US2485452A

US2485452A - Press

Info

Publication number: US2485452A
Application number: US581648A
Authority: US
Inventors: Lyijynen Fred
Original assignee: Briggs Manufacturing Co
Current assignee: Briggs Manufacturing Co
Priority date: 1945-03-08
Filing date: 1945-03-08
Publication date: 1949-10-18
Anticipated expiration: 1966-10-18

Description

Oct. 18, 1949.

PRESS Filed March 8, 1945 4 Sheets-Sheet 1 E w BYy F. LYJJYNEN' 2,485,452

Oct. 18, 1949. F. LYIJYNEN 2,485,452

'PRESSl Filed March s, 1945 v 4 sheets-sheet 2 Oct. 1s, 1949. F YUYNEN 2,485,452

PRESS Filed March 8, 1945 4 Sheets-Sheet 5 VNm F. LYUYNEN oa. 1s, 1.949.

PRESS i 4 Sheets-Sheet 4 Filed March, 8, 1945 4 INVENToR. ai gfyefz N i .r w

Patented Oct. 18, 1949 PRESS Fred Lyijynen, Detroit, Mich., assigner to Briggs Manufacturing Company, Detroit, Mich., a corporation of Michigan Application March 8, 1945, Serial No. 581,648

6 Claims.

This invention relates to the manufacture of plastic articles and more particularly to improvements in apparatus for molding or forming under heat and pressure materials containing plastic substances, such as thermoplastic or thermosetting resinous compositions, which require the application of heat thereto during the molding or pressing operation in order to carry forward and complete the reaction or polymerization of the resinous substances.

The molding of articles from materials of the foregoing character is customarily accomplished by means of heated dies in a press, usually hydraulically operated. According to conventional practice the charge of partially reacted plastic material is placed in the lower die member of the press after which the upper ram of the press is caused to descend to bring the upper and lower die members together and subject the charge to heat and pressure. It has been necessary, in accordance with previous practice, to maintain the press closed for a substantial interval of time in order to bring the plastic charge upto temperature and thereafter to hold the material at the desired temperature or temperatures in order to carry forward and complete the reaction thereof. During this period of time required to perform the molding operation with the press closed, not only is the press completely idle but also the press operator and any other workmen engaged a in serving the press. When taking into consideration the high cost of hydraulic presses used for these purposes, the cost of maintenance thereof, the long periods of idleness of the presses and operators while waiting for the plastic materials to progress through the reaction stages, and the cost of plant space occupied by these presses, it

will be apparent that production costs of the plastic articles are greatly enhanced on account of these conditions.

It is an object of the invention to provide apparatus by which the foregoing objectionable conditions may be ameliorated and the lperiods of idleness of the press during the molding or pressing operations measurablyreduced thereby def.;

creasing production costs with a consequent large increase in the` output capacity of the press.

A further object of the invention is to provide an apparatus for molding plastic articles in which the time required for the mold and its charge of plastic material to remain in the press during one cycle of operation will ,be reduced to a minimum, thereby enabling the press to carry out successive molding operations over shorter intervals of time.

Another object of the invention is to providel apparatus which only necessitates the mold and its charge remaining in the press during the relatively short interval of time needed to initiate the molding operation, to open the mold for the escape of gases and thereupon to close the mold, after which the mold is immediately removed from the press topermit completion of the reaction or polymerization of the plastic material outside the press. As a consequence each molding operation requires but a minimum of press time and, hence, with a much shorter cycle of operation the productive capacity of the press is greatly increased.

A further object of the invention is to provide an improved mold comprising cooperating die or gether in closed position so that the mold as a unit may be withdrawn from the press for completion of the reaction or polymerization of the material outside the press, thereby freeing the press for a successive molding operation.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specication wherein like reference characters designate corresponding parts in the several views.

- Fig. 1 is a, fragmentary side elevation illustrating a press and associated apparatus including a series of mold units for carrying out the present invention.

Fig. 2 is an enlarged fragmentary sectional view of a mold unit illustrating the position of the parts before pressure is applied to the mold through operation of the ram of the press.

Fig. 3 is a view similar to Fig. 2 illustrating a partially closed position of the mold during one step of the molding operation.

Fig. 4 is an enlarged fragmentary sectional View taken substantially through lines 4-4 of Fig. 1 looking in the direction of the. arrows, this view showing the mold in closed locked position preparatory to withdrawal of the mold unit from the press.

Fig. 5 is a plan View of a mold unit constructed in accordance with a second embodiment of the invention. l

Fig. 6 is an enlarged fragmentary sectional view taken substantially through lines 6 6 of Fig. 5 looking in the direction of the arrows.

