DE102019107235B4 - Reflow unit for a molding machine and molding machine with such - Google Patents

Abstract

Melting unit for a shaping machine, with a discharge device (8), which discharge device (8) is designed to discharge a material melted in a melting chamber (4) from the melting chamber (4), at least one seal (11) being provided to Sealing off the dispensing device (8) from a component surrounding the dispensing device (8), characterized in that the at least one seal (11) has at least one cavity (20), it being possible for the pressure prevailing in the at least one cavity (20) to be influenced by a filling medium and- directly on the dispensing device (8) and the dispensing device (8) surrounding component.

Description

The present invention relates to a melting unit for a shaping machine with the features of the preamble of claim 1 and a shaping machine with such a melting unit.

Shaping machines can be understood as meaning die-casting machines, transfer presses, injection molding machines, vacuum pressure-casting machines or the like. The state of the art is presented below using a die-casting machine. The same applies to general shaping machines.

Generic shaping machines have a discharge device which is designed to discharge a material that has been melted in a melting chamber from the melting chamber, with at least one seal being provided to seal the discharge device from a component surrounding the discharge device.

With certain die-casting machines, it is common to introduce at least one (raw) material in the form of an ingot into the melting chamber. This ingot contains the desired amount of the material to be processed and is also referred to as an ingot.

As soon as the melting chamber has been loaded, the (raw) material is melted by the melting unit. In certain die-casting machines, an induction coil is used, which causes the material to melt through induction.

Depending on requirements, the ambient air can be extracted from the melting chamber by a vacuum pump and the system can be partially or completely evacuated. Alternatively or additionally, the melting chamber can be flooded with a protective gas or flushed completely with protective gas. This evacuation and/or supply of protective gas prevents the melted material from reacting with the oxygen contained in the ambient air.

It is therefore desirable to be able to seal the melting chamber from the environment, for example in order to be able to prevent ambient air from flowing in, to be able to prevent the escape of protective gas and/or to prevent the escape of gases resulting from the melting of the material.

However, the process requires an ejection device by which the molten material can be ejected from the melting chamber and optionally (in the case of a die casting machine) injected into a mold cavity. Consequently, it is necessary to grant this discharge device access to the melting chamber and to seal this discharge device from the environment.

This discharge device can be realized by an injection piston, which can be guided into the melting chamber by a linear movement and can thus push the melted material out of the melting chamber.

The injection piston could be sealed off from the environment by bellows. However, the bellows has the major disadvantage that the internal volume is increased by the volume of the bellows and thus a space to be evacuated or a space to be flooded with protective gas is increased. Furthermore, the folds of the bellows and the associated projections in the interior result in major disadvantages in terms of flow when the interior is evacuated, because the evacuation time increases (which has a negative effect on a cycle time).
One embodiment is through the DE 40 02 263 A1 known, wherein the melting chamber, more precisely, a bore forming the melting chamber, is sealed off from a piston rod by means of a sealing element. This sealing element has two sealing rings and a dimensionally stable intermediate ring. The sealing rings are made of rubber and can be subjected to a compressive force due to the bevel of the contact surfaces between the sealing rings and the intermediate ring. This compressive force is exerted by means of a pressure sleeve, with the compression of the pressure element causing a radial expansion and sealing the sealing element.

A disadvantage of such an embodiment, however, is the high cost of production due to the many individual parts (two sealing rings, intermediate ring, pressure sleeve) of the seal. Furthermore, a very high force must always be applied through the pressure sleeve in order to deform the sealing rings, which means that there is also an increased space requirement in the longitudinal direction in order to provide the linear drive for the pressure sleeve, with sufficient space also being provided for the pressure sleeve.

A basic problem with generic shaping machines is that the at least one seal should be able to provide a good seal (in order to maintain the negative pressure or a protective gas) and at the same time achieve a long service life due to low wear.

The object of the invention is to provide a melting unit for a shaping machine and a shaping machine with such a melting unit, which has a sealing system with an improved sealing effect and/or a longer service life.

