Die casting cooled pistons

Abstract

A pressure die casting piston assembly has a pressure die casting piston. The die casting piston has a front head, a substantially cylindrical side wall extending upwardly from the front head in fixed position relative thereto. A cup-shaped chamber is defined by the front head and the side wall. The side wall is closed by the front head. The die casting piston has a coolant channel passing through the side wall to allow a coolant to pass through the side wall and within the side wall.

Claims

1. A pressure die casting piston comprising: a front head; a substantially cylindrical side wall extending upwardly from the front head and fixedly mounted therewith in a fixed position relative thereto to eliminate relative movement during use, wherein the front head fluidly closes an end of the side wall to form a cup-shaped chamber; and at least one coolant channel for a coolant flow passing through the side wall, so as to let the coolant flow within the side wall wherein the at least one coolant channel is also in fixed position relative to the front head.

2. The pressure die casting piston of claim 1, wherein the side wall comprises a distribution chamber and a collection chamber arranged respectively upstream and downstream of said at least one coolant channel with reference to a direction of the coolant flow.

3. The pressure die casting piston of claim 2, wherein the distribution and collection chambers have a substantially annular shape.

4. The pressure die casting piston of claim 1 further comprising at least one through aperture in the side wall and a means for clamping the side wall onto a mounting support wherein the means for clamping is inserted within the at least one through aperture.

5. The pressure die casting piston of claim 4, wherein the means for clamping the side wall comprises at least one key removably secured to a wall support.

6. The pressure die casting piston of claim 1, wherein seats are provided around the front head for engaging with radial teeth of a sealing ring associated with the piston.

7. The pressure die casting piston of claim 1 further comprising: a plurality of straight channels extending longitudinally along the cylindrical side wall, and wherein the straight channels are provided for inserting tools adapted to create said coolant channels, the straight channels being closed by means for sealing.

8. The pressure die casting piston of claim 7, wherein the means for sealing the holes comprises caps which can be deformed permanently.

9. The pressure die casting piston of claim 1 further comprising: a support within the chamber comprising a base for mounting the piston onto a pressure die casting equipment and a body extending from said base and further a groove for a sealing gasket adjacent an end of the body.

10. The pressure die casting piston of claim 9, wherein the support further comprises a plurality of collectors extending in the body from near the base, in a region between two sealing gaskets.

11. The pressure die casting piston of claim 10, wherein the gaskets are ring-shaped and respective seats are provided on the body for housing said sealing gaskets, between which the collectors for the coolant flow are arranged.

12. The pressure die casting piston of claim 11, wherein the support is axially hollow.

13. The pressure die casting piston of claim 1, wherein the side wall is integral with the front head.

14. A pressure die casting piston comprising: a front head; a substantially cylindrical side wall extending upwardly from the front head in a fixed position relative thereto, wherein the front head fluidly closes an end of the side wall to form a cup-shaped chamber; and at least one coolant channel for a coolant flow passing through the side wall, so as to let the coolant flow within the side wall wherein the at least one coolant channel is also in fixed position relative to the front head, wherein the side wall is provided in one piece and the channels are obtained by removing material therefrom.

15. A pressure die casting piston comprising: a front head; a substantially cylindrical side wall extending upwardly from the front head and fixedly mounted therewith to eliminate relative movement during use and defining a space with the front head wherein the side wall is closed by the front head; at least one coolant channel for a coolant flow passing through the side wall, so as to let the coolant flow within the side wall wherein the at least one coolant channel is also in fixed position relative to the front head; and a support within the space defined by the side wall and the front head and separable therefrom, the support having a cavity therein which is in fluid communication with the at least one coolant channel in the side wall.

16. The pressure die casting piston of claim 15, wherein the side wall is integral with the front head.

17. The pressure die casting piston of claim 15, wherein the at least one coolant channel has an entrance at a distribution chamber in the side wall and an exit at a collection chamber in the side wall wherein a coolant flow path extends sequentially from the support to the distribution chamber and from the distribution chamber to the at least one channel and from the at least one channel to the collection chamber and from the collection chamber back into the support.

18. The pressure die casting piston of claim 15, wherein the support is in fixed position relative to the side wall and the front head.

