Box end sucker rod shear coupling

Abstract

Box-end rotary sucker rod shear couplings including a substantially cylindrical housing having an interior surface defining a passage from an upper end to a lower end along a longitudinal axis and an exterior surface. The shear coupling also includes a set of threads around an inner circumference of the upper end for receiving a rotary sucker rod coupled directly into the upper end of the passage without an intervening adaptor; a set of threads around an inner circumference of the lower end for receiving a pump pin coupled directly into the lower end of the passage without an intervening adaptor; and one or more circumferential grooves machined into the cylindrical housing between the threads for causing rod shear failure at a predetermined axial load. In some embodiments, the shear couplings are conventional box-end sucker rod couplings. Also disclosed are rotary sucker rod assemblies including such rod shear couplings.

1 . A box-end rotary sucker rod shear coupling comprising:
 a substantially cylindrical housing having
 an upper end; 
 a lower end; 
 an interior surface defining a passage from the upper end to the lower end along a longitudinal axis of the substantially cylindrical housing; 
 an exterior surface; 
 a first set of threads around an inner circumference of the upper end adapted to directly receive a rotary sucker rod without an intervening adaptor, the rotary sucker rod having complementary threads on an outer circumference for engaging the rod shear coupling; 
 a second set of threads around an inner circumference of the lower end adapted to directly receive a pump pin without an intervening adaptor, the pump pin having complementary threads on an outer circumference for engaging the rod shear coupling; and 
 one or more circumferential grooves machined into the cylindrical housing between the threads so as to cause rod shear failure at a predetermined load. 
   
   
   
       2 . The rod shear coupling of  claim 1  wherein the one or more circumferential grooves in the cylindrical housing between the threads comprise at least one circumferential groove in the interior surface. 
   
   
       3 . The rod shear coupling of  claim 1  wherein the one or more circumferential grooves in the cylindrical housing between the threads comprise at least one circumferential groove in the exterior surface. 
   
   
       4 . The rod shear coupling of  claim 1  wherein the one or more circumferential grooves comprise at least one circumferential groove in the exterior surface and at least one circumferential groove in the interior surface. 
   
   
       5 . The rod shear coupling of  claim 4  wherein at least one circumferential groove in the interior surface is aligned with at least one circumferential groove in the interior surface. 
   
   
       6 . The box-end rotary sucker rod shear coupling of  claims 1 - 5  wherein the cylindrical housing comprises a conventional box-end sucker rod coupling. 
   
   
       7 . A rotary sucker rod assembly comprising a box-end rotary sucker rod shear coupling according to any of  claims 1 - 5 . 
   
   
       8 . A method for manufacturing a box-end sucker rod shear coupling, the method comprising:
 providing a conventional box-end sucker rod coupling having an elongated body having
 an upper end; 
 a lower end; 
 an interior surface defining a passage from the upper end to the lower end along a longitudinal axis of the body; 
 an exterior surface; 
 a first set of threads at the upper end adapted to directly receive a sucker rod; and 
 a second set of threads at the lower end adapted to directly receive a pump pin; and 
   machining one or more circumferential grooves in the box-end sucker rod coupling between the first set of threads and the second set of threads.   
   
   
       9 . The method of  claim 8  wherein the one or more circumferential grooves are machined in the interior surface of the box-end sucker rod coupling. 
   
   
       10 . The method of  claim 9  wherein the one or more circumferential grooves are machined in the exterior surface of the box-end sucker rod coupling. 
   
   
       11 . The method of  claim 8  wherein the one or more circumferential grooves are machined in the exterior surface of the box-end sucker rod coupling.