Abstract:
Crown assemblies are described, having novel extension units, selectable vibrational lengths, stoppers with flexible coupling to the crown and regulated pressure against a headjoint tube, and crowns with radial-arm contact surfaces. The novel extension units are situated between the embouchure and the crown and extend the vibrational length between those points. This extension gives the flute tone greater depth and resonance and gives the player greater control over the vibration of the flute tube. A selectable extension unit features distinct vibrational lengths at indexed points of rotation of the crown, providing a means for rapidly changing the tone and response of the instrument in a fashion heretofore unknown on flutes. Improvements to crown and stopper design allow freer vibration of the headjoint tube between embouchure and crown, further enhancing the benefits of the novel extension unit.

Description:
BACKGROUND 
     Prior Art 
     The following is a tabulation of some prior art that presently appears relevant: 
     U.S. Patents 
     
       
         
               
               
               
               
             
           
               
                   
               
               
                 Pat. No. 
                 Kind Code 
                 Issue Date 
                 Patentee 
               
               
                   
               
             
             
               
                   444,830 
                 B1 
                 Jan. 20, 1891 
                 Guenther 
               
               
                   734,438 
                 B1 
                 Jul. 21, 1903 
                 Skinner 
               
               
                   859,714 
                 B1 
                 Jul. 9, 1907 
                 Wurlitzer 
               
               
                   920,471 
                 B1 
                 May 4, 1909 
                 Jenner 
               
               
                 1,013,037 
                 B1 
                 Dec. 26, 1911 
                 Melfi 
               
               
                 1,376,004 
                 B1 
                 Apr. 26, 1921 
                 Christensen 
               
               
                 2,805,291 
                 B1 
                 Sep. 3, 1957 
                 Eickhorst 
               
               
                 3,098,130 
                 B1 
                 Jul. 16, 1963 
                 Clavel 
               
               
                 3,487,742 
                 B1 
                 Jan. 6, 1970 
                 Mills 
               
               
                 3,763,737 
                 B1 
                 Oct. 9, 1973 
                 Sandner 
               
               
                 4,058,046 
                 B1 
                 Nov. 15, 1977  
                 Fajardo 
               
               
                 4,240,320 
                 B1 
                 Dec. 23, 1980 
                 Pellerite 
               
               
                 4,499,810 
                 B1 
                 Feb. 19, 1985  
                 Ferron 
               
               
                   
               
             
          
         
       
     
     Foreign Patent Documents 
     
       
         
               
               
               
               
               
             
           
               
                   
               
               
                 Foreign  
                 Cntry  
                 Kind  
                   
                   
               
               
                 Doc. Nr. 
                 Code 
                 Code 
                 Pub. Date 
                 App. or Patentee 
               
               
                   
               
             
             
               
                 6338 (1832) 
                 UK 
                   
                 Nov. 27, 1832 
                 Rudall and Rose 
               
               
                 2563 (1895) 
                 UK 
                   
                 Dec. 7, 1895  
                 Lillicrap 
               
               
                 369459 
                 FR 
                   
                 Jan. 12, 1907 
                 Couesnon et Cie 
               
               
                 WO 01/80217 
                 WO 
                 A1 
                 Oct. 25, 2001 
                 Dong 
               
               
                 WO 2005/022507 
                 WO 
                 A1 
                 Mar. 10, 2005 
                 Wilhelmus 
               
               
                   
               
             
          
         
       
     
     Nonpatent Literature Documents 
     
         
         Rockstro, Richard,  The Flute , Rudall, Carte and Co., London 1890, second revised edn. 1928, reprinted by Musica Rara, London 1967. p. 154-156. 
         Toff, Nancy,  The Development of the Modern Flute , Taplinger Publishing Company, New York 1979. p. 179-182. Arthur Lora, “‘Corkless’ Headjoint Stopper,” illustrated on p. 181. 
         Maclagen, Susan,  A Dictionary for the Modern Flutist , The Scarecrow Press, Lanham 2009. Article “Bigio Crown and Stopper”, p 17. Article “Crown” including discussion of Nagahara “Locking Crown,” p. 40. Article “O-ring,” p. 123. Article “Stopper,” p. 176. 
       
