JPH08142138A - Reverse flow preventing device for injection molding machine - Google Patents

Abstract

PURPOSE: To mount a reverse stop ring at a small-diameter screw without decreasing the strength. CONSTITUTION: A flange 10 protrudes from the base end side of the screw head 9 of a screw 5 having a small diameter. A reverse stop ring 11 is rotatably mounted at the base end side of the head 9. At the time of plasticizing, the first groove 10a of the outer periphery of the flange 10 is opposed to the second groove 11a of the outer periphery of the ring 11 to allow the passage of molten resin to the head 9 side. At the time of injecting, the groove 10a of the flange 10 is circumferentially deviated from the groove 11a of the ring 11 to prevent the reverse flow of the resin from the head 9 side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a backflow prevention device of an injection molding machine, and more particularly to a screw head of a small-diameter screw used when a resin molded product is small and uses a small amount of resin. The present invention relates to improvement of a backflow prevention device to be mounted.

[0002]

2. Description of the Related Art Generally, in an injection molding machine, a resin molding material charged into a heating cylinder is kneaded and plasticized by frictional heat while being fed to a screw head side by rotation of a screw, and the plasticized molten resin is molded into a mold. It is designed to be injected into the cavity to mold a resin molded product.

A backflow prevention device for preventing backflow of the molten resin during injection is incorporated in the screw head. Examples of the backflow prevention device include a ball check for preventing the molten resin from flowing backward by retracting a ball interposed in the branch portion of the resin passage inside the screw head by the resin pressure at the time of injection to block the resin passage. There is a method. Further, as disclosed in, for example, Japanese Patent Application Laid-Open No. 4-71817, a check ring having a resin passage formed therethrough is externally fitted to a screw head, and when the screw is injected, the screw is rotated in the direction opposite to the plasticizing direction. There is also a ring system in which the resin passage of the check ring is blocked by the screw head tip side wall portion and the screw head base end side wall portion by rotating so that the molten resin does not flow backward.

In a screw incorporating the above-described backflow prevention device, the screw head is generally manufactured separately from the screw body due to the structure of the backflow prevention device. That is, in the case of the former ball check method, since the ball is inserted in the resin passage inside the screw head, it is not possible to form the resin passage and insert the ball when the screw is an integral body. This is possible and therefore the screw head and the screw body must be constructed separately.
In the case of the latter back flooring method, the check ring is fitted outside the small diameter portion formed on the screw head, and the resin passage is provided with the screw head tip side wall portion and the base end which are the large diameter portions on both sides of the small diameter portion. Since the structure is made to face the side wall portion, the screw head and the screw body must be configured separately in order to fit the check ring onto the small diameter portion. In this way, the backflow prevention device is incorporated into the screw head that is configured separately from the screw main body, and then the screw head is screwed into the screw main body so that they are integrally connected.

[0005]

By the way, when the resin molded product is small and the amount of resin used is small, a small injection molding machine having a small injection capacity is used according to the size of the resin molded product. And, of course, a screw with a small diameter is also used.

However, in the case of a small-diameter screw, if the method of screwing and connecting the screw head to the screw body is adopted as described above, a male screw portion (screw rod) is formed on the screw head side and a female screw portion is formed on the screw body side. Since the (screw hole) is formed, the strength of the connecting portion may be reduced and the connecting portion may be broken. In particular, the smaller the diameter of the screw, the stronger the tendency. In the case of the commercially available screw with the minimum diameter of 14 mm at present, the strength of the connecting portion is extremely reduced, so the backflow prevention device is not incorporated. is the current situation.

The present invention has been made in view of the above points, and an object thereof is to use a check ring as in the latter case, but a resin passage is formed through the check ring. Instead of forming the screw head and the screw body separately from each other, it is possible to mount the non-return ring without changing the screw head and the screw body.Therefore, there is no problem of strength reduction due to the presence of the connecting portion. Even if the screw has a small diameter, it tries to incorporate the backflow preventive device while maintaining sufficient strength.

