Abstract:
A molten metal pump shaft coupling system for use in the coupling or connection of elongated shafts to other components and equipment, and for the disconnection thereof. A coupling with internal discontinuous threads may be coupled with an externally threaded shaft, with either continuous or discontinuous threads. Aspects of the invention include multiple external threads which may be pitched to accomplish a quicker and more efficient disconnect system. Furthermore, a shaft removal system is provided which provides two points of contact to assist in rotating a broken shaft end out of a coupling.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
         [0001]    There are no related applications.  
         TECHNICAL FIELD  
         [0002]    This invention pertains to a molten metal pump shaft coupling system for use in the coupling or operational attachment and detachment of elongated shafts to drive systems other components and equipment.  
         BACKGROUND OF THE INVENTION  
         [0003]    This invention relates to molten metal processing systems and more particularly to a coupling system for use in molten metal processing systems. There are several different types of molten metal processing systems, such as pumps, degassing unites, and flux injection devices, all of which are well known in the art.  
           [0004]    In many of these systems, a shaft is used to transmit rotation from a motor or other drive system or device to an impeller, rotor or other system component. In the molten metal pump application, this coupling device provides an operational attachment of the top part of the shaft to the drive system or motor. In prior art designs, a straight threaded design is utilized such that one external thread is machined into the external surface of the top portion of the graphite shaft and a corresponding internal thread is provided in a coupling mechanism, which is then attached or operationally attached to the motor drive system. The shaft is then rotated into the coupling by typically turning it at least one revolution, until it is securely fastened to the coupling. Long continuous corresponding threads are more cumbersome to rotate together and tend to have a relatively high failure rate.  
           [0005]    In other prior art systems, a vertical channel, an elbow and an approximately horizontal channel are cut into the shaft, and corresponding protrusions or bumps within the inner or internal cavity of the coupling system slide up into the vertical channel and then over in the horizontal channel. However these systems are not believed as reliable as a system which includes a partial thread for greater engagement area between the shaft and the coupling, such as provided by this invention.  
           [0006]    Molten metal may be one of the more difficult environments in which to maintain a pump or a coupling system, due to the heat and corrosive factors within the molten metal. The submerged components of these pumps and coupling systems are typically made of graphite, ceramics or similar materials due to the ability of these types of material compositions to withstand the heat and corrosive effects of the molten metal environment. If there is a failure of the shaft such as the shaft breaking, it is necessary to remove the stub within the coupling with a chisel and hammer, which causes additional potential problems with the coupling.  
           [0007]    It is an object of aspects of this invention to provide an improved coupling system for use in coupling or attaching a molten metal shaft to another component.  
           [0008]    It is also an object of embodiments of this invention to provide a way to remove the stub once an end of the shaft has broken off within the coupling.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    Preferred embodiments of the invention are described below with reference to the following accompanying drawings.  
         [0010]    [0010]FIG. 1 is an elevation view of one embodiment of a coupling member which may be utilized in a coupling system contemplated by this invention;  
         [0011]    [0011]FIG. 2 is section  2 - 2  from FIG. 1;  
         [0012]    [0012]FIG. 3 is section  3 - 3  from FIG. 1;  
         [0013]    [0013]FIG. 4 is a top view of one embodiment of a discontinuous thread which may be utilized within the coupling member illustrated in FIGS. 1 through 3;  
         [0014]    [0014]FIG. 5 is an elevation view of the discontinuous thread illustrated in FIG. 4;  
         [0015]    [0015]FIG. 6 is an end view of the discontinuous thread illustrated in FIG. 5;  
         [0016]    [0016]FIG. 7 is an elevation view of an embodiment of a coupling member operationally attached to a drive system, the coupling member including a discontinuous thread configured therein, which may be utilized in this invention;  
         [0017]    [0017]FIG. 8 is a bottom view of the coupling member illustrated in FIG. 7;  
         [0018]    [0018]FIG. 9 is an elevation view of one embodiment of a shaft member which may be utilized in combination with a coupling member as contemplated by this invention;  
         [0019]    [0019]FIG. 10 is a top view of the shaft member illustrated in FIG. 9;  
         [0020]    [0020]FIG. 11 is section view  11 - 11  from FIG. 9; and  
         [0021]    [0021]FIG. 12 is an elevation view of another embodiment of a shaft member which may be utilized in a coupling system contemplated by this invention, only with a greater number of parallel threads than illustrated in prior Figures.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    Many of the fastening, connection, manufacturing and other means and components utilized in this invention are widely known and used in the field of the invention described, and their exact nature or type is not necessary for an understanding and use of the invention by a person skilled in the art or science; therefore, they will not be discussed in significant detail. Furthermore, the various components shown or described herein for any specific application of this invention can be varied or altered as anticipated by this invention and the practice of a specific application or embodiment of any element may already be widely known or used in the art or by persons skilled in the art or science; therefore, each will not be discussed in significant detail.  
