Patent Publication Number: US-9905212-B1

Title: Bridge with pickup for hybrid arched top guitar or the like

Description:
RELATED APPLICATION 
     This application is related to and claims priority from U.S. Provisional Application 62/460,396, filed on Feb. 17, 2017, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to arched top guitars and, more particularly to a bridge with a pickup for arched top guitar. 
     BACKGROUND 
     Stringed musical instruments typically generate sounds of specific pitches by the vibration of stretched strings. In one common arrangement, which is used, for example in guitars, several strings, side by side, are stretched from an anchor near a tail of the guitar body, over a bridge that supports the strings, and up along a fretted neck to an attachment at the head with a device for adjusting the tension of each string. By holding a string down onto one of the frets, a player defines the length of string between the bridge and the chosen fret, and thus chooses the note to be played. 
     In an acoustic guitar, the vibration of the string, assisted by construction of the guitar body, which is at least partially hollow, causes sound in the air. That sound can then be detected by a microphone and amplified. In an electric guitar, the vibration of the string is converted into an electrical signal by a transducer, and the electrical signal is amplified and then converted into sound, usually by a loudspeaker. The commonest form of transducer is an electromagnetic pickup, in which the vibration of the strings, which are typically at least partially metallic, within a magnetic field induces an electric current in a coil of wire. The amount of current generated is correlated to the sound that is produced. Electric and acoustic guitars sound very different. That is important, because a particular sound may better suit a particular style of music, or a particular musician. 
     A “hybrid” guitar is a guitar in which the vibration of the strings is converted into an electrical signal by a piezoelectric sensor in the bridge. The piezoelectric sensor may be the only way of producing an output, or may be used in addition to an electromagnetic electric-guitar pickup, or may be mounted on an amplified acoustic guitar. Hybrid guitars tend to produce a sound somewhere between an acoustic guitar and a conventional electric guitar. 
     The configuration of the instrument body also affects the sound. Arched top and flattop guitars are two well-known guitar constructions. As a function of traditional construction techniques known to those who are versed in the art of building both flattop and arched top acoustic guitars, the arched top guitar&#39;s construction uses an arched or carved top plate that is typically braced with only two braces, as the arched structure is sufficient to withstand the downward pressure exerted by the strings on the top through the bridge. This construction creates a strong initial “attack,” which is the initial transient response when the string is plucked, that decays rapidly, causing the typical arched top guitar to have a short duration to the length of time that the string sounds, which is commonly called “sustain.” Flattop guitar construction uses a non-arched, flat top plate normally significantly braced to withstand the pull of the strings on the guitar&#39;s bridge. This construction typically results in an instrument with a less pronounced initial attack than an arched top guitar, but one with significantly more sustain—the plucked note sustains for a longer duration than with an arched top construction. 
     Many modern guitarists are drawn to the physical and cosmetic attributes of arched top guitars, but are unable to utilize them for live performance or recording as such guitars lack the desired sustain and full range frequency response associated with flattop guitars. These issues are compounded in existing hybrid guitars. Typically, the bridge in a hybrid guitar has a slot in its top surface, which is a “saddle” on which the strings actually rest. The piezoelectric element is located in the bottom of the slot, under the saddle. However, that location can result in inconsistent contact between the top surface of the slot and the underside of the saddle, and thus inconsistent transmission of the vibration from the strings. There is a desire in guitar aficionados to have an instrument with the physical characteristics of an arch top with the sound and response of a flattop guitar, when played both acoustically and amplified. 
     One remedy that has been attempted to make an arched top guitar respond more similarly to a flattop guitar has been the use of a bridge top section made entirely of metal. That compares with conventional methods of making the base section that contacts the guitar&#39;s top, and which often provides an anchor point for a mechanism to adjust the height of the strings relative to the face of the fingerboard, made of metal. Commonly used metals for entirely metal arched top bridge top sections are zinc, aluminum or brass. Using an all-metal bridge top section does not appreciably alter the response of an arched top guitar so as to be more similar to that of a flattop guitar. The resulting guitar tends to sound less warm tonally (lacking in low frequencies) than a typical flattop acoustic guitar, and the sustain of the plucked note is not appreciably extended towards the longer sustain found in typical flattop acoustic guitars. 
     Another remedy that is common is to install a long piezoelectric pickup strip below a full-length string saddle in a wooden bridge top section, and alter the frequency response electronically using filters and equalization. However, that is not satisfactory, especially with a two-piece adjustable bridge, where the bridge top section is usually mounted to the base section by adjustable posts at both ends, and unsupported in between. 
     A typical wooden bridge top section suspended between two posts will flex, especially when slotted to hold an acoustic style saddle. That creates problems in two ways. The flexing bridge top section means that the slot can bend or bow under string pressure such that the piezoelectric element no longer being in equal contact across all strings, resulting in differing amplified output for each string and differences in the tone of each string when amplified. The flexible bridge can also absorb certain frequencies of vibration, lessening sustain. 
