JPH0352328B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an injection molding method for synthetic resin valve bodies to be attached to gate valves, stop valves, etc. The present invention relates to a method of injection molding the valve body so as to embed the valve body into the valve body.

[Conventional technology]

A valve body attached to a gate valve or the like is used to block water that is forced to flow in the direction of arrow A from the valve body 1 side, as shown in FIG. 5, for example.
It is freely supported at the lower end of a valve shaft 4 which is threaded through the center of the cap fitted above, and is configured so that the valve body 2 can be opened and closed by raising and lowering the valve shaft 4. . A plurality of water supply holes 5 are bored in the upper side wall of the main body 1, and as a result of the rising of the valve body 2 opening the water passage, the blocked water flows through the valve body 2.
The water passes through the side of the water as shown by arrow B, and is further discharged from the water supply hole 5 along arrow C.

On the other hand, a packing 6 as shown is fitted into the valve body 2 to close the gap formed between the inner wall 1a of the main body and the valve body 2, thereby exhibiting a water-stopping effect. However, since the gasket 6 is subjected to friction with the inner wall 1a of the main body and water pressure from the main body 1 side as the valve body moves up and down, it is subjected to a force that causes it to detach from the valve body 2 each time. Therefore, the gasket 6 is given an undercut shape that makes it difficult to separate and is held between the valve seat 7 and the ring 8.

[Problem that the invention seeks to solve]

However, in the valve body 2 configured as described above, the clamping pressure between the valve seat 7 and the ring 8 determines the holding force of the seal 6, so the clamping state between the valve seat 7 and the ring 8 may change due to some circumstances. However, if, for example, the seal 6 is bent or a gap is formed, the gripping force of the seal 6 will be deteriorated, the fitting of the seal 6 will be incomplete, and the seal 6 will easily come off. Such an accident becomes more likely to occur as the period of use of the valve body 2 increases.
This is due to the fact that the holding structure of the seal 6 is a clamping structure made up of two articles, and this type of combination of two articles is complicated and inconvenient from the viewpoint of the workability of attaching the seal 6. It was hot.

Therefore, the present inventors believe that if a part of the packing can be buried within the valve body when injection molding a synthetic resin valve body, the separation of the packing will be prevented and the inconvenience of assembly work will be eliminated. We thought that this might be the case, and after conducting various researches, we were able to provide the injection molding method shown below.

[Means for solving problems]

That is, the structure of the present invention that can solve the above problems consists of a fitting part with a synthetic resin valve body and a sealing lip part formed on the outer circumferential side of the fitting part, and an undercut part in the valve body fitting part. A mold for gripping the lip portion when injecting synthetic resin into the valve body fitting portion of the annular sealing elastic packing formed with the synthetic resin valve body so as to integrally fit with the synthetic resin valve body. The distance in the thickness direction of the gripping space is made smaller than the thickness of the lip part, the lip part is gripped and positioned in the mold gripping space, and the lip part is positioned at the undercut part of the valve body fitting part protruding into the cavity. The gist is to flow the synthetic resin and embed it in the synthetic resin material so as to wrap the upper, lower and inner surfaces of the valve body fitting part.

[Function] According to the injection molding method of the present invention, the packing can be embedded at the same time as the valve body is molded, so the shape of the packing itself to prevent separation does not need to be very complicated. Furthermore, since the packing is accurately positioned and held within the mold cavity, it is not deformed by the pressure of the injection resin. Therefore, a part of the seal is insert-molded into the valve body, so the seal and the valve body are highly integrated, and the seal will not come off when the valve body is opened or closed or by water pressure from within the body. There isn't. Furthermore, since the entire valve body is molded as one piece, not only is there no inconvenience during assembly, but also the wobbling of the valve body itself is eliminated, greatly improving its function as a valve.

〔Example〕

The valve body molding method of the present invention will be explained below based on the drawings. FIG. 1 is a partially cutaway side view showing a valve body obtained by the molding method of the present invention, in which the fitting part (insert part) 6a of the packing 6 is inserted into the head part 10, and the seal of the packing 6 is inserted. The fitting portion (rip portion) 6b protrudes toward the outer periphery of the head portion 10, and the fitting portion 6a extends from the head portion 10.
A fitting recess (undercut portion) 6 that is stably held by a detachment prevention convex edge 10a formed at 0
form c. Therefore, the packing 6 and the head part 10
is in a state where it is held in by the protruding edge 10a for preventing detachment, and the integrity of the two is extremely high.Moreover, since the head part 10 itself is integrated, the above-mentioned part of the gasket 6 when opening/closing the valve body, etc. Breakaway accidents are completely prevented.

