FLAT-TOP GUITAR ANTI-WARPING DEVICE
United States Patent 3853031
An anti-warping device of a length to extend between the terminal end of the fingerboard at one side of the sound hole in the flat top or sound table of a classical or acoustical guitar, and the bridge secured on said top spaced from the opposite side of said hole. One section of the device at one end thereof has a bridge-engageable surface and another section has a fingerboard-engageable surface at the opposite end of the device, and a quick acting manually actuatable element between said sections extends them longitudinally of the device from a released retracted position to react between said bridge and fingerboard to relieve the top of the guitar from tension applied thereto from the strings through the bridge when the guitar is not in use. The thickness of the device is less than the space between the strings and the top or sound board thus enabling the device to remain in extended position on the top to effect muting of the sound, when desired, without interfering with the playing.
US Patent References:
Means and method of treating stringed instruments to improve quality of tone
Floresco - September 1920 - 1352442
Means and method of treating stringed instruments to improve quality of tone
Floresco - September 1920 - 1352442
Inventors:
Dewitt, Herman W. (Yuba City, CA)
Williams, Connie E. (Yuba City, CA)
Williams, Connie E. (Yuba City, CA)
Application Number:
05/467962
Publication Date:
12/10/1974
Filing Date:
05/08/1974
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
84/453
International Classes:
G10D1/08; G10D1/00; G10D1/08
Field of Search:
84/267,453,173,290,291
Primary Examiner:
Wilkinson, Richard B.
Assistant Examiner:
Gonzales, John F.
Attorney, Agent or Firm:
Townsend, And Townsend
Claims:
We claim
1. The method of releasing the tension of a set of tuned strings on a flat-top guitar having a sound hole in its top and a bridge at one side of said hole rigidly secured on said top to which one of the ends of said strings are secured, and a fingerboard rigid with said top having a terminal end facing said bridge at the side of said hole opposite the latter with the set of tuned and tensioned strings extending over said hole and supported by said bridge in a position spaced over said top and fingerboard, comprising the steps of:
2. In the method as defined in claim 1:
3. A device for relieving the tension of a set of tensioned strings on a flat-top guitar having a sound hole in its top and a fingerboard rigid with said top having a terminal end adjacent one side of said hole and a bridge secured on said top adjacent the side of said hole opposite said terminal end supporting said strings in a position extending across said hole and spaced above said hole, top and fingerboard, comprising;
4. In a device as defined in claim 3:
5. In a device as defined in claim 3:
6. In a device as defined in claim 5:
7. In a device as defined in claim 3:
8. In combination with a flat-top guitar having a top formed with a sound hole and having a fingerboard and a bridge at opposite sides of said hole rigid relative to said top with a set of strings secured to and supported by said bridge in a position extending across said hole and spaced above the latter and above said fingerboard:
9. In a combination as defined in claim 8:
10. In a combination as defined in claim 8:
1. The method of releasing the tension of a set of tuned strings on a flat-top guitar having a sound hole in its top and a bridge at one side of said hole rigidly secured on said top to which one of the ends of said strings are secured, and a fingerboard rigid with said top having a terminal end facing said bridge at the side of said hole opposite the latter with the set of tuned and tensioned strings extending over said hole and supported by said bridge in a position spaced over said top and fingerboard, comprising the steps of:
2. In the method as defined in claim 1:
3. A device for relieving the tension of a set of tensioned strings on a flat-top guitar having a sound hole in its top and a fingerboard rigid with said top having a terminal end adjacent one side of said hole and a bridge secured on said top adjacent the side of said hole opposite said terminal end supporting said strings in a position extending across said hole and spaced above said hole, top and fingerboard, comprising;
4. In a device as defined in claim 3:
5. In a device as defined in claim 3:
6. In a device as defined in claim 5:
7. In a device as defined in claim 3:
8. In combination with a flat-top guitar having a top formed with a sound hole and having a fingerboard and a bridge at opposite sides of said hole rigid relative to said top with a set of strings secured to and supported by said bridge in a position extending across said hole and spaced above the latter and above said fingerboard:
9. In a combination as defined in claim 8:
10. In a combination as defined in claim 8:
Description:
SUMMARY OF THE INVENTION
This invention has application to flat-top classic/flamenco guitars and to flat-top steel-string guitars not having tailpieces or truss rods to take the tensions of the strings. The designation "flat-top" hereinafter applies to guitars of the foregoing types, in both of which the bridge is glued to the upper face of the top or sound table, although in some instances it is bolted, resulting in the tensioned strings applying a tilting or lifting force to the bridge that is transferred to the sound table, causing warpage of the latter unless the tension on the bridge is relieved during storage between daily or nightly periods of performance. This means tuning down the strings, requiring retuning for use, a time consuming task frequently neglected with the result that the warpage becomes permanent.
