US 3372556 A
Description (OCR text may contain errors)
March 12, 1968 M. `WALDMAN 3,372,556
l RETRACTABLE CRYOGENIC ASSEMBLY Fild March 25, 1966 @Alia2 I cana/any 55 SSE/77 y 30 ,Q6
United States Patent l 3,372,556 RETRACTABLE CRYOGENIC ASSEMBLY Marvin Waldman, Ontario, Calif., assigner to General Dynamics Corporation, a corporation of Delaware Filed Mar. 25, 1966, Ser. No. 537,535 9 Claims. (Cl. 62.-45)
ABSTRACT OF THE DESCLOSURE Broadly, the disclosure relates to an infrared tracking or seeking head provided with a cryostat cooling means, this being such that the cryostat is detachable from the seeker head so as to permit the detector section to be gimbaled. The cryostat unit extends into the detector cooling chamber through an O-ring seal and is provided with a solenoid control unit which operates to withdraw the cryostat from the cooling chamber. The chamber is provided with an internal spring loaded door which seals the chamber when the cryostat is removed.
This invention relates to refrigeration devices, particularly to refrigeration devices for cooling radiation sensing devices, and more particularly to detachable refrigeration devices for gimbaled radiation detection devices.
Much effort has 4been directed to the development of refrigeration devices, particularly those utilizing the Joule- Thomson effect. With the advent of missiles and space vehicles, the need for effective refrigeration devices or heat exchangers has greatly increased.
As is well known, many of the present day missiles and space vehicles, as well as land based equipment, utilize energy-detecting units such as those used for detecting infrared or heat radiation.
Infrared detectors, for example, are being used for a variety of purposes especially by the military forces, and to provide a detector of requisite sensitivity, namely, one having optimum spectral response and capable of detecting small temperature differences, requiring that the detector cell be maintained at cryogenic temperatures. One common method of accomplishing this low temperature is by expanding a pressurized refrigerant in the vicinity of the cell and returning the cool expanded refrigerant in regenerative heat exchange with the incoming refrigerant to cool the refrigerant before or during expansion and thereby to attain a greater Joule-Thomson effect.
Low temperature regulators of this type, often referred to as cryostats, have the advantage of being free of moving parts which are susceptible to low temperature malfunctioning, in addition to being of extreme structural compactness. While cryostats operating on the expansion or Joule-Thomson cooling principle exist in a multitude of forms, they typically comprise a tightly wound coil of high-heat-conductivity tubing housed in an insulating sheath and adapted to transport gaseous media under high pressure to an expansion orifice or throttling yvalve, through which the gas is expanded to approximately atmospheric pressure. The Joule-Thomson cooling resulting from expansion causes a lowering of temperature, and the cooled expanded gas is constrained to pass back over the incoming passages of the cryostat or heat exchanger, to cool the incoming high-pressure stream.
The application of infrared to airborne -lire control system is being rapidly expanded, and infrared detectors are now being designed to replace the radar gear in certain air vehicles. Infrared equipment is finding increased use as it has many advantages over other types of fire control equipment. Infrared equipment is inherently more accurate than radar as it has greater resolution and no side lobes to give ground return or sea clutter. However,
3,372,555 Patented Mar. l2, 1968 the most important advantage of infrared equipment is the passive nature of the equipment and the difficulty of successful enemy countermeasures. No energy is emitted by the fire control system which can -be used by an enemy for either detection or jamming.
As pointed out above, the infrared detection cell is most effective when maintained at an extremely low ternperature, such as the temperature of liquid nitrogen. Normally, the detection cell is mounted in a fixed position when mounted in a hunting device, such as the seeker head of a missile which moves up, down, and sideways in order to cover the greatest possible searching area. With such fixed position detection cells, it is readily easy to provide a cryogenic device for cooling the cell. However, it has been found desirable to gimbal the detection unit to provide a better scanning-tracking detector systern. With a gimbaled detection unit, the prior known cooling methods are unsatisfactory in that they have been fixed with respect to the cell. Therefore, a need has been developed for a means of cooling a gimbaled detector unit.
