Abstract:
A bolt on drive assembly for a core drill which utilizes a spoked reinforcer mounted between a pair of discs. The discs are removably mounted on the tube by bolt fasteners. A drive connection is removably mounted and centrally located on a outer disc of the pair of discs. The drive connection is adapted to connect with a drive shaft to cause rotation of the tube.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The field of this invention relates to cutting implements and more particularly to the construction of a core drill. 
   2. Description of the Related Art 
   Core drills are commonly used for drilling holes in hard materials, such as concrete and masonry. These holes are then used to support a structural member, such as a post, which is used on a support member for a building structure or for forming a large diameter borehole with the borehole being used for the passage of pipe lines or conduits. A typical core drill is constructed of hard metal, such as steel, and takes the shape of a tube with hardened cutting segments mounted at one end of the tube. The opposite end of the tube is closed generally by a solid steel plate with there being a drive connection mounted on this steel plate. The drive connection is to be connected to a rotating shaft of a drive machine which will cause the tube to be  rotated and affect the cutting operation. The cutting segments at one end normally comprise diamonds but also it has been known to use silicon carbide. The diamonds are held together by a suitable resin adhesive. 
   The plate at the closed end of the tube is of substantial thickness, generally one half to one and a half inch thick. These core drills are frequently designed to be from six inches to thirty-six inches and more in diameter. The steel plate at the closed end is of substantial weight. It is important to have an extremely strong member at this closed end because all the force from the driving machine is being transferred to this member to the tube. The force encountered by the tube in cutting the hole in masonry and concrete is substantial so it is important that the plate at the closed end of the tube establish an extremely strong connection. However, most often these core drills are carried by a human from one location to another. The plate member at the closed end of a sixteen inch core drill is fifteen pounds heavier than the core drill constructed in accordance with this invention. That extra fifteen pounds of weight can actually make the difference as to whether a core drill can be carried by a single human from one location to another. It is readily apparent that the greater the diameter of the core drill the greater of the additional amount of weight. It would be desirable to design some type of closed end structure for a core drill which would be substantially lighter in weight than if a solid plate is used.  
   At times, when operating of a core drill, a plug of material, which would be normally masonry or cement, gets caught within the hollow chamber of the core drill adjacent the closed end plate. At the present time, access into this area is only provided through the open end of a core drill which means some kind of an elongated member has to be extended up through the hollow chamber of the core drill and this member wedged against the caught material and somehow loosen it to dislodge it. It would be desirable to construct a core drill so that the closed end portion of the core drill could be removed from the tube which would provide immediate local access to any wedged material that is caught within the hollow chamber and located directly adjacent the closed end. 
   SUMMARY OF THE INVENTION 
   A first basic embodiment of the present invention is a bolt on drive assembly for a core drill which uses a cylindrical open ended tube which has a cutting edge at one longitudinal end and an open end at an opposite longitudinal end. A mounting means is provided at the open end with a spoked reinforcer, which has a center hub from which extends radially a plurality of spoked members, being attached to this mounting means. An outer disc is mounted on the spoked reinforcer covering same and also onto the mounting means. A drive connection is centrally mounted on this outer disc with this drive connection adapted to connect to a  drive shaft to cause rotation of the tube. A series of removable fasteners are used to secure the outer disc and the spoked reinforcer to the mounting means. 
   A further embodiment of the present invention is where the first basic embodiment is modified by the mounting means as being defined as a mounting ring which is mounted inside the hollow cylindrical chamber of the cylindrical tube. 
   A further embodiment of the present invention is where there is included an inner water stop disc located across the hollow chamber of the tube mounted against the inside surface of the spoked reinforcer. 
   A further embodiment of the present invention is where the first basic embodiment is modified by the drive connection being defined as a coupler which is threadably securable to a drive shaft. 
   A further embodiment of the present invention is where the just previous embodiment is modified by the coupler being mounted by bolt fasteners to an outer disc. 
   A second basic embodiment of the present invention is directed to a method of making a core drill which comprises the steps of utilizing a cylindrical open ended tube which has a hollow chamber, forming a cutting edge at one end of this tube, forming a mounting means at an opposite end of this tube and bolting on a spoked reinforcer onto the mounting means where the spoked reinforcer is connected to a driving connection. 
   A further embodiment of the present invention is where  the second basic embodiment is modified by prior to bolting inserting a thin water stop disc across the hollow chamber located against the spoked reinforcer essentially closing of this hollow chamber to prevent passage of water therethrough. 
   A further embodiment of the present invention is where the just previous embodiment is modified by after the bolting step placing a second thin disc across the hollow chamber, further providing a stop for water, covering the outside surface of the spoked reinforcer with the bolting also functioning to secure this second thin disc in place. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the present invention, reference is to be made to the accompanying drawings. It is to be understood that the present invention is not limited to the precise arrangement shown in the drawings. 
       FIG. 1  is an external isometric view of a first embodiment of core drill constructed in accordance with this invention; 
       FIG. 2  is an exploded isometric view of the bolt on drive assembly of the first embodiment that is constructed in accordance with this invention where the connector of the drive assembly is welded in location onto an outer disc; 
       FIG. 3  is a view similar to  FIG. 2  but of a second  embodiment where the drive connection instead of being welded is bolted in place on the outer disc; 
       FIG. 4  is a transverse cross-sectional view through the assembled drive assembly of the core drill of the first embodiment of this invention; and 
       FIG. 5  is a view similar to  FIG. 4  but of the second embodiment of this invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring particularly to the drawings, there is shown the first embodiment 10 of core drill in  FIGS. 1 and 2  constructed in accordance with this invention. The core drill  10  has a body that is in the shape of a tube  12 . Typically, this tube  12  will be of a diameter of between six and sixteen inches. The tube  12  has a through hollow chamber  14 . The hollow chamber  14  at one longitudinal end  16  is open. On the peripheral edge about the end  16  there is adhesively or otherwise permanently affixed a series of cutting segments  18 . Generally, the cutting segments  18  will comprise diamonds. The cutting segments  18  is what produces the cut within the material that is being cut, which is generally cement or masonry. This cut is produced by rotating of the tube  12 . 
