Internal fault detector and method for using same

Abstract

A fault detector for detecting the occurrence of a sudden pressure rise in an electrical device, the fault detector having a chamber having an interior, a diaphragm in sealing engagement with the chamber, and an opening providing fluid communication between the interior of the chamber and an environment external to the chamber.

Description

[Technical field]

[0001] Some embodiments of the present invention relate to an apparatus or method for monitoring the performance of electrical equipment such as transformers, reactors, capacitors, etc. Some embodiments of the present invention relate to an apparatus or method for detecting and / or indicating faults in electrical equipment. Some embodiments of the present invention have particular application to electrical components used in electrical distribution systems. [Background technology]

[0002] Electrical grids use electrical components such as transformers, capacitors, and reactors. Potentially dangerous conditions can occur within such devices when ageing or operating stresses cause failures in the insulation system. A short circuit within such devices can release large amounts of energy in a split second. In the worst case scenario, the device can explode due to a sudden increase in internal pressure caused by vaporization of the insulating oil and the decomposition of the oil vapor into flammable or volatile gases.

[0003] It is known that when an oil-filled electrical device, such as a transformer or voltage regulator, suffers an internal arc fault, there is a momentary or sudden increase in pressure inside the device. This occurs because the arcing causes local vaporization of some of the oil or insulating fluid. Some electrical devices are filled with an electrical insulating gas, such as SF6. Devices are known for detecting such sudden pressure increases and indicating that such sudden pressure increases have occurred within the electrical device, such as those described in U.S. Pat. Nos. 5,233,331; 5,399,621; 5,433,635; and 5,433,625, all of which are incorporated herein by reference. Such devices may also include pressure relief valves or rupture disks for alleviating pressure increases within the electrical device during normal operation.

[0004] The foregoing examples of the related art and limitations associated therewith are intended to be illustrative and not exhaustive. Other limitations of the related art will become apparent to those of ordinary skill in the art upon reading this specification and studying the drawings. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 6,812,713 [Patent Document 2] U.S. Patent No. 6,429,662 [Patent Document 3] U.S. Pat. No. 5,078,078 [Patent Document 4] International Publication No. 2011 / 153604 [Patent Document 5] International Publication No. 2016 / 134458 Summary of the Invention

[0006] The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools, and methods that are intended to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the problems discussed above are mitigated or eliminated, while other embodiments are directed to other improvements.

[0007] In one aspect, a fault detector for detecting the occurrence of a sudden pressure increase may include a chamber having an interior, a diaphragm in sealing engagement with the chamber and defining a portion of a surface of the chamber, and an opening providing fluid communication between the interior of the chamber and an environment external to the chamber, the diaphragm having a spring constant of 0.88 N / mm (5 lbs / inch) or less.

[0008] In one aspect, a fault detector for indicating the occurrence of a sudden pressure increase within a housing of an electrical device includes a barrel and an actuating mechanism in fluid communication with an interior of the housing, the actuating mechanism including a sealed chamber having an orifice communicating between an environment external to the chamber and the interior of the chamber, and an actuating member movable in response to a pressure differential between the interior of the housing and the interior of the chamber, the actuating member having a spring constant of 0.88 N / mm (5 lbs / in) or less. A plunger is provided within the bore of the barrel, the plunger being biased forward within the barrel and normally held in an armed position by the actuating member, and when the pressure differential exceeds a positive threshold, the actuating member is moved to permit forward movement of the plunger to a triggered position.

[0009] In one aspect, a fault detector for indicating the occurrence of a pressure surge within a housing of an electrical device includes a barrel and an actuation mechanism in fluid communication with an interior of the housing, the actuation mechanism including a sealed chamber having an orifice communicating between an environment external to the chamber and the interior of the chamber, and an actuation member movable in response to a pressure differential between the interior of the housing and the interior of the chamber to move the actuation member from an inactivated configuration to an activated configuration, a plunger is provided within the bore of the barrel, and a locking member is provided having a first position and a second position, in the first position the locking member is positioned to restrain forward movement of the plunger within the barrel to prevent a force applied to the plunger from being transferred to the actuation member, and in the second position the locking member is positioned to permit forward movement of the plunger, the plunger being initially held in the inactivated configuration by the locking member when the locking member is in the first position and being forwardly movable within the bore of the barrel when the locking member is in the second position.

[0010] In one aspect, a fault detector is provided for indicating the occurrence of a sudden pressure increase within a housing of an electrical device, the fault detector having a barrel, an actuation mechanism in fluid communication with an interior of the housing and configured to release an actuation member in response to the sudden pressure increase within the housing, a plunger within a bore of the barrel, the plunger being biased forwardly within the barrel and normally held in an armed position by the actuation member, and a static seal having a first end fixedly held to the plunger and a second end fixedly held to the barrel, the static seal having a central portion that allows relative movement between the plunger and the barrel while maintaining a seal between the interior of the housing and an environment external to the housing as the fault detector moves from an armed configuration to a triggered configuration.

[0011] In some embodiments, a Hall effect sensor can be used to detect the relative movement of the plunger and barrel and generate a signal that a pressure surge has occurred. In one aspect, there is provided a pressure relief valve for relieving pressure from an electrical device, the pressure relief valve having a one-way flow obstruction that, in use, reduces inward fluid flow into an interior of a housing of the electrical device relative to outward fluid flow from the interior of the housing. The one-way flow obstruction may be an axially movable sealing sleeve.

[0012] In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following detailed descriptions. Exemplary embodiments are illustrated in the referenced figures in the drawings. It is intended that the embodiments and figures disclosed herein should be considered illustrative and not restrictive. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic, partially cut-away view of a power transformer mounted on a utility pole, equipped with an internal fault detector according to the present invention, and connected to an energy supply source; [Diagram 2] FIG. 2 is a perspective cross-sectional view of one embodiment of an internal fault detector. [Diagram 3] FIG. 3 is an exploded view of the embodiment of FIG. 2 with a portion of the housing omitted for clarity. [Figure 4] FIG. 3 is a cross-sectional view of the actuation mechanism of the embodiment of FIG. 2. [Figure 5A] FIG. 2 is a perspective view of a pre-folded diaphragm according to an exemplary embodiment of the present invention. [Figure 5B] 1 is a cross-sectional view of a pre-folded diaphragm according to an exemplary embodiment of the present invention. [Figure 5C] FIG. 2 is a cross-sectional view of a top hat diaphragm. [Figure 6] FIG. 2 is a perspective view of the collar and the inner and outer portions of the barrel. [Figure 7] FIG. 13 is a bottom view of one embodiment of an internal fault detector including an anti-rotation tab and a drainage opening. [Figure 8] 11 is a schematic diagram illustrating one possible configuration for preventing rotation of the barrel of one embodiment of an internal fault detector in an opening in a housing. FIG. [Figure 9A] FIG. 2 shows a perspective view of a ready-to-operate configuration of a seal for sealing between a barrel and a plunger when installed within the internal fault detector of the present invention; [Figure 9B] FIG. 13 shows a perspective view of a triggering arrangement for a seal for sealing between a barrel and a plunger when installed in the internal fault detector of the present invention. [Figure 10A] 13 illustrates the positioning of a seal between a barrel and a plunger according to an exemplary embodiment of the internal fault detector when the internal fault detector is in an armed configuration. [Figure 10B] 13 illustrates the positioning of a seal between the barrel and the plunger according to an exemplary embodiment of the internal fault detector when the internal fault detector is in a trigger configuration. [Figure 11] FIG. 2 is a perspective view of a locking bar according to an exemplary embodiment of the present invention. [Figure 12] FIG. 12 is a perspective view of the locking bar of FIG. 11 assembled together with the inner portion of the barrel. [Figure 13A] FIG. 2 is a perspective view of a shuttle in accordance with an exemplary embodiment of the present invention; [Figure 13B] FIG. 2 is a side view of a shuttle in accordance with an exemplary embodiment of the present invention. [Figure 14A] FIG. 13 is a top perspective view of an inner end of an indicator according to an exemplary embodiment. [Figure 14B] FIG. 13 is a bottom perspective view showing an exemplary assembly of an inner end of a plunger, a biasing spring, and a shuttle. [Figure 14C] 11A-11C are cross-sectional views showing portions of an indicator mechanism transitioning between an armed configuration and a triggered configuration; [Figure 14D] FIG. 11 is a cross-sectional view showing portions of the indicator mechanism in a trigger configuration. [Figure 14E] FIG. 13 is a perspective view showing the relative positions of the locking bar and the shuttle in an unactuated configuration. [Figure 14F] FIG. 13 is a perspective view showing the relative positions of the locking bar and the shuttle in an actuated configuration. [Figure 14G] FIG. 13 is a partial side view showing the shuttle and locking bar in an unactuated configuration. [Figure 14H] FIG. 13 is a cross-sectional view showing the shuttle and locking bar in an unactuated configuration. [Figure 14I] FIG. 13 is a partial side view showing the shuttle and locking bar in an actuated configuration. [Figure 14J] FIG. 13 is a cross-sectional view showing the shuttle and locking bar in an actuated configuration. [Figure 15A] FIG. 2 is a perspective view of one embodiment of an internal fault detector in an armed state. [Figure 15B] FIG. 1 illustrates a perspective view of an embodiment of an internal fault detector in a deployed state. [Figure 16] FIG. 1 is a perspective cross-sectional view of an internal fault detector in an armed configuration and a pressure relief valve in an open configuration according to an embodiment of the invention, in which a coil spring is used to provide a biasing force to the indicator. [Figure 17] 1 is a cross-sectional view of a pressure relief valve according to an exemplary embodiment of the present invention. [Figure 18A] FIG. 13 illustrates a side view of a dust cover engaged with a spring retainer for a pressure relief valve of one embodiment of the internal fault detector. [Figure 18B] FIG. 18B is an exploded perspective view of the embodiment of FIG. 18A. [Figure 19] FIG. 1 is a perspective view of one embodiment of an internal fault detector including an installed shipping fastener. [Figure 20A] FIG. 2 is a close-up view of one embodiment of a shipping fastener. [Figure 20B] FIG. 13 is a close-up perspective view of the outer end of the barrel of one embodiment of the internal fault detector showing the shipping fastener engagement features. [Figure 21A] FIG. 13 is a cross-sectional view of an internal fault detector according to one embodiment with a shipping fastener installed. [Figure 21B] FIG. 21B is a detailed view of the interface between the actuator mechanism and the indicator mechanism within the internal fault detector of FIG. 21A. [Figure 22A] FIG. 13 is a partial enlarged view showing an exemplary embodiment of a one-way flow obstruction used in conjunction with an embodiment of a pressure relief valve when internal pressure is being released. [Figure 22B] 1 illustrates an exemplary embodiment of a one-way flow obstructor when the interior of the housing is under vacuum (i.e., at a pressure lower than atmospheric pressure) when the internal pressure is equalized. [Figure 23A] FIG. 1 is a perspective view of an exemplary embodiment of a magnetic sensor. [Figure 23B] FIG. [Figure 24A] FIG. 13 is a perspective view showing an exemplary means for decoupling the actuator mechanism from the indicator mechanism through the use of a laterally oriented locking bar. [Figure 24B] FIG. 13 is a perspective view showing an exemplary means for decoupling the actuator mechanism from the indicator mechanism through the use of a laterally oriented locking bar. [Figure 24C]FIG. 13 is a perspective view showing an exemplary means for decoupling the actuator mechanism from the indicator mechanism through the use of a laterally oriented locking bar. [Figure 25A] FIG. 13 is a perspective view illustrating an exemplary means for decoupling the actuator mechanism from the indicator mechanism through the use of a pivoting lock bar for selectively engaging a trigger pin of the actuator mechanism. [Figure 25B] FIG. 13 is a perspective view illustrating an exemplary means for decoupling the actuator mechanism from the indicator mechanism through the use of a pivoting lock bar for selectively engaging a trigger pin of the actuator mechanism. [Figure 25C] FIG. 13 is a perspective view illustrating an exemplary means for decoupling the actuator mechanism from the indicator mechanism through the use of a pivoting lock bar for selectively engaging a trigger pin of the actuator mechanism. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Throughout the following specification, specific details are described to provide a more complete understanding to those skilled in the art. However, well-known elements may not be shown or described in detail to avoid unnecessarily obscuring the present disclosure. Thus, the specification and drawings should be regarded in an illustrative sense rather than a restrictive one.

[0015] As used herein, the relative directional terms "up", "down", "top", "bottom", "vertical", "horizontal", etc. are used in reference to the intended orientation of the internal fault detector in its installed configuration in a typical exemplary embodiment. The relative directional terms "forward", "front", etc. are used in reference to the orientation defined by the radially outer side of the generally cylindrical transformer housing. Conversely, the relative directional terms "rear", "aft", etc. are used in reference to the orientation defined by the radially inner side of the transformer housing. It will be understood that such terms are merely relative, and that the internal fault detector may have other orientations when not in use, and that the internal fault detector may be installed in alternative orientations other than the exemplary configuration described herein and still perform the same function. As used herein, the term "axial" refers to a direction along the longitudinal axis of the barrel of the internal fault detector.

