Patent EA-004482-B1 (EA)
Title: Process for making a toothbrush
Inventor: MULLER WOLF-DIETER
IPC: B29K21/00
Filed: 2001-08-13
Abstract: 1. A process for making a toothbrush characterised by: providing a stack mould assembly (1,2,3,4) comprising a stack of at least three mould blocks arranged for use along a longitudinal stack axis (A-A), comprising two end mould blocks (3,4), and an intermediate mould block (1,2) longitudinally between the two end mould blocks (3,4); there being at least one part mould cavity (31,41) in a surface of one end mould block (3,4) which mates with a part mould cavity (11A, 21) in a facing surface (1A, 1B, 2A, 2B) of the intermediate mould block (1,2) when the one end mould block (3,4) and the intermediate mould block (1,2) are brought together to define a first cavity (11A, 21,31) into which a first moulding material may be injected; there being at least one part mould cavity (41) in a surface of the other end mould block (4) which mates with a part mould cavity (11A, 21) in the intermediate mould block (1,2) when the said other end mould block (4) and the intermediate mould block (4) are brought together to define a second cavity (41,51) into which a second moulding material may be injected; bringing the one end mould block (3) and the intermediate mould block (1,2) together to thereby form the first cavity (11A, 21); injecting a first moulding material being a plastic material suitable for forming the hard plastic part (105) of a toothbrush head and handle into said first cavity (11A, 41); at least partly enclosing the so formed hard plastic part (105) in a second cavity (41,51) formed by bringing together the other end mould block (4) and the intermediate mould block (1,2), and a second moulding material, different to the first plastic material and suitable for forming part of a toothbrush head and/or handle is injected therein. 2. A process according to claim 1 characterised in that the so formed hard plastic part (105) is transferred to the part mould cavity (41) in the other end mould block by retaining at least part of the so formed hard plastic part (105) in the part mould cavity (11A) in the intermediate mould block (1,2) and rotating the intermediate mould block (1,2) so that the surface (1A) of the intermediate mould block (1,2) in which is the part mould cavity faces the surface (4A) of the said other end mould block (4) in which is the part mould cavity (41). 3. A process according to claim 1 or 2 characterised by: providing an injection mould assembly (1,2,3,4) comprising: first mould block (1) having at least two first part mould cavities(11A) therein for forming part of a toothbrush head therein, at least one such first part mould cavity (11A) being respectively in each of two opposite-facing surfaces (1A, 1B) of the first mould block (1); a second mould block (2) having at least one second part mould cavity (21) therein for forming part of a toothbrush handle therein, the first (11A) and second (21) part mould cavities capable of mating together to form a part mould cavity (11A, 21) defining part of the head and handle of a toothbrush to be formed therein; a third mould block (3) having at least one third part mould cavity (31) therein for forming part of a toothbrush therein, the third part mould cavity (31) capable of mating together with the first and second part mould cavities (11A, 21) to form a part mould cavity(11A, 21,31) defining part of the head and handle of a toothbrush to be formed therein; a fourth mould block (4) having at least one fourth part mould cavity (41) therein for forming part of a toothbrush, the fourth part mould cavity (41) and first part mould cavity(11A) being capable of mating together to form a part mould cavity (11A, 41) defining part of the head and handle of a toothbrush to be formed therein; the said first (1), second (2), third (3) and fourth (4) mould blocks being arranged in a stack mould assembly such that the first (1) and second (2) mould blocks are intermediate in a stack between the said third (3) and fourth (4) mould blocks; a fifth part mould cavity(51) being provided in a mould block (2), the fifth part mould cavity (51) capable of mating together with the first and fourth part mould cavities (11A, 41) to form a part mould cavity (41,51) defining part of the head and handle of a toothbrush to be formed therein, the process comprising the steps of: (I) bringing the first (1), second (2) and third (3) mould blocks together so that the respective first (11A), second (21) and third (31) part mould cavities therein mate together to form a mould cavity (11A, 21,31) for forming part of a toothbrush head and handle therein; (II) injecting a first fluid plastic material into the so-formed mould cavity (11A, 21,31) to thereby form part of a toothbrush head and handle (105) therein, and allowing the first material to harden; (III) separating the third mould block (3) from the assembly of first (1) and second (2) mould blocks whilst retaining the part toothbrush (105) by its head (102) in a first