USRE14604E - Process of and apparatus for making hollow rubber articles - Google Patents

Description

F. T. ROBERTS.

PRpcEss OF AND APPARATUS FOR MAKING HOLLOW RUBBER ARTICLES.

APPLICATION FILED JUNE 3,1918.

Reissued Mar, 4, 1919.

5o F I EUR/72271,? rJ imw WW 1.? M: 171? 11-04 &

Eli i757.

F. T. ROBERTS. PROCESS OF-AND APPARATUS FOR APPLICATION r1 MAKING HOLLOW RUBBER ARTICLES.

LED JUNE 3.1918. Reissued Mar. 4, 1919.

2 smi iz qi UNITED STATES PATENT OFFICE.

1mm) THOMAS ROBERTS, or CLEVELAND HEIGHTS, OHIO, ASSIGNOR To THE marten.

COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO.

PROCESS OF AND APPARATUS FOR MAKING HOLLOW RUBBER ARTICLES.

Specification of Reissued Letters Patent. Ri ed Mar, 4, 1919.

Original No. 1,219,351, dated March is, 1917, Serial No. 125,595, filed October 14,1918. Application for reissue filed .Tune 3, 1918. Serial No. 238,014;

DIVISION B.

To all whom it may concern: Be it known that I, FRED THOMAS Roe- ERTS, a citizen of the United States, residing at Cleveland Heights, in the county of Cuyahoga and State of Ohio, have invented a certain new and useful Improvement in Processes of and Apparatus for Making Holow Rubber Articles, of which the following is a full, clear, and exact description, refer- 1e ence being had to the accompanying drawings. 1

This invention relates to the production of hollow rubber articles which-may contain,

either permanently or temporarily, internal l5 fluid pressure. A convenient illustration of such an article is a playing ball, though many sorts of articles may be constructed by the same process and apparatus, as for example, bulbs of various sorts, rubber toys,

30 hot water bottles, tubes for pneumatictires,

etc, in all of which cases an internal fluid pressure is desirable, at least until after the article has been vulcanized.

One of the objects of the invention is to provide for the cheap and rapid formation of the article by pneumatic pressure from sheet rubber stock. In many cases, it is very desirable that the wall of the article be of a substantially uniform thickness throughout. I have found that when stock is seated in a mold cavity by pneumatic pressure,

there is a tendency to stretch the stock in the regions'adjaoent to the center of the sheet which prevents the uniform thickness de- 36 sired. To enable the pneumatic seating and at the same time preserve uniform thickness, I seat the stock pneumatically in a distorted mold which is arranged with one or more inward protwberancas, forming a fixed 0 portion of the mold. These protuberances support the stock adjacent to the central region and prevent the stretching, so that a wall of substantially uniform thickness is provided when the stock has become seated IS in this forming mold.

My mold is so made that the inward projection corresponds substantially in surface extent tothe normal outward convexity, at this region. In other word t Su a 'in my distorted mold, I vulcanize it in a mold having the shape of the finished article' In such mold, the inward protuberance 1n the formed article bows outwardly and becomes a normal outward convexity without material local, stretching.

,In addition to the feature of substantially uniform thickness of the wall, .pro-

vided' by my system of forming and vulcanizing articles, the inward protuberance enables the mold to be of materially less depth from that normally required,re sulting'in a truer and quicker seating, of the article, and thus enablinga more rapid production of high grade articles.

invention comprising both the process of making hollow rubber articles and the apparatus or. mold therefor, is hereinaftermore fully described and its essential charac-' teristics set out in the claims In the drawings, Figure 1 is a side elevation of a mold'press equipped with my peculiar forming molds and with means for causingth'e pneumatic seating of'the stock; Fig. 2 is a plan of a mold plate which may be employed; Fig. 3 is a cross section of two of such mold plates showing their relative position before they are brought together;

Fig. 4 is a plan of a clamp which may be used to hold a rubber sheet to one of the mold plates, as illustrated in Fig. 3; Fig. 5 is an enlarged view in vertical section illus trating one of the. mold cavities and showingrubber stock seated therein; Fig. 6 is a view on the same scale as Fig. 5, showing a vulcanizing mold which may be employed for the article formed by the distorted mold of Fig. 5; Fig. 7 is an outside view of a ball produced by the molds of Figs. 5 and 6;

Fig. 8 is a detail illustrating the hollow wedge for clamping two mold plates, this wedge being shown in cross section in Fug. 6.