[0016] The internal fault detector as described herein may be used with a variety of high power electrical devices, including pole-mounted transformers, ground-mounted transformers, or voltage regulators. Although exemplary embodiments are described in the context of oil-filled pole-mounted transformers, some embodiments of the invention are also used with gas-filled transformers.

[0017] 1 illustrates an exemplary embodiment of an internal fault detector 22 for use in conjunction with an oil-immersed pole-mounted transformer. A typical distribution pole 10 has an arm 12 that supports a power line 14. The transformer 16 has a housing or "tank" 20. An exemplary embodiment of an internal fault detector 22 is mounted in an opening (not shown) in a sidewall of the tank 20. In some embodiments, the opening is a small hole, e.g., having a diameter of about 1.35 inches, a hole size commonly used for inserting various instruments into transformers and the like. The tank 20 contains an electrically insulating fluid 26, which may be, for example, an oil such as insulating mineral oil or Nynas Nytro® (made from naphthenic oil), or an ester-based fluid such as Envirotemp FR3® fluid (made from seeds), or an electrically insulating gas such as SF6. The internal fault detector 22 is located in a space 28 above the fluid level of the electrically insulating fluid 26 in the tank 20 for a fluid-filled transformer, or preferably above the core or coil for a gas-filled transformer.

[0018] 1 is mounted to the side of the tank 20, in alternative embodiments, the internal fault detector 22 is installed through an opening formed in the lid 21 of the tank 20. In some such embodiments, installing the internal fault detector 22 in the lid 21 of the tank 20 allows the internal fault detector 22 to be installed higher in the tank 20, which may result in increased sensitivity of the internal fault detector 22 and / or facilitate easier installation of the internal fault detector 22.

[0019] In yet a further alternative embodiment, the internal fault detector 22 may be located partially or wholly outside the tank 20, as may be done, for example, to retrofit an existing transformer, so long as the internal fault detector 22 is placed in fluid communication with the interior of the tank 20 so that changes in pressure within the tank 20 are transmitted to the internal fault detector 22.

[0020] 2 and 3, the internal fault detector 22 includes an actuator mechanism, generally indicated at 30, that detects a sudden increase in pressure within the housing 20, and an indicator mechanism, generally indicated at 32, that changes appearance when the actuator mechanism 30 detects a sudden increase in pressure. As used herein, a "sudden increase in pressure" refers to a change in pressure having a peak pressure of about 0.7 to 140 kPa (0.1 to 20 pounds per square inch (psi)) or more within a rise period of about 5 to 15 milliseconds. This includes all values ​​and subranges within these ranges, for example, 1.4, 2.1, 2.8, 3.4, 4.1, 4.8, 5.5, 6.2, 6.9, 7.6, 8.3, 9.0, 9.7, 10.3, 11, 11.7, 12.4, 13.1, 13.8, 15.2, 16.5, 17.9, 19.3, 20.7, 24.1, 27.6, 31, 34.5, 41.4, 42.6, 43.3, 44.2, 45.1, 46.2, 47.1, 48.1, 49.2, 50.0, 51.0, 52.0, 53.0, 54.0, 55.0, 56.0, 57.0, 58.0, 59.0, 60.0, 61.0, 62.0, 63.0, 64.0, 65.0, 66.0, 67.0, 68.0, 69.0, 70.0, 71.0, 72.0, 73.0, 74.0, 75.0, 76.0, 77.0, 78.0, 79.0, 80.0, 81.0, 82.0, 83.0, 84.0, 85.0, 86.0, 87.0, 88.0, 89.0, 90.0, 91.0, 92.0, 93.0, 94.0, 95.0, 96.0, 97.0, 9 Examples of pressures that may be used include 48.3, 55.2, 62.1, 68.9, 82.7, 96.5, 110, or 124 kPa (0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.5, 4.0, 4.5, 5.0, 6, 7, 8, 9, 10, 12, 14, 16, or 18 psi) or more. Various embodiments of the internal fault detector 22 may have different levels of sensitivity to sudden pressure increases depending on the desired application. Alternative ways of adjusting the sensitivity of the internal fault detector 22 are discussed below.

[0021] As an example, an arc may occur if the insulation surrounding the energized or "active" components of the transformer 16 breaks down. Other scenarios in which an arc may occur include when a short circuit occurs, or when manufacturing defects or parts touch each other, or when the insulation surrounding the active transformer components has insufficient dielectric strength. An electric arc dissipates a large amount of energy. The sudden dissipation of energy in the housing 20 causes a sudden increase in pressure in the housing 20. Even at a level of short circuit current on the order of 100 amps, the pressure in the housing 20 rises at a rate that is significantly higher than other pressure fluctuations that are reasonably expected to occur during normal operation of the transformer 16. This sudden, or momentary, pressure increase is detected by the actuator mechanism 30, which triggers the indicator mechanism 32. That is, the sudden pressure increase triggers the indicator 32 from the armed configuration to the triggered configuration.

[0022] To facilitate normal operation and expected pressure changes during normal operating conditions, the internal fault detector 22 may include a pressure relief valve 34. If pressure rises to a value greater than the set point of the pressure relief valve 34, the pressure relief valve 34 opens until the pressure is relieved. Pressure within the housing 20 may rise to a level that may cause the pressure relief valve 34 to open as a result of normal fluctuations in ambient temperature and load. Maintenance personnel may also manually operate the pressure relief valve 34 to equalize the ambient pressure inside the housing 20 with the air pressure outside the housing 20, as described below.

[0023] 2 and 3, the actuator mechanism 30 has a chamber 36 that is in fluid communication with the interior of the housing 20 only by a small orifice 38 disposed in the shell 33. That is, the chamber 36 is generally sealed except for the small orifice 38, which places the interior of the chamber 36 in fluid communication with the interior of the housing 20. In the illustrated embodiment, a diaphragm 40, which functions as a gas barrier, forms one wall of the chamber 36. A second wall of the chamber 36 is provided by the shell 33.

[0024] In some embodiments, the shell 33 includes multiple adjacent components. As best shown in FIG. 4, the shell 33 includes an actuator housing wall 33A. The exterior surface of the wall 33A includes a generally cylindrical wall extending downward, while the interior surface of the wall 33A includes features for interfacing with other components of the actuator mechanism 30, as described later in this specification. The shell 33 further includes a lid 33B for enclosing an upper end of the actuator mechanism 30 from inside the housing 20. The lid 33B can be secured to the actuator housing wall 33A in any suitable manner (e.g., by clips, clamps, adhesives, ultrasonic welding, overmolding, etc.). In the illustrated embodiment, an overmolded part 33C is attached substantially over the exterior joint edges of the wall 33A and the lid 33B. In other embodiments, the entire shell 33 is integrally formed.

[0025] The diaphragm 40 has one side 40A within the chamber 36 and a second side 40B that is exposed to the ambient pressure of the housing 20 by being positioned within the housing 20 or by being placed in fluid communication with the interior of the housing 20. The chamber 36 is preferably approximately hemispherical so that it may occupy a reasonably small space when positioned within the housing 20, although the chamber 36 may have other shapes. The diaphragm 40 preferably has a reasonably large surface area so that a pressure differential across the diaphragm 40 generates sufficient force to trigger the indicator mechanism 32. In some embodiments, the diaphragm 40 may have a diameter of 7.6 cm (3 inches) or more. In other embodiments, smaller diameters may be used for diaphragm 40, such as diameters in the range of 0.5 to 2 inches, including any value therebetween, such as 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, or 1.9 inches.

[0026] In the illustrated embodiment, the spindle 31 is provided to provide support for the diaphragm 40 in a downward direction. A support wheel 35 can be provided to support the diaphragm 40 in an upward and radially inward direction. The support wheel 35 includes a vertical circular protrusion 37 that is generally defined by the radially inner surface of the diaphragm 40. The support wheel 35 extends radially inward from the bottom of the circular protrusion 37 to substantially conform to an inner portion of the face 40A of the diaphragm 40. The support wheel 35 is made of a material that is stiffer than the diaphragm 40 to protect the diaphragm 40 from damage that may be caused by excessive deflection. Other designs and configurations for the spindle 31 and the support wheel 35 can also be used to support the diaphragm 40. For example, the spindle can be formed of a plurality of connected concentric rings as a sheet of a suitable elastic material, or the like.

[0027] The size and shape of the chamber 36 may also affect the sensitivity of the indicator mechanism 32. For example, the height 45 of the chamber 36 above the surface 40A of the diaphragm 40 affects the sensitivity, and various heights may be used depending on the type of equipment in which the internal fault detector 22 is deployed. For example, a transformer or voltage regulator having more space may provide a larger cup volume, for example, by making the height 45 taller. In some embodiments, the height 45 of the chamber 36 above the surface 40A of the diaphragm 40 may be on the order of about 0.5 to about 3 inches, including any value or subrange therebetween, such as 0.75, 1.0, 1.25, 1.50, 1.75, 2.00, 2.25, 2.50, or 2.75 inches.

[0028] Because the orifice 38 allows air to enter and leave the chamber 36, the air pressure in the chamber 36 will follow relatively slow changes in the ambient pressure in the housing 20. Such changes may occur, for example, when the temperature in the transformer 16 changes. On the other hand, if the pressure in the housing 20 suddenly increases, it will take some time for the air pressure in the chamber 36 to increase due to the small size of the orifice 38. In response to a sudden increase in pressure, the diaphragm 40 should move far enough to reliably trigger the indicator mechanism 32. During this period, the pressure against the face 40B of the diaphragm 40 will momentarily greatly exceed the pressure against the face 40A. The diaphragm 40 will therefore be pushed inward towards the chamber 36, resulting in a translational movement of the diaphragm 40 in the axial direction.

[0029] A sudden pressure rise would occur, for example, if an electrical fault in an active component of the transformer 16 caused an electrical arc within the housing 20. The diaphragm 40 should be insensitive to ambient pressure fluctuations within the housing 20 that occur slower than about 1 psi per second to avoid triggering the internal fault detector 22 due to internal pressure changes that are lower than those caused by an internal fault.

[0030] To reduce the effects of oil splashing on the diaphragm 40, such as may occur if the housing 20 is shaken by an earthquake, a splash cover 44 may be provided. A spacer ring 46 is interposed between the diaphragm 40 and the splash cover 44 to elevate the diaphragm 40 above the surface of the splash cover 44. As best seen in Figures 3 and 4, the spacer ring 46 is a circular ring having an outwardly extending shoulder 46A that surrounds the diaphragm 40, the spindle 31, and the support wheel 35.

[0031] The shell 33 may be secured to the splash cover 44 in any suitable manner (e.g., by clips, clamps, adhesive, ultrasonic welding, overmolding, etc.). In the illustrated embodiment, a threaded portion of the inner portion 47 of the shell 33 is threaded onto a threaded portion of the outer portion 49 of the splash cover 44. At the upper end of the threaded portion of the inner portion 47, where the threads terminate, the inner portion 47 extends inwardly a short distance to form a circular shape, and at the end of this extension, the inner portion 47 includes a downward projection (see FIG. 4).

[0032] When the shell 33 is threaded onto the splash cover 44, the inward extension of the inner portion 47 concentrically surrounds the outer peripheral lip 51. When the shell 33 is threadably engaged onto the splash cover 44, the downwardly facing surface of the lip 51 abuts the spacer ring 46, which in turn abuts the outer portion 49 of the splash cover 44, thereby retaining the diaphragm 40 within the chamber 36. By retaining the diaphragm 40 in such a configuration, the pressure in the chamber 36 and the pressure inside the housing 20 are sealed against each other, except for air entering and exiting through the orifice 38 and / or the oil drain opening 151, which is a small opening provided to allow any oil entering the chamber 36 to exit. The presence of the spacer ring 46 is beneficial because it allows the downward force exerted by the shell 33 on the diaphragm 40 to be distributed over the larger surface area of ​​the spacer ring 46. Advantageously, secure retention of diaphragm 40 in the illustrated configuration enhances the sensitivity of actuator mechanism 30 by improving the seal between the interior of housing 20 and chamber 36. Additional sealing can be provided, for example, by an O-ring disposed on the lower surface of the downwardly protruding portion of inner portion 47 interposed between surface 40A and chamber 36.

[0033] An axial guide rod 55 extending from the diaphragm 40 may protrude into the cavity 41. In such an embodiment, the location of the upper end of the axial guide rod 55 protruding into the cavity 41 can be used to verify that the diaphragm 40 is properly positioned within the chamber 36 during assembly. Furthermore, the protrusion of the guide rod 55 into the cavity 41 serves to limit excessive upward movement and prevent the diaphragm 40 from inverting, which may cause damage to the diaphragm 40. In the illustrated embodiment, the spindle 31 and the guide rod 55 are integrally formed as a single unit. While these components need not be integrally formed, having fewer parts may allow for easier assembly and may result in greater consistency in the deployment of the internal fault detector 22 from unit to unit.

[0034] 4, the guide rod 55 has a tapered lower portion and projects into a cavity 41 defined between a pair of opposing tabs 48 disposed on the shell 33. Although not shown, in some embodiments, the orifice 38 can be located just above the top of the cavity 41.

