WO2007051857A2 - Thermoplastic material injection moulding device - Google Patents

Abstract

The invention relates to a device for thermoplastic material injection moulding. An injection longitudinal nozzle (13) arranged in the channel (15, 16, 17) of an injection matrix (1) is supplied by means of a distributor (18). The front end (74) of the nozzle (13) forwardly abuts against the collar (86) of the channel (15, 16, 17), whereas the rear end area (48) of the nozzle (13) is arranged in the longitudinal output channel (28) of a distributor (18) in such a way that it is longitudinally slidable therein and is mutually sealed therewith. Elastic means (100) presses the nozzle forwardly with respect to the distributor (18). Said invention is particularly suitable for slender nozzles.

Description

 DEVICE FOR INJECTING-MOLDING A THERMOPLASTIC MATERIAL

The present invention relates to a device for injecting a thermoplastic material in the liquid state into a mold cavity, comprising, with reference to a determined longitudinal direction of injection:

a rigid matrix, having a front face partially delimiting the molding cavity, a rear face and at least one longitudinal passage passing through the matrix, from its rear face to its front face, along a determined longitudinal axis, said passage opening into the front face by an injection port and forming immediately behind it, around it, a transverse shoulder, transverse, facing rearwardly, a longitudinal injection nozzle disposed coaxially inside said passage and having a rear end, adjacent to said rear face and located behind it, and a front end, adjacent to said front face and located behind the annular shoulder of said passage, an inner periphery delimiting a longitudinal channel , coaxial, opening longitudinally in the rear end and in the front end, and a longitudinal outer periphery,

a distributor for supplying the nozzle channel made of thermoplastic material in the liquid state, located behind said rear face and mechanically connected to the matrix, said distributor having internally a transit network of the thermoplastic material in the liquid state, having a forwardly extending outlet longitudinal channel disposed coaxially with said passageway and fluidly communicating with the nozzle channel at the rear end thereof; this.

A device of this type is well known in itself, in many embodiments which generally comprise several examples of the nozzle and the passage arranged to receive it in the matrix, in association with a single molding impression or with as many respective copies of moldings.

In these known embodiments, in common:

- The front end of the or each nozzle is resiliently longitudinal support, forward, against the shoulder of the corresponding passage, through a longitudinally elastically compressible ring, ensuring a sealing against a leak of thermoplastic material in the liquid state, and the rear end of the nozzle has a plane transverse face, facing rearwardly and bearing back against a flat transverse face of the dispenser, under conditions such that an elastic longitudinal compression prestressing of the ring between the front end of the nozzle and the annular shoulder of the passage, transmitted by the nozzle, is reflected in a sufficiently strong support of the rear end face thereof, backwards, against the corresponding side dispenser for sealing against a leak of thermoplastic material in the liquid state at this level.

This energetic support must naturally be preserved regardless of the thermal expansion, in particular longitudinal, experienced by the nozzle during the operation of the injection-molding device, and the longitudinal bearing ring of the front end of the nozzle against the shoulder of the receiving passage thereof must be able to fulfill all the functions of elastic return of the nozzle to the rear, in view of this energetic support, and sealing between the front end of the nozzle and the annular shoulder of the receiving passage thereof, while absorbing at its level the apparent longitudinal dimension variations of the nozzle by thermal expansion. Indeed, these apparent longitudinal dimensions of the nozzle can not be absorbed at the rear end thereof, given the need to maintain the support of this rear end backwards against the distributor for the purpose of maintain watertightness at this level.

One can certainly obtain a aptitude of the longitudinal bearing ring of the front end of the nozzle against the annular shoulder of the receiving passage thereof to fulfill all these functions, but at the cost of an embodiment of this ring. in special materials, particularly expensive, and a more or less complex machining of this ring and its counterparts respectively at the front end of the nozzle and on the annular shoulder of the receiving passage thereof.

The shape complexity of the ring results in particular from a concern to involve the thermoplastic material in the liquid state, namely more precisely the pressure to which it is carried, to help the ring to perform its various functions, which leads to providing, between the front end of the nozzle, the ring and the annular shoulder of the nozzle receiving passage, a more or less large annular chamber for receiving a certain volume, variable depending on the state of thermal expansion of the nozzle, thermoplastic material in the liquid state.

However, the presence of the thermoplastic in the liquid state in this chamber can certainly prove to be a little troublesome when the injection-molding device operates continuously with a thermoplastic material always identical, that is to say in particular of same color, but it is particularly troublesome at each stop of the injection-molding device, since the thermoplastic material in question then tends to freeze and block the front end of the nozzle, and every change of thermoplastic material and in particular of color, since the thermoplastic material initially present in the annular chamber must be evacuated, at the cost of losses, before it is possible to practice the injection-molding of a new thermoplastic material.

In addition, the thermoplastic material in the liquid state, moving longitudinally forwards inside the nozzle channel, tends to move it forward frictionally against its inner periphery, that is to say to break the seal between the rear end of the nozzle and the distributor, the risk of leakage between them, and the support ring of the front end of the nozzle against the shoulder of the receiving passage thereof in the die must be designed to resist this tendency to shift the nozzle forward with respect to the dispenser. This further complicates the conformation of the ring and that of its counterparts respectively on the front end of the nozzle and on the annular shoulder of the receiving passage thereof, and further limits the choice of possible materials for this ring.

In any case, technical requirements of possible choice of materials constituting the ring and possible conformation thereof, to reconcile the set of requirements that it must meet to fulfill its various functions, limit the possibilities of absorption by this ring, variations of the longitudinal dimension of the nozzle by thermal expansion, that is to say makes it necessary to limit the value of these variations, expressed not in percentage but in units of length, by limiting the longitudinal dimension of the nozzle, which creates an additional constraint in the design of the injection-molding device, or even difficulties in this design depending on the shape of the parts to be molded and the possible choice of the location of the traces of molding on those -this . The object of the present invention is to remedy these drawbacks and, for this purpose, the present invention proposes an injection device of the type indicated in the preamble, characterized in that: the rear end of the nozzle and a rear end zone of the outer periphery thereof are housed coaxially in said outlet channel and mounted at the longitudinally sliding therein, relative to the distributor, with mutual sealing against a leak of thermoplastic material in the liquid state, in that - the front end of the nozzle is in support longitudinally closed, forwards, against the annular shoulder of said passage, with mutual sealing against a leakage of thermoplastic material in the liquid state, and in that - longitudinally elastic biasing means are interposed functionally between the distributor and the nozzle, to urge it elastically forwardly and permanently maintain said longitudinal support firm allowing said longitudinal sliding during variations in the longitudinal dimension of the nozzle by thermal expansion during the operation of the device.

A person skilled in the art will readily understand that, in such a device according to the invention, the means providing the functions hitherto attributed to the elastic support ring of the front end of the nozzle against the annular shoulder of the passage of reception thereof and sealing at this level, removing this ring, since: the tightness between the front end of the nozzle and the shoulder of the receiving passage thereof is ensured by firm mutual support, direct, especially under the action of elastic biasing means whose role is limited to urging the nozzle forward to maintain such support despite the thermal expansions that may be experienced by the nozzle during operation of the device, without there being to provide compatibility of the means used to ensure this seal with any relative movement by thermal expansion at this level,

the thermal expansions in question are absorbed by longitudinal sliding of the rear end of the nozzle and of the rear end zone of the outer periphery thereof inside the dispenser outlet channel, without the means of resilient bias play a role in the sealing at this level, and without there being any provision for complex arrangements for this purpose, - the thermoplastic material in the liquid state, passing through the nozzle channel while moving from behind to the inside thereof, contributes on the one hand to maintain the firm support of the front end of the nozzle against the shoulder of the receiving passage thereof, in complementing the action of elastic biasing means in this sense, the presence of which is essentially justified by the need to maintain the support in question when the transit of the thermoplastic material in the liquid state ceases, and on the other hand to the mutual sealing of the mutual end zone of the outer periphery of the nozzle and the dispenser by applying inside the channel of the nozzle, the latter, a radial force tending to energetically apply its outer periphery against the dispenser, inside the outlet channel thereof, instead of tend to break the seal at this level.

Thus, the device according to the invention makes it possible to meet all the requirements necessary for the proper functioning of an injection-molding device, without however implementing the traditional elastic support ring of the front end against the shoulder of the receiving passage thereof and sealing at this level, which removes all the disadvantages inherent in the need to manufacture such a ring, to cooperate with the front end of the nozzle and with the shoulder of the receiving passage thereof, and enhance its action by the presence of a certain volume of thermoplastic material in the liquid state, in an annular chamber provided for this purpose.

Compared with the injection-molding device of the prior art, the device according to the invention is therefore not only effective in terms of sealing despite the need to absorb the thermal expansion of the nozzle, particularly convenient to use avoiding the need to deal with the presence of a certain volume of thermoplastic material, which particularly facilitates in particular the stops and restarting of the injection device especially in case of color change, and in terms economy of use, since the losses of thermoplastic material and the waste of time necessary for the cleaning of devices during its stops and changes of material are considerably reduced, but also in terms of simplicity and economy of manufacture.

