[0001] The present invention pertains to apparatus for buffing and polishing painted surfaces and, more particularly, to a supporting back-up plate for a double-sided rotary buffing pad.
[0002] The finishing of painted or clear coated surfaces of automobiles and the like includes the use of a variety of buffing, polishing and finishing tools, finishing compounds and apparatus, including both manually operated devices and power driven buffing machines. Rotary buffing pads used with power buffers include tufted wool pads, polymeric foam pads, and pads of other types and constructions of buffing and finishing materials.
[0003] A power buffer typically has a driven output shaft or spindle to which a rotary buffing pad is attached, usually by a threaded connection. Because a rotary buffing pad has a buffing surface that is inherently soft and somewhat flexible, such pads are typically mounted on or attached to some sort of backing plate against which the rear face of the pad opposite the working surface rests and is supported. The backing plate may be relatively rigid or may provide substantial flexibility, depending on the nature of the buffing pad itself and/or the type of finishing work being done.
[0004] Rotary buffing pads having a reversible double-sided construction are also known in the art. Such pads are made of both tufted wool and polymeric foam and typically include identical opposite finishing faces such that when one face becomes excessively worn or dirty, the pad is detached from the drive spindle of the power buffer, reversed and reattached to present a fresh buffing face. One such reversible pad is shown in U.S. Pat. No. 5,461,750. In a typical construction of a double-sided pad, the opposite facing finishing pads are mounted back-to-back on an annular interior backing disk which is secured to a center hub that carries the threaded connection for attachment to the buffing machine spindle. To provide the necessary strength and yet provide needed flexibility, the backing disk typically has a heavier section where it is attached to the hub, which section thins in a radially outward direction so that the peripheral edge of the backing disk is quite thin and flexible. In use, the flexible backing disk allows the operator to move easily over contoured surfaces and into more confining areas and, in general, provides a necessary flexibility that skilled workers desire. Unfortunately, the strain and fatigue to which a solid plastic backing disk is subjected through high speed rotation and cyclical bending pressure from the operator often results in premature cracking, fracture and ultimate failure of the backing disk. The very nature of a double-sided pad simply does not lend it to the use of backing plates of the type used with single faced rotary buffing pads. It would, therefore, be desirable and useful to provide some means of supporting a double-sided rotary buffing pad to eliminate or reduce the problem of fracture of the backing disk and yet retain some of the necessary flexibility of the working face.
[0005] In accordance with the present invention, a separate back-up plate for a double-sided buffing pad is interposed between the power buffer drive spindle and the double-sided pad. The back-up plate provides intermittent supporting contact through the use of circumferentially spaced peripheral fingers in contact with the non-working face of the pad.
[0006] A back-up plate is provided for a reversible double-sided buffing pad of the type having a center hub adapted for attachment to the drive shaft of a power buffer. The back-up plate comprises a plate body that is mounted on a center plate hub which hub includes an upper fastener attachable to the drive shaft of the power buffer and a lower fastener attachable to the center hub of the pad. The plate body has a generally circular shape when viewed in plan, including a center body portion that extends radially outward and generally perpendicular to the plate hub axis. The radial outer peripheral edge of the body portion terminates of the plurality of circumferentially spaced, downturned fingers. The free distal ends of the fingers engage the non-working face of the pad when the pad is attached to the plate body via the lower fastener.
[0007] The plate hub preferably comprises a generally tubular sleeve including a threaded ID portion forming the upper fastener and an axially extending threaded stud forming the lower fastener. The plate body is preferably rotatably mounted on the plate hub to facilitate attachment of the pad thereto. In a preferred embodiment, the plate hub is made of metal and the plate body is made of a thermoplastic material. Preferably, the plate body has a cylindrical axial through bore and the OD of the plate hub is received in the through bore with a slip fit to provide relative rotation therebetween.
[0008] In the preferred embodiment, the outer peripheral edge of the center body portion of the back-up plate is rounded to blend smoothly into the fingers and to define a downwardly facing continuous edge comprising convergent curved edge portions defining the fingers, the distal ends of which fingers define flat contact edge surfaces. Each finger includes an integral reinforcing rib that extends from the distal ends thereof into the body portion and terminates adjacent the plate hub.
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[0013] As best seen in
[0014] The double-sided pad
[0015] The back-up plate
[0016] The center of the plate body
[0017] The back-up plate fingers
[0018] Referring to
[0019] Because the back-up plate hub