JPH0692137B2 - Cylindrical or columnar protrusion integrated with the plastic plate surface - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a cylindrical or pillar-shaped projection that is usually integrally molded on the back surface of a plastic plate, and more specifically, the projection is processed. The present invention relates to a cylindrical or columnar protrusion that prevents a recess from being formed on a plate surface opposite to a plate surface to be formed and obtains a smooth surface.

[Conventional technology]

As shown in FIG. 6, conventionally, when the cylindrical projection 2 is integrally formed on one side surface of the plastic plate 1, the volume thereof shrinks as the cooling progresses, and the end surface of the cylinder on the other side surface of the plate 1 contracts. An annular recess 3, which is generally called a sink mark, lower than the other side surface was formed in the corresponding portion, and thus the appearance of the surface of the plastic plate was significantly impaired.

As a conventional technique for preventing the formation of the recess 3, first,
First, it is well known that the wall thickness of the cylinder is made uniformly thin or the diameter of the column is made thin.

Next, as a second conventional means, as shown in FIGS. 7 and 8, the thickness of the cylindrical projection 2 itself is processed to be sufficiently thick, but the thickness of the base of the cylindrical projection 2 is centered from one side. It is well known to provide an eccentric hole 4 which is machined by sliding (commonly called “Nusum”) to a depth exceeding a part.

As a third conventional means, it is known that the injection pressure of the resin is increased and the resin is cooled at a high pressure to cancel the volume contraction.

[Problems to be Solved by the Invention]

However, the conventional first means has a problem that the strength of the protrusion is weak and lacks in durability, and the second means is
Not only is the strength weak when an eccentric load is applied, but it also takes time and labor to process the eccentric hole 4, and the third means requires a lot of time to adjust the appropriate value of the injection pressure. In the case of excessive pressure, the length of the projection is changed, or burr is generated, which causes inconvenience in removing the burr.

An object of the present invention is to provide, when a cylindrical or columnar projection is provided on a plastic plate surface, a projection on which a dent (commonly called a sink mark) never occurs on the surface opposite to the plate surface,
Furthermore, it is to provide a simple and inexpensive projection in which the strength of the projection is not slightly reduced.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the present invention provides an annular groove having a uniform depth along the outer surface of the base of the cylindrical projection that contacts the surface of the plastic plate. However, when the strength of the projection is reduced by the ring groove, a plurality of ribs are provided at equal intervals in the radial direction between the bottom surface and the both side surfaces forming the ring groove.

The comparison between the thickness a of the plastic plate and the wall thickness b of the constricted portion formed by the ring groove is set to approximately b ≦ 1 / 3a.

A surface of the protrusion that is adjacent to the outer surface and forms the annular groove is an outwardly-opened slope.

Even when the cylindrical protrusion is a columnar protrusion, the same configuration as described above is possible.

[Work]

In the present invention, the annular groove having a uniform depth is provided along the outer surface of the base portion of the protrusion that is in contact with the plate surface, and since the annular groove is not eccentric, a constant strength is always provided against an eccentric load from all directions. It is possible to deal with it, and the strength does not vary depending on the orientation.
However, when the strength of the protrusions is uniformly reduced by the annular groove having the uniform depth, the reduced strength is reinforced by the ribs arranged at equal intervals in the radial direction.

It was clarified experimentally that a dent (commonly called a sink mark) on the plate surface does not occur when the thickness b of the protrusion is set to 1/3 or less than the plate thickness a of the plastic. However,
It has also been clarified that this value causes a significant decrease in strength. Therefore, in the present invention, on the other hand, the thickness of the constricted portion in contact with the plate surface of the projection is reduced to the value indicated by the above numerical value, and at the same time, the strength reduction is reinforced by the ribs arranged at equal intervals in the radial direction. Is.

The reason why the ring groove forming surface on the side adjacent to the outer surface of the protrusion is an inclined surface that is opened outward is for facilitating attachment and detachment of the molding die.

〔Example〕

A concrete embodiment of the cylindrical projection integrated with the plastic plate surface according to the present invention is, as shown in FIGS. 1 and 2, a cylindrical projection on one side surface of the plastic plate 1 having a plate thickness a, for example, When the boss 2 is integrally molded, a ring groove 5 having a uniform depth is provided along the outer surface of the base of the protrusion 2 contacting one side surface of the plate 1, and the bottom surface 5a and both sides of the ring groove 5 are formed. surface
A plurality of ribs arranged at equal intervals in the radial direction between 5b and 5c
Reinforce with 6,6a, 6b and 6c. The base of the protrusion 2 becomes a constricted portion 7 having a wall thickness b due to the formation of the ring groove 5,
It contacts the plate 1 through the constricted portion 7.

The thickness b of the constricted portion 7 with respect to the plate thickness a of the plate 1 is b ≦
By setting it to 1 / 3a, the dent 3 on the opposite side of the plate 1
(See FIG. 6) can be prevented. That is,
When the plate thickness a is 3 mm, the wall thickness b of the constricted portion 7 is set to 1 mm or less.

