GB2153879A - Rotary power slips with pneumatic slip lock - Google Patents

Abstract

Rotary power slips mounted in the rotary table of an earth drilling rig and having slips operated by pneumatic cylinders 21 supplied by conduits 39, 41, one conduit being provided with a pilot-operated check valve 85 for maintaining fluid pressure in one end of the cylinders to keep the slips in their upper retracted position even if the applied pressure is lost. Valve 85 opens when pressure is applied to the other end of the cylinder. <IMAGE>

Description

SPECIFICATION Rotary power slips with pneumatic slip lock This invention relates in general to earth drilling equipment and in particular to rotary power slips mounted concentrically with the pipe opening in a rotary drilling table.

U.S. Patent No. 4 333 209 entitled "Rotary Power Slips", issued on June 8, 1 982, discloses rotary power slips having a housing mounted in a rotary table of an earth drilling rig. Air, from a stationary fluid source on the drilling rig, is transferred to pneumatic cylinders in the housing to operate the slips. A perforated annular bladder is expanded to form an expansive fluid duct between a stationary seal ring, connected to the stationary fluid source, and an air transfer plate, which rotates with the housing.

After the slips have been raised by the cylinders, the fluid pressure is cut off, releasing fluid pressure to the cylinders from the stationary source, and the seal ring disengages. In prior art devices, such as Herst, mechanical means are used to lock the slips in the raised position. Such mechanical means are subject to jolts and vibrations common to drilling floors. An improved apparatus was needed to lock the slips in the raised position.

Rotary power slips have been improved by replacing the annular perforated bladder with a pair of annular expansive rings, having inner and outer edges mounted in grooves on the upper surface of the stationary air transfer ring. The edges of the expansive rings are held in the grooves by retaining rings. The grooves in the air transfer ring are preferably undercut to form counterbores, around which the edges of the expansive rings are mounted.

The expansive rings of the invention can withstand more abrasion than the rotary power slips in the prior art. The expansive rings of the invention also leak less and are able to take more pressure than the prior art designs.

Additionally, the expansive rings, held in place by retaining rings. are easier to service and to replace under field conditions.

The improved rotary power slips of the invention have a pilot operated check valve for holding the air pressure in one end of the pneumatic cylinders to lock the slips in the released position. The check valve is piloted off of the fluid conduit to the other end of the cylinders, so that whenever pneumatic pressure is applied to the other end of the cylinders, the check valve will open and allow the slips to be lowered to the gripping position.

The pilot operated check valve will thus hold the slips in the upper retracted position when pneumatic pressure from the stationary air source is removed. The slips are not allowed to return to the gripping position, until pneumatic pressure is applied to the proper end of the pneumatic cylinders.

The above, as well as additional objects, features, and advantages of the invention, will become apparent in the following detailed description.

Fig. 1 is a perspective view, partially in section, of the improved rotary power slips of the invention, with the slips in the lower, gripping position.

Fig. 2 is a perspective view, partially in section, of the improved rotary power slips of the invention, with the slips in the upper, retracted position.

Fig. 3 is a close-up sectional view of the seal ring, the air transfer ring, and the annular expansive rings.

Fig. 4 is a top view of the expansive rings.

Fig. 5 is a sectional view of the air transfer ring and expansive rings as seen along lines 5-5 in Fig. 4.

Fig. 6 is a schematic drawing of the pneumatic system for raising and lowering the slips.

The improved rotary power slips 11, shown in Figs. 1 and 2, have a body 1 3 which is mounted concentrically with the pipe opening in a rotary table of an earth drilling rig. The body 1 3 is supported by, and rotates with, the rotary table. The body 1 3 supports three slips 1 5 which are linked together with a slip ring 1 7. Each slip 1 5 has a multitude of replaceable toothed inserts 19, and the slips 1 5 together form slip means for gripping a pipe within the rotary table when the slips 1 5 are in their lower, gripping position shown in Fig. 1.When the slips 1 5 are raised to their upper. retracted position shown in Fig.2, the slips 1 5 release the pipe and the pipe may travel freely through the rotary table.

The slips 1 5 are raised and lowered by means of pneumatic pistons and cylinders 21, which are connected to the slip ring 1 7. The slips 1 5 are connected to the slip ring 1 7 by means of rollers 23 which are inserted through elongated slots 25 in the slip ring 1 7. The rollers 23 move back and forth in the slots 25 as the slips 1 5 move up and down between the gripping position shown in Fig. 1 and the retracted position shown in Fig. 2.

The slips 1 5 have frusto-conical surfaces 27,29 which contact the inner surface of the body 1 3 to move the slips 1 5 inward and outward between the two slip positions.

The slips 1 5 and cylinders 21 rotate with the body 1 3 of the power slips 11. When the body 1 3 stops rotating, the cylinders 21 may be located in any position around the hole. Air pressure must be delivered to the pneumatic cylinders 21, from a stationary air tank 31 (Fig. 6), regardless of the positions of the cylinders 21 when the rotation of the power slips 11 has ceased. The transfer of air pressure from the stationary components of the power slips 11 to the rotary components is accomplished by means of a seal ring 33, shown in detail in Fig. 3. The seal ring 33 is attached to the bottom of the body 1 3 by means of bolts 35 and rotates therewith. A pair of annular air passageways 37,38 are located on the upper side of the seal ring 33.