[0035] A trigger pin 50 extends downward from the diaphragm 40 to hold the plunger 64 in place until the actuator mechanism 30 is triggered. Movement of the diaphragm 40 in response to a sudden pressure increase triggers the indicator mechanism 32, as described below. In the illustrated embodiment, the trigger pin 50 protrudes from a pair of opposed tabs 52 integrally formed on the bottom surface of the spindle 31. The trigger pin 50 can be held between the tabs 52 of the spindle 31 by an interference fit. In other embodiments, the tabs 52 are omitted from the spindle 31, and the trigger pin 50 is held by an interference fit in a hub located in a central portion of the diaphragm 40. In another embodiment, the pin 50 is integrally formed with the spindle 31. Under normal operating conditions, the chamber 36 is subjected to a variety of mechanical vibrations and shocks, including seismic shaking. To avoid false triggering due to such mechanical vibrations and to allow rapid operation, the mass of the diaphragm 40 should be small.

[0036] 5A and 5B show perspective and cross-sectional views of diaphragm 40 according to an exemplary embodiment of the invention. In the illustrated embodiment, the outer diameter of diaphragm 40 has a lip 51. As described herein, the configuration of lip 51 allows diaphragm 40 to be secured within chamber 36 by clamping inner portion 47 of shell 33 and spacer ring 46 onto opposing faces of diaphragm 40. However, any suitable mechanism or manufacturing technique may be used in alternative embodiments to sealingly engage diaphragm 40 with chamber 36 such that diaphragm 40 provides at least a portion of the surface of chamber 36.

[0037] Radially inward of lip 51, concentric annular ridge 53 is provided on diaphragm 40, having a diameter less than the outer diameter of diaphragm 40. Ridge 53 can be described as a fold in the shape of diaphragm 40, and diaphragm 40 as shown has one fold. The fold provided by annular ridge 53 has a diameter 43 less than diameter 25 of diaphragm 40.

[0038] At the inner end of ridge 53, diaphragm 40 features a downwardly depending depression having a height 57 and extending radially inward to form a shallow cup portion 54. In some embodiments, height 57 is in the range of 0.05 to 0.5 inches, including any value therebetween, such as 0.25, 0.51, 0.76, or 1.0 cm (0.1, 0.2, 0.3, or 0.4 inches). In some embodiments, cup portion 54 has a diameter corresponding to diameter 43 in the range of 0.5 to 2.5 inches, including any value therebetween, such as 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, or 2.4 inches. In some embodiments, cup portion 54 has a diameter of about 2 inches. In some embodiments, the diaphragm 40 has a total diameter 25 in the range of 0.5 to 5 inches, including any value therebetween, for example, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2.0, 2.5, 3, or 4 inches.

[0039] A single turn in the diaphragm 40 as shown may be used for a number of reasons. The diameter 43 of the turn as shown is equal to the total diameter 25 of the diaphragm 40 minus the dimension of the radially outer feature of the annular ridge 53. This diameter 43 establishes the surface area over which the diaphragm 40 is sensitive to pressure increases within the transformer 16. Diaphragms with larger surface areas will generally be more sensitive to pressure changes because they can generate a greater force for a given pressure acting on the diaphragm than a diaphragm with a smaller surface area. It has been found that when two or more turns are present, only the diameter of the innermost turn serves as the area over which the diaphragm 40 is sensitive to pressure changes. It has been found that a larger area sensitive to pressure changes results in improved sensitivity of the diaphragm 40 and actuator mechanism 30.

[0040] It has been found that the sensitivity of the diaphragm 40 to pressure increases within the transformer 16 depends in part on the geometry of the diaphragm 40. If the diaphragm 40 is provided with zero folds (i.e., the diaphragm 40 is generally flat without any folds or cups), the movement of the diaphragm 40 in response to pressure increases will depend solely on the elastic deformation of the material from which the diaphragm 40 is made (i.e., any deflection of the center point of the diaphragm 40 will occur solely as a result of the elastic deformation of such material). In contrast, the folds provided by the annular ridge 53 allow the cup portion 54 to invert relative to itself in response to pressure increases by changing the shape of the cup portion 54 without requiring significant elastic deformation of the material from which the diaphragm 40 is made, although the elastic deformation of the material requires a relatively higher threshold pressure than that required to change the shape of the cup portion 54. Therefore, while the use of zero folds may maximize the pressure sensitive surface area available for pressure to act upon, the advantage provided by a more pressure sensitive trigger mechanism (i.e., inversion of cup portion 54) is not present relative to a flat diaphragm. Therefore, increased sensitivity for a diaphragm 40 of a given diameter 25 can be achieved by providing a single fold, as shown.

[0041] In the illustrated embodiment, the amount that the diaphragm 40 can move in response to a pressure increase in the transformer 16 is primarily a function of the height 57. Specifically, the notional stroke length available for the movement of the diaphragm 40 is twice the value of the height 57, i.e., the available stroke length if the base of the cup portion 54 were to fully invert. In practice, the displacement of the base of the cup portion 54 during a sudden pressure increase is approximately half this stroke length, which corresponds to a displacement slightly less than the height 57. A desirably high stroke length is advantageous because it reduces the possibility of false triggering of the actuator mechanism 30. The turn-up provided by the annular ridge 53 allows for a greater height 57, and therefore stroke distance, than would be the case for a corresponding flat diaphragm.

[0042] Although diaphragm 40 is shown and described as having a generally circular shape, diaphragm 40 can have other shapes (e.g., triangular, square, rectangular, or other polygonal or asymmetric shapes) so long as the corresponding components with which diaphragm 40 must engage have corresponding shapes. The generally circular shape of diaphragm 40 may be more sensitive than other shapes.

[0043] The diaphragm 40 is preferably constructed of a suitable resilient material of a thickness and flexibility that provides a detectable movement in response to a sudden increase in pressure to actuate the actuator mechanism 30, as described herein. In some embodiments, the diaphragm 40 is formed from a malleable or liquid material that is molded into the final shape of the diaphragm 40. The material for the diaphragm 40 can be selected such that it is suitable for being molded by a manufacturing process such as injection molding, compression molding, transfer molding, etc. In some embodiments, manufacturing the diaphragm 40 involves first forming a suitable material into the desired shape of the diaphragm 40 and then hardening the material by any suitable means.

[0044] The diaphragm 40 undergoes large inelastic movements in response to pressure differentials created by sudden pressure increases. The diaphragm 40 is designed to maximize lateral movement while minimizing elastic deformation of the material from which the diaphragm 40 is made. The diaphragm 40 is preferably made from a material that is flexible or stretchable but does not easily elastically deform. In contrast, the overall shape of the diaphragm 40 is designed to be elastic to allow deformation of its shape upon the occurrence of a sudden pressure increase. Without being bound by theory, the elastic deformation of the material from which the diaphragm 40 is made reduces the sensitivity of the actuator mechanism 30 by not causing large translational movements (i.e., deflection) of the diaphragm 40. It is the vertical deflection of the diaphragm 40 itself, via compression of the cup portion 54, to move the trigger pin 50 that results in the actuation of the internal fault detector 22.

[0045] The material from which diaphragm 40 is made is also preferably resilient to high temperatures and will not degrade when exposed to various types of fluids, such as mineral oil or ester-based fluids, or electrical insulating gases that may be used in electrical devices.

[0046] In some embodiments, the material used to form the diaphragm 40 is an elastomer. The elastomer may be a thermosetting polymer. According to a more specific embodiment, the material used to form the diaphragm 40 is fluorosilicone rubber (FVMQ). In other embodiments, the material used to form the diaphragm 40 may be nitrile, fluoroelastomer, fluorocarbon, or neoprene. In some embodiments, the diaphragm 40 is formed from a composite material having embedded fibers. In some embodiments, the embedded fibers are polymer fibers. In some embodiments, the embedded fibers, including embedded polymer fibers, are embedded in only one surface of the diaphragm 40. In some embodiments, the embedded fibers, including embedded polymer fibers, are embedded in both sides of the diaphragm 40. The use of polymer fibers may advantageously increase the toughness of the diaphragm 40 while allowing the diaphragm to remain flexible. In some embodiments, the material used to form the diaphragm 40 is fiber-embedded fluorosilicone.

[0047] In some embodiments, the diaphragm 40 (excluding the lip portion 51) may have a thickness of 0.005 to 0.02 inches, including any value therebetween, such as 0.25 or 0.38 mm (0.01 or 0.015 inches). According to more specific embodiments, the diaphragm 40 has a thickness of about 0.012 inches. In some embodiments, the material from which the diaphragm 40 is made may have a hardness in the range of 50 to 95 Shore A durometer, including any value therebetween, such as 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, or 94 Shore A durometer. In one specific embodiment, the material from which diaphragm 40 is made has a hardness of approximately 71 Shore A durometer. The material used to form diaphragm 40 is preferably resilient to high strains when a sudden increase in pressure within housing 20 pushes diaphragm 40 upward.

[0048] In addition to the material from which the diaphragm 40 is made, the shape and configuration of the diaphragm 40 also affect the ease with which the diaphragm 40 can be actuated. As an example, the illustrated configuration of the diaphragm 40 has been found to provide good sensitivity to the occurrence of failure while at the same time being suitably resilient against tearing. In some applications, it is desirable to improve the sensitivity of the diaphragm 40 (and therefore the actuator mechanism 30) to pressure differences. For example, a more flexible diaphragm 40 allows for the construction of a smaller actuator mechanism 30 than would be possible if the diaphragm 40 were less flexible. The upward force generated by the pressure difference across the diaphragm 40 acts against a downward counteracting spring force generated by the diaphragm 40, which biases the diaphragm 40 towards its initial position. Furthermore, in order for the actuator mechanism 30 to trigger, it must overcome the downward force generated by the weight of the support wheel 35, spindle 31, and trigger pin 50 to which the diaphragm 40 is attached. In some embodiments, a spring may be integrally formed with or biased against the diaphragm 40 to provide additional downward force that the diaphragm 40 must overcome to trigger the actuator mechanism 30. As described later herein, the asymmetric biasing of the positioning of the diaphragm 40 increases the pressure required to trigger the actuator mechanism 30 if the horizontal force generated by the spring 70 that is part of the indicator mechanism 32 and acting on the trigger pin 50 is not otherwise limited, such as through some embodiments described further herein.

[0049] The inventors have determined that the spring constant of the diaphragm 40 provides a representative indication of the ease with which the diaphragm 40 can be actuated, with a lower spring constant k resulting in an actuator that can be actuated by a lower increase in pressure within the housing of the electrical device. A low spring constant for the diaphragm 40 can be achieved in the illustrated configuration by a combination of the geometry of the diaphragm 40 and the materials selected. Prior art diaphragms employed in devices for detecting sudden pressure increases in electrical devices, such as in Patent Cooperation Treaty Publication WO 2011 / 153604, may have a spring constant of about 1.2 N / mm (about 7 lbs / in). By comparison, in some exemplary embodiments, the diaphragm 40 of the present invention may have a spring constant of about 0.30 N / mm (about 1.7 lbs / in) or less. In some embodiments, the diaphragm 40 of the present invention has a spring constant in the range of about 0.18 to about 0.88 N / mm (about 1 to about 5 lbs / in), including any value therebetween, such as 0.18, 0.19, 0.21, 0.23, 0.25, 0.26, 0.28, 0.30, 0.32, 0.33, 0.35, 0.37, 0.39, 0.40, 0.42, 0.44, 0.46, 0.47, 0.49, 0.51, 0.53, 0.54, 0.56, 0.58, 0.60, 0.61, 0.63, 0.65, 0.67, 0.68, 0. Includes 70, 0.72, 0.74, 0.75, 0.77, 0.79, 0.81, 0.82, 0.84, 0.86, or 0.88 N / mm (1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, or 5 lbs / in).

[0050] In some embodiments, a light compression spring is provided on top of the diaphragm 40 within the chamber 36. This has the effect of biasing the diaphragm 40 downwards, making the actuator mechanism 30 relatively insensitive to pressure changes within the housing 20. A relatively insensitive actuator mechanism 30 may be desirable in situations where the cost of a false positive activation of the internal fault detector 22 is high, such as where the transformer 16 is located in a location that is relatively difficult to access.

[0051] In the illustrated embodiment of Figures 5A and 5B, the diaphragm 40 is a pre-folded diaphragm, i.e., the fold provided by the annular ridge 53 is formed in the diaphragm 40 during manufacture. In an alternative embodiment, the annular ridge is formed in the diaphragm having a top-hat configuration as shown in cross section in Figure 5C during assembly or operation as known in the art. The top-hat diaphragm 40A has a lip portion 51A that allows the diaphragm 40A to be secured within the chamber 36, and a downwardly depending cup portion 54A (shown in solid lines in Figure 5C) positioned radially inward of the lip portion 51A. A force applied manually during installation or against the base of the cup portion 54A during a momentary pressure surge can cause the downwardly depending cup portion 54A to assume a configuration as shown in dashed lines in Figure 5C, forming a fold defined by the annular ridge 53A. Therefore, in some embodiments, a single fold in the diaphragm is present only during a portion of the actuation process.

