Patent Application
20180264700
The invention relates to a clamping unit of an injection molding machine having columns according to the preamble of claim 1.
It is, for example, known in the art to equip a clamping unit for a two-platen injection molding machine with short-stroke cylinders, e.g., pressure pads for producing the clamping force, and to mechanically implement the locking action between a column and a platen for transferring the clamping force. In this case, it is customary to realize a locking in particular by a form fit, with the columns having, in a certain region, teeth into which locking means can swing or pushed in so as to establish a form fit between a platen and the column.
Such a hydro-mechanical principle has established itself and has been proven as standard for high clamping forces. In the range of small clamping forces, such a system has cost disadvantages, since a great number of components is necessary for forming the locking actions. Swinging or pushing the locking elements inwards requires furthermore a certain degree of cycle time, which is undesirable.
In addition, a fully hydraulic operating principle has also been established for a clamping unit of an injection molding machine and involves a purely hydraulic action both to move the platens in relation to one another, the clamping force buildup, and to effect the locking action. This principle has as advantage a small number of components. However, it is disadvantageous that, as a result of the need for a high amount of oil (long oil column), significant drawbacks have to be accepted in terms of energy consumption. The reason for that is, i.a. the need to carry along the high oil quantity (oil column) during movement and to compress the oil column during the clamping force buildup.
WO 2010/109374 A1 discloses a locking device for columns of injection molding machines, based on a wedge-type clamping principle. A clamping sleeve is arranged in a clamping jacket and interacts, on one hand, with the column to be clamped and, on the other hand, with an actuating sleeve via a wedge surface and/or conical surface. The actuating sleeve is hydraulically shiftable to a small extent within the clamping jacket, so that a column which is shiftable in the released state with respect to the clamping sleeve can be held in a clamped manner with respect to the clamping device during actuation of the actuating sleeve.
Such a clamping apparatus has the drawback that the movement of the column can cause various types of contaminations, e.g., water, cooling water, dirt, grease, release agent and the like can migrate between the clamping sleeve and the column region to be clamped, so that loss due to unwanted frictional force or excessive wear can occur between the clamping sleeve and the column. In such a case, it is not always ensured that the locking force is sufficiently high to maintain the required clamping force, or the life of the apparatus is substantially shortened due to wear processes.
A mold clamping head of the FSK type is known from the technical information document TI-P11-DE-05/2013 from the company Sitema GmbH & Co. KG, and can be used as a hydraulically actuated clamping device for fixing a platen with respect to a column of an injection molding machine. This mold clamping head utilizes the wedge-type clamping principle with a clamping sleeve and an actuating sleeve, with the clamping head being shiftable relative to the column along the travel path together with the platen onto which the mold clamping head is attached, and capable to build up radially inwardly acting locking forces with respect to the column in the event of a clamping. Such a mold clamping head has the same disadvantages as described above with regard to WO 2010/109374 A1 There is a risk of contamination of the friction surface between the clamping sleeve and the corresponding surfaces of the column.
Object of the invention is to provide a clamping unit with a clamping-type locking apparatus which permits, on one hand, to keep a diameter of the column to be fixed as small as possible and still to produce sufficiently high frictional forces. On the other hand, provision shall be made for the clamping-type locking apparatus to be insensitive to external environmental influences, e.g. oil leaks, cooling water, deposits, dust, grease or other dirt that may come into contact with the column.
Furthermore, a particular embodiment of the invention shall have minimal exposure to wear.
In addition, the number of required components shall be minimal and, in particular, low energy consumption should be realized.
Furthermore, the operational safety of the system shall be significantly enhanced in comparison to existing frictionally-locked clamping-type locking apparatuses and/or a time requirement for establishing a sufficient fixing of the platens in comparison to mechanical systems shall be significantly reduced.
These objects are achieved by a clamping unit having the features of claim 1. Advantageous embodiments are set forth in the subclaims.
