Abstract:
A tuning machine for a musical instrument includes a base configured to engage a headstock of the musical instrument, an actuator rotatably connected to the base, a shaft rotatably connected to the base, the shaft providing a first aperture sized to receive a string of the musical instrument, the shaft being connected to the actuator such that actuation of the actuator causes rotation of the shaft about an axis of the shaft, a clamp member movably connected to the shaft and configured to engage the string, and a bias member connected to the clamp member and the shaft to bias the clamp member toward a closed position to engage the string when received by the shaft, where the clamp member and the shaft cooperate to inhibit removal of the string received by the shaft with the clamp member engaging the string.

Description:
BACKGROUND 
   Tuning machines are used to adjust the tension of strings of musical instruments, such as guitars, to affect the sound provided by the strings when plucked or strummed or otherwise played. For a guitar, the tuning machines are typically mounted to the headstock of the guitar. The strings extend from the body of the guitar, along the neck to the headstock. The strings extend over the frets on the neck of the guitar and over a nut at the junction between the neck and the headstock. The strings extend through respective tuning machines mounted to the headstock. Finger plates or knobs on the tuning machines can be rotated to cause shafts of the tuning machines, through which the strings respectively extend, to rotate to adjust the tensions on the strings. 
   New strings can be inserted into tuning machines as appropriate, e.g., when the guitar is first assembled or after a string breaks. To restring the guitar, the new string is affixed to the body of the guitar and run up the neck, over the nut, and into the respective tuning machine. The string is threaded through a hole in a shaft of the tuning machine, cut (as appropriate/desired), and wrapped around the neck of the tuning machine. The tuning machine is then rotated in the direction of the wrapping such that the string coils around the neck of the tuning machine until the desired tension is achieved. After the initial threading, the person restringing the guitar holds the guitar string wrapped about the neck of the tuning machine and begins rotating the tuning machine finger plate. The user typically holds the string in place until the string has been wrapped about the neck of the tuning machine such that the string can be let go without the string slipping back through the hole in the shaft of the tuning machine. Alternatively, the user can wrap the string, after threading it through the hole in the shaft, about the neck several times before beginning to rotate the finger plate of the tuning machine. 
   SUMMARY 
   In general, in an aspect, the disclosure provides a tuning machine for a musical instrument, the tuning machine including a base configured to engage a headstock of the musical instrument, an actuator rotatably connected to the base, a shaft rotatably connected to the base, the shaft providing a first aperture sized to receive a string of the musical instrument, the shaft being connected to the actuator such that actuation of the actuator causes rotation of the shaft about an axis of the shaft, a clamp member movably connected to the shaft and configured to engage the string, and a bias member connected to the clamp member and the shaft to bias the clamp member toward a closed position to engage the string when received by the shaft, where the clamp member and the shaft cooperate to inhibit removal of the string received by the shaft with the clamp member engaging the string. 
   Implementations of the tuning machines may include one or more of the following features. The clamp member is slidably connected to the shaft to slide parallel to the axis of the shaft. The clamp member provides a second aperture sized to receive the string and the clamp member is connected to the shaft to slide between the closed position and an open position, where in the closed position the first and second apertures are disposed relative to each other to inhibit receipt of the string by the first and second apertures concurrently and in the open position the first and second apertures are disposed relative to each other to receive the string by the first and second apertures concurrently. The first and second apertures are substantially circular through holes each with a diameter of about 2 mm. The clamp member and the shaft are configured such that the clamp member can slide a total of about 2 mm relative to the shaft. The shaft is hollow along its length and the clamp member is disposed at least partially inside the shaft. 
   In general, in another aspect, the disclosure provides a tuning machine for a musical instrument, the tuning machine including a base configured to engage a headstock of the musical instrument, an actuator rotatably connected to the base, a shaft rotatably connected to the base, the shaft providing a first aperture sized to receive a string of the musical instrument, the shaft being connected to the actuator such that actuation of the actuator causes rotation of the shaft about an axis of the shaft, a slider slidably connected to the shaft such that the slider can move substantially parallel to the axis relative to the shaft, the slider being substantially rotatably fixed relative to the shaft such that rotation of the shaft by the actuator causes substantially similar rotation of the slider, the slider providing a second aperture sized to receive the string of the musical instrument, the first and second holes having substantially parallel axes, the slider being slidable relative to the shaft between a first, open position where the first and second apertures are aligned sufficiently to receive the string in the shaft and the slider from outside the tuning machine and a second, closed position where the first and second apertures are misaligned sufficiently to prevent receipt of the string into both the shaft and the slider, and a spring disposed in the shaft and connected to the slider to bias the slider toward the closed position. 
