VERTICAL DIE CASTING MACHINE

Abstract: A vertical die casting machine of a vertically clamping type provided with a hydraulic piston-cylinder (42, 43) to actuate movable parting plates (40, 41) disposed between an injection sleeve (30) and a stationary mold for constricting a melt passage including a runner hole formed in the stationary mold and a hollow end portion of the sleeve by an axial through-hole formed by the parting plates in a clamped state. The parting plates enable to prevent a semi-solidified part of the melt "shell" formed in the sleeve before an injection operation from intruding into a mold cavity with the other hot melt part. With a narrow runner hole having a diameter smaller than that of the sleeve, the parting plates are actuated to move in a clamped state in a direction to thereby shear a cold melt runner so that a molded product is allowed to move upward from the stationary mold with the runner separated from a cold melt bisket formed in the sleeve, but integral with the product. With an enlarged runner hole having a diameter not less than that of the sleeve, the parting plates are actuated to separate from each other to thereby allow the bisket integral with the runner to move upward from the stationary mold through the enlarged runner hole with the mold product integral with the runner.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical die casting machine, i.e, a so called "Vertical Squeeze Casting machine", in which machine a molten metal or melt in a casting sleeve is injected by actuating an injection plunger into a cavity defined by a mold arrangement of a vertically clamping type including lower stationary and upper movable molds through a runner hole formed in the stationary mold, and the melt is poured into the casting sleeve while the sleeve is spaced apart from the stationary mold. 2. Description of the Related Art Machines such as the above are disclosed in U.S. Pat. No. 4,088,178 and No. 4,287,935, having the same inventors as that of the present invention. Such conventional machines of the vertically clamping type have the following inherent serious problems: The casting or injection sleeve for use in the vertical die casting machine has a hollow head portion defining, with the head of the plunger therein, a melt space where the melt is received. The sleeve head portion has the same diameter over the length thereof and is not constricted at the free end thereof, which end abuts against the stationary mold from below. A melt passage from the surface of the melt received in the sleeve to the cavity is formed to include an enlarged runner hole. The injection of the melt for producing a molded product in the cavity is carried out in two stage operations. At the initial injec­ tion stage, the plunger is forced to move at a relative­ ly high speed so that the melt is filed in the cavity. As the final injection stage, the plunger is actuated to move upward at a relatively low speed with an ad­ ditional short stroke to have the melt filled in the cavity subjected to an increased pressure by the plunger. When the melt is injected into the cavity through the melt passage and then cooled, the solidified melt or cold melt forms, in an integral body, a molded product in the cavity, a melt part, i.e., "runner", in the runner hole, and the remaining melt part, i.e., "brisket", in the upper end portion of the sleeve. The enlarged runner hole is required to allow the bisket to pass through the runner hole so that the entire solidified melt is removed from the stationary mold when the upper movable mold is moved upward and separated from the lower stationary mold. In this regard, the diameter of the runner hole must be not less than that of the sleeve head. One of the problems resides in that such enlarged runner hole occupies a substantial area of the lower surface of the cavity on the side of the lower stationary mold, since the runner hole opens to the lower surface. This occupation restricts a degree of freedom in designing contoured decorations to be formed at the lower surface of a molded product integrated with the melt runner. The other problem resides in that such an enlarged runner hole causes the quality of a molded product to be reduced, for the following reason. After the hot melt is poured in the melt space in the sleeve, the received melt is partially cooled at the circumferential inner surface of the sleeve and the surface of the plunger tip to form a semi-solidified part of the melt along the circumferential surface before the injection, i.e., a "shell" of a cylindrical vessel shape. When the melt is injected into the cavity, the shell is forced into pieces and a substantial amount of the shell is forced to enter the cavity, accompanying the remaining hot melt part. In order to avoid this intrusion of the shell, it has been attempted to provide the station­ ary mold with a detachable metal net covering the entire cross sectional area of the runner hole therein, as disclosed in Japanese Unexamined Patent Publication (KOKAI) No. 55-42116. Alternatively, in another prior art, the upper end portion of the injection sleeve is provided with a ring detachably mounted therein, as shown in Japanese Unexamined Patent Publication (KOKAI) No. 56-5621. However, it is noted that these prior art solutions cause difficulties in manual handling of the net or the ring at each injection cycle. Further it is recognized that such means are likely to cause the production of a molded product to require an increased amount of the melt to be wasted as a non-product material. SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved vertical die casting machine of a vertically clamping type by which the above mentioned problems are overcome or solved in practice. According to the present invention, there is provided a vertical die casting machine of a vertically clamping type, comprising: lower stationary and upper movable platens, a mold arrangement clamped between the platens to define a die cavity, a casting sleeve, a plunger slidably disposed in the