Patent Application
20180264543
The invention relates to a valve device for venting die-casting moulds according to the preamble of claim 1.
In die-casting, the casting mould or the mould cavity thereof is made to vent during the casting process to reliably prevent air pockets or gas pockets in the finished cast part. Not only must any air present in the cavities of the casting machine and the casting mould be able to escape, but it must also be ensured that the gases exiting from the liquid casting compound can also escape.
A valve device for venting die-casting moulds is known from EP 0 612 573 A2. The valve device has a venting duct for connection to the mould cavity of the die-casting mould, a venting valve arranged in the venting duct, and an actuating device for closing the venting valve. The actuating device comprises a force-receiving element which is actuated by casting material and a force-transmitting element for transmitting the closing movement from the force-receiving element to the venting valve. The valve device is preferably connected to a vacuum system, which allows forced venting of the die-casting mould.
DE 27 51 431 A1 discloses a further generic venting valve device for die-casting moulds, which is provided with two venting valves. Each venting valve has an axially displaceable venting piston. The actuating device comprises five actuating pistons which are actuated by casting material and act on an axially displaceable transmission piston, which for its part bears a driver plate. The actuating piston and the transmission piston are arranged below the two venting valves. The driver plate engages interlockingly in an annular groove in the respective venting piston, as a result of which the actuated parts are connected to each other in the manner of drivers. The transmission piston is arranged in an axially movable manner in a cylinder. A pressure medium line coming from a pressure source opens into said cylinder. The operation of the venting valve can thus be checked before the casting process.
The object of the invention consists in creating a valve device belonging to the technical field mentioned in the introduction, for venting die-casting moulds, said valve device on the one hand allowing high venting outputs while having a simple structure at the same time, operating reliably and allowing very short closing times.
This object is achieved with a valve device according to claim 1.
The fact that the valve device has at least two venting valves and a force-receiving element, which is directly operatively connected to the valve piston of the respective venting valve without a separate intermediate element, provides the fundamental requirement of being able to implement high venting outputs with at the same time very short closing times and comparatively low force effort, since force-transmitting element between the force-receiving element and the respective valve piston can be omitted. At the same time, the number and mass of the movable elements needed for the process of closing the two venting valves can thus also be reduced, which has the further advantage of the structure of the valve device being comparatively simple and favouring a reliable operation.
Preferred developments of the valve device are outlined in dependent claims 2 to 16.
Thus, in a preferred development it is provided, that the force-receiving element is arranged centrally between the valve pistons. This favours a compact structure of the valve device and allows a symmetrical structure of the movable parts.
A particularly preferred development of the valve device provides that the same has two venting valves, the two valve pistons of which are arranged in a plane with the force-receiving element. This particularly favours a compact structure of the valve device, especially since the two valve pistons are arranged close to the force-receiving element and the force-transmitting parts can be made simple in this embodiment.
Preferably, the force-receiving element is provided with radial protrusions which engage in a cut-out in the respective valve piston or pass through the respective valve piston.
This embodiment favours a simple and lightweight structure and allows particularly short closing times.
In a further, particularly preferred development, the force-receiving element is formed integrally with the radial protrusions. This embodiment likewise helps to reduce the mass of the movable elements needed for the process of closing the two venting valves further and to make the structure of the valve device simple.
In a further preferred development of the valve device, the force-receiving element is axially displaceable between a pushed-forward starting position and a pushed-back effective position; the force-receiving element, when in the starting position, tries to hold the valve pistons in a pushed-forward open position, and, when in the effective position, tries to hold the valve pistons in a pushed-back closed position; the force-receiving element is loaded by means of at least one spring in the direction of the starting position of the force-receiving element; the force-receiving element is provided with a pressure face, and the valve device is provided with a pressure space which at least partially surrounds the force-receiving element and is pneumatically loadable to exert a force, directed counter to the spring force, on the pressure face of the force-receiving element and to displace the force-receiving element into the effective position thereof and/or to hold same in the effective position. This embodiment allows direct pneumatic loading of the force-receiving element without separate elements being necessary as in the valve devices known from the prior art.
