Abstract:
An injection valve includes an injection channel ( 17 ) that opens outwards via an outlet ( 18 ) and has a specific inlet for the arrival of the molding material ( 19 A) remote from the outlet ( 18 ), in addition to a slider unit ( 20 ) that is moveably mounted in the injection channel ( 17 ) and controls the outlet thereof ( 18 ). The injection channel ( 17 ) has a specific outlet ( 19 B) for discharging the molding material. The invention can be used to mold an optical lens made from a polymerizable synthetic material.

Description:
The present invention relates generally to injection valves of the kind used to feed a mold of any kind with a molding material of any kind. 
   It is aimed more particularly at injection valves that have an injection channel, which opens to the outside via an outlet, and a slider unit which is mounted in the injection channel so as to be mobile in translation therein and which controls the outlet thereof. The injection channel has an inlet orifice to which the molding material is fed and which is located at a distance from the outlet. 
   DESCRIPTION OF THE RELATED ART 
   Injection valves of the above type are described in the following U.S. patents, for example: U.S. Pat. Nos. 5,221,509, 5,378,138, 5,470,219. 
   The present invention is more particularly aimed at the situation in which the nature of the molding material itself causes problems. 
   This is the case, for example, with polymerizable synthetic materials usually employed in molding optical lenses, and in particular ophthalmic lenses, that is to say spectacle lenses. 
   These polymerizable synthetic materials give rise to two kinds of problem during molding. 
   First of all, they frequently lead to unwanted deposition of a film of material on the inside of the injection valve through which they pass, even if the latter valve has been internally treated with a material supposedly opposing any such deposition, and this leads to unwanted fouling and even clogging of the injection valve. 
   Also, as soon as there is a certain level of discontinuity in their path, which obviously tends to be the case when they pass through an injection valve, these polymerizable synthetic materials are frequently subject to a phenomenon known as “bubbling”, i.e. bubbles tend to form spontaneously in them, which can lead to rejection of the products, for example optical lenses, molded under these conditions. 
   SUMMARY OF THE INVENTION 
   A general object of the present invention is an arrangement which is advantageous in that, somewhat unexpectedly, it minimizes or even cancels out the risk of fouling and “bubbling”. 
   It is based on the observation, not previously disclosed, that maintaining the molding material fed to the injection valve in circulation after the mold has been properly filled minimizes these risks of fouling and “bubbling”. 
   Thus the present invention provides an injection valve for feeding molding material to a mold, of the kind including an injection channel which opens to the outside via an outlet and which has, at a distance from said outlet, an inlet orifice to which the molding material is fed, and further including a slider unit that is mounted in the injection channel to be mobile in translation therein, and that controls the outlet thereof, characterized in that the injection channel has an outlet orifice for evacuating molding material. 
   Accordingly, once the mold has been filled, the molding material reaching the injection valve continues to circulate, being evacuated from the injection valve via the outlet orifice provided for this purpose. 
   This advantageously avoids stagnation of the molding material in the injection valve, as normally occurs when the molding material dead-ends at the closed end of the injection channel once the mold has been filled. 
   As a result of this, the risks of fouling of the injection valve are themselves advantageously minimized, which is what was wanted. 
