US2339792A - Apparatus for producing molded plastic articles - Google Patents

Description

Jan. 25, 1944. s. MILANO 2,339,792

APPARATUS F9R PRODUCING MOLDED PLASTIC ARTICLES Filed Sept. 10, 1941 z I l u f4 f2 INVENTOR 1/ f8 .o-e

ATTORNEY Patented Jan. 25, 1 944 UNITED STATES PATENT OFFICE;

APPARATUS FOR- PBODUCING MOLDED PLASTIC ARTICLES 7 Sylvester Milano. Federalsburg, Md, asslgnor to Maryland-Plastics, 1110., Federalsburg, Md.

Applicationseptember 10, 1941, Serial No. 10,309

11 Claims.

This invention relates to the art of producing articles from thermoplastic and thermosetting materials, such as artificial resins, and more particularly refers to a novel and improved type of die for molding buttons and other articles provided with holes which aredeslrably produced at the same time as the molding operation is completed.

In theart of molding buttons it is customary to compress suitable molding material between two sections of a suitably shaped die, while sub- Jecting the material to the action of heat to render the material plastic and thus causing it to take the shape of the cavity formed by the two sections of the die when closed together.

It is also customary to provide these dies with lying the invention, I have also described, but

not claimed, a type of-die adapted to carry-the method into practice.

- The primary object of the present invention is to provide a die of a novel and improved construction,- representing the preferred type of die for carrying the aforesaid method into practice. Another object is to provide a die of a novel and improved construction designed so that all pins penetrating the plastic mass to form thread holes at the same time that the material is subjected to the action of heat and pressure. In some types of dies one of the sections is provided with pins long enough to project beyond the, thickness of the button and into corresponding holes provided in the other die section.

In another type of die only one section of the die is provided with pins extending substantially through the entire thickness of the body of the button without going beyond said .ody, so that easily breakable thin films will be formed at the backof the button, which films may be removed by a subsequent tumbling'operation.

In still another type of die both provided with pins. meeting about the body of the button when the two sections of the die are closed.

In a copending application for patent entitled sections are 1 Method of producing molded plastic articles, Se-' rial No. 410,308, flledsimultaneously herewith, I have explained how by forming thread holes in the body of a button at the same time that the molding operation is performed, a serious loss of material is incurred because of cracking of the preformed tabletsand distorting of the sprayed or stenciled design thereon due to the pins being'forced into the material before said material has become sufliciently plastic. In said application I have described and claimed amethod whereby this wastage may be practically eliminated and the quality of the product improved by subjecting the material to pressure after it has had a chance to become fused between the halfway 0! ing pins acting as suspension n'iembers tion; and

of its parts will be easilyaccessible for maintenance and repairs, said die comprising'individual die units adapted to be replaced by other units, interchangeable therewith, for the production of buttons and other articlesfof different shapes.

Other objects and advantages of the present invention will more fully appear as the description proceeds and will be set forth and claimed in the appended claims.

My invention is illustrated by way of exam-,

ple in the accompanying drawing in which:

Fig. 1 is a fragmentary sectional view of a die embodying my invention, with its two sections apart ready to be moved to their closed posi- F'ig. 2 is a similar view showing the various parts of the die after its two sections have reached the closed position and the thread hole producing pins have penetrated through the mass.

My improved die comprises a lower section l to the upper plate (not shown) of the press and a floating portion carried by guiding pins depending from said stationary portion, said guidfloating portion.

The lower section consistsof a retaining plate l2 provided with a number of housings l3, each adapted to snugly receive'a lower unit die section N. The lower end of the housings l8 has an enlarged diameterto provide a peripheral shoulder l5, and the unit die section is correspondingly provided with a peripheral flange l6 registering with said shoulder and acting to retain the unit die section in position.

two sections of the die so as to have reached The lowe section further comprises a backing plate Il secured to the underside of the retaining plate and mounted on the lower press plate ll, said backing plate being provided with steam passages I8, which may be suitably connected to a steam supply system, inorder to maintain the die section at a sufficiently high for said ings I 3 of. the lower-retaining plate, said housings 26 being formed with a retaining peripheral shoulder 2| and being adapted to snugly receive the upper unit die sections 22 which are also provided with a peripheral retaining flange 23. Said upper section also comprises a backing plate 2! secured to the retaining .plate i8 and is provided with steam passages 25, maintaining the upper die section at the required temperature.