The present invention provides a means of cooling a gimbaled detector unit, whereby a more ecient scanningtracking detector system can be utilized. This is accomplished by providing a means for retractably positioning the cryostat such that it is withdrawn after the detector cell has been cooled, thus allowing the detector to be readily gimbaled.
Therefore, it is an object of this invention to provide a cryogenic assembly for cooling radiation-sensitive detectors.
Another object of the invention is to provide a retractably mounted cryogenic apparatus.
Another object of the invention is to provide a detachable cryostat for infrared detection units.
Another object of the invention is to provide a retractable cryostat for infrared sensitive scanning-tracking systems whereby the detector unit thereof may be gimbaled.
Other objects of the invention will become readily apparent from the following description and accompanying drawings wherein:
FIG. 1 is a perspective view of an air vehicle capable of utilizing the invention;
FIG. 2 is a view partially in cross section of a prior art seeker head illustrating the fixed type detector cell; and
FIG. 3 is a diagrammatic view illustrating the invention.
Referring now to the drawings, FIG. l shows, for purposes of illustration, a missile 10 including an infraredtracking seeker section 11; a guidance and control section 12 including electronic processing circuitry and two fixed and two movable, single-plane, variable-incidence folding control surfaces 13 and 14, respectively, only one movable control surface 14 being shown; a warhead/fuze section 15; a dual stage rocket motor section 16; and a tail section 17 having four folding nonvariable tail surfaces 18.
The intelligence necessary for missile guidance is developed in the infrared-sensing seeker section 11, whose primary functions are to track heat radiated from the target and to provide a signal proportional to the rate of change of the angular line-of-sight to the target. Seeker intellegince is converted into airframe corrective maneuvers by the guidance and control section 12 to maintain the missile on a collision course. Since the operation of the control section 12 is not part of this invention, a detailed description thereof is not deemed necessary, but the control section may be of the type described in the U.S. patent application Ser. No. 397,674, and assigned to the assignee of the present application.
FIG. 2 shows portions of a prior art seeker head 19 of the seeker section 11 illustrating the fixed type detector cell and the associated cryostatic cooling mechanism. Generally, the seeker head 19 includes a support member 20 adapted to be attached to the missile 10, a support or gimbal post `21 operatively attached to support member 20, a gimbal 22 operatively mounted 'via bearings 23 and 24. within post 21, and a detector 25 gas cooled by a cryostat 26 which is supplied with high pressure coolant via intake line 27, the coolant being discharged through exhaust line 28 in conventional manner. Operatively connected to gimbal 22 is a bearing mount 29 within which is positioned a reticle assembly 30 and spin bearings 31. An optical barrel 32 is connected via bearings 31 with bearing mount 29 and gimbal 22. Barrel 32 supports a magnet 33, primary mirror 34, and secondary mirror 35 having sunshade 36 thereon.
As can be readily seen, the optical barrel 32 is gimbaled so that it may move with respect to the post 21 while spinning on bearings 29 in a manner known in the art. With the FIG. 2 arrangement, the detector 25 is fixed with respect to post 21 and thus does not move with the optical barrel 32 and the associated optics thereon.
Referring now to FIG. 3 which diagrammatically shows the inventive concept of providing a retractable or detachable cryostat which allows the detector to be gimbaled with the associated optics. Generally, the invention, as illustrated, comprises a housing 40 within -which is mounted at window 41, a detector support structure 42 and a chamber sealing door 43. Detector support structure is provided with a filter 44 on the forward side and a detector unit 45 on the opposite or rearward side thereof, and is spaced in chamber 46 by spacers 47 and 4.8, support structure 42 and window 41 defining an evacuated area 49 therebetween. Chamber sealing door 43 is movably mounted on pins 50 which are xedly attached to wall 51 of housing 40. Door 43 is adapted to be closed against housing wall 51 by resilient means such as springs 52 operatively mounted on pins 50. Housing wall 51 is provided with an aperture 53 through which a cryostat 54 enters to cool detector 45 and chamber 46. The cryostat 54 includes a supply line 55 and an exhaust line 56, and may be of the type illustrated in FIG. 2 or any other suitable configuration. Cryostat 54 is mounted within a cryostat housing 57 which is abutted on housing 40 via a sealing washer 58. An O-ring 59 is mounted in aperture -v 53 of housing 40 surrounds the inner end of cryostat 54 and prevents leakage of coolant therearound. Operatively connected to cryostat housing 57 is a housing`60 within which is positioned a solenoid indicated by legend 61 which, while not shown, is operatively connected with cryostat 54.. A spring 62 surrounds cryostat 54 and functions along with solenoid 61 to move the cryostat within aperture 53 of housing wall 51.
