Method and apparatus for machining workpieces

Method and apparatus providing a tool turret for a machine tool with at least one motor-driven tool that is suitable for machining of wavy or tubular workpieces. The transport of the workpieces from one machining station to the next is effected in a simpler, more reliable, and less expensive fashion, because the machine tool has a tool turret that includes a gripping element for taking hold of, transporting, and positioning workpieces, rather than using an additional tool.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method and apparatus for machining workpieces, and more particularly to a machine tool equipped in a novel way with a tool turret to enable machining of wavy or tubular workpieces.

2. Prior Art

EP 0 978 351 A2 describes a device for machining workpieces with at least two adjacently arranged lathes that respectively contain a vertically arranged, rotationally driven work spindle for clamping the workpiece and at least one device for accommodating several machining tools. The rotational axes of all lathes are essentially arranged vertically in this case, and one rotating/pivoting device is respectively provided between the lathes in order to transfer the workpiece from one lathe to the next lathe after each respective machining step is completed. One disadvantage of this arrangement can be seen in the fact that a completely separate lathe with its own control, its own drive, and its own miscellaneous equipment must be provided for each machining step that is to be carried out. Another disadvantage is that a separate rotating/pivoting device needs to be provided for each transfer from one lathe to the next lathe, significantly increases construction expenses.

DE 199 59 961 A1 describes a machine tool, in particular a lathe, with several vertical workpiece spindles, wherein the workpiece can be directly transferred from one spindle to another spindle by means of receiving devices for the workpiece provided on the respective spindles. This device can only be used for machining of very specific workpieces and is particularly unsuitable for any machining of wavy or tubular workpieces.

DE 199 50 706 C2 describes a device for clamping and/or holding workpieces on a machine tool. This device comprises a gripping element that is suitable for wavy or tubular workpieces and that can be arranged on the tool table of a machine tool. The gripping element requires its own holding arrangement and its own drive, and frequently obstructs the work region of a machine tool due to the small available space. In addition, its manufacture is comparatively expensive because the gripping element requires its own holding arrangement and its own drive.

German Utility Model DE 93 21 397 U1 pertains to a lathe, wherein a tool carrier may be equipped with a gripping hand that is able to take hold of the workpiece being machined in the associated spindle and deposit said workpiece from the top onto a delivery stack arranged adjacent to the lathe.

WO 01/89761 A1 describes a device for taking hold of and transporting workpieces in lathes with several machining stations, wherein two gripping devices arranged to the right and left of each machining station serve to take hold of, transport and position the workpieces. This device also has a tool turret. However, the device merely comprises a series of individual elements, in particular gripping elements and a tool turret, but no combination of these elements, so that significant construction expenses and correspondingly high costs result.

SUMMARY OF THE INVENTION

Consequently, the invention relates to a method and apparatus comprising a machine tool that is designed in such a way that the transport of the workpieces from one machining station to the next machining station can be carried out in a much simpler, more reliable, and less expensive fashion.

This objective is attained with a machine tool with at least one machining station, with at least two gripping devices that are arranged to the right and the left of the machining station and serve for taking hold of, transporting, and positioning workpieces, and with at least one tool turret. The tool turret is provided with a gripping device that is arranged to the left and to the right, respectively, of the machining station for the purposes noted. Advantageous embodiments are disclosed herein. One embodiment of the invention is described in greater detail below with reference to the enclosed figures of the drawing.

FIG. 1shows a machine tool1, in which components that are not essential for the invention, in particular details of the drive, the control, and the housing, are not illustrated in order to provide a better overview. The described machine tool is particularly suitable for machining workpieces4of wavy shape, and the following description pertains to wavy workpieces4. The machine tool1consists of three successively arranged machining stations7,7′,7″, wherein it is assumed that the workpiece4arriving from the workpiece feed station8in the form of a magazine is transported to the machining stations7,7′,7″, and that processing of the workpiece4takes place in each machining station. The machining may differ from station to station, or be carried out similarly or identically in accordance with the so-called step-by-step method. In the embodiment shown, the workpiece4is machined differently in the successive machining stations7,7′,7″.

InFIG. 1, the workpiece feed station8, realized in the form of a magazine with wavy workpieces4, is situated to the left of the machine tool. This magazine is followed by the first machining station7that contains a stationary rest9suitable for holding the workpiece4to be machined in the vertical position. The first machining station7also contains a slide6in the form of a cross slide. This slide can be displaced vertically as well as horizontally and carries a tool turret2on its upper side. The tool turret2is conventionally equipped with a series of different tools5. This is illustrated quite clearly inFIG. 5(top view of two tool turrets2). The tool turret conventionally comprises an active drive for activating the tools5.FIG. 5also shows that in one position the tool turret2contains a gripping element3instead of a tool5. This gripping element can also be activated by the drive of the tool turret2, and moved at least into an open position and a closed position.

The first machining station7is followed by a second machining station7′ that in the embodiments shown has a motor spindle10with a vertical axis. This motor spindle10is able to take hold of the workpiece4to be machined from the top and to set said workpiece in rotation, wherein the bottom of the workpiece is stabilized with a tailstock11and its center is, if so required, stabilized with a steady rest12. Analogously to the first machining station7, the second machining station7′ also contains a tool turret2supported on a slide6in the form of a cross slide. This tool turret2, as well as its slide, its support, and its gripping element, are realized identically to the first machining station7.

