Circuit protection device

A voltage suppression device for suppressing voltage surges in an electrical circuit, said device comprised of:

• a tubular casing formed of an electrically insulating material;
• a first conductive component attached to a first end of said casing;
• a second conductive component attached to a second end of said casing;
• a voltage sensitive element having a predetermined voltage rating, said voltage sensitive element increasing in temperature as voltage applied across said voltage sensitive element exceeds said voltage rating;
• terminals for electrically connecting said voltage sensitive element between said first conductive component and said second conductive component;
• a normally closed, thermal switch comprised of one end of one of said terminals, a surface of said voltage sensitive element and a thermal element, said one end of one of said terminals being maintained in electrical contact with said surface of said voltage sensitive element by said thermal element, said thermal switch being electrically connected in series with said voltage sensitive element between one of said conductive components and said voltage sensitive element, said thermal switch being thermally coupled to said voltage sensitive element wherein said one of said terminals moves from a normally closed position wherein said one of said terminals is maintained in electrical contact with said surface of said voltage sensitive element to an open position wherein said one of said terminals moves out of electrical contact with said surface of said voltage sensitive element to form a gap between said one of said terminals and said voltage sensitive element when the temperature of said voltage sensitive element reaches a level causing said thermal element to soften;
• said one of said terminals including a contact portion and a second portion that extends away from the contact portion;
• a non-conductive barrier operable to move into said gap when said one of said terminals moves to an open position, said barrier preventing line voltage surges from arcing between said one of said terminals and said voltage sensitive element,
• the second portion of said one of said terminals extending over at least a portion of the non-conductive barrier and bending toward the thermal element so that the contact portion is held by the thermal element until said thermal element begins to soften, and
• said non-conductive barrier being biased toward the thermal element, but being constrained from movement toward the thermal element by contact with the second portion of said one of said terminals at a location that is spaced away from the contact portion, until said thermal element begins to soften.

A voltage suppression device for suppressing voltage surges in an electrical circuit, said device comprised of:

• a tubular casing formed of an electrically insulating material;
• a first conductive component attached to a first end of said casing;
• a second conductive component attached to a second end of said casing;
• a voltage sensitive element disposed within said casing, said voltage sensitive element having a first surface and a second surface and a predetermined voltage rating across said first and second surfaces, said voltage sensitive element increasing in temperature as voltage applied across said first and second surfaces exceeds said voltage rating;
• a first terminal electrically connected to said first surface of said voltage sensitive element and said first conductive component;
• a thermal element electrically connected to said second surface of said voltage sensitive element, said thermal element being an electrically conductive solid at room temperature and having a predetermined softening temperature;
• a second terminal formed of a spring metal having one end in electrical connection with said second surface of said voltage sensitive element and another end connected to said second conductive component, said voltage sensitive element sensing a voltage drop between said first conductive component and said second conductive component, said second terminal being bent from a normal and relaxed configuration to be maintained in contact with said voltage sensitive element by said thermal element, said second terminal being inherently biased away from said voltage sensitive element toward said normal and relaxed configuration, wherein said second terminal springs away from electrical contact with said voltage sensitive element softens and breaks said electrical current path if an over-voltage condition sensed by said voltage sensitive element exceeds the voltage rating of said voltage sensitive element and causes said voltage sensitive element to heat said thermal element beyond its softening point;
• and
• an arc shield movable from a first position wherein said arc shield allows contact between said second terminal and said voltage sensitive element to a second position wherein said arc shield is disposed between said second terminal and said voltage sensitive element when said second terminal moves from electrical contact with said voltage sensitive element;
• the second terminal having a contact portion for making electrical contact with the thermal element and a second portion, the second portion extending through the path of the arc shield and blocking the movement of the arc shield until the thermal element reaches its softening point.