PROCEDURE FOR CONNECTING METAL PIPES TO METAL SHEETS.

Description

TITLE PRIORITY METALLIC PROCEDURE FOR CONNECTING. PIPES AND METAL SHEETS. ISRAEL PATENT DOM., N. 52508 OF 12 JULY 1977 f SEP. 1885 THE DIRECTOR Coiee· TJvc-IJ 5320;Τ8042.121,1 fiepisiro A Protocol No. 25202. A / 78. MINISTRY OF INDUSTRY, TRADE AND ARTICLES Provincial Office of Industry, Commerce and Crafts of Milan COPY OF THE MINUTES OF FILING FOR AN INDUSTRIAL INVENTION PATENT In the year 1978, on the THIRTYth day, at eleven minutes past the hour of the month of JUNE, zero two, the pitta TECHNION RESEARCH & DEVELOPMENT FOUNDATION LTD MXW&X based in , . of Israeli nationality in HaIFA Israel) Via = » =«* through the agent BUGNION SPA and with domicile for legal purposes in Milan - Via Vincenzo Monti 55 at the agent has presented to me, the undersigned: - Stamped application for the granting of a patent for an industrial invention MAIN xmRmxwix titled: PROCEDURE FOR CONNECTING METAL PIPES TO METAL SHEETS iXKscèfltìaKxxwiiWix Patent Application Priority in: ISRAEL No. 52508 of July 12, 1977 x xtojtoìxx WtìiKXXXXXXXXXXXXXX accompanied by: - Description in duplicate of 8 pages of writing. - Drawings, plates η. 1 in duplo. - Letter of appointment · - Priority document and Italian translation (with reservation) -X9ùMXìXimii©iXXlU^^ - 5« - Proof of payment into the postal account in the name of the Tax and Concession Registry Office Rome of L. 56,000 issued by the Post Office of Milan 41 on 30.6.1978 n. 660 - Revenue stamp of L50GCKX 2,000 The application, descriptions and drawings listed above have been signed by the applicant and countersigned by me and stamped with the office seal. THE DEPOSITOR ..0ÌAofn.Gfi>r...... For copy conioriit arl original p, the Director (Federico Nappi} the officer of the Office (Vdillìa Russo) Hon. Ministry of Industry, Commerce and Crafts Central Patent Office - ROME -ooo-oThe company TECHNION RESEARCH & DEVELOPMENT FOUNDATION LTD, of Israeli nationality, with headquarters in HAIFA (Israel) and domiciled in Milan, Via Vincenzo Monti, 55 at the office of the agent and domiciliary BUGNION SpA; applies for a patent certificate for: INDUSTRIAL INVENTION entitled: METHOD FOR CONNECTING METAL PIPES WITH METALLIC SHEETS Priority of patent application in: ISRAEL No. 52508 of July 12, 1977 For this purpose, the following are attached: 1) Description of the finding in duplicate n, g pages 2) No. of duplo drawing boards 00668004 3) Proof of payment into postal account No. JQtlOOOiX of L. 56,000 4) Letter of appointment 5) Priority document with Italian translation (with reservation) Milan, June 30, 1978 more of the company P TECHNION RESEARCH & DEVELOPMENT FOUNDATION LTD. In faith The Agent ^ΝΙ0Ν^4·' α; 2620 2O io61 1 Λ 5320.TQ042,121.1 / es Ughi ον s. pa DESCRIPTION attached to a patent application for an INDUSTRIAL INVENTION entitled: PROCEDURE FOR CONNECTING METAL PIPES TO METAL SHEETS Applicant: TECHNION RESEARCH & DEVELOPMENT FOUNDATION LTD, Company t » · « * ♦ ··· • · » ♦ Israeli nationality, with registered office in HA1FA (Israel) Agent: EJUGNION SpA - Via Vincenzo Monti, 55 - Milan Deposited on G / U. oi No. 2&202kilt d1»»·» • · · · · :♦ • · · · · ···· •i · ·· ·· « • * • « ·· · · • » · 9 · .< * • · · • · · • 9 9 The present invention relates to the connection of metal tubes to a metal foil in order to form an intimate thermally conductive contact between their respective surfaces. More specifically, it relates to a process for manufacturing metal brushes with spaced tubes integrally connected for solar heat collectors or other heat exchangers. The most commonly used type of solar collector consists of an absorber plate made of a color-conductive metal and having tubes attached to it, curved or welded in the form of grids or coils. The absorber plate is sealed in an insulating casing which is equipped with a transparent front port positioned towards the sun in a manner that allows the absorption of a maximum of solar radiation. * It is imperative to provide a good connection between the plate and the tubes in order to obtain the best possible heat transfer characteristics for the run from the plate through the tube walls to the water flowing in the tubes, and with this objective in mind several processes have been developed in the past, the characteristics of which represent EUGNION SpA sententials will be listed below. Connect the tubes and the foils by means of a lil&ti^ta silver solder ·· ·· • · * in an excellent connection but with relatively low production costs.w ·? · • · ·. Furthermore, this process often leads to the deformation of the • · 4 4 4 •*4 4 4 4 Ordinary soft soldering on the other hand does not cause deformation, Λ&.· filled with water. 