     There is still a need for a hybrid guitar bridge that contributes tonally to the sound of an arched top guitar to give it sound characteristics more similar to an acoustic guitar of flattop construction, and for a hybrid guitar bridge with more consistent string-to-string output when using a piezoelectric pickup element that is sandwiched between the string saddle and the bottom of the saddle slot for amplification purposes. 
     SUMMARY OF THE INVENTION 
     In one aspect, there is provided an arched top style bridge upper section consisting of a wood top element that is slotted to accept a string saddle that may be made from plastic, bone or any similar material. The upper wooden bridge section is laminated or affixed with screws, pins or any other connecting element, to a lower machined or cast metal section. The top wooden section contains a slot that is routed completely through the wood section to expose the top flat surface of the lower metal part. A piezo pickup element is installed below a solid or segmented string saddle element so that the piezo element is pressed uniformly against the lower metal section by the downward force of string pressure on the string saddle to ensure even response on all strings. 
     The string pressure forcing the saddle element against the piezo pickup element and, in turn, against the metal lower section of the bridge top section, enhances the transfer of string energy more efficiently than standard all-wood arch top guitar bridge construction, resulting in greater sustain of plucked notes and a broader frequency response, when compared to standard all-wood arch top bridge construction or the use of a solid metal bridge top section. The result is that an arch top guitar utilizing the hybrid bridge construction will have more similar tonal and sustain characteristics to a typical flattop acoustic guitar while also ensuring consistent contact with a piezo element sandwiched between the saddle and lower metal bridge section resulting in even string-to-string output and response. 
     The aluminum bridge section of the invention adds rigidity, ensuring even response from the piezo pickup, and allowing more of the string&#39;s natural tone and sustain. The wooden top section of the invention, due to the nature of wood as a light, porous material, maintains tonal warmth and helps smooth any harsh overtones that the metal bridge section may impart. 
     The unique combination of elements in this invention serve to allow arched top guitars to more accurately emulate the tonal and sustain characteristics of the typical flattop guitar while solving inconsistency issues commonly found when a piezo pickup system is used in the usual manner in a standard arched top guitar bridge. 
     In another aspect, there is provided a bridge for a stringed musical instrument, comprising a lower element of a first material, an upper element of a second material that is less dense and less rigid than the first material secured to an upper surface of the lower element, the upper element having a slot through it, a piezoelectric transducer mounted on the lower element within the slot, and a saddle within the slot, operatively engaging the piezoelectric transducer and projecting from the slot through an upper surface of the upper element for receiving at least one string of the musical instrument. 
     The first material may be metal, preferably aluminum, and the second material may be wood. 
     The bridge may be elongated, with the slot, saddle, and piezoelectric transducer extending in a lengthwise direction of the bridge, for receiving a plurality of strings of musical instrument, the strings extending in a common direction, with the lengthwise direction of the bridge transverse to the common direction of the strings. 
     The bridge lower element may then be mounted on a bridge base by adjustable posts at two opposite ends of the bridge. 
     In a further aspect there is provided a stringed musical instrument equipped with a bridge as mentioned, with one or more strings of the musical instrument stretched over the bridge saddle, and with an electrical output from the piezoelectric transducer to an exterior of the musical instrument. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For the purpose of illustrating the invention, the drawings show a form of the invention which is presently preferred. However, it should be understood that this invention is not limited to the precise arrangements and instrumentalities shown in the drawings. 
         FIG. 1  is a perspective view of a representative arched top guitar. 
         FIG. 2  is a perspective view of a bridge according to the present invention for use with a guitar of  FIG. 1 . 
         FIG. 3  is an exploded view of the bridge of  FIG. 2 . 
         FIG. 4A  is a side elevation view of the top of the bridge of  FIG. 2 . 
         FIG. 4B  is a top plan view of the top of the bridge of  FIG. 2 . 
         FIG. 4C  is a cross-section through the top of the bridge, taken along the line A-A of  FIG. 4A . 
         FIG. 5A  is a side elevation view of the base of the bridge of  FIG. 2 . 
         FIG. 5B  is a top plan view of the base of the bridge of  FIG. 2 . 
         FIG. 5C  is an end view of the base of the bridge of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings, and initially to  FIG. 1 , a guitar indicated generally by the reference numeral  10  has a body  12 , a neck  14  with frets  16 , and a headstock  18 . The body  12  typically consists of a carved or formed arched top plate  20 , a flat or arched back plate (not shown), curved sides  22  that may be made from either solid or plywood wood material and a provision at the upper bout end of the body to affix the neck  14 . The top plate  20  is typically braced with two braces (not shown). The downward pressure exerted by the strings  30  on the top plate  20  through a bridge indicated generally by the reference numeral  40  is supported partly by the braces, and partly by the arched structure of the top plate. The construction of the body  12  may be conventional, and in the interests of conciseness is not further described. 
