Abstract:
A string for musical instruments comprises a core including a gut material and a coating covering the core. The coating includes a material of a polyaryletherketon (PAEK) material class.

Description:
This is a U.S. National Phase Application under 35 U.S.C. §371 of International Application No. PCT/EP2007/008846, filed on Oct. 11, 2007, which claims priority to German Application No. DE 10 2006 053 406.9, filed on Nov. 10, 2006. The International Application was published in German on May 15, 2008 as WO 2008/055574 A2 under PCT 21 (2). 
     The invention relates to a string for musical instruments. 
     BACKGROUND 
     Strings for musical instruments are manufactured in a multitude of types, made of different materials and material compositions. The type of string is designed, in accordance with the specific application, for the tone range and the musical instrument in question. To fulfill the musical requirements, different materials can be used for the manufacture of a string. Musical strings of particularly high quality are made of gut. 
     Gut strings for musical instruments are usually made of the guts of hoofed animals, mostly of sheeps, and are used as a rule in plucked or bowed string instruments. However, the fact that the strings are stretched on the instrument under a certain tension and that they are hit, plucked or bowed when the instrument is played, results in high wear of the musical string. Therefore, nowadays, gut strings are usually manufactured in the form of so-called gut core strings, in which an inner, carrying area of the string, also called the core, consisting of gut, is provided with an external spinning made of poly plastic, such as nylon, or metal, such as aluminum and titanium. The external spinning can in particular be provided for giving the string sufficient mass, in order to generate also relatively deep tones. 
     In general, such strings based on gut possess good tonal properties. However, in the course of time, such strings show relatively great changes in tone, due to their water-absorbing capacity. Consequently, the string has to be re-tuned relatively frequently. Strings with a nylon-based coating have, furthermore, the disadvantage that the water-absorbing capacity of nylon (absorption of humidity of nylon: ˜3-4%) is also very high and, in addition, the expansion properties of nylon are poor. 
     The re-tensioning of the musical strings, in particular for tuning the musical instruments by tensioning the string, and the degree of wear through the bowing of the string may lead to the formation of fissures inside the string and possibly even to a rupture of the entire string. In addition, there are aging phenomena of the string material used. Therefore, for intensely used orchestra instruments, it may be necessary relatively frequently to exchange a string, to prevent a deterioration of the specific musical characteristics of the instrument, in particular the quality of tone and sound. In view of the possibly long playing-in times of the strings, it is, however, desirable to reduce the frequency of string exchanges. 
     SUMMARY OF THE INVENTION 
     Therefore, an aspect of the invention is to provide a musical string of the above-mentioned type, which possesses a relatively long expectancy of service life, in particular with good sound quality. 
     The present invention provides a string comprising a core and a coating covering it, made of a material of the polyaryletherketon (PAEK) material class. 
     The invention is based on the consideration that in view of the usually high stress of the strings, special measures should be taken to stabilize the strings, for a particularly long service life of the strings. For this purpose, it is provided, in order to strengthen the strings, to provide the core with a coating made of a specifically selected material. Such a material should, on the one hand, through its special molecular arrangement, be highly extensible and extremely stressable and possess a high tensile strength, but, on the other hand, still elastic in view of the requirements imposed on the string. Surprisingly, it has turned out that these material properties and technical-physical characteristics can be achieved to a particularly high degree with a material of the polyaryletherketon (PAEK) material class. 
     Polyetheretherketon, abbreviated PEEK, has turned out to be a particularly well suited material from the polyaryletherketon (PAEK) material class. The technical-physical characteristics of polyetheretherketon (PEEK) are very similar to those of gut, and, furthermore, PEEK possesses the musical and tonal properties required for a musical string. Both materials, polyetheretherketon (PEEK) as well as gut, have a density in the range of ρ=1.27 to 1.32 g/cm 3 . Due to these comparable properties, a particularly homogeneous sound pattern and a high compatibility are reached especially with a pairing of the materials polyetheretherketon (PEEK) and gut. In addition, contrary to other coating materials made of polymer plastics, polyetheretherketon (PEEK), having an absorption of humidity of only 0.1%, is far less sensitive to humidity. In other words, polyetheretherketon (PEEK) possesses a good water resistence. Especially when using PEEK in the coating for the core, the latter can also be protected to a certain extent against humidity, which is even more favorable for the durability of the string as a whole. Furthermore, a musical string coated with polyetheretherketon (PEEK) shows a higher tuning stability and, surprisingly, also a shorter playing-in time. 
