US3417588A

US3417588A - Device for obtaining mechanical material deformations by means of compression waves

Info

Publication number: US3417588A
Authority: US
Inventors: Schmidt Siegfried
Original assignee: US Philips Corp
Current assignee: US Philips Corp; North American Philips Co Inc
Priority date: 1965-02-27
Filing date: 1966-02-23
Publication date: 1968-12-24
Anticipated expiration: 1985-12-24
Also published as: FR1470188A; BE677150A; CH453271A; GB1107955A; NL6602287A; SE313031B

Description

3,41 7,588 ATIOINS S. SCHMIDT Dec. 24, 1968 DEVICE FOR OBTAINING MECHANICAL MATERIAL DEFORM BY MEANS OF COMPRESSION WAVES 4 Sheets-Sheet 1 Filed Feb. 23. 1966 INVENTOR.

SIEGFRIED SCHMIDT BY a K AGEN Dec. 24, 1968 s. SCHMIDT 3,417,588

DEVICE FOR OBTAINING MECHANICAL MATERIAL DEFORMATIONS BY MEANS OF COMPRESSION WAVES 4 Sheets-Sheet 2 Filed Feb. 23, 1966 INVENTOR.

SIEGFRIED SCHMIDT BY AGENT Dec. 24, 1968 s SCHMIDT 3,417,588

DEVICE FOR OBTAINING MECHANICAL MATERIAL DEFORMATIONS BY MEANS OF COMPRESSION WAVES Filed Feb. 23, 1966 4 Sheets-Sheet 3 F ig.4

INVENTOR.

SIEGFRIED SCHMIDT BY jzwa AGENT Dec. 24, 1968 s. SCHMIDT 3,417,588

DEVICE FOR OBTAINING MECHANICAL MATERIAL DEFORMATIONS I BY MEANS OF COMPRESSION WAVES Filed Feb. 23, 1966 4 Sheets-Sheet 4 1% 2 Z I Q' P W ThT SIEGFRIED SCHMIDT BY 2 F I AGENT United States Patent 3,417,588 DEVICE FOR OBTAINING MECHANICAL MATERIAL DEFORMATIONS BY MEANS OF COMPRESSION WAVES Siegfried Schmidt, Hamburg, Germany, assignor to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed Feb. 23, 1966, Ser. No. 529,518 Claims priority, application Germany, Feb. 27, 1965, P 36,179 6 Claims. (Cl. 7256) ABSTRACT OF THE DISCLOSURE A device for producing mechanical deformations in a material, comprising an electric discharge chamber and spaced electrodes projecting into the chamber. The material to be deformed is held to form one boundary surface of the chamber and a liquid layer extending between the electrodes forms the opposing boundary surface. The construction minimizes erosion of the electric discharge chamber. In a second embodiment the liquid layer is formed on the surface of a rotating disc which thereby continuously replenishes the liquid layer forming the boundary surface.

The invention relates to a device for producing mechanical material deformations by means of compression waves which are obtained by means of electrical spark discharges in a discharge space of which at least one of the boundary walls is constituted by the material to be processed.

Producing compression waves by spark discharges is known. In order to use the compression wave produced by a spark discharge as effectively as possible the discharge; space should be limited. The material of the Wall used for the said space which, with the exception of the electrode, usually consists of an insulator, is stressed rather heavily in particular when the spark substantially travels along said wall (sliding spark). Even if insulators, for example, aluminum oxide, which are very suitable for the said purpose, are used the wear is large so that as a result the use of such sliding spark gaps is restricted. If the insulator consists of organic material (for example polyethyleneterephthalate) which during the stress by the spark discharge develops gas which is favourable for producing the pressure, the wear of course, is even larger. To obtain nevertheless a useful device, the wear should be distributed over a larger area. This is obtained by using comparatively large rotating discs or hollow cylinders of the insulating material in question which are arranged so that each time only a very small part of the insulator surface constitutes a wall of the spark discharge space, a new part of the insulator surface being each time chosen as a result of the rotation. However, this measure can not prevent either that the insulator has to be replaced rather often or has to be processed again.

It is the object of the invention to decrease the Wear of the insulator considerably. According to the invention this is attained in that in a device of the type mentioned above one of the boundary surfaces of the discharge space is constituted by the surface of a liquid.

