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Publication numberUS3312538 A
Publication typeGrant
Publication dateApr 4, 1967
Filing dateOct 22, 1965
Priority dateMar 21, 1962
Publication numberUS 3312538 A, US 3312538A, US-A-3312538, US3312538 A, US3312538A
InventorsAnts Hansson
Original AssigneeContinental Can Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Rolled metal strip
US 3312538 A
Abstract  available in
Previous page
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Claims  available in
Description  (OCR text may contain errors)

April 4, i967 HANssoN 3,312,538

ROLLED METAL STRIP Original Filed March 21, 1962 4 Sheets-Sheet 1 PIB 4', E967 A. HANSSON 3,32,538

ROLLED METAL STRIP Original Filed March 21, 1962 4 Sheets-Sheet 2 INVENTOR n.' j AN-rs Fil-Nason A ORNEYJ April 4, 1967 A. HANssoN 3,312,538

ROLLED METAL STRIP original Filed March 21, 1962 4 sheets-sheet s INVENTQR AN-rs H Au ssoN ATTOR NEYS pl 4, 1967 A. HANSSON 3,312,538

ROLLED METAL STRIP' Original Filed March 2l, 1962 4 Sheets-Sheet 4 INVENTOR Ann-s HANSSON ATTORNEYS United States Patent O This application is a division lof application Ser. No. 181,347, filed Mar. 21, 1962, now Patent No. 3,239,922.

This invention relates to articles having a plurality of channels therein.

An object of the invention is to provide articles which have a plurality of internal passages separated by partitions which are integral and monolithic with the outer walls.

A further object of the invention is to provide an article having a plurality of internal channels separated from one another by partition walls which are integral with the outer closing walls and have externally projecting fins which are also integral with the outer closing walls.

Another object of this invention is to provide an article of manufacture consisting of integral metal providing continuous outer walls and internal septa defining quadrilateral internal longitudinal channels in the article, each septum merging with an inner surface of an outer wall by a curved surface at one face of the septum, and by a reentrant angle at the other, at least one of the outer walls having fins integral with said wall and extending away therefrom.

Another object of this invention is to provide an article of manufacture having outer walls and septa integral with said walls and extending therebetween for defining quadrilateral internal channels and end closures attached to said walls, some of the septa being excised at the ends to provide communications between adjacent channels.

Another object `of this invention is to provide an article of manufacture, of the type set forth above, wherein the end excisions are at atlernate ends of adjacent septa to provide a tortuous flow passage through the article.

Another `object of this invention is to provide an article of manufacture, of the type set forth above, in which two first septa extend between the end closures, and at least one second septum is located between the rst septa, both ends of the second septum being excised to provide manifold spaces adjacent the end closures.

Another object of this invention is to provide an article of manufacture comprising spaced wall portions, septa integral with and located in parallel planes extending between the wall portions, the sidemost septa being spaced from the edges of the wall portions parallel thereto, the wall portions between the respective sidemost septum and the adjacent edge being directed toward and into abutment and connected with one another.

Another object of this invention is t-o provide an article of manufacture comprising a rolled metal strip of essentially uniform thickness and having integral angularly directed and overlapping rst longitudinal discontinuities between metal portions extending from side to side of the strip, and having angularly directed llongitudinal second discontinuities extending from a roller surface thereof, the second discontinuities defining between them integral scales having thin edges at the surface and being thicker at the region of integration with the metal portions overlying the integral discontinuities.

With the above and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claimed subject matter and the 3,312,538 Patented Apr. 4, 1967 Mice several views illustrated in the accompanying drawings.

In the drawings:

FIGURE 1 is an end view of a billet prepared under the practice of this invention;

FIGURE 2 is an end view tof a section of the Strip product made by rolling the billet of FIGURE 1;

FIGURE 3 is a like View, showing the surface separations and a partial opening of the strip of FIGURE 2;

FIGURE 4 is a like view, showing the strip opened until the septa are essentially at right angles to the surface layers;

FIGURE 5 is a like view, showing the product of trimming and joining the lateral edges of the surface;

FIGURE 6 is a sectional view substantially on line 6 6 `of FIGURE 5, with end closures in place;

FIGURE 6a is a partial sectional View substantially on line a-a of FIGURE 6;

