GB1584961A - Shaping mould - Google Patents

Description

(54) SHAPING MOLD (71) We, POLYPLASTICS CO. LTD., a Japanese body corporate, of 30, 2-chome, Azuchimachi, Higashi-ku, Osaka-shi, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: This device relates to a mold used for so-called outsert molding (see below).

Heretofore, parts having various functional or operating elements on a substrate or base such as for example a recorder chassis have been manufactured by complicated steps such as sheet metal processing, assembling, etc.

Recently, however, with progress in the application of techniques of the so-called engineering plastics possessed of the various desirable properties, such as strength, frictional resistance, etc., required of the various operating elements, it has become common in the art to manufacture such parts according to a specific insert molding method in which the substrate alone is first made from a hard material such as metal and then the various functional or operating elements made from a synthetic resin are formed thereon integrally by a single molding operation. This molding method is called "outsert" molding as a resin member is inserted into a metal substrate in a way quite contrary to that of normal insert molding, wherein a metal member is inserted in a resin substrate.

This "outsert" molding is briefly described hereinbelow with reference to the accompanying drawings, particularly with reference to Figs. 1 to 3 which show the basic relationship between the mold, substrate and resin used in such outsert molding: Figures 1 to 4 relate to the prior art.

Figure 1 is a sectional view of a conventional mold shown in an open state; Figure 2 is a sectional view of the mold of Fig. 1 as it is in a clamped state; Figure 3 is a perspective view of a part molded from the mold shown in Figs. 1 and 2; Figure 4 is a sectional view of a conventional mold having templates provided with a projection in the mold cavity; Figure 5 is a sectional view of a mold according to the present invention, said mold being shown in an open state; Figure 6 is a sectional view of the mold of Fig. 5 as it is in a clamped state; and Figures 7 to 12 are drawings showing various modifications of the mold according to the present invention.

Fig. 1 is a sectional view of a mold, shown in an open state, comprising two templates A and B, a pair of cavities D and E formed therein, a runner C for introducing resin into said cavities, and a substrate F, such as a metal sheet.

Fig. 2 is a similar sectional view showing the mold of Fig. 1 as observed when the mold is clamped.

Fig. 3 is a perspective view of a part molded from this mold, where G indicates an operating element shaped on the substrate F.

When putting such mold to practical use, cavities D and E are formed in conformity to the .desired configurations of the respective operating elements to be shaped, and in most cases, sets of cavities D and E are provided, one of the sets being provided with the runner C and all the sets being connected to each other by sub-runners provided on or in the substrates.

Although not shown in the drawings, a guide pin or pins may be used, when so desired, for positioning and securing in position the metal sheet F. Usually, two or more such pins are used, but in the case where the pin configuration is of low symmetry, use of only one such pin may suffice. The end of each such pin is tapered for facilitating fit ment thereof in position. Such pins are also designed to be replaceable because of rapid wear caused by contact with the substrate.

In some applications, there are employed templates oa a complicated structure such as those usually used in a two-plate mold or a three-plate mold. However, the templates of such structure have some serious defects such as mentioned below.

For instance, in injection molding where resin is introduced under high pressure, the template must be pressed by a high pressure to maintain proper clamping against the resin-introduced pressure. This may cause deformation of the substrate sufficient to make it unable to maintain its required precision.

This becomes a serious problem particularly when the substrate used is made of a relatively soft material such as aluminium.

Also, if clamping should be made with the substrate mounted in an incorrect position as a result of a misoperation, serious damage to the mold may result particularly when the mold is of a conventional type using a template or templates provided with a projection G in the cavity as shown in Fig. 4.

The present invention is intended to provide an improved mold structure which is capable of precluding or reducing occurrence of such trouble and also allows obtainment of high-precision molded articles with high reliability and safety.

