Abstract:
Various kinds of members are located on the body of an electric guitar, and strings are supported by the members at predetermined positions along the longitudinal direction. The strings are adjusted by a fine-tuning element and a harmonic tuning element. A base plate is pivotally supported on the guitar body. Each of saddles is rotatably coupled to one of saddle holders, the position of which can be adjusted in the longitudinal direction of the strings, and corresponds to one of the strings. Each saddle contacts the corresponding string at a predetermined point. Each string holder, which is located in one of the saddles, holds the corresponding string at a part that is below the contact point of the string. The fine-tuning element fine-tunes each string by changing the rotational angle of the corresponding saddle without actually changing the contact point of the corresponding string. The harmonic tuning element adjusts the position of each saddle holder in the longitudinal direction of the strings. A manipulation portion, which is located on the harmonic tuning element, tunes the harmonic of each string at a position above the base plate while the string is held by the associated string holder.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a tremolo unit for an electric guitar. 
   An electric guitar that has a tremolo unit prevents the electric guitar from being off-key by changes in the tension (pitch) of strings while playing the guitar using the tremolo unit. U.S. Patent Publication No. 4,171,661 discloses an electric guitar that has a tremolo unit. According to the guitar of the above publication, each string is locked by a bolt and a pressing member at a saddle of the tremolo unit. A fixing member is also arranged on a nut in the vicinity of a head to fix the strings. This prevents the guitar to be off-key even when using the tremolo unit. 
   However, when the strings are locked with the nut, tuning of the strings with tuning pegs is difficult. Therefore, a fine-tuning device is provided on the saddle to permit the guitar to be fine-tuned even after the strings are locked with the nut. The tremolo unit also includes harmonic tuning means, which adjusts the position of a contact point of the strings at the saddle portion in the tuning direction. 
     FIG. 10  illustrates a tremolo unit that has harmonic tuning means. The tremolo unit is mounted on the body  12  of a guitar and includes a base plate  23 , which is supported at the upper portion of the body  12  with hinge mechanisms  22  (only one is shown) such that the base plate  23  can be rotated up and down. Saddle holders  35  (only one is shown) are supported by the base plate  23  such that the saddle holders  35  can be moved forward and backward. Each saddle holder  35  corresponds one of the strings  15  (only one is shown) of the guitar. A saddle  37  is supported by each saddle holder  35  with a pin  38  such that the saddle  37  can be rotated up and down. 
   Each saddle  37  supports a pad  39 , which clamps the corresponding string  15 . A string fixing bolt  40  is threaded into each saddle  37 . Thus, the string fixing bolt  40  presses and clamps the string  15  with the clamp pad  39 . Fine-tuning bolts  42  are threaded into the rear end  230  of the base plate  23 . When each fixing bolt  40  is moved up and down with the corresponding fine-tuning bolt  42 , force is transmitted to the saddle  37  through the pad  39 . This rotates the saddle  37  about the corresponding pin  38 . Accordingly, the associated string  15  is fine-tuned. 
   Harmonic tuning bolts  49  are inserted through pin supports  35   e  formed at the rear end of the base plate  23 . A threaded hole  61  is formed in the rear end of each saddle holder  35 . The distal end of each harmonic tuning bolt  49  is threaded into the corresponding threaded hole  61  to adjust the forward and backward position of the associated saddle holder  35 . Accordingly, the harmonic of the associated string  15  is tuned. 
   However, according to the above mentioned tremolo unit, the harmonic tuning bolts  49 , which move the saddle holders  35  forward and backward, are located at a position lower than the top surface of the body  12 . Therefore, to rotate any of the harmonic tuning bolts  49 , the base plate  23  is rotated counterclockwise about the hinge mechanisms  22  by a certain amount using a tremolo bar (not shown). That is, the harmonic tuning bolt  49  needs to be moved to a position above the body  12  before being rotated. Therefore, the harmonic tuning operation is troublesome. 
   Furthermore, when the base plate  23  is rotated, the position of each saddle holder  35  is changed by force transmitted through the associated bolt  49 . This rotates the saddle  37  and thus changes the pitch of the corresponding string  15 . 
   SUMMARY OF THE INVENTION 
   The objective of the present invention is to provide a tremolo unit for an electric guitar that permits the harmonic of strings to be easily tuned. 
   Further objective of the present invention is to provide a tremolo unit for an electric guitar that permits the harmonic of strings to be tuned while keeping the strings in tune. 
