Abstract:
A swingable tremolo for a string instrument. A tremolo block connected with the tremolo body is in turn connected through a link with a sliding block on the bottom of the instrument. A first spring urges the sliding block against the tensile force of the strings. A movable stopper is engageable by the sliding block as it moves rearward. A second spring also urges the movable stopper forward. The tensile force of the instrument strings is greater than the opposite force of first spring but less than the sum of the spring forces of the first and second springs, whereby the tremolo body may be tilted up or forwardly to reduce string tension or tilted down or rearwardly to increase string tension, and upon release of the tremolo body, the forces of the springs acting on the sliding block and the movable stopper act against the tensile force of the strings to bring the tremolo body into an equilibrium state.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to the tremolo device for stringed musical instruments.  
         TECHNOLOGY ACCORDING TO PRIOR ART  
         [0002]    Tremolo devices for stringed instruments are widely used, particularly for electric guitars. The tremolo is operable for providing impressive acoustic effects by simultaneously increasing or decreasing the tension of all strings of a stringed instrument.  
           [0003]    [0003]FIG. 14 shows a conventional tremolo device  120 , installed on a body B of a stringed instrument, here a guitar. The tremolo is comprised of a tremolo body which serves as a guitar (bridge)  130  on which there is a string support  131  including a bridge saddle, etc. for the support of the guitar strings S. The string support  131  is arranged at the top surface of the body, while a tremolo block  132  protrudes below the top surface. A spring  140  maintains a state of equilibrium of the tremolo body  130  by working together with an arm  135  for manipulating the swinging of the tremolo body  130  installed on the surface of the instrument and the guitar string S that is spaced above the surface of the body B as the spring extends between the tremolo block  132  and the body B.  
           [0004]    The tremolo body  130  remains at a location and orientation at which there is a balance between the tensile forces exerted by all of the strings S and the force of the spring  140  that works in the opposite direction for maintaining a state of equilibrium. As the tremolo body  130  is swung by moving the arm  135 , the tension of all the strings S is simultaneously either increased or decreased, causing the musical intervals of the various strings S to either rise or drop. The tremolo body  130  returns to its original equilibrium position when the arm  135  is released. The musical intervals of the strings S are restored to the original intervals as the state of equilibrium is restored.  
           [0005]    However, a balancing system for a tremolo body  130 , which is based on the force of the spring  140  and on the tensile strength of the strings S, is extremely sensitive. Its tuning becomes out of order if the tremolo body  130  is not completely restored to its original state of equilibrium (which position in a balanced state serves as the central point) after the swinging of the tremolo body  130  due to such factors as friction at the swaying fulcrum of the tremolo body  130 , the incompleteness of the restoring force of the spring  140 , a performer&#39;s hand touching the tremolo body  130  or the arm  135  during a performance, choking (bending of the string) or fluttering (blurring of sound due to the moment of inertia that is produced at the time when the hand is suddenly taken away from the arm  135 ), or the mutilation of a string S.  
           [0006]    Another major shortcoming of this tremolo device  120  is that tuning it is extremely difficult, because when tuning is performed until a certain string is raised to its target interval, the sum of the tensions of all of the strings S also increases. This moves the position of the state of equilibrium of the tremolo body  130  in the direction toward the neck of the guitar to the front, shortening the distance from the nut of the guitar to the string support part of the tremolo body, thereby reducing the tension of the other strings S, in turn causing the intervals of the other strings to decrease. Conversely, when the tension of some string S is lowered, the musical intervals of other strings S increases. Accordingly, it is theoretically impossible to completely and perfectly tune all of the strings S, and it requires an extremely large effort to bring the strings near to a perfectly tuned state.  
           [0007]    For each string S there is a prescribed relationship among the target intervals, string density and the length of the string. Where one terminal end of the string S moves like the tremolo device  120  having a conventional structure, there are numerous neutral points that strike the balance in the tuning of the open strings, except for the scale length of the conventional stringed instruments, depending upon the strength of the spring  140 . Accordingly, the desired musical intervals cannot be obtained if a state of equilibrium is achieved in front or at the back of the design location of the state of equilibrium (neutral point), even when the fretting on the guitar neck may be controlled.  
           [0008]    There has been great interest in overcoming the above described shortcomings of the tremolo device  120 . Recently, many tremolo devices employing a string which is stronger than the tensile force of known strings have been proposed, as described in Toku Kai Hei 1-93793 and Toku Ko Hei 2-48120, etc.  
           [0009]    The mechanism described in Toku Kai Hei 1-93793, however, requires applying an extremely strong force for operating the tremolo arm when the musical intervals are to be raised through an increase in the tensile force of the string.  
           [0010]    In the tremolo device in Toku Kai Hei 2-48120, on the other hand, the restoring force of the spring may be affected because the spring is tilted or deformed in a direction other than its direction of expansion or contraction when the tremolo body is swung, as the tremolo block and the spring are directly connected to each other. Moreover, in this tremolo device, the sound created at contact between a stopper and the tremolo body for stopping the tremolo body is quite large. When a buffer member, e.g. of rubber, etc. is interposed between the two elements to control the sound, the small size of the contact area contributes toward increasing the amount of the deformation of the buffer member and produces erroneous tuning.  
           [0011]    In addition, this tremolo device has many places requiring adjustment. It is difficult for the user to determine locations requiring adjustment and the appropriate method for such adjustment.  
