Electricity: electrical systems and devices – Electrostatic capacitors – Fixed capacitor
Reexamination Certificate
2002-03-29
2004-09-28
Ngo, Hung V. (Department: 2831)
Electricity: electrical systems and devices
Electrostatic capacitors
Fixed capacitor
C174S050510
Reexamination Certificate
active
06798638
ABSTRACT:
BACKGROUND OF THE INVENTION
Capacitor windings are preferably accommodated in pot-shaped housings. These housings are limited at one side by a floor and are terminated at the other side by a cover. Two electrical terminals are usually located on the cover, and these terminals serve the purpose of contacting the capacitor winding that is impregnated with an electrolyte solution and located in the inside of the pot-shaped housing. Since the housing and, thus, the cover as well are charged with a potential, at least one of the electrical terminals must be electrically insulated from the rest of the cover to prevent a short.
Traditional covers usually comprise two openings through which the electrical terminals provided, for example, with a thread are passed and are then secured. Insulating disks are also employed for one electrical terminal in order to achieve an electrical insulation from the rest of the cover. In order to seal these electrical terminals so that no electrolyte solution can emerge toward the outside, these terminals are frequently welded, soldered or riveted. This is often extremely time-consuming and, thus, cost-incurring.
In order to eliminate the waste heat that occurs during the operation of the capacitor, the capacitors are often externally cooled, which likewise represents a considerable outlay.
In order to close the capacitor housing, the cover must often be firmly pressed into the opening of the housing, so that the cover must be especially stiff so that it does not warp while it is being pressed in. Frequently, covers which have thicker wall thicknesses are therefore utilized. This has the disadvantage that a high use of materials is also necessary for the cover.
Capacitor covers are usually milled from solid material given polygonal covers, so that the two openings are provided for conducting the electrical terminals through and an impregnation opening is also provided for the subsequent impregnation or introduction of the electrolyte to the capacitor windings located in the housing. The milling of the cover is thereby extremely time-consuming and, thus, a cost-intensive procedure. However, it is possible to manufacture the covers by extrusion. Since these covers and, thus, the extruded pot-shaped housing, however, are round, they have an increased space requirement in the bank of capacitors, due to unavoidable interspaces.
SUMMARY OF THE INVENTION
It is, thus, an object of the present invention to provide a pot-shaped capacitor housing with a cover that avoids the above-mentioned disadvantages.
The invention discloses a pot-shaped housing for a capacitor, whereby at least the cover was extruded from one piece of aluminum and the cover and the housing, respectively, comprise different spatial expanses along two principal axes. In addition, a first electrical terminal is fashioned on the cover and an opening is provided through which a second electrical terminal is passed. The peripheral edge of the cover is bent up in the direction of the pot opening and thereby comprises an all-around region that terminates in an interlocking fashion with the inside wall of the pot.
The advantage of the inventive cover is that all important features of the cover, which include at least a portion of the first electrical terminal, the opening for the second electrical terminal as well as the bent-over or bent-up edges of the cover, can be formed by extruding in a single method step. The bent-up, all-around edge of the cover thereby allows an especially advantageous interlocking contact with the pot-shaped housing, so that the cover can be terminated especially tightly, for example by either a tungsten inert gas welding or by a laser welding. Traditional capacitor housings often require particularly complicated seals and beads for the cover in order to be tightly terminated.
Another advantage of the inventive housing is that the first electrical terminal is already fashioned on the cover as a result of the extruding, so that, differing from traditional covers, it need not be separately conducted through an opening and then secured. In addition, the inventive housing and its cover comprise different expanses along two principal axes, so that the housing and its cover are non-round, for example are square or rectangular in shape, wherein the corners are often rounded-off. This has the advantage that the inventive housings can be arranged in a bank of capacitors in an especially easy and space-saving way.
In an advantageous development, it is possible to fashion fixing elements in the cover at the opening for the second electrical terminal that fix an insulation of the second electrical terminal. These fixing elements that, for example, can be fashioned in the form of a web or rib, especially advantageously allow the electrical insulation of the second terminal to be fixed, so that the second terminal can be tightly closed and protected against twisting.
It is also possible that at least one reinforcing and cooling element is fashioned on the cover of the capacitor. This reinforcing and cooling element can, for example, be fashioned in the form of at least one straight-line rib that is arranged on an outside of the cover. In an especially advantageous way, this rib is formed together with the rest of the cover by means of extruding. The reinforcing and cooling elements have the job of reinforcing the cover, so that it can be pressed especially well into the pot-shaped housing without warping. In addition, the forming of an elevation on the cover enlarges the surface of the cover, so that waste heat occurring during the operation of the capacitor can be better eliminated.
Especially strong forces act on the center of the cover while the cover is being pressed into the housing. An especially good stabilization of the cover thus results when the reinforcing elements are especially advantageously arranged centrally on the cover. In addition, it is especially advantageous when the straight-line ribs extend over a majority of at least one principal axis of the cover, since an especially good stabilization of the cover can now be achieved with this arrangement.
In an advantageous verison of the inventive housing, spacers can be fashioned on the cover. Thus, a printed circuit board that contacts the electrical terminals of the capacitors in a bank of capacitors lies, for example, against the spacers. For electrical insulation, electrically insulating material, for example plastic disks, can be located between the printed circuit board and the spacers. The advantage of such a cover is that the printed circuit boards can be especially advantageously supported so that one can prevent the printed circuit boards from touching parts of the cover that are not electrically insulated during operation so that no short circuit is formed. The spacers can, for example, be formed in the form of flattened elevations or pegs on the cover.
It is also possible that at least one impregnation hole is provided in the cover. This impregnation hole serves the purpose of allowing an impregnation of the capacitor windings already located in the capacitor housings with the electrolyte solution.
In another advantageous development of the housing, a rated break point can be formed in the cover. This break point is formed in a region that has a reduced wall thickness compared to the rest of the housing part or pot and a notch is additional formed in this region. Advantageously, the region having the reduced wall thicknesses formed by extruding and the additional notching is subsequently produced. The rated break point advantageously allows a controlled bursting of the capacitor given excessively high pressures in the capacitor housing, so that the electrolyte solution flows out in a controlled fashion and does not splatter.
The rated break point can be fashioned both in the cover as well as in the housing pot, whereby it is particularly advantageously fashioned in the floor of the housing pot.
A number of aluminum alloys, for example aluminum 99.5 or aluminum 99.9 as well as wrought aluminum alloys are especia
Erhardt Werner
Goesmann Hubertus
Nowak Stefan
Schoch Klaus
EPCOS AG
Hardin LLP Schiff
Ngo Hung V.
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