Patent Publication Number: US-2010111639-A1

Title: Antigalling anchor bolt and method

Description:
BACKGROUND 
     Galling is a condition that can occur when two pieces of the same metal are rubbed together. Galling can be a problem if the two surfaces are intended to move relative to each other in use. Friction between the surfaces results in localized material transfer between the surfaces. Generally galling occurs when the two surfaces experience relative motion while subject to a sufficient compressive stress to permit the transfer of material. The stress between the surfaces tends to disrupt any protective oxide layer that is naturally present and allow metal-to-metal contact. Pure metal-to-metal contact without an oxide or other separating layer will facilitate a cold welding process thereby joining the surfaces together and preventing further relative motion therebetween. 
     Galling often occurs between an expander portion and an expansion sleeve of an anchor bolt when installing the anchor bolt into a base material. Depending upon the severity of the galling, the expander sleeve may be pulled from the base material rather than expanded properly by the expander portion of the bolt, thereby defeating the anchor. Additionally, galling increases the force required for removal of the anchor during intended disassembly. The art will be receptive to alternative configurations minimizing or eliminating galling. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention, an anchor bolt includes a wedge having a surface with a plurality of protrusions and a sleeve in operable communication with the surface, the sleeve expandably receptive to the surface. 
     According to another aspect of the invention, a method to reduce galling of an anchor bolt includes reducing contact area between a wedge surface and a sleeve of the anchor bolt. 
     According to yet another aspect of the invention, a method to reduce a breaking force between galled components of an anchor bolt includes, reducing contact area between a wedge surface and a sleeve of the anchor bolt. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
         FIG. 1  depicts a side view of an anchor bolt having a diamond knurled wedge according to an embodiment of the present invention; 
         FIG. 2  depicts a cross sectional side view of the anchor bolt of  FIG. 1  at arrows  2 - 2 ; 
         FIG. 3  depicts a side view of an anchor bolt having a cross knurled wedge according to another embodiment of the present invention; 
         FIG. 4  depicts a side view of an anchor bolt having longitudinal ridges according to yet another embodiment of the present invention; and 
         FIG. 5  depicts a side view of an anchor bolt having latitudinal ridges according to still another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-5 , an embodiment of an anchor bolt  10  disclosed herein is shown. The anchor bolt  10  includes, a stud  12 , a sleeve  14 , a nut  16  and an optional washer  18 . The stud has a wedge  20  that is configured to radially expand the sleeve  14  during setting of the anchor bolt  10  into a base material  22 . To set the anchor bolt  10 , the anchor bolt  10  is first inserted into a hole  24  made in the base material  22 , the hole  24  having a diameter only slightly larger than that of the wedge  20 . The nut  16  engages threads  26  on a portion  27  of the stud  12  that protrudes from the base material  22 . Turning the nut  16  pulls the stud  12  and the wedge  20  in a setting direction as shown by arrow  28  while the sleeve  14  remains stationary in the base material  22  due to friction therebetween. As the wedge  20  moves in the direction of arrow  28 , the sleeve  14  is expanded radially outwardly. Since the diameter of the hole  24  does not change appreciably due to the expansion input, the anchor bolt  10  becomes substantially anchored in the base material  22 . In embodiments disclosed herein, an outer tapered surface  29  of the wedge  20  includes a plurality of protrusions  30 . The protrusions  30  on the surface  29  reduce galling between the surface  29  and the sleeve  14  during setting. Additionally, in the event that some galling does occur, the existence of the protrusions  30  reduces a force needed to break the galled components apart. 
     The surface  29  of the wedge  20  has a generally tapered shape that may be conical for wedges  20  having a round cross section. Further, an angle  40  of the taper of the surface  29  may remain constant over a longitudinal length of the surface  29  as illustrated herein. Alternately, the angle  40  may be variable over the longitudinal length. Embodiments herein are not limited to being conical in shape, however, and may be any other shape that is effective in acting as a wedge. 
     The surface  29  as shown includes a plurality of recessions  31  that correspond with the plurality of protrusions  30 . The plurality of protrusions  30  may have a knurled pattern. In the example depicted in  FIG. 1 , the protrusions  30  have a diamond pattern. In other embodiments, the protrusions  30  may have a cross knurled pattern, as shown in  FIG. 3 , for example. Additionally, the protrusions  30  may be in the form of a series of longitudinal ridges  32 , as shown in  FIG. 4 , or a series of latitudinal ridges  33 , as shown in  FIG. 5 . Alternately, the protrusions  30  may not have any particular pattern. It should be understood that the protrusions  30  reduce the contact surface area between the surface  29  and the sleeve  14  during setting and may take any form that achieves this purpose. 
     As detailed above, the wedge  20  is in operable communication with the sleeve  14  during setting of the anchor bolt  10 . In the embodiment shown in the Figures, the sleeve  14  is a fully bored formed cylindrical sleeve having an inner diameter  34  that is greater than the outer diameter  35  of a shank  36  of the anchor bolt  10 . In this embodiment, the sleeve  14  is free to rotate around the shank  36  before setting. The sleeve  14  is also shown having the at least one gripping projection  37 . The at least one gripping projection  37  helps to grip the base material  22  and increase friction between the sleeve  14  and the hole  24  during setting of the anchor bolt  10 . The at least one gripping projection  37  is shown oriented in a latitudinal direction but may also be a longitudinal projection or may have a non-axial shape. Additionally, sleeve  14  is shown having at least one longitudinal slot  38  on the body of the sleeve  14 . The at least one longitudinal slot  38  allows the sleeve  14  to be radially deflected without the necessity of stretching the material of the sleeve  14  itself In other embodiments, the sleeve  14  may be configured for being stretched. 
     It should be understood that the invention is not limited to the configurations depicted in the Figures. The anchor bolt  10  may be any anchor having a metallic wedge that expands a metallic portion of the anchor during setting. Furthermore, the stud  12  and the sleeve  14  may be fabricated of any metal susceptible to galling, such as, stainless steel, low carbon steel, cast iron, copper, aluminum, magnesium, and titanium, for example. 
     While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims.