Machine tool

A machine tool having a machine frame which has a stand and a machine sub-structure, a workpiece carrier arrangement which can be moved on linear guides, and a machining unit which is arranged on the stand. The machining unit can be moved along at least one coordinate axis and comprises an exchangeable cutting tool. The linear guides and the linear drives of the workpiece carrier arrangement are covered by longitudinally continuous, stationary cover elements and are thus protected against chip deposits.

FIELD OF INVENTION

The present apparatus relates to a machine tool having a movable workpiece carrier arrangement on linear guides, a machining unit movable in at least one coordinate axis, and having an exchangeable cutting tool, and cover elements arranged over the linear guides to protect against chipfall during machining operations.

BACKGROUND OF THE INVENTION

Relatively small and inexpensive drilling and milling machines are usually made in a cross table design, that is, two of the three main axes are arranged in the machine table. This design results in a horizontally two-dimensional design of the machine bed for receiving the axes. The linear guides aligned along the machine bed in the two coordinate axes and the linear drives thereof must be protected from chipfall and deposits. This is usually done by what is called telescopic covers made of formed sheet segments which can be pushed on top of each other. A drawback of such telescopic covers is the rather large area that, is covered by traveling, which calls far a corresponding enlargement of the machine cabin and the set-up area for the machine. Due to the necessity of arranging the workpiece table at a user-friendly height and due to the necessary stable design of the machine bed, the covers cannot be arranged at an angle of inclination favorable for the chipfall so the chips stay on the covers during the operation. This results in an early wear of the covers, in particular in the bordering area.

In the case of machines having a cross table design, the top side of the machine bed is usually made in a horizontally two-dimensional fashion to receive the table axes or the linear guides, or both. The discharge chutes provided in the bed, which serve for transporting of the chips, can only have a very small gradient of up to 10° on account of the limited workpiece table height and the necessary height of the machine bed. Complex additional devices for cleaning the respective components from the chips and for removing the chips by rinsing or blowing are not always fully effective and increase the technical effort.

SUMMARY OF EMBODIMENTS OF THE INVENTION

It is a purpose of the apparatus to create a machine tool, in particular for milling and drilling, which achieves improved chipfall without the necessity of costly additional devices and which has a set-up area and cabin size that are reduced with respect to machine tools having conventional covers.

According to the embodiments disclosed, the linear guides and drive members of the workpiece carrier arrangement, which can be moved along the machine sub-structure, are covered by longitudinally continuous fixed or stationary cover elements so as to be protected against chipfall.

The chipfall space preferably has a funnel-type shape confined by lateral angular faces, which enables a favorable automatic chipfall into a chip disposal located at the funnel bottom. This makes it possible to reduce the effort for removing the chips and to decrease the number of machine stand-stills for cleaning. According to this concept, the linear guides and the drive members of at least one machine axis are arranged along the machine bed in such a way that the linear guides and the drive members are covered by the cover elements which are attached to the machine bed and are stationary therewith so as to be protected from chipfall and coolant deposits. The cover elements are preferably made as profiled sheets or continuously folded sheet strips and arranged in stationary fashion. With this structure the guide rails and drive members, for example, the spindles of the ball recirculation drives, are covered with adequate intermediate distance and over their entire effective length.

An advantage of this arrangement is that the sheet cover does not extend the area traveled over by the table assembly when moving in the axial direction since the cover elements are stationary and no block dimensions of the covers must be observed. Furthermore, the cover elements can be small and thin-walled since they only prevent the attachment of chips and other solids and otherwise do not have to comply with any supporting function. The inclination of these cover sheets should be chosen to be large enough for chips which might strike to slide downwardly into the chip disposal. Therefore, what is useful in this concept is that the chipfall and the removal of chips can be significantly improved compared with the known cross table machines. This enables shorter non-productive times and longer trouble-free running times. Since conventional complex telescopic covers can be omitted, it is thus possible to reduce the manufacturing costs, to increase the operational reliability, and to also reduce the size of the cabin and of the set-up area for the machine.

In a particularly useful embodiment of the apparatus, only one of the main axes of the machine, that is, the linear guide for the workpiece, is arranged along the machine bed, while the linear guides in the two other main axes are assigned to the machining unit with the work spindle. As a result, complex covers which are moved along and have the above described drawbacks are no longer required since the two spindle-side linear guides are protected by covers which make do without movable parts. In order to avoid the relatively large variable projections of the spindle sleeve in this concept, the linear guide can advantageously be assigned to the machine sub-structure in the main Z-axis.

In another useful embodiment, one of the two linear guides for the workpiece table can be provided on the sub-structure, that is, on both side walls of the sub-structure. This arrangement is a cross table machine concept which is optimized with respect to the chipfall and the set-up area of which is only minimized with respect to the bed axis.