[0052] FIG. 6 shows the barrel 56, which is part of the indicator mechanism 32. In the illustrated embodiment, the barrel 56 has two separate parts, an inner part 56A and an outer part 56B. The outer part 56B is the part of the barrel 56 that passes through the housing 20. The outer part 56B can be coupled to the inner part 56A in any suitable manner. In the illustrated embodiment, the outer part 56B includes a receiving slot 86. The inner part 56A includes a corresponding key 59 that is received by the slot 86 when the indicator mechanism 32 is assembled. Assembly of the barrel 56 using the illustrated configuration ensures that relative rotation between the parts 56A and 56B is prevented. Any other suitable mechanism can be employed to prevent relative rotation between the parts 56A and 56B when installed. When the parts 56A and 56B are engaged, the threaded collar 58 can engage a corresponding external thread provided on the outer rear extension 113 of the outer part 56B. Collar 58 serves to hold portions 56A and 56B in the assembled configuration of barrel 56 when installed within internal fault detector 22 .

[0053] The barrel 56 may be provided with an anti-rotation element, such as a locking tab 60 shown in FIG. 7. The locking tab 60 engages a locking slot 62 to further prevent relative rotation between the inner and outer portions 56A, 56B and prevent accidental disengagement of the collar 58. To separate the inner and outer portions 56A, 56B, a user may depress the locking tab 60 away from the slot 62, thereby allowing the collar 58 to be disengaged by unscrewing it from the outer portion 56B. Preferably, one or more openings are provided through the lower surface of the barrel 56 to facilitate drainage of any fluids therefrom. In the illustrated embodiment, a drainage opening 150 is provided in the inner portion 56A of the barrel 56.

[0054] The outer portion 56B of the barrel 56 projects through the opening 24 and includes an outer flange 61. As best shown in FIG. 3, a weatherproof gasket 63 is interposed between the outer flange 61 and a nut 65 that is threaded onto an outer threaded shoulder 69 of the outer portion 56B. The nut 65 is tightened against the outer wall surface of the housing 20 to ensure the integrity of the seal around the opening 24. When the nut 65 is tightened, the gasket 63 presses against the inner wall of the housing 20, thereby sealing the interior of the housing 20 against the outside environment. The nut 65 may also be provided with a collared shoulder 67 to provide a larger surface area for engaging the housing 20 to prevent the internal fault detector 22 from sliding in or through the opening 24.

[0055] In some embodiments, the barrel 56 is prevented from rotating within the opening 24. This can be accomplished, for example, by providing a protrusion 66 within the opening 24 that engages with a corresponding notch 68 in the outer portion 56B (see FIG. 8). Increasing the depth of the notch 68 and the size of the protrusion 66 can provide more secure insertion and retention of the internal fault detector 22 within the housing 20.

[0056] Preferably, in embodiments intended to be mounted within the housing 20, the barrel 56 is small enough to fit within the opening 24, which may be about 1.35 inches in diameter. The barrel 56 is made of a non-conductive material such that the barrel 56 does not provide a conductive path through the wall of the housing 20. The barrel 56 may be fabricated from, for example, fiber reinforced polypropylene, including additives to provide resistance to degradation from the action of sunlight and / or additives to improve flammability characteristics. For example, polybutylene terephthalate, optionally including glass fiber reinforcement, may be used in combination with suitable additives.

[0057] A plunger 64 is disposed within the bore 56C of the barrel 56. The plunger 64 is biased forward relative to the housing 20 in any suitable manner. For example, in the illustrated embodiment, an ejection spring 70, shown as a compression spring, is compressed between a receiving cavity 71 in the inner end 64A of the plunger 64 and a flanged surface 131 of the shuttle 72 (see FIGS. 2 and 13A). Alternatively, instead of the illustrated compression spring, the ejection spring could be a tension spring disposed to pull the plunger 64 forward within the bore 56C, or any other suitable type of spring or biasing member. In the illustrated embodiment, the inner and outer ends 64A and 64B of the plunger 64 can be coupled together by corresponding mating threads. In an alternative embodiment, the plunger 64 is formed as a single unit.

[0058] The barrel 56 includes structural features that sealingly engage a seal 74 (see FIGS. 9A-10B ), which is also sealingly engaged with the plunger 64. The seal 74 is a static seal that fixedly engages the plunger 64 at a first end and the barrel 56 at a second end to maintain a seal between the interior of the housing 20 and the outside atmosphere, regardless of whether the internal fault detector 22 is in an armed (i.e., unactivated) or triggered (i.e., activated) state. The flexible central region of the seal 74, provided in the illustrated embodiment by a conical wall 79, is sufficiently long and sufficiently flexible to move freely between an unactivated position and an activated position, thereby maintaining a seal between the barrel 56 and the plunger 64 at all times before, during, and after activation of the internal fault detector 22.

[0059] Maintaining a seal between the interior of housing 20 and the external atmosphere, as described above, helps ensure that fluid remains contained within housing 20 while not allowing external elements, such as moisture and dirt, to enter housing 20. By maintaining stationary sealing surfaces on both barrel 56 and plunger 64, the seal achieved by seal 74 is independent of relative axial movement of barrel 56 and plunger 64 as plunger 64 moves between the inactivated and activated states of internal fault detector 22, as shown in Figures 10A and 10B, respectively.

[0060] 9A and 9B show an exemplary seal 74 in a non-activated configuration and an activated configuration, respectively, according to an exemplary embodiment of the present invention. In some embodiments, the seal 74 is a static seal. In the illustrated embodiment, the seal 74 is a rolling seal having two ends that sealingly engage and remain fixed in place against corresponding portions of the barrel 56 and the plunger 64, respectively, while a central portion, which in the illustrated embodiment is a conical wall 79 of the seal 74, allows relative movement between these two components. When the seal 74 is positioned within the internal fault detector 22, the seal 74 maintains sealing engagement with the barrel 56 at all times during operation of the internal fault detector 22 by including a sealing lip 75 at a first end of the seal 74 that is in constant contact with a mating inner surface 98 of the inner portion 56A and a mating inner surface 96 of the outer portion 56B, as best shown in FIGS. 10A and 10B and described below. Similarly, a circular surface 78 at a second end of the seal 74 sealingly engages a flange 80 on the inner portion 64A of the plunger 64. The inner rearward extension 73, in conjunction with the outer rearward extension 113, is provided on the outer portion 56B radially inward of the sealing lip 75 to maintain the radial position of the sealing lip 75 relative to the barrel 56. The sealing engagement of the seal 74 with both the barrel 56 and the plunger 64 provides a seal between the interior of the housing 20 and the external atmosphere regardless of whether the internal fault detector 22 is in an inoperative or activated configuration.

[0061] The first and second ends of the seal 74 are joined by a length of material which, in the illustrated embodiment, forms a conical wall 79. In the illustrated embodiment, the sealing lip 75 extends radially outward from the conical wall 79 at the first end of the seal 74. At its second end, the seal 74 features an annular ridge 88 before extending radially inward to form a generally circular sealing surface 78.

[0062] The seal 74 may be formed from any suitable elastic and flexible material. For example, in some embodiments, the seal 74 is formed from an elastomer. The elastomer may be a thermosetting polymer. According to more specific embodiments, the material used for the seal 74 is a fluorosilicone rubber (e.g., FVMQ). In other embodiments, the material used to form the seal 74 may be a nitrile, a fluoroelastomer, a fluorocarbon, or a neoprene. In some embodiments, the seal 74 is formed from a composite material having embedded fibers. In some embodiments, the embedded fibers are polymer fibers. In some embodiments, the polymer fibers are embedded in only one surface of the seal 74. In some embodiments, the polymer fibers are embedded in both sides of the seal 74. The use of polymer fibers may advantageously increase the toughness of the seal 74 while allowing the seal to remain flexible. In some embodiments, the material used to form the seal 74 is a fiber-embedded fluorosilicone. In some embodiments, the seal 74 is constructed from the same material as the diaphragm 40 as previously described herein.

[0063] The hardness (i.e., durometer) of the material from which the seal 74 is made can be selected to ensure that the seal is maintained over the range of normally expected operating conditions of the internal fault detector 22. The material should be selected to be sufficiently flexible to ensure that the cone wall 79 can move freely during actuation, but the material used should not be overly elastic so as to increase the force required to eject the plunger 64. The friction, flexure, and profile characteristics provided by the seal 74 can vary depending on the type of material used to construct the seal 74. In some embodiments, the seal 74 may have a hardness ranging from 50 to 95 Shore A durometer, including any value therebetween, such as 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, or 94 Shore A durometer. The seal 74 should be made from a material capable of sealing in various types of fluids, such as mineral oil or ester-based fluids, or electrically insulating gases that may be used in electrical devices, at high operating temperatures. In some embodiments, the seal 74 (excluding the lip 75) may have a thickness of 0.005 to 0.02 inches, including any value therebetween, such as 0.006, 0.007, 0.008, 0.009, 0.010, 0.012, 0.014, 0.016, or 0.018 inches. According to a more specific embodiment, the seal 74 has a thickness of about 0.017 inches.

[0064] During transition of the internal fault detector 22 from the inactivated to the activated configuration, the flange 80 on the inner end 64A of the plunger 64 abuts the second end 78 of the seal 74 and exerts a forward force (towards the outer portion 56B). The forward movement of the plunger 64 has the effect of flipping the flexible conical wall 79 of the seal 74 into the configuration shown in FIG. 9B, where the conical wall 79 rolls over itself and the second end 78 moves forward over the sealing lip 75 in the illustrated embodiment. The seal created by the static compression of the lip 75 in the illustrated embodiment and the construction of the seal 74 from a flexible material allow the plunger 64 to move freely during operation without any loss of sealing effectiveness.

[0065] Conical wall 79 has a height 79A defined by the distance between lip 75 and annular ridge 88. In the illustrated embodiment, as seal 74 reverses due to forward movement of plunger 64, plunger 64 may travel a distance equivalent to approximately twice height 79A before seal 74 fully reverses and exerts a counteracting spring force against the force exerted by spring 70, thereby effectively countering both axial forces.

[0066] Because the seal 74 does not slide relative to either the barrel 56 or the plunger 64, the amount of friction that must be overcome to move the plunger 64 relative to the barrel 56 is reduced as compared to prior designs which maintained a sliding frictional engagement between the seal and plunger.

[0067] Some embodiments of the present invention provide a means for decoupling an indicator mechanism (e.g., indicator mechanism 32) from an actuator mechanism (e.g., actuator mechanism 30), both mechanisms being part of the internal fault detector. Preferably, this decoupling transfers any externally induced movement or force on the indicator mechanism to a wall of the electrical device in which the internal fault detector is installed, rather than to the actuator mechanism 30. The means for decoupling the indicator mechanism from the actuator mechanism includes a locking mechanism that engages with the indicator mechanism to transfer forces encountered by the indicator mechanism to components other than the actuator mechanism, e.g., the wall of the electrical device, via other components of the internal fault detector.

[0068] In one exemplary embodiment, the means for decoupling further includes an intermediate component in communication with both the indicator mechanism and the actuator mechanism. The intermediate component is biased in a forward direction (i.e., towards a triggered position) and moves forward only upon triggering of the actuator mechanism to disengage the locking mechanism, which allows free axial forward movement of the indicator mechanism. Optionally, the locking mechanism may be re-engaged immediately after the internal fault detector is triggered, thereby further restricting, for example, axial rearward movement of the indicator mechanism and / or complete ejection in a forward direction.

[0069] In the illustrated embodiment, the means for decoupling the indicator mechanism from the actuator mechanism is a locking bar 110 that interacts with the shuttle 72, serving as an interface to effectively decouple the indicator mechanism 32 from the actuator mechanism 30, as compared to prior designs. More specifically, the indicator mechanism 32 is decoupled from the actuator mechanism 30, since any force applied to the indicator mechanism 32, for example by a user placing the internal fault detector 22 or by a user pulling the pull ring 107, is not transferred to the trigger pin 50 and therefore to the actuator mechanism 30. The only forces affecting the deployment of the actuator mechanism 30 are the forces associated with the various components of the actuator mechanism 30 and the biasing force of the spring 70 against the trigger pin 50. The shuttle 72 serves as an intermediate component that interfaces with both the indicator mechanism 32 and the actuator mechanism 30. Specifically, when the actuator mechanism 30 is triggered, the shuttle 72 moves forward to disengage the locking bar 110, thereby allowing the indicator mechanism 32 to move freely. This allows the design of the actuator mechanism 30 to be optimized without having to consider additional forces that the indicator mechanism 32 may contribute if it is not decoupled from the actuator mechanism 30, as in prior devices.

[0070] In some embodiments, the locking bar 110 may also help ensure that the internal fault detector 22 is not tampered with inappropriately when in either the inactivated or activated configuration. As shown in FIG. 11, the locking bar 110 has a rearwardly extending catch portion 112 at the end of a downwardly extending portion at a first longitudinal end 108 of the locking bar 110. Proximate the first longitudinal end 108, the locking bar 110 has an upwardly extending hook portion 114. At an opposite second longitudinal end 109 of the locking bar 110, the locking bar 110 has two pairs of downwardly extending arm portions 116 disposed on either lateral side of the locking bar 110. An inclined surface 118A and an inclined surface 118B are disposed transversely between the two pairs of arm portions 116. The angled surface 118A is provided at a leading edge of the second longitudinal end 109 and slopes upwardly and forwardly from a midpoint 118C between the angled surfaces 118A and 118B. The angled surface 118B is provided at a trailing edge of the second longitudinal end 109 and slopes upwardly and rearwardly from the midpoint 118C.

