ES2389530B1 - INJECTION MOLD FOR THE OBTAINING OF ANNULAR PARTS WITH A HELICOIDAL TOOTHED OUTSIDE SURFACE. - Google Patents

Abstract

Injection mold for obtaining annular parts with a helical serrated outer surface. # The injection mold comprises a fixed part (1) and a mobile part (2) that can be closed on the fixed part (1) to define a cavity of injection (6). The fixed part (1) comprises an annular support piece (3) with radial grooves (4) distributed throughout the piece (3) and a plurality of forming pieces (5) that can move in the radial grooves (4) of the piece annular support (3), presenting a part of the forming pieces (5) a profile (7) corresponding to a part of the geometry of the piece to be obtained. The mold comprises displacement means (9) configured to move the forming parts (5) in said radial grooves (4) so that they can occupy a first position in which the profiles (7) of the forming parts (5) form a continuous surface that reproduces the complete geometry of the toothed outer surface of the piece to be obtained and a second position in which the forming pieces allow the extraction of the piece obtained.

Description

INJECTION MOLD FOR THE OBTAINING OF ANNULAR PARTS WITH A HELICOIDAL TOOTHED OUTSIDE SURFACE

5 1O

TECHNICAL FIELD OF THE INVENTION The invention encompasses in the field of injection molding devices and, more specifically, molds that allow obtaining parts with a metal core and an outer plastic part injected on the metal core that presents a helical serrated outer surface.

BACKGROUND OF THE INVENTION

15 20

At present, injection molds for obtaining plastic parts are widely known. These molds generally comprise a fixed part and a movable part that can be enclosed on the fixed part, forming a cavity between the movable part and the fixed part that presents the geometry of the piece to be obtained. The plastic material is injected into said cavity through injection channels. Once the plastic material has solidified, the movable part of the mold opens to allow the extraction or demoulding of the shaped plastic part.

25 30

It is also known to obtain parts comprising a metal core and a plastic outer part. In order to obtain these bi-material pieces, an injection mold of similar configuration to that described above is used but with the particularity that the metal core (obtained in a separate process) is placed inside the mold cavity and, then, the plastic material is injected into said metal core. As a result, the mentioned bi-material part is obtained.

5

The extraction of the pieces obtained by injection, generally consists in the separation of the movable part of the mold from the fixed part so that there is sufficient space between both parts to allow the extraction of the injected part. The problem is when the exterior configuration of the piece obtained is complex (for example, a helical cogwheel) and its extraction with respect to the fixed part of the mold is not possible.

1 o

In order to obtain complex parts, such as a helical cogwheel, a part with a smooth outer surface is generally obtained by injection which must be machined in later to carve the helical cog.

DESCRIPTION OF THE INVENTION

fifteen

20 25

The object of the invention is an injection mold for obtaining annular parts with an outer toothed surface (for example helical sprockets) comprising a fixed part and a movable part that can be closed on the fixed part to define an injection cavity. As is conventional, the injection material (for example plastic) can be introduced into the injection cavity by means of injection. To remove the injected part, the movable part of the mold is removed. The mold of the invention is specially designed to allow the injected part to be removed from the fixed part of the mold, when the part has an external toothed surface, such as a helical cogwheel, without its subsequent machining being necessary.

According to the invention, the fixed part of the injection mold comprises:

30

An annular support piece with radial grooves distributed throughout the part (preferably, the grooves are evenly distributed along the entire perimeter of the support piece),

a plurality of forming pieces that can move in

the

radial grooves of the annular support piece, presenting a part of the

forming pieces a profile that corresponds to a part of the geometry

of the piece to obtain, and

5

displacement means configured to move the parts

forming in said radial grooves so that they can occupy a

first position in which the profiles of the forming pieces make up

a continuous surface that reproduces the complete surface geometry

serrated outside of the piece to be obtained and a second position in which the

1 o

forming pieces allow the extraction of the piece obtained.

The first position corresponds to a position in which the pieces

trainers have moved radially to approach the center of the

annular support piece defining a continuous surface approximately

fifteen

circular (with a geometry corresponding to the toothed outer surface

of the piece to obtain). In the second position, the forming pieces have been

moved radially to move away from the center of the annular support piece,

leaving a free space between the toothed outer surface of the piece a

obtain and the forming pieces, allowing the extraction of the piece

twenty

obtained by injection.

The moving part may comprise a guide piece with a

annular protrusion of inclined section (for example, a configuration

divergent conical trunk) and forming pieces may have a groove

25

inclined configured to allow annular protrusion housing

of the guide piece in such a way that when the moving part moves to

approach the fixed part to close the mold the guide piece displaces the

forming pieces to the first position (the first position is achieved

when the mold is completely closed and the movable part is coupled

30

on the fixed part) and when the mobile part moves to move away from the

moving part to open the mold, the guide piece displaces the forming parts

until the second position (the second position is achieved with the mold

open and the mobile part separated from the fixed part a distance that

allows the extraction of the piece obtained.

35

The fixed part of the mold can comprise injection channels

configured to allow the passage of an injection fluid into the injection cavity, from the injection means.

5 1 O

The mold of the invention can comprise a closure ring that is attached to the annular support piece and that is configured to cover at least partially the grooves of the support piece to keep the forming parts inside the said grooves of the support piece during the movement of the moving part of the mold. In this way, the displacement of the mobile part of the mobile with respect to the fixed part, in accordance with the axial direction with respect to the annular support piece, is transformed (through the action of the annular protuberance in the inclined grooves of the pieces forming) in a displacement of the forming pieces in radial direction with respect to the annular support piece.

15 20 25

The injection cavity defined between the fixed part and the mobile part is configured to house a metal part (for example, a metal core that will constitute the core of a cogwheel) such that it enters between the outer surface of the metal part and the profile of the forming pieces in said first position defines an annular injection cavity that allows obtaining a piece with a metal core constituted by the metal part and an annular outer part over-injected onto the metal core. This outer part will have a toothed surface with a configuration corresponding to the continuous surface defined by the profiles of the forming pieces (for example, a cogwheel with a metal core and a cogged outer part of plastic material can be obtained).

30

The profiles of the forming pieces can form an annular toothed surface comprising alternating teeth and channels and the profile of each forming piece can have a geometry corresponding to a channel and half a tooth of the annular toothed outer surface.

35

DESCRIPTION OF THE FIGURES

5

To complement the description and in order to help a better understanding of the features of the invention, according to some preferred examples of practical implementation thereof, a set of figures is attached as an integral part of said description in which Illustrative and non-limiting, the following has been represented:

1 o

Figure 1.- Shows a schematic perspective of the movable part and the fixed part of the mold in a position in which the mold is open. This figure shows the annular support of the fixed part and of the forming parts housed in the radial grooves.

fifteen

Figure 2.- Shows a schematic perspective of the mobile and fixed part of the mold in a position in which the mold is open. In our figure the guide piece of the moving part is represented.

twenty

Figure 3.- shows an exploding perspective of the fixed part of the mold, the annular support piece, a forming part, the closing ring and a metal core on which the over injection with plastic material is to be carried out.

25

Figure 4.- Shows a piece with a metal core and a plastic outer part with a helical toothed surface obtained with the mold of the invention.

30

Figure 5 shows a section of the mold of the invention open position, just before the guide part of the moving part enters the inclined grooves of the forming parts. in himself

Figure 6.- Shows a section of the mold of the invention in an open position but at an intermediate point in which the guide part of the movable part is partially inserted into the grooves of the forming parts such that the forming parts have been displaced

5 radially with respect to the position of figure 5.

Figure 7.- Shows a section of the mold of the invention in a closed position with the guide part of the movable part completely inserted in the grooves of the forming parts. In such a way that

1 O forming pieces are in the injection position.

Figure 8.- Shows a representation of the profile of a forming part.

Figure 9 shows a representation similar to that of Figure 8 for two contiguous forming pieces in the molding position.

Figure 10. - It shows three views of the piece to be obtained in the mold of the invention, on which lines that delimit the part of the teeth of the annular outer surface that is obtained from

each of the forming pieces.

PREFERRED EMBODIMENT OF THE INVENTION

25 Figure 1 shows a mold that is composed of a fixed part (1) and a movable part (2). The movable part (2) is represented in the aforementioned separate figure with respect to the fixed part (1), that is, in an open mold position that allows for example the extraction of the obtained injection part.

The fixed part (1) comprises an annular support (3) with radial grooves

(4) evenly distributed throughout the contour or periphery of the piece

ring support (3). These radial grooves (4) form guide channels

in whose interior they lodge with possibility of displacement a plurality

5

of forming pieces (5). A single piece is shown in figure 3

forming machine (5) it being understood that the mold incorporated a forming part

(5) in each of the radial grooves (4) of the annular support piece (3).

The forming pieces (5) can move radially with respect to

1 o

of the annular support piece (3) so that they can occupy a first

position, corresponding to the maximum displacement towards the center of the

piece, in which they define a continuous circular surface that delimits the

injection cavity (6). This position is observed for example in the figure

7. The forming pieces have a part (7), corresponding to the part

fifteen

of the forming pieces (5) closest to the injection cavity (6), which

has a profile that corresponds to a part of the geometry of the piece to

obtain in such a way that in the first position the surface continues

formed by the forming pieces (5) reproduces the complete geometry of

the toothed outer surface of the piece to be obtained (the surface continues

twenty

constitutes as the sum of each of the parts of the profiles of the

forming pieces).

The forming pieces (5) can occupy a second position of

displacement, radially away from the center of the piece

25

ring support (3) as seen for example in figure 5. In this

position the profiles of the forming pieces (5) constitute a surface

circular, does not continue with a diameter greater than the injection cavity and

therefore a diameter greater than the outer diameter of the piece obtained.

In this way, it is possible to easily unmold the piece obtained with respect to

30

of the fixed part (1) of the mold.

The device also comprises a closing ring (8) that is

tie over the ring support piece (3) so that it covers at least

partially the grooves of the support piece (3) so that the pieces

Formers (5) can only move radially, in the

5

inside the radial grooves (4), having limited movement in a

direction parallel to the displacement of the movable part (2) of the mold.

As can be seen in figure 2, the mobile part (2) comprises a

guide piece (9) comprising an annular protuberance (approximately

1 o

conical trunk). This annular protuberance is configured to be able to

stay inside of inclined grooves (1 O) of the pieces

trainers (5). When the mobile part (2) closes on the fixed part (1) the

annular protuberance (9) is introduced simultaneously in all slots

inclined (1 O) of the forming pieces (5) causing their sliding

fifteen

radial towards the center of the annular support piece (2), inside the

radial grooves (4). This position has been represented in Figure 6.

At the moment the moving part (2) contacts the fixed part (1) the

mold is completely closed and the forming pieces have

twenty

reached its first position defining the injection cavity (6) that

present a continuous contour or serrated surface according to the profiles (7)

of the forming pieces (5) .This is the position represented in figure 7.

When the mold is opened, by displacement of the movable part (2), the

25

annular protrusion (9) leaves the inclined grooves simultaneously

(1 O) of the forming pieces (5) causing their radial distance from the

center of the ring support piece (2), inside the radial grooves

(4). This position has been represented in figure 5. In this way the pieces

Formers form a cavity of greater diameter than the cavity of

30

injection (6) allowing the extraction of the toothed part.

The fixed part (1) of the mold comprises injection channels (11) a

through which an injection plastic is injected into the cavity of

injection (6).

5

As seen in figures 6, 7 and 8 inside the

Injection cavity (6) of the mold a metal part (12) has been arranged

such that between the outer surface of the metal part (12) and the

continuous surface of the forming pieces (5) in said first

position (mold closing position) an injection cavity is defined

1 o

annular (13) that allows to obtain a piece with a constituted metal core

by the metal part (12) and an outer part (14) of plastic on

injected over the metal core (12).

fifteen

The outer part (14), as shown in Figure 4,

it has a serrated, helical outer surface, comprising teeth

(14 ') and alternating channels (14 "), obtained as a sum of the profiles (7) of

each of the forming pieces (5). Specifically, the profile (7) of each

forming piece has a protuberance (71) with a geometry

twenty

corresponding to a channel (14 ") and a wall (72) with a geometry that

reproduces approximately half a tooth (14 ') complete from the surface

outer (14) annular toothed, that is to say that the profiles (7) of two pieces

trainers (5) that are contiguous allow to obtain a tooth (14 ')

of the outer annular surface (14). The configuration of a profile (7) is

25

see in figure 8. In figure 9 two pieces have been represented

forming machines (5) contiguous in molding position forming a surface

of molding that allows to obtain a tooth (14 ') complete of the piece.