   This advantageously further proves to apply to the risks of “bubbling” occurring in the molding material during molding thereof. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the invention will emerge further from the following description, which is given by way of example and with reference to the accompanying diagrammatic drawings, in which: 
       FIG. 1  is an elevation view of an injection valve in accordance with the invention, shown in position on a mold and to a relatively small scale; 
       FIG. 2  is a side view of the combination, as seen in the direction of the arrow II in  FIG. 1 ; 
       FIG. 3  is a view of the valve body of the injection valve in accordance with the invention, to a relatively larger scale and in cross section taken along the line III—III in  FIG. 1 ; 
       FIG. 4  shows to a relatively still larger scale the detail IV from  FIG. 3 ; 
       FIG. 5  is a top view of the valve body, as seen in the direction of the arrow V in  FIG. 3 ; 
       FIG. 6  is a view of one of two shells constituting the valve body in section taken along the line VI—VI in  FIG. 5 ; 
       FIG. 7  is an elevation view of the slider unit of the injection valve according to the invention; 
       FIG. 8  is a view of the slider unit in longitudinal section taken along the line VIII—VIII in  FIG. 7 ; 
       FIG. 9  is a view of the slider unit in cross section taken along the line IX—IX in  FIG. 7 ; 
       FIGS. 10A and 10B  are partial views in section, derived from, but to a larger scale than,  FIG. 6 , showing two successive phases of operation of the slider unit in the valve body; 
       FIG. 11  is a sectional view analogous to  FIG. 3  of a different embodiment; 
       FIG. 12  shows the detail XII from  FIG. 11  to a larger scale; 
       FIG. 13  is a view of the  FIG. 11  embodiment analogous to that of  FIG. 6  and in section taken along the line XIII—XIII in  FIG. 11 ; 
       FIG. 14  is a view in longitudinal section of a further embodiment of an injection valve according to the invention; 
       FIG. 15  is a view of this further embodiment in cross section taken along the line XV—XV in  FIG. 14 ; 
       FIG. 16  is an elevation view of the corresponding slider unit to a larger scale; 
       FIG. 17  is a partial view of the slider unit in longitudinal section taken along the line XVII—XVII in  FIG. 16 ; 
       FIG. 18  is a partial view of a still further embodiment in longitudinal section and analogous to  FIG. 17 ; and 
       FIG. 19  is a partial elevation view of this still further embodiment as seen in the direction of the arrow XIX in  FIG. 18 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The figures show, by way of example, the application of the invention to molding an optical lens, to be more precise an ophthalmic lens, not shown. 
   The mold  10  used for such molding is formed of two molding shells  11 A,  11 B at whose periphery is an annular closure member  12  defining with them the necessary molding cavity  13 . This is known in the art. 
   In the embodiment shown, the molding shells  11 A,  11 B are on edge and the closure member  12  is formed of two jaws  12 ′,  12 ″ which are carried by a common frame, not shown, and whose edges conjointly grip the molding shells  11 A,  11 B, having a semicircular inside contour for this purpose; at least one of the jaws, for example the top jaw  12 ″, is mobile relative to the other jaw, here the bottom jaw  12 ′, to enable the molding shells  11 A,  11 B to be inserted between them. 
   These arrangements are well known in the art, for example from French patent application No. 94/14926, filed Dec. 12, 1994, publication No. 2 727 894; being in themselves irrelevant to the present invention, they are not described in further detail here. 
   An injection valve  15  feeds the mold  10 , to be more precise its molding cavity  13 , with molding material. This is also known in the art. 
   As described in the previously cited French patent No. 94/14926, for example, the injection valve  15  is at the bottom of the molding cavity  13 , to be more precise at the lowest point thereof. 
   To this end, the bottom jaw  12 ′ of the closure member  12  has a localized casting opening  16  to which the injection valve  15  is applied. 
   The injection valve  15  has an internal injection channel  17  which opens to the outside via an outlet  18  at one end, in corresponding relationship with the casting opening  16  of the mold  10 , and which has, as described in more detail later, an inlet orifice  19 A at a distance from the outlet  18 , and to which the molding material is fed, and a slider unit  20  that is mounted in the injection channel  17  so that it is mobile in translation therein, and which controls the outlet  18  thereof. This is also known in the art. 
   In accordance with the invention, the injection channel  17  has an outlet orifice  19 B for evacuating the molding material. 
   In the embodiments shown in  FIGS. 3 to 13  in particular, like its outlet  18 , the inlet orifice  19 A and the outlet orifice  19 B of the injection channel  17  are both controlled by the slider unit  20 . 
   As shown here, for example, the inlet orifice  19 A and the outlet orifice  19 B of the injection channel  17  are disposed laterally on a section T of the injection channel  17 , in contact with whose wall the slider unit  20  is slidably mounted. 
