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Oct. 22, 1946. Y o. w. HOSKING ‘ 2,409,759 DIRECT BONDING OF RUBBER TO METAL Filed Sep1i.'13. 1941 ’ - A‘ I @m "6 \A 245%; 23 > / 2 v , 2, \ 26/ . 33 //V///J/%/ 3'6 3‘4 ' 35 ' ‘ 25 . 5'“. 35 § . “>2”? - X32 5"“\\\\\“?“4’/ ~ 33 a4 M33056 , - UaZZe‘y -; 141212912359 ' BY . ,wén; ATTORNEYS ' / Patented Oct. 22, 1946 2,409,759 UNITED STATES PATENT OFFICE 'QDIREGTKBGNDING OF RUBEER T0 METAL Oakley 'W. Hosking, Monroe, N. '-Y., as'signor to - Composite Rubber Products Corporation, ‘Bridgeport, Conn, a corporation of Connecti cut "Application September 13, 1941, Serial No.410,696 17 Claims. (Cl. 154-430) 2 1. ‘This invention ‘ relates ' to-the art of bonding rubber to metal, and to a process for theproduc ‘tion of-composite‘rubber-metal articles wherein rubber or a rubber-like sub-stance is securely bonded directly‘ to ‘a metal surface. More speci?cally, ‘the invention relates to a . stand the strains to which they were to ‘be sub jected in use. . Fair results ‘have been ‘obtained by applying adhesives, tie gums or cements to certain mate ‘ rials including metals, and then vulcanizing or otherwise securing the rubber‘substance thereto. The use of such tie gums‘and cements‘usually provides a more uniformdegree of adhesion,‘ but, in general, the layer of ‘cement is of consider metal piece to 'which‘it'is‘tofbe directly bonded, 10 ably lower tensile ‘s‘trength‘than the rubber ‘and accordingly, such methods vwere not‘ capable‘of and then subjectedto a'treatment‘io'r e?ecting producing a sumcient bond between "a'metal'an‘d direct bonding of the rubber to the metal. rubber substance to satisfy many requirements The invention ‘especially relates‘ to ‘processes of in the arts. ' the 'aforesaid‘type, in which arubber composition, adapted to be bonded'directly'to a‘ metal piece'is ‘ In prior processes for ‘bonding rubber‘to metal,‘ it has been proposed to ‘pretreat the surface prevul'canized, either partially or completely, and of the metal to which‘ the rubber'is to be bonded, subsequently bonded directly to apiece of rubber‘ in such a manner that the ‘surface is rough ‘a.dherent metal. ened, as for instance by pickling "the metaLsand The present application .is a continuation in blasting the same, or'forming actual protuber part of my copending application, Serial No. process for producing rubberemetal articles, wherein a'r‘ubber‘or rubb‘erelike substance is pre mcl‘ded or preformed, then assembled with the ‘234,616, ?led October 12, 1938, nowPatent No. 2,337,555, granted December ‘28, 1943, and of my \ copending application . SeriaTNo. ‘352,578, “filed August 4, 1940. It haslong-ibeen a desideratum in the artrto form a strong and'lasting bondbetween rubber ances or notches around which and "between which the rubber is intended to' ?ow, thus ‘mak ing possible a mechanically ‘interlocked ‘bond between the'rubber and metal. However, since the strength of the ‘bond depends upon the ex tent to which ‘the rubber and‘metal interlock, ‘the .e?ectiven‘ess of such a physical union depends upon the kind and strength of the destructive ‘force ‘app-lied'to-‘the ‘bonded rubber and‘metal andmetal pieces ‘so-‘that therubberand metal would remain united in?rm-and fastrelation ship and‘resist. mechanical forces; such ‘as .afforce tending to pullthe rubber and-metal apart, tor 30 article. The use “of metal having a roughened surface yields somewhat better results when a torsion tending .to twist ‘the rubber fromithe metal. It has ‘been attempted heretofore to produce rubber and metal articles wherein the rubber is bonded to-a metal surface by vulcanizingthe rubber indirect‘ contact with said metalvysurtace. Many proposals have ‘been, made heretoforeioi' accomplishing-‘this result in“ this mannenibut (so cement or tie gum is applied thereto, but the bond produced is'still of inferior‘strength be cause ‘of ‘the use of the cement. Furthermore, such methods of pretreatment for the metal-sur face are relatively “expensive ‘and ‘tedious and materially increase the cost'of the ?nished article. ‘ It is ‘often oi‘great technical ‘advantage in pro ducing composite articles of rubber and metal wherein the rubber'is to be‘bonded to themetal, 40 the "metal" and ‘rubber are to‘ be'secured together ‘to mold or form the rubber prior to its assembly by ‘direct contact between the ‘metal and ‘the with the metal pieces, then to assemble the rub rubber, haveproduced satisfactoryresults. The her with apiece of metal, and ?nally ‘to bond the 5 bond produced is of ‘relativelyAinferioristrength, rubber thereto. This is especially true in mass and‘ upon ‘subjecting .the ‘article to stresses ‘tend ' production where it is desired to form the rubber ing to tear the rubber v‘away’ from the 1metal. in one part of a manufacturing plant and bond separation occurs at thebond. 1 ‘ . it to the metal in another part thereof. In mold far as I am aware, none of theseproposals, where Moreover, in general, the‘strength of *the‘bond produced accordingfto such prior art‘ processes .‘generally occurs and in this case,‘the only method was variable ‘and could not be "controlled; _. The known heretofore of bonding suchpieces ‘subsee resulting unreliability of the ‘rubber and metal quently to metal was the use of a tie gumgcement; articles wasespecially disadvantageous since in ing the vrubber pieces, however, vulcanization or adhesive. .Because‘of the inferior nature of the bond produced with such ‘tie gums and adhe general it is impossibleto test the'?nished arti sives, ithe articles produced were often unsuit cles to the point of ‘failure of 'the‘b'on‘d‘ in order to determine whether theiarti‘cles would ‘with 55 able gfo-r the purpose for which they were destined‘. 