GB2354730A

GB2354730A - Apparatus for, and method of, moulding an article

Info

Publication number: GB2354730A
Application number: GB9922965A
Authority: GB
Inventors: Christopher David Farley
Original assignee: TECNOSERBATOI SpA; Neutron Holdings Inc
Current assignee: TECNOSERBATOI SpA; Neutron Holdings Inc
Priority date: 1999-09-28
Filing date: 1999-09-28
Publication date: 2001-04-04
Anticipated expiration: 2019-09-28
Also published as: EP1088607A1; GB9922965D0; GB2354730B

Abstract

An apparatus for, and method of, moulding an article (5) from a sheet of material (9), wherein the apparatus comprises a mould formed of a plurality of mould members (3). The sheet of material is pre-formed and is disposed on the seat (10) of the fixed table (7) of a hydraulic press. The mould members are then moved over the table to close the mould around the pre-formed sheet, such that a bottom portion (14) of each mould member holds the periphery (21) of the sheet against the surface (19) of the table. A mould clamp (2) is then lowered onto the mould members by means of the moveable table (1) of the hydraulic press. The mould clamp biases the mould members against the table and freezes the clamp in the closed position. Fluid is then introduced into the mould at high pressure from below the pre-formed sheet to force the pre-formed sheet against the internal surface of the mould thereby moulding the article.

Description

2354730 APPARATUS FOR, AND METHOD OF, MOULDING AN ARTICLE The present

invention relates to an apparatus for, and method of, moulding, an article from, for example sheet metal. The article may, for example, be a fluid container or a cap for a petrol tank.

The process of forming, sheet metal has been known for many years. The forming process entails disposing a sheet of metal between a table and a mould. A rubber diaphragm is disposed between the sheet to be moulded and the table. A high pressure fluid is supplied and contained by the rubber diaphragm. The high pressure fluid has the effect of plastically deforming the sheet of metal, such that it conforms to the internal surface of the mould.

However, the fluid has a tendency to escape from the moulding apparatus between the sheet and the table, in spite of the presence of the rubber diaphragm and so problems have been experienced in containing, the high pressure fluid in the mould, leading to concomitant defects in the moulded article.

Moreover, when using sheet material such as a metal, the metal sheet has considerable strength which necessitates the fluid to be introduced at very high pressures and the problems of containing the fluid are exacerbated.

In addition, the necessity of using a rubber diaphragm has created a number of additional manufacturing difficulties. Such difficulties include a considerably increased time to perform the set-up operation for the moulding of each article because the article and the diaphragm must be accurately aligned. Additionally, manufacturing equipment costs are increased significantly by the need to supply, install and regularly replace the rubber diaphragm.

A further problem of known methods of forming, is that as the sheet is plastically deformed by the introduction of the high pressure fluid, it becomes elongated or stretched and its thickness is consequently significantly reduced. This results in articles of an inferior quality or necessitates the use of thicker sheet metal. The use of thicker sheet metal entails consequent additional costs in materials, equipment and manufacturing time, as well as furthering the possibility of high pressure fluid leakage from the mould, due to the higher pressures required to deform the sheet.

2 Thus, in the light of the problems associated with known methods of forming, forming, techniques have often been disregarded in industrial applications.

Taking the example of a cap for a motorcycle petrol tank, such a cap includes outward bends at the juncture of the neck of the cap with both the bowl-shaped closure of the cap and the rim at the opening of the cap. Since these portions of the cap have a greater diameter than the neck of the cap, the cap is said to have a negative shape. It is not possible to mould a one-piece article having a negative shape using conventional moulding techniques, whether by means of forming or more conventional casting techniques, due to the impossibility of removing the article from the mould. Similarly, it is not possible to manufacture such an article usinz stamping techniques. Accordingly, motorcycle tank caps are currently manufactured by moulding or stamping two metal sheets, to form two half-caps. The two ID -7 half-caps are then joined, for example by means of welding, to form the completed cap.

0 However, such caps are undesirable because the seam lying at the join of the two half-caps provides an area of reduced structural integrity. In view of the highly flammable nature of C, ZD petrol contained in the tank, such areas of reduced structural integrity can lead to considerable hazards, such as the risk of fumes escaping from the tank and subsequently being ignited. The hazard becomes particularly great in the event of a crash. Accordingly, the production of one-piece unitary caps without welds would be of considerable benefit.

According, to one aspect of the present invention, there is provided an apparatus for moulding an article from a sheet of material, the apparatus comprising:

a mould for receiving said material; a mould clamp which in use traps the material aloncr the periphery of the mould and so provides a fluid seal for said mould; and means for providing high pressure fluid in said mould thereby endbling said material to be moulded.

