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(11) | EP 0 714 718 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | A fluid-tight coupling device for a feeder pipe conveying molten material, in the connection of a low pressure diecasting machine to a receptacle containing the molten material |
| (57) A pipe (1) conveying molten material upwards from a pressurized receptacle into the
mould (17) of a low pressure diecasting machine (2), positioned on and supported by
the selfsame receptacle, is secured in a fluid-tight fit by an adjustable coupling
device; the pipe (1) extends through the top wall (4) of the receptacle and comprises
a body (5) of which one end extends into the receptacle so as to pick up the molten
material and the other terminates in a head (6), located externally of the receptacle
and tightened together with a seal (28) against the mould (17). The outer surface
(10) of the pipe (1) presents at least one substantially frustoconical portion (13)
matched to the surfaces (15) of three wedges (12), disposed circumferentially around
the pipe and mounted on slide ways (20), which can be directed by suitable actuators
(16) from an at-rest position to an operating position in which the pipe is subjected
to an axial force and distanced from the receptacle, and the head (6) clamped together
with the seal (28) against the machine (2). |
[0001] The present invention relates to a device by means of which 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 affording an inlet end, located internally of the receptacle, and a head coinciding with an outlet end of which the frontal surface can be coupled in fluid-tight association with a mould fitted to the low pressure diecasting machine.
[0002] A low pressure diecasting machine of the type in question is connected with a receptacle containing molten material generally from above, surmounting the receptacle in such a manner that the pipe is aligned and connected with the injection nozzles of the mould fitted to the machine.
[0003] The systems employed in making such a connection, while based on a variety of techniques, are similar inasmuch as all permit of 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.
[0004] To ensure the feature of a removable connection can be successfully incorporated, the pressure-tight fit between the nozzles and the frontal surface presented by the head of the pipe is obtained by interposing seals or gaskets of suitable thickness. The efficiency of the sealing action in containing the pressure of the molten material is nonetheless somewhat critical, given that the tightness of the fit between the frontal surface of the pipe and the nozzle of the mould relies on nothing other than a suitably strong force of compression.
[0005] 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 substantially equivalent to the total weight of the low pressure diecasting machine.
[0006] Quite apart from the operational inconvenience and the empirical nature of such a system, with arrival at the optimum condition depending 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.
[0007] Owing to the intense and uncontrollable impact of these stresses, rupture of the pipe is a frequent occurence, particularly when the pipe, as already intimated, is fashioned from a notoriously fragile material such as silicon nitride or other ceramics typically utilized in the context of low pressure diecasting processes for aluminium alloys.
[0008] Conversely, the application of a lesser compressive force to the sealing medium might well diminish the risk of rupture, but would not ensure an efficient sealing action in opposition to 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 difficult compromise between the two opposing requirements outlined above.
[0009] 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 mould by adopting a novel method of compressing the interposed sealing medium, and allowing for adjustment of the force by which the sealing action is assured.
[0010] The stated object is realized with the adoption of a device as characterized in the appended claims, by 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.
[0011] The pipe passes through one wall of the receptacle and exhibits a body affording an inlet end, located inside the receptacle, also a head, coinciding with an outlet end, of which the frontal surface can be offered to the mould of the low pressure diecasting machine together with an interposed sealing medium. The design of the device requires or rather takes account of the fact that the outer surface of the pipe as supplied by the manufacturer will exhibit at least one portion, disposed between the head and the body, which is angled in relation to the axis of the pipe itself. In a preferred solution, to be described in due course, the outer surface of the pipe comprises a portion between the head and the body that appears substantially frustoconical in shape, and the device itself comprises three wedges disposed circumferentially around the pipe between the head and the wall of the receptacle. Each wedge presents a surface matched to the aforementioned portion of the outer surface presented by 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 capable thus of movement in relation to the wall of the receptacle, transversely to the axis of the pipe, through the agency of actuator means. The movement in question is brought about between a non-operating at-rest position, distanced from the pipe, and an operating position of close proximity 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 mould of the low pressure diecasting machine. The three wedges are thus able to generate the requisite sealing action, at least across the frontal surface of the head, in opposition to the pressure of the molten material flowing along the pipe.
[0012] 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 steplessly incremental type of adjustment in which the weight of the machine plays no part whatever.
