Metal fusion bonding – Process – Encasing a rodlike core within a substantially coextensive...
Reexamination Certificate
2000-01-24
2001-06-26
Shaw, Clifford C. (Department: 1725)
Metal fusion bonding
Process
Encasing a rodlike core within a substantially coextensive...
C228S125000, C228S174000
Reexamination Certificate
active
06250535
ABSTRACT:
The present invention relates to an improved method for brazing tubular parts in coaxial relationship with the bore of another part where one end of the tubular part nests with respect to the end of a second part.
BACKGROUND OF THE INVENTION
Where a cylindrical member rotates within a complementary cylindrical bore, the useful life of the parts can be extended by providing a counter sink at one of the bore into which is inserted a tubular, hardened wear ring. For example, machines used to cut hard surfaces such as concrete and asphalt have a rotatable cutting wheel with a plurality of cutting tools mounted on the wheel which are moved against a hard surface to advance the cut. Each of the cutting tools has a cylindrical shank which is rotatably mounted in a complementary cylindrical aperture in a mounting block. As disclosed in my co-pending application, Ser. No. 09/121,726 filed Jul. 24, 1998, the useful life of a tool and the mounting block can be extended by providing a tungsten carbide tubular insert at the forward end of the aperture in the mounting block or holder.
It is customary to use a braze to retain parts, such as a tubular insert fitted in a countersink at the end of a cylindrical aperture. The brazing process consists of providing a ring of braze material which is fitted between the inner surface of the countersink and the outer surface of tubular sleeve. The ring of braze material prevents the hardened ring from becoming seated within the countersink until the braze material is heated and melts, after which the ring can be forced into the countersink until it has become seated. After the parts cool, a substantial portion of the braze material should remain between the inner surface of the countersink and the outer surface of the insert to retain the parts in the assembled relationship. I have found, however, that when the braze material melts and a tubular insert is forced into a countersink most of the liquefied braze material flows into the cylindrical bore leaving an insufficient amount of braze material to retain the parts in the assembled relationship. When a tungsten carbide insert is brazed into a countersink around the bore of a tool block, as described above, it has been found that the braze will fail when the tool is subjected to the forces required to cut hard material such as concrete or asphalt.
An improved method is therefore needed for brazing of tubular parts in nested relationship in which a greater portion of braze material would be retained between the parts.
SUMMARY OF THE INVENTION
Briefly, the present invention is embodied in a method of assembling a tubular part in coaxial relationship with the bore of another part where the end of the tubular part nests with respect to the second part. For the purposes of this discussion, two parts are considered to be nest when the end of a first part is complimentary in shape to the end of a second part such that the outer surface of the first part will fit in near proximity to the complementary surface of the second part with the spacing between the surfaces being sufficient for retaining a brazing material. A tubular sleeve having an outer diameter sized to slide within a countersink surrounding the end of a cylindrical bore is an example of parts which can be assembled in nested relationship.
In accordance with the present invention, to braze a tubular part in nested relationship to a second part having a coaxial bore therein, a ring of braze material is provided where the ring has an inner diameter at least equal to the inner diameter of the tubular part, and an outer diameter which is no greater than the outer diameter of the tubular part. The parts are arranged in coaxial relationship with the ring of braze material and a viscous flux positioned between the complementarily shaped surfaces.
A tubular sleeve made of a soft metal material having an outer diameter which is a little larger than the inner diameter of the cylindrical bore is thereafter press fitted into the bore of both the block or holder and slip fitted into the bore of the insert. The assembled parts are thereafter heated, causing the braze material to melt, after which the parts are moved into nested relationship. As the parts are moved into nested relationship, the braze material is retained between the parts by the tubular sleeve fitting into the coaxial tubular bores of the parts.
When the parts are thereafter cooled, causing the braze material to harden, the parts will be retained in the assembled relationship. Thereafter, the soft metal of the tubular sleeve can be removed in a machining process. Following the removal of the tubular sleeve, the parts will be retained together by the braze remaining between them.
In a second embodiment of the invention, a body part can be made having a bore therein and a tubular member brazed into a countersink around one end of the bore. In this embodiment a body part blank for which the bore has not been made therein is provided with an annular recess in the surface thereof. The recess has an outer surface complimentary in shape to the outer surface of the tubular member and the inner surface of the recess forms a cylindrical stub having a diameter slightly less than the inner diameter of the bore of the completed body part. An annular piece of braze material is placed in the recess and the tubular member is positioned over the braze material, and the parts are heated to melt the braze material. After the parts cool the tubular member will be brazed into the countersink. Thereafter the cylindrical stub can be drilled and bored out to form the bore of the body part after which the tubular member will be in a countersink surrounding the bore.
REFERENCES:
patent: 3555964 (1971-01-01), Fleming
patent: 5076484 (1991-12-01), Ito et al.
patent: 5098233 (1992-03-01), Patterson et al.
Johnson Jonathan
Marsh Robert L.
Shaw Clifford C.
The Sollami Company
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