According to a further aspect of the present invention, there is provided a method of moulding an article using the aforementioned apparatus, said method comprising: placing the material within the apparatus; clamping the mould with the clamp, such that at least a periphery of the material is trapped; and supplying fluid at high pressure into the mould.

I 3 Embodiments of the present invention will now be described by way of further example only and with reference to the accompanying drawings, in which:

Figure I is a cross-sectional view of a moulding apparatus in an open position, prior to the moulding of an article; Figure 2 is a cross-sectional view of a moulding apparatus in a closed position after the moulding of an article; Figure 3 is an enlarged cross-sectional view of a mould member; and Figure 4 is an enlarged cross-sectional view of a preformed sheet seated on the apparatus prior to the moulding of an article.

With reference to figures 1 and 4, the apparatus comprises a fixed table 7, which forms a part of a hydraulic or pneumatic press. A support 6 is disposed to lie on the table and acts to support a mould. A depression is provided on the upper surface 19 of the support 6 to form a seat 10 for seating a sheet of metal or preformed sheet 9 prior to moulding. A C) In conduit 11 is further provided in the support 6 for supplying high pressure fluid 13 into the I mould from a source 8, by means of an aperture 12 disposed in the seat 10.

The mould has a shaped inner surface corresponding to the shape of the article 5 to be moulded and is disposed to lie on the support 6. The mould comprises at least two mould members 3, but may comprise more than two mould members 3, for example if it is required to mould articles having, negative shapes of greater complexity. In the present embodiment there are two mould members 3. Each mould member 3 is arranged such that it can slide on the surface of the support 6 to open and close the mould. The operation of sliding may be performed by means of transport cylinders 4, which may be hydraulic or pneumatic rams. Thus, each mould member 3 may be provided with a respective transport cylinder 4, which may be attached to a peripheral portion of the table 7 or the support 6.

A mould clamp 2 is disposed to lie above the mould and is arranged to be moveable in a substantially vertical direction by a moveable table 1. The moveable table 1 and the fixed table 7 form the hydraulic or pneumatic press.

As shown in figure 3, each mould member 3 is provided with a shaped inner surface 15 for forming a respective portion of the shaped inner surface of the mould. Each mould member is further provided with a bottom sliding surface 14, which lies contiguous with the upper surface of the support 6, and a further closing surface 16, which lies contiguous with 4D I the closing surface of the other mould member when the mould is closed. A transitional curved surface 22 may be provided between the bottom surface 14 and the closing surface 16. Each mould member is further provided on its outer surface with a face 17 forming a truncated half-cone, having a semi-circular cross-section. Thus, when the two mould members are moved such that the closing surfaces 16 lie contiguous to one another, the closed mould has a portion of its outer surface in the form of a truncated cone, with its apex lying above the surfaces 17.

The mould clamp 2 is preferably formed of a one-piece unitary body, having an internal face 18 corresponding to the faces 17 of the mould members 3. Thus, an internal surface 18 of the clamp 2 is also in the shape of a truncated cone, its apex lying above the surfaces 17.

In operation of the apparatus, the mould is first opened and a preformed sheet 9 to be moulded is placed on the seat 10, as shown in figure 1. The preformed sheet 9 is disposed on the seat 10 such that the bottom of at least a peripheral portion 21 of the preformed sheet 9 lies on the seat 10 and the edge of the preformed sheet 9 lies adjacent to the edge 20 of the seat 10 (as shown in figure 4). The preformed sheet 9 is of a thickness such that the peripheral portion 21 does not protrude significantly above the upper surface 19 of the support 6. Preferably the upper surface of the AF-formed sheet 9 lies in the same plane as the upper surface 19 of the support.

The sheet may be a flat sheet or it may be a preformed sheet 9 having the rough outline of the article 5. Typically the rough outline is formed by the most cost efficient method, usually stamping, and so the outline does not include any negative shapes.

As shown in figure 2, the mould members 3 are then slid over the upper surface 19 of the support 6 by means of the transport cylinders 4 to close the mould around the sheet. In this position, the closing surfaces 16 of the mould members are contiguous and a portion of the bottom surface 14 of each mould member 3 lies over a part of the peripheral portion 21 of the preformed sheet 9. Thus, the peripheral portion 21 is held between the bottom surfaces 14 of the mould members 3 and the seat 10.

Subsequently, the mould clamp 2 is moved vertically downwards over the mould by means of the moveable table 1 of the hydraulic press. As the mould clamp 2 is moved downwards, the corresponding truncated conical faces 17 and 18 of the mould members 3 and t he mould clamp 2 respectively come into contact with each other. Further downwards movement of the clamp 2 therefore acts to bias the mould members 3 against each other, thereby freezing the mould and preventing the mould from opening during the moulding process. Further downwards movement of the clamp 2 also acts to bias the mould members 3 against the support 6, thereby creating an effective fluid seal between the mould and the support 6 and tightly clamping the sheet between the mould members 3 and the support 6.