    
     This invention relates in general to headjoints for musical instruments of the flute family and in particular to crown assemblies with a novel extension unit which increases the vibrational length between embouchure and crown to give enhanced depth, resonance, and control. 
     Flutes of today, including concert flutes, piccolos, and alto flutes are often constructed of metal and include a body portion that is detachably connected to a headjoint. The body portion includes the body tube, finger-holes, and keys and the headjoint includes the embouchure and headjoint tube. Received in the free end of the headjoint is a crown assembly comprising a crown and stopper. The cylindrical stopper is placed at a predetermined distance from the embouchure hole. The crown is placed on the free end of the headjoint tube at a distance from the embouchure hole established by the manufacturer. The exact distance varies from maker to maker but is generally about 67 millimeters. 
     The stopper is held in place by action of elastic material such as cork or rubber, which expands outwardly into tight-sealing and firm-positioning engagement with the inner surface of the headjoint tube. The stopper may be formed entirely of elastic material, elastic material compressed between rigid discs, or inelastic material covered completely or in part by elastic material. 
     In  FIG. 1 , the crown is held in place by action of elastic material that expands outwardly into firm-positioning engagement with the inner surface of the headjoint. 
     In  FIG. 2  the planar contact surface of the crown is held firmly against the free end of the headjoint tube when the crown is engaged on a threaded stem attached to the stopper. Crown, stopper, and headjoint tube are thus firmly coupled together. 
     It is well known that the vibration of the flute tube affects the quality and character of the flute sound and that tubes of differing thickness and material produce different tone qualities. The tube acts as a vibrational transmission line, providing a feedback mechanism for vibrations at all points of the instrument to act upon the embouchure, the critical point at which vibrations within the air column of the instrument are generated. 
     I have observed that the concentrated mass of the crown can serve as an anchored fulcrum for the vibrating tube much as the bridge of a guitar or violin serves as an anchored fulcrum for a vibrating string. The embouchure is the point at which the flutist drives and controls this vibration and the embouchure to crown vibrational length affects the timbre of the flute much as the bridge to bow vibrational length affects the timbre of the violin. Lengthening the embouchure to crown vibrational transmission line enhances the flutist&#39;s ability to drive and control the vibration of the tube as well as adding depth and resonance to the flute sound. 
     I have also observed that the tube in the area of the stopper and crown must be free to vibrate without constraint to produce the most resonant and flexible tone. 
     And I have observed that the crown must contact the end of the headjoint tube in such a way as to provide a solidly anchored fulcrum for vibration of the tube without unduly restricting the flexing of the free end of the tube as required for optimal vibration. 
     All prior crown and stopper constructions have drawbacks. First, none provide means for lengthening or adjusting the embouchure to crown vibrational length beyond that predetermined by the manufacturer of the headjoint. Second, all prior devices either make ineffectual use of the crown as a fulcrum for the vibrating tube or draw the crown and stopper into a rigid unit that restricts vibration of the tube. All prior devices fall into two general categories as illustrated in  FIG. 1  and  FIG. 2 . 
     In  FIG. 1 , the crown is friction-fitted to the inner surface of the headjoint tube with elastic material, a connection that is inadequate to allow the crown to serve as an anchored fulcrum for the vibrating tube. Flutes of the Baroque period make use of this design. Bigio and Symington offer crowns and stoppers of this design for modern concert flutes, utilizing O-rings as elastic material. Fajardo dispenses with the crown entirely in one embodiment while Couesnon and Melfi replace the crown with an acoustic horn to transmit sound from the stopper area to the player. In these three cases there is no crown to act as a fulcrum. Jenner, Sandner, and Fajardo disclose unified crown and stoppers in which the planar face of the crown is not drawn against the free end of the headjoint tube in a manner sufficient for the crown to act as a fulcrum for the vibrating tube. 
     In  FIG. 2 , a crown with a uniform planar contact area is drawn firmly against the entire radius of the free end of the headjoint tube by means of a threaded engagement, greatly restricting the vibration of the tube. The crown is firmly coupled to the stopper by means of a solid threaded stem attached to the stopper. Crown, tube, and stopper are thus bound into a rigid unit, further restricting vibration of the headjoint tube. In addition, the outward pressure exerted by the stopper upon the inner surface of the headjoint tube is determined only by the nature of the elastic material used and any pressure exerted upon it. As there is no means to monitor this pressure when installing a traditional stopper, it often greatly exceeds that which is needed to simply create a seal and prevent movement of the stopper. Excessive pressure against the inner surface of the headjoint tube at the stopper further restricts vibration of the headjoint tube. 
     Modifications to the design of  FIG. 2  have been made for several purposes. Rudall and Rose, and Lillicrap disclose mechanisms to more easily control the tuning of the octaves by facilitating the adjustment of the stopper position. Pellerite and Ferron disclose alterations to the stopper face shape to improve the response of certain tones. Lora, Pellerite, Dong, and Wilhelmus disclose alterations to the construction of the stopper and to the choice of elastic material to enhance the weak vibrations that pass from the embouchure area of the air column through the stopper into the area between stopper and crown. Nagahara provides a crown that locks into position on the threaded stem of the stopper rather than against the end of the headjoint tube, eliminating the possibility of the crown acting as a fulcrum for the vibrating tube. None of these modifications address the disadvantages disclosed above and none take into consideration the vibration of the flute tube or the role of the crown as a fulcrum for the vibrating tube. 
     The invention disclosed herein overcomes each of the disadvantages outlined above and provides additional improvements in the design of headjoint crown assemblies. 
     SUMMARY 
     As will become apparent from the following discussion, this invention provides a novel extension unit and crown assembly with components that enable the vibrational length of the vibrational transmission line connecting the embouchure with the crown of the headjoint of an instrument of the flute family to be extended, thereby enhancing the quality and resonance of the sound produced. The novel extension unit and crown assembly are applicable to both new and existing headjoints. 
     One embodiment utilizes an extension tube folded in upon itself to form the extension unit to be inserted within the chamber existing between the free end of the headjoint tube and the stopper, contacting the headjoint tube by means of a flange attached to the free end of the outer member of the folded extension. A crown is drawn against the free end of the inner member of the folded extension by threaded engagement, thus drawing the folded extension against the free end of the headjoint tube. The vibrational transmission line from embouchure to crown follows the path of the headjoint tube from embouchure to the free end of the headjoint tube where it is extended by passing along first the outer and then the inner member of the folded extension before reaching the crown. The vibrational length between crown and stopper is thus increased by the combined length of the inner and outer extension tubes while the pre-existing lateral length between crown and stopper remains essentially unchanged, thereby preserving the aesthetic appearance of the headjoint. 
     The new extension unit may be combined with a novel headjoint stopper that provides a flexible coupling with the crown, thereby allowing the headjoint tube to vibrate more freely between crown and stopper. This novel stopper may also be provided with a pressure-regulating spring to limit the outward pressure of the elastic sealing material against the inner surface of the headjoint, ensuring free vibration of the headjoint tube at the stopper. 
     According to another embodiment, the player can, by manual rotation of the crown, quickly select one of several predetermined vibrational lengths for the extension unit, thus changing the sound and response of the instrument. In this embodiment, the crown is provided with multiple radial contact arms. The outer member of the folded extension is coupled with an intermediary tube or tubes of varying length(s), terminating on their free ends at the plane of the radial contact arms of the crown where the tubes are supplied with a circular sequence of contacts each having a certain surface which is suitable for contact and sliding. The crown is drawn by threaded engagement against contact points at the free end of an individual tube when rotated to any of several specific index positions, thus selecting a vibrational length for the extension unit. 
     Crown assemblies utilizing the novel extension may be applied to any instrument of the flute family without affecting the operation and aesthetic appearance of the instrument. Student instruments as well as handmade professional instruments will benefit equally from the novel extension. Embodiments with selectable vibrational lengths provide instant adjustments to tone and response hitherto unknown to instruments of the flute family. 
     There are additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto. In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of the description and should not be regarded as limiting. 
     These together with other objects of the invention, along with the various features of novelty, which characterize the invention, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages, and the specific objects attained by its uses, reference should be made to the accompanying drawings and descriptive matter in which there are illustrated preferred embodiments of the invention. 
    
