DE1168540B - Electric switches, especially for high currents - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: H 02 c

German class: 21 c - 40/52

Number:
File number:
Registration date:
Display day:

G 27793 VIIId / 21 c 25 August 1959 23 April 1964

The invention relates to an electrical switch, in particular for high currents, with two contact forces Contact pieces of different hardness that can be exposed, of which the harder contact piece is one has flat contact surface, to which the softer material consisting of S is a deformable material Switching piece is pressed when switching on, the deformation of the caused by the contact force softer contact piece determines the size of the effective contact area.

In electrical switches, it is known that the heat caused by the resistance of the contact point to be kept as low as possible by applying an appropriate contact force. This prepares for low-voltage switches, in which a relatively weak spring force ensures good contact can, no difficulties. On the other hand, one has a considerable effect with increasing current strength increased contact force, especially with high-voltage switches, insofar as that with very high The large contact force applied to the currents results in a relatively rapid wear of the Switch contact pieces brings with it.

There has already been a contact arrangement for high currents, in particular for short-circuiters in high-current systems proposed in which the contacts are made of materials of different hardness and the contact-making material of a contact piece is so plastically deformable that it Safe and bounce-free contact, disruptive kinetic energy of the moving contacts when switching on absorbs by deformation. But this has the disadvantage that the plastically deformable Contact piece is subject to a high degree of wear.

There is also the risk of damaging heat build-up at the contact point It is necessary that the contact force in the proposed contact arrangement without regard to the deformability of the contact piece and the current to be switched remain constant.

The invention creates the possibility, in each case the greatest possible and essentially only apply contact force limited by the strength of the switch and on this Way to largely avoid signs of wear and tear and undesirable heating of the contact pieces.

The invention is based on the consideration that every metal surface, no matter how finely polished, is microscopic has small projections that allow the simultaneous application of all points of the metal surface to one Electric switches, especially for high currents

Applicant:

Jean Louis Gratzmuller, Neuilly-sur-Seine, Seine (France)

Representative:

Dipl.-Ing. R. Müller-Börner, Berlin 33, Podbielskiallee 68, and Dipl.-Ing. H. Wey, Munich 22, Patent attorneys

Named as inventor:

Jean Louis Gratzmuller, Neuilly-sur-Seine, Seine (France)

Claimed priority:
France of August 27, 1958 (773 286), of August 24, 1959 (803 388)

prevent other metal surface. If, for example, a freely tiltable contact piece is attached to an immovable one Contact created, the moving contact initially comes with no less than three of the small protrusions or irregularities of the fixed contact surface in contact. For the purpose of enlarging the effective ones consisting of only three tiny points of contact Contact surface, it is sufficient to exert a contact force that more or less deforms or flattens the tiny projections in order to achieve this the number of points of contact and thus the effective total area of contact between the adapt both contact pieces to the current to be switched.

In the case of relatively low currents, the appropriate contact force can be determined by a small gram Increasing the force can be determined quickly in an extremely simple manner, since z. B. for the flawless switching of an amperage of 20A and when working with a deformable contact piece made of copper, a contact force of only 20 g is sufficient.

The invention is based on the knowledge that it is necessary to prevent harmful heat generation at the point of contact, the contact force is sufficient

+09 560 / 39O

not as high a value as possible, but always a predetermined one, depending on the contact deformation and to give the respective nominal current strength calculated minimum value. According to the invention a perfect contact is always achieved even with 5 highest currents that at an electrical switch of the type identified at the outset, the softer contact piece from at least there is a contact pin that is perpendicular to the flat contact surface of the harder contact, its free end face progressively plastic when switched on under the action of the contact force is deformed, and that the contact force is such that that achieved by this deformation and consequently

and assuming that, =

/ K

/
K

or

F - K

It can therefore be seen that the contact force is proportionally

The size of the effective contact area is just sufficient, 15 nal the square of the constant current strength

to prevent excessive heating of the same.

The invention is based on the following theory: If two metal bodies with a predetermined have to be.

To show that this theory can easily be implemented in commercial applications, the inventor has the values of the for high amperage

Force are pressed against each other, an actual 20 (z. B. of about 1000 A) forces to be applied becomes apparent Metal contact surface achieved that calculates this force and determines that the required force only proportional and the hardness of the softer metal is about 50 kg, whereby this result in contradiction

is inversely proportional.

If an electric current is to pass through this effective contact surface, the maximum value of the current through the resulting from the relatively small dimension of the area Heating determined, with the other hand the maximum heating by the type of metal and the surrounding medium is determined.