The second machining station7′ is followed by a third machining station7″ that is realized exactly like the second machining station7′, i.e., it is also equipped with a motor spindle10with a vertical axis, a tailstock11, and, if applicable, a steady rest12. The machine tool shown is also equipped with an additional tool turret2downstream of the third machining station such that each respective machining station7,7′,7″ has an essentially identical tool turret2arranged on the left and on the right side on a cross slide.

The functions of the machine tool1and the tool turret2are described in greater detail below with reference toFIGS. 2-6.

The wavy workpieces4that arrive from the workpiece feed station8and lie adjacent to one another in a parallel fashion are arranged in a magazine to the left of the machine tool1. In a first step, the cross slide6is displaced downward and toward the left, wherein the cross slide rotates about the vertical axis and aligns the tool turret2such that the gripping element faces the nearest workpiece4. The gripping element, which can be rotated about a horizontal axis, is oriented such that it can take hold of the wavy workpiece4. After the gripping element3has closed around the workpiece4, the slide6is displaced upward and assumes the second position shown in FIG.3. Subsequently, the gripping element3rotates about the horizontal axis by 90° such that the workpiece4assumes the vertically aligned third position shown in FIG.4. The entire tool turret2then rotates about its central axis, as indicated by the arrow inFIG. 5, where the workpiece4is situated in a fourth transfer position. The tool turret ultimately reaches the fifth position, illustrated inFIG. 6, in which the workpiece4is taken hold of by the stationary rest9and clamped in this machining position.

The workpiece4is subsequently machined by the two tool turrets2arranged to the left and the right of this first machining station7, wherein the various tools5of both tool turrets2may be conventionally utilized in order to produce holes, milled cuts, and the like on the workpiece4. In this first machining station7, the upper side of the workpiece4in particular is machined, such that it can be taken hold of by a motor spindle10. In the embodiment shown, a face milling cutter13is provided for machining the walls of the wavy workpiece4.

After the workpiece4has been machined in this first machining station7, it is taken hold of, turned, and ultimately transferred to the second machining station7′ by the gripping element3of the tool turret2arranged to the right of this machining station7. In the embodiment shown, this machining station consists of a motor spindle10into which the top of the wavy workpiece4is clamped. The bottom of the workpiece is fixed by a tailstock11, and the central section is fixed by a steady rest12. The so-called rough-turning of the workpiece4is carried out in this second machining station7′. After this machining step is completed, the gripping element3of the corresponding tool turret2that is arranged [missing words: to the right] of the second machining station7′ takes hold of and transports the workpiece4to the third machining station7″, which also comprises a motor spindle10, a tailstock11and a steady rest12in the embodiment shown, and in which the finish-turning of the workpiece is carried out. After this machining step is completed, the tool turret2arranged to the right of the third machining station7″ and its gripping element3, respectively, transport the workpiece4to the delivery stack14.

FIG. 7shows another embodiment of the invention which, among other things, is characterized by the fact that an additional tool turret2is provided for the same number of machining stations7. It is particularly important, with respect to the efficiency of the machine tool1, to adapt the machining times in the various machining stations7,7′ and7″ to one another. Due to the special arrangement of the tool turrets2and the ability to horizontally displace said tool turrets, they can be used selectively in the machining station that is adjacent on the right or the left side, depending on the respective requirements. In the embodiment according toFIG. 7, two tools of different tool turrets2are used simultaneously in the last machining station7,″ such that 4-axis turning of the workpiece becomes possible. Since the finish-turning carried out in this second machining station7″ usually requires more time than the two other machining steps (end machining, and rough-turning), the time required for finish-turning can be cut in half by utilizing two tools. These measures make it possible to achieve approximately identical cycle times in the three machining stations7,7′ and7″.

For example, it would also be conceivable that a milling cutter of the tool turret2would mill a groove in the adjacent machining station on the left side, and a grinding wheel would subsequently grind a shaft seat in the adjacent machining station on the right side. The highly flexible utilization of the tools makes it possible to significantly increase the productivity of the machine tool.

In the machine tool according to the invention and the tool turret2utilized therein, it is particularly advantageous that a separate device is not required to transport the workpieces4from one machining station to the next machining station because a gripping element3is integrated into the respective tool turrets2. This eliminates components that are susceptible to wear, and the manufacturing costs are also significantly lowered, and a more compact structural design is achieved.

Another advantage of the machine tool according to the invention is that a single machine can be universally utilized for several machining steps, in particular on wavy workpieces4. Since the invention proposes the utilization of a highly integrated construction, it is no longer necessary to arrange several independent lathes in series and to connect said lathes by means of transport devices, as is the case in the prior art.

In addition, it is particularly advantageous that the workpieces are machined in the vertical position. In contrast to devices known from the prior art in which the workpieces are arranged horizontally, this provides significant advantages with respect to available space, as well as improved accessibility for the operator and the ability to better monitor the machining steps.