Floating tremolo-unit with front mounted spring assembly

Abstract

A floating-tremolo unit comprises a string saddle-assembly means 13 with a tremolo-arm 11 and Z shaped bracket. The Z shaped bracket extends outwardly backwards and beneath the surface height of an electric guitar, engaging with ball bearings (2, 5, figure 3). The ball bearings are in contact with cushioning means in the form of disc shaped compression springs such as Belleville washers. Ideally the bracket is suspended between two axially mounted columnar sets of the compression springs (3, 4, 6, 7, figure 3). The upper set may have clearance for threaded fasteners to adjust the preloading tension. The string saddle-assembly means may be rotated clockwise or anticlockwise, about a pivoting means to generate augmented or diminished pitch-shifting of notes. The entire unit is front-mounted, thereby not requiring machining operations to the rear face of the guitar body during manufacture. Conventional steel or brass ‘sustain’ block may be incorporated optionally. A multitude of spring tensions may be realised by varying combinations.

Description

DESCRIPTION BACKGROUND OF THE INVENTION This invention relates to a device for varying the note pitch (vibrato) on stringed instruments known conventionally as tremolounits . On electric guitars particularly, the use of tremolo-arms or 'whammy - bars' dates to the 1950s. Paul Bigsby had a US patent granted in 1953 (USD169120S) for a system in which the string could wrap and unwrap around a bar affixed to the top of a guitar body using a tailpiece. The units continue in popular use today, however provided limited frequency-adjustment range and suffered with tuning instability. Drifting of notes out of tune is partly driven from non-idealised stretching and contracting of string lengths upon winding and unwinding. Later systems employed by a range of manufacturers, made use of a pivoting point and rear-mounted coil springs which vary string tension when the tremolo-arm is used to create clockwise or anticlockwise motion around the pivot point. These are termed 'fulcrum' tremolo systems. The pivoting point may be via six screws fixing the saddle assembly to the top face of the guitar, or via two-posts and two-hardened edges pivoting around said posts. The former has been a standard for Fender® Stratocaster® since the 1950s, noteworthy as the world's most popularised model. The latter method is typically employed in more expensive systems and said to provide less friction and better tuning stability. Additional tuning stability is sometimes realised by use of locking features at the ends of a vibrating strings length, namely locking-nuts and locking bridgesaddles. This is termed a 'double-locking' tremolo system. Where locking is not employed at either end, the use of roller-saddles or roller-nuts reduces friction and is said to provide more tuning stability as the string stretches and contracts most consistently with presumably less non-linear hysteresis effects. The timbre of a stringed instrument is a complex science however 'good tone' is often sought and said to relate to the geometry and density of an instrument. Conventional string instruments which incorporate tremolo systems, have a slot routed through an entire guitar's body and a large rectangular section routed from the rear face in which to house coil springs. Whilst these springs are designed for use in extension, they do also provide dissipative force in compression. As a tremolo-arm is depressed, the springs extend in length and the force generated according to Hooke's Law counteracts a reduction in guitar string tension (along with a small reduction in string length) thereby lowering the note. When releasing the tremolo-arm, the spring force pulls the tremolo-system back towards its rest position thereby restoring the default string tension and note pitches. In 'floating-tremolo' systems, the note pitch can also be increased by 'pulling upward' the tremolo-arm, which reduces the extended length of rear springs. Upon release, the springs again restore relative position to its default datum position. It is hypothesised that not requiring to route a large cavity at the back of an instrument, may improve the tonal qualities of an instrument and its resonant properties. A smaller cavity routed on the front-face of an instrument, maintains a geometry closer to an idealised shape with no cavity at all. By not requiring routing of a guitar body on its top and rear surface, manufacturing costs are also reduced greatly by virtue of less machine operations and not requiring alignment of top and bottom machined surfaces. An extant system by Kahler® ( 'Locking cam tremolo device' US Patent 7521616) makes use of ball bearings and cam components such that the unit is mounted on the top of the guitar and no rear routing is required. It