casting sleeve, and a hydraulic piston-cylinder having the sleeve mounted at the lower end thereof for actuating the plunger. The plunger has a plunger tip at the upper end thereof. The tip together with the sleeve defines a melt space wherein a melt is received for an upward injection of the melt by the plunger into the cavity through a melt passage. The melt passage is freely defined between the cavity and the surface of the melt received in the melt space. The piston-cylinder, for example, is pivotably mounted to the stationary platen so that the sleeve can be tilted for receiving the melt. The machine is characterized by a means provided for constricting the melt passage. The constricting means comprises at least two movable flat parting plates disposed between the sleeve and the lower stationary mold. Each of the parting plates has a groove forming a semi-circle at the parting face thereof. When the melt is injected, the parting plates are clamped to define a vertically extending through-hole formed by the semi-circular grooves. The through-hole is preferably coaxial with the sleeve and has a cross sectional area at the upper end thereof smaller than that at the upper end of the sleeve. The upper end of the sleeve abuts against the parting plates from below during the injection operation, and the parting plates are allowed to move along a first line on a horizontal plane. The constricting means further comprises a first pair of hydraulic piston-­ cylinders for actuating the parting plates horizontally along the first line. Preferably a means is provided for preventing the parting plates, when clamped, from being forced to move horizontally along a second line perpendicular to the first line by a force caused by an injection of the melt. The preventing means comprises a pair of hydraulic or air piston cylinders for actuating opposing piston rods extending along the second line. The piston rods may have flat free end surfaces parallel to the first line. Alternatively, the piston rods may have free end surfaces in a zig-zag fashion to be engagable with the corresponding surface parts of the parting plates. The parting plates preferably have a converse T-shaped rectangular form, and in the clamped state, are made symmetrical about the first and second lines in such a manner that each parting plate has a flat parting face along the second line where the semi-circular groove is formed. The parting plates further have flat side faces parallel to the first line. One of the piston rods in the preventing means urges the clamped parting plates at the side faces thereof on one side against the other piston rod at the other side faces of the parting plates along the second line during the injection operation. Alternatively, one of the pair of the piston cylinders in the preventing means may be replaced by a support which abuts against the parting plate at one side flat faces thereof. According to the present invention, the machine of a vertically clamping type is incorporated with a mold arrangement having a narrow runner hole forming a part of the melt passage in the stationary mold, the diameter of the hole at the lower end thereof being smaller than that of the sleeve at the upper end thereof, the first pair of piston cylinders in the constricting means are provided for driving the parting plates to move in a direction along the first line together in a clamped state against a melt solidified in the melt passage, to thereby shear the melt solidified after completion of the injection into two pieces at the through-hole of the clamped parting plates. Preferably the diameter of the narrow runner hole at the lower end thereof may be smaller than that of the through-hole at the upper end thereof. The injection plunger is preferably provided with a hydraulic supplemental piston-cylinder therein for axially actuating a supplement piston rod. The plunger is actuated during the injection operation at the initial stage thereof so that the hot melt is filled in the cavity. The supplemental piston rod is actuated during the injection operation at the final stage thereof so that the filled melt is subjected to an increased pressure. The supplemental piston rod has an upper rod tip having a diameter smaller than that of the plunger tip and coaxial with the through-hole defined by the clamped parting plates, and the rod tip has preferably a diameter smaller than that of the through-hole at the upper end thereof. Alternatively, according to the present invention the machine may be incorporated with a mold arrangement having an enlarged runner hole forming a part of the melt passage in the stationary mold, the diameter of the hole being not less than that of the sleeve at the upper end thereof as that in the conventional machine. The first pair of piston-cylinders, however, is provided for driving the parting plates to move in opposite directions to separate the parting plates from each other, to thereby allow a solidified melt as a whole in the cavity and the melt passage to be upwardly removed from the stationary mold through the separated parting plates. The injection piston-cylinder is provided for actuating the plunger to move upward at the initial stage of the injection operation. The parting plates are clamped to constrict the melt passage to define the through-hole at the initial and final injection stages, and are separated from each other after the final injection stage. Of course, the plunger may be used to carry out the final stage injection. To attain more complete injection, preferably, a supplemental piston-­ cylinder is provided in the plunger for carrying out the injection at the final stage thereof. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a sectional view illustrating a first embodiment of a vertical die casting machine incorporated with a mold arrangement having a narrow runner hole therein, according to the present invention, the machine featuring means for constricting a melt passage during the injection operation and shearing the melt solidified in the melt passage after the injection is completed; Fig. 2 is a cross sectional view of the machine shown in Fig. 1 taken along the line II-II; Figs. 3(a) to 3(f) are sectional views of the main portions of the first embodiment of the machine illus­ trating the operations of the machine at various stages; Fig. 4 is a sectional view corresponding to Fig. 1, illustrating a second embodiment of the vertical die casting machine according to the present invention, featuring a mold arrangement having a narrow runner hole therein and defining a cavity having a configuration designed to be the reverse of that of the mold arrange­ ment shown in Fig. 1; and Fig. 5 is a sectional view corresponding to Fig. 1, illustrating a third embodiment of the vertical die casting machine incorporated with a mold arrangement having an enlarged runner hole, according to the present invention, the machine featuring means for constricting a melt passage during the injection operation and for having the constriction released after the injection is completed. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Figs.1 to 3, a vertical die casting machine comprises a stationary platen 21 fixed on a machine base (not shown) and a movable platen 22 movable upward or downward along four tie rods extending verti­ cally from the base at the four corners thereof. A lower stationary mold 23 and a upper movable mold 24 are mounted on the stationary and movable platens 21 and 22, respectively. A clamping piston-cylinder (not shown) is provided over the movable platen 22 for actuating the movable platen to move upwards or downward, so that the movable mold 24 is clamped or unclamped relative to the stationary mold 23. Between the stationary and movable molds, a pair of laterally movable molds 25 and 26 forming "cores" are disposed while supported on the side of the movable mold 24. The cores 25 and 26 are actuated by a driving device (not shown) to move forward or backward in a horizontal direction D. A mold arrangement of the present embodiment consists of the stationary mold 23, the movable mold 24, and the pair of cores 25 and 26, for use in casting an aluminium wheel of a motor car. The mold arrangement, when clamped, is designed to define a die cavity 27, which forms a space in the mold arrangement having the same configuration as that of the aluminium wheel. A hydraulic injection piston-cylinder (not shown) is pivotably mounted on the machine base so that it can be tilted from a vertical position. A block 29 is provided on the side of the injection piston-cylinder and is actuated by another piston-cylinder (not shown). A casting or injection sleeve 30, having a plunger 28 movably disposed therein, is axially mounted on the block 29 at the upper end thereof. The casting sleeve 30 is movable with the block 29, and the head portion of the sleeve can be received and fitted in a sleeve hole 23a formed in the stationary mold 23, when the block 29 is actuated to move upward. The stationary platen 21 has a notch 21a at which the sleeve 30 and the block 29 are disposed. The block 29 is forced to move downward to remove the sleeve from the sleeve hole 23a, and then the sleeve is forced to be tilted with the injection piston-cylinder in a direction E for receiving a melt or molten metal 31 in a melt space defined between the tip 28a of the plunger 28 and the sleeve 30. After the melt is poured into the melt space, the sleeve 30 is raised vertically and then is moved upward to fit in the sleeve hole 23a. In the arrangement, the melt is extruded into the cavity by the plunger head 28a through a melt passage defined between the surface of the melt received in the sleeve and the cavity. The above melt extrusion by the plunger 29 forms an initial stage of the injection or casting operation. A hydraulic supplemental piston-cylinder, comprising a cylinder 32a formed in the plunger 28 at a rod 28b thereof and a piston rod 32b axially extending through an axial hole formed in the rod 28b, is provided for actuating the piston rod 32b to pressurize the melt in the cavity against the clampled molds at a final stage of the injection operation. The stationary mold 23 consists of an upper plate 23b and a lower plate 23c connected by means of bolts. The upper plate 23b has a narrow runner hole 46 communicating with the cavity. The lower plate 23c has a through-hole extending vertically and forming a central hole portion 33 having a rectangular shape and a pair of narrow guiding hole portions 34 and 35 extending horizontally in opposite directions from the central hole portion 33 along a first line X. The through-hole forms a hollow space defined by the upper plate 23b and the lower plate 23c. A gate plate arrangement 36 is provided so as to slidably move along the first line in the hollow space of the lower plate 23c, and consists of a pair of parting plates 40 and 41 having opposite parting faces. The parting faces are located, in a combined or clamped state of the plates, along a second line perpendicular to the first line. The first and second lines lie on a horizontal plane. The parting plates 40 and 41 are designed so as to be converse T-shaped rectangular flat forms symmetrical to the first and second lines. The parting plates 40 and 41 have grooves forming a semi-­ circle at the parting faces thereof, respectively, and define an axial through-hole formed by the semi-circular grooves in the clamped state. The axial through-hole is coaxial with the casting sleeve 30 and the sleeve hole 23a. The axial through-hole formed by the pair of the parting plates 40 and 41 has a lower enlarged portion 38 and an upper constricted portion 39. The T-shaped parting plates 40 and 41 have enlarged gating portions 40a and 41a slidable in the central hole portion 33 and constricted guiding portions 40b and 41b slidable in the narrow guiding hole portions 34 and 35. A tolerance of the gating portions 40a and 41a in the central hole portion 33 on each side thereof is designed to be about 0.5 mm, while another tolerance of the parting plates 40 and 41 in the guiding