    
     
       DRAWINGS 
       Figures 
       In the drawings, closely related figures have the same number but different alphabetic suffixes. 
         FIG. 1  illustrates a longitudinal sectional view a conventional crown and stopper utilizing elastic material to hold each in place independently in a flute headjoint. 
         FIG. 2  illustrates a longitudinal sectional view of a conventional crown and stopper utilizing elastic material to hold the stopper in place and an externally threaded stem to draw the crown against the free end of the headjoint tube. 
         FIG. 3  illustrates a longitudinal sectional view of an extension unit utilizing an extension tube fitted to the free end of a headjoint tube and held in place by a traditional crown and stopper of the type shown in  FIG. 2 . 
         FIG. 4  illustrates a longitudinal sectional view of an extension unit utilizing a tube folded in upon itself to form an inner and outer tube and held in place exterior to the headjoint tube by a traditional crown and stopper of the type shown in  FIG. 2 . 
         FIG. 5A  illustrates a longitudinal sectional view of an extension unit utilizing a tube folded in upon itself to form an inner and outer tube and held in place interior to the headjoint tube by a traditional crown and stopper of the type shown in  FIG. 2 . 
         FIG. 5B  illustrates a longitudinal sectional view of the extension unit of  FIG. 5A  permanently attached to a crown to form a unified crown and extension unit. 
         FIG. 5C  illustrates the free ends of the array of bars of the extension unit of  FIG. 5D . 
         FIG. 5D  illustrates a longitudinal sectional view of an extension unit wherein an array of bars has replaced the inner tube of the extension unit of  FIG. 5A . 
         FIG. 5E  illustrates a longitudinal sectional view of the extension unit of  FIG. 5D  permanently attached to a crown to form a unified crown and extension unit. 
         FIG. 6  illustrates a longitudinal sectional view of a stopper with helical spring coupling between inner and outer stem members. 
         FIG. 7  illustrates a longitudinal sectional view of a stopper with a curved disc spring applying regulated pressure against an elastic washer and utilizing the helical spring coupling between inner and outer stem members of  FIG. 6 . 
         FIG. 8  illustrates a perspective view of a headjoint-facing side of a crown with three equally-spaced radial arms having planar contact surfaces. 
         FIG. 9A  illustrates the free end of the selectable extension unit of  FIG. 9B  showing three concentric sets of contact tabs for selectable sliding engagement with the crown of  FIG. 8 . 
         FIG. 9B  illustrates a longitudinal sectional view of a selectable extension unit utilizing a tube folded in upon itself to form an inner and outer tube, and fitted with an additional intermediary tube. 
         FIG. 9C  illustrates the free end of the selectable extension unit of  FIG. 9D  showing three concentric sets of contact tabs for selectable sliding engagement with the crown of  FIG. 8 . 
         FIG. 9D  illustrates a longitudinal sectional view of a selectable extension unit utilizing an array of bars, equivalent in function to the extension unit of  FIG. 9B . 
         FIG. 10  illustrates an exploded perspective view of a crown assembly utilizing the crown of  FIG. 8  with the selectable extension unit of  FIG. 9B  and the stopper of  FIG. 7 , installed on a headjoint. 
     
    
    
     REFERENCE NUMERALS 
     
         
         
           
               11  embouchure 
               12  headjoint tube 
               13  crown 
               13 A crown 
               13 B crown 
               13 C crown 
               13 D crown 
               14  elastic material 
               15  stopper 
               15 A stopper 
               16  elastic material 
               17  free end of headjoint tube  12   
               18  planar contact surface 
               21  metal disc face plate 
               21 A metal disc face plate 
               22  elastic material 
               22 A elastic material 
               22 B elastic washer 
               23  back washer 
               23 A back washer 
               24  threaded nut 
               25  externally threaded stem 
               26  back side of metal disc face plate  21   
               26 A back side of metal disc face plate  21 A 
               27  front side of metal disc face plate  21   
               28  internally threaded stem 
               28 A internally threaded stem 
               28 B internally threaded stem 
               29  head 
               31  extension tube 
               32  outward-facing flange 
               32 A inward-facing flange 
               32 B outward-facing flange 
               33  alignment ring 
               34  externally threaded extension stem 
               35  internally threaded coupling 
               41  inner tube 
               41 A outer tube 
               41 B outer tube 
               42  outer tube 
               42 A inner tube 
               42 B inner tube 
               43  lower coupling ring 
               43 A lower coupling ring 
               43 B lower coupling ring 
               51  contact tab 
               51 A contact tab 
               51 B contact tab 
               51 C contact tab 
               52  bar 
               61  internally and externally threaded stem 
               62  externally threaded inner stem 
               63  tubular housing 
               63 A tubular housing 
               64  helical spring 
               65  externally threaded outer stem 
               66  outer flange 
               67  inner flange 
               68  stopper 
               71  curved disc spring 
               72  stop 
               73  stopper 
               81  radial arm 
               82  contact surface 
               91  contact tab 
               91 A contact tab 
               91 B contact tab 
               91 C contact tab 
               92  upper coupling ring 
               93  selectable extension unit 
               94  intermediary tube 
               95  bar 
               96  bar 
               97  bar 
               98  selectable extension unit 
               101  stamped numeral “1” 
               102  stamped numeral “2” 
               103  stamped numeral “3” 
               104  index notch 
               105  slit 
               106  slit 
               107  slit 
           