2,409,759 3 4 Accordingly, it is an object of the present in vention to provide a process of bonding rubber proportions of other metals such as lead for modi fying the properties of the alloy. While “Monel” is a trade-mark, it is used here in in the sense de?ned by the dictionaries. That is, Monel metal is an alloy comprising approxi mately 67% nickel, 28% of copper and ?ve other elements, chiefly, iron and manganese, made by the direct reduction from ore in which the con stituent metals occur in these proportions. This de?nition is very similar to the published analysis of Monel metal as given by the exclusive pro or rubber-like substances to metal articles, where in the rubber may be preformed or premolded, and vulcanized either partially or completely, prior to its assembly with the metal piece to which it is to be secured, and thereafter bonded di rectly to said metal piece without the use of tie gums, cements or the like. It is an object to provide a process of the afore- . said type in which the bond produced is of such strength that it exceeds the tensile strength of ducers thereof, namely, the International Nickel Corporation. The analysis given by the pro the rubber itself so that upon tearing the rub ber away from the metal, the failure occurs in ducers of said alloy is as follows: the rubber and not in the bond; and especially to produce bonds of such reliability that the proc Per cent Nickel ________________________________ __ ess may be used in any instance where the strength of the bond is of critical importance. A further object is to simplify the pretreat 68 Copper _______________________________ __ 29 Iron __________________________________ __ 1.6 Manganese ___________________________ __ 1.0 ment of the metal surfaces to which the rubber is 20 Silicon _______________________________ __ 0.10 to be secured in order to provide a superior bond Carbon ________________________________ __ 1.15 of the aforesaid type, whereby substantial econ Sulphur ______________________________ __ 0.005 omies may be secured. The basis for the present invention is the dis Throughout the speci?cation where I mention covery that in processes wherein rubber is vu1-.,_.75 Monel metal, I refer to the alloy embraced within canized in direct contact with metal surfaces, the de?nition given by the dictionaries and set bonding between the rubber and a metal to which ' out above. One of the more important advan it may be caused to adhere directly, occurs not tages of Monel metal is that this alloy is sub only during the latter stages of vulcanization, stantially uncorrodible, and is worked as easily as but also after vulcanization of the rubber com 30 other metals of the same toughness and wearing pound is complete. This observation has led to qualities. the surprising discovery that partially vulcan In practicing the present invention, where ized or completely vulcanized rubber can be bonded directly to a metal surface without the use of tie gums or cements. In order to produce a composite rubber and practically the entire face of the metal piece is to be bonded to the rubber and the metal piece has relatively little mass, the whole metal piece may be made economically of rubber-adherent metals metal article, according to the present invention, of the aforesaid types. a metal piece is used, the surface of which is Where, however, the metal piece has a great deal of mass and a com made of an alloy or metal to which a given rub paratively small surface is to be bonded to the ber composition or rubber-like substance is 40 rubber piece, it will be found in many cases de adapted to adhere. In order to prepare the sur sirable to make the metal piece of a base metal face of the rubber-adherent metal piece to which such as iron, steel or the like and to secure by rubber is to be bonded, the surface thereof is any of the usual methods, for instance, by weld rendered clean, smooth, bright and continuous. ing, a layer such as a thin plate of the rubber The rubber or rubber-like substance to be adherent metal to the surface of the base metal. bonded to the metal piece is compounded in such I have discovered contrary to expectations that a manner as to provide a composition adapted in order to produce a superior bond according to to adhere directly to the said metal. t is then the present invention between the rubber and the preformed or premolded in a shape having a rubber-adherent metal, the surface of the metal surface conforming substantially to those por 50 must be not only clean, smooth and polished, but tions of the metal piece to which it is to be se cured. At the same time, the mass of rubber is also continuous, i. e., the contacting surface being then assembled with the metal piece in the de sired relation and con?ned, for instance in a mold, the rubber being in direct contact with the metal. Sufficient pressure is applied to insure free from macroscopic or microscopic depres sions, crevices or ?ssures. If this is not the case, an inferior bond is produced. I have found, for instance not only that metal surfaces which are macroscopically roughened, as for instance by sand blasting or pickling, are un suitable for producing superior bonds, but also intimate contact between the metal and the rub» that metal surfaces having microscopic depres vulcanized, either partially or completely. The premolded and prevulcanized rubber is berw and su?icient heat to cause bonding of the 60 sions, crevices, or ?ssures are similarly unsuitable. If the nature of .the metal is such that micro rubber to the metal surface. In general, if the rubber has only been partially vulcanized, the heat thus applied is also utilized to complete vul canization of the rubber. The composite rubber 65 and metal article is then stripped from the mold by any of the usual methods. As metals especially adapted for bonding of rubber thereto, I have found that Monel metal scopic openings are present below its surface, the metal cannot be rendered suitable for direct bonding according to the present invention, by polishing alone. Such metal surfaces are, for in stance those produced by electroplating or by hot spraying. Although such surfaces, especially when polished, may appear to the naked eye to be bright and continuously smooth, the minute and cuprous alloys of the class of brass or bronze 70 crevices or ?ssures