Abstract:
An adjustable safety rest for grinding wheel includes a notch in one of a base edge defining side walls and an inner wall conformable in a spaced relationship around outer side edges and the outer edge of a grinding wheel. A wheel edge gap conformable member or special shape member is mounted in a base fixed to the grinder and is axially adjustable in position to maintain a first end of member in a fixed spaced dimensional relationship relative to one portion of the outer surface of the grinding wheel as the grinding wheel undergoes wear. The member may be disposed in a recess in the base at a 45° degree angle intersecting at least one inner corner of the notch in the base. The member may also be centrally mounted on the base to intersect only the inner wall of the base.

Description:
BACKGROUND 
     This invention relates, in general, to tool grinders and, more particularly, to safety rests for tool grinders. 
     Grinding wheels are employed in tool fabrication to smooth the surfaces of tools or parts during the fabrication of the tools or machine parts. 
     A typical bench grinder has one or two side-by-side, rotatable grinding wheels formed of abrasive material. A safety rest is mounted in front of each grinding wheel to provide a stationary surface for the operator to rest the part being ground. 
     OHSA regulation 191.215A4 requires a 1-3 mm gap between the grinding wheel and the safety rest to prevent equipment damage or bodily injury to the operator. 
     Typical safety rests have a straight edge facing the originally flat outer circumferential edge of the grinding wheel or a U-shaped notch in the straight edge of the safety rest which surround the originally flat front edge and a portion of the adjacent outer sides of the grinding wheel. The entire safety rest can be adjusted to maintain the required 1-3 mm spacing as the outer edge of the grinding wheel wears. 
     However, the notches in the safety rest have flat perpendicularly oriented sides to accommodate the original perpendicularly oriented flat sides and end surface of a new grinding wheel. The flat edge surface of the safety rest can be adjusted, as described above, relative to the grinding wheel as the flat end surface of the grinding wheel wears away in order to maintain the required 1-3 mm safety gap. 
     However, special shaped wheels which do not have a flat corner between the front edge and the sides of the grinding wheel or a wearing down of the originally flat corner of a grinding wheel by operators using the edge of the grinding wheel for smoothing radius cuts, etc., cause the originally flat corner edge of the grinding wheel to wear away into a curved radius. This curved radius edge on the grinding wheel becomes spaced further and further away from the corresponding inner corner edge of the safety rest as the grinding wheel edge wears away. This opens a gap larger than that required by safety regulations. 
     It will be desirable to provide a grinding wheel safety rest which accommodates grinding wheel edge wear or grinding wheels having special edge shapes during the useful life of the grinding wheel. 
     SUMMARY 
     An adjustable safety rest for a grinder wheel rotatably mounted on a fixed support includes a base, an inward extending notch formed in one edge of the base and defining two side walls and an inner wall, the inner wall connected to the sidewalls at inner corners, and a gap control member having a grinding wheel edge conformable end surface adjustably mounted in the base and intersecting one portion of the notch. 
     A groove is formed in the base and adjustably receiving the gap control member. 
     A longitudinal axis of the recess and the gap control member intersect one of the inner corners of the recess in the notch in the base at a substantially 45° angle. 
     In another aspect, an axis of the recess and the gap control member intersect the inner wall of the notch in the base. 
     The safety rest includes a mounting plate is fixed to the base and attachable to the fixed support. The mounting plate has at least one threaded bore, a slot carried in the plate and a fastener extendable through the slot into the bore in the plate for mounting the plate and the base on the fixed support. The slot, the fastener, and the mounting plate cooperate to allow adjustment of the mounting plate relative to the fixed support. 
     The gap control member includes a slide plate. Fasteners are engageable with the slide plate and the base to adjustably fix the slide plate in the selected position along the axial extent of the recess in the base. 
     A stop member can be fixed to a second end of the slide plate for limiting axial movement of the slide plate relative to the base in one direction. 
     In one aspect, the first end of the slide plate has an arcuate shape. In another aspect, the first end of the slide plate has a concave arcuate shape. In another aspect, the first end of the slide plate has a linear shape. 