         
       
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which are shown, by way of illustration, specific embodiments that may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized, and that changes may be made without departing from the scope of the embodiments. The following detailed description is, therefore, not to be taken in a limiting sense. 
     This invention relates to novel extension units and crown assemblies utilizing the novel extension units for headjoints of musical instruments of the flute family. Although the term “flute” is used herein, it is to be understood that this term refers generally to musical instruments of the flute family, such instruments including concert flutes, alto flutes, and piccolos. 
     Crown assemblies incorporating the new extension units provide greatly increased depth and resonance to the flute sound and enhance the flutist&#39;s ability to drive and control the vibration of the flute tube. Crown assemblies containing particular embodiments of the new extension unit provide freer vibration of the headjoint tube, significantly augmenting the benefits of the novel extension unit. In addition, crown assemblies containing particular embodiments provide means for quickly changing the tone and response characteristics of the instrument by means of a simple rotation of the crown. Such significant changes in tone and response of the headjoint were previously known only by replacing the entire headjoint with one of differing construction, a costly and an impractical option for most performance situations. The benefits of the novel crown assembly are obtained without sacrificing the traditional aesthetic appearance of the headjoint to which it is applied. Embodiments of this invention are applicable to both new and existing headjoints of any material for musical instruments of the flute family. 
     COMMON TERMS 
     Traditional crown assemblies are composed of two or more components described in detail below. As used herein, the term “crown assembly” refers to two or more members that form terminations for the free end of the headjoint tube and for the air column within. Traditional crown assemblies comprise a sealed stop for the air column, herein referred to as a “stopper”, and a covering for the free end of the headjoint tube, herein referred to as a “crown”. As used herein, the term “headjoint” refers to a detachable section of an instrument of the flute family, comprising a headjoint tube and a mouthpiece, herein referred to as an “embouchure”. The headjoint tube may be constructed of wood, rubber, plastic, carbon fiber, brass, silver, nickel-silver, gold, platinum, or combinations thereof. As used herein, the term “elastic material” refers to deformable materials such as rubber, O-rings, neoprene, cork, or any similar material. Cork is traditionally utilized on stoppers as an elastic material to expand outwardly into tight-sealing and firm-positioning engagement with the inner surface of the headjoint tube, though rubber was used as early as 1895 and O-rings are not uncommon today. 
     Two general types of traditional crown assemblies may be distinguished: those with a crown drawn against the free end of the headjoint tube through a coupling to the stopper and those with an independent crown coupled to the inner surface of the headjoint tube by elastic material. The concentrated mass of the crown acts as an anchored fulcrum at the end-point of the vibrating flute tube when drawn into direct contact with the free end of the headjoint tube, but its function is essentially reduced to that of an ornament when loosely coupled to the inner surface of the headjoint tube by elastic material. 
     The term “vibrational transmission line” as utilized herein refers to a connected path of vibrational material, such as thin metal tubing, to transmit vibrations from one point to another along a flute tube and crown assembly. The term “vibrational length” refers to the distance travelled from one specified point to another by vibrations along a vibrational transmission line. An “extension unit” is a section of vibrational transmission line interposed between the free end of a headjoint tube and a crown to increase the total vibrational length between the embouchure and the crown of a flute. An extension unit may form part of a complete crown assembly including a crown and a stopper. A “selectable extension unit” offers a choice of multiple vibrational lengths when utilized in an appropriate crown assembly. The term “index position” refers to specific points of alignment between the crown and the selectable extension unit that produce specific vibrational lengths for a crown assembly utilizing such a unit. Index positions may be identified by a series of numbers or other markings on the perimeter of the crown and a corresponding index notch on the perimeter of the selectable extension unit flange. 
     A more detailed description of the invention follows and refers to the appended drawings. 
       FIG. 1  and FIG.  2 —Prior Art Crown Assemblies 
       FIG. 1  shows a traditional crown  13  and stopper  15  mounted by means of elastic materials  14  and  16  in a headjoint comprising an embouchure  11  and a headjoint tube  12 . The elastic materials  14  and  16  may be cork, waxed string, rubber O-rings, or other suitable material. Both crown  13  and stopper  15  may be constructed of wood, plastic, or metal. The stopper may be constructed entirely of elastic material such as cork and may be faced with a metal disc on the side facing the embouchure. The crown is coupled to the headjoint tube by elastic material  14  only. The planar contact surface  18  of the crown is not drawn against the free end  17  of the headjoint tube. The crown may be constructed as a solid piece or hollowed out as desired to reduce weight. 
       FIG. 2  shows a traditional crown  13 A and stopper  15 A coupled by an externally threaded stem  25 . The stopper is installed in a headjoint comprising an embouchure  11  and a headjoint tube  12 . Stopper  15 A includes an externally threaded stem  25  that is integral with and concentric to metal disc face plate  21 , and extending outwardly from the back side  26  of face plate  21 . Stopper  15 A utilizes an elastic material  22  such as cork or rubber which is compressed between face plate  21  and a back washer  23  when an internally threaded nut  24  is received on externally threaded stem  25  and drawn against washer  23 . The washer may be combined with the nut to form an internally threaded washer. Crown  13 A comprises a head  29  and an internally threaded stem  28  which may or may not extend beyond a planar contact surface  18 . The head may be constructed as a solid piece or hollowed out as desired to reduce weight. The crown is coupled to the headjoint tube  12  when the internally threaded stem  28  is received on externally threaded stem  25  and the planar contact surface  18  of the crown is drawn against the free end  17  of headjoint tube  12 . The vibrational length of the vibrational transmission line formed by headjoint tube  12  between the center of the embouchure and the surface  18  of the crown is equal to the lateral distance from the center of the embouchure to the free end  17  of the headjoint tube. 
