US2544140A

US2544140A - Process of forming an article from at least two plastics

Info

Publication number: US2544140A
Application number: US790676A
Authority: US
Inventors: Floyd J Dofsen; Elmer L Danielson
Original assignee: Individual
Current assignee: Individual
Priority date: 1947-12-09
Filing date: 1947-12-09
Publication date: 1951-03-06
Anticipated expiration: 1968-03-06

Description

March 6, 1951 F. J. DoFsEN ET AL 2,544,140

PROCESS OF' FORMING AN ARTICLE FROM AT LEAST Two PLASTICS Filed Dec. 9, 1947 2 Sheets-Sheet l @ifea/ff lll llllll MW, my MM March 6, 1951 F. J. DOFSEN ET AL 2,544,140

\ PROCESS oF FORMTNG AN ARTICLE FROM AT LEAST Two PLASTICS 2 Sheets-Sheet 2 Filed Dec. 9, 1947 @IgM/f fand branch runners. from the rst mold as aunit and transferred to a second mold having a plurality of cavities for receiving the precast bodies and also having .grooves for receiving the precast main and branch :branches Patented Mar. 61, 195i vUNITED STATES OFFICE PROCESS OF FORMING AN ARTICLE FROM AT LEAST TWO PLASTICS Y y Floyd J. Dofsen, Millbrae, and Elmer L.

Danielson, Oakland, Calif.

Application December 9, 1947, Serial No. 790,676

. 3 Claims.

The present invention relates to a process for forming an article from at least two plastics.

It consists or" the steps of the process hereinafter described and claimed.

An object of our invention is toprovide a process for forming an article from at least two fplastics, which embody improvements over the -orm of the invention shown in our copending aplplication on a Process and Apparatus for Bonding Thermoplastic Materials, Serial No. 761,128, filed `VJuly-l5, l947,`now Patent No. 2,492,973. In the ccpendin'g application, one part of the article is cast in a mold so that a pluralityof these parts l"will be interconnected to each other by a runner, Tand branch runners will extend from the main -runner to the individual parts. Cits branches interconnect all of the parts as a -'unit at the completion of the first casting operation and then the device is removed from the `fiirst mold and placed over a plurality of cavities The runner and in a second mold corresponding in number to the Anumber of parts, the parts being positioned above the cavities. The parts then are severed from their branch runners and drop into their respec- :tive cavities by gravity. The second mold then is closed and a second plastic forced into the `,cavities to combine with the cast articles already disposed therein and produce a completed article comprising two different plastics. l :,L The principal object of our invention is to d away with the necessity of severing the parts from the `branch runners after the rst casting :and dropping them into the cavities of the second "mold We have 'fo-und it ,possible to manufacture .the two-plastic articles by casting a plurality of 'the article bodies in one mold, these bodies `being connected to each other as a unit by the main The bodies can be lifted runners. The second.. mold is provided with an additional groove and branchgrooves paralleling the grooves receiving the precast runner and its The additional grooves in the second mold have their outer faces closed by the precast -runners when the second mold is closed. The

`injection of a second plastic into the second mold :will form the other partof the plastic article; and then upon opening the second mold, the completed two-plastic' articles` can be removed `withtheir integral two run'n'ers and their branch *runners as `a single unit;v` The articles then may be separated from theiri'branch runners, thus ously molding a second plastic to the part.

`"Ihis requires two position with respect to the bodies. ofmakingkeys, for example, where the characters'on the keys are initially formed as slots -in the bodies during the iirst casting operation, =`thesubsequent addition of the secondv plastic to ll the slots and also to lill a portion of the key i interiors can be'made with the keys in their same relative positions land, therefore, the provision of 4fkey'shank-receiving bores in the keys can be' ar'- Ycompleting the manufacture of the two-plastic articles.

VIn the forming of the bodies in the rst operation, the mo-ld may form recesses in the outer surface of the bodies and these recesses will be -ffilled with the second plastic during the second molding operation.

The present invention is also an improvement over the invention shown in another copending application on a method and apparatus for severing sprues irorn a molded part and simultane- That application was filed August 26, 1947, and the serial number is 770,594 and is now Patent No. 2,510,091. In that application the several plastic parts going to make up a plurality of articles are -cast simultaneously and are inter-connected by a runner and branch runners.

These precast parts then are transferred to a second mold hav- `inga groove and branch grooves for receiving the precast runner and its branches. The closing of Athe two parts 'of the second mold prior to the injection of the second plastic, severs the branch runners from their parts. At the completion of the second molding operation, the branch run- 'ners formed during the second injection of plastic must be severed from the completed articles. distinct steps of severing branch runners from plastic articles at two sepa- `rate time intervals; the rst being accomplished' upon the closing of the second mold, and the 'second being carried out after the articles are removed from the second mold. In the present invention, a single severing of both branch runners, one to each plastic, at the same time is accomplshed after the two-plastic articles and their runners are removed from the second mold.