4··· * 4 the weld metal is subject to be melted whenever the pipes are not 'Sano • 4 • 4 *4 4 · 4 44 4 A very satisfactory procedure consists in preforming metal sheets4 44 4 * which by pressing grooves or depressions into them in the desired shape V'donconnecting two symmetrically formed sheets to an absorbent plate by resistance or spot welding. This process, however, is only suitable for steel sheets, since neither copper nor aluminum sheets can be welded in this way, and the process is therefore only suitable for systems involving closed circuits using a non-corrosive liquid. A simpler procedure is to clamp the pipes onto sheets that are either flat or have semi-circular grooves that fit snugly into the perimeter of the outer pipe. Common hose clamps are spaced appropriately along the hose and press it against the metal sheet, From a cost point of view this process is satisfactory, but the heat transfer is very poor. In light of the numerous defects listed, it is the object of the present invention to manufacture absorber plates from metal sheets and metal tubes at a low manufacturing cost and to ensure, at the same time, a -3BUGNION S.pA. good thermally conductive connection of the assembled parts. In accordance with the invention, the process of connecting a straight nifetal tube to a flat metal sheet along a predetermined axis, .·· ···· • · * · · takes the steps of: ....ί ;*·· • · · · · * · ·*··· · · · - blanking of the sheet with a plurality of parallel cuts, diataà»i«~C** * * ΐ · ,··;· ·· ti and symmetrical with respect to, and perpendicular to, said axis, each cut ί , ί . Ζ···· *β * * * »* being of a length not less than the external diameter of the tube, ” · ··*·· ····· .... ·· · · · - deformation of the foil by pressing the areas between every two consex>Ì·· ***** tive cuts so as to form semi-cylindrical bulges along the said axis'*cFi and protruding from the plane of the foil alternately in opposite directions, said bulges having a concave semi-circular cross-section of a diameter slightly larger than the external diameter of said tube, - insertion of said tube axially into the space formed by said alternating swellings, and - expansion of the tube towards the internal swelling surface, the expansion force being sized to stress the tube material beyond its yield point and to stress the surrounding sheet material below its elastic limit. In a preferred embodiment of such a connection the cuts are spaced equally along the axis* To form an absorber plate the foil is cut and deformed along several parallel lines according to the number of tubes that are to be connected, tubes are preferably longer than the width of the foil and are, at their ends, connected to heaters common to all the tubes on a BUGNION S.pA lamina. • * It is also possible to connect a narrow foil to a single tube, with a**buu Υ·*°* • · ♦ ♦ resulting bo equipped with two fins protruding from the opposite long sides • · · dinaii. Yy This type of threaded tube is frequently used in solar collectors*: with staggered absorber plates. . •And · · THE The expansion of the tube 6 is advantageously carried out by means of a mandrel • 1 pulled through the tube from one end to the other. • M ··. • · · · · .· • * · • · · Another procedure is to cap the ends of the pipe, fill the pipe with a liquid such as oil or water, and apply hydraulic pressure to the required size. In the attached drawing which illustrates, by way of example, a type of connection between tubes and a foil in accordance with the invention, -Figure 1 is an isometric view of part of an absorber plate before the tubes are inserted, and - Figure 2 shows the same portion of the plate as shown in Figure 1 with two tubes inserted and expanded there. Not referring to Figure 1 of the drawing, an originally flat plate is provided with a number of alternating relatively short semi-cylindrical swellings 2 and 2' extending along parallel axes, the swellings 2 projecting upwards and the swellings 2' projecting downwards, as seen from the upper surface of the plate. bulges are formed» in accordance with the Invention, by making a number of parallel cuts 3, transversely to said parallel axis and at a distance corresponding to the required length of a bulge - 5 BUGNION S.pA thread, each being of a length not less than the diameter of the ♦ · · · tube that is to be inserted. *·.··* « * » * * « » ' » · i> · « After cutting, the sheet is placed in a mold of a power press, • « Λ « which is equipped with alternating semi-cylindrical cavities and protrusions corresponding to the shape and dimensions of said bulges, and the bulges are formed by operating the power press and moving the sheet through strokes, from axis to axis, until a complete sheet is shaped as illustrated in figure 1. · · » · · ^ · · Φ »« , · · t · • · « • « · Figure 2 illustrates a portion of the assembled absorber plate in which two tubes 4 and 4' have been inserted into the cylindrical spaces formed by the alternating swellings. As the drawing illustrates, there is no gap between the bulges and the tubes, the latter having been expanded either by a mandrel of suitable size being pulled through them from end to end or by closing the ends, filling the tubes with a liquid, and