Abstract:
A protective cover for the work area of a machine tool having a plurality of frame-like segments disposed so as to be limitedly shiftable within each other and respectively provided with a sealing strip on at least one edge. A plurality of connecting elements formed as slidable lattice grates connect the frame-like segments, the respective link pins of the slidable lattice grates being fixed to a respective rear segment of a segment. For simplified assembly and removal of the protective cover the slidable lattice grates are detachably fixed to the frame-like segments.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates generally to a protective cover for the work area of a machine tool comprising a plurality of frame-like segments disposed so as to be limitedly shiftable within each other and respectively provided with a sealing strip on at least one edge and connecting elements formed as slidable lattice grates connecting the frame-like segments, the respective link pins of the slidable lattice grates being fixed to a rear segment of a respective segment. 
   2. Background 
   Protective covers of this type generally comprise a plurality of frames arranged so as to be relatively shiftable within each other, the outermost one of the frames being fixedly connected to a component of the machine tool and the innermost frame being attached to a machine slide or a spindle housing movable in at least one coordinate axis. An example of such a protective cover is shown in EP 0 673 712. The frames are formed of a resistant sheet metal and comprise a broad front bridge or segment which forms the effective part of the protective cover and is provided with a sealing strip at its edge section, a transverse bridge and a shorter rear segment extending parallel to the front segment. The broad front segments of the adjacent segments overlap each other so that all of the bridges together form a virtually continuous protective wall. The inner frames or frame-like segments are shiftably disposed in the respective outer frames having the same shape and greater dimensions and connected to each other by connecting elements formed as slidable lattice grates, the respective link pins of the slidable lattice grates being permanently fixed to a rear segment of a respective segment. In practice, work-related problems have occurred when maintenance and repair work had to be carried out and the protective cover had to be totally or partially removed for this purpose. In such cases not only the frame-like segments but also the slidable lattice grates, including the respective guiding and attachment elements of the protective cover and therefore the whole protective cover, had to be removed, which entailed a significant amount of work. 
   SUMMARY OF THE INVENTION 
   According to the invention the desired reduction of the mounting operations on a machine tool is accomplished by detachably fixing slidable lattice grates to the frame-like segments. By releasing the connecting means between the respective slidable lattice grate or its link pins and the associated frame-like segment, one or more of the frame-like segments may be removed while the slidable lattice grates, including their attachment and guiding elements, remain on the machine. 
   An embodiment of the releasable attachment means which is, on the one hand, stable, and, on the other hand, easily movable, is characterised in that the link pins attached to the narrower rear segments of the frame-like segments are surrounded by a flange sleeve on which the two crossed arms of the slidable lattice grate are non-detachably supported, the flange sleeve being detachably connected to the associated link pin. Efficiently the flange sleeve contacts a distance shim fixedly connected to the respective segment with its flange and is detachably connected to the respective link pin through a disk as well as by a screw. The largely dimensioned support of the flange sleeve on the distance shim by means of its flange ensures a tilting-free positioning of the flange sleeve, and the end side screw connection provides a safe, bilateral fixation of the two arms of the slidable lattice grate which are pivotable with respect to each other. 
   A particularly efficient further development of the invention is characterised in that the frame-like segments are, at least partly, particularly in their lower segments, held in tight mutual contact by a resilient pressure. With the resilient pressure acting on the frame-like segments a tight contact of their wide front side segments is achieved so that gaps between the two front bridges or segments of adjacent frame-like segments, through which flushing liquid or chips might enter the space behind the protective cover, are avoided. The resilient pressure forces acting on the individual segments should be finely adjustable so that the ready movability of the frames is not affected during their relative movements. The elastic abutment should, however, be sufficiently large to ensure a sufficiently tight contact of the edge side sealing strips of one segment to the wider front segments of the adjacent segment so that a wiper effect is accomplished during the shifting movements of the frame-like segments. An effective resilient pressure acting on two frame-like segments may be achieved in a technically simple manner by rendering at least some link pins of the slidable lattice grates spring-biased and having them disposed axially movable within their flange sleeves. To maintain the spring bias a pressure spring acting on the link pin may be provided in a jack surrounding the end portion of a link pin. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     The objects, features, and advantages of the invention will be more clearly perceived from the following detailed description, when read in conjunction with the accompanying drawing, in which: 
       FIG. 1  is a schematic front view of an embodiment of the protective cover of the invention for the work area of a machine tool; 
       FIG. 2  is a cross sectional view of a plurality of the frame-like segments of the protective cover shown in  FIG. 1  fully inserted into each other, together with their connection means; and 
       FIG. 3  is a cross sectional view of a plurality of the frame-like segments of the protective cover shown in  FIG. 1  fully inserted into each other, together with their spring-biased connection means. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   With reference to the drawing, and more particularly to  FIGS. 1 and 2 , a protective cover in accordance with the invention is shown which comprises rectangular, rigid outer frame  1  having a broad front segment  2  covered by profiled sheet metal  3 . The front segment rests on sealing strip  4  at its edge. Angle section  5  is connected to broad plane segment  2 , the angle section being fixed to the vertical bridge of angular beam  7  by means of angle profile  6 , using screws  8 , for example. In the inner space covered by outer frame  1  are provided three respectively frame-like segments  9 ,  10 ,  11 , each comprising an upper sheet metal strip, these frame-like segments  9 ,  10 ,  11  being slid into each other in the illustrated embodiment. On the right edge ( FIG. 2 ) of each sheet metal strip of segments  9 ,  10 ,  11 , respective sealing strip  4  is fixed to the upper side. The width of the sheet metal strips of segments  9 ,  10 ,  11  is chosen so that sealing strips  4  are overlapping with a slight lateral displacement in the illustrated, fully inserted operating state. As can be seen in  FIG. 2 , the left edge of the sheet metal strip of the segment  9  is connected to an L-shaped, rigid profile sheet, narrower lower segment  13  of which is bent to the outside and carries reinforcing beam  12  in the angle area. The sheet metal strips of frame-like segments  10 ,  11  are also fixedly connected to L-shaped, rigid sheet metal profiles on their left edge, horizontal segments  14 ,  15  of these sheet metal profiles pointing inward. Under frame-like segment  11  a flat frame  17  is provided which comprises a plane metal sheet  18  and a support plate  19  attached to its bottom side. Right-angle bend  20  provided on its right edge, the height of which approximately corresponds to the height of the segment package. Right-angle bend  20  is fixed to a machine part (for example, a spindle head) movable in two coordinate axes. 
