Abstract:
A capo device has a clamping assembly and individually selectable pressure pad assemblies for compressing selected strings of a stringed instrument to selectively tune the stringed instrument. The pressure pad assemblies are adapted to be selectively vertically lifted or lowered relative to the strings of the stringed instrument to vary the permutations for chord tunings.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to capos and, more particularly, to a capo device constructed and arranged to permit selective string compression. 
   2. Background Information 
   A capotasto (hereinafter referred to as a “capo”) applies compression simultaneously to some or all strings at the same fret of a stringed musical instrument. Examples of conventional partial capos (capos providing selective compression) are described in U.S. Pat. Nos. 5,623,110, 4,334,457 and 4,183,279. 
   The conventional capos are constructed to use straps or other means of attachment of the capos to the fretboard of the stringed instrument and are cumbersome to use. Thus, the conventional capos have been difficult to use because they are not easily attached and detached in an expeditious fashion while also being capable of producing a precise compression suitable for an expert guitarist. 
   Moreover, the conventional capos do not provide a toggle pad that can be easily lifted from and lowered to a compression state to vary the tuning of a chord by simply turning a knob wherein the knob can be used by the guitarist to adjust the toggle pad in both the X-axis and Y-axis. Furthermore, the toggle pad cannot be adjusted in both the X-axis and Y-axis quickly and conveniently while the capo is installed. 
   Moreover, conventional capos do not provide a clamping assembly that includes a two-piece rigid yoke hinged by a pin and having a cushioned cradle wherein the yoke is capable of expansion and contraction along the X-axis as the capo is slid or moved up and down the fretboard. Furthermore, the conventional capos do not provide a universally adaptable fretboard clamping assembly that allows the assembly to be easily locked and unlocked by a simple turn of a fastener or knurled screw. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a capo device which is easily attached to and detached from the fretboard of a stringed instrument in an expeditious fashion. 
   It is another object of the present invention to provide a capo device which is capable of producing a precise compression suitable for an expert guitarist. 
   It is another object of the present invention to provide a capo device having a universally adaptable fretboard clamping assembly that allows the assembly to be easily locked and unlocked relative to the fretboard of a stringed instrument. 
   It is another object of the present invention to provide a capo device which is simple to use and economical to manufacture. 
   It is yet another object of the present invention to provide a method of tuning a stringed instrument using the capo device according to the present invention. 
   The foregoing and other objects of the present invention are carried out by a capo device comprising a clamp assembly and a plurality of pad assemblies. The clamp assembly has a yoke and a strut. The strut has a first end hingedly coupled to a first side of the yoke, a second end securable to a second side of the yoke, and a slide channel arranged to traverse a longitudinal axis of a length of strings on a stringed instrument. Each of the pad assemblies is mounted for undergoing slidable movement in the slide channel of the strut in the direction traversing the longitudinal axis of the instrument strings to a position over an underlying string and for being selectively vertically lowered to compress the underlying string. 
   In a preferred embodiment, the clamp assembly further comprises an elastomeric member received in the yoke, the elastomeric member having a concave recess formed therein to provide a cradle for a fretboard of the stringed instrument. The yoke preferably comprises a two-piece member hinged together via a hinge pin for undergoing pivotal movement relative one another and relative to the fretboard of the stringed instrument. 
   In a preferred embodiment, each of the pad assemblies comprises a traveler plate, a toggle rod, and a toggle pad. The traveler plate has a threaded hole and two wings, the two wings radiating from front and back edges of the traveler plate and being arranged to mate with and slide in the slide channel of the strut. The toggle rod has a threaded bore coupled in the threaded hole of the traveler plate and a turn knob. The toggle pad is coupled to a bottom end of the threaded bore so that turning of the toggle rod via the turn knob in a clockwise or counterclockwise direction vertically lowers or vertically lifts the toggle pad. 