This object is achieved by a melting unit having the features of claim 1.
This is done by the at least one seal having at least one cavity, wherein a pressure prevailing in at least one cavity can be influenced by a filling medium and is in direct contact with the dispensing device and the component surrounding the dispensing device.

It can be provided that a contact pressure force of the seal can be increased by increasing the pressure prevailing in the at least one cavity.

By providing at least one cavity in the at least one seal, a cross-sectional expansion of the at least one seal can be influenced by influencing the pressure prevailing in the at least one cavity. It can thus be provided that a sealing factor can be influenced. In particular, this can greatly improve the sealing effect when it is necessary, while the wear at low pressure in the seal is greatly reduced. The latter allows greatly improved service life.

This configuration also forms a very compact design. Furthermore, such a configuration creates fewer flow obstacles, which have to be bypassed during evacuation, for example, which also results in a particularly favorable configuration in terms of flow technology.

Advantageous embodiments of the invention are defined in the dependent claims.

An evacuation device can preferably be provided, which evacuation device is designed to apply a negative pressure to at least the melting chamber. Provision can particularly preferably be made for the evacuation device to have a vacuum pump. In addition, for example, a piston chamber of a dispensing device and/or a discharge channel or the like can be evacuated.

It can be provided that the discharge device discharges melted material from the melting chamber by means of a linear movement, preferably by means of an injection piston. For example, an injection piston can be provided and the injection piston and/or a piston rod assigned to the injection piston can be sealed off from a piston chamber in which this injection piston and/or the assigned piston rod is guided by means of the at least one seal.

In an exemplary embodiment of the invention, it can be provided that at least one feed device—preferably comprising at least one feed line—is provided in order to supply the at least one cavity of the seal with a filling medium. Furthermore, it can be provided that this at least one feed device can be controlled or regulated, so that a pressure in the at least one cavity can be controlled or regulated, if necessary, in order to influence the pressing force of the seal on the components to be sealed. An expansion of the at least one seal can also be influenced by controlling or regulating the pressure.

It can be provided that the filling medium is air. This can result in the advantage that an already existing compressed air system can be used on the shaping machine. However, the use of fluid filling media, such as hydraulic oil, is also entirely conceivable.

Provision can preferably be made for the at least one seal to be formed from a rubber material—preferably from a type of rubber, perfluoro rubber, polyethylene and/or polytetrafluoroethylene. However, other materials known from the prior art for seals are also entirely conceivable.

Provision can preferably be made for the dispensing device to have an injection piston and/or a piston rod, with the injection piston and/or a piston rod being sealed off by the at least one seal.

For example, it can also be provided that the at least one seal is at least partially tubular.

At least one scraper can be provided between the at least one dispensing device and/or the component surrounding the dispensing device on the one hand and the at least one seal on the other hand. The at least one scraper can be arranged on a side of the seal facing away from the melting chamber and/or on a side of the seal facing the melting chamber. At least one wiper can significantly extend the service life of the at least one seal, by the at least one seal being protected from contamination by the at least one wiper.

At least one second seal (in addition to the at least one seal) can preferably be provided, with the at least one second seal sealing the dispensing device in relation to the component surrounding the dispensing device. The at least one second seal can be provided in order to increase a sealing effect of the at least one seal or to maintain a sealing effect with respect to the environment when, for example, a pressure in the cavity of the at least one (first) seal is reduced. The at least one second seal can also be designed according to the invention or according to an embodiment known from the prior art. A conventional seal (e.g., an O-ring) as the secondary seal can prevent very rapid flow or leakage into or out of the melt chamber when the at least one seal is not pressurized.

• - vorzugsweise durch die schlauchförmige Ausbildung der wenigstens einen Dichtung
• - das abzudichtendes Bauteil zumindest teilweise umgibt.

In a particularly preferred embodiment variant, it can be provided that only one cavity is provided, the cavity

• - Preferably by the tubular design of the at least one seal
• - At least partially surrounds the component to be sealed.

It can preferably be provided that the dispensing device—preferably comprising an injection piston—has a cylindrical, in particular circular-cylindrical, cross-sectional area of the outer wall.