Y Anotherladvantage of holding the precast bodies of the articles to a main runner while transposing them` from one mold to a second .mold lies' in the fact thatall of the bodies are `retained in a particular position with respect to reach other While being transferred and, there- Tore, the addition of the second plastic to the articles will cause it to form bores in the proper In the case ranged in proper relation with respect to the characters.

Other objects and advantages will appear in the following specication, and the novel features of the device will be particularly pointed out in the appended claims.

Our invention is illustrated in the accompanying drawings forming a part of this application, in which:

Figure 1 is a transverse section through our first mold showing the casting of the plastic body of the article;

Figure 2 is a transverse section through a second mold and illustrates the placing of the precast body and its main and branch runners in position ready for the second molding operation;

Figure 3 is a transverse section through the second mold and shows the completion of the second molding operation;

Figure 4 is a bottom plan View of the completed article, looking in the direction of the arrows IV-IV in Figure 3, the article shown attached to the two branch runners and removed from the mold;

Figure 5 is a perspective view of the top of an article as it appears after the rst casting operation;

Figure 6 is a top plan view of a plurality of the articles interconnected by the runners and branch runners formed of the two plastics;

Figure 7 is a transverse section taken along the line VII- VII of Figure 3, and shows the completed article when removed from the second mold and freed from its branch runners;

Figure 8 is a top perspective view of the completed two-plastic article;

Figure 9 is a bottom perspective View oi the same article;

Figure 10 is a transverse section of a mold used in making the rst part of a moded form of the article;

Figure 11 is a transverse section through a second mold and shows the precast article from the modied rst mold placed therein;

Figure 12 is a view similar to Figure 11 and illustrates the complete two-plastic article at the end of the second molding operation;

Figure 13 is a perspective View of the bottom side of the completed modied article still attached by two branch runners to the two main runners; and

Figure 14 is a bottom plan view of two of the completed modied articles interconnected to each other by the branch and main runners.

While we have shown only the preferred forms of our invention, it should be understood that various changes or modications may be made within the scope of the appended claims without departing from the spirit and scope of the invention.

In carrying out our invention, we provide a mold in Figure 1 comprising a lower half AI and an upper half A2. The lower mold half has a plurality of cavities I provided therein, although we show only one cavity in Figure 1. Any type of plastic article can be formed and we have shown the cavity shaped to form the body B of a key. The key may have any desired character on its concave face and, therefore, we show the bottom of the cavity as being made convex at 2 and provided with a projection 3 to form the desired character. The character chosen to be represented is the number 8 and a cross section through the mold will show the projection 3 as composed 4 of three portions representing the top, middle and bottom of the number 8.

The upper mold half A2 has a longitudinallyextending groove 4 therein that has inclined sides so that any thermoplastic which sets in the groove may be readily removed therefrom due to the draft or inclination of the sides. The groove 4 has branch grooves 4a. extending laterally therefrom at an angle and these branch grooves communicate with the cavities I in the lower mold half AI as indicated in Figure 1. When the two halves of the mold are closed and the plastic is injected from one end of the mold into the groove 4, it will flow along the groove and then into the branch grooves 4a and nally into the cavities I to form the bodies B of the keys.

The upper mold half A2 carries depending cores 5 that enter the cavities I and cause the plastic to form hollow bodies. Each body will have a slot in its outer concave surface corresponding to the shape of the character formed by the projection 3 and extending up to the end of the core 5. In the forming of an entirely enclosed circular character, such as the number 8, a bridge 6 must be formed, see Figure 5, so as to support the central portions 'I of the number. The lower end of the core 5,` therefore is provided with a groove 5a and the plastic in the first molding operation will iill this groove to form the bridge 6. The top portion of the key body is indicated at B in Figure 5 and the bridge 6 is clearly shown connecting and supporting the central portions 'I of the number 8 to the body.

The injection of the plastic at one end of the mold will cause a runner C to be formed in the groove 4 and branch runners CI or sprues to be formed in the branch grooves 4a. The branch runners will be integral withthe key body B. When the plastic has set, the mold is opened and the runner C will lie on top of the lower mold half AI where it may be readily removed from the mold and will carry with it the bodies B. Figure 6 illustrates how branch runners or sprues CI project from both sides of the main runner C so key bodies B can be cast on both sides of the main runner.