[0071] FIG. 12 illustrates installation of the locking bar 110 onto the inner portion 56A of the barrel 56. The inner portion 56A includes a slot 120 (also visible in FIG. 6) for receiving the catch portion 112 of the locking bar 110. The inner portion 56A further includes an upwardly extending angled protrusion 122 spaced longitudinally from the groove 120. To install the locking bar 110 onto the inner portion 56A of the illustrated embodiment, the catch portion 112 is positioned within the slot 120 while the second end 109 of the locking bar 110 is pivoted at an upward angle relative to the inner portion 56A of the barrel 56. The second end 109 of the locking bar 110 is then pivoted downwardly to its locked position resulting in the configuration shown in FIG. 12 in the inoperative position. In this configuration, the locking bar 110 is pivotally coupled at a first end 108 to the inner portion 56A of the barrel 56 so that the second end 109 can be displaced vertically upwardly by the shuttle 72, as described below.

[0072] In some embodiments, including the illustrated embodiment, the locking bar 110 is also slidably engaged with the inner portion 56A of the barrel 56, thereby allowing longitudinal, i.e., forward and rearward, movement of the locking bar 110. An embodiment of the locking bar 110 that is slidably and pivotally engaged with the inner portion 56A can be used in conjunction with a shipping fastener to further secure the detector 22 against actuation during shipping, as described below. To achieve this slidable and rotatable engagement of the locking bar 110 of the illustrated embodiment, the catch portion 112 of the locking bar 110 is sufficiently elongated to remain secured within the slot 120 even while the locking bar 110 is displaced rearward by the shipping fastener 90, as described below, and also allows rotation of the locking bar 110 to allow the second end 109 to be displaced upward by the shuttle 72, as described below.

[0073] In the illustrated embodiment, both ends of the retention spring 125 (shown in the illustrated embodiment as a tension spring) are secured around the projection 122 and hook 114, respectively, to retain the catch 112 within the groove 120, thereby preventing significant relative axial movement between the lock bar 110 and the inner portion 56A. In embodiments in which the lock bar 110 is slidably and rotatably engaged with the inner portion 56A, the retention spring 125 should be selected to allow a sufficient degree of rearward displacement of the lock bar 110 relative to the inner portion 56A to allow the lock bar 110 to engage the catch 162, as described below. The retention spring 125 also exerts a downward force on the second end 109 of the lock bar 110 to help hold the lock arm 116 in place and inhibit movement of the plunger 64, as described below.

[0074] In the illustrated embodiment, a shuttle 72 (see FIGS. 13A, 13B, 14B, 14C, and 14D) is provided to serve as an interface between the actuator mechanism 30 and the indicator mechanism 32. As best seen in FIG. 2, in the unactuated configuration, the trigger pin 50 rests within a trigger notch 139 of the shuttle 72. When the actuator mechanism 30 is actuated by a sudden increase in pressure, the trigger pin 50, in the illustrated embodiment, moves upwardly out of the trigger notch 139 to release the shuttle 72 under the force exerted by the spring 70. This allows the spring 70 to release its potential energy and push the shuttle 72 forward, which forward movement releases the locking bar 110 and allows the indicator mechanism 32 to enter the actuated configuration as described below.

[0075] As best seen in FIG. 2, the shuttle 72 is primarily disposed radially inward of the inner end 64A of the plunger 64. The inner end 64A includes upper and lower slots 102, 104 that receive upper and lower portions 132, 134 of the shuttle 72, respectively, to permit relative axial movement between the plunger 64 and the shuttle 72 while preventing relative rotation (see FIG. 14B). FIGS. 13A and 13B show an exemplary embodiment of the shuttle 72. The shuttle 72 includes a flanged surface 131 for engaging one end of the ejection spring 70. The shuttle 72 further includes a front angled surface 135 and a rear angled surface 137 on the upper portion 132 with a trigger notch 139 interposed therebetween. The front sloped surface 135 slopes generally upward at a smooth angle from front to rear, while the rear sloped surface 137 slopes generally downward at a smooth angle from front to rear.

[0076] As best seen in FIG. 13B, in some embodiments, including the illustrated embodiment, the front ramp 135 and rear ramp 137 can be provided at different angles. For example, in the illustrated embodiment, the front ramp 135 has an angle θ of about 45 degrees from horizontal, which is steeper than the rear ramp 137, which has an angle φ of about 30 degrees from horizontal. The angles of the ramps 118B and 118A of the locking bar 110 are selected to be complimentary to the angles used for the front ramp 135 and rear ramp 137, respectively, to facilitate smooth movement of the locking bar 110 by the shuttle 72. Using different values ​​for the angles θ and φ allows the movement of the shuttle 72 from a non-activated configuration to an activated configuration to be relatively easier to accomplish than the movement of the shuttle 72 from an activated configuration to a non-activated configuration, such as when resetting the internal fault detector 22. Also, the locking bar 110 is restrained against forward movement through the engagement of its first longitudinal end 108 with the inner portion 56A of the barrel 56 (with the catch 112 engaged in the slot 120). However, the locking bar 110 is restrained against rearward movement by the spring 125. It is therefore desirable to minimize the level of rearward force exerted on the locking bar 110 through the rearward angled surface 137 of the shuttle 72, which can be accomplished by minimizing the angle φ. However, reducing the angle φ requires increasing the axial length of the rearward angled surface 137, so a balance is required to avoid making the rearward angled surface 137 excessively long.

[0077] Reasonable ranges of values ​​for angle φ include about 25° to about 45°, including any value therebetween, such as 30°, 35°, or 40°. Typically, angle θ can be about 45°, but other values, such as 40° or 50°, or any value therebetween, can be used as needed. Correspondingly, the complementary angles for inclined surface 118B and inclined surface 118A can each range from about 45° to about 65°, including any value therebetween, such as 50°, 55°, or 60°, and any value therebetween, including about 40° to 50°, or 45°. Such values ​​are merely exemplary and not limiting, as other values ​​may also work.

[0078] Until the internal fault detector 22 is triggered, the plunger 64 is prevented from being ejected from the barrel 56 by the engagement of the trigger pin 50 in the trigger notch 139 of the shuttle 72 (which locks the shuttle 72 against forward longitudinal movement and prevents the shuttle 72 from releasing the locking bar 110, preventing the shuttle 72 to a large extent from transmitting the biasing force exerted by the ejection spring 70 to the plunger 64) and by the engagement of the locking bar 110 with a retention surface of the plunger 64, as described below. The trigger pin 50 passes through a chamfered guide opening 77 into the bore 56C of the barrel 56 (see FIG. 2). The diaphragm 40 may provide a slight downward force that tends to seat the trigger pin 50 in the trigger notch 139. When a sudden pressure increase occurs, the diaphragm 40 actuates the trigger pin 50 upwardly and out of engagement with the trigger notch 139, allowing the ejection spring 70 to extend in length and push the shuttle 72 forward (towards the outer portion 56B) by displacing the locking bar 110 as described below.

[0079] 14A and 14B, the inner end 64A of the plunger 64 includes upwardly extending inward and outward projections 106A, 106B along the longitudinal length of the slot 102. The projections 106A, 106B provide a locking member that can engage a locking bar 110 to restrain movement of the plunger 64. Under normal operating conditions of the transformer 16, the plunger 64 is prevented from moving forward by the forward facing surface 106B-1 of the projection 106B engaging the rearward facing surface 116-2 of the arm 116 of the locking bar 110 when the locking bar 110 is in its locked configuration. Similarly, rearward movement of plunger 64 (such as may be caused by a user pressing externally on plunger 64) is prevented by rearward surface 106C-1 (best shown in FIG. 14B) of plunger 64 engaging with forward surface 116-1 of arm portion 116 of locking bar 110.

[0080] As the shuttle 72 is pushed forward, the ramped surface 135 of the shuttle 72 engages the ramped surface 118B of the locking bar 110 (an interaction best shown in FIG. 14C). Continued forward movement of the shuttle 72 following such engagement causes the locking bar 110 to rotate about the catch portion 112 by pivoting the second longitudinal end 109 of the locking bar 110 upwardly to a released configuration as the ramped surface 135 of the shuttle 72 slides against the ramped surface 118B of the locking bar 110 (shown in FIG. 14D). The upward pivoting of the second longitudinal end 109 of the locking bar 110 disengages the mating surface 106B-1 of the wall 106B from the arm portion 116. This allows the plunger 64 to move forward through the action of the spring 70 (which in the illustrated embodiment acts on the shuttle 72). In the illustrated embodiment, the shuttle 72 is positioned between the opposing pair of arms 116, between the width of ramps 118A and 118B. Therefore, the shuttle 72 is not restricted in movement by the arms 116 and protrusions 106A and 106B, and is free to move to disengage the locking bar 110 as described herein, as shown in Figures 14E and 14F.

[0081] Once positioned within the indicator mechanism 32, the retaining spring 125 biases the locking bar 110 into a horizontal configuration as shown in Figure 12. After the plunger 64 has advanced a certain distance, the ramp 137 of the shuttle 72 slides past the ramp 118A of the locking bar 110, allowing the second longitudinal end 109 of the locking bar 110 to pivot back downward about the catch 112 and seat the arm 116 of the locking bar 110 within the recess defined by the projections 106A and 106B, returning the locking bar 110 to the second locked configuration. This movement is facilitated by the downward aspect of the force exerted by the retaining spring 125 on the locking bar 110. 14D, rearward facing surface 116-2 of arm portion 116 engages forward facing surface 106A-1 of projection 106A to block further advancement of plunger 64, thereby preventing full ejection of plunger 64 from internal fault detector 22. As an additional or alternative means for preventing full ejection of plunger 64, outer end 64B of plunger 64 includes an outward facing flange 115 that contacts an inward facing flange 117 on outer portion 56B of barrel 56, thereby preventing further forward axial movement of plunger 64.

[0082] The illustrated embodiment decouples the indicator mechanism 32 from the actuator mechanism 30. If any force is applied to the plunger 64 by a human pulling or pushing on the ring 107 when the internal fault detector 22 is in the inactivated configuration, the engagement of the arms 116 of the locking bar 110 with the surfaces of the plunger 64 (e.g., the forward facing surface 106B-2 of the protrusion 106B and the rearward facing surface 106C-1 of the protrusion 106C) will prevent the plunger 64 from moving, which in turn will prevent the plunger 64 from interfering with the actuator mechanism 30 by exerting a force on the trigger pin 50 via the shuttle 72. Any such force applied to the plunger 64 will be received by the barrel 56 through the coupling of the locking bar 110 to the barrel 56 and may be transferred, for example, to a wall of the electrical device in which the internal fault detector 22 is installed. In some embodiments, the indicator mechanism 32 will support an externally applied force of 120 pounds force or more in any axial direction. An exemplary advantage of such a configuration is that design considerations, including the ability of trigger pin 50 to withstand axially directed forces, can be determined solely by the expected force that spring 70 will apply to trigger pin 50 by shuttle 72, without having to consider any additional externally applied forces that could potentially be applied via plunger 64.

[0083] FIG. 15A shows the internal fault detector 22 in a deactivated state, while FIG. 15B shows the internal fault detector 22 in an activated state. Preferably, after the plunger 64 is pushed forward in the bore 56C, the outer end of the plunger 64 extends significantly beyond the outer opening of the barrel 56. This provides a highly visible indication that a fault has occurred in the transformer 16. The shape of the internal fault detector 22 is therefore changed after the plunger 64 is ejected. Furthermore, the side 64C of the plunger 64, or a portion thereof, can be light colored and can have a color that has a high contrast with colors typically found in the environment of the transformer 16. Suitable colors include light colors such as blaze orange and bright yellow. Therefore, after the plunger 64 is ejected, the light colored side 64C is exposed and easily visible. The internal fault detector 22 may be mounted to a side wall of the housing 20, thereby providing an easily visible indication that an internal fault has occurred.

[0084] When the internal fault detector 22 is in the trigger configuration, the arm 116 can engage the rearward facing surface 106B-2 of the protrusion 106B to prevent the plunger 64 from being pushed back into the bore 56C. This prevents the transformer 16 from being unknowingly returned to service without passing the internal inspection. In general, whenever an electrical device malfunctions so as to trigger the internal fault detector 22, the device should be inspected before being returned to service. By providing an indicator element that cannot be easily returned to its initial position after the internal fault detector 22 has been triggered without opening the housing 20, the possibility of the electrical device being returned to service by human error before it has been properly inspected and serviced is reduced. Alternatively, a separate pawl mechanism, or other one-way ratchet mechanism, can be provided so that the internal fault detector 22 can only be reset from inside the housing 20.

[0085] More generally, the operation of the locking bar 110 and shuttle 72 can be described as follows: The locking bar 110 provides a pivotable locking member pivotable about a first end (108 in the illustrated embodiment) and having a locking edge (116-2 in the illustrated embodiment) at its second end (109) that is normally biased in a first direction (downward in the illustrated embodiment) to prevent forward movement of the indicator mechanism 32 (e.g., in the illustrated embodiment, by restraining forward movement of the plunger 64 via engagement with the projection 106B).