part mould cavity (11A) of the first mould block (1); (IV) separating the second mould block (2) from the first mould block (1) whilst leaving the part toothbrush (105) retained by its head (102) in a first part mould cavity (11A) of the first mould block (1); (V) bringing the first mould block (1) and fourth mould block (4) together so as to enclose the so-formed toothbrush head (102) retained in the first part mould cavity (1) in a cavity (11A, 41) formed between the first mould block (1) and the fourth part mould cavity (41) in the fourth mould block (4); (VI) with the so-formed toothbrush head (102) retained in the cavity (11A, 51) between the first (1) and fourth (4) mould blocks, enclosing the so-formed part toothbrush handle (105) in a handle mould cavity (41,51) formed by mating a fourth mould cavity (41) in the fourth mould block (4) with a fifth mould(51) cavity in a mould block (2) brought together with the fourth mould block (4), (VII) injecting a second fluid material into the so-formed handle mould cavity (41,51) and allowing the second material to harden, so as to form parts of the toothbrush (106) made of the second material; (VIII) removing the part formed toothbrush (105) from the mould block assembly (1,2,4). 4. A process according to claim 3 characterised in that the third part mould cavity (31) in the third mould block (3) defines part of-a toothbrush head (102) and handle (103). 5. A process according to claim 3 or 4 characterised in that the second mould block (2) has the fifth part mould cavity (51) therein in a surface (2B) opposite that (2A) in which the second part mould cavity (21) is present. 6. A process according to any one of claims 3 or 4 characterised by a fifth mould block having the fifth part mould cavity therein. 7. A process according to any one of claims 3 to 6 characterised in that step (V) involves a rotation operation in which the first mould block (1), with the part formed toothbrush (105) retained therein, is rotated, suitably through180 so that its first part mould cavity (ies) (11A) in which the part formed toothbrush head (102) is retained faces the fourth mould block (4). 8. A process according to any one of claims 3 to 7 characterised in that the first mould block(1B) has a surface opposite to that in which the first part mould cavity (11A) is present, and in this opposite surface (1B) there is one or more further first part mould cavity (11B). 9. A process according to claim 8 characterised in that the further first part mould cavity (11B) is identical to the first part mould cavity (11A). 10. A process according to claim 8 or 9 characterised in that step (VI) involves an operation in which at least one said empty further first part mould cavity (11B) is brought together with an empty second part mould cavity (21) in a second mould block (2). 11. A process according to any one of claims 3 to 10 characterised in that steps (I) and (VI) are performed substantially simultaneously. 12. A process according to any one of claims 3 to 11 characterised in that injection steps (II) and (VII) are performed substantially simultaneously using first (11A) and further first (11B) part mould cavities on opposite sides (1A, 1B) of the first mould block (1). 13. A process according to any one of claims 3 to 12 characterised in that in step (III) the toothbrush head (102) is retained in the first part mould cavity (11A) by bristle pins (13) projecting into the first part mould cavity (11A). 14. A process according to any one of the preceding claims characterised in that the second injected fluid material is a thermoplastic elastomer material. 15. A stack mould assembly (1,2,3,4) comprising a stack of at least three mould blocks arranged for use along a longitudinal stack axis (A-A), comprising two end mould blocks (3,4), and an intermediate mould block (1,2) longitudinally between the two end mould blocks (3,4); there being at least one part mould cavity (31,41) in a surface of one end mould block (3,4) which can mate with a part mould cavity (11A, 21) in a facing surface (1A, 1B, 2A, 2B) of the intermediate mould block (1,2) when the one end mould block (3,4) and the intermediate mould block (1,2) are brought together to define a first cavity (11A, 21,31) defining the shape of part of a toothbrush, and into which a first moulding material may be injected; there being at least one part mould cavity (41) in a surface of the other end mould block (4) which can mate with a part mould cavity (11A, 21) in the intermediate mould block (1,2) when the said other end mould block (4) and the intermediate mould block (4) are brought together to define a second cavity (41,51) defining the shape of part of a toothbrush, and into which a second moulding material may be injected. 16. A stack mould assembly (1,2,3,4) comprising; a first mould block (1) having at least two first part mould cavities(11A) therein for forming part of a toothbrush head therein, at least one such first part mould cavity (11A) being respectively in each of two opposite-facing sur