Patent Publication Number: US-6700043-B2

Title: Electric guitar with tremolo unit

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to electric guitars with tremolo units, and, more particularly, to lock devices that are attached to electric guitars to prevent strings from being shifted to offset positions. 
     In an electric guitar with a tremolo unit, tensions of all strings are adjusted at the same time by the tremolo unit for generating an impressive sound effect. The U.S. Pat. Publication No. 4,171,661 describes a conventional electric guitar, which maintains tuning of the guitar in a stable state even when a tremolo sound effect is used. More specifically, a tremolo unit of the electric guitar includes a saddle that locks proximal ends of strings. Further, with reference to FIG. 6, a lock device  30 , which is fixed near the head of the guitar, locks distal portions of the strings  15 . As locked by the lock device  30 , the strings  15  cannot be tuned by pegs. Thus, to enable the strings  15  to be finely tuned even in this state, the guitar is provided with a fine tuning device, which is located at the saddle of the tremolo unit. 
     With reference to FIGS. 6 and 7, the lock device  30  includes a nut  31 , which is fixed to an upper side of a neck  13  of the guitar, and clamp pads  32 . The nut  31  supports the clamp pads  32 . The clamp pads  32  are pressed against an upper side (a support surface  31   a ) of the nut  31  by fastening bolts  33 , such that the strings  15  are clamped between the clamp pads  32  and the support surface  31   a . The support surface  31   a  of the nut  31  is inclined with respect to a hypothetical line L 1 , which extends along an edge of the nut  31  close to the proximal ends of the strings  15  (a contact point P 1 ) and the proximal ends of the strings  15  (a contact point P 2  between the tremolo unit and the strings  15 ), at angle α. The angle α is, for example, five degrees. A hypothetical line L 2 , which extends along the contact point P 1  and a front edge of the nut  31  (a contact point P 3 ), is parallel with a hypothetical line L 3 , which extends along a contact point P 4  between the strings  15  and pegs (not illustrated) and the contact point P 1 . The head  14  is bent with respect to the neck  13  at angle γ. The angle γ is, for example, 10 degrees. 
     In the lock device  30 , the support surface  31   a  of the nut  31  is parallel with the line L 3 . The strings  15  are thus easily separated from the support surface  31   a . In this case, tuning of the strings  15  becomes unstable. Also, the strings  15  are easily shifted to offset positions. Accordingly, to avoid these problems, the clamp pads  32  need be firmly pressed against the nut  31  by the fastening bolts  33  such that the strings  15  are reliably held by the support surface  31   a . However, this may damage the strings  15  and decrease the durability of the fastening bolts  33  or damage the bolts  33 . 
     Further, to solve the problems, the electric guitar may include a retainer bar, which is located between the lock device  30  and the pegs for pressing the strings  15  against an upper side of the head  14 . However, in this case, when installing the strings  15 , the fastening bolts  33  and the clamp pads  32  must be removed from the nut  31 . The strings  15  are then passed through the space between the retainer bar and the head  14 . This complicates the installation of the strings  15 . 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an objective of the present invention to provide an electric guitar with a tremolo unit that maintains tuning of strings in a stable state and prevents the strings from being shifted to offset positions. 
     It is another objective of the present invention to provide an electric guitar with a tremolo unit and a lock device that makes it easy to install strings. 
     To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, the invention provides an electric guitar with a tremolo unit that adjusts tensions of strings at the same time. The electric guitar includes a body, a neck, a head, a plurality of pegs, and a lock device. The body fixes proximal ends of the strings. The neck projects from the body and has an upper side that faces the strings. The head is fixed to a distal end of the neck and is bent downward from the upper side of the neck. The pegs are attached to the head. Each of the pegs is connected to a distal end of a different one of the strings. The lock device is fixed to the upper side of the neck for preventing strings from being shifted to offset positions. The lock device includes a nut, a pad, and a bolt. The nut has a support surface that supports the strings, a rear edge close to the body, and a front edge close to the pegs. The nut is located such that the front edge is located upward from a hypothetical line that extends along a contact point between the strings and the pegs and the rear edge. The pad presses at least one of the strings against the support surface. The bolt connects the pad to the nut. 
