Patent Application
20140199923
The invention relates to an apparatus for surface finishing workpieces by moving the workpieces relative to the grinding and/or polishing granules in a bed of the same, in particular in the form of a drag finishing and/or plunge finishing machine, having at least one workpiece holder, on which at least one chucking device for releasably fixing the workpieces to be machined is secured, and having a container arranged underneath the workpiece holder in order to receive the grinding and/or polishing granules, which can be moved relative to the workpiece holder. The invention furthermore relates to a chucking device for releasably fixing workpieces to be machined for an apparatus for surface finishing workpieces by moving the workpieces relative to the grinding and/or polishing granules in a bed of the same, in particular in the form of a drag finishing and/or plunge finishing machine, having at least one workpiece holder for releasably fixing the chucking device, and having a container arranged underneath the workpiece holder in order to receive the grinding and/or polishing granules, which can be moved relative to the workpiece holder.
Apparatuses of this kind for surface finishing workpieces are known in the form of “drag finishing machines”, for example. Their action is based on plunging the workpiece to be machined into a bed of grinding and/or polishing granules held in a container and moving the workpiece relative to the granules, with the result that the surface of the workpiece is ground and/or polished, depending on the type of granules.
Drag finishing machines represent a special form of mass finishing machines, wherein the workpieces to be machined are mounted in a hanging position, e.g. individually on one or more chucking devices of a workpiece holder. To enable the workpiece holder to be moved relative to the container, drag finishing machines of this kind often comprise a, generally rotating, part essentially in the form of a plate driven in rotation, e.g. by a motor via a suitable transmission, on which the workpiece holders are secured directly or indirectly, e.g. via lifting devices. This takes place, in particular, eccentrically with respect to the axis of rotation of the rotating part of the drag finishing machine. If this part—the “plate”—of the drag finishing machine is rotated, the workpiece holders secured thereon describe a curved path. In this process, the workpieces secured releasably on the chucking devices of the workpiece holders are plunged into the working container, which is filled with the bed of grinding or polishing granules in particle form, if appropriate with the addition of liquid media, such as water, surfactants etc. The movement of the workpieces relative to the granules results in the surface finishing thereof in the form of mass finishing. Drag finishing machines of this kind are known from DE 102 04 267 C1, DE 200 05 361 U1 or DE 10 2010 052 222 A1, for example.
As an alternative or in addition, the container holding the finishing medium can be moved relative to the workpieces, e.g. being rotated about its own axis and/or along a curved path, e.g. in the form of a circular path, the workpieces likewise being moved, being rotated at least about their own axis for example, or being stationary. If only the container is moved and the workpieces themselves do not perform any translatory movement, this is also referred to as “plunge grinding” or “plunge polishing” as a special form of drag finishing.
In principle, the grinding or polishing granules can vary very greatly in nature, depending on the workpieces to be treated, and can be of natural origin (e.g. consisting of organic material, such as walnut or coconut shells, wood, cherry stones etc.), of mineral origin (e.g. consisting of silicates, oxides etc.) and/or of synthetic origin (e.g. consisting of plastics), for example. As already indicated, it is furthermore possible to carry out the mass finishing operation dry or—with the addition of a liquid machining medium, e.g. water, which can be doped with additives, e.g. surfactants—in the form of wet machining.
In order to provide not only for a translatory movement of the workpieces relative to the machining medium in particle form but also in addition for a rotary movement of the workpieces, e.g. about their own axis, leading to a particularly effective grinding or polishing action, the workpiece holders are often driven in rotation, which can be accomplished by means of suitable motors (DE 10 2010 052 222 A1), for example. Moreover, the prior art includes workpiece holders for drag finishing machines, the chucking devices of which are mounted rotatably to allow releasable fixing of the workpieces and can be set in rotation by means of a shaft mounted rotatably in the workpiece holder. For this purpose, the workpiece holder has, for example, a planetary transmission having a central sun wheel, which is in engagement with planet wheels which, for their part, is connected for conjoint rotation to a supporting shaft of a respective toggle-type fastener, which are arranged distributed around the circumference of the sun wheel of the workpiece holder. By virtue of such a movement of the chucking devices, mounted rotatably on the workpiece holder, with the workpieces, said movement being composed of a translatory movement (in the direction of rotation of the supporting part or “plate” of the drag finishing machine) and of a rotary movement (about the axis of the respective chucking device or about the workpiece axis), through the machining medium, a very uniform quality of machining combined with considerably shorter machining times as compared with a purely translatory movement is achieved. It is furthermore possible, as an alternative or in addition, for the workpiece holder itself to be secured rotatably in an appropriate manner on the supporting part of the drag finishing machine (DE 20 2009 008 070 U1).