More specifically there is provided according to the present invention a shaping mold having molding templates providing a cavity for shaping members of synthetic resin on a substrate and holding the substrate partly within the cavity, wherein one or more of said templates is/are provided with a raised portion or portions at at least a part of that area of said template(s) which plays no part in shaping the synthetic resin member and exerting pressure on the substrate, said raised portions contacting on opposing template and the substrate being clamped between the templates, the space between opposing templates at the place where the substrate is clamped being equal to the greater of the following two values of thickness: the minimum allowable thickness of the substrate and the smallest thickness of the substrate resulting from variation in thickness of the substrate used; and the dimensions of the substrate being such that there is a space between the substrate and the raised portion extending completely around the substrate.

The invention includes a method of forming an article comprising a shaped synthetic resin member fixed on a substrate, which comprises clamping the substrate between the templates of a shaping mold as claimed in any one of claims 1 to 6 and supplying synthetic resin to the cavity thereof.

Embodiments of the present invention will now be described in detail in conjunction with the remainder of the accompanying drawings.

Referring to Fig. 5, there is shown the basic form of the mold according to this invention, said mold being shown in an open state. In the drawing, a designates a raised portion of the lower template having a height t i and provided at a position outside of the substrate, F.

Fig. 6 shows the clamped state of the mold shown in Fig. 5. As will be seen from this drawing, height t, of said raised portion a is selected so that said portion will contact the upper template in the proper clamping position. In other words, supposing that the greater of the practically allowable minimum thickness of the substrate and the minimum thickness presumable from variations of thickness of the substrate in Fig. 5 is t2, then t, is equal tot2.

In using the mold of Figs. 5 and 6 for a molding operation wherein the substrate has not been duly set in position as a result of a misoperation, then clamping is ended at the position of Fig. 6 where the raised portion a is contacted with the other template, thus inbibiting any further movement of the said portion a. Accordingly, the projection b on the mold is also checked against any further movement from the position of Fig. 6, thus eliminating any risk of damage to the mold.

For the same reason, no excessive force is applied to the substrate to keep it free of any undesirable deformation.

On the other hand, where the situation has changed to t2 > t1 owing to variations in the substrate, then since the entire clamping pressure is loaded on the substrate until the position shown in Fig. 6 is reached, the substrate is deformed. Clamping is ended at the time when t2 becomes equal to t l. This proves to be rather advantageous for improvement of precision particularly when using a substrate made of aluminium or like material.

When using a substrate where t2 < t1, a space is left between the substrate and the mold after completion of clamping, so that resin flows into such space to give rise to thick flashes. Such moldings can be easily distinguished from the other moldings.

Thus, it becomes very easy to detect the products (defective moldings) using a substrate which is too thin to be acceptable in practical use. Generally, detection of such defective moldings is very difficult, resulting in formation of many defective or nonconforming end products. However, when molding is performed by using a mold of this invention, it is possible to detect the defective moldings immediately after completion of molding. Clearly, this is of great economical significance.

While the effect of this invention has been described in application to a basic mold, it will be apparent that the configuration and number of the raised portions a can be suitably selected in accordance with the mold structure, clamping pressure and/or other factors.

Some additional embodiments are therefore shown in Figs. 7 to 12.

Fig. 7 shows an embodiment provided with four rectangular raised portions a, and Fig. 8 shows an embodiment having four round raised portions a. In the embodiment shown in Fig. 9, such raised portions a are provided on the inside of the substrate. In these drawings, letter H indicates the holes cut in the substrate F where the operating elements are to be shaped.

Fig. 10 is a sectional view of an embodi- ment where a raised portion a is provided on each of the two templates A and B, Fig. 11 is a similar view showing an embodiment where the raised portions a are provided on both of the templates A and B, and Fig. 12 is a similar sectional view of an example where recessed portions c are provided on the template A and raised portions a are provided at the corresponding position on the template B.

