Improved dart and clutch assembly

Abstract

Described herein are embodiments of systems and apparatuses that include a dart and/or a clutch for a dart plunger. In an exemplary embodiment, the clutch consists of a one-piece unit having a length, an outside diameter, and an inside diameter where at least a portion of the inside diameter is sized to create a frictional interface with a dart. The clutch may also include a gap, a slot, and/or a spiral cut. The dart may include a shaft having opposite ends and a shaft diameter that varies between the opposite ends.

1 . A dart plunger, comprising:
 a dart having a first position in the dart plunger and a second position in the dart plunger, wherein the dart is configured in the dart plunger to repeatedly transition between the first and the second position;   the dart including a shaft having a first terminal end, a second terminal end, a midpoint equidistant between the first terminal end and the second terminal end,   wherein the dart further includes a region of increased diameter at the midpoint.   
     
     
         2 . The dart plunger of  claim 1  wherein the dart further includes a first region of decreased diameter between the first terminal end and the midpoint, and a second region of decreased diameter between the second terminal end and the midpoint. 
     
     
         3 . The dart plunger of  claim 2  further comprising a clutch for retarding transition of the dart between the first and the second position via a frictional interface with the dart's shaft, wherein the frictional interface imparts more friction in the region of increased diameter than either of the first region of decreased diameter or the second region of decreased diameter. 
     
     
         4 . The dart plunger of  claim 3  wherein the clutch is a one-piece unit having a length, an outside diameter, and an inside diameter, where the inside diameter is sized to create the frictional interface with the shaft. 
     
     
         5 . The dart plunger of  claim 4  wherein the shaft's region of increased diameter has a length longer than the length of the clutch. 
     
     
         6 . The dart plunger of  claim 5  wherein the clutch includes a spiral cut in at least a portion of the outside diameter of the clutch. 
     
     
         7 . The dart plunger of  claim 6  wherein the spiral cut in at least the portion of the outside diameter of the clutch begins on a top surface of the clutch and ends on a bottom surface of the clutch. 
     
     
         8 . The dart plunger of  claim 7  wherein the inside diameter of the clutch further includes an undulating surface so that the entire inside diameter of the clutch does not create the frictional interface with the dart. 
     
     
         9 . The dart plunger of  claim 8  wherein the undulating surface extends parallel to a central axis of the clutch. 
     
     
         10 . The dart plunger of  claim 9  wherein the first region of decreased diameter has a first length, the second region of decreased diameter has a second length, and the first length and the second length are substantially equal. 
     
     
         11 . The dart plunger of  claim 10  wherein the region of increased diameter has a third length, whereby the third length is substantially equal to the first length and the second length. 
     
     
         12 . The dart plunger of  claim 11  wherein the length, the outside diameter, and the inside diameter of the clutch change during dart transitions between the first and second position. 
     
     
         13 . The dart plunger of  claim 12  wherein the first region of decreased diameter has a constant diameter between the region of increased diameter and the first terminal end. 
     
     
         14 . The dart plunger of  claim 13  wherein the second region of decreased diameter has a constant diameter between the region of increased diameter and the second terminal end. 
     
     
         15 . The dart plunger of  claim 3  wherein the clutch is a one-piece unit having a length, a first inside diameter sized to create a frictional interface with the dart, and at least one slot so that the entire inside diameter of the clutch does not impart a frictional force on the dart. 
     
     
         16 . The dart plunger of  claim 15  wherein the clutch includes a second inside diameter sized to not create a frictional interface with the dart. 
     
     
         17 . The dart plunger of  claim 16  wherein the clutch includes a plurality of slots spaced equidistant around the first inside diameter. 
     
     
         18 . The dart plunger of  claim 17  wherein the dart's region of increased diameter has a length longer than the length of the clutch. 
     
     
         19 . The dart plunger of  claim 18  wherein each slot extends parallel to a central axis of the clutch. 
     
     
         20 . The dart plunger of  claim 19  wherein the first region of decreased diameter has a first length, the second region of decreased diameter has a second length, and the first length and the second length are substantially equal. 
     
     
         21 . The dart plunger of  claim 20  wherein the region of increased diameter has a third length, whereby the third length is substantially equal to the first length and the second length. 
     
     
         22 . The dart plunger of  claim 21  wherein the first region of decreased diameter has a constant diameter between the region of increased diameter and the first terminal end. 
     
     
         23 . The dart plunger of  claim 22  wherein the second region of decreased diameter has a constant diameter between the region of increased diameter and the second terminal end. 
     
     
         24 . The dart plunger of  claim 3  wherein the clutch is a one-piece unit having a length, an inside diameter, an outside diameter, and a gap extending from the outside diameter to the inside diameter along the entire length. 
     
     
         25 . The dart plunger of  claim 24  wherein the inside diameter of the clutch includes an undulating surface so that the entire inside diameter of the clutch does not create the frictional interface with the dart. 
     
     
         26 . The dart plunger of  claim 25  wherein the undulating surface extends parallel to a central axis of the clutch. 
     
     
         27 . The dart plunger of  claim 26  wherein a center point of the outside diameter of the clutch is not the same as a center point of the inside diameter of the clutch, such that a sidewall of the clutch opposite the gap is thicker than a sidewall of the clutch near the gap. 
     
