Abstract:
A string clamping and tuning mechanism for stringed instruments is disclosed, where the string tension actuates one or more levers to generate two points of clamping force along the string. In a first embodiment, a single lever is used to generate two points of clamping force along the string. In a second embodiment, the clamping force is less concentrated at a first point of clamping force than a second point of clamping force to optimize the holding power of the mechanism. In a third embodiment, a second lever with a screw adjusted stop causes an increase or decrease in the tension in the string.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 62/053,367 filed Sep. 22, 2014, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to musical instruments and, in particular, to stringed musical instruments. 
     BACKGROUND OF THE INVENTION 
     Over the years, many systems have been devised for securing and tensioning the strings of stringed musical instruments. Strings for musical instruments are usually provided with one ball end and one non-ball end. 
     One common tuning system in use today creates tension in the strings by wrapping the non-ball ends around tuning posts fixed at the head end of the instrument neck, which posts are tuned through a worm gear arrangement to create the required tension. The ball ends of the strings pass through openings in a tail piece, through which the balls or rings cannot pass. This system, while in common use, has stability problems because the worm gear drives needed to operate the tuning posts have backlash making precise tuning difficult, and also the strings can tighten around the posts after once being tightened, detuning the instrument. 
     In an alternative tuning system, the ball end of the string is held in a jaw, which is threaded to accept a screw that pulls the string taut. In this kind of tuning system, the non-ball end of the string is held in a clamp which ordinarily requires a tool of some sort to operate. To avoid the use of tools, this type of tuning system can alternatively hold the non-ball end of the string in a clamp that uses the tension of the string itself to provide a clamping force at a single point. By providing a clamping force at a single point, the clamping force is limited to the minimum force required to sever the string. For string players who pull aggressively on the strings when they play the instrument, the clamping force provided by a single point of clamping can be inadequate to hold the string, causing the instrument to detune. 
     The present invention permits the non-ball end of the string to be clamped without using tools, using the tension in the string itself to provide the clamping force in multiple locations along the string. In a second embodiment, the present invention distributes the clamping force over a wider area of the string at the point where the string is first clamped, as compared to the second point of clamping, to reduce the occurrence of the string severing at the first point. In a third embodiment, the present invention also provides an improved tuning system which has greater stability than the worm gear tuning posts of the past and a greater clamping force than the single point string tension clamps of the past without severing the strings. 
     Accordingly, it is an object of the present invention to provide a system for clamping the strings of a musical instrument that can be operated without tools and provides an adequate clamping force to withstand extreme bending of the strings without slipping. It is a further object of the invention to provide a stable tuning system for a stringed musical instrument that can be operated without tools and provides an adequate clamping force to withstand extreme bending of the strings without slipping. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention utilizes the tension in a string to provide more than one clamping force on the string, restraining the string from slipping longitudinally (and thereby altering the tension). The clamping forces are obtained by using one or more levers and two or more stops to convert string tension into clamping force. 
     The invention has application to all classes or families of stringed musical instruments, i.e., lutes (including violins), zithers, lyres, and harps. Such instruments include a plurality of strings under tension, the strings being anchored at each end. At one end of each string are means for adjusting the string tension, i.e., means for tuning the instrument. 
     For clarity, a representative structure of a musical instrument to which the invented clamping means is attached is shown in the drawings. While only a single type of instrument is shown in the drawings, those skilled in the art will readily appreciate how the mechanism described would be integrated into a particular instrument. The invention may be installed at either end of the string as is convenient in a particular situation. 
     In a first embodiment of the invention is a clamping mechanism to exert a clamping force on the non-ball end of a string in two locations. In the clamping mechanism, a single simple lever (one associated with each string) can rotate around an axis substantially perpendicular to the direction of string pull. The lever can also be slidably displaced in a direction substantially parallel to the direction of string pull, guided by a slotted opening in the lever. A first pinch pin passes through the slotted opening in the lever, allowing the lever to rotate around its axis and be displaced in a direction substantially parallel to direction of string pull. Each string passes over the end of its associated lever and through a downward opening in the lever. The downward opening is open to the slotted opening, allowing the string to pass between the first pinch pin and the wall of the downward opening. The string exits the downward opening and passes along the surface of the lever arm opposite the direction of string pull. 
     When the force of the string pull is exerted on the lever arm, the lever tends to both rotate on its axis and be displaced in the direction of string pull. The string passing between the first pinch pin and the wall of the downward opening is pinched, thereby anchoring the string and providing a first point of clamping force. The lever arm opposite the point of application of string pull is arranged to pinch the string against a fixed stop, thereby providing a second point of clamping force. Excess string may be cut off or inserted into an opening in the instrument. 
     In a second embodiment of the invention, the first point of clamping force distributes the clamping force over a wider area of the string, as compared to the second point of clamping force, thereby reducing the tendency of the string to be severed at the first point of clamping force. 