Naturally, these advantages are found regardless of the longitudinal dimensions of the nozzle, but it is observed that the characteristic features of the present invention make it possible to absorb longitudinal variations in the longitudinal dimensions of the nozzle, by thermal expansion, which are much greater than is permitted. the traditional elastic bearing ring of the front end of the nozzle against the annular shoulder of the passage for receiving it and sealing at this level, since these variations in longitudinal dimensions are absorbed by longitudinal sliding of the rear end of the nozzle and the rear end zone of the outer periphery thereof within the dispenser outlet channel, on a stroke that can be dimensioned at will by appropriately selecting the dimension longitudinal penetration of the nozzle in the outlet channel of the dispenser, while the support ring and known sealing, even carried out in a particularly complex and neat manner, can absorb, by elastic deformation, only low values of longitudinal stroke of the front end of the nozzle relative to the annular shoulder of the receiving passage thereof . It follows that it is possible according to the present invention to produce an injection device having nozzles that are much slenderer than in the prior art, where the term "slender" nozzle refers to a nozzle whose longitudinal dimension is much larger than its transverse dimension. Indeed, the more a nozzle is slender, that is to say the longer its longitudinal dimension is important, and the greater the variation of this longitudinal dimension, expressed in units of length and not in percentage, is important. One skilled in the art will readily understand that a large stroke, in particular of thermal expansion, can be much more easily absorbed by longitudinal sliding than by elastic longitudinal compression of a ring, or can be absorbed only by such longitudinal sliding.

As a result, a device according to the invention is particularly suitable for injecting hollow products of small size, such as capsules or bottle or bottle closure caps, from the inside of these products. that is to say, by their concave side, and not by their convex side as it is traditional. This is particularly advantageous when the products must have a convex side as free as possible of traces of molding, since the traces of molding are then present exclusively on the concave side, generally not visible, and thus allows to offer the public products molded aesthetic particularly neat. Various embodiments of the rear end of the nozzle, the rear end zone of the outer periphery thereof and the outlet channel of the distributor can be chosen to ensure on the one hand the possibility of relative sliding and on the other hand the mutual sealing against a thermoplastic material leak to the liquid state but, in a particularly simple manner, it is preferred to provide for this purpose that the rear end zone of the outer periphery of the nozzle has a uniform cross section and that said outlet channel has, at least in a longitudinal zone cooperating with said rear end zone, a longitudinal inner periphery of uniform cross section, complementary to said cross section, so as to establish a mutual guide contact to the relative longitudinal sliding and, preferably, is made so that said contact is sufficiently intimate, sufficiently circumferentially continuous and sufficiently extended longitudinally for ensure said mutual sealing between the nozzle and the dispenser. Then, by a simple careful machining of the rear end zone of the nozzle, the outer periphery thereof and the outlet channel of the distributor, the desired effects of guiding relative longitudinal sliding and mutual sealing are obtained. and, in particular, no seal and no additional special provision are necessary for the latter purpose. Only the pressure exerted, radially, by the thermoplastic material inside the channel of the nozzle contributes in addition, and this especially as it is more important, to this mutual sealing. Preferably, to avoid any tendency of the thermoplastic in the liquid state to insinuate between the rear end zone of the outer peripheral face of the nozzle and the inner periphery of the outlet channel, by the rear end of the nozzle. the nozzle, it is expected that the inner periphery of the nozzle flares rearwardly, in the immediate vicinity of the rear end of the nozzle, in particular in the form of an annular ring, transverse, flared towards the rear of the nozzle the inner periphery at the outer periphery of the nozzle.

Other forms could however be chosen for this purpose without departing from the scope of the present invention. Various means may also be chosen to ensure the firm forward longitudinal support of the front end of the nozzle against the annular shoulder of the receiving passage thereof in the matrix, with mutual sealing to the against a leakage of thermoplastic material in the liquid state, but an embodiment is preferred in which: - the front end of the nozzle has the shape of a transverse annular edge, facing forward, the the outer periphery of the nozzle widens rearwardly in a front end zone, immediately behind said ridge, from the latter, and a transverse annular ring, substantially incompressible, force distribution is interposed longitudinally between said front end zone and the annular shoulder of said passage, around said edge, and presents respectively forward and rearward a front face complementary to the annular shoulder of said passage and a rear face complementary to the front end zone of said outer periphery of the nozzle.

It is understood that this substantially incompressible transverse annular ring of force distribution is fundamentally different, in its nature and in its function, from the elastically compressible ring providing the elastic support between the front end of the nozzle and the annular shoulder of the receiving passage thereof and the sealing at this level in the devices of the prior art, since it has in no way the role of absorbing the thermal expansion of the nozzle, fully deferred at the rear of the latter and slidably absorbed in the outlet channel of the distributor, but to ensure without a longitudinal crush a force distribution and an effect of self-centering between the outer periphery of the nozzle, in the front end region thereof, and the annular shoulder of the nozzle receiving passage, in particular according to a preferred embodiment in which this shoulder annulai it flares backward from the injection port.

In this regard, it is preferably provided that the front end zone of the outer periphery of the nozzle flares less towards the rear than the annular shoulder of said passage and connects to said edge by an annular groove, transverse, which ensures matting of this edge against the shoulder of the passage of receiving the nozzle, immediately around the injection orifice, sealing as good as possible at this level while avoiding, due to the distribution of forces provided by the annular ring, a risk of damage to this edge and or the periphery of the injection port by penetrating the front end region of the nozzle therein.

It will be observed that the annular connecting groove between the front end region of the outer periphery of the nozzle and the aforementioned edge thereof forms a chamber around the injection orifice, but that this chamber is fundamentally different. of that of the chamber arranged to receive thermoplastic material in the liquid state and to make it contribute to the seal in the case of the elastically compressible ring used for elastic support of the front end of the nozzle against the annular shoulder of the receiving passage thereof and sealing at this level in the devices of the prior art since this groove, in principle sealed by the contact between the edge of the the front end of the nozzle and the shoulder of the receiving passage thereof, should in principle not receive thermoplastic material in the fluid state and that, in any event, it presents a negligible volume compared to that of the chamber of known devices.

In order to strengthen the support of the front end zone of the outer periphery of the nozzle, forwards, against the shoulder of the passage for receiving the passage thereof, it is preferably provided that this of the outer periphery of the nozzle, the shoulder and the annular ring of force distribution, which transverse in the transmission of the corresponding longitudinal forces and makes part of the shear force distribution ring. For this purpose, it is preferably provided that the outer periphery of the nozzle has a flat, transverse, forward-facing, front-facing annular shoulder behind said front end region, and that said annular ring has a rear annular shoulder. flat, transverse, facing back, against which said shoulder of the outer periphery of the nozzle is flat, forward, which is advantageously completed by providing that the annular shoulder of said passage comprises, longitudinally opposite the front shoulder of the outer periphery of the nozzle, a flat, transverse annular zone, turned towards the rear, and that said annular ring has a front shoulder flat, transverse, facing forward, in support flat against said flat annular zone of the annular shoulder of said passage. Part of the longitudinal forces is then transmitted through the transverse shoulders, that is to say longitudinally, without creating transverse components, from the front end zone of the outer periphery of the nozzle to the shoulder of the receiving passage from it, through the force distribution ring which then works in longitudinal compression.

Providing at the outer periphery of the nozzle the flat front annular shoulder, supra, in addition to a flat rear annular shoulder, of the annular ring has the additional advantage of considerably facilitating the manufacture and assembly of the nozzle. when the latter, in a manner known per se, comprises a nozzle body constituting the nozzle over most of its longitudinal dimension, and a nozzle tip defining the front end edge of the nozzle and a nozzle zone. longitudinal dimension comparably reduced thereof, located in the immediate vicinity of this front end. Indeed, one can then choose to make the device according to the invention so that the nozzle comprises a nozzle body delimited forwardly by an annular, transverse, flat edge, constituting a radially outer portion of said shoulder before the outer periphery of the injection nozzle, and a nozzle tip defining said front end region of the outer periphery of the nozzle and said edge thereof and constituting a radially inner portion of said front shoulder of the outer periphery of the nozzle; nozzle.

Thus, on the one hand, it is ensured that, each in part, the nozzle body and the nozzle tip participate in the support of the nozzle forward against the shoulder of the nozzle receiving passage. and, on the other hand, one can dispense with any proper means of fixing the nozzle tip to the nozzle body. In Indeed, it can then be provided that the tip of the nozzle is simply nested coaxially in the nozzle body and immobilized longitudinally with respect thereto by abutment rearwardly against the latter behind said radially inner portion and by abutment. forward against said rear shoulder of the annular ring.

The assembly and disassembly of the nozzle tip relative to the nozzle body is considerably simplified, as well as their respective manufacture since it is simply necessary to perform machining proper neat interlocking.

Just as it is preferable to partially achieve the mutual support of the nozzle, the force distribution ring and the shoulder, in the longitudinal direction, by respective transverse shoulders or zones, it is preferable to improve the distribution of the transverse or radial forces of self - centering, between these different components, by a direct radial support and, for this purpose, it is preferably provided that:

- the shoulder of said passage is connected, in the direction of a distance relative to said axis, to a longitudinal inner periphery of said passage,

the outer periphery of the nozzle has, between said front shoulder and said front end zone, a longitudinal section placed radially opposite a portion of said longitudinal inner periphery of said passage, and

- The force distribution ring has inner and outer peripheral faces, longitudinal, respectively complementary to said longitudinal section of the outer periphery of the nozzle and said portion of said longitudinal inner periphery of said passage.