One of the objects of this invention is the provision of a simple anti-warping device, adapted to be quickly removably installed in a position on the sound table of a flat-top guitar, and manually actuated to relieve the tension of the strings on the sound table without loosening the strings, thereby preventing warpage of the sound table during the time period between playing sessions.
Another object of the invention is the provision of a simple device that is quickly removably installed on a flat-top guitar during storage periods that will progressively restore a warped sound table to substantially normal condition.
A still further object of the invention is the provision of a device having the foregoing objects, that, when installed on the guitar, will have a muting effect on the sound, but will not interfere in any way with playing of the instrument, and which device may be instantly removed to again transmit full tension of the strings to the sound table, and the full tone of the sounds.
An additional object is the provision of a method of preventing warpage of a flat-top guitar, the strings of which have been tensioned and tuned, and without interfering with the normal playing of the guitar, by transmitting tension of the strings on the sound table, from the table to the rigid fingerboard carrying the frets.
Other objects and advantages will appear in the description and in the drawings.
DESCRIPTION OF DRAWINGS
FIG. 1 is a fragmentary top plan view of the portion of a flat-top guitar showing the terminal end portion of the fingerboard, and the bridge, with the device of this invention in position between the strings and the top of the guitar, taking the tension of the strings normally transmitted to the top;
FIG. 2 is an enlarged top plan view of the anti-warping device shown in FIG. 1 separate from the guitar, with the actuating lever also indicated in loosened position;
FIG. 3 is an edge elevation view of the device of FIG. 2;
FIG. 4 is an enlarged fragmentary view along line 4--4 of FIG. 1, with the sound table shown in cross-section;
FIG. 5 is an enlarged cross-sectional view along line 5--5 of FIG. 1;
FIG. 6 is a plan view of a modification of the form shown in FIGS. 1-5;
FIG. 7 is an edge view of the form shown in FIG. 6;
FIG. 8 is an enlarged, fragmentary sectional view along line 8--8 of FIG. 6; and
FIG. 9 is an enlarged, fragmentary elevational view of the tensioning lever as seen from line 9--9 of FIG. 6.
DETAILED DESCRIPTION OF INVENTION
The device illustrated in FIGS. 1-5 comprises two main body sections 1, 2. Section 1 may be a generally rectangular, elongated strip.
The flat lower side of section 1 is covered with felt 3, or the like, which covering extends at 4 over the end of section 1 that will engage the lower terminal end of the fingerboard 5 of the guitar when the device is in operative position on the guitar (FIG. 1). When in such operative position, section 1 will extend across the sound hole 6 in the sound table 7, and the terminal lower end of the fingerboard 5 will be adjacent one side of the sound hole.
The felt-covered end of section 1 will have the same, or substantially the same horizontally extending contour as the end of the fingerboard it is adapted to engage, which contour may, in some instances, be curved to follow the circular contour of the sound hole. Also, in many instances, the lower terminal end of the fingerboard terminates short of the sound hole, in which case one end of the section 1 will rest on the portion of the sound table adjoining the end of the fingerboard.
The end portion of section 1 that is opposite the fingerboard-engageable end, is formed with a parallel-sided slot 8 extending longitudinally of section 1 and opening outwardly of said opposite end. The opposedly facing sides of slot 8 have parallel ribs 9 (FIG. 5) projecting toward each other and extending longitudinally of said slot. Section 2 is formed with an elongated tongue 10 that extends into slot 8 longitudinally of the latter. Opposite sides of tongue are recessed at 11 (FIG. 5) to slidably fit on ribs 9, whereby section 2 will be slidably supported on section 1 for reciprocable movement longitudinally of the latter.
