Patent Publication Number: US-2016232881-A1

Title: String bender attachment for guitar vibrato

Description:
BACKGROUND OF THE INVENTION 
     The present invention adds an intermediate part between the handle and string bar of a vibrato unit of the type most commonly referred to as a Bigsby® Vibrato. The string being bent or changed in pitch is attached to this part, rather than the string bar, as are the balance of the string set of the guitar. By manipulation of the handle of the Bigsby® unit in the usual manner toward or away from the body of the guitar, all strings, including the one attached to intermediate part are given a vibrato by slight rotation of the string bar and attached handle bracket. However, when handle is moved parallel to body toward strings, only the string attached to intermediate part is stretched, by a precise interval, increasing the pitch of the attached string by one half, or generally a full tone. The position of the handle is adjustable before its movement parallel to body, placing handle in the most convenient place for player, by an adjustment screw on the intermediate part. A second adjustment screw on the same part controls the final position of the part and thus the pitch of the raised note. The additional bending function is quickly and easily added to a standard Bigsby® Vibrato, and can easily be removed, and original parts replaced, restoring original appearance and function without any damage or disfigurement to either the vibrato or the guitar to which it is attached. 
     In the years following the invention and refinement of the pedal steel guitar during the 1950-1970 period, players of the electric guitar desired a way to simulate the “bend”, which is the gradual variation of one note&#39;s pitch from one defined note to another defined note, rather than an abrupt change to another note as would be achieved by simply fretting the string one or two frets higher on the guitar&#39;s neck. This gradual, continuous variation is what gives the pedal steel its distinctive sound, as differentiated from the earlier Hawaiian steel guitar, where several notes at once were all given an identical slurred change to another pitch. The ability to vary notes smoothly to another note one or two at a time, while leaving the rest of the chord&#39;s notes stationary, was a new sound, and quickly became a fixture of the musical style known a “Country Music”. 
     It was obvious that it would not be practical to add all the features of the pedal steel guitar to the standard electric guitars of the time, since many mechanical parts were required, and the forces involved in changing several notes at once would not only take more force than the player could readily spare, without interfering with playing, but the changes in total string tension on the neck of the guitar, would result in distortion of the neck itself, impairing tuning and string positions relative to the frets. It was found that one string could be fitted with a device to change its tension, and thus pitch, with an accurate stop at each of the two notes achieved, without undue loss of tuning accuracy of the remaining 5 strings, thus the string bender was born. 
     The first successful and well known unit was by Gene Parsons, and Clarence White, U.S. Pat. No. 3,512,443, of 1970. This required hollowing out a solid body guitar and adding several rods, springs, and levers internally, to allow raising the “B” string to “C#”, which has been the preferred string and change in pitch used till the present, in devices of this type. The change is achieved by lowering the neck of the guitar when change is desired, and one end of the shoulder strap of the guitar then pulls on a lever carrying the strap button. The weight of the guitar which normally carried by this end of the strap is balanced by a spring attached to the lever. Several more recent patents of the same basic type of mechanism are: U.S. Pat. No. 3,686,993-Fender-1972, U.S. Pat. No. 4,354,417-Glaser-1982, U.S. Pat. No. 5,481,954-Parsons-1996, and U.S. Pat. No. 5,567,897-McEwen-1996. 
     Other units have been created to bend a string, or in some cases, two strings, which don&#39;t require the guitar to be hollowed out, and mount on the surface, near the bridge, and are operated by wrist, palm or finger pressure. Such examples are: U.S. Pat. No. 3,479,917-Zitnik-1967, U.S. Pat. No. 5,140,884-Bowden-1990, U.S. Pat. No. 7,329,808-Davis-2008, and U.S. Pat. No. 7,696,420-Thompson-2010. All these are much simpler than the shoulder operated units, and are installed without severely altering the body of the guitar, which is non-reversible, and generally alters tone and response of guitar somewhat, as well as diminishing the value of a rare or vintage guitar. 
     Another actuation method is seen in U.S. Pat. No. 4,534,670-Borisoff-1985, which used a lever extending over the lower bout and reaches behind the body of the guitar to be actuated by hip or leg action of the player. This seems to work well for some, but requires removal of the lever to place guitar in its case. 