   In another aspect, the present invention is directed to a method of tuning a stringed instrument. A capo device is provided which has a plurality of pressure pad assemblies mounted for undergoing sliding movement in a first direction transverse to a longitudinal axis of a length of strings of the stringed instrument, each of the pressure pad assemblies having a pressure pad mounted for undergoing vertical movement in a second direction transverse to the longitudinal axis of the strings and transverse to the first direction. The capo device is clamped about a fretboard of the stringed instrument at a fret. The pressure pad assemblies are slid and aligned with underlying strings of the stringed instrument. Selected ones of the pressure pads of the pressure pad assemblies are moved vertically towards corresponding selected underlying strings of the stringed instrument and the selected underlying strings are compressed to selectively tune the stringed instrument at the fret. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing summary, as well as the following detailed description of preferred embodiments of the invention, will be better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the invention, there is shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangement and instrumentalities shown. In the drawings: 
       FIG. 1  illustrates a perspective view of a capo device according to the present invention; 
       FIG. 2  illustrates an exploded view of the capo device of  FIG. 1 ; 
       FIG. 3  illustrates a top view of the capo device of  FIG. 1 ; 
       FIG. 4  illustrates a side view of the capo device of  FIG. 1 ; 
       FIG. 5  illustrates a bottom view of the capo device of  FIG. 1 ; 
       FIG. 6  illustrates a perspective view of the adjustable string pressure pad assembly; 
       FIG. 7  illustrates a side view of the adjustable string pressure pad assembly of  FIG. 6 . 
       FIG. 8  illustrates a top view of the hinged strut member; 
       FIG. 9  illustrates a side view of the hinged strut member; 
       FIG. 10  illustrates a bottom view of the hinged strut member; 
       FIG. 11  illustrates a perspective view of the hinged strut member; and 
       FIG. 12  illustrates a fretboard with a capo device installed thereon. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   While this invention is susceptible of embodiments in many different forms, this specification and the accompanying drawings disclose only some forms as examples of the use of the invention. The invention is not intended to be limited to the embodiments so described, and the scope of the invention will be pointed out in the appended claims. 
   The preferred embodiment of the capo device according to the present invention is described below with a specific application to a guitar. However, it will be appreciated by those of ordinary skill in the art that the present invention is also well adapted for other types of stringed instruments. 
   Referring now to the drawings in detail, wherein like numerals are used to indicate like elements throughout, there is shown in  FIGS. 1-12  an embodiment of a capo device, generally designated at  10 , according to the present invention. 
   Referring first to  FIGS. 1-5 , the capo device  10  includes a universal fretboard clamping assembly  20  having a yoke  22  and a hinged strut member  50  hingedly coupled to one side of the yoke  22 . The hinged strut member  50  is intended to be fastened to the other side of the yoke  22  via a fastener  90 . The yoke  22  is a two-piece rigid member comprised of members  26 ,  28  connected together by a hinge pin  24 . The two-piece rigid member  26 ,  28  forms a quasi or generally V-shaped support structure or rigid frame for placement of an elastomeric member  40  therein. The top of the elastomeric member  40  includes a concave recess  42  contoured to provide a cradle  44  for placement of a fretboard  5  of a stringed instrument ( FIG. 12 ) within the fretboard clamping assembly  20 . 
   In the exemplary embodiment, the elastomeric member  40  is made of rubber. The elastomeric member  40  may be made of other elastomeric or resilient material capable of automatically and resiliently conforming or adapting to the structural contour of the fretboard  5 . The elastomeric member  40  also prevents scratches or other nicks in the fretboard during clamping, sliding or when the fretboard is being positioned in yoke  22 . The elastic and resilient properties of the elastomeric member  40  allow the capo device  10  to be used with and readily adapted for use with different fretboard shapes and styles of stringed instruments. The two-piece rigid member  26 ,  28  may be made of metal, plastic or other rigid and durable material. 
   The first member  26  of the yoke  22  is generally V-shaped and has two legs  26   a  and  26   b  separated by an obtuse angle. The free end of the first leg  26   a  includes a hinge member  27   a  for mating connection with one end of the hinged strut member  50 . The free end of the second leg  26   b  has a hinge member  27   b.    