         SUMMARY OF THE INVENTION  
         [0012]    This invention was directed toward the above described circumstances. Its purpose is to provide a tremolo device for the stringed instruments, which is capable of minimizing erroneous tuning, making it possible to easily and accurately carry out tuning, and to reduce the contact sound produced when the tremolo body is swung, and where the number of the locations requiring adjustment is small.  
           [0013]    The invention relates to a tremolo for a stringed instrument, constructed to obtain musical intervals by changing the tension of a string of the instrument through the swinging of the tremolo body based on the operation of an arm. A tremolo body is installed on the body of the stringed instrument to swing freely, with a string support for the support of the string being arranged on the top surface and a tremolo block protruding toward the bottom side. An arm installed on the tremolo body is operated to manipulate the swinging of the tremolo body. A reverse side mechanism base is arranged below said body. A positioning stopper is provided at the bottom of the base or body. A slide block is constructed to be able to move freely to the front or to the rear. A movable stopper is movable back and forth freely and is capable of contacting or moving away from the slide block. A link links the tremolo block and the slide block.  
           [0014]    A first spring between the bottom side mechanism base and the slide block urges the slide block toward the front. A second spring between the movable stopper and the bottom side mechanism base also urges the movable stopper to the front. When the tremolo arm is not being operated, the slide block and the movable stopper contact and the movable stopper and the positioning stopper contact due to the tensile strength of the string disposed above the body. The forces of the first and second springs bring the tremolo body into a state of equilibrium.  
           [0015]    When the tremolo body is swung to tilt toward the front by operating the arm, the tremolo block is rotated to the rear. As a result, the slide block and the movable stopper slide rearward joined by the link. When the movable stopper has been separated from the positioning stopper, and while the operation of the tremolo arm has been discontinued, the slide block and the movable stopper are restored to their original positions where the movable stopper contacts the positioning stopper due to the urging strength of the first spring and the second spring. This brings the tremolo body into a state of equilibrium.  
           [0016]    When the tremolo body is swung to tilt rearward by the operation of the tremolo arm, the tremolo block rotates to the front, which slides the slide block to the front through the link. That separates the slide block from the movable stopper. When operation of the tremolo arm has been discontinued, the slide block is returned to its original position touching the movable stopper by the tensile force of the string, thereby restoring the tremolo body to the state of equilibrium.  
           [0017]    An axial slide is provided between a first bearing and a second bearing on the bottom side mechanism base. The slide block and the movable stopper are movable freely back and forth along the axial slide. The positioning stopper is provided between the first bearing and the second bearing at the rear or bottom of the base.  
           [0018]    The movable stopper has a front which can either touch or move away from the slide block and has a rear which can touch or move away from the positioning stopper.  
           [0019]    The second spring is provided between the front of the movable stopper and the second bearing.  
           [0020]    The first spring is provided between the first spring front side installation block that has been provided on the front end of the bottom side mechanism base and the first spring rear-side installation block provided on the slide block.  
           [0021]    The rotation fulcrum for the tremolo block and the link are positioned approximately right under the swing axis of the tremolo body.  
           [0022]    The first spring front side installation block is installed such that its position may be adjusted with respect to the bottom side mechanism base.  
           [0023]    A buffer is interposed between the slide block and the movable stopper. A buffer is also interposed between the movable stopper and the positioning stopper.  
           [0024]    The link between the tremolo block and the slide block is capable of expansion and contraction.  
           [0025]    The action direction of the forces of both the first spring and the second spring is opposite to the direction of the tensile force of the strings. The spring force of the first spring is smaller than the total tensile force of the string, while the sum of the spring forces of the first spring and the second spring is greater than the total tensile force of the string, for achieving equilibrium no matter whether the tremolo body is raised or lowered.  
           [0026]    An engagement mechanism, which is capable of being engaged or disengaged, is provided between the slide block and movable stopper. The slide block and the movable stopper are engaged by the engagement mechanism, thereby regulating the movement of the slide block to the front.  
           [0027]    Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]    [0028]FIG. 1 is an oblique view of an electric guitar which incorporates a tremolo device for a stringed instrument according to one embodiment of the invention.  
         [0029]    [0029]FIG. 2 is a front view of the tremolo device.  
         [0030]    [0030]FIG. 3 is a side cross sectional view of the tremolo device, with some of its members having been removed, and showing surrounding elements.  
         [0031]    [0031]FIG. 4 is a bottom view showing the reverse side mechanism of the tremolo device.  
         [0032]    [0032]FIG. 5 is a cross section along line  5 - 5  in FIG. 3.  
         [0033]    [0033]FIG. 6 is a cross section along line  6 - 6  in FIG. 4.  
         [0034]    [0034]FIG. 7 is a cross section of the tremolo device, with some members removed when the musical intervals are coming down, and its surrounding elements.  
         [0035]    [0035]FIG. 8 is a bottom view showing the reverse side mechanism of the tremolo device during lowering intervals.  
         [0036]    [0036]FIG. 9 is a cross section of the tremolo device, with members removed, during rising intervals, and surrounding elements.  
         [0037]    [0037]FIG. 10 is a bottom view showing the reverse mechanism of the tremolo device during rising intervals.  
         [0038]    [0038]FIG. 11 shows the essential part of the tremolo device of another embodiment wherein FIG. 11A is a partial bottom view of the tremolo device and FIG. 11B is a partial side view of the same reverse side mechanism.  
