JPH0698645B2 - Steel pipe screw protector mold - Google Patents

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a collapsible mold, and in particular, a plastic protector for protecting a threaded portion threaded at the end of a medium or large diameter steel pipe, such as a seamless pipe, is formed. The present invention relates to a die for forming a screw protector for a steel pipe.

[Prior art]

When a seamless pipe, for example, a steel pipe having a diameter of 2 (3/8) ″ to 16 ″ is connected and used, one end of this steel pipe is usually threaded with a male screw part while the other end is screwed with a female screw part. It By the way, such a threaded portion has a drawback that it is easily deformed by an impact when being loaded and unloaded during transportation in a factory or transportation by a vehicle, a ship and the like. In addition, there is a problem that the threaded portion is exposed to wind and rain during transportation and rusts from the threaded portion. Therefore, conventionally, a protector (protector) for protecting the threaded portion is mounted immediately after the steel pipe is threaded, and a plastic protector by a thick insert molding method is generally used. This uses a perforated steel pipe with a thickness of about 2 mm as a reinforcing insert metal fitting, which is held in the cavity space at the time of injection molding and is an insert member embedded in the protector after molding. It is designed to increase strength. For this reason, the plastic protector provided with the insert member is superior in strength, shock absorption and rust prevention to the steel pipe protector which has been widely used in the past. However, this type of protector is a means for holding the insert member so that the insert member does not deviate when the resin is injected by holding the insert member in the cavity space at the time of molding, and a molded product at the time of mold opening. It was necessary to provide a means for allowing the core to stand still and pulling it out while rotating the core die side provided with the screw portion. For this reason, the mold and the molding device are large-scaled and expensive. Further, there is also a problem that the mold opening time becomes long and the production efficiency is lowered because of the mechanism of unscrewing while rotating the core mold. Therefore, recently, a mold for forming a steel pipe screw protector has been adopted, which uses a collapsible system in which the core mold side is shrunk to improve the production efficiency and reduce the manufacturing cost. As shown in FIG. 10, the mold has a central mold (32) of a substantially hexagonal shape, and its outer side surfaces (32a), (32a ′) are tapered toward the tip as shown in FIGS. It has become a tapered shape.
On the other hand, the peripheral molds (33), (33 ') have a half-moon shape in cross section, and the inner surfaces (33a), (33a') are in contact with the tapered surfaces (32a), (32a ') of the central mold (32), Threaded part (33
b) and (33b ') are threaded. Also, the surrounding type (3
3) and (33 ') can be shrunk in the direction perpendicular to the axis center. As a result, the insert holding pin is pulled out when the mold is opened, and can be taken out.

[Prior art and its problems]

By the way, in this type of mold, generally, the threaded surface of the molded product and the tip of the insert holding pin are set to be close to each other. That is, when the protector for medium / large diameter steel pipe is molded by the collapsible method, the peripheral molds (33) and (33 ') having the two-divided structure have a stroke of 2 to 3 mm or more at the time of narrowing. There was a constraint that I couldn't. Therefore, there is a problem that the insert holding pin is not fully pulled out, and the tip of the insert holding pin is damaged when the molded product is taken out. Therefore, in order not to hinder the insert holding pin,
It is conceivable that the strokes for purging the peripheral molds (33), (33 ′) are set to about 3 to 4 times the depth of the screw so that the peripheral molds (33), (33 ′) are sufficiently curled. (3
Due to the structural reason that 3 ') is divided into two, no commercially available mold can meet this demand. For this,
The core type shown in FIG. 10 has the central type (32b) as a non-threaded part to increase the amount of recession by increasing the amount of retreat. However, by increasing the collapsible stroke, it is possible to pull out the insert holding pin without hindrance, but with the molded protector,
Since there is a non-threaded portion, there is a problem that a gap is formed between the protector and the threaded portion when the steel tube is screwed into the threaded portion. Then, during transportation or the like, there is a problem that moisture or water penetrates through this gap and the threaded portion of the steel pipe rusts. The present invention has been made in view of the above problems, the tip of the insert support pin is deeper than the inner surface of the molded product to a depth that is more inward, and performs a large collapsible action of the stroke for purging the mold, and An object of the present invention is to provide a metal mold for a steel pipe screw protector capable of efficiently producing a steel pipe screw protector excellent in rust prevention by injection-molding a protector without a non-threaded portion.

