Abstract: A method for increasing working gas flow rate through gas bearings of a free piston, gamma configured Stirling heat pump to avoid failure of the gas bearings while maintaining thermal cooling power. The Stirling heat pump lifts heat from a storage chamber and has pistons that are driven in reciprocation at an operating frequency by linear electric motors. A temperature control maintains a steady state storage chamber temperature by sensing storage chamber temperature and modulating piston amplitude. The invention comprises (a) driving the pistons with linear electric motors that are driven by a variable frequency, AC power source; (b) sensing the pistons' amplitude of reciprocation; and (c) if the sensed piston amplitude is less than a selected piston activation amplitude, increasing the frequency of the AC power source to increase the Stirling heat pump's operating frequency. That decreases thermal cooling power which causes the temperature control to increase piston amplitude.

Abstract: In a gamma free-piston Stirling cooler driven by linear electric motors, a motor operating frequency for consuming minimum electric power is detected and a different motor operating frequency that delivers maximum thermal cooling power is detected. The frequencies are detected by varying the operating frequency in small steps while sensing (1) the motor power input to maintain a steady temperature or (2) the thermal cooling power of the Stirling cooler. A mode detection routine detects whether the appropriate freezer operation is the electric power minimization mode or the thermal cooling power maximization mode based upon the current thermal conditions in the freezer. When the freezer is sufficiently cold, the pistons of the Stirling cooler are driven at the minimum electric power consumption frequency. When the temperature is, or is likely to become, too warm, the pistons of the Stirling cooler are driven at the maximum thermal cooling power frequency.

Abstract: A method and apparatus for detecting the displacement amplitude of an armature of a linear motor or alternator that is drivingly coupled to a load or prime mover. The method and apparatus require only three inputs all derived from the input terminals of the linear motor or alternator: (1) the voltage measured across the linear motor terminals; (2) the current consumed by the linear motor; and (3) the phase between the voltage and current. The three inputs are sensed at the terminals of the linear motor or alternator and used to perform mathematical calculations in the microcomputer of a control system or controller. The mathematical calculations are based on equivalent circuits that are modifications of the equivalent circuit for the linear motor or alternator. The detected displacement amplitude can be used by a controller to limit the displacement amplitude of the armature to prevent collisions.

Abstract: An automated, ultra-low temperature freezer having multiple structural features that reduce heat transfer into the freezer, protect its internal mechanical devices against low temperature mechanical binding of their movements, allow defrosting and autoclaving as a result of only minimal changes to the conventional CO2 emergency backup system. A group of freezers are arranged so they can simultaneously provide an HVAC function. A vial management system allows biological samples or vials to be automatically placed in and recovered from the freezer and associates the temperature history with each sample or vial that it was subjected to during its storage.

Abstract: An auxiliary thermosiphon has an auxiliary refrigerant conduit with an auxiliary evaporation segment in thermally conductive connection to an interior wall of the freezer. The auxiliary refrigerant conduit contains an auxiliary refrigerant that is isolated from the primary refrigerant of the primary cooling apparatus. The auxiliary refrigerant conduit also extends upward to an auxiliary condensation segment of the auxiliary refrigerant conduit at an elevation above the auxiliary evaporation segment. A thermal bridge is in physical thermal contact with the auxiliary condensation segment and in physical thermal contact with a portion of a primary evaporation segment of the primary refrigeration apparatus. Heat is transported through the thermal bridge from the auxiliary thermosiphon to the primary refrigerant conduit and consequently to the primary refrigeration apparatus for removal from the freezer.

Abstract: An automated, ultra-low temperature freezer having multiple structural features that reduce heat transfer into the freezer, protect its internal mechanical devices against low temperature mechanical binding of their movements, allow defrosting and autoclaving as a result of only minimal changes to the conventional CO2 emergency backup system. A group of freezers are arranged so they can simultaneously provide an HVAC function. A vial management system allows biological samples or vials to be automatically placed in and recovered from the freezer and associates the temperature history with each sample or vial that it was subjected to during its storage.