         [0039]    [0039]FIG. 12 is a cross section of a third embodiment of a tremolo device with some of the members removed and showing surrounding elements.  
         [0040]    [0040]FIG. 13 is a rear side view showing the reverse side mechanism of the third embodiment of a tremolo device.  
         [0041]    [0041]FIG. 14 is a side cross section of a prior art embodiment of a tremolo device. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0042]    The example of a stringed instrument shown in FIG. 1 is an electric guitar G carrying an embodiment of the invention. The guitar includes a neck N and a body B. A head H is provided at the front end of the neck N. One terminal end region of each string S is securely held at the head H guitar by a respective string key Nb. A tremolo  1  which provides a guitar bridge is installed on the body B as a tuning device and an interval changing device. The end of each string S opposite the head H is held and fixed by the tremolo  1 . A nut Na supports the head side terminal region of each string as the nut is positioned at the front edge of the neck N. A bobbin Nc for tuning as is linked to each string key Nb.  
         [0043]    Referring to FIGS. 2 through 6, the tremolo  1  is comprised of an arm  50  for swinging the tremolo body  10 . The arm  50  is installed on the tremolo body  10  to be movable freely along with tremolo body  10 . A bottom side or reverse side restoring mechanism  60  restores the tremolo body  10  to an equilibrium state position, which is a neutral position in a balanced state subsequent to the swinging of the tremolo body  10 . In this example, the reverse side mechanism  60  is arranged inside a concave Bb that is formed in the reverse or bottom side of the body B.  
         [0044]    The tremolo body  10  in this example comprises a base plate  11  that is installed to swing freely with respect to the surface Ba of the body B. A string support, here a bridge saddle  20 , supports the string S. A tremolo block  40  protrudes below the reverse side or bottom of the base plate  11 .  
         [0045]    In this example, a plurality, here six, of string supports  20  are arranged on the base plate  11 , each for a respective strings S, for enabling tone color adjustment for each string S. FIG. 3 is a cross section that shows the tremolo device  1  when the tremolo body is in a state of equilibrium as it is not being used and also shows its surrounding elements. FIG. 4 is a bottom view showing the bottom side mechanism during the equilibrium state. In FIG. 3, the first spring  90 , described below, is omitted for convenience of explanation. That same drawing modification is also made in FIGS. 7 and 9.  
         [0046]    The base plate  11  in this embodiment is supported to swing around stud bolts Bs and Bs at the knife edges  12  at both lateral sides of the front (on the neck N side) of the base plate.  
         [0047]    A plurality of opening grooves  13  are formed in the base plate aligned with the positions of the various string supports  20  approximately at the center of the base plate  11 .  
         [0048]    Referring to FIGS. 2 and 3, each string support  20  has a saddle holder  21 , a main saddle body  25  and a rotation adjusting rod  31 . The saddle holder  21  is fixed on the base plate  11  to be adjustable back and forth (left and right in FIG. 3) along the body B. The main saddle body  25  is supported to be rotatably adjusted back and forth on the saddle holder  21  through an axle  26  that extends across the stretching direction of the string at a right angle.  
         [0049]    The main saddle body  25  has a string receiver  27  formed like a curved surface on its front part. A concave  28  for fixing the strings is formed at the rear of the body  25 . Each string S is fixed by holding the terminal region of the string S against the inner wall of the string fixing concave  28  by the string fixing block  29 . In addition, the string fixing block  29  is fixed by the tip of a rotation adjusting rod  31  that is screwed into the concave  28  for fixing the string.  
         [0050]    To the rear of each main saddle body  25 , there is a rotation adjusting rod  31  for freely manipulating the rotation adjustment of the main saddle body  25  back and forth. The bar  31  protrudes rearward and is inserted into the respective opening groove  13  in the base plate  11 .  
         [0051]    A plate spring  35  on the underside of the base plate  11  continuously urges each rotation adjustment bar  31  in the direction of forward rotation of the main saddle body  25 .  
         [0052]    An adjusting, fine tuning bolt  36  adjusts string stretching through rotation of each saddle body  25  by the forward and backward movement (or the vertical movement in the drawing) by contacting each rotation adjusting bar  31  against the urging of its plate spring  35 .  
         [0053]    If the adjusting screw  36  is rotated clock-wise, the rotation adjustment bar  31  is moved down (in the rotation direction to the rear). As the main saddle body  25  is rotated backward together with the bar  31 , the tensile force (the musical interval) rises. Contrarily, if the adjustment screw  36  is rotated counter clock-wise, the rotation adjusting bar  31  rises (in the rotation direction to the front). This rotates the main saddle body  25  to the front, reducing the tensile force of the string (or the interval).  
         [0054]    Each string support  20  is of the rocking type including a saddle holder member  21  and a main saddle body  25 . However, the invention is not limited to this and each string support may be of the non-rocking type which is more general.  
         [0055]    In this example, there are a plurality of independent string supports  20  each for a string S, thereby enabling tone color adjustment for each string S. However, it is possible to provide a string support member of the one-piece type on the base plate.  
         [0056]    Referring to FIGS. 3 and 4, tremolo block  40  protrudes below the reverse side of the base plate  11  and is inside the opening Bc that links the front and rear of the body B. At both sides of the tip or free end of the tremolo block  40 , there are link installation journals  41 , globular shaped in the drawing, that engage respective links  85 , described below, in a freely rotatable fashion.  