   In the embodiments shown in  FIGS. 3 to 13  in particular, the injection valve  15  is separate from the mold  10  and in practice includes a valve body  23  containing the injection channel  17  and adapted to be attached to the mold  10 , to be more precise to the bottom jaw  12 ′ of the closure member  12  of the mold  10 , having a fixing flange  24  at the bottom for this purpose. 
   Conjointly, in these embodiments, the injection channel  17  has the same cross section throughout its length, passing completely through the valve body  23  from the fixing flange  24  to its outlet  18 . As described in more detail later, the slider unit  20 , which is shown separately in  FIGS. 7 to 9 , has a transverse opening  25  passing completely through it and by means of which the inlet orifice  19 A and the outlet orifice  19 B of the injection channel  17  can communicate with each other. 
   In practice, in the embodiments shown in  FIGS. 3 to 13 , the cross section of the injection channel  17  is rectangular, with a width L 1  very much less than its length L 2  (see  FIG. 5 ), and the overall shape of the slider unit  20  is that of a thin blade, whose rectangular cross section is complementary to that of the injection channel  17 , and whose contour, as seen in elevation, is also rectangular. 
   It results from the foregoing that, in the embodiments shown in  FIGS. 3 to 13 , the section T of the injection channel  17  including the inlet orifice  19 A and the outlet orifice  19 B is not materialized in concrete form, given the uniformity of the cross section of the injection channel  17  throughout its length. 
   In the embodiments shown in  FIGS. 3 to 13 , the valve body  23  is formed of two shells  23 A,  23 B that meet face-to-face on a joint plane P that intersects the injection channel  17  longitudinally. 
   As is the case in these embodiments, the joint plane P is preferably the plane of one of the larger faces of the injection channel  17 , and is therefore entirely part of one of the shells  23 A,  23 B, in this example the shell  23 B, as is clear from  FIGS. 5 and 6 . 
   Thus only the shell  23 B has to be machined to form the injection channel  17 . 
   In contrast, the corresponding face of the shell  23 A is advantageously smooth. 
   The two shells  23 A,  23 B constituting the valve body  23  are suitably fastened together, of course, for example by screws, not shown, which pass transversely through the injection channel  17 . 
   To this end, and as can be seen in the case of the shell  23 B in  FIG. 6 , each of the shells  23 A,  23 B has appropriate bores  26  spaced along the injection channel  17 . 
   Similarly, the fixing flange  24  of the valve body  23 , which in practice is divided half-and-half between the two shells  23 A,  23 B, has spaced bores  27  through which screws, not shown, are passed to fix the valve body  23  to the mold  10 . 
   Also, in the embodiments shown in  FIGS. 3 to 13 , the valve body  23  has a nozzle-like external profile at the location of the outlet  18  of the injection channel  17 . 
   In other words, it forms a more or less tapered external nose  28 . 
   The free edge of the nose  28  is straight and substantially perpendicular to the axis A of the injection channel  17 , for example (see  FIG. 6 ). 
   As an alternative to this it can be concave, having the same profile as the contour of the molding cavity  13  (see  FIG. 13 ). 
   In the embodiments shown in  FIGS. 3 to 13 , the inlet orifice  19 A and the outlet orifice  19 B of the injection channel  17  are offset longitudinally from each other along the axis A of the injection channel  17 . 
   In practice, the inlet orifice  19 A of the injection channel  17  is then preferably nearer its outlet  18  than the outlet orifice  19 B. 
   However, when projected onto a common plane, and as is clear from  FIGS. 10A and 10B , the inlet orifice  19 A and the outlet orifice  19 B of the injection channel  17  partly overlap each other. 
   In practice, the inlet orifice  19 A and the outlet orifice  19 B of the injection channel  17  are on respective opposite sides of the injection channel  17  and therefore on respective opposite sides of its axis A, one being part of the shell  23 A of the valve body  23  and the other being part of the shell  23 B. 
   In the embodiments shown in  FIGS. 3 to 13 , the inlet orifice  19 A and the outlet orifice  19 B of the injection channel  17  are both at the ends of pipes  30 A,  30 B at least the end parts of which are substantially perpendicular to the axis of the injection channel  17 . 
