US 2246258 A
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Description (OCR text may contain errors)
June 1941- 1-; G. LEHMAN 2,246,258
' umnon OF MAKING HEAT EXCHANGE APPARATUS Filed Oct. 12, 1938 2 Shets-Sheet 1 Zmnentor (Ittomegs June 17, 1941; E. ca. LEHMAN METHOD OF MAKING HEAT EXCHANGE APPARATUS 7 Filed Oct. 12, 1938 2 Sheets-Sheet 2 I ([0 (Mom 0 m m mom 0m 0m M m (u 0m 0m 0 Patented June 1 7, 1941 UNITED lHETHOD OFMAENG HEAT EXGHAN GE APPARATUS Edward G. Lehman, York, Pa, asslgnor to' York Ice Machinery Corporation, York, Pin, a corporation of Delaware Application OctoberlZ, 1938, Serial No. 234,681
tion (and the two dieing operations can be carried out in any desired order) the bosses are 3 Claims.
This invention relates to methods 01' producing finned heat exchangers of the type in which a plurality of fin plates, which may be corrugated, are threaded on a series of parallel tubes with which they are in frictional contact, though they might be sweated in place if so desired. Where frictional contact with the tubes is relied upon, it is desirable, and in fact almost necessary, to provide some means to maintain the spacingof the relatively thin fins, and one method which has heretofore been proposed is to strike up bosses or tongues from the material of the fin itself, and rely on these bosses or tongues to maintain the spacing. Where this is done some means must be provided to keep the bosses or tongues from registering with each other, as otherwise they would not serve to space the fins.
The proposal has been to adopt an asymmetrical arrangement of the bosses or fins and to reverse alternate plates end for end so that each boss or tongue of one plate came opposite a dition to the reversal of the .position of the plates. More important still, since the fins are very closely spaced, the spacing and location of the tube openings must be absolutely precise. The precision required isgreater than that attainable by commercial manufacturing methods, and even if attainable could not be maintained because of the unavoidable wear which occurs in the use of the dies. Hence, the proposal to use reversible plates while geometrically possible, is commercially unworkable, and has never attained commercial success so far as applicant is advised. I Y
The object of the present invention is to secure the desired result without requiring reversal of the plates. With such a scheme symmetrical spacing of the tubes is not necessary and precise spacing of tube holes is not'vital, because successive plates, if directly superposed, will register whether the dies are geometrically accurate or not. Whatever errors are present in one plate will be present in the next.
According to the present method, instead oi forming the holes and bosses .by a single dieing operation, the tube openings are produced by one operation between a pair of dies, and those tube openings are located in substantially uniform position relatively to the margins of the fin plates produced. In another dieing opera.-
It can two types of fin plates are diflerentiated in that difierently spaced in formed. At .least formed, these plates being the bosses or tongues are the two series relatively to the margins of the A fin plates and consequently relatively to the tube openings. Two types oi. plate are enough, and it is simpler to use two then more, but the use of more than two is within the scopeof the inventive concept.
Assuming that only two types of plate are used, the desired result can be secured in either of two ways. A first series of identical plates can be produced and then a second series of identical plates, the two series being differentiated as stated. Then the two types of plate are interleaved.
However, from a commercial standpoint, and for practical reasons, the simpler procedure is to feed the strip from which plates are stamped so that it passes through two dieing stations. In the first station the bosses are formed. In the second station the tube openings are formed. The dies at the two stations each have one element mounted on a single platen, and the other element mounted on a single head. The dies of one set are shifta'ole back and forth on the platen and head to produce the desired differentiation. The shift occurs after each dieing operation so that alternate plates belong to the two difierentlated classes and will stack with the bosses or tongues of successive plates always out of register, and the tube openings always in register, if they are simply stacked as they come from the machine.
With this general statement of the principles of the invention a more elaborate description is given in the accompanying drawings, in which:
Figure 1 is a plan view of one type of fin plate embodying the invention;
Fig. 2 is a plan view of a second type of fin plate embodying the invention;
Fig. 3 is .a longitudinal section through a part- 1y assembled unit, showing several fin plates in stacked relation and threaded over fluid conducting tubes with which they are adapted to be employed; 1
Fig. 4 is an end view of an assembled unit with the tubes omitted; Y
.Fig. 5 is a plan view of a preferred form oi die head having stamping dies suitable for use in carrying out methods embodying the present 7 invention;
Fig. 6 is a plan view of a sheet of fin material showing one step of manufacture with the boss forming die of Fig. indotted line position; and
Fig. 7' is a view similar to Fig. 6, showing another step of manufacture with the boss forming die of Fig. 5 in full line position.
In the drawings. Figs. 1 and 2 illustrate the two types of fin which are preferably used in making heat exchangers according to the present invention, the fln plates being designated A and B in Figs. 1 and 2, respectively. Bothv of these plates are of the same outside oonflg uration and have tube receiving openings II which will register when the plates are superposed. The plates are preferably corrugated as at IS. The plates contain spacing bosses l2a and In, the bosses l2a being in the plates A and the bosses lib in the plates B. These bosses as shown are of. concavo-convex form, but are located differently with respect to the margin of the plates and the tube openings il in the plates.
