Temperature-responsive actuator

A temperature and pressure-responsive actuator comprising:

• a support member;
• a spaced pair of thermally expandable members extending longitudinally in parallel alignment, one of said expandable members having one end fixedly connected to said support member and an opposite end connected to a corresponding end of the other expandable member;
• means effective for directing a pressurized flow of fluid into contact with both said expandable members;
• and
• pressure-responsive means restricting the flow of said fluid into contact with one of said expandable members in a first mode of operation wherein the pressure of said fluid is below a predetermined value, and enabling relatively unrestricted flow of said fluid in contact therewith in a second mode of operation wherein the pressure of said fluid is above said predetermined value;
• whereby said one expandable member expands longitudinally in one direction during said first mode, and the other of said expandable members expands longitudinally in an opposite direction during said second mode for retracting said one expandable member.

An actuator responsive to the temperature and pressure of a fluid comprising:

• an outer casing having a fluid inlet and a fluid outlet;
• a thermally expandable inner casing having a fluid inlet and a fluid outlet and being coaxially slidably mounted and radially spaced in said outer casing for thereby defining an annular outer passage for fluid from said inlet to said outlet of said outer casing;
• a thermally expandable elongated member positioned coaxially and radially spaced in said inner casing for thereby defining an annular inner passage for fluid between said inlet and outlet of said inner casing;
• means for restraining axial movement of one end of said elongated member and permitting axial movement relative to the corresponding end of said inner casing;
• means connecting the other end of said elongated member to the opposite end of said inner casing;
• means effective for directing a pressurized flow of fluid into both said passages;
• and
• pressure-responsive means restricting the flow of said fluid through said inner passage in a first mode of operation wherein the pressure of said fluid is below a predetermined value, and enabling relatively unrestricted flow of said fluid through said inner passage in a second mode of operation wherein the pressure of said fluid is above said predetermined value;
• whereby said inner casing expands longitudinally in one direction during said first mode, and said elongated member expands longitudinally in an opposite direction during said second mode for retracting said inner casing.

An actuator for positioning a controllable element in a control system of a gas turbine engine having an axial flow compressor and variable stator vanes, said actuator being responsive to the temperature and pressure of the fluid flowing in said compressor and comprising:

• a cylindrical outer casing having a fluid inlet and a fluid outlet;
• a thermally expandable cylindrical inner casing coaxially slidably mounted and radially spaced in said outer casing for thereby defining an annular outer passage for fluid from said inlet to said outlet of said outer casing, said inner casing being imperforate except for at least one inlet aperture adjacent said inlet of said outer casing for receiving a portion of fluid entering said outer casing, and having an axial outlet for exhausting said fluid;
• a thermally expandable solid rod member positioned coaxially and radially spaced in said inner casing for thereby defining an annular inner passage receiving fluid from said inlet aperture in said inner casing and directing said fluid to said axial outlet of said inner casing, said rod member having a first end fixedly connected to the corresponding end of said outer casing and a second end fixedly connected to a corresponding end of said inner casing;
• means connecting the opposite end of said inner casing to the controllable element and permitting relative axial movement between said inner casing and said rod member;
• and
• a pressure-actuated, spring-loaded, poppet-valve assembly mounted within said axial outlet of said inner casing and effective for restricting the flow of fluid in said inner passage during a first mode of operation wherein the pressure of said fluid is below a predetermined value, and for allowing relatively unrestricted flow of fluid through said inner passage in a second mode of operation wherein the pressure of said fluid is above said predetermined value;
• wherein said inner casing expands longitudinally in one direction during said first mode for actuating the controllable member, and said rod member expands longitudinally in an opposite direction during said second mode for retraction of said inner casing and said controllable element.

A temperature-responsive actuator for a controllable element comprising:

• a cylindrical outer casing having a fluid inlet and a fluid outlet;
• a thermally expandable cylindrical inner casing slidably mounted and radially spaced in said outer casing for thereby defining an annular outer passage for fluid from said inlet to said outlet of said outer casing, said inner casing being imperforate except for a plurality of circumferentially spaced inlet apertures at one end thereof for receiving a portion of said fluid from said inlet of said outer casing, and an axial outlet at the opposite end thereof for exhausting said fluid;
• a thermally expandable rod member positioned coaxially and radially spaced in said inner casing for thereby defining an annular inner passage for fluid received through said inlet apertures and directing said fluid to said axial outlet of said inner casing, said rod member having a first end fixedly connected to one end of said outer casing and a second end fixedly connected to an opposite end of said inner casing;
• and
• means connecting said one end of said inner casing to the controllable element and permitting relative axial movement between said inner casing and said rod member;
• whereby said inner casing expands longitudinally in one direction for actuating the controllable element and said rod member expands longitudinally in an opposite direction for retraction of said inner casing and controllable element.