[0013] 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, seen fitted to a low pressure diecasting machine associated with a receptacle containing molten material, in which the pipe is shown in a first possible embodiment;
- fig 2 shows the device according to the invention in a further section, enlarged in relation to fig 1 and taken through 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 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 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;
- figs 12, 13, 14 and 15 illustrate four alternative embodiments of the pipe.
[0014] With reference to the accompanying drawings, and to fig 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 asssociated with a pressurizable receptacle 3 in which the molten material is prepared.
[0015] The low pressure diecasting machine 2 is supported during operation by the receptacle 3, of which the top horizontal wall 4 affords a set of stands 30 for this same purpose. When not in operation, the machine 2 can be distanced 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.
[0016] The pipe 1 is embodied in fragile ceramic material, preferably silicon nitride, and passes through the top horizontal wall 4 of the receptacle 3. Seen in its entirety, the pipe exhibits a body 5 affording an inlet end 27, which extends into a crucible 33 positioned within the receptacle 3, and a head 6 coinciding with an opposite outlet end 7 of which the frontal surface 8 is designed to locate against a mould 17 fitted to the low pressure diecasting machine 2, impinging on an interposed seal 28 as will shortly be made clear.
[0017] 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 presents an annular portion 13 of frustoconical shape, located between the head 6 and the body 5, advantageously exhibiting an angle of 30° relative to the axis 11 of the pipe 1. It will of course be sufficient in practice that the annular portion 13 of the outer surface 10 is discernibly tapered 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 consists in a cylindrical body with a separately embodied flange 34, of which the outer surface 10 affords the frustoconical annular portion 13. The pipe 1 of fig 13 exhibits 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 is embodied as a splayed flange 36 of which the "V" shaped profile serves to create the frustoconical portion 13.
[0018] Referring in particular to figs 2, 4 and 5, the device 9 also comprises three identical wedges 12 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.
[0019] Each wedge 12 will present a surface 15 matched to the frustoconical portion 13 afforded by the outer surface 10 of the pipe 1, in such a manner that the three wedges can be coupled circumferentially with the selfsame portion 13.
[0020] In addition, the wedges 12 are mounted slidably to respective slide ways 20 (see figs 6 and 7) formed partly within the wedges themselves and partly, as indicated by the number 20a, within a flange 19 by which the entire device 9 is secured to the wall 4 of the receptacle 3, and are thus rendered capable of movement in relation to the wall 4 transversely to the axis 11 of the pipe 1 through the agency of relative actuator means 16.
[0021] In an alternative and wholly equivalent embodiment, illustrated in fig 15, the head 6 of the pipe 1 presents a downwardly directed surface 37 disposed obliquely in relation to the pipe's own axis 11 and performing the same function as the aforementioned frustoconical annular portion 13. More exactly, 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.
[0022] In particular, it will be discernible 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 20a of the slide way formed in the flange 19 affords a fixed key 31 insertable into the slide way 20 of the wedge 12 and serving thus to guide the sliding movement. 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 affords 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 8 and 9, the annular plate 18 is secured to the flange 19 with relative bolts 29 and exhibits 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 receptacle 3 by which the machine is supported from beneath. In addition, the peripheral rim 24 freely encompasses the head 6 and the wedges 12, so that there is no structural interaction between these components and the plate 18.
[0023] Nonetheless, the peripheral rim 24 of the plate 18 can be coupled with the wedges 12. As discernible from fig 2, in effect, the rim 24 and the wedges 12 are embodied with 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 relative frustoconical surface 25 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 impinge on the matching frustoconical portion 13 afforded by the outer surface 10 of the head 6, generating 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 afforded by the peripheral rim 24 of the annular plate 18 that provides the aforementioned actuator means 16 to drive the wedges 12.
[0024] As regards the operation of the device 9, it will be discernible 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 impinging on each of the wedges 12, the wedges can be translated further along the respective slide ways 29 to the end of obtaining a fine adjustment of the clamping action applied to the pipe 1.
[0025] As a result of the axial force generated through the clamping action, the frontal surface 8 afforded by 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.
[0026] A device 9 thus embodied permits definitively of ensuring 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, but 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, 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.
[0027] Figs 10 and 11 illustrate an alternative embodiment of the device 9 wherein the plate 18 is eliminated altogether and the flange 19 exhibits 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 that consist in a screw 21 operating between the peripheral projection 39 and the wedge 12.