functions quite differently to a fulcrum unit yet makes use of coil springs for cushioning means. Other US Patents relate to top mounted units such as 1984 US Pat. No. 4632005 pertaining to Steinberger® TransTrem® Bridge. This unit allows simple pitch transposition of all strings (inspiring the name), utilises balls as bearing means however requires coil springs also for cushioning means. The transposition implies an immediate change in the instrument's tuning, in such a way that all strings are augmented or diminished correspondingly. Pivot points are tailored for each string to account for 'bridge compensation'; generally, each string saddle is positioned differently to create marginally different vibrational string lengths. Without a compensated bridge, the intonation would not be correct (the consistency of tuning across the length of a fretboard). Similarly, by utilising tailored pivoting points, a tremolo-arm can be used in conjunction with fretted notes on multiple strings (chords). A Seymour-Duncan® blog (REF 1), refers to the unique ability to bend pitches of entire chords though notes device availability on specific models only: "due to the strict tolerances needed for accurate transposition, [the device] could not be installed aftermarket on any other instruments". The same source notes a further unit Washburn® Wonderbar®, requiring no routing of the guitar body whatsoever but consequently sitting proud of the body substantially: "It used springs, but they were inside the mechanism, making the body of the whole system pretty tall and awkward to play with". The following invention described herein aims to replicate range and improve fine adjustment of leading floating-tremolo systems. It aims to be entirely front-mounted whilst not requiring coil-springs as principal cushioning means. It aims to use locking features preferably, though these are non-essential components of the invention. Instead, they reflect common best practices for impervious string length and thereby tuning consistency following use of tremolo systems. OTHER PRIOR ART (NON-MUSICAL INSTRUMENT BASED) Large diesel engines used for marine, or power generation applications contain large valve stems facilitating inlet and exhaust of fuel and expellant. These may heat asymmetrically causing early failure. In order to extend service-life, a Valve-Rotator unit is supplemented to the valve assembly, often in place of a retainer for the main reciprocating coil spring. US Patent US4424773A (granted 1984, expired 2001) pertains to a Valve-Rotator device utilising Belleville washers. Many such devices exist with variations including garter springs and ball-bearings travelling down angled pockets before being returned to position with small coil springs within said pockets. The common feature of these units of varying design is the inclusion of Belleville washer to deflect a small but precise, repeatable distance under heavy loading. Belleville washers may be considered 'disc springs' given their relatively linear dissipative force with deflection rate. They are typically found in heavy duty applications with small space envelope. All materials and objects have a modulus of rigidity and for example a pneumatic tyre may be represented as a spring of a given stiffness in an automotive physics model. All mechanical systems may be represented by mass, spring and dampers when describing damped natural frequencies and vibrational kinematics. SUMMARY OF THE INVENTION This virtue of exclusively front mounting components may be achieved by use of 'Belleville washers' (disc springs) as the cushioning agent in place of conventional rear-mounted coil springs. Since these are substantially stiffer than coil springs, they may be stacked in series to achieve lower spring rates whilst still requiring a much smaller space envelope than that of a coil spring equivalent. Since the disc spring does not have shaped ends for attachment such as the hook and eyelet of the coil springs (typically attaching to the tremolo-block and tremolo-claw respectively), disc spring stacks may be employed above and below a string saddle assembly such that a 'floating-bridge' is fully suspended. This ensures dissipative force applies clockwise and anticlockwise about the pivot point(s) during tremolo use. The bridge saddle assembly, and Z shaped bracket which collectively rotate around pivot points are referred here as the saddle-assembly means. Preferably a 'two-point tremolo' is considered with two steel posts inserted into the guitar body adjustably using threaded brass inserts. This two-point preference is typical for some extant systems as noted above though non-essential to this invention. The use of 6 screws or roller bearings are further examples of fulcrum (pivoting) means. A stiff U-shaped frame is fixed to a routed recess on top surface of the