Abstract:
A pipe conveying molten material upwards from a pressurized receptacle into the mold of a low pressure diecasting machine, positioned on and supported by the receptacle, is secured in a fluid-tight fit by an adjustable coupling device. One end of the pipe extends through the topmost wall of the receptacle to pick up the molten material and the other terminates in a head located externally of the receptacle and tightened together with a seal against the mold. The outer surface of the pipe head has at least one substantially frusto conical portion matched to the surfaces of a plurality of wedges disposed circumferentially around the pipe and mounted on slide ways which can be directed by suitable actuators from an at-rest position to an operating position in which the pipe is subjected to an axial force with the pipe head clamped together with the seal against the machine.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a device to effect a fluid-tight coupling around a pipe serving to convey molten material, as part of the connection between a low pressure diecasting machine and a pressurizable receptacle in which the molten material is prepared. The device disclosed is well suited for application to a pipe fashioned from fragile material, insertable typically through one wall of the receptacle, which comprises a body having an inlet end that is located internally of the receptacle and a head at the pipe outlet end whose surface can be coupled in fluid-tight association with a mold coupled to the low pressure diecasting machine. 
     A low pressure diecasting machine of the type in question is mounted on and connected to a receptacle containing molten material in a manner such that the pipe is aligned and connected with the injection nozzles of a mold connected to the machine. 
     The prior art systems employed in making such a connection, while based on a variety of techniques, are similar inasmuch as all permit removing the machine from the receptacle. In effect, the machine rests on the receptacle during operation and can be moved to a non-operating position whenever the need arises to gain access to the inside of the receptacle. To ensure the features of a removable connection that can be successfully operated, the pressure-tight fit between the nozzles and the front end surface of the head of the pipe is obtained by interposing seals of gaskets of suitable thickness. The efficiency of the sealing action in containing the pressure of the molten material is somewhat critical, given that the tightness of the fit between the front end surface of the pipe and the nozzle of the mold relies only on a suitably strong force of compression. 
     In practice, this is achieved by packing the space between the machine and the head of the pipe to an overall depth nominally greater than that of the existing gap, so that the fluid-tight barrier will be established by a compressive force provided by the total weight of the low pressure diecasting machine. 
     Quite apart from the operational inconvenience and the empirical nature of such a system, selection of the optimum condition depends on a process of trial and error. The working principle underlying this method of connection tends to result in a high degree of structural stress on the pipe. In other solutions, the receptacle is forced vertically into association with the diecasting machine through the agency of suitable lifting means, the force in this instance being applied laterally. 
     Owing to the intense and uncontrollable impact of these stresses, rupture of the pipe frequently occurs, particularly when the pipe, as already intimated, is made of a fragile material, such as silicon nitride or other ceramics typically utilized in the context of low pressure diecasting processes for aluminum alloys. 
     Conversely, the application of a smaller compressive force to the sealing medium might well diminish the risk of pipe rupture, but would not ensure an efficient sealing action to accommodate the pressure of the fluid flowing at high temperature through the pipe. In short, a solution that succeeds both in avoiding the risk of rupture to the pipe and in ensuring an efficient seal must necessarily involve a compromise between the two opposing requirements outlined above. 
     OBJECT OF THE INVENTION 
     Accordingly, the object of the present invention is to overcome the aforementioned drawbacks, providing a solution to the problem of ensuring an efficient sealing action between pipe and mold by adopting a novel arrangement for compressing the interposed sealing medium, and allowing for adjustment of the force by which the sealing action is assured. 
     SUMMARY OF THE INVENTION 
     The stated object is realized by a device in which a pipe for conveying molten material can be coupled adjustably and in a pressure-tight fit as part of the connection between a low pressure diecasting machine and a pressurizable receptacle for preparation of the molten material. 
     The pipe passes through one wall of the receptacle and has a body affording a head coinciding with an outlet end whose front surface can be coupled to the mold of the low pressure diecasting machine together with an interposed sealing medium. The design of the device takes account of the fact that the outer surface of the pipe as supplied by the manufacturer has at least one portion which is angled in relation to the axis of the pipe itself. In a preferred embodiment described below, the outer surface of the pipe comprises a portion of the head that has a substantially frustoconical shape. 
     The device itself comprises three wedges disposed circumferentially around the pipe between the head and the wall of the receptacle. Each wedge has a surface matched to the aforementioned angled portion of the pipe in such a manner that the surfaces can be coupled together. In addition, the three wedges are mounted slidably on corresponding ways and are thus capable of movement in relation to the wall of the receptacle, transversely to the axis of the pipe through the agency of an actuator means. The movement is brought about between a non-operating at-rest position of the wedges spaced from the pipe, and an operating position of close proximity of the wedges to the pipe in which the wedges apply an axial force such as will tend to draw the pipe outward from the receptacle and, in consequence, cause the head to be clamped together with the sealing medium against the mold of the low pressure diecasting machine. The three wedges are thus able to generate the requisite sealing action, at least across the front end surface of the head, in opposition to the pressure of the molten material flowing along the pipe. 
