Vibration damper for reducing vibrations of a low frequency sound generator

Abstract

The invention relates to a vibration damper (1) configured to be provided on a low frequency sound generator, which comprises a feeder unit (2) with a positive feedback system regulated by a reciprocating spring loaded piston (3) and a resonator tube (4). The vibration damper (1) may be positioned outside the resonator tube (4). The vibration damper (1) comprises a first flange (5) connected to the resonator tube (4), a number of springs (6), a second flange (7) and a number of weights (8).

Claims

1. A vibration damper (1) configured to be provided on an air-driven low frequency sound generator, which comprises a feeder unit (2) with a positive feedback system regulated by a reciprocating spring loaded piston (3) and a resonator tube (4), whereby the vibration damper (1) is configured to be positioned outside the resonator tube (4), and comprises a first flange (5) connected to the resonator tube (4), a number of springs (6), a second flange (7) and a number of weights (8) characterized in that the second flange (7) is free to move in relation to the first flange (5).

2. The vibration damper (1) according to claim 1, whereby a total mass of the weights (8) and of the second flange (7) versus a spring constant of the springs (6) are determined in such a way that, when the low frequency sound generator vibrates, the vibration velocity amplitude of the second flange (7) is higher than the vibration velocity amplitude of the first flange (5).

3. The vibration damper (1) according to claim 1, whereby the number of springs (6) is six or more.

4. The vibration damper (1) according to claim 1, whereby the mass of the weights (8) and the second flange (7) is lower than 20% of the total weight of the low frequency sound generator.

5. Use of a vibration damper (1) according to claim 1 for damping of vibrations of a low frequency sound generator.

6. A low frequency sound generator which comprises a compressed air supply system (12), a feeder unit (2) and a resonator tube (4), characterized in that the low frequency sound generator further comprises a vibration damper (1) configured to be positioned outside the resonator tube (4) and comprises a first flange (5) connected to the resonator tube (4), a number of springs (6), a second flange (7) and a number of weights (8).

7. The low frequency sound generator according to claim 6, whereby a total mass of the weights (8) and of the second flange (7) versus a spring constant of the springs (6) are determined in such a way that, when the low frequency sound generator vibrates, the vibration velocity amplitude of the second flange (7) is higher than the vibration velocity amplitude of the first flange (5).

8. The low frequency sound generator according to claim 6, whereby the number of springs (6) is six or more.

9. The low frequency sound generator according to claim 6, whereby the mass of the weights (8) and the second flange (7) is lower than 20% of the total weight of the low frequency sound generator.

10. A method of using the low frequency sound generator according to claim 6, the method of using comprising cleaning of a boiler or a heat exchanger.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The present description is now to be explained more closely by means of embodiments, which are disclosed as examples, and with reference to the attached drawing.

(2) FIG. 1 shows schematically a vibration damper.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION

(3) FIG. 1 shows a feeder unit 2 of a low frequency sound generator mounted on a resonator tube 4. The resonator tube may be a quarter wave resonator tube 4. The feeder unit 2 comprises a piston 3 that is arranged to perform a reciprocating movement inside a cylinder 9. The piston 3 is spring-loaded by means of a spring 10, which is attached to the closed end of the cylinder 9. The cylinder 9 and the piston 3 are mounted in a surge tank 11. A compressed air supply system 12 is connected to the surge tank 11.

(4) The feeder unit 2 feeds air pulses into the resonator tube 4. The dimensions of the resonator tube 4 are chosen in such a way that a standing sound wave may be generated in the resonator tube 4 by said air pulses. Further details regarding the low frequency sound generator are described in U.S. Pat. No. 5,005,511, which is hereby included in its entirely by reference.

(5) FIG. 1 shows also a vibration damper 1 according to the present invention. The vibration damper 1 is configured to be positioned outside the resonator tube 4 on a low frequency sound generator as described above.

(6) The vibration damper 1 comprises a first flange 5 attached to the resonance tube 4, a number of springs 6 attached to the first flange 5, a second flange 7 attached to said springs 6 and a number of weights 8 attached to said second flange 7.

(7) The second flange 7 is only attached to the springs 6. Thereby the second flange 7 can move in relation to the first flange 5. The frequency of the movement of the second flange 7, the vibration velocity amplitude of the movement of the second flange 7 in relation to the movement of the first flange 5 and the phase difference of the movement of the second flange 7 in relation to the movement of the first flange 5 depends on the frequency of the vibration velocity amplitude of the first flange 5, the spring constant of the springs 6 and the total mass of the weights 8 and the second flange 7.

(8) The vibration velocity amplitude of the movement of the first flange 5, and thereby the resonator tube 4, is lower the more the second flange 7 moves in relation to the first flange 5. That means that the vibration damper 1 may reduce the harmonic movement of the resonator tube 4 and hence of the total low frequency sound generator.

(9) The vibration velocity amplitude movement of the second flange 7 can be increased by selecting the masses of the weights 8 and the second flange 7 versus the spring constant of the springs 6. That also means that the vibration velocity amplitude of the entire low frequency sound generator can be reduced by selecting the masses of the weights 8 and the second flange 7 versus the spring constant of the springs 6.

(10) The force acting on each of the springs 6 is lower if the number of springs 6 is higher. Practical tests have showed that minimum six springs 6 are needed.

(11) The reduction of vibration velocity amplitude of the first flange 5 is higher at higher total mass of the weights 8 and the second flange 7. Practical tests have shown that it is possible to reduce the vibration velocity amplitude of the first flange 5 by up to 80% or even more at a total mass of the weights 8 and the second flange 7 of less than 20% of the mass of the entire low frequency sound generator by correct selection of the mass of the weights 8 and the second flange 7 versus the spring constant of the springs 6.

(12) The expression “low frequency sound” as used herein is meant to include sound of a frequency below approximately 38 Hz. A suitable operation frequency would be between approximately 15 and 30 Hz.

(13) The expression “vibration velocity amplitude” as used herein is the peak value of the velocity of a harmonic back and forth movement of a solid component.

(14) The present invention is not limited to the embodiments disclosed but may be varied and modified within the scope of the following claims.