   On the bottom side of horizontal segment  8  of beam  7  is link pin  24  permanently attached to segment  8 . Two arms  25 ,  26  of a slidable lattice grate are pivotably supported on link pin  24 . Locating disk  27  is detachably fixed to the end of link pin  24  by means of bolt  28 . 
   On rear horizontal segments  13 ,  14 ,  15  of frame-like segments  9 ,  10 ,  11  further link pins  30  are permanently attached via spacers  31  of different thicknesses. On each link pin  30  is provided detachable flange sleeve  32 . This flange contacts a large area of the respective spacer  31 . On each flange sleeve  32  the respectively two arms  33 ,  34  of one of the four slidable lattice grates A, B, C, D (shown in dashed lines in  FIG. 1 ) are supported in roller bearings shown in  FIG. 2 . Cheaper plain bearings, or other operative bearings could also be used. On the free end portion of each flange sleeve  32  is spacer ring  35 . On spacer ring  35  is annular or ring-shaped disk  36  which is in engagement with the end portion of flange sleeve  32  by means of a collar-shaped extension. This engagement may be by means of a threaded connection. Disk  37  is pressed against the outer surface of disk  36  by suitable means such as stud bolt  38  screwed into the face of the narrow end portion of link pin  30 . After the removal of stud bolt  38  and the detachment of pressure disk  37  it is possible to obtain axial release movement between respective link pin  30  and the assembly comprising flange sleeve  32 , arms  33 ,  34  of the slidable lattice grate supported on the flange sleeve, spacer ring  35 , and ring-shaped disk  36 . 
   On the support sheet  19  of lowest, plane, frame-like segment  18 , support arm fastening  40  is directly and permanently fixed. The two ends of the inner arms  33 ,  34  of the slidable lattice grate are supported on the narrower pivoting pins  41  of support arm fastening  40 . An end side safety disk  43  attached to pivoting pin  41 , typically by means of stud bolt  44 , prevents an axial displacement of arms  33 ,  34  on pin  41 . 
   The protective cover shown in a partial cross section in  FIG. 3  corresponds to the embodiment according to  FIG. 2  to a large extent so that components corresponding to each other are indicated by the same numerals. In this case also the frame-like segments are in their fully inserted state, that is, the spindle head possibly built into right-angle bend  20  of lower, plane segment  18  is in the right end position. The three connecting means between the three frame-like segments  9 ,  10 ,  11  and the slidable lattice grates differ from those of the embodiment shown in  FIG. 2 . The connecting means also comprise link pins  30  on which flange sleeves  32  are supported in roller or plain bearings. Instead of the pressure or spacer ring shown in  FIG. 2 , bowl-shaped support  50  may be screwed into the inner space of flange sleeve  32  via a collar-shaped extension is used in this  FIG. 3  embodiment. The narrower end portion of link pin  30  to which disk  52  is fixed by means of screws protrudes into bowl-shaped support  50 . The bowl-shaped support is closed to the outside by termination disk  54 , preferably detachably fixed by means of screws. Between termination disk  54  and disk  52 , and fixed on link pin  30 , is mounted pressure spring  55 . This pressure spring is supported by termination disk  54  and exerts an axial force on link pin  30 . That force is transmitted to the frame-like segment which is pushed against the adjacent frame-like segment with its sealing strip  4  in this way whereby a sufficiently tight contact is achieved and therefore a leakage and an entry of chips are prevented even during mutual displacement movements of the segments. The pressing forces generated by the various pressure springs  55  are finely adjustable so that, on the one hand, a sufficiently tight contact of the sealing strips  4  is achieved and, on the other hand, the frame-like segments remain readily movable during their shifting movements. 
   In case of the connecting means shown in  FIG. 3 , the individual segments may also be separated from the bearings of the arms of the slidable lattice grates in an easy manner to remove the frame-like segments without having to detach the slidable lattice grates. Instead of springs  55  other suitable pressure elements may be used which generate corresponding pressure forces due their resilient deformability.