   To achieve the foregoing objective, the present invention provides a tremolo unit for an electric guitar. Various kinds of members are located on the body of the guitar. Strings are supported by the members at predetermined positions along the longitudinal direction. The strings are tuned by fine-tuning means and harmonic tuning means. The tremolo unit includes a plurality of saddle holders, a plurality of saddles, a plurality of string holders, and a manipulation portion. The saddle holders are located on a base plate. The base plate is pivotally supported on the guitar body. The position of each saddle holder can be adjusted in the longitudinal direction of the strings. Each saddle is rotatably coupled to one of the saddle holders and corresponds to one of the strings. Each saddle contacts the corresponding string at a predetermined point. Each string holder is located in one of the saddles. Each string holder holds the corresponding string at a part that is below the contact point of the string. The fine-tuning means fine-tunes each string by changing the rotational angle of the corresponding saddle without actually changing the contact point of the corresponding string. The harmonic tuning means adjusts the position of each saddle holder in the longitudinal direction of the strings. The manipulation portion is located on the harmonic tuning means. The manipulation portion tunes the harmonic of each string at a position above the base plate while the string is held by the associated string holder. 
   Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
       FIG. 1  is a cross-sectional view illustrating a tremolo unit according to a preferred embodiment of the present invention; 
       FIG. 2  is a plan view illustrating a bridge saddle and harmonic tuning means; 
       FIG. 3  is an exploded perspective view illustrating the bridge saddle and the harmonic tuning means; 
       FIG. 4  is an exploded perspective view illustrating the tremolo unit; 
       FIG. 5  is a front view illustrating an electric guitar; 
       FIG. 6  is a partial cross-sectional view illustrating a further embodiment of the present invention; 
       FIG. 7  is a cross-sectional view illustrating a bridge saddle and harmonic tuning means according to a further embodiment of the present invention; 
       FIG. 8  is a cross-sectional view illustrating a modification with its major parts; 
       FIG. 9  is a plan view of  FIG. 8 ; and 
       FIG. 10  is a cross-sectional view illustrating a prior art tremolo unit. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   An electric guitar  11  that is provided with a tremolo unit  21  according to a preferred embodiment of the present invention will now be described with reference to  FIGS. 1  to  5 . 
     FIG. 5  is a view illustrating the entire electric guitar  11  observing from the top surface side. The near side of  FIG. 5  along the direction perpendicular to the surface of the sheet of  FIG. 5  is referred to as the upper direction of the electric guitar  11  and the upper side of  FIG. 1  is referred to as the front side of the electric guitar  11 . 
   The electric guitar  11  includes a solid body  12  and a neck  13 , which extends from the body  12 . A head  14  is located at the distal end of the neck  13 . Six tuning posts  16  are arranged on the head  14  and can be rotated to wind up strings  15 . A gear mechanism (not shown) is arranged on the backside of each tuning post  16 . Tuning pegs  17 , each of which is provided for one of the tuning posts  16 , are located on the head  14 . Each tuning peg  17  rotates the corresponding tuning post  16  by the gear mechanism. That is, each set of the tuning post  16 , the gear mechanism, and the tuning peg  17  tunes the corresponding string  15 . A nut  18  is located at the distal end of the neck  13  and the strings  15  contact the nut  18 . The strings  15  are pressed by a pressing member from above and tightened to the nut  18  with bolts. 
   The tremolo unit  21  is located at the center of the body  12  shifted slightly rearward. The six strings  15 , which are pressed against the nut  18 , are pressed against the tremolo unit  21 . The strings  15  are tightly stretched at a predetermined tension and substantially parallel to one another. The body  12  has a pick-up, which detects vibration of the strings and converts the vibration into electric signals. The electric signals generated by the pick-up are transmitted to an amplifier via a cable (not shown) to be amplified and subsequently converted into sound. 
   The structure of the tremolo unit  21  will now be described with reference to an exploded perspective view shown in FIG.  4 . 
   The tremolo unit  21  includes a base plate  23  and bridge saddles  24 . The base plate  23  is rotatably arranged on the body  12  by hinge mechanisms  22 . The bridge saddles  24  are arranged on the upper surface of the base plate  23  and supports the strings  15 . The tremolo unit  21  includes a tension applying mechanism  25  and a tremolo manipulation mechanism  26 . The tension applying mechanism  25  urges the base plate  23  such that the base plate  23  is rotated in a direction to apply tension to the strings  15 . The tremolo manipulation mechanism  26  is located on the base plate  23  and rotates the base plate  23  about the hinge mechanisms  22 . 
   The hinge mechanisms  22 , the tension applying mechanism  25 , and the tremolo manipulation mechanism  26  will now be described. 
