Liquid level sensor

An oil level sensing apparatus for determining that the level of oil in an internal combustion engine is above or below a predetermined level comprising:

• a mounting member securely mountable within an opening, defined by a wall of the internal combustion engine, at the level above which it is desired to maintain said oil within said internal combustion engine;
• an electrically conductive output terminal member, insulatively mounted within a hole extending axially through said mounting member, said output terminal extending beyond both surfaces of the wall of said internal combustion engine and terminating with a spring type contact on that end which extends internally to the internal combustion engine;
• a body of semiconductor material having a peak electrical resistivity of between 100 ohm-cm and 200 ohm-cm, said peak resistivity occurring at a temperature between 150.degree. centigrade and 164.degree. centigrade;
• a cylindrical cup having a flange at its open end, constructed of a metal alloy having a thermal coefficient of conductivity closely matching that of the semiconductive material said cup being coated on both its inside and outside surface with a layer of gold;
• said body of semiconductor material having a thickness of less than en one-thousandths of an inch, and a cross section area of between 0.015 and 0.035 square inches;
• a first conducting means, disposed upon the upper surface of said body of semiconductive material, comprising a first layer of nickel approximately 1 micron thick and a second layer of aluminum of between 6 and 12 microns thick, said first layer of nickel being joined to the upper surface of the second layer of aluminum which is joined to the upper surface of said body of semiconductive material;
• a second conducting means, disposed upon the lower surface of said body of semiconductive material, comprising a first layer of nickel approximately 1 micron thick and a second layer of aluminum of 6 to 12 microns thick, said first layer of nickel being joined to the lower surface of the second layer of aluminum which is joined to the lower surface of said body of semiconductive material;
• said first layer of nickel of said second conducting means being joined to the layer of gold on the interior bottom surface of said cup by a solder means less than two thousandths of an inch thick;
• said cup and its attached semiconductor material being mounted upon said mounting member so as to completely enclose that end of said output terminal which terminates with the spring contact and cause said spring contact to make electrical connection with the first layer of nickel of said first conducting means;
• a shield member mounted upon said mounting member and surrounding said cup so as to protect the cup from impact, said shield being so constructed as to permit the free flow of oil around said cup.

An oil level sensing circuit for determining that the level of oil in an internal combustion engine is above or below a predetermined level comprising:

• a mounting member securely mountable within an opening, defined by a wall of the internal combustion engine, at the level above which it is desired to maintain said oil within said internal combustion engine;
• an electrically conducting output terminal member insulatively mounted within a hole, extending axially through said mounting member, said output terminal extending beyond both surfaces of the wall of said internal combustion engine and terminating with a spring type contact on that end which extends internally to the internal combustion engine;
• a body of semiconductor material having a peak electrical resistivity of between 100 ohm-cm and 200 ohm-cm, said peak resistivity occurring at a temperature between 150.degree. centigrade and 165.degree. centigrade;
• a cylindrical cup having a flange at its open end, constructed of a metal alloy having a thermal coefficient of conductivity closely matching that of the semiconductive material said cup being coated on both its inside and outside surface with a layer of gold;
• said body of semiconductor material having a thickness of less than ten one-thousandths of an inch, and a cross sectional area of between 0.015 and 0.035 square inches;
• a first conducting means, disposed upon the upper surface of said body of semiconductive material, comprising a first layer of nickel approximately 1 micron thick and a second layer of aluminum of between 6 and 12 microns thick, said first layer of nickel being joined to the upper surface of the second layer of aluminum which is joined to the upper surface of said body of semiconductive material;
• a second conducting means, disposed upon the lower surface of said body of semiconductive material, comprising a first layer of nickel approximately 1 micron thick and a second layer of aluminum of between 6 and 12 microns thick, said first layer of nickel being joined to the lower surface of the second layer of aluminum which is joined to the lower surface of said body of semiconductive material;
• said first layer of nickel of said second conducting means being joined to the layer of gold on the interior bottom surface of said cup by a solder means less than one-thousandth of an inch thick;
• said cup and its attached semiconductor material being mounted upon said mounting member so as to completely enclose that end of said output terminal which terminates with the spring contact and cause said spring contact to make electrical connection with the first layer of nickel of said first conducting means;
• a 12 volt D.C. power source having a first and second terminal, said first terminal being electrically connected to said mounting member;
• an indicator light having a first and second terminal, said first terminal being electrically connected to said second terminal of said 12 D.C. volt power source, and said second terminal being electrically connected to said output terminal member;
• a shield member mounted upon said mounting member and surrounding said cup so as to protect the cup from impact, said shield being so constructed as to permit the free flow of oil around said cup.