         [0057]    The bottom side mechanism  60  comprises a bottom side base  61 , a first bearing block  62  and a second bearing block  63 , an axial slide  70 , positioning stoppers  71 , a slide block  75 , a movable stopper  80 , links  85 , first springs  90  and a second spring  95 .  
         [0058]    The bottom side base  61  serves as the installation part for the bottom side mechanism  60  and it is fixed to the bottom side of the body B in the concave Bb  610  by a screw, etc. In FIG. 6, an opening  61   o  that corresponds in location to the opening Bc in the body B is formed slightly to the front at the center of the base  61 . The tip of the tremolo block  40  is positioned in the opening  61   o . A first bearing  62  is provided approximately at the center (the periphery on the rear side of the opening  61   o ) of the base  61 . A second bearing  63  is provided at the rear. An axial slide  70  is disposed between the first bearing  62  and the second bearing  63 .  
         [0059]    First spring front side installation blocks  64  support the front end of each first spring  90 . The blocks  64  are installed such that their positions may be adjusted relative to the bottom side base  61 .  
         [0060]    The blocks  64  are screw threaded on the adjustment screw  66  which is screwed into a screw hole of a bracket  65  that protrudes at the front of the bottom side base  61 . The blocks  64  are adjustable in position by operating the adjusting screw  66 .  
         [0061]    The foregoing enables the forces exerted by the first springs  90  to match the tension of the respective strings S at various string gauges that are used, by positional adjustment of the blocks  64 . In addition, positioning stoppers  71  regulate the progress or movement of a movable stopper  80  between the first bearing  62  and the second bearing  63  at the side base  61 .  
         [0062]    A slide block  75  is provided on the front of the axial slide  70 , and a movable stopper  80  is mounted on the rear of the axial slide  70  in such a manner and the block  75  and stopper  80  can be freely moved back and forth along the axial slide  70 .  
         [0063]    [0063]FIGS. 5, 6 shows an axial hole  76  for the slide block  75  and an axial hole  83  for the movable stopper  80 . The slide block  75  includes the first spring rear installation blocks  77  for supporting the rear ends of the first springs  90 .  
         [0064]    There are also link installation parts  78  (globular in the drawing) that engage with the links  85 , as explained below.  
         [0065]    The movable stopper  80  has a front part  81  that can either touch or be separated from the rear surface of the slide block  75 , through a buffer M 1 , on the rear surface of the slide block  75 . The moveable stopper  80  has two rear parts  82  that can touch the rear surface of the positioning stoppers  71 , through the buffers M 2 . The rear parts  82  that may protrude parallel to the positioning stoppers  71  at both ends of the front part  81  which is approximately U-shaped in FIG. 5. The number of positioning stoppers  71  that correspond to the shape of the movable stopper  80  and the shape of the movable stopper itself  80  are not limited by those mentioned above.  
         [0066]    The buffer M 1  is comprised of rubber, etc. and is interposed between the slide block  75  and the movable stopper  80 . The buffer can absorb the impact of the slide block  75  and the front  81  of the movable stopper  80  contacting each other, thereby reducing the generation of strange noise, such as contact noise, etc. The buffer M 1  is fixed to the surface of the front portion  81  of the movable stopper  80 , although the buffer M 1  can be fixed to the rear surface of the slide block  75 .  
         [0067]    Buffers M 2  are comprised of rubber, etc. and are interposed between the rear parts  82  of the movable stopper  80  and the positioning stoppers  71 , enabling the buffers M 2  to absorb the impact of contact between the rear parts  82  of the movable stopper  80  and the positioning stoppers  71  and thus reducing generation of strange noise, such as contact noise, etc. The buffers M 2  are fixed to the rear surfaces of the positioning stoppers  71 , but the buffers M 2  may be fixed to the rear surfaces  82  of the movable stopper  80 .  
         [0068]    In addition, contact between the slide block  75  and the front part  81  of the movable stopper  80  and contact between the rear parts  82  of the movable stopper  80  and the positioning stoppers  71  are surface contacts, over comparatively large areas, making it difficult for such deformation of the buffers M 1  and M 2  as will have some effect on tuning.  
         [0069]    The links  85  link the tip of the tremolo block  40  and the slide block  75 , converting the rotary or swinging movement of the tremolo block  40  into straight-line sliding of the slide block  75 . The links  85  are engaged, in a freely rotatable fashion, on the link installation parts  41  on both sides of the tip of the tremolo block  40  through the tremolo block side engaging holes  86  in the links  85 .  
         [0070]    Linkage between the links  85  and the tremolo block  40  and the slide block  75  is through a ball-joint system. This makes it easy to cope with the incline of the tremolo body  10 , back and forth and right and left, etc. in connection with the adjustment of the tilting of the tremolo body  10  by the stud bolts Bs.  
         [0071]    Preferably, the rotation fulcrums of the links  85  and the tremolo block  40  at the link installation parts  41  of the tremolo block  40  are preferably positioned immediately below the swinging axis of the tremolo body  10  (the line linking two stud bolts Bs for fixing the base plate  11  in a freely swinging fashion). This has an advantage of being able to convert swinging of the tremolo body  10  effectively into the sliding movement of the slide block  75  and the movable stopper  80 .  
