Abstract:
A rotary tool for moldings fabricated preferably from wood. The tool has a one-part or multi-part pad and at least one peripheral row of abrasive-coated sanding segments that are slipped onto pad elements affixed to the pad. A locking unit is movable in the axial direction such that at least the sanding segments of one peripheral row can be mounted on the pad elements.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to a rotary sanding tool for moldings fabricated preferably from wood, having a one-part or multi-part pad and having at least one peripheral row of abrasive-coated sanding segments that are slipped onto pad elements affixed to the pad.  
           [0003]    2. Description of Prior Art  
           [0004]    The pad of the rotary sanding tool under consideration is usually fabricated from metal, for example aluminum. The pad elements are made for example of a metal section rail and a body of elastic material, for example sponge rubber, the shape thereof being adapted to the outline of the surfaces to be sanded. The sanding segment is slipped onto the pad elements. The sanding segment is made up of a substrate molded from a plastic. The substrate is coated with the abrasive on the outside. The sanding segment is likewise adapted to the outline of the surfaces to be sanded or to the outline of the pad element body made of flexible material. The rotary sanding tool can be fashioned as a single sanding wheel or as a double sanding wheel. If it is a double sanding wheel, two pads are interlaced into each other. The sanding segments of one row are then angularly spaced apart from one another so that the sanding segments of the other row lie therebetween. The double sanding wheel offers the advantage that more than two surfaces can be sanded at the same time.  
           [0005]    In a known rotary sanding tool the sanding segments are held by two clamping covers frontally overreaching projections of the sanding segments, which clamping covers are mounted on the sanding shaft. If the sanding wheel is a double sanding wheel, four clamping covers are accordingly necessary.  
           [0006]    These previously known rotary sanding tools have proven optimal in practice. On economic grounds, so-called “throughfeed” machines, in which a plurality of rotary sanding tools are mounted on one sanding shaft, are increasingly being used. The workpiece passes along an arbitrary number of machining assemblies. As a rule these are one-sided or double-sided automated molding or edging machines, so that the axis values therefore are controlled/adjusted by CNC. These rotary sanding tools are then used one after another for machining. In the previously known rotary sanding tools, the rotary sanding tool must be dismounted in order to change the sanding segments and also to change the pad elements. This, however, is particularly time-consuming if a plurality of rotary sanding tools are mounted on one sanding shaft, because at least some of the rotary sanding tools whose sanding segments and pad elements do not have to be changed out must also be taken off the sanding shaft.  
         SUMMARY OF THE INVENTION  
         [0007]    It is a goal of the invention to design a rotary sanding tool of the kind described at the outset in such a way that the changing of sanding segments and if applicable also of pad elements can be performed in a very simple manner and in a very short time, in particular the rotary sanding wheel is to be designed in such a way that the changing of sanding segments and if applicable also of pad elements can be performed without the necessity of dismounting, so that the changing of sanding segments and if applicable of pad elements is possible without the need to take these off the sanding shaft.  
           [0008]    The stated goal is achieved with a locking unit movable in the axial direction, with which at least the sanding segments of one peripheral row can be affixed to the pad elements.  
           [0009]    With the locking unit it is now possible that, after the sanding segments have been slipped onto the pad elements, the sanding segments are locked simultaneously. For changing and preliminary unlocking, the locking unit is moved in the opposite direction. The locking unit does away with the dismounting of the rotary sanding tool in order to change sanding segments. In this way it is possible for these sanding segments to be changed when the rotary sanding tool is situated on the sanding shaft. This is particularly advantageous when a plurality of rotary sanding tools are arranged on one sanding shaft. The locking unit must be configured in such a way that the sanding segments do not come loose during the sanding process, when the rotational speed of the rotary sanding tool is relatively high. Provision is therefore made that the locking unit is displaceable in the axial direction relative to the pad or pads. The centrifugal forces arising during the sanding process then do not contribute to a displacement of the locking unit. In terms of design, the locking unit can be fashioned in a particularly simple way if it has a cage and if, in the lower lateral marginal regions of the sanding segments, which regions are averted from the abrasive coatings, profilings are provided in such a way that the sanding segments are positively connected to the cage in the locked position. The positive connection between the locking unit and the sanding segments offers the advantage that no mechanical connectors are necessary. What is more, the sanding segments, preferably fabricated by deep drawing from a foil of relatively great thickness, are treated gently. This profiling must be designed so that movement, for example tipping, of the sanding segments is avoided. It is therefore provided that on each lateral margin of a sanding segment there are at least two projections forming the profiling and that the locking cage has webs adjoining the lateral marginal region, which webs are provided with snap-in holes into which the projections engage. These snap-in holes are designed such that in the locking position of the locking unit they form a positive fit with the profilings of the sanding segments and in the releasing position the sanding segments can be removed from the pad elements without tools. In order to generate the axial movement of the locking unit, i.e., its movement running in the direction of the rotation axis of the rotary sanding tool, provision is made for it to have a retaining ring on which the locking cage is mounted and for the retaining ring to be coupled by a rotatable adjusting nut in such a way that the locking unit executes a linear movement by turning of the adjusting nut. To this end it is expedient if the hub of each rotary sanding tool has a threaded stud onto which the adjusting nut is screwed. In a preferred embodiment it is provided that the rotary sanding tool is fashioned as a double-segment sanding wheel and that on each of the averted sides of the double sanding wheel there is an axially movable retaining ring. The cage for locking of the sanding segments is then arranged in turn on each retaining ring. The thickness of the locking cage is configured such that it is inherently stable in shape and does not deform even at the relatively high rotational speed of the rotary sanding tool in service.  