19. The pressure die casting piston of claim 15 further comprising: a pipe fixedly attached within the cavity of the support and extending therefrom wherein the coolant flow path includes the pipe wherein having the coolant flow path travels into the support via the pipe.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) To understand the present invention, it will now be described by way of example, with reference to the accompanying drawings in which:

(2) FIGS. 1 and 2 are two exploded views from different angles of a piston and a piston support according to the present invention;

(3) FIG. 3 shows the piston and the support of the preceding figures in the assembled condition;

(4) FIG. 4 is a detailed view of the piston of the preceding figures, without the support;

(5) FIG. 5 is a longitudinal sectional view of the piston of the preceding figures mounted on its support;

(6) FIG. 6 is a longitudinal view in a plane intersecting both the piston and the piston support, showing the coolant supply duct; and

(7) FIG. 7 is a longitudinal cross-section of the piston and of a portion of the piston support, highlighting the radial collectors.

DETAILED DESCRIPTION

(8) Referring now to the above-listed drawings, numeral 1 designates as a whole a pressure die casting piston-support assembly in accordance with the invention.

(9) The assembly comprises a support 2 having a cylindrical geometry, with a base 3 having the usual bevelled faces 4 to be engaged with tools (such as spanners or the like) for mounting the assembly onto the die casting fixture.

(10) Extending from base 3, support body 5 is axially hollow and has, at its front end, grooves 7 extending outwards from the centre, which will be described in detail later on. On support body 5 there are seats 9 to be engaged with piston clamping keys 10; in this example, seats 9 are three, spaced by 120: their number may however be greater or smaller than three, depending on specific requirements.

(11) At the bottom of seats 9 there is a threaded hole 11 having the same diameter as the shank of screws 12 used for securing the keys 10.

(12) Finally, along the piston support body 5 there are annular grooves 13, 13 and 13 for respective ring-type sealing gaskets (O-rings) 15, 15 and 15; the number of grooves and gaskets may differ from this example, but the number suggested herein ensures optimal coolant circulation in the wall.

(13) Referring now to piston 20, it comprises a cylindrical side wall 21 closed at the front by a head 22, around which a sealing ring 23 is applied.

(14) According to a preferred embodiment, sealing ring 23 has radial inner teeth 24 to be engaged into matching seats 25 obtained in the base of piston head 22.

(15) The outer surface of ring 23 may be smooth, like most known rings, or it may have a groove 26 which in this example has a fret design, as can be seen in the drawings, but may also have an annular or a different profile.

(16) Radial apertures 29 in the wall 21 align with seats 9 when the piston is mounted on support 2, thus allowing for the insertion of keys 10: the latter lock wall 21 to support body 5, preventing it from turning or moving axially.

(17) Clamping the piston by means of keys is the preferred solution of the invention, because the piston is locked securely to support 2 both rotationally and translationally; however, this is not the only feasible method.

(18) For example, a conceivable alternative may be a traditional threaded system allowing the piston to be screwed onto piston body 5, or else a bayonet-type system, both of which are known in the art.

(19) For cooling piston 20, channels 30 are obtained in cylindrical wall 21 and extend parallel to one another along the wall generatrices, between an annular distribution chamber 32 encircling the front end of support body 5 and an annular collection chamber 33.

(20) The collection chamber is arranged at the wall base, in the space defined between two seats 13, 13 for respective sealing rings 15, 15.

(21) The liquid collected in chamber 33 can thus flow towards a series of radial collectors 35 formed inside body 5 of support 2.

(22) As aforesaid, the latter is hollow axially; in particular, cavity 38 passing through it in the longitudinal direction houses a pipe 40 (sectioned in FIG. 6) which delivers the coolant to the end of body 5.

(23) From there, the coolant flow branches off into grooves 7 to reach the above-mentioned distribution chamber 32, and then follows the path along channels 30.

(24) Coolant evacuation takes place along a path outside pipe 40: the coolant flow coming from collection chamber 33 is conveyed axially by collectors 35 into the interspace surrounding pipe 40, from where it flows on inside base 3 of support 2 to be drained out.

(25) In this respect, it should be pointed out that the position of ring-type gaskets 15, 15, 15 and of respective seats 13, 13, 13 on support body 5 turns out to be particularly advantageous for piston cooling, in that it prevents any coolant leakage.

(26) In fact, the coolant is fed axially to distribution chamber 32 by pipe 40 and grooves 7; at this stage, the presence of gasket 15 adjacent to the end of support body 5 proves to be extremely important to prevent coolant dispersion.

(27) Thanks to this seal, in fact, the liquid will flow on from grooves 7 to distribution chamber 32 and then into channels 30, downstream of which it will enter collection chamber 33; in this case as well, it must be highlighted that, if gaskets 15, 15 were not present, the liquid would spread between the inner wall of wall 21 and body 5 instead of flowing through radial collectors 35 to be evacuated.

