Background of the Invention Heat exchangers are commonly employed apparatuses for exchanging heat from one medium to another, such as from one fluid to another fluid, from fluid to a gas or from a gas to a fluid. A common type of heat exchanger employs a plurality of lengths of parallel tubes through which one fluid circulates, the tubes being normally confined in an enclosure with provisions for flowage of fluid past the tubes and externally of them. In this way liquid passes concurrently through all of the tubes and

the fluid with which heat is to be exchanged, such as air, passes externally of the tubes. Normally, a header is provided at each end of the paralleled tubes to connect the ends of the tubes to a common enclosure by which one fluid is conveyed to and from the heat exchanger.

Heat exchangers are frequently employed in the aircraft industry. The typical commercial passenger transport plane has many heat exchangers, such as for

maintaining lubricant within a preselected temperature range, for heating and cooling the interior of the aircraft and so forth. While aircraft heat exchangers work in the same fundamental way as the heat exchangers for any other industrial or building application, aircraft heat exchangers are subjected to increased stress due to

acceleration, such as when the aircraft is taking off or landing, and to a high degree of vibration. Acceleration and vibration are not typically a problem with most heat exchanger applications, such as heat exchangers used in residential or commercial air conditioning. For this reason, aircraft heat exchangers have posed special problems

and additional attention must be paid in the design and manufacture of aircraft heat exchangers to combat the combined stress of acceleration and vibration.

In the typical heat exchanger that includes a multiplicity of spaced apart tube it is important that the tubes be supported with relationship to each other between th

headers affixed to each end of the tubes. This is particularly true in aircraft he

exchangers since vibration and acceleration can cause movement of the tubes if no properly supported, resulting in failure of the heat exchanger. This disclosure i directed to an improved stiffener plate for use in heat exchangers, particularly of th type employed in the aircraft industry, although the invention is not limited to aircraf heat exchangers.

For reference to others who have provided heat exchanger designs applicabl for aircraft industry and particularly for stiffener plates, reference may be had to the following previously issued United States Patents: 2,488,627; 3,245,465; 4,054,355; 4,070,751; 4,131,332; 4,150,556; 4,191,040; 4,234,041; 4,381,135; 4,647,086; 4,634,208; 4,635,711; 4,653,779; 4,699,403; 4,890,867; 4,924,586; 4,940,263; and ,958,757.

Summary of the Invention

This invention provides an improved stiffener plate for use in a heat exchanger of the type employing a plurality of parallel tubes, the stiffener plate serving to support the tubes at locations intermediate the headers affixed to the opposed ends of the tubes in a way so as to reduce the effect of vibration and acceleration. The improved

stiffener plate is in the form of a unitary relatively thin planar metal plate. The plate has an opening therethrough for each tube to be supported. Each opening is in the form of an integral short-length tubular ferrule portion of an internal diameter slightly greater than the external diameter of the tube to be received therethrough. Each integral ferrule portion has an end surface that is in a plane parallel to and spaced from the plate. The ferrules have an inner tubular surface defined in part by an arcuate portion of a selected first radius from the plate first surface and an outer tubular surface defined in part by an arcuate portion selected of a radius smaller than the first radius from the plate second surface. This arrangement provides a method of supporting heat exchanger tubes in a secure manner wherein areas of high stress concentration are not imposed on the heat exchanger tubes by the stiffener plate.

Further, the stiffener plate of this disclosure is substantially less time consuming to manufacture than other types of stiffener plates, particularly those which include a short-length tubular ferrule brazed to the plate for each opening therethrough.

A better understanding of the invention will be had by reference to the following description and claims, taken in conjunction with the attached drawings.

Description of the Drawings

Figure 1 is an isometric view of a typical aircraft type heat exchanger employin the improved stiffener plate of this disclosure.

Figure 2 is an elevational view of a core from an aircraft heat exchanger of th type illustrated in Figure 1 showing multiple tubes and the type of stiffener plate of thi

disclosure used therewith.

Figure 3 is a cross-sectional view taken along the line 3-3 of Figure 2 showin an elevational view of a stiffener plate of this disclosure as positioned within the hea exchanger core member.

Figure 4 is an enlarged elevational view of the stiffener plate of Figure 3. Figure 5 is an isometric partial view of one portion of a stiffener plate of thi

disclosure showing tubes extending through the stiffener plate.