Fig. 7 is an enlarged fragmentary sectional view taken substantially through lines 'I-l of Fig. 5 looking in the direction of the arrows.

Fig. 8 is a view somewhat similar to Fig. 7 illustrating particularly the mechanism arranged outside the press for unlocking or funclamping the upper and lower mold or die members of the mold unit to permit the mold to be opened for removal of the nished article.

Before explaining in detail the present invention it is to be understood that the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

In carrying out the invention I utilize in connection with a press, preferably of the hydraulic type, a number of pre-heated transitory mold units which are self-contained so as to embody the necessary mold or die members cooperable to form the desired article or articles from a charge of plastic material introduced into the mold unit before the latter is fed into the press. Each mold unit preferably comprises upper and lower pressure plates which carry or engage the interposed die or mold members and which are provided at opposite sides with devices for locking or clamping the upper and lower mold members of the unit tightly together so as to permit them to be withdrawn from the press in .order to properly complete the reaction or polymerization of the plastic material outside the press. The mold units are fed in succession into and out of the press and each unit remains in the press for a short interval .of time during which the preliminary pressing and heating of the plasticl material to moldable temperature are carried out. Also during the short interval of time the mold unit is in the press the unit may be relieved from the pressure of the ram so as to permit breathing or escape of gases after which final pressure is applied by the ram so as to fully close the mold and enable it to be clamped tightly'in closed position for withdrawal from the press. When the mold unit is withdrawn from the press, the final polymerization or reaction of the plastic material is allowed to proceed to the final stage and during this time the press is freed for operation upon a succeeding mold unit which may be introduced into the press as soon as the preceding unit has been withdrawn therefrom.

In Fig. l there is illustrated at I@ any conventional type of hydraulic press having a vertically reciprocating ram II carrying at its lower end a platen I2 which is heated to the proper temperature by any conventional means. The lower platen of the press is indicated at It, this platen being shown as fixed and adapted to support the mold unit which is compressed between the upper and lower platens I2 and I3 upon the descent of the ram Il. At one .open side of the press there is provided a suitable guiding table or frame I4 carrying anti-friction rollers I5 upon which the mold units A may be guided in succession to the press and from which each mold unit may be propelled into the press after a preceding press operation has beenperfcrmed. The mold units are withdrawn from the press in succession over a guide table or frame I6 carrying anti-frictional rollers I5a upon which the mold units travel as they are propelled away from the press. Since the final stage of polymerization or reaction of the plastic material within the mold unit is accomplished after withdrawal of the mold unit from the press, the mold unit may, if desired, be subjected to heat after withdrawal from the press in order to ensure maintenance of the proper temperature .of the material until polymerization is completed. For this purpose the successive mold units may pass out of the press through a suitable oven I'I which will maintain the heat in the mold for a suitable interval of time. The use of the oven I? for this purpose is not essential in connection with the molding of certain types of plastic materials inasmuch as the mold, after withdrawal from the press, will in many instances retain sufficient heat during an interval of time at a temperature necessary to complete the reaction or polymerization of the material.

The conveyor table over which the molds travel may be circular in construction with the table I4 forming a continuation of the table IE. Hence, after completion of the curing or polymerization or" the plastic material within each mold on the outgoing portion I6 of the conveyor table, the mold may be opened to remove the finished article and then propelled over the table to a station where the mold is cleaned. Thence, the mold progresses over the table to a loading station where a fresh charge of material is introduced thereinto, and from this point the mold travels over the incoming section I6 of the conveyor to the press for a succeeding operation.

The plastic materials which I use preferably are composed of one or more thermosetting resins as the principal constituent thereof which may be ,combined with a suitable reinforcing filler of brous nature. Typical thermosetting resins which have been used satisfactorily are the phenolformaldehyde, urea formaldehyde and melamine type resins.

Inthe embodiment illustrated in Figs. 2 to 4 inclusive each mold unit A comprises upper and lower pressure or die plates I8 and I9. Secured to the underside of the upper plate I8 is the upper die or mold 20 of the unit which is held in place by an upper backing ring 2l. The lower die, which is mounted on the bottom pressure plate I 9, comprises an outer die or mold section 22 held in place by a'backing ring 23 and an inner die section 24 which is piloted within an opening Za in the -upper die 2E. Extending within an opening 2da in the die section 24 is a compression spring 25 which engages a vertically shiftable ejector slide 2B mountedwithin a recess 24h in the lower die sections. The ejector slide 2B carries .one or more vertically extending knock-out pins 21 which are adapted to eject the finished article B from the lower mold or die when the slide is shifted upwardly by means of a plunger 28 when the ymold is opened outside the press, The-plunger 28 is actuated pneumatically when the mold is shifted to a predetermined position on the. table I6 and after the mold has been unclamped and opened.