The main body of section 2 that is outwardly of the outwardly opening end of slot 8, may be rectangular and of substantially the same width as the length of the slotted terminal end of section 1. The lower surface of section 2 is covered with felt 12 or the like, which material extends over the free outer end of section 2 at 13. The end of section 2 at 13 is adapted to engage the slide of bridge 14 of the guitar that faces the terminal lower end of the fingerboard 5. Bridge 14 is spaced from the sound hole 6 so that the section 2 and the slotted end portion of section 1 will usually be supported on the portion of the sound table between sound hole 6 and the bridge 14.
A machine screw 15 is threadedly supported within the end of tongue 10 at the closed end of slot 8. Thus, the screw may be adjusted longitudinally of tongue 10 so its head 16 will project different distances from the tongue toward the closed end of slot 8.
A lever arm 17 extends into section 1 from and through one side edge of the latter within a flat-sided passageway 18 formed in said section (FIG. 3). One end portion of said lever 17 projects from section 1 and is formed with a finger-engageable element 19, and the other end of the arm 17 is formed with a cam portion 20 having an arcuately extending cam surface 21 eccentrically positioned relative to the axis of a pivot 22 (FIG. 3) supporting the lever arm for rotation. The axis of said pivot is slightly offset to one side of a line parallel with the central longitudinal axis of section 1 so as to hold the sections 1, 2 in extended position when the lever arm is in the full line position shown in FIGS. 1, 2, as will be described.
When lever arm 17 is rotated about pivot 22 to the position 23, indicated in dot-dash lines in FIG. 2, the section 20 will be released for movement from an extended position as seen in FIGS. 1, 2 to a retracted position in which the device may be readily positioned between the terminal lower end of the fingerboard 5 and the bridge 14 (FIG. 1). Upon then swinging the lever arm 17 to the full line position of FIGS. 1, 2 the cam surface 20 will react against the head 16 of screw 15 to move section 2 to extended position in which the thrust on section 2 will be sufficient to transmit the tension of the tuned strings 24 from the sound table to the bridge thereby relieving the sound table of the warping strain thereon.
The sections 1, 2 will be releasably locked in extended position due to the offset of pivot 22 relative to the longitudinal axis of sections 1, 2 on which the axis of screw 15 is positioned.
The spacing between the lower end of the fingerboard 5 and the bridge 14 may vary in different models and in the guitars of different makers. Where such variations are within the range of efficient adjustments of the screw 15, the length of the device may be changed to suit the variation. It is obvious that the lengths of sections 1, 2 may be longer or shorter to suit abnormally great or abnormally small spacings between the fingerboard and the bridge.
As seen in FIG. 2 the section 1 is of greater width intermediate its end portions. This not only strengthens the section at one side of the pivot 22 where the strain on the device is greatest when it is actuated to relieve the tension of the strings on the top 7, but it enables the forming of a shoulder 25 facing toward the fingerboard. This shoulder provides a surface adapted to be engaged by the thumb of a hand with the forefinger engaging the element 19 on the outer end of the lever arm 17 when the arm is in position 23 to facilitate application of the necessary force to swing the lever to the full line position for applying pressure against the bridge to relieve the tension of the strings on the sound table. It may be noted that this tension may be approximately 480 pounds.
In FIG. 4 it is seen that the device is of less thickness than the space between the strings and the sound table thus leaving the strings free for manipulation by a player in the normal manner, whereby the guitar may be played while the device is in tension-relieving position. The tone is muted when the guitar is played while the device is in this position, which effect is highly desirable in many instances.
FIG. 4 clearly shows the manner in which the tensioning of the strings applies a warping force on the sound table. The degree of movement of the section 2 against the bridge is normally quite small, being only sufficient to prevent warpage of the sound table during the periods of time between sessions of use when the strings heretofore must be loosened to prevent such warpage. In instances where permanent warpage has occured, it has been found that such warpage may ultimately be partially, if not wholly, corrected by the consistent use of the device during storage periods.
While FIG. 4 shows a string held to the bridge by a peg, it is to be understood that NYLON strings on classical guitars may be tied or connected to the bridge in one of several conventional ways, each of which transmits the tension of the strings to the sound table in the same manner.
