Patent Publication Number: US-6710235-B2

Title: Electric guitar with tremolo unit

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an electric guitar with a tremolo unit. 
     An electric guitar that has a tremolo unit prevents the electric guitar from being detuned by changes in the tension (pitch) of strings while the guitar is being played using the tremolo unit. U.S. Pat. No. 4,171,661 discloses an electric guitar that has a tremolo unit. According to the guitar of the publication, each string is locked by a bolt and a presser member at a saddle of the tremolo unit. A fixing member is also arranged on a nut, which is located in the vicinity of the head, to fix the strings. This structure prevents the guitar to be detuned even if the tremolo unit is used. 
     FIG. 8 illustrates another type of tremolo unit. This tremolo unit has a base plate  23  and a hinge mechanism for connecting the base plate  23  to a guitar body. A pair of pin supports  61 ,  61  is integrally formed with the base plate  23  at the sides of the base plate  23 . A bore  61   a  is formed in each pin support  61 . A coupling pin  62  is connected to each pin support  61  by press fitting the proximal end of the pin  62  into the bore  61   a . A pair of brackets  64 ,  64  is coupled to the body with support pins  63 ,  63 . Each bracket  64  can pivot about the corresponding support pin  63 . A bearing device comprising a single bearing  65  fits in each bracket  64 . Each coupling pin  62  fits into the central bore of the corresponding bearing  65 . 
     Since the coupling pins  62  receive relatively great tension of the strings, the bores  61   a  need to be sufficiently deep to bear the tension. Also, since the bearings  65 ,  65  receive the tension of the strings, the bearings  65  need to be sufficiently long to bear the tension. The distance D1 between the centers O 1 , O 1  of the bores  61   a ,  61   a  and the distance between the center O 1  of each bore  61   a  and the axial midpoint O 2  of the corresponding bearing  65  are determined to ensure sufficient depth of the bores  61   a  and sufficient length of bearings  65   
     The distance D3 between the axial midpoint O 2  of each bearing  65  (the corresponding midpoint O 3 ) and the outer edge of the corresponding bracket  64  is determined such that the midpoint O 3  of each support pin  63  is included in a line that contains the axial midpoint O 2  of the corresponding bearing  65  and is parallel to the strings. Accordingly, the tension of the strings evenly acts on the bearings  65 ,  65 . In this structure, the distance between the outer edges of the brackets  64 ,  64  is represented by a formula D1+2×D2+2×D3. The brackets  64  thus require a relatively large lateral space. If widely separated, the brackets  64  impair the appearance of the guitar. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an objective of the present invention to provide an electric guitar with a tremolo unit that minimizes the space required for a hinge mechanism supporting the base plate. 
     To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, an electric guitar having a plurality of strings is provided. Each string has a first contact point defined on a neck and a second contact point defined on a base plate attached to a body. The guitar includes a hinge mechanism for supporting the base plate such that the base plate pivots relative to the body. The hinge mechanism includes a pair of bores, a pair of bearing devices, a pair of support pins, a pair of brackets, and a pair of bracket pins. Each bore is formed at a side of the base plate. Each bearing device is located in one of the bores. The support pins protrude from the body. Each support pin corresponds to one of the bearing devices and is located closer to the neck than the corresponding bearing device. Each bracket is coupled to one of the support pins. Each bracket pin is coupled to one of the brackets and fits into the corresponding bearing device. The axial midpoint of each bearing device and the center of the corresponding support pin are located on a line that is substantially parallel to the strings. 