FIGURE 7 is a sectional view corresponding to FIG- URE 6, but showing different end closures and excisions from the septa;

FIGURE 8 is a view similar to that of FIGURE 1, showing a form of billet for providing cells in two rows;

FIGURE 9 is a view similar to that of FIGURE 2, of the strip product from the billet of FIGURE 8;

FIGURE 10 is a view at a larger scale showing the expansion of the strip of FIGURE 9;

FIGURE 11 is a View similar to that of FIGURE 1, showing a third form `of billet, for producing an article having a plurality of internal channels and pluralities of external fins;

FIGURE 12 is a View similar to that of FIGURE 2, showing the strip product of rolling the billet of FIG- URE ll;

FIGURE 13 is a like view at a larger scale, of a part og the article made by expanding the strip of FIGURE 1 FIGURE 14 is a view similar to that of FIGURE 1, showing a fourth form of billet;

- FIGURE 15 is a view similar to that of FIGURE 2, showing the strip product of rolling the billet of FIG- URE 14;

FIGURE 16 is a view showing an article made by eX- panding the strip of FIGURE 15;

FIGURE 17 is a View similar to that `of FIGURE 11, showing a fth form of billet;

FIGURE 18 is a view similar to that of FIGURE 12, showing the strip product of rolling the billet of FIG- URE 17;

FIGURE 19 is a like View on a larger scale, showing an article made by expanding the stripl of FIGURE 18;

FIGURE 20 is a View of a strip as in FIGURE 2, showing the raising of a surface scale by sh-ot peening.

In the form of practice shown in FIGURES 1 to 4, a billet 10 is prepared, illustratively of rectangular crosssection, and provided with a plurality of inclined and overlapping internal channels 11, 12, 13, 14, 15, 16 which have parallel walls with original billet metal between pairs of the channels, as shown at 17, 18, 19, 20, 21. Therewith, the billet has integrated solid metal lateral portions 22, 23 at its ends, and upper and lower portions 24, 25 of solid metal. The channels are wider than they are thick and extend parallel to one another along the length of the billet. Longitudinal grooves or notches 26 are formed in the upper and lower faces of the billet to preclude weakenings therein in line with the outermost edges of the two sidemost channels 1.1, 16: these notches extending for, for example, about one-half of t-he thickness of the respective metal face portions 24, 25. The grooves or notches 26 preferably have their base or root located adjacent to the end of sidemost channels 11 and 16 nearest to the respective lateral edge of the billet 10.

Such billets may be prepared by casting molten metal into a mold and around central portions of nondbonding and removable cores positioned therein. For example, in making an aluminum billet, the cores can be at pieces of stainless steel preferably having thin coatings of a weldpreventing material such as a refractory oxide. Such cores may be single sheets of the cross-section for providing a respective channel and later removed by stretching until their sections are smaller than the respective channel in the ingot: or the cores may be composite, e.g. each being of three pieces having interlitting ribs and grooves at their interfaces, the central piece being convergently tapered and the side pieces having the interfitted edges correspondingly tapered, so that the central piece can later be easily withdrawn and thereby free the side pieces for like withdrawal. When the ingot is col-d, the cores are enga-ged at their projecting ends and stretched by tension thereon so they are removed. Flattened hollow tubes maybe positioned in inclined overlapping relation in a mold, and ingot metal cast around them for bonding them to an integral Whole ingot: this practice being of particular advantage when the tubes a-re of a cladding metal such as pure aluminum wit-h the cast metal being an aluminum alloy, or of stainless steel when the cast met-al is cheaper carbon steel. Another procedure is to prepare plain strips of cross-sectional dimensions at least equal to those of the inter-channel metal portions 17, 18, 19, 20,

'21 of FIIGURE 1, coating most of one s-urface of each strip with a resist such as flame-sprayed alumina or other refractory material, while leaving a longitudinal marginal portion bare and of bondable metal, placing a pack of such strips in a mold while leaving such marginal portion exposed along with a like marginal width a-t the other surface of t-he individual strip at the other side of the pack, and casting metal around the pack for bonding to the exposed margins of the strips a-nd therewith presenting the-resist coatings as the channels 11, 12, 13, 14, 15, 16 of FIGURE 1. Such billets may also be prepared by extruding through so-called blind hole dies, in which the metal is forced along like cores and passes therefrom in the illustrative multi-channeled form.