Particularly preferably, the force-receiving element has a cylindrical main body and a cylindrical head part, the head part having a smaller diameter than the main body, and the end face of the head part projecting into the venting duct. Both the main body and the head part can be easily adapted thereby to the requirements in question. Thanks to the low weight of the elements which are moved for the closing process, the end face of the head part, which is loaded by the liquid casting material, can be kept comparatively small, while the main body can be made correspondingly larger and more robust and is particularly suitable for the radial protrusions to be arranged thereon.
Said pressure face is preferably formed on the force-receiving element at the transition from the cylindrical main body to the cylindrical head part. This is a particularly elegant and simple solution for implementing a pressure face for pneumatically loading the force-receiving element.
In a further preferred development, the valve device has an outlet chamber, which is integrated into the valve housing and in which the venting duct(s) open, the outlet chamber being connected to a flange which leads outwards. This embodiment makes it possible to connect the valve device quickly and easily to a suction device.
Preferably, the valve device is provided with a spring-loaded pressure plate which is operatively connected to a plurality of pressure rods, the pressure rods protruding from the front face of the housing when in the starting state; when a sealing plate is fixed to the front face of the housing, the pressure rods push the pressure plate backwards counter to the force of the compression springs, and, when the sealing plate is removed, the pressure plate pushes the force-receiving element together with the valve pistons forwards into the starting position. Such an embodiment allows the displaceable elements, namely the force-receiving element together with the valve pistons, to be used to eject the solidified casting compound out of the venting duct.
Particularly preferably, the force-receiving element covers an axial distance between 1 and 7 millimetres, in particular between 3 and 5 millimetres, to pass from the starting position to the effective position. This comparatively small distance means that the kinetic energy transmitted from the liquid casting compound to the force-receiving element is kept at a low level.
The end face of the head part, which opens into the venting duct, of the force-receiving element preferably has a diameter between 5 and 25 millimetres. This comparatively small diameter or the corresponding area additionally helps to keep the kinetic energy transmitted from the liquid casting compound to the force-receiving element comparatively small.
In a further, preferred development of the valve device, the venting duct has an inlet duct which branches into a number of branches corresponding to the number of venting valves, the force-receiving element being arranged in the region of the branching, and a venting valve being arranged in the region of the end of the respective branch. Thanks to this embodiment, good and fast transmission of the kinetic energy from the liquid casting compound to the force-receiving element is achieved and the respective venting valve can be arranged far away in flow terms from the force-receiving element.
Preferably, the respective branch of the venting duct is provided with at least two, in particular at least three deflections; at least two deflections effect a change in direction of the inflowing casting material by at least 60°. This embodiment helps to slow the speed of the casting material before it meets the respective valve piston.
In a further preferred development, the respective branch of the venting duct is provided with at least one material collection chamber in the form of a dead end for the advancing casting material. This embodiment helps to slow the speed of the casting material so that enough time remains after the casting material meets the force-receiving element for the two valve pistons to close, so that the casting material advances as far as the respective valve piston only when the latter is already in the pushed-back closed position.
Finally, in a further preferred development, a block bushing is inserted into the valve housing, said block bushing being made of a harder material than the valve housing and being designed to accommodate and guide the force-receiving element and the valve pistons. A block bushing of this type can be adapted specifically to the requirements, in particular in respect of thermal expansion and wear, and can be changed simply and quickly when necessary.
The invention is explained in more detail below using drawings. In the figures:
The valve device 1 comprises a valve housing 2, in which a venting duct, which is denoted overall by 3, is made. The venting duct 3 comprises: an inlet 4 in the form of an inlet duct 5, which opens into the valve housing 2 at the bottom; two partial ducts in the form of two branches 7, 8; and an outlet in the form of an outlet duct (not visible) which leads upwards out of the valve housing 2. In addition, the venting duct comprises further ducts running inside the housing 2, which are discussed further below.
