Pressure-resistant valve for casting mold

Abstract

A vent valve for a casting mold includes a valve piston in a valve opening. The valve opening has a funneled portion and a straight portion. The valve piston slidingly engages the straight portion. The valve has a shank matching the shape of the funneled portion. The valve may be closed by a stream of the melt entering the valve opening. When the valve piston is in the open position, air trapped in the mold cavity escapes through a gap between the shank and the funneled portion. When the valve piston is in the closed position, the gap is closed to prevent the melt from escaping the mold cavity.

Description

PRESSURE-RESISTANT VALVE FOR CASTING MOLDREFERENCE TO RELATED APPLICATION

[0001] This application claims priority from U.S. Provisional Patent Application No. 63 / 697,734 entitled “Pressure-Resistant Valve for Casting Die”, filed on September 23, 2024, and incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The present disclosure relates to die casting, and in particular to venting systems for die casting.BACKGROUND

[0003] In a die casting process, molten metal is rapidly injected at high pressure into a cavity formed between mold halves. The injected metal is allowed to cool down and solidify to form a mechanical component or part having the shape of the mold cavity. Due to quick casting time and the ability to rapidly produce a large number of parts, die casting has found widespread application.

[0004] Resident air in the mold cavity may be cornered and compressed by the injection molten metal to cause porosity in the part being manufactured. Accordingly, it is desired to evacuate as much air as possible, so that the remaining trapped air is compressed to sufficiently small volume to cause acceptable levels of porosity.

[0005] Some die casting systems use vent valves that allow the air to escape as the molten metal enters the mold cavity of the casting die. The vent valves need to be operated with precise timing, allowing as much air to escape as possible while closing on time to prevent the molten metal from escaping the die, which may present a safety hazard and / or fill the vent valve mechanism and solidify, making the valve unusable for subsequent molding cycles. The valve mechanism needs to be small, simple to construct, responsive to seal the mold vent quickly and reliably, yet capable of repeatedly withstanding a significant pressure of the molten metal as it cools down.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Exemplary embodiments will now be described in conjunction with the drawings, in which:

[0007] FIG. 1 A is a schematic side cross-sectional view of a casting mold incorporating a valve of this disclosure and showing the mold in a closed configuration ready for molding;

[0008] FIG. IB is a schematic side cross-sectional view of the casting mold of FIG. 1 A showing the mold open with mold halves spaced apart;

[0009] FIG. 2A is a side cross-sectional view of a vent valve usable in the casting mold of FIGs. 1A and IB in an open position of the valve;

[0010] FIG. 2B is a side cross-sectional view of the vent valve of FIG. 2A in a closed position of the valve;

[0011] FIG. 2C is a close-up view of the vent valve of FIG. 2B;

[0012] FIG. 3 is the vent valve of FIG. 2C with added simulated molten metal flow;

[0013] FIGs. 4A to 4H are side cross-sectional views of the vent valve of FIG. 3 with simulated molten metal flow at different moments of time of a molding cycle, illustrating the process of the molten metal filling the valve cavity;

[0014] FIG. 5 A is a side cross sectional view of a venting valve embodiment with an extra plate for driving and / or cooling the venting valve, in an open position of the valve;

[0015] FIG. 5B is a side cross-sectional view of the venting valve embodiment of FIG. 5 A in a closed position of the valve; and

[0016] FIG. 6 is a flow chart of a method for venting a mold cavity in accordance with this disclosure.DETAILED DESCRIPTION

[0017] While the present teachings are described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to such embodiments. On the contrary, the present teachings encompass various alternatives and equivalents, as will be appreciated by those of skill in the art. All statements herein reciting principles, aspects, and embodiments of this disclosure, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure.

[0018] As used herein, the terms "first", "second", and so forth are not intended to imply sequential ordering but rather are intended to distinguish one element from another, unless explicitly stated. Sequential ordering of method steps does not imply a sequential order of their execution, unless explicitly stated.

[0019] One goal of the present disclosure is to provide a venting valve for a die casting mold, the valve being small enough to be positioned close to the mold cavity without reducing the mold area. According to the present disclosure, the valve is shaped to make use of the momentum of the incoming melt to force the valve shut. A simple valve mechanism of small mass further decreases the time to slide the piston from its open position to closed position down to milliseconds. When in the closed position, the valve mechanism can withstand a significant pressure exerted by the molten metal without leaking the metal into the valve and out of the mold.

