Motor protector

• US 4,476,452 A
• Filed: 09/27/1982
• Issued: 10/09/1984
• Est. Priority Date: 09/27/1982
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: D'Entremont, John R.
• Primary Examiner(s): Broome, Harold
• Application Number:
  US06/424,826
• Time in Patent Office: 743 Days
• Field of Search: 337/102, 337/107, 337/105, 337/103
• US Class Current: 337/102
• CPC Class Codes: H01H 37/5418 using cantilevered bimetallic snap elements
• CPC Class Codes: H01H 61/02 wherein the thermally-sensitive member is heated indirectly, e.g. resistively, inductively

Abstract

A miniature motor protector particularly suitable for low current applications has a generally rectangular parallelepiped configured metallic housing open at the top and has a bottom wall and side walls extending upwardly therefrom, the side walls having a flange forming a ledge portion at their free ends extending around all four sides. An electrically insulative gasket is disposed on the ledge with a lid having two discrete portions spaced from one another placed on top of the gasket. Extensions of the flange portions are bent over the gasket and lid to clampingly engage them. A heater element having two ends extends between the two portions of the lid with one end electrically and mechanically attached to one portion and the other end electrically and mechanically attached to the other portion. A first switch element is mounted on one of the lid portions and a second switch element is mounted on the bottom wall of the housing with one of the switch elements including a cantilever mounted snap-acting thermostatic member adapted to move into and out of engagement with the other of the switch elements upon selected thermal conditions of the thermostatic member.

Claims

1. A thermally responsive electrical circuit protector comprising an electrically and thermally conductive housing having a bottom wall and upstanding side walls with an open top, the side walls having free ends formed into a ledge portion, a lid disposed on the ledge portion with an electrically insulative gasket interposed therebetween to electrically separate the housing from the lid, means to clampingly attach the lid to the housing, heat responsive electrical switch means disposed in the housing adapted to electrically connect and disconnect the housing and the lid upon the occurrence of selected thermal conditions characterized in that the lid comprises first and second spaced, discrete portions, the first portion mounts a portion of the switch means and the second portion is formed with an elongated portion extending beyond housing to serve as a terminal and a heater element is provided having two opposite ends, one end electrically and mechanically connected to the first portion and the other end electrically and mechanically connected to the second portion.

2. A thermally responsive electrical circuit protector according to claim 1 further characterized in that the heater element is configured as a coil of selected electrically resistive material.

3. A thermally responsive electrical circuit protector according to claim 2 further characterized in that the housing has a longitudinal axis with the first and second discrete portions of the lid spaced along the axis and the coil has a longitudinal axis which is parallel to the longitudinal axis of the housing.

4. A thermally responsive electrical circuit protector according to claim 2 further characterized in that the housing has a longitudinal axis with the first and second discrete portions of the lid spaced along the axis and the coil has a longitudinal axis which is generally perpendicular to the longitudinal axis of the housing.

5. A thermally responsive electrical circuit protector according to claim 1 further characterized in that the lid portions have two opposed surfaces including an internal surface facing a cavity within the housing and an external surface facing away from the housing, and the ends of the heater element are welded to respective portions of the lid on the internal surface thereof.

6. A thermally responsive electrical circuit protector according to claim 1 further characterized in that the lid portions have two opposed surfaces including an internal surface facing a cavity within the housing and an external surface facing away from the housing, and the ends of the heater element are welded to respective portions of the lid on the external surface thereof.

7. A thermally responsive electrical circuit protector according to claim 1 in which the first and second portions of the lid are formed of cold rolled steel and the heater element is formed of a nickel alloy.

8. A thermally responsive protector according to claim 1 further including means to provide environmental protection for the protector comprising a housing of electrically insulative material, the housing formed with a cavity adapted to receive the thermally responsive protector, the protector received in the cavity with the open end of the protector covered by the housing, the housing formed with electrical sockets connectable to the terminals of the protector, the sockets adapted to be pressed onto pins of a connector of an electrical device to be protected.