In addition, the amount of heat brought to the contact surface as a result of the current flow must apparently be derived from the mass of the contact body, so that the amount of heat is a function of the Thermal conductivity of metals is. In the case of a constant current, the determination is a temperature equilibrium corresponding to the maximum heating possible.

For the same temperature difference between the contact surface and the surrounding medium, the amount of heat Q ¹ dissipated from this contact surface increases with the square root of the surface of this surface, i.e. with the square root of the force pressing the contact bodies against each other:

Spruch on what can be expected by extrapolating the usual excessive contacts for low currents Values, and this extrapolation would lead to pressures between 10 and 1001.

In the case of simple cylindrical cross-wise and each other consequently on a single Point-touching wires existing contacts, as described in detail below, performed The inventor has achieved the following results in experiments (wire diameter: 1 mm; Amperage: 2OA; Contact heating: negligible):

where F is this force and α is a constant that depends on the type of metals used (hardness, electrical and thermal conductivity, etc.).

On the other hand, the amount of heat developed by the flow of a current of a given strength decreases β * with the square root of the contact force and with the square of the current intensity to what can be expressed by:

= b

ff

Copper / copper 20 g

Copper / hard bronze 20 g

hard bronze / hard bronze 400 g

chrome plated copper /

Chrome-plated copper impossible

oxidized copper / oxidized copper 20 g

From the table above it is easy to see that with sufficient deformability one of the Metals the required contact force is very small (20 g).

Thus for IA it is sufficient to use a 400 times smaller (20 *) contact force (see formula I), ie | ° ₂ = 0.05, and for '1000 A: 0.05 · 10 «g = 50 kg.

It also shows that only one of the two contacts has a high thermal conductivity got to.

Another object of the invention is the formation of these peaks in the form of in the on position rods arranged essentially perpendicular to the contact surface, the diameter of which is selected in this way

mentioned contact force,

is that the above
where / is the current strength and b is one of the type 60 while it can blunt the tips, not in

of the metals used (hardness, electrical and thermal conductivity, etc.) is a constant.

Since both amounts of heat are inevitably the same (Q ₁ = Q ₂ ) , the following formula can be set up:

F = b

is able to cause permanent deformation of the main sections of these rods, the Pressure means for this purpose are designed so that they only have a predetermined contact on the contact Exercise maximum value limited force, which is between two predetermined limit values, of one of which depends on the current to be controlled, while the other depends on the

5 6

mechanical resistance of the contact tips is selected by a regularity of the surfaces 62 and 63. Careful machining as far as possible. Another object of the invention is to reduce the force F in an on and off switch of the type described to create further points and consequently to provide further convergence in which the aforementioned contact surfaces are of sufficient extent Tact bars are made of copper, which greatly increased shaping of parts 60 and 61. From high electrical and thermal conductivity, it is easy to see that the achievement of suitable deformability and appropriate additional contact points through progressive resistance to permanent deformation with an axial increase in the contact force only at random instead of pressure, the other contact body io Since, for example, the additional component is preferably made of a metal such as, for example, taktpunkt 67 only after a certain deformation of hard bronze, it has sufficient electrical conductivity that forms the original contact points, great hardness and small protrusions or unevenness of the contact, adequate corrosion resistance having. surfaces can arise. The inventor has established that the contact force required for the use of copper for only one contact body, as never calculated in advance, because the heat dissipation through the copper rods to switch off a relatively high contact force cools the formed from their blunt tips - need not be taken into account and the contact area is sufficient. In the following detailed description, the invention will form many contact points of the contact force from the description on the basis of which, for example, a maximum value limited only by the strength of the switch, but not restricting, was given from the outset the drawing representing the invention in more detail. 2 is one of the contact points, such as B. explained. It shows 64, shown on an enlarged scale, and shows FIG. 1 which results from the individual contact points 25 of the line of force that the greatest heat is developed in the non-composing effective contact area between the immediate vicinity of the two switching bodies formed by this point, the effective contact area. The not Fig. 2 is a restrictive, on the electrical coming into mutual contact surface centric and heat flow acting processes parts of the switching pieces 60 and 61 are mutually illustrative enlarged view of one of the _3o so close that the remaining narrow air gap contact points according to Fig. 1, lead to the formation of arcs or sparks Fig. 3 which can be used by the inventor to check his, ie to processes, the simplest theory used experimental device, by a corresponding increase in the contact Fig. 4 is a side view of the contact body of a force avoidable. In the case of high-voltage switches according to the invention in the switched-on position, it seemed obvious, in any case, to exert the greatest possible contact force in order to avoid an unpredictable situation. 5 the same device as FIG. 4, but anticipated excessive heat generation in the switched-off position, to safely avoid the contact point. F i g. 6 a schematic view of an inventive such high contact forces led to circumstantial switches with a hydraulic control 40 borrowed large switching devices, tion, the inventor has also shown that to limit F i g. 7 shows an axial longitudinal section through an exten- sion of the heating to a reasonable value and guidance of the switch according to the invention, consequently to ensure the flow of the ge 8 a partial section along the line VIII-VIII desired amperage under the required leg F i g. 7, 45 conditions one, as explained in the introduction to the description Fig. 9, another embodiment of the tiltable, relatively weak and precisely defined contact and nated contact force is sufficient. For the experimental Fig. 10 a section along the line XX in the determination of the forces, the inventor used the test device shown in Fig. 9, Fig. 3, which shows two switching contacts 60 and 61 50, one crosswise on two other cylindrical sections , the under the action of a weak tern 69 and 70 lying cylindrical conductor 68 entKraft F, such as the weight of the body, and he has succeeded in proving that it is 60, lie on top of each other. The irregularities of the relatively weak forces perfectly possible individual contact surfaces 62 and 63 are strongly borrowed, a relatively high amperage is shown to show that the parts 55 increase provided that at least one of the Metals are sufficiently deformable, which is the case with len machining as long as there is no deformation.

