Brake system with two independent mechanical brakes

• US 5,480,009 A
• Filed: 09/09/1994
• Issued: 01/02/1996
• Est. Priority Date: 09/11/1993
• Status: Expired due to Fees

• Current Assignee: Andreas Stihl
• Original Assignee: Andreas Stihl
• Inventors: Meyer, Gerhard, Wieland, Dieter, Armbruster, Herbert
• Primary Examiner(s): Le, Mark T.
• Assistant Examiner(s): Poon, Peter M.
• Application Number:
  US08/303,375
• Time in Patent Office: 480 Days
• Field of Search: 188/78, 188/77 R, 188/77 W, 188/105, 188/110, 188/166, 188/168, 301/382, 301/383
• US Class Current: 188/77.00W
• CPC Class Codes: B27B 17/083 Devices for arresting movement of the saw chain
• CPC Class Codes: F16P 3/00 Safety devices acting in conjunction with the control or operation of a machine; Control arrangements requiring the simultaneous use of two or more parts of the body F16P5/00 takes precedence
• CPC Class Codes: H02K 7/102 with friction brakes
• CPC Class Codes: H02P 3/04 Means for stopping or slowing by a separate brake, e.g. friction brake or eddy-current brake

Abstract

The device for braking an electric drive motor of a hand-held working tool has a safety brake for an immediate stopping of the working tool and an independent mechanical brake for coasting the working tool to a stop after switching off the drive motor. The mechanical brake acts on a rotational part connected to the drive motor and is activated when a switch element for activating the drive motor is released.

Claims

1. A device for braking an electric drive motor of a hand-held working tool, said device comprising:

a safety brake for an immediate stopping of the working tool;

an independent mechanical coasting brake for coasting the working tool to a stop after switching off the drive motor;

said mechanical coasting brake acting on a rotational part connected to the drive motor;

said mechanical coasting brake being activated when a switch element for activating the drive motor is released;

wherein said rotational part is a component of said safety brake and is a brake drum; and

wherein said safety brake acts on one side of said brake drum and said mechanical coasting brake acts on the other side of said brake drum.

2. A device according to claim 1, wherein said one side is an outer mantle surface of said brake drum and said other side is an inner mantle surface of said brake drum.

3. A device according to claim 1, wherein said mechanical coasting brake is a shoe brake biased in a braking direction.

4. A device according to claim 3, wherein said shoe brake comprises a brake lever and a spring acting on said brake lever.

5. A device according to claim 4, wherein:

said switch element of the drive motor comprises a transmission lever;

said brake lever is connected to said transmission lever of said switch element; and

said transmission lever acts in a direction counter to said spring.

6. A device according to claim 5, wherein:

said switch element comprises a connecting lever; and

said transmission lever and said connecting lever form a one-part linkage.

7. A device according to claim 6, wherein said one-part linkage is pivotably supported at a pivot axis.

8. A device according to claim 6, wherein a length of said transmission lever is different from a length of said connecting lever.

9. A device according to claim 4, wherein said brake lever comprises a first curved part and a second part and is pivotable about a pivot axis, said first curved part having connected thereto a brake shoe.

10. A device according to claim 9, wherein said pivot axis extends parallel at a distance to a central axis of said brake drum within a radius of said brake drum.

11. A device according to claim 1, wherein said brake drum has an open end covered by a housing cover of the working tool and wherein said brake drum is rotatable relative to said housing cover.