In Fig.1, 10 indicates the base of a mold press from which rlse' standards 11, carrying a head 12. On the base is shown a frame-13 supporting a pair of cylinders 14,

from which rise plungers 15, which carry at their tops a hollow platen 16. The hollow platen 18 is also shown assecured to the under side of the head 12. Each of these platens has passageways which communicate with cavities in the mold members 20 and 21, secured'tothe respective platens.

Figs. 2 and 3 illustrate one form of mold plate which may be secured to the platens by screws'22. he cavities 23 as they appear in Fig. 3, have the peculiar inward pro' tuberancesof this invention heretofore referred to and which will be hereinafter more fully described. These cavities have vents 24, which are adapted to register with the openings in the hollow platens.

30 in Fig 1 indicates a vent pipe leading from the platen 18. 31'designates a passageway within one of the lungers 15 lead ing from the platen 16. .his passageway communicates with a flexible pipe 33. The pipes and 33 are shown as joining and leading outwardly by a T connection through the plpe 35 which 'is provided with a V valve 36. r

If the pipe 35, beyond the valve be connected with a suitable vacuum pump, vacuum may be established in the mold cavities and thereby cause the rubber stock. stretched across the mouths of themolds to be pneumatica'lly seated. .7

Fig. 3 shows a sheet of stock A held across the upper mold, and asimilar sheet may be held across the lower mold. Suitable means is provided to clamp-these sheets at the edges of the: mold plate. For this purpose, I may employ a rectangular frame shown in Fig. 4. As shown, this frame consists of two members 40 and -11, each extend- .ing about two sides of the mold and provi e d at theirends with means for drawing the members together, as for example,

the thumb nuts 43 on bolts li.

After the stock has been pneumatically seated by suction as described, the twomolds are brought together to bring the two parts of the article into conjunction, thus entrapping. withineach article air having whatever.

pressure surrounds the mold. It is convenient to bring the mold members together by hydraulic pressure. For this purpose the cylinders. 14 and plungers 15 are provided. 50 indicates a pipe adapted to convey liquid under pressure to the c linders 14. 51 is a valve controlling this pipe, adapted to place it in communication with the supply or close it entirely ordrain; it to the pipes 52 and 53.

It should be noted that when these two mold parts are brought together with rubber stock seated in them respectively they produce a series of hollow articles as shown MA in Fig. 5 with air entrapped within cavity and bring the walls about the cavities to an annular edge as shown at 27. By this. construction the sheets of'rubber are cut in, two around the article as the mold members come together, the excess rubber passing into .the space 26 surrounding the cavities. It will be noted that the annular wall be.- tween the mold cavities and the surrounding space is tapered both inwardly and out Wardly in coming to the cutting edge. This enables the rubber of the two sections to be squeezed together between metal mold surfaces as the molds come together, thus makingan effective seam. The outward'rib thus produced is absorbed in the vulcanization.

F or.many purposes air of atmospheric pressure within the article is sufficient, or such pressure may be increasedby some heat-expanding chemical placed in the article before it is closed, as is well under-- stood in' this art. In. either case I prefer to effect the seating of the article by vacuum applied to the pipe 35. Whenever a high fluid pressure is desired to be permanently maintained within the article I prefer to effect this by surrounding the molds with com-pressed air and entrapping such air within the article as the parts are brought together. Fig.1 shows mechanism for'accomplishing this, as will be described.

Within the frame member 13 is a central hydraulic cylinder 60. adapted to be fed by a pipe 61- controlled by a valve 62 which ovide a. depressed P01'- 35 may drain through the passageway. 63 to the pipe53. Rising from this cylinder 60 is. a plunger 65 carrying a box 66 which has cars 67 slidably embracing the standards 11.

The plungers 15 extend through the base of this box 66 in a slidable but air-tight man- .ner, stuffing boxes, which may be employed,

being omitted for simplicity in the drawing.

.Directly above thewall of the box 66 is a pheric, hydraulic pressure may be admitted to the cylinder 60, raising the box 66 and forming a closed chamber about the separated mold members; then the valve 71 is opened and compressed airof any pressure desiredadmitted to the interior of the box 66, this pressure being indicated by. the gage 73. -When this surrounding atmosphere of compressed air is employed. the vacuum pump need not be used and the pipe 35 may be simply a vent pipe. Wheu the valve 36 and entrap atmospheric air, or to seat the article by compressed air and entrap some of such air, or vacuum seating may be employed in conjunction with supplying compressed air to the interior. The vacuum seating has the advantage that it enables visible inspection to the interior of the article after its parts have been formed.