From the foregoing, it is seen that the device as shown and described prevents tilting of the bridge and lifting or distortion of the sound table. Also, the classical guitar does not usually have a truss rod in the neck, and the use of the present device relieves the tension on the neck where it usually warps.
In operation, when the device is in the position shown in FIG. 1, and the lever 17 is swung from position 23 (FIG. 2) toward the full line position, the player can readily determine the correct adjustment of the screw 15 as the tone of the strings would be higher if the pressure were so sufficient to tilt the bridge in a direction opposite to the direction of the pull of the strings. Except in the case where the sound table is permanently warped, and an attempt is being made to gradually correct such warpage, the pressure applied by the device should be substantially only enough for the device to take the tension that normally would be taken by the sound table.
It has been found that the use of the device on flat-top guitars displayed for sale enables the merchant to show and to demonstrate immediately, any of many different pre-tuned models, and to insure against warpage of their sound tables over a long period of time and under favorable conditions. Heretofore, this has not been possible.
In a conventional flat-top guitar the strings are secured at one of their ends to a tuning machine on a peg head (not shown) that is at the outer end of the neck 26, a portion of the latter being shown in FIG. 1.
From the tuning machine, which generates the tension, the strings extend over the usual nut (not shown) that is at the outer end of the fingerboard 5, and then successively over the frets 27 on said fingerboard, the sound hole 6, and a portion of the sound table 7, to and over saddle portion 28 of the bridge 14 to the points of securement of the strings to the bridge.
The anti-warping device shown in FIGS. 6-9 comprises a member 30 and a member 31 respectively adapted to engage the terminal end of the fingerboard on a flat-top guitar and the bridge, the same as sections 1, 2. Members 30, 31 are elongated in the direction of their fingerboard and bridge engageable surfaces, and their correspondingly positioned ends are connected by a pair of toggle arms generally designated 32 and 33. The adjacent ends of the arms 32 are pivotally connected by pivots 34 to an internally threaded sleeve 35 having lugs 36 projecting from opposite sides for the pivotal connections. Sleeve 35 is threadedly supported on one end portion of a rod 37 for movement longitudinally of the rod upon rotation of the latter.
The outer ends of arms 32 are pivotally connected by pivots 39 to one of the correspondingly positioned ends of members 30, 31.
The adjacent ends of arms 33 are pivotally connected by pivots 40 to a sleeve 41 that is supported on the end of rod 37 opposite sleeve 35 for reciprocable sliding movement on said rod longitudinally of the latter. Lugs 42 on said sleeve 41 support pivots 40, while the outer ends of arms 33 are connected by pivots 43 with members 30, 31.
The pairs of arms 32, 33 extend divergently from the members 31, 32 to sleeves 35, 41 hence movement of the sleeves toward each other will effect movement of the members 30, 31 away from each other while movement of the sleeves away from each other will effect movement of the members 30, 31 away from each other.
The end of rod 37 supporting sleeve 41 projects outwardly of said sleeve, and carries the tensioning element generally designated 44 thereon. This element is a lever arm 45 that performs the same function as lever arm 17, as will be seen.
Arm 45 is pivotally connected at one end to the outwardly projecting end of rod 37 by a pivot 46. Said end of arm 45 may be in the form of a clevis-like cam 47 between which the projecting end of the rod 37 projects, the opposite sides of the cam 47 having corresponding cam surfaces 48 extending arcuately about the axis of pivot 46 and eccentrically of said axis. These surfaces slidably engage the axially facing surface of sleeve 41. In the full line position of the arm 45 the members 30, 31 are in extended position, as they would be when the device is positioned on a guitar in the same position as the device of FIG. 1, and when the arm is swung along path (FIG. 6) to a position at the opposite side of pivot 46, the members 30, 31 will be in a tension-releasing position 50 indicated in dot-dash lines.
The rod 37 may be rotated about its axis relative to sleeve 35 to vary the pressure applied by members 30, 31 when in an operative position.
In both forms of the invention it is seen that there is a cam-follower for each cam that is given a linear movement upon rotation of the cam by actuation of the cam lever, and the follower in each instance is connected with the fingerboard-engaging member and with the bridge-engaging member to effect movement of said members from retracted position to extended pressure-applying position.