resulting from the method of are especially suitable. their formation are present in the surface and Cuprous alloys of the type of brass or bronze impair the bond with the rubber substantially to may contain, for instance from 60 to 85% cop .the same extent as the visible depressions in sur per, the principal remaining ingredients being tin or zinc and may also include relatively small 75 faces of obviously rough nature. It is believed that the reason for this effect $2,409,759 $5 "almoIu-gteniperature ofisi'o"inriforrazperidd of 110 is jthat Lair 'or‘other gases are occluded "in “the macroscopic for Lmicroscopic ‘depressions -‘ of the minutes. a _ ,1Nnmerous-compos1tions>are also'knbwn'linTthe metal surface when .an 3attempt -‘ is ‘made 'itob'ond the-l rubber "thereto, holding the; rubber awayi‘from ‘alirtliai‘s suitable‘ ‘for idir‘ect‘ bonding ‘itof-fcupr‘ous Jal the metal at these points. This resultsin‘i‘dis‘con tinuousl‘bonding -so that vthe tensile "strength of lloys of thetype-of ‘brass'orlb'ronz‘e. According to the presentfinventionlivhasbeen thefbon‘d is greatly impaired. ‘ , ifoun'd that an‘!especiallwsatisfactory‘composition ‘ iyiel'ding highly ifsfuperior T results ‘with ‘brass "or T‘Thus the rubber-adherent metalfforming the biforizel‘maylbe‘preparedby use 6ffa‘quantity of v‘surface.of‘lithe-metalarticle to~which the rubber ‘composition to be ‘bonded must be ofea. continu 10 lsmoke‘dlsheetl'or pale crepe,"‘a1suitable quantity of sulphur; an accelerator, especially of theim‘er ous nature and 'be ‘free ‘of iminute depressions, "captoarylthiazole type,-a softener of?the'iclass of ‘crevices ~ or the like ‘resulting "from the manner inwhich‘it'isl-produced. “higher ‘fatty acids; and a quantity of “chemically pureWzin‘c» oxide. l'I'heilatterinl conjunction ‘with ‘As statediabove,“the'surface ofithel rubber-rad here'ntlmetal must ‘also be‘ rendered" clean; smooth 15 ‘the aforesaid jtype Jof accelerator ‘appears 'to The essential for‘ the “superior bonding properties fof sand-‘bright andiito this *end, it merely neces the composition, ‘sary to-‘polishiit. “The polishingioperationlmay ' ~By ‘~‘chemicallylpu‘re” zinc oxide is meant that which “listlordinarily 1‘sold. as a chemicallreagent buffing iwlie‘eliha'ving criocus ‘martis (a form‘of 20 rather“ than for 'te‘chnical‘purposes and which". is prepared by ‘combustion -of pure molten Jzinc ‘ferric JoXide) thereon-as ianfabrasive. Since the ‘metaliirr air-llor‘by heatinglzinc compounds‘which polishing ‘operation alone is a‘ satisfactory, in Lthe yielditheoxidelby‘ thermal decompositionat rela case ‘of rubber-adherent metals of continuous tively moderate temperatures, such as precipi nature, for producing the superior ‘results of ‘the ‘be carried ‘but 'for instanceiby 5 bii?i'ng ‘the :sur ifa'cei‘o'f the metal Ionvai‘crocus” wheel, that is a present inveritiongo‘ther?forms of pretreatment, ' 'suohlas fpickling,i sand-‘blasting ‘or-‘the- like 1 are ren~ tated basic zinc carbonate or zinc nitrate. Com amercial or technical zinc oxide which ‘is that ordinarily used in rubber. compositions as well was for pigmenting paints, is produced'by a dif 'dered Iunnecessary. ‘This ("results in "material economy in the production" of the ‘composite rub ber and metallarticles. ‘ iferent ‘method, ordinarily comprising the com bustion of the vapors‘produced/from rheating'a mixture ‘of zinc ore-in combination withireduc ing agents. Apparently, the-difference between order to ‘avoid flthelformation' of a him of ‘oxide-‘or accumulation "of “dirt, the polishing of the (rubber-adherent metal surface is preferably the two types of zinc oxide is a physicalzrather than a chemical one. It is not‘fully understood )carried x‘out-directly prior to "application‘of the rubber thereto. why “chemically pure” zinc ‘oxide, when used in The-rubber‘pieces which‘ are to be bonded to the hrubbereadherent metal article are prepared from rubber compositions"designed to adhere to ‘rubber compositions endows 3‘ them with greatly ‘superior bonding qualities relative to brass or "bronze, ‘as 1 compared “with similar ‘compositions the v‘particular metal ‘to which “they are to be b‘onded. The nature of such compositions varies . somewhat according to vthe kind‘ of rubber-ad 'herant' metal used,‘but thena'turepf the composi 40 containing‘technioallor commercial zinc oxide, but'i‘t‘lis thought-that the peculiar physical form of tthe“chemically pure” zinc oxide results‘in ' properties which render it more readily available ‘It-hasalso been‘foundac‘cording to the'pres forreaction with the-other components of the tions are in general well known in the~ar-t. rubber mixture and the commercial grades ent invention that not only ‘compositions contain ing-natural ‘ rubber but also‘ those prepared from ; thereof. In the speci?c composition adapted‘ for bonding to brass or bronze by the process of ‘the present invention, the quantity‘of sulphur may be‘fr'om Duprene; chloroprene and the like can be similar about'Btobparts by weight per 100 parts of crude ly use'd with‘excellentlresultsfThus, in the present ispelcifi'catiomwhere I have mentioned rubber ‘or ’ ‘rubber substance, about 5 parts of sulphur being ‘preferably used. As a vulcanization accelerator, rubber-like substances, 5I intend these-terms‘ to ~mercaptoarylthiazole accelerators which com include all natural caoutchouc, ‘derivatives there prise mercaptobenzothiazole, its homologues and ‘of, and‘substi-tutes therefor, which ‘are vulcaniz synthetic rubber substances, ~especially of “the class of butedienoid polymers such ‘- as neoprene, ‘able. derivatives such ‘as for instance the 'zinc salts and ' In the case of Monel'm'etal;it‘hasbeen found ‘that the bond'producedwith most metal=adherent rubber’ compositions *and- various synthetic ma - ignated herein as mercaptoarylthiazole accelera ‘teria-ls‘such ‘as‘n‘eoprene is superior to thatpro “duced ‘with other‘metals. ‘ A composition, suitable for’bondin‘g ‘to 'Monel "metalfa'ccording to ‘ this invention, ‘may contain the followingiin'gredients; parts are ‘by ‘weight. , thosefin which the hydrogen of the mercapto ‘group is rep-laced by an ‘organic ‘residue, are es-, pecially satisfactory. Such compounds are des Parts ‘tors. it is preferred, howevento use an accelera tor of the aforesaid type wherein a mercaptoben zothiazole radical is coupled withthe residue of ‘an aromatic amine of the benzene series through the sulphur of the mercapto group by a methylene ‘bridge which joins the mercaptobenzothiazole "Rubber (smoked sheet‘) _________________ __ 100 residue with the aromatic amino group. A pre ‘Mercaptobenzothiazole __________________ .._ “ferred' accelerator of this class is for instance a , 1 fPe‘trolatum ________________ __‘___‘___; ____ __ l mixture 00f mercaptobenzothiazoleemethylene LSte'aric' acid __________ _’____‘____‘ _________ __.