A clamping unit according to the invention of an injection molding machine with columns has at least one clamping-type locking apparatus, in particular a clamping unit of a two-platen injection molding machine, and includes according to the invention at least one column which can be secured by means of the clamping-type locking apparatus with respect to one of the platens, and at least one clamping device for locking the at least one column with respect to a clamping jacket at any positions along a travel path of a first platen relative to a second platen. According to the invention, such a clamping unit is characterized in that, in the released state, the clamping device is displaceable together with the column along the travel path within the clamping jacket and a locking force which is radially outwardly directed in relation to a column longitudinal axis can be effected between the clamping jacket and the clamping device by means of the clamping device.
With such a configuration according to the invention of the clamping unit or its clamping-type locking apparatus, it is possible to keep the column diameter as small as possible, since an outer side of the column is not required for generating a sufficiently high locking force. Rather, according to the invention, the clamping device is designed in such a way as to form a locking force which is directed radially outwards towards the surrounding clamping jacket. The clamping jacket surrounds the clamping device on the outside and thus has a greater inner diameter relative to the column, thereby enlarging the inner peripheral surface that is a partial surface of the clamping jacket and is available for clamping.
Furthermore, the clamping jacket is arranged encapsulating around the column over the entire length of the distance required for the travel path, so that the column and the clamping device is located inside the clamping jacket and thus removed in a positive manner from exposure to unwanted dirt or other deposits, like e.g. oil, grease, cooling water or the like. This ensures, in particular, the long-term operational safety, since the frictional contact between the clamping device and the inner side of the clamping jacket, which preferably is tubular in shape, can be held lastingly free of contamination.
For this purpose, provision is made in particular for a stripping device in a region before a column section enters into the interior of the clamping jacket to wipe off undesired dirt and/or grease and/or cooling water and/or deposits, like e.g. dust or oil leakage, from the column. Such contaminations can reach the outer side of the column, when partial regions of the column are outside of the clamping jacket, for example, when the tool is fully open.
It has proven to be of advantage to form the clamping jacket as a grease-tight and/or dirt-tight tubular body.
According to a first structural variant, the clamping jacket can be made stationary in relation to a platen, i.e. in relation to the fixed platen or in relation to the moving platen. At the same time, it is also possible for the clamping jacket to be connected to the platen with the interposition of a pressure cylinder or a pressure pad. In this embodiment, the clamping jacket can act on one end as a piston of the pressure cylinder or the pressure pad or can be in direct operative contact thereto, for example via a tie rod/push rod.
It is preferred that an interior of the clamping jacket is filled with air or oil. It has been found that an equally reliable clamping can be attained with an oil filling. An air filling is advantageous because flushing loss is minimized when air in the clamping jacket is moved around from the one side of the clamping element to the other side of the clamping element.
In a preferred manner, the clamping device can have at least one pressure chamber which can be hydraulically supplied with fluid, wherein the at least one pressure chamber of the clamping device can be expanded radially elastically by fluid under pressure for generating the locking force. A radially elastically expanded state ensures hereby a clamping via an outer peripheral surface of the clamping device with an inner side of the clamping jacket. When a fluid pressure is reduced, an effective outside diameter of the clamping device decreases in relation to the inner side of the clamping jacket and thus again liberates the clamping device from the clamping jacket so as to be able to move again in relation to the clamping jacket.
According to a further advantageous embodiment, the clamping device is designed as a hydraulically actuatable wedge-type clamping apparatus with a clamping sleeve and an actuating sleeve, with the actuating sleeve being arranged within a housing of the clamping device and hydraulically shiftable in an axial direction and interacting with the clamping sleeve via a wedge or conical surface.
For the embodiment of the clamping device as wedge-type clamping device, there is the advantageous option to provide the clamping device with an open clamping chamber that points radially inwardly towards the column, and to enable the housing of the clamping device to be expanded elastically by reaction forces of the part clamping device radially with respect to its outside diameter.