     In particular in view of the intended application, it will be expedient if the coating material is adapted, through a suitable selection of the parameters, for example with regard to the dimensioning, to the specific musical, tonal or sound-technical requirements, as well as to the elongation resistence and the tensile strength to be fulfilled by the string. In this way, in particular a good musical tone, a simple handling while playing and, in addition, a particularly long service life can be achieved. For this purpose, the coating material is expediently manufactured as a fiber. This makes the handling of the coating material in the manufacturing process of the musical string relatively simple, and, in addition, the future total diameter, the mass and possibly also the pitch level of the string can be influenced by a suitable dimensioning of the fiber. 
     The fineness of fibers and yarns is a textile quantity indicated in the unit tex. The unit tex is expressed in SI units with the conversion factor of 1 tex=1 g/1000 m, so that the fineness of the fiber expresses a weight per length of the fiber to be manufactured. In other words, the unit tex describes a length-related mass of a fiber or a yarn. Advantageously, the fiber of the coating material has, for the above-mentioned reasons, a fineness, depending on the musical application, in a range of 20 dtex to 280 dtex. This range covers the intended musical application in view of the different pitch levels of the musical string and the application of the string with regard to its dimensioning in different instruments in a particularly favorable manner. 
     Furthermore, it is expedient to construct such a fiber with a number of 5 to 80 very fine threads per fiber. By selecting the number of threads from the above-mentioned range, a good adjustment of the fineness of the fiber is already given during the manufacturing process. Furthermore, the future tensile and elongation strength of the fiber can be adjusted by means of the type of twist of the threads in relation to the fiber. In this way, the fiber can be manufactured, as to its dimensioning, with the exact desired total diameter of the future finished musical string. 
     The coating of the core can be executed as a so-called spinning, in which the coating material is helically led, in the form of one or more helical ropes, around or along the core. 
     To further increase stability and durability of the musical string, the coating is, however, advantageously executed as a braiding, i.e. the coating material is led around the core in several ropes crossing each other. Such a braided structure also increases the tear strength of the musical string and reduces the formation of fissures. Furthermore, the coating executed as a braiding protects the core of the string in particular against excessive absorption of humidity, because it can be executed in a relatively dense manner. As such a braiding can cover the core of the string in one or more layers, it has also an influence on the dimensioning of the string. 
     As material of the core, common materials, such as metals or plastics, e.g. nylon, can generally be provided. Especially in view of the particularly good compatibility of the materials gut and polyetheretherketon (PEEK), however, gut is provided as the basic material of the core in a particularly advantageous embodiment. The value of the gut-core string is particularly increased especially through the coating and can, therefore, also be used for particularly high-quality applications, such as the stringing of plucked and bowed string instruments and even baroque instruments. Surprisingly, it has turned out that especially a string with such a material pairing offers clear advantages as compared with known strings, as far as playability and tuning stability are concerned, and, furthermore, possesses a particularly short playing-in time. 
     Expediently, the diameter of the core lies in the range of 0.15 mm to 5 mm, to cover the common tone ranges of high-quality plucked and bowed string instruments with a particularly good sound. 
     In another advantageous embodiment, the coating is additionally provided with an outer spinning, preferably made of plastic or metal, which covers the coating. For this purpose, a flat metal strip, wound firmly and helically around the coating, can be provided. Furthermore, such an outer spinning offers advantages in the processing of the musical string through cyclindrical fine grinding. The cylindrical precision-grinding may be necessary to obtain the truth in the fifth of the musical string. Furthermore, the outer spinning protects the string against premature fraying. 
     Advantageously, it is provided to use at least one string comprising a gut core and a coating made of polyetheretherketon (PEEK) in musical instruments belonging to the family of bowed or plucked string instruments. 
     The advantages achieved with the invention consist in particular in that the gut-core string coated with polyetheretherketon (PEEK) fiber possesses a particularly long service life and, at the same time, a good sound quality. Thus, it is possible to make use in a particularly favorable way of the favorable properties of polyetheretherketon (PEEK), in particular of the relatively high humidity resistence and the density range of the material, which is comparable to that of gut. In addition, the polyetheretherketon (PEEK) coating protects the gut core against excessive absorption of humidity. Furthermore, it has turned out that the so-called playing-in time of the string can clearly be reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An exemplary embodiment of the invention is explained in detail by means of a drawing, in which 
         FIG. 1  is a schematic view of a classical violin, 
         FIG. 2  shows a musical string for a violin with the bridge, the upper nut and a tuning peg being indicated, 
         FIG. 3  is a cross-section of the musical string shown in  FIG. 2 , and 
         FIG. 4  shows the chemical structure of a polyetheretherketon monomer unit. 
     