   Each hinge mechanism  22  includes a bracket  28  and a bearing  30 . The bracket  28  is secured to the base plate  23  by a stud bolt  31 . The bearing  30  is coupled to the distal end of the bracket  28  by a pin  29 . A pair of pin supports  27  is formed integrally with the base plate  23  on both left and right side of the base plate  23 . Each pin support  27  includes a bore  27   a . The bearing  30  of each hinge mechanism  22  is fitted into the corresponding bore  27   a.    
   The number of the bridge saddles  24  corresponds to the number of the strings  15 . Since the bridge saddles  24  are identical, the structure of one of the bridge saddles  24  will be described with reference to  FIGS. 1  to  4 . As shown in  FIG. 1 , each bridge saddle  24  includes a saddle holder  35 . The saddle holder  35  has a front slot  35   a  at its distal end. Threaded holes  23   a  are formed in the base plate  23 . A bolt  36  is inserted downward in the front slot  35   a . The bolt  36  is then threaded into the corresponding threaded hole  23   a  so that the saddle holder  35  is secured at a predetermined position on the base plate  23 . A saddle  37  is mounted on the saddle holder  35 , and a saddle support  35   b  is formed integrally with the saddle holder  35 . The distal end of the saddle  37  is coupled to the saddle support  35   b  with a pin  38  so that the saddle  37  can be rotated up and down. A clamp pad  39  is supported by the upper surface of the saddle  37 . The clamp pad  39  is securely tightened to the saddle  37  with a string fixing bolt  40 . A threaded hole  37   a  is formed in the saddle  37 . The string fixing bolt  40 , which is inserted through the clamp pad  39 , is threaded into the threaded hole  37   a  of the saddle  37 . A string receiver  37   b , which is formed at the front end of the saddle  37 , contacts the string  15  at a contact point Z. 
   The clamp pad  39  includes a retainer  39   a , which retains the corresponding string  15  in cooperation with a receiving surface  37   c  of the saddle  37 . A fulcrum  39   b  is provided at the rear portion of the clamp pad  39  and contacts a support surface  37   d  of the saddle  37 . A through hole  37   c  through which the string fixing bolt  40  is inserted is formed between the retainer  39   a  and the fulcrum  39   b . The end of the corresponding string  15 , from which the end ring has been removed, is held between the retainer  39   a  of the clamp pad  39  and the receiving surface  37   c  of the saddle  37 . A spring  41 , which is fitted to the string fixing bolt  40 , is arranged between the clamp pad  39  and the saddle  37  for urging the clamp pad  39  upward. 
   A slot  37   e  is formed at the rear end of the saddle  37 . A threaded portion  42   a  of a fine-tuning bolt  42  is inserted downward through the slot  37   e  of the saddle  37 . A head  42   b  of the fine-tuning bolt  42  is engaged with the top edge of the slot  37   e  of the saddle  37 . A mounting plate  43  is attached to the under surface at the rear end of the base plate  23  with a screw  44 . Threaded holes  43   a  are formed in the mounting plate  43 . The threaded portion  42   a  of the fine-tuning bolt  42  is threaded into the corresponding threaded hole  43   a . Guide holes  23   b  are formed in the base plate  23 . One of the guide holes  23   b  guides the outer circumferential surface  42   c  of the fine-tuning bolt  42 . Through holes  23   c  are also formed in the base plate  23 . As shown in  FIG. 4 , a leaf spring member  47 , which has leaf springs, is attached to the lower surface of the base plate  23 . Each leaf spring projects upward through one of the through holes  23   c.    
   As shown in  FIG. 2 , the front slot  35   a  of the saddle holder  35  is offset by a predetermined distance in the lateral direction of the saddle holder  35 . 
   A pair of elongate and thick portions extend between pin holders  35   b . The saddle  37  has a pair of steps respectively formed on both side of the bottom, each of said steps being supported by the thick portion of the saddle holder (see FIGS.  3  and  4 ). 
   The tension applying mechanism  25  will now be described. 
   As shown in  FIG. 4 , a tremolo block  45  is secured to the lower surface of the base plate  23  with bolts  46 . The leaf spring member  47  is secured between the lower surface of the base plate  23  and the top surface of the tremolo block  45 . As shown in  FIG. 1 , the distal end of a leaf spring of the leaf spring member  47  is guided through the corresponding through hole  23   c  and pressed against the under surface of the corresponding saddle  37 . Therefore, the side edge of the slot  37   e  is pressed against the head  42   b  of the fine-tuning bolt  42 . This prevents the noise and improves the operational performance of the fine-tuning bolt  42 . 