[0008]

In order to achieve the above object, the present invention is to knead the resin molding material charged in the heating cylinder while sending it to the screw head side by the rotation of a screw having a small diameter, and by frictional heat. For the backflow prevention device of the injection molding machine that plasticizes and injects this plasticized molten resin into the cavity of the mold to form a small resin molded product with a small amount of resin used, the following solution measures are taken. It was

That is, according to a first solution means of the present invention, a flange having a first concave groove for passing a molten resin formed on an outer periphery thereof is provided so as to protrude radially outward on the screw head base end side of the screw. Further, a non-return ring having a second recessed groove for passing the molten resin formed on the outer periphery is mounted on the screw head base end side of the screw so as to be rotatable by a predetermined angle in the circumferential direction. Then, when plasticizing, the first concave groove of the flange and the second concave groove of the check ring are opposed to each other to allow passage of the molten resin to the screw head side, while at the time of injection, the first concave groove of the flange. It is characterized in that the concave groove and the second concave groove of the check ring are displaced from each other in the circumferential direction to prevent the reverse flow of the molten resin from the screw head side.

A second solution of the present invention is the first solution according to the first solution, wherein the first concave groove of the flange and the second groove of the check ring are provided.
A plurality of concave grooves are formed in the circumferential direction at the same intervals and in the same number.

According to a third solving means of the present invention, in the first solving means, a second concave shape of the check ring is formed so as to bias the check ring by a resin pressure in a direction opposite to the rotation of the screw at the time of injection. The groove is inclined at a predetermined angle with respect to the center of rotation of the ring.

A fourth solution means of the present invention is the first solution means, wherein a plurality of engagement projections are provided radially inwardly on the inner circumference of the check ring. Further, a plurality of mounting grooves with which the respective engaging protrusions engage are formed in the screw head, and the respective mounting grooves have a narrow width portion on the screw head tip side and a head wider in the circumferential direction than the narrow width portion. It is composed of a wide portion on the base end side. When the check ring is attached, the engagement protrusions are engaged with the narrow width portions of the attachment grooves to guide the check ring from the screw head tip side to the screw head base side, while plasticizing, It is characterized in that each engagement protrusion is moved in the circumferential direction at the wide portion of each mounting groove to engage with the step portion of the wide portion and the narrow portion so that the check ring does not separate from the screw head. To do.

[0013]

With the above structure, in the first means for solving the problems of the present invention, the resin molding material charged into the heating cylinder is kneaded while being sent to the screw head side by the rotation of the screw having a small diameter, and is plasticized by frictional heat. The plasticized molten resin has a first concave groove on the outer periphery of the flange projecting on the screw head base end side of the screw and a second concave groove on the outer periphery of the check ring mounted on the screw head base end side. Are supplied to the screw head side through a resin passage formed by both the first and second concave grooves while facing each other. The molten resin supplied to the tip side of the screw head is injected into the cavity of the mold when the amount required for molding is reached, and a small-sized resin molded product with a small amount of resin used is molded. During this injection, the screw is rotated in the opposite direction. As a result, the first recessed groove of the flange and the second recessed groove of the check ring are displaced from each other in the circumferential direction, blocking the resin passage, and preventing the molten resin from flowing back from the screw head side.

As described above, the resin passage is formed by the first concave groove on the outer circumference of the flange of the screw and the second concave groove on the outer circumference of the check ring. The resin passage is formed by the positional relationship in the circumferential direction between the first and second concave grooves. Since the resin passage is opened or blocked, the screw is installed in the screw main body and the screw head in order to install the check ring in the small diameter part in the middle of the screw head as in the case of the conventional ring system. It is not necessary to divide the screw and it is possible to use a single screw, so there is no connecting part that causes strength reduction in the screw, and even if a backflow prevention device is incorporated, a small diameter screw with excellent strength can be obtained and injection It is possible to incorporate the backflow prevention device into a compact injection molding machine with a small capacity.

In the second solution of the present invention, the plasticized molten resin is supplied all at once to the tip end side of the screw head through the plurality of first and second concave grooves formed around the screw head. Therefore, the supply of the molten resin is promptly performed without delay.

According to the third solution of the present invention, the resin pressure at the time of injection is easily applied to the side wall of the inclined second concave groove of the check ring, and the check ring is reliably rotated in the direction opposite to the rotation of the screw. The resin is urged dynamically, and the blocked state of the resin passage is secured.

In the fourth solution of the present invention, the check ring has a plurality of engaging projections formed on the inner periphery thereof engaged with the narrow width portions of the plurality of mounting grooves formed on the screw head. In this state, the screw head is guided from the screw head tip side to the screw head base end side, and is mounted on the screw head base end side. The stop ring is easily installed.