     In one aspect, the safety rest has a special shape member adjustably fixedly coupled to a base for adjustable repositioning of a first edge of the special shape member relative to the base to maintain predetermined gap between the first edge of the special shape member and an adjacent edge of a grinding wheel. 
     The safety rest has a groove formed in the base, with the special shape member adjustably moveable in the groove. 
     The safety rest has a mount coupled to the base and adjustably positionably fixable to support structure surrounding a grinding wheel. The mount is repositionable to maintain the two side walls and the inner end wall of a notch in the base at a predetermined gap spacing from adjacent edges of a grinding wheel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The various features, advantages and other uses of the present grinding wheel safety rest will become more apparent by referring to the following detailed description and drawing in which: 
         FIG. 1  is a perspective view of a bench grinder using a safety rest with special shaped adjustment; 
         FIG. 2  is an enlarged, right side perspective view of the right side grinding wheel and safety rest shown in  FIG. 1 ; 
         FIG. 3  is an enlarged, left side perspective view showing the attachment of the safety rest to the grinding wheel housing; 
         FIG. 4  is a perspective view of one aspect of the safety rest; 
         FIG. 5  is a front elevational view of the safety rest shown in  FIG. 4 ; 
         FIG. 6  is a plan view of the safety rest shown in  FIG. 4 ; 
         FIG. 7  is a bottom right side perspective view of the safety rest shown in  FIG. 4 ; 
         FIG. 8  is an exploded perspective view showing the attachment of the special shape apparatus to the base of the safety rest shown in  FIG. 4 ; 
         FIG. 9  is a pictorial representation of the orientation of the safety rest relative to a new grinding wheel; and 
         FIG. 10  is pictorial representation showing the adjustment of the special adjustment shape relative to the safety rest base and a grinding wheel having a worn curved edge. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIGS. 1-9 , there is depicted, by way of example only, a bench grinder  20  rotatably driving at least one and, as shown in  FIG. 1 , two grinding wheels  22  and  24 . Grinding wheels  22  and  24  are mounted on separately rotatable spindles  26  which are coupled to an electric motor housed within a grinder housing  30 . 
     A wheel shield  31  is fixed to the housing  30  of the bench grinder  20  and is disposed in a surrounding or encompassing position with respect to each grinding wheel  22  and  24 . The shield  31  has a cut away opening  32  along the front edge allowing access to a front position of the grinding wheel  22  or  24 . For safety, the shield  31  has opposed sidewalls and edges all denoted by reference number  33  which surround a major portion of the grinding wheel  22  or  24 . 
     Each grinding wheel  22  and  24 , as shown in  FIG. 9  for the grinding wheel  22 , when in an original, new state, has a flat outer circumferential edge  36  and opposed sides  38  and  40 . In an original, new state, the outer edge  36  and the sides  38  and  40  form sharp, 90° outer corners or corner edges  42  and  44  at the intersection of the ends of the outer edge  36  and the sides  38  and  40 . 
     However, during use, at least one of the corner edges, such as the corner edge  44  located further away from the housing  30  than the opposed inner corner edge  42 , experiences extreme wear thereby rounding off the original sharp corner edge  44  to a curved or arcuate radiussed edge  46  shown in  FIGS. 1 and 10 . 
     Referring now to  FIGS. 1-3  and, in greater detail to  FIGS. 4-8 , there is depicted an adjustable safety rest or grinder guard apparatus  50  associated with the grinding wheel  22 . A mirror image adjustable safety rest or grinder guard apparatus  52  is associated with the other grinding wheel  24 . 
     The apparatus  40  includes a base  54  having a generally planar or flat shape defined by a top surface  56 , an opposed bottom surface  58 , first and second opposed edges  60  and  62  interconnected at opposite ends by sides  64  and  66 . The first edge  60 , which is a front edge with respect to the normal operating position of the safety rest  50  with respect to the grinding wheel  22 , has an angled chamfer  68  between the front edge  60  and the top surface  56 . 
     A plurality of small bores  80  are formed in the base  54  and extend completely through the base  54  to the top surface  56  to the bottom surface  58 . The bores  80  allow grinding dusts and sparks to pass through the base  54  instead of bouncing up towards the operator. Typical grinding machines have a dust collector with a vacuum mounted below the grinder wheel  22  to draw and capture the dust as it falls through the base  54 . 