In the normal process of firing the FIG. 1 missile, for example, the gyro of seeker head, which would be attached to the optics and detector unit 45, starts to spin up by an appropriate power source, and the detector is cooled by high pressure coolant being supplied via line 55, expanded into chamber 46, and exhausted via line 56. The force of the pressurized coolant causes door 43 to move slightly away from cryostat 54. After the cooling cycle has been completed and the gyro is still caged, the cryostat 54 is retracted by the solenoid 51 which overcomes the tension of spring 62 which normally holds the cryostat in the position shown in FIG. 3. As the cryostat 54 is retracted from within chamber 46 the aperture 53 in housing wall 51 is automatically sealed by the door 43 due to the expanding of springs S2 leaving the expanded coolant in contact with detector 45. The gyro is then uncaged and the missile 10 fired. Retracting of the cryostat 54 from within housing 4,0 allows the detector 4S to be gimbaled along with the optical barrel 32 (see FIG. 2).
The advantages of the present invention are: (1) shorter cooling-down time; (2) lower temperatures in cooling 4 chamber; (3) less area to cool; and (4) coolant in contact with the detector for a longer period of time.
It has thus been shown that the present invention provides a system wherein a cryogenic apparatus cools the radiation detector unit, withdraws itself, and seals the detector containing chamber, whereby the detector can be readily gimbaled with other associated equipment such as those elements of a seeker head of a homing type missile. Thus, with this invention a more effective scanning-tracking radiation detector system serves to advance the state of the art.
Although a specific embodiment has been shown for purposes of illustration, modifications and changes will become apparent to those skilled in the art, and it is intended to cover in the appended claims all such modifications and changes as come within the true spirit and scope of the invention.
What I claim is:
1. In a radiation sensitive scanning-tracking device, a retractable cryogenic apparatus comprising: a housing defining la chamber, said housing being provided with an aperture, movable means operatively connected to said housing for sealing said aperture, a cryostat operatively associated with said housing and adapted to extend through said aperture and adapted to at least partially move said sealing means, and means for extending said cryostat to within said chamber and retracting same from therein, whereby coolant under pressure is supplied by said cryostat to said chamber for cooling same and whereafter said cryostat is retracted from within said chamber and said sealing means seals said aperture.
2. The apparatus defined in claim 1, wherein said housing contains a radiation sensitive means.
3. The apparatus defined in claim 2, wherein said radiation sensitive means comprises an infrared sensitive detector unit.
4. The apparatus defined in claim 1, wherein said aperture sealing means includes a door-like member slidably mounted on pin-like means fixedly attached to said housing, and resilient means operatively mounted with respect to said pin-like means and said door-like means so as to move said door-like means against said housing aperture to seal said housing chamber.
5. The apparatus defined in claim 1, wherein said housing aperture is provided with a sealing member, said sealing member extending around said cryostat, thereby preventing leakage of coolant therebetween when said cryostat is extended into said chamber.
6. The apparatus defined in claim 1, wherein said cryostat moving means includes a solenoid and a spring member, said spring member normally functioning to maintain said cryostat extending into said chamber, said solenoid functioning to retract said cryostat from within said chamber.
7. The apparatus defined in claim 1, in combination with a seeker head, said seeker head including an optical assembly for directing a signal to a radiation sensitive means mounted within said seeker head, and means for movably supporting at least said optical assembly.
8. The combination defined in claim 7, in combination with an air vehicle, said seeker head being mounted in said vehicle and adapted for guiding same via a plurality of control surfaces operatively mounted on said vehicle.
9. The combination defined in claim 7, wherein said radiation sensitive means comprises an infrared sensitive detector unit.
References Cited UNITED STATES PATENTS LLOYD L. KING, Primary Examiner.