Magnetic pressure indicator for a container

• US 3,946,175 A
• Filed: 12/03/1973
• Issued: 03/23/1976
• Est. Priority Date: 12/03/1973
• Status: Expired due to Term

• Current Assignee: HTL Industries Incorporated
• Original Assignee: HTL Industries Incorporated
• Inventors: Sitabkhan, Abdul N.
• Primary Examiner(s): Tolin, Gerald P.
• Application Number:
  US05/421,152
• Time in Patent Office: 841 Days
• Field of Search: 200/83 R, 200/83 C, 200/83 D, 200/83 L, 200/81.9 M, 337/321, 335/205, 73/40, 73/410, 340/240, 340/242
• US Class Current: 200/83.00L
• CPC Class Codes: A62C 3/08 in aircraft A62C3/0207 takes precedence
• CPC Class Codes: A62C 37/50 Testing or indicating devices for determining the state of readiness of the equipment
• CPC Class Codes: G01L 19/04 Means for compensating for effects of changes of temperature , i.e. other than electric compensation
• CPC Class Codes: H01H 35/247 the switch being of the reed switch type
• CPC Class Codes: H01H 35/28 Compensation for variation of ambient pressure or temperature

Abstract

A temperature compensated pressure indicator adapted to be mounted within a pressure container includes a reservoir housing and housing member welded together to form a secondary pressure chamber. A bellows member is hermetically mounted within the secondary pressure chamber and communicates with the exterior pressure of the container. Mounted on the bellows member is a movable magnetic member adapted to slide on a hollow guide post as a result of any pressure differentials. A reed switch assembly is held stationary in the guide post by a pair of band springs. The switch assembly is electrically connected to a source of power and an external indicator such as a light. When the bellows member moves the magnetic member close to the switch assembly due to a pressure differential, the magnetic field closes the switch assembly to activate the light. The indicator is substantially non-responsive to wide variations in the ambient temperature.

Claims

1. In a pressurized fluid container system subject to temperature variations having a temperature compensated pressure indicator for determining any fluidic leaks from a pressurized storage container of a first fluid such as fire extinguisher fluid in an aircraft and a primary pressure chamber connected to the first fluid pressure in the storage container, the improvement comprising:

a housing having a secondary pressure chamber adjacent the primary pressure chamber and containing a quantity of a second fluid having substantially the same pressure temperature response characteristics as the first fluid in the storage container, the secondary pressure chamber housing primarily formed from a material having a high thermal conductivity capable of transmitting thermal changes in the first fluid of approximately 150°

F per minute to the second fluid within the secondary pressure chamber whereby the pressure temperature response characteristics of both fluids will be substantially the same;

a movable metal bellows formed of welded metal rings sealed in the housing between the primary and secondary pressure chambers and repetitively responsive to their relative pressure changes throughout a temperature range of at least 68°

F to a minus 65°

F;

a magnetic member operatively connected to the metal bellows; and

switch means operatively controlled by the movement of said magnetic member and fluidically isolated from the primary and secondary pressure chambers, including a hollow guide post member attached to the housing and a relatively movable and replaceable switch assembly positioned within the hollow guide post member, the switch assembly including a pair of cantilevered electrodes, the switch means responsive to a predetermined strength of the magnetic force field for moving the cantilevered electrodes to provide a signal representative of any pressure differential in the primary and secondary pressure chambers indicating a leak in the storage container, wherein the metal bellows connected between the primary and secondary pressure chambers includes a post member movably mounted around the guide post member.

2. The invention of claim 1 further comprising a safety means for preventing a destructive deformation of the bellows member including a spring encircling and biasing the bellows member towards an expanded position.

3. The invention of claim 1 wherein the magnetic member is mounted on the post member.

4. The invention of claim 3 wherein a secondary pressure chamber wall is primarily formed from beryllium copper.

5. The invention of claim 1 further including safety means operatively contacting the metal bellows for preventing any deformational movement of the metal bellows.