Of the surfaces forming the ring groove 5, the side surface 5c adjacent to the outer peripheral surface of the projection 2 is preferably an outwardly open inclined surface in order to facilitate the operation of the mold during molding.

An example of a mold for molding the cylindrical projection 2 integral with the surface of the plastic plate 1 is shown in FIGS. 3 to 5.

Both side surfaces of the plate 1 are processed by one mold 8 and the other mold 9, and a circular through hole 10 (see FIG. 4) for processing the protrusion 2 is formed in the other mold 9. ing.

The projection 2 is processed by the four-divided molds 11, 11a, 11b and 11c whose tips are gathered in the circular through hole 10 and the core rod 12 for forming the cavity of the projection 2. 4 above
As shown in FIG. 5, each of the divided molds has a protrusion 2
A concave portion 13 for forming the outer peripheral surface and a protrusion 14 for forming the constricted portion 7.
And a pair of recesses 15 and 15 for forming the rib 6.

The other mold 9 is displaced in the direction away from the plate 1 along the outer peripheral surfaces of the four-divided molds 11, 11a, 11b and 11c (displaced downward in FIG. 3) when the injection molding of the resin is completed. ), The displacement allows each mold to be displaced outward in the radial direction, and thus each mold is separated from the outer peripheral surface of the protrusion 2, the constricted portion 7 and the ribs 6, 6a, 6b and 6c. .

The embodiments described above are not intended to limit the invention, which extends to all modifications within the scope of the claims.

〔The invention's effect〕

As described in detail above, when a cylindrical or columnar protrusion is integrally formed on one side of a plastic plate, conventionally, a portion corresponding to the end face of the protrusion on the other side of the plate is dented by heat shrinkage (commonly called a sink mark). According to the present invention, the ring groove having a uniform depth is removed along the outer surface of the base of the protrusion that is in contact with the plate surface. Further, according to the present invention, by providing a plurality of reinforcing ribs arranged at equal intervals in the radial direction between the bottom surface forming the annular groove and the both side surfaces, the mechanical strength is not lowered at all. ,
I succeeded in eliminating it.

Further, in the present invention, the comparison between the thickness a of the plastic plate and the thickness b of the constricted portion formed by the annular groove is approximately b ≦ 1 /
If it is set to 3a, it becomes possible to almost certainly eliminate the occurrence of the depression due to the heat contraction.

[Brief description of drawings]

1 is a longitudinal sectional view taken along line 1-1 of FIG. 2 showing an embodiment of a cylindrical projection integrated with a plastic plate surface according to the present invention, and FIG. 2 is taken along line 2-2 of FIG. FIG. 4 is a cross-sectional elevation view along FIG. 3, illustrating the relationship between the cylindrical projection integral with the plastic plate surface shown in FIG. 1 and the molding die.
-3 is a longitudinal sectional view taken along line -3, Fig. 4 is a horizontal cross-sectional view taken along line 4-4 of Fig. 3, and Fig. 5 is an exploded view of a part of the mold shown in Figs. 3 and 4. FIG. 6 is a vertical cross-sectional view of a cylindrical projection integrally formed with a plastic plate surface that has been conventionally produced, and shows a state where an annular recess is formed on the plate surface. FIG. 7 is a vertical cross-sectional view of a cylindrical projection integral with a conventionally known improved plastic plate surface, and FIG. 8 is a cross-sectional view taken along line 8-8 of FIG. 1 ... Plastic plate, a ... thickness, 2 ... cylindrical protrusion, for example, boss, 3 ... annular recess, 4 ... eccentric hole, 5 ... ring groove, 5a ... bottom surface, 5b And 5c ... sides thereof, 6,6a, 6b and 6c ... reinforcing ribs, 7 ... constricted portion, b ... thickness, 8 ... one mold, 9 ... other mold , 10 ... Circular through-holes, 11, 11a, 11b and 11c ... 4-divided mold, 12 ... Core bar for forming cavity of protrusion 2, 13 ... Recess for forming outer peripheral surface of protrusion 2, 14 ... Projections for forming the constricted portion 7, 15, 15 ... A pair of recesses for forming the rib 6.

Claims (4)

[Claims] 1. A cylindrical projection integral with a plastic plate surface, wherein a ring groove having a uniform depth is provided along an outer surface of a base of the projection in contact with the plate surface, and a bottom surface forming the ring groove. A cylindrical projection integrated with a plastic plate surface, which is reinforced by a plurality of ribs arranged at equal intervals in the radial direction between both side surfaces. 2. The thickness a of the plastic plate and the thickness b of the constricted portion formed by the annular groove are compared with each other by approximately b ≦.
The cylindrical projection integral with the plastic plate surface according to claim 1, set to 1 / 3a. 3. The surface on which the ring groove is formed on the side adjacent to the outer surface of the protrusion is an inclined surface that is open outward.
Cylindrical projections integral with the described plastic plate surface. 4. The columnar protrusion as the cylindrical protrusion,
A columnar protrusion integrated with the plastic plate surface according to the item 2 or 3.