Abstract:
A tremolo assembly is implemented for modulating the string tension on a guitar by mounting a bridge carrier on a sliding mount with the fore and aft displacement thereof effected by a transverse cam implemented fulcrum piece opposing the string tension. The sliding mount limits the bridge translation to the string plane, thus resolving all bending and lateral string forced. A forwardly and rearwardly aligned set of manual levers is then useful in modulating downward and upward the tension of the strings in unison against a set of bias springs.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to tremolo devices useful in modulating the pitch of the strings on a guitar, and more particularly to a tremolo assembly that allows for linear modulation of an array of individually adjustable string terminals in response to the movement of a tremolo bar.  
         [0003]     2. Description of the Prior Art  
         [0004]     The rendition of music is often found more pleasing when the individual sounds are varied by small pitch modulations which combine in complex beats and harmonics with other concurrent sounds to produce a rich tone pattern. In popular music the convenience in attaining this pitch modulation is a highly desired facility and stringed instruments like guitars have had some mechanical developments in the past for the convenient rendition of this effect. The rendition of this effect, however, entails substantial manual facility which has led to a simplification of the mechanism itself, most often resulting in a structure that modulates all the strings in unison. With time and experience the richness of sound obtainable by these modulations became a matter of some further refinement and those engaged in the endeavor now desire the facility of selective modulation both upward and also downward from the selected tone with precise adjustment control over each excursion.  
         [0005]     The past development of devices for manually modulating the pitch of a guitar has been extensive, to a point of acquiring its own nomenclature now referred to as a ‘tremolo,’ and one early example of such a mechanism can be found in the teachings of U.S. Pat. No. 2,741,146 to Fender. This and similar tremolo mechanisms are characterized by a pivotal structure supported in a transverse recess adjacent the string bridge and pivoted by manual articulation of a cantilevered bar, known as the tremolo bar, against a spring bias, thereby modulating the tensioning contact, and thus the pitch, of the strings. Various modifications of this general arrangement have been developed since then, as exemplified by the teachings of U.S. Pat. Nos. 6,015,945 to Borisoff, 6,084,166 to Lee, 5,783,763 to Schaller, et al. and others. While suitable for the purposes intended devices of this nature rely on pivotal motion of a common transverse structure against a bias spring, thus resulting in a string contact which induces repetitive application of bending stresses thereto. Since the pivotal center of this displacement is determined by the balance between the string contact and a return spring the resulting equilibrium contact position is poorly defined and the tuning precision of the instrument is therefore often compromised. Moreover, this same point of contact imprecision is exacerbated by the varying heights to which the various string are adjusted relative the pivotal center resulting in a resulting variation in the tremolo excursion of each string. The contact imprecision also tends to dampen string oscillations, reducing the length of time that a note is ‘sustained’ and the consequent absence of any individual string adjustment further reduces any effective adjustment for the interplay between the performer&#39;s fingers and the individual strings. A linear tremolo mechanism that allows precise adjustment of the tremolo excursions while also accommodating full adjustment control of each individual string is therefore extensively desired and it is one such mechanism that is disclosed herein.  
       SUMMARY OF THE INVENTION  
       [0006]     Accordingly, it is the general purpose and object of the present invention to provide a bridge carrier that may be linearly translated in response to manual articulation of any one of a plurality of individually cantilevered tremolo bars.  
         [0007]     Other objects of the invention are to provide a tremolo mechanism for modulating the pitch of all the strings of a guitar by way of linear displacement of a string bridge carrier.  
         [0008]     Yet further objects of the invention are to provide a tremolo mechanism for a guitar in which the range of the tremolo excursion is conveniently adjusted by advancing a single screw.  
         [0009]     Yet additional objects of the invention are to provide a tremolo mechanism effected by linear translation of a carrier supporting a bridge of a string instrument.  
         [0010]     Briefly, these and other objects are accomplished within the present invention by providing a linear tremolo mechanism installed in a bridge recess formed in the guitar defined by a generally flat bridge carrier received for longitudinal movement within a peripheral recess formed around a central cavity in the guitar surface. This fore and aft carrier movement is fixed by longitudinal slides on the edges of a base piece secured within this central base cavity that also engage the edges of the carrier. All the string ends tied to the carrier exterior by individual string end fixtures are then displaced in unison according to the fore and aft motion of the carrier, modulating the tension and thus the pitch of the strings according to the direction of their movement. To induce this linear movement a fore and aft tremolo bar are each cantilevered from one end of a spring biased transverse fulcrum piece deployed in front of the bridge carrier on adjustable knife edge pivots to articulate an adjustably extended cam opposing the front edge of the carrier.  