         [0072]    The links  85  are designed to permit both their expansion and contraction. This makes it possible to adjust the initially set angle (the angle at the time when the tremolo is not in use) of the tremolo body  10  (base plate  11 ) by expansion or contraction of the links  85 . An additional advantage is that this can cope with tilting of the stud bolts Bs.  
         [0073]    An example of a freely expandable and contractable link  85  uses a turn-buckle construction of each link  85 . The link  85  comprises a main link body  85   a  with outer screw threads provided on its outside periphery, a tremolo block side engagement part  85   b  with internal screw threads that fit the outer screw threads of the main link body  85   a  as it has the tremolo block side engagement hole  86 , and a slide block side engagement part  85   c  with inner screw threads that fit the outer screw threads of the main link body  85   a  as the part  85   c  has a slide block side engagement hole  87 . When the main link body  85   a  is rotated or moved back and forth with respect to the tremolo side engagement part  85   c , the link  85  is either expanded or contracted in length. The structure for making each link  85  expandable or contractable freely is not limited to the example shown above.  
         [0074]    The first springs  90  and the second spring  95  maintain a state of equilibrium (a balanced state) of the tremolo body  10  (base plate  11 ) by their own spring forces which counters the tensile forces of the strings S installed on the Ba side on the surface of the body. Together, these elements restore the slide block  75  and the movable stopper  80 , whether they have been moved by the swinging of the tremolo body  10 , to their original positions prior to the shift.  
         [0075]    The first springs  90  are interposed between the first spring front-side installation blocks  64  toward the front of the bottom side base  61  and the first spring rear-side installation blocks  77  provided on the slide block  75 . The first springs  90  are elongated from their natural length when the tremolo body  10  assumes a state of equilibrium and urges the slide block  75  in the forward direction, the direction of the first spring front-side installation block.  
         [0076]    The second spring  95  extends between the front  81  of the movable stopper  80  and the second bearing  63 . Moreover, the second spring  95  is externally installed on the axial slide  70 . Meanwhile, the second spring  95  between the front  81  of the movable stopper  80  and the second bearing  63  is contracted, as compared with its natural length when the tremolo body  10  assumes a state of equilibrium, and this urges the movable stopper  80  in a forward direction, in the direction of the slide block.  
         [0077]    Therefore, the forces of the first springs  90  and the second spring  95  work in the same direction in the tremolo device  1 . The second bearing  63  may be installed so that its position is adjustable with respect to the bottom side mechanism base  61 , and the force of the first springs  90  may be adjusted by adjusting the position of the second bearing  63 .  
         [0078]    The slide block  75  is positioned at its first slide block position P 1  by the tensile force of the string S and the forces of the first springs  90  and the second spring  95  when the tremolo arm  50  is not in operation. The movable stopper  80  is then positioned at the first movable stopper position Q 1 , and the slide block  75  and the front part  81  of the movable stopper  80 , plus the rear parts  82  of the movable stopper  80  and the positioning stoppers  71  touch each other, causing the tremolo body  10  to assume a state of equilibrium.  
         [0079]    If there were no strings S, the slide block  75  would remain positioned to the front of the first slide block position P 1  due to the force of the first springs  90  and, at the time of tuning by fixing each string S to the string support member  20 , the slide block  75  is caused to gradually move backward (to the movable stopper side  80 ) due to balancing between the tensile force of the string S and the force of the first springs  90 .  
         [0080]    In an example of a six-string guitar, the total force of the first springs  90  can be set at [⅚×To−(alpha)] equivalent value where To indicates the total string tensile force after tuning. At the same time, the force of the second spring  95  can be set at [⅙×To+(beta)] equivalent value. The (alpha) and (beta) are values such that no difference stemming from the change in spring chord is produced, no change is produced in the string tensile force at the time when the hand is placed on the arm or at the time of choking and no fluttering takes place. Moreover, (alpha) and (beta) are set such that (beta) is larger than (alpha) which is larger than zero.  
         [0081]    The slide block  75  is positioned at the first slide block position P 1  so as to touch the front part  81  of the movable stopper  80  when the total string tensile force has reached said [⅚×To−(alpha)] equivalent value during the course of tuning.  
         [0082]    The sum of the force of the first springs  90  and the force of the second spring  95  becomes [⅚×To−(alpha)]+[⅙×To+(beta)]=To+(beta)−(alpha). As this is greater than the total string tensile force To subsequent to tuning, the slide block  75  and the movable stopper  80  do not move even if the tensile force of the string is increased from the time when the slide block  75  has touched the front part  81  of the movable stopper  80  to the completion of tuning.  
         [0083]    If the tensile forces of the first springs  90  and the force of the second spring  95  are set as described above, mutilation of one of the six strings would produce a remaining tensile force of approximately 5/6×To. In view of the fact that the force of the first spring  90  is [⅚×To−(alpha)] and that the remaining string tensile force is greater than that force, the slide block  75  does not move, as it stays at the first slide block P 1  where it touches the front  81  of the movable stopper  80 .  
         [0084]    Even if one of the six strings has been mutilated, the equilibrium state of the tremolo body  10  can be maintained, thereby keeping the remaining strings in their tuned states. Thus, any change in the musical intervals of the remaining strings can be prevented.  
