Abstract:
A method of and device for manufacturing a hollow anchor with a radial, helical contour on its outer surface is provided. The contour is preferably a raised external contour or helix that is formed on the outer wall of the anchor and is suitable for tapping a thread in masonry. The hollow anchor formed by the method has an internal cavity that can receive another member and an outer surface with a raised external contour that is suitable for tapping a thread in a blind bore in a masonry member.

Description:
BACKGROUND OF THE INVENTION 
     The present invention provides: a method of manufacturing a hollow anchor with a threaded outer surface, the device for carrying out the method and the anchor made thereby. 
     The anchor of the present invention has many uses, but it is designed specifically to be used as a masonry anchor in construction environment where a designer would like a threaded female coupling embedded in a cementitious or other masonry member. 
     There are many internally threaded, female coupling anchors for cementitious members. The anchor of the present invention installs easily because it is formed with an outer thread or helical contour that allows the anchor to be driven into an unthreaded, cylindrical masonry bore. The outer, radial thread formed on the anchor taps its own thread groove in the wall of the bore, making a strong and positive attachment with the concrete member. 
     The anchor is particularly useful for being installed in overhead ceilings where it is difficult for workman to operate. The anchor is installed in the concrete after the concrete has set which allows for the anchor to be place exactly where it is needed, and on an as-needed basis. In overhead applications, the goal is to require as few placement steps as is necessary as working overhead can be very tiring. With the present anchor, there are only two major steps. A blind hole is drilled in the concrete with a powered driver. Preferably, the driver can be used both to drill the bore, and then the drill attachment can be removed and a driver, such as a hex head driver can be fitted. There are also drivers that can fit over drill bits on powered drivers which can be used. The hole is cleaned and then using the driver with an attachment that couples with a mating surface of the anchor, the anchor is rotatably driven into the hole. The anchor cuts its own threads in the wall of the hole or bore and is thus called a self-tapping masonry anchor. 
     Anchors having an internally threaded bore and a self-tapping, outer thread for use in masonry are not new in the art. U.S. Pat. No. 7,056,075, granted to Powers, teaches such an anchor. The self-tapping outer thread of U.S. Pat. No. 7,056,075 differs from the present invention in many respects, but perhaps most importantly, in U.S. Pat. No. 7,056,075, the outer thread and the inner driving portion are formed in two separate operations. A cold forming draw process is used to form the internal driving area, while in a separate step, a rolling pin is used to create the thread on the outer surface. With any self-tapping, threaded masonry anchor the proper formation of the self-tapping outer thread is critical. The ability of the anchor to make a strong connection with the masonry substrate depends soley on the way the thread or threads of the anchor interact with the masonry. Thus it is important that thread can be made accurately and that the dimensions and tolerances for the outer thread remain uniform over production runs. It is believed that particular features of the present anchor are unique and the method of manufacture provided herein allows for high quality anchors to be produced economically. 
     According to the method of the present invention, the outer thread is formed on a hollow blank in a non-cutting operation with the outer surface of the blank being plastically deformed by the action of radial forces generated by a mandrel inserted through the hollow blank. Not only does this method of formation allow for an anchor to be formed with a self-cutting thread that will create a strong connection with the masonry substrate, it allows the anchor to be made with unique features that further add to the quality of the connection made with the anchor. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention it to provide a method of manufacturing a hollow anchor with a radial contour on its outer surface, where the contour is formed precisely and efficiently. The contour is preferably a raised external helix that is formed on the outer wall of the anchor and is suitable for tapping a threaded groove in masonry. 
     It is a further object of the present invention to provide a device for carrying out the method of forming the hollow anchor with an external thread. 
     It is a further object of the present invention to provide a hollow anchor having an internal cavity that can receive another member and an outer surface with a raised external contour that is suitable for tapping a thread in a blind bore in a masonry member. Preferably, the hollow anchor has an internal bore that passes all the way through the anchor along a longitudinal axis of the anchor from the rear end to the front end. 
     These objects of the present invention are provided in part by using a multi-part split die for forming the anchor, where the die inserts having inner surface profiling that forms the intended radial outer contour on a hollow blank when a mandrel is inserted through the hollow blank and causes plastic deformation of the material of the blank. 
     These objects of the present invention are provided in part by using a mandrel to create the outward radial forces to cause material flow into the radial contour-forming die segments. By using a mandrel to create the outward radial forces to cause material flow into the radial contour-forming die segments, the die segments merely need to be held in place at the correct locations, when the die is in the closed position and the mandrel is acting on the hollow blank. This method of operating the die and mandrel achieves, in part, the object of forming the anchors with an outer thread contour in a reliable and economically efficient manner. 
     These objects of the present invention are also provided in part by using a mandrel having a stepped diameter where it interacts with the hollow blank. 
     It is also an object of the present invention to provide the mandrel with a forming portion that creates the driving tool fitting portion of the internal bore in the anchor. The driving tool fitting portion can releasably engage an anchor inserting and driving tool such as a powered driver fitted with a hexagonal driving head. Preferably, the driving tool fitting portion is formed in the upper portion of the axial internal bore of the blank. 