[Means for Solving the Problems]

In order to achieve the above object, the metal mold for forming a steel pipe screw protector according to the present invention comprises a plastic protector (5) for a male pipe of a steel pipe reinforced by (1) insert metal fitting (6) in claim (1). From a central mold (2) that moves forward and backward in the axial direction in synchronization with opening and closing of the mold, and a peripheral mold (3) that is divided into a plurality of inner surfaces and is in sliding contact with the outer surface of the central mold (2). A steel pipe screw protector injection having a core mold (1) which is formed by the collapsible action of the core mold (1) in which the peripheral mold collapses in the axial direction as the central mold (2) retracts during the mold opening process. In the molding die, the central mold (2) has a polygonal cross-section, and the outer surface thereof has a taper shape such that the outer mold is tapered toward the tip, and the peripheral mold has both sides through the central mold (2). From the sub-peripheral type (4) (4 ') The main mold (3) (3 ') having a substantially half-moon shape in cross section which is in sliding contact with both sides through the center mold (2) and the sub-perimeter molds (4) (4'), and the sub-perimeter. The molds (4) and (4 ') are engaged so as to slide without being separated from the central mold (2), and the main peripheral molds (3) and (3') are engaged with the central mold (2). Instead, the collapsible stroke of the collapsible action due to the retreat of the central mold (2) is set to be larger than the depth of the thread of the molded product (5), and the peripheral mold is (3) (3 ') (4) (4') is provided on the outer periphery of the insert retaining pin (16) for holding the insert metal fitting (6), the tip of the molded product (5) The technical means of retracting further inward than the inner side is adopted, and further, in claim (2), (2) the peripheral die ( 3) (3 '), (4), and (4') have a threaded portion (5b) threaded on the entire outer circumference, the pitch and thread depth are the same as those of the steel pipe, and the groove width is a male thread. Only the shape of the thread surface of the female thread is deformed so that the thread is clamped by the thread surface of the female thread when it is formed smaller than the width of the female thread and the male thread is screwed in. The technical means is adopted.

[Action]

In the above-mentioned configuration, in injection molding, in the cavity space of the cavity mold (7), the center mold (2) which is the core mold (1), and the plurality of peripheral molds (3) (3 ') (4) (4'). , The insert member (6) is inserted, and the insert member (6) is held by the insert holding pin (16).
Then, when the resin is injected into the cavity space (G),
The insert member (6) is molded while being embedded in resin without being offset. Next, in the mold opening step, the central mold (2) is retracted in the axial direction and the peripheral mold (3) is moved.
(3 '), (4), and (4') shrink toward the axis. At this time, since the peripheral molds (3), (3 '), (4) and (4') are divided into a plurality of pieces, the core mold (1) has a large collapsible stroke and the thread of the molded product (5b) is large. Can be deeper than the depth of. For this reason, the tip end portions of the plurality of insert holding pins (16) are pulled in to a point further inside the inner surface of the molded product. Therefore, it is possible to prevent the problem that the tip of the insert holding pin (16) is cut off when the molded product is taken out. If only the thread surface of the threaded portion (5b) threaded on the outer periphery of the peripheral die (3), (3 '), (4), (4') is deformed, protect the threaded portion of the steel pipe with a protector. When (5) is screwed in, the thread of the steel pipe is clamped by the thread groove of the protector (5) so that it can be tightly screwed, and the protector (5) is loose from the threaded part of the steel pipe. The threaded portion of the steel pipe is firmly protected without coming off.