portions 40b and 41b is designed to be over 0.1 mm. A pair of hydraulic piston cylinders 42 and 43 are conversely mounted to the lower plate 23c of the station­ ary mold 23 for actuating piston rods 42a and 43a, which are connected to the parting plates 40 and 41 at the ends of the guiding portions 40b and 41b, respectively. In this embodiment, a piston stroke of the piston-­ cylinder 42 on the right side is set to about 15 mm from the position as shown in the figure to the left, and a piston stroke of the piston-cylinder 43 on the left side is set to about 30 mm from the position as shown in the figure to the left. In connection with the stroke designs, the central hole portion 33 has a length along the first line X larger than that of the gating plate portions 40a and 41a in the clamped state by over 15 mm, so that the gating plate arrangement in the clamped state is allowed to move along the first line X by the stroke gap, i.e., 15 mm. The second line Y is biased to the right by 15 mm from the center line of the central hole portion 33 parallel to the second line. When the melt is injected to the cavity 27, the left piston-cylinder 43 actuates the parting plates 40 and 41 to move to the right and thus urge the plates against the lower mold plate 23c at a shoulder 23d thereof. In this urged state, a shoulder 40c of the plate 40 abuts against the shoulder 23c, and the plates 40 and 41 are clamped with the through-hole having the hole portions 38 and 39 coaxial with the sleeve 30. Such clamping and positioning can be alternatively effected by driving both the piston-cylinders 42 and 43 simultaneously in opposing directions. Compared with this alternative positioning method, the former position­ ing method as embodied by using the shoulders 23c and 40c is more advantageous in that the position can be more assuredly and easily adjusted as required. The right piston-cylinder 42 is driven to actuate the clamped parting plates to move to the left by 15 mm. By this movement, the melt solidified in the melt passage is sheared at the upper end of the through-hole formed in the clamped parting plates. The melt passage includes the end portion of the sleeve 30, the through-hole (38, 39) of the parting plates, and the runner hole 46. Alternatively, this movement can be effected by driving both the piston-cylinders 42 and 43 simultaneously in a direction toward the left side. A pair of hydraulic piston-cylinders 44 and 45 are conversely mounted to the stationary mold 23 for actuat­ ing piston rods 44a and 45a. The lower plate 23c of the stationary mold 23 has holes along the second line Y wherein the piston rods 44a and 45a are slidably dis­ posed. Both of the piston-cylinders 44 and 45 are driven to actuate the piston rods so that the flat end of one of the piston rods 44a urges the clamped parting plates 40 and 41 at the flat side faces on one side of both the plates against the flat end of the other piston rod 45a at the flat side faces on the other side of the plates. During the movement of the parting plates 40 and 41, the piston rods 44a and 45a are withdrawn and spaced apart from the parting plates. The upper hole portion 39 of the clamped parting plates 40 and 41 has a diameter larger than that of the runner hole 46, and larger than that of the piston rod 32b of the supplemental piston-cylinder 32, but smaller than that of the head of the sleeve 30. With the above arrangement, the vertical die casting machine is operated as follows, with reference to Figs. 3(a) to 3(f). Referring to Fig. 3(a), the injection sleeve 30 is in a lower position with the block 29, where the plunger 28 is in the lower position relative to the sleeve. A predetermined amount of the melt 31 is contained in the melt space of the sleeve defined by the sleeve and the plunger, subsequent to the tilting of the sleeve for receiving the melt. The piston rod 42a is in a retired position, while the piston rod 43a is in a forward position, so that the shoulder 40a of the parting plate 40 abuts against the shoulder 23d of the lower stationary mold plate 23c. The piston rods 44a and 45a are in forward positions and urge the parting plates 42 and 43 against each other. In the above state, the block 29 is forced to rise so that the sleeve 30 is engaged with the sleeve hole 23a and the enlarged hole portions 37 and 38 of the clamped parting plates 42 and 43 and abuts against the clamped parting plates 42 and 43. Thereafter, the injection cylinder is driven to actuate the plunger 28 to inject the melt 31 into the cavity through the melt passage. At the final stage of the injection operation, the supplemental cylinder 32 is driven to actuate the piston rod 32b so that the rod 32b extends upward from the plunger tip 28a, thus completing the final injection of the melt, that is, pressurizing the melt against the clamped molds. After the melt is received in the melt space, a shell of the melt is formed at the inner surface of the melt space. This shell is prevented from rising by the circumferential edge of the constricted hole portion 39 of the clamped plates 40 and 41 and is compressed, with the result that the shell is deformed into the shape of a bellows fashion and does not enter the cavity. During the injection as shown in Fig. 3 (b), the melt causes the parting plates 40 and 41 to be thermally expanded due to the high thermal energy thereof, and thus the melt injection causes the clamped parting plates 40 and 41 to be subjected to a high pressure such as 1000 kg/cm² at the through-hole (37, 38, 39), thus forcing the clamped parting plates apart from each other. Such a parting phenomenon as above is prevented by the pressure exerted on the parting plates by the opposite piston rods 44a and 45a along the second line Y in cooperation with the clamping of the parting plates in the direction X. In connection with this prevention, the gating plate portions 40a and 41a are prevented from seizure with the guiding central hole portion 33 to be pressurized against the gating plate portions, and thus the slidability of the