JPH0615005Y2 - Screw head device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a screw head device of an injection molding machine using a ring valve.

(Prior Art) In one cycle process of injection molding, a plasticizing and measuring process of plasticizing and melting a resin and storing a predetermined amount in front of a screw, and a fixed amount of the plasticized and measured resin are held in a mold cavity. An injection process of injecting is included. Therefore, a screw head device is provided in the front part of the screw of a normal injection molding machine so that the resin melted at the time of plasticization and measurement can pass toward the nozzle side of the tip of the heating cylinder and prevents backward flow backward at the time of injection. There is. There are various types of screw head devices such as a ring valve system and a ball check system.

Among these, in the ring valve system related to the present invention, the screw head of the screw head is provided between the large-diameter rear surface of the screw head provided with a plurality of grooves for resin to pass through and the wear plate provided at the tip of the screw. A cylindrical ring valve is loosely fitted to the outside of the small diameter portion so as to be movable back and forth. The space between the inner circumference of the ring valve and the outer circumference of the small diameter portion of the screw head is a resin passage. In addition, the clearance between the ring valve and the heating cylinder inner hole is the minimum value that does not allow the two to bite and does not allow backflow during injection of the molten resin.

In such a screw head device, when measuring resin, the ring valve is pushed forward by the pressing force of the molten resin and comes into contact with the rear surface of the large diameter portion of the screw head.

(Problems to be solved by the invention) The state of contact between the ring head and the large-diameter back surface of the screw head at the time of the measurement has only a slight clearance between the screw head rotating at a constant speed and the heating cylinder inner hole. It is a sliding contact with a ring valve that does not rotate because it is not provided. For this reason, great wear and severe galling are likely to occur between the two.

(Means for Solving the Problem) The present invention has been made to solve the problem, and includes a screw head having a large diameter portion and a small diameter portion screwed and fixed to the tip of a screw via a wear plate. A plurality of grooves are provided in the large diameter portion of the screw head so that molten resin can pass through, and a ring valve for opening and closing a resin passage is loosely fitted in the small diameter portion so as to be movable back and forth. An elastic member is disposed on the large diameter portion, and the contact force between the rear surface of the large diameter portion of the screw head and the end surface of the ring valve is reduced by the reaction force of the elastic member during plasticization.

(Operation) When the back surface of the large diameter portion of the screw head and the ring valve are in contact with each other, the elastic member separately arranged on the large diameter portion of the screw head and the annular protrusion provided on the ring valve receive the reaction force of the elastic member. Since the structure is such that they come into contact with each other in a state, the contact pressure between the rear surface of the large diameter portion of the screw head and the ring valve is reduced, and wear and galling are eliminated.

(Embodiment) An embodiment of the present invention will be described with reference to FIGS. 1 to 4.

Reference numeral 1 is a heating cylinder of the injection molding machine, and 1A is an inner hole of the heating cylinder.

Reference numeral 2 is a screw that is inserted into the inner hole 1A of the heating cylinder so as to be rotatable and reciprocally movable.

Reference numeral 3 is a screw head fixedly provided at the tip of the screw 2. The head of the screw head 3 has a conical tip end portion followed by a cylindrical large-diameter portion, and the large-diameter portion is provided with a plurality of grooves 3A serving as passages for the molten resin.
In this example, four grooves are shown. Subsequent to the large-diameter portion, a small-diameter portion 3D, a collar portion 3E, and a shaft portion 3F provided with a screw at the end portion are formed. The small diameter portion 3D and the plurality of grooves 3A are smoothly connected without a step.

Further, the end faces of the four divided large-diameter portions 3B form a back surface 3C which is perpendicular to the small-diameter portion 3D and is orthogonal thereto.

Further, a cutout groove 3G is provided on the outer circumference of each of the four large-diameter divided portions 3B at a position separated from the back surface 3C by a certain distance, as clearly shown in FIG.

Reference numeral 4 denotes a wear plate provided between the flange portion 3E of the screw head 3 and the tip surface of the screw 2, and the screw head 3 screws the screw of the shaft portion 3F and the screw formed on the screw 2. When they are fixed together, they are pressed and pinched.

Reference numeral 5 denotes a thick-walled cylindrical ring valve, the inner diameter of which is larger than the outer diameter of the small-diameter portion 3D of the screw head 3, and the space between the two serves as a resin passage 6. The clearance between the outer circumference of the ring valve 5 and the inner hole 1A of the heating cylinder 1 is a minimum value that neither galls and does not allow backflow at the time of injection of the molten resin. Reference numeral 5A is a base surface of the ring valve 5 that contacts the back surface 3C of the screw head 3. In this state, the ring valve 5 is loosely fitted between the back surface 3C of the screw head 3 and the wear plate 4 provided at the tip of the screw 2 so as to be movable back and forth.

In the present invention, an annular protrusion 5B having a predetermined height is further provided from the base surface 5A of the ring valve 5. The annular protrusion 5
The inner diameter of B is slightly larger than the outer diameter of the large diameter portion of the screw head 3.

Reference numeral 7 is a leaf spring provided at four positions in this example, which receives a pressing force from the tip end surface of the annular protrusion 5B of the ring valve 5 when plasticizing and measuring the resin.