         [0085]    In the tremolo  1 , if the arm  50  is brought into an “arm down” state or if it is held in the direction of the body surface Ba, the tremolo body  10  (base plate  11 ) swings to tilt to the front (neck N direction) with the stud bolts Bs as the fulcrum. The tensile force of each string S is reduced and the musical interval of each string comes down (flat). The tremolo block  40  that protrudes down from the base plate  11  rotates to the rear, counter clock-wise in the drawing. This moves the slide block  75  and slides the movable stopper  80  rearward along the axial slide  70  through the links  85 , which separates the rear parts  82  of the movable stopper  80  away from the positioning stoppers  71 .  
         [0086]    Subsequent to the arm-down position, if the force on the arm  50  is removed or if operation of the arm  50  is stopped, the slide block  75  and the movable stopper  80  slide forward, while touching each other. When the rear parts  82  of the movable stopper  80  have touched the positioning stoppers  71 , that movement stops restoring the slide block  75  and the movable stopper  80  to their original positions (the first slide block position and the first stopper position), and restores the tremolo body  10  to a state of equilibrium.  
         [0087]    On the other hand, when the arm  50  is pulled in the direction away from the body surface Ba, the tremolo body  10  and the base plate  11  swing to tilt backward in the direction opposite to the neck N, around the stud bolts Bs and Bs as the fulcrum. This increases the tensile force of each string S and the intervals of each string rise (become sharp). This rotates the downwardly protruding tremolo block  40  to the front (clockwise in the drawing). As a result, only the slide block  75  slides to the front along the axial slide  70  through the links  85 . Thus, the slide block  75  separates from the front part  81  of the movable stopper  80 .  
         [0088]    If the total string tension when the tremolo body  10  is in a state of equilibrium is expressed by To and the force of the first springs  90  (initially set value) is expressed by U 1 , the force required for the arm-up operation will become [To−U 1 ]. A tremolo device having this construction enables raising the arm (elevation of the musical intervals) with a force which is smaller by the force U 1  of the first springs  90 , as compared with the tremolo device which is described in Toku Kai Hei 1-93793.  
         [0089]    If, subsequent to the arm-up operation, the force applied on the arm  50  is removed or if operation of the arm  50  is stopped, the slide block  75  is slid rearward by the tensile force of each string S and the block  75  stops when the slide block  75  has touched the front part  81  of the movable stopper  80 , followed by the restoration to the original position. This restores the tremolo body  10  to a state of equilibrium. The rearward slide or return movement of the slide block  75  after stopping of operation of the arm  50  can be made smooth by setting the force of the first springs  90  smaller than the total string tensile force.  
         [0090]    Because the tremolo body  10  always returns to its original equilibrium state after a tremolo operation, in a stringed instrument equipped with the tremolo device  1  (a six-string guitar in this case), this enables eliminating inconvenience such as tuning failure which was experienced in the past. In addition, generation of noise stemming from contacts among the members of the restoration mechanism for restoring the tremolo body, when the tremolo body  10  returns to its original equilibrium state, can be prevented by action of the buffers M 1  and M 2 .  
         [0091]    In the tremolo device  1 , the tremolo body  10  is maintained in the state of equilibrium at all times by the restoring action of the restoration mechanism  80  comprised of axial slide  70 , positioning stoppers  71 , a slide block  75 , a movable stopper  80 , links  85 , the first springs  90 , and the second spring  95  when the tremolo is not in operation. As a consequence, failures in tuning stemming from choking, fluttering or string mutilation, etc. can be prevented to a maximum degree.  
         [0092]    A tremolo device  1 A according to another example of the invention is explained, with reference to FIG. 11. As tremolo device  1 A has approximately the same construction as the tremolo device  1 , the same elements as in the tremolo device  1  have the same numbers and their explanations are omitted. The characteristic feature of the tremolo device  1 A is described.  
         [0093]    The tremolo device  1 A includes an engagement mechanism  100  which is capable of engagement or disengagement and is provided between the slide block  75  of the bottom side mechanism  60 A and the movable stopper  80 . The slide block  75  and the movable stopper  80  are engaged by the engagement mechanism  100 , for regulating the forward movement of the slide block  75 . In this example, the engagement mechanism  100  is comprised of a rotatable member  101  which is approximately L-shaped including a bent piece  102  on the tip side (free terminal side). It is installed freely rotatably on the slide block  75  and is also located at a protrusion  110  which protrudes to the back side (side which is opposite to the bottom side base  61 ) which protrusion is at the front of the movable stopper  80 .  
         [0094]    As the bending piece  102  on the tip side of the rotary member  101  is positioned behind the protrusion  110  and both are engaged as shown in solid lines in FIG. 11, forward movement of the slide block  75  is regulated.  
         [0095]    On the other hand, the slide block  75  is enabled to move to the front as the rotary member  101  is rotated to the front (counter clock-wise in the drawing) and as the engagement between the rotary member  101  and the protrusion  110  is released, as shown by the broken or chain line of FIG. 11A.  
         [0096]    An axle  103  installs the rotary member  101  freely rotatably on the slide block  75 . A rotary upward member  104  of rubber, etc. is disposed for making the rotation of the rotary member  101  smooth. A concave  105  is provided on the tip of the rotary member  101  for facilitating its rotation.  
         [0097]    The rotary member  101  is installed on the slide block  75  while the protruding part  110  is provided on the movable stopper  80 . However, it is possible to reverse that and provide the rotary member on the movable stopper and the protruding part on the slide block. Moreover, the engagement mechanism is not restricted to the construction shown.  
