Plastic and nonmetallic article shaping or treating: processes – Outside of mold sintering or vitrifying of shaped inorganic... – Including specified molding pressure or controlling of...
Reexamination Certificate
2001-03-26
2003-08-12
Derrington, James (Department: 1731)
Plastic and nonmetallic article shaping or treating: processes
Outside of mold sintering or vitrifying of shaped inorganic...
Including specified molding pressure or controlling of...
C264S678000, C264S681000, C083S820000
Reexamination Certificate
active
06605249
ABSTRACT:
FIELD OF THE INVENTION
The following invention relates to guide blocks for use in supporting saw blades and particularly band saw blades to prevent undesirable lateral motion of the saw blade. More specifically, this invention relates to methods for manufacturing saw blade guide blocks out of ceramic materials for replacements of non-ceramic saw blade guide blocks.
BACKGROUND OF THE INVENTION
Band saws and other related saws have an elongate blade with teeth on at least one edge and with lateral sides spaced apart by a thickness of the blade. The band saw moves in the direction in which the elongate blade extends so that the teeth on the edge of the blade can impact material being cut and form a cut in the material. The blade must be thin so that the cut can be thin and still not bind against the saw. The blade's thinness makes the blade susceptible to bending out of position laterally. To prevent such bending of the blade, guide blocks are provided adjacent to each of the lateral surfaces of the blade. These guide blocks abut directly against the lateral surfaces of the blade and keep the blade precisely aligned in the desired position.
Because the guide blocks are stationary and the blade is moving, the guide blocks typically experience a great amount of wear. While the guide blocks can be tightened so that they can continue to perform even after wearing somewhat, the guide blocks must eventually be replaced.
Guide blocks benefit from having high strength as well as low friction surfaces. Additionally, guide blocks benefit from experiencing minimal distortion when heated by the friction associated with abutting against the moving blade and benefit from resistance to heat related breakdown.
While ceramic materials have desireable strength, friction and thermal expansion/thermal strength characteristics, ceramics have not been utilized as guide blocks for a variety of reasons. First, ceramic materials in their hardened state are extremely difficult to machine. While they can be ground somewhat, grinding of such guide blocks is time consuming and expensive. Additionally, the hardness of the ceramics makes them susceptible to fracture during the grinding procedure. While ceramics can be formed to the desired size, such forming techniques are difficult because of the drastic dimensional changes which ceramics undergo when they are fired and transformed from an initial easily machined state to a final hardened state.
Accordingly, a need exists for a method of manufacturing guide blocks from ceramic materials which can simply and reliably form hardened ceramic materials in the precise shape necessary to function as guide blocks within a band saw or other saw blade supporting environment.
SUMMARY OF THE INVENTION
The following steps are typically involved in forming a saw blade guide block from ceramic materials according to this invention. Initially, a non-ceramic guide block to be replaced is identified. This prior guide block has a geometry, including a size and shape, which are to be precisely matched by this ceramic guide block replacement so that the ceramic guide block can fit within the guide block support structure provided by the band saw or other machine for supporting the prior guide block being replaced. A ceramic powder is selected and compressed into a billet having dimensions which are oversized relative to the geometry of the prior guide block being replaced. The ceramic powder is preferably compressed sufficiently so that it binds together into a solid mass which has not yet been fired and so does not have its final hardness, but which does have sufficient structural cohesiveness to allow it to be machined utilizing typical machining techniques such as shaping by a milling machine.
The billet of ceramic material is then milled to a shape which is similar to that of the prior guide block but with a size that is larger than the prior guide block being replaced. Specifically, the dimensions of the billet after machining must be oversized an amount precisely equal to an amount of shrinkage experienced by the ceramic material when fired into its final hardened form.
The oversized properly shaped billet of ceramic material is then heated such as at a temperature of at least 1500° F. and for a sufficient time so that the ceramic material can be completely fused together into a solid hardened mass of the ceramic material. When the billet is returned to room temperature, it shrinks down to the dimensions matching that of the prior guide block being replaced. A ceramic guide block is thus provided which can replace the prior guide block within the machine in which the prior guide block was configured for use.
OBJECTS OF THE INVENTION
Accordingly, a primary object of the present invention is to provide a guide block for totaling supporting a blade within a machine.
Another object of the present invention is to provide a method for manufacturing a saw blade guide block from ceramic material.
Another object of the present invention is to provide a ceramic guide block which can replace a non-ceramic guide block in a saw.
Another object of the present invention is to provide a method for manufacturing a ceramic guide block which does not require grinding other machining procedures on the hardened ceramic material and otherwise is easy to perform.
Another object of the present invention is to provide ceramic guide blocks which last longer than non-ceramic guide blocks.
Another object of the present invention is to provide a method for forming a ceramic material into a guide block of appropriate size to replace a prior non-ceramic guide block of known dimensions.
Another object of the present invention is to provide a guide block with high strength, high hardness, low thermal distortion and low friction surfaces, such that the guide block has good performance and long life.
In addition to the above objects, various other objects of this invention will be apparent from a careful reading of this specification including the detailed description contained herein below.
REFERENCES:
patent: 2525324 (1950-10-01), Twells
patent: 4665617 (1987-05-01), Maier
patent: 4848200 (1989-07-01), McGehee
patent: 5286323 (1994-02-01), Bagley
patent: 5490854 (1996-02-01), Fisher
patent: 5730928 (1998-03-01), Ghosh et al.
patent: 1289040 (1991-09-01), None
patent: 2 232 411 (1990-12-01), None
Hyatt Clifford D.
Osa Nicholas
Derrington James
Heisler & Associates
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