drive, only at three points, as described in detail in

64, 65 and 66 shown, lie against one another. examples consists only of the movable contact piece

However, the action of the force F causes a relatively easily deformable metal,

slight deformation of the shown in the drawing, such as copper, whose deformation is below

theoretical contact points provided, whereby a given force can be determined in advance,

Total metal contact surface area arises from very while the moving contact piece consists of a hard

low value, which is equal to the sum of the three separate metals, such as bronze,

from the deformation of the three points 64, 65 or 66 65 As explained in the introduction to the description, is

resulting three surfaces. According to the level of the intended contact force is not inadmissibly high,

Technique tried to make this effective metal and from the simple one described below

to increase contact area by the un- Embodiment of the invention it can be seen that

this force can be obtained, for example, by means of a simple force-limiting spring, the control of the displacements of the movable contact being effected in an appropriate manner by means of a hydraulic system capable of both compressing the spring and closing the displacements at a suitable speed cause.
F i g. 4 and 5 show a particularly simple and

connected to the stationary part 25 by means of anchor bolts 26, which at 27 in holes 28 of the stationary Part 25 is screwed in and with the aid of nuts 29 cooperating with threaded ends 30 5 of the insulating plate 2 are attached. A similar arrangement with anchor bolts 31, threads 32 and 33 and nuts 34 connect the stationary part 25 to a fixed base 35. In this base, too, is Housing 36 of a hydraulic cylinder attached,

effective construction of the contact body of an inven- io whose piston is connected to the switch according to the invention only for the impact effect with the switch in the switched on or off 19 via two balls 38, 39, between the switched position. In this embodiment, in which a substantially axial bumper 40 is set, three fixed, insulated and rod-shaped design is set, the ball 38 being provided in one in the contact body 1, of which only two electrical conductors 6 and are provided with the speaking surface of the piston 37 7 are connected, while 15 is recess, while the ball 39 rests in a recess 41 of the rod 19 in an axial recess 41 of the movable contact body. This consists, which is tiltable at 76 on a movable rod 19, is arranged on a bead 42 of the housing 36, part 75 which carries stops 77 which, slidably arranged, are used to effect a movement as shown in FIG. 5, limit the possible tilting of the axial guidance of the rod 19 in two essential plates 8 around the tilting point 76 so that, when the contact bodies are removed from one another for the purpose of interrupting the circuit, the plate 8, for example in the in FIG. 5, at a sufficient distance
is stopped by the solid contact bodies.

In Fig. 6, a circuit breaking spring is shown at 22, which when closing the Switch by one of an air-oil container 71

mentioned edge 23 cooperates.