     The lateral distance from the center of embouchure  11  to the free end  17  of the headjoint tube varies by manufacturer but is generally 66 to 68 millimeters on concert flutes. The lateral distance from the center of the embouchure to the front side  27  of face plate  21  can be adjusted by the player but is generally between 17 and 18 millimeters on concert flutes for correct tuning of the octaves. This leaves a lateral distance of 48 to 51 millimeters between the front side  27  of face plate  21  and the free end  17  of the headjoint tube. 
     FIG.  3 —Basic Extension Unit 
     Referring to  FIG. 3 , there is illustrated an embodiment of the invention unit installed on a headjoint comprising an embouchure  11  and a headjoint tube  12  in which a crown  13 A and a stopper  15 A are identical to that of  FIG. 2  with an extension unit interposed between the free end  17  of headjoint tube  12  and the planar contact surface  18  of crown  13 A. The extension unit comprises an extension tube  31 , an outward-facing flange  32 , and an alignment ring  33 . Extension tube  31  may be constructed of thin brass, silver, gold, or other vibrant material. Although the extension tube may be made to any length, a length range of 10 to 100 millimeters is contemplated. Externally threaded stem  25  is affixed to a metal disc face plate  21  and coupled to externally threaded extension stem  34  by means of an internally threaded coupling  35 . The planar contact surface  18  of the crown is drawn against the free end of the extension tube, causing flange  32  affixed to the opposite end of the extension tube to be drawn against the free end  17  of the headjoint tube when the internally threaded stem  28  of the crown is received on externally threaded extension stem  34 . In this way, a vibrational transmission line between the embouchure and the crown is completed and the vibrational length of this transmission line is greater than that of the traditional assembly of  FIG. 2  by the length of extension tube  31 . 
     FIG.  4 —External Folded Extension Unit 
       FIG. 4  illustrates an embodiment of the invention installed on a headjoint comprising an embouchure  11  and a headjoint tube  12  in which a crown  13 B and a stopper  15 A are essentially the same as that of  FIG. 2  and  FIG. 3 , and in which the extension tube  31  of  FIG. 3  has been folded in upon itself to form a coaxial inner tube  41  and outer tube  42 , coupled by a lower coupling ring  43  and fitted with an inward-facing flange  32 A attached to the free end of inner tube  41 . This folded extension unit is so arranged as to be coaxial to and exterior to headjoint tube  12  in the area between the embouchure and the crown. The planar contact surface  18  of the crown is drawn against the free end of outer tube  42  causing inward-facing flange  32 A to be drawn against the free end  17  of the headjoint tube when the internally threaded stem  28  of the crown is received on an externally threaded stem  25  affixed to the metal disc face plate  21 . In this way, a vibrational transmission line between the embouchure and the crown is completed and the vibrational length of this transmission line is greater than that of the traditional assembly of  FIG. 2  by the sum of the lengths of outer tube  42  and inner tube  41 . The lateral length between embouchure  11  and crown  13 B remains essentially unchanged from that of a similar headjoint without the extension unit installed. 
     FIG.  5 A Through  5 E—Internal Folded Extension Units 
       FIG. 5A  illustrates a similar embodiment of the invention installed on a headjoint comprising an embouchure  11  and a headjoint tube  12  in which a crown  13 C and a stopper  15 A are essentially the same as that of  FIG. 2  and  FIG. 3 , and in which the folded extension unit of  FIG. 4  is so altered as to be placed within the cavity formed at the free end of headjoint tube  12 . In this embodiment, an outer tube  41 A is coupled to a coaxial inner tube  42 A with a lower coupling ring  43 A and fitted with an outward-facing flange  32 B attached to the free end of outer tube  41 A. This folded extension unit is so arranged as to be coaxial to and interior to headjoint tube  12 . The planar contact surface  18  of the crown is drawn against the free end of inner tube  42 A causing outward-facing flange  32 B to be drawn against the free end  17  of the headjoint tube when the internally threaded stem  28 A of the crown is received on an externally threaded stem  25  affixed to the metal disc face plate  21 . In this way, a vibrational transmission line between the embouchure and the crown is completed and the vibrational length of this transmission line is greater than that of the traditional assembly of  FIG. 2  by the sum of the lengths of outer tube  41 A and inner tube  42 A. The lateral length between embouchure  11  and crown  13 C remains essentially unchanged from that of a similar headjoint without the extension unit installed, thus maintaining the traditional aesthetic appearance of the headjoint. 
     In this embodiment, the length of outer tube  41 A is limited by the depth of the cavity formed between the back end of the stopper assembly at washer  23  and the free end  17  of headjoint tube  12 . Decreasing the length of elastic material  22  will increase this length. Cork is the most common elastic material used in traditional stoppers and the length of cork utilized is generally about 30 millimeters. The length of this cork cannot be reduced below about 20 millimeters without risking slippage of the cork against the inner surface of headjoint tube  12  when the crown is received upon stem  25  and drawn against the extension unit and headjoint tube. The large space occupied by a stopper of traditional construction limits the length of outer tube  41 A to about 25 millimeters. The length of elastic material  22  can be substantially reduced by replacing the cork with a thin neoprene washer or an O-ring assembly, allowing the length of outer tube  41 A to increase to about 40 millimeters. 