Figure 6 is an enlarged fragmentary view of the stiffener plate as taken along the line 6-6 of Figure 4 showing one opening through the stiffener plate with the integral ferrule portion as employed to receive one heat exchanger tube therethrough. Figure 7 is a prior art illustration of one rudimentary type of stiffener plate as used in heat exchangers.

Figure 8 is a fragmentary view of a prior art stiffener plate of another configuration utilizing a type of ferrule that is secured through an opening through the stiffener plate by mechanical fastening, such as by expansion of the ferrule. Figure 9 is a fragmentary view of a stiffener plate having a tubular ferrule brazed to an opening in the plate, the tubular ferrule serving to receive a heat exchanger tube therethrough.

Figures 7, 8 and 9 are representative of the most commonly employed prior art type of stiffener plates as used in aircraft heat exchangers and to which the improved stiffener plate of this invention is an improvement.

Description of the Preferred Embodiments

Referring to the drawings and first to Figure 1 , a typical aircraft heat exchanger is illustrated in Figure 1 , the heat exchanger being indicated generally by the numeral 10. The heat exchanger includes a core, generally indicated by the numeral 12, that

is, in effect, a bundle of tubes, the tubes being indicated by the numeral 14. The tubes

are supported as a package and arranged for passage of fluids, such as a liquid or a gas, through the interior of the tubes. A first header 16 is affixed to heat exchanger

10 at one end which provides communication with one end of each of tubes 14, and the second header 18 at the opposite end of the heat exchanger provides communication with the other end of the tubes. A support bracket 20 is used to add structural rigidity to the heat exchanger and provides for passage of a second fluid, such as gas which is typically air or exhaust gases, through the heat exchanger to

exchange heat with the fluid passing within the interior of tubes 14.

It is to be emphasized that the apparatus described to this point is to form background for the invention that is the subject of this disclosure and heat exchanger 10 in Figure 1 is merely illustrated as an example, as heat exchangers can take a great deal of different forms. In order to support tubes 14 within the heat exchanger core, it is usually necessary, unless the tubes are of very short length, to provide stiffener plates 22. The function of stiffener plates 22 is to structurally support tubes 14 in a manner to resist the forces of acceleration, vibration, and gravity and to maintain the tubes in their preselected spacing.

Heat exchangers of the type illustrated in Figure 1 have long used stiffener plates of various embodiments. Figure 7 is a diagrammatic view of a stiffener plate 24 having an opening 26 therethrough which receives a heat exchanger tube 14. In this arrangement, there is an opening 26 for each heat exchanger tube. The opening is

of a diameter slightly greater than that of the exterior diameter of tube 14 so that tube

14 may be inserted through the openings in the heat exchanger during assembly the heat exchangers -- that is, tubes 14 are not affixed to stiffener plate 24. it can b seen that opening 26 in plate 24 provides relatively sharp edges in an area of hig stress concentration so that the possibility of the plate damaging or penetrating a tub

14 exists, particularly in aircraft applications wherein vibration is a constant problem.

Figure 8 is another example of the prior art arrangement for a stiffener plate 2 having an opening 30 for each of the heat exchanger tubes 14. In this arrangemen a short-length tubular ferrule 32 is positioned within opening 30. In the commonly employed arrangement as illustrated, ferrule 32 is enlarged at ends 32A and 32B.

Further, ferrule 32 is mechanically secured to stiffener plate 28 such as by expansion of the ferrule after it is positioned within opening 30. This expansion step attempts to mechanically secure the ferrule to plate 28 but the ferrule is not otherwise secured to the plate. This effort to mechanically attach a ferrule of the type shown in Figure 8 has not been completely successful since heat exchangers, particularly as used in aircraft, are frequently subjected to widely varying temperatures, and the expansion and contraction of support plate 28 tends to destroy the mechanical bond between the plate and the ferrule.

The embodiment of Figure 8 has substantial advantages over that of Figure 7, but attempts to mechanically bond the ferrule to the plate have not been completely successful. Further, it can be seen that providing a stiffener plate with the large number of ferrules required wherein each ferrule must be internally expanded into mechanical engagement with the plate is extremely time consuming and expensive.