It will be observed that, even thus improved, the force distribution ring has a simple conformation, requiring no machining necessary to allow the elastically compressible bearing ring of the front end of the nozzle against the annular shoulder of the passage of receiving thereof and sealing to meet all of its functions in the devices of the prior art; in particular, the force distribution ring of a device according to the invention can be massive, that is to say full and devoid of any particular machining in its different faces and in its different shoulders, unlike the case of the elastically compressible ring of the prior art, whose forms are considerably complicated in various attempts to make it compatible with the functions assigned to it.

In this respect, the resilient biasing means provided in the device according to the invention can also be considerably simpler than this elastically compressible ring of the prior art.

Thus, according to a preferred embodiment, these longitudinal elastic biasing means comprise a spring disposed coaxially with said rear end zone and operatively interposed between an annular rear shoulder, transverse, turned towards the rear, constituting a front limit of said rear end zone, and the distributor.

It will be observed that this spring acts on the nozzle towards the front, that is to say opposite to the elastically compressible ring of the devices of the prior art.

It will also be observed that, unlike the latter, it can be placed so as not to come into contact with the thermoplastic material in the liquid state, which makes its operation immune from any influence of this material. ci, namely in particular a tendency of it to freeze at the stop of the injection, and allows to freely choose its conformation.

This spring may thus have any known conformation, and for example be in the form of a helical spring disposed coaxially around the nozzle, in the rear end zone thereof, but it may more simply present the shape of the nozzle. an annular disc, transverse, having a radially inner marginal zone longitudinally bearing, forwards, on said rear shoulder of the outer periphery of the nozzle and a radially outer marginal zone in longitudinal support, towards the rear, on the distributor, which is generally sufficient to meet the needs in longitudinal travel possible, even in the case of particularly slender nozzles, that is to say, capable of significant variations in their longitudinal dimension by thermal expansion. Other features and advantages of an injection device according to the invention will emerge from the description below, relating to a non-limiting example of embodiment, and the accompanying drawings, which accompany this description.

FIG. 1 shows part of an injection device according to the invention, in section through a plane including the longitudinal axis of an injection nozzle, it being understood that this device may comprise this injection nozzle in several parts. copies.

Figures 2 and 3 show, on a larger scale, details respectively marked II and III in Figure 1.

The illustrated part of a device according to the invention constitutes a part of such a device intended to simultaneously produce, by injection molding, several identical products, such as plugs for bottles of water, household detergents, cosmetics, or similar products, in which case there are provided as many nozzles, having the same orientation, as products to be produced simultaneously, but it is understood that one could also achieve in accordance with the present invention a device for molding the d a single piece of larger dimensions than those of a plug, or any other part, using a single injection nozzle or several injection nozzles of the same orientation. The adaptations, in each case, of the arrangements which will be described by way of nonlimiting example are apparent from the normal abilities of a person skilled in the art. In its version illustrated in FIG. 1, the injection device thus comprises a matrix rigid 1, which, with reference to a given longitudinal direction of injection 2, which will serve as a reference to the notions of front and rear, except explicit exception, as well as longitudinality and transversality for the entire description , has a front face 3 for example flat but locally shaped so as to delimit as many copies of a mold cavity 4 that it is desired to simultaneously mold products, cooperating for this purpose with a non-referenced counterform, illustrated in dashed line in Figures 1 and 2.

As is well known to those skilled in the art, the matrix 1 is formed of a stack, flat, parallel to the direction 2, of a plurality of flat plates, namely in the example illustrated a front plate 5 having two main flat faces, mutually parallel and perpendicular to the direction 2, due to the front face 3 of the die 1 and a rear face 6, a spacer plate 7 also having two planar main faces, mutually parallel and perpendicular to the direction 2, due to a front face 8 which is flat against the rear face 6 of the front plate 5 and a rear face 9, and a rear plate 10 also having two planar main faces, mutually parallel and perpendicular to the direction 2, due to a front face 11 which is flat against the rear face 9 of the spacer plate 7 and a rear face 12 which constitutes a rear face for the matrix 1 considered in its together. The front plate 5 can directly define the impression 4, by its front face 3, in a non illustrated but well known to a person skilled in the art, especially when this footprint 4 is unique.

However, particularly in the case where the same matrix delimits a plurality of indentations 4, the or each imprint may also be defined by a respective part, attached integrally in or on the front plate 5 to locally complete the front face 3 of the latter. this.

Thus, in the non-limiting example illustrated, wherein the or each product to be molded has a convex side, intended to be seen during use and must therefore have an aesthetic as free as possible of injection traces, and a concave side, intended to be hidden during use and can therefore have without disadvantages such traces, it has been chosen to perform the injection of the thermoplastic material in the or each imprint 4 by the concave side of the product, and, to this end, the front face 3 of the die 1 delimits the or each cavity 4 by a respective localized boss 109, complementary to this concave side and defined by a projecting portion of a rigid part not referenced, called "piston d "imprint" or "punch", further comprising a portion nested tightly in a corresponding bore of the front plate 5 and integrally retained by clamping between the latter and the plate spacer 7.

Such a design of the front plate 5 is well known to a person skilled in the art and will not be described further, but it is understood that the terms "front plate" include an assembly then constituted by the front plate itself and by the or each piece thus reported on it, and that the terms "front face" of the matrix or the "front plate" thus defined relate to a front face of the assembly thus formed, including in the illustrated example the or each boss 109, considered here as a localized area of the front face 3.

The number of plates thus stacked longitudinally to form the matrix 1 may also be different. The three plates 5, 7 and 10 also have external peripheral edges, not shown, which complement each other longitudinally to define an outer peripheral edge for the die 1. The plates 5 and 7 are joined together by means of longitudinal screws. not shown, accessible by the front face 3 of the front plate 5, and the plates 7 and 10 are also assembled together by means of longitudinal screws not shown and accessible either by the front face 6 of the spacer plate 7, after disassembly of the front plate 5, or through through longitudinal holes, also not shown, the front plate 5. Such an assembly is well known to a person skilled in the art and therefore does not require further description.

Similarly, in a manner well known to a person skilled in the art, which will not be described in detail, impression 4 is associated with a respective longitudinal nozzle 13 for injecting thermoplastic material with the liquid state, being well extended that several copies of a nozzle 13 could be associated with the same footprint 4, in particular in the case of a single footprint 4. The or each nozzle 13, which will be described in more detail later, is arranged along a respective axis 14 which is fixed relative to the matrix 1 and oriented parallel to the direction 2, that is to say longitudinally, and, as in the example illustrated, advantageously constitutes an axis of symmetry for the nozzle 13 as well as for the associated boss 109, which this axis intersects at its vertex, that is to say in its zone of maximum longitudinal projection with respect to areas of the front face 3 which adjoin. To receive the or each nozzle 13, the plates 5, 7 and 10 are pierced with a respective longitudinal passage 15, 16, 17 which passes right through them along the axis 14, that is to say respectively from the rear face 6 towards the front face 3, where the passage 15, in practice arranged in the insert constituting the boss 109 in the illustrated example, opens at the top of this boss 109 in this example, from the rear face 9 to the front face 8 and rear face 12 to the front face 11, in the direction 2. Back of the rear plate 10 is disposed a distributor 18 of thermoplastic material in the liquid state, having a front face 19 and a rear face 20, planar and perpendicular to the direction 2.

The front face 19 of the distributor 18 is thus placed parallel to the rear face 12 of the plate 10, behind it, and defines with this rear face 12 a flat space essentially filled by a flat plate 21 of thermal insulation and transmission of longitudinal forces between the faces 12 and 19, against which the plate 21 rests flat, respectively, by a front face 26 and by a front face 27, planar and perpendicular to the direction 2.

Inside the distributor 18 is arranged a transverse channel 22 or network of transverse channels 22 for dispensing the thermoplastic material in the liquid state to the single nozzle 13 or between the different nozzles 13, and the or each channel 22 opens into an inner peripheral face 23, cylindrical of revolution about the axis 14 of the corresponding nozzle 13, of a respective bore 24 arranged in the distributor 18 and passing therethrough from one side to the other, from its face 20 to its face 19 in the direction 2.

In this bore 24 is nested coaxially, integrally, for example by press fit, an insert 25 which will be considered thereafter as an integral part of the distributor 18.

Along the axis 14, the insert 25 is hollowed out with a longitudinal channel 28 of thermoplastic material outlet in the liquid state, which opens outwards in a plane, transverse front face 29 of the insert 25, which front face is placed slightly protruding forwardly with respect to the front face 19 of the distributor 18, at a level intermediate those of the front 26 and rear 27 of the plate 21, inside a longitudinal bore coaxial thereof. The front face 29 of the insert 25 is annular in revolution about the axis 14 and, in the direction of a distance relative thereto, connects an inner peripheral face 31, cylindrical of revolution about the axis 12 and delimiting the outlet channel 28 in the direction of a distance relative thereto, to an outer peripheral face 32, also cylindrical of revolution about the axis 14 and delimiting the insert 25 in the direction of a distance from it.

The outer peripheral face 32 of the insert 25 has a diameter substantially identical to that of the inner peripheral face 23 of the bore 24 of the distributor 18, with which it thus establishes a tight contact with the thermoplastic material in the liquid state, but advantageously, projecting in the direction of a distance relative to the axis 12, an annular flange 33 of revolution about the axis 14 and bearing back against the front face 19 of the distributor 18 to the the interior of the bore 30 of the plate 21, in a relative position of insertion which has been illustrated in the figures and in which the insert 25 has towards the rear a plane rear face 34, coplanar with the rear face 20 of the distributor.