Pivotally mounted within a recess in the backing ring 23 on a fixed `pivot pin 29 isa clamping dog 3|). This dog terminates lat its :upper inner end in a hook-shaped member 30a which is adapted to :cooperate with a xed pin 3I carried by the upper backing ring 2I so as to lock the mold in fully closed -position in the manner shown in Fig. 4. 'I'he lower` inner end yof the dog is pro- 'y vided with a `projecting arm 30h the undersidel of which is cam shaped or tapered Afor engagement by a pneumatically operated plunger 32 in order to swing the dog outl of locking position with respect to the 'pin 3| when it is desired to unlock and open the mold. The plunger 32 is Operated from a compressed air cylinder 33 mounted beneath-the conveyor table I6. Hence, `when the mold unit A. reaches a predetermined position on the conveyor table, the plunger 32 is shifted vertically through an `aperture in the bottom pre.,- sure plate I9 of the mold in the manner shown in dotted lines in Fig. 4 so as to swing the locking dog out Iof engagement with the pin 3|. In :the construction of the mold unit shown in Figs. 2 to 4 inclusive it will :be understood that a pair `of locking dogs 30 and associated parts are provided at lopposite sides of the mold and, hence, the loc-king mechanism illustrated in Figs. 2 to 4 inclusive is duplicated at the opposite side of the mold.

Each locking dog 39 is n-ormally held in Open position by means of Ia spring pressed plunger 34 having a tapered inner end 34a adapted to extend into a wedge shaped notch 38o formed in the locking dog. The plunger 34 is urged outwardly by means of a compression spring 35 housed within a bore 38 in the backing ring 23. The locking dog 3|! is swung toward its locking position by means of a vertically shift'able plunger 31 carried by the upper pressure plate I8 and terminating in a wedge shaped or tapered lower end 38. The plunger is urged upwardly to its position shown in Figs. 2 land 4 -by means of a spring 48 mounted within an opening 4| in the upper pressure plate and engaging the underside yof the head 39 of the plunger. the upper heated platen I2 first engages the head 39 of the plunger 31 and shifts it downwardly against the action of spring 40 to a position flush with the upper face of the pressure plate I8. During this operation the tapered end 38 of the plunger rides over a scam surface 42 on the dog 38 and thus swings the dog from the position yof Fig. 2 to the position shown in Fig. 3. After the spring has been fully compressed by the descent of the platen I2 the latter will exert pressure against the pressure plate I8 and force it downwardly the desired distance so as to compress the charge of plastic material between the upper and lower ydie members interposed between the upper and lower pressure plates I8 and I9. Y

The stroke of the ram will be such that the plunger 31 and the dog 30 will reach the position shown in Fig. 3 Iat :the conclusion rof this preliminary pressing operation with the end 38 of the plunger positioned substantially against a shoulder 43 at the lower end of the cam surface 42. It will be understood that coaction of the plunger 31 with the locking dog in the manner above described will cam the end 34a of the plunger 34 out of the notch 30o against the action of spring 35.

After :the ram has descended to the limit of its stroke so as to exert pressure von the plastic charge through the medium of the die or mold members 28, 22 :and 24, and with the locking mechanism disposed in substantially the manner shown in Fig. 3, the press is allowed to dwell for a short interval of time so as to heat the plastic charge to a moldable temperature. During this dwell the plastic material is formed by the mold or die members into the approximate shape of the iin-a1 article B. The ram is then caused to ascend thus moving :the upper platen I2 away from the pressure yplate I8 and releasing the pressure on the mold. When this occurs the plungers 31 are Upon descent of the ram rf shifted upwardly by their springs 40 away from the locking -dogs 30 a distance sufcient rto cause the tapered ends 38 of the plungers to clear the shoulders 43 and thereby release the dogs. Each dog is thereupon shifted `from the position shown in Fig. 3 to or toward the position shown in Fig. 4 by means of an actuating k plunger 45 slidable within a cylindrical hole 4B in the backing ring Z3, the plunger being actuated by means Iof a compression spring 41. During this interval of time when the ram is raised, relieving the pressure on the mold, gases are Iallowed to escape from the mold. Thereupomth-e ram again descends and exerts final pressure :upon the mold. During this operation the Iplungers 31 are again depressed and in the event the dogs are not fully engaged with the locking pins 3| the tapered ends 38a of the plungers 38 will contact the cam surfaces 44 on the locking dogs and force the hook shaped ends 38a of the dogs -fully home over the locking pins 3i. In this manner the pressure plates I8 Iand i8, las Ishown in Fig. 4, are securely clamped together with the die members in fully closed position. As soon as the mold unit is fully locked in its closed position shown in Fig. 4, the ram is raised and the mold unit is shifted from the press onto the conveyor table I6.

