Abstract:
For battery-operated guitars and other stringed musical instruments, a coaxial battery-access cover cap mounts an audio phone jack that delivers the instrument&#39;s audio output. For battery access, the cover cap, which has a knurled rim for easy finger-gripping, can be removed from an attachment collar secured to the instrument with simple rotation of less than a half turn. As an option to enable the cap assembly to be installed in the instrument in place of an existing strap-peg, a strap-peg may be formed integrally on the cover cap around the jack opening. Extended embodiments can include an integral battery compartment with provision for mounting an electronic module enabling features including amplification, buffering, DSP and other effects in a self-contained system that requires only a single round opening for mounting in the instrument. The invention can be incorporated in original manufacture or as an after-market upgrade to practically any stringed instrument.

Description:
FIELD OF THE INVENTION 
   The present invention is in the field of musical instruments, and more particularly electric stringed instruments such as guitars, including those that may be originally equipped with electrical/electronic devices such as an on-board electric pickup, associated preamplifier, battery power supply, DSP (digital signal processing) and other sound processing effects. 
   BACKGROUND OF THE INVENTION 
   Apart from strictly acoustic instruments, it has become common practice to equip stringed instruments such as guitars with electronic sound reinforcement, typically, in an “electric” guitar, utilizing a magnetic pickup device that senses vibration of steel strings electro-magnetically, or in an “acoustic” instrument with non-metallic strings, utilizing a microphone pickup. The audio signal from the pickup is normally transmitted from the guitar to an external power amplifier/sound reinforcement system via a flexible audio cable fitted at each end with a connector plug, typically of the well known quarter-inch audio phone plug type, one end engaging a mating phone jack mounted in a suitable location on the instrument and the other end engaging a mating phone jack at the input of the external amplifier. 
   Many such instruments are in use without on-board amplification, with the pickup signal, usually modified by passive controls/components, fed directly at relatively high source impedance via the flexible audio cable. Such passive high impedance systems are inherently subject to environmental interference such as power line hum and to audio/musical performance degradation as a function of cable type, length, shielding integrity, characteristic impedance and termination impedance. As a technological refinement to mitigate such problems, with the advance of electronic technology there has been a trend to provide active on-board electronics: at least a pre-amplifier and buffer, typically powered from an on-board battery. The resultant lower source impedance and higher signal level make the system inherently far less vulnerable to degradation due to the above-mentioned audio cable variations, allowing much greater cable lengths and offering the player the potential of a wide variety of on-board control capabilities and special musical performance effects. 
   Guitars and other lute family instruments are typically supported for playing purposes by a shoulder strap attached to opposite ends of the guitar. At the body end, it is traditional to provide a central “strap-peg” or “end-pin” made of wood, plastic or metal, and configured with an annular flange to engage an opening, e.g. a slotted hole, in the shoulder strap end in a manner that is both secure for playing and readily removable. 
   DESCRIPTION OF KNOWN ART 
   Whether provided originally or added as after-market, an on-board battery generally requires modification of the basic original guitar body to provide a storage compartment for the battery, as well as an access opening needed for replacement, typically utilizing a hinged or removable cover. Particularly in high quality acoustic instruments such as guitars and violins, the extent of the modification required for battery access, even when enclosed with a metal or plastic plate, raises concerns regarding the degree of negative impact such modification will have on acoustic playing quality. It is typically problematic to decide where to locate the battery opening on the instrument for least potential detrimental impact. 
   U.S. patent publication 2004/0074380 to Fishman for a PACKAGED PREAMP discloses a packaged preamp with an integral pickup, a battery holder, an output jack, and a plurality of control mechanisms. A relatively large rectangular panel  12  is shown mounted to a side wall region  14  at the head end of an acoustic guitar  10 , offset from the centrally-located strap-peg and is configured with an opening and cover for battery access. 
   U.S. Pat. No. 5,693,898 to Fishman for a HINGED CONTROL PANEL FOR ELECTRIFIED ACOUSTIC GUITAR shows a relatively large opening in a wall  1  of an acoustic guitar to accommodate assembly  2  having a fixed frame  10  hinged at  16  to panel  20  carrying a set of controls and output jack on its outer face and supporting, on the rear side, a circuit board  60 , shield panel  70  and battery compartment  73 . 