- l aniline and ‘ mercaptobenzothiazole-methylene-o *3Zinc‘o$cide___ 8 , ‘ _ ' _ ‘Whiting--. _______ -‘. _______________ __,__‘__‘__ ‘40 "Iron oxide_____________________ __'___'__‘____" 5 ‘Sulfur _______________________ _‘____,,_‘__‘____ 2.5 ‘toluidine, The quantity of accelerator used may vary fromaboutl to about 2 parts by weight per 100'parts ‘of rubber substance, but preferably about 1 part of the accelerator is used. ' The softeners included in the preferred com ‘Thelingre'dients‘ are-mixed on alniill‘in the ‘usual *manner. ‘The"compositionl‘may*be-vulcanized'at position may be higher fatty. acids, such as ‘stearic, “ole'ic "or lauric ‘acids, ‘ but *stearic ‘acid ‘is 2,409,759 7 preferred. The quantity of higher fatty acid may 8 vary Within the reasonable limits usual in com eration may be used, but relatively high pres sures are preferably applied, and accordingly, the pounding rubber. About 2 to 4 parts of-higher fatty acid ‘to each 100 parts by weight of rubber rubber is so con?ned as to prevent lateral move ment thereof with respect to the rubber-adherent substance are used, and preferably about 2 parts metal surface. of stearic acid are used. , The quantity of chemically pure zinc oxide should be at least 5 parts by weight per 100 parts of crude rubber. Larger quantities may be used, but substantially the same effect is produced thereby. . 1 Heat is applied in such a manner that the _ . metal and rubber are raised to a temperature su?icient to cause the rubber to bond to the metal. Such temperatures are generally comparable with those required for vulcanization of the rub ber compounds suitable for use in the present procedure. For instance, temperatures from 300 to 320° F. have been found satisfactory in the The remaining components of the said com position may be selected as desired. These may comprise ?llers, such as carbon black and com case of the rubber composition adapted for use mercial zinc oxide; additional softeners, as for 15 with brass disclosed above, as well as for the instance asphaltum, pine tar and the like; and speci?c composition adapted for use with Monel it is generally advantageous to add a, suitable metal. As a result, if the rubber is only par quantity of an antioxidant such as phenyl-beta tially vulcanized prior to its assembly with the naphthylamine in order' to prevent, premature metal, vulcanization is completed in the present aging of the rubber. Agents which increase the 20 process. The duration of the heating vvaries ac heat resistance of the rubber may also be used. cording to the composition of the rubber and the metal used. For example in the case of A suitable recipe for the aforesaid composi rubber compositions which are completely vul tion, in which parts are by weight, is as fol lows: canized before assembly with a metal, heating ' Parts 25 from 3 to 10 minutes, preferably for about 5 minutes, was found suf?cient to effect the forma Rubber (smoked sheet or pale crepe) _____ -_ 100 tion of the desired bond. In the case of partially Phenylbetanapthylamine _______________ __ 1 vulcanized rubber, the time for heating is gen vStearic acid ____________________________ __ 2 erally increased by a period su?icient to effect Sulphur _______________________________ __ 5 complete vulcanization. From about 3 to about Chemically pure zinc oxide ______________ __ 5 15 minutes is generally satisfactory. When the Mercaptobenzothiazole methylene aniline bonding is complete, the pressure is released, the plus mercaptobenzothiazole methylene o composite rubber and metal article removed from toluidine ____________________________ __ 1 the mold and allowed to cool. Soft carbon black _______________________ __ 40 35 In the accompanying drawing, several articles The above ingredients are thoroughly mixed by are shown by way of illustration which may be milling in the usual manner and calendered to a produced according to the present process. sheet of the desired thickness. This composi Figs. 1 and 2 show tire valve stems partially tion can be vulcanized in a mold temperature of in cross-section having a tubular metal insert about 310° F. for a period of about 10 to about 15 40 bonded to a rubber base. minutes at a pressure of 300 pounds per square Fig. 3 shows a cross-section of a rubber-like inch. " metal tube. In practicing the process of the present inven Fig. 4 shows in cross-section a rubber layer tion, the uncured rubber composition is pre bonded to a metal plate. formed or premolded in a shape adapted, to con Fig. 5 shows partially in cross-section a metal form to that of the metal article to which it rod secured in a rubber sleeve surrounded by a is to be subsequently ‘bonded. A slug of the rub sleeve of metal. ber composition is placed in the mold or form and Fig. 6 shows in cross-section a mold adapted con?ned under pressure. Heat is applied to- ren for use in forming a rubber and metal article der the mass plastic so that it acquires the form wherein the rubber may be vulcanized and in the mold, and the heat is continued for a su?