One of these air passageways 37 is in fluid contact with return conduits 39 which lead to the upper ends of the pneumatic cylinders 21.

The other air passageway 38 is in fluid contact with power conduits 41 which lead to the lower ends of the pneumatic cylinders 21.

The transverse lower surface 43 of the seal ring 33 also has a pair of annular, triangular grooves 45, 46. The outer air passageway 37 and the outer triangular groove 45 are connected by a single port 47 as shown in Fig. 3.

The inner air passageway 38 and the inner groove 46 are likewise connected by a port (not shown) which is located on the opposite side of the seal ring 33.

An annular bearing support ring 49 is also attached to the body 1 3 by the bolts 35. The bearing support ring 49 supports six rollers 51, which are attached to an annular air transfer ring 53 as shown in Fig. 5. The air transfer ring 53 remains stationary as the bearing support ring 49 and the body 1 3 of the rotary power slips 11 rotate. There are three concentric grooves 55 in the transverse upper surface 57 of the air transfer ring 53.

These grooves 55 have undercuts to form annular counterbores 59 in the grooves 55. A pair of concentric expansive rings 61,62 are secured to the upper surface 57 of the air transfer ring 53 by mounting the inner and outer edges of the expansive rings 61, 63 in the counterbores 59 in the grooves 55 on the upper surface 57 of the air transfer ring 53.

Retainer rings 63 are placed in the grooves 55, compressed against the edges of the expansive rings 61,63 to lock the expansive rings 61,63 in place. A pair of primary fluid conduits 65 pass through the air transfer ring 53 from the bottom surface 67 to the top surface 57. One of the primary fluid conduits 65 exits beneath the outer expansion ring 61, as shown in Fig. 3. The other primary fluid conduit (not shown) exits the top surface 57 of the air transfer ring 53 beneath the inner expansion ring 62. The primary fluid conduits 65 are in fluid contact with lines 69,70 which lead to a foot control 71 as shown in Fig. 6.

Each expansive ring 61, 62 has a small hole 73, 74 located 1 80 degrees away from the primary fluid conduit 65 beneath the expansive ring 61,62. Thus, when air pressure is applied through the primary fluid conduit 65, the expansive ring 61 will be expanded upwards as shown in Fig. 3. The air pressure will then travel around the expansive ring 61 and exit through the hole 73. When the expansive ring 61 is expanded, the expansive ring 61 contacts the lower surface of the seal ring 33 on each side of the groove 45. This forms an annular expansive fluid duct 75.

When air pressure is applied through the other primary fluid conduit (not shown), the other expansive ring 62 will be expanded. The air pressure then travels around the expansive ring 62 and exists through the hole 74.

Expanded ring 62 contacts the seal ring 33 to form an annular expansive fluid duct in the same manner as the outer expansive ring 61.

An inner wear strip 76 is located between the air transfer ring 53 and the bearing support ring 49. An outer mud skirt 77 is located on the outer circumference of the air transfer ring 53 to keep drilling mud away from the expansive rings 61,62.

Fig. 6 illustrates the pneumatic system of the rotary power slips 11. The pneumatic source is an air tank 31 mounted on the drilling rig. Air flow passes from the air tank 31 through a filter 78, a regulator 79, and a lubricator 81 to the safety valve 83. The foot valve 71 then passes the air flow through a selected one of the lines 69,70 to the seal ring 33. The air flow passes from one of the lines, 69 or 70, to one of the primary fluid conduits 65 through the air transfer ring 53.

The air pressure expands one of the expansive rings 61 or 62, until the expansive ring contacts the seal ring 33 to form one of the expansive fluid ducts 75. The air flow passes beneath the expansive ring, 61 or 62, to the hole, 73 or 74, and then through the expansive fluid duct 75 to the port 47. The port 47 passes the air flow to the air passageways. 37 or 38, and then on to the power conduit 41 or the return conduit 39. The power conduit 41 passes the air pressure to the bottom of the cylinder 21 to raise the slip means 15, or the return conduit 39 passes the air pressure to the top of the cylinder 21 to lower the slip means 15.

A pilot operated check valve 85 is located in the power conduit 41 leading to the bottom of the air cylinders 21. Thus, when pneumatic pressure from the external source 31 is re moved, air pressure is not lost from the bottom of the air cylinders 21. The check valve 85 is a check valve means for holding the pressure in one end of the fluid cylinders 21 to keep the slip means 1 5 in the raised position. The purpose of the check valve 85 is to lock the slips 1 5 in the raised position after air pressure from the stationary source 31 is removed. The check valve 85 is piloted off of one of the return conduits 39 leading to the upper half of the air cylinders 21. Thus, as air pressure is applied to the return conduit 39, the check valve 85 is opened to allow air to escape from the bottom of the air cylinders 21 through the power conduits 41. As air pressure escapes the bottom of the air cylin ders 21 the slips 1 5 are lowered to their gripping position as shown in Fig.1.