This billet of FIGURE l is then subjected to a schedule of rolling and heat treatment, after a suitable anti-welding resist material has been formed or is present in the channels 11, 12, 13, 14, and 16. Such resist may also be employed in the notches 26, but is not usual- =ly necessary, noting that surface lubrica-nts are customarily employed in rolling. Suitable resists are metal salts such as sodium and barium chloride which undergo lthe phenomenon called cold flow under the pressure and temperature of rolling. Organic high molecular substances such as silicones, metal stearates, polymers of et-hylene linkage structure, polycarbona-tes, epoxy resins, and phenol aldehyde resins are usable. Dependent upon the met-al and the conditions of rolling, refractory powder resists such as mica, talc, graphite, aluminum and other metal oxides can be employed.

As a result of a schedule of hot and cold rolling, the strip S of FIGURE 2 is produced, in which the primed numerals are employed as in FIGURE 1 to show the relationship of the corresponding parts after they have been reduced by rolling. As a result of the reduction in thickness with extension of length, the channels become essentially closed upon thin residual layers of the likewise extended resist material, and their angles relative to the billet surfaces are flattened. The metal portions 17 '-21' are correspondingly reduced in thickness in the strip S. The notches l26' are likewise closed and reduced in height but remain essentially opposite the outer ends of the channel residues 11,`16'.

The strip has smooth surfaces, and the locations of the channel residues 26 are essentially invisible; and the residues 11, 12', `13','1l', 15', 16 are likewise essentially invisible at exposed cross-sections produced by cutting the strip transversely. 'Howeven these external notch residues 26 provide weaknesses in the rolled strip, and can now be broken through by flexing as indicated in FIGURE 3, so that the separation occurs along longitudinal lines determined by the positions of the notches 26, in the original billet of FIGURE 1, and then by tension, `as shown by the arrows, in opposite direction-s upon the lateral portions 22', 23' of the strip, the continuous surface metal portions 24', 25' are caused to shift laterally with respect to one another, wherewith the metal wall portions or layers 1'7'-21, located between pairs of the resist residues of the original channels, rock essentially about their end connections to the surface metal as fulcra. Therewith, the distances between the rolled surfaces of the strip S are increased.

Ultimately, as shown in FIGURE 4, the metal wall portions or septa 1?' 21' can be brought to essentially right angles to the outer surfaces of the strip, and therewith form a series of channels 12"-15" which are of a `general quadrilateral shape. The upper and lower walls of these passages or channels are not parallel to the outer surfaces of the strip S, but are at an angle thereto corresponding to the angle occupied by the resist residues of the channels 11-16 as shown in FIGURE 2. The walls 1721' are of essentially uniform thickness in the illustrative form.

The product thus made may have any desired number of channels 11'-16' in the original billet, and a corresponding number, less two, of passages 12"-15" in the finished structure. The height of the respective walls 1721', and .thus of the individual passages, is determined by the amount of overlap of the channels 11-16 in the original billet: and the ratio of thickness of the individual walls 11W-21 to the average thickness of the surface metal portions 24', 25 of the opened strip is determined by the ratio of the distance between lines a and b to the total billet thickness, noting that the lines a and b extend tangent to the tops and bottoms of the channels in the illustrative form, and define the surface metal portions 24', 25 which extend from side to side of the billet, as compared to the central portion between the lines a and b which contains the overlapping channels.

Such a structure forms a member which can be employed for structural purposes, as a wall or stiffener: and can also be used in the form shown as a conduit, for example, for heat exchange.

Where small heat exchange bodies, such as those for the evaporators of mechanical refrigerators, are to be made, the extending thicker ends 22', 23 of the opened strip of FIGURE 4 can be cut away, leaving portions extending laterally from the walls 17', 21', and these portions can then be brought together as shown in FIGURE 5 and joined by cement or by welding.