In a useful design of this machine tool, the outer sides of the side walls of the machine bed are aligned in a substantially vertical fashion and at least part of the inner surfaces of these side walls are inclined toward one another in a funnel-shaped fashion. This enables the chips produced during processing to slide over these inclined inner wall sides to the bed bottom, funnels made of plate-like or sheet-like, or both, elements having inclined lateral faces can advantageously be mounted between the side walls of the machine sub-structure, wherein the inner surfaces of the side walls can then extend vertically, in offset fashion or in another way.

In a variant, a linear guide is usefully provided in the Y-coordinate axis along the inner surfaces of each of the side walls, each linear guide being covered by a strip-like protective plate. These protective plates mounted on the side walls should also have an inclination sufficient for the striking chips and liquids to slide down. These protective plates are configured to cover the linear guides fully and over the entire length thereof so as to prevent chips and other substances from depositing on these longitudinal guides. The same applies correspondingly to the linear drives which extend in the longitudinal direction and which are here formed as what is called “ball screw spindles.” In the design in question, a ball screw spindle is usefully provided in the central area between the two linear guides below the workpiece table as a drive element, which extends in parallel to the side walls of the bed and is covered by an angular strip-like protective plate.

In a further embodiment of the machine tool, it is advantageous to arrange a first linear guide on the front side of the stand and a second linear guide on a cross-beam which extends between the side walls of the bed, that form a fall funnel, below the workpiece table. The workpiece table may be formed by a ball screw spindle. In this embodiment, the first linear guide and a linear drive for the workpiece table can advantageously be covered by a protective plate strip mounted continuously on the stand. A saddle-like, longitudinally continuous protective plate can be mounted on the flexurally rigid cross-beam for the second linear guide. The cross-beam is rigidly fixed, to the bottom or to the side walls of the bed and the protective plate covers the second lower linear guide.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Machine tools of the type shown are milling and drilling machines having three axes of motion. As is evident, machine frame1has stationary stand2made as a frame structure and bed-like sub-structure3which is advantageously designed therewith in what is called a single block design. The structure has side walls4,5and bottom6according toFIG. 1. As shown inFIG. 2, the inner surfaces of the side walls are inclined toward each other and form a funnel tapering downwards to the bottom. The angles of inclination of the side walls are chosen in such a way that chips and other material falling thereon slide downwardly. A chip discharge extends above bottom6. Endless conveyor7of the chip discharge departs the tool below the rear side of stand2.

As shown inFIG. 1, spindle housing8is movably arranged on linear guides9by a motor (not shown) in the Y-direction on the top of stand2. Machining unit10, which has work spindle11and an integrated spindle motor, is mounted in linear guides12on the front of spindle housing8so as to be moveable by a monitor (not shown) in the direction of the Z-coordinate axis. In work spindle11, machining tools from a conventional tool magazine (not shown) can automatically be exchanged and replaced by means of a conventional tool changer.

As is also evident fromFIG. 1, workpiece carrier15is arranged on the front-side of front wall2aof stand2in a free space between the side walls4,5. The workpiece carrier has a table configuration with conventional mounting plate16for receiving workpieces and support structure17winch is here shown as a continuous thick plate for mounting plate16. Vertical web18is mounted on the right end of support structure17, as shown inFIG. 1. Guide shoes19are mounted on web18. The guide shoes cooperate with continuous guide rail20that is attached to the outer surface of front wall2aof the stand2and extends over the effective length of the stand. In the embodiment as shown, lead screw21of a linear drive is arranged next to web18. The linear drive is made in conventional fashion as a ball screw spindle having a drive motor (not shown).

Spindle21and guide rail20are covered over their entire lengths by protective plate22. The top end of plate22is permanently mounted on wall2aand the plate extends over the effective length of guide rail20and ball screw spindle21. The central part23of this strip-like protective plate22is inclined at a steep angle and confines the stand-side end of the work chamber. The chips accumulating during machine tool operation slide downwardly over this central part23of protective plate22and reach chipfall space25between side walls4,5of the stand. Lower end region24of protective plate22, in turn, extends vertically and ends directly above the support structure17. Guide rail20and threaded spindle21of the ball screw drive are covered over the entire effective length in the X-direction by the above described protective plate22, as shown inFIGS. 1 and 3. Thus, chips or other solids and rinsing liquids are prevented from being deposited on these components.

In the exemplary embodiment according toFIGS. 1 to 3, support structure17of workpiece table16has in the front region thereof a downwardly facing shoulder26which transitions into rearwardly offset bar27. Movable shoe28and guide rail29constitute a linear guide which is mounted on the vertical face of bar27which faces stand2. Guide rail29of the linear guide, which extends in the X-coordinate axis, is attached to cross-beam30, which is triangular in cross-section. In the exemplary embodiment as shown, this cross-beam extends horizontally through the entire chipfall space25and is attached at either end to a side wall4,5. In order not to disturb the chipfall in the chipfall space, the hypotenuse surface of cross-beam30can be sloped at an angle which ensures that the chips slide over this inclined face (seeFIGS. 1 and 3). In the embodiment shown, strip-like protective plate33, which is angled several times, is fixed over die ridge area of cross-beam30. The end portion of this protective plate, which is angled in the vertical, meshes with a groove34at the bar27with predetermined clearance and is movable therein. Protective plate33is stationary and covers the cross-beam30over its entire length and protects guide rail29against chip deposits. This effect is achieved by the off-set of shoulder26of support structure17and by the positioning of linear guide28,29as shown, so as to enable a roof-like cover by protective plate33.