(28) In other words, locating collectors 35 in the region comprised between sealing gaskets 15 and 15 is important for cooling the piston properly.

(29) Moreover, it is barely worth mentioning that, although in this example the gaskets are installed into seats 13, 13 formed on body 5, said seats may alternatively be obtained on the inner wall of the wall.

(30) Finally, as a further characteristic feature of the invention, it is necessary to point out that in this example, for mechanically drilling the channels 30 into the wall (by using a cutter, a drill or the like), a tool penetrating into the wall 21 from the lower edge thereof has been advantageously used: this is a low-cost solution, since it can be implemented by using traditional machinery and tools.

(31) Sealing elements 42 are used for closing tool entry holes 41 (visible in FIG. 4); these may be removable elements provided, for example, in the form of threaded plugs (of course, entry holes 41 will have to be threaded too), or permanent elements obtained by lead sealing or through deformable caps or bushes.

(32) Removable plugs bring the advantage of allowing maintenance of channels 30, even though the latter are generally more costly to make (in addition to tapping holes 41), whereas lead sealing or using non-removable, permanently deformable caps is to be preferred for small piston applications.

(33) It can be easily understood from the above description how piston 20 can solve the technical problem addressed by the invention.

(34) In fact, it is apparent that, since channels 30 that carry the coolant are obtained inside piston wall 21, the thermal exchange between coolant and piston is considerably improved; as a result, more heat is removed, all other conditions being equal (coolant flow rate, temperature of the molten metal to be die cast, die casting speed, etc.).

(35) In particular, it must be observed that in this case the coolant exchanges heat with a generally larger surface than in prior-art pistons.

(36) In fact, in the latter the liquid only touches the inner wall of the piston wall, which wall has a shorter radius than the inner region comprised between channels 30 and the outer surface of wall 21; in addition, according to the present invention the liquid exchanges heat with the whole inner wall of channels 30, the area of which, if said channels are sized appropriately and in a sufficient number, is larger than the inner surface of the piston wall.

(37) It must also be added that the presence of channels 30 in the wall 21, i.e. the presence of gaps in the latter's wall, reduces its heat-conductive metallic mass (of copper or the like) and hence the wall's thermal capacity (as known, thermal capacity is given by the relation Q=cMT, where c is the specific heat of the material, M is the overall mass thereof, and T is the temperature variation).

(38) It follows that in the present invention the coolant is put into thermal exchange with a smaller metallic mass, and therefore, the flow rate being equal, it is necessary to remove less heat in order to cool down said mass.

(39) These advantageous effects are attained without modifying the outside dimensions of piston 20, which is thus compatible with the existing ones and can be used on die casting fixtures currently in use.

(40) It must nevertheless be remarked that channels 30 may also be obtained through a different type of machining, e.g. by laser or electroerosion.

(41) In such a case, tool entry holes 41 may be unnecessary, and even the shape of channels 30 may not be straight as in the example shown. For example, it may be conceivable to provide a spiral channel extending along the wall 21.

(42) It should also be pointed out that wall 21, though preferably made in one piece, may however also be obtained by coupling together two pieces, i.e. an external sleeve coupled to a tubular inner part.

(43) In such a case, channels 30 or the single spiral channel may be obtained on one of the two pieces coupled together, still obtaining a wall equivalent to that of the example described above, wherein the wall is a single piece.

(44) In this frame, the invention also achieves further advantages related to the particular technical solutions employed.

(45) For example, keys 10 allow piston 20 to be firmly locked onto support 2, preventing them from turning and moving axially relative to each other, while still remaining easily accessible from the outside, in order to be removed by undoing bolts 12, at every maintenance inspection.

(46) Likewise, radial teeth 24 on sealing ring 23 and seats 25 on piston 20 allow the sealing ring to be locked to the piston; to this end, the ring is preferably of the open type, i.e. it has a cutout that allows it to expand elastically, so that it can be easily removed when necessary.

(47) It is apparent that both the key-type piston clamping system and the radial-tooth-type ring locking system may be replaced with different solutions, like those used for prior-art pistons.

(48) As far as the sealing ring is concerned, it is finally necessary to underline that the groove provided on its outer surface, which improves the lubrication of the piston to advantage of the die casting process, may be omitted without jeopardizing the other effects achieved by the invention.

(49) These variants will still fall within the scope of the following claims.