# US 5,325,757 A · Fret retractable neck for stringed musical instruments > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,325,757 A - Document ID: US5325757A - Status: Granted - Kind: A - Application number: 07/943,527 - Filed: 1992-09-11 - Granted: 1994-07-05 - Earliest claimed: 1992-09-11 - Inventors: Serban Ghenea - Web page: https://patentgrep.com/patent/US5325757A ## CPC - G10D 1/08: Guitars - G10D 3/06: Necks; Fingerboards, e.g. fret boards - G10D: STRINGED MUSICAL INSTRUMENTS; WIND MUSICAL INSTRUMENTS; ACCORDIONS OR CONCERTINAS; PERCUSSION MUSICAL INSTRUMENTS; AEOLIAN HARPS; SINGING-FLAME MUSICAL INSTRUMENTS; MUSICAL INSTRUMENTS NOT OTHERWISE PROVIDED FOR (organs, harmoniums or similar wind musical instruments with associated blowing apparatus G10B; pianos, harpsichords, spinets or similar stringed musical instruments with one or more keyboards G10C; automatic musical instruments G10F; electrophonic musical instruments in which tones are generated by electromechanical means G10H) ## Abstract A stringed musical instrument (12) that can be played either in a fretted or a fretless mode includes an interconnected fret assembly (38) including frets (24) and a longitudinal fret interconnecting member (40) that is attached to, and movable with, the frets. A movable linear cam structure (46) has two cams at each fret, one positioned on each side of the fret interconnecting member, and includes rack teeth (52) which mesh with a pinion (62) driven by a lever (66) for causing linear movement of the linear cam structure. The interconnecting member is an elongated slat (40) which is positioned in a slot (50) between the cams. The linear-movable cam includes an elongated guide protrusion (56) and an interior cavity (30) of the fingerboard, in which the cam rides, defines an elongated guide slot (58) for receiving the guide protrusion and thereby limiting lateral movement of the linear cam. The linear cam structure and the interior cavity have tapered lateral sides. ## Claims ### Claim 1 A stringed musical instrument that can be played either as a fretted or as a fretless instrument of a type comprising a fret fingerboard having a fingerboard surface defining fret slots with movable frets mounted therein, said stringed musical instrument comprising: a cam structure movably mounted within an interior cavity of the fingerboard for impinging on respective ones of the frets for selectively moving the frets outwardly through the slots in the fingerboard to extend exteriorly of the fingerboard surface and for allowing the frets to be returned into the interior of the fingerboard approximately at or below the fingerboard surface; an interconnected fret assembly comprising said frets and a longitudinal fret interconnecting member that is attached to and movable with the frets. ### Claim 2 (depends on 1) A stringed musical instrument as in claim 1 wherein is further included a biasing means acting on the fret interconnecting member tending to move said frets between said fretted and fretless modes. ### Claim 3 (depends on 2) A stringed musical instrument as in claim 2 wherein said cam structure is linearly movable. ### Claim 4 (depends on 3) A stringed musical instrument as in claim 3 wherein said cam structure comprises an elongated rigid member having two cams at each fret, one cam positioned on each side of the fret interconnecting member. ### Claim 5 (depends on 4) A stringed musical instrument as in claim 4 wherein said cam structure includes rack teeth and said musical instrument comprises a pinion driven by a lever having teeth which engage with the rack teeth for moving the cam structure longitudinally for thereby affecting movement of said frets. ### Claim 6 (depends on 4) A stringed musical instrument as in claim 4 wherein said interconnecting member comprises an elongated slat and said linearly-movable cam defines a fret guide slot between said cams for receiving said elongated slat. ### Claim 7 (depends on 6) A stringed musical instrument as in claim 6 wherein said linearly-movable cam includes an elongated-guide-protrusion means and said fingerboard defines an elongated guide slot for receiving said guide protrusion for thereby limiting lateral movement of said linear cam while allowing linear movement thereof. ### Claim 8 (depends on 7) A stringed musical instrument as in claim 7 wherein said linearly-movable cam has tapered lateral side edges and said cavity in said fingerboard has tapered dimensions corresponding to the taper of the side edges of said linearly-movable cam. ### Claim 9 (depends on 3) A stringed musical instrument as in claim 3 wherein said linearly-movable cam includes an elongated-guide-protrusion means and said fingerboard defines an elongated guide slot for receiving said guide protrusion for thereby limiting lateral movement of said linear cam while allowing linear movement thereof. ### Claim 10 (depends on 9) A stringed musical instrument as in claim 9 wherein said linearly-movable cam has tapered lateral side edges and said cavity in said fingerboard has tapered dimensions corresponding to the taper of the side edges of said linearly-movable cam. ### Claim 11 (depends on 1) A stringed musical instrument as in claim 1 wherein said cam structure is linearly movable. ### Claim 12 (depends on 11) A stringed musical instrument as in claim 11 wherein said cam structure comprises an elongated rigid member having two cams at each fret, one cam positioned on each side of the fret interconnecting member. ### Claim 13 (depends on 12) A stringed musical instrument as in claim 12 wherein said cam structure includes rack teeth and said musical instrument comprises a pinion driven by a lever having teeth which engage with the rack teeth for moving the cam structure longitudinally for thereby affecting movement of said frets. ### Claim 14 A stringed musical instrument that can be played either as a fretted instrument or as a fretless instrument of a type comprising a fingerboard having a fingerboard surface defining fret slots with movable frets therein, said stringed musical instrument comprising: a linearly-movable cam structure movably mounted within an interior cavity of the fingerboard for impinging on each of the frets for selectively moving the frets between a fretted position in which they extend outwardly through the fret slots in the fingerboard exteriorly of the fingerboard surface, and a fretless position in which they are in the interior thereof approximately at or below the fingerboard surface. ### Claim 15 (depends on 14) A stringed musical instrument as in claim 14 wherein said cam structure is coupled to rack teeth and said musical instrument comprises a pinion driven by a lever having teeth which engage with the rack teeth for moving the cam structure longitudinally for thereby affecting movement of said frets. ### Claim 16 (depends on 15) A stringed musical instrument as in claim 15 wherein said linearly-movable cam includes an elongated-guide-protrusion means and said fingerboard defines an elongated guide slot for receiving said guide protrusion for thereby limiting lateral movement of said linear cam while allowing linear movement thereof. ### Claim 17 (depends on 16) A stringed musical instrument as in claim 16 wherein said linearly-movable cam has tapered lateral side edges and said cavity in said fingerboard has tapered dimensions corresponding to the taper of the side edges of said linearly-movable cam. ### Claim 18 A stringed musical that can be played either as a fretted or as a fretless instrument of a type comprising a fret fingerboard having a fingerboard surface defining fret slots with movable frets mounted therein, said stringed musical instrument comprising: a cam structure movably mounted within an interior cavity of the fingerboard for impinging on respective ones of the frets for selectively moving the frets outwardly through the slots in the fingerboard to extend exteriorly of the fingerboard surface and for allowing the frets to be returned into the interior of the fingerboard approximately at or below the fingerboard surface; laterally-extending internal members attached to each of the frets positioned in the interior of the fingerboard and biasing means impinging on the laterally-extending internal members for biasing the frets inwardly; wherein the fingerboard is an elongated neck and the laterally-extending internal members extend away from the frets in the direction of elongation of the neck. ### Claim 19 (depends on 18) A stringed musical instrument as in claim 18 wherein the laterally-extending internal members of adjacent frets are not interconnected. ### Claim 20 (depends on 18) A stringed musical instrument as in claim 18 wherein the laterally-extending internal members of adjacent frets are interconnected.