Process for Molding the Plastic Body of an Air Intake Collector for Internal Combustion Engine

Field of the Invention

The present invention relates to a process for molding in a single piece the body made of plastic of an air intake collector for internal combustion engine.

State of the Art

Conventionally internal combustion engines are equipped with an air intake collector essentially constituted of a collector body made by molding plastic.

Such a collector body comprises a main intake manifold or plenum which is essentially cylindrical and comprises an intake orifice and out of the plenum a respective distribution orifice opens a series of lateral intake conduits each associated with one cylinder head intake channel and with one of the cylinders of the engine.

Each of these intake conduits is conventionally equipped near the plenum with a flared segment with rounded radius surrounding the associated distribution orifice. These flared segments are commonly referred to as a "scroll".

Considering the presence of these flared segments which correspond to overhang elements, the air intake body is conventionally made by molding two distinct parts which must next be welded; this requirement increases to a large extent the time necessary for making the collector body and therefore the cost thereof.

Furthermore, the welding process inevitably leads to irregularities on the inner surface of the plenum which could be sources of loss of pressure. Purpose of the Invention

The purpose of the present invention is to propose a process for molding a collector body in a single piece in a manner to remedy these disadvantages. Brief Description and Advantages of the Invention

The first step of the process according to the invention consists of making a mold constituted of at least two mold shells and having an inner surface corresponding to the outer surface of the collector body to be molded and also openings corresponding to the intake orifice and the outlet orifices of the intake conduits.

This mold comprises a longitudinal cylindrical cavity corresponding to the plenum into which open out a series of transverse cylindrical cavities corresponding to the intake conduits and each equipped with a flared segment with rounded radius near the longitudinal cavity.

These various cylindrical cavities open out towards the outside by associated openings.

The second step of the process according to the invention consists of inserting into the cylindrical cavities, through the openings in the mold thus made, both at least one main mold core extending over the entire length of the mold and corresponding to the inner periphery of the plenum and the flared segments of the intake conduits, and also a series of auxiliary cores each corresponding to the inner periphery of the remaining segment of the associated intake conduit.

To enable the extraction thereof after molding of the collector body, the main mold core is constituted of two longitudinal core elements nested in each other and capable of sliding on each other.

These two core elements which extend over the entire length of the mold consist of a first core element having an essentially smooth surface and corresponding to a first portion of the periphery of the plenum, and of a second core element which corresponds to the remaining portion of the periphery of the plenum and also to the flared segments of the intake conduits.

The second core element thus comprises the transverse flared end pieces which project from the periphery thereof.

After introduction of the mold cores in the cavities corresponding to the plenum and the intake conduits of the mold, the step of molding the collector body is implemented in a manner well- known per se.

The auxiliary cores can then be extracted conventionally.

Considering the specific configuration thereof, the main mold core can also be easily extracted from the mold.

This extraction is done in three phases.

The first phase consists of extracting the first core element longitudinally through the mold opening corresponding to the intake orifice by sliding it along the second core element.

The second phase consists of moving the second core element transversely so as to position it in the volume thus released by the first core element and to release the flared end corresponding to the flared segments of the intake conduits. According to the invention, the first and second phases are performed simultaneously.

During the third phase of this extraction, the second core element can itself also be easily extracted longitudinally just like the first core element.

The only thing remaining is to then unmold the collector body.

According to the invention, the first or second core element is advantageously equipped with a longitudinal rib extending the entire length thereof whereas the second or first core element is equipped with an associated longitudinal groove which also extends the entire length thereof.

This rib and this groove enable easier introduction and positioning of the main mold core in the mold by locking the two core elements relative to each other and additionally defining a guiding rail during the first extraction phase of the first core element through the opening of the mold corresponding to the intake orifice.

According to a preferred feature of the invention, the first and second core elements are wedge shaped.

This feature is also of a type to facilitate to a great extent the extraction of the first core element.

According to a first variant of the invention, a single main mold core with a length corresponding to the length of the mold and constituted of two core elements nested in each other is used.

This mold core is inserted in the mold through the opening corresponding to the intake orifice

According to a second variant of the invention, two main mold cores are used having a length corresponding essentially to half of the length of the mold and each constituted of two core elements nested in each other.

