Abstract:
A bow equipped with an improvement enabling adjustment of its rigidity. According to the invention, a longitudinal recess is made in the stick of the bow and this recess encloses a core stiffener linked to a screw-nut system (26-27) actuated by a knob (32). The stick can, for instance, be of molded synthetic material.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a bow for stringed musical instrument and particularly concerns an improvement to the stick of this bow, enabling adjustment of the stiffness thereof. 
     2. Description of the Related Art 
     A classical bow is composed of a curved stick with a widened hatched-shaped head and equipped at the other end with an adjustable frog. A horsehair ribbon is stretched between the head and the frog using a screw and nut system. Conventionally, the stick is cut from a fairly rare hard and resistant brazilwood, Pernambuco. More recently, it was proposed to make this stick of a synthetic material, usually composite such as a carbon-fibre based or similar material. 
     The qualities of a bow depend essentially on the characteristics of the stick, such as its curve and its greater or lesser rigidity. In fact, one same bow may be considered satisfactory by one instrumental performer yet disliked by another. Indeed, the best instrumentalists consider it necessary to change the bow to suit the musical work being performed, or merely their sensitivity of the moment. This therefore causes them to possess several bows. Yet, good bows are expensive. 
     Also, bows in a synthetic material, if reproducible on an industrial scale, are too similar in characteristics from one model to another to satisfy all instrumentalists. Indeed, one cannot conceive of an ideal bow to suit all instrumentalists, precisely because of the varied, and sometimes even contradictory, demands of these latter. Such variety, which can be obtained by a skilled craftsman making each bow individually, raises difficulties for manufacture on an industrial scale. 
     SUMMARY OF THE INVENTION 
     Among its other qualities, the invention provides a solution for these problems by proposing a bow structure which enables varying the mechanical characteristics of the stick. In particular, it enables an adjustment of the rigidity of any bow equipped with this improvement. 
     In this spirit, the invention essentially concerns a bow comprising a curved stick, and a first screw-nut system for horsehair tension. The screw is actuated by a first knob situated at the end of the stick and the nut. It includes a longitudinal recess extending substantially up to its head, a core stiffener being lodged in this recess and linked to a second screw-nut system coaxial to the first. 
     The term core stiffener refers to any rod or thread suitable to be tensioned or, on the contrary, axially compressed by the screw-nut system inside the longitudinal recess, in order to significantly modify the rigidity of the stick. 
     This improvement therefore enables an instrumentalist to adapt the bow to his style of playing or his repertoire. 
     The invention is particularly well suited for a bow including a stick of a synthetic material of the type mentioned above, a bow adaptable to the instrumentalist&#39;s wishes since it enables, from a reproducible stick structure with precise characteristics. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A better understanding and clearer view of the other advantages of the invention can be obtained from the following description, given solely as an example and in reference to the appended drawings, in which: 
     FIG. 1 is partial longitudinal section, partially cut away of a bow complying with the invention; 
     FIG. 2 is a partial cross-section on a larger scale of the handle of the bow shown in FIG. 1; and 
     FIG. 3 is a detailed cross-section illustrating an alternative. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 and 2 in particular, we show a bow 10 comprising a curved stick 11 of conventional appearance, and a horsehair hank 12 stretched between the head 13 and a frog 14 whose position is adjustable along a handle 15 of the said stick. This rectilinear handle is octagonal in cross-section and serves to guide the frog 14, which for this purpose has a groove open on three longitudinal facets espousing the shape of the lateral surface of the handle. The frog 14 comprises a nut 16 lodged in a mortise 17 cut out in the frog. This latter is in addition drilled with an axial hole 18 opening to extremity 19 near to where a first knob 20 incorporating a screw 21 is located. This latter is inserted in the hole 18 and the mortise 17 and fits into the nut 16. This first screw-nut system (21-16) enables the position of frog 14 and consequently the tension of the hairs to be adjusted. 
     The design as described hereabove is that of any conventional bow. 
     According to the invention, the stick 11 is hollow and comprises a longitudinal recess 24 extending along virtually its entire length up to the region of the head 13. This groove contains a core stiffener 25, this latter being linked to a second screw-nut system (26-27) coaxial to the first. This second screw-nut system is provided in order to subject the core stiffener to tensile or compressive stress, depending on the chosen assembly. Depending on the stress exerted on the core stiffener, it is possible to modify and adjust the rigidity of the stick. 
     As shown in FIG. 2, the nut 27 of the second screw-nut system is lodged in a cavity 29 near to the said mortise. In addition, the screw 21 of the first screw-nut system is tubular (it has a hole 31a drilled along its axis) and is traversed longitudinally by the screw 26 of the second screw-nut system. The nut 27 is of cap nut type and is fixed to core stiffener 25. The cavity 29 and the mortise 17 communicate via axial hole 30 to enable the passage of screw 26. This latter also extends through an axially drilled hole 31b of the knob 20 extending the hole of screw 21, and is fixed to a second knob 32. In the example described in reference to FIGS. 1 and 2, the second screw-nut is clearly designed to exert tensile stress on the core stiffener 25. In this case, this latter must be anchored near to head 13, by a widening 25a. It can be of synthetic (nylon or other) material or in metal. Of the example shown, the two knobs 20 and 32 are separated by a spacer 34 in an antifriction material such as polytetrafluorethylene, for instance. A recess 24 enclosing the core stiffener is advantageously filled with silicone grease or a similar substance or material to enable easy sliding of the core. 
     As mentioned earlier, the stick 11 can be of a moulded synthetic material, which greatly facilitates manufacture. 
     In the embodiment shown in FIG. 3, the second screw-nut system (26a-27a) is designed to exert compression on the core stiffener 25. In this case, this latter is of metal. The screw 26a here consists of a threaded portion of the corresponding end of the core, whereas the nut 27a is a segment with a blind hole threaded on the inside. This segment rests against an internal abutment 36 of the stick, here an axial end wall of the cavity 29. The nut 27a, in this instance, comprises a so-called hexagonal hole 38 to manipulate the screw-nut system using a hexagonal key 39, this latter being inserted via tubular screw 21 and knob 20 of the first screw-nut system.