   U.S. patent publication 2005/0045021 to Berger et al for a STRAP BUTTON AND ATTACHMENT shows the strap button  11 , i.e. “strap-peg”, retained by screw  12  enclosed by a threadedly attached face cap  16  which is ornamentally shaped as a human face, optionally skeletal. 
   U.S. Pat. No. 5,809,136 to Turner for a CIRCUMFERENTIAL-CONTACT PHONE JACK SOCKET shows a jack socket with an entry opening  252  in an end cap that may optionally be shaped as a strap-peg  158  for an acoustic guitar. 
   OBJECTS OF THE INVENTION 
   It is a main object of the invention to enable original incorporation or after-market addition of active electronic apparatus into stringed musical instruments such guitars and the like, including an audio output jack along with convenient accessibility for replacement of on-board batteries, in a manner that requires minimal detrimental structural modification of the instrument and that imposes minimal impairment of the original inherent musical quality of the instrument, particularly if it is an acoustic instrument. 
   It is a further object to enable such incorporation and addition in a manner that requires only a single opening of relatively small size in a strategically located region of the body wall of the musical instrument. 
   BRIEF DESCRIPTION OF THE INVENTION 
   The foregoing objects and others have been met in the present invention which, in a basic embodiment for instruments that may be already equipped with active electronics, provides battery access via a coaxial cap assembly including a cover cap configured with a knurled rim for finger-gripping and a cylindrical rear cavity that fits over and engages a cap-attachment collar that is affixed to the host instrument in a manner that enables the cover cap to be readily removed by the user for battery access. Attached to the cover cap and extending to the rear is an audio phone jack that accepts a standard audio cable phone plug inserted though a central circular opening in the cover cap. The phone jack supports a battery contact spring that extends rearward into a battery compartment and makes contact with one of the battery cells. As an option to enable the cap assembly to be installed in the instrument in place of an existing strap-peg, a strap-peg may be formed integrally on the cover cap around the jack opening. The attachment collar may be internally threaded and mounted to the instrument via an externally threaded bushing that is dimensioned internally to serve as the battery access opening. 
   In an extended embodiment, this bushing may be made part of a main body of a battery compartment that is closed at the opposite end. In a further extended embodiment for introducing a first or additional electronic module into an instrument, the main body is adapted to support an electronic module physically and to connect it electrically to form a self-contained active electronic system that can receive input from the instrument&#39;s string pickup and deliver output at the phone jack. The entire assembly can mount in a single circular mounting hole through the instrument body wall, which becomes clamped between the collar at the open outer end and a hex nut tightened against the inner surface of the instrument wall. The invention can be incorporated in original manufacture or as an after-market upgrade to practically any stringed instrument. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and further objects, features, and advantages of the present invention will be more fully understood from the following description taken with the accompanying drawings in which: 
       FIG. 1  is a perspective view of a preferred extended embodiment of the present invention shown in an assembled condition. 
       FIG. 2  is a front view of the subject matter of  FIG. 1 . 
       FIG. 3  is a rear view of the subject matter of  FIG. 1 . 
       FIG. 4  is a side view of the subject matter of  FIG. 1 . 
       FIG. 5  depicts the subject matter of  FIG. 4  rotated to show a bottom view. 
       FIG. 6  depicts the subject matter of  FIG. 5  further rotated to show an inverted view of the side opposite that shown in  FIG. 4 . 
       FIG. 7  is a three dimensional exploded view showing the subject matter of  FIGS. 1-6  with the internal cover, cap assembly and batteries removed. 
       FIG. 8  is an enlarged front end view of the collar of  FIG. 7 . 
   

   DETAILED DESCRIPTION 
     FIG. 1  depicts an assembled unit  10  of the present invention in an illustrative extended embodiment for incorporating active electronics into an instrument. The main body  12  is configured as a tubular sleeve of non-metallic material forming a cylindrically-shaped battery compartment that is closed at the rearward end, and that extends forwardly as a sleeve portion  12 A that is externally threaded for mounting purposes and that is dimensioned internally to provide access at an open front end for battery installation and replacement. 