Further, in the non-return ring, each engaging projection is engaged with the step portion of the wide width portion and the narrow width portion of each engaging groove during plasticization to prevent the engagement ring from being detached from the screw head. The backflow of the molten resin during injection is reliably prevented.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 10 shows an injection molding machine to which the backflow prevention device A according to the embodiment of the present invention is applied. In the figure, reference numeral 1 denotes a heating cylinder provided with a heater (not shown) on the outer periphery, and a hopper for introducing a resin molding material such as pellets into the base end (right end in FIG. 10) of the heating cylinder 1. 2 is attached,
A mold 3 is attached to the tip (left end in FIG. 10) side. The mold 3 is a cavity 4 having a small capacity (for example, about 0.22 cc) formed corresponding to the shape of a resin molded product R such as a high load transmission belt used in a belt type continuously variable transmission of a vehicle. The cavity 4 is formed corresponding to the shape of the resin molded product R such as a high load transmission belt. Therefore, the amount of the molten resin used for molding is naturally small, and the obtained resin molded product R is small.

A screw 5 is rotatably arranged inside the heating cylinder 1, and the screw 5 is provided with a fluid pressure cylinder 6 and a drive motor 7 installed at the base end (right end in FIG. 10) side.
And the fluid pressure cylinder 6 expands and contracts to move forward.
While moving backward, the drive motor 7 is rotated in the clockwise direction / counterclockwise direction by the forward rotation / reverse rotation activation. The screw 5 may be small in size according to the small resin molded product R to be molded, that is, the amount of resin used is small, and is a small screw having a diameter of 14 mm, for example. The screw 5 is of a type in which the screw body 8 and the screw head 9 are integrated.

In this injection molding machine, the resin molding material is charged into the heating cylinder 1 from the hopper 2 while the screw 5 having a small diameter is rotated by the activation of the drive motor 7, and the counterclockwise rotation of the screw 5 is performed. The resin molding material is kneaded while being fed to the screw head 9 side by the rotation in the circumferential direction, and is plasticized by the friction heat and the heat of the heater, and the plasticized molten resin is accumulated on the screw head 9 side. When the molten resin accumulated on the screw head 9 side reaches a predetermined amount, the screw 5 is moved to the fluid pressure cylinder 6
Is injected into the cavity 4 of the mold 3 by the expansion operation of (1) and waits for the molten resin to cool and solidify to form a small resin molded product R with a small amount of resin used.

As shown in FIGS. 1 and 2, the screw 5 is provided with a so-called right-handed screw main body 8 having a screw thread 8a which is screwed clockwise in FIG. By rotating counterclockwise in FIG. 1, the resin molding material is kneaded and plasticized while being fed to the screw head 9 side.

As shown in FIGS. 5 to 7, a flange 10 which is a constituent element of the backflow prevention device A of the present invention is provided on the base end side of the screw head 9 so as to project outward in the radial direction. Are formed on the outer periphery of the first concave grooves 10a, 10a, 10a, 10a, 10a, 10a, ...
The first protrusion 10b is formed between a and a.

On the base end side of the screw head 9, a non-return ring 11 which constitutes a backflow preventive device A together with the flange 10 is mounted rotatably by a predetermined angle in the circumferential direction.
And, as shown in FIG. 9, on the outer circumference of the check ring 11,
The same number as each first concave groove 10a of the flange 10 (6
Second concave grooves 11a, 11a, ...
Are formed at predetermined intervals at positions that divide the circumference into six equal parts, that is, at the same intervals, and the second protrusion 11b is formed between the adjacent second concave grooves 11a.

As shown in FIGS. 1 and 2, when plasticizing, the first concave grooves 10a of the flange 10 and the second concave grooves 11a of the check ring 11 are made to correspond to each other in the front and rear directions. The resin passage formed by the first and second concave grooves 10a and 11a is opened to allow passage of the molten resin from the screw body 8 side to the screw head 9 side, while, as shown in FIGS. 3 and 4, At the time of injection, each first concave groove 10a of the flange 10 and each second protrusion 11b of the check ring 11
The second recessed groove 11a of the check ring 11 and the first protrusion 10b of the flange 10 are made to correspond to each other in the front-rear direction so that the first recessed groove 10a and the second recessed groove 11a are displaced from each other in the circumferential direction. Both first and second concave grooves 10a, 11
The resin passage formed by a is blocked to prevent the molten resin from flowing back from the screw head 9 side to the screw body 8 side.

