The invention relates to a chuck for an apparatus for machining a tubular workpiece rotating about a rotation axis that coincides with the center of the chuck, comprising at least two chuck slides movable radially relative to the rotation axis for gripping and freeing the workpiece, mounted on a front face of a chuck head plate, equiangularly spaced on it, and carrying jaws.
An apparatus for machining pipe ends, particularly for cutting threaded connectors, of a tubular workpiece that rotates about a rotation axis, is known from DE 10 2009 053 679. The pipe thread is generally produced in a single pass over the pipe end of the chucked tubular workpiece or pipe, with the movements of the tools being controlled numerically. To clamp the pipe, a machining apparatus has a headstock chuck at the front end where an indexing head with tools is effective, and a tailstock chuck on the back end that together with the headstock chuck grips the pipe concentrically relative to the rotation axis. A machining center with at least two opposite machining apparatuses is accordingly equipped with four chucks. Both the front end chuck and the back end chuck preferably have three chuck slides with jaws, in order to release and clamp the workpiece.
In such thread-cutting machines with a rotating pipe and indexing heads carrying tools, controlled by NC shafts, machining requires at least two clamping functions. First of all, it must be possible to clamp the pipes on center in exact alignment with the machine center, and second, with adaptation to clamped pipes clamped externally in centered and eccentrically. Eccentric clamping by the chuck slides means that the chuck slides must be able to engage against the pipe, which might be slightly curved over its length, in a compensatory manner, and therefore not precisely centered. This then allows adaptation to pipes that are otherwise clamped externally on center. External centered clamping is understood to mean additional clamping of the pipe ends that project out of the front end chuck, spaced from or close to the threads to be produced later. Such chucks, particularly headstock chucks, are therefore very complex, and, in practice, tightening and loosening of the chuck slides or of the jaws carried by them takes place by wedge systems with a radial deflection relative to the center or the rotation axis of the chuck. This requires large diameters and lengths of the chucks, with a corresponding large mass, which is disadvantageous for operation.
The object of the invention is therefore to provide a chuck of the type described above but having improved operating properties.
This object is attained according to the invention, in that transverse slides transverse slides movable in the head plate tangentially relative to the rotation axis and each acted on by a respective actuator each have a slide block formed on one longitudinal side as a rack meshing with a respective gear of each chuck slide, each chuck slide being provided on a respective back face with a follower claw engaging in a respective guide groove formed in the slide block of the respective transverse slide to convert its movement into a positioning movement of the respective chuck slide that moves radially of the rotation axis, the gears having a coupling pinion that can be engaged and disengaged axially relative to the rotation axis.
Therefore a movement conversion, without wedge systems, parallel to the center of the chuck by engagement of the transverse slides that can be acted on by the actuator in the plane of the head plate, and, at the same time, radially of the rotation axis, can be achieved. This results in a lesser mass accompanied by increased dynamics and shortened run-up and braking times of the cycles that are unavoidable after each machining operation. During clamping and release of the pipe, large surface areas, namely those of the follower claw and of the guide groove in which the complementary follower claw slides, is compulsorily displaced during setting movements of the transverse slide, to transfer great forces with advantageous surface pressure. The centered and eccentric clamping does not require any increase in the construction height or length of the chuck. Centered clamping takes place by the gears connected separately with a chuck slide, in each instance, the synchronous running of which, and thereby also that of the three gears, is guaranteed by the engaged coupling pinion, while when the coupling pinion is disengaged, eccentric clamping is possible.
A preferred embodiment of the invention provides that the coupling pinion, which can be moved between an engaged and a disengaged end position, meshes with all three gears in the engaged end position, and with only one gear in the disengaged end position. Engagement and disengagement of the coupling pinion can take place manually, from the front of the chuck or of the head plate so that, when the coupling pinion is disengaged, all three slide systems and the related gears can move independently of one another, adapt to the pipe around of the center, and can clamp the pipe.
According to one suggestion of the invention, the transverse slides and the chuck slide are disposed so as to intersect at an acute angle, with an engagement angle of the travel path of the follower claw and guide groove that transfers the setting stroke of the transverse slide to the setting stroke of the chuck slide, with a gear reduction. If this angle amounts to 30°, a gear reduction of 1 to 2 (sin 0°=0.5) can be achieved, which promotes rapid clamping and release.
According to an embodiment of the invention, a cylinder is provided as the actuator of the transverse slides, the slide block of the transverse slides being connected with the piston by a piston rod. The required movements during clamping and release can thereby be implemented in a simple manner.
According to an advantageous suggestion of the invention, a position-indicating bolt that shows the engaged and disengaged position of the coupling pinion extends axially in the chuck head plate, is displaced synchronously with the coupling pinion as a function of its movement, and has a front end that can be seen from the outside on the head plate. The machine operator therefore always has precise knowledge about the functional position of the coupling pinion and can engage or disengage the coupling pinion accordingly, depending on the machining requirement (centered with direct alignment relative to the machine center, or noncentric clamping).
Further characteristics and details of the invention are evident from the claims and from the following description of an exemplary embodiment of the invention shown in the drawings. These show:
A chuck 1 of an apparatus for cutting threads or threaded connectors on pipe ends, shown in
To move the chuck slides 7a, 7b, and 7c with the jaws 8a, 8b, and 8c radially of the center rotation axis 5 of the chuck 1, each chuck slide 7a, 7b, and 7c, has a respective transverse slide 9a, 9b, and 9c recessed in the head plate 2 it and movable tangentially to the rotation axis 5. These slides each consist, as can be seen in
At their fronts, which lie at the back in the drawing plane in
Each transverse slide 9a, 9b, and 9c has a respective gear 19a, 19b, and 19c in the chuck 1 axially stacked along the central throughgoing passage 4, from the front to the rear (see
If, on the other hand eccentric clamping is to take place, the coupling pinion 20 is disengaged and is then in engagement only with one gear, the outermost gear 19a. Thus, all three slide systems, with the respective connected gears can move independently, adapt to the pipe at different spacings from the center, and clamp it in place.
As can be seen in
The chuck 1 described is suitable both as a tailstock chuck and, in particular, as a headstock chuck, and fulfills the required chucking function of clamping with direct alignment relative to the machine center, in centered manner, and/or of eccentric clamping of the pipes to be machined.
Number | Date | Country | Kind |
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102011117883.3 | Nov 2011 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2012/004199 | 10/6/2012 | WO | 00 | 4/17/2014 |