[0020] Therefore, in accordance with one aspect of this disclosure, there is provided an improved valve mechanism for an injection mold which is quick acting, simple to construct, and self-adjusting to increasing melt pressure. The shape of thevalve is selected such that, as the pressure increases, the seal between the valve and the mold body tightens.

[0021] The valve includes an inlet coupled to the mold cavity and an outlet for venting gas from the mold cavity. The valve may further include a truncated cone shaped piston oriented substantially perpendicularly to the inlet and movable between open and closed positions for closing off the outlet. The valve is configured to move the piston into the closed position by directing the melt passing through the inlet to impinge substantially coaxially upon the piston, to transfer a majority of the momentum of the melt to the piston for closing it shut before the melt has a chance to leak through the valve.

[0022] In accordance with the present disclosure, there is provided a valve for a casting mold having first and second mold portions defining a mold cavity. The valve comprises a valve opening in the first mold portion for engaging a valve piston. The valve opening comprises a funneled portion and a straight portion extending coaxially from a narrow end of the funneled portion into the first mold portion. A vent opening couples the straight portion to outside environment. The valve piston comprises a shank matching the funneled portion of the valve opening and a shaft extending from a narrow end of the shank for slidably engaging the straight portion of the valve opening to move between open and closed positions. When the valve piston is in the open position, air trapped in the mold cavity escapes through a gap between the shank and the funneled portion. When the valve piston is in the closed position, the gap is closed to prevent molten metal from escaping the mold cavity. The second mold portion may have a cavity shaped to direct a flow of the molten metal at a center of the shank to move the valve piston from the open position to the closed position due to a momentum of the molten metal impinging onto the shank. The cavity may have an arcuate shape for directing the flow of molten metal substantially perpendicularly to a top surface of the shank.

[0023] In embodiments where the funneled portion of the valve opening has a conical shape, the shank of the valve piston may also have a conical shape that matches the conical shape of the funneled portion. The straight portion of the valveopening may have a cylindrical shape coaxial with the conical shape of the funneled portion. The shaft of the valve piston may have a cylindrical shape matching the cylindrical shape of the straight portion of the valve opening.

[0024] In some embodiments, at least one of the funneled portion of the valve opening or the shank of the valve piston is shaped to provide a space between a radial stream of the molten metal and the gap, the radial stream being formed by a top surface of the shank redirecting the impinging molten metal radially outwards. To provide the above-mentioned space, the funneled portion of the valve opening may include a trench at a wide end of the funneled portion; the shank may include a bevel at a wide end; etc. A top surface of the shank may include a raised outer portion for directing the radial stream of the molten metal up and away from the gap. A distance between the gap and the radial stream may be e.g. at least 0.5mm. The shank may include a central bulge for receiving and redirecting a flow of the molten metal radially outwards.

[0025] In accordance with the present disclosure, there is provided a casting mold comprising first and second mold portions defining a mold cavity between them and including a valve described above.

[0026] In accordance with the present disclosure, there is provided a method for venting a mold cavity defined by first and second joined mold portions of a casting mold. The method comprises providing a valve opening in the first mold portion in fluid communication with the mold cavity, the valve opening comprising a funneled portion comprising wide and narrow ends and facing, at the wide end, the second mold portion and narrowing with distance, and a straight portion extending coaxially from the narrow end of the funneled portion into the first mold portion. A vent opening is provided coupling the straight portion to outside environment.

[0027] A valve piston is provided. The valve piston has a shank matching the funneled portion of the valve opening and a shaft extending from a narrow end of the shank and slidably engaging the straight portion of the valve opening to move between open and closed positions. The method comprises bringing the valve pistonto the open position, directing a flow of the molten metal into the mold cavity while allowing air trapped in the mold cavity to escape through the gap and the vent opening into the outside environment, and directing the flow of the molten metal into a cavity at a center of the shank to move the valve piston from the open position to the closed position due to a momentum of the molten metal impinging onto the shank, thereby preventing the molten metal from escaping the casting mold.

