US 3430685 A
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Description (OCR text may contain errors)
March 4, 1969 H. D
COLD CHAMBER-PRESSURE CASTING MACHINE WITH SIEVELIKE BARRIER FOR PISTON-PUMP Sheet 1 of 2 Filed Sept. 21, 1965 27 37 31 1 v 33 p 22 I 7 28 1: 5 O
' a lZ////d 21 INVENTOR. HELLMUT D'RUGOVLTSM BY M m.
March 4, 1969 H. DRUGOWITSCH COLD CHAMBER-PRESSURE CASTING MACHINE WITH SIEVE-LIKE BARRIER FOR PISTON PUMP Filed Sept. 21, 1965 Sheet INVENTOR. HELLM UT DRUGOWITSCH WM M W United States Patent 12,381/ 64 U.S. Cl. 164314 8 Claims Int. Cl. 322d 17/08 ABSTRACT OF THE DISCLOSURE A cold chamber-pressure casting machine is disclosed as including a melt retaining crucible and a piston pump extending into the melt in the crucible. The cylinder of the pump has at least one melt feed opening into its bore and below the surface of the melt in the crucible, and above the upper dead center position of the lower end of the piston, the upper portion of the bore has a crosssectional area greater than that of the piston. This enlarged cross-sectional area has at least one opening into the melt space surrounding the piston pump.
A separating wall is spaced laterally of the body of the piston pump and extends from the region above the melt surface to a level at least as low as the lower end of the piston pump in the melt, the separating wall preferably surrounding laterally the piston pump. The separating wall may have a lower end or may be formed with very small apertures to have a sieve-like construction.
Background of the invention This invention relates to cold-chamber casting machines and, more particularly, to a novel machine of this type including a piston pump extending into melt in a crucible and formed with a melt intake beneath the melt surface, and further including novel means preventing jamming of the pump piston and entry of slag and the like into the working space of the pump.
Cold chamber-pressure casting machines, having piston pumps feeding the melt to casting apparatus, are known. However, the usual machines of this type have the disadvantage that melt oxides and melt residues, which deposit on the walls of the cylinder bore, have a tendency to interfer with the proper reciprocation of the piston, or, in other words, they tend to jam the piston, and thus may cause significant disturbances in the operation of the machine. In addition, these oxides and residues have a tendency to re-enter the pump working space and thus be introduced into the injection mold. The prior art constructions furthermore do not assure that slag is prevented from being fed from the crucible into the pump.
An object of the present invention is to provide a cold chamber-pressure casting machine having novel constructional features which avoid the disadvantages of prior art machines.
Another object of the invention is to provide a cold chamber-pressure casting machine in which the upper portion of the cylinder bore of a piston pump, above the upper center position of the lower end of the piston, has a cross-sectional area greater than that of the piston.
Another object of the invention is to provide a cold chamber-pressure casting machine, with the construction just mentioned, including means forming an opening from the upper portion of the cylinder bore into the melt space surrounding the piston pump.
Still another object of the invention is to provide a cold chamber-pressure casting machine of the type just mentioned including additional means for reducing or even eliminating the feed of slag into the pump working space and thus into the mold.
The advantage of the cold chamber-pressure casting machine of the invention is that, with each piston stroke, there occurs an automatic or self-cleaning of the pump cylinder due to the leakage flow which cannot be avoided. Another advantage is that any leakage past the piston is directed l'ack into the melt. Furthermore, the possibility of the piston becoming jammed is greatly decreased since, in the region of the transition from the hot area to the cold area, the cylinder bore has a cross-sectional area greater than that of the pistion.
For an understanding of the principles of the invention, reference is made to the following description of typical embodiments thereof illustrated in the drawings.
In the drawings:
FIG. 1 is a transverse sectional view of one embodiment of cold chamber-pressure casting machine in accordance with the invention, illustrating the crucible and the piston pump as well as the provision of a container-like insert surrounding the piston pump;
FIG. 2 is a partial transverse sectional view illustrating a modification of the insert;
FIG. 3 is a partial transverse sectional view of another embodiment of the invention illustrating a jacket-like covering for the piston pump; and
IG. 4 is a partial transverse sectional view of still another embodiment of the invention, illustrating a separating Wall provided adjacent the piston pump.
