MACHINE TOOL WITH HORIZONTAL SPINDLES

Abstract: The machine tool comprises two headstocks (16, 17), arranged on a support (10), which are movable independently of each other along their height and their longitudinal direction. A respective one (17) of the headstocks is active in the treatment of a workpiece attached on a workpiece carrier (20), while the other headstock (16) can be moved behind a tool magazine (24) for receiving a tool therefrom. While the one headstock is still working on the workpiece, the other headstock with the next tool can already be accelerated to the required working rotational speed and be advanced to the tool. Thus, the time required for exchange of tools is extremely shortened.

Description: MACHINETOOLWITHHORIZONTALSPINDLES The invention is directed to a machine tool for the drilling and/or grinding treatment of workpieces, comprising at least two headstocks. Machine tools are known wherein the headstock removes or resp. returns the tools directly from/ into a fixed or movable tool magazine. In such ma¬ chine tools, the headstock must be advanced to the tool magazine upon completion of a treatment pro¬ cess. At the tool magazine, the tools are exchanged, and the headstock is subsequently guided back to the workpiece. The exchanging of tools requires a con¬ siderable length of time, which is caused not only by the movement processes to be performed by the headstock but also by the time losses due to the decelerating and accelerating of the working spin¬ dle. Throughout the exchanging of tools, the machine tool is not available for treatment processes. In machine tools comprising a large number of work¬ ing spindles in a revolver configuration, the remov¬ ing of one working spindle from the workpiece and the advancing of another working spindle to the workpiece along with the coupling and accelerating processes takes considerable time. Although, during operation of one working spindle, another working spindle can be equipped with new tools, this will require high expenditure in working spindles. Fur¬ ther, such an approach necessitates the use of a tool magazine which is advanced to the revolver sys¬ tem located in its operating position. A machine tool forming basis of the preamble of claim 1 is known from JP 59-69242 A (Patent Ab¬ stracts of Japan M-317, August 15, 1984, Vol. 8, No. 177) . This machine tool is provided with a support whereon two headstocks are movable in vertical di¬ rection independently of each other. Each headstock has a dedicated tool magazine arranged thereabove which is moved together with the headstock. The transfer of the tools from a tool magazine to the appertaining headstock is performed by a swivel arm. The whole support of the machine tool is displace- able in feeding direction (towards the tool) . This machine tool offers the advantage that a respective one of the headstocks can engage the workpiece while an exchange of tools can be carried out on another headstock. Thus, considerable time is saved because no time requirements exist for exchanging the tools. Further, a machine tool known from Patent DD 263 725 Al comprises a single headstock to be displaced ver¬ tically on the support. Additionally, the headstock can be moved horizontally in its longitudinal direc¬ tion to allow exchange of tools using a tool maga¬ zine. The tool magazine is arranged before the ma- chine support and carries various tools on a hori¬ zontally moveable slider, such that each tool can be moved into a transfer position for the headstock. The guiding path for the tool magazine must be at least twice as long as the magazine slider carrying the tools. It is an object of the invention to provide a ma¬ chine tool which is very straightforward in con¬ struction and allows a very quick exchange of tools. According to the invention, the above object is solved by the features indicated in claim 1. In the machine tool of the invention, two headstocks are movable independently of each other on the sup¬ port along vertical guides. Further, each headstock is movable horizontally in its longitudinal direc¬ tion. While one of the headstocks carries out a treatment on the workpiece by means of a tool, the other headstock is free to move to a workpiece maga¬ zine, deposit the old tool and take up a new tool. When the headstock performing the treatment has fin¬ ished its operation, it will be retreated, and the headstock carrying the new tool will be applied to the workpiece. In this manner, the tool exchange time after completion of a treatment step can be limited to that length of time which is normally needed for the process from one operating position to the next one. Thus, nearly no additional time or no time at all is required for exchanging the tools. The exchange of tools can be carried out in about one second. Treatment of the workpieces is performed by alternative operation of the two headstocks, wherein respectively one headstock is active in treating the workpiece while the other either per¬ forms an exchange of tools or is kept waiting in a standby position. The tool magazine provided in common for both head¬ stocks has two exchange positions, i.e. one for each headstock. Under