[0028] The method may include forming the cavity in the second mold portion to have an arcuate shape for directing the flow of molten metal substantially perpendicularly to a top surface of the shank; shaping at least one of the funneled portion of the valve opening or the shank of the valve piston to provide a space between a radial stream of the molten metal and the gap, the radial stream being formed by a top surface of the shank redirecting the impinging molten metal radially outwards; and / or actively cooling the valve piston with a flow of coolant directed into an opening in the straight portion of the valve piston.

[0029] Referring now to FIGs. 1 A and IB, a mold 100 includes first 112 and second 114 mold portions. A mold cavity 116 is machined, or otherwise formed, in one or both of the mold portions 112, 114. The mold cavity 116 defines the shape of the part being cast. One of the mold portions 112, 114 may be stationary and fixed to a die casting machine, not shown for brevity, and the other portion may be mounted to a moving platen of the die casting machine. For example, the first mold portion 112 may be stationary, and the second mold portion 114 may be movable.

[0030] The stationary mold portion, i.e. the first mold portion 112, may be connected to a cylindrical sleeve referred to herein as shot sleeve 118, with a piston 120 positioned in the shot sleeve 118. The inside of the shot sleeve 118 is in fluid communication with the mold cavity 116. The casting process begins with tightly closing the first 112 and second 114 mold portions, pouring melt 180 (e.g. molten aluminum) into the shot sleeve 118 and rapidly accelerating the piston 120 to force the melt 180 into the mold cavity 116. Typical speeds as the melt 180 enters the mold cavity 116 are in the range of 50 m / s. The melt 180 is then allowed to solidify, and thecasting is ejected. The mold cavity 116 must be shaped in such a way to prevent any undercuts, so that the casting may be easily extracted from the mold 100.

[0031] To ensure that the mold cavity 116 is completely filled with the melt 180 and that there is no air mixed in with the melt 180 as the part is being molded, air contained in mold cavity 116 must be vented out as the melt 180 is injected into the mold cavity 116. To that end, a valve 124 may be formed in the first 112 and second 114 mold portions as first 172 and second 174 portions, respectively, of the valve 124. The valve 124 has an inlet 128 and an outlet 130. As the melt 180 is forced into the mold cavity 116, air in the mold cavity 116 is forced through the inlet 128 and out of the outlet 130. The valve 124 is shut, or moved to the closed position, by a stream of the melt 180 itself. This will be described in detail further below.

[0032] Referring to FIGs. 2A, 2B, and 2C, a valve 224 is an example embodiment of the valve 124 of FIGs. 1A and IB. As compared to the depiction of the valve 124 in FIGs. 1A and IB, the valve 224 of FIGs. 2A, 2B, and 2C is flipped, with a first mold portion 212 being on the bottom and the second mold portion 214 being on the top.

[0033] A valve opening 202 is provided in the first mold portion 212. The valve opening 202 includes a funneled portion 204 and a straight portion 206 extending coaxially from a narrow end of the funneled portion 204 into the first mold portion 212, as illustrated (i.e. downwards in FIGs. 2A-2C). A vent opening 230 couples the straight portion 206 of the valve opening 202 to outside environment.

[0034] The valve 224 includes a valve piston 208 having a shank 210 with its outer shape matching the inner shape of the funneled portion 204. By way of a non-limiting example, both can have matching conical shapes. The valve piston 208 further includes a shaft 211 extending from a narrow end of the shank 210 for slidably engaging the straight portion 206 of the valve opening 202 to move between an open position illustrated in FIG. 2A and a closed position illustrated in FIG. 2B. In the embodiment shown, both the straight portion 206 of the valve opening 202 and the shaft 211 of the valve piston 208 have matching cylindrical shapes.

[0035] When the valve piston 208 is in the open position of FIG. 2A, air trapped in the mold cavity escapes through a gap 215 between the shank 210 of the valve piston 208 and the funneled portion 204 of the valve opening 202. When the valve piston 208 is in the closed position shown in FIGs. 2B and 2C, the gap 215 is closed to prevent the melt 22 from escaping the mold cavity 16 as depicted in FIGs. 1A and IB.

