Tools – Hammer – Having plural striking faces
Reexamination Certificate
2002-03-15
2004-03-09
Hail, III, Joseph J. (Department: 3723)
Tools
Hammer
Having plural striking faces
C081S020000, C081S025000, C254S018000, C254S019000, C125S023010, C125S041000
Reexamination Certificate
active
06701805
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to hand tools, and specifically concerns a hammer for shaping stone and masonry by manually striking the stone to break away material at the surface. Multiple working tool edges are provided by plates that are replaceably mounted, preferably on each of two opposite striking faces on the tool. Each plate can be re-oriented on the tool, for placing a fresh edge in a selected exposed position for use. Each plate also can be reversed for moving a fresh set of edges from a protected side to an exposed side of that plate.
BACKGROUND
Stone working hammers are used to trim natural stone, masonry, and the like (herein generally described as “stone”), for example to size pieces of stone or masonry so as to fit at a given place in a structure, or to normalise the size or shape of stones in a supply to be used for building or paving, etc. A stone working hammer for such a purpose generally comprises a striking head mounted on a handle, to be swung against the stone by the craftsman. At least the part that impacts the stone is advantageously made of a relatively durable material so that the tool has a reasonable service life, such as hardened steel.
For detail work, the striking head preferably has a sharply defined striking edge, thus concentrating the point of impact and permitting accurate cutting and trimming of the stone by controlled chipping away of material at selected edges. A striking edge that is sharply defined, however, is also inherently thin at its edge, and wears rapidly with repeated impact. The striking edge becomes rounded, and it is more difficult for the craftsman precisely to cut the stone because the force of the impact is less controllable and localised.
It will be appreciated that stone working hammers are thus unlike many familiar sorts of hammers and mallets, such as claw hammers for driving nails, ball peen hammers for metal working, etc., because the edge of the striking face of the stone working hammer is critical, not the mass of the hammer along its midline. When the striking edge of a stone hammer becomes rounded and worn, the head of the hammer must be replaced or sharpened by grinding away material down to a new discrete cutting edge.
There are disadvantages associated with sharpening stone hammers. Sharpening procedures may be relatively complex, costly and time consuming. The process is comparable to the steps needed to make a new tool from scratch. A stone hammer is typically sent to a blacksmith to be sharpened. The blacksmith heats the hammer to remove its hardening, and then reshapes the hammer to restore its sharp edges. It is often necessary to re-treat the hammer to harden its working surfaces, for example to nitride, or temper by heat treatment and quenching. A hammer needing sharpening could alternatively be sent to a machinist to grind or mill away material up to planes that meet at the cutting edge. However, the hammer will lose its hardening, thus limiting its usefulness as a stone working tool. Also, grinding the hammer removes steel, which limits the useful lifetime of the hammer.
While a worn hammer is being refurbished and sharpened, it is out of service. Given the limited number of blacksmiths in an area, it is conceivable that hammers can be out of service for several months. Thus the stock of hammers kept available must be large enough to account for some of the hammers being out of service at any given time for sharpening.
It is also conceivable that the majority of the hammers owned by a stone cutting operation can be out of service at any given time. The striking edge of a stone hammer can be worn to an extent that it needs sharpening after one full day's use. If the operation is such that it takes the machinist several days to sharpen and return worn stone hammers, then the inventory of stone hammers must be several times the number of users.
Stone cutting craftsmen tend to use their tools in a characteristic way. For example a right-handed cutter is likely to wear one edge of the cutting face of a hammer more than another edge, that a left-handed cutter might be more prone to use. Even given that fact, a relatively large investment in a working inventory of stone hammers may be needed. With regular use there is a constant workload on the machinists who refurbish the hammers. After a few sharpening operations the tool is reduced by the trimming operations associated with sharpening and must be replaced. There is a need to reduce or eliminate the associated expense and effort by stone cutting operations to keep an available stock of stone hammers with fresh edges to use for stone cutting and trimming.
SUMMARY OF THE INVENTION
The invention meets this need by providing quickly, easily, and inexpensively replaced striking plates whose tooling faces and mounting define selectively deployed polygonal straight edges. Preferably, for example, the striking plates have a rectilinear shape and are mounted in a symmetrical manner whereby the plates are removably attachable to a tool head base part at any selected 90 degree increment. Thus a fresh edge on one side of the plate can be moved readily into a given position on the tool for use in cutting. The striking plates are reversible. The number of polygonal edges is thereby doubled. Furthermore, the tool itself preferably has opposite faces, again doubling the number of available edges. As a result, in a rectilinear cutting plate arrangement, as many as sixteen fresh cutting edges can be worn before the tool requires service, and such service can be quickly and conveniently accomplished by replacing the striking plates rather than refurbishing the tool as a whole.
Thus according to the invention, a manual stone hammer is provided with at least one polygonal faceplate, and preferably two opposite faceplates, both being individually reversible and thereby providing selectively available striking edges in four times the number of faces of the polygon.
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Baum William E.
Souder Richard B.
Duane Morris LLP
Grant Alvin J.
Hail III Joseph J.
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