Patent Publication Number: US-6712683-B2

Title: Backing plate for abrasive flap wheels

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a backing plate for abrasive flap wheels, having an inner part with a location hole for a shaft of a driving machine and an outer flange for abrasive flaps to be adhesively bonded in place. 
     2. Description of the Related Art 
     For a long time there have been backing plates for abrasive flap wheels which are made of a fiber material impregnated with plastic and in which sheet-metal reinforcement is provided around the location hole. These relatively thin backing plates are put onto the shaft, provided with a thread, of a driving machine and screwed tight with a nut. The same type of fastening also exists in abrasive flap wheels in which the backing plates are made of injection molded plastic. In this case, too, only a location hole is provided in the inner part, so that fastening to the machine by means of a nut is necessary. 
     Such a type of fastening is time-consuming, since, when a wheel is changed, the nut has to be slackened and unscrewed, the new wheel has to be put on and the nut has to be screwed on again. In addition, there is the risk of the nut falling down or of even being lost, which considerably further increases the time needed. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to design a backing plate for abrasive flap wheels of the type specified further above in such a way that a quick and nonetheless reliable means of fastening the abrasive flap wheels to the driving machine is possible. 
     According to the invention, this object is achieved by forming the inner part with a hub which has an internal thread for the threaded shaft of the driving machine. 
     On account of this design, it is possible to screw the abrasive flap wheel in a simple manner onto the shaft, provided with a thread, of the driving machine without locking having to be carried out with an additional nut. The intended direction of rotation of the driving machine runs in such a way as to tighten the abrasive flap wheel upon coming into working engagement with a workpiece. On the other hand, on account of the relatively large diameter of the abrasive flap wheel, it is possible to slacken said abrasive flap wheel by hand without requiring a tool, which was necessary during the fastening by means of the nut. 
     In an advantageous development of the invention, provision is made for the hub to be designed so as to project beyond the sunk surface of the backing plate and to have a length which essentially corresponds to the distance between the surface of the outer flange and the surface of the sunk inner part. 
     In order to achieve a reliable fastening, it is advantageous if the internal thread extends over the entire length of the hub. In this case, it is advantageous if the internal thread has at least three thread turns. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a section through an abrasive flap wheel according to the invention; and 
     FIG. 2 shows an abrasive flap wheel in section in combination with a driving machine. 
    
    
     DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
     The abrasive flap wheel  1  shown in section in the drawing has a backing plate  2  which comprises a sunk inner part  3  and an outer flange  4 . Abrasive flaps  6  are in each case arranged in a partly overlapping form on the front side  5  of the outer flange, as is typical of abrasive flap wheels of this type. The abrasive flaps  6  are fastened by adhesive bonding. The sunk inner part  3  has a hub  7  which projects toward the front side  3   a , i.e. toward the side of the abrasive flaps, and is provided with a location hole  8  and an internal thread  9 . A step-like recess  11  is provided on the rear side  10  of the inner part  3 . 
     As can be seen from FIG. 2, a driving machine  12  has a shaft  13  with an external thread  14 . Furthermore, a driver plate  15 , which is provided in driving machines of this type for the various abrasive wheels, is put onto the shaft  13 . In accordance with FIG. 2, the abrasive flap wheel  1  is screwed onto the shaft  13 , the internal thread  9  of the hub  7  of the abrasive flap wheel  1  interacting with the external thread  14  of the shaft  13 . In the process, the rear side  10  of the inner part  3  comes to bear on the driver plate  15 , a step  16  of this driver plate engaging in the recess  11  of the backing plate  2  in order to ensure reliable centering of the abrasive flap wheel  1  on the shaft  13  of the driving machine  12 . The hub  7  has a length projecting beyond the surface  3   a  of the inner part  3 , this length corresponding to the distance  17  between the surface  3   a  of the inner part  3  and the front side  5  of the outer flange  4 . Thus the hub  7 , in combination with the wall thickness of the inner part  3  of the backing plate  2 , is long enough and is provided with sufficient thread turns in order to be firmly screwed onto the shaft  13  of the driving machine  12 .