     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 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 plan view illustrating a tremolo unit of an electric guitar according to the present invention; 
     FIG. 2 is a side view of the tremolo unit shown in FIG. 1; 
     FIG. 3 is a cross-sectional view taken along line  3 — 3  of FIG. 1; 
     FIG. 4 is a cross-sectional view taken along line  4 — 4  of FIG. 1; 
     FIG. 5 is an enlarged cross-sectional view illustrating the bridge saddle of the tremolo unit shown in FIG. 1; 
     FIG. 6 is an exploded perspective view illustrating the tremolo unit shown in FIG. 1; 
     FIG. 7 is a front view illustrating an electric guitar; and 
     FIG. 8 is a plan view illustrating the hinge mechanism of a prior art tremolo unit. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An electric guitar  11  with a tremolo unit  21  according to one embodiment of the present invention will now be described with reference to FIGS. 1 to  7 . 
     FIG. 7 shows the entire 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 contact points between the nut  18  and the strings  15  will be referred to as first contact points. The strings  15  are pressed against the nut  18  by a pressing member and are tightened to the nut  18  with bolts. 
     The tremolo unit  21  is located substantially at the center of the body  12 . The six strings  15  contact the nut  18  and the tremolo unit  21 . The strings  15  are tightly stretched at a predetermined tension and substantially parallel to one another. The body  12  has pick-ups, which detect vibration of the strings  15  and convert the vibration into electric signals. The electric signals generated by the pick-ups are transmitted to an amplifier via a cable (not shown) to be amplified. 
     As shown in FIG. 6, the tremolo unit  21  includes a base plate  23  and bridge saddles  24 . The base plate  23  is pivotally arranged on the body  12  by a hinge mechanism  22 . The bridge saddles  24  are arranged on the upper surface of the base plate  23  and support 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 pivoted in a direction to apply tension to the strings  15 . The tremolo manipulation mechanism  26  is located on the base plate  23  and is used to pivot the base plate  23  about the hinge mechanism  22 . 
     The hinge mechanism  22  includes a pair of brackets  28  and two bearing devices, each bearing device comprising two bearings  30 . Each bracket  28  is secured to the base plate  23  by a support pin, which is a stud bolt  31  in this embodiment. Each bearing device is coupled to the distal end of the corresponding bracket  28  by a bracket pin  29 . A pair of pin supports  27  is formed integrally with the base plate  23  on both left and right sides. Each pin support  27  includes a bore  27   a . The bearings  30  of each bearing device are fitted into the corresponding bore  27   a.    
     FIG. 5 illustrates one of the bridge saddles  24 . Since the bridge saddles  24  are identical, the structure of one of the bridge saddles  24  will be described with reference to FIGS. 5 and 6. A saddle holder  35  is mounted on the bridge saddle  24 . As shown in FIG. 5, the saddle holder  35  has a slot  35   a  at its distal end. As shown in FIGS. 5 and 6, threaded holes  23   a  are formed in the base plate  23 . A bolt  36  is inserted downward in the slot  35   a . The bolt  36  is then threaded into the corresponding threaded hole  23   a  so that the saddle holder  35  is secured to the upper surface of the base plate  23 . A saddle  37  is mounted on the saddle holder  35 . A pin support  35   b  is formed integrally with the saddle holder  35 . The distal end of the saddle  37  is coupled to the pin support  35   b  with a pin  38  so that the saddle  37  can pivot. A clamp pad  39  is located on 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 . A string receiver  37   b , which is formed at an end of the saddle  37 , contacts the corresponding string  15  at a contact point Z. 
     The clamp pad  39  includes a retainer  39   a  and a fulcrum  39   b . The retainer  39   a  retains the corresponding string  15  in cooperation with a receiving surface  37   c  of the saddle  37 . The fulcrum  39   b  contacts the saddle  37 . A through hole  39   c  is formed in the clamp pad  39 . The through hole  39   c  loosely receives the string fixing bolt  40 . The end of the corresponding string  15  is held between the retainer  39   a  of the clamp pad  39  and the receiving surface  37   c  of the saddle  37 . 