       FIG. 5B  illustrates the extension unit of  FIG. 5A  constructed with crown  13 C permanently attached to the free end of inner tube  42 A, forming a unified crown and extension unit. 
     One or both of the pair of coaxial inner and outer tubes  42 A and  41 A of the embodiment of  FIG. 5A  may be replaced with an array of folded lateral rods or bars such as illustrated in the embodiment of  FIG. 5C  and  FIG. 5D  where inner tube  42 A of  FIG. 5A  is replaced with an array of bars  52  terminating on their free ends in contact tabs  51 . The contact tabs are drawn against the planar contact surface  18  of crown  13 C of  FIG. 5A  when the internally threaded stem  28 A of the crown is received on externally threaded stem  25  affixed to metal disc face plate  21 . A vibrational transmission line is thus completed between embouchure and crown and the vibrational length of this transmission line is greater than that of the traditional assembly of  FIG. 2  by the sum of the lengths of outer tube  41 A and bars  52  of  FIG. 5D . The lateral length between embouchure  11  and crown  13 C of  FIG. 5A  remains essentially unchanged from that of a similar headjoint without the extension unit installed, thus maintaining the traditional aesthetic appearance of the headjoint. 
       FIG. 5E  illustrates the extension unit of  FIG. 5C  and  FIG. 5D  with crown  13 C permanently attached to the free ends of bars  52 , forming a unified crown and extension unit. 
       FIG. 6  and FIG.  7 —Stoppers with Helical Spring Coupling 
       FIG. 6  shows a stopper  68  in which a section of the solid externally threaded stem  25  of  FIG. 2  is replaced with a helical spring  64  which is friction fitted to an externally threaded inner stem  62  on one end and an externally threaded outer stem  65  on the other end, forming a flexible coupling between a metal disc face plate  21 A and a crown, thereby allowing a headjoint tube to vibrate more freely in the area between crown and stopper. Stopper  68  utilizes an externally threaded inner stem  62  installed on an internally and externally threaded stem  61  that is affixed to the back side  26 A of metal disc face plate  21 A. Helical spring  64  of the stopper is encased in an internally threaded tubular housing  63  that is surrounded by an elastic material  22 A such as cork, neoprene, or an O-ring assembly. The elastic material is held between face plate  21 A and an outer flange  66  affixed to internally threaded tubular housing  63 . Helical spring  64  is extended when the internally threaded stem of the crown is received on externally threaded outer stem  65  of stopper  68  and the crown is drawn against the free end of the headjoint tube or the extension unit installed in the free end of the headjoint tube. Extension of helical spring  64  is limited by inner flange  67  affixed to the free end of tubular housing  63 . The pressure of the crown against the headjoint tube or extension unit may be precisely adjusted when the helical spring is gradually extended while the crown is gradually rotated several turns to arrive at the desired spring tension. Such precise control over the pressure of the crown against the headjoint tube or extension unit is impossible with stoppers utilizing a solid stem, as the pressure will increase from zero to an undesirably high amount within a few degrees of rotation of the crown. 
       FIG. 7  illustrates a similar stopper  73  in which the pressure exerted by an elastic washer  22 B against the inner surface of a headjoint tube is regulated by a curved disc spring  71  to ensure free vibration of the headjoint tube in the area of the stopper. Inasmuch as the elastic washer is a rubber or rubber compound, although similar material may be suitable, the overall volume remains virtually the same regardless of the shape it assumes. Consequently, a decrease in thickness of elastic washer  22 B causes an increase in perimeter length of the washer. This increase in perimeter length causes the outside diameter dimension of the elastic washer to increase and to expand outwardly into tight-sealing and firm-positioning engagement with the inner surface of the headjoint tube. With a traditional stopper, such as that illustrated in  FIG. 2 , the more nut  24  is tightened against washer  23 , the greater the compression of elastic material  22  and the greater the outside diameter dimension growth of material  22 , increasing the outward pressure against the headjoint tube. A similar situation occurs in stopper  68  of  FIG. 6  when outer flange  66  is tightened against elastic material  22 A. But in the double-spring stopper  73  of  FIG. 7 , the internal threads of tubular housing  63 A stop at  72 , limiting the compression of curved disc spring  71  at a predetermined point. Spring  71  will thereby apply a constant predetermined pressure against back washer  23 A that will cause a predetermined compression of elastic washer  22 B. Spring  71  will thus maintain a constant predetermined outward pressure on the inner surface of the headjoint tube at elastic washer  22 B regardless of minor variations in diameter of the headjoint tube due to variations in manufacture. 
     FIG.  8 —Crown with Radial Arms 
       FIG. 8  shows a crown  13 D with three equally-spaced radial arms  81  formed with planar contact surfaces  82  and an internally threaded stem  28 B. These surfaces  82  will make contact with the free end of a headjoint tube or extension unit when internally threaded stem  28 B is received on an externally threaded stem such as stem  25  of  FIG. 5A . Surfaces  82  contact only a small percentage of the total area of the free end of a headjoint tube or extension unit, leaving the remaining area free to flex and vibrate. This stands in contrast to the traditional crowns of  FIG. 2  through  FIG. 5A  where uniform contact is made along the entire circumference of the free end of a headjoint tube or extension unit, preventing any flexing of the tube the point of contact. Crown  13 D may replace a traditional crown in any of the embodiments shown in  FIG. 2  through  FIG. 5A . 
     FIG.  9 A Through  9 D—Selectable Extension Units 
