US 3429743 A
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1959 N. e. BRANSON 3,429,743
v SHOCK WAVE TREATMENT METHOD AND APPARATUS Filed Nov. 1'7. 1966 F l G. 1 5 Z ./|2 :=:"T FIG. 2
NORMAN 5. BRANSON INVENTOR.
United States Patent 3,429,743 SHOCK WAVE TREATMENT METHOD AND APPARATUS Norman G. Branson, Stamford, Conn., assignor to Branson Instruments, Incorporated, Stamford, Conn., a corporation of Delaware Filed Nov. 17, 1966, Ser. No. 595,112
US. Cl. 134-1 18 Claims Int. Cl. B08b 3/10 ABSTRACT OF THE DISCLOSURE Method and apparatus providing high intensity shock waves caused by electrical spark discharges in a sonically degassed liquid for the purpose of cleaning, sterilization, etc. The sonic energy means causing degassing and the electrical discharge circuit means may be operated simultaneously or sequentially.
This invention refers to a method and apparatus for subjecting a liquid, or articles confined therein, to high intensity shock waves. More particularly, the present invention concerns a method and apparatus which employs high energy shock waves propagated in a liquid and produced by electrical discharges for treating articles. Such treatment may comprise sterilization, disloding of particles, removal of surface soil and the like.
While the prior art shows various arrangements for producing high intensity shock waves resulting from electrical discharges, the method and apparatus used heretofore have not been particularly effective because gas absorbed in the liquid has impeded the forceful propagation of such shock waves. The method and apparatus described hereinafter attempt to overcome this heretofore existing shortcoming by including means for degassing the liquid, hence, providing an improved arrangement which accomplishes more work in relation to the input power. Moreover, the arrangement disclosed hereafter is suited particularly for cleaning of parts. For instance, it is well known that ultrasonic cleaning is most effective for removing soil and contamination from the surface of articles. However, when heavy contamination, such as rust or carbonaceous deposits, is involved, the ultrasonic energy propagated in the cleaning liquid is not possessed of sufiicient power to remove such deposits.
As has been found these deposits can readily be dislodged by the application of repetitive high intensity shock waves which result from electrical discharges in the cleaning liquid. Therefore, both processes can advantageously be used to cause first the removal of heavy and strongly adhering contaminants using high intensity shock waves, followed by the more gentle sonic or ultrasonic cleaning method for removing the remaining smaller and finer contamination still adhering to the article surface. Hence, heavily contamination articles may be cleaned to a fine degree in a single step method.
One of the principal objects of this invention is, therefore, the provision of an improved arrangement for treating articles using high intensity shock waves.
Another important object of this invention is the provision of an improved method and apparatus for cleaning articles by high intensity shock waves using a substantially degassed cleaning liquid.
Another object of this invention is the provision of a cleaning method which combines the desirable characteristics of high intensity shock waves with those produced by ultrasonic cleaning.
A further important object of this invention is the provision of an improved method and apparatus for treating articles in a container which is provided with electrical spark gap means and ultrasonic energy means.
Further and still other objects of this invention will be more clearly apparent by reference to the following description when taken in conjunction with the accompanying drawings in which:
FIGURE 1 is an elevational view, partly in cross sectlon, of a typical embodiment of the invention;
FIGURE 2 is a sectional view of the typical spark gap device used in connection with FIGURE 1;
FIGURE 3 is a schematic diagram of the electrical circuit which provides the electrical discharges for producing high intensity shock waves in the liquid, and
FIGURE 4 is a sectional view of an alternative arrangement for treating a liquid.
Referring now to the figures and FIGURE 1 in particular, numeral 12 refers to a heavy-walled open-ended, tubular metal container 12 which contains a liquid 14. An article 16 to be treated, such as a heavily corroded metal part, is suspended in the liquid 14 by a wire 18. The liquid may be a caustic solution or another suitable cleaning liquid, preferably having a small amount of electrical conductivity. In a typical embodiment the container 12 is fitted with a set of electro-acoustic transducers 20 which are adapted to be energized by a high frequency generator 22 providing electrical current at 20 kHz. The transducers may be of the piezoelectric or of the magnetostrictive type. It should be understood that the frequency at which the transducers are operating is not critical and frequencies in the lower or higher region may be used.
Additionally, the container 12 is fitted with a spark gap device 24 which comprises, as seen in FIGURE 2, an insulating bushing 25 and a central metal electrode 26. This spark gap device 24 is connected to an electrical circuit 28 which, when energized, produces periodic pulses of energy. When a potential of sufiicient magnitude is applied between the electrode 26 and the tank 12, an electrical discharge occurs between this electrode and the tank wall, which discharge produces high intensity shock waves in the liquid 14. These shock waves impinge upon the surface of the article 16, thereby causing gross contamination to be dislodged therefrom. In order to enhance the intensity of the shock waves, avoiding the absorption of energy by entrained gas, the liquid 14 is subjected to sonic or ultrasonic energy generated by the transducers 20, such energy, as is known, causing a degassification of the liquid. This degassification process may be carried out either prior to the operation of the spark gap discharge device or concurrently therewith, depending upon the circumstances. Alternatively, both energy devices may be operated in alternate manner.
