Abstract:
A tuning mechanism for a stringed instrument consists of a plurality of levers, one for each string, each lever having a pivoting point at one end, and a tuning screw at the opposite end with its tip pressing against a structural point of the instrument. The tension of the string is applied on the central portion of the lever. Each lever has a rotatable capstan to which the string is anchored and winded until it acquires tension as a sort of coarse tuning. A locking device prevents the capstan to turn backwards and the tuning screw is used for fine tuning. The levers can be placed parallel to each other and receive the strings in a compact arrangement that makes possible their placement as a block behind the nut, with a sizable reduction of length and bulk of the instrument by the virtual elimination of the peg head.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation In Part of application Ser. No. 12/798,486. 
     This application claims the benefit Patent Application Ser. No. 61/166,294 filed on Apr. 3, 2009 by the present inventor. 
    
    
     BACKGROUND 
     Previous Art 
     The most widely used mechanisms for tuning stringed instruments are machine heads. A single machine head consists of a cylinder or capstan, linked to a knob or button through a pinion and worm gears mechanism. The capstan has a hole through the far end from the gear, the string is made to go through that hole, and is wrapped around the capstan. The string is tightened by turning the capstan using the tuning knob. The machine heads, one per string, are normally mounted on the peg head, which is an extension of the neck of the instrument and can have a variety of shapes. 
     Machine heads have disadvantages. One is that the tuning process is somewhat made difficult by the change in pitch not being linear when the direction of the pitch change is reversed from low-to-high to high-to-low. This due to the play between the gears and the friction forces of the mechanism. This makes it hard to control the pitch when it has to be slightly lowered, making necessary to tune always from low to high pitch to have enough precision and tuning stability, which limits the tuning accuracy, since often players will rather accept a slight tuning error than having to restart the process. 
     Another disadvantage of machine heads is that the peg head adds to the length and bulk of the instrument. One way to eliminate this bulk is to mount the machine heads behind the bridge on the body of the guitar, but this makes the tuning process awkward because the player has to turn the buttons with the opposite hand to which he is used to, and it prevents the use of some accessories like a tremolo bar and in some cases a regular pick guard and/or multiple pickups. 
     There are other mechanism which tension the string by turning a screw that has a knob and is threadly linked to a piece having the string attached to it, so the string is tensioned by the linear movement of said piece as the screw is turned using the knob. An example of this mechanism is used in Portuguese Guitars. A variant of this mechanism has the string attached to the screw, which is prevented to turn but can move in the direction of its axis, said screw threading into a rotatable piece having a female thread and a knob and being prevented from moving except for its rotation. The string is tensioned by the displacement of the screw produced by the rotation of the knob. An example of this mechanism is Steinberger U.S. Pat. No. 5,277,095 
     These tuning screw systems solve the non linearity problem since the threaded pieces are always pressed in the same direction and other friction forces are minimal. Also they are less bulky than peg heads, but present the inconvenience of having a limited tuning range or a range which is difficult to modify, or requiring the use of special strings having anchoring rings, balls or loops at both ends which are hard to find in music stores. They also limit the amount that the string can be stretched, making necessary the replacement of the string if it stretches beyond the range of the movement of the threaded piece to which it is anchored. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the problems presented by machine heads and tuning screw systems by combining some elements of both in a compact arrangement which virtually eliminates the peg head allowing the smooth bidirectional operation of a screw system for fine tuning and the use of regular strings winded around a rotatable capstan, extending the tuning range. This is accomplished by the use of a lever with its pivoting point close to one of its ends having a rotatable cylinder or capstan mounted on it to which the string is attached by winding it as in a machine head. 
     Locking means are provided preventing the capstan from turning backwards when the string is under tension. The lever has an opening close to its end opposite to its pivoting point in which a tuning screw is threadly mounted. The tuning screw has means to turn it at one end while its opposite end pushes against a structural point of the instrument, counteracting the tension of the string which goes through the body of the lever and applies its tension in a direction essentially parallel to the tuning screw, so the string is stretched when the tuning screw is turned. 
     Turning the capstan until the string is under tension provides coarse tuning, while the tuning screw provides the fine tuning. If the tuning screw gets to the end of its range, it is turned all the way backwards loosening the string, and then the capstan is unlocked, turned to tension the string, and locked again, after which the string can be fine tuned using the tuning screw. 
     In the described embodiments the six tuners can be easily removed from the neck as a block, making this invention particularly suitable for instruments that are collapsible and can be disassembled or folded for travel. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is the frontal view of the guitar showing the tuning block with a view of the tuning knobs in the second embodiment. 
         FIG. 2  is the top view of the alternate position of the tuning knobs in the 4th embodiment. 