Referring to FIG. 1, a melt and heatretaining crucible 2, accommodating a melt 3, is illustrated as arranged within the casing 1. Slag 4 floats on the surface of melt 3. Crucible 2 has an open upper end closed by cover means 6 having formed therein an opening 8 which can be closed by a plug or lid 7. A heating means 9 is posi-.
tioned in the space between casing l and crucible 2.
A container or tank-like insert 11 is secured to the cover means 6, and at least the surfaces of this insert 11 are of a ceramic material. Insert 11, which surrounds a piston pump extending into melt 3, is formed with melt inlet openings 12. The piston pump comprises a block 13 of a material which is thermically and chemically inert with respect to the melt to be pumped. This block 13 has a cylinder bore 14 in which the piston of the pump is reciprocable, and is formed with a melt discharge bore or passage 16 as well as with a melt feed opening 17 disposed beneath the melt surface. An exit trough or conduit 18 extends from the piston pump through heating or firing means 19 and into a container or feed line 21 from which the melt may be injected into an injection mold. A protective gas line 22 extends into the space between the piston pump and insert 11. The upper portion of the cylinder bore, above the lower end of piston 23 in the upper dead center position of the piston, has a cross-sectional area greater than the cross-sectional area of the piston 23, for a purpose which will be mentioned hereinafter.
A piston 23, which is made of material thermically and chemically inert to the melt, is reciprocable in the bore 14 of the pump, and a rod 24 connects piston 23 with a piston 26 in a cylinder 27. A hydraulic pump 31 is positioned in communication with a tank 28 holding a working fluid 29. Lines 32 and 33 are connected to cylinder 27 above and beneath piston 26, respectively. Control of the operation of piston 26 is effected by means of a fourway valve 34 which is spring biased to the position shown in the drawing by a compression spring 37, and which may be operated to the reverse position by means of a magnetic coil or solenoid device 36.
With the parts occupying the position shown in FIG.
1, hydraulic pump 31 feeds the working fluid through line 32 and through valve 34 into line 33 and thus into cylinder 27. Thus, piston 26, connected by rod 24 with piston 23, is lifted. In accordance with the principles of communicating vessels, the melt level is at the same height throughout. If magnetic winding or solenoid 36 is now energized, valve 34 is moved to the reverse position. Hydraulic pump 31 nowfeeds working fluid 29 through line 32 into the cylinder 27 above piston 26. Piston 26 moves downwardly, whereby, through rod 24, piston 23 of the piston pump is moved downwardly. Feed openings 17 are closed so that no melt can flow into cylinder bore 14 and no melt can be forced out through openings 17. The melt 3 present in bore 14 and in discharge passage or bore 16- is forced by piston 23 into exit trough or conduit 18 and thus into the filling container 21.
In order to maintain flowability or fluidity of the melt until the casting is efiected, the exit conduit 18 is heated by heating means 19. As soon as the casting procedure has taken place, magnetic Winding 36 is de-energized, whereupon compression spring 37 moves valve 34 back into the position illustrated in the drawings. Thereby, pump 31 feeds working fluid 29 from line 32 into line 33 and thus into cylinder 37 beneath piston 26, so that the latter moves upwardly moving piston 23 upwardly. The feed openings 17 are thus opened and melt 3 enters bore 14 from insert 11. However, and again due to the principles of communicating vessels, melt 3- also flows from crucible 2 proper through melt inlet openings 12 into insert 11. Due to insert 11, it is not possible for slag 4 to enter the piston pump and thus be discharged into the casting apparatus. If melt 3 is readily oxidized, protective gas can be fed through line 22 into the space between the pump and insert 11.