     The principal advantage of a device according to the invention is that the optimum clamping force for a given pipe can be determined by a continuous incremental type of adjustment in which the weight of the machine plays no part whatever. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described in detail, by way of example, with the aid of the accompanying drawings, in which: 
     FIG. 1 is an overall sectional view illustrating a device according to the invention, shown fitted to a low pressure diecasting machine associated with a receptacle containing molten material, in which the pipe is shown in a first embodiment; 
     FIG. 2 shows the device according to the invention in a further section, enlarged in relation to FIG.  1  and taken through lines II—II of FIG. 3; 
     FIG. 3 illustrates the device of FIG. 2 viewed in plan from above; 
     FIG.  4  and FIG. 5 illustrate a first detail of the device viewed respectively in plan and in a section through V—V of FIG. 4; 
     FIG.  6  and FIG. 7 illustrate a second detail of the device viewed respectively in plan and in a section through lines VII—VII of FIG. 6; 
     FIG.  8  and FIG. 9 illustrate a third detail of the device viewed respectively in plan and in a section through lines IX—IX of FIG. 8; 
     FIG.  10  and FIG. 11 show a detail of the device in an alternative embodiment, illustrated respectively in a partial sectional view and in plan; and 
     FIGS. 12,  13 ,  14  and  15  illustrate four alternative embodiments of the pipe. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the accompanying drawings, and to FIGS. 1 and 2 in particular, the present invention relates substantially to an adjustable coupling device  9  by means of which a feeder pipe  1  conveying molten material is connected in a pressure-tight fit to a low pressure diecasting machine  2  associated with a pressurizable receptacle  3  in which the molten material is prepared. 
     The low pressure diecasting machine  2  is supported during operation by the receptacle  3 , of which the top horizontal wall  4  has thereon a set of stands  30  for this purpose. When not in operation, the machine  2  can be removed from the receptacle  3  (see phantom lines in FIG. 1) by a combination of lateral translation and elevation on angled ways, not illustrated in the drawings, in such a way as to afford internal access to the receptacle  3 . 
     The pipe  1  is typically of fragile ceramic material, preferably silicon nitride, and passes through the top horizontal wall  4  of the receptacle  3 . Seen in its entirety, the pipe has a body  5  with an inlet end  27  which extends into a crucible  33  positioned within the receptacle  3 . The pipe also has a head  6  at an opposite outlet end  7  of which the front surface  8  is designed to locate against a mold  17  fitted to the low pressure diecasting machine  2  with an interposed seal  28  as will be described. 
     A preferred embodiment of the device  9  (shown in FIG. 2) is designed for use in conjunction with a pipe  1  of which the outer surface  10  has an annular portion  13  of frustoconical shape located at the head end  6 , which preferably has an angle of 30° relative to the longitudinal axis  11  of the pipe  1 . It will, of course, be sufficient in practice that the annular portion  13  of the outer surface  10  has a different type of taper in relation to the axis  11  of the pipe  1 , as indicated in FIGS. 12,  13  and  14 . To this end, the pipe  1  shown in FIG. 12 has a separately embodied flange  34  whose outer surface  10  affords the frustoconical annular portion  13 . The pipe  1  of FIG. 13 has an enlarged collar with a plain shoulder, the frustoconical portion  13  in this instance provided by a thrust ring  35 . In the example of FIG. 14, the entire head  6  of the pipe  1  has a splayed flange  36  of “V” shaped profile which creates the frustoconical portion  13 . 
     Referring in particular to FIGS. 2,  4  and  5 , the device  9  has three identical wedges  12  to be disposed around the head  6  of the pipe  1  at equal angular intervals of 120° and designed to operate between the head  6  of the pipe  1  and the wall  4  of the receptacle  3 . 
     Each wedge  12  has a surface  15  matched to the frustoconical portion  13  of the outer surface  10  of the pipe  1  in such a manner that the three wedges can be coupled circumferentially with the pipe portion  13 . 
     In addition, the wedges  12  are mounted slidably to respective slide ways  2  (see FIGS. 6 and 7) formed partly within the wedges themselves and partly, as indicated by the number  20   a , within a flange  19  by which the entire device  9  is secured to the wall  4  of the receptacle  3 . This makes each of the wedges capable of movement in relation to the wall  4  transversely to the axis  11  of the pipe  1  through the agency of a corresponding actuator means  16 . 
     In an alternative embodiment, illustrated in FIG. 15, the head  6  of the pipe  1  has a downwardly directed surface  37  disposed obliquely in relation to the pipe longitudinal axis  11  and performs the same function as the aforementioned frustoconical annular portion  13 . More specifically, the downwardly directed surface  37  affords an inclined plane that can be coupled with a wedge  12  mounted in such a way as to operate and interact adjustably with the head  6  essentially in the same manner as described above for other embodiments. 