The chucking devices for releasably fixing the workpieces on the workpiece holder during the surface treatment thereof can be formed by conventional collets, for example. Another chucking device for a drag or plunge finishing machine of the type in question for releasable, suspended fixing of the workpieces can be found in DE 10 2010 024 247 A1.
The releasable fixing of the unprocessed workpieces on such chucking devices and the removal of the finished workpieces is often relatively complex in terms of handling, and this can lead to not insignificant downtimes of the machine. Moreover, especially when the loading of the chucking device with the workpieces and the removal thereof is supposed to be automated, e.g. by means of manipulators, such as robots, more or less involved programming of the handling device is required for virtually every workpiece.
DE 27 31 135 A1 describes a drag finishing machine having a chucking device for releasably securing a workpiece to be machined, which can be in the form of a clamping chuck or can suck in the workpiece by means of a vacuum. Apart from the fact that it is not obvious from the publication how this is supposed to occur, it has been found that mere suction on the workpiece does not enable it to be held suspended on the chucking device during surface finishing.
DE 33 32 786 A1 discloses another drag finishing machine for surface finishing of workpieces, the workpiece carriers of which are provided with receptacles in the form of horizontally extending pins which are matched in shape and alignment to the workpieces, enabling the latter to be mounted on the pins with a clamping action. However, even to this extent, it has been found that such releasable fixing of the workpieces is not sufficient to hold them reliably in a fixed manner during surface finishing. This applies especially to suspended fixing of the workpieces on the workpiece holder, which is not envisaged in the publication mentioned.
Finally, clamping tables for machine tools of a different kind are known, these serving to secure a workpiece releasably while it is being machined. DE 87 00 766 U1 relates to a clamping table of this kind for workpieces for machining on machine tools, wherein the clamping table has a clamping plate, onto the clamping surface of which the workpieces are, on the one hand, sucked by means of a vacuum. In addition, stop elements in the form of cut-outs or recesses are provided in order to fix the workpieces laterally on the clamping plate and to preserve them from displacement along the plate surface during machining.
It is therefore the underlying object of the invention to develop an apparatus for surface finishing workpieces of the type stated at the outset and a chucking device of an apparatus of this kind, said chucking device also being suitable, in particular, for the suspended fixing of the workpieces, and to do so in a simple and economical manner such that both loading of the chucking device with the workpieces to be machined in a manner which is simple, quick and easy in terms of handling, and removal of the workpieces in the same way, are possible while at least largely avoiding the abovementioned disadvantages.
According to the invention, this object is achieved in the case of an apparatus for surface finishing workpieces of the type stated at the outset by virtue of the fact that the chucking device has a chuck, which is designed for at least partially positive holding of the workpiece for conjoint rotation, and that the chucking device furthermore has at least one vacuum duct, which can be connected to a vacuum generator and which opens into the chuck in order to hold the workpiece in such a way that it is fixed axially by the application of a vacuum to the vacuum duct, wherein the chuck of the chucking device is arranged on an adapter piece, which can be fixed releasably on a supporting part of the chucking device.
To achieve this object, the invention furthermore makes provision, in a chucking device of the type stated at the outset, which is suitable for such an apparatus for surface finishing workpieces, for the chucking device to have a chuck, which is designed for at least partially positive holding of the workpiece for conjoint rotation, and for the chucking device furthermore to have at least one vacuum duct, which can be connected to a vacuum generator and which opens into the chuck in order to hold the workpiece in such a way that it is fixed axially by the application of a vacuum to the vacuum duct, wherein the chuck of the chucking device is arranged on an adapter piece, which can be fixed releasably on a supporting part of the chucking device.