   Two springs  48  are attached to the lower surface of the tremolo block  45  at one end. The other end of each spring  48  is attached to a bracket, which is fixed to a predetermined position of the body  12 . The springs  48  urges the tremolo block  45  to rotate clockwise as viewed in FIG.  1 . This rotates the base plate  23  about the pins  29  in the same direction. Therefore, tension is applied to the strings  15 , each of which is arranged on the corresponding bridge saddle  24 . 
   The tremolo manipulation mechanism  26  will now be described with reference to FIG.  4 . 
   The tremolo manipulation mechanism  26  includes a hollow bolt  51  and a nut  52 . The hollow bolt  51  is inserted through one side of the base plate  23  downward. The nut  52  is tightened to the lower end of the hollow bolt  51  to secure the hollow bolt  51  to the base plate  23 . The distal end of the bent portion of a tremolo bar  53  is detachably inserted into the hollow bolt  51 . When the tremolo bar  53  is tilted upward or downward, the base plate  23 , the bridge saddles  24 , and the tremolo block  45  of the tremolo unit  21  are slightly rotated about the pins  29  against the force of the springs  48 . 
   The main structure of the present invention will now be described. 
   The rear end of the saddle holder  35  extends toward the rear end of the base plate  23 . A rear slot  35   c  is formed in the extended rear portion of the saddle holder  35 . The fine-tuning bolt  42  is inserted through the rear slot  35   c.  A middle slot  35   d  is formed at the middle portion of the saddle holder  35 . The corresponding leaf spring of the leaf spring member  47  is guided to the lower surface of the saddle  37  through the middle slot  35   d.  A threaded hole  35   f  is formed in the rear upright portion of the saddle holder  35 . A threaded portion  49   a  of the harmonic tuning bolt  49 , which functions as harmonic tuning means, is threaded into the threaded hole  35   f  of the pin holder  35   e  integrally formed with the rear portion of the saddle holder  35 . The distal end of the threaded portion  49   a  of the harmonic tuning bolt  49  contacts the outer circumferential surface  42   c  of the fine-tuning bolt  42 . When a manipulation portion  49   b  of the harmonic tuning bolt  49  is rotated, the saddle holder  35  is moved forward or rearward since the distal end of the threaded portion  49   a  of the harmonic tuning bolt  49  is restricted by the outer circumferential surface  42   c . That is, when the harmonic tuning bolt  49  is threaded toward the outer circumferential surface  42   c,  the saddle holder  35  is pulled rearward and the contact point Z of the corresponding string  15  is moved rearward. On the contrary, when the harmonic tuning bolt  49  is threaded rearward from the outer circumferential surface  42   c,  the saddle holder  35  is pulled forward by the tension of the string  15 . Thus, the contact point Z of the string  15  is moved forward. 
   The operation of the tremolo unit  21  of the electric guitar  11 , which is structured as above, will now be described. 
   To adjust the tension of each string  15 , which is connected to one of the bridge saddles  24 , without actually changing the position of the contact point Z in the tuning direction, the operator rotates the head  42   b  of the corresponding fine-tuning bolt  42  with the fingers. Turning the head  42   b  moves the top end of the slot  37   e  of the saddle  37  up and down. Thus, the saddle  37  is rotated clockwise or counterclockwise about the pin  38 . This adjusts the tension of the string  15 . 
   To tune the harmonic of each string  15  by changing the position of the contact point Z in the tuning direction, the operator unlocks the nut  18  and loosens the corresponding bolt  36 . The operator then rotates the harmonic tuning bolt  49  and moves the saddle holder  35  in the tuning direction along the front slot  35   a . This adjusts the position of the saddle  37  of the bridge saddle  24 . Accordingly, the pitch of the string  15  is changed. In this state, the operator rotates the tuning post  16  that corresponds to the string  15  with the associated tuning peg  17 . If the harmonic of the string  15  is not appropriate, the operator performs the above described procedure again. If the harmonic of the string  15  is appropriate, the operator tightens the bolt  36  to secure the saddle holder  35  to the base plate  23 . The operator then locks the string  15  with the nut  18 . Furthermore, the operator rotates the fine-tuning bolt  42  to fine-tune the string  15 . 