     In a third embodiment of the invention, string pull is exerted on the end of a lever as in the first embodiment or second embodiment, but a second lever, pivotally connected to the first lever and bearing against an adjustable stop, is used to provide the string pinching force. The first pinch pin passing through the slotted opening of the first lever is rigidly connected to the second lever, allowing the second lever to rotate and be displaced relative to the first lever. The second lever bears against an adjustable screw, thereby providing a means for adjusting string tension for tuning purposes. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a partially sectioned trimetric view of a first embodiment of the invention, shown installed on a stringed instrument. 
         FIG. 2  is a side sectioned view of a first embodiment of the invention, configured to accept the non-ball end of a string. 
         FIG. 3  is a side sectioned view of a first embodiment of the invention, shown applying multiple points of clamping force on the non-ball end of the string. 
         FIG. 4  is a side sectioned view of a second embodiment of the invention, shown applying multiple points of clamping force on the non-ball end of the string. 
         FIG. 5  is a side sectioned view of a third embodiment of the invention, sectioned down the center of the clamping mechanism, shown applying multiple points of clamping force on the non-ball end of the string. 
         FIG. 6  is a side sectioned view of a third embodiment of the tuner, sectioned through the housing between two clamping mechanisms, configured to accept the non-ball end of a string. 
         FIG. 7  is a side sectioned side view of a third embodiment of the invention, sectioned through the center of the clamping mechanism, shown with the levers being installed into the housing. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIGS. 1-3  is a first embodiment of the invention, a clamping mechanism to exert a clamping force on the non-ball end of a string  26  in two or more locations.  FIG. 1  shows the invention mounted to the head of a stringed instrument  20 . It is understood that the invention can be applied to either end of a stringed instrument. 
     The levers  21  are rotatable about the first pinch pins  22  which are fixed to the housing  23 . The first pinch pins  22  pass through a slotted opening  24  in the lever, allowing the lever  21  to be slidably displaced in a direction substantially parallel to the direction of string pull. The levers contain a downward opening  25  for the non-ball end of a string  26  to pass that is substantially perpendicular to the direction of string pull. The downward opening  25  is open to the slotted opening  24 , allowing the first pinch pin  22  to contact the interior wall of downward opening  25  that is oriented away from the direction of string pull. Lever rotation is limited by second pinch pin  27 , also fixed to the housing  23 . Elements  22  and  27  are called pinch pins because the string is pinched by it against the lever  21 . It will be appreciated that the “pin”  27  need not be a distinct part, but could, as well, be integral with the structure of the housing. 
     The string  26  passes between the first pinch pin  22  and the wall of the downward opening  25  and then between lever  21  and second pinch pin  27 . The non-ball end of the string  26  is then pulled taut in a generally downward direction (as denoted by the numeral  28  in  FIG. 1 ). This motion of the string causes the lever to rotate about the first pinch pin  22  and pinch the string at second pinch pin  27 . The motion of the string also causes the lever  21  to slide along the first pinch pin  22  through its slotted opening  24 . The movement of the lever  21  relative to the first pinch pin  22  causes the first pinch pin to pinch the string  26  against the wall of downward opening  25 . 
     The amount of pinch pressure relative to the string tension is determined by the ratio of the lever arms, in accordance with the elementary principles of mechanics. By appropriately setting the lever arm ratio, the amount of pinch pressure may be made sufficient to prevent string slippage, while at the same time not severing the string due to excess pressure. The relevant lever arms are 1) the distance from the contact between the string  26  and the lever  21  to the first pinch pin  22 , and 2) the distance between the second pinch pin  27  and the first pinch pin  22 . The pinch force can be varied by changing the distance between the first pinch pin  22  and the second pinch pin  27  or by changing the distance from the first pinch pin  22  to the point on the lever  21  where the string tension acts to cause the lever  21  to rotate about first pinch pin  22 . The actual pinch force is influenced both by the lever arm ratio and the angle at which the string pulls in relation to lever  21 . 
       FIGS. 2 and 3  illustrate the embodiment of  FIG. 1  in various conditions.  FIGS. 2 and 3  show in detail one string clamping mechanism of the first embodiment of the invention in  FIG. 1 . It is understood that the mechanism is replicated for each string of the instrument.  FIG. 2  shows the clamping mechanism oriented to accept the non-ball end of a string  26 .  FIG. 3  shows the non-ball end of a string  26  held by a first clamping force exerted between first pinch pin  22  and the wall of downward opening  25  and a second clamping force exerted between second pinch pin  27  and lever  21 . Excess string can either be cut off or tucked into opening  29 . 
     As seen in  FIG. 4  is a second embodiment of the invention, a clamping mechanism to exert a different amount of clamping force on the non-ball end of a string  26  at each of two locations. The elements in the alternative embodiments which are substantially the same as the corresponding elements of the first embodiment described are identified with the same numeral. Elements which are similar (but not necessarily identical) in function are denoted by the same numeral plus 100. 