Unlike the front face 29 of the insert 25, its rear face 34 is continuous and, between the two faces 29 and 34, the outlet channel 28 is connected rearwardly to a connecting channel 35 bent at 90 °, opening into the outer peripheral face of the insert 25 at a level corresponding to that of the channel 22 associated with the nozzle 13, to ensure a fluid connection between the channels 22 and 28.

Along an axis 36 parallel to the axis 14 and arranged between the various axes 14 when the die 1 comprises several nozzles 13, preferably approximately at the same distance from each of them, the channel or network of channels 22 of the distributor 18 is connected, by a longitudinal channel 37 thereof, to a conduit 38 for supplying the distributor 18 of thermoplastic material in the liquid state, which conduit 38 is also arranged along the axis 36 and forms a projection, towards the rear, relative to a rear face 20 of the dispenser 18.

The mode of cooperation between the conduit 38 and the distributor 18 is well known in itself to a person skilled in the art, and will not be detailed. Similarly, this duct 38 and the distributor 18 are provided with respective regulated electrical heating means 25, 40 which are well known to those skilled in the art and will not be detailed. Behind the distributor 18 is a flat bed 41, perpendicular to the direction 2 and having towards the rear face 20 of the distributor 18 a front face 21 which is flat and parallel to the face 20, with which the face 21 defines a flat space filled essentially, around the duct 38, by a flat plate 43 of thermal insulation and transmission of longitudinal forces between the faces 20 and 21.

Towards the rear, the bed base 41 is delimited by a rear face 44 which, in the example illustrated, is also flat and perpendicular to the direction 2. In any transverse direction, particularly at its front 21 and rear 44, the bed 41 has dimensions substantially identical to those of the matrix 1, in particular at its front faces 3 and rear 12, and greater than those of the distributor 18, in particular at its front 19 and rear 20 faces, and it is the same for the plates 21 and 43. Around the distributor 18 are interposed therebetween unreferenced peripheral shims through which a mutual assembly the bed base 41, the matrix 1 and the plates 21 and 43 is provided by longitudinal rods not shown, under conditions known to a person skilled in the art.

Also known to a person skilled in the art, the distributor 18 is simply held by pinching between the plates 21 and 43, in the longitudinal direction, while it is retained in the transverse direction, with respect to the matrix 1 in particular, by known means, not shown, which can advantageously comprise firstly a pin disposed along the axis 36 and longitudinally fitted in a respective cavity of the face 19 of the distributor 18 and the face 12 of the rear plate 10, through the plate 21, and secondly a thermal insulation layer with respect to the wedges, creating with the plates 21 and 43 a continuous thermal insulation around the distributor 18.

Along the axis 36, that is to say coaxially with the supply duct 38, the bed base 41 is pierced right through, that is to say from its rear face 44 to its front face 41, d a passage 15 allowing its free passage through the conduit 38. Similarly, in known manner in itself and not shown, when the or each nozzle 13 is of a controlled shutter type and internally comprises a longitudinal rod, coaxial, controlled shutter, this rod being guided to longitudinal sliding by the insert 25, with sealing vis-à-vis the thermoplastic material in the liquid state, behind the bent channel 35 and freely traversing the plate 43 from one side to the other, the bed base 41 is drilled from one side, along the or each axis 14, d a channel also allowing a free passage, parallel to the direction 2, for the respectively corresponding shutter rod, and the connection of this rod to controlled means to cause the passage of this rod from one to the other of a closed position of the corresponding nozzle 13 and an open position thereof; such an arrangement is well known in itself to a person skilled in the art, and will not be further described. It is understood that, as illustrated, the or each nozzle 13 may also be blank shutter, in a manner equally compatible with the implementation of the present invention.

In general, the arrangements which have just been described are known to those skilled in the art, and therefore do not require further description.

On the other hand, the design and the assembly of the or each nozzle 13 is characteristic of the present invention, in relation with a specific mode of cooperation on the one hand with the distributor 18 and on the other hand with the matrix 1, in particular with immediate proximity of the footprint 4. Indeed, in the injection-molding devices of the prior art, the or each nozzle 13 is simply placed in longitudinal support towards the rear, flat, against a face corresponding to the front face 29 of the insert 25 and this support is maintained sufficiently firm to seal against a leakage of thermoplastic material in the liquid state at this level, under all possible conditions of thermal expansion of the nozzle 13 under normal conditions. use of the injection device, by an elastically compressible ring longitudinally, interposed between a front end zone of the nozzle 13 and a counterpart arranged in the front plate 5, in the immediate vicinity of the cavity 4, this ring also having function to ensure a seal against a leak of thermoplastic material in the liquid state at this level regardless of the conditions of expansion of the nozzle 13 in conditio ns normal use of the injection device, absorbing the apparent longitudinal dimensions of the nozzle 13 consecutive variations in these thermal expansions.

In the case of a device according to the present invention, on the other hand, the sealing support of the nozzle 13, towards the front, against the front plate 5 in the immediate vicinity of the cavity 4 is a firm support, and c is in a rear end zone 48 of the nozzle 13 which are provided on the one hand the compensation of the apparent longitudinal dimension variations of the nozzle 13 by thermal expansion, with maintaining a seal vis-à-vis the insert 25, and on the other hand an elastic return of the nozzle 13, which then takes place forward to maintain the aforementioned firm support instead of exercising to the rear as in currently known injection devices.

Provisions for this purpose are limited on the one hand at the rear end zone 48 of the nozzle 13, the outlet channel 28 of the insert 25 and the passage 30 arranged to partially receive it in the plate 21, as shown in Figure 3, and secondly at a front end zone 46 of the nozzle 13 and a front end zone 47 of the passage 15 of the front plate 5, to know inside the boss 109 in the illustrated example, as shown in Figure 2.

Between the front end zone 47 of the passage 15 and a level of the intermediate rear plate 10 between the respective levels of its front face 11 and its rear face 12, the passages 15, 16, 17 may furthermore have any known conformation. , indifferent to the present invention, and for example be delimited, in the direction of a distance relative to the axis 14, by a respective inner peripheral face 49, 50, 51 cylindrical of revolution about the axis 14 with an identical diameter.

In the example illustrated, the inner peripheral face 51 of the passage 17 of the rear plate 10 extends only 3a front face 11 thereof to a level intermediate those of the front faces 11 and rear 12, at which point this passage 17 presents an enlargement. More specifically, the inner peripheral face 51 is connected at this level by a transverse shoulder 52, for example frustoconical of revolution around the axis 14, and turned upward, to another inner peripheral face 53 also cylindrical in revolution about the axis 14 but with a diameter greater than that of the inner peripheral face 51, this face 53 continuing until at the rear face 12 of the rear plate 10 or the matrix 1. This localized enlargement facilitates the electrical connection to power supply means and control of this supply, external to the injection device, means of heating arranged over most of the longitudinal dimension of the nozzle 13, in the illustrated example in the form of a coaxial tubular sleeve 54, carrying Joule heating resistors advantageously made by screen printing, in a manner well known in the art. itself, it being understood that means other than a sleeve 54 could be provided for this purpose without departing from the scope of the present invention.

In the direction of a distance from the axis 14, the sleeve 54 is delimited by an outer circumferential face 55 cylindrical in revolution about the axis 14 with a diameter smaller than that of the inner peripheral faces 49, 50, 51 passages 15, 16, 17, in order to arrange a radial clearance vis-à-vis these inner peripheral faces, while it is delimited towards the axis 14 by an inner peripheral face 56 also cylindrical of revolution around this axis but with a diameter smaller than that of the outer peripheral face 55. Longitudinally, the heating sleeve 54 is delimited in the direction 2 by a front edge 57 plane, crosswise, annularly of revolution about the axis 14 and located slightly behind the respective front end regions 46 and 47 of the nozzle 13 and the passage 15, and in the opposite direction in the direction 2 by a singing 58 also plane, transverse , annular revolution around the axis 14 and meanwhile located slightly in front of the rear face 12 of the rear plate 10 or the matrix 1, that is to say at an intermediate level between the respective levels of the shoulder 52 and this face 12, regardless of the thermal expansion state of the nozzle 13 and the sleeve 54 under normal conditions of use of the inj ection device.

The sleeve 54 is retained integrally but removably on the nozzle 13 by longitudinally pressing and frictionally pressing its inner peripheral face 56 against an outer peripheral face 59 of the nozzle 13, this outer peripheral face 59 being cylindrical of revolution around the liner. 14 and having a substantially identical diameter to that of the inner peripheral face 56 of the sleeve 54.

The outer peripheral face 59 of the nozzle 13 delimits it in the direction of a distance relative to the axis 14, over most of the longitudinal dimension of this nozzle 13, namely on the whole of this dimension longitudinal axis with the exception of the front end zone 46 and the rear end zone 48. In the preferred embodiment which has been illustrated, in which the nozzle 13 is formed of the mutual assembly of a tubular nozzle body 60, constituting the nozzle 13 over most of its longitudinal dimension, and a nozzle tubular nozzle 61, defining the front end zone 46 of the nozzle 13, this outer peripheral face 59 is an outer peripheral face of the nozzle body 60, which also has towards the axis 14 an inner peripheral face 62, cylindrical of revolution about this axis 14, with a diameter smaller than that of the outer peripheral face 59 and, in connection with the implementation of the present invention, that of the inner peripheral face 31 the outlet channel 28 of the insert 25.