Abstract: A door latch which provides leverage to the door in both the closing and opening operations of the latch's door handle. The door latch has a door axle attached to an edge of the door and a striker is attached to the cabinet. A latch pivoting component has a base bearing journaled to the door axle and a handle attached to the base bearing for manually rotating the base bearing about the door axle. A cam is attached to the base bearing and is engageable with the striker by rotation of the base bearing. The cam includes a closing cam segment and an opening cam segment. The opening cam segment engages and slides along the striker as the latch pivoting component is rotated in an opening direction of rotation. The closing cam segment engages and slides along the striker as the latch pivoting component is rotated in a closing direction of rotation.

Abstract: An automated, ultra-low temperature freezer having multiple structural features that reduce heat transfer into the freezer, protect its internal mechanical devices against low temperature mechanical binding of their movements, allow defrosting and autoclaving as a result of only minimal changes to the conventional CO2 emergency backup system. A group of freezers are arranged so they can simultaneously provide an HVAC function. A vial management system allows biological samples or vials to be automatically placed in and recovered from the freezer and associates the temperature history with each sample or vial that it was subjected to during its storage.

Abstract: A method for use in controlling a free piston Stirling machine having a cold end and a warm end and driven by a linear motor having an armature winding to which a drive voltage is applied. The method comprises (a) sensing internal mechanical collisions; (b) repeatedly sensing the temperature of the cold end, the temperature of the warm end and the drive voltage; (c) storing, as associated data, a value representing drive voltage, the temperature of the cold end and the temperature of the warm end at the time of sensed collisions; and (d) limiting the drive voltage to less than the drive voltage that was sensed at a collision and is stored in association with stored warm end and cold end temperatures that are proximate currently sensed warm end and cold end temperatures.

Abstract: An opposed piston gamma type Stirling machine has its displacer driven by a linear electromagnetic transducer that is drivingly linked to the displacer and is located on the opposite side of the power piston's axis of reciprocation from the displacer preferably in the bounce space. The linear transducer is controlled by an electronic control as a function of sensed inputs of Stirling machine operating parameters. In addition to allowing improvements in stability and efficiency, such a Stirling machine operated as a cooler/heat pump can also be controlled so that its displacer can be driven at (1) a phase angle that pumps heat in one direction through the machine or (2) at another phase angle that pumps heat in the opposite direction through the machine and allows selectively switching between the heat pumping directions.

Abstract: A free-piston Stirling machine drivingly coupled to at least one rotary electromagnetic transducer. At least one pulley is oriented in a plane of a reciprocating piston connecting rod. At least one motion translating drive link connects the connecting rod to the pulley by at least two straps so that the pulley moves in rotationally oscillating motion. The two straps extend along an arcuate surface of the pulley into connection to the piston rod at two spaced locations. The pulley is linked to a rotary electromagnetic transducer so that both move in rotationally oscillating motion. Preferably a piston spring resonates the piston at an operating frequency of the Stirling machine and a torsion spring resonates the pulley in rotational oscillation at the operating frequency of the Stirling machine.

Abstract: An improved free piston Stirling machine having a gamma configuration. The displacer and each piston is reciprocatable within a cylinder having an unobstructed opening at its inner end into a common volume of the workspace. The common volume is defined by the intersection of inward projections of the displacer cylinder and the piston cylinders. The displacer and the pistons each have a range of reciprocation that extends into the common volume. A displacer drive rod is reciprocatable in a drive rod cylinder and both are positioned outside the common volume and on the opposite side of the common volume from the displacer. The displacer is connected to the displacer drive rod by a displacer connecting rod. Importantly, the displacer and pistons have complementary interfacing surface contours formed on their inner ends which substantially reduces the dead volume of this gamma configured machine.

Abstract: A passive vacuum relief valve for an ultra-low temperature freezer. A thermally conductive tube extends through a freezer cabinet wall and opens into the interior cabinet space. The tube also extends outwardly from the cabinet wall in thermal exposure to ambient air so that it can receive heat from the ambient air. A valve enclosure has a chamber opening into the tube and is also positioned in the ambient air. A check valve, preferably a ball type, is formed in the valve enclosure and is polarized in a direction permitting ambient air to flow through the chamber and the tube into the freezer cabinet. The exposed tube is passively heated by the ambient air and provides a thermal conduction path to the valve and to the portion of the tube extending through the freezer cabinet wall to prevent moisture from freezing and locking the valve and/or obstructing the tube.

