GB2040200A - Manufacturing cooking utensils - Google Patents

Abstract

A hollow ware cooking utensil 38 is formed by pressing a flat disc of ductile metal in a die between male and female die members to form an intermediate product. This product has a relatively thick base and a relatively thick, relatively low upstanding sidewall, that intermediate product is then subjected to a further pressing operation between male and female die members in which the sidewall is thinned by moving metal along the upstanding sidewall to extend it and to form a relatively thick outwardly projecting rim 40 around the upper edge of the sidewall. <IMAGE>

Description

SPECIFICATION Improvements in and relating to cooking utensils This invention relates to the manufacture of metal hollow ware cooking utensils such as saucepans, frying pans, pots and pans.

Hollow ware cooking utensils of this type are well known and have been produced from a ductile metal such as aluminium or an aluminium alloy by spinning or flow forming the metal. The products of such a process can be produced relatively simply and cheaply and are reasonably satisfactory. Spinning, however, is a slow process.

Shallow hollow ware cooking untensils can also be produced by drawing a sheet of metal in a mould.

Deeper untensils such as saucepans cannot be produced in this way since the depth to which sidewalls can be drawn before the metal is disrupted is very limited.

According to the invention there is provided a process for producing a hollow ware cooking utensil from a ductile metal in which a flat sheet of metal is pressed in a mould between male and female mould members to form an intermediate product comprising a relatively thick base and a relatively thick, relatively low upstanding sidewall, and that intermediate product is subjected to a further moulding operation between male and female mould members in which the sidewall is thinned by moving metal along the upstanding sidewall to extend the sidewall and to form a relatively thick outwardly projecting rim around the upper edge of the sidewall.

The invention also extends to a hollow ware cooking utensil which has been made by moulding a ductile metal and which has a relatively thick base, a relatively thin upstanding sidewall and a relatively thick outwardly projecting rim around the upper edge of the sidewall.

The process of the invention involves at least two moulding steps. In the first step, a substantially flat disc of metal is pressed to shape between male and female mould members which provide a substantially flat and thick base and form a relatively thick upstanding sidewall, the base and sidewall being roughly equal in thickness. In practice the base may be approximately the same thickness as the original flat disc of metal. At this stage the required interior cross-sectional dimensions and shape of the sidewall and base have been formed. The thickness and size of the original flat disc does not have to be of a high tolerance since minor differences in the amount of metal as between due disc and another are accommodated by slight differences in length of the sidewall.

In the second moulding step that intermediate product is formed in another mould. The female mould member fits within the interior of the intermediate product and forces it into a male mould member of smaller cross-section which shapes the exterior face of the sidewall of the final product and displaces metal from the upstanding sidewall along that sidewall to form a relatively thick rim around the upper edge of the sidewall. At the same time the height of the sidewall if increased and it is thinned. In this second stage there need be substantially no change in the cross-sectional interior dimensions of the sidewall and thickness of the base will not normally change significantly.Any differences in the volume of metal as between one intermediate product and another are accommodated as slight differences in the size of the rim and in a finishing step the rim can be machined to make it accurately circular or of a shape corresponding to the section of the sidewall and so remove any excess metal.

The resulting product has a number of advantages. The base can be relatively thick which is important to provide good heat conductivity throughout the whole area of the base so preventing hot spots and local burning of food and in addition the base is relatively rigid. By contrast, the sidewall can be relatively thin and this reduces the amount of material needed in the product. This both gives a cheaper product and provides a lighter-weight product which is advantageous for the user. Although the sidewall can be thin, the overall product can have satisfactory rigidity because of the presence of the thick rigid rim around the top of the sidewall and in addition that rim gives the product a pleasing appearance.

By way of example the sidewall can be about half the thickness of the base. Thus the sidewall need be no thicker than about 11/2 to 2mm or up to about 3mm, whilst the base and flange can be relatively thick, e.g. of the order of 3 or 4 to 6mm.

As noted above, the metal from which the product is made needs to be ductile and preferred materials are aluminium or an aluminium alloy and suitable materials are already well known for use in the production of hollow ware cooking utensils.

If desired, the product can be subjected to a further pressing operation in which the shape of the rim is altered to reduce its height or thickness in a direction parallel to the sidewall and to increase its width so that it projects outwardly further from the sidewall.

Also as noted above the rim may be machined to remove excess metal and in addition the underside of the base may be machined in conventional fashion to ensure that it is accurately flat.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a section through a mould used in the first step showing the mould in the open position; Figure2 is a section showing the mould of Figure 1 at the completion of the first moulding step; Figure 3 is a section through the mould used in the second step at the commencement of the second moulding step; and Figure 4 shows that mould at the completion of the second step.