‘i molded separately from the metal and subse cient period to partially or preferably to com quently bonded thereto. . pletely vulcanize the rubber. The mold is then Fig. 7 is a view similar to Fig. 6 showing the opened, the rubber article removed, and assem same mold during bonding of the premolded rub bled in the desired relation with the metal piece ber piece to a, metal piece. having a surface of rubber-adherent metal to Fig. 8 is a plan view of another composite arti which itis to be bonded, the metal piece hav cle with part of the rubber substance omitted ing been previously prepared, as described above, to show the way the metal may be formed so by polishing to give it a, smooth, clean continu that the area of the bond between the rubber and ousrpolished surface. ’ the metal is‘ reduced. . Sui?cient pressure is then applied, preferably perpendicular tothe contact surface of the rub ber and metal to maintain intimate contact at the rubber-metal interface and in such a man neras to prevent ‘distortion of the rubber. The assembled article is preferably con?ned, for in stance by placing it in a mold which ?ts snugly around'the rubber portions and the contiguous exposed metal surfaces thereof. Suitable means is provided for maintaining pressure at the rub ber-metal interface throughout the bonding oper ation. - > . Any pressure which is su?icient to maintain an ‘intimate substantial pressure contact at the rub ' In order to produce the valve stems shown in Figs. 1 and 2, the rubber bases l0 and H are pre molded and vulcanized. In order that a substan tial pressure may be conveniently applied at the rubber-metal interface between metal inserts l2 and I3 and rubber bases H) and H, the inside diameter'o'f the rubber sleeves l4 and I5 into 'which'the'metal'inserts l2 and I3 ?t is- made slightly'smaller th'a'nthe outside diameter of the 'metal inserts. The latter are made of a rubber adher'ent metal adapted to be bonded to the com position of the rubber bases [0 and II and their surfaces polished ‘until they are smooth and bright,iand are of a continuous nature. The in ber-metal interface throughout the bonding pop‘ 75 serts are then inserted into the rubber ‘bases as 2,409,759v 10 shown,v and the" articles positioned in a mold adapted to con?ne the rubber. The mold is closed and'su?icient pressure‘ applied to the rubber to maintain a‘ substantial positive pressure at the rubber-metal interface. The contents of the mold is heated'until bonding occurs between the rubber and‘ the metal», and the valve‘stem thereafter is stripped fi'cmthe mold. Referring to Fig. 3, the‘ tubular rubber lining I8 is premolded and vulcanized. Its outside di ameter is preferably made. slightly larger than the: inside diameter of the metal sleeve l‘! to which it is to be bonded. The sleeve I1 is‘ con the'otherfhalf'?t- of‘ the moldmay contain cavities‘ 3:8'rfor1 receiving’ metal‘ pieces 34‘. Between the two‘ molds, a plate or platen 35- may be‘ initially inserted, on which pieces‘ of unvulcanized rub b‘er, compounded to adhere‘ to a metal-adherent surface are then placed under the cavities 36 in‘ the part’- oi‘ the mold‘. The parts of the mold are/‘brought together‘ under‘heat and pressure as j illustrated‘ in Fig. 6, and the ‘rubber pieces 3T are formed and vulcanized either completely or par-‘ tially, depending upon the length‘ of time they are subjected to the vulcanizing action. When‘ this: has been done; the platen 35' is Withdrawn structed'v of a metal such as Monel metal'or brass, fromnbetw'een the‘ parts 32‘ and 33‘ of the mold having a continuous surface, to which the rub 15 and‘ the metal‘pieces 34- inserted in the cavities ber composition is adapted to be dire'ctlyibonded, 38 in the part 33 of the mold if they were‘ not already placedthe‘re before the molding opera and its‘ inner surface rendered clean, smooth and bright by polishing. The rubber lining [8' is in tion began. serted into the bore of the sleeve l1 and the com When the" platen 35‘ is‘ withdrawn from the posite article placed in a mold having a‘ core pin 20 mold parts, any ?ash‘ formed by the molding of adapted to ?t into‘ the axial bore [6 of the rubber the- rubber pieces‘ 31 that will‘ adhere to the' mass l8‘. On‘ closing the mold; pressure is applied platen 555 will be carried‘ away‘ ‘with the platen to to the surfaces‘ l9. and‘ 20“ of the rubber mass, be scraped‘ off‘ later. The parts 32 and 33', one whereby‘ positive‘ pressure is maintained at the containing‘ the precured or semicured rubber rubber-metal interface and supported by the pin - pieces‘ 3?, and the other containing the metal extending through the bore of‘ the rubber mass pieces 34' having? a‘ rubber-adherent metal sur face, are‘brb‘ught together under heat and pres i8‘. Upon application of heat, the rubber is se sure'to bond the rubber to the‘ metal; curely bonded to the inner surface of the sleeve. When the’ bonding operation is completed, and’ If ‘ desired, the rubber lining l8imay be premold‘ed the mold separated,‘ the metal and‘ rubber pieces to have‘ the same outside diameter as the inside being new united m‘ay be‘removed' from the mold diameter of the sleeve ll, but the bore 16 may‘ as a composite‘ article‘by‘ any suitable‘ stripping‘ be made slightly smaller than the core pin of the mold in which‘bonding is to be effected. Closure means.‘ The practice of the method‘ just‘ de‘-" of the mold thereby causes pressure to be ap scrib'edand the apparatus‘ used therefor‘ avoids‘ plied at' the rubberemetal interface by com the necessity'of stripping the premolded rubber" pieces'from the mold and‘ replacing them in an‘ pression oflthe‘rubber between‘the oversized pin and the inner’ surface of the metal sleeve, said other mold to be bonded totne metal‘ pieces‘. pressure being supported by the mold con?ning The hereinbefore described process‘ can be‘a'p'l‘ plied‘ for bonding- a plurality‘ of‘ metal‘ piece‘st‘o the‘ends l9 and“ 2B» of the rubber mass: ‘ Iii-order to bond the rubber layer‘ 21- to the surface of ‘the plate 22, as-shownin‘ Fig. 4; the rubber 21!? is‘ premolded and vulcanized‘ in the desired‘ form from‘ a composition compounded ’ forms‘ allinkibetween the various metal‘pieces, or" to have metal-adherent‘ qualities,‘ brought into“ bridge between the‘ various‘rubb'er parts‘. More the same mass of rubber, whereby‘ the’rubb'er several: pieces of? rubber‘ may be‘ bonded to the same piece of metal, whereby‘the‘ latter forms a‘ contact‘ with the metal plate 22 of rubber-ad over, if‘ it is desired, additional pieces of‘rubber herent metal, the surface of‘ which isfcontinuous, may- be‘ secured by any of the well-known and polished to render-lit smooth and clean. Pres methods‘,- for!