     Another perspective of the invention is an electric guitar with a tremolo unit that adjusts tensions of strings at the same time. The electric guitar includes a neck, a plurality of pegs, and a nut. The neck has an upper side that faces the strings. Each of the pegs is connected to a distal end of a different one of the strings. The nut is attached to the upper side of the neck. The nut supports the strings such that the strings are substantially parallel with one another. The nut has a front edge close to the distal ends of the strings, a rear edge close to proximal ends of the strings, and a support surface formed between the front edge and the rear edge. The support surface is inclined with respect to the upper side of the neck at a predetermined angle. The predetermined angle is smaller than an angle of portions of the strings between the pegs and the front edge with respect to the upper side of the neck. 
     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 objectives 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 an enlarged view showing a lock device for strings according to an embodiment of the present invention; 
     FIG. 2 is an exploded perspective view showing the lock device of FIG. 1; 
     FIG. 3 is a plan view showing a head of an electric guitar according to the embodiment of the present invention; 
     FIG. 4 is a side view showing the head of the electric guitar; 
     FIG. 5 is a plan view showing the electric guitar according to the embodiment of the present invention; 
     FIG. 6 is a plan view showing a prior art lock device of an electric guitar; and 
     FIG. 7 is a cross-sectional view taken along line  7 — 7  of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERED EMBODIMENTS 
     An electric guitar  11  of an embodiment of the present invention will now be described with reference to FIGS. 1 to  5 . 
     FIG. 5 is a plan view showing the electric guitar  11 . In the following description, a side of the electric guitar  11  close to a viewer of the drawing is defined as an upper side of the electric guitar  11 . 
     The electric guitar  11  includes six strings  15 , a solid type body  12 , a neck  13 , and a head  14 . Proximal ends of the strings  15  are fixed to the body  12 . The neck  13  projects from the body  12 , while the head  14  is attached to a distal end of the neck  13 . The head  14  includes six pegs  16  and six knobs  17 . Each of the strings  15  is associated with a different one of the pegs  16 , and the distal end of each string  15  is wound around the associated peg  16 . Likewise, each of the knobs  17  is associated with a different one of the pegs  16 . A gear mechanism (not illustrated) connects each knob  17  to the associated peg  16 . In FIG. 1, only the peg  16  closest to the neck  13  is illustrated. The knobs  17  are manipulated to rotate the associated pegs  16 . This adjusts tensions of the strings  15  such that the pitches of the strings  15  are tuned. A lock device  18 , which is attached to an upper side of the neck  13 , locks the strings  15  without affecting the tensions of the strings  15 . 
     A tremolo unit  19  is attached to the body  12 . Between the tremolo unit  19  and the lock device  18 , the strings  15  are held substantially parallel with the upper side of the neck  13  and extend substantially parallel with one another. Pickups  12   b , each of which converts vibration of an associated one of the strings  15  to an electric signal, are attached to the body  12 . The electric signal is sent to an amplifier by a cable (not illustrated) and is amplified and converted to a sound by the amplifier. 
     The tremolo unit  19  includes a tremolo arm  20 . The tremolo arm  20  is manipulated to adjust tensions of all strings  15  at the same time. This generates an impressive sound effect. 
     The lock device  18  will hereafter be described. 
     With reference to FIG. 1, a plurality of bolts B secures a nut  21  to the upper side of the neck  13 . The nut  21 , as shown in FIG. 2, includes a distal guide wall  21   b , a proximal guide wall  21   c , and a support surface  21   a . The distal guide wall  21   b  and the proximal guide wall  21   c  respectively include guide grooves  21   d  and guide grooves  21   e , which guide the strings  15 . The support surface  21   a  is formed between the guide walls  21   b ,  21   c  for supporting the strings  15 . Securing holes  21   f , which are formed in the support surface  21   a , receive the bolts B. 