The inlet duct 5 leading vertically from below into the housing 2 branches in the lower half of the valve housing 2 into the two branches 7, 8. In the region of the branching 6 of the venting duct 3 is arranged an actuating member in the form of a force-receiving element 10 which is actuated by casting material. Each of the said branches 7, 8 of the venting duct 3 consists of a plurality of partial ducts, a venting valve 18, 24 being arranged in the region of the end of each branch 7, 8. Each venting valve 18, 24 is provided with a valve piston 19, 25 which is axially movable between a pushed-forward open position and a pushed-back closed position. In
In the region of the force-receiving element 10 and of the two venting valves 18, 24, there is in each case a round opening 9, 17, 23 in the bottom of the venting duct 3 or of the respective branch 7, 8. The size of this opening 9, 17, 23 depends on the element behind it, force-receiving element 10 or valve piston 19, 25. The diameter of the opening 9 provided for the force-receiving element 10 is slightly larger than the diameter of the head part 12 of the force-receiving element 10, while the diameter of the openings 17, 23 provided for the venting valves 18, 24 is in each case slightly larger than the diameter of the two valve pistons 19, 25. The diameter of the head part 12 of the force-receiving element 10 preferably has a diameter between 5 and 25 millimetres. The area of the force-receiving element 10 which can be loaded by the casting material is approximately 19.6 to 490 mm2. Particularly preferably, the loadable area of the force-receiving element 10 is between approx. 50 and 200 mm2.
It can be seen from the shape of the venting duct 3 that the liquid casting material is deflected a total of four to five times in the respective branch 7, 8 after meeting the force-receiving element 10 or the head part 12 thereof before it advances to the respective venting valve 18, 24. Directly after meeting the force-receiving element 10, the liquid casting material is deflected for the first time into the respective branch 7, 8. In the present example, the liquid casting material is deflected by approximately 140°-160° after meeting the force-receiving element 10, as a result of which good transmission of the kinetic energy from the liquid casting compound to the force-receiving element 10 is achieved and at the same time the advance of the casting material is decelerated. Of the further deflections, three of them effect a deflection, i.e. a change in the direction of the inflowing casting material by at least 60°, two of them by at least 90°, the first deflection in the respective branch 7, 8 effecting a change in the direction of the inflowing casting material by approximately 50°. In addition, four material collection chambers 7a-7d; 8a-8d, which receive a certain volume of liquid casting compound and help to slow the advance of the casting material are arranged in the manner of dead ends in each branch 7, 8. In any case, the formation of the venting duct 3 downstream of the force-receiving element 10 means that the liquid casting material entering the inlet 4 at a speed of approximately 100-150 m/s takes approximately 3 to 5 milliseconds to advance from the force-receiving element 10 to the respective venting valve 18, 24. In contrast, the closing mechanism is dimensioned such that it takes approximately 0.5 to 1.5 milliseconds for the two valve pistons 19, 25 to be displaced into the closed position after the casting material meets the end face of the head part 12 of the force-receiving element 10. It is self-evident that the above figures should be understood merely as reference values and can vary on the basis of many parameters. In this respect, the following can be mentioned by way of example: the speed of the inflowing casting material, the specific weight of the casting material, the length, the cross-sectional area, the type and design of the entire venting duct including the branches thereof and the mass of the elements moved for the closing process, the closing distance of the force-receiving element and of the valve pistons, and the area of the head part of the force-receiving element which can be loaded with casting material. In spite of this, the venting duct 3 has a cross-sectional area of consistent size to conduct or discharge a sufficient gas volume per unit time. With smaller valve device, it can also be sufficient if the casting material is deflected only two or three times and/or if only one or two material collection chambers are provided.
Since the specific weight of the casting material and the entry speed of the casting material can vary in particular depending on the application, these two parameters can also in particular affect the closing time. This circumstance can be taken into account for example by modifying the end face of the head part 12 of the force-receiving element 10 which is loaded with casting material. Examples of casting materials are aluminium, magnesium, zinc and brass.
The sectional line A-A or sectional plane A-A of the valve device 1 at the same time forms the line of symmetry or the plane of symmetry. The valve device 1 has a symmetrical structure in relation to a plane running through the sectional line A-A.
