vNov._5, 1946. N_ LESTER ‘ I 2,410,510 MOLDING THERMOSETTING MATERIAL Filed July 4, \1942 INVENTOR. N ATHAN LESTE R ATTORNEYS Patented Nov. 5, 1946 2,410,510‘ UNITED ‘STATES PATENT OFFICE 2,410,510 MOLDING THERMOSETTING MATERIAL ' Nathan Lester, Cleveland Heights, Ohio, assignor to Lester Engineering Company, Cleveland, Ohio, a corporation of Ohio Application July 4, 1942, Serial No. 449,758 14 Claims. (Cl. 18-30) 1 2 The present invention relates to the pressure molding of thermosetting plastic material, 1. e., the formation of such material into desired shape in a molding die cavity by the application of proper pressures and temperatures thereon. Thermosetting Or “hot-set” plastic materials un mittal of a given quantity or charge of the plastic material in its initially, ?nely divided solid form from a pressure chamber into the mold proper in one continuous operation, and wherein the ma terial is plasticized during its travel from the such as that of a powdered or granulated mate-g rial, the second plasticized form wherein the ma? ' terial enters the plastic or sufficiently fluid state to be caused to ?ow into and‘ completely ?ll the pressure chamber to the mold cavity, and all of the so plasticized material is incorporated into the mold body and removed from the pressure molding machine at each and every stroke. The temperature conditions imposed upon the material to be molded, during its transmittal from the in itial and solid to the plasticized and ?nally to the infusible state, are such that if there is any mold cavity, and thirdly, the permanently solidi excess material present over and above that nec ?ed or infusible state wherein the material under latter phase change is usually referred to in the essary to completely ?ll the mold proper, such excess will be maintained in its original granular or powdered form when in the pressure Cylinder practice as “the cure.” The thermosetting or hot and will not operate to cause a clogging of the dergo, during the pressure molding operation, phase changes involving three different phases or physical forms, namely: The initial solid form, goes a chemical change or polymerization, which I latter. set molded plastic materials are exempli?ed by the phenolic and urea resinoid condensation products. 20 Additional objects and advantages of the in vention shall become apparent as the following Heretofore the thermosetting plastic materials -' description proceeds. have been molded by means of the compression To the accomplishment of the foregoing and molding and the transfer molding processes. In the ?rst, the material is loaded directly into the related ends, said invention, then, consists of the mold cavity wherein an initial pressure and heatv .25 means hereinaftenfully described and particu is applied until plasticization occurs, and then ' larly pointed out in the claims, the annexed draw ing and the following description setting forth additional pressure exerted during the curing in detail certain means and one mode of carrying stage. In the transfer molding method the ma terial is plasticized by heat at a point removed, out the invention, such disclosed means and mode or outside of the mold body itself, and then as a :30 illustrating, however, but one of various ways in plastic, it is transferred through an ori?ce into" ' which the principle of the invention may be used. In said annexed drawing: ' the mold cavity Where it becomes cured or solidi ?ed. Compression molding has been subject to Fig. 1 is a sectional view taken through the the disadvantage of requiring a relatively long pressure plunger cylinder and die blocks of a period of time for the performance of the molding. machine embodying the principle of my inven cycle, two to ten minutes being necessary for the " tion and‘ adapted to perform the novel process polymerizing or curing stage alone. The transfer thereof; molding method is more rapid, but is subject to Fig. 2 is an elevational view of Fig. 1 but show the disadvantage of producing an over-heating ing the die blocks in open position; ’ or over-curing of the material retained in the 40 ~Fig'. 3 is an enlarged, perspective view of that plasticizing chamber. Quite frequently, a hard- " part of the die blocks forming the plasticizing ened and infusible slug will form in the plasticiz runners or gates of the mold cavity and also the ing chamber of the transfer molding apparatus, removable discharge end wall of the pressure thus interrupting the operation of the process and 7 45 plunger cylinder; apparatus until such slug can be removed. Fig. 4 is an enlarged cross sectional view taken It is therefore the general object and nature substantially along line ll—4 of Fig. 2; and of my invention to provide a process and appara Fig. 5 is an enlarged, perspective view of the tus for molding thermosetting material wherein end of the gate or runner slug of the casting, illus the complete molding operation or cycle can be performed at a relatively rapid rate and wherein 50 trating the occurrence at that point of both the cured and the unplasticized molding material. the pressure chamber is discharged or evacuated The pressure molding process embodying the of the entire charge of material at each stroke, so principle of my invention involves the following that there is no opportunity for the solidi?cation detailed steps, wherein those having to do with or curing of a slug of excess material therein. Brie?y outlined, my process involves the trans 55 the phase change of the thermosetting plastic 3 4 to the interior of the insert 12 at a point im tinuous operation: mediately behind the end Wall 13. This is ac 1. Charging of given quantity of solid, ?nely complished by means of the concentric Water divided thermosetting material into the pressure tubes léi and 55 which terminate at the inner chamber. . 