Abstract:
An abrasive cutting-off wheel for stationary use is comprised of two partial abrasive wheels which are joined to each other. Each of these partial abrasive wheels comprises an interior supporting disk and a radially adjoining interior layer of abrasive grain. It further comprises an exterior layer of abrasive grain and an exterior supporting disk which is located radially there-within. A reinforcement layer is provided between the supporting disks and the layers of abrasive grain. Another reinforcement layer can be disposed between the supporting disks and the interior layers of abrasive grain.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates to an abrasive cutting-off wheel for stationary use.  
         [0003]     2. Background Art  
         [0004]     Abrasive cutting-off wheels of the generic type are used on stationary abrasive cutting-off machines, serving for severing workpieces, in particular of metal. A clearance is cut in the work being severed, corresponding to the total thickness of the abrasive cutting-off wheel. The material that is cut out constitutes a loss of material. In particular because of their large diameter, abrasive cutting-off wheels of that type must be very rigid towards side forces that act parallel to the central longitudinal axis. That is why known designs of those abrasive cutting-off wheels have a comparatively important overall thickness. Abrasive cutting-off wheels have several layers of abrasive grain which are composed of abrasive grain, binding agent and filler. Reinforcement layers are provided between the individual layers of abrasive grain, extending across the total diameter. Reinforcement layers are also disposed externally, extending only across a part of the diameter. The overall thickness of such an abrasive cutting-off wheel amounts for example to approximately 15 mm, given an outside diameter of 1250 mm. On the one hand, these known abrasive cutting-off wheels require lots of material because of their important thickness, which makes them rather costly; on the other hand, a user, when severing works, will have a comparatively high loss of material in the clearance being cut, which is not desirable.  
       SUMMARY OF THE INVENTION  
       [0005]     It is an object of the invention to embody an abrasive cutting-off wheel of special rigidity towards side forces which can thus be provided with reduced overall thickness.  
         [0006]     According to the invention, this object is attained by an abrasive cutting-off wheel for stationary use, comprising an outside diameter; a total thickness; two interior supporting disks, which are concentric of a joint central longitudinal axis, each of which have a periphery of an outside diameter; each of which have a thickness, and which are connected to each other; two interior layers of abrasive grain, which are concentric of the central longitudinal axis, which have a thickness that corresponds to the thickness of the interior supporting disks, which adjoin the periphery of the interior supporting disks, and which have an outside diameter; two reinforcement layers, which are concentric of the central longitudinal axis, each of which rests on the interior supporting disk and on the layer of abrasive grain, which are united with the interior supporting disk, and which have an outside diameter; two exterior supporting disks, which are concentric of the central longitudinal axis ( 10 ), each of which have a periphery of an outside diameter, which are united with the respective reinforcement layer, which have a thickness, and the outside diameter of which is less than the outside diameter of the interior supporting disks; and two exterior layers of abrasive grain, which are concentric of the central longitudinal axis, which have a thickness, which adjoin the periphery of the exterior supporting disks, and which have an outside diameter. The design according to the invention confers extraordinarily strong rigidity towards side forces to the abrasive cutting-off wheel; it can therefore be configured to have very little overall thickness accompanied with a very large diameter.  
         [0007]     Further features, advantages and details of the invention will become apparent from the ensuing description of exemplary embodiments, taken in conjunction with the drawing. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0008]      FIG. 1  is a plan view of details of an abrasive cutting-off wheel of the invention in accordance with the arrow I of  FIG. 2 ;  
         [0009]      FIG. 2  is a side view of the abrasive cutting-off wheel in accordance with the arrow II of  FIG. 1 ;  
         [0010]      FIG. 3  is a cross-sectional view of details of the abrasive cutting-off wheel in accordance with the detail III of  FIG. 2  on a strongly enlarged scale as compared to  FIG. 1  and  FIG. 2 ; and  
         [0011]      FIG. 4  is a cross-sectional view of details of an abrasive cutting-off wheel that is slightly modified as compared to the abrasive cutting-off wheel of  FIG. 3 . 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0012]     As seen in the drawing, the abrasive cutting-off wheel is a wheel for use on stationary abrasive cutting-off machines i.e., an abrasive cutting-off wheel that is not used on a freely hand-operated grinding machine. It has an outside diameter A to which applies: 500 mm≦A≦1800 mm, and preferably 500 mm≦A≦1600 mm. The abrasive cutting-off wheel comprises two inner, annular cylindrical and rigid supporting disks  1 ,  1 ′ as a rule of steel sheet of identical configuration which have an outside diameter B. They are identical with each other, continuously having the same thickness  a . Centrally they have an opening  2  of an inside diameter C. The supporting disks  1 ,  1 ′ have circular cylindrical peripheries  3 ,  3 ′, from each of which an annular cylindrical interior layer of abrasive grain  4 ,  4 ′ extends outwardly, likewise of the thickness  a  and an outside diameter A. Customarily they consist of abrasive grain  5 , binding agent  6  and filler  7 .  