    
    
     Identical parts are marked with the same reference numbers in all figures. 
     DETAILED DESCRIPTION 
     A classical violin  1  according to  FIG. 1  comprises four strings  2  stretched over a resonance body  4 . At a first end, the tailpiece end  6 , the strings  2  are fastened on a tailpiece  8 , whereas at their second end, the tuning-peg end  10 , they are fastened on tuning pegs  12  of a tuning mechanics, the so-called pegbox  14 . For this purpose, the tuning pegs  12  include a hole through which the tuning-peg end  10  of the string  2  is passed. The area adjacent to the tuning-peg end  10  is wound several times around the peg  12 . The pegs  12  can be turned by means of their peg handle plates  16 , whereby the tension of the string and thus the tone of the string  2  can be changed. 
     On the tailpiece end  6 , the string  2  is provided with an end head  18 , which is fastened in the tailpiece  8 . Furthermore, an adjuster  20  is fastened on the tailpiece  8 , with the help of which the tension of each string  2  is precision-adjusted. The adjuster  20  helps the musician in tuning the tone of the string  2  even more precisely than this is possible by means of the tuning pegs  12 . 
     A mounting section  22  of the string  2  is situated between the tailpiece  8  and a bridge  24  and is partially spun over, from the end head  18  in the area of the tailpiece end  6 , with colored yarn. The colored yarn serves for indicating the quality of the string. The tuning-peg end  10  of the string  2 , which is wound around the peg  12 , is also spun over with colored yarn, which informs the musician of the exact tone range of the string. 
     The area between the bridge  24  and a fingerboard  26  is the playing area  28 , in which the musician plucks or bows the strings  2 . For playing the violin  1 , the musician plays the tones on the strings  2  along the fingerboard  26  and bows the strings  2  in the playing area  28 . 
     On the other end of the fingerboard  26 , an upper nut  30  is provided, over which the strings  2  are led to the tuning pegs  12  in the pegbox  14 . The end piece of the pegbox  14 , and thus also of the violin  1 , is formed by a scroll  32 . 
     In a soundboard  34  of the resonance body  4 , the two f-holes  36  of the violin  1  are formed laterally at the level of the bridge  24 . The f-holes  36  serve for unhampered movement of the air contained in the resonance body, and, furthermore, the vibration capacity of the soundboard  34  in the acoustic center around the bridge feet  38  is considerably increased. 
     The outer structure of the string  2  is explained in detail by means of  FIG. 2 . This figure shows the end button  18  with the mounting section  22 , partially spun over with colored yarn and forming the tailpiece end  6 , and the string body  40 , which is in most cases polished, with the adjacent tuning-peg end  10  of the string, which is also spun over with colored yarn. In a perspective view, the bridge  24  and the upper nut  30  are indicated. The string body  40 , in most cases polished, is a sound-generating section  42 , forming the playing area  28  and the area of the string  2  above the fingerboard  26  up to the upper nut  30 . 
     The cross-sectional representation of  FIG. 3  shows the inner structure of the string  2 . The string  2  is executed with a core  44 , a coating  46  and an outer spinning  48 . The coating  46  made of polyetheretherketon (PEEK) fiber is executed as a braiding. The outer spinning  48  consists of a flat metal strip, which is spun firmly and helically around the coating  46  and is in most cases ground, depending on the application. 
     The core  44  of the string  2  consists of gut which, after having been processed into the core  44 , shows a kind of monofil structure. 
     The coating  46  of the string  2  is made of polyetheretherketon (PEEK) fiber  50 , the fiber  50  consisting of individual threads with a thread number of 5 to 80 and having a fineness in the range of 20 dtex to 280 dtex. Furthermore, the fibers  50  are interlaced to form a braided structure, the so-called braiding, in order to give the coating  46  a higher stressability and tear strength. In additon, such a braided structure prevents a premature fraying of the string  2  as well as a premature formation of fissures within the coating  46 . 
     Furthermore, the string  2 , consisting of the core  44 , the outer spinning  48  and the coating  46 , which includes a braiding made of polyetheretherketon (PEEK) fiber, has a longer service life. Furthermore, due to its good elongation resistence and tensile strength, such a string  2  is better to play and simple to handle. 
     The violin  1  is designed, among others, for a particularly long service life and a high musical quality of the string  2  used. For this purpose, some or all strings  2  are manufactured from a gut core and a coating of polyetheretherketon (PEEK) fiber, which, through a suitable selection of the parameters, for example composition and thread thickness, is adapted to the specific requirements of the string  2  in question. 
     The tailpiece  8  is fastened at its end area  52  via a so-called tailgut under prestress on a holding button. For this tailgut, too, polyetheretherketon (PEEK) can be provided as the coating material. 
     The chemical structure of a polyetheretherketon (PEEK) monomer unit  58  is shown in  FIG. 4 . The polyetheretherketon (PEEK) polymer has a long-chain structure made of a repetitive number n of monomer units  54 . The monomer unit  54  is made up of phenyl rests  60  linked through keto bridges  56  and ether bridges  58 . Each monomer unit  58  contains one keto bridge  56 , two ether bridges  58 , and three phenyl rests  60 . The monomer units  54  are polymerized in the polyetheretherketon (PEEK) polymer exclusively through the keto bridge  56  of one monomer unit  54  with a phenyl rest  60  of another monomer unit  54 . The material purity of the polyetheretherketon (PEEK) polymer is subject to the known chemico-technical purity requirements of polymer manufacture. 
       FIGS. 1 to 3  represent the gut-core string with polyetheretherketon (PEEK) fiber coating and outer metal spinning as a musical string by means of the example of a string  2  in the violin  1 . Of course, the invention also covers the use of such a gut-core string with polyetheretherketon (PEEK) fiber coating in any other string instrument, in particular bowed and plucked string instruments, as well as the execution of the core  44  as a multifilament structure and with other core materials. 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 List of reference numbers 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 Violin 
               
