Note: Descriptions are shown in the official language in which they were submitted.
CA 02221~83 1997-10-17
WO 9~ '3~0 PCT/F~96/00213
Process and apparatus for the manufacture of a cooking
vessel by roll forming.
5 The object of the invention is a process for the m~mlf~cture of a cooking pot or pan,
such as a frying pan or a kettle, in which the pot is produced from a metal blank by
forming techniques. In addition, the invention is related to equipment intended for
the application of the process.
10 Heretofore, frying pans and other vessels, inten(led for cooking, have been
m~nllf~ctured from metal blanks by slfil~ g. In s~ ing, a sheet-like blank is
attached to a rotating arbor so that the irmer bottom of the produced pan is placed
~g~in~t the supporting surface in the arbor, after which the sides of the pan are
formed by bending the edges of the blank against the sides of the arbor which serves
15 as a mould, by using a tnrnin~ tool.
One disadvantage of s~ i,,g in the m~mlf~cture of frying pans is that the said
hlrnin~ of the blank into the form of a pan only provides one stage in a multi-phase,
time-con~llming m~nnf~cturing process. The finichin~ of the upper edge of the pan
20 and the outer edge of the pan's bottom are carried out by ~lrnin~ in dirrc~cllL stages,
and the p~ ...;..g of the bottom and the sides of the pan is carried out either by
chi~ lg with a turn lathe or by cold working. The grease pockets at the inner
bottom of the pan, for example, are formed by compression. In the serial production
of the pans, about 3 minutes in total are spent for the said procedures.
The purpose of the invention is to provide a new solution for the m~nllf~cture of
cooking pots and pans, especially frying pans, but also saucepans and kettles, which
is simpler than the known s~ g techniques. The invention is characterised in that
the pot is manufactured by roll forming by using a lower tool that rotates around its
30 axis and the form face of which is designed so that it corresponds to the outer face
of the produced pot, and an upper tool that rotates around its own, separate axis, the
profile of the upper tool surface corresponding to the inner surface that is formed to
the pot, the m~nnf~cture being carried out by placing the blank on the form face of
the lower tool and by m~kin~ the tools rotate so that the blank is rotated along with
35 the lower tool and the surface of the upper tool is in linear roll contact with the
blank, whereby the metal is reshaped in the slot between the tools, spreading out
into the desired form of the pot.
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WO 96/33030 PCI/1il96100213
Roll forming is a cold-moulding process based on malleability of metal, in whichthe forming tool that rolls on the blank forms and spreads the metal in a way that
could be compared with dough kne~t1ing Consequently, roll forming is
characterised in that the blank is expanded on the area which is formed, while its
5 material thickness is decreased. An advantage, as compared with the known
spim~illg, is that the blank can be given a form that corresponds to the form faces of
the tools in a single step of operation, which makes the process faster than before;
the estimated forming time in series production is less than one mimlte, it onlyrequires one m~chine tool which indicates space-saving and, unlike turning with a
10 lathe, no waste is produced. Furthermore, the material thickness of the pot produced
by roll forming is easy to adjust in dirîelent points in the pot, resulting in material
saving and reduction in the weight of the pot. For the attachment of the frying pan
handle, for example, the point of attachment of the handle is provided with a
sufficient material thickness while the pan in the areas surrounding the point in
15 question can be thinner.
In roll forming, the axis of the upper tool t~hat is in linear contact with the blank, is
preferably inclined relative to the lower tool, and the forming is carried out in the
radial slot between the tools, whereby the edge of the blank is moved outwards
20 during the forming. The blank may consist of a straight, sheet-like metal body the
form of which more or less corresponds to the bottom of the vessel to be
m~nllf~ctured, such as a frying pan, for example, whereby the sides of the vessel are
not created until during the forming with the blank spreading outwards at its edges
between the tools. However, the shape of the blank is not cri~ical with respect to the
25 method and thus the blank does not necessarily have to be either round, of the same
diameter, or even straight. In every case, the vessel will find a desired form during
the forming process.
