Abstract:
A threaded nozzle for use in a cutter bit is disclosed. Threads are either machined into or pressed into a pressed powder nozzle then the nozzle is sintered. Threads of the nozzles of the present invention exhibit improved hardness and have a rougher surface finish than threads machined post-sintering. Shaping of the threads into the nozzle before sintering is also more economical and efficient than post-sintering machining.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to earth-boring drill bits and, in particular, to nozzles utilized in earth-boring drill bits. 
       BACKGROUND INFORMATION 
       [0002]    Earth-boring bits such as roller cone bits and fixed cutter bits are often equipped with threaded nozzles which provide fluid for flushing a bore hole of debris, flushing the bit and may also be a source for hydraulic drilling action. These threaded nozzles are often made from a hardened material such as cemented carbide, i.e., tungsten-carbide cobalt. 
         [0003]    The standard method of manufacturing threaded nozzles for use in earth-boring bits has been to first press and sinter a nozzle having the general shape of a nozzle. The unfinished nozzle is then machined to its final finish and dimensions. This machining includes threading the nozzle. Machining of the sintered tungsten-carbide is extremely difficult due to the material&#39;s hardness and often requires the use of expensive diamond cutting products. 
         [0004]    The present invention was developed in view of the foregoing. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention provides a threaded nozzle for use in a cutter bit. Threads are either machined into or pressed into a powder nozzle then the nozzle is sintered. Threads of the nozzles of the present invention have a rougher surface finish and are believed to be harder than threads machined post-sintering. Shaping of the threads into the nozzle before sintering is also more economical and efficient than post-sintering machining. 
         [0006]    One aspect of the present invention provides an unsintered, pressed powder nozzle for use in a cutter bit comprising a body comprising an exterior face, an inlet end and a discharge end, a bore extending through the body from the inlet end to the discharge end and external threads extending at least partially along the exterior face of the body of the unsintered nozzle. 
         [0007]    Another aspect of the present invention provides a threaded nozzle for use in a cutter bit comprising a body comprising an exterior face, an inlet end and a discharge end, a bore extending through the body from the inlet end to the discharge end and external threads extending at least partially along the exterior face of the body of the threaded nozzle, wherein the external threads have a surface roughness of at least 40 microinches. 
         [0008]    Another aspect of the present invention provides a method of producing a threaded nozzle for use in a cutter bit comprising the steps of first providing a pressed powder nozzle blank, second machining threads into the pressed powder nozzle blank and third sintering the pressed powder nozzle blank. 
         [0009]    Another aspect of the present invention provides a method of producing a threaded nozzle for use in a cutter bit comprising the steps of providing a die comprising a first end, a second end, a sleeve and a split insert having a thread forming section inserted into the sleeve, inserting a first punch into a first end of the die, filling the die with a metal powder or ceramic powder, inserting a second punch into the second end of the die, applying pressure to the powder within the die to create a pressed powder blank, removing the pressed powder blank from the die, and sintering the pressed powder blank. 
         [0010]    These and other aspects will become more apparent from the following description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is an oblique view of a threaded nozzle installed in a fixed cutter bit according to one embodiment of the present invention. 
           [0012]      FIG. 2  is a side view of a threaded nozzle according to one embodiment of the present invention. 
           [0013]      FIG. 3  is a front view of the threaded nozzle shown in  FIG. 2 . 
           [0014]      FIG. 4  is a cross section of the threaded nozzle of  FIG. 3  along section line  4 - 4 . 
           [0015]      FIG. 4A  is an expanded view of detail  4 A in  FIG. 4 . 
           [0016]      FIG. 5  is a top view of a thread cutting tool according one embodiment of the present invention. 
           [0017]      FIG. 6  is an expanded view of the cutting end of the thread cutting tool of  FIG. 5 . 
           [0018]      FIG. 7  is front view of the thread cutting tool of  FIG. 5 . 
           [0019]      FIG. 8  is side view of the thread cutting tool of  FIG. 5 . 
           [0020]      FIG. 9  is a front view of a die for pressing threads according to one embodiment of the present invention. 
           [0021]      FIG. 10  is a cross section of the die of  FIG. 9  along section line  10 - 10 . 
           [0022]      FIG. 11  is an expanded view of the detail B of  FIG. 10 . 
           [0023]      FIG. 12  is a front view of a top punch for use in conjunction with the die of  FIG. 9  according to one embodiment of the present invention. 
           [0024]      FIG. 13  is a side view of the top punch of  FIG. 12 . 
           [0025]      FIG. 14  is an expanded view of detail C shown in  FIG. 12 . 
           [0026]      FIG. 15  is a side view of a bottom punch for use in conjunction with the die of  FIG. 9  according to one embodiment of the present invention. 