     While the refinement of the string bender has occurred, the vibrato units have also been refined, and today, a very large number of different models are available. All of these create a change in string pitch, but on all 6 strings at one time, and generally not to a specific alternate note, although some complex units exist, that will adjust the amount of change of each string pitch proportionately, so that the chord will remain true in its intervals, even as it is raised or lowered by the vibrato unit. Still, after 60 years, the Bigsby® Vibrato is still a favorite, and is still sold in large quantities, and is supplied as standard equipment on some models from almost all manufacturers. Its known limitations are its tendency to not return to pitch after large excursions in pitch, limited amount of total range of pitch variation, excessive friction in some models, and limited variation in string departure angle, which can cause either excessive or inadequate down pressure on the bridge of guitars so equipped. Still, its distinctive, classic appearance, surface mounting, availability in many models, and ability to produce a pleasant, modest amount of vibrato, make it desirable to the point that many players will have no other type of vibrato, and some, in fact, will not have any guitar without a Bigsby® Vibrato. 
     A number of guitars have been built having a bender of one type or other incorporated on a guitar carrying a Bigsby® Vibrato, but the string being bent is detached from the rotating shaft and connected only to the separate bending unit. Thus the vibrato occurs only on 5 strings and bending occurs on one string which no longer has vibrato capability. It would be desirable to produce a device for the Bigsby® Vibrato which would allow full vibrato on all 6 strings but allow one of these strings to be tensioned to a different pitch while retaining any vibrato being imparted to the other 5 strings. It also would be desirable to produce both the vibrato and bend with one handle which is convenient and readily accessible to the player&#39;s hand without major disturbance to the hand as it picks notes or chords. It also would be desirable to allow the handle to be moved aside for occasions when neither bending nor vibrato is desired. 
     It would also be desirable to add bending capability without altering or defacing the guitar or the Bigsby® Vibrato in any way, allowing restoration to pre-bender status merely by removing b-bender components and replacing original handle. 
     SUMMARY OF THE INVENTION 
     One object of the present invention is to add the capability of raising the pitch of one string of a guitar to a note either one half tone or one full tone above its normal tuned pitch, and adjusting the raised pitch to precisely blend with one or more of the other, unmodified 5 pitches, to create a correct chord, or interval. This requires precision and repeatability of the motion imposed on the affected string, and the capability of adjusting the exact amount of tension increase, and subsequent pitch rise of the affected string. 
     Therefore another object of the present invention is to create a precise means of stopping the string travel at both its un-actuated or normal state, and at its actuated or raised state. 
     Another object of the present invention is to allow the pitch of one string, to be raised without compromising the pitch of any of the other 5 strings. 
     Another object of the present invention is to create the precise variation in pitch of one string, utilizing only the same handle which is used to produce the normal vibrato effect of the Bigsby® Vibrato unit. The handle thus is used to produce a small, non-precise variation in pitch of all 6 strings (vibrato), which varies during the operator&#39;s operation of the handle, as well as a precise, larger variation, of one string, which is superimposed upon the vibrato pitch variation of all 6 strings. It should be noted that in normal vibrato mode, the pitch variation of each of the 6 strings of the guitar will be slightly different, as each string has a different diameter, tension, rate of tension change with length variation, rate of pitch variation with length variation, and in fact operates at slightly different radius about the rotating shaft as it is rocked by the handle and handle bracket. This last effect is due to the stretching characteristics of the string being controlled by the core and not the winding of the wound strings, the core of each wound string operating at a slightly different radius about the shaft. 
     Another object of the present invention is to utilize handle motion essentially parallel to the top of the guitar to produce the large, precise pitch rise of one string, while utilizing handle motion toward or away from the top of the guitar, to produce the smaller, non-precise pitch change of all 6 strings simultaneously. 
     Another object of the present invention is to allow easy removal of original handle and handle bracket of the Bigsby® Vibrato unit, and replace it with the assembly previously described, by removing one screw, sliding the original handle bracket off the shaft, and replacing with the new aforementioned assembly, and installing and tightening one screw. 