In the present invention, such a valve body is molded according to the following procedure.
That is, FIGS. 2 to 4 exemplarily explain the injection molding method according to the present invention, and the injection mold 11 consists of a fixed mold 12 and a movable mold 13, and a cavity 14 formed between them. The valve body is molded by injecting a heated and molten synthetic resin material into the cavity 14. During injection molding, the packing 6 is first placed inside the cavity 14. The lip portion 6b of the packing 6 is gripped by the lip gripping portion 15 formed between the mold and the moving mold 13. In this way, the outer peripheral side of the lip portion 6b is gripped by the injection mold 11, but the fitting recess 6c of the packing 6 must be gripped so as to be opened into the cavity 14. Therefore, in this embodiment, the thickness t of the lip portion 6b of the packing 6 is made larger than the size of the gripping space T when the molds are connected, in order to prevent the resin from entering the gripping portion during injection. In addition, in order to prevent deformation due to resin pressure during injection, the hardness of Packin 6 is set at 70 to 80Hs.
The gripping length l is set to be 1/3 or more of the protruding length L of the packing. These hold the packing in an accurate position, and deformation of the packing itself is very small, so that a valve body with high dimensional accuracy can be continuously molded with little deformation due to press-fitting of the resin material, which will be described later. That is, when the packing 6 is gripped, a synthetic resin material is press-fitted from the gate part 16 of the fixed mold 12. The molten resin press-fitted into the cavity enters the cavity 14. The resin fills the fitting part 6a and the fitting recess 6c so as to wrap around the upper, lower and inner surfaces of the valve fitting part 6a, and the entire valve fitting part 6a including the undercut part is filled with resin. The protruding stripes 17 formed on the fixed mold 12, which are buried so as to be surrounded by the resin material, enhance the heat dissipation effect of the molten resin material after injection, and reduce the influence of heat on the packing 6. There is. When the molten resin material is cooled and solidified in the cavity 14, the movable mold 13 is moved in the direction of the white arrow to release the mold 11, as shown in FIG.

As the molten resin material is cooled in the cavity as described above, the resin material injected to surround the core pin 13a of the movable mold 13 strongly hugs the core pin 13a due to the contraction force received during cooling. Therefore, when the movable mold 13 is moved in the direction of the outlined arrow, the head portion 10 continues to hold the core pin 13a, so that it moves together with the movable mold 13 and is removed from the fixed mold 12. Next, as shown in FIG. 4, move the protrusion plate 19 and remove the protrusion pin 1.
The head portion 10 is pushed out at 9a, and the head portion 10 is taken out from the movable mold 13. The packing 6 is stably held in the injection-molded head portion 10 by fitting the fitting recess 6c and the detachment prevention protrusion 10a. Furthermore, since the head portion 10 is formed as a complete fitting body of two articles, the fitted state of the packing 6 is stable and maintained over a long period of time.

〔Effect of the invention〕

Since the present invention is constructed as described above, the integrity of the valve body and the packing is extremely high, and the seal will not come off due to opening/closing operations of the valve body or water pressure applied from the valve body. In addition, when molding the valve body, the lip part of the seal is reliably held in an accurate position within the mold, and the valve body fitting part is placed inside the cavity so that the upper, lower and inner surfaces of the valve body fitting part are Since it is injection molded so that it is inserted into the synthetic resin valve body, there is no need to go through the trouble of fitting the gasket after molding the valve body, which is required in the past, and the manufacturing time for the valve body can be significantly shortened. It became possible to continuously manufacture products with dimensional accuracy.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway side view showing a valve body obtained by the molding method of the present invention, FIGS. 2 to 4 are partially cutaway side views showing the molding method of the present invention, and FIG. 5 is a publicly known valve body. It is a sectional view showing a valve body of. 1...Main body, 2...Valve body, 3...Cap, 4
...Valve stem, 5...Water supply hole, 6...Packskin, 7...
...Valve seat, 8...Ring, 12...Fixed mold, 13
...Moving mold, 6a... Fitting part, 6b... Seal part.

Claims (1)

[Claims] 1. The valve in an annular sealing elastic packing consisting of a fitting part with a synthetic resin valve body and a sealing lip part formed on the outer periphery thereof, and an undercut part formed in the valve body fitting part. The body fitting part,
When injection molding a synthetic resin material in a form that integrally fits into a synthetic resin valve body, the distance in the thickness direction of the mold gripping space that grips the lip part of the packing is made smaller than the thickness of the lip part, gripping and positioning the lip part in the mold gripping space, and flowing a synthetic resin material into the undercut part of the valve body fitting part protruding into the cavity of the mold;
A method for molding a valve body, comprising embedding the valve body fitting portion in a synthetic resin material so as to enclose the upper and lower surfaces and inner surfaces of the valve body fitting portion with the synthetic resin material.