This invention has application to flat-top classic/flamenco guitars and to flat-top steel-string guitars not having tailpieces or truss rods to take the tensions of the strings. The designation "flat-top" hereinafter applies to guitars of the foregoing types, in both of which the bridge is glued to the upper face of the top or sound table, although in some instances it is bolted, resulting in the tensioned strings applying a tilting or lifting force to the bridge that is transferred to the sound table, causing warpage of the latter unless the tension on the bridge is relieved during storage between daily or nightly periods of performance. This means tuning down the strings, requiring retuning for use, a time consuming task frequently neglected with the result that the warpage becomes permanent.
One of the objects of this invention is the provision of a simple anti-warping device, adapted to be quickly removably installed in a position on the sound table of a flat-top guitar, and manually actuated to relieve the tension of the strings on the sound table without loosening the strings, thereby preventing warpage of the sound table during the time period between playing sessions.
Another object of the invention is the provision of a simple device that is quickly removably installed on a flat-top guitar during storage periods that will progressively restore a warped sound table to substantially normal condition.
A still further object of the invention is the provision of a device having the foregoing objects, that, when installed on the guitar, will have a muting effect on the sound, but will not interfere in any way with playing of the instrument, and which device may be instantly removed to again transmit full tension of the strings to the sound table, and the full tone of the sounds.
An additional object is the provision of a method of preventing warpage of a flat-top guitar, the strings of which have been tensioned and tuned, and without interfering with the normal playing of the guitar, by transmitting tension of the strings on the sound table, from the table to the rigid fingerboard carrying the frets.
Other objects and advantages will appear in the description and in the drawings.
DESCRIPTION OF DRAWINGS
FIG. 1 is a fragmentary top plan view of the portion of a flat-top guitar showing the terminal end portion of the fingerboard, and the bridge, with the device of this invention in position between the strings and the top of the guitar, taking the tension of the strings normally transmitted to the top;
FIG. 2 is an enlarged top plan view of the anti-warping device shown in FIG. 1 separate from the guitar, with the actuating lever also indicated in loosened position;
FIG. 3 is an edge elevation view of the device of FIG. 2;
FIG. 4 is an enlarged fragmentary view along line 4--4 of FIG. 1, with the sound table shown in cross-section;
FIG. 5 is an enlarged cross-sectional view along line 5--5 of FIG. 1;
FIG. 6 is a plan view of a modification of the form shown in FIGS. 1-5;
FIG. 7 is an edge view of the form shown in FIG. 6;
FIG. 8 is an enlarged, fragmentary sectional view along line 8--8 of FIG. 6; and
FIG. 9 is an enlarged, fragmentary elevational view of the tensioning lever as seen from line 9--9 of FIG. 6.
DETAILED DESCRIPTION OF INVENTION
The device illustrated in FIGS. 1-5 comprises two main body sections 1, 2. Section 1 may be a generally rectangular, elongated strip.
The flat lower side of section 1 is covered with felt 3, or the like, which covering extends at 4 over the end of section 1 that will engage the lower terminal end of the fingerboard 5 of the guitar when the device is in operative position on the guitar (FIG. 1). When in such operative position, section 1 will extend across the sound hole 6 in the sound table 7, and the terminal lower end of the fingerboard 5 will be adjacent one side of the sound hole.
The felt-covered end of section 1 will have the same, or substantially the same horizontally extending contour as the end of the fingerboard it is adapted to engage, which contour may, in some instances, be curved to follow the circular contour of the sound hole. Also, in many instances, the lower terminal end of the fingerboard terminates short of the sound hole, in which case one end of the section 1 will rest on the portion of the sound table adjoining the end of the fingerboard.
The end portion of section 1 that is opposite the fingerboard-engageable end, is formed with a parallel-sided slot 8 extending longitudinally of section 1 and opening outwardly of said opposite end. The opposedly facing sides of slot 8 have parallel ribs 9 (FIG. 5) projecting toward each other and extending longitudinally of said slot. Section 2 is formed with an elongated tongue 10 that extends into slot 8 longitudinally of the latter. Opposite sides of tongue are recessed at 11 (FIG. 5) to slidably fit on ribs 9, whereby section 2 will be slidably supported on section 1 for reciprocable movement longitudinally of the latter.
