Music – Instruments – Stringed
Patent
1984-08-31
1988-07-05
Fuller, Benjamin R.
Music
Instruments
Stringed
G10D 102
Patent
active
047546816
DESCRIPTION:
BRIEF SUMMARY
For some years, professionals in the stringed instrument industry have been wondering about the scarcity, the quality and the prices of the woods used in the constitution of musical stringed instruments.
Concerning bows requiring hard woods with high mechanical performance, such as PERNAMBOUC, imported from Brazil, the problems of supply are raised in the same manner. The considerable increase, during recent decades, in consumption for building and furniture necessitate fellings made increasingly towards the hotter and more humid heart of the forest. This results in species of trees which have increasingly slack fibrous structures, which gives the objects reduced mechanical characteristics.
Furthermore, exporters faced with this situation, conscious of the perspectives of shortage (the cycles of regeneration of these species of trees last centuries), tend to raise their prices and institute more and more rigid supply regulations, particularly concerning the freedom of choice of the batches.
This situation therefore incites a search for satisfactory solutions of replacement, in order to protect this branch of art.
Thus, the new composite materials with high mechanical performance (high modulus of elasticity and high resistance for a low density) such as the carbon fibers recently marketed, are the only ones to be able to provide a solution, as we have been able to check by making prototypes in accordance with the process described hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1--shows open mould half-shells used in preparing the present invention,
FIG. 2--shows a cross-sectional view of the present invention.
FIG. 3--shows a graph of force verses deflection showing the characteristics of the present invention,
FIG. 4--shows an apparatus used in preparing the bundles used in the present invention, and
FIG. 5--shows an apparatus used in testing the present invention.
This process, which we propose to develop, is dependant on the technique of moulding by mould in symmetrical half-shells with respect to the plane of symmetry of a conventional model stick (FIG. 1) and on that of "draping" or "stratification" of the unidirectional filamentary materials coated with resin polymerizing at ambient temperature.
It consists, more precisely (FIG. 2), in disposing, longitudinally, bundles 201 of roves of carbon fibers, previously impregnated with a pigmented resin, in the two half-cavities of the moulds 101, 102.
These half-shell moulds 101, 102 are provided with two centering studs ensuring perfect position of the two elements at the moment of assembly thereof by gluing or overmoulding. Moreover, they are provided with "cores" ensuring reproduction of all the functional recesses of the conventional bow stick (FIGS. 1 and 2), namely: cores 105, 105)
These moulds may either be metallic with the cavity engraved thereinto or made much more economically with the aid of a wooden frame filled with a silicon resin which will ensure direct overmoulding of the model stick.
The number and the different lengths of the roves of carbon constituting the bundles 201 on which the mechanical properties of the stick finally depend are defined by the calculation which takes into account the characteristics of the fiber (density, section, modulus of elasticity), those of the resin (density, modulus of elasticity) and of the rigidity which it is desired to give the stick.
The mathematical expression giving the number N of roves as a function of the section D (variable along the stick) is for a half-impression: ##EQU1## where E.sub.F is the modulus of the carbon fiber
The system of resin intended for coating the carbon fibers has been chosen as a function of the following criteria: view of wettability, deformations after firing),
The system retained is of the "supple epoxide resin" type polymerizing "cold" which gives it the expected properties, i.e.:
A violincello bow stick has been made in accordance with the present process by way of demonstration.
Its definition has been established from the characteristics of weight and of elast
REFERENCES:
patent: 2693107 (1954-11-01), Paden
patent: 3304770 (1967-11-01), Dixon
patent: 3308706 (1967-03-01), Brilhart
patent: 3440918 (1969-04-01), Wurlitzer
patent: 4015501 (1977-04-01), Schaller
PCT International Application No. PCT/CH82/00034 dated Mar. 4, 1982, (WO82/03274 Sep. 30, 1982).
"Making Better Musical Instruments from Graphite Composites" from Mechanical Engineering, Mar. 1976.
Cayuela Joseph
Maigret Jean-Pierre
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