Random orbit sander having braking member

• US 5,392,568 A
• Filed: 12/22/1993
• Issued: 02/28/1995
• Est. Priority Date: 12/22/1993
• Status: Expired due to Term

• Current Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Sutton, David L., Howard, Thomas J. Jr.
• Primary Examiner(s): Rachuba, Maurina T.
• Application Number:
  US08/173,644
• Time in Patent Office: 433 Days
• Field of Search: 51/170 MT, 51/170 R, 51/170 J, 51/174, 51/177, 188/379, 188/380, 188/378
• US Class Current: 451/357
• CPC Class Codes: B24B 23/03 the tool being driven in a combined movement
• CPC Class Codes: C09K 3/10 Materials in mouldable or extrudable form for sealing or packing joints or covers filling pastes C09D5/34

Abstract

A random orbit sander having a braking member for frictionally controlling the speed of a platen of the sander when the sander is removed from a workpiece during operation. The braking member includes a base portion, an outwardly flaring, relatively thin wall portion and an enlarged outermost edge portion adapted to frictionally engage an upper surface of the platen. The braking member is secured to the bottom of the shroud of the housing via a groove formed in its base portion. The braking member exerts a relatively constant spring force against the upper surface of the platen which limits the rotational speed of the platen to approximately 1200 rpm when the platen is lifted off of a work surface, without significantly degrading the performance of the sander under load. This prevents swirl marks and other undesirable scratches from being made in a workpiece when the platen is reapplied to the workpiece as a result of the platen having increased in speed to an unloaded, free-wheeling speed, and yet allows the platen to operate at or above the minimum desired working speed of about 800 rpm. The braking member is formed from polyester butylene terephthalate which is doped with approximately 2% silicon and approximately 15% teflon in the preferred embodiments. This material formulation, plus its geometry, allows the braking member to exert and maintain a relatively constant spring force of about 3.5 lbs. against the platen and to resist frictional wear once past an initial break-in period. The braking member also acts as a seal between the lower surface of the shroud and the upper surface of the platen.

Claims

1. A random orbit sander having a motor, a platen driven rotationally by said motor and spaced axially apart from a lower surface of a housing of said sander, the improvement comprising:

brake means comprising a flexible annular seal that is secured to the lower surface of the housing and frictionally engaged to an upper surface of said platen for controllably, frictionally braking said platen to maintain the rotational speed of said platen within a predetermined range when said platen is lifted off of a work surface during operation of said sander, and for sealing the axial gap between the lower surface of the housing and said platen;

said brake means including a base portion adapted to be secured to said housing, a flexible, flaring wall portion protruding from said base portion, and an outer edge portion having a thickness greater than said wall portion for contacting said upper surface of said platen.

2. The sander of claim 1, wherein said annular seal is formed from polyester butylene terephthalate doped with silicon and teflon.

3. The sander of claim 2 wherein said doping of said polyester butylene terephthalate comprises about two percent silicon and about fifteen percent teflon.

4. The apparatus of claim 1, wherein said brake means provides a braking spring force of approximately three to four lbs.

5. A random orbit sander comprising a motor, a platen driven rotationally by said motor and spaced axially apart from a lower surface of a housing of said sander, the platen having at least one opening therethrough, a fan for drawing dust and particulate matter through said opening, and braking means for controllably, frictionally braking said platen to control the rotational speed of said platen when said platen is lifted off of a work surface during operation of said sander without significantly degrading the performance of the sander under load;

said braking means further forming an annular seal comprising;

a base portion adapted to be secured to said lower surface of said housing,

a flexible wall portion extending from said base portion, and

an outer edge portion adapted to frictionally contact said upper surface of said platen, said braking means operating to limit the rotational speed of said platen to approximately 1200 rpm when said platen is lifted off of said work surface and to increase the suction force through said opening in said platen by forming a peripheral seal between said lower surface of said housing and said upper surface of said platen.

6. The sander of claim 5, wherein said upper surface of said platen includes a metallic ring secured thereto upon which said outer edge portion of said braking means rides during rotation of said platen.

7. The sander of claim 5, wherein said flexible wall portion has a relatively thin cross section and is adapted to permanently deform after an initial period of use of said sander.

8. The sander of claim 5, wherein said braking means is formed from polyester butylene terephthalate doped with silicon and teflon.

9. The sander of claim 8, wherein said silicon comprises approximately two percent and said teflon comprises approximately fifteen percent of said doping of said polyester butylene terephthalate.

10. The sander of claim 5, wherein said braking means provides a relatively constant spring force of approximately 3.5 lbs. against said upper surface of said platen.

11. The sander of claim 5, wherein said braking means is constructed of a material having a flex modulus within a range of approximately 35 kpsi to approximately 75 kpsi.

12. A random orbit sander comprising a motor, a platen driven rotationally by said motor and spaced axially apart from a lower surface of a housing of said sander, and a braking member interposed between the lower surface of the housing and an upper surface of the platen for controllably, frictionally engaging said upper surface of said platen to thereby effect a braking action on the rotation of said platen to limit the rotational speed of said platen when said platen is lifted off of a work surface during operation of said sander without significantly degrading the performance of the sander under load;

said braking member comprising;

an annular member having a base portion adapted to engage a lower portion of said housing,

a flexible wall portion extending from said base portion,

and an enlarged outer edge portion integrally formed with said wall portion, said outer edge portion being adapted to frictionally engage said upper surface of said platen to thereby frictionally limit the rotational speed of said platen to a predetermined maximum speed when said platen is lifted off of said work surface.

13. The sander of claim 12, wherein said braking member is formed from polyester butylene terephthalate and doped with silicon and teflon.

14. The sander of claim 13, wherein said doping comprises approximately two percent silicon and approximately fifteen percent teflon.

15. The sander of claim 12, wherein said predetermined maximum speed is approximately equal to 1200 rpm.

16. The sander of claim 12, wherein said upper surface of said platen includes a metallic ring secured thereto upon which said outer edge portion of said braking member rides during rotation of said platen.

17. The sander of claim 12, wherein said braking member is further adapted to seal the axial space between the lower surface of the housing and the upper surface of the platen.

18. The sander of claim 16 wherein said braking member provides a relatively constant spring force of approximately 3.5 lbs. against said upper surface of said platen.

19. The sander of claim 12 wherein said flexible wall portion of said brake member permanently deforms after an initial period of use of said sander.