Provision can furthermore be made for the at least one seal to be designed with a closed cross-section surrounding the dispensing device.

Protection is also sought for a shaping machine, preferably a vacuum pressure casting machine, with a melting unit according to the invention, in which case a cavity can preferably be provided, with melted material being able to be introduced from the melting chamber into the cavity for a shaping process by the discharge device.

• 1a ein Ausführungsbeispiel einer erfindungsgemäßen Aufschmelzeinheit,
• 1b einen Schnitt durch die Aufschmelzeinheit der 1a,
• 2 eine Detailansicht einer Eindüsvorrichtung,
• 3 a eine Detailansicht der Evakuierungsvorrichtung,
• 3 b die in 3a gekennzeichnete Schnittdarstellung und
• 4 eine Detailansicht einer Dichtung

Further advantages and details of the invention result from the figures and the associated description of the figures. show:

• 1a an embodiment of a melting unit according to the invention,
• 1b a section through the melting unit 1a ,
• 2 a detailed view of an injection device,
• 3 a a detailed view of the evacuation device,
• 3 b in the 3a marked sectional view and
• 4 a detailed view of a seal

1a shows an exemplary embodiment of a shaping machine in the area of a melting unit 1. This in 1a The melting unit 1 shown has a bearing housing 3 , the bearing housing 3 being equipped with cooling fins 2 . These cooling fins 2 allow heat generated when the melting unit 1 is used to be effectively dissipated.

By providing cooling fins 2 of a bearing housing 3, an existing cooling system of a melting unit 1 can be supplemented or improved. It can even be provided that, due to the cooling fins 2, individual or even all fluid cooling circuits (as known from the prior art), which work with a fluid cooling medium, can be dispensed with. It is also entirely conceivable for the cooling fins 2 of the melting unit 1 to be equipped with additional fans or ventilators in order to increase the efficiency of the heat dissipation through the cooling fins 2 .

1b shows a section through the melting unit 1a , so that the individual components of the melting unit 1 are better visible. These are to be explained in more detail below using a generally described process flow.

In a first step of the melting unit 1, the melting unit 1 is supplied with a material to be melted (also called an ingot 5). In the present exemplary embodiment, this load of ingot 5 is fed to the melting chamber 4 via a pick-and-place handling system via the discharge opening 9, with this discharge opening 9 being located on a side of the melting unit 1 facing the cavity.

The ingot 5 is deposited in the melting chamber 4 in the effective range of an induction coil 6 . For this purpose, the injection piston 7 is moved into a storage reference position and serves as a mechanical stop or as an additional positioning aid for the loading system. After depositing the ingot 5 in the melting chamber 4, the loading system moves out again.

In a next step, the melting chamber 4, in which the ingot 5 is located, is evacuated and/or flooded with an inert gas, so that the ingot 5, more precisely the melted material, does not come into contact with the ambient air (more precisely with the oxygen in the ambient air) reacts, whereby impurities (e.g. through the reaction of ferrous molten material with oxygen to form iron carbide) would arise.

Recesses 15 are provided in order to generate a relatively large flow cross section so that a negative pressure can be generated in a short time when the melting chamber 4 is evacuated.

In addition, air or gas is discharged from the melting chamber 4 via an annular gap 17 (annular gap fluid connection) between the injection plunger 7 and the melting chamber 4 . However, thanks to a large flow cross section, the recesses 15 allow much faster evacuation than just an annular gap 17.
Alternatively or additionally, a feed device can be provided which floods the melting chamber 4 with an inert gas.

In order to seal the melting chamber 4 from the environment, two seals 11 are provided in a rear area of the injection plunger 7, which seal the piston rod 13 of the injection plunger 7 from the bearing housing 3 (with regard to these seals 11, reference is made to the 4 referenced, which is a detailed view).

After introducing a protective gas and/or evacuating the melting chamber 4, the ingot 5 is inductively heated and melted via the induction coil 6.