According to an advantageous embodiment of the invention, the inner and/or outer30 surfaces of the manufactured vessel are patterned in connection with the rollforming by using protrusions and/or recesses in the form face of the lower tool
and/or on the roll surface of the upper tool. Consequently, the desired patterns are
provided directly in the roll forming process and not in separate turning or
compression stages as in the present manufacturing techniques. Roll forming does35 not set any limit~hons on the p~U~ illg oiF the outer surface of the vessel because
the blank remains in place on the form face of t~he lower tool during the forming,
completely conforming to its shapes. Annular protrusions and recesses can be
formed on the inner surface of the vessel without restrictions by using
CA 02221~83 1997-10-17
WO 96/33030 PCT/FI96/00213
corresponding figures on the surface of the upper tool. Regarding other types ofpaL~ g, the synchronisation of the movements of the tool roll surface and the
blank surface on the lower tool must be ensured by dividing the surfaces in suitable
sectors, for example, so that the corresponding patterns of the surfaces meet
repeatedly during the forming process. The conical roll surface of the suitably
inclined upper tool can consist of, for example, five sectors with identical F~ttern~
which mould the six corresponding sectors that constitute the round surface of the
blank and which can be patterned in accordance with the patterns on the upper tool
surface. Other synchronisation between the blank and the upper tool roll surface,
and the tilt angles of the upper tool axis required by them are equally viable and
obvious to those skilled in the art. The suggested design of the inner surface of the
vessel is particularly viable when grease pockets are formed on the bottom of the
frying pan.
In roll forming, the lower tool can be rotated by a motor, whereby the blank that is
being formed remains in place on the form face of the lower tool under the
infln~nce of friction, and the upper tool that is provided with bearings that allow
free rotation and which carries out the roll forming, can be made to rotate along
with the blank and the lower tool by the influence of friction.
The equipment according to the invention for the manufacture of a heated cookingvessel by the above-described roll forming techniques is characterised in comprising
a lower tool that rotates around its own axis, the form face of the lower tool having
been shaped to correspond to the outer surface of the vessel to be m~nllf~ctured; and
an upper tool rotated around its axis and inclined with respect to the lower tool, the
surface of the upper tool having a profile that corresponds to the inner surface of the
m~mlf~ctured vessel, and the tools can be placed against one another so that a vessel
is formed from the metal blank in the radial slot between the lower tool and theupper tool that rolls with respect to the lower tool.
An embodiment of the equipment well-suited for the manufacture of fiying pans inr particular is characterised in that the form face of the lower tool comprises a
horizontal centre that corresponds to the bottom of the m~nllfActured pan, and arising edging that corresponds to the outer side of the manufactured pan, and that
the roll surface of the upper tool consists of two parallel, conical surfaces which
form the inner bottom and the sides of the pan.
- - -
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WO 96133030 PCT11il96/00213
The equipment according to the invention may preferably consist of replaceable
modules, whereby the equipment can be used to m~nllf~cture Lrre~ t size and
shape frying pans and other similar cooking vessels by replacing some parts.
5 In the following, the invention is described in detail with the aid of examples and
with reference to the appended drawings in which:
Fig. 1 presents the lower and upper tools of the roll forming equipment and the
metal blank placed on the form face of the lower tool,
10 Fig. 2 presents roll forming in which the blank is being spread outwards in the slot
between the tools,
Fig. 3 presents the end result of the forming phase in which the blank has been
formed into the form of a frying pan,
Fig. 4 is a top view of a finished frying pan provided with a handle, the bottom of
15 which is provided with nodular protrusions provided by the roll forming, and
Fig. 5 presents the roll forming equipment according to another embodiment in the
starting phase of the forming process.
Figs. 1 to 3 present diL[el~ stages of the manufacture of frying pan by roll forming
20 from an essentially round, sheet-like metal blank 1 which can be of, for example,
~1.. ;.. ;.. or stainless steel. The roll fornning equipment consists of lower tool 3
that rotates around its axis 2 and of upper tool 5 that rotates around its axis 4. Axis 4
of upper tool 5 is inclined in angle A relative to axis 2 of lower tool 3 (Fig. 3).
Lower tool 3 comprises a form face the shape of which corresponds to the outer
25 surface of the m~nllf~ctured frying pan, comprising horizontal centre 6 that
corresponds to the bottom of the pan, and a rising edge 7 that corresponds to the
outer sides of the pan. Said centre 6 of the form face is part of ejector pin 8 that
moves in the direction of axis 2 included in lower tool 3, the ejector pin being used
to remove the completed pan from the equipment to conclude the forming. Upper
30 tool 5 comprises a roll surface that forms blank 1 into a pan, the roll surface
consisting of two parallel conical surfaces 9, 10 which together provide a profile
that corresponds to the inner bottom 14 and sides 17 of the pan (cf. Fig. 4).
