Cooling device and die-casting piston having a cooling device

Abstract

The invention relates to a cooling device (5) for a die-casting piston (1), comprising a main part (2) which can be secured to a piston rod. The cooling device (5) comprises a cooling element (51) having a melt-side circular end face (52), and cooling channels (53) are provided in the cooling element (51) at a depth of at least 18% to 25% of the diameter of the end face (52) starting from the melt-side end face (52).

Description

[0001] Wieland-Werke AG

[0002] Description

[0003] Cooling device and die casting piston with a cooling device

[0004] The invention relates to a cooling device according to the preamble of claim 1 and a die-casting piston with a cooling device according to the invention according to the preamble of claim 9.

[0005] From the publication DE 10 2011 052 446 A1, a die-cast piston head for light metal die casting is known, which comprises a one-piece piston head made of copper or a copper alloy and a closed wear ring arranged on the piston head and made of a harder material than that of the piston head. The wear ring is arranged in the area between the end face and the outer surface of the piston head. In order to provide a die-cast piston head with an extended service life and ease of maintenance, it is proposed that the wear ring have a radially inward-facing web on its radially inward-facing edge facing the end face. This web forms a barrier to protect the joint between the piston head and the wear ring against penetration of the molten metal, since the extension and multiple deflection according to the invention cause the metal penetrating the joint to solidify early near the end face.The piston head consists of an alloy essentially comprising copper, nickel, chromium, and silicon, or of an alloy essentially comprising copper, cobalt, nickel, and beryllium. Such alloys are highly thermally conductive and wear-resistant. Also known from the document DE 44 41 735 A1 is a die-casting piston with a support part that can be attached to a piston rod, with devices for supplying coolant, and a sliding body that can be attached to the support part, with the outer surface of which the piston slides along in a filling chamber of a die-casting machine. A ring made of a harder material than the sliding body is arranged between the end face of the piston and the end face of the sliding body. The end face of the piston is formed in the center by an insert made of a material with good thermal conductivity, for example, copper. The insert is in contact with the piston's coolant on its inner surface.

[0006] Furthermore, DE 10 2013 017 261 A1 discloses a die-casting piston with a base body that can be attached to a piston rod and has a melt-side end face, on whose outer surface at least one hollow cylindrical sliding body and optionally a stripping element can be mounted. A closed end ring is arranged between the end face of the base body and the end face of the sliding body, wherein the closed end ring can be mounted and secured axially over the end face of the base body on the outer surface of the base body. The closed end ring serves as the first end-face retaining element for the hollow cylindrical sliding body and the stripping element.

[0007] The first retaining element, a ring made of a harder material than the sliding body, is arranged between the end face of the base body and the end face of the sliding body. This makes it possible to manufacture the sliding body from a softer, more gliding material, such as copper or a copper alloy. The base body, on the other hand, can be made of steel or copper. A copper base body offers advantages in terms of die-casting machine cycle times due to its better heat dissipation, especially for aluminum die casting.

[0008] Also known from EP 3 388 167 A1 is a die-casting piston having a receiving unit attachable to a piston rod, comprising a cooling device and a connecting device for the piston rod, and having a cup-shaped, hollow-cylindrical support body with a melt-side end face. At least one hollow-cylindrical sliding body can be mounted on the outer surface of the support body, with a preferably closed end ring being arranged between the end face of the support body and an end face of the sliding body. The end ring serves as a first end-face holding element for the at least one hollow-cylindrical sliding body. The support body can be made of copper or a copper alloy. A support body made of copper offers advantages with regard to the cycle times of the die-casting machine due to its better heat dissipation capacity, particularly in aluminum die casting.The end face of the support body, where the temperature is highest during operation, is where the piston's end face cooling is particularly effective. The cooling system can be designed there to effectively dissipate the heat introduced by the molten metal through the piston's end face.

