Driving device

Details Driving device Driving device

1999-12-09

2001-06-12

Watts, Douglas D. (Department: 3724)

Cutlery

Cutting tools

Saw

C474S174000, C474S177000

Reexamination Certificate

active

06243956

ABSTRACT:

TECHNICAL FIELD
The invention relates to a drive wheel for off-centre drive of an annular saw blade in a cutting machine.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 4,472,880 describes a cutting machine with annular saw blade, which has an inner edge which is bevelled in a wedge-shaped manner, co-operating with a drive wheel inside the inner edge of the blade. The drive wheel consisted according to this patent of two halves which were pressed against each other in axial direction by a strong string. At the same time, the two halves of the drive wheel pressed the inner edge of the cutting blade between themselves, which gave a good grip but which also resulted in a hard wear. This design therefor was abandoned for an undivided drive wheel with a design disclosed in U.S. Pat. No. 4,793,065, FIG. 3. The grip between the inner edge of the saw blade and the drive wheel with its groove in this design is provided by the blade being pressed in a radial direction into a groove in the drive wheel. The wear thereby is reduced in comparison with the wear in the first embodiment according to U.S. Pat. No. 4,472,880 but is nevertheless substantial. Both the drive wheel and the saw blade are therefor to be considered as replacement parts which must be replaced when they have been worn out. The drive wheel in general certainly has a longer lifetime than the saw blade, but the costs for the exchange are nevertheless considerable. Nor is it beneficial from all parts of view that the saw blade and the drive wheel are replacement parts with substantially different lifetime, since this may increase the number of necessary replacement operations.
BRIEF DESCRIPTION OF THE INVENTION
The object of the invention is to address the above problem complex. This is accomplished by the drive wheel consisting of at least two annular components which are separable but held together during the operation, namely a holder disc and a drive ring, the latter having an encircling drive groove for the inner edge of the saw blade, and that the drive ring is arranged radially outside of a central portion of the holder disc. By this design, the drive ring can be made as a very simple machine element with a small mass, which in its turn opens up for possibilities to manufacture the drive ring of a comparatively plane construction material, preferably a plane structural steel, which suitably wears down at the same rate as the saw blade and is replaced at the same time as the saw blade, while the holder part—the holder disc—is made of a more high-grade constructional material. As an alternative, the drive ring is made of a still more high-grade constructional material than the holder disc, e.g. a high-grade high speed steel or cemented carbide material with very long lifetime and is in this case not to be considered as a replacement part in the normal sense of the word.
Additional characteristics and aspects of the invention appear from the claims and from the following detailed description of a preferred embodiment.


REFERENCES:
patent: 3186247 (1965-06-01), Burrell
patent: 3805661 (1974-04-01), Tuomaala
patent: 4472880 (1984-09-01), Johansson
patent: 4646607 (1987-03-01), Johansson
patent: 4793065 (1988-12-01), Johansson
patent: 4934238 (1990-06-01), Lauffer
patent: 5381723 (1995-01-01), Nilsson et al.
International Search Report for PCT/SE98/01099 dated Sep. 4, 1998.
PCT Application (PCTSE98/01099) Published by WIPO No. WO 98/58757, Dec. 30, 1998.
PCT Application (PCTAU93/00638) Published by WIPO No. WO 94/13964, Jun. 23, 1994.
International Preliminary Examination Report for PCT/SE98/01099 dated May 17, 1999.

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