Stone working – Sawing – Endless
Reexamination Certificate
1998-12-14
2001-01-30
Rada, Rinaldi I. (Department: 3724)
Stone working
Sawing
Endless
C030S381000, C451S355000
Reexamination Certificate
active
06178960
ABSTRACT:
The present invention relates to hand-held motor-driven saws of the kind comprising a machine housing with a handle, a drive motor, and a saw guide bar, in which the saw guide bar projects out from the machine housing and a continuous wire loop, which carries axially spaced cutting elements thereon, is arranged to run around the saw guide bar between a drive wheel in the drive motor and a loop-guiding sprocket wheel at the free end of the saw guide bar, the cutting width of the cutting elements being greater than the width of the saw guide bar and of the guide sprocket wheel.
RELATED ART
Portable power saws of this kind normally include belt-like elements in the form of chains comprised of mutually pivotal links that are guided in the longitudinal direction of guides on the saw guide bar. Examples of such saws are found in patent publications WO 88/04602 (EP A 293.399) and U.S. Pat. No. 4,654,972. Despite constructing the chain guides from special material or sawing with a free-hanging chain run as suggested in these publications, the problem of wear is still critical at least in that part of the saw guide bar most subjected to strain, namely in the guide sprocket wheels at the outer ends of the bars. When sawing stone, the stone debris that is generated becomes mixed with water and forms a sticky abrasive mass that quickly wears down joints and the surfaces of metal guides. When sawing wood, the wood cut repeatedly becomes clogged with sawdust, causing disturbances in the work on hand. This latter problem can be counteracted with the use of oil, although such use creates an environmental problem instead.
Patent Publications U.S. Pat. No. 4,907,564 and U.S. Pat. No. 3,958,332 disclose examples of sawing stone and wood with the use of band-type elements other than linked saw chains, namely continuous wire loops on which cutting elements are mounted. Available wire or cable constructions, however, require the use of mechanical equipment when cutting stone, often heavy equipment, which does not allow the portable power saw to be used in a typical comfortable manner, with plunging penetration of the guide sprocket wheel directly into stone or wood in the manner of a circular saw.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a portable power saw that includes a wire loop which carries cutting elements and which coacts with a guide sprocket wheel on the saw guide bar in a manner such as to enhance the wear strength and increase the useful life of the saw by virtue of improving the exclusion of debris cuttings and wood dust and chips, so that straight-in plunge cuts can be made effectively in the material being cut with the aid of the guide sprocket wheel, in the manner of a circular saw. A further object is to enable such a straight-in cut to be made to a depth that extends beyond the centre of the guide sprocket wheel with the aid of an enlarged guide sprocket wheel, therewith achieving with simple saw guide bar equipment a working method that has hitherto been reserved for ring saws with high tool costs. Another object is to provide a wire saw that can be provided with cutting elements having a directed abrasive or cutting effect without the cutting elements twisting as the wire loop runs around the saw guide bar. These objects are achieved with an inventive motor saw that has the characteristic features set forth in the following claims.
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Patent Abstract Of Japan, vol. 14, No. 499, (M-1042) re JP-A-2-205410, Aug. 1990.
Hagby Asahi AB
Pillsbury Madison & Sutro LLP
Rada Rinaldi I.
Tran Kim Ngoc
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