[0086] In some embodiments, the pivotable locking member can also prevent rearward movement of the indicator mechanism 32 in the unactuated configuration (e.g., in the illustrated embodiment, via engagement of forward-facing surface 116-1 with protrusion 106C) (note that while surfaces 116-1 and 116-2 are provided on separate arms in the illustrated embodiment, in alternative embodiments these surfaces can be provided as opposite-facing surfaces on the same arm).

[0087] The pivotable locking member cooperates with a sliding unlocking member (provided by the shuttle 72 in the illustrated embodiment) to displace the trigger pin 50 out of engagement with the shuttle 72 (e.g., from the trigger notch 139 in the illustrated embodiment) such that when the shuttle 72 is released for forward movement, a ramped surface of the sliding unlocking member (135 in the illustrated embodiment) acts as a wedge to displace the second end (109) of the pivotable locking member in a second direction (upward in the illustrated embodiment) to disengage the locking edge (116-2) and release the indicator mechanism 32 for forward movement. In some embodiments, including the illustrated embodiment, the sliding unlocking member is provided with a cooperating ramped surface (118B in the illustrated embodiment) that is complementary to and slides over the ramped surface 135 of the sliding unlocking member.

[0088] The pressure relief valve 34 may be integral with the plunger 64 and is housed within the outer portion 64B of the plunger 64. The pressure relief valve 34 has an axially movable valve member 81 biased into engagement with a valve seat 83 by a low constant spring 82. Typically, the valve member 81 is sealingly biased against the valve seat 83 to maintain a seal between the external atmosphere and the interior of the housing 20, thereby preventing the ingress of moisture into the interior of the housing 20. When the ambient pressure within the housing 20 exceeds the atmospheric pressure outside the housing 20, there is a net forward force at the end of the valve member 81. When this force exceeds a force corresponding to a pressure differential of a predetermined value, for example, 34.5 kPa, 48.3 kPa, 68.9 kPa, or 82.7 kPa (5 psi, 7 psi, 10 psi, or 12 psi), the spring 82 compresses to allow gas to exit the housing 20 through the vent gap 148 (see FIG. 16). This predetermined value that allows gas to escape can be varied by modifying the characteristics of the low constant spring 82, such as by changing the uncompressed spring length, number of turns available, wire diameter, inner and outer diameters, or by otherwise varying its spring constant. For ease of reference, the springs used in the pressure relief valve 34 can be color coded according to the range of pressures that will activate the pressure relief valve in which they are housed. The venting characteristics of the pressure relief valve 34 can also be varied by changing the diameter of the vent gap.

[0089] 3 and 17, the valve member 81 projects through the spring retainer 84. The low constant spring 82 is received between the valve seat 83 and the spring retainer 84. In the illustrated embodiment, the spring retainer 84 has a generally cylindrical central portion 142 disposed about and in sliding contact with the valve member 81. Four legs 85 extend axially and radially outwardly from the central portion 142 and terminate in feet 87. The feet 87 are engageable with receiving notches 89 (FIG. 3) formed in the body of the plunger 64 to secure the spring retainer 84 within the bore 64D of the plunger 64 and hold the low constant spring 82 in compressive engagement with the valve seat 83. The degree to which the spring retainer 84 securely holds the spring 82 can be adjusted by varying the length and / or width of the legs 85 and feet 87. 17, a centering feature such as an angled surface 93 can be provided in contact with one end of the spring 82 to assist in centering the spring 82 on the spring contact surface 95 of the spring retainer 84, thus resulting in more repeatable operation. Alternatively, the centering feature can be a protruding ring or multiple protrusions (not shown) extending axially inward from the outer edge of the spring surface 95 and positioned to align the outer edge of the spring 82 in a desired location.

[0090] As the valve member 81 moves axially forward, gas can escape from the housing 20 through a vent gap 148 (FIG. 16) between the valve member 81 and the outer end 64B of the plunger 64. Increasing the size of the vent gap may allow for a higher flow rate. Increasing the length of the valve member 81 may allow for easier reassembly of the pressure relief valve 34 into the internal fault detector 22 after actuation. A ring or other graspable member 107 may be attached to the outer end of the valve member 81 to allow for manual venting of the housing 20 (i.e., by pulling the valve member 81 forward). Combining the internal fault detector and pressure relief valve into a single device avoids the need for two openings in the housing 20.

[0091] The dust cover 97 may be placed over and inserted into the pressure relief valve 34 to prevent the ingress of debris or other material from the external environment into the pressure relief valve 34 while still allowing the release of fluid. The dust cover 97 may be configured to float in and out to accomplish these functions. The dust cover 97 preferably covers both the outer end 64B of the plunger 64 and the outer end 56D of the barrel 56, and may have an outer lip 111 (as shown in the embodiment of Figures 16 and 17) that extends axially inwardly and overlaps a portion of the outer end 56D of the barrel 56. The dust cover 97 may include a mounting tab 99 on its outer surface that may be oriented vertically or horizontally to assist in identifying when the pressure relief valve 34 is properly installed.

[0092] A plurality of insert tabs 101 (FIG. 18B) may be provided on the inner end of the dust cover 97 to facilitate installation of the pressure relief valve 34 by allowing the valve 34 to be rotated until the feet 87 of the spring retainer 84 engage the receiving notches 89. The insert tabs 101 are sized and positioned to engage with a plurality of corresponding insert tabs 103 provided on the outer edge of the central portion 142 of the spring retainer 84. The insert tabs 101 and / or the insert tabs 103 may have rounded edges, as best shown in FIGS. 18A-B, to prevent the pressure relief valve 34 from being easily twisted and thereby stripped from the internal fault detector 22 after it is installed.

[0093] To further assist with installation, the dust cover 97 may be provided with crosshairs or marks or other visual indicia to assist in proper orientation of insertion of the pressure relief valve 34 and dust cover 97. Alternatively, or in addition, one or more guide channels (not shown) may be formed in the bore 64D of the plunger 64 to receive and guide the feet 87 into the receiving notches 89.

[0094] The exact order of assembly of the component parts to install the internal fault detector 22 is not critical. As best shown in FIG. 14B, the slot 104 of the inner end 64A may have a wider rear opening 104A. In one exemplary embodiment for assembling the internal fault detector 22, the shuttle 72 is inserted into the interior of the inner end 64A through the wider opening 104A and then advanced forward until the upper and lower portions 132, 134 are interposed between the slots 102, 104, respectively, to prevent relative rotation. The ejection spring 70 may be inserted into the inner end 64A through the bore 64D such that the end of the spring 70 contacts the flanged surface 131 of the shuttle 72. The assembly of the inner portion 64A, shuttle 72, and spring 70 may be slid into the bore 56C of the inner portion 56A such that the ejection spring 70 is biased against the inner end 56E of the barrel 56. The shuttle 72 can be pushed rearwardly toward the inner end 56E to compress the spring 70. The trigger pin 50 can be inserted through the chamfered guide opening 77 into the trigger notch 139 to lock the shuttle 72 and plunger 64 in the armed position within the barrel 56. In embodiments where the trigger pin 50 is fastened to the spindle 31 by an interference fit, it may be desirable to position the spindle 31 and trigger pin 50 simultaneously. The locking bar 110 can then be installed as described above to prevent relative axial movement between the barrel 56 and the plunger 64.

[0095] The inner portion 56A can be snap-fit ​​into a groove 91 in the splash guard 44 and held therein by a resilient outer edge 91A of the groove 91 (FIG. 3). A longitudinally extending retention arm 92 can be provided on the exterior surface of the barrel 56 to better engage and hold the outer edge 91A. The groove 91 engages and grips the barrel 56 when it is received in the groove 91. A seal 74 can be interposed between the inner portion 56A and the outer portion 56B as the engagement of the two portions of the barrel 56 is guided by the positioning of the key 59 within the slot 86 (FIG. 6). The collar 58 can then be threaded onto the corresponding outer threads on the outer rearward extension 113 of the outer portion 56B. When the collar 58 is fully threaded, the inward flange of the collar 58 compresses the flange 76 (FIG. 10A) of the inner portion 56A against the outer rearward extension 113 of the outer portion 56B, thereby locking the two portions of the barrel 56 against relative axial movement.

[0096] The pressure relief valve 34 can then be assembled by threading the spring 82 over the moveable valve member 81 and then threading the spring retainer 84 over the valve member 81. The pressure relief valve 34 assembly can be inserted into the outer end 64B of the plunger 64 and the feet 87 are engaged with the receiving notches 89 to secure the pressure relief valve 34 in place, with engagement of the locating tabs 103 on the spring retainer 84 with the locating tabs 101 on the dust cover 97 for proper insertion and rotation of the pressure relief valve 34.

[0097] The shoulder 46A (FIG. 3) of the spacer ring 46 may be placed over and supported by the upper periphery of the splash guard 44. The diaphragm 40 may then be placed between the spindle 31 and the support wheel 35 by inserting the spindle 31 through the centrally located openings of the diaphragm 40 and the support wheel 35. The assembly of the spindle 31, diaphragm 40, and support wheel 35 is concentrically positioned over the spacer ring 46, and the shell 33 is threaded onto a correspondingly threaded outer portion of the splash cover 44 to complete the assembly of the actuator mechanism 30. The outer portion 56B may then be inserted forward through the opening 24, and the gasket 63 and nut 65 may then be secured to the outer portion 56B to secure the internal fault detector 22 in place on the transformer 16.

[0098] According to an exemplary embodiment of the present invention, the following steps may be performed to reset the internal fault detector 22 from the triggered position: First, remove the pressure relief valve 34 by depressing the foot 87 through the notch 89 of the plunger 64, thereby allowing the pressure relief valve 34 to be withdrawn from within the bore 64D (see FIGS. 3 and 17). Removal of the pressure relief valve 34 may be facilitated by pulling on the ring 107 or the mounting tab 99.

[0099] Following this, an elongated object can be inserted into the bore 64D and advanced therethrough until it pushes the shuttle 72 against the force exerted by the ejection spring 70. Continued rearward movement of the shuttle 72 engages the ramped surface 137 of the shuttle 72 with the ramped surface 118A of the locking bar 110, causing the locking bar 110 to pivot at an upward angle relative to the inner portion 56A of the barrel 56 (see Figures 11, 13A and 14F). At this stage, the front surface 116-1 of the arm portion 116 is no longer in contact with the retention surface 106B-2 of the projection 106B, so that the contact of the elongated object with the plunger 64 can be used to apply a rearward force to advance the plunger 64 in a rearward direction. When the trigger notch 139 and the trigger pin 50 are vertically aligned, the trigger pin 50 will seat in the trigger notch 139. At this point, surface 118B of locking bar 110 slides along inclined surface 135 of shuttle 72, causing second longitudinal end 109 of locking bar 110 to pivot back downward and engage protrusions 106B and 106C of plunger 64, preventing further movement, thereby returning internal fault detector 22 to the ready-to-operate position.

[0100] The outer end 56D of the barrel 56 can receive a locking device that prevents the plunger 64 from inadvertently moving to its actuated position before the internal fault detector 22 is enabled. For example, FIG. 19 shows the internal fault detector 22 with a locking device in the form of a shipping lock 90 installed. The shipping lock 90 is attached to the outer end 56D of the barrel 56 and prevents the plunger 64 from moving forward within the bore 56C through interaction with a locking bar 110, as described below. The shipping lock 90 can be kept in place until installation of the transformer 16 is complete and can be configured to allow the diaphragm 40 to float when the shipping lock 90 is in place, for example, by slightly compressing the ejection spring 70 such that the trigger pin 50 is positioned slightly away from the trigger notch 139 of the shuttle 72 (best shown in FIG. 21A). After the transformer 16 is installed, the shipping fasteners 90 are removed before the transformer 16 is placed into service.

[0101] Operation of the shipping fastener 90 is shown in Figures 21A and 21B. According to an exemplary embodiment, installation of the shipping fastener 90 includes pressing the shipping fastener 90 against the dust cover 97, which in turn presses against the outer end 64B of the plunger 64. Figure 21B is a detailed view showing the engagement of the locking bar 110 with the catch portion 162 of the barrel 56. Rearward movement of the plunger 64 causes the rearward facing surface 106C-1 of the third projection 106C of the plunger 64 to engage with the forward facing surface 116-1 of the arm portion 116 of the locking bar 110. This movement causes further engagement of the rearward facing surface 116-2 of the arm portion 116 with the forward angled surface 135 of the shuttle 72, thereby pushing the shuttle 72 rearward. Immediately after engagement of the arm portion 116 with the shuttle 72, the rear end 116-3 of the arm portion 116 engages a catch 162 disposed on the inside surface of the inner portion 56A of the barrel 56. The engagement with the catch 162 prevents the locking bar 110 from lifting and further prevents the aforementioned components (e.g., locking bar 116, plunger 64, shuttle 72, etc.) from moving further rearward as the barrel 56 transmits these forces to the housing 20 of the transformer 16. Furthermore, the locking bar 110 cannot pivot upwards at its second end, thus preventing forward movement of the shuttle 72.

