US 3507972 A
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United States Patent Int. 01. 01011 3/00,- G10d /00 U.S. Cl. 841.14 3 "Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a microphone bridge for string instruments made of two parts, one part engaging the strings and the other the resonator. A piezoelectric crystal is situated between the said two parts for transforming the vibration of the strings into sound frequency.
The present invention relates to the amplification of the sound of string instruments. This was achieved so far mainly by means of electromagnetic pick-ups in such a way that the string vibrating in the field of a permanent magnet induces in the coil surrounding the magnet an alternating current corresponding to the sound frequency, this current being then amplified and fed to a loudspeaker. The most important condition for employing said pick-ups was that the material of the strings be magnetizable, i.e. that they be made e.g. of iron or steel.
For the transformation of the sound or plastic or gutstrings into an electric signal there are solutions known in which by means of an auxiliary clamping arrangement of various designs a piezo-electric crystal is fastened to a selected point on the musical instrument, said crystal taking over the vibration existing at the given point. These devices have many drawbacks: first the clamping systems do not force the crystal to take over from the musical instrument the entire vibration, second the self-vibration of the crystal and of the clamping arrangement may modify the signal taken off from the musical instrument, and third the selected points on the musical instrument do not comprise the whole characteristic range of sound of the musical instrument.
The invention eliminates these drawbacks because the crystal producing the sound frequency is forced-owing to its arrangementto become deformed only according to the movement achieved by the strings on the resonator, therefore the crystal takes'over invariably the vibration arising from the string, and so a very good amplification or modification is obtained. For this purpose a microphone bridge according to the invention takes over the vibration of the strings for the excitation of sound frequency in the same way as it is taken over by the resonator of the musical instruments from the traditional bridge. As a result thereof, the characteristics of the sound obtained are the same or almost the same as those of the accepted traditional sound of the musical instruments.
The invention relates thus to a microphone bridge for string instruments, characterized in that the bridge transmitting mechanically the vibration of the strings is divided in two, or consists of two parts, and between these parts there is a flat elastic distance piece parallel to the plane of the strings or of the resonator enabling the relative displacement and vibration of said parts, and a piezoelectric crystal is also between thetwo parts so that it is deformed in consequence of the relative displacement of the two parts of the bridge, thus electrical signals are produced which may be amplified and transformed into sound in a manner well known per se.
3,507,972 Patented Apr. 21, 1970 The invention is described in detail with reference to the enclosed drawing which represents an embodiment by way of example. The figure shows the schematic crosssection of the microphone bridge.
The strings 1 bear against a bridge 2 which supports the strings at an appropriate location and transmits their vibration to the resonator 3 of the musical instrument by way of direct contact. Parallel with the plane of strings 1 and/or of resonator 3 the bridge 2 is cut in two, the lower part 5 and the upper part 6 of the bridge being at a distance from one another which allows placing therebetween an elastic distance piece 7 enabling the independent elastic movement of the upper part 6, and a piezo-electric crystal 8 transforming the vibrations of strings 1 into sound frequency is also between parts 5 and 6.
Between the lower part 5 and the upper part 6 of bridge 2 the piezo-electric crystal 8' of prismatic shape is placed obliquely in such a way that its one end bears against a cavity 9 of the lower part, and the other end engages a surface 10 of the upper part. Thus the crystal touches the parts 5 and 6 along two diagonally opposite edges, the engagement being ensured by elastic pads 11.
The mass of the two parts 5, 6 of the bridge is almost equal to that of the usual undivided bridge.
The upper part 6 of bridge 2 transmits the vibration of strings I by moving together with the strings, and deforms in the rhythm of the vibration the piezo-electric crystal 8 touching the same. As a result thereof the crystal 8 produces an alternating current the frequency of which corresponds to the vibration of the strings. This can be amplified in a manner known per se as "required, in an electric amplifier and the amplified current can be used in an electric loud-speaker.
The device according to the invention allows of transforming any vibration of strings into a perfect sound frequency.
1. A microphone bridge for string instruments having a resonator, the bridge supporting the'strings and transmitting mechanically their vibration to the resonator, the bridge comprising an upper and a lower part the upper part engaging the said strings and the lower the resonator, an elastic distance piece between said parts disposed parallel to the plane of the strings and permitting a displacement of the upper part relative to the lower one, and at least one pieZo-electric crystal engaging the two bridge parts to produce electrical signals upon relative movement of said parts.
2. A microphone bridge according to claim 1, wherein said crystal has a prismatic shape with diagonally opposite edges bearing one against each of said bridge parts, the crystal being disposed between said bridge parts obliquely with respect to the plane of said elastic distance piece.
3. A microphone bridge according to claim 2, and resilient means by which said crystal is supported in said oblique position.
References Cited UNITED STATES PATENTS 2,334,744 11/1943 Benioif 841.16 2,494,485 1/ 1950 Notara 84-1.16 3,076,903 2/ 1963 Schwartz 3108.3 3,113,990 12/1963 Zanessi 84-1.l6 3,394,275 7/1968 Lippmann 310-83 HERMAN KARL SAALBACH, Primary Examiner T. VEZEAU, Assistant Examiner U.S. Cl. X.R. 841.16