JPH035731Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a check valve formed in a screw used in an injection molding machine or the like.

(Prior art) For example, some screws are used in injection molding machines, and this screw fits into a heating cylinder and rotates to transfer molten resin and inject it into a mold. It has the role of A backflow prevention valve is provided at the tip of the screw to prevent the resin from flowing back toward the screw due to the high injection force when the resin is injected.
For example, when the diameter of the screw is 25 mm or less, a ring valve is generally used as a check valve, but there is also a ball check valve shown in Figure 4, which is formed as a screw head 1. has been done. This screw head 1 is divided into a distal end 2 and a base end 3, and the base end 3 is formed with a passage 5 through which resin passes from the outer periphery of the screw 4.
It communicates with a recessed hole 6 formed in its center. A spire-shaped tip 2 formed separately from the hollow hole 6 is located, and inside thereof, the above-mentioned hollow hole 6 is located.
is formed into a continuous shape, into which the steel ball 7 is fitted. A passage 8 is formed from the recessed hole 6 of the distal end portion 2 to the outer periphery, and the distal end portion 2 and the base end portion 3 are screwed together.

(Problems to be Solved by the Invention) In the above configuration, the screw head forming the check valve is divided into a proximal end and a distal end, which are screwed together, so that the resin under high pressure can It can get into that area, or it can get between the steeple-shaped part at the tip and the heating cylinder.
This resin that has entered causes so-called "scorch" and "silver" to occur in the molded product. This may cause molding defects,
The structure has a high retention of resin.

Therefore, the present invention was devised to solve the above-mentioned problems, and it is possible to form a relatively thin screw by forming a hollow hole and a pawl on the end face of the screw and inserting a steel ball therein. The object of the present invention is to provide a backflow prevention valve which is formed integrally with a ball valve having the same diameter as a valve and a ball valve having the same diameter, and which causes less resin retention.

(Means for Solving the Problems) The feature of the present invention for achieving the above object is that the tip end face of the screw is provided with a recessed hole and a protruding claw portion surrounding the recessed hole so that the screw can be moved into the recessed hole. A steel ball is inserted as far as possible, the claw portion is bent in accordance with the spherical surface of the steel ball, and a passage is provided that communicates the outer periphery of the tip of the screw with the recessed hole. The passage was opened and closed.

(Function) With the above configuration, during injection, the molten resin is
The resin is pushed out from one passage through the hollow hole and into the other passage, and after injection, the steel ball blocks one passage of the hollow hole and there is no screwed place, so the subsequent accumulation of resin is minimized. It can be done.

(Example) Hereinafter, an example of the present invention will be described based on the drawings. First, FIG. 1 shows an embodiment of the check valve 9 of the present invention, which is attached to a screw 4 used in an injection molding machine. Note that parts common to the configuration already described as the conventional technique based on FIG. 4 are given the same reference numerals. 1st
The screw 4 shown in the figure is fitted into a heating cylinder (not shown) for melting resin, which is a molding material, and is rotated by a drive mechanism to transport the resin forward, and also to melt a molding material (not shown). It is designed to be injected into a mold. A valve body 10 having the same external shape is screwed into the tip of the screw 4 and fixed thereto. Note that the outer diameter of the screw 4 is 25 mm or less. An open recess 6 is formed in the valve body 10, and from the bottom of the valve seat 11, which has a somewhat smaller diameter in the recess 6, the valve main body 1 can be seen as shown in FIG.
A passage 5 is formed on the outside of the screw 0 at a location corresponding to the boundary between the valley portion 12 and the peak portion 13 having the same outer diameter as the screw 4 described above. A steel ball hole 1 has a somewhat larger diameter from the valve seat 11 and communicates with the inlet 14 of the recessed hole 6.
5 is formed, and a steel ball 7 is fitted into this so as to block the valve seat 11 to form a ball valve. Before the steel ball 7 is fitted into the steel ball hole 15, the claw portion 16 extending from the valve body 10, which prevents the steel ball 7 from coming out, has the same diameter as the inside diameter of the steel ball hole 15 and is recessed. 6, and as shown in FIG. 3, a passage 8 is formed inclined from the steel ball hole 15 to the inlet 14 on the side closer to the valve seat 11 than the claw portion 16. FIG. 3 shows the state after the steel ball 7 has been inserted into the steel ball hole 15, and the tip of the claw portion 16 extending from the valve body 10 is inserted into the steel ball 7 to prevent the steel ball 7 from flying out. It is bent with a curvature that corresponds to the spherical surface. In this way, the steel ball 7 blocks the valve seat 11 and communicates from the passage 5 to the passage 8.

With the above configuration, when injection molding is performed, the molten resin enters from one passage 5 and is normally under high pressure, so by pushing the steel ball 7 forward, one passage 5 is Since it communicates with the passage 8, it is ejected from the other passage 8. After injection, when a reverse pressure is generated, the steel ball 7 is pushed back and blocks the valve seat 11. By this, the accumulation of resin in the valve body 10 is limited to between the steel ball 7 and the entrance 14 of the recessed hole 6, and can be minimized, thereby preventing molding defects caused by accumulation. It will be possible.

(Effects of the invention) As stated above, the valve body of the non-return valve of the present invention can be formed into a ball check valve type even when the screw diameter is 25 mm or less, and since there is no screwed part, the structure is simpler than that of the present invention. Since there is less resin stagnation compared to the screw type, it is possible to reduce molding defects that cause check valves. Moreover, since the claw portion is simply bent, a check valve that is easy to manufacture and has few failures can be realized.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical cross-sectional view of a screw equipped with a check valve of the present invention, FIG. 2 is an enlarged view of the check valve shown in FIG. 1, and FIG. 3 is an arrow A-- The front view indicated by A in FIG. 4 is a schematic vertical sectional view showing a conventional check valve. 4: Screw, 5: Passage, 6: Hole, 7: Steel ball, 8: Passage, 16: Claw portion.

Claims (1)

[Scope of utility model registration request] A recessed hole and a protruding claw portion surrounding the recessed hole are provided on the tip end face of the screw, a steel ball is movably fitted into the recessed hole, and the claw portion is bent in accordance with the spherical surface of the steel ball. A non-return valve characterized in that a passage is provided which communicates the outer periphery of the tip of the screw with the recessed hole, and the passage is opened and closed by movement of the steel ball.