         [0098]    An engagement mechanism  100  that regulates the forward movement of the slide block  75  makes it possible to regulate the forward movement of the slide block  75  by the engagement mechanism  100  and to effect the arrangement and tuning of each string in the state where the slide block  75  has been put to the first slide block position or in the state where the tremolo body  10  has been brought into a state of equilibrium from the standpoint of initial setting. When a string is to be tuned, therefore, it becomes possible to prevent the intervals of other strings which have been tuned from moving up or down thereby facilitating the placement of the string or its tuning. Further, the force required at the time of placing the string or its tuning can be reduced and, removal of the string becomes simpler.  
         [0099]    Another tremolo device embodiment  1 B of the invention is explained with reference to FIGS. 12 and 13. The tremolo device  1 B has approximately the same construction as the tremolo devices  1  and  1 A in the previous examples. Those elements which are the same as in the tremolo devices  1  and  1 A are identified by the same reference numbers. For convenience, the first spring and the second spring, which are described later, are omitted from FIG. 12. Characteristic features of the tremolo device  1 B are described.  
         [0100]    The bottom side mechanism  60 B of this tremolo device  1 B comprises a bottom side mechanism base  61 B arranged on the bottom side of the body B, the positioning stoppers  71 B at the rear of the base  61 B, a slide block  75 B that moves freely back and forth, a movable stopper  80 B which is positioned on the rear side of said slide block  75 B and moves freely back and forth, and which is capable of touching or getting away from the slide block  75 B and the positioning stoppers  71 B, and the links  85 B that link the tremolo block  40  and the slide block  75 B. The first springs  90 B that urge the slide block  75 B to the front are arranged between the first spring front-side installation blocks  64  that are on the front part of the bottom side mechanism base  61 B and the first spring rear side installation blocks  77 B on the front part of the reverse side mechanism base  61 B. The second springs  95 B which urge the movable stopper SOB to the front are provided between the second spring front side installation blocks  68 B that are erected approximately at the center of the bottom side base  61 B and the second spring rear side installation blocks  80   a  on the movable stopper  80 B.  
         [0101]    In this example, the positioning stoppers  71 B are erected on the rear part of the bottom side base  61 B such that they are in parallel and face each other. Moreover, the front-side windows  71   x  permit insertion of the first spring rear-side installation blocks  77 B of the slide block  75 B. The windows are formed on the front part of the positioning stoppers  71 B. The rear-side windows  71   y  that permit the insertion of the second spring rear-side installation blocks  80   a  of the movable stopper  80 B are formed on the rear part.  
         [0102]    As the first spring rear-side installation blocks  77 B on the slide block  75 B or the second spring rear-side installation blocks  80   a  on the movable stopper  80 B touch the periphery of the front end and the periphery of the rear end of the front-side windows  71   x  or the rear-side windows  71   y , movement of the slide block  75 B or of the movable stopper  80 B either to the front or to the rear is regulated.  
         [0103]    The first spring rear-side installation blocks  77 B of the slide block  75 B play the role of the link installation part that engages with the links  85 B. Moreover, an axial part  79 B for the movable stoppers protrudes from the rear of the slide block  75 B. The movable stopper  80 B can freely move back and forth along the axial part  79 B for the movable stopper.  
         [0104]    A buffer M 3  made of rubber, etc. is interposed between the rear face of the slide block  75 B and the front face of the movable stopper  80 B for reducing the generation of strange sounds like contact noise, etc. by absorbing the impact produced at contact. The buffer M 3  is fixed to the rear surface of the slide block  75 B. However, it is possible to fix the buffer M 3  on the front of the movable stopper  80 B.  
         [0105]    Like the tremolo devices  1  and  1 A, the tremolo device  1 B is constructed such that the slide block  75 B, the movable stoppers  80 B, but specifically the second spring rear-side installation blocks  80   a , and the positioning stoppers  71 B but specifically the front end peripheries of the rear side windows  71   y , touch each other because of the tensile force of the string S that has been stretched on the body surface Ba side and the forces exerted by the first springs  90 B and the second springs  95 B, thereby causing the tremolo body  10  to stay in a state of equilibrium.  
         [0106]    When the tremolo body  10  is swung to tilt it to the front through operation of the arm.  50 , moreover, the tremolo block  40  rotates rearward. This slides the slide block  75 B and the movable stopper  80 B rearward, via the links  85 B and the movable stopper  80 B, but particularly the second spring rear-side installation blocks  80   a . The slide block moves away from the positioning stoppers  71 B, particularly the front end peripheries of the rear-side windows  71   y . When operation of the arm  50  has stopped, the slide block  75 B and the movable stopper  80 B are returned to their original positions where the movable stopper  80 B touches the positioning stoppers  71 B under the forces of the first springs  90 B and the second springs  95 B, thereby restoring the tremolo body  10  to the equilibrium state.  
         [0107]    When the tremolo body  10  is swung to tilt it rearward by operation of the arm  50 , further, the tremolo block  40  rotates to the front. This slides the slide block  75 B to the front through the links  85 B and the slide block  75 B moves away from the movable stopper  80 B. When operation of the arm  50  stops, the slide block  75 B is restored to its original position where it is urged to touch the movable stopper  80 B by the tensile force of the string S, thereby restoring the tremolo body  10  into the state of equilibrium.  
         [0108]    As explained above, the tremolo  1 B functions approximately in the same manner as the tremolos  1  and  1 A producing a similar effect to the tremolo devices  1  and  1 A.  