In :the embodiment shown in Figs. 5 to 8 inclusive the molding method is :the same as previously described. In this instance, however, the upper and lower mold or die members 49 and 5I) are constructed and designed to form a plastic garnish molding C for the window reveal of an automobile body. The upper and lower ydies 49 and 58 are hinged together at 5| along corresponding edges thereof so as to permit the die member 49 to be swung upwardly in order rto charge the mold or remove the fini-shed article therefrom. In this embodiment the lower die 50 is suitably recessed to receive die inserts or sections l52 and 52a which cooperate with contoured die portions on the upper die or pressure plate 49 to form the article to the desired shape as shown in Figs. 5 to 8 inclusive. In this embodiment of the invention a somewhat different form of mechanism is provided for locking or clamping the upper and Y lower die members together while the die or mold unit is in the press and for unlocking these members when the mold unit is outside the press and after :the reaction or polymerization of the plastic material has been completed.

The upper pressure plate or die member 49 is formed at opposite sides with projecting ledges 53 upon the upper surface :of each of which is secured a wedge shaped hardened piece 54. Pivotally mounted at each side of the mold unit upon a pivot pin 55 secured within a bifurcated extension 56 of the lower die or pressure member 5e is a swinging locking dog or clamping member 51 which is in the form of a bell crank lever having a vertical projecting arm 51a terminating in a hook portion 51h tapered at its underside for cooperation with the tapered surface of the hardened piece 54. The lever 51 has a laterally projecting arm 51e positioned for engagement by a vertically shiftable pneumatically operated plunger 58 suitably mounted within the base of the press.

After completion of the preliminary molding and breathing operations within the press and when the ram descends to exert its nal pressure upon the mold in order to fully close the mold, the plunger 58 is shifted upwardly to engage the arm 51o of the bell crank` lever thereby shifting the hook shaped end 51h thereof over the piece 54. Since -the cooperating surfaces yof the 'parts 54-and lbareftaperedor wedge shaped, the force exertedby the plunger 5B will result in a'wedging action between these parts tending to .draw down the upper and lower die members 49 .and 5t tightly together. This action of Ithe 'clamps ensures the mold being held in tightly v'closed position. With the mold in this condition it may be withdrawn from the press .and shifted onto the conveyor table I6 as soon as the ram has 'been causedfto ascend. After ythe completion ofthe reaction or polymerization of the material within the mold while it is outside the press, the levers 51 may be released to enable the mold to `be opened by means of pneumatically operated plungers 62 actuated from air cylinders `beneath the table substantially in the manner shown in Fig. 1. Each plunger is adapted to engage one end of-a lever 559 fulorumed at 60 on a bracket 5l projecting upwardly through the conveyor table I :between .a pair of anti-friction rollers lia. When the plunger v(52 is shifted upwardly to rock the lever 59 the end 59a will be forced down into engagement with the arm 51e of the clamping lever 51 and thus force the clamping lever out of locking position as vshown in dotted lines in Fig.7.

Before a succession of press operations are undertaken the upper and lower press Aplatens `I l and I3 are `heated and brought up to a predetermined temperature which is substantially maintained during operation. Also, the mold ordie units are pre-heated to the desired temperature before they are charged and introduced in succession into the press. The charge for the mold is .usually in the form of one `or more pieces or pellets preferably contoured or cut to approximately the shape of the bottom mold or die cavity so as to permit vthe piece to be readily inserted thereinto. Upon charging the `heated `mold unit the latter is closed withthe dies lin superimposed relation and the charge therebetween. The mold unit is then shifted into the press in proper position with respect to the upper and lower press platens and the press closed by descent of the ram which carries lthe upper platen. The press remains closed for the proper interval of time to bring the charge into moldable condition and to initiate the shaping of the article. The ram is then raised torelieve ythe pressure on the mold or die members and permit the escape of gases therefrom. This op- 1 eration is generally called breathing and ordinarily requires but a few seconds, such as four or five seconds. Upon completion of the ibreathing period the ram descends and again exerts pressure on the molds cr dies, while valso heating the same. This final pressing Aoperation may require but several seconds and fduring this 'interval the mold or die members vare securely locked or clamped together. As soon as the ram ascends after this operation the mold unit is removed from the press andallowed to stand for such period of time ras may be necessary to car-ry the reaction or polymerization of the material to the final stage. While this occursy the moldremai-ns in locked, closed position voutsidefthe press which is thus freed for a succeeding operation orioperations capable of .being carried lout before or during the time the molding of the material iin the previous operation still progresses. The closed mold when withdrawn from the press .may :be introduced into an oven, such as indicated l-at l'l, so as to receive additional heat for polymerization of the material or the polymerization for curing may be .carried out lby .the heat retained in .the dies themselves w'ithout requiringadditional heat.