According to this variant, it is necessary to equip the mold with an extra opening located opposite the opening corresponding to the intake orifice at the end of the longitudinal cylindrical cavity.

One of the main mold cores is inserted in this longitudinal cavity by the opening corresponding to the intake orifice whereas the second main mold core is inserted in it by the extra opening.

These two main mold cores come to bear against each other at the median part to the longitudinal cylindrical cavity.

According to the second variant of the invention, after the step of molding the collector body, the first core element of each of the main mold cores is extracted longitudinally respectively from either side of the mold by sliding it along the second associated core element.

Next the second core element of each of the principal mold cores is moved transversely for clearing the flared ends corresponding to the flared segments of the intake conduits and then it is extracted longitudinally, respectively from either side of the mold.

The extraction of the two main mold cores is here again done in three phases.

After the step of unmolding the collector body, this second variant of the invention requires implementation of an additional step consisting of welding a cap in order to close the orifice corresponding to the extra opening of the mold.

In the preferred case where the two core elements of the main mold core are wedge-shaped, these are arranged head to toe in the mold. Drawings

The features of the process which is the subject of the invention will be described in more detail with reference to the attached nonlimiting drawings in which:

- Figure 1 is a perspective and transparent view of the collector body. - Figure 2 is a sectional view representing a main mold core inserted in a mold according to the first variant of the invention.

- Figures 3 and 4 are illustrative drawings of the three phases of the extraction step of this main mold core, according to the first variant of the invention.

- Figure 5 is a sectional view similar to Figure 2 but corresponding to the second variant of the invention.

- Figure 6 and 7 are respectively illustrative drawings of the three phases of the extraction step of the main mold cores, according to the second variant of the invention. Description of an Embodiment of the Invention

According to Figure 1 , the collector body needing to be molded comprises essentially a collector body 1 comprising a main cylindrical intake manifold or plenum 2 in which the pressurized air enters by an intake orifice 3 located at one of the ends thereof and which is closed at the opposite end 4 thereof located facing this intake orifice 3.

A series of intake conduits 5 open out latterly into the plenum 2 by a respective distribution orifice 6.

The intake conduits 5 are each equipped with an outlet orifice 7 at their end opposite the distribution orifice 6 and are respectively associated with a cylinder head intake channel and with one of the cylinders of the engine in a manner not shown in Figure 1.

Each of the intake conduits 5 is equipped, near the plenum 2, with a flared segment also called a rounded core scroll 8 which surrounds the associated distribution orifice 6.

According to Figure 2, the first step of the implementation of the process according to the invention consists of making a mold 10 constituted of at least two mold shells and having an inner surface which corresponds to the outer surface of the collector body 1 needing to be molded.

This mold 10 comprises a longitudinal cylindrical cavity 12 corresponding to the plenum 2 into which open out a series of transverse cylindrical cavities 15 corresponding to the intake conduits 5.

The transverse cylindrical cavities are each equipped with a flared segment 18 with rounded radius corresponding to the flared segment 8 near the longitudinal cavity 12.

Additionally the mold 10 is equipped with an opening 13 located at one of the ends of the longitudinal cylindrical cavity 12 and corresponding to the intake orifice 3, along with a series of opening 17 located respectively at the free ends of the lateral cylindrical cavities 15 and corresponding to the outlet orifices 7 of the intake conduits 5. According to Figure 1, to mold the collector body 1 in the mold 12, a main mold core 20 which extends the entire length of the longitudinal cylindrical cavity 12 and corresponds to the inner periphery of the plenum 2 and the flared segments 8 of the intake conduits 5 is inserted through the opening 13 into this cavity 12.

The main mold core 20 is more specifically constituted of two wedge-shaped longitudinal core elements 21 , 22 which are nested in each other and which are capable of sliding on each other.

These two core elements 21 , 22 extend the entire length of the longitudinal cylindrical cavity 12.

The first element of the core 21 has an essentially smooth surface and corresponds to a first portion of the periphery of the plenum 2, meaning to the part opposite distribution orifices 6.

The second core element 22 corresponds to the remaining portion of the periphery of the plenum 2 and also to the flared segments 8 of the intake conduits 5.