Forward, the outer peripheral face 59 of the nozzle body 60 is directly connected to an annular planar annular plane 63, transverse, facing forward and delimiting the nozzle body 60 forwards, while the inner peripheral face 62 is connected indirectly to this edge 63, namely via an inner peripheral face 64 also cylindrical in revolution about the axis 14 but with an intermediate diameter between the respective diameters of the inner peripheral face 62 and the outer peripheral face 59, this face 64 being connected directly, towards the front, to the edge 63 while it is connected to the inner peripheral face 62, towards the rear, via a shoulder 65 plane, transverse annular revolution around the axis 14 and turned forward].

The inner peripheral face 64, whose longitudinal dimensions are much smaller than those of the inner peripheral face 62, and the shoulder 65 which connects it to the latter constitute longitudinal coaxial engagement means of the nozzle 61 inside the nozzle body 60, by the edge 63 thereof.

For this purpose, the nozzle tip 61 is delimited, in the direction of a distance relative to the axis 14, on a longitudinal dimension substantially identical to that which mutually separates the shoulder 65 and the front edge 63 of the body nozzle 60, by an outer circumferential face 66 cylindrical of revolution about the axis 14, with a substantially identical diameter to that of the inner peripheral face 64 of the nozzle body 60, and is delimited to the rear by a song 67 plane, transverse, annular of revolution about the axis 14, so that the tip 61 is nested inside the nozzle body 60 under conditions such that its outer peripheral face 66 is placed in guiding contact relative longitudinal sliding with the inner peripheral face 64 of the nozzle body 60 and its edge 67 comes to rest flat against the shoulder 65, in a service position illustrated in FIGS. t 2 in particular.

Referring to this operating position, the outer peripheral face 66 of the nozzle 61 is connected forwardly to a shoulder 68 plane, transverse, annular of revolution about the axis 14 and facing the before, which shoulder 68 is then coplanar with the front edge 63 of the nozzle body 60 so that the edge 63 and the shoulder 68 constitute respectively radially outer and radially inner portions of the same shoulder 69 of the nozzle 13, which shoulder 69 is flat, transverse, annular of revolution about the axis 14 and facing forward.

The shoulder 68, which is thus connected to the outer peripheral face 66 of the end piece 61 in the direction of a distance relative to the axis 14, is connected, in the direction of an approaching vis-à-vis of this, at an outer peripheral face 70 of the nozzle tip 61, which is cylindrical in revolution about the axis 14 with an intermediate diameter between the respective diameters of the inner peripheral faces 64 and 62 of the nozzle body 60 and, thus placed in longitudinal projection out of the nozzle body 60, constitutes a rear section of the outer peripheral face of the front end zone 46 of the nozzle 13.

Forwards, this outer peripheral face 70 is connected directly, that is to say by means of a circular ridge not referenced, to another outer peripheral face 71 of the nozzle tip 61 or the front end zone 46 of the nozzle 13, which face 71 is frustoconical of revolution about the axis 14 and converges in the direction 2, forming with respect to the axis 14 an unreferenced angle which can be for example of the order of 30 °. Forward, this frustoconical outer circumferential face 71 connects itself directly, that is to say by a circular ridge not referenced, to another frustoconical external peripheral face 72 of revolution about the axis 14, with a convergence turned in the same direction as that of the outer peripheral face 71 but forming an angle higher relative to the axis 14, namely for example an angle of the order of 60 °.

This outer peripheral face 72 thus connects, in the direction of approaching the axis 14, the outer peripheral face 71 to another outer peripheral face 73 also frustoconical of revolution about the axis 14 with a convergence towards the before, this face 73 forming opposite against the axis 14 an angle substantially identical to that formed by the outer peripheral face 71.

Forwards, the outer peripheral face 73 is connected to a transverse edge 74, circular, of revolution about the axis 14, which edge 74 defines the front end of the nozzle tip 61 and the nozzle 13 considered in general.

This edge 74 constitutes the connection of the outer peripheral face 73 to an inner peripheral face 75 of the nozzle tip 61, which is cylindrical of revolution about the axis 14 and has a diameter smaller than that of the inner peripheral face 62. of the nozzle body 60.

This inner peripheral face 75 is connected to the shoulder 75, with a diameter identical to that of the inner peripheral face 62 of the nozzle body 60, by a frustoconical inner peripheral face 76 of revolution about the axis 14 with a convergence turned forward and an angle, relative to the axis 14, less than that of the outer peripheral face 71. It will be observed that in a nozzle 13 thus formed, it is not necessary to provide means for securing the end piece 61 with the nozzle body 60, for example in the form of mutual coaxial screwing means or in other forms, which makes it possible to limit the diameter of the nozzle 13, in particular the diameter of its face external device 59, as well as the diameter of the inner peripheral faces 49, 50, 51 of the passages 15, 16, 17. It thus becomes possible, in comparison with conventional design nozzles, to bring the nozzles 13 closer together when several of these nozzles are associated with the same matrix 1, that is to say in particular to multiply the fingerprints 4 corresponding to the same matrix 1 to simultaneously produce a larger number of products by means of the same matrix 1, or to distribute at best, in the case of a complex form of single footprint 4, different nozzles 13 serving this footprint 4 single, without unduly weaken the matrix 1, as will readily be understood by one skilled in the art. In relation to this preferred conformation of the front end zone 46 of the nozzle 13, that is to say of the shoulder 69 consisting partly of the edge 63 of the nozzle body 60 and partly of the shoulder 68 the nozzle tip 61, and the different outer peripheral faces 70, 71, 72, 73, as well as the edge 74, which externally define the projection that the nozzle tip 61 forms forward out of the body nozzle 60, the leading end region 47 of the passage 15 has a conformation which will now be described. Since, in the example illustrated, the front end zone 47 of the passage 15 has maximum radial dimensions smaller than the diameter of the inner peripheral face 49 of the passage 15, it is connected to this inner peripheral face 49 by an inner peripheral face 77 of the passage 15, which is frustoconical of revolution about the axis 14, converges towards the before forming an angle with respect to this axis 14 which is for example of the order of 60 °, and lies slightly in front of the edge 67 of the sleeve 54, whatever the thermal expansion conditions of this sleeve 54 of the nozzle 13 under normal operating conditions of the device. This face 77 connects the inner peripheral face 49, towards the front, to another inner peripheral face 78 cylindrical in revolution about the axis 14 but with an intermediate diameter between the respective diameters of the outer peripheral face 59 of the nozzle body 60 and the inner peripheral face 49 of the passage 15.

The mutual connection of the inner peripheral faces 77 and 78 is effected by a circular ridge, unreferenced, situated approximately in the same non-illustrated geometric plane as the shoulder 69, or slightly behind this shoulder 69, so that the cylindrical outer peripheral face 70 of the nozzle tip 61 is entirely located facing a portion of the face 78, radially with reference to the axis 14.

The face 78, however, has longitudinal dimensions greater than those of the face 70, and is connected forwardly to a planar, transverse surface 79, annular of revolution about the axis 14 and turned to the rear, which face 74 is thus placed longitudinally opposite a portion of the shoulder 69, namely more precisely the edge 63 of the nozzle body 60, while being spaced longitudinally.

The face 79 is thus connected to the face 78 in the direction of a distance relative to the axis 14, while, in the direction of a connection with respect thereto, it is connected to an inner peripheral face 80 frustoconical around the axis 14 and converging towards the front forming with respect to this axis 14 an angle substantially identical to that which forms with respect to the outer peripheral face 72 of the nozzle tip 61. In the direction of a rapprochement vis-à-vis the axis 14, this face 80 is connected by a circular circular edge 81, transverse, of revolution about the axis 14, with a diameter at most equal to that of the edge 74 forming the front end of the tubular end piece 61 and preferably slightly less than this diameter, to another outer peripheral face 82 also frustoconical of revolution about the axis 14 and converging towards the front, forming with respect to the axis 14 an angle that can be p for example substantially identical to that formed with respect to it the outer peripheral face 71 of the nozzle nozzle 69.

The inner peripheral face 82 is connected as for it to the front face 3 of the front plate 5 or the matrix 1, at the top of the boss 109 in the example shown, by a ridge 83 which is circular, flat , transverse and revolution around axis 14 when, as illustrated, the boss 109 of the face 3 has a shape of revolution around this axis 14 at least in the immediate vicinity thereof, and which may also have a different shape depending, in particular, on the shape and orientation of the face 3 or the boss 109 thereof relative to the axis 14, in the immediate vicinity thereof.

The edge 83 thus defines in the boss 109 of the face 3 an orifice 84 for injecting the thermoplastic material in the liquid state into the cavity 4 and, for this purpose, communicates rearwardly with a longitudinal channel referenced defined in the front plate 5 by the inner peripheral face 82 and with a longitudinal inner channel 85 defined, inside the nozzle tip 61, by the inner peripheral faces 75 and 76 thereof and, in the nozzle body 60, by the inner peripheral face 62 thereof. When, in a manner not shown, the nozzle 13 is associated with a controlled shutter rod, it is housed coaxially inside the channel 85, respecting a continuous annular clearance vis-à-vis the inner peripheral faces 62 and 76; in the closed position, it comes to fit by a front end zone in the inner peripheral face 82 to close the injection orifice 84 while, to allow the injection, this front end zone is shifted rearwards with respect to the inner peripheral face 84.

