Absolute gravity inline measuring apparatus incorporating improved operating features

An inline interferometer arrangement, comprising:

• (a) means for generating a light beam;
• and
• (b) means for defining a variable length leg and a fixed length leg of a light beam path;
• (c) said defining means including splitting and recombining means for receiving and splitting the light beam into first and second split beam portions for travel along said fixed and variable legs and for receiving and recombining the first and second split beam portions into a recombined light beam;
• (d) said defining means also including separate upper and lower reflecting means facing toward one another and disposed above and below and on opposite upper and lower sides of said splitting and recombining means for receiving said second split beam portion and reflecting said second split beam portion toward one another and toward said splitting and recombining means so as to define therewith upper and lower light path portions of said variable length leg of sad interferometer extending in substantially vertical alignment with one another and in opposite directions from said splitting and recombining means, said splitting and recombining means including a first beam splitter for receiving and splitting said light beam into first and second split beam portions and a second beam splitter for receiving and recombining said first and second split beam portions into a recombined light beam, said first beam splitter being disposed between and in vertical alignment with said upper and lower reflecting means, said second beam splitter being offset laterally from said first beam splitter and from said vertical alignment between said upper and lower reflecting means and first beam splitter.

A test mass tracking method comprising the steps of:

• (a) providing an absolute gravity measuring apparatus comprising a housing having an evacuated chamber,
• an interferometer with a variable length leg and a fixed length leg, the variable length leg extending vertically in said housing chamber and defining an upper gravity measuring portion and a lower motion compensating portion extending in opposite directions and in substantially vertical alignment with one another.
• a cart disposed in said chamber and movable along said variable leg of said interferometer, and
• a test mass releasably supported by said cart in said chamber and incorporating a reflector for reflecting a light beam along said variable leg of said interferometer.
• (b) selecting in the same absolute gravity measuring apparatus either one of a drop mode or a throw mode of operation of the cart for tracking the test mass and reflector incorporated by the test mass in free fall along said variable length leg of said interferometer;
• (c) moving the cart relative to the test mass in order to release the test mass and thereby either drop or throw the test mass into free flight depending upon whether the drop mode or throw mode was selected;
• (d) maintaining a substantially constant separation between the moving cart and test mass throughout the free flight of the test mass while absolute gravity measurements are being taken;
• and
• (e) moving the cart relative tot he test mass in order to catch the test mass at completion of taking of the absolute gravity measurements.

A temperature-compensated superspring mechanism, comprising:

• (a) an inertial mass;
• (b) motion compensating means incorporating a support housing and an elongated superspring arrangement being variable in length and supported by said housing and supporting said inertial mass and being operable to maintain said inertial mass in a motionless state in response to motion of said support housing, said superspring arrangement includes an elongated main spring extending vertically and supporting said inertial mass at a lower end of said spring;
• and
• (c) a temperature-responsive lever mechanism connected to said superspring arrangement and being operable to change the length of said superspring arrangement to compensate for temperature-induced changes in effective length of said superspring arrangement, said temperature-responsive lever mechanism including a lever arm pivotally mounted at one end and supporting an upper end of said main spring at an opposite end of said lever arm and an actuating means having an actuating member engaged with said lever arm and a containing body containing a fixed quantity of hydraulic fluid connected in communication with said actuating member, said actuating member being expandable or contractable in volume in response to increase or decrease in ambient temperature for causing axially-directed expansion or contraction of said actuating member and thereby pivoting of said lever arm to provide a change of the length of said main spring to cancel out a temperature-induced change int he length thereof.

A temperature-compensated superspring mechanism, comprising:

• (a) an inertial mass;
• (b) motion compensating means incorporating a support housing and an elongated superspring arrangement being variable in length and supported by said housing and supporting said inertial mass and being operable to maintain said inertial mass in a motionless state in response to motion of said support housing, said superspring arrangement includes an elongated main spring extending vertically and supporting sis inertial mass at a lower end of said spring;
• and
• (c) a temperature-responsive lever mechanism connected to said superspring arrangement and being operable to change the length of said superspring arrangement to compensate for temperature-induced changes in effective length of said superspring arrangement, said temperature-responsive lever mechanism including a lever arm pivotally mounted at one end and supporting an upper end of said main spring at an opposite end of said lever arm and an aneroid wafer assembly having a substantially non-expandable and non-contractable elongated container body, an axially expandable and contractable actuating member engaged with said lever arm to pivot said lever arm in response to expansion and contraction of said actuating member, and an elongated tubular conduit interconnecting in fluid communication an interior cavity of said container body with an interior cavity of said actuating member, said interior cavities containing a predetermined quantity of a hydraulic fluid which will expand and contract in volume in response to increase and decrease in ambient temperature so as to correspondingly expand and contract said actuating member.