Patent Publication Number: US-6213860-B1

Title: Grinding wheel

Description:
This is a continuation of U.S. application Ser. No. 09/018,804, filed Feb. 4, 1998 pending. 
    
    
     This invention relates to a grinding wheel and to a method of making a grinding wheel. It is particularly intended to provide a grinding wheel that is lighter in weight than corresponding wheels of conventional construction, such as comprise an abrasive outer rim portion. 
     Accordingly, it is an object of the invention to provide an improved grinding wheel of lighter weight whereby advantages such as more efficient power usage and lower torque exerted on the motors used to drive the wheel may be realised. Such benefits are of particular value in the grinding of glass, e.g. automotive glass. 
     According to the invention in one aspect there is provided a grinding wheel comprising an annular body portion having an inner periphery which is attached to an annular wheel centre and an outer periphery which is attached to an outer circumferential layer of abrasive material, the body portion having been cast about and thereby secured to the outer periphery and the inner periphery, the cast body portion having a low density. 
     In a second aspect the invention provides a method of making a grinding wheel in which a ring of abrasive material is positioned in a mould, the ring surrounding and being spaced from an annular wheel centre which is also positioned in the mould, whereby an annular gap is formed in the mould, and a lightweight material is cast into the mould to fill the annular gap and to bond to the ring of abrasive material and to the annular wheel centre. 
     The ring of abrasive material is preferably comprised of a bonded diamond composition, e.g. an impregnated metal, resin or vitreous composition containing the abrasive diamond. Preferably it is made as a complete insert ring, or it may be as a series of segments which form a ring. The ring is made by any convenient means, e.g. a conventional technique such as pressure sintering or cold pressing and sintering. 
     The ring is preferably formed with a dovetail or other undercut cross-section or otherwise shaped cross-section to assist its bonding or keying to the cast body portion. 
     The lightweight cast body portion is formed of a low density material, e.g. a plastics such as polyurethane or epoxy resin; aluminium or an aluminium alloy, and preferably has a density in its final condition of less than about 4 g/cc. 
     In a particularly preferred embodiment the lightweight cast body portion is formed by die-casting. 
     The annular wheel centre may be any conventional wheel centre, e.g. of metal, and having a channel-shaped outer perimeter to receive and bond to the cast body portion, with a central hole to receive a spindle to drive the grinding wheel. 
     The lightweight wheels of the invention have a number of advantages over conventional wheels. This is particularly notable when grinding glass. As indicated above, wheels of the invention exert lower torque on driving motors during use and they incur less power loss due to the weight of the wheel leaving more power available for grinding. Alternatively, lower power consumption can lead to improved grinding speed with a reduced need for abrasive dressing. The wheel may have improved corrosion protection in aqueous environments and cause less vibration leading to better surface finish. Wheel life may be improved. 
    
    
     Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which: 
     FIG. 1 is a plan view of a portion of a grinding wheel according to the invention; 
     FIG. 2 is a cross-section along line II—II of FIG. 1; and 
     FIG. 3 is an enlarged view of a portion of the section of FIG.  2 . 
    
    
     In the drawings grinding wheel  10  has an annular wheel centre  11 , a lightweight die-cast aluminium body portion  12  and an abrasive outer circumferential layer  13 . The abrasive outer circumferential layer  13 , which forms the abrasive outer rim of the wheel, is of trapezoidal or dovetail shape so as to be firmly keyed into a corresponding hollow annular groove  14  in the outer periphery  14 A of the cast body portion  12 . The annular groove  14  is of course formed in-situ when the body portion is cast against the circumferential layer  13  after the latter has been positioned in a suitable mould. 
     A similar dovetail connection is made between the inner periphery  14 B of body portion  12  and wheel  11 , which has sloping shoulders  15  to receive the inner periphery as it is cast in the mould. 
     As is conventional, the body portion  12  may include a series of equi-spaced holes  16 , drilled or cast in-situ for attachment/location purposes. 
     Wheels of the invention may be found particularly useful as superabrasive wheels for glass edging but it will be appreciated that the invention is not limited thereto. 
     In the example, the body is die cast of aluminium; it may however be cast of resin or other lightweight material, including composite.