Feeding of the melt or an ingot to crucible 2 is effected through opening 8 in cover means 6, and which is closed by removable cover or lid 7. Insert 11 has the advantage that the penetration of slag into the pump working space and thus into the casting apparatus is impossible, and thereby disturbances and defective casting pieces are avoided. Furthermore, and only if necessary, only the relatively small space between the piston pump and insert 11 has to be supplied with protective gas.
As illustrated in FIG. 2, the insert 11 may be provided with a sieve-like bottom having openings 42 for entry of melt into the insert in crucible 2.
In the embodiment of the invention shown in FIG. 3, piston pump body 13 is embraced by an annular jacketlike wall 51 in such a manner as to define an annular space between wall 51 and body 13. Wall 51 is interconnected or integral with piston pump body 13 by means of a web 52 formed with openings 54 therethrough.
As already mentioned in connection with the embodiment of FIG. 1, the upper portion of the cylinder bore 14, above the lower end of piston 23 in the upper dead center position of the piston, has a cross sectional area, as indicated at 58, greater than the cross sectional area of piston 23. Thus, leakage flow of melt bypassing piston 23 can escape upwardly between bore 14 and piston 23 into the larger diameter region 58 and, by means of a plurality of bores 53 communicating with this larger diameter region, the melt leakage is returned into the melt 3 through the openings 54.
Instead of a sieve-like insert provided as the bottom of a basin or container which surrounds the piston pump, or instead of individual openings in such an insert, the diameters of feed openings 57 are greatly reduced and their number is substantially increased. This forms a sieve-like region, having the openings 57, in the piston pump body 13. The portion of the piston pump above cover 6 of the crucible, and which cover supports the piston pump, is enclosed by a heat-insulating protective hood 70 to prevent cooling of the piston pump due to the ambient temperature.
The embodiment of the invention shown in FIG. 3 functions in essentially the same manner as that of FIGS. 1 and 2. However, a certain simplification is obtained since the insert or barrier is no longer closed at its bottom end. As in the embodiment of FIGS. 1 and 2, no slag can enter the piston pump or its feed inlets 57. Thus, only clean melt is forced by piston pump into the pressure casting apparatus. Due to the provision of insulating hood 70, a significant reduction of the disadvantageous temperature drop in piston 23, caused by the ambient temperature, is obtained, so that no undesired premature cooling of the melt to be fed can occur. A
FIG. 4 illustrates a further embodiment of the invention. In this embodiment, a separating wall or barrier 61 extends downwardly from partial cover 6 and extends laterally of crucible 2 directly to the crucible walls. At least a portion of the bottom edge of barrier 61 is spaced somewhat from the bottom of crucible 2, as indicated at 62. The piston pump is offset very substantially toward a wall of crucible 2, and its body 13 is formed with a plurality of the fine bores 57 constituting, in effect, a sieve-like feed portion. Cylinder bore 14 is formed with an enlarged portion '58 in the same manner as previously described :for the embodiments of FIGS. 1 and 3, and one or more passages or openings 53 extend from enlarged bore portion 58 into the crucible space surrounding the piston pump body 13.
Piston 23 is constructed so that, even if the level of melt 3 is very low, the upper end of the piston will still be below the level of the melt. Thereby, the melt is in communication through openings 53 with the larger diameter cylinder bore portion 58. The separating wall or barrier 61 divides crucible 2 in a manner which, in principle, is equvalent to that of a two-chamber crucible. The melt does not flow from one crucible to the other in the form of an overflow, but rather through an opening beneath the melt surface, in the manner of communicating vessels. The slag will always remain on the surface of the melt in one of the crucible spaces and cannot flow over into that crucible space containing the piston pump and which is separated from the other space.
This arrangement has the advantage that a clean melt is always fed to the pressure casting apparatus, and the further advantage that, with crowded space conditions, the piston pump can be moved to an eccentric position adjacent a crucible wall, while the separated residual crucible space is ready for feeding of melt thereinto. Furthermore, the means for separating one of the crucible spaces from the other, surrounding the piston pump, is very simple. Due to the heat insulating protective hood 17, and due to the fact that piston 23 is always within melt 3, the temperature and heat drop in this region of the pump is very small.
