Manually guided machine tool with a safety device

• US 6,055,142 A
• Filed: 04/23/1998
• Issued: 04/25/2000
• Est. Priority Date: 04/23/1997
• Status: Expired due to Term

• Current Assignee: Hilti Aktiengesellschaft (Hilti Martin Family Trust)
• Original Assignee: Hilti Aktiengesellschaft (Hilti Martin Family Trust)
• Inventors: von Keudell, Leopold, Echtler, Karl
• Primary Examiner(s): Jackson, Stephen W.
• Application Number:
  US09/065,355
• Time in Patent Office: 733 Days
• Field of Search: 361/42, 361/45, 361/93.1, 361/115
• US Class Current: 361/42
• 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: H02H 5/083 responsive to the entry or leakage of a liquid into an electrical appliance moisture alarm G08B21/20

Abstract

A hand held machine tool has a protective electrode (1; 1a, 1b, 1c) located within a housing with a leakage current protective switch (2; 2a, 2b, 2c) triggered by a fixed leakage current (Σ1.sub.Δ), for example, 10 mA, for interrupting power supply leads (4, 5) of the machine tool with a protective conductor (3) connected to the protective electrode (1; 1a, 1b, 1c) and not being switched off.

Claims

1. A hand held machine tool comprises a housing (6), a protective electrode (1) located within said housing and constructed of several spaced parts (1a, 1b, 1c), a protective conductor (3) connected to said protective electrode, a leakage current protective switch (2) connected to protective switch (2) connected to said protective electrode and triggered by a fixed leakage current (Σ

1Δ

) for interrupting power supply leads (4,

     5) of the machine tool with said protective conductor (3) not being switched off when the fixed leakage current is exceeded, said housing (6) having an overhead working position with an upper working end and a lower end forming a handle, said protective electrode (11) including said several parts (1a, 1b, 1c) positioned at a lowest region of such housing (6) in said overhead working position where moisture is likely to collect, said housing having openings therein (A, B, C) in the lowest region thereof and said parts (1a, 1b, 1c) of said protective electrode (1) located adjacent said openings (A, B, C), and said parts (1a, 1b, 1c) of said protective electrode adjacent said openings (A, B, C) being located where conductive media can accumulate.

2. A hand held machine tool, set forth in claim 1, wherein said leakage current protective switch (2) is triggered by a leakage current (Σ

1.sub.Δ

) of at most 10 mA.

3. A hand held machine tool, as set forth in claim 1 or 2, wherein said protective electrode (1) is grounded.

4. A hand held machine tool, as set forth in claim 3, wherein said leakage current protective switch (2) determines the leakage current on the basis of a current flowing to ground.

5. A hand held machine tool, as set forth in claim 1 or 2, including a summation transformer (2a), said leakage current protective switch (2) detects the leakage current by means of said summation transformer, and said summation transformer detects the difference between the currents flowing in said power supply leads (4, 5) of the machine tool.

6. A hand held machine tool, as set forth in claim 1 or 2, wherein said protective electrode parts (1a, 1b, 1c) are located in said handle in an original position and remain in the original position when said handle is opened or a lid of the handle is removed.

7. A hand held machine tool, as set forth in claim 1 or 2, wherein said protective electrode parts (a, 1b, 1c) are branched and held by the branches.

8. A hand held machine tool, as set forth in claim 1 or 2, wherein said protective electrode parts (1a, 1b, 1c) work in all operating positions of said machine tool.

9. A hand held machine tool, as set forth in claim 1 or 2, wherein said protective electrode parts (1a, 1b, 1c) have at least one of pans, ribs and barriers.

10. A hand held machine tool, as set forth in claim 1 or 2, wherein said protective electrode parts (1a, 1b, 1c) have a surface as large as possible.

11. A hand held machine tool, as set forth in claim 1 or 2, wherein said protective electrode parts (1a, 1b, 1c) are formed of a corrosion resistant material.

12. A hand held machine tool, as set forth in claim 1 or 2, wherein said housing is axially elongated with said working end and such lower end including said handle being in substantially axially aligned relation.