A heat exchange body having an upper inlet and a bottom outlet is shown in FIGURE 6 as comprising a structure prepared from a body as in FIGURE 5, with the end septum walls 27 left for the full length, while the intervening walls 28 have their ends excised or cut away, between the surface metal portions 24;', 25' to provide connecting spaces 29. The ends of the body are then provided with closing walls 34, 36 having respective conduit connections 35, 37. These end walls may be assembled as shown in FIGURE 6-A, where an end wall 34 has the turned anges 34a closely tting the surface metal portions 24, 25 and sealed thereto. In the structure of FIGURE 6, a fluid entering at 35 is distributed in the space 29, which operates as a manifold, and then passes downward in the several passages, being collected again at a lower manifold portion 29, and passing out through the conduit connection 37. In FIGURE 6, the connection at the pinched lips 3@ is illustratively by spot-welding at points 31.

In the form of heat exchange device shown in FIGURE 7, the general section and the end septum Walls 27 are as in FIGURE 6, but inthis case alternate intermediate walls 38, 38 are clipped at the bottom and the intervening walls 39, 39 clipped at the top, all between the surface portions 24', 25'. End walls 34, 36 with conduit connections 35, 37 are provided as before. Illustratively, in this form, the pinched lips 30 are connected by a roll-forged seam 32 at each lateral edge. In this structure, a fluid entering at connection 35 passes in zigzag fashion as shown by the arrows, and issues from the other conduit connection 37.

The same principle can be employed for providing a body having a number of rows of lonigtudinal passages. Thus, in FIGURES 8-10, two such rows are provided.

In FIGURE 8, the billet Ba is provided with two rows of inclined channels 11-16, each with the intervening metal portions 17-21. The longitudinal notching grooves 26 are provided as before, in alignment with the outer ends of the lateral channels 11: while the other lateral channels 16 are extended by horizontal branches 41, 42 for the lower and upper rows of channels, noting that these branches 41, 42 terminate short of the lateral sides of the billet Ba. Above the respective branches 41, 42 are the metal end portions 22a, 23a: while below them are the metal end portions 22h, 23h. The roll engaging surfaces of the ingot are provided by the solid metal portions 24, 25 as in FIGURE l, these being in parallel planes. At the median plane of the billet, represented by the dotted lines M-M, there is also a continuous metal portion 43, extending from side to side of the billet.

Upon rolling this billet to the strip Sa as shown in FIGURE 9, the product is much as in FIGURE 2, except that two sets of overlapped resist residues respectively above and below the median plane M-M are provided from the channels 11-16 with intervening metal portions 1'7-21. The surfaces of the strip Sa of FIGURE 9 are planes and are provided by the metal 24, 25: while a median continuous strip of metal extends from side to side, between the two rows of resist residues.

For opening the strip of FIGURE 9, its lateral edges may be cut away at planes illustrated by the upright lines 44, these cuts extending through the residues of the channel extensions 41, 42, and thereby giving access to these channel residues at the edges of the strip. By bending the edges of the strip to separate the remaining parts of the metal portions 22a', 22b' and 23a', 23b', and exerting tensions on the portions 2217' and 23a as indicated by the arrows, the structure may be opened to the form shown in FIGURE 10. Therewith, opposing tension on the parts 22a', 23b can be employed to assure the proper positioning of the intervening walls 17'-21 of the two series shown. Here, as with FIGURE 4, the individual walls 17'-21 are of uniform thickness in the illustrative practice and are directed at right angles to the outer surfaces provided by the metal portions 24'-25, noting that the inner surfaces of these metal portions have the inclined direction as before. The opened structure thus has the two rows of channels as shown in FIGURE 10.

By employing more than two rows of channels 11-16, it is obviously feasible to prepare a cellular body having any number of rows of channels as may be desired.

The principle can also be employed for the making of bodies having internal passages and external fins.

In the practice of FIGURES l1 to 13, the billet 50 has the inclined overlapping channels 11416 as before, with the end channels having the extensions 41, 42. Between these channels are the metal portions 17-21 as before. Inclined grooves 51 are cut into the upper and lower surfaces of the billet 50 and, in the illustrative form, the grooves are slits of uniform width and depth with the inner ends of the grooves 51 respectively aligned with the ends ofthe internal channels 11-16, as shown by the dotted lines c.