applying pressure to the liquid. Both the mandrel and the liquid pressure are designed to expand the tubes towards the surrounding foil material and continue to expand them along with it; however, it is important that the tube is expanded beyond its yield strength while the foil material is only stressed within its elastic limit. This ensures that the foil material returns to its original shape and seals over the now expanded tube in a thermally conductive bond. This operation requires small tolerances between the cylinder formed by the bulges and the tubes, as well as accurate sizing of the mandrel diameter. After the tube ends 5 and 5* which project beyond the near edge of the plate, as well as the ends which project beyond the far edge of the plate - the latter are not illustrated in the drawing - have been expanded, they are each connected to a common heater, in a known manner; technique. • E • · a » · » · a · • · · · · a » a !· aaaa • · · aa » , Instead of connecting the ends of the tube to the heaters, it is of course possible to connect adjacent tubes with 100° bends to form a serpentine tube. ***** t *····· • aaaaaaaaa On the other hand, the tubes can be connected to the plate, along axes that are convergent rather than parallel, and connected at their ends by return bends. Instead of joining several tubes or a common plate, it is equally possible to form a longitudinally finned tube by attaching a tube to a plate in the form of a thin strip, using the above-described method of connection. This type of tube is advantageously used to form solar collectors with staggered absorber plates, In this regard it should be noted that figure 1 illustrates, for demonstration purposes, the swellings at the edge of the plate of the two connecting axes, the first extending upwards (2) and the other (2·) downwards, and similarly the following swellings in the same row. It is obvious that pressing the bulges by repeated pressing strokes with a common tool would result in all rows having similarly protruding bulges, however Figure 1 gives a clearer illustration of the deformation of the sheet as it was pulled.

Claims

1. CLAIMS 1 ) Method of connecting at least one straight metal tube to a flat metal sheet along a predetermined axis, characterised by Qatfò !··· • ·. * · of comprising the steps of: • · * · · · • * * * * · • ♦ · · · * · • · · · · * ϊ · · · · * ♦ ·«· ·· - blanking the sheet with a plurality of spaced parallel cuts! .··· · · ···.. ; : symmetrical with respect to, and perpendicular to, said axis, said cuts being ··*♦· • · » · · · ·* · of a length not less than the external diameter of the tube, ··...t*** • « · · · · • * · · · · - deformation of the foil by pressing the areas between every two consecutive cuts so as to form semi-cylindrical bulges along the axis alternately protruding from the foil plane in opposite directions, said bulges having a concave semi-circular cross-section slightly larger than the outside diameter of said tube, - insertion of said tube into the space formed by said alternating bulges, c - expansion of the tube towards the internal bulge surfaces, the expansion force being sized to stress the tube material beyond its yield point and to stress the surrounding foil material below its elastic point. 2) Method of connecting a tube to a plate according to claim 1, characterised in that said cuts are spaced equally along said axis. 3) A method of connecting a tube to a plate according to claim 1, characterised in that it comprises expanding the tube « jna lamànX • » · » · ♦ · • · ·· · of a · • ·· · e. · ·> ·· made of / • Λ - β by means of a mandrel pulled through it from one end to the other. 4) A method of connecting a tube to a plate according to claim 1, characterized in that it comprises the expansion of the tube by hydraulic pressure. B) A method of connecting a straight metal tube or metal tube according to claim 1 suitable for manufacturing an absorber plate for a solar collector, characterized in that 1. connecting a predetermined number of tubes to a rectangular plate having a parallel alignment, the length of the tubes being greater than the length of the plate, and the ends of said tubes protruding beyond the edges of the plate by a substantially equal length. 6) A method of manufacturing an absorber plate for a solar collector according to claim 5, characterised in that it comprises the connection of the protruding ends of the tubes or a common heater or each edge of the plate. 7) A process for manufacturing an absorber plate for a solar collector according to claim 5, characterized in that the protruding ends of each two adjacent tubes are connected by a 100° tube bend. 8) A process for connecting a tube to a plate according to claim 1, characterized in that a straight tube is connected to a strip-shaped metal plate, plus the company TECHNION RESEARCH & DEVELOPMENT FOUNDATION LTO. I' LJ ffi Η al e Rjfg an^ (fi. dèi THE AUTHORISED REPRESENTATIVE ourjrLON e* pa 1620 itili