[0009] From the publication DE 199 38 076 A1, a press piston for cold-chamber die-casting machines is known, which has a piston head and a piston rod firmly connected to the piston head. As part of the piston head, a sleeve extending as far as the piston rod is designed such that a cooling system with a plurality of cooling channels is formed between the sleeve and the interior of the piston head. A flat head plate is arranged on the front side of the sleeve and is fixed from the front to the front side of the piston head by means of screws. The head plate rests flatly on the front end of the sleeve, whereby the front side of the press piston also forms a counterbearing for absorbing the forces during pressing.

[0010] The invention is based on the object of developing a cooling device for a die-cast piston with regard to good heat dissipation.

[0011] The invention is characterized by the features of the

[0012] Claim 1 and, with respect to a die-cast piston, by the features of claim 9. The further dependent claims relate to advantageous developments and refinements of the invention.

[0013] The invention includes a cooling device for a die-casting piston with a base body attachable to a piston rod, comprising a cooling element with a circular end face on the melt side. Cooling channels are arranged in the cooling element, starting from the melt side end face, at a depth of at least 18% to 25% of the diameter of the end face. The end face of the cooling element is thus sufficiently thick so that no thermal cracks occur in the material during operation due to temperature and pressure influences.

[0014] Preferably, cooling channels can be arranged in the cooling element, starting from the melt-side end face, at a depth of at least 20% to 25% of the diameter of the end face. The end face of the cooling element is thus designed to be particularly thick, so that no thermal cracks occur in the material during operation due to temperature and pressure influences.

[0015] The cooling element with the cooling channels can preferably be in one piece and can be replaced as an independent component of the cooling device.

[0016] The invention is based on the idea that the cooling element is constructed from a solid material with good to excellent heat conductivity in front of the cooling channels arranged at a certain depth, i.e., between the front contact surface facing the melt and the cooling channels. This solid head area is designed to reliably absorb the force load acting on the front face of a die-casting piston during the casting process. This requires a certain wall thickness of solid material on the front face before the internal cooling channels serving for cooling are arranged.

[0017] A particular advantage of the cooling element is its dual function: on the one hand, it optimally directs the cooling fluid to the parts of the piston that are most exposed to heat during the casting process for heat dissipation, and on the other hand, its solid front area provides sufficient stability for force absorption and force dissipation.

[0018] In a preferred embodiment of the invention, the cooling channels can be connected to a cooling device on the piston rod. This connection can be fixed or detachable and allows the supply and removal of the cooling fluid via the piston rod to a typically separate control and supply unit.

[0019] Advantageously, the cooling element can have a thermal conductivity of at least 200 W / mK, extending from the melt-side end face to the depth of the cooling channels. This allows a suitable material to be used, starting from the end face, which quickly dissipates the heat introduced into the die-cast piston via the end face to the cooling channels.

[0020] Advantageously, the cooling element can be made of copper or a copper alloy. With this type of cooling element design, thermal conductivities of up to 400 W / mK can be achieved. Such high thermal conductivities ensure particularly efficient heat dissipation via the cooling channels.

[0021] In an advantageous embodiment of the invention, several cooling channels can extend radially outward from a central supply channel. The cooling channels can fan out radially outward from a supply channel near the axis and be directed away from the end face near the outer circumference of the cooling element. At a sufficient distance from the end face, the cooling channels can then be reunited in a discharge channel.

[0022] In an advantageous embodiment of the invention, the cooling channels can extend outward at an angle of at least 10° away from the end face. This continuously increases the stability of the cooling element for absorbing force radially outward. In this radially outer region, heat dissipation also takes place via the base body of the die-casting piston, so the cooling channels can be slightly relocated there.

[0023] Advantageously, a temperature measuring unit can be arranged in the cooling element. Using a temperature measurement, the heat input of the die-casting piston can be measured and used to regulate the amount of cooling fluid in the cooling element.