     Another object of the present invention is to retain the actuation forces, original vertical positioning, and leverage of the original Bigsby® Vibrato unit, when utilized as a vibrato. 
     Another object of the present invention is to provide a low operating force at the handle in raising the pitch of one string a half or full tone by adding an assist spring to balance a variable portion of the normal string tension when in the un-actuated position. Furthermore, said spring should be of spring rate low enough so that when string is raised a half or full tone, the force of the spring decreases a minimal amount. Thus when string force rises as it is stretched tighter to higher pitch, the decrease in spring length (extension spring), or increase in length (compression spring), causes as small a change in spring forces as is practicable in the space available for the spring. Also, the basic assist force of the spring can be adjusted by adjusting the spring to two or more initial extension lengths, giving more or less assist. 
     Another object of the present invention is to reduce actuation forces required by incorporating a second pivot axis on the handle bracket which provides a location to mount the puller and, by utilizing the handle and its separate pivot axis, to give a compound leverage to the player. 
     Another object of the present invention is to allow variation in the mechanical advantage of the lateral handle motion, by varying the position of a friction-reducing bearing between the two moving parts of the new assembly, thus changing the radius of contact point of each moving part relative to its pivot center. This in turn varies force required on handle to actuate string bending motion, as well as handle travel required. 
     Another object of the present invention is to add a contour to the handle of the new embodiment allowing easier grasping by one finger, which would in some cases be used to provide the lateral motion parallel to guitar top in raising one string to its half or full tone raised pitch. This shape would prevent slipping of the finger along the handle, altering mechanical advantage, and changing operating force required. The contour provides both constant operating position and constant sensitivity of the pitch variation. 
     Another object of the present invention is to provide a swing-away motion to the handle, in direction opposite to actuation direction, to mimic the same function of the original handle, This allows the handle to be moved out of the way for actions such as strumming the guitar, in which case the hand or pick could impact the handle, if left in position for bending or vibrato. 
     Another object of the present invention is to provide for the adjustment of the start or un-actuated position of the handle&#39;s lateral position. This affects the reach necessary for the player to grasp the handle with one or more fingers, and is desirable to accommodate a player&#39;s hand size, and preferences. 
     Another object of the present invention is providing easy adjustment of both aforementioned start position of handle, as well as actuated position, which controls final raised pitch, without the necessity of tools. 
     Another object of the present invention is provision for easy adjustment of friction controlling lateral motion of handle without necessity for access underneath handle bracket, as is case with present Bigsby® handle. This friction is necessary to prevent handle from falling away from accessible position when it is desired to be instantly available for use, but must be low enough to not hinder lateral motion to raise a string a half or full tone. 
     Another object of the present invention is to provide a common assembly to adapt the string bending function to multiple models of Bigsby® Vibrato. Domestic models have for many years utilized a ⅜ inch diameter shaft about which the strings wrap, and to which the handle bracket is attached. Imported models use a 10 mm diameter shaft, which is nominally 0.019 in. larger in diameter. By using a non-circular mounting hole in the handle bracket of the new assembly, a single assembly can be made, which will attach solidly and simply, to either diameter shaft, and will be firmly retained in position by one setscrew. 
     Another object of the present invention is to retain the original feel and sensitivity of the Bigsby® Vibrato unit after adding the string bending capability to the unit. For this reason the string attached to the string bending assembly must pass as close to the mounting shaft as is practicable without rubbing upon the shaft. This ensures that the string motion in vibrato mode will be essentially as before the modification since the effective operating radius for that string will only be a tiny bit more than it would be if touching the shaft. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The features and operation of the string bender attachment will become apparent, when all the component parts are defined, and their relations to each other and the existing Bigsby® vibrato are explained. The item numbers are consistent in referring to the same part in all drawings. 
         FIG. 1  is a plan view of the string bender attachment, mounted on a guitar, showing positions of the handle and puller both when released and when actuated to raise the pitch of attached string. Also indicated is an alternate retracted position of the handle where it will be conveniently out of reach of player&#39;s right hand when neither vibrato nor bending is desired. 