     In particular, it is seen from FIG. 2 that the flange  19  is secured to the wall  4  of the receptacle  3  by means of screws  32  with a gasket  38  interposed. In addition, the part  20   a  of the slide way formed in the flange  19  affords a fixed key  31  insertable into the slide way  20  of the wedge  12  serving to guide the sliding movement of the wedge. The device  9  further comprises an annular plate  18  providing a structural interface between the low pressure diecasting machine  2  and the receptacle  3 . The plate  18  is positioned coaxially in relation to the pipe  1 , between the machine  2  and the head  6 , and has a bush  22  of ceramic material disposed in axial alignment with the pipe through which the molten material flows during the injection stage. 
     As indicated in FIGS. 2 and 3, the annular plate  18  is secured to the flange  19  with bolts  29  and has a peripheral rim  24  shaped in such a way as to transmit the structural loads deriving from the force of mass exchanged between the low pressure diecasting machine  2  and the pressurized receptacle  3  on which the machine is supported. In addition, the peripheral rim  24  encompasses the head  6  and the wedges  12 , so that there is no structural interaction between these components and the plate  18 . 
     Nonetheless, the peripheral rim  24  of the plate  18  can be coupled with the wedges  12 . As seen from FIG. 2, in effect, the rim  24  and the wedges  12  have respective matching frustoconical surfaces  25  and  26  positioned so as to engage one with another when the plate  18  is secured to the receptacle  3 , with the result that the wedges  12  are clamped against the head  6  by a force applied at right angles to the axis  11  of the pipe  1 . Thus, whenever the annular plate  18  is bolted onto the flange  19 , the frustoconical surface  25  of rim  24  is caused to slide against the matching surfaces  26  of the wedges  12 , forcing the wedges in their turn to slide along the respective ways  20  and move from an at-rest position distanced from the pipe  1  toward an operating position of close proximity to the pipe  1 . In this close-coupled position, and indeed during any further movement in the same direction, the inner surfaces  15  of the wedges will engage on the matching frustoconical portion  13  of the outer surface  10  of the head  6  producing an axial force that tends to lift the pipe  1  from the receptacle  3 . The orientation of the taper on the surfaces denoted  25  and  26  is opposite to that of the frustoconical annular portion  13  afforded by the outer surface  10  of the pipe  1 , and the angle of inclination also different, for example 20° in the embodiment illustrated. Thus, it is the angled surface  25  of the peripheral rim  24  of the annular plate  18  provides the aforementioned actuator means  16  to drive the wedges  12 . 
     As regards the operation of the device  9 , it is seen from FIG. 2 that the action of the flange  18  on the wedges  12  can be optimized by the adoption of actuator means  16  in a wide variety of different yet substantially equivalent solutions; for example, by including setscrews  21  insertable through the peripheral rim  24  of the plate  18  and engaging each of the wedges  12 . The wedges can be moved further along the respective slide ways  29  and thereby obtain a fine adjustment of the clamping action applied to the pipe  1 . 
     As a result of the axial force generated through the clamping action, the front end surface  8  of the head  6  of the pipe  1  is driven against and ultimately impeded by the plate  18 . Accordingly, the seal  28  can be pinched securely between the head  6  and the plate  18  creating a pressure-tight barrier to the molten material flowing through the pipe  1 . Clearly, any leakage of the molten material between the head  6  and the surrounding wedges  12  will be prevented by locating similar seals  28  at least against the frustoconical annular portion  13  extending between the head  6  and the body  5  of the pipe  1 . 
     A device  9  as shown ensures the fluid-tight fit needed to prevent any egress of the molten material from the pipe  1  and of setting the clamping force at the exact values required to produce an efficient seal. This is accomplished without inducing overloads liable to present an excessive risk to the integrity of the pipe  1 . Moreover, not only does the weight of the low pressure diecasting machine  2  have no bearing whatever on the clamping force, but the force is applied statically and at a velocity that can be selected and controlled at will. This is in contrast to prior art type solutions where the inevitably high load generated by the weight of the machine  2  is applied instantaneously, hence in the manner of a dynamic load and with particularly adverse consequences for fragile materials. 
     FIGS. 10 and 11 illustrate an alternative embodiment of the device  9  wherein the plate  18  is eliminated and the flange  19  has peripheral projections  39  on which the low pressure diecasting machine  2  rests directly, supported thus by the receptacle  3 . The wedges  12  in this instance are clamped against the head  6  of the pipe  1 , and the relative surfaces  15  coupled consequently with the frustoconical portion  13  of the outer surface  10 , by actuator means  40  comprising a screw  21  operating between the peripheral projection  39  and the wedge  12 . 
     Finally, other possible variations in embodiment of the actuator means  16  include the adoption of fluid power actuators  23  associated with the wedges  12  in place of the screws  21  (see FIG.  9 ).