5 bore or space it inside the insert 12 and are 2. Evacuating material under pressure from connected at their outer ends by means of the material are conducted, in e?ect, as one con pressure chamber. 3. Maintaining temperature of material, While in pressure chamber, at below the plasticization ?ttings It and i8, respectively, to ?exible water line conduits (not shown). Cooling water ducts, seen at 28 and ill in Fig. 1 are also provided in point. 1-9 the wall of the pressure cylinder 1 immediately 4. subjecting material in elongated gates or adjacent its left hand or discharge end. The runners to a temperature sui?cient to produce cooling water, or other coolant medium is circu plasticization thereof (in the case of phenolic lated through the concentric tubes 14 and I5 thermosetting plastic material, about 350° R). . and the ducts "2H and 2| at a temperature and 5. subjecting plasticized material in mold cavi rate sufticient to'maintain the outer surface of ties to further curing heat and pressure to cure the Wall 13 and the interior of the pressure cyl or hot set the material. inder ‘i at'a'point below that at which plasticiza 6. Opening die blocks and evacuating entire tion of the material M, under the pressure ap-} body of material in the form of castings proper, plied, might occur. runners and gate slug. . An electrical resistant heating coil 22 is mount 20 Steps 2 -toi5 as delineated above are conducted ed in the insert 52 exteriorly of'the cooling tubes in ‘what is in practical effect one continuous ill and 15. The heat produced and generated operation, ‘wherein the material is transformed from the heating coil 22' is transmitted through from its ‘initially solid to its ?nally cured or the body of the insert I2, and also through the solidi?ed state in a relatively short period of 25 body of the die block 4, so as to heat the runners time, i. e., less than one minute. .This is to be ii. Such heat in the runners H is maintained compared to the 2’ to 10 minutes of curing time at'a temperature (viz. about 350ml“. in the case alone required in the compression molding meth of phenolic thermosetting material) su?icient to produce av plasticization of the ‘material as it od as heretofore practiced. Furthermore,‘ since none ‘of the material is subjected to a plasticizing 30 passes‘ therethrough under pressure, and into the temperature in the pressure chamber, there is mold cavity portions 19.‘ ‘Additional ‘electrical heating elementsl23 and 2d ‘are provided in the . no opportunity for'the'formatio'n of a set slug 'in the'ilatter, as compared to the transfer mold ing method. , die blocksii and ii,’ respectivelyfat points adjacent the mold cavity ‘ portions "it which ‘form the 35 castingsproper. lt‘is‘at this latter 'point‘that the ‘plasticia‘ed material is‘ subjected to‘ the‘?nal performance-of the above process, and a detailed cure or additional 'heat and‘ pressure’ treatment description of such'apparatus will serve to fur sumcient itofp'olymer'iz'e‘ and “hot set” the plastic The apparatus as illustrated in the accom panyingdraiving is’pa'rticul‘arly designed ‘for the ther illustrate the practice of such process. material "to its ?nal‘solidi?ed 'or infusible state. ‘ 71_‘n?§F-igs. -1 and’2 there are shown a pair or 40 . Ejector fpins’fz?, connected’to the ejector plate separable platens 'l and 2, such as heretofore 'Ztfrhbve outwardly ‘and operate to'eject the'en found'in an injection molding machine for the pressure molding of thermoplastic. plastic ma terials. ~The-platen I is‘?xed or stationary and tire castingincluding the casting portions proper l6’, runners H’ and gate slug [3’, as the die blocks‘ 3 anew: are moved into open position. ,the- platen 2 ‘is'movable with respect thereto. 45 ‘Simultaneously, the'pressurefplunger-ii is moved to a‘position slightly outwardly of the face or ;D_ie blocks 3 and ‘4 are carriedby ‘the'plat‘ens I parting line of the “die block '3 to completely and 2; respective1y,and ‘insulated therefrom 'by the‘. respective layers" 5' and 6"of insulating'ma ’ terial- ‘Apres'sure cylinder ‘Lin Which'the'pr'es evacuate'the press'ure'cy'linde‘r ‘l and clean all of the materialv out of it. sure plunger 8 is adapted to reciprocate, is mount 50 "As illustrated in Fig. \5,"the material'found in "e‘d in‘the platen I 'a’nd'has its left‘hand‘or dis the gate slug 13’ is partially solidi?ed and par .chargeend terminating in the die block 3._ A tially in its‘original'unplasticized state, ‘such as . v"feed "opening 9' is provided for the introduction that indicated at 'Z'I'in'the central portion of the s1ug‘l3'. ‘of the'powdered-or-granular thermo'setting plas tic ‘material ‘s‘uch‘as that illustrated at Min 55 Thus,‘ ‘it‘will be seen, ‘that as the 'pressure "Fig. 1. plunger moves ifrorn‘itsfposition 8 to ‘So in Fig. The die blocks 3 and 4 form a mold cavity 1 1,, that ‘the initially" ‘?nely divided,‘ ‘solid material comprising the portions 10 which 'formtlie cast M‘is forced ‘throughi’the "elongated runners H ing proper, and ‘the ‘relatively’ narrow or elongated where ‘it’ is simultaneously plasticized under the runners or 'gatejchannels v‘I! leading from the 60 application of heat and pressure-and thence to cavity portions It‘! 