The main body of section 2 that is outwardly of the outwardly opening end of slot 8, may be rectangular and of substantially the same width as the length of the slotted terminal end of section 1. The lower surface of section 2 is covered with felt 12 or the like, which material extends over the free outer end of section 2 at 13. The end of section 2 at 13 is adapted to engage the slide of bridge 14 of the guitar that faces the terminal lower end of the fingerboard 5. Bridge 14 is spaced from the sound hole 6 so that the section 2 and the slotted end portion of section 1 will usually be supported on the portion of the sound table between sound hole 6 and the bridge 14.
A machine screw 15 is threadedly supported within the end of tongue 10 at the closed end of slot 8. Thus, the screw may be adjusted longitudinally of tongue 10 so its head 16 will project different distances from the tongue toward the closed end of slot 8.
A lever arm 17 extends into section 1 from and through one side edge of the latter within a flat-sided passageway 18 formed in said section (FIG. 3). One end portion of said lever 17 projects from section 1 and is formed with a finger-engageable element 19, and the other end of the arm 17 is formed with a cam portion 20 having an arcuately extending cam surface 21 eccentrically positioned relative to the axis of a pivot 22 (FIG. 3) supporting the lever arm for rotation. The axis of said pivot is slightly offset to one side of a line parallel with the central longitudinal axis of section 1 so as to hold the sections 1, 2 in extended position when the lever arm is in the full line position shown in FIGS. 1, 2, as will be described.
When lever arm 17 is rotated about pivot 22 to the position 23, indicated in dot-dash lines in FIG. 2, the section 20 will be released for movement from an extended position as seen in FIGS. 1, 2 to a retracted position in which the device may be readily positioned between the terminal lower end of the fingerboard 5 and the bridge 14 (FIG. 1). Upon then swinging the lever arm 17 to the full line position of FIGS. 1, 2 the cam surface 20 will react against the head 16 of screw 15 to move section 2 to extended position in which the thrust on section 2 will be sufficient to transmit the tension of the tuned strings 24 from the sound table to the bridge thereby relieving the sound table of the warping strain thereon.
The sections 1, 2 will be releasably locked in extended position due to the offset of pivot 22 relative to the longitudinal axis of sections 1, 2 on which the axis of screw 15 is positioned.
The spacing between the lower end of the fingerboard 5 and the bridge 14 may vary in different models and in the guitars of different makers. Where such variations are within the range of efficient adjustments of the screw 15, the length of the device may be changed to suit the variation. It is obvious that the lengths of sections 1, 2 may be longer or shorter to suit abnormally great or abnormally small spacings between the fingerboard and the bridge.
As seen in FIG. 2 the section 1 is of greater width intermediate its end portions. This not only strengthens the section at one side of the pivot 22 where the strain on the device is greatest when it is actuated to relieve the tension of the strings on the top 7, but it enables the forming of a shoulder 25 facing toward the fingerboard. This shoulder provides a surface adapted to be engaged by the thumb of a hand with the forefinger engaging the element 19 on the outer end of the lever arm 17 when the arm is in position 23 to facilitate application of the necessary force to swing the lever to the full line position for applying pressure against the bridge to relieve the tension of the strings on the sound table. It may be noted that this tension may be approximately 480 pounds.
In FIG. 4 it is seen that the device is of less thickness than the space between the strings and the sound table thus leaving the strings free for manipulation by a player in the normal manner, whereby the guitar may be played while the device is in tension-relieving position. The tone is muted when the guitar is played while the device is in this position, which effect is highly desirable in many instances.
FIG. 4 clearly shows the manner in which the tensioning of the strings applies a warping force on the sound table. The degree of movement of the section 2 against the bridge is normally quite small, being only sufficient to prevent warpage of the sound table during the periods of time between sessions of use when the strings heretofore must be loosened to prevent such warpage. In instances where permanent warpage has occured, it has been found that such warpage may ultimately be partially, if not wholly, corrected by the consistent use of the device during storage periods.
While FIG. 4 shows a string held to the bridge by a peg, it is to be understood that NYLON strings on classical guitars may be tied or connected to the bridge in one of several conventional ways, each of which transmits the tension of the strings to the sound table in the same manner.