guitar and houses the said disc spring assembly. This is referred to as the retaining means. Steel balls are used preferably between disc spring stacks and the saddle-assembly means, for reduced friction in the mating arrangement. These balls are tangential to the disc spring surface whose angle varies with relative deflection under loading and unloading. Above the saddle-assembly means, a threaded steel ball is used preferably which allows an adjustment screw to vary the preloading of the spring stack held between the ball and top surface of the retaining means. Disc springs allow for fine adjustment of displacement and spring tension thereby allowing for fine adjustment of instrument tuning. A wide range of spring ratios may be achieved by parallel and series stacking arrangements, allowing for potentially different guitar tunings being alternated between. This would require each string saddle to be pivoted separately with independent cushioning means (i.e. six disc spring stack assemblies for a six stringed instrument) supposing that tuning variants encompassed different relative string tuning and not uniform pitch augmentation or diminishing (such as the use of a Capo to change the apparent nut position). Preferably three stacks are illustrated here, suspending all strings at once for simplicity of manufacture and minimal use of space envelope. Specification D2010204 disc spring and D1052025 (referred as such by numerous suppliers and standard DIN 2093) allow for use respectively in three stacks (preferably) or six stacks as noted. Specifications D83202 and D84202 are yet smaller disc spring variants that may also be used as main cushioning means (though requiring parallel stacking, or else reduction to service life may result if a mechanical stop is not engaged beyond a certain load). These smaller springs are preferred for use in fine-tuning adjustment rather than offsetting the primary string tension loading. A common issue for extant floating-tremolo systems is that upon breaking a string the instrument falls 'out of tune' since the rearmounted springs are calibrated to offset the entire instrument's tension yet are now suspended by 5 remaining strings (in the case of 6 stringed instrument). Independent saddle pivot operation would resolve this as noted above though invalidate the use of conventional tremolo-arm connected to all string tensions at once. The use of a switch or latch to engage or disengage subsets of disc springs from the total stack, could be used to rebalance a system where a string had broken. Where tension across all strings was equal, this would imply reducing the counteracting spring tension by 5 . .... a factor -. In practice, the gauge of string and vibrating string length would need to be known or calibrated to, a-priori. The former may depend upon varying strings employed by an end-user whilst the latter determined by the scale-length selected by an instrument designer . If springs of varying specification are used in a disc spring stack, it can be arranged that the softer spring, compresses a specified distance under a given load, until mechanical contact prevents further deflection. Beyond this load, only the stiffer springs continue to deflect which results overall in a 'progressive' spring rate. This may be desirable as smooth, frictionless feel with light use yet increasing resistance towards the outer envelope of usage range. It could be arranged such that the difference in tension between 5 and 6 strings (typically the thinnest E string breaking most frequent) is the point in which a softer disc spring engages or reaches a mechanical stop in the disc spring stack above the saddleassembly. The string tension typically pulls the bridge and creates a torque in the Z shaped bracket which in turn pushes upwards to this disc spring assembly against the retainer means. If collective tension suddenly reduces as a spring breaks, the tension in this stack can be calibrated to lessen such that overall string tension does not change and the remaining 5 strings are 'in tune' relative to each other. This would be the case with a fixed bridge unit with no 'floating' bridge mechanism and a major reason some guitar players choose not to use tremolo units at all: such is the importance of remaining in tune should a string break in a live-performance setting. Given the ease of precise tension control with disc springs suspending the saddle-assembly means, variable tunings can be realised by adjusting stacking arrangements and engaging or disengaging subsets. More complex systems where the tremolo-arm moves in discretised intervals relating to musical note intervals may be envisaged as further designs depending on this invention. A major scale for instance, has the following ratios defining the 7 notes (or intervals) in the scale; - —. 