US3500453A

US3500453A - Fiber glass cooling jacket for directing air across an infrared scanning tube

Info

Publication number: US3500453A
Application number: US702614A
Authority: US
Inventors: Jack F Mcclelland
Original assignee: US Air Force
Current assignee: US Air Force
Priority date: 1968-02-02
Filing date: 1968-02-02
Publication date: 1970-03-10
Anticipated expiration: 1987-03-10

Description

March 10, 1970 J. F. M CLELLAND 3,500,453

FIBER GLASS COOLING JACKET FOR DIRECTING AIR ACROSS AN INFRARED SCANNING TUBE 2 Sheets-Sheet 1 Filed Feb. 2, 1968 INVENTOR. JACK F- Mc CL ELL AND BY 2%, y

lrroklrtys March 10, 1970 MccLELLAND 3,500,453

FIBER GLASS COOLING JACKET FOR DIRECTING AIR ACROSS AN INFRARED SCANNING TUBE' Filed Feb. 2, 1968 2 Sheets-Sheet 2,

v INVENTOR. JACK F- Mc CLELL AND in w United States Patent O US. Cl. 313- 22 6 Claims ABSTRACT OF THE DISCLOSURE The invention relates to a cooling shroud of fiber glass which surrounds the casing of an infrared scanner but spaced therefrom to leave a substantially annularspace for receiving cool air. The shroud is closed at the end opposite from the viewing or forward end of the scanner except for openings for receiving the supply wires of the scanner and for introducing the cooling air. An air passageway is provided between the rear end of the scanner and the closed end of the shroud which passageway communicates with the annular space about the scanner. There is a circumferential slot between the inner surface of the forward end of the shroud and the outer surface of the scanner which slot serves as an exit for the cooling air. The shroud is made up of upper and lower halves, molded to shape, and secured together by screws so as to be readily fitted about the scanner and easily disassembled.

BACKGROUND OF THE INVENTION Under certain flight conditions, on a hot day, at speeds in the order of 350 knots and at low altitudes, high ambient temperatures are encountered in the nose of an aircraft. When the latter is equipped with an infrared scanner for visualizing the terrain or for seeking out an enemy aircraft through the heat emitted by the exhaust or from the aircraft itself, the circuitry within the scanner unit dissipates suflicient wattage in the form of heat, which together with the effects of the high ambient temperature might raise the internal temperature to the melting point of the scanner metal components such as the solder used in making the necessary contacts.

SUMMARY OF THE INVENTION An object of the invention is to provide apparatus for reducing and preferably for eliminating this overheating effect within an infrared scanner brought about by increased ambient temperatures.

This object is attained in brief by providing a shroud about the scanner device which is so shaped as to direct cooling air about the circumferential and end surfaces of the scanner. The shroud is constituted for two halves, upper and lower, detachably secured together so as to be readily applied to the scanner device and disassembled when necessary.

Other objects andfeatures will be apparent as the specification is perused in connection with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 represents a vertical, section view of the improved cooling shroud together with parts of the scanner,

all within the broken line area. The remainder of the scanner is shown in elevation, including the contents thereof, which are indicated in dotted line;

FIG. 2 is a cross section taken along line 22 in FIG. 1 and looking in the direction of the arrows;

FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 1; and

FIG. 4 depicts an end view of the improved shroud with the end view of the scanner shown in dotted line.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, reference character 1 generally designates an infrared scanner of well-known type. This element comprises a cylindrical casing 2 of metal having a beveled portion 3 which is adapted to hold the dome 4 in place. The latter is usually constituted of silicon which is readily permeable to infrared rays. The rear end 5 of the casing is provided with openings 6, 7. These openings accommodate a pipe 8 which delivers liquid nitrogen to the totally enclosed detector unit 9 of the usual type (shown in dot-dash line) within the scanner. The opening 7, of which there are two, accommodates bundles 10 of wire insulated within sheaths 11 for delivering power to the scanner and for receiving signals from the device. Any spacebetween the pipe 8, also between the sheaths and their respective openings, in hermetically sealed in any suitable and well-known manner so that the casing is completely closed at the rear. The contents of the scanner are well known and these contents are indicated by dot-dash rectangle 9 which identifies the detector, also the rectangles 12 which broadly include the rotary optical system, the motor for driving the same, and the preamplifiers, as well as other necessary units and the circuitry. A mounting ring 13 is secured to the casing at the forward dome end. The scanner casing is formed, for convenience of assembly, of two semicyclindrical portions, split at the horizontal plane, and screwed together as indicated at 14. An outwardly extending protuberance 15 at each side and near the parting line is provided for accommodating a ledge 16 which receives the screws. A relatively long and thin plate of metal 17 may be interposed between the contacting surfaces of the casing portions and the ledges, the plates being secured in position by the screws 14. These plates serve to support the scanner from the undercarriage of the plane, as will be explained hereinafter.