When the billet of FIGURE 11 is rolled, with antiwelding resist in the channels 11-16, and preferably also in the grooves 51, a strip Sb as in FIGURE l2 is produced in which the internal residues 11'16' have the metal wall portions 17'-21 between them: and a series of metal scales 52 are formed on the upper and lower surfaces of the strip Sb of FIGURE l2, overlying the respective residues S1 of the grooves 51. When the strip Sb is cut along planes such as that shown by line 44 with intersection of the residues of channel portions 41, 42 at the two edges, and opened, a structure as in FIG- URE 13 can be formed. Therewith, the scales 52 have been raised substantially to right angles and thus provide longitudinally extending iins parallel to one another and to the septum walls 17', 18', 19', 20' provided by the metal from the corresponding parts of the billet in FIGURE l1. Between the septum walls and the ns are continuous laterally extending metal portions 24a, 25a which .are of essentially uniform thickness between the ns, but are inclined relative to the general horizontal lateral plane of the body shown in FIGURE 13, in general as described above for FIGURES 4 and l0. Between the internal walls 17', 18', 19', 20' are the individual channels 12", 13" and 14".

As an illustrative practice under FIGURES 1-4, the billet may be three inches thick after scalping. The channels 11-16 can be one-eighth of an inch thick, and 1.4 inches wide so that the distance between lines a and b is about one inch with the channels extending at an angle of about 45 degrees to the horizont-al and thus overlapping by half their respective horizontal extensions. When this is rolled to a final strip S as in FIGURE 2 having a thickness of 0.040 inch, the face layers 24', 25' have an average thickness of 0.015 inch each, while the septum walls 17'-21 are about 0.010 inch each, noting that their surfaces are at a very small angle relative to the strip surfaces. These walls overlap, in the strip, by about one inch: so that when the strip is opened into the channeled body of FIGURE 4, the internal wall spacing of the respective upper and lower 'body Walls is about one inch: and the quadrilateral passagesV have a section of about one inch by one inch. With the same dimensions in FIGURE 1l, and the surface grooves 51 thin and cut for about half the depth of the surface metal, the -cell dimensions are the same, and the fins 52 of FIGURE 13 are about 0.007 inch thick at their bases and extend about an inch.

FIGURES 14 to 16 show a procedure like that of FIGURES 8 to l0, for producing articles having more than one row or layer -of cells in its thickness. In FIG- URES 14 to 16 the two rows of original channels 11-16 are arranged symmetrically or in herringbone fashion relative to one another, converging toward the median plane M. The billet 40a has the surface grooves 26 located opposite the outer ends of channels 11, and a further internal separation channel 42a is provided at the median plane M, illustratively of T-shape with the stem directed toward but terminating short of the lateral surface of the billet, and with the cross-bar extending from the median plane toward the rollengaged surfaces of the billet. This cross-bar thus is adjacent lbut spaced from the inner ends of the channels 16, with its ends above Iand below the planes c, d of the inner ends of the rows of channels. Upon rolling, the strip Sd of FIG- URE 15 is formed: which, upon cutting -along the plane of line 44, permits engagement of the two lateral masses 22d', 23d' and the employment of laterally directed tensions thereon, opposed Iby engagement with the lateral mass 22)" at the other side, and the opening of the structure to the form shown in FIGURE 16, noting that the weaknesses adjacent the mass 22j', produced by the adjacency of the respective residues of a channel 11' and a groove 26' permit tearing -or breakage so that the surface bodies 24', 25 are freed for movement from one another and from the median body 43'.

FIGURES 17-19 show a practice corresponding to.

that of FIGURES 11-13, for forming -articles having lnternal channels and external tins. Here the external grooves 51 are symmetrical, and with rolling by feeding the billet to the roll nip in the transverse direction shown by the arrow permit a preliminary widening of the billet before, longitudinal rolling is done to bring the billet to the desired final thickness. Likewise, the surface grooves 51 can be at low angles to the roll-engaged surfaces, and can overlap one another as shown. The strip of FIGURE 18, thus produced, can then be opened to the form shown in FIGURE 19. When the grooves 51 of the billet overlap, as shown in FIGURE 17, the ribs 52 `are higher than the spacing between ribs, and can have the composite shape of essentially uniform thickness adjacent the lbody layers 24a', 25a', and tapering at their margins.

