Abstract:
A string clamping and tuning mechanism for stringed instruments is disclosed. String tension, through lever action, provides the clamping force on the string to anchor the string. A screw adjusted stop causes a change in the position of the lever system to increase or decrease the tension in the string.

Description:
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 end enlarged (as by having an attached ball or small ring), while the other end (the free end) is unfinished. 
     One common tuning system in use today creates tension in the strings by wrapping the free ends around tuning posts fixed at the head end of the instrument neck, which posts are turned 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 alternate 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 system, the free end of the string is held in a clamp which ordinarily requires a tool of some sort to operate. This is obviously inconvenient at any time, but particularly in the course of a performance. 
     The present invention permits the free end of the string to be clamped without using tools, using the tension in the string itself to provide the clamping force. In one of its aspects, the present invention also provides (in combination with the string tension actuated clamp previously mentioned) a tuning system which has greater stability than the worm gear tuning posts of the past. 
     Accordingly, it is an object of the present invention to provide a system for clamping the strings of a stringed musical instrument wherein the force holding the string is provided by the tension in the string itself. It is a further object of the invention to provide a stable tuning system for a stringed musical instrument combined with a clamp actuated by string tension. 
     SUMMARY OF THE INVENTION 
     The present invention utilizes the tension in a string to provide a clamping force on the string, restraining the string from slipping longitudinally (and thereby altering the tension). The clamping force is obtained by using one or more levers 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, the structure of the musical instrument to which the invented clamping means is attached is not shown in the drawings. Nevertheless, 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, a single simple lever (one lever associated with each string) is aligned with its axis substantially perpendicular to the direction of string pull. Each string passes over the end of its associated lever such that the force of the string pull is exerted on the lever arm, and the lever tends to turn. The lever arm opposite the point of application of string pull is arranged to pinch the string against a fixed stop, thereby anchoring the string. Excess string may be cut off. 
     In a second embodiment of the invention, string pull is exerted on the end of a lever as in the first. embodiment, but a second lever, pivotally connected to the first lever and bearing against a stop, is used to provide the string pinching force. 
     In a third embodiment of the invention, instead of bearing against a fixed stop, the second lever bears against an adjustable screw, thereby providing a means for adjusting string tension for tuning purposes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partially sectioned trimetric view of a first embodiment of the invented system, shown installed near the tail of a stringed musical instrument. 
     FIG. 2 is a side sectioned view of a second embodiment of the invention. 
     FIG. 2A is a partial side sectioned view of an alternate construction of the embodiment of FIG.  2 . 
     FIG. 3 is a side sectioned view of a third embodiment of the invention. 
     FIG. 4 is a side sectioned view of the embodiment of FIG. 3, with the clamp open to accept a string. 
     FIG. 5 is a side sectioned view of the embodiment of FIG. 3 with greater tension applied to the string. 
     FIG. 6 is a side sectioned view of an alternate construction of the embodiment of FIG.  3 . 
     FIG. 7 is a side sectioned view of an alternate construction of the embodiment of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As seen in FIG. 1, a housing  10 , which supports the mechanism of a first embodiment of the invention, is set into the face  11  of a stringed musical instrument body. One end of the strings  12  are bent around the ends of levers  13 , as shown, and the remote ends are anchored at an appropriate location, as will be understood by those skilled in the art. The invented mechanism may, for example, be positioned near the tail of a violin, in which case the strings preferably pass over a bridge  16 , and conventional tuning mechanisms may be provided at the distal ends of the strings, i.e., at the head. Three strings are shown in the figures for illustrative purposes, but it will be understood that any number of strings may be utilized, as required by the instrument involved. 
     The levers  13  are rotatable about pivot pins  14 , which are fixed to the housing  10 . Lever rotation is limited by pinch pins  15 , also fixed to the housing  10 . Element  15  is called a pinch pin because the string is pinched by it against the lever  13 . It will be appreciated that the “pin”  15  need not be a distinct part, but could, as well, be integral with the structure of the housing. 