After the parts of the raw rubber article have been brought together and their edges joined by pressure and at the same time the individual articles cut out as explained, the articles are removed from the molds 20 and 21 for vulcanizing. It is to be understood that if compressed air is entrapped within the formed article its pressure does not exceed the surrounding atmosphere by an amount which the unvulcanized seam can "hold. Accordingly it is possible to separate the forming molds and take out the closed article and transfer it to a vulcanizing mold. Such vul-canizing mold is illustrated in Fig. 6 and is shown as having two mold plates 80 and 81 clamped together by a beveled wedgeshaped stirrup 82' (shown also in Fig. 8) which overhangs wedge ribs 83 and 84 on the mold members.

It will readily be seen that by forming the parts of a number of articles from raw rubber sheet stock pneumatically seated and cut out as the mold members are brought together a very rapid and economical operation may be effected. The delay, incident to formin the parts by male and female dies,

is avoi ed, as 1n my process it is all accomplished in one mechanism and without transfer. As raw rubber sheets are employed in my operation, the arts out out around the articles are not wasted (as would be semicured or vulcanized stock) but may be returned immediately to the calendering machine and rerolled into sheets without waste.

While the pneumatic seating of sheet stock stretched across the mouths of mold cavities has advantages of economy and rapidity, as above explained, the natural effect of such neumatic'seating is to stretch the stock ada'cent to the center of the disk portion stretched over the cavity, as such central region has the least support. Accordin ly this central region is naturally thinner t an the stock nearer-the edges when it is seated.

, This is a great disadvantage asmany articles require walls of substantially uniform thickness. I have discovered that the advantages of the neumatic seating of sheet stock may be retained without the disadvantages of the central stretching by making the mold cavities with inward protuberances to support the stock in the central region and prevent undue stretching. These inward protuberances are rigid and preferably integral parts of the mold so that no extra mechanism is required on accountof them. They result in the article being formed with a substantially uniform thickness of wall, but with normally convex portions concaved or bowed inwardly. The amount of the inward bowing is substantially the same as the normal outward bowing for the same region so that after the article is formed with the concave portions these readily assume the normal ity and a substantially uniform thickness of wall is maintained.

It will be seen from these views that the inward protuberances merge by easy curves with the spherical zones of the mold and are of such size and shape that the superficial area of the distorted mold is substantially the same as that of a spherical mold of the same diameter. The result is that when the article forced pneumatically to its seat in the disto d mold shown, it is of the proper size to become a sphere Without serious stretching, and is of substantially the same thickness throughout.

Another advantage of a forming mold having inwardvprotuberances is that when the formed article assumes its true shape it has an increased cubical content, resulting in a corresponding reduction in internal pressure. Accordingly the compressed air entrapped within the formed article may exceed the pressure of the surrounding atmosphere by even a greater amount than can be retained simply by the adhesion of dents outwardly and thus reduce such pressure.

hen the distorted ball is removed from the mold of Figs. 3 and 5, it is put into a spherical vnlcanizing cavity, as, shown in Fig; 6. It is convenient to make the article slightly smaller in diameter than that of the vulcanizing cavity, asillustratctl A" in Fig. '6, as this provides for the expansion of (the article (luring vulcanization also enables the article to very placed in the vuloanizing mold. The increased si ce of the article after vulcanization and its re:

moval from the vulcanirzing mold illnssoon as removed the mold of Figs. 1S

and "5. If the higher-internal pressure, obtaiiied by the hox 66, is not emploved, the article may of a dented sha e when it is placed the vulcanizing :moi' but it will assume true sphericalfshapew on the vulcani'zing mold is heated, the air in the mold cavity outside of the article will leak out between the mold plates.

Having described my invention what claim is:

1. The process of masking hollow rubber articles, consisting of pneumatically seating a part of the article in a mold cavity w ch has a rigid inward protuberance closing such seated part upon another part of the article, then transtcrring such closed article to a .vulcanizing mold having a cavity oi the shape of the finished article, and thereafter vulcani-zin the article while in such moi.