         FIG. 3  is the exploded isometric view of the tuner mechanism for one of six devices according to the first embodiment. 
         FIG. 4  is a cross section of the tuner of the first embodiment. 
         FIG. 5  is an exploded isometric view of a second embodiment in which the tuning screw is pivotally mounted. 
         FIG. 6  is a cross-section of the second embodiment. 
         FIG. 7  is a cross-section of a third embodiment in which the tuning screw is turned with a driver tool. 
         FIG. 8  is a fourth embodiment in which the tuning knobs are placed alternated in an horizontal plane. 
         FIG. 9  is an exploded isometric view of a fifth embodiment in which the capstan locking mechanism is a ratchet device. 
         FIG. 10  is a cross section of a sixth embodiment in which the capstan is placed in the same direction of the tuner body and a ratchet device is created by machined indentations on the capstan&#39;s shaft and a spring loaded locking pin. 
         FIG. 11  is cross section view  11 - 11  of  FIG. 10 , showing the teeth forming the gear of the ratchet. 
     
    
    
     DESCRIPTION OF THE PARTS BY NUMBER 
     
         
           1 —Body of the guitar 
           2 .—Neck of the guitar 
           3 .—Tuner block 
           7 .—Any one of the strings 
           8 .—Base plate of the tuner block 
           9 .—Any one of the plates perpendicular to the Base Plate that hold the tuner bodies 
           10 .—Any one of the tuner bodies 
           11 .—Capstan where the string is anchored 
           11 A.—Socket (or bolt head) to turn capstan  11   
           11 C—End of capstan  11  machined to be turned with multiple tools. 
           12 .—Tuning Screw 
           12 A.—Tuning Knob 
           12 B.—Tuning screw with cone point 
           12 C.—Tuning screw with socket (or head) for driver tool 
           13 .—Resting cavity for pivoting tuner screw 
           14 .—Capstan set screw 
           15 .—Threaded hole for the tuning screw on tuner body  10   
           15 B.—Threaded hole on pivot for tuning screw on second embodiment 
           16 .—Horn shaped hole through which the string crosses the tuner&#39;s body 
           17 .—Capstan receptacle hole 
           18 .—Capstan set screw threaded hole 
           19 .—Hole to insert the pivot of the tuner&#39;s body 
           20 A.—Pivoting pin common to the tuners mounted straight 
           20 B.—Pivoting pin common to the tuners mounted upside down 
           21 A,  21 B.—Passing holes on plates  9  to hold pins  20 A,  20 B 
           22 .—String threading hole on capstan  11   
           24 .—Pivot for tuning screw on second embodiment 
           25 .—Hole to insert pivot  24  on second embodiment 
           26 .—Holding extensions to hold pivot  24  on second embodiment 
           28 .—Holes where the strings cross the base plate  8   
           30 .—Gear of ratchet mechanism 
           30 B.—Machined indentation (one of several) on capstan shaft 
           30 C.—Tooth (one of several) on capstan shaft formed by machining. 
           31 .—Pawl of ratchet mechanism 
           32 .—Pawl pivoting pin 
           32 A.—Hole on pawl for its pivoting pin 
           32 B.—Hole for locking pin 
           32 C.—Locking pin 
           33 .—Hole on tuner body to receive pawl pivoting pin 
           34 .—Holding pin for loading spring 
           34 A.—Hole for holding pin  34   
           34 B.—Holding pin for loading spring 
           35 .—Pawl loading spring 
           35 A.—Locking pin loading spring 
           36 .—Hole on tuner body to receive opposite end of spring 
           37 .—Hole on pawl to receive loading end of spring 
           38 .—Retaining grove on capstan 
           39 .—Hole on tuner body to receive capstan retaining pin 
           40 .—Capstan retaining pin 
           41 .—Female thread on capstan end 
           42 .—Headless set screw 
       
    
     DETAILED DESCRIPTION 
     The following description refers to the invention applied on a guitar, but it is applicable to other stringed instruments and it can be installed as a block or individually in any position or configuration that is practical to operate, and it can use any type of knob or driver to perform the tuning process, as well as a variety of mechanisms to lock the capstan. 
       FIG. 1  illustrates an electric guitar comprising a body  1 , a neck  2  and a tuner block  3  and a plurality of strings  7 , showing how the reduced dimensions of the tuner block  3  render the guitar almost headless, reducing the bulk of the instrument. 
     First Embodiment of the Tuner Mechanism 
       FIG. 3  is an exploded isometric view of the first embodiment of the tuner mechanism showing one of the six devices used on a guitar as it relates to the other components, and it is complemented by  FIG. 4  which is a cross section of one of the tuners. 