automatic control of the tool maga¬ zine, the individual tools are moved into the exch¬ ange position for the respective headstock for which they are determined. The headstocks are guided be¬ hind the tool magazine to take over the tool posi¬ tioned in the exchange position, by carrying out a simple advance movement. Therefore, no transfer de¬ vices are required between the tool magazine and the headstock. The tool magazine has a short construct¬ ional length and a high storing capacity for tools, both headstocks being serviced by the horizontal lower strand of the circulating magazine, with the exchange positions being arranged at the same height. The double arrangement of the headstocks provides for a decoupling between the moving sequence for treatment (essential operating time) and the exch¬ ange of tools (auxiliary process time) . Through the alternating use of the respective headstock equipped with the new tool and accelerated to the operating rotational speed, the nonproductive auxiliary pro¬ cess times are practically eliminated. Because of said decoupling effect, the moving processes in¬ volved in the exchanging of tools can be determined in such a manner that acceleration jumps and jolts are largely prevented, especially during run-up and slow-down of the working spindle of a headstock, during magazine and tool clamping movements and dur¬ ing axial movement of the headstock for tool ex¬ change. Thus, the lifespan of the mechanical and electrical components is increased. The headstocks can be designed for different power specifications, the respective current task being performed by that headstock which is suited for the treatment process in question. Thus, for instance, one headstock can be dimensioned for power machining by means of large grinding tools, and the other one can be dimensioned for the use of high-speed drill¬ ing tools. A further advantage resides in that the operability of the machine tool is still maintained even in case of failure of one headstock, although more time will be required in this case for the exchange of tools. Further, it is possible under certain conditions to treat two workpieces simultaneously and in parallel. Preferably, the support of the machine tool is a portal support comprising two vertical posts and a crosshead. In this arrangement, the guiding paths of the headstocks are located on the mutually confront¬ ing inner sides of the posts. Alternatively, use can be made of a support which consists of a single post and wherein the guiding paths of the spindle heads are located on the mutually averted outer sides. The tool magazine is arranged in an advanced position on the front side of the support. Preferably, the tool magazine is arranged on the upper end of the support, although it can likewise be arranged on the lower end, e.g. in the base por¬ tion of the machine. If the tool magazine is provid¬ ed on the upper end of the support, the large height will make it difficult for the operating person to load the tool magazine with tools. According to a preferred embodiment of the invention, the tool mag¬ azine can be pivoted about an axis near one of its ends to thus lower the other end into a loading po¬ sition. The machine tool preferably comprises a workpiece carrier which transversely to the lengthwise orien¬ tation of the headstocks is displaceable in a hori¬ zontal direction. A machine tool of this type con¬ stitutes a self-contained treatment unit. By inte¬ gration of the workpiece carrier into a transfer line, the machine can also be used as a flexible working station in interlinked systems. Preferably, the controlling of the machine tool is performed completely in numerical fashion, i.e. all of the moving processes of the headstocks, the tool magazine and the workpiece carrier are controlled according to a predetermined program sequence and are coordinated with each other, so that all move¬ ments are carried out automatically. An embodiment of the invention will be explained in greater detail hereunder with reference to the draw¬ ings. Fig. 1 is a partially cut-out perspective view of the machine tool, Fig. 2 is a side view of the machine tool, with the upper portion and the tool magazine viewed in cross section, and Fig. 3 is a partial view of Fig. 1, with the tool magazine pivoted down into the loading posi¬ tion. According to Fig. 1, the machine tool comprises a support 10 projecting from a base 11. Support 10 is provided as a portal support comprising two mutually spaced vertical posts 12 having their upper ends connected to each other by a crosshead 13. Arranged on the mutually confronting inner sides of the posts 12 are vertical guides 14 for respectively one vertically movable slider 15. Each slider 15 comprises a horizontal guide for horizontal movement of a headstock 16 or resp. 17 therealong. Within the headstock 16 or resp. 17, there is arranged a drive unit for a working spindle 18 which projects from the front end of the headstock and comprises a re¬ ceiving portion for a tool. In front of support 10, a workpiece carrier 20 is arranged on base 11 in a manner allowing displace- ment along a horizontal guide means 21 transversely to the lengthwise direction