V 12* The process of making hollow :rubhcr articles, consisting of pneumatically seating the arts of the article in mold cavities which have rigid inward protubcrances, bringing two of such seated parts together under pressure to form a seam, then trans-- ferring such closed article to a vulcanizing mold having a cavity of the on e of the article, and thereafter canizing the article while such vulcanizi'ug mold. u

3. The process of making hollow articles, comprising the placing of plastic stock across the mouth of a mold cavity which has a rigid wall inwardly distorted the shape which the finished article to have, establishing a preponderance of air pressure on the side of the stock opposite to the cavity, whereby the stock becomes seated in the cavity, such seated part conjunction with another part to make a closed article, then transferring such article to a mold having the shape of the article and curing the article while so e 4. "The process of makinghollow orticlcs,

comprising the placing of plastic stock across the mouth of a mold cavity which has a wall inwardly distorted from the shape which the finished article is to have,

partially exhausting the air from-such camity to cause the stock to scat therein, bring Ling such seated part nto coniuuctionwith "the concavity of the so e to a conv pressed air to the article,

another art make a closet! a trahstermng such a i the sha'p tho finished a; 'e while so old.

having The process of making convex hollow rubber acticles consisting of 1y forming the article a distorted mo hava rigid inner-sum of ally the same area as the tiul hing mold t inwardly protuherantoo 1 th' forming the article to :suc:

trans g 1 having a continuously convex contour, :am' l vulcanizing it *6. The proccssot lhoilo aiticles havi a convex ex of primarily owning the a tain regions I its wall extc'm lyconcavc, thereafter transterri g he article o a *vut cam ing mold ha g a convex surfac P081156 such cone stantially y of oh the same supcrfic 1 area a sa d cavity, ternal pressure being video ch y correspondiq to the surface oi the vulcan g'mol' g 7.. "The process of making holio'w rubber articles, consisting of h the p rts oithe articletogether in an enveloping atmosphere of compressed fluid, such parts held in mold cavities which havciu war protuberances, then transtcmi g such closed article to a vulcanizingmoldf a cavity of the shape of the finished ar e, and thereafter vulcanizing the article white in such 'vulcanicing moi-d.

1 8. The process of malzi hollow articles,

comprising the placing of plastic stock across the mouth of a mu cavity which has a rigid wall inwardly distorted from the shape which the finished article is to have, ventitm such cavity while suppl mg 1 compressed f uid to the other side of the stock. bringing such seated part into conjunction with another part to make a closed article, then transferring such article a mold having the shape of the finished article, and the article while so held.

9,.The of ow rubber articles, comprising the pi :mg of rubber stock across the mouth of a m d c ity while said cavity" is located w nan inclosure which contains air unfl r'pressure, said molii cavity'heing inwardly distorted the shape which the hcd article is to have, venting such ca side of the inclosure, to

y to :apoin't out cause the comseated part into I g 1 part tomalce is closed a I coontaining so, then transferring such art c a mold havin' the shape of he hed article, and vu canizing the a 'whileso held.

i1 0. As a new art e, a forming mold tor a, hollow rubber article of convex exterior,

' the same area as the exterior of the article in rubber articles t its normal shape.

12. A mold for forming a hollow rubber.

article of convex exterior, having a cavity provided with a rigidinward protuberance, and cutting edges surrounding the mold cavity. v r

13. -A separable mold for forming a hollow rubber article of convex exterior, said mold having. cavities each provided with a rigid inward protuberance whereby stock forced into the mold is caused to retain uniform thickness, and cutting edges at the perimeter of each cavity.

14. In an apparatus for forming hollow rubber articles, the combination of a forming. mold and a vulcanizing mold, the'latt'er having spherical cavities, and the forming mold having its cavities spherically convex adjacent to the edge of the cavity but concaved inwardly in the central region by a grad ual hump which does not rise to the plane of the rim of the cavity.

15. In an apparatus for forming hollow e combination of a forming mold and a vulcanizing mold, the latter having spherical cavities, and the-forming mold havin cavities provided with rigid inward protu erances, the surface of the latter cavities being substantially the same as the cavities of the vulcanizing mold.

16. The combination of a mold for hollow rubber articles of convex exterior,- the mold cavities having rigid inward protu'berances and passages leading from the cavitles.

17. The combination of a multiple mold for hollow rubber articles of convex exterior, the mold cavities each having rigid inward protuberances, passages leading from substantially the deepest points in the cavities, and means connected with the passages for exhausting the cavities.

'18. Thecombination of a separable mold for hollow rubber articles of convex exterior, the mold cavity having a rigid in ward protuberance, cutting edges on each mold member around the cavity, passages leading from each cavity and connected with a means for exhausting the air therefrom.

19. In an apparatus of the character described, the combination of a forming mold having a rigid inner surface which has an inward protuberance, producing a central region of the article wh1ch is externally concave and a corresponding vulcanizing mold to which the article is transferred and which has an inner surface of substantially the same area but of a continuously convex contour.