     Several strings  30  are attached to an anchorage at a tailpiece  32  near a tail end  34  of the body  12 , and extend over the bridge  40  and up the neck  14  to the headstock  18 , where they are attached to rotatable pegs  36  of a tuning machine  38 . The tension of each string  30  can be adjusted in the usual way by rotating the respective peg  36  to wind string onto or off the peg, thereby increasing and decreasing tension, respectively. 
     Referring now also to  FIGS. 2 and 3 , the bridge  40  has a top  42  and a base  44 . The base  44  has two feet  46 , one at each end, that rest on the guitar body  12  and may be attached to the guitar body in any convenient manner. The base  44  also includes a middle portion  48  that is concave so that it does not contact the guitar body. The bridge base  44  has a flat upper surface  50 , and two posts  52  are screw-threaded into holes in the bridge base  44 . Two thumbwheels  54  are threaded onto the posts  52 , and the bridge top  42  rests on the thumbwheels, so that by rotating the thumbwheels  54 , the bridge top  42  can be raised away from the bridge base  44 , against the tension in the strings  30 , or lowered towards the bridge base  44 . This adjustment allows a user to alter the height of the strings  42  in relation to the fingerboard, to select the amount of pressure (called “action”) the player prefers to press the string down to the fret  16  to sound a note. 
     A hole  56  near one end of the bridge base upper surface  50  allows an electrical output wire  58  from the bridge top  42  to be led down into the body  12  of the guitar. 
     Referring now also to  FIGS. 4A-4C , the bridge top  42  comprises at least two pieces, a lower element or saddle support  60  of metal, which in this embodiment is aluminum, and an upper element or cap  62  of wood. The wood may be rosewood or ebony, which are used in conventional arch top guitar bridge construction, though other hardwood material is sufficient. The upper element  62  has a slot  64  extending for most of its length. The slot  64  opens through from the lower element  60  to the upper surface of the upper element  62 . A piezoelectric element  66  is positioned in the bottom of the slot  64 , in contact with the aluminum lower element  60 . The piezoelectric element  66  may be of a sort commercially available for piezoelectric bridge pickups of hybrid guitars, and in the interests of conciseness is not further described here. The slot  64  is dimensioned to receive the piezoelectric element  66  snugly. The piezoelectric element  66  is held into the slot by the tension of the strings  30  pressing on the top of the piezoelectric element, and adhesives or other fastenings are not typically necessary although optionally could be added. 
     At one end of the slot  64 , there is a hole  68  formed through the lower element  60 , preferably aligned with the hole  56  in the bridge base  44 , for the output lead  58  from the piezoelectric element  66  to extend through. The lead may pass through the guitar body  12  to an external amplifier, or may be connected to a preamplifier or control mounted in or on the guitar body  12 . All such circuitry is conventional and, therefore, no further description is necessary. 
     A saddle  70  is mounted within the slot  64 , on top of the piezoelectric element  66 . The saddle  70  is held in place by the downward pressure exerted on it by the tension of the strings  30 . As may be seen in  FIG. 2 , the saddle  70  may have notches  72  for individual strings  30 . The ends of the saddle  70  are shaped as shown at  74  to allow the saddle to automatically position itself properly in the slot  64 . That is a common feature of what are called “compensated saddles,” which are molded in such a way as to allow the different string diameters to play in tune up and down the fingerboard by “compensating” for the differing string diameters. 
     In use, the bridge  40  is mounted on the guitar body  12  in the same way as a conventional bridge, the strings  30  are stretched over the bridge, and the guitar may be tuned and played in the conventional manner. The rigidity provided by the aluminum lower element  60  both improves the support for, and thus the reliability of, the piezoelectric element  66  and provides a channel for vibration from the strings  30  to the guitar body  12  and from the guitar body  12  to the piezoelectric element  66 . The softer, lighter, and more absorbent material of the wooden upper element  62  increases the tonal warmth and smooths harsh overtones by preferentially absorbing higher frequencies. 
     Although an example of a six-stringed guitar is shown in the drawings, those skilled in the art will understand how the teachings of the present application may be applied to other stringed musical instruments. 
     Aluminum is mentioned as the material for the bridge lower element  60 , and hardwood is mentioned as the material for the bridge upper element  62 , because they have satisfactory and well understood mechanical properties, are easy to machine, and are reasonably economical. However, for the bridge lower element  60 , other metals such as steel or brass may be used. For the bridge upper element  62 , other moderately stiff and moderately absorbent materials may be suitable. 
     For the purposes of promoting an understanding of the principles of the invention, reference has been made to the preferred embodiments illustrated in the drawings, and specific language has been used to describe these embodiments. However, no limitation of the scope of the invention is intended by this specific language, and the invention should be construed to encompass all embodiments that would normally occur to one of ordinary skill in the art.