Acoustic guitar under the saddle piezo pickup

Details Acoustic guitar under the saddle piezo pickup Acoustic guitar under the saddle piezo pickup

2002-07-30

2004-11-23

Fletcher, Marlon T. (Department: 2837)

Music

Instruments

Electrical musical tone generation

C084S734000

Reexamination Certificate

active

06822156

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to guitar pickups and, more specifically, to an improved acoustic guitar pickup system consisting of two components that provide the signal that is representative of the guitar sound, a primary device and a secondary device. The primary device is the piezoelectric pickup array that is situated beneath the saddle of a guitar. The device is designed to detect the bulk of the sound as well as the tonal nuances. The primary device provides minimal ambience. The secondary device makes use of the physically induced charge modulation properties along both the longitudinal and transverse axis of the interconnecting coax cable that runs from the under the saddle pickup system of the present invention to the impedance changing preamplifier to provide ambiance.
The piezoelectric elements are placed in the center between each pair of strings. A six string guitar could use five piezoelectric elements. The vibration shock wave produced by the string actuation is not directly over the piezoelectric element. The vibrations are diffused by the saddle and the offset (between the strings not directly beneath them) elements react to those diffused vibrations which also make them react to the strings vibrating sympathetically. The effect being that the transduced signal produced by the sum of the piezoelectric elements is very much like the instrument that it is installed in without the excessively percussive sound produced by piezoelectric elements placed directly below or below but adjacent to the string.
On each side of a piezoelectric element is a spacer. (See
FIGS. 2
,
3
and
4
.) The spacer is a very important aspect of this invention as it is of a specially selected material which would provide acceptable mechanical compliance without degrading the tonal qualities of the signal. The function of the spacers is to relieve the piezoelectric elements of the total downward loading forces of the strings thus giving greater bandwidth, dynamic range and lower distortion.
It is well known that the under the saddle style pickups, which use individual piezoelectric elements, have problems that appear to be caused by partially or completely malfunctioning elements. The apparent malfunction causes the amplified acoustic guitar to sound uneven from string to string and the unevenness also changes the tonal qualities.
The reason for this malfunction may not be a failed element but a failure of the individual element to couple mechanically to the guitar. For instance, when a pickup is installed, each element may work perfectly, until the strings are tuned and tension is applied to the saddle, then one or more of the piezoelectric elements fail to be active. The reason for this and the cure, which is a subtle but important part of this invention, is as follows: the force of the string in the downward direction on the saddle is not perfectly even from string to string. The bridge and the top have some flexure, which may not be quite the same as the saddle and/or the pickup. The saddle and/or the pickup can bow just enough so that it does not sit perfectly on the pickup. The result is that the saddle bows just slightly so that the bottom of the saddle does not seat perfectly with the bridge. Any air gap at all, above or below the element, will cause the element to appear not to function.
This problem occurs whether there is a pickup installed or not because the saddle is a different material than the bridge. Because of this, the mechanical coupling is less than perfect and affects not only the amplified sound but the acoustic sound as well. That this problem exists as defined here, is not obvious to the pickup manufacturing community which is one of the reasons why it has gone from individual elements to piezoelectric film. One solution to this problem is to use filler such as an RTV Silicon Rubber above and below the under the saddle pickup. Less than one mil (0.001 inch) is all that is needed. The problem with this system is the pickup is not easily removable. Furthermore, a void can still occur in the form of an air bubble. A better approach, as illustrated in
FIG. 5
, is a material, which is compressible and does not act as an adhesive, but as a compressible gasket that can easily be removed from the system and make the pickup removable as well as replaceable.
This material would do three things:
1. Prevent the mechanical decoupling of the individual piezoelectric elements of the under the saddle pickup.
2. Couple the saddle to the bridge with no void thus making the saddle drive the top more evenly resulting in a more even sound.
3. Absorbing some of the harshness due to mechanical noise of the string being actuated by the fingers or a pick.
This invention also includes an optional auxiliary pickup whose function is to detect the vibrations within the plane of the top. It adds a component that improves the tonalities of the system. The auxiliary pickup is otherwise considered part of the primary system-since the pickup is activated vibrationally.
2. Description of the Prior Art
There are other pickup devices designed for piezoelectric transducer and pickup means. Typical of these is U.S. Pat. No. 4,160,401 issued to Tomioka on Jul. 10, 1979. Another patent was issued to Saito et al. on Jul. 14, 1981 as U.S. Pat. No. 4,278,000.
Another patent was issued to Baggs on Feb. 9, 1982 as U.S. Pat. No. 4,314,495. Yet another U.S. Pat. No. 4,491,051 was issued to Barcus on Jan. 1, 1985 and still yet another was issued on Mar. 1, 1988 to Fishman as U.S. Pat. No. 4,727,634.
Another patent was issued to Turner on Jun. 23, 1992 as U.S. Pat. No. 5,123,325. Yet another U.S. Pat. No. 5,265,513 was issued to Smith on Nov. 30, 1993. Another was issued to Ekhaus on Apr. 5, 1994 as U.S. Pat. No. 5,300,730 and still yet another was issued on Jun. 21, 1994 to Aaroe et al. as U.S. Pat. No. 5,322,969.
Another patent was issued to Vice on Mar. 2, 1999 as U.S. Pat. No. 5,877,447. Yet another U.S. Pat. No. 6,166,309 was issued to Hoshino on Dec. 26, 2000. Another was issued to Hoshino on Mar. 6, 2001 as U.S. Pat. No. 6,198,036.
U.S. Pat. NO. 4,160,401
Inventor: Michiaki Tomioka
Issued: Jul. 10, 1979
A string vibration transducer bridge for an electric string instrument including a plurality of string tension mechanism provided side by side in the bridge and which are adjustably movable along the direction of the string and includes a plurality of string supporting electrode parts which are slidably movable along the direction of the string and rotatable along a direction perpendicular to the string, a plurality of independent piezoelectric transducers which each engage with an undersurface of an electrode part, and a plurality of piezoelectric transducer pushing mechanisms for pushing the piezoelectric transducers against the electrode parts whereby the tension of the string may be adjusted by both the string tension mechanism and the transducer pushing mechanism and the vibration from each string is independently sensed.
U.S. Pat. No. 4,278,000
Inventor: Shigeo Saito et al.
Issued: Jul. 14, 1981
The present invention provides a piezoelectric transducer and pickup means using the same for electrical string instruments, the transducer comprising a long and flat outer layer of flexible material and a flexible piezoelectric cable which is buried therein and has a center electrode, a piezoelectric layer formed on the outer periphery of the said electrode and an outer electrode formed on the outer periphery of the said layer, the stiffness thereof being enhanced by either using elastomer of the hardness of more than 80 as measured by the Spring Hardness Test Method in the Physical Testing Method for Vulcanizing Rubber of Japanese Industrial Standard (JIS K 6301) as the material for the outer layer, or by plaiting (braiding) metal wires or by winding the outer electrode of the piezoelectric cable in such a manner as to enable it to press against the piezoelectric layer.
U.S. Pat. No. 4,314,495
Inventor: Lloyd Baggs
Issued: Feb. 9, 1982
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