This arrangement, together with the without any guidance by the balls 38, 39 and the bumper 40 shear connection caused the transmission of the required forces in a generally axial direction Direction without any risk of the sliding structure jamming, even with a slight misalignment. The ones used to cause a circuit breakdown

A strong spring, which is provided with a collapse of the cylinder 36 fed with hydraulic fluid, is pressed into place in 43 the supply and the distortion. This spring is between a flange 44 of the

Emptying of the cylinder 36 from a distributor 72, rod 19 and the stationary part 25 are used. she

be controlled. At 73 is the oil container and at 74 the rod 19 presses steadily in the direction of the KoI-

a pump is shown, which the container 71 under ben 37, which the arrangement described above

Can hold pressure. justifies, according to which the rod and the piston

In the case of the constructive 35 shown in FIGS. 7 to 10, the skid is positively connected only for an impact effect. Embodiment of the invention consists of the tiltable fixed base 35 is provided with a series of Contact from a plate 8, which is provided with a hemispherical bores of different diameters. At the gene part 9 is rigidly connected, the lower end of the base 35 with a shaft (in Fig. 7) is one of these 10 is provided, the free end of which is threaded on-bores internally threaded, and one and a threaded unit 45 consisting of a washer 12 nipping 40 is incorporated therein Nut 11 carries existing retaining head. screws. The threaded assembly 45 This whole group swims slightly in an axial position on the one hand provides a connection between the pressure bore 13, the outer edge of which forms a spherical source of fluid and the cylinder 36 and others is, with the bore in the bottom 14 on one side via suitable channels (not shown) Shell 15 is provided, into which one end 45 see the cylinder and an emptying line. an insulating body 16 is screwed in, whose on- If the circuit is to be interrupted, whose end is arranged in a sleeve 17. to release the spring 43, the emptying unit is

In the example shown, the middle of the semi-detached, so that the spring is the movable contact spherical Part 9 on the active surface of the body can give a very high acceleration, clock plate 8 in the middle. The insulating body 16 is 50. The emptying is for example by a in the shell 15 and in the sleeve 17 with HiKe caused by rapid emptying device. Pin 18 fixedly attached. The sleeve 17 is finally at 46 a kind of check valve Slidably arranged on a rod 19, the illustrated being that of a small one in one of the Bohaxiale Displacement of the rod 19 to the outside wrestle the base 35 sliding bushing the sleeve 17 by means of one with an inner 55 and at its opposite the unit 45 ring-shaped switch 21 of the sleeve 17 together- end in one with a third in the cylinder 36 acting piano wire 20 is limited. Partition wall 47 provided between leading bore 48 see the insulating body 16 and an axial one in which ends. The small socket 46 itself contains one associated end of the rod 19 provided separation wall 49, which with a calibrated opening 50 expansion is a force-limiting compression spring 22 60 is provided, while a cylindrical section used. their wall with a smaller diameter than that

The structure described above forms a portion that slides in the bore of the base 35

movable contact construction with variable length, also with between the partition 49 and the

the extended by means of the force-limiting spring 22 in the vicinity of the unit 45 end of the

is held. This version is provided on the edge 65 bushing 46 arranged radial channels 51

the rod 19 can in turn be seen in a bore 24. A weak spring 52 is eager to the

a stationary part 25 arranged displaceably. Bush 46 pressed steadily against the wall 47 to hold

The insulating plate 2 carrying the contact tips is th, in which position the cylinder 36 with the

Unit 45 is only connected via the calibrated opening 50, while when the socket 46 opposes the action of the spring 52 is taken from this position, the connection not only via the Opening 50, but also via the channels 51.

In another in FIG. 9, the movable contact body does not contain any physical Knee joint connection, and the contact plate 8 'is steady with the aid of three springs 53 pressed outward, which strive to the head 11 'against the partition 14' of the movable contact body to press, but when closing the switch to enable the required tilting of the Plate 8 'can give way individually.

Thus, while the springs 53 are deformed, there becomes a freedom (a margin) in the direction of the transverse axis achieved so that the desired tilting effect is achieved without any friction.