     Assuming, for example, that rotatable tuning posts are used to tune the instrument, upon installation each string is first wrapped around a tuning post and then passed over the bridge and through the space between lever  13  and pinch pin  15 . The free end of each string is then pulled taut in a generally downward direction (as denoted by the numeral  17  in FIG.  1 ). This motion of the string causes the lever to rotate about the pivot pin and pinch the string at pinch pin  15 . Turning the tuning post to increase tension on the string then causes the pinch pressure to increase. The amount of pinch pressure relative to 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 and the lever  13  to the pivot pin  14 , and  2 ) the distance between the pinch pin  15  and the pivot pin  14 . The actual pinch force is influenced both by the lever arm ratio and the angle at which the pinch pin  15  presses against lever  13 . 
     Additional mechanical advantage to pinch the string may be obtained by including a second lever, as shown in the embodiment illustrated in FIG.  2 . The elements in the alternate 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 . 
     Only a cross sectional view showing the details of one string mechanism is shown in FIG. 2, it being understood that the mechanism is replicated for each string of the instrument. According to the embodiment of FIG. 2, a housing  110  contains a plurality of levers  113 , each corresponding to one of the strings  12  of the instrument. Each lever  113  pivots around a corresponding pivot pin  114 . Additionally, a second lever  121  (which has a clevis-like shape) pivots around second pivot pin  122 . The second pivot pins  122  are not attached to the housing  110 , but are rather attached to the respective lever  113 . Tension in string  12  causes the lever  121  to bear against stop pin  123  (which is attached to housing  110 ). Pinch pin  115  is therefore pressed against string  12 , pinching it and preventing the string from slipping. The pinching function need not be performed by a separate part ( 115 ), but as illustrated in FIG. 2A, “pin”  115  can be integral with lever  121  (as indicated by the numeral  115 ′) 
     As shown in FIG. 2, pivot pin  114  is shown positioned below pivot pin  122 . This relationship is not required, however. Pivot pin  114  could, for example, be located coincident with pivot pin  122 , or even above it, depending on the mechanical advantages desired in a particular case. 
     FIG. 3 illustrates an embodiment similar to that of FIG. 2, but further includes means for changing the tension in the strings for tuning purposes. In the embodiment of FIG. 3, the stop pin  123  is replaced with a threaded screw  231 . A ball shaped section  232  on screw  231  engages a mating socket in housing  210 , permitting the screw to exert downward force on lever  221 . Screw  231  passes through a threaded pin  233  in lever  221 , the threaded pin being a loose fit in the lever, so as to allow alignment of the screw as lever  221  moves. Turning the screw  231  so as to make the second lever  221  rotate clockwise (as shown in FIG. 3) will increase tension in the string. The positional relationship between pivot pins  214  and  222  can be varied in the same manner as described in connection with FIG.  2 . 
     FIGS. 4 and 5 illustrate the embodiment of FIG. 3 in various conditions. FIG. 4 shows the mechanism with the screw  231  turned to completely retract lever  221 . In this condition, there is space between pinch pin  215  and lever  213  so as to permit a string to be easily threaded through the instrument. FIG. 5 shows the embodiment of FIG. 3 with even more tension applied to the string than is illustrated in FIG.  3 . Screw  231  has been turned to move the lever  221  downward, thereby rotating lever  213  so as to increase tension. 
     FIGS. 6 and 7 depict further alternate constructions of the invention, and illustrate the versatility available in the locations of the pivot axes. 
     FIG. 6 shows an alternate construction of the embodiment of FIGS. 3-5. In this construction, the first lever  313  and the second lever  321  pivot around the same axis, pivot pin  322 . The first lever  213  in the construction of FIG. 4 is shown bent and pinch pin  315  moved laterally so that the motion of pinch pin  315  is about 90° as compared to the motion of pinch pin  215  in the construction shown in FIG.  3 . The lever  321  is shown bent to illustrate that so long as the desired lever ratios are obtained, the directions taken by the lever arms are not important. 
     FIG. 7 illustrates a variant of the embodiment illustrated in FIG. 6 wherein the lever  413  is not bent, as is the lever  313  in FIG.  6 . In both the embodiments of FIGS. 6 and 7, the two levers are shown rotating about a common axis (shown as pivot pins  322  and  422 ). While presently preferred, it is not necessary that the axes be coincident. If desired, the pivot pins for the two levers could be carried by the housing at locations other than as shown in the figures. 
     Irrespective of the locations of the pivot 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 Persons skilled in the art will no doubt be able to make various modifications and adaptations of the invention but yet be within the inventive teachings disclosed both explicitly and implicitly herein. The limits of the invention sought to be protected are defined by the following claims.