US2293633A - Method and means for molding telephone handsets from plastics - Google Patents

Description

F. H. SHAW Aug. 18, 1942.

METHOD AND MEANS FOR MOLDING TELEPHONE HAND SETS FROM PLASTICS Filed Aug. 13, 1938 2 Sheets-Sheet 1 Wz'im e55 4773f! w,

A g- 8., 4 F. H. SHAW 2,293,533

, METHOD AND MEANS FQR MOLDING TELEPHONE HAND SETS FROM PLASTICS Filed Aug. 13, 1938 2 Sheets-Sheet 2 I I L9 27 22 Paten ted Aug. 18, 1942 7 METHOD AND MEANS FOR MOLDING TELE- PHONE HANDSETS FROM PLASTICS,

Frank H. Shaw, South Orange, N. 1., ass lgnor to Shaw Insulator Company, Irvington, N. .L, a corporation of New Jersey Application August 13, 1938, Serial No. 224,740

9 Claims.

This invention relates to the molding of plastics and has particular relation to the molding of telephone handsets from plastics such as phenol aldehyde resins which became insoluble and iniusible when molded under heat and pressure.

A telephone handset of what is commonly referred to as the French style of telephone, comprises a handle having a transmitter at one end and a receiver at the other end. The handle is shaped to fit the hand and the transmitter and receiver portions of the set each extend from the handle at angles thereto for convenience in use. Provision for wiring is made in the set. The cord for connecting the set to the telephone circuit enters the set at the end which carries the transmitter, and is connected to the'transmitter. In order to connect the receiver to the cord, wires must extend from the transmitter portion through the handle to the receiver portion.

Heretofore telephone handsets have been made from phenol formaldehyde resins. by compression of the molding material in heated molds. A high degree of pressure must be applied to the molds to compress the material into the mold cavities and to produce articles of the desired density. 1

While all the telephone sets heretofore produced have been made by compression molding, this method has several disadvantages.

The principal objection to the prior method of compression molding is that the wires for connecting the receiver to the telephone cord must be embedded in the handle as the set is molded.

Because of the high pressure applied to the molding material and the condition of the material, these wires are apt to be broken in the molding operation. Obviously, repair of such wires is impossible and, therefore, whenever a, wire is broken, the set must be thrown away.

Another objection to the prior method of compression molding is that a flash must be formed on the set at the parting line of the mold or die in order to permit the escape of excess molding compound, which excess is added'to the mold charge to insure filling of the mold cavity and to obtain the desired density in the article. This flash has to be removed by a grinding or machining operation which cuts through the surface layer or coating on the set. The surface layer or coating has a high gloss or finish which is desirable for appearance anddurabillty and when the flash is removed by grinding or cutting, a dull surface is left of undesirable ap- A further objection to the prior method of compression molding concerns the angular relation of the receiver and transmitter to the handle. In the prior method the handle is molded top up, that is, the upper die member forms the 4 upper portionand the. lower die member the lower portion of the handle,-regarding the handle in the position in which it rests on the telephone stand. It will be apparent that when molded in this manner, the portions of the handle which carry transmitter-and receiver can not be atless than a right'angle with the handle because of the draft required for removing the handle from the die. The result of this is that the casings or shells ior receiver and transmitter as well as'the caps for said shells have been made in separate pieces and attached to the handle,-although it is obviously desirable to form such portions integrally with the handle.

The general object of this invention is to pro- I vide a novel method and novel means for molding telephone handsets by the employment oi which the above and other disadvantages in -mo1ding by compression are largely it not entirely overcome. The invention obviates the necessity of embedding wires in the handle as in the compression method by making, possible the use of a slender core which forms a passage through the handle through which wires may be run to connect the receiver to the telephone cord. Such a core could not be used in compression molding, because, the pressure of material thereon would bend or break it.

A more specific object of the invention is to mold a telephone handset from a plastic such as phenol formaldehyde resin in such a manner as to make it unnecessary to cut or grind on a flash or to cut away a flash line. This preserves intact the gloss of the outer layer-oi plastic at the parting line.

Another object is to mold a telephone handset which comprlses a-handle having shells or casings for receiver and transmitter formed integrally therewith and which may extend at less than right angles from the handle.

Otherobjects and advantages of the invention will be pointed out in, or will become apparent from, the detailed description of an embodiment of the invention illustrated in the accompanying drawings, wherein:

Fig. 1 is a. view in vertical sectional elevation of a mold assembly for carrying out the method;

Fig. 2 is a view in horizontal sectional top plan taken on the line 2-2 of Fig. 1; v

Figs. 3, 4 and are views in vertical section on lines 33, 4-4 and 5-5 respectively of Fig. 2, each looking in the direction of the arrows on the respective lines;

Fig. 6 is a view similar to Fig. 4 with parts removed and broken away to show features of construction not revealed in Fig. 4; and

Fig. 7 is a view in side elevation of a telephone handset which may be made according to the present invention. y

In order to accomplish the objects set forth above and other objects and advantages, the invention in its preferred form provides an improvement in method and means for molding telephone handsets by transfer molding. "Transfer molding, in the broader aspects, comprises subjecting a thermosetting molding compound to heat and pressure in a cylinder to render it fluent and then forcing the plastic through narrow passages into the cavity of a heated die under hydrostatic pressure and continuing the application of heat and hydrostatic pressure to harden the plastic in the die and thus form a molded article.

In molding telephone handsets according to the present invention; I provide a die indicated generally at 8 in which a cavity is so formed that a handset may be molded on its side when the die is held in horizontal position. Associated with die 8 is a cylinder 9 which receives a piston II whch acts on molding compound in cylinder 9 to make it fluent and to deliver it to the die cavity under hydrostatic pressure.

The die 8 and cylinder 9 containing piston ll may be assembled as a unit and placed between the heated platens l2 and [3 of a press, the remaining parts of which are not shown, and the mold assembly subjected to the necessary heat and pressure to form a telephone handset.

The die or mold 8 comprises the upper member [4 and lower member [5 and these each form one side half of a telephone handset instead of upper and lower portions of the set as in positive pressure molding. In other words, the die cavity is divided in a plane extending vertically and longitudinally through a telephone ,set with reference to the position of the set on a telephone stand.

The die cavity includes the handle forming portion I6, Figs. 1, 2, 5 and 6, a receiver shell forming portion ll, Figs. 2 and 3, and transmitter shell forming portion I8, Figs. 2, 4 and 6, and which shell forming portions may be arranged at less than right angles to handle forming portion I6 as shown. In the drawings, the cavity portions I1 and I8 are each arranged at an angle of approximately 83 degrees to handle forming portion IS. The axial center lines of portions I1 and I3 lie in the plane of the parting line of the die.

One side of cavity portion I6 is made flat to form a fiat bottom on a handle which engages parts of a telephone stand on which the handle rests. This flat side may be formed in part by a plate [9, Figs. 2 and 5, pins 2| of which fit in holes 22 in the bottom die member [5 to hold it in complementary recesses in the two die members as shown in Fig. 5. Said plate I9 may bear letters or other insignia or may be specially shaped and may be exchangeable with other similar plates.

Mold cavity portions l1 and I8 have cores 23 and 24 positioned therein to form the interiors of receiver and transmitter shells or casings. Said cores are provided with collars 25 and 26 which carry pins 21 and 28 received in holes 29 and 3| in the lower die member l5. See Figs. 1 and 3 to 5. Said collars are fitted in complementary recesses in the upper and lower die members and hold in said recesses rings 32 and 33 which are internally threaded at 34 and 35 to form exterior threads on the shells upon which threads receiver and transmitter caps are screwed. The cores 23 and 24 fit tightly in rings 32 and 33 respectively and said rings form the outer ends of the receiver and transmitter shells. The axial center lines of said cores and rings are located in the plane of the parting line of the die.

Extending through the handle forming portion [5 of the die cavity is a core 35, Figs. 1, 2 and 5, which is provided for the purpose of forming a hole through the handle of a telephone set through which hole a wire or wires may be drawn for connecting the receiver to a telephone cord. Core 36 extends through a lug 31 on the end of core 24 and its end enters a hole in the end of core 23. The enlarged portion 38 of the core has a collar 39 thereon which holds the core against endwise movement, such portions fitting into recesses in the die members. Core 36 is provided with handle 4|.

As shown in Fig. 1, the cylinder 9 has no bottom, the top of upper die member 14 serving as the bottom of the cylinder. However, if desired, cylinder 9 may be provided with a separate bottom. Plastic from cylinder 9 is introduced to the die cavity through sprues 42 and 43, Figs. 1 and 6, provided in upper die member M. The sprues 42 and 43 lead into horizontal gates 44 and 45, Figs. 1, 2 and 6 respectively, each gate being cut partly in the upper and partly in the lower die members I4 and I 5. The gates 44 and 45 enter the die cavity through the rounded corners 46 and 47 of the die members which are located on each side of the plate l9 and which will form fillets in the corners between the handle and shells or casings of a telephone set. The gates may be located elsewhere, but the locations shown are preferred because they insure proper filling of the die cavity particularly the portions I1 and I8 into and through which the flow of plastic is restricted. A further advantage of such locations of the gates is that any blemish left upon removal of sprue material from a telephone set will be hidden and will not be touched.

In order to provide for binding posts or screws for connecting a telephone cord to receiver and transmitter, it is desirable to provide metallic inserts in the telephone handset. My novel method and means permit such inserts to be embedded in the handset when it is molded. This may be accomplished as illustrated in Figs. 1, 2 and 4. As shown in these figures core 24 has three holes formed therein. Two of these, shown at 48 and 49, being located in the upper part of the core near the edge thereof and the third at 5| being in the lower part of said core. Slidably fitted into these holes are pins 52, 53 and 54 on the inner ends of which are screw threaded inserts 55, 56 and 5'! which are held against the inner end of core 24 by the pins. The inserts are thus supported in the proper positions to become embedded at selected points in the end top of the transmitter shell of a telephone set. v I

In performing the method of the invention the mold parts are assembled as shown in Figs. 1, 3, 4, and 5. With plate I9 already in the die member I5, rings 32 and 33 are placed on cores 23 and 24, pins 52, I3, 54 with inserts thereon are inserted in core 24 and core 36 passed through lug 36 into'the hole in core 23. The core members may then be placed as a unit in the die member I5, pins 21 and 28 entering holes 29 and 3| in said die member and the collar 39 entering a recess provided for it in said member. The upper die member I4 may now be placed over the lower die member. To guide the upper die member into place, it may be provided at its four corners with heavy pins, 58, which fit into holes 59 in the lower die member. This prevents possible damage to core and mold surfaces as the upper die member comes into engagement with the lower die member.

Cylinder 9 is now placed in position and molding compound such as powdered phenol formaldehyde resin is placed therein in a quantity in excess of that needed to fill the mold cavity and passages in order that hydrostatic pressure may be continued after the cavity and passages are filled. Piston II is now placed in cylinder 9.

Although not shown in the drawings, suitable means may be provided for clamping the .die members together and for clamping cylinder 9 to the upper die member. The cylinder and die members also may be mounted in chases, not shown, to prevent damage to their edges in handling.

The mold assembly is now placed between the press platens I2 and I3 which apply heat and pressure to the mold parts. The resin is softened and as it softens it is forced through sprues 42 and 43 and gates 44 and 45 into the die cavity and around the cores which will have been heatedto the required molding temperature by the platens, by preceding operations, on a hot plate, or by combination of such heating methods.

After the die cavity has been filled the application of heat and hydrostatic pressure are continued until the resin has hardened. The maintenance of hydrostatic pressure on the mold charge is made possible by the presence of excess material in cylinder 9. If desired, the application of pressure may be further continued while the die cools. Cooling of the die may be accelerated by passing a cooling medium through platens I2 and I3.

Upon completion of the molding operation, the mold assembly is removed from between the press platens and taken apart. The upper and lower die member may first be separated. If the upper die member is raised from the lower, set sprue and gate material will break away from the molded article, together with set excess material formed in cylinder 9. If the assembly is inverted and the lower die member raised from the upper, the article will be left in the upper die member connected to the set gate material which may be cut or broken before or as the molded article is removed. The sprue material may then be driven out of the sprues and this will remove the set excess material from the top of die member I4 if not previously removed.

The molded article and the cores and rings are removed from either die member as a unit. Core 39 then is pulled after which cores 23 and 24 are pulled out of the article. Rings 32 and 33 are unscrewed and pins 52, 53 and 54 are unthe" parting line of the die because of leakage I of plastic under high pressure through the joint of the die which cannot always ,be kept tightenough to prevent such leakage. If formed, this fin will be so thin that it can be removed by a soft wheel without impairing the finish of the article which cannot be done with the relatively thick flash which must be formed on the sides of a set in positive pressure molding in order to permit the escape of excess material from the mold.

A finished telephone handset produced in accordance with the invention is shown in Fig. 7. It comprises a handle I6a, receiver shell or casing Na and transmitter shell or casing I9a. Extending through the handle is passage 36a through which wires may be drawnto connect the receiver to a telephone cord which enters through an opening also formed by core 36. Two of the inserts are shown at 55 and 56 into which screws or binding posts for wiring connections are threaded.

The casings I la and I8a are large enough to contain receiver and transmitter. In other words the housings for receiver and transmitter posts are formed integrally and simultaneouslywith the handle. This is true even though the casings Ila and I8a may converge toward each other as shown and each may form an acute angle with the handle. The casings Ila and Mia have threads 3211 and 33a formed thereon upon which receiver and transmitter caps (not shown) may be screwed. By making the shells Na and I8a integral with the handle, the cost of pro ducing the telephone set is reduced.

Variations may be made in the method and in the construction of the molding means without departing from the scope of the appended claims. Although it is preferred to form a hole through the handle of the telephone set, it will be understood that instead of forming a hole, wires may be embedded in the handle if desired and without the danger of breaking the wires which exists in the previously described compression molding operation. It'might be supposed that a hole could be formed in the handle of a set made by compression molding by the use of core such as core 36 in the drawings. However, that would be impractical because the core would be bent by the pressure of the plunger or upper die' member exerted on the core through the molding compound.

Having thus described my invention, what. I

7 claim is:

compound to heat and pressure to render it fluent, forcing said plastic under pressure into said cavity and hardening said plastic in said cavity to form said converging casings simultaneously and integrally with said handle, said die members being held in engagement to prevent the escape of plastic from said die cavity.

2. The method of molding a telephone handset from an organic plastic which comprises providing upper and lower die members having cavities therein for forming the side half portions of said set and of such shape that when said die members are engaged a cavity is provided for molding a handle and converging casings for receiver and transmitter parts of said set, inserting cores in the die cavity to form the interiors of said casings, subjecting said organic thermosetting molding compound to heat and pressure to render it fluent, and forcing said plastic under pressure into said cavity and maintaining said pressure and applying heat to the die after the cavity is filled to harden said plastic to mold said casings simultaneously and integrally with said handle, said die members being held in engagement to prevent the escape of plastic from said die cavity.

3. The method of molding a telephone handset from an organic plastic which comprises providing mating die members having cavities in the engaging faces thereof so formed as to mold the side half portions of said set and shaped so that when said members are engaged a cavity is provided for forming a handle and casings for receiver and transmitter extending at less than right angles to said handle, assembling with said members cores for forming the interiors of said casings and a core for forming a passage through said handle whereby said casings will be in communication, subjecting a molding compound to heat and pressure to render it fluent, and forc- 4 ing said plastic into said cavity and hardening said plastic therein to mold simultaneously and integrally the handle and casings of said set, said die members being held in engagement to prevent the escape of plastic from said die cavity.

4. The method of molding a telephone handset from a plastic which comprises providing mating die members having cavities in the engaging faces thereof so formed as to mold the side halves of said set and shaped so that when said members are engaged a cavity is provided for forming a handle and casings for receiver and transmitter extending at less than right angles to said handle, assembling with said members cores for forming the interiors of said casings located in the corners between the handle and easing forming portions of said cavity. V

6. A mold assembly for molding a telephone handset from organic plastics comprising upper and lower die members, said members being shaped to form the side halves of said set and when mated, a cavity comprising a handle forming portion and portions for forming receiver and transmitter casings of said telephone set, each of said portions extending from an end of the handle forming portion at less than a right angle thereto, and cores located in said casing forming portions for shaping the interiors of said casings, and passage means for delivering organic plastic under pressure into said cavity to mold simultaneously and integrally the handle and casings of said telephone set in said die.

7. A mold assembly for molding a telephone handset from organic plastics comprising upper and lower die 'members, said members being shaped to form the side halves of said set and, when mated, a cavity comprising a handle forming portion and portions for forming receiver and transmitter casings, each of said portions ex-, tending from an end of the handle forming portion at less than a right angle thereto, cores located in said casing forming portions for shaping the interiors of said casings, a third core located in the handle forming portion of said cavity and supported by said first named cores for forming a passage through the handle of the set, and passage means for delivering organic plastic under pressure into said cavity to mold integrally and simultaneously the handle and casings of said telephone set in said die.

8. A mold assembly for molding a telephone handset comprising upper and lower die members, said members being shaped to form the side halves of said set and, when mated, a cavity comprising a handle forming portion and portions for forming receiver and transmitter casings, each of said portions extending from an end of the handle forming portion at less than a right angle thereto, cores located in said casing forming portions, each of said cores having internally threaded rings associated therewith for forming threads on the ends of the receiver and transmitter casings of said set, and passage means for delivering organic plastic under pressure into said cavity to form integrally and simultaneously the handle and casings of said telephone set in said die.

9. A mold assembly for molding a telephone handset comprising upper and lower die members, said members being shaped to form the side halves of said set and, when mated, a cavity comprising a handle forming portion and por tions for forming receiver and transmitter casings, each of said portions extending from an end of the handle forming portion at less than a right angle thereto, cores located in said casing forming portions for shaping the interiors of said casings, and means for delivering organic plastic under pressure into said cavity, said means including gates leading into said cavity at points located in the corners between said handle and casing forming portions of said cavity.

FRANK H. SHAW.

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