The scanners are usually pointed at an angle with respect to the ground and their purpose is to collect and focus the infrared radiation which originates on the ground or on airborne craft. The heat radiation is picked up by the rotating optical system on a linear scanning basis and the contained detector is responsive to this radiation. After being amplified, the signals from the detector are put on a translucent screen, not unlike television, in view of the personnel in the plane. Thepicture would represent the temperature contrast within the target relative to its surroundings.

However, when the plane is moving at low altitudes and the ambient temperature is relatively high, considerable heat may be built up within the scanner. This excess heat is derived from many sources, such as the motor employed to rotate the scanning system, also the heat of the amplifiers and other circuitry. Special forms of solder,

such as indium, are used in making the electrical connections to the various elements within thescanner and any marked increase in temperature may cause the solder to soften and perhaps melt, which would decrease the effectiveness of contact. Any increase in temperature may also give rise to a de-focusing efiect in the optical system. For these and other reasons, it is desirable to keep the internal temperature of the scanner preferably below 85 F. and, in no case, higher than an average of about 110 F.

In accordance with my invention, 1 provide a cooling device for the scanner which will serve the entire'scanning unit and its contents, except the detector for which other forms of protection against heat are provided. The improved cooling device may take the form of a molded body of fiber glass, indicated generally at 17' (FIG. 1), and comprising two substantially cylindrical shaped halves, secured together after being positioned about the scanner. The upper half, designated at 18 (FIGS. 1 and 2) is spaced from the metal casing of the scanner and stops short of the left-hand end (as seen in FIG. 1) of the scanner to leave a circumferential slot 18 between the edge and the mounting ring 13. The top rear portion of the shroud is preferably flattened as at 19 (FIG. 3) so as to contact the external surface of the scanner casing. However, the lower rear portion and the entire front portion is of circular shape and is spaced a considerable distance from the casing as is shown more clearly in FIG. 2. The shroud is preferably flattened as at 19 (FIG. 3) so as to contact the external surface of the scanner casing. However, the lower rear portion and the entire front portion is of circular shape and is spaced a considerable distance I from the casing as is shown more clearly in FIG. 2. The shroud is preferably molded in halves, similar to the easing, and made of fiber glass. Each half is provided with outwardly extending protuberances 19 in the region of the protuberances 15 of the casing and which terminate in outwardly extending flanges 20. The latter are secured to the plate 17 by screws 21. Thus, there is an annular space between the shroud and the casing of substantially the same width throughout to receive cooling air as explained hereinafter. The rear end of the shroud extends beyond the casing and is adapted to receive a cover 21 of a shape including a flattened top as to fit snugly within the extended portion of the shroud. The cover has a curved circumferential flange 22 to facilitate securement at the edges to the shroud. A number of screws 23 are distributed about the shroud to hold the cover in place. The latter is provided with openings for receiving the pipe 8 which carries the liquid nitrogen for the detector and also for receiving the pipes 11 which carry the two bundles of wires 10. A number of spacers 24 of hard rubber may be distributed throughout the space between the rear end of the casing and the cover 21. These spacers prevent any bowing of the cover and also serve to cause the cooling air to pass through a circuitous path across the end of the casing and thus increase the cooling effect.