'to the'dischargeend of the the mold’cavi-ty portions in where’ itis subjected ‘ pressure cylinder 1. Themovable die block 4 has a central insert I2 which ‘projects outwardly therefrom and is ' adaptedto form the removable lefthand end wall 65 !3 oftheip're'ssuré' cylinder 1‘ when'the die blocks 'are'ini_closedlposition as ‘shown in Fig, 1. The to a further curing heat and'pres'sure; and that as the v?nishedcasting‘is. ejected from the ‘dies, and the plunger‘ 8 moved out'throu‘gh the end ‘of the pressure cylinder 1; all ‘of'the original charge of material Miis likewise removed from the ma chine and the latter is ready to perform a ‘repeat - ‘outer diameter of the end wall i3 is substantially cycle of} operations. " Thus, there is no opportu ‘equal to‘ the inner diameter of the pressure cyl nity for any excess of material becomingc'ured or inder 11,80 that it can‘make a slight re-entrant 70 set-in the pressure ‘chamber, or of contamination or telescopic ?t into the end thereof. The pro of one casting with material left over from a'pre ~ jectin'g insert !2 also has the channels II which vious ‘fshot” or operation. fform'aportion of the runners leading to the My‘ above described ‘method ‘andfapparatus ren ldersllit possible to obtaina high rate of operation mold cavity‘ portions l0. A cooling medium, such'as water, is introduced ' ‘ ‘ and increased quantity'of production in‘ the pres 2,410,510 5 '6 sure molding'of thermosetting material, while at the same time eliminating certain‘de?nite di?icuL ties and disadvantages heretofore encounteredin 6. The injection molding method for thermo settingv plastic material, consisting in the steps of transmitting a quantity of ?nely dividedsolid the pressure molding of such materials, My in material ‘from _ a pressure injection chamber vention has rendered possible the practical and 5 through a connecting passage to'a mold cavity, operative adaptation of injecting molding prin maintaining ‘such material, while in said pres ciples to the thermosetting plastic material ?eld. sure chamber, at a temperature low. enough to Other modes of applying the principle of the retain it in said state, and subjecting said mate invention may be employed, change being made rial, while passing through said passage, to a tem as regards the details described, provided the perature su?icient to cause a plasticization there features stated in any of the following claims of. or the equivalent of such be employed. ‘. 7. Themethod of molding thermosetting plas I therefore particularly point out‘ and distinctly tic material, consisting in the steps of providing a quantity of ?nely divided solid material to be molded, forcing such material under pressure from a pressure chamber into a molding cavity, maintaining the temperature in said pressure chamber su??ciently low to retain such material pressure chamber and While in the solid state therein in the solid state, applying heat to such educting the material from the pressure chamber 20 materialsu?icient to cause a plasticization there toward a molding cavity, and applying heat to of at a point between the pressure chamber and claim as my invention: ; , 'i. The method of molding thermosetting plas tic material, comprising the steps of providing a quantity of ?nely divided solid material to be molded, applying pressure to such material in a the molding cavity, and subjecting such plasti such material sufficient to cause a plasticization thereof at a point between the pressure chamber cized material when in said cavity, to further heat and pressure su?icient to produce s0lidi?ca— 2. The injection molding method for thermo 25 tion thereof. 8. The injection molding method for thermo setting plastic material, consisting in the steps setting plastic material, consisting in the steps of of charging a quantity of ?nely divided solid ma transmitting a quantity of ?nely divided solid terial into a pressure ejection chamber, dischar material from a pressure injection chamber ing said material from said injection chamber and maintaining said material While within the 30 through a connecting passage to a mold cavity, maintaining such material, while in said pres con?nes of said chamber, in such ?nely divided and the molding cavity. solid state, passing said material through a con necting passage to a mold cavity, and heating ‘ sure chamber, at a temperature low enough to said material, while passing through said passage, while passing through said passage, to a tem perature suf?cient to cause a plasticization there-= to a temperature suflicient to cause a plasticiza tion thereof. ’ 3. The method of molding thermosetting plas tic material, comprising the steps of providing a quantity of ?nely divided solid material to be molded, applying pressure to such material in a pressure chamber and while in the solid state, educting the material from the pressure chamber toward a molding cavity, applying heat to such material sufficient to cause a plasticization there of at a point between the pressure chamber and 45 the molding cavity, and subjecting such plasti cized material when in said cavity, to further heat and pressure sufficient to produce solidi?ca tion thereof. retain it in said state, subjecting said material, of, and subjecting such plasticized material When in said cavity, to further heat and pressure suffi cient to produce solidi?cation thereof. 