       FIG. 9A  and  FIG. 9B  illustrate a further embodiment in which the folded extension unit of  FIG. 5A  is given an additional intermediary tube  94  to form a selectable extension unit  93  that allows a choice of extension lengths when combined with a crown of the type shown in  FIG. 8  and a stopper of the types shown in  FIG. 6  or  FIG. 7 . In the selectable extension unit  93 , intermediary tube  94  is coupled to an outer tube  41 B by an upper coupling ring  92 . Inner tube  42 B is reduced in diameter to make room for tube  94  and coupled to outer tube  41 B by a thickened lower coupling ring  43 B. The three tubes,  41 B,  94 , and  42 B are so arranged as to be coaxial with and internal to a headjoint tube when a selectable extension unit  93  is installed on a headjoint.  FIG. 9A  illustrates the free ends of the three tubes,  41 B,  94 , and  42 B, each of which has a series of three equally-spaced contact tabs  91  forming a total of nine contact tabs lying in the same plane. Three equally-spaced tabs  91 A are affixed to the free end of tube  41 B, three equally-spaced tabs  91 B are affixed to the free end of tube  94 , and three equally-spaced tabs  91 C are affixed to the free end of tube  42 B. These tabs are angularly staggered, disposing each series symmetrically with respect to the other two series and resulting in a contact tab of one series lying in line with spaces between adjacent contact tabs in the other two series. Because the three series of contact tabs are disposed along concentric circles of differing radii, the radial arms  81  of crown  13 D of  FIG. 8  will make tripartite contact with three contact tabs of an individual tube when the crown is rotated to each of three predetermined index positions. Because the angular length of the contact surfaces  82  of radial arms  81  is greater than the angular length between contact tabs  91 , contact surfaces  82  will remain in continuous sliding contact with three or more contact tabs  91  when the crown is rotated from one index position to the next. 
     One or more tubes  41 B,  94 , and  42 B of selectable extension unit  93  may be replaced with an array of folded lateral rods or bars such as in selectable extension unit  98 , illustrated in  FIG. 9C  and  FIG. 9D . In this embodiment, tube  41 B has been replaced with bars  95 , tube  94  has been replaced with bars  96 , and tube  42 B has been replaced with bars  97 .  FIG. 9D  illustrates the length of the folded lateral bars of selectable extension unit  98 . 
       FIG. 9C  illustrates the free ends of the folded lateral bars of selectable extension unit  98 . Each set of three bars,  95 ,  96 , and  97 , end in equally-spaced contact tabs  51  forming a total of nine contact tabs lying in the same plane. Three equally-spaced contact tabs  51 A form the ends of bars  95 , three equally-spaced contact tabs  51 B form the ends of bars  96 , and three equally-spaced contact tabs  51 C form the ends of bars  97 . These contact tabs are angularly staggered, disposing each series symmetrically with respect to the other two series and resulting in a contact tab of one series lying in line with spaces between adjacent contact tabs in the other two series. The radial arms  81  of crown  13 D of  FIG. 8  will make tripartite contact with three contact tabs of an individual set of bars  95 ,  96 , or  97 , when the crown is rotated to each of three predetermined index positions. Because the angular length of the contact surfaces  82  of radial arms  81  is greater than the angular length between contact tabs  51 , contact surfaces  82  will remain in continuous sliding contact with three or more contact tabs  51  when the crown is rotated from one index position to the next. 
     FIG.  10 —Crown Assembly with Selectable Vibrational Lengths 
       FIG. 10  is an exploded view of an embodiment of a complete crown assembly, comprising crown  13 D of  FIG. 8 , selectable extension unit  93  of  FIG. 9B , and double-spring stopper  73  of  FIG. 7 . The contact surfaces of radial arms  81  of the crown are drawn against contact tabs  91  of the extension unit when internally threaded stem  28 B is received on externally threaded outer stem  65 . An essentially constant pressure is maintained between the radial arms and the contact tabs by helical spring  64  ( FIG. 7 ) while radial arms  81  are rotated to each of three index positions, the variation in extension of the helical spring due to rotation of stem  28 B on stem  65  being negligible. The index positions are indicated by the alignment of stamped numerals  101 ,  102 , and  103  on the perimeter of crown  13 D with index notch  104  on the perimeter of flange  32 B of the selectable extension unit. Because the contact area of flange  32 B against the free end  17  of headjoint tube  12  is much greater than the sliding contact area of radial arms  81  against tabs  91 , the selectable extension unit will not rotate with respect to the headjoint tube when the crown is rotated from one index position to the next. 
     The vibrational length of the vibrational transmission line between embouchure  11  and crown  13 D is increased by three predetermined lengths from that of a similar headjoint without the selectable extension unit installed. When crown  13 D is rotated with respect to flange  32 B such that the number “1” at  101  is aligned with index notch  104  on the flange, radial arms  81  of crown  13 D make tripartite contact with contact tabs  91 A ( FIG. 9A ) at the free end of outer tube  41 B. These contact tabs are closely linked to flange  32 B, which is drawn against the free end  17  of the headjoint tube. Therefore, the length of the vibrational transmission line between radial arms  81  and free end  17  is a distance of only 2 to 5 millimeters. This small extension to the overall vibrational transmission line from embouchure to crown will result in almost no difference in tone and response from that of an instrument without extension unit, utilizing a similar crown and stopper. When crown  13 D is rotated with respect to flange  32 B such that the number “2” at  102  is aligned with index notch  104  on the flange, the radial arms  81  of crown  13 D make tripartite contact with contact tabs  91 B ( FIG. 9A ) at the free end of intermediary tube  94 . In this case, the path of the vibrational transmission line between radial arms  81  and free end  17 , as formed by extension unit  93 , follows the length of intermediary tube  94  to upper coupling ring  92  and returns an equal distance along outer tube  41 B, arriving at flange  32 B ( FIG. 9B ). Therefore, the total extension in index position “2” is equal to twice the length of tube  94 . When crown  13 D is rotated with respect to flange  32 B such that the number “3” at  103  is aligned with index notch  104  on the flange, the radial arms  81  of crown  13 D make tripartite contact with contact tabs  91 C ( FIG. 9A ) at the free end of inner extension tube  42 B. In this case, the path of the vibrational transmission line between radial arms  81  and free end  17 , as formed by extension unit  93 , follows the length of inner tube  42 B to lower coupling ring  43 B and returns an equal distance along outer tube  41 B, arriving at flange  32 B ( FIG. 9B ). Therefore, the total extension in index position “3” is equal to twice the length of tube  41 B. 