The faces 79 and 80 of the front end zone 47 of the passage 15 thus define in the front plate 5, around this passage 15, a shoulder annular 86, of revolution about the axis 14, facing rearward to provide a forward support to the nozzle 13, with respect to the front plate 5 and the matrix 1 considered as a whole. According to the present invention, this support is firm, instead of being elastic as is the case in the injection devices of the prior art, and is carried out on the one hand by direct support of the edge 74 constituting the front end of the nozzle tip 61 and the nozzle 13 considered as a whole against the inner peripheral face 80, in the immediate vicinity of the edge 81 constituting the limit of the face 80 towards the axis 14, if necessary with a matting edge 74 establishing at this level a seal against a leak of the thermoplastic material in the liquid state to a groove 87, annular of revolution about the axis 14, remaining between the faces 72 and 73 of the nozzle 61 and a corresponding marginal zone of the face 80, and secondly, and essentially, indirectly, via a ring 88, annular, transverse , substantially incompressible, in particular longitudinally, longitudinally interposed between the shoulder 69 and the outer peripheral face 71 of the front end zone 46 of the nozzle 13 and the shoulder 86 of the front end zone 47 of the passage 15 of the front plate 5, on the one hand , and radially between the outer peripheral faces 70 and 71 of the front end zone 47 of the nozzle 13 and the inner peripheral faces 78 and 80 of the front end zone 47 of this passage 15. For this purpose, the ring 88, made for example based on glass fibers agglomerated by means of a binder, for example a polyimide, is in the form of a solid solid body delimited by: rear face 89 plane, transverse, of revolution about the axis 14 which it is perpendicular, this face 89 s' flat against the shoulder 69, that is to say both against the shoulder 88 of the nozzle tip 61 and against the front edge 63 of the nozzle body 60 to maintain the engagement of the nozzle tip 61 in the nozzle body 60 in the absence of any other means of mutual attachment for this purpose, this face 89 having an inner diameter substantially identical to the diameter of the outer peripheral face 70 of the nozzle tip 61 and an outer diameter substantially identical to the diameter of the inner peripheral face 78 of the front end zone 47 of the passage 15, an inner peripheral face 90, cylin rotation of the gun about the axis 14 with a diameter substantially identical to that of the face 70 to marry it at best, in radial directions, this face 90 connecting rearwardly to the annular face 89, at the level of the inner diameter thereof, an inner circumferential peripheral face and 91 rear circumferential revolution about the axis 14 and taper identical to that of the outer peripheral face 71 of the nozzle tip 61, to which this face 91 serves forwards and radially outwards, this face 91 thus extending over a longitudinal dimension greater than that of the face 71 to join the inner peripheral face 80 of the front end zone 47 of the passage 15, locally defining the groove 72 in the direction of a distance relative to the axis 14,

an outer and front peripheral face 92 to which the inner and rear peripheral face 91 is connected by a circular edge 94, transverse, of revolution about the axis 14 with a diameter greater than the respective diameter of the ridges 75 and 81, this face 92 having a frustoconical shape of revolution about the axis 14 with a conicity identical to that of the inner peripheral face 80 of the front end zone 47 of the passage 15 and being turned towards the front and radially outwards for in these two directions, bear continuously against the inner peripheral face 80 of the front end zone 47 of the passage 15, a plane, transverse face 93, annular of revolution about the axis 14 to which it is perpendicular, this face 93 is connected in the direction of a rapprochement vis-à-vis the axis 14 to the face 92, according to a substantially identical diameter to that of the mutual connection of the faces 79 and 80 of the front end zone 47 of the passage 15, so as to bear flat, continuously, forwardly, against the face 79 of the front end zone 47 of the passage 15, and a face outer peripheral device 95 cylindrical in revolution about the axis 14 with a diameter substantially identical to that of the inner peripheral face 78 of the front end zone 47 of the passage 15, this outer peripheral face 95 mutually interconnecting, longitudinally, the plane annular faces 89 and 93 and being supported continuously, radially in the direction of a distance relative to the axis 14, on the inner peripheral face 78 of the front end area 47 of the passage 15.

It will be observed that, under these conditions and since the nozzle 13 is held in abutment against the shoulder 86 inside the passage 15, due to the presence of resilient return means 100 located in the zone rear end 48 of the nozzle 13, as is characteristic of the presenbe invention and will be described later: - the support of the outer peripheral face 71 of the nozzle tip 61 forward and radially to the outside on the inner peripheral face 91 of the ring 88, whose outer peripheral face 92 is also placed in support forwards and radially outwards against the face 80 of the front end zone 47 of the passage 15, provides on the one hand a coaxiality of the nozzle 13 and the passage 15 at this level, and on the other hand a distribution of the forces, forwards, of the front end zone 46 of the nozzle 13 towards the shoulder 86 of the front plate 5, the outer peripheral face 70 and a portion, adjacent thereto, of the outer peripheral face 71 of the nozzle tip 61 respectively transmit to the inner peripheral face 90 of the ring 88 and to a zone of its inner peripheral face 91 adjacent thereto. face 90 efforts radial, which themselves are transmitted from the ring 88 to the front plate 5 by radial support of the outer peripheral face 95 of the ring 88, in the direction of a distance relative to the axis 14, against the face inner device 78, which contributes to maintain the coaxiality of the nozzle 13 and the passage 15 at this level, and avoids a risk of bursting of the ring 88, and longitudinal forces, forward, are transmitted from the shoulder 69, that is to say part of the shoulder 68 and part of the edge 63, to the face 89 of the ring 88 and extend longitudinally, the face 93 of the ring 88 and a part of the face 92 thereof, adjacent to this face 93, to the face 79 of the front end zone 47 of the passage 15 and to a zone of the inner peripheral face 80 of the latter, adjacent to this zone 79, which contributes to the recovery of the efforts exerted on the nozzle 13 forward one hand because of the presence of means Elastics 100 which will be described later and secondly because of the friction applied by] the thermoplastic material in the liquid state, moving in the direction 2 inside the channel 85, against the inner peripheral faces 62 and 76.

It will be observed that, instead of being made in two parts, constituting respectively the nozzle body 60 and the nozzle tip 61, the nozzle 13 could also be made in one piece, in a manner particularly suitable for the production of slender nozzles. In such a variant, which has not been shown but whose design falls within the normal abilities of a person skilled in the art, the conformations would preferably be preserved. respective of the front end zone 46 of the nozzle 13, of the front end zone 47 of the passage 15 and of the ring 88 which have just been described, including as regards the shoulder 69, then defined by the single piece constituting the nozzle 13 in this variant, and the face 89 of the ring 88, which would thus retain all the functions described above, with the sole exception of its function of retaining the nozzle of nozzle 61 in the state fitted into the nozzle body 60. The ring 88 thus designed, unlike the elastically compressible rings similarly arranged in the injection devices of the prior art, is only suitable for transmitting the efforts of the nozzle 13 to the front plate 5, between the respective front end regions 46 and 47 of the nozzle 13 and the passage 15, so as to limit the bearing pressure of the edge 74 of the nozzle tip 61 against the inner peripheral face 80 of the end zone before the passage 47 to what is just necessary to ensure at this level a seal, against a leakage of thermoplastic material in the liquid state, but it is in no way designed to create it even this sealing, on the one hand, and absorb, in operation, the longitudinal dimension variations of the nozzle 13 by thermal expansion, on the other hand. In other words, if we ignore any differences in thermal expansion between the nozzle tip 61 in the front end zone 46 of the nozzle 13, the ring 88 and the front plate 5 in the zone front end 47 of the passage 15, the ring 88 provides a substantially constant positioning, particularly in longitudinal direction, of the front end zone 46 of the nozzle 13 with respect to the front end zone 47 of the passage 15.

In contrast, according to the present invention, these longitudinal dimension variations of the nozzle 13 by thermal expansion are absorbed in the rear end zone 48 of the nozzle 13, and behind the rear face 12 of the die 1, as FIG. 3 shows that, in the illustrated embodiment, the nozzle 13, or more precisely the nozzle body 60, forms a longitudinal projection behind this rear face 12, not until to the front face 29 of the insert 25 as would be the case in the injection devices of the prior art, but as far back as the front face 29, coaxially inside the outlet channel 28 of the insert 25.

More precisely, at a level which, as a function of the apparent longitudinal dimension of the nozzle 13, that is to say of its state of thermal expansion, corresponds more or less precisely with that of the rear face 12 of the rear plate 10 or the matrix 1 taken as a whole, the outer peripheral face 59 of the nozzle body 60 is connected to a plane, transverse shoulder 96, annular of revolution about the axis 14 and turned towards the rear, which defines a front limit of the rear end zone 48 and connects, in the direction of approaching the axis 14, the outer peripheral face 59 to an outer peripheral face 97 of the nozzle body 60. This outer peripheral face 97, which delimits the nozzle body 60 in the direction of a distance relative to the axis 14 in the rear end zone 48, is cylindrical of revolution about the axis 14 with an intermediate diameter. between the respective diameters of the outer peripheral face 59 and the inner peripheral face 62 of the nozzle body 60, and to which the diameter of the inner peripheral face 31 of the outlet channel 28 is substantially identical.

Thus is established between the inner peripheral face 31 of the outlet channel 28 and the outer peripheral face 97 of the rear end zone 48 of the nozzle 13 or the nozzle body 60 a guide contact to the mutual longitudinal sliding, with maintenance coaxiality, as well as mutual sealing against a leak, between these faces 31 and 97, of the thermoplastic material in the liquid state coming from the channel 22 or network of channels 22 via the channel elbow connection 35.

