Electric pickups used in connection with “acoustic type” stringed musical instruments have been in use for many years. Indeed, the present inventors have previously co-invented and patented two different designs that are in common use today (U.S. Pat. No. 6,018,120, and U.S. Pat. No. 8,455,749). Others have also designed and patented various configurations.
The present invention is designed for use with instruments that use a bridge having a string height adjustment mechanism in each leg (i.e., height adjustment wheels). Generally, this means the larger stringed instruments, such as the upright bass. There is no actual limit on size of the present invention; the preceding comment arising merely because smaller instruments ordinarily do not use adjustment wheels. While the invention is expected to find its primary use as described above, it is not so limited, and the invented pickup can also be used in connection with other bridge types. Accordingly, the example shown herein with the invention installed on an upright bass bridge with adjuster wheels should be taken as illustrative, and not limiting.
Depending on the type of adjustment mechanism used (there are currently two general types in use, as will be explained below), the invented pickup fits and is clamped between the adjusting wheel and either (1) the bridge foot or (2) the bridge leg. The pickup can be installed on either the bass or treble side of the bridge, but is more commonly installed on the bass side. The pickup, which includes three piezo-electric elements connected in parallel, bears substantially the entire force that is transmitted from the strings, through the bridge, to the instrument face on the selected side. The term “piezo-electric element” as used herein refers to an element fabricated from any one of a number of materials that generates a voltage between its faces when subjected to compression. Such elements are common in the industry, and need not be further described.
The three piezo-electric elements, as installed on an instrument, are arranged at the apexes of an equilateral triangle, i.e., a substantially symmetrical disposition around the adjuster screw. The static loads on the elements are approximately equal. The “tripod” support configuration provides a very stable base for the forces transmitted downward through the bridge. Unintended asymmetries in installation and adjustment may create some differences, but such differences are not believed to be significant in terms of affecting performance.
The invented pickup is a sandwich of parts, as can be seen in the exploded view of
Adjacent bottom cap 17, is bottom plate 19, which is preferably fabricated from stainless steel, but other materials may also be used, if desired. Bottom plate 19 (and the top plate 25, which will be described below) may be used to provide stiffness to the assembly and therefore, in such case, should be relatively heavy. The plates, particularly top plate 25, also provide electrical shielding for the pickup. The plate parts in the preferred embodiment are about 0.030 inches thick. If mechanical stiffness is not deemed important, thinner plates may be used. Also, it is preferred that the plates be bent slightly inward before assembly to keep the assembly from “opening up”.
Ground foil 20, preferably made of copper or brass, rests on bottom plate 19. The term “foil” is used herein for convenience, since the preferred embodiment of the invention uses metal a few thousandths thick, however, the actual conductor thickness used can be whatever is convenient. Pliant spacer 21A rests on the ground foil, and has three openings 22 to position and retain the piezo-electric elements 12. Pliant spacer 21A is preferably fabricated from plastic foam sheet having about the same thickness as the sensors, i.e., in the preferred embodiment about 0.030 inches. Rigid spacer 21B is placed adjacent to the pliant spacer 21A (between the caps 16 and 17). Rigid spacer 21B is preferably made of fiberboard or the like, and also has a thickness about the same as the sensors. The sensors rest on ground foil 20, in the openings 22.
Hot foil 22 lays on top of spacer 21, and makes contact with the upper surfaces of the sensors 12. Paper insulating sheet 24 covers hot foil 23, and insulates it from top plate 25.
Top plate 25 and top cap 16 complete the sandwich, which, as previously noted, is held together by screws 18 threaded into bottom cap 17. Depending on how the caps are finished, it may be necessary to remove the finish in some area(s) so that electrical contact (for shielding purposes) can be maintained between top cap 16, top plate 25, bottom plate 19, and bottom cap 17. Bottom and top plates 19 and 25 are preferably unfinished stainless steel.
There is another type of adjusting mechanism in common use wherein the adjusting wheel and the stud are combined as one piece, and the threads on the stud mate with internal threads in the bridge foot, with the top portion of the stud being a slip fit into the bridge leg.
Since the piezo-electric elements 12 are symmetrically disposed about opening 13, they form a very stable support for the bridge leg. The use of three equally spaced transducers makes it easy to locate the array such that the forces on all three are substantially equal whereby all three contribute substantially equal portions of the total pickup output. Equalizing transducer loading is important both from transducer life and performance points of view. Using three transducers, as opposed to two or four, makes equalization easier.
Placing the pickup in the bridge leg, relatively close to the strings, results in a more percussive, articulated sound output from the amplifier. This effect is highly desirable, especially when amplifying an instrument during a “live” presentation. Placing the pickup in the bridge leg, relatively close to the strings also helps to get a “cleaner”, less “fluffy”, or a more articulated tone. It has been found, also, that when the total load is substantially evenly shared, there is a significant reduction of the possibility of an intermittent popping” sound.
This application claims the benefit under 35 USC §119(e) of the filing date of U.S. Provisional Patent Application No. 61/848,003 entitled “The Lifeline”, filed Dec. 20, 2012.
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Number | Date | Country | |
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61848003 | Dec 2012 | US |