   The threaded sleeve portion  12 A of main body  12  provides mounting for the entire unit  10 , traversing a hole in the enclosure wall in the body of the instrument with a hex nut  14  bearing against the inside surface of the enclosure wall. 
   In cap assembly  16 , a machined metal cover cap  16 A with a knurled finger-grip rim may be further configured with a concentric strap peg  16 B affixed at the front surrounding a central circular opening  16 C of an audio phone jack that accepts a standard quarter-inch audio phone plug. 
   Inside a cylindrical cavity region configured in the rear of cover cap  16 A, a cap-attachment collar (not visible in this view), threaded onto the end of the threaded portion  12 A, serves the dual purpose of securing the unit  10  to the enclosure wall of the instrument body in co-operation with hex nut  14 , and enabling convenient attachment/removal of cover cap  16 A which engages the collar in a manner to be easily removed by the user for access to the battery compartment through the open front end of the threaded portion  12 A of main body  12 . 
   Mounted above main body  12  on pillars  12 C, molded integrally with main body  12 , is an electronics module  18  with a main chassis  18 A and a cover  18 B. Shielded wire  18 C delivers the audio signal from the instrument pickup as input to module  18 . 
   Behind hex nut  14  at the rearward end of the threaded portion  12 A, a non-metallic annular terminal-retaining ring  20  surrounds and secures three electrical terminals, of which only terminal  12 D is visible in this view. 
     FIG. 2 , a front view of unit  10  of  FIG. 1 , shows the front panel of module chassis  18 A and the front view of cap assembly  16  with cover cap  16 A, strap-peg  16 B, and jack opening  16 C. 
     FIG. 3 , a rear view of unit  10  of  FIG. 1 , shows the rear panel of chassis  18 A, the rear panel  12 H of the tubular main body, a battery connection terminal  12 G, a portion of jack connection terminals  12 D,  12 E and  12 F surrounded and secured in place by ring  20 , and the outline of the cover cap ( 16 ,  FIG. 2 ) shown in broken lines. 
     FIG. 4 , a side view of unit  10 , shows the electronics module  18 , supported by the four pillars  12 C. On the bottom side of main body  12 , battery connector terminal  12 G is shown with wire  18 D connecting the (+) battery terminal to module  18 . Terminals  12 D and  12 E are visible in this view, surrounded and secured in place by ring  20 . 
     FIG. 5  is bottom view of unit  10  rotated to show terminal  12 G secured onto body  12 , connecting wire  18 D, the underside of electronics module  18  and terminals  12 D,  12 E and  12 F, surrounded and secured in place by ring  20 . 
     FIG. 6  depicts unit  10  having been further rotated to show an inverted side view of module  18  beneath main body  12  including battery terminal  12 G and wire  18 D. Jack terminals  12 E and  12 F are visible in this view, surrounded and secured by terminal-retaining ring  20 , with hook-up wires leading into module  18 . 
     FIG. 7  is an exploded three-dimensional view of unit  10  showing module  18  with cover  18 B removed and an electronic circuit board  18 C in place. A pair of AA-sized battery cells  24  are shown having been removed from the battery compartment through the open end of the threaded portion  12 A. 
   The cap assembly  16 , with cover cap  16 A, strap-peg  16 B and jack opening  16 C on the front side, includes the phone jack assembly in a plastic housing  16 D which is mounted rotatably to cover cap  16 A and extends to the rear as shown. Three internal contacts, one contacting the tip and two contacting the sleeve of an inserted mono audio phone plug, are extended through housing  16 D to its outer surface where they constitute sliding contacts; of the three contacts only the exterior sliding portion of contact  16 E is visible in this view. 