     The center piece of the mechanism is the tuner body  10 , which works as a class  2  lever, with the pivoting point at its hole  19  crossed by pin  20 A, which rests against holes  21 A on plates  9  which transmit the forces to plate  8 . 
     String  7  goes through hole  28  on plate  8  and then crosses through the tuner body  10  at its hole  16  which has rounded edges. From hole  16  the string threads into hole  22  on capstan  11  and it is winded around it by turning capstan  11  using a driver that fits its socket (or head)  11 A. Since the most significant force securing the string to the capstan is the friction created by the winding, the string can also be secured to the capstan by the friction force only without crossing it through a hole, or instead of a hole it can go through a slot or a cut on capstan  11 . 
     Capstan  11  is turned by applying a tensioning torque on its socket head  11 A with the proper driver tool until string  7  acquires enough tension (just below its normal pitch) and then it is locked using set screw  14  which fits hole  18  on tuner body  10  and pushes on capstan  11  sideways, preventing it from turning backwards under the torque exerted by the string. 
     Capstan  11  may have flattened sides at its point of contact with set screw  14  to improve the locking effect of set screw  14 . Although a socket head is assumed to apply the tensioning torque on  11 A, capstan  11  can use any type of head and driver tool able to apply the proper torque. 
     The tension of the string is now counteracted by the pivot point of tuner body  10  at hole  19  crossed by pin  20 A and by the force acting on tuner body  10  through tuning screw  12  which works as the working force of a class  2  lever in which the load (the string tension) is applied between the pivoting point and the working force. Hence, the turning of tuning screw  12  will make the lever pivot around pin  20 A and move the “free” end of the string, and as a result change its tension, thus allowing precise tuning of the string within the range of motion of tuner body  10  when turning screw  12  with its knob (or button). 
     The pitch range can be modified by tightening or loosening the initial tension on the string exerted by capstan  11 , providing a virtually unlimited range of tuning. 
     Alternated Orientation of the Tuners 
     The distance between the tuner mechanisms is quite small, so there is not enough room to use knobs on tuner screws  12  if all the knobs were on the same row. This problem has been solved by alternating the position of the tuners in opposite directions so that instead of having six knobs in a row, there are two rows of three knobs each in alternate positions in a zig-zag configuration, with increased distance between each knob, providing enough room between the knobs to insert the fingers, the knobs being of such a diameter as to be comfortable to operate. Hole rows  21 B and pin  20 B provide the pivoting points for the tuners installed upside down. 
     In the embodiment of  FIG. 3  and  FIG. 4  the tip of the tuning screw  12  pushing on plate  8  will move on the surface of plate  8  as the tuning screw is turned because of the rotation of tuner body  10  around its pivoting point, the angle between tuner body  10  and tuning screw  12  being fixed. This does not affect the precision of the tuning process, but it does change the angle of screw  12 A in reference to the guitar&#39;s neck and the tuners of the other strings, limiting the practical range of the fine tuning screw. 
     Second Embodiment of the Tuner 
       FIG. 5  is an exploded isometric view of an embodiment in which the tuning screw can pivot on body  10  so that the position of its tip on plate  8  can remain the same through the tuning range and the angle it forms with base plate  8  essentially unchanged.  FIG. 6  is a cross-section of the tuner of this embodiment. 
     Pivot  24  is inserted into holes  25  on body  10 . Screw  12  threads into threaded hole  15 B on pivot  24 , and its cone tip fits cone cavity  13  on plate  8 , where it exerts the working force of the lever on plate  8 . The applied force is transmitted to body  10  through pivot  24  and extensions  26  on body  10 , which is machined to allow enough pivoting range to tuning screw  12 . 
     Under string tension the tip of the tuning screw  12  will remain in cavity  13 , with the effect that the swing motion of screw  12  will be unnoticeable and it will not interfere with the other tuners over a wider tuning range. 
     Third Embodiment of the Tuner 
       FIG. 7  is a cross section of an embodiment of the tuner in which no knob is used, reducing the bulk even further. Tuning screw  12 C threads directly into threaded hole  15  on body  10 , and tuning is achieved by turning screw  12 C with a driver that fits its socket (or head). 
     Since there is no need to alternate the orientation of the tuners, the upper holes  21 B on plates  9  can be omitted and the height of the tuner block reduced. Although tuning screw  12 C requires a tool to be operated, the accuracy of the tuning is improved by the better grip and torque provided by a driver tool compared to a knob. Although a socket headless screw is used in the drawings, the tuning screw can use any type of head and driver tool. 