   As shown in dashed outline in  FIG. 3 , the pipes  30 A,  30 B can themselves be connected, via chambers  31 A,  31 B, to tubes  32 A,  32 B in which the molding material circulates. 
   In practice, the pipes  30 A,  30 B have circular contours and likewise therefore the inlet orifice  19 A and the corresponding outlet orifice  19 B. 
   Likewise, in practice, the inlet orifice  19 A and the outlet orifice  19 B both have the same diameter D. 
   As a corollary of this, the opening  25  in the slider unit  20  is an elongate buttonhole whose length extends along the axis A of the injection channel  17 . 
   The width L 3  of the opening  25  is at least equal to the diameter D of the inlet orifice  19 A and the outlet orifice  19 B, so as to enclose them. 
   In practice, the width L 3  is substantially equal to the diameter D. 
   Conjointly, the length L 4  of the opening  25  is much greater than the overall contour of the combination of the inlet orifice  19 A and the outlet orifice  19 B. 
   In the embodiment shown in  FIGS. 3 to 9  in particular, the shells  23 A,  23 B constituting the valve body  23  are relatively massive, and are made of metal, for example. 
   Conjointly, the slider unit  20  is itself made of metal, preferably stainless steel. 
   Also, in this embodiment, the free end  33  of the slider unit  20  is straight, like the free edge of the nose  28  of the valve body  23 . 
   In service, the slider unit  20  is mobile between an advanced position, in which, as shown in  FIG. 10A , its free end  33  is level with the outlet  18  of the injection channel  17 , and a retracted position, in which, as shown in continuous outline in  FIG. 10B , it partly uncovers the inlet orifice  19 A but covers the outlet orifice  19 B. 
   In the advanced position, the opening  25  in the slider unit  20  establishes communication between the inlet orifice  19 A and the outlet orifice  19 B but completely blocks the injection channel  17 . 
   The molding material therefore circulates continuously through the injection valve  15 , without feeding the molding cavity  13  of the mold  10 . 
   In contrast, in the retracted position of the slider unit  20  the molding cavity  13  of the mold  10  is fed with the molding material, which is not diverted to the outlet orifice  19 B. 
   In all intermediate positions of the slider unit  20 , as long as its free end  33  has at least reached, and passed beyond, the inlet orifice  19 A, as shown in dashed outline in  FIG. 10B , the molding cavity  13  of the mold  10  is advantageously fed, at a more or less variable flow rate. 
   Obviously, the fact that, when projected onto a plane, the inlet orifice  19 A and the outlet orifice  19 B of the injection channel  17  overlap has the advantage that this limits the stroke of the slider unit  20 . 
   To limit this stroke further, and optimally, the inlet orifice  19 A is preferably as close as possible to the outlet  18  of the injection channel  17 . 
   As will also be noted, the molding material is in contact with the walls of the injection channel  17  only when the slider unit  20  is in the retracted position, and its contact with those walls is then limited to just the end portion of the injection channel  17 . 
   This advantageously minimizes the risk of fouling of the injection channel  17 , especially as, on each outward and return movement, the slider unit  20  sweeps the walls of the injection channel  17  completely. 
   As a corollary of this, the risks of “bubbling” of the molding material are themselves minimized. 
   In the embodiment shown in  FIGS. 11 to 13 , the shells  23 A,  23 B constituting the valve body  23  are thinner than previously, ignoring the fixing clamp  24 . 
   They are made from a synthetic material, for example, preferably a fluoropolymer-based synthetic material such as PTFE, for example. 
   As shown in dashed outline in  FIG. 11 , the shells  23 A,  23 B can then each be reinforced laterally by a metal plate  34 A,  34 B, if required. 
   As a corollary of this, the slider unit  20 , not shown, is preferably still made of metal. 
   Also, in this embodiment, at least one of the pipes  30 A,  30 B with the inlet orifice  19 A and the outlet orifice  19 B at their ends is connected to the orifice by an enlargement  36 A,  36 B that is elongate in the direction of the outlet  18  of the injection channel  17 . 