1. A fluid-tight coupling device for a pipe conveying molten material utilized in the
connection of a low pressure diecasting machine (2) to a receptacle (3) containing
the molten material, wherein the pipe (1) passes through a wall (4) of the receptacle
(3) and exhibits a body (5) affording an inlet at one end, extending internally of
the receptacle (3) so as to admit the molten material, also a head (6) located externally
of the receptacle and affording a frontal surface (8) such as can be associated with
a mould (17) fitted to the machine (2) by way of an interposed seal (28), the outer
surface (10) of the pipe (1) presenting at least one portion (13) located between
the head (6) and the body (5) which is angled in relation to its own axis (11), characterized
- in that it comprises at least one wedge (12), operating between the head (6) of the pipe (1) and the wall (4) of the receptacle (3) and affording a surface (15) matched to the angled portion (13) of the outer surface (10) of the pipe in such a way as to interact adjustably therewith, which is mounted to a slide way (20) and capable thus of movement in relation to the wall (4) of the receptacle (3) brought about transversely to the axis (11) of the pipe (1) through the agency of actuator means (16) between a non-operating position, distanced from the pipe (1), and an operating position of close proximity to the pipe (1) in which the surface (15) of the wedge (12) is coupled to the angled portion (13), applying an axial force by which the pipe (1) is caused to move away from the receptacle (3) and the head (6) tightened against the low pressure diecasting machine (2) and against the interposed seal (28), resulting in a tight fit at least across the frontal surface (8) such as will contain the pressure of the molten material flowing through the pipe (1).
2. A device as in claim 1, comprising a plate (18) of annular embodiment affording a
structural interface between the low pressure diecasting machine (2) and the receptacle
(3), disposed coaxial with the pipe (1) and positioned between the low pressure diecasting
machine (2) and the pipe (1) in such a manner as to engage the head (6) and thus oppose
the axial action generated through the pipe (1) by the movement of the wedge (12)
toward the operating position.
3. A device as in claim 2, wherein the annular plate (18) affords a peripheral rim (24)
shaped in such a manner as to channel the structural bearing loads transmitted between
the low pressure diecasting machine (2) and the receptacle (3) and proportioned to
encompass the head (6) of the pipe (1) and the wedge (12).
4. A device as in claim 3, wherein the peripheral rim (24) of the annular plate (18)
presents an angled inner surface (25) matched to a correspondingly angled surface
(26) of the wedge (12), so that when the plate (18) is secured to the receptacle (3),
the two selfsame surfaces (25, 26) will be coupled mutually in such a way as to allow
of clamping the wedge (12) against the head (6) of the pipe (1) in a direction transverse
to the pipe axis (11) : the surface (25) of the plate (18) thus constituting the actuator
means (1) by which the wedge (12) is operated.
5. A device as in claim 4, wherein the two mutually coupled surfaces (25, 26) are angled
oppositely to the surface (15) of the wedge (12) matching the angled portion (13)
presented by the outer surface (10) of the pipe (1).
6. A device as in claim 1, comprising three distinct, independent wedges (12) disposed
circumferentially and peripherally around the head (6) of the pipe (1).
7. A device as in claim 6, wherein the wedges (12) are identical and distributed around
the head (6) of the pipe (1) at equal angular distances.
8. A device as in claim 1, comprising a plate (18) of annular embodiment affording a
structural interface between the low pressure diecasting machine (2) and the receptacle
(3), also a flange (19) interposed between the plate (18) and the wall (4) of the
receptacle (3) and serving to secure the plate (18) to the wall (4), wherein the flange
(19) affords at least one part (20a) of at least one slide way (20) accommodating
the movement of the wedge (12).
9. A device as in claim 1, wherein actuator means (16) comprise at least one screw (21)
by means of which to traverse the wedge (12) along the slide way (2).
10. A device as in claim 1, wherein actuator means (16) comprise fluid power actuators
(23) associated with and serving to traverse the wedge (12) along the slide way (20).
11. A device as in claim 8, wherein the annular plate (18) is replaced by a flange (19)
presenting at least one peripheral projection (39), on which the low pressure diecasting
machine (2) rests directly and is supported thus by the receptacle (3), and associated
with actuator means (16) designed to operate between the peripheral projection (39)
and at least one wedge (12) in such a way as to ensure that the wedge is clamped against
the head (6) of the pipe (1) and the surface (15) of the wedge (12) coupled with the
angled portion (13) presented by the outer surface (10) of the pipe.
12. A device as in claim 2, wherein the annular plate (18) comprises a bush (22) ocupying
a position of coaxial alignment with the pipe (1) and fashioned from a ceramic material.