   Implementations of the tuning machines may provide one or more of the following features. The shaft includes a hollow neck portion and the first aperture is a first hole provided through a wall of the neck portion. The slider includes a rod portion at least partially disposed within the hollow neck portion of the shaft. The second aperture is a second hole provided through the rod portion. 
   In general, in another aspect, the disclosure provides a tuning machine for a musical instrument, the tuning machine including a base configured to engage a headstock of the musical instrument, an actuator having a finger portion disposed outside the base and a first gear portion disposed inside the base, the actuator being rotatably connected to the base, a shaft having a second gear portion disposed inside the base meshing with the first gear portion and a neck portion disposed outside the base, the shaft being rotatably connected to the base, the shaft having a hollow neck portion providing a first hole through a wall of the neck portion, the first hole being sized to receive a string of the musical instrument therethrough, a plunger including a rod portion disposed at least partially inside the hollow neck portion of the shaft and providing a second hole through the rod portion, the second hole being sized to receive the string of the musical instrument therethrough, the first and second holes having substantially parallel axes, the rod portion being slidable within the neck portion of the shaft between a first, open position where the first and second holes align to provide a first opening sufficient to receive the string and a second, closed position where the first and second holes are misaligned to prevent receipt of the string into the plunger, and a spring disposed in the shaft and connected to the plunger to bias the plunger to the closed position. 
   Embodiments of the tuning machines may provide one or more of the following capabilities. Musical instruments can be strung and tuned using one hand. Safety can be improved for stringing a musical instrument. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of a tuning machine in a closed position. 
       FIG. 2  is a partially cut-away view of a shaft assembly of the tuning machine shown in  FIG. 1 , in the closed position. 
       FIG. 3  is a side view of a tuning machine shown in  FIG. 1 , in an open position. 
       FIG. 4  is a partially cut-away view of the shaft assembly of the tuning machine shown in  FIG. 3 , in the open position, and a portion of a worm gear. 
       FIG. 5  is a block flow diagram of a process of using the tuning machine shown in  FIG. 1  to string and tune a guitar string. 
       FIG. 6  is a side view of the tuning machine shown in  FIG. 1  in use with a guitar string. 
   

   DETAILED DESCRIPTION 
   Embodiments of the disclosure provide techniques for tuning musical instrument strings. For example, a tuning machine for a guitar includes a shaft with a through hole in its neck and a spring-biased plunger extending axially along the length of the shaft. The through hole extends transverse to the axis of the shaft. A through hole extending transverse to an axis of the plunger, and sized similarly to the hole through the shaft, is biased such that, in its normal on default position, the two holes overlap little, if at all. The plunger can be actuated to oppose the bias of the spring such that the hole through the shaft and the hole through the plunger are substantially aligned and overlapping to allow a guitar string to pass through the aligned holes. Release of the plunger allows the spring bias to push the plunger axially along the shaft such that the guitar string will be pinched and held in place by the walls of the holes through the plunger and the shaft. The tuning machine can have its shaft rotated by turning a finger plate of the tuning machine without holding the guitar string against the shaft or coiling the guitar string around the shaft prior to rotating the finger plate of the tuning machine. Other embodiments are within the scope of the disclosure, including the claims. 
   Referring to  FIG. 1 , a tuning machine  10  includes a plunger  12 , a rotating shaft  14 , a nut  16 , a washer  18 , a guide  20 , a base  22 , an arm  24 , and a finger plate  26 . The tuning machine  10  is configured to fit through, cooperate with, and be attached to a headstock  28  of a guitar, or other musical instrument. The nut  16  includes a threaded tube portion  30 , including threads  32 , that threadably fits into the guide  20 . The guide  20  is configured to fit snugly within a through hole  34  provided through the headstock  28 . The nut  16  can be tightened into the guide  20  such that the washer  18  will be pressed against one side of the headstock  28  and the base  22  will be pressed against the other side of the headstock  28  to secure the tuning machine  10  in place with respect to the guitar. The tuning machine  10  is configured to assist with gripping a guitar string that is inserted through the shaft  14  for use in tuning the sound provided by the string. 
   Referring also to  FIGS. 2-4 , the tuning machine  10 , in particular a shaft assembly  11  portion shown in  FIGS. 2 and 4 , is configured to move between a resting, closed state/position shown in  FIGS. 1-2  and an actuated, fully-open state/position shown in  FIGS. 3-4 . As shown in  FIGS. 2 ,  4 , the shaft assembly  11  includes a spring  40  and a support post  42 . The support post  42  is fixedly attached to the shaft  14  such that the post  42  is fixed, not moving, relative to an axial length of the shaft  14  and rotates with the shaft  14 . The plunger  12  and the shaft  14  are configured and connected such that the plunger  12  is slidable relative to the shaft  14  along an axis  70  of the plunger  12  and the shaft  14 . The plunger  12  is connected to the shaft  14  such that rotation of the shaft  14  induces rotation of the plunger (e.g., one or more tabs can extend from a rod portion  56  of the plunger into one or more slots provided in an interior wall of the shaft  14 ). The compression spring  40  is configured to press against the post  42  and a flange portion  44  of the plunger  12  to bias the plunger  12  away from the post  42 . The post  42  is sized and disposed within the shaft  14  relative to a ledge  46  provided by the shaft  14  such that the plunger  12  is biased against the ledge  46  in the absence of downward force on the plunger  12  toward the post  42 . The spring  40  thus biases the plunger  12  into the fully-closed state in the absence of external forces, and can be moved into the fully-open state by applying pressure to a head  48  of the plunger  12 . That is, the machine  10  can be opened by applying opposing, squeezing, forces on the plunger head  48  and the bottom of the post  42  such that the plunger  12 , and, in particular the plunger flange  44 , moves toward the post  42 . 
   The shaft  14  and the plunger  12  each provide through holes for receiving a guitar string. The shaft  14  provides a through hole  50  and the plunger  12  provides a through hole  52 . The hole  50  is provided in a neck portion  54  of the shaft  14  and the hole  52  is provided in the rod portion  56  of the plunger  12 . The plunger  12  and the shaft  14  are aligned relative to each other and holes  50 ,  52  are sized and disposed in conjunction with each other such that, in the fully-closed position shown in  FIGS. 1-2 , the holes  50 ,  52  overlap slightly such that the overlap provides a line-of-sight opening though the shaft  14  and the rod  56  that is less than a diameter of any string to be inserted through the tuning machine  10 . Alternatively, the holes  50 ,  52  may be sized and disposed not to overlap at all with the machine  10  in the fully closed position. The holes  50 ,  52  are further sized and disposed such that, when the tuning machine  10  is in the fully-open position shown in  FIGS. 3-4 , the holes  50 ,  52  overlap to provide a line-of-sight opening through the tuning machine to accommodate guitar strings (or other object) to be used in conjunction with the tuning machine  10 . For example, the holes  50 ,  52  may both be substantially circular through holes with diameters of about two millimeters each and parallel axes  51 ,  53 . Further, an amount of travel of the plunger  12 , i.e., a distance between a top of the shaft  14  and a bottom of the plunger head  48  when the tuning machine  10  is in the fully-closed position, here about two millimeters, is preferably about the same as the diameter of the holes  50 ,  52 . The hole  50  is disposed substantially in the middle of the axial length of the neck  54 , which is a concave contoured portion of the shaft  14  for accommodating the guitar string when wrapped around the tuning machine shaft  14 . 
   The holes  50 ,  52  and the spring  40  are configured such that, with a string inserted through the holes  50 ,  52 , and opening force released from the plunger  12 , the spring  40  will bias the plunger rod  56  against the inserted string, and the rod  56  and the shaft  14  will cooperate to provide sufficient friction to hold the guitar string in place while the shaft  14  is rotated. For example, while the through holes  50 ,  52  may be smooth-walled, one or both of the holes  50 ,  52  may have rough (e.g., serrated, jagged, rough-coated, etc.) surfaces to provide extra friction versus a smooth-walled hole. 
   The tuning machine  10  is configured to rotate the shaft  14  and the plunger  12  in response to rotation of the finger plate  26 . As shown in  FIG. 4 , a worm gear  72  (shown in end view), that is connected to the finger plate  26 , includes a spiral tooth  74  that meshes with the teeth  60  of the shaft  14 . Rotation of the gear  72  causes the tooth  74  to push against one or more of the teeth  60  to turn the shaft  14  and thus the plunger  12 . 
