US3853437A

US3853437A - Split cycle cryogenic cooler with rotary compressor

Info

Publication number: US3853437A
Application number: US00407764A
Authority: US
Inventors: S Horn; B Walters
Original assignee: US Department of Army
Current assignee: US Department of Army
Priority date: 1973-10-18
Filing date: 1973-10-18
Publication date: 1974-12-10
Anticipated expiration: 1991-12-10

Abstract

A rotary compressor providing modulated pressure pulses to a remotely located free displacer. The rotary compressor employs a novel modified Wankel-type mechanism in which two adjacent chamber regions are shorted to the crankcase of the device or to a bypass volume while the third chamber region develops the pressure pulses which are communicated to the free displacer by means of a valveless line.

Description

tates Horn et al.

[ 1 Dec. 10, 1974 SPLIT CYCLE CRYOGENIC COOLER WITH ROTARY COMPRESSOR [75] Inventors: Stuart B. Horn, Fairfax; Buford T. Walters, Woodbridge, both of Va.

[73] Assignee: The United States of America as represented by the Secretary of the Army, Washington, DC.

[22] Filed: Oct. 18, 1973 [21] Appl. No.1 407,764

52 U.S. c1. 418/61, 62/6 [51 Int. Cl. F016 1/02 [58] Field 6: Search 62/6; 418/61 A [56] References Cited UNITED STATES PATENTS 3,426,525 2/1969 Rubin 62/6 3,509,718 5/1970 Fezer 62/6 3,647,327 3/1972 Manthey. 418/61 3,765,187 10/1973 Horn 62/6 Primary Examiner-Williati1 J. Wye I Attorney, Agent, or FirmNathan Edelberg; Milton W. Lee; T. Major 57] ABSTRACT A rotary compressor providing modulated pressure pulses to a remotely located free displacer. The rotary compressor employs a novel modified Wankel-type mechanism in which two adjacent chamber regions are shorted to the crankcase of the device or to a bypass volume while the third chamber region develops the pressure pulses which are communicated to the free displacer by means of a valveless line.

2 Claims, 3 Drawing Figures.

PAIENIED M 3.85%437 FIG. 2

SPLIT CYCLE CRYOGENIC COOLER WITH ROTARY COMPRESSOR The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to us of any royalty thereon.

BACKGROUND OF THE INVENTION Recent years have seen a great deal of effort directed to the development of cryogenic coolers for use with infrared detectors. Since these detectors must undergo rapid scanning motion for area surveillance, a cooler including a cold head of low mass remotely located from the compressor is a necessity. A review of a number of cryogenic devices and techniques can be found in application Ser. No. 279,145 of Stuart B. Horn now U.S. Pat. No. 3,765,187.

SUMMARY OF THE INVENTION A remote cooler having a cold head for cooling an infrared detector and utilizing a free displacer is completely described in the above noted application Ser. No. 279,145 now U.S. Pat. No. 3,765,187. The invention described in the instant application utilizes a similar free displacer and incorporates a novel Wankel-type mechanism for developing modulated pressure or pressure pulses in a working gas, such as helium, between this mechanism and the remote free displacer which cause the free displacer to reciprocate and produce net refrigeration by the process described in the incorporated reference.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows. the combination of the rotary compressor and the remotely located free displacer; 7

FIG. 2 is a cross-sectional view of the rotary compressor;

FIG. 3 is a top view and cut-away of the compressor of FIG. 2 showing the gearing and porting arrangement.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 diagrammatically shows the rotary compressor 10, the remote cooler 11 with a free displacer therein and having-a cold head 12 and a connecting tube 13 through which the pressure waves generated by the compressor travel.

Turning to FIG. 2, a cross-section of the compressor can be seen. The compressor consists of a housing made up of a motor housing and the rotor housing 21. The motor housing contains an electric motor 22 and is sealed by end cap 23. A keyed drive shaft 24 is joined to a keyed rotorshaft 25 by a balancing sleeve 26, located in crankcase 27; which sleeve provides dynamic balance to the system made necessary by the epitrochoidal motion of the rotor 28. Needle bearings 29 support the rotor shaft 25.

carries a purging port 40 which permits the compressor to be purged and filled with a working gas such as helium.

Turning to FIG. 3, the details of the novel compressor can be seen. The chamber 33, carrying the rotor 28 therein, is formed by a two-lobed epitrochoid, peritrochoid or is generated by several arcs.

The rotor 28 having three sides and being generated from epitrochoid, peritrochoid, coordinate transformation or from arcs, divides the chamber volume 33 into three regions. Each of the vertices of the rotor retains a wiper seal 43 made of dry lubricated material such as graphite-type plastic called Dupont Vespel. This results in a compressor that is dry lubricated and thus free of condensible gases which might otherwise impair the operation of the cooler section.

As can be seen here, three

ports

30, 31 and 32 are located in the chamber 33 and are 'angularly' spaced apart. As was noted before, two adjacent ports and 31 are shorted to the crankcase 27 or to some other reservoir volume as would be appropriate to a particular design. This prevents gas compression on one side of the compressor chamber 33.

The port 32 is located in that region of the chamber wherein the pressure waves are developed. The waves are transmitted through this port to the remote cooler 11 via the connecting tube 13.

The drive means for the rotor 28 comprises a ring gear 41 positioned centrally of the rotor and the bearing 29 and a spur gear 42 centrally fixed in the chamber volume 33; which gear 42 engages the ring gear 41. The drive shaft 24, powered by the motor 22, passes axially through the spur gear 42 and carries an eccentric lobe 44 which engages the rotor 28. As the driveshaft 24 is turned, 'it drives the rotor in an epitrochoidal path.

course, that the pressure waves and free displacer rnotion are properly phased to achieve the desired results.

While just one embodiment of the invention is herein disclosed it is to be understood that many modifications may be made while remaining within the spirit and scope of the invention which is to be limited only by the following claims.

We claim:

1. A rotary compressor for generating pressure pulses comprising:

a two-lobed chamber;

a rotor positioned in said chamber and coupled to a drive means for rotating said rotor in said chamber in an epitrochoidal path, said rotor having three arcuate sides and dividing said chamber into three volume regions as it revolves;

three ports located in said chamber;

one of said ports, utilize as an output port far said pressure pulses, being located substantially at a perigee of the two-lobed chamber in a region in which said pressure pulses are developed; and with one of each of the other two remaining ports being located respectively in each lobe of the chamber; and I 2. The compressor of claim 1, wherein said common volume means comprises a crank case adjacent said,

chamber with which said two remaining ports communicate and are thereby shorted to prevent said pressure mon volume means to. prevent pressure increase in 5 increase.

the regions of these two remaining ports.

Claims

1. A rotary compressor for generating pressure pulses comprising: a two-lobed chamber; a rotor positioned in said chamber and coupled to a drive means for rotating said rotor in said chamber in an epitrochoidal path, said rotor having three arcuate sides and dividing said chamber into three volume regions as it revolves; three ports located in said chamber; one of said ports, utilize as an output port far said pressure pulses, being located substantially at a perigee of the twolobed chamber in a region in which said pressure pulses are developed; and with one of each of the other two remaining ports being located respectively in each lobe of the chamber; and the two remaining ports being angularly spaced about said one of said ports with one of each of the remaining ports being located respectively in each lobe of the chamber and being shorted to a common volume means to prevent pressure increase in the regions of these two remaining ports.

2. The compressor of claim 1, wherein said common volume means comprises a crank case adjacent said chamber with which said two remaining ports communicate and are thereby shorted to prevent said pressure increase.