As can be seen in figures 8 and 9, the profile (7) of each piece

30

trainer (5) presents two vertical sections (73), in the upper part and

lower profile (7) and an oblique intermediate section (74) presenting a

inclination similar to that of the teeth (14 ') of the piece. This configuration of

the forming pieces (5) allows the removal of the forming pieces from

the first position (molding position) to the second position (part removal position).

5

Finally, in figure 1 O the piece to be obtained is shown and on it lines have been represented that delimit the part of the outer surface (14) that are obtained from each forming piece (5).

1 o

In this text, the word "comprises" and its variants (such as "understanding", etc.) should not be construed as excluding, that is, they do not exclude the possibility that what is described includes other elements, steps, etc.

fifteen

On the other hand, the invention is not limited to the specific embodiments that have been described but also covers, for example, the variants that can be made by the average person skilled in the art (for example, in terms of the choice of materials, dimensions , components, configuration, etc.), within what follows from the claims.

Claims (5)

1.-Injection mold for obtaining annular parts with a helical serrated outer surface comprising a fixed part (1) and a mobile part (2) that can be closed on the fixed part (1) to define an injection cavity (6) characterized in that the fixed part (1) comprises: An annular support piece (3) with radial grooves (4) distributed throughout the part (3), 10 a plurality of forming pieces (5) that can move in the radial grooves (4) of the annular support piece (3), a part of the forming pieces (5) having a profile (7) corresponding to a part of the geometry of the piece to obtain, 15 displacement means (9) configured to move the forming parts (5) in said radial grooves (4) so that they can occupy a first position in which the profiles (7) of the forming parts (5) form a surface continues to reproduce the 20 complete geometry of the helical toothed outer surface of the piece to be obtained and a second position in which the forming pieces allow the extraction of the piece obtained, where the movable part comprises a guide piece with a protuberance 25 annular (9) of inclined section and because the forming pieces have an inclined groove (10) configured to allow the annular protuberance (9) of the guide piece to be accommodated in such a way that when the movable part (2) moves to approach the fixed part (1) to close the mold the inclined protrusion (9) of the guide piece displaces the forming parts 30 (5) to the first position and when the movable part (2) moves to move away from the fixed part (1) to open the mold, the guide piece moves the forming parts (5) to the second position. 2. Mold according to claim 1 wherein the fixed part (1) comprises 35 injection channels (11) configured to allow the passage of an injection fluid into the injection cavity. 13 3. Mold according to any of the preceding claims comprising a closure ring (8) that can be attached to the annular support piece (3) and which is configured to cover at least partially 5 the radial grooves (4) of the support part (3) to keep the forming parts (5) inside said radial grooves (4) of the support part during the movement of the moving part (2) of the mold. 4.-Mold according to any of the preceding claims in which the 10 injection cavity (6) defined between the fixed part (1) And the mobile part (2) is configured to accommodate a metal part (12) such that between the outer surface of the metal part (12) and the profile (7) of the forming pieces (5) in said first position an annular injection cavity (13) is defined that allows obtaining a piece with a metal core 15 constituted by the metal part (12) and an annular outer part (14) superinjected on the metal core. 5.-Mold according to any of the preceding claims in which the profiles (7) of the forming pieces (5) form an outer surface, 20 helical toothed comprising teeth (14 ') and alternating channels (14 "), said profile (7) of each forming part comprising a protuberance (71) with a geometry corresponding to a channel (14") and a wall (72 ) with a geometry that reproduces approximately half a tooth (14 ') of the helical toothed outer surface. 6. A mold according to claim 5 in which the profile (7) of each forming part (5) has two vertical sections (73), at the top and bottom of the profile (7) and an oblique intermediate section (74) which has an inclination similar to that of the teeth (14 ') of the toothed outer surface 30 helical