         [0023]    The terms “a”, “an”, and “the” as used in the claims herein are used in conformance with long-standing claim drafting practice and not in a limiting way. Unless specifically set forth herein, the terms “a”, “an”, and “the” are not limited to one of such elements, but instead mean “at least one”.  
         [0024]    [0024]FIG. 1 is a front elevation view of a coupling  100  which may be utilized in an embodiment of this invention, the coupling  100  including top portion  101 , bottom portion  102 , inner cavity  104 , configured with internal threads  105  for receiving an externally threaded shaft rotationally.  
         [0025]    [0025]FIG. 1 further shows discontinuous thread bolts  106 ,  107  and  112  which are utilized to attach discontinuous threads (shown in FIG. 7) in the proper location to act as discontinuous threads to engage with external threads on a shaft member.  
         [0026]    [0026]FIG. 1 further shows apertures  103  and  112 , pin aperture  110  and transverse aperture  111 , at or toward the top portion  101  of coupling  100 . The top portion  101  of the coupling  100  is generally configured to engage, operatively attach to, or interconnect with a drive system for rotating the coupling and a shaft to which the coupling is attached.  
         [0027]    The bottom portion  102  of the coupling  100 , including inner cavity  104 , is configured to operatively attach to an externally threaded shaft in a threaded manner, preferably by relative rotation. FIG. 1 also shows bolt apertures  134  in the coupling body, the bolt apertures being configure to receive bolts which secure discontinuous threads (shown in later Figures) on the inner wall with the inner cavity  104 . FIG. 1 shows as hidden line possible thread passageway  105 , which may be merely representative of a path that external threads on a shaft may follow, or the pathway may be machined into the inner wall of the inner cavity  104  of the coupling  100 .  
         [0028]    It will be noted by those of ordinary skill in the art that the terms top and bottom as used herein are for identification or orientation in the Figures, and the invention is not limited to such, but instead the components and systems disclosed herein may be used in any one of a number of configurations.  
         [0029]    [0029]FIG. 2 is section  2 - 2  from FIG. 1, and shows coupling  100 , top portion  101 , bottom portion  102 , inner cavity  104 , bolt apertures  134 , internal thread pathway  105 , internal aperture  112 , aperture  103 , and transverse aperture  111 . Again, the thread passageway  105  shown may be representative only or it may actually be imparted into the inner wall of the inner cavity  104  of the coupling  100 , as described above.  
         [0030]    [0030]FIG. 3 is section  3 - 3  from FIG. 1, illustrating the coupling  100 , bolt apertures  134 , with the inner cavity  104  being appropriately sized and configured to receive a corresponding end of the shaft, and inner wall  128  within inner cavity  104 .  
         [0031]    [0031]FIG. 4 is a top view of one embodiment of a discontinuous thread  130  which may be utilized in the embodiment of the invention shown in FIG. 1, illustrating thread body  132  with inner surface  133 , bolt apertures  134  and side  131 . The bolt apertures  134  may (but need not be) be internally threaded to attach and secure to bolts to secure discontinuous thread  130  within inner cavity  104  in such a way to provide a discontinuous thread to engage external threads on a shaft. Other fastening ways may also be employed, with no one in particular being required to practice the invention. Outer surface  129  of discontinuous thread  130  preferably approximately corresponds to the inner surface or inner wall (shown as item  128  in FIG. 3) of the inner cavity of the coupling, and the inner surface  133  preferably approximately corresponds to the outer surface of the shaft to be rotated therein.  
         [0032]    [0032]FIG. 5 is a front elevation view of the embodiment of the discontinuous thread  130  shown in FIG. 4, illustrating inner surface  133 , and a pitch or angle and bolt apertures  134 . The pitch or angle would correspond to the thread passageway. Bolts  106 ,  107  or  112  (shown in FIG. 7) may be inserted through bolt apertures  134  to connect to discontinuous threads  130 . The discontinuous threads  130  form an approximate discontinuous threaded pathway configuration to allow the coupling to rotatably engage an externally threaded shaft.  