         [0013]     The two supporting disks  1 ,  1 ′, and correspondingly the layers of abrasive grain  4 ,  4 ′, bear against each other. Each of their outsides is provided with a reinforcement layer  8 ,  8 ′ of a fabric, for instance glass cloth coated with a customary phenolic resin. The reinforcement layers  8  and  8 ′, each in the form of a ring wheel, have an outside diameter A and an inner opening  2 ′ of an inside diameter D which is definitely not less than, but may exceed, the inside diameter C of the opening  2 .  
         [0014]     Annular cylindrical, rigid, exterior supporting disks  11 ,  11 ′ of steel are disposed externally on the reinforcement layers  8 ,  8 ′, likewise concentrically of the joint central longitudinal axis; they too have an opening  2  of an inside diameter C. Their outside diameter E is definitely less than the outside diameter B of the interior supporting disks  1 ,  1 ′, but also definitely exceeds the inside diameter D of the opening  2 ′ of the reinforcement layers  8 ,  8 ′. This provides for sufficient lap of the interior supporting disks  1 ,  1 ′ and the exterior supporting disks  11 ,  11 ′ over the reinforcement layers  8 ,  8 ′.  
         [0015]     As regards the relationship of the abrasive-cutting-off-wheel outside diameter A to the supporting-wheel- 11 ,  11 ′ outside diameter E, the following applies: 0.25 A≦E≦0.8 A, and preferably 0.25a≦E≦0.67 A. As for the lap of the interior supporting disks  1 ,  1 ′ over the exterior supporting disks  11 ,  11 ′, 0.005 A≦(B−E)&lt;0.05A applies. D is definitely less than E so that sufficient lap is ensured of the respective supporting disk  1 ,  1 ′ and  11  ,  11 ′ over the reinforcement layers  8 ,  8 ′. The reinforcement layers  8 ,  8 ′ are fixedly united with the respective interior supporting disk  1 ,  1 ′ by means of an adhesive layer  9 ,  9 ′ and with the respective exterior supporting disk  11 ,  11 ′ by means of an adhesive layer  14 ,  14 ′.  
         [0016]     The circular cylindrical peripheries  12 ,  12 ′ of the exterior supporting disks  11 ,  11 ′ are each followed by an annular cylindrical exterior layer of abrasive grain  13 ,  13 ′, the thickness b of which in the direction of the axis  10  exceeds the thickness c of the exterior supporting disks  11  and  11 ′. The layers of abrasive grain  13 ,  13 ′ project axially from the exterior supporting disks  11  and  11 ′. The composition of the exterior layer of abrasive grain  13 ,  13 ′ may fundamentally be the same as that of the interior layer of abrasive grain  4 ,  4 ′.  
         [0017]     As seen in the illustration of  FIGS. 1 and 2 , the total thickness d of the abrasive cutting-off wheel is very restricted as compared to its outside diameter A. 0.01≦d/A≦0.011 applies as an upper boundary and 0.006≦d/A≦0.008 as a lower boundary.  
         [0018]     The abrasive cutting-off wheel is produced in such a way that two identical partial abrasive wheels  15 ,  15 ′ are made first. This takes place by the interior supporting disks  1  and  1 ′, each by itself, being placed on a plane base and by the blend of abrasive grain  5 , binding agent  6  and filler  7  being incorporated for forming the interior layer of abrasive grain  4  and  4 ′ in such a way that it tightly adjoins the periphery  3  and  3 ′.  
         [0019]     The respective adhesive layer  9  and  9 ′ has been attached to the supporting disks  1 ,  1 ′ beforehand. Then the reinforcement layers  8  and  8 ′ are being placed on. Afterwards the exterior supporting disks  11  and  11 ′, provided with the adhesive layer  14  and  14 ′, are being placed on the reinforcement layers  8  and  8 ′, after which the exterior layer of abrasive grain  13  and  13 ′ is being applied in such a way that it tightly adjoins the respective pheriphery  12  and  12 ′. The respective partial wheels  15  and  15 ′ are then being compacted and compressed i.e., appropriately solidified, for sufficient inherent stability. They are then being placed on each other by the two free sides of the interior supporting disks  1  and  1 ′ and by the corresponding free inward sides of the interior layer of abrasive grain  4  and  4 ′ after an adhesive layer  16 ,  16 ′ has been applied to each of the two supporting disks  1  and  1 ′. The two partial abrasive wheels  15  and  15 ′ are then being pressed together and cured in a furnace, constituting an abrasive cutting-off wheel.  
         [0020]     The embodiment according to  FIG. 4  differs from that according to  FIG. 3  in that another reinforcement layer  17  is provided between the two partial abrasive wheels  15 ,  15 ′; it can be designed in the same way as the reinforcement layers  8 ,  8 ′. Both supporting disks  1 ,  1 ′ are united with this inside reinforcement layer  17  by the respective adhesive layer  16  and  16 ′. Placing this additional inside reinforcement layer  17  takes place before the two partial abrasive wheels  15 ,  15 ′ are assembled and subsequently compressed and cured in a furnace. The total thickness d′ of this abrasive cutting-off wheel exceeds the total thickness d of the abrasive cutting-off wheel of  FIG. 3  by the thickness of the reinforcement layer  17 .