As is apparent from the perspective view of FIG. 4, the leaf spring 7 has a fitting insertion portion 7A which is fitted into the notch groove G provided in the dividing large diameter portion 3B of the screw head 3 without any play, and each dividing large diameter A pair of holding portions 7B formed by bending both ends so as not to be displaced from the portion 3B, and an annular protrusion 5B of the ring valve 5.
The pressure receiving surface 7C receives a pressing force from the tip surface of the. Therefore, the leaf spring 7 is fitted into the cutout groove 3G of the split large-diameter portion 3B of the screw head 3 without any play, and is held by the pair of holding portions 7B. Pressure receiving surface 7C extending radially from 3B
Are arranged in the large-diameter split portion 3B so as to receive a pressing force from the tip end surface of the annular protrusion 5B of the ring valve 5 during plasticization.

Next, the operation will be described.

The screw 2 that has been injected in the previous cycle is at the forward limit position. The screw 2 starts to rotate again and the plasticizing and measuring process is started. The raw material resin is transferred to the front by the screw 2 which rotates while being plasticized by the heat transfer from the heating cylinder 1 and its own shear heat generation.

As shown in FIGS. 1 and 3, the ring valve 5 is pushed to the screw head 3 side by the pressure of the molten resin sent forward. That is, the rear surface 3C of the divided large diameter portion 3B of the screw head 3 rotating at a constant speed and the inner hole 1A of the heating cylinder 1.
Since there is only a slight clearance between the ring valve 5 and the base surface 5A of the ring valve 5 which hardly rotates, a sliding contact under the pressed state is caused.

However, at the same time, the divided large diameter portion 3B of the screw head 3 is
When the pressure receiving surface 7C of the leaf spring 7 fitted in each of the fitting insertion portions 7A is pressed by the annular projection 5B of the ring valve 5, the elastic force of the leaf spring 7 is generated by the screw head. The contact pressure between the back surface 3C of 3 and the base surface 5A of the ring valve 5 is reduced to prevent wear and galling between them.

There is no contamination of foreign matter due to wear or galling, and the molten resin flows from the outer periphery of the wear plate 4 to the small diameter portion 3 of the screw head 3.
It passes through the resin passage 6 formed between the outer circumference of D and the inner circumference of the ring valve 5, and further passes through the groove 3A of the large-diameter divided portion 3B of the screw head 3 and is stored at the tip of the screw head 3. It

When a certain amount of molten resin is stored at the tip of the screw head 3, a position detection device such as a limit switch or an encoder detects the position of the screw 2 retracted by that amount, and the rotation of the screw 2 is stopped to plasticize and measure. The process ends.

Then, when the mold clamping of the mold clamping device (not shown) is completed, the injection process is started, and the screw 2 advances. At this time, the elastic force of the leaf spring 7 forcibly pushes back the ring valve 5 to the screw 2 side, so that the injection resin pressure is easily applied to the ring valve 5 and the ring valve 5 is closed to the wear plate 4 side. Is done quickly and reliably.

When the injection process is completed, the plasticizing and weighing process starts again.

(Effect) Since the ring valve is configured to receive the reaction force of the elastic member provided on the screw head side at the time of contact between the screw head and the ring valve at the time of plasticizing and weighing, the ring valve and the screw head are provided with The contact pressure is reduced and wear and galling are eliminated. As a result, damage to the expensive screw head and ring valve is prevented, and no foreign metal is mixed into the molded product.

Further, when the injection is started, the elastic member forcibly pushes the ring valve back to the wear plate side, so that the injection resin pressure is well applied to the ring valve, and the ring valve is closed quickly and reliably. Therefore, the reverse flow of the molten resin is prevented, and stable molding can be performed without variations in the weight of the molded product.

[Brief description of drawings]

FIG. 1 is a main part view including a cross section showing one embodiment of the present invention, FIG. 2 is a cross sectional view taken along the line II-II in FIG. 1, and FIG. 3 is a view taken along the line III-III in FIG. A sectional view and FIG. 4 are perspective views of the leaf spring. 1: Heating cylinder 2: Screw 3: Screw head 3B: Divided large diameter part 3C: Rear surface 4: Wear plate 5: Ring valve 5A: Base surface 5B: Annular protrusion 6: Resin passage 7: Leaf spring

Claims (1)

[Scope of utility model registration request] 1. A screw head comprising a large diameter portion and a small diameter portion screwed and fixed to a tip of a screw rotatably and reciprocally inserted in a heating cylinder of an injection molding machine through a wear plate, and the screw head. In a screw head having a structure in which a plurality of grooves for allowing molten resin to pass through are provided in a large diameter part of the screw head, and a ring valve for opening and closing a resin passage is loosely fitted in the small diameter part so as to be movable back and forth. A cutout groove is provided in the large-diameter portion that constitutes the plurality of grooves, and a plate spring is tightly fitted in the cutout groove in the plate thickness direction, and the portion facing the close fitting portion of the plate spring is plastic with the end face of the ring valve. The screw head device is adapted to reduce contact pressure between the rear surface of the large-diameter portion of the screw head and the other end surface of the ring valve due to the reaction force of the leaf spring when they contact each other.