           [0027]      FIG. 16  is a cross section of the bottom punch of  FIG. 15  along section line  302 . 
           [0028]      FIG. 17  is a side view of a core rod according to one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    For purposes of the following detailed description, it is to be understood that the invention may assume various alternative variations and step sequences, except where expressly specified to the contrary. Moreover, other than in any operating examples, or where otherwise indicated, all numbers expressing, for example, quantities of ingredients used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. 
         [0030]    Also, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of “1 to 10” is intended to include all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10. 
         [0031]    In this application, the use of the singular includes the plural and plural encompasses singular, unless specifically stated otherwise. In addition, in this application, the use of “or” means “and/or” unless specifically stated otherwise, even though “and/or” may be explicitly used in certain instances. 
         [0032]    Referring now to  FIG. 1 , an example of a fixed cutter bit  10  which may be used in an earth-boring application is shown. In this example, the fixed cutter bit  10  has a mandrel  12  with a threaded end  14 . The threaded end  14  mates with a rotating hollow drill pipe (not shown) which is connected to other rotating equipment of an earth-boring machine. The lower end of the fixed cutter bit may have one or more cutting edges  16 , often equipped with cutting inserts  18 . Cutting inserts  18  may be brazed onto the cutting edge or attached by any suitable means known to those skilled in art. Junk slots  20  which allow cuttings and fluid to flow upward past the rotating cutter bit  10  may separate the cutting edges  16 . One or more ducts  22  exit about the exterior of a lower portion of the fixed cutter bit  10 . The ducts  22  are in fluid communication with the rotating hollow drill pipe (not shown) connected to a threaded portion  14  of the mandrel  12 . Threaded nozzles  30  may be inserted into an outer end  24  of the duct  22 . The outer end  24  of the duct  22  may also have a countersunk portion  26  so that the threaded nozzle  30  is recessed into the duct  22 . 
         [0033]    Referring now to  FIGS. 2-4 , a threaded nozzle according to one embodiment of the present invention is shown. The threaded nozzle  30  comprises a body  32  disposed about a longitudinal axis  40 . The threaded nozzle has an inlet end  34  and a discharge end  36 . External threads  50  are circumferentially located at least about a portion of the exterior face  38  of the body  32  of the threaded nozzle  30 . A hex head  60  may be located at the discharge end  36  of the threaded nozzle  30 . Although a hex head  60  is shown, any configuration of screw or bolt head may be used including a recess in the discharge end  36  for receiving a driver bit. As can be seen in  FIG. 3 , a nozzle bore  70  extends through the body  32  of the threaded nozzle  30 . The nozzle bore  70  may be centered about the longitudinal axis  40  extending axially through the threaded nozzle  30 . 
         [0034]      FIG. 4  shows a cross section of the nozzle of  FIG. 3  along section line  4 - 4 . The nozzle bore  70  may have a flared portion  72  at an inlet end  34  of the threaded nozzle  30 . A detail view of Section A of  FIG. 4  is shown in  FIG. 4A . The external threads  50  have a leading face  54  and a trailing face  52 . A flat or radiused transition between the leading face  54  and trailing face  52  is located at the radially outermost portion of the threads  50 . Between each thread  50  is an undercut  80 . 
         [0035]    According to one embodiment of the present invention, the threaded nozzle may be made from tungsten carbide-cobalt or other material which is pressed, then sintered. For example, carbides including tungsten carbide, titanium carbide and tantalum carbide, aluminum oxide, titanium nitride, cubic boron nitride, and including ceramics, and alloys and cermets of these materials. Suitable binder materials for these materials includes, by way of example, cobalt, copper, iron and nickel. 
         [0036]    According to the present invention, the external threads of the threaded nozzle are formed in the green threaded nozzle blank prior to sintering. As used herein, the term “green” refers to powdered material that has been pressed but not sintered. In one embodiment of the present invention, threads are machined into the threaded nozzle blank which has already undergone a first forming or pressing process to make the general shape of the nozzle. 
         [0037]    The thread cutting tool  100  shown in  FIGS. 5-8  may be used in a turning operation to machine external threads into the nozzle blank. As used herein, the term “nozzle blank” refers to a nozzle made by a pressing and sintering process which has been pressed but not sintered and includes a green nozzle. As seen most clearly in  FIG. 5 , the thread cutting tool  100  has a shank  110  and cutting end  120  for cutting the external threads of a green threaded nozzle. Cutting end  120  comprises a cutting tip  130 . Extending from the cutting tip  130  is a projection  140  to create an appropriately sized undercut  80  between each external thread. The undercut  80  aides in the sintering process in at least one respect by reducing cracks in the finished product. 
         [0038]    As mentioned above, the threads are machined into the nozzle blank in the pre-sintered stated. This can be done utilizing equipment such as a CNC machine or manual lathe, CNC or manual mill, thread die or other turning equipment. The nozzle blank may be held by mandrels, a vacuum apparatus or other gripping assembly to allow machining. The thread cutting tool  100  may be wholly or partially made from a hardened material such as diamond (PCD), boron nitride, tungsten carbide, or ceramic. The thread cutting tool  100  may also be coated with, for example, titanium nitride. Additionally, the thread cutting tool  100  may be a tool like that shown in  FIGS. 5-8  but may also be a cutting wheel. 
         [0039]    It should also be noted that while thread-forming is described above, other shapes suitable for a powder metallurgy process may also be formed. For example, threaded nozzles  30  and insert cutter bits may also accommodate a locking mechanism, for example, a pin. The threaded nozzles  30  may accommodate such locking mechanism by having, for example, a notch in the hex head  60  or a slot running axially through the external threads  50  and remainder of a threaded nozzle. 
         [0040]    In another embodiment of the present invention, threads are pressed into a nozzle using a die. For example, a die  150 , like that shown in  FIG. 9-11  may be used to press threads into a nozzle blank. The die  150  may have a split insert  160  comprising two opposing segments  162 ,  164 . When opposing segments  162 ,  164  are pressed together at interface  166 , the split insert  160  may have a generally cylindrical shape with the exception of planar faces  168 ,  170  on each opposing segment  162 ,  164 . Each opposing segment  162 ,  164  has a thread forming section  172 ,  174  on its respective interior face  176 ,  178 . As best seen in  FIG. 10 , the split insert  160  is inserted into sleeve  190 . Sleeve  190  has an interior face  192  which is congruently shaped to mate with the exterior surface  180  of the split insert  160 . Planar surfaces  168 ,  170  abut the interior face  192  of the sleeve  190  to prevent rotation of the split insert  160 . As seen in  FIG. 10 , the die  150  has a top end  152  and a bottom end  154 . The top end  152  has a top end punch opening  156 . The bottom end  154  has a bottom end punch opening  158 . When fully seated within the sleeve  190 , the split insert  160  abuts a stop  194  at the bottom end  154  and is flush with the sleeve  190  at the top end  152 . 
         [0041]    With the split insert  150  is installed in the sleeve  190 , top punch  200  may be inserted into the top end punch opening  156 . The die  150  is then filled with a predetermined amount of powdered metal or ceramic material. Bottom punch  300 , shown in  FIGS. 15-16 , may then be inserted into the bottom end punch opening  158 . A core rod  400 , an example of which is shown in  FIG. 17 , extends through the bore of the bottom punch  300  and contact the top punch  200 . With the top punch  200 , bottom punch  300  and core rod  400  installed and the die charged with powder, pressure is applied and the pressing process begins. 
         [0042]    Threaded blanks produced by the green machining or green pressing processes described above have significant advantages over other threaded nozzles. Notably, the threaded nozzles of the present invention are less time consuming and less costly to produce than other nozzles due in large part to the net shape of the green threaded nozzle being closer to the ultimate shape of the final product. The threaded nozzles of the present invention are also believed to have several physical improvements over other threaded nozzles. For example, the threaded nozzles of the present invention are believed to have higher edge strength in the external threads than other threaded nozzles due to an increased amount of cobalt on the surface of the threaded nozzle since cobalt migrates to the surface during the sintering process. Using a post-sintering hard grinding process removes the higher cobalt exterior surface resulting in a lower-strength thread. Pre-sintering machining eliminates this problem. External threads produced according to the present invention are tougher than those produced by a post-sintering grinding process. 
         [0043]    The external threads produced by the pre-sintering machining or pressing processes of the present invention also have an increased surface roughness (Ra) which in improves friction between the mating surface of the nozzle and the bit. As used herein, surface roughness, refers to the measure of finer surface irregularities in an article. As used herein, Ra, refers to the arithmetic average of the surface irregularities, namely surface peak and valleys, expressing in microinches. The Ra value for threads of the present invention is, for example, at least 40 microinches, for example greater than 50 microinches, for example, about 55 microinches to about 65 microinches. The increased friction decreases the probability that the bit will loosen during drilling. The pre-sintered threads also have less residual stresses than a hard-ground thread making the nozzles of the present invention tougher, less susceptible to cracking and more damage tolerant. 
         [0044]    Testing between a standard ground thread and the shaped thread of the present invention has shown improved holding of the nozzle in the cutter bit. A shaped nozzle according to the present invention was compared to a nozzle with machined threads. The shaped nozzle had a mean surface roughness of 57 microinches. The machined nozzle had a mean surface roughness of 34 microinches. Each nozzle was torque tested after being tightened to 80 psi. The shaped nozzle required and average of 72 psi to release while the machined nozzle released at 66 psi. 
         [0045]    Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.