The cooling air is introduced into the end space and also into the circumferential space between the scanner casing and the surrounding shroud by providing a pipe 25 extending outwardly from the cover 21. This pipe is in communication with the cooling spaces through an opening 26. The pipe may be provided with a circular flange 27 having a circumferential abutting ring. Screws 28 may secure the member to the cover element.

It is apparent that cooling air from any suitable and well-known source aboard the plane can be introduced into the pipe. The air will pass through the space between the portions 5 and 21 and then through the annular space between the casing and the shroud, being exhausted at the annular slot 18 between the shroud and the mounting ring 13. The air may be cooled to a temperature such that the interior parts of the scanner are maintained at about 110 F. This will insure that the sensitive parts, such as indium solder that is normally used in infrared scann'ers, willnot deteriorate. The air should be introduced under slight pressure so as to obtain the optimum cooling effect when passing through the shroud.

The scanner and the improved shroud are supported in any suitable manner to the undercarriage of the plane. A typical support is shown in FIGS. 2, 3 and 4. A pair of angle iron straps 29 are held to the plate 17 at each end of the shroud by the screws 21 and on both sides. The upright portion of each strap can be secured as by screw bolts (not shown) to the U-shaped iron member 30 of the undercarriage (not shown).

The improved shroud has the advantage that it can be removed from its support and readily taken apart by removing screws 21 without disturbing the interior parts of the scanner. The shroud is adaptable to most sizes of scanners since thesize of the latter merely affects the width of the air space about the scanner. The temperature within the scanner can be controlled within any range limits desired by regulating the temperature of the cooling air or the speed with which the air is caused to pass through the shroud.

From the foregoing, it is evident that I have disclosed an'improved cooling system for maintaining the interior of an infrared scanner at a temperature as will prevent any damage to the heat-sensitive devices contained therein. Thus the scanner can perform at its optimum efliciency in providing a true picture of the temperature contrast of a target whether on the ground or in the air, relative to its surroundings.

While a certain specific embodiment has been described, it is obvious that numerous changes may be made without departing from the general principles and scope of the invention.

What is claimed is:

1. In combination, an infrared scanning device formed of a cylindrical casing containing electrical and optical devices, also circuitry, which dissipate heat under operating conditions, means for reducing the internal temperature of the casing to a point as will preclude the melting of the operating parts thereof, said means including a cylindrical shroud member which surrounds said casing and spaced therefrom, the end portion of said member at the rear of the scanning device being closed and spaced from the rear portion of said device, and means for receiving cooling air which flows into and through said rear space, also through the circumferential space between the shroud member and said casing.

2. The combination set forth in claim 1 and in which the scanning device is provided with a mounting ring at the forward end, and the cylindrical shroud member at the forward end extending short of said mounting ring to leave an annular slot between the edge of the shroud and the mounting ring, said slot serving as an exit for the cooling air after passing through the circumferential space between the shroud and the casing.

3. A cooling shroud for a cylindrical infrared scanning device, said shroud being constituted of a method cylinder of fiber glass, open at one end and closed by a cover at the other end, said shroud being of greater diameter and of longer length than the scanning device in order to provide an annular space and an end space between the shroud and said device, said spaces being adapted to receive cooling air for maintaining the scanning device at an optimum temperature.

4. The combination set forth in claim 3 and in which said last-mentioned means comprises an opening in the end portion of said member to which a pipe is attached in communication with a source of cooling air.

5. The combination set forth in claim 3 and in which the shroud is formed of two halves which when placed about the scanning device are detachably joined together.

6. The combination set forth in claim 3 and in which the molded cylinder has a flattened portion extending approximately one-half of its length, said flattened portion 5 being adapted to bear against the scanning device but permitting the unflattened portion at the opposite side of the cylinder to maintain its spacial relation with respect to the scanner.

References Cited UNITED STATES PATENTS 2,583,417 1/1952 Eitelet a1 31322 X 2,829,290 4/1958 Van Warmerdam 313-22 X 3,126,498 3/1964 Bendell 313-17 X 3,306,975 2/1967 Donnay 31317 X JAMES W. LAWRENCE, Primary Examiner 5 C. R. CAMPBELL, Assistant Examiner US. Cl. X.R.