[0102] In the illustrated embodiment, the shipping fastener 90 includes a pair of inwardly directed flanges 92 (best seen in FIG. 20A) that engage receiving slots 94 in the outer end 56D of the barrel 56. Referring to FIG. 20B, the receiving slot 94 is formed with a receiving portion 96 that opens toward the outer end 56D of the barrel 56 to receive the flanges 92, and a locking portion 98. The flanges 92 can be fully inserted into the receiving portion 96, and then the shipping fastener 90 can be twisted to lock the flanges 92 into the locking portion 98 of the receiving slot 94. In one embodiment, the outer end 56D is provided with four receiving slots 94 that are equally spaced at 90° intervals. In one embodiment, the outer end 56D is provided with two receiving slots 94 that are equally spaced at 180° intervals. Thus, the shipping fastener 90 is secured to the barrel 56 by inserting the flanges 94 into the receiving portions 96 and rotating the shipping fastener 90, for example, 45° or 90° in some embodiments. Other numbers and orientations of receiving slots 94 and flanges 92 may be used to secure the shipping fastener 90 to the internal fault detector 22. In some embodiments, the location and orientation of the slots 94 and flanges 92 are such that, when properly installed, they result in a particular orientation of the shipping fastener 90. Thus, for example, the shipping fastener 90 may include an extending arm 105 to provide an easily observable visual indication that the shipping fastener 90 is installed in the correct orientation. For example, as shown in FIG. 19, the arms 105 extending vertically may indicate that the shipping fastener 90 is installed correctly.

[0103] Providing a mechanical lock on the shipping fastener 90 can provide more resistance to locking the shipping fastener 90 in place. For example, in the exemplary embodiment of FIGS. 20A-B, a small recess 156 is formed on the support protrusion 158 of the shipping fastener 90. A corresponding engageable protrusion 160 is formed on the outer end 56D of the barrel 56, which engages and fits within the recess 156 when the shipping fastener 90 is in its fully installed position. The shipping fastener 90 can be provided with an opening 100 for receiving a ring (shown as ring 107) or other graspable member of the pressure relief valve 34 when the shipping fastener 90 is secured. The opening 100 can include a radial extension 102 to allow the ring 107 to easily pass through the shipping fastener 90 in only one orientation. Once the internal fault detector 22 is deployed and ready for use, it can be placed in its inactivated position by removing the shipping fastener 90. Once the shipping fastener 90 is removed, the rearward force on the plunger 64 is removed, allowing the ejection spring 70 to move the shuttle 72 and the rear end 110-3 of the locking bar 116 forward, thereby releasing the rear end 116-3 of the locking bar 110 from the catch 162.

[0104] Other types of engagements can also be used to releasably secure the shipping fastener 90 to the barrel 56 prior to deployment. For example, a protrusion could be provided in place of the flange 92 to frictionally engage an appropriately located cavity in place of the slot 94. Furthermore, the orientation of the flange 92 and the slot 94 could be reversed, such that the flange 92 is formed on the barrel 56 and a corresponding slot 94 is formed in the shipping fastener 90. Alternatively, the locking member can be secured by a threaded engagement with the barrel 56. Alternatively, the locking device can be a pin (not shown) that passes through an opening in the plunger 64, thus preventing longitudinal movement of the plunger 64 within the barrel 56 until the pin is removed. The locking device can also be, for example, a sliding or pivoting or breakaway member at the outer end of the plunger 64 that prevents forward movement of the plunger 64 within the barrel 56.

[0105] In some embodiments, a one-way flow obstruction is provided within the pressure relief valve 34. The one-way flow obstruction preferentially reduces fluid flow through the pressure relief valve 34 in one direction compared to fluid flow in the opposite direction. The one-way flow obstruction may serve to prevent the actuator mechanism 30 from being actuated due to a change in pressure within the housing 20 caused by operation (including manual operation) of the pressure relief valve 34. In particular, the inventors have found that some embodiments of the actuator mechanism 30 are so sensitive that a change in pressure caused by manual operation of the pressure relief valve 34 may trigger the actuator mechanism 30 to move the indicator mechanism 32 to the actuated configuration. Such unintended actuation may occur particularly in embodiments in which the interior of the housing 20 is maintained at a vacuum, i.e., a pressure below atmospheric pressure.

[0106] 22A and 22B, in one embodiment, the one-way flow obstruction is an axially movable sealing sleeve 155 disposed concentrically around the valve member 81. In FIG. 22A, the interior of the housing 20 is pressurized relative to the outside atmosphere (i.e., the pressure inside the housing 20 is greater than the surrounding atmospheric pressure) and when the pressure relief valve 34 is actuated (either manually or to allow excess pressure within the housing 20 to be released), the flow of fluid through the vent gap 148 (as indicated by arrows 157) pushes the sealing sleeve 155 axially outwardly around the valve member 81 to a flow position. Thus, the flow of fluid through the vent gap 148 is relatively unimpeded by the sealing sleeve 155. In some embodiments, this configuration of the sealing sleeve 155 meets the IEEE flow rate specifications for pressure relief valves when venting the housing 20 under overpressure conditions.

[0107] 22B, when the interior of the housing 20 is at vacuum pressure relative to the outside atmosphere (i.e., the pressure inside the housing 20 is less than the surrounding atmospheric pressure), when the pressure relief valve 34 is manually actuated, inward fluid flow through the vent gap 148, represented by arrows 159, causes the sealing sleeve 155 to transition inwardly such that it partially or completely blocks the vent gap 148. This reduces (or, in some embodiments, eliminates) the inflow of fluid into the housing 20 sufficiently to avoid inadvertently triggering the actuator mechanism 30. In this manner, the sealing sleeve 155 does not significantly interfere with the desired venting function provided by the pressure relief valve 34 that allows applicable performance specifications for the pressure relief valve 34 to be met, but does reduce inward fluid flow into the housing 20 under vacuum pressure sufficiently to avoid the unintended effect of triggering the actuator mechanism 30 when the pressure relief valve 34 is actuated, including when the pressure relief valve 34 is manually actuated.

[0108] In alternative embodiments, other structures may be used to provide a one-way flow block. For example, a two-way or three-way umbrella valve may be used to retard the ingress of fluid into the housing 20 while preferentially allowing fluid to exit the housing 20 when the pressure relief valve 34 is activated. A two-part seal may be used with an O-ring in floating contact with a breathable base, where the O-ring is drawn into sealing engagement with the breathable base when the interior of the housing 20 is at a vacuum relative to the external atmosphere, and the O-ring is pushed away from sealing engagement with the breathable base when fluid is exiting the interior of the housing 20 (i.e., when the interior of the housing 20 is pressurized relative to the external atmosphere), thereby minimizing any reduction in fluid flow. Various flow restrictors, or shapes and dimensions of various components of the pressure relief valve 34 may be used to prioritize the outflow of fluid from the housing 20 over the inflow of fluid into the housing 20. Various check valves or one-way valves may be used, etc., to restrict the inflow of fluid into the housing 20.

[0109] The internal fault detector 22 optionally includes a facility for generating a control signal when the internal fault detector 22 is activated. The facility may include one or more sets of electrical contacts that open or close when the internal fault detector 22 is activated. The electrical contacts may be operable to generate the control signal, for example, by passage of the plunger 64 within the bore 56C or by movement of the trigger pin 50. The electrical contacts may be in a first position (either closed or open) when the plunger 64 is in its armed position. When the internal fault detector 22 is activated, the electrical contacts are switched such that they are in a second position (either open or closed) when the plunger 64 is in its actuated position. The facility may include other mechanisms, such as optical fibers or cellular communication signals, for communicating a control signal that indicates to a transmitter that the internal fault detector 22 has been activated. The transmitter may generate a fault signal, such as a radio signal or a cellular telephone transmission, in response to the control signal.

[0110] In one particular embodiment, a magnetic sensor is used to provide an indication that the internal fault detector 22 has been activated. In one embodiment, the magnetic sensor uses the Hall effect to provide an indication that the internal fault detector 22 has been activated. The Hall effect utilizes the change in voltage across an electrical conductor caused by a change in a magnetic field.

[0111] An exemplary embodiment of such a sensor 210 is shown in Figures 23A and 23B. In one exemplary embodiment, a magnetic element 212 is attached to the plunger 64 such that when the internal fault detector 22 is activated, the magnetic element 212 moves longitudinally forward. In some embodiments, the magnetic element 212 is attached to the forward end of the plunger 64.

[0112] A corresponding Hall effect sensor 214 is mounted in a stationary manner to a component of the internal fault detector 22 that does not move during activation (e.g., to the shell 33) or to the housing or tank 20 of the electrical device to which the internal fault detector 22 is attached. In this manner, when the internal fault detector 22 is activated, the magnetic element 212 will move forward while the Hall effect sensor 214 remains stationary, resulting in relative movement between the magnetic element 212 and the Hall effect sensor 214 that can be detected by the Hall effect sensor 214.

[0113] Movement of the magnetic element 212 will cause a change in voltage in the electrical conductor contained within the Hall effect sensor 214, which can be detected and output via suitable equipment, for example via a wired connection 216 to a processor as in the illustrated embodiment, or via wireless communication equipment allowing communication of the detected signal, for example via a cellular communication system or a local wireless communication system.

[0114] This signal can be used to provide an alert to a remote location, such as a central control station, that the internal fault detector 22 has been activated, thereby providing rapid notification of a possible fault within the electrical device in which the internal fault detector 22 is installed. Such remote notification can also avoid or reduce the frequency of manual visual inspection of the internal fault detector 22, since a user can be remotely notified that the internal fault detector 22 has been activated without requiring an on-site visual inspection to make such a determination.

[0115] Although in the illustrated embodiment, the magnetic element 212 is shown and described as being movable during operation of the internal fault detector 22, in alternative embodiments, the magnetic element 212 may be held in a stationary position during operation of the internal fault detector 22 while the Hall effect sensor 214 may be mounted to move during operation of the internal fault detector 22, or the two components may be mounted in any suitable manner that causes relative motion between them when the internal fault detector 22 is activated.

[0116] The magnetic element 212 and / or the Hall effect sensor 214 may be enclosed within any suitable housing or component of the internal fault detector 22, for example, to protect these components from adverse environmental conditions. For example, in some embodiments, the magnetic element 212 may be mounted inside the dust cover 97. In some embodiments, the Hall effect sensor 214 may be protected from adverse environmental conditions by being enclosed within a suitable housing having a front portion 220, a rear portion 222, and a sealing gasket 224.

[0117] An embodiment of the internal fault detector can be designed to protrude only a minimal amount from the housing 20. Such a design can limit, for example, any surfaces on which snow and ice may accumulate.

[0118] In some embodiments, the entire internal fault detector 22 is located outside the housing 20 of the transformer 16. For example, instead of the opening 24, a fluid flow path can be provided to allow fluid communication between the interior of the housing 20 and the externally located internal fault detector 22. Such a fluid flow path allows the externally located internal fault detector 22 to detect a sudden increase in pressure within the housing 20. In such an embodiment, the fluid flow path should be fluidly connected to or integral with a connection structure sealingly engaged with the bottom end of the splash cover 44 such that the pressure acting on the face 40B of the diaphragm 40 is the same as the pressure within the housing 20. In an exemplary embodiment, the fluid flow path is provided by a threaded joint between a corresponding thread of the external rigid connector and a threaded orifice located on the surface of the housing 20. In some embodiments, the threaded orifice can be located in the side wall of the housing 20 above the fluid 26 or in the lid 21.

[0119] Some exemplary embodiments of the present invention described above employ the use of a locking bar (e.g., locking bar 110) that interacts with a shuttle (e.g., shuttle 72). The shuttle functions as an interface for decoupling the indicator mechanism from the actuator mechanism by interfacing with both the trigger pin (of the actuator mechanism) and the locking bar (of the indicator mechanism). Other embodiments of the present invention provide a means for decoupling the indicator mechanism from the actuator mechanism without the use of an intermediate shuttle.

[0120] 24A-24C illustrate an exemplary internal fault detector 200 (only a portion of which is shown) that includes a laterally oriented locking bar 250 as a means for decoupling the indicator mechanism 32-1 from the actuator mechanism 30-1. The internal fault detector 200 may be similar to the internal fault detector 22 described above, except for the differences noted. FIG. 24A illustrates a configuration in which the indicator mechanism 32-1 and the actuator mechanism 30-1 are unactuated (or armed). As shown, the locking bar 250 includes a protrusion 252 that is proximate the trigger pin 50. A spring 254 is provided at a longitudinal end of the locking bar 250 to bias the locking bar 250 laterally against the plunger 64-1.

[0121] Although hidden from view in FIG. 24B, the spring 254 of the locking bar 250 is shown compressed against the inner surface of the splash guard 260 in the inactivated configuration. Referring to FIG. 24A, the compressed spring 254 biases the locking bar 250 transversely to the central axis of the plunger 64-1 and away from the surface of the splash guard 260 against which the spring 254 is compressed. This biasing force acts against the trigger pin 50 by the projection 252 in the inactivated configuration, thereby preventing movement of the locking bar 250. As discussed in other embodiments herein, the spring 70 biases the plunger 64-1 toward the activated configuration of the indicator mechanism 32-1. As best shown in FIG. 24A, the plunger 64-1 is held in the inactivated position by the engagement of the forward facing surface 206-1 of the projection 206 against the rearward facing surface 250-1 of the locking bar 250.