   The second member  28  of the yoke  22  is generally V-shaped and has two legs  28   a  and  28   b  separated by an obtuse angle. The free end of the first leg  28   a  includes a threaded hole  29   a  as shown in phantom in  FIG. 2 . The threaded hole  29   a  has a center axis that aligns with the longitudinal length of the first leg  28   a . The threaded hole  29   a  is adapted to receive a threaded shaft  92  of the fastener  90  which in the exemplary embodiment is a knurled screw. The knurled screw is but one example of a fastener  90  intended to fasten, secure or lock the hinged strut member  50  the top of the second member  28 . The free end of the second leg  28   b  has a hinge member  29   b  for mating connection via pin  24  with the hinge member  27   b  of the second leg  26   b  of the first member  26 . 
   The hinged connection defined by the hinge members  27   b ,  29   b  and the pin  24  allows the first and second members  26 ,  28  of the yoke  22  to undergo pivotal movement relative to one another. Thus, the defined hinged connection allows the yoke  22  to expand or contract such that the angle between the second legs  26   b  and  28   b  of each member  26 ,  28 , respectively, increases or decreases. Thus, the two-piece yoke  22  is capable of selectively adjustable expansion and contraction along the X-axis as the capo device  10  is slid or moved up and down the fretted neck of the stringed instrument. The expansion and contraction capability is one variability provided by the capo device  10  to enable precisely applied compression and universal adaptability. 
   In the exemplary embodiment, the first legs  26   a  and  28   a  are arranged to be essentially parallel. On the other hand, the second legs  26   b  and  28   b  form a generally V-shaped cavity. The bottom perimeter surface of the elastomeric member  40  is contoured to trace the profile of the interior surfaces of the two-piece yoke  22 . However, instead of forming a V shape that tracks the V shape defined by the second legs  26   b  and  28   b , the bottom apex of the elastomeric member  40  is truncated. Accordingly, as the yoke  22  contracts and expands, the elastomeric member  40  may slide down in the V-shaped cavity during expansion or, alternately, slide up during contraction. 
   The first leg  28   a  on the second member  28  is thicker than the other legs. Moreover, the top surface of the free end of the first leg  28   a  includes a plurality of ribs  30 , the purpose of which is described later. 
   With specific reference to  FIGS. 8-11 , the hinged strut member  50  includes, in general, a rectangular structure  52  having two ends  53   a  and  53   b . The first end  53   a  is hingedly coupled via the hinge pin  32  to the hinge member  27   a . The second end  53   b  includes, on the underside of the rectangular structure  52 , a plurality of ribs  31  intended to mate with ribs  30  of the yoke  22 . When the capo device  10  is locked (as will be described later), the ribs  30  and  31  interleave and frictionally engage one another to minimize if not prevent slipping. 
   The rectangular structure  52  also has formed therein a slide channel  54  for placement of a plurality of adjustable string pressure pad assemblies  70  ( FIGS. 1-4 ) and a slot  51 , the slide channel  54  and the slot  51  being separated by a bridge  55 . The slot  51  has an open end toward the second end  53   b . On the other hand, the slide channel  54  has an open end toward the first end  53   a.    
   The hinged strut member  50  and the slide channel  54  extend across the fretboard  5  along an axis (X-axis) that traverses the longitudinal length (Z-axis) of strings  6  of the stringed instrument ( FIG. 12 ). Likewise, the plurality of adjustable string pressure pad assemblies  70  are in a line along the X-axis, the line being transverse to the longitudinal length of the strings  6 . Moreover, the length of the slot  51  extends along the X-axis. 