Reference to Fig. 3 of the drawings shows how these plates appear when they are stacked in superposed relation as they come from the punch press and are threaded over fluid conducting tubes l3. It will be apparent that all of the openings II are in precise register, whereas the bosses Ho and no are staggered with respect to one another in the successive plates. The flange portions around the tube openings II are adapted to contact tightly with the exterior surfaces of the tubes while the spacing bosses hold the fin plates apart as clearly indicated in'Fig. 4 of the drawings.
As has been indicated above, different methods may be employed in producing fin plates according to the invention, but for purposes of illustration the preferred form only will be described briefly in connection with Figs. 5, 6 and '7 of the drawings.
Fig. 5 shows the face of the die head which carries a tube opening die IS with punches l6 located thereon. The die head also carries a boss forming die I! having b'oss forming projections I 8, the die I 1 being capable of reciprocating movement between the two positions, one indicated by dotted lines and the other by full lines. In the press, the die l5 will perform straight vertical movement only, into and out of contact with its associated platen, this movement of the die taking place concurrently with a similar movement of the die I1. However, mechanism is provided to shift die I! horizontally from one of its two positions to the other between successive stamping operations. This shifting of the die I I will, of course, be accompanied by appropriate shifting of the companion platen.
Comparison of Figs. 6 and 7 of manufacture of the fin plates from continuous strip material by means of the dies of Fig. 5. As the material enters the press from the left as far as line X-X, we shall assume that the die IT is its full line position so as to produce the bosses lZa shown at the right in Fig. 6. As the material is advanced under the die l5 up to the line YY of Fig. 6, the die IE will form the openings II for the plate A and the die I! the spacing bosses l2b for the plate B. Comparison of Figs. 6 and 7 will indicate that the bosses I 2b are formed by the die H in its dotted line position, and the bosses lZa by the same die in its full line position, whereas the openings H formed by the die IE will always bear the same relations to the margins of the plates.
As the material passes through the press and will show the steps beyond the line YY in Figs. 6 and 7, itwill be ready for cutting off, and the cutting operation may be carried out by a suitable cutting blade 2| carried at the outgoing end of die I I. In practice, it may be also desirable to distinguish one end of a plate from another by some means such as cutting ofl. a small comer, for example 22, on all of the plates (Figs. 1 and 2). Such a distinguishing cut is not necessary where the plates are stacked immediately as they leave the press, but it may be adopted, for example, where the sets of plates are separately formed and later interleaved. The location of the spacing bosses will serve to distinguish one type of plate from another. The dies in Fig. 5 may conveniently form the corrugations I8 at the same time that the bosses and openings are produced in the plates, but the corrugating means on the die have been omitted from the drawings for the sake of clearness.
As has been pointed out above, several methods may be adopted for practicing the present invention, and all capable of producing fin plates which will always have accurately registering tube openings and non-registering spacing bosses when successive plates are stacked as they leave the machine which produces them. Inasmuch as the details of machines for carrying out methods of the present invention may embody various types of construction, the basic principle of the invention in its preferred form only has been illustrated, but it is to be understood that no limitations to this particular form are intended except as such limitations may be required by the claims.
What is claimed is:
1. The method of producing a series of fin plates having registering tube openings which must align irrespective of the unavoidable inaccuracies in the construction of the punching die, and-spacing bosses which must not align on .successive fin plates, which method consists in operating on a fin blank at two successive stations, in one of which a pair of dies produces the bosses and in the other of which another pair of dies produces the openings, the two pairs of dies operating simultaneously on two successive blanks and the boss-forming die only being shifted relatively to its blank positioning means after each operation, whereby the completed plates may be stacked in the positions they occupy as they come from the machine with their openings in-strict register and their bosses always out of register.
2. The method of producing perforated fins intended to be threaded on parallel tubes and when so threaded spaced by bosses struck from the material of the fin, which method consists in feeding a strip of material from which the fins are to be formed successively between two pairs of dies, either of which pairs forms all the perforations for a fin plate, and the other of which pairs forms all the bosses for a fin plate, and between successive operations of the dies shifting one pair of dies relatively to the other, whereby the bosses of successive fin plates are staggered when the perforations of such fin plates are brought into alignment by superposing successive plates in the positions they occupy as they leave the second pair of dies.
3. The method of producing from a'continuous strip of material a series of fin plates having registering tube openings which must align irrespective of the unavoidable inaccuracies in the construction of the punching die, and spacing bosses which must not align on successive fin plates, which method consists in feeding a continuous strip of material through a press having two stations, in one of which a pair of dies produces the bosses,
and in the other of which another pair of dies after each operation of the dies, and cutting off the blank as each completed blank leaves the machine, whereby the completed 'b1anks may be stacked in the positions they occupy as they leave the machine with their openings in strict register and their bosses of successive plates out of register.
EDWARD G. LEHMAN.