[0122] When actuator mechanism 30-1 is triggered, trigger pin 50 disengages from projection 252, allowing locking bar 250 to move freely laterally under the biasing force applied by spring 254. Locking bar 250 advances laterally (away from spring 254) until it is blocked by an opposing surface (not shown) of splash guard 260, similar to the actuated configuration shown in FIG.

[0123] As shown, two slots 256 are defined in the locking bar 250, both of which are configured to align with the position of the protrusion 206 when the internal fault detector 200 is in the activated configuration. The dimensions of the slots 256 may be related to the dimensions of the protrusion 206 such that when they are aligned with one another, the slots 256 have a greater overall width than the protrusion 206. In this manner, when the actuator mechanism 30-1 is triggered and the locking bar 250 is free to move laterally under the action of the spring 254, the protrusion 206 and the slots 256 align, as best shown in FIG. 24C, allowing the plunger 64-1 to advance, thereby indicating that a fault has occurred.

[0124] 25A-25C illustrate an exemplary internal fault detector 300 (only a portion of which is shown) that includes a locking bar 350 as a means for decoupling the indicator mechanism 32-2 from the actuator mechanism 30-2. The internal fault detector 300 may be similar to the internal fault detector 22 described above, except for the differences noted. FIGS. 25A and 25B illustrate a configuration in which the actuator mechanism 30-2 and the indicator mechanism 32-2 are unactuated. FIG. 25B illustrates that the plunger 64-2 is housed within the barrel 56-2 on which the locking bar 350 is mounted. FIG. 25A illustrates the relative positioning of the components with the barrel 56-2 omitted. In the illustrated embodiment, the locking bar 350 features a similar overall geometry compared to the overall geometry of the locking bar 110, although this is not required. Proximate a first longitudinal end 352, the locking bar 350 has a downwardly extending portion 354 and an upwardly extending portion 356. At an opposite, second longitudinal end 358, the locking bar 350 has a downwardly extending arm portion 360.

[0125] FIG. 25B illustrates the installation of the locking bar 350 onto the barrel 56-2. The barrel 56-2 includes a groove 380 for receiving the downward extension 354 of the locking bar 350. The barrel 56-2 further includes a spring housing 382 capable of retaining the spring 364 therein. Similar to that discussed in other embodiments herein, the spring 70 biases the plunger 64-2 toward the activated configuration of the indicator mechanism 30-2. When positioned within the indicator mechanism 32-2, the arm portion 360 of the locking bar 350 includes a rearward facing surface 360-1 that engages the forward facing surface 64-2A of the plunger 64-2 and prevents forward movement of the plunger 64-2 in the non-activated configuration shown in FIGS. 25A and 25B.

[0126] The spring 364 biases the locking bar 350 to a vertical angular position as engagement of the spring 350 with the forward facing surface of the upward extension 356 causes the second longitudinal end 358 of the locking bar 350 to pivot upwardly about the end of the downward extension 354. In the unactuated configuration, the rearward facing surface of the upward extension 356 engages the trigger pin 50 of the actuator mechanism 30-2, preventing the locking bar 350 from pivoting and therefore preventing the plunger 64-2 from advancing when the internal fault detector 300 is in the unactuated configuration.

[0127] When actuator mechanism 30-2 is triggered, trigger pin 50 disengages from upward extension 356, thereby allowing locking bar 350 to rotate due to the force exerted by spring 364. This action therefore disengages the surface of locking bar 350 from plunger 64-2, allowing plunger 64-2 to advance, indicating that a fault has occurred, as best seen in FIG. EXAMPLES

[0128] Further embodiments are described with reference to the following examples, which are intended to be illustrative rather than limiting in nature. Example 1.0 - Determining the Spring Constant for Various Diaphragms The spring constant k of various diaphragms was experimentally determined using the laser gravitational method. Briefly, the vertical displacement of an exemplary diaphragm was measured using a laser sensor while adding a weight to the top side of the diaphragm. In this scenario, the force exerted by the added weight under gravity (F=mg, where m is the added mass and g is the gravitational acceleration, i.e., 9.8m / s / s) is equal to kx, where k is the spring constant and x is the measured displacement.

[0129] It has been experimentally determined that a diaphragm having a double fold and made from polybutylene terephthalate, such as that shown in PCT Publication WO 2011 / 153604, has a spring constant on the order of 1.23 N / mm (7 lbs / in). In contrast, an exemplary diaphragm having only a single fold and made from a fluoroelastomer material had a spring constant on the order of 0.30 N / mm (1.7 lbs / in).

[0130] While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions, and subcombinations thereof. For example: The single orifice 38 shown in the drawings could be replaced with a number of smaller orifices, or a porous membrane through which air can flow but not fluid 26, or some other configuration that limits the rate at which the pressure in chamber 36 can follow fluctuations in ambient pressure within housing 20.

[0131] The shape of the orifice 38 may be annular, as shown, or it may be some other shape. Instead of a chamber 36 that is closed on one side by a flexible diaphragm 40, the actuator mechanism 30 may include a chamber that is closed by both a relatively high mass piston and a relatively low mass piston, as described in U.S. Pat. No. 5,078,078 to Cuk. The two pistons may be concentric with one another and connected to springs having the same spring constant. The inertia of the high mass piston prevents it from moving in response to a sudden pressure increase. Both the high mass piston and the low mass piston may move in response to slow pressure variations. Relative motion between the high mass piston and the low mass piston may be used to release the indicator mechanism 32.

[0132] The chamber 36 may comprise the interior of a bellows having rigid end faces joined by a flexible cylindrical wall. Relative movement of the rigid end faces can trigger the indicator mechanism 32 by a suitable mechanical linkage. One or more openings in the bellows prevent the end faces from moving in response to slow variations in ambient pressure within the housing 20.

[0133] In a non-preferred embodiment of the present invention, diaphragm 40 may be replaced with a rigid or semi-rigid movable piston that displaces toward chamber 36 in response to a sudden increase in pressure within housing 20 .

[0134] a chamber 36, closed on one side by a diaphragm as described above, or any of these alternative mechanisms, constitutes a "pressure rise detection means" that responds to a pressure rise within the housing 20 by displacing a portion of the cavity wall with sufficient force to operate the indicator mechanism 32; or The plunger 64 may have a shape different from that described above, for example, the plunger 64 may include a flag, rod, plate, etc. having a hidden portion that is hidden and not visible within the bore 56C when the plunger 64 is in its armed position and is revealed when the plunger 64 is moved to the triggered position. The plunger 64 as described above and any of the alternative forms described herein for displaying an indication that the internal fault detector has detected a fault constitutes an "indicator means."

[0135] It is therefore intended that the following appended claims, as well as any claims hereafter introduced, be interpreted to include all such modifications, permutations, additions, and subcombinations as are within their true spirit and scope.

[0136] While a number of exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain modifications, permutations, additions, and subcombinations thereof. It is therefore intended that the following appended claims, and any claims hereafter introduced, be interpreted to include all such modifications, permutations, additions, and subcombinations consistent with the broadest interpretation of the entire specification.

Claims

1. 1. A fault detector for indicating the occurrence of a sudden pressure rise within a housing of an electrical device, comprising: Barrel and an actuation mechanism in fluid communication with an interior of the housing, a sealed chamber having an orifice communicating between an environment outside the chamber and an interior of the chamber; a pressure rise detection means comprising an actuating member having a pressure sensitive surface area available for pressure to act upon, said actuating member being movable in response to a pressure differential between the interior of the housing and the interior of the chamber, said actuating member having a spring constant of 0.88 N / mm or less; an actuation mechanism including: a plunger within the bore of the barrel, the plunger being biased forwardly within the barrel and normally held in an armed position by the actuating member; Equipped with When the pressure differential exceeds a positive threshold, the actuation member is moved to allow the plunger to move forward to a trigger position. Fault detector.

2. The actuating member includes a diaphragm in sealing engagement with the chamber at a sealing surface of the chamber to define a portion of a surface of the chamber; the diaphragm includes a cup portion, the cup portion including a downwardly facing recess extending radially inward; 2. The fault detector of claim 1, wherein the diaphragm further includes a single annular ridge disposed inside the lip of the diaphragm, and the downwardly facing recess of the cup portion is disposed on an inner edge of the annular ridge.

3. 3. The fault detector of claim 2, wherein the diaphragm comprises a top hat diaphragm, and the single annular ridge is provided during at least a portion of the period during which a sudden pressure rise is detected.

4. The actuating member is movable to move the actuating member from a non-actuated configuration to an actuated configuration; the fault detector further comprises a locking member having a first position and a second position, in the first position the locking member is positioned to restrain forward movement of the plunger within the barrel to prevent a force applied to the plunger from being transmitted to the actuating member, and in the second position the locking member is positioned to allow forward movement of the plunger, the plunger being initially held in the non-actuated configuration by the locking member when the locking member is in the first position and being forwardly movable within the bore of the barrel when the locking member is in the second position; The fault detector of claim 1 , wherein the locking member is movable from the first position to the second position in response to movement of the actuating member from the unactuated configuration to the actuated configuration.

5. Further comprising a shuttle urged forward within the barrel by a biasing force, the shuttle being initially held in the non-actuated configuration by the actuating member and configured to move forward to transmit the biasing force to the plunger as the actuating member moves from the non-actuated configuration to the actuated configuration, the shuttle being configured to displace the locking member from the first position to the second position when the actuating mechanism is triggered. A fault detector as claimed in claim 4.

6. In the first position, an arm portion of the locking member engages with a first protrusion of the plunger to prevent forward movement of the plunger within the barrel; 6. The fault detector of claim 5, wherein in the first position, the arm of the locking member engages a second projection of the plunger to restrain rearward movement of the plunger within the barrel.

7. 5. The fault detector of claim 4, wherein in the second position, the arm of the locking member is deflected by the shuttle to disengage the arm of the locking member from the first projection of the plunger.

8. 8. The fault detector of claim 7, wherein the shuttle includes a first ramped surface that is complementary to and in contact with a second ramped surface of the locking member, the first ramped surface and the second ramped surface being configured such that forward horizontal movement of the shuttle causes vertical movement of a first end of the locking member via sliding displacement of the second ramped surface relative to the first ramped surface.

9. The fault detector of claim 8 , wherein the locking member is moved from the first position to the second position by sliding the first angled surface over the second angled surface.

10. 10. The fault detector of claim 9, wherein the stop member has a third position in which the stop member is positioned to prevent further forward movement of the plunger.

11. 5. The fault detector of claim 4, wherein the shuttle includes a third ramped surface that is complementary to and in contact with a fourth ramped surface of the locking member, the third ramped surface and the fourth ramped surface being configured such that rearward horizontal movement of the shuttle causes vertical movement of the first end of the locking member via sliding displacement of the fourth ramped surface relative to the third ramped surface.

12. 1. A method of operating an internal fault detector, comprising: allowing a pressure sensor to be activated by a sudden increase in pressure; moving a retaining pin in response to the actuation of the pressure sensor to enable a locking member to move from an unactuated configuration to an actuated configuration; allowing a plunger, which is retained by the locking member when the locking member is in the inactivated configuration, to be displaced forward by a biasing force when the locking member is in the activated configuration to provide an indication that a sudden pressure rise has occurred; Including, the locking member in the unactuated configuration is configured to prevent a force applied to the plunger from being transmitted to the retaining pin. method.

13. The step of moving the retaining pin further comprises: allowing a shuttle, initially held in place by said retaining pin, to be displaced by a biasing force upon movement of said retaining pin; displacing the first end of the locking member from a first position to a second position by sliding a first angled surface of the shuttle against a complementary second angled surface of the locking member to translate horizontal movement of the shuttle into vertical displacement of the first end of the locking member; The method of claim 12, comprising:

14. 14. The method of claim 13, further comprising the step of allowing the locking member to move from the second position to a third position in which the locking member prevents rearward movement of the plunger after allowing the plunger to be displaced.

15. 5. The fault detector of claim 4, wherein the locking member is biased laterally within the barrel by a first biasing force and the plunger is biased forward within the barrel by a second biasing force, the locking member being initially held in the unactuated configuration by a retaining pin, and wherein the first biasing force displaces the locking member from the first position to the second position when the actuating member is moved.

16. A fault detector as described in any one of claims 1 to 11 or 15, further comprising a static seal having a first end fixedly held to the plunger and a second end fixedly held to the barrel, the static seal having a central portion that allows relative movement between the plunger and the barrel while maintaining a seal between the interior of the housing and the environment external to the housing as the fault detector moves from a ready-to-operate configuration to a trigger configuration.

17. A method as described in any one of claims 12 to 14, further comprising the steps of holding a first end of a static seal in sealing engagement with a barrel that houses the plunger and holding a second end of the static seal in sealing engagement with the plunger while a flexible central portion of the static seal slides over itself.

18. A magnetic element; a Hall effect sensor positioned to detect relative movement between the magnetic element and the Hall effect sensor; Equipped with at least one of the magnetic element and the Hall effect sensor is mounted for relative movement during operation of the fault detector; A fault detector according to any one of claims 1 to 11 or 15.

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