The embodiment according to the invention ensures both simple, quick and easy, e.g. manual, loading of the chucking device with workpieces and removal of the workpieces from the chucking device in the same way, since the workpieces are held for conjoint rotation on the chuck of the chucking device solely by positive engagement, i.e., by positive fit of form fit, and therefore they need only be inserted or mounted in a chucking device chuck structure which is at least partially complementary to a particular workpiece structure. The axial fixing of the workpiece on the chuck of the chucking device is then accomplished by sucking it against the chuck, wherein the vacuum duct opening into the chuck can be subjected to a vacuum as required in order to fix or release the workpiece. Consequently, the chucking device according to the invention allows releasable retention of the workpieces to be machined without the need for clamping or other fixing elements, such as locking bars, bolts and the like, and this has proved advantageous also particularly in respect of automatic loading by means of suitable handling devices, such as robots, since the sequence of motion of the handling device for fixing/releasing the workpiece on/from the chucking device is the same or very similar for almost any workpieces since the workpiece has only to be moved toward the chuck in the axial direction until it is held for conjoint rotation in the corresponding contours thereof, after which the vacuum duct opening into the chuck is subjected to reduced pressure or a vacuum in order to secure the workpiece in an axially fixed manner on the chucking device by suction thereon. Corresponding statements apply to the release of finished workpieces.
By means of the separation according to the invention of the retention of the workpieces for conjoint rotation by positive engagement, on the one hand, and of the retention of the workpieces in an axially fixed manner by means of a vacuum, on the other hand, suspended fixing of the workpieces on the chucking device, in particular, is furthermore possible in order to enable them to be plunged into the bed of grinding and/or polishing granules from above and, if appropriate, moved there—whether in rotation and/or in translation—in a simple manner.
Owing to the two-part configuration of the chucking device according to the invention, the chucking device can furthermore be adapted in a simple manner to workpieces of different geometry that have to be machined since the adapter piece matched to the respective workpiece structure has merely to be substituted and secured on the supporting part, while the supporting part can be used universally for almost any workpieces.
There are various ways of adapting the chuck of the adapter piece to different workpiece structures in order to enable the respective workpiece to be secured for conjoint rotation on the chuck by means of positive engagement. Thus, for example, provision can be made for the chuck of the chucking device to have at least one structure from the group comprising
In each case, retention of the workpiece for conjoint rotation on the chuck of the adapter piece of the chucking device is ensured.
In an expedient embodiment, the chuck of the chucking device has, according to a first variant embodiment, at least one seal, which surrounds the vacuum duct opening into the chuck in order to seal off the vacuum duct with respect to a workpiece inserted into the chuck. It may be advantageous here if the seal is arranged as close as possible to the outer circumference of the chuck or of a workpiece situated therein in order to ensure that the area over which the workpiece is sucked against the chuck by a vacuum when the workpiece is secured on the chuck is as large as possible. As an alternative or in addition, provision can be made, according to a second variant embodiment, for the chuck of the chucking device to be coated with a flexible sealing material on its end surrounding the mouth of the vacuum duct, in order to seal off the vacuum duct with respect to a workpiece inserted into the chuck. Rubber, for example, may be considered as a coating material.
A seal of this kind can be inserted into an annular groove in the chuck of the chucking device, for example, wherein the diameter of the seal should advantageously be greater than the depth of the circumferential groove, ensuring that the workpiece rests only against the seal and that there is a gap within the sealing ring between the workpiece and the chuck of the chucking device in order to transmit the vacuum to the workpiece.
According to an advantageous development, provision can be made for the adapter piece of the chucking device to be penetrated by the vacuum duct and to be fixed on the supporting part of the chucking device in such a way that the vacuum duct which penetrates the adapter piece is connected to a suction duct in the supporting part, which can be connected to the vacuum generator. In this way, a simple and reliable fluid connection between the supporting part and the adapter piece of the chucking device is ensured.
Simple, quick and easily performed fixing of the adapter piece on the supporting part can be ensured in various ways. Thus, according to an advantageous embodiment, provision can be made for the adapter piece of the chucking device to be capable of being fixed releasably on the supporting part of the chucking device by means of screws, bolts, clips or toggle-type fasteners.