Another type of stiffener plate is shown in the fragmentary view of Figure 9 in

which the stiffener plate 34 has opening 36 therein for each tube and each such

opening 36 receives a short-length tubular ferrule 38. The ferrule 38 is attached to stiffener plate 34 by brazing at 40. The tubular ferrule 38 has opposed ends 38A and

38B that are in planes parallel to plate 34.

The arrangement of Figure 9 is a distinct improvement over that of Figures 7

and 8. By the brazing 40 of Figure 9, tubular ferrule 38 remains secured to the fastener plate 34, but brazing a ferrule in each opening is exceedingly time consuming

and expensive. Further, the tubular ferrule 38 does not have the advantage of an arcuate internal surface, as does that of Figure 8.

Thus, the prior art illustrated in Figures 7, 8, and 9 has disadvantages which are overcome by the stiffener plate of this invention, as illustrated best in Figures 5 and 6.

Turning now to Figures 2-6, the improved stiffener plate of this invention is disclosed. Figure 2 shows the use of three stiffener plates 42 of the type of this

invention. Figure 3 shows, in elevational view, one side of one of the stiffener plates

42, and Figure 4 shows a stiffener plate alone before it is used to become a part of a

heat exchanger core assembly.

The stiffener plate 42 is a unitary relatively thin planar metallic plate having a first

surface 44 and a second opposed surface 46. There is provided an opening 48 for each of the tubes 14 making up the core of a heat exchanger.

The unique feature of the stiffener plate of this invention is best seen in Figures

5 and 6, and particularly in Figure 6 which is an enlarged view of one opening 48 in

plate 42. The opening 48 is configured to provide an integral short-length tubular ferrule portion 50 for each opening 48 in stiffener plate 42. The integral ferrule portion

has an end surface 52 that is in a plane parallel to and spaced from the stiffener plate second surface 46.

The opening 48 through plate 42 and the integral ferrule portion 50 is form by an inner surface formed in part by an arcuate portion 56 at a selected first radi

formed in the plate second surface 46. The arcuate portion 50A of the integral tubul ferrule portion 50 is further formed in part by an arcuate surface 60 at a radius 62 th is smaller than the first radius 58. The inner arcuate surface 56 is a continuation of t stiffener plate first surface 44 and the outer arcuate surface 60 is a continuation of t plate second surface 46.

Figure 5 shows a small portion of stiffener plate 42 of this disclosure wit fragmentary lengths of heat exchanger tubing 14 extending through openings 48. The integral ferrule employed for each opening in stiffener plate 42 ha advantages over the prior art devices as represented by Figures 7, 8 and 9. First, th integral ferrule, as best seen in Figure 6, provides an opening in which the stres transferred between the heat exchanger tube and the stiffener plate is not concentrate as in the arrangement of Figure 7 but, instead, a short-length tubular portion 50B o the plate receives each of the tubes so that contact between the plate and the tube is spread over a length of the tube rather than concentrated only in an area equal t the thickness of the plate, as is illustrated in Figure 7. Further, the integral ferrul cannot become disengaged from plate 42 as can occur in the prior art embodiment of Figure 8. The integral ferrule of this disclosure eliminates the requirement of brazing of a tubular ferrule for each opening through the plate, as in the embodiment of Figure

9, resulting in substantial cost saving.

Thus, the stiffener plate of this disclosure with the integral ferrules has substantial advantages over the known prior art.

It should be emphasized that the illustration of the prior art in Figures 7, 8 and

9 is not intended to be exhaustive but merely illustrative of commonly employed stiffener plates to which the present invention is directed as an improvement.

The claims and the specification describe the invention presented and the terms

that are employed in the claims draw their meaning from the use of such terms in the specification. The same terms employed in the prior art may be broader in meaning than specifically employed herein. Whenever there is a question between the broader

definition of such terms used in the prior art and the more specific use of the terms herein, the more specific meaning is meant. While the invention has been described with a certain degree of particularity, it

is manifest that many changes may be made in the details of construction and the arrangement of components without departing from the spirit and scope of this disclosure. It is understood that the invention is not limited to the embodiments set forth herein for purposes of exemplification, but is to be limited only by the scope of the attached claim or claims, including the full range of equivalency to which each element thereof is entitled.