[0036] Still referring to FIGs. 2A-2C, the second mold portion 214 may include a cavity 216 shaped to direct a flow of melt, also termed herein molten metal, approximately at a center of the shank 210 to move the valve piston 208 from the open position of FIG. 2A to the closed position of FIG. 2B due to a momentum of the molten metal being transferred to the valve piston 208. To facilitate a proper momentum / impulse transfer, the cavity 216 may have an arcuate shape with the right side being taller than the left side as illustrated, for directing the flow of molten metal substantially perpendicularly to atop surface of the shank 210. A lead-in channel 218 may be provided in the first mold portion 212 for leading the molten metal into the cavity 216. The flow of melt is illustrated in FIGs. 3 and 4A-4H.

[0037] In some embodiments, a bottom plate 240 (FIGs. 2A and 2B) may be coupled to the first mold portion 212 for providing hydraulic or pneumatic force for driving the valve piston 208 between open and closed positions, e.g. for initial setup of the valve 224. The valve piston 208 may be further equipped with a flange 220 controllable by a fluid and / or air pressure provided to a bottom cavity 222 using appropriate piping and / or channels, not shown for brevity.

[0038] Referring now specifically to FIG. 2C, the lead-in channel 218 may be provided with a ramp 238. The funneled portion 204 of the valve opening 202 may include a trench 232 around the funneled portion 204 at a wide end of the funneled portion 204. The shank 210 of the valve piston 208 may include a bevel 233 at a wide end of the shank 210. A top surface of the shank 210 may include a raised outer portion, as indicated by a dashed line 236 drawn radially along the surface of the raised outer portion. A central bulge 234 may be provided at the top of the shank 210. These optional features have been added by the inventor after multiple and costly tryouts. Multiple molten metal fluid dynamics simulations have been performed in anattempt to find clues for reducing seepage of the melt through the valve and thus increasing reliability and production yields of molding. The purpose and function of these features, specifically the ramp 238 of the lead-in channel 218, the trench 232 around the wide end of the funneled portion 204, the bevel 233 on the shank 210 of the valve piston 208, and the raised outer portion and the bulge 234 of the shank 210 top surface, will be considered below with reference to an illustration presented in FIG. 3.

[0039] Referring to FIG. 3, molten metal or melt 380, shown in a dark gray shade, enters the valve 224 via the lead-in channel 218. The ramp 238 directs the molten metal 380 upwards and into the larger toroidal portion of the cavity 216 (the righthand side in FIG. 3). The toroidal portion then directs the molten metal 380 onto the shank 210 of the valve piston 208, as illustrated with black arrows 302. From there, the melt 380 spreads over the top surface of the shank 210 radially outwards, conveying a mechanical impulse to the valve piston 208 and forming a toroidal loop 304 above and around the shank 210 of the valve piston 208. Importantly, the melt 380 flow misses the trench 232, at least initially, as it spreads out. This slows down the arrival of the molten metal at the closed gap 215 between the valve piston 208 and the valve opening 202, providing sufficient time for the valve piston 208 to close.

[0040] Thus, the trench 232 and the bevel 233 both contribute to providing the space between the radial stream of the molten metal 380 and the gap 215. Another contributor to providing the space is the raised outer portion of the shank 210, which directs the flow upwards in FIG. 3 and away from the closed gap 215. The provided space allows for a more reliable closure of the valve 224 before the melt 380 has any chance of reaching the gap 215, which effectively prevents the melt 380 from seeping through the closed gap 215 and jamming or blocking the entire valve mechanism.

[0041] One function of the central bulge 234 (FIG. 2C) is to receive the flow of the melt impinging onto the shank 210 of the valve piston 208 and redirect the flow radially outwards while avoiding turbulence of the flowing melt 380 as much as possible. The turbulence needs to be avoided because it may create local melt vortices which may redirect the melt in random directions including a direction toward theclosed gap 215. This is similar to a bulge at a bow of an oceanic lines which perform a similar function of avoiding turbulence and thus improving fuel efficiency of the oceanic liner.

