US4924675A — Linear motor compresser with stationary piston

Claim 1

Independent Claim 99 words

A cryogenic refrigerator having a compressor comprising a reciprocating armature which alternately compresses and expands to cool a portion of a working fluid to cryogenic temperatures, and a linear drive motor for driving the armature, the linear drive motor comprising; a housing for hermetically sealing the gaseous fluid in a volume; a coil assembly surrounding the housing; a stationary piston within the volume and attached to the housing at one end; and a permanent magnet armature which reciprocates within the volume, concentric about the stationary piston, and which forms a clearance seal along an outer surface of the piston.

Claim 2

Dependent Claim 99 words

A cryogenic refrigerator having a compressor comprising a reciprocating armature which alternately compresses and expands to cool a portion of a working fluid to cryogenic temperatures, and a linear drive motor for driving the armature, the linear drive motor comprising; a housing for hermetically sealing the gaseous fluid in a volume; a coil assembly surrounding the housing; a stationary piston within the volume and attached to the housing at one end; and a permanent magnet armature which reciprocates within the volume, concentric about the stationary piston, and which forms a clearance seal along an outer surface of the piston.

Claim 3

Dependent Claim 18 words

The cryogenic refrigerator of claim 1 wherein the stationary piston is the sole mechanical support of the armature.

Claim 4

Dependent Claim 20 words

The cryogenic refrigerator of claim 1 further comprising an axial bore along the stationary piston for conveying the working fluid.

Claim 5

Dependent Claim 27 words

The cryogenic refrigerator of claim 1 wherein the stationary piston is comprised of aluminum such that the piston is used to conduct heat away from the volume.

Claim 6

Dependent Claim 28 words

The cryogenic refrigerator of claim 4 further comprising a liner attached to the outer surface of the stationary piston by a flexible material to form the clearance seal.

Claim 7

Dependent Claim 15 words

The cryogenic refrigerator of claim 1 wherein the coil assembly is concentric about the armature.

Claim 8

Dependent Claim 16 words

The cryogenic refrigerator of claim 1 wherein the driven armature freely reciprocates relative to the housing.

Claim 9

Dependent Claim 83 words

A linear drive motor for a cryogenic refrigerator comprising: a housing for hermetically sealing a gaseous fluid in a working volume; a stationary piston with an axial bore for conveying the fluid within the volume; a coil assembly surrounding the housing; and a permanent magnet armature having a center of gravity and having a linearly reciprocating motion within the volume, the armature being concentric about the stationary piston such that the center of gravity lies within the stationary piston throughout the reciprocating motion.

Claim 10

Dependent Claim 83 words

A linear drive motor for a cryogenic refrigerator comprising: a housing for hermetically sealing a gaseous fluid in a working volume; a stationary piston with an axial bore for conveying the fluid within the volume; a coil assembly surrounding the housing; and a permanent magnet armature having a center of gravity and having a linearly reciprocating motion within the volume, the armature being concentric about the stationary piston such that the center of gravity lies within the stationary piston throughout the reciprocating motion.

Claim 11

Dependent Claim 18 words

The linear drive motor of claim 8 wherein the armature forms a clearance seal with the stationary piston.

Claim 12

Dependent Claim 17 words

The linear drive motor of claim 8 wherein the driven armature freely reciprocates relative to the housing.

Claim 13

Dependent Claim 96 words

A linear drive motor for a cryogenic refrigerator with a position sensor comprising: a housing for hermetically sealing a gaseous fluid in a volume; a stationary piston within the volume and attached to the housing; a permanent magnet armature which reciprocates within the volume about the stationary piston; a coil assembly concentric about the armature; a nonmagnetic member attached to the armature and supporting a target magnet whose magnetic flux lines are substantially decoupled from magnetic flux lines about the coil; and a sensor for detecting the position of said target magnet relative to the housing.

Claim 14

Dependent Claim 96 words

A linear drive motor for a cryogenic refrigerator with a position sensor comprising: a housing for hermetically sealing a gaseous fluid in a volume; a stationary piston within the volume and attached to the housing; a permanent magnet armature which reciprocates within the volume about the stationary piston; a coil assembly concentric about the armature; a nonmagnetic member attached to the armature and supporting a target magnet whose magnetic flux lines are substantially decoupled from magnetic flux lines about the coil; and a sensor for detecting the position of said target magnet relative to the housing.

Claim 15

Dependent Claim 31 words

The linear drive motor of claim 11 wherein the volume is comprised of an armature volume in which the armature reciprocates and a volume extension in which the target magnet reciprocates.

Claim 16

Dependent Claim 38 words

The linear drive motor of claim 12 wherein the housing is comprised of a cylinder surrounding the armature volume and a cylinder extension about the volume extension such that the target magnet does not enter the armature volume.