     
         28 . The dart plunger of  claim 27  wherein the dart's region of increased diameter has a length longer than the length of the clutch. 
     
     
         29 . The dart plunger of  claim 28  wherein the first region of decreased diameter has a first length, the second region of decreased diameter has a second length, and the first length and the second length are substantially equal. 
     
     
         30 . The dart plunger of  claim 29  wherein the region of increased diameter has a third length, whereby the third length is substantially equal to the first length and the second length. 
     
     
         31 . The dart plunger of  claim 30  wherein the outside diameter and the inside diameter of the clutch change during dart transitions between the first and second position. 
     
     
         32 . The dart plunger of  claim 31  wherein the first region of decreased diameter has a constant diameter between the region of increased diameter and the first terminal end. 
     
     
         33 . The dart plunger of  claim 32  wherein the second region of decreased diameter has a constant diameter between the region of increased diameter and the second terminal end. 
     
     
         34 . A dart plunger, comprising:
 a dart having an open position as the dart plunger descends in a well and a closed position as the dart plunger ascends in a well, wherein the dart is configured to transition between the open position and the closed position when the plunger reaches a bottom of the well, and between the closed position and the open position when the plunger reaches the top of the well;   the dart including a region of increased diameter having a first end and a second end, a first region of decreased diameter contiguous with the first end of the region of increased diameter, and a second region of decreased diameter contiguous with the second end of the region of increased diameter;   a clutch for retarding transition of the dart via a frictional interface only with the dart's region of increased diameter, the first region of decreased diameter, and the second region of decreased diameter.   
     
     
         35 . A dart plunger, comprising:
 a dart having an open position as the dart plunger descends in a well and a closed position as the dart plunger ascends in a well, wherein the dart is configured to transition between the open position and the closed position when the plunger reaches a bottom of the well, and between the closed position and the open position when the plunger reaches the top of the well;   the dart including a region of increased diameter having a first end and a second end, a first region of decreased diameter contiguous with the first end of the region of increased diameter, and a second region of decreased diameter contiguous with the second end of the region of increased diameter;   a clutch for retarding transition of the dart via a frictional interface only with the dart's region of increased diameter.   
     
     
         36 . A dart plunger, comprising:
 a dart having a first position in the dart plunger and a second position in the dart plunger, wherein the dart is configured in the dart plunger to repeatedly transition between the first and the second position;   the dart including a shaft having a first terminal end and a second terminal end;   a clutch for retarding transition of the dart between the first and the second position via a frictional interface with the dart's shaft,   wherein the clutch is a one-piece unit having a length, an outside diameter, and an inside diameter, where the inside diameter is sized to create the frictional interface with the shaft, and   wherein the clutch includes a spiral cut in at least a portion of the outside diameter of the clutch.   
     
     
         37 . The dart plunger of  claim 36  wherein the spiral cut in at least the portion of the outside diameter of the clutch begins on a top surface of the clutch and ends on a bottom surface of the clutch. 
     
     
         38 . The dart plunger of  claim 37  wherein the inside diameter of the clutch further includes an undulating surface so that the entire inside diameter of the clutch does not create the frictional interface with the dart. 
     
     
         39 . The dart plunger of  claim 38  wherein the undulating surface extends parallel to a central axis of the clutch. 
     
     
         40 . A dart plunger, comprising:
 a dart having a first position in the dart plunger and a second position in the dart plunger, wherein the dart is configured in the dart plunger to repeatedly transition between the first and the second position;   the dart including a shaft having a first terminal end and a second terminal end; and   a clutch for retarding transition of the dart between the first and the second position via a frictional interface with the dart's shaft,   wherein the clutch is a one-piece unit having a length, a first inside diameter sized to create a frictional interface with the dart, and at least one slot so that the entire inside diameter of the clutch does not impart a frictional force on the dart.   
     
     
         41 . The dart plunger of  claim 40  wherein the clutch includes a second inside diameter sized to not create a frictional interface with the dart. 
     
     
         42 . The dart plunger of  claim 41  wherein the clutch includes a plurality of slots spaced equidistant around the first inside diameter. 
     
     
         43 . The dart plunger of  claim 42  wherein each slot extends parallel to a central axis of the clutch. 
     
     
         44 . A dart plunger, comprising:
 a dart having a first position in the dart plunger and a second position in the dart plunger, wherein the dart is configured in the dart plunger to repeatedly transition between the first and the second position;   the dart including a shaft having a first terminal end and a second terminal end; and   a clutch for retarding transition of the dart between the first and the second position via a frictional interface with the dart's shaft,   wherein the clutch is a one-piece unit having a length, an inside diameter, an outside diameter, and a gap extending from the outside diameter to the inside diameter along the entire length.   
     
     
         45 . The dart plunger of  claim 44  wherein the inside diameter of the clutch includes an undulating surface so that the entire inside diameter of the clutch does not create the frictional interface with the dart. 
     
     
         46 . The dart plunger of  claim 45  wherein the undulating surface extends parallel to a central axis of the clutch. 
     
     
         47 . The dart plunger of  claim 46  wherein a center point of the outside diameter of the clutch is not the same as a center point of the inside diameter of the clutch, such that a sidewall of the clutch opposite the gap is thicker than a sidewall of the clutch near the gap.