This provides the advantage that during operation liquid can easily be replenished. Instead of undesired wear only "ice a low liquid consumption occurs. Moreover, by using readily vaporizing liquids the known effect of promoting the production of pressure can be obtained in a simple manner. Pure water can particularly readily be used as the liquid; it is cheap, safe and leaves no residue. As a result of a possible low conductivity the spark gap may exhibit even when not operative, a relatively low resistance. This, however, is not disturbing at all if the sparking voltage is applied to the spark gap for a short time only. This is the case if the discharge circuit comprises a switch (for example, a spark gap switch) or if voltage is applied to the spark gap by means of a suitable circuit each time only a short period of time before a discharge (for example, by controlled charging of the capacitor to be discharged). If a voltage is continuously applied to the spark gap, which is the case if the spark gap itself also serves as a switch, and if for simplicity a controlled capacitor charge is not utilized, the current flowing as a result of the resistance of the water must be supplied by the voltage source. Said current can be kept small by suitable structural measures and by using water of a maximum purity. Said current may be used to advantage as a control current in a circuit for controlling the liquid level.

Alternatively insulating liquids, for example, transformer oil, clophene and the like may be used. In this case it is favourable to cause the liquid to circulate in a circulating system, which circulation in such circumstances, is also suitable if water is used. The circulation system may comprise filters or other purifying devices. Harmful impurities which are formed by the spark discharges and in the absence of such a circulation system might give rise to short-circuiting of the electrodes can thus be removed. If the discharge is effected in a protective gas, for example, argon or nitrogen, readily vaporising liquids may also be used. By supplementary supply of oxygen the energy released due to combustion of a certain amount of liquid may be used to advantage for producing the pressure.

The use of liquids as a boundary of the discharge space has an additional advantage, namely that the excess heat can be dissipated in a simple and effective manner. By vaporisation of the liquid acooling effect is obtained and, in case of circulation of the liquid, an additional cooling is obtained by convection. In the case of large powers it is efficacious to provide in known manner a cooler in the circulation of the liquid.

In order that thejinvention may readily be carried into effect, a few embodiments of the device according to the invention will now be described in greater detail, by way of example, with reference to the diagrammatic drawings, in which,

FIGURE 1 is a cross-sectional view of a device employing electrodes producing sliding sparks along a liquid surface.

FIGURE 2 is a plan view of the part of this device comprising the electrodes.

FIGURE 3 shows a device having an insulator covered with a layer of liquid.

FIGURE 4 is a cross-sectional view taken on the line A-B of FIGURE 3.

FIGURES 5 and 6 show a circuit arrangement for producing the spark discharges.

FIGURE 1 is a cross-sectional view of a device for punching holes in a paper tape or sheet 8. FIGURE 2 shows a plan view of this device having three spark gaps. The main electrodes 1 and the ignition electrodes 2 are arranged in the bottom of a trough-shaped insulating liquid container 3 filled with liquid 5. The ignition electrodes 2 just emerge above the surface 4 of liquid 5. The surface of the liquid 5 is covered with a thin insulating plate 6 which, however, does not cover the space between the electrodes 1 in which the discharge occurs. The perforated strips 7 only serve for supporting the plate 6. The plate ensures that the material 8 to be punched does not contact the liquid. By suitable shape of the liquid container, the surface 4 of the liquid might be limited beforehand to the space between the electrodes but this has the drawback that, as a result of liquid consumption, the liquid level is easily influenced. Compared with the free working surface 4, the total upper surface of the-liquid is therefore chosen to be large. In the diagrammatic arrangement shown in FIGURE 1, the prescribed level should not be higher than the lower side of the plate 6. The main electrodes 1 are surrounded by insulated tubes 9 which do not cover the sides of the ends of the electrodes facing the surface of the liquid. As a result of this, an electric current, if any, through the liquid is restricted to a value which is as small as possible. In circumstances it may be of advantage to provide the greater part of the ignition electrodes 2 also with an insulating jacket.

The punch matrix is indicated by 11. The springs 11 force the matrix 11 against the material 8 to be punched and said material is forced against the plate 6 so that only a very small gas-filled space 12 remains in which the spark discharge can form.

Devices for supplying liquid through pipes and for keeping the liquid level constant are known and are not shown in the drawing. The liquid level can very easily be controlled by means of an overflow pipe, particularly if the liquid circulates in a specially provided circulation system. In contrast with the known devices the embodiment described has the advantage that no structural difficulties occur when several spark gaps operating independently of one another are arranged in close proximity to one another.

FIGURES 3 and 4 diagrammatically show a device for producing sliding sparks along an insulator covered with a layer of liquid. In the embodiment shown the sliding sparks are used for punching. FIGURE 4 is a cross-sectional view of the device shown in FIGURE 3 taken on the line A-B.