The program-controlled milling and drilling machine embodiment shown inFIGS. 4 and 5also has a vertically aligned machining unit11, which is mounted on headstock10guided in the vertical Z-axis by means of linear guides12. In this exemplary embodiment, too, side walls4,5of bed3are inclined in oblique inward fashion, defining a funnel-shaped chipfall space. In the bottom area of the chipfall space is a chip removal device, not shown inFIGS. 2 and 4. A linear guide is provided in each shoulder40,41of respective side wall4,5. Guide rail42,43of the linear guide is mounted on side walls4,5. Guide shoes44,45of this linear guide carry panel-shaped wall members46of carrier arrangement47which supports workpiece table48. The carrier arrangement is composed of vertical and highly rigid wall members40and is movable along guide rails42,43in the direction of the horizontal Y-coordinate axis by means of a linear drive (not shown). Workpiece table48of the carrier arrangement is movable in the direction of the horizontal X-coordinate axis on guide rails50,51by means of a linear motor (not shown). As illustrated inFIG. 5, strip-like protective plates52,53are provided in this exemplary embodiment as well, protective plate52in the area of side wall4and protective plate53in the area of the wall5. These protective plates span the linear guides42,43and mesh with a respective groove54,55in panel component40via the vertical end portions thereof. Furthermore, a worm drive56is arranged the central area and is covered by an angular protective plate57to protect against chip deposits.

The embodiment shown inFIGS. 6 and 7largely corresponds to the exemplary embodiment according toFIGS. 1 to 3as regards its technical concept, wherein equal components are designated by equal reference signs.

According toFIG. 6, machine frame1has a stand62modified with respect to the embodiment shown inFIGS. 1 to 3. The stand has relatively narrow upper part63and relatively wide bed-like sub-structure64. These two parts of the stand are connected to each other via protruding central part65in a single block design. Stand62is defined by side faces66,67which are upwardly inclined. Front face68of the central part of the stand is also inclined (seeFIG. 7), the inclination of which is chosen such a way that depositing chips and other solids slide downwardly. The same applies correspondingly to side walls69,70which laterally confine the sub-structure. These lateral side walls can either be made in integral fashion with the sub-structure or can be installed as separate wall elements. The inner surfaces aside walls69,70define a funnel-shaped chipfall space, the machine-side rear wall of which is defined by inclined face68of central part65.

In the embodiment according toFIG. 6, which is similar to the embodiment according toFIG. 1, workpiece carrier15is arranged on the front wall of stand62in the free space between inclined side walls69,70. Here the design of the workpiece table carrier largely corresponds to that of table carrier15inFIG. 1. This applies in particular to the support bearing of the workpiece canter structure, which is shown in the right-hand top ofFIGS. 3 and 7. Reference is made to the corresponding statements regardingFIG. 3.

The embodiment according toFIGS. 6 and 7differs from the embodiment ofFIGS. 1 to 3not only by the different form of the machine stand but also by a different support of mounting plate16of workpiece carrier15on the machine stand. Mounting plate16is supported by panel71which has front inclined face72and shoulder73offset toward the stand side at the lower end region thereof. Guide shoes74are mounted on the vertical front face of shoulder73and run in a stand-fixed guide rail75. As is evident fromFIG. 6, the guide arrangement of panel71is considerably narrower titan the upper port of panel. The upper guide arrangement has, at the right-hand end of mounting plate16, an upwardly protruding web78, on the right-hand vertical side of which guide shoes19are mounted.

The embodiment ofFIGS. 6 and 7has the same advantages as the embodiment according toFIGS. 1 to 3as regards the set-up area and the chipfall. However, a special rigidity and favorable oscillating properties are more advantageous, which is achieved, inter alia, by the supporting bearing and the support of the table design directly on the front side of the machine stand. This also leads to a particularly favorable collecting space for the chips, cooling lubricant and other particles due to the rear wall of the chipfall space, which is adequately inclined to the front and which is thus not only confined by lateral inclined faces69,70but also by rear inclined face68.

The apparatus here described not limited to the exemplary embodiments presented and described above. For example, it is not absolutely necessary for the chipfall funnel to be directly confined by the inner surfaces of the two side walls of the machine bed. It is also possible instead to use inclined sheet or plate elements which might also be installed subsequently, if necessary.