Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Shaping against forming surface
Patent
1982-12-13
1985-02-05
Lowe, James
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Shaping against forming surface
249 56, 26432812, 425542, B29C 100
Patent
active
044977662
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of and a means for the manufacture of a wheel construction of plastic material for vehicles or the like, which comprises a number of spokes together with a hub and a rim forming an integrated unit.
In previously known methods for the manufacture of similar wheel constructions of plastic material the gates of the mould for the injection of plastic material have been designed in such a manner that the points, where the material flows are joined, the fusing line, will be located at points, which adversely affect the strength of the wheel construction, by way of example on the rim between two spokes. The strength of the wheel construction has thereby been quite substantially affected in a negative manner, as such portions of such a wheel made of plastic material and subjected to a load in zones where the material flow of the plastic shows discrepances, run the risk of suffering breakages in said zones.
It is a principal object of the invention to provide a method for the manufacture of a wheel construction of plastic material of the type mentioned above, in which the material flows, the fusing lines, will be located at such points of the wheel construction, that the strength properties of the construction are essentially improved compared with such wheel constructions of the prior art.
Said object is obtained by means of a method according to the present invention, which is substantially characterized by injecting the plastic material in a mould, the cavity of which has a shape that corresponds to the one of the desired wheeel construction, the design of the wheel being chosen to comprise an even number of spokes and the gates being located at such points near to every second one of the spoke portions of said mould that the zones, where the flows of material join each other, will be located near to the points, where the spokes, free from inlets, blend into the rim.
The invention is described in the following, reference being made to the accompanying drawing, in which
FIG. 1 is a schematic view of a mould suitable for use in connection with a method according to the present invention.
FIGS. 2a-e are schematical views showing different phases of the flow of the plastic material in a mould in connection with a method according to the present invention, and
FIG. 3 is a view of the manner, in which a moulded wheel construction of plastic material is taken out of the mould, in which it has been moulded.
A mould 1 suitable to be used in connection with a method for the manufacture of such a wheel construction, that is related to the present invention, can suitably be of the kind, which is illustrated in FIG. 1 of the drawing. Such a mould that serves as an example only comprises a lower part 1A and an upper part 1B, which are designed to be put together in a tight fit and to be separated from each other in order to permit the extraction of a moulded wheel construction 2, as is shown in FIG. 3. The mould 1 can also be designed in such a manner that it can be split up in more components than the two illustrated parts. The lower part can for example be designed in such a manner that it can be split across the plane of rotation of the same and of the wheel in order to facilitate the extraction of a moulded wheel from the mould, and especially, if the wheel has a complicated profile with undercut portions etc. making it impossible to extract such a wheel from the mould in the manner illustrated in FIG. 3.
The mould 1 is provided with a suitable number of injection inlets. Said inlets can then to advantage be arranged as connecting inlets 3, 4, 5 and 6 of the lid of the mould 1B, as is shown in FIGS. 1 and 3.
The lower portion 1A of the mould 1 exhibits a cavity 7, which together with the lid 1B defines a form that corresponds to the desired wheel construction. A pin 8 for the hub and a number of sector-shaped mould elements 9 which are distributed around said pin 8, are received in a circular recess, which defines the periphery of the peripherical form of the desired wheel constru
REFERENCES:
patent: 1510231 (1924-09-01), Keller
patent: 2043584 (1936-06-01), Husted
patent: 2199144 (1940-04-01), Tegarty
"Weld-line Fracture in Molded Parts", Hagerman, Plastics Engineering, Oct. 1973, pp. 67-69.
Olsson Jan G.
Samuelsson Lars Erik
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