In the first step of the process according to the invention, the mould shown in Figures 1 and 2 is used. This mould comprises an outer male member 12 into which is forced by suitable means, e.g.

hydraulic pressure, a female member 14. A relatively thick flat disc 16 of aluminium alloy is to be shaped in the mould.

The member 14 has a moulding surface 14a which is shaped and dimensioned to the desired interior dimensions and shape of the base and lower parts of the sidewall of the finished article. Around the lower edge of the moulding surface 14a is a ring 17 and, when the mould is fully closed, the lower surface 12a of the male member is designed to abut on the top surface of this ring 17.

The disc 16 is placed between the two members 12 and 14 and the member is forced together so that the female member enters the male member until the ledge 146 abuts the upper surface 12a. As member 14 enters the mould cavity in the member 12 the disc 16 is pressed, pulled down and formed into an intermediate product 20 in the form of a shallow thick bowl. Air trapped in the mould member 12 can escape through a small vent 12b.

This intermediate product has a relatively thick base 20a and a relatively thick upstanding sidewall 20b. The interior dimensions and shape of the base and lower parts of the sidewall of the intermediate product 20 are the same as those which are desired in the finished article.

The two mould members are then opened and the intermediate product 20 is removed from the moulding surface 14a by forcing the ring 17 upwardly by means of the rods 18 which extend down through the member 14. These rods 18 can be moved hydraulically or alternatively they can be mounted on compression springs which are compressed by the closing of the mould members.

The intermediate product 20 is then subjected to a further moulding step in a mould comprising an outer male member 32 and an inner female member 34. The female member has a moulding surface 34a which in the regions of the base and lower part of the sidewalls of the intermediate product 20, is substantially identical with the mould surface 14a of the female member used in the first step except that there is desirably a slight clearance between the interior of the product 20 and the exterior of the mould surface 34a. This clearance can be of the order of 0.012cm to 0.025cm difference in diameters between the two.

The male member 32 has a mould cavity 32a whose shape corresponds to that to be given to the exterior surface of the finished article. Around the upper edge of the cavity 32a is an annular recess 32b in which the intermediate product 20 is initially placed. This recess 32b is also designed to mould a rim round the upper edge of the sidewall in the finished article as will be described below. The lower surface 32c of the male member is arranged to abut a ledge 34b on the female member 34 once the mould is fully shut. Through the top of the mould member 32 is a vent hole 32d.

In operation, the intermediate product 20 is placed over the moulding surface 34a of the female member 34 and when the mould is brought to the position shown in Figure 3 the product 20 fits into the recess 32b. The female member 34 is forced into the male member 32 and the annular edge 36 at the top surface of the mould surface 32a has the effect of preventing some of the metal in the sidewall of the intermediate product from entering into the gap between mould surfaces 32a and 34a. Therefore this metal is squeezed or ironed towards the upper end of the sidewall.

As the mould 34 progressively enters the mould surface 32a, the sidewall of the intermediate product is lengthened and excess metal is retained around the top edge until the final position shown in Figure 4 is reached. In this final position, the finished article 38 has been shaped with a relatively thin sidewall and the excess metal from the sidewall of the intermediate product remains as an outwardly projecting annular rim 40 around the top of the finished sidewall 42. The shape of the rim 40 is determined by the shape of the annular recess 32b.

When the mould is opened the finished article 38 may tend to remain within the mould cavity 32a. It can be removed by, for example, a push rod or the like inserted through the vent hole 32d.

If it is desired that this rim 40 be less high and project further from the sidewall 42 then it may well be desirable in an additional step to take the product 38 and subject it to a further pressing operation in a mould which has a different shaped recess 32b but which has more or less identical moulding surfaces 32a and 34a so that no further shaping of the base 44 and sidewalls 42 of the finished product occur.

Claims (5)

1. A process for producing a hollow ware cooking utensil from a ductile metal in which a flat sheet of metal is pressed in a mould between male and female mould members to form an intermediate product comprising a relatively thick base and a relatively thick, relatively low upstanding sidewall, and that intermediate product is subjected to a further moulding operation between male and female mould members in which the sidewall is thinned by moving metal along the upstanding sidewall to extend the sidewall and to form a relatively thick outwardly projecting rim around the upper edge of the sidewall.

2. A process as claimed in Claim 1 in which the thickness of the sidewall in the finished product is about half the thickness of the base.

3. A process for producng a hollow ware cooking utensil substantially as herein described with reference to the accompanying drawings.

4. A hollow ware cooking utensil when made by a process as claimed in any of claims 1 to 3.

5. Ahollowwarecooking utensil has been made by moulding a ductile metal, which has a relatively thick base, a relatively thin upstanding sidewall and a relatively thick outwardly projecting rim around the upper edge of the sidewall.