               
                 2 
                 String 
               
               
                 4 
                 Resonance body 
               
               
                 6 
                 Tailpiece end  
               
               
                 8 
                 Tailpiece 
               
               
                 10 
                 Tuning-peg end 
               
               
                 12 
                 Tuning peg 
               
               
                 14 
                 Pegbox 
               
               
                 16 
                 Peg handle plate 
               
               
                 18 
                 End head 
               
               
                 20 
                 Adjuster 
               
               
                 22 
                 Mounting section 
               
               
                 24 
                 Bridge 
               
               
                 26 
                 Fingerboard 
               
               
                 28 
                 Playing area 
               
               
                 30 
                 Upper nut 
               
               
                 32 
                 Scroll 
               
               
                 34 
                 Soundboard 
               
               
                 36 
                 f-hole 
               
               
                 38 
                 Bridge feet 
               
               
                 40 
                 String body 
               
               
                 42 
                 Sound-generating section 
               
               
                 44 
                 Core 
               
               
                 46 
                 Coating 
               
               
                 48 
                 Outer spinning 
               
               
                 50 
                 Fiber 
               
               
                 52 
                 End area 
               
               
                 54 
                 Monomer unit 
               
               
                 56 
                 Keto bridge 
               
               
                 58 
                 Ether bridge 
               
               
                 60 
                 Phenyl rest 
               
               
                 n 
                 Number of monomer units in the polymer