The longitudinal dimension on which the rear end zone 48, through its outer peripheral face 97, coaxially penetrates inside the outlet channel 28, and the longitudinal dimension of the inner peripheral face 31 of the outlet channel 28, are calculated. so that these effects are preserved not only when the nozzle 13 has its minimum longitudinal dimension, as is shown in solid lines in Figure 3, but also when its apparent longitudinal dimension increases by expansion thermal, as has been schematized in dotted lines in Figure 3. The determination, for this purpose, the respective longitudinal dimensions of the faces 97 and 31 is within the normal abilities of a skilled person, who will choose these dimensions such so that:

- Never, when the nozzle 13 has its minimum longitudinal dimensions, the end zone 48 escapes the outlet channel 28 coinciding with the front face 29 of the insert 25, and a fortiori coming to be placed forward of this face 29, and that never, when the expansion of the nozzle 13 is maximum, the end zone 48 reaches the elbow 35.

Preferably, as illustrated, it facilitates the penetration of the thermoplastic material from the channel 35, inside the channel 85, by mutually connecting the inner peripheral faces 62 and outer 97 by an annular, transverse edge 98 which is turned towards the rear and flares backwards, from its connection to the inner peripheral face 62 to its connection to the outer peripheral face 97, presenting for example a frustoconical shape of revolution about the axis 14, with an angle of the order of 45 ° with respect thereto. The connection of this edge 98 to the outer peripheral face 97 is effected by a circular circular edge 99, of revolution about the axis 14, which constitutes with the edge 98 the rear end of the nozzle 13 or the nozzle body 60. Such flaring of the back channel 85 is preferred, but could also be obtained by others. means, for example by gradually widening the inner peripheral face 62 rearwardly, to an edge similar to the edge 99, ensuring its connection to the face 97 without defining the song 98 of mutual connection. As will be readily understood by a person skilled in the art, the thermoplastic material in the liquid state, passing through the channel 85 of the nozzle 13, in particular in the rear end zone 48 thereof, applies to this rear end zone Radial forces directed outwards, due to the pressure at which this thermoplastic material is carried in the liquid state, which is transmitted by the outer peripheral face 97 to the inner peripheral face 31 of the outlet channel 28 and contributes to maintaining a seal between the faces 97 and 31 by simple mutual contact; the longitudinal penetration dimension of the face 97 inside the face 31 can also be chosen as a function of this effect.

Furthermore, by friction against the faces 62 and 76 delimiting the channel 85, as well as by longitudinal support, forward, according to the edge 98, the thermoplastic material in the liquid state transiting through the channel 85, towards the before, tends to maintain the aforesaid support, forwards, of the front end zone 46 of the nozzle 13 against the front end zone 47 of the passage 15 via the ring 88.

To prevent this support ceases when the device does not work, that is to say when the thermoplastic material in the liquid state does not transit in the direction 2 inside the channel 85, and in particular for s' ensure that this support towards the front exists at the moment when an injection process is started, that is to say at the moment when thermoplastic material is introduced in the liquid state into channel 85 after a downtime of the injection device, there is provided around the rear end zone 48 of the nozzle 13 or the nozzle body 60 means 300 of longitudinal elastic biasing bearing backward on the distributor 18, which will be recalled that the insert 25 is considered as an integral part, and forwards on the nozzle 13, namely more precisely on the shoulder 96 of the nozzle body 60, to urge the nozzle 13 forward with respect to the distributor 18 and maintaining permanently the longitudinal support of the front end zone 46 of the nozzle 13 forwards on the front end zone 47 of the passage 15 by the edge 74 and by means of the ring 88, without to oppose the aforementioned longitudinal sliding of the rear end zone 48 of the bu 13 or the nozzle body 60 inside the outlet channel 28 of the insert 25 during variations in longitudinal dimension of the nozzle 13 by thermal expansion.

In the illustrated example, the support of these means 100, towards the rear, on this distributor 18 is indirect, ie is effected by means of the plate 21 which is substantially incompressible and of which, for this purpose, the passage 30 is floor.

More specifically, the passageway 30 has two sections mutually juxtaposed longitudinally, with a section adjacent to the rear face 27 of the plate 21 and delimited, in the direction of a distance from the axis 14, by a face peripheral inner 101 having a diameter greater than that of the inner peripheral face 23 of the bore 24 of the distributor 18, but just enough to allow the reception of the flange 33, and a section adjacent to the front face 26 of the plate 19 and delimited by an outer peripheral face 102, cylindrical of revolution about the axis 14 with a diameter greater than the respective diameter of the inner peripheral face 101 of the bore 30 and the inner peripheral face 53 of the passage 17 of the rear plate 10.

These two inner peripheral faces 101 and 102 are mutually connected by a plane, transverse shoulder 103, annular of revolution about the axis 14 and turned forward to serve as support, towards the rear, the means 100 of solicitation elastic.

These could be made in different ways, but considering that the shoulder 103 has an inside diameter much greater than the outer diameter of the shoulder 96, these diameters being respectively that of the inner peripheral face 101 of the bore 30 and that of the inner peripheral face 101 of the bore 30. of the outer peripheral face 59 of the nozzle body 60, they are advantageously constituted, as illustrated, by a spring 104 flat, transverse, annular disc-shaped revolution about the axis 14 and elastically flexible longitudinally between a zone marginal 105, radially inner, and a marginal zone 106, radially outer, having both longitudinal dimensions greater than those of the disk 104 so as to be comparatively rigid. More specifically, the radially outer marginal zone 106 has the general shape of a tubular skirt, of revolution about the axis 14, having a front edge 107 and a rear edge 108 planes, transverse, annular of revolution about the axis 14 to which they are perpendicular, these two edges 107 and 108 being mutually spaced longitudinally by a dimension which corresponds to the longitudinal spacing between the shoulder 103 of the bore and the front face 26 of the plate 21, so that the zone outer margin 106 is inserted substantially without longitudinal clearance between the shoulder 103, against which its edge 108 applies flat under conditions suitable for transmitting forces, backwards, to this shoulder 103 and, via of the plate 21, to the front face 19 of the distributor 18, and the rear face 12 of the rear plate 10 or the matrix 1, which constitutes a forward stop for the edge 107.

Respectively in the direction of a distance and in the direction of a rapprochement with respect to the axis 14, the marginal zone 106 is delimited by outer and outer peripheral faces 110 and inner 111, both cylindrical of revolution. around the axis 14, with respective diameters intermediate between those of the inner peripheral faces 101 and 102 of the bore 30.

The disk 104, of longitudinal dimension much smaller than that which mutually separates the edges 107 and 108, between two main faces 112 and 113 of the disk 104, respectively facing forwards and backwards and one and the other ring of revolution about the axis 14, is integrally connected, in one piece, to the outer marginal zone 106, at a substantially identical longitudinal distance from the two edges 107 and 108. Towards the axis 14, by contrast, its face 113, turned towards the rear, is connected directly to an inner peripheral face 114, cylindrical of revolution about the axis 14 with a diameter substantially identical to that of the outer peripheral face 97 of the rear end zone 48 of the nozzle 13 or the nozzle body 60, which face 114 also constitutes an inner peripheral face for the marginal zone 105, projecting longitudinally on the face 112 facing forwards and integrally formed with the spring disc 104.

More precisely, this marginal zone 105 is delimited, on the one hand, towards the axis 14 by the inner peripheral face 114 mentioned above, and on the other hand in the direction of a distance from the axis 14 by an outer peripheral face. 115 also cylindrical of revolution about the axis 14 with a diameter less than that of the inner peripheral face 111 of] the marginal zone 106, but also that of the inner peripheral face 53 of the passage 17 of the rear plate 10 and it is bounded forwards by a plane, transverse, annular edge 116 of revolution about the axis 14 to which it is perpendicular, this edge 116 mutually connecting the inner and outer peripheral faces 114 and 115 forward then that the peripheral face 115 is connected rearwardly to the face 112 of the spring disk 104.

While the edge 108 of the marginal zone 106 bears back against the shoulder 103 of the bore 30 of the plate 21, the edge 116 of the zone 105 bears forward against the shoulder 96 of the nozzle body 60, the inner peripheral face 114 being slid coaxially on the outer peripheral face 97 of the rear end zone 48 of the nozzle body 60 or the nozzle 13.

Longitudinally, the marginal zones 105 and 106 and the spring disc 104, which interconnects them in one piece, are sized in relation to the longitudinal positioning of the front face 29 of the insert 25, so that:

in a state of minimum longitudinal expansion of the nozzle 13, illustrated in FIGS. 1 and 3, the spring disc 104 is preferably elastically prestressed so that the support of the songs 108 and 116, respectively towards the rear against the shoulder 103 and forward against the shoulder 96, results in the application to the nozzle 13, with respect to the distributor 18, a thrust bearing the front end zone 46 forward against the front end zone 47 of the passage 15 through the edge 74 and through the ring 88, the faces 112 and 113 then being approximately flat and perpendicular to the axis 14 and the face 113 being offset longitudinally towards the front relative to the front face 29 of the insert, and that in a state of maximum longitudinal expansion of the nozzle 13, as shown schematically in phantom in FIG. 3, this state resulting in a recoil of the edge 98 and the edge 99, as well as the shoulder 96 and, with it, the shoulder 116, as well as the marginal zone 116, while the faces 112 and 113 of the spring disk 104 take a backward taper, the rear face 113 remains spaced longitudinally, to the front, of the front face 29 of the insert 25. A suitable longitudinal dimensioning of the elastic biasing means 100 and the insert 25 is easily determinable by a person skilled in the art.