‘- instance‘by‘ vulcanizing, to a mass sure is applied, tending to con?ne the rubber of ' rubber ‘secured to the metal article by? the" and force it against the surface‘of the plate, and above-described methods. the temperature is raised to caus'e'bonding of‘ 50 One of the more important features‘ of‘ this‘ the rubber to the metal surface; invention is’ that“ the metal and'rubb‘e'r m'ayibe bonded together‘by' processes similar to‘the 'pro‘cé In order to‘ make the rubber-metal article essiof- vulcanizingrubber, and‘the' same apparatus,‘ . shown in Fig. 5, a tubular‘ rubber mass 23*may be‘ premolded and vulcanized to have anoutsidedi used for molding and vulcanizing rubber, may ameter‘slightly larger than the inside diameter‘ 55 be usedin the present case. ‘ I Contrary to expectations on’ the basis of the of the cup-like metal sleeve 24; or the‘ central bore of the rubber mass 23 which'is to receive prior 'art, I‘ha‘ve‘ discovered that rougheningl or" the metal rod 25‘ may be constructed slightly serrating the surfaces of the rubber-adherent metal prior to the application of a premolded, smaller than the‘outside diameter: of ‘saidmetal rod.‘ The rubber mass is inserted into the sleeve 60 prevulcani‘zed metal-adherent“ rubber composi- ' 25 and the rod Z5~into the central'bore of the tion‘thereto reduces the union between the rub rubber. Intimate contact is maintained between ber and metal to such an extent, when it is sub» the metal‘ surfaces and‘the-rubber- mass‘ by the jected to heat and pressure‘; that onlyva'pa‘rtial oversized ‘construction of the rubber or of the rod or very‘inferio'r bond is produced. ‘Thus; when 25; Application ofjpressure at the surface 26 of 65 it is‘ desired to reduce the bond between the rub; the rubber con?nes it within the sleeve and causes ber'eadh'eren‘t ‘metal surface‘ and‘ that‘ of \ rubber ' positive"pressurettorbe'maintained at’th'e'rubber bonded thereto; it is’ merely necessary to‘ pro vide grooves 011 the surface ‘or otherwise roughenr metal ‘conta‘ct‘surfaces: The'temperature is'raised“ sufficiently" tobond'the rubber to ‘the metal, re‘-‘ it locally before bringing the‘ surface of the metal 70 and the rubber‘ substance into direct’ contact. ‘If metal‘ article’ in: which the“ metal" is‘ securely‘ this is done‘solely on a portion of ‘the metal sur sulting: in "the" formation “ of -‘ a: composite ‘rubber bonded‘ to? the " rubber. _ ' According to‘theistructure illustrated in Figs. 6. and“ 7, ,one‘h‘alf‘ 32 ‘of the *mo‘ld‘may-"be'rprovided “ face contacting the rubber, while the remainder of the 'said surfa‘ce'is continuous,‘ smooth, clean and'polished,‘ the ‘bond “will occur“, only‘ at the‘ lat‘ with“ cavities“ 36" forrshaping “ rubber“ ‘pieces, while“ 75 ter'portions; n'o secure-bond being obtained where ‘" 2,409,759 12 11 the metal is roughened. A surface of this type is illustrated in Fig. 8, wherein roughened grooves 39 are provided on the surface of a rubber-adherent metal 40 to which a mass of article of the class consisting of brass and bronze articles; placing said cuprous alloy article and an untreated surface of the mass of prevulcanized rubber in a mold; applying su?icient pressure to the mold to maintain a pressure of at least 300 rubber M is to be bonded according to the present pounds per square inch at the contact surface of invention. The remainder of the surface 42 is the rubber with the cuprous alloy article; and continuous, smooth and polished. When the rub heating at a temperature of from 300 to 320° F., ber is bonded according to the present process, until the rubber is bonded to the polished surface secure bonding occurs only at the portions 42 of the said surface, while at the portions 39 sub 10 of the cuprous alloy article. 5. In the art of bonding a metal-adherent rub stantially no bonding in the sense used herein is produced. ber substance, compounded to be directly bond able to metal, to a smooth, polished and con Variations and modi?cations may be made tinuous rubber-adherent surface of a cuprous within the scope of this invention and portions of the improvements may be used without others. 15 alloy of the class consisting of bronze or brass to which said rubber substance is adapted to be I claim: bonded directly, the steps which comprise pre 1. The art of bonding a completely cured metal vulcanizing a mass of said rubber substance; adherent rubber composition directly to a cu bringing an untreated surface of said prevul prous alloy article of the class consisting of brass and bronze articles, comprising the steps of pro 20 canized mass of rubber substance into direct con tact with said rubber-adherent surface; and sub viding said cuprous alloy article with a clean, jecting the rubber substance and alloy to heat and continuously smooth polished surface; bringing an untreated surface of the cured rubber com pressure suflicient to cause cohesion between the contacting areas of said rubber substance and position into direct contact with said polished cuprous alloy surface; maintaining sufficient 25 surface. 