In operation, to raise the slips to their retracted position as shown in Fig. 2, air pressure from the air tank 31 is applied through the filter 78, the regulator 79 and the lubricator 81 to the safety valve 83. The foot valve 71 then applies the air pressure through one of the lines 69 to the air transfer ring 53.

The air passes through one of the primary fluid conduits 65 to beneath one of the expansive rings 61. The air pressure causes the expansive ring 61 to expand to contact the bottom of the seal ring 33. The expansive ring 61 and the groove 45 in the seal ring 33 create an expansive fluid duct 75. The air beneath the expansive ring 61 passes through the hole 73 into the expansive fluid duct 75.

The air then passes through the port 47 to an air passageway 37. The air passageway 37 conducts the air to the power conduits 41 in the body 1 3 of the rotary power slip 11. The air in the top of the air cylinders 21 is exhausted through the return conduits 39, and the power conduits 41 conduct the air to the bottom of the air cylinders 21 to raise the slip ring 1 7 and the slips 1 5 to the upper retracted position shown in Fig. 2. The check valve 85 prevents the air pressure in the lower half of the air cylinder 21 from escaping and locks the slips 1 5 in the raised position.

The foot valve 71 is then moved to a neutral position, removing fluid pressure from the seal ring 33.

In order to lower the slips 15, air pressure from the air tank 31 is fed by the foot control 71 through the other line 70 to the air transfer ring 53. The line 70 is connected to the other primary fluid conduit (not shown).

The primary fluid conduit (not shown) conducts the air to beneath the other expansive ring 62. The expansive ring 62 is expanded to contact the seal ring 33 and to form the expansive fluid duct 75. The air escapes through the hole 74 into the expansive fluid conduit 76. The air travels through the port (not shown) into the air passageway 38 and then into the return conduit 39. The return conduit 39 carries the air pressure to the upper half of the pneumatic cylinders 21. The check valve 85 is piloted off of one of the return conduits 39, to open the check valve 85 when fluid pressure is applied to the return conduit 39. This allows air pressure in the bottom half of the air cylinders 21 to escape through the power conduits 41 and allows the slips 1 5 to be lowered to their gripping position.

The rotary power slips 11 of the invention provide several significant advantages over the prior art. The expansive rings 61,62 are more reliable and can withstand more pressure and more abrasion than the expansive means used in prior devices. The expansive rings 61,62 are also easier to service and to replace under field conditions.

The pilot operated check valve 85 makes the improved rotary power slips 11 safer and more economical than prior art devices. The check valve 85 holds the slips 1 5 in the upward, retracted position, even when air pressure from the stationary source 31 is removed.

While the invention has been shown in only one of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes and modifications without departing from the spirit thereof.

Claims (3)

1. Rotary power slips, comprising in combination: a body mounted concentrically with the pipe opening in a rotary table of an earth drilling rig; slip means carried on the body for gripping and releasing pipe in the rotary table; a fluid cylinder carried by the body and attached to the slip means to raise and lower the slip means; a pair of fluid conduits, each conduit fluidly connected to one end of the fluid cylinder to supply fluid pressure to the fluid cylinder: and check valve means in one of the fluid conduits for maintaining fluid pressure in one end of the fluid cylinder to keep the slip means in the raised position, even if fluid pressure in the fluid conduits is lost.

2. Rotary power slips, comprising in combination a body mounted concentrically with the pipe opening in a rotary table of an earth drilling rig; slip means carried on the body for gripping and releasing pipe in the rotary table; a fluid cylinder carried by the body and attached to the slip means to raise and lower the slip means; a pair of fluid conduits, each conduit fluidly connected to one end of the fluid cylinder to supply fluid pressure to the fluid cylinder; check valve means in one of the fluid conduits for maintaining fluid pressure in one end of the fluid cylinder to keep the slip means in the raised position, even if fluid pressure in the fluid conduits is lost; and pilot means for releasing the check valve means to allow fluid pressure to escape and to allow the slip means to be lowered.

3. Rotary power slips, comprising in combination: a body mounted concentrically with the pipe opening in a rotary table of an earth drilling rig; slip means carried on the body for gripping and releasing pipe in the rotary table; a pneumatic piston and cylinder carried by the body and attached to the slip means to raise and lower the slip means; a power conduit fluidly connected to one end of the cylinder to provide fluid pressure to one side of the piston to raise the slip means; a return conduit fluidly connected to the opposite end of the cylinder to provide fluid pressure to the opposite side of the piston to lower the slip means; a check valve in the power conduit to allow fluid to freely pass toward the cylinder ,but to prevent fluid flow through the power conduit away from the cylinder; and a pilot line from the return conduit to the check valve to open the check valve to allow fluid flow through the power conduit away from the cylinder whenever fluid pressure is applied through the return conduit to the cylinder to lower the slip means.