Such a person skilled in the art will readily understand that, under these conditions, any increase in the longitudinal dimensions of the nozzle 13 by thermal expansion results in an increase in the elastic stress of the spring disk 104, which thus tends to maintain firm support. of the front end zone 46 of the nozzle 13 against the front end zone 47 of the passage 15, by the edge 74 and by means of the force distribution ring 88, whatever the state thermal expansion of the nozzle 13 under the normal operating conditions of the injection device and even if, during the injection process, the effect applied the thermoplastic material in the liquid state transiting in the direction 2 to the Inside the channel 85 comes to weaken or disappear, for example at the end of the injection process before a stop of the device.

However, a person skilled in the art will also readily understand that the embodiment of an injection device according to the invention which has just been DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is merely a non-limitative example, with respect to which many variations of practical embodiment can be provided without departing from the scope of the present invention.

Claims

1. Device for injecting a thermoplastic material in the liquid state into a molding cavity (4), having, with reference to a given longitudinal direction (2) of injection:

a rigid matrix (1) having a front face (3) partially delimiting the molding cavity (4), a rear face (12) and at least one longitudinal passage (15, 16, 17) passing through the matrix (1 ), from its rear face (12) to its front face (3), along a predetermined longitudinal axis (14), said passage (15, 16, 17) opening into the front face (3) via an injection orifice ( 84) and immediately forming behind it, around the latter, a transverse shoulder (86), transversely, turned towards the rear, a longitudinal injection nozzle (13) arranged coaxially inside said passageway (15, 16, 17) and having a rearward end (98, 99) adjacent to and rearward from said rear face (12), and a front end (74) adjacent to said front face ( 3) and located behind the annular shoulder (86) of said passage (15, 16, 17), an inner periphery (62, 76) delimiting a longitudinal channel (75), axial, opening longitudinally in the rear end (99) and in the front end (74), and a periphery outer (59, 69, 70, 71, 72, 73, 96, 97) longitudinal,

a distributor (18) supplying the channel (85) of the nozzle (13) made of thermoplastic material in the liquid state, located behind said rear face (12) and mechanically connected to the matrix (1), said dispenser (18) having internally a network (22, 28, 35, 37) for transit of the thermoplastic material in the liquid state, having a longitudinal outlet channel (28) opening towards the front, arranged coaxially with said passage (15). , 16, 17) and fluidly communicating with the channel (85) of the nozzle (13) at the rear end (99) thereof, characterized in that: the rear end (98, 99) of the nozzle (13) and a rear end region (48, 97) of the outer periphery (59, 69, 70, 71, 72, 73, 96, 97) thereof are coaxially accommodated in said outlet channel ( 31) and mounted longitudinally sliding inside thereof, with respect to the distributor (18), with mutual sealing against a leak of a thermoplastic material in the liquid state, in that the front end (74) of the nozzle (13) is firmly supported forwards against the annular shoulder (86) of said passage (15, 16, 17), with mutual sealing against a leakage of thermoplastic material in the liquid state, and in that - means (100) of longitudinal elastic biasing are interposed functionally between the distributor (18) and the nozzle (13), for biasing it elastically forwards and permanently maintaining said longitudinal support firm allowing said longitudinal sliding during longitudinal dimension variations of the nozzle (13) by thermal expansion during the operation of the device.

Injection device according to claim 1, characterized in that the rear end region (48, 97) of the outer periphery (59, 69, 70, 71, 72, 73, 96, 97) of the nozzle (13) has a uniform cross-section and in that said outlet channel (28) has, at least in a longitudinal zone of cooperation with said rear end zone (48, 97), a longitudinal inner periphery (31) of uniform cross-section, complementary to said cross section, so as to establish a mutual guiding contact relative longitudinal sliding.

3. Injection device according to claim 2, characterized in that said contact is sufficiently intimate, circumferentially sufficiently continuous and sufficiently extended longitudinally to ensure said mutual sealing between the nozzle (13) and the distributor (18).

4. Injection device according to any one of claims 1 to 3, characterized in that the inner periphery (62, 76) of the nozzle (13) flares towards the rear, in the immediate vicinity of the rear end (99) of the nozzle (13).

Injection device according to claim 4, characterized in that the rear end (98, 99) of the nozzle is in the form of an annular (98), transverse, flared backward edge of the periphery. interior (62, 76) at the outer periphery (59, 69, 70, 71, 72, 73, 96, 97) of the nozzle (13).

6. Injection device according to any one of claims 1 to 5, characterized in that:

the front end (74) of the nozzle (13) is in the form of a transverse annular edge (74) facing forward, in that

- the outer periphery (59, 69, 70, 71, 72, 73, 96,

97) of the nozzle (13) flares rearward in a front end region (46), immediately behind said ridge (74), therefrom, and in that an annular ring cross-section (88), substantially incompressible force distribution is interposed longitudinally between said front end zone (46) and the annular shoulder (86) of said passage (15, 16, 17), around said ridge (74); ), and has respectively a front face (92, 93) complementary to the annular shoulder (86) of said passage (15, 16, 17) and a complementary rear face (89, 91) forward and backward respectively. the front end area (46, 69, 71) of said outer periphery (59, 69, 70, 71, 72, 73, 96, 97) of the nozzle (13).

7. Injection device according to claim 6, characterized in that the annular shoulder (86) of said passage (15, 16, 17) flares backwards from the injection orifice (84). .

Injection device according to claim 7, characterized in that the front end region (46, 69, 71) of the outer periphery (59, 69, 70, 71, 72, 73, 96, 97) of the nozzle (13) flares less towards the rear than the annular shoulder (86) of said passage (15, 16, 17) and is connected to said ridge (74) by an annular groove (87), transverse .

9. Injection device according to any one of claims 6 to 8, characterized in that: - the outer periphery (59, 69, 70, 71, 72, 73, 96, 97) of the nozzle (13) presents a front, flat, transverse, front-facing annular shoulder (69) rearward of said front end region (46), and in that said annular ring (88) has a flat rear annular shoulder (89) , transverse, facing back, against which said shoulder (69) of the outer periphery (59, 69, 70, 71, 72, 73, 96, 97) of the nozzle (13) is flat, towards forward.

10. Injection device according to claim 9, characterized in that the annular shoulder (86) of said passage (15, 16, 17) comprises, longitudinally opposite the front shoulder (69) of the outer periphery (59). , 69, 70, 71, 72, 73, 96, 97) of the nozzle (13), a flat, transverse, rear-facing annular zone (79), and that said annular ring (88) has a front shoulder (93) flat, transverse, facing forwards, resting flat against said flat annular zone (79) of the annular shoulder (86) of said passage (15, 16, 17).

11. Injection device according to any one of claims 9 and 10, characterized in that the nozzle (13) comprises a nozzle body (60) bounded in the front by a ring (63) annular, transverse, flat , constituting a radially outer portion of said front shoulder (69) of the outer periphery (59, 69, 70, 71, 72, 73, 96, 97) of the injection nozzle (13), and a nozzle tip (61 ) defining said front end region (46, 69, 71) of the outer periphery (59, 69, 70, 71, 72, 73, 96, 97) of the nozzle (13) and said edge (74) of that and constituting a radially inner portion (68) of said front shoulder (69) of the outer periphery (59, 69, 70, 71, 72, 73, 96, 97) of the nozzle (13).

12. Injection device according to claim 11, characterized in that the nozzle tip (61) is nested coaxially in the body of nozzle (60) and immobilized longitudinally with respect thereto abutting against it rearwardly of said radially inner portion (68) and abutting against said rear shoulder (89) of the ring annular

13. Injection device according to any one of claims 9 to 12, characterized in that: the shoulder (86) of said passage (15, 16, 17) is connected, in the sense of a distance from said audit axis (14), at a longitudinal inner periphery (78) of said passage (15, 16, 17), in that

- the outer periphery (59, 69, 70, 71, 72, 73, 96,

97) of the nozzle (13) has, between said front shoulder (69) and said front end zone (46, 71), a longitudinal section (70) placed radially facing a section of said longitudinal inner periphery ( 78) of said passage (15, 16, 17), and in that - the force distribution ring (88) has inner (90) and outer (95) longitudinal peripheral faces, respectively complementary to said longitudinal section (70). ) of the outer periphery (59, 69, 70, 71, 72, 73, 96, 97) of the nozzle (13) and said portion of said longitudinal inner periphery (78) of said passage (15, 16, 17).

14. Injection device according to any one of claims 1 to 13, characterized in that the means (100) of longitudinal elastic biasing comprise a spring (104) disposed coaxially with said rear end area (48, 97) and operatively interposed between a rearwardly facing transverse rear shoulder (96) constituting a front boundary of said end zone rear (48, 97), and the distributor (18).

15. Injection device according to claim 14, characterized in that said spring (104) has the shape of a disc (104) annular, transverse, having a radially inner marginal zone (105) bearing longitudinally, towards the before, on said rear shoulder (96) of the outer periphery (59, 69, 70, 71, 72, 73, 96, 97) of the nozzle (13) and a radially outer marginal zone (106) in longitudinal support, to the rear, on the distributor (18).