     A U-shaped notch  70  is formed in the second edge  62  of the base  54 . The second edge  62  is also referred to as rear or back edge in the normal mounting position of base  54  relative to the grinding wheel  22 . The notch  70  is generally located intermediate to the opposed sides  64  and  66  of the base  54 . 
     The notch  70  is defined by a generally planar inner end wall  72  and opposed side walls  74  and  76 . The side walls  74  and  76  of the notch  70  are spaced apart a sufficient distance to provide a 1-3 mm gap between the surfaces of the side walls  74  and  76  and the adjacent sides  38  and  40  of the grinding wheel  22  when the safety rest  50  is in its normal mounting position surrounding a front portion of the grinding wheel  22  as shown in  FIG. 1 . 
     The inner wall  72  and the side walls  74  and  76  of the notch  70  form inner corners  73  and  75  respectively at the junctions of the ends of the sidewall  74  and one end of the inner wall  72 , and at the other end of the inner wall  72  and the opposed side wall  76 . Generally, the inner wall  72  and the side walls  74  and  76  of the notch  70  form 90° corners  73  and  75 . 
     A mounting support or leg  90 , generally in the form of a flat plate  91 , is fixed to the bottom surface  58  of the base  54 , generally along one side, such as side  66  of the base  54 . The plate  91  extends downward from the bottom surface  58  relative to the normal mounting position of the safety rest  50 . 
     An elongated slot  92  is formed in the plate  91 . One or more fasteners, with two fasteners  94  shown by way of example only in  FIGS. 4 and 5 , extend through the slot  92  into tapped holes  95  in a back plate  96 . Threading and unthreading of the fasteners or bolts  94  enables the distance or space between the plate  91  and the back plate  96  to be adjusted to fix the entire safety rest  50  on the sidewall  33  on the shield  31  surrounding the grinding wheel  22 . The fasteners or bolts  94  may be loosened and the entire safety rest  50 , the plate  91  and the back plate  96  adjusted in an adjacent direction toward the grinding wheel  22  to maintain the safety gap of 1-3 mm between the surfaces of the base  54  and the grinding wheel  22  as the grinding wheel  22  experiences wear. 
     A support rib  100 , which is illustrated as having a generally triangular shape by example only, can be fixed, such as by welding, to the bottom surface  58  of the base  54  and an inner surface of the leg  90  to maintain a substantially perpendicular angle between the base  54  and the leg  90 . 
     As shown in  FIGS. 1 ,  3 ,  4 ,  6 ,  8 ,  9 , and  10  the safety rest includes an adjustable special shape apparatus or gap control member  120  which maintains the required 1-3 mm gap between all portions of the inner walls  72 ,  74  and  76  of the notch  70  and the adjacent surfaces of the grinding wheel  22  when the grinding wheel  22  has a special exterior shape or experiences a shape change due to wear. A groove  122  is recessed into the top surface  56  of the base  54 . The groove  122 , which is shallower than the overall depth of the base  54  between the top and bottom surfaces  56  and  58 , may, in one application, be mounted substantially at a 45° angle with respect to the inside corner  73  between the inner end wall  72  and the side wall  74  of the notch  70 . At this angle, the longitudinal axis of the groove  122  intersects the original sharp outer corner edge  44  of the grinding wheel  22 . 
     A slot  124  is formed along the longitudinal axis of the groove  122  in the base  54  through the top surface  56  and the bottom surface  58  of the base  54 . The slot  124  extends inward into the base  54  from the top surface of the groove  122  has a first diameter sufficient to receive the threaded shaft of adjustable screws. The slot  124  opens to a larger slot  126  extending from the bottom surface  58  of the base  54 . The larger size slot  126  receives a slide lock  128  having a pair of apertures  130 . 
     The adjustably positionable special shape member can be in the form of a slide  136 . The slide  136  is sized to fit flush within the groove  122  and has a first end  138  and an opposed second end  140 . An enlarged stop plate  142  is attached, such as by fasteners or welding, to the second end  140  on the slide  136 . The slide  136  includes a pair of spaced chamfered bores  134  which receive the fasteners  132  in a flush arrangement. The fasteners  132  extend through the bores  134  and into the bores  130  in the slide lock  128  to allow adjustable positioning of the slide  136  in the groove  122  as described hereafter. 