         [0033]    [0033]FIG. 6 is a side elevation view of the embodiment of the discontinuous thread  130  shown in FIGS. 4 and 5 and illustrates inner surface  133 , bottom surface  136 , outer surface  129  which preferably approximately matches up against the internal surface in the inner cavity of the coupling, and bolt aperture  134 .  
         [0034]    [0034]FIG. 7 is a front elevation view of an embodiment of a coupling  130  contemplated by this invention, wherein the discontinuous threads  140 ,  141  and  142  are shown bolted into inner cavity  104 . Bolts  106 ,  107  and  112  are inserted through bolt apertures in the coupling wall, and the discontinuous threads  140 ,  141  and  142  are placed in the thread pattern  105  to form a discontinuous thread pattern to receive an externally threaded shaft therein, effectively coupling the shaft to the device coupled to the top portion  101  of the coupling.  
         [0035]    Further illustrated in FIG. 7 are transverse apertures  110  and  111  and top portion  101 , vertical apertures  112  and  103  from top portion to inner cavity  104  and bottom portion  102  of coupling  130 . FIG. 7  also depicts drive system  182 , which may be a motor or other drive device with hardware to allow coupling  130  to be operatively attached thereto. No particular type or design of drive system  182  is required to practice this invention as drive systems are well known and any one of a number of drive systems  182  may be utilized in aspects of this invention.  
         [0036]    [0036]FIG. 8 is a bottom view of the embodiment of the coupling illustrated in FIG. 7, showing coupling  130 , inner cavity  104 , discontinuous threads  140 ,  141  and  142  with bolt apertures  106 ,  107  and  112 .  
         [0037]    [0037]FIG. 9 is a front elevation view of an end of an elongated shaft to be coupled with a coupling, such as that shown in prior Figures. FIG. 9 illustrates shaft  170 , shaft body  171 , shaft threaded portion  172  with threads  174  and grooves  173 . The threads  174  are configured to slidingly engage with discontinuous threads within the coupling such as those shown in prior Figures. It will be appreciated by those of ordinary skill in the art that rotating shaft  170  into a coupling such as that shown in prior Figures, will easily and quickly connect the shaft  170  to the coupling.  
         [0038]    [0038]FIG. 10 is a top view of the shaft  170  illustrated in FIG. 9, showing shaft top surface  177 , grooves  173  and threads  174 .  
         [0039]    [0039]FIG. 11 is section  11 - 11  from FIG. 9 and illustrates shaft  170 , shaft body  171 , first shaft aperture  180 , second shaft aperture  179 , threads  174  and grooves  173 . A third shaft aperture  164  is provided off center from aperture  180 . First shaft aperture  180  may be utilized as a passageway for the introduction of chemicals and the like in degassing units, or for any other desired purpose. FIG. 11 further shows molten metal processing component  181 , which those of ordinary skill in the art may be any one of a number of components, such as a rotor, an impeller, or any other, with no one in particular being required to practice aspects of the invention.  
         [0040]    [0040]FIG. 11 illustrates an additional embodiment of this invention which configures shaft  170  with two internal apertures which may be utilized to more easily remove the shaft end in the event the shaft  170  breaks within the coupling. Shaft removal tool  168  is shown above the shaft end for illustrative purposes to show how peg  166  matches with first shaft aperture  179  and peg  167  corresponds to third shaft aperture  164 . If the shaft breaks and the threaded portion is stuck within the coupling, shaft removal tool  168  may be positioned with the first peg  166  and the second peg  167  directed toward into first shaft aperture  179  and third shaft aperture  164 , such that the first and second pegs of the shaft removal tool may be inserted into the shaft apertures (and then rotated) to allow the end of the shaft to be more easily rotated out of the coupling. Arrow  164  illustrates that the rotation of shaft removal tool  168  is accomplished to rotate the shaft out of the coupling, and arrows  165  illustrate the potential movement of shaft removal tool  168  toward the corresponding apertures for engagement.  
         [0041]    [0041]FIG. 12 shows an alternative embodiment of a threaded portion  201  of a shaft  200  which may be used in embodiments of this invention, illustrating shaft  200 , threaded portion  201 , top  202 , threads  204  and grooves  203 . The shaft body  205  terminates at a first end in a threaded portion  201  and the threads overlap such that there is only threaded or rotational movement between the coupling and shaft  200 . With multiple parallel threads and an appropriate angle, the shaft can be easily and quickly rotated into a coupling in one-half turns or less, or even less than ¼ or ⅓ of a rotation of shaft  200 . The discontinuous threads in the coupling may then be provided at an appropriate angle approximately corresponding to the angle of the parallel threads  204  or to the grooves  203 . There may be a plurality of threads  204  around the external surface of the shaft, with the particular number being dependant on the application and the design choices made for the application. A top lip may be provided in the grooves  203  to allow better seating or securing of the discontinuous threads in the inner cavity of the coupling, depending on the application.  