plates 40 and 41 in the central hole portion 33 is ensured. Further, parting of the clamped plates from each other at the through-hole (37, 38, 39) due to deformation of the plates is prevented. Still further, the shearing operation with the parting plates 40 and 41 is not affected, and entrance of some part of the solidified melt forming "flashes" between the clampled parting faces is prevented. After the melt in the cavity is solidified, the injection sleeve 30 is forced to descend, and then the piston rods 44a and 45a are retired and release the parting plates from the clamping pressure. At this stage, the right piston rod 42a is forced to move forward by about 15 mm, and concurrently, the left piston rod 43a is retired by the same stroke, so that the solidified melt is sheared at a position between the lower end of the runner hole 46 and the constricted hole portion 39 of the clamped parting plates 40 and 41 as shown in Fig. 3(c). In this shearing operation, the parting plates 40 and 41 are released from the pressure exerted by the piston rods 44a and 45a and thus a smooth shearing operation is attained. Prior to opening of the molds, the piston rod 42a is forced to move back by a stroke of 15 mm, that is, to the retired position from the position as shown in Fig. 3(c). Concurrently, the opposing piston rod 43a is forced to move back in the opposite direction by a stroke of 15 mm, from the piston as shown in Fig. 3(c). As a result, the parting plates 40 and 41 are allowed to part by 30 mm, as shown in Fig. 3(d), and this parting operation causes a bisket 47, that is a lower portion of the solidified melt sheared off from the runner of the solidified melt is removable from the parting plates 40 and 41, so that the bisket 47 can drop out of the stationary mold 23. In such a removing operation as above, preferably a supporting rod 47a, as shown by phantom lines in Fig. 3(d), supports the bisket 47 from below, when the parting plates 40 and 41 are forced to move in opposite directions. This supporting means prevents the bisket 47 from accompanying the moving parting plates, and thus removal of the bisket 47 from the parting plates is assured even if adhesion of the bisket with the parting plates is high. Figure 3(e) shows the bisket 47 dropping out of the mold 23. After the removal of the bisket 47, the parting plate 40 is forced by the piston rod 43a to return to the forward position by the maximum stroke of 30 mm for a subsequent injection, while the other parting plate 41 remains in the retired position at which the shoulder 41c of the plate 41 abuts against the lower plate 23c of the stationary mold 23 at the shoulder 23d and 40c thereof, as shown in Fig. 2 and Fig. 3(e). Thereafter, as shown in Fig. 3(f), the movable platen 22 is raised to part the molds 23 and 24 from each other, while a molded product 48 is held by the movable mold 24 and the cores 25 and 26. The cores 25 and 26 are then removed from the product 48, and the product is removed from the movable mold 24 by projecting ejector pins provided in the movable mold (not shown) moving from the inner surface thereof against the product. The removed product is transferred out of the system by a product take-out apparatus (not shown) having an arm for carrying the product. One cycle of the injection is completed after the operation of taking out the product and the mold clamping operation. The obtained product has a runner 49, and this runner 49 is cut off by using a lathe having a cutting tool. Alternatively, the runner 49 is notched and then broken away from the product 48 at the notch by, for example, a punch. The above embodiment of the present invention is directed to a vertical clamping and vertical casting type machine of a single unit. In practice, however, it is preferable to apply the present invention for a rotary type die casting machine having a rotary table provided with a plurality of mold clamping units, each including a mold arrangement having molds such as the above mentioned molds 23, 24, 25 and 26, which mold clamping units are arranged at respective equiangular positions along a periphery of the rotary table. Separate stations provided with a unit for die casting, a unit for taking out a mold product, and a unit for mold spraying are also arranged along the periphery of the rotary table. The mold clamping units are forced to move around the stations intermittently so that each station unit cooperates with the mold clamping unit at that station, to thereby carry out die-casting, shearing the bisket 47, taking out a molded product, mold-­ spraying, and other operations necessary to carry out one cycle during one rotation of the rotary table. Another embodiment of the present invention, directed to a vertical die casting machine, is shown in Fig. 4, wherein members or elements of this machine corresponding to those of the above-mentioned machine as shown in Figs. 1 to 3 are denoted by the same reference numerals, respectively. In comparison with the first embodied machine, this second embodied machine is characterized in that a cavity 27′ defined by a stationary mold 23, a movable mold 24, and cores 25 and 26 has a reverse configuration to that of the first machine. That is, a runner hole 46 communicates with the cavity 27′ on the lower side thereof 23d, where a decorative surface of an aluminium wheel product is formed. Contrary to this, according to the first machine as shown in Fig. 1, such a decorative surface of the wheel product is formed at the upper side of the cavity 27, at which the runner hole 46 does not open. Generally speaking, in the reversed mold arrangement as shown in Fig. 4, a degree of freedom in designing a decorative surface of the wheel product is reduced relative to the other mold arrangement, since a cavity has a decorative surface on the runner hole side and thus the runner hole occupies a substantial area in the decorative surface. The reversed mold arrangement for the wheel as shown in Fig. 4, however, has an advantage in that the runner hole 46 has a shorten length than that of the first machine shown in Figs. 1 to 3, and thus the reversed mold arrangement for the wheel product is economical in the light of the fact that the cast runner of aluminium must be removed from the final product. Further, the shorter runner hole causes the cast product to have a reduced amount of air accompanying the injected melt, resulting in the production of a high quality aluminium wheel. The parting plates 40 and 41 as shown in Figs. 1 and 4 must be used for shearing the runner. In marked contrast in the following embodiment as shown in Fig. 5, these parting plates are used only for constricting a melt passage through which the melt is injected into a cavity. Figure 5 illustrates an vertical die casting machine of a vertically clamping type incorporated with a mold arrangement having an enlarged runner hole therein having a diameter not less than that of the sleeve, as that used in the conventional machine of the vertically clamping type. In the figure, the same reference numerals as those of the above-mentioned first and second machines shown in Figs. 1 to 4 denote the substantially the same numbers or elements of the machines. Referring to Fig. 5, a parting plate 40A and another parting plate 41A are connected to piston rods 42a and 43a of hydraulic piston-cylinders 42A and 43A, respectively. The parting plates are forced to move in opposite directions by the cylinders 42A and 43A. The strokes of the piston rods 42a and 43a are larger than in the above-mentioned first and second machines. When the parting plates are clamped at the forward positions of the opposite piston rods 42a and 43a, the melt passage is constricted to have a reduced diameter of D₁ by the clamped parting plates. When the piston rods are in the respective retired positions, the diameter of the melt passage defined by the released parting plates is the same as or not less than that D₂ of the internal diameter of the injection sleeve 30. A pair of hydraulic piston-cylinders 44 and 45 are provided for actuating one of the piston rods 44a and 45a to urge the parting plates against the other piston rod, as in the machine shown in Fig. 2 A plunger 28 is forced to move upward to inject the melt into the cavity through the constricted melt passage at the initial injection stage. During this injection operation, the shell of the melt formed at the circumferential inner surface of the sleeve 30 is forced to move upward by the plunger tip 28a, but is prevented from entering the cavity 27′, communicating a runner hole 46′ which has a same diameter not less than that D₂ of the sleeve, by the clamped parting plates 40A and 41A. This causes the shell to be compressed and deformed to a bellows shape. A supplemental hydraulic piston-cylinder 32 is preferably provided in the sleeve 30 as that in the first machine in Fig. 1 for actuating a piston rod 32b in a cylinder 32a to carry out the final stage injection to the effect that the melt filled in the cavity 27′ by the initial stage injection is to be subjected to an increased pressure, while the parting plates 40 A and 41 A are clamped to form the constricted part of the melt passage between the sleeve 30 and the upper plate 23 b of the stationary mold 23. The provision of the supplemental piston-cylinder 32 is preferable for the following reason: The deformed shell of the bellows shape would be likely to prevent the piston rod 28a from moving upward at the end of the final injection stage, so long as the plunge 28 were used as in the conventional machine for carrying out the final stage injection in the machine. In turn the supplemental piston rod 32b, if provided, is not affected for an upward movement, since the diameter of the rod 28a is smaller than that of the deformed shell, and thus ensures a complete pressurizing operation against the injected melt. After completion of the two stage operation, the piston rods 44a and 45a are moved back to the retired positions to release the parting plates 40A and 41A from the clamping state, and then the piston rods 42a and 43a are actuated and moved back to the respective retired positions, so that the parting plates 40A and 41A are separated, At this stage, the bisket of the solidified melt below and integrated with the constricted melt runner is allowed to move upward over the removed parting plates. The molded product having the runner and the bisket is then elevated with the movable mold 24 and finally taken out from the machine. The bisket is removed from the molded product by breaking the runner at the part thereof constricted by the clamped parting plates, by using a hammer. In the above three embodiments, the means for preventing the clamped parting plates 40 or 40A and 41 or 41A from moving along the second line Y is comprised by the pair of piston-cylinders 44 and 45. This means may consist of a stationary stopper on one side, in place of the piston-cylinder 45, and an piston-cylinder on the other side, corresponding to the cylinder 44, so that the single piston-cylinder is driven to urge the parting plates 40 and 41 against the stationary stopper. With a mold arrangement having an enlarged runner hole as shown in Fig. 5, the injection sleeve may be a combination of separate lower and upper parts, unlike the sleeve having an integral body as shown in Fig. 1. The lower part of the sleeve is mounted on the injection piston-cylinder for actuating the plunger, while the upper part is mounted in the stationary platen. The lower movable part of the sleeve abuts against the upper stationary part from below during the injection oper­ ation, to enable communication therebetween. Preferably, the stationary upper part of the sleeve has a circumferential groove formed at an internal surface thereof at the upper end of the stationary upper sleeve part so as to enlarge the sleeve hollow at the top end thereof. The deformed shell may be received by the circumferential groove during the initial stage of the injection and thus the final stage injection is not affected by the shell. With respect to the diameter D₁ of the through-hole defined by the clamped parting plates relative to that D₂ of the sleeve, a difference in the diameter between the through-hole and the sleeve is preferably 5 to 20 mm. Three or more parting plates may be provided, as long as they are designed so that they can be clamped to define a through-hole having a predetermined diameter. In summary, the first and second vertical die casting machines as shown in Fig. 1 and Fig. 4 are incorporated with mold arrangements, each defining a cavity having a narrow runner hole 46 of which diameter is smaller than that of the injection sleeve 30. The mold arrangement preferably requires the supplemental piston-cylinder 32, but absolutely required is means for shearing a small runner formed in the runner hole 46 to separate a bisket 47 of the solidified melt having the same diameter as that of the sleeve 30 from a cast product formed in the cavity. This is because the bisket, otherwise, prevents the cast product from being removed from the mold arrangement. The mold arrangement having the narrow runner hole 46 is advantageous in that it allows the cast product to have a large surface area where contoured decorations can be formed by the die casting, so long as a decorative surface of the cavity has such narrow runner hole 46. Further, the narrow runner hole 46 is advantageous in that it prevents the shell of the melt formed in the sleeve 30 in cooperation with the shearing means comprising the constricting parting plates 40 and 41, from being forced to enter the cavity. Otherwise, the shell is likely to enter the cavity, reducing the quality of the cast product. Still further, the design of such narrow runner hole is advantageous in saving a substantial amount of the melt solidified in the runner hole, compared with the enlarged runner hole. With the mold arrangement, as shown in Fig. 5, defining a cavity having an enlarged runner hole 46′ having a diameter the same as or not less than that of the sleeve, no problem arises in removing a cast product from the cavity, since a bisket of the solidified melt formed in the sleeve 30 is allowed to pass freely through the runner hole 46, and thus there is no need to separate the bisket from the cast product when the product is taken out of the mold arrangement. The parting plate means for constricting the melt passage including the head hollow portion of the sleeve 30 and the enlarged runner hole 46′ must prevent the shell from intruding into the cavity during the first stage of the injection. However, the above constricting means is not required to shear the solidified melt runner, unlike the narrow runner hole case, but is required to actuate the pair of the parting plates 40A and 41A so that they are separated, to thereby allow the solidified melt as a whole in the cavity and the melt passage to be upwardly removed from the stationary mold through the separated parting plates. The above function of the constricting means is desirable, because the most rational and economical operation for removing the melt solidified in the melt passage from a final molded product resides in that such removal is carried out after the stationary and movable molds are separated from each other. If the solidified melt runner were sheared, the lower part of the melt, i.e., the "bisket", would remain in the sleeve 30, and thus an additional operation to take out the bisket from the sleeve would be required, or alternative­ ly means or operations for avoiding dropping of the bisket into the sleeve is required. The present invention is not limited to the above mentioned embodiments directed to die casting machine for producing aluminium wheels for use in motor cars, but can be applied for producing other products not only of metal materials but also of plastic materials.

Claims: 1. In a vertical die casting machine of a verti­ cally clamping type comprising: stationary and movable platens; a mold arrangement including lower stationary and upper movable molds which are clamped between said platens to define a die cavity; a casting sleeve; a plunger slidably disposed in said casting sleeve, said plunger having a plunger tip at the upper end thereof, which tip together with said sleeve defines a melt space wherein a melt is received for an upward injection of the melt by said plunger into said cavity through a melt passage, said melt passage being freely defined between said cavity and the surface of the melt received in said melt space; a hydraulic piston-cylinder having said sleeve for actuating said plunger therein, improvements comprising means provided for constricting said melt passage, said constricting means comprising at least two movable flat parting plates disposed between said sleeve and said stationary mold or in said stationary mold, each of said parting plates having a groove forming a semi-circle at the parting face thereof, said parting plates being clamped, when the melt is injected, to define a vertically extending through-hole formed by said semi-circular grooves, said through-hole having a cross sectional area at the upper end thereof smaller than that at the upper end of said sleeve, the upper end of said sleeve being in contact with said parting plates from below during the injection operation. 2. A vertical die casting machine according to claim 1, wherein said constricting means comprises a first pair of hydraulic piston-cylinders for actuating said parting plates horizontally along said first line. 3. A vertical die casting machine according to claim 2, wherein said parting plates are allowed to move along a first line on a horizontal plane, and means is provided for preventing said parting plates, when clamped, from being forced to move horizontally along a second line along the parting line of said clamped parting plates and perpendicular to said first line by a force caused by an injection of said melt. 4. A vertical die casting machine according to claim 3, wherein said preventing means comprises a second pair of a piston-cylinders for actuating opposing piston rods extending along said second line, one of said pistons urging said clamped parting plates at the side faces thereof on one side against said other piston at the other side faces of said parting plates along said second line during the injection operation. 