     The different diameter portions of the slots  124  and  126  and the sidewalls of the groove  122  cooperate with the slide plate  136  to allow adjustable movement of the slide  136  along the axial length of the groove  122  between selectable positions to adjust the position of the first end  138  of the slide  136  at the predetermined required safety gap of 1-3 mm from the adjacent edge  44  of the grinding wheel  22 , as the edge  46  of the grinding wheel  22  wears during use. 
     As shown in  FIGS. 1 ,  4 , and  9 , the first end  138  of the slide  136  will initially be positioned in a fixed location in the groove  122  such that the first end  138  is located over the lower surface of the recess  122  and spaced from inner corner  73  of the notch  70 . This allows the inner corner  75  of the notch  70  between adjoining edges of the inner wall  72  and the side wall  74  to provide the required 1-3 mm small gap spacing between the safety rest  50  and all of the exterior portions of the grinding wheel  22 . 
     However, as shown in  FIG. 9 , through particular use of the outer corner edge  42  of the grinding wheel  22 , the outer corner edge  42  will wear away and take a more rounded or arcuate shape  46  as shown in  FIG. 10 . Gradually, as the inner corner  73  of the notch  70  becomes increasingly spaced from the corner edge  42  of the grinding wheel  22  as the corner edge  42  wears away, the adjustable slide plate  136  can be released through unthreading of the fasteners  132 , slid in a direction along the groove  122  toward the grinding wheel  22  and again tightened into a fixed position to maintain the first end  138  of the slide plate  136  in the desired 1-3 mm spacing with respect to the adjacent corner  46  of the grinding wheel  22 . 
     It will be understood that since the typical wear of the originally sharp edge  42  of the grinding wheel  22  is to the arcuate shape  46  shown in  FIG. 10 , the first end  138  of the slide plate  136  can have a complimentary curved or arcuate shape. This will maintain all portions of the curved edge  46  of the grinding wall  22  spaced the required 1-3 mm distance from the first end  138  of the slide  136   
     It will also be understood that the first end  138  of the slide plate  136  can have other shapes so as to conform to a grinding wheel having a special edge shape, such as a 45° corner, or an original curved arcuate shape, etc. 
     As shown in  FIGS. 1 and 2 , the adjustable safety rest  52  with special adjustable apparatus for the grinding wheel  24  is constructed in a mirror image from the adjustable safety rest  50  described above. When viewed in plan, in the adjustable safety rest  52 , the grooves  122  and the slide  136  are still oriented at 45° angle to the outer edge  42  of the grinding wheel  24 . However, due to the left side mounting of the grinding wheel  24  on the bench grinder  20 , the recess  122  on the slide plate  136  are located on the opposite corner of the base  54  than for the adjustable safety rest  50 . 
     It will also be understood that a single adjustable safety rest  50  of  52  can be constructed with two recesses, each extending at an approximate 45° angle from the inner corners of the notch  70 . This provides the conforming first end surface  138  on the adjustable slide  136  to be provided for each side edge of the grinding wheel  22  or  24  regardless of which side edge is subject to wear. The slides are adjustable independently with respect to the conforming grinding wheel edge to maintain the required 1-3 mm gap. 
     It is also possible to provide the groove  122  in line with the notch  70  generally central or intermediate the oppose sides  64  and  66  of the base  54 . This provides two features. First, the entire safety rest may be fixed in a stationary position relative to the grinding wheel  22  and only the slide  136  adjusted as the front edge of the grinding wheel  22  experiences wear. Second, the central location of the groove  122  on the base plate  54  can utilize a slide  136  having a specially configured first end  138  for use with specially shaped grinding wheels, such as grinding wheels having a T-shaped slot formed in the outer edge. 
     The intermediate or central location of the groove  122  and the slide  136  may also be combined with either or both of the left hand and right hand angularly positioned recess  122  and slide  136  described above in a single unit.