WO1997038840A1

WO1997038840A1 - Two-material moulding

Info

Publication number: WO1997038840A1
Application number: PCT/GB1997/001090
Authority: WO
Inventors: Louis William Sanderson
Original assignee: J & W Sanderson Limited
Priority date: 1996-04-18
Filing date: 1997-04-18
Publication date: 1997-10-23
Also published as: GB9608079D0

Abstract

A method of moulding articles, especially toothbrushes, from two materials comprises the steps of introducing a first moulding material into a mould, retracting a portion of the mould to form a cavity between the retracted portion and the first material, and introducing a second moulding material into the cavity. The invention also relates to apparatus for carrying out the method.

Description

TWO-MATERIAL MOULDING

This invention relates to the moulding of articles from two materials and is more particularly concerned with the moulding of toothbrushes from two materials.

Recently, toothbrushes have been manufactured with handles which include a grip portion of a different material from the remainder of the handle. Generally, the grip portion is formed from an additional layer of rubber or elastomeric material which enhances a user's grip on the brush when wet. Manufacture of such brushes tends to be expensive since complex robotics are needed to move the toothbrush during the manufacturing process to allow for the addition of the second material to form the grip portion. Problems may also arise with the repositioning of th« toothbrush following its movement.

It is therefore an object of the present invention to provide a method of moulding which is applicable to the manufacture of toothbrushes from two materials and which does not require the movement and repositioning of the brush by robotic equipment during manufacture.

Accordingly, the invention provides a method of moulding articles, particularly but not exclusively toothbrushes, from two materials, the method comprising the steps of introducing a first moulding material into a mould, retracting a portion of the mould to form a cavity between the retracted portion and the first material, and introducing a second moulding material into the cavity.

According to a second aspect of the invention, the invention provides moulding apparatus, particularly but not exclusively for manufacturing toothbrushes, the apparatus comprising a mould with inlets for first and second moulding materials, a movable portion which is retractable relative to the remainder of the mould to form a cavity between the retracted portion and a body moulded from the first material prior to retraction, and means for the opening the inlet for the second material when the movable portion is retracted.

Preferably, the first inlet is in the form of a gate and, for the moulding of toothbrushes, may be situated in a position which corresponds to the end of the toothbrush opposite the head.

The second inlet may be a duct or passage formed in the movable portion and opening onto the moulding surface thereof. In this case, the means for opening the second inlet may comprise a pin slidable in the duct or passage and retractable therealong to open communication between a source of the second material and the cavity formed by the retraction of the movable portion.

In one alternative, the second inlet may be formed in the remaining, fixed part of the mould, adjacent the movable portion, so that it is opened by the retraction of the movable portion itself. In another alternative, the second inlet may be in the wall of the mould opposite the movable portion and may be closed by a pin slidable in the movable portion between an advanced position in which it extends across the mould to close the inlet and a retracted position in the movable portion; in this embodiment, after moulding, the second material extends through the first material as a plug occupying the space left by the pin upon retraction and this plug conveniently serves to anchor the second material to the first material. For the manufacture of toothbrushes, the movable portion of the mould preferably corresponds to the grip portion of the handle of the toothbrush and the moulding surface of the movable portion may be profiled to form ribs, grooves or the like on the surface of the grip portion.

The natural shrinkage of the first material on cooling is taken into account in determining the distance to be moved by the movable portion: provided that the distance moved by the movable portion is greater than the natural shrinkage of the first material, the second material will contact and attach or adhere to the first material. The attachment or adhesion may be enhanced if the moulding surface of the movable portion is profiled because the ribs or grooves formed in the moulded body of the first material by the surface before retraction will enable positive keying of the second material to the first.

For the moulding of toothbrushes, two movable portions may be provided on opposite sides of the mould to produce grip portions on both sides of the handles of the brushes.

Preferably, for toothbrushes, the first material is a rigid plastics material, for example polypropylene, and the second material is rubber or an elastomeric material.

