Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – To produce composite – plural part or multilayered article
Reexamination Certificate
1999-08-12
2002-10-15
Chin, Randall E. (Department: 1744)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
To produce composite, plural part or multilayered article
C264S255000, C264S273000, C264S279000, C300S021000, C015S143100, C015S167100
Reexamination Certificate
active
06464920
ABSTRACT:
This invention relates to an injection moulding process for making articles out of two injectable components, particularly being respectively a plastics material and an elastomeric polymer material. In particular the invention relates to an injection moulding process for making toothbrush bodies, in which a first component is a plastics material and a second component is an elastomeric polymer.
The invention also relates to a toothbrush made using the process of the invention and to moulds and machines for carrying out the process.
Toothbrush bodies, i.e. comprising a grip handle and a head with generally a neck part between all arranged along a longitudinal toothbrush axis, which are made of two components being a hard plastic and a softer elastomer, are known e.g. from EP 0336641A, WO 92/17092 WO 92/17093, and U.S. Pat. No. 5,054,154 among others. Often in such toothbrushes the elastomer is present in two or more places on the toothbrush body, e.g. on the grip handle to enhance grip, and in the neck region to modify flexibility. The elastomer may also be present in other places for decoration.
Usually such toothbrushes are made by firstly moulding the plastic parts of the toothbrush then injecting in the fluid elastomer under conditions which cause the plastic and elastomer to bond. Often when the elastomer is present in two or more places on the toothbrush body these places are linked by a moulding channel so that injection of fluid elastomer at only one injection point into the pre-formed plastic parts of the body, and the fluid elastomer is able to flow along the moulding channels from one part to another. When the elastomer is present in numerous parts separated from one another the presence of a corresponding number of moulding channels to link them is an untidy solution and can lead to weakness of the structure. A self-evident alternative solution to the problem is disclosed in WO 94/05183 in which a number of separate injection points corresponding to the number of places where the elastomer is to be present is used. If the elastomer is present in numerous separated places this can lead to a complex arrangement of injection channels, with consequent difficulty and complexity in making the moulds and ancillary injection moulding machinery.
A further problem is encountered in that if the toothbrush is to have a bulky handle, e.g. in the shape of a character such as an animal, as used for children's toothbrushes, the bulk also assisting a child's small hand to grip the handle, a large amount of moulding plastic may be necessary. This adds to weight, cost and use of excessive quantities of materials.
It is an object of this invention to provide an alternative injection moulding process which in part at least overcomes these problems. Other objects and advantages of the invention will be apparent from the following account.
According to this invention a process for making a moulded article comprises the steps of:
in a first mould cavity, having a first internal core within the cavity and distanced from the inner wall surface of the cavity, and having one or more members which extend between the said inner wall and the core, forming by injection moulding of a plastics material a body part having an internal body cavity corresponding substantially to the shape of the first core and having apertures passing through the body from the said body cavity to the outer surface of the body corresponding substantially to the shape and position of the member(s);
separating the formed body from the first mould cavity and removing the first core from the body cavity;
enclosing the formed body in a second mould cavity, and inserting a second internal core into the body cavity, between the second core and the inner surface of the body cavity there being one or more channels in communication with the said apertures when the second core is in place in the body cavity;
injecting a fluid mouldable settable material into the said channels such that the material flows along the channels and into the apertures and then sets;
separating the so-formed article from the second mould cavity and the second core from the body cavity.
Preferred embodiments of the process of the invention will now be described.
The moulded article made by the process is preferably a toothbrush body, i.e. comprising a grip handle and a head with generally a neck part between all arranged along a longitudinal toothbrush axis, with the body cavity within the grip handle. The process of the invention enables the handle to be made bulky but hollow and therefore light in weight. The grip handle may for example be in an attractive shape such as the shape of a character such as a representation of an animal character or cartoon character, so that the toothbrush handle is attractive to children, and preferably to adults as well.
When the moulded article is a toothbrush body as defined above the grip handle is generally a structure elongated along the direction of the toothbrush axis. In this case the body cavity is suitably also an elongate cavity generally following the elongate shape of the body, and the internal cores will consequently be structures elongated along the direction of the toothbrush axis.
The first and second mould cavities are defined in first and second injection moulds which can be provided by known technologies. Injection moulds for toothbrushes, whether pilot or production moulds, the process of the invention being suitable for both, comprise parts, usually two mating halves, made of machined hardened metal, usually steel, which must fit together with great precision and which when fitted together enclose an accurately dimensioned internal cavity which defines the shape of the final toothbrush product, and into which is injected the material of the toothbrush. The crucial part of such moulds are their internal cavity, the features of which are dictated by the function of defining the shape of the final toothbrush product. The mould cavities within such moulds are normally formed by a process of spark erosion otherwise known as electrical discharge machining, which is for example practiced by such European toothbrush mould manufacturers as Anton Zahoransky GmbH (DE) and Machines Boucherie NV (BE). Such moulds also necessarily incorporate ancillary operative and constructional features, for example a mould frame, e.g. comprising injection points for plastic and elastomer materials, to enable the mould to match a standard injection moulding machine as used by a toothbrush manufacturer.
The first mould cavity and the second mould cavity are preferably made in a multi-part, e.g. two-part mould construction, each part defining a respective part of the mould cavity thereby allowing the mould cavity to be opened to allow the body to be separated from the mould. Moulds of this general type, of multi-part construction, for use in injection moulding processes for the manufacture of toothbrushes and similar moulded articles, and in which the article is formed by injection moulding into a mould cavity within the mould are well known in the art. Typically each part of such a two-part mould may comprise a block of the metal having cut into it a part mould cavity, and when the two blocks are put together the two part cavities define the entire mould cavity.
Toothbrush moulds generally are of such two part construction, each part defining a part mould cavity which corresponds to the entire mould cavity split generally along the toothbrush axis. In such a mould the first and second mould cavities may have an open end at the end remote from the toothbrush head, and through which the mould cores may extend. In such a construction the mould cores may taper along the length of the toothbrush grip handle, being wider at the end remotest from the toothbrush head. This enables the mould core to be easily withdrawn from the body cavity.
The one or more members are preferably located on the inner wall surface of the first mould cavity, and are preferably made integrally with the mould, enabling the members to be easily remov
Chin Randall E.
Kinzig Charles M.
SmithKline Beecham Consumer Healthcare GmbH
Stein-Fernandez Nora
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