The force-receiving element 10 has a substantially cylindrical main body 11 and a substantially cylindrical head part 12, the head part 12 having a smaller diameter than the main body 11. An annular face 16 is formed by the step between the main body 11 and the head part 12. The force-receiving element 10 is provided on the rear with a cut-out in which a compression spring 54, which is supported on the cover plate 42, is partially accommodated. Said compression spring 54 loads the force-receiving element 10 in the direction of the pushed-forward starting position thereof, in which the two venting valves are open. The pressure plate 37 is provided with a cut-out (not visible in this diagram) which is complementary to the contour of the force-receiving element 10 and on the bottom of which the rear of the main body 11 of the force-receiving element 10 can be supported in a frictional manner. Finally, another outlet chamber 30 can be seen, which is integrated in the valve housing 2 and is connected to an outwardly opening flange 33. The inside of the flange 33 is provided with an outlet bore 32, which is connected to the outlet chamber 30. In addition, two tappets 39 protruding from the front face 40 can be seen, the function of which is explained in more detail below.
A duct 58 leads from the top into the housing 2. This duct 58 opens via a radial bore into a central inner space of the block bushing 46, which is used to accommodate the force-receiving element 10. A pressure space 59, to which compressed air can be applied via the said duct 58, is formed in the block bushing 46 between the annular face 16 of the force-receiving element 10 and the front end of the inner space of the block bushing 46. If the pressure plate 37 is in the pushed-back position thereof, the application of pressure to the pressure space 59 can move the force-receiving element 10 out of the pushed-forward starting position shown here into the pushed-back effective position thereof, in which the two venting valves are closed.
Application of pressure to the pressure space 59 can thus displace the force-receiving element 10 backwards in the direction of the cover plate 42, counter to the force of the compression spring 54, into the effective position of the force-receiving element and/or hold the force-receiving element in the effective position.
The block bushing 46 is produced from a temperature-resistant and wear-resistant material which is harder than the valve housing 2. The block bushing 46 is replaceable; for example, cold-formed steel is a suitable material for the block bushing 46.
It can also be seen that the block bushing 46 is provided in the region of the venting valve 18 with a vertically upwardly leading bore 52, which opens into a vertically upwardly leading duct 20. The bore 52 together with the duct 20 form a further part of the venting duct and lead into the common outlet chamber 30. The front of the block bushing 46, which faces the front face 40, comes to bear tight against the bottom of the front cut-out 35. The block bushing 46 is larger in both height and width than the openings 9, 17, 23 (
It can also be seen that the block bushing 46 is provided with two cylindrical bores 47, 48 for accommodating and guiding the two valve pistons 19, 25. In the centre between the two cylindrical bores 47, 48, a cut-out for accommodating the force-receiving element 10 is made in the block bushing 46. This central cut-out comprises two cylindrical bores 50, 51, the front bore 50 being used to accommodate the head part of the force-receiving element 10, and the rear bore 51 being used to accommodate most of the main body of the force-receiving element 10.
If the sealing plate 56 is attached to the housing, closing of the valve device can also be initiated pneumatically. Although the two tappets 39 push the pressure plate 37 backwards when the sealing plate 56 is attached, the force-receiving element 10 remains in the starting position thereof under the effect of the compression spring 54. After the sealing plate 56 is attached, however, compressed air can be applied to the pressure space 59 in the block bushing 46 via the air duct 58 (
Owing to the direct coupling between the two valve pistons 19, 25 and the force-receiving element 10, the force-receiving element 10 drives the two valve pistons 19, 25 with its backward movement. Because the force-receiving element 10 is arranged in the centre between the two valve pistons 19, 25 and together with them in a horizontal plane, symmetrical loading of the force-receiving element 10 can be achieved, which is advantageous with respect to reliable operation. At the same time, this embodiment helps to keep the mass and weight of the force-receiving element 10 comparatively low, since only two radial protrusions 14, 15 have to be provided, rather than a driver plate or the like as in the devices according to the prior art. In addition, the said arrangement together with the symmetrical structure of the valve device 1 means that the distance which the liquid casting material travels from the force-receiving element 12 to each valve piston 19, 25 is equal.