As stated, the floating portion of the, upper die section is slidably supported by guiding pins, such as 26, depending from said upper press plate. To this end, the upper press plate I is equipped with a punch and guiding pin retaining plate 21, which is secured thereto through v the intermediary of a backing plate 28.

The guiding pins 26 extend downwardly from said plate 2.1 and are formed with a lower head portion 29 having an enlarged, diameter and forming a rest for a. spacing bushing 30 interposed between said head and the retaining plate l9. The weight of the floating portion l624 will normally hold said portion in its lower or extended position in which it'is supported by the spacing bushings 30 and is spaced a. certain distance from the plate 21, as indicated at 3 l.

' l2, It, said distance being such that when the;

two unit sections exactly meet, the distance between retaining plates 12 and I9 will correspondto the length of spacing bushings 30.

When the die is in the open position, shown in Fig. l, the previously prepared tablets of plastic material are placed within the lower unit die sections, as shown at 42'. Said tablets are produced by-means of a special machine delivering them in compressed solid form sothat they can be easily and speedily handled.

The press'is then operated to slowly raise the lower die section towards the upper section while the tablets of plastic material are gradually reduced' to a plastic condition by the heat transmitted from the steam passages to the unit die sections.

- However, in practice, I prefer to also provide arrangements to help release the die from.the stationary plate, for instance,.springs, such as 32, interposed between the stationary and floating portions of the upper die section, said springs serving to gradually increase the working pressure when the floating portion l9-24 is forced against the stationary plate 21. Said springs are preferably encased in heat insulating hous- Y ings 33, 34, in order to prevent their being adversely affected by the action of heat.

The head portion 29 of the guiding pins 26 registers with corresponding bushings 36 provided in the lower die section for the purpose of properly aligning the unit die sections when the lower die section the upper die section by the action of the press.

The unit die sections, or molds, shown, are of the type in which the thread holes in the button are produced by pins extending within the plastic mass from both sides, said pins almost meeting at a pointabout midway of the thickness of the button. The lower unit die section is accordingly formed with pins 36 upwardly extending a relatively short distance from the bottom thereof, said pins being slightly tapered from top to bottom and being connected to the bottom of the unit by rounded fillets 31'.

' The upper unit die section is provided with openings 38 registering with pins 36 of the lower unit die section, said openings forming passages for stems 40 formed integral with and depending in a cluster from a punch 40, the lower end of said stems being tapered to form thread hole forming pins ll, adapted to complete the holes generated by pins 36. I

is forced upwardly against cracking of the preformed tablet, whether When the upper surface of the tablet comes in contact with the surface of ,the upper unit die section, if the tablet has not yet softened to a material degree,-the floating upper section will be forced upwardly until the plastic material having flnally become fused, the two unit die sections will be enabled to meet and shape the body of the button. At the same time, the lower portion of the die will continue to rise, forcing the floating upper section upwardly against the action of springs 32, the pressure from the lower to the upper section being transmitted through spacing bushings 30 so as to relieve the unit die sections of any extra pressure.

As the floating upper section continues to move towards plate 21, pin portions 4| of stems II) will gradually emerge from openings 36 in the upper unit die section until, when backing-plate 2i finally comes to abut against retaining plate 21, as shown in Fig. 2, pin portions 4|, together with pins 36 of the lower unit die section; will have formed the thread holes in the button, leaving a very thin wall of plastic .material across such holes, as Fig. 2 clearly shows.

Due to the shape of the pins, the thread holes thus produced will be slightly flaring and with rounded edges at bothends, so that the button .can be sewed in place without difficulty and the rounded edges will be easy on the thread.

