Fail safe control device
AssigneeTemp. Systems, Inc.
InventorsJohn J. Theiss, Paul T. Durst
Life of this patent
Estimating the term…
Abstract
A fail safe temperature control device which consists of a nonelastic container or bulb adapted to be subjected to temperature changes, a capillary tube and a pressure responsive device. The container generally is located in the area in which the heat is to be controlled, typically an oven or other heated area. The capillary tube is connected to the container at a first end and to the pressure responsive device at a second end. The nonelastic container, capillary tube and pressure responsive device form a closed system which is filled with a thermally responsive material. The pressure responsive device operates a control device, typically consisting of a normally closed contact and a normally open contact.
Claims14
A fail safe control device consisting of a nonelastic container adapted to be subjected to temperature changes;
- a capillary tube connected to said container;
- a single pressure responsive device connected to said capillary tube and said nonelastic container, said capillary tube and said pressure responsive device forming a closed system;
- a thermally responsive material filling said closed system;
- a control device operated by said pressure responsive device, said control device containing a normally closed contact and normally open contact, said normally closed contact being a primary operator of a secondary device;
- and a predetermined minimum volume of thermally responsive material maintaining said pressure responsive device in a partially deflected condition so as to maintain said normally open contact in a closed position, said normally open contact opening upon movement of said pressure responsive device to an "at rest" condition which occurs upon loss of said minimum volume of said thermally responsive material, such that when said normally open contact opens, said secondary device is rendered inoperative.
A fail safe control device comprising a nonelastic container adapted to be subjected to temperature changes, said nonelastic container being an elongated bulb contained within an area to be heated;
- a capillary tube connected at a first end to said nonelastic container, said capillary tube consisting of nonelastic tubing extending from said nonelastic container and from said heated area;
- a single pressure responsive device connected to a second end of said capillary tube, said second end being outside of the heated area;
- said nonelastic container, said capillary tube and said pressure responsive device forming a closed system;
- a thermally responsive material filling said closed system and partially expanding said pressure responsive device, said thermally responsive material having the characteristic of reproducible changes in volume when heated or cooled;
- and a control device operated by said pressure responsive device containing a normally closed contact and a normally open contact, said control device operating a secondary device, said normally open contact and said normally closed contact being operated by changes in volume of said thermally responsive material within said pressure responsive device due to changes in temperature surrounding said nonelastic container, said normally closed contact being opened at a specific volume, said specific volume relating to a predetermined temperature, the opening and closing of said normally closed contact controlling said secondary device, said normally open contact being maintained in a closed position by the partial deflection of said pressure responsive device, which partial deflection is produced by a predetermined minimum volume of thermally responsive material in said pressure responsive device, and said normally open contact being permitted to open when the volume of thermally responsive material within the pressure responsive device falls below the predetermined minimum volume thereby allowing said pressure responsive device to move to an "at rest" condition and rendering said secondary device safe.
A method of providing a fail safe control device comprising the following steps:
- (1) adapting a nonelastic container to be subjected to temperatures, (2) connecting a capillary tube to said container, (3) connecting a single pressure responsive device to said capillary tube, such that said nonelastic container, said capillary tube, and said pressure responsive device form a closed system, (4) filling said closed system with a thermally responsive material, (5) operating a secondary device with said control device wherein a normally closed contact is the primary operator of said secondary device;
- and (6) maintaining a minimum volume of said thermally responsive material within said pressure responsive device, said minimum volume being sufficient to partially actuate said pressure responsive device, said partial deflection being sufficient to maintain said normally open contact in the closed position, said normally open contact opening when said pressure responsive device moves to an "at rest" condition which occurs upon loss of said minimum volume of said thermally responsive material such that when said normally open contact opens, said secondary device is rendered inoperative.
Dependencies are inferred from the claim text.