   The slide channel  54  includes opposing recessed grooves  56   a ,  56   b , shown in phantom in  FIGS. 8 ,  9  and  10 , along opposing interior perimeter sides of the channel  54 . Moreover, the hinged strut member  50  is constructed and arranged to include a feed hole  58  for receiving and feeding the adjustable string pressure pad assemblies  70  into the slide channel  54 . In the exemplary embodiment, six (6) adjustable string pressure pad assemblies  70  are shown. Alternatively, the feed hole  58  can be used to remove the adjustable string pressure pad assemblies  70  to adapt the capo device  10  to a four (4) or five (5) string stringed instrument. For example, a bass guitar typically has four (4) strings. 
   In the exemplary embodiment, a through hole  60  extends from side-to-side (across the opening of the slide channel  54 ) of the hinged strut member  50 . The through hole  60  is adapted to receive a locking pin  62  ( FIG. 2 ) to lock the plurality of adjustable string pressure pad assemblies  50  in the slide channel  54 . A second through hole  64  is formed in the hinged strut member  50 . The second through hole  64  is provided in close proximity to the first end  53   a  and receives the hinge pin  32  ( FIG. 2 ), the first end  53   a  being a hinged end. The locking pin  62  prevents the assemblies  70  from sliding out of the slide channel  54 . Once the locking pin  62  is removed, the assemblies  70  can slide in or out of the slide channel  54  via the feed hole  58 . Therefore, the capo device  10  can be adapted for or varied for the number of strings of the stringed instrument. 
   In the exemplary embodiment, since the slide channel  54  is open to the end  53   a , the frame of the hinged strut member  50  is formed to provide a gap for placement of the hinge member  27   a . Thus, one side of the hinged strut member  50  is capable of rotation about a Y-axis via the hinge connection with the yoke  22 . When installing the capo device  10 , the user simply rotates the hinged strut member  50  to an open position via the hinge connection about the pin  32 . Thereafter, the fretboard is placed in the cradle  44  in the yoke  22 . 
   The capo device  10  is intended to be securely fastened or locked to the other side of the yoke  22  via the fastener  90 . In the exemplary embodiment, the fastener  90  includes a threaded portion  92  and a top knob  94 . Below the knob  94 , the fastener  90  includes a collar  96  which has a diameter smaller than the diameter of the knob  94  but larger than the width of the slot  51  of the strut member  50 . When locking the clamping assembly  20 , the fastener  90  is rotated either clockwise or counterclockwise in the threaded hole  29   a  of yoke  22  to enable the guitarist to tighten or untighten the fastener  90 . As the fastener  90  is tightened, the collar  96  presses down on the top surface of the hinged strut member  50 . Stated otherwise, the collar  96  clamps down on the top surface of the hinged strut member  50 . This process allows the universal fretboard clamping assembly  20  to be clamped and then locked to the fretboard. However, in some instances, the compression force exerted by the assemblies  70  to the selected string combination is not applied or may need to be removed. 
   To move the capo device  10  from a first location on the fretboard  5  to a second location, the clamping force exerted by the collar  96  needs to be removed. To remove the clamping force of the collar  96 , the fastener  90  is rotated to raise the collar  96 . Thus, the capo device  10  becomes unlocked. Thereafter, the capo device  10  can be slid to a second fret location without the need to remove the clamping assembly  20 . Once the capo device  10  is moved to the second fret location, the clamping assembly  20  is re-locked by turning the fastener  90 . 
   As can be appreciated, the width of the fretboard  5  tapers toward the end thereof. The two-piece yoke  22  is capable of expansion and contraction along the X-axis as the capo device  10  is slid or moved up and down the fretboard along the Z-axis. Accordingly, the fastener  90  is slid in the slot  51  of the strut member  50  to accommodate for the expansion and contraction variances of the yoke  22 . Moreover, after the universal fretboard clamping assembly  20  is re-locked, the string pressure pad assemblies  70  may need to be adjusted such that the gap G ( FIG. 3 ) between adjacent assemblies  70  is increased or decreased to enhance the precision of the compression to the underlying string  6  of the stringed instrument. 