Further, each of the second concave grooves 11a is inclined at a predetermined angle α with respect to the rotation center direction of the check ring 11, and the resin pressure at the time of injection of the molten resin supplied to the screw head 9 side. Is received by the side wall of each second concave groove 11a, and the check ring 11 is urged to rotate counterclockwise in FIG. That is, at the time of injection, the screw 5 is rotated in the clockwise direction in FIG. 3 to block the resin passage so as to shift the positions of the first concave grooves 10a and the second concave grooves 11a in the circumferential direction. However, at this time, the check ring 11
Rotates in the opposite direction to the screw 5 and presses each engaging projection 11c described later against the side wall of the wide portion 12b of the mounting groove 12 to secure the blocked state of the resin passage so as to prevent the reverse flow of the molten resin. .

Further, the check ring 11 has three inner circumferences.
The engagement projections 11c, 11c, ... Are provided so as to protrude radially inward at predetermined intervals. On the other hand, the screw head 9 is formed with three mounting grooves 12, 12, 12 which are engaged with the engaging protrusions 11c from the base end side of the screw head 9 to the tip end side of the screw head 9. Each of the mounting grooves 12 includes a narrow portion 12a on the tip side of the screw head 9 and a wide portion 12b on the base end side of the screw head 9 that is wider in the circumferential direction than the narrow portion 12a. When the check ring 11 is mounted on the screw head 9, the engagement protrusions 11c of the check ring 11 are engaged with the narrow portions 12a of the mounting grooves 12 of the screw head 9 from the tip side of the screw head 9. Then, the check ring 11 is guided from the tip end side of the screw head 9 to the base end side of the screw head 9. When the resin molding material is plasticized, the engagement protrusions 11c of the check ring 11 are moved in the circumferential direction by the wide portions 12b of the mounting grooves 12 of the screw head 9 by the rotation of the screw 5 to move the wide portions 12b. And the stepped portion 12c of the narrow portion 12a,
The check ring 11 is designed so as not to be separated from the screw head 9.

Thus, in this embodiment, the screw 5
A resin passage is formed by each first concave groove 10a on the outer circumference of the flange 10 and each second concave groove 11a on the outer circumference of the check ring 11, and the positional relationship in the circumferential direction between the first and second concave grooves 10a, 11a. Since the resin passage is opened or shut by the above-mentioned method, the screw 5 may be an integral screw 5 instead of the split type such as the ring method of the conventional example, and the connecting portion that causes a decrease in strength can be eliminated. The small-diameter screw 5 having excellent strength can be obtained. Therefore, although the diameter of the screw 5 is small, a small injection molding machine incorporating the backflow prevention device A and having a small injection capacity can be obtained.

Further, in the above embodiment, the plasticized molten resin is supplied all at once through the plurality of first and second concave grooves 10a and 11a formed around the screw head 9. The molten resin can be quickly supplied in a short time without any delay.

In addition, in the above-described embodiment, the non-return ring 11 is provided on the screw head 9 side with respect to the screw 5 which is rotated in the opposite direction to that in the plasticizing process so as to block the resin passage during injection. Since the resin is biased to rotate in the opposite direction by the resin force, the blocked state of the resin passage can be secured and the reverse flow of the molten resin can be prevented.

In addition, in the above embodiment, the check ring 11
When the screw head 9 is mounted on the base end side of the screw head 9, the engagement protrusions 11c of the check ring 11 are engaged with the narrow width portions 12a of the mounting grooves 12 of the screw head 9 to attach the screw head 9 to the screw head 9.
Since the screw 5 is guided from the distal end side to the proximal end side of the screw head 9, the check ring 11 can be easily attached to the screw 5 of an integral body without dividing the screw 5 into the screw body 8 and the screw head 9. Can be attached to. In addition, when the plasticizing is performed, the engaging protrusions 11c are attached to the mounting grooves 1
The non-return ring 11 is prevented from coming off from the screw head 9 by engaging with the stepped portion 12c of the two wide width portions 12b and the narrow width portion 12a, so that the reverse flow of the molten resin at the time of injection is surely prevented. be able to.

[0033]

As described above, according to the present invention of claim 1, when the molten resin is fed to the screw head, the resin passage is provided with the first concave groove on the outer periphery of the flange on the screw head base end side. It is composed of a second concave groove on the outer periphery of the check ring mounted on the screw head base end side, and opens and closes the resin passage depending on the positional relationship between the first concave groove and the second concave groove in the circumferential direction. As in the case of the ring method of the conventional example, since the check ring is attached to the small diameter part in the middle of the screw head, it is not necessary to divide the screw into two parts, the screw body and the screw head, and the strength of the integrated screw causes a decrease in strength. It is possible to obtain a small-diameter screw having excellent strength.

