Electric heating – Metal heating – By arc
Reexamination Certificate
2000-12-22
2001-10-30
Heinrich, Samuel M. (Department: 1725)
Electric heating
Metal heating
By arc
C219S121640, C228S231000, C228S232000
Reexamination Certificate
active
06310314
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a procedure for fastening a carbide tooth at a saw blade, with the carbide tooth fabricated according to the saw tooth geometry being held butt-jointed to the prepared front-side abutting surface of the saw blade and then being attached to the saw blade under addition of heat along the joint between the saw blade and the carbide tooth.
1. Description of the Prior Art
To be able, for instance, when cutting wooden lamellas, to keep the wood losses due to machining as small as possible and thus to better exploit the wooden material, cutting gaps as thin as possible are desired, which demands accordingly thin saw blades. However, with such thin saw blades the advantages of resharpenable carbide teeth cannot be utilized, as by fastening carbide teeth at the saw blade via hard-soldering as usual the required strength for cutting in an inhomogeneous wooden material without teeth breaking off cannot be achieved. Although it is known to fix spherical or cylinder-shaped carbide blanks to the tooth tips of saw blades by means of resistance welding, these carbide blanks in fact require complicated finishing by grinding to obtain the desired tooth geometry. As the carbide blanks have to be pressed tightly against the abutting surfaces of the saw blades during resistance welding, an exact positioning of the carbide blanks relative to the saw tooth is impossible due to material melting open in the joint area, which, on the one hand, demands spherical or cylinder-shaped carbide blanks, and, on the other hand, excludes the use of carbide teeth that have already been fabricated according the later tooth geometry before being welded on. To be able to keep the grinding work for finishing the welded-on carbide blanks comparatively low, only the tips of the teeth are made of carbide, so that resharpening such saws with welded-on saw tooth tips made of carbide is hardly possible.
SUMMARY OF THE INVENTION
The invention has therefore the objective to provide a procedure for fastening a carbide tooth at a saw blade in the above mentioned kind, to establish a sufficiently fast connection between the saw blade and the carbide tooth, that is with the carbide tooth being position ed sufficiently accurate to permit the use of carbide teeth fabricated according to the saw tooth geometry, thus making complicated finishing unnecessary.
The objective of the invention is achieved in that the carbide tooth is welded to the saw blade by means of a focal spot of a laser beam extending over the whole joint length.
By the application of a sufficiently powerful laser beam the carbide tooth need not be pressed against the related abutting surface of the saw blade during welding, so that the carbide tooth can be fabricated according to the saw to both geometry before welding and can be exactly attached to the saw blade in a defined position. The welding process is performed simply, as, due to the specific shape of the focal spot of the laser beam, the carbide tooth is welded to the saw blade at the same over the whole joint length, which leads to a largely regular heat load of the carbide tooth and the saw blade with the effect that a sufficiently fast connection between the carbide tooth and the saw blade at a very low risk of fissures is established, that is at a comparatively low welding expenditure, as the laser beam does not require any displacement toward the joint between the carbide tooth and the saw blade. Thus, conditions are achieved that can be compared to those of spot welding, with the welding area, however, not being restricted locally to a section of the joint, but extending over the whole joint length. The desired shape of the focal spot, which is essentially lenticular, can, at a given cross section of the laser beam, be ensured without difficulties via an appropriate optical system.
As the whole welding area for a carbide tooth is covered by the accordingly shaped focal spot of the laser beam, the saw blade and the carbide tooth, in another embodiment of the invention, can be preheated prior to welding in the area of the joint by means of the laser beam proper at a reduced output, so that the risk of fissures is further reduced.
To reduce thermal stress, it is common practice for welding to subject the weld joint to a secondary thermal treatment. For this purpose the welding area between the saw blade and the carbide to both may be reannealed after welding by means of the laser beam, too, at reduced output, so that, for completion of the saw, the welded-on carbide teeth need only be resharpened by grinding.
REFERENCES:
patent: 4337750 (1982-07-01), Dutcher
patent: 4488882 (1984-12-01), Dausinger et al.
patent: 34 34 714 (1986-04-01), None
patent: 195 01 442 (1996-07-01), None
patent: 09201720 (1996-01-01), None
Liedl Gerhard
Nöbauer Franz
Collard & Roe P.C.
Heinrich Samuel M.
Wintersteiger GmbH
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