         [0109]    This invention is not limited by the examples described above, but can be changed in construction within the invention. In each of the examples, for instance, two first springs and two links are provided. Their number, however, is not limited and one of each or three of each can be suitably used. In each example, one or two second springs are used. However, three or more second springs may also be used.  
         [0110]    In each of the examples, the positioning stopper that regulates the back and forth movement of the movable stopper is provided on the bottom side mechanism base. However, it is not limited to this, and the positioning stopper may be directly provided on the bottom side of the body.  
         [0111]    Each of the examples shows a tremolo that is to be installed on a six-string guitar. However, the invention can be used for other stringed instruments, such as a bass guitar, etc.  
         [0112]    The tremolo for stringed instruments of this invention includes a tremolo body that is restored to its original state of equilibrium subsequent to operation of the tremolo by a restoration mechanism which is comprised of the positioning stopper, slide block, movable stopper, links, first springs, second spring, etc. As a result, any failure in tuning after operation of the tremolo can be limited to a minimum. As the tremolo body is maintained in an equilibrium state at all times, further, it becomes possible to prevent possible failures in tuning stemming from choking, fluttering or string mutilation, etc. at the normal time when the tremolo is not being operated. In this tremolo device, moreover, the number of locations requiring adjustment is comparatively small, so that both the locations requiring adjustment and the method for such adjustment are easily understandable to the user, and the tuning becomes easier.  
         [0113]    In addition, in the restoration mechanism of the tremolo, the rotary movement of the tremolo block at the time when the tremolo body is swinging is converted into straight-line movement through the link, thereby sliding the slide block and the movable stopper. This makes it possible to prevent possible tilting of the first spring or the second spring or possible deformation in a direction other than the direction of expansion and contraction, which eliminates such inconvenience as the effect upon the restoration force of these springs. Accordingly, it is possible to expect a stable restoration action of the tremolo body.  
         [0114]    If the axial slide is installed between the first bearing and the second bearing on the bottom mechanism base, and if the slide block and the movable stopper are constructed in a manner to be freely movable back and forth, in particular, the back and forth movement of the slide block and the movable stopper becomes smooth, smoothing the swinging and restoration of the tremolo body.  
         [0115]    If the positioning stopper is provided between the first bearing and the second bearing of the bottom mechanism base, further, the bottom side mechanism can be made compact which is advantageous in terms of design work.  
         [0116]    If, on the other hand, the movable stopper is constructed such that a front part is capable of touching and moving away from the slide block and a rear part is capable of touching and moving away from the positioning stopper, this makes it possible to cause the movable stopper to touch and move away from the slide block and the positioning stopper using a simple and compact structure.  
         [0117]    If the second spring is provided between the front portion of the movable stopper and the second bearing, or if the first spring is provided between the first spring front side installation block that is provided on the front portion of the bottom side mechanism base and the first spring rear-side installation block that has been provided on the slide block, this has an advantage that the installation structure of each spring can be made simple and compact.  
         [0118]    Moreover, if the rotation fulcrum for the tremolo block and the link is positioned approximately right under the swing axis of the tremolo body, it is possible to easily convert the rotation of the tremolo block effectively into sliding movement of the slide block and the movable stopper, thereby making it possible to stabilize the recovery action of the tremolo body to a greater degree.  
         [0119]    If the first spring front-side installation block for the installation of the front-end side of the first spring is installed so that its position may be adjusted, with respect to the bottom side mechanism base, this makes it possible to cause the force of the first spring to agree with the tensile force of the string on string gauges that are to be used, thereby making it possible to accommodate various tastes of performers.  
         [0120]    If a buffer is interposed between the slide block and the movable stopper or between the movable stopper and the positioning stopper, this makes it possible to absorb the impact at the time of a contact among the members by the buffer when the tremolo body is restored to the state of equilibrium, thereby reducing generation of the contact noise.  
         [0121]    In the tremolo, moreover, the contact between the slide block and the movable stopper and the contact between the movable stopper and the positioning stopper becomes a surface contact and the contact area becomes comparatively large. As a result, their surface pressure becomes lower making it difficult to cause such deformation of the buffer that may produce some effect upon tuning.  
         [0122]    If the link between the tremolo block and the slide block is capable of expansion and contraction, this enables adjusting the initial setting angle of the tremolo body while the tremolo is not in operation, thereby accommodating various tastes of performers.  
         [0123]    If the forces of the first spring and the second spring are directed opposite the direction of the tensile force of the string, if the force of the first spring is made smaller than the total string tension and if, the sum of the forces of the first spring and the second spring is made larger than the total string tension, the slide block and the movable stopper do not move and the tremolo body maintains the state of equilibrium even when the tensile force of the string may be increased from the time when the slide block touches the front portion of the movable stopper to the time when tuning is completed, thereby making it possible to tune in a concise and accurate manner.  
         [0124]    Because the force of the first spring is smaller than the total string tension, moreover, the return of the slide block after tremolo operation and, accordingly, the restoration of the tremolo body to the state of equilibrium can be carried out smoothly.  
         [0125]    If the engagement mechanism that regulates the forward movement of the slide block is interposed between the slide block and the movable stopper, it becomes possible to regulate the forward movement of the slide block by the engagement mechanism and to carry out the tuning of each string in the state where the state of equilibrium in design is being maintained, thereby making it possible to effect tuning in a more simple and accurate manner.  
         [0126]    Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.