Safety clutch for electrical hand-held tool

• US 20020066632A1
• Filed: 11/30/2001
• Published: 06/06/2002
• Est. Priority Date: 12/01/2000
• Status: Active Grant

• Current Assignee: Hilti Aktiengesellschaft (Hilti Martin Family Trust)
• Original Assignee: Hilti Aktiengesellschaft (Hilti Martin Family Trust)
• Inventors: Hellmann, Peter, Bongers-Ambrosius, Hans-Werner, Kristen, Ferdinand
• Granted Patent: US 6,644,450 B2
• Time in Patent Office: Days
• US Class Current: 192/17C
• CPC Class Codes: B25D 16/003 Clutches specially adapted therefor
• CPC Class Codes: B25D 2211/003 Crossed drill and motor spindles
• CPC Class Codes: B25D 2250/145 Electro-magnetic parts
• CPC Class Codes: B25F 5/00 Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
• CPC Class Codes: F16D 2027/008 Details relating to the magnetic circuit, or to the shape of the clutch parts to achieve a certain magnetic path
• CPC Class Codes: F16D 2121/14 Mechanical
• CPC Class Codes: F16D 2121/22 for releasing a normally applied brake
• CPC Class Codes: F16D 2123/00 Multiple operation forces
• CPC Class Codes: F16D 27/112 with flat friction surfaces, e.g. discs
• CPC Class Codes: F16D 59/02 spring-loaded and adapted to be released by mechanical, fluid, or electromagnetic means
• CPC Class Codes: F16D 67/06 electromagnetically actuated

Abstract

A safety clutch for an electric hand-held tool and including a rotor (8), an anchor disc (9) frictionally engageable with the rotor (8) for transmitting a torque there-between, a stationary axial stop (13) for limiting the air gap (s) between the rotor and the anchor disc and engageable by the anchor disc under an axial reserved pre-stress applied to the anchor disc (g); and a stationary electromagnetic coil (11) provided on a side of the rotor (8) remote from the anchor disc (9) and coaxial with the rotor (8) for generating a rotationally symmetrical magnetic flux (φ) for attracting of the anchor disc (g) to magnetic poles (12a, 12b) associated with the rotor (8).

Claims

1. A safety clutch for an electric hand-held tool, comprising a rotor (8);

an anchor disc (9) frictionally engageable with the rotor (8) for transmitting a torque therebetween and spaced from the rotor (8) by an air gap (5) in a disengagement position of the anchor disc (9);

a stationary axial stop (13) for limiting the air gap (5) and engageable by the anchor disc under an axial reserved pre-stress applied to the anchor disc (9); and

a stationary electromagnetic coil (11) provided on a side of the rotor (8) remote from the anchor disc (9) and coaxial with the rotor (8) for generating a rotationally symmetrical magnetic flux (φ

) for attracting of the anchor disc (9) to magnetic poles (12a, 12b) associated with the rotor (8) to provide for a frictional engagement of the anchor disc (9) with the rotor (8).

2. A safety clutch according to claim 1, wherein the axial stop (13) is formed of a gliding material, and wherein the anchor disc (9) forms only a linear contact with the stop (13).

3. A safety clutch according to claim 1, wherein the axial stop (13) is formed as an annular member.

4. A safety clutch according to claim 1, further comprising an axially prestressed spring (14) for applying the reserved prestress to the anchor disc (9).

5. A safety clutch according to claim 4, wherein the spring (14) is axially prestressed for applying the reserved prestress of from 1 to 5 N.

6. A safety clutch according to claim 1, wherein the air gap (5) amounts from 0.3 to 0.5 mm.

7. A safety clutch according to claim 1, wherein the magnetic poles (12a, 12b) are formed as pole shoes extending between the anchor disc (9) and the rotor (8) and radially spaced from each other.

8. A safety clutch according to claim 7, wherein the rotor (8) is formed as a cup-shaped member narrowly surrounding the electromagnetic coil (11) from three sides.

9. A safety clutch according to claim 1, wherein the rotor (8) is provided on a driving side of a torque transmission means, and the anchor disc (9) is provided on a driven side of the torque transmission means.

10. A safety clutch according to claim 1, further comprising a controllable, radially displaceable brake element (10) with which the rotor (8) cooperates.

11. A safety clutch according to claim 10, wherein the brake element (10) is formed as one of small, electro-magnetically controlled brake shoe and electromagnetically controlled braking hand.

12. A safety clutch according to claim 10, wherein the brake element (10) has a friction surface (17) engageable with a radially outer surface (15) of the rotor (8).

13. A safety clutch according to claim 12, wherein the radially outer surface (15) of the rotor (8) is provided with a nitride layer (16).