Abstract: A bearing support system for a piston and its connecting rod in which the bearing system supports the combined piston and connecting rod by only two bearings, a gas bearing at the piston and a radially acting spring bearing at its connecting rod. A non-compliant connecting rod is fixed to an end of a piston which has a clearance seal length in the range of 0.3 times the diameter of the piston and 1.5 times the diameter of the piston. The distance from the gas bearing to the effective point of connection of the radially acting spring bearing to the connecting rod is greater than the seal length of the piston. The piston and connecting rod unit is not supported by additional bearings that introduce additional alignment problems.

Abstract: An automated, ultra-low temperature freezer having multiple structural features that reduce heat transfer into the freezer, protect its internal mechanical devices against low temperature mechanical binding of their movements, allow defrosting and autoclaving as a result of only minimal changes to the conventional CO2 emergency backup system. A group of freezers are arranged so they can simultaneously provide an HVAC function. A vial management system allows biological samples or vials to be automatically placed in and recovered from the freezer and associates the temperature history with each sample or vial that it was subjected to during its storage.

Abstract: A method for use in controlling a free piston Stirling machine having a cold end and a warm end and driven by a linear motor having an armature winding to which a drive voltage is applied. The method comprises (a) sensing internal mechanical collisions; (b) repeatedly sensing the temperature of the cold end, the temperature of the warm end and the drive voltage; (c) storing, as associated data, a value representing drive voltage, the temperature of the cold end and the temperature of the warm end at the time of sensed collisions; and (d) limiting the drive voltage to less than the drive voltage that was sensed at a collision and is stored in association with stored warm end and cold end temperatures that are proximate currently sensed warm end and cold end temperatures.

Abstract: An opposed piston gamma type Stirling machine has its displacer driven by a linear electromagnetic transducer that is drivingly linked to the displacer and is located on the opposite side of the power piston's axis of reciprocation from the displacer preferably in the bounce space. The linear transducer is controlled by an electronic control as a function of sensed inputs of Stirling machine operating parameters. In addition to allowing improvements in stability and efficiency, such a Stirling machine operated as a cooler/heat pump can also be controlled so that its displacer can be driven at (1) a phase angle that pumps heat in one direction through the machine or (2) at another phase angle that pumps heat in the opposite direction through the machine and allows selectively switching between the heat pumping directions.

Abstract: A free-piston Stirling machine drivingly coupled to at least one rotary electromagnetic transducer. At least one pulley is oriented in a plane of a reciprocating piston connecting rod. At least one motion translating drive link connects the connecting rod to the pulley by at least two straps so that the pulley moves in rotationally oscillating motion. The two straps extend along an arcuate surface of the pulley into connection to the piston rod at two spaced locations. The pulley is linked to a rotary electromagnetic transducer so that both move in rotationally oscillating motion. Preferably a piston spring resonates the piston at an operating frequency of the Stirling machine and a torsion spring resonates the pulley in rotational oscillation at the operating frequency of the Stirling machine.

Abstract: A bearing support system for a piston and its connecting rod in which the bearing system supports the combined piston and connecting rod by only two bearings, a gas bearing at the power piston (or displacer) and a radially acting spring bearing at its connecting rod. The spacing between them meets prescribed relationships and preferably exceeds a calculated value based upon chosen engineering parameters. A non-compliant connecting rod is fixed to an end of a piston which has a clearance seal length in the range of 0.3 times the diameter of the piston and 1.5 times the diameter of the piston. The distance from the gas bearing to the effective point of connection of the radially acting spring bearing to the connecting rod is greater than the seal length of the piston.

Abstract: An improved free piston Stirling machine having a gamma configuration. The displacer and each piston is reciprocatable within a cylinder having an unobstructed opening at its inner end into a common volume of the workspace. The common volume is defined by the intersection of inward projections of the displacer cylinder and the piston cylinders. The displacer and the pistons each have a range of reciprocation that extends into the common volume. A displacer drive rod is reciprocatable in a drive rod cylinder and both are positioned outside the common volume and on the opposite side of the common volume from the displacer. The displacer is connected to the displacer drive rod by a displacer connecting rod. Importantly, the displacer and pistons have complementary interfacing surface contours formed on their inner ends which substantially reduces the dead volume of this gamma configured machine.