         [0011]     Those in the art will appreciate that this novel arrangement is particularly effective in developing both an increased and a decreased pitch modulation while also providing a very accurate knife edged pivot fulcrum for an accurately adjustable forcing point. The closely controlled linear displacement of the sliding carrier, moreover, renders the whole mechanism more accurate in retaining the preselected string tuning while also limiting any further repetitive bending, and sometimes breaking, the strings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a front view of a guitar provided with an inventive linearly articulated bridge carrier for effecting upward and also downward pitch modulations of the strings of the guitar;  
         [0013]      FIG. 2  is a perspective illustration, separated by parts, of the inventive bridge carrier and its articulation mechanism;  
         [0014]      FIG. 3  is a plan view detail illustrating the adjustment and manipulation aspects of the inventive bridge carrier;  
         [0015]      FIG. 4  is a side view detail, in section, taken along line  4 - 4  of  FIG. 3 ; and  
         [0016]      FIG. 5  is an end view detail, in section, taken along line  5 - 5  of  FIG. 3 .  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0017]     As shown in  FIGS. 1 through 5  the inventive tremolo mechanism generally designated by the numeral  10  is installed into the body BD of a guitar GT at the location usually occupied by the string bridge from which the guitar strings GS are stretched over one or more pick-ups PU to extend over the neck NC. To accommodate the mechanism the guitar body BD is modified to include a generally rectangular base cavity  11  partly surrounded by a peripheral recess  12 , with the base cavity then receiving a conforming rectangular base piece  15  secured in place by threaded fasteners  16  and  17 . A generally planar bridge carrier  20  is then positioned within the recess  12  over base piece  15  with both the opposed longitudinal edges  15   l  and  15   r  of base piece  15  recessed to accept the interior portions of corresponding parallel slides  25   l  and  25   r  with the exterior portions thereof attached by strips  22   l  and  22   r  to each lateral edge of carrier  20 . In this manner carrier  20  is engaged for sliding translation within the guitar body BD, displacing at the transverse rear edge thereof an upwardly turned lip  21  perforated with a row of openings  21   p  corresponding in number and in spacing to the number and spacing of the strings GS. Each one of these openings  21   p  then receives a screw  21   s  threadably engaged to a an end block  23  securing the ends of each individual one of the strings GS.  
         [0018]     At the forward edge bridge carrier  20  is provided with an upwardly extending bearing surface  24  aligned to oppose a cam or ball end  31   b  of an adjustable screw  31  threaded into a transverse fulcrum piece  30  deployed to pivot within a transverse cavity  13  formed in front cavity  11 . The pivoting fulcrum of piece  30  is then determined by the left and right forward edges  32   l  and  32   r  thereof, each shaped as a forwardly directed knife edge received within the waist pinch in corresponding reduced section portions of two threaded fulcrum posts  33   l  and  33   r.  A transverse spring bias arm  35  is then attached in cantilever to the rear surface of the fulcrum piece  30 , extending into the interior of cavity  13  to engage a plurality of bias springs  36  therein. Thus the tuning tension of the strings GS and that of the bias springs  36  draws both the bridge carrier  20  and the fulcrum piece  30  forward, with the forward translation of the carrier  30  then opposed by contact between the ball end  31   b  and the bearing surface  24  while the forward translation of the fulcrum piece, in turn, is limited by the opposing contact between the knife edges  32   l  and  32   r  and the corresponding posts  33   l  and  33   r.    
         [0019]     It will be appreciated that the foregoing arrangement resolves all fore and aft motion of the carrier  20  at the contact point between the spherical surface of ball end  31   b  and the vertical plane of the bearing surface  24 . In consequence this contact geometry essentially fixes the carrier motion to a horizontal plane that is further so limited by the longitudinal slides  25   l  and  25   r,  thereby eliminating all bending input to the strings GS. Moreover, the lever multiple advantage of the arm  3   5  relative the vertical spacing between the ball end  31   b  and the knife edges  32   l  and  32   r  allows for manipulative convenience in both directions, effected by a forwardly cantilevered tremolo bar  37  and a rearward tremolo bar  38  extending from arm  35 . The geometric multiples of these cantilevered tremolo bars reduce even further the manual force levels required from the performer.  
         [0020]     Those in the art will appreciate that in this arrangement the sole and substantial mode of carrier motion obtained by the manipulation of each of the tremolo bars is a linear motion in the plane of the strings GS. Thus the string ends are moved in unison exactly along their tuning axes allowing for precise control over their pitch modulation without any sound degradation or loss attributed to the mechanism. Moreover, the neutral point of this mechanism is developed at the hard cam interface between the ball end  31   b  and the surface  24 , a hard interface that renders the tuning both positive and fixed. Further tuning precision is then obtained by the knife edge contacts of the edge segments  32   l  and  32   r  within the waist recesses on posts  33   l  and  33   r  with one edge segment  32   l  formed as a notched planform to fix and resolve all lateral force components by capturing the waist of post  33   l  in the notch.  
         [0021]     Those in the art will further appreciate that the cam interface between the ball end  31   b  and its opposed surface  24  can be variously implemented by analogous mechanisms that resolve pivotal articulation into linear displacement. In each instance, however, it is the assembly convenience and the hard well fixed contacts that provide the necessary precision for effective use in the course of a performance. Furthermore, full adjustment convenience of each of the individual end blocks  23  is retained, including set screw pairs  23   s  for controlling the height of each string. In this manner all the tuning and adjustment features that are desired by a performer are retained in a mechanism that also accommodates tremolo manipulation.  
         [0022]     It will be appreciated that the foregoing mechanism is particularly convenient in the course of adjusting or servicing the guitar once all the tension of strings GS is released. In this condition the bias arm  35  is free to pivot around the knife edge pivots formed by the interface of edges  32   l  and  32   r  with posts  33   l  and  33   r,  releasing the tension of bias springs  36  and allowing the disengagement of the fulcrum assembly. Once the fulcrum mechanism is removed the carrier  20  can be disengaged from the base piece, thus effecting a full disassembly that allows complete inspection, repair and adjustment. These conveniences are particularly significant for those performers that seek the necessary controls for optimizing tone quality of the instrument before a performance. Thus a simple and effective mechanism is provided that is particularly useful by those seeking optimum sound production.  
         [0023]     Obviously many modifications and variations are possible without departing from the spirit of the invention instantly disclosed. It is therefore intended that the scope of the invention be determined solely by the claims appended hereto.