[0042] The fluid dynamics of the melt 380 are further illustrated in FIGs. 4A-4H, which show a progression of the melt 380 propagation in the valve 224. The moment of time in the simulation is indicated in FIGs. 4A-4H to the right of the valve piston 208, in seconds. Specifically, FIG. 4A corresponds to the initial state of 0.000 seconds, before the melt 380 arrives at the valve 224. FIG. 4B corresponds to 0.003 seconds, with the melt 380 entering the toroidal cavity in the second mold portion 214. FIG. 4C corresponds to 0.006 seconds, showing the melt impinging onto the valve piston 208. FIG. 4D corresponds to 0.009 seconds, showing the melt forming loops in the toroidal cavity, similar to FIG. 3. FIG. 4E corresponds to 0.012 seconds; FIG. 4F corresponds to 0.015 seconds; FIG. 4G corresponds to 0.018 seconds, with the melt 380 gradually filling the valve cavity. Finally, FIG. 4H corresponds to 0.02 seconds when the valve cavity is completely filled with the melt.

[0043] FIG. 4C, corresponding to 6 milliseconds, is particularly interesting. By this time, the melt 380 has impinged onto the valve 208, which begins to close; and by 9 milliseconds of FIG. 4D, the valve 208 is completely shut. Importantly, while the valve 208 is shut at 9 milliseconds and the melt 380 continuing to fill in the top cavity, the trench 232 remains unfilled. Only by 12 milliseconds as illustrated in FIG. 4E, the trench 232 begins to get filled; it gets completely filled by 15 milliseconds (FIG. 4F), however by that time, the valve 208 is reliably shut and is under the growing pressure of the melt 380 which shuts the valve 208 even tighter, such that no leak of the melt 380 under the valve 208 can occur.

[0044] Referring now to FIGs. 5A and 5B, a valve 524 is an embodiment of the valve 124 if FIGs. 1A and IB, the valve 224 of FIGs. 2A-2C and FIG. 3 and includes similar elements. The valve 524 of FIGs. 5A and 5B includes first 512 and second 514 portions. The first portion 512 has a cylindrical opening 506 extending into a conical opening 504. A valve piston 508 slidably engages the cylindrical opening 506. The valve piston 508 has a conical surface portion 510 matching the shape of theconical opening 504 for a snug fit The second portion 514 includes a toroidal cavity 516, shown in a side view on FIG. 5 A, for receiving and redirecting a stream of the melt 580 as illustrated with a thick black arrow.

[0045] Operation of the valve 524 will now be considered. When the melt 580 is injected into the mold cavity of the casting die, air 540 (FIG. 5 A) escapes the mold cavity traveling through an inlet 528, then through the gap formed between the conical surface portion 510 of the valve piston 508 and the conical opening 504 in the first portion 512 of the valve 514, and then through the outlet 530, as illustrated in FIG. 5 A. The melt stream 580 arriving at the valve 524 is redirected by a concave portion 516A of the toroidal cavity 516 to impinge onto the valve piston 508 substantially along its axis of symmetry, which coincides with the axis of movement of the piston 508. The kinetic energy of movement of the melt 580 is transferred to the valve piston 508, which quickly moves downwards in FIG. 35 and closes shut, preventing the melt 580 from escaping into the outlet 530.

[0046] The valve piston 508 heats up due to the contact with the melt 580 during the molding process. An optional cooling apparatus 550 may be provided to cool down the valve piston 508. The cooling apparatus 550 includes a base 560 mountable to the first mold portion 512 (i.e. the one receiving the valve piston 508). The valve piston 508 includes opposed front and back ends, the back end slidably engaging the cylindrical opening 506 in the first portion 512 of the valve 524. The front end (shank) of the valve piston 508 is configured to face the molten metal 580 injected into the mold during the casting process.

[0047] An opening 552 may be provided at the back end of the valve piston 508. The opening 552 may extend from the back end towards the front conical end of the valve piston 508. A hollow shaft 554 may extend from the opening 552 towards the base 560, for slidably engaging the base 560. The cooling apparatus 550 may further include a coolant delivery apparatus for delivery of coolant into the opening through the opening 552 in the hollow shaft 554. The coolant apparatus 550 may include a coolant delivery tube 568 extending from the base 560 into the opening in the valve piston 508. The base 560 may include an inlet opening 571 and an outlet opening573. The inlet opening 571 is in fluid communication with the coolant delivery tube 568, and the outlet opening 573 is in fluid communication with the with the opening 552 in the hollow shaft 554 when the cooling apparatus 550 is assembled for operation. The coolant flow direction may be reversed.