     If tube  94  ( FIG. 9B ) is given a length of 15 millimeters and tube  41 B given a length of 40 millimeters, then the extensions to the vibrational lengths will be about 3 millimeters in index position “1”, 30 millimeters in index position “2”, and 80 millimeters in index position “3”. This gives the player the ability to select between three very different tone and response settings with a simple rotation of the crown to any of the three index positions. In  FIG. 10 , the lateral length between embouchure  11  and crown  13 D remains essentially unchanged from that of a similar headjoint without selectable extension unit  93  installed, thus maintaining the traditional aesthetic appearance of the headjoint. 
     The selectable extension unit  98  of  FIG. 9D  may replace the selectable extension unit  93  of  FIG. 9B  in the embodiment of  FIG. 10 . Contact tabs MA at the ends of bars  95  of extension unit  98  are closely linked to flange  32 B ( FIGS. 9C and 9D ). The portion of bars  95  extending behind flange  32 B does not contribute to the vibrational transmission line. Therefore, the length of the vibrational transmission line extension between radial arms  81  and free end  17  ( FIG. 10 ) is a distance of only 2 to 5 millimeters when index position “1” is selected, just as with selectable extension unit  93 . If the lateral length from contact tabs  51  to the fold of bars  96  and  97  of unit  98  ( FIG. 9D ) are made equal to the lengths of unit  93 &#39;s tubes  94  and  41 B respectively ( FIG. 9B ) then the extension to the vibrational transmission line from embouchure to crown of the extension unit  98  will be found to be equal to that of extension unit  93  when crown  13 D is rotated to index positions “2” and “3” as well when unit  98  replaces unit  93  in the embodiment of  FIG. 10 . The lateral length between embouchure  11  and crown  13 D remains essentially unchanged from that of a similar headjoint without selectable extension unit  98  installed, thus maintaining the traditional aesthetic appearance of the headjoint. 
     Flanges and coupling rings such as flange  32 B and rings  43 B and  92  ( FIG. 9B ) create points of increased thickness and rigidity. Excess rigidity can dampen vibrations passing through these points. This rigidity can be eliminated while maintaining vibrational coupling by cutting slits  105 ,  106 , and  107  in these flanges and rings as illustrated in  FIG. 10 . The number of slits contemplated for each flange or ring can range from about three to as many as 30. Nine slits are employed in the embodiment of  FIG. 10 . Similar slits may also be introduced to eliminate excess rigidity at flanges and rings on all other embodiments of extension units. 
     Design Considerations 
     The crown assemblies with selectable extension units utilize crowns with radial arms and stoppers with helical spring coupling. These crowns may be produced as a single casting. Optimal pressure of the crown against the selectable extension unit is between about 1 and 4 pounds. A helical spring of about 1 inch length with a rate of 15 to 20 pounds per inch will generate a pull of about 2.3 to 3.1 pounds when a crown is drawn down 5 turns on a stem with 32 pitch threads, resulting in a 0.156″ extension of the helical spring. A stop may be so placed as to limit spring extension at 0.2″ or just over 6 turns of the crown. If a stopper utilizing a neoprene washer compressed by a curved disc spring is employed, a soft neoprene with Shore durometer scale A rating of about 30 will be most effective and will make sufficiently tight-sealing and firm-positioning engagement with the inner surface of the headjoint tube without creating excess tension when a curved disc spring of about 8 pound load rating is utilized. 
     Placed in close proximity to the embouchure, the most sensitive point on the instrument, the specific vibrational characteristics of the extension unit have a significant impact on the sound of the instrument. An extension unit utilizing stock brass tubes of about 0.009″ to 0.014″ wall thickness will produce effective results while hard drawn sterling silver tubes of about 0.009″ to 0.012″ wall thickness will be more effective and will be smoother in overall tonal quality. A combination of a hard drawn sterling silver outer tube and a stock brass inner tube will produce nearly the same result at a reduced cost. The best results can be obtained with extensively hand-worked and hard drawn sterling silver tubes of 0.009″ to 0.012″ wall thickness. Such tubes provide a greatly increased level of warmth and homogeneity to the instrument, aspects which will be particularly noticeable on high-grade student-level instruments that may be mechanically sound but lacking in tonal quality and refinement. Sterling silver tubes of this quality are, however, labor intensive and costly to produce. Tubes of gold may also be used for those players who prefer the exceptional warmth and clarity of a gold flute sound. The selectable feature of certain embodiments offers the possibility of not only changing vibrational transmission line lengths but also selecting between silver, gold, platinum, and other materials for portions of the vibrational transmission line. The individual needs of a wide range of performers may be met through the appropriate choice of extension unit lengths and materials. 
     The new crown assemblies having a selectable extension unit not only are more vibrant in the area of the crown and stopper, thus increasing the depth and resonance of the flute, but also provide the musician with a simple and quick means of changing the tone and response of their instrument. As a result, the musician has a significantly improved instrument with a heretofore-unknown means for adjusting the instrument as needed for a particular performance environment. 
     While the invention has been described in detail above with reference to specific embodiments, it will be understood that modifications and alterations in embodiments disclosed may be made by those practiced in the art without departing from the spirit and scope of the invention. All such modifications and alterations are intended to be covered. In addition, all publications cited herein are indicative of the level of skill in the art and are hereby incorporated by reference in their entirety as if each had been individually incorporated by reference and fully set forth.