In Figure 2, we show -a second mold comprising a lower half DI .and an upper half D2. The lower half has cavities 8 therein for receiving the precast plastic bodies B. and the upper mold half has a groove 9 therein for receiving the runner C and branch grooves. 9a for receiving the branch runners or sprues CI. In addition, the lower mold half DI has a groove I 0 paralleling the groove 9 when the two halves of the second mold are closed and the groove I0 is substantially the same in `cross sectional dimensions and shape as the groove 9. The arrangement isy such that when the second mold is closed the outer face of the runner C will close the top of the groove IU. Figure 2 represents the second mold with the key body B and its runner in position just prior to the injection of the second plastic.

In Figure 3 we show the same mold as in Figure 2 and further illustrate the completed injection of the second plastic. It will be noted from Figures 2 and 3 that a branch groove Illa extends from the groove IIJ and this groove cornmunicates with a second branch groove II that parallels the branch groove 9a and is arranged along its side. If desired, the branch groove II may be of less depth than the groove 9a and this is indicated in Figure 3. This arrangement allows the branch runners or sprues CI to project into the branched grooves 9a above the tops of the branch grooves II, thus holding the branch runners CI relating to the mold half D2. The branch groove II extends to the cavity 8 at a point where the second plastic may be injected into the interior of the key body B.

A bore I2, see Figure 9, for receiving a key shank, not shown, is formed in the key and this is accomplished by providing a core member I3 of the shape of the desired bore I2, this core member being carried by the upper mold half D2 and extending into the interior of the body B of the key. A second core, not shown, and carried by' I I in the upper mold half D2. The second plastic .in the branch grooves will form the branch Vrunners or sprues FI. From the branch grooves I I, the second plastic will flow into the interior of the key body B and will form a key plug E or insert that will have the bore I2 and the recess I4 formed therein.

It will be seen from Figure 3 that a portion of the second plastic will fill the slot I5 formed by the projection 3 to form the character I5a on the key, such as the number 8. When the recess I5 is filled with plastic, the bridge 6 will be concealed with the result that the number "8 will appear on the top of the key land be of a diierent color than the key body. This number is shown at I5a in both Figures 6 and 8. As soon as the second plastic has set, the second mold may be opened and the completed keys with their runners C and F and branch runners CI and FI removed therefrom as a unit. The resulting article of manufacture is shown at Figure 6.

The flowing of the second plastic in the grooves I0 and branch grooves Illa and II will form the second runner F which will parallel the first runner C and -will also form branch runners or sprues FI which will parallel the branch runners CI. Figure 4 illustrates how the branch runners Fl are arranged along the sides of the branch runners CI, while Figure 3 illustrates how the runner F is positioned under the runner C. The completed two-plastic keys may be readily removed from the branch runners CI and FI by breaking the keys therefrom at the points where the branch runners or sprues join the keys. The

iinished keys are shown in Figures 'l to 9, inclusive.

vOne advantage of retaining the key bodies on the branch runners CI is to maintain the recesses I5 forming the diiferent characters Ion the keys in proper relation with respect to each other :and the molds. When now the second plastic is injected into the second mold after the key bodies and their runners have been placed in .the second mold, the formation of the bores I2 in the key plugs or inserts E will dispose the bores in their proper relation vwith respect to the characters I5a on the keys. The mounting of the keys on the key Shanks, not shown. of the machine will dispose the key characters in their proper positions on the key board.

Another advantage of injecting the second plastic so that the runners and branch runners vF and FI will parallel the runners and branch runners C and CI, lies in the fact that the keys may be severed from both branches CI and FI with substantially the same ease as if only one branch runner were being severed. The key bodies B lact as the cavities for receiving the second plastic to form the inserts E.

In Figures 10 to 14, inclusive, we show a slightly modified form of the invention. The mold illustrated in Figure 10 consists of a lower' half GI and an upper half G2. 'Iihe latter has a plurality of cavities I 6 therein. These cavities are in the shape of the articles to be cast and We have indicated these articles as being key bodies BI. The upper half G2 has an elongated groove I'I with branch grooves IIa leading therefrom and communicating with the cavities' IB. Cores I8 are carried by the upper mold half G2 and there are as many cores as there are cavities I6. The cores extend into the cavities asV illustrated. The lower half GI has a projection I9 in the shape of the desired key character, such as the number 8, and this projection extends above the convex bottom 20 of the cavity. The lower end of the core I8 has a diametrically-extending groove 2| for forming the bridge 6 shown in Figure 5.

The first operation is the injection of the plas.-A tic material under the desired pressure at the end of the mold and the material is directed into the groove I'I, branch grooves I'Ia and cavities I6, to form an elongated runner H with branch runners or sprues HI. The branch runners or sprues are connected to the key bodies BI so that opening of the mold will permit the exposed runner H to be removed and carry with it the key bodies connected thereto. This completes the first operation of forming the keys. The key bodies are hollow and will have slots or recesses I5 in their concave tops corresponding to the desired characters which are to be formed in the keys.

Figure 11 shows the second mold comprising the lower half J I and the upper half J2 in cross section. The runner H is received in a 'groove 22 formed in the upper half and the branch runners HI are received in lbranch grooves 23. It will be noted that the elongated groove 22 is deeper than the thickness of the runner H; also, the branch grooves 23 are deeper than the thickness of the branch runners HI. This arrangement provides the groove 22 with an interior space for receiving the second plastic material and likewise the branch grooves 23 are made deep enough to have an interior space for receiving the second plastic material.

Figure 12 illustrates the completion of the second operation in flowing of the second plastic material under pressure into the portion of the groove 22 that has been left open by the runner H. The second material forms a runner K that overlies the runner H. The second plastic will flow into the portions of the branch grooves 23 not occupied by the branch runners HI and will form branch runners or sprues KI that are superimposed on the branch runners HI. The

grooves

22 and 23 are formed in the upper mold section J2. This mold section carries core members 24 that project into the hollow interior of the key bodies BI. The second plastic will flow into the hollow key bodies and surround the core members 24. At the completion of the second molding operation, the mold may be opened and the completed keys with their runners removed as a unit.

The core members 24 will form the key shank- 7 receiving recesses 25 shown in Figure 14. The recess 25 is shaped so as to receive the key shank, not shown, of the machine using the keys. Other core members, not shown, will form the recesses 26 in the key plugs or inserts El. In Figure 13, we show the runners H and K in perspective and the runner H has been shaded to indicate a different color from that of the runner K. The same gure also shows the branch runners HI and Kl and it will be seen that the branch HI is integral with the key body BI, while the branch KI is integral with the key plug or insert Ei. This form of the invention has all of the ad vantages enumerated for the form shown in Figures 1 to 9, inclusive.

The diierence between the two forms lies in the fact that the two runners and their branch runners or sprues are superimposed one above the other in Figures 12 to 14, inclusive, while in the form shown in Figures 1 to 9, inclusive, the branch runners or sprues are arranged side by side. Furthermore, the two runners and their branches in the form shown in Figures 10 to 14, inclusive, are formed from grooves provided in the upper mold half G2, whereas in the first form of our invention, the second runner F iS formed in the lower mold section. By arranging the branch runners one above the other as indicated in Figure 13, it is easier to break the completed keys from their branches than where the branch runners are arranged side .by side.

We claim:

1. The herein described method of forming an article from more than one plastic consisting of placing a preformed plastic structure comprising a hollow body with a slot extending therethrough, a main sprue and a branch sprue connecting the body and main sprue into a mold having channels of greater size than said Iirst mentioned sprues, with said sprues in said channels, of injecting a second plastic through the channels into said slot so that the sprues formed by the second plastic lie adjacent said preformed sprues.

the sprues formed by the second plastic lie adjacent said preformed sprues and are coextensive therewith.

3. The herein described method of forming an article from more than one plastic consisting oi placing a preformed plastic structure comprising a hollow body with a slot extending therethrough, a main sprue and a branch sprue connecting the body and main sprue into a mold having channels of greater size than said first mentioned sprues with said sprues in said channels, of injecting a second plastic through the channels into said slot so that the sprues formed by the second plastic will extend alongside the sprues of the rst plastic in contacting relation therewith.

FLOYD J. DOFSEN. ELMER L. DANIELSON.

REFERENCES 'CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,266,433 Morin et al, Dec. 16, 1941 2,333,059 Tucker s Oct. 26, 1943 2,345,305 Thornton Mar. 28, 1944 FOREIGN PATENTS Number Country Date 198,417 Switzerland Sept. 1, 1988

Claims

1. THE HERERIN DESCRIBED METHOD OF FORMING AN ARTICLE FROM THE MORE THAN ONE PLASTIC CONSISTING OF PLACING A PREFORMED PLASTIC STRUCTURE COMPRISING A HOLLOW BODY WITH A SLOT EXTENDING THERETHROUGH A MAIN SPRUE AND A BRANCH SPRUE CONNECTING THE BODY AND MAIN SPRUE INTO A MOLD HAVING CHANNELS OF GREATER SIZE THAN SAID FIRST MENTIONED SPRUES, WITH SAID SPRUES IN SAID CHANNELS, OF INJECTING A SECOND PLASTIC THROUGH THE CHANNELS INTO SAID SLOT SO THAT THE SPRUES FORMED BY THE SECOND PLASTIC LIE ADJACENT SAID PREFORMED SPRUES.