18 4 3 2 3 8 Similarly, some systems employing locking nut devices have fine tuning adjustment supplemented to the bridge assembly. The primary purpose of this, is to avoid using (typically) Allen-key tools to loosen a clamp upon the preferred locking-nut repeatedly. This allows access to the string tuners found typically on an instrument's headstock to be used. Once the clamp upon a locking nut is reengaged, these tuners are ineffectual and hence fine adjustment is presented on the bridge with saddles typically pivoting relative to the rest of the bridge assembly independently on leaf-springs. This could be accomplished using disc springs whereas the main example presented provides adjustment for spring tension at three points, distributing load across all strings collectively. To achieve this within suitable space constraints, the specifications D83202 or D84202, noted above would be needed. The invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 shows a top-down view of the main invention, using disc spring specification D2010204 (3,4,6 and 7). Dials (12) above the U-Shaped Retaining means (1) allow for adjustment of disc spring preloading tension. This is facilitated by a threaded steel ball (5), and the dial screwing a bolt in or out of said threaded ball. Figure 2 shows an isometric view of the main invention. Figure 3 shows a cross-sectional view of the main invention, using disc spring specification D2010204. 3 stacks are utilised above and below the Z-Shaped Bracket (8), which rotates upon use of tremolo arm (11). Figure 4 shows a housing unit for the disc spring stacks, where a mechanical stop (18) may be rotated to engage or disengage. This optional configuration illustrates supplementary claims whereby string tension can be rebalanced following a broken string, or more generally that tension / tuning can be adjusted easily. Ordinarily, on a 6-string instrument, upon breaking a string, the tension is now shared across 5 remaining strings; which would make the tension 6 / 5 the desired rate rendering remaining strings 'out of tune'. Disc springs stacked in series, collectively share loading meaning that when all 6 disc springs are engaged, the spring rate becomes -what it would otherwise be, with just 5 disc springs stacked. The top-piece (mechanical stop) when rotated such that its protruding lug aligns to that of the corresponding lug on the lower housing, ensures that the 6th disc spring is not activated. Figure 5 shows a cross-sectional view of the components noted in optional configuration of Figure 4. Here we can see the disc springs stacked in series, with alternate springs 'upturned' such that outer or inner edges are in contact. Figure 6 shows an optional configuration of fine-tuning adjustment with the use of D83202 or D84202. Whilst D1052025 is also capable of physically sitting within the space envelope, only a small spring force is needed to return the screw adjustments which alter the angle of the saddle seating. The bulkier appearance of D1052025 makes the two other stated specifications preferred. The saddle-seats (15), pivot around a roller (17) and their relative angle is adjustable via screws (16) , situated close to screws used commonly to adjust intonation (string length) merely moving the string saddles (13) back and forth along the saddle seats. Figure 7 shows merely a zoomed-up detail of Figure 6, with the same components noted. Figure 8 shows an isometric view, of the optional configuration noted in Figure 6. This highlights the roller (17) about which the saddle-seats may pivot. Figure 9 shows a secondary isometric view of the configuration from Figure 6. This highlights the adjustment location for saddle-seat angles, utilised in fine-tuning adjustments. The table below provides component numbering references for the drawings . Number Quantity Description 1 1 U Shaped Retaining means 2 3 Ball Bearing (Lower stack) 3 9 D2010204 (Disc Spring) - Lower Stack 4 9 D2010204 upturned - Lower Stack 5 3 Threaded Ball Bearing (Upper stack) 6 9 D2010204 (Disc Spring) - Upper Stack 7 9 D2010204 upturned - Upper Stack 8 1 ZShaped Bracket 9 1 Bridge Top 10 1 Bridge Middle 11 1 Tremolo Arm (Whammy-bar) Assembly 12 1 Dial (Adjustment of tension) 13 6 String Saddle Assembly (including intonation screws) 14 6 D83202 Stack (for each saddle seat) 15 6 Adjustable Saddle Seats 16 6 Saddle Angle Adjustment Screws 17 1 Roller (Pivot for Saddle Seats) 18 3 Mechanical Stop (Toggle by rotating) 19 3 Disc Spring Housing REFERENCED DOCUMENTS REF 1 BLOG, SEYMOUR DUNCAN Seymour Duncan The Most interesting Whammy Bars In the Worjd: Guitar Pickups, Bass Pickups, Pedals REFERENCED PATENTS US PAT. NO. USD169120S 'Tailpiece vibrato for string instrument' US PAT. NO. 7521616 'Locking cam tremolo device' US PAT. NO. 4632005 (1984) 'Tremolo mechanism for an electric guitar' US PAT. NO. US4424773A 'Valve Rotator'