   The tuning machine  10  can be assembled relatively easily. The base  22 , the arm  24 , and the guide  20  can be cast out of appropriate metal. The finger plate  26  can be attached to the worm gear  72  disposed inside of the base  22  (e.g., by screwing). The plunger rod  56  and the flange  44  can be machined or cast or otherwise made and inserted through a counter-bored hole  58  through the shaft  14  that also provides the ledge  46  such that the holes  50 ,  52  are angularly aligned (i.e., their axes  51 ,  53  are parallel). The plunger head  48  can be attached to the rod  56 , e.g., by welding. The spring  40  can be inserted into the hole  58 , and the post  42  can be inserted into the hole  58  behind the spring  40  and affixed to the walls of the shaft  14 . The shaft assembly  11  can be inserted through a hole in the base  22  and the guide  20  such that the teeth  60  in a gear portion of the shaft  14  mesh with the worm gear  72  attached to the finger plate  26 . The hole through which the shaft assembly  11  is inserted can be sealed. The guide  20  can be inserted through the hole  34  provided in the headstock  28 , and the washer  18  and the nut  16  slid over the top of the shaft assembly  11  such that the threaded tube  30  is fit into the guide  20 . The washer  18  can be turned to tighten the washer  18  against the top of the headstock  28  to fix the tuning machine  10  in place relative to the headstock  28 . 
   In operation, referring to  FIG. 5 , with further reference to  FIGS. 1-4  and  6 , a process  110  of adjusting the tension of a guitar string includes the stages shown. The process  110  is exemplary only and not limiting. The process  110  can be altered, e.g., by having stages added, removed, or rearranged. 
   At stage  112 , a user pushes the plunger  12  relative to the base  22 . The tuning machine  10  is in its normally-closed resting position and the user squeezes the plunger  12  and the base  22  such that the plunger  12  moves relative to the base  22 . The plunger  12  moves toward the base  22 , compressing the spring  40 . The holes  50 ,  52  move from their slightly-overlapping closed state to a greater-overlapping relative position. 
   At stage  114 , the user inserts a guitar string  62  through the holes  50 ,  52 . At stage  112 , the user has moved the plunger  12  enough such that the holes  50 ,  52  overlap to provide sufficient room for the desired guitar string  62  to be inserted through the holes  50 ,  52 . The user preferably inserts the guitar string  62  completely through the holes  50 ,  52  such that the string  62  protrudes from the opposite side of the shaft  14  into which the string  62  was inserted. The user releases the plunger  12  once the string  62  extends through the holes  50 ,  52 . The plunger  12  moves away from the base  22  until the guitar string  62  impedes further movement of the plunger  12 . The plunger  12  is then in a relative position with respect to the shaft  14  that is an intermediate, partially-closed position between fully-open and fully-closed. This string-engaging position, as shown in  FIG. 6 , will vary depending upon the dimensions of the particular string  62  inserted through the tuning machine  10 . The user preferably pushes or pulls the guitar string  62  through the overlapping holes  50 ,  52  until the guitar string  62  can be inserted no more through the holes  50 ,  52 . 
   At stage  116 , the tension on the guitar string  62  can be adjusted to tune the guitar string  62  to the desired pitch. The user twists the finger plate  26  relative to the base  22  to cause the worm gear  72  to push against the teeth  60  to cause the shaft  14  to rotate to increase tension on the guitar string  62 . The user can twist the finger plate  26  and cause the shaft  14  to rotate to coil the string  62  about the neck  54  without having to hold the string  62  or wrap the string  62  around the neck  54  before beginning to twist the finger plate  26 . 
   Other embodiments are within the scope of the disclosure. For example, while the hole  50  has been shown and described as a through hole through the shaft  14 , non-through holes may be used. For example, a hole may be provided in one side of the tube portion comprising the neck  54  of the shaft  14  such that a guitar string may be inserted into the neck  54  but will not pass all the way through the neck  54 . This may, for example, improve safety by limiting exposure of a potentially sharp end of a guitar string. Further, the plunger may be equipped to cut guitar strings in addition to hold guitar strings. For example, the plunger rod may include a sharp cutting portion configured to cut through a guitar string and a secondary portion configured to provide friction to hold the guitar string in place relative to the shaft  14 . Or the plunger rod may comprise a knife edge that will cut the string if sufficient force, greater than that provided by the spring, is applied to the plunger and will help hold the string with only the spring force applied. Further still, multiple openings may be provided in the plunger rod with one opening providing a cutting mechanism for cutting a guitar string and another opening through the plunger rod providing frictional engagement for holding the guitar string in place. Further, while the discussion focused on guitars and guitar strings, disclosed embodiments can be applied to other uses, e.g., other musical instruments. Further still, the sliding member (the plunger, as described) could be on the outside of the shaft, the neck could be on the sliding member, and/or mechanisms other than a neck could be used to help retain a coiled string (e.g., pegs above and below holes for the string through the tuning machine). Alternatively, there may be no mechanism to retain the string around the tuning machine. 
   Still other embodiments are within the scope of the disclosure.