       FIG. 4  illustrates the use of a first pinch pin  122  of a larger diameter than second pinch pin  127 . Increasing the diameter of first pinch pin  122  distributes the clamping force exerted on the string  26  over a broader area of the string between the first pinch pin  122  and the wall of downward opening  125 . Reducing the diameter of second pinch pin  127  concentrates the clamping force to a smaller area of string  26  between the second pinch pin  127  and lever  121 . By distributing the clamping force between the first pinch pin  122  and the wall of downward opening  125  over a broader area relative to the distribution of the clamping force on the string between the second pinch pin  127  and lever  121 , the string  26  is less likely to be severed at the former. It is understood that the area over which the clamping force is distributed can be adjusted by means other than changing the diameter of the pins, such as through the use of different surface textures or materials or through the use of non-cylindrical pins. 
       FIG. 5  illustrates a third embodiment similar that further includes a second lever for additional mechanical advantage and a means for changing the tension in the strings for tuning purposes. Only a cross sectional view showing the details of one string mechanism is shown in  FIG. 5 , it being understood that the mechanism is replicated for each string of the instrument. According to the embodiment of  FIG. 5 , a housing  223  contains a plurality of levers  221 , each corresponding to one of the strings  26  of the instrument. Each lever  221  rotates about a corresponding pivot pin  231 . Additionally, a second lever  232  (which has a clevis-like shape) rotates about a first pinch pin  233 . The first pinch pins  233  are not attached to the housing  223 , but rather attached to the respective lever  232 . The first pinch pins  233  pass through a slotted opening  224  in the lever  221 , allowing the lever  221  to rotate in a limited range about an axis substantially perpendicular to the direction of string pull. The levers  221  contain a downward opening  225  for the string  26  to pass that is substantially perpendicular to the direction of string pull. The downward opening  225  is open to the slotted opening  224 , allowing the first pinch pin  233  to contact the interior wall of opening  225  that is oriented away from the direction of string pull. There is also a second pinch pin  227  attached to lever  232  that limits the rotation of lever  221 . 
     Tension in string  26  causes the lever  221  to rotate about the pivot pin  231  and pinch the string at second pinch pin  227 . The motion of the string also causes the first pinch pin  233  to slide through slotted opening  224 , causing the first pinch pin  233  to pinch the string  26  against the wall of downward opening  225 . The tension of string  26  can be adjusted using a threaded screw  234  with a removable head  235 . A ball shaped section  236  on screw  234  engages a mating socket  237  in housing  223 , permitting the screw to exert downward force on lever  232 . Screw  234  passes through a threaded pin  238  in lever  232 , the threaded pin being a loose fit in the lever, so as to allow alignment of the screw as lever  232  moves. Turning the screw  234  so as to move the second lever  232  downward rotates lever  221  counterclockwise so as to increase tension in the string  26 . The positional relationship between the first pinch pin  233  and the second pinch pin  227  can be varied in the same manner as described in connection with  FIGS. 1-3 . 
       FIGS. 6 and 7  illustrate the embodiment of  FIG. 5  in various conditions.  FIG. 6  is a sectioned side view showing a side view of the mechanism where the housing between two adjacent clamping mechanisms is cut away.  FIG. 6  shows the mechanism with the screw  234  turned to completely retract lever  232 . In this condition, there is space between first pinch pin  233  and the wall of downward opening  225  and a space between second pinch pin  227  and lever  221  so as to permit a string to be easily threaded through the clamping mechanism.  FIG. 6  also shows an alternate view of pivot pin  231 . 
       FIG. 7  shows the method of installing the moveable components of the embodiment of  FIG. 5  into the housing  223 . Adjacent to pivot pin  231  is a protrusion  241  on lever  221 . Pivot pin  231  engages a mating socket  242  in housing  223  that is rounded to correspond with the shape of the pivot pin  231 . Mating socket  242  has a further opening  243  in the direction of the string pull from mating socket  242  that roughly corresponds to the shape of the protrusion  241 . 
     The first step in the installation sequence is to place the pivot pin  231  into the mating socket  242  in housing  223 . Once the pivot pin  231  is in contact with the mating socket  242 , the lever assembly is rotated in the direction indicated by the arrow  244 . As the assembly is rotated, the screw  234  is inserted through mating socket  237  in housing  223  until the ball shaped section  236  is in contact with mating socket  237 . The removable head  235  is then reattached to screw  234 , preventing the screw  234  from falling away from housing  223 . 
     When the lever assembly is installed in the housing  223 , the protrusion  241  engages its corresponding opening  243  in the housing  223 . In the range of motion allowed by the screw  234 , protrusion  241  prevents the lever  221  from movement other than in the axial direction about pivot pin  231 . 
     Irrespective of the locations of the pinch pins, the pinching forces and the forces required to adjust the string tension may be set as desired by making the lever arms of appropriate length. The elementary principles of mechanics may be applied in making the calculations. 
     What has been described is a system for clamping the strings of a stringed musical instrument and for tuning the instrument. In this disclosure, there are shown and described only the preferred embodiments of the invention, but, as aforementioned, it is to be understood that the invention is capable of use in various other combinations and environments and is capable of changes or modifications within the scope of the inventive concept as expressed herein.