According to another embodiment, the clamping device includes an open clamping chamber which points radially outwards towards the clamping jacket and in which the clamping sleeve is arranged for frictional interaction with an inner side of the clamping jacket. By means of an actuating sleeve, which interacts with the clamping sleeve via a wedge or conical surface, the diameter of the clamping sleeve can be reduced and increased, wherein the clamping action toward the outwardly surrounding clamping jacket can be made ineffective, when the diameter is reduced.
The invention thus for the first time pursues the approach to render the clamping device together with the column movable, especially shiftable, in the released state along the travel path, especially the entire travel path, rather than rendering the column movable in relation to the clamping device in the released state, so as to establish a clamping between the clamping jacket and the clamping device along an effective diameter which is greater than the column diameter. This makes it possible, on one hand, to keep the column diameter to a minimum and, on the other hand, to use the clamping jacket, which is also effective as an encapsulation, as clamping partner.
Further advantageous embodiments are specified in further patent claims or the following description of exemplary embodiments.
In the following, the invention is explained in more detail by way of example with reference to the drawing. It is shown in:
Each of the columns 3 has a column longitudinal axis 3a. A clamping device 12 is located at a first end 11 of the columns 3 and is movably mounted in an associated clamping jacket 13 in the released state along the opening and closing direction 9. Pressure cylinders 15 are preferably arranged on a second end 14 of the columns and may be configured in particular as pressure pads 16. The pressure cylinders 15, in particular the pressure pads 16, are intended in a known manner to buildup the clamping force, when the platens 4, 5 have moved towards each other by means of the displacement cylinders 10 so that the half-molds 6,7 abut one another.
The clamping device 12 is capable to generate in relation to the column longitudinal axis 3a radially outwardly directed locking forces Fk, which are supported on an inner side 17 of the clamping jacket 13. The clamping jacket 13 is preferably configured as a tubular body 18 which, e.g. has a circular or, optionally, also a square or rectangular cross-section. The clamping jacket 13 is secured with a first end 19 to the second platen 5. At a second end 20, the clamping jacket 13 is closed and has an end wall 21. With regard to the longitudinal extent between the first end 19 and the second end 20 or the end wall 21, the clamping jacket 13 is configured such as to be capable to surround the clamping device 12 and the column 3 along the entire travel path along the opening and closing direction 9.
In the clamping-type locking apparatus 2 according to the invention, the clamping device 12 is firmly connected to the associated column 3 and, in the released state of the clamping device 12, is shiftable within the clamping jacket 13 together with the first end 11 of the column along the entire travel path in the opening and closing direction 9.
Thus, an encapsulated clamping-type locking apparatus 2 is provided, which remains free of dirt during operation of the injection molding machine 1. The encapsulation ensures that the inner side 17 of the clamping jacket 13 and a radially outer peripheral surface 22 of the clamping device 12 are able to effect a reliable clamping or blockage of the column 3 in relation to the clamping jacket 13 at any application of the locking force Fk, because the interacting surfaces (peripheral surface 22; inner side 17) remain effectively spared from contamination.
In order to prevent dirt to migrate into an interior space 23 of the clamping jacket 13 via the column 3 during travel of the platens 4, 5 along the opening and closing direction 9, stripping devices 24 are suitably provided, which are arranged, e.g., within a through-opening of the second platen 5 for passage of the column 3. The stripping devices 24 cooperate hereby with an outer side of the columns 3 and clean them before the column can reach the interior space 23 of the clamping jacket 13.
The clamping-type locking apparatus 2 according to the invention is thus formed at least by the clamping jacket 13, the clamping device 12, and a respectively associated column 3. One or more clamping-type locking apparatuses 2 according to the invention form together with one or more pressure cylinders 15 or pressure pads 16 a clamping unit 25, which ensures a reliable locking of the platens 4, 5 on one hand, and application of sufficiently high clamping forces via the pressure cylinders 15 or the pressure pads 16 on the other hand.