9. The method of molding thermosetting plas tic material, comprising the steps of providing a quantity of ?nely divided solid material to be‘ molded, forcing said material under pressure and while in the solid state from a pressure cham ber to an elongated passage and thence into a mold cavity, cooling the entrance end of said passage and heating its remaining portion to a temperature suf?cient to cause plasticization of material traveling therethrough, and subjecting said material while in said mold cavity and while 4. The injection molding method for thermo 50 in the heated portion of said passage, to further heat and pressure su?icient to cause solidi?ca setting plastic material, consisting in the steps of tion of such material therein. _ charging a quantity of ?nely divided solid ma 10. The injection method of molding plastic terial into a pressure injection chamber, dis material which transforms from initially solid charging said material from said injection cham 55 to plastic and ?nally to infusible state during the ber and maintaining said material while within molding operation, consisting in the steps of in the con?nes of said chamber, in such ?nely divid jecting a ?nely divided body of such material in ed solid state, passing said material through a the initial solid state from a pressure injection connecting passage to a mold cavity, heating said chamber into a forming mold, maintaining the material, while passing through said passage, to co temperature of said material throughout its trav a temperature sul?cient to cause a plasticization el through said chamber at a point su?iciently thereof, and subjecting such plasticized material low to remain in such solid state subjecting all when in said cavity, to further heat and pressure but a small fraction of such body of material, sufficient to produce solidi?cation thereof, after passing through said chamber, to a, tem 5. The method of molding thermosetting plas 65 perature sufficient to transform the material into tic material, consisting in the steps of providing the plastic state, further subjecting such ma a quantity of ?nely divided solid material to be terial when in said mold to su?icient heat and molded, forcing such material under pressure pressure to transform it into the infusible state, from a pressure chamber into a molding cavity, and evacuating the entire body of the originally maintaining the temperature in said pressure 70 providedmaterial from the injection chamber on chamber su?iciently low to retain such material each stroke of operation. therein in the solid state, and applying heat to 11. In a pressure molding machine having a such material su?icient to cause a plasticization pressure chamber, separable die blocks forming thereof at a point between the pressure/chamber a, plurality of mold cavities with a plurality of and the molding cavity. 75 runners for said cavities located in their parting 2,410,510 a 7 line, the improvement which comprises a pro parting line, the improvement which comprises jection mounted on one of said die blocks and an insert ?xed in one of said die blocks and pro entrant into the discharge end of said pressure jecting into the discharge end of said cylinder, said insert having an outer diameter substantially equal to the inner diameter of said cylinder, and ‘chamber, and divergent runners in the outer sur face of said projection forming a continuation of said ?rst-named runners, heating means lo cated adjacent said mold cavities and said run ners for heating the surfaces thereof, and cool ing means adjacent said discharge end of said pressure chamber for cooling the interior of the latter. 12, In a pressure molding machine having a pressure chamber, separable die blocks forming a plurality of mold cavities with a ‘plurality of runners for said cavities located in their parting line, the improvement which comprises a pro jection mounted on one of said die blocks and entrant into the discharge end of said pressure chamber, and curved runners in the outer sur face of said projection forming a continuation of said ?rst-named runners, heating means lo cated adjacent said mold cavities and said run ners for heating the surfaces thereof, and cooling means adjacent said discharge end of said pres sure chamber for cooling the interior of the lat ter. 13. In a pressure molding machine having a curved runners in the outer surface of said in sert leading from the parting line of said die blocks and each forming a, continuation of said ?rst-named runners, heating means located ad 10 jacent said mold cavities and said runners for heating the inner surfaces thereof, cooling means located in said insert for cooling the surface of the latter, and a, second cooling means located in the wall of said cylinder for cooling the interior 15 thereof. 14. Apparatus for molding heat plasticizable material, comprising in combination cooperating dies providing molding cavities, one of said dies having a bore extending from the outer face 20 thereof to the parting line between the dies, a cylinder having an open end extending into said bore, a plunger movable within said cylinder to force said material as a cylindrical mass in the direction of said dies, a nose secured in the die 25 beyond the parting line in alignment with said bore and extending into the cylinder‘ and means for supplying heat to said nose to raise the same to a temperature above the temperature of the material injection cylinder and a pressure plung er reciprocable therein, separable die blocks material Within said cylinder. forming a, plurality of mold cavities with a plu 30 rality of runners for said cavities located in their NATHAN LESTER.