         FIG. 2  is an exploded view of the string bender attachment, along with a Bigsby® Vibrato (minus its original handle assembly), and typical bridge and pickup assembly. 
         FIG. 3  is an assembled view of the string bender attachment mounted on a Bigsby® Vibrato, along with bridge and pickup assembly. 
         FIG. 4  is a side view of the handle bracket, showing configuration of aperture designed to solidly attach handle bracket to either a ⅜ in. diameter shaft or 10 mm diameter shaft, as would be encountered on domestic or imported versions of Bigsby® vibratos, respectively. 
         FIG. 5  is a bottom view of the vibrato unit, when normal tuning is desired, and handle is not displaced laterally toward strings, parallel to top of guitar. This also would apply if vibrato alone were being used, and handle were being moved perpendicular to top of guitar, varying pitch of all strings. 
         FIG. 6  is the bottom view as in  FIG. 5 , but with the handle moved toward strings, parallel to top of guitar, and puller is pivoted, providing increased string length to one string and consequently raising its pitch. The vibrato on all 6 strings may be employed at same time, by handle being moved perpendicular to top of guitar. 
         FIG. 7  is an exploded view of the handle bracket and puller, minus the handle and associated hardware, to indicate parts and surfaces contacted during operation. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows a plan view of a typical guitar body  1  with a bridge-pickup assembly  2  mounted on its top surface and a vibrato unit carrying b-bender attached to the same top surface with screws  44 . The vibrato unit is of a type commonly referred to as a Bigsby® Vibrato, and is characterized as having a frame  40  which supports a string bar  41  pivotally mounted in frame  40 , about which the string set of the guitar is wrapped and retained by pins mounted to shaft of string bar. Frame  40  also supports tension roller  42  which is used on some models of the Bigsby® Vibrato to lower the path of the strings as they exit the vibrato unit to provide a greater angular wrap and resultant down force on top of string saddles on bridge-pickup assembly  2 . A handle bracket  10  is rigidly attached to string bar  41  and carries handle  20  which is pivotally attached to handle bracket  10  by screw  21 , allowing handle  20  to approach strings as shown by CCW alternate position  20 A, or swing completely away from strings as shown by CW alternate position  20 B. The typical playing position of handle  20  is essentially parallel to strings typified by string  51 , although its static position is determined by setting of stop screw  32 , and CCW actuated position  20 A is determined by setting of tuning screw  33 . These two positions of handle  20  are due to the contact of bearing  24  ( FIG. 2 ) against side of puller  30  which mounts both stop screw  32  and tuning screw  33 . Puller  30  is shown in its CCW actuated position  30 A, which corresponds to handle position  20 A. There is no position of puller  30  corresponding to handle posit  20 B, since its rotation in CW direction is limited by stop screw  32 . Before, after, or during CCW rotation of handle  20  in plane essentially parallel to top of guitar body  1 , handle  20  can be moved toward or away from body  1  as is the customary actuation of the handle of a Bigsby® Vibrato to create its customary lowering or raising of pitch respectively of all 6 strings. This action will cause handle bracket  10  and attached string bar  41  to rotate in frame  40  and decrease or increase respective wrap of strings about string bar  41 . Puller  30  pivots upon rigidly attached pin  31  which rotates in hole  14  ( FIG. 2 ) of handle bracket  10 . String  51  is terminated by string ball  50  contacting puller  30  and thus when string bar  41  rotates in frame  40 , string  51  is loosened or tightened since string  51  passes string bar  41  either touching surface of string bar  41  or slightly above it, creating variation in its length the same as or slightly greater than balance of string set. 
       FIG. 2  shows all the component parts of the string bending attachment and their relationship to each other and the existing. Bigsby® Vibrato (minus its original handle assembly) in exploded view as well as bridge-pickup assembly  2 . 