The closing elements consisting of the force-receiving element 10 and the two valve pistons 19, 25 are dimensioned and coordinated with each other such that the two valve pistons 19, 25 are in the pushed-back closed position before the casting material G has advanced as far as the respective venting valve, specifically the head part 22, 28 of the respective valve piston 19, 25. This circumstance is indicated by the fact that there is still no casting material present and shown in the respective branch 7, 8, specifically in the space upstream of the valve piston 19, 25. To pass between the starting position and the effective position, the force-receiving element 10 covers an axial distance of between 1 and 7 mm, preferably between 3 and 5 mm.
The shape and design of the venting duct 3 with the two branches 7, 8 thereof is coordinated with the force-receiving element 10 and the two valve pistons 19, 25 such that the two valve pistons 19, 25 are pushed backwards into the closed position before the casting material has advanced as far as the valve pistons 19, 25. Tests and simulations relating to this with a valve device according to the invention have shown that an average closing process takes approximately 1 millisecond, measured from the point in time at which the casting material meets the force-receiving element 10 to the point in time at which the two valve pistons 19, 25 close. In contrast, the casting material takes approximately 4 milliseconds to advance from the force-receiving element 10 to the two valve pistons 19, 25. In any case, the elements consisting of force-receiving element 10, valve pistons 19, 25 and venting duct 3 or the branches 7, 8 are dimensioned and coordinated with one another such that the two valve pistons 19, 25 are in the pushed-back closed position before the casting material has advanced as far as them. Thanks to the comparatively low mass to be moved (force-receiving element, valve pistons), the closing process is no longer as time-critical as in comparable valve devices. In comparable valve devices, a mass approximately 2 to 4 times greater must be moved for a closing process.
At the end of a casting process, the sealing plate 56 is removed from the front face 40. In the process, the tappets 39 (
In summary, it can be stated that such a valve device allows high venting outputs thanks to the provision of two venting valves. Also, force-transmitting elements between the force-receiving element and the respective valve piston can be omitted, thanks to the direct coupling of the force-receiving element, which is actuated by casting material, to the valve piston of the respective venting valve. This means that the number of elements needed for the process of closing the venting valves can be reduced to a minimum. For instance, a driver plate does not have to be provided. In addition, the weight of the parts needed for closing the valve pistons can be considerably reduced, which allows faster closing of the venting valves and/or a lower amount of energy required for the closing process. In the present example, a total of only 3 elements, specifically the force-receiving element 10 and the two valve pistons 19, 25, must be moved for the process of closing the two venting valves. If necessary, the end face of the head part, which is loaded with casting material, of the force-receiving element can also be made smaller. In addition, the closing distance of the force-receiving element and of the valve pistons can also be reduced. Finally, the total weight, where appropriate, the size of the valve device can also be reduced. In any case, the valve device has a very simple structure and favours an operation which is reliable and stable in the long term. The substantially symmetrical structure also means the risk of the movable parts jamming or wearing away on one side is also reduced. Compared with known and comparable valve devices, the total number of components, the size and the total weight can also be reduced.
It is self-evident that the above exemplary embodiment should not be considered exhaustive, but that embodiments deviating therefrom are possible within the scope defined in the claims. For instance, three or four venting valves can be provided instead of two venting valves. The force-receiving element in such an embodiment is preferably also arranged centrally between the venting valves, with the venting valves preferably being distributed on a circular face. Instead of two radial protrusions, the force-receiving element could also be provided with one projection which runs around in an annular or collar-like manner and is coupled to the valve pistons. A further advantage consists in a filter being integrated into the valve device. For example, a filter could be integrated into the outlet chamber.
Where force-receiving elements which are actuated by casting material are mentioned above, this does not necessarily mean a force-receiving element actuated by casting material directly; embodiments in which the force-receiving element is actuated by the casting material indirectly are also conceivable. To this end, an element could be arranged upstream of the force-receiving element, said element coming into direct contact with the casting material and transmitting the force needed to close the valve pistons from the casting material to the force-receiving element. Such an embodiment could be practical if, for example, the element coming into contact with the casting material is intended to cover only a fraction of the closing distance of the force-receiving element, to reduce the transmitted kinetic energy.
The essential advantages of the presented valve device can be summarised as follows:
| Number | Date | Country | Kind |
|---|---|---|---|
| 00321/17 | Mar 2017 | CH | national |