Claim 17

Dependent Claim 70 words

A shielded linear drive motor for a cryogenic refrigerator comprising: a housing for hermetically sealing a pressurized fluid in a volume; a permanent magnet armature which reciprocates within the volume to alternatively compress and expand a working fluid to cool a portion thereof; a coil assembly surrounding the housing and configured about the armature; and a shield configured about the coil for confining magnetic flux lines generated about the coil.

Claim 18

Dependent Claim 70 words

A shielded linear drive motor for a cryogenic refrigerator comprising: a housing for hermetically sealing a pressurized fluid in a volume; a permanent magnet armature which reciprocates within the volume to alternatively compress and expand a working fluid to cool a portion thereof; a coil assembly surrounding the housing and configured about the armature; and a shield configured about the coil for confining magnetic flux lines generated about the coil.

Claim 19

Dependent Claim 19 words

A shielded linear drive motor of claim 14 wherein said coil assembly is comprised of a split laminated stator.

Claim 20

Dependent Claim 48 words

A shielded drive motor of claim 14 further comprising a member, attached to the armature, and supporting a magnet whose magnetic flux lines are substantially decoupled from magnetic flux lines about the coil, and a sensor for detecting the position of said magnet with respect to the housing.

Claim 21

Dependent Claim 130 words

A cryogenic refrigerator having a compressor comprising a reciprocating armature which alternatively compresses and expands a gas in a working volume, a linear drive motor for driving the armature, and a vibration isolator system, wherein the vibration isolator system comprises: a mounting frame supporting the compressor; 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 the mounting frame; and an isolator mounted between the compressor and the frame comprising a flat spring with an outer rim affixed to the frame that is concentric about an inner rim affixed to the compressor, and a plurality of flexible arms extending from the outer rim to the inner rim.

Claim 22

Dependent Claim 130 words

A cryogenic refrigerator having a compressor comprising a reciprocating armature which alternatively compresses and expands a gas in a working volume, a linear drive motor for driving the armature, and a vibration isolator system, wherein the vibration isolator system comprises: a mounting frame supporting the compressor; 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 the mounting frame; and an isolator mounted between the compressor and the frame comprising a flat spring with an outer rim affixed to the frame that is concentric about an inner rim affixed to the compressor, and a plurality of flexible arms extending from the outer rim to the inner rim.

Claim 23

Dependent Claim 20 words

The cryogenic refrigerator of claim 17 wherein the flexible arms spiral inward from the outer rim to the inner rim.

Claim 24

Dependent Claim 53 words

The cryogenic refrigerator of claim 17 wherein said isolator is comprised of a first flat spring mounted at one end of the linear drive unit along a linear axis of the unit and further comprising a second flat spring mounted at the opposite end of the linear drive unit along the linear axis.

Claim 25

Dependent Claim 31 words

The cryogenic refrigerator of claim 17 wherein said isolator further comprises an elastomeric material having a damping ratio of 0.1 or greater configured between the flat spring and the mounting frame.

Claim 26

Dependent Claim 32 words

The cryogenic refrigerator of claim 17 wherein the counterbalance mass is concentrically mounted about an armature extension supporting a magnet wherein said magnet is used to detect the position of the armature.

Claim 27

Dependent Claim 63 words

A linear drive motor comprising: a housing for sealing a working fluid in a volume; a stationary piston secured to the housing within the volume; a magnetic armature which reciprocates within the volume, concentric about the stationary piston, and which forms a clearance seal along an outer surface of the piston; and a coil assembly concentric with the armature to drive the armature.

Claim 28

Dependent Claim 63 words

A linear drive motor comprising: a housing for sealing a working fluid in a volume; a stationary piston secured to the housing within the volume; a magnetic armature which reciprocates within the volume, concentric about the stationary piston, and which forms a clearance seal along an outer surface of the piston; and a coil assembly concentric with the armature to drive the armature.

Claim 29

Dependent Claim 17 words

The linear drive motor of claim 22 wherein the driven armature freely reciprocates relative to the housing.

Claim 30

Dependent Claim 24 words

The linear drive motor of claim 22 wherein the linear drive motor drives the working fluid of a compressor of a Stirling cycle refrigerator.

Claim 31

Dependent Claim 33 words

The linear drive motor of claim 24 further comprising a cold finger in fluid communication with a compression waves are generated in the wording fluid transmitted through the fluid to the cold finger.

Claim 32

Dependent Claim 25 words

The linear drive motor of claim 25 further comprising a conduit extending through the stationary piston to couple the compression space with the cold finger.

Claim 33

Dependent Claim 22 words

The linear drive motor of claim 22 wherein the linear drive motor drives the working fluid to and from a valveless compressor.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1993-05-14	1993-11-13	1994-05-15	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1997-05-14	1997-11-13	1998-05-15	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2001-05-14	2001-11-13	2002-05-15	$7700.00	Window Closed / Lapsed

Linear motor compresser with stationary piston

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