         [0042]    This embodiment may be preferable for a quick disconnect and reconnect system, while still providing substantial surface area of interaction between threads  203  and discontinuous threads which may be provided in the inner cavity of a coupling corresponding to the shaft  200 .  
         [0043]    As will be appreciated by those of reasonable skill in the art, there are numerous embodiments to this invention, and variations of elements and components which may be used, all within the scope of this invention.  
         [0044]    One embodiment of this invention, for example, is a coupling system for use in molten metal processing in attaching a shaft to a drive system, the coupling system comprising: a coupling with a first end configured for operational attachment to a drive system, and a second end with an open inner cavity configured to receive an elongated shaft, the inner cavity including a plurality of discontinuous threads patterned to rotationally engage external threads on the elongated shaft; a shaft with an elongated body having a first end and a second end, the first end being configured to be coupled to a drive and the second configured for coupling to a molten metal processing component; wherein the first end includes a plurality of parallel threads configured for engagement with a plurality of corresponding discontinuous threads, and further wherein the plurality of parallel threads each extend less than one revolution around the shaft.  
         [0045]    Further embodiments of the coupling system described may be: wherein the plurality of parallel threads on the shaft each extend less than one-half of a revolution around the shaft; wherein the plurality of parallel threads each extend less than one-third of a revolution around the shaft; wherein the shaft further includes: a first shaft aperture extending longitudinally through at least a portion of the shaft; a second shaft aperture extending longitudinally through at least a portion of the shaft and offset a transverse distance from the first shaft aperture; and/or wherein the first shaft aperture and the second shaft aperture are each configured to receive part of a shaft removal tool.  
         [0046]    In another embodiment, a method may be provided for coupling a shaft utilized in a molten metal processing system to a drive system, comprising the following: machining at least one external thread into a first end of the shaft; providing a coupling with an inner cavity, the inner cavity including a plurality of discontinuous thread sections configured to threadingly engage the at least one external thread in the first end of the shaft; aligning the coupling with an entrance of the at least one external thread; and rotating the at least one external thread into the coupling until securely attached.  
         [0047]    Further method embodiments of the foregoing may be: wherein the at least one external thread machined into the first end of the shaft consists of a plurality of parallel threads about the shaft; wherein the shaft is rotated less than one revolution before it effectively attaches the shaft to the coupling; and/or wherein the shaft is rotated less than one-third of a revolution before it effectively attaches the shaft to the coupling.  
         [0048]    In another embodiment of the invention, a molten metal processing system may be provided which comprises: a drive system; a coupling extending downward from the drive system; an elongated shaft having a first end and a second end, the coupling operatively attaching the first end of the shaft to the drive system; a first shaft aperture extending longitudinally through at least a portion of the shaft; a second shaft aperture extending longitudinally through at least a portion of the shaft and offset a transverse distance from the first shaft aperture; and wherein the first shaft aperture and the second shaft aperture are each configured to receive part of a shaft removal tool. Further embodiments of this may be wherein the first shaft aperture and the second shaft aperture extend through the same portion of the shaft and/or wherein the molten metal processing system is a degassing device and one of the first shaft aperture and the second shaft aperture provide an injection aperture during operation.  
         [0049]    In another embodiment, a coupling may be provided for use in molten metal processing, the coupling comprising: a first end configured for operational attachment to a drive system; a second end with an open inner cavity configured to receive an elongated shaft, the inner cavity including a plurality of discontinuous threads patterned to rotationally engage external threads on the elongated shaft.  
         [0050]    In another embodiment of the invention, a shaft may be provided for use in molten metal processing, the shaft comprising: an elongated body having a first end and a second end, the first end being configured to be coupled to a drive and the second configured for coupling to a molten metal processing component; wherein the first end includes a plurality of parallel threads configured for engagement with a plurality of corresponding discontinuous threads, and further wherein the plurality of parallel threads each extend less than one revolution around the shaft. Further embodiments of the shaft may be wherein the plurality of parallel threads each extend less than one-half of a revolution around the shaft; or wherein the plurality of parallel threads each extend less than one-third of a revolution around the shaft.  
         [0051]    In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.