Claims

1. A tremolo unit for electric guitar utilising disc springs as cushioning means, such that rear-mounted coil springs are not required whilsta. a string saddle assembly pivots around an axis by use of tremolo-arm referred to collectively as the saddleassembly meansb. a Z shaped bracket within the saddle-assembly means extends outwardly backwards and beneath the surface height of the guitar, engaging with ball-bearings and via these, the cushioning means2. A cushioning means is applied above and below the saddleassembly means such that a restitution force applies in clockwise or anti-clockwise motion and the relative displacement and stiffness of cushioning means corresponds to musical note adjustment by the end-user.

3. A rigid housing unit contains the spring assembly and is fixed to the top surface of a guitar, such that no rear routing of guitar body is required where conventional coil springs would be housed.

4. A tremolo unit according to claims 1,2 and 3, in which the cushioning means is provided by disc springs stacked in series above and below the saddle-assembly means preferably with three columns aligned to the centreline, left and right pivot posts when viewed in plan: sitting further perpendicularly from the pivot point than the string saddles within the saddle-assembly means .

5. A tremolo unit according to any of the preceding claims, in which the cushioning means below and above the saddle-assembly means comprises series-stacked disc springs and a bearing means between.

6. A tremolo unit according to claim 5, where the bearing means preferably constitutes a steel ball whose outer diameter exceeds the inner diameter of the disc spring's marginally such that an angled seating arrangement (disc tangent to sphere) is realised.

7. A tremolo unit according to any of the preceding claims where the spring preloading of cushioning means may be adjusted. This may be to:a. vary the rate of pitch-shift upon using tremolo-arm, b. the 'feel' or ease upon playing strings (increased tension can make bending strings require more force), c. or finally to adjust the tuning of the instruments' strings themselves.

8. A tremolo unit according to any of the preceding claims, in which the cushioning means above the saddle-assembly means comprises series-stacked disc springs and preferably a threaded steel ball bearing means, such that an angled seating arrangement (tangential) is found with additional adjustment of spring height and thereby preloading amount by advancing screw axially.

9. A tremolo unit according to claim 8, where the disc spring inner diameter should preferably be less than the ball diameter yet allow clearance for threaded fasteners to pass-through the stack and mate with the steel ball for screw adjustment without fowling (collision).

10. A tremolo unit according to any of the preceding claims where a conventional tremolo-block is maintained for the purposes of sustain or user-experience as a result of its mass and inertia during rotation despite no coil-spring attachments .

11. A tremolo unit according to any of the preceding claims where a conventional tremolo-block is not used, and strings may be optionally top loading or fed through the instrument with no rear-routing of instrument necessary.

12. A tremolo unit according to any of the preceding claims where disc spring assembly is used for fine-tuning of the instrument without removing any 'locking features' such as locking nut and locking saddle that may be used preferably for string mounting and control of vibrating length consistency within saddle-assembly means.

13. A tremolo unit according to any of the preceding claims where the reduced collective tension from breaking a string during use, can optionally be accounted by disengaging or reengaging portions of a disc spring stack to ensure commensurate counteracting spring force.

14. A tremolo unit according to any of the preceding claims where the disc spring arrangements allow for the settings of multiple instrument tunings calibrated a-priori and seamlessly switched-between.

15. A tremolo unit according to any of the preceding claims where the rotation rate of tremolo-arm may be toggled to differing rates during use.

