AU643472B2 - Thermo-mechanical electrical switch - Google Patents

Description

This invention is a modification in the operation of the Thermo-Mechanical Electrical Switch as claimed in claim 1 of Patent Anplication No. 52947/90.

When I first described the operation of the ThermiD-Mechanical Electrical Switch as claimed in claims 1 of Patent Application No.52947/90, wherein l-only had considered the possibilities of the switch being disengaged in the thermal equal state of both the male component I and female component 2, and engagement when 0 the shank 4 thermal energy level was increased in order to engage with recess 5 thereby transmitting electrical energy. However, after some considerable thought I realized that the switch could also work in reverse i.e., where the shank and recess are engaged in the thermal equal state, and disengaged when the recess' thermal energy level is increased greater than the shank.

"The modification of the invention will be now described, by way of an example, with reference to F'igures 3 3 which are schematic-technical graphical 20 representations of the invention in whichg- ;Figure 3 is a cross sectional v:ew of the arranq-- ,ment in a state of thermal equilibrium, a and Figure 4 is a cross sectional view of same with o* female component in a higher thermal level.

There are two principlal components in the

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invention both composed of electrical conductive material, a male component 9 and a female component concentrically mounted and prevented from axial travel from each other by way of typical location arranqement 11. Male component 9 has concentric shank 12 tightly positioned inside concentric recess 14 of femal.e component and connected to a potential difference supply (not shown) forming a continuous electrical circuit as shown in Figure 3.

I.0 When thermal energy 15 is applied to female component 10 said component will begin to expand due to thermal expansion as shown in Figure 4. When sufficient thermal energy is applied to female component t1 recess diameter 14 will expand to the point where it will disengage with shank diameter 12 thereby interrupting the transmission of electrical current between components iv and 10. When thermal energy 15 is no longer applied or removed recess diameter 14 will begin to cool down and contract thereby engaging with shank diameter 12 and reverting to operation as shown in Figure 3.

An example of the practicality of the Thermo-Mechanical Switch will now be given, of a switch arrangement of 100 mm nominal diameter, of carbon steel material.

The linear expansion per unit length per Deg. F for carbon steel 0.00000633 (Machinery's Handbook Industrial Press Inc) Interference Fits H7 for the recess 14 selected and s6 for the shank 12 (Standards Association of Australia., Limits Fits for Engineering, AS 1654).

Recess Diameter 100.000 to 100.035 at 68 Deg F, and Shank Diameter 100.071 to 100.093 at 68 Deg F.

The recess 14 temperature will be increased by 212 Deg F, by thermal energy Linear Expansion 100 mm (nom) x 212 Deg F x 0.00000633 0.134 mm.

Recess Diameter 100.134 to 100.169 at 280 Deg F.

Q~~As can be seen from the example, although we started with an interference fit, we now have a clearance fit between the shank 12 .ind recess 14.

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