   As shown here, for example, the enlargement  36 A,  36 B is produced by a bevel  37 A,  37 B which intersects the pipe  30 A,  30 B concerned obliquely. 
   In the embodiment shown, there is an enlargement  36 A,  36 B for each of the pipes  30 A,  30 B, and the enlargement  36 A,  36 B extends as far as the immediate vicinity of the outlet  18  of the injection channel  17 . 
   In practice, in the embodiment shown, the angle between the bevel  37 A,  37 B of the enlargement  36 A,  36 B of a pipe  30 A,  30 B and the axis A of the injection channel  17  is different for the two pipes  30 A,  30 B. 
   For example, it is greater for the pipe  30 A corresponding to the inlet orifice  19 A than for the pipe  30 B corresponding to the outlet orifice  19 B. 
   Otherwise, the features are of the same kind as previously. 
   In the embodiment shown in  FIGS. 14 to 17 , the injection valve  15  according to the invention is an integral part of the mold  10 . 
   In other words, it is incorporated into the mold  10 . 
   To be more precise, in the embodiment shown, it is incorporated into the bottom jaw  12 ′ of the closure member  12  of the mold  10 , and is in one piece with the remainder of the bottom jaw  12 ′. 
   Also, in this embodiment, the injection channel  17  has, successively, starting from its outlet  18 , which is coincident with the casting opening  16  of the mold  10 , at least two sections T′, T, namely a smaller first section T′, at the end of which is the outlet  18 , and a larger second section T, which incorporates the inlet orifice  19 A and the outlet orifice  19 B, and, conjointly, the slider unit  20  has two sections T′ 1 , T 1  whose dimensions are complementary to those of the sections T′, T of the injection channel  17 . 
   As shown here, for example, the two sections T′, T of the injection channel  17  are both cylindrical and are connected by a frustoconical transition section T″. 
   In practice, the inlet orifice  19 A and the outlet orifice  19 B of the injection channel  17  are in diametrally opposed positions relative to each other, on respective opposite sides of the axis A of the injection channel  17 . 
   In the embodiment shown, the inlet orifice  19 A and the outlet orifice  19 B are at the ends of pipes  30 A,  30 B at least end parts of which are oblique to the axis A of the injection channel  17 , at an acute angle thereto. 
   As shown here, for example, this angle is the same for both pipes  30 A,  30 B. 
   In the embodiment shown, the profile of the free end  33  of the slider unit  20  is globally concave from its central part to its periphery. 
   In the advanced position of the slider unit  20 , its section T′ 1  is interengaged with the section T′ of the injection channel  17 , which prevents feeding of the molding cavity  13 , and, conjointly, its section T 1  is interengaged with the section T of the injection channel  17 . 
   However, because of the length of the section T′ 1  of the slider unit  20 , on the one hand, and because of the difference between the diameters of the section T′ 1  and the section T 1  from which it follows on, on the other hand, the molding material still circulates continuously through the injection valve  15 , bypassing the section T′ 1 . 
   This circulation of the molding material through the injection valve  15  continues in the retracted position of the slider unit  20 , but the molding cavity  13  is fed because of the proximity of the corresponding flow to the outlet  18  of the injection channel  17 , which is uncovered at this time, and because of the oblique nature of the passage  30 A through which the molding material is discharged into the injection channel  17 . 
   In the embodiment shown diagrammatically in  FIGS. 18 and 19 , instead of being cylindrical, the end section T′ 1  of the slider unit  20  is in the form of a blade, as in the embodiments shown in  FIGS. 3 to 13 . 
   However, as shown here, its free end  33  can be profiled, as previously. 
   It is found that a profiled free end  33  on the slider unit  20  minimizes the risks of “bubbling” of the molding material in the molding cavity  13  at the location of the injection channel  17 . 
   Of course, the present invention is not limited to the embodiments described and shown, but encompasses any variant execution and/or combination of the components thereof.