In this embodiment of a clamping unit 25 of an injection molding machine 1, a plurality of identical or only slightly modified components are present compared to the embodiment according to
In contrast to the embodiment according to
Like in the embodiment according to
The bottom wall 26 can, for example, serve as a hydraulic piston of the pressure cylinder 15 or of the pressure pad 16 and configured accordingly.
The advantages described in connection with
The interior space 23 of the clamping-type locking apparatus 2 according to the invention can be filled with air or oil. It has been found that also an oil filling is suitable for high reproducibility and for sufficiently high clamping forces Fk. Within the scope of the invention, it has been recognized that it is particularly important to keep moisture, dust, dirt and, in particular, grease away from the interacting surfaces for the locking force buildup of the clamping force Fk. The interacting surfaces involve hereby in particular the inner side 17 of the clamping jacket 13 and the peripheral surface 22 of the clamping device 12.
A first embodiment of the clamping device 12 of the clamping-type locking apparatus 2 according to the invention is shown schematically by way of a longitudinal section in
The column 3 with its column longitudinal axis 3a extends through a platen 4, 5. The stripping device 24 is situated in the platen 4, 5. The clamping jacket 13 is firmly arranged on the platen 4, 5, so that the embodiment according to
Furthermore, for all embodiments, the clamping-type locking apparatus 2 according to the invention can selectively be arranged on a fixed or a moving platen 4, 5.
At the first end 11 of the column 3, the clamping device 12 is firmly attached, for example, by means of a screw connection. The clamping device 12 has a substantially cup-shaped three-dimensional shape and is placed on the end of the first end 11 of the column 3 and is displaceable in the opening and closing direction 9 within the clamping jacket 13, when the clamping device 12 assumes the released state (solid lines of
A residual wall 32 thus remains between the pressure chamber 31 and the peripheral surface 22 and has a wall thickness which is reduced compared to the cup-shaped wall 28. This residual wall 32 is elastically deformable radially outwards, when pressure fluid under excess pressure is present in the pressure chamber 31 (dashed line 33 in
As already described above, the interior space 23 of the clamping jacket 13 can preferably be filled with air or oil. Particularly in the case of an oil filling, it is, of course, necessary to ensure suitable overflow openings or overflow passages so as to ensure a movement of the clamping device 12 within the clamping jacket 13 as unimpeded as possible. The embodiment of the clamping-type locking apparatus 2 according to
A second embodiment of the clamping-type locking apparatus 2 according to the invention is shown in the upper sectional view above the column longitudinal axis 3a according to
A third embodiment of the clamping-type locking apparatus 2 according to the invention is shown schematically in
Both embodiments of the clamping-type locking apparatus 2 according to the invention, as shown in
Via pressure oil lines 50, 51, which communicate with pressure oil chambers 52, 53, the actuation sleeve 42 can be slightly moved along the axial direction 43 toward the clamping sleeve 41 or away from the clamping sleeve 41 by appropriately acting upon the pressure oil chambers 52. When the actuating sleeve 42 is moved toward the clamping sleeve 41, a radially outwardly acting locking force Fk is generated, while the actuating sleeve 42 is supported on the cup-shaped wall 28 and the actuating sleeve 42 is supported on the wedge or conical surface 45, so that the cup-shaped wall 28 is elastically expanded and contacts with its circumferential surface 22 the inner side 17 of the clamping jacket 13, thereby building up the radially outwardly acting locking force Fk. To release the clamping action, the pressure oil chambers 52, 53 are pressurized with pressure oil or subjected to a pressure reduction, such that the actuating sleeve 42 is slightly moved away from the clamping sleeve 41 in axial direction 43. Thus, the cup-shaped wall 28 can slightly spring back radially inwards so as to release the clamping action.
The second embodiment of the clamping device 12 according to the invention as shown in
The support of the clamping force Fk in the embodiment according to
In the embodiment according to
In the embodiment according to
In both embodiments according to
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2015 101 570.6 | Feb 2015 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2015/080189 | 12/17/2015 | WO | 00 |