   At the opposite longitudinal end of the tube  12  there is located a mounting ring  20 . The mounting ring  20  has a series of  spaced apart threaded holes  22 . The mounting ring  20  is generally no more than one-half to three-quarters of an inch wide and is to be fixedly mounted to the wall of the hollow chamber  14  a slight distance spaced from the outer edge  24  of the tube  12 . Normally, this spacing of the mounting ring  20  will be no more than one-half inch. The mounting ring  20  is generally fixedly secured to the tube  12  by welding. 
   Water stop disc  26  is placed within the hollow chamber  16  and is supported on the mounting ring  20 . Adjacent the peripheral edge of the disc  26  there is located a series of through holes  28 . A single through hole  28  is to align with a single threaded hole  22 . The disc  26  has a center hole  30 . The center hole  30  is to facilitate handling of the disc  26  to locate such on the mounting ring  20 . 
   A spoked reinforcer  32  is then to be placed on the water stop disc  26 . The spoked reinforcer  32  has a centrally located hub  34  which also has a center hole  36  to facilitate handling. Extending radially outward from the hub  34  are a plurality of spaced apart radial arms  38 . There are shown six in numbers of the arms  38  in the first embodiment of  FIG. 2  and eight in number of the arms  38  in the second embodiment 11  FIG. 3  of spoked reinforcer  33 . Typically, there will only be used six in number of the arms  38  when the diameter of the tube  12  is thirty inches and less. When the diameter of the tube  12  exceeds thirty inches, then there will generally be used eight in number of the arms  38 . Directly adjacent the outer end of each of the arms  38   is a through hole  40 . A through hole  40  is to be in alignment with a through hole  28 . 
   Mounted also within the hollow chamber  14  and located against the exterior surface of the spoked reinforcer  32  is an outer disc  42 . Outer disc  42  functions as a cover. The outer disc  42  has a series of through holes  44  located directly adjacent the peripheral edge of the disc  42 . There is to be a through hole  44  to align with a through hole  40  for each of the radial arms  38 . A bolt fastener  46  is to be placed through each of the aligned holes  44 ,  40 ,  28  and then be threadably tightened within the threaded hole  22 . This will secure in place the drive assembly which is composed minimally of the spoke reinforcer  32  and the outer disc  42 . The only reason for the disc  26  is to prevent the passage of water through the hollow chamber  14  and prevent such from being discharged from the tube  12  past the mounting ring  20 . Water is frequently used when drilling of cement and masonry in order to minimize the creation of heat. The drive assembly, which is composed of water stop disc  26 , spoke reinforcer  32  and outer disc  42 , as shown in  FIGS. 2 and 3 , is exceedingly strong but is much lighter in weight than if it were a completely solid steel plate. This has an advantage in that the overall core drill is lessened in weight therefore facilitating its carryablity by a human. 
   In  FIG. 2 , centrally mounted on the outer disc  42  is a drive connection  48 . Drive connection  48  is shown to be in the shape of a hexagonal nut and has an internal threaded opening  50 .  This internal threaded opening  50  is to connect to a drive shaft of a driving machinery, which is not shown. The driving machinery is to affect rotation of the drive connection  48  and the entire core drill  10 . The drive connection  48 , shown in  FIGS. 1 ,  2  and  4 , is to be welded about center hole  52  formed within the outer disc  42 . 
   Referring particularly to  FIGS. 3 and 5  of the drawings, there is shown the second embodiment 11 which is directed to a modified version of a drive connection  54  which is again in the shape of a hexagonal nut which has an internally threaded opening  56 . The drive connection  54  is fixedly secured as by welding or integral with an attaching flange  58 . Formed within the attaching flange  58  are a series of through holes  60 . Each through hole  60  is to align with a through hole  62  formed within the outer disc  42  and also with a threaded hole  63  formed within the hub  34  of the spoked reinforcer  33 . The holes  62  are located about center hole  64  formed within the outer disc  42 . Connecting with each set of aligned holes  60  and  62  is a bolt fastener  66 . It is to be understood that there is a separate bolt fastener  66  for each set of aligned holes. 
   The advantage of the second embodiment of this invention is that the driving connection can be removed from the outer disc  42  if for any reason such would fail. In  FIGS. 1 and 2 , if the driving connection  48  fails, replacement of the outer disc  42  will be required. It is to be understood that a shaft from a machine that is to cause rotation of the tube  12  is to be threadably  connected to the threaded connection  56 . 
   Typically, the thickness of each of the spoke reinforcers  32  would be in the range of three-eights to one-half of an inch. By removal of the drive assemblies in both  FIGS. 1 and 3 , access to the upper end of the hollow chamber  14  is permitted in order to affect dislodgement of any wedged material that may be caught in the area of the hollow chamber  14 . The reason this is permitted is by the removing of the bolts, which permits the outer plate  42 , spoked reinforcer  32  or  33  and water stop disc  26  to be removed from the mounting ring  20  to provide access to the hollow chamber  14 .