After the ingot 5 has been melted, the injection plunger 7 is moved linearly in the direction of the discharge opening 9 by means of a linear drive, not shown, whereby the melted material is pushed out of the melting chamber 4 and, if necessary, injected into a cavity of the molding machine (not shown for reasons of clarity).

After the melted material has been discharged from the melting chamber 4, a finished workpiece can be removed from the cavity of a mold of the molding machine and the injection plunger 7 is retracted.

However, since the injection piston 7 does not always discharge all of the melted material from the melting chamber 4 (sometimes due to the annular gap 17), the injection piston 7 is brought into a (retracted) blow-out position, as a result of which an opening 10 in the melting chamber 4 is uncovered.

It is thus possible for the injection device 14 to blow a medium (compressed air in this exemplary embodiment) into the melting chamber 4 via the opening 10 and thus to blow out residues of the melted material from the melting chamber 4 via the discharge opening 9 .

After the blow-out is complete, the injection plunger 7 can be returned to a (as shown by 1b shown) filing reference position are moved and the cycle can begin again.

2 shows a detailed view of the injection device 14, it being easy to see how the injection piston 7 is moved into a retracted position by means of its piston rod 13, so that an opening 10 of the melting chamber 4 is uncovered. The melting chamber 4 is formed by the inner wall of the melting cylinder 16 .

In order to blow residues out of the melting chamber 4 , the injection device 14 can inject a medium into the melting chamber 4 , as a result of which residues from the melting chamber 4 are blown out of the melting chamber 4 via the discharge opening 9 .

These residues are characterized by high surface hardness and sharp burrs or edges. Because these residues are carried along with the injection plunger 7, there is increased wear between the injection plunger 7 and the inner wall of the melting cylinder 16 if these residues are not removed from the melting chamber 4. Consequently, the service life of the melting unit 1 suffers drastically.

Since the residues in the melting chamber 4 do not adhere, they can easily be removed via an injection device 14 and thus blown out. For this reason, the provision of a single compressed air nozzle directly on the melting chamber 4 on the bearing housing 3, which blows in compressed air, can already be sufficient. Of course, several compressed air nozzles can also be used.

3a shows a detailed view of the evacuation device 12 in the area of the suction opening 18, via which the evacuation device 12 builds up a negative pressure.

3b shows the in 3a labeled sectional view AA.

When a negative pressure builds up in the melting chamber 4 (and/or when the melting chamber 4 is flooded with an inert gas), ambient air is evacuated from the melting chamber 4 via the recess 15 and the annular channel 17, which forms between the injection plunger 7 and the inner wall of the melting cylinder 16 discharged and / or the melting chamber 4 is supplied with an inert gas.

The evacuation and/or the supply of protective gas is carried out either by an evacuation device 12 and/or a delivery device, which removes air or other gases via the suction opening 18 or supplies a protective gas. In order to accelerate this process of supplying or removing, the recesses 15 are provided, which greatly enlarge the cross section for evacuation or for supplying protective gas, for example compared to an embodiment with only one annular gap 17 .

By providing such recesses 15, the annular gap 17 can optionally also be dispensed with. In this exemplary embodiment, the recesses 15 are designed as grooves which are provided in the inner wall of the melting cylinder 16 .

Particularly favorable in this configuration 3a and 3b is that the recesses 15 are released only in a certain position of the injection piston 7 . When the injection piston 7 is moved linearly in the direction of the discharge opening 9 via the piston rod 13, the recesses 15 are covered, as a result of which the cross section for evacuation or delivery to the annular gap 17 is reduced. A subsequent flow of ambient air into the melting chamber 4 can thus be slowed down during the discharge cycle.

the 4 shows a detailed view of two structurally identical seals 11 , the bearing housing 3 being sealed off from the piston rod 13 by means of the seals 11 .

In this special exemplary embodiment, the seals 11 are designed with a tubular cross-section which bears against the piston rod 13 in the form of a ring. The seals 11 also have cavities 20 which are connected to a supply device for supplying compressed air via valve bodies 19 forming supply lines 21 .