6. The art of bonding a metal-adherent rubber pressure at the rubber-metal interface to in substance directly to a smooth, polished and con sure intimate contact between the rubber and the tinuous rubber-adherent surface of a cuprous cuprous alloy; and applying sufficient heat to alloy of the class consisting of bronze or brass, cause the rubber to adhere to said alloy surface. which comprises partly curing said rubber sub 2. The art of bonding a partially cured mctal~ stance; bringing an untreated surface of the adherent rubber composition directly to a cuprous partly cured rubber substance into direct contact alloy article of the class consisting of brass and with said rubber-adherent surface; and subject bronze articles, comprising the steps of providing il'ig the rubber substance and alloy to sui?cient said cuprous alloy article with a clean, continu heat and pressure to completely cure said rubber ously smooth polished surface; bringing an un treated surface of the partly cured rubber compo substance and to cause the latter to cohere to the sition into direct contact with said polished areas of said rubber-adherent surface in contact cuprous alloy surface; maintaining sufficient therewith. , 7. The art of bonding a metal-adherent rubber pressure at the rubber-'netal interface to insure intimate contact between the rubber and the 40 substance directly to a smooth, polished and con~ cuprous alloy; and applying sufficient heat to completely cure the rubber, and to cause the rub ber to adhere to said alloy surface. 3. A method of forming a composite rubber and metal article wherein the rubber is securely bonded directly to the surface of a cuprous alloy article of the class consisting of brass and bronze articles, which comprises compounding a rub ber composition to contain, in addition to a suit able quantity of a crude rubber substance, a suit tinuous rubber-adherent metal surface, which comprises bringing an untreated surface of a ma terial of a class consisting of cured and partially cured substance into direct contact with said rubber-adherent surface of a cuprous alloy of the class consisting of bronze or brass; and subjecting the rubber substance and alloy to heat and pres sure su?icient to cause cohesion between the con tacting areas of said rubber substance and rub ber-adhering surface. ableportion of sulphur, a mercapto-aryl-thiazole 8. In the art of bonding a metal-adherent rub accelerator, stearic acid as a softener, and a pro— ber substance, compounded to be directly bond able to metal, to a rubber-adherent alloy of the class consisting of brass and bronze to which said rubber substance is adapted to be bonded di rectly, the steps which comprise providing said alloy with a clean, bright, continuously smooth polished surface; prevulcanizing said rubber sub portion of chemically pure zinc oxide; prevul canizing a quantity of said compound in the de sired shape; placing an untreated surface of the prevulcanized rubber compound and a cuprous alloy article of the class consisting of brass and bronze articles having a continuously smooth, stance; placing an untreated surface of said pre clean, polished surface in a mold; applying suf? cient pressure to maintain intimate contact at 60 vulcanized rubber substance in direct contact the rubber-metal interface; and applying suffi cient heat to cause bonding of the rubber to the . surface of the metal article. 4. .A method of forming a composite rubber and metal article wherein the rubber is securely bonded directly to the surface of a cuprous alloy article of the class consisting of brass and bronze articles, which comprises compounding a rubber composition to contain, in addition to a suitable quantity of a crude rubber substance, a suitable proportion of sulphur, a mercapto-aryl-thiazole accelerator, stearic acid as a softener, and a pro portion of chemically pure zinc oxide; prevulcan izing a quantity of said compound in the desired shape; polishing the surface of a cuprous alloy with said polished rubber-adherent alloy surface; and subjecting the rubber substance and alloy to heat and pressure su?cient to cause cohesion be tween the contacting areas of said rubber sub stance and the polished surface of the rubber adherent alloy. 9. In the art of making composite rubber and metal articles in which the rubber is securely bonded directly to the metal, the steps which comprise prevulcanizing a mass of directly metal adherent rubber substance; applying a piece of a rubber-adherent alloy of the class consisting of brass and bronze having a smooth, polished and continuous surface to which said rubber is adapt ed to be directly bonded, in surface contact with 2,409,759 ‘ 13 to;.cohere;,directly, in asmold adapted1to. con?ne‘ the-iirubber-iagainsti distortion, with ‘an untreated surfaceohthe rubber compositioniin‘ direct con; tact with said'rubber-adherent surface; applying an untreated‘; surface. of,“ saidlrubberl substance ; and applying‘: suf?cient “heat: and pressure to: said: alloy ‘piece and ‘ rubber; substance - to cause-cohe sionib'etween‘ .the ‘contacting, areas of. theirubber andzalloy: 1 10. In thelartpflmaking: a composite-‘rubber, 5 suf?cientr pressuretothe mold ‘to ‘maintain a sub stantialipositive pressure. atJthe contact surface and metaliarticle, thesteps aWhiCll comprise pre of~,the;metal piece and‘ithe-mass, of prevulcanized rubberg-oomposition; and‘: heating; thecontents: of vulcanizing a mass of a directly metal-adherent‘ rubber-substance; securinga thin continuous lay the; mold: at vaztemneraturerof the same ,order- as er of a rubber-adherent alloy of the class consist ing of brass and bronze to which said rubber sub that required to vulcanize the rubber until the rubber is bonded to the rubber-adherent surface stance is adapted to be directly bonded,‘to the of the article. surface of a metal piece to which the rubber is ‘ 14. In a process of forming a composite article to be bonded; polishing said rubber-adherent al loy layer to render it continuously smooth, clean of metal and rubber substance, the steps which comprise premolding and precuring a body of a and bright; bringing an untreated surface of said prevulcanized mass of rubber into direct contact rubber substance, compounded to cohere directly to a rubber-adherent metal, in the desired shape; exposing one surface of the molded rubber With out stripping the rubber from the mold; applying and metal to heat and pressure sufficient to cause 20 an alloy piece of the class consisting of bronze cohesion between the contacting areas of said and brass having a