[0048] In FIG. 5B, the valve 524 is shown in a closed position that blocks the outflow of molten metal. The second portion 514 is omitted for brevity. As explained above, the valve 524 may be closed shut by directing the stream of molten metal 580 to impinge at a near normal angle onto the top surface of the valve piston 508. The top surface may be concave as shown in FIG. 5B, or convex with flared-up outer perimeter as shown in FIG. 2C. The molten metal 580 (FIG. 5B) is directed to push the valve piston 508 by mere kinetic momentum of the molten metal stream 580. The concave top surface of the valve piston 602 facilitates redirection of the stream of molten metal sideways and upwards, providing enough time for the valve 524 to close before the molten metal 580 reaches the sides of the valve piston 508.

[0049] In the closed position illustrated in FIG. 5B, the conical surface 510 of the valve piston 508 rests on the matched conical surface 504 of the first mold portion 512. One advantage provided by the matching conical surfaces 510 and 504 is that, as the liquid metal pressure builds above the valve piston 508, the two conical surfaces are pressed together more strongly, preventing the molten metal outflow at the elevated pressure. The matching conical surfaces (or the other types of slanted matching surfaces) provide a mechanism for automatic tightening of the seal as the molten metal pressure builds, improving quality and increasing manufacturing yields.

[0050] Referring now to FIG. 6 with further reference to FIGs. 1 A-1B, 2A-2C, FIG. 3, 4A-4H, and FIG. 5A, a method 600 (FIG. 6) for venting a mold cavity is presented. The mold cavity is defined by first and second joined mold portions of a casting mold. The method 600 may be used e.g. to vent the mold cavity 124 of the mold 100 of FIGs. 1A and IB.

[0051] The method 600 includes providing (602) a valve opening in the first mold portion in fluid communication with the mold cavity. For example, the valve openingmay be machined in the first mold portion. As explained above with reference to FIGs. 2A-2C, the valve opening 202 includes a funneled portion 204 comprising wide and narrow ends. The valve opening 202 faces, at its wide end, the second mold portion 214 and narrows down with a distance from the second mold portion 214. The valve opening 202 further includes a straight portion 206 (FIG. 2C) extending coaxially from the narrow end of the funneled portion 204 into the first mold portion 212.

[0052] A vent opening is provided (604) in the first mold portion. The vent opening, e.g. the vent opening 230 in FIG. 2C, couples the straight portion 206 of the valve opening 202 to outside environment. A valve piston is provided (606). The valve piston, e.g. valve piston 208 in FIG. 2C, includes the shank 210 matching the funneled portion 204 of the valve opening 202, and the shaft 211 extending from a narrow end of the shank 210 and slidably engaging the straight portion 206 of the valve opening 202 to move between open and closed positions depicted in FIGs. 2A and 2B respectively.

[0053] The method 600 further includes bringing (608) the valve piston into the open position (if not already in the open position). This may be achieved e.g. by applying fluid pressure to the bottom cavity 222 (FIG. 2B), causing the flange 220 to push the valve piston 208 into the open position. A flow of the molten metal may then be directed (610) into the mold cavity while allowing air trapped in the mold cavity to escape through the gap and the vent opening into the outside environment. This is illustrated e.g. in FIG. 5 A, where the air 540 pushed by the flow of molten metal 580 escapes through the gap between the conical surface 504 of the valve opening and the conical surface 510 of the valve piston 508, and further through the vent opening 530.

[0054] The method 600 further includes directing (610) the flow of the molten metal into the mold cavity while allowing air trapped in the mold cavity to escape through the gap around the valve piston and the vent opening into the outside environment.

[0055] The method 600 further includes directing (612) the flow of the molten metal into a cavity in the second mold portion shaped to direct the flow of the molten metal at a center of the shank to move the valve piston from the open position to the closed position. The valve piston is moved due to transfer of a momentum of the molten metal impinging onto the shank onto the valve piston, thereby preventing the molten metal from escaping the casting mold. This is illustrated e.g. in FIG. 3 and FIGs. 4B and 4C, where the flow of the melt 380 impinges on the valve piston 208 closing it shut.

