US 4,170,138 A · Thermometer and method of making same

Abstract

A thermometer comprises a transparent flexible tubular outer shield, a slender solid rod or core positioned within the shield, the core having a fine groove in the external surface thereof which together with the shield forms a capillary passageway and a bulb housing attached to one end of said tubing to provide a reservoir for expansible temperature indicating fluid. All of the thermometer components can be formed of inexpensive plastic materials. The manufacturing method for the thermometer includes the steps of inserting the core into the tube by expanding the tube and forcing the core therein to form a thermometer stem, and inserting the lower end of the tubing into the bulb housing, filling the bulb housing with the expansible fluid, and sealing the bulb housing and the top of the thermometer stem. The amount of fluid within the bulb housing can be accurately controlled by using a cap having an escape port and a plunger portion to express any excess fluid from the bulb through the escape port during assembly of the cap, after which the escape port is sealed. Alternatively, the end cap may be eliminated and the reservoir filled through a vent hole in the end thereof by immersing the bulb housing in a heated bath of fluid and utilizing vacuum to draw fluid to a level controlled by a clamp which temporarily crimps the flexible tubing into a capillary closing position at a location corresponding to the temperature of the fluid in the heated bath.

Claims40

Dependent claims

A thermometer comprising:

an elongated tubular shield of resilient transparent material having an internal surface which defines an elongated bore extending the length thereof;
a solid core in said bore, substantially coextensive therewith and having a channel in the external surface of said core and extending longitudinally along at least a major portion of said core, the internal surface of said shield cooperating with said channel to form therebetween a capillary passage having an open end and a closed end;
fluid reservoir means connected in liquid-tight relationship with said shield and communicating with the open end of said capillary passage;
and a thermally responsive fluid contained in the interior of said reservoir means;
said fluid being adapted to expand into said capillary passage in response to an increase in temperature.

2 more elements

A method of forming a thermometer comprising the steps of;

forming an elongated core member with a surface groove extending end to end;
directing said core member into a length of flexible tubing;
collapsing said tubing about said core member so as to form a capillary passage with said surface groove;
applying a bulb housing having a filling port over one end of said collapsed tubing so as to form a liquid-tight seal therebetween;
filling said bulb housing with an expansible fluid through said filling port;
and sealing said bulb housing to provide a closed chamber containing said expansible fluid and communicating with said capillary passage.

3 more elements

Dependencies are inferred from the claim text.

Thermometer and method of making same

Life of this patent

Thermometer and method of making same

Life of this patent

Abstract

Claims40