High pressure fluid 13 is then supplied from the source 8 into the mould via conduit 11 and aperture 12. The high pressure fluid may be a specially prepared fluid, comprising mainly water with specific additives. The fluid may be supplied at pressures varying from approximately 150 x 106 Pa to 300 x 106 Pa or greater, depending for example on the material to be moulded and the size and shape of the mould. Moreover, one or more of the high pressure fluid, the mould and the preformed sheet 9 may be heated to a high temperature to assist the moulding process. The high pressure fluid exerts a force on the underside of the preformed sheet 9, thus causing the material to plastically deform until the upper side of the preformed sheet 9 conforms to the shape of the inner surface 15 of the mould.

Without the use of a rubber diaphragm, the peripheral portion 21 of the preformed sheet 9 may be allowed to slide between the table and the mould, thereby reducing the amount of stretching of the sheet in the mould and subsequently reducing the amount by which the thickness of the sheet is reduced. This process, of enabling material from the periphery to be deformed in to the article, is known as enrichment. Typically, between 1. 5 % and 4 % of the volume of the moulded article 5 may comprise material deformed in to the article 5 from the periphery. Moreover, since the periphery stretches, the thickness of the moulded article 5 is more uniform. Accordingly, the quality of molded articles produced by the method of the present invention is significantly improved and discard of defective articles may be greatly minimised or even entirely avoided.

In addition, because the peripheral portion 21 is clamped between the seat 10 and the mould members 3 and because the mould members 3 form a seal with the upper surface 19 of the support 6, the pressure exerted by the table 1 of the hydraulic press on the mould members 3 by means of the clamp 2 can be dosed such that the peripheral portion 21 slides during moulding. This allows enrichment of the moulded article 5, without allowin leakage 9 C 6 of the high pressure fluid. Thus, significant benefits are imparted by the fact that the apparatus of the present invention eliminates the need for a rubber diaphragm yet provides a fluid seal by virtue of the co- operating mould and mould clamp.

Once the moulding operation is complete, the clamp 2 is raised by the moveable table I and the mould is opened by the transport cylinders 3. The moulded article 5 may then be removed and the moulding operation repeated for the next article.

By means of the process and apparatus described above, it is possible to produce an article having a negative shape without welds or oins. Accordingly, the method and apparatus of the present invention provides an article which can be manufactured more cheaply and with a higher quality than is possible using conventional manufacturing techniques. Moreover, because no welding process is required, equipment costs and the efficiency of use of that equipment are maximised.

As noted above, the sheet placed on the seat of the moulding apparatus may either be a flat sheet or a pre-formed sheet 9, having, the rough outline of the article 5. Significant improvements in manufacturing time and quality can be further enhanced by pre-forming the sheet 9 before it is moulded. Thus, once the final shape of the article to be moulded has been defined, a simulation may be run with the aid of advanced-generation electronic machinery with a view to constructing a tool capable of producing a pre-formed sheet 9 having a rough outline for the article to be moulded 5. The simulation takes account of the chemical composition and the mechanical properties of the sheet material to be used, as well as any enrichment. Thus, the use of a pre-formed sheet 9 reduces actual moulding time and improves the quality of the moulded article 5.

The face 17 provided on the outer surface of each mould member 3 need not form a truncated semi-cone. The function of face 17 and corresponding interna'l face 18 is to allow the alignment and freezing of the mould and to bias the mould against the upper surface 19 of the support 6. Thus, each mould member may be provided with any face or combination of faces on its outer surface which in combination with the mould clamp allows at least the functions of freezing the mould and creating a fluid seal.

As noted above, it is possible to use more than two mould members 3) to form the mould. Thus, it is possible to mould articles having very complex shapes where it would not be possible to remove a moulded article 5 from a mould having only two mould members 3.

7 Similarly, in the event that the article to be moulded does not have a negative shape, it is possible to use only one mould member.

Moreover, although it is preferable that each mould member 3 be arranged such that its bottom sliding surface 16 lies on the upper surface 19 of the support 6, it is further possible for two or more mould members to lie on the upper surface 19 of the support 6 and for further mould members to be then stacked on the bottom mould members. Each mould member is provided with at least one closing surface 16 to lie contiguous with a closing surface of another mould member. Moreover, each mould member is further provided with a face 17 on which a force may be exerted, either directly or indirectly by the mould clamp 2, to close the mould and to bias each mould member downwards in the direction of the support 6. In this case, face 17 may also have the function of aligning the mould members.

I el Although the mould clamp 2 has been described as a one-piece unitary body in the aforegoing, description, it is also possible for the mould clamp to be formed from a number of clamp members. As an example, the mould clamp may comprise two or more clamp members, each provided on a separate transport cylinder and arranged to move both downwards and in the direction of the centre of the mould.

The seat 10 provided on the upper surface 19 of the support 6 need not comprise a depression in the upper surface 19 of the support 6. Rather, the seat 10 may be provided by forming a raised portion on the upper surface 19 of the support 6, disposed to surround the edcye of the sheet. The transitional surface 22 of each mould member may then be designed to accommodate the raised portion such that the peripheral portion 21 is clamped between the upper surface 19 of the support 6 lying within the seat 10 and each mould member 3.

Alternatively, the mould members may include a recess with boundaries cotern-iinus with the sheet. I Moreover, the sheet may be of a thickness such that the top of the peripheral portion 21 lies significantly below the upper surface 19 of the support 6, when placed in the seat. At the same time, projections may be disposed such that they extend downwards from the bottom sliding surface 14 or the transitional surface 22 of each mould member to clamp the peripheral portion 21.

8 Also, it is not necessary for the upper surface 19 of the support 6 to lie in a horizontal plane. It is equally possible for the upper surface 19 to lie in a vertical plane or not even in a single plane and for the remaining components of the apparatus to be arranged accordingly.

Z:1 17 Although the support 6 is described as separate from the table 7 of the hydraulic press, it is equally possible for the support 6 and the table 7 to be comprised of a one-piece unitary body.

As will be clear, articles that can be manufactured by the apparatus or method accordina to the present invention are not limited to fluid tanks and tank caps or to articles 1D moulded from metal sheets.

The aforegoing description has been given by way of example only and it will be appreciated by a person skilled in the art that modifications can be made without departing from the scope of the present invention.

r I 9 CLAMS 1. An apparatus for inoulding an article from a sheet of material, the apparatus comprising;: a mould for receiving said material; a mould clamp which in use traps the material along the periphery of the mould and so provides a fluid seal for said mould; and means for providing high pressure fluid in said mould thereby enabling said material to be moulded.

2. An apparatus as claimed in claim 1, in which said mould clamp comprises a clamp and a table upon which said mould is disposed.

3. An apparatus as claimed in claim 2, in which said clamp has an internal surface and said mould has an external surface which cooperate when in use.

4. An apparatus as claimed in claim 3, in which said internal surface of the clamp and the external surface of the mould both form truncated cones.

5. An apparatus as claimed in any one of claims I to 4, in which said mould comprises two or more mould members.

6. An apparatus as claimed in any one of claims 2 to 5, in which said clamp moves in a first direction.

7. An apparatus as claimed in claim 6, in which said mould members are arranged to move in a second direction perpendicular to the first direction.

8. An apparatus as claimed in claim 7, in which said mould members are arranged to slide over said table.

9. An apparatus as claimed in any one of claims 6 to 8 in which said movement is provided by pneumatic or hydraulic action.

10. An apparatus as claimed in any one of claims 2 to 9, wherein the clamp is a one piece unitary body.

11. An apparatus as claimed in any one of claims 2 to 9, wherein an aperture is provided in the table for supplying the fluid into the mould.

12. An apparatus as claimed in any one of the preceding claims, wherein the apparatus is controlled by a computer.

13, An apparatus as claimed any one of the preceding claims, in which the sheet is a preformed sheet having a rough outline of the article to be moulded.

ZD 14. An apparatus as claimed in any one of the preceding claims, in which the sheet comprises a metal.

15. A method of moulding an article using the apparatus as claimed in any one of the previous claims, said method comprising: placing the material within the apparatus; clamping the mould with the mould clamp, such that the material is trapped along the periphery of the mould; and supplying fluid at high pressure into the mould.

16. A method as claimed in claim 15 when dependent upon claims 5 to 8, in which said clamping comprises, sliding the mould members in the second direction and then moving the I C clamp in the first direction to form the fluid seal.

11 17. A method as claimed in either claim 15 or 16, further comprising pre- forming the sheet C> of material into a rough outline of the article to be moulded, prior to placing the material in the apparatus.

18. A method as claimed in any one of claims 15 to 17, further comprising unclamping the mould and mould clamp; moving the mould away from the material; and removing the moulded article from the apparatus.

19. An article formed by the method of any one of claims 15 to 18.

20. An article formed using the apparatus of any one of claims 1 to 14.

21. An article as claimed in either claim 19 or 20, wherein the article is a fluids container.

22. An article as claimed in either claim 19 or 20, wherein the article is a cap for a petrol tank.

23. An apparatus for moulding an article from a sheet of material substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

24. A method for mouldina an article from a sheet of material substantially as hereinbefore described with reference to and as illustrated in the accompanying draA;ings.