[0056] In some embodiments, the method 600 may include forming (614) the cavity in the second mold portion to have an arcuate shape for directing the flow of molten metal substantially perpendicularly to a top surface of the shank. This is illustrated in FIG. 2C where the right-side portion of the toroidal cavity in the second mold portion 214 is larger than left-side portion, for making sure the melt follows an arcuate path as close to perpendicular impinging onto the valve piston 208 as possible. The perpendicular flow of the melt onto the valve piston is preferable because, firstly, it conveys maximum impulse to the valve piston, and secondly, it conveys the impulse symmetrically and along the axis of movement of the valve piston, which reduces chances of jamming or the melt flowing asymmetrically and contacting the gap between the valve piston and valve opening on one side much sooner than on the other.

[0057] According to the method 600, at least one of the funneled portion of the valve opening or the shank of the valve piston may be shaped (616) to provide a space between a radial stream of the molten metal and the gap, the radial stream being formed by a top surface of the shank redirecting the impinging molten metal radially outwards

[0058] In some embodiments, the method 600 may include actively cooling (618) the valve piston with a flow of coolant directed into an opening in the straight portion of the valve piston. This has been described with reference to FIGs. 5 A and 5B above.

[0059] Persons skilled in the art will appreciate in view of the teachings and disclosures presented herein that the internal cooling apparatus according to this disclosure offers significant advantageous utilities and / or functionality in comparison to the prior art, including, but not limited to: (a) an ability to cool the piston substantially as needed, i.e. without requiring the die to be opened or any external spraying of coolant onto the piston; and / or (b) the coolant fluid can be directed through the piston, while allowing it to move freely and / or without requiring any direct plumbing fitting onto the piston. U-cup seals may reduce, minimize, and / or prevent leakage to / from the hollow shaft that directs the coolant fluid to the piston. O-ring(s) or other types of sliding seals may be used in place of the U-cup seals.

[0060] The present disclosure helps solve, obviate, and / or mitigate one or more problems associated with the prior art relating to movable pistons in high-pressure die cast valves. The apparatuses and methods of this disclosure may be used by or in association with cooling mechanisms for die casting machinery, as described above; however, the present disclosure is not to be limited in scope by the specific embodiments described herein, as these are disclosed for the purposes of illustration.

[0061] Other various embodiments and modifications, in addition to those described herein, may be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in view of the full breadth of the present disclosure as described herein.

Claims

WHAT IS CLAIMED IS:

1. A valve for a casting mold having first and second mold portions defining a mold cavity therebetween, the valve comprising: a valve opening in the first mold portion, the valve opening comprising a funneled portion and a straight portion extending coaxially from a narrow end of the funneled portion into the first mold portion; a vent opening coupling the straight portion to outside environment; and a valve piston comprising a shank matching the funneled portion and a shaft extending from a narrow end of the shank for slidably engaging the straight portion of the valve opening to move between open and closed positions, wherein: when the valve piston is in the open position, air trapped in the mold cavity escapes through a gap between the shank and the funneled portion; and when the valve piston is in the closed position, the gap is closed to prevent molten metal from escaping the mold cavity.

2. The valve of claim 1, wherein the second mold portion has a cavity shaped to direct a flow of the molten metal at a center of the shank to move the valve piston from the open position to the closed position due to a momentum of the molten metal impinging onto the shank.

3. The valve of claim 2, wherein the cavity comprises an arcuate shape for directing the flow of molten metal substantially perpendicularly to a top surface of the shank.

4. The valve of claim 1, wherein: the funneled portion of the valve opening has a conical shape; the shank of the valve piston has a conical shape matching the conical shape of the funneled portion;the straight portion of the valve opening has a cylindrical shape coaxial with the conical shape of the funneled portion; and the shaft of the valve piston has a cylindrical shape matching the cylindrical shape of the straight portion of the valve opening.

5. The valve of claim 1, wherein at least one of the funneled portion of the valve opening or the shank of the valve piston is shaped to provide a space between a radial stream of the molten metal and the gap, the radial stream being formed by a top surface of the shank redirecting the impinging molten metal radially outwards.

6. The valve of claim 5, wherein the funneled portion of the valve opening comprises a trench at a wide end of the funneled portion for providing the space between the radial stream of the molten metal and the gap.

7. The valve of claim 5, wherein the shank comprises a bevel at a wide end thereof for providing the space between the radial stream of the molten metal and the gap.