According to another advantageous embodiment, provision can be made, in particular, on the one hand, for the supporting part of the chucking device to have a holding structure, which is designed for holding the adapter piece for conjoint rotation and which is of complementary design to a holding structure of the adapter piece, and, on the other hand, for the adapter piece to be held in an axially fixed manner on the supporting part by applying a vacuum to the suction duct in the supporting part and sucking the adapter piece against the supporting part when the vacuum duct in the adapter piece has been closed by inserting a workpiece into the chuck thereof. Such an embodiment offers particularly simple and easy fixing of the adapter piece on the supporting part of the chucking device since, once again, the holding structures provide only retention of said parts on one another for conjoint rotation by virtue of positive engagement, while retention of said parts on one another in an axially fixed manner is once again accomplished by means of a vacuum, with the result that the adapter piece together with a workpiece secured thereon is sucked against the supporting part of the chucking device.
As regards the mutually complementary holding structures of the supporting part and of the adapter piece of the chucking device, which serve for retention one upon the other for conjoint rotation, provision can be made, in particular, for said holding structures to have
Corresponding to the sealing of the adapter piece of the chucking device with respect to a workpiece secured thereon, there is also the preferred possibility, for sealing the adapter piece with respect to the supporting part of the chucking device, that the supporting part and/or the adapter piece of the chucking device, on its end facing the adapter piece and/or facing the supporting part,
The chucking device itself can be fixed releasably on the workpiece holder, e.g. by means of a quick release fastener arranged on its supporting part, which expediently ensures a releasable connection to the workpiece holder which is both fixed against relative rotation and against axial movement and, for example, can comprise latching and/or clamping joints. Instead, the supporting part of the chucking device can also be formed integrally with the workpiece holder or integrated into the latter.
In another advantageous embodiment, provision can be made for the vacuum duct of the chucking device and/or the suction duct of a supporting part to be fitted with at least one shutoff valve in order to supply the chuck with a vacuum or with ambient pressure as required. In this way, simple and quick release of the workpiece from the chucking device in particular is possible by closing the valve, thus ensuring that the workpiece is no longer sucked in.
As an alternative or in addition, it is, of course, also conceivable for a vacuum line connecting the chucking device to the vacuum generator to be fitted with at least one shutoff valve of this kind in order to supply the chuck of the chucking device with a vacuum or with ambient pressure as required.
In order to ensure as far as possible fully automatic operation of the apparatus, it may furthermore be advantageous if the workpiece holder is arranged on at least one lifting device, which is fixed on a movable part of the apparatus and which is designed for moving the workpiece holder backward and forward between an upper position, which is arranged above the container and in which machined workpieces can be removed from the chucking device of the workpiece holder and said chucking device can be loaded with unprocessed workpieces, and a lower position, in which the workpieces releasably secured on the chucking device of the workpiece holder dip into the container to enable them to be machined.
In this way, it is possible to ensure semicontinuous delivery of machined workpieces which have been mounted on the chucking device or to ensure semicontinuous loading of the chucking devices with unprocessed workpieces since the part which can be moved, in particular, in a horizontal plane continuously transfers the respective workpiece holder with one or more workpieces which has/have undergone grinding and/or polishing for a sufficient period of time into the loading/removal position, in which the workpiece(s) can be removed—after its/their workpiece holder/s with the chucking device has/have been moved by means of the respective lifting device to its/their upper position above the container, after which the chucking device of the workpiece holder can be loaded with one or more unprocessed, as yet unmachined, workpiece(s). The unprocessed workpiece(s) can then be plunged into the bed of granules in the container and machined by moving its/their workpiece holders with the chucking device into the lower position thereof by means of the lifting device, while another workpiece holder with the chucking device is transferred to the loading/removal position etc. A loading/removal station for the removal of machined workpieces from the chucking device of the workpiece holder and for loading same with unprocessed workpieces can be arranged to the side of the container, for example, if the respective workpiece holder with the chucking device thereof (or indeed with a plurality of chucking devices thereof) is in the loading/removal position.
The lifting device(s) and/or the movable part are preferably motor-driven under control, in particular under programmable control. Here, the movable part should preferably be connected to a control unit which can be programmed in such a way that it moves each workpiece holder into the loading/removal position after an adjustable machining time, wherein the transfer of the various workpiece holders to the loading/removal position or from there back into the working position should preferably take place at substantially identical time intervals, ensuring that the time intervals for workpiece exchange at the chucking devices of the various workpiece holders are always approximately the same, it being possible for these time intervals to correspond approximately to the total preset machining time divided by the number of workpiece holders.