It will be observed that by virtue of the construction described, the thread hole forming pins cannot be forced through the molding material until such material has reached a sufllciently plastic state. The press piston moves at a rela-' tively slow pace so that after the tablets of mold. ing material have become clamped between the two unit diesections there is ample time for such material to become fused or plastic before the thread hole forming pins are actually forced through it. As a result of the conditions thus created the plastic material can be formed exactly to shape and pressed about the thread hole forming pins without danger of breakage or sprayed, stenciled, or of one color, and a perfectly smooth product of uniform texture is obtained.

It is. of course, understood that the thin fllm of material produced across the thread holes can be subsequently removed by suitable operations.

' It isthus apparent that by virtue of my in vention I'insure conditions whereby no undue strain is placed on the molding material while said material is still in a relatively solid state, so that the material is reduced to the best conditions of plasticity before any actual forming or piercing operations are performed upon it. Dueto the conditions thus created, I also make it possible to produce holes with smooth surfaces and rounded edges without the necessity of using special reaming or drilling tools.

Minor constructional details of my invention may vary from those shown without departing from the inventive idea. The drawing should, therefore, be'understood as being intended for illustrative purposes only and not in a limiting sense.

I, accordingly, reserve the right to carry my invention into practice in all those ways and mannerswhich may enter, fairly, into the scope of the appended claims.

I claim:

1. A sectional mold of the character described, comprising two cooperating sections, one of said sections having a fixed portion with guiding pins extending therefrom and a floating portion sections while being subjected to the action of 1 heat, said material may be reduced to a certain degree of plasticity before full forming pressure is applied thereto as said floating portion comes to rest against said fixed portion with said pins in said recesses, and. before said punch may emerge from said floating portion and penetrate said material, said sections being provided with passages through which a heating fluid may be supplied thereto.

2. A sectional mold of the character described, comprising a lower section consisting of a base plate and a unit. die section secured thereto, and an upper section comprising a retaining plate, guiding pins depending therefrom, said pins being provided with an enlarged head, a spacing bushing resting on said head,'and a floating portion having a backing plate and an upper unit die section secured thereto, registering with and cooperating with the lower unit die section, said floating portion being mounted in telescopic relation with said guiding pins and being supported by said bushings when in its extended position.

3. A sectional mold of the character described, comprising a. lower section consisting of a base plate and a unit die section secured thereto, and an upper section, comprising a retaining plate, guiding pins depending therefrom, said pins being provided with anenlarged head, a spacing bushing resting on said head, and a floating portion having a backing plate and an upper unit die section secured thereto, registering with and cooperating with' the lower unit dies section, said floating portion being mounted in telescopic relation with said guiding pins and being supported by said bushings when in its extended position,

said base plate and backing plate being provided with passages through which a heating fluid may be supplied thereto.

4. A sectional mold of the character described, comprising a lower section consisting of a base plate and a unit die section secured thereto, and an upper section comprising a retaining plate, guiding pins depending therefrom, said pins being provided with an enlarged head, a spacing bushing resting on said head, a floating portion having a backing plate and an upper unit die section secured thereto, registering with and cooperating with the lower unit die section, said floating portion being mounted in telescopic relation with tion being mounted in telescopic relation with said guiding pins and being-supported by said said'guiding pins and being supported by said plied thereto. and springs interposed between said retaining plate and backing plate, urging said 4 floating portion to its extended position.

5. A sectional mold of the character described, comprising a lower section consisting of a base plate and a unit die section secured thereto, and an upper section comprising a retaining plate, guiding pins depending therefrom, said pins being provided with an enlarged head, a spacing bushing resting on said head, a floating portion having a'backing plate and an upper unit die section secured thereto, registering with and cooperating with the lower unit die section, said floating portion being mounted in telescopic relation with said guiding pins and being supported by said bushings when in its extended position, and a punch extending from said retaining plate through said backing plate and upper unit die section, said punch penetrating into the molding material held between said two unit sections, when said lower section forces said floating portion of the upper section towards and against said backing plate.