A typical electrical circuit for connection to the spark gap device 24 is shown in FIGURE 3. It should be clearly understood that the circuit may serve to energize several spark gap devices connected in parallel and provided on the container 12, although for the sake of simplicity only one such device is illustrated. The circuit comprises a charging circuit which includes a transformer 30, a bridge rectifier 32, a series inductance 34 and a capacitor 36. The discharge circuit comprises two series connected controlled rectifiers 38 connected to the capacitor 36 and two indutcances 40 and 42. The capacitor 36 periodically is charged with direct current from the rectifier 32 and is discharged through the series connected rectifiers and the spark gap device. In this way there is produced a train of electrical discharges, each discharge causing the propagation of a high intensity shock wave in the liquid 14, and, as is known, such shock wave, in turn, by reflection generates additional shock waves.
The embodiment per FIGURE 1 is well suited for cleaning parts which are heavily corroded. The sonic energy produced by the transducers 20 not only degasses the liquid to enhance the effect of the high intensity shock waves but causes also a fine scrubbing of the surface of article 16. Hence, heavy contamination which requires high impact forces may be removed by the high intensity shock waves, While follow-up cleaning is done with the sonic energy, preferably operating at a power level which produces cavitation in the liquid 14.
The entire process may advantageously be carried out in a single container. The procedure comprises (a) immersing the article 16 in the liquid 14; (b) degassing the liquid 14 by operating the transducers 20; (c) repetitively producing high intensity shock waves =by firing the spark gap device 24 until coarse particles are dislodged from the article surface, and (d) finishing the cleaning of the article surface under the influence of sonic or ultrasonic energy propagated from the transducers 20. In this last step, it is desirable that there exists cavitation in the liquid. Obviously steps (c) and ((1) may be combined to be effective substantially simultaneously.
FIGURE 4 shows an alternative arrangement which is particularly adapted for treating a flowing liquid or particles suspended within the liquid. Numeral 50 refers to a section of a pipe through which the liquid 14 flows. A spark gap device 24 is mounted into the pipe wall and transducers 20A and 20B are mounted at either side. In order to vent liberated gas, a vent valve 52 is provided. Liquid can be treated as it flows past this treatment station.
While there have been described and illustrated certain preferred embodiments of my invention, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the broad principle and scope of my invention.
What is claimed is:
1. The method for treating an article in a liquid comprising the steps of:
(a) immersing the article surface to be treated in the liquid, and while said surface is immersed,
(b) subjecting said liquid to:
(b-l) sonic energy of suflicient intensity to cause degassification, and
(b-2) high intensity shock waves resulting from electrical spark gap discharges produced within said liquid.
2. The method for treating an article as set forth in claim 1 wherein said sonic energy and said shock waves are produced sequentially.
3. The method for treating an article as set forth in claim 1 wherein said sonic energy and said shock Waves are produced substantially concurrently.
4. The method for treating an article as set forth in claim 1 wherein said sonic energy is of an intensity sufficient to cause cavitation in said liquid.
5. The method for treating an article as set forth in claim 1 wherein said sonic energy is in the ultrasonic frequency range.
6. The method for treating an article as set forth in claim 1 wherein said liquid is a cleaning solution.
7. The method for treating an article as set forth in' claim 1 wherein said liquid is stationary.
8. The method for treating an article as set forth in claim 1 wherein said liquid is flowing while being subjected to said sonic energy and to said high enregy shock waves.
9. The method for treating an article as set forth in claim 1 wherein said liquid is electrically conductive.
10. The combination of:
a container adapted to hold a liquid;
sonic energy means coupled to said container for imparting sonic energy to the liquid disposed in said container, and
electrical spark gap discharge means coupled to said container for causing in said liquid high intensity shock waves.
11. The combination per claim.10 wherein said sonic energy means comprises electro-mechanical transducers and an electrical high frequency generator coupled thereto for supplying electrical energy to said transducers.
12. The combination per claim 11 wherein said sonic energy means is adapted to cause cavitation in said liquid.
13. The combination per claim 10 wherein said spark gap discharge means comprises a spark gap device in contact with the liquid and an electrical circuit for causing periodic firing thereof.
14. The combination per claim 13 wherein said sonic energy means comprises a set of electro-mechanical transducers straddling said spark gap device.
15. The combination per claim 10 wherein said container holds a stationary quantity of liquid.
16. The combination per claim 10 wherein said container is a section of a pipe and the liquid is adapted to flow therethrough while said sonic energy means and said discharge means are actuated.
17. The combination per claim 16 wherein said pipe section is fitted with a gas vent valve for discharging gas liberated by the operation of said sonic energy means.
18. The combination per claim 10 wherein said container is metal and said discharge means produces an electrical discharge between an electrode in contact with the liquid and the container.
References Cited UNITED STATES PATENTS 2/1966 Olson 1341 XR 11/1966 Ploeger et al. 55277 XR US. Cl. X.R.