Electricity: electrothermally or thermally actuated switches – Electrothermally actuated switches – Fusible element actuated
Reexamination Certificate
2001-03-12
2003-04-29
Vortman, Anatoly (Department: 2835)
Electricity: electrothermally or thermally actuated switches
Electrothermally actuated switches
Fusible element actuated
C337S182000, C337S409000, C337S401000, C307S010100, C307S119000, C180S279000, C180S283000, C200S061080
Reexamination Certificate
active
06556119
ABSTRACT:
The invention relates to a device for isolating an electric circuit, especially for high current intensities.
Switches, or in the most general of meanings, devices are needed for the most diverse applications, which will quickly and safely, in irreversible manner, isolate an electrical circuit, especially in case of injury or other emergencies, in order to prevent damage to technical equipment or endangerment of human beings. Such devices are especially required when high current intensities are present in technical equipment,.for example in energy distribution networks or in automotive engineering. Such devices for isolating an electric circuit must meet high safety requirements; in particular, the electric circuit must be isolated sufficiently quickly and securely, in irreversible fashion, without possibility of causing injury to technical equipment or human beings by the switching process itself In addition, such devices must be highly maintenance free, and be able to function reliably, even after long periods of inactivity, for example, even after up to 20 years.
In automotive engineering, it is necessary or desirable, in case of accident, to definitely and irreversibly separate, in the shortest possible time, the battery from the wiring of the vehicle. In this fashion it is possible to avoid sources of ignition formed by sparks and plasma, which are created when cable isolations are scraped off during an accident due to sheet metal penetration from the car or loose cable ends hitting against each other or against sheet metal parts, and which may ignite escaping gasoline or cause an explosion of ignitable gasoline-air mixtures developing after an accident.
An electric safety switch is known from DE 297 00 594 U1 to realize a device for isolation of an electric circuit in which high intensity current flows, in regard to which a conductor, located in a housing, is isolated by means of a pyrotechnically accelerated, electrically isolating separation body.
In its original position, the separation body is located at a certain distance from the conductor element to be severed and is accelerated in the direction toward the conductor element, following the triggering of a propellant charge provided in a combustion chamber, for example due to a signal which also serves for triggering an air bag.
As a result of an indentation in the otherwise relatively large cross-section of the conductor element, the conductor element or this separation area breaks very quickly. Underneath the conductor element to be severed, space is provided into which are bent the conductor ends to be severed, and which also accepts the separation body. Thus, with this device, the conductor ends are not torn off or ejected in uncontrolled fashion. However, if with this type of a device, a high intensity current flows within the conductor element, an electric arc is formed as soon as a cut-off occurs in the conductor element, so that initially the flow of current continues at practically full intensity.
The electric arc is then, however, extinguished extremely quickly via the electrically isolating separation element. While this results in achieving a quick, irreversible shut-off of the current flowing from the battery to the consumers or of a short-circuit current, very high tension peaks are created by self-induction, due to the always existing inductivities in the load of the circuit, as a result of which there is the risk of causing irreversible damage to connected instruments and isolations.
In addition, a pyro-technical separation device is known from DE 44 38 157 C1, which likewise operates according to the same principle. Here also, an isolating separation element is accelerated by means of a propellant charge and cuts-off an element to be severed. Toward that end, the separation element is preferably provided with a frontally formed concave recess, so that a circumferential cutting edge is formed in the marginal region. This device is to ensure safe and very quick separation of also heavier conductor elements with a relatively low force propellant charge. If such a separation device is employed as electrical switch, there again results the problem of high induction voltages due to the very rapid interruption of the flow of current.
Moreover, the known devices require, for adequate acceleration of the separation element, propellant charges which constitute a certain risk potential, despite a correspondingly designed massive housing. The known device must pass costly approval tests, which involves considerable expenditure in terms of time and finances.
Differently constructed devices for the isolation of power currents, as they are known from power engineering, are not being considered here, since they are constructed in relay fashion. and thus do not begin to achieve the specified reliability (to also function reliably after 20 years without single switching and without maintenance) given the mechanical and thermal/climatic environmental conditions which occur in a motor vehicle. Moreover, such devices are still too expensive by far and/or too heavy or too large for application in automotive engineering, even with corresponding simple design.
Starting from the initially mentioned state of the art, the invention is based on the object of creating a device for isolating an electric circuit, especially for high current intensities, which, on the one side, irreversibly isolates the circuit to be severed, safely and with sufficient speed, and which, on the other side, avoids damage to structural components located within the electric circuit by induced voltage peaks.
The invention solves said object with the characteristics of Patent Claim
1
.
The invention initially proceeds from the knowledge that an acceptable compromise must found with respect to the speed of the process with which an interruption takes place of the current flowing in the electric circuit, which, on the one hand, assures quick enough interruption of the current in order to avoid danger to equipment and persons from the (perhaps unduly high) current, and, on the other hand, does not interrupt the current so quickly that there may be danger to equipment and persons from induced voltage peaks; in other words, quantity-wise, the changes in electricity di(t)/dt must not become too significant.
According to the invention, in contrast to the known devices, no separation element is employed which has already been accelerated to high speeds of 150 to 200 m/s for example prior to impact on the conductor element or the isolating area of the conductor element, which isolates the conductor element extremely rapidly and extinguishes the potentially developing electric arc. Instead, the isolating area is directly acted upon by a triggering pressure or via a driving surface impinging already in the original position on the isolating area. Needless to say, the driving surface in its original position can also be located at such short distance from the isolating area that upon impact, the latter has only a relatively low speed of several meters or several tenth of meters per second.
As a result, following the generation of the triggering pressure, the separating area is isolated with sufficient speed, but not so quickly that unacceptably high induction voltages develop. Since no acceleration path is needed for an isolation element that is to be accelerated, it is possible to realize extremely small construction sizes. Such devices can be attached, for example, directly to the battery clamp of a car battery.
According to the invention, in an alternative [solution] the entire conductor cross-section can be isolated in the isolating area by actuation of pressure on the isolating area.
In another alternative, it is possible to isolate only a portion of the conductor cross-section in the isolating area, with ability for the remaining portion to still maintain, for a predetermined period of time, consumer emergency functions, especially in automotive vehicles. To that end, the remaining conductor cross-section is dimensioned in such fashion that the
Fay Sharpe Fagan Minnich & McKee LLP
TRW Automotive Electronics & Components GmbH & Co. KG
Vortman Anatoly
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