TAMPER RESISTANT PLUG

Abstract

A tamper resistant plug that has particular application for sealing a fill port in a hermetically sealed and gas-insulated tank associated with medium-voltage switchgear. The plug includes a body portion and a top annular rim defining a central recess and having an internal surface facing the recess, where the internal surface has a polygon shape with only rounded edges. In one embodiment, the polygon shape is a trilobe.

Claims

1. A plug for sealing a fill port in a tank, the plug comprising: a body portion; and a top annular rim defining a central recess, the rim having an internal surface facing the recess, the internal surface having a polygon shape with only rounded edges.

2. The plug according to claim 1 wherein the polygon shape is a trilobe defined by three lobe indentations.

3. The plug according to claim 1 wherein the recess has a diameter of about 0.850″.

4. The plug according to claim 1 wherein the tank is a steel tank and the plug is a steel plug.

5. The plug according to claim 1 wherein the tank is part of switchgear.

6. The plug according to claim 5 wherein the switch gear is medium-voltage switchgear.

7. The plug according to claim 1 wherein the body portion is threaded.

8. A plug for sealing a fill port in a tank, the plug comprising: a body portion; and a top annular rim defining a central recess, the rim having an internal surface facing the recess, the internal surface having a polygon shape with no corners.

9. The plug according to claim 8 wherein the polygon shape is a trilobe defined by three lobe indentations.

10. The plug according to claim 8 wherein the recess has a diameter of about 0.850″.

11. The plug according to claim 8 wherein the tank is a steel tank and the plug is a steel plug.

12. The plug according to claim 8 wherein the tank is part of switchgear.

13. The plug according to claim 12 wherein the switch gear is medium-voltage switchgear.

14. The plug according to claim 8 wherein the body portion is threaded.

15. Switchgear including a hermetically sealed tank having a fill port and a plug for sealing the fill port, the plug comprising: a body portion; and a top annular rim defining a central recess, the rim having an internal surface facing the recess, the internal surface having a polygon shape with only rounded edges.

16. The switchgear according to claim 15 wherein the polygon shape is a trilobe defined by three lobe indentations.

17. The switchgear according to claim 15 wherein the recess has a diameter of about 0.850″.

18. The switchgear according to claim 15 wherein the tank is a steel tank and the plug is a steel plug.

19. The switchgear according to claim 15 wherein the switch gear is medium-voltage switchgear.

20. The switchgear according to claim 15 wherein the body portion is threaded.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is an isometric view of medium-voltage switchgear including a hermetically sealed and gas insulated tank;

[0009] FIG. 2 is a cutaway isometric view of the tank in the switchgear shown in FIG. 1 and illustrating a fill port sealed with a tamper resistant plug;

[0010] FIG. 3 is a side view of the tamper resistant plug separated from the fill port;

[0011] FIG. 4 is a top view of the tamper resistant plug separated from the fill port; and

[0012] FIG. 5 is an isometric view of a specially configured tool operable to be seated in the plug for rotating the plug.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0013] The following discussion of the embodiments of the disclosure directed to a tamper resistant plug is merely exemplary in nature, and is in no way intended to limit the disclosure or its applications or uses. For example, the tamper resistant plug has particular application for sealing a fill port of a hermetically sealed and gas-insulated tank in medium-voltage switchgear. However, as will appreciated by those skilled in the art, the plug may have application for sealing other enclosures.

[0014] FIG. 1 is an isometric view of medium-voltage switchgear 10 mounted on a pad 12 and including an enclosure 14. The switchgear 10 is intended to represent any suitable switchgear employed in an electrical power distribution network as discussed above, and can include any and all components for a particular application.

[0015] FIG. 2 is a cutaway isometric view of a hermetically sealed steel tank 20 that can be used in the switchgear 10 shown in FIG. 1. Typically, vacuum circuit breakers, disconnect switches and other components and electrical equipment (not shown) associated with the operation of the switchgear 10 would be enclosed in the tank 20 to provide the equipment in a gas-insulated environment. The tank 20 is filled with an insulating gas, such as CO.sub.2-Novec, through a circular, threaded fill port 22 during manufacture of the switchgear 10, and the fill port 22 is sealed with a circular, tamper resistant steel plug 24.

[0016] FIG. 3 is a side view and FIG. 4 is a top view of the plug 24 separated from the tank 20. The plug 24 includes a threaded body portion 28 that attaches to the threaded fill port 22 to allow the plug 24 to be rotated and be inserted and removed from the fill port 22. The plug 24 also includes an outer top annular rim 30 that defines a recess 32 in the top of the plug 24. An inner surface 34 of the rim 30 facing the recess 32 has a specially configured shape that prevents off-the-shelf, readily available and/or common tools, such as screw drivers, sockets, pliers, channel locks, etc., from engaging the rim 30 in a manner that allows the tool to rotate the plug 24 and remove it from the fill port 22. Particularly, the inner surface 34 has a polygonal shape with only rounded edges, i.e., no corners or flat edges, that might otherwise allow the common tool to engage the surface 34. In one embodiment, the polygonal shape is a trilobe defined by lobe indentations 36, 38 and 40. Therefore, the plug 24 cannot generally be removed from the fill port 22 by an owner of the switchgear 10 after the switchgear 10 has left the factory. In one non-limiting embodiment, the recess 32 has a diameter of about 0.850″.

[0017] FIG. 5 is an isometric view of a specially designed tool 50 that is operable to engage the inner surface 34 of the rim 30 to rotate the plug 24. The tool 50 includes a cylindrical portion 52 and a head portion 54. The head portion 54 includes an outer surface 56 that is the same size and shape as the recess 32. Thus, when the head portion 54 is inserted into the recess 32, the outer surface 56 perfectly engages the inner surface 34 such then when the tool 50 is rotated, the plug 24 also rotates. Thus, the plug 24 can initially be inserted in the fill port 22 and can later be removed at the factory if the tank 20 needs to be refilled with gas.

[0018] The foregoing discussion discloses and describes merely exemplary embodiments of the present disclosure. One skilled in the art will readily recognize from such discussion and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the spirit and scope of the disclosure as defined in the following claims.