According to the second aspect of the present invention, since the first concave groove of the flange and the second concave groove of the check ring are formed in the circumferential direction at the same intervals and in the same number, a plurality of them are formed.
By simultaneously supplying the molten resin from around the screw head, it is possible to rapidly supply the molten resin in a short time without delay.

According to the third aspect of the present invention, the second concave groove of the check ring is inclined at a predetermined angle with respect to the center of rotation of the ring, and is reversed by the resin pressure applied to the side wall of the second concave groove. Since the stop ring is urged to rotate in the opposite direction to the screw, the blocked state of the resin passage can be ensured and the reverse flow of the molten resin can be prevented.

According to the present invention of claim 4, when the check ring is mounted, the engagement projections are engaged with the narrow width portions of the mounting grooves so that the check ring is moved from the screw head front end side to the screw head base end side. On the other hand, while being guided to the side, at the time of plasticization, each of the engaging projections is moved in the circumferential direction at the wide portion of each mounting groove to engage with the step portion of the wide portion and the narrow portion, and the check ring Since the screw is not separated from the head, the check ring can be easily attached to the integrated screw without splitting the screw into two parts, the screw body and the screw head. Can be reliably prevented.

[Brief description of drawings]

FIG. 1 is a side view showing a positional relationship between a check ring and a screw head during plasticization.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a side view showing the positional relationship between the check ring and the screw head during injection.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is a side view of a screw head.

6 is a sectional view taken along line VI-VI in FIG.

7 is a sectional view taken along line VII-VII of FIG.

FIG. 8 is a front view of the check ring.

FIG. 9 is a side view of the check ring.

FIG. 10 is a schematic configuration diagram of an injection molding machine.

[Explanation of symbols]

 1 Heating Cylinder 3 Mold 4 Cavity 5 Screw 9 Head 10 Flange 10a 1st Recessed Groove 11 Check Ring 11a 2nd Recessed Groove 11c Engagement Protrusion 12 Mounting Groove 12a Narrow Width 12b Wide Width 12c Step A Backflow Prevention Device R Resin molded product

Claims (4)

[Claims] 1. A resin molding material charged into a heating cylinder is kneaded while being sent to the screw head side by rotation of a screw having a small diameter to be plasticized by frictional heat, and the plasticized molten resin is injected into a cavity of a mold. Is a backflow prevention device of an injection molding machine for molding a small-sized and resin-molded product with a small amount of resin used, the first concave shape for radially outwardly projecting on the screw head base end side for passing molten resin. A flange having a groove formed on the outer circumference and a check ring having a second concave groove for passing the molten resin formed on the outer circumference, which is mounted on the screw head base end side so as to be rotatable by a predetermined angle in the circumferential direction. During plasticization, the first concave groove of the flange and the second concave groove of the check ring are opposed to each other to allow passage of the molten resin to the screw head side, while at the time of injection, the first concave groove of the flange is provided. Concave A backflow prevention device for an injection molding machine, wherein the groove and the second recessed groove of the check ring are circumferentially displaced from each other to prevent backflow of the molten resin from the screw head side. 2. The first recessed groove of the flange and the second recessed groove of the check ring are formed in the circumferential direction at the same intervals and in the same number, and a plurality of them are formed. Backflow prevention device for injection molding machines. 3. The second concave groove of the check ring at a predetermined angle with respect to the ring rotation center direction so as to bias the check ring by resin pressure in the direction opposite to the rotation of the screw during injection. The backflow prevention device for an injection molding machine according to claim 1, wherein the backflow prevention device is inclined. 4. A plurality of engaging projections are provided radially inward on the inner circumference of the check ring, and a plurality of mounting grooves with which the engaging projections engage are formed in the screw head. Further, each of the mounting grooves is composed of a narrow portion on the tip side of the screw head and a wide portion on the base end side of the screw head wider in the circumferential direction than the narrow portion. While engaging each engagement protrusion with the narrow portion of each mounting groove to guide the check ring from the screw head distal end side to the screw head proximal end side, at the time of plasticization, each engagement protrusion is engaged with each mounting groove. The injection according to claim 1, characterized in that the check ring is adapted to move in the circumferential direction at the wide width portion and engage with the step portion of the wide width portion and the narrow width portion so that the check ring does not separate from the screw head. Backflow prevention device for molding machine.