The seals 11 are formed from an elastic rubber material, such as caoutchouc, polyethylene or polytetrafluoroethylene.

A pressure in the cavities 20 of the seals 11 can be influenced, more precisely even adjusted or regulated, by supplying or removing a filling medium (air in this exemplary embodiment), as a result of which a cross section of the seals 11 can be influenced.

Thus, by pressurizing the seals 11, more precisely the cavities 20 of the seals 11, the cross section of the seals 11 can be enlarged or reduced. The cross section of the seals 11 cannot increase due to the installation situation in the bearing housing 3, which leads to an increased contact pressure of the seal 11 on the piston rod 13 when the pressure in the cavity 20 increases.

Accordingly, a sealing factor by the seals 11 can be controlled or regulated by means of the feeding device, whereby higher sealing can be performed. If it is necessary (possibly with a movement of the piston rod 13) to reduce the sealing factor in order to avoid unnecessary wear of the seal 11 on the piston rod 13 by abrasion, the pressure in the cavities 20 of the seals 11 can be reduced.

Reference List

1

melting unit

2

cooling fins

3

bearing housing

4

melting chamber

5

ingot

6

induction coil

7

injection piston

8th

discharge device

9

discharge opening

10

Opening of the melting chamber

11

poetry

12

evacuation device

13

piston rod

14

injection device

15

recess

16

melting cylinder

17

annular gap

18

suction port

19

valve body

20

cavity

21

supply line

Claims (14)

Melting unit for a shaping machine, with a discharge device (8), which discharge device (8) is designed to discharge a material melted in a melting chamber (4) from the melting chamber (4), at least one seal (11) being provided to sealing the dispensing device (8) against a component surrounding the dispensing device (8), characterized in that the at least one seal (11) - has at least one cavity (20), it being possible for a pressure in the at least one cavity (20) to be influenced by a filling medium and - rests directly on the dispensing device (8) and the component surrounding the dispensing device (8). melting unit after claim 1 , characterized in that the at least one seal (11) is at least partially tubular. Melting unit according to at least one of the preceding claims, characterized in that the dispensing device (8) - preferably comprising an injection plunger (7) - has a cylindrical, in particular circular-cylindrical, cross-sectional area of the outer wall. Melting unit according to one of the preceding claims, characterized in that the at least one seal (11) surrounding the dispensing device (8) is designed with a closed cross-section. Melting unit according to at least one of the preceding claims, characterized in that at least one feed device - preferably comprising at least one feed line (22) - is provided in order to supply the at least one cavity (20) of the seal (11) with a filling medium. Melting unit according to at least one of the preceding claims, characterized in that at least one feed device - preferably comprising at least one feed line (22) - is provided in order to discharge a filling medium from the at least one cavity (20) of the seal (11). Melting unit according to at least one of the preceding claims, characterized in that air is provided as the filling medium. Melting unit according to at least one of the preceding claims, characterized in that the at least one seal (11) is made of a rubber material - preferably of a rubber type, perfluoro rubber, polyethylene and/or polytetrafluoroethylene. Melting unit according to at least one of the preceding claims, characterized in that a pressing force of the seal (11) can be increased by increasing the pressure prevailing in the at least one cavity (20). Melting unit according to at least one of the preceding claims, characterized in that the dispensing device (8) has an injection piston (7) and/or a piston rod (13), the injection piston (7) and/or a piston rod (13) being connected by the at least one Seal (11) are sealed. Melting unit according to at least one of the preceding claims, characterized in that an evacuation device (12) is provided, which evacuation device (12) is designed to apply a negative pressure to at least the melting chamber (4). Melting unit according to at least one of the preceding claims, characterized in that the discharge device (8) is designed to discharge melted material from the melting chamber (4) by a linear movement, preferably by means of an injection piston (7). Shaping machine, preferably vacuum pressure casting machine, with a melting unit (1) according to at least one of the preceding claims. shaping machine Claim 13 , characterized in that a cavity is provided, wherein the discharge device (8) melted material from the melting chamber (4) can be introduced into the cavity for a shaping process.

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