WHAT WE CLAIM IS: 1. A shaping mold having molding templates providing a cavity for shaping members of synthetic resin on a substrate, and holding the substrate partly within the cavity, wherein one or more of said templates is/are provided with a raised portion or portions at at least a part of that area of said template(s) which plays no part in shaping the synthetic resin member and exerting pressure on the substrate, said raised portion or portions contacting an opposing template and the substrate being clamped between the templates, the space between opposing templates at the place where the substrate is clamped being equal to the greater of the following two values of thickness: the minimum allowable thickness of the substrate and the smallest thickness of the substrate resulting from variations in thickness of the substrate used; and the dimensions of the substrate being such that there is a space between the substrate and the raised portion extending completely around the substrate.

2. A mold as claimed in claim 1 in which one of the templates also carries a projection in the mold cavity.

3. A mold as claimed in claim 1 or claim 2 in which the raised portions are arranged outside the position occupied by the substrate, during molding.

4. A mold as claimed in any one of claims 1 to 3 in which one of the templates is provided with recesses for mating with raised portions on the other template.

5. A mold as claimed in claim 1 and substantially as hereinbefore described with reference to and as illustrated in Figs. 5 and 6 of the accompanying drawings.

6: A mold as claimed in claim 5, modified substantially as hereinbefore described with reference to and as illustrated in any one of Figs. 7 to 12 of the accompanying drawings.

7. A method of forming an article com rising a shaped synthetic resin member fixed on a substrate, which comprises clamping the substrate between the templates of a shaping mold as claimed in any one of claims 1 to 6, and supplying synthetic resin to the cavity thereof.

8. A method as claimed in claim 7 in which the substrate is a metal substrate.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. While the effect of this invention has been described in application to a basic mold, it will be apparent that the configuration and number of the raised portions a can be suitably selected in accordance with the mold structure, clamping pressure and/or other factors. Some additional embodiments are therefore shown in Figs. 7 to 12. Fig. 7 shows an embodiment provided with four rectangular raised portions a, and Fig. 8 shows an embodiment having four round raised portions a. In the embodiment shown in Fig. 9, such raised portions a are provided on the inside of the substrate. In these drawings, letter H indicates the holes cut in the substrate F where the operating elements are to be shaped. Fig. 10 is a sectional view of an embodi- ment where a raised portion a is provided on each of the two templates A and B, Fig. 11 is a similar view showing an embodiment where the raised portions a are provided on both of the templates A and B, and Fig. 12 is a similar sectional view of an example where recessed portions c are provided on the template A and raised portions a are provided at the corresponding position on the template B. WHAT WE CLAIM IS:

1. A shaping mold having molding templates providing a cavity for shaping members of synthetic resin on a substrate, and holding the substrate partly within the cavity, wherein one or more of said templates is/are provided with a raised portion or portions at at least a part of that area of said template(s) which plays no part in shaping the synthetic resin member and exerting pressure on the substrate, said raised portion or portions contacting an opposing template and the substrate being clamped between the templates, the space between opposing templates at the place where the substrate is clamped being equal to the greater of the following two values of thickness: the minimum allowable thickness of the substrate and the smallest thickness of the substrate resulting from variations in thickness of the substrate used; and the dimensions of the substrate being such that there is a space between the substrate and the raised portion extending completely around the substrate.

2. A mold as claimed in claim 1 in which one of the templates also carries a projection in the mold cavity.

3. A mold as claimed in claim 1 or claim 2 in which the raised portions are arranged outside the position occupied by the substrate, during molding.

4. A mold as claimed in any one of claims 1 to 3 in which one of the templates is provided with recesses for mating with raised portions on the other template.

5. A mold as claimed in claim 1 and substantially as hereinbefore described with reference to and as illustrated in Figs. 5 and 6 of the accompanying drawings.

6: A mold as claimed in claim 5, modified substantially as hereinbefore described with reference to and as illustrated in any one of Figs. 7 to 12 of the accompanying drawings.

7. A method of forming an article com rising a shaped synthetic resin member fixed on a substrate, which comprises clamping the substrate between the templates of a shaping mold as claimed in any one of claims 1 to 6, and supplying synthetic resin to the cavity thereof.

8. A method as claimed in claim 7 in which the substrate is a metal substrate.