     The object of efficiently and reliably producing female anchors with threaded outer surface is also achieved in part by forming the insert segments of the die so they easily move between their open and their closed positions. This is accomplished by forming the die inserts with keyed, tapering outer surfaces and, by operation of the die, forcing them downward in keyed and tapering raceways in the insert segment holder such that they are brought closer together and into closed position from the open position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of the die inserts of the present invention shown in contact as they would be in the closed position of the die. 
         FIG. 2  is cross-sectional side view of the die inserts of  FIG. 1 , taken along the view line shown in  FIG. 1 . 
         FIG. 3  is a top view of the die inserts of  FIG. 1  shown separated from each other as they would be in the opened position of the die. 
         FIG. 4  is a cross sectional side view of the die inserts of  FIG. 3 , taken along the view line shown in  FIG. 2 . 
         FIG. 5  is an exploded top view of the die inserts of  FIG. 1 . 
         FIG. 6  is a side view of the die inserts of  FIG. 5  taken along the view line shown in  FIG. 6 . 
         FIG. 7  is a cross-sectional side view of the die inserts and mandrel, with the die inserts shown in the closed position and the mandrel shown fully inserted into the die inserts. 
         FIG. 8  is a cross-sectional side view of the dies inserts and mandrel similar to  FIG. 7  with a formed anchor shown in cross-section. 
         FIG. 9  is side view of the anchor of the present invention. 
         FIG. 10  is a cross-sectional side view of the anchor of the present invention. 
         FIG. 11  is a cross-sectional side view of the anchor of the present invention with internal threads formed on the inner surface of the anchor. 
         FIG. 12  is side view of the mandrel of the present invention. 
         FIG. 13  is a top view of the die insert holder of the present invention. 
         FIG. 14  is a cross-sectional side view of the die insert holder of the present invention taken along the view line in  FIG. 14 . 
         FIG. 15  is top view of the die inserts received in the holder of the present invention with the die inserts in the closed position. 
         FIG. 16  is a side view of the die inserts and holder shown in  FIG. 15  taken along the view line in  FIG. 16 . 
         FIG. 17  is a top view of the holder, lifter and lower mandrel guide of the present invention. 
         FIG. 18  is a cross-sectional side view of the holder, lifter and lower mandrel shown in  FIG. 17  taken along the view line shown in  FIG. 17 . 
         FIG. 19  is a cross-sectional side view of the present invention similar to  FIG. 18  with the die inserts shown received in the holder in the closed position. 
         FIG. 20  is a cross-sectional side view of the present invention similar to  FIG. 19  with the mandrel and a anchor shown received in the holder. 
     
    
    
     DETAILED DESCRIPTION 
     In the simplest form of the method of the invention, a hollow, generally cylindrical blank  1 , preferably formed of steel, is placed in a cavity  2  in a contour-forming die  3 , and a mandrel  4 , both the mandrel  4  and die  3  being preferably formed of steel, having extruding portions  28  is inserted through the hollow blank so as to force the material of the blank  1  to flow and shift radially outwardly into the contour forming portions  5  of the die inserts  6  of the multi-part, split die  3  and also to shift and form around the outer surface  7  of the mandrel  4 . The die inserts or insert segments  6  are also sometimes called negative dies in the art. Operation of the die  3  creates an external contour  8  on the outer surface  9  of the hollow anchor  10  which as shown is a helical thread suitable for tapping a masonry bore. 
     The insert segments  6  are mounted on the holder  11  so as to be radially movable. The outer surfaces  12  of the die inserts  6  and the inner surfaces  13  of the holder  11  on which they ride are tapered such that the die inserts  6  are movable into the closed position  14  and the opened position  15  by the axial movement of the die inserts  6  in relation to the insert segment holder  11 . Upward movement of the die inserts  6  allows them to open and increase the size of the cavity  2 , while downward movement brings the die inserts  6  together and makes the cavity  2  smaller. 
     The term external contour  8  covers projections, projecting threads, individual grooves or undercuts. The external contour  8  is generally a radial helix, such as a thread, but it can take other forms. The radial outer contour or contours  8  can be arranged over the entire area of the blank  1  or only at specific points. 
     The hollow blank  1  can be cylindrical or cone shaped. 