In this embodiment the insulator which bounds the spark discharge space consists of a disc 23 driven by a rotating shaft 24. In this case, the rotating disc 23 dips in the liquid 26 in the container 25 and the surface of this disc is coated with a layer of liquid. The spark discharge which produces the compression waves occurs between the two main electrodes 21 which are arranged on either side of the insulator disc so that the spark slides along the insulator which is coated with a layer of liquid. The layer of liquid prevents the insulator disc 23 from being attacked by the spark discharge. If the sliding spark gap is also to be used for switching the discharge, a third electrode, an ignition electrode 22, is provided. A plate 27 serves as a support for the material 28 to be punched which is forced against the plate 27 by the springs 29 of the punch matrix 30. The plate 27 is provided with a recess in which the disc 23 is arranged so that between the ends of the

electrodes

21 and 22 opposite to the hole in the matrix 30 a limited discharge space is formed. The insulator which limits the discharge space may also be wetted in a different manner. For example, a stream of liquid may be conducted through the insulator which in that case may be stationary, or a porous or perforated insulator may be used through which the liquid required on the surface is forced.

FIGURES 5 and 6 show two electric circuit diagrams suitable for operating spark gaps of the type as described above.

FIGURE 5 shows a circuit arrangement employing an additional circuit element in the discharge circuit. This circuit element is, for example, a spark gap switch T, sometimes termed trigatron. A capacitor C is charged, for example, through a resistor R by a voltage source U and the working spark gap F constituted by the electrodes 1' and 21 respectively of the device shown in FIGURES 1 and 2 and 3 and 4 respectively is operated with the energy accumulated in the capacitor. A discharge of the capacitor C through the spark gap F is first blocked by the' spark gap switch T which is connected in series with the working spark gap F. Now if an ignition signal is applied to the ignition generator ZG, the latter produces ahi gh voltage pulse which is conducted to the ignition electrode 2 of the spark gap switch T.

As a result of this the spark gap switch T is ignited. The capacitor voltage which was first applied to the spark gap switch T by way of the resistor R is now suddenly applied to the working spark gap F 50 that the latter breaks down. The resistor R connected parallel to the spark gap F may be present as such as a resistance of the liquid between the electrodes or is included in the circuit as an additional circuit element.

FIGURE 6 shows a circuit arrangement in which the working spark gap F is also operative as a spark gap switch. Therefore the circuit arrangement comprises the ignition electrode 2 in addition to the two main electrodes 1. The discharge is started, as was the case in the circuit arrangement shown in FIGURE 5, by an ignition signal at the ignition generator ZG which produces a high voltage pulse which is applied to the ignition electrode 2 of the working spark gap as a result of which the discharge occurs. Since in the method described which employs a liquid between the electrodes, the parallel resistor R in circumstances may be small so that it causes a disturbing discharge of the capacitorC before the desired spark discharge, the capacitor C is charged only a short period of time before the desired main discharge. For that purpose, the charging of the capacitor C is controlled, for example, with a circuit arrangement as shown in FIGURE 6 comprising a choke coil L, a transformer Tr, a pulse trans former U and a thyristor Th. A short time before the occurrence of the ignition signal the control electrode G of the thyristor Th receives a charging signal through the pulse transformer U as a result of which the thyristor ignites. As a result of this, the capacitor C is charged inductively in known manner from the voltage source U through the choke coil L. The transformer serves for adapting the operating voltage U of the thyristor to the desired voltage of the capacitor. As soon as the voltage across the capacitor has reached its maximum value, the spark discharge is ignited. Thus voltage is set up at the resistor R only for a short period of time so that the losses caused by the resistor remain low.

What is claimed is:

1. A device for producing mechanical deformations of a material, comprising means defining an electric discharge chambcr, electrode means spaced apart and terminating within said chamber, means positioning said material to form a first boundary surface of said chamber thereby to subject said material to the action of electric discharges in said chamber, and means for forming a second bound-a ry surface of said discharge chamber extending between said spaced electrodes comprising meahs for supporting a liquid layer in the space between said electrodes 2. A device as claimed in claim 1 wherein said first and second boundary surfaces are in spaced confronting relationship.

3. A device as claimed in claim 1 wherein said electrodes extend through said liquid layer and further comprising insulating coatings on said electrodes over the portions thereof extending through the said liquid layer.

4. A device as claimed in claim 1 comprising a movable References Cited member having a portion thereof arranged in the space UNITED STATES PATENTS between said electrode means, and means for forming a liquid layer on the surface of said portion. 2,737,882 3/1956 Early et a1 5. A device as claimed in claim 4, wherein said mov- 5 3,027,791 4/1962 Early et 29 421 able member is a rotatable disc member having a first 3,232,085 2/1966 9 72 56 peripheral portion thereof arranged in the space between 3,266,355 8/1966 Wlnlamson 83 177 said electrode means, and a second peripheral portion thereof arranged in liquid supply means. RICHARD HERBST P r 1mm y Exammer' 6. A device as claimed in claim 1 wherein said liquid 10 US. Cl. X.R. layer is an electrically circulating liquid layer. 83177