The present invention will now be described, purely by way of example, with reference to the accompanying drawings of which:

Figure 1 is a partial side view in section of a mould according to the invention in the first position;

Figure 2 is a partia.l sectional side view of the mould of Figure 1 in a second position; and

Figure 3 is a top view of a finished handle portion of a toothbrush made in the mould of Figures 1 and 2.

Referring to Figure 1 , a mould 10 for forming toothbrushes is provided with an inlet 11 for a first moulding material, a movable portion 12 which forms part of one of the sides of the mould 10, and an inlet 13 for a second moulding material, the outlet 13 being formed in the movable portion 12. The portion 12 has a surface 12A profiled with a series of transverse grooves and ribs for forming grip portions on the handles of the toothbrushes made in the mould 10 and the portion 12 is displaceable relative to the remainder of the mould between an advanced position, shown in Figure 1 , in which the surface 12A .is substantially coplanar with the corresponding side of the mould, and a retracted position.

In use, the first material, for example molten polypropylene, is introduced into the mould 10 through the inlet 11, with the movable portion 12 in its advanced position and the inlet 13 therein closed by a pin 16 or other closure means, and is allowed to harden to form a toothbrush body 20. The inlet 11 is closed after the introduction of the first material. The movable portion 12 is then retracted (Figure 2) to create between the body 20 and the surface 12A a cavity 14 of a width corresponding to che desired thickness of the grip portion to be forrred, and the pin 16 is retracted or removed from the inlet 13 to connect the inlet 13 to a source (not shown) of the second material. The second material, preferably an elastomeric material, is introduced into the cavity 14 through the inlet 13 and the inlet 13 is then closed again by the readvance of the pin 16. Sharp transverse ridges 15 at opposite ends of the surface 12A of the portion 12 form notches in the first material of the body 20 to ensure efficient adhesion of the second material to the first. The second material is allowed to cure or harden to form a grip portion 21 and the finished toothbrush handle (Figure 3) is removed from the mould. The finished handle 20 thus comprises a grip portion 21 of a different material from the body of the brush.

Claims

1. A method moulding articles, particularly but not exclusively toothbrushes, from two materials, the metho_d comprising the steps of introducing a first moulding material into a mould, retracting a portion of the mould to form a cavity between the retracted portion and the first material, and introducing a second moulding material into the cavity.

2. Moulding apparatus, particularly but not exclusively for manufacturing toothbrushes, the apparatus comprising a mould with inlets for first and second moulding materials, a movable portion which is retractable relative to the remainder of the mould to form a cavity between the retracted portion and a body moulded from the first material prior to retraction, and means for the opening of the inlet for the second material when the movable portion is retracted.

3. Apparatus according to claim 2, in which the first inlet is in the form of a gate and, for the moulding of toothbrushes, is situated in a position which corresponds to the end of the toothbrush opposite the head.

4. Apparatus according to claim 2 or claim 3, in which the second inlet comprises a duct or passage formed in the movable portion and opening onto the moulding surface thereof.

5. Apparatus according to claim 4, in which the means for opening the second inlet comprises a pin slidable in the duct or passage and retractable therealong to open communication between a source of the second material and the cavity formed by the retraction of the movable portion.

6. Apparatus according to any of claims 2 to 5, in which the second inlet is formed in the remaining, fixed part of the mould, adjacent the movable portion, so that it is opened by the retraction of the movable portion itself.

7. Apparatus according to any one of claims 2 to 5, in which the second inlet is in the wall of the mould opposite the movable portion and is closed by a pin slidable in the movable portion between an advanced position in which it extends across the mould to close th.6' inlet and a retracted position in the movable portion.

8. Apparatus according to any of claims 2 to 7 for the manufacture of toothbrushes, in which the movable portion of the mould corresponds to the grip portion of the handle of the toothbrush and the moulding surface of the movable portion is profiled to form ribs, grooves or the like on the surface of the grip portion.

9. Apparatus according to any of the claims 2 to 8 for the moulding of toothbrushes, in which two movable portions are provided on opposite sides of the mould to produce grip portions on both sides of the handles of the brushes.

10. A method according to claim 1, in which the moulding of toothbrushes, in which the first material comprises a rigid plastics material, fox example polypropylene, and the second material comprises rubber or an elastomeric material.