The operation of opening the rolled strip into multicellular form is simple; and the ns when present can be raised by mechanical operations. A preferred manner of raising the fins is illustrated in FIGURE 20, where a strip Sb as in FIGURE l2 is subjected to surface blasting with particles as in shot-peening, e.g. as indicated by the arrows 80. An air blast ofy such particles acts differentially on thicker and thinner parts of the scales, so that the edges are raised as shown by the dotted lines 51a, thus providing easy entry and engagement with their lower surfaces by knife-like edges for completing the lifting to the upright position without damage to the edges. Such shot-peening and edge lifting can be effected lby moving the article opposite a transverse row 81 of blast nozzles, e.g. in the direction of the arrow 82.

The ingots can be prepared in various ways, and billets prepared other than by casting can be employed for the purpose. For example, metal strips of a material not bonded by the ingot metal can be held spaced in proper position in an ingot mold, and the ingot metal cast around them. For example, with aluminum, stainless steel strips can be employed having a dimension of one-eighth inch thick by 1.4 inches wide in the above illustrative practice. Alternatively, refractory resist powders, such as talc,

chalk, mica, graphite, lime, aluminum oxide, and other refractory material can be formed into bars and positioned in a mold and the metal cast around them to form ingots of the desired cross-section. When the channels are thin, it is preferred to form them by the use of the non-welding metal core strips, which are then placed under tension in the cold ingot, so that they may be pulled therefrom and leave the channels: or by use of flattened integratable tubes: these channels can then be lled with anti-welding material, followed by closure of the ends of the ingot and subjection to the desired schedule of hot and cold-rolling.

The procedure permits the use of ductile metals such as aluminum and its alloys, steels of carbon and alloy types, copper and copper alloys' including brass and bronze, tin, for making cellular structures with or Without external fins, which are monolithic and present surfaces of the selected metal and thus having the same electrochemical resistance, and competent of retaining, in the finished article, the work-hardening effects of cold working.

The strips rolled from the `billets can be coiled, stored, shipped and sold as articles of commerce. They can -be cut to desired lengths and then expanded, lbefore or preferably after raising the fins when present.

The invention is not limited to the illustrative practices and products shown, `and may be employed in many ways within the scope of the appended claims.

What is claimed is:

1. An article of manufacture comprising a rolled metal strip having opposed rolled surfaces and being of essentially uniform thickness and having internal angularly directed and overlapping first longitudinal discontinuities between metal portions extending from side to side 0f the strip, and having angularly directed longitudinal second discontinuities extending inwardly from said 4opposed rolled surfaces thereof, said second discontinuities defining between them integral scales having thin edges at said surface and being thicker at the region of integration with the said metal portions overlying the internal discontinuities.

2. An article of manufacture comprising a rolled metal strip of essentially uniform thickness and having internal angul-arly directed and overlapping first longitudinal discontinuities between metal portions extending from side to side of the strip, and having angularly directed longitudinal second discontinuities extending inwardly from a rolled surface thereof, said second discontinuities deiining between them integral scales having thin edges at said surface and being thicker at the region of integration with the said metal portions overlying the internal discontinuities, each of said second discontinuities being disposed in overlapping arrangement with an adjacent one thereof.

References Cited by the Examiner .UNITED STATES PATENTS 2,597,343 5/1952 Lang 29-19O X 2,981,520 4/1961 Chadburn 165-170 2,996,792 8/1961 Mackie 29-157.3 3,205,560 9/1965 Lochlein 165-170 X FOREIGN PATENTS 237,974 10/ 1959 Australia. 1,191,345 4/1959 France.

159,933 3/ 1921 Great Britain.

vROBERT A.y OLEARY, Primary Examiner.

M. A. ANTONAKAS, Assistant Examiner.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2597343 *Dec 21, 1945May 20, 1952Bocjl CorpConnected strip of fastener units
US2981520 *Nov 9, 1959Apr 25, 1961Borg WarnerPlate-type heat-exchangers
US2996792 *Oct 15, 1957Aug 22, 1961Aluminium Lab LtdMethods for producing hollow metallic sheets
US3205560 *Apr 27, 1956Sep 14, 1965Reynolds Metals CoMethod of making a pressure welded finned panel
AU237974B * Title not available
FR1191345A * Title not available
GB159933A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4390599 *Jul 31, 1980Jun 28, 1983Raychem CorporationEnhanced recovery memory metal device
U.S. Classification428/596, 428/583, 428/573
International ClassificationB21D53/02, B21D53/04
Cooperative ClassificationB21D53/04
European ClassificationB21D53/04