6. A sectional mold of the character described, comprising a lower section consisting of a base plate and a unit die section secured thereto, and

an upper section comprising a retaining plate,

guiding pins depending therefrom, said pins being provided with an enlarged head, a spacing bushing resting on said head, a floating portion having a backing plate and an upper unit die section secured thereto, registering with and cooperating with the lower unit die section, said floating porbushings when in its extended position, and a punch extending from said retaining plate through said backin plate .and upper unit die section, said punch penetrating through molding material held between said two unit sections, when said lower section forces said floating portionof the upper section towards and against said backing plate, said base plate and backing plate beingprovided with passages through which a heating fluid may be supplied thereto.

7. A sectional mold of the character described. comprising a' lower section consisting of a, base plate and a unit die section secured thereto, and an upper section comprising a retaining plate, guiding pins depending therefrom, said pins being provided with an enlarged head, a spacing bushing resting on said head, a floating portion having a backing plate and an upper unit die section secured thereto, registering with and cooperating with the lower unit diesection, said floating portion being mounted in telescopic relation with said guiding pins and being supported by said bushings when in its extended position, a punch extending from said retaining plate through said backing plate and upper unit die section, said punch penetrating through molding material held between said two unit sections, when said lower section forces said floating portion of the upper section towards and against said backing fluid may be supplied thereto, and springs interposed between said retainingplate and backing plate, urging said floating portion to its extended position.

8. A sectional mold for producing buttons, comagainst said backin plate.

prising a lower sectionconsisting or a base plate and a unit die section secured thereto, and an upper section comprising a retaining plate, guiding pins depending therefrom, said pins being provided with an enlarged head, a spacing bushing resting on said head, a floating portion having a backing plate and an upper unit die section secured thereto, registering with and cooperating with the lower unit die section in molding a, button therebetween, said floating portion being mounted in telescopic relation to said guiding pins and being supported by said bushings when in its extended position, and a punch having its lower end formed with a cluster of thread hole iorming pins, extending through said backing plate and upper die section, said pins penetrating the button material held between said two unit sections, when said lower section forces said floating portion of the upper section towards and 9. A sectional mold for producing buttons, comprising a lower section consisting of a base plate and a unit die section secured thereto, and an upper section comprising a retaining plate, guid-- ing pins depending therefrom, said pins being provided with an enlarged head,-a spacing bushing resting on said head, a floating portion having a backing plate and an upper unitii die section secured thereto, registering with and cooperating with the lower unit die section in molding a button therebetween, said floating portion being I provided with an enlarged head, a-spacing bush-- ing. resting on said head, a floating portion having a backing plate and an upper unit die section secured thereto, registering with and cooperating with the lower unit die section in molding a button therebetween, said floating portion being mounted in telescopic relation to said guiding pins and being supported by said bushings when in its extended position, and a punch having its lower end formed with a cluster of thread hole forming pins, extending through said backing plate and upper die section, said pins penetrating about half way through the button material held between said two unit sections, when said lower section forces said floating portion of the upper section towards and against said backing plate, said lower unit die section having a cluster of pins registering with said punch pins-extending through the remainder of the thickness of said button material, to complete the thread holes therethrough, said base plate and backing plate being provided with passages through which a heating fluid may be supplied thereto.

,11. A sectional mold of the character'described, comprising two cooperating sections, one of said sections having a fixed portion and a floating mounted in telescopic relation to said guiding pins and being supported by said bushings when in its extended position, and a punch having its lower end formed with a cluster of thread hole forming pins, extending through said backing plate and upper die section, said pins penetrating portion, guiding pins rigidly fixed in one of said portions and slidably mounted in the other of said portions to permit said floating portion to move toward and against said flxed portion under the action of pressure, said guiding pin having enlargements which limit the movement of the floating portion away from the fixed portion, said cooperating sections having interfltting means ior accurately aligning said sections when they are brought to closed position, a punch extending from said fixed portion through said floating portion, whereby when molding material is clamped between said two sections while being subjected to the action of heat, said material may be reduced to a certain degree of plasticity before full forming pressure is applied thereto as said floating portion comes to rest against said flxed portion with said aligning means retaining said section accurately in alignment, and before said punch may emerge from said floating portion andpenetrate said material,- said sections being provided with passages through which a heating fluid may be supplied thereto.

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