【Example】

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing a cross section of a part of a metal mold for forming a steel pipe screw protector, FIG. 2 is a plan view of a core mold, and FIG. 3 is II of FIG.
It is a cross-sectional view of the core type taken along the line I-III. A steel pipe screw protector molding die according to this embodiment is a plastic mold of a protector protector (5) for protecting male and female screw parts threaded at both ends of a steel pipe (not shown), and is a cavity mold (7). Core type combined with (1)
, A central mold (2) having a substantially hexagonal cross section, and a plurality of peripheral molds (3) slidably contacting the outer surface of the central mold (2),
(3 '), (4), (4'). In this embodiment, the steel pipe (2
A case will be described in which the female protector (5) mounted on the male screw portion (28a) threaded on the outer periphery of 8) is injection molded. In FIGS. 1 to 3, (2) is a central type having a hexagonal cross section, and the outer side surfaces (2a), (2a ′), (2b), (2
b ') is formed in a taper shape such that it becomes thinner toward the tip. The central mold (2) is fixed to the first core back plate (20) via bolts (11) and is adapted to move forward and backward in the axial direction in synchronization with mold opening and closing. (2c)
Is a rib-shaped guide protruding from the outer surface of the central mold (2). (3) and (3 ') shown in FIGS. 1 and 2
Is a semicircular cross section with a pair of left and right main perimeter types, and the inner surface (3
a) is in sliding contact with the guide (2c) of the central mold (2), while the inner surface (3a ') is in sliding contact with the outer surface (2a'), and the threaded portions (3b) (3b ') are on the outer peripheral surface of each. Is threaded.
The threaded portions (3b) and (3b ') are the male threaded portions (28a) of the steel pipe (28) to which the female protector (5) which is a molded product is screwed.
And the pitch and thread depth are the same. As another embodiment of this threaded surface, as described above, the pitch and the depth of the crest are the same as those of the threaded part of the steel pipe, and the groove width is smaller than the width of the threaded part of the screw so that the threaded part of the steel pipe is Only the shape of the screw surface is deformed so as to be clamped by the screw groove of 5), and when the female protector (5) is mounted on the steel pipe (28), the screw is tightly fitted and the male screw portion (28a) of the steel pipe (28) is ), The female protector (5) may be shaped so as not to easily fall off.
Then, the peripheral types (3), (3 '), (4), (4')
Are respectively fixed to the core plate (12) so as to move forward and backward in the direction perpendicular to the axis.
A first spring (13) is provided between the base end (3c) of the main peripheral type (3), (3 ') and the locking groove (12a) provided in the core plate (12). The main perimeter type (3)
Is pressed and biased in the axial direction. (4) and (4 ') shown in FIGS. 2 and 3 are a pair of left and right sub-peripheral molds having a trapezoidal cross section, and one sub-peripheral mold (4).
Inner surface (4a) of the central mold (2) is in sliding contact with the outer surface (2a), while the inner surface (4a ') of the other sub-peripheral mold (4') is in sliding contact with the outer surface (2b '). The outer peripheral surface of the main peripheral die (3), (3 ') is threaded with threaded portions (4b), (4b') continuous with the threaded portions (3b), (3b '). And
The base end (4c) of the sub-peripheral type (4) has a pin insertion hole (4d).
Has been established. (14) is an inclined pin (angular pin), which is inserted into the pin insertion hole (4d),
When the center mold (2) is retracted at the time of mold opening, a force in the B direction in FIG. 3 is applied to bring the sub-peripheral mold (4) into sliding contact in the B direction, and the sub-peripheral molds (4) and (4 ′) are axially moved. It is designed to purify toward the heart. (15) is a spring provided between the locking hole (4e) provided in the base end portion (4c) of the sub-peripheral type (4) and the side surface of the second core back plate (21), A pressing force is applied to the sub peripheral type (4). Shown in Figures 1 and 3 (1
6) is an end holding pin that holds the end edge of the insert member (6), and the tip end (16a) is the cavity space (G).
Four of them are arranged in the recesses (12b) of the core plate (12) toward the sides via the fixing screws (17). (1
Reference numeral 8) is a peripheral surface holding pin that holds the periphery of the insert member (6), and the front end portion (18a) faces the cavity space (G).
They are respectively arranged in the mounting holes (19) provided in (3 '). (20) is the first core back plate, and the second core back plate (21)
And the screw portion (22a) of the bolt (22). In addition, this bolt (22) is the spacer block (23)
Is inserted into the through hole (23a) of the core, and the base end (22b) is fixed to the core mounting plate (24).
When the mold moves, the hollow mold (2) and the core plate (12) move backward. Reference numeral (25) is an ejector pin, the tip end (25a) of which is directed toward the core plate (12) side, and the base end (25b) of which is fixed to the ejector plate (26) via a mounting screw (27). . The ejector plate (26) is moved forward by a cylinder (not shown) to eject the injection-molded product from the cavity (G) and take it out of the mold. (7) is a cavity type, which molds the outer peripheral surface of the female protector (5) and is fixed to the cavity mounting plate (8). (9) is a sprue bush, through which a sprue (9a) for guiding the molten resin to the shaft is penetrated, and one end communicates with the cavity space (G) and the other end communicates with the sprue tip (9b). Reference numeral (10) is a locate ring that holds the sprue bush (9) and is fixed to the cavity mounting plate (8). Next, the operation will be described. First, the insert member (6) is inserted into the cavity space (G). In this case, the mold is opened and the insert member (6) is inserted into the cavity space (G) shown in FIGS. 1 and 3,