of headstocks 16 and 17. This moving direction of workpiece carrier 20 is the X-direction, the vertical direction is the Y-direc- tion and the longitudinal direction of headstocks 16,17 is the Z-direction. In the illustrated embodiment, the workpiece carrier 20 is movable exclusively in the X-direction. The movements in the Y- and Z-directions are carried out by the respective headstock. Workpiece carrier 20 can be provided with a rotary table, a turning arrangement, a pallet clamping device, a pallet exchange device and the like. It is imperative that the workpiece carrier 20 be able to receive and position the workpiece in an exactly defined manner. Drive units 22,23 for the vertical movements of headstocks 16,17 are arranged on crosshead 13. The headstocks are individually displaceable indepen¬ dently from each other in Y- and Z-directions. While, for instance, headstock 17 is involved in treatment of a workpiece, headstock 16 can be moved into a take-up position for tool exchange. A tool magazine 24 is arranged in an advanced posi¬ tion (i.e. in front of the support) at a fixed height on support 10. The tool magazine comprises an endless conveying means, i.e. a chain, arranged for endless movement in a vertical plane and having out¬ wardly projecting tool holding units 25 attached thereon. Tool magazine 24 is of an elongate shape, and those of the tool holding units 25 which project from the horizontal lower strand can be engaged by the headstocks. The tool holding units 25 are pro¬ vided with gripper arms for holding respectively one tool 26. As shown in Fig. 2, headstock 16 can be moved up¬ wards into a takeover position UP behind tool maga¬ zine 24. The takeover position is the upper end po¬ sition of headstock 16 in the Y-direction and at the same time the rear end position in the Z-direction. In the takeover position, the spindle 18 is in axial alignment behind that tool 26 which is in the ex¬ change position WP in the horizontal lower strand of tool magazine 2 . When headstock 16 is slightly ad¬ vanced out of takeover position UP in the direction of the Z-axis, headstock 16 seizes the rear end of tool 26 by the receiving portion of working spindle 18. Simultaneously, tool 26 is being secured in working spindle 18. Subsequently, the headstock 16 can move downwardly and, in doing so, detach the tool 26 from the tool magazine 24. At the height of its lower strand, tool magazine 24 has two exchange positions, notably one for each headstock. To make it easier for an operating person to manual¬ ly load tools into the tool magazine 24 arranged on the upper end of support 10, the tool magazine can be pivoted about a horizontal pivot axis 30 which is schematically indicated - although not explicitly shown - in Fig. 1. The pivot axis 30 is arranged in the vicinity of one end of the elongate tool maga- zine. When pivoting the tool magazine about pivot axis 30, it will take the pivoting position shown in Fig. 3 wherein the end 24a has been pivoted down¬ wards. Thus, the tools 26 near the downwardly pivot¬ ed end 24a are easily accessible. For pivoting the tool magazine, a cylinder 31 is arranged on cross¬ head 13. The chain of tool magazine 24 is driven by a numerically controlled drive unit so that the in¬ dividual tool holding units 25 can be moved respec¬ tively into the desired position. The tool magazine 24 is covered by a hood 32 at¬ tached on the upper end of support 10 and being open only in downward direction.

Claims: Claims A machine tool, comprising a support (10) having two headstocks (16,17) arranged thereon to be moved independently of each other along vertical guides (14) , c h a r a c t e r i z e d i n that each headstock (16,17) is additionally mov¬ able in its longitudinal direction horizontally on the support (10) , that the support (10) has arranged thereon a common tool magazine (24) for both headstocks (16,17) which is arranged as a circulating magazine comprising a circulating endless conveying means, and that each of the headstocks (16,17) is movable into a takeover position (UP) for receiving a tool (26) from the tool magazine (24) . 2. The machine tool according to claim 1, charac¬ terized in that the tool magazine (24) is ar¬ ranged at a fixed height on the upper end of the support (10) . The machine tool according to claim 1 or 2, characterized in that the tool magazine (24) is of an elongate shape and can be pivoted about a pivot axis (30) near one of its ends to lower the other end into a loading position. The machine tool according to any one of claims 1-3, characterized in that a workpiece carrier (20) is arranged in front of the support (10) , to be horizontally displaceable transversely to the lengthwise direction of the headstocks (16, 17) .

Inventors: FEIN HORST, KOELBLIN ROLF, MUELLER WERNER, SCHNEIDER REINHARD, FEIN, HORST, KOELBLIN, ROLF, MUELLER, WERNER, SCHNEIDER, REINHARD
Applicants: FEIN HORST, HONSBERG LAMB SONDERWERKZEUGMA, KOELBLIN ROLF, MUELLER WERNER, SCHNEIDER REINHARD, FEIN, HORST, HONSBERG LAMB SONDERWERKZEUGMASCHINEN GMBH, KOELBLIN, ROLF, MUELLER, WERNER, SCHNEIDER, REINHARD
Application year: 1996
Main classification: B23C1
IPC codes: B23B39, B23C1, B23Q3, B23Q39