JPS63172625A - Manufacture of case for clock mechanical body - Google Patents

Abstract

PURPOSE:To manufacture efficiently at a low cost a case for a clock mechanical body where a surface layer part is smooth and an inner layer part is in a foamed structure, by a method wherein when a foaming action of a foamed plastic material is controlled by casting high-pressure gas into a cavity, and the foamed plastic material is solidified only in a layer which comes into contact with the inside of the cavity, the remaining foaming action is allowed to progress by suspending feed of high-pressure gas. CONSTITUTION:A foamed plastic material which is about 60-70% of inner capacity of a cavity of a molding mold for a lower case 1 is injected into the cavity at a temperature of about 260 deg.C. Then high-pressure nitrogen gas is cast immediately into the cavity. Although the molten plastics spreads over to every corner of the cavity, a foaming action is controlled by high pressure gas. Then as a mold temperature is low, solidification of the plastics begins from the surface of the cavity. With this construction, a smooth surface layer part 10 free from swirl marks is obtained. When feed of the high-pressure gas within the cavity is suspended after the solidification has to come extent, the foaming action which has been controlled progresses, through which an inner layer part 11 becomes a foamed structure.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to manufacturing a case for a watch machine body, more specifically, a case for a watch machine body having a smooth surface layer and a foamed inner layer layer. It is about the method.

[Conventional technology] In the past, the ratio and vibration generated from the watch mechanical body were prevented from leaking to the outside! For example, in order to
As disclosed in No. 9910, a rubber body was mounted on the support column of the case to support and fix the watch mechanical body.

However, this increased the number of parts and made assembly difficult. Also, although it has the effect of absorbing vibrations, it has the disadvantage that it is not very effective in terms of proportions.

Therefore, in order to be able to effectively reduce both the ratio and vibration of the watch mechanism body with zero cases, the case for the watch mechanism body should be made with a smooth surface layer that is almost non-porous and has good vibration or acoustic properties. JP-A-48-17761 proposed a structure consisting of a spongy inner layer having excellent absorbency.

[Problems to be solved by the invention] However, this uses two types of plastic materials, and in reality, the surface layer and inner layer are formed separately and pasted together, or two-color molding is used. Since it needs to be formed using technology, it has had problems such as poor productivity and high manufacturing costs.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to make it possible to efficiently manufacture a case for a timepiece machine body having a smooth surface layer and a foamed inner layer layer at low cost.

[Example] Hereinafter, details of the present invention will be explained along with examples.

FIG. 1 shows a lower case 1 as a watch machine body case manufactured by the method of the present invention, in which a battery holder part 2 and a machine body accommodating part 3 are separated by a partition wall 4. A support column 5°6 and bearings 7, 8 for the watch mechanism (not shown) are integrally formed on the inner bottom surface of the mechanism body accommodating portion 3, and a pointer shaft (not shown) is integrally formed therein. A penetrating central hole 9 is provided. Incidentally, a first case (not shown) is attached to the lower case.

Although the lower case 1 is no different from the conventional one in appearance, it has the following special internal structure.

That is, the lower case 1 is made of a foamed plastic material such as polypherine ether, and the surface layer 10 has a smooth appearance without swirl marks (foam patterns), but the inner layer 11 has a smooth appearance without swirl marks (foam patterns). has a foam structure.

Such a double structure can be easily obtained as follows.

A foamed plastic material such as polypherine ether in an amount of about 60 to 70% of its internal volume is injected into the cavity of a molding die (not shown) for the lower case 1 at around 260°C, and then immediately High pressure (approximately 100
0 N/cj) nitrogen gas is injected. The molten plastic then spreads to every corner of the cavity, but the foaming action is suppressed by the high pressure gas. Since the mold temperature is low, the plastic begins to solidify from the cavity surface. This creates a smooth surface layer 1 without swirl marks.
0 is obtained. When the supply of high-pressure gas inside the cavity is stopped after solidification has progressed to a certain extent, the foaming action that has been suppressed until now progresses, and as a result, the inner layer portion 11 takes on a foamed structure.

According to the case with the internal double-walled structure as described above, since the surface layer 10 is smooth, there is no problem with the bearing properties of gears, etc., and the foamed structure of the inner layer 11 allows it to be easily removed from the watch mechanical body. Can absorb the rate and vibration that occurs. Also,
According to this case, there is no need to mount a rubber body or the like as in the conventional case, so assembly becomes easy.

[Effects of the Invention] According to the manufacturing method of the present invention described in detail above, a case for a watch machine body having a smooth surface layer and a foamed inner layer can be manufactured continuously using a single foamed plastic material. Therefore, productivity is excellent and cost reduction is achieved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a lower case as a watch mechanical case formed by the manufacturing method of the present invention, and FIG. 2 is an enlarged sectional view showing its internal sectional structure. 1...Case for watch mechanical body (lower case), 10φ...
Surface layer part, 11... Inner layer part. that's all

Claims (1)

[Claims] Injecting 60 to 70% of the internal volume of a foamed plastic material in a molten state into the cavity of a molding die having a predetermined cavity, and immediately injecting high-pressure gas into the cavity to expand the foam. The foaming action of the plastic material is suppressed, and when the foamed plastic material solidifies only in the layer contacting the inner surface of the cavity under this foaming action suppressed state, the supply of the high pressure gas is stopped, thereby causing the foamed plastic material to A method for manufacturing a case for a watch machine body having a smooth surface layer and a foamed inner layer layer, the method comprising: allowing the remaining foaming action to proceed.