From the foregoing, it is seen that the device as shown and described prevents tilting of the bridge and lifting or distortion of the sound table. Also, the classical guitar does not usually have a truss rod in the neck, and the use of the present device relieves the tension on the neck where it usually warps.
In operation, when the device is in the position shown in FIG. 1, and the lever 17 is swung from position 23 (FIG. 2) toward the full line position, the player can readily determine the correct adjustment of the screw 15 as the tone of the strings would be higher if the pressure were so sufficient to tilt the bridge in a direction opposite to the direction of the pull of the strings. Except in the case where the sound table is permanently warped, and an attempt is being made to gradually correct such warpage, the pressure applied by the device should be substantially only enough for the device to take the tension that normally would be taken by the sound table.
It has been found that the use of the device on flat-top guitars displayed for sale enables the merchant to show and to demonstrate immediately, any of many different pre-tuned models, and to insure against warpage of their sound tables over a long period of time and under favorable conditions. Heretofore, this has not been possible.
In a conventional flat-top guitar the strings are secured at one of their ends to a tuning machine on a peg head (not shown) that is at the outer end of the neck 26, a portion of the latter being shown in FIG. 1.
From the tuning machine, which generates the tension, the strings extend over the usual nut (not shown) that is at the outer end of the fingerboard 5, and then successively over the frets 27 on said fingerboard, the sound hole 6, and a portion of the sound table 7, to and over saddle portion 28 of the bridge 14 to the points of securement of the strings to the bridge.
The anti-warping device shown in FIGS. 6-9 comprises a member 30 and a member 31 respectively adapted to engage the terminal end of the fingerboard on a flat-top guitar and the bridge, the same as sections 1, 2. Members 30, 31 are elongated in the direction of their fingerboard and bridge engageable surfaces, and their correspondingly positioned ends are connected by a pair of toggle arms generally designated 32 and 33. The adjacent ends of the arms 32 are pivotally connected by pivots 34 to an internally threaded sleeve 35 having lugs 36 projecting from opposite sides for the pivotal connections. Sleeve 35 is threadedly supported on one end portion of a rod 37 for movement longitudinally of the rod upon rotation of the latter.
The outer ends of arms 32 are pivotally connected by pivots 39 to one of the correspondingly positioned ends of members 30, 31.
The adjacent ends of arms 33 are pivotally connected by pivots 40 to a sleeve 41 that is supported on the end of rod 37 opposite sleeve 35 for reciprocable sliding movement on said rod longitudinally of the latter. Lugs 42 on said sleeve 41 support pivots 40, while the outer ends of arms 33 are connected by pivots 43 with members 30, 31.
The pairs of arms 32, 33 extend divergently from the members 31, 32 to sleeves 35, 41 hence movement of the sleeves toward each other will effect movement of the members 30, 31 away from each other while movement of the sleeves away from each other will effect movement of the members 30, 31 away from each other.
The end of rod 37 supporting sleeve 41 projects outwardly of said sleeve, and carries the tensioning element generally designated 44 thereon. This element is a lever arm 45 that performs the same function as lever arm 17, as will be seen.
Arm 45 is pivotally connected at one end to the outwardly projecting end of rod 37 by a pivot 46. Said end of arm 45 may be in the form of a clevis-like cam 47 between which the projecting end of the rod 37 projects, the opposite sides of the cam 47 having corresponding cam surfaces 48 extending arcuately about the axis of pivot 46 and eccentrically of said axis. These surfaces slidably engage the axially facing surface of sleeve 41. In the full line position of the arm 45 the members 30, 31 are in extended position, as they would be when the device is positioned on a guitar in the same position as the device of FIG. 1, and when the arm is swung along path (FIG. 6) to a position at the opposite side of pivot 46, the members 30, 31 will be in a tension-releasing position 50 indicated in dot-dash lines.
The rod 37 may be rotated about its axis relative to sleeve 35 to vary the pressure applied by members 30, 31 when in an operative position.
In both forms of the invention it is seen that there is a cam-follower for each cam that is given a linear movement upon rotation of the cam by actuation of the cam lever, and the follower in each instance is connected with the fingerboard-engaging member and with the bridge-engaging member to effect movement of said members from retracted position to extended pressure-applying position.