16. A tremolo unit according to any of the preceding claims where the rotation rate of tremolo-arm is discretised into steps which correspond to ratios of diatonic musical scales using tailored stacking arrangements.17 . A tremolo unit according to any of the preceding claims where a conventional tremolo-block and coil spring assembly is maintained whilst using supplementary stacked disc spring assembly for the ancillary purposes outlined in claim 7 or any other preceding claims.Amendments to the claims are filed as follows:03 02 25CLAIMS1. A front-mounted tremolo unit for electric guitar utilising disc springs as cushioning means, such that rear-mounted coil springs are not required whilsta. a string saddle assembly pivots around an axis by use of tremolo-arm referred to collectively as the saddleassembly meansb. a Z shaped bracket within the saddle-assembly means extends outwardly backwards and beneath the surface height of the guitar, engaging with ball-bearings and via these, the cushioning means2. A tremolo unit according to claim 1, whereby a cushioning means is applied above and below the saddle-assembly means such that a restitution force applies in clockwise or anticlockwise motion and the relative displacement and stiffness of cushioning means corresponds to musical note adjustment by the end-user.

3. A tremolo unit according to claims 1 and 2, whereby a rigid housing unit contains the spring assembly and is fixed to the top surface of a guitar, such that no rear routing of guitar body is required where conventional coil springs would be housed.

4. A tremolo unit according to claims 1,2 and 3, in which the cushioning means is provided by disc springs stacked in series above and below the saddle-assembly means preferably with three columns aligned to the centreline, left and right pivot posts when viewed in plan: sitting further perpendicularly from the pivot point than the string saddles within the saddle-assembly means .

5. A tremolo unit according to any of the preceding claims, in which the cushioning means below and above the saddle-assembly means comprises series-stacked disc springs and a bearing means between.

6. A tremolo unit according to claim 5, where the bearing means preferably constitutes a steel ball whose outer diameter exceeds the inner diameter of the disc spring's marginally such that an angled seating arrangement (disc tangent to sphere) is realised.

7. A tremolo unit according to any of the preceding claims where the spring preloading of cushioning means is capable of being adjusted.

8. A tremolo unit according to any of the preceding claims, in which the cushioning means above the saddle-assembly means comprises series-stacked disc springs and preferably a threaded steel ball bearing means, such that an angled seating arrangement (tangential) is found with additional adjustment of spring height and thereby preloading amount by advancing screw axially.

9. A tremolo unit according to claim 8, where the disc spring inner diameter should preferably be less than the ball diameter yet allow clearance for threaded fasteners to pass-03 02 25through the stack and mate with the steel ball for screw adjustment without fowling (collision).

10. A tremolo unit according to any of the preceding claims where a conventional tremolo-block is maintained for the purposes of sustain or user-experience as a result of its mass and inertia during rotation despite no coil-spring attachments.

11. A tremolo unit according to preceding claims 1-9 where a conventional tremolo-block is not used, and strings may be optionally top loading or fed through the instrument with no rear-routing of instrument necessary.

12. A tremolo unit according to any of the preceding claims where disc spring assembly is used for fine-tuning of the instrument without removing any 'locking features' such as locking nut and locking saddle that may be used preferably for string mounting and control of vibrating length consistency within saddle-assembly means.

13. A tremolo unit according to any of the preceding claims where the reduced collective tension from breaking a string during use, can optionally be accounted by disengaging or reengaging portions of a disc spring stack to ensure commensurate counteracting spring force.

14. A tremolo unit according to any of the preceding claims where the disc spring arrangements allow for the settings of multiple instrument tunings calibrated a-priori and switched-between by engaging or disengaging a mechanical stop which loads or unloads a subset of springs.

15. A tremolo unit according to any of the preceding claims where the rotation rate of tremolo-arm may be toggled to differing rates during use.

16. A tremolo unit according to any of the preceding claims where the rotation rate of tremolo-arm is discretised into steps which correspond to ratios of diatonic musical scales using tailored stacking arrangements.

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