Set in place by a plurality of perimeter insert retention pins (18) and end retention pins (16). Next, the peripheral molds (3), (3 '), (4), (4') are advanced to abut against the outer peripheral surface of the central mold (2) to be integrated, and then the cavity mold (7) side. Move the core mold (1) to the
Subsequently, an injection nozzle (not shown) is brought into contact with the sprue bush (9), and the molten resin is injected into the cavity space (G) by injection and filled. At this time, the insert member (6) is
Since it is held by each holding pin (16), (18), there is no problem of deviation in the cavity space (G). After that, when the resin is cooled and solidified, the mold opening is started.
In this case, the central mold (2), the first and second core back plates (20),
(21), spacer block (23), core mounting plate (24),
Both of the ejector plates (26) are moved backward (in the direction A in FIGS. 1 and 3). As a result, the cavity mold (7) and the core plate (12) are separated from the first parting surface, and the molded product is the peripheral mold (3) (3 ').
(4) It is removed from the cavity mold (7) while being fixed to the outer circumference of (4 '). Next, since the central mold (2) is retracted in the axial direction, the tilt pin (14) forces the code B.
The directional action is urged, and at the same time as the central mold (2) is retracted, the sub-peripheral mold (4) is narrowed at right angles to the axial direction. Subsequently, the main peripheral die (3), which is in sliding contact with the guide (2C) of the central die (2), is pushed out by the spring (13), and this is also squeezed at a right angle toward the axis. When the central mold (2) is retracted in this way, main peripheral molds (3), (3 ')
And the sub-peripheral molds (4) and (4 ') are displaced from each other along the axis, and the sub-peripheral mold (4) is further recessed, so that the main peripheral mold (3) is also more inwardly recessed. Go on. At this time, the peripheral molds (3) and (4) are divided into four parts, and the number of the surfaces in sliding contact in the central mold (2) is increased as compared with the conventional two-divided type, so that the axial mold is smoothed. The entire collapsible action can be increased. In this example, the collapsible stroke is set in advance to 3 to 4 times the depth of the threaded portion (5b) of the female protector (5), and the depth of the thread thread normally threaded into this type of steel pipe is 2 Since it is about 3 mm,
The tip portion (18a) of the peripheral holding pin (18) can be retracted sufficiently inward from the screw portion (5b) of the molded product (5). Therefore, at the time of collapsible, the tip portion (18a) of the holding pin (18) on the peripheral surface is pulled to a position where it does not interfere with the ejection of the molded product (5), and the molded product (5) is surrounded by the peripheral mold (3). It is separated from (3 '), (4) and (4'), and is held only by the insert holding pin (16) for holding the end portion. Finally, the eject cylinder (50) is operated to move the ejector plate (26) forward, the ejector pin (25) ejects the molded product (5), and the protector body (5a) is taken out from the mold. 4 to 6 show a female protector (5) injection-molded as described above. In the figure, (5a) is a protector body, which is injection-molded from a thermoplastic such as high-density polyethylene, low-density polyethylene, polypropylene, etc., which itself has sufficient strength and high impact absorption. (5b) is a female threaded portion that is threaded on the entire inner circumference of the protector body (5a).
(5C) is a trail of the end holding pin (16), and (5d) is a hole of the peripheral surface holding pin (18). (5e) is a recess formed in the upper surface of the protector body (5a), and (5f) is a recess groove provided in the peripheral edge of the upper surface. (6) is an insert member which is an insert fitting, and is formed of a steel ring having a large number of holes as shown in FIG. By the way, the female protector (5) is integrated with the lid (29) as shown in FIG. 8 for use. In the figure, reference numeral (29) is a lid, which is injection-molded by a usual die using the above-mentioned polyethylene or the like as a raw material.
The lid (29) is provided with a fitting portion (29a) on its inner edge, and the fitting portion (29a) is press-fitted and fitted into the recess (5e) of the protector body (5a). Then, the joining line portion (29b) between the lid body (29) and the protector body (5a) is welded by the high frequency dielectric heating method, and both (5) and (29) are welded.
Are integrated. As a result, the upper surface of the protector body (5a) is shielded from the outside air, so that the insert member (6)
Of corrosion is prevented. Then, the female protector (5) configured as described above is provided with a steel pipe (28) as shown in FIG.
It is screwed to the male screw part (28a) of this, and this male screw part (28a)
Is to protect. Although the female protector (5) for protecting the male screw portion (28a) of the steel pipe (28) has been described in the above embodiment, as shown in FIG.
The male protector (30) for protecting b) can be injection-molded in exactly the same manner. In the figure, (30a) is a protector body of the male protector (30), and a male screw portion (30b) is threaded on the outer peripheral surface thereof. (6) is the same insert member as the previous term, (31) is the protector body (30a)
Is the upper part of the lid, and is a fitted lid. With the above structure, the protector body (30a) is shielded from the outside air, so that the insert member (6) can be prevented from being corroded. The male protector (30) can be firmly protected by being screwed into the female screw portion (28b) of the steel pipe (28).