     Clamp pads  22 , which press the strings  15  against the support surface  21   a  of the nut  21 , are fixed to the nut  21  by clamp bolts  23 . The clamp bolts  23  each include a threaded shaft  23   a , which is engaged with a through hole  22   c  formed in each of the clamp pads  22 . A pair of pressing projections  22   a ,  22   b  projects from a lower side of each clamp pad  22  to face the support surface  21   a  of the nut  21 . The strings  15  are clamped between the pressing projections  22   a ,  22   b  and the support surface  21   a  of the nut  21 . Each clamp pad  22  has two upper side sections that are uniformly slanted in opposite directions with respect to a ridge  22   d . The clamp pads  22  are fixed to the nut  21  such that the ridges  22   d  are substantially parallel with the strings  15 . A groove  23   c  is formed in a head  23   b  of each clamp bolt  23 . The clamp bolt  23  is thus easily rotated by a coin, for example, which is engaged with the groove  23   c.    
     A coil spring  24  is located between the nut  21  and each clamp pad  22  and serves as an elastic member for urging the clamp pad  22  upward. 
     In the following description, with reference to FIG. 1, a rear edge of the nut  21  close to the body  12  is defined as a first contact point P 1 , a bridge saddle of the tremolo unit  19  is defined as a second contact point P 2 , and a front edge of the nut  21  close to the peg  19  is defined as a third contact point P 3 . A contact point between the peg  16  and the string  15  is defined as an engaging point P 4 . A line that extends along the first contact point P 1  and the second contact point P 2  is indicated by L 1 . A line that extends along the first contact point P 1  and the third contact point P 3  is indicated by L 2 . A line that extends along the first contact point P 1  and the engaging point P 4  is indicated by L 3 . The inclination angle of the line L 2  with respect to the line L 1  is indicated by α, and the inclination angle of the line L 3  with respect to the line L 2  is indicated by β. The bending angle of the head  14  with respect to the neck  13  (the line L 1 ) is indicated by γ. 
     It is preferred that the inclination angle α be 2.0-12.5 degrees. In this embodiment, the inclination angle α is 4.2 degrees. Likewise, it is preferred that the inclination angle β be 2.0-12.5 degrees. In this embodiment, the inclination angle β is 5.0 degrees. The bending angle γ is generally 10.0-18.0 degrees and, in this embodiment, is 14.0 degrees. The interval between the third contact point P 3  and the line L 3  is changed in relation to the angles α, β, γ. For example, the third contact point P 3  is spaced from the line L 3  by, for example, 0.5 to 3.5 millimeters. 
     If the bending angle γ is 14.0 degrees, it is preferred that the inclination angle α be 3.0-7.0 degrees and the inclination angle β be 3.0-7.0 degrees. In this embodiment, the pegs  16  at the standard height of 9.5 millimeters are used. Further, the interval between the contact points P 1 , P 3  is 15.5 millimeters, while the interval between the contact point P 3  and the engaging point P 4  is 36.5 millimeters. In addition, a minimum value of the inclination angle α and a minimum value of the inclination angle β are both set at 3.0 degrees such that the friction resistance between the strings  15  and the nut  21  exceeds a required minimum level. However, if the pegs  16  at the standard height of 3.7 millimeters, which are relatively short, are used, a maximum value of the inclination angle α and a maximum value of the inclination angle γ are both set at 7.0 degrees such that the friction resistance between the strings  15  and the nut  21  exceeds the required minimum level. For example, if the inclination angles α, β are both 3.0 degrees, the string  15  is spaced from the line L 3  at the contact point P 3  by 0.8 millimeters. Likewise, if the inclination angles α, β are both 7.0 degrees, the string  15  is spaced from the line L 3  at the contact point P 3  by 1.5 millimeters. 
     The operation of the lock device  18  will hereafter be described. 