Although the actual press time required for each ymolding operation will vary depending Vupon thetype of material, the initial reactive stage thereof andthe thickness of the charge, typical examples have :shown savings in .press `time per molding operation from one and one-half minutes to as much as four minutes. For example, in molding one type of article the actual time of the mold within the press was approximately thirty seconds and the time the mold remained closed outside the press for nal polymerization was approximately one and one-half minutes. This represented a saving in occupied time per operation of the press of one and one-half minutes as compared with previous practice and an increase in productive capacity of the press .of three hundred percent. In another example the saving in occupied time of the press was over four minutes, resulting in an increase in the productive capacity of thepress in this particular instance of approximately four hundred percent. In other words, the .present `invention has enabled the volume output of a press to be increased as much as threefold and fourfold during the same period of operation.

I claim.:

l. An apparatus for forming a plastic article in a mold 'having a pair of separable die members and releasable locking means for locking said members together, comprising a press having a base for supporting said mold during operation of the press, a guide table extending laterally from the press at substantially the level of the base, means in said press for actuating said locking means to lock said die members together, and fiuid actuated means supported beneath said guide table and including a vertically reciprocable plunger 'shiftable through said table for releasing said locking `means upon movement of the mold out of the press to a predetermined position on said table.

2. An apparatus for forming a plastic article in a mold having a pair of separable die members and releasable locking means for locking said members together, comprising a press having a bottom platen for supporting said mold during operationof the press, a guide table extending laterally from Vthe press at substantially the level of the platen, a fluid actuated vertically reciprocable plunger shiftable through said bottom platen fora'ctuating said locking means 'to lock said vdie members together, and a uid actuated vertically reciprocable plunger shiftable through said guide table for releasing said locking means upon `movement of the mold out of the press to a `predetermined position on said table.

3. An :apparatus for forming a plastic article in a mold having a pair of separable die members and releasable locking means for locking said members together, comprising a press having a oase for supporting said mold during operation of the press, a guide table extending laterally from thepress and over which said mold is shiftable out of the press, reciprocable means shiftable upwardly through said base for actuating said locking means to lock said die members together, and reciprocable means associated with said guide table and shiftable upwardly therethrough for vreleasing said locking means upon movement of the mold out of the press to a predetermined position on said table.

fi, In an apparatus for forming a plastic article, a press, a pair of die members adapted to receive therebetween material to be formed, means operative to clamp said die members together Ain closed position, means in said press for operating said clamping means, a guide table extending laterally from the press to receive said clamped die members, and fluid actuated means located at one side of the press beneath the table and having a reciprocable plunger shiftable upwardly through the table for releasing the clamping means.

5. In an apparatus for forming a plastic article, a press having a bottom platen, a pair of upper and lowei1 die members adapted to receive therebetween material to be formed, means operative to clamp said die members together in closed position, means in said press for operating said clamping means and comprising a fluid actuated device located beneath said bottom platen and provided with a reciprocable plunger shiftable vertically through said platen, a guide table eX- tending laterally from the press to receive said clamped die members, and fluid actuated means beneath the table and having a reciprocable plunger shiftable vertically through the table for releasing the clamping means.

6. In an apparatus for forming a plastic article, a press having a stationary lower platen and a movable upper platen, a pair of separate upper and lower die members, means operative to clamp said die members together in a closed position in- 10 cluding a bell crank lever pivotally mounted on the lower die member, and fluid actuating means beneath said lower platen including a plunger movable vertically through the platen for operating said lever to clamp said die members together, said actuating means being operable independently of said upper platen.

FRED LYIJYNEN.

REFERENCES CITED The following references are of record in the 1ile of this patent:

UNITED STATES PATENTS