     Handle bracket  10  as attached to shaft  41  and is firmly retained by setscrew  11  using tapped hole in bottom of handle bracket  10  and bottoming in existing recess in shaft  41 . This locates handle bracket  10  both axially and rotationally on shaft  41 . Pin  12  is rigidly retained in handle bracket  10  and serves as mounting point for end of extension spring  13 . The other end of spring  13  is attached to pin  34  in end of puller  30 . Spring  13  is selected to counteract a portion of the tension of the string  51  and reduce force necessary on handle at position  26  to move puller  30  to point where tuning screw  33  contacts handle bracket  10 . Spring  13  and string  51  each invoke a torque load on puller  30  about its pin  31 , but in opposite directions. Moving pin  34  to hole  37  in puller  30  will reduce spring force and provide less assist to player in actuating handle  20  at position  26 . Washer  36  serves to separate puller  30  from handle bracket  10  to keep puller in same plane as handle  20  which is separated from handle bracket  10  by friction washer  23 . Handle  20  is held against friction washer  23  by screw  21  and washer  28  and located radially by bearing  22 . Screw  21  is retained in handle bracket  10  by threads in aperture  15  and adjusted to provide proper level of friction to prevent handle  20  from falling out of reach of player when guitar is in normal playing position. 
     The cumulative tension loads of strings  51 - 56  produce a torque on string bar  41  and attached handle bracket  10  which is balanced by spring  46  producing an equal torque in opposite direction. Variations in spring rate and free length of spring  46  as well as variations in string diameters and tuning tensions of strings  51  thru  56  will cause variations in static rotational position of string bar  41  and subsequent static rotational position of handle bracket. This will cause the static position of surface  17  ( FIG. 7 ) of handle bracket  10  to deviate from parallel to top of guitar and cause handle  20  to have the same deviation. This can be corrected to some degree by selection of spring  46  from several different lengths and spring rates available from numerous suppliers. 
     Tension roller  42  is retained in frame  40  by pin  43  which serves as a shaft allowing slight rotation of roller  42  as handle  20  is moved toward or away from top of guitar to produce vibrato. String  51  when moved by puller  30  will move a greater amount than any of the 6 strings normally see in vibrato application, and will normally slip on surface of roller rather than cause rotation since roller is retained by 5 strings exerting much greater torque. For this reason, a slight amount of lubricant on string at contacting area will prevent excessive wear or noise. 
     Puller  30  is attached to handle bracket  10  by rigidly attached pin  31  which is inserted into close fitting hole  14  in handle bracket  10 . Puller  30  is rotationally stopped on handle bracket  10  by tuning screw  33  which contacts handle bracket  10  when actuated and serves to limit rotation of puller  30  in CCW direction when viewed from top as in  FIG. 1 . Puller  30  is rotationally stopped in CW direction by stop screw  32  which contacts string bar  41  when puller  30  is not actuated and no force is being applied to handle  20 . Since string bar  41  is rigidly attached to handle base  10  the operational travel or stroke of puller  30  is determined by the gap between screw  33  and handle bracket  10  when no actuation of handle  20  or puller  30  is occurring. String ball  50  is attached to end of string  51  and is retained in thru hole  35 . 
     Handle  20  is attached to handle bracket  10  by screw  21  passing thru bearing  22  which is inserted in hole  27  in end of handle  20 . Friction washer  23  serves to separate handle  20  and handle bracket  10  and allows adjustment of rotational drag on handle  20  to prevent handle falling away from player&#39;s hand when not being touched but allowing rotating to position  20 B. Screw  21  is tightened in threaded hole  15  in handle bracket  10  to set drag from friction washer  23 . 
     Contact bearing  24  is attached to handle  20  by screw  25  allowing a low friction contact between handle  20  and side surface of puller  30  when actuating puller to raise string pitch. There may be  2  or more holes in handle  20  allowing a variation in positioning slide bearing  24  and consequently the overall mechanical advantage of handle  20  to puller  30 . Item  24  can take several forms and can be as simple as a nylon tie-wrap retained in one of the holes in handle  20  and wrapped around side to provide a low friction surface to bear on side of puller  30 . It is understood that optimum performance would require a slight lubrication of pin  31  as it fits in hole  14  as well as on both surfaces of washer  36 . 
     Typically handle  20  is kept in contact with puller  30  at contact bearing  24  when guitar is in playing position by drag from friction washer  23  after careful adjustment of screw  21 . 
     The frame  40  of the vibrato is attached to top of guitar by screws  44  and also retains bearings  45  which allow shaft  41  to rotate freely along with the rigidly attached handle bracket  10 . 