continuously smooth clean rubber substance and the polished layer of rub polished surface of the said alloy to which the ber-adherent alloy. said rubber substance is adapted to cohere di 11. In a method of forming a composite and rectly, to the untreated exposed surface of the rubber-metal article wherein the rubber is se 25 molded rubber substance, the polished surface curely bonded directly to the surface of a metal of said alloy forming direct contact with the ex piece, the steps which comprise prevulcanizing a posed rubber substance; reclosing the mold; and mass of a rubber composition adapted to cohere app-lying suflicient heat and pressure to bond the directly to the metal of said article in the desired rubber directly to said alloy surface. shape; placing said mass of prevulcanized rubber 15. In a method of making a composite rubber composition and a piece of metal, having a and metal article wherein the rubberportion is smooth, polished and continuous surface of a securely bonded directly to- the surface of a metal cuprous alloy of the class consisting of bronze or piece, the steps which comprise preforming and brass to which said rubber composition is adapted at least partially prevulcanizing said rubber por to cohere directly, in a mold adapted to con?ne D) ;'V. tion from a metal-adherent rubber composition, adapted to be bonded directly to metal; assem the rubber mass against distortion, an untreated with the polished surface of said rubber-adherent alloy layer; and subjecting the rubber substance surface of said rubber mass being in direct con bling said preformed rubber portion with an un treated surface in the desired relation with a tact with said alloy surface; applying sufficient pressure to the 111016.130 maintain intimate contact piece of metal of the desired shape having a between the surface of the metal piece and the if) smooth, polished and continuous surface of a prevulcanized rubber composition; and applying cuprous alloy of the class consisting of bronze or sui?cient heat to cause bonding of the rubber to brass to which said rubber composition is adapted the alloy surface of said metal piece. to be directly bonded, the rubber being in direct 12. In a method of forming a composite rubber contact with said surface; and applying sufficient and metal article wherein the rubber is securely vi heat to bond the rubber to the metal while main bonded to the surface of a metal piece, the steps taining a substantial pressure at the rubber which comprise prevulcanizing a mass of a rubber metal interface throughout the bonding operation composition adapted to cohere directly to the metal of said article, in the desired shape; placing said mass of prevulcanized rubber composition and a piece of metal, having a smooth, polished to insure intimate pressure contact between the rubber and the surface. 16. In a method of making a composite rub ber and metal article wherein the rubber portion is securely bonded directly to the surface of a and continuous surface of a cuprous alloy of the class consisting of bronze or brass to which said rubber composition is adapted to cohere directly, in a mold adapted to con?ne the rubber mass against distortion, an untreated surface of said rubber mass being in direct contact with said alloy surface; applying sufficient pressure to the mold to maintain a substantial positive pressure at the contact surface of the metal piece with the prevulcanized rubber composition substantially perpendicular to said contact surface; and apply ing sufficient heat to cause bonding of the rubber to the surface of said metal piece. 13. In a method of forming a composite rubber metal piece, the steps which comprise preforming and precuring said rubber portion from a metal ardherent rubber composition adapted to be di rectly bonded to metal; providing a piece of metal of the desired shape with a continuously smooth clean polished surface of an alloy of the class consisting of bronze and brass to which the said L. rubber composition is adapted to cohere directly; assembling said preformed rubber portion in the desired relation with said rubber-adherent sur face with an untreated surface of the rubber in direct contact with said surface; and applying ’ su?icient head to bond the rubber to the surface and metal article, wherein the rubber is securely while maintaining a substantial pressure at the bonded directly to the surface of a metal piece, the steps which comprise prevulcanizing a mass of a rubber composition adapted to cohere directly to the metal surface of said metal piece, in the desired shape; placing said mass of prevulcanized rubber composition and a piece of metal having a smooth, polished and continuous surface of a cuprous alloy of the class consisting of bronze or brass to which said rubber composition is adapted 75 interface throughout the bonding operation to insure intimate pressure contact between the rubber and the rubber-adherent surface. 17. In a method of forming a composite rubber and metal article wherein the rubber is securely bonded directly to the surface of a metal piece, the steps which comprise preforming and at least partially prevulcanizing a rubber composition adapted to be adhered to the surface of the said 2,409,759 15 metal piece in the desired shape; placing said preformed rubber composition and said metal piece, having a smooth, polished and continuous rubber-adherent surface of‘ a cuprous alloy of the class consisting of bronze or brass to which said rubber composition is adapted to cohere di rectly, in a mold adapted to con?ne the pre formed rubber against distortion, an untreated surface of said rubber being in direct contact 16 with said rubber-adherent surface, applying suf ficient pressure to the mold to maintain intimate contact between the said surface of the piece and the preformed rubber composition; and applying suf?cient heat to cause bonding of the rubber to “the surface of the metal article, said heat being at least suf?cient to completely vulcanize the rubber. OAKLEY W. HOSKENG.