COUNTERBALANCE FOR ECCENTRIC SHAFTS

• US 20110067894A1
• Filed: 09/24/2009
• Published: 03/24/2011
• Est. Priority Date: 09/24/2009
• Status: Active Grant

• Current Assignee: Credo Technology Corporation
• Original Assignee: Credo Technology Corporation, Robert Bosch GmbH
• Inventors: Bernardi, Walter M.
• Granted Patent: US 8,381,833 B2
• Time in Patent Office: Days
• US Class Current: 173/1
• CPC Class Codes: B25B 28/00 Portable power-driven joining or separation tools B25B21/00 takes precedence
• 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: B25F 5/006 Vibration damping means

Abstract

A power tool includes a housing, a motor having a motor output shaft and located within the housing, the motor being configured to rotate the motor output shaft about a first axis, a drive component having (i) a body attached to the motor output shaft, and (ii) an output drive pin attached to the body, the output drive pin defining a second axis which is offset from the first axis, the body being caused to rotate about the first axis in response to rotation of the motor output shaft about the first axis, and the output drive pin being caused to be eccentrically driven in response to rotation of the body about the first axis, and further the body having a hub and a counterbalance arrangement attached to the hub, the counterbalance arrangement being positioned and configured to offset forces generated by the output drive pin when eccentrically driven, a linkage configured to oscillate in response to the output drive pin being eccentrically driven, and a tool mount configured to oscillate in response to oscillation of the linkage.

A method of oscillating a tool is also described.

Claims

1. A power tool, comprising:

a housing;

a motor having a motor output shaft and located within said housing, said motor being configured to rotate said motor output shaft about a first axis;

a drive component having (i) a body attached to said motor output shaft, and (ii) an output drive pin attached to said body, said output drive pin defining a second axis which is offset from said first axis, said body being caused to rotate about said first axis in response to rotation of said motor output shaft about said first axis, and said output drive pin being caused to be eccentrically driven in response to rotation of said body about said first axis, and further said body having a hub and a counterbalance arrangement attached to said hub, said counterbalance arrangement being positioned and configured to offset forces generated by said output drive pin when eccentrically driven;

a linkage configured to oscillate in response to said output drive pin being eccentrically driven; and

a tool mount configured to oscillate in response to oscillation of said linkage.

2. The power tool of claim 1, wherein:

said hub defines a bore aligned with said first axis, and

said motor output shaft is received within said bore.

3. The power tool of claim 1, wherein said counterbalance arrangement includes:

a first counterbalance structure extending radially from said hub, and

a second counterbalance structure extending radially from said hub.

4. The power tool of claim 3, wherein said first counterbalance structure is spaced apart from said second counterbalance structure.

5. The power tool of claim 4, wherein said first counterbalance structure and said second counterbalance structure are offset from each other along said first axis.

6. The power tool of claim 5, wherein:

said second axis is offset from said first axis by X inches, and 0.025 inches<

X<

0.045 inches,

said first counterbalance structure possesses a first weight of Y mg, and 1.7<

Y<

3.2, and

said second counterbalance structure possesses a second weight of Z mg, and 2.7<

Z<

5.1.

7. The power tool of claim 1, further comprising a drive bearing mounted on said output drive pin, wherein:

said drive bearing is caused to be eccentrically driven in response to said output drive pin being eccentrically driven, and

said linkage is caused to oscillate in response to said drive bearing being eccentrically driven.

8. The power tool of claim 7, wherein:

said linkage includes (i) an input link having a bearing surface positioned in contact with said drive bearing, and (ii) an output link on which said tool mount is supported,

said input link is caused to oscillate in response to said drive bearing being eccentrically driven,

said output link is caused to oscillate in response to oscillation of said input link, and

said tool mount is caused to oscillate in response to oscillation of said output link.

9. The power tool of claim 8, wherein:

said output link is secured to said housing so as to be rotatable with respect to said housing about a third axis, and

said output link oscillates about said third axis in response to oscillation of said input link.

10. The power tool of claim 9, further comprising a first bearing structure and a second bearing structure, wherein:

said housing defines a bearing recess for receiving said first bearing structure,

said output link has a first end portion and a second end portion,

said first bearing structure is positioned in said bearing recess in a friction fit manner,

said first bearing structure supports said first end portion of said output link, and

said second bearing structure supports said second end portion of said output link within said housing.

11. The power tool of claim 10, further comprising a third bearing structure positioned to support said hub of said body of said drive component within said housing.

12. The power tool of claim 1, further comprising a tool secured to said tool mount, said tool being caused to oscillate in response to oscillation of said tool mount.

13. The power tool of claim 13, wherein said tool includes one of a sanding pad, a cutting blade, and a grout removal blade.

14. A method for oscillating a tool, comprising:

rotating a motor output shaft of a motor about a first axis;

rotating a body of a drive component about said first axis in response to rotation of said motor output shaft, said body having a hub and a counterbalance arrangement;

eccentrically driving an output drive pin of said drive component in response to rotation of said body, said output drive pin defining a second axis which is offset from said first axis;

oscillating a linkage in response to eccentrically driving said output drive pin;

oscillating a tool mount in response to oscillating said linkage; and

oscillating a tool in response to oscillating said tool mount.

15. The method of claim 14, wherein said counterbalance arrangement includes:

a first counterbalance structure extending radially from said hub, and

a second counterbalance structure extending radially from said hub.

16. The method of claim 15, wherein said first counterbalance structure and said second counterbalance structure are offset from each other along said first axis and configured to offset forces generated by said output drive pin when said output drive pin is eccentrically driven.

17. The method of claim 16, wherein:

said second axis is offset from said first axis by X inches, and 0.025 inches<

X<

0.045 inches,

said first counterbalance structure possesses a first weight of Y mg, and 1.7<

Y<

3.2, and

said second counterbalance structure possesses a second weight of Z mg, and 2.7<

Z<

5.1.

18. The method of claim 14, further comprising:

eccentrically driving a drive bearing in response to said output drive pin being eccentrically driven;

oscillating an input link of said linkage in response said drive bearing being eccentrically driven;

rotatably oscillating an output link of said linkage about a third axis in response to oscillation of said input link; and

oscillating said tool mount in response to oscillation of said output link.

19. The method of claim 18, wherein:

said input link includes a bearing surface positioned in contact with said drive bearing; and

said tool mount supported on said output link;

20. The method of claim 14, wherein said tool includes one of a sanding pad, a cutting blade, and a grout removal blade.