The device according to the invention works as follows: When through the unit 45 a pressure fluid is admitted, this penetrates into the cylinder 36, the supply through the calibrated opening 50 is limited. The piston 37 is displaced by this liquid and pushes Via the balls 38 and 39 and the bumper 40, the rod 19 is pushed forward by compressing the spring 43. The contact plate 8 initially comes into contact with a single tip 1, for example. With the further displacement of the movable contact body as a result of its ability to tilt, the tilts Plate 8 then around the tip 1 without leaving it and comes with a second one, for example Tip 1 in contact. Finally, it is determined by the first two peaks 1 in this way Contact line is tilted until it is also brought into contact with the third and last tip 1. Then the displacement of the movable contact body is stopped while the rod 19 is moves further under the action of the pressure fluid and penetrates into the sleeve 17 by the force-limiting spring 22 compresses. At the end of the rod 19 in turn by the against the stationary part 25 running up edge 23 stopped. Thus is between the ends of the three Tips 1 and the slidable plate 8 under a predetermined, evenly divided between the three tips and one of the force of the spring 22 calibrated as defined in the introduction to the description appropriate pressure ensures excellent electrical contact. The inventive The device therefore not only allows excellent electrical contact to be achieved under a predetermined pressure, but also keeping this pressure constant, even if the Pressure source is subject to certain fluctuations. In addition, the compression stroke allows the spring 22 the automatic recording of the wear of the contact ends. This contact is maintained as long as like the hydraulic pressure prevailing in the cylinder 36, the force of the strong spring 43 overcomes. If the cylinder 36 is now, for example, by means of the rapid emptying device mentioned above is emptied, the piston 37 gives way, and the spring 43 is released for rapid displacement of the rod 19 in the direction their removal from the stationary contact body. The spring 22 expands, the rod 19 begins to exit from the sleeve 17 with the insulating body 16 and shell 14. Finally, the shell 14 comes with it the head 11 in contact and suddenly separates the tip 1 from the contact plate 8, which tilted slightly until they rest against suitable stops, such as stops 77 (Fig. 5) comes (see above). It should be noted that the liquid which is discharged from the cylinder 36 tries to flow out, the small bushing 46 lifts off the wall 47 by the weak spring 52 compresses so that the liquid not only through the opening 50, but also through the channels 51, d. H. in an amount sufficient to avoid any damping braking effect of the piston 37 can flow out.

The invention is of course not limited to the exemplary embodiments described and illustrated limited. You can use numerous, the skilled person according to the intended in each case Make changes that are obvious to the application without affecting the area of the Invention leaves.

In particular, the three fixed contact pieces 1 could be arranged at the tips of any triangle be, the structure is not necessarily coaxial, and the relative displacement between the contact bodies can be caused by movements other than longitudinal displacement. Finally, it is also possible to have just one or two Provide tips 1, but the embodiment described and shown has the advantage that it is extremely simple and the tilting device allows the movable contact body around the axis of the system any angular freedom to let, thereby radically eliminating any problem of leadership, friction, etc. The one in the The hydraulic control shown in the drawing is for illustrative purposes only. It is clear that they are through any hydraulic. System that could be used to deliver the required contact pressure is able, the hydraulic shown in the drawing Control, however, is particularly good a control for the longitudinal displacement of a movable contact body is adapted without any jamming, despite the fact that there is no exact alignment between the different parts must be provided.

Claims (7)

Patent claims: 1. Electrical switch, especially for high currents, with two exposable to a contact force Contact pieces of different hardness, of which the harder contact piece has a flat contact surface has to which the softer contact piece made of a deformable material is pressed when switching on, the deformation caused by the contact force of the softer contact piece determines the size of the effective contact surface, characterized in that that the softer contact piece consists of at least one perpendicular to the flat contact surface of the harder contact piece (8) There is a contact pin (1) whose free end surface is under the action when switched on the contact force is progressively plastically deformed, and that the contact force is so dimensioned is that the one achieved by this deformation 409 560/390 The size of the effective contact area is just sufficient to prevent excessive heating of the same to prevent. 2. Switch according to claim 1, characterized in that starting from one for a given Strength of the current to be switched to achieve the effective contact area depending on the Deformability of the contact pin (1) determined contact force this becomes the required Contact force for a nominal current strength that deviates from the given strength of the current to be switched behaves like the square numbers of these two currents. 3. Switch according to claim 1 or 2, characterized in that at least one of the switching pieces has a high thermal conductivity. 4. Switch according to claims 1, 2 and 3, characterized in that this is at most four Has contact pieces, one of them being a has a harder contact surface than the other contact pieces and with each one contact point forms. 5. Switch according to claim 4, characterized in that the harder contact surface is flat is and each of the other contact pieces consists of a rod (1) with one of its ends with comes into contact with the harder flat contact surface. 6. Switch according to claim 5, characterized in that the rods (1) insulated from one another and are arranged immovably, while the harder contact piece (8) can be tilted as well as in relation is axially movable on the ends of the rods (1) facing its flat surface. 7. Switch according to claims 5 and 6, characterized in that the rods (1) made of copper and the movable contact piece (8) are made of bronze. 1 sheet of drawings 409 560/390 4.64 © Bundesdruckerei Berlin