     When installing the strings  15 , the clamp bolts  23  are loosened to separate the clamp pads  22  from the support surface  21   a  of the nut  21  at a predetermined interval. In this state, one end of each string  15  is fixed to the bridge saddle of the tremolo unit  19 , while the other is passed through an associated one of the guide grooves  21   e . This end is then passed through the space between the support surface  21   a  of the nut  21  and the lower side of the associated clamp pad  22  and the guide groove  21   d . The end of the string  15  is thus engaged with the associated peg  16 . Subsequently, while maintaining the clamp pads  22  as separated from the support surface  21   a , the knobs  17  are manipulated to rotate the pegs  16  such that a predetermined tension is applied to each string  15  to tune the pitch of the string  15 . In this state, the strings  15  contact the support surface  21   a  of the nut  21  at the first contact point P 1  and the third contact point P 3  in a bent manner. The strings  15  are fixed to the nut  21  by fastening the clamp pads  22  to the support surface  21   a  of the nut  21  by the clamp bolts  23 . 
     The advantages of the lock device  18  are as follows. 
     (1) In the illustrated embodiment, the inclination angle β is 2.0-12.5 degrees and the third contact point P 3  is spaced upward from the line L 3  by 0.5-3.5 millimeters. The strings  15  are thus bent by the nut  21  at the first and third contact points P 1 , P 3 . This firmly holds the strings  15  in a state supported by the support surface  21   a  of the nut  21 , without using a retainer. The friction resistance between the nut  21  and the strings  15  is thus increased. This maintains tuning of the strings  15  in a stable state and prevents the strings  15  from being shifted to offset positions. 
     Further, the clamp pads  22  press the strings  15  against the support surface  21   a  of the nut  21 . Thus, without using a retainer, the tuning of the strings  15  is maintained in the stable state while the strings  15  are prevented from being shifted to offset positions. Also, the clamp pads  22  prevent the strings  15  from being longitudinally shifted to offset positions when the strings  15  are being locked. In addition, since it is unnecessary to fasten the clamp pads  22  by excessive force, the strings  15  are prevented from being damaged. 
     (2) In the illustrated embodiment, the support surface  21   a  of the nut  21  is flat. It is thus easy to fabricate the nut  21  such that the third contact point P 3  is located upward from the line L 3 . 
     (3) In the illustrated embodiment, the clamp pads  22  each include two pressing projections  22   a ,  22   b . The projections  22   a ,  22   b  press the strings  15  against the support surface  21   a  of the nut  21  at two positions. This enables the clamp pads  22  to reliably clamp the strings  15  near the first contact point P 1  and the third contact position P 3 . The strings  15  thus reliably contact the nut  21  at the first and third contact points P 1 , P 3 . 
     (4) In the illustrated embodiment, the coil springs  24  are located between the support surface  21   a  of the nut  21  and the clamp pads  22 . When the clamp bolts  23  are fastened, the coil springs  24  urge the clamp pads  22  upward from the support surface  21   a  of the nut  21 . Thus, without removing the clamp pads  22 , the strings  15  can be installed and tuned. If the coil springs  24  are not provided, the clamp pads  22  contact the strings  15  when the clamp bolts  23  are loosened. This hampers accurate tuning of the strings  15 . 
     Further, tuning of the strings  15  can be maintained in a stable state when the strings  15  are being locked. In addition, the strings  15  are prevented from being shifted to offset positions when the clamp pads  22  are being fastened. 
     The support surface  21   a  of the nut  21  is inclined with respect to the upper side of the neck  13 . The angle between the support surface  21   a  and the upper side of the neck  13  is smaller than the angle of portions of the strings  15  between the pegs  16  and the front edge of the nut  21 , which corresponds to the first contact point P 3 , with respect to the upper side of the neck  13 . Accordingly, the strings  15  are bent by the nut  21  at two positions (the first and third contact positions P 1 , P 3 ). The strings  15  are thus prevented from being separated from the support surface  21   a  of the nut  21 . 
     The illustrated embodiment may be modified as follows. 
     The height of the pegs  16 , or the projecting amount of the pegs  16  from the upper side of the head  14 , may be substantially minimized. In this case, the bending angle of the strings  15  at the third contact point P 3  is increased. The strings  15  thus contact the nut  21  by an accordingly increased friction force. 
     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.