   When the cap assembly  16  is fastened in place in a working closed disposition by the user for normal playing of the instrument, the three contacts make electrical contact with a corresponding set of three contacts, inside threaded portion  12 A of the main tubular body  12 , which terminate at jack terminals  12 D,  12 E and  12 F (refer to  FIG. 5 ) located to the rear of threaded portion  12 A, exemplified by the only one visible in this view: terminal  12 D. A spiral spring  16 F extends rearward from the cap assembly  16  to contact the (−) battery terminal. The two internal jack contacts that act on the sleeve portion complete the battery powering to the module  18  whenever there is a phone plug inserted into jack opening  16 C, and thus the module  18  becomes automatically switched off whenever the phone plug is removed. 
   The cap-attachment collar  22 , shown threaded onto the forward end of the threaded portion  12 A of main body  12 , is configured around its circumference with a pair of inclined channels  22 A; these engage a pair of pins inside cover cap  16 B to enable convenient attachment/removal of the cap assembly  16  with approximately a quarter turn of cover cap  16 B. 
   When hex nut  14  is tightened against the rear side of the instrument body wall with collar  22  in place bearing against the front side, the unit  10  becomes firmly secured to the instrument via the threaded portion  12 A of main body  12  extending through the enclosure wall of the instrument. 
     FIG. 8  is a frontal view of the open end of sleeve  12  and collar  22  as they would appear on the musical instrument with cap assembly  16  removed. Collar  22  is configured with a diametrically-opposed pair of flat regions to facilitate tightening, e.g. with a spanner wrench. The central entrance to the battery compartment at the open end of main body  12  inside threaded portion  12 A and the phone jack housing  16 D are made to have a special shape, generally rectangular at the top, so as to provide keying that ensures proper orientation for alignment of the sliding contacts. For user convenience, distinctive color markings, e.g. white dots, are provided on the top side of the jack housing  16 D and on the top region of the forward end of the threaded portion  12 A of main body  12  to clearly indicate proper orientation for insertion when replacing the cap assembly  16 . Three longitudinal channels  12 K,  12 L and  12 M indicate the internal locations of sliding contacts associated with jack connection terminals  12 D,  12 E and  12 F ( FIG. 5 ) respectively, and correspond to small raised regions on the three mating sliding contacts associated with the phone jack, e.g. contact  16 E on jack housing  16 D ( FIG. 7 ). 
   The plug portion, once inserted in place, is held non-rotatable relative to main body  12  by the entrance keying pattern ( FIG. 8 ) to ensure proper sliding contact alignment; therefore the rear plug portion is attached to cover cap  16 A in a freely rotatable manner to allow the quarter-turn rotation for attachment/removal of the cap assembly  16 . Such rotatable attachment is accomplished by providing an integral hub, extending back from the center of the front panel of cover cap  16 A, configured with an annular groove engaging four plastic fingers extending forward from the rear plug portion. 
   As an alternative to the illustrative embodiment described above which includes several optional elements that are not essential to basic practice of the invention, a basic embodiment for instruments already equipped with active electronics could include only the cap assembly  16  with the phone jack and associated audio/battery connection system extending into the inner wall of the battery access opening, and collar  22  attached to the instrument in a suitable manner, surrounding the battery access opening, utilizing a generic battery compartment. 
   The implementation of the battery compartment  12  as shown is not essential to the practice of the invention: a battery compartment with its single contact at the closed rear end could be provided in an alternative known implementation as a separate component initially independent of the cap assembly and its fastening collar. The threaded portion  12 A could be provided separately as a threaded sleeve not directly attached to the main battery compartment  12 . 
   While the embodiment as shown, with the strap-peg in location in place of an existing strap-peg, is believed to be beneficial to most guitars and other instruments in the lute group, the invention and/or the instrument itself could be practiced without a strap-peg. The location suggested as preferred for mounting an assembly according to the invention, i.e. in place of an existing strap-peg at a central end location of the instrument body, is not essential to the invention, which could be practiced with the assembly and/or the strap-peg located elsewhere on the instrument. 
   In an alternative to the one-piece main body/battery compartment shown in the illustrative embodiment, for manufacturing purposes, e.g. to facilitate molding, it may be beneficial to divide the main body shape at a central longitudinal plane into two generally mirror-image half parts to be assembled and fastened together in fabrication. 
   The invention may be embodied and practiced in other specific forms without departing from the spirit and essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description; and all variations, substitutions and changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.