     An elastic member, which is a coil spring  41  in this embodiment, is located between the clamp pad  39  and the saddle  37  to urge the clamp pad  39  away from the saddle  37 . A slot  37   e  is formed at the distal 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 . The fine-tuning bolts  42  and the saddles  37  form a fine-tuning device. A head  42   b  of the fine-tuning bolt  42  is engaged with the top edge of the slot  37   e . A mounting plate  43  is attached to the lower surface at the rear end of the base plate  23  with screws  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 . The fine-tuning bolt  42  extends through one of the guide holes  23   b.    
     As shown in FIGS. 5 and 6, a tremolo block  45  is secured to the lower surface of the base plate  23  with bolts  46 . A leaf spring member  47 , which has leaf springs, is held between the lower surface of the base plate  23  and the top surface of the tremolo block  45 . As shown in FIG. 5, the distal end of each leaf spring of the leaf spring member  47  is guided through the corresponding through hole  23   c  and pressed against the lower 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 . The tension applying mechanism  25  includes a pair of springs  48 . One end of each spring  48  is engaged with the lower, or distal, end of the tremolo block  45 . The other end of each spring  48  is engaged with a bracket  70 , which is fixed to the body  12  at a predetermined position. The springs  48  urge the tremolo block  45  in the clockwise direction as viewed in FIGS. 2 and 5. Accordingly, the base plate  23  is urged clockwise about the pins  29  and causes the bridge saddles  24  to apply tension to the strings  15 . 
     As shown in FIG. 6, the tremolo manipulation mechanism  26  includes a hollow bolt  51 , a nut  52 , and a bent tremolo bar  53 . The hollow bolt  51  is inserted downward through one side of the base plate  23 . 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 the tremolo bar  53  is detachably inserted into the hollow bolt  51 . When the tremolo bar  53  is tilted toward or away from the body  12 , the base plate  23  of the tremolo unit  21 , the bridge saddles  24 , and the tremolo block  45  are slightly pivoted about the pins  29  against the force of the springs  48 . 
     The hinge mechanism  22  will now be described with reference to FIGS. 1 to  4 . 
     Nuts  32  are embedded in the body  12 . Each nut  32  has a threaded hole  32   a . As shown in FIG. 4, each stud bolt  31  has a threaded portion  31   a  and a coupling portion  31   b . The threaded portion  31   a  is threaded into the threaded hole  32   a  of the corresponding nut  32 . A seat  31   c  is defined between the threaded portion  31   a  and the coupling portion  31   b  of each stud bolt  31 . The seat  31   c  has a convex support surface. 
     A slot  31   d  is formed at the distal end of the coupling portion  31   b  of each stud bolt  31 . The slot  31   d  is used when the stud bolt  31  is rotated with a tool such as a screwdriver. An annular groove  31   e  is formed in the vicinity of the slot  31   d . A fastener, which is an E-shaped snap ring  33  in this embodiment, is engaged with the annular groove  31   e . As shown in FIG. 1, each bracket  28  is formed like an elbow and includes a proximal portion  28   a  and an arm  28   b . An elastic ring  34  made of rubber is located between the proximal portion  28   a  of the bracket  28  and the E-shaped snap ring  33  to elastically support the bracket  28 . A bore  28   c  is formed in the end of the arm  28   b . The corresponding bracket pin  29  fits into the bore  28   c . An elongated hole  28   d  is formed in the proximal portion  28   a . The coupling portion  31   b  of the corresponding stud bolt  31  extends through the elongated hole  28   d . Each elongated hole  28   d  is elongated in a direction perpendicular to the strings  15 . 
     As shown in FIG. 3, the two bearings  30  are located in the bore  27   a  of each pin support  27 . A spacer ring  49  is located between the bearings  30 . The two bearings  30  and the spacer ring  49  comprise one embodiment of the bearing device. 
     The operation of the tremolo unit  21  will now be described. 
     To change the tension of each string  15  while substantially maintaining the position of the second contact point Z, the head  42   b  of the corresponding fine-tuning bolt  42  is manually rotated. The engagement between the head  42   b  and the corresponding saddle  37  pivots the saddle  37  clockwise or counterclockwise about the pin  38 , which fine-tunes the tension of the string  15 . 
     To tune the harmonics of all the strings  15  while changing the second contact points Z, the strings  15  are unlocked at the first contact points by loosening the pressing member of the nut  18 . Then, the strings  15  are loosened by rotating the tuning posts  16  with the tuning pegs  17 . In this state, the bolts  36  are loosened, and each saddle holder  35  is moved along the slot  35   a  to adjust the position of the saddle  37 . Then, the bolts  36  are fastened to fix the saddle holders  35  to the base plate  23 . Thereafter, the tuning posts  16  are rotated by the tuning pegs  17  to tune the strings  15 . The strings  15  are then locked by the pressing member of the nut  18 . A rough adjustment of the harmonics is thus completed. 
     Each string  15  is then fine-tuned by rotating the corresponding fine tuning bolt  42 . After fine-tuning all the strings  15 , whether the harmonics of the strings  15  are properly set is determined. If the harmonics are not properly set, the position of each saddle holder  35  is further adjusted. 
     The advantages of the tremolo unit  21  will now be described in connection with the structure. 
     (1) As shown in FIG. 1, the bearings  30  are fitted into the hole  27   a  of each pin support  27 , and the bracket pin  29  extending from the elbow shaped bracket  28  is inserted into the bearings  30 . The stud bolts  31  are located forward of the pin supports  27  to be laterally aligned with the bearings  30 . Although, the distance D1 between the centers O 1 , O 1  of the stud bolts  31  is substantially the same as the distance D1 (see FIG. 8) of the prior art tremolo unit, the distance D4 from the center O 1  to the outer edge of the arm  28   b  of the bracket  28  is relatively short. Therefore, the space required for the hinge mechanism  22  is smaller than the prior art (see the distances D1, D2, D3). 
     (2) As shown in FIG. 1, the center O 1  of each stud bolt  31  and the axial midpoint O 2  of the corresponding bearing device are located on a line that is parallel to the strings  15 . Therefore, the tension of the strings  15  is applied to the center O 1  of each stud bolt  31  through the base plate  23 , the corresponding pin support  27 , the corresponding bearing device, the corresponding bracket pin  29  and the corresponding bracket  28 . Thus, bending moment does not act on the bearings  30 . Therefore, the tremolo manipulation mechanism  26  is stably controlled. 
     (3) The elastic ring  34  is provided between the proximal portion  28   a  of each bracket  28  and the corresponding E-shaped snap ring  33 . Thus, even if the sides of the base plate  23  are displaced toward or away from the body  12 , the displacement is absorbed by the elastic rings  34 , which stabilizes the state of the brackets  28 . 
     (4) The elongated hole  28   d  is formed in the proximal portion  28   a  of each bracket  28 , and the elongated hole  28   d  extends in a direction perpendicular to the strings  15 . Each elongated hole  28   d  receives the coupling portion  31   b  of the corresponding stud bolt  31 . This permits a slight displacement of the base plate  23  along a direction perpendicular to the strings  15 , and the states of the brackets  28  are stably changed accordingly. 
     (5) The seat  31   c  on each stud bolt  31  is convex. Thus, even if the attitudes of the brackets  28  are changed, the circumference of each elongated hole  28   d  is stably supported. 
     (6) The number of the bearings  30 , which fit into the hole  27   a  of each pin support  27 , is two. The spacer ring  49  is located between each pair of the bearings  30 , which increases the axial dimension of the bearing device. Thus, the pins  29  are stably supported by the pin supports  27 . 
     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. 
     The snap rings  33  fitted about the coupling portions  31   b  of the stud bolts  31  may be replaced by nuts, and the proximal portions  28   a  of the bracket  28  may be fixed to the steps  31   c  of the stud bolts  31 . Alternatively, the support surface of each seat  31   c  may be formed conical. The E-shaped snap rings  33  may be replaced with C-shaped snap rings. 
     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.