【The invention's effect】

As described above in detail, the steel pipe screw protector molding die according to the present invention includes a core die having a polygonal cross-sectional outer surface, and a central die having a taper shape such that the outer surface is tapered toward the tip. Each inner surface is in sliding contact with the outer surface of the central mold, while a plurality of peripheral molds are formed on all the outer surfaces. Therefore, in the mold opening process, the collapsible stroke of the peripheral mold is set to be larger than the thread depth of the molded product, and the tip of the insert holding pin that holds the insert fitting is retracted further inward than the inner surface of the molded product. Therefore, it is possible to avoid the problem that the tip of the insert holding pin is cut off when the molded product is taken out. Moreover, since the core mold can be sufficiently recessed, the problem that the corners and the like of the core mold are lost can be solved. Furthermore, the peripheral die can be divided into at least four or more pieces, and each of them can perform a collapsible action with a large stroke, so that the outer periphery generated when two peripheral die are used as in the conventional case. It is possible to eliminate the non-threaded portion of the surface and provide a threaded portion on the entire outer peripheral surface. Therefore, when the protector provided with the threaded portion is threaded on the threaded portion of the steel pipe, moisture and water can be blocked, so that the problem of corrosion of the threaded portion of the steel pipe is prevented. In addition, only the threaded surface of the threaded portion of the peripheral type has the same pitch and thread depth as the threaded portion of the steel pipe, and the groove width is smaller than the thread width of the thread. Since it is deformed so as to be sandwiched by the groove, when it is deformed with respect to the threaded portion of the steel pipe, the protector can be tightly screwed and held on the threaded portion of the steel pipe. Therefore, the problem that the protector is loosened and detached from the threaded portion of the steel pipe is avoided, and the threaded portion of the steel pipe is protected more firmly.

[Brief description of drawings]

1 to 8 show an embodiment of the present invention, FIG. 1 is a side view showing a cross section of a part of a steel pipe screw protector molding die, and FIG. 2 is a plan view of a core die. Figure 3 is III-II in Figure 2.
Sectional view of the core mold along the line I, FIG. 4 is a longitudinal sectional view of the molded protective equipment, FIG. 5 is the same plan view, FIG. 6 is the same rear view,
FIG. 7 is a perspective view of an insert fitting, FIG. 8 is a vertical sectional view of a female protector screwed to a steel pipe, FIG. 9 is a vertical sectional view of a male protector showing another embodiment, and FIG. 10 is a conventional core. It is a top view showing a model. (1) …… Core type, (2) …… Center type, (3),
(3 ') ... Main perimeter type, (4), (4') ... Sub-perimeter type, (5) ... Protective equipment (female protector), (5b) ... Screw part, (6) ... Insert Metal fittings (insert member),
(7) …… Cavity type, (9) …… Sprue bush, (12) …… Core plate, (14) …… Inclined pin,
(16) …… Insert holding pin (end holding pin), (1
8) …… Insert retaining pin (peripheral surface retaining pin).

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B29L 1:00 4F

Claims (2)

[Claims] 1. A plastic protector made of a steel pipe male screw reinforced by an insert metal fitting, which has a central mold that moves forward and backward in the axial direction in synchronization with opening and closing of a mold, and a plurality of divided inner faces of the central mold. Steel pipe screw protector injection that has a core mold consisting of a peripheral mold that is in sliding contact with the outer surface, and the core mold retracts during the mold opening process, and the peripheral mold shrinks in the axial direction by the collapsible action of the core mold In the molding die, the central die has a polygonal cross-section, and the outer surface is tapered so that the outer die is tapered toward the tip, and the peripheral die is a sub die that is slidably contacted from both sides through the central die. It is composed of a peripheral die and a main peripheral die having a substantially half-moon shape in cross-section that is in sliding contact with both sides through the central die and the sub-peripheral die, and the sub-peripheral die slides without separating from the central die. Is engaged as The main peripheral die is pressed and biased toward the axis without engaging with the central die, and the collapsible stroke of the collapsible action accompanying the retreat of the central die is larger than the depth of the thread of the molded product. The tip of a plurality of insert holding pins that are set and are arranged on the outer periphery of the peripheral die to hold the insert fittings,
A mold for forming a steel pipe screw protector, characterized in that the mold is retracted further inside than the inside of the molded product. 2. The threaded portion of the peripheral die, which is threaded to the entire outer circumference, has the same pitch and thread depth as the threaded portion of the steel pipe, and the groove width is smaller than the thread width of the thread. The metal mold for forming a steel pipe screw protector according to claim 1, wherein only the shape of the screw surface is deformed so as to be held by the groove.