   Since each of the plurality of adjustable string pressure pad assemblies  70  are the same, only one such pressure pad assembly will be described in detail. As best seen in  FIGS. 6 and 7 , the assembly  70  includes a traveler plate  72  having two wings  74   a  and  74   b  radiating from the front and back edges of traveler plate  72  and arranged to mate with and slide in the opposing recessed grooves  56   a ,  56   b  along the length of the slide channel  54 . The center of the traveler plate  72  includes a threaded hole  76 . The assembly  70  further includes a toggle rod  78  having a threaded portion  80  coupled in the threaded hole  76  (shown in phantom in  FIG. 7 ). The bottom end of the threaded portion  80  has a toggle pad  82  coupled thereto. The top end of the threaded portion  80  has a turn knob  84 . In the exemplary embodiment, the toggle pad  82  is adapted to be snapped on and off of the bottom end of the threaded portion  80 . 
   In operation, the travelers  72  are slid in the slide channel  54  to align the toggle pads  82  to a position over the strings  6  of the stringed instrument. This provides adjustability along the X-axis by the capo device  10  to provide a more precise compression. Moreover, the assemblies  70  can be removed by sliding the travelers  72  out of the slide channel  54  via the feed hole  58 . 
   The turn knobs  84  provide an expedient and readily accessible means for selectively providing or adjusting compression on any one string  6  by a simple rotation either clockwise or counterclockwise of the toggle rod  78 . Screwing the toggle rod  78  clockwise lowers the respective toggle pad  82  to compress the corresponding underlying string  6  down on top of the fretboard  5  at a predetermined fret. Unscrewing the toggle rod  78  counterclockwise raises or lifts the respective toggle pad  82  to reduce or even eliminate any compression on the underlying string  6 . Accordingly, any combination of selected toggle pads  82  can be used to create new alternate tunings. Other tunings and permutations can be achieved by moving the capo device  10  up and down the fretboard  5  to a different fret location and picking out various string combinations for compression. Additionally, two or more capo devices  10  can be combined for obtaining additional chords or alternate tunings. 
   The adjusting capability of the toggle pad  82  in the X-axis and Y-axis directions is another variability provided by the capo device  10  to enable precisely applied compression and various tuning permutations quickly and conveniently. All of the strings  6 , or any combination thereof, can be utilized to create new chords or alternate tunings. Thus, the precision to compress the strings  6  is specific and more significant than existing capos. 
   When using the capo device  10 , the universal fretboard clamping assembly  20  is clamped and locked before the compression force is applied by the toggle pad  82 . This minimizes damage to the strings. The compression force exerted by the toggle pads  82  applies pressure to the strings selectively, allowing the musician to create new alternate tunings. When sliding, the compression force of all assemblies  70  is lifted or removed as the fastener  90  is unscrewed and the collar  96  lifted. As the collar  96  is lifted, the end  53   b  of the hinged strut member  50  becomes unlocked to eliminate the compression forces. More specifically, as the fastener  90  is rotated counterclockwise, the threaded bore  92  is moved upward in the threaded hole  29   a . Thereby, the collar  96  is raised. 
   The universal fretboard clamping assembly  20  is readily adapted for both a typical 6-string guitar and a 4-string bass guitar, by simply sliding off (removing) two of the adjustable string pressure pad assemblies  70 . The embodiment shown herein is for a regular 6-string guitar. 
   The toggle pads  82  are designed to be independent of the threaded rod  78 . When the plastic or other material of the toggle pads  82  touches the strings, the toggle pads  82  discontinue rotating to prevent damage or torque to the strings, yet the threaded rods  78  will allow a continued downward pressure, thus locking the strings against the fretboard  5 . 
   The unique construction of the capo device of the present invention allows the capo device to be easily attached to and detached from the fretboard of a stringed instrument in an expeditious fashion. The capo device has a universally adaptable fretboard clamping assembly that allows the assembly to be easily locked and unlocked relative to the fretboard of a stringed instrument. The capo device of the present invention is capable of producing a precise compression suitable for an expert guitarist, and is simple to use and economical to manufacture. 
   The foregoing description of the embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents.