US3896648A

US3896648A - Blow molding process for container of superplastic alloy

Info

Publication number: US3896648A
Application number: US474964A
Authority: US
Inventors: Francis Schertenleib
Original assignee: ALTER LICENSING ESTABLISHMENT
Current assignee: ALTER LICENSING ESTABLISHMENT
Priority date: 1973-10-02
Filing date: 1974-05-31
Publication date: 1975-07-29
Anticipated expiration: 1992-07-29
Also published as: JPS5062171A; DE2426601B2; DE2426601C3; JPS5640652B2; DE2426601A1; AU6954074A; FR2245428A1; FR2245428B1; IT1013378B; CA991023A; GB1468214A

Abstract

A container of a superplastic alloy material is manufactured by causing a fluid to blow into a bottomed cylinder. Prior to the blow molding, the cylinder has its surfaces finished smooth and is preheated in a temperature range of 200* - 300*C at least two minutes. Within a metal mold, the cylinder is subjected to an initial pressure of at least 8 atm., and is thereafter subjected to a molding pressure in the range of 7 - 20 atm. into the container blown out to the final dimensions. Since the molding pressure is lastly bestowed after somewhat inflating the cylinder by the initial pressure, the product is blowmolded finely, and a beautiful container having neither a flaw nor a crack on the surface is obtained.

Description

Umted States Patent 1191 1111 3,896,648 Schertenleib July 29, 1975 [54] BLOW MOLDING PROCESS FOR 3,529,458 9/1970 Butler et a1. 72/60 CONTAINER 0F SUPERPLASTIC ALLOY 3,535,766 10/1970 Hymes 29/42l [75] inventor: Francis Schertenleib, Furstentum, Primary Examiner Richard J. Herbst Llechtenstem Attorney, Agent, or Firm-Stevens, Davis, Miller & [73] Assignee: Alter Licensing Establishment, Moshe" Vaduz, Liechtenstein 221 Filed: May 31, 1974 [571 f ABSTRACT I A container 0 a superplastic alloy material is manu- [211 Appl' 474964 factured by causing a fluid to blow into a bottomed cylinder. Prior to the blow molding, the cylinder has [30] Foreign Application Priority Data its surfaces finished smooth and i8 preheated in temo 2, 1973 J 48-110915 Peratue range 300C at least two ct apan Within a metal mold, the cylinder is subjected to an 52 US. 01. 72/61; 72/364' 29/421 initial Pressure Ofat least 8 and is thereafter 51 Int. Cl B2l d 26/04 J'ected a "mlding Pressure in the range of 7 20 [58] Field of S 72/56 57 58 59 60, atm. into the container blown out to the final dimen- 72/6l 62 364 i l sions. Since the molding pressure is lastly bestowed Q5/3875: after somewhat inflating the cylinder by the initial pressure, the product is blowmolded finely, and a [56] References Cited beautiful container having neither a flaw nor a crack UNITED STATES PATENTS on the surface is obtained.

3,340,101 9/1967 Fields Jr. et al. 148/] 1.5 6 Claims, 10 Drawing Figures -IrllIIIIIIIII The present invention relates to a container manufactured of an alloy of superplasticity, and more particularly to a method of manufacturing a container by blowing a tube of a superplastic alloy.

Since the superplastic alloy spreads extraordinarily largely by a low working stress, it is subjected to such molding working as rolling. drawing, sheet working, press forging and extrusion. Further, the development of a manufacturing technique based on the blow molding is attempted recently. Unlike glass or plastics, however, the superplastic alloy is narrow in the temperature region in which it exhibits the superplastic flow, and does not always respond to a sudden working stress. It is therefore limited in moldability. ln consequence, even when the superplastic alloy is extraordinarily expanded compulsorily by merely raising the blow pressure, it cannot be uniformly molded. Particularly the molding of elaborate parts becomes imperfect, and a non-uniform thickness of the molded article or cracks in the surface arise. In this manner, the manufacture with the superplastic alloy has been technically unsolved.

The present invention intends to produce a novel container by utilizing the property of the superplastic alloy. Since the conventional techniques have worked the superplastic alloy under a condition exceeding the limit of thee moldability thereof, they have been incapable of manufacturing a product enduring practical use. The invention has therefore accomplished the intention by the blow formation of the container in such way that a material is preheated so as to manifest the superplastic phenomenon, that it is somewhat inflated by a low initial pressure of at least 8 atm., and that it is thereafter given a molding pressure in the range of 7 atm. Previously to the preheating of the superplastic alloy, the material is formed into a bottomed cylinder, the surfaces are smoothed and the dimensional precisions are arranged. Thus, the external appearance of the product by the blow molding is made beautiful, and the outward dimensions of the finished article are made accurate.

Used the superplastic alloy are Zn Al (78 22), Al Cu (67 33), Al Si (88.3 11.7), Mg A1 (67.7 32.3), Mg Cu (69.3 30.7), Mg Ni (76.5 23.5), and so forth. These alloys are preheated at 200 300C at least 2 minutes, and while kept at a molding temperature below 600C, they are molded by the blow formation at a blow ratio of at the greatest 3 under the two stages of molding pressures.

In accordance with the present invention, there are two cases. one of which starts from the stage of work of making a bottomed cylinder from a slab or discshaped member of the superplastic alloy material, while the other starts from the stage of work of making a bottomed cylinder by closing the bottom ofa pipe obtained by the extrusion molding. In either case, a container of desired size and shape can be readily manufactured by placing the bottomed cylinder in a metal mold and subjecting it to the blow formation under the conditions as mentioned above.

As apparent from the foregoing, the principal object of this invention is to provide a method which can manufacture a container of a superplastic alloy material.

Another object of this invention is to provide a method which can manufacture a container by the technique of blowforming a superplastic alloy material.

Still another object of this invention is to provide a container which is made of a superplastic alloy material.

The above-mentioned and further objects of the present invention will become more definite from the following detailed description when read with reference to the accompanying drawings. In the drawings, like reference symbols indicate like constituent parts.

FIG. 1 is a perspective view ofa slab ofa superplastic alloy material.

FIG. 2 is a sectional view of a bottomed cylinder which is obtained by the impact molding. the compression molding or the vacuum molding of the slab;

FIG. 3 is a sectional view illustrating the state under which the cylinder is ironing-worked;

FIG. 4 is a sectional view illustrating the state under which the inside surface of the cylinder at its opening is machined;

FIG. 5 is a sectional view illustrating the state under which the inside surface of an inner part of the cylinder as is distant from the opening part is machined;

FIG. 6 is a sectional view illustrating the state under which the cylinder is inserted into a metal mold assembly in the open state;

FIG. 7 is a sectional view illustrating the state under which the metal mold assembly in FIG. 6 is closed and under which the cylinder is blown out;

FIG. 8 is a front view of a finished product (container);

FIG. 9 is a perspective view ofa tube ofa superplastic material; and

FIG. 10 is a sectional view of the tube in FIG. 9 as is made a bottomed cylinder.

As previously stated, the present invention has the case of starting from the slab of a superplastic alloy and the case of starting from the tube thereof. In either case, it includes the various steps of preparation of the bottomed cylinder, mechanical preprocessing, preheating, blow formation, cooling, taking out the molded article, and finishing.

(Embodiment) 7 Description will now be made of the first case.

lst Step: A slab l as shown in FIG. 1 is made in such way that a rolled material of superplastic alloy (Zn 78 Al 22 percent) having a suitable thickness as required for manufacturing a final product, for example, a container 10 shown in FIG. 8 is punched into a predetermined size and shape. Alternatively, the slab is made by slicing an extruded bar of predetermined sectional shape at a fixed thickness.

2nd Step: A bottomed cylinder 2 as shown in FIG. 2 is made by subjecting the slab 1 to the impact molding, the compression molding or the vacuum molding. In the middle of the bottom 12 of the cylinder 2, a lug 15 is formed. Up to this step, the molding must be executed within the region of the superplastic property of the alloy. The temperature, the heating period of time, etc. need be sufficiently considered.

3rd Step: For the external appearance, thickness distribution, molding etc. of the final product (container) 10, the surfaces of the cylinder are subjected to a preprocessing such as polishing, ironing working (drawing working) and machining. The expression polishing" signifies that with a file and/or buff, and it serves to increase the luster and smoothness of the outside surface of the cylinder. The ironing working draws or squeezes the cylinder 2 with a die 3 as illustrated in FIG. 3. Thus, the material of the cylinder surface 2,, is stretched, to enhance the smoothness of the surface, to remove cavities created in the outside surface and to render the structure of the material finer. so as to obtain a container whose outside surface is beautiful. The machining signifies to cut and work the inside surface 2,, of the cylinder in conformity with the shape of the final container as illustrated in FIG. 5. Thus. the thickness distribution is made uniform. In order to relieve a small protuberance, for example. a screw portion 11 to be formed on the outer periphery of the neck portion of the final container 10 as shown in FIG. 8, the inside surface 2,- of the corresponding part of the cylinder is cut and worked thin as illustrated in FIG. 4. Thus, the neck portion is inflated well at the stage of work of blowing-out.

4th Step: Before the cylinder having undergone the first to third steps is shifted to the blow step, it is subjected at this fourth step to preheating at 260C i lC for about 10 to 15 minutes. In this case, when the temperature of 270C is exceeded, the thermoplasticity decreases. When the cylinder is held at 300C for a certain period of time (for example, 15 minutes), the thermoplastic property is conspicuously lost, and the blowing-out becomes impossible. However, when the alloy is quenched at 350C again, the superplastic property is restored. A furnace structure for executing the preheating shall be one which changes little in the temper ature difference at the opening and closure. It is further necessary to make control so that an abrupt temperature fall may be prevented when the preheated cylinder is transferred to a blow mold assembly.

5th Step: The fifth step is the blow step. The preheated cylinder 2 is shifted to the blow step, which is generally performed in the order of the following substeps (I (5)- l. The right and left split molds of the metal mold assembly are closed.

2. The bottom mold of the metal mold assembly is pushed up and set, to construct the blow mold assembl 5. The preheated cylinder is inserted and arranged in the blow mold assembly.

4. The cylinder is heated. It is held at 260C i C by heaters inside the metal mold assembly.

5. A nozzle is inserted into the heated cylinder, and air or a gas is caused to blow thereinto. The cylinder is blown out until it becomes the shape of the final container.

FIG. 6 illustrates the state under which the metal mold assembly is open. The metal mold assembly consists of the right and left split

molds

4, 4 and the bottom mold 6. Each of the

split molds

4, 4 contains the heater 7 therein. A cavity 8 for molding the final product 10 is formed inside each split mold, while a neck portion 9 for molding the port portion of the final product is formed at the upper edge. When the metal mold assembly is open, the cylinder 2 is inserted into a position shown in FIG. 6. Subsequently, the

split molds

4, 4 are registered, and the bottom mold 6 is raised. At this time, the lug located in the middle of the bottom 12 of the cylinder 2 is inserted into a depression 16 in the middle of the bottom mold 6. Subsequently, as illustrated in FIG. 7, the metal mold assembly is closed, and

the cylinder is inflated by causing the fluid to blow thereinto from the blast port 14 of the nozzle portion 13. Since the cylinder has its central position held with the lug 15 of the bottom portion inserted into the depression 16 of the bottom mold 6, it is inflated at equal rates in the radial direction, and any partial thickness is prevented. As a modification, it is also allowed to provide the lug in the middle of the bottom mold 6 and to form the depression at the bottom of the cylinder.

The conditions of the blow molding at the sub-step (5) are as follows.

The blow time is 45 to 60 seconds. the initial pressure is 10 atm. (2 to 3 seconds), and the molding pressure is 17 atm. (43 to 57 seconds). As the pressure-applying medium, an inert gas, such as nitrogen and argon. heated to C C is used in order to prevent the molding compact from being oxidized and lowering in temperature. The molding pressure is not once given at the molding, but an appropriate ratio for the elongation of the material is promoted by the initial pressure so that the cylinder can be molded into the precise shape of the final container. When the cylinder is blown out directly by the molding pressure without going through the initial pressure, a weak part dependent upon the thickness distribution is suddenly inflated to give rise to a thickness change and a shape change. This drawback is eliminated by the initial pressure. The maximum blow ratio at this time was 2.7 in experiments.

6th Step: After the molding. cooling with air is carried out in order to facilitate the release of the molding compact from the metal mold assembly. The cooling time is 5 to 6 seconds.

7th Step: This is a mold opening and product takingout step. The blown-out container of the final shape is taken out from the metal mold assembly manually or automatically.

8th Step: This is a finishing step. The molded container is subjected to the various finishing sub-steps of l slicing and cutting the port portion. (2) washing the inside and outside of the container, (3) plating the outer surface of the container or coating it with paint. and (4) coating the inner surface of the container. (Modified Method) Description will now be made of the second case, namely. the method which starts from making a bottomed cylinder by providing a bottom for an extrusionmolded tube.

lst Step: By the extrusion molding, a tubular body 20 is molded as shown in FIG. 9.

2nd Step: A bottom portion 22 is formed by blocking one end of the tube 20, so that a cylindrical body 21 as shown in FIG. 10 is prepared. In the middle of the bottom 22, a lug 23 is provided. In this case, there is employed either a method (A) in which the bottom portion is formed by heating and welding a separate component of the same alloy as that of the cylinder, or a method (B) in which the bottom portion is formed by nipping one end of the cylinder by means of a metal mold or any other mechanism.

The third and succeeding steps are the same as in the first case. However, since the thickness change of the cylinder is achieved at the extrusion molding, the ironing working and the machining as seen at the third step of the first case are omitted.

As described above, the present invention can readily mold a metallic container in such way that, after finishing the inside and outside surfaces of a cylinder of a superplastic alloy material, the stepped blow molding from the initial pressure to the molding pressure is carried out. With the conventional compression and impact workings, the molding of the container of the superplastic alloy material is attended with difficulties. In contrast. according to the present invention, a beautiful final container can be smoothly molded without losing the smoothness of the surfaces and without causing partiality in thickness and cracks, in such way that the blow pressure is bestowed stepwise while maintaining the temperature of the process in which the internal structure of the material changes.

The container produced by the present invention can be extensively used likewise to metallic containers which are usually employed for receiving drinks, cosmetics, liquid medicines, etc.

What is claimed is:

l. A method of manufacturing a blow-molded article of a container made of a superplastic alloy, comprising the steps of:

a. forming a bottomed cylinder from a starting material of said superplastic alloy,

b. performing a mechanical finish processing for smoothing the surfaces of said cylinder and for enhancing the dimensional accuracy,

c. preheating the finish-processed cylinder by holding it in a temperature range of 200 to 300C for at least two minutes,

d. receiving the heated cylinder in a metal mold assembly, and blowing out said cylinder from the port side towards the interior thereof by fluid pressures of an initial pressure of at least 8 atm. and a mold- LII ing pressure in the range of 7 20 atm., and

e. cooling said metal mold assembly by air blast before it is opened to take out the inflated product therefrom.

2. The method according to claim 1, wherein the superplastic alloy material is a member selected from the group consisting of Zn Al, Al Cu, Al Si, Mg Al, Mg Cu and Mg Ni.

3. The method according to claim 1, wherein a lug is formed at the bottom of said bottomed cylinder, while a depression corresponding to said lug is formed in a bottom mold of said metal mold assembly, and when said metal mold assembly is closed. said lug is inserted into said depression so as to hold the central position of said cylinder.

4. The method according to claim 1, wherein the superplastic alloy material is subjected to the preheating treatment at 260C 10C for 10 minutes to [5 minutes, it is subsequently held under the initial pressure of 10 atm. for 2 to 3 seconds in said metal mold assembly heated to at most 600C, and it is thereafter blown therein under the molding pressure of 17 atm. for 43 to 57 seconds, so that it is made the inflated container having a maximum blow ratio of 3.

5. The method according to claim 1, wherein said bottomed cylinder is obtained by subjecting a slab of the superplastic alloy material to any of impact molding, compression molding and vacuum molding.

6. The method according to claim 1, wherein said bottomed cylinder is obtained by providing a bottom at one end of an extrusion-molded tube.

Claims

1. A method of manufacturing a blow-molded article of a container made of a superplastic alloy, comprising the steps of: a. forming a bottomed cylinder from a starting material of said superplastic alloy, b. performing a mechanical finish processing for smoothing the surfaces of said cylinder and for enhancing the dimensional accuracy, c. preheating the finish-processed cylinder by holding it in a temperature range of 200* to 300*C for at least two minutes, d. receiving the heated cylinder in a metal mold assembly, and blowing out said cylinder from the port side towards the interior thereof by fluid pressures of an initial pressure of at least 8 atm. and a molding pressure in the range of 7 - 20 atm., and e. cooling said metal mold assembly by air blast before it is opened to take out the inflated product therefrom.

2. The method according to claim 1, wherein the superplastic alloy material is a member selected from the group consisting of Zn - Al, Al - Cu, Al - Si, Mg - Al, Mg - Cu and Mg - Ni.

3. The method according to claim 1, wherein a lug is formed at the bottom of said bottomed cylinder, while a depression corresponding to said lug is formed in a bottom mold of said metal mold assembly, and when said metal mold assembly is closed, said lug is inserted into said depression so as to hold the central position of said cylinder.

4. The method according to claim 1, wherein the superplastic alloy material is subjected to the preheating treatment at 260*C + or - 10*C for 10 minutes to 15 minutes, it is subsequently held under the initial pressure of 10 atm. for 2 to 3 seconds in said metal mold assembly heated to at most 600*C, and it is thereafter blown therein under the molding pressure of 17 atm. for 43 to 57 seconds, so that it is made the inflated container having a maximum blow ratio of 3.