As already mentioned, the movable part can preferably be a rotatable part (“plate”), on which the lifting devices carrying the workpiece holders with the chucking devices are arranged eccentrically with respect to the axis of rotation thereof and one behind the other in the circumferential direction, wherein it should be possible to rotate the rotatable part backward and forward at least through an angle in order to be able to transfer each workpiece holder successively to the loading/removal position. Here, it must be possible to rotate the part which is rotatable, in particular rotatable about a vertical axis, backward and forward at least through an angle, thus ensuring that all the workpiece holders with the chucking devices thereof can be moved back and forward between the loading/removal position and a working position. If, for example, three workpiece holders are provided, arranged equidistantly one behind the other on lifting devices in the circumferential direction of the rotatable part, it must be possible to rotate the rotatable part through at least 240°, in the case of four workpiece holders through 270° and, in the case of n workpiece holders, through at least (360°/n)×(n−1).
In order to ensure uniform machining of all the workpieces, the workpiece holders with the chucking devices should furthermore be arranged at equal distances from one another and, in particular, also at the same radial spacing from the rotational axis of the container, which is therefore preferably in alignment with the axis of rotation of the rotating part. This ensures that the relative speed of all the workpieces in relation to the grinding and/or polishing granules in the rotating container is the same.
As already indicated, it may furthermore be advantageous as regards effective surface finishing if the workpiece holders are rotatable, in particular under control, with the chucking devices thereof secured for conjoint rotation thereon. In this case, the workpiece holders can be driven in rotation at a selectable, in particular programmable, rotational speed, for example, and it is also possible for the direction of rotation to be variable in order to ensure as homogeneous and uniform surface finishing of the workpieces as possible.
Further features and advantages of the invention will become apparent from the following description of an illustrative embodiment with reference to the drawings, in which:
The illustrative embodiment, shown in
In the illustrative embodiment under consideration, each lifting device 5 comprises, for example, a supporting unit 9 which can be moved backward and forward along a vertical guide 8 and which can be moved up and down by means of a chain or belt drive, for example. In the illustrative embodiment under consideration, the lifting devices 5 can furthermore be moved up and down individually and independently of the other lifting devices 5, independently of one another, by means of a motor (not visible in the drawings), likewise fixed on the underside of the rotatable part 3. One of the workpiece holders 6 with one or more chucking devices 7 is in each case secured on the vertically movable supporting unit 9 (see also
Arranged underneath the lifting devices 5 fitted with the workpiece holders 6 is a container 11 for holding grinding and/or polishing granules (not shown), which can be rotated by motor about a vertical axis, wherein the rotational axis of the container 11 is preferably in alignment with the axis 2 of rotation of the rotatable part 3, thus ensuring that the resulting relative movement between the workpieces mounted on the chucking devices 7 of the workpiece holders 6 and the bed of granules in the container 11 is the same. Each lifting device 5 can move the workpiece holder 6 fixed to its supporting unit 9 vertically backward and forward along the arrow P2 between an upper position, arranged above the container 11, in which machined workpieces 17 can be removed from the chucking device 7 of the respective workpiece holder 6 and the chucking device can be loaded with unprocessed workpieces 17, and a lower position, in which the workpieces 17 mounted on the chucking device 7 of the workpiece holders 6 dip into the container to enable them to be machined.
Moreover, the rotatable part 3 can be moved in such a way about its axis 3 in the direction of the arrow P1 that it can transfer each workpiece holder 6 with its respective chucking device 7 fixed thereon successively to one and the same loading/removal position, the workpiece holder 6 on the right in
In this context, it is possible, in particular, for a loading/removal station (not shown) arranged to the side of the container 11, for example, to be associated with the apparatus in the loading/removal position of the workpiece holders 6, said station serving for the removal of machined workpieces 17 from the chucking devices 7 of the workpiece holders 6 and for loading same with unprocessed workpieces 17 when the respective workpiece holder 6 is situated with its chucking device 7 in the loading/removal position. Here, the loading/removal station can, for example, comprise an automated manipulator, such as a multi-axis (e.g. six-axis) industrial robot, the sequences of motion of which can likewise be programmed in a conventional manner in order to define the handling steps of loading or removal of workpieces 17.