In all embodiments of the invention, it is essential that the diameter of the cylinder bore above the lower end of the piston in the upper dead center position of the latter be larger than the diameter of the piston. The advantages obtained are self-cleaning and a significant reduction in obstruction to reciprocation of the piston in the cylinder bore. Furthermore, leakage flow bypassing the piston is returned directly into the melt so that no difiiculties are encountered with respect to the taking of clean melt into the casting apparatus.
As will be understood, the four embodiments shown in the drawings can be modified. For example, the crucible may be formed as a two-chamber crucible proper, and the two chambers may be connected by a channel or passage located very substantially below the surface of the melt. Furthermore, two separate crucibles can be provided, one being, for example, a relatively large melting and heat-retaining crucible, and the other being a smaller crucible serving merely as the heat retaining crucible. These two crucibles may be so constructed so that they have openings substantially below the surface of the melt and interconnected by a suitable conduit or pipe. It is furthermore possible to feed the melt by means of piston acting in the manner of a suction type lifting device and through a tube from the region of one of the crucible bottoms to the other crucible.
While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.
What is claimed is:
1. A cold chamber-pressure casting machine compris ing, in combination, a crucible having an open upper end; cover means at least partially closing the open upper end of said crucible; a piston pump suspended from said cover means and extending into said crucible; said pump including a body having a cylinder bore and a piston reciprocable in said cylinder bore, said body having at least one melt feed opening into said cylinder bore below the upper end of said crucible; said body being formed with a melt discharge bore communicating, at its lower end, with the lower end of said cylinder bore and extending upwardly through said body and opening through the upper end of said body; the upper portion of said cylinder bore, above the upper dead center position of the lower end of said piston, having a cross sectional area greater than that of said piston; a separating wall supported from said cover means and spaced laterally from the body of said piston pump, and extending from the region of the upper end of said crucible to a level at least as low as the lower end of the piston pump body; said separating wall separating the working space of said crucible into a portion which is outside the range of said pump and a portion which is within the range of said pump; leakage bore means communicating said greater cross-sectional area with said portion within the range of said pump; and a sieve-like, insert positioned between said portion outside the separating wall and the working space of the piston pump below said piston.
2. A cold chamber-pressure casting machine, as claimed in claim 1, in which said separating wall is in the form of a basin shape barrier surrounding said piston pump; said sieve-like insert comprising a plurality of apertures in said barrier.
3. A cold chamber-pressure casting machine, as claimed in claim 2, in which said last-mentioned apertures are formed in the lowermost portion of said barrier.
4. A cold chamber-pressure casting machine, as claimed in claim 2, in which the bottom wall of said barrier is formed as a mesh comprising said sieve-like insert.
5. A cold chamber-pressure casting machine as claimed in claim 1, in which said separating wall is in the form of an annular wall in embracing spaced relation to the body of said piston pump.
6. A cold chamber-pressure casting machine, as claimed 5, in which said annular separating wall is formed integrally with the body of said piston pump.
7. A cold chamber-pressure casting machine, as claimed in claim 5, in which at least a portion of the lower end of said annular wall is spaced a distance above the bottom of said crucible.
8. A cold chamber-pressure casting machine, as claimed in claim 1, in which said piston pump extends upwardly through said cover means; and a heat insulating protective hood enclosing that portion of the piston pump extending above said cover means.
References Cited UNITED STATES PATENTS 2,206,211 7/1940 Wagner 164-259 2,557,551 6/1951 Linder 164-315 2,830,340 4/1958 Morin 164259 3,292,218 12/1966 Kozma 164-315 FOREIGN PATENTS 687,011 1/1940 Germany.
699,787 12/ 1940 Germany.
745,583 3/1944 Germany.
145,775 3/ 1952 Australia.
J. SPENCER OVERHOLSER, Primary Examiner.
ROBERT D. BALDWIN, Assistant Examiner.
US. Cl. X.R. 164259