JPS597022A - Rotary wheel with hollow shaft and apparatus for molding the same - Google Patents

Abstract

PURPOSE:To prevent a gate mark from remaining on the outer circumferential surface of a rotary wheel, by allowing the gate mark of a molded item such as an hour hand wheel to remain only on the end surface of its hollow shaft. CONSTITUTION:A cavity 1 has liners 2, 3 on the stationary side, and liners 4, 5 on the movable side, and slide cores 6, 7 are arranged vertically movably between the liners 3, 5. The liner 2 is provided with a pin point gate 11. To make the open end surface of the hollow shaft 14 thin, part of it is cut off to expose an end surface 17 of a thick-walled section 16, and the gate 11 opened to its opposed surface. The thick-walled section 16 has such a thickness that when a synthetic resin is injected, the flow thereof is made smooth. Accordingly, the resin flows from the point where the end surface 17 of the end surface 17 is molded, and the gate mark 18 due to the excess resin of the gate projects only at this end surface.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotating wheel having a hollow shaft, such as an hour wheel and an alarm wheel, which are rotating members that are incorporated into a gear mechanism of a timepiece and come into contact with each other, and a molding device therefor. It is.

Traditionally, rotary wheels with hollow shafts (hereinafter referred to as molded products) have been injection-molded with synthetic resin, and in order to ensure a smooth flow of resin during molding, gates are molded on the outer peripheral surface of the rotary wheel, especially the shaft side, in the cavity. It is often opened in a position where

However, in the case of injection molding, excess resin from the gate adheres to the shaft side of the molded product and this protrudes as a gate mark, and sometimes resin adheres to the inner wall of the cavity. Therefore, molded products with protruding gate marks on the shaft side may not work smoothly when mating with other hour wheels, etc., may be damaged by the gate marks, or the frictional force will be large, resulting in rotational load. In addition, if resin adhered to the inner wall of the cavity, when the molded product was pulled out in the axial direction, the molded product would be stuck at the resin adhered part, causing so-called gate slippage. .

Therefore, the present invention provides a molded product that eliminates the above-mentioned drawbacks by eliminating gate marks on the molded product only on the end face of its hollow shaft, and also provides a molding device that allows the resin to flow smoothly during molding. The purpose is to

A feature of the present invention is that a portion of the hollow shaft is removed to expose a thick portion, and a gate mark is formed on the exposed end surface.

A molding apparatus according to the present invention will be explained based on the drawings to further clarify the content of the present invention. In FIG. 1, centering on the cavity 1, on one side there are inserts 2 and 3 on the fixed side,
The movable side insert 4゜5 is located on the other side, and both inserts 3
, 5, a slide core 6.7 is provided so as to be slidable in the vertical direction. Inside the insert 5 on the movable side, a protruding pin 8 and a sleeve 9 for protruding the molded product are installed.
Furthermore, a cylindrical core pin 10 can be inserted freely.

A pinpoint gate 11 is provided on the fixed side insert 2, and this gate communicates with the inside of the cavity 1.

Incidentally, in this embodiment, the cavity 1 is used to mold the hour hand wheel 12 as shown in the second figure as a molded product. The shaft 14 is the open end mj15 of the hollow shaft 14.
Since it is thin, a portion thereof is removed to expose the end surface 17 of the thick portion 16. The cavity 1 is formed by injection molding the hollow shaft 14 having such a shape, and the gate 11 is opened in the end face 17 of the thick walled part 16. This thick portion 16 has a thickness that allows the synthetic resin to flow smoothly when it is injected. Therefore, nests 2, 3, 4.
When synthetic resin is injected from the gate 11 with the slide cores 6 and 5 in the state shown in the first figure, the thick part 1
The resin flows in from the place where the end face 17 of the gate 6 is molded, and the gate mark 18 made of the excess resin of the gate protrudes only on this end face.

Although a molded product having the Iρ configuration described above may have protrusions on the open end surface of the hollow shaft, no protrusions are produced on the contact surface with other engaging members, so it is difficult for the rotating body to rotate. There is no load and frictional resistance does not change discontinuously. Furthermore, the resin flows smoothly when injecting the synthetic resin.

For other molded products in which protrusions are formed on the outer circumferential surface of the shaft, a slide core is essential, which made it difficult to install a gate in the past, but with the new BIJJ, it is easy to install a gate even in this case. be.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a sectional view of a molding device, and FIG. 2 is a partially cutaway side view of a molded product. 1...Cavity 11...Gate 12...Rotating body 15...Hollow shaft 16...Thick wall portion 17...・・・End face 1 day・・・・・・Gate ruins and above Applicant Seikosha Co., Ltd. Agent Patent attorney Tsutomu Mogami-10 (

Claims (1)

[Claims] 1. A part of the thin opening end face of the hollow shaft is removed to expose the end face of a thick enough part for injection molding of the hollow shaft, and only this end face has gate marks. A rotary wheel with a hollow shaft. A molding device for a rotary wheel with a hollow shaft, characterized in that a gate is opened at a position in the Z cavity where a thick part of the open end face of the hollow shaft is molded.