           [0010]    In a preferred embodiment, the pad elements are mounted on the pad by mechanical connectors. Because the pad and the pad elements are designed such that a positive fit results, it is sufficient if one connector is used for each pad element. Screws that are screwed into the pad in the radial direction are preferred. For true running, each locking unit must be worked precisely. The truth of running should be less than {fraction (1/10)} mm. As already indicated, the rotational speed of the rotary sanding tool in service is relatively high, a maximum of about 3000 rpm but in the normal case around 1500 rpm. For this reason, provision is further made that each rotary tool has an internal hub extending over the width or approximately over the entire width of the rotary sanding tool and that the hub is fashioned as a centering cone or equipped with a conical centering bushing. The rotary sanding tool under consideration can also be fashioned as a single-segment sanding wheel. It is particularly advantageous then that a workpiece held by a support plate can be sanded approximately down to the support surface. The so-called interference height in this embodiment is extremely small, thus making the use still more versatile. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The invention will now be explained in more detail on the basis of the appended drawings, in which:  
         [0012]    [0012]FIG. 1 shows two rotary sanding tools mounted on a sanding shaft, not shown, and  
         [0013]    [0013]FIG. 2 is a partial view showing in particular the unlocking of the sanding segments. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]    For purposes of illustration, FIG. 1 shows only two rotary sanding tools  10  and  11 , which are mounted on a sanding shaft, not shown. In practice, more than two rotary sanding tools  10 ,  11  are commonly mounted on a sanding shaft. Contrary to the illustration in FIG. 1, the sanding shaft in a machining center is vertical. Rotary sanding tool  10  shown in FIG. 1 is fashioned as a double-segment sanding wheel. In such an embodiment, two internal pads, which cannot be seen, are stuck one into the other or interlaced one with the other. The pad elements are alternately assigned to the one and the other pad, accordingly also sanding segments  12 ,  22  visible in FIG. 1, which are externally coated with an abrasive coating or an abrasive paper. The shape of the pad elements and of the slipped-on sanding segments is dictated by the outline of the surface to be sanded. In FIG. 1 sanding segments  12 ,  22  of rotary sanding tools  10 ,  11  are designed alike for simplicity in depiction even though this does not conform to practice. Each rotary sanding tool  10 ,  11  is equipped with a locking mechanism  13 , yet to be explained in more detail, the rotary sanding tool in the case of the rotary sanding wheel at bottom in the illustration being equipped with two locking units  13 , which locking mechanism is assigned to each row of sanding segments  12 ,  22 . Each locking unit  13  is essentially made up of a peripheral locking cage  14 , each of which is mounted on a retaining ring  15 . FIG. 1 shows that sanding segments  12  are alternately assigned to left-hand retaining ring  15  and right-hand retaining ring  15 . Each sanding segment is provided with a profiling on the two lower averted sides, i.e. the side averted from abrasive coating  12   a , which profiling is positively connected to assigned locking cage  14  in the locked position shown in FIG. 1. In the exemplary embodiment shown, the profiling is formed by semicircular projections  16 , which can be seen particularly from FIG. 2. These projections  16  of sanding segments  12 ,  22  are slipped onto protruding lugs  17  of the pad, which is otherwise not further shown. Locking cage  14  is provided with groove-like holes, which are designed such that in the unlocked position according to FIG. 2 each sanding segment  12 ,  22  can be removed from assigned pad element  18  or slipped on by hand. The movement of each locking unit  13  from the locking position shown in FIG. 1 to the unlocking position shown in FIG. 2 is effected by axial displacement. To this end, each retaining ring  15  is coupled to a rotatable adjusting nut  19  in such a way that the axial movement results from turning of adjusting nut  19 . To this end, each adjusting nut  19  is screwed onto an externally threaded stud of the hub, not shown. The locking cage is essentially made up of profile pieces perpendicularly attached to retaining ring  15 , which profile pieces are assigned to the two longitudinal edge regions, leading and trailing in the rotation direction of rotary sanding tool  10 ,  11 . It can be seen in particular from FIG. 1 that sanding segments  12 ,  22  can be changed without the need to take rotary sanding tools  10  off the sanding shaft in the event that a plurality of these rotary sanding tools are stuck onto one sanding shaft. The changing of sanding segments  12 ,  22  becomes necessary when abrasive coating  12   a  is worn out. If they must be replaced by sanding segments with a different outline, changing of pad elements  18  is also necessary. These are connected to the pad in a fashion not shown in greater detail. In a preferred embodiment, this is effected by screws running in the radial direction, because the screw holes are then covered by sanding segments  12 . For the changing of pad elements  18 , these are then particularly accessible, for example with a screwdriver or with a pin wrench.  
         [0015]    From FIG. 1 it can be seen in particular that a workpiece held by a support plate can be sanded approximately down to the surface of the support surface with upper rotary sanding tool  11  fashioned as a single sanding wheel. The so-called interference height is extremely small because of the way in which the sanding wheel is constructed. In the embodiment of FIG. 1, the underlying threaded stud with adjusting nut  19  would already belong to lower rotary sanding tool  10 , so that the support surface could be equated with the frontal surface of the threaded stud.  
         [0016]    The invention is not restricted to the exemplary embodiment shown. What is essential is that, in a machining center for moldings of wood or a wood-like material, sanding segments  12  and if applicable also pad elements  18  can be changed without the need to take rotary sanding tools  10  off the sanding shaft.