     Fourth Embodiment of the Tuner 
       FIG. 8  is a cross section of an embodiment in which the knobs are placed in alternate positions on an horizontal plane by alternating “long” and “short” tuning screws, allowing the use of knobs that fit between the screws as shown in  FIG. 2 , eliminating the need to use tools for tuning or to alternate tuners in upside down and straight position, which renders passing holes  16  unnecessary since the string does not need to cross body  10  close to its center, allowing the string to cross tuner body  10  through the opening between holding extensions  26 , whose edges are rounded to protect the string. 
     Fifth Embodiment of the Tuner 
       FIG. 9  is an isometric exploded view of an embodiment that uses a ratchet mechanism to lock capstan  11 . This renders the coarse tuning much easier since there is no need to loosen and tighten the set screw, is suffices to turn capstan  11  in the proper sense and it will stay locked by the ratchet mechanism. Capstan  11  enters hole  17  and is held in place by a pin (not shown) on hole  39  engaging groove  38  on capstan  11 . Pawl  31  pivots on pressure pin (or screw)  32  which crosses pawl hole  32 A and is inserted in (or threaded into) hole  33  of body  10 , pivotally connecting pawl  31  to body  10 . The lower end of spring  35  enters hole  37  spring-loading pawl  31  to engage gear  30 . Spring  35  is held in place by pin (or screw)  34  which enters hole  34 A (shown only in outline) in body  10  and its upper end has a bent which enters hole  36  (shown only in outline) on body  10  providing angular locking. Pawl  31  has an extended arm that protrudes to the back of body  10  to allow the manual release of the ratchet mechanism to remove the string or reduce its tension. 
     Instead of a socket or screw head for turning capstan  11 , it has an opening and two slots at its end  11 C, allowing the use of a variety of drivers to turn it, including flat and philips screw drivers, any flat shaped object and even paper clips, rendering its operation less dependent on the availability of any particular tool. 
     Sixth Embodiment of the Tuner 
       FIG. 10  is a cross section of an embodiment in which capstan  11  is mounted parallel to lever  10  and uses a ratchet mechanism created by machining several indentations  30 B on the shaft of capstan  11 , which produces the same number of teeth  30 C in such a way that a pin  32 C sliding in opening  32 B plays the role of the pawl of the ratchet. Pin  32 C is loaded by spring  35 A which is held in place by pin (or screw)  34 A and locked in position by its far end entering a hole in body  10 . The ratchet is released by pushing downwards on ring  31 B, which disengages pin  32 C. 
       FIG. 11  is cross section view  11 - 11  of  FIG. 10 , showing the teeth forming the gear of the ratchet. Their asymmetrical shape as well as the off-center position of pin  32 C has the effect of locking capstan  11  without pushing pin  32 C outwards, since the force exerted by the tooth  30 C in contact with it is perpendicular to its surface at the point of contact, hence perpendicular to the axis of pin  32 C. Also Pin  32 C is not subjected to any torque, since the force from tooth  30 C is transmitted directly to the wall of hole  32 B. In this embodiment the string  7  loops around body  10  and is wound around capstan  11  after crossing hole  22 . Body  10  had rounded edges where the string is bent. Capstan  11  has a coaxial hole at its end  11 C and perpendicular slots cut into it to allow the use of a variety of driver tools as in the fifth embodiment. 
     String Locking Device 
     When installing a new string, the string is passed through its path which normally begins at the bridge and ends with the crossing of hole  22  on capstan  11 , after which the string is wound by turning the capstan. A certain excess length must be left on the string to be wound around the capstan and it is important that such length be within certain limits to avoid the string under tension from sliding out of hole  22  if there are not enough turns, or a build up of overlapped string turns if there are too many turns. 
     The additional length for winding is difficult to control since the string tends to slide freely inside hole  22  when it is loose. For this reason a sizable length of string is normally left after crossing hole  22  and the capstan is turned with that excess length hanging out of hole  22 . All these inconveniences can be avoided if the string can be firmly locked in hole  22  and cut as close as possible to the capstan before winding it. For this purpose the hole at the tip  11 C of capstan  11  is provided with a female thread  42  and is made to cross hole  22 . Headless set screw  42  is threaded into to allow the locking of the string  7  as it crosses capstan  11  through hole  22 . 
     Screw  42  can be of any driver type like hex socket, slot, or any other headless driver type available. It can be left permanently tightened to improve the holding of the string at the capstan if the availability of the driver tool is assured. 
     Other Embodiments 
     The specific embodiments of the invention that have been shown and described in detail do not bar the possibility of embodiments that combine elements of the embodiments described above or other embodiments and variations that will not depart from the principles of this invention. For instance, the gears of the ratchet devices described use four teeth, but a different number of teeth can be used.