Upon placing blank 1 on form face 6 at the beginning of the forming process, lower
35 tool 3 is made to rotate around its axis 2 by using a motor (not shown), whereby the
blank rotates along with the lower tool under the influence of friction. Thereafter,
upper tool 5, provided with a bearing that allows free rotation, is lowered against
the surface of blank 1, whereby the movement of the blank makes it rotate around
CA 02221~83 1997-10-17
WO 9f '33~30 PcT/~ 2l3
s
its axis 4 so that the upper tool rolls on the blank in radial linear contact with its
surface. Consequently, the roll forming begins to form blank 1, as though in dough
kneading, reshaping it in a malleable m~nner, resulting in the blank beginning to
spread radially outwards in slot 11 between the tools (Fig. 2). The edges of the5 originally straight blank 1 are thus formed into the rising sides of the pan.
Simultaneously, the outer surface of the pan is formed so that a hardecker-type
bottom is formed into the pan. In the concluding stage of the roll forming according
to Fig. 3, the metal material of the blank has filled slot 11 between the lower and
upper tools completely, and has thus reached the final shape of frying pan 12
defined by tool surfaces 6, 7, 9, 10. Finally, upper tool 5 is removed and the
completed pan 12 is lifted from the form face of the lower tool by a linear
movement of ejector pin 8. To finish pan 12 to provide the final product, only
handle 13 (Fig. 4) must be attached after this.
15 The above-described roll forming process enables the outer and inner surfaces of the
m~m~f~ctured frying pan 12 to be provided with patterns or marks consisting of
protrusions and/or recesses, in cormection with the roll forming. The pall~lllillg of
the outer surface of the pan is carried out with the aid of protrusions and recesses
corresponding to the p~1ttorn~ made on form face 6, 7 of lower tool 3. Blank I that is
20 stationary with respect to the form face conforms perfectl~ to the figures of the form
face in the roll forming. It is possible to pattern the inner surface of the pan,
correspondingly, with the aid of protrusions and recesses made on conical surfaces
9, 10 of upper tool 5. Inner bottom 14 of pan 12 presented in Fig 4 is provided with
a pattern consisting of projecting nodules 15 which can be created by using the
25 corresponding recesses on conical surface 9 that begins from the tip of upper tool 5.
Bottom 14 of the pan according to Fig. 4 can be divided in six identical sectors the
limits of which are indicated by dashed lines 16 in the figure. This kind of bottom is
created in roll forming with tool 5 whose conical surface 9 consists of four or five
corresponding sectors, whereby the surfaces are in continuous synchronisation with
30 one another with respect to the patterning during the roll forming.
Fig. 5 presents an ~lt.orn~hve embodiment of the invention in which, unlike the one
presented in Figs. 1-3, arm 2 of ejector pin 8, which constitutes the rotation axis of
lower tool 3, is provided with spring 18 that is loaded against upper tool 5 during
35 the forming process. The starting point of the process is that ejector pin 8 is slightly
above form face 7 of lower tool 3, pushed by spring 18, and blank 1 from which the
frying pans is formed is placed on the ejector pin. Upper tool 5 that is inclined with
respect to lower tool 3, comprising roll surface 9 that corresponds to form face 7 of
CA 02221~83 1997-10-17
WO ~13~' 20 PCIlli'I96100213
the lower tool is then pressed against blank 1 to the position according to Fig. 5, and
further downwards against spring 18 so that ejector pin 8 is pressed to
corresponding recess 19 in lower tool 3. The roll forming process in which blank 1
is formed into the form of a frying pan is then carried out in a manner similar to the
5 embodiment of Figs. 1-3. In this case, form face 7 of the lower tool and roll surface
9 of the upper tool are shaped so that the sides of the frying pan will be rounded.
After the forming process, upper tool 5 is lifted back to its starting position,whereby spring 18 of ejector pin 8 automatically lifts the pan in its final shape from
form face 7 of the lower tool.
It is clear to those skilled in the art that the dirrt;~ t applications of the invention
are not limited to the examples presented above but can vary within the appendedClaims. Consequently, even though only the m~mlf~cture of a frying pan is
described in the examples, to which the roll forming process is particularly well-
15 suited because of the shape of the pan, the corresponding techniques may also beused for the m~mlf~cture of a saucepan or a kettle, according to the invention. The
possible patterns of the outer and inner surfaces of the vessel may also be varied
extensively.
