Temperature control system for a cryogenic refrigeration
First Claim
1. A cryogenic refrigerator having a displacer within a refrigeration cylinder and a compressor comprising a reciprocating armature within an hermetically sealed housing which alternately compresses and expands to cool a portion of a working fluid flowing through the cylinder to cryogenic temperatures, a linear drive motor with a coil assembly for driving the armature, and a temperature control system comprising:
- a sensor to detect the temperature of the working fluid and,an analog control circuit that adjusts an amplitude of a reference signal in response to a signal generated by the temperature sensor to vary the displacement of the armature reciprocating at a predetermined frequency such that the temperature of the working fluid is adjustable, the control circuit having a pulse width modulation circuit to convert an input signal to a pulse width modulated drive signal that is applied to the coil.
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Accused Products
Abstract
In a cryogenic refrigeration utilizing a linear drive motor, a temperature control system controls the displacement of an armature reciprocating at a fixed frequency to adjust the operating temperature of a working fluid at the cold end of a cold finger. Linear drive motors using dynamic absorbers to reduce vibration operate within the narrow frequency range to which the absorber is tuned. Controlling the maximum displacement of the armature used to compress the working fluid results in the ability to adjust the temperature at the cold end of the refrigeration without altering the frequency of operation.
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Citations
10 Claims
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1. A cryogenic refrigerator having a displacer within a refrigeration cylinder and a compressor comprising a reciprocating armature within an hermetically sealed housing which alternately compresses and expands to cool a portion of a working fluid flowing through the cylinder to cryogenic temperatures, a linear drive motor with a coil assembly for driving the armature, and a temperature control system comprising:
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a sensor to detect the temperature of the working fluid and, an analog control circuit that adjusts an amplitude of a reference signal in response to a signal generated by the temperature sensor to vary the displacement of the armature reciprocating at a predetermined frequency such that the temperature of the working fluid is adjustable, the control circuit having a pulse width modulation circuit to convert an input signal to a pulse width modulated drive signal that is applied to the coil. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A cryogenic refrigerator having a compressor comprising a reciprocating armature which alternately compresses and expands a gas in a working volume, a linear drive motor for driving the armature, a vibration isolator system comprising a counterbalance mass attached to the compressor such that an antiphase movement is produced relative to the reciprocating movement of the armature for substantially countering a resulting force exerted by the armature on a refrigerator mounting frame, and a temperature control system, the temperature control system comprising;
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a reciprocating magnetic armature; and a control circuit to control the maximum displacement of the armature with respect to the coil to adjust the temperature of the working fluid. - View Dependent Claims (8, 9)
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10. A linear drive motor with a temperature control system comprising:
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a reciprocating magnetic armature within a housing; a coil assembly concentric with the armature to drive the armature; a dynamic absorber attached to the housing such that an antiphase movement is produced relative to the reciprocating armature for substantially countering a resulting force exerted by the armature on the housing; and a control circuit coupled to the coil to drive the armature of a selected frequency such that control of the armature displacement adjusts the temperature of the working fluid.
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Specification