The second core element 22 thus comprises the flared end pieces which project from the periphery thereof.

These flared and pieces 23 are shown more clearly in Figure 4.

The first core element 21 is furthermore equipped with a longitudinal groove 21 i which extends over the entire length thereof whereas the second core element 22 is equipped with a longitudinal rib 221 associated which also extends on the entire length thereof.

This groove 21 i and this rib 221 , which facilitate sliding of the two core elements 21, 22 on each other, are shown more clearly in Figure 4.

In a manner not shown in the figures, auxiliary cores are also inserted into the lateral cylindrical cavities 15.

These auxiliary cores are extracted from the mold 10 after the molding operation of the collector body 1 in a manner known per se.

According to Figure 2, the main mold core 20 cannot be directly extracted from the mold 10 through the orifice 13 after the step of molding the collector body 1 because of the presence on the periphery of the second core element 22 of flared end pieces 23 corresponding to the flared segments 8 of the intake conduits 5 which constitute overhanging elements.

Consequently, this extraction is done in three phases.

As shown in Figure 3, the first of these phases consists of longitudinally extracting the first core element 21 through the opening 13 of the mold 10 by sliding it along the second core element 22 as indicated by the arrow A.

The second phase consists of moving the second core element 22 transversely in the space thus freed by the first core element 21 as indicated by the arrow B so as to clear the flared end pieces 23.

As shown in Figure 4, these end pieces 23 having been cleared, the second core element 22 can itself also be extracted longitudinally from the mold 10 by the open opening 13 according to arrow A.

As shown in Figures 5, 6 and 7 according to the second variant of the invention, the main mold core 20 from the first variant of the invention is replaced by two main mold cores 30, 30' that are inserted respectively into the longitudinal cylindrical cavity 12 from either side of this cavity through the opening 13 which corresponds to the intake orifice 3 and through an extra opening 1 1 of the mold 10 which is located opposite the opening 13.

These main molding cores 30, 30' have a length corresponding to half the length of cavity 12 of the mold 10 and in molding position come to bear against each other by their frontal surface at the median part of this cavity.

As shown in Figures 5, 6 and 7, the two main molding cores 30, 30' are more specifically constituted of two wedge-shaped longitudinal core elements 31 , 32, 3 , 32' which are nested in each other and located "head to toe" in the molding position shown in Figure 1.

The core elements 31 , 32 and 3 , 32' of the main mold cores 30, 30' have a configuration essentially similar to that of the core elements 21 , 22 of the main mold core 20 according to the first variant of the invention.

The first core elements 31 , 3 thus have an essentially smooth surface and correspond to a first portion of the periphery of the plenum 2 of the collector body 1 whereas the second core elements 32, 32' correspond to the remaining portion of the periphery of the plenum 2 and also to the flared segments 8 of the intake conduits 5.

Consequently, the second core elements 32, 32' comprise flared end pieces 34, 34' which project on their periphery.

The core elements 31 , 3 Γ and 32, 32' are also equipped with associated ribs 3 1 i, 31 i' and grooves 321 , 321 ' as shown more precisely in Figure 7 in order to facilitate their sliding on each other.

After the molding step, the extraction of the main cores 30, 30' is here again done in three phases in a manner essentially similar to the extraction of the main mold core 20 according to the first variant of the invention, but symmetrically from both sides of the mold 10 respectively through the openings 13 and 1 1 thereof.

As shown in Figure 6, the first phase of this extraction step consists of longitudinally extracting the first core elements 31 , 3 from both sides of the mold 10 by sliding them along the second core elements 32, 32' as indicated by the arrows A and A'.

The second phase that this extraction step consists of moving the second core elements 32, 32' transversely as indicated by the arrows B and B' into the space freed by the first core elements 31 , 3 so as to release the flared end pieces 34, 34'.

According to the Figure 7, the second core elements 32, 32' thus released can themselves also be extracted longitudinally according to the arrows A and A' through the openings 13, 1 1 respectively on either end of the mold 10.

The implementation of the process conforming to this second variant of the invention requires an additional step consisting of welding a cap 33 allowing closure of the orifice in the molded collector body 1 corresponding to the extra opening 1 1 of the mold 10.