   According to the tremolo unit  21  of the present invention, the threaded hole  35   f  is formed in the boss or pin holder  35   e  in the rear upright portion of each saddle holder  35 . The harmonic tuning bolt  49  is threaded into the threaded hole  35   f  formed in the boss  35   e  of the saddle holder  35 . The distal end of the threaded portion  49   a  of the harmonic tuning bolt  49  contacts the outer circumferential surface of the rod portion  42   c  of the fine-tuning bolt  42 . The manipulation portion  49   b  of the harmonic tuning bolt  49  is located above the top surface of the body  12 . Therefore, the manipulation portion  49   b  can be rotated to move the saddle holder  35  and the saddle  37  while keeping the string  15  tuned. This permits the harmonic of strings to be easily tuned without rotating the tremolo unit  21 . 
   In addition, the guide holes  23   b  of the base plate  23  guide the fine-tuning bolts  42 . Therefore, even when the outer circumferential surface  42   c  of the fine-tuning bolt  42  is pressed by the harmonic tuning bolt  49 , the fine-tuning bolt  42  is prevented from becoming loose in the threaded hole  43   a.    
   The front slot  35   a  of the saddle holder  35  is offset in the lateral direction. Therefore, the bolt  36  is threaded into the threaded hole  23   a  without interfering with the corresponding string  15 . 
   It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the invention may be embodied in the following forms. 
   According to a further embodiment shown in  FIG. 6 , bolt support  23   d  extends upward from the rear end of the base plate  23 , and through holes  23   e  is formed in the bolt support  23   d . The harmonic tuning bolts  49  are inserted through the through holes  23   e  and the threaded portion  49   a  of each harmonic tuning bolt  49  is threaded into the threaded hole  35   f  of the corresponding saddle holder  35 . In addition, the threaded portion  42   a  of the fine-tuning bolt  42  is threaded into a threaded hole  35   h , which is formed the boss  35   g  on the top surface of the saddle holder  35 . When the harmonic tuning bolt  49  is rotated, the saddle holder  35  is moved forward or backward with the fine-tuning bolt  42  and the saddle  37 . A recess  37   f  is formed in the rear of the saddle  37  in association with the slot  37   e  so that the interference between the saddle  37  and boss  35   g  is avoided. 
   According to the further embodiment shown in  FIG. 6 , the fine-tuning bolt  42  is not pressed by rotating the harmonic tuning bolt  49 . Therefore, the harmonic of strings can easily be tuned while keeping the strings appropriately fine-tuned. 
   According to a further embodiment shown in  FIG. 7 , the threaded portion  49   a  of the harmonic tuning bolt  49  is threaded into a threaded hole  37   h  of the pin holder  37   g  formed in the rear end of the saddle  37 . The distal end of the threaded portion  49   a  of the harmonic tuning bolt  49  is pressed against the outer circumferential surface of the rod portion  42   c  of the fine-tuning bolt  42 . 
   When the harmonic tuning bolt  49  is rotated toward the fine-tuning bolt  42 , the distal end of the threaded portion  49   a  of the harmonic tuning bolt  49  presses the outer circumferential surface of the rod portion  42   c . Thus, the saddle  37  is moved backward by the reaction force and the tension of the corresponding string  15  increases. As a result, the position of the contact point Z is displaced backward to tune the harmonic of the string  15 . 
   The above described further embodiment provides the same advantages as the illustrated embodiment. 
   Another modification is illustrated in  FIGS. 8 and 9 , in which a cylindrical boss  23   f  is integrally formed on the top of the base plate  23 . The threaded portion  42   a  of the fine-tuning bolt  42  in fitted within the threaded hole  23   g  of the boss  23   f . The threaded portion  49   a  of the harmonic tuning bolt  49  is fitted in the threaded hole  35   f  of the pin holder  35   e  formed in the rear of the saddle holder  35 . The tip of the threaded portion  49   a  abuts the outer surface of the boss  23   f . The recess  37   f  is formed in the rear of the saddle  37  in association with the slot  37   e  so that the saddle  37  and the boss  23   f  do not interfere with each other. 
   In the above modification, the rotation of the harmonic-tuning bolt  49  urges its tip against the outer surface of the boss  23   f  to adjust the position of the saddle in the tuning direction. The rod portion  42   c  of the fine-tuning bolt  42  does not take a place in the above urging portion. Accordingly, the tuning status of the bolt  42  is stably maintained. 
   The harmonic tuning means may be located between the base plate or each saddle holder and the fine-tuning means. In this case, the manipulation member such as the fine-tuning bolts, which form the fine-tuning means, are preferably used. 
   The fine-tuning means may be located between each saddle holder and the corresponding saddle, and the harmonic tuning means may be located between each saddle holder and the base plate. 
   Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.