Capacitor Disconnection

This invention relates to disconnecting a capacitor section contained in a sealed casing in response to pressure buildup in the casing.

In one disconnection scheme, terminals extending through the sealed cover are connected to the capacitor section by breakable electrical conductors. A flexible plate lies within the casing between the capacitor section and the terminals. Opposite ends of the plate abut the interior walls of the casing to assure that the plate will bow away from the cover when internal pressure collapses the interior walls against the ends of the plate. When the plate bows, the conductors break.

In a general feature of the invention, an electrical conductor connected between a capacitor section and a terminal of a capacitor is disconnected with the aid of an actuator having at least two hinged-together sections that move relative to one another in response to deformation of the capacitor's casing.

Preferred embodiments of the invention include the following features. The casing includes a can and a cover sealed to the can; a pair of terminals are mounted in the cover projecting into the inside of the casing, with tips of the terminals connected via electrical conductors to the capacitor section; the actuator has a central (rectangular) panel with two flanges hinged to opposite edges of the central panel; and the actuator is positioned between the terminals and the conductor with the flanges positioned to receive forces produced by the deformation of the casing and to translate the forces into motion of the panel away from the cover, aiding disconnection. The central panel has holes (one elongated) to receive the tips of the terminals and the electrical conductors are connected to the tips adjacent the actuator. The panel and the flanges are set at an angle to one another. The flange ends are seated in the corners where the cover is sealed to the can edge.

Disconnection is rapid, and the chance of reconnection is reduced. The actuator plate can be easily molded, die punched, or formed from any material which remains rigid enough to break the weld between the capacitor and the terminals. The plate is easily installed, is self supporting, and cooperates with the bulging cover to provide double-action disconnection. Because the plate is supported at the corners where the cover meets the side walls, the bulginq of the cover has minimal effect on the vertical position of the plate. The plate may be used with any shape or style (round, oval, or rectangular) which deforms under internal pressure, and may be used with any number of terminals.

Other advantages and features will become apparent from the following description of the preferred embodiment, and from the claims.

We first briefly describe the drawings.

FIG. 1 is a sectional side view of a portion of a sealed casing capacitor.

FIG. 2 is a perspective view of the disconnection plate of the capacitor.

FIG. 3 is a sectional side view of the capacitor after distortion of the casing.

FIGS. 4A, 4B are top views of the disconnection plate in two stages of operation.

FIG. 5 is a sectional side view of an alternate embodiment.

Referring to FIG. 1, in a capacitor 10, an oval sheet metal can 12 holds a conventional liquid dielectric impregnated capacitor section 14. A sheet metal cover 16 is hermetically sealed to the top of the can along a rim 18 formed by rolling (and thus interlocking) the peripheral edge of the cover 16 and the upper edge 17 of the can wall. Posts 20, 22, of two terminals 24, 26 are riveted to the cover 16 and are insulated from the cover 16 by washers 28, 30 and insulators 32, 34. The tips 36, 38 of posts 20, 22 lie within the can 12 and are electrically connected to the installed, is self supporting, and cooperates with the capacitor section 14 by welding to copper tabs 40, 42.

Referrinq also to FIG. 2, the tips of terminal posts 36, 38 lie in two clearance holes 44, 46 formed in a vulcanized fiber plate 48. The plate 48 is 0.062"thick, has a hardness of 65 to 75 on the Rockwell T scale after 24 hours post cure at 150.degree. C., and includes a rectangular center panel 50 with flanges 52, 54 at opposite ends. Flanges 52, 54 join panel 50 at two hinge lines 49, 51 with flanges 52, 54 lying at 35 degrees to the plane of panel 50. The outer edges of flanges 52, 54 touch the inner walls of the can 12 and the cover 16 at the corner formed on the inside of rim 18. Plate 48 is supported by tabs 40, 42. Hole 44 is elongated to provide room for movement of tips 36, 38 when bulginq of the cover causes them to be withdrawn from holes 44, 46

Referring to FIGS. 3, 4, when internal pressure builds up, e.g., due to qas released during thermal runaway or other malfunction, the walls of the casing are deformed. Cover 16, the mid parts of can 12, and the longer sides 65, 67 of rim 18 bulge outward (as suggested by arrows 60, 62, 64, 66, 68) and the ends 69, 71 of rim 18 collapse (as suggested by arrows 56, 57, 58, 59). The collapse of rim 18 causes flanges 52, 54 of plate 48 to bend inward relative to panel 50 about lines 49, 51 (which serve as hinges), forcing the panel 50 (and hence tabs 40, 42) down, away from the cover 16. The terminals 24, 26 are forced up, away from panel 50, as cover 16 bulges. Thus, as internal pressure increases, sufficient tension is applied between the terminals and the tabs to break the welds, disconnecting capacitor section 14, and preventing rupture of the casing. Disconnection is aided by the combination of upward motion of the bulging cover and the downward motion of panel 50. The chance that the tabs may become reconnected to the terminals as the capacitor cools is reduced because panel 50 is held down by flanges 52, 54.

Other embodiments are within the following claims. For example, referring to FIG. 5, plate 48 may be placed in the can in a lower position where the ends of the flanges touch the inside of the can but not the lid. The plate is then held down by friction.