[0024] A further aspect of the invention includes a die-casting piston with a base body that can be attached to a piston rod,

[0025] - with a melt-side end face and a lateral surface on which at least one sliding body can be mounted

[0026] - with a connection device for the piston rod, and

[0027] - with a cooling device.

[0028] A receiving space is provided on the front side of the base body. A cooling element of the cooling device according to the invention can be mounted in the receiving space.

[0029] This aspect of the invention is based on the idea that the cooling element represents a separate and replaceable element of the cooling system of the die-casting piston. With a solid head area, it is designed to reliably absorb the force load acting on the end face of a die-casting piston during the casting process, and the internal cooling channels used for cooling are advantageously recessed. The replaceability of a cooling element therefore allows the cooling performance of the die-casting piston to be adjusted in practice according to the process conditions.

[0030] In an advantageous embodiment of the invention, the cooling element can be mounted axially in the receiving space from the melt-side end face of the base body. The front of a die-cast piston is an easily accessible area. To replace a cooling element on the front, the die-cast piston does not have to be removed from the piston rod.

[0031] Advantageously, the cooling element of the cooling device can be secured and removed again in the final position in the receiving space. Reliable holding devices can be fixed screw connections or positive locking devices, such as bayonet locks.

[0032] Embodiments of the invention are explained in more detail with reference to the schematic drawings.

[0033] Showing:

[0034] Fig. 1 is an axial longitudinal section through a die-casting piston with a cooling device according to the invention,

[0035] Fig. 2 an axial longitudinal section through a base body of a die-casting piston,

[0036] Fig. 3 is an axial longitudinal section through a die-casting piston with a further embodiment of the cooling device, and

[0037] Fig. 4 shows a partial axial longitudinal section through a die-casting piston with a temperature measuring unit in the cooling device. Corresponding parts are provided with the same reference numerals in all figures.

[0038] Fig. 1 schematically shows an axial longitudinal section along the piston longitudinal axis A through a die casting piston 1 with a cooling device 5 according to the invention. The die casting piston 1 has a base body 2 which is cup-shaped. A cooling device 5 with a cooling element 51 is arranged in the cup-shaped recess in the die casting piston 1. In the cooling element 51, starting from the melt-side end face 52, in the present embodiment, cooling channels 53 are arranged at a depth of approximately 18% of the diameter D of the end face 52. The cooling channels 53 run radially outward and are supplied with cooling fluid from a central supply channel 54. In this way, the cooling channels 53 fan out in a radial direction from a supply channel 54 near the axis. Close to the outer circumference of the cooling element 51, the cooling channels 53 are then centrally reunited in a discharge channel 55 at a sufficient distance from the end face 52.In the further course, the fluid is passed on via the connection device 24 of the die-casting piston 1 into the piston rod, not shown in Fig. 1.

[0039] On the outer contour of the die-casting piston 1, sliding bushings (not shown in Figure 1) can be arranged as hollow cylindrical sliding elements on the outer surface 22 of the base body 2. The melt-side end face 52 of the cooling device 5, which represents the contact surface with the molten metal during the casting process, is flat in this case and flush with the melt-side end face 21 of the base body 2.

[0040] Fig. 2 shows an axial longitudinal section through a base body 2 of a die-casting piston. The base body 2 has a cylindrical receiving space 23 into which the cooling device can be inserted until it is flush with the melt-side end face 21 of the base body 2. The base body 2 is therefore designed as a hollow cylinder with a suitable wall thickness, the outer surface 22 of which can also support hollow-cylindrical sliding elements. The area of ​​the base body 2 facing away from the molten metal is designed to be more solid toward the piston rod as a connecting device 24.

[0041] Fig. 3 shows an axial longitudinal section through a die-casting piston 1 with a further embodiment of the cooling device 5. In this advantageous embodiment, the cooling channels 53 are arranged at an angle of approximately 15°, extending outwardly away from the melt-side end face 52. This further increases the stability of the cooling element 51 for absorbing forces radially outward.