     The insert segments  6  of the die  3  in combination with the mandrel  4  also form the flared upper outer portion  16  of the anchor  10  and the tapering bottom entry portion  17  of the anchor  10 . The hollow blank  1  has a forward end  18  and a trailing end  19 . In the preferred embodiment, the outer surface  9  of the forward end  18  is preferably formed with a camfer or angled face  20  to assist with aligning the anchor  10  in a masonry hole  21 . In the preferred embodiment, a camfer or angled face  22  is also formed between the threaded portion  23  of the anchor  10  and the trailing end or crown  19  of the anchor  10 . The camfers  20  and  22  are formed as the outer surfaces of truncated cones. Preferably, the outer diameter of the external contour  8  is larger than the diameter of the trialing end  19  of the anchor  10 . Preferably, when the anchor  10  is approximately 1.625 inches long the portion of the outer surface  9  formed with an external contour  8  extends over more than half the length of the anchor  10  and preferably extends approximately 1.175 inches. Preferably, the external contour  8  is a helical thread with a thread profile of 50 degrees, and a thread spacing of approximately 0.35 inches, an outer thread diameter of approximately 0.632 inches, and with a thread that runs out smoothly at both trailing end  19  and the forward end  18  with the run out at the forward end  18  not exceeding an angle of 60 degrees around the anchor  10  and the run out at the trailing end  19  not exceeding 135 degrees. The steel of the anchor  10  is preferably SAE J403 Grade 10B21. 
     The hollow anchor blank  1  is formed by known methods with a bore  38  that extends through the blank  1  along the longitudinal axis  39  of the blank. 
     The blank  1  is held within the cavity  2  created by a plurality of inserts  6 , preferably three. The die inserts  6  are preferably “open” in a starting or opened position  15  for receiving the blank  1 . Even when the die inserts  6  are fully closed the cavity  2  still exists between them where the blank  1  is held. 
     The die inserts  6  are keyed on their outer surfaces  12  to attach to the insert segment holder  11 . The outer surfaces  12  of the die inserts  6  are tapered and travel in tapered race ways  24  in the insert segment holder  11 . The insert holder  11  can be contained within an outer casing that is not shown. 
     As the blank  1  is set into position within the segments/inserts  6 , a punch or mandrel  4  with an outer diameter that widens from the bottom portion  44  of the mandrel  4  to the top portion  45  of the mandrel  4 , preferably in a stepped fashion, and in the preferred embodiment also has a specially shaped top portion  25 , is inserted through a top guide (not shown) on top of the die  3  which aligns the mandrel  4  with the cavity  2  formed by the die inserts  6 . A first smooth section  26  of the punch/mandrel shaft passes through the inner hollow  38  of the blank  1  and engages with a lower punch guide  27 . 
     As the punch or mandrel  4  travels further through the blank  1 , the steps or shoulders  28  on the punch  4  start to engage with the inner surface or wall  29  of the blank  1  and begin to exert outward or lateral pressure on the inner wall  29  of the blank  1 . The steps  28  are formed such that the diameter of the mandrel increases in size after each step  28  as the steps travel up the mandrel  4 . This upsets the material around the outer perimeter of the blank  1  and thus this material extrudes outwardly and fills the contour profiles  5  cut into the die insert segments  6 . The contour profile  5  is preferably a radial helix consisting of aligned thread cavities  5  in each inner surface  30  of each die segment  6 . 
     As the mandrel or punch  4  continues to travel through the blank  1 , the upper section of the mandrel  25  with the specially shaped top engages the crown  19  of the blank  1  and further forces material down and into the upper thread cavities  5  in the segments or die inserts  6 . In the preferred embodiment, the specially shaped top  25  also generates the hexagonal socket  31  in the crown  19  of the blank  1 . 
     In the preferred embodiment when the hexagonal formation  31  has been made sufficiently deep, the punch  4  reverses direction and the mandrel  4  is extracted from the trailing end of the anchor or blank  1 . When the punch  4  reverses direction, the keyed and tapered die segments  6  also move upwardly in the segment holder  11  by operation of a lifter  32  until the inset segments  6  open wide enough to release the anchor  10 . 
     An additional step creates an internal thread  33  on the inner surface of the anchor  10 . In the preferred embodiment, the thread  33  is formed below the internal hexagonal driver receiving portion  31  in the crown  19  of the anchor  10 . 
     The anchor  10  can be heat treated and plated following the formation of the internal thread. The formation of the anchor  10  can be carried out on a multi-stage press known in the art. 
     As shown in  FIG. 1 , the die inserts  6  have planar side faces  34  that interface with each other when the die inserts  6  are in the closed position  14 . As shown in  FIG. 2 , the inner surfaces  30  of the die inserts  6  are preferably formed with a lower inwardly tapering portion  35  and an upper inwardly tapering portion  36  that bracket the portion of the inner surface  30  of the die segments  6  where the contour forming portions  5  of the die  3  are provided. Above the upper inwardly tapering portion  36  the inner surface is preferably cylindrical. The keyed portions  37  of the outer surfaces  12  of the die inserts  6  fit within the cavities or race ways  24  provided in the holder  11 . 
     As shown in  FIG. 1 , each race way  24  has a pair of side walls  40  that extend along the tapering inner surface  13  towards the bottom  41  of the holder  11  along and at an angle to the longitudinal axis  46  of the holder  11 . The surfaces  42  of the pair of side walls  40  are set at an angle to each other such that they hold the keyed portions  37  of the die insets  6 . Matching walls  43  in the keyed portions of the insert segments  6  align with and slide along the side walls  40 . These walls  40  and  43  travel along the die inserts  6  and the holder  11  in parallel relation.