As can furthermore be seen from
As can furthermore be seen from
As can be seen, in particular, from
The chucking device 7 is of two-part design and comprises, on the one hand, a supporting part 7a and, on the other hand, an adapter piece 7b, which is provided with the chuck 71, wherein the adapter piece 7b can be fixed releasably on the supporting part 7a in the manner explained below in order to enable the adapter piece 7b, which is matched to the particular workpiece geometry, to be replaced by other adapter pieces suitable for other workpiece geometries. The supporting part 7a can have a fixing device (likewise not shown specifically), preferably in the form of a quick-release fastener, in particular on its side facing away from the adapter piece 7b, in order to fix the chucking device on the tool holders 6 (
In order to ensure not only retention of the workpiece 17 for conjoint rotation on the chucking device 7 but also for retention of the workpiece 17 in an axially fixed manner, the adapter piece 7b of the chucking device 7 has a vacuum duct 73 (
In the illustrative embodiment under consideration, the suction duct 74 of the supporting part 7a widens in the direction of the adapter piece 7b secured thereon in order to take account of different configurations of adapter pieces 7b with different arrangements of the vacuum ducts 73 thereof. As can be seen from
While the releasable fixing of the adapter piece 7b of the chucking device 7 on the supporting part 7a thereof can, in principle, be accomplished by means of any known fixing means that can be secured and released simply and quickly, e.g. screws, bolts, clips, toggle-type fasteners or the like (not shown), there is also to this extent a functional separation, in the illustrative embodiment under consideration, between the retention of the adapter piece 7b for conjoint rotation on the supporting part 7a of the chucking device, on the one hand, and the retention of said adapter piece 7b in an axially fixed manner on the supporting part 7a of the chucking device, on the other hand. For retention of the adapter piece 7b for conjoint rotation on the supporting part 7a, these are provided with holding structures 79, which, in the present case, comprise two or more projections 79a on the supporting part 7a on the side thereof facing the adapter piece 7b, which projections are complementary to two or more depressions 79b in the adapter piece 7b, on the side thereof facing the supporting part 7a, in order to enable the projections 79a to be introduced into the depressions 79b. The retention of the adapter piece 7b in an axially fixed manner on the supporting part 7a, in contrast, is accomplished by the above-described application of a vacuum to the suction duct 74 of the supporting part 7a, sucking the adapter piece 7b firmly against the supporting part 7a when its vacuum duct 73 has been closed by a workpiece 17 inserted into its chuck 71. In order to ensure satisfactory sealing of the vacuum duct 73 of the adapter piece 7b with respect to the suction duct 74 of the supporting part 7a in this case, the supporting part 7a (or, alternatively, the adapter piece 7b; not shown) has, on the side thereof facing the adapter piece 7b, an annular groove 77, which is provided with an annular seal 78, expediently extends within the holding structures 79 in the radial direction and surrounds both the suction duct 74 of the supporting part 7a and the vacuum duct 73 of the adapter piece 7b. As an alternative, it is also possible for the supporting part 7a and/or the adapter piece 7b to be coated (not shown) with a suitable sealing material, e.g. rubber, on the end thereof facing the respective other part 7b, 7a. In this way, particularly simple and quick workpiece exchange is possible since the workpiece 17 is arranged in positive engagement on the chuck 71 of the adapter piece 7b and the latter is arranged in positive engagement on the supporting part 7a via the holding structures 79, after which the suction duct 74 of the supporting part 7a is subjected to a vacuum in order to secure the adapter piece 7b, together with the workpiece 17, in an axially fixed manner as well. When the suction duct 74 of the supporting part 7a is once again supplied with ambient pressure, the adapter piece 7b can simply be released from the supporting part 7a of the chucking device 7 again. Corresponding statements apply, as described above, to the release of the workpiece 17 from the chuck 71 of the adapter piece 7b.
The above-described apparatus for surface finishing workpieces can be operated as follows:
In the situation, illustrated in
| Number | Date | Country | Kind |
|---|---|---|---|
| 20 2012 012 137.5 | Dec 2012 | DE | national |