[0042] The cooling device 5 is connected to the base body 2 by screws 7 as fixing elements. These screws 7 are covered by a retaining ring 33, which holds the sliding bushings 3 on the lateral surface 22 at the rear of the base body 2.

[0043] Fig. 4 shows a partial view of an axial longitudinal section through a die-casting piston 1, showing a temperature measuring unit 6 in the cooling device 5. The temperature measuring unit 6 is inserted into the cooling element 51 from the rear side. The measuring tip 61 is arranged as close as possible to the melt-side end face 52. The measuring tip 61 is also positioned at a suitable distance from the central supply channel 54 and the cooling channels, so that the heat input into the die-casting piston 1 and the cooling capacity of the cooling device 5 can be reliably measured for a control unit. List of Reference Symbols

[0044] 1 die-casting piston

[0045] 2 basic bodies

[0046] 21 melt-side end face of the base body

[0047] 22 lateral surface

[0048] 23 Recording room

[0049] 24 connection device

[0050] 3 sliding bushings

[0051] 31 hollow cylindrical sliding body

[0052] 32 forehead ring

[0053] 33 Retaining ring

[0054] 4 retaining sleeve

[0055] 5 Cooling device

[0056] 51 Cooling element

[0057] 52 melt-side end face cooling element

[0058] 53 Cooling channel

[0059] 54 central supply channel

[0060] 55 discharge channel

[0061] 6 Temperature measuring unit

[0062] 61 measuring tip

[0063] 7 Fixing element, screw

[0064] A Piston longitudinal axis

[0065] D Diameter of the front surface of the cooling element

Claims

Patent claims 1. Cooling device (5) - for a die-casting piston (1) with a base body (2) which can be fastened to a piston rod - comprising a cooling element (51) with a melt-side circular end face (52), characterized in that - cooling channels (53) are arranged in the cooling element (51), starting from the melt-side end face (52), at a depth of at least 18% to 25% of the diameter of the end face (52).

2. Cooling device (5) according to claim 1, characterized in that cooling channels (53) are arranged in the cooling element (51), starting from the melt-side end face (52), at a depth of at least 20% to 25% of the diameter of the end face (52).

3. Cooling device (5) according to claim 1 or 2, characterized in that the cooling channels (53) can be connected to a cooling device of the piston rod.

4. Cooling device (5) according to one of claims 1 to 3, characterized in that starting from the melt-side end face (52) to the depth of the cooling channels, the cooling element (51) has a thermal conductivity of at least 200 W / mK.

5. Cooling device (5) according to one of claims 1 to 4, characterized in that the cooling element (51) consists of copper or a copper alloy.

6. Cooling device (5) according to one of claims 1 to 5, characterized in that a plurality of cooling channels (53) extend radially outwards from a central supply channel (54).

7. Cooling device (5) according to one of claims 1 to 6, characterized in that the cooling channels (53) extend outwards at an angle of at least 10° away from the end face (52).

8. Cooling device (5) according to one of claims 1 to 7, characterized in that a temperature measuring unit (6) is arranged in the cooling element (51).

9. Die-casting piston (1) with a base body (2) that can be attached to a piston rod - with a melt-side end face (21) and a lateral surface (22) on which at least one sliding body (3, 31, 32) can be mounted - with a connecting device (24) for the piston rod, and - with a cooling device (5), characterized in that - a receiving space (23) is formed on the front side of the base body (2), and - a cooling element (51) of the cooling device (5) according to one of claims 1 to 7 can be mounted in the receiving space (23).

10. Die-casting piston (1) according to claim 9, characterized in that the cooling element (51) can be mounted axially from the melt-side end face (21) of the base body (2) in the receiving space (23).

11. Die-casting piston (1) according to claim 9 or 10, characterized in that the cooling element (51) of the cooling device (5) can be fastened and released again in the final position in the receiving space (23).

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