5. A vertical die casting machine according to claim 4, wherein said parting plates having converse T-shaped rectangular forms which in the clamped state are made symmetrical about said first and second lines in such a manner that each parting plate has a flat parting face along said second line, where said semi-­ circular groove is formed. 6. A vertical die casting machine according to any one of claims 1 to 5, wherein said first pair of piston-cylinders are provided for driving said parting plates to move in a direction along said first line together in a clamped state against a melt solidified in said melt passage, to thereby shear the melt solidified after completion of the injection into two pieces at said through-hole. 7. A vertical die casting machine according to claim 6, wherein said melt passage has a part defined by a runner hole formed in said stationary mold and communi­ cating said cavity with said through-hole defined by said clamped parting plates, said runner hole having a diameter at the lower end thereof not larger than that of said through-hole at the upper end thereof and that of said sleeve. 8. A vertical die casting machine according to claim 7, wherein said plunger is provided with a supple­ mental piston-cylinder therein for axially actuating a supplemental piston rod having a diameter smaller than that of said plunger tip, said plunger being actuated during the injection operation at the initial stage thereof so that the cavity is filled with the melt and said supplemental piston rod being actuated during the injection operation at the final stage thereof, so that the melt in the cavity is subjected to an increased pressure. 9. A vertical die casting machine according to claim 8, wherein said sleeve is an integral body, and said stationary mold comprises upper and lower mold plates forming a space therebetween, said parting plates being slidably disposed in said space, said lower mold plate having a vertically extending through-hole in which the upper end portion of said sleeve is receivable, said through-hole formed in said clamped parting plates having a lower enlarged portion and an upper constricted portion, the upper end of said sleeve abutting against said clamped parting plates from below in such a manner that said upper end portion of said sleeve is received in said lower enlarged portion during the injection operation, and said sleeve being removed downwards from said clamped parting plates during the shearing operation for the solidified melt. 10. A vertical die casting machine according to any one of claims 1 to 5, wherein said melt passage has a part defined by a runner hole formed in said stationary mold and communicating said cavity with said through-hole defined by said clamped parting plates, said runner hole having a diameter not less than that of said injection sleeve, said first pair of piston-cylinder being provided for driving said parting plates to move in opposite di­ rections to separate said parting plates from each other to thereby allow a solidified melt as a whole in said cavity and said melt passage to be upwardly removed from said stationary mold through said separate parting plates. 11. A vertical die casting machine according to to claim 10, wherein said plunger is provided with a supplemental piston-cylinder therein for axially actuating a supplemental piston rod having a diameter smaller than that of said plunger tip, said injection piston-cylinder being provided for carrying out an initial stage injection whereby the cavity is filled with the melt, said supplemental piston-cylinder being driven for carrying out the final stage injection whereby the melt received in the cavity is subjected to an increased pressure, while said parting plates are clamped to form said through-hole constricting said melt passage. 12. A vertical die casting machine according to claim 11, wherein said sleeve is a combination of separate lower and upper parts, said upper part being mounted in said stationary platen, said lower part being provided with said plunger therein and abutting against said upper part from below during the injection operation to communicate with each other. 13. A vertical die casting machine of a vertically clamping type provided with a hydraulic piston-cylinder to actuate movable parting plates disposed between an injection sleeve and a stationary mold for constricting a melt passage including a runner hole formed in the stationary mold and a hollow end portion of the sleeve by an axial through-hole formed by the parting plates in a clamped state, the parting plates being arranged to prevent a semi-solidified part of the melt "shell" formed in the sleeve before an injection operation from intruding into a mold cavity with the other hot melt part. 14. A machine according to claim 13 in which the narrow runner hole has a diameter smaller than that of the sleeve, the parting plates are arranged to be actuated to move in a clamped state in a direction to thereby shear a cold melt runner so that a molded product is allowed to move upward from the stationary mold with the runner separated from a cold melt bisket formed in the sleeve, but integral with the product. 15. A machine according to claim 13, in which the runner hole has a diameter not less than that of the sleeve, the parting plates are arranged to be actuated to separate from each other to thereby allow the bisket integral with the runner to move upward from the stationary mold through the enlarged runner hole with the mold product integral with the runner.

Inventors: DANNOURA, SADAYUKI UBE IND.LTD. UBEKIKAISEISAKUSHO, UCHIDA, MASASHI UBE IND., LTD. UBEKIKAISEISAKUSHO, UENO, TOYOAKI UBE IND., LTD. UBEKIKAISEISAKUSHO
Applicants: UBE INDUSTRIES, LTD.
Application year: 1987
Main classification: B22D17
IPC codes: B22D17