20. In an apparatus of the character described, the combination of a cavitary mold distorted from the finished shape of the article to provide an inward projection, means for establishing an atmosphere of compressed fluid about the mold, means for venting the cavity of the mold to a oint outside of said atmosphere to cause 15 e article to seat in said cavity, and a mold of the shape of the finished article having an internal surface ofsubstantially the same area as that of the distorted mold.

21. In an apparatus of the character described, the combination of a finishin mold corresponding to the shape of the ished article, a-forming mold having substantially the same internal area as the finished mold but having an inward pro'ection, means for venting said forming mol to the outside air, means for establishing an atmosphere of compressed air about the forming mold,

whereby .rubber stock placed across the .mouth thereof may be seated in its cavity,

and means for bringing such stock into conjunction with other stock while within the atmosphere of compressed air.

22. In an apparatus of the character described, a tWoart mold, each member having a series 0 cavities bounded by wallscomlng to an annular edge, whereby when two of such mold members are brought together material may be sheared oif around the edges of the-cavities, there being vents from said cavities, and means for opening and closing the vents.

23. In an apparatus of the character described, a forming mold having a series of cavities bounded by walls coming to an annular edge, whereby when two of such mold members are brought together material may be sheared ofl around the edges of the cavities, said cavities having vents, means for controlling the vents, and means for establishing a, greater pneumatic pressure between two pieces of interposed stock than there is between either piece of stock and the base of the cavity.

24. In an apparatus of the character described, the combination with an inclosure to which compressed fluid is supplied, of a two-part forming mold therein having a series of cavities bounded by walls which come to an annular edge and rise above the adjacent surrounding surface of the mold,

whereby when two of such mold members are brought together interposed material may entrap fluid and may be sheared oii around the edges of the cavities.

25. In an apparatus of the character described, the combination with a vulcanizing mold having substantially the form of the finished article, of a forming mold having I a distorted shape but substantially the internal area of the vulcanizing mold and having a series of cavities boundedby walls coming to an annular edge, whereby when two of such mold members are brought together material may be .sheared ofi around the edges of the cavities, means for establishing an atmosphere of compressed fluid about such mold members, and means for venting the cavities to a point outside of said atmosphere.

26. A mold for forming a hollow rubber article of convex exterior, comprising a plate having cavities each provided with a rigid inward protuberance at the base and an annular cutting edge at the rim.

27. A forming mold for a hollow rubber article having a convex exterior, said mold comprising a plate having a multiplicity of cavities, each rovided with a rigid inward protuberance the superficial area of the cavity being-substantially the same as that of the exterior of vthe corresponding part of the article in its normal shape.

.28. The combination with a formin mold for a hollow rubber article, said mol having a cavity formed with a rigid inward hump, a passageway communicating with the cavity at one side of the hump, and means for applying suction to said pasageway.

29. The combination, in amold for hollow rubber articles of convex exterior, of mold cavities having a rigid inward protuberance and passages leading from substantially the deepest points of the cavities. i

30. The process of making hollow rubber articles, consisting of pneumatically seating a part of the article in a mold cavity which has a rigid inward protuberance, the top of which is below the plane of the rim of the cavity, closing such seated part upon another part of the article, then transferring such closed'article to a vulcanizing mold having a cavity of the shape of the finished article,

' of which is below'the and thereafter vulcaniz'mg thearticle while ing a gradual-inward protuberance, the top f plane of the rim of the cavity.

32. The process of making'hollow rubber articles consisting of forming the article in a distorted shape with an inward projection which is existent at the completion of the forming operation, and thereafter vulcanizing the article in a mold which provides space for such inward proj ection to be moved outwardly,

33. The process of making hollow rubber articles having an external convexitly consisting of primarily forming the artic e with an inward convexity which is existent at the end of the forming operation, and thereafter vulcanizing the article within a mold which has a concavity opposite'that region of the article which, when formed, is inwardly convex.

34. The process of making hollow rubber articles WlJlCh when finished have an external convexity comprising forming a portion of the article with an inward convexity having a superficial area substantially equal to that of the corresponding outward convexity of the finished article, such inward convexity being existent at the end of the forming op oration, thereafter transferring the article to a vulcanizing mold which has a concavity in the region corresponding to said inward convexity and of substantially the same superficial area, and vulcanizingthe article in such vulcanizing mold. a a y In testimony whereof, I hereunto afiix my signature.

FRED THOMAS ROBERTS.

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