       FIG. 3  shows items of  FIG. 2  assembled with string  51  and string ball  50  located in puller  30  and stop screw resting upon string bar  41  as would appear with guitar tuned to pitch on all strings and no bending activated. 
       FIG. 4  shows the configuration of the aperture in handle bracket  10  to allow fitting to either domestic 0.375 in. diameter string bar  41  or imported 10 mm diameter string bar  41 . The configuration is a modified V-block with the setscrew  11  forcing shaft  41  securely into V form to provide positive positioning. The tiny difference in center locations of the different shaft diameters relative to handle bracket  10  is of no functional or visual consequence. 
       FIG. 5  is a bottom view of frame  40  with string bar  41 , tension roller  42 , handle bracket  10 , handle  20 , and puller  30  installed, and all strings  51 - 56  installed. String  51  passes on nearside of tension roller  42 , far side of string bar  41  and passes thru puller  30  where retained by string ball  51 (behind screw  32  this view). One of the pins for retaining strings on string bar  41  is shown as string  51  is not anchored to string bar. The other 5 strings are attached to remaining 5 pins by means of string ball  51  on end of each string. In this view the strings pass to right on nearside of string bar  41  then proceed around string bar to proceed to left on far side of string bar and pass on nearside of tension roller  42 . All strings would proceed to bridge-pickup assembly  2  (not shown) from tension roller  42 . The handle is not moved from rest position, and stop screw  32  contacts string bar  41 . Tuning screw  33  is not touching handle bracket  10  and resultant gap represents motion necessary for pitch of string  51  to be changed from B note to C# note on open string (at typical tuning). It should be noted that the initial setting of stop screw  32  varies the basic length of string  51 , and changes to this setting will require retuning of the string at opposite end of string  51  at tuner on head of guitar. It should also be noted that the setting of stop screw  32  serves to set position of end of handle  20 , relative to strings, and in fact is the primary adjustment required after installation of the b-bender attachment to place handle in convenient position relative to strings. 
       FIG. 6  is the bottom view of  FIG. 5  repeated, but with handle moved toward strings, pivoting about its screw  21 (far side) and actuating puller  30  thru contact bearing  24 . The pitch of string  51  has now been raised from B to C# (at typical tuning) and stop screw  32  has been lifted from contact with string bar  41 . Tuning screw  33  now contacts handle bracket  10  and any fine tuning of raised string pitch is accomplished by slight rotation of tuning screw  33 . The sequence of tuning the guitar&#39;s string  51  is: adjust stop screw  32  to place handle  20  where desired, relative to strings, then tune string  51  at headstock of guitar with normal tuner, then actuate handle  20 , and adjust tuning screw  33  to get pitch of raised note as desired. 
       FIG. 7  shows handle bracket  10  with surface  16  perpendicular to axis of string bar  41  and perpendicular to aperture shown in  FIG. 4 . Surface  17  is perpendicular to surface  16  and is penetrated by  2  apertures,  14  and  15 . Spring  13  attaches to pin  12  which lies parallel to string bar  41 . Aperture  15  is concentric with end of spring  46 . 
     Puller  30  has primary surface  3  and has two surfaces perpendicular to surface  3 , the first being surface  5  on formed tab  7  and the second being surface  4  on formed tab  6 . Surface  4  is perpendicular to surface  5 . Tuning screw  33  is threaded thru tab  6 , perpendicular to surface  4 . Stop screw  32  is threaded thru tab  7 , perpendicular to surface  5 . Rigidly attached pivot pin is perpendicular to surface  3 . Formed tab  7  also carries aperture  35  which is parallel to and offset from stop screw  32 . 
     In use, contact bearing  24  ( FIG. 2 ) mounted on handle  20  ( FIG. 2 ) contacts surface  8  on puller  30  causing it to pivot about pin  31  in hole  14  until tuning screw  33  contacts surface  16  on handle bracket  10 . At this same time stop screw  32  has been raised from contact with string bar  41 . Spring  13  assists in this same pivoting of puller  30 , decreasing the required force on handle  20 .