaller than a second length of the second magnet coil.

11. The power tool as recited in claim 10 wherein a ratio of the second length to the first length is between 1 . 75 and 2 . 25 .

12. The power tool as recited in claim 1 further comprising a guide tube oriented coaxially to the axis of movement, the first magnet coil, the ring magnet and the second magnet coil being arranged around the guide tube, the air cushion and the striker being arranged inside the guide tube.

13. A power tool comprising:
a bit socket configured to hold a chiseling bit movable along an axis of movement; and
a magneto-pneumatic striking mechanism including a primary drive arranged around the axis of movement and having a first magnet coil, a ring magnet and a second magnet coil arranged consecutively in a striking direction, and, on the axis of movement, inside the magnet coils, the striking mechanism having a striker and a striking block arranged consecutively in the striking direction, and the striking mechanism having an air cushion acting upon the striker in the striking direction, the ring magnet being permanently magnetic and magnetized radially relative to the axis of movement;
further comprising a magnetic yoke surrounding the first and second magnet coils and the ring magnet.

14. The power tool as recited in claim 13 wherein the magnetic yoke has a ring-shaped first cap covering the first magnetic coil and a ring-shaped second cap covering the second coil.

15. A power tool comprising:
a bit socket configured to hold a chiseling bit movable along an axis of movement; and
a magneto-pneumatic striking mechanism including a primary drive arranged around the axis of movement and having a first magnet coil, a ring magnet and a second magnet coil arranged consecutively in a striking direction, and, on the axis of movement, inside the magnet coils, the striking mechanism having a striker and a striking block arranged consecutively in the striking direction, and the striking mechanism having an air cushion acting upon the striker in the striking direction, the ring magnet being permanently magnetic and magnetized radially relative to the axis of movement
further comprising a control unit controlling a current and a prognosis device continually measuring a potential energy of the air cushion.

16. The power tool as recited in claim 15 wherein the control unit controls the current on the basis of a control signal emitted by the prognosis device.

17. The power tool as recited in claim 15 wherein the prognosis device receives a signal from a pressure sensor measuring a pressure in the air cushion.

18. The power tool as recited in claim 17 wherein the prognosis device receives a further signal from a temperature sensor measuring a pressure in the air cushion.

19. The power tool as recited in claim 17 wherein the prognosis device estimates a speed of the striker as a function of a pressure change.

Assignees

• Hilti Ag

Inventors

• Binder Albert
• Hakenholt Christoph
• Kuntner Jochen

Classifications

• B25D11/064 Primary

  using an electromagnetic drive · CPC title

• H01F7/1615

  Armatures or stationary parts of magnetic circuit having permanent magnet · CPC title

• H02K33/12

  with armatures moving in alternate directions by alternate energisation of two coil systems · CPC title

• H01F2007/1692

  Electromagnets or actuators with two coils · CPC title