8. The valve of claim 5, wherein a top surface of the shank comprises a raised outer portion for directing the radial stream of the molten metal up and away from the gap.

9. The valve of claim 5, wherein a distance between the gap and the radial stream is at least 0.5mm.

10. The valve of claim 1, wherein the shank comprises a central bulge for receiving and redirecting a flow of the molten metal radially outwards.

11. A casting mold comprising: first and second mold portions defining a mold cavity therebetween; a valve opening in the first mold portion in fluid communication with the mold cavity, the valve opening comprising a funneled portion comprising wide and narrow ends and facing, at the wide end, the second mold portion and narrowing with a distance therefrom, and a straight portion extending coaxially from the narrow end of the funneled portion into the first mold portion;a vent opening coupling the straight portion to outside environment; a valve piston comprising a shank matching the funneled portion and a shaft extending from a narrow end of the shank for slidably engaging the straight portion in the valve opening to move between open and closed positions, wherein: when the valve piston is in the open position, air trapped in the mold cavity escapes through a gap between the shank and the funneled portion; and when the valve piston is in the closed position, the gap is closed to prevent molten metal from escaping the mold cavity; and a cavity in the second mold portion shaped to direct a flow of the molten metal at a center of the shank to move the valve piston from the open position to the closed position due to a momentum of the molten metal impinging onto the shank.

12. The casting mold of claim 11, wherein the cavity comprises an arcuate shape for directing the flow of molten metal substantially perpendicularly to a top surface of the shank.

13. The casting mold of claim 11, wherein: the funneled portion of the valve opening has a conical shape; the shank of the valve piston has a conical shape matching the conical shape of the funneled portion; the straight portion of the valve opening has a cylindrical shape coaxial with the conical shape of the funneled portion; and the shaft of the valve piston has a cylindrical shape matching the cylindrical shape of the straight portion of the valve opening.

14. The casting mold of claim 11, wherein at least one of the funneled portion of the valve opening or the shank of the valve piston is shaped to provide a space between a radial stream of the molten metal and the gap, the radial stream being formed by a top surface of the shank redirecting the impinging molten metal radially outwards.

15. The casting mold of claim 14, wherein at least one of:the funneled portion of the valve opening comprises a trench at a wide end of the funneled portion for providing the space between the radial stream of the molten metal and the gap; the shank comprises a bevel at a wide end thereof for providing the space between the radial stream of the molten metal and the gap; or a top surface of the shank comprises a raised outer portion for directing the radial stream of the molten metal up and away from the gap.

16. The casting mold of claim 14, wherein the shank comprises a central bulge for receiving and redirecting a flow of the molten metal radially outwards.

17. A method for venting a mold cavity defined by first and second joined mold portions of a casting mold, the method comprising: providing a valve opening in the first mold portion in fluid communication with the mold cavity, the valve opening comprising a funneled portion comprising wide and narrow ends and facing, at the wide end, the second mold portion and narrowing with a distance therefrom, and a straight portion extending coaxially from the narrow end of the funneled portion into the first mold portion; providing a vent opening coupling the straight portion to outside environment; providing a valve piston comprising a shank matching the funneled portion of the valve opening and a shaft extending from a narrow end of the shank and slidably engaging the straight portion of the valve opening to move between open and closed positions; bringing the valve piston to the open position; directing a flow of the molten metal into the mold cavity while allowing air trapped in the mold cavity to escape through the gap and the vent opening into the outside environment; and directing the flow of the molten metal into a cavity in the second mold portion shaped to direct the flow of the molten metal at a center of the shank to move the valve piston fromthe open position to the closed position due to a momentum of the molten metal impinging onto the shank, thereby preventing the molten metal from escaping the casting mold.

18. The method of claim 17, further comprising forming the cavity in the second mold portion to have an arcuate shape for directing the flow of molten metal substantially perpendicularly to a top surface of the shank.

19. The method of claim 17, further comprising shaping at least one of the funneled portion of the valve opening or the shank of the valve piston to provide a space between a radial stream of